Sodium dehydroacetate induces coagulation dysfunction by inhibiting liver vitamin K epoxide reductase complex subunit 1 in Wistar rats

Sodium dehydroacetate (Na-DHA), an antibiotic agent that combats growth of bacteria, fungi, and yeast, is used as a preservative in animal feed, food, and cosmetics. We previously reported that Na-DHA induces coagulation anomalies in Wistar rats, but the anticoagulant mechanism of Na-DHA remains to be established. Here we report that Na-DHA prolonged prothrombin time (PT) and activated partial thromboplastin time (APTT) in male and female Wistar rats. In addition, Na-DHA decreased vitamin K (VK) levels and increased the levels of protein induced by vitamin K absence/antagonist-II (PIVKA-II) in rat serum. Moreover, we found that treatment with VK not only reversed Na-DHA-decreased serum VK and -increased PIVKA-II levels, but also attenuated Na-DHA-prolonged PT and APTT, suggesting that Na-DHA-decreased serum VK level contributes to the anticoagulation due to Na-DHA. Further we found that Na-DHA inhibited vitamin K epoxide reductase complex subunit 1 (VKORC1), a key enzyme in VK recycling, in the liver tissue of Wistar rats, as evidenced by reduced mRNA and protein levels of VKORC1 following Na-DHA treatment. Taken together, our data indicate that Na-DHA inhibits liver VKORC1, resulting in a decrease of serum VK levels, leading to abnormal coagulation in rats.

Impact of gene polymorphism on the initiation and maintenance phases of warfarin therapy in Chinese patients undergoing heart valve replacement

AIM

To determine whether VKORC1 rs9923231, CYP2C9 rs1057910, CYP4F2 rs2108622 and ORM1 rs17650 genotypes contribute to warfarin therapy in patients during initiation and maintenance anticoagulation treatment after heart valve surgery.

METHODS

287 Chinese patients with warfarin treatment more than three month after heart valve replacement operations were enrolled. Blood was collected from each subject for DNA extraction and genotyping. Analyzing the relationship between genotypes and warfarin curative effect.

RESULTS

Their mean age was 48.0 ± 10.5 years old. During the initiation phase, the growth rate of INR was partial correlated with VKORC1 rs9923231, CYP2C9 rs1057910 and ORM1 rs17650, respectively. Compared with AG or GG genotypes of VKORC1 c.-1639 carriers, patients with VKORC1 c.-1639AA reached target INR therapeutic range faster (P<0.001) and has a high risk of overanticoagulation (P<0.001). Carriers of at least one CYP2C9 *3 allele reached the target INR therapeutic range and supra-therapeutic INR were faster than CYP2C9 wild-type carriers (P=0.032, P=0.032, respectively). CYP4F2 rs2108622 could significantly influence on time to the target INR therapeutic range and time to INR above 3.0 after hierarchical analysis with VKORC1, CYP2C9 and ORM1 (P=0.011, P=0.044, respectively). VKORC1 rs9923231, CYP2C9 rs1057910 and ORM1 rs17650 were significantly influence the %TTR in three months (P=0.031, P=0.008, P=0.001, respectively). During the maintenance phase, VKORC1 c.-1639AA carriers spent more time at supra-therapeutic INRs (P<0.001). CYP2C9 rs1057910, CYP4F2 rs2108622 and ORM1 rs17650 gene variants did not affect outcome parameters in maintenance phase.

CONCLUSIONS

This study found that genetic factors could significantly affected on warfarin therapy in Chinese. Meanwhile, genetic variations play a more important role in the initial phase than did in maintenance phase of warfarin therapy.

Effects of CYP2C9 and VKORC1 polymorphisms on warfarin sensitivity and responsiveness during the stabilization phase of therapy

The main objective of this study is to assess the effects of CYP2C9 and VKORC1 polymorphisms on warfarin sensitivity and responsiveness in a Jordanian population during the stabilization phase of treatment. This study was conducted at the Queen Alia Heart Institute (QAHI) anticoagulation clinic in Amman, Jordan. We assessed three CYP2C9 (rs1799853, rs1057910, rs4086116) and four VKORC1 (rs10871454, rs8050894, rs9934438, rs17708472) polymorphisms in 139 Jordanian cardiovascular patients. Demographic and clinical data were also collected. Of the 139 patients in the cohort, 80% had the VKORC1 polymorphisms rs10871454 and rs9934438, while 22.3% and 24.5% of patients had the rs1799853 and rs1057910 CYP2C9 alleles, respectively. Carriers of the CYP2C9 polymorphisms rs1057910 and rs4086116 had an increased risk of warfarin sensitivity compared to subjects with no or only one polymorphism. Similarly, carriers of all four VKORC1 variants had an increased risk of warfarin sensitivity (over anticoagulation) compared to those with no or only one polymorphism. Patients with a CYP2C9 or VKORC1 polymorphism required significantly lower doses than patients with no polymorphisms. The presence of any of CYP2C9 or VKORC1 polymorphisms is associated with sensitivity to warfarin during the stabilization period. Being a CYP2C9 or VKORC1 polymorphism carrier is associated with a variation in doses required to achieve the therapeutic INR compared to non-carrier patients.

