Effects of Free Fatty Acid on Insulin Secretion in Cultured Rat Pancreatic Islets

Kim, Hong Kyu; Kim, Young Il; Kim, Chul Hee; Park, Joong Yoel; Hong, Sung Kwan; Lee, Jae Dam; Lee, Ki Up

Abstract

BACKGROUND: It has been recently suggested that enhanced fat oxidation is responsible for the abnormal insulin secretory pattern in non-insulin-dependent diabetes mellitus. This study was undertaken to assess the effect of chronic exposure of pancreatic islets to free fatty acid on insulin secretion.
METHODS
Rat pancreatic islets were cultured in various concentrations of glucose(5.5, 11, 27 mM) for 48 hrs with or without addition of free fatty acid(90 upM linoleic acid), and the basal and glucose-stimulated insulin secretion were measured. The effect of fatty acid oxidation inhibitor(2-bromopalmitate) was also tested.
RESULTS
Islets cultured in high glucose concentrations showed a marked increase in basal insulin secretion. Free fatty acid stimulated the basal insulin secretion in islets cultured at 5.5 or 11 mM glucose, but no additional effect was seen in islets eultured at 27 mM glucose. In contrast, glucose-stimulated insulin secretion was decreased in islets cultured in high glucose media. Exposure to free fatty acid exerted an additive inhibitory effect on glucose-induced insulin secretion in islets cultured at 5.5 or 1 1 mM glucose, but not in islets cultured at 27M glucose, An inhibitor of fatty acid oxidation, 2-bromopalmitate, prevented the fatty acid-induced changes in both basal and glucosestimulated insulin secretion.
CONCLUSION
These results showed that longterm exposure of pancreatic islets to free fatty acid altered the dynamics of insulin secretion, probably through a glucosefatty acid cycle.