Phenotypes of hypertriglyceridemia caused by excess very-low-density lipoprotein.

Objective: To characterize the composition of very-low-density lipoprotein (VLDL) particles and the proportion of VLDL to total apolipoprotein B (apoB) particles in patients with hypertriglyceridemia caused by excess VLDL.

Methods: Subjects were selected from 2023 consecutive patients attending the Lipid Clinic at the Laval University Centre. Plasma lipids, apoB, and apoA-I were measured and chylomicron lipids and VLDL and LDL lipids and apoB determined after ultracentrifugation. Patients with hypertriglyceridemia caused by excess VLDL were divided into four groups on the basis of triglyceride and apoB.

Results: A total of 440 controls, 387 subjects with normotriglyceridemic hyperapoB, 38 with type III dysbetalipoproteinemia, 270 with mild hypertriglyceridemic normoapoB, 163 with moderate hypertriglyceridemic normoapoB, 458 with mild hypertriglyceridemic hyperapoB, and 295 subjects with moderate hypertriglyceridemic hyperapoB were compared. In patients with hypertriglyceridemia caused by excess VLDL, the VLDL particles were triglyceride and cholesterol-enriched. HyperapoB is associated with greater low-density lipoprotein (LDL) apoB than normoapoB, whereas greater triglycerides are associated with greater VLDL apoB. Thus, the ratio of VLDL apoB/total apoB was significantly less in those with mild hypertriglyceridemia compared with those with moderate hypertriglyceridemia, irrespective of the plasma apoB.

Conclusions: The apoB phenotypes in hypertriglyceridemia caused by excess VLDL appear to be determined by the extent to which VLDL secretion increases, the extent to which VLDL particles can be converted to LDL particles, and the effects of core lipid exchange. More accurate characterization of hypertriglyceridemia caused by excess VLDL should lead to a better understanding of the determinants of VLDL clearance and conversion to LDL as well as of the atherogenic potential of VLDL.