Genetic polymorphisms of UGT1A6 in a Japanese population

Thirteen single nucleotide polymorphisms (SNPs), including 6 novel ones, were found in exon 1 and its flanking region of UDP-glucuronosyltransferase (UGT) 1A6 from 195 Japanese subjects. Several novel SNPs were identified, including 269G>A (R90H), 279A>G (S93S), and 308C>A (S103X) in exon 1, and IVS1+109C>T, IVS1+120A>G, and IVS1+142C>T in the intron downstream of exon 1. Among these SNPs, 308C>A confers termination of translation at codon 103, resulting in the production of an immature protein that probably lacks enzymatic activity. The allele frequencies were 0.003 for all the 6 SNPs. In addition, the 3 known nonsynonymous SNPs were detected: 19T>G (S7A), 541A>G (T181A), and 552A>C (R184S) with frequencies of 0.226, 0.218, and 0.226, respectively. High linkage disequilibrium was observed among 19T>G (S7A), 315A>G (L105L), 541A>G (T181A), 552A>C (R184S), and IVS1+130G>T, as reported in Caucasian and African-American populations. Then, 11 haplotypes in UGT1A6 were estimated. The novel nonsynonymous variant, 269A or 308A, was shown to be located on the same DNA strand together with 19G, 315G, 541G, 552C, and IVS1+130T. Our results provide fundamental and useful information for genotyping UGT1A6 in the Japanese, and probably Asian populations.     

Influence of UGT1A8 and UGT2B7 genetic polymorphisms on mycophenolic acid pharmacokinetics in Japanese renal transplant recipients

Objective UGT1A8 and UGT2B7 are important uridine diphosphate-glucuronosyltransferase isoforms for the glucuronidation of mycophenolic acid (MPA). The aim of this investigation was to elucidate MPA pharmacokinetics in UGT1A8 and UGT2B7 genotypes in Japanese renal transplant recipients. Methods Seventy-two recipients received repeated doses of mycophenolate mofetil and tacrolimus. On day 28 after renal transplantation, plasma MPA concentrations were measured for the next 24 h using high-performance liquid chromatography. UGT1A8*2 (A¹⁷³G) and UGT2B7*2 (Y²⁶⁸) were detected using a PCR-RFLP-based procedure. Results There were no significant differences in daytime and nighttime pharmacokinetics of MPA between UGT1A8 or UGT2B7 genotypes. The mean daytime dose-adjusted AUC_0–12 of MPA in UGT1A8*1/*1, *1/*2 and *2/*2 were 2.47, 2.33 and 2.57 ng·h/ml/mg/kg (P = 0.7711), and the mean nighttime AUC_0–12 were 2.15, 2.00 and 2.08 ng·h/ml/mg/kg (P = 0.4656). The mean daytime and nighttime dose-adjusted AUC_0–12 of MPA in UGT2B7*1/*1, *1/*2 and *2/*2 were 2.61, 2.24 and 2.03 ng·h/ml/mg/kg and 2.18, 1.94, and 1.45 ng·h/ml/mg/kg, respectively (P = 0.3475 and 0.2575). The mean nighttime C_max, t_max, and AUC_6–12/AUC_0–12 ratio (enterohepatic circulation and recirculation ratio) of MPA in all UGT1A8 and UGT2B7 genotypes were lower, longer, and higher, respectively, than the daytime values. Conclusions Both UGT1A8 and UGT2B7 allelic variants seem not to affect Japanese interindividual variability for plasma MPA concentration. Regardless of UGT1A8 and UGT2B7 genetic polymorphisms, the absorption of MPA through enterohepatic recirculation is higher at night.     

Involvement of human hepatic UGT1A1, UGT2B4, and UGT2B7 in the glucuronidation of carvedilol.

