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Combined acute hyperglycemic and hyperinsulinemic clamp induced profibrotic and proinflammatory responses in the kidney

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AJP Cell Physiology

Published online on

Abstract

Increase in matrix protein content in the kidney is a cardinal feature of diabetic kidney disease. While renal matrix protein content is increased by chronic hyperglycemia, whether it is regulated by acute elevation of glucose and insulin has not been addressed. In this study, we aimed to evaluate if short duration of combined hyperglycemia and hyperinsulinemia, mimicking metabolic environment of pre-diabetes and early type 2 diabetes, induces kidney injury. Normal rats were subjected to either saline infusion (control, n=4) or seven hours of combined hyperglycemic-hyperinsulinemic clamp (HG+HI clamp; n=6). During the clamp, plasma glucose and plasma insulin were maintained at about 350 mg/dl and 16 ng/ml, respectively. HG+HI clamp increased the expression of renal cortical TGFβ and renal matrix proteins, laminin and fibronectin. This was associated with the activation of SMAD3, Akt, mTOR complexes and Erk signaling pathways and their downstream target events in the initiation and elongation phases of mRNA translation, an important step in protein synthesis. Additionally, HG+HI clamp provoked renal inflammation as shown by the activation of toll like receptor 4 (TLR4) and infiltration of CD68 positive monocytes. Urinary F2t isoprostane excretion, an index of renal oxidant stress, was increased in the HG+HI clamp rats. We conclude that even a short duration of hyperglycemia and hyperinsulinemia contributes to activation of pathways that regulate matrix protein synthesis, inflammation and oxidative stress in the kidney. This finding could have implications for the control of short term rises in blood glucose in diabetic individuals at risk of developing kidney disease.