Rapid genotyping for relevant CYP1A2 alleles by pyrosequencing

Objective To develop a rapid and reliable screening method for identifying the relevant cytochrome P450 (CYP) 1A2 alleles CYP1A2*1D (−2467Tdel), *1F (−163A>C), and *1K (−739T>G, −729C>T, −163A>C) that are in linkage disequilibrium with the functionally relevant CYP1A2 polymorphisms and therefore are considered to be predictive for the CYP1A2 phenotype. Methods CYP1A2 single nucleotide polymorphisms (SNPs) −2467Tdel, −739T>G, −729C>T, and −163A>C were screened for in 495 healthy Caucasian volunteers using newly developed pyrosequencing duplex and simplex assays. Conventional sequencing of randomly selected samples served as quality control. Results Frequencies were 7.9% for CYP1A2*1D, 31.8% for *1F, and 0.4% for *1K. The observed distribution of homozygous and heterozygous carriers of the alleles corresponded to the predicted one according to the Hardy-Weinberg law. It also corresponded to reported allelic frequencies from Caucasians but differed significantly from the distribution seen in other ethnicities. The most frequent haplotype was −2467T/−739T/−729C/−163A (allelic frequency 61.6%), followed by −2467T/−739T/−729C/−163C (30.5%), −2467Tdel/−739T/−729C/−163A (5.1%), −2467Tdel/−739G/−729C/−163A (1.2%), and −2467Tdel/−739T/−729C/−163C (1.1%). Complete linkage disequilibrium (value of D’ nearly 1) existed between −2467Tdel, −739T>G, and −729C>T and between −729T>G and −163A>C. Conclusions Pyrosequencing facilitates rapid and reliable detection of those CYP1A2 alleles that, based on current knowledge, can be considered predictive for the CYP1A2 phenotype.     

Identification of CYP2D6 impaired functional alleles in Mexican Americans

Objectives To extend the genotyping analysis of the CYP2D6 gene and further explain variability of CYP2D6 activity in Mexican Americans by genetic factors. Methods CYP2D6 gene sequence variations associated with *6, *7, *8, *9, *11, *14, *29, *41, *45, and *46 alleles as well as the 2988G>A SNP were examined in 264 Mexican Americans; 236 had previously been phenotyped with dextromethorphan. All subjects were previously genotyped for CYP2D6*2, *3, *4, *5, *10, *17, and the presence of a gene duplication. Associations between genotype and CYP2D6 activity were determined. Results Mexican Americans revealed a high frequency of functional alleles (CYP2D6*1 and *2; 73.1%), followed by CYP2D6*4 (non-functional, 10.0%) and the reduced-function allele *41 (9.5%). The frequencies of CYP2D6*5, *6, *9, *10, duplication, and 2988A were 1.7%, 0.4%, 1.1%, 2.8%, 0.8%, and 5.7%, respectively. CYP2D6*3, *17, and *29 were found only in one individual (CYP2D6*2/*3, *1/*17, and *4/*29), while CYP2D6*7, *8, *11, *14, *45, and *46 were absent in this study population. Decreased CYP2D6 activity was more accurately predicted by the presence *41[−1584C] compared to *41[2988A]. One genotype/phenotype discordant subject was resolved by the presence of a CYP2D6*6 allele (*4/*6), while two other cases remained discordant (*41/*41 and *1/*1). Conclusions The CYP2D6*4, *5, and *6 null alleles along the reduced function alleles *9, *10, and *41 are the major cause for diminished dextromethorphan oxidative capacity in Mexican Americans. These findings may have implications for the safety and efficacy of CYP2D6 substrates taken by Mexican Americans.     

Influence of sex and CYP2D6 genotype on mirtazapine disposition, evaluated in Spanish healthy volunteers

