The association of CYP2D6 gene polymorphisms in the full-length coding region with higher recurrence rate of vivax malaria in Yunnan Province, China.

BACKGROUND: Accumulating evidence suggest that compromised CYP2D6 enzyme activity caused by gene mutation could contribute to primaquine failure for the radical cure of vivax malaria. The current study aims to preliminarily reveal the association between the recurrence of vivax malaria in Yunnan Province and CYP2D6 gene mutation by analysing polymorphisms in the entire coding region of human CYP2D6 gene. METHODS: Blood samples were collected from patients with vivax malaria, who received "chloroquine and 8-day course of primaquine therapy" in Yunnan Province. The suspected relapsed cases were determined by epidemiological approaches and gene sequence alignment. PCR was conducted to amplify the CYP2D6 gene in the human genome, and the amplified products were then sequenced to compare with the non-mutation "reference" sequence, so as to ensure correct sequencing results and to determine 9 exon regions. Subsequently, the DNA sequences of 9 exons were spliced into the coding DNA sequence (CDS), which, by default, is known as maternal CDS. The paternal CDS was obtained by adjusting the bases according to the sequencing peaks. The mutation loci, haplotypes (star alleles), genotypes and odds ratios (OR) of all the CDSs were analysed. RESULTS: Of the119 maternal CDS chains in total with 1491 bp in length, 12 mutation sites in the 238 maternal and paternal CDS chains were detected. The c.408G > C mutation was most frequently detected in both suspected relapsed group (SR) and non-relapsed group (NR), reaching 85.2% (75/88) and 76.0% (114/150), respectively. The c.886C > T mutation was most closely related to the recurrence of vivax malaria (OR = 2.167, 95% CI 1.104-4.252, P < 0.05). Among the 23 haplotypes (Hap_1 ~ Hap_23), Hap_3 was non-mutant, and the sequence structure of Hap_9 was the most complicated one. Five star alleles, including *1, *2, *4, *10 and *39, were confirmed by comparison, and CYP2D6*10 allele accounted for the largest percentage (45.4%, 108/238). The frequency of CYP2D6*2 allele in the SR group was significantly higher than that in the NR group (Χ2 = 16.177, P < 0.05). Of the defined 24 genotypes, 8 genotypes, including *4/*4, *4/*o, *2/*39, *39/*m, *39/*x, *1/*r, *1/*n, and *v/*10, were detected only in the SR group. CONCLUSION: Mutation of CYP2D6*10 allele accounts for the highest proportion of vivax malaria cases in Yunnan Province. The mutations of c. 886C > T and CYP2D6*2 allele, which correspond to impaired PQ metabolizer phenotype, are most closely related to the relapse of vivax malaria. In addition, the genotype *4/*4 with null CYP2D6 enzyme function was only detected in the SR group. These results reveal the risk of defected CYP2D6 enzyme activity that diminishes the therapeutic effect of primaquine on vivax malaria.

CYP2D6 activity and the risk of recurrence of Plasmodium vivax malaria in the Brazilian Amazon: a prospective cohort study.

