中国汉族和回族药物代谢酶细胞色素P450(CYP)3A4、CYP2C9、CYP2C19及CYP2D6基因多态性分析

目的对中国汉族、回族健康人群细胞色素P450(CYP)3A4、CYP2C9、CYP2C19及CYP2D6进行基因多态性分析,比较汉族和回族健康人群基因表型和基因频率分布。方法多聚酶链反应-限制性片段长度多态性(PCR-RFLP)法,对300名志愿者的几种基因进行分型。结果汉族、回族CYP3A4*5等位基因频率均为0,CYP3A4*18等位基因频率分别为0.18,0.19;汉族、回族CYP2C9*2等位基因频率分别为0.01,0.05;CYP2C9*13等位基因频率均为0;汉族、回族CYP2C19*2等位基因频率分别为0.39,0.50;CYP2C19*3等位基因频率分别为0.05,0.05;汉族、回族CYP2D6*10等位基因频率分别为0.57,0.39。结论汉族、回族健康人群的CYP3A4*18、CYP2C9*2、CYP2C19*2、CYP2C19*3均没有显著性差异;在汉族、回族健康人群中未发现CYP3A4*5和CYP2C9*13突变;汉族、回族CYP2D6*10等位基因频率有显著性差异(P<0.01);回族人群CYP2D6中速代谢型(*10/*10)频率为13.4%,明显低于汉族的33.1%(P<0.01)。     

中国汉族和维吾尔族药物代谢酶CYP3A4、CYP2C9、CYP2C19、CYP2D6基因多态性分析

目的对中国汉族、维吾尔族健康人群CYP3A4、CYP2C9、CYP2C19、CYP2D6进行基因多态性分析,并对汉族和维吾尔族人群等位基因频率和基因型频率进行比较。方法聚合酶链反应一限制性片段长度多态性(PCR-RFLP)法对CYP3A4、CYP2C9、CYP2C19、CYP2D6进行分型。结果汉族、维吾尔族健康人群CYP3A4*5等位基因频率为0,CYP3A4*18等位基因频率分别为0.183 8、0.140 2;CYP2C9*2等位基因频率分别为0.011 0、0.095 8,CYP2C9*13等位基因频率分别为0、0.002 3;CYP2C19*2等位基因频率分别为0.386 0、0.324 8,CYP2C19*3等位基因频率分别为0.051 5、0.021 0;CYP2D6*10等位基因频率分别为0.573 5、0.224 3。结论本研究在汉族、维吾尔族健康人群中未发现CYP3A4*5等位基因。汉族、维吾尔族健康人群CYP3A4*18、CYP2C9*13、CYP2C19*2、CYP2C19*3等位基因频率差异均无统计学意义。维吾尔族健康人群CYP2C9*2等位基因频率远高于汉族(P<0.01);CYP2D6*10等位基因频率远低于汉族(P<0.01),存在民族差异。     

中国哈萨克族人硫嘌呤甲基转移酶活性分布和基因多态性

目的 研究硫嘌呤甲基转移酶(TPMT)在中国哈萨克族的活性分布和4 种常见TPMT基因突变等位基因频率。方法 用高效液相色谱法测定TPMT 活性;用等位基因特异性聚合酶链反应检测TPMT*2;用限制性片段长度多态性 检测TPMT*3A、TPMT*3B和TPMT*3C的等位基因频率。结果 哈萨克族T PMT活性呈正态分布,活性的均值为(12．27±3．42)U·mL-1 Rbc,其中发现6 例TPMT*3C杂合子和2例TPMT*3A杂合子,总TPMT基因突变频率是1．2％。 结论 中国哈萨克族TPMT活性呈正态分布,总TPMT基因突变频率同汉族相 比差异无显著性。     

