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Acta Physiologica

Impact factor: 4.382 5-Year impact factor: 3.853 Print ISSN: 1748-1708 Online ISSN: 1748-1716 Publisher: Wiley Blackwell (Blackwell Publishing)

Subject: Psychology

Most recent papers:

  • Mechanisms of sphingosine‐1‐phosphate‐mediated vasoconstriction of rat afferent arterioles.
    Z. Guan, F. Wang, X. Cui, E. W. Inscho.
    Acta Physiologica. 8 days ago
    Aim Sphingosine‐1‐phosphate (S1P) influences resistance vessel function and is implicated in renal pathological processes. Previous studies revealed that S1P evoked potent vasoconstriction of the pre‐glomerular microvasculature, but the underlying mechanisms remain incompletely defined. We postulated that S1P‐mediated pre‐glomerular microvascular vasoconstriction involves activation of voltage‐dependent L‐type calcium channels (L‐VDCC) and the rho/rho kinase pathway. Methods Afferent arteriolar reactivity was assessed in vitro using the blood‐perfused rat juxtamedullary nephron preparation, and diameter was measured during exposure to physiological and pharmacological agents. Results Exogenous S1P (10−9–10−5 mol L−1) evoked concentration‐dependent vasoconstriction of afferent arterioles. Superfusion with nifedipine, a L‐VDCC blocker, increased arteriolar diameter by 39 ± 18% of baseline and significantly attenuated the S1P‐induced vasoconstriction. Superfusion with the rho kinase inhibitor, Y‐27632, increased diameter by 60 ± 12% of baseline and also significantly blunted vasoconstriction by S1P. Combined nifedipine and Y‐27632 treatment significantly inhibited S1P‐induced vasoconstriction over the entire concentration range tested. In contrast, depletion of intracellular Ca2+ stores with the Ca2+‐ATPase inhibitors, thapsigargin or cyclopiazonic acid, did not alter the S1P‐mediated vasoconstrictor profile. Scavenging reactive oxygen species (ROS) or inhibition of nicotinamide adenine dinucleotide phosphate oxidase activity significantly attenuated S1P‐mediated vasoconstriction. Conclusion Exogenous S1P elicits potent vasoconstriction of rat afferent arterioles. These data also demonstrate that S1P‐mediated pre‐glomerular vasoconstriction involves activation of L‐VDCC, the rho/rho kinase pathway and ROS. Mobilization of Ca2+ from intracellular stores is not required for S1P‐mediated vasoconstriction. These studies reveal a potential role for S1P in the modulation of renal microvascular tone.
    July 13, 2017   doi: 10.1111/apha.12913   open full text
  • Cerebrocortical activity during self‐paced exercise in temperate, hot and hypoxic conditions.
    Julien D. Périard, Kevin De Pauw, Frank Zanow, Sébastien Racinais.
    Acta Physiologica. July 07, 2017
    Aim Heat stress and hypoxia independently influence cerebrocortical activity and impair prolonged exercise performance. This study examined the relationship between electroencephalography (EEG) activity and self‐paced exercise performance in control (CON, 18°C, 40% RH), hot (HOT, 35°C, 60%RH) and hypoxic (HYP, 18°C, 40%RH FiO2: 0.145) conditions. Methods Eleven well‐trained cyclists completed a 750 kJ cycling time trial in each condition on separate days in a counter‐balanced order. EEG activity was recorded with α and β activity evaluated in the frontal (F3 and F4) and central (C3 and C4) areas. Standardised low‐resolution brain electromagnetic tomography (sLORETA) was also utilised to localise changes in cerebrocortical activity. Results Both α and β activity decreased in the frontal and central areas during exercise in HOT relative to CON (P<0.05). α activity was also lower in HYP compared with CON (P<0.05), whereas β activity remained similar. β activity was higher in HYP than HOT (P<0.05). sLORETA revealed that α and β activity increased at the onset of exercise in the primary somatosensory and motor cortices in CON and HYP, whilst only β activity increased in HOT. A decrease in α and β activity occurred thereafter in all conditions, with α activity being lower in the somatosensory and somatosensory association cortices in HOT relative to CON. Conclusion High‐intensity prolonged self‐paced exercise induces cerebrocortical activity alterations in areas of the brain associated with the ability to inhibit conflicting attentional processing under hot and hypoxic conditions, along with the capacity to sustain mental readiness and arousal under heat stress. This article is protected by copyright. All rights reserved.
    July 07, 2017   doi: 10.1111/apha.12916   open full text
  • Exercise training increases skeletal muscle mitochondrial volume density by enlargement of existing mitochondria and not de novo biogenesis.
    A.‐K. Meinild Lundby, R. A. Jacobs, S. Gehrig, J. Leur, M. Hauser, T. C. Bonne, D. Flück, S. Dandanell, N. Kirk, A. Kaech, U. Ziegler, S. Larsen, C. Lundby.
    Acta Physiologica. July 06, 2017
    Aims (i) To determine whether exercise‐induced increases in muscle mitochondrial volume density (MitoVD) are related to enlargement of existing mitochondria or de novo biogenesis and (ii) to establish whether measures of mitochondrial‐specific enzymatic activities are valid biomarkers for exercise‐induced increases in MitoVD. Method Skeletal muscle samples were collected from 21 healthy males prior to and following 6 weeks of endurance training. Transmission electron microscopy was used for the estimation of mitochondrial densities and profiles. Biochemical assays, western blotting and high‐resolution respirometry were applied to detect changes in specific mitochondrial functions. Result MitoVD increased with 55 ± 9% (P < 0.001), whereas the number of mitochondrial profiles per area of skeletal muscle remained unchanged following training. Citrate synthase activity (CS) increased (44 ± 12%, P < 0.001); however, there were no functional changes in oxidative phosphorylation capacity (OXPHOS, CI+IIP) or cytochrome c oxidase (COX) activity. Correlations were found between MitoVD and CS (P = 0.01; r = 0.58), OXPHOS, CI+CIIP (P = 0.01; R = 0.58) and COX (P = 0.02; R = 0.52) before training; after training, a correlation was found between MitoVD and CS activity only (P = 0.04; R = 0.49). Intrinsic respiratory capacities decreased (P < 0.05) with training when respiration was normalized to MitoVD. This was not the case when normalized to CS activity although the percentage change was comparable. Conclusions MitoVD was increased by inducing mitochondrial enlargement rather than de novo biogenesis. CS activity may be appropriate to track training‐induced changes in MitoVD.
    July 06, 2017   doi: 10.1111/apha.12905   open full text
  • Myoendothelial coupling through Cx40 contributes to EDH‐induced vasodilation in murine renal arteries: evidence from experiments and modelling.
    J. C. Brasen, C. de Wit, C. M. Sorensen.
    Acta Physiologica. July 02, 2017
    Regulation of renal vascular resistance plays a major role in controlling arterial blood pressure. The endothelium participates in this regulation as endothelial derived hyperpolarization plays a significant role in smaller renal arteries and arterioles, but the exact mechanisms are still unknown. Aim To investigate the role of vascular gap junctions and potassium channels in the renal endothelial derived hyperpolarization. Methods In interlobar arteries from wild‐type and connexin40 knockout mice, we assessed the role of calcium‐activated small (SK) and intermediate (IK) conductance potassium channels. The role of inward rectifier potassium channels (Kir) and Na+/K+‐ATPases was evaluated as was the contribution from gap junctions. Mathematical models estimating diffusion of ions and electrical coupling in myoendothelial gap junctions were used to interpret the results. Results Lack of connexin40 significantly reduces renal endothelial hyperpolarization. Inhibition of SK and IK channels significantly attenuated renal EDH to a similar degree in wild‐type and knockout mice. Inhibition of Kir and Na+/K+‐ATPases affected the response in wild‐type and knockout mice but at different levels of stimulation. The model confirms that activation of endothelial SK and IK channels generates a hyperpolarizing current that enters the vascular smooth muscle cells. Also, extracellular potassium increases sufficiently to activate Kir and Na+/K+‐ATPases. Conclusion Renal endothelial hyperpolarization is mainly initiated by activation of IK and SK channels. The model shows that hyperpolarization can spread through myoendothelial gap junctions but enough potassium is released to activate Kir and Na+/K+‐ATPases. Reduced coupling seems to shift the signalling pathway towards release of potassium. However, an alternative pathway also exists and needs to be investigated.
    July 02, 2017   doi: 10.1111/apha.12906   open full text
  • Astroglial vesicular network: Evolutionary trends, physiology and pathophysiology.
    Robert Zorec, Vladimir Parpura, Alexei Verkhratsky.
    Acta Physiologica. June 30, 2017
    Intracellular organelles, including secretory vesicles, emerged when eukaryotic cells evolved some 3 billion years ago. The primordial organelles that evolved in Archaea were similar to endolysosomes, which developed, arguably, for specific metabolic tasks, including uptake, metabolic processing, storage and disposal of molecules. In comparison to prokaryotes, cell volume of eukaryotes increased by several orders of magnitude and vesicle traffic emerged to allow for communication between distant intracellular locations. Lysosomes, first described in 1955, a prominent intermediate of endo‐ and exocytotic pathways, operate virtually in all eukaryotic cells including astroglia, the most heterogeneous type of homeostatic glia in the central nervous system. Astrocytes support neuronal network activity in particular through elaborated secretion, based on a complex intracellular vesicle network dynamics. Deranged homeostasis underlies disease and astroglial vesicle traffic contributes to the pathophysiology of neurodegenerative (Alzheimer's disease, Huntington's disease), neurodevelopmental diseases (intellectual deficiency, Rett's disease) and neuroinfectious (Zika virus) disorders. This review addresses astroglial cell‐autonomous vesicular traffic network, classified into primary and secondary vesicular network defects in diseases, targets for developing new therapies for neurologic conditions. This article is protected by copyright. All rights reserved.
    June 30, 2017   doi: 10.1111/apha.12915   open full text
  • Isolated pulmonary regurgitation causes decreased right ventricular longitudinal function and compensatory increased septal pumping in a porcine model.
    S. Kopic, S. S. Stephensen, E. Heiberg, H. Arheden, P. Bonhoeffer, M. Ersbøll, N. Vejlstrup, L. Søndergaard, M. Carlsson.
    Acta Physiologica. June 29, 2017
    Aim Longitudinal ventricular contraction is a parameter of cardiac performance with predictive power. Right ventricular (RV) longitudinal function is impaired in patients with free pulmonary regurgitation (PR) following corrective surgery for Tetralogy of Fallot (TOF). It remains unclear whether this is a consequence of the surgical repair, or whether it is inherent to PR. The aim of this study was to assess the relationship between longitudinal, lateral and septal pumping in a porcine model of isolated PR. Methods Piglets were divided into a control (n = 8) group and a treatment (n = 12) group, which received a stent in the pulmonary valve orifice, inducing PR. After 2–3 months, animals were subjected to cardiac magnetic resonance imaging. A subset of animals (n = 6) then underwent percutaneous pulmonary valve replacement (PPVR) with follow‐up 1 month later. Longitudinal, lateral and septal contributions to stroke volume (SV) were quantified by measuring volumetric displacements from end‐diastole to end‐systole in the cardiac short axis and long axis. Results PR resulted in a lower longitudinal contribution to RV stroke volume, compared to controls (60.0 ± 2.6% vs. 73.6 ± 3.8%; P = 0.012). Furthermore, a compensatory increase in septal contribution to RVSV was observed (11.0 ± 1.6% vs. −3.1 ± 1.5%; P < 0.0001). The left ventricle (LV) showed counter‐regulation with an increased longitudinal LVSV. Changes in RV longitudinal function were reversed by PPVR. Conclusion These findings suggest that PR contributes to decreased RV longitudinal function in the absence of scarring from cardiac surgery. Measurement of longitudinal RVSV may aid risk stratification and timing for interventional correction of PR in TOF patients.
    June 29, 2017   doi: 10.1111/apha.12904   open full text
  • Endothelial colony forming cells and proangiogenic cells: clarifying definitions and their potential role in mitigating acute kidney injury.
    David P. Basile, Jason A. Collett, Mervin C. Yoder.
    Acta Physiologica. June 28, 2017
    Acute kidney injury (AKI) represents a significant clinical concern that is associated with high mortality rates and also represents a significant risk factor for the development of chronic kidney disease (CKD). This article will consider alterations in renal endothelial function in the setting of AKI that may underlie impairment in renal perfusion and how inefficient vascular repair may manifest post‐AKI and contribute to the potential transition to CKD. We provide updated terminology for cells previously classified as “endothelial progenitor” that may mediate vascular repair such as pro‐angiogenic cells and endothelial colony forming cells. We consider how endothelial repair may be mediated by these different cell types following vascular injury, particularly in models of AKI. We further summarize the potential ability of these different cells to mitigate the severity of AKI, improve perfusion and maintain vascular structure in pre‐clinical studies. This article is protected by copyright. All rights reserved.
    June 28, 2017   doi: 10.1111/apha.12914   open full text
  • Acute toll‐like receptor 4 activation impairs rat renal microvascular autoregulatory behaviour.
    J. P. Van Beusecum, S. Zhang, A. K. Cook, E. W. Inscho.
    Acta Physiologica. June 27, 2017
    Aim Little is known about how toll‐like receptor 4 (TLR4) influences the renal microvasculature. We hypothesized that acute TLR4 stimulation with lipopolysaccharide (LPS) impairs afferent arteriole autoregulatory behaviour, partially through reactive oxygen species (ROS). Methods We assessed afferent arteriole autoregulatory behaviour after LPS treatment (1 mg kg−1; i.p.) using the in vitro blood‐perfused juxtamedullary nephron preparation. Autoregulatory behaviour was assessed by measuring diameter responses to stepwise changes in renal perfusion pressure. TLR4 expression was assessed by immunofluorescence, immunohistochemistry and Western blot analysis in the renal cortex and vasculature. Results Baseline arteriole diameter at 100 mmHg averaged 15.2 ± 1.2 μm and 12.2 ± 1.0 μm for control and LPS groups (P < 0.05) respectively. When perfusion pressure was increased in 15 mmHg increments from 65 to 170 mmHg, arteriole diameter in control kidneys decreased significantly to 69 ± 6% of baseline diameter. In the LPS‐treated group, arteriole diameter remained essentially unchanged (103 ± 9% of baseline), indicating impaired autoregulatory behaviour. Pre‐treatment with anti‐TLR4 antibody or the TLR4 antagonist, LPS‐RS, preserved autoregulatory behaviour during LPS treatment. P2 receptor reactivity was normal in control and LPS‐treated rats. Pre‐treatment with Losartan (angiotensin type 1 receptor blocker; (AT1) 2 mg kg−1; i.p.) increased baseline afferent arteriole diameter but did not preserve autoregulatory behaviour in LPS‐treated rats. Acute exposure to Tempol (10−3 mol L−1), a superoxide dismutase mimetic, restored pressure‐mediated vasoconstriction in kidneys from LPS‐treated rats. Conclusion These data demonstrate that TLR4 activation impairs afferent arteriole autoregulatory behaviour, partially through ROS, but independently of P2 and AT1 receptor activation.
    June 27, 2017   doi: 10.1111/apha.12899   open full text
  • Control of breathing and ventilatory acclimatization to hypoxia in deer mice native to high altitudes.
    Catherine M. Ivy, Graham R. Scott.
    Acta Physiologica. June 22, 2017
    Aim We compared the control of breathing and heart rate by hypoxia between high‐ and low‐altitude populations of Peromyscus mice, to help elucidate the physiological specializations that help high‐altitude natives cope with O2 limitation. Methods Deer mice (P. maniculatus) native to high altitude and congeneric mice native to low altitude (P. leucopus) were bred in captivity at sea level. The F1 progeny of each population were raised to adulthood and then acclimated to normoxia or hypobaric hypoxia (12 kPa, simulating hypoxia at ~4300 m) for 5 months. Responses to acute hypoxia were then measured during step‐wise reductions in inspired O2 fraction. Results Lowlanders exhibited ventilatory acclimatization to hypoxia (VAH), in which hypoxia acclimation enhanced the hypoxic ventilatory response, made breathing pattern more effective (higher tidal volumes and lower breathing frequencies at a given total ventilation), increased arterial O2 saturation and heart rate during acute hypoxia, augmented respiratory water loss, and led to significant growth of the carotid body. In contrast, highlanders did not exhibit VAH – exhibiting a fixed increase in breathing that was similar to hypoxia acclimated lowlanders – and they maintained even higher arterial O2 saturations in hypoxia. However, the carotid bodies of highlanders were not enlarged by hypoxia acclimation and were similar in size to those of normoxic lowlanders. Highlanders also maintained consistently higher heart rates than lowlanders during acute hypoxia. Conclusions Our results suggest that highland deer mice have evolved high rates of alveolar ventilation and respiratory O2 uptake without the significant enlargement of the carotid bodies that is typical of VAH in lowlanders, possibly to adjust the hypoxic chemoreflex for life in high‐altitude hypoxia. This article is protected by copyright. All rights reserved.
    June 22, 2017   doi: 10.1111/apha.12912   open full text
  • Adaptations to endurance training depend on exercise‐induced oxidative stress: exploiting redox interindividual variability.
    N. V. Margaritelis, A. A. Theodorou, V. Paschalis, A. S. Veskoukis, K. Dipla, A. Zafeiridis, G. Panayiotou, I. S. Vrabas, A. Kyparos, M. G. Nikolaidis.
    Acta Physiologica. June 21, 2017
    Aim The aim of this study was to reveal the role of reactive oxygen and nitrogen species (RONS) in exercise adaptations under physiological in vivo conditions and without the interference from other exogenous redox agents (e.g. a pro‐oxidant or antioxidant). Methods We invented a novel methodological set‐up that exploited the large redox interindividual variability in exercise responses. More specifically, we used exercise‐induced oxidative stress as the ‘classifier’ measure (i.e. low, moderate and high) and investigated the physiological and redox adaptations after a 6‐week endurance training protocol. Results We demonstrated that the group with the low exercise‐induced oxidative stress exhibited the lowest improvements in a battery of classic adaptations to endurance training (VO2 max, time trial and Wingate test) as well as in a set of redox biomarkers (oxidative stress biomarkers and antioxidants), compared to the high and moderate oxidative stress groups. Conclusion The findings of this study substantiate, for the first time in a human in vivo physiological context, and in the absence of any exogenous redox manipulation, the vital role of RONS produced during exercise in adaptations. The stratification approach, based on a redox phenotype, implemented in this study could be a useful experimental strategy to reveal the role of RONS and antioxidants in other biological manifestations as well.
    June 21, 2017   doi: 10.1111/apha.12898   open full text
  • Temporal overexpression of SIRT1 in skeletal muscle of adult mice does not improve insulin sensitivity or markers of mitochondrial biogenesis.
    K. Svensson, S. A. LaBarge, V. F. Martins, S. Schenk.
    Acta Physiologica. June 13, 2017
    Aims Activation of the NAD+ dependent protein deacetylase SIRT1 has been proposed as a therapeutic strategy to treat mitochondrial dysfunction and insulin resistance in skeletal muscle. However, lifelong overexpression of SIRT1 in skeletal muscle does not improve parameters of mitochondrial function and insulin sensitivity. In this study, we investigated whether temporal overexpression of SIRT1 in muscle of adult mice would affect skeletal muscle mitochondrial function and insulin sensitivity. Methods To circumvent potential effects of germline SIRT1 overexpression, we utilized an inducible model of SIRT1 overexpression in skeletal muscle of adult mice (i‐mOX). Insulin sensitivity was assessed by 2‐deoxyglucose uptake, muscle maximal respiratory function by high‐resolution respirometry and systemic energy expenditure was assessed by whole body calorimetry. Results Although SIRT1 was highly, and specifically, overexpressed in skeletal muscle of i‐mOX compared to WT mice, glucose tolerance and skeletal muscle insulin sensitivity were comparable between genotypes. Additionally, markers of mitochondrial biogenesis, muscle maximal respiratory function and whole‐body oxygen consumption were also unaffected by SIRT1 overexpression. Conclusion These results support previous work demonstrating that induction of SIRT1 in skeletal muscle, either at birth or in adulthood, does not impact muscle insulin action or mitochondrial function.
    June 13, 2017   doi: 10.1111/apha.12897   open full text
  • Isopimaric acid – a multi‐targeting ion channel modulator reducing excitability and arrhythmicity in a spontaneously beating mouse atrial cell line.
    S. Salari, M. Silverå Ejneby, J. Brask, F. Elinder.
    Acta Physiologica. June 09, 2017
    Aim Atrial fibrillation is the most common persistent cardiac arrhythmia, and it is not well controlled by present drugs. Because some resin acids open voltage‐gated potassium channels and reduce neuronal excitability, we explored the effects of the resin acid isopimaric acid (IPA) on action potentials and ion currents in cardiomyocytes. Methods Spontaneously beating mouse atrial HL‐1 cells were investigated with the whole‐cell patch‐clamp technique. Results 1–25 μmol L−1 IPA reduced the action potential frequency by up to 50%. The effect of IPA on six different voltage‐gated ion channels was investigated; most voltage‐dependent parameters of ion channel gating were shifted in the negative direction along the voltage axis, consistent with a hypothesis that a lipophilic and negatively charged compound binds to the lipid membrane close to the positively charged voltage sensor of the ion channels. The major finding was that IPA inactivated sodium channels and L‐ and T‐type calcium channels and activated the rapidly activating potassium channel and the transient outward potassium channel. Computer simulations of IPA effects on all of the ion currents were consistent with a reduced excitability, and they also showed that effects on the Na channel played the largest role to reduce the action potential frequency. Finally, induced arrhythmia in the HL‐1 cells was reversed by IPA. Conclusion Low concentrations of IPA reduced the action potential frequency and restored regular firing by altering the voltage dependencies of several voltage‐gated ion channels. These findings can form the basis for a new pharmacological strategy to treat atrial fibrillation.
    June 09, 2017   doi: 10.1111/apha.12895   open full text
  • Microparticles of healthy origins improve endothelial progenitor cell dysfunction via microRNA transfer in an atherosclerotic hamster model.
    N. Alexandru, E. Andrei, L. Niculescu, E. Dragan, V. Ristoiu, A. Georgescu.
    Acta Physiologica. June 08, 2017
    Aim In this study, we aimed: (i) to obtain and functionally characterize the cultures of late endothelial progenitor cells (EPCs) from the animal blood; (ii) to investigate the potential beneficial effects of circulating microparticles (MPs) of healthy origins on EPC dysfunctionality in atherosclerosis as well as involved mechanisms. Methods Late EPCs were obtained and expanded in culture from peripheral blood isolated from two animal groups: hypertensive–hyperlipidaemic (HH) and control (C) hamsters. In parallel experiments, late EPC cultures from HH were incubated with MPs from C group. Results The results showed that late EPCs display endothelial cell phenotype: (i) have ability to uptake 1,1‐dioctadecyl‐3,3,3,3 tetramethylindocarbocyanine‐labelled acetylated low‐density lipoprotein and Ulex europaeus agglutinin lectin‐1; (ii) express CD34, CD133, KDR, CD144, vWF, Tie‐2. Late EPCs from HH exhibited different morphological and functional characteristics compared to control: (i) are smaller and irregular in shape; (ii) present decreased endothelial surface marker expression; (iii) display reduced proliferation, migration and adhesion; (iv) lose ability to organize themselves into tubular structures and integrate into vascular network; (v) have diminished function of inward rectifier potassium channels. The incubation of late EPCs with MPs improved EPC functionality by miR‐10a, miR‐21, miR‐126, miR‐146a, miR‐223 transfer and IGF‐1 expression activation; the kinetic study of MP incorporation into EPCs demonstrated MP uptake by EPCs followed by the miRNA transfer. Conclusion The data reveal that late EPCs from atherosclerotic model exhibit distinctive features and are dysfunctional, and their function recovery can be supported by MP ability to transfer miRNAs. These findings bring a new light on the vascular repair in atherosclerosis.
    June 08, 2017   doi: 10.1111/apha.12896   open full text
  • Age‐related endothelial dysfunction in human skeletal muscle feed arteries: the role of free radicals derived from mitochondria in the vasculature.
    S.‐Y. Park, O. S. Kwon, R. H. I. Andtbacka, J. R. Hyngstrom, V. Reese, M. P. Murphy, R. S. Richardson.
    Acta Physiologica. June 08, 2017
    Aim This study sought to determine the role of free radicals derived from mitochondria in the vasculature in the recognized age‐related endothelial dysfunction of human skeletal muscle feed arteries (SMFAs). Methods A total of 44 SMFAs were studied with and without acute exposure to the mitochondria‐targeted antioxidant MitoQ and nitric oxide synthase (NOS) blockade. The relative abundance of proteins from the electron transport chain, phosphorylated (p‐) to endothelial (e) NOS ratio, manganese superoxide dismutase (MnSOD) and the mitochondria‐derived superoxide (O2−) levels were assessed in SMFA. Endothelium‐dependent and endothelium‐independent SMFA vasodilation was assessed in response to flow‐induced shear stress, acetylcholine (ACh) and sodium nitroprusside (SNP). Results MitoQ restored endothelium‐dependent vasodilation in the old to that of the young when stimulated by both flow (young: 68 ± 5; old: 25 ± 7; old + MitoQ 65 ± 9%) and ACh (young: 97 ± 4; old: 59 ± 10; old + MitoQ: 98 ± 5%), but did not alter the initially uncompromised, endothelium‐independent vasodilation (SNP). Compared to the young, MitoQ in the old diminished the initially elevated mitochondria‐derived O2− levels and appeared to attenuate the breakdown of MnSOD. Furthermore, MitoQ increased the ratio of p‐eNOS to NOS and the restoration of endothelium‐dependent vasodilation in the old by MitoQ was ablated by NOS blockade. Conclusion This study demonstrated that MitoQ reverses age‐related vascular dysfunction by what appears to be an NO‐dependent mechanism in human SMFAs. These findings suggest that mitochondria‐targeted antioxidants may have utility in terms of counteracting the attenuated blood flow and vascular dysfunction associated with advancing age.
    June 08, 2017   doi: 10.1111/apha.12893   open full text
  • Improvement in baroreflex control of renal sympathetic nerve activity in obese Sprague Dawley rats following immunosuppression.
    S. A. Khan, M. Z. A. Sattar, N. A. Abdullah, H. A. Rathore, A. Ahmad, M. H. Abdulla, E. J. Johns.
    Acta Physiologica. June 07, 2017
    Aim This investigation explored the hypothesis that in obesity an inflammatory response in the kidney contributed to a renal nerve‐dependent blunting of the baroreflex regulation of renal sympathetic nerve activity. Methods Rats received a normal (12% kcal) or high‐fat (45% kcal) diet for 8 weeks plus daily injections of vehicle (0.9% NaCl i.p) or tacrolimus (0.25 mg kg−1 day−1 i.p) from weeks 3–8. Following anaesthesia, left renal sympathetic nerve activity was recorded, baroreflex gain curves were generated, by infusing phenylephrine and sodium nitroprusside, and cardiopulmonary baroreceptors challenged by infusing a saline load. Results The high‐fat diet elevated weight gain and adiposity index by 89 and 129% (both, P < 0.001). Mean blood pressure (132 ± 4 vs 103 ± 5 mmHg), fractional noradrenaline excretion and creatinine clearance (5.64 ± 0.55 vs 3.32 ± 0.35 mL min−1 kg−1) were 28, 77 and 69% higher (all P < 0.05), but urine flow and fractional sodium excretions were 42 and 72% (both P < 0.001) lower compared to normal rats. Plasma and renal TNF‐α and IL‐6 concentrations were fourfold to fivefold (P < 0.001) and 22 and 20% higher (both, P < 0.05), in obese rats but normalized following tacrolimus. In obese rats, baroreflex sensitivity was reduced by 80% (P < 0.05) but restored by renal denervation or tacrolimus. Volume expansion reduced renal sympathetic nerve activity by 54% (P < 0.001) in normal and obese rats subjected to renal denervation and tacrolimus, but not in obese rats with an intact renal innervation. Conclusion Obesity induced a renal inflammation and pointed to this being both the origin of autonomic dysregulation and a potential focus for targeted therapy.
    June 07, 2017   doi: 10.1111/apha.12891   open full text
  • Inhibitory action of oxytocin on spontaneous contraction of rat distal colon by nitrergic mechanism: involvement of cyclic GMP and apamin‐sensitive K+ channels.
    R. Wang, M. T. Han, X. L. Lv, Y. A. Yu, S. Q. Chai, C. M. Qu, C. Y. Liu.
    Acta Physiologica. May 20, 2017
    Aim The mechanisms underlying the inhibitory effects of oxytocin (OT) on colon tone are not totally understood. We explore the mechanisms of OT on spontaneous contractility in rat distal colon and identify the mediators involved in this action. Methods In rat distal colon strips, mechanical activity was analysed and the production of nitric oxide (NO) in tissue loaded with the fluorochrome DAF‐FM was visualized by confocal microscopy. OT receptor (OTR) expression was determined by Western blotting and immunofluorescence. Results In rat distal colon, OT produced a concentration‐dependent reduction in the spontaneous contraction, which was abolished by the OTR antagonist atosiban, the neural blocker tetrodotoxin and the inhibitor of neuronal nitric oxide synthase (nNOS) NPLA. The inhibitory effects of OT were not affected by propranolol, atropine, the nicotinic cholinoceptor blocker hexamethonium, the vasoactive intestinal peptide receptor antagonist VIPHyb, the P2 purinoceptor antagonist PPADS, the adenosine A1 receptors antagonist DPCPX and the prostacyclin receptor antagonist Ro1138452. The soluble guanylyl cyclase (sGC) inhibitor ODQ and the small conductance Ca2+‐activated K+ (CaK+) channels blocker apamin significantly reduced the relaxation induced by OT, nicotine, sodium nitroprusside and the sGC activator BAY 41‐2272. The neural release of NO elicited by OT was prevented by NPLA, tetrodotoxin and atosiban. The presence of the OTR and its co‐localization with nNOS was detected by immunohistochemistry and Western blotting experiments. Conclusion These results demonstrate the NO release from enteric neurones induced by activation of OTR mediates distal colon relaxation. sGC and small conductance CaK+ channels are involved in this relaxation.
    May 20, 2017   doi: 10.1111/apha.12890   open full text
  • Deferoxamine‐activated hypoxia‐inducible factor‐1 restores cardioprotective effects of sevoflurane postconditioning in diabetic rats.
    P. Xie, L. Yang, A. Talaiti, J. J. Wu, J. Yu, T. Yu, H. Y. Wang, B. Huang, Q. Wu, Y. Maimaitili, J. Wang, H. P. Ma, Y. N. Yang, H. Zheng.
    Acta Physiologica. May 15, 2017
    Aim The cardioprotective effects of sevoflurane postconditioning (SpostC) are eliminated under diabetic conditions, and the underlying mechanism for this phenomenon remains unclear. Many studies have demonstrated that the hypoxia‐inducible factor‐1 (HIF‐1) signalling pathway in the myocardium is impaired under diabetic conditions. This study was to investigate whether deferoxamine (DFO)‐induced activation of HIF‐1 signalling pathway can restore the cardioprotective effects of SpostC in diabetic rats. Methods A model of myocardial ischaemia/reperfusion (I/R) injury was induced via ligation of the left anterior descending artery. SpostC was conducted by administering 1.0 MAC sevoflurane. After inducing the I/R injury, the following parameters were measured: myocardial infarct size, cardiac function, myocardial ultrastructure, mitochondrial respiratory function, respiratory chain enzyme activity, rate of reactive oxygen species (ROS) generation, and protein expression of HIF‐1α, vascular endothelial growth factor (VEGF), cleaved caspase‐3, Bcl‐2 and Bax. Results After DFO activated HIF‐1 in the impaired myocardium of diabetic rats, SpostC significantly upregulated the protein expression of HIF‐1α and its downstream mediator VEGF. This improved myocardial mitochondrial respiratory function and respiratory chain enzyme activity and reduced ROS generation as well as the protein expression of cleaved caspase‐3 and Bax. As a result, myocardial infarct size decreased, and cardiac function and mitochondrial ultrastructure improved. Conclusion This study demonstrates for the first time that abolishment of the cardioprotective effects of SpostC in diabetic rats is associated with impairment of the HIF‐1 signalling pathway and that DFO can activate HIF‐1 to restore these cardioprotective effects of SpostC in diabetic rats.
    May 15, 2017   doi: 10.1111/apha.12874   open full text
  • CO2 permeability and carbonic anhydrase activity of rat cardiomyocytes.
    M. Arias‐Hidalgo, S. Al‐Samir, N. Weber, C. Geers‐Knörr, G. Gros, V. Endeward.
    Acta Physiologica. May 15, 2017
    Aim To determine the CO2 permeability (PCO2) of plasma membranes of cardiomyocytes. These cells were chosen because heart possesses the highest rate of O2 consumption/CO2 production in the body. Methods Cardiomyocytes were isolated from rat hearts using the Langendorff technique. Cardiomyocyte suspensions exhibited a vitality of 2–14% and were studied by the previously described mass spectrometric 18O‐exchange technique deriving PCO2. We showed by mass spectrometry and by carbonic anhydrase (CA) staining that non‐vital cardiomyocytes are free of CA and thus do not contribute to the mass spectrometric signal, which is determined exclusively by the fully functional vital cardiomyocytes. Results Lysed cardiomyocytes yielded an intracellular CA activity for vital cells of 5070; that is, the rate of CO2 hydration inside the cell is accelerated 5071‐fold. Using this number, analyses of the mass spectrometric recordings from cardiomyocyte suspensions yield a PCO2 of 0.10 cm s−1 (SD ± 0.06, n = 15) at 37 °C. Conclusion In comparison with the PCO2 of other cells, this value is quite high and about identical to that of the human red cell membrane. As no major protein CO2 channels such as aquaporins 1 and 4 are present in rat cardiac sarcolemma, the high PCO2 of this membrane is likely due to its low cholesterol content of about 0.2 (mol cholesterol)·(mol total membrane lipids)−1. Previous work predicted a PCO2 of ≥0.1 cm s−1 from this level of cholesterol. We conclude that the low cholesterol establishes a PCO2 high enough to render the membrane resistance to CO2 diffusion almost negligible, even under conditions of maximal O2 consumption of the heart.
    May 15, 2017   doi: 10.1111/apha.12887   open full text
  • Neurological and Neuropsychological Effects of Low and Moderate Prenatal Alcohol Exposure.
    Erika Comasco, Jenny Rangmar, Ulf J. Eriksson, Lars Oreland.
    Acta Physiologica. May 04, 2017
    Several explanations for the diverse results in research on Foetal Alcohol Spectrum Disorders (FASD) or Alcohol‐Related Neuro‐developmental Disorder (ARND) might be at hand: timing, amount and patterns of alcohol exposure, as well as complex epigenetic responses. The genetic background of the offspring and its interaction with other prenatal and postnatal environmental cues are likely also of importance. In the present report, key findings about the possible effects of low and moderate doses of maternal alcohol intake on the neuropsychological development of the offspring are reviewed and plausible mechanisms discussed. Special focus is put on the serotonergic system within developmental and gene‐environment frameworks. The review also suggests guidelines for future studies, as well as summarises some of to be‐answered questions of relevance to clinical practice. Contradictory findings and paucity of studies on the effects of exposure to low alcohol levels during foetal life for the offspring's neuropsychological development call for large prospective studies, as well as for studies including neuroimaging and multi‐omics analyses to dissect the neurobiological underpinnings of alcohol exposure‐related phenotypes and to identify biomarkers. Finally, it remains to be investigated whether any safe threshold of alcohol drinking during pregnancy can be identified. This article is protected by copyright. All rights reserved.
    May 04, 2017   doi: 10.1111/apha.12892   open full text
  • Extracellular acidosis and very low [Na+] inhibit NBCn1‐ and NHE1‐mediated net acid extrusion from mouse vascular smooth muscle cells.
    L. Bonde, E. Boedtkjer.
    Acta Physiologica. April 25, 2017
    Aim The electroneutral Na+, HCO3− cotransporter NBCn1 and Na+/H+ exchanger NHE1 regulate acid–base balance in vascular smooth muscle cells (VSMCs) and modify artery function and structure. Pathological conditions – notably ischaemia – can dramatically perturb intracellular (i) and extracellular (o) pH and [Na+]. We examined effects of low [Na+]o and pHo on NBCn1 and NHE1 activity in VSMCs of small arteries. Methods We measured pHi by 2′,7′‐bis‐(2‐carboxyethyl)‐5‐(and‐6)‐carboxyfluorescein‐based fluorescence microscopy of mouse mesenteric arteries and induced intracellular acidification by NH4+ prepulse technique. Results NBCn1 activity – defined as Na+‐dependent, amiloride‐insensitive net base uptake with CO2/HCO3− present – was inhibited equally when pHo decreased from 7.4 (22 mm HCO3−/5% CO2) by metabolic (pHo 7.1/11 mm HCO3−: 22 ± 8%; pHo 6.8/5.5 mm HCO3−: 61 ± 7%) or respiratory (pHo 7.1/10% CO2: 35 ± 11%; pHo 6.8/20% CO2: 56 ± 7%) acidosis. Extracellular acidosis more prominently inhibited NHE1 activity – defined as Na+‐dependent net acid extrusion without CO2/HCO3− present – at both pHo 7.1 (45 ± 9%) and 6.8 (85 ± 5%). Independently of pHo, lowering [Na+]o from 140 to 70 mm reduced NBCn1 and NHE1 activity <20% whereas transport activities declined markedly (25–50%) when [Na+]o was reduced to 35 mm. Steady‐state pHi decreased more during respiratory (ΔpHi/ΔpHo = 71 ± 4%) than metabolic (ΔpHi/ΔpHo = 30 ± 7%) acidosis. Conclusion Extracellular acidification inhibits NBCn1 and NHE1 activity in VSMCs. NBCn1 is equivalently inhibited when pCO2 is raised or [HCO3−]o decreased. Lowering [Na+]o inhibits NBCn1 and NHE1 markedly only below the typical physiological and pathophysiological range. We propose that inhibition of Na+‐dependent net acid extrusion at low pHo protects against cellular Na+ overload at the cost of intracellular acidification.
    April 25, 2017   doi: 10.1111/apha.12877   open full text
  • Alpha adrenergic receptor blockade increases capillarization and fractional O2 extraction and lowers blood flow in contracting human skeletal muscle.
    S. P. Mortensen, S. Egginton, M. Madsen, J. B. Hansen, G. D. W. Munch, U. W. Iepsen, T. Åkerström, B. K. Pedersen, Y. Hellsten.
    Acta Physiologica. April 11, 2017
    Aim To assess the effect of elevated basal shear stress on angiogenesis in humans and the role of enhanced skeletal muscle capillarization on blood flow and O2 extraction. Methods Limb haemodynamics and O2 extraction were measured at rest and during one‐leg knee‐extensor exercise (12 and 24 W) in 10 healthy untrained young men before and after 4‐week treatment with an α1 receptor‐antagonist (Terazosin, 1–2 mg day−1). Corresponding biopsies were taken from the m. vastus lateralis. Results Resting leg blood flow was increased by 57% 6 h following Terazosin treatment (P < 0.05), while basal capillary‐to‐fibre ratio was 1.69 ± 0.08 and increased to 1.90 ± 0.08 after treatment (P < 0.05). Leg O2 extraction during knee‐extensor exercise was higher (4–5%; P < 0.05), leg blood flow and venous lactate levels lower (6–7%; P < 0.05), while leg VO2 was not different after Terazosin treatment. Conclusions These results demonstrate that daily treatment with an α‐adrenergic receptor blocker induces capillary growth in human skeletal muscle, likely due to increased shear stress. The increase in capillarization resulted in an increased fractional O2 extraction, a lower blood flow and venous lactate levels in the exercising leg. The increase in capillarization, and concomitant functional readouts in the exercising leg, may provide a basis for novel angiotherapy.
    April 11, 2017   doi: 10.1111/apha.12857   open full text
  • Release of calcium into the myofibrillar space in response to active shortening of striated muscle.
    K. A. P. Edman, C. Caputo.
    Acta Physiologica. April 11, 2017
    Aim The study was undertaken to explore whether shortening of striated muscle during activity is associated with release of bound Ca2+ into the myofibrillar space as has previously been proposed in order to explain the depressant effect of active shortening. Methods The experiments were carried out on single muscle fibres isolated from the anterior tibialis muscle of Rana temporaria. The fibres were loaded with the calcium sensitive indicator Fluo‐3. The fibres, stimulated to produce a partially fused isometric tetanus, were subjected to a shortening ramp or, alternatively, to a stretch ramp during activity while force, fibre length, sarcomere length and the Fluo‐3 signal were recorded. Results A shortening ramp performed during a partially fused tetanus caused an increase in the myofibrillar free calcium concentration and produced, simultaneously, a decrease in active force. The isometric force recovered gradually after the shortening ramp, while the intracellular Ca2+ concentration stayed above the control level during the remainder of the stimulation period. A stretch ramp applied during a partially fused tetanus caused a considerably smaller change in the myofibrillar Ca2+ concentration. Conclusion The results provide evidence that the myosin cross‐bridges interact with the calcium binding sites on the thin filaments during active shortening, causing sustained release of calcium and reduced contractile strength.
    April 11, 2017   doi: 10.1111/apha.12876   open full text
  • Weak by the Machines: Muscle Motor Protein Dysfunction ‐NDASH‐ a side Effect of Intensive Care Unit Treatment.
    O Friedrich, S Diermeier, L Larsson.
    Acta Physiologica. April 07, 2017
    Intensive care interventions involve periods of mechanical ventilation, sedation and complete mechanical silencing of patients. Critical illness myopathy (CIM) is an ICU‐acquired myopathy that is associated with limb muscle weakness, muscle atrophy, electrical silencing of muscle and motor‐proteinopathy. The hallmark of CIM is a preferential muscle myosin loss due to increased catabolic and reduced anabolic activity. The ubiquitin‐proteasome pathway plays an important role, apart from recently identified novel mechanisms affecting nonlysosomal protein degradation or autophagy. CIM is not reproduced by pure disuse atrophy, denervation atrophy, steroid‐induced atrophy or septic myopathy, although combinations of high‐dose steroids and denervation can mimic CIM. Novel animal models of critical illness and ICU‐treatment (i.e. mechanical ventilation and complete immobilization) provide novel insights regarding the time course of protein synthesis and degradation alterations, and the role of protective chaperone activities in the process of myosin loss. Altered mechano‐signaling seems involved in triggering a major part of myosin loss in experimental CIM models and passive loading of muscle potently ameliorates the CIM phenotype. We provide a systematic overview of similarities and distinct differences in the signaling pathways involved in triggering muscle atrophy in CIM and isolated trigger factors. Since preferential myosin loss is mostly determined from biochemistry analyses providing no spatial resolution of myosin loss processes within myofibres, we also provide first results monitoring myosin signal intensities during experimental ICU‐intervention using multiphoton Second harmonic Generation microscopy. Our results confirm that myosin loss is an evenly distributed process within myofibres rather than being confined to hot spots. This article is protected by copyright. All rights reserved.
    April 07, 2017   doi: 10.1111/apha.12885   open full text
  • Calcium‐dependent Nedd4‐2 upregulation mediates degradation of the cardiac sodium channel Nav1.5: implications for heart failure.
    L. Luo, F. Ning, Y. Du, B. Song, D. Yang, S. C. Salvage, Y. Wang, J. A. Fraser, S. Zhang, A. Ma, T. Wang.
    Acta Physiologica. April 06, 2017
    Aim Reductions in voltage‐gated sodium channel (Nav1.5) function/expression provide a slowed‐conduction substrate for cardiac arrhythmias. Nedd4‐2, which is activated by calcium, post‐translationally modulates Nav1.5. We aim to investigate whether elevated intracellular calcium ([Ca2+]i) reduces Nav1.5 through Nedd4‐2 and its role in heart failure (HF). Methods Using a combination of biochemical, electrophysiological, cellular and in vivo methods, we tested the effect and mechanism of calcium on Nedd4‐2 and in turn Nav1.5. Results Increased [Ca2+]i, following 24‐h ionomycin treatment, decreased sodium current (INa) density and Nav1.5 protein without altering its mRNA in both neonatal rat cardiomyocytes (NRCMs) and HEK 293 cells stably expressing Nav1.5. The calcium chelator BAPTA‐AM restored the reduced Nav1.5 and INa in NRCMs pre‐treated by ionomycin. Nav1.5 was decreased by Nedd4‐2 transfection and further decreased by 6‐h ionomycin treatment. These effects were not observed in cells transfected with the catalytically inactive mutant, Nedd4‐2 C801S, or with Y1977A‐Nav1.5 mutant containing the impaired Nedd4‐2 binding motif. Furthermore, elevated [Ca2+]i increased Nedd4‐2, the interaction between Nedd4‐2 and Nav1.5, and Nav1.5 ubiquitination. Nav1.5 protein is decreased, whereas Nedd4‐2 is increased in volume‐overload HF rat hearts, with increased co‐localization of Nav1.5 with ubiquitin or Nedd4‐2 as indicated by immunofluorescence staining. BAPTA‐AM rescued the reduced Nav1.5 protein, INa and increased Nedd4‐2 in hypertrophied NRCMs induced by isoproterenol or angiotensin II. Conclusion Calcium‐mediated increases in Nedd4‐2 downregulate Nav1.5 by ubiquitination. Nav1.5 is downregulated and co‐localizes with Nedd4‐2 and ubiquitin in failing rat heart. These data suggest a role of Nedd4‐2 in Nav1.5 downregulation in HF.
    April 06, 2017   doi: 10.1111/apha.12872   open full text
  • The role of neuropeptide W in energy homeostasis.
    Hui Li, Stephen J Kentish, Gary A Wittert, Amanda J Page.
    Acta Physiologica. April 04, 2017
    Neuropeptide W is the endogenous ligand for G‐protein‐coupled receptors GPR7 and GPR8. In this review, we summarize findings on the distribution of neuropeptide W and its receptors in the central nervous system and the periphery, and discuss the role of NPW in food intake and energy homeostasis. This article is protected by copyright. All rights reserved.
    April 04, 2017   doi: 10.1111/apha.12884   open full text
  • Transcriptional regulation of voltage‐gated Ca2+ channels.
    Ricardo González‐Ramírez, Ricardo Felix.
    Acta Physiologica. March 31, 2017
    The transcriptional regulation of voltage‐gated Ca2+ (CaV) channels is an emerging research area that promises to improve our understanding of how many relevant physiological events are shaped in the central nervous system, the skeletal muscle, and other tissues. Interestingly, a picture of how transcription of CaV channel subunit genes is controlled is evolving with the identification of the promoter regions required for tissue‐specific expression, and the identification of transcription factors that control their expression. These promoters share several characteristics that include multiple transcriptional start sites, lack of a TATA box, and the presence of elements conferring tissue‐selective expression. Likewise, changes in CaV channel expression occur throughout development, following ischemia, seizures, or chronic drug administration. This review focuses on insights achieved regarding the control of CaV channel gene expression. To further understand the complexities of expression and to increase the possibilities of detecting CaV channel alterations causing human disease, a deeper knowledge on the structure of the 5’ upstream regions of the genes encoding these remarkable proteins will be necessary. This article is protected by copyright. All rights reserved.
    March 31, 2017   doi: 10.1111/apha.12883   open full text
  • Role of renal vascular potassium channels in physiology and pathophysiology.
    Max Salomonsson, Jens Christian Brasen, Charlotte M. Sorensen.
    Acta Physiologica. March 30, 2017
    The control of renal vascular tone is important for the regulation of salt and water balance, blood pressure and the protection against damaging elevated glomerular pressure. The K+ conductance is a major factor in the regulation of the membrane potential (Vm) in vascular smooth muscle (VSMC) and endothelial cells (EC). The vascular tone is controlled by Vm via its effect on the opening probability of voltage operated Ca2+channels (VOCC) in VSMC. When K+ conductance increases Vm becomes more negative and vasodilation follows, while deactivation of K+ channels leads to depolarization and vasoconstriction. K+ channels in EC indirectly participate in the control of vascular tone by endothelium derived vasodilation. Therefore, by regulating the tone of renal resistance vessels, K+ channels have a potential role in the control of fluid homeostasis and blood pressure as well as in the protection of the renal parenchyma. The main classes of K+ channels (calcium activated (KCa), inward rectifier (Kir), voltage activated (Kv) and ATP sensitive (KATP)) have been found in the renal vessels. In this review, we summarize results available in the literature and our own studies in the field. We compare the ambiguous in vitro and in vivo results. We discuss the role of single types of K+ channels and the integrated function of several classes. We also deal with the possible role of renal vascular K+ channels in the pathophysiology of hypertension, diabetes mellitus and sepsis. This article is protected by copyright. All rights reserved.
    March 30, 2017   doi: 10.1111/apha.12882   open full text
  • Exercise and epigenetic inheritance of disease risk.
    Joshua Denham.
    Acta Physiologica. March 30, 2017
    Epigenetics is the study of gene expression changes that occur in the absence of altered genotype. Current evidence indicates a role for environmentally induced alterations to epigenetic modifications leading to health and diseases changes across multiple generations. This phenomenon is called intergenerational or transgenerational epigenetic inheritance of health or disease. Environmental insults, in the form of toxins, plastics and particular dietary interventions, perturb the epigenetic landscape and influence the health of F1 through to F4 generations in rodents. There is, however, the possibility that healthy lifestyles and environmental factors, such as exercise training, could lead to favourable, heritable epigenetic modifications that augment transcriptional programs protective of disease, including metabolic dysfunction, heart disease and cancer. The health benefits conferred by regular physical exercise training are unquestionable, yet many of the molecular changes may have heritable health implications for future generations. Similar to other environmental factors, exercise modulates the epigenome of somatic cells and researchers are beginning to study exercise epigenetics in germ cells. The germ cell epigenetic modifications affected by exercise offer a molecular mechanism for the inheritance of health and disease risk. The aims of this review are to: 1) provide an update on the expanding field of exercise epigenetics; 2) offer an overview of data on intergenerational/transgenerational epigenetic inheritance of disease by environmental insults; 3) to discuss the potential of exercise‐induced intergenerational inheritance of health and disease risk; and finally, outline potential mechanisms and avenues for future work on epigenetic inheritance through exercise. This article is protected by copyright. All rights reserved.
    March 30, 2017   doi: 10.1111/apha.12881   open full text
  • Vagal nerve stimulation reduces infarct size via a mechanism involving the alpha‐7 nicotinic acetylcholine receptor and downregulation of cardiac and vascular arginase.
    A. Kiss, Y. Tratsiakovich, A. Mahdi, J. Yang, A. T. Gonon, B. K. Podesser, J. Pernow.
    Acta Physiologica. March 24, 2017
    Aims Vagal nerve stimulation (VNS) protects from myocardial and vascular injury following myocardial ischaemia and reperfusion (IR) via a mechanism involving activation of alpha‐7 nicotinic acetylcholine receptor (α7 nAChR) and reduced inflammation. Arginase is involved in development of myocardial IR injury driven by inflammatory mediators. The aim of the study was to clarify whether VNS downregulates myocardial and vascular arginase via a mechanism involving activation of α7 nAChR following myocardial IR. Methods Anaesthetized rats were randomized to (i) sham‐operated, (ii) control IR (30‐min ischaemia and 2‐h reperfusion, (iii) VNS throughout IR, (iv) the arginase inhibitor nor‐NOHA+IR, (v) nor‐NOHA+VNS+IR, (vi) selective α7 nAChR blockade by methyllycaconitine (MLA) followed by VNS throughout IR and (vii) MLA+IR. Results Infarct size was reduced by VNS compared to control IR (41 ± 3% vs. 67 ± 2% of the myocardium at risk, P < 0.001). Myocardial IR increased myocardial and aortic arginase activity 1.7‐ and 3.1‐fold respectively (P < 0.05). VNS attenuated the increase in arginase activity compared to control IR both in the myocardium and aorta (P < 0.05). MLA partially abolished the cardioprotective effect of VNS and completely abrogated the effect of VNS on arginase activity. Arginase inhibition combined with VNS did not further reduce infarct size. Conclusion Vagal nerve stimulation reduced infarct size and reversed the upregulation of arginase induced by IR both in the myocardium and aorta via a mechanism depending on α7 nAChR activation. The data suggest that the cardioprotective effect of VNS is mediated via reduction in arginase activity.
    March 24, 2017   doi: 10.1111/apha.12861   open full text
  • Hypoxia‐stimulated membrane trafficking requires T‐plastin.
    M. Wottawa, S. Naas, J. Böttger, G. J. van Belle, W. Möbius, N. H. Revelo, D. Heidenreich, M. von Ahlen, A. Zieseniss, K. Kröhnert, S. Lutz, C. Lenz, H. Urlaub, S. O. Rizzoli, D. M. Katschinski.
    Acta Physiologica. March 23, 2017
    Aim Traffic between the plasma membrane and the endomembrane compartments is an essential feature of eukaryotic cells. The secretory pathway sends cargoes from biosynthetic compartments to the plasma membrane. This is counterbalanced by a retrograde endocytic route and is essential for cell homoeostasis. Cells need to adapt rapidly to environmental challenges such as the reduction of pO2 which, however, has not been analysed in relation to membrane trafficking in detail. Therefore, we determined changes in the plasma membrane trafficking in normoxia, hypoxia, and after reoxygenation. Methods Membrane trafficking was analysed by using the bulk membrane endocytosis marker FM 1‐43, the newly developed membrane probe mCLING, wheat germ agglutinin as well as fluorescently labelled cholera toxin subunit B. Additionally, the uptake of specific membrane proteins was determined. In parallel, a non‐biased SILAC screen was performed to analyse the abundance of membrane proteins in normoxia and hypoxia. Results Membrane trafficking was increased in hypoxia and quickly reversed upon reoxygenation. This effect was independent of the hypoxia‐inducible factor (HIF) system. Using SILAC technology, we identified that the actin‐bundling protein T‐plastin is recruited to the plasma membrane in hypoxia. By the use of T‐plastin knockdown cells, we could show that T‐plastin mediates the hypoxia‐induced membrane trafficking, which was associated with an increased actin density in the cells as determined by electron microscopy. Conclusion Membrane trafficking is highly dynamic upon hypoxia. This phenotype is quickly reversible upon reoxygenation, which suggests that this mechanism participates in the cellular adaptation to hypoxia.
    March 23, 2017   doi: 10.1111/apha.12859   open full text
  • Muscle oxygen saturation increases during head‐up tilt‐induced (pre)syncope.
    A. Lund, H. Sørensen, T. W. Jensen, M. J. Niemann, N. D. Olesen, H. B. Nielsen, N. V. Olsen, N. H. Secher.
    Acta Physiologica. March 22, 2017
    Aim To evaluate whether muscle vasodilatation plays a role for hypotension developed during central hypovolaemia, muscle oxygenation (SmO2) was examined during (pre)syncope induced by head‐up tilt (HUT). Skin blood flow (SkBF) and oxygenation (SskinO2) were determined because evaluation of SmO2 may be affected by superficial tissue oxygenation. Furthermore, we evaluated cerebral oxygenation (ScO2) and middle cerebral artery mean blood flow velocity (MCAvmean). Methods Twenty healthy male volunteers (median age 24 years; range 19–38) were subjected to passive 50° HUT for 1 h or until (pre)syncope. ScO2 and SmO2 (near‐infrared spectroscopy), MCAvmean (transcranial Doppler) along with mean arterial pressure (MAP), heart rate (HR), stroke volume (SV), cardiac output (CO) and total peripheral resistance (TPR) (Modelflow®) were determined. Results (Pre)syncopal symptoms appeared in 17 subjects after 11 min (median; range 2–34) accompanied by a decrease in MAP, SV, CO and TPR, while HR remained elevated. During (pre)syncope, ScO2 decreased [73% (71–76; mean and 95% CI) to 68% (65–71), P < 0.0001] along with MCAvmean [40 (37–43) to 32 (29–35) cm s−1, P < 0.0001]. In contrast, SmO2 increased [63 (56–69)% to 71% (65–78), P < 0.0001], while SskinO2 [64% (58–69) to 53% (47–58), P < 0.0001] and SkBF [71 (44–98) compared to a baseline of 99 (72–125) units, P = 0.020] were reduced. Conclusion We confirm that the decrease in MAP during HUT is associated with a reduction in indices of cerebral perfusion. (Pre)syncope was associated with an increase in SmO2 despite reduced SskinO2 and SkBF, supporting that muscle vasodilation plays an important role in the circulatory events leading to hypotension during HUT.
    March 22, 2017   doi: 10.1111/apha.12863   open full text
  • Chronically elevated bilirubin protects from cardiac reperfusion injury in the male Gunn rat.
    B. Bakrania, E. F. Du Toit, K. J. Ashton, K‐H. Wagner, J. P. Headrick, A. C. Bulmer.
    Acta Physiologica. March 14, 2017
    Aims Bilirubin is associated with reduced risk of cardiovascular disease, as evidenced in conditions of mild hyperbilirubinaemia (Gilbert's Syndrome). Little is known regarding myocardial stress resistance in hyperbilirubinaemic conditions or whether life‐long exposure modifies cardiac function, which might contribute to protection from cardiovascular disease. Methods Hyperbilirubinaemic rats and littermate controls underwent echocardiography at 3, 6 and 12 months of age, with hearts subsequently assessed for resistance to 30 min of ischaemia. Heart tissue was then collected for assessment of bilirubin content. Results No difference in baseline cardiac function was evident until 6 months onwards, where Gunn rats demonstrated aortic dilatation and reduced peak ejection velocities. Additionally, duration of ventricular ejection increased progressively, indicating a negative inotropic effect of bilirubin in vivo. Ex vivo analysis of baseline function revealed reduced left ventricular pressure development (LVDP) and contractility in hyperbilirubinaemic rats. Furthermore, stress resistance was improved in Gunn hearts: post‐ischaemic recoveries of LVDP (76 ± 22% vs. 29 ± 17% Control, P < 0.01) and coronary flow (96 ± 9% vs. 86 ± 16% Control, P < 0.01) were improved in Gunn hearts, accompanied by reduced infarct area (21 ± 5% vs. 47 ± 15% Control, P < 0.01), and ventricular malondialdehyde and protein carbonyl content. Expression of myocardial nitric oxide‐regulating genes including Nos1 and Noa1 were not significantly different. Conclusions These data reveal life‐long hyperbilirubinaemia induces age‐dependent hypocontractility in male Gunn rats, and improved stress resistance. In addition, bilirubin exerts sex‐independent effects on vascular structure, myocardial function and ischaemic tolerance, the latter likely mediated via bilirubin's antioxidant properties.
    March 14, 2017   doi: 10.1111/apha.12858   open full text
  • Mind the gap: mechanisms regulating the endothelial barrier.
    Mariya Y. Radeva, Jens Waschke.
    Acta Physiologica. February 23, 2017
    The endothelial barrier consists of intercellular contacts localized in the cleft between endothelial cells, which is covered by the glycocalyx in a sieve‐like manner. Both types of barrier‐forming junctions, i.e. the adherens junction (AJ) serving mechanical anchorage and mechanotransduction and the tight junction (TJ) sealing the intercellular space to limit paracelullar permeability, are tethered to the actin cytoskeleton. Under resting conditions, the endothelium thereby builds a selective layer controlling the exchange of fluid and solutes with the surrounding tissue. However, in the situation of an inflammatory response such as in anaphylaxis or sepsis intercellular contacts disintegrate in postcapillary venules leading to intercellular gap formation. The resulting edema can cause shock and multi‐organ failure. Therefore, maintenance as well as coordinated opening and closure of interendothelial junctions is tightly regulated. The two principle underlying mechanisms comprise spatiotemporal activity control of the small GTPases Rac1 and RhoA and the balance of the phosphorylation state of AJ proteins. In the resting state, junctional Rac1 and RhoA activity is enhanced by junctional components, actin‐binding proteins (ABPs), cAMP signaling and extracellular cues such as sphingosine‐1‐phosphate (S1P) and angiopoitin‐1 (Ang‐1). In addition, phosphorylation of AJ components is prevented by junction‐associated phosphatases including vascular endothelial protein tyrosine phosphatase (VE‐PTP). In contrast, inflammatory mediators inhibiting cAMP/Rac1 signaling cause strong activation of RhoA and induce AJ phosphorylation finally leading to endocytosis and cleavage of VE‐cadherin. This results in dissolution of TJs the outcome of which is endothelial barrier breakdown. This article is protected by copyright. All rights reserved.
    February 23, 2017   doi: 10.1111/apha.12860   open full text
  • The water channel AQP1 is expressed in human atherosclerotic vascular lesions and AQP1 deficiency augments angiotensin II‐induced atherosclerosis in mice.
    P. Wintmo, S. H. Johansen, P. B. L. Hansen, J. S. Lindholt, S. Urbonavicius, L. M. Rasmussen, P. Bie, B. L. Jensen, J. Stubbe.
    Acta Physiologica. February 22, 2017
    Aim The water channel aquaporin 1 (AQP1) promotes endothelial cell migration. It was hypothesized that AQP1 promotes neovascularization and growth of atherosclerotic plaques. Methods AQP1 immunoreactivity and protein abundance was examined in human and murine atherosclerotic lesions and aortic aneurysms. Apolipoprotein E (ApoE) knockout (−/−) and AQP1−/−ApoE−/− mice were developed and fed Western diet (WD) for 8 and 16 weeks to accelerate the atherosclerosis process. In ApoE−/− and AQP1−/−ApoE−/− mice abdominal aortic aneurysms (AAA) were induced by angiotensin II (ANGII) infusion by osmotic minipumps for 4 weeks. Results In human atherosclerotic lesions and AAA, AQP1 immunoreactive protein was associated with intralesional small vessels. In ApoE−/− mouse aorta, APQ1 mRNA levels were increased with time on WD (n = 7–9, P < 0.003). Both in murine lesions at the aortic root and in the abdominal aortic aneurysmal wall, AQP1 immunoreactivity was associated with microvascular structures. The atherosclerotic lesion burden was enhanced significantly in ANGII‐infused AQP1−/−ApoE−/− mice compared with ApoE−/− mice, but neither incidence nor progression of AAA was different. The aortic lesion burden increased with time on WD but was not different between ApoE−/− and AQP1−/−ApoE−/− mice at either 8 or 16 weeks (n = 13–15). Baseline blood pressure and ANGII‐induced hypertension were not different between genotypes. Conclusion AQP1 is expressed in atherosclerotic lesion neovasculature in human and mouse arteries and AQP1 deficiency augments lesion development in ANGII‐promoted atherosclerosis in mice. Normal function of AQP1 affords cardiovascular protection.
    February 22, 2017   doi: 10.1111/apha.12853   open full text
  • Maternal–fetal cholesterol transport in the second half of mouse pregnancy does not involve LDL receptor‐related protein 2.
    M. V. Zwier, M. E. Baardman, T. H. Dijk, A. Jurdzinski, L. J. Wisse, V. W. Bloks, R. M. F. Berger, M. C. DeRuiter, A. K. Groen, T. Plösch.
    Acta Physiologica. February 22, 2017
    Aim LDL receptor‐related protein type 2 (LRP2) is highly expressed on both yolk sac and placenta. Mutations in the corresponding gene are associated with severe birth defects in humans, known as Donnai–Barrow syndrome. We here characterized the contribution of LRP2 and maternal plasma cholesterol availability to maternal–fetal cholesterol transport and fetal cholesterol levels in utero in mice. Methods Lrp2+/− mice were mated heterozygously to yield fetuses of all three genotypes. Half of the dams received a 0.5% probucol‐enriched diet during gestation to decrease maternal HDL cholesterol. At E13.5, the dams received an injection of D7‐labelled cholesterol and were provided with 1‐13C acetate‐supplemented drinking water. At E16.5, fetal tissues were collected and maternal cholesterol transport and fetal synthesis quantified by isotope enrichments in fetal tissues by GC‐MS. Results The Lrp2 genotype did not influence maternal–fetal cholesterol transport and fetal cholesterol. However, lowering of maternal plasma cholesterol levels by probucol significantly reduced maternal–fetal cholesterol transport. In the fetal liver, this was associated with increased cholesterol synthesis rates. No indications were found for an interaction between the Lrp2 genotype and maternal probucol treatment. Conclusion Maternal–fetal cholesterol transport and endogenous fetal cholesterol synthesis depend on maternal cholesterol concentrations but do not involve LRP2 in the second half of murine pregnancy. Our results suggest that the mouse fetus can compensate for decreased maternal cholesterol levels. It remains a relevant question how the delicate system of cholesterol transport and synthesis is regulated in the human fetus and placenta.
    February 22, 2017   doi: 10.1111/apha.12845   open full text
  • Repeated maximal‐intensity hypoxic exercise superimposed to hypoxic residence boosts skeletal muscle transcriptional responses in elite team‐sport athletes.
    F. Brocherie, G. P. Millet, G. D'Hulst, R. Van Thienen, L. Deldicque, O. Girard.
    Acta Physiologica. February 22, 2017
    Aim To determine whether repeated maximal‐intensity hypoxic exercise induces larger beneficial adaptations on the hypoxia‐inducible factor‐1α pathway and its target genes than similar normoxic exercise, when combined with chronic hypoxic exposure. Methods Lowland elite male team‐sport athletes underwent 14 days of passive normobaric hypoxic exposure [≥14 h·day−1 at inspired oxygen fraction (FiO2) 14.5–14.2%] with the addition of six maximal‐intensity exercise sessions either in normobaric hypoxia (FiO2 ~14.2%; LHTLH; n = 9) or in normoxia (FiO2 20.9%; LHTL; n = 11). A group living in normoxia with no additional maximal‐intensity exercise (LLTL; n = 10) served as control. Before (Pre), immediately after (Post‐1) and 3 weeks after (Post‐2) the intervention, muscle biopsies were obtained from the vastus lateralis. Results Hypoxia‐inducible factor‐1α subunit, vascular endothelial growth factor, myoglobin, peroxisome proliferator‐activated receptor‐gamma coactivator 1‐α and mitochondrial transcription factor A mRNA levels increased at Post‐1 (all P ≤ 0.05) in LHTLH, but not in LHTL or LLTL, and returned near baseline levels at Post‐2. The protein expression of citrate synthase increased in LHTLH (P < 0.001 and P < 0.01 at Post‐1 and Post‐2, respectively) and LLTL (P < 0.01 and P < 0.05 at Post‐1 and Post‐2, respectively), whereas it decreased in LHTL at Post‐1 and Post‐2 (both P < 0.001). Conclusion Combined with residence in normobaric hypoxia, repeated maximal‐intensity hypoxic exercise induces short‐term post‐intervention beneficial changes in muscle transcriptional factors that are of larger magnitude (or not observed) than with similar normoxic exercise. The decay of molecular adaptations was relatively fast, with most of benefits already absent 3 weeks post‐intervention.
    February 22, 2017   doi: 10.1111/apha.12851   open full text
  • The innervation of the kidney in renal injury and inflammation: A cause and consequence of deranged cardiovascular control.
    Mohammed H Abdulla, Edward J Johns.
    Acta Physiologica. February 09, 2017
    Extensive investigations have revealed that renal sympathetic nerves regulate renin secretion, tubular fluid reabsorption and renal haemodynamics which can impact on cardiovascular homoeostasis normally and in pathophysiological states. The significance of the renal afferent innervation and its role in determining the autonomic control of the cardiovascular system is uncertain. The transduction pathways at the renal afferent nerves have been shown to require pro‐inflammatory mediators and TRPV1 channels. Reno‐renal reflexes have been described, both inhibitory and excitatory, demonstrating that a neural link exists between kidneys and may determine the distribution of excretory and haemodynamic function between the two kidneys. The impact of renal afferent nerve activity on basal and reflex regulation of global sympathetic drive remains opaque. There is clinical and experimental evidence that in states of chronic kidney disease and renal injury there is infiltration of T‐helper cells with a sympatho‐excitation and blunting of the high and low pressure baroreceptor reflexes regulating renal sympathetic nerve activity. The baroreceptor deficits are renal nerve‐dependent as the dysregulation can be relieved by renal denervation. There is also experimental evidence that in obese states there is a sympatho‐excitation and disrupted baroreflex regulation of renal sympathetic nerve activity which is mediated by the renal innervation. This body of information provides an important basis for directing greater attention to the role of renal injury/inflammation causing an inappropriate activation of the renal afferent nerves as an important initiator of aberrant autonomic cardiovascular control. This article is protected by copyright. All rights reserved.
