Ezetimibe promotes CYP7A1 and modulates PPARs as a compensatory mechanism in LDL receptor-deficient hamsters

Background The LDL-C lowering effect of ezetimibe has been attributed primarily to increased catabolism of LDL-C via up-regulation of LDL receptor (LDLR) and decreased cholesterol absorption. Recently, ezetimibe has been demonstrated to have reverse cholesterol transport (RCT) promoting effects in mice, hamsters and humans. However, the underlying mechanisms are still not clear. The aim of this study is to investigate whether ezetimibe improves RCT-related protein expression in LDLR-/- hamsters. Methods A high-fat diet was used to induce a human-like hyperlipidemia in LDLR-/- hamsters. Lipid profiles were assayed by commercially available kits, and the effects of ezetimibe on lipid metabolism-related protein expression were carried out via western blot. Results Our data demonstrated that ezetimibe administration significantly reduced plasma total cholesterol (similar to 51.6% reduction, P < 0.01) and triglyceride (from similar to 884.1 mg/dL to similar to 277.3 mg/dL) levels in LDLR-/- hamsters fed a high-fat diet. Ezetimibe administration (25 mg/kg/d) significantly promoted the protein expression of cholesterol 7 alpha-hydroxylase A1 (CYP7A1), LXR beta and peroxisome proliferator-activated receptor (PPAR) gamma; and down-regulated the protein expression of PPAR alpha and PPAR beta. However, it showed no significant effect on sterol regulatory element-binding protein (SREBP)-1c, SREBP-2, proprotein convertase subtilisin/kexin type 9 (PCSK9), Niemann-Pick C1-like 1 (NPC1L1), and ATP-biding cassette (ABC) G5/G8. Conclusion Ezetimibe may accelerate the transformation from cholesterol to bile acid via promoting CYP7A1 and thereby enhance RCT. As a compensatory mechanism of TG lowering, ezetimibe promoted the protein expression of PPAR gamma and decreased PPAR alpha and beta. These results are helpful in explaining the lipid-lowering effects of ezetimibe and the potential compensatory mechanisms.