PT  - JOURNAL ARTICLE
AU  - Anand K. Deo
AU  - Stelvio M. Bandiera
TI  - Identification of Human Hepatic Cytochrome P450 Enzymes Involved in the Biotransformation of Cholic and Chenodeoxycholic Acid
AID  - 10.1124/dmd.108.022194
DP  - 2008 Oct 01
TA  - Drug Metabolism and Disposition
PG  - 1983--1991
VI  - 36
IP  - 10
4099  - http://dmd.aspetjournals.org/content/36/10/1983.short
4100  - http://dmd.aspetjournals.org/content/36/10/1983.full
SO  - Drug Metab Dispos2008 Oct 01; 36
AB  - 3α,7α,12α-Trihydroxy-5β-cholan-24-oic (cholic) and 3α,7α-dihydroxy-5β-cholan-24-oic (chenodeoxycholic) acids are the predominant hepatic and biliary bile acids of most mammalian species including humans. Cholic and chenodeoxycholic acids are synthesized from cholesterol and accumulate in the liver during cholestasis. Biotransformation by hepatic cytochrome P450 (P450) enzymes represents a potentially effective pathway for elimination of these lipid-soluble bile acids. We developed a liquid chromatography/mass spectrometry-based assay to identify and quantify the human hepatic microsomal metabolites of cholic acid and chenodeoxycholic acid, and using a panel of human recombinant P450 enzymes, we determined the P450 enzymes involved. Incubation of cholic acid with human hepatic microsomes and NADPH produced a single metabolite, 7α,12α-dihydroxy-3-oxo-5β-cholan-24-oic (3-dehydrocholic) acid. Of the recombinant P450 enzymes tested, only CYP3A4 catalyzed 3-dehydrocholic acid formation. Similar experiments with chenodeoxycholic acid revealed the formation of 7α-hydroxy-3-oxo-5β-cholan-24-oic acid and 3α,6α,7α-trihydroxy-5β-cholan-24-oic (γ-muricholic) acid as major metabolites and 3α-hydroxy-7-oxo-5β-cholan-24-oic (7-ketolithocholic) acid and cholic acid as minor metabolites. Among the human recombinant P450 enzymes examined, CYP3A4 exhibited the highest rates of formation for 7α-hydroxy-3-oxo-5β-cholan-24-oic acid and γ-muricholic acid from chenodeoxycholic acid. Formation of 7-ketolithocholic acid and cholic acid from chenodeoxycholic acid has not been reported previously and could not be attributed to any of the recombinant P450 enzymes tested. In conclusion, the predominant pathway for the biotransformation of both cholic and chenodeoxycholic acids in human hepatic microsomes was oxidation at the third carbon of the cholestane ring. This study highlights a major role for CYP3A4 and suggests a possible route for the elimination of these two bile acids. The American Society for Pharmacology and Experimental Therapeutics