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The bradykinin(BK)-cGMP-PKG pathway augments insulin sensitivity via upregulation of MAPK phosphatase-5 and inhibition of Jun kinase (JNK).

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AJP Endocrinology and Metabolism

Published online on

Abstract

Bradykinin (BK) promotes insulin sensitivity and glucose uptake in adipocytes and other cell types. We demonstrated that in rat adipocytes BK enhances insulin-stimulated glucose transport via endothelial nitric oxide synthase (eNOS), nitric oxide (NO) generation, and decreased activity of the mitogen activated protein kinase (MAPK), JNK (c-Jun-N-terminal kinase). In endothelial cells, NO increases soluble guanylate cyclase (sGC) activity which in turn, activates protein kinase G (PKG) by increasing cGMP levels. In this study, we investigated whether BK acts via the sGC-cGMP-PKG pathway to inhibit the negative effects of JNK on insulin signaling and glucose uptake in rat adipocytes. BK augmented cGMP concentrations. The BK-induced enhancement of insulin-stimulated glucose uptake was mimicked by the sGC activator, YC-1 and a cell permeable cGMP analog, CPT-cGMP, and inhibited by the sGC inhibitor, ODQ and the PKG inhibitor, KT-5823. Transfection of dominant-negative PKG reduced the BK augmentation of insulin-induced Akt phosphorylation. The activation of JNK and ERK1/2 by insulin was attenuated by BK, which was mediated by the sGC-cGMP-PKG pathway. While insulin-stimulated phosphorylation of upstream activators of JNK and ERK, i.e., MKK4 and MEK1/2, was unaffected, BK augmented insulin-mediated induction of MKP-5 mRNA and protein levels. Furthermore, zaprinast, a phophodiesterase inhibitor, enhanced cGMP and MKP-5 and prolonged the action of BK. These data indicate that BK enhances insulin action by inhibition of negative feedback by JNK and ERK via upregulation of MKP-5, mediated by the sGC-cGMP-PKG signaling pathway.