Structural Insights into Phylloquinone (Vitamin K1), Menaquinone (MK4, MK7), and Menadione (Vitamin K3) Binding to VKORC1

Vitamin K family molecules-phylloquinone (K1), menaquinone (K2), and menadione (K3)-act as γ-glutamyl carboxylase (GGCX)-exclusive cofactors in their hydroquinone state, activating proteins of main importance for blood coagulation in the liver and for arterial calcification prevention and energy metabolism in extrahepatic tissues. Once GGCX is activated, vitamin K is found in the epoxide state, which is then recycled to quinone and hydroquinone states by vitamin K epoxide reductase (VKORC1). Nevertheless, little information is available concerning vitamin K1, K2, or K3 tissue distribution and preferential interactions towards VKORC1. Here we present a molecular modeling study of vitamin K1, menaquinones 4, 7 (MK4, MK7), and K3 structural interactions with VKORC1. VKORC1 was shown to tightly bind vitamins K1 and MK4 in the epoxide and quinone states, but not in the hydroquinone state; five VKORC1 residues were identified as crucial for vitamin K stabilization, and two other ones were essential for hydrogen bond formation. However, vitamin MK7 revealed shaky binding towards VKORC1, induced by hydrophobic tail interactions with the membrane. Vitamin K3 exhibited the lowest affinity with VKORC1 because of the absence of a hydrophobic tail, preventing structural stabilization by the enzyme. Enzymatic activity towards vitamins K1, MK4, MK7, and K3 was also evaluated by in vitro assays, validating our in silico predictions: VKORC1 presented equivalent activities towards vitamins K1 and MK4, but much lower activity with respect to vitamin MK7, and no activity towards vitamin K3. Our results revealed VKORC1's ability to recycle both phylloquinone and some menaquinones, and also highlighted the importance of vitamin K's hydrophobic tail size and membrane interactions.

Value of VKORC1 (-1639G>A) rs9923231 genotyping in predicting warfarin dose: A replication study in South Indian population

OBJECTIVE

Warfarin is the most commonly prescribed oral anticoagulant, although having a narrow therapeutic index and wide interindividual variability. The aim of this study was to replicate the utility of VKORC1 (-1639G>A) rs9923231 genotyping in predicting the mean daily dose and to evaluate its ability to categorize warfarin-treated patients to high-, intermediate-, or low-dose categories in the South Indian population.

MATERIALS AND METHODS

A cohort of 222 warfarin-treated patients was genotyped using restriction fragment length polymorphism method. The influence of the rs9923231 polymorphism on the variations in the mean daily dose was compared using one-way analysis of variance and linear regression analysis. Discriminatory ability of the rs9923231 polymorphism to group the patients into ordered dose categories was assessed by estimating the proportional odds ratios using the ordered logit regression analysis.

RESULTS

The frequency of AA genotype and A allele in the study sample was found to be 1.8% and 9.23%, respectively, which was similar to reports from other South Indian populations. The mean daily dose required to achieve the optimum international normalized ratio was significantly lower in AA homozygous genotype carriers (3.99 ± 1.67 mg/day) and GA heterozygous (4.26 ± 1.57 mg/day) compared to the GG genotype carriers (5.51 ± 2.13 mg/day), p = 0.003. The A allele carriers (GA+AA genotypes) had a 3.23 higher odds of being grouped as a low-dose requiring category compared to non-carriers (95% CI 1.49-6.98, p = 0.003).

CONCLUSIONS

These preliminary results strongly support the use of VKORC1 (-1639G>A) rs9923231 polymorphism for genetically guided initial warfarin dosing in South Indian patients with heart valve replacements.