Carvedilol ((+/-)-1-carbazol-4-yloxy)-3-[[2-(o-methoxyphenoxy)ethyl]amino]-2-propanol) is metabolized primarily into glucuronide conjugates. In the present study, we identified the human UDP-glucuronosyltransferase (UGT) isoforms involved in the glucuronidation of carvedilol by thin-layer chromatography using microsomes from human liver or insect cells expressing recombinant UGT isoforms. We observed two forms of carvedilol glucuronides, namely G1 and G2, in hepatic microsomes. The glucuronidation of carvedilol was catalyzed by at least three recombinant UGT isoforms: UGT1A1, UGT2B4, and UGT2B7. UGT2B4 formed both G1 and G2, whereas UGT1A1 and UGT2B7 were responsible for the formation of glucuronide G2 and G1, respectively. The enzyme kinetics for carvedilol glucuronidation by UGT1A1, UGT2B4, and UGT2B7 in addition to human liver microsomes were examined by Lineweaver-Burk analysis. The values of Km and Vmax for human liver microsomes were 26.6 microM and 106 pmol/min/mg protein for G1, and 46.0 microM and 44.5 pmol/min/mg protein for G2, respectively. The Km values for UGT1A1, UGT2B4, and UGT2B7 for G1 and G2 (22.1-55.1 microM) were comparable to those of the liver microsomes, whereas the Vmax values were in the range of 3.33 to 7.88 pmol/min/mg protein. The Km and Vmax/Km values for UGT2B4 and UGT2B7 for G1 were similar, whereas UGT2B4 had lower Km and higher Vmax/Km values for G2 compared with those of UGT1A1. These results suggest that G1 formation is catalyzed by UGT2B4 and UGT2B7, whereas G2 is formed by UGT2B4 and UGT1A1. These three hepatic UGT isoforms may have important roles in carvedilol metabolism.     

Single nucleotide polymorphisms of ABCB1 (MDR1) gene and distinct haplotype profile in a West Black African population

Objective The ABCB1 (MDR1) multidrug transporter plays a key role in determining drug bioavailability. Differences in drug response exist among different ethnic groups. However, until now, no haplotype data are available in a Black African population.Methods Exons 2, 7, 10, 11, 12, 14, 17, 21, 26, and the surrounding intronic regions were sequenced using genomic DNA from 111 Beninese subjects to examine 19 intragenic single nucleotide polymorphisms (SNPs). Linkage disequilibrium analysis and haplotypes were generated using the expectation–maximization algorithm.Results We identified 12 SNPs, 3 of which were novel: IVS9-57delA, IVS9-8T>A, 1662G>C (exon 14). The most common SNP was IVS14+38A>G. At the MRD1 locus, 53 haplotypes were inferred from the SNP data sets. The 4 SNPs, IVS6+139C>T, IVS9-44A>G, 1236C>T, and 3435C>T, showed strong linkage disequilibrium with each other, confirming the block concept. Moreover, our findings suggest that ABCB1 exonic SNPs are less frequently observed in our population than in African-Americans.Conclusion Our data are compatible with a close evolutionary relationship in Black Africans from Benin.     

Novel single nucleotide polymorphism of UGT1A7 gene in Japanese

We sequenced exon 1 of the UDP-glucuronosyltransferase (UGT) 1A7 gene from 52 Japanese cancer patients. Four single nucleotide polymorphisms (SNPs) were found. Three of them caused UGT1A7*2 and UGT1A7*3. A novel SNP (98973G>C) causing amino acid substitution (Ser141Cys) was found. The sequence is as follows: SNP, 050824FujitaK002; Gene Name, UGT1A7; Accession Number, AF297093; Length, 25 bases; 5'-TAAAGGAGAGTTG/CTTTTGATGCAGT-3'. One out of 52 cancer patients was heterozygous for the variant allele, resulting in the allele frequency of 0.96%. The patient did not possess UGT1A7*2 or UGT1A7*3.     

