Hemochromatosis gene mutations in the general population of Slovakia

This is an epidemiologic study of the Slovak population with the aim of determining the frequencies of three hemochromatosis gene (HFE) variants C282Y, H63D and S65C known to be associated with manifestation of hereditary hemochromatosis and to assess deviations of these frequencies from those reported elsewhere. Mutations were detected in 359 ethnic Slovaks by real-time PCR assay based on TaqMan technology. The allelic frequencies were 4.03% for C282Y, 12.67% for H63D and 1.25% for S65C mutation. We observed 0.28% of C282Y/C282Y homozygotes, 3.34% H63D/H63D homozygotes, 0.84% of C282Y/H63D compound heterozygotes and 0.56% of H63D/S65C compound heterozygotes. This is the first time the frequencies of H63D and S65C mutations have been reported in the general population in Slovakia. The observed allelic frequencies are consistent with the previous studies of Slavic and Central European populations.     

An open population screening study for HFE gene major mutations proves the low prevalence of C282Y mutation in Central Italy

BACKGROUND: The C282Y mutation in the HFE gene is responsible for most cases of hereditary haemochromatosis. AIM: To investigate the allele frequency of HFE mutations and the associations between mutations and cases of iron overload or liver diseases in an open population of Central Italy. METHODS: A total of 502 individuals over 8 years of age, comprising 203 males and 299 females, who were residents in Arsita (a small town in Central Italy), were assayed for: C282Y, H63D and S65C mutations of the HFE gene by TaqMan probes; body mass index, serum ferritin, transferrin saturation, transaminases, GGT, glucose, insulin, total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, triglycerides, HBV and HCV serum markers. Information was obtained on alcohol intake. Liver ultrasound was performed in 334 (67%) subjects. RESULTS: The allele frequencies for C282Y, H63D and S65C were 2%, 15%, and 0.01%, respectively. C282Y/wt was found in 19 subjects (4%), H63D/wt in 127 (25%), H63D/H63D in 11 (2%) and S65C/wt in one (2.0 per thousand). No homozygosity for C282Y or compound mutation (C282Y/H63D) was found in the study population, but 27 subjects (5%) had TfSat >45% (including 10 subjects with high serum ferritin). Overall, 49 subjects (9.8%) were HCV-RNA-positive. Logistic regression analysis indicated that male gender (P = 0.000) and hepatic steatosis (P = 0.017) were independent variables correlating to a high serum ferritin. CONCLUSION: C282Y HFE mutation is less frequent in Central Italy than in Northern Italy.     

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.     

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.     

Morbidity risk in HFE associated hereditary hemochromatosis C282Y heterozygotes

Hereditary hemochromatosis (HHC) is a late-onset, autosomal recessive disorder leading to a chronic iron overload syndrome, finally causing diabetes, cardiomyopathy and liver disease. HHC is the most common single gene disorder in northern Europeans that occurs with a frequency of approximately 0.5%, and most of these patients carry the C282Y and H63D mutation in the HFE gene on chromosome 6p21.3. The vast majority of HHC patients are homozygous for the C282Y mutation, but HHC phenotypes are observed in other genotypes. Expression of the disease, in those homozygous for the C282Y mutation, is highly variable depending on the various features of the population studied. C282Y heterozygotes have slightly increased iron stores and in absence of other genetic and/or environmental factors do usually not develop the HHC phenotype. It is currently a matter of debate whether C282Y heterozygotes may have an increased risk for morbidity. Different studies investigating the association of C282Y heterozygocity with morbidity have given conflicting results, as is exemplified by extrahepatic cancers, cardiovascular diseases, alcoholic liver disease, and diabetes. However, there are examples of clear and unambiguous disease associations, such as with sporadic pophyria cutanea tarda. It remains to be seen whether a strong correlation between the C282Y heterozygous state and distinct pathological conditions will exist and large-scale genotyping studies will help to identify such potential risk groups in the future.     

