3β-Isoobeticholic acid efficiently activates the farnesoid X receptor (FXR) due to its epimerization to 3α-epimer by hepatic metabolism.
Bile acids (BAs) are important signaling molecules acting via the farnesoid X nuclear receptor (FXR) and the membrane G protein-coupled bile acid receptor 1 (GPBAR1). Besides deconjugation of BAs, the oxidoreductive enzymes of colonic bacteria and hepatocytes enable the conversion of BAs into their epimers or dehydrogenated forms. Obeticholic acid (OCA) is the first-in-class BA-derived FXR agonist approved for the treatment of primary biliary cholangitis. Herein, a library of OCA derivatives, including 7-keto, 6-ethylidene derivatives and 3β-epimers, was synthetized and investigated in terms of interactions with FXR and GPBAR1 in transaction assays and evaluated for FXR target genes expression in human hepatocytes and C57BL/6 mice. The derivatives were further subjected to cell-free analysis employing in silico molecular docking and a TR-FRET assay. The conversion of the 3βhydroxy epimer and its pharmacokinetics in mice were studied using LC-MS. We found that only the 3β-hydroxy epimer of OCA (3β-isoOCA) possesses significant activity to FXR in hepatic cells and mice. However, in a cell-free assay, 3β-isoOCA had about 9-times lower affinity to FXR than did OCA. We observed that 3β-isoOCA readily epimerizes to OCA in hepatocytes and murine liver. This conversion was significantly inhibited by the hydroxy-Δ5-steroid dehydrogenase inhibitor trilostane. In addition, we found that 3,7-dehydroobeticholic acid is a potent GPBAR1 agonist. We conclude that 3β-isoOCA significantly activates FXR due to its epimerization to the more active OCA by hepatic metabolism. Other modifications as well as epimerization on the C3/C7 positions and the introduction of 6-ethylidene in the CDCA scaffold abrogate FXR agonism and alleviate GPBAR1 activation.
['Stefela|Alzbeta|A|', 'Kaspar|Miroslav|M|', 'Drastik|Martin|M|', 'Holas|Ondrej|O|', 'Hroch|Milos|M|', 'Smutny|Tomas|T|', 'Skoda|Josef|J|', 'Hutníková|Miriama|M|', 'Pandey|Amit V|AV|', 'Micuda|Stanislav|S|', 'Kudova|Eva|E|', 'Pavek|Petr|P|']
D000818:Animals D002460:Cell Line D002635:Chenodeoxycholic Acid D002522:Chlorocebus aethiops D006801:Humans D007536:Isomerism D008099:Liver D008297:Male D008810:Mice, Inbred C57BL D018160:Receptors, Cytoplasmic and Nuclear D043562:Receptors, G-Protein-Coupled
Metabolism Bile acids Nuclear receptors Pharmacokinetics Gene regulation