PT - JOURNAL ARTICLE AU - Wushuang Zeng AU - Lanlan Gui AU - Xianwen Tan AU - Pingping Zhu AU - Yiting Hu AU - Qingliang Wu AU - Xuejing Li AU - Lian Yang AU - Wei Jia AU - Changxiao Liu AU - Ke Lan TI - Tertiary oxidation of deoxycholate is predictive of CYP3A activity in dogs AID - 10.1124/dmd.121.000385 DP - 2021 Jan 01 TA - Drug Metabolism and Disposition PG - DMD-AR-2021-000385 4099 - http://dmd.aspetjournals.org/content/early/2021/03/05/dmd.121.000385.short 4100 - http://dmd.aspetjournals.org/content/early/2021/03/05/dmd.121.000385.full AB - Deoxycholate (DCA) is the major circulating secondary bile acid (BA), which is synthesized by gut flora in lower gut and selectively oxidized by CYP3A into tertiary metabolites including DCA-1β-ol and DCA-5β-ol in human. Since DCA has the similar "exogenous" nature and disposition mechanisms as xenobiotics, this work aimed to investigate whether the tertiary oxidations of DCA are predictive of in vivo CYP3A activities in beagle dogs. In vitro metabolism of midazolam (MDZ) and DCA in recombinant canine CYP1A1, 1A2, 2B11, 2C21, 2C41, 2D15, 3A12, 3A26 enzymes clarified that CYP3A12 was primarily responsible for either the oxidation elimination of MDZ or the regioselective oxidation metabolism of DCA into DCA-1β-ol and DCA-5β-ol in dog liver microsomes. Six male dogs completed the CYP3A intervention studies including phases of baseline, inhibition (ketoconazole treatments), recovery and induction (rifampicin treatments). The oral MDZ clearance after a single dose was determined on the last day of the baseline, inhibition and induction phases, and subjected to correlation analysis with the tertiary oxidation ratios of DCA detected in serum and urine samples. The results confirmed that the pre-dosing serum ratios of DCA oxidation, DCA-5β-ol/DCA and DCA-1β-ol/DCA, were significantly and positively correlated both intra-individually and inter-individually with oral MDZ clearance. It was therefore concluded that the tertiary oxidation of DCA is predictive of CYP3A activity in beagle dogs. Clinical transitional studies following the preclinical evidence are promising to provide novel biomarkers of the enterohepatic CYP3A activities. Significance Statement Drug development, clinical pharmacology and therapeutics are under insistent demands of endogenous CYP3A biomarkers that avoid unnecessary drug exposure and invasive sampling. This work has provided the first proof-of-concept preclinical evidence for that the CYP3A catalyzed tertiary oxidation of deoxycholate, the major circulating secondary bile acid synthesized in lower gut by bacteria, may be developed as novel in vivo biomarkers of the enterohepatic CYP3A activities.