广东连南汉族和瑶族儿童硫嘌呤甲基转移酶研究

目的本文对硫嘌呤甲基转移酶(Thiopurine S-methyltransferase,TPMT)在广东连南地区健康汉族儿童(n=87)和瑶族儿童(n=1 26)中的活性分布和4种常见TPMT基因突变的等位基因频率进行研究.方法采用高效液相色谱法测定红细胞的TPMT活性;采用等位基因特异性的PCR(allelespecific PCR,ASPCR)方法和限制性片断长度多态性(PCR-restrictionfragmentlength polymorphism,RFLP)的方法检测TPMT*2(G238C)、TPMT*3A(A719G/G460A)、TPMT*3B(G460A)和TPMT*3C(A719G)的等位基因频率.结果健康汉族儿童和瑶族儿童的TPMT活性都呈正态分布,活性的平均值分别为13.01±2.80U.ml-1pRBC和13.54±3.89U.ml-1 pRBC,两者的差异无显著性.在健康汉族儿童中只找到1例TPMT*3C杂合子(该汉族儿童的TPMT活性为12.36U.ml-1 pRBC),没有找到TPMT*2、TPMT*3A和TPMT*3B,汉族儿童总的TPMT基因突变频率是0.6%.在健康瑶族儿童中没有找到这几种突变.结论广东连南地区汉族和瑶族儿童TPMT的活性分布和总的TPMT基因突变频率没有显著性差异.     

161例服用华法林的房颤患者CYP2 C19*2基因多态性研究

目的：了解161例服用华法林房颤患者CYP2C19*2（681G／A）基因多态性及不同人群的基因频率分布差异。方法采用聚合酶链反应-限制性片段长度多态性（PCR-RFLP）技术,测定161例服用华法林的房颤患者CYP2C19*2（681G／A）基因型,并比较不同人群的基因分布差异。结果 CYP2C19*1及CYP2C19*2等位基因频率分别为63.04％和36.96％。 CYP2C19*1／*1、CYP2C19*1／*2及 CYP2C19*2／*2频率分别为40.4％,44.1％和15.5％。结论本研究人群CYP2C19*2等位基因频率分布与报道的汉族人群、日本、韩国人群相似;但显著高于高加索人群、美籍非州人群。     

中国新疆维吾尔族硫嘌呤甲基转移酶基因突变研究

目的 研究硫嘌呤甲基转移酶(thiopurine S-methyltransferase，TPMT)在新疆维吾尔族中的基因突变频率。方法 用等位基因特异性的PCR方法和限制性片断长度多态性的方法检测4种常见的导致酶活性降低的突变类型：TPMT*2、TPMT*3A、TPMT*3B和TPMT*3C。结果 在160名维吾尔族中发现了1例TPMT*3A(A719G／G460A)杂合子、5例TPMT*3C(A719G)杂合子，TPMT*3A和TPMT*3C的等位基因频率分别是0．3％和1．6％。结论 维吾尔族总的TPMT突变等位基因频率(1．9％)同中国其他民族相近；TPMT*3C是维吾尔族最主要的突变类型。     

新疆维吾尔族健康人群细胞色素P450基因多态性研究

目的了解CYP2C9基因多态性在新疆维吾尔族健康人群中的分布以及与其他不同民族之间的差异。方法采用序列特异性引物聚合酶链反应和限制性内切酶反应(PCR-RFLP)技术对197名乌鲁木齐地区维吾尔族健康个体CYP2C9*2和CYP2C9*3位点进行了检测,计算其基因型和等位基因频率,并与国外多个民族CYP2C9基因多态性分布进行比较。结果国内首次在新疆维吾尔族健康人群中发现CYP2C9*2等位基因,新疆维吾尔族健康人群中共检测到3种等位基因:CYP2C9*1、CYP2C9*2、CYP2C9*3,等位基因频率分别为80%、3%、17%。新疆维吾尔族健康人群CYP2C9共检测到5种基因型,以CYP2C9*1*1常见,基因型频率为77%,其次为CYP2C9*3*3,基因型频率为15%。CYP2C9*1*2、CYP2C9*1*3和CYP2C9*2*2的基因型频率分别为4%、3%和1%。结论新疆维吾尔族CYP2C9基因多态性的分布与欧美人群接近,而与日本、韩国以及国内报道的汉族人群CYP2C9基因多态性分布有较大差异。     

