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。     

细胞色素P450 2C9和血管紧张素Ⅱ1型受体基因多态性与血管紧张素Ⅱ受体拮抗剂厄贝沙坦降压疗效的关系

目的 观察血管紧张素Ⅱ1型受体(AT1R)和细胞色素 P450 2C9(CYP2C9)基因变异对高血压患者血管紧张素Ⅱ1 型受体拮抗剂降压疗效个体差异的影响.方法 入选高血压患者 76 例,予单药厄贝沙坦每天 150 mg,治疗 8 周,观察降压疗效.提取血中 DNA,分别用聚合酶链反应-限制性片段长度多态性(PCR-RFLP)和微阵列技术进行单核苷酸多态性(SNP)位点(AT1R 1166A/C、573 T/C、-521 C/T,CYP 2C9 1075A/C、1080C/G)的基因型分析.结果 含 AT1R 573 T 等位基因患者,服用厄贝沙坦后,收缩压下降幅度明显大于 CC 基因型患者,分别为(16.47±11.75) vs (7.44±7.50)mm Hg(P＜0.05)而 AT1R 1166A/C、-521 C/T、CYP 2C9 1075A/C、1080C/G 各基因型服药后,血压下降幅度均无显著差异.结论 厄贝沙坦作用受体 AT1R 基因 SNP 位点 573 T/C 可能与其降压疗效有关;未发现 CYP 2C9 基因上的两个 SNP 位点与厄贝沙坦的降压疗效有关.     

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。     

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。     

新疆维吾尔族和哈萨克族健康人群CYP2C9和VKORC1基因多态性研究

目的：了解细胞色素P450（CYP）2C9、维生素K环氧化还原酶复合体1（VKORC1）基因单核苷酸多态性在新疆维吾尔族和哈萨克族健康人群中的频率分布及与其他不同民族之间的差异,为新疆维吾尔族和哈萨克族人群实施华法林个体化用药剂量提供理论依据。方法：采用BaiO华法林敏感性基因检测试剂盒的芯片检测技术对506位新疆维吾尔族和哈萨克族健康者的CYP2C9＊2和CYP2C9＊3位点以及VKORCI（-1639A/G和1173T/C）位点基因多态性进行检测,统计其等位基因和基因型频率,并与国外多个民族的这两个基因多态性分布进行比较。结果：506份样本中共检测到CYP2C9的3种等位基因CYP2C9＊1、CYP2C9＊2和CYP2C9＊3,等位基因频率分别为89.6%、2.8%和7.6%;5种等位基因型分别为CYP2C9＊1/＊1,CYP2C9＊1/＊2,CYP2C9＊1/＊3,CYP2C9＊2/＊3和CYP2C9＊3/＊3。VKORC1-1639A/G检测出两种等位基因A和G,其频率分别为63.8%和36.2%;三种等位基因型AA（41.7%）、AG（44.3%）和GG（14%）的频率分别与1173T/C的TT、TC和CC型完全相同。结论：新疆维吾尔族和哈萨克族人群CYP2C9和VKORC1存在明显的基因多态性,其分布与中国汉族等亚洲人群以及欧美人群均存在较大差异。     

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)。     

河南地区汉族人群药物代谢酶CYP2C19，NAT2和TPMT基因多态性分析(英文)

目的：了解细胞色素P450(cytochromes P450,CYP)2C19,N-乙酰基转移酶2(arylamine N- acetyltransferase 2,NAT2)和硫嘌呤甲基转移酶(thiopurine S-methyltransferase,TPMT)基因常见的遗传多态性在河南地区汉族人群中的分布及其频率。方法：应用聚合酶链反应-限制性片段长度多态性分析(PCR-RFLP)对210名河南地区汉族人群的CYP2C19突变基因(*2和*3)、NAT2突变基因(*6和*7)和TPMT突变基因(*3A,*3B和*3C)进行检测。用聚合酶链反应-等位基因特异性扩增(PCR-ASA)对NAT2突变基因(*5)和TPMT突变基因(*2)进行检测。结果：CYP2C19*2和*3等位基因分布频率分别为34．76%和6．4%,同时携带2个等位突变基因的慢基因型频率占14．8%。NAT2*4(wt),*5(341C),*6(590A)和*7(857A)等位基因分布频率分别为59．1%,4．1%,26．4%和9．5%,慢基因型分布频率占19．5%。TPMT*3C等位基因分布频率为1．2%,未发现TPMT*2,TPMT*3A或TPMT*3B。结论：CYP2C19,NAT2和TPMT基因常见的遗传多态性在汉族人群中的分布及其频率与白人存在明显差异,这将有助于我国汉族人群临床药动学研究和给药剂量的确定。     

