Vitamin K Epoxide Reductase Complex Subunit 1 Research Articles

Linkage disequilibrium between the CYP2C19*2,*17 and CYP2C9*1 alleles and impact of VKORC1, CYP2C9, CYP2C19 gene polymorphisms and gene-gene interactions on warfarin therapy.

Warfarin therapy is complicated by its large inter-individual and intra-individual variability. Both genetic and non-genetic factors can affect warfarin therapy. This study aims to investigate the allele distribution of VKORC1, CYP2C9 and CYP2C19, contribution of different allele variants and possible gene-gene interaction on warfarin therapy. Four hundreds and ninety-two patients were enrolled and single nucleotide polymorphisms for vitamin K epoxide reductase complex subunit 1 (VKORC1), cytochrome P450 CYP2C9 and cytochrome P450 CYP2C19 were genotyped. CYP2C9*1 allele is in complete linkage disequilibrium with CYP2C19*2 and CYP2C19*17 (D' = 1) in our study population. Patient with VKORC1-1639 G > A, CYP2C9*2 and CYP2C9*3 genetic variants need significant lower warfarin dose than patient with wild type allele of VKORC1 1639 G or CYP2C9*1. There is no significant differences between CYP2C19 allele variants for warfarin stable dose and INR > 5 event. Because of the complete linkage disequilibrium between CYP2C19*2,*17 and CYP2C9*1, patient with CYP2C19 *2/*2, *2/*17 and *17/*17 genotypes tend to have higher warfarin dose than patient with CYP2C19*1/*1 genotype. Stepwise regression analysis showed that VKORC1, CYP2C9, body mass index (BMI), age and gender were included as a factor significantly contributing to warfarin dose, whereas CYP2C19 did not contribute to warfarin dose. No statistically significant interaction between CYP2C9 and VKORC1 on warfarin dose and INR > 5 event was detected in univariate general linear model analysis. Our study suggests that polymorphic variants of VKORC1 and CYP2C9 affect warfarin dose independently, whereas CYP2C19 did not contribute to warfarin therapy.

Lack of Association Between Type 2 Diabetes and the 3673G / A and 9041G / A Gene Variants of Vitamin K Epoxide Reductase Complex Subunit 1 (VKORC1).

The vitamin K epoxide reductase complex subunit 1 (VKORC1) gene is expressed in many tissue types, and encodes the VKORC1 protein, which is a key enzyme in the vitamin K cycle. Although researchers have focused on the effects of vitamin K on glucose metabolism, and on its role in the development of type 2 diabetes (T2DM), no consensus has yet been reached. Therefore, here we aimed to investigate the association between VKORC1 variants and the risk of T2DM. The 3673G / A (rs9923231) and 9041G / A (rs7294) VKORC1 variants were investigated by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) in 100 control individuals and 100 patients with T2DM. The genomic regions were amplified by PCR; amplicons were digested using the AciI and NciI enzymes and visualized by agarose gel electrophoresis. The genotype frequencies of the 3673G / A variants were GG (22%), GA (56%), and AA (22%) in the control group and GG (19%), GA (52%), and AA (29%) in patients with T2DM (p > 0.05). The genotype frequencies of the 9041G / A variants were GG (37%), GA (53%), and AA (10%) in the control group and GG (46%), GA (45%), and AA (9%) in patients with T2DM (p > 0.05). In conclusion, we found no significant correlation between the control group and patients with T2DM, with regard to the different genetic models of the 3673G / A and 9041G / A variants. These data suggest that these VKORC1 gene variants may not be linked to T2DM.

G-1639A but Not C1173TVKORC1Gene Polymorphism Is Related to Ischemic Stroke and Its Various Risk Factors in Ukrainian Population

Vitamin K epoxide reductase complex subunit 1 (VKORC1) is integral 163-amino acid long transmembrane protein which mediates recycling of vitamin K 2,3-epoxide to vitamin K hydroquinone and it is necessary for activation of vitamin K-dependent proteins (VKDPs). Herein, the association between G-1639A (rs9923231) and C1173T (rs9934438) single-nucleotide polymorphisms (SNPs) of the VKORC1 gene and ischemic stroke (IS) was tested in Ukrainian population. Genotyping was performed in 170 IS patients and 124 control subjects (total 294 DNA samples) using PCR-RFLP (polymerase chain reaction with following restriction fragment length polymorphism analysis) method. Our data showed that G-1639A but not C1173T polymorphism was related to IS, regardless of adjustment for age, sex, body mass index, smoking status, and arterial hypertension. The risk for IS in -1639A allele carriers (OR = 2.138, P = 0.015) was higher than in individuals with G/G genotype. Haplotype analysis demonstrated that -1639G/1173T and -1639A/1173C were related to increased risk for IS (OR = 3.813, P = 0.010, and OR = 2.189, P = 0.011, resp.), while -1639G/1173C was a protective factor for IS (OR = 0.548, P < 0.001). Obtained results suggested that -1639A allele can be a possible genetic risk factor for IS in Ukrainian population.

