Raised hepatic bile acid concentrations during pregnancy are associated with reduced Farnesoid-X-Receptor
function.
Alexandra Milona1, Bryn M Owen1, Jeremy Cobbold2, Ellen CL Willemsen3, Jane Cox2, Mohamed Boudjelal4,
William Cairns4, Kristina Schoonjans5, Simon Taylor-Robinson2, Leo WJ Klomp3, Malcolm G Parker1, Roger
White1, Catherine Williamson1, Saskia WC van Mil5
1
Institute of Reproductive and Developmental Biology, Division of Medicine, Imperial College London, U.K.
Translational MR Spectroscopy Grouping, Division of Clinical Sciences, Imperial College London, U.K.
3
Department of Metabolic and Endocrine Diseases and Netherlands Metabolomics Center, University Medical
Center Utrecht, The Netherlands.
4
GlaxoSmithKline, New Frontiers Science Park, Essex, U.K.
5
Ecole Polytechnique Federale de Lausanne, Lausanne, Switzerland.
2
Intrahepatic cholestasis of pregnancy (ICP) is associated with raised maternal bile acid levels, fetal distress and
unexplained intrauterine death. The etiology of ICP is poorly understood. However, heterozygous mutations in
bile acid homeostasis genes together with the high estrogen and progesterone concentrations during pregnancy,
are thought to unmask cholestatic disease in otherwise asymptomatic individuals.
In this report, in order to obtain better insights in the etiology of ICP, we aimed to study bile acid homeostasis in
pregnant mice. Therefore, bile acid concentrations in liver and serum were assayed and gene expression profiling
in livers of normal and pregnant mice was conducted.
We show that normal pregnant mice have raised hepatic and serum bile acid levels in the presence of procholestatic gene expression profile. The bile acid sensor Farnesoid X receptor (Fxr) regulates transcription of the
majority of these differentially expressed genes and we show that in Fxr null mice and in CA fed mice the
accumulation of hepatic bile acids during pregnancy did not occur, suggesting that the function of Fxr is
perturbed during pregnancy in wild-type mice. In subsequent in vitro experiments, serum from pregnant mice
and humans repressed Fxr target gene expression in rat hepatoma-derived FAO cells. This inhibition was
abolished by co-incubation with the estrogen receptor (ER) antagonist Fulvestrant (ICI 182780), suggesting that
ER and estrogens circulating in pregnant serum play a role in Fxr repression in the liver. We next showed that in
reporter assays, FXR transcriptional activation was repressed upon cotransfection with ER and estrogen
stimulation. Finally, Fxr interacts with ERα/β in vitro in a ligand-dependent manner in GST pulldown assays,
suggesting that estrogens via their receptor ER transrepress Fxr function.
In conclusion, we provide evidence that ligand-activated ERα/β inhibits Fxr function during pregnancy resulting
in a pro-cholestatic gene expression profile and raised hepatic and serum bile acid concentrations. We propose
that this will cause ICP in genetically pre-disposed individuals.