AimsTo evaluate the influence of sex and CYP2D6 genotype on mirtazapine disposition within two bioequivalence studies in healthy volunteers.MethodsSeventy-two healthy volunteers were included in two standard 2 × 2 crossover bioequivalence trials. Subjects received a single 30-mg oral dose of each mirtazapine formulation in each study period. Plasma concentrations were measured from 0 to 96 or 120 h by a HPLC with coupled mass spectrometry validated method. CYP2D6 genotyping was available for 68 subjects that were classified into three phenotypic groups depending on the number of active gene copies: extensive/ultrarapid metabolizers (UM-EM), intermediate (IM) and poor metabolizers (PM). To evaluate the influence of sex and genotype on mirtazapine disposition we performed a linear mixed model for repeated measures. Pharmacokinetic data were log-transformed and AUC and C_max adjusted to the administered dose/weight. Factors included in the model were centre, formulation, period, sequence, sex and genotype as fixed effects, and subject nested sequence × sex × genotype as random one. A second model was also performed adding the interaction sex × genotype to the previous model.ResultsMirtazapine disposition evaluated as AUC_0–∞ is influenced by sex (p = 0.007) and CYP2D6 phenotype group (p = 0.01). Attending to the theoretical figures provided by the model, mean (95% CI) dose/weight adjusted AUC_0–∞ (ng h/ml)/(mg/kg) is 1516.62 (1411.27–1628.22) in EM/UM, 1613.63 (1482.14–1758.55) in IM and 2049.28 (1779.78–2357.24) in PM. In the case of C_max these figures also show a trend to higher values in PM, but it did not reach statistical significance. Females show a lower dose/weight adjusted AUC_0–∞: 1594.39 (1477.70–1720.28) vs. 1837.65 (1694.67–1992.70). On the contrary dose/weight adjusted C_max is higher in females than in males: 38.33 (34.79–42.28) vs. 32.66 (29.44–36.21).ConclusionsBoth CYP2D6 genotype group and sex influence the disposition of mirtazapine in healthy volunteers and confirm reported data in the literature obtained by different methods. No sex-by-genotype interaction could be detected.     

Frequencies of CYP2D6 mutant alleles in a normal Japanese population and metabolic activity of dextromethorphan O-demethylation in different CYP2D6 genotypes

AIMS: To determine the frequencies of 11 CYP2D6 mutant alleles (CYP2D6*2, *3, *4, *5, *8, *10, *11, *12, *14, *17 and *18), and their relation to the metabolic capacity of CYP2D6 in Japanese subjects. METHODS: One hundred and sixty-two unrelated healthy Japanese subjects were genotyped with the polymerase chain reaction amplification method and 35 subjects were phenotyped with dextromethorphan. RESULTS: The frequencies of CYP2D6*2,*5, *10 and *14 were 12.9, 6.2, 38.6 and 2.2% in our Japanese subjects, respectively. CYP2D6*3, *4, *8, *11, *12, *17 and *18 were not detected. The mean log metabolic ratio of dextromethorphan in subjects with genotypes predicting intermediate metabolizers was significantly greater than that of heterozygotes for functional and defective alleles. CONCLUSIONS: CYP2D6*5 and CYP2D6*14 are the major defective alleles found in Japanese subjects. In addition, CYP2D6*10 may play a more important role than previously thought for the treatment of Japanese patients with drugs metabolized by CYP2D6.     

中国人群CYP2D6基因多态性对美托洛尔药代动力学的影响

目的：研究中国人群CYP2D6基因多态性对美托洛尔药代动力学的影响。方法：使用基因芯片技术测定中国健康志愿者CYP2D6的基因型,按照分型结果将志愿者分为四组,第1组：CYP2D6＊2W＊10W,第2组：CYP2D6＊2H＊10W或CYP2D6＊2M＊10W,第3组：CYP2D6＊2M＊10H,第4组：CYP2D6＊2M＊10M,每组筛选10人,共40人。各组志愿者单次口服100mg美托洛尔后,使用HPLC方法测定血和尿中美托洛尔及其代谢产物α-羟基美托洛尔（HM）的浓度,研究其在不同基因型志愿者体内的药代过程。结果：第2组美托洛尔及其HM的主要药动学参数与第1组相比均没有统计学差异。第3组美托洛尔的t1/2、AUC、Cmax显著高于第1组（P〈0.05）;而HM的t1/2延长47.3%,AUC降低56.0%（P〈0.05）。第4组美托洛尔的t1/2、AUC、Cmax均显著高于第1组（P〈0.05）和第3组（P〈0.05）;HM的t1/2、AUC、Cmax与第1组和第3组相比均有统计学差异（P〈0.05）,且呈现基因剂量效应。第3组和第4组的口服清除率和肾清除率均低于第1组,而0-24h代谢比率分别为第1组的1.82倍和3.96倍。结论：CYP2D6＊2对于美托洛尔的药代动力学过程没有影响;但CYP2D6＊10可降低酶活性,且CYP2D6＊10纯合子变异比杂合子变异对美托洛尔药代动力学的影响更大,呈现基因剂量效应。     

