VKORC1 haplotypes are associated with arterial vascular diseases (stroke, coronary heart disease, and aortic dissection)

Association among VKORC1 rs9923231, CYP4F2 rs2108622, GGCX rs11676382 polymorphisms and acute ischemic stroke

Acute ischemic stroke is a major cause of morbidity and mortality worldwide, and genetic factors play a role in the risk of stroke. Single nucleotide polymorphisms (SNPs) in the VKORC1, CYP4F2, and GGCX genes have been linked to clinical outcomes, such as bleeding and cardiovascular diseases. This study aimed to investigate the association between specific polymorphisms in these genes and the risk of developing the first episode of acute ischemic stroke in patients without a known embolic source. This retrospective, cross-sectional, observational, analytical, case-control study included adult patients diagnosed with acute ischemic stroke. The SNPs in VKORC1 rs9923231, CYP4F2 rs2108622, GGCX rs11676382 genes were genotyped and analyzed together with the demographic and clinical factors of the 2 groups of patients. The presence of SNPs in VKORC1 or CYP4F2 genes significantly increased the risk of ischemic stroke in the context of smoking, arterial hypertension, and carotid plaque burden. The multivariate logistic model revealed that smoking (odds ratio [OR] = 3.920; P < .001), the presence of carotid plaques (OR = 2.661; P < .001) and low-density lipoprotein cholesterol values >77 mg/dL (OR = 2.574; P < .001) were independently associated with stroke. Polymorphisms in the VKORC1 and CYP4F2 genes may increase the risk of ischemic stroke in patients without a determined embolic source. Smoking, the presence of carotid plaques, and high low-density lipoprotein cholesterol levels were reconfirmed as important factors associated with ischemic stroke.

Application of rivaroxaban in patients with non-valvular atrial fibrillation and end-stage kidney disease: A systematic review and meta-analysis

Background

Nowadays, the number of patients with non-valvular atrial fibrillation (NVAF) complicated by end-stage renal disease (ESKD) is increasing. There are significant challenges in anticoagulation with prescription drugs because of the high risk of bleeding and embolism among these patients. However, no randomized controlled trials (RCTs) of warfarin in combination with any non-vitamin K oral anticoagulant (NOACs) have been performed in patients with baseline creatinine clearance (CrCl) <25 ml/min, which makes it difficult to justify the use of anticoagulants in such patients. Then, we aimed to collect and summarize all evidence to enable the anticoagulation of rivaroxaban, which is less cleared by the kidneys, in patients with severe renal insufficiency and to complement and improve the evidence on the use of rivaroxaban for anticoagulation.

Methods

The present systematic review and meta-analysis searched the databases of PubMed, Embase, the Cochrane Library, CNKI, CBM, and Google Scholar for relevant studies from inception to 1 June 2022, with the restriction of English and Chinese. Eligible cohort studies and RCTs that reported efficacy outcomes [composite of stroke and systemic embolism (SSE), ischemic stroke (ICS), and systemic embolization] or safety outcomes [major bleeding, intracranial hemorrhage (ICH), and gastrointestinal bleeding (GIB)] of rivaroxaban in NVAF patients with ESKD were enrolled. Two authors completed the data extraction and quality assessment work, respectively. The Cochrane Collaboration tool for assessing the risk of bias was used for RCTs, and the NEW-Castle Ottawa scale was used for study quality assessment for cohort studies. Dichotomous variables were calculated as risk factors with 95% confidence intervals (CIs), and meta-analysis was performed to probe the effect of research design, rivaroxaban dose, and controlled drug factors on outcomes.

Results

In total, three studies were included for meta-analysis, involving 6,071 NVAF patients with ESKD, and two studies were included for qualitative analysis. All included studies were at low risk of bias. A meta-analysis demonstrated that mix-dose rivaroxaban caused no statistical discrepancy in the occurrence of thrombotic and bleeding events when compared to the control group (embolism, LogOR: -0.64, 95% CI: -1.05 to -0.23, P:0.25; bleeding, LogOR: -0.33, 95% CI: -0.63 to -0.03, P:0.15), and low-dose rivaroxaban produced similar results (embolism, LogOR: -1.04, 95% CI: -2.15 to 0.07, P:0.61; bleeding, LogOR: -0.81, 95% CI: -1.19 to -0.44, P:0.93).

Conclusion

In this study, low-dose rivaroxaban (10 mg, once a day) may benefit more than warfarin in patients with NVAF and ESKD.

Systematic review registration

https://www.crd.york.ac.uk/prospero/#recordDetails, identifier CRD42022330973.

Vitamin K and cardiovascular complications in CKD patients

Vitamin K, well known for its role in coagulation, encompasses two major subgroups: Vitamin K1 is exclusively synthesized by plants, whereas vitamin K2 mostly originates from bacterial synthesis. Vitamin K serves as a cofactor for the enzyme γ-glutamyl carboxylase, which carboxylates and thereby activates various vitamin K dependent proteins. Several vitamin K-dependent proteins are synthesized in bone but the role of vitamin K for bone health in CKD patients, in particular the prevention of osteoporosis is still not firmly established. Here we focus on another prominent action of vitamin K, in particular vitamin K2, namely the activation of matrix Gla protein (MGP), the most potent inhibitor of cardiovascular calcifications. Multiple observational studies link relative vitamin K deficiency or low intake to cardiovascular calcification progress, morbidity and mortality. Patients with advanced chronic kidney disease (CKD) are particularly vitamin K deficient, in part because of dietary restrictions but possibly also due to impaired endogenous recycling of vitamin K. At the same time this population is characterized by markedly accelerated cardiovascular calcifications and mortality. High dose dietary supplementation with vitamin K2, in particular the most potent form menaquinone-7 (MK7), can potently reduce circulating levels of dephosphorylated uncarboxylated, i.e. inactive MGP in patients with end stage kidney disease. However, despite this compelling data basis, several randomized controlled trials with high dose MK7 supplements in patients with advanced CKD have failed to confirm cardiovascular benefits. Here we discuss potential reasons and solutions for this.

