title: Metabolism of 1'- and 4-hydroxymidazolam by glucuronide conjugation is largely mediated by UDP-glucuronosyltransferases 1A4, 2B4, and 2B7.
abstract: Midazolam undergoes oxidative hydroxylation by CYP3A to its metabolites, which are excreted mainly as glucuronidated conjugates into the urine. In this study, we examined the glucuronidation of hydroxymidazolam in human liver microsomes (HLMs) and characterized the UDP-glucuronosyltransferases (UGTs) involved in 1'- and 4-hydroxymidazolam glucuronidation. Among the 12 UGT isoforms tested, the O- and N-glucuronidation of 1'-hydroxymidazolam was mediated by UGT2B4/2B7 and 1A4, respectively. In contrast, the glucuronidation of 4-hydroxymidazolam was mediated by UGT1A4. Consistent with these observations, the UGT1A4 inhibitor hecogenin and the UGT2B7 substrate diclofenac potently inhibited the N- and O-glucuronidation of 1'-hydroxymidazolam in HLMs, respectively. A correlation analysis of UGT enzymatic activity and the formation rate of glucuronide metabolites from 1'- and 4-hydroxymidazolam in 25 HLMs showed that hydroxymidazolam glucuronidation is correlated with UGT1A4-mediated lamotrigine glucuronidation and UGT2B7-mediated diclofenac glucuronidation activity. Taken together, these findings indicate that UGT1A4, 2B4, and 2B7 are major isoforms responsible for glucuronide conjugate formation from 1'- and 4-hydroxymidazolam, which are the two major oxidative metabolites of midazolam.
authors: Department of Pharmacology and PharmacoGenomics Research Center, Inje University College of Medicine, Busan, Korea.
authors: Kyung-Ah
authors: KA
authors: Seo
authors: Soo Kyung
authors: SK
authors: Bae
authors: Young-Kil
authors: YK
authors: Choi
authors: Chang Soo
authors: CS
authors: Choi
authors: Kwang-Hyeon
authors: KH
authors: Liu
authors: Jae-Gook
authors: JG
authors: Shin
mesh_terms: D002851:Chromatography, High Pressure Liquid; D020719:Glucuronides / Q000378:metabolism*; D014453:Glucuronosyltransferase / Q000378:metabolism*; D006801:Humans; D006900:Hydroxylation; D066298:In Vitro Techniques; D050217:Metabolic Detoxication, Phase II; D008862:Microsomes, Liver / Q000201:enzymology / Q000378:metabolism; D008874:Midazolam / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism; D015394:Molecular Structure; D011994:Recombinant Proteins / Q000378:metabolism; D053719:Tandem Mass Spectrometry
chemical_list: D020719:Glucuronides; D011994:Recombinant Proteins; C019787:bilirubin glucuronoside glucuronosyltransferase; C042940:4-hydroxymidazolam; C040081:1-hydroxymethylmidazolam; C491474:UGT2B7 protein, human; D014453:Glucuronosyltransferase; C486404:UGT2B4 protein, human; D008874:Midazolam