CYP2C19基因多态性与中国汉族人群急性冠脉综合征的相关性研究

目的：探讨细胞色素 P450（CYP）2C19基因常见多态性位点与中国汉族人群急性冠脉综合征（ACS）的相关性。方法提取206例 ACS 患者和232例对照者外周血 DNA,采用 DNA 微阵列芯片法对 CYP2C19*2（681G ＞A）、CYP2C19*3（636G ＞ A）进行基因型检测,对比2组间及不同 ACS 分型患者间基因型及等位基因突变频率的分布差异,同时运用 Logistic 回归分析探讨 ACS 发生的独立危险因素。结果 CYP2C19*1、*2、*3分布比例依次为64.38％、29.46％和6.16％,不同性别人群的等位基因及基因型分布差异无统计学意义（ P ＞0.05）。ACS 组CYP2C19*1/*1的分布频率明显少于对照组（ P ＜0.05）,但 CYP2C19*1/*2与 CYP2C19*1/*3的分布频率之和明显高于对照组（ P ＜0.05）。CYP2C19*1/*1所占比例 STEMI 组明显低于 NSTEMI 组（ P ＜0.01）,CYP2C19*1/*2的分布频率 NSTEMI 组最低,且与 STEMI 及 UA 组间差异均有统计学意义（ P ＜0.01）。Logistic 回归分析显示CYP2C19*2（681G ＞ A）GA 基因型是中国汉族人群 ACS 发生的独立危险因素（OR ＝5.97,95％ CI 为1.09～12.35, P ＝0.007）。结论 CYP2C19*2（681G ＞ A）GA 基因型可能与中国汉族人群 ACS 风险增高有关。     

浙江沿海汉族人群CYP2C9基因多态性与甲苯磺丁脲代谢活性关系

目的探讨浙江沿海地区汉族人群CYP2C9基因多态性与甲苯磺丁脲代谢关系。方法采用寡核苷酸基因芯片,对浙江沿海地区汉族人群137名健康志愿者进行基因分型;选择含有突变型等位基因CYP2C9*3志愿者和部分野生型志愿者共20名参加甲苯磺丁脲药代动力学试验;统计分析不同CYP2C9基因型个体的代谢参数。结果在137名健康受试者DNA标本中发现CYP2C9*1/*3杂合突变型个体9名,CYP2C9*3/*3纯合突变个体1名,未发现CYP2C9*2、*4和*53种突变型等位基因,其中本研究受试人群中CYP2C9等位基因频率CYP2C9*1/*1占92.7%,CYP2C9*1/*3占6.6%,CYP2C9*3/*3占0.7%。药物代谢显示,CYP2C9*3纯合子个体的药物清除率显著低于CYP2C9*1纯合子个体。CYP2C9*1/*3杂合突变型个体组及1名CYP2C9*3/*3纯合型突变个体组,甲苯磺丁脲的代谢显著慢于野生型个体组。野生型(*1/*1)个体组、*1/*3杂合型突变个体组及1名*3/*3纯合型突变个体组,甲苯磺丁脲的药物代谢动力学参数差异与基因分型结果一致。结论CYP2C9多态性是甲苯磺丁脲药物代谢临床表现复杂性的主要因素,建立高效可靠的药代酶基因分型方法对CYP2C9代谢相关药物的临床个体化医疗具有一定的指导作用。     

细胞色素P450 3A4基因多态性与中国汉族女性乳腺癌易感性的相关性研究

目的 探讨细胞色素P450 3A4(CYP3A4)基因多态性与中国汉族女性乳腺癌易感性的相关性。方法 用聚合酶链反应-限制性片段长度多态性(PCR-RFLP)的方法检测148例中国汉族女性乳腺癌患者及160例健康受试者的CYP3A4*1G多态性,分析2组CYP3A4*1G基因型及等位基因分布频率。结果 中国汉族女性乳腺癌患者和健康受试者CYP3A4*1G基因型分布均符合Hardy-Weinberg平衡。乳腺癌患者和健康受试者CYP3A4*1G等位基因频率分别为15.9%和22.2%(P<0.05),CYP3A4*1G基因型的分布频率在2组间差异有统计学意义(P<0.01)。结论 CYP3A4*1G多态性与中国汉族女性乳腺癌的易感性存在负相关性。     

Genotype and allele frequencies of TPMT,NAT2, GST,SULT1A1 and MDR-1 in the Egyptian population

