CCK and obesity due to melanocortin 4 receptor deficiency: DCA is a secondary bile acid formed by intestinal bacteria from cholic acid; TCA and TCDCA are primary bile acids formed from cholic acid and kenodeoxycholic acid conjugated with taurine and have been used as cholecystokinin agents; and TCA and DCA have been reported to improve obesity via the G protein-coupled bile acid receptor Gpbar1 (TGR5)-dependent pathway [60,61].