Objective   To investigate the molecular mechanism of the effect of fatty acid on cholesterol homeostasis.

  Methods   C57BL/6J mice(n=75)were randomly divided into five groups and respectively received formula mash for 6 weeks.

  Results   Compared with the results observed in mice fed Chol diet, the mice fed Chol+PUFA diet had signiacant higher(P<0.05)serum total cholesterol and bile acid pool, lower(P<0.05)liver cholesterol; Chol+MUFA diet resulted the same serum total cholesterol, higher(P<0.05)bile acid pool, lower(P<0.05)liver cholesterol level; Chol+SFA diet resulted higher(P<0.05)serum total cholesterol and liver cholesterol, lower(P<0.05)bile acid pool. In addition, PUFA, MUFA and SFA all decreased mRAN and protein expression of C YP7a1 in liver.

  Conclusion   The effect of fatty acid on cholesterol level was related to C YP7a1 and the type of dietary fat important in elaborating the regulatory potential on it. PU FA and MUFA may maintain body cholesterol homeostasis by increasing the conversion of cholesterol to bile acid, and the lowered C YP7a1 gene expression likely resulted from the rising feedback inhibition of total bile acid returning to the liver rather than direct inhibition. Hypercholesterolemia SFA may be mediated through its inhibitory effect or no effect on cyp7a1 in the liver directly.