Impact of CYP2C9 and VKORC1 Polymorphisms on Warfarin Sensitivity and Responsiveness in Jordanian Cardiovascular Patients during the Initiation Therapy

Warfarin is an oral anticoagulant frequently used in the treatment of different cardiovascular diseases. Genetic polymorphisms in the CYP2C9 and VKORC1 genes have produced variants with altered catalytic properties. A total of 212 cardiovascular patients were genotyped for 17 Single Nucleotide Polymorphisms (SNPs) within the CYP2C9 and VKORC1 genes. This study confirmed a genetic association of the CYP2C9*3 and VKORC1 rs10871454, rs8050894, rs9934438, and rs17708472 SNPs with warfarin sensitivity. This study also found an association between CYP2C9 and VKORC1 genetic haplotype blocks and warfarin sensitivity. The initial warfarin dose was significantly related to the CYP2C9*3 polymorphism and the four VKORC1 SNPs (p < 0.001). There were significant associations between rs4086116 SNP and TAT haplotype within CYP2C9 gene and rs17708472 SNP and CCGG haplotype within VKORC1 gene and warfarin responsiveness. However, possessing a VKORC1 variant allele was found to affect the international normalized ratio (INR) outcomes during initiation of warfarin therapy. In contrast, there was a loose association between the CYP2C9 variant and INR measurements. These findings can enhance the current understanding of the great variability in response to warfarin treatment in Arabs.

mTOR and ERK regulate VKORC1 expression in both hepatoma cells and hepatocytes which influence blood coagulation

Deficiency of γ-glutamyl carboxylation of coagulation factors, as evidenced by the elevated level of Des-γ-carboxyl prothrombin (DCP), is a common feature in hepatocellular carcinoma patients. Additionally, treatment of cancer patients with mTOR inhibitors significantly increases hemorrhagic events. However, the underlying mechanisms remain unknown. In the present study, Vitamin K epoxide reductase complex subunit 1 (VKORC1) was found to be significantly down-regulated in clinical hepatoma tissues and most tested hepatoma cell lines. In vitro investigations showed that VKORC1 expression was promoted by p-mTOR at the translational level and repressed by p-ERK at the transcriptional level. By exploring Hras12V transgenic mice, a hepatic tumor model, VKROC1 was significantly down-regulated in hepatic tumors and showed prolonged activated partial prothrombin time (APTT). In vivo investigations further showed that VKORC1 expression was promoted by p-mTOR and repressed by p-ERK in both hepatoma and hepatocytes. Consistently, APTT and prothrombin time were significantly prolonged under the mTOR inhibitor treatment and significantly shortened under the ERK inhibitor treatment. Conclusively, these findings indicate that mTOR and ERK play crucial roles in controlling VKORC1 expression in both hepatoma and hepatocytes, which provides a valuable molecular basis for preventing hemorrhage in clinical therapies.

VKORC1L1, An Enzyme Mediating the Effect of Vitamin K in Liver and Extrahepatic Tissues

Vitamin K is an essential nutrient involved in the regulation of blood clotting and tissue mineralization. Vitamin K oxidoreductase (VKORC1) converts vitamin K epoxide into reduced vitamin K, which acts as the co-factor for the γ-carboxylation of several proteins, including coagulation factors produced by the liver. VKORC1 is also the pharmacological target of warfarin, a widely used anticoagulant. Vertebrates possess a VKORC1 paralog, VKORC1-like 1 (VKORC1L1), but until very recently, the importance of VKORC1L1 for protein γ-carboxylation and hemostasis in vivo was not clear. Here, we first review the current knowledge on the structure, function and expression pattern of VKORC1L1, including recent data establishing that, in the absence of VKORC1, VKORC1L1 can support vitamin K-dependent carboxylation in the liver during the pre- and perinatal periods in vivo. We then provide original data showing that the partial redundancy between VKORC1 and VKORC1L1 also exists in bone around birth. Recent studies indicate that, in vitro and in cell culture models, VKORC1L1 is less sensitive to warfarin than VKORC1. Genetic evidence is presented here, which supports the notion that VKORC1L1 is not the warfarin-resistant vitamin K quinone reductase present in the liver. In summary, although the exact physiological function of VKORC1L1 remains elusive, the latest findings clearly established that this enzyme is a vitamin K oxidoreductase, which can support γ-carboxylation in vivo.

Genotype-guided versus traditional clinical dosing of warfarin in patients of Asian ancestry: a randomized controlled trial

BACKGROUND

Genotype-guided warfarin dosing has been shown in some randomized trials to improve anticoagulation outcomes in individuals of European ancestry, yet its utility in Asian patients remains unresolved.

METHODS

An open-label, non-inferiority, 1:1 randomized trial was conducted at three academic hospitals in South East Asia, involving 322 ethnically diverse patients newly indicated for warfarin (NCT00700895). Clinical follow-up was 90 days. The primary efficacy measure was the number of dose titrations within the first 2 weeks of therapy, with a mean non-inferiority margin of 0.5 over the first 14 days of therapy.

