DEPENDENCE OF THE PLASMA TRIACYLGLYCEROL-LOWERING EFFECT OF FISH OIL ON INSULIN REPLACEMENT IN STREPTOZOTOCIN DIABETIC RATS

Streptozotocin diabetic rats, with and without insulin replacement, an d sham-injected controls were fed a high-fat (30% of energy) menhaden oil (MO) or corn oil (CO) diet for 2 weeks. After an overnight fast, p lasma and livers were collected for analysis of insulin, glucose, tria cylglycerol, cholesterol and glucose-6-phosphate dehydrogenase activit y. Streptozotocin treatment resulted in decreased plasma insulin and e levated glucose. MO-feeding to insulin-replaced diabetic rats resulted in higher insulin and lower glucose levels compared to the respective CO-fed rats, suggesting decreased hepatic insulin extraction and grea ter peripheral utilization of glucose with MO. Plasma triacylglycerol and cholesterol, and hepatic glucose-6-phosphate dehydrogenase activit y were reduced in MO-fed vs. CO-fed control rats. These effects of MO were prevented in the diabetic rats but were restored by insulin repla cement. We conclude from our data that the presence of insulin is requ ired to observe at least some of the effects of fish oil (FO). To expl ain our observations we propose that many of the effects of FO on hepa tic metabolism are mediated by an inhibition of insulin action in the liver, thus providing a possible central mechanism for the regulation of hepatic lipid metabolism by dietary FO.