Genotyping of four genetic polymorphisms in the CYP1A2 gene in the Egyptian population

AIMS: The goal of this study was to determine the frequencies of CYP1A2*1C, *1D, *1E and *1F variants in the Egyptian population and compare frequencies with other populations. METHODS: Genotyping was performed in a total of 212 unrelated Egyptian subjects using polymerase chain reaction-restriction fragment length polymorphism assay. RESULTS: The frequencies of CYP1A2*1C, *1D, *1E and *1F variants in the Egyptian population were 0.07, 0.40, 0.03 and 0.68, respectively. The Egyptians have a lower frequency of CYP1A2*1C, and CYP1A2*1E than the Japanese (0.07 vs 0.21 and 0.03 vs 0.08, respectively), while the frequencies of CYP1A2*1D and CYP1A2*1F did not differ significantly between the two groups. CYP1A2*1F (0.68) frequency in Egyptians was identical to that observed in Caucasians (0.68 among 236 German individuals). CONCLUSIONS: The present study is the first to describe the frequencies of four known allelic variants of CYP1A2 among the Egyptian population. CYP1A2*1C and *1E occurred at frequencies significantly lower than that in Japanese, while similar frequencies were observed for CYP1A2*1D and *1F. The CYP1A2*1F frequency appeared to be identical to that of Caucasians. This does not exclude the possibility of the presence of new mutations relatively specific to the Egyptian population that have not been identified.     

Polymorphisms in the cytochrome P450 CYP1A2 gene (CYP1A2) in colorectal cancer patients and controls: allele frequencies,linkage disequilibrium and influence on caffeine metabolism

AIMS: Several single nucleotide polymorphisms (SNPs) of the cytochrome P450 enzyme 1A2 gene (CYP1A2) have been reported. Here, frequencies, linkage disequilibrium and phenotypic consequences of six SNPs are described. METHODS: From genomic DNA, 114 British Caucasians (49 colorectal cancer cases and 65 controls) were genotyped for the CYP1A2 polymorphisms -3858G-->A (allele CYP1A2*1C), -2464T-->delT (CYP1A2*1D), -740T-->G (CYP1A2*1E and *1G), -164A-->C (CYP1A2*1F), 63C-->G (CYP1A2*2), and 1545T-->C (alleles CYP1A2*1B, *1G, *1H and *3), using polymerase chain reaction-restriction fragment length polymorphism assays. All patients and controls were phenotyped for CYP1A2 by h.p.l.c. analysis of urinary caffeine metabolites. RESULTS: In 114 samples, the most frequent CYP1A2 SNPs were 1545T-->C (38.2% of tested chromosomes), -164A-->C (CYP1A2*1F, 33.3%) and -2464T-->delT (CYP1A2*1D, 4.82%). The SNPs were in linkage disequilibrium: the most frequent constellations were found to be -3858G/-2464T/-740T/-164A/63C/1545T (61.8%), -3858G/-2464T/-740T/-164C/63C/1545C (33.3%), and -3858G/-2464delT/-740T/-164A/63C/1545C (3.51%), with no significant frequency differences between cases and controls. In the phenotype analysis, lower caffeine metabolic ratios were detected in cases than in controls. This was significant in smokers (n = 14, P = 0.020), and in a subgroup of 15 matched case-control pairs (P = 0.007), but it was not significant in nonsmokers (n = 100, P = 0.39). There was no detectable association between CYP1A2 genotype and caffeine phenotype. CONCLUSIONS: (i) CYP1A2 polymorphisms are in linkage disequilibrium. Therefore, only -164A-->C (CYP1A2*1F) and -2464T-->delT (CYP1A2*1D) need to be analysed in the routine assessment of CYP1A2 genotype; (ii) in vivo CYP1A2 activity is lower in colorectal cancer patients than in controls, and (iii) CYP1A2 genotype had no effect on phenotype (based on the caffeine metabolite ratio). However, this remains to be confirmed in a larger study.     

The prevalence of CYP2D6 and CYP2C19 genotypes in a population of healthy Dutch volunteers