BACKGROUND: CYP2D6 pathway mediates the activation of primaquine into active metabolite(s) in hepatocytes. CYP2D6 is highly polymorphic, encoding CYP2D6 isoforms with normal, reduced, null or increased activity. It is hypothesized that Plasmodium vivax malaria patients with defective CYP2D6 function would be at increased risk for primaquine failure to prevent recurrence. The aim of this study was to investigate the association of CYP2D6 polymorphisms and inferred CYP2D6 phenotypes with malaria recurrence in patients from the Western Brazilian Amazon, following chloroquine/primaquine combined therapy. METHODS: The prospective cohort consisted of P. vivax malaria patients who were followed for 6 months after completion of the chloroquine/primaquine therapy. Recurrence was defined as one or more malaria episodes, 28-180 days after the initial episode. Genotyping for nine CYP2D6 SNPs and copy number variation was performed using TaqMan assays in a Fast 7500 Real-Time System. CYP2D6 star alleles (haplotypes), diplotypes and CYP2D6 phenotypes were inferred, and the activity score system was used to define the functionality of the CYP2D6 diplotypes. CYP2D6 activity scores (AS) were dichotomized at ≤ 1 (gPM, gIM and gNM-S phenotypes) and ≥ 1.5 (gNM-F and gUM phenotypes). RESULTS: Genotyping was successfully performed in 190 patients (44 with recurrence and 146 without recurrences). Recurrence incidence was higher in individuals presenting reduced activity CYP2D6 phenotypes (adjusted relative risk = 1.89, 95% CI 1.01-3.70; p = 0.049). Attributable risk and population attributable fraction were 11.5 and 9.9%, respectively. The time elapsed from the first P. vivax malaria episode until the recurrence did not differ between patients with AS of ≤ 1 versus ≥ 1.5 (p = 0.917). CONCLUSIONS: The results suggest that CYP2D6 polymorphisms are associated with increased risk of recurrence of vivax malaria, following chloroquine-primaquine combined therapy. This association is interpreted as the result of reduced conversion of primaquine into its active metabolites in patients with reduced CYP2D6 enzymatic activity.

CYP2D6 allele distribution in Macedonians, Albanians and Romanies in the Republic of Macedonia.

Cytochrome P450 2D6 (CYP2D6) is an enzyme of great importance for the metabolism of clinically used drugs. More than 100 variants of the CYP2D6 gene have been identified so far. The aim of this study was to investigate the allele distribution of CYP2D6 gene variants in 100 individuals of each of the Macedonian, Albanian and Romany population, by genotyping using long range polymerase chain reaction (PCR) and a multiplex single base extension method. The most frequent variants and almost equally distributed in the three groups were the fully functional alleles *1 and *2. The most common non functional allele in all groups was *4 that was found in 22.5% of the Albanians. The most common allele with decreased activity was *41 which was found in 23.0% of the Romany ethnic group, in 11.0% of the Macedonians and in 10.5% of the Albanians. Seven percent of the Albanians, 6.0% of the Romani and 4.0% of the Macedonians were poor metabolizers, while 5.0% of the Macedonians, 1.0% of Albanians and 1.0% of the Romanies were ultrarapid metabolizers. We concluded that the CYP2D6 gene locus is highly heterogeneous in these groups and that the prevalence of the CYP2D6 allele variants and genotypes in the Republic of Macedonia is in accordance with that of other European populations.

Effects of CYP2D6 gene polymorphism on plasma concentration and therapeutic effect of olanzapine.

This study aimed to evaluate the relationship between gene polymorphisms of metabolic enzymes, particularly the CYP2D6 gene, and the plasma concentration of olanzapine, as well as treatment response in patients with chronic schizophrenia. We recruited olanzapine-treated patients and examined their plasma olanzapine levels. Additionally, a common mutation site within each of the nine exons of the full-length CYP2D6 sequence was assayed. The Positive and Negative Syndrome Scale, Brief Psychiatric Rating Scale, and Overall Clinical Impression were used to assess schizophrenic symptoms, whereas the Barnes Akathisia Scale and Extrapyramidal Symptom Rating Scale were used to evaluate adverse effects. The results showed no significant differences in plasma olanzapine concentrations, treatment response, or the occurrence of adverse effects among different CYP2D6 genotypes. However, an association between olanzapine concentrations and improvement in clinical symptoms and adverse reactions was observed. In conclusion, the CYP2D6 genotype did not significantly impact plasma olanzapine concentrations, treatment response, or the occurrence of adverse effects.

Genetic polymorphisms in ADRB1, ADRB2 and CYP2D6 genes and response to beta-blockers in patients with acute coronary syndrome.

