FIGURE 7.
A proposal of the regulatory loop of miR-24, miR-34a, and HNF4α in bile acid synthesis. Bile acids are known to activate PKC and ROS generation, resulting in the activation of MAPK pathway. The miR-24 and miR-34a expression are induced by MAPK-dependent and -independent pathways, respectively. In turn, miR-24 and miR-34a negatively regulate the HNF4α. The down-regulation of HNF4α decreases the expression of bile acid-synthesizing enzymes CYP7A1 and CYP8B1, resulting in the decrease of bile acids.