title: The human UGT1A3 enzyme conjugates norursodeoxycholic acid into a C23-ester glucuronide in the liver.
abstract: Norursodeoxycholic acid (norUDCA) exhibits efficient anti-cholestatic properties in an animal model of sclerosing cholangitis. norUDCA is eliminated as a C(23)-ester glucuronide (norUDCA-23G) in humans. The present study aimed at identifying the human UDP-glucuronosyltransferase (UGT) enzyme(s) involved in hepatic norUDCA glucuronidation and at evaluating the consequences of single nucleotide polymorphisms in the coding region of UGT genes on norUDCA-23G formation. The effects of norUDCA on the formation of the cholestatic lithocholic acid-glucuronide derivative and of rifampicin on hepatic norUDCA glucuronidation were also explored. In vitro glucuronidation assays were performed with microsomes from human tissues (liver and intestine) and HEK293 cells expressing human UGT enzymes and variant allozymes. UGT1A3 was identified as the major hepatic UGT enzyme catalyzing the formation of norUDCA-23G. Correlation studies using samples from a human liver bank (n = 16) indicated that the level of UGT1A3 protein is a strong determinant of in vitro norUDCA glucuronidation. Analyses of the norUDCA-conjugating activity by 11 UGT1A3 variant allozymes identified three phenotypes with high, low, and intermediate capacity. norUDCA is also identified as a competitive inhibitor for the hepatic formation of the pro-cholestatic lithocholic acid-glucuronide derivative, whereas norUDCA glucuronidation is weakly stimulated by rifampicin. This study identifies human UGT1A3 as the major enzyme for the hepatic norUDCA glucuronidation and supports that some coding polymorphisms affecting the conjugating activity of UGT1A3 in vitro may alter the pharmacokinetic properties of norUDCA in cholestasis treatment.
authors.affiliation: Laboratory of Molecular Pharmacology, CHUQ Research Center, and the Faculty of Pharmacy, Laval University, Québec, Québec G1V 4G2, Canada.
authors.forename: Jocelyn
authors.initials: J
authors.lastname: Trottier
authors.forename: Diala
authors.initials: D
authors.lastname: El Husseini
authors.forename: Martin
authors.initials: M
authors.lastname: Perreault
authors.forename: Sophie
authors.initials: S
authors.lastname: Pâquet
authors.forename: Patrick
authors.initials: P
authors.lastname: Caron
authors.forename: Sylvie
authors.initials: S
authors.lastname: Bourassa
authors.forename: Mélanie
authors.initials: M
authors.lastname: Verreault
authors.forename: Ted T
authors.initials: TT
authors.lastname: Inaba
authors.forename: Guy G
authors.initials: GG
authors.lastname: Poirier
authors.forename: Alain
authors.initials: A
authors.lastname: Bélanger
authors.forename: Chantal
authors.initials: C
authors.lastname: Guillemette
authors.forename: Michael
authors.initials: M
authors.lastname: Trauner
authors.forename: Olivier
authors.initials: O
authors.lastname: Barbier
mesh_terms: D000818:Animals; D002460:Cell Line; D015209:Cholangitis, Sclerosing / Q000188:drug therapy / Q000201:enzymology / Q000235:genetics; D002793:Cholic Acids / Q000737:chemistry* / Q000627:therapeutic use; D004195:Disease Models, Animal; D004952:Esters / Q000737:chemistry / Q000378:metabolism; D020719:Glucuronides / Q000096:biosynthesis / Q000737:chemistry*; D014453:Glucuronosyltransferase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007527:Isoenzymes / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D008862:Microsomes, Liver / Q000201:enzymology*; D009654:Norsteroids / Q000737:chemistry* / Q000627:therapeutic use; D011110:Polymorphism, Genetic; D012293:Rifampin / Q000737:chemistry
chemical_list: D002793:Cholic Acids; D004952:Esters; D020719:Glucuronides; D007527:Isoenzymes; D009654:Norsteroids; C122075:UDP-glucuronosyltransferase, UGT1A3; D014453:Glucuronosyltransferase; D012293:Rifampin