妊娠期高血压疾病与血管紧张素转换酶基因和血管紧张素Ⅱ-1型受体基因多态性的相关性研究

目的探讨妊娠期高血压疾病与血管紧张素转换酶（ACE）基因插入／缺失（I／D）、血管紧张素Ⅱ-1型受体（AT1R）基因A^1166-C多态性的相关关系。方法采用聚合酶链反应．限制性内切酶片段长度多态性技术（PCR-RFLP）分别检测87例妊娠期高血压疾病患者和175例正常对照的ACE基因I／D多态性、AT1R基因A^1166-C突变位点的基因型。结果妊娠期高血压疾病患者中ACEI／D基因的ID和DD基因型频率，明显高于正常对照组，分别为41．4％和28．7％；相对于Ⅱ基因型，携带ID和DD基因型人群的OR值分别为1．981和2．347；D等位基因频率也显著高于正常对照组（49．42％），差异有显著性；相对于Ⅰ等位基因，D等位基因OR值为1．737；妊娠期高血压疾病患者中AT1R基因的AC基因型频率为33．3％；相对于AA基因型，携带AC基因型人群的OR值为1．803，C等位基因频率为17．2％，相对于A等位基因，C等位基因OR值为1．711；两组ACE和AT1R联合基因分析：相对于Ⅱ—AA联合基因型，同时携带AC-ID联合基因型的OR值为3．655；AC-DD的OR值为3．045，其余联合基因型差异均无统计学意义（P〉0．05）。结论ACE基因中D等位基因及AT，R基因A1166点突变等位基因C可能增加妊娠期高血压疾病的遗传易感性；在妊娠期高血压疾病的发生中，ACE基因及AT1R基因，可能共同对妊娠期高血压疾病的发生起作用。     

佳木斯地区健康人群与高血压患者CYP3A4* 1G基因多态性分析

目的:通过比较本地区健康人与高血压患者CYP3A4*1G基因多态性的差异,探讨CYP3A4*1G基因多态性与高血压病的易感关系。方法 :采用聚合酶链式反应-限制性片段长度多态性(PCR-RFLP)方法检测本地区健康人与高血压患者的CYP3A4*1G基因型分布及等位基因频率,通过χ2检验来比较本地区健康人与高血压患者基因型分布差异和等位基因频率差异。结果:高血压患者与健康人的基因分布及等位基因频率差异有显著性和高度显著性(P<0.05和P<0.01)。结论:高血压病的发生与CYP3A4*1G的碱基变异具有相关性。     

湖北地区原发性高血压人群药物相关基因多态性研究

目的 研究湖北地区原发性高血压人群中抗高血压药物相关的7种基因多态性的分布特征,探讨高血压药物相关基因检测的临床应用价值。方法 选取2020年9月至2022年6月在湖北省中医院和各课题参与单位就诊的500例原发性高血压患者为研究对象,采用PCR-熔解曲线法检测7种基因位点,统计基因频率和基因型频率在高血压患者中的分布情况,比较不同性别、年龄患者之间基因型频率分布差异,与正常人群比较等位基因分布频率的差异。结果 500例患者中,男、女患者之间基因型分布频率差异无统计学意义（P> 0.05）;AGTR1(1166A>C)基因型分布在不同年龄组间差异有统计学意义（P <0.05）;与正常人群比较等位基因分布频率差异无统计学意义（P> 0.05）。结论 湖北地区原发性高血压患者中CYP2D6*10、ADRB1(G/C)、CYP3A5*3的突变频率均超过50%,NPPA(2238T>C)的突变频率不足1%,本研究为个体化基因导向治疗奠定了理论基础。     