Limited influence of UGT1A1*28 and no effect of UGT2B7*2 polymorphisms on UGT1A1 or UGT2B7 activities and protein expression in human liver microsomes

AIMS: UGT1A1 and UGT2B7 are enzymes that commonly contribute to drug glucuronidation. Since genetic factors have been suggested to contribute to variability in activities and expression levels of these enzymes, a quantitative assessment of the influence of the major genotypes (UGT1A1*28 or UGT2B7*2) on enzyme activities was conducted. METHODS: Using a bank of microsomal samples from 59 human livers, the effect of UGT1A1*28 or UGT2B7*2 polymorphisms were investigated on rates of estradiol 3-glucuronidation (a marker of UGT1A1 enzyme activity) or zidovudine glucuronidation (a marker of UGT2B7 enzyme activity) and levels of immunoreactive protein for each enzyme. Glucuronidation rates for both enzymes were measured at K(m)/S(50) and 10 times K(m)/S(50) concentrations. RESULTS: UGT1A1 and UGT2B7 enzyme activities varied up to 16-fold and sixfold, respectively. Rates at K(m)/S(50) concentration closely correlated with rates at 10 times K(m)/S(50) concentration for both enzymes (but not at 1/10th K(m) for UGT2B7). Enzyme activities correlated with relative levels of immunoreactive protein for UGT1A1 and UGT2B7. Furthermore, rates of zidovudine glucuronidation correlated well with rates of glucuronidation of the UGT2B7 substrate gemcabene, but did not correlate with UGT1A1 enzyme activities. For the UGT1A1*28 polymorphism, consistent with levels of UGT1A1 immunoreactive protein, mean UGT1A1 activity was 2.5- and 3.2-fold lower for TA(6)/TA(7) (P < 0.05) and TA(7)/TA(7) (P < 0.001) genotypes in comparison with the TA(6)/TA(6) genotype. CONCLUSIONS: Relative to the observed 16-fold variability in UGT1A1 activity, these data indicate only a partial (approximately 40%) contribution of the UGT1A1*28 polymorphism to variability of interindividual differences in UGT1A1 enzyme activity. For the UGT2B7*2 polymorphism, genotype had no influence on immunoreactive UGT2B7 protein or the rate of 3'-azido-3'-deoxythymidine glucuronidation.     

Genetic variations and haplotypes of UGT1A4 in a Japanese population

Nineteen genetic variations, including 11 novel ones, were found in exon 1 and its flanking region of the UDP-glucuronosyltransferase (UGT) 1A4 gene from 256 Japanese subjects, consisting of 60 healthy volunteers, 88 cancer patients and 108 arrhythmic patients. These variations include -217T>G and -36G>A in the 5'-flanking region, 30G>A (P10P), 127delA (43fsX22; frame-shift from codon 43 resulting in the termination at the 22nd codon, codon 65), 175delG (59fsX6), 271C>T (R91C), 325A>G (R109G), and 357T>C (N119N) in exon 1, and IVS1+1G>T, IVS1+98A>G and IVS1+101G>T in the following intron. Among them, 127delA and 175delG can confer early termination of translation, resulting in an immature protein that probably lacks enzymatic activity. Variation IVS1+1G>T is located at a splice donor site and thus may lead to aberrant splicing. Since we did not find any significant differences in the frequencies of all the variations among the three subject groups, the data were analyzed as one group. The allele frequencies of the novel variations were 0.006 for IVS1+101G>T, 0.004 for 30G>A (P10P) and 357T>C (N119N), and 0.002 for the 8 other variations. In addition, the two known nonsynonymous single nucleotide polymorphisms (SNPs), 31C>T (R11W) and 142T>G (L48V), were found at 0.012 and 0.129 frequencies, respectively. The SNP 70C>A (P24T), mostly linked with 142T>G (L48V) in German Caucasians, was not detected in this study. Sixteen haplotypes were identified or inferred, and some haplotypes were confirmed by cloning and sequencing. It was shown that most of 142T>G (L48V) was linked with -219C>T, -163G>A, 448T>C (L150L), 804G>A (P268P), and IVS1+43C>T, comprising haplotype *3a; haplotype *4a harbors 31C>T (R11W); 127delA (43fsX22) and 142T>G (L48V) were linked (haplotype *5a); 175delG (59fsX6) was linked with 325A>G (R109G) (*6a haplotype); and -219C>T, -163G>A, 142T>G (L48V), 271C>T (R91C), 448T>C (L150L), 804G>A (P268P), and IVS1+43C>T comprised haplotype *7a. Our results provide fundamental and useful information for genotyping UGT1A4 in the Japanese and probably Asian populations.     