CYP2D6 polymorphism in a Gabonese population: contribution of the CYP2D6*2 and CYP2D6*17 alleles to the high prevalence of the intermediate metabolic phenotype

AIMS: To determine the molecular basis of the intermediate extensive metaboliser (EM) CYP2D6 phenotype in healthy Gabonese subjects. METHODS: The CYP2D6 phenotype of 154 healthy Gabonese subjects was assessed by giving the subject a single dose of 30 mg dextromethorphan, and collecting their urine for the next 8 h. The CYP2D6 genotype was determined for 50 individuals of the EM phenotypic group by Southern blotting and various PCR-based procedures aimed at identifying different CYP2D6 alleles. RESULTS: We found that in the studied Gabonese population, as compared with a French population, there is significantly higher frequency of intermediate EM phenotype having lower frequency of CYP2D6 PM alleles. To clarify this discrepancy phenotype-genotype relationship was studied. We found that the CYP2D6*17 and CYP2D6*2 alleles, prevalent in this black population, are characterised by their low capacity for dextromethorphan demethylation. Our data also show that the CYP2D6*1 allele is associated with the highest in vivo activity followed by the CYP2D6*2 allele and then the CYP2D6*17 allele. CONCLUSIONS: The higher frequencies of the CYP2D6*2 and CYP2D6*17 alleles than the CYP2D6*1 allele account for the high frequency of the intermediate EM phenotype in this black population. The polymorphism of the CYP2D6 enzyme activity in African populations could have important implications for use of drugs that are substrates for CYP2D6 and have a narrow therapeutic window.     

细胞色素P4502D6基因多态性和药物相互作用

细胞色素P4502D6（CYP2D6）是一种重要的P450系氧化代谢酶,参与多种重要药物的代谢.CYP2D6具有基因多态性,对药物的代谢呈现明显的个体差异.而且CYP2D6能被多种药物竞争性抑制和诱导,药物联用时易产生相互作用.本文从CYP2D6的基因多态性与代谢表型、底物竞争作用、代谢酶的诱导和抑制等方面,探讨CYP2D6基因多态性与药物相互作用的关系.     

以普罗帕酮为探针测定人肝微粒体中CYP2D6的活性

目的:测定普罗帕酮(PPF)和5-羟基普罗帕酮(5-OHP)的比值以表达人肝微粒体中CYP2D6的活性.方法:以1g·L-1微粒体蛋白浓度37℃孵育PPF 1 h,以HPLC测定PPF和5-OHP的含量.结果:PPF和5-OHP的线性方程分别为Y=0.452 0 C 0.003 0,r=0.999 7;Y=0.749 4 C-0.020 5,r=0.997 5.结论:人肝微粒体CYP2D6酶的活性可以通过测定5-OHP与PPF的比值进行预测.     

Genetic polymorphism of debrisoquine (CYP2D6) and proguanil (CYP2C19) in South Pacific Polynesian populations

Objective: Genetic oxidation polymorphisms of debrisoquine (CYP2D6) and proguanil (CYP2C19) were studied in unrelated healthy South Pacific Polynesian volunteers recruited in the South Island of New Zealand. Methods: Phenotyping for CYP2D6 and CYP2C19 activities was determined using debrisoquine and proguanil, respectively, as probe drugs by measuring the urinary metabolic ratio of parent drug and its␣metabolite. Results: Of 100 Polynesian subjects phenotyped, the metabolic ratio of debrisoquine ranged from 0.01 to 9.94. Therefore, all South Pacific Polynesians were classified as extensive metabolizers of debrisoquine according to previously established criteria of the antimode. The prevalence of poor metabolizers of debrisoquine (CYP2D6) in this Polynesian population is 0% (95% confidence interval of 0–3.6%). Oxidation polymorphism of CYP2C19 using proguanil as a probe was also studied in 59 Polynesian volunteers. The frequency distribution of the proguanil/cycloguanil ratio was bimodal. The proguanil/cycloguanil ratios for these subjects ranged from 0.09 to 34.4. Using a recommended proguanil/cycloguanil ratio cut-off point of 10 established in Caucasian populations, eight Polynesian subjects were identified as poor metabolizers of proguanil (CYP2C19), which corresponds to a poor metabolizer phenotype frequency of 13.6% (a 95% confidence interval of 5.9–24.6%). Conclusion: The incidence of poor metabolizer phenotypes for debrisoquine (CYP2D6) in South Pacific Polynesians appears to lower than in Caucasian populations, while the prevalence of poor metabolizers for proguanil (CYP2C19) in this ethnic population is higher. The frequencies of the poor metabolizer phenotype for debrisoquine and also for proguanil in South Pacific Polynesians are similar to those reported in Asian populations. Received: 18 December 1997 / Accepted in revised form: 30 April 1998     

