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. Author manuscript; available in PMC: 2023 Apr 1.
Published in final edited form as: Neurogastroenterol Motil. 2021 Nov 9;34(4):e14287. doi: 10.1111/nmo.14287

Figure 1. Synthesis, secretion, and enterohepatic circulation of BAs in humans.

Figure 1.

(1) Primary BAs are synthesized in hepatocytes from cholesterol. (2) BAs are conjugated to glycine and taurine and are stored in the gallbladder at high concentrations. (3) After feeding, conjugated BAs are secreted in the intestine where they emulsify dietary fats and form mixed micelles that facilitate digestion and absorption of the products of triglyceride digestion. (4) Conjugated BAs are actively absorbed by the apical sodium BA co-transporter (IBAT) at the apical membrane of enterocytes of the terminal ileum. (5) In the colon, bacteria deconjugate and dehydroxylate primary BAs to form secondary BAs, which are passively absorbed. (6) Conjugated and unconjugated BAs enter the portal vein and recirculate to the liver for reuse. BA, bile acid; CA, cholic acid; CDCA, chenodeoxycholic acid; DCA, deoxycholic acid; IBAT, ileal bile acid transporter; LCA, lithocholic acid; Na, sodium; UDCA, ursodeoxycholic acid. Reproduced with permission from ref. 1, Bunnett NW. Neuro-humoral signalling by bile acis and the TGR5 receptor in the gastrointestinal tract. J Physiol 2014;592:2943–2950. All permission requests for this image should be made to the copyright holder.