Development and Comparison of Warfarin Dosing Algorithms in Stroke Patients.

PurposeThe genes for cytochrome P450 2C9 (CYP2C9) and vitamin K epoxide reductase complex subunit 1 (VKORC1) have been identified as important genetic determinants of warfarin dosing and have been studied. We developed warfarin algorithm for Korean patients with stroke and compared the accuracy of warfarin dose prediction algorithms based on the pharmacogenetics.Materials and MethodsA total of 101 patients on stable maintenance dose of warfarin were enrolled. Warfarin dosing algorithm was developed using multiple linear regression analysis. The performance of all the algorithms was characterized with coefficient of determination, determined by linear regression, and the mean of percent deviation was used to predict doses from the actual dose. In addition, we compared the performance of the algorithms using percentage of predicted dose falling within ±20% of clinically observed doses and dividing the patients into a low-dose group (≤3 mg/day), an intermediate-dose group (3–7 mg/day), and high-dose group (≥7 mg/day).ResultsA new developed algorithms including the variables of age, body weight, and CYP2C9 and VKORC1 genotype. Our algorithm accounted for 51% of variation in the warfarin stable dose, and performed best in predicting dose within 20% of actual dose and intermediate-dose group.ConclusionOur warfarin dosing algorithm may be useful for Korean patients with stroke. Further studies to elucidate clinical utility of genotype-guided dosing and find the additional genetic association are necessary.

Abstract 18405: Warfarin Dose Requirements and Polymorphisms in MicroRNA and Nuclear Receptor Genes

Background and Aim: The marked inter-individual variability in warfarin dose requirement is mainly attributed to the variants of the main target genes across the warfarin pharmacological pathway, i.e. cytochrome P-450 (CYP) 2C9, CYP3A4, ABCB1, vitamin K epoxide reductase complex subunit 1 (VKORC1) and epoxide hydrolase 1 (EPHX1). The expression of these genes is primarily regulated by a complex network of nuclear receptors (NR) which are encoded, in turn, by polymorphic genes. Furthermore, microRNAs (miRNA) can reduce the expression of both warfarin target genes and the genes encoding NRs. We investigated whether the variants of genes encoding i) warfarin targets, ii) NRs involved in the regulation of the targets and iii) miRNA involved in the regulation of NRs and the targets, are associated with warfarin dose requirements. Methods and Results: The study was performed using the Quebec Warfarin Cohort consisting of 988 new warfarin users who were recruited over a period of 3 years and were followed-up for 12 months. The candidate genes were selected according to the literature and included 5 warfarin target genes, 9 NRs genes and 29 miRNA genes. SNPs with MAF&gt;0.01 within these genes were selected for the present study from the NCBI database. Genotyping was previously performed using Omni 2.5 array (Illumina, CA) and iPLEX ADME CYP2C9/VKORC1 panel (Agena, CA) and missing SNPs were imputed. We tested the effect of SNPs on the log-transformed values of dose at 3-month post-initiation using multivariate linear regression analysis, and the adjusted significance threshold was set to 2.49 x 10-4. A total of 3970 SNPs, including 702 in target genes, 3162 in NRs and 106 in miRNA genes were studied. For the association with warfarin dose, 137 SNPs in CYP2C9 and VKORC1 were significant, as well as 3 SNPs in nuclear vitamin D receptor (VDR) gene: rs4760658, β = -0,0852, P = 7,32x10-5; rs11168293, β = -0,0809, P = 1,78x10-4; rs4760655, β = -0,0799, P = 2,15x10-4. None of the variants in miRNA genes showed a significant association with warfarin dose. Conclusions: Variants in the gene encoding VDR, a nuclear receptor which has been previously shown to be involved in the regulation of CYP2C9, CYP3A4 and ABCB1, may contribute to the variability in response to warfarin.

