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* Robarts Research Institute and Departments of Medicine and Biochemistry, University of Western Ontario, London, Ontario, Canada
Departments of Medicine, University of Western Australia, Perth, Australia
Pathology, University of Western Australia, Perth, Australia
** Department of Core Clinical Pathology and Biochemistry, Division of Laboratory Medicine, Royal Perth Hospital, Perth, Australia

Western Australian Institute for Medical Research, Perth, Australia

Cardiovascular and Metabolic Diseases Discovery Research, Pharmacia Corporation, St. Louis, MO 63167
1 To whom correspondence should be addressed. e-mail: mhuff{at}uwo.ca
Discovery of the ileal apical sodium-dependent bile acid transporter (ASBT) permitted development of specific inhibitors of bile acid reabsorption, potentially a new class of cholesterol-lowering agents. In the present study, we tested the hypothesis that combining the novel ASBT inhibitor, SC-435, with the HMG-CoA reductase inhibitor, atorvastatin, would potentiate reductions in LDL cholesterol (LDL-C) and LDL apolipoprotein B (apoB). ApoB kinetic studies were performed in miniature pigs fed a typical human diet and treated with the combination of SC-435 (5 mg/kg/day) plus atorvastatin (3 mg/kg/day) (SC-435+A) or a placebo. SC-435+A decreased plasma total cholesterol by 23% and LDL-C by 40%. Multicompartmental analysis (SAAM II) demonstrated that LDL apoB significantly decreased by 35% due primarily to a 45% increase in the LDL apoB fractional catabolic rate (FCR). SC-435+A significantly decreased hepatic concentrations of free cholesterol and cholesteryl ester, and increased hepatic LDL receptor mRNA consequent to increased cholesterol 7
-hydroxylase expression and activity. In comparison, SC-435 (10 mg/kg/day) monotherapy decreased LDL apoB by 10% due entirely to an 18% increase in LDL apoB FCR, whereas atorvastatin monotherapy (3 mg/kg/day) decreased LDL apoB by 30% due primarily to a 22% reduction in LDL apoB production.
We conclude that SC-435+A potentiates the reduction of LDL-C and LDL apoB due to complementary mechanisms of action.
Abbreviations: ASBT, apical sodium-dependent bile acid transporter; FCR, fractional catabolic rate; FXR, farnesoid X receptor; GAPDH, glyceraldehyde 3-phosphate dehydrogenase; LRH-1, liver receptor homolog-1; SHP, short heterodimer partner; SREBP, sterol regulatory element binding protein
Supplementary key words bile acid reabsorption atorvastatin kinetics cholesterol 7
-hydroxylase LDL receptor
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