Epirubicin glucuronidation and UGT2B7 developmental expression.

The usefulness of epirubicin in the treatment of adult and childhood malignant diseases is related in part to the potential reduction in cardiac toxicity compared with that of other anthracyclines given at equivalent doses. An important pathway for epirubicin detoxification is UGT2B7-dependent glucuronidation. This study was implemented to provide a preclinical evaluation of the metabolism of epirubicin with respect to age-related changes in epirubicin glucuronidation in pediatric liver microsomes. Rates of epirubicin glucuronidation and levels of UGT2B7 were determined for liver microsomes from four pediatric age categories (n = 32) and one adult age category (n = 8). Both sets of data showed an increase in UGT2B7 activity and content with increasing age. Epirubicin glucuronidation activity in the adult group was statistically higher compared with all pediatric age groups (p < or = 0.01). UGT2B7 expression also was statistically higher in adults compared with children below 11 years of age, with evidence of significant differences in protein levels among the pediatric age categories. A positive correlation (r = 0.68) between UGT2B7 levels and postnatal age was observed, suggesting a progressive increase in UGT2B7 protein expression with increasing age. However, allometric scaling using the (3/4) power rule suggested no difference in activity between any of the pediatric age categories and the adult, although only a single neonatal sample was included in the analysis. In summary, these in vitro data show differences in epirubicin glucuronidation and UGT2B7 content within pediatric age groups and support the use of epirubicin in pediatric patients at least 6 months of age.     

Involvement of human UGT2B7 and 2B15 in rofecoxib metabolism.

O-Glucuronidation of 5-hydroxyrofecoxib is the major biotransformation pathway of rofecoxib in human, rat, and dog. The glucuronide conjugate is also involved in the reversible metabolism of rofecoxib in rat and human. Atypical bimodal phenomena were observed in their plasma concentration-time curves with a large variability among different human subjects. It is unclear which family members of human UDP-glucuronosyltransferases (UGT) are involved in the formation of the glucuronide. O-Glucuronidation of 5-hydroxyrofecoxib by human liver microsomes and eight cDNA-expressed human UGT isoforms were investigated. Human liver microsomes formed 5-hydroxyrofecoxib glucuronide with apparent V(max) value of 1736 pmol/min/mg of protein and K(m) value of 44.2 microM. Eight individual cDNA-expressed human UGT isozymes (1A1, 1A3, 1A4, 1A6, 1A8, 1A9, 2B7, and 2B15) were evaluated for glucuronidation of 5-hydroxyrofecoxib. Among them UGT2B15 exhibited the highest metabolism rate with apparent V(max) value of 286 pmol/min/mg of protein and K(m) value of 16.1 microM, whereas UGT2B7 showed apparent V(max) value of 47.1 pmol/min/mg of protein and K(m) value of 41.6 microM. These results indicated that human UGT2B15 has the highest level of activity for catalyzing the glucuronidation of 5-hydroxyrofecoxib. Because polymorphisms have been identified in human UGT2B7, 2B15 genes and O-glucuronidation of 5-hydroxyrofecoxib plays a major role in biotransformation of rofecoxib, it is possible that human UGT2B7 and 2B15 polymorphisms for O-glucuronidation of 5-hydroxyrofecoxib are responsible for the high variability in bimodal patterns in human plasma concentration-time curves.     

