Bile acids and their signaling pathways: eclectic regulators of diverse cellular functions

The field of bile acids has witnessed an impulse in the last two decades. This has been the result of cloning the genes encoding enzymes of bile acid synthesis and their transporters. There is no doubt that the identification of Farnesoid X Receptor (FXR, NR1H4) as the bile acid receptor has contributed substantially to attract the interest of scientists in this area. When FXR was cloned by Forman et al. [1], farnesol metabolites were initially considered the physiological ligands. After identifying FXR and other nuclear receptors as bile acid sensors [2-4], it has become clear that bile acids are involved in the regulation of lipid and glucose metabolism and that these molecules are eclectic regulators of diverse cellular functions. In this review, we will summarize the current knowledge of the functions regulated by bile acids and how their physiological receptors mediate the signaling underlying numerous cellular responses.