Lack of Association between Common Polymorphisms in UGT1A9 and Gene Expression and Activity

Abstract

ABSTRACT:Interindividual variability in the glucuronidation of xenobiotics metabolized by UDP-glucuronosyltransferase 1A9 (UGT1A9) suggests the presence of functional UGT1A9 variants. The aim of this study was to evaluate whether the putative functionality of the UGT1A9 variants ؊118T 9Ͼ10 (rs3832043), I399C>T (rs2741049), ؊275T>A (rs6714486), and ؊2152C>T (rs17868320) could be confirmed in an independent study. UGT1A9 genotypes and UGT1A9 activity (i.e., flavopiridol and mycophenolic acid glucuronidation) were determined in 46 Caucasian human livers. mRNA levels were quantitated by real-time polymerase chain reaction in 35 of these livers. In addition, samples from 60 unrelated Caucasians belonging to the HapMap Project were also genotyped to confirm the allele frequencies and linkage disequilibrium (LD) pattern observed in our Caucasian livers. The allele frequencies of the ؊118T 9Ͼ10 , I399C>T, ؊275T>A, and ؊2152C>T variants were 0.39, 0.39, 0.02, and 0.02 in the livers, respectively. The I399C>T variant was in complete LD (r 2 ‫؍‬ 1) with ؊118T 9Ͼ10 (linked alleles: C and T 9 , respectively). Complete LD between these two variants was also found in the HapMap samples (frequencies of ؊118T 9Ͼ10 and I399C>T ‫؍‬ 0.38). I399C>T and ؊118T 9Ͼ10 correlated with neither UGT1A9 activities nor mRNA levels. Because of the low frequencies of the ؊275T>A and ؊2152C>T variants, an effect on phenotype could not be evaluated. Our data demonstrate that the common I399C>T and ؊118T 9Ͼ10 polymorphisms do not explain interindividual variation in hepatic UGT1A9 activity and mRNA expression and are in complete LD in the donor liver samples we studied.

Close Association of UGT1A9 IVS1+399C>T with UGT1A1*28, *6, or *60 Haplotype and Its Apparent Influence on 7-Ethyl-10-hydroxycamptothecin (SN-38) Glucuronidation in Japanese

“…Girard et al (2006) have shown that I399CϾT was associated with increased UGT1A9 protein levels and enzyme activity toward an UGT1A9 probe drug propofol using 48 human liver microsomes derived mainly from whites. In contrast, using human liver microsomes from 46 white subjects, Ramírez et al (2007) have revealed that the I399CϾT had no significant effects on UGT1A9 mRNA levels and in vitro glucuronidation activities toward the two UGT1A9 substrates, flavopiridol and mycophenolic acid. Furthermore, another report has demonstrated that I399CϾT had no influence on the pharmacokinetic parameters (such as AUC and C max ) of mycophenolic acid in 80 Japanese renal transplant recipients (Inoue et al, 2007).…”

“…With the same UGT1A1 diplotypes, patients with I399T/T (and UGT1A9 Ϫ126_Ϫ118T 10 /T 10 ) have shown higher SN-38G C max than I399C/T (and T 9 /T 10 ) patients. UGT1A9*1b (UGT1A9 Ϫ126_Ϫ118T 9 ϾT 10 ) has been shown to have no affect on UGT1A9 expression levels (Girard et al, 2006;Ramírez et al, 2007;Sandanaraj et al, 2008). Thus, two groups did suggest that I399T allele was associated with higher glucuronidation activity.…”

“…Thus, two groups did suggest that I399T allele was associated with higher glucuronidation activity. However, using human liver microsomes, Ramírez et al (2007) showed that I399CϾT had no significant effect on both UGT1A9 mRNA levels and glucuronidation activities for two UGT1A9 substrates. Therefore, the roles of I399CϾT in UGT1A9 activities as well as SN-38 glucuronidation remain inconclusive.…”

Influence of sex on propofol metabolism, a pilot study: implications for propofol anesthesia

“…Additionally, the UGT1A9 allele carrying the regulatory polymorphisms at positions -275 A/-2152 T in the promoter region was associated with higher UGT1A9 expression level and increased rate of propofol glucuronidation in 48 human liver microsomes (HLM) panel [14]. Conversely, a more recent study by Ramirez and colleagues found no relationship between -275 A/-2152 T SNPs and UGT1A9 gene expression or activity studied in 106 HLM [15].…”

Glucuronidation of OTS167 in Humans Is Catalyzed by UDP-Glucuronosyltransferases UGT1A1, UGT1A3, UGT1A8, and UGT1A10

“…Measurements of glucuronidation activities toward thyroxine (UGT1A1 and UGT1A3 substrate) (Tong et al, 2007;Yamanaka et al, 2007;Yoder Graber et al, 2007;Kato et al, 2008), SN-38 (UGT1A1 substrate) (Iyer et al, 1998;Hanioka et al, 2001;Gagné et al, 2002), mycophenolic acid (UGT1A9 substrate) (Bernard and Guillemette, 2004;Miles et al, 2005), and testosterone (UGT2B17 substrate) , and quantitation of mRNA levels (UGT1A1, UGT1A3, UGT1A9, and UGT2B17) in this set of HLM were previously described (Iyer et al, 1999;Ramírez et al, 2007;Yoder Graber et al, 2007;Kang et al, 2010;Liu et al, 2014).…”