AIMS: The goal of this study was to determine the frequencies of important allelic variants in the TPMT, NAT2, GST, SULT1A1 and MDR-1 genes in the Egyptian population and compare them with the frequencies in other ethnic populations. METHODS: Genotyping was carried out in a total of 200 unrelated Egyptian subjects. TPMT*2 was detected using an allele-specific polymerase chain reaction (PCR) assay. TPMT*3C and NAT2 variants (*5,*6 and *7) were detected using an allele-specific real-time PCR assay. Detection of GSTM1 and GSTT1 null alleles was performed simultaneously using a multiplex PCR assay. Finally, a PCR-restriction fragment length polymorphism assay was applied for the determination of TPMT*3A (*3B), SULT1A1*2 and MDR-1 (3435T) variants. RESULTS: Genotyping of TPMT revealed frequencies of 0.003 and 0.013 for TPMT*3A and TPMT*3C, respectively. No TPMT*2 or *3B was detected in the analysed samples. The frequencies of specific NAT2 alleles were 0.215, 0.497, 0.260 and 0.028 for *4 (wild-type), *5 (341C), *6 (590A) and *7 (857A), respectively. GSTM1 and GSTT1 null alleles were detected in 55.5% and 29.5% of the subjects, respectively. SULT1A1*2 was detected at a frequency of 0.135. Finally, the frequencies of the wild-type allele (3435C) and the 3435T variant in the MDR-1 gene were found to be 0.6 and 0.4, respectively. CONCLUSIONS: We found that Egyptians resemble other Caucasians with regard to allelic frequencies of the tested variants of NAT2, GST and MDR-1. By contrast, this Egyptian population more closely resemble Africans with respect to the TPMT*3C allele, and shows a distinctly different frequency with regard to the SULT1A1*2 variant. The predominance of the slow acetylator genotype in the present study (60.50%) could not confirm a previously reported higher frequency of the slow acetylator phenotype in Egyptians (92.00%), indicating the possibility of the presence of other mutations not detectable as T341C, G590A and G857A. The purpose of our future studies is to investigate for new polymorphisms, which could be relatively unique to the Egyptian population.     

Allele and genotype frequencies of polymorphic cytochromes P450 (CYP2C9, CYP2C19, CYP2E1) and dihydropyrimidine dehydrogenase (DPYD) in the Egyptian population

AIMS: The goal of this study was to determine the frequencies of important allelic variants of CYP2C9, CYP2C19, CYP2E1 and DPYD in the Egyptian population and compare them with the frequencies in other ethnic populations. METHODS: Genotyping of CYP2C9 (*2 and *3), CYP2C19 (*2 and *3), c2 variant of CYP2E1 and DPYD alleles (*2 A-*6 ) was carried out in a total of 247 unrelated Egyptian subjects. An allele-specific fluorogenic 5' nuclease chain reaction assay was applied for detection of CYP2C9 and CYP2C19 variants. Other variants of the CYP2E1 and DPYD genes were determined using polymerase chain reaction (PCR)-restriction fragment length polymorphism and allele-specific PCR based assays. RESULTS: CYP2C9 allele frequencies in 247 Egyptian subjects were 0.820 for CYP2C9*1, 0.120 for CYP2C9*2 and 0.060 for CYP2C9*3. For CYP2C19, the frequencies of the wild type (CYP2C19*1) and the nonfunctional (*2 and *3) alleles were 0.888, 0.110 and 0.002, respectively. CYP2C19*3, which is considered an Asian mutation, was detected in one subject (0.40%) who was heterozygous (*1/*3). Two subjects (0.80%) were homozygous for *2/*2, while no compound heterozygotes (*2/*3) or homozygotes for *3 were detected. For CYP2E1, only four subjects (1.70%) had the rare c2 variant, expressed heterozygously, giving an allele frequency of 0.009. Five variants of DPYD were analysed, with no splice sites (*2 A) or DeltaC1897 (*3) found in this population. The frequencies of other variants were 0.028, 0.115 and 0.090 for *4, *5 and *6, respectively. CONCLUSIONS: Comparing our data with that obtained in several Caucasian, African-American and Asian populations, we found that Egyptians resemble Caucasians with regard to allelic frequencies of the tested variants of CYP2C9, CYP2C19, CYP2E1 and DPYD. Our results may help in better understanding the molecular basis underlying ethnic differences in drug response, and contribute to improved individualization of drug therapy in the Egyptian population.     