CYP4F2 and VKORC1 Polymorphisms Amplify the Risk of Carotid Plaque Formation

Introduction: Atherosclerosis represents the process by which fibrous plaques are formed in the arterial wall, increasing its rigidity with a subsequent decrease in blood flow which can lead to several cardiovascular events. Seeing as vitamin K antagonists are involved in the pathogenesis of atherosclerosis, we decided to investigate whether polymorphisms in genes that influence vitamin K metabolism might have an impact in modulating the risk of plaque formation. Patients and Methods: In the current study we included adult patients admitted in the Clinical Municipal Hospital of Cluj-Napoca without any carotid or femoral plaques clinically visible at the initial investigation, and a five year follow-up was subsequently performed. We recorded the following patient characteristics: age at inclusion, gender, area of living, smoking, presence of carotid and/or femoral plaques at five years, ischemic heart disease, arterial hypertension, atrial fibrillation, heart failure, diabetes mellitus, obesity, dyslipidemia, drug (oral anticoagulants, antihypertensives, hypolipidemic, anti-diabetic) use and status for the following gene polymorphisms: VKORC1 1639 G>A, CYP4F2 1347 G>T and GGCX 12970 C>G. Results: We observed that the major predictor of both carotid and femoral plaque formation is represented by ischemic cardiac disease. VKORC1 and CYP4F2 polymorphisms did not predict plaque formation, except for VKORC1 homozygous mutants. Nonetheless, both VKORC1 and CYP4F2 interacted with ischemic cardiac disease, increasing the risk of developing a carotid plaque, while only CYP4F2, but not VKORC1, interacted with ischemic cardiac disease to increase the risk of femoral plaque formation. Conclusions: We documented that CYP4F2 and VKORC1 polymorphisms boost the proinflammatory plaque environment (observed indirectly through the presence of ischemic heart disease), increasing the risk of plaque development.

Genome-Wide Association Study of VKORC1 and CYP2C9 on acenocoumarol dose, stroke recurrence and intracranial haemorrhage in Spain

Acenocoumarol is an oral anticoagulant with significant interindividual dose variations. Variants in CYP2C9 and VKORC1 have been associated with acenocoumarol maintenance dose. We analysed whether any of the 49 polymorphisms in CYP2C9 and VKORC1 previously associated with acenocoumarol maintenance dose in a Genome-Wide Association study (GWAs) in Dutch population are associated with stroke recurrence, intracranial haemorrhage (ICH) and acenocoumarol maintenance dose in a Spanish population. We performed a GWAs using Human Core Exome-chip (Illumina) in 78 patients stroke patients treated with acenocoumarol for secondary prevention enrolled as part of the prospective investigator-initiated study (IIS) SEDMAN Study. Patients were followed-up a median of 12.8 months. Three and eight patients had recurrent stroke and ICH events, respectively. We found 14 of the 49 published variants associated with acenocoumarol maintenance dose (p < 0.05). Six polymorphisms were associated with stroke recurrence and four variants with ICH (p < 0.05). In conclusion, variants in VKORC1 and CYP2C9 are associated with acenocoumarol maintenance dose, stroke recurrence and ICH in a Spanish cohort. These results highlight the relevance of studying pharmacogenetics associated with efficacy and safety of anticoagulant drugs and justify studies with larger sample size and different ethnic populations.

Stroke Prophylaxis in Patients with Atrial Fibrillation and End-Stage Renal Disease

Atrial fibrillation (AF) is an important comorbidity in patients with end-stage renal disease (ESRD) undergoing dialysis that portends increased health care utilization, morbidity, and mortality in this already high-risk population. Patients with ESRD have a particularly high stroke risk, which is further compounded by AF. However, the role of anticoagulation for stroke prophylaxis in ESRD and AF is debated. The ESRD population presents a unique challenge because of the combination of elevated stroke and bleeding risks. Warfarin has been traditionally used in this population, but it is associated with significant risks of minor and major bleeding, particularly intracranial, thus leading many clinicians to forgo anticoagulation altogether. When anticoagulation is prescribed, rates of adherence and persistence are poor, leaving many patients untreated. The direct oral anticoagulants (DOACs) may offer an alternative to warfarin in ESRD patients, but these agents have not been extensively studied in this population and uncertainties regarding comparative effectiveness (versus warfarin, each other, and no treatment) remain. In this review, we discuss the current evidence on the risk and benefits of anticoagulants in this challenging population and comparisons between warfarin and DOACs, and review future directions including options for non-pharmacologic stroke prevention.

Effect of gene-gene and gene-environment interaction on the risk of first-ever stroke and poststroke death

BACKGROUND

Multiple genetic and environmental factors contribute to the individual-level heterogeneity in stroke. This study aimed to assess how the genetic interactions confer risk of stroke.

METHODS

In a Chinese case-control study including 1,405 strokes and 1,263 controls who were followed up (range, 0.1-6.0 years), eight genes, including apolipoprotein(a) (APOA1), methylenetetrahydrofolate reductase (MTHFR), vitamin K epoxide reductase complex subunit 1 (VKORC1), arachidonate 5-lipoxygenase-activating protein (ALOX5AP), NOTCH3, chromosome 9p21.3(Chr.9p21.3), vascular endothelial growth factor (VEGFA), and kinase insert domain-containing receptor (KDR), were analyzed for interactions by the generalized multifactor dimensionality reduction method and validated by the multivariate logistic regression models. The genetic associations with carotid artery intima-media thickness (IMT) were examined.