Betablockers (BBs) are prescribed for ischaemia in patients with acute coronary syndrome (ACS). In Spain, bisoprolol and carvedilol are the most prescribed BBs, but patients often had to discontinue them due to adverse effects. Single nucleotide polymorphisms (SNPs) in ADRB1, ADRB2 and CYP2D6 genes have strong evidence of pharmacogenetic association with BBs in heart failure or hypertension, but the evidence in ACS is limited. Therefore, our study focuses on investigating how these genes influence the response to BBs in ACS patients. We analysed the association between SNPs in ADRB1 Gly389Arg (rs1801253) and Ser49Gly (rs1801252), ADRB2 Gly16Arg (rs1042713) and Glu27Gln (rs1042714), and CYP2D* 6 (*2- rs1080985, *4- rs3892097, *10 - rs1065852) and the occurrence of bradycardia/hypotension events during one year of follow-up. We performed an observational study and included 285 ACS-PCI-stent patients. A first analysis including patients treated with bisoprolol and a second analysis including patients treated with other BBs were performed. We found that the presence of the G allele (Glu) of the ADRB2 gene (rs1042714; Glu27Gln) conferred a protective effect against hypotension-induced by BBs; OR (CI 95%) = 0,14 (0,03-0,60), p < 0.01. The ADRB2 (rs1042713; Gly16Arg) GG genotype could also prevent hypotensive events; OR (CI 95%) = 0.49 (0.28-0.88), p = 0015. SNPs in ADRB1 and CYP2D6 * 2, CYP2D6 * 4 weren´t associated with primary events. The effect of CYP2D6 * 10 does not seem to be relevant for the response to BBs. According to our findings, SNPs in ADRB2 (rs1042713, rs1042714) could potentially affect the response and tolerance to BBs in ACS-patients. Further studies are necessary to clarify the impact of ADRB2 polymorphisms.

Relevance of CYP2D6 Gene Variants in Population Genetic Differentiation.

A significant portion of the variability in complex features, such as drug response, is likely caused by human genetic diversity. One of the highly polymorphic pharmacogenes is CYP2D6, encoding an enzyme involved in the metabolism of about 25% of commonly prescribed drugs. In a directed search of the 1000 Genomes Phase III variation data, 86 single nucleotide polymorphisms (SNPs) in the CYP2D6 gene were extracted from the genotypes of 2504 individuals from 26 populations, and then used to reconstruct haplotypes. Analyses were performed using Haploview, Phase, and Arlequin softwares. Haplotype and nucleotide diversity were high in all populations, but highest in populations of African ancestry. Pairwise FST showed significant results for eleven SNPs, six of which were characteristic of African populations, while four SNPs were most common in East Asian populations. A principal component analysis of CYP2D6 haplotypes showed that African populations form one cluster, Asian populations form another cluster with East and South Asian populations separated, while European populations form the third cluster. Linkage disequilibrium showed that all African populations have three or more haplotype blocks within the CYP2D6 gene, while other world populations have one, except for Chinese Dai and Punjabi in Pakistan populations, which have two.

From Croatian Roma to 1000 Genomes: The Story of the CYP2D6 Gene Promoter and Enhancer SNPs.

The CYP2D6 gene encodes an enzyme responsible for the metabolism of ~20% of clinically prescribed drugs. In this study, 18 SNPs from the enhancer and promoter regions of CYP2D6 in 323 Roma from Croatia were genotyped, to find out whether the demographic history of Roma affected the distribution of the studied SNPs and their linkage disequilibrium (LD) values, with the major SNPs defining the CYP2D6 star alleles. No differences were found between the three Roma groups in allele and genotype frequencies. The distribution of LD values of Roma was compared with LD values of European and Asian populations. Regulatory CYP2D6 SNPs (rs5758550, rs28624811, rs1080985 and rs1080983) showed similar distribution and the highest LDs with rs16947 from the gene-coding region in all populations. In the promoter region, a complete LD between rs1080989 and rs28588594, and between rs1080983 and rs28624811, was found in Croatian Roma and investigated populations from 1000 genomes. A high LD was also found between rs1080985 from the promoter and rs5758550 from the enhancer region. SNP rs28735595 from the gene promoter region had the highest LD, with two gene region SNPs, rs1058164 and rs1135840. To conclude, the Croatian Roma population shows an LD pattern of the CYP2D6 gene region similar to the 1000 Genomes European and Asian populations.