Population differences in major functional polymorphisms of pharmacokinetics/pharmacodynamics-related genes in Eastern Asians and Europeans: implications in the clinical trials for novel drug development

Drug lag, recently discussed extensively in Japan, can be divided into two phases: clinical development time and application review time. The former factor is still an important problem that might be improved by promoting multi-regional clinical trials and considering the results from other similar populations with Japanese, such as Koreans and Chinese. In this review, we compare the allelic or genotype frequencies of 30 relatively common functional alleles mainly between Eastern Asians and Europeans as well as among 3 major populations in Eastern Asian countries, Japan, Korea, and China, in 12 pharmacokinetics (PK)/pharmacodynamics (PD)-related genes; CYP2C9 (*2 and *3), CYP2C19 (*2, *3 and *17), 13 CYP2D6 haplotypes including *4, *5 and *10, CYP3A5 (*3), UGT1A1 (*28 and *6), NAT2 (*5, *6 and *7), GSTM1 and GSTT1 null genotypes, SLCO1B1 521T>C, ABCG2 421C>A, and HLA-A*31:01 and HLA-B*58:01. In this review, differences in allele frequencies (AFs) or genotype frequencies (GFs) less than 0.1 (in the cases of highest AF (GF) ≥0.1) or less than 0.05 (in the cases of lowest AF (GF) <0.1) were regarded as similar. Between Eastern Asians and Europeans, AFs (or GFs) are regarded as being different for many alleles such as CYP2C9 (*2), CYP2C19 (*2, *3 and *17), CYP2D6 (*4 and *10), CYP3A5 (*3), UGT1A1 (*28 and *6), NAT2 (*5*7), GSTT1 null and ABCG2 421C>A. Among the 3 Eastern Asian populations, however, only AFs of CYP2C19*3, CYP2D6*10, HLA-A*31:01 and HLA-B*58:01 are regarded as dissimilar. For CYP2C19*3, the total functional impact on CYP2C19 could be small if the frequencies of the two null alleles CYP2C19*2 and *3 are combined. Regarding CYP2D6*10, frequency difference over 0.1 is observed only between Japanese and Chinese (0.147). Although environmental factors should be considered for PK/PD differences, we could propose that among Japan, Korea, and China, genetic differences are very small for the analyzed common PK-related gene polymorphisms. On the other hand, AFs of the two HLA alleles important for cutaneous adverse drug reactions are diverse even among Eastern Asians and thus should be taken into account.     

Phenotyping and genotyping study of thiopurine S-methyltransferase in healthy Chinese children: a comparison of Han and Yao ethnic groups

AIMS: Ethnicity is an important variable influencing drug response. Thiopurine S-methyltransferase (TPMT) plays an important role in the metabolism of thiopurine drugs. Previous population studies have identified ethnic variations in both phenotype and genotype of TPMT, but limited information is available within Chinese population that comprises at least 56 ethnic groups. The current study was conducted to compare both phenotype and genotype of TPMT in healthy Han and Yao Chinese children. METHODS: TPMT activity was measured in healthy Chinese children by a HPLC assay (n = 213, 87 Han Chinese and 126 Yao Chinese). Allele-specific polymerase chain reaction (PCR) and PCR-restriction fragment length polymorphism (RFLP) were used to determine the frequency of TPMT mutant alleles (TPMT*2, TPMT*3 A, TPMT*3B and TPMT*3C) in these children. RESULTS: There was no significant difference in the mean TPMT activity between Han and Yao Chinese children. A unimodal distribution of TPMT activity in Chinese children was found and the mean TPMT activity was 13.32 +/- 3.49 U ml(-1) RBC. TPMT activity was not found to differ with gender, but tended to increase with age in Yao Chinese children. TPMT*2, TPMT*3B and TPMT*3A were not detected, and only one TPMT*3C heterozygote (Han child) was identified in 213 Chinese children. Erythrocyte TPMT activity of this TPMT*3C heterozygote was 12.36 U ml(-1) RBC. The frequency of the known mutant TPMT alleles was 0.2%[1/426] in Chinese children. CONCLUSION: The frequency distribution of RBC TPMT activity was unimodal. The frequency of the known mutant TPMT alleles in Chinese Children is low and TPMT*3C appears to be the most prevalent among the tested mutant TPMT alleles in this population.     

