Simvastatin Promotes The Expression Of Genes Associated With Reverse Cholesterol Transport In ApoE-knockout Mice Fed High-fat Diet

Objective:Statins are first-line phannacotherapeutic agents for hypercholesterolemia treatment in humans. However the effects of statins on atherosclerosis in mouse are very paradoxical. In this work, we wanted to evaluate the effects of simvastatin on serum cholesterol, atherogenesis, and the expression of several factors playing important roles in reverse cholesterol transport (RCT) in apoE-/-mice fed a high-fat diet.Methods:At8weeks of age,5male C57B/L6mice were definited to normal control group(n=5, vehicle treated group),20male apoE-/-mice were randomly divided into2groups, the model group (n=10, vehicle treated group) and the simvastatin (5mg/kg/d) treated group (n=10). All groups were fed an atherogenic high-fat diet (15.8%fat and1.25%cholesterol) supplemented with vehicle or simvastatin for6weeks. Vehicle or simvastatin were administered intragastrically once daily. After6weeks of treatment, blood was collected from the retro-orbital sinus of the mice. Concentrations of plasma total cholesterol (TC), HDL-C, and triglycerides (TG) were determined by enzymatic methods. Plasma concentrations of apolipoprotein A-I (apoA-I) was determined by ELISA kit. Endogenous lecithin-cholesterol acyltransferase (LCAT) activity was measured as the utilization rate of free cholesterol (FC) in native plasma. The mRNA abundance of genes involved in HDL-C metabolism in the peritoneal macrophage and the liver were determined by Quantitative Real-Time PCR methods. The protein abundance of transporters involved in HDL-C metabolism in the peritoneal macrophage and the liver were determined by Wstern Blot methods.Results:Plasma analysis by enzymatic method or ELISA showed that high-density lipoprotein-cholesterol (HDL-C) and apolipoprotein A-I (apoA-I) contents were remarkably increased by treatment with simvastatin (p<0.01). And plasma lecithin-cholesterol acyltransferase (LCAT) activity was markedly increased by simvastatin treatment (p<0.05). Real-time PCR detection disclosed that the expression of several transporters involved in reverse cholesterol transport, including macrophage scavenger receptor class B type Ⅰ (p0.05), hepatic ATP-binding cassette (ABC) transporters ABCG5(p<0.01), and ABCB4(p<0.01) were induced by simvastatin treatment, the expression of hepatic ABCAl (p<0.05) and apoA-Ⅰ(p<0.05), which play roles in the maturation of HDL-C, were also elevated in simvastatin treated groups. The elevation of the expression of macrophage scavenger receptor class B type Ⅰ (p<0.05) and hepatic ABCA1(p<0.01) and apoA-Ⅰ (p<0.05) in simvastatin treated groups were also be found by western blot.Conclusions:We demonstrated the anti-atherogenesis effects of simvastatin in apoE-/-mice fed a high-fat diet. We confirmed here for the first time simvastatin increased the expression of hepatic ABCB4and ABCG5, which involved in secretion of cholesterol and bile acids into the bile, besides upregulated ABCA1and apoA-Ⅰ. The elevated HDL-C level, increased LCAT activity and the stimulation of several transporters involved in RCT may all contribute to the anti-atherosclerotic effect of simvastatin.