The effect of perazine on the CYP2D6 and CYP2C19 phenotypes as measured by the dextromethorphan and mephenytoin tests in psychiatric patients

There is evidence that the antipsychotic drug perazine is an inhibitor of CYP2D6. This study aimed at evaluating its effect on CYP2D6 and CYP2C19 activities in submitting psychiatric patients to phenotyping with dextromethorphan and mephenytoin, respectively, substrates of these enzymes, before and during a treatment with perazine. A total of 31 patients were phenotyped with dextromethorphan (CYP2D6) and mephenytoin (CYP2C19) before and after a 2‐week treatment with 450 ± 51 mg/day (mean ± sd) perazine. At baseline, five patients appeared to be poor metabolizers (PM) of dextromethorphan and two patients of mephenytoin. The metabolic ratio (MR) of dextromethorphan/dextrorphan as determined in collected urine increased significantly (Wilcoxon; P < .0001) from baseline (0.39 ± 1.38 [mean ± sd]) till day 14 (1.46 ± 2.22). In 19 out of 26 extensive metabolizers (EM) of dextromethorphan, the phenotype changed from EM to PM. This suggests an almost complete inhibition of CYP2D6 by perazine and/or its metabolites. On the other hand, perazine (or some of its metabolites) did seemingly not inhibit CYP2C19. In conclusion, this study suggests that in patients treated with perazine and co‐medicated with CYP2D6 substrates, there could be an increased risk of adverse effects as a consequence of a pharmacokinetic interaction.     

Influence of donor and recipient genotypes on CYP2D6 phenotype after liver transplantation: a study of mutations CYP2D6*3 and CYP2D6*4

Objective: After liver transplantation (LT), genotypic differences between the recipient and the transplanted liver, medications and post-LT complications may all affect drug metabolism. We have studied the effect of two CYP2D6 mutations in the donor and the recipient on post-LT CYP2D6 phenotype. Method: The CYP2D6 phenotype was assessed in 48 patients before and after LT with debrisoquine or␣dextromethorphan. CYP2D6*3 (CYP2D6A) and CYP2D6*4 (CYP2D6B) mutations were detected in the donor and the recipient using polymerase chain reaction. Results: Before LT, 40 subjects were classified as extensive metabolisers (EM) and 8 as poor metabolisers (PM); after transplantation, 41 were EMs and 7 were PMs. Genotype and phenotype were in agreement in 100% of EMs and 40% of PMs. The low percentage of agreement in PMs could not be explained by severely altered liver function. The phenotype of 13 subjects was apparently changed by LT: 6 EMs became PMs and 7 PMs became EMs. All four subjects in whom genotype changed following LT had a corresponding change in phenotype: two EM subjects became PMs and two PM subjects became EMs. Conclusion: The low percentage of agreement in PMs may be partly explained by mutations other than CYP2D6*3 and CYP2D6*4. Nevertheless, our study shows that the CYP2D6 genotype of the donor controls the phenotype of the recipient of a liver transplantation. Received: 2 June 1997 / Accepted in revised form: 9 October 1997     

CYP2D6 and CYP2C19 genotypes in an elderly Swedish population

Objective: Eighty-three healthy elderly Swedish subjects (age 87 ± 4 years, mean ± SD, range 80–98 years) were genotyped with respect to the two genetic polymorphisms of oxidative drug metabolism, CYP2D6 and CYP2C19, using allele-specific polymerase chain reaction (PCR). A control population consisted of 248 younger unrelated healthy volunteers (age 31 ± 9 years, range 19–63 years) for CYP2D6, and 162 (age 30 ± 8 years, range 19–55 years) for CYP2C19. Results: No significant differences were found between the control groups and the elderly subjects with respect to the frequencies of the defect alleles CYP2D6*3, CYP2D6*4, CYP2C19*2 and CYP2C19*3. Neither were there any differences in the genotype frequencies, or the predicted phenotype frequencies. The study indicates that the CYP2D6 and CYP2C19 genotypes play no major role in the probability of reaching high age. Conclusion: No genetically determined differences in the pharmacokinetics of drugs metabolized by these two polymorphic enzymes are to be expected in the oldest age groups compared with younger adults. Received: 10 March 1998 / Accepted: 1 May 1998     

