Fatty Acid Composition and Vitamin E Content of Experimental Diets Component Study Diet Oleic Linoleic Oleic

We investigated the effect of different interventions on aortic atherosclerosis in Watanabe rabbits. Four groups of rabbits were fed either an oleic acid-enriched diet (80% of total fat intake) with or without vitamin E supplementation (250 IU/kg) or a diet enriched in linoleic acid with or without vitamin E supplementation for 6 months. At the start of the study, plasma cholesterol concentration was 21.4±3.6 mmol/L (n=32). The diets did not influence the mean plasma lipids and lipoprotein concentrations except for HDL cholesterol, which was increased more on the oleic acid— enriched diets than on the linoleic acid-enriched diets. Vitamin E levels in plasma and LDL were increased on the oleic acid diet and reduced on the linoleic acid diet. On the latter diet, supplementation of vitamin E was quantitatively less effective in raising plasma or LDL vitamin E levels. The susceptibility of LDL to oxidation was determined in vitro. Both oleic acid-enriched diets increased the lag time by 140% from baseline. The linoleic acid diet supplemented with vitamin E increased lag time by 59%. Linoleic acid alone, how­ ever, decreased the lag time by 30%. Similar but inverse effects were seen on LDL oxidation rate. Thus, intervention protected LDL to oxidation in the following order: oleic acid plus vitamin E>oleic acid>linoleic acid plus vitamin E>linoleic acid. Despite the differences in LDL oxidizability induced by the four experi­ mental diets, assessment of aortic atherosclerosis at the end of the 6-month dietary study period revealed no differences among the four study groups. These results suggest that a decrease in the oxidative susceptibility in vitro alone is not sufficient to attenuate atherogenesis when cholesterol levels remain markedly elevated. (Arterioscler Thromb Vase Biol. 1995;15:290-297.)