Influence of CYP2D6 gene polymorphisms on the pharmacokinetics of aripiprazole in healthy Chinese subjects.

Background: Pharmacogenetics study was added into 2 bioequivalence trials of aripiprazole. The correlation between CYP2D6 polymorphisms and aripiprazole pharmacokinetics (PK) was analyzed. Materials & methods: A total of 140 subjects were included. A total of 26 CYP2D6 gene alleles were detected. The plasma concentration of aripiprazole was measured by liquid chromatography-tandem mass spectrometry. SPSS Statistics 21 was used to analyze the correlation between CYP2D6 polymorphisms and aripiprazole PK parameters. Results: All of the four PK parameters were significantly influenced by CYP2D6rs1058164 and rs28371699. t1/2 and area under the concentration-time curve exhibited significant difference between CYP2D6 extensive metabolizers and intermediate metabolizers. Conclusion: Aripiprazole PK was greatly influenced by CYP2D6. Attention should be paid to the possible dose adjustment for CYP2D6 intermediate metabolizer population when the drug is used in Chinese patients.

Allelic and phenotypic characterization of CYP2D6 and its encoded P450 cytochrome enzyme in a serie of Spanish type 1 Gaucher disease patients.

BACKGROUND: Cytochrome p450 is the main drug metabolic pathway. CYP2D6 is a highly polymorphic gene that encodes a cytochrome p450 enzyme with three activity levels: null, reduced and normal. Apart from another type of mutations CYP2D6 can suffer duplications and deletions of the entire gene. This is the pathway to metabolize one of the Gaucher disease treatments, whose dose administration is regulated according to the metabolizer phenotype, this being one of the administration limitations. OBJECTIVES: The aim of this paper is to evaluate the allelic frequencies and the metabolizer status of Gaucher type 1 patients in the Spanish population and compare it with the general Spanish population and other Gaucher disease groups. METHODS: In this study, 109 type 1 Gaucher disease patients were analyzed with the xTAG®CYP2D6 kit to identify the CYP2D6 gene alleles. RESULTS: We observed that eighty-seven patients could be classified as extensive, 14 as intermediate, 6 as poor and 2 as ultra-rapid metabolizers. The allelic duplication frequency is 5.5% and deletion is 4.5%. The most common allele is wild-type and the second is the null *4 allele. Intermediate phenotype frequency is higher than expected (p<0.05). CONCLUSIONS: Our Spanish GD series shows an unexpected distribution of some alleles and phenotypic metabolizer status, in contrast to that previously reported in the Spanish population.

The Genetic Variation of CYP2D6 Gene in the Bosnian Population.

INTRODUCTION: Genetic polymorphism is associated with individual responses to medication and susceptibility to diseases, and it represents the basis for individualized medical treatment and drug genomics studies. Genetic variation at CYP2D6 is high, both among populations and among individuals in the same population. AIM: The aim of the study was to investigate the CYP2D6 gene duplication and the non-synonymous single-nucleotide polymorphisms (SNP) 100C>T in the CYP2D6 gene in members of the Bosnian population. MATERIAL AND METHODS: The blood samples were collected from 151 unrelated and healthy donors from Bosnian populations consisted of 94 females and 57 males. Duplex long-range PCR was used to determine whether individuals carrying CYP2D6 gene duplication. The resulting PCR product of 5.1 kb, containing all nine CYP2D6 exons, was used as template for detection of the CYP2D6 100C>T allele by nested PCR. RESULTS: The CYP2D6 gene duplication frequency found in the Bosnian population (2.73%) was related to the frequencies of this allele in other Caucasians. The gene duplication is the result of inheritance of more than two copies of the fully functional CYP2D6 alleles. In contrast, the frequency of the CYP2D6 100C>T variant, with possibly damaging function, in the Bosnian population (15.56%) was significantly higher when compared with the other Caucasians but significantly lower when compared with Asians. CONCLUSION: CYP2D6 metabolizes many commonly prescribed drugs. Variations in the gene encoding this enzyme have been associated with individual differences in drug metabolism rates. The individuals with multiple CYP2D6 gene copies metabolize drugs more rapidly and therapeutic plasma levels will not be achieved at ordinary drug dosages. The non-synonymous coding SNP (100C>T) were predicted to have damaging effects on the protein function.