RESULTS

Among 322 randomized patients, 269 were evaluable for the primary endpoint. Compared with traditional dosing, the genotype-guided group required fewer dose titrations during the first 2 weeks (1.77 vs. 2.93, difference -1.16, 90% CI -1.48 to -0.84, P < 0.001 for both non-inferiority and superiority). The percentage of time within the therapeutic range over 3 months and median time to stable international normalized ratio (INR) did not differ between the genotype-guided and traditional dosing groups. The frequency of dose titrations (incidence rate ratio 0.76, 95% CI 0.67 to 0.86, P = 0.001), but not frequency of INR measurements, was lower at 1, 2, and 3 months in the genotype-guided group. The proportions of patients who experienced minor or major bleeding, recurrent venous thromboembolism, or out-of-range INR did not differ between both arms. For predicting maintenance doses, the pharmacogenetic algorithm achieved an R² = 42.4% (P < 0.001) and mean percentage error of -7.4%.

CONCLUSIONS

Among Asian adults commencing warfarin therapy, a pharmacogenetic algorithm meets criteria for both non-inferiority and superiority in reducing dose titrations compared with a traditional dosing approach, and performs well in prediction of actual maintenance doses. These findings imply that clinicians may consider applying a pharmacogenetic algorithm to personalize initial warfarin dosages in Asian patients.

TRIAL REGISTRATION

ClinicalTrials.gov NCT00700895 . Registered on June 19, 2008.

Genotype-guided warfarin dosing vs. conventional dosing strategies: a systematic review and meta-analysis of randomized controlled trials

AIMS

Previous trials on the effectiveness of genotype-guided warfarin dosing vs. conventional dosing have been inconclusive. We conducted a systematic review and meta-analysis of randomized trials comparing genotype-guided to conventional dosing strategies.

METHODS

PubMed and the Cochrane Library were searched up to 23 October 2017.

RESULTS

A total of 76 and 94 entries were retrieved were retrieved from PubMed and the Cochrane Library, respectively. A total of 2626 subjects in the genotype-guided dosing (mean age 63.3 ± 5.8 years; 46% male) and 2604 subjects in the conventional dosing (mean age 64.7 ± 6.1 years; 46% male) groups (mean follow-up duration 64 days) from 18 trials were included. Compared with conventional dosing, genotype-guided dosing significantly shortened the time to first therapeutic international normalized ratio (INR) (mean difference 2.6 days, standard error 0.3 days; P < 0.0001; I² 0%) and time to first stable INR (mean difference 5.9 days, standard error 2.0 days; P < 0.01; I² 94%). Genotype-guided dosing also increased the time in therapeutic range (mean difference 3.1%, standard error 1.2%; P < 0.01; I² 80%) and reduced the risks of both excessive anticoagulation, defined as INR ≥4 [risk ratio (RR) 0.87; 95% confidence interval (CI) 0.78, 0.98; P < 0.05; I² : 0%), and bleeding (RR 0.82; 95% CI 0.69, 0.98; P < 0.05; I² 31%). No difference in thromboembolism (RR 0.84; 95% CI 0.56, 1.26; P = 0.40; I² 0%) or mortality (RR 1.16; 95% CI 0.46, 2.91; P = 0.76; I² 0%) was observed between the two groups.

CONCLUSIONS

Genotype-guided warfarin dosing offers better safety with less bleeding compared with conventional dosing strategies. No significant benefit on thromboembolism or mortality was evident.

Pharmacogenetics of vitamin K antagonists and bleeding risk prediction in atrial fibrillation

BACKGROUND

Polymorphisms in the vitamin K epoxide reductase complex 1 (VKORC1) and cytochrome P450 2C9 (CYP2C9) genes increase the bleeding risk in anticoagulated atrial fibrillation (AF) patients. Here, we aimed to investigate whether VKORC1 and CYP2C9 polymorphisms improved the predictive performance for major bleeding using the HAS-BLED score.

MATERIAL AND METHODS

We recruited 652 consecutive AF patients stable on vitamin K antagonist (INR 2.0-3.0) during at least the previous 6 months. A baseline venous blood sample was obtained for DNA extraction. We gave an extra point to the HAS-BLED score if the patient was a simultaneous carrier of the VKORC1 and CYP2C9 polymorphisms related to bleeding, and we called this modified score "GEN|HAS-BLED." During a median follow-up of 7.6 years (IQR 5.6-8.0), all major bleeding events were recorded.

RESULTS

During follow-up, 106 (16.2%) patients experienced a major bleeding (2.81%/y; 42 intracranial haemorrhages and 44 gastrointestinal bleeding) and 24 (3.7%) died from major bleeding (0.48%/y). Cox regression analyses demonstrated a significant association between HAS-BLED or GEN|HAS-BLED and major bleeds, both as continuous or categorical scores. Comparison of receiver operating characteristic (ROC) curves shows that original HAS-BLED clinical score had better predictive ability than GEN|HAS-BLED (0.660, 95% CI 0.622-0.696 vs 0.645, 95% CI 0.607-0.682; P = .030). Discrimination and reclassification analyses showed that GEN|HAS-BLED did not improve sensitivity compared with the original score and even showed significant negative reclassification.