Allele and genotype frequencies of polymorphic cytochromes P4502D6, 2C19 and 2E1 in aborigines from western Australia

The polymorphisms of the important xenobiotic metabolizing enzymes CYP2D6, CYP2C19 and CYP2E1 have been studied extensively in a large number of populations and show significant heterogeneity in the frequency of different alleles/genotypes and in the prevalence of the extensive and poor metabolizer phenotypes. Understanding of inter-ethnic differences in genotypes is important in prediction of either beneficial or adverse effects from therapeutic agents and other xenobiotics. Since no data were available for Australian Aborigines, we investigated the frequencies of alleles and genotypes for CYP2D6, CYP2C19 and CYP2E1 in a population living in the far north of Western Australia. Because of its geographical isolation, this population can serve as a model to study the impact of evolutionary forces on the distribution of different alleles for xenobiotic metabolizing enzymes. Twelve CYP2D6 alleles were analysed. The wild-type allele *1 was the most frequent (85.81%) and the non-functional alleles (*4, * 5, * 16) had an overall frequency of less than 10%. Only one subject (0.4%) was a poor metabolizer for CYP2D6 because of the genotype *5/*5. For CYP2C19, the frequencies of the *1 (wild-type) and the non-functional (*2 and *3) alleles were 50.2%, 35.5% and 14.3%, respectively. The combined CYP2C19 genotypes (*2/*2, *2/*3 or *3/*3) correspond to a predicted frequency of 25.6% for the CYP2C19 poor metabolizer phenotype. For CYP2EI, only one subject had the rare c2 allele giving an overall allele frequency of 0.2%. For CYP2D6 and CYP2C19, allele frequencies and predicted phenotypes differed significantly from those for Caucasians but were similar to those for Orientals indicating a close relationship to East Asian populations. Differences between Aborigines and Orientals in allele frequencies for CYP2D6* 10 and CYP2E1 c2 may have arisen through natural selection, or genetic drift, respectively.     

Polymorphisms of drug-metabolizing enzymes CYP2C9, CYP2C19, CYP2D6, CYP1A1, NAT2 and of P-glycoprotein in a Russian population

Objective The frequency of functionally important mutations and alleles of genes coding for xenobiotic metabolizing enzymes shows a wide ethnic variation. However, little is known of the frequency distribution of the major allelic variants in the Russian population.Methods Using polymerase chain reaction/restriction fragment length polymorphism (PCR/RFLP) genotyping assays and the real-time PCR with fluorescent probes, the frequencies of functionally important variants of the cytochromes P₄₅₀ (CYP) 2C9, 2C19, 2D6, 1A1 as well as arylamine N-acetyltransferase 2 (NAT2) and P-glycoprotein (MDR1) were determined in a sample of 290 Russian volunteers derived from Voronezh area.Results CYP2C9*2 and *3 alleles were found with allelic frequencies of 10.5% and 6.7%, respectively. The novel intron-2 T>C mutation at exon 2 +73 bp occurred in 24.8% of alleles. CYP2C19*2 and *3 alleles occurred in 11.4% and 0.3%, respectively. Six persons (2.1%) carried two of these CYP2C19 alleles responsible for poor metabolizing activity. Of all subjects, 5.9% were CYP2D6 poor metabolizers, whereas 3.4% were addressed to ultra-rapid metabolizers (CYP2D6*1×2/*1). The CYP1A1*2A allele was found in 4.7%, *2B in 5.0%, *4 in 2.6%, and the 5-mutations –3219C>T, –3229G>A, and the novel –4335G>A in 6.0%, 2.9% and 26.0% of alleles, respectively. Genotyping of eight different single nucleotide polymorphisms in the NAT2 gene provided in 58.0% a genotype associated with slow acetylation. The MDR1 triple variants G2677T and G2677A in exon 21 had an allelic frequency of 41.9% and 3.3%, respectively, and the variant C3435T in exon 26 one of 54.3%. Frequencies of functionally important haplotypes were calculated.Conclusion The overview of allele distribution of important xenobiotic-metabolizing enzymes among a Russian population shows similarity to other Caucasians. The data will be useful for clinical pharmacokinetic investigations and for drug dosage recommendations in the Russian population.     