    February 09, 2017   doi: 10.1111/apha.12856   open full text
  • Targeting multiple pathways reduces renal and cardiac fibrosis in rats with subtotal nephrectomy followed by coronary ligation.
    N. R. Oosterhuis, L. G. Bongartz, M. C. Verhaar, C. Cheng, Y. J. Xu, A. Koppen, M. J. Cramer, R. Goldschmeding, C. A. Gaillard, P. A. Doevendans, B. Braam, J. A. Joles.
    Acta Physiologica. February 07, 2017
    Aim Multiple interacting pathways contribute to progression of renal and cardiac damage in chronic kidney disease followed by chronic heart failure (renocardiac syndrome). We hypothesized that simultaneous pharmacological modulation of critical pathways implicated in renocardiac syndrome would effectively reduce fibrosis in and preserve function of heart and kidney. Methods Rats were subjected to subtotal nephrectomy followed 9 weeks later by coronary artery ligation. From week 11 until week 16, rats received vehicle or losartan, or a combination of the NF‐kB inhibitor PDTC, the NO donor molsidomine and superoxide dismutase mimetic tempol, or a combination of all four of these plus metoprolol together. At week 16, renal and cardiac structure, function and gene expression were assessed. Results Individual and combined treatments were similarly effective in limiting cardiac fibrosis and further decline in systolic function. Combined treatment with all five drugs reduced renal fibrosis and CTGF gene expression more effectively than other strategies. Combining all five drugs reduced heart rate, inotropy and mean arterial pressure (MAP). Conclusion Thus, in our model of chronic renocardiac syndrome, combined treatments similarly decreased cardiac fibrosis and stabilized systolic function as losartan alone, perhaps suggesting a dominant role for a single factor such as angiotensin II type 1 (AT1) receptor activation or inflammation in the network of aberrant systems in the heart. However, tubulointerstitial fibrosis was most effectively reduced by a five‐drug regimen, pointing to additive effects of multiple pathophysiological pathways in the kidney.
    February 07, 2017   doi: 10.1111/apha.12829   open full text
  • Enhanced contractility of intraparenchymal arterioles after global cerebral ischaemia in rat – new insights into the development of delayed cerebral hypoperfusion.
    S. Spray, S. E. Johansson, A. Radziwon‐Balicka, K. A. Haanes, K. Warfvinge, G. K. Povlsen, P. A. T. Kelly, L. Edvinsson.
    Acta Physiologica. January 29, 2017
    Aim Delayed cerebral hypoperfusion is a secondary complication found in the days after transient global cerebral ischaemia that worsens the ischaemic damage inflicted by the initial transient episode of global cerebral ischaemia. A recent study demonstrated increased cerebral vasoconstriction in the large arteries on the brain surface (pial arteries) after global cerebral ischaemia. However, smaller arterioles inside the brain (parenchymal arterioles) are equally important in the regulation of cerebral blood flow and yet their pathophysiology after global cerebral ischaemia is largely unknown. Therefore, we investigated whether increased contractility occurs in the intraparenchymal arterioles. Methods Global cerebral ischaemia was induced in male Wistar rats by bilateral common carotid occlusion for 15 min combined with hypovolaemia. Regional cerebral blood flow was determined by quantitative autoradiography. Intraparenchymal arterioles were isolated and pressurized, and concentration–response curves to endothelin‐1 with and without the endothelin B receptor‐selective antagonist BQ788 was generated. Endothelin B receptor expression was investigated by quantitative flow cytometry and immunohistochemistry. Results We observed increased endothelin‐1‐mediated contractility of parenchymal arterioles correlating with reduced cerebral blood flow of the cortex, hippocampus and caudate nucleus 48 h after global cerebral ischaemia. The increased endothelin‐1‐mediated contractility was abolished by BQ788, and the vascular smooth muscle cell‐specific expression of endothelin B receptors was significantly increased after global cerebral ischaemia. Conclusion Increased endothelin‐1‐mediated contractility and expression of endothelin B receptors in the intraparenchymal vasculature contributes to the development of delayed cerebral hypoperfusion after global cerebral ischaemia in combination with vascular changes of the pial vasculature.
    January 29, 2017   doi: 10.1111/apha.12834   open full text
  • The effect of physical fatigue on oscillatory dynamics of the sensorimotor cortex.
    A. Fry, K. J. Mullinger, G. C. O'Neill, M. J. Brookes, J. P. Folland.
    Acta Physiologica. January 29, 2017
    Aim While physical fatigue is known to arise in part from supraspinal mechanisms within the brain, exactly how brain activity is modulated during fatigue is not well understood. Therefore, this study examined how typical neural oscillatory responses to voluntary muscle contractions were affected by fatigue. Methods Eleven healthy adults (age 27 ± 4 years) completed two experimental sessions in a randomized crossover design. Both sessions first assessed baseline maximal voluntary isometric wrist‐flexion force (MVFb). Participants then performed an identical series of fourteen test contractions (2 × 100%MVFb, 10 × 40%MVFb, 2 × 100%MVFb) both before and after one of two interventions: forty 12‐s contractions at 55%MVFb (fatigue intervention) or 5%MVFb (control intervention). Magnetoencephalography (MEG) was used to characterize both the movement‐related mu and beta decrease (MRMD and MRBD) and the post‐movement beta rebound (PMBR) within the contralateral sensorimotor cortex during the 40%MVFb test contractions, while the 100%MVFb test contractions were used to monitor physical fatigue. Results The fatigue intervention induced a substantial physical fatigue that endured throughout the post‐intervention measurements (28.9–29.5% decrease in MVF, P < 0.001). Fatigue had a significant effect on both PMBR (anova, session × time‐point interaction: P = 0.018) and MRBD (P = 0.021): the magnitude of PMBR increased following the fatigue but not the control interventions, whereas MRBD was decreased post‐control but not post‐fatigue. Mu oscillations were unchanged throughout both sessions. Conclusion Physical fatigue resulted in an increased PMBR, and offset attenuations in MRBD associated with task habituation.
    January 29, 2017   doi: 10.1111/apha.12843   open full text
  • Autophagy in Renal Tubular Injury and Repair.
    Fangming Lin.
    Acta Physiologica. January 23, 2017
    Autophagy is a fundamental cellular process that maintains normal function and structure of the cell. It can be induced during stress and serves as an adaptive response for cell survival. Normal kidneys have high metabolic demands yet are relatively hypoxic, especially in the medulla and papilla. Injury or aging aggravates metabolic perturbation and activates autophagy in many types of renal cells. In the kidney, tubular epithelial cells consume the most energy due to active transport mechanisms and therefore are the most susceptible to injuries from hypoxic or low energy states. This brief review will summarize current understandings of the biological function and molecular regulation of epithelial autophagy during tubular injury and repair. This article is protected by copyright. All rights reserved.
    January 23, 2017   doi: 10.1111/apha.12852   open full text
  • A comparison of left and right atrial fibroblasts reveals different collagen production activity and stress‐induced mitogen‐activated protein kinase signalling in rats.
    C.‐C. Chung, Y.‐H. Kao, C.‐J. Yao, Y.‐K. Lin, Y.‐J. Chen.
    Acta Physiologica. January 16, 2017
    Aim Atrial fibrosis plays a pivotal role in the pathophysiology of heart failure (HF). The left atrium (LA) experiences greater fibrosis than the right atrium (RA) during HF. It is not clear whether LA cardiac fibroblasts contain distinctive activities that predispose LA to fibrosis. Methods LA and RA fibrosis were evaluated in healthy and isoproterenol‐induced HF Sprague Dawley rats. Rat LA and RA primary isolated fibroblasts were subjected to proliferation assay, oxidative stress assay, cell migration analysis, collagen measurement, cytokine array and Western blot. Results Healthy rat LA and RA had a similar extent of collagen deposition. HF significantly increased fibrosis to a greater severity in LA than in RA. Compared to isolated RA fibroblasts, the in vitro experiments showed that isolated LA fibroblasts had higher oxidative stress and exhibited higher collagen, transforming growth factor‐β1, connective tissue growth factor production and less vascular endothelial growth factor (VEGF) production, but had similar migration, myofibroblast differentiation and proliferation activities. VEGF significantly increased the collagen production ability of LA fibroblasts, but not RA fibroblasts. LA fibroblasts had more phosphorylated ERK1/2 and P38 expression. ERK inhibitor (PD98059, 50 μmol L−1) significantly attenuated collagen production and increased VEGF production in RA fibroblasts but not in LA fibroblasts. P38 inhibitor (SB203580, 30 μmol L−1) significantly attenuated collagen production in LA fibroblasts but not in RA fibroblasts. P38 inhibitor also significantly increased VEGF production in RA and LA fibroblasts. Conclusions Differences in profibrotic activity between LA and RA fibroblasts may be caused by different responses to mitogen‐activated protein kinase signalling.
    January 16, 2017   doi: 10.1111/apha.12835   open full text
  • Neuromuscular changes and the rapid adaptation following a bout of damaging eccentric exercise.
    S. Goodall, K. Thomas, M. Barwood, K. Keane, J. T. Gonzalez, A. St Clair Gibson, G. Howatson.
    Acta Physiologica. January 05, 2017
    Introduction An initial bout of eccentric exercise is known to protect against muscle damage following a repeated bout of the same exercise; however, the neuromuscular adaptations owing to this phenomenon are unknown. Aim To determine whether neuromuscular disturbances are modulated following a repeated bout of eccentric exercise. Methods Following eccentric exercise performed with the elbow flexors, we measured maximal voluntary force, resting twitch force, muscle soreness, creatine kinase (CK) and voluntary activation (VA) using motor point and motor cortex stimulation at baseline, immediately post‐exercise and at 1, 2, 3, 4 and 7 days post‐exercise on two occasions, separated by 3 weeks. Results Significant muscle damage and fatigue were evident following the first exercise bout; maximal voluntary contraction (MVC) was reduced immediately by 35% and remained depressed at 7 days post‐exercise. Soreness and CK release peaked at 3 and 4 days post‐exercise respectively. Resting twitch force remained significantly reduced at 7 days (−48%), whilst VA measured with motor point and motor cortex stimulation was reduced until 2 and 3 days respectively. A repeated bout effect (RBE) was observed with attenuated soreness and CK release and a quicker recovery of MVC and resting twitch force. A similar decrement in VA was observed following both bouts; however, following the repeated bout there was a significantly smaller reduction in, and a faster recovery of, VA measured using motor cortical stimulation. Conclusion Our data suggest that the RBE may be explained, partly, by a modification in motor corticospinal drive.
    January 05, 2017   doi: 10.1111/apha.12844   open full text
  • Cutaneous exposure to hypoxia does not affect skin perfusion in humans.
    C. Siebenmann, M. E. Keramidas, H. Rundqvist, S. Mijwel, A. S. Cowburn, R. S. Johnson, O. Eiken.
    Acta Physiologica. November 30, 2016
    Aim Experiments have indicated that skin perfusion in mice is sensitive to reductions in environmental O2 availability. Specifically, a reduction in skin‐surface PO2 attenuates transcutaneous O2 diffusion, and hence epidermal O2 supply. In response, epidermal HIF‐1α expression increases and facilitates initial cutaneous vasoconstriction and subsequent nitric oxide‐dependent vasodilation. Here, we investigated whether the same mechanism exists in humans. Methods In a first experiment, eight males rested twice for 8 h in a hypobaric chamber. Once, barometric pressure was reduced by 50%, while systemic oxygenation was preserved by O2‐enriched (42%) breathing gas (HypoxiaSkin), and once barometric pressure and inspired O2 fraction were normal (Control1). In a second experiment, nine males rested for 8 h with both forearms wrapped in plastic bags. O2 was expelled from one bag by nitrogen flushing (AnoxiaSkin), whereas the other bag was flushed with air (Control2). In both experiments, skin blood flux was assessed by laser Doppler on the dorsal forearm, and HIF‐1α expression was determined by immunohistochemical staining in forearm skin biopsies. Results Skin blood flux during HypoxiaSkin and AnoxiaSkin remained similar to the corresponding Control trial (P = 0.67 and P = 0.81). Immunohistochemically stained epidermal HIF‐1α was detected on 8.2 ± 6.1 and 5.3 ± 5.7% of the analysed area during HypoxiaSkin and Control1 (P = 0.30) and on 2.3 ± 1.8 and 2.4 ± 1.8% during AnoxiaSkin and Control2 (P = 0.90) respectively. Conclusion Reductions in skin‐surface PO2 do not affect skin perfusion in humans. The unchanged epidermal HIF‐1α expression suggests that epidermal O2 homoeostasis was not disturbed by HypoxiaSkin/AnoxiaSkin, potentially due to compensatory increases in arterial O2 extraction.
    November 30, 2016   doi: 10.1111/apha.12825   open full text
  • PGC‐1α4 gene expression is suppressed by the IL‐6—MEK—ERK 1/2 MAPK signalling axis and altered by resistance exercise, obesity and muscle injury.
    J. L. Brown, M. E. Rosa‐Caldwell, D. E. Lee, L. A. Brown, R. A. Perry, K. L. Shimkus, T. A. Blackwell, J. D. Fluckey, J. A. Carson, S. Dridi, T. A. Washington, N. P. Greene.
    Acta Physiologica. November 25, 2016
    Aim PGC‐1α4 is a novel regulator of muscle hypertrophy; however, there is limited understanding of the regulation of its expression and role in many (patho)physiological conditions. Therefore, our purpose was to elicit signalling mechanisms regulating gene expression of Pgc1α4 and examine its response to (patho)physiological stimuli associated with altered muscle mass. Methods IL‐6 knockout mice and pharmacological experiments in C2C12 myocytes were used to identify regulation of Pgc1α4 transcription. To examine Pgc1α4 gene expression in (patho)physiological conditions, obese and lean Zucker rats with/without resistance exercise (RE), ageing mice and muscle regeneration from injury were examined. Results In IL‐6 knockout mice, Pgc1α4mRNA was ~sevenfold greater than wild type. In C2C12 cells, Pgc1α4mRNA was suppressed ~70% by IL‐6. Suppression of Pgc1α4 by IL‐6 was prevented by MEK–ERK–MAPK inhibition. RE led to ~260% greater Pgc1α4mRNA content in lean rats. However, obese Zucker rats exhibited ~270% greater Pgc1α4mRNA than lean, sedentary with no further augmentation by RE. No difference was seen in IL‐6mRNA or ERK‐MAPK phosphorylation in Zucker rats. Aged mice demonstrated ~50% lower Pgc1α4mRNA and ~fivefold greater ERK‐MAPK phosphorylation than young despite unchanged Il‐6mRNA. During muscle regeneration, Pgc1α4 content is ~30% and IL‐6mRNA >threefold of uninjured controls 3 days following injury; at 5 days, Pgc1α4 was >twofold greater in injured mice with no difference in IL‐6mRNA. Conclusion Our findings reveal a novel mechanism suppressing Pgc1α4 gene expression via IL‐6–ERK‐MAPK and suggest this signalling axis may inhibit Pgc1α4 in some, but not all, (patho)physiological conditions.
    November 25, 2016   doi: 10.1111/apha.12826   open full text
  • Acute physical exercise and long‐term individual shear rate therapy increase telomerase activity in human peripheral blood mononuclear cells.
    A. Zietzer, E. E. Buschmann, D. Janke, L. Li, M. Brix, H. Meyborg, P. Stawowy, C. Jungk, I. Buschmann, P. Hillmeister.
    Acta Physiologica. November 22, 2016
    Aim Physical activity is a potent way to impede vascular ageing. However, patients who suffer from peripheral artery disease (PAD) are often unable to exercise adequately. For those patients, we have developed individual shear rate therapy (ISRT), which is an adaptation of external counterpulsation and enhances endovascular fluid shear stress to increase collateral growth (arteriogenesis). To evaluate the effects of physical exercise and ISRT on the telomere biology of peripheral blood mononuclear cells (PBMCs), we conducted two clinical trials. Methods In the ISRT‐1 study, we assessed PBMC telomerase activity in 26 young healthy volunteers upon a single (short‐term) ISRT session and a single treadmill running session. In the ISRT‐2 study, we investigated PBMC telomere biology of 14 elderly patients with PAD, who underwent 30 h of (long‐term) ISRT within a 5‐week period. Results We demonstrate that telomerase activity significantly increased from 39.84 Total Product Generated (TPG) Units ± 6.15 to 58.10 TPG ± 10.46 upon a single treadmill running session in healthy volunteers. In the ISRT‐2 trial, PBMC telomerase activity and the mRNA expression of the telomere‐protective factor TRF2 increased from 40.87 TPG ± 4.45 to 60.98 TPG ± 6.83 and 2.10‐fold ± 0.40, respectively, upon long‐term ISRT in elderly patients with PAD. Conclusion In summary, we show that acute exercise and long‐term ISRT positively affect PBMC telomerase activity, which is indicative for an improved regenerative potential of immune cells and vascular tissues. Long‐term ISRT also enhances the gene expression of the telomere‐protective factor TRF2.
    November 22, 2016   doi: 10.1111/apha.12820   open full text
  • Striated muscle activator of Rho signalling (STARS) is reduced in ageing human skeletal muscle and targeted by miR‐628‐5p.
    A. P. Russell, M. A. Wallace, M. Kalanon, E. Zacharewicz, P. A. Della Gatta, A. Garnham, S. Lamon.
    Acta Physiologica. November 18, 2016
    Aim The striated muscle activator of Rho signalling (STARS) is a muscle‐specific actin‐binding protein. The STARS signalling pathway is activated by resistance exercise and is anticipated to play a role in signal mechanotransduction. Animal studies have reported a negative regulation of STARS signalling with age, but such regulation has not been investigated in humans. Methods Ten young (18–30 years) and 10 older (60–75 years) subjects completed an acute bout of resistance exercise. Gene and protein expression of members of the STARS signalling pathway and miRNA expression of a subset of miRNAs, predicted or known to target members of STARS signalling pathway, were measured in muscle biopsies collected pre‐exercise and 2 h post‐exercise. Results For the first time, we report a significant downregulation of the STARS protein in older subjects. However, there was no effect of age on the magnitude of STARS activation in response to an acute bout of exercise. Finally, we established that miR‐628‐5p, a miRNA regulated by age and exercise, binds to the STARS 3’UTR to directly downregulate its transcription. Conclusion This study describes for the first time the resistance exercise‐induced regulation of STARS signalling in skeletal muscle from older humans and identifies a new miRNA involved in the transcriptional control of STARS.
    November 18, 2016   doi: 10.1111/apha.12819   open full text
  • 3,5‐diiodothyronine (3,5‐T2) reduces blood glucose independently of insulin sensitization in obese mice.
    S. Silva Teixeira, C. Filgueira, D. H. Sieglaff, C. Benod, R. Villagomez, L. J. Minze, A. Zhang, P. Webb, M. T. Nunes.
    Acta Physiologica. November 17, 2016
    Aim Thyroid hormones regulate metabolic response. While triiodothyronine (T3) is usually considered to be the active form of thyroid hormone, one form of diiodothyronine (3,5‐T2) exerts T3‐like effects on energy consumption and lipid metabolism. 3,5‐T2 also improves glucose tolerance in rats and 3,5‐T2 levels correlate with fasting glucose in humans. Presently, however, little is known about mechanisms of 3,5‐T2 effects on glucose metabolism. Here, we set out to compare effects of T3, 3,5‐T2 and another form of T2 (3,3‐T2) in a mouse model of diet‐induced obesity and determined effects of T3 and 3,5‐T2 on markers of classical insulin sensitization to understand how diiodothyronines influence blood glucose. Methods Cell‐ and protein‐based assays of thyroid hormone action. Assays of metabolic parameters in mice. Analysis of transcript and protein levels in different tissues by qRT‐PCR and Western blot. Results T3 and 3,5‐T2 both reduce body weight, adiposity and body temperature despite increased food intake. 3,3′‐T2 lacks these effects. T3 and 3,5‐T2 reduce blood glucose levels, whereas 3,3′‐T2 worsens glucose tolerance. Neither T3 nor 3,5‐T2 affects markers of insulin sensitization in skeletal muscle or white adipose tissue (WAT), but both reduce hepatic GLUT2 glucose transporter levels and glucose output. T3 and 3,5‐T2 also induce expression of mitochondrial uncoupling proteins (UCPs) 3 and 1 in skeletal muscle and WAT respectively. Conclusions 3,5‐T2 influences glucose metabolism in a manner that is distinct from insulin sensitization and involves reductions in hepatic glucose output and changes in energy utilization.
    November 17, 2016   doi: 10.1111/apha.12821   open full text
  • Of Channels and Pumps: Different Ways to Boost the Aldosterone?
    Sascha Bandulik.
    Acta Physiologica. November 15, 2016
    The mineralocorticoid aldosterone is a major factor controlling the salt and water balance and thereby also the arterial blood pressure. Accordingly, primary aldosteronism characterized by an inappropiately high aldosterone secretion is the most common form of secondary hypertension. The physiological stimulation of aldosterone synthesis in adrenocortical glomerulosa cells by angiotensin II and an increased plasma K+ concentration depends on a membrane depolarization and an increase of the cytosolic Ca2+ activity. Recurrent gain‐of‐function mutations of ion channels and transporters have been identified in a majority of cases of aldosterone producing adenomas and in familial forms of primary aldosteronism. In this review, the physiological role of these genes in the regulation of aldosterone synthesis and the altered function of the mutant proteins as well are described. The specific changes of the membrane potential and the cellular ion homeostasis in adrenal cells expressing the different mutants are compared and their impact on autonomous aldosterone production and proliferation is discussed. This article is protected by copyright. All rights reserved.
    November 15, 2016   doi: 10.1111/apha.12832   open full text
  • Electrical Pulse Stimulation of Cultured Skeletal Muscle Cells as a Model for in vitro Exercise – Possibilities and Limitations.
    Nataša Nikolić, Sven W. Görgens, G. Hege Thoresen, Vigdis Aas, Jürgen Eckel, Kristin Eckardt.
    Acta Physiologica. November 10, 2016
    The beneficial health‐related effects of exercise are well recognized, and numerous studies have investigated underlying mechanism using various in vivo and in vitro models. Although electrical pulse stimulation (EPS) for the induction of muscle contraction has been used for quite some time, its application on cultured skeletal muscle cells of animal or human origin as a model of in vitro exercise is a more recent development. In this review, we compare in vivo exercise and in vitro EPS with regard to effects on signaling, expression level, and metabolism. We provide a comprehensive overview of different EPS protocols and their applications, discuss technical aspects of this model including critical controls and the importance of a proper maintenance procedure and finally, discuss the limitations of the EPS model. This article is protected by copyright. All rights reserved.
    November 10, 2016   doi: 10.1111/apha.12830   open full text
  • Biology of VO2max: looking under the physiology lamp.
    Carsten Lundby, David Montero, Michael Joyner.
    Acta Physiologica. November 07, 2016
    In this review we argue that several key features of maximal oxygen uptake (VO2max) should underpin discussions about the biological and reductionist determinants of its inter‐individual variability: 1) Training induced increases in VO2max are largely facilitated by expansion of red blood cell volume and an associated improvement in stroke volume, which also adapts independent of changes in red blood cell volume. These general concepts are also informed by cross sectional studies in athletes that have very high values for VO2max. Therefore, 2) variations in VO2max improvements with exercise training are also likely related to variations in these physiological determinants. 3) All previously untrained individuals will respond to endurance exercise training in terms of improvements in VO2max provided the stimulus exceeds a certain volume and/or intensity. Thus genetic analysis and/or reductionist studies performed to understand or predict such variations might focus specifically on DNA variants or other molecular phenomena of relevance to these physiological pathways. This article is protected by copyright. All rights reserved.
    November 07, 2016   doi: 10.1111/apha.12827   open full text
  • Renoprotection: Focus on TRPV1, TRPV4, TRPC6 and TRPM2.
    Lajos Markó, Marwan Mannaa, Timo Nicolas Haschler, Stephanie Krämer VMD, Maik Gollasch.
    Acta Physiologica. November 07, 2016
    Members of the transient receptor potential (TRP) cation channel receptor family have unique sites of regulatory function in the kidney which enables them to promote regional vasodilatation and controlled Ca2+ influx into podocytes and tubular cells. Activated TRP vanilloid 1 receptor channels (TRPV1) have been found to elicit renoprotection in rodent models of acute kidney injury following ischemia/reperfusion. Transient receptor potential cation channel, subfamily C, member 6 (TRPC6) in podocytes is involved in chronic proteinuric kidney disease, particularly in focal segmental glomerulosclerosis (FSGS). TRP vanilloid 4 receptor channels (TRPV4) are highly expressed in the kidney, where they induce Ca2+ influx into endothelial and tubular cells. TRP melastatin (TRPM2) non‐selective cation channels are expressed in the cytoplasm and intracellular organelles, where their inhibition ameliorates ischemic renal pathology. Though some of their basic properties have been recently identified, the renovascular role of TRPV1, TRPV4, TRPC6, and TRPM2 channels in disease states such as obesity, hypertension and diabetes is largely unknown. In this review, we discuss recent evidence for TRPV1, TRPV4, TRPC6 and TRPM2 serving as potential targets for acute and chronic renoprotection in chronic vascular and metabolic disease. This article is protected by copyright. All rights reserved.
    November 07, 2016   doi: 10.1111/apha.12828   open full text
  • Urothelium update. How the bladder mucosa measures bladder filling.
    D.A.W. Janssen, J.A. Schalken, J.P.F.A. Heesakkers.
    Acta Physiologica. November 02, 2016
    Aim This review critically evaluates the evidence on mechanosreceptors and pathways in the bladder urothelium that are involved in normal bladder filling signaling. Methods Evidence from in vitro and in vivo studies on 1) signaling pathways like the adenosine triphosphate pathway, cholinergic pathway and Nitrc Oxide and adrenergic pathway will be evaluated and 2) different urothelial receptors that are involved in bladder filling signaling like purinergic receptors, sodium channels and TRP channels will be evaluated. Other potential pathways and receptors will also be discussed. Results Bladder filling results in continuous changes in bladder wall stretch and exposure to urine. Both barrier and afferent signaling functions in the urothelium are constantly adapting to cope with these dynamics. Current evidence shows that the bladder mucosa host essential pathways and receptors that mediate bladder filling signaling. Intracellular calcium ion increase is a dominant factor in this signaling process. However, there is still no complete understanding how interacting receptors and pathways create a bladder filling signal. Currently, there are still novel receptors investigated that that could also be participating in bladder filling signaling. Conclusions Normal bladder filling sensation is dependent on multiple interacting mechanoreceptors and signaling pathways. Research efforts need to focus on how these pathways and receptors interact in order to fully understand normal bladder filling signaling. This article is protected by copyright. All rights reserved.
    November 02, 2016   doi: 10.1111/apha.12824   open full text
  • High glucose concentration abrogates sevoflurane post‐conditioning cardioprotection by advancing mitochondrial fission but dynamin‐related protein 1 inhibitor restores these effects.
    J. Yu, Y. Maimaitili, P. Xie, J. J. Wu, J. Wang, Y. N. Yang, H. P. Ma, H. Zheng.
    Acta Physiologica. October 26, 2016
    Aim Hyperglycaemia‐induced cell injury is a primary cause of cardiovascular complications in patients with diabetes. In vivo studies demonstrated that sevoflurane post‐conditioning (SpostC) was cardioprotective against ischaemia/reperfusion injury, which was blocked by hyperglycaemia. This study investigated whether high glucose concentration abrogated SpostC cardioprotection in vitro by advancing mitochondrial fission and whether mitochondrial division inhibitor‐1 (Mdivi‐1) restored SpostC cardioprotection in cultured primary neonatal rat cardiomyocytes (NCMs). Methods Primary cultured NCMs in low and high glucose concentrations were subjected to hypoxia/reoxygenation (H/R) injury. SpostC was carried out by adding 2.4% sevoflurane to the cells at the beginning of reoxygenation for 15 min. Cell viability, lactate dehydrogenase (LDH) level, cell death, mitochondrial morphology, mitochondrial membrane potential and mitochondrial permeability transition pore (mPTP) opening level, as well as fission‐ and fusion‐related proteins, were measured after H/R injury. Mdivi‐1 treatment was performed 40 min before hypoxia to inhibit DRP1. Results SpostC protected cultured cardiomyocytes by increasing cell viability and reducing the LDH level and cell death following H/R, but high glucose concentration eliminated the cardioprotective effect. High glucose concentration abrogated SpostC cardioprotection via mitochondrial fragmentation (evidenced by decreased mitochondrial interconnectivity and elongation) and facilitation of mPTP opening. Decreased mitochondrial membrane potential was investigated with increased DRP1, FIS1 and MFN2 and decreased MFN1 and OPA1 expressions. Mdivi‐1 (100 μmol L−1) inhibited excessive mitochondrial fission and restored the cardioprotective effect of SpostC in high glucose conditions. Conclusion SpostC‐induced cardioprotection against H/R injury was impaired under high glucose concentrations, but the inhibition of excess mitochondrial fission restored these effects.
    October 26, 2016   doi: 10.1111/apha.12812   open full text
  • Cyclosporin a induces renal episodic hypoxia.
    M. Fähling, S. Mathia, J. Scheidl, R. Abramovitch, Z. Milman, A. Paliege, H. Peters, P. B. Persson, S. N. Heyman, C. Rosenberger.
    Acta Physiologica. October 18, 2016
    Aim Cyclosporin A (CsA) causes renal toxicity. The underlying mechanisms are incompletely understood, but may involve renal hypoxia and hypoxia‐inducible factors (Hifs). We sought for hypoxia and Hif in mouse kidneys with CsA‐induced toxicity, assessed their time course, Hif‐mediated responses and the impact of interventional Hif upregulation. Methods Mice received CsA or its solvent cremophore for up to 6 weeks. Low salt diet (Na+↓) was given in combination with CsA to enhance toxicity. We assessed fine morphology, renal function, blood oxygen level‐dependent magnetic resonance imaging under room air and following changes in breathing gas composition which correlate with vascular reactivity, pimonidazole adducts (which indicate O2 tensions below 10 mmHg), Hif‐α proteins, as well as expression of Hif target genes. Stable Hif upregulation was achieved by inducible, Pax8‐rtTA‐based knockout of von Hippel–Lindau protein (Vhl‐KO), which is crucial for Hif‐α degradation. Results Cyclosporin A transiently increased renal deoxyhaemoglobin (R2*). Augmented vascular reactivity was observed at 2 h, but decreased at 24 h after CsA treatment. Na+↓/CsA provoked chronic renal failure with tubular degeneration and interstitial fibrosis. Nephron segments at risk for injury accumulated pimonidazole adducts, as well as Hif‐α proteins. Remarkably, Hif target gene expression remained unchanged, while factor‐inhibiting Hif (Fih) was enhanced. Na+↓/CsA/Vhl‐KO aggravated morpho‐functional outcome of chronic renal CsA toxicity. Conclusions Cyclosporin A provokes episodic hypoxia in nephron segments most susceptible to chronic CsA toxicity. Fih is upregulated and likely blocks further Hif activity. Continuous tubular Hif upregulation via Vhl‐KO worsens the outcome of chronic CsA‐induced renal toxicity.
    October 18, 2016   doi: 10.1111/apha.12811   open full text
  • Adopting an external focus of attention alters intracortical inhibition within the primary motor cortex.
    Y.‐A. Kuhn, M. Keller, J. Ruffieux, W. Taube.
    Acta Physiologica. October 17, 2016
    Aim Although it is well established that an external (EF) compared to an internal (IF) or neutral focus of attention enhances motor performance, little is known about the underlying neural mechanisms. This study aimed to clarify whether the focus of attention influences not only motor performance but also activity of the primary motor cortex (M1) when executing identical fatiguing tasks of the right index finger (first dorsal interosseous). Transcranial magnetic stimulation (TMS) at intensities below motor threshold was applied over M1 to assess and compare the excitability of intracortical inhibitory circuits. Methods In session 1, 14 subjects performed an isometric finger abduction at 30% of their maximal force to measure the time to task failure (TTF) with either an IF or EF. In session 2, the same task was performed with the other focus. In sessions 3 and 4, subthreshold TMS (subTMS) and paired‐pulse TMS were applied to the contralateral M1 to compare the activity of cortical inhibitory circuits within M1 during EF and IF. Results With an EF, TTF was significantly prolonged (P = 0.01), subTMS‐induced electromyographical suppression enhanced (P = 0.001) and short‐interval intracortical inhibition (SICI) increased (P = 0.004). Conclusion The level of intracortical inhibition was previously shown to influence motor performance. Our data shed new light on the ability to instantly modulate the activity of inhibitory circuits within M1 by changing the type of attentional focus. The increased inhibition with EF might contribute to the better movement efficiency, which is generally associated with focusing externally.
    October 17, 2016   doi: 10.1111/apha.12807   open full text
  • Peroxynitrite formed during a transient episode of brain ischaemia increases endothelium‐derived hyperpolarization‐type dilations in thromboxane/prostaglandin receptor‐stimulated rat cerebral arteries.
    Y. Onetti, A. P. Dantas, B. Pérez, A. J. McNeish, E. Vila, F. Jiménez‐Altayó.
    Acta Physiologica. October 16, 2016
    Aim Increased thromboxane A2 and peroxynitrite are hallmarks of cerebral ischaemia/reperfusion (I/R). Stimulation of thromboxane/prostaglandin receptors (TP) attenuates endothelium‐derived hyperpolarization (EDH). We investigated whether EDH‐type middle cerebral artery (MCA) relaxations following TP stimulation are altered after I/R and the influence of peroxynitrite. Methods Vascular function was determined by wire myography after TP stimulation with the thromboxane A2 mimetic 9,11‐dideoxy‐9α, 11α ‐methano‐epoxy prostaglandin F2α (U46619) in MCA of Sprague Dawley rats subjected to MCA occlusion (90 min)/reperfusion (24 h) or sham operation, and in non‐operated (control) rats. Some rats were treated with saline or the peroxynitrite decomposition catalyst 5,10,15,20‐tetrakis(4‐sulfonatophenyl)porphyrinato iron (III) (20 mg kg−1). Protein expression was evaluated in MCA and in human microvascular endothelial cells submitted to hypoxia (overnight)/reoxygenation (24 h) (H/R) using immunofluorescence and immunoblotting. Results In U46619‐pre‐constricted MCA, EDH‐type relaxation by the proteinase‐activated receptor 2 agonist serine–leucine–isoleucine–glycine–arginine–leucine–NH2 (SLIGRL) was greater in I/R than sham rats due to an increased contribution of small‐conductance calcium‐activated potassium channels (SKCa), which was confirmed by the enlarged relaxation to the SKCa activator N‐cyclohexyl‐N‐2‐(3,5‐dimethyl‐pyrazol‐1‐yl)‐6‐methyl‐4‐pyrimidinamine. I/R and H/R induced endothelial protein tyrosine nitration and filamentous‐actin disruption. In control MCA, either cytochalasin D or peroxynitrite disrupted endothelial filamentous‐actin and augmented EDH‐type relaxation. Furthermore, peroxynitrite decomposition during I/R prevented the increase in EDH‐type responses. Conclusion Following TP stimulation in MCA, EDH‐type relaxation to SLIGRL is greater after I/R due to endothelial filamentous‐actin disruption by peroxynitrite, which prevents TP‐induced block of SKCa input to EDH. These results reveal a novel mechanism whereby peroxynitrite could promote post‐ischaemic brain injury.
    October 16, 2016   doi: 10.1111/apha.12809   open full text
  • Mode of perfusion influences infarct size, coronary flow and stress kinases in the isolated mouse heart.
    M. Bliksøen, A. Rutkovskiy, J. Vaage, K.‐O. Stensløkken.
    Acta Physiologica. October 14, 2016
    Aim The isolated, retrogradely perfused heart (modified Langendorff model) is a widely used method in experimental heart research. The presence of an intraventricular balloon is necessary to get functional measurements. We have previously shown that the balloon induces phosphorylation of some suggested cardioprotective mitogen‐activated protein kinases (MAPK): P38‐MAPK, ERK 1/2 and JNK. We hypothesized that the balloon could influence cardioprotection, protect against ischaemia reperfusion injury and interfere with coronary flow. Methods and Results Isolated mouse hearts were perfused for 5, 10, 20, 40 and 60 min with a balloon in the left ventricle. We found a wavelike phosphorylation of all MAPK while AKT displayed a gradual dephosphorylation when compared to non‐perfused hearts. Hearts were subjected to 20 min of stabilization with or without the balloon, followed by 35 min of ischaemia and 120 min of reperfusion. Although the MAPK were phosphorylated, the infarcts were larger in the balloon group. When the balloon was present during the entire protocol, compared to removal at the end of ischaemia, the infarct size was also larger, especially in the endocardial layer. The balloon reduced post‐ischaemic endocardial coronary flow, despite a higher average flow, indicating a hyperperfused epicard. Blocking the balloon‐induced ERK 1/2 phosphorylation during stabilization did not affect infarct size. The effect of post‐conditioning was influenced by the balloon, showing reduced infarct size when the balloon was present. Conclusion The balloon used for pressure measurements may contributes to cell death possibly by reducing endocardial coronary flow.
    October 14, 2016   doi: 10.1111/apha.12773   open full text
  • Receptor‐interacting Protein 140 represses Sirtuin 3 to facilitate hypertrophy, mitochondrial dysfunction and energy metabolic dysfunction in cardiomyocytes.
    J. You, Z. Yue, S. Chen, Y. Chen, X. Lu, X. Zhang, P. Shen, J. Li, Q. Han, Z. Li, P. Liu.
    Acta Physiologica. October 12, 2016
    Aim The transcriptional cofactor receptor‐interacting protein 140 (RIP140) is known as a deleterious regulator of cardiac mitochondrial function and energy metabolic homeostasis. This study revealed that RIP140 repressed Sirtuin 3 (SIRT3), a mitochondrial deacetylase that plays an important role in regulating cardiac function. Methods RIP140 was overexpressed by adenovirus infection or was knocked down by RNA interference in neonatal rat cardiomyocytes. Results RIP140 overexpression repressed, while RIP140 silencing elevated the expression and activity of SIRT3. Ad‐RIP140 enhanced the expressions of the cardiac hypertrophic markers and increased cardiomyocyte surface area, whereas SIRT3 overexpression prevented the effect of Ad‐RIP140. Additionally, SIRT3 overexpression reversed Ad‐RIP140‐induced mitochondrial dysfunction and energy metabolic dysfunction, such as increase in oxidative stress, decrease in mitochondrial membrane potential and ATP production, as well as downregulation of mitochondrial DNA‐encoded genes and genes related to mitochondrial genome replication and transcription, mitochondrial oxidative phosphorylation and fatty acid oxidation. In contrast, SIRT3 silencing exacerbated RIP140‐induced cardiomyocyte hypertrophy and mitochondrial dysfunction. Furthermore, the repression of SIRT3 by RIP140 was dependent on estrogen‐related receptor‐α (ERRα). The involvement of peroxisome proliferator‐activated receptor‐γ coactivator‐1α (PGC‐1α) was ruled out of SIRT3 suppression by RIP140. RIP140 and PGC‐1α might act as functional antagonists on the regulation of SIRT3. Conclusion This study indicates that suppression of SIRT3 by RIP140 facilitates the development of cardiomyocyte hypertrophy, mitochondrial dysfunction and energy metabolic dysfunction. Strategies targeting inhibition of RIP140 and upregulation of SIRT3 might improve cardiac energy metabolism and suggest therapeutic potential for heart diseases.
    October 12, 2016   doi: 10.1111/apha.12800   open full text
  • Beneficial effects of renal denervation on cardiac angiogenesis in rats with prolonged pressure overload.
    D. Lu, K. Wang, S. Wang, B. Zhang, Q. Liu, Q. Zhang, J. Geng, Q. Shan.
    Acta Physiologica. October 12, 2016
    Aim Renal denervation (RDN) has beneficial effects on cardiac remodelling and function in resistant hypertension. We aimed to investigate the impact of RDN on cardiac angiogenesis during prolonged pressure overload. Methods Cardiac pressure overload was reproduced by transverse aorta constriction (TAC) procedure in adult Sprague Dawley male rats (n = 35). RDN/sham‐RDN procedure was performed in surviving rats at 5 weeks after TAC. Results Five weeks post‐TAC, transthoracic echocardiography revealed that myocardial hypertrophy occurred in TAC rats, with ejection fraction and fractional shortening not significantly changed. At the end of 10 weeks, cardiac systolic function was preserved in RDN group, but not in sham group. CD31 immunohistochemical staining showed that RDN‐treated rats had higher cardiac capillary density than sham rats. However, no significant between‐group difference was observed in the kidneys. A decreased protein expression of left ventricle vascular endothelial growth factor (VEGF) was observed in sham group, while RDN attenuated this decrease. Compared with sham, RDN resulted in a higher protein expression of VEGF receptor 2 (VEGFR2) and phosphorylated endothelial nitric oxide synthase (p‐eNOS) in the heart. Conclusion Renal denervation benefits cardiac angiogenesis during sustained pressure overload, involving regulation of VEGF and VEGFR2 expression as well as activation of eNOS.
    October 12, 2016   doi: 10.1111/apha.12793   open full text
  • Dopamine enhances duodenal epithelial permeability via the dopamine D5 receptor in rodent.
    X.‐Y. Feng, D.‐N. Zhang, Y.‐A. Wang, R.‐F. Fan, F. Hong, Y. Zhang, Y. Li, J.‐X. Zhu.
    Acta Physiologica. October 06, 2016
    Aim The intestinal barrier is made up of epithelial cells and intercellular junctional complexes to regulate epithelial ion transport and permeability. Dopamine (DA) is able to promote duodenal epithelial ion transport through D1‐like receptors, which includes subtypes of D1 (D1R) and D5 (D5R), but whether D1‐like receptors influence the duodenal permeability is unclear. Methods FITC–dextran permeability, short‐circuit current (ISC), Western blot, immunohistochemistry and ELISA were used in human D5R transgenic mice and hyperendogenous enteric DA (HEnD) rats in this study. Results Dopamine induced a downward deflection in ISC and an increase in FITC–dextran permeability of control rat duodenum, which were inhibited by the D1‐like receptor antagonist, SCH‐23390. However, DA decreased duodenal transepithelial resistance (TER), an effect also reversed by SCH‐23390. A strong immunofluorescence signal for D5R, but not D1R, was observed in the duodenum of control rat. In human D5R knock‐in transgenic mice, duodenal mucosa displayed an increased basal ISC with high FITC–dextran permeability and decreased TER with a lowered expression of tight junction proteins, suggesting attenuated duodenal barrier function in these transgenic mice. D5R knock‐down transgenic mice manifested a decreased basal ISC with lowered FITC–dextran permeability. Moreover, an increased FITC–dextran permeability combined with decreased TER and tight junction protein expression in duodenal mucosa were also observed in HEnD rats. Conclusion This study demonstrates, for the first time, that DA enhances duodenal permeability of control rat via D5R, which provides new experimental and theoretical evidence for the influence of DA on duodenal epithelial barrier function.
    October 06, 2016   doi: 10.1111/apha.12806   open full text
  • Development of somatosensory‐evoked potentials in foetal sheep: effects of betamethasone.
    P. Anegroaie, M. G. Frasch, S. Rupprecht, I. Antonow‐Schlorke, T. Müller, H. Schubert, O. W. Witte, M. Schwab.
    Acta Physiologica. October 04, 2016
    Aim Antenatal glucocorticoids are used to accelerate foetal lung maturation in babies threatened with premature labour. We examined the influence of glucocorticoids on functional and structural maturation of the central somatosensory pathway in foetal sheep. Somatosensory‐evoked potentials (SEP) reflect processing of somatosensory stimuli. SEP latencies are determined by afferent stimuli transmission while SEP amplitudes reveal cerebral processing. Methods After chronic instrumentation of foetal sheep, mothers received saline (n = 9) or three courses of betamethasone (human equivalent dose of 2 × 110 μg kg−1 betamethasone i.m. 24 h apart, n = 12) at 0.7, 0.75 and 0.8 of gestational age. Trigeminal SEP were evoked prior to, 4 and 24 h after each injection and at 0.8 of gestational age before brains were histologically processed. Results Somatosensory‐evoked potentials were already detectable at 0.7 of gestation age. The early and late responses N20 and N200 were the only reproducible peaks over the entire study period. With advancing gestational age, SEP latencies decreased but amplitudes remained unchanged. Acutely, betamethasone did not affect SEP latencies and amplitudes 4 and 24 h following administration. Chronically, betamethasone delayed developmental decrease in the N200 but not N20 latency by 2 weeks without affecting amplitudes. In parallel, betamethasone decreased subcortical white matter myelination but did not affect network formation and synaptic density in the somatosensory cortex. Conclusion Somatosensory stimuli are already processed by the foetal cerebral cortex at the beginning of the third trimester. Subsequent developmental decrease in SEP latencies suggests ongoing maturation of afferent sensory transmission. Antenatal glucocorticoids affect structural and functional development of the somatosensory system with specific effects at subcortical level.
    October 04, 2016   doi: 10.1111/apha.12795   open full text
  • Desoxycorticosterone pivalate‐salt treatment leads to non‐dipping hypertension in Per1 knockout mice.
    K. Solocinski, M. Holzworth, X. Wen, K.‐Y. Cheng, I. J. Lynch, B. D. Cain, C. S. Wingo, M. L. Gumz.
    Acta Physiologica. October 03, 2016
    Aim Increasing evidence demonstrates that circadian clock proteins are important regulators of physiological functions including blood pressure. An established risk factor for developing cardiovascular disease is the absence of a blood pressure dip during the inactive period. The goal of the present study was to determine the effects of a high salt diet plus mineralocorticoid on PER1‐mediated blood pressure regulation in a salt‐resistant, normotensive mouse model, C57BL/6J. Methods Blood pressure was measured using radiotelemetry. After control diet, wild‐type (WT) and Per1 (KO) knockout mice were given a high salt diet (4% NaCl) and the long‐acting mineralocorticoid deoxycorticosterone pivalate. Blood pressure and activity rhythms were analysed to evaluate changes over time. Results Blood pressure in WT mice was not affected by a high salt diet plus mineralocorticoid. In contrast, Per1 KO mice exhibited significantly increased mean arterial pressure (MAP) in response to a high salt diet plus mineralocorticoid. The inactive/active phase ratio of MAP in WT mice was unchanged by high salt plus mineralocorticoid treatment. Importantly, this treatment caused Per1 KO mice to lose the expected decrease or ‘dip’ in blood pressure during the inactive compared to the active phase. Conclusion Loss of PER1 increased sensitivity to the high salt plus mineralocorticoid treatment. It also resulted in a non‐dipper phenotype in this model of salt‐sensitive hypertension and provides a unique model of non‐dipping. Together, these data support an important role for the circadian clock protein PER1 in the modulation of blood pressure in a high salt/mineralocorticoid model of hypertension.
    October 03, 2016   doi: 10.1111/apha.12804   open full text
  • Unsung Renal Receptors: Orphan G‐protein coupled receptors play essential roles in renal development and homeostasis.
    Premraj Rajkumar, Jennifer L. Pluznick.
    Acta Physiologica. October 03, 2016
    Recent studies have shown that orphan GPCRs of the GPR family are utilized as specialized chemosensors in various tissues to detect metabolites, and in turn to activate downstream pathways which regulate systemic homeostasis. These studies often find that such metabolites are generated by well‐known metabolic pathways, implying that known metabolites and chemicals may perform novel functions. In this review, we summarize recent findings highlighting the role of deorphanized GPRs in renal development and function. Understanding the role of these receptors is critical in gaining insights into mechanisms that regulate renal function both in health and in disease. This article is protected by copyright. All rights reserved.
    October 03, 2016   doi: 10.1111/apha.12813   open full text
  • Bradykinin receptor blockade restores the baroreflex control of renal sympathetic nerve activity in cisplatin‐induced renal failure rats.
    M. H. Abdulla, M. Duff, H. Swanton, E. J. Johns.
    Acta Physiologica. September 29, 2016
    Aim This study investigated the effect of renal bradykinin B1 and B2 receptor blockade on the high‐ and low‐pressure baroreceptor reflex regulation of renal sympathetic nerve activity (RSNA) in rats with cisplatin‐induced renal failure. Methods Cisplatin (5 mg/kg) or saline was given intraperitoneally 4 days prior to study. Following chloralose/urethane anaesthesia, rats were prepared for measurement of mean arterial pressure (MAP), heart rate and RSNA and received intrarenal infusions of either Lys‐[des‐Arg9, Leu8]‐bradykinin (LBK), a bradykinin B1 receptor blocker, or bradyzide (BZ), a bradykinin B2 receptor blocker. RSNA baroreflex gain curves and renal sympatho‐inhibitory responses to volume expansion (VE) were obtained. Results In the control and renal failure groups, basal MAP (89 ± 3 vs. 80 ± 8 mmHg) and RSNA (2.0 ± 0.3 vs. 1.7 ± 0.6 μV.s) were similar but HR was lower in the latter group (331 ± 8 vs. 396 ± 9 beats/min). The baroreflex gain for RSNA in the renal failure rats was 39% (P < 0.05) lower than the control but was restored to normal values following intrarenal infusion of BZ, but not LBK. VE had no effect on MAP or HR but reduced RSNA by some 40% (P < 0.05) in control but not renal failure rats. Intrarenal LBK infusion in the renal failure rats normalized the VE induced renal sympatho‐inhibition whereas BZ only partially restored the response. Conclusion These findings suggest that pro‐inflammatory bradykinin acting at different receptors within the kidney generates afferent neural signals which impact differentially within the central nervous system on high‐ and low‐pressure regulation of RSNA.
    September 29, 2016   doi: 10.1111/apha.12801   open full text
  • Non‐linear effects of potassium channel blockers on endothelium‐dependent hyperpolarization.
    Harold A. Coleman, Marianne Tare, Helena C. Parkington.
    Acta Physiologica. September 17, 2016
    In a number of published studies on endothelium‐dependent hyperpolarization and relaxation, the results of the effects of K+ blockers have been difficult to interpret. When the effects of two blockers have been studied, often either blocker by itself had little effect, whereas the two blockers combined tended to abolish the responses. Explanations suggested in the literature include an unusual pharmacology of the K+ channels, and possible blocker binding interactions. In contrast, when we applied the same blockers to segments of small blood vessels under voltage‐clamp, the blockers reduced the endothelium‐dependent K+ current in a linearly additive manner. Resolution of these contrasting results is important since endothelium‐derived hyperpolarization (EDH) makes its greatest contribution to vasorelaxation in arterioles and small resistance arteries, where it can exert a significant role in tissue perfusion and blood pressure regulation. Furthermore, EDH is impaired in various diseases. Here we consider why the voltage‐clamp results differ from earlier free‐running membrane potential and contractility studies. We fitted voltage‐clamp derived current‐voltage relationships with mathematical functions and considered theoretically the effects of partial and total block of endothelium‐derived K+‐currents on the membrane potential of small blood vessels. When the K+‐conductance was partially reduced, equivalent to applying a single blocker, the effect on EDH was small. Total block of the endothelium‐dependent K+ conductance abolished the hyperpolarization, in agreement with various published studies. We conclude that nonlinear summation of the hyperpolarizing response evoked by endothelial stimulation can explain the variable effectiveness of individual K+ channel blockers on endothelium‐dependent hyperpolarization and resulting relaxation. This article is protected by copyright. All rights reserved.
    September 17, 2016   doi: 10.1111/apha.12805   open full text
  • A review of wave mechanics in the pulmonary artery with an emphasis on wave intensity analysis.
    Junjing Su, Ole Hilberg, Luke Howard, Ulf Simonsen, Alun D Hughes.
    Acta Physiologica. September 16, 2016
    Mean pulmonary arterial pressure and pulmonary vascular resistance remain the most common hemodynamic measures to evaluate the severity and prognosis of pulmonary hypertension. However, pulmonary vascular resistance only captures the non‐oscillatory component of the right ventricular hydraulic load and neglects the dynamic compliance of the pulmonary arteries and the contribution of wave transmission. Wave intensity analysis offers an alternative way to assess the pulmonary vasculature in health and disease. Wave speed is a measure of arterial stiffness and the magnitude and timing of wave reflection provide information on the degree of impedance mismatch between the proximal and distal circulation. Studies in the pulmonary artery have demonstrated distinct differences in arterial wave propagation between individuals with and without pulmonary vascular disease. Notably, greater wave speed and greater wave reflection are observed in patients with pulmonary hypertension and in animal models exposed to hypoxia. Studying wave propagation makes a valuable contribution to the assessment of the arterial system in pulmonary hypertension and here, we briefly review the current state of knowledge of the methods used to evaluate arterial waves in the pulmonary artery. This article is protected by copyright. All rights reserved.
    September 16, 2016   doi: 10.1111/apha.12803   open full text
  • Progesterone‐induced miR‐133a inhibits the proliferation of endometrial epithelial cells.
    J.‐l. Pan, D.‐z. Yuan, Y.‐b. Zhao, L. Nie, Y. Lei, M. Liu, Y. Long, J.‐h. Zhang, L. J. Blok, C. W. Burger, L.‐m. Yue.
    Acta Physiologica. September 15, 2016
    Aim This study aimed to understand the role of miR‐133a in progesterone actions, explore the regulative mechanism of the progesterone receptor, and investigate the effects of miR‐133a on the progesterone‐inhibited proliferation of mouse endometrial epithelial cells. Methods The expression of miR‐133a induced by progesterone was detected by quantitative real‐time PCR both in vivo and in vitro. Ishikawa subcell lines stably transfected with progesterone receptor subtypes were used to determine the receptor mechanism of progesterone inducing miR‐133a. Specific miR‐133a mimics or inhibitors were transfected into mouse uteri and primary cultured endometrial epithelial cells to overexpress or downregulate the miR‐133a. The roles of miR‐133a in the cell cycle and proliferation of endometrial epithelial cells were analysed by flow cytometry and Edu incorporation analysis. The protein levels of cyclinD2 in uterine tissue sections and primary cultured endometrial epithelial cells were determined by immunohistochemistry and Western blot analysis. Results Progesterone could induce miR‐133a expression in a PRB‐dependent manner in endometrial epithelial cells. miR‐133a inhibited endometrial epithelial cell proliferation by arresting cell cycle at the G1‐S transition. Moreover, miR‐133a acted as an inhibitor in downregulating cyclinD2 in endometrial epithelial cells. Conclusion We showed for the first time that progesterone‐induced miR‐133a inhibited the proliferation of endometrial epithelial cells by downregulating cyclinD2. Our research indicated an important mechanism for progesterone inhibiting the proliferation of endometrial epithelial cells by inducing special miRNAs to inhibit positive regulatory proteins in the cell cycle.
    September 15, 2016   doi: 10.1111/apha.12762   open full text
  • Physiological aspects of Toll‐like receptor 4 activation in sepsis‐induced acute kidney injury.
    Sara Bülow Anderberg, Tomas Luther, Robert Frithiof.
    Acta Physiologica. September 07, 2016
    Sepsis‐induced acute kidney injury (SI‐AKI) is common and associated with high mortality. Survivors are at increased risk of chronic kidney disease. The precise mechanism underlying SI‐AKI is unknown and no curative treatment exists. Toll‐like receptor 4 (TLR4) activates the innate immune system in response to exogenous microbial products. The result is an inflammatory reaction aimed at clearing a potential infection. However, the consequence may also be organ dysfunction as the immune response can cause collateral damage to host tissue. The purpose of this review is to describe the basis for how ligand binding to TLR4 has the potential to cause renal dysfunction and the mechanisms by which this may take place in gram‐negative sepsis. In addition, we highlight areas for future research that can further our knowledge of the pathogenesis of SI‐AKI in relation to TLR4 activation. TLR4 is expressed in the kidney. Activation of TLR4 causes cytokine and chemokine release as well as renal leukocyte infiltration. It also results in endothelial and tubular dysfunction in addition to altered renal metabolism and circulation. From a physiological standpoint inhibiting TLR4 in large‐animal experimental SI‐AKI significantly improves renal function. Thus, current evidence indicates that TLR4 has the ability to mediate SI‐AKI by a number of mechanisms. The strong experimental evidence supporting a role of TLR4 in the pathogenesis of SI‐AKI in combination with the availability of pharmacological tools to target TLR4 warrants future human studies. This article is protected by copyright. All rights reserved.
    September 07, 2016   doi: 10.1111/apha.12798   open full text
  • Evidence for a functional role of calsequestrin 2 in mouse atrium.
    U. Gergs, C. M. Fahrion, P. Bock, M. Fischer, H. Wache, S. Hauptmann, W. Schmitz, J. Neumann.
    Acta Physiologica. August 31, 2016
    Aim Several genetically modified mice models were studied so far to investigate the role of cardiac calsequestrin (CSQ2) for the contractile function of the ventricle and for the occurrence of ventricular tachycardia. Using a CSQ2 knockout mouse, we wanted to study also the atrial function of CSQ2. Methods The influence of CSQ2 on atrial function and, for comparison, ventricular function was studied in isolated cardiac preparations and by echocardiography as well as electrocardiography in mice with deletion of CSQ2. Results Using deletion of exon 1, we have successfully generated a constitutive knockout mouse of the calsequestrin 2 gene (CSQ2−/−). CSQ2 protein was absent in the heart (atrium, ventricle), but also in oesophagus and skeletal muscle of homozygous knockout mice. In 6‐month‐old CSQ2−/− mice, relative left atrial weight was increased, whereas relative heart weight was unchanged. The staircase phenomena in paced left atrial preparations on force of contraction and the post‐rest potentiation were different between wild type and CSQ2−/− indicative for a decreased sarcoplasmic Ca2+ load and supporting an important role of CSQ2 also in the atrium. The incidence of arrhythmias was increased in CSQ2−/−. In 2‐year‐old CSQ2−/− mice, cardiac hypertrophy and heart failure were noted possibly as a result of chronically increased cytosolic Ca2+ levels. Conclusion These data suggest a functional role of CSQ2 not only in the ventricle but also in the atrium of mammalian hearts. Loss of CSQ2 function can cause not only arrhythmias, but also cardiac hypertrophy and heart failure.
    August 31, 2016   doi: 10.1111/apha.12766   open full text
  • Hypoxia exposure and B‐type natriuretic peptide release from Langendorff heart of rats.
    K. Anttila, T. Streng, J. Pispa, M. Vainio, M. Nikinmaa.
    Acta Physiologica. August 26, 2016
    Aim We studied whether available oxygen without induced mechanical stretch regulates the release of the biologically active B‐type natriuretic peptide (BNP) from Langendorff heart. Methods Rat hearts were isolated and perfused with a physiological Krebs–Henseleit solution at a constant hydrostatic pressure in Langendorff set‐up. The basal O2 level of perfusate (24.4 ± 0.04 mg L−1) was gradually lowered to 3.0 ± 0.01 mg L−1 over 20 min using N2 gas (n = 7). BNP and O2 level were measured from coronary flow. During control perfusions (n = 5), the O2 concentration was kept at 26.6 ± 0.3 mg L−1. Results A low oxygen concentration in the perfusate was associated with a significant increase in BNP release (F = 40.4, P < 0.001). Heart rate decreased when the oxygen concentration in the perfusate reached 9.1 ± 0.02 mg L−1 and continued to fall in lower oxygen concentrations (F = 14.8, P < 0.001). There was also a significant but inverse correlation between BNP and oxygen in the coronary flow (R2 = 0.27, P < 0.001). Conclusion In the spontaneously beating Langendorff rat heart, a decreasing concentration of oxygen in the ingoing perfusion increased the secretion of BNP. The effect of oxygen was independent of mechanical stretch of the heart as it occurred even when the heart rate decreased but the pressure conditions remained constant. The difference in the oxygen capacitance of blood and Krebs–Henseleit solution appears to be a major factor affecting secretion of BNP, which is correlated with the oxygen tension of myocardial cells and affected both by the oxygen concentration and capacitance of solution perfusing the heart and by the coronary flow.
    August 26, 2016   doi: 10.1111/apha.12767   open full text
  • Body ownership and a new proprioceptive role for muscle spindles.
    Annie A. Butler, Martin E. Héroux, Simon C. Gandevia.
    Acta Physiologica. August 26, 2016
    Knowledge of which body parts belong to us is referred to as the sense of body ownership. There is increasing evidence that this important aspect of human proprioception is highly malleable. Research into ownership of individual body parts was stimulated by Botvinick and Cohen's rubber‐hand illusion (1998), which demonstrated that an artificial body part can be incorporated in one's body representation and can cause real body parts to be sensed erroneously. Here, we review key studies that have advanced our understanding of the sense of body ownership, including the important role played by multisensory integration and spatiotemporal congruence of sensory signals. We also discuss our recent discovery that body ownership can be induced in response to movement stimuli by signals from a single class of sensory receptor, namely, muscles spindles. This article is protected by copyright. All rights reserved.
    August 26, 2016   doi: 10.1111/apha.12792   open full text
  • Back‐calculating baseline creatinine overestimates prevalence of acute kidney injury with poor sensitivity.
    F. Kork, F. Balzer, A. Krannich, M. H. Bernardi, H. K. Eltzschig, J. Jankowski, C. Spies.
    Acta Physiologica. August 25, 2016
    Aim Acute kidney injury (AKI) is diagnosed by a 50% increase in creatinine. For patients without a baseline creatinine measurement, guidelines suggest estimating baseline creatinine by back‐calculation. The aim of this study was to evaluate different glomerular filtration rate (GFR) equations and different GFR assumptions for back‐calculating baseline creatinine as well as the effect on the diagnosis of AKI. Methods The Modification of Diet in Renal Disease, the Chronic Kidney Disease Epidemiology (CKD‐EPI) and the Mayo quadratic (MQ) equation were evaluated to estimate baseline creatinine, each under the assumption of either a fixed GFR of 75 mL min−1 1.73 m−2 or an age‐adjusted GFR. Estimated baseline creatinine, diagnoses and severity stages of AKI based on estimated baseline creatinine were compared to measured baseline creatinine and corresponding diagnoses and severity stages of AKI. Results The data of 34 690 surgical patients were analysed. Estimating baseline creatinine overestimated baseline creatinine. Diagnosing AKI based on estimated baseline creatinine had only substantial agreement with AKI diagnoses based on measured baseline creatinine [Cohen's κ ranging from 0.66 (95% CI 0.65–0.68) to 0.77 (95% CI 0.76–0.79)] and overestimated AKI prevalence with fair sensitivity [ranging from 74.3% (95% CI 72.3–76.2) to 90.1% (95% CI 88.6–92.1)]. Staging AKI severity based on estimated baseline creatinine had moderate agreement with AKI severity based on measured baseline creatinine [Cohen's κ ranging from 0.43 (95% CI 0.42–0.44) to 0.53 (95% CI 0.51–0.55)]. Conclusion Diagnosing AKI and staging AKI severity on the basis of estimated baseline creatinine in surgical patients is not feasible. Patients at risk for post‐operative AKI should have a pre‐operative creatinine measurement to adequately assess post‐operative AKI.
    August 25, 2016   doi: 10.1111/apha.12763   open full text
  • Ventricular repolarization time, location of pacing stimulus and current pulse amplitude conspire to determine arrhythmogenicity in mice.
    T. Speerschneider, S. Grubb, S. P. Olesen, K. Calloe, M. B. Thomsen.
    Acta Physiologica. August 24, 2016
    Aim In this study, we investigate the impact of altered action potential durations (APD) on ventricular repolarization time and proarrhythmia in mice with and without genetic deletion of the K+‐channel‐interacting protein 2 (KChIP2−/− and WT respectively). Moreover, we examine the interrelationship between the dispersion of repolarization time and current pulse amplitude in provoking ventricular arrhythmia. Methods Intracardiac pacing in anesthetized mice determined refractory periods and proarrhythmia susceptibility. Regional activation time (AT), APD and repolarization time (=AT + APD) were measured in isolated hearts using floating microelectrodes. Results Proarrhythmia in WT and KChIP2−/− was not sensitive to changes in refractory periods. Action potentials were longer in KChIP2−/− hearts compared to WT hearts. Isolated WT hearts had large apico‐basal dispersion of repolarization time, whereas hearts from KChIP2−/− mice had large left‐to‐right ventricular dispersion of repolarization time. Pacing from the right ventricle in KChIP2−/− mice in vivo revealed significant lower current pulse amplitudes needed to induce arrhythmias in these mice. Conclusion Large heterogeneity of repolarization time is proarrhythmic when pacing is delivered from the location of earlier repolarization time. Ventricular repolarization time, location of the pacing stimulus and the amplitude of the stimulating current pulse are critical parameters underlying arrhythmia vulnerability.
    August 24, 2016   doi: 10.1111/apha.12761   open full text
  • Insight towards the identification of cytosolic Ca2+‐binding sites in ryanodine receptors from skeletal and cardiac muscle.
    Marta Gaburjakova, Jana Gaburjakova.
    Acta Physiologica. August 20, 2016
    Ca2+ plays a critical role in several processes involved in skeletal and cardiac muscle contraction. One key step in cardiac excitation‐contraction (E‐C) coupling is the activation of the cardiac ryanodine receptor (RYR2) by cytosolic Ca2+ elevations. Although this process is not critical for skeletal E‐C coupling, the activation and inhibition of the skeletal ryanodine receptor (RYR1) seems to be important for overall muscle function. The RYR1 and RYR2 channels fall within the large category of Ca2+‐binding proteins that harbour highly selective Ca2+ ‐binding sites to receive and translate the various Ca2+ signals into specific functional responses. However, little is known about the precise localization of these sites within the cytosolic assembly of both RYR isoforms, although several experimental lines of evidence have highlighted their EF‐hand nature. EF‐hand proteins share a common helix‐loop‐helix structural motif with highly conserved residues involved in Ca2+ coordination. The first step in predicting EF‐hand positive regions is to compare the primary protein structure with the EF‐hand motif by employing available bioinformatics tools. Although this simple method narrows down search regions, it does not provide solid evidence regarding which regions bind Ca2+ in both RYR isoforms. In this review, we seek to highlight the key findings and experimental approaches that should strengthen our future efforts to identify the cytosolic Ca2+‐binding sites responsible for activation and inhibition in the RYR1 channel, as much less work has been conducted on the RYR2 channel. This article is protected by copyright. All rights reserved.
    August 20, 2016   doi: 10.1111/apha.12772   open full text
  • The translationally relevant mouse model of the 15q13.3 microdeletion syndrome reveals deficits in neuronal spike firing matching clinical neurophysiological biomarkers seen in schizophrenia.
    J. Thelin, P. Halje, J. Nielsen, M. Didriksen, P. Petersson, J. F. Bastlund.
    Acta Physiologica. August 16, 2016
    Aim To date, the understanding and development of novel treatments for mental illness is hampered by inadequate animal models. For instance, it is unclear to what extent commonly used behavioural tests in animals can inform us on the mental and affective aspects of schizophrenia. Methods To link pathophysiological processes in an animal model to clinical findings, we have here utilized the recently developed Df(h15q13)/+ mouse model for detailed investigations of cortical neuronal engagement during pre‐attentive processing of auditory information from two back‐translational auditory paradigms. We also investigate if compromised putative fast‐spiking interneurone (FSI) function can be restored through pharmacological intervention using the Kv3.1 channel opener RE1. Chronic multi‐array electrodes in primary auditory cortex were used to record single cell firing from putative pyramidal and FSI in awake animals during processing of auditory sensory information. Results We find a decreased amplitude in the response to auditory stimuli and reduced recruitment of neurones to fast steady‐state gamma oscillatory activity. These results resemble encephalography recordings in patients with schizophrenia. Furthermore, the probability of interneurones to fire with low interspike intervals during 80 Hz auditory stimulation was reduced in Df(h15q13)/+ mice, an effect that was partially reversed by the Kv3.1 channel modulator, RE1. Conclusion This study offers insight into the consequences on a neuronal level of carrying the 15q13.3 microdeletion. Furthermore, it points to deficient functioning of interneurones as a potential pathophysiological mechanism in schizophrenia and suggests a therapeutic potential of Kv3.1 channel openers.