Effects of NAD(P)H quinone oxidoreductase 1 polymorphisms on stable warfarin doses in Korean patients with mechanical cardiac valves.

NAD(P)H dehydrogenase, encoded by NAD(P)H quinone oxidoreductase 1 (NQO1), is an enzyme that catalyzes the reduction of quinones, including vitamin K. Given its potential role in vitamin K metabolism, this study aimed to investigate the effects of NQO1 polymorphisms on stable warfarin doses. We tested a possible effect of gene polymorphisms on variability in warfarin response using 206 Korean patients with mechanical cardiac valves. Single nucleotide polymorphisms (SNPs) of NQO1 with a minor allele frequency of at least 15% were included. Also, genotypes of vitamin K epoxide reductase complex subunit 1 (VKORC1), cytochrome P450 (CYP) 2C9, CYP4F2, gamma-glutamyl carboxylase (GGCX), and GATA4 were determined. NQO1 rs1800566 (C>T) and rs10517 (C>T) were significantly associated with stable warfarin doses. Variant homozygote carriers required lower stable warfarin doses than those with wild-type C allele in rs1800566 (4.85 ± 1.61 vs. 5.61 ± 1.94 mg; p = 0.033), whereas patients with wild homozygote required lower doses than those with T allele in rs10517 (5.11 ± 1.73 vs. 5.75 ± 1.98 mg; p = 0.017). Similar results were obtained from stratified analysis using VKORC1 variant homozygote carriers in both SNPs. Multivariate analysis showed that rs10517 (C>T) increased contribution of gene variations to the overall warfarin dose variability from 42.5 to 43.8%. Our results demonstrate that NQO1 gene polymorphisms influence stable warfarin doses in Korean patients.

Warfarin Metabolites in Patients Following Cardiac Valve Implantation: A Contribution of Clinical and Genetic Factors.

Warfarin, a racemic mixture of S- and R-enantiomers, is the cornerstone of therapy in patients following cardiac valve replacement. S-warfarin is metabolized to 7-S-hydroxywarfarin by the cytochrome P450 isoform 2C9 encoded by CYP2C9 gene. R-warfarin is metabolized by multiple cytochromes P450. We sought to assess the impact of clinical and genetic factors on circulating warfarin metabolites following valve implantation. Venous blood was collected from 120 patients after 3 months since elective mitral and/or aortic valve replacement. Plasma S-warfarin, R-warfarin, S-7-hydroxywarfarin, and R-7-hydroxywarfarin were determined using high-performance liquid chromatography. The S-7-hydroxywarfarin/S-warfarin and S-warfarin/R-warfarin (S/R) ratios, along with warfarin sensitivity index (WSI), defined as INR/S-warfarin ratio, were calculated. Vitamin K epoxide reductase complex subunit 1 (VKORC1) c.-1639A, CYP2C9*3 and CYP2C9*2 alleles were determined using real-time polymerase chain reaction. The S-warfarin was higher in former smokers (p = 0.047) and the VKORC1 c.-1639A allele carriers (p < 0.0001). The S-7-hydroxywarfarin was lower in carriers of the VKORC1 c.-1639A allele (p = 0.0005) and CYP2C9*3 (p = 0.047). The S-7-hydroxywarfarin/S-warfarin ratio was lower in the carriers of CYP2C9*3 (p = 0.008), but not in those with VKORC1 -c.1639A allele. The S/R ratio was higher in patients with hypertension (p = 0.01). The independent predictors of elevated S/R ratio defined as the upper quartile were diabetes (p = 0.045), CYP2C9*3 (p < 0.0001) and CYP2C9*2 (p = 0.0002). The independent predictors of elevated WSI were current smoking (p = 0.049), implantation of mechanical valve (p = 0.006) and VKORC1c.-1639A allele (p = 0.007). We conclude that not only genetic, but also several clinical factors affect warfarin metabolites in patients following cardiac valve implantation.