三维凝胶基因芯片法研究中国人群CYP2C9与CYP2C19基因多态性

目的：应用三维凝胶基因芯片方法研究中国人群CYP2C9与CYP2C19基因多态性,为临床合理用药提供新的技术手段与研究方法。方法：提取207名男性健康志愿者基因组DNA,PCR分别扩增包含CYP2C9＊3、＊13与CYP2C19＊2、＊3多态位点目标片段,制备三维凝胶基因芯片,荧光标记探针杂交,芯片扫描并基因分型,用直接测序法对结果进行验证。结果：207人中,11人为CYP2C9＊1/＊3基因型,1人为CYP2C9＊1/＊13基因型,1人为CYP2C9＊3/＊3基因型。2C9＊3、＊13等位基因发生率分别为2.90%、0.24%,慢代谢型发生率为0.48%。CYP2C19突变杂合子有97人,突变纯合子有26人,2C19＊2、＊3等位基因发生率分别为32.85%、3.62%,慢代谢型发生率为12.56%。四种等位基因型分布均符合Hardy-Weinberg平衡。结论：三维凝胶基因芯片方法可为临床快速基因分型提供高效平台。CYP2C9与CYP2C19基因在中国人群存在普遍多态性,检测其基因型可有效指导相关临床治疗药物应用,提高药效,降低不良反应。     

Allele and genotype frequencies of CYP2C9 in a Korean population

AIMS: To determine the frequencies of the variant alleles and the genotypes of CYP2C9 in a Korean population. METHODS: Three hundred and fifty-eight healthy Korean subjects were studied. CYP2C9 alleles were detected by polymerase chain reaction-restriction fragment length polymorphism assays and direct sequencing assays. RESULTS: The allele frequencies were 0.934 for CYP2C9*1, 0.060 for CYP2C9*3 and 0.006 for CYP2C9*13. The CYP2C9*2,*4,*5 and *11 alleles were not detected. The frequencies of the CYP2C9*1/*1, *1/*3 and *1/*13 genotypes were 0.869, 0.120 and 0.011, respectively. CONCLUSION: The frequency of the CYP2C9*3 allele in the Korean population studied was significantly higher than reported elsewhere, and a novel allele, CYP2C9*13, was found at a frequency of 0.006 (95% confidence interval 0, 0.012). Only three genotypes of CYP2C9, CYP2C9*1/*1,*1/*3 and *1/*13 were observed in this Korean population.     

中国2型糖尿病人中CYP2C8、CYP2C9基因多态性

目的：查明CYP2C9、CYV2C8等抗糖尿病药物主要代谢酶的基因多态性在中国2型糖尿病（T2DM）A-群中的分布频率和分布特征。方法：运用多聚酶链反应．限制性长度多态性（PCR．RFLP）方法和变性高效液相色谱法（DHPLC）对222名中国T2DM患者进行了有功能意义的CYP2C8＊3、CYP2C8P404A和CYP2C9＊3,以及可能存在功能意义的CYP2C8IVs2（-5insertt）突变体等等位基因型检测,并计算了各等位基因的频率。结果：222名中国T2DM患者的CYP2C8基因中未检出CYP2C8＊3、P404A型,CYP2C8IVS2（-5insertt）和CYP2C9＊3等位基因的频率分别为43．0％、2．48％,二者突变等位基因在男、女性别分布中不存在差异（P〉0．05）,同时为CYP2C8IVS2（-5insertt）和CYP2C9＊1＊3基因的频率为6．3％,该联合突变基因型的分布也不存在性别差异（P〉0．05）。结论：中国T2DM患者中CYP2C9＊3的等位基因频率为2．48％;未检出CYP2C8。3和P404A型,CYP2C81VS2（-5insertt）突变体发生频率为43．0％,其是否影响CYV2C8的代谢活力有待于进-步研究。     