    August 16, 2016   doi: 10.1111/apha.12746   open full text
  • High‐salt diet induces outward remodelling of efferent arterioles in mice with reduced renal mass.
    L. Zhao, Y. Gao, X. Cao, D. Gao, S. Zhou, S. Zhang, X. Cai, F. Han, C. S. Wilcox, L. Li, E. Y. Lai.
    Acta Physiologica. August 15, 2016
    Aim The glomerular filtration rate (GFR) falls progressively in chronic kidney disease (CKD) which is caused by a reduction in the number of functional nephrons. The dysfunctional nephron exhibits a lower glomerular capillary pressure that is induced by an unbalance between afferent and efferent arteriole. Therefore, we tested the hypothesis that oxidative stress induced by CKD differentially impairs the structure or function of efferent vs. afferent arterioles. Methods C57BL/6 mice received sham operations (sham) or 5/6 nephrectomy (RRM) and three months of normal‐ or high‐salt diet or tempol. GFR was assessed from the plasma inulin clearance, arteriolar remodelling from media/lumen area ratio, myogenic responses from changes in luminal diameter with increases in perfusion pressure and passive wall compliance from the wall stress/strain relationships. Results Mice with RRM fed a high salt (vs. sham) had a lower GFR (553 ± 25 vs. 758 ± 36 μL min−1 g−1 kidney, P < 0.01) and a larger efferent arteriolar diameter (9.6 ± 0.8 vs. 7.4 ± 0.7 μm, P < 0.05) resulting in a lower media/lumen area ratio (1.4 ± 0.1 vs. 2.4 ± 0.2, P < 0.01). These alterations were corrected by tempol. The myogenic responses of efferent arterioles were about one‐half that of afferent arterioles and were unaffected by RRM or salt. Passive wall compliance was reduced by high salt in both afferent and efferent arterioles. Conclusion A reduction in renal mass with a high‐salt diet induces oxidative stress that leads to an outward eutrophic remodelling in efferent arterioles and reduced wall compliance in both afferent and efferent arterioles. This may contribute to the lower GFR in this model of CKD.
    August 15, 2016   doi: 10.1111/apha.12759   open full text
  • c‐Jun N‐terminal Kinase mediates prostaglandin‐induced sympathoexcitation in rats with chronic heart failure by reducing GAD1 and GABRA1 expression.
    R. Wang, W. Zhang, Z. Dong, Y. Qi, M. Hultström, X. Zhou, E. Y. Lai.
    Acta Physiologica. August 12, 2016
    Aim Prostaglandin E2 mediates sympathoexcitation in chronic heart failure (CHF) through EP3 receptors (PTGER3) in the paraventricular nucleus (PVN). The aim of this study was to investigate the role of c‐Jun N‐terminal kinase (JNK) in expressional regulation of gamma‐aminobutyric acid signalling in PVN in CHF rats. Methods Chronic heart failure was induced by left coronary ligation in Wistar rats. Renal sympathetic nerve discharge (RSND) and mean arterial pressure (MAP) responses to the PVN infusion were determined in anaesthetized rats. Osmotic minipumps were used for chronic PVN infusion. PTGER3 expression was examined with immunofluorescence staining, quantitative real‐time PCR and Western blot. Results Chronic heart failure rats had increased JNK activation and decreased glutamate decarboxylase 1 (GAD1) and GABAA receptor alpha 1 subunit (GABRA1) expression in the PVN. PVN infusion of the PTGER3 agonist SC‐46275 caused sympathoexcitation in sham‐operated control (Sham) rats and increased it further in CHF. The PTGER3 antagonist L798106 reduced sympathoexcitation and cardiac dysfunction in CHF. PVN infusion of EP1 receptor antagonist SC‐19220, EP2 receptor antagonist AH6809 or EP4 receptor antagonist L‐161982 had no effect on sympathoexcitation. The JNK inhibitor SP600125 normalized sympathoexcitation and GAD1 and GABRA1 expression in PVN in CHF rats. Both the p44/42 and p38 mitogen‐activated protein kinase inhibitors PD98059 and SB203580 could not prevent the downregulation of GAD1 and GABRA1 expression in PVN in CHF. PTGER3 agonist activated JNK but downregulated GAD1 and GABRA1 expression in NG108 neuronal cells. Conclusion Prostaglandin signalling through upregulated PTGER3 activates JNK which reduces GAD1 and GABRA1 expression in the PVN, and contributes to sympathoexcitation in CHF.
    August 12, 2016   doi: 10.1111/apha.12758   open full text
  • Expression of sex steroid hormone receptors in human skeletal muscle during the menstrual cycle.
    L. Ekenros, Z. Papoutsi, C. Fridén, K. Dahlman Wright, A. Lindén Hirschberg.
    Acta Physiologica. August 09, 2016
    Aim Variations in sex hormone levels during the menstrual cycle may affect neuromuscular performance and the risk of sustaining musculoskeletal injury in women. The aim of this study was to investigate mRNA and protein levels for sex steroid hormone receptors in skeletal muscle in three distinct phases of the menstrual cycle. Methods Fifteen, healthy women with regular menstrual cycles participated in the study. Muscle biopsies from the vastus lateralis were obtained in three hormonally verified phases of the menstrual cycle for each individual, that is the follicular phase, the ovulatory phase and the luteal phase. mRNA and protein levels of oestrogen (ERα and ERβ), progesterone (PR) and androgen (AR) receptors were analysed. Results There was an overall significant variation in mRNA and protein levels of ERα and PR across the menstrual cycle. mRNA and protein levels of ERα were highest in the follicular phase when oestradiol levels were low, whereas protein levels of PR were highest in the luteal phase when progesterone levels were high. mRNA levels of PR were highest in the ovulatory phase. No significant variation in AR levels was detected across the menstrual cycle. ERβ levels were very low in all three phases of the menstrual cycle. Conclusion Significant variations in mRNA and protein levels of ERα and PR were detected in skeletal muscle during three confirmed phases of the menstrual cycle. These results may have an impact on effects of muscular training and sports injuries in women.
    August 09, 2016   doi: 10.1111/apha.12757   open full text
  • Emerging roles of calcium‐activated K channels and TRPV4 channels in lung oedema and pulmonary circulatory collapse.
    Ulf Simonsen, Christine Wandall‐Frostholm, Aida Oliván‐Viguera, Ralf Köhler.
    Acta Physiologica. August 06, 2016
    It has been suggested that the transient receptor potential cation (TRP) channel subfamily V (vanilloid) type 4 (TRPV4) and intermediate‐conductance calcium‐activated potassium (KCa3.1) channels contribute to endothelium‐dependent vasodilation. Here we summarize very recent evidence for a synergistic interplay of TRPV4 and KCa3.1 channels in lung disease. Among the endothelial Ca2+‐permeable TRPs, TRPV4 is best characterized and produces arterial dilation by stimulating Ca2+‐dependent NO synthesis and endothelium‐dependent hyperpolarization. Besides these roles, some TRP channels control endothelial/epithelial barrier functions and vascular integrity, while KCa3.1 channels provide the driving force required for Cl‐ and water transport in some cells and most secretory epithelia. The three conditions, increased pulmonary venous pressure caused by left heart disease, high inflation pressure, and chemically‐induced lung injury may lead to activation of TRPV4 channels followed by Ca2+ influx leading to activation of KCa3.1 channels in endothelial cells ultimately leading to acute lung injury. We find that a deficiency in KCa3.1channels protects against TRPV4‐induced pulmonary arterial relaxation, fluid extravasation, hemorrhage, pulmonary circulatory collapse, and cardiac arrest in vivo. These data identify KCa3.1 channels as crucial molecular components in downstream TRPV4‐signal transduction and as a potential target for the prevention of undesired fluid extravasation, vasodilatation, and pulmonary circulatory collapse. This article is protected by copyright. All rights reserved.
    August 06, 2016   doi: 10.1111/apha.12768   open full text
  • Salt‐losing nephropathy in mice with a null mutation of the Clcnk2 gene.
    A. Grill, I. M. Schießl, B. Gess, K. Fremter, A. Hammer, H. Castrop.
    Acta Physiologica. August 01, 2016
    Aim The basolateral chloride channel ClC‐Kb facilitates Cl reabsorption in the distal nephron of the human kidney. Functional mutations in CLCNKB are associated with Bartter's syndrome type 3, a hereditary salt‐losing nephropathy. To address the function of ClC‐K2 in vivo, we generated ClC‐K2‐deficient mice. Methods ClC‐K2‐deficient mice were generated using TALEN technology. Results ClC‐K2‐deficient mice were viable and born in a Mendelian ratio. ClC‐K2−/− mice showed no gross anatomical abnormalities, but they were growth retarded. The 24‐h urine volume was increased in ClC‐K2−/− mice (4.4 ± 0.6 compared with 0.9 ± 0.2 mL per 24 h in wild‐type littermates; P = 0.001). Accordingly, ambient urine osmolarity was markedly reduced (590 ± 39 vs. 2216 ± 132 mosmol L−1 in wild types; P < 0.0001). During water restriction (24 h), urinary osmolarity increased to 1633 ± 153 and 3769 ± 129 mosmol L−1 in ClC‐K2−/− and wild‐type mice (n = 12; P < 0.0001), accompanied by a loss of body weight of 12 ± 0.4 and 8 ± 0.2% respectively (P < 0.0001). ClC‐K2−/− mice showed an increased renal sodium excretion and compromised salt conservation during a salt‐restricted diet. The salt‐losing phenotype of ClC‐K2−/− mice was associated with a reduced plasma volume, hypotension, a slightly reduced glomerular filtration rate, an increased renal prostaglandin E2 generation and a massively stimulated renin–angiotensin system. Clckb−/− mice showed a reduced sensitivity to furosemide and were completely resistant to thiazides. Conclusion Loss of ClC‐K2 compromises TAL function and abolishes salt reabsorption in the distal convoluted tubule. Our data suggest that ClC‐K2 is crucial for renal salt reabsorption and concentrating ability. ClC‐K2‐deficient mice in most aspects mimic patients with Bartter's syndrome type 3.
    August 01, 2016   doi: 10.1111/apha.12755   open full text
  • 4D in vivo imaging of glomerular barrier function in a zebrafish podocyte injury model.
    F. Siegerist, W. Zhou, K. Endlich, N. Endlich.
    Acta Physiologica. August 01, 2016
    Aim Zebrafish larvae with their simplified pronephros are an ideal model to study glomerular physiology. Although several groups use zebrafish larvae to assess glomerular barrier function, temporary or slight changes are still difficult to measure. The aim of this study was to investigate the potential of in vivo two‐photon microscopy (2‐PM) for long‐term imaging of glomerular barrier function in zebrafish larvae. Methods As a proof of principle, we adapted the nitroreductase/metronidazole model of targeted podocyte ablation for 2‐PM. Combination with a strain, which expresses eGFP‐vitamin D‐binding protein in the blood plasma, led to a strain that allowed induction of podocyte injury with parallel assessment of glomerular barrier function. We used four‐dimensional (4D) 2‐PM to assess eGFP fluorescence over 26 h in the vasculature and in tubules of multiple zebrafish larvae (5 days post‐fertilization) simultaneously. Results By 4D 2‐PM, we observed that, under physiological conditions, eGFP fluorescence was retained in the vasculature and rarely detected in proximal tubule cells. Application of metronidazole induced podocyte injury and cell death as shown by TUNEL staining. Induction of podocyte injury resulted in a dramatic decrease of eGFP fluorescence in the vasculature over time (about 50% and 90% after 2 and 12 h respectively). Loss of vascular eGFP fluorescence was paralleled by an endocytosis‐mediated accumulation of eGFP fluorescence in proximal tubule cells, indicating proteinuria. Conclusion We established a microscopy‐based method to monitor the dynamics of glomerular barrier function during induction of podocyte injury in multiple zebrafish larvae simultaneously over 26 h.
    August 01, 2016   doi: 10.1111/apha.12754   open full text
  • Biomarkers in acute kidney injury – pathophysiological basis and clinical performance.
    Eva V. Schrezenmeier, Jonathan Barasch, Klemens Budde, Timm Westhoff, Kai M. Schmidt‐Ott.
    Acta Physiologica. July 30, 2016
    Various biomarkers of acute kidney injury (AKI) have been discovered and characterized in the recent past. These molecules can be detected in urine or blood and signify structural damage to the kidney. Clinically, they are proposed as adjunct diagnostics to serum creatinine and urinary output to improve the early detection, differential diagnosis and prognostic assessment of AKI. The most obvious requirements for a biomarker include its reflection of the underlying pathophysiology of the disease. Hence, a biomarker of AKI should derive from the injured kidney and reflect a molecular process intimately connected with tissue injury. Here, we provide an overview of the basic pathophysiology, the cellular sources and the clinical performance of the most important currently proposed biomarkers of acute kidney injury: neutrophil gelatinase‐associated lipocalin (NGAL), kidney injury molecule‐1 (KIM‐1), liver‐type fatty acid–binding protein (L‐FABP), interleukin 18 (IL‐18), insulin‐like growth factor binding protein 7 (IGFBP7), tissue inhibitor of metalloproteinase 2 (TIMP‐2), and calprotectin (S100A8/9). We also acknowledge each biomarker's advantages and disadvantages as well as important knowledge gaps and perspectives for future studies. This article is protected by copyright. All rights reserved
    July 30, 2016   doi: 10.1111/apha.12764   open full text
  • Novel Routes of Albumin Passage Across the Glomerular Filtration Barrier.
    Hayo Castrop, Ina Maria Schießl.
    Acta Physiologica. July 25, 2016
    Albuminuria is a hallmark of kidney diseases of various etiologies and an unambiguous symptom of the compromised integrity of the glomerular filtration barrier. Furthermore, there is increasing evidence that albuminuria per se aggravates the development and progression of chronic kidney disease. This review covers new aspects of the movement of large plasma proteins across the glomerular filtration barrier in health and disease. Specifically, this review focuses on the role of endocytosis and transcytosis of albumin by podocytes, which constitutes a new pathway of plasma proteins across the filtration barrier. Thus, we summarize what is known about the mechanisms of albumin endocytosis by podocytes and address the fate of the endocytosed albumin, which is directed to lysosomal degradation or transcellular movement with subsequent vesicular release into the urinary space. We also address the functional consequences of overt albumin endocytosis by podocytes, such as the formation of pro‐inflammatory cytokines, which might eventually result in a deterioration of podocyte function. Finally, we consider the diagnostic potential of podocyte‐derived albumin‐containing vesicles in the urine as an early marker of a compromised glomerular barrier function. In terms of new technical approaches, the review covers how our knowledge of the movement of albumin across the glomerular filtration barrier has expanded by the use of new intravital imaging techniques. This article is protected by copyright. All rights reserved.
    July 25, 2016   doi: 10.1111/apha.12760   open full text
  • Activation of the hypoxia‐inducible factor pathway induced by prolyl hydroxylase domain 2 deficiency enhances the effect of running training in mice.
    A. Nunomiya, J. Shin, Y. Kitajima, T. Dan, T. Miyata, R. Nagatomi.
    Acta Physiologica. July 25, 2016
    Aims Hypoxic response mediated by hypoxia‐inducible factor (HIF) seems to contribute to the benefit of endurance training. To verify the direct contribution of HIF activation to running training without exposure to atmospheric hypoxia, we used prolyl hydroxylase domain 2 (PHD2) conditional knockout mice (cKO), which exhibit HIF activation independent of oxygen concentration, and we examined their maximal exercise capacity before and after 4 weeks of treadmill exercise training. Methods Phd2f/f mice (n = 26) and Phd2 cKO mice (n = 24) were randomly divided into two groups, trained and untrained, and were subjected to maximal running test before and after a 4‐week treadmill‐training regimen. Results Prolyl hydroxylase domain 2 deficiency resulted in HIF‐α protein accumulation. Phd2 cKO mice exhibited marked increases in haematocrit values and haemoglobin concentrations, as well as an increase in the capillary number in the skeletal muscle. The 4‐week training elicited an increase in the capillary‐to‐fibre (C/F) ratio and succinyl dehydrogenase activity of the skeletal muscle. Importantly, trained Phd2 cKO mice showed a significantly greater improvement in running time than trained control mice (P < 0.05). Collectively, these data suggest that the combination of training and the activation of the HIF pathway are important for maximizing the effect of running training. Conclusion We conclude that the activation of the HIF pathway induced by PHD2 deficiency enhances the effect of running training.
    July 25, 2016   doi: 10.1111/apha.12751   open full text
  • Claudin‐2‐mediated cation and water transport share a common pore.
    R. Rosenthal, D. Günzel, S. M. Krug, J.‐D. Schulzke, M. Fromm, A. S. L. Yu.
    Acta Physiologica. July 20, 2016
    Aim Claudin‐2 is a tight junction protein typically located in ‘leaky’ epithelia exhibiting large paracellular permeabilities like small intestine and proximal kidney tubule. Former studies revealed that claudin‐2 forms paracellular channels for small cations like sodium and potassium and also paracellular channels for water. This study analyses whether the diffusive transport of sodium and water occurs through a common pore of the claudin‐2 channel. Methods Wild‐type claudin‐2 and different claudin‐2 mutants were expressed in MDCK I kidney tubule cells using an inducible system. Ion and water permeability and the effect of blocking reagents on both were investigated on different clones of the mutants. Results Neutralization of a negatively charged cation interaction site in the pore with the mutation, D65N, decreased both sodium permeability and water permeability. Claudin‐2 mutants (I66C and S68C) with substitution of the pore‐lining amino acids with cysteine were used to test the effect of steric blocking of the claudin‐2 pore by thiol‐reactive reagents. Addition of thiol‐reactive reagents to these mutants simultaneously decreased conductance and water permeability. Remarkably, all experimental perturbations caused parallel changes in ion conductance and water permeability, disproving different or independent passage pathways. Conclusion Our results indicate that claudin‐2‐mediated cation and water transport are frictionally coupled and share a common pore. This pore is lined and determined in permeability by amino acid residues of the first extracellular loop of claudin‐2.
    July 20, 2016   doi: 10.1111/apha.12742   open full text
  • Bladder pain induced by prolonged peripheral alpha 1A adrenoceptor stimulation involves the enhancement of transient receptor potential vanilloid 1 activity and an increase of urothelial adenosine triphosphate release.
    R. Matos, J. M. Cordeiro, A. Coelho, S. Ferreira, C. Silva, Y. Igawa, F. Cruz, A. Charrua.
    Acta Physiologica. July 20, 2016
    Aim Pathophysiological mechanisms of chronic visceral pain (CVP) are unknown. This study explores the association between the sympathetic system and bladder nociceptors activity by testing the effect of a prolonged adrenergic stimulation on transient receptor potential vanilloid 1 (TRPV1) activity and on urothelial adenosine triphosphate (ATP) release. Methods Female Wistar rats received saline, phenylephrine (PHE), PHE + silodosin, PHE + naftopidil or PHE + prazosin. TRPV1 knockout and wild‐type mice received saline or PHE. Visceral pain behaviour tests were performed before and after treatment. Cystometry was performed, during saline and capsaicin infusion. Fos immunoreactivity was assessed in L6 spinal cord segment. Human urothelial ATP release induced by mechanical and thermal stimulation was evaluated. Results Subcutaneous, but not intrathecal, PHE administration induced pain, which was reversed by silodosin, a selective alpha 1A adrenoceptor antagonist, but not by naftopidil, a relatively selective antagonist for alpha 1D adrenoceptor. Silodosin also reversed PHE‐induced bladder hyperactivity and L6 spinal cord Fos expression. Thus, in subsequent experiments, only silodosin was used. Wild‐type, but not TRPV1 knockout, mice exhibited phenylephrine‐induced pain. Capsaicin induced a greater increase in voiding contractions in PHE‐treated rats than in control animals, and silodosin reversed this effect. When treated with PHE, ATP release from human urothelial cells was enhanced either by mechanical stimulation or by lowering the thermal threshold of urothelial TRPV1, which becomes abnormally responsive at body temperature. Conclusion This study suggests that the activation of peripheral alpha 1A adrenoceptors induces CVP, probably through its interaction with TRPV1 and ATP release.
    July 20, 2016   doi: 10.1111/apha.12744   open full text
  • Adipocytokine, progranulin, augments acetylcholine‐induced nitric oxide‐mediated relaxation through the increases of cGMP production in rat isolated mesenteric artery.
    K. Kazama, K. Hoshino, T. Kodama, M. Okada, H. Yamawaki.
    Acta Physiologica. July 15, 2016
    Aim Progranulin (PGRN) is a novel adipocytokine with anti‐inflammatory effects in vascular cells. The aim of this study was to clarify the effects of PGRN on reactivity of isolated blood vessel. Methods Isometric contraction of rat isolated superior mesenteric artery was measured. Results Pre‐treatment with PGRN (10–100 ng mL−1, 30 min) had no effect on noradrenaline‐ or 5‐hydroxytriptamine‐induced contraction. On the other hand, pre‐treatment with PGRN (100 ng mL−1) augmented acetylcholine (ACh; 30 nm)‐induced endothelium‐dependent relaxation. Pre‐treatment with PGRN (100 ng mL−1) augmented ACh (10 μm)‐induced nitric oxide (NO)‐mediated relaxation in the presence of indomethacin (10 μm), a cyclooxygenase inhibitor, and tetraethyl ammonium (10 mm), a non‐selective potassium channel blocker. In contrast, pre‐treatment with PGRN (100 ng mL−1) had no effect on ACh‐induced endothelium‐derived hyperpolarizing factor‐mediated relaxation. Pre‐treatment with PGRN (100 ng mL−1) had no effect on ACh (10 μm, 1 min)‐induced endothelial NO synthase phosphorylation (at Ser1177) as determined by Western blotting. Pre‐treatment with PGRN (100 ng mL−1) augmented an NO donor, sodium nitroprusside (SNP; 30 nm–1 μm)‐ but not a membrane‐permeable cGMP analogue, 8‐bromo‐cGMP‐induced relaxation. In the presence of 3‐isobutyl‐1‐methylxanthine (100 μm), a phosphodiesterase inhibitor, pre‐treatment with PGRN (100 ng mL−1) increased SNP (30 nm, 5 min)‐induced cGMP production as determined by enzyme immunoassay. Conclusion We for the first time demonstrate that PGRN augments ACh‐induced NO‐mediated relaxation through the increases of cGMP production in smooth muscle. These results indicate PGRN as a possible pharmacotherapeutic target against cardiovascular diseases including obesity‐related hypertension.
    July 15, 2016   doi: 10.1111/apha.12739   open full text
  • Right ventricle dimensions and function in response to acute hypoxia in healthy human subjects.
    N. C. Netzer, K. P. Strohl, J. Högel, H. Gatterer, R. Schilz.
    Acta Physiologica. July 15, 2016
    Aim Acute hypoxia produces acute vasoconstriction in the pulmonary circulation with consequences on right ventricular (RV) structure and function. Previous investigations in healthy humans have been restricted to measurements after altitude acclimatization or were interrupted by normoxia. We hypothesized that immediate changes in RV dimensions in healthy subjects in response to normobaric hypoxia differ without the aforementioned constraints. Methods Transthoracic echocardiography was performed in 35 young, healthy subjects exposed to 11% oxygen, as well as six controls under sham hypoxia (20.6% oxygen, single blind) first at normoxia and after 30, 60, 100, 150 min of hypoxia or normoxia respectively. A subgroup of 15 subjects continued with 3‐min cycling exercise in hypoxia with subsequent evaluation followed by an assessment 1 min at rest while breathing 4 L min−1 oxygen. Results During hypoxia, there was a significant linear increase of all RV dimensions (RVD1 + 29 mm, RVD2 + 42 mm, RVD3 + 41 mm, RVOT + 13 mm, RVEDA + 18 mm, P < 0.01) in the exposure group vs. the control group. In response to hypoxia, right ventricular systolic pressure (RVSP) showed a modest increase in hypoxia at rest (+7.3 mmHg, P < 0.01) and increased further with physical effort (+11.8 mmHg, P < 0.01). After 1 min of oxygen at rest, it fell by 50% of the maximum increase. Conclusion Acute changes in RV morphology occur quickly after exposure to normobaric hypoxia. The changes were out of proportion to a relatively low‐estimated increase in pulmonary pressure, indicating direct effects on RV structure. The results in healthy subjects are basis for future clinically oriented interventional studies in normobaric hypoxia.
    July 15, 2016   doi: 10.1111/apha.12740   open full text
  • Brain‐derived neurotrophic factor of the cerebral microvasculature: a forgotten and nitric oxide‐dependent contributor of brain‐derived neurotrophic factor in the brain.
    A. Monnier, A. Prigent‐Tessier, A. Quirié, N. Bertrand, S. Savary, C. Gondcaille, P. Garnier, C. Demougeot, C. Marie.
    Acta Physiologica. July 15, 2016
    Aim Evidence that brain‐derived neurotrophic factor (BDNF), a neurotrophin largely involved in cognition, is expressed by cerebral endothelial cells led us to explore in rats the contribution of the cerebral microvasculature to BDNF found in brain tissue and the link between cerebrovascular nitric oxide (NO) and BDNF production. Methods Brain BDNF protein levels were measured before and after in situ removal of the cerebral endothelium that was achieved by brain perfusion with a 0.2% CHAPS (3‐[(3‐cholamidopropyl) dimethylammonio]‐1‐propane sulphonate) solution. BDNF protein and mRNA levels as well as levels of endothelial NO synthase phosphorylated at serine 1177 (P‐eNOSser1177) were measured in cerebral microvessel‐enriched fractions. These fractions were also exposed to glycerol trinitrate. Hypertension (spontaneously hypertensive rats) and physical exercise training were used as experimental approaches to modulate cerebrovascular endothelial NO production. Results CHAPS perfusion resulted in a marked decrease in brain BDNF levels. Hypertension decreased and exercise increased P‐eNOSser1177 and BDNF protein levels. However, BDNF mRNA levels that were increased by exercise did not change after hypertension. Finally, in vitro exposure of cerebral microvessel‐enriched fractions to glycerol trinitrate enhanced BDNF production. Conclusion These data reveal that BDNF levels measured in brain homogenates correspond for a large part to BDNF present in cerebral endothelial cells and that cerebrovascular BDNF production is dependent on cerebrovascular endothelial eNOS activity. They provide a paradigm shift in the cellular source of brain BDNF and suggest a new approach to improve our understanding of the link between endothelial function and cognition.
    July 15, 2016   doi: 10.1111/apha.12743   open full text
  • Increased hydrogen peroxide impairs angiotensin II contractions of afferent arterioles in mice after renal ischaemia–reperfusion injury.
    Q. Huang, Q. Wang, S. Zhang, S. Jiang, L. Zhao, L. Yu, M. Hultström, A. Patzak, L. Li, C. S. Wilcox, E. Y. Lai.
    Acta Physiologica. July 15, 2016
    Aim Renal ischaemia–reperfusion injury (IRI) increases angiotensin II (Ang II) and reactive oxygen species (ROS) that are potent modulators of vascular function. However, the roles of individual ROS and their interaction with Ang II are not clear. Here we tested the hypothesis that IRI modulates renal afferent arteriolar responses to Ang II via increasing superoxide (O2−) or hydrogen peroxide (H2O2). Methods Renal afferent arterioles were isolated and perfused from C57BL/6 mice 24 h after IRI or sham surgery. Responses to Ang II or noradrenaline were assessed by measuring arteriolar diameter. Production of H2O2 and O2− was assessed in afferent arterioles and renal cortex. Activity of SOD and catalase, and mRNA expressions of Ang II receptors were assessed in pre‐glomerular arterioles and renal cortex. Results Afferent arterioles from mice after IRI had a reduced maximal contraction to Ang II (−27±2 vs. −42±1%, P < 0.001), but retained a normal contraction to noradrenaline. Arterioles after IRI had a 38% increase in H2O2 (P < 0.001) and a 45% decrease in catalase activity (P < 0.01). Contractions were reduced in normal arterioles after incubation with H2O2 (−22±2 vs. −42±1%, P < 0.05) similar to the effects of IRI. However, the impaired contractions were normalized by incubation with PEG catalase despite a reduced AT1R expression. Conclusions Renal IRI in mice selectively impairs afferent arteriolar responses to Ang II because of H2O2 accumulation that is caused by a reduced catalase activity. This could serve to buffer the effect of Ang II after IRI and may be a protective mechanism.
    July 15, 2016   doi: 10.1111/apha.12745   open full text
  • The principal pathways involved in the in vivo modulation of hypoxic pulmonary vasoconstriction, pulmonary arterial remodelling and pulmonary hypertension.
    David Kylhammar, Göran Rådegran.
    Acta Physiologica. July 06, 2016
    Hypoxic pulmonary vasoconstriction (HPV) serves to optimize ventilation‐perfusion matching in focal hypoxia and thereby enhances pulmonary gas exchange. During global hypoxia, however, HPV induces general pulmonary vasoconstriction, which may lead to pulmonary hypertension (PH), impaired exercise capacity, right‐heart failure and pulmonary oedema at high altitude. In chronic hypoxia, generalized HPV together with hypoxic pulmonary arterial remodelling, contribute to the development of PH. The present article reviews the principal pathways in the in vivo modulation of HPV, hypoxic pulmonary arterial remodelling and PH with primary focus on the endothelin‐1, nitric oxide, cyclooxygenase and adenine nucleotide pathways. In summary, endothelin‐1 and thromboxane A2 may enhance, whereas nitric oxide and prostacyclin may moderate, HPV as well as hypoxic pulmonary arterial remodelling and PH. The production of prostacyclin seems to be coupled primarily to cyclooxygenase‐1 in acute hypoxia, but to cyclooxygenase‐2 in chronic hypoxia. The potential role of adenine nucleotides in modulating HPV is unclear, but warrants further study. Additional modulators of the pulmonary vascular responses to hypoxia may include angiotensin II, histamine, serotonin/5‐hydroxytryptamine, leukotrienes and epoxyeicosatrienoic acids. Drugs targeting these pathways may reduce acute and/or chronic hypoxic PH. Endothelin receptor antagonists and phosphodiesterase‐5 inhibitors may additionally improve exercise capacity in hypoxia. Importantly, the modulation of the pulmonary vascular responses to hypoxia varies between species and individuals, with hypoxic duration and age. The review also define how drugs targeting the endothelin‐1, nitric oxide, cyclooxygenase and adenine nucleotide pathways may improve pulmonary haemodynamics, but also impair pulmonary gas exchange by interference with HPV in chronic lung diseases. This article is protected by copyright. All rights reserved.
    July 06, 2016   doi: 10.1111/apha.12749   open full text
  • Dexamethasone promotes long‐term functional recovery of neuromuscular junction in a murine model of tourniquet‐induced ischaemia–reperfusion.
    D. Zhang, D. Wang, I. I. Pipinos, R. L. Muelleman, Y.‐L. Li.
    Acta Physiologica. July 05, 2016
    Aim Tourniquet‐induced ischaemia and subsequent reperfusion cause serious ischaemia–reperfusion (IR) injury in the neuromuscular junction (NMJ) and skeletal muscle. Here, we investigated whether dexamethasone (Dex) promotes long‐term functional recovery of the NMJ and skeletal muscle in tourniquet‐induced hindlimb IR. Methods Unilateral hindlimb of C57/BL6 mice was subjected to 3 h of ischaemia following 6 weeks of reperfusion (6‐wk IR). Dex treatment began on the day of IR induction and lasted for different periods. Sciatic nerve‐stimulated gastrocnemius muscle contraction was detected in situ. Function of the NMJ was measured in situ using electrophysiological recording of the miniature endplate potential (mEPP) and endplate potential (EPP). Western blot was used to detect protein expression of nicotinic acetylcholine receptors (nAChRs) in gastrocnemius muscles. Results Gastrocnemius muscle contraction in mice with 6‐wk IR was about 60% of normal skeletal muscle contraction recorded in age‐matched sham mice. The amplitude of the mEPP and EPP was lower in mice with 6‐wk IR, compared to sham mice. Dex treatment for 1 or 3 days did not restore the function of the NMJ and improve gastrocnemius muscle contraction in mice with 6‐wk IR. Dex treatment for 1 week exerted a maximum effect on improving the function of the NMJ and skeletal muscle, with the effect of Dex gradually lessening with prolonged Dex treatment. There are no significant differences in protein expression of nAChR‐α1 and nAChR‐β1 subunits in the gastrocnemius muscle among all groups. Conclusion Dex promotes repair of the NMJ and subsequently restores skeletal muscle contractile function in tourniquet‐induced 6‐wk IR.
    July 05, 2016   doi: 10.1111/apha.12737   open full text
  • Hypometabolism as the ultimate defense in stress response: how the comparative approach helps understanding of medically relevant questions.
    Thomas A. Gorr.
    Acta Physiologica. July 01, 2016
    First conceptualized from breath‐hold diving mammals, later recognized as the ultimate cell‐autonomous survival strategy in anoxia‐tolerant vertebrates and burrowing or hibernating rodents, hypometabolism is typically recruited by resilient organisms to withstand and recover from otherwise life‐threatening hazards. Through the coordinated down‐regulation of biosynthetic, proliferative and electrogenic expenditures at times when little ATP can be generated, a metabolism turned “down to the pilot light” allows the re‐balancing of energy demand with supply at a greatly suppressed level in response to noxious exogenous stimuli or seasonal endogenous cues. A unifying hallmark of stress‐tolerant organisms, the adaptation effectively prevents lethal depletion of ATP, thus delineating a marked contrast with susceptible species. Along with disengaged macromolecular syntheses, attenuated trans‐membrane ion shuttling and pO2‐conforming respiration rates, the metabolic slowdown in tolerant species usually culminates in a non‐cycling, quiescent phenotype. However, such a reprogramming also occurs in leading human pathophysiologies. Ranging from microbial infections through ischaemia‐driven infarcts to solid malignancies, cells involved in these disorders may again invoke hypometabolism to endure conditions nonpermissive for growth. At the same time, their reduced activities underlie the frequent development of a general resistance to therapeutic interventions. On the other hand, a controlled induction of hypometabolic and/or hypothermic states by pharmacological means has recently stimulated intense research aimed at improved organ preservation and patient survival in situations requiring acutely administered critical care. The current review article therefore presents an up‐to‐date survey of concepts and applications of a coordinated and reversibly down‐regulated metabolic rate as the ultimate defense in stress responses. This article is protected by copyright. All rights reserved.
    July 01, 2016   doi: 10.1111/apha.12747   open full text
  • Heat stress‐induced phosphorylation of FoxO3a signalling in rat skeletal muscle.
    T. Yoshihara, H. Kobayashi, R. Kakigi, T. Sugiura, H. Naito.
    Acta Physiologica. July 01, 2016
    Aim A recent study demonstrated that FoxO3a was directly induced by the overexpression of Hsp72 in rat soleus muscle. However, whether heat stress treatment induces FoxO3a phosphorylation in rat skeletal muscle remains unclear. This study examined the effects of heat stress on the regulation of the FoxO3a signalling pathway in rat skeletal muscle. Methods Thirty‐two male Wistar rats (15 weeks old) were randomly assigned into two groups; sedentary control group (Sed, n = 8) and experimental group (n = 24). After an overnight fast, one leg of each rat (HS leg) in the experimental group was immersed in hot water (43 °C) for 30 min, and the soleus and plantaris muscles in both legs were removed immediately (0 min), 30 min, 60 min, or 24 h after the heat stress (n = 6 each group). The contralateral, non‐heated leg in the experimental group served as an internal control (CT leg). Results Heat stress treatment resulted in a significant increase in FoxO3a phosphorylation (Ser253) in the soleus and plantaris muscles of heat‐stressed legs after 24 h. Hsp72 expression in heat‐stressed legs was significantly higher at 60 min and 24 h in these muscles. Activation of the PTEN/Akt and MEK/ERK pathways was also observed in these muscles immediately after stress, but not at 24 h. There were no differences in FoxO1 and AMPKα phosphorylation in either muscle. Conclusion Heat stress in rat skeletal muscle induces phosphorylation of FoxO3a signalling, and it may be related to Hsp72 upregulation, and the activation of the PTEN/Akt and MEK/ERK pathways.
    July 01, 2016   doi: 10.1111/apha.12735   open full text
  • Shear stress‐induced angiogenesis in mouse muscle is independent of the vasodilator mechanism and quickly reversible.
    S. Egginton, A. Hussain, J. Hall‐Jones, B. Chaudhry, F. Syeda, K. E. Glen.
    Acta Physiologica. July 01, 2016
    Aim Is modulation of skeletal muscle capillary supply by altering blood flow due to a presumptive shear stress response per se, or dependent on the vasodilator mechanism? Methods The response to four different vasodilators, and cotreatment with blockers of NO and prostaglandin synthesis, was compared. Femoral artery blood flow was correlated with capillary‐to‐fibre ratio (C:F) and protein levels of putative angiogenic compounds. Results All vasodilators induced a similar increase in blood flow after 14 days, with a similar effect on C:F (1.62 ± 0.05, 1.60 ± 0.01, 1.57 ± 0.06, 1.57 ± 0.07, respectively, all P < 0.05 vs. control 1.20 ± 0.01). Concomitant inhibitors revealed differential effects on blood flow and angiogenesis, demonstrating that a similar response may have different signalling origins. The time course of this response with the most commonly used vasodilator, prazosin, showed that blood flow increased from 0.40 mL min−1 to 0.61 mL min−1 by 28 days (P < 0.05), dropped within 1 week after the cessation of treatment (0.54 mL min−1; P < 0.05) and returned to control levels by 6 weeks. In parallel with FBF, capillary rarefaction began within 1 week (P < 0.05), giving C:F values similar to control by 2 weeks. Of the dominant signalling pathways, prazosin decreased muscle VEGF, but increased its cognate receptor Flk‐1 (both P < 0.01); levels of eNOS varied with blood flow (P < 0.05), and Ang‐1 initially increased, while its receptor Tie‐2 was unchanged, with only modest changes in the antiangiogenic factor TSP‐1. Conclusion Hyperaemia‐induced angiogenesis, likely in response to elevated shear stress, is independent of the vasodilator involved, with a rapid induction and quick regression following the stimulus withdrawal.
    July 01, 2016   doi: 10.1111/apha.12728   open full text
  • Role of transient receptor potential vanilloid 1 in regulating erythropoietin‐induced activation of endothelial nitric oxide synthase.
    Y.‐B. Yu, K.‐H. Su, Y. R. Kou, B.‐C. Guo, K.‐I. Lee, J. Wei, T.‐S. Lee.
    Acta Physiologica. June 29, 2016
    Aims Erythropoietin (EPO), the key hormone involved in erythropoiesis, beneficially affects endothelial cells (ECs), but the detailed mechanisms are yet to be completely understood. In this study, we investigated the role of transient receptor potential vanilloid type 1 (TRPV1), a ligand‐gated non‐selective calcium (Ca2+) channel, in EPO‐mediated endothelial nitric oxide synthase (eNOS) activation and angiogenesis. Methods and results In ECs, EPO time dependently increased intracellular levels of calcium; this increase was abrogated by the Ca2+ chelators and pharmacological inhibitors of TRPV1 in bovine aortic ECs (BAECs) and TRPV1‐transfected HEK293 cells. In addition, EPO‐induced nitrite oxide (NO) production, phosphorylation of eNOS, Akt and AMP‐activated protein kinase (AMPK) and the formation of TRPV1–Akt–AMPK–eNOS complex as well as tube formation were diminished by the pharmacological inhibition of TRPV1 in BAECs. Moreover, EPO time dependently induced the phosphorylation of phospholipase C‐γ1 (PLC‐γ1). Inhibition of PLC‐γ1 activity blunted the EPO‐induced Ca2+ influx, eNOS phosphorylation, TRPV1–eNOS complex formation and NO production. The phosphorylated level of eNOS increased in the aortas of EPO‐treated wild‐type (WT) mice or EPO‐transgenic (Tg) mice but not in those of EPO‐treated TRPV1‐deficient (TRPV1−/−) mice or EPO‐Tg/TRPV1−/− mice. Matrigel plug assay showed that EPO‐induced angiogenesis was abrogated in TRPV1 antagonist capsazepine‐treated WT mice and TRPV1−/− mice. Conclusion These findings indicate the EPO‐induced Ca2+ influx via the activation of the PLC‐γ1 signalling pathway, which leads to TRPV1 activation and consequently increases the association of the TRPV1–Akt–AMPK–eNOS complex, eNOS activation, NO production and angiogenesis.
    June 29, 2016   doi: 10.1111/apha.12723   open full text
  • P/Q‐type and T‐type voltage‐gated calcium channels are involved in the contraction of mammary and brain blood vessels from hypertensive patients.
    A. D. Thuesen, K. S. Lyngsø, L. Rasmussen, J. Stubbe, O. Skøtt, F. R. Poulsen, C. B. Pedersen, L. M. Rasmussen, P. B. L. Hansen.
    Acta Physiologica. June 29, 2016
    Aim Calcium channel blockers are widely used in cardiovascular diseases. Besides L‐type channels, T‐ and P/Q‐type calcium channels are involved in the contraction of human renal blood vessels. It was hypothesized that T‐ and P/Q‐type channels are involved in the contraction of human brain and mammary blood vessels. Methods Internal mammary arteries from bypass surgery patients and cerebral arterioles from patients with brain tumours with and without hypertension were tested in a myograph and perfusion set‐up. PCR and immunohistochemistry were performed on isolated blood vessels. Results The P/Q‐type antagonist ω‐agatoxin IVA (10−8 mol L−1) and the T‐type calcium blocker mibefradil (10−7 mol L−1) inhibited KCl depolarization‐induced contraction in mammary arteries from hypertensive patients with no effect on blood vessels from normotensive patients. ω‐Agatoxin IVA decreased contraction in cerebral arterioles from hypertensive patients. L‐type blocker nifedipine abolished the contraction in mammary arteries. PCR analysis showed expression of P/Q‐type (Cav2.1), T‐type (Cav3.1 and Cav3.2) and L‐type (Cav1.2) calcium channels in mammary and cerebral arteries. Immunohistochemical labelling of mammary and cerebral arteries revealed the presence of Cav2.1 in endothelial and smooth muscle cells. Cav3.1 was also detected in mammary arteries. Conclusion P/Q‐ and T‐type Cav are present in human internal mammary arteries and in cerebral penetrating arterioles. P/Q‐ and T‐type calcium channels are involved in the contraction of mammary arteries from hypertensive patients but not from normotensive patients. Furthermore, in cerebral arterioles P/Q‐type channels importance was restricted to hypertensive patients might lead to that T‐ and P/Q‐type channels could be a new target in hypertensive patients.
    June 29, 2016   doi: 10.1111/apha.12732   open full text
  • Pro‐inflammatory cytokines, IL‐1β and TNF‐α, produce persistent compromise in tonic immobility defensive behaviour in endotoxemia guinea‐pigs.
    A. B. Ribeiro, P. C. G. Barcellos‐Filho, C. R. Franci, L. Menescal‐de‐Oliveira, R. S. Saia.
    Acta Physiologica. June 28, 2016
    Aim Sepsis has been associated with acute behavioural changes in humans and rodents, which consists of a motivational state and an adaptive response that improve survival. However, the involvement of peripheral cytokines synthesized during systemic inflammation as modulators of the tonic immobility (TI) defensive behaviour remains a literature gap. Our purposes were to characterize the TI defensive behaviour in endotoxemia guinea‐pigs at acute phase and after recovery from the initial inflammatory challenge. Furthermore, we investigated whether peri‐aqueductal grey matter (PAG) exists as a brain structure related to this behaviour and also pro‐inflammatory cytokines, tumour necrosis factor (TNF)‐α and interleukin (IL)‐1β, act at this mesencephalic nucleus. Methods Endotoxemia was induced by lipopolysaccharide (LPS) administration in guinea‐pigs. The parameters evaluated included TI defensive behaviour, survival, cytokines production, as well as neuronal activation and apoptosis in the PAG. Results Endotoxemia guinea‐pigs exhibited a reduction in the duration of TI episodes, starting at 2 h after LPS administration and persisting throughout the experimental period evaluated over 7 days. Moreover, endotoxemia increased the c‐FOS immunoreactivity of neurones in the ventrolateral PAG (vlPAG), as well as the caspase‐3 expression. The LPS microinjection into vlPAG reproduces the same compromise, that is a decrease in the duration of TI defensive behaviour, observed after the peripheral administration. The immunoneutralization against IL‐1β and TNF‐α into vlPAG reverts all the effects produced by peripheral LPS administration. Conclusion Our findings confirm that vlPAG is an important brain structure involved in the behavioural alterations induced by endotoxemia, possibly changing the neuronal activity caused by pro‐inflammatory cytokines produced peripherally.
    June 28, 2016   doi: 10.1111/apha.12729   open full text
  • Long‐term exercise training prevents mammary tumorigenesis‐induced muscle wasting in rats through the regulation of TWEAK signalling.
    A. I. Padrão, A. C. C. Figueira, A. I. Faustino‐Rocha, A. Gama, M. M. Loureiro, M. J. Neuparth, D. Moreira‐Gonçalves, R. Vitorino, F. Amado, L. L. Santos, P. A. Oliveira, J. A. Duarte, R. Ferreira.
    Acta Physiologica. June 27, 2016
    Aim Exercise training has been suggested as a non‐pharmacological approach to prevent skeletal muscle wasting and improve muscle function in cancer cachexia. However, little is known about the molecular mechanisms underlying such beneficial effect. In this study, we aimed to, firstly, examine the contribution of TWEAK signalling to cancer‐induced skeletal muscle wasting and, secondly, evaluate whether long‐term exercise alters TWEAK signalling and prevents muscle wasting. Methods Female Sprague‐Dawley rats were randomly assigned to control and exercise groups. Fifteen animals from each group were exposed to N‐Methyl‐N‐nitrosourea carcinogen. Animals in exercise groups were submitted to moderate treadmill exercise for 35 weeks. After the experimental period, animals were killed and gastrocnemius muscles were harvested for morphological and biochemical analysis. Results We verified that exercise training prevented tumour‐induced TWEAK/NF‐κB signalling in skeletal muscle with a beneficial impact in fibre cross‐sectional area and metabolism. Indeed, 35 weeks of exercise training promoted the upregulation of PGC‐1α and oxidative phosphorylation complexes. This exercise‐induced muscle remodelling in tumour‐bearing animals was associated with less malignant mammary lesions. Conclusion Data support the benefits of an active lifestyle for the prevention of muscle wasting secondary to breast cancer, highlighting TWEAK/NF‐ κB signalling as a potential therapeutic target for the preservation of muscle mass.
    June 27, 2016   doi: 10.1111/apha.12721   open full text
  • Haemodiafiltration at increased plasma ionic strength for improved protein‐bound toxin removal.
    D. H. Krieter, E. Devine, T. Körner, M. Rüth, C. Wanner, M. Raine, J. Jankowski, H.‐D. Lemke.
    Acta Physiologica. June 22, 2016
    Aim Protein‐bound uraemic toxin accumulation causes uraemia‐associated cardiovascular morbidity. Enhancing the plasma ionic strength releases toxins from protein binding and makes them available for removal during dialysis. This concept was implemented through high sodium concentrations ([Na+]) in the substituate of pre‐dilution haemodiafiltration at increased plasma ionic strength (HDF‐IPIS). Methods Ex vivo HDF‐IPIS with blood tested increasing [Na+] to demonstrate efficacy and haemocompatibility. Haemocompatibility was further assessed in sheep using two different HDF‐IPIS set‐ups and [Na+] between 350 and 600 mmol L−1. Safety and efficacy of para‐cresyl sulphate (pCS) and indoxyl sulphate (IS) removal was further investigated in a randomized clinical pilot trial comparing HDF‐IPIS to HD and HDF. Results Compared to [Na+] of 150 mmol L−1, ex vivo HDF‐IPIS at 500 mmol L−1 demonstrated up to 50% higher IS removal. Haemolysis in sheep was low even at [Na+] of 600 mmol L−1 (free Hb 0.016 ± 0.001 g dL−1). In patients, compared to HD, a [Na+] of 240 mmol L−1 in HDF‐IPIS resulted in 40% greater reduction (48.7 ± 23.6 vs. 67.8 ± 7.9%; P = 0.013) in free IS. Compared to HD and HDF (23.0 ± 14.8 and 25.4 ± 10.5 mL min−1), the dialytic clearance of free IS was 31.6 ± 12.8 mL min−1 (P = 0.017) in HDF‐IPIS, but [Na+] in arterial blood increased from 132 ± 2 to 136 ± 3 mmol L−1 (0 vs. 240 min; P < 0.001). Conclusion HDF‐IPIS is technically and clinically feasible. More effective HDF‐IPIS requires higher temporary plasma [Na+], but dialysate [Na+] has to be appropriately adapted to avoid sodium accumulation.
    June 22, 2016   doi: 10.1111/apha.12730   open full text
  • Adenine‐induced chronic renal failure in rats decreases aortic relaxation rate and alters expression of proteins involved in vascular smooth muscle calcium handling.
    L. Nguy, E. Shubbar, M. Jernås, I. Nookaew, J. Lundgren, B. Olsson, H. Nilsson, G. Guron.
    Acta Physiologica. June 19, 2016
    Aim Rats with adenine‐induced chronic renal failure (A‐CRF) develop a reduced rate of relaxation of the thoracic aorta. The aim of this study was to elucidate the mechanisms underlying this abnormality. Methods Male Sprague Dawley rats received either chow containing adenine or were pair‐fed with normal chow (controls). After 8–14 weeks, arterial function was analysed ex vivo using wire myography and the expression of proteins involved in vascular smooth muscle excitation–contraction coupling in the thoracic aorta was analysed. Results The rate of relaxation following washout of KCl was reduced in A‐CRF rats vs. controls in the thoracic aorta (P < 0.01), abdominal aorta (P < 0.05), and common carotid artery (P < 0.05), but not in the common femoral artery. Relaxation rates of thoracic aortas increased (P < 0.01), but were not normalized, in response to washout of KCl with Ca2+‐free buffer. Microarray and qRT‐PCR analyses of genes involved in excitation–contraction coupling identified 10 genes, which showed significantly altered expression in A‐CRF thoracic aortas. At the protein level, the α2 subunit of the Na,K‐ATPase (P < 0.001) and SERCA2 (P < 0.05) was significantly downregulated, whereas stromal interaction molecule 1 and calsequestrin‐1 and calsequestrin‐2 were significantly upregulated (P < 0.05). Conclusions Rats with A‐CRF show a marked alteration in relaxation of larger conduit arteries localized proximal to the common femoral artery. This abnormality may be caused by reduced cytosolic Ca2+ clearance in vascular smooth muscle cells secondary to dysregulation of proteins crucially involved in this process.
    June 19, 2016   doi: 10.1111/apha.12724   open full text
  • Morphometry of skeletal muscle capillaries: the relationship between capillary ultrastructure and ageing in humans.
    M. Bigler, D. Koutsantonis, A. Odriozola, S. Halm, S. A. Tschanz, A. Zakrzewicz, A. Weichert, O. Baum.
    Acta Physiologica. June 16, 2016
    Aim To determine whether the ultrastructure of the capillary system in human skeletal muscle changes during advancing senescence, we evaluated the compartmental and subcompartmental organization of capillaries from vastus lateralis muscle (VL) biopsies of 41 non‐diseased persons aged 23–75 years. Methods From each VL biopsy, 38–40 randomly selected capillaries were assessed by transmission electron microscopy and subsequent morphometry with a newly established tablet‐based image analysis technique. Results Quantification of the compartmental organization revealed most indicators of the capillary ultrastructure to be only non‐significantly altered (P > 0.05) over age. However, the peri‐capillary basement membrane (BM) was thicker in the older participants than in the younger ones (P ≤ 0.05). Regression analysis revealed a bipartite relationship between the two parameters: a homogenous slight increase in BM thickness up to the age of approximately 50 years was followed by a second phase with more scattered BM thickness values. In 44.5% of the capillary profiles, projections/filopodia of the pericytes (PCs) traversed the BM and invaded endothelial cells (ECs) visible as PC pegs in pale cytoplasm holes (EC sockets). Strikingly, PC pegs were often in proximity to the EC nucleus. In PC profiles, sockets were likewise detected in 14.2% of the capillaries. Within these PC sockets, cellular profiles were frequently seen, which could be assigned to EC filopodia, internal PC curling or PC–PC interactions. Quantification of the occurrence of peg–socket junctions revealed the proportions of empty EC sockets and empty PC sockets to increase (P ≤ 0.05) during ageing. Conclusion Our investigation demonstrates advancing senescence to be associated with increase in BM thickness and loss of EC and PC filopodia length in skeletal muscle capillaries.
    June 16, 2016   doi: 10.1111/apha.12709   open full text
  • Na+ dependence of K+‐induced natriuresis, kaliuresis and Na+/Cl− cotransporter dephosphorylation.
    I. S. Jensen, C. K. Larsen, J. Leipziger, M. V. Sørensen.
    Acta Physiologica. June 15, 2016
    Aim High dietary K+ intake is associated with protection against hypertension. In mammals, acute K+ intake induces natriuresis and kaliuresis, associated with a marked dephosphorylation of the renal Na+/Cl− cotransporter (NCC). It has been suggested that reduced activity of NCC increases the driving force for more distal tubular epithelial Na+ channel (ENaC)‐dependent K+ secretion. This study investigated the ENaC dependence of urinary K+ and Na+ excretion following acute K+ loading. Methods Mice were fed low (0.03%), control (0.2%) or high (2%) Na+ diets for 25 days to preserve or promote Na+ loss and thus ENaC activity. Once a week, the mice received either K+‐containing gavage or a control gavage. Following the gavage treatment, the mice were placed in metabolic cages and urine was collected in real time. ENaC dependence of kaliuresis was assessed by benzamil injections prior to gavage. Results We confirmed that dietary Na+ content is inversely related to plasma aldosterone, NCC phosphorylation and ENaC cleavage products. The novel findings were as follows: (i) acute K+ feeding caused NCC dephosphorylation in all dietary groups; (ii) under all dietary conditions, K+ loading induced natriuresis; (iii) high Na+ diet markedly reduced the K+ excretion following K+ gavage; (iv) benzamil injection prior to K+ loading increased natriuresis, decreased kaliuresis and eliminated the differences between the dietary groups. Conclusion These data indicate that acute K+‐induced kaliuresis is ENaC dependent. Maximal K+ excretion rates are attenuated when ENaC is physiologically down‐regulated or pharmacologically blocked. NCC is dephosphorylated following acute K+ loading under all dietary Na+ regimens. This leads to natriuresis, even in severely Na+‐restricted animals.
    June 15, 2016   doi: 10.1111/apha.12707   open full text
  • Coupling of myocardial stress resistance and signalling to voluntary activity and inactivity.
    B. P. Budiono, L. E. See Hoe, A. R. Brunt, J. N. Peart, J. P. Headrick, L. J. Haseler.
    Acta Physiologica. June 15, 2016
    Aims We examined coupling of myocardial ischaemic tolerance to physical activity and inactivity, and whether this involves modulation of survival (AKT, AMPK, ERK1/2, HSP27, EGFR) and injury (GSK3β) proteins implicated in ischaemic preconditioning and calorie restriction. Methods Proteomic modifications were assessed in ventricular myocardium, and tolerance to 25‐min ischaemia in ex vivo perfused hearts from C57Bl/6 mice subjected to 14‐day voluntary activity in running‐naïve animals (Active); 7 days of subsequent inactivity (Inactive); brief (day 3) restoration of running (Re‐Active); or time‐matched inactivity. Results Active mice increased running speed and distance by 75–150% over 14 days (to ~40 m min−1 and 10 km day−1), with Active hearts resistant to post‐ischaemic dysfunction (40–50% improvements in ventricular pressure development, diastolic pressure and dP/dt). Cardioprotection was accompanied by ~twofold elevations in AKT, AMPK, HSP27 and GSK3β phosphorylation and EGFR expression. Ischaemic tolerance was reversed in Inactive hearts, paralleling reduced EGFR expression and GSK3β and ERK1/2 phosphorylation (AKT, AMPK, HSP27 phosphorylation unaltered). Running characteristics, ischaemic tolerance, EGFR expression and GSK3β phosphorylation returned to Active levels within 1–3 days of restored activity (without changes in AKT, AMPK or HSP27 phosphorylation). Transcriptional responses included activity‐dependent Anp induction vs. Hmox1 and Sirt3 suppression, and inactivity‐dependent Adora2b induction. Conclusions Data confirm the sensitive coupling of ischaemic tolerance to activity: voluntary running induces cardioprotection that dissipates within 1 week of inactivity yet recovers rapidly upon subsequent activity. While exercise in naïve animals induces a molecular profile characteristic of preconditioning/calorie restriction, only GSK3β and EGFR modulation consistently parallel activity‐ and inactivity‐dependent ischaemic tolerance.
    June 15, 2016   doi: 10.1111/apha.12710   open full text
  • Elk‐1‐mediated 15‐lipoxygenase expression is required for hypoxia‐induced pulmonary vascular adventitial fibroblast dynamics.
    Y. Li, L. Zhang, X. Wang, M. Chen, Y. Liu, Y. Xing, X. Wang, S. Gao, D. Zhu.
    Acta Physiologica. June 03, 2016
    Aim 15‐Lipoxygenase (15‐LO) is an important factor in the pathogenesis of pulmonary artery hypertension (PAH). However, the role of 15‐LO in the adventitia of the pulmonary arterial wall is unclear. The aim of this study was to explore the role of 15‐LO in the modulation of pulmonary adventitial fibroblast (PAF) dynamics. Methods Rats were exposed to normoxic or hypoxic (fraction of inspired O2 = 0.12) treatments for 7 days. PAF proliferation and cell cycle alterations were measured by MTT assay, cell immunofluorescence, flow cytometry and Western blot analysis. The 15‐LO promoter was analysed by luciferase reporter and ChIP assays. Results Our results showed that hypoxia induced 15‐LO expression in PAFs both in vivo and in vitro. In addition, hypoxia stimulated JNK phosphorylation in PAFs. Blocking 15‐LO or JNK suppressed 15‐LO‐induced PAF proliferation and cell cycle alterations. The inhibition of p27kipl by gene silencing attenuated 15‐LO‐induced PAF proliferation and cell cycle alterations. Furthermore, JNK inhibition or Elk‐1 knockdown suppressed hypoxia‐induced 15‐LO expression in PAFs. Luciferase reporter and ChIP assays revealed that the 15‐LO promoter contains Elk‐1‐binding sites and also that Elk‐1 increased the hypoxia‐induced activity of the 15‐LO promoter. Conclusion These results suggest that hypoxia promotes changes in the cellular dynamics of PAFs by inducing 15‐LO expression, which leads to vascular adventitial remodelling. The modulation of p27kipl expression by 15‐LO enhances PAF proliferation and cell cycle alterations. Furthermore, the JNK‐dependent increase in Elk‐1 signalling is required for hypoxia‐induced 15‐LO expression in PAFs.
    June 03, 2016   doi: 10.1111/apha.12711   open full text
  • Reduction in central venous pressure enhances erythropoietin synthesis: role of volume‐regulating hormones.
    D. Montero, S. Rauber, J. P. Goetze, C. Lundby.
    Acta Physiologica. June 01, 2016
    Aims Erythropoiesis is a tightly controlled biological event, but its regulation under non‐hypoxic conditions, however, remains unresolved. We examined whether acute changes in central venous blood pressure (CVP) elicited by whole‐body tilting affect erythropoietin (EPO) concentration according to volume‐regulating hormones. Methods Plasma EPO, angiotensin II (ANGII), aldosterone, pro‐atrial natriuretic peptide (proANP) and copeptin concentrations were measured at supine rest and up to 3 h during 30° head‐up (HUT) and head‐down tilt (HDT) in ten healthy male volunteers. Plasma albumin concentration was used to correct for changes in plasma volume and CVP was estimated through the internal jugular vein (IJV) aspect ratio with ultrasonography. Results From supine rest, the IJV aspect ratio was decreased and increased throughout HUT and HDT respectively. Plasma EPO concentration increased during HUT (13%; P = 0.001, P for linear component = 0.017), independent of changes in albumin concentration. Moreover, ANGII and copeptin concentrations increased during HUT, while proANP decreased. The increase in EPO concentration during HUT disappeared when adjusted for changes in copeptin. During HDT, EPO, ANGII and copeptin concentrations remained unaffected while proANP increased. In regression analyses, EPO was positively associated with copeptin (β = 0.55; 95% CI = 0.18, 0.93; P = 0.004) irrespective of changes in other hormones and albumin concentration. Conclusion Reduction in CVP prompts an increase in plasma EPO concentration independent of hemoconcentration and hence suggests CVP per se as an acute regulator of EPO synthesis. This effect may be explained by changes in volume‐regulating hormones.
    June 01, 2016   doi: 10.1111/apha.12708   open full text
  • Is Plasminogen Activator Inihibitor‐1 a Physiological Bottleneck Bridging Major Depressive Disorder (MDD) and Cardiovascular Disease (CVD)?
    Calan Savoy, Ryan J. Van Lieshout, Meir Steiner.
    Acta Physiologica. June 01, 2016
    Major Depressive Disorder (MDD) is estimated to affect one in twenty people worldwide. MDD is highly co‐morbid with cardiovascular disease (CVD), itself one of the single largest causes of mortality worldwide. A number of pathological changes observed in MDD are believed to contribute to the development of cardiovascular disease, although no single mechanism has been identified. There are also no biological markers capable of predicting the future risk of developing heart disease in depressed individuals. Plasminogen Activator Inhibitor 1(PAI‐1) is a pro‐thrombotic plasma protein secreted by endothelial tissue and has long been implicated in CVD. An expanding body of literature has recently implicated it in the pathogenesis of Major Depressive Disorder as well. In this paper we review candidate pathways implicating MDD in CVD and consider how PAI‐1 might act as a mediator by which MDD induces CVD development; chiefly through sleep disruption, adiposity, Brain Derived Neurotrophic Factor (BDNF) metabolism, systemic inflammation, and Hypothalamic‐Pituitary‐Adrenal (HPA) axis dysregulation. As both MDD and CVD are more prevalent in women than men, and both incidence of either condition is dramatically increased during reproductive milestones, we also explore hormonal and sex specific associations between MDD, PAI‐1 and CVD. Of special interest is the role PAI‐1 plays in perinatal depression and in cardiovascular complications of pregnancy. Finally, we propose a theoretical model whereby PAI‐1 might serve as a useful biomarker for CVD risk in those with depression, and as a potential target for future treatments. This article is protected by copyright. All rights reserved.
    June 01, 2016   doi: 10.1111/apha.12726   open full text
  • Uraemia: an unrecognised driver of central neurohumoral dysfunction in chronic kidney disease?
    Conor F. Underwood, Cara M. Hildreth, Benjamin F. Wyse, Rochelle Boyd, Ann K. Goodchild, Jacqueline K. Phillips.
    Acta Physiologica. June 01, 2016
    Chronic kidney disease (CKD) carries a large cardiovascular burden in part due to hypertension and neurohumoral dysfunction – manifesting as sympathetic overactivity, baroreflex dysfunction and chronically elevated circulating vasopressin. Alterations within the central nervous system (CNS) are necessary for the expression of neurohumoral dysfunction in CKD however the underlying mechanisms are poorly defined. Uraemic toxins are a diverse group of compounds that accumulate as a direct result of renal disease and drive dysfunction in multiple organs, including the brain. Intensive haemodialysis improves both sympathetic overactivity and cardiac baroreflex sensitivity in renal failure patients, indicating that uraemic toxins participate in the maintenance of autonomic dysfunction in CKD. In rodents exposed to uraemia, immediate early gene expression analysis suggests upregulated activity of not only presympathetic but also vasopressin‐secretory nuclei. We outline several potential mechanisms by which uraemia might drive neurohumoral dysfunction in CKD. These include superoxide‐dependent effects on neural activity, depletion of nitric oxide and induction of low‐grade systemic inflammation. Recent evidence has highlighted superoxide production as an intermediate for the depolarising effect of some uraemic toxins on neuronal cells. We provide preliminary data indicating augmented superoxide production within the hypothalamic paraventricular nucleus in the Lewis Polycystic Kidney rat, which might be important for mediating the neurohumoral dysfunction exhibited in this CKD model. We speculate that the uraemic state might serve to sensitise the central actions of other sympathoexcitatory factors, including renal afferent nerve inputs to the CNS and angiotensin II, by way of recruiting convergent superoxide‐dependent and pro‐inflammatory pathways. This article is protected by copyright. All rights reserved.
    June 01, 2016   doi: 10.1111/apha.12727   open full text
  • Effects of shear stress on endothelial cells: go with the flow.
    Dmitry A. Chistiakov, Alexander N. Orekhov, Yuri V. Bobryshev.
    Acta Physiologica. June 01, 2016
    Hemodynamic forces influence functional properties of vascular endothelium. Endothelial cells have a variety of receptors, which sense flow and transmit mechanical signals through mechanosensitive signaling pathways to recipient molecules, that lead to phenotypic and functional changes. Arterial architecture varies greatly exhibiting bifurcations, branch points, and curved regions, which are exposed to various flow patterns. Clinical studies showed that atherosclerotic plaques develop preferentially at arterial branches and curvatures, i.e. in the regions exposed to disturbed flow and shear stress. In the atheroprone regions, the endothelium has a proinflammatory phenotype associated with low nitric oxide production, reduced barrier function, and increased proadhesive, procoagulant, and proproliferative properties. Atheroresistant regions are exposed to laminar flow and high shear stress that induce prosurvival antioxidant signals and maintain the quiescent phenotype in endothelial cells. Indeed, various flow patterns contribute to phenotypic and functional heterogeneity of arterial endothelium whose response to proatherogenic stimuli is differentiated. This may explain the preferential development of endothelial dysfunction in arterial sites with disturbed flow. This article is protected by copyright. All rights reserved.
    June 01, 2016   doi: 10.1111/apha.12725   open full text
  • TRPV4 channels in the human urogenital tract play a role in cell junction formation and epithelial barrier.
    D. A. W. Janssen, C. J. F. Jansen, T. G. Hafmans, G. W. Verhaegh, J. G. Hoenderop, J. P. F. A. Heesakkers, J. A. Schalken.
    Acta Physiologica. May 25, 2016
    Aim The molecular interactions between transient receptor potential vanilloid subtype 4 channels (TRPV4) and cell junction formation were investigated in the human and mouse urogenital tract. Materials and Methods A qualitative study was performed to investigate TRPV4 channels, adherence junctions (AJs) and tight junctions (TJs) in kidney, ureter and bladder tissues from humans and wild‐type and transgenic TRPV4 knockout (−/−) mice with immunohistochemistry, Western blotting, immunoprecipitation and reverse trasnscription‐PCR. Cell junction formation in the wild‐type and TRPV4 knockout (−/−) mouse was evaluated with immunohistochemistry and transmission electron microscope (TEM) techniques. Results TRPV4 channels are predominantly located in membranes of epithelial cells of the bladder, ureter and the collecting ducts of the kidney. There is a molecular interaction between the TRPV4 channel and the AJ. TEM evaluation showed that AJ formation is disrupted in the TRPV4 −/− mouse resulting in deficient intercellular connections and integrity of the epithelium. Conclusions TRPV4 is believed to be a mechanoreceptor in the bladder. This study demonstrates that TRPV4 is also involved in intercellular connectivity and structural integrity of the epithelium.
    May 25, 2016   doi: 10.1111/apha.12701   open full text
  • Reversing dobutamine‐induced tachycardia using ivabradine increases stroke volume with neutral effect on cardiac energetics in left ventricular post‐ischaemia dysfunction.
