title: Palmitate activates insulin signaling pathway in pancreatic rat islets.
abstract: OBJECTIVE
  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).
  
  
  METHODS
  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]).
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  Palmitate at physiological concentration associated with 5.6-mmol/L glucose activates IR signaling pathway in pancreatic beta cells.
authors.affiliation: Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil. mafe@icb.usp.br
authors.forename: Maria Fernanda R
authors.initials: MF
authors.lastname: Graciano
authors.forename: Tatiane C A
authors.initials: TC
authors.lastname: Nogueira
authors.forename: Carla R O
authors.initials: CR
authors.lastname: Carvalho
authors.forename: Rui
authors.initials: R
authors.lastname: Curi
authors.forename: Angelo R
authors.initials: AR
authors.lastname: Carpinelli
mesh_terms: D000818:Animals; D053148:Caspase 3 / Q000378:metabolism; D002460:Cell Line; D005260:Female; D005947:Glucose / Q000494:pharmacology; D015151:Immunoblotting; D047468:Immunoprecipitation; D066298:In Vitro Techniques; D055504:Insulin Receptor Substrate Proteins / Q000378:metabolism; D007515:Islets of Langerhans / Q000187:drug effects* / Q000378:metabolism; D008264:Macrophages / Q000166:cytology / Q000187:drug effects / Q000201:enzymology; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D010168:Palmitates / Q000494:pharmacology*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D051381:Rats; D011972:Receptor, Insulin / Q000378:metabolism*; D050796:STAT3 Transcription Factor / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects*; D013997:Time Factors
chemical_list: D055504:Insulin Receptor Substrate Proteins; C526296:Irs1 protein, rat; C526299:Irs2 protein, rat; D010168:Palmitates; D050796:STAT3 Transcription Factor; C494088:Stat3 protein, rat; D019869:Phosphatidylinositol 3-Kinases; D011972:Receptor, Insulin; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D053148:Caspase 3; D005947:Glucose