Palmitate activates insulin signaling pathway in pancreatic rat islets.

Maria Fernanda R Graciano, Tatiane C A Nogueira, Carla R O Carvalho, Rui Curi, Angelo R Carpinelli

Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil. mafe@icb.usp.br

Pancreas 2009 Jul

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To investigate the action of palmitate on insulin receptor (IR) signaling pathway in rat pancreatic islets. The following proteins were studied: IR substrate-1 and -2 (IRS1 and IRS2), phosphatidylinositol 3-kinase, extracellular signal-regulated protein kinase-1 and -2 (ERK1/2), and signal transducer and activator of transcription 3 (STAT3). Immunoblotting and immunoprecipitation assays were used to evaluate the phosphorylation states of IRS1 and IRS2 (tyrosine [Tyr]), ERK1/2 (threonine 202 [Thr202]/Tyr204), and STAT3 (serine [Ser727]). The exposure of rat pancreatic islets to 0.1-mmol/L palmitate for up to 30 minutes produced a significant increase of Tyr phosphorylation in IRS2 but not in IRS1. The association of phosphatidylinositol 3-kinase with IRS2 was also upregulated by palmitate. Exposure to 5.6-mmol/L glucose caused a gradual decrease in ERK1/2 (Thr202/Tyr204) and STAT3 (serine [Ser727]) phosphorylations after 30-minute incubation. The addition of palmitate (0.1 mmol/L), associated with 5.6-mmol/L glucose, abolished these latter effects of glucose after 15-minute incubation. Palmitate at physiological concentration associated with 5.6-mmol/L glucose activates IR signaling pathway in pancreatic beta cells.

Citation

Maria Fernanda R Graciano, Tatiane C A Nogueira, Carla R O Carvalho, Rui Curi, Angelo R Carpinelli. Palmitate activates insulin signaling pathway in pancreatic rat islets. Pancreas. 2009 Jul;38(5):578-84