    J. P. Bakkehaug, T. Næsheim, E. Torgersen Engstad, A. B. Kildal, T. Myrmel, O.‐J. How.
    Acta Physiologica. May 24, 2016
    Aim Compensatory tachycardia can potentially be deleterious in acute heart failure. In this study, we tested a therapeutic strategy of combined inotropic support (dobutamine) and selective heart rate (HR) reduction through administration of ivabradine. Methods In an open‐chest pig model (n = 12) with left ventricular (LV) post‐ischaemia dysfunction, cardiac function was assessed by LV pressure catheter and sonometric crystals. Coronary flow and blood samples from the coronary sinus were used to measure myocardial oxygen consumption (MVO2). LV energetics was assessed by comparing MVO2 with cardiac work at a wide range of workloads. Results In the post‐ischaemia heart, dobutamine (5 μg kg−1 min−1) increased cardiac output (CO) by increasing HR from 102 ± 21 to 131 ± 16 bpm (beats per min; P < 0.05). Adding ivabradine (0.5 mg kg−1) slowed HR back to 100 ± 9 bpm and increased stroke volume from 30 ± 5 to 36 ± 5 mL (P < 0.05) by prolonging diastolic filling time and increasing end‐diastolic dimensions. Adding ivabradine had no adverse effects on CO, mean arterial pressure and cardiac efficiency. Similar findings on efficiency and LV function were also seen using an ex vivo working mouse heart protocol. Conclusions A combined infusion of dobutamine and ivabradine had a neutral effect on post‐ischaemia LV efficiency and increased left ventricular output without an increase in HR.
    May 24, 2016   doi: 10.1111/apha.12704   open full text
  • Normotension, hypertension and body fluid regulation: Brain and kidney.
    Peter Bie, Roger G. Evans.
    Acta Physiologica. May 23, 2016
    The fraction of hypertensive patients with essential hypertension (EH) is decreasing as the knowledge of mechanisms of secondary hypertension increase, but in most new cases of hypertension the pathophysiology remains unknown. Separate neurocentric and renocentric concepts of etiology have prevailed without much interaction. In this regard, several questions regarding the relationships between body fluid and blood pressure regulation are pertinent. Are all forms of EH associated with sympathetic overdrive or a shift in the pressure natriuresis curve? Is body fluid homeostasis normally driven by the influence of arterial blood pressure directly on the kidney? Does plasma renin activity, driven by renal nerve activity and renal arterial pressure, provide a key to stratification of EH? Our review indicates that (i) a narrow definition of EH is useful, (ii) in EH, indices of cardiovascular sympathetic activity are elevated in about 50% of cases, (iii) in EH as in normal conditions, mediators other than arterial blood pressure are the major determinants of renal sodium excretion, (iv) chronic hypertension is always associated with a shift in the pressure natriuresis curve, but this may be an epiphenomenon, (v) plasma renin levels are useful in the analysis of EH only after metabolic standardization and then determination of the renin function line (plasma renin as a function of sodium intake), and (vi) angiotensin II mediated hypertension is not a model of EH. Recent studies of baroreceptors and renal nerves as well as sodium intake and renin secretion help bridge the gap between the neurocentric and renocentric concepts. This article is protected by copyright. All rights reserved.
    May 23, 2016   doi: 10.1111/apha.12718   open full text
  • Fibroblast growth factor 21 (FGF21) therapy attenuates left ventricular dysfunction and metabolic disturbance by improving FGF21 sensitivity, cardiac mitochondrial redox homoeostasis and structural changes in pre‐diabetic rats.
    P. Tanajak, P. Sa‐nguanmoo, X. Wang, G. Liang, X. Li, C. Jiang, S. C. Chattipakorn, N. Chattipakorn.
    Acta Physiologica. May 20, 2016
    Aims Fibroblast growth factor 21 (FGF21) acts as a metabolic regulator and exerts cardioprotective effects. However, the effects of long‐term FGF21 administration on the heart under the FGF21‐resistant condition in obese, insulin‐resistant rats have not been investigated. We hypothesized that long‐term FGF21 administration reduces FGF21 resistance and insulin resistance and attenuates cardiac dysfunction in obese, insulin‐resistant rats. Methods Eighteen rats were fed on either a normal diet (n = 6) or a high‐fat diet (HFD; n = 12) for 12 weeks. Then, rats in the HFD group were divided into two subgroups (n = 6 per subgroup) and received either the vehicle (HFV) or recombinant human FGF21 (rhFGF21, 0.1 mg kg−1 day−1; HFF) injected intraperitoneally for 28 days. The metabolic parameters, inflammation, malondialdehyde (MDA), heart rate variability (HRV), left ventricular (LV) function, cardiac mitochondrial redox homoeostasis, cardiac mitochondrial fatty acid β‐oxidation (FAO) and anti‐apoptotic signalling pathways were determined. Results HFV rats had increased dyslipidaemia, insulin resistance, plasma FGF21 levels, TNF‐α, adiponectin and MDA, depressed HRV, and impaired LV and mitochondrial function. HFV rats also had decreased cardiac Bcl‐2, cardiac PGC‐1α and CPT‐1 protein expression. However, FGF21 restored metabolic parameters, decreased TNF‐α and MDA, increased serum adiponectin, and improved HRV, cardiac mitochondrial and LV function in HFF rats. Moreover, HFF rats had increased cardiac Bcl‐2, cardiac PGC‐1α and CPT‐1 protein expression. Conclusion Long‐term FGF21 therapy attenuates FGF21 resistance and insulin resistance and exerts cardioprotection by improving cardiometabolic regulation via activating anti‐apoptotic and cardiac mitochondrial FAO signalling pathways in obese, insulin‐resistant rats.
    May 20, 2016   doi: 10.1111/apha.12698   open full text
  • PAFAH1B1 and the lncRNA NONHSAT073641 maintain an angiogenic phenotype in human endothelial cells.
    I. Josipovic, C. Fork, J. Preussner, K‐K. Prior, D. Iloska, A. E. Vasconez, S. Labocha, C. Angioni, D. Thomas, N. Ferreirós, M. Looso, S. S. Pullamsetti, G. Geisslinger, D. Steinhilber, R. P. Brandes, M. S. Leisegang.
    Acta Physiologica. May 20, 2016
    Aim Platelet‐activating factor acetyl hydrolase 1B1 (PAFAH1B1, also known as Lis1) is a protein essentially involved in neurogenesis and mostly studied in the nervous system. As we observed a significant expression of PAFAH1B1 in the vascular system, we hypothesized that PAFAH1B1 is important during angiogenesis of endothelial cells as well as in human vascular diseases. Method The functional relevance of the protein in endothelial cell angiogenic function, its downstream targets and the influence of NONHSAT073641, a long non‐coding RNA (lncRNA) with 92% similarity to PAFAH1B1, were studied by knockdown and overexpression in human umbilical vein endothelial cells (HUVEC). Results Knockdown of PAFAH1B1 led to impaired tube formation of HUVEC and decreased sprouting in the spheroid assay. Accordingly, the overexpression of PAFAH1B1 increased tube number, sprout length and sprout number. LncRNA NONHSAT073641 behaved similarly. Microarray analysis after PAFAH1B1 knockdown and its overexpression indicated that the protein maintains Matrix Gla Protein (MGP) expression. Chromatin immunoprecipitation experiments revealed that PAFAH1B1 is required for active histone marks and proper binding of RNA Polymerase II to the transcriptional start site of MGP. MGP itself was required for endothelial angiogenic capacity and knockdown of both, PAFAH1B1 and MGP, reduced migration. In vascular samples of patients with chronic thromboembolic pulmonary hypertension (CTEPH), PAFAH1B1 and MGP were upregulated. The function of PAFAH1B1 required the presence of the intact protein as overexpression of NONHSAT073641, which was highly upregulated during CTEPH, did not affect PAFAH1B1 target genes. Conclusion PAFAH1B1 and NONHSAT073641 are important for endothelial angiogenic function.
    May 20, 2016   doi: 10.1111/apha.12700   open full text
  • Increased microvascular permeability in mice lacking Epac1 (Rapgef3).
    R. K. Kopperud, C. Brekke Rygh, T. V. Karlsen, C. Krakstad, R. Kleppe, E. A. Hoivik, M. Bakke, O. Tenstad, F. Selheim, Å. Lidén, L. Madsen, T. Pavlin, T. Taxt, K. Kristiansen, F.‐R. E. Curry, R. K. Reed, S. O. Døskeland.
    Acta Physiologica. May 17, 2016
    Aim Maintenance of the blood and extracellular volume requires tight control of endothelial macromolecule permeability, which is regulated by cAMP signalling. This study probes the role of the cAMP mediators rap guanine nucleotide exchange factor 3 and 4 (Epac1 and Epac2) for in vivo control of microvascular macromolecule permeability under basal conditions. Methods Epac1−/− and Epac2−/− C57BL/6J mice were produced and compared with wild‐type mice for transvascular flux of radio‐labelled albumin in skin, adipose tissue, intestine, heart and skeletal muscle. The transvascular leakage was also studied by dynamic contrast‐enhanced magnetic resonance imaging (DCE‐MRI) using the MRI contrast agent Gadomer‐17 as probe. Results Epac1−/− mice had constitutively increased transvascular macromolecule transport, indicating Epac1‐dependent restriction of baseline permeability. In addition, Epac1−/− mice showed little or no enhancement of vascular permeability in response to atrial natriuretic peptide (ANP), whether probed with labelled albumin or Gadomer‐17. Epac2−/− and wild‐type mice had similar basal and ANP‐stimulated clearances. Ultrastructure analysis revealed that Epac1−/− microvascular interendothelial junctions had constitutively less junctional complex. Conclusion Epac1 exerts a tonic inhibition of in vivo basal microvascular permeability. The loss of this tonic action increases baseline permeability, presumably by reducing the interendothelial permeability resistance. Part of the action of ANP to increase permeability in wild‐type microvessels may involve inhibition of the basal Epac1‐dependent activity.
    May 17, 2016   doi: 10.1111/apha.12697   open full text
  • Acute temperature effects on function of the chick embryonic heart.
    F. Vostarek, J. Svatunkova, D. Sedmera.
    Acta Physiologica. May 12, 2016
    Aim We analysed the effects of acute temperature change on the beating rate, conduction properties and calcium transients in the chick embryonic heart in vitro and in ovo. Methods The effects of temperature change (34, 37 and 40 °C) on calcium dynamics in isolated ED4 chick hearts in vitro were investigated by high‐speed calcium optical imaging. For comparison and validation of in vitro measurements, experiments were also performed in ovo using videomicroscopy. Artificial stimulation experiments were performed in vitro and in ovo to uncover conduction limits of heart segments. Results Decrease in temperature from 37 to 34 °C in vitro led to a 22% drop in heart rate and unchanged amplitude of Ca2+ transients, compared to a 25% heart rate decrease in ovo. Increase in temperature from 37 to 40 °C in vitro and in ovo led to 20 and 23% increases in heart rate, respectively, and a significant decrease in amplitude of Ca2+ transients (atrium −35%, ventricle −38%). We observed a wide spectrum of arrhythmias in vitro, of which the most common was atrioventricular (AV) block (57%). There was variability of AV block locations. Pacing experiments in vitro and in ovo suggested that the AV blocks were likely caused by relative tissue hypoxia and not by the tachycardia itself. Conclusion The pacemaker and AV canal are the most temperature‐sensitive segments of the embryonic heart. We suggest that the critical point for conduction is the connection of the ventricular trabecular network to the AV canal.
    May 12, 2016   doi: 10.1111/apha.12691   open full text
  • Intra‐cranial mechanisms for preserving brain blood flow in health and disease.
    Fiona D McBryde, Simon C Malpas, Julian FR Paton.
    Acta Physiologica. May 12, 2016
    The brain is an exceptionally energetically demanding organ with little metabolic reserve, and multiple systems operate to protect and preserve the brain blood supply. But how does the brain sense its own perfusion? In this review, we discuss how the brain may harness the cardiovascular system to counter threats to cerebral perfusion sensed via intracranial pressure (ICP), cerebral oxygenation and ischemia. Since the work of Cushing over 100 years ago, the existence of brain baroreceptors capable of eliciting increases in sympathetic outflow and blood pressure has been hypothesized. In the clinic, this response has generally been thought to occur only in extremis, to perfuse the severely ischemic brain as cerebral autoregulation fails. We review evidence that pressor responses may also occur with smaller, physiologically‐relevant increases in ICP. The incoming brain oxygen supply is closely monitored by the carotid chemoreceptors, however, hypoxia and other markers of ischemia are also sensed intrinsically by astrocytes or other support cells within brain tissue itself, and elicit reactive hyperaemia. Recent studies suggest that astrocytic oxygen signalling within the brainstem may directly affect sympathetic nerve activity and blood pressure. We speculate that local cerebral oxygen tension is a major determinant of the mean level of arterial pressure, and discuss recent evidence that this may be the case. We conclude that intrinsic intra‐ and extra‐cranial mechanisms sense and integrate information about hypoxia/ischemia and intracranial pressure, and play a major role in determining the long‐term level of sympathetic outflow and arterial pressure, in order to optimise cerebral perfusion. This article is protected by copyright. All rights reserved.
    May 12, 2016   doi: 10.1111/apha.12706   open full text
  • Heat shock transcription factor 1‐associated expression of slow myosin heavy chain in mouse soleus muscle in response to unloading with or without reloading.
    S. Yokoyama, Y. Ohno, T. Egawa, K. Yasuhara, A. Nakai, T. Sugiura, Y. Ohira, T. Yoshioka, M. Okita, T. Origuchi, K. Goto.
    Acta Physiologica. May 09, 2016
    Aim The effects of heat shock transcription factor 1 (HSF1) deficiency on the fibre type composition and the expression level of nuclear factor of activated T cells (NFAT) family members (NFATc1, NFATc2, NFATc3 and NFATc4), phosphorylated glycogen synthase kinase 3α (p‐GSK3α) and p‐GSK3β, microRNA‐208b (miR‐208b), miR‐499 and slow myosin heavy chain (MyHC) mRNAs (Myh7 and Myh7b) of antigravitational soleus muscle in response to unloading with or without reloading were investigated. Methods HSF1‐null and wild‐type mice were subjected to continuous 2‐week hindlimb suspension followed by 2‐ or 4‐week ambulation recovery. Results In wild‐type mice, the relative population of slow type I fibres, the expression level of NFATc2, p‐GSK3 (α and β), miR‐208b, miR‐499 and slow MyHC mRNAs (Myh7 and Myh7b) were all decreased with hindlimb suspension, but recovered after it. Significant interactions between train and time (the relative population of slow type I fibres; P = 0.01, the expression level of NFATc2; P = 0.001, p‐GSKβ; P = 0.009, miR‐208b; P = 0.002, miR‐499; P = 0.04) suggested that these responses were suppressed in HSF1‐null mice. Conclusion HSF1 may be a molecule in the regulation of the expression of slow MyHC as well as miR‐208b, miR‐499, NFATc2 and p‐GSK3 (α and β) in mouse soleus muscle.
    May 09, 2016   doi: 10.1111/apha.12692   open full text
  • Muscle immobilization activates mitophagy and disrupts mitochondrial dynamics in mice.
    C. Kang, D. Yeo, L. L. Ji.
    Acta Physiologica. April 30, 2016
    Aim Skeletal muscle atrophy following prolonged immobilization (IM) is a catabolic state characterized by increased proteolysis and functional deterioration. Previous research indicates that discord of mitochondrial homoeostasis plays a critical role in muscle atrophy. We hypothesized that muscle IM would activate the ubiquitin‐proteolysis, autophagy–lysosome (mitophagy) pathway, mitochondrial dynamics remodelling and apoptosis partially controlled by the FoxO signalling pathway. Methods Female FVB/N mice were randomly divided into five groups (n = 8 each): control (CON), IM with banding of one of the hindlimbs for 1, 2 and 3 weeks (1w‐, 2w‐ and 3w‐IM) and 2w‐IM followed by 1 week of remobilization (RM). Results Mitochondrial density and DNA copies in tibialis anterior (TA) muscle were reduced by approx. 80% (P < 0.05 for 2w‐IM; P < 0.01 for 3w‐IM), along with activation of FoxO3a, atrogin‐1 and MuRF1 following 2w‐ and 3w‐IM (P < 0.01). Protein markers of autophagy/mitophagy, such as beclin 1 (approx. 2.7‐fold; P < 0.01), LC3, ubiquitin‐binding adaptor (approx. 1.47‐fold; P < 0.01), Rheb (approx. 1.9‐fold; P < 0.05) and parkin (approx. 70%; P < 0.05), were all increased by IM and remained activated after RM, whereas BNIP3 and PINK1 levels were decreased by IM (P < 0.05), but elevated upon RM (P < 0.01). IM decreased Mfn2 expression (approx. 50%; P < 0.01) and increased Fis‐1 expression (approx. 2.4‐fold; P < 0.05). Muscle apoptosis indicator Bax/Bcl2 ratio was elevated at 2w‐ to 3w‐IM (approx. 3.7‐fold; P < 0.01), whereas caspase‐3 activity was five‐ to sixfold higher (P < 0.01) and remained threefold higher above CON (P < 0.05). Conclusion Our data indicate that IM‐induced mitochondrial deterioration is associated with altered protein expressions in the autophagic/mitophagic pathway, more fragmented mitochondrial network and activation of apoptosis partly under the influence of FoxO3 activation.
    April 30, 2016   doi: 10.1111/apha.12690   open full text
  • Lactobacillus reuteri increases mucus thickness and ameliorates dextran sulphate sodium‐induced colitis in mice.
    D. Ahl, H. Liu, O. Schreiber, S. Roos, M. Phillipson, L. Holm.
    Acta Physiologica. April 30, 2016
    Aim The aim of this study was to investigate whether two Lactobacillus reuteri strains (rat‐derived R2LC and human‐derived ATCC PTA 4659 (4659)) could protect mice against colitis, as well as delineate the mechanisms behind this protection. Methods Mice were given L. reuteri R2LC or 4659 by gavage once daily for 14 days, and colitis was induced by addition of 3% DSS (dextran sulphate sodium) to drinking water for the last 7 days of this period. The severity of disease was assessed through clinical observations, histological evaluation and ELISA measurements of myeloperoxidase (MPO) and pro‐inflammatory cytokines from colonic samples. Mucus thickness was measured in vivo with micropipettes, and tight junction protein expression was assessed using immunohistochemistry. Results Colitis severity was significantly reduced by L. reuteri R2LC or 4659 when evaluated both clinically and histologically. The inflammation markers MPO, IL‐1β, IL‐6 and mKC (mouse keratinocyte chemoattractant) were increased by DSS and significantly reduced by the L. reuteri strains. The firmly adherent mucus thickness was reduced by DSS, but significantly increased by L. reuteri in both control and DSS‐treated mice. Expression of the tight junction proteins occludin and ZO‐1 was significantly increased in the bottom of the colonic crypts by L. reuteri R2LC. Conclusion These results demonstrate that each of the two different L. reuteri strains, one human‐derived and one‐rat‐derived, protects against colitis in mice. Mechanisms behind this protection could at least partly be explained by the increased mucus thickness as well as a tightened epithelium in the stem cell area of the crypts.
    April 30, 2016   doi: 10.1111/apha.12695   open full text
  • Translational machinery of mitochondrial mRNA is promoted by physical activity in Western diet‐induced obese mice.
    D. E. Lee, J. L. Brown, M. E. Rosa, L. A. Brown, R. A. Perry, T. A. Washington, N. P. Greene.
    Acta Physiologica. April 25, 2016
    Aim Mitochondria‐encoded proteins are necessary for oxidative phosphorylation; however, no report has examined how physical activity (PA) and obesity affect mitochondrial mRNA translation machinery. Our purpose was to determine whether Western diet (WD)‐induced obesity and voluntary wheel running (VWR) impact mitochondrial mRNA translation machinery and whether expression of this machinery is dictated by oxidative phenotype. Methods Obesity was induced with 8‐wk WD feeding, and in the final 4 wks, half of mice were allowed VWR. Mitochondrial mRNA translation machinery including initiation factors (mtIF2/3), elongation factor Tu (TUFM) and translational activator (TACO1), and mitochondria‐encoded proteins (CytB and ND4) was assessed by immunoblotting. The relation of mitochondrial mRNA translation to muscle oxidative phenotype was assessed using PGC‐1α transgenic overexpression (MCK‐PGC‐1α vs. wild‐type mice) and comparing across muscle groups in wild‐type mice. Results mtIF3 and TACO1 proteins were ~45% greater in VWR than sedentary (SED), and TACO1 and mtIF2 proteins were ~60% and 125% greater in WD than normal chow (NC). TUFM protein was ~50% lower in WD‐SED than NC‐SED, but ~50% greater in WD‐VWR compared to NC‐SED. CytB and ND4 were ~40% greater in VWR and ND4 was twofold greater with WD. TUFM, TACO1, ND4 and CytB were greater in MCK‐PGC‐1α compared to wild‐type, and mtIF2/3 contents were not different. In oxidative muscle (soleus), mitochondrial translation machinery was elevated compared to mixed (gastrocnemius) or glycolytic (extensor digitorum longus) muscles. Conclusion These data suggest a novel mechanism promoting mitochondrial function by translation of mitochondrial protein following PA. This may act to promote muscle health by PA in obesity.
    April 25, 2016   doi: 10.1111/apha.12687   open full text
  • Characterization of cold‐induced remodelling reveals depot‐specific differences across and within brown and white adipose tissues in mice.
    R. Jia, X.‐Q. Luo, G. Wang, C.‐X. Lin, H. Qiao, N. Wang, T. Yao, J. L. Barclay, J. P. Whitehead, X. Luo, J.‐Q. Yan.
    Acta Physiologica. April 24, 2016
    Aim Brown and beige adipose tissues dissipate energy in the form of heat via mitochondrial uncoupling protein 1, defending against hypothermia and potentially obesity. The latter has prompted renewed interest in understanding the processes involved in browning to realize the potential therapeutic benefits. To characterize the temporal profile of cold‐induced changes and browning of brown and white adipose tissues in mice. Methods Male C57BL/6J mice were singly housed in conventional cages under cold exposure (4 °C) for 1, 2, 3, 4, 5 and 7 days. Food intake and body weight were measured daily. Interscapular brown adipose tissue (iBAT), inguinal subcutaneous (sWAT) and epididymal white adipose tissue (eWAT) were harvested for histological, immunohistochemical, gene and protein expression analysis. Results Upon cold exposure, food intake increased, whilst body weight and adipocyte size were found to be transiently reduced. iBAT mass was found to be increased, whilst sWAT and eWAT were found to be transiently decreased. A combination of morphological, genetic (Ucp‐1, Pgc‐1α and Elov13) and biochemical (UCP‐1, PPARγ and aP2) analyses demonstrated the depot‐specific remodelling in response to cold exposure. Conclusion Our results demonstrate the differential responses to cold‐induced changes across discrete BAT and WAT depots and support the notion that the effects of short‐term cold exposure are achieved by expansion, activation and increasing thermogenic capacity of iBAT, as well as browning of sWAT and, to a lesser extent, eWAT.
    April 24, 2016   doi: 10.1111/apha.12688   open full text
  • Crosstalk between cardiomyocyte‐rich perivascular tissue and coronary arteries is reduced in the Zucker Diabetic Fatty rat model of type 2 diabetes mellitus.
    L. Bonde, P. Shokouh, P. B. Jeppesen, E. Boedtkjer.
    Acta Physiologica. April 21, 2016
    Aim We tested the hypothesis that crosstalk between cardiomyocyte‐rich perivascular tissue (PVT) and coronary arteries is altered in diabetes. Methods We studied the vasoactive effects of PVT in arteries from the Zucker Diabetic Fatty (ZDF) rat model of type 2 diabetes, streptozotocin (STZ)‐treated Wistar rats with type 1 diabetes, and corresponding – heterozygous Zucker Lean (ZL) or vehicle‐treated Wistar – control rats. Vasocontractile and vasorelaxant functions of coronary septal arteries with and without PVT were investigated using wire myography. Results After careful removal of PVT, vasoconstriction in response to serotonin and thromboxane analogue U46619 was similar in arteries from ZDF and ZL rats, whereas depolarization‐induced vasoconstriction – caused by elevating extracellular [K+] – was reduced in arteries from ZDF compared to ZL rats. PVT inhibited serotonin‐, U46619‐ and depolarization‐induced vasoconstriction in arteries from ZL rats, but this anticontractile influence of PVT was attenuated in arteries from ZDF rats. Methacholine‐induced vasorelaxation was smaller in arteries from ZDF than ZL rats both with and without PVT, and the antirelaxant influence of PVT was comparable between arteries from ZDF and ZL rats. We observed no differences in vasoconstriction, vasorelaxation or PVT‐dependent vasoactive effects between arteries from STZ‐ and vehicle‐treated Wistar rats. Conclusion Anticontractile influences of PVT are attenuated in coronary arteries from ZDF rats but unaffected in arteries from STZ‐treated rats. Signs of endothelial dysfunction are evident in coronary septal arteries – with and without PVT – from ZDF rats but not STZ‐treated rats. We propose that altered signalling between cardiomyocyte‐rich PVT and coronary arteries can contribute to cardiovascular complications in type 2 diabetes mellitus.
    April 21, 2016   doi: 10.1111/apha.12685   open full text
  • Day‐restricted feeding during pregnancy and lactation programs glucose intolerance and impaired insulin secretion in male rat offspring.
    J. Almeida Faria, T. M. F. Araújo, R. I. Mancuso, J. Meulman, D. Silva Ferreira, T. M. Batista, J. F. Vettorazzi, P. M. R. Silva, S. C. Rodrigues, A. Kinote, E. M. Carneiro, S. Bordin, G. F. Anhê.
    Acta Physiologica. April 21, 2016
    Aim The maternal environment during pregnancy and lactation plays a determining role in programming energy metabolism in offspring. Among a myriad of maternal factors, disruptions in the light/dark cycle during pregnancy can program glucose intolerance in offspring. Out‐of‐phase feeding has recently been reported to influence metabolism in adult humans and rodents; however, it is not known whether this environmental factor impacts offspring metabolism when applied during pregnancy and lactation. This study aims to determine whether maternal day‐restricted feeding (DF) influences energy metabolism in offspring. Methods Pregnant and lactating Wistar rats were subjected to ad libitum (AL) or DF during pregnancy and lactation. The offspring born to the AL and DF dams were intra‐ and interfostered, which resulted in 4 group types. Results The male offspring born to and breastfed by the DF dams (DF/DF off) were glucose intolerant, but without parallel insulin resistance as adults. Experiments with isolated pancreatic islets demonstrated that the male DF/DF off rats had reduced insulin secretion with no parallel disruption in calcium handling. However, this reduction in insulin secretion was accompanied by increased miRNA‐29a and miRNA34a expression and decreased syntaxin 1a protein levels. Conclusion We conclude that out‐of‐phase feeding during pregnancy and lactation can lead to glucose intolerance in male offspring, which is caused by a disruption in insulin secretion capacity. This metabolic programming is possibly caused by mechanisms dependent on miRNA modulation of syntaxin 1a.
    April 21, 2016   doi: 10.1111/apha.12684   open full text
  • Cardiotrophin‐1 decreases intestinal sugar uptake in mice and in Caco‐2 cells.
    M. López‐Yoldi, R. Castilla‐Madrigal, M. P. Lostao, A. Barber, J. Prieto, J. A. Martínez, M. Bustos, M. J. Moreno‐Aliaga.
    Acta Physiologica. April 07, 2016
    Aim Cardiotrophin‐1 (CT‐1) is a member of the IL‐6 family of cytokines with a key role in glucose and lipid metabolism. In the current investigation, we examined the in vivo and in vitro effects of CT‐1 treatment on intestinal sugar absorption in different experimental models. Methods rCT‐1 effects on α‐Methyl‐D‐glucoside uptake were assessed in everted intestinal rings from wild‐type and CT‐1−/− mice and in Caco‐2 cells. rCT‐1 actions on SGLT‐1 expression in brush border membrane vesicles and the identification of the potential signalling pathways involved were determined by Western blot. Results In vivo administration (0.2 mg kg−1) of rCT‐1 caused a significant decrease on α‐Methyl‐D‐glucoside uptake in everted intestinal rings from wild‐type and CT‐1−/− mice after short‐term and long‐term treatments. Similarly, in vitro treatment (1–50 ng mL−1) with rCT‐1 reduced α‐Methyl‐D‐glucoside uptake in everted intestinal rings. In Caco‐2 cells, rCT‐1 treatment (20 ng mL−1, 1 and 24 h) lowered apical uptake of α‐Methyl‐D‐glucoside in parallel with a decrease on SGLT‐1 protein expression. rCT‐1 promoted the phosphorylation of STAT‐3 after 5 and 15 min treatment, but inhibited the activation by phosphorylation of AMPK after 30 and 60 min. Interestingly, pre‐treatment with the JAK/STAT inhibitor (AG490) and with the AMPK activator (AICAR) reversed the inhibitory effects of rCT‐1 on α‐Methyl‐D‐glucoside uptake. AICAR also prevented the inhibition of SGLT‐1 observed in rCT‐1‐treated cells. Conclusions CT‐1 inhibits intestinal sugar absorption by the reduction of SGLT‐1 levels through the AMPK pathway, which could also contribute to explain the hypoglycaemic and anti‐obesity properties of CT‐1.
    April 07, 2016   doi: 10.1111/apha.12674   open full text
  • Biosensor cell assay for measuring real‐time aldosterone‐induced release of histamine from mesenteric arteries.
    E. G. Dalgaard, K. Andersen, P. Svenningsen, P. B. L. Hansen.
    Acta Physiologica. April 05, 2016
    Aims The aims were to develop a method for real‐time detection of histamine release and to test whether incubation with aldosterone induces histamine release from isolated, perfused mice mesenteric arteries. Methods Fura‐2‐loaded HEK‐293 cells transfected with the histamine H1 receptor was used as a sensitive biosensor assay for histamine release from isolated mouse mesenteric arteries. Activation of the H1 receptor by histamine was measured as an increased number of intracellular Ca2+ transient peaks using fluorescence imaging. Results The developed biosensor was sensitive to histamine in physiological relevant concentrations and responded to substances released by the artery preparation. Aldosterone treatment of mesenteric arteries from wild‐type mice for 50 min resulted in an increased number of intracellular Ca2+ transient peaks in the biosensor cells, which was significantly inhibited by the histamine H1 blocker pyrilamine. Mesenteric arteries from mast cell‐deficient SASH mice induced similar pyrilamine‐sensitive Ca2+ transient response in the biosensor cells. Mesenteric arteries from wild‐type and SASH mice expressed histamine decarboxylase mRNA, indicating that mast cells are not the only source of histamine release. Conclusion The developed biosensor assay can measure release of substances from vascular preparations. Histamine is released from the vessel preparation in response to aldosterone treatment independently of mast cells. The assay enables us to study a new signaling mechanism for vascular responses induced by aldosterone.
    April 05, 2016   doi: 10.1111/apha.12680   open full text
  • Polyunsaturated fatty acids are potent openers of human M‐channels expressed in Xenopus laevis oocytes.
    S. I. Liin, U. Karlsson, B. H. Bentzen, N. Schmitt, F. Elinder.
    Acta Physiologica. March 23, 2016
    Aim Polyunsaturated fatty acids have been reported to reduce neuronal excitability, in part by promoting inactivation of voltage‐gated sodium and calcium channels. Effects on neuronal potassium channels are less explored and experimental data ambiguous. The aim of this study was to investigate anti‐excitable effects of polyunsaturated fatty acids on the neuronal M‐channel, important for setting the resting membrane potential in hippocampal and dorsal root ganglion neurones. Methods Effects of fatty acids and fatty acid analogues on mouse dorsal root ganglion neurones and on the human KV7.2/3 channel expressed in Xenopus laevis oocytes were studied using electrophysiology. Results Extracellular application of physiologically relevant concentrations of the polyunsaturated fatty acid docosahexaenoic acid hyperpolarized the resting membrane potential (−2.4 mV by 30 μm) and increased the threshold current to evoke action potentials in dorsal root ganglion neurones. The polyunsaturated fatty acids docosahexaenoic acid, α‐linolenic acid and eicosapentaenoic acid facilitated opening of the human M‐channel, comprised of the heteromeric human KV7.2/3 channel expressed in Xenopus oocytes, by shifting the conductance‐vs.‐voltage curve towards more negative voltages (by −7.4 to −11.3 mV by 70 μm). Uncharged docosahexaenoic acid methyl ester and monounsaturated oleic acid did not facilitate opening of the human KV7.2/3 channel. Conclusions These findings suggest that circulating polyunsaturated fatty acids, with a minimum requirement of multiple double bonds and a charged carboxyl group, dampen excitability by opening neuronal M‐channels. Collectively, our data bring light to the molecular targets of polyunsaturated fatty acids and thus a possible mechanism by which polyunsaturated fatty acids reduce neuronal excitability.
    March 23, 2016   doi: 10.1111/apha.12663   open full text
  • Peroxisome proliferator‐activated receptor γ activation favours selective subcutaneous lipid deposition by coordinately regulating lipoprotein lipase modulators, fatty acid transporters and lipogenic enzymes.
    P. G. Blanchard, V. Turcotte, M. Côté, Y. Gélinas, S. Nilsson, G. Olivecrona, Y. Deshaies, W. T. Festuccia.
    Acta Physiologica. March 12, 2016
    Aim Peroxisome proliferator‐activated receptor (PPAR) γ activation is associated with preferential lipoprotein lipase (LPL)‐mediated fatty acid storage in peripheral subcutaneous fat depots. How PPARγ agonism acts upon the multi‐level modulation of depot‐specific lipid storage remains incompletely understood. Methods We evaluated herein triglyceride‐derived lipid incorporation into adipose tissue depots, LPL mass and activity, mRNA levels and content of proteins involved in the modulation of LPL activity and fatty acid transport, and the expression/activity of enzymes defining adipose tissue lipogenic potential in rats treated with the PPARγ ligand rosiglitazone (30 mg kg−1 day−1, 23 days) after either a 10‐h fasting period or a 17‐h fast followed by 6 h of ad libitum refeeding. Results Rosiglitazone stimulated lipid accretion in subcutaneous fat (SF) ~twofold and significantly reduced that of visceral fat (VF) to nearly half. PPARγ activation selectively increased LPL mass, activity and the expression of its chaperone LMF1 in SF. In VF, rosiglitazone had no effect on LPL activity and downregulated the mRNA levels of the transendothelial transporter GPIHBP1. Overexpression of lipid uptake and fatty acid transport proteins (FAT/CD36, FATP1 and FABP4) and stimulation of lipogenic enzyme activities (GPAT, AGPAT and DGAT) upon rosiglitazone treatment were of higher magnitude in SF. Conclusions Together these findings demonstrate that the depot‐specific transcriptional control of LPL induced by PPARγ activation extends to its key interacting proteins and post‐translational modulators to favour subcutaneous lipid storage.
    March 12, 2016   doi: 10.1111/apha.12665   open full text
  • Long‐term facilitation of expiratory and sympathetic activities following acute intermittent hypoxia in rats.
    E. V. Lemes, S. Aiko, C. B. Orbem, C. Formentin, M. Bassi, E. Colombari, D. B. Zoccal.
    Acta Physiologica. March 03, 2016
    Aim Acute intermittent hypoxia (AIH) promotes persistent increases in ventilation and sympathetic activity, referred as long‐term facilitation (LTF). Augmented inspiratory activity is suggested as a major component of respiratory LTF. In this study, we hypothesized that AIH also elicits a sustained increase in expiratory motor activity. We also investigated whether the expiratory LTF contributes to the development of sympathetic LTF after AIH. Methods Rats were exposed to AIH (10 × 6–7% O2 for 45 s, every 5 min), and the cardiorespiratory parameters were evaluated during 60 min using in vivo and in situ approaches. Results In unanesthetized conditions (n = 9), AIH elicited a modest but sustained increase in baseline mean arterial pressure (MAP, 104 ± 2 vs. 111 ± 3 mmHg, P < 0.05) associated with enhanced sympathetic and respiratory‐related variabilities. In the in situ preparations (n = 9), AIH evoked LTF in phrenic (33 ± 12%), thoracic sympathetic (75 ± 25%) and abdominal nerve activities (69 ± 14%). The sympathetic overactivity after AIH was phase‐locked with the emergence of bursts in abdominal activity during the late‐expiratory phase. In anesthetized vagus‐intact animals, AIH increased baseline MAP (113 ± 3 vs. 122 ± 2 mmHg, P < 0.05) and abdominal muscle activity (535 ± 94%), which were eliminated after pharmacological inhibition of the retrotrapezoid nucleus/parafacial respiratory group (RTN/pFRG). Conclusion These findings indicate that increased expiratory activity is also an important component of AIH‐elicited respiratory LTF. Moreover, the development of sympathetic LTF after AIH is linked to the emergence of active expiratory pattern and depends on the integrity of the neurones of the RTN/pFRG.
    March 03, 2016   doi: 10.1111/apha.12661   open full text
  • Conducted dilatation to ATP and K+ in rat skeletal muscle arterioles.
    K. A. Dora.
    Acta Physiologica. February 22, 2016
    Aim During exercise in humans, circulating levels of ATP and K+ increase at a time when blood flow increases to satisfy metabolic demand. Both molecules can activate arteriolar K+ channels to stimulate vasodilatation; here, it is established whether conducted dilatation is observed in a skeletal muscle bed. Methods Isolated and cannulated rat cremaster arterioles were used to assess both local and conducted responses. Agents were either added to the bath, focally pulse‐ejected to the downstream end of arterioles, or in triple‐cannulated arterioles, luminally perfused into the downstream branches to assess both local and conducted responses. Results The endothelium‐dependent agonist ACh and the KATP channel opener levcromakalim each stimulated both local and conducted vasodilatation. Focal, bolus delivery of ATP (10 μm) or KCl (33 mm) to the outside of arterioles stimulated a biphasic vasomotor response: rapid vasoconstriction followed by dilatation as each washed away. At lower concentrations of KCl (19 mm), constriction was avoided, and instead, Ba2+‐sensitive local dilatation and conducted dilatation were both observed. Luminal perfusion of ATP avoided constriction and activated P2Y1 receptors stimulating vasodilatation secondary to opening of KCa channels. In triple‐cannulated arterioles, either ATP (10 μm) or K+ (15 mm) luminally perfused into daughter branches of a bifurcation stimulated local dilatation which conducted into the parent arteriole. Conclusion The recognized physiological autocrine and paracrine mediators ATP and K+ each act to evoke both local and conducted vasodilatation in rat cremaster arterioles. Therefore, in situations when circulating levels are raised, such as during exercise, these agents can act as important regulators of blood flow.
    February 22, 2016   doi: 10.1111/apha.12656   open full text
  • Muscle force loss and soreness subsequent to maximal eccentric contractions depend on the amount of fascicle strain in vivo.
    G. Guilhem, V. Doguet, H. Hauraix, L. Lacourpaille, M. Jubeau, A. Nordez, S. Dorel.
    Acta Physiologica. February 02, 2016
    Aim Defining the origins of muscle injury has important rehabilitation and exercise applications. However, current knowledge of muscle damage mechanics in human remains unclear in vivo. This study aimed to determine the relationships between muscle–tendon unit mechanics during maximal eccentric contractions and the extent of subsequent functional impairments induced by muscle damage. Methods The length of the muscle–tendon unit, fascicles and tendinous tissues was continuously measured on the gastrocnemius medialis using ultrasonography, in time with torque, during 10 sets of 30 maximal eccentric contractions of plantar flexors at 45°s−1, in seventeen participants. Results Muscle–tendon unit, fascicles and tendinous tissues were stretched up to 4.44 ± 0.33 cm, 2.31 ± 0.64 cm and 1.92 ± 0.61 cm respectively. Fascicle stretch length, lengthening amplitude and negative fascicle work beyond slack length were significantly correlated with the force decrease 48 h post‐exercise (r = 0.51, 0.47 and 0.68, respectively; P < 0.05). Conclusions This study demonstrates that the strain applied to human muscle fibres during eccentric contractions strongly influences the magnitude of muscle damage in vivo. Achilles tendon compliance decreases the amount of strain, while architectural gear ratio may moderately contribute to attenuating muscle fascicle lengthening and hence muscle damage. Further studies are necessary to explore the impact of various types of task to fully understand the contribution of muscle–tendon interactions during active lengthening to muscle damage.
    February 02, 2016   doi: 10.1111/apha.12654   open full text
  • Thyroid hormone reduces inflammatory cytokines improving glycaemia control in alloxan‐induced diabetic wistar rats.
    A. C. Panveloski‐Costa, S. Silva Teixeira, I. M. R. Ribeiro, C. Serrano‐Nascimento, R. X. Neves, R. R. Favaro, M. Seelaender, V. R. Antunes, M. T. Nunes.
    Acta Physiologica. January 30, 2016
    Aim This study aimed at evaluating whether thyroid hormone treatment could improve glycaemia and insulin response in alloxan‐induced diabetic rats by altering cytokine expression in the skeletal muscle and epididymal white adipose tissue (eWAT) as well as altering inflammatory cell infiltration in eWAT. Methods Diabetes mellitus (DM) was induced in male Wistar rats by alloxan injection, and a subset of the diabetic rats was treated with T3 (1.5 μg per 100 g body weight) for a 28‐day period (DT3). Cytokines were measured in serum (MILIplex assay kit) as well as in soleus and EDL skeletal muscles and eWAT by Western blotting. Thyroid function was evaluated by morphological, molecular and biochemical parameters. Cardiac function was assessed by measuring heart rate, blood pressure, maximal rate of pressure development (dp/dtmax) and decline (dp/dtmin) as well as the contractility index (CI). Sixty rats were used in the study. Results Diabetic rats exhibited decreased thyroid function and increased inflammatory cytokines in serum, soleus muscle and eWAT. T3 treatment decreased glycaemia and improved insulin sensitivity in diabetic animals. These alterations were accompanied by decreased TNF‐alpha and IL‐6 content in soleus muscle and eWAT, and inflammatory cell infiltration in eWAT. T3 treatment did not affect cardiac function of diabetic rats. Conclusions The present data provide evidence that T3 treatment reduces glycaemia and improves insulin sensitivity in diabetic rats, and that at least part of this effect could result from its negative modulation of inflammatory cytokine expression.
    January 30, 2016   doi: 10.1111/apha.12647   open full text
  • Longitudinal evaluation of functional connectivity variation in the monkey sensorimotor network induced by spinal cord injury.
    J.S. Rao, Z. Liu, C. Zhao, R.H. Wei, W. Zhao, Z.Y. Yang, X.G. Li.
    Acta Physiologica. January 13, 2016
    Aim Given the unclear pattern of cerebral function reorganization induced by spinal cord injury (SCI), this study aimed to longitudinally evaluate the changes in resting‐state functional connectivity (FC) in the sensorimotor network after SCI and explore their relationship with gait performance. Methods Four adult female rhesus monkeys were examined using resting‐state functional magnetic resonance imaging during their healthy stage and after hemitransected SCI (4, 8 and 12 weeks after SCI), and the gait characteristics of their hindlimbs were recorded (except 4 weeks after SCI). Twenty sensorimotor‐related cortical areas were adopted in the FC analysis to evaluate the functional network reorganization. Correlation analyses were then used to explore the relationship between functional network variations and gait characteristic changes. Results Compared with that during the healthy stage, the FC strength during post‐SCI period was significantly increased in multiple areas of the motor control network, including the primary sensorimotor cortex, supplementary motor area (SMA) and putamen (Pu). However, the FC strength was remarkably reduced in the thalamus and parieto‐occipital association cortex of the sensory network 8 weeks after SCI. Most FC intensities gradually approached the normal level 12 weeks after the SCI. Correlation analyses revealed that the enhanced FC strength between Pu and SMA in the left hemisphere, which regulates motor functions of the right side, was negatively correlated with the gait height of the right hindlimb. Conclusion The cerebral functional network presents an adjust–recover pattern after SCI, which may help us further understand the cerebral function reorganization after SCI.
    January 13, 2016   doi: 10.1111/apha.12645   open full text
  • Vascular hepoxilin and trioxilins mediate vasorelaxation through TP receptor inhibition in mouse arteries.
    L. Siangjong, D. H. Goldman, T. Kriska, K. M. Gauthier, E. M. Smyth, N. Puli, G. Kumar, J. R. Falck, W. B. Campbell.
    Acta Physiologica. January 04, 2016
    Aim 12/15‐lipoxygenase (12/15‐LO) metabolizes arachidonic acid (AA) into several vasoactive eicosanoids. In mouse arteries, we previously characterized the enzyme's 15‐LO metabolites 12(S)‐hydroxyeicosatetraenoic acid (HETE), 15‐HETE, hydroxyepoxyeicosatrienoic acids (HEETAs) and 11,12,15‐trihydroxyeicosatrienoic acids (11,12,15‐THETAs) as endothelium‐derived relaxing factors. However, the observed 12‐LO metabolites remained uncharacterized. The purpose of this study was to determine the structure and biological functions of eicosanoids generated by the enzyme's 12‐LO activity. Methods Metabolites extracted from aortas of C57BL/6 male mice were separated using a series of reverse and normal phase chromatographic steps and identified as hepoxilin A3, trioxilin A3 and trioxilin C3 by mass spectrometry. Activities of these natural compounds were tested on isometric tension and intracellular calcium release. The role of thromboxane (TP) receptor was determined in HEK293 cells overexpressing TPα receptor (TPα ‐HEK). Results All identified vascular 12‐LO metabolites were biologically active. In mouse mesenteric arteries, trioxilin A3, C3 and hepoxilin A3 (3 μm) relaxed arteries constricted with the thromboxane mimetic, U46619‐constricted arteries (maximum relaxations of 78.9 ± 3.2, 29.7 ± 4.6, 82.2 ± 5.0 and 88.0 ± 2.4% respectively), but not phenylephrine‐constricted arteries. In TPα‐HEK cells, trioxilin A3, C3 and hepoxilin A3 (10 μm) inhibited U46619 (10 nM)‐induced increases in intracellular calcium by 53.0 ± 7.2%, 32.8 ± 5.0% and 37.9 ± 13.5% respectively. In contrast, trioxilin B3 and hepoxilin B3 were not synthesized in arteries and exhibited little biological activity. Conclusion Trioxilin A3 and C3 and hepoxilin A3 are endogenous vascular relaxing factors. They are not endothelium‐derived hyperpolarizing factors but mediate vascular relaxation by inhibiting TP agonist‐induced increases in intracellular calcium. Thus, they regulate vascular homeostasis by acting as endogenous TP antagonists.
    January 04, 2016   doi: 10.1111/apha.12642   open full text
  • Gastric bypass surgery is protective from high‐fat diet‐induced non‐alcoholic fatty liver disease and hepatic endoplasmic reticulum stress.
    J. D. Mosinski, M. R. Pagadala, A. Mulya, H. Huang, O. Dan, H. Shimizu, E. Batayyah, R. K. Pai, P. R. Schauer, S. A. Brethauer, J. P. Kirwan.
    Acta Physiologica. December 29, 2015
    Aim High‐fat diets are known to contribute to the development of obesity and related co‐morbidities including non‐alcoholic fatty liver disease (NAFLD). The accumulation of hepatic lipid may increase endoplasmic reticulum (ER) stress and contribute to non‐alcoholic steatohepatitis and metabolic disease. We hypothesized that bariatric surgery would counter the effects of a high‐fat diet (HFD) on obesity‐associated NAFLD. Methods Sixteen of 24 male Sprague Dawley rats were randomized to Sham (N = 8) or Roux‐en‐Y gastric bypass (RYGB) surgery (N = 8) and compared to Lean controls (N = 8). Obese rats were maintained on a HFD throughout the study. Insulin resistance (HOMA‐IR), and hepatic steatosis, triglyceride accumulation, ER stress and apoptosis were assessed at 90 days post‐surgery. Results Despite eating a HFD for 90 days post‐surgery, the RYGB group lost weight (−20.7 ± 6%, P < 0.01) and improved insulin sensitivity (P < 0.05) compared to Sham. These results occurred with no change in food intake between groups. Hepatic steatosis and ER stress, specifically glucose‐regulated protein‐78 (Grp78, P < 0.001), X‐box binding protein‐1 (XBP‐1) and spliced XBP‐1 (P < 0.01), and fibroblast growth factor 21 (FGF21) gene expression, were normalized in the RYGB group compared to both Sham and Lean controls. Significant TUNEL staining in liver sections from the Obese Sham group, indicative of accelerated cell death, was absent in the RYGB and Lean control groups. Additionally, fasting plasma glucagon like peptide‐1 was increased in RYGB compared to Sham (P < 0.02). Conclusion These data suggest that in obese rats, RYGB surgery protects the liver against HFD‐induced fatty liver disease by attenuating ER stress and excess apoptosis.
    December 29, 2015   doi: 10.1111/apha.12640   open full text
  • Vaspin prevents elevation of blood pressure through inhibition of peripheral vascular remodelling in spontaneously hypertensive rats.
    S. Kameshima, Y. Sakamoto, M. Okada, H. Yamawaki.
    Acta Physiologica. December 24, 2015
    Aim Visceral adipose tissue‐derived serine protease inhibitor (vaspin) is a relatively novel adipocytokine with protective effects on metabolic diseases including obesity and type II diabetes. We have previously demonstrated that vaspin exerts anti‐inflammatory and antimigratory roles through antioxidative effects in vascular smooth muscle cells. As inflammatory responses and migration of smooth muscle in peripheral vascular wall are key mechanisms for the pathogenesis of hypertension, we hypothesized that vaspin could prevent the development of hypertension in in vivo hypertensive animal model. Methods Vaspin (1 μg kg−1 day−1) was administered intraperitoneally to 5‐week‐old male spontaneously hypertensive rats (SHR) for 4 weeks. Superior mesenteric artery was isolated and used for measurement of isometric contraction and histological analysis. Results Long‐term vaspin treatment significantly prevented an elevation of systolic blood pressure (SBP) at 8 weeks of age. Vaspin had no effect on reactivity of isolated mesenteric artery from SHR. In contrast, vaspin significantly inhibited mesenteric arterial wall hypertrophy in SHR. Moreover, vaspin significantly inhibited an increase of tumour necrosis factor‐α expression and a production of reactive oxygen species in isolated mesenteric artery from SHR. Conclusion This study for the first time demonstrates that vaspin prevents the increase of SBP in SHR through inhibiting peripheral vascular hypertrophy possibly via antioxidative and anti‐inflammatory mechanisms.
    December 24, 2015   doi: 10.1111/apha.12636   open full text
  • Inhibition of mitogen‐activated protein kinase 1/2 in the acute phase of stroke improves long‐term neurological outcome and promotes recovery processes in rats.
    M. Mostajeran, L. Edvinsson, K. Warfvinge, R. Singh, S. Ansar.
    Acta Physiologica. December 17, 2015
    Aim Extracellular signal‐regulated kinase (ERK) 1/2 is activated during acute phase of stroke and contributes to stroke pathology. We have found that acute treatment with MEK1/2 inhibitors decreases infarct size and neurological deficits 2 days after experimental stroke. However, it is not known whether benefits of this inhibition persist long‐term. Therefore, the aim of this study was to assess neurological function, infarct size and recovery processes 14 days after stroke in male rats to determine long‐term outcome following acute treatment with the MEK1/2 inhibitor U0126. Methods Transient middle cerebral artery occlusion was induced in male rats. U0126 or vehicle was given at 0 and 24 h of reperfusion. Neurological function was assessed by staircase, 6‐point and 28‐point neuroscore tests up to 14 days after induction of stroke. At day 14, infarct volumes were determined and recovery processes were evaluated by measuring protein expression of the tyrosine kinase receptor Tie‐2 and nestin. Levels of p‐ERK1/2 protein were determined. Results Acute treatment with U0126 significantly improved long‐term functional recovery, reduced infarct size, and enhanced Tie‐2 and nestin protein expression at 14 days post‐stroke. There was no residual blockade of p‐ERK1/2 at this time point. Conclusion It is demonstrated that benefits of early treatment with U0126 persist beyond subacute phase of ischaemic stroke in male rats. Prevention of ERK1/2 activation in the acute phase results in improved long‐term functional outcome and enhances later‐stage recovery processes. These results expand our understanding of the benefits and promise of using MEK1/2 inhibitors in stroke recovery.
    December 17, 2015   doi: 10.1111/apha.12632   open full text
  • Response to exercise and mechanical efficiency in non‐ischaemic stunning, induced by short‐term rapid pacing in dogs: a role for calcium?
    M. De Pauw, K. Mubagwa, D. Hodeige, M. Borgers, W. Flameng, J. Van de Voorde, G. R. Heyndrickx.
    Acta Physiologica. December 15, 2015
    Aim Rapid pacing (RP) is a regularly used model to induce heart failure in dogs. The aim of the study was to evaluate Ca2+ handling, left ventricular (LV) contractile response during Ca2+ administration compared to exercise, as well as oxygen consumption and mechanical efficiency after 48 h of RP. Methods Fifty‐three mongrel dogs were instrumented to measure LV pressure, LV fractional shortening, regional wall thickening and coronary blood flow. Contractile reserve was measured with isoproterenol and intravenous (IV) Ca2+ administration. To assess the function of the sarcoplasmic reticulum (SR), post‐extrasystolic potentiation (PESP) and SR Ca2+ uptake were measured. A graded treadmill test was performed in baseline and after RP (n = 14). In a separate group of animals (n = 5), myocardial performance and oxygen consumption were measured using a wide range of loading conditions. Results Left ventricular contractility was significantly decreased upon cessation of pacing. The contractile response to isoproterenol was blunted compared to a preserved response to IV Ca2+. Post‐extrasystolic potentiation was slightly increased after RP. Maximal velocity (Vmax) of SR Ca2+ uptake was unchanged. Contractile response during exercise is attenuated after RP. External work is reduced, whereas oxygen consumption is preserved, provoking a reduced mechanical efficiency. Conclusion Forty‐eight‐hours RP provokes a reversible LV dysfunction, while the SR function and response to exogenous Ca2+ are preserved. This is compatible with an intracellular functional remodelling to counteract Ca2+ overload provoked by RP. Left ventricular dysfunction is accompanied by a reduced contractile reserve, but an unchanged oxygen consumption, illustrating an alteration in oxygen utilization.
    December 15, 2015   doi: 10.1111/apha.12629   open full text
  • Nitric oxide and Na,K‐ATPase activity in rat skeletal muscle.
    C. Juel.
    Acta Physiologica. November 03, 2015
    Aim It has been suggested that nitric oxide (NO) stimulates the Na,K‐ATPase in cardiac myocytes. Therefore, the aims of this study were to investigate whether NO increases Na,K‐ATPase activity in skeletal muscle and, if that is the case, to identify the underlying mechanism. Method The study used isolated rat muscle, muscle homogenates and purified membranes as model systems. Na,K‐ATPase activity was quantified from phosphate release due to ATP hydrolysis. Results Exposure to the NO donor spermine NONOate (10 μm) increased the maximal Na,K‐ATPase activity by 27% in isolated glycolytic muscles, but had no effect in oxidative muscles. Spermine NONOate increased the maximal Na,K‐ATPase activity by 58% (P < 0.05) in homogenates from glycolytic muscle, but had no effect in oxidative muscle. The stimulatory effect of NONOate was not related to one specific Na,K‐ATPase α‐isoform. Incubation with cGMP (1 mm) increased the maximal Na,K‐ATPase activity in homogenates from glycolytic muscle by 16% (P < 0.05), but had no effect on homogenates from oxidative muscle. cGMP had no effect on phospholemman phosphorylation at serine 68. Spermine NONOate had no effect in muscle membranes in which the ATPase activity was depressed by oxidized glutathione. Conclusion NO and cGMP stimulate the Na,K‐ATPase in glycolytic skeletal muscle. Direct S‐nitrosylation and interference with S‐glutathionylation seem to be excluded. In addition, phosphorylation of phospholemman at serine 68 is not involved. Most likely, the NO/cGMP/protein kinase G signalling pathway is involved.
    November 03, 2015   doi: 10.1111/apha.12617   open full text
  • The change in motor unit firing rates at derecruitment relative to recruitment is correlated with type I myosin heavy chain isoform content of the vastus lateralis in vivo.
    Trent J. Herda, Jonathan D. Miller, Michael A. Trevino, Eric M. Mosier, Philip M. Gallagher, Andrew C. Fry, John P. Vardiman.
    Acta Physiologica. October 29, 2015
    Aim To investigate the change in motor unit (MU) firing rates (FR) at derecruitment relative to recruitment and the relation to percent type I myosin heavy chain isoform content (type I %MHC) of the vastus lateralis (VL) in vivo. Methods Ten subjects performed a 22 second submaximal isometric trapezoid muscle action that included a linearly increasing, steady force at 50% maximal voluntary contraction, and linearly decreasing segments. Surface electromyographic signals were collected from the VL and were decomposed into constituent MU action potentials trains. A tissue sample from the VL was taken to calculate type I %MHC. Y‐intercepts and slopes were calculated for the changes (Δ) in FR at derecruitment (FRDEREC) relative to FR at recruitment (FRREC) versus FRREC relationship for each subject. Correlations were performed between the y‐intercepts and slopes with type I %MHC. Results The majority of MUs had greater FRDEREC than FRREC. The y‐intercepts (r=‐0.600, P=0.067) were not significantly correlated, but the slopes (r=‐0.793, P=0.006) were significantly correlated with type I %MHC. Conclusion The majority of the motoneuron pool had greater FRDEREC than FRREC, however, individuals with higher type I %MHC had a greater propensity to have MUs with FRREC > FRDEREC as indicated by the slope values. Overall, the contractile properties of the muscle (MHC) could partially explain the differences in MU firing rates at derecruitment relative to recruitment. Thus, suggesting the fatigability of the muscle influences the alterations in MU firing rates from recruitment to derecruitment. This article is protected by copyright. All rights reserved.
    October 29, 2015   doi: 10.1111/apha.12624   open full text
  • The NADPH Oxidase Nox4 mediates tumour angiogenesis.
    V. Helfinger, N. Henke, Sabine Harenkamp, Maria Walter, Jeremy Epah, Cornelia Penski, Michel Mittelbronn, K. Schröder.
    Acta Physiologica. October 29, 2015
    Aim The aim of this work was to identify the role of the NADPH oxidase Nox4 for tumour angiogenesis in a slow growing tumour model in mice. Methods Tumour angiogenesis was studied in tumours induced by the carcinogen 3‐methylcholanthrene (MCA) in wild‐type and Nox knock out mice. Mice were sacrificed when the tumour reached a diameter of 1.5 cm and tumour tissue was used for histological and molecular analysis. Results 3‐methylcholanthrene induced fibro sarcoma in wildtype, Nox1y/‐, Nox2y/‐ and Nox4‐/‐ mice. Histological analysis of vessel density using anti‐CD31 staining showed a significant 38% reduction in tumour vascularization in fibro sarcomas of Nox4‐/‐ mice. In contrast tumour angiogenesis was doubled in Nox1 knock out mice, whereas knock out of Nox2 had no effect on tumour vessel density. As underlying mechanisms we identified a defect in hypoxia signalling in Nox4‐/‐ mice. Hypoxia‐ inducible factor 1‐alpha (Hif‐1α) accumulation in the tumours was attenuated as was the expression of the Hif‐1α‐dependent pro‐angiogenic genes vascular endothelial growth factor‐A, glucose transporter 1 and adrenomedullin. Conclusion By regulating the tumour vessel density through stabilization of Hif‐1α and induction of VEGF expression Nox4 promotes tumour angiogenesis and may represent a novel target for anti‐angiogenic tumour therapy. This article is protected by copyright. All rights reserved.
    October 29, 2015   doi: 10.1111/apha.12625   open full text
  • The bitter truth about bitter taste receptors: Beyond sensing bitter in the oral cavity.
    Bert Avau, Inge Depoortere.
    Acta Physiologica. October 23, 2015
    The bitter taste receptor (TAS2R)‐family of GPCRs has been identified on the tongue as detectors of bitter taste over a decade ago. In the last few years, they have been discovered in an ever growing number of extra‐oral tissues, including the airways, the gut, the brain and even the testis. In tissues that contact the exterior, protective functions for TAS2Rs have been proposed, in analogy to their function in the tongue as toxicity detector. However, TAS2Rs have also been found in internal organs, suggesting other roles for these receptors, perhaps involving as yet unidentified endogenous ligands. The current review gives an overview of the different proposed functions for TAS2Rs in tissues other than the oral cavity; from appetite regulation to the treatment of asthma, regulation of gastrointestinal motility and control of airway innate immunity. This article is protected by copyright. All rights reserved.
    October 23, 2015   doi: 10.1111/apha.12621   open full text
  • Deficiency or inhibition of lysophosphatidic acid receptor 1 protects against hyperoxia‐induced lung injury in neonatal rats.
    Xueyu Chen, Frans J Walther, Ruben Boxtel, El Houari Laghmani, Rozemarijn M A Sengers, Gert Folkerts, Marco C. DeRuiter, Edwin Cuppen, Gerry T M Wagenaar.
    Acta Physiologica. October 23, 2015
    Aim Blocking of lysophosphatidic acid (LPA) receptor (LPAR) 1 may be a novel therapeutic option for bronchopulmonary dysplasia (BPD) by preventing the LPAR1‐mediated adverse effects of its ligand (LPA), consisting of lung inflammation, pulmonary arterial hypertension (PAH) and fibrosis. Methods In Wistar rats with experimental BPD, induced by continuous exposure to 100% oxygen for 10 days, we determined the beneficial effects of LPAR1 deficiency in neonatal rats with a missense mutation in cytoplasmic helix 8 of LPAR1 and of LPAR1 and ‐3 blocking with Ki16425. Parameters investigated included survival, lung and heart histopathology, fibrin and collagen deposition, vascular leakage, and differential mRNA expression in the lungs of key genes involved in LPA signalling and BPD pathogenesis. Results LPAR1 mutant rats were protected against experimental BPD and mortality with reduced alveolar septal thickness, lung inflammation (reduced influx of macrophages and neutrophils, and CINC1 expression), and collagen III deposition. However, LPAR1 mutant rats were not protected against alveolar enlargement, increased medial wall thickness of small arterioles, fibrin deposition, and vascular alveolar leakage. Treatment of experimental BPD with Ki16425 confirmed the data observed in LPAR1 mutant rats, but did not reduce the pulmonary influx of neutrophils, CINC1 expression, and mortality in rats with experimental BPD. In addition, Ki16425 treatment protected against PAH and right ventricular hypertrophy. Conclusion LPAR1 deficiency attenuates pulmonary injury by reducing pulmonary inflammation and fibrosis, thereby reducing mortality, but does not affect alveolar and vascular development and, unlike Ki16425 treatment, does not prevent PAH in neonatal rats with experimental BPD. This article is protected by copyright. All rights reserved.
    October 23, 2015   doi: 10.1111/apha.12622   open full text
  • Effects of renal denervation on renal pelvic contractions and connexin expression in rats.
    A. Koenen, A. Steinbach, K. Schaper, U. Zimmermann, B. Miehe, B. Kurt, R. Rettig, O. Grisk.
    Acta Physiologica. October 22, 2015
    Aims The renal pelvis shows spontaneous rhythmic contractile activity. We assessed to what extent this activity depends on renal innervation and studied the role of connexins in pelvic contractions. Methods Rats underwent unilateral renal denervation or renal transplantation. Renal pelvic pressure and diuresis were measured in vivo. Spontaneous and agonist‐induced contractions of isolated renal pelves were investigated by wire myography. Rat and human renal pelvic connexin mRNA abundances and connexin localization were studied by real‐time PCR and immunofluorescence respectively. Results Renal denervation or transplantation increased renal pelvic pressure in vivo by about 60 and 150%, respectively, but did not significantly affect pelvic contraction frequency. Under in vitro conditions, isolated pelvic preparations from innervated or denervated kidneys showed spontaneous contractions. Pelves from denervated kidneys showed about 50% higher contraction frequencies than pelves from innervated kidneys, whereas contraction force was similar in pelves from denervated and innervated kidneys. There was no denervation‐induced supersensitivity to noradrenaline or endothelin‐1. Renal denervation did not increase pelvic connexin37, 40, 43 or 45 mRNA abundances. Gap junction blockade had no effect on spontaneous pelvic contractile activity. Conclusions The denervation‐induced effect on pelvic pressure may be the consequence of the enhanced diuresis. The mechanisms underlying the denervation‐induced effects on pelvic contraction frequency remain unknown. Our data rule out a major role for two important candidates, by showing that renal denervation neither induced supersensitivity to contractile agonists nor increased connexin mRNA abundance in the pelvic wall.
    October 22, 2015   doi: 10.1111/apha.12612   open full text
  • Altered neurotrophic factors expression profiles in the nucleus of the solitary tract of spontaneously hypertensive rats.
    Sabine S Gouraud, Miwa Takagishi, Akira Kohsaka, Masanobu Maeda, Hidefumi Waki.
    Acta Physiologica. October 20, 2015
    Aim Our previous findings suggest that the nucleus of the solitary tract (NTS), a pivotal region for regulating the set‐point of arterial pressure, exhibits abnormal inflammation in pre‐hypertensive and spontaneously hypertensive rats (SHRs), with elevated anti‐apoptotic and low apoptotic factor levels compared with that of normotensive Wistar‐Kyoto (WKY) rats. Whether this chronic condition affects neuronal growth and plasticity in the NTS remains unknown. To unveil the characteristics of the neurodevelopmental environment in the NTS of SHRs, we investigated the expression of neurotrophic factors transcripts in SHRs. Methods RT2 Profiler PCR Array targeting rat neurotrophins and their receptors was used to screen for differentially expressed transcripts in the NTS of SHRs compared to that of WKY rats. Protein expression and physiological functions of some of the differentially expressed transcripts were also studied. Results Gene and protein expressions of glial cell line‐derived neurotrophic factor family receptor alpha‐3 (Gfrα‐3) factor were both upregulated in the NTS of adult SHRs. Gene expressions of corticotropin releasing hormone binding protein (Crhbp), Interleukin‐10 receptor alpha (Il10ra), and hypocretin (Hcrt) were downregulated in the NTS of adult SHRs. The Gfrα‐3 transcript was increased and the Hcrt transcript was decreased in the NTS of young pre‐hypertensive SHRs, suggesting that these profiles are not secondary to hypertension. Moreover, microinjection in the NTS of hypocretin‐1 decreased blood pressure in adult SHRs. Conclusion These results suggest that altered neurotrophic factors transcript profiles may affect the normal development and function of neuronal circuitry that regulates cardiovascular autonomic activity; thereby resulting in manifestations of neurogenic hypertension in SHRs. This article is protected by copyright. All rights reserved.
    October 20, 2015   doi: 10.1111/apha.12618   open full text
  • Impaired sodium‐evoked paraventricular nucleus neuronal activation and blood pressure regulation in conscious Sprague–Dawley rats lacking central Gαi2 proteins.
    C. Y. Carmichael, A. C. T. Carmichael, J. T. Kuwabara, J. T. Cunningham, R. D. Wainford.
    Acta Physiologica. October 19, 2015
    Aim We determined the role of brain Gαi2 proteins in mediating the neural and humoral responses of conscious male Sprague–Dawley rats to acute peripheral sodium challenge. Methods Rats pre‐treated (24‐h) intracerebroventricularly with a targeted oligodeoxynucleotide (ODN) (25 μg per 5 μL) to downregulate brain Gαi2 protein expression or a scrambled (SCR) control ODN were challenged with an acute sodium load (intravenous bolus 3 m NaCl; 0.14 mL per 100 g), and cardiovascular parameters were monitored for 120 min. In additional groups, hypothalamic paraventricular nucleus (PVN) Fos immunoreactivity was examined at baseline, 40, and 100 min post‐sodium challenge. Results In response to intravenous hypertonic saline (HS), no difference was observed in peak change in mean arterial pressure between groups. In SCR ODN pre‐treated rats, arterial pressure returned to baseline by 100 min, while it remained elevated in Gαi2 ODN pre‐treated rats (P < 0.05). No difference between groups was observed in sodium‐evoked increases in Fos‐positive magnocellular neurons or vasopressin release. V1a receptor antagonism failed to block the prolonged elevation of arterial pressure in Gαi2 ODN pre‐treated rats. A significantly greater number of Fos‐positive ventrolateral parvocellular, lateral parvocellular, and medial parvocellular neurons were observed in SCR vs. Gαi2 ODN pre‐treated rats at 40 and 100 min post‐HS challenge (P < 0.05). In SCR, but not Gαi2 ODN pre‐treated rats, HS evoked suppression of plasma norepinephrine (P < 0.05). Conclusion This highlights Gαi2 protein signal transduction as a novel central mechanism acting to differentially influence PVN parvocellular neuronal activation, sympathetic outflow, and arterial pressure in response to acute HS, independently of actions on magnocellular neurons and vasopressin release.