Efficiency of Exome Sequencing for the Molecular Diagnosis of Pseudoxanthoma Elasticum

The molecular etiology of pseudoxanthoma elasticum (PXE), an autosomal recessive connective tissue disorder, has become increasingly complex as not only mutations in ATP-binding cassette family C member 6 (ABCC6) but also ectonucleotide pyrophosphatase/phosphodiesterase 1 (ENPP1) and gamma-glutamyl carboxylase (GGCX) can cause resembling phenotypes. Identification of modifier genes, such as vascular endothelial growth factor A, has further contributed to the molecular heterogeneity of PXE. In such heterogeneous diseases, next-generation sequencing (NGS) allows to perform mutation screening of several genes in a single reaction. We explored whole-exome sequencing (WES) as an efficient diagnostic tool to identify the causal mutations in ABCC6, GGCX, ENPP1, and vitamin K epoxide reductase complex, subunit 1 (VKORC1) in 16 PXE patients. WES identified a causal ABCC6 mutation in 30 out of 32 alleles and one GGCX mutation, whereas no causal mutations in ENPP1 or VKORC1 were detected. Exomes with insufficient reads (⩽20 depth) for the four genes and patients with single mutations were further evaluated by Sanger sequencing (SS), but no additional mutations were found. The potential of WES compared with targeted NGS is the ease to examine target genes and the opportunity to search for novel genes when targeted analysis is negative. Together with low cost, rapid and less laborious workflow, we conclude that WES complemented with SS can provide a tiered approach to molecular diagnostics of PXE.

Impact of gamma-glutamyl carboxylase gene polymorphisms on warfarin dose requirement: A systematic review and meta-analysis

BackgroundThe Gamma-glutamyl carboxylase (GGCX) gene, as with Vitamin K Epoxide Reductase Complex Subunit 1(VKORC1), CytochromeP450 Complex Subunit 14 F2 (CYP4F2) and CytochromeP450 Complex Subunit2C9 (CYP2C9), is a candidate predictor for appropriate maintenance warfarin dose. However, the association between GGCX gene polymorphisms and warfarin dose requirement is still controversial. To quantify the influence of GGCX polymorphisms on warfarin dose requirements, we performed a systematic review and meta-analysis. MethodsAccording to PRISRM statement (Preferred reporting items for systematic reviews and meta-analyses), a comprehensive literature search was undertaken through August 2014 looking for eligible studies in Embase, Pubmed,Web of Science and the Cochrane Library. The impact of GGCX polymorphisms on mean daily warfarin dose (MDWD) was counted by means of Z test. RevMan 5.2.7 software (developed by the Cochrane Collaboration) was applied to analyze the relationship between GGCX gene polymorphisms and warfarin dose requirements. ResultsNineteen articles including 21 studies with a total of 6957 patients were included in the meta-analysis. Among three investigated single nucleotide polymorphisms (SNPs), rs11676382 showed higher CC genotype frequencies in Asian than those in Caucasian(97.7% vs. 86.9%); patients who were “G carriers” (that is, carried the GGCX rs11676382 CG or GG genotypes) required 27% lower warfarin dose than CC genotype[95%Confidence Interval(CI)=17%-37%, P=0.000, I2%=82.0 and PQ=0.000], moreover, stratified analysis by ethnicity showed similar results in Caucasian(23% lower, 95%CI=12%-33%), but not in Asian. With respect to genetic variation of rs699664 and rs121714145 SNPs, no significant impact on warfarin dose requirements were demonstrated. ConclusionsThis meta-analysis suggested that GGCX rs11676382 polymorphism may be one of factors affecting the dose of warfarin requirement, and the effects are different in different ethnicities. Further studies about this topic in different ethnicities with larger samples are expected to be conducted to validate our results.

The effect of CYP2C9 and VKORC1 genetic polymorphisms on warfarin dose requirements in a pediatric population.

Objective:The aim was to investigate the frequency of genetic polymorphisms of cytochrome P4502C9 (CYP2C9) and vitamin K epoxide reductase complex subunit1 (VKORC1) and determine the effect of these polymorphisms on warfarin dose requirements in pediatric patients.Methods:Fifty-eight pediatric patients with cardiac disease, thrombophilia, or other conditions, taking a stable warfarin dose, aged 0.2–18 years, and with international normalized ratio (INR) between 2 and 3 and 149 healthy children as a control group were included in this prospective, observational study. Patients receiving drugs that interact with warfarin, having chronic liver or renal disease, obesity, or thyroid dysfunctions were excluded. Polymerase chain reaction (real time and restriction fragment length polymorphism) was used to analyze the CYP2C9*2, CYP2C9*3, and VKORC1 polymorphisms. The ideal warfarin dose was calculated according to the patient’s age, height, and the presence of CYP2C9*2, CYP2C9*3, and VKORC1 genetic polymorphisms. The mean daily administered doses and ideal doses were compared. Analysis of variance, Student’s t-test, logistic regression analysis, and Pearson’s correlation analysis were used for statistical analyses.Results:The frequency of the CYP2C9 and VKORC1 genetic polymorphisms was determined as CYP2C9*1/*1 (54.6%), *1/*2 (16.4%), *1/*3 (24.2%), *2/*3 (2.9%), *3/*3 (1.9%), wild-type VKORC1 (26.6%), heterozygote alleles (52.7%), and mutant alleles (20.8%). Patients with allelic variants were found to require lower warfarin doses, and a 64.5% correlation was found between the calculated ideal doses and the administered warfarin doses.Conclusion:Considering CYP2C9 and VKORC1 genetic polymorphisms prior to commencing warfarin treatment will make it easier to reach target INRs and reduce the rate of complications.

