Cholestasis-induced bile acid elevates estrogen level via farnesoid X receptor-mediated suppression of the estrogen sulfotransferase SULT1E1.

The liver is the main site of estrogen metabolism, and liver disease is usually associated with an abnormal estrogen status. However, little is known about the mechanism underlying this connection. Here, we investigated the effects of bile acid (BA)-activated farnesoid X receptor (FXR) on the metabolism of 17β-estradiol (E2) during blockage of bile flow (cholestasis). Correlations between BA levels and E2 concentrations were established in patients with cholestasis, and hepatic expression profiles of key genes involved in estrogen metabolism were investigated in both WT and FXR^-/- mice. We found that the elevated E2 level positively correlated with BA concentrations in the patients with cholestasis. We further observed that bile duct ligation (BDL) increases E2 levels in mouse serum, and this elevation effect was alleviated by deleting the FXR gene. Of note, FXR down-regulated the expression of hepatic sulfotransferase SULT1E1, the primary enzyme responsible for metabolic estrogen inactivation. At the molecular level, we found that FXR competes with the protein acetylase CREB-binding protein (CBP) for binding to the transcription factor hepatocyte nuclear factor 4α (HNF4α). This competition decreased HNF4α acetylation and nuclear retention, which, in turn, repressed HNF4α-dependent SULT1E1 gene transcription. These findings suggest that cholestasis induces BA-activated FXR activity, leading to downstream inhibition of SULT1E1 and hence impeding hepatic degradation of estrogen.

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