Mechanism of ethanol-induced insulin secretion from INS-1 and INS-1E tumor cell lines.

ABSTRACT

UNLABELLED Alcohol causes reactive hypoglycemia by attenuating the release of counter regulatory hormones, redistribution of pancreatic blood flow and direct stimulation of insulin secretion. Objective of this study was characterization of ethanol-induced insulin secretion. Signaling of ethanol- and glucose-induced insulin release from INS-1 and INS-1E cells was compared. Both cell lines responded similarly to all experimental interventions. In contrast to glucose, ethanol-induced insulin secretion was not hindered in calcium depleted medium or by addition of 10 microM BAPTA/AM (intracellular chelator). Inhibitor of protein kinase C Bisindolylmaleimide (3 microM) abolished glucose- but not ethanol-induced insulin secretion. Tetanus toxin (20 nM), inhibitor of SNARE proteins complex formation, blocked ethanol-induced insulin secretion. Both 5 mM N-ethylamaleimide and 10 microM ZnCl(2) (inhibitor of protein tyrosine phosphatases), which block disassembly of SNARE complexes and their further participation in exocytosis, increased basal insulin secretion. In contrast to glucose, already high insulin secretion was further increased after ethanol stimulation in either treatment. CONCLUSION: Signaling of ethanol-induced insulin secretion from INS-1 and INS-1E cell lines bypasses calcium and PKC involving steps, is sensitive to tetanus toxin but resistant to N-ethymaleimide and ZnCl(2). An extra pool of secretory vesicles not available for glucose is exploited for exocytosis after ethanol stimulation.