INFLUENCE OF DIETARY N-3 FATTY-ACIDS ON THE BIOSYNTHESIS OF POLYUNSATURATED FATTY-ACIDS IN STZ-DIABETIC RATS

Experimental diabetes in rats produces a generalized defect in liver m icrosomal polydesaturase activity and hence in the total fatty-acid co mposition. The present study was devised to determine whether or not t hose enzymic defects in the diabetic animal might be offset by alterat ions in the profile of fatty acids consumed in the diet. Accordingly, streprozotocin-induced diabetic rats were fed nutritionally adequate b asal diets for 2 weeks supplemented with equivalent amounts of free fa tty acids from either corn oil, rich in n-6 species, or cod-liver oil, abundant in n-3 acids. Both classes of dietary polyunsaturates were i ncorporated into hepatic microsomes and caused elevations in the respe ctive levels of those acids in cellular membranes. The unsaturation in dices, however, were higher under the latter regime than under the for mer. Dietary supplementation with the n-3, but not the n-6, fatty acid s increased plasma glucose levels in both control and diabetic rats. N either regime, however, affected microsomal desaturase or fatty acyl-C oA synthetase activity in either experimental group. Therefore, we con clude that the deficiency in hepatic-desaturase activity accompanying diabetes occurs independently of the nature of the fatty acids present in the hepatic membranes. An enhanced dietary intake of n-3 fatty aci ds thus fails to alleviate the depression in the enzymes involved in h epatic polyunsaturated fatty acid biosynthesis in diabetic rats.