Figure 2).

Regulation of bile acid (BA) absorption and transport. Adapted and used with permission from reference 10. In ileal enterocytes, farnesoid X receptor (FXR)-retinoid X receptor (RXR) regulates BA homeostasis by reducing BA uptake by the apical sodium-dependent bile acid transporter (ASBT), reducing intestinal absorption of BAs (A); and (B) increasing BA export by organic solute transporter alpha/beta (OSTα/β), reducing intracellular accumulation of BA. C Ileal bile acid binding protein (IBABP) is involved in FXR expression. D FXR effects are mediated by small heterodimer partner (SHP). E Ileal FXR also regulates BA production via fibroblast growth factor (FGF)19. F In hepatocytes, intracellular BA levels are regulated by Na⁺ taurocholate cotransporting polypeptide transporter (NTCP) and (G) the bile salt export pump (BSEP). H FGF19 activates FGFR4. I FGF receptor 4 (FGFR4) via FXR-RXR downregulates cholesterol 7α-hydroxylase (CYP7A) synthesis of BAs