butaprost and Insulin-Resistance

To understand the mechanism by which oxidants are linked to insulin resistance, bovine aortic endothelial cells were exposed to oxidized low-density lipoproteins (oxLDL) or peroxynitrite.. OxLDL transiently increased phosphorylation of Erk and Akt within 5 minutes, but 60 minutes later, resulted in decreased insulin-induced Akt phosphorylation. OxLDL promoted a 2- to 5-fold increase in oxidant generation as measured by dihydrorhodamine or dihydroethidium oxidation that was ascribed to peroxynitrite. Exogenous peroxynitrite (25 to 100 micromol/L) or oxidized glutathione mimicked the effects of oxLDL. OxLDL increased the S-glutathiolation of p21ras, and adenoviral transfection with either a mutant p21ras (C118S) lacking the predominant site of S-glutathiolation or a dominant-negative mutant restored insulin-induced Akt phosphorylation. The requirement for oxidant-mediated S-glutathiolation and activation of p21ras in mediating insulin resistance was further implicated by showing that insulin signaling was restored by Mek inhibitors or by overexpression of glutaredoxin-1. Furthermore, oxLDL increased Erk-dependent phosphorylation of insulin receptor substrate-1 serine-616 that was prevented by inhibiting oxidant generation, Erk activation, or by the p21ras C118S mutant.. This study provides direct evidence for a novel molecular mechanism by which oxidants can induce insulin resistance via S-glutathiolation of p21ras and Erk-dependent inhibition of insulin signaling.

Topics: Alprostadil; Animals; Aorta; Cattle; Dinoprostone; Endothelial Cells; Endothelium, Vascular; Enzyme Activation; Extracellular Signal-Regulated MAP Kinases; Glutathione; Glutathione Disulfide; Insulin; Insulin Receptor Substrate Proteins; Insulin Resistance; Lipoproteins, LDL; Lysophosphatidylcholines; Oncogene Protein p21(ras); Oxidants; Peroxynitrous Acid; Phosphoproteins; Phosphorylation; Prostaglandins E, Synthetic; Signal Transduction