Preliminary experimental research on the mechanism of liver bile secretion stimulated by peppermint oil.

To investigate the choleretic effect and molecular mechanisms of action of peppermint oil (PO), the main component of Danshu capsules (Sichuan Jishengtang Pharmaceutical Co., Ltd., Pengzhou, Sichuan Province, China). Bile secretion was measured by biliary drainage in rats. Total bile acids, total cholesterol and bilirubin in bile were determined. Cholesterol 7α-hydroxylase (CYP7A1), and farnesoid X receptor (FXR) messenger ribonucleic acid (mRNA) levels were assessed in HepG2 cells (a human hepatocellular carcinoma cell line) by reverse transcription polymerase chain reaction (RT-PCR). PO significantly promoted bile and bile acid secretion in rats. It also increased bile acid efflux and decreased cholesterol levels (P < 0.01) in bile. In HepG2 cells the mRNA levels of CYP7A1 and FXR were significantly upregulated after treatment with PO. PO stimulates bile fluid secretion and thus has a choleretic effect. PO might play a role in upregulating CYP7A1 and FXR mRNA levels, suggesting that the molecular mechanisms are related to gene expression involved in bile acid synthesis.