Cholestyramine alters bile acid amounts and the expression of cholesterol-related genes in rabbit intestinal and hepatic tissues

OBJECTIVE: Cholestyramine (CHO), as a bile acid sequestering exchange resin, has been widely used to treat hypercholesterolemia. The aim of this study was to explore how CHO regulated serum cholesterol amounts and bile acid levels in animal models. METHODS: New Zealand White rabbits were randomly assigned to the control (given distilled water) and CHO-treated (given CHO solution 1 g/kg per day for 2 weeks) groups. To assess bile acid pool size, bile fistulas were constructed in five rabbits in each group. Serum cholesterol levels and biliary and fecal bile outputs were determined. Liver cholesterol 7 alpha-hydroxylase (CYP7A1), small heterodimer partner (SHP), bile salt export pump (BSEP), ileal bile acid-binding protein (IBABP) and LDL receptor (LDL-R) mRNA expressions were assessed by real-time polymerase chain reaction. CYP7A1 activity was also determined. RESULTS: CHO treatment decreased serum cholesterol levels by 12.1%. Although CHO did not change the bile acid pool size and biliary bile acid output, it significantly increased fecal bile acid output. Interestingly, CHO also significantly increased the expression and activity of CYP7A1, as well as IBABP and LDL-R mRNA expressions, but decreased hepatic SHP and BSEP gene expressions. CONCLUSION: CHO markedly alters bile acid and cholesterol amounts in rabbit intestinal and liver tissues, downregulating genes responsible for cholesterol homeostasis.