CONCLUSION

Adding pharmacogenetic factors (ie polymorphisms of the VKORC1 and CYP2C9 genes) to the HAS-BLED score does not improve the prediction or discrimination performance for major bleeding.

Impact of VKORC1, CYP4F2 and NQO1 gene variants on warfarin dose requirement in Han Chinese patients with catheter ablation for atrial fibrillation

Background

The anticoagulation of atrial fibrillation catheter ablation during the perioperative stage does matter and should be treated with discretion. We aimed to assess impact of three important genes participating in vitamin K cycle (i.e. VKORC1 rs9923231, CYP4F2 rs2108622 and NQO1 rs1800566) on the daily stable warfarin dose requirement in Sichuan Han Chinese patients with catheter ablation of atrial fibrillation.

Methods

A total of 222 atrial fibrillation patients taking stable warfarin therapy after catheter ablation operation were enrolled in this study. The study population included had high (≥2) risk according to the CHA2DS2-VASc risk score. Genotypes of VKORC1 rs9923231, CYP4F2 rs2108622 and NQO1 rs1800566 were analyzed by using the polymerase chain reaction restriction fragment length polymorphism method (PCR-RFLP). Multiple linear regression analysis was applied to depict the impact of VKORC1 rs9923231, CYP4F2 rs2108622 and NQO1 rs1800566 on the daily stable warfarin dose requirement.

Results

Carriers of VKORC1 rs9923231 AG/GG genotypes required significantly higher warfarin dose (3.03 ± 0.28 mg/day, 7.19 mg/day, respectively) than AA carriers (2.52 ± 0.07 mg/day; P < 0.001). Carriers of CYP4F2 rs2108622 CT/TT genotypes required significantly higher warfarin dose (3.38 ± 0.22 mg/day, 2.79 ± 0.19 mg/day, respectively) than CC carriers (2.41 ± 0.08 mg/day; P < 0.001). However, the warfarin dose for carriers of NQO1 rs1800566 CT/TT genotypes (2.46 ± 0.24 mg/day, 3.01 ± 0.27 mg/day, respectively) was not significantly higher than that for the CC carriers (2.33 ± 0.1 mg/day). The multiple linear regression model including genotypes and demographic characteristics, could explain 20.1% of individual variations in the daily stable warfarin dose in Sichuan Han Chinese. VKORC1 rs9923231 contributed most (15%) to the individual variations in daily stable warfarin dose, while CYP4F2 rs2108622 contributed least (3%).

Conclusion

NQO1 rs1800566 is not a significant genetic factor of warfarin dose for Han Chinese, whereas VKORC1 rs9923231 and CYP4F2 rs2108622 are significant genetic factors, which could explain 15% and approximately 3% of individual variations in the daily stable warfarin dose respectively.

The Influence of CYP2C9 and VKORC1 Gene Polymorphisms on the Response to Warfarin in Egyptians

Warfarin is the most commonly used drug for chronic prevention of thromboembolic events, it also ranks high among drugs that cause serious adverse events. The variability in dose requirements has been attributed to inter-individual differences in medical, personal, and genetic factor. Cytochrome P-450 2C9 is the principle enzyme that terminates the anticoagulant effect of warfarin by catalyzing the conversion of the pharmacologically more potent S-enantiomer to its inactive metabolites. Warfarin exerts its effect by inhibition of vitamin K epoxide reductase. This protein is encoded by vitamin K epoxide reductase complex subunit 1 gene (VKORC1). The current study aimed to investigate the pharmacogenetic effect of CYP2C9 and VKORC1 gene polymorphisms on the patients response to warfarin. One hundred cases starting warfarin treatment and 20 healthy controls were enrolled. The mean daily dose of warfarin was calculated from patient's medical records. For each patient, less than 10 % variability in warfarin dose and a target international normalized ratio (INR) within the therapeutic target range were required for at least 3 months for one of the following indications (deep vein thrombosis, pulmonary embolism, cerebrovascular stroke and myocardial infarction) prior to inclusion in the study. Tetraprimer amplification refractory mutation system PCR was performed to determine CYP2C9*2, CYP2C9*3, and the VKORC1 1639 G > A genetic polymorphisms. Plasma warfarin determination was performed using rapid fluorometric assay. Plasma warfarin concentration ranged from 2.19 to 10.98 μg/ml with a median 3.52 μg/ml. Supratherpeutic INR was observed in 11 % of the cases. Thromboembolic complications occurred in 7 % of the cases and 8 % of cases experienced major bleeding. High maintenance dose (>7 mg/day) was associated with the combined non VKORC1*2 and homozygous wild type CYP2C9 (CYP2C9*1*1) alleles, while low maintenance dose was associated with the Variant (AG + AA)/Wild (*1/*1). (p value <0.001). CYP2C9 variant was a risk factor for supratherapeutic INR in the multivariate logistic regression model. Thromboembolic complication and incidence of supratherapeutic INR were observed in patients carrying combined VKORC1 Variant (AG + AA) and CYP2C9 Variant (*2/*3). Data from our study suggest that together with clinical factors, VKORC1 and CYP2C9 polymorphisms are important contributors to warfarin dosing and may help predict adverse effects in Egyptian patients.

