Journal of Lipid Research (Jul 1999)
Inhibition of ACAT by avasimibe decreases both VLDL and LDL apolipoprotein B production in miniature pigs
Abstract
An orally bioavailable acyl coenzyme A:cholesterol acyltransferase (ACAT) inhibitor, avasimibe (CI-1011), was used to test the hypothesis that inhibition of cholesterol esterification, in vivo, would reduce hepatic very low density (VLDL) apolipoprotein (apo) B secretion into plasma. ApoB kinetic studies were carried out in 10 control miniature pigs, and in 10 animals treated with avasimibe (10 mg/kg/d, n = 6; 25 mg/kg/d, n = 4). Pigs were fed a diet containing fat (34% of calories) and cholesterol (400 mg/d; 0.1%). Avasimibe decreased the plasma concentrations of total triglyceride, VLDL triglyceride, and VLDL cholesterol by 31–40% 39–48%, and 31–35%, respectively. Significant reductions in plasma total cholesterol (35%) and low density lipoprotein (LDL) cholesterol (51%) concentrations were observed only with high dose avasimibe. Autologous 131I-labeled VLDL, 125I-labeled LDL, and [3H]leucine were injected simultaneously into each pig and apoB kinetic data were analyzed using multicompartmental analysis (SAAM II). Avasimibe decreased the VLDL apoB pool size by 40–43% and the hepatic secretion rate of VLDL apoB by 38–41%, but did not alter its fractional catabolism. Avasimibe decreased the LDL apoB pool size by 13–57%, largely due to a dose-dependent 25–63% in the LDL apoB production rate. Hepatic LDL receptor mRNA abundances were unchanged, consistent with a marginal decrease in LDL apoB FCRs. Hepatic ACAT activity was decreased by 51% (P = 0.050) and 68% (P = 0.087) by low and high dose avasimibe, respectively. The decrease in total apoB secretion correlated with the decrease in hepatic ACAT activity (r = 0.495; P = 0.026). We conclude that inhibition of hepatic ACAT by avasimibe reduces both plasma VLDL and LDL apoB concentrations, primarily by decreasing apoB secretion.—Burnett, J. R., L. J. Wilcox, D. E. Telford, S. J. Kleinstiver, P. H. R. Barrett, R. S. Newton, and M. W. Huff. Inhibition of ACAT by avasimibe decreases both VLDL and LDL apolipoprotein B production in miniature pigs. J. Lipid Res. 1999. 40: 1317–1327.