Genetic polymorphisms of CYP2C9 and CYP2C19 in the Beninese and Belgian populations

AIMS: To investigate the distribution of cytochrome P450 2C9 (CYP2C9) and 2C19 (CYP2C19) genotype frequencies in the Beninese and Belgian Caucasian populations. METHODS: Beninese (n = 111) and Belgian (n = 121) were genotyped for CYP2C9*2, *3, *4, *5, and *11 as well as for CYP2C19*2 and*3. RESULTS: The distribution of alleles was: CYP2C9*1: 95.5 vs. 82.2% (P < 0.001); CYP2C9*2: 0 vs. 10% (P < 0.001); CYP2C9*3: 0 vs. 7.4% (P < 0.01); CYP2C9*4: both 0%; CYP2C9*5: 1.8 vs. 0% (P = 0.05); and CYP2C9*11: 2.7 vs. 0.4% (P < 0.05). The frequencies of the CYP2C19*2 allele were 13 vs. 9.1%, respectively. CYP2C19*3 was not detected in either population. The 95% confidence intervals for the differences of frequencies of CYP2C9*1, CYP2C9*2, CYP2C9*3, CYP2C9*4, CYP2C9*5, CYP2C9*11, CYP2C19*1, CYP2C19*2 and CYP2C19*3 between Belgian and Beninese were 7%, 19%; - 14%, - 6%; - 11%, - 4%; - 1%, 1%; 0%, 4%; 0%, 5%; - 10%, 2%; - 2%, 10%; - 1%; respectively. The distributions of CYP2C9 genotypes in the Beninese and Belgian individuals were: CYP2C9*1/*1: 91 vs. 67% (P < 0.00001); CYP2C9*1/*2: 0 vs. 18.2% (P < 0.0001); CYP2C9*1/*3: 0 vs. 11.6% (P < 0.001); CYP2C9*1/*5: 3.6 vs. 0% (P = 0.05); CYP2C9*1/*11: 5.4 vs. 0.8% (P = 0.05); CYP2C9*2/*3: 0 vs. 1.6% (NS); CYP2C9*3/*3: 0 vs. 0.8% (NS). The distributions of CYP2C19 genotypes between these ethnic groups were: CYP2C19*1/*1: 73.9 vs. 83.5% (NS); CYP2C19*1/*2: 26.1 vs. 14.9% (P < 0.05); CYP2C9*2/*2: 0 vs. 1.6% (NS). CONCLUSIONS: Differences of allele frequencies between Beninese and Belgian populations were statistically significant for CYP2C9*2, *3, *5 and *11, but not for CYP2C9*4 or for CYP2C19*2 and *3.     

Phenytoin metabolic ratio: a putative marker of CYP2C9 activity in vivo

CYP2C9 mediates the oxidative metabolism of approximately 10% of drugs, some of which are characterized by a narrow therapeutic index. We aimed to validate genotype method and phenotype methodology, for evaluation of CYP2C9 activity in vivo. Thirty-one healthy subjects (22 male) received a single 300 mg dose of phenytoin. Blood was drawn periodically and urine was collected at intervals for 96 h. Plasma phenytoin and 5-(4-hydroxyphenyl)-5-phenylhydantoin (p-HPPH) and urine S and R enantiomers of p-HPPH were determined by high-performance liquid chromatography. CYP2C9 genotyping was obtained by polymerase chain reaction followed by digestion with Sau96I and StyI for the identification of CYP2C9*2 and CYP2C9*3, respectively. Eighteen subjects were CYP2C9*1 homozygous, seven were CYP2C9*2 heterozygous, four were CYP2C9*3 heterozygous, one was CYP2C9*2 homozygous and one was compound CYP2C9*2/CYP2C9*3 heterozygous. The allele frequencies of CYP2C9*1, CYP2C9*2 and CYP2C9*3 were 0.76 [95% confidence interval (CI) 0.73-0.79], 0.16 (95% CI 0.13-0.19) and 0.08 (95% CI 0.05-0.11), respectively. The CYP2C9-mediated production of (S)-p-HPPH represented the major metabolic pathway of phenytoin biotransformation as its excretion accounted for 95.6 + 0.9% of 'total' p-HPPH excretion over the 96 h collection interval. Phenytoin metabolic clearance to produce (S)-p-HPPH (PMC), correlated significantly with (S)-p-HPPH (or 'total' p-HPPH) content in 0-8, 0-12 and 0-24 urine collections (r = 0.88, 0.85 and 0.89, respectively) and with phenytoin metabolic ratio (PMR) defined as the ratio of urine (S)-p-HPPH (or 'total' p-HPPH) to mid-interval plasma phenytoin (r = 0.90, 0.88 and 0.94, respectively). PMC and PMR exhibited a gene-dose effect so that the highest and lowest values were noted in homozygous subjects CYP2C9*1 and subjects carrying two defective alleles, respectively, whereas heterozygous subjects had intermediate values. CYP2C9 genotyping and several phenytoin metabolic indices are correlated with CYP2C9 activity in vivo. The utility of phenytoin to predict the metabolism of other CYP2C9 substrates justifies further evaluation.     

