Broad-β disease versus endogenous hypertriglyceridemia: Levels and lipid composition of chylomicrons and very low density lipoproteins during fat-free feeding and alimentary lipemia

Abstract

To assess the roles of endogenous and exogenous lipid in the production of the abnormal lipoprotein patterns characteristic of broad-β disease (with a type III lipoprotein pattern) and endogenous hypertriglyceridemia (with a type IV pattern), oral fat loads (50 g/M 2) were administered to six subjects with broad-β disease and to eight with endogenous hypertriglyceridemia following at least 72 hr of 0% fat, 85% carbohydrate isocaloric formula feeding. Total plasma and S f > 400, 100–400, 60–100, 30–60, and 20–30 lipoprotein cholesterol, triglyceride, and phospholipid levels were measured at 0 hr, 6 hr (at or before the peak of alimentary lipemia), and 24 hr following the fat load. Following fat-free feeding the levels and composition of the endogenous S f > 400 lipoproteins were similar in both disorders; whereas total S f20–400, and most notably, S f30–60 and 20–30 levels were increased and enriched in cholesterol in the subjects with broad-β disease. The latter phenomenon persisted both early and late following the oral fat load. At peak alimentary lipemia, chylomicrons were equally increased and triglyceriderich in both subject groups, but by 24 hr this fraction was becoming more enriched in cholesterol in the group with broad-β disease. These experiments thus suggest that both endogenous and exogenous triglyceride-rich lipoproteins are of normal composition when first secreted in broad-β disease, but become abnormal during their catabolic conversion to lipoproteins of higher density.