AbstractThe present study compared the short-term effect of feeding 18:2n-6 and its metabolite, 18:3n-6 on plasma cholesterol and plasma and liver fatty acid composition. weanling female rats were maintained on a fat-free semi-synthetic diet supplemented with l0% saturated fat, 1% cholesterol and 0.5% bile salt for 5 weeks to induce hypercholesterolemia and fatty liver. The hypercholesterolemic rats (group H) were then switched to a steroid-free fat-free diet supplemented with either 5% linoleic acid-rich oil (group L, containing 80% 18:2n-6) or 5% gamma-linolenic acid concentrate (group G, containing 84% 18:3n-6 and 16% 18:2n-6 ethyl esters). After 2 days on the diet, plasma cholesterol and free fatty acid levels in both groups were significantly reduced. The extent of reduction was significantly greater in group G than in group L. The concentrations of triglycerides and phospholipids in plasma were not affected but those in liver were significantly changed by the dietary manipulation (increased liver phospholipids and reduced triglycerides) . Both n-6 fatty acid treatments significantly modified the fatty acid compositions all lipid fractions - reducing the levels of monounsaturates, and 20:3n-9, but elevating those of n-6 fatty acids. The elevations of C-20 and C-22 n-6 fatty acids were consistently greater in group G than in group L. These results indicate that gamma-linolenate in comparison with linoleate was more effectively and rapidly metabolized into long chain metabolites which might account for the difference in cholesterol-lowering ability between gamma-linolenate and linoleate.
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