Effect of Ezetimibe on the In Vivo Kinetics of ApoB-48 and ApoB-100 in Men With Primary Hypercholesterolemia

OBJECTIVE—To examine the impact of ezetimibe, a selective inhibitor of intestinal cholesterol absorption, on the in vivo kinetics of apolipoproteins (apo) B-48 and B-100 in humans. METHODS AND RESULTS—Kinetics of triglyceride-rich lipoprotein (TRL) apoB-48 and very-low-density lipoprotein (VLDL), intermediate-density lipoprotein (IDL), and low-density lipoprotein (LDL) apoB-100 labeled with a stable isotope were assessed at baseline and at the end of 8 weeks of treatment with 10 mg/d of ezetimibe in 8 men with moderate primary hypercholesterolemia. Data were fit to a multicompartmental model using SAAMII to calculate fractional catabolic rate (FCR) and production rate (PR). Ezetimibe significantly decreased total and LDL cholesterol concentrations by −14.5% and −22.0% (P=0.004), respectively, with no significant change in plasma triglyceride and high-density lipoprotein (HDL) cholesterol levels. Ezetimibe had no significant effect on TRL apoB-48 kinetics and pool size (PS). However, VLDL and IDL apoB-100 FCRs were significantly increased (+31.2%, P=0.02 and +20.8%, P=0.04, respectively) with a concomitant elevation of VLDL apoB-100 PR (+20.9%, P=0.04). Furthermore, LDL apoB-100 PS was significantly reduced by −23.2% (P=0.004), caused by a significant increase in FCR of this lipoprotein fraction (+24.0%, P=0.04). CONCLUSIONS—These results indicate that reduction of plasma LDL cholesterol concentration after treatment with ezetimibe is associated with an increase in FCR of apoB-100–containing lipoproteins.