RESULTS

The interaction of VKORC1 and Chr.9p21.3 was identified for stroke and its worse prognosis, and subjects having the VKORC1 rs2359612C and Chr.9p21.3 rs10757274G alleles had higher risks for stroke (OR = 1.83, 95% CI = 1.32-2.52) as well as for stroke recurrence (HR = 1.84, 95% CI = 1.24-2.73), cardiovascular events (HR = 1.65, 95% CI = 1.15-2.38), and cardiovascular mortality (HR = 2.16, 95% CI = 1.24-3.79). Supporting, they were associated with higher IMT. Hypertension or physical inactivity increased the risk effect. The interaction of VEGFA rs833061C and KDR rs2305948T was identified for hemorrhagic stroke.

CONCLUSIONS

Our findings identified two novel genetic interactions of VKORC1 and Chr.9p21.3 and of VEGFA and KDR for risk of stroke and subtypes as well as future stroke prognosis.

Role of Vascular Smooth Muscle Cell Phenotypic Switching and Calcification in Aortic Aneurysm Formation

Aortic aneurysm is a vascular disease whereby the ECM (extracellular matrix) of a blood vessel degenerates, leading to dilation and eventually vessel wall rupture. Recently, it was shown that calcification of the vessel wall is involved in both the initiation and progression of aneurysms. Changes in aortic wall structure that lead to aneurysm formation and vascular calcification are actively mediated by vascular smooth muscle cells. Vascular smooth muscle cells in a healthy vessel wall are termed contractile as they maintain vascular tone and remain quiescent. However, in pathological conditions they can dedifferentiate into a synthetic phenotype, whereby they secrete extracellular vesicles, proliferate, and migrate to repair injury. This process is called phenotypic switching and is often the first step in vascular pathology. Additionally, healthy vascular smooth muscle cells synthesize VKDPs (vitamin K-dependent proteins), which are involved in inhibition of vascular calcification. The metabolism of these proteins is known to be disrupted in vascular pathologies. In this review, we summarize the current literature on vascular smooth muscle cell phenotypic switching and vascular calcification in relation to aneurysm. Moreover, we address the role of vitamin K and VKDPs that are involved in vascular calcification and aneurysm. Visual Overview- An online visual overview is available for this article.

Missense mutation of VKORC1 leads to medial arterial calcification in rats

Vitamin K plays a crucial role in the regulation of vascular calcifications by allowing activation of matrix Gla protein. The dietary requirement for vitamin K is low because of an efficient recycling of vitamin K by vitamin K epoxide reductase (VKORC1). However, decreased VKORC1 activity may result in vascular calcification. More than 30 coding mutations of VKORC1 have been described. While these mutations have been suspected of causing anticoagulant resistance, their association with an increase in the risk of vascular calcification has never been considered. We thus investigated functional cardiovascular characteristics in a rat model mutated in VKORC1. This study revealed that limited intake in vitamin K in mutated rat induced massive calcified areas in the media of arteries of lung, aortic arch, kidneys and testis. Development of calcifications could be inhibited by vitamin K supplementation. In calcified areas, inactive Matrix Gla protein expression increased, while corresponding mRNA expression was not modified. Mutation in VKORC1 associated with a limited vitamin K intake is thus a major risk for cardiovascular disease. Our model is the first non-invasive rat model that shows spontaneous medial calcifications and would be useful for studying physiological function of vitamin K.

Utilizing Whole-Exome Sequencing to Characterize the Phenotypic Variability of Sickle Cell Disease

BACKGROUND

Sickle cell disease (SCD) is a monogenic disease that has wide variety of phenotypes with both and environmental factors contributing to its severity.

METHODS

We performed whole-exome sequencing (WES) in 22 Saudi SCD patients to identify variants that could explain differences in disease phenotypes. All variants, except those that were benign and likely benign, described in the ClinVar database, were considered in our analysis. Gene-based association testing using sequence kernel association optimal unified test (SKAT-O) with small sample adjustment was performed to evaluate the effect of multiple variants in genes on SCD phenotypes.

RESULTS

The mean age of participants was 28 (range, 10-48 years). All patients were homozygous for the sickle cell mutation. The Benin haplotype was present in 15 patients and the Arab-Indian haplotype in 7 patients. One patient who had both SCD and CHARGE association was heterozygous for pathogenic mutation p.Arg987Ter in the CHD7 gene. One SCD individual who had a stroke was a carrier of the pathogenic variant p.Asp36Tyr in the VKORC1 gene which is, associated with warfarin resistance. Two patients with steady hemoglobin levels of 7.5 and 7.1 g/dL were carriers of the pathogenic mutation p.Gly140Ser in the RPL5 gene that is associated with Diamond-Blackfan anemia. None of the patients were transfusion dependent. A heterozygous pathogenic mutation in the LDLR gene associated with autosomal dominant familial hypercholesterolemia was present in one patient with deep venous thrombosis, although their cholesterol level was normal. One individual with stroke was a carrier for the p.Arg284Ter variant in the NLRP12 gene, which is associated with familial cold autoinflammatory syndrome 2. Another patient with stroke and a pulmonary embolism was heterozygous for the p.Pro106Leu variant of the MPL gene, which has been associated with thrombocytosis. Coding variants in the GOLGB1, ENPP1, and PON1 genes showed no association with stroke in our study. SKAT-O analysis did not explain SCD heterogeneity.

CONCLUSION

WES provided limited information to explain the severity of SCD. Whole genome sequencing, epigenetic studies, and assessment of environmental factors might expand our knowledge of SCD heterogeneity.

Significant Association between OPG/TNFRSF11B Variant and Common Complex Ischemic Stroke

BACKGROUND

The serum level of osteoprotegerin (encoded by OPG or TNFRSF11B) was previously shown to be increased in patients with ischemic stroke. A single nucleotide polymorphism rs3134069 in the TNFRSF11B gene was previously associated with ischemic stroke in a population of diabetic patients in Italy. It remains to be determined whether rs3134069 is associated with ischemic stroke in the general population or populations without diabetes.

