DIETARY MODIFICATION OF HIGH-DENSITY-LIPOPROTEIN PHOSPHOLIPID AND INFLUENCE ON CELLULAR CHOLESTEROL EFFLUX

African green monkeys fed fat-specific diets served as a model to inve stigate the effect of phospholipid acyl chain modification on high den sity lipoprotein (HDL)mediated cellular cholesterol efflux, Diets enri ched in saturated, monounsaturated, n-6 polyunsaturated, or n-3 polyun saturated fats were provided during both low cholesterol and cholester ol-enriched stages; sera and HDL3 samples were obtained at specific po ints during the treatment period. Analysis of the HDL phospholipid com position revealed significant acyl chain modification, consistent with the respective fat-specific diet. Cholesterol efflux from mouse L-cel l fibroblasts to HDL3 isolated from the specific diet groups was measu red and revealed no differences in the abilities of the particles to a ccept cellular cholesterol; determination of the bidirectional flux of cholesterol between the cells and HDL3 species further demonstrated n o effect of phospholipid acyl chain modification on this process, The effects of dietary modification of phospholipid acyl chains on cellula r cholesterol efflux were directly examined by isolating the HDL phosp holipid and combining it with human apolipoprotein A-I to form well-de fined reconstituted HDL particles, These complexes did not display any differences with respect to their ability to stimulate cellular chole sterol efflux, Incubations with 5% sera further confirmed that the fat -specific diets do not influence cholesterol efflux. These results sug gest that the established influences of specific dietary fats on the p rogression of atherosclerosis are due to effects on cholesterol metabo lism other than the efflux of cellular cholesterol in the first step o f reverse cholesterol transport.