Time sequence of changes in hepatic fatty acid synthesis in rats meal fed polyunsaturated fatty acids

Abstract

Rats were meal-fed once daily methyl esters of palmitate (C(16:0)); stearate (C(18:0)); linoleate (C(18:2)) and linolenate (C(18:3)) to determine the influence of these fatty acids on glucokinase and fatty acid synthetase activities and on in vivo rates of fatty acid synthesis in the liver. Addition of 7% C(16:0) or 3% C(18:3) to a fat-free basal diet did not alter the rate at which the diet was removed from the stomach and small intestine. Consumption of a diet containing C(18:2) for eight meals significantly reduced hepatic fatty acid synthetase activity and in vivo rates of fatty acid synthesis by 40%, but did not alter glucokinase activity. At least three meals of a diet containing C(18:2) or C(18:3) were required to inhibit hepatic fatty acid synthesis. Conversely, after rats consumed C(18:2), more than two meals of a fat-free diet were required to increase hepatic rates of fatty acid synthesis. Dietary C(16:0) and C(18:0) did not alter rates of fatty acid synthesis in rat liver. Glucokinase was not influenced by any of the methyl esters fed in all trials except one. The results of this study suggest that poly-unsaturated fatty acids can specifically influence hepatic fatty acid synthesis and fatty acid synthetase activity without altering glucokinase activity, and that meal-fed rats must consume at least three meals containing polyunsaturated fatty acids before hepatic fatty acid synthesis or fatty acid synthetase activity is altered.