Three novel single nucleotide polymorphisms of the FMO3 gene in a Japanese population

We sequenced all exons and exon-intron junctions of the flavin-containing monooxygenase 3 (FMO3) gene from 2 Japanese individuals and their family members, who were case subjects that showed low FMO3 metabolic capacity among a population of self-reported trimethylaminuria Japanese volunteers. We found two novel single nucleotide polymorphisms (SNPs) (21,254 C>A and 24,006 A>G) causing amino acid substitutions, Thr(201)Lys in exon 5 and Met(260)Val in exon 6, respectively. The Thr(201)Lys and Met(260)Val also presented together with known SNPs (Glu(158)Lys-Glu(308)Gly and Val(257)Met, respectively) in the same alleles of the FMO3 gene to form novel haplotypes. A SNP (30,398 C>T) in the FMO3 gene causing a stop codon at Arg(500) in exon 9 was also discovered. These sequences are as follows: 1) SNP, 060116Shimizu001; GENE NAME, FMO3; ACCESSION NUMBER, AL021026; LENGTH, 25 base; 5'-GTGATATTGCCAC/AAGAACTCAGCCG-3'. 2) SNP, 060116Shimizu002; GENE NAME, FMO3; ACCESSION NUMBER, AL021026; LENGTH, 25 base; 5'-TAC(G/A)TGAAGCAGA/GTGAATGCAAGAT-3'. 3) SNP, 060116Shimizu003; GENE NAME, FMO3; ACCESSION NUMBER, AL021026; LENGTH, 25 base; 5'-CCCATGCAGACAC/TGAGTGGTCGGGA-3'.     

焦磷酸测序技术检测UGT1A3和UGT2B7在中国汉族人群中的基因多态性

目的建立焦磷酸测序技术(pyrosequencing)研究二相代谢酶UGT1A3和UGT2B7基因多态性在中国汉族人群中的分布。方法应用带生物素标记扩增引物并经PCR扩增和Beads分离,制备UGT1A3和UGT2B7焦磷酸测序单倍摸板。在PYroMarkID焦磷酸测序上进行焦磷酸测序,检测233血样的DNA标本的17个SNP位点,以确定血样DNA标本的的基因型。结果 233例血样的DNA标本中,UGT1A3等位基因有9种表型,分别为UGT1A3*1*1、UGT1A3*1*2、UGT1A3*1*3、UGT1A3*1*4、UGT1A3*1*5、UGT1A3*2*3、UGT1A3*2*4、UGT1A3*3*3和UGT1A3*3*5。UGT2B7-1和UGT2B7-2各有3种基因型,分别为G/G型、G/T型、T/T和C/C型、C/T型、T/T型。结论我国汉族人群中UGT1A3和UGT2B7基因突变较高。     

UDP-glucuronosyltransferase 1A4 polymorphisms in a Japanese population and kinetics of clozapine glucuronidation.

The UDP-glucuronosyltransferase (UGT) family plays a major role in the excretion of endobiotics and xenobiotics and their metabolites. Human UGT1A4 catalyzes the glucuronidation of primary, secondary, and tertiary amines, sapogenins, androgens, and progestins. We directly sequenced polymerase chain reaction-amplified fragments of the UGT1A4 gene from 100 healthy adult Japanese volunteers and calculated their mutation frequency. We identified four single nucleotide polymorphisms (SNPs): three in exon 1 (142T > G: L48V, 448T > C: L150L, 804G > A: P268P), and one in intron 1 (867 + 43C > T). We found three types of alleles with distinct SNP combinations that coded for different amino acid sequences: L48V-L150L-P268P-867 + 43C > T (frequency, 0.155), L48V (0.01), and P268P (0.01) (wild-type frequency was 0.825). The L48V mutant gave twice the efficiency (V(max)/K(m)) for the antipsychotic drug clozapine as the wild-type. Efficiencies of L48V for trans-androsterone, imipramine, and cyproheptadine were increased, but the efficiency for tigogenin was reduced. L48V therefore increased or decreased the glucuronidation activity, depending upon the substrates. This study shows the importance of identifying patients with the L48V polymorphism when calculating dosage, and when considering the potential adverse effects of drugs that are substrates of UGT1A4.     

