Trans fatty acid effects in experimental atherosclerosis.

Trans unsaturated fatty acids are formed during hydrogenation of edible oils and their consumption in the United States has increased with increasing utilization of margarines. The effect of elaidic acid and trielaidin on atherosclerosis in cholesterol-fed rabbits were studied many years ago by Weigensberg and McMillan, who found these fatty acids to be significantly more hypercholesterolemic but not more atherogenic. Jackson et al. have found that trans fatty acids are not inordinately atherogenic in swine. We have fed rabbits semipurified, cholesterol-free diets containing either 3.2 or 6.0% of trans fatty acid. The diets were slightly hyperlipidemic but no more atherogenic than the control diet. We measured the activities of five hepatic enzymes (glucose-6-phosphatase, fatty acid synthetase, malate dehydrogenase, beta-hydroxybutyrate dehydrogenase, and monoamine oxidase [EC 1.4.3.4]). The diets affected only the activity of monoamine oxidase, which was lower in the livers of rabbits fed 6.0% trans fatty acid. Vervet monkeys were fed the same diets either for 1 year or for 6 months and then returned to the control diet for 6 months. The dietary manipulations had no effect on serum or lipid levels or aortic sudanophilia. Trans fatty acid levels of the serum reflected dietary concentration. Six months after cessation of feeding of the trans fat the levels of trans fatty acids in serum were virtually normal. Trans fatty acids appear to exert a hypercholesterolemic effect but do not influence aortic atherosclerosis in rabbits or aortic sudanophilia in vervet monkeys.