VKORC1 rs2359612 and rs9923231 polymorphisms correlate with high risks of cardiovascular and cerebrovascular diseases.

We aimed to confirm the correlations between rs2359612 and rs9923231 single nucleotide polymorphisms (SNPs) in the vitamin K epoxide reductase complex subunit 1 (VKORC1) gene and the risk of cardiovascular and cerebrovascular diseases (CCVDs) using meta-analysis. Electronic databases were exhaustively searched for relevant case-control studies by employing stringent inclusion and exclusion criteria. Manual retrieval was also conducted to obtain additional pertinent literature. The STATA statistical software was employed for the process of evidence synthesis. The initial literature search broadly identified 225 studies relevant to our topic of interest, and after multiple rounds of screening, 10 clinical case-control studies met the final inclusion criteria and were selected for this meta-analysis. The selected studies represented a combined total of 7329 patients with CCVD and 7951 healthy controls. Our meta-analysis demonstrated that the VKORC1 rs2359612 and rs9923231 SNPs were closely associated with high risk for CCVD (rs2359612: allelic: OR = 1.23, 95%CI = 1.00- 1.50, P = 0.047; dominant: OR = 1.32, 95%CI = 1.19-1.46, P < 0.001; rs9923231: allelic: OR = 0.74, 95%CI = 0.63-0.87, P < 0.001; dominant: OR = 0.67, 95%CI = 0.55-0.82, P < 0.001). Our meta-analysis provides strong evidence that two SNPs in the VKORC1 gene, rs2359612 and rs9923231, contribute to the risk of CCVD.

Genetic polymorphisms in very important pharmacogenomic (VIP) variants in the Tibetan population.

Genetic polymorphisms of very important pharmacogenomic (VIP) variants are important for personalized medicine. However, these have not been extensively studied in the Tibetan population. In this study, 82 VIP variants were detected in the Tibetan and Han (HAN) populations from northwestern China. Subsequently, we compared the differences between the Tibetan population and ten populations, including the HAN, Japanese in Tokyo (JPT), Mexican ancestry in Los Angeles (MEX), Toscans in Italy (TSI), African ancestry in Southwest USA (ASW), Luhya in California Webuye, Kenya (LWK), Gujarati Indians in Houston, Texas (GIH), Maasai in Kinyawa, Kenya (MKK), Yoruba in Ibadan, Nigeria (YRI), and Utah residents with Northern and Western European ancestry from the CEPH collection (CEU). Using the χ(2) test, we identified differences in the frequency distribution of 4, 4, 7, 10, 11, 11, 13, 15, 19, and 20 loci in the Tibetan population, compared to the HAN, JPT, MEX, TSI, ASW, LWK, GIH, MKK, YRI, and CEU populations, respectively [P < 0.05/(82*10)]. rs2115819, rs9934438, and rs689466, located in the ALOX5 (arachidonate 5-lipoxygenase), VKORC1 (vitamin K epoxide reductase complex, subunit 1) and PTGS2 (prostaglandin-endoperoxide synthase 2) genes, respectively, in the Tibetan population were different from those in most of the populations. Our results complement the information provided by the database of pharmacogenomics on Tibetan people, and provide an avenue for personalized treatment in the Tibetan population.

How to use warfarin assays in patient management: analysis of 437 warfarin measurements in a clinical setting.

