Tissue Lipid Fatty Acid Changes Following the Feeding of High-Cholesterol, Essential Fatty Acid-Supplemented Diets to Rabbits

Abstract

Rabbits were fed a normal stock diet supplemented with 1 gm of cholesterol per day plus either one of the following: 150 mg olive oil, 150 mg linoleic acid, 150 mg linoleic acid plus 3 mg pyridoxine, and 150 mg ethyl arachidonate. A control group fed the stock diet was run in parallel. The animals were sacrificed after 9 weeks, the aorta graded visually and the tissues analyzed for lipids and lipid fatty acid composition by gas-liquid chromatography. All of the cholesterol-fed groups showed moderate degrees of atherosclerosis. There did not appear to be any differences with respect to the effect of the various diets on the development of atherosclerosis with the possible exception of the group receiving linoleic acid and pyridoxine. The cholesterol, triglycerides and phospholipids of the aorta were elevated in all experimental groups above the control. Increases in the liver and serum cholesterol occurred, but no differences were noted among the cholesterol-fed groups. There were marked differences in tissue lipid fatty acid composition between the several cholesterol-fed groups and the control animals. The serum cholesterol ester fraction of the rabbits with atherosclerosis had substantially more oleic acid and less linoleic acid than that fraction in the serum of normal animals. The cholesterol esters deposited in the aorta of the cholesterol-fed groups contained a significantly greater proportion of saturated and oleic acids and significantly less linoleic acid than that fraction in the serum of normal animals. No significant differences occurred in the fatty acid composition of the aorta triglyceride and phospholipid fractions between normal and atherosclerotic animals. In the animals with atherosclerosis, however, there was an increase in the proportion of linoleic acid in the serum phospholipid fraction. The group fed ethyl arachidonate had significantly more of that acid in the liver phospholipid fraction than the other fatty acid-supplemented groups. The results of this study provide further evidence that the essential fatty acids may play an important role in the pathogenesis of atherosclerosis, and in particular that arachidonic acid and cholesterol ester metabolism require further investigation.