MATERIALS AND METHODS

We genotyped rs3134069 and performed a case-control association study to test whether rs3134069 is associated with ischemic stroke in 2 independent Chinese Han populations, including a China-Central population with 1629 cases and 1504 controls and a China-Northern population with 1206 cases and 720 controls.

RESULTS

rs3134069 showed significant association with ischemic stroke in the China-Central population (P = 9.24 × 10^-3, odds ratio [OR] = 1.50). The association was replicated in the independent China-Northern population (P = 2.45 × 10^-4, OR = 1.53). The association became more significant in the combined population (P = 7.09 × 10^-6, OR = 1.41). The associations remained significant in the male population, female population, and population without type 2 diabetes. Our expression quantitative trait loci analysis found that the minor allele C of rs3134069 was significantly associated with a decreasedexpression level of TNFRSF11B (P = .002).

CONCLUSIONS

This study demonstrates that rs3134069 in TNFRSF11B increases risk of ischemic stroke by decreasing TNFRSF11B expression.

Effects of warfarin on biological processes other than haemostasis: A review

Warfarin is the world's most widely used anticoagulant drug. Its anticoagulant activity is based on the inhibition of the vitamin K-dependent (VKD) step in the complete synthesis of a number of blood coagulation factors that are required for normal blood coagulation. Warfarin also affects synthesis of VKD proteins not related to haemostasis including those involved in bone growth and vascular calcification. Antithrombotic activity of warfarin is considered responsible for some aspects of its anti-tumour activity of warfarin. Some aspects of activities against tumours seem not to be related to haemostasis and included effects of warfarin on non-haemostatic VKD proteins as well as those not related to VKD proteins. Inflammatory/immunomodulatory effects of warfarin indicate much broader potential of action of this drug both in physiological and pathological processes. This review provides an overview of the published data dealing with the effects of warfarin on biological processes other than haemostasis.

Lack of association between the APLNR variant rs9943582 with ischemic stroke in the Chinese Han GeneID population

Stroke is one of the most common causes of death worldwide. Genetic risk factors have been found to play important roles in the pathology of ischemic stroke. In a previous genome-wide association study, a functional variant (rs9943582, –154G/A) in the 5’ flanking region of the apelin receptor gene (APLNR) was shown to be significantly associated with stroke in the Japanese population. However, the association required validation in other ethnicities. To validate the genetic relationship between APLNR and ischemic stroke in the Chinese Han population, we genotyped rs9943582 in a case–control population containing 1,158 ischemic stroke patients and 1,265 common controls enrolled from the GeneID database, and performed a genetic association study. We detected no allelic or genotypic associations between rs9943582 and ischemic stroke in the Chinese Han GeneID population, although the study population provided sufficient statistical power. This finding indicates that the association between the APLNR variant and ischemic stroke or atherosclerosis may need further validation.

Vascular Calcification, Vitamin K and Warfarin Therapy - Possible or Plausible Connection?

Atherosclerosis is a pathological process underpinning many cardiovascular diseases; it is the main cause of global mortality. Atherosclerosis is characterized by an invasion of inflammatory cells, accumulation of lipids and the formation of fatty streaks (plaques) which subsequently allow accumulation of calcium and other minerals leading to a disturbance in the vascular endothelium and its regulatory role in arterial function. Vascular calcification is a different process, stringently regulated mainly by local factors, in which osteoblast-like cells accumulate in the muscular layer of arteries ultimately taking on the physiological appearance of bone. The elevated stiffness of the arteries leads to severe vascular complications in brain, heart and kidneys. Recently, evidence from animal experiments as well as clinical and epidemiological results suggests that long-term treatment with warfarin, but not with the novel direct anticoagulants, can increase the risk or even induce vascular calcification in some individuals. Gamma-carboxylation is an enzymatic process not only needed for activation of vitamin K but also other proteins which participate in bone formation and vascular calcification. Thus, reduced expression of the vitamin K-dependent proteins which physiologically inhibit calcification of cellular matrix could be postulated to lead to vascular calcification. Published clinical data, describing at present a few thousand patients, need to be supplemented with controlled studies to confirm this interesting hypothesis.

Dietary reference values for vitamin K

Following a request from the European Commission, the EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA) derives dietary reference values (DRVs) for vitamin K. In this Opinion, the Panel considers vitamin K to comprise both phylloquinone and menaquinones. The Panel considers that none of the biomarkers of vitamin K intake or status is suitable by itself to derive DRVs for vitamin K. Several health outcomes possibly associated with vitamin K intake were also considered but data could not be used to establish DRVs. The Panel considers that average requirements and population reference intakes for vitamin K cannot be derived for adults, infants and children, and therefore sets adequate intakes (AIs). The Panel considers that available evidence on occurrence, absorption, function and content in the body or organs of menaquinones is insufficient, and, therefore, sets AIs for phylloquinone only. Having assessed additional evidence available since 1993 in particular related to biomarkers, intake data and the factorial approach, which all are associated with considerable uncertainties, the Panel maintains the reference value proposed by the Scientific Committee for Food (SCF) in 1993. An AI of 1 μg phylloquinone/kg body weight per day is set for all age and sex population groups. Considering the respective reference body weights, AIs for phylloquinone are set at 70 μg/day for all adults including pregnant and lactating women, at 10 μg/day for infants aged 7-11 months, and between 12 μg/day for children aged 1-3 years and 65 μg/day for children aged 15-17 years.