    October 19, 2015   doi: 10.1111/apha.12610   open full text
  • Training‐induced anti‐atherosclerotic effects are associated with increased vascular PPARgamma expression in apolipoprotein E deficient mice.
    Justyna Szostak, Carole Miguet‐Alfonsi, Alain Berthelot, Pascal Laurant.
    Acta Physiologica. October 15, 2015
    Aim Physical exercise prevents cardiovascular risk and atherosclerosis lesions. However, the molecular aspects are still unknown. Vascular Peroxisome Proliferator‐Activated Receptors (PPARs) exert anti‐atherogenic effects. The aim of this study was to determine whether exercise‐induced anti‐atherosclerotic effect is associated with change in PPARs vascular expression in apolipoprotein E deficient (ApoE‐/‐) mice. Methods Male ApoE‐/‐ mice were fed with a high fat diet and randomized into two groups: one trained group undergoing swimming training for 3 months, and one sedentary group. Sedentary and trained C57BL/6J mice were used as control. PPAR‐α, ‐β/δ and ‐γ mRNA were measured in aorta by quantitative PCR. Pro‐ (TNF‐α, IL‐1β) and anti‐inflammatory (IL‐10, IL‐1Ra) cytokines mRNA were also measured. Results Atherosclerotic lesion size was significantly reduced in trained ApoE‐/‐ mice compared to sedentary ones. In contrast, reduction of atherosclerotic lesion size was not observed in trained ApoE‐/‐ mice supplied with BADGE, an antagonist of PPAR‐ γ. Exercise training significantly increased PPAR‐γ expression in aorta. PPAR‐γ expression was inversely correlated with the atherosclerotic plaque area. Aortic PPAR‐α and ‐β/δ mRNA expression were not changed in response to exercise training. Atherosclerosis increased the aortic mRNA expression of TNF‐α, IL‐1β, IL‐10, and IL‐1Ra. Exercise training decreased aortic IL‐1β mRNA expression in ApoE‐/‐ mice, but did not change expression of TNF‐α, IL‐10, and IL‐1Ra. IL‐1β mRNA expression was also significantly lower in atherosclerosis lesions from trained ApoE‐/‐ compared with those from sedentary ones. Conclusions Exercise training increases vascular PPAR‐γ expression in ApoE‐/‐ mice that could potentially underlie training‐related beneficial effects on atherosclerosis. This article is protected by copyright. All rights reserved.
    October 15, 2015   doi: 10.1111/apha.12615   open full text
  • The effect of exercise mode on the acute response of satellite cells in old men.
    J. P. Nederveen, S. Joanisse, C. M. L. Séguin, K. E. Bell, S. K. Baker, S. M. Phillips, G. Parise.
    Acta Physiologica. October 14, 2015
    Aim A dysregulation of satellite cells may contribute to the progressive loss of muscle mass that occurs with age; however, older adults retain the ability to activate and expand their satellite cell pool in response to exercise. The modality of exercise capable of inducing the greatest acute response is unknown. We sought to characterize the acute satellite cell response following different modes of exercise in older adults. Methods Sedentary older men (n = 22; 67 ± 4 years; 27 ± 2.6 kg*m−2) were randomly assigned to complete an acute bout of either resistance exercise, high‐intensity interval exercise on a cycle ergometer or moderate‐intensity aerobic exercise. Muscle biopsies were obtained before, 24 and 48 h following each exercise bout. The satellite cell response was analysed using immunofluorescent microscopy of muscle cross sections. Results Satellite cell expansion associated with type I fibres was observed 24 and 48 h following resistance exercise only (P ˂ 0.05), while no expansion of type II‐associated satellite cells was observed in any group. There was a greater number of activated satellite cells 24 h following resistance exercise (pre: 1.3 ± 0.1, 24 h: 4.8 ± 0.5 Pax7 + /MyoD+cells/100 fibres) and high‐intensity interval exercise (pre: 0.7 ± 0.3, 24 h: 3.1 ± 0.3 Pax7 + /MyoD+cells/100 fibres) (P ˂ 0.05). The percentage of type I‐associated SC co‐expressing MSTN was reduced only in the RE group 24 h following exercise (pre: 87 ± 4, 24 h: 57 ± 5%MSTN+ type I SC) (P < 0.001). Conclusion Although resistance exercise is the most potent exercise type to induce satellite cell pool expansion, high‐intensity interval exercise was also more potent than moderate‐intensity aerobic exercise in inducing satellite cell activity.
    October 14, 2015   doi: 10.1111/apha.12601   open full text
  • Changes in myonuclear domain size do not precede muscle hypertrophy during prolonged resistance‐type exercise training.
    T. Snijders, J. S. J. Smeets, J. Kranenburg, A. K. Kies, L. J. C. Loon, L. B. Verdijk.
    Acta Physiologica. October 09, 2015
    Aim Muscle fibre hypertrophy is accompanied by an increase in myonuclear number, an increase in myonuclear domain size or both. It has been suggested that increases in myonuclear domain size precede myonuclear accretion and subsequent muscle fibre hypertrophy during prolonged exercise training. In this study, we assessed the changes in muscle fibre size, myonuclear and satellite cell content throughout 12 weeks of resistance‐type exercise training in young men. Methods Twenty‐two young men (23 ± 1 year) were assigned to a progressive, 12‐weeks resistance‐type exercise training programme (3 sessions per week). Muscle biopsies from the vastus lateralis muscle were taken before and after 2, 4, 8 and 12 weeks of exercise training. Muscle fibre size, myonuclear content, myonuclear domain size and satellite cell content were assessed by immunohistochemistry. Results Type I and type II muscle fibre size increased gradually throughout the 12 weeks of training (type I: 18 ± 5%, type II: 41 ± 6%, P < 0.01). Myonuclear content increased significantly over time in both the type I (P < 0.01) and type II (P < 0.001) muscle fibres. No changes in type I and type II myonuclear domain size were observed at any time point throughout the intervention. Satellite cell content increased significantly over time in both type I and type II muscle fibres (P < 0.001). Conclusion Increases in myonuclear domain size do not appear to drive myonuclear accretion and muscle fibre hypertrophy during prolonged resistance‐type exercise training in vivo in humans.
    October 09, 2015   doi: 10.1111/apha.12609   open full text
  • Insulin‐like growth factor 1 prevents diastolic and systolic dysfunction associated with cardiomyopathy and preserves adrenergic sensitivity.
    S. R. Roof, J. Boslett, D. Russell, C. Rio, J. Alecusan, J. L. Zweier, M. T. Ziolo, R. Hamlin, P. J. Mohler, J. Curran.
    Acta Physiologica. October 08, 2015
    Aims Insulin‐like growth factor 1 (IGF‐1)‐dependent signalling promotes exercise‐induced physiological cardiac hypertrophy. However, the in vivo therapeutic potential of IGF‐1 for heart disease is not well established. Here, we test the potential therapeutic benefits of IGF‐1 on cardiac function using an in vivo model of chronic catecholamine‐induced cardiomyopathy. Methods Rats were perfused with isoproterenol via osmotic pump (1 mg kg−1 per day) and treated with 2 mg kg−1 IGF‐1 (2 mg kg−1 per day, 6 days a week) for 2 or 4 weeks. Echocardiography, ECG, and blood pressure were assessed. In vivo pressure–volume loop studies were conducted at 4 weeks. Heart sections were analysed for fibrosis and apoptosis, and relevant biochemical signalling cascades were assessed. Results After 4 weeks, diastolic function (EDPVR, EDP, tau, E/A ratio), systolic function (PRSW, ESPVR, dP/dtmax) and structural remodelling (LV chamber diameter, wall thickness) were all adversely affected in isoproterenol‐treated rats. All these detrimental effects were attenuated in rats treated with Iso+IGF‐1. Isoproterenol‐dependent effects on BP were attenuated by IGF‐1 treatment. Adrenergic sensitivity was blunted in isoproterenol‐treated rats but was preserved by IGF‐1 treatment. Immunoblots indicate that cardioprotective p110α signalling and activated Akt are selectively upregulated in Iso+IGF‐1‐treated hearts. Expression of iNOS was significantly increased in both the Iso and Iso+IGF‐1 groups; however, tetrahydrobiopterin (BH4) levels were decreased in the Iso group and maintained by IGF‐1 treatment. Conclusion IGF‐1 treatment attenuates diastolic and systolic dysfunction associated with chronic catecholamine‐induced cardiomyopathy while preserving adrenergic sensitivity and promoting BH4 production. These data support the potential use of IGF‐1 therapy for clinical applications for cardiomyopathies.
    October 08, 2015   doi: 10.1111/apha.12607   open full text
  • Deficiency of heat shock transcription factor 1 suppresses heat stress‐associated increase in slow soleus muscle mass of mice.
    Y. Ohno, T. Egawa, S. Yokoyama, A. Nakai, T. Sugiura, Y. Ohira, T. Yoshioka, K. Goto.
    Acta Physiologica. September 28, 2015
    Aim Effects of heat shock transcription factor 1 (HSF1) deficiency on heat stress‐associated increase in slow soleus muscle mass of mice were investigated. Methods Both HSF1‐null and wild‐type mice were randomly assigned to control and heat‐stressed groups. Mice in heat‐stressed group were exposed to heat stress (41 °C for 60 min) in an incubator without anaesthesia. Results Significant increase in wet and dry weights, and protein content of soleus muscle in wild‐type mice was observed seven days after the application of the heat stress. However, heat stress had no impact on soleus muscle mass in HSF1‐null mice. Neither type of mice exhibited much effect of heat stress on HSF mRNA expression (HSF1, HSF2 and HSF4). On the other hand, heat stress upregulated heat shock proteins (HSPs) at the mRNA (HSP72) and protein (HSP72 and HSP110) levels in wild‐type mice, but not in HSF1‐null mice. The population of Pax7‐positive nuclei relative to total myonuclei of soleus muscle in wild‐type mice was significantly increased by heat stress, but not in HSF1‐null mice. Furthermore, the absence of HSF1 gene suppressed heat stress‐associated phosphorylation of Akt and p70 S6 kinase (p‐p70S6K) in soleus muscle. Conclusion Heat stress‐associated increase in skeletal muscle mass may be induced by HSF1 and/or HSF1‐mediated stress response that activates muscle satellite cells and Akt/p70S6K signalling pathway.
    September 28, 2015   doi: 10.1111/apha.12600   open full text
  • Inverse gradient of nitrergic and purinergic inhibitory cotransmission in the mouse colon.
    N. Mañé, R. Viais, M. Martínez‐Cutillas, D. Gallego, P. Correia‐de‐Sá, M. Jiménez.
    Acta Physiologica. September 28, 2015
    Aim Gastrointestinal smooth muscle relaxation is accomplished by the neural corelease of ATP or a related purine and nitric oxide. Contractions are triggered by acetylcholine and tachykinins. The aim of this work was to study whether regional differences in neurotransmission could partially explain the varied physiological roles of each colonic area. Methods We used electrophysiological and myography techniques to evaluate purinergic (L‐NNA 1 mm incubated tissue), nitrergic (MRS2500 0.3 μm incubated tissue) and cholinergic neurotransmission (L‐NNA 1 mm and MRS2500 0.3 μm incubated tissue) in the proximal, mid and distal colon of CD1 mice (n = 42). Results Purinergic electrophysiological responses elicited by single pulses (28 V) were greater in the distal (IJPfMAX = −35.3 ± 2.2 mV), followed by the mid (IJPfMAX = −30.6 ± 1.0 mV) and proximal (IJPfMAX = −11.7 ± 1.1 mV) colon. In contrast, nitrergic responses decreased from the proximal colon (IJPsMAX = −11.4 ± 1.1 mV) to the mid (IJPsMAX = −9.1 ± 0.4 mV), followed by the distal colon (IJPsMAX = −1.8 ± 0.3 mV). A similar rank of order was observed in neural mediated inhibitory mechanical responses including electrical field stimulation‐mediated responses and neural tone. ADPβs concentration–response curve was shifted to the left in the distal colon. In contrast, NaNP responses did not differ between regions. Cholinergic neurotransmission elicited contractions of a similar amplitude throughout the colon. Conclusion An inverse gradient of purinergic and nitrergic neurotransmission exists through the mouse colon. The proximal and mid colon have a predominant nitrergic neurotransmission probably due to the fact that their storage function requires sustained relaxations. The distal colon, in contrast, has mainly purinergic neurotransmission responsible for the phasic relaxations needed to propel dehydrated faeces.
    September 28, 2015   doi: 10.1111/apha.12599   open full text
  • Antihypertensive and cardioprotective effects of the dipeptide isoleucine–tryptophan and whey protein hydrolysate.
    M. Martin, I. Kopaliani, A. Jannasch, C. Mund, V. Todorov, T. Henle, A. Deussen.
    Acta Physiologica. September 22, 2015
    Aims Angiotensin‐converting enzyme inhibitors are treatment of choice in hypertensive patients. Clinically used inhibitors exhibit a structural similarity to naturally occurring peptides. This study evaluated antihypertensive and cardioprotective effects of ACE‐inhibiting peptides derived from food proteins in spontaneously hypertensive rats. Methods and Results Isoleucine–tryptophan (in vitro IC50 for ACE = 0.7 μm), a whey protein hydrolysate containing an augmented fraction of isoleucine–tryptophan, or captopril was given to spontaneously hypertensive rats (n = 60) over 14 weeks. Two further groups, receiving either no supplement (Placebo) or intact whey protein, served as controls. Systolic blood pressure age‐dependently increased in the Placebo group, whereas the blood pressure rise was effectively blunted by isoleucine–tryptophan, whey protein hydrolysate and captopril (−42 ± 3, −38 ± 5, −55 ± 4 mm Hg vs. Placebo). At study end, myocardial mass was lower in isoleucine–tryptophan and captopril groups but only partially in the hydrolysate group. Coronary flow reserve (1 μm adenosine) was improved in isoleucine–tryptophan and captopril groups. Plasma ACE activity was significantly decreased in isoleucine–tryptophan, hydrolysate and captopril groups, but in aortic tissue only after isoleucine–tryptophan or captopril treatment. This was associated with lowered expression and activity of matrix metalloproteinase‐2. Following isoleucine–tryptophan and captopril treatments, gene expression of renin was significantly increased indicating an active feedback within renin–angiotensin system. Conclusion Whey protein hydrolysate and isoleucine–tryptophan powerfully inhibit plasma ACE resulting in antihypertensive effects. Moreover, isoleucine–tryptophan blunts tissue ACE activity, reduces matrix metalloproteinase‐2 activity and improves coronary flow reserve. Thus, whey protein hydrolysate and particularly isoleucine–tryptophan may serve as innovative food additives with the goal of attenuating hypertension.
    September 22, 2015   doi: 10.1111/apha.12578   open full text
  • The exercise‐regulated myokine chitinase‐3‐like protein 1 stimulates human myocyte proliferation.
    S. W. Görgens, M. Hjorth, K. Eckardt, S. Wichert, F. Norheim, T. Holen, S. Lee, T. Langleite, K. I. Birkeland, H. K. Stadheim, K. J. Kolnes, D. S. Tangen, A. J. Kolnes, J. Jensen, C. A. Drevon, J. Eckel.
    Acta Physiologica. September 08, 2015
    Aim Chitinase‐3‐like protein 1 (CHI3L1) is involved in tissue remodelling and inflammatory processes. Plasma levels are elevated in patients with insulin resistance and T2DM. We recently showed that CHI3L1 and its receptor protease‐activated receptor 2 (PAR‐2) are expressed in skeletal muscle. Activation of PAR‐2 by CHI3L1 protects against TNF‐α‐induced inflammation and insulin resistance. However, the effect of exercise on CHI3L1 and PAR‐2 signalling remains unknown. The aim of this work was to study the impact of exercise on CHI3L1 production and the effect of CHI3L1/PAR‐2 signalling on skeletal muscle growth and repair. Methods Three human exercise studies were used to measure CHI3L1 plasma levels (n = 32). In addition, muscle and adipose tissue CHI3L1 mRNA expression was measured in response to acute and long‐term exercise (n = 24). Primary human skeletal muscle cells were differentiated in vitro, and electrical pulse stimulation was applied. In addition, myoblasts were incubated with CHI3L1 protein and activation of MAP kinase signalling as well as proliferation was measured. Results Circulating CHI3L1 levels and muscle CHI3L1 mRNA were increased after acute exercise. In addition, CHI3L1 mRNA expression as well as CHI3L1 secretion was enhanced in electrically stimulated cultured myotubes. Incubation of cultured human myoblasts with CHI3L1 protein leads to a strong activation of p44/42, p38 MAPK and Akt as well as enhanced myoblast proliferation. Conclusion Our findings suggest that CHI3L1 is induced by acute exercise and that CHI3L1/PAR‐2 signalling activates myocyte proliferation, which is important for restructuring of skeletal muscle in the response to exercise training.
    September 08, 2015   doi: 10.1111/apha.12579   open full text
  • Visceral adipose tissue‐derived serine protease inhibitor augments acetylcholine‐induced relaxation via the inhibition of acetylcholine esterase activity in rat isolated mesenteric artery.
    S. Kameshima, K. Yamada, T. Morita, M. Okada, H. Yamawaki.
    Acta Physiologica. August 31, 2015
    Aim Visceral adipose tissue‐derived serine protease inhibitor (vaspin) is an adipocytokine with insulin‐sensitizing activity originally identified in visceral adipose tissues of obesity‐related type II diabetic rats. We previously showed that vaspin inhibits vascular cell migration and apoptosis as well as inflammatory responses, which are crucial for the development of hypertension. However, little is known about the effects of vaspin on vascular reactivity. The aim of this study was thus to explore the effects of vaspin on contraction and relaxation of isolated blood vessel. Methods After mesenteric arteries were isolated from male Wistar rats, the effects of pretreatment with vaspin (3 ng mL−1, 30 min) on concentration–contraction and concentration–relaxation relationships for each agent were examined. The effects of vaspin on acetylcholine (ACh)‐induced phosphorylation of endothelial nitric oxide (NO) synthase (eNOS) and ACh esterase (AChE) activity were also examined using Western blotting and colorimetric method respectively. Results Vaspin did not affect noradrenaline‐ or 5‐hydroxytryptamine‐induced contraction. In contrast, vaspin augmented ACh‐ but not histamine‐, A23187‐ or carbachol‐induced NO‐mediated relaxation. Vaspin significantly increased ACh‐induced eNOS phosphorylation and inhibited AChE activity. Conclusion We for the first time demonstrate that vaspin augments the ACh‐induced NO‐mediated endothelium‐dependent relaxation via the inhibition of AChE activity.
    August 31, 2015   doi: 10.1111/apha.12563   open full text
  • Circulating microparticles from diabetic rats impair endothelial function and regulate endothelial protein expression.
    K. Ishida, K. Taguchi, M. Hida, S. Watanabe, K. Kawano, T. Matsumoto, Y. Hattori, T. Kobayashi.
    Acta Physiologica. August 20, 2015
    Aim Diabetes mellitus increases the risk of cardiovascular disease, which is accompanied by functional and structural changes in the vascular system. Microparticles (MPs) have been described as biological vectors of endothelial dysfunction in other pathologies. However, the molecular mechanisms underlying their formation and signalling are unclear. We investigated the role of MPs derived from streptozotocin (STZ)‐induced diabetic rats in endothelial function. Methods Male Wistar rats were injected with STZ to induce diabetes, and MPs isolated from control or STZ‐induced diabetic rats were characterized by dot blotting (assessed by CD62P detections), flow cytometry (assessed by annexin V detections) and ELISA. Carotid arteries from rats were incubated with MPs, and expressions of enzymes and endothelium‐dependent relaxation were analysed. Results The circulating levels of MPs, particularly the levels of platelet‐derived microparticles, from diabetic rats were higher than those present in controls. Endothelium‐dependent relaxation induced by acetylcholine (ACh) was attenuated in carotid arteries from STZ‐induced diabetic rats. Following the incubation of control carotid arteries with MPs isolated from STZ rats, ACh‐induced endothelium‐dependent relaxation was impaired, but MPs isolated from control rats had no such effect. Furthermore, the effect of MPs was mediated by a decrease in expression of endothelial nitric oxide synthase (eNOS) and the overexpression of caveolin‐1. Conclusion Circulating MPs isolated from STZ‐induced diabetic rats induce endothelial dysfunction in carotid arteries and regulate protein expressions of eNOS and caveolin‐1. These data advance our understanding of the deleterious effects of circulating MPs observed in disorders with diabetic complications.
    August 20, 2015   doi: 10.1111/apha.12561   open full text
  • Claudin expression in follicle‐associated epithelium of rat Peyer's patches defines a major restriction of the paracellular pathway.
    A. G. Markov, E. L. Falchuk, N. M. Kruglova, J. Radloff, S. Amasheh.
    Acta Physiologica. August 18, 2015
    Aim Members of the tight junction protein family of claudins have been demonstrated to specifically determine paracellular permeability of the intestinal epithelium. In small intestinal mucosa, which is generally considered to be a leaky epithelium, Peyer's patches are a primary part of the immune system. The aim of this study was to analyse the tight junctional barrier of follicle‐associated epithelium covering Peyer's patches (lymphoid follicles). Methods Employing small intestinal tissue specimens of male Wistar rats, electrophysiological analyses including the Ussing chamber technique, marker flux measurements and one‐path impedance spectroscopy were performed. Morphometry of HE‐stained tissue sections was taken into account. Claudin expression and localization was analysed by immunoblotting and confocal laser scanning immunofluorescence microscopy. Results Almost twofold higher parameters of epithelial and transepithelial tissue resistance and a markedly lower permeability for the paracellular permeability markers 4 and 20 kDa FITC–dextran were detected in follicle‐associated epithelium compared to neighbouring villous epithelium. Analysis of claudin expression and localization revealed a stronger expression of major sealing proteins in follicle‐associated epithelium, including claudin‐1, claudin‐4, claudin‐5 and claudin‐8. Therefore, the specific expression and localization of claudins is in accordance with barrier properties of follicle‐associated epithelium vs. neighbouring villous epithelium. Conclusion We demonstrate that follicle‐associated epithelium is specialized to ensure maximum restriction of the epithelial paracellular pathway in Peyer's patches by selective sealing of tight junctions. This results in an exclusive transcellular pathway of epithelial cells as the limiting and mandatory route for a controlled presentation of antigens to the underlying lymphocytes under physiological conditions.
    August 18, 2015   doi: 10.1111/apha.12559   open full text
  • The calcium‐activated potassium channel KCa3.1 plays a central role in the chemotactic response of mammalian neutrophils.
    C. Henríquez, T. T. Riquelme, D. Vera, F. Julio‐Kalajzić, P. Ehrenfeld, J. E. Melvin, C. D. Figueroa, J. Sarmiento, C. A. Flores.
    Acta Physiologica. July 19, 2015
    Aim Neutrophils are the first cells to arrive at sites of injury. Nevertheless, many inflammatory diseases are characterized by an uncontrolled infiltration and action of these cells. Cell migration depends on volume changes that are governed by ion channel activity, but potassium channels in neutrophil have not been clearly identified. We aim to test whether KCa3.1 participates in neutrophil migration and other relevant functions of the cell. Methods Cytometer and confocal measurements to determine changes in cell volume were used. Cells isolated from human, mouse and horse were tested for KCa3.1‐dependent chemotaxis. Chemokinetics, calcium handling and release of reactive oxygen species were measured to determine the role of KCa3.1 in those processes. A mouse model was used to test for neutrophil recruitment after acute lung injury in vivo. Results We show for the first time that KCa3.1 is expressed in mammalian neutrophils. When the channel is inhibited by a pharmacological blocker or by genetic silencing, it profoundly affects cell volume regulation, and chemotactic and chemokinetic properties of the cells. We also demonstrated that pharmacological inhibition of KCa3.1 did not affect calcium entry or reactive oxygen species production in neutrophils. Using a mouse model of acute lung injury, we observed that Kca3.1−/− mice are significantly less effective at recruiting neutrophils into the site of inflammation. Conclusions These results demonstrate that KCa3.1 channels are key actors in the migration capacity of neutrophils, and its inhibition did not affect other relevant cellular functions.
    July 19, 2015   doi: 10.1111/apha.12548   open full text
  • Ca2+‐activated K+ current is essential for maintaining excitability and gene transcription in early embryonic cardiomyocytes.
    S. Karppinen, R. Rapila, N. Naumenko, T. Tuomainen, J. T. Koivumäki, S. L. Hänninen, T. Korhonen, P. Tavi.
    Acta Physiologica. June 28, 2015
    Aim Activity of early embryonic cardiomyocytes relies on spontaneous Ca2+ oscillations that are induced by interplay between sarcoplasmic reticulum (SR) – Ca2+ release and ion currents of the plasma membrane. In a variety of cell types, Ca2+‐activated K+ current (IK(Ca)) serves as a link between Ca2+ signals and membrane voltage. This study aimed to determine the role of IK(Ca) in developing cardiomyocytes. Methods Ion currents and membrane voltage of embryonic (E9‐11) mouse cardiomyocytes were measured by patch clamp; [Ca2+]i signals by confocal microscopy. Transcription of specific genes was measured with RT‐qPCR and Ca2+‐dependent transcriptional activity using NFAT‐luciferase assay. Myocyte structure was assessed with antibody labelling and confocal microscopy. Results E9‐11 cardiomyocytes express small conductance (SK) channel subunits SK2 and SK3 and have a functional apamin‐sensitive K+ current, which is also sensitive to changes in cytosolic [Ca2+]i. In spontaneously active cardiomyocytes, inhibition of IK(Ca) changed action and resting potentials, reduced SR Ca2+ load and suppressed the amplitude and the frequency of spontaneously evoked Ca2+ oscillations. Apamin caused dose‐dependent suppression of NFAT‐luciferase reporter activity, induced downregulation of a pattern of genes vital for cardiomyocyte development and triggered changes in the myocyte morphology. Conclusion The results show that apamin‐sensitive IK(Ca) is required for maintaining excitability and activity of the developing cardiomyocytes as well as having a fundamental role in promoting Ca2+‐ dependent gene expression.
    June 28, 2015   doi: 10.1111/apha.12540   open full text
  • In search for better pharmacological prophylaxis for acute mountain sickness: looking in other directions.
    Hui Lu, Rong Wang, Juan Xiong, Hua Xie, Bengt Kayser, Zheng‐ping Jia.
    Acta Physiologica. March 09, 2015
    Despite decades of research, the exact pathogenic mechanisms underlying acute mountain sickness (AMS) are still poorly understood. This fact frustrates the search for novel pharmacological prophylaxis for AMS. The prevailing view is that AMS results from an insufficient physiological response to hypoxia and that prophylaxis should aim at stimulating the response. Starting off from the opposite hypothesis that AMS may be caused by an initial excessive response to hypoxia we suggest that directly or indirectly blunting specific parts of the response might provide promising research alternatives. This reasoning is based on the observations that 1) humans, once acclimatized, can climb Mt Everest experiencing arterial partial oxygen pressures (PaO2) as low as 25 mmHg without AMS symptoms, 2) paradoxically AMS usually develops at much higher PaO2 levels, and 3) several biomarkers, suggesting initial activation of specific pathways at such PaO2, are correlated with AMS. Apart from looking for substances that stimulate certain hypoxia triggered effects, such as the ventilatory response to hypoxia, we suggest to also investigate pharmacological means aiming at blunting certain other specific hypoxia activated pathways, or stimulating their agonists, in the quest for better pharmacological prophylaxis for AMS. This article is protected by copyright. All rights reserved.
    March 09, 2015   doi: 10.1111/apha.12486   open full text
  • Actin Sliding Velocity On Pure Myosin Isoforms From Hindlimb Unloaded Mice.
    Manuela Maffei, Emanuela Longa, Rizwan Qaisar, Valentina Agoni, Jean‐François Desaphy, Diana Conte Camerino, Roberto Bottinelli, Monica Canepari.
    Acta Physiologica. May 29, 2014
    Aim Notwithstanding the widely accepted idea that following disuse skeletal muscles become faster, an increase in shortening velocity was previously observed mostly in fibers containing type 1 myosin, whereas a decrease was generally found in fibers containing type 2B myosin. In this study unloaded shortening velocity of pure type 1 and 2B fibers from hindlimb unloaded mice was determined and a decrease in type 2B fibers was found. Methods To clarify whether the decrease in shortening velocity could depend on alterations of myosin motor function, an in vitro motility assay approach was applied to study pure type 1 and pure type 2B myosin from hindlimb unloaded mice. The latter approach, assessing actin sliding velocity on isolated myosin in the absence of other myofibrillar proteins, enabled to directly investigate myosin motor function. Results Actin sliding velocity was significantly lower on type 2B myosin following unloading (2.70±0.32 μms‐1) than in control conditions (4.11±0.35 μms‐1), whereas actin sliding velocity of type 1 myosin was not different following unloading (0.89±0.04 μms‐1) compared to control conditions (0.84±0.17 μms‐1). Myosin light chain isoform composition of type 2B myosin from hindlimb unloaded and control mice was not different. No oxidation of either type 1 or 2B myosin was observed. Higher phosphorylation of regulatory myosin light chain in type 2B myosin after unloading was found. Conclusion Results suggest that the observed lower shortening velocity of type 2B fibers following unloading could be related to slowing of acto‐myosin kinetics in the presence of myosin light chain phosphorylation. This article is protected by copyright. All rights reserved.
    May 29, 2014   doi: 10.1111/apha.12320   open full text
  • The force‐velocity relationship at negative loads (assisted shortening) studied in isolated, intact muscle fibres of the frog.
    K.A.P. Edman.
    Acta Physiologica. May 29, 2014
    Aim The study was undertaken to explore the force‐velocity relationship under conditions where the myofilament system is subjected to an external force that serves as a negative load and assists the shortening movement. Methods The experiments were carried out on single muscle fibres isolated from the anterior tibialis muscle of Rana temporaria. The fibres, being operated under load‐clamp control, were released to shorten during tetanic stimulation at sarcomere lengths where the fibres carried different degrees of passive tension. The shortening thus occurred while the sarcomeres were subjected to a force that may be characterized as a “negative load”, i.e. a force assisting the shortening movement. Results The force‐velocity relationship below zero load was found to be a smooth continuation of the force‐velocity curve recorded at positive loads the shortening velocity increasing steeply at loads below zero. A negative load amounting to merely 10% of the isometric force thus raised the shortening velocity to a level 2‐3 times higher than V0, the velocity recorded at zero load. Conclusion The results provide evidence that, even in the presence of a longitudinal compressive force, the speed of shortening of the muscle fibre is determined by the cycling rate of the interacting cross‐bridges. The force‐velocity relationship at negative loads may play a relevant part during fast movements of striated muscle as pointed out in the discussion. This article is protected by copyright. All rights reserved.
    May 29, 2014   doi: 10.1111/apha.12321   open full text
  • The Effect of Tendon Vibration on Motor Unit Activity, Intermuscular Coherence, and Force Steadiness in the Elbow Flexors of Males and Females.
    B Harwood, KMD Cornett, DL Edwards, RE Brown, JM Jakobi.
    Acta Physiologica. May 28, 2014
    Compartmentalized responses in motor unit (MU) activity of the short (SH) and long (LH) heads of the biceps brachii are observed following forearm position change. Differential muscle spindle afferent distribution has been proposed as a potential mechanism underlying this behavior. Tendon vibration is an effective, non‐invasive method of increasing muscle spindle afferent activity of a target muscle group offering a paradigm in which this hypothesis may be investigated further. Aim To determine the effect of tendon vibration on MU recruitment and discharge rates of the SH and LH, muscle activity of the elbow flexors and triceps brachii, intermuscular coherence among the SH, LH, brachioradialis and triceps brachii, and force steadiness in young male and females during isometric elbow flexion. Methods Intramuscular electromyography (EMG) of the SH and LH, and surface EMG of the elbow flexors were recorded pre‐ and post‐vibration during low force isometric contractions. Motor unit recruitment thresholds, MU discharge rates, and MU discharge variability; surface EMG amplitude, intermuscular coherence, and force steadiness were determined pre‐ and post‐vibration. Results Differential changes in all MU properties, EMG amplitude and intermuscular coherence were observed among elbow flexors. Although MU properties exhibited differential changes, they accounted for little variance in isometric force steadiness. However, intermuscular EMG coherence among all muscles investigated was reduced post‐vibration. Conclusion Uncoupling of common oscillatory input as a result of differential muscle spindle afferent inputs to elbow flexors may be responsible for the reduction in force steadiness following tendon vibration and a forearm position change. This article is protected by copyright. All rights reserved.
    May 28, 2014   doi: 10.1111/apha.12319   open full text
  • Estrogen‐dependent satellite cell activation and proliferation following a running exercise occurs via the PI3K signalling pathway and not IGF‐1.
    Gary Mangan, Eric Bombardier, Andrew Mitchell, Joe Quadrilatero, Peter M. Tiidus.
    Acta Physiologica. May 24, 2014
    Aim The purpose of this study was to determine whether 17β‐Estradiol (E2) enhances the activation, proliferation and differentiation of muscle satellite cells (SC) following eccentric exercise either via Insulin‐like Growth Factor‐1 (IGF‐1) or through phosphatidylinositol 3‐kinase (PI3K) signaling. Methods This study used 64, nine‐week old, ovariectomized Sprague‐Dawley rats that were divided into eight treatments groups based on: estrogen status (0.25 mg estrogen pellet or sham), exercise status (90 min run @ 17 m/min, ‐13.5° or unexercised), PI3K signaling inhibition (0.7 mg Wortmannin·kg−1 Body Weight or DMSO control). Results Significant increases in total SCs were found in both soleus and white gastrocnemius muscles (immunofluorescent co‐localization of Pax7+ nuclei) 72 hr following eccentric exercise (p < 0.05). Estrogen‐supplementation caused a further enhancement in total SCs in exercised rats (p < 0.05). In animals where the PI3K pathway was inhibited, regardless of estrogen or exercise status, there was no significant enhancement of SC number in both the soleus or white gastrocnemius muscles. Interestingly, estrogen‐supplementation lowered muscle levels of IGF‐1 with this effect being most prominent in the soleus muscle. While IGF‐1 was increased following exercise (p < 0.05), estrogen‐supplementation abrogated this increase back to sedentary levels. Conclusion This data suggests that the increase in SC population following exercise in estrogen‐supplemented females may be mediated via PI3K pathway signaling and not IGF‐1. This article is protected by copyright. All rights reserved.
    May 24, 2014   doi: 10.1111/apha.12317   open full text
  • Acute response and subcellular movement of HSP27, αB‐crystallin and HSP70 in human skeletal muscle after blood‐flow‐restricted low‐load resistance exercise.
    K. T. Cumming, G. Paulsen, M. Wernbom, I. Ugelstad, T. Raastad.
    Acta Physiologica. May 23, 2014
    Aim Heat‐shock proteins (HSP) are important chaperones for stressed and damaged proteins. Low‐load blood‐flow‐restricted resistance exercise (BFRE) is generally believed not to induce significant muscle damage, but is hitherto unverified with intracellular markers. Consequently, the aim of this study was to investigate the HSP response after BFRE in human skeletal muscle. Methods Nine healthy volunteers performed five sets to failure of unilateral knee extension at 30% of 1RM with partial blood‐flow restriction. The contralateral leg performed the same work with free blood flow. Muscle biopsies were collected before exercise, 1, 24 and 48 h after exercise and analysed for HSP27, αB‐crystallin, HSP70, desmin, glycogen content and myosin heavy chain by immunohistochemistry, ELISA and western blotting. Results One hour after exercise, HSP27 and αB‐crystallin levels were reduced in the cytosolic and increased in the cytoskeletal fraction in the BFRE leg. HSP70 showed a delayed response and was increased over 48 h in the BFRE leg. Immunohistochemical analyses showed higher staining intensity of HSP70 in type 1 fibres in the BFRE leg at 24 and 48 h post‐exercise. PAS staining showed decreased glycogen levels after BFRE, and interestingly, glycogen was still depleted 48 h after exercise in the same fibres displaying high HSP70 staining (type 1 fibres). Conclusion Translocation of HSP27 and αB‐crystallin from cytosol to cytoskeletal structures indicates that cytoskeletal proteins are stressed during BFRE. However, overt signs of myofibrillar disruptions were not observed. Interestingly, the stress response was more pronounced in type 1 than in type 2 fibres and coincided with low glycogen levels.
    May 23, 2014   doi: 10.1111/apha.12305   open full text
  • Metformin induces lactate production in peripheral blood mononuclear cells and platelets through specific mitochondrial complex I inhibition.
    S. Piel, J. K. Ehinger, E. Elmér, M. J. Hansson.
    Acta Physiologica. May 23, 2014
    Aim Metformin is a widely used antidiabetic drug associated with the rare side effect of lactic acidosis which has been proposed to be linked to drug‐induced mitochondrial dysfunction. Using respirometry, the aim of this study was to evaluate mitochondrial toxicity of metformin to human blood cells in relation to that of phenformin, a biguanide analogue withdrawn in most countries due to a high incidence of lactic acidosis. Methods Peripheral blood mononuclear cells and platelets were isolated from healthy volunteers, and integrated mitochondrial function was studied in permeabilized and intact cells using high‐resolution respirometry. A wide concentration range of metformin (0.1–100 mm) and phenformin (25–500 μm) was investigated for dose‐ and time‐dependent effects on respiratory capacities, lactate production and pH. Results Metformin induced respiratory inhibition at complex I in peripheral blood mononuclear cells and platelets (IC50 0.45 mm and 1.2 mm respectively). Phenformin was about 20‐fold more potent in complex I inhibition of platelets than metformin. Metformin further demonstrated a dose‐ and time‐dependent respiratory inhibition and augmented lactate release at a concentration of 1 mm and higher. Conclusion Respirometry of human peripheral blood cells readily detected respiratory inhibition by metformin and phenformin specific to complex I, providing a suitable model for probing drug toxicity. Lactate production was increased at concentrations relevant for clinical metformin intoxication, indicating mitochondrial inhibition as a direct causative pathophysiological mechanism. Relative to clinical dosing, phenformin displayed a more potent respiratory inhibition than metformin, possibly explaining the higher incidence of lactic acidosis in phenformin‐treated patients.
    May 23, 2014   doi: 10.1111/apha.12311   open full text
  • On the antioxidant properties of erythropoietin and its association with the oxidative–nitrosative stress response to hypoxia in humans.
    D. M. Bailey, C. Lundby, R. M. G. Berg, S. Taudorf, H. Rahmouni, M. Gutowski, C. W. Mulholland, J. L. Sullivan, E. R. Swenson, J. McEneny, I. S. Young, B. K. Pedersen, K. Møller, S. Pietri, M. Culcasi.
    Acta Physiologica. May 23, 2014
    Aim The aim of this study was to examine if erythropoietin (EPO) has the potential to act as a biological antioxidant and determine the underlying mechanisms. Methods The rate at which its recombinant form (rHuEPO) reacts with hydroxyl (HO˙), 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH˙) and peroxyl (ROO˙) radicals was evaluated in‐vitro. The relationship between the erythopoietic and oxidative–nitrosative stress response to poikilocapneic hypoxia was determined separately in‐vivo by sampling arterial blood from eleven males in normoxia and following 12 h exposure to 13% oxygen. Electron paramagnetic resonance spectroscopy, ELISA and ozone‐based chemiluminescence were employed for direct detection of ascorbate (A˙−) and N‐tert‐butyl‐α‐phenylnitrone spin‐trapped alkoxyl (PBN‐OR) radicals, 3‐nitrotyrosine (3‐NT) and nitrite (NO2−). Results We found rHuEPO to be a potent scavenger of HO˙ (kr = 1.03–1.66 × 1011 m−1 s−1) with the capacity to inhibit Fenton chemistry through catalytic iron chelation. Its ability to scavenge DPPH˙ and ROO˙ was also superior compared to other more conventional antioxidants. Hypoxia was associated with a rise in arterial EPO and free radical‐mediated reduction in nitric oxide, indicative of oxidative–nitrosative stress. The latter was confirmed by an increased systemic formation of A˙−, PBN‐OR, 3‐NT and corresponding loss of NO2− (P < 0.05 vs. normoxia). The erythropoietic and oxidative–nitrosative stress responses were consistently related (r = −0.52 to 0.68, P < 0.05). Conclusion These findings demonstrate that EPO has the capacity to act as a biological antioxidant and provide a mechanistic basis for its reported cytoprotective benefits within the clinical setting.
    May 23, 2014   doi: 10.1111/apha.12313   open full text
  • Truncated splice variant PGC‐1α4 is not associated with exercise‐induced human muscle hypertrophy.
    T. R. Lundberg, R. Fernandez‐Gonzalo, J. Norrbom, H. Fischer, P. A. Tesch, T. Gustafsson.
    Acta Physiologica. May 21, 2014
    Introduction A truncated PGC‐1α splice variant (PGC‐1α4) has been implicated in the regulation of resistance exercise (RE)‐induced muscle hypertrophy, and basal expression levels said to be augmented in response to concurrent aerobic (AE) and RE training. Aim The current study investigated human muscle truncated and non‐truncated PGC‐1α transcripts in response to both acute and chronic RE, and with or without preceding AE (AE+RE). Methods Ten men performed 5 weeks of unilateral AE+RE and RE training. Before (untrained) and after (trained) this intervention, PGC‐1α transcripts were assessed in vastus lateralis muscle biopsies obtained before and 3 h after acute RE, with or without preceding AE. Additionally, samples were collected 72 h after the last exercise bout of the training programme. Results The truncated splice variant increased (P < 0.05) its expression after acute exercise regardless of mode. However, the expression was greater (P < 0.05) after AE+RE than RE. Other PGC‐1α transcripts showed similar response. Truncated transcripts originated from both the alternative and proximal promoter, and AE+RE increased PGC‐1α expression from both promoter sites. RE induced transcripts from the alternative promoter only. PGC‐1α expressions after acute exercise were comparable across isoforms in both untrained and trained muscle. Steady‐state levels of isoforms were unchanged after 5‐week training (P > 0.05). Exercise‐induced expression of PGC‐1α variants did not correlate with changes in muscle size or strength (P > 0.05). Conclusion Our results do not support the view that truncated PGC‐1α coordinates exercise‐induced hypertrophy in human skeletal muscle. Rather, all PGC‐1α isoforms appear to be regulated transiently in response to acute exercise and regardless of mode.
    May 21, 2014   doi: 10.1111/apha.12310   open full text
  • MicroRNAs: potential therapeutic targets in diabetic complications of the cardiovascular and renal systems.
    Miriam Frankenthal Figueira, Gustavo Monnerat‐Cahli, Emiliano Medei, Adriana Bastos Carvalho, Marcelo Marcos Morales, Marcelo Einicker Lamas, Rodrigo Nunes da Fonseca, Jackson Souza‐Menezes.
    Acta Physiologica. May 19, 2014
    Diabetes mellitus is a serious health problem that can lead to several pathologic complications in numerous organs and tissues. The most important and most prevalent organs affected by this disease are the heart and the kidneys and these complications are the major causes of death in patients with diabetes. MicroRNAs (miRNAs), short non‐coding RNAs, have been found to be functionally important in the regulation of several pathologic processes and they are emerging as an important therapeutic tool to avoid the complications of diabetes mellitus. This review summarizes the knowledge on the effects of miRNAs in diabetes. The use of miRNAs in diabetes from a clinical perspective is also discussed, focusing on their potential role to repair cardiovascular and renal complications. This article is protected by copyright. All rights reserved.
    May 19, 2014   doi: 10.1111/apha.12316   open full text
  • Contraction‐evoked vasodilation and functional hyperaemia are compromised in branching skeletal muscle arterioles of young pre‐diabetic mice.
    N. M. Novielli, D. N. Jackson.
    Acta Physiologica. May 16, 2014
    Aim To investigate the effects of pre‐diabetes on microvascular network function in contracting skeletal muscle. We hypothesized that pre‐diabetes compromises contraction‐evoked vasodilation of branching second‐order (2A), third‐order (3A) and fourth‐order (4A) arterioles, where distal arterioles would be affected the greatest. Methods Intravital video microscopy was used to measure arteriolar diameter (in 2A, 3A and 4A) and blood flow (in 2A and 3A) changes to electrical field stimulation of the gluteus maximus muscle in pre‐diabetic (The Pound Mouse, PD) and control (c57bl6, CTRL) mice. Results Baseline diameter and blood flow were similar between groups (2A: ~20 μm, 3A: ~14 μm and 4A: ~8 μm; 2A: ~1 nL s−1 and 3A: ~0.5 nL s−1). Single tetanic contraction (100 Hz; 200, 400, 800 ms duration) evoked rapid‐onset vasodilation (ROV) and blood flow responses that were blunted by ~50% and up to 81%, respectively, in PD vs. CTRL (P < 0.05). The magnitude of ROV was up to 2‐fold greater at distal arterioles (3A and 4A) vs. proximal arterioles (2A) in CTRL; however, in PD, ROV of only 4A was greater than 2A (P < 0.05). Rhythmic contraction (2 and 8 Hz, 30 s) evoked vasodilatory and blood flow responses that were also attenuated by ~50% and up to 71%, respectively, in PD vs. CTRL (P < 0.05). The magnitude of vasodilatory responses to rhythmic contraction was also up to 2.5‐fold greater at 4A vs. 2A in CTRL; however spatial differences in vasodilation across arteriolar branch orders was disrupted in PD. Conclusions Arteriolar dysregulation in pre‐diabetes causes deficits in contraction‐evoked dilation and blood flow, where greatest deficits occur at distal arterioles.
    May 16, 2014   doi: 10.1111/apha.12297   open full text
  • Bile deficiency induces changes in intestinal Cl− and HCO3− secretions in mice.
    P. Song, Y. Du, W. Song, X. Liu, L. Hong, H. Li, H. Xie, L. Zhou, B. Tuo, S. Zheng.
    Acta Physiologica. May 16, 2014
    Aims Biliary tract obstruction is a common clinical lesion. However, the effect of biliary tract obstruction on intestinal secretion is poorly understood. In this study, we made an investigation on intestinal HCO3− and Cl− secretions in an experimental model of murine biliary duct ligation. Methods Murine intestinal mucosal HCO3− and Cl− secretions were examined in vitro in Ussing chambers by pH‐stat and short‐circuit current (Isc) techniques. The mRNA and protein expressions of the cystic fibrosis transmembrane conductance regulator (CFTR) and the Na+–K+–2Cl− cotransporter (NKCC1) were analysed by real‐time PCR, western blot and immunohistochemistry. Results Basal Cl− secretion and forskolin‐stimulated duodenal and jejunal mucosal HCO3− and Cl− secretions in mice with common biliary duct ligation were markedly elevated, compared with controls (P < 0.05 and P < 0.01). Further experiments showed that basal Cl− secretion and forskolin‐stimulated duodenal and jejunal mucosal HCO3− and Cl− secretions in mice with external bile drainage were also markedly elevated. CFTRinh‐172 inhibited forskolin‐stimulated HCO3− and Cl− secretions. The mRNA and protein expression levels of CFTR and NKCC1 in the intestinal mucosa with both biliary duct ligation and external bile drainage were markedly higher than those in controls (P < 0.001). Bile acid administration restored the changes in function and expression of CFTR and NKCC1 in the intestinal mucosa. Conclusion Bile deficiency in the intestine up‐regulates the expressions of intestinal mucosal CFTR and NKCC1 and enhances intestinal mucosal HCO3− and Cl− secretion capacity, which contributes to the understanding of intestinal physiological function for patients with biliary duct obstruction.
    May 16, 2014   doi: 10.1111/apha.12301   open full text
  • Alterations of calcium homeostasis in cultured rat astrocytes evoked by bioactive sphingolipids.
    Matjaž Stenovec, Saša Trkov, Marko Kreft, Robert Zorec.
    Acta Physiologica. May 13, 2014
    Aim In the brain, alterations in sphingolipid metabolism contribute to several neurologic disorders; however, their effect on astrocytes is largely unknown. Here, we identified bioactive sphingolipids that affect intracellular free calcium concentration ([Ca2+]i), mobility of peptidergic secretory vesicles, signaling pathways involved in alterations of calcium homeostasis and explored the relationship between the stimulus‐evoked increase in [Ca2+]i and attenuation of vesicle mobility. Methods Confocal time‐lapse images were acquired to explore [Ca2+]i signals, the mobility of fluorescently tagged peptidergic vesicles and the structural integrity of the microtubules and actin filaments before and after the addition of exogenous sphingolipids to astrocytes. Results Fingolimod (FTY720), a recently introduced therapeutic for multiple sclerosis, and sphingosine, a releasable constituent of membrane sphingolipids, evoked long‐lasting increases in [Ca2+]i in the presence and absence of extracellular Ca2+; the evoked responses were diminished in the absence of extracellular Ca2+. Activation of phospholipase C and inositol‐1,4,5‐triphosphate receptors was necessary and sufficient to evoke increases in [Ca2+]i as revealed by the pharmacologic inhibitors; Ca2+ flux from the extracellular space intensified these responses several fold. The lipid‐evoked increases in [Ca2+]i coincided with the attenuated vesicle mobility. High and positive correlation between increase in [Ca2+]i and decrease in peptidergic vesicle mobility was confirmed independently in astrocytes exposed to evoked, transient Ca2+ signaling triggered by purinergic and glutamatergic stimulation. Conclusion Exogenously added cell‐permeable sphingosine‐like lipids exert complex, Ca2+‐dependent effects on astrocytes and likely alter their homeostatic function in vivo. This article is protected by copyright. All rights reserved.
    May 13, 2014   doi: 10.1111/apha.12314   open full text
  • L‐type calcium channels in sympathetic α3β2‐nAChR‐mediated cerebral nitrergic neurogenic vasodilation.
    Celeste Yin‐Chieh Wu, Reggie Hui‐Chao Lee, Po‐Yi Chen, Andy Po‐Yi Tsai, Mei‐Fang Chen, Jon‐Son Kuo, Tony Jer‐Fu Lee.
    Acta Physiologica. May 13, 2014
    Aim Nicotine stimulation of α3β2‐nicotinic acetylcholine receptors (α3β2‐nAChRs) located on sympathetic nerves innervating basilar arteries causes calcium‐dependent norepinephrine release, leading to activation of parasympathetic nitrergic nerves and dilation of basilar arteries. This study aimed to investigate the major subtype of calcium channels located on cerebral perivascular sympathetic nerves, which is involved in nicotine‐induced α3β2‐nAChR‐mediated nitrergic vasodilation in basilar arteries. Methods Nicotine‐ and transmural nerve stimulation (TNS)‐induced dilation of isolated porcine basilar arteries was examined using in vitro tissue bath. Nicotine‐induced calcium‐influx, norepinephrine‐release, and inward‐currents were evaluated in rat superior cervical ganglion (SCG) neurons, perivascular sympathetic nerves of porcine basilar arteries, and α3β2‐nAChRs‐expressing oocytes, respectively. mRNA and protein expression of Cav1.2‐ and Cav1.3‐channels were detected by RT‐PCR, Western blotting, and immunohistochemistry. Results Nicotine‐induced vasodilation was not affected by ω‐agatoxin TK (selective P/Q‐type calcium‐channel blocker) or ω‐conotoxin GVIA (N‐type calcium‐channel blocker). The vasodilation, however, was inhibited by nicardipine (L‐type calcium‐channel blocker) in concentrations which did not affect TNS‐induced vasodilation, suggesting the specific blockade. Nicardipine concentration‐dependently inhibited nicotine‐induced calcium‐influx in rat SCG neurons and reduced nicotine‐induced norepinephrine release from perivascular sympathetic nerves of porcine basilar arteries. Nicardipine (10 μM), which significantly blocked nicotine‐induced vasorelaxation by 70 %, did not appreciably affect nicotine‐induced inward currents in α3β2‐nAChRs‐expressing oocytes. Furthermore, the mRNAs and proteins of Cav1.2 and Cav1.3 channels were expressed in porcine SCG and perivascular nerve terminals. Conclusion The sympathetic neuronal calcium‐influx through L‐type calcium‐channels is modulated by α3β2‐nAChRs. This calcium‐influx causes norepinephrine release, initiating sympathetic‐parasympathetic (axo‐axonal) interaction‐induced nitrergic dilation of porcine basilar arteries. This article is protected by copyright. All rights reserved.
    May 13, 2014   doi: 10.1111/apha.12315   open full text
  • Function and evolution of vertebrate globins.
    Thorsten Burmester, Thomas Hankeln.
    Acta Physiologica. May 08, 2014
    Globins are heme‐proteins that bind O2 and thus play an important role in the animal's respiration and oxidative energy production. However, globins may also have other functions such as the decomposition or production of NO, the detoxification of reactive oxygen species, or intracellular signalling. In addition to the well‐investigated haemoglobins and myoglobins, genome sequence analyses have led to the identification of six further globin types in vertebrates: androglobin, cytoglobin, globin E, globin X, globin Y and neuroglobin. Here, we review the present state of knowledge on the functions, the taxonomic distribution and evolution of vertebrate globins, drawing conclusions about the functional changes underlying present‐day globin diversity. This article is protected by copyright. All rights reserved.
    May 08, 2014   doi: 10.1111/apha.12312   open full text
  • Quantification of skeletal muscle mitochondrial function by 31P magnetic resonance spectroscopy techniques: a quantitative review.
    Graham J Kemp, Raja Elina Ahmad, Klaas Nicolay, Jeanine J Prompers.
    Acta Physiologica. April 28, 2014
    Magnetic resonance spectroscopy (MRS) can give information about cellular metabolism in vivo which is difficult to obtain in other ways. In skeletal muscle, noninvasive 31P MRS measurements of the post‐exercise recovery kinetics of pH, [PCr], [Pi] and [ADP] contain valuable information about muscle mitochondrial function and cellular pH homeostasis in vivo, but quantitative interpretation depends on understanding the underlying physiology. Here, by giving examples of the analysis of 31P MRS recovery data, by some simple computational simulation, and by extensively comparing data from published studies using both 31P MRS and invasive direct measurements of muscle O2 consumption in a common analytical framework, we consider what can be learnt quantitatively about mitochondrial metabolism in skeletal muscle using MRS‐based methodology. We explore some technical and conceptual limitations of current methods, and point out some aspects of the physiology which are still incompletely understood. This article is protected by copyright. All rights reserved.
    April 28, 2014   doi: 10.1111/apha.12307   open full text
  • Fatty acids and cardiac disease: Fuel carrying a message.
    Marc Bilsen, Anna Planavila.
    Acta Physiologica. April 28, 2014
    From the viewpoint of the prevention of cardiovascular disease (CVD) burden, there has been a continuous interest in the detrimental effects of the Western‐type high‐fat diet for more than half a century. More recently, this general view has been subject to change as epidemiological studies showed that replacing fat by carbohydrate may even be worse and that various polyunsaturated fatty acids (FA) have beneficial rather than detrimental effects on CVD outcome. At the same time advances in lipid biology have provided insight into the mechanisms by which the different lipid components of the Western diet affect the cardiovascular system. In fact, this still is a rapidly growing field of research and in recent years novel FA derivatives and FA receptors have been discovered. This includes fish‐oil derived FA‐derivatives with anti‐inflammatory properties, the so‐called resolvins, and various G‐protein coupled receptors that recognize FA as ligands. In the present review we will extensively discuss the role of FA and their metabolites on cardiac disease, with special emphasis on the role of the different saturated and polyunsaturated FA and their respective metabolites in cellular signal transduction and the possible implications for the development of cardiac hypertrophy and cardiac failure This article is protected by copyright. All rights reserved.
    April 28, 2014   doi: 10.1111/apha.12308   open full text
  • L‐type Ca2+ channel current characteristics are preserved in rat tail artery myocytes after one‐day storage.
    P. Mugnai, M. Durante, G. Sgaragli, S. Saponara, G. Paliuri, S. Bova, F. Fusi.
    Acta Physiologica. April 23, 2014
    Aim To develop a cheap and simple method of storing for 24‐h vascular tissue and single myocytes while preserving therein the biophysical and pharmacological characteristics of L‐type Ca2+ channels and contractile activity. Methods Rings or vascular smooth muscle cells obtained from the rat tail main artery were used either freshly (R0h and VSMC0h) or stored for 24 h (R24h and VSMC24h) at 4 °C, to record whole‐cell L‐type Ca2+ currents (ICa(L)) or measure contractile responses. Results R0h/VSMC0h and R24h/VSMC24h comparably contracted when stimulated with phenylephrine, high KCl or ATP. In both VSMC0h and VSMC24h, ICa(L) was identified and characterized as a stable inward current for at least 35 min; ICa(L) was comparably inhibited by the Ca2+ antagonists nifedipine, verapamil and diltiazem and increased by the Ca2+ channel agonist (S)‐(‐)‐Bay K 8644; current density and current–voltage relationships were similar; at more hyperpolarized holding potentials, ICa(L) intensity increased comparably; nifedipine shifted the steady‐state inactivation curve towards more negative potentials, while verapamil blocked ICa(L) in a frequency‐dependent manner and slowed down the rate of recovery from inactivation in a comparable way. Conclusion Findings show that smooth muscle contractile activity and the biophysical and pharmacological features of L‐type Ca2+ channels are similar in VSMC24h and VSMC0h. The fact that reproducible results were obtained in vascular myocytes up to 24 h after dissociation may facilitate vascular smooth muscle cell investigation by increasing throughput and reducing the number of animals required.
    April 23, 2014   doi: 10.1111/apha.12282   open full text
  • Changes in the activity and expression of protein phosphatase‐1 accompany the differential regulation of NHE3 before and after the onset of hypertension in spontaneously hypertensive rats.
    R. O. Crajoinas, T. D. Pessoa, M. V. Rodrigues, G. Malnic, A. C. C. Girardi.
    Acta Physiologica. April 23, 2014
    Aim The Na+/H+ exchanger NHE3 activity decreases in the proximal tubule of spontaneously hypertensive rats (SHRs) as blood pressure increases, and this reduction is correlated with higher NHE3 phosphorylation levels at the PKA consensus site serine 552. This study tested the hypothesis that this lowered NHE3 activity is associated with an increase in PKA activity and expression, and/or a decrease in protein phosphatase‐1 (PP1) activity and expression. Methods Proximal tubule NHE3 activity was measured as the rate of bicarbonate reabsorption by stationary microperfusion. NHE3 phosphorylation and protein expression were determined by immunoblotting. PKA and PP1 activities were determined using specific substrates under optimal enzymatic conditions. Results The PKA activator, 6‐MB‐cAMP, increased the phosphorylation levels of NHE3 at serine 552 in the renal cortex; this increase happens to a much greater extent in young pre‐hypertensive SHRs (Y‐SHRs) compared to adult SHRs with established hypertension (A‐SHRs). Likewise, the inhibitory effect of 6‐MB‐cAMP on NHE3 transport activity was much more pronounced in the proximal tubules of Y‐SHRs than in those of A‐SHRs. Renal cortical activity of PKA was not significantly different between Y‐SHRs and A‐SHRs. On the other hand, Y‐SHRs exhibited higher protein phosphatase 1 (PP1) activity, and their expression of the PP1 catalytic subunit PP1α in the renal cortex was also higher than in A‐SHRs. Conclusion Collectively, these results support the idea that the lower NHE3 transport activity and higher phosphorylation occurring after the development of hypertension in SHRs are due, at least in part, to reduced PP1‐mediated dephosphorylation of NHE3 at serine 552.
    April 23, 2014   doi: 10.1111/apha.12288   open full text
  • Associations of subjective vitality with DNA damage, cardiovascular risk factors and physical performance.
    S. Maynard, G. Keijzers, Å.‐M. Hansen, M. Osler, D. Molbo, L. Bendix, P. Møller, S. Loft, M. Moreno‐Villanueva, A. Bürkle, C. P. Hvitby, S. H. Schurman, T. Stevnsner, L. J. Rasmussen, K. Avlund, V. A. Bohr.
    Acta Physiologica. April 23, 2014
    Aim To examine associations of DNA damage, cardiovascular risk factors and physical performance with vitality, in middle‐aged men. We also sought to elucidate underlying factors of physical performance by comparing physical performance parameters to DNA damage parameters and cardiovascular risk factors. Methods We studied 2487 participants from the Metropolit cohort of 11 532 men born in 1953 in the Copenhagen Metropolitan area. The vitality level was estimated using the SF‐36 vitality scale. Cardiovascular risk factors were determined by body mass index (BMI), and haematological biochemistry tests obtained from non‐fasting participants. DNA damage parameters were measured in peripheral blood mononuclear cells (PBMCs) from as many participants as possible from a representative subset of 207 participants. Results Vitality was inversely associated with spontaneous DNA breaks (measured by comet assay) (P = 0.046) and BMI (P = 0.002), and positively associated with all of the physical performance parameters (all P < 0.001). Also, we found several associations between physical performance parameters and cardiovascular risk factors. In addition, the load of short telomeres was inversely associated with maximum jump force (P = 0.018), with lowered significance after exclusion of either arthritis sufferers (P = 0.035) or smokers (P = 0.031). Conclusion Here, we show that self‐reported vitality is associated with DNA breaks, BMI and objective (measured) physical performance in a cohort of middle‐aged men. Several other associations in this study verify clinical observations in medical practice. In addition, the load of short telomeres may be linked to peak performance in certain musculoskeletal activities.
    April 23, 2014   doi: 10.1111/apha.12296   open full text
  • Influence of age on leptin induced skeletal muscle signalling.
    A. Guadalupe‐Grau, S. Larsen, B. Guerra, J. A. L. Calbet, F. Dela, J. W. Helge.
    Acta Physiologica. April 18, 2014
    Aim Age associated fat mass accumulation could be because of dysregulation of leptin signalling in skeletal muscle. Thus, we investigated total protein expression and phosphorylation levels of the long isoform of the leptin receptor (OB‐Rb), and leptin signalling through janus kinase 2 (JAK2)/signal transducer and activator of transcription 3 (STAT3), insulin receptor substrate 1 (IRS‐1), AMP‐activated protein kinase (AMPK) and acetyl‐coenzyme A carboxylase (ACC), combined with the leptin signalling inhibitors suppressor of cytokine signalling 3 (SOCS3) and protein tyrosine phosphatase 1B (PTP1B) in human skeletal muscle of different age. Methods Vastus lateralis muscle biopsies were obtained from 39 men matched for BMI < 30 kg m−2 and separated into three groups: 13 young (Y, 24 ± 4 years); 14 middle aged (MA, 44 ± 5 years) and 12 aged (A, 58 ± 8 years) subjects. Results Whole body fat percentage and plasma leptin were higher (P < 0.05), whereas lean mass, plasma free testosterone and total testosterone were lower (P < 0.05) in A compared to Y. Skeletal muscle OB‐Rb (170 KDa) protein expression and pTyr1141‐OB‐R170 were comparable between groups, whereas pTyr985‐OB‐R170 was lower in A compared to Y (P < 0.05). pSTAT3 levels tended (P = 0.09) to be lower (50%) in A compared to Y. In A, muscle PTP1B was greater and IRS‐1 lower than Y and MA respectively (P < 0.05). PTyr612‐IRS‐1 tended to be lower in A than in Y (P = 0.09). Suppressor of cytokine signalling 3 (SOCS3) protein expression, pJAK2, pSer1101‐IRS‐1, pAMPKα and pACCβ were similar between groups. Conclusion Age is associated with dysregulation of the leptin signalling and increased PTP1B protein expression in skeletal muscle.
    April 18, 2014   doi: 10.1111/apha.12273   open full text
  • Activation of histamine H1 receptors in the nucleus tractus solitarii attenuates cardiac baroreceptor reflex function in rats.
    M. Takagishi, S. S. Gouraud, M. E. R. Bhuiyan, A. Kohsaka, M. Maeda, H. Waki.
    Acta Physiologica. April 18, 2014
    Aim The nucleus tractus solitarii (NTS) is a central brainstem structure that plays an important role in regulating cardiovascular homeostasis. In this study, we examined whether H1 receptors in the NTS can control the baroreceptor reflex function by modulating synaptic transmission. Methods Cardiac baroreceptor reflex function was assessed before and after the microinjection of 2‐pyridylethylamine (10–25 nmol), a histamine H1 receptor‐specific agonist, into the NTS of urethane‐anaesthetized Wistar rats. The cardiovascular responses induced by l‐glutamate microinjection into the NTS were also examined before and after the NTS administration of 2‐pyridylethylamine. Results Nucleus tractus solitarii microinjections of 2‐pyridylethylamine significantly inhibited the gain of the cardiac baroreceptor reflex and bradycardiac/depressor responses induced by l‐glutamate microinjection into the NTS. These findings suggest that histamine H1 receptors regulate the cardiac baroreceptor reflex in a post‐synaptic manner to inhibit barosensitive NTS neurons. Conclusion Taken together with our previous findings, the present results provide further evidence that histamine may play a role within the NTS in regulating cardiovascular homeostasis.
    April 18, 2014   doi: 10.1111/apha.12278   open full text
  • The role of nitric oxide in the cardiovascular response to chronic and acute hypoxia in White Leghorn chicken (Gallus domesticus).
    N. K. Iversen, T. Wang, E. Baatrup, D. A. Crossley.
    Acta Physiologica. April 18, 2014
    Aim Prenatal hypoxia due to placental insufficiency results in deleterious phenotypes and compensatory mechanisms including increased sympathetic tone. Utilizing the embryonic chicken model, we investigated (i) changes in nitric oxide (NO)‐mediated tone in response to chronic hypoxic development and (ii) the in vivo role of NO‐mediated tone during acute hypoxic exposure, which has not been previously studied. We hypothesized that NO tone on the cardiovascular system would be unaffected by chronic hypoxic incubation in White Leghorn chicken (Gallus domesticus) embryos. Methods We measured arterial pressure, heart rate and femoral blood flow (via a Doppler flow probe) in response to acute hypoxia (10% O2) and pharmacological manipulations in normoxic‐ and hypoxic (15% O2)‐incubated embryos. This was performed at 70 and 90% of total incubation time (21 days). At 70% of incubation (day 15), blood volume and chorioallantoic membrane development are maximal; 90% of incubation (day 19) is 1 day prior to lung ventilation. Results Acute hypoxic exposure decreased femoral flow in both 90% groups, but increased femoral artery resistance in the hypoxic group. NO tone increased during development, but was not affected by hypoxic incubation. Inhibition of NO production by L‐NAME (100 mg kg−1) revealed that NO plays a significant role in the flow response to hypoxia. Conclusion Chronic hypoxic incubation has no effect on cardiovascular NO tone during White Leghorn chicken development. In the intact animal, NO function during acute hypoxic stress is suppressed by hypoxic incubation, indicating that chronic hypoxic stress dampens the NO contribution.
    April 18, 2014   doi: 10.1111/apha.12286   open full text
  • Assessment of human baroreflex function using carotid ultrasonography: what have we learnt?
    Chloe E Taylor, Christopher K Willie, Philip N Ainslie, Yu‐Chieh Tzeng.
    Acta Physiologica. April 17, 2014
    The arterial baroreflex is critical to both short and long‐term regulation of blood pressure. However, human baroreflex research has been largely limited to the association between blood pressure and cardiac period (or heart rate) or indices of vascular sympathetic function. Over the past decade, emerging techniques based on carotid ultrasound imaging have allowed new means of understanding and measuring the baroreflex. In this review, we describe the assessment of the mechanical and neural components of the baroreflex through the use of carotid ultrasound imaging. The mechanical component refers to the change in carotid artery diameter in response to changes in arterial pressure, and the neural component refers to the change in R‐R interval (cardiac baroreflex) or muscle sympathetic nerve activity (sympathetic baroreflex) in response to this barosensory vessel stretch. The key analytical concepts and techniques are discussed, with a focus on the assessment of baroreflex sensitivity via the modified Oxford method. We illustrate how the application of carotid ultrasound imaging has contributed to a greater understanding of baroreflex physiology in humans, covering topics such as ageing and diurnal variation, and physiological challenges including exercise, postural changes and mental stress. This article is protected by copyright. All rights reserved.