Approximately 50% of inter-individual variation in warfarin dose requirements is attributed to the polymorphisms of cytochrome P450 (CYP) 2C9 (CYP2C9) and vitamin K epoxide reductase complex, subunit 1 (VKORC1) genotypes. What contributes to the remaining 50% of variation remains unclear. The aim of this study is to assess the clinical usefulness of monitoring plasma warfarin concentrations. We examined genotypic and clinical factors influencing high and low warfarin concentrations. We included 325 Korean patients who received warfarin therapy for more than 7 days whose plasma warfarin concentrations were measured and whose genotypes for VKORC1 and CYP2C9 were determined. The plasma concentrations of total warfarin and 7-hydroxywarfarin were determined by high-performance liquid chromatography-tandem mass spectrometry. Using 437 warfarin measurements obtained from 325 patients, we found a correlation between plasma warfarin concentration and warfarin dose (r (2) = 0.356; P < 0.001) and a significant difference in the warfarin/7-hydroxywarfarin ratios of the CYP2C9*1/*1 and CYP2C9*1/*3 genotypes combined with drugs that inhibited warfarin (P = 0.003). Insufficient warfarin dose and patient noncompliance were the most common causes of low warfarin concentrations (<0.54 µg/mL, <5th percentile). Genetic factors that cause pharmacodynamic resistance (e.g., VKORC1 genotype) and thus require high warfarin doses were the most common causes of high warfarin concentrations (>1.85 µg/mL, >95th percentile). Monitoring warfarin concentrations along with the prothrombin time-international normalized ratio may be clinically useful for managing patients with long-term warfarin therapy and identifying factors contributing to inter- or intra-individual variability such as genetic polymorphisms, underlying diseases, drug interactions with warfarin, and patient compliance.

A PCR method for VKORC1 G-1639A and CYP2C9 A1075C genotyping useful to warfarin therapy among Japanese.

Warfarin is widely prescribed for patients with the risk of thromboembolism around the world. The inter-individual and inter-racial differences in appropriate dosage depend highly on age, body weight, and genetic factors. A lot of studies including genome-wide association studies revealed that vitamin K epoxide reductase complex, subunit 1 (VKORC1) G-1639A and Cytochrome P450 (CYP) 2C9 A1075C are the most strong genetic factors for determining warfarin effects in Asians and Africans. Since we developed a quick and inexpensive genotyping method, polymerase chain reaction with confronting two-pair primers (PCR-CTPP), the method was applied for these genotypes to examine the possibility to clinical use. Subjects were 436 examinees (117 males and 319 females, aged 32 to 85 years) who attended a health checkup program in Japan. The PCR-CTPP for VKORC1 G-1639A and CYP2C9 A1075C was conducted for the subjects, as well as the samples genotyped by DigiTag2 method. The allele frequencies of VKORC1 G-1639A were 0.085 for G and 0.915 for A, and those of CYP2C9 A1075C were 0.979 for A and 0.021 for C, being in Hardy-Weinberg equilibrium (p = 0.658 and p = 0.514, respectively). These frequencies were similar to those reported in the HapMap project. Genotyping for both SNPs by PCR-CTPP was replicated by DigiTag2 method. Our results indicated that the PCR-CTPP could be one of the alternative methods for genotyping VKORC1 G-1639A and CYP2C9 A1075C for Asians and Africans with similar allele frequencies to Japanese.

Pharmacogenetics of warfarin in a paediatric population: time in therapeutic range, initial and stable dosing and adverse effects.

Warfarin is used in paediatric populations, but dosing algorithms incorporating pharmacogenetic data have not been developed for children. Previous studies have produced estimates of the effect of polymorphisms in CYP2C9 and VKORC1 on stable warfarin dosing, but data on time in therapeutic range, initial dosing and adverse effects are limited. Participants (n=97) were recruited, and routine clinical data and salivary DNA samples were collected from all participants, and analysed for CYP2C9*2, *3 and VKORC1-1639 polymorphisms.VKORC1 -1639 was associated with a greater proportion of the first six months’ treatment time spent within the target INR range, accounting for an additional 9.5% of the variance in the proportion of time. CYP2C9*2 was associated with a greater likelihood of INR values exceeding the target range during the initiation of treatment (OR [per additional copy] 4.18, 95% CI 1.42, 12.34). CYP2C9*2 and VKORC1-1639 were associated with a lower dose requirement, and accounted for almost 12% of the variance in stable dose. VKORC1-1639 was associated with an increased likelihood of mild bleeding complications (OR [heterozygotes vs homozygotes] 4.53, 95% CI 1.59, 12.93). These data show novel associations between VKORC1-1639 and CYP2C9*2 and INR values in children taking warfarin, as well as replicating previous findings with regard to stable dose requirements. The development of pharmacogenomic dosing algorithms for children using warfarin has the potential to improve clinical care in this population.