中国汉族、维吾尔族、哈萨克族人群中可溶性细胞黏附分子的表达与CYP2D6基因多态性

目的:探讨可溶性细胞黏附分子-1在汉族、维吾尔族、哈萨克族正常人血清中的表达水平是否存在民族间差异以及与CYP2D6基因多态性是否有关。方法:ELISA双抗体夹心法。结果:血清中可溶性细胞黏附分子-1含量:汉族为35~1 086μg.L-1,维吾尔族为40~1 024μg.L-1,哈萨克族为45~975μg.L-1。结论:可溶性细胞黏附分子-1的含量在汉族与维吾尔族、汉族与哈萨克族、维吾尔族与哈萨克族之间差异均无显著性。     

宁夏回族人群CYP2D6*10基因多态性及功能分析

目的 探讨基因突变对人CYP2D6蛋白结构与功能的影响.方法 采用等位基因特异扩增(ASA-PCR)及DNA测序技术分析宁夏网族人群CYP2D6*10(C188T)基因多态性,以生物信息学方法对突变造成的肝药酶活性的下降做出合理的解释.结果 蛋白质基本性质分析工具(ProtParam)分析显示,在溶液中CYP2D6*10突变型蛋白的不稳定指数高于野生型,都高于阈值40;二级结构预测软件(DNAStar/Protean)分析显示,突变型蛋白的二级结构在第33位多了一个转角(Gamier-Robson Turn);功能佗点预测程序(Motif Scan)对蛋白功能位点进行预测,结果显示CYP2D6*10野生型蛋白有2个P450酶激活位点.而突变型没有;信号肽预测程序(Signal P)分析显示.神经网络模型(NN)C-score计算结果为突变型蛋白没有信号肽,而野牛型有.结论 基因突变可引起CYP2D6蛋白结构与功能的改变;应用生物信息学方法对CYP2D6基因突变致使的酶活性的下降做出一些可能的解释是可行的.     

Metoclopramide is metabolized by CYP2D6 and is a reversible inhibitor,but not inactivator,of CYP2D6

Abstract

1. Metoclopramide is a widely used clinical drug in a variety of medical settings with rare acute dystonic events reported. The aim of this study was to assess a previous report of inactivation of CYP2D6 by metoclopramide, to determine the contribution of various CYPs to metoclopramide metabolism, and to identify the mono-oxygenated products of metoclopramide metabolism.

2. Metoclopramide interacted with CYP2D6 with Type I binding and a K_s value of 9.56?±?1.09?µM. CYP2D6 was the major metabolizer of metoclopramide and the two major products were N-deethylation of the diethyl amine and N-hydroxylation on the phenyl ring amine. CYPs 1A2, 2C9, 2C19, and 3A4 also metabolized metoclopramide.

3. While reversible inhibition of CYP2D6 was noted, CYP2D6 inactivation by metoclopramide was not observed under conditions of varying concentration or varying time using Supersomes^TM or pooled human liver microsomes.

4. The major metabolites of metoclopramide were N-hydroxylation and N-deethylation formed most efficiently by CYP2D6 but also formed by all CYPs examined. Also, while metoclopramide is metabolized primarily by CYP2D6, it is not a mechanism-based inactivator of CYP2D6 in vitro.     