Susceptiveness of Vitamin K epOxide Reductase Complex Subunit 1 Gene Polymorphism in Essential Hypertension

BACKGROUND

Essential hypertension (EH) is defined as a worldwide public health problem and one of the important risk factors for development of human coronary artery disease. Increased peripheral arterial resistance is one of the distinguishing characteristics of EH. The extracellular deposition of calcium in the arterial wall is defined as vascular calcification, which results in aortic stiffness and elevation of blood pressure. Regulation of vascular calcification is physiologically limited by γ-carboxylated proteins that regulate mineralization. Any deficiencies related to mineralization influence vascular calcification. As a result of vitamin-K deficiency or any problem associated with the vitamin K epOxide reductase complex subunit 1 (VKORC1) gene, Glu cannot be transformed to Gla and calcification initiates in blood vessels, myocardium, and cardiac.

OBJECTIVE

The aim of the study was to investigate the potential association of VKORC1 polymorphisms with the risk of EH.

MATERIALS AND METHODS

There were 100 individuals diagnosed with EH and 100 healthy individuals involved in the study. 3673G/A (rs9923231) and 9041G/A (rs7294) polymorphisms in the VKORC1 gene were determined by the PCR-restriction fragment length polymorphism method.

RESULTS

A significant difference was found between the rs7294 polymorphisms ratios of the case and control groups, but significant differences weren't found in distribution of the rs9923231 alleles. Finally it was determined that the GG genotype provides a 3.97-fold increased risk for EH compared to the AA genotype for the rs7294 polymorphism.

CONCLUSIONS

Our results suggest that the VKORC1 gene rs7294 polymorphism is important for the development of EH.

Bone Health and Osteoporosis: The Role of Vitamin K and Potential Antagonism by Anticoagulants

BACKGROUND

Vitamin K's effects extend beyond blood clotting to include a role in bone metabolism and potential protection against osteoporosis. Vitamin K is required for the gamma-carboxylation of osteocalcin. Likewise, this gamma-carboxylation also occurs in the liver for several coagulation proteins. This mechanism is interrupted by coumarin-based anticoagulants in both the liver and bone.

METHODS

A thorough review of the literature on vitamin K, osteocalcin and their role in bone metabolism and osteoporosis, as well as the potential bone effects of anticoagulant therapy was conducted.

CONCLUSIONS

Epidemiological studies and clinical trials consistently indicate that vitamin K has a positive effect on bone mineral density and decreases fracture risk. Typical dietary intakes of vitamin K are below the levels associated with better BMD and reduced fracture risk; thus issues of increasing dietary intakes, supplementation, and/or fortification arise. To effectively address these issues, large-scale, intervention trials of vitamin K are needed. The effects of coumarin-based anticoagulants on bone health are more ambiguous, with retrospective studies suggesting that long-term therapy adversely affects vertebral BMD and fracture risk. Anticoagulants that do not affect vitamin K metabolism are now available and make clinical trials feasible to answer the question of whether coumarins adversely affect bone. The research suggests that at a minimum, clinicians should carefully assess anticoagulated patients for osteoporosis risk, monitor BMD, and refer them to dietitians for dietary and supplement advice on bone health. Further research is needed to make more efficacious decisions about vitamin K intake, anticoagulant therapy, and bone health.

Stroke in Patients with Chronic Kidney Disease…: How do we Approach and Manage it?

Renal failure is a potent risk factor for stroke, which is a leading cause of morbidity and mortality worldwide. The risk of stroke is 5–30 times higher in patients with chronic kidney disease (CKD), especially on dialysis. Case fatality rates are also higher reaching almost 90%. It is therefore important to understand the factors that predispose to stroke in this vulnerable population to better apply preventive strategies. The heightened risk of stroke in CKD represents the interplay of the vascular co-morbidities that occur with renal impairment and factors specific to renal failure such as malnutrition-inflammation-atherosclerosis complex, the effect of uremic toxins, dialysis techniques, vascular access, and the use of anticoagulants to maintain flow in the extracorporeal circuit. Old age, hypertension, diabetes, and previous cerebrovascular disease are all risk factors for stroke with the period of dialysis initiation constituting the highest risk period for developing new stroke. Patients with CKD-stage 3–5 have worse survival and diminished functional outcomes following stroke. Thrombolytic therapy for stroke in CKD has shown an increased risk of symptomatic intracranial hemorrhage or serious systemic hemorrhage, and the therapeutic effects may be attenuated. Benefit of statin therapy in dialysis patient as preventive therapy has not been shown to be beneficial. Control of hypertension and the judicious use of antiplatelet agents form the mainstay of stroke prevention. The benefit of antiplatelet therapies and oral anticoagulants has to be balanced against the real and increased risk of bleeding that is most evident in dialysis cohorts. An increased risk of vascular calcification particularly intracerebral vascular calcification has been seen in patientsreceiving warfarin as prophylaxis in atrial fibrillation. Newer anticoagulants have not been tested in patients with glomerular filtration rate <30 ml/min and hence have to be used with caution. This article is a review of stroke in patients with CKD and approach to managing it.

Plasma phylloquinone, menaquinone-4 and menaquinone-7 levels and coronary artery calcification

Vitamin K is considered to be involved in the pathological mechanisms of coronary artery calcification (CAC). Correlation between CAC and plasma vitamin K levels was studied. A total of 103 patients, with at least one coronary risk factor, were studied. CAC was measured using 64-slice multislice computed tomography (MSCT) and divided into three groups: none (CAC score = 0; n 25), mild to moderate (0 < CAC score < 400; n 52) and severe (CAC score > 400; n 26). Phylloquinone (PK) and menaquinone (MK)-4 and MK-7 were measured by HPLC-tandem MS. Mean age of patients was 64 (sd 13) years, of which 57 % were male. Median CAC score was 57·2. Median levels of PK, MK-4 and MK-7 were 1·33, 0 and 6·99 ng/ml, showing that MK-7 was the dominant vitamin K in this population. MK-7 showed a significant inverse correlation with uncarboxylated osteocalcin (ucOC, P = 0·014), protein induced by vitamin K absence of antagonist-2 (PIVKA-2, P = 0·013), intact parathyroid hormone (P = 0·007) and bone-specific alkaline phosphatase (P = 0·018). CAC showed an inverse correlation with total circulating uncarboxylated matrix Gla protein (t-ucMGP, P = 0·018) and Hb (P = 0·05), and a positive correlation with age (P < 0·001), creatinine, collagen type 1 cross-linked N-terminal telopeptide (NTX, P = 0·03), pulse wave velocity (P < 0·001) and osteoprotegerin (P < 0·001). However, CAC did not have a significant correlation with plasma levels of PK, MK-4 or MK-7. In conclusion, plasma MK-7, MK-4 or PK level did not show significant correlation with CAC despite the association between plasma vitamin K levels and vitamin K-dependent proteins such as ucOC or PIVKA-2.

