DIETARY (N-3) POLYUNSATURATED FATTY-ACIDS IMPROVE ADIPOCYTE INSULIN ACTION AND GLUCOSE-METABOLISM IN INSULIN-RESISTANT RATS - RELATION TO MEMBRANE FATTY-ACIDS

To study the effects of dietary fish oil on insulin-stimulated glucose metabolism in adipocytes of insulin-resistant rats (rats fed 50% sucr ose and 30% fat), eighteen 5-wk-old Sprague-Dawley rats were fed, for 6 wk, a diet containing 30% fat as either fish oil (FO) or a mixture o f vegetable and animal oils [control oils (CO)]. A third reference gro up was fed a standard diet (62% corn starch and 13% fat). At the end o f the 6-wk period, the two experimental groups had comparable plasma g lucose concentrations that were higher than that found in the referenc e group. FO feeding corrected the hyperinsulinemia of the experimental rats (P < 0.05) to reach values in the reference group. Plasma triacy lglycerol (P < 0.01) and cholesterol (P < 0.001) concentrations were a lso lower in rats fed FO than in those fed CO. The body weights of FO- fed rats were similar to that of CO-fed rats, but epididymal adipose t issue weight was lower (P < 0.01). Adipocytes of FO-fed rats, compared with those of CO-fed rats, had high insulin-stimulated glucose transp ort (P < 0.05), oxidation (P < 0.001) and incorporation into total lip ids (P < 0.05). The incorporation of (n-3) polyunsaturated fatty acids in adipocyte membrane phospholipids was higher in FO-fed rats than in those fed CO (P < 0.0001). Insulin action was positively correlated w ith the fatty acid unsaturation index in membrane phospholipids. Thus dietary fish oil has beneficial effects on insulinemia, plasma lipids and insulin-stimulated glucose metabolism in insulin-resistant slightl y diabetic rats.