Soybean- and olive-oils-enriched diets increase insulin secretion to glucose stimulus in isolated pancreatic rat islets

Islets isolated from rats fed a lipid-enriched diet have shown an impairmen t of insulin secretion, but there is no available data comparing the effect of diet containing different dietary fat. This may be important in prevent ing or facilitating the establishment of diabetes. In this study, the effec t of diets enriched (10%) with different fatty acids on insulin secretion b y isolated pancreatic islets was investigated. The sources of the fatty aci ds tested were: saturated long chain from animal fat (AF), polyunsaturated from soybean oil (SO), and monounsaturated from olive oil (OL). The results were compared with those from rats receiving a diet enriched (10%) with a balanced mixture of fatty acids (the same proportion of AF, SO, and OL). Th e effect of fat-rich diets on insulin release was tested in vivo by giving a glucose load (glucose tolerance test-GTT) and in vitro in perfused islets . The mechanism involved was also examined by measuring Ca-45(2+) and Rb-86 (+) fluxes, GLUT-2 content, and glucose oxidation in isolated islets. A sig nificant increase of insulin secretion and glucose oxidation without any al teration of the ionic movements were detected in islets from SO and OL rats . GLUT-2 content was increased in islets of the OL group but diminished in AF rats. The results led us to postulate that soybean and olive oils may in crease the response of insulin secretion to glucose stimulus in pancreatic islets. (C) 1998 Elsevier Science Inc.