THE GREATER ATHEROGENICITY OF NONPURIFIED DIETS VERSUS SEMIPURIFIED DIETS IN HAMSTERS IS MEDIATED VIA DIFFERENCES IN PLASMA-LIPOPROTEIN CHOLESTEROL DISTRIBUTION, LDL OXIDATIVE SUSCEPTIBILITY, AND PLASMA ALPHA-TOCOPHEROL CONCENTRATION

In the current study, plasma lipid, lipoprotein cholesterol and alpha- tocopherol concentrations, LDL oxidative susceptibility, and early aor tic atherosclerotic responses of feeding a hypercholesterolemic nonpur ified or semipurified diet containing similar levels of macro- and cer tain micro-nutrients were compared in hamsters. Although plasma total cholesterol (TC) concentrations in the hamsters fed the semipurified v ersus nonpurified diet were significantly higher (P < 0.05), non-high density lipoprotein cholesterol (non-HDL-C) concentrations were 41% gr eater in hamsters fed the non-purified diet (P < 0.05). This greater p lasma non-HDL-C concentration, coupled with significantly lower plasma concentrations of high-density lipoprotein cholesterol (HDL-C) (P < 0 .05), resulted in a greater plasma non-HDL-C/HDL-C and TC/HDL-C ratios for the nonpurified versus the semipurified diet (P < 0.05). Despite comparable amounts of dietary vitamin E, plasma ol-tocopherol concentr ations were 233% higher in the semipurified versus nonpurified diet (P < 0.05). Resistance of LDL to oxidation, as measured by lag phase of conjugated diene formation, was reduced nearly 50%, and the rate of fo rmation of conjugated dienes was 105% higher in the nonpurified versus the semipurified diet, respectively (P < 0.05). Early aortic atherosc lerosis was fivefold greater in hamsters fed the nonpurified versus se mipurified diet. These results suggest that, despite similar dietary c oncentrations of many of the macro- and micro-nutrients, ingestion of hypercholesterolemic nonpurified diets by hamsters is associated with a more atherogenic lipoprotein profile, greater LDL oxidative suscepti bility, lower plasma alpha-tocopherol levels, and greater early aortic atherosclerosis compared to semipurified diets. (C) Elsevier Science Inc. 1998.