Green tea catechin enhances cholesterol 7alpha-hydroxylase gene expression in HepG2 cells

Green tea catechins are known to have hypocholesterolaemic effects in animals and human subjects. In the present study, we investigated the effects of green tea catechins on the mRNA level and promoter activity of hepatic cholesterol 7alpha-hydroxylase (CYP7A1), the rate-limiting enzyme in the conversion of cholesterol to bile acids, in human hepatoma cells. Real-time PCR assays showed that different catechins, (-)-epicatechin gallate (ECG), (-)-epigallocatechin-3-gallate (EGCG), (-)-epigallocatechin (EGC) and (-)-epicatechin (EC), up regulated the CYP7A1 mRNA level by 5.5-, 4.2-, 2.9- and 1.9-fold, respectively, compared with the control. The -1312/+358 bp of the CYP7A1 promoter was subcloned into the pGL3 basic vector that includes luciferase as a reporter gene. ECG or EGCG significantly increased CYP7A1 promoter activity by 6.0- or 4.0-fold, respectively, compared with the control. Also, EGCG stimulated CYP7A1 at both mRNA level and promoter activity in a dose-dependent manner. These results suggest that the expression of the CYP7A1 gene may be directly regulated by green tea catechins at the transcriptional level.