Genetic polymorphism of cytochrome P450 2C9 in a Caucasian and a black African population

AIMS: CYP2C9 is a major enzyme in human drug metabolism and the polymorphism observed in the corresponding gene may affect the therapeutic outcome during treatment with several drugs. The distribution of variant CYP2C9 alleles was therefore investigated in an Italian and an Ethiopian population. METHODS: Allele-specific PCR analysis was carried out in order to determine the frequencies of the two most common variant alleles, CYP2C9*2 and CYP2C9*3 in genomic DNA isolated from 157 Italians and 150 Ethiopians. RESULTS: The frequencies of CYP2C9*1 (80%), CYP2C9*2 (11%) and CYP2C9*3 (9%) found in the Italian population were similar to other Caucasian groups. However in the Ethiopian population CYP2C9*1, CYP2C9*2 and CYP2C9*3 were present at a frequency of 94, 4 and 2% respectively. The 95% confidence intervals in CYP2C9*1, CYP2C9*2 and CYP2C9*3 between Italians and Ethiopians were 0.098, 0.176, 0.040, 0.098 and 0.040, 0.098, respectively. CONCLUSIONS: Our results indicate that the Ethiopian population has a unique relative distribution of the CYP2C9 alleles, which is not similar to any other ethnic group hitherto described.     

Gender specific association of CYP2C9*3 with hyperlipidaemia in Chinese

AIMS: To investigate the association of CYP2C9*3 and *6 with hyperlipidaemia in Chinese. METHODS: Four hundred and seventy-six Chinese participated in the study, including 211 uncomplicated hyperlipidaemic patients and 265 healthy controls. PCR-RFLP was used to identify CYP2C9*3 and *6. RESULTS: CYP2C9*6 was not detected in this study. The allelic frequency of CYP2C9*3 was 0.039 (95% CI 0.022, 0.056). A nonsignificant difference existed in CYP2C9*3 frequencies between males and females (P = 0.605, OR = 1.194, 95% CI 0.610, 2.336), patients and controls (P = 0.063, OR = 0.506, 95% CI 0.244, 1.049) in the total population. However, in the female group, CYP2C9*3 frequency in patients with hyperlipidaemia was significantly lower than that in controls (P < 0.0001, OR = 0.062, 95% CI 0.008, 0.476). CONCLUSIONS: The association of CYP2C9*3 with hyperlipidaemia was specific for females in this Chinese population.     