UGT1A9 C-2152T和UGT2B7 G211T突变在中国汉族人群中的分布

目的：建立Touch-down PCR/RFLP的方法检测UGT1A9C-2152T突变,建立PCR/RFLP的方法检测UGT2B7G211T突变,确定其在中国汉族人群中的突变频率。方法：采用Touch-down PCR/RFLP方法,对100名无亲缘关系的汉族男性志愿者进行UGT1A9C-2152T的基因分型。采用PCR/RFLP方法,对363名无亲缘关系的汉族志愿者（其中男性263名、女性100名）进行UGT2B7 G211T的基因分型。结果：在100名中国汉族男性受试者中,末发现UGT1A9C-2152T的突变,与亚洲人通过测序报道的结果基本一致。在363名汉族受试者中,UGT2B7G211T突变发生频率为0.158,与日本人通过测序报道的结果基本一致。中国男性和女性的等位基因频率分别为0.128和0.110,男性的突变频率比女性高（χ^2=6.784,P=0.034）。结论：用PCR/RFLP的方法对UGT2B7 G211T突变分型的方法简便、快速、重复性好,可用于大样本人群的基因检测。UGT2B7G211T突变在中国汉族人中发生频率较高。     

UGT2B7基因多态性与抗结核药物性肝损伤的相关性分析

目的 探讨UGT2B7基因多态性与抗结核药物性肝损伤(ADIH)易感性之间的关系.方法 在2012年9月到2013年3月唐山市结核病医院确诊并接受规范抗结核治疗的结核病患者中选取发生肝损伤的182例结核病患者为病例组,未发生肝损伤的193例患者为对照组.对两组患者进行流行病学调查、提取DNA、鉴定基因型并进行统计学分析.结果 UGT2B7基因第268位点突变型杂合子AG和802位点突变型杂纯合子TT携带者发生抗结核药致肝损伤的危险性高于野生型携带者,差异有统计学意义(P＜0.01);在调整了个别不相关因素的影响后,UGT2B7 268和802位点的基因多态性与抗结核药致肝损伤的发生仍显著相关.结论 UGT2B7的-268和802位点基因多态性与抗结核药物性肝损伤具有相关性.     

UGT1A9C-2152T和UGT2B7G211T突变在中国汉族人群中的分布

目的建立Touch-down PCR/RFLP的方法检测UGT1A9 C-2152T突变,建立PCR/RFLP的方法检测UGT2B7 G211T突变,确定其在中国汉族人群中的突变频率.方法采用Touch-down PCR/RFLP方法,对100名无亲缘关系的汉族男性志愿者进行UGT1A9 C-2152T的基因分型.采用PCR/RFLP方法,对363名无亲缘关系的汉族志愿者(其中男性263名、女性100名)进行UGT2B7 G211T的基因分型.结果在100名中国汉族男性受试者中,末发现UGT1A9 C-2152T的突变,与亚洲人通过测序报道的结果基本一致.在363名汉族受试者中,UGT2B7 G211T突变发生频率为 0.158,与日本人通过测序报道的结果基本一致.中国男性和女性的等位基因频率分别为 0.128 和 0.110,男性的突变频率比女性高(χ2=6.784, P=0.034).结论用PCR/RFLP的方法对UGT2B7 G211T突变分型的方法简便、快速、重复性好,可用于大样本人群的基因检测.UGT2B7 G211T突变在中国汉族人中发生频率较高.