Bilirubin and Bile Acids

Bilirubin and bile acids are essential endogenous metabolites primarily managed by the hepatobiliary system. Bilirubin is a yellow tetrapyrrole pigment produced from the breakdown of heme, while bile acids are steroid-based detergents synthesized from cholesterol in the liver (PubChem CID 5280352). Both substances play critical roles in physiology: bile acids facilitate the emulsification and absorption of dietary fats and vitamins, while bilirubin acts as a potent antioxidant at physiological levels. In clinical medicine, they are primarily utilized as diagnostic biomarkers; elevated levels in the blood (hyperbilirubinemia and elevated serum bile acids) are hallmark indicators of liver dysfunction, biliary obstruction, or hemolytic disorders (StatPearls: Jaundice). Although they are not therapeutic targets in the classical sense, the proteins that regulate their transport (such as OATPs, NTCP, and BSEP) and signaling (such as FXR and TGR5) are major targets for treating cholestatic liver diseases and metabolic conditions (UniProt Q96RI1, Q8TDU6). Drugs like obeticholic acid and ursodeoxycholic acid are used to modulate these pathways to prevent hepatotoxicity and improve bile flow. Additionally, bilirubin metabolism is a key consideration in drug-drug interactions, as many pharmaceuticals compete for the same hepatic transporters and enzymes (Frontiers in Pharmacology, 2018).

Other names

Bile saltsHematoidinCholic acidsBilirubinoidsBile pigments

FXR agonism, TGR5 agonism, ASBT inhibition, UGT1A1 induction, and bile acid sequestration.