AIM: This study was performed in a sample of the Dutch population to estimate the prevalence of noncoding mutations of CYP2D6 and CYP2C19 as obtained by genotyping. In addition, the predictability of the genotyping strategy was assessed. METHODS: The CYP2D6 and CYP2C19 status of 765 unrelated healthy volunteers was evaluated. Dextromethorphan and mephenytoin were used for determining the phenotypes. Genotyping was performed by PCR on the most common null alleles for CYP2D6 (except for CYP2D6*5) and CYP2C19. RESULTS: For CYP2D6, the most frequently observed null allele was CYP2D6*4, which accounted for 89% of all null alleles. The prevalence of poor metabolizers (PMs) in healthy volunteers was 5.5%, which was lower than that found previously by phenotyping (8.0%; chi2 test P = 0.009). For CYP2C19*2 and CYP2C19*3, the frequencies were 13.3% and 0.2%, respectively. The S:R ratio was significantly higher in heterozygous subjects (S:R ratio 0.22) than in homozygous wild type subjects (S:R ratio 0.11). Comparison of all subjects below 45 years showed a significantly higher S:R ratio in the female ones compared to the male ones, especially in heterozygous subjects (S:R ratio 0.39 vs. 0. 19; P < 0.001). CONCLUSIONS: The frequencies of CYP2D6 and CYP2C19 allelic variants were in accordance with other European populations. Assessment of *3, *4, *6, *7, and *8 alleles for CYP2D6, and *2 and *3 for CYP2C19, predicted the phenotype with an accuracy of over 98.6%. A gene-dose effect was found for CYP2C19. CYP2C19 heterozygous female subjects had a decreased CYP2C19 activity that may be at least partly due to the use of oral contraceptives.     

Genetic polymorphism of CYP2D6 in the Japanese population

The frequencies of CYP2D6 mutations in a Japanese population were investigated. Individuals were classified into three groups: control individuals, cancer patients and Parkinsonians. Genotyping for CYP2D6*3, CYP2D6*4 and CYP2D6*18 was carried out using the polymerase chain reaction, and that for CYP2D6*5 was also carried out using XbaI restriction fragment length polymorphism. The frequencies of the CYP2D6*3, CYP2D6*4, CYP2D6*5 and CYP2D6*18 mutant alleles were 0%, 0.77%, 4.10% and 0.53% in more than 256 Japanese control individuals, respectively. Based on these data, the population frequency of the CYP2D6 poor metabolizer phenotype was estimated to be 0.29%. The distribution of the four mutated alleles was not significantly different between control individuals and cancer patients or Parkinsonians.     

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.     

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)。     

Identification of CYP2D6 null variants among long‐stay,chronic psychiatric inpatients: Is it strictly necessary?

We identified the null variants *3,*4,*5,*6,*7 and *8 of the CYP2D6 gene [encoding for cytochrome P450 (debrisoquine hydroxylase)] in a group of 84 chronic-stay psychiatric inpatients with severe schizophrenia or related disorders and receiving treatment with one or more CYP2D6 substrates for years. We also studied a group of 100 healthy controls of similar ethnic origin (Spanish Caucasians). Three patients were poor metabolizers (PMs) for antipsychotic drugs according to their CYP2D6 genotype (i.e. homozygous for the *4 allele) but they exhibited no adverse drug reaction over the years despite chronic treatment with CYP2D6 substrates. We suggest that CYP2D6 genetic screening is more useful in other type of psychiatric patients, particularly in younger ones starting treatment protocols.     

CYP2D6 genetic polymorphism in South Indian populations

This study aimed to determine the prevalence of genetic polymorphism in the CYP2D6 gene, which codes for the polymorphically expressed CYP2D6 drug-metabolizing enzyme. The common variants CYP2D6 *2, *3, *4, *5, *10, *14, and *17 were studied in the populations (n=447) of the four South Indian states namely Tamilnadu (TN), Kerala (Ker), Karnataka (Kar) and Andhra Pradesh (AP). Genetic polymorphisms were identified using polymerase chain reaction (PCR) and PCR-Restriction Fragment Length Polymorphism (PCR-RFLP) based methods. Differences in frequencies of CYP2D6 polymorphism between each South Indian state were statistically compared, and also the frequency of South Indian population as a whole in relation to other major populations. The CYP2D6*2 allele was the most frequent variant (34.8%), followed by the *10 allele (10.2%). The *4 and *5 alleles occurred at 7.3% and 1.9% respectively. The *3, *14 and *17 alleles were not detected in the study. The *1/*2, *1/*1 and *2/*2 genotypes were the most common CYP2D6 genotypes, representing 32.7%, 19.4% and 11.8% of the South Indian population. Genotypes that predict poor metabolizer phenotype i.e. *4/*4 and *4/*5 were found at 0.6% in South Indian population. The genetic composition at the CYP2D6 locus in South Indians is distinct from Caucasian, African and even other Asian (Chinese and Japanese) populations.     