CYP2C19 genotype and S-mephenytoin 4′-hydroxylation phenotype in a Chinese Dai population

AIMS: To investigate the incidence of the CYP2C19 polymorphism in the Chinese Dai population. METHODS: One hundred and ninety-three healthy Chinese Dai volunteers were identified with respect to CYP2C19 by genotype and phenotype analyses. A polymerase chain reaction-restriction fragment length polymorphism method was performed for genotyping procedures. The 4'-hydroxymephenytoin (4'-OH-MP) and S/R-mephenytoin ( S/R-MP) excreted in the urine were determined by high-performance liquid chromatography and gas chromatography, respectively. RESULTS: Eighteen subjects were identified as poor metabolisers (PMs). The frequency of PMs in the Chinese Dai subjects was 9.3% (95% confidence interval 5.2, 13.4), which is lower than that in the Chinese Han population ( P<0.05). Chinese Dai subjects had a higher frequency of the mutant CYP2C19*2 allele (0.303) and a lower frequency of the mutant CYP2C19*3 allele (0.034). These two mutant alleles could explain all deficiencies of CYP2C19 activity in the Chinese Dai subjects. The frequency of the CYP2C19*3 allele is significantly lower than that in the Chinese Han population ( P<0.05). The mean S/R ratio was lower in the homozygous extensive metabolisers (EMs) compared with that in heterozygous EMs ( P<0.01), and the latter was lower than that in the PMs ( P<0.01). Furthermore, the mean S/R ratio in CYP2C19*3/ CYP2C19*2 heterozygous PMs was possibly lower than that in the CYP2C19*2/ CYP2C19*2 homozygous PMs ( P<0.05). CONCLUSION: The frequencies of PMs and CYP2C19*3 allele in the Chinese Dai population are significantly lower than those in the Han population. The CYP2C19 genotype analysis is largely consistent with the mephenytoin phenotype analysis. The variability of S/R ratios in EMs and PMs shows a gene-dosage effect.     

Functional characterization of CYP2C19 variants in nebivolol 4‐hydroxlation in vitro

Cytochrome P450 2C19 (CYP2C19) allelic variants are thought to play an important part in inter‐individual variability in drug metabolism. We evaluated the in vitro hydroxylation of nebivolol by 31 CYP2C19 alleles identified in a Chinese Han population recently. Wild‐type CYP2C19*1B and 30 isoforms were highly expressed in insect cells, and the enzymatic activities of CYP2C19 variants towards nebivolol hydroxylation were characterized. Among the 30 CYP2C19 alleles, most of the recombinant CYP2C19 variants exhibited no or significantly low activity compared with CYP2C19*1B. Three variants, CYP2C19*29 (K28I), L16F, and CYP2C19*23 (G91R), showed increased intrinsic clearance of >140% CYP2C19*1B. Combined with a previous study on the effects of CYP2D6 variants on nebivolol metabolism, our comprehensive analyses on the enzymatic activities of CYP2C19 variants towards nebivolol in the present study may contribute to determination of the optimal doses of nebivolol for the treatment of hypertension and understanding of “individualized” medication.     

Detection assay of rare variants of the thiopurine methyltransferase gene by PCR-RFLP using a mismatch primer in a Japanese population

Thiopurine methyltransferase (TPMT) catalyzes the metabolism of important drugs such as 6-mercaptopurine, 6-thioguanine, and azathioprine. The identification and frequency distributions of several variant TPMT alleles (TPMT*2--*8) have been described recently in many ethnic groups. We have recently demonstrated that TPMT*3C is the most common allele in Japanese subjects; however, it remains to be elucidated whether TPMT*4--*8 variants also exist in Japanese subjects. To detect polymorphisms in the TPMT gene (TPMT*4--*8), we have developed a mismatch polymerase chain reaction and restriction fragment length polymorphism method and conducted a population study of Japanese subjects. Genotyping of these variant forms was carried out in 192 Japanese healthy volunteers. The TPMT*4, TPMT*5, TPMT*6, TPMT*7, and TPMT*8 variants were not detected in any of the samples analyzed. This study provides the first analysis of the TPMT*4--*8 variants in a sample of the Japanese population and indicates that TPMT*4--*8 variants do not occur or are rare alleles in this population.