    April 17, 2014   doi: 10.1111/apha.12302   open full text
  • Three‐dimensional reconstruction of the human skeletal muscle mitochondrial network as a tool to assess mitochondrial content and structural organization.
    R. Dahl, S. Larsen, T. L. Dohlmann, K. Qvortrup, J. W. Helge, F. Dela, C. Prats.
    Acta Physiologica. April 15, 2014
    Aim Mitochondria undergo continuous changes in shape as result of complex fusion and fission processes. The physiological relevance of mitochondrial dynamics is still unclear. In the field of mitochondria bioenergetics, there is a need of tools to assess cell mitochondrial content. To develop a method to visualize mitochondrial networks in high resolution and assess mitochondrial volume. Methods Confocal fluorescence microscopy imaging of mitochondrial network stains in human vastus lateralis single muscle fibres and focused ion beam/ scanning electron microscopy (FIB/SEM) imaging, combined with 3D reconstruction was used as a tool to analyse mitochondrial morphology and measure mitochondrial fractional volume. Results Most type I and type II muscle fibres have tubular highly interconnected profusion mitochondria, which are thicker and more structured in type I muscle fibres (Fig. 1). In some muscle fibres, profission‐isolated ellipsoid‐shaped mitochondria were observed. Mitochondrial volume was significantly higher in type I muscle fibres and showed no correlation with any of the investigated molecular and biochemical mitochondrial measurements (Fig. 2). Three‐dimensional reconstruction of FIB/SEM data sets shows that some subsarcolemmal mitochondria are physically interconnected with some intermyofibrillar mitochondria (Fig. 3). Conclusion Two microscopy methods to visualize skeletal muscle mitochondrial networks in 3D are described and can be used as tools to investigate mitochondrial dynamics in response to life‐style interventions and/or in certain pathologies. Our results question the classification of mitochondria into subsarcolemmal and intermyofibrillar pools, as they are physically interconnected.
    April 15, 2014   doi: 10.1111/apha.12289   open full text
  • Cardiovascular and metabolic responses to tap water ingestion in young humans: does the water temperature matter?
    M. Girona, E. K. Grasser, A. G. Dulloo, J. P. Montani.
    Acta Physiologica. April 15, 2014
    Aim Drinking water induces short‐term cardiovascular and metabolic changes. These effects are considered to be triggered by gastric distension and osmotic factors, but little is known about the influence of water temperature. Methods We determined, in a randomized crossover study, the acute cardiovascular and metabolic responses to 500 mL of tap water at 3 °C (cold), 22 °C (room) and 37 °C (body) in 12 young humans to ascertain an effect of water temperature. We measured continuous beat‐to‐beat haemodynamics, skin blood flux with laser‐Doppler flowmetry and resting energy expenditure by indirect calorimetry starting with a 30‐min baseline followed by a 4‐min drink period and a subsequent 90‐min post‐drink observation. Results Ingestion of cold‐ and room‐tempered water led to decreased heart rate (P < 0.01) and double product (P < 0.01), and increased stroke volume (P < 0.05); these effects were not observed with body‐tempered water. Drinking cold‐ and room‐, but not body‐tempered water, led to increased high frequency power of heart rate variability (P < 0.05) and baroreflex sensitivity (P < 0.05). Cold‐ and room‐tempered water increased energy expenditure over 90 min by 2.9% (P < 0.05) and 2.3% (ns), respectively, accompanied by a diminished skin blood flux (P < 0.01), thereby suggesting that both small increases in heat production together with decreased heat loss contribute to warming up the ingested water to intra‐abdominal temperature levels. Conclusions Overall, ingestion of cold‐ and room‐, but not body‐tempered water reduced the workload to the heart through a reduction in heart rate and double product which could be mediated by an augmented cardiac vagal tone.
    April 15, 2014   doi: 10.1111/apha.12290   open full text
  • Ca2+ signals, NAADP and Two Pore Channels: Role in Cellular Differentiation.
    John Parrington, Ruth Tunn.
    Acta Physiologica. April 07, 2014
    Ca2+ signals regulate a wide range of physiological processes. Intracellular Ca2+ stores can be mobilized in response to extracellular stimuli via a range of signal transduction mechanisms, often involving recruitment of diffusible second messenger molecules. The Ca2+ mobilizing messengers InsP3 and cADPR release Ca2+ from the endoplasmic reticulum via the InsP3 and ryanodine receptors, respectively, while a third messenger, NAADP, releases Ca2+ from acidic endosomes and lysosomes. Bidirectional communication between the ER and acidic organelles may have functional relevance for endolysosomal function as well as for the generation of Ca2+ signals. The two‐pore channels (TPCs), are currently strong candidates for being key components of NAADP‐regulated Ca2+ channels. Ca2+ signals have been shown to play important roles in differentiation; however, much remains to be established about the exact signalling mechanisms involved. The investigation of the role of NAADP and TPCs in differentiation is still at an early stage but recent studies have suggested that they are important mediators of differentiation of neurons, skeletal muscle cells, and osteoclasts. NAADP signals and TPCs have also been implicated in autophagy, an important process in differentiation. Further studies will be required to identify the precise mechanism of TPC action and their link with NAADP signalling, as well as relating this to their roles in differentiation and other key processes in the cell and organism. This article is protected by copyright. All rights reserved.
    April 07, 2014   doi: 10.1111/apha.12298   open full text
  • Pathophysiology and Potential Treatments of Pulmonary Hypertension due to Systolic Left Heart Failure.
    Jakob Lundgren, Göran Rådegran.
    Acta Physiologica. April 05, 2014
    Pulmonary hypertension (PH) due to left heart failure is becoming increasingly prevalent, and is associated with poor outcome. The precise pathophysiological mechanisms behind PH due to left heart failure are, however, still unclear. In its early course, PH is caused by elevated left ventricular filling pressures, without pulmonary vessel abnormalities. Conventional treatment for heart failure may partly reverse such passive PH by optimizing left ventricular function. However, if elevated pulmonary pressures persists, endothelial damage, excessive vasoconstriction and structural changes in the pulmonary vasculature may occur. There is, at present, no recommended medical treatment for this active component of PH due to left heart failure. However, as the vascular changes in PH due to left heart failure may be similar to those in pulmonary arterial hypertension (PAH), a selected group of these patients may benefit from PAH treatment targeting the endothelin, nitric oxide or prostacyclin pathways. Such potent pulmonary vasodilators could, however, be detrimental in patients with left heart failure without pulmonary vascular pathology, as selective pulmonary vasodilatation may lead to further congestion in the pulmonary circuit, resulting in pulmonary oedema. The use of PAH therapies is therefore, currently not recommended, and would require the selection of suitable patients based on the underlying causes of the disease, and careful monitoring of their progress. The present review focuses on: i. the pathophysiology behind PH resulting from systolic left heart failure and: ii. the current evidence for medical treatment of this condition, especially the role of PAH‐targeted therapies in systolic left heart failure. This article is protected by copyright. All rights reserved.
    April 05, 2014   doi: 10.1111/apha.12295   open full text
  • Acylated and unacylated ghrelin inhibit doxorubicin‐induced apoptosis in skeletal muscle.
    A. P. Yu, X. M. Pei, T. K. Sin, S. P. Yip, B. Y. Yung, L. W. Chan, C. S. Wong, P. M. Siu.
    Acta Physiologica. April 02, 2014
    Aim Doxorubicin, a potent chemotherapeutic drug, has been demonstrated previously as an inducer of apoptosis in muscle cells. Extensive induction of apoptosis may cause excessive loss of muscle cells and subsequent functional decline in skeletal muscle. This study examined the effects of acylated ghrelin, a potential agent for treating cancer cachexia, on inhibiting apoptotic signalling in doxorubicin‐treated skeletal muscle. Unacylated ghrelin, a form of ghrelin that does not bind to GHSR‐1a, is also employed in this study to examine the GHSR‐1a signalling dependency of the effects of ghrelin. Methods Adult C57BL/6 mice were randomly assigned to saline control (CON), doxorubicin (DOX), doxorubicin with treatment of acylated ghrelin (DOX+Acylated Ghrelin) and doxorubicin with treatment of unacylated ghrelin (DOX+Unacylated Ghrelin). Mice in all groups that involved DOX were intraperitoneally injected with 15 mg of doxorubicin per kg body weight, whereas mice in CON group received saline as placebo. Gastrocnemius muscle tissues were harvested after the experimental period for analysis. Results The elevation of apoptotic DNA fragmentation and number of TUNEL‐positive nuclei were accompanied with the upregulation of Bax in muscle after exposure to doxorubicin, but all these changes were neither seen in the muscle treated with acylated ghrelin nor unacylated ghrelin after doxorubicin exposure. Protein abundances of autophagic markers including LC3 II‐to‐LC3 I ratio, Atg12‐5 complex, Atg5 and Beclin‐1 were not altered by doxorubicin but were upregulated by the treatment of either acylated or unacyated ghrelin. Histological analysis revealed that the amount of centronucleated myofibres was elevated in doxorubicin‐treated muscle while muscle of others groups showed normal histology. Conclusions Collectively, our data demonstrated that acylated ghrelin administration suppresses the doxorubicin‐induced activation of apoptosis and enhances the cellular signalling of autophagy. The treatment of unacylated ghrelin has similar effects as acylated ghrelin on apoptotic and autophagic signalling, suggesting that the effects of ghrelin are probably mediated through a signalling pathway that is independent of GHSR‐1a. These findings were consistent with the hypothesis that acylated ghrelin inhibits doxorubicin‐induced upregulation of apoptosis in skeletal muscle while treatment of unacylated ghrelin can achieve similar effects as the treatment of acylated ghrelin. The inhibition of apoptosis and enhancement of autophagy induced by acylated and unacylated ghrelin might exert myoprotective effects on doxorubicin‐induced toxicity in skeletal muscle.
    April 02, 2014   doi: 10.1111/apha.12263   open full text
  • High‐intensity interval training alters ATP pathway flux during maximal muscle contractions in humans.
    R. G. Larsen, L. Maynard, J. A. Kent.
    Acta Physiologica. April 02, 2014
    Aim High‐intensity interval training (HIT) results in potent metabolic adaptations in skeletal muscle; however, little is known about the influence of these adaptations on energetics in vivo. We used magnetic resonance spectroscopy to examine the effects of HIT on ATP synthesis from net PCr breakdown (ATPCK), oxidative phosphorylation (ATPOX) and non‐oxidative glycolysis (ATPGLY) in vivo in vastus lateralis during a 24‐s maximal voluntary contraction (MVC). Methods Eight young men performed 6 sessions of repeated, 30‐s ‘all‐out’ sprints on a cycle ergometer; measures of muscle energetics were obtained at baseline and after the first and sixth sessions. Results Training increased peak oxygen consumption (35.8 ± 1.4 to 39.3 ± 1.6 mL min−1 kg−1, P = 0.01) and exercise capacity (217.0 ± 11.0 to 230.5 ± 11.7 W, P = 0.04) on the ergometer, with no effects on total ATP production or force–time integral during the MVC. While ATP production by each pathway was unchanged after the first session, 6 sessions increased the relative contribution of ATPOX (from 31 ± 2 to 39 ± 2% of total ATP turnover, P < 0.001) and lowered the relative contribution from both ATPCK (49 ± 2 to 44 ± 1%, P = 0.004) and ATPGLY (20 ± 2 to 17 ± 1%, P = 0.03). Conclusion These alterations to muscle ATP production in vivo indicate that brief, maximal contractions are performed with increased support of oxidative ATP synthesis and relatively less contribution from anaerobic ATP production following training. These results extend previous reports of molecular and cellular adaptations to HIT and show that 6 training sessions are sufficient to alter in vivo muscle energetics, which likely contributes to increased exercise capacity after short‐term HIT.
    April 02, 2014   doi: 10.1111/apha.12275   open full text
  • Time‐course effect of exercise‐induced muscle damage on localized muscle mechanical properties assessed using elastography.
    L. Lacourpaille, A. Nordez, F. Hug, A. Couturier, C. Dibie, G. Guilhem.
    Acta Physiologica. April 02, 2014
    Aim Changes in muscle stiffness after exercise‐induced muscle damage have been classically inferred from passive torque–angle curves. Elastographic techniques can be used to estimate the shear modulus of a localized muscular area. This study aimed to quantify the changes in shear elastic modulus in different regions of the elbow flexors after eccentric exercise and their relation to muscle length. Methods Shear elastic modulus and transverse relaxation time (T2) were measured in the biceps brachii and brachialis muscles of sixteen participants, before, 1 h, 48 h and 21 days after three sets of ten maximal isokinetic eccentric contractions performed at 120° s−1. Results The shear elastic modulus of the elbow flexors significantly increased 1 h (+46%; P = 0.005), with no significant change at 48 h and 21D, post‐exercise. In contrast, T2 was not modified at 1 h but significantly increased at 48 h (+15%; P < 0.05). The increase in shear elastic modulus was more pronounced at long muscle lengths and reached a similar extent in the different regions of the elbow flexors. The normalized hysteresis area of shear elastic modulus–length relationship for the biceps brachii increased 1 h post‐exercise (31%) in comparison with the pre‐exercise value (18%), but was not significantly altered after five stretching cycles (P = 0.63). Conclusion Our results show homogeneous changes in muscle shear elastic modulus within and between elbow flexors. The greater increase in shear elastic modulus observed at long muscle lengths suggests the putative involvement of both cross‐bridges number and titin in the modifications of muscle shear elastic modulus after damaging exercise.
    April 02, 2014   doi: 10.1111/apha.12272   open full text
  • Andrographolide inhibits HMGB1‐induced inflammatory responses in human umbilical vein endothelial cells and in murine polymicrobial sepsis.
    W. Lee, S. Ku, H. Yoo, K. Song, J. Bae.
    Acta Physiologica. March 24, 2014
    Aim Nuclear DNA‐binding protein high‐mobility group box 1 (HMGB1) protein acts as a late mediator of severe vascular inflammatory conditions, such as septic shock, upregulating pro‐inflammatory cytokines. Andrographolide (AG) is isolated from the plant of Andrographis paniculata and used as a folk medicine for treatment of viral infection, diarrhoea, dysentery and fever. However, the effect of AG on HMGB1‐induced inflammatory response has not been studied. Methods Firstly, we accessed this question by monitoring the effects of post‐treatment AG on lipopolysaccharide (LPS) and caecal ligation and puncture (CLP)‐mediated release of HMGB1 and HMGB1‐mediated regulation of pro‐inflammatory responses in human umbilical vein endothelial cells (HUVECs) and septic mice. Results Post‐treatment AG was found to suppress LPS‐mediated release of HMGB1 and HMGB1‐mediated cytoskeletal rearrangements. AG also inhibited HMGB1‐mediated hyperpermeability and leucocyte migration in septic mice. In addition, AG inhibited production of tumour necrosis factor‐α (TNF‐α) and activation of AKT, nuclear factor‐κB (NF‐κB) and extracellular‐regulated kinases (ERK) 1/2 by HMGB1 in HUVECs. AG also induced downregulation of CLP‐induced release of HMGB1, production of interleukin (IL) 1β/6/8 and mortality. Conclusion Collectively, these results suggest that AG may be regarded as a candidate therapeutic agent for the treatment of vascular inflammatory diseases via inhibition of the HMGB1 signalling pathway.
    March 24, 2014   doi: 10.1111/apha.12264   open full text
  • Changes in arterial function in a mouse model of human familial hypercholesterolaemia.
    O. Brinkmann, K. Schmerbach, U. J. F. Tietge, T. Dietrich, H. Guski, D. Linz, H. Kühn, A. Patzak, K. Wilfert.
    Acta Physiologica. March 24, 2014
    Aim Atherosclerosis is the most common cause of cardiovascular disease. The ApoB mouse is a model for human familial hypercholesterolaemia and has a lipoprotein profile similar to that of humans with atherosclerosis. Therefore, it is a suitable model to investigate the changes in vasoreactivity during atherogenesis. This study investigates contractile and dilatative properties of arteries in this model in relation to age. Methods Male ApoB mice and B6, wild‐type (WT), mice were examined at age four or 18 months. Isometric measurements of 2‐mm ring preparations of the aorta thoracica were performed using a wire myograph. Histological and biochemical methods served to determine atherosclerosis, lipid status and endothelial markers respectively. Results Morphometric analysis showed that all old ApoB mice had severe atherosclerosis in the aorta. Atherosclerotic alteration of the aorta of the ApoB mice coincided with a diminished vasodilatation to acetylcholine. The phenylephrine response was significantly attenuated already to the same degree in the non‐atherosclerotic aorta of the young ApoB mice as in the atherosclerotic aorta of the older ApoB mice. Serum parameters showed a rise in total cholesterol and triglycerides in the ApoB strain compared to WT mice. Soluble intercellular adhesion molecule (sICAM)‐1 and soluble vascular adhesion molecule (sVCAM)‐1 were increased in old compared to young ApoB mice. Conclusion The study shows that reduced acetylcholine‐induced dilatation is related to the presence of atherosclerosis in old ApoB mice. Remarkably, the impaired vessel reactivity to phenylephrine already in young ApoB mice indicates early changes in vascular function in this model.
    March 24, 2014   doi: 10.1111/apha.12262   open full text
  • Low‐intensity training increases peak arm VO2 by enhancing both convective and diffusive O2 delivery.
    R. Boushel, I. Ara, E. Gnaiger, J. W. Helge, J. González‐Alonso, T. Munck‐Andersen, H. Sondergaard, R. Damsgaard, G. Hall, B. Saltin, J. A. L. Calbet.
    Acta Physiologica. March 17, 2014
    Aim It is an ongoing discussion the extent to which oxygen delivery and oxygen extraction contribute to an increased muscle oxygen uptake during dynamic exercise. It has been proposed that local muscle factors including the capillary bed and mitochondrial oxidative capacity play a large role in prolonged low‐intensity training of a small muscle group when the cardiac output capacity is not directly limiting. The purpose of this study was to investigate the relative roles of circulatory and muscle metabolic mechanisms by which prolonged low‐intensity exercise training alters regional muscle VO2. Methods In nine healthy volunteers (seven males, two females), haemodynamic and metabolic responses to incremental arm cycling were measured by the Fick method and biopsy of the deltoid and triceps muscles before and after 42 days of skiing for 6 h day−1 at 60% max heart rate. Results Peak pulmonary VO2 during arm crank was unchanged after training (2.38 ± 0.19 vs. 2.18 ± 0.2 L min−1 pre‐training) yet arm VO2 (1.04 ± 0.08 vs. 0.83 ± 0.1 L min1, P < 0.05) and power output (137 ± 9 vs. 114 ± 10 Watts) were increased along with a higher arm blood flow (7.9 ± 0.5 vs. 6.8 ± 0.6 L min−1, P < 0.05) and expanded muscle capillary volume (76 ± 7 vs. 62 ± 4 mL, P < 0.05). Muscle O2 diffusion capacity (16.2 ± 1 vs. 12.5 ± 0.9 mL min−1 mHg−1, P < 0.05) and O2 extraction (68 ± 1 vs. 62 ± 1%, P < 0.05) were enhanced at a similar mean capillary transit time (569 ± 43 vs. 564 ± 31 ms) and P50 (35.8 ± 0.7 vs. 35 ± 0.8), whereas mitochondrial O2 flux capacity was unchanged (147 ± 6 mL kg min−1 vs. 146 ± 8 mL kg min−1). Conclusion The mechanisms underlying the increase in peak arm VO2 with prolonged low‐intensity training in previously untrained subjects are an increased convective O2 delivery specifically to the muscles of the arm combined with a larger capillary–muscle surface area that enhance diffusional O2 conductance, with no apparent role of mitochondrial respiratory capacity.
    March 17, 2014   doi: 10.1111/apha.12258   open full text
  • Impaired epicardial activation–repolarization coupling contributes to the proarrhythmic effects of hypokalaemia and dofetilide in guinea pig ventricles.
    O. E. Osadchii.
    Acta Physiologica. March 17, 2014
    Aim Activation–repolarization coupling refers to the inverse relationship between action potential duration and activation time in myocardial regions along the path of ventricular excitation. This study examined whether the activation–repolarization coupling plays a role in coordinating repolarization times between the right ventricular (RV) and left ventricular (LV) chambers, and if impaired coordination contributes to electrical instability produced by hypokalaemia or dofetilide, a blocker of the delayed rectifier K+ current. Methods In Langendorff‐perfused, isolated guinea pig hearts, six monophasic action potential recording electrodes were attached to RV and LV epicardium. Local activation time and action potential duration (APD90) were determined during spontaneous beating, regular pacing and extrasystolic excitation. Results In regularly beating hearts, the RV epicardial sites had longer APD90, but exhibited earlier activation times, as compared to LV sites, which minimized the interventricular difference in repolarization time. Upon extrasystolic stimulation, the APD90 was reduced to a greater extent in RV compared with LV, which translated to a reversed slope of APD90‐to‐activation time relationship, and increased spatial repolarization gradients. Hypokalaemia and dofetilide prolonged APD90, with the effect being greater in LV compared with RV. In hypokalaemic hearts, LV activation was delayed. These changes contributed to increased asynchrony in repolarization times in the LV and RV in both regular and extrasystolic beats, and enhanced susceptibility to tachyarrhythmia. Conclusion Impaired RV‐to‐LV activation–repolarization coupling is an important determinant of electrical instability in the setting of non‐uniformly prolonged epicardial APD90 or slowed interventricular conduction.
    March 17, 2014   doi: 10.1111/apha.12259   open full text
  • Endogenous α‐calcitonin‐gene‐related peptide promotes exercise‐induced, physiological heart hypertrophy in mice.
    B. Schuler, G. Rieger, M. Gubser, M. Arras, M. Gianella, O. Vogel, P. Jirkof, N. Cesarovic, J. Klohs, P. Jakob, M. Brock, T. A. Gorr, O. Baum, H. Hoppeler, V. Samillan‐Soto, M. Gassmann, J. A. Fischer, W. Born, J. Vogel.
    Acta Physiologica. March 13, 2014
    Aim It is unknown how the heart distinguishes various overloads, such as exercise or hypertension, causing either physiological or pathological hypertrophy. We hypothesize that alpha‐calcitonin‐gene‐related peptide (αCGRP), known to be released from contracting skeletal muscles, is key at this remodelling. Methods The hypertrophic effect of αCGRP was measured in vitro (cultured cardiac myocytes) and in vivo (magnetic resonance imaging) in mice. Exercise performance was assessed by determination of maximum oxygen consumption and time to exhaustion. Cardiac phenotype was defined by transcriptional analysis, cardiac histology and morphometry. Finally, we measured spontaneous activity, body fat content, blood volume, haemoglobin mass and skeletal muscle capillarization and fibre composition. Results While αCGRP exposure yielded larger cultured cardiac myocytes, exercise‐induced heart hypertrophy was completely abrogated by treatment with the peptide antagonist CGRP(8‐37). Exercise performance was attenuated in αCGRP−/− mice or CGRP(8‐37) treated wild‐type mice but improved in animals with higher density of cardiac CGRP receptors (CLR‐tg). Spontaneous activity, body fat content, blood volume, haemoglobin mass, muscle capillarization and fibre composition were unaffected, whereas heart index and ventricular myocyte volume were reduced in αCGRP−/− mice and elevated in CLR‐tg. Transcriptional changes seen in αCGRP−/− (but not CLR‐tg) hearts resembled maladaptive cardiac phenotype. Conclusions Alpha‐calcitonin‐gene‐related peptide released by skeletal muscles during exercise is a hitherto unrecognized effector directing the strained heart into physiological instead of pathological adaptation. Thus, αCGRP agonists might be beneficial in heart failure patients.
    March 13, 2014   doi: 10.1111/apha.12244   open full text
  • The effects of equal caloric high fat and western diet on metabolic syndrome, oxidative stress and vascular endothelial function in mice.
    I. Heinonen, P. Rinne, S. T. Ruohonen, S. Ruohonen, M. Ahotupa, E. Savontaus.
    Acta Physiologica. March 13, 2014
    Aim Nutrition contributes to increased adiposity, but it remains to be determined whether high fat rather than Western diet exacerbates the development of obesity and other characteristics of metabolic syndrome and vascular function. Methods We studied the effects of high fat (45% kcal) diet (HFD) and equal caloric Western diet (WD) high in fat, sucrose and cholesterol for 8 weeks in male C57B1/6N mice. Results Mice fed with HFD and WD showed substantially higher body adiposity (body fat %) compared with control mice receiving low fat (10%) diet (LFD). However, total body weight was higher only in HFD mice compared with other groups. The amount of liver triglycerides, cholesterol and oxidative damage was higher in WD mice compared with mice on LFD. There were no significant differences in fasting blood glucose or serum insulin, serum or muscle triglycerides, glucose tolerance or systolic blood pressure between the groups, but serum free fatty acids were increased in HFD mice compared with LFD. Increased levels of tissue and serum diene conjugation as a marker of oxidative stress were evident especially in WD mice. The endothelium‐dependent relaxations were significantly impaired in the small mesenteric arteries of HFD mice, but not in the aorta. Maximal relaxations correlated negatively with body adiposity in WD but not in HFD mice. Conclusions The major finding in the present study is that without changing body weight, Western diet induces marked whole‐body oxidative stress and elevates body adiposity, which associates with the endothelial function of resistance arteries.
    March 13, 2014   doi: 10.1111/apha.12253   open full text
  • Task‐related changes in sensorimotor integration influence the common synaptic input to motor neurones.
    C. M. Laine, Ş. U. Yavuz, D. Farina.
    Acta Physiologica. March 13, 2014
    Aim The purpose of this investigation was to understand how visual information, when used to guide muscle activity, influences the frequency content of the neural drive to muscles and the gain of afferent feedback. Methods Subjects maintained static, isometric contractions of the tibialis anterior muscle by matching a visual display of their ankle dorsiflexion force to a target set at 10% of their maximum voluntary contraction level. Two visual feedback conditions were studied. The first was a high‐sensitivity feedback, in which small changes in force were of large on‐screen visual magnitude. The second was a low‐sensitivity feedback, in which the on‐screen scaling of feedback was reduced by a factor of 10, making small force fluctuations difficult to perceive. Force tremor and Hoffmann reflex (H‐reflex) amplitudes were compared between the two conditions, as well as coherence among single motor unit spike trains derived from high‐density EMG recordings. Results The high‐sensitivity feedback condition was associated with lower error, larger force tremor (4–12 Hz) and larger H‐reflex amplitudes relative to the low‐sensitivity feedback condition. In addition, the use of high‐sensitivity feedback was associated with lower 1–5 Hz coherence among pairs of motor units, but larger coherence at high frequencies (6–12, approx. 20, >30 Hz). Conclusion Alteration of visual feedback influences nearly the entire frequency spectrum of common input to motor neurones, as well the gain of afferent feedback. We speculate that task‐related modulation of afferent feedback could be the origin of many of the observed changes in the neural drive to muscles.
    March 13, 2014   doi: 10.1111/apha.12255   open full text
  • Leptin into the ventrolateral medulla facilitates chemorespiratory response in leptin‐deficient (ob/ob) mice.
    M. Bassi, W. I. Furuya, J. V. Menani, D. S. A. Colombari, J. M. do Carmo, A. A. da Silva, J. E. Hall, T. S. Moreira, I. C. Wenker, D. K. Mulkey, E. Colombari.
    Acta Physiologica. March 13, 2014
    Aim Leptin, an adipocyte‐derived hormone, is suggested to participate in the central control of breathing. We hypothesized that leptin may facilitate ventilatory responses to chemoreflex activation by acting on respiratory nuclei of the ventrolateral medulla. The baseline ventilation and the ventilatory responses to CO2 were evaluated before and after daily injections of leptin into the retrotrapezoid nucleus/parafacial respiratory group (RTN/pFRG) for 3 days in obese leptin‐deficient (ob/ob) mice. Methods Male ob/ob mice (40–45 g, n = 7 per group) received daily microinjections of vehicle or leptin (1 μg per 100 nL) for 3 days into the RTN/pFRG. Respiratory responses to CO2 were measured by whole‐body plethysmography. Results Unilateral microinjection of leptin into the RTN/pFRG in ob/ob mice increased baseline ventilation (VE) from 1447 ± 96 to 2405 ±174 mL min−1 kg−1 by increasing tidal volume (VT) from 6.4 ± 0.4 to 9.1 ± 0.8 mL kg−1 (P < 0.05). Leptin also enhanced ventilatory responses to 7% CO2 (Δ = 2172 ± 218 mL min−1 kg−1, vs. control: Δ = 1255 ± 105 mL min−1 kg−1), which was also due to increased VT (Δ = 4.71 ± 0.51 mL kg−1, vs. control: Δ = 2.27 ± 0.20 mL kg−1), without changes in respiratory frequency. Leptin treatment into the RTN/pFRG or into the surrounding areas decreased food intake (83 and 70%, respectively), without significantly changing body weight. Conclusion The present results suggest that leptin acting in the respiratory nuclei of the ventrolateral medulla improves baseline VE and VT and facilitates respiratory responses to hypercapnia in ob/ob mice.
    March 13, 2014   doi: 10.1111/apha.12257   open full text
  • Brain‐derived neurotrophic factor promotes angiogenic tube formation through generation of oxidative stress in human vascular endothelial cells.
    T. Usui, A. Naruo, M. Okada, Y. Hayabe, H. Yamawaki.
    Acta Physiologica. March 10, 2014
    Aim Brain‐derived neurotrophic factor (BDNF), a major type of neurotrophins, plays a role in the regulation of synaptic function. Recent studies suggest that BDNF promotes angiogenesis through its specific receptor, tropomyosin‐related kinase B (TrkB). However, the detailed mechanisms for this still remain to be determined. Reactive oxygen species (ROS) generation contributes to the regulation of angiogenesis. Thus, we investigated the mechanisms by which BDNF regulates angiogenesis with focusing on ROS in cultured human vascular endothelial cells (ECs). Methods and results In human umbilical vein ECs, BDNF increased ROS generation as measured fluorometrically using 2′ 7′‐dichlorofluorescein diacetate as well as NADPH oxidase (NOX) activity as measured by lucigenin assay. BDNF‐induced ROS generation and NOX activity were inhibited by K252a, a TrkB receptor inhibitor. BDNF induced phosphorylation of p47 phox, a regulatory component of NOX, which was inhibited by K252a as measured by Western blotting. BDNF increased angiogenic tube formation in ECs, which was completely inhibited by K252a or gp91ds‐tat, a NOX inhibitor. BDNF caused Akt phosphorylation in ECs, which was inhibited by K252a or gp91ds‐tat. Conclusion The present results for the first time demonstrate that BDNF induces NOX‐derived ROS generation through activation of p47 phox in a TrkB receptor‐dependent manner, which leads to the promotion of angiogenic tube formation possibly via Akt activation.
    March 10, 2014   doi: 10.1111/apha.12249   open full text
  • Extensive changes in the transcriptional profile of human adipose tissue including genes involved in oxidative phosphorylation after a 6‐month exercise intervention.
    T. Rönn, P. Volkov, Å. Tornberg, T. Elgzyri, O. Hansson, K.‐F. Eriksson, L. Groop, C. Ling.
    Acta Physiologica. March 10, 2014
    Aim Adipose tissue has an important function in total energy homeostasis, and its dysregulation may contribute to lifestyle‐related diseases such as type 2 diabetes, cancer and cardiovascular diseases. The aim of this study was to investigate genome‐wide mRNA expression in adipose tissue in healthy men before and after an exercise intervention to identify genes or pathways that mediate the beneficial effect of regular exercise. We also investigated the difference in adipose tissue mRNA expression between individuals with or without a family history of type 2 diabetes. Methods The 6‐month supervised exercise intervention was conducted in 47 healthy men (age 37.8 ± 4.3 years, BMI 28.5 ± 3.6 kg m−2) with a previous low level of physical activity. RNA was analysed using GeneChip Human Gene 1.0 ST arrays (Affymetrix) before and after the exercise. Results We identified 2,560 significant transcripts differentially expressed before vs. after exercise with a false discovery rate (FDR) < 0.1%, including genes encoding the respiratory chain, histone subunits, small nucleolar RNAs and ribosomal proteins. Additionally, pathways enriched in response to exercise include the ribosome, oxidative phosphorylation, proteasome and many metabolic pathways, whereas the WNT and MAPK signalling pathways were down‐regulated (FDR < 5%) after exercise. There were no significant differences in mRNA expression between individuals with or without a family history of type 2 diabetes. Conclusion Exercise increased the expression of genes involved in oxidative phosphorylation, which is the opposite of what has been seen in adipose tissue from elderly or obese individuals with low physical fitness, and our study thereby demonstrates a mechanism for the beneficial effect of exercise.
    March 10, 2014   doi: 10.1111/apha.12247   open full text
  • Participation of the dorsal periaqueductal grey matter in the hypoxic ventilatory response in unanaesthetized rats.
    L. T. Lopes, V. Biancardi, E. B. Vieira, C. Leite‐Panissi, K. C. Bícego, L. H. Gargaglioni.
    Acta Physiologica. March 10, 2014
    Aim Although periaqueductal grey matter activation is known to elicit respiratory and cardiovascular responses, the role of this midbrain area in the compensatory responses to hypoxia is still unknown. To test the participation of the periaqueductal grey matter in cardiorespiratory and thermal responses to hypoxia in adult male Wistar rats, we performed a chemical lesion of the dorsolateral/dorsomedial or the ventrolateral/lateral periaqueductal grey matter using ibotenic acid. Methods Pulmonary ventilation, mean arterial pressure, heart rate and body temperature were measured in unanaesthetized rats during normoxic and hypoxic exposure (5, 15, 30 min, 7% O2). Results An ibotenic acid lesion of the dorsolateral/dorsomedial periaqueductal grey matter caused a higher increase in pulmonary ventilation (67.1%, 1730 ± 282.5 mL kg−1 min−1) compared to the Sham group (991.4 ± 194 mL kg−1 min−1) after 15 min in hypoxia, whereas for the ventrolateral/Lateral periaqueductal grey matter lesion, no differences were observed between groups. Mean arterial pressure, heart rate and body temperature were not affected by a dorsolateral/dorsomedial or ventrolateral/lateral periaqueductal grey matter lesion. Conclusion Middle to caudal portions of the dorsolateral/dorsomedial periaqueductal grey matter neurones modulate the hypoxic ventilatory response, exerting an inhibitory modulation during low O2 situations. In addition, the middle to caudal portions of the dorsolateral/dorsomedial or ventrolateral/lateral periaqueductal grey matter do not appear to exert a tonic role on cardiovascular or thermal parameters during normoxic and hypoxic conditions.
    March 10, 2014   doi: 10.1111/apha.12254   open full text
  • Repeated fear‐induced diurnal rhythm disruptions predict PTSD‐like sensitized physiological acute stress responses in F344 rats.
    R. S. Thompson, P. V. Strong, P. J. Clark, T. M. Maslanik, K. P. Wright, B. N. Greenwood, M. Fleshner.
    Acta Physiologica. February 25, 2014
    Aim To identify objective factors that can predict future sensitized stress responses, thus allowing for effective intervention prior to developing sensitization and subsequent stress‐related disorders, including post‐traumatic stress disorder (PTSD). Methods Adult male F344 rats implanted with biotelemetry devices were exposed to repeated conditioned fear or control conditions for 22 days followed by exposure to either no, mild or severe acute stress on day 23. Diurnal rhythms of locomotor activity (LA), heart rate (HR) and core body temperature (CBT) were biotelemetrically monitored throughout the study. In a subset of rat not implanted, corticosterone and indices of chronic stress were measured immediately following stress. Results Rats exposed to repeated fear had fear‐evoked increases in behavioural freezing and HR/CBT during exposure to the fear environment and displayed indices of chronic stress. Repeated fear produced flattening of diurnal rhythms in LA, HR and CBT. Repeated fear did not sensitize the corticosterone response to acute stress, but produced sensitized HR/CBT responses following acute stress, relative to the effect of acute stress in the absence of a history of repeated fear. Greater diurnal rhythm disruptions during repeated fear predicted sensitized acute stress‐induced physiological responses. Rats exposed to repeated fear also displayed flattened diurnal LA and basal increases in HR. Conclusions Exposure to repeated fear produces outcomes consistent with those observed in PTSD. The results suggest that diurnal rhythm disruptions during chronic stressors may help predict sensitized physiological stress responses following traumatic events. Monitoring diurnal disruptions during repeated stress may thus help predict susceptibility to PTSD.
    February 25, 2014   doi: 10.1111/apha.12239   open full text
  • Effects of walking combined with restricted leg blood flow on mTOR and MAPK signalling in young men.
    H. Ozaki, R. Kakigi, H. Kobayashi, J. P. Loenneke, T. Abe, H. Naito.
    Acta Physiologica. February 25, 2014
    Walking combined with blood flow reduction (BFR‐walk) elicits muscle hypertrophy. However, the skeletal muscle intracellular signalling behind this response is currently unknown. Aim To investigate the effects of BFR‐walk on mechanistic target of rapamycin (mTOR) and mitogen‐activated protein kinase (MAPK) signalling pathways in young men. Methods Six young men performed 20 min of treadmill walking at 55% of their predetermined maximum oxygen uptake. A pressure cuff belt was applied to the most proximal thigh of only one leg (BFR‐Leg, external compression was 240 mmHg), whereas the other leg (CON‐Leg) was without BFR during walking. Muscle biopsies were taken from the vastus lateralis of the CON‐Leg before exercise and in both legs 3 h after exercise. Results Erk1/2 phosphorylation levels were significantly (P < 0.05) increased after exercise in both legs; however, only the BFR‐Leg saw an increased phosphorylation of p38. For mTOR signalling, there were no changes in Akt, mTOR or S6K1 phosphorylation levels before or after walking. However, eEF2 phosphorylation level was significantly (P < 0.05) lower for the BFR‐Leg 3 h after walking compared with CON‐Leg. Conclusion BFR‐walk exercise may activate some intracellular signalling cascades that are associated with muscle hypertrophy in young men.
    February 25, 2014   doi: 10.1111/apha.12243   open full text
  • The role of the vagal pathway and gastric dopamine in the gastroparesis of rats after a 6‐hydroxydopamine microinjection in the substantia nigra.
    L.‐F. Zheng, J. Song, R.‐F. Fan, C.‐L. Chen, Q.‐Z. Ren, X.‐L. Zhang, X.‐Y. Feng, Y. Zhang, L.‐S. Li, J.‐X. Zhu.
    Acta Physiologica. February 19, 2014
    Aim Gastroparesis is a common non‐motor system symptom of Parkinson's disease (PD). However, the mechanism responsible for the gastric motor abnormality is not clear. We previously reported on the impaired gastric motility in 6‐hydroxydopamine (6‐OHDA) rats, which were treated with a bilateral microinjection of 6‐OHDA in the substantia nigra (SN). We hypothesize that the enhanced dopamine system and reduced acetylcholine (Ach) in gastric tissues might contribute to the delayed gastric emptying observed in PD. Methods A strain gauge force transducer, digital X‐ray imaging system, Western blot, immunofluorescence and Radio Immunoassay were used in this study. Results Dopaminergic neurones in the SN were greatly reduced following the bilateral microinjection of 6‐OHDA. 6‐OHDA rats exhibited impaired gastric motility and delayed gastric emptying, accompanied by increased dopamine content and the overexpression of D2 receptors in the stomach. The administration of the D2 receptor antagonist domperidone relieved gastric dysmotility in 6‐OHDA rats, but the D1 receptor antagonist SCH23390 failed to do so. Subdiaphragmatic vagotomy prevented the increase in the gastric dopamine content and D2 receptor expression and improved gastric dysmotility in 6‐OHDA rats. Conclusion Dopaminergic deficiency in the SN results in impaired gastric motility, possibly as a result of the enhanced activity of dopamine system and reduced Ach in gastric tissue. The vagus nerve plays an important role in peripheral gastric motility disorder.
    February 19, 2014   doi: 10.1111/apha.12229   open full text
  • Chronic glucocorticoid treatment enhances lipogenic activity in visceral adipocytes of male Wistar rats.
    P. Chimin, T. da S. M. Farias, F. L. Torres‐Leal, A. Bolsoni‐Lopes, A. B. Campaña, S. Andreotti, F. B. Lima.
    Acta Physiologica. February 13, 2014
    Aim Glucocorticoid (GC) in excess promotes the redistribution of adipose tissue from peripheral to central sites of the body. In this study, we characterized an experimental condition of prolonged GC excess and investigated its effect on the lipogenic metabolism in white adipose tissue. Methods Twenty male Wistar rats were divided into control (CON) and dexamethasone‐treated (DEX) groups. DEX group received dexamethasone (0.25 mg kg−1 day−1) during 4 weeks, while CON group received saline. Animals were killed and subcutaneous (SC), retroperitoneal (RP) and mesenteric (MS) fat pads were excised, weighed and processed for adipocyte isolation, morphometric cell analysis and incorporation of glucose into lipids. Results The treatment effectively blocked hypothalamic–pituitary–adrenal axis, as verified by a 58% decrease in plasma corticosterone levels and 19% atrophy in adrenal glands in DEX group. Animals from DEX group presented insulin resistance, glucose intolerance, dyslipidaemia and increased insulin and leptin plasma levels and hypertrophied adipocytes. They showed increased lipogenesis in RP and MS depots, with increased incorporation of glucose into fatty acids of triacylglycerol. Increased activity of lipogenic enzymes ATP‐citrate lyase, fatty acid synthase, glucose‐6‐phosphate dehydrogenase and malic was only seen in the MS depot in DEX group, while gene expression of these enzymes was enhanced in SC and MS fat depots. Conclusion The adaptations promoted by GC treatment in adipose metabolism seemed to be mainly due to the increased activity of enzymes that supply the NADPH required for lipogenesis than to the increase in enzymes that more directly deal with fatty acid synthesis itself.
    February 13, 2014   doi: 10.1111/apha.12226   open full text
  • Iron: the hard player in diabetes pathophysiology.
    Jakob Bondo Hansen, Ingrid Wahl Moen, Thomas Mandrup‐Poulsen.
    Acta Physiologica. February 12, 2014
    The interest in the role of ferrous iron in diabetes pathophysiology has been revived by recent evidence of iron as an important determinant of pancreatic islet inflammation and as a biomarker of diabetes risk and mortality. The iron metabolism in the β‐cell is complex. Excess free iron is toxic, but at the same time iron is required for normal β‐cell function and thereby glucose homeostasis. In the pathogenesis of diabetes, iron generates reactive oxygen species (ROS) by participating in the Fenton chemistry, which can induce oxidative damage and apoptosis. The aim of this review is to present and discuss recent evidence suggesting that iron is a key pathogenic factor in both type 1 and type 2 diabetes with a focus on inflammatory pathways. Pro‐inflammatory cytokine‐induced β‐cell death is not fully understood, but may include iron induced ROS formation resulting in de‐differentiation by activation of transcription factors, activation of the mitochondrial apoptotic machinery or of other cell‐death mechanisms. The pro‐inflammatory cytokine IL‐1β facilitates divalent metal transporter 1 (DMT1) induced β‐cell iron‐uptake and consequently ROS‐formation and apoptosis, and we propose that this mechanism provides the relay between inflammation and oxidative β‐cell damage. Iron chelation may be a potential therapeutic approach to reduce disease severity and mortality among diabetes patients. However, the therapeutic effect and safety of iron reduction needs to be tested in clinical trials before dietary interventions of the use of titrated iron chelation therapy to avoid anaemia. This article is protected by copyright. All rights reserved.
    February 12, 2014   doi: 10.1111/apha.12256   open full text
  • Renal denervation restores the baroreflex control of renal sympathetic nerve activity and heart rate in Wistar‐Kyoto rats with cisplatin‐induced renal failure.
    S. A. Khan, M. A. Sattar, H. A. Rathore, M. H. Abdulla, F. ud din Ahmad, A. Ahmad, S. Afzal, N. A. Abdullah, E. J. Johns.
    Acta Physiologica. February 06, 2014
    Aim There is evidence that in chronic renal failure, the sympathetic nervous system is activated. This study investigated the role of the renal innervation in suppressing high‐ and low‐pressure baroreflex control of renal sympathetic nerve activity and heart rate in cisplatin‐induced renal failure. Methods Renal failure was induced using cisplatin (5 mg kg−1, i.p.) and the rats used 7 days later. Groups of rats were anaesthetized and prepared for measurement of renal sympathetic nerve activity and heart rate. Acute unilateral or bilateral renal denervation was performed, and renal sympathetic nerve activity and heart rate baroreflex gain curves were generated while the cardiopulmonary receptors were stimulated using an acute saline volume load. Results Cisplatin administration reduced (P < 0.05) glomerular filtration rate by 27%, increased sodium fractional excretions fourfold, plasma creatinine and kidney index by 39 and 30% respectively, (all P < 0.05) compared with control rats. In the renal failure rats, baroreflex sensitivity for renal sympathetic nerve activity and heart rate was reduced (P < 0.05) by 29% and 27% (both P < 0.05) compared with control animals. Bilateral, but not unilateral, renal denervation restored baroreflex sensitivity to normal values. Volume expansion reduced (P < 0.05) renal sympathetic nerve activity by 34% in control rats, but remained unchanged in the renal failure rats. Unilateral and bilateral renal denervation progressively restored the volume expansion induced renal sympathoinhibition to control values. Conclusion These findings reveal a significant role of the renal sensory innervation in cisplatin‐damaged kidneys which blunt the normal baroreflex control of renal sympathetic nerve activity.
    February 06, 2014   doi: 10.1111/apha.12237   open full text
  • Input–output characteristics of soleus homonymous Ia afferents and corticospinal pathways during upright standing differ between young and elderly adults.
    S. Baudry, F. Penzer, J. Duchateau.
    Acta Physiologica. February 06, 2014
    Aim This study investigated the effects of ageing on the excitability of soleus homonymous Ia afferents and corticospinal pathways during bipedal upright standing. Methods The input–output relations for the Hoffmann (H) reflex and motor‐evoked potential (MEP) were computed for the soleus in response to electrical nerve stimulation and transcranial magnetic stimulation, respectively, in young (n = 16) and elderly (n = 16) adults. In subsets of subjects, the input–output relations were compared between normal and supported upright standing, and corticomotoneuronal excitability was assessed during upright standing with an H‐reflex conditioning method. For the H‐reflex and MEP threshold, maximal amplitude (Hmax, MEPmax) and the slope of the input–output relation (Hslope, MEPslope) were measured and normalized to the corresponding M‐wave value. Results In normal standing, the Hmax/Mmax [mean (SD); young: 48.3 (14.2)%; elderly: 17.3 (6.4)%] and Hslope/Mslope were significantly (P < 0.05) lower in elderly than in young adults, whereas the MEPmax/Mmax [young: 13.6 (7.5)%; elderly: 24.5 (12.8)%] and MEPslope/Mslope were greater in elderly adults (P < 0.05). The Hslope/Mslope and MEPslope/Mslope decreased and increased, respectively, from supported to normal standing for both age groups but more so in elderly adults. Furthermore, the conditioned H reflex was greater (P < 0.05) in elderly [175.1 (34.3)%] than in young adults [141.8 (29.8)%] during normal standing. Conclusion This is the first study that clearly indicates lower efficacy of Ia afferents to discharge spinal motor neurones accompanied by greater corticospinal excitability in elderly adults, suggesting an increased contribution of the descending drive in controlling soleus activity during upright standing with ageing.
    February 06, 2014   doi: 10.1111/apha.12233   open full text
  • Architectural, functional and molecular responses to concentric and eccentric loading in human skeletal muscle.
    M. V. Franchi, P. J. Atherton, N. D. Reeves, M. Flück, J. Williams, W. K. Mitchell, A. Selby, R. M. Beltran Valls, M. V. Narici.
    Acta Physiologica. February 06, 2014
    Aim We investigated architectural, functional and molecular responses of human skeletal muscle to concentric (CON) or eccentric (ECC) resistance training (RT). Methods Twelve young males performed 10 weeks of concentric (CON) or eccentric (ECC) resistance training (RT) (n = 6 CON, 6 ECC). An additional 14 males were recruited to evaluate acute muscle fascicle behaviour and molecular signalling in biopsies collected from vastus lateralis (VL) after 30 min of single bouts of CON or ECC exercise. VL volume was measured by magnetic resonance imaging. Muscle architecture (fascicle length, Lf; pennation angle, PA) was evaluated by ultrasonography. Muscle remodelling signals to CON or ECC loading [MAPK/AKT‐mammalian target of rapamycin (mTOR) signalling] and inflammatory pathway (TNFαMurf‐1‐MAFbx) were evaluated by immunoblotting. Results Despite the ~1.2‐fold greater load of the ECC group, similar increases in muscle volume (+8% CON and +6% ECC) and in maximal voluntary isometric contraction (+9% CON and +11% ECC) were found after RT. However, increases in Lf were greater after ECC than CON (+12 vs. +5%) while increases in PA were greater in CON than ECC (+30 vs. +5%). Distinct architectural adaptations were associated with preferential growth in the distal regions of VL for ECC (+ECC +8% vs. +CON +2) and mid belly for CON (ECC +7 vs. CON +11%). While MAPK activation (p38MAPK, ERK1/2, p90RSK) was specific to ECC, neither mode affected AKT‐mTOR or inflammatory signalling 30 min after exercise. Conclusion Muscle growth with CON and ECC RT occurs with different morphological adaptations reflecting distinct fibre fascicle behaviour and molecular responses.
    February 06, 2014   doi: 10.1111/apha.12225   open full text
  • Levosimendan improves contractility in vivo and in vitro in a rodent model of post‐myocardial infarction heart failure.
    Solveig Moss Kolseth, Natale Pinheiro Lage Rolim, Øyvind Salvesen, Dag Ole Nordhaug, Alexander Wahba, Morten Andre Høydal.
    Acta Physiologica. February 05, 2014
    Aim Since few studies have presented a thorough analysis of the effect of levosimendan (LEV) on contractility, our purpose was to investigate in vivo cardiac function as well as in vitro cardiomyocyte function and calcium (Ca2+) handling following LEV treatment. Methods Rats with post‐myocardial infarction heart failure (HF) induced by ligation of the left anterior descending coronary artery and sham‐operated animals were randomized to infusion of LEV (2.4 μg∙ kg−1∙ min−1) or vehicle for 40 min. Echocardiographic examination was coupled to pressure‐volume sampling in the left ventricle before (B) and after (40 min) infusion. Isolated left ventricular cardiomyocytes were studied in an epifluorescence microscope. Results HF LEV (n=6), HF vehicle (n=7), sham LEV (n=5) and sham vehicle (n=6) animals were included. LEV infusion compared to vehicle in HF animals reduced left ventricular end‐diastolic pressure and mean arterial pressure (both P<0.001) and improved the slope of the preload‐recruitable stroke work (P<0.05). Administrating LEV to HF cardiomyocytes in vitro improved fractional shortening and Ca2+ sensitivity index ratio, and increased the diastolic Ca2+ (all P<0.01). Conclusion In HF animals LEV improved the contractility by increasing the Ca2+ sensitivity. Furthermore loading conditions were changed, and LEV could consequently change organ perfusion. An observed increase in diastolic Ca2+ following LEV treatment and clinical implications of this should be further addressed. This article is protected by copyright. All rights reserved.
    February 05, 2014   doi: 10.1111/apha.12248   open full text
  • Adipose Tissue and its Role in Organ Crosstalk.
    Tania Romacho, Manuela Elsen, Diana Röhrborn, Juergen Eckel.
    Acta Physiologica. February 04, 2014
    The discovery of adipokines has revealed adipose tissue as a central node in the inter‐organ crosstalk network, which mediates the regulation of multiple organs and tissues. Adipose tissue is a true endocrine organ that produces and secretes a wide range of mediators regulating adipose tissue function in an auto‐/paracrine manner and important distant targets like the liver, skeletal muscle, the pancreas and the cardiovascular system. In metabolic disorders such as obesity, enlargement of adipocytes leads to adipose tissue dysfunction and a shift in the secretory profile with an increased release of pro‐inflammatory adipokines. Adipose tissue dysfunction has a central role in the development of insulin resistance, type 2 diabetes and cardiovascular diseases. Besides the well‐acknowledged role of adipokines in metabolic diseases, and the increasing number of adipokines being discovered in the last years, the mechanisms underlying the release of many adipokines from adipose tissue remain largely unknown. In order to combat metabolic diseases, it is crucial to better understand how adipokines can modulate adipose tissue growth and function. Therefore, we will focus on adipokines with a prominent role in auto‐/paracrine crosstalk within the adipose tissue such as RBP4, HO‐1, WISP2, SFRPs and chemerin. In order to depict the endocrine crosstalk between adipose tissue with skeletal muscle, the cardiovascular system and the pancreas, we will report the main findings regarding the direct effects of adiponectin, leptin, DPP4 and visfatin on skeletal muscle insulin resistance, cardiovascular function and β‐cell growth and function. This article is protected by copyright. All rights reserved.
    February 04, 2014   doi: 10.1111/apha.12246   open full text
  • Slc26a3 deficiency is associated with loss of colonic HCO3− secretion, absence of a firm mucus layer and barrier impairment in mice.
    F. Xiao, Q. Yu, J. Li, M. E. V. Johansson, A. K. Singh, W. Xia, B. Riederer, R. Engelhardt, M. Montrose, M. Soleimani, D. A Tian, G. Xu, G. C. Hansson, U. Seidler.
    Acta Physiologica. January 31, 2014
    Aim Downregulated in adenoma (DRA, Slc26a3) is a member of the solute carrier family 26 (SLC26), family of anion transporters, which is mutated in familial chloride‐losing diarrhoea (CLD). Besides Cl−‐rich diarrhoea, CLD patients also have a higher‐than‐average incidence of intestinal inflammation. In a search for potential explanations for this clinical finding, we investigated colonic electrolyte transport, the mucus layer and susceptibility against dextran sodium sulphate (DSS)‐induced colitis in Slc26a3−/− mice. Methods HCO3− secretory (JHCO3−) and fluid absorptive rates were measured by single‐pass perfusion in vivo and in isolated mid‐distal colonic mucosa in Ussing chambers in vitro. Colonocyte intracellular pH (pHi) was assessed fluorometrically, the mucus layer by immunohistochemistry and colitis susceptibility by the addition of DSS to the drinking water. Results HCO3− secretory (JHCO3‐) and fluid absorptive rates were strongly reduced in Slc26a3−/− mice compared to wild‐type (WT) littermates. Despite an increase in sodium/hydrogen exchanger 3 (NHE3) mRNA and protein expression, and intact acid‐activation of NHE3, the high colonocyte pH in Slc26a3−/− mice prevented Na+/H+ exchange‐mediated fluid absorption in vivo. Mucin 2 (MUC2) immunohistochemistry revealed the absence of a firm mucus layer, implying that alkaline secretion and/or an absorptive flux may be necessary for optimal mucus gel formation. Slc26a3−/− mice were highly susceptible to DSS damage. Conclusions Deletion of DRA results in severely reduced colonic HCO3− secretory rate, a loss of colonic fluid absorption, a lack of a firmly adherent mucus layer and a severely reduced colonic mucosal resistance to DSS damage. These data provide potential pathophysiological explanations for the increased susceptibility of CLD patients to intestinal inflammation.
    January 31, 2014   doi: 10.1111/apha.12220   open full text
  • AltitudeOmics: Exercise‐induced supraspinal fatigue is attenuated in healthy humans after acclimatisation to high altitude.
    Stuart Goodall, Rosie Twomey, Markus Amann, Emma Z. Ross, Andrew T. Lovering, Lee M. Romer, Andrew W. Subudhi, Robert C. Roach.
    Acta Physiologica. January 22, 2014
    Aims We asked whether acclimatisation to chronic hypoxia (CH) attenuates the level of supraspinal fatigue that is observed after locomotor exercise in acute hypoxia (AH). Methods Seven recreationally‐active participants performed identical bouts of constant‐load cycling (131±39W, 10.1±1.4min) on three occasions: 1) in normoxia (N, PIO2, 147.1mmHg); 2) in AH (FIO2, 0.105; PIO2, 73.8mmHg); 3) after 14 days in CH (5,260m; PIO2, 75.7mmHg). Throughout trials, prefrontal‐cortex tissue oxygenation and middle cerebral artery blood velocity (MCAV) were assessed using near‐infrared‐spectroscopy and transcranial Doppler sonography. Pre‐ and post‐exercise twitch responses to femoral nerve stimulation and transcranial magnetic stimulation were obtained to assess neuromuscular and corticospinal function. Results In AH, prefrontal oxygenation declined at rest (Δ7±5%) and end‐exercise (Δ26±13) (P<0.01); the degree of deoxygenation in AH was greater than N and CH (P<0.05). The cerebral O2 delivery index (MCAv×CaO2) was 19±14% lower during the final minute of exercise in AH compared to N (P=0.013) and 20±12% lower compared to CH (P=0.040). Maximum voluntary and potentiated twitch force were decreased below baseline after exercise in AH and CH, but not N. Cortical voluntary activation decreased below baseline after exercise in AH (Δ11%, P=0.014), but not CH (Δ6%, P=0.174) or N (Δ4%, P=0.298). A twofold greater increase in motor evoked potential amplitude was evident after exercise in CH compared to AH and N. Conclusion These data indicate that exacerbated supraspinal fatigue after exercise in AH is attenuated after 14 days of acclimatisation to altitude. The reduced development of supraspinal fatigue in CH may have been attributable to increased corticospinal excitability, consequent to an increased cerebral O2 delivery. This article is protected by copyright. All rights reserved.
    January 22, 2014   doi: 10.1111/apha.12241   open full text
  • Reduced aerobic capacity causes leaky ryanodine receptors that trigger arrhythmia in a rat strain artificially selected and bred for low aerobic running capacity.
    MA Høydal, TO Stølen, AB Johnsen, M Alvez, D Catalucci, G Condorelli, LG Koch, SL Britton, GL Smith, U Wisløff.
    Acta Physiologica. January 20, 2014
    Aim Rats selectively bred for inborn Low Capacity of Running (LCR) display a series of poor health indices whereas rats selected for High Capacity of Running (HCR) display a healthy profile. We hypothesized that selection of low aerobic capacity over generations leads to a phenotype with increased diastolic Ca2+ leak that trigger arrhythmia. Methods We used rats selected for HCR (N=10) or LCR (N=10) to determine the effect of inborn aerobic capacity on Ca2+ leak and susceptibility of ventricular arrhythmia. We studied isolated FURA2/AM loaded cardiomyocytes to detect Ca2+‐handling and function on an inverted epi‐fluorescence microscope. To determine arrhythmogenicity we did a final experiment with electrical burst pacing in Langendorff perfused hearts. Results Ca2+‐handling was impaired by reduced Ca2+ amplitude, prolonged time to 50% Ca2+ decay, and reduced sarcoplasmic reticulum (SR) Ca2+‐content. Impaired Ca2+ removal was influenced by reduced SR Ca2+ATP‐ase 2a (SERCA2a) function and increased sodium/Ca2+‐exchanger (NCX) in LCR rats. Diastolic Ca2 leak was 87% higher in LCR rats. The leak was reduced by CaMKII inhibition. Expression levels of phosphorylated theorine‐286 CaMKII levels and increased RyR2 phosphorylation at the Serine‐2814 site mechanistically support our findings of increased leak in LCR. LCR rats had significantly higher incidence of ventricular fibrillation. Conclusion Selection of inborn low aerobic capacity over generations leads to a phenotype with increased risk of ventricular fibrillation. Increased phosphorylation of CaMKII at serine‐2814 at the cardiac ryanodine receptor appears as an important mechanism of impaired Ca2+ handling and diastolic Ca2+ leak that results in increased susceptibility to ventricular fibrillation. This article is protected by copyright. All rights reserved.
    January 20, 2014   doi: 10.1111/apha.12238   open full text
  • Sex Differences in Human Fatigability: Mechanisms and Insight to Physiological Responses.
    Sandra K. Hunter.
    Acta Physiologica. January 17, 2014
    Sex‐related differences in physiology and anatomy are responsible for profound differences in neuromuscular performance and fatigability between men and women. Women are usually less fatigable than men for similar intensity isometric fatiguing contractions. This sex difference in fatigability, however, is task specific because different neuromuscular sites will be stressed when the requirements of the task are altered, and the stress on these sites can differ for men and women. Task variables that can alter the sex difference in fatigue include the type, intensity and speed of contraction, the muscle group assessed, and the environmental conditions. Physiological mechanisms that are responsible for sex‐based differences in fatigability may include activation of the motor neuron pool from cortical and subcortical regions, synaptic inputs to the motor neuron pool via activation of metabolically‐sensitive small afferent fibres in the muscle, muscle perfusion, and skeletal muscle metabolism and fibre type properties. Non‐physiological factors such as the sex bias of studying more males than females in human and animal experiments can also mask a true understanding of the magnitude and mechanisms of sex‐based differences in physiology and fatigability. Despite recent developments, there is a tremendous lack of understanding of sex differences in neuromuscular function and fatigability, the prevailing mechanisms and the functional consequences. This review emphasises the need to understand sex‐based differences in fatigability in order to shed light on the benefits and limitations that fatigability can exert for men and women during daily tasks, exercise performance, training and rehabilitation in both health and disease. This article is protected by copyright. All rights reserved.
    January 17, 2014   doi: 10.1111/apha.12234   open full text
  • The incretin effect does not differ in trained and untrained, young, healthy men.
    M. T. Lund, S. Dalby, B. Hartmann, J. Helge, J. J. Holst, F. Dela.
    Acta Physiologica. January 16, 2014
    Aim After both oral and intravenous glucose administration, peripheral insulin concentrations are lower in trained compared with untrained humans. Part of this is explained by an adaptation within the β‐cell. The insulin secretion rate is higher after oral compared with intravenous glucose administration due to the release of glucagon‐like peptide‐1 (GLP‐1) and glucose‐dependent insulinotropic polypeptide (GIP) enhancing the glucose‐induced insulin secretion (the incretin effect). Our aim was to investigate whether GIP or GLP‐1 release or the incretin effect was different in trained compared with untrained humans after oral and intravenous glucose administration. Methods A 3½‐h oral glucose tolerance test was performed in eleven trained and ten untrained, young, healthy men. On a separate day, an isoglycaemic intravenous glucose infusion was performed matching the individual glucose concentrations obtained during the oral glucose tolerance test. Blood samples for insulin, C‐peptide, GIP and GLP‐1 analyses were obtained frequently during both tests, and the insulin secretion rate, incretin effect and insulin clearance were calculated. Results Plasma GIP and GLP‐1 concentrations, the incretin effect and the insulin clearance did not differ, and plasma glucose, insulin and C‐peptide concentrations and the insulin secretion rate were lower in trained compared with untrained subjects during both tests. Conclusion With no difference in incretin effect and insulin clearance between the two groups, the lower plasma insulin concentrations found in trained compared with untrained, young, healthy men are most likely explained by lower β‐cell sensitivity to glucose and enhanced glucose uptake in skeletal muscle in the former group.
    January 16, 2014   doi: 10.1111/apha.12218   open full text
  • Whole‐body fluid distribution in humans during dehydration and recovery, before and after humid‐heat acclimation induced using controlled hyperthermia.
    M. J. Patterson, J. M. Stocks, N. A. S. Taylor.
    Acta Physiologica. January 16, 2014
    Aim This experiment was designed to test the hypothesis that the plasma volume is not selectively defended during exercise‐ and heat‐induced dehydration following humid‐heat acclimation. Methods Eight physically active males were heat acclimated (39.8 °C, relative humidity 59.2%) using 17 days of controlled hyperthermia (core temperature: 38.5 °C). Inter‐compartmental fluid losses and movements were tracked (radioisotopes and Evans blue dye) during progressive dehydration (cycling) in these same conditions and also during a resting recovery without fluid replacement (28 °C), before (day 1), during (day 8) and after heat acclimation (day 22). Results On days 8 and 22, there were significant increases in total body water, interstitial fluid and plasma volume (P < 0.05), but the intracellular compartments did not change (P > 0.05). The baseline plasma volume remained expanded throughout: 43.4 [±2.6 (day 1)], 49.1 [±2.4 (day 8); P < 0.05] and 48.9 mL kg−1 [±3.0 (day 22); P < 0.05]. During progressive dehydration, plasma reductions of 9.0% (±0.9: day 1), 12.4% (±1.6: day 8) and 13.6% (±1.2: day 22) were observed, with day 8 and 22 losses significantly exceeding day 1 (P < 0.05). During recovery, plasma volume restoration commenced, with the intracellular fluid contribution becoming more pronounced as acclimation progressed. Conclusion It is concluded that the plasma volume was not defended more vigorously following humid‐heat acclimation. Indeed, a greater fluid loss may well underlie the mechanisms for enhancing plasma volume recovery when heat acclimation is induced using the controlled‐hyperthermia technique.
    January 16, 2014   doi: 10.1111/apha.12214   open full text
  • Endothelial cationic amino acid transporter‐1 overexpression can prevent oxidative stress and increases in arterial pressure in response to superoxide dismutase inhibition in mice.
    G. Konstantinidis, G. A. Head, R. G. Evans, T.‐P. Nguyen‐Huu, K. Venardos, K. D. Croft, T. A. Mori, D. M. Kaye, N. W. Rajapakse.
    Acta Physiologica. January 16, 2014
    Aim Oxidative stress may play an important role in the pathogenesis of hypertension. The aim of our study is to examine whether increased expression of the predominant endothelial l‐arginine transporter, cationic amino acid transporter‐1 (CAT1), can prevent oxidative stress‐induced hypertension. Methods Wild‐type mice (WT; n = 9) and endothelial CAT1 overexpressing (CAT+) mice (n = 6) had telemetry probes implanted for the measurement of mean arterial pressure (MAP), heart rate (HR) and locomotor activity. Minipumps were implanted for infusion of the superoxide dismutase inhibitor diethyldithiocarbamic acid (DETCA; 30 mg kg−1 day−1; 14 days) or its saline vehicle. Baseline levels of MAP, HR and locomotor activity were determined before and during chronic DETCA administration. Mice were then killed, and their plasma and kidneys collected for analysis of F2‐isoprostane levels. Results Basal MAP was less in CAT+ (92 ± 2 mmHg; n = 6) than in WT (98 ± 2 mmHg; n = 9; P < 0.001). During DETCA infusion, MAP was increased in WT (by 4.2 ± 0.5%; P < 0.001) but not in CAT+, when compared to appropriate controls (PDETCA*genotype = 0.006). DETCA infusion increased total plasma F2‐isoprostane levels (by 67 ± 11%; P = 0.05) in WT but not in CAT+. Total renal F2‐isoprostane levels were greater during DETCA infusion in WT (by 72%; P < 0.001), but not in CAT+, compared to appropriate controls. Conclusion Augmented endothelial l‐arginine transport attenuated the prohypertensive effects of systemic and renal oxidative stress, suggesting that manipulation of endothelial CAT1 may provide a new therapeutic approach for the treatment of cardiovascular disease associated with oxidative stress.
    January 16, 2014   doi: 10.1111/apha.12215   open full text
  • Mortality and Morbidity in Different Immunization Protocols for Experimental Autoimmune Myocarditis in Rats.
    Patrick Schmerler, Sarah Jeuthe, Darach O h‐Ici, Katharina Wassilew, Dilyara Lauer, Elena Kaschina, Ulrich Kintscher, Susanne Müller, Frédéric Muench, Titus Kuehne, Felix Berger, Thomas Unger, U. Muscha Steckelings, Ludovit Paulis, Daniel Messroghli.