Genetic polymorphism of CYP2D6 and CYP2C19 in East- and Southern African populations including psychiatric patients

OBJECTIVES: The study was carried out to investigate the distribution of cytochrome P450 2D6 (CYP2D6) and CYP2C19 genotype frequencies in three African populations and to compare these frequencies between healthy individuals and psychiatric patients. METHODS: Three hundred and eighty-four subjects from South Africa (Venda), Tanzania, and Zimbabwe who consented to the study were genotyped for CYP2D6 (CYP2D6*1, *2, *3, *4, *5, and *17) and CYP2C19 (CYP2C19*1, *2, and *3) by PCR-RFLP (polymerase chain reaction restriction fragment length polymorphism) techniques. RESULTS: The genotypes for CYP2D6 predicted a poor metabolizer frequency of 2.3% (2/88) in Tanzanian psychiatric patients, 1.9% (2/106) in Tanzanian healthy controls and 2.6% (2/76) in the South African Venda. The low-activity CYP2D6*17 allele frequency was higher in psychiatric patients (30%, 53/176) than in healthy individuals (20%, 43/212) in Tanzanians. The frequencies for CYP2C19*2 genotypes were predictive of a low prevalence of poor metabolizers (PMs). The CYP2C19*3 allele was absent in the three populations studied. There was no difference in CYP2D6 or CYP2C19 PM genotype frequencies between psychiatric patients and healthy subjects. CONCLUSION: The genotype results predict a low prevalence of people with deficient CYP2D6 and CYP2C19 activity among linguistically (Bantu) related populations of East and Southern Africa. The high frequency of the low-activity CYP2D6*17 allele predicts that the Bantu people have a reduced capacity to metabolise drugs that are CYP2D6 substrates.     

Pharmacogenetics of warfarin elimination and its clinical implications

Warfarin is one of the most widely prescribed oral anticoagulants. However, optimal use of the drug has been hampered by its >10-fold interpatient variability in the doses required to attain therapeutic responses. Pharmacogenetic polymorphism of cytochrome P450 (CYP) may be associated with impaired elimination of warfarin and exaggerated anticoagulatory responses to the drug in certain patients. Clinically available warfarin is a racemic mixture of (R)- and (S)-warfarin, and the (S)-enantiomer has 3 to 5 times greater anticoagulation potency than its optical congener. Both enantiomers are eliminated extensively via hepatic metabolism with low clearance relative to hepatic blood flow. CYP2C9 is almost exclusively responsible for the metabolism of the pharmacologically more active (S)-enantiomer. Several human allelic variants of CYP2C9 have been cloned, designated as CYP2C9*1 (reference sequence or wild-type allele), CYP2C9*2, CYP2C9*3 and CYP2C9*4, respectively. The allelic frequencies for these variants differ considerably among different ethnic populations. Caucasians appear to carry the CYP 2C9*2 (8 to 20%) and CYP2C9*3 (6 to 10%) variants more frequently than do Asians (0% and 2 to 5%, respectively). The metabolic activities of the CYP2C9 variants have been investigated in vitro. The catalytic activity of CYP2C9*3 expressed from cDNA was significantly less than that of CYP2C9*1. Human liver microsomes obtained from individuals heterozygous for CYP2C9*3 showed significantly reduced (S)-warfarin 7-hydroxylation as compared with those obtained from individuals genotyped as CYP2C9*1. The influence of the CYP2C9*3 allele on the in vivo pharmacokinetics of (S)-warfarin has been studied in Japanese patients. Patients with the homozygous CYP2C9*3 genotype, as well as those with the heterozygous CYP2C9*1/*3 genotype, had significantly reduced clearance of (S)-warfarin (by 90 and 60%, respectively) compared with those with homozygous CYP2C9*1. The maintenance dosages of warfarin required in Japanese patients with heterozygous and homozygous CYP2C9*3 mutations were significantly lower than those in patients with CYP2C9*1/*1. In addition, 86% of British patients exhibiting adequate therapeutic responses with lower maintenance dosages of warfarin (<1.5 mg/day) had either the CYP2C9*2 or CYP2C9*3 mutation singly or in combination, whereas only 38% of randomly selected patients receiving warfarin carried the corresponding mutations. Furthermore, the former group showed more frequent episodes of major bleeding associated with warfarin therapy. These data indicate that the CYP2C9*3 allele may be associated with retarded elimination of (S)-warfarin and the resulting clinical effects. However, relationships between CYP2C9 genotype, enzyme activity, metabolism of probe substrates, dosage requirements and bleeding complications should be interpreted with caution, and further studies are required.