Properties of triglyceride-rich and cholesterol-rich lipoproteins in the remnant-like particle fraction of human blood plasma.

An immunoassay procedure that quantifies remnant-like particle (RLP) cholesterol in human blood plasma has shown considerable promise as a clinically applicable risk marker for atherosclerotic disease. The lipoproteins included in this assay include not only certain TG-rich lipoproteins [all particles containing apolipoprotein B-48 (apoB-48) and a fraction of those containing apoB-100] but also a very small proportion of plasma cholesterol-rich lipoproteins. The TG-rich lipoprotein component of RLP has been partially characterized, but relatively little is known about the component cholesterol-rich lipoproteins. We have further characterized the properties of the TG-rich component that is included in RLP in which about 25% of the particles contain apoB-48 and the remainder apoB-100. We show that the cholesterol-rich component is comprised mainly of beta-migrating LDLs that contain predominantly apoB-100. ApoE found in the LDL fraction of RLP resides on pre-beta lipoproteins that lack apoA-I as well as apoB. The TG-rich component of RLP is responsible for increased RLP-cholesterol concentrations associated with hypertriglyceridemia. By contrast, the cholesterol-rich component is a major contributor to plasma RLP-cholesterol in individuals with low plasma TG. Our results suggest that particle heterogeneity in the RLP fraction is likely to affect the ability of RLP-cholesterol concentration to predict atherosclerotic risk. RLP-cholesterol concentrations in individuals with low plasma TG may not have the same clinical significance as they do in those with hypertriglyceridemia.