An extract from red ginseng [steamed and dried roots of Panax ginseng C.A. Meyer (RGE)] has been shown to have various actions on physiological functions. The mechanisms by which RGE promotes cholesterol metabolism in the liver are unclear, but RGE decreases the plasma levels of cholesterol. We investigated whether RGE affected the mRNA expression of cholesterol metabolism-related proteins such as cytochrome P450 (CYP)7A1 and bile salt export pump (BSEP) in the liver in hypercholesterolemic rats and rat primary hepatocytes. In-vivo studies showed the upregulation of CYP7A1 mRNA in hypercholesterolemic rats treated with RGE. Treatment with RGE exhibited decreased ratios of low-density lipoprotein-cholesterol to high-density lipoprotein-cholesterol compared with hypercholesterolemia without RGE. In-vitro studies also showed the upregulation of CYP7A1 mRNA and protein levels by the addition of RGE to rat primary hepatocytes. The mRNA levels of BSEP exhibited few changes. The sustained levels of the liver X receptor (LXR) in vivo and the increased levels of LXR in vitro on RGE treatment could be involved in the upregulation of CYP7A1. To clarify the effects of 11 ginsenosides including RGE on the mRNA levels of CYP7A1 and BSEP, we performed in-vitro experiments using rat primary hepatocytes. The ginsenosides Ro, Rg3, Re, Rg1, and Rg2 exhibited increased mRNA levels of CYP7A1. These results suggest that several ginsenosides including RGE promoted cholesterol metabolism due to upregulation of CYP7A1.

An extract from red ginseng (steamed and dried roots of Panax ginseng C.A. Meyer; RGE) has been shown to promote cholesterol metabolism in the liver. We have reported that RGE induced the hepatic expression of cytochrome P450 (CYP)7A1, involved in cholesterol metabolism. Other cholesterol metabolism-related proteins, such as CYP8B1, CYP27A1, multidrug resistance-associated protein (MRP)2, MRP3, and Na(+) taurocholate cotransporting polypeptide (NTCP), are involved in cholesterol metabolism. The purpose of this study was to clarify whether RGE affected mRNA expression of cholesterol metabolism-related CYPs and transporters in the liver of hypercholesterolemic rats and rat primary hepatocytes. In-vivo studies showed little differences in CYP8B1, CYP27A1, MRP2, MRP3, and NTCP mRNA expression levels between hypercholesterolemic rats with or without RGE treatments. However, the disruption of the membrane localization of MRP2 was suppressed by RGE treatments in hypercholesterolemic rats. In-vitro studies using rat primary hepatocytes showed upregulation of CYP8B1 and MRP2 mRNA by the addition of RGE (100 and 500 μg/mL). We further examined which ginsenosides contributed to the upregulation of CYP8B1 and MRP2 mRNA levels. Ginsenoside Re enhanced the mRNA level of CYP8B1, whereas ginsenosides Rb2 and Rg2 enhanced MRP2 mRNA levels. These results suggest that the in-vitro exposure of hepatocytes to RGE or some ginsenosides could lead to upregulation of CYP8B1 and MRP2, resulting in the alteration of biosynthesis and disposition of bile acids.