    Acta Physiologica. January 11, 2014
    Aim We aimed to investigate the histological and clinical presentations of EAM induced by different immunization schemes. Methods Male young Lewis rats were divided into 5 groups immunized by porcine myocardial myosin: subcutaneously (SC) 1 2 mg (in two 1 mg doses on day 0 and 7); 0 mg (sham group) subcutaneously into rear footpads (RF), 0.25 mg RF, 0.5 mg RF or 1 mg RF (all RF once on day 0). On day 21 left ventricular (LV) function was assessed by cardiac magnetic resonance imaging and cardiac catheterization. The type and degree of myocardial inflammatory infiltrates were determined by conventional histology and immunohistochemistry. Results In the SC immunized rats and in the RF sham group we observed 0% mortality, while in the actively RF immunized rats mortality was 20%, 20% and 44% for the 0.25 mg, 0.5 mg and 1 mg myosin doses respectively. Morbidity as defined by inflammatory infiltrates on HE staining was 22% in the SC immunized rats, 0% in the RF sham group and 100% in all actively RF immunized groups. We observed augmented relative ventricle weight and spleen weight, increased LV end‐diastolic pressure, reduced LV developed pressure and reduced LV ejection fraction in all with myosin immunized RF groups without any systematic dose effect. Conclusion Subcutaneous immunization to the neck and flanks did not induce a reproducible EAM, while RF myosin administration reliably led to EAM. Lower myosin doses seem to induce the complete histological and clinical picture of EAM while being associated with lower mortality, non‐specific symptoms and animal distress. This article is protected by copyright. All rights reserved.
    January 11, 2014   doi: 10.1111/apha.12227   open full text
  • Differential localization and characterization of functional calcitonin gene‐related peptide receptors in human subcutaneous arteries.
    L. Edvinsson, H. Ahnstedt, R. Larsen, M. Sheykhzade.
    Acta Physiologica. January 07, 2014
    Aim Calcitonin gene‐related peptide (CGRP) and its receptor are widely distributed within the circulation and the mechanism behind its vasodilation not only differs from one animal species to another but is also dependent on the type and size of vessel. The present study examines the nature of CGRP‐induced vasodilation, characteristics of the CGRP receptor antagonist telcagepant and localization of the key components calcitonin receptor‐like receptor (CLR) and receptor activity modifying protein 1 (RAMP1) of the CGRP receptor in human subcutaneous arteries. Methods CGRP‐induced vasodilation and receptor localization in human subcutaneous arteries were studied by wire myograph in the presence and absence of the CGRP receptor antagonist telcagepant and immunohistochemistry respectively. Results At concentrations of 1, 3, 5, 10 and 30 nm, telcagepant had a competitive antagonist‐like behaviour characterized by a parallel rightwards shift in the log CGRP concentration‐tension/calcium curve with no depression of the maximal relaxation. CGRP‐induced vasodilation was not affected by mechanical removal of the endothelium or addition of L‐NG‐nitroarginine methyl ester and indomethacin, antagonists for synthesis of nitric oxide and prostaglandins, respectively. CLR and RAMP1 were localized in the vascular smooth muscle and endothelial cells. Conclusion The present results indicate that CGRP exerts its vasodilatory effect in human subcutaneous arteries by binding to its receptors located on the smooth muscle cells and is suggested to be endothelium‐independent. In conclusion, these results underline the dynamic distribution of CGRP receptor components in the human circulation reflecting the important role of CGRP in fine tuning of the blood flow in resistance arteries.
    January 07, 2014   doi: 10.1111/apha.12213   open full text
  • Fatigue effects on the electromechanical delay components during the relaxation phase after isometric contraction.
    E. Cè, S. Rampichini, E. Limonta, F. Esposito.
    Acta Physiologica. January 02, 2014
    Aim By a combined electromyographic (EMG), mechanomyographic (MMG) and force (F) analysis, the electromechanical delay during muscle relaxation (R‐DelayTOT) was partitioned into electrochemical and mechanical components. The study aimed to evaluate the effects of fatigue on R‐DelayTOT components and to assess their intersession and interday reliability Intraclass correlation coefficient (ICC). Methods During tetanic stimulations, EMG, MMG and F were recorded from the human gastrocnemius medialis muscle before and after fatigue. The latency between EMG and MMG ripple cessations (R‐Δt EMG‐MMGR, electrochemical R‐DelayTOT component); between MMG ripple cessation and F decay onset (R‐Δt MMGR‐F, first R‐DelayTOT mechanical component); and between F decay onset and maximum MMG negative peak (R‐Δt F‐MMGp‐p, second R‐DelayTOT mechanical component) was calculated. Results Before fatigue, R‐Δt F‐MMGp‐p was the major contributor (61.9 ± 1.7 ms, 75%) to R‐DelayTOT (82.7 ± 1.0 ms), while R‐Δt EMG‐MMGR and R‐Δt MMGR‐F accounted for 16% (13.3 ± 1.2 ms) and 9% (7.5 ± 1.0 ms) respectively. After fatigue, R‐DelayTOT, R‐Δt EMG‐MMGR and R‐Δt MMGR‐F increased by 11, 41 and 67%, respectively (P < 0.05), whereas R‐Δt F‐MMGp‐p did not change. Consequently, the relative contribution of R‐Δt EMG‐MMGR, R‐Δt MMGR‐F and R‐Δt F‐MMGp‐p, to R‐DelayTOT changed to 20 ± 2, 12 ± 1 and 68 ± 2% respectively. Measurement reliability was always from high to very high (ICC 0.705–0.959). Conclusion Fatigue altered the processes between neuromuscular activation cessation and force decay onset, but not the second mechanical component (cross‐bridges detachment rate and series elastic components release). This combined approach provided reliable measurement of the different R‐DelayTOT components and it may represent a valid tool to get more insights on muscle electromechanical behaviour.
    January 02, 2014   doi: 10.1111/apha.12212   open full text
  • Activation of soluble guanylyl cyclase prevents foam cell formation and atherosclerosis.
    C.‐Y. Tsou, C.‐Y. Chen, J.‐F. Zhao, K.‐H. Su, H.‐T. Lee, S.‐J. Lin, S.‐K. Shyue, S.‐H. Hsiao, T.‐S. Lee.
    Acta Physiologica. December 27, 2013
    Aims Soluble guanylyl cyclase (sGC) is a key modulator in the regulation of vascular tone. However, its role and involving mechanism in cholesterol metabolism of macrophages and atherosclerosis remain unclear. Methods Oil red O staining, Dil‐oxidized low‐density lipoprotein (oxLDL)‐binding assay and cholesterol efflux assay were performed in biology of foam cells. Levels of cytokines or intracellular lipid were evaluated by ELISA or colorimetric kits. Expression of gene or protein was determined by quantitative real‐time PCR or Western blotting. Histopathology was examined by haematoxylin and eosin staining. Results Soluble guanylyl cyclase was expressed in macrophages of mouse atherosclerotic lesions. Treatment with 1H‐[1, 2, 4]oxadiazolo[4,3‐a]quinoxalin‐1‐one (ODQ, sGC inhibitor) exacerbated oxLDL‐induced cholesterol accumulation in macrophages. In contrast, 3‐(5′‐hydroxymethyl‐2′furyl)‐1‐benzyl indazole (YC‐1, sGC activator) attenuated the oxLDL‐induced cholesterol accumulation because of increased cholesterol efflux. Additionally, YC‐1 dose dependently increased the protein expression of ATP‐binding cassette transporter A1 (ABCA1) but did not alter that of scavenger receptor class A (SR‐A), CD36, SR‐BI or ABCG1. Moreover, YC‐1‐upregulated ABCA1 level depended on liver X receptor α (LXRα). Inhibition of the LXRα‐ABCA1 pathway by LXRα small interfering RNA (siRNA), ABCA1 neutralizing antibody or ABCA1 siRNA abolished the effect of YC‐1 on cholesterol accumulation and cholesterol efflux. In vivo, YC‐1 retarded the development of atherosclerosis, accompanied by reduced serum levels of cholesterol and pro‐inflammatory cytokines, in apolipoprotein E‐deficient mice. Conclusion Activation of sGC by YC‐1 leads to LXRα‐dependent upregulation of ABCA1 in macrophages and may confer protection against atherosclerosis.
    December 27, 2013   doi: 10.1111/apha.12210   open full text
  • Nitric oxide impacts on angiotensin AT2 receptor modulation of high‐pressure baroreflex control of renal sympathetic nerve activity in anaesthetized rats.
    M. H. Abdulla, E. J. Johns.
    Acta Physiologica. December 17, 2013
    Aim Nitric oxide (NO) interacts with the local brain renin‐angiotensin system to modulate sympathetic outflow and cardiovascular homoeostasis. This study investigated whether NO influenced the ability of angiotensin AT2 receptor activation to modify the high‐pressure baroreceptor regulation of renal sympathetic nerve activity (RSNA) and heart rate (HR). Methods Anaesthetized (chloralose/urethane) rats were prepared to allow generation of baroreflex gain curves for RSNA or HR following intracerebroventricular (I.C.V.) CGP42112 (AT2 receptor agonist), PD123319 (AT2 receptor antagonist) or losartan (AT1 receptor antagonist), and then in combination with L‐NAME (NO synthase inhibitor). Results I.C.V. PD123319, CGP42112, and Losartan did not change baseline mean arterial pressure, HR or RSNA. Baroreflex sensitivities for RSNA and HR were increased following AT2 receptor activation with CGP42112 by 112 and 157%, respectively, but were reduced following PD123319 by 20% (all P < 0.05). L‐NAME alone increased baroreflex sensitivity for both RSNA and HR, by 62 and 158%, respectively, but when co‐infused with either CGP42112 or PD123319, the baroreflex sensitivity fell to values comparable to those obtained during I.C.V. saline infusion. The baroreflex sensitivities for RSNA and HR were increased by losartan by 92% and 192%, respectively, but in the presence of L‐NAME were no different from those obtained during I.C.V. saline infusion. Conclusion There is an important facilitatory role for AT2 receptors in the high‐pressure baroreflex regulation of RSNA and HR which is dependent on a functional NO/NOS system. Conversely, AT1 receptors have an inhibitory effect on the baroreflex, an action that relies on a tonic inhibition of NO.
    December 17, 2013   doi: 10.1111/apha.12207   open full text
  • Neuromuscular electrical stimulation prevents muscle disuse atrophy during leg immobilization in humans.
    M. L. Dirks, B. T. Wall, T. Snijders, C. L. P. Ottenbros, L. B. Verdijk, L. J. C. Loon.
    Acta Physiologica. December 12, 2013
    Aim Short periods of muscle disuse, due to illness or injury, result in substantial skeletal muscle atrophy. Recently, we have shown that a single session of neuromuscular electrical stimulation (NMES) increases muscle protein synthesis rates. The aim was to investigate the capacity for daily NMES to attenuate muscle atrophy during short‐term muscle disuse. Methods Twenty‐four healthy, young (23 ± 1 year) males participated in the present study. Volunteers were subjected to 5 days of one‐legged knee immobilization with (NMES; n = 12) or without (CON; n = 12) supervised NMES sessions (40‐min sessions, twice daily). Two days prior to and immediately after the immobilization period, CT scans and single‐leg one‐repetition maximum (1RM) strength tests were performed to assess quadriceps muscle cross‐sectional area (CSA) and leg muscle strength respectively. Furthermore, muscle biopsies were taken to assess muscle fibre CSA, satellite cell content and mRNA and protein expression of selected genes. Results In CON, immobilization reduced quadriceps CSA by 3.5 ± 0.5% (P < 0.0001) and muscle strength by 9 ± 2% (P < 0.05). In contrast, no significant muscle loss was detected following immobilization in NMES although strength declined by 7 ± 3% (P < 0.05). Muscle MAFbx and MuRF1 mRNA expression increased following immobilization in CON (P < 0.001 and P = 0.07 respectively), whereas levels either declined (P < 0.01) or did not change in NMES, respectively. Immobilization led to an increase in muscle myostatin mRNA expression in CON (P < 0.05), but remained unchanged in NMES. Conclusion During short‐term disuse, NMES represents an effective interventional strategy to prevent the loss of muscle mass, but it does not allow preservation of muscle strength. NMES during disuse may be of important clinical relevance in both health and disease.
    December 12, 2013   doi: 10.1111/apha.12200   open full text
  • Contribution of calpain to myoglobin efflux from cardiomyocytes during ischaemia and after reperfusion in anaesthetized rats.
    T. Sonobe, T. Akiyama, C.‐K. Du, D.‐Y. Zhan, M. Shirai.
    Acta Physiologica. December 12, 2013
    Aim Calpain activation has a putative role in ischaemia‐reperfusion injury of cardiomyocytes. This study clarified the in vivo contribution of calpain to disruption of cardiomyocyte sarcolemma during ischaemia and after reperfusion in anaesthetized rats. Methods Using a microdialysis technique in the hearts of anaesthetized rats, we investigated the effects of the calpain inhibitors on myocardial interstitial myoglobin level in the ischaemic region during coronary occlusion and after reperfusion. The calpain inhibitors were administered locally via a dialysis probe. Two durations of coronary occlusion were tested. Results Thirty‐minute coronary occlusion: dialysate myoglobin concentration increased markedly from 385 ± 46 ng mL−1 at baseline to 3701 ± 527 ng mL−1 at 20–30 min of occlusion. After reperfusion, dialysate myoglobin concentration further increased, reaching a peak (12 296 ± 1564 ng mL−1) at 10–20 min post‐reperfusion and then declined gradually. The calpain inhibitors, MDL‐28170 and SNJ‐1945 did not change dialysate myoglobin concentration during occlusion but attenuated the increase after reperfusion to 6826 ± 1227 and 8130 ± 938 ng mL−1 at 10–20 min post‐reperfusion (P < 0.05), respectively. Ninety‐minute coronary occlusion: dialysate myoglobin concentration increased from 516 ± 33 ng mL−1 at baseline to 5463 ± 387 ng mL−1 at 80–90 min after occlusion. After reperfusion, there was no significant increase in dialysate myoglobin concentration. MDL‐28170 did not affect dialysate myoglobin concentration during occlusion or after reperfusion. Conclusion Calpain contributes to sarcolemmal disruption immediately after reperfusion following 30‐min coronary occlusion, but has little effects during ischaemia and after reperfusion in 90‐min coronary occlusion.
    December 12, 2013   doi: 10.1111/apha.12205   open full text
  • Differential satellite cell density of type I and II fibres with lifelong endurance running in old men.
    A. L. Mackey, A. Karlsen, C. Couppé, U. R. Mikkelsen, R. H. Nielsen, S. P. Magnusson, M. Kjaer.
    Acta Physiologica. December 12, 2013
    Aim To investigate the influence of lifelong endurance running on the satellite cell pool of type I and type II fibres in healthy human skeletal muscle. Methods Muscle biopsies were collected from 15 healthy old trained men (O‐Tr) who had been running 43 ± 16 (mean ± SD) kilometres a week for 28 ± 9 years. Twelve age‐matched untrained men (O‐Un) and a group of young trained and young untrained men were recruited for comparison. Frozen sections were immunohistochemically stained for Pax7, type I myosin and laminin, from which fibre area, the number of satellite cells, and the relationship between these variables were determined. Results In O‐Un and O‐Tr, type II fibres were smaller and contained fewer satellite cells than type I fibres. However, when expressed relative to fibre area, the difference in satellite cell content between fibre types was eliminated in O‐Tr, but not O‐Un. A strong positive relationship between fibre size and satellite cell content was detected in trained individuals. In line with a history of myofibre repair, a greater number of fibres with centrally located myonuclei were detected in O‐Tr. Conclusion Lifelong endurance training (i) does not deplete the satellite cell pool and (ii) is associated with a similar density of satellite cells in type I and II fibres despite a failure to preserve the equal fibre type distribution of satellite cells observed in young individuals. Taken together, these data reveal a differential regulation of satellite cell content between fibre types, in young and old healthy men with dramatically different training histories.
    December 12, 2013   doi: 10.1111/apha.12195   open full text
  • Prevention of duodenal ileus reveals functional differences in the duodenal response to luminal hypertonicity in Sprague‐Dawley and Dark Agouti rats.
    J. Sedin, M. Sjöblom, O. Nylander.
    Acta Physiologica. December 12, 2013
    Aim The mechanism by which the duodenum adjusts the luminal osmolality remains unclear. The aim was to compare the duodenal osmoregulation in response to different hyperosmolar solutions in Sprague‐Dawley and Dark Agouti rats and to elucidate whether cyclooxygenase‐2 inhibition affects these responses. Methods The duodenum was perfused in situ with a 700‐milliosmolar solution (NaCl alone, D‐glucose ± NaCl, D‐mannitol ± NaCl or orange juice), and the effects on the duodenal motility, mucosal permeability, luminal alkalinization, fluid flux and osmoregulation were assessed in anaesthetized rats. Results The change in net fluid flux and luminal osmolality, in response to a given hyperosmolar solution, was almost identical in control rats of both strains. In control rats, hypertonic D‐glucose–NaCl induced fluid secretion only in the presence of phlorizin, an inhibitor of SGLT1. Cyclooxygenase‐2 inhibition potentiated the hypertonicity‐induced fluid secretion and increased the osmolality‐adjusting capability in both strains, but the responses were greater in Dark Agouti rats. While cyclooxygenase‐2‐inhibited Dark Agouti rats responded to the hyperosmolar solutions with depression of motility and increased mucosal permeability, these effects were absent or smaller in the Sprague‐Dawley strain. In contrast, orange juice induced the same duodenal responses in cyclooxygenase‐2‐inhibited Dark Agouti and Sprague‐Dawley rats. Conclusion The duodenum possesses the ability to absorb fluid despite a very high luminal osmolality. Inhibition of cyclooxygenase‐2 markedly enhanced the capability of the duodenum to secrete fluid and to decrease luminal osmolality, irrespective of the hyperosmolar solution or the rat strain used, and revealed notable differences between the two strains with regard to their osmolality‐adjusting capability.
    December 12, 2013   doi: 10.1111/apha.12201   open full text
  • The hypoxic ventilatory response and TRPA1 antagonism in conscious mice.
    M. Pokorski, K. Takeda, Y. Sato, Y. Okada.
    Acta Physiologica. December 12, 2013
    Aim Recently, TRPA1 channels, richly expressed in both peripheral and central neural systems, have been proposed as novel sensors of changes in oxygen concentration along the hypoxic–hyperoxic continuum. In this study, we investigated the hypothesis that TRPA1 channels blockade should profoundly affect the hypoxic ventilatory response (HVR). Methods We examined the chemosensory ventilatory responses in conscious mice before and after intraperitoneal administration of the specific TRPA1 antagonist HC‐030031 in two doses of 50 and 200 (cumulative dose 250) mg kg−1. Ventilation and its responses to mild 13% and severe 7% hypoxia, pure O2, and 5% CO2 in O2 were recorded in a whole‐body plethysmograph. Results TRPA1 antagonism caused a dose‐dependent attenuation of the HVR. Ventilatory stimulation was virtually abrogated in response to the mild, but it remained viable, albeit slashed, at severe hypoxia after the bigger dose of HC‐030031. The TRPA1 function seemed specific for the hypoxic chemoreflex as neither the response to pure O2 nor hypercapnia was appreciably influenced by the TRPA1 antagonist. Conclusions The study unravelled the role of TRPA1 in shaping the ventilatory response to low‐intensity hypoxia, liable to be mediated by vagally innervated respiratory chemosensors of lower functional rank, but contradicted the TRPA1 being indispensable for the powerful carotid body chemoreflex in face of a severe hypoxic threat.
    December 12, 2013   doi: 10.1111/apha.12202   open full text
  • Ventricular remodelling in rabbits with sustained high‐fat diet.
    M. Zarzoso, S. Mironov, G. Guerrero‐Serna, B. Cicero Willis, S. V. Pandit.
    Acta Physiologica. December 05, 2013
    Aim Excess weight gain and obesity are one of the most serious health problems in the western societies. These conditions enhance risk of cardiac disease and have been linked with increased prevalence for cardiac arrhythmias and sudden death. Our goal was to study the ventricular remodelling occurring in rabbits fed with high‐fat diet (HFD) and its potential arrhythmogenic mechanisms. Methods We used 15 NZW rabbits that were randomly assigned to a control (n = 7) or HFD group (n = 8) for 18 weeks. In vivo studies included blood glucose, electrocardiographic, and echocardiographic measurements. Optical mapping was performed in Langendorff‐perfused isolated hearts. Results Body weight (3.69 ± 0.31 vs. 2.94 ± 0.18 kg, P < 0.001) and blood glucose levels (230 ± 61 vs. 141 ± 14 mg dL−1, P < 0.05) were higher in the HFD group vs. controls. The rate‐corrected QT interval and its dispersion were increased in HFD rabbits vs. controls (169 ± 10 vs. 146 ± 13 ms and 37 ± 11 vs. 9 ± 2 ms, respectively; P < 0.05). Echocardiographic analysis showed morphological and functional alterations in HFD rabbits indicative of left ventricle (LV) hypertrophy. Isolated heart studies revealed no changes in repolarization and propagation properties under conditions of normal extracellular K+, suggesting that extrinsic factors could underlie those electrocardiographic modifications. There were no differences in the dynamics of ventricular fibrillation (frequency, wave breaks) in the presence of isoproterenol. However, HFD rabbits showed a small reduction in action potential duration and an increased incidence of arrhythmias during hyperkalaemia. Conclusion High‐fat feeding during 18 weeks in rabbits induced a type II diabetes phenotype, LV hypertrophy, abnormalities in repolarization and susceptibility to arrhythmias during hyperkalaemia.
    December 05, 2013   doi: 10.1111/apha.12185   open full text
  • Superoxide anions involved in sympathoexcitation and pressor effects of salusin‐β in paraventricular nucleus in hypertensive rats.
    H.‐J. Sun, L.‐L. Zhang, Z.‐D. Fan, D. Chen, L. Zhang, X.‐Y. Gao, Y.‐M. Kang, G.‐Q. Zhu.
    Acta Physiologica. December 05, 2013
    Aims Salusin‐β in paraventricular nucleus (PVN) increases renal sympathetic nerve activity (RSNA), mean arterial pressure (MAP), heart rate (HR) and arginine vasopressin (AVP) release in hypertensive rats but not in normal rats. The present study was designed to investigate the downstream molecular mechanism of salusin‐β in the PVN in hypertension. Method Renovascular hypertension was induced by two‐kidney, one‐clip (2K1C) in male SD rats. Acute experiments were carried out 4 weeks after 2K1C or sham operation under anaesthesia. Results MrgA1 mRNA expression and salusin‐β level in the PVN as well as plasma salusin‐β level were increased in 2K1C rats. Bilateral PVN microinjection of salusin‐β increased the RSNA, MAP and HR in 2K1C rats, which were abolished by the pre‐treatment with polyethylene glycol–superoxide dismutase (PEG‐SOD), the superoxide anion scavenger tempol, the NAD(P)H oxidase inhibitor apocynin or the protein kinase C (PKC) inhibitor chelerythrine chloride (CLC), but not affected by the AT1 receptor antagonist losartan, the Mas receptor antagonist A‐779, the NOS inhibitor L‐NAME or the GABAA and GABAB receptor antagonists gabazine+CGP‐35348. Salusin‐β‐induced increases in superoxide anion level and NAD(P)H oxidase activity in the PVN were abolished by the PVN pre‐treatment with CLC. Salusin‐β increased AVP levels in rostral ventrolateral medulla and plasma, which were prevented by the pre‐treatment with PEG‐SOD, apocynin or CLC in 2K1C rats. Salusin‐β augmented the enhanced activity of PKC in the PVN in 2K1C rats. Conclusion Protein kinase C‐NAD(P)H oxidase‐superoxide anions pathway in the PVN is involved in salusin‐β‐induced sympathetic activation, pressor response and AVP release in renovascular hypertension.
    December 05, 2013   doi: 10.1111/apha.12188   open full text
  • Substantial skeletal muscle loss occurs during only 5 days of disuse.
    B. T. Wall, M. L. Dirks, T. Snijders, J. M. G. Senden, J. Dolmans, L. J. C. Loon.
    Acta Physiologica. December 05, 2013
    Aim The impact of disuse on the loss of skeletal muscle mass and strength has been well documented. Given that most studies have investigated muscle atrophy after more than 2 weeks of disuse, few data are available on the impact of shorter periods of disuse. We assessed the impact of 5 and 14 days of disuse on skeletal muscle mass, strength and associated intramuscular molecular signalling responses. Methods Twenty‐four healthy, young (23 ± 1 year) males were subjected to either 5 (n = 12) or 14 (n = 12) days of one‐legged knee immobilization using a full leg cast. Before and immediately after the immobilization period, quadriceps muscle cross‐sectional area (CSA), leg lean mass and muscle strength were assessed, and biopsies were collected from the vastus lateralis. Results Quadriceps muscle CSA declined from baseline by 3.5 ± 0.5 (P < 0.0001) and 8.4 ± 2.8% (P < 0.001), leg lean mass was reduced by 1.4 ± 0.7 (P = 0.07) and 3.1 ± 0.7% (P < 0.01) and strength was decreased by 9.0 ± 2.3 (P < 0.0001) and 22.9 ± 2.6% (P < 0.001) following 5 and 14 days of immobilization respectively. Muscle myostatin mRNA expression doubled following immobilization (P < 0.05) in both groups, while the myostatin precursor isoform protein content decreased after 14 days only (P < 0.05). Muscle MAFBx mRNA expression increased from baseline by a similar magnitude following either 5 or 14 days of disuse, whereas MuRF1 mRNA expression had increased significantly only after 5 days. Conclusion We conclude that even short periods of muscle disuse can cause substantial loss of skeletal muscle mass and strength and are accompanied by an early catabolic molecular signalling response.
    December 05, 2013   doi: 10.1111/apha.12190   open full text
  • Detrimental effects of acute hyperglycaemia on the rat heart.
    R. F. Mapanga, D. Joseph, B. Symington, K.‐L. Garson, C. Kimar, R. Kelly‐Laubscher, M.Faadiel Essop.
    Acta Physiologica. November 29, 2013
    Aim Hyperglycaemia is an important risk factor for acute myocardial infarction. It can lead to increased induction of non‐oxidative glucose pathways (NOGPs) – polyol and hexosamine biosynthetic pathways, advanced glycation end products and protein kinase C – that may contribute to cardiovascular diseases onset. However, the precise underlying mechanisms remain poorly understood. Here we hypothesized that acute hyperglycaemia increases myocardial oxidative stress and NOGP activation resulting in cardiac dysfunction during ischaemia–reperfusion and that inhibition of, and/or shunting flux away from NOGPs [by benfotiamine (BFT) treatment], leads to cardioprotection. Methods We employed several experimental systems: (i) Isolated rat hearts were perfused ex vivo with Krebs‐Henseleit buffer containing 33 mm glucose vs. controls (11 mm glucose) ± global ischaemia and reperfusion ± BFT (first 20 min of reperfusion); (ii) Infarct size determination as per the ischaemic protocol, but with regional ischaemia and reperfusion ± BFT treatment; in separate experiments, NOGP inhibitors were also employed for (i) and (ii); and (iii) In vivo coronary ligations performed on streptozotocin‐treated rats ± BFT treatment (early reperfusion). Results Acute hyperglycaemia generated myocardial oxidative stress, NOGP activation and apoptosis, but caused no impairment of cardiac function during pre‐ischaemia, thereby priming hearts for later damage. Following ischaemia–reperfusion (under hyperglycaemic conditions), such effects were exacerbated together with cardiac contractile dysfunction. Moreover, inhibition of respective NOGPs and shunting away by BFT treatment (in part) improved cardiac function during ischaemia–reperfusion. Conclusion Coordinate NOGP activation in response to acute hyperglycaemia results in contractile dysfunction during ischaemia–reperfusion, allowing for the development of novel cardioprotective agents.
    November 29, 2013   doi: 10.1111/apha.12184   open full text
  • L‐3‐n‐butylphthalide protects rats' cardiomyocytes from ischaemia/reperfusion‐induced apoptosis by affecting the mitochondrial apoptosis pathway.
    Y.‐G. Wang, Y. Li, C.‐Y. Wang, J.‐W. Ai, X.‐Y. Dong, H.‐Y. Huang, Z.‐Y. Feng, Y.‐M. Pan, Y. Lin, B.‐X. Wang, L.‐L. Yao.
    Acta Physiologica. November 29, 2013
    Aims This study investigated the role of L‐3‐n‐Butylphthalide (NBP) in cardiac protection. Methods The left anterior descending coronary arteries (LAD) of the rats were occluded for 30 min following by 2‐h reperfusion to make the ischaemia/reperfusion models. Neonatal cardiomyocytes were cultured and subjected to hypoxia. L‐3‐n‐Butylphthalide was administered intraperitoneally 2 h before the surgery and right after the reperfusion in the in vivo experiments or added to the culture medium in vitro. Haemodynamic parameters were recorded to evaluate the cardiac functions, triphenyltetrazolium chloride (TTC) and Evens blue staining were used to determine the area of risk and infarct area, apoptotic cell numbers were counted with terminal deoxynucleotidyl transferase dUTP nick end labelling (TUNEL) staining. Western blotting was used to determine the apoptotic protein levels and immune staining to determine the translocation of Glyceraldehyde‐3‐phosphate dehydrogenase (GAPDH) protein. Results Our research showed for the first time that L‐3‐n‐Butylphthalide had great effects in improving cardiac hemodynamic function and decreasing cardiac infarct areas and apoptotic cell numbers in the peri‐infarct areas. The apoptotic signals investigation showed that L‐3‐n‐Butylphthalide affected the mitochondrial pathway including Bcl‐2 protein expression, inhibition of caspase 3 activation and cytochrome C releasing. Besides, Glyceraldehyde‐3‐phosphate dehydrogenase protein translocation was inhibited by L‐3‐n‐Butylphthalide treatment, and this effect was mediated by endogenous reactive oxygen species (ROS). Conclusion L‐3‐n‐Butylphthalide protects cardiomyocytes from ischaemia/reperfusion‐induced apoptosis by antioxidant effect and affecting mitochondrial apoptotic pathway.
    November 29, 2013   doi: 10.1111/apha.12186   open full text
  • Acute molecular responses in untrained and trained muscle subjected to aerobic and resistance exercise training versus resistance training alone.
    R. Fernandez‐Gonzalo, T. R. Lundberg, P. A. Tesch.
    Acta Physiologica. November 14, 2013
    Aim This study assessed and compared acute muscle molecular responses before and after 5‐week training, employing either aerobic (AE) and resistance exercise (RE) or RE only. Methods Ten men performed one‐legged RE, while the contralateral limb performed AE followed by RE 6 h later (AE+RE). Before (untrained) and after (trained) the intervention, acute bouts of RE were performed with or without preceding AE. Biopsies were obtained from m. vastus lateralis of each leg pre‐ and 3 h post‐RE to determine mRNA levels of VEGF, PGC‐1α, MuRF‐1, atrogin‐1, myostatin and phosphorylation of mTOR, p70S6K, rpS6 and eEF2. Results PGC‐1α and VEGF expression increased (P < 0.05) after acute RE in the untrained, but not the trained state. These markers showed greater response after AE+RE than RE in either condition. Myostatin was lower after AE+RE than RE, both before and after training. AE+RE showed higher MuRF‐1 and atrogin‐1 expression than RE in the untrained, not the trained state. Exercise increased (P < 0.05) p70S6K phosphorylation both before and after training, yet this increase tended to be more prominent for AE+RE than RE before training. Phosphorylation of p70S6K was greater in trained muscle. Changes in these markers did not correlate with exercise‐induced alterations in strength or muscle size. Conclusion Concurrent exercise in untrained skeletal muscle prompts global molecular responses consistent with resulting whole muscle adaptations. Yet, training blunts the more robust anabolic response shown after AE+RE compared with RE. This study challenges the concept that single molecular markers could predict training‐induced changes in muscle size or strength.
    November 14, 2013   doi: 10.1111/apha.12174   open full text
  • Maternal western diet primes non‐alcoholic fatty liver disease in adult mouse offspring.
    Maurien G.M. Pruis, Ágnes Lendvai, Vincent W. Bloks, Mathijs V. Zwier, Julius F.W. Baller, Alain Bruin, Albert K. Groen, Torsten Plösch.
    Acta Physiologica. November 14, 2013
    Aim Metabolic programming via components of the maternal diet during gestation may play a role in the development of different aspects of the metabolic syndrome. Using a mouse model we aimed to characterize the role of maternal western type diet in the development of non‐alcoholic fatty liver disease (NAFLD) in the offspring. Methods Female mice were fed either a western (W) or low‐fat control (L) semi‐synthetic diet before and during gestation and lactation. At weaning, male offspring were assigned either the W or the L diet, generating four experimental groups: WW, WL, LW and LL offspring. Biochemical, histological and epigenetic indicators were investigated at 29 weeks of age. Results Male offspring exposed to prenatal and post‐weaning western‐style diet (WW) showed hepatomegaly combined with accumulation of hepatic cholesterol and triglycerides. This accumulation was associated with up‐regulation of de novo lipid synthesis, inflammation and dysregulation of lipid storage. Elevated hepatic transaminases and increased expression of Tnfa, Cd11, Mcp1 and Tgfb underpin the severity of liver injury. Histopathological analysis revealed the presence of advanced steatohepatitis in WW offspring. In addition, alterations in DNA methylation in key metabolic genes (Ppara, Insig, and Fasn) were detected. Conclusion Maternal dietary fat intake during early development programs susceptibility to liver disease in male offspring, mediated by disturbances in lipid metabolism and inflammatory response. Long lasting epigenetic changes may underlie this dysregulation. This article is protected by copyright. All rights reserved.
    November 14, 2013   doi: 10.1111/apha.12197   open full text
  • Programming effects of FTO in the development of obesity.
    Sylvain Sebert, Tuire Salonurmi, Sirkka Keinänen‐Kiukaanniemi, Markku Savolainen, Karl‐Heinz Herzig, Michael E Symonds, Marjo‐Riitta Järvelin.
    Acta Physiologica. November 12, 2013
    It is becoming increasingly recognised that early‐life nutritional, metabolic and environmental factors can have a long term impact on the early onset of obesity, type 2 diabetes and cardiovascular diseases. Numerous experimental and epidemiological observations support the concept that an individual's response to its adult life‐style and nutritional environment depends not only on their genetic susceptibility but also their previous early‐life experiences. The current research challenge is to determine the primary pathways contributing to “non‐ or epi‐genetic” causes of excess adult weight gain and adiposity. Evidence from the fields of genetic epidemiology, life‐course modelling and diet‐induced fetal programming all support a role for the FTO gene in this complex biological interaction. It may provide a missing link in the developmental regulation of energy metabolism. Our review therefore considers the role of the FTO gene in the early‐life determination of body weight, body composition and energy balance. We will summarise current knowledge on FTO biology combining human genetic epidemiology, molecular models and findings from animal studies. Notably, we will focus on the role of FTO in energy balance in humans, the importance of FTO polymorphisms in childhood growth and the impact of fetal nutrition. Ultimately we propose a new hypothesis for future research designed to understand the role of FTO in setting gene expression in metabolically active tissues. This article is protected by copyright. All rights reserved.
    November 12, 2013   doi: 10.1111/apha.12196   open full text
  • The homoeobox gene SIX1 alters myosin heavy chain isoform expression in mouse skeletal muscle.
    K. L. Hetzler, B. C. Collins, R. A. Shanely, H. Sue, M. C. Kostek.
    Acta Physiologica. November 11, 2013
    Aim Six1 is necessary for the genesis of several tissues, but in adults, it is expressed primarily in skeletal muscle where its function is unclear. Overexpression of Six1 with a cofactor in skeletal muscle causes slow‐to‐fast fibre‐type transition. We sought to characterize the effects of a physiologically relevant Six1 knockdown. Methods The tibialis anterior (TA) muscles of C57BL/6 mice were electroporated with Six1 knockdown vector (siRNA) or empty vector. Muscles were collected at 2 or 14 days after transfection for Six1 and myosin heavy chain (MHC) expression analysis. C2C12 mouse myoblasts were grown in standard conditions. Cells were cotransfected with MHC promoter vectors and Six1 expression vectors. Cells were harvested after 4 days of differentiation. Results In vivo, the Six1 siRNA caused a decreased expression of Six1,1.8‐fold (±0.1, P < 0.05). With decreased Six1, MHC IIB expression decreased 2.7‐fold (±0.7, P = 0.04). Proportion of muscle fibres expressing MHC IIB decreased (45.3 ± 4.8% vs. 65.1 ± 7.3% in control group, P = 0.04), and total area expressing MHC IIB decreased with decreased Six1 (59.6 ± 4.3% vs. 75.2 ± 5.4% in control group, P < 0.05). Decreased Six1 increased MHC IIA expression 1.9‐fold (±0.3, P = 0.04). In vitro, Six1 overexpression increased promoter activation of MHC IIB 2.9‐fold (±0.3, P < 0.01). Six1 knockdown repressed MHC IIB promoter 2.9‐fold (±0.1, P < 0.05) and MHC IIX 3.7‐fold (±0.08, P < 0.01). Conclusion Six1 knockdown caused a fast‐to‐slow shift in MHC isoform, and this was confirmed by promoter activity of MHC genes. Six1 may ultimately control the contractile and metabolic properties that define muscle fibre phenotype.
    November 11, 2013   doi: 10.1111/apha.12168   open full text
  • ET‐1 signalling controls early embryonic heart rate in vitro and in vivo.
    Sari Karppinen, Risto Rapila, Kaarin Mäkikallio, Sandra Hänninen, Jaana Rysä, Olli Vuolteenaho, Pasi Tavi.
    Acta Physiologica. November 08, 2013
    Aim Spontaneous activity of embryonic cardiomyocytes originates from sarcoplasmic reticulum (SR) Ca2+ release during early cardiogenesis. However, the regulation of heart rate during embryonic development is still not clear. The aim of this study was to determine how endothelin‐1 (ET‐1) affects the heart rate of embryonic mice, as well as the pathway through which it exerts its effects. Methods The effects of ET‐1 and ET‐1 receptor inhibition on cardiac contraction were studied using confocal Ca2+ imaging of isolated mouse embryonic ventricular cardiomyocytes and ultrasonographic examination of embryonic cardiac contractions in utero. In addition, the amount of ET‐1 and ET receptor a (ETa) and b (ETb) mRNA levels during different stages of development of the cardiac muscle was measured. Results High ET‐1 concentration and expression of both ETa‐ and ETb‐receptors was observed in early cardiac tissue. ET‐1 was found to increase the frequency of spontaneous Ca2+ oscillations in E10.5 embryonic cardiomyocytes in vitro and non‐specific inhibition of ET‐receptors with Tezosentan caused arrhythmia and bradycardia in isolated embryonic cardiomyocytes and in whole embryonic hearts both in vitro (E10.5) and in utero (E12.5). ET‐1 mediated stimulation of early heart rate was found to occur via ETb – receptors and subsequent inositol trisphosphate receptor activation and increased SR Ca2+ leak. Conclusion ET‐1 is required to maintain a sufficient heart rate, as well as to prevent arrhythmia during early development of the mouse heart. This is achieved through ETb‐receptor, which stimulates Ca2+ leak through IP3‐receptors. This article is protected by copyright. All rights reserved.
    November 08, 2013   doi: 10.1111/apha.12194   open full text
  • Passive leg movement‐induced hyperaemia with a spinal cord lesion: evidence of preserved vascular function.
    M. Venturelli, M. Amann, G. Layec, J. McDaniel, J. D. Trinity, A. S. Fjeldstad, S. J. Ives, G. Yonnet, R. S. Richardson.
    Acta Physiologica. November 05, 2013
    A spinal cord injury (SCI) clearly results in greater cardiovascular risk; however, accompanying changes in peripheral vascular structure below the lesion mean that the real impact of a SCI on vascular function is unclear. Aim Therefore, utilizing passive leg movement‐induced (PLM) hyperaemia, an index of nitric oxide (NO)‐dependent vascular function and the central hemodynamic response to this intervention, we studied eight individuals with a SCI and eight age‐matched controls (CTRL). Methods Specifically, we assessed heart rate (HR), stroke volume (SV), cardiac output (CO), mean arterial pressure (MAP), leg blood flow (LBF) and thigh composition. Results In CTRL, passive movement transiently decreased MAP and increased HR and CO from baseline by 2.5 ± 1 mmHg, 7 ± 2 bpm and 0.5 ± 0.1 L min−1 respectively. In SCI, HR and CO responses were unidentifiable. LBF increased to a greater extent in CTRL (515 ± 41 ∆mL min−1) compared with SCI, (126 ± 25 ∆mL min−1) (P < 0.05). There was a strong relationship between ∆LBF and thigh muscle volume (r = 0.95). After normalizing ∆LBF for this strong relationship (∆LBF/muscle volume), there was evidence of preserved vascular function in SCI (CTRL: 120 ± 9; SCI 104 ± 11 mL min−1 L−1). A comparison of ∆LBF in the passively moved and stationary leg, to partition the contribution of the blood flow response, implied that 35% of the hyperaemia resulted from cardioacceleration in the CTRL, whereas all the hyperaemia appeared peripheral in origin in the SCI. Conclusion Thus, utilizing PLM‐induced hyperaemia as marker of vascular function, it is evident that peripheral vascular impairment is not an obligatory accompaniment to a SCI.
    November 05, 2013   doi: 10.1111/apha.12173   open full text
  • Autophagy is altered in skeletal and cardiac muscle of spontaneously hypertensive rats.
    D. Bloemberg, E. McDonald, D. Dulay, J. Quadrilatero.
    Acta Physiologica. November 05, 2013
    Aim Autophagy is a subcellular degradation mechanism important for muscle maintenance. Hypertension induces well‐characterized pathological changes to the heart and is associated with impaired function and increased apoptotic signalling in skeletal muscle. We examined whether essential hypertension affects several autophagy markers in skeletal and cardiac muscle. Methods Immunoblotting and qRT‐PCR were used to measure autophagy‐related proteins/mRNA in multiple skeletal muscles as well as left ventricle (LV) of spontaneously hypertensive rats (SHR) and normotensive Wistar–Kyoto rats (WKY). Results Skeletal muscles of hypertensive rats had decreased (P < 0.01) cross‐sectional area of type I fibres (e.g. soleus WKY: 2952.9 ± 64.4 μm2 vs. SHR: 2579.9 ± 85.8 μm2) and a fibre redistribution towards a ‘fast’ phenotype. Immunoblot analysis revealed that some SHR skeletal muscles displayed a decreased LC3II/I ratio (P < 0.05), but none showed differences in p62 protein. LC3 and LAMP2 mRNA levels were increased approx. 2–3‐fold in all skeletal muscles (P < 0.05), while cathepsin activity, cathepsin L mRNA and Atg7 protein were increased 16–17% (P < 0.01), 2–3‐fold (P < 0.05) and 29–49% (P < 0.01), respectively, in fast muscles of hypertensive animals. Finally, protein levels of BAG3, a marker of chaperone‐assisted selective autophagy, were 18–25% lower (P < 0.05) in SHR skeletal muscles. In the LV of SHR, LC3I and p62 protein were elevated 34% (P < 0.05) and 47% (P < 0.01), respectively. Furthermore, p62 mRNA was 68% higher (P < 0.05), while LAMP2 mRNA was 45% lower (P < 0.05), in SHR cardiac muscle. There was no difference in Beclin1, Atg7, Bnip3 or BAG3 protein in the LV between strains. Conclusion These results suggest that autophagy is altered in skeletal and cardiac muscle during hypertension.
    November 05, 2013   doi: 10.1111/apha.12178   open full text
  • The adrenergic regulation of proximal tubular Na+/H+ exchanger 3 in the rat.
    V. Healy, C. Thompson, E. J. Johns.
    Acta Physiologica. November 05, 2013
    Aim This study in the anaesthetized rat investigated how renal sympathetic nerve activity and catecholamine release influenced NHE3 abundance and activity in proximal tubular brush border membranes using both in vivo and in vitro approaches. Methods Renal excretory function and brush border NHE3 abundance and activity were measured in rat kidneys which underwent renal denervation, renal nerve electrical stimulation and renal infusion of phenylephrine and the NHE3 inhibitor S1661. NHE3 activity and cell surface abundance were also measured in primary cultures of proximal tubular cells treated with noradrenaline and prazosin. Results Acute renal denervation caused a natriuresis and diuresis, which occurred with a reduction in NHE3 abundance and activity in the brush border membranes. By contrast, low‐level electrical stimulation of the renal innervation causing an antinatriuresis and antidiuresis increased NHE3 activity in the brush border membranes. Intrarenal infusion of phenylephrine caused an antinatriuresis and antidiuresis, while blockade of NHE3 activity, using local infusion of the blocker S1661, caused a natriuresis and diuresis. Exposure of primary cultures of proximal tubular cells to noradrenaline increased brush border NHE3 abundance and activity which was blocked by prior exposure to prazosin, indicating it as an α1‐adrenoceptor‐mediated mechanism. Conclusion Together, these findings demonstrate that the renal sympathetic nerves not only have a direct action to modulate tubular sodium reabsorption via stimulation of the NHE transporter, but also have an indirect effect, whereby NHE3 abundance is increased within the brush border membrane, thereby increasing the capacity for fluid reabsorption.
    November 05, 2013   doi: 10.1111/apha.12181   open full text
  • Salt Sensitivity Of Renin Secretion, Glomerular Filtration Rate, And Blood Pressure In Conscious Sprague Dawley Rats.
    Gustaf L. Isaksson, Jane Stubbe, Per Lyngs Hansen, Boye L. Jensen, Peter Bie.
    Acta Physiologica. November 04, 2013
    Aim We hypothesized that in normal rats in metabolic steady state, (i) the plasma renin concentration (PRC) is log‐linearly related to Na+ intake (NaI), (ii) the concurrent changes in mean arterial pressure (MABP) and glomerular filtration rate (GFR) are negligible, and (iii) the function PRC = f(NaI) is altered by β1–adrenoceptor blockade (metoprolol) and surgical renal denervation (DNX). Methods In catheterized, conscious rats on low‐Na+ diet (0.004 % Na+), NaI was increased by up to 120‐fold, in four 3‐day steps, by intravenous saline infusion. MABP was recorded continuously, PRC measured in arterial blood, and GFR estimated by inulin clearance. Results Steady states were achieved within 3 days. PRC [mIU/l] was log‐linearly related to NaI [mmol/kg/d]: PRC = −9.9·log (NaI) + 22. Set point (22 mIU/l at NaI = 1) and slope (9.9 mIU per decade NaI) were independent of metoprolol administration and DNX. MABP and GFR were markedly salt sensitive: MABP [mmHg] = 4.9·log (NaI) + 99 (p<0.01), and GFR [ml/min] = 1.4·log (NaI) + 8.3 (p<0.01). MABP increased similarly (~10%, p<0.001) irrespective of pretreatment. Metoprolol, but not DNX, reduced MABP, HR, and GFR (all p<0.01). Salt‐sensitivity of GFR was not observed in DNX rats. Conclusion Log‐linear relations to sodium intake exist not only for PRC, but also for MABP and GFR, which per 10‐fold increase in sodium intake rose by 5 mmHg and 1.4 ml/min, respectively. Steady state levels of PRC appear independent of renal nerves. MABP and GFR seem markedly salt sensitive in normal rats. This article is protected by copyright. All rights reserved.
    November 04, 2013   doi: 10.1111/apha.12191   open full text
  • High and low protein gestation diets do not provoke common transcriptional responses representing universal target‐pathways in muscle and liver of porcine progeny.
    Michael Oster, Eduard Murani, Cornelia C. Metges, Siriluck Ponsuksili, Klaus Wimmers.
    Acta Physiologica. November 04, 2013
    Aim Maternal diets introduce transcriptional changes in the offspring, highlighting the concept of genetic and physiological plasticity. Our previous analyses investigated stage‐dependent transcriptional responses to either maternal high or low protein:carbohydrate ratios in either muscle or liver. Fetal programming is proposed to be mediated by a small number of gatekeeper processes, such as cytoskeleton remodeling and cell cycle regulation. Here, we conducted an overall analysis of a three‐dimensional dataset aiming to elucidate, whether there are universally targeted pathways of adaptive transcriptional response to different protein:carbohydrate ratios. Methods Microarray analyses were performed on liver and skeletal muscle tissue sampled at 94 days post‐conception and 1, 28, and 188 days post‐natum from offspring (n=253) of German Landrace gilts that were fed isoenergetic diets containing low, high, or adequate protein. Results Cluster analyses revealed a hierarchical influence of tissue, ontogenetic stage, and diet on transcript levels. Considering results cumulatively over stages, liver showed only marginal transcriptional differences between the dietary groups, whereas considerable differences appeared in muscle. Considering results cumulatively over tissues, nutrition responsive transcriptions were observed along ontogenesis. Pathway analyses revealed transcript differences in genes related to tissue remodeling, cell cycle regulation, and mitochondrial function. Conclusion The factors tissue, stage, and diet impact gene expression in a hierarchical order. Porcine liver appeared to be a tissue that was more resilient to nutritional modulation compared to skeletal muscle tissue. In muscle, differential modulation between tissues and dietary groups reveal that there are no universal target‐pathways of adaptive transcriptional response to different protein diets. This article is protected by copyright. All rights reserved.
    November 04, 2013   doi: 10.1111/apha.12192   open full text
  • A mechanistic look at the effects of adversity early in life on cardiovascular disease risk during adulthood.
    Analia S. Loria, Dao H. Ho, Jennifer S. Pollock.
    Acta Physiologica. October 29, 2013
    Early origins of adult disease may be defined as adversity or challenges during early life that alter physiological responses and prime the organism to chronic disease in adult life. Adverse childhood experiences or early life stress (ELS) may be considered a silent independent risk factor capable of predicting future cardiovascular disease risk. Maternal separation (MatSep) provides a suitable model to elucidate the underlying molecular mechanisms by which ELS increases the risk to develop cardiovascular disease in adulthood. The aim of this review is to describe the links between behavioral stress early in life and chronic cardiovascular disease risk in adulthood. We will discuss: 1) adult cardiovascular outcomes in humans subjected to ELS, 2) maternal separation (MatSep) as an animal model of ELS as well as the limitations and advantages of this model in rodents, and 3) possible ELS‐induced mechanisms that predispose individuals to greater cardiovascular risk. Overall, exposure to a behavioral stressor early in life sensitizes the response to a second stressor later in life, thus unmasking an exaggerated cardiovascular dysfunction that may influence quality of life and life expectancy in adulthood. This article is protected by copyright. All rights reserved.
    October 29, 2013   doi: 10.1111/apha.12189   open full text
  • Adenosine increases LPS‐induced nuclear factor kappa B activation in smooth muscle cells via an intracellular mechanism and modulates it via actions on adenosine receptors.
    J. Yang, X. Zheng, F. Haugen, E. Darè, C. Lövdahl, G. Schulte, B. B. Fredholm, G. Valen.
    Acta Physiologica. October 28, 2013
    Aim In inflamed and damaged cardiovascular tissues, local extracellular adenosine concentrations increase coincidentally with activation of the transcription factor nuclear factor kappa B (NFκB). To investigate whether adenosine influences NFκB activation in vascular smooth muscle cells (VSMCs) and, if so, to examine the role of its receptors. Methods VSMCs were isolated from NFκB–luciferase reporter mice, cultured and then treated by lipopolysaccharide (LPS) to activate NFκB signalling. Adenosine, adenosine receptor agonists and antagonists, adenosine deaminase and uptake inhibitors were used together with LPS to evaluate the role of adenosine and its receptors on NFκB activation, which was assessed by luciferase activity and NFκB target gene expression. Results Adenosine potentiated LPS‐induced NFκB activation. This was dependent on adenosine uptake and enhanced by an adenosine deaminase inhibitor, suggesting that intracellular adenosine plays an important role. Non‐selective adenosine receptor agonists (2Cl‐Ado and NECA) inhibited NFκB activation induced by LPS. Selective A1 or A2A antagonist given alone could not completely antagonize the NECA effect, indicating that the inhibitory effect was due to multiple adenosine receptors. The activation of the A3 receptor further increased LPS‐induced NFκB activation. Conclusions Adenosine increases LPS‐induced nuclear factor kappa B activation in smooth muscle cells via an intracellular mechanism and decreases it via actions on A1 and A2A receptors. These results provide novel insights into the role of adenosine as a regulator of inflammation‐induced NFκB activation.
    October 28, 2013   doi: 10.1111/apha.12176   open full text
  • Fetal and placental 11β‐HSD2: a hub for developmental programming.
    Elizabeth C Cottrell, Jonathan R Seckl, Megan C Holmes, Caitlin S Wyrwoll.
    Acta Physiologica. October 28, 2013
    Fetal growth restriction (FGR), reflective of an adverse intrauterine environment, confers a significantly increased risk of perinatal mortality and morbidity. In addition, low birthweight associates with adult diseases including hypertension, metabolic dysfunction and behavioural disorders. A key mechanism underlying FGR is exposure of the fetus to glucocorticoids which, while critical for fetal development, in excess can reduce fetal growth and permanently alter organ structure and function, predisposing to disease in later life. Fetal glucocorticoid exposure is regulated, at least in part, by the enzyme 11β‐hydroxysteroid dehydrogenase type 2 (11β‐HSD2), which catalyzes the intracellular inactivation of glucocorticoids. This enzyme is highly expressed within the placenta at the maternal‐fetal interface, limiting passage of glucocorticoids to the fetus. Expression of 11β‐HSD2 is also high in fetal tissues, particularly within the developing central nervous system. Down‐regulation or genetic deficiency of placental 11β‐HSD2 is associated with significant reductions in fetal growth and birth weight, and programmed outcomes in adulthood. To unravel the direct significance of 11β‐HSD2 for developmental programming, placental function, neurodevelopment and adult behaviour have been extensively investigated in a mouse knockout of 11β‐HSD2. This review highlights the evidence obtained from this mouse model for a critical role of feto‐placental 11β‐HSD2 in determining adverse programming outcomes. This article is protected by copyright. All rights reserved.
    October 28, 2013   doi: 10.1111/apha.12187   open full text
  • Physiology and analysis of the electrocardiographic T wave in mice.
    T. Speerschneider, M. B. Thomsen.
    Acta Physiologica. October 24, 2013
    Aim The murine electrocardiogram (ECG) is a valuable tool in cardiac research, although the definition of the T wave has been a matter of debate for several years potentially leading to incomparable data. By this study, we seek to make a clear definition of the murine T wave. Moreover, we investigate the consequences of performing QT interval correction in anaesthetized mice. Methods Electrocardiograms from conscious mice were recorded by implanted telemetry devices. Surface ECGs were recorded from anaesthetized mice before and during pharmacological interventions, ventricular ischaemia and heart failure. Right atrial pacing was performed to evaluate the relationship between heart rate and QT intervals. Results Electrocardiogram traces of conscious and anaesthetized mice (lead II) showed separable positive J waves and negative T waves. The end of the T wave was determined as the point where the T wave returned to the isoelectric line. Atrial pacing revealed that the duration of the QT interval is independent of heart rate in anaesthetized mice. The calcium channel blocker, verapamil, prolonged the PR interval; however, the polarities of the J and T waves were not changed. Local cardiac ischaemia and β‐adrenergic stimulation caused indistinguishable positive J and T waves. In contrast, chronic heart failure caused entirely negative J and T waves. In every case, the end of the T wave was clearly distinguishable on the ECG. Conclusion The end of the T wave is readily available from conscious and anaesthetized mice. Heart rate correction of QT interval duration in the anaesthetized mouse is not recommended.
    October 24, 2013   doi: 10.1111/apha.12172   open full text
  • Endogenous preoptic hydrogen sulphide attenuates hypoxia‐induced hyperventilation.
    M. Kwiatkoski, R. N. Soriano, G. S. F. da Silva, H. D. Francescato, T. M. Coimbra, M. L. Glass, E. C. Carnio, L. G. S. Branco.
    Acta Physiologica. October 22, 2013
    Aim We hypothesized that hydrogen sulphide (H2S), acting specifically in the anteroventral preoptic region (AVPO – an important integrating site of thermal and cardiorespiratory responses to hypoxia in which H2S synthesis has been shown to be increased under hypoxic conditions), modulates the hypoxic ventilatory response. Methods To test this hypothesis, we measured pulmonary ventilation (V˙E) and deep body temperature of rats before and after intracerebroventricular (icv) or intra‐AVPO microinjection of aminooxyacetate (AOA; CBS inhibitor) or Na2S (H2S donor) followed by 60 min of hypoxia exposure (7% O2). Furthermore, we assessed the AVPO levels of H2S of rats exposed to hypoxia. Control rats were kept under normoxia. Results Microinjection of vehicle, AOA or Na2S did not change V˙E under normoxic conditions. Hypoxia caused an increase in ventilation, which was potentiated by microinjection of AOA because of a further augmented tidal volume. Conversely, treatment with Na2S significantly attenuated this response. The in vivo H2S data indicated that during hypoxia the lower the deep body temperature the smaller the degree of hyperventilation. Under hypoxia, H2S production was found to be increased in the AVPO, indicating that its production is responsive to hypoxia. The CBS inhibitor attenuated the hypoxia‐induced increase in the H2S synthesis, suggesting an endogenous synthesis of the gas. Conclusion These data provide solid evidence that AVPO H2S production is stimulated by hypoxia, and this gaseous messenger exerts an inhibitory modulation of the hypoxic ventilatory response. It is probable that the H2S modulation of hypoxia‐induced hyperventilation is at least in part in proportion to metabolism.
    October 22, 2013   doi: 10.1111/apha.12177   open full text
  • Growth hormone‐induced insulin resistance in human subjects involves reduced pyruvate dehydrogenase activity.
    Birgitte Nellemann, Mikkel H Vendelbo, Thomas S Nielsen, Ann M Bak, Morten Høgild, Steen B Pedersen, Rasmus S Biensø, Henriette Pilegaard, Niels Møller, Niels Jessen, Jens Otto L Jørgensen.
    Acta Physiologica. October 21, 2013
    Aim Insulin resistance induced by growth hormone (GH) is linked to promotion of lipolysis by unknown mechanisms. We hypothesized that suppression of the activity of pyruvate dehydrogenase in the active form (PDHa) underlies GH‐induced insulin resistance similar to what is observed during fasting. Methods Eight healthy male subjects were studied four times in a randomized, single‐blinded parallel design: Control, GH, Fasting (36h), and GH + Fasting. GH (30 ng x kg−1 x min−1) or saline was infused throughout the metabolic study day. Substrate metabolism and insulin sensitivity were assessed by indirect calorimetry and isotopically determined rates of glucose turnover before and after a hyperinsulinemic euglycemic clamp. PDHa activity, PDH‐E1α phosphorylation, PDK4 expression, and activation of insulin signaling proteins were assessed in skeletal muscle. Results Both fasting and GH promoted lipolysis, which was associated with ≈50% reduction in insulin sensitivity compared to the control day. PDHa activity was significantly reduced by GH as well as fasting. This was associated with increased inhibitory PDH‐E1α phosphorylation on site 1 (Ser293) and 2 (Ser300) and up‐regulation of PDK4 mRNA while canonical insulin signaling to glucose transport was unaffected. Conclusion Competition between intermediates of glucose and fatty acids seems to play a causal role in insulin resistance induced by GH in human subjects. This article is protected by copyright. All rights reserved.
    October 21, 2013   doi: 10.1111/apha.12183   open full text
  • Adipose afferent reflex: sympathetic activation and obesity hypertension.
    Xiao‐Qing Xiong, Wei‐Wei Chen, Guo‐Qing Zhu.
    Acta Physiologica. October 14, 2013
    Excessive sympathetic activity contributes to the pathogenesis of hypertension and the progression of the related organ damage. Adipose afferent reflex (AAR) is a sympatho‐excitatory reflex that the afferent activity from white adipose tissue (WAT) increases sympathetic outflow and blood pressure. Hypothalamic paraventricular nucleus (PVN or PVH) is one of the central sites in the control of the AAR, and ionotropic glutamate receptors in the nucleus mediate the AAR. The AAR is enhanced in obesity and obesity hypertension. Enhanced WAT afferent activity and AAR contribute to the excessive sympathetic activation and hypertension in obesity. Blockage of the AAR attenuates the excessive sympathetic activity and hypertension. Leptin may be one of sensors in the WAT for the AAR, and is involved in the enhanced AAR in obesity and hypertension. This review focuses on the neuroanatomical basis and physiological functions of the AAR, and the important role of the enhanced AAR in the pathogenesis of obesity hypertension. This article is protected by copyright. All rights reserved.
    October 14, 2013   doi: 10.1111/apha.12182   open full text
  • PPARγ Activation Inhibits Cerebral Arteriogenesis in the Hypoperfused Rat Brain.
    André Duelsner, Nora Gatzke, Philipp Hillmeister, Johanna Glaser, Andreas Zietzer, Stephanie Nagorka, Doreen Janke, Julia Pfitzner, Philipp Stawowy, Heike Meyborg, Daniel Urban, Anja Bondke Persson, Ivo R. Buschmann.
    Acta Physiologica. October 07, 2013
    Aims PPARγ stimulation improves cardiovascular (CV) risk factors, but without improving overall clinical outcomes. PPARγ agonists interfere with endothelial (EC), monocyte and smooth muscle cell (SMC) activation, function and proliferation, physiological processes critical for arterial collateral growth (arteriogenesis). We therefore assessed the effect of PPARγ stimulation on cerebral adaptive and therapeutic collateral growth. Methods In a rat model of adaptive cerebral arteriogenesis (3‐VO), collateral growth and function were assessed (a) in controls, (b) after PPARγ stimulation (pioglitazone 2.8mg/kg; 10mg/kg compared to metformin 62.2mg/kg or sitagliptin 6.34mg/kg) for 21 days or (c) after adding pioglitazone to G‐CSF (40μg/kg every other day) to induce therapeutic arteriogenesis for 1 week. Pioglitazone effects on endothelial and SMC morphology and proliferation, monocyte activation and migration were studied. Results PPARγ stimulation decreased cerebrovascular collateral growth and recovery of hemodynamic reserve capacity (CVRC controls: 12±7%; pio low: ‐2±9%; pio high: 1±7%; metformin: 9±13%; sitagliptin: 11±12%.), counteracted G‐CSF induced therapeutic arteriogenesis and interfered with EC activation, SMC proliferation, monocyte activation and migration. Conclusion Pharmacologic PPARγ stimulation inhibits proarteriogenic EC activation, monocyte function, SMC proliferation and thus adaptive as well as G‐CSF induced cerebral arteriogenesis. Further studies should evaluate whether this effect may underlie the cardiovascular risk associated with thiazolidinedione use in patients. This article is protected by copyright. All rights reserved.
    October 07, 2013   doi: 10.1111/apha.12179   open full text
  • Relative contribution of foetal and post‐natal nutritional periods on feeding regulation in adult rats.
    A. Martin Agnoux, M. ‐C. Alexandre‐Gouabau, G. Le Dréan, J. ‐P. Antignac, P. Parnet.
    Acta Physiologica. October 07, 2013
    Aim The aim of this study was to assess the contribution of both foetal and/or post‐natal nutritional periods on feeding regulation in adult rats. Methods Body weight gain, adipose tissue development, food preferences and feeding pattern under regular chow or Western diets were characterized on four experimental groups of rats: pups born from protein‐restricted dams (R) and weaned by control (RC) or R dams (RR) and pups born from control dams weaned by C (CC) or R dams (CR). Results Rats born with intrauterine growth restriction (IUGR) and fed a Western diet at adulthood appeared predisposed to body weight gain and more fat accretion, whereas CR rats, despite their preference for high‐fat diet and their hyperphagia for Western diet, did not show significant increase in fat tissue. Daytime food intakes, as well as their speed of ingestion, were found modified in RC and RR. Alterations in the hypothalamic appetite regulatory mechanisms were investigated through neuropeptide expression analysis. IUGR rats showed altered expression of key elements of leptin and NPY signalling, while CR rats exhibited lesser expression of enterostatin, MC4r and HT‐1Br mRNA. Conclusion Altogether, these results indicate that peri‐natal nutrition has different lasting effects on feeding pattern and hypothalamic appetite regulation, depending on the time window insult.
    October 07, 2013   doi: 10.1111/apha.12163   open full text
  • Activation of nuclear factor erythroid 2‐related factor 2 (Nrf2) and Nrf‐2‐dependent genes by ischaemic pre‐conditioning and post‐conditioning: new adaptive endogenous protective responses against renal ischaemia/reperfusion injury.
    A. A. Shokeir, A. M. Hussein, N. Barakat, A. Abdelaziz, M. Elgarba, A. Awadalla.
    Acta Physiologica. October 07, 2013
    Aim To investigate the impact of ischaemic pre‐conditioning (Ipre) and post‐conditioning (Ipost) on expression of nuclear factor erythroid 2‐related factor 2 (Nrf2) gene and its dependent genes, haem oxygenase‐1 (HO‐1) and NADPH‐quinone oxidoreductase‐1 (NQO‐1); inflammatory cytokines TNF‐α, IL1β and ICAM‐1; and apoptotic markers such as caspase‐3 in renal ischaemia/reperfusion (I/R) injury. Methods One hundred and fifty male Sprague Dawley rats were classified into five groups (each consisted of 30 rats): sham, control (I/R), Ipre + I/R, Ipre without I/R and Ipost + I/R. Serum creatinine and blood urea nitrogen (BUN) were measured at 2, 24 and 48 h after ischaemia. In kidney tissues, mRNA of Nrf2, HO‐1, NQO‐1, TNF‐α, IL‐1β and ICAM‐1 and immunohistochemical expression of Nrf2 and caspase‐3 were assessed. Results Serum creatinine and BUN improved significantly in Pre + I/R group; however, they did not show any significant improvement in Post + I/R group. Also, Ipre‐I/R group showed non‐significant change in serum creatinine and BUN. The expression of Nrf2, HO‐1 and NQO‐1 is increased significantly in Pre + I/R and Pre − I/R groups, while the enhancement in Post + I/R group was non‐significant. Moreover, the expression of proinflammatory cytokines (TNF‐α, IL‐1 and ICAM‐1) and apoptotic (caspase‐3) markers showed high significant attenuation in Pre + I/R group, but slight significant attenuation in Pre + I/R group. Conclusion The renoprotective action of Ipre might include early activation and enhanced expression of Nrf2 gene and its dependent antioxidant genes, HO‐1 and NOQ1, as endogenous adaptive renoprotective genes, as well as reduction in TNF‐α, IL‐1β, ICAM‐1 and caspase‐3.
    October 07, 2013   doi: 10.1111/apha.12164   open full text
  • Responses of iliac conduit artery and hindlimb resistance vessels to luminal hyperfructosemia in the anaesthetized pig.
    T. Ruane‐O'Hora, D. Edge, C. M. Shortt, F. Markos, M. I. M. Noble.
    Acta Physiologica. October 07, 2013
    Aims High fructose levels are found in diabetes mellitus, associated with high corn syrup diets, and have been claimed to cause hypertension. As the direct effects on conduit and resistance arteries have not been previously reported, we measured these in vivo in the anaesthetized pig with instrumented iliac arteries. Methods Experiments were performed on the iliac artery preparation in the anaesthetized pig: blood flow, diameter and pressure were measured in the iliac. Results The change in diameter of an occluded iliac artery segment filled with hyperfructosemic (15 μm) blood was 89.5 ± 22.1 μm (mean ± SE), contrasted with 7.7 ± 13.06 μm control (P = 0.005, paired t‐test, n = 6). There was no significant difference when compared with blood containing both hyperfructosemic blood and the nitric oxide synthesis inhibitor, N(G)‐nitro‐l‐arginine methyl ester (250 μg mL−1). Step changes in pressure and flow were achieved by progressive arterial stenosis during control saline and 15 μm min−1 fructose downstream intra‐arterial infusions. Linear regression of the step changes in blood pressure versus the instantaneous step changes in blood flow showed a statistically significant decrease in slope of the conductance (P < 0.001, analysis of covariance), indicating an increase in instantaneous peripheral vascular resistance. Peripheral autoregulation and conduit artery shear‐stress‐mediated dilatation were not significantly altered. Conclusion An elevated level of fructose caused dilatation of a conduit artery but constriction of resistance vessels. The latter effect could account, if maintained long‐term, for the hypertension claimed to be due to hyperfuctosemia.
    October 07, 2013   doi: 10.1111/apha.12167   open full text
  • Blockade of mitochondrial calcium uniporter prevents cardiac mitochondrial dysfunction caused by iron overload.
