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Expression of UDP-Glucuronosyltransferase 1 (UGT1) and Glucuronidation Activity toward Endogenous Substances in Humanized UGT1 Mouse Brain.

ABSTRACT: Although UDP-glucuronosyltransferases (UGTs) are important phase II drug-metabolizing enzymes, they are also involved in the metabolism of endogenous compounds. Certain substrates of UGTs, such as serotonin and estradiol, play important roles in the brain. However, the expression of UGTs in the human brain has not been fully clarified. Recently, humanized UGT1 mice (hUGT1 mice) in which the original Ugt1 locus was disrupted and replaced with the human UGT1 locus have been developed. In the present study, the expression pattern of UGT1As in brains from humans and hUGT1 mice was examined. We found that UGT1A1, 1A3, 1A6, and 1A10 were expressed in human brains. The expression pattern of UGT1As in hUGT1 mouse brains was similar to that in human brains. In addition, we examined the expression of UGT1A1 and 1A6 in the cerebellum, olfactory bulbs, midbrain, hippocampus, and cerebral cortex of hUGT1 mice. UGT1A1 in all brain regions and UGT1A6 in the cerebellum and cerebral cortex of 6-month-old hUGT1 mice were expressed at a significantly higher rate than those of 2-week-old hUGT1 mice. A difference in expression levels between brain regions was also observed. Brain microsomes exhibited glucuronidation activities toward estradiol and serotonin, with mean values of 0.13 and 5.17 pmol/min/mg, respectively. In conclusion, UGT1A1 and UGT1A6 might play an important role in function regulation of endogenous compounds in a region- and age-dependent manner. Humanized UGT1 mice might be useful to study the importance of brain UGTs in vivo.

SUBMITTER: Kutsuno Y

PROVIDER: S-EPMC4468441 | biostudies-literature | 2015 Jul

REPOSITORIES: biostudies-literature

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Project description:Interindividual variability in polymorphic uridine diphosphate-glucuronosyltransferase 1A1 (UGT1A1) ascribed to genetic diversity is associated with relative glucuronidation level among individuals. The present research was aimed to study the effect of 2 important single nucleotide polymorphisms (SNPs; rs8330 and rs10929303) of UGT1A1 gene on glucuronidation status of acetaminophen in healthy volunteers (n = 109). Among enrolled volunteers, 54.13% were male (n = 59) and 45.87% were female (n = 50). The in vivo activity of UGT1A1 was investigated by high-performance liquid chromatography-based analysis of glucuronidation status (ie, acetaminophen and acetaminophen glucuronide) in human volunteers after oral intake of a single dose (1000 mg) of acetaminophen. The TaqMan SNP genotyping assay was used for UGT1A1 genotyping. The wild-type genotype (C/C) was observed the most frequent one for both SNPs (rs8330 and rs10929303) and associated with fast glucuronidator phenotypes. The distribution of variant genotype (G/G) for SNP rs8330 was observed in 5% of male and 8% of the female population; however, for SNP rs10929303, the G/G genotype was found in 8% of both genders. A trimodal distribution (fast, intermediate, and slow) based on phenotypes was observed. Among the male participants, the glucuronidation phenotypes were observed as 7% slow, 37% intermediate, and 56% fast glucuronidators; however, these findings for the females were slightly different as 8%, 32%, and 60% respectively. The k-statistics revealed a compelling evidence for good concordance between phenotype and genotype with a k value of 1.00 for SNP rs8330 and 0.966 for SNP rs10929303 in our population.

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Project description:Wushanicaritin, a natural polyphenol compound, exerts many biological activities. This study aimed to characterize wushanicaritin glucuronidation by pooled human liver microsomes (HLM), human intestine microsomes and individual uridine diphosphate-glucuronosyltransferase (UGT) enzyme. Glucuronidation rates were determined by incubating wushanicaritin with uridine diphosphoglucuronic acid-supplemented microsomes. Kinetic parameters were derived by appropriate model fitting. Reaction phenotyping, the relative activity factor (RAF) and activity correlation analysis were performed to identify the main UGT isoforms. Wushanicaritin glucuronidation in HLM was efficient with a high CLint (intrinsic clearance) value of 1.25 and 0.69 mL/min/mg for G1 and G2, respectively. UGT1A1 and 1A7 showed the highest activities with the intrinsic clearance (CLint) values of 1.16 and 0.38 mL/min/mg for G1 and G2, respectively. In addition, G1 was significantly correlated with ?-estradiol glucuronidation (r = 0.847; p = 0.0005), while G2 was also correlated with chenodeoxycholic acid glucuronidation (r = 0.638, p = 0.026) in a bank of individual HLMs (n = 12). Based on the RAF approach, UGT1A1 contributed 51.2% for G1, and UGT1A3 contributed 26.0% for G2 in HLM. Moreover, glucuronidation of wushanicaritin by liver microsomes showed marked species difference. Taken together, UGT1A1, 1A3, 1A7, 1A8, 1A9 and 2B7 were identified as the main UGT contributors responsible for wushanicaritin glucuronidation.

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