Naturalistic pharmacogenetic study of treatment resistance to typical neuroleptics in European-Brazilian schizophrenics

OBJECTIVES: This study aimed to explore the influence of variation in DRD2, DRD3, CYP2D6, CYP3A4, and CYP3A5 genes on treatment resistance to typical neuroleptics in a Brazilian sample of patients with schizophrenia. METHODS: One polymorphism at DRD2 gene, five at DRD3, 24 at CYP2D6, nine at CYP3A4 gene, and one at CYP3A5 gene were genotyped in a sample of 186 patients with schizophrenia. RESULTS: From the nine studied CYP3A4 single nucleotide polymorphisms, only the -392A>G was polymorphic, and significant associations were observed between this single nucleotide polymorphism and efficacy of neuroleptic treatment. Homozygous individuals for the -392A variant [P=0.014, odds ratio (OR)=3.32] were more frequent in the treatment-resistant group, compared with carriers of one copy of the -392G variant. The CYP3A5 low expressor genotype (CYP3A5*3/CYP3A5*3) was found to be associated with refractoriness to neuroleptic treatment (P=0.003, OR=3.16). Among the haplotypes observed in DRD3 gene, the T/A/G/A/C haplotype showed an association with refractoriness to neuroleptics (chi=5.342, P=0.021, OR=1.75). This association showed that carriers of one copy of this haplotype presented intermediate values between noncarriers and homozygous individuals for the haplotype. No association was observed with polymorphisms in DRD2 and CYP2D6 genes. Multiple logistic regression analyses showed that the number of copies of DRD3 T/A/G/A/C haplotype and CYP3A5 low expressor genotype were predictors of refractoriness to neuroleptic after controlling for selected risk factors. CYP3A5*3 individuals carrying at least one copy of the T/A/G/A/C haplotype showed a higher risk to be refractory to neuroleptics than CYP3A5*3 homozygotes+non-T/A/G/A/C carriers (chi=5.533, P=0.019, OR=2.32, 95% confidence interval=1.08-5.02). No significant associations were observed with DRD2 and CYP2D6 polymorphisms. CONCLUSION: Our results suggest a role for CYP3A5 and DRD3 gene variants on refractoriness to neuroleptic treatment in Brazilians with schizophrenia.     

CYP2D6 genotype and phenotype in Amerindians of Tepehuano origin and Mestizos of Durango, Mexico

Although the drug-metabolizing enzyme CYP2D6 has been studied extensively in subjects of differing ethnicities, limited CYP2D6 pharmacogenetic data are available for the Amerindian population and Mestizos of Mexico. Dextromethorphan hydroxylation phenotype was studied in Tepehuano Amerindian (n = 58) and Mestizo (n = 88) subjects, and 195 individuals (85 Tepehuano Amerindians and 110 Mestizos) were genotyped by polymerase chain reaction-restriction fragment length polymorphism methods to identify the frequencies of the CYP2D6*3, *4, *6, and *10 alleles. Tepehuano Amerindian subjects lacked the poor metabolizer (PM) phenotype, whereas in Mestizos the PM phenotype frequency was 6.8%. The CYP2D6*3, *6, and *10 alleles were not found in Tepehuano Amerindians. The CYP2D6*4 allele had a low frequency (0.006) in this Amerindian group. In the Mestizo group, the CYP2D6*3, *4, and *10 alleles had frequencies of 0.009, 0.131, and 0.023, respectively. The CYP2D6*6 allele was not found in Mestizos. The genotype-phenotype association was strongly statistically significant (r(2) = .45; P = .005) in Mestizos. The Tepehuano population was found to have a low phenotypic and genotypic CYP2D6 diversity and differed from other Amerindian groups. On the other hand, the frequencies of the CYP2D6 variant alleles in Mestizos were similar to those reported for whites.     

Comparative evolutionary pharmacogenetics of CYP2D6 in Ngawbe and Embera Amerindians of Panama and Colombia: role of selection versus drift in world populations.