Genotype-Guided Dosing of Warfarin

Vitamin K antagonists (VKAs)2 have been used to treat thromboembolic disease for over 60 years, and they continue to be the most commonly prescribed anticoagulants worldwide. However, VKAs such as warfarin have a narrow therapeutic index, and the mean daily dose of warfarin varies widely from patient to patient. Underdosing can leave patients undertreated for their thromboembolic diseases; overdosing can result in bleeding. As such, patients are forced to undergo frequent blood testing, and dose adjustments are made on the basis of the resulting international normalized ratio (INR) values. To achieve a therapeutic INR, which is defined as a value between 2.0 and 3.0 for conditions such as atrial fibrillation and venous thromboembolism, the daily dosing of warfarin can range over 20-fold, from <1 to over 20 mg (1). The variability in warfarin dosing depends on several factors, including demographics, the environment, and genetics. Specifically, variants in the genes that encode an enzyme responsible for the metabolism of warfarin [cytochrome P450, family 2, subfamily C, polypeptide 9 ( CYP2C9 )3] and the molecular target of warfarin [vitamin K epoxide reductase complex, subunit 1 ( VKORC1 )] influence warfarin dosing. The Food and Drug Administration has noted these findings, and the warfarin label recommends that if a patient's genotype is known, then this information should be considered when initiating therapy. Nonetheless, debate continues about the utility of routine genetic testing in this setting, a topic that has been addressed by several studies, including the EUropean Pharmacogenetics of AntiCoagulant Therapy (EU-PACT) and Clarification of Optimal Anticoagulation through Genetics (COAG) trials (2, 3). The EU-PACT trial enrolled 455 patients initiating warfarin treatment, of whom approximately 72% had atrial fibrillation and 28% venous thromboembolism. In this open-label study, patients were randomized to either warfarin dosing based on an algorithm that included …

北京军区总医院基因导向的个体化给药项目及其临床应用

This paper describes detections of gene-directed personalized medication based on pyrophosphoric acid sequencing typing of genes in the Department of Pharmacology,General Hospital of Beijing Military Command of PLA,including β1 adrenergic receptor(β1AR)and CYP2 D6 genes;CYP2C19 gene;vitamin K epoxide reductase complex subunit 1(VKORC1)and CYP2C9 genes;thiopurine methyltransferase(TPMT)gene;epidermal growth factor receptor(EGFR)gene;IL28B gene;O6-methylguanine-DNA methyltransferase(MGMT)gene;SLCO1B1 gene;HLA-B *1502and HLA-B *5801 alleles,etc.The implementation of these gene detection programs could provide sound evidence for the prediction of clinical efficacy and adverse effects of drugs possibly induced by genetic factors.

Involvement of VKORC1 in the inhibition of calcium oxalate crystal formation in HK-2 cells

The vitamin K epoxide reductase complex subunit 1 (VKORC1), the rate-limiting enzyme for vitamin K recycling, is significantly down-regulated in the kidneys of urolithiasis patients. This study searched for direct evidence to define the inhibitory activity of VKORC1 against calcium oxalate (CaOx) crystal formation. In the experiment of VKORC1 overexpression, HK-2 cells were transfected with the pFLAG-CMV-7.1-VKORC1 plasmid as a pFLAG-CMV-7.1-VKORC1 transfection group or the pFLAG-CMV-7.1 plasmid as a pFLAG-CMV-7.1 control group. In the experiment of VKORC1 knockdown, HK-2 cells were transfected with the PGPU6/GFP/Neo-VKORC1shRNA-2 as a PGPU6/GFP/Neo-VKORC1shRNA-2 transfection group or the PGPU6/GFP/Neo-shRNA-NC plasmid as a PGPU6/GFP/Neo-shRNA-NC control group. The expression of VKORC1 in HK-2 cells was detected by real-time quantitative PCR and Western blotting. The CaOx crystal formation was observed under the laser-scanning confocal microscope. It was found that the expression levels of VKORC1 mRNA and protein were significantly higher in the pFLAG-CMV-7.1-VKORC1 transfection group than in the pFLAG-CMV-7.1 control group (P<0.01). The number of CaOx crystals in HK-2 cells incubated in fluorescently labeled CaOx monohydrate (COM) crystal medium for 48 h was 14±4 per field (100×) in the pFLAG-CMV-7.1-VKORC1 transfection group and 26±5 per field (100×) in the pFLAG-CMV-7.1 control group respectively under the laser-scanning confocal microscope. The amount of CaOx crystal aggregation and formation in the pFLAG-CMV-7.1-VKORC1 transfection group was significantly reduced as compared with the pFLAG-CMV-7.1 control group (P<0.05). The expression levels of VKORC1 mRNA and protein were significantly lower in the PGPU6/GFP/Neo-VKORC1shRNA-2 transfection group than in the PGPU6/GFP/Neo-shRNA-NC control group (P<0.05). The number of CaOx crystals in HK-2 cells incubated in fluorescently labeled COM crystal medium was 65±11 per field (100×) in the PGPU6/GFP/Neo-VKORC1shRNA-2 transfection group and 24±6 per field (100×) in the PGPU6/GFP/Neo-shRNA-NC control group respectively under the laser-scanning confocal microscope. The amount of CaOx crystal aggregation and formation in the PGPU6/GFP/Neo-VKORC1shRNA-2 transfection group was significantly increased as compared with the PGPU6/GFP/Neo-shRNA-NC control group (P<0.05). These findings suggested that the VKORC1 protein could inhibit CaOx salt crystallization, adhesion and aggregation. This research would help us to understand the mechanisms involving the interaction between crystallization and epithelial cells and the formation of CaOx.

