Discovery of novel cholic acid derivatives as highly potent agonists for G protein-coupled bile acid receptor

In this study, fourteen new cholic acid (CA) derivatives were designed and synthesized, and the GloSensor cAMP accumulation assay indicated that all derivatives could activate the Takeda G protein-coupled receptor 5 (TGR5). Methylation of 7- and 12-hydroxyl groups in CA significantly increased TGR5 agonism for the new derivatives. For example, 7,12-dimethoxy derivative B1 exhibited 78-fold higher potency for TGR5 than the 7,12-dihydroxyl derivative A1 and 258-fold higher potency than CA itself. On the other hand, A1 positively modulated chenodeoxycholic acid (CDCA) functional activity in TGR5, whereas B1 did not show similar activity. Molecular docking experiments indicated that A1 formed a hydrogen bond between the 12-OH and amino acid Thr131 of TGR5, which is significant for its allosteric property. However, methylation at the 12-hydroxyl group in CA (derivative B1) disrupted this pivotal H-bond. Therefore, the free 12-hydroxyl group is essential for the CA derivatives in TGR5 allosteric agonism. Overall, we discovered a highly potent TGR5 agonist, B1, which can be used as lead compound for further study.