Hepatic farnesoid X-receptor isoforms ?2 and ?4 differentially modulate bile salt and lipoprotein metabolism in mice.

ABSTRACT: The nuclear receptor FXR acts as an intracellular bile salt sensor that regulates synthesis and transport of bile salts within their enterohepatic circulation. In addition, FXR is involved in control of a variety of crucial metabolic pathways. Four FXR splice variants are known, i.e. FXR?1-4. Although these isoforms show differences in spatial and temporal expression patterns as well as in transcriptional activity, the physiological relevance hereof has remained elusive. We have evaluated specific roles of hepatic FXR?2 and FXR?4 by stably expressing these isoforms using liver-specific self-complementary adeno-associated viral vectors in total body FXR knock-out mice. The hepatic gene expression profile of the FXR knock-out mice was largely normalized by both isoforms. Yet, differential effects were also apparent; FXR?2 was more effective in reducing elevated HDL levels and transrepressed hepatic expression of Cyp8b1, the regulator of cholate synthesis. The latter coincided with a switch in hydrophobicity of the bile salt pool. Furthermore, FXR?2-transduction caused an increased neutral sterol excretion compared to FXR?4 without affecting intestinal cholesterol absorption. Our data show, for the first time, that hepatic FXR?2 and FXR?4 differentially modulate bile salt and lipoprotein metabolism in mice.

SUBMITTER: Boesjes M 

PROVIDER: S-EPMC4266635 | biostudies-literature | 2014

REPOSITORIES: biostudies-literature