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Role of bile acids in the gut-liver axis

Published:March 05, 2018DOI:https://doi.org/10.1016/j.jhep.2017.11.025
      Bile acids (BAs) are the end products of hepatic cholesterol metabolism, assembled in the liver and transported across the canalicular membrane of hepatocytes as primary conjugated BAs into the biliary system, which finally drains them into the small intestine. Here, gut microbiota shape BAs’ biological activity by enzymatic modifications, yielding secondary BAs (Box 1). A total of 95% of BAs are reabsorbed in the terminal small intestine and cycle as much as six times per day within the enterohepatic circulation.
      • De Aguiar Vallim T.Q.
      • Tarling E.J.
      • Edwards P.A.
      Pleiotropic roles of bile acids in metabolism.
      They assist important physiological functions in nutrient absorption and biliary secretion of lipids, toxic metabolites and xenobiotics. Beside these well-known functions, accumulating data identify BAs as pleiotropic signaling molecules that control gut-liver crosstalk.
      • De Aguiar Vallim T.Q.
      • Tarling E.J.
      • Edwards P.A.
      Pleiotropic roles of bile acids in metabolism.
      • Wahlstrom A.
      • Sayin S.I.
      • Marschall H.-U.
      • Backhed F.
      Intestinal crosstalk between bile acids and microbiota and its impact on host metabolism.
      Figure thumbnail gr1
      Box 1Bile acid synthesis, circulation and biological signaling activity. CA, cholic acid; CDCA, chenodeoxycholic acid; Cyp7A1, colesterol 7 α-hydroxylase; DCA, deoxcholic acid; FXR, farnesoid X receptor; GCA, glycocholic acid; GCDCA, glycochenodeoxycholic acid; HCA, hyocholic acid; HDCA, hyodeoxycholic acid; LCA, lithocholic acid; MCA, muricholic acid; MDCA, murideoxycholic acid; TCA, taurocholic acid; TCDCA, taurochenodeoxycholic acid; TGR5, G protein-coupled bile acid receptor 1; T(α/β)MCA, tauro-(alpha/beta)-muricholic acid; UDCA, ursodeoxycholic acid.

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