Population Diversity in Pharmacogenetics: A Latin American Perspective

Pharmacogenetics/pharmacogenomics (PGx) relies on human genetic diversity. In this review we initially examine the PGx implications of human demographic history and genetic diversity, and highlight results from recent studies on the worldwide distribution of common and rare variants in pharmacogenes. The abundance of rare variants implies that a substantial effort will be required to identify their putative functional effects and to develop reliable algorithms for PGx-guided prescription. Furthermore, variants in all pharmacogenes relevant to a drug treatment must be considered. This implies a shift of the current paradigm of PGx-informed prescription based on genotyping a few common variants in selected genes toward comprehensive sequencing approaches. The following sections deal with the impact of population admixture on PGx diversity focusing on Latin America, where a kaleidoscopic combination of individual proportions of Native American, European, and sub-Saharan African ancestries prevails. We illustrate this diversity by contrasting Brazil and Mexico, the two most populous countries in Latin America, and show that population average admixture proportions are not predictive of the corresponding proportions at the individual level. As a consequence of admixture, the genetic differentiation of common pharmacogenetic variants in Latin Americans is much attenuated in comparison to their most relevant ancestral populations. Finally, we review data for tacrolimus and warfarin to illustrate the opportunities and challenges presented by Latin American populations for PGx studies and clinical implementation.

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.

Evaluation of CYP2C9- and VKORC1-based pharmacogenetic algorithm for warfarin dose in Gaza-Palestine

Aim

To evaluate applicability of CYP2C9*2, *3 and VKORC1-1639G > A based algorithm to predict warfarin stable dose (WSD) in a group of Palestinian patients.

Patients & methods

Warfarin doses were retrospectively calculated for 101 Palestinian patients under warfarin therapy using three models. Performance of the three models was assessed in 47 patients found to take WSD.

Results

Frequency of CYP2C9*2, *3 and VKORC1-1639G > A alleles is 13.6, 0.0 and 46.5% respectively. The international warfarin pharmacogenetics consortium algorithm was more reliable (MAE = 8.9 ± 1.4; R² = 0.350) than both the clinical algorithm (MAE = 10.4 ± 1.4; R² = 0.128;) and the fixed-dose algorithm (MAE = 11.1 ± 1.7).

Conclusion

The international warfarin pharmacogenetics consortium algorithm can be reliably applied for predicting the WSD in Palestinian population.

Role of CYP4F2, CYP2C19, and CYP1A2 polymorphisms on acenocoumarol pharmacogenomic algorithm accuracy improvement in the Greek population: need for sub-phenotype analysis

BACKGROUND

We have earlier developed a pharmacogenomic algorithm for acenocoumarol dose prediction in Greek patients that included CYP2C9/VKORC1 genetic information. This study aims at analyzing the potential effect of CYP4F2, CYP2C19, and CYP1A2 gene polymorphisms on acenocoumarol dose requirements and at further improving the Greek-specific pharmacogenomic algorithm.

METHODS

A total of 205 Greek patients taking acenocoumarol (140 who reached and 65 who did not reach stable dose), participants of acenocoumarol EU-PACT trial, were included in the study. CYP4F2, CYP2C19, and CYP1A2 polymorphisms were genotyped by use of the PCR-RFLP method. All patients were previously genotyped for CYP2C9/VKORC1 polymorphisms.

RESULTS

In the pooled sample, CYP4F2, CYP2C19, and CYP1A2 polymorphisms do not affect independently acenocoumarol dose requirements. For CYP4F2, significant effects were found on patients' ability to reach stable dose and on acenocoumarol dose requirements when CYP2C9/VKORC1 sub-phenotypes were analyzed. Specifically, when the patients were stratified according to their CYP2C9/VKORC1 functional bins, in sensitive responders, CYP4F2*3 allele carriers (CYP4F2 *1/*3 and *3/*3 genotypes) were more frequent in the patient group who reached stable dose (p=0.049). Additionally, in CYP2C9 intermediate metabolizers (IMs), after adjusting for age, weight, and VKORC1 genotypes, CYP4F2 genotypes were significantly associated with acenocoumarol stable dose (β: 0.07; 95% CI: 0.006-0.134; p=0.033).