VKORC1 and CYP2C9 polymorphisms related to adverse events in case-control cohort of anticoagulated patients

Vitamin K antagonists (VKAs) are highly effective but have a narrow therapeutic index and require routine monitoring of the INR. The primary aim of pharmacogenetics (PGx) is to optimize patient care, achieving drug treatments that are personalized according to the genetic profile of each patient. The best-characterized genes involved in VKA PGx involve pharmacokinetics (VKORC1) and pharmacodynamics (CYP2C9) of VKA metabolism. The role of these genes in clinical outcomes (bleeding and thrombosis) during oral anticoagulant (OAC) therapy is controversial. The aim of the present study was to evaluate any potential association between genotype VKORC1 and CYP2C9 and adverse events (hemorrhagic and/or thrombotic), during initiation and long-term VKA treatment, in Caucasian patients. Furthermore, we aimed to determine if the concomitant prescription of other selected drugs affected the association between genotype and adverse events.We performed a retrospective, matched case-control study to determine associations between multiple gene variants, drug intake, and any major adverse effects in anticoagulated patients, monitored in 2 Italian anticoagulation clinics.Our results show that anticoagulated patients have a high risk of adverse events if they are carriers of 1 or more genetic polymorphisms in the VKORC1 (rs9923231) and CYP2C9 (rs1799853 and rs1057910) genes.Information on CYP2C9 and VKORC1 variants may be useful to identify individualized oral anticoagulant treatment for each patient, improve management and quality of VKA anticoagulation control, and monitor drug surveillance in pharmacovigilance programs.

G-1639A but Not C1173T VKORC1 Gene 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.

Circulating Des-gamma-carboxy prothrombin is not associated with cardiovascular calcification or stiffness: The Multi-Ethnic Study of Atherosclerosis (MESA)

BACKGROUND AND AIMS

Vitamin K-dependent protein (VKDP) activity may have a role in preventing cardiovascular calcification, but has not previously been studied in large, generally healthy populations.

METHODS

Using an elevated ankle-brachial index (ABI) as a measure of medial vascular calcification, we performed a case-cohort analysis within the Multi-Ethnic Study of Atherosclerosis, measuring Des-gamma-carboxy prothrombin (DCP) to estimate VKDP activity. In secondary analyses of the weighted subcohort, we examined the cross-sectional associations between DCP and prevalent vascular calcification of the coronary vessels, aortic and mitral valves, and aortic wall, and with vascular stiffness.

RESULTS

In adjusted analysis, cases (n = 104) had 0.21 ng/ml (-0.94-0.52) lower DCP concentrations than the subcohort (n = 613). Furthermore, amongst the 717 participants in the weighted cohort, VKDP activity was not associated with coronary artery, mitral valve, aortic valve or aortic wall calcification, nor was it associated with vascular stiffness.

CONCLUSIONS

Our negative results do not support a role of circulating VKDP activity in cardiovascular calcification in community-dwelling adults.

Navigating pleiotropy in precision medicine: pharmacogenes from trauma to behavioral health

A strong emerging principle in the field of precision medicine is that variation in any one pharmacogene may impact clinical outcome for more than one drug. Variants tested in the acute care setting often have downstream implications for other drugs impacting chronic disease management. A flexible framework is needed as clinicians and scientists move toward deploying automated decision support for gene-based drug dosing in electronic medical records.

VKORC1 -1639 G>A Polymorphism in Romanian Patients With Deep Vein Thrombosis

AIM

The purpose of the research was to study the influence of several genetic factors, especially the -1693 G>A polymorphism of the VKORC1 gene, on the risk of acute unprovoked lower extremity deep vein thrombosis (DVT).

MATERIALS AND METHODS

The study included 127 patients (median age 63 [53.2; 72] years; 61 [48%] women and 66 [52%] men) who were diagnosed with acute lower extremity DVT and 114 controls (median age 62 [53; 73] years; 64 [56.1%] women and 50 [43.9%] men) without DVT. We recorded data regarding the history of DVT and the presence of varicose veins. We determined the genotypes for factor V Leiden (FVL) mutation, prothrombin G20210A mutation, VKORC1 -1639 G>A mutation, and PAI-1 -675 4G/5G polymorphism.

RESULTS AND CONCLUSION

Varicose veins were found in 67 (52.8%) patients and 29 (25.4%) controls (P < .001). FVL was present in 29 (22.8%) patients and 10 (8.8%) controls (P = .005). The VKORC1 (-1693 G>A) GG genotype was found in 42 (33.1%) patients and 41 (36%) controls, the GA genotype in 71 (55.9%) patients and 47 (41.2%) controls, and AA genotype in 14 (11%) patients and 26 (22.8%) controls (P = .020). Multivariate analysis showed that the presence of varicose veins, FVL, and VKORC1 -1639 G>A was independently associated with the risk of DVT. The VKORC1 (-1693 G>A) AA genotype was associated with fewer cases of DVT (odds ratio = 0.435; 95% confidence interval 0.205-0.991; P = .031).