    J. Sripetchwandee, S. B. KenKnight, J. Sanit, S. Chattipakorn, N. Chattipakorn.
    Acta Physiologica. October 04, 2013
    Aim Iron overload in the heart can lead to iron‐overload cardiomyopathy and cardiac arrhythmia. In the past decades, growing evidence has suggested that cardiac mitochondrial dysfunction is associated with the development of cardiac dysfunction and lethal arrhythmias. Despite these facts, the effect of iron overload on cardiac mitochondrial function is still unclear. In this study, we determined the effects of iron overload on the cardiac mitochondrial function and the routes of cardiac mitochondrial iron uptake. We tested the hypothesis that iron overload can lead to cardiac mitochondrial dysfunction and that mitochondrial calcium uniporter (MCU) plays a major role for cardiac mitochondrial iron uptake under iron‐overload condition. Cardiac mitochondrial function was assessed via the determination of mitochondrial swelling, mitochondrial reactive oxygen species (ROS) production and mitochondrial membrane potential changes. Methods Isolated cardiac mitochondria from male Wistar rats were used in this study. To determine the routes for cardiac mitochondrial iron uptake, isolated mitochondria were exposed to MCU blocker (Ru360), mitochondrial permeability transition pore (mPTP) blocker (cyclosporin A) and an iron chelator (deferoxamine). Results We found that (i) iron overload caused cardiac mitochondrial dysfunction, indicated by increased ROS production, mitochondrial membrane depolarization and mitochondrial swelling; and (ii) only MCU blocker completely protected cardiac mitochondrial dysfunction caused by iron overload. Conclusions These findings strongly suggest that MCU could be the major route for iron uptake into cardiac mitochondria. The inhibition of MCU could be the novel pharmacological intervention for preventing iron‐overload cardiomyopathy.
    October 04, 2013   doi: 10.1111/apha.12162   open full text
  • Lipotoxicity and the role of maternal nutrition.
    Maurien G.M. Pruis, Petronella A. Ewijk, Vera B. Schrauwen‐Hinderling, Torsten Plösch.
    Acta Physiologica. October 01, 2013
    Intrauterine malnutrition predisposes the offspring towards the development of type 2 diabetes and cardiovascular disease. To explain this association, the Developmental Origins of Health and Disease (DOHaD) hypothesis was introduced, meaning that subtle environmental changes during embryonic and fetal development can influence postnatal physiological functions. Different mechanisms, including epigenetics, are thought to be involved in this fetal programming, but the link between epigenetics and disease is missing. There is increasing evidence that ectopic lipid accumulation and/or lipotoxicity is induced by fetal programming. The aim of this review is to provide insights into the mechanisms underlying lipotoxicity through programming which contributes to the increase in hepatic and cardiac metabolic risk. This article is protected by copyright. All rights reserved.
    October 01, 2013   doi: 10.1111/apha.12171   open full text
  • Comparative cardiovascular physiology: future trends, opportunities and challenges.
    W.W. Burggren, V.M. Christoffels, D.A. Crossley, S. Enok, A.P. Farrell, M.S. Hedrick, J.W. Hicks, B. Jensen, A.F.M. Moorman, C.A. Mueller, N. Skovgaard, E.W. Taylor, T. Wang.
    Acta Physiologica. September 30, 2013
    The inaugural Kjell Johansen lecture in the Zoophysiology Department of Aarhus University (Aarhus, Denmark), afforded the opportunity for a focused workshop comprising comparative cardiovascular physiologists to ponder some of the key unanswered questions in the field. Discussions were centered around three themes. The first considered function of the vertebrate heart in its various forms in extant vertebrates, with particular focus on the role of intracardiac shunts, the trabecular (“spongy”) nature of the ventricle in many vertebrates, coronary blood supply and the building plan of the heart as revealed by molecular approaches. The second theme involved the key unanswered questions in the control of the cardiovascular system, emphasizing autonomic control, hypoxic vasoconstriction and developmental plasticity in cardiovascular control. The final theme involved poorly understood aspects of the interaction of the cardiovascular system with the lymphatic, renal and digestive systems. Having posed key questions around these three themes, it is increasingly clear that an abundance of new analytical tools and approaches will allow us to learn much about vertebrate cardiovascular systems in the coming years. This article is protected by copyright. All rights reserved.
    September 30, 2013   doi: 10.1111/apha.12170   open full text
  • Gender differences in fascicular lengthening during eccentric contractions: the role of the patella tendon stiffness.
    K. M. Hicks, G. L. Onambele‐Pearson, K. Winwood, C. I. Morse.
    Acta Physiologica. September 19, 2013
    Aim Elastic tendons have been suggested to attenuate fascicle lengthening during eccentric contractions; however, there is no in vivo evidence to support this hypothesis. Therefore, the aim of this study was to determine whether patella tendon stiffness modulates vastus lateralis (VL) fascicle lengthening during eccentric contractions in males and females. Method Vastus lateralis and patella tendon properties were measured in males and females owing to previously reported intrinsic gender differences in tendon properties. During maximal voluntary eccentric knee extensions, VL fascicle lengthening and torque were recorded at every 10° (range of motion 20–90°). Results A significant correlation between maximal patella tendon stiffness and change in fascicle length (r = 0.476, P = 0.023) was observed. Similarly, there was a significant correlation between maximal Young's modulus and change in fascicle length (r = 0.470, P = 0.049). As expected, patella tendon stiffness and Young's modulus were significantly higher in males compared with females (P < 0.05). Interestingly, change in VL fascicle length during the eccentric contractions was significantly greater in males compared with females (P < 0.05). Based on patella tendon moment arm measurements, VL muscle‐tendon unit elongation was estimated to be significantly greater in males compared with females (5.24 and 4.84 cm respectively). Conclusion The significant difference in fascicle lengthening during eccentric contractions may be partly explained by the significantly higher patella tendon moment arm, patella tendon stiffness and Young's modulus found in males compared with females. The current study provides in vivo evidence to support the hypothesis that the tendon acts as a ‘mechanical buffer’ during eccentric contractions.
    September 19, 2013   doi: 10.1111/apha.12159   open full text
  • Perturbations to the IGF1 growth pathway and adult energy homeostasis following disruption of mouse chromosome 12 imprinting.
    M. Charalambous, S. T. da Rocha, A. Hernandez, A. C. Ferguson‐Smith.
    Acta Physiologica. September 18, 2013
    Aim Disruption to insulin‐like growth factor (IGF) signalling pathways during early life causes growth retardation and defects of developing metabolic organs that can alter set points of energy homeostasis for a lifetime. Inheritance of two maternal copies of human chromosome 14q32.2 (Temple syndrome) causes severe foetal growth retardation and post‐natal failure to thrive. Disruption of imprinted gene dosage in the orthologous region on mouse chromosome 12 also affects growth. Here, we investigated whether altering chromosome 12‐imprinted gene dosage can affect IGF signalling. Methods We investigated mice with a transgene insertion at the imprinted domain of chromosome 12. This lesion causes misexpression of neighbouring genes such that the expression of non‐coding RNAs is elevated, and levels of delta‐like homologue 1 (Dlk1), retrotransposon‐like 1 (Rtl1) and deiodinase 3 (Dio3) transcripts are reduced. Results We observed three key phenotypes in these mice: (i) embryonic growth retardation associated with altered expression of IGF1 binding proteins, (ii) peri‐natal failure to thrive accompanied by hypothyroidism and low serum IGF1. Unexpectedly this phenotype was growth hormone independent. (iii) Adult animals had reduced glucose tolerance as a result of endocrine pancreatic insufficiency. Conclusions We propose that all of these phenotypes are attributable to impaired IGF action and show for the first time that the chromosome 12 cluster in the mouse is an imprinted locus that modulates the IGF signalling pathway. We propose that growth retardation observed in human Temple syndrome might have a similar cause.
    September 18, 2013   doi: 10.1111/apha.12160   open full text
  • Effect of testosterone replacement therapy on cardiac performance and oxidative stress in orchidectomized rats.
    S. M. Eleawa, H. F. Sakr, A. M. Hussein, A. S. Assiri, N. M. K. Bayoumy, M. Alkhateeb.
    Acta Physiologica. September 13, 2013
    Aim To investigate the effects of testosterone on myocardial contractility, oxidative stress status and expression of sodium channel protein (Nav1.5) and inward rectifying K channels (Kir 2.x) in normal and orchidectomized (ORX) rats. Methods One hundred four rats were randomly assigned into four groups (n = 26, each) as follows: (i) untreated controls, (ii) testosterone treated, (iii) orchidectomized rats and (iv) orchidectomized, testosterone‐treated rats. Treatments with the vehicle or testosterone were carried out for 12 weeks, three times per week. At the end of treatment, surface ECG, isolated heart, tissue oxidative stress and lipid peroxidation experiments were carried out on the cardiac tissues. Also, immunohistochemical examination for Nav1.5 and PCR detection of mRNA of Kir2.1, Kir2.2 and Kir2.4 subunits of K channels were carried out. Results Orchidectomy impaired cardiac contractile function parameters left ventricular developed pressure (LVDP) and the peaks of the positive and negative pressure derivatives (dP/dtmax and −dP/dtmax respectively), increased heart rate and prolonged QT and QTc intervals, elevated pro‐oxidant state in rat's hearts and decreased the expression of Kir 2.1 but not Kir2.2, Kir 2.4 and Nav1.5 channels. Exogenous testosterone administration to orchidectomized rats restored heart contractility and shortened QT and QTc intervals to their normal values, ameliorated the generated pro‐oxidant state and improved the expression of Nav1.5 and Kir2.1, but not Kir2.2 or Kir2.4 channels. Conclusion Testosterone improved cardiac contractility and shortened QT and QTc intervals in ORX rats. An effect that might be dependent of reduction in oxidative stress and enhancement of Kir2.1 channels but independent of Nav1.5 channel protein.
    September 13, 2013   doi: 10.1111/apha.12158   open full text
  • Activation of transient receptor potential vanilloid 1 decreases endothelial nitric oxide synthase phosphorylation at Thr497 by protein phosphatase 2B‐dependent dephosphorylation of protein kinase C.
    L.‐C. Ching, J.‐F. Zhao, K.‐H. Su, S.‐K. Shyue, C.‐P. Hsu, T.‐M. Lu, S.‐J. Lin, T.‐S. Lee.
    Acta Physiologica. August 29, 2013
    Aims We investigated the effects and underlying molecular mechanism of transient receptor potential vanilloid 1 (TRPV1), a calcium (Ca2+)‐permeable non‐selective cation channel, on phosphorylation of endothelial nitric oxide synthase (eNOS) at threonine 497 (Thr497) in bovine aortic endothelial cells (BAECs) and in mice. Methods Western blotting and immunoprecipitation were used for the evaluation of protein phosphorylation; protein phosphatase 2B (PP2B) activity was assessed by convention kit; Griess assay was for NO production; tube formation and Matrigel plug assay were used for angiogenesis. Results In BAECs, treatment with the TRPV1 ligand evodiamine decreased the phosphorylation of eNOS at Thr497, protein kinase Cα (PKCα) at Serine 657 (Ser657) and PKCβ2 at Ser660. Evodiamine increased protein phosphatase 2B (PP2B) activity and promoted the formation of a PP2B–PKC complex. Inhibition of TRPV1 activation by the pharmacological antagonists, removal of extracellular Ca2+ or pharmacological inhibition of PI3K/Akt/calmodulin‐dependent protein kinase II/AMP‐activated protein kinase signalling pathway abolished the evodiamine‐induced alterations in phosphorylation of eNOS at Thr497, PKCα at Ser657, PKCβ2 at Ser660 and PP2B activity, as well as the formation of a PP2B–PKC complex. Inhibition of PP2B activation partially reduced the evodiamine‐induced NO bioavailability and tube formation in endothelial cells (ECs) and angiogenesis in mice. Moreover, evodiamine decreased the phosphorylation of eNOS at Thr497, PKCα at Ser657 and PKCβ2 at Ser660 in apolipoprotein E (ApoE)‐deficient mouse aortas but not TRPV1‐deficient or ApoE/TRPV1 double‐knockout mice. Conclusion TRPV1 activation in ECs may elicit a Ca2+‐dependent effect on PP2B–PKC signalling, which leads to dephosphorylation of eNOS at Thr497 in ECs and in mice.
    August 29, 2013   doi: 10.1111/apha.12157   open full text
  • Modulation of murine gastric vagal afferent mechanosensitivity by neuropeptide W.
    H. Li, S. J. Kentish, S. Kritas, R. L. Young, N. J. Isaacs, T. A. O'Donnell, L. A. Blackshaw, G. A. Wittert, A. J. Page.
    Acta Physiologica. August 28, 2013
    Aim Neuropeptide W (NPW) is an endogenous ligand for the receptors GPR7 and GPR8 and is involved in central regulation of energy homeostasis. NPW in the periphery is found in gastric gastrin (G) cells. In the stomach, energy intake is influenced by vagal afferent signals, so we aimed to determine the effect of NPW on mechanosensitive gastric vagal afferents under different feeding conditions. Methods Female C57BL/6 mice (N > 10 per group) were fed a standard laboratory diet (SLD), high‐fat diet (HFD) or were food restricted. The relationship between NPW immunopositive cells and gastric vagal afferent endings was determined by anterograde tracing and NPW immunohistochemistry. An in vitro gastro‐oesophageal preparation was used to determine the functional effects of NPW on gastric vagal afferents. Expression of NPW in the gastric mucosa and GPR7 in whole nodose ganglia was determined by quantitative RT‐PCR (QRT‐PCR). The expression of GPR7 in gastric vagal afferent neurones was determined by retrograde tracing and QRT‐PCR. Results Neuropeptide W immunoreactive cells were found in close proximity to traced vagal afferents. NPW selectively inhibited responses of gastric vagal tension receptors to stretch in SLD but not HFD or fasted mice. In the nodose ganglia, GPR7 mRNA was specifically expressed in gastric vagal afferent neurones. In fasted mice gastric mucosal NPW and nodose GPR7, mRNA was reduced compared with SLD. A HFD had no effect on gastric NPW mRNA, but down‐regulated nodose GPR7 expression. Conclusion Neuropeptide W modulates gastric vagal afferent activity, but the effect is dynamic and related to feeding status.
    August 28, 2013   doi: 10.1111/apha.12154   open full text
  • Bicarbonate‐dependent transport of acetate and butyrate across the basolateral membrane of sheep rumen epithelium.
    F. Dengler, R. Rackwitz, F. Benesch, H. Pfannkuche, G. Gäbel.
    Acta Physiologica. August 28, 2013
    Aim This study aimed to assess the role of HCO3− in the transport of acetate and butyrate across the basolateral membrane of rumen epithelium and to identify transport proteins involved. Methods The effects of basolateral variation in HCO3− concentrations on acetate and butyrate efflux out of the epithelium and the transepithelial flux of these short‐chain fatty acids were tested in Ussing chamber experiments using 14C‐labelled substrates. HCO3−‐dependent transport mechanisms were characterized by adding specific inhibitors of candidate proteins to the serosal side. Results Effluxes of acetate and butyrate out of the epithelium were higher to the serosal side than to the mucosal side. Acetate and butyrate effluxes to both sides of rumen epithelium consisted of HCO3−‐independent and ‐dependent parts. HCO3−‐dependent transport across the basolateral membrane was confirmed in studies of transepithelial fluxes. Mucosal to serosal fluxes of acetate and butyrate decreased with lowering serosal HCO3− concentrations. In the presence of 25 mm HCO3−, transepithelial flux of acetate was inhibited effectively by p‐hydroxymercuribenzoic acid or α‐cyano‐4‐hydroxycinnamic acid, while butyrate flux was unaffected by the blockers. Fluxes of both acetate and butyrate from the serosal to the mucosal side were diminished largely by the addition of NO3− to the serosal side, with this effect being more pronounced for acetate. Conclusion Our results indicate the existence of a basolateral short‐chain fatty acid/HCO3− exchanger, with monocarboxylate transporter 1 as a primary candidate for acetate transfer.
    August 28, 2013   doi: 10.1111/apha.12155   open full text
  • Effect of reactive oxygen species and nitric oxide in the neural control of intrarenal haemodynamics in anaesthetized normotensive rats.
    A. F. Ahmeda, M. G. Rae, E. J. Johns.
    Acta Physiologica. August 27, 2013
    Aims This study examined the interaction between reactive oxygen species and nitric oxide (NO) in mediating the decrease in renal blood flow (RBF) evoked by sympathetic renal nerve stimulation (RNS). Methods Groups of male Wistar rats were subjected to RNS at different frequencies prior to, and following, an infusion of: (i) tempol, the superoxide dismutase (SOD) mimetic, (ii) tempol plus the hydrogen peroxide‐degrading enzyme catalase (tem + cat), (iii) diethyldithiocarbamic acid (DETC), a SOD inhibitor, (iv) the nitric oxide synthase (NOS) inhibitor, L‐nitro‐arginine methyl ester (L‐NAME) alone, or (v) L‐NAME followed by tempol, into the kidney cortico‐medullary border (CMB). Blood perfusion within the cortical (CBP) and medullary (MBP) regions of the kidney was measured using Laser‐Doppler flowmetry. Results Infusion of tempol CMB significantly attenuated RNS‐evoked reductions in CBP (by 22% at 8 Hz; P < 0.05), but not MBP. When tempol and catalase were co‐infused to reduce both ROS and hydrogen peroxide (H2O2), respectively, there was a significantly greater attenuation of the RNS‐evoked reduction in CBP compared with that of tempol alone. Infusion of either DETC or L‐NAME alone did not significantly affect the CBP or MBP responses to RNS. Similarly, RNS following tempol infusion with L‐NAME also had no effect on CBP and MBP over and above the group that received tempol alone. Conclusion These results suggest that reactive oxygen species such as superoxide and H2O2 have a direct role in reducing renal vascular compliance in response to RNS, rather than indirectly through scavenging NO.
    August 27, 2013   doi: 10.1111/apha.12150   open full text
  • Inhibition of sodium‐linked glucose reabsorption normalizes diabetes‐induced glomerular hyperfiltration in conscious adenosine A1‐receptor deficient mice.
    J. Sällström, T. Eriksson, B. B. Fredholm, A. E. G. Persson, F. Palm.
    Acta Physiologica. August 27, 2013
    Aim Glomerular hyperfiltration is commonly observed in diabetics early after the onset of the disease and predicts the progression of nephropathy. Sustained hyperglycaemia is also closely associated with kidney hypertrophy and increased electrolyte and glucose reabsorption in the proximal tubule. In this study, we investigated the role of the increased tubular sodium/glucose cotransport for diabetes‐induced glomerular hyperfiltration. To eliminate any potential confounding effect of the tubuloglomerular feedback (TGF) mechanism, we used adenosine A1‐receptor deficient (A1AR−/−) mice known to lack a functional TGF mechanism and compared the results to corresponding wild‐type animals (A1AR+/+). Methods Diabetes was induced by an intravenous bolus injection of alloxan. Glomerular filtration rate (GFR) was determined in conscious mice by a single bolus injection of inulin. The sodium/glucose cotransporters were inhibited by phlorizin 30 min prior to GFR measurements. Results Normoglycaemic animals had a similar GFR independent of genotype (A1AR+/+ 233 ± 11 vs. A1AR−/− 241 ± 25 μL min−1), and induction of diabetes resulted in glomerular hyperfiltration in both groups (A1AR+/+ 380 ± 25 vs. A1AR−/− 336 ± 35 μL min−1; both P < 0.05). Phlorizin had no effect on GFR in normoglycaemic mice, whereas it reduced GFR in both genotypes during diabetes (A1AR+/+ 365 ± 18 to 295 ± 19, A1AR−/− 354 ± 38 to 199 ± 15 μL min−1; both P < 0.05). Notably, the reduction was more pronounced in the A1AR−/− (P < 0.05). Conclusion This study demonstrates that increased tubular sodium/glucose reabsorption is important for diabetes‐induced hyperfiltration, and that the TGF mechanism is not involved in these alterations, but rather functions to reduce any deviations from a new set‐point.
    August 27, 2013   doi: 10.1111/apha.12152   open full text
  • Effect of a mixture of bovine milk oligosaccharides, Lactobacillus rhamnosus NCC4007 and long‐chain polyunsaturated fatty acids on catch‐up growth of intra‐uterine growth‐restricted rats.
    E. Castañeda‐Gutiérrez, M. Moser, C. García‐Ródenas, F. Raymond, R. Mansourian, I. Rubio‐Aliaga, S. Viguet‐Carrin, S. Metairon, C. Ammon‐Zufferey, O. Avanti‐Nigro, K. Macé, I. Silva‐Zolezzi.
    Acta Physiologica. August 08, 2013
    Aim To investigate the effect of a nutritional mixture (bovine milk oligosaccharides, Lactobacillus rhamnosus NCC4007, arachidonic and docosahexaenoic acid) on growth of intrauterine growth‐restricted (IUGR) rats. Methods IUGR was induced by maternal food restriction. The offspring (males and females) were assigned to: REF (non‐IUGR, no mixture), IUGRc (IUGR, no mixture), or IUGRmx (IUGR, mixture). The mixture was given from day 7 to day 58, when tissues and plasma from half of the animals were collected for hormones, metabolites and microarray analysis. The rest received a high‐fat diet (HFD) until day 100. Glucose tolerance was measured at 56 and 98 days, and body fat content at 21, 52 and 97 days. Results IUGRmx had the greatest growth during lactation, but from day 22 to day 54, both IUGR groups gained less body weight than the REF (P < 0.05). In the short‐term (58 days), IUGRmx tended to be longer (P = 0.06) and had less body fat (P = 0.03) than IUGRc. These differences were not seen after HFD. Microarray analysis of hepatic mRNA expression at 58 and 100 days revealed a gender‐dependent treatment effect, and expression of genes related to lipid metabolism was the most affected. Twelve of these genes were selected for studying differences in DNA methylation in the promoter region, for some, we observed age‐ and gender‐related differences but none because of treatment. Conclusion The nutritional intervention promoted catch‐up growth and normalized excessive adiposity in IUGR animals at short‐term. The benefits did not extend after a period of HFD. IUGR and early diet had gender‐dependent effects on hepatic gene expression.
    August 08, 2013   doi: 10.1111/apha.12145   open full text
  • Mechanisms of cytolysin‐induced cell damage – a role for auto‐ and paracrine signalling.
    Marianne Skals, Helle A. Praetorius.
    Acta Physiologica. August 08, 2013
    Cytolysins inflict cell damage by forming pores in the plasma membrane. The Na+ conductivity of these pores results in an ion influx that exceeds the capacity of the Na+/K+‐pump to extrude Na+. This net load of intracellular osmolytes results in swelling and eventual lysis of the attacked cell. Many nucleated cells have the capacity to reduce the potential damage of pore‐forming proteins, whereas erythrocytes have been regarded as essentially defenceless against cytolysin induced cell damage.This review adresses how autocrine/paracrine signalling and the cells intrinsic volume regulation markedly influence the fate of the cell after membrane insertion of cytolysins. Moreover, it regards the various steps that may explain the relative large degree of diversity between cell types and species as well as highlights some of the current gaps in the mechanistic understanding of cytolysin‐induced cell injury. This article is protected by copyright. All rights reserved.
    August 08, 2013   doi: 10.1111/apha.12156   open full text
  • Human spinal cord injury: motor unit properties and behavior.
    Christine K. Thomas, Rob Bakels, Cliff Klein, Inge Zijdewind.
    Acta Physiologica. August 01, 2013
    Spinal cord injury (SCI) results in widespread variation in muscle function. Review of motor unit data shows that changes in the amount and balance of excitatory and inhibitory inputs after SCI alter management of motoneurons. Not only are units recruited up to higher than usual relative forces when SCI leaves few units under voluntary control, the force contribution from recruitment increases due to elevation of twitch/tetanic force ratios. Force gradation and precision are also coarser with reduced unit numbers. Maximal unit firing rates are low in hand muscles, limiting voluntary strength, but are low, normal or high in limb muscles. Unit firing rates during spasms can exceed voluntary rates, emphasizing that deficits in descending drive limit force production. SCI also changes muscle properties. Motor unit weakness and fatigability seem universal across muscles and species, increasing the muscle weakness that arises from paralysis of units, motoneuron death and sensory impairment. Motor axon conduction velocity decreases after human SCI. Muscle contractile speed is also reduced, which lowers the stimulation frequencies needed to grade force when paralyzed muscles are activated with patterned electrical stimulation. This slowing does not necessarily occur in hind limb muscles after cord transection in cats and rats. The nature, duration, and level of SCI underlie some of these species differences, as do variations in muscle function, daily usage, tract control and fiber type composition. Exploring this diversity is important to promote recovery of the hand, bowel, bladder and locomotor function most wanted by people with SCI. This article is protected by copyright. All rights reserved.
    August 01, 2013   doi: 10.1111/apha.12153   open full text
  • Human baroreflex rhythms persist during handgrip and muscle ischaemia.
    D. L. Eckberg, W. H. Cooke, A. Diedrich, B. D. Levine, J. A. Pawelczyk, J. C. Buckey, A. C. Ertl, I. Biaggioni, J. F. Cox, D. Robertson, F. J. Baisch, C. G. Blomqvist, T. A. Kuusela, K. U. O. Tahvanainen.
    Acta Physiologica. July 25, 2013
    Aim To determine whether physiological, rhythmic fluctuations of vagal baroreflex gain persist during exercise, post‐exercise ischaemia and recovery. Methods We studied responses of six supine healthy men and one woman to a stereotyped protocol comprising rest, handgrip exercise at 40% maximum capacity to exhaustion, post‐exercise forearm ischaemia and recovery. We measured electrocardiographic R‐R intervals, photoplethysmographic finger arterial pressures and peroneal nerve muscle sympathetic activity. We derived vagal baroreflex gains from a sliding (25‐s window moved by 2‐s steps) systolic pressure–R‐R interval transfer function at 0.04–0.15 Hz. Results Vagal baroreflex gain oscillated at low, nearly constant frequencies throughout the protocol (at approx. 0.06 Hz – a period of about 18 s); however, during exercise, most oscillations were at low‐gain levels, and during ischaemia and recovery, most oscillations were at high‐gain levels. Conclusions Vagal baroreflex rhythms are not abolished by exercise, and they are not overwhelmed after exercise during ischaemia and recovery.
    July 25, 2013   doi: 10.1111/apha.12143   open full text
  • Interaction between NO synthase and NADPH oxidase in control of sodium transport by the renal thick ascending limb during diabetes.
    C. De Miguel, J. M. Foster, P. K. Carmines, J. S. Pollock.
    Acta Physiologica. July 25, 2013
    Aim During type 1 diabetes (T1D), the medullary thick ascending limb (mTAL) displays an NADPH oxidase‐dependent increase in sodium transport, in concert with increased NO production by NO synthase 1 (NOS1) and NOS2. We hypothesized that NOS1‐ and/or NOS2‐derived NO blunts T1D‐induced activation of sodium transport in the mTAL. Methods T1D was induced by streptozotocin injection (STZ rats); sham rats received vehicle. Three‐to‐four weeks later, mTAL were isolated from both groups for assay of nitrite and superoxide production, and O2 consumption in the absence or presence of various inhibitors. Results Apocynin (NADPH oxidase inhibitor) normalized superoxide production and ouabain‐sensitive O2 consumption and furosemide‐sensitive O2 consumption by mTALs from STZ rats, without altering O2 consumption by mTALs from sham rats. Apocynin also unmasked a T1D‐induced increase in nitrite production. NOS inhibition did not alter superoxide production in either group. In sham mTAL, total NOS inhibition, but not isoform‐specific inhibition of NOS1 or NOS2, increased ouabain‐ and furosemide‐sensitive O2 consumption, confirming a tonic inhibitory impact of NOS3 on sodium transport. In contrast, neither total nor isoform‐specific NOS inhibition altered O2 consumption by STZ mTAL. Apocynin treatment of STZ mTAL unveiled the ability of isoform‐specific NOS inhibition to significantly increase O2 consumption, without further increase in O2 consumption with total NOS inhibition. Conclusion Under normal conditions, NOS3‐derived NO inhibits sodium transport in the mTAL. T1D dismantles the impact of NOS‐mediated inhibition of sodium transport as a result of NADPH oxidase‐dependent NO scavenging. Inhibition of NADPH oxidase to preserve NO bioavailability reveals an inhibitory impact of NOS1‐ and NOS2‐derived NO on sodium transport in the mTAL.
    July 25, 2013   doi: 10.1111/apha.12144   open full text
  • Small head circumference at birth and early age at adiposity rebound.
    J. G. Eriksson, E. Kajantie, M. Lampl, C. Osmond, D. J. P. Barker.
    Acta Physiologica. July 14, 2013
    Aims The adiposity rebound is the age in childhood when body mass index is at a minimum before increasing again. The age at rebound is highly variable. An early age is associated with increased obesity in later childhood and adult life. We have reported that an early rebound is predicted by low weight gain between birth and 1 year of age and resulting low body mass index at 1 year. Here, we examine whether age at adiposity rebound is determined by influences during infancy or is a consequence of foetal growth. Our hypothesis was that measurements of body size at birth are related to age at adiposity rebound. Methods Longitudinal study of 2877 children born in Helsinki, Finland, during 1934–1944. Results Early age at adiposity rebound was associated with small head circumference and biparietal diameter at birth, but not with other measurements of body size at birth. The mean age at adiposity rebound rose from 5.8 years in babies with a head circumference of ≤33 cm to 6.2 in babies with a head circumference of >36 cm (P for trend = 0.007). The association between thinness in infancy and early rebound became apparent at 6 months of age. It was not associated with adverse living conditions. In a simultaneous regression, small head circumference at birth, high mother's body mass index and tall maternal stature each had statistically significant trends with early adiposity rebound (P = 0.002, <0.001, 0.004). Conclusion We hypothesize that the small head size at birth that preceded an early adiposity rebound was the result of inability to sustain a rapid intra‐uterine growth trajectory initiated in association with large maternal body size. This was followed by catch‐up growth in infancy, and we hypothesize that this depleted the infant's fat stores.
    July 14, 2013   doi: 10.1111/apha.12142   open full text
  • Maternal chocolate and sucrose soft drink intake induces hepatic steatosis in rat offspring associated with altered lipid gene expression profile.
    M. Kjaergaard, C. Nilsson, A. Rosendal, M. O. Nielsen, K. Raun.
    Acta Physiologica. July 12, 2013
    Aim According to the World Diabetes Foundation, there is an urgent need to investigate the impact of maternal health and nutrition during pregnancy to understand the background for the accelerating incidence of obesity and type 2 diabetes. In this study, we specifically concentrated on the role of overfeeding during different developmental periods. Methods Sprague–Dawley rats were offered chow or high‐fat/high‐sucrose diet (chow plus chocolate and soft drink) during gestation and lactation. At birth, offspring were randomly cross‐fostered within each dietary group into small and normal litter sizes until weaning, giving four dietary groups. Results At postnatal day 1, offspring from high‐fat/high‐sucrose‐fed dams were heavier and had increased hepatic triglycerides (TG), hepatic glycogen, blood glucose and plasma insulin compared with offspring from chow‐fed dams. Hepatic genes involved in lipid oxidation, VLDL transport and insulin receptor were down‐regulated, whereas FGF21 expression was up‐regulated. Independent of postnatal litter size, offspring from high‐fat/high‐sucrose‐fed dams aged 21 days had still increased hepatic TG and up‐regulated FGF21 expression, while plasma insulin started to decrease. Litter size reduction in offspring from high‐fat/high‐sucrose‐fed dams further increased body weight and adiposity, and up‐regulated genes involved in hepatic mitochondrial lipid oxidation and VLDL transport compared with all other groups. Litter size reduction did not have any impact on body weight gain and adiposity in offspring born to chow‐fed dams. Conclusion Our results suggest that supplementation of chocolate and soft drink during gestation and lactation contributes to early onset of hepatic steatosis associated with changes in hepatic gene expression and lipid handling.
    July 12, 2013   doi: 10.1111/apha.12138   open full text
  • Vaspin prevents methylglyoxal‐induced apoptosis in human vascular endothelial cells by inhibiting reactive oxygen species generation.
    S. Phalitakul, M. Okada, Y. Hara, H. Yamawaki.
    Acta Physiologica. July 10, 2013
    Aim Vaspin (visceral adipose tissue‐derived serine protease inhibitor) is a novel adipocytokine found in visceral white adipose tissues of obese type 2 diabetic rats. We have previously shown that vaspin has anti‐inflammatory and antimigratory effects in vascular smooth muscle cells. Methylglyoxal (MGO) is an active metabolite of glucose and mediates diabetic vascular complications including endothelial cell (EC) apoptosis. Nonetheless, effects of vaspin on MGO‐induced apoptosis of vascular EC remain to be determined. We investigated the effects of vaspin on MGO‐induced apoptosis of human umbilical vein ECs (HUVECs). Methods Human umbilical vein ECs were treated with MGO (560 μm, 12 h) in the absence or presence of vaspin (1 ng mL−1, pre‐treatment for 2 h). Cell death was evaluated by a cell counting assay. Apoptosis was determined by a terminal deoxyribonucleotide transferase‐mediated deoxyuridine triphosphate nick‐end labelling (TUNEL) assay. Cleaved caspase‐3 expression was determined by Western blotting. Reactive oxygen species (ROS) generation was fluorometrically measured using 2′, 7′‐dichlorodihydrofluorescein diacetate. NADPH oxidase (NOX) activity was determined by a lucigenin assay. Results Vaspin significantly inhibited MGO‐induced HUVEC death. Vaspin significantly attenuated MGO‐increased TUNEL‐positive ECs. Moreover, vaspin significantly inhibited MGO‐induced caspase‐3 cleavage. Vaspin significantly inhibited MGO‐induced ROS generation as well as NOX activation. Conclusions The present results for the first time demonstrate that vaspin inhibits MGO‐induced EC apoptosis by preventing caspase‐3 activation via the inhibition of NOX‐derived ROS generation.
    July 10, 2013   doi: 10.1111/apha.12139   open full text
  • Consuming a low‐fat diet from weaning to adulthood reverses the programming of food preferences in male, but not in female, offspring of ‘junk food’‐fed rat dams.
    Z. Y. Ong, B. S. Muhlhausler.
    Acta Physiologica. July 10, 2013
    Aim This study aimed to determine whether the negative effects of maternal ‘junk food’ feeding on food preferences and gene expression in the mesolimbic reward system could be reversed by weaning the offspring onto a low‐fat diet. Methods Offspring of control (n = 11) and junk food‐fed (JF, n = 12) dams were weaned onto a standard rodent chow until 6 weeks (juvenile) or 3 months (adult). They were then given free access to both chow and junk food for 3 weeks and food preferences determined. mRNA expression of key components of the mesolimbic reward system was determined by qRT‐PCR at 6 weeks, 3 and 6 months of age. Results In the juvenile group, both male and female JF offspring consumed more energy and carbohydrate during the junk food exposure at 6 weeks of age and had a higher body fat mass at 3 months (P < 0.05). Female juvenile JF offspring had higher tyrosine hydroxylase, dopamine receptors and dopamine active transporter expression in the ventral tegmental area (P < 0.05). In the adult group, there was no difference between control and JF offspring in energy and macronutrient intakes during exposure to junk food; however, female JF offspring had a higher body fat mass at 6 months (P < 0.05). Conclusion These results suggest that the effects of perinatal junk food exposure on food preferences and fat mass can be reversed by consuming a low‐fat diet from weaning to adulthood in males. Females, however, retain a higher propensity for diet‐induced obesity even after consuming a low‐fat diet for an extended period after weaning.
    July 10, 2013   doi: 10.1111/apha.12132   open full text
  • Changes in phosphorylated heat‐shock protein 27 in response to acute ureteral obstruction in rats.
    I. Carlsen, L. Nilsson, J. Frøkiær, R. Nørregaard.
    Acta Physiologica. July 09, 2013
    Aim In vivo, renal medullary interstitial cells (RMICs) and collecting duct principal cells (mpkCCD cells) are subjected to inflammatory, oxidative and mechanical stress as a result of unilateral ureteral obstruction (UUO). Because heat‐shock protein (HSP) 27 and HSP70 are induced by cellular stresses and play a role in cytoprotection, we hypothesized that HSP27 and HSP70 are increased in rats subjected to acute UUO and in RMICs and mpkCCD cells exposed to inflammatory, oxidative or mechanical stress. Methods Rats were subjected to acute UUO for 6 h and 12 h. To examine the expression of HSP27, phosphorylated HSP27 (pHSP27) and HSP70 in response to inflammatory, oxidative and mechanical stress in vitro, we exposed RMICs and mpkCCD cells to interleukin 1β (IL‐1β), hydrogen peroxide (H2O2), and stretch stimulation over time. Results The phosphorylated form of HSP27 (pHSP27) was increased in the renal inner medulla (IM) after 6‐h and 12‐h UUO, while HSP27 and HSP70 were unchanged. Furthermore, after 6 h and 12 h of UUO, the expression of inflammatory (IL‐1β) and oxidative [haem oxygenase 1 (HO‐1)] markers was induced. Exposure to inflammatory, oxidative and mechanical stress changed HSP27 and pHSP27 expression in RMICs but not in mpkCCD cells, while HSP70 was not affected by any of the stress conditions. Exposure of RMICs to oxidative and mechanical stress induced HSP27 phosphorylation via a p38‐dependent mechanism. Conclusion These data demonstrate that, in response to acute UUO, different forms of cellular stresses modulate HSP27 expression and phosphorylation in RMICs. This may affect the ability of renal cells to mount an effective cytoprotective response.
    July 09, 2013   doi: 10.1111/apha.12135   open full text
  • Swim training restores glucagon‐like peptide‐1 insulinotropic action in pancreatic islets from monosodium glutamate‐obese rats.
    P. V. Svidnicki, N. de Carvalho Leite, A. C. Venturelli, R. L. Camargo, M. R. Vicari, M. C. Almeida, R. F. Artoni, V. Nogaroto, S. Grassiolli.
    Acta Physiologica. July 01, 2013
    Aims Glucagon‐like peptide‐1 (GLP‐1) is an important modulator of insulin secretion by endocrine pancreas. In the present study, we investigated the effect of swim training on GLP‐1 insulinotropic action in pancreatic islets from monosodium glutamate (MSG)‐obese rats. Methods Obesity was induced by neonatal MSG administration. MSG‐obese and control (CON) exercised rats swam for 30 min (3 times week−1) for 10 weeks. Pancreatic islets were isolated by colagenase technique and incubated with low (5.6 mm) or high (16.7 mm) glucose concentrations in the presence or absence of GLP‐1 (10 nm). In addition, GLP‐1 gene expression in ileum was quantified in fasting and glucose conditions. Results Exercise reduced obesity and hyperinsulinemia in MSG‐obese rats. Swim training also inhibited glucose‐induced insulin secretion in islets from both groups. Islets from MSG‐obese rats maintained GLP‐1 insulinotropic response in low glucose concentration. In contrast, in the presence of high glucose concentration, GLP‐1 insulinotropic action was absent in islets from MSG‐obese rats. Islets from MSG‐exercised rats showed reduced GLP‐1 insulinotropic action in the presence of low glucose. However, in high glucose concentration swim training restored GLP‐1 insulinotropic response in islets from MSG‐obese rats. In all groups, glucose intake increased GLP‐1immunoreactivity and gene expression in ileum cells in relation to fasting conditions. Swim training reduced these parameters only in ileum cells from CON‐exercised rats. Neither MSG treatment nor exercise affected GLP‐1 expression in the ileum. Conclusions Exercise avoids insulin hypersecretion restoring GLP‐1's insulinotropic action in pancreatic islets from MSG‐obese rats.
    July 01, 2013   doi: 10.1111/apha.12128   open full text
  • Late gestation over‐ and undernutrition predispose for visceral adiposity in response to a post‐natal obesogenic diet, but with differential impacts on glucose–insulin adaptations during fasting in lambs.
    P. Khanal, S. V. Husted, A. M. D. Axel, L. Johnsen, K. L. Pedersen, M. S. Mortensen, A. H. Kongsted, M. O. Nielsen.
    Acta Physiologica. June 25, 2013
    Aim To investigate if late gestation under‐ or overnutrition has similar adverse impacts on visceral adiposity, metabolic and endocrine function in sheep, and if subsequent exposure to a high‐fat diet in early post‐natal life exaggerates the prenatal programming outcomes later in life. Methods Thirty‐six twin‐pregnant ewes were fed a NORM (fulfilling 100% of daily requirements for energy and protein), LOW (50% of NORM) or HIGH diet (150% of energy and 110% of protein requirements) during the last 6 weeks of gestation (term = 147 days). Post‐natally, the twin lambs were subjected to a high‐fat or a moderate diet until 6 months of age (around puberty), where metabolic and endocrine adaptability to fasting was examined, and subgroups of animals were killed. Results Animals exposed to either prenatal under‐ or overnutrition had reduced subcutaneous fat deposition when fed a high‐fat diet, resulting in higher ratios of mesenteric and peri‐renal fat relative to subcutaneous fat compared to controls. This was not related to prenatal influences on plasma glucose or insulin. Irrespective of the prenatal diet, high‐fat‐fed lambs underwent changes resembling the metabolic syndrome with higher plasma glucose, cholesterol, non‐esterified fatty acids, triglyceride and lactate combined with abdominal obesity. Peri‐renal fat appeared to be a particular target of a high‐fat diet post‐natally. Conclusion Both prenatal under‐ and overnutrition predisposed for abdominal adiposity, apparently by reducing the expandability of subcutaneous adipose tissue and induced differential physiological adaptations to fasting. This study does not suggest that exposure to gestational overnutrition will provide a protective effect against development of hyperglycaemia later in life.
    June 25, 2013   doi: 10.1111/apha.12129   open full text
  • A maternal diet of fatty fish reduces body fat of offspring compared with a maternal diet of beef and a post‐weaning diet of fish improves insulin sensitivity and lipid profile in adult C57BL/6 male mice.
    A. Hussain, I. Nookaew, S. Khoomrung, L. Andersson, I. Larsson, L. Hulthén, N. Jansson, R. Jakubowicz, S. Nilsson, A.‐S. Sandberg, J. Nielsen, A. Holmäng.
    Acta Physiologica. June 25, 2013
    Aim The maternal diet during pregnancy and lactation may affect the long‐term health of the offspring. Our aim was to study how a fish or meat diet perinatal and after weaning affects body composition, insulin sensitivity and the profile of n‐3 and n‐6 polyunsaturated fatty acids (PUFAs) in breast milk, fat depots, skeletal muscle and liver in male adult mice offspring. Methods During gestation and lactation, C57BL/6 dams were fed a herring‐ or beef‐based diet. Half of the pups in each group changed diets after weaning. In offspring, body composition measured by DEXA, plasma lipid profile and insulin sensitivity measured by euglycemic clamp or QUICKI were monitored to adulthood. Analysis of total FAs by GC‐MS were performed in the diet, breast milk and in different tissues. Results At 9 week of age, offspring of herring‐fed dams had less body fat than offspring of beef‐fed dams. Mice fed herring after weaning had increased insulin sensitivity at 15 week of age, reduced total plasma cholesterol and triglyceride levels, and compared with beef‐fed mice, larger interscapular brown adipose tissue depots. The FA composition of the maternal diet was mirrored in breast milk, and the herring diet significantly affected the FA profile of different tissues, leading to an increased content of n‐3 PUFAs. Conclusion A herring‐based maternal diet reduces body fat in the offspring, but the insulin sensitivity, plasma lipids and amount of brown adipose tissue are affected by the offspring's own diet; the herring diet is more beneficial than the beef diet.
    June 25, 2013   doi: 10.1111/apha.12130   open full text
  • Neurobiological insight into hyperbaric hyperoxia.
    A. Micarelli, H. Jacobsson, S. A. Larsson, C. Jonsson, M. Pagani.
    Acta Physiologica. June 19, 2013
    Aim Hyperbaric hyperoxia (HBO) is known to modulate aerobic metabolism, vasoreactivity and blood flow in the brain. Nevertheless, mechanisms underlying its therapeutic effects, especially in traumatic brain injury (TBI) and stroke patients, are debated. The present study aimed at investigating regional cerebral blood flow (rCBF) distribution during acute HBO exposure. Methods Regional cerebral blood flow response was investigated in seven healthy subjects exposed to either normobaric normoxia or HBO with ambient pressure/inspired oxygen pressure of 101/21 and 250/250 kPa respectively. After 40 min at the desired pressure, they were injected a perfusion tracer and subsequently underwent brain single photon emission computed tomography. rCBF distribution changes in the whole brain were assessed by Statistical Parametric Mapping. Results During HBO, an increased relative rCBF distribution was found in sensory‐motor, premotor, visual and posterior cingulate cortices as well as in superior frontal gyrus, middle/inferior temporal and angular gyrus and cerebellum, mainly in the dominant hemisphere. During normobaric normoxia, a higher 99mTc‐HMPAO distribution in the right insula and subcortical structures as well as in bilateral hippocampi and anterior cingulated cortex was found. Conclusions The present study firstly confirmed the rCBF distribution increase during HBO in sensory‐motor and visual cortices, and it showed for the first time a higher perfusion tracer distribution in areas encompassed in dorsal attention system and in default mode network. These findings unfold both the externally directed cognition performance improvement related to the HBO and the internally directed cognition states during resting‐state conditions, suggesting possible beneficial effects in TBI and stroke patients.
    June 19, 2013   doi: 10.1111/apha.12116   open full text
  • Ionotropic glutamate receptors in paraventricular nucleus mediate adipose afferent reflex and regulate sympathetic outflow in rats.
    B.‐P. Cui, P. Li, H.‐J. Sun, L. Ding, Y.‐B. Zhou, J.‐J. Wang, Y.‐M. Kang, G.‐Q. Zhu.
    Acta Physiologica. June 19, 2013
    Aim Chemical stimulation of white adipose tissue (WAT) induces adipose afferent reflex (AAR) and results in increases in renal sympathetic nerve activity (RSNA) and mean arterial pressure (MAP). The enhanced AAR contributes to sympathetic activation and hypertension in obesity rats. This study was designed to investigate whether N‐methyl‐D‐aspartate receptors (NMDAR) and non‐NMDAR in paraventricular nucleus (PVN) modulate AAR and sympathetic outflow. Methods Renal sympathetic nerve activity and MAP were recorded in anesthetized rats. AAR was evaluated by the RSNA and MAP responses to the injection of capsaicin into the four sites of right inguinal WAT (8.0 nmol for each site). Results Bilateral PVN microinjection of NMDAR antagonist AP5 or MK‐801, or non‐NMDAR antagonist CNQX attenuated AAR, RSNA and MAP. AP5 + CNQX caused greater effects than AP5 or CNQX alone and almost abolished AAR. NMDAR agonist NMDA or non‐NMDAR agonist AMPA enhanced the AAR, and increased RSNA and MAP, which were prevented by AP5 or CNQX pre‐treatment respectively. Casein kinase 2 inhibitor DRB, NR2A antagonist NVP‐AAM077 or NR2B antagonist CP‐101,606 attenuated AAR, RSNA and MAP. NVP‐AAM077 + CP‐101,606 caused greater effects than NVP‐AAM077 or CP‐101,606 alone. Bilateral baroreceptor denervation and vagotomy enhanced AAR, which was abolished by PVN pre‐treatment with AP5 + CNQX. Furthermore, AP5 + CNQX abolished the AAR induced by leptin in iWAT. Conclusion Both NMDAR and non‐NMDAR in the PVN mediate AAR and contribute to the tonic control of sympathetic outflow and blood pressure. CK2, NR2A and NR2B subunits of NMDAR in the PVN are involved in the NMDAR‐mediated tonic control of AAR, RSNA and MAP.
    June 19, 2013   doi: 10.1111/apha.12125   open full text
  • Increased susceptibility to streptozotocin and impeded regeneration capacity of beta‐cells in adult offspring of malnourished rats.
    K. Goosse, T. Bouckenooghe, G. Sisino, S. Aurientis, C. Remacle, B. Reusens.
    Acta Physiologica. June 17, 2013
    Background Epidemiological studies related poor maternal nutrition and subsequent growth retardation in the progeny to the development of diabetes later in life. Low‐protein diet during gestation altered the beta‐cell development of the rat progeny by decreasing beta‐cell proliferation and increasing their sensitivity to nitric oxide and cytokines in the foetus. This disturbed maternal environment had long‐lasting consequences because the higher beta‐cell vulnerability was maintained at adulthood. Aim The aim of this study was to determine whether early malnutrition influences the vulnerability and the regeneration capacity of beta‐cells after streptozotocin (STZ) damage at adulthood. Methods Gestating rats were fed either a control or a low‐protein diet until weaning. Adult female offspring received injections of Freund's adjuvant weekly for 5 weeks followed 24 h later by STZ. Half of the cohort was killed at d34, whereas the other half was maintained until d48 to analyse the regeneration capacity of the beta‐cells. Results Although control and low‐protein rats had equivalent pancreatic insulin content and beta‐cell volume density at d34, hyperglycaemia appeared earlier and was more dramatic in low‐protein rats than in control rats. STZ treatment increased beta‐cell proliferation similarly in both groups. At d48, apoptotic rate was higher in the low‐protein group. Regeneration appeared in control, but not in the low‐protein rats, where beta‐cell aggregates/surface area and Reg1‐positive area were decreased compared to control. Conclusion Maternal malnutrition programmes a more vulnerable endocrine pancreas in the progeny which is unable to regenerate after injury, therefore predisposing it to develop glucose intolerance and diabetes later in life.
    June 17, 2013   doi: 10.1111/apha.12121   open full text
  • Sympathetic afferent stimulation inhibits central vagal activation induced by intravenous medetomidine in rats.
    T. Kawada, T. Akiyama, S. Shimizu, A. Kamiya, K. Uemura, M. J. Turner, M. Shirai, M. Sugimachi.
    Acta Physiologica. June 15, 2013
    Aim To examine whether sympathetic afferent stimulation (SAS) inhibits central vagal activation induced by α2‐adrenergic stimulation. Methods In anaesthetized Wistar‐Kyoto rats, a cardiac microdialysis technique was applied to the left ventricle, and the effect of α2‐adrenergic stimulation by medetomidine on myocardial interstitial acetylcholine (ACh) levels was examined in the absence (n = 6) or the presence (n = 6) of SAS delivered from the left stellate ganglion. The effect of electrical vagal efferent stimulation on myocardial interstitial ACh release was also examined in the absence or the presence of SAS (n = 6). Results Intravenous medetomidine (0.1 mg kg−1) significantly increased myocardial interstitial ACh levels in the absence of SAS (from 1.95 ± 0.79 to 3.36 ± 1.61 nm, P < 0.05), but not in the presence of SAS (from 1.67 ± 0.67 to 2.01 ± 0.78 nm). In contrast, electrical vagal nerve stimulation increased myocardial interstitial ACh level to the same degree regardless of SAS (from 1.66 ± 0.16 to 3.93 ± 0.72 nm without SAS vs. 4.05 ± 0.89 nm with SAS). Conclusion Sympathetic afferent stimulation inhibited medetomidine‐induced ACh release, but not electrical stimulation‐induced ACh release, suggesting that SAS inhibited medetomidine‐induced vagal activation via central mechanisms. While central vagal activation by α2‐adrenergic agonists could be an alternative to electrical vagal activation, blocking sympathetic afferent input may be important to increase the efficacy of α2‐adrenergic agonists in enhancing vagal nerve activity.
    June 15, 2013   doi: 10.1111/apha.12123   open full text
  • The expression of heat shock protein in human skeletal muscle: effects of muscle fibre phenotype and training background.
    M. Folkesson, A. L. Mackey, H. Langberg, E. Oskarsson, K. Piehl‐Aulin, J. Henriksson, F. Kadi.
    Acta Physiologica. June 15, 2013
    Aim Exercise‐induced adaptations of skeletal muscle are related to training mode and can be muscle fibre type specific. This study aimed to investigate heat shock protein expression in type I and type II muscle fibres in resting skeletal muscle of subjects with different training backgrounds. Methods Three groups of subjects were included: healthy active not engaged in any training programme (ACT, n = 12), resistance trained (RES, n = 6) and endurance trained (END, n = 8). Biopsies were obtained from vastus lateralis, and immunohistochemistry was performed using monoclonal antibodies against myosin heavy chain I and IIA, αB‐crystallin, HSP27, HSP60 and HSP70. Results In ACT and RES, but not in END, a fibre type–specific expression with higher staining intensity in type I than type II fibres was seen for αB‐crystallin. The opposite (II > I) was found for HSP27 in subjects from ACT (6 of 12 subjects) and RES (3 of 6), whereas all subjects from END displayed uniform staining. HSP60 showed no fibre‐specific expression. HSP70 displayed a fibre‐specific expression pattern (I > II) in ACT (4 of 12), but not in END or RES. Conclusion This study shows that the level of expression of the different HSPs in human skeletal muscle is influenced by muscle fibre phenotype. The fibre type–specific expression of HSP70 is influenced by resistance and endurance training, whereas those of αB‐crystallin and HSP27 is influenced only by endurance training, suggesting the existence of a training‐modality‐specific action on the adaptive processes including heat shock proteins in human skeletal muscle.
    June 15, 2013   doi: 10.1111/apha.12124   open full text
  • Glucose homoeostasis in rats exposed to acute intermittent hypoxia.
    A. Rafacho, L. M. Gonçalves‐Neto, F. B. D. Ferreira, A. O. P. Protzek, A. C. Boschero, E. A. Nunes, D. B. Zoccal.
    Acta Physiologica. June 08, 2013
    Aim Chronic exposure to intermittent hypoxia commonly induces the activation of sympathetic tonus and the disruption of glucose homoeostasis. However, the effects of exposure to acute intermittent hypoxia (AIH) on glucose homoeostasis are not yet fully elucidated. Herein, we evaluated parameters related to glucose metabolism in rats exposed to AIH. Methods Male adult rats were submitted to 10 episodes of hypoxia (6% O2, for 45 s) interspersed with 5‐min intervals of normoxia (21%), while the control (CTL) group was kept in normoxia. Results Acute intermittent hypoxia rats presented higher fasting glycaemia, normal insulinaemia, increased lactataemia and similar serum lipid levels, compared to controls (n = 10, P < 0.05). Additionally, AIH rats exhibited increased glucose tolerance (GT) (n = 10, P < 0.05) and augmented insulin sensitivity (IS) (n = 10, P < 0.05). The p‐Akt/Akt protein ratio was increased in the muscle, but not in the liver and adipose tissue of AIH rats (n = 6, P < 0.05). The elevated glycaemia in AIH rats was associated with a reduction in the hepatic glycogen content (n = 10, P < 0.05). Moreover, the AIH‐induced increase in blood glucose concentration, as well as reduced hepatic glycogen content, was prevented by prior systemic administration of the β‐adrenergic antagonist (P < 0.05). The effects of AIH on glycaemia and Akt phosphorylation were transient and not observed after 60 min. Conclusions We suggest that AIH induces an increase in blood glucose concentration as a result of hepatic glycogenolysis recruitment through sympathetic activation. The augmentation of GT and IS might be attributed, at least in part, to increased β‐adrenergic sympathetic stimulation and Akt protein activation in skeletal muscles, leading to a higher glucose availability and utilization.
    June 08, 2013   doi: 10.1111/apha.12118   open full text
  • Cardiovascular changes during SCUBA diving: an underwater Doppler echocardiographic study.
    C. Marabotti, A. Scalzini, D. Menicucci, M. Passera, R. Bedini, A. L'Abbate.
    Acta Physiologica. May 22, 2013
    Aim Body immersion induces blood redistribution (from peripheral to intrathoracic vessels) and is a powerful autonomic stimulus (activating both parasympathetic and sympathetic systems). For these reasons, concerns have been raised about the safety of diving for subjects with previous heart disease. The aim of this study was to evaluate cardiovascular changes occurring during recreational SCUBA diving, as assessed by underwater Doppler echocardiography. Methods Eighteen healthy experienced divers underwent a 2D Doppler echocardiography basally, during two 15' steps of still SCUBA diving at different depths (10 m followed by 5 m) and shortly after the end of immersion. Results During dive, left ventricular (LV) diastolic volume and early left ventricular filling significantly increased (5 m vs. basal: P < 0.05 and P < 0.01, respectively), while both deceleration time of the early filling rate and late diastolic filling velocity significantly decreased (5 m and 10 m dive vs. basal: P < 0.01). LV volume increase and diastolic filling changes persisted at postdive evaluation, where a significant decrease in heart rate was also observed (P < 0.01 as compared to basal, 5‐m and 10‐m dive). Conclusion This study documents that shallow‐depth SCUBA diving induces LV enlargement and diastolic dysfunction. Direct underwater evaluation by Doppler echocardiography could be an appropriate tool for unmasking subjects at risk for underwater‐related accidents.
    May 22, 2013   doi: 10.1111/apha.12112   open full text
  • Effect of hypoxia exposure on the phenotypic adaptation in remodelling skeletal muscle submitted to functional overload.
    T. Chaillou, N. Koulmann, A. Meunier, A. Malgoyre, B. Serrurier, M. Beaudry, X. Bigard.
    Acta Physiologica. May 10, 2013
    Aim To determine whether hypoxia influences the phenotypic adaptation of skeletal muscle induced by mechanical overload. Methods Plantaris muscles of female rats were submitted to mechanical overload following synergist ablation. After 3 days of overload, rats were exposed to either hypobaric hypoxia (equivalent to 5500 m) or normoxia. Muscles were collected after 5, 12 and 56 days of overload (i.e. after 3, 9 and 53 days of hypoxia). We determined the myosin heavy chain (MHC) distribution, mRNA levels of myocyte‐enriched calcineurin‐integrating protein 1 (MCIP1) to indirectly assess calcineurin activity, the changes in oxidative capacity from the activities of citrate synthase (CS) and cytochrome c oxidase (COX), and the expression of regulators involved in mitochondrial biogenesis (Pgc‐1α, NRF1 and Tfam) and degradation (BNIP‐3). Results Hypoxia did not alter the fast‐to‐slow MHC shift and the increase in calcineurin activity induced by overload; it only transiently slowed down the overload‐induced transition in MHC isoforms. Hypoxia similarly decreased CS and COX activities in overloaded and control muscles. Nuclear respiratory factor 1 (NRF1) and transcription factor A (Tfam) mRNA and BNIP‐3 protein were not influenced by hypoxia in overloaded muscles, whereas Pgc‐1α mRNA and protein contents did not correlate with changes in oxidative capacity. Conclusion Hypoxia is not a critical stimulus to modulate the fast‐to‐slow MHC transition associated with overload. Thus, the impairment of the fast‐to‐slow fibre shift often observed during post‐natal development in hypoxia could be explained by the lower voluntary locomotor activity associated with hypoxia. Hypoxia alters mitochondrial oxidative capacity, but this adaptive response is similar in overloaded and control muscles.
    May 10, 2013   doi: 10.1111/apha.12110   open full text
  • Programming of glucose–insulin homoeostasis: long‐term consequences of pre‐natal versus early post‐natal nutrition insults. Evidence from a sheep model.
    A. H. Kongsted, M. P. Tygesen, S. V. Husted, M. H. Oliver, A. Tolver, V. G. Christensen, J. H. Nielsen, M. O. Nielsen.
    Acta Physiologica. March 22, 2013
    Aim Exposure to adverse intra‐uterine conditions can predispose for metabolic disorders later in life. By using a sheep model, we studied (i) how programming of glucose–insulin homoeostasis during late gestation is manifested later in life depending on the early post‐natal dietary exposure and (ii) whether dietary alteration in obese individuals can prevent adverse outcomes of early life programming. Methods During late gestation, twin‐pregnant sheep were fed 100% (NORM) or 50% (LOW) of energy and protein requirements. After birth, offspring were exposed to a moderate (CONV) or high‐carbohydrate–high‐fat (HCHF) diet until around puberty. Offspring remaining thereafter (exclusively females) were fed a moderate diet until young adulthood. Results LOW lambs had increased insulin secretory responses during intravenous glucose tolerance tests indicative of reduced insulin sensitivity. HCHF lambs were hypertriglyceridaemic, 75% had mild pancreatic collagen infiltration, and their acute insulin secretory response and insulin clearance during intravenous glucose and insulin tolerance tests, respectively, were reduced. However, NORM‐HCHF in contrast to LOW‐HCHF lambs had normal glucose tolerance, indicating that later health outcomes are highly influenced by pre‐natal nutrition. Dietary alteration normalized glucose–insulin homoeostasis in adult HCHF females, whereas late‐gestation undernutrition (LOW) permanently depressed insulin sensitivity. Conclusion Maintenance of glucose tolerance in sheep exposed to pre‐natal undernutrition relied on pancreatic hypersecretion of insulin to compensate for reduced insulin sensitivity. A mismatching high‐fat diet in early post‐natal life interfered with this pancreatic hypersecretion resulting in reduced glucose tolerance. Early post‐natal, but not late pre‐natal, impacts on glucose–insulin homoeostasis could be reversed by dietary correction later in life.
    March 22, 2013   doi: 10.1111/apha.12080   open full text
  • Differential developmental programming by early protein restriction of rat skeletal muscle according to its fibre‐type composition.
    R. da Silva Aragão, O. Guzmán‐Quevedo, G. Pérez‐García, A. E. Toscano, C. Gois Leandro, R. Manhães‐de‐Castro, F. Bolaños‐Jiménez.
    Acta Physiologica. March 11, 2013
    Aims Differences in fibre‐type composition of skeletal muscle have been associated with obesity and insulin resistance. As a poor nutrient environment early in life is a predisposing factor for the development of obesity and related metabolic diseases at adulthood, this study aimed at determining the long‐term consequences of maternal undernutrition on the structural and metabolic properties of two skeletal muscles characterized by their different fibre‐type composition and metabolic properties. Methods The fibre‐type composition and enzymatic activities of hexokinase (HK), beta‐hydroxyacyl‐CoA dehydrogenase (β‐HAD) and citrate synthase (CS) were measured in soleus and extensor digitorum longus (EDL) muscles from adult rats born to dams fed a control (17% protein) or a low‐protein [8% protein (PR)] diet throughout pregnancy and lactation. In addition, the expression levels of several genes regulating glycolysis, fatty acid oxidation and mitochondrial biogenesis were determined by real‐time PCR. Results Protein rats exhibited enhanced density of type II fibres along with decreased rate of fatty acid oxidation and glycolysis in soleus but not EDL. Malnourished rats exhibited also a different gene expression profile in soleus and EDL. Altogether, these alterations correspond to a state of energy deficiency and are present in animals which do not show yet any sign of obesity or glucose intolerance. Conclusion We conclude that maternal protein restriction alters in the long term the structural and enzymatic properties of offspring skeletal muscle in a fibre‐type‐dependent manner. These alterations might have a causative role in the development of obesity and related metabolic disorders later in life.
    March 11, 2013   doi: 10.1111/apha.12073   open full text
  • Sprint exercise enhances skeletal muscle p70S6k phosphorylation and more so in females than in males.
    Mona Esbjörnsson, Håkan C Rundqvist, Henrik Mascher, Ted Österlund, O. Rooyackers, Eva Blomstrand, Eva Jansson.
    Acta Physiologica. December 26, 2011
    Aim:Sprint exercise is characterized by repeated sessions of brief intermittent exercise at a high relative workload. However, little is known about the effect on mTOR pathway, an important link in regulation of muscle protein synthesis. An earlier training study showed a greater increase in muscle fibre cross sectional area in females than males. Therefore, we tested the hypothesis that activation of mTOR signalling is more pronounced in females than in males. Healthy males (n=9) and females (n=8) performed three bouts of 30‐s sprint exercise with 20 min rest between.Methods:Multiple blood samples were collected over time and muscle biopsy specimens were obtained at rest and 140 min after the last sprint.Results:Serum insulin increased by sprint exercise and more so in females than in males (gender (g) x time (t):P=0.04. In skeletal muscle, phosphorylation of Akt increased by 50% (t, P=0.001) and mTOR by 120% (t, P=0.002) independent of gender. The elevation in p70S6k phosphorylation was larger in females (g x t, P=0.03) and averaged 230% (P=0.006) as compared to 60% in males (P=0.04). Phosphorylation rpS6 increased by 660% over time independent of gender (t, P=0.003). Increase in phosphorylation of p70S6k was directly related to increase in serum insulin (r=0.68, P=0.004).Conclusion:It is concluded that repeated 30‐s all out bouts of sprint exercise separated by 20 min of rest, increases Akt/mTOR signalling in skeletal muscle. Secondly, signalling downstream of mTOR was stronger in females than in males after sprint exercise indicated by increased phosphorylation of p70S6k.
    December 26, 2011   doi: 10.1111/j.1748-1716.2011.02404.x   open full text
  • The effects of early exercise on brain damage and recovery after focal cerebral infarction in rats.
    Fumiyo Matsuda, Harutoshi Sakakima, Yoshihiro Yoshida.
    Acta Physiologica. August 17, 2010
    Aim:  Exercise can be used to enhance neuroplasticity and facilitate motor recovery after a stroke in rats. We investigated whether treadmill running could reduce brain damage and enhance the expression of midkine (MK) and nerve growth factor (NGF), increase angiogenesis, and decrease the expression of caspase‐3.Methods:  77 Wistar rats were split unto 3 experimental groups (ischemia‐control: 36, ischemia‐exercise: 36, sham‐exercise: 5). Stroke was induced by 90 min left middle cerebral artery occlusion using an intraluminal filament. Beginning on the following day, the rats were made to run on a treadmill for 20 min once a day for a maximum of 28 consecutive days. Functional recovery after ischemia was assessed using the beam walking test and a neurological evaluation scale in all rats. Infarct volume, and the expression of MK, NGF, PECAM‐1, and caspase‐3 were evaluated at 1, 3, 5, 7, 14, and 28 days after the induction of ischemia.Results:  Over time motor coordination and neurological deficits improved more in the exercised group than in the non‐exercised group. The infarct volume in the exercised group (12.4 ± 0.8%) subjected to treadmill running for 28 days was significantly decreased compared with that in the control group (19.8 ± 4.2%, P<0.01). The cellular expression levels of MK, NGF, and PECAM‐1 were significantly increased while that of caspase‐3 was decreased in the peri‐infarct area of the exercised rats.Conclusions:  Our findings show that treadmill exercise improves motor behavior and reduces neurological deficits and infarct volume, suggesting that it may aid recovery from central nervous system injury.
    August 17, 2010   doi: 10.1111/j.1748-1708.2010.02174.x   open full text
  • Effects of exercise training on adipogenesis of stromal‐vascular fraction cells in rat epididymal white adipose tissue.
    Takuya Sakurai, Satohiro Endo, Daisuke Hatano, Junetsu Ogasawara, Takako Kizaki, Shuji Oh‐ishi, Tetsuya Izawa, Hitoshi Ishida, Hideki Ohno.
    Acta Physiologica. June 28, 2010
    Aim:  Previous studies have shown that exercise training reduced white adipose tissue (WAT) mass compared to that in sedentary controls, and that the smaller mass contained fewer adipocytes. However, the effect of exercise training on adipogenesis is not completely clear. Therefore, we reexamined the effect of exercise training on adipocyte numbers in WAT and, if such an effect was found tested the adipogenic responses of stromal‐vascular fraction (SVF) cells containing adipose tissue‐derived stem cells (ADSC) in epididymal WAT from exercise‐trained (TR) rats.Methods:  Wistar male rats were divided into two groups: control (C) and TR. The TR rats were subjected to exercise on a treadmill for 9 weeks. SVF cells containing ADSC were separated from epididymal WAT by centrifugation. Expression of adipocyte differentiation‐related genes and adipogenesis of SVF cells were examined.Results:  In SVF cells of TR rats, the expression of peroxisome proliferator‐activated receptor γ (PPARγ) and that of PPARγ target lipogenic genes were dramatically downregulated, whereas that of preadipocyte factor‐1 gene was significantly upregulated. Lipid accumulation in SVF cells of TR rats after the induction of adipocyte differentiation was significantly suppressed in comparison to that of C rats. Moreover, increased expression of hypoxia inducible factor‐1α (HIF‐1α) protein was observed in SVF cells of TR rats. Pretreatment of YC‐1, a potent HIF‐1α inhibitor, in SVF cells of TR rats restored adipogenesis.Conclusion:  These results suggest that exercise training suppresses the ability of SVF cells to differentiate into adipocytes, and that underlying mechanisms involve the upregulation of HIF‐1α expression.
    June 28, 2010   doi: 10.1111/j.1748-1708.2010.02159.x   open full text