EFFECTS OF DIETARY VITAMIN-C AND VITAMIN-E SUPPLEMENTATION ON THE COPPER MEDIATED OXIDATION OF HDL AND ON HDL MEDIATED CHOLESTEROL EFFLUX

Copper mediated oxidative modification of high density lipoprotein (HD L) diminishes its capacity to promote cholesterol efflux from cells in culture. In the present study, HDL was isolated from eight subjects b efore and after a 10 day administration of the antioxidant vitamins C and E. After incubation of HDL (1.25 mg protein/ml) with 10 mu M coppe r for 0-4 h or with 0-20 mu M copper for 4 h, thiobarbituric acid reac tive substances (TEARS) production was significantly decreased followi ng vitamin administration suggesting that the vitamins decreased the s usceptibility of HDL to oxidation. However, two other assays of lipopr otein oxidation, trinitrobenzene sulfonic acid reactivity and conjugat ed diene formation, did not show a consistent effect of vitamin admini stration. To study cholesterol efflux, J774 macrophages were labeled w ith H-3 cholesterol (0.1 mu Ci/ml, 50 mu g/ml) and incubated with HDL or oxidized HDL (100 mu g protein/ml) for 24 h. HDL isolated before vi tamins and oxidized in vitro was 39% less effective in mediating efflu x compared to unmodified HDL, while HDL isolated after vitamins and ox idized was 22% less effective (before vs. after vitamins, P < 0.015). HDL oxidation determined by measuring TEARS production correlated with decreased cholesterol efflux (r = -0.73, P < 0.050). These data sugge st that oxidation of HDL interferes with its role in reverse cholester ol transport and that antioxidant vitamins have a protective effect.