[Association of allelic polymorphisms of genes matrix Gla-protein system with ischemic atherothrombotic stroke]

There are results of the determination of 10 polymorphisms of matrix Gla-protein system (gene MGP-T(-138)-->C (rs1800802), G(-7)-->A (rs1800801), Thr83-->Ala (rs4236), gene VDR-FokI (rs2228570), BsmI (rs1544410), ApaI (rs7975232), TaqI (rs731236), gene GGCX-Arg325-->Gln (rs699664), gene VKORS1-T(2255)-->C (rs2359612), gene BMP-2-Ser37-->Ala (rs2273073)) into 170 patients with ischemic atherothrombotic stroke (IATS) and 124 healthy individual is (control group). It is established that there is a connection between the IATS and polymorphic variants of genes MGP (G(-7)-->A) and VKORC1 (T(2255)-->C). The risk of IATS in carriers of minor allele A/A (G(-7)-->A polymorphism) in 2.6 times higher than in carriers of the major allele (G/A + G/G), and C/C genotype (T(2255)-->C polymorphism) in 2.2 times higher than the homozygotes of major allele. The coincidence of patients T/C and G/G, C/C and G/A genotypes, and A/A genotype (G(-7)-->A polymorphism) with any genotype T(2255)-->C polymorphism are increases the risk of IATS.

Haemostaseome-associated SNPs: has the thrombotic phenotype a greater influence than ethnicity? GMT study from Aquitaine including Basque individuals

The Genetic Markers for Thrombosis (GMT) study compared the relative influence of ethnicity and thrombotic phenotype regarding the distribution of SNPs implicated in haemostasis pathophysiology ("haemostaseome"). We assessed 384 SNPs in three groups, each of 480 subjects: 1) general population of Aquitaine region (Southwestern France) used as control; 2) patients with venous thromboembolism from the same area; and 3) autochthonous Basques, a genetic isolate, who demonstrate unusual characteristics regarding the coagulation system. This study sought to evaluate i) the value of looking for a large number of genes in order to identify new genetic markers of thrombosis, ii) the value of investigating low risk factors and potential preferential associations, iii) the impact of ethnicity on the characterisation of markers for thrombosis. We did not detect any previously unrecognised SNP significantly associated with thrombosis risk or any preferential associations of low-risk factors in patients with thrombosis. The sum of ϰ² values for our 110 significant SNPs demonstrated a smaller genetic distance between patients and controls (321 cumulated ϰ² value) than between Basques and controls (1,570 cumulated ϰ² value). Hence, our study confirms the genetic particularity of Basques especially regarding a significantly lower expression of the non-O blood group (p< 0.0004). This is mitigated by a higher prevalence of factor II Leiden (p< 0.02) while factor V Leiden prevalence does not differ. Numerous other differences covering a wide range of proteins of the haemostaseome may result in an overall different genetic risk for venous thromboembolism.

A pharmacogenetics-based warfarin maintenance dosing algorithm from Northern Chinese patients

Inconsistent associations with warfarin dose were observed in genetic variants except VKORC1 haplotype and CYP2C9*3 in Chinese people, and few studies on warfarin dose algorithm was performed in a large Chinese Han population lived in Northern China. Of 787 consenting patients with heart-valve replacements who were receiving long-term warfarin maintenance therapy, 20 related Single nucleotide polymorphisms were genotyped. Only VKORC1 and CYP2C9 SNPs were observed to be significantly associated with warfarin dose. In the derivation cohort (n = 551), warfarin dose variability was influenced, in decreasing order, by VKORC1 rs7294 (27.3%), CYP2C9*3(7.0%), body surface area(4.2%), age(2.7%), target INR(1.4%), CYP4F2 rs2108622 (0.7%), amiodarone use(0.6%), diabetes mellitus(0.6%), and digoxin use(0.5%), which account for 45.1% of the warfarin dose variability. In the validation cohort (n = 236), the actual maintenance dose was significantly correlated with predicted dose (r = 0.609, P<0.001). Our algorithm could improve the personalized management of warfarin use in Northern Chinese patients.

Sequence Variation in Vitamin K Epoxide Reductase Gene Is Associated With Survival and Progressive Coronary Calcification in Chronic Kidney Disease

Objective—

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.

Approach and Results—

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.

Conclusions—

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.

Association between VKORC1 gene polymorphisms and ischemic cerebrovascular disease in Chinese Han population

The vitamin K epoxide reductase subunit 1 gene (VKORC1) plays a key role in vitamin K recycling, and there is a close association between VKORC1 gene single-nucleotide polymorphisms (SNPs) and the required dose of warfarin, an anticoagulant. However, the association between VKORC1 SNPs and ischemic cerebrovascular disease (ICVD) has not been defined. This case-control study involved 370 patients with ICVD and 408 healthy individuals (controls) from Chinese Han population. Two VKORC1 gene SNPs (1639A/G and 1173T/C) were genotyped by PCR-RFLP method. The G allele frequencies of the 1639A/G locus and C allele frequencies of the 1173T/C locus were higher in the ICVD group than in the control group (p = 0.014 and p = 0.008, respectively). Haplotype analysis showed that 1639G-1173C was associated with an increased risk of ICVD (odds ratio (OR) = 1.163, 95 % confidence interval (CI) = 1.137~2.288), while 1639A-1173T was associated with decreased risk of ICVD (OR = 0.620, 95 % CI = 0.437~0.880). Our findings suggested that individuals carrying the 1639G or 1173C allele might be at increased risk for ICVD. Furthermore, the 1639G-1173C haplotype was a risk factor for ICVD, and 1639A-1173T was a protective factor in Chinese Han population.

