Atherogenic diets enriched in saturated, n-6 polyunsaturated, and
monounsaturated fatty acids were fed to African green monkeys for 5 years to define effects on plasma
lipoproteins and coronary artery
atherosclerosis. The monkeys fed polyunsaturated and monounsaturated fat had similar plasma concentrations of
LDL cholesterol, and these values were significantly lower than for
LDL in the animals fed saturated fat. Plasma
HDL cholesterol concentrations were comparable in animals fed saturated and monounsaturated fat and were significantly higher than in animals fed polyunsaturated fat. Thus, the monounsaturated fat group had the lowest
LDL/HDL ratio.
LDL particle size was largest in the saturated and monounsaturated fat groups, significantly larger than in the polyunsaturated fat group.
LDL particle enrichment with
cholesteryl oleate was the greatest in the animals fed monounsaturated fat, next greatest in the saturated fat-fed animals, and was least in the polyunsaturated fat-fed animals. Coronary artery
atherosclerosis as measured by intimal area was less in the polyunsaturated fat compared with the saturated fat groups, was less in the animals fed polyunsaturated fat compared with the monounsaturated fat-fed animals, but did not differ between the monounsaturated and saturated fat groups.
Cholesteryl ester, particularly
cholesteryl oleate, accumulation in the coronary arteries was also similar between groups fed monounsaturated and saturated fat but was minimal in the animals fed polyunsaturated fat. In sum, the monkeys fed monounsaturated fat developed equivalent amounts of coronary artery
atherosclerosis as those fed saturated fat, but monkeys fed polyunsaturated fat developed less. The beneficial effects of the lower
LDL and higher HDL in the animals fed monounsaturated fat apparently were offset by the atherogenic shifts in
LDL particle composition. Dietary polyunsaturated fat appears to result in the least amount of coronary artery
atherosclerosis because it prevents
cholesteryl oleate accumulation in
LDL and the coronary arteries in these primates.