CONCLUSIONS

CYP4F2 gene shows a prominent weak association with acenocoumarol dose requirements. Sub-phenotype analysis is potentially important in determining additional gene polymorphisms that are associated with acenocoumarol dose requirements.

VKORC1-1639A allele influences warfarin maintenance dosage among Blacks receiving warfarin anticoagulation: a retrospective cohort study

AIM

The study objectives were to investigate the association between selected CYP2C9 and VKORC1 single nucleotide polymorphisms with serious bleeding or thrombotic risk, and to estimate mean daily maintenance dose of warfarin and international normalized ratio measurements among Blacks receiving warfarin anticoagulation.

METHODS

We conducted a retrospective cohort study among 230 Black adults receiving warfarin for a minimum of three consecutive months with a confirmed date of first dosage.

RESULTS

A lower mean daily maintenance dosage of warfarin was required to maintain an international normalized ratio measurement within the therapeutic range among Blacks with the VKORC1-1639G>A variant alleles ([G/A vs G/G, p = 0.02], [A/A vs G/A, p = 0.008] and [A/A vs G/G, p = 0.001]).

CONCLUSION

Data indicated that VKORC1-1639A variant allele influenced warfarin daily maintenance dosage among our small, likely admixed Black patient population.

CYP2C9 and VKORC1 in therapeutic dosing and safety of acenocoumarol treatment: implication for clinical practice in Hungary

The purpose of this work was to investigate the contribution of CYP2C9 and VKORC1 to acenocoumarol (AC) dose variability, bleeding events in Hungary. The study recruited 117 patients on long-term AC therapy (INR 2-3), and 510 healthy individuals to model the findings. Patients were genotyped for alleles proved to affect lower AC overdose CYP2C9*2, CYP2C9*3, VKORC1*2. Additionally, we tested VKORC1*3, VKORC1*4 to examine their effect in patients with higher AC requirements. Most impact on dose reduction is accountable for CYP2C9*2/*3 (59%) and for VKORC1*2/*2 (45.5%), and on dose increase for newly evaluated VKORC1*3/*4 (22.5%) diplotypes. VKORC1*3 and *4 alleles seem to balance the dose-reducing effect of VKORC1*2 allele. Being a carrier of combination of VKORC1*2 and CYP2C9*2,*3 polymorphisms, rather than of one of these SNPs, is associated with higher risk of over-anticoagulation (up to 34.3%) in long-term AC treatment. The pharmacogenetic dosing algorithm involving VKORC1, CYP2C9 diplotypes and age explains 30.4% of AC dosing variability (p<6.10×10^-9). Correlation between the studied diplotypes and bleeding events could not be revealed.

Genotyping of CYP2C9 and VKORC1 polymorphisms predicts south Indian patients with deep vein thrombosis as fast metabolizers of warfarin/acenocoumarin

Deep vein thrombosis (DVT) is a life-threatening disease. Warfarin and acenocoumarol are anticoagulants used to treat DVT and vary among individuals in terms of treatment response/toxicity. Single nucleotide polymorphisms (SNPs) in CYP2C9 and VKORC1 play a role in the pharmacokinetics and dynamics of warfarin and acenocoumarol and they determine the efficacy of treatment by controlling drug clearance in treated individuals. The aim of the current study was to genotype the critical SNPs of CYP2C9 and VKORC1 genes in a south Indian population in order to understand the metabolizer phenotype of patients with DVT. CYP2C9 (rs1799853, rs1057910, rs1057909, rs28371686) and VKORC1 (rs9923231) SNPs were genotyped in 124 cases of DVT. Genomic regions of these SNPs from genomic DNA were amplified with PCR and directly sequenced using Sanger sequencing except for the SNP rs1799853, which was detected using Sau96I restriction endonuclease-based digestion of variant alleles. Among south Indian patients with DVT, 6.5% (8/124) had the rs1799853 SNP of CYP2C9 and 11% (14/124) had the rs1057910 SNP while 16% (20/124) had the rs9923231 SNP of VKORC1 which were associated with the response to warfarin treatment. None of the patients tested positive for poor drug metabolizing genotypes of the CYP2C9 gene and only 1.6% of the south Indian population was sensitive to warfarin treatment. Genotyping results suggest that a relatively greater amount of the therapeutic drug is required to achieve/maintain the international normalized ratio (INR) in south Indian patients with DVT.

Genetics and clinical response to warfarin and edoxaban in patients with venous thromboembolism

OBJECTIVE

The aim of this study was to investigate whether genetic variants can identify patients with venous thromboembolism (VTE) at an increased risk of bleeding with warfarin.