Pharmacogenetics in Jewish populations.

Spanning over 2000 years, the Jewish population has a long history of migration, population bottlenecks, expansions, and geographical isolation, which has resulted in a unique genetic architecture among the Jewish people. As such, many Mendelian disease genes and founder mutations for autosomal recessive diseases have been discovered in several Jewish groups, which have prompted recent genomic studies in the Jewish population on common disease susceptibility and other complex traits. Although few studies on the genetic determinants of drug response variability have been reported in the Jewish population, a number of unique pharmacogenetic variants have been discovered that are more common in Jewish populations than in other major racial groups. Notable examples identified in the Ashkenazi Jewish (AJ) population include the vitamin K epoxide reductase complex subunit 1 (VKORC1) c.106G>T (p.D36Y) variant associated with high warfarin dosing requirements and the recently reported cytochrome P450 2C19 (CYP2C19) allele, CYP2C19*4B, that harbors both loss-of-function [*4 (c.1A>G)] and increased-function [*17 (c.-806C>T)] variants on the same haplotype. These data are encouraging in that like other ethnicities and subpopulations, the Jewish population likely harbors numerous pharmacogenetic variants that are uncommon or absent in other larger racial groups and ethnicities. In addition to unique variants, common multi-ethnic variants in key drug metabolism genes (e.g., ABCB1, CYP2C8, CYP2C9, CYP2C19, CYP2D6, NAT2) have also been detected in the AJ and other Jewish groups. This review aims to summarize the currently available pharmacogenetics literature and discuss future directions for related research with this unique population.

Sequence variation in vitamin K epoxide reductase gene is associated with survival and progressive coronary calcification in chronic kidney disease.

Sequence variations in the gene(s) encoding vitamin K epoxide reductase complex subunit 1 (VKORC1), the enzyme target of warfarin, have been associated with increased cardiovascular disease in the general population. Coronary artery calcification (CAC) is a prevalent form of cardiovascular disease in chronic kidney disease. We tested the hypothesis that the VKORC1 rs8050894 CC genotype would be associated with mortality and progression of CAC ≤ 4 years. This study is an observational, prospective study of 167 individuals with stages 3 to 5 chronic kidney disease. Survival ≤ 4 years was assessed in all participants, and CAC progression was measured in a subset of 86 patients. Participants with the CG/GG genotype of VKORC1 had higher baseline CAC scores (median score, 112 versus 299; P=0.036). Of those 86 patients who had a 4-year CAC score, those with the CG/GG genotype had an increased risk of progressive CAC (adjusted for age, diabetes mellitus, estimated glomerular filtration rate, and hypertension) compared with those with the CC genotype. Four-year mortality risk was 4 times higher for individuals with the CG/GG genotypes compared with individuals with the CC genotype (odds ratio, 3.8; 95% confidence interval, 1.2-12.5; P=0.02), adjusted for age, sex, diabetes mellitus, estimated glomerular filtration rate, baseline CAC, and hypertension. Patients with the CG/GG genotype of VKORC1 had a higher risk of CAC progression and a poorer survival. These data provide new perspectives on the potential extrahepatic role of VKORC1 in individuals with chronic kidney disease.