奥扎格雷钠对大鼠CYP2D6亚型酶的影响

目的通过奥扎格雷钠的大鼠体内、外实验,观察奥扎格雷钠对大鼠CYP2D6亚型酶的影响。方法对照组和奥扎格雷钠诱导组大鼠分别经口给予生理盐水和奥扎格雷钠1wk,HPLC法测定大鼠尿样及肝微粒体中CYP2D6的探针药物右美沙芬的代谢率,观察奥扎格雷钠对CYP2D6活性的影响。结果①大鼠给予奥扎格雷钠(37mg·kg-1),其尿样中右美沙芬的代谢率明显高于对照组(P<0·01);②奥扎格雷钠诱导组大鼠肝微粒体中加入右美沙芬(0·324mmol·L-1),其右美沙芬的代谢率明显高于对照组(P<0·01);③奥扎格雷钠与CYP2D6特异性抑制剂西米替丁可明显降低右美沙芬的代谢率(P<0·01),并且奥扎格雷钠组其右美沙芬的代谢率低于西米替丁组(P<0·05);④奥扎格雷钠IC50=26·5μmol·L-1,西咪替丁IC50=86·3μmol·L-1,奥扎格雷钠诱导组肝微粒体Km=0·67mmol·L-1,Vmax=2·13nmol·min-1·g-1protein;对照组肝微粒体Km=0·29mmol·L-1,Vmax=0·91nmol·min-1·g-1protein;⑤体内和体外相应实验数据具有很好的相关性(r=0·9811)。结论奥扎格雷钠可诱导CYP2D6酶的活性。     

In vivo inhibition of CYP2C19 but not CYP2D6 by fluvoxamine

Studies were performed in eight healthy extensive metabolizers of mephenytoin and debrisoquine to determine the effect of fluvoxamine on the activities of S-mephenytoin 4'-hydroxylase (CYP2C19) and metoprolol α-hydroxylase (CYP2D6). Therapeutic dosing with fluvoxamine (100  mg day⁻¹) for 2 weeks caused a significant increase in the 0–8  h urinary S/R ratio of mephenytoin from 0.16 to 0.55 (95% confidence interval for difference between means: 0.28–0.50; P <0.01), accompanied by a 54% reduction in the 0–8  h urinary recovery of 4'-hydroxymephenytoin (95% confidence interval for difference between means: 3.64–16.24  mg; P <0.05). However, this did not alter the assigned phenotype of any of the subjects based on the established antimode of 0.95 (S/R-mephenytoin ratio). Two weeks after fluvoxamine was discontinued, both metabolic indices returned to their pre-study values. By contrast, fluvoxamine had no effect on either 0–8  h urinary metoprolol/α-hydroxymetoprolol ratio (95% confidence interval for difference between means: −0.38–0.46; P >0.05) or the 0–8  h urinary recovery of α-hydroxymetoprolol (95% confidence interval for difference between means: −0.61–0.70  mg; P >0.05). These results indicated fluvoxamine has a modest inhibitory effect on the activity of CYP2C19, but no effect on that of CYP2D6 in vivo .     

The <Emphasis Type="Italic">CYP2D6</Emphasis> gene locus in South African Coloureds: unique allele distributions,novel alleles and gene arrangements

Objective The highly polymorphic CYP2D6 gene locus has been extensively scrutinised in the major ethnic populations, but little is known about the locus for many indigenous and unique admixed populations, including the Coloureds of South Africa. This study aimed at characterising the CYP2D6 gene locus in Coloured subjects and predict their phenotype status. Methods CYP2D6 genotyping was performed on 99 Coloured subjects by long-range polymerase chain reaction (PCR) and PCR restriction fragment length polymorphism (RFLP). Testing included 25 allelic variants as well as gene duplications. Novel alleles were cloned and sequenced. A novel strategy for CYP2D7/2D6 hybrid gene detection is described. Results Thirteen alleles had a frequency of = 1%, three were infrequent (<1%) and 16 of the tested alleles were not detected. CYP2D6*5 had a frequency of 17.2%, one of the highest ever observed in any population. Two novel alleles, CYP2D6*64 and *65, were identified. In addition, four samples carried CYP2D7/2D6 hybrid genes, of which one matched the CYP2D6*66 allele of a resequenced Caucasian control subject. CYP2D6*66 is similar to CYP2D6*16, but its putative recombination point is further upstream. Genotyping identified three poor metabolisers (3%; predicted incidence 6.6%), and 12% of the population had an activity score of 0.5 indicative of intermediate metabolism. Conclusions The Coloured population has a unique composition of alleles and a distinct frequency distribution. The preliminary data presented suggest decreased CYP2D6 activity compared with Caucasians. Follow-up studies including both genotyping and phenotyping will need to be conducted to further assess the relationship between genotype and phenotype in this population of complex ancestry.