Further evidence for the association of CYP2D6*4 gene polymorphism with Parkinson's disease: a case control study.

BACKGROUND: Genetic and environmental risk factors play an important role for the susceptibility to sporadic Parkinson's disease (PD). It was hypothesized that a splice variant of the CYP2D6 gene (CYP2D6*4 allele) is associated with PD because it alters the ability to metabolize toxins and in particular neurotoxins. CYP2D6 codes for the drug metabolizing enzyme debrisoquine 4-hydroxylase. The CYP2D6*4 variant results in an undetectable enzyme activity and consequently in a reduction in metabolism of some toxins. METHODS: Some of agricultural chemicals have neurotoxic potential and CYP2D6 is involved in their detoxification. Thus, we conducted a case control study to investigate the association of the CYP2D6*4 with PD in a Pakistani subpopulation that is known to be exposed to high levels of some agricultural pesticides, insecticides and herbicides. RESULTS: We found a significantly higher allele and genotype frequency of the CYP2D6*4 variant in 174 sporadic PD patients when compared to 200 controls. In addition, there was a trend to an earlier age of PD onset and a tremor dominant phenotype in CYP2D6*4 variant carriers. CONCLUSION: Our data provide further evidence that a poor metabolizer status may increase the risk to develop PD especially in populations that are exposed to environmental toxins.

CYP2D6 and CYP2C19 in Papua New Guinea: High frequency of previously uncharacterized CYP2D6 alleles and heterozygote excess.

PURPOSE: A high frequency of previously unknown CYP2D6 alleles have been reported in Oceania populations. Genetic and functional properties of these alleles remain unknown. METHODS: We performed analyses of the genetic variability of CYP2D6 and CYP2C19 genes using AmpliChip genotyping in cohorts from two distinct Papua New Guinea (PNG) populations (Kunjingini, n=88; Alexishafen, n=84) focussing on the genetic characterisation of PNG-specific alleles by re-sequencing. RESULTS: Previously unknown CYP2D6 alleles have population frequencies of 24% (Kunjingini) and 12% (Alexishafen). An allele similar to CYP2D6*1, but carrying the 1661G>C substitution, was the second most frequent CYP2D6 allele (20% Kunjingini and 10% Alexishafen population frequency). Sequencing suggests the CYP2D6* 1661G>C allele originated from a cross-over between CYP2D6*1 and *2 and thus is predicted to confer fully active CYP2D6 enzyme. Two additional predicted full activity alleles [1661G>C;4180G>C] and 31G>A were found in the Kunjingini cohort (frequencies 3 c/c and 1%, respectively) and a novel predicted reduced activity allele [100C>T;1039C>T] was found in the Alexishafen cohort (frequency 2%). A high frequency of ultra-rapid (15%) and notably low frequencies of intermediate and poor CYP2D6 metabolizers (<5%) and a high frequency of poor CYP2C19 metabolizers were observed in PNG. Both CYP2D6 and CYP2C19 showed heterozygote excess that may be explained by exogamy and recent introduction of alleles by migration that are yet to reach HWE in relatively isolated populations. CONCLUSION: The CYP2D6*1661 allele common in Oceania may be regarded as functionally equivalent to the full activity CYP2D6*1 allele.