PLASMA OXIDIZABILITY IN MEXICAN-AMERICANS AND NON-HISPANIC WHITES

Several lines of evidence support an atherogenic role for oxidized low -density lipoprotein (LDL). Previous studies have suggested that altho ugh Mexican-Americans have an increased rate of diabetes, obesity, ele vated triglyceride levels, and low high-density lipoprotein (HDL) chol esterol revels, their rates of coronary heart disease (CHD) are simila r or possibly lower than in non-Hispanic whites. Mexican-Americans hav e smaller, denser LDL than non-Hispanic whites. On the basis of this l atter observation, we postulated that lipid peroxide (LPO) levels woul d be increased in Mexican-Americans. We examined the oxidizability of plasma in 50 Mexican-Americans and 50 non-Hispanic whites from the San Antonio Heart Study, a population-based study of diabetes and cardiov ascular disease, at baseline and after coincubation with a metal-indep endent system (2',2'-azobis-2-amidinopropane hydrochloride [AAPH]) and a metal-dependent system (Fe2+/H2O2) of oxidation. LPO revels were me asured by a modified fluorimetric assay, Vitamin E and plasma fatty ac id composition were also determined. We found significantly higher LPO levels at baseline and after AAPH coincubation in Mexican-Americans t han in non-Hispanic whites (baseline, 2.75 +/- .09 v 2.07 +/- .09 mu m ol/L, P < .001; post-AAPH, 5.49 +/- .14 v 5.07 +/- .04 pmol/L, P = .03 7). However, no significant ethnic differences were seen after coincub ation with Fe2+/H2O2. Diabetes and cigarette-smoking were also associa ted with higher LPO levels. Mexican-Americans also had lower levels of vitamin E (the predominant lipid-soluble antioxidant in plasma) than non-Hispanic whites, although these differences only partially explain ed the differences in susceptibility to oxidation. Plasma fatty acids were similar in Mexican-Americans and non-Hispanic whites, suggesting only small differences in diet composition. We conclude that LPO level s are higher in Mexican-Americans than in non-Hispanic whites, and tha t these results are only partially related to differences in vitamin E levels. Copyright (C) 1996 by W.B. Saunders Company