CARBOHYDRATE TYPE AND AMOUNT ALTER INTRAVASCULAR PROCESSING AND CATABOLISM OF PLASMA-LIPOPROTEINS IN GUINEA-PIGS

To test the effects of exchanging dietary complex and simple carbohydr ate for fat calories on lipoprotein metabolism, guinea pigs were fed t wo different fat/carbohydrate ratios: 2.5:58% (w/w) or 25:29% (w/w) wi th either sucrose or starch as the carbohydrate source. Animals fed hi gh-fat had higher plasma low-density lipoprotein (LDL) and hepatic cho lesterol concentrations than animals fed low-fat diets (P < 0.01). The cholesteryl ester content per particle was higher, and the number of triacylglycerol (TAG) molecules was lower in very low density lipoprot ein (VLDL) and LDL from animals fed high-fat diets. Intake of high-fat /sucrose resulted in higher plasma LDL concentrations than intake of h igh-fat/starch, and animals fed low-fat/starch had the highest plasma TAG concentrations associated with VLDL particles containing more TAG molecules, as well as a TAG-enriched LDL. The activity of plasma lecit hin cholesteryl:acyl transferase (LCAT) was highest in animals fed hig h-fat/sucrose, and heart lipoprotein lipase (LPL) activity was higher in animals fed high-fat diets. Hepatic apoprotein BIE (ape B/E) recept or number (B-max) was increased 21% with low-fat diets (P < 0.01). The se results suggest that the hypercholesterolemia induced by high-fat a nd by sucrose intake are associated with a higher plasma LCAT activity which results in a cholesteryl ester-enriched VLDL which, by the acti on of LPL, might be more readily converted to LDL through the delipida tion cascade leading to downregulation of hepatic apo BIE receptors. T he hypertriglyceridemia associated with low-fat intake may result from increased production of VLDL TAG, which would explain the increased T AC content and the higher TAG/CE ratio of VLDL from animals fed the lo w-fat/starch diet.