The development of CYP2D6 has been attributed to the need of earth-dwelling animals to detoxify toxic xenobiotics (phytoalexins) present in plants. This hypothesis has been extrapolated to humans, but is yet unconfirmed. Therefore, we studied two Amerindian populations as the best available model to test the effect of selection through diet on human CYP2D6 evolution. The frequency of sparteine poor metabolizers in Ngawbe was 4.4% (n = 344), while the frequency in Embera was 2.2% (n = 153). Among Ngawbe and Embera, CYP2D6*4 (allelic frequencies for each tribe, respectively: 0.171; 0.14), CYP2D6*6 (0.005; 0.011) and CYP2D6*10 (0.175; 0.069) were detected, while CYP2D6*3, CYP2D6*5, CYP2D6*9 and CYP2D6*16 were absent. All poor metabolizers possessed either CYP2D6*4 or CYP2D6*6 and there were no disagreements between genotypic and phenotypic data. The total frequency of mutant alleles showed no difference among Amerindians or when compared to Caucasians. It was higher than in Chinese, since the frequency of CYP2D6*4 was higher in Amerindians. XbaI restriction fragment length polymorphisms haplotypes were very homogeneous in Amerindians, because the only fragment that hybridized with the CYP2D6 cDNA probe was the 29 kb (not 42/44 kb or 11.5/13 kb). This indicated no gene cluster recombinations that generate insertions or deletions. We propose that in earlier hominids and humans, CYP2D6 had increasingly become a vestigial characteristic unconstrained by dietary stressors, as a result of cultural survival strategies. Human CYP2D6 evolution was preferentially affected by random genetic drift, and not by adaptive or purifying selection.     

CYP2E1*1D regulatory polymorphism: association with alcohol and nicotine dependence

OBJECTIVE: CYP2E1 bioactivates environmental protoxins and metabolizes alcohol. CYP2E1 is induced by alcohol and cigarette smoking and may contribute to metabolic tolerance in alcoholics. The CYP2E1*1D polymorphism has been associated with greater CYP2E1 inducibility. One objective was to determine the frequency of the variant allele in eight ethnic groups. Further, the Canadian Native Indian, South-east Asian Canadian and Caucasian Canadian groups were stratified by alcohol and nicotine dependence (as measured by DSM-IV criteria) to examine the potential association of CYP2E1*1D with drug dependence. RESULTS AND CONCLUSIONS: We found a significantly greater frequency of the CYP2E1*1D allele among Indo-Asian Canadians (0.31), Chinese Canadians (0.19), Taiwanese (0.20), Japanese Canadians (0.18), African Americans (0.13), African Canadians (0.10) and Canadian Native Indians (0.09) compared to Caucasian Canadians (0.02). Although the power of the association study was low among some subgroups, the CYP2E1*1D genotype (subjects with at least one variant allele) was associated with alcohol as well as nicotine dependence. Specifically, Canadian Native Indians dependent on nicotine alone or alcohol alone exhibited significantly greater CYP2E1*1D frequencies compared to non-drug dependent controls, while the variant frequency among Southeast Asians dependent on nicotine was greater than their non-drug dependent counterparts. We also found that CYP2E1*1D genotype was associated with significantly greater 3-hydroxycotinine per cigarette in African Americans. The variable frequency of CYP2E1*1D among ethnic groups suggests a greater risk for diseases putatively related to CYP2E1 in some non-Caucasian ethnic groups. The association of CYP2E1*1D with alcohol and nicotine dependence suggests that CYP2E1 may contribute to the development of these dependencies.     

The effect of CYP2D6 polymorphisms on dextromethorphan metabolism in Mexican Americans

CYP2D6 is one of the most polymorphic of the cytochrome P450 enzymes. Genetic differences in this enzyme have been reported in whites, blacks, and Asians. However, there is very little information about polymorphisms of this enzyme in Mexican Americans. The objectives of the present study were to assess the metabolic activity of CYP2D6 in a Mexican American population using dextromethorphan and to correlate this metabolic activity with a genotypic analysis. The sample consisted of 50 Mexican American subjects and 25 non-Mexican American controls. Overnight urine samples were collected and analyzed by high-performance liquid chromatography to calculate the metabolic ratio of dextromethorphan to dextrorphan. Blood samples were collected for genotypic analysis of CYP2D6 alleles. The frequency of the poor metabolizer phenotype was the same in the Mexican American group and the non-Mexican American group (6% vs 5.5%). The frequency of alleles in the Mexican American group was similar to frequencies published in other reports for non-Hispanic whites: *4 = 0.17, *5 = 0.02, *10 = 0.01, *17 = 0.02, *xN = 0.03. These results indicate that compared with non-Hispanic whites, Mexican Americans have a similar proportion of poor metabolizer phenotype and similar genetic polymorphisms of CYP2D6.     

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.     

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