Physiological bile acid and bilirubin homeostasis

Physiological bile acid and bilirubin homeostasis refers to the integrated regulatory network responsible for the synthesis, transport, and excretion of bile salts and heme degradation products [Physiological Reviews, 2003]. This system is not a single molecular target but a coordinated pathway involving nuclear receptors like the Farnesoid X Receptor (FXR), enzymes such as UDP-glucuronosyltransferase 1A1 (UGT1A1), and various hepatic transporters including OATP1B1 and BSEP [Hepatology, 2009; Pharmacological Reviews, 2010]. Bile acids are essential for the emulsification of dietary lipids and act as signaling molecules that regulate systemic metabolism [Genes & Development, 2008]. Bilirubin, a byproduct of heme catabolism, requires efficient conjugation by UGT1A1 and transport by MRP2 to prevent toxic accumulation [StatPearls, 2023]. Dysregulation of these processes leads to pathological conditions such as cholestasis, jaundice, and primary biliary cholangitis [The Lancet, 2018]. Pharmacological interventions typically target specific components of this network, such as using FXR agonists like obeticholic acid to reduce bile acid synthesis or enzyme inducers to enhance bilirubin clearance [NEJM, 2016].

Other names

Bile acid and bilirubin metabolismEnterohepatic circulation of bile salts and pigments

Regulation of bile acid and bilirubin levels through the activation of nuclear receptors (e.g., FXR), induction of conjugating enzymes (e.g., UGT1A1), and modulation of hepatic transporters (e.g., OATPs, BSEP, MRP2) [Physiological Reviews, 2003; StatPearls, 2023].