METHODS

Hokusai-venous thromboembolism (Hokusai VTE), a randomised, multinational, double-blind, non-inferiority trial, evaluated the safety and efficacy of edoxaban versus warfarin in patients with VTE initially treated with heparin. In this subanalysis of Hokusai VTE, patients genotyped for variants in CYP2C9 and VKORC1 genes were divided into three warfarin sensitivity types (normal, sensitive and highly sensitive) based on their genotypes. An exploratory analysis was also conducted comparing normal responders to pooled sensitive responders (ie, sensitive and highly sensitive responders).

RESULTS

The analysis included 47.7% (3956/8292) of the patients in Hokusai VTE. Among 1978 patients randomised to warfarin, 63.0% (1247) were normal responders, 34.1% (675) were sensitive responders and 2.8% (56) were highly sensitive responders. Compared with normal responders, sensitive and highly sensitive responders had heparin therapy discontinued earlier (p<0.001), had a decreased final weekly warfarin dose (p<0.001), spent more time overanticoagulated (p<0.001) and had an increased bleeding risk with warfarin (sensitive responders HR 1.38 [95% CI 1.11 to 1.71], p=0.0035; highly sensitive responders 1.79 [1.09 to 2.99]; p=0.0252).

CONCLUSION

In this study, CYP2C9 and VKORC1 genotypes identified patients with VTE at increased bleeding risk with warfarin.

TRIAL REGISTRATION NUMBER

NCT00986154.

Influence of common and rare genetic variation on warfarin dose among African-Americans and European-Americans using the exome array

AIM

We conducted a genome-wide association study using the Illumina Exome Array to identify coding SNPs that may explain additional warfarin dose variability.

PATIENTS & METHODS

Analysis was performed after adjustment for clinical variables and genetic factors known to influence warfarin dose among 1680 warfarin users (838 European-Americans and 842 African-Americans). Replication was performed in an independent sample.

RESULTS

We confirmed the influence of known genetic variants on warfarin dose variability. Our study is the first to show the association between rs12772169 and warfarin dose in African-Americans. In addition, genes COX15 and FGF5 showed significant association in European-Americans.

CONCLUSION

We identified some novel genes/SNPs that underpin warfarin dose response. Further replication is needed to confirm our findings.

Genetic variants associated with warfarin dosage in Kuwaiti population

Assessing the distinct prevalence or absence of genetic variants associated with differential response to the anticoagulant medication of warfarin in different population groups is actively pursued by pharmacogenomics community. Populations from Arabian Peninsula are underrepresented in such studies. By way of examining exome- and genome-wide genotype data from 1395 Arab individuals in Kuwait, we report distinct occurrence of warfarin response-related variants rs12460590_A/CYP2A7, rs2108622_T/CYP4F2, rs2884737_C/VKORC1 and distinct absence of rs11150606_C/PRSS53 in Kuwaiti population. The presented results in conjunction with similar literature reports on Qatari population enhance the worldwide understanding on population-specific distributions of genetic variants associated with warfarin drug dosage.

The impact of non-genetic and genetic factors on a stable warfarin dose in Thai patients

Purpose

The aim of this study was to investigate the contributions of non-genetic and genetic factors on the variability of stable warfarin doses in Thai patients.

Methods

A total of 250 Thai patients with stable warfarin doses were enrolled in the study. Demographics and clinical data, e.g., age, body mass index, indications for warfarin and concomitant medications, were documented. Four single nucleotide polymorphisms in the VKORC1 − 1639G > A, CYP2C9*3, CYP4F2 rs2108622, and UGT1A1 rs887829 genes were detected from gDNA using TaqMan allelic discrimination assays.

Results

The patients with variant genotypes of VKORC1 − 1639G > A required significantly lower warfarin stable weekly doses (SWDs) than those with wild-type genotype (p < 0.001). Similarly, the patients with CYP2C9*3 variant allele required significantly lower warfarin SWDs than those with homozygous wild-type (p = 0.006). In contrast, there were no significant differences in the SWDs between the patients who carried variant alleles of CYP4F2 rs2108622 and UGT1A1 rs887829 as compared to wild-type allele carriers. Multivariate analysis, however, showed that CYP4F2 rs2108622 TT genotype accounted for a modest part of warfarin dose variability (1.2%). In contrast, VKORC1 − 1639G > A, CYP2C9*3, CYP4F2 rs2108622 genotypes and non-genetic factors accounted for 51.3% of dose variability.

Conclusions

VKORC1 − 1639G > A, CYP2C9*3, and CYP4F2 rs2108622 polymorphisms together with age, body mass index, antiplatelet drug use, amiodarone use, and current smoker status explained 51.3% of individual variability in stable warfarin doses. In contrast, the UGT1A1 rs887829 polymorphism did not contribute to dose variability.

Electronic supplementary material

The online version of this article (doi:10.1007/s00228-017-2265-8) contains supplementary material, which is available to authorized users.