Association of functional VKORC1 promoter polymorphism with occurrence and clinical aspects of ischemic stroke in a Greek population

Genetic factors are considered to play an important role in determining the susceptibility to the occurrence, clinical course, and functional outcome of an acute ischemic stroke (IS). Undercarboxylation of specific vitamin K-dependent proteins, due to genetic polymorphisms of VKORC1, can affect both vascular calcification and thrombogenicity. We sought to determine the association of VKORC1 −1639G > A polymorphism with IS incidence, age of onset, severity of disease, and functional outcome after an acute IS. VKORC1 −1639G > A polymorphism was determined in 145 consecutive patients with first ever IS and 145 age- and sex-matched control subjects of Greek Caucasian origin using PCR-RFLP. Stroke severity and functional outcome were assessed on admission and at one month after stroke, respectively. Frequency of VKORC1 −1639G > A genotypes did not differ between IS patients and controls (OR = 1.12, P = 0.51). Moreover, carriage of the A allele was not associated with age of stroke onset, severity of disease (Scandinavian stroke scale score 32.2 versus 32.9, resp., P = 0.96), or poor outcome at 1 month post-stroke (52.9 versus 64.4%, resp., P = 0.31). In conclusion, VKORC1 −1639G > A polymorphism is not a genetic determinant of IS occurrence, age of onset, severity, or functional outcome of disease in a Greek population.

Molecular mechanisms of thoracic aortic dissection

Thoracic aortic dissection (TAD) is a highly lethal vascular disease. In many patients with TAD, the aorta progressively dilates and ultimately ruptures. Dissection formation, progression, and rupture cannot be reliably prevented pharmacologically because the molecular mechanisms of aortic wall degeneration are poorly understood. The key histopathologic feature of TAD is medial degeneration, a process characterized by smooth muscle cell depletion and extracellular matrix degradation. These structural changes have a profound impact on the functional properties of the aortic wall and can result from excessive protease-mediated destruction of the extracellular matrix, altered signaling pathways, and altered gene expression. Review of the literature reveals differences in the processes that lead to ascending versus descending and sporadic versus hereditary TAD. These differences add to the complexity of this disease. Although tremendous progress has been made in diagnosing and treating TAD, a better understanding of the molecular, cellular, and genetic mechanisms that cause this disease is necessary to developing more effective preventative and therapeutic treatment strategies.

Does CALU SNP rs1043550 contribute variability to therapeutic warfarin dosing requirements?

OBJECTIVES

Calumenin, a molecular chaperone, exerts a regulatory effect on the vitamin K-dependent γ-carboxylation redox cycle that inhibits transfer of the reduced vitamin K from VKORC1, the pharmacological target of warfarin, to the γ-carboxylase. Because of its polymorphic structure and central role in the warfarin metabolic pathway, a contributory role for calumenin to warfarin dose variability has been posited. The current study sought to validate modulation of therapeutic dosing requirements by a single nucleotide polymorphisms (SNP) occurring in the calumenin gene (CALU) reported in previous studies. The CALU SNP was further modeled to detect interaction with SNPs occurring in VKORC1, CYP2C9, and CYP4F2 genes and characterize any additional contribution to variability in therapeutic warfarin dose requirement.

SETTING

The study was undertaken in an established, well-characterized cohort of subjects treated with warfarin in the Anticoagulation Clinic of Marshfield Clinic in Marshfield, Wisconsin.

METHODS

Subjects (N=491) previously genotyped for SNPS known to contribute variability to therapeutic warfarin dose requirement were genotyped for CALU SNP rs1043550, using TaqMan assays. Contribution of CALU SNP rs1043550 was modeled relative to other genotypic and phenotypic characteristics including gender, diagnosis, age, body surface area, underlying indication for warfarin, comorbidities, and pharmacological exposures. Interaction between SNPs impacting on warfarin dose requirements and calumenin SNPs was also modeled.

RESULTS

Small differences in warfarin dosing requirements detected among individuals encoding the mutant G allele in the calumenin SNP were not statistically or clinically significant relative to therapeutic warfarin dose requirement and did not independently contribute significantly to the warfarin dosing model. Interaction between calumenin and VKORC1 SNPs contributed only minor additional variability to that ascribed to the wild type VKORC1 genotype.

CONCLUSIONS

The impact of the CALU SNP on warfarin dose variability was minor and did not contribute significantly to therapeutic warfarin dose requirement in our study cohort. While no contribution was noted for the SNP examined in the present study, further examination of interaction between genetic elements contributing major impact on therapeutic warfarin dose requirements and genes exhibiting a lesser contribution is warranted.

Biological features of thoracic aortic diseases. Where are we now, where are we heading to: established and emerging biomarkers and molecular pathways

Thoracic aortic aneurysms (TAAs) and aortic dissections (ADs) are among the main causes of mortality and morbidity in Western countries. For this reason, the diagnosis, prevention and prediction of TAAs and ADs have become a very active area of research; in fact, it is important to monitor and predict the evolution of these diseases over time. It is also critical, in cases of doubtful diagnosis, to receive some guidance from biochemical assays, particularly in the case of ADs. Although biological testing for disease prediction has already been discussed several times, the role of biomarkers in TAAs and ADs is still under discussion for routine patient screening, periodical follow-up or for prompt diagnosis in emergency conditions. In this review, we update the current knowledge and new trends regarding the role of biomarkers in thoracic aortic diseases, focusing on established and emerging biomarkers in the fields of genetics, inflammation, haemostasis and matrix remodelling as well as on substances released upon cell damage. Other than D-dimer, a sensitive but not a specific marker for the diagnosis of AD that has been widely tested by several authors and currently seems a viable option in ambiguous cases, the remaining markers have been most frequently assessed in limited or mixed patient populations. This currently precludes their widespread adoption as diagnostic or prognostic tools, even if many of these markers are conceptually promising. In years to come, we expect that future studies will further clarify the diagnostic and prognostic features of several established and emerging biomarkers that, to date, are still in the translational limbo separating biological discovery from a practical clinical role.

VKORC1 rs2359612C allele is associated with increased risk of coronary artery disease in the presence of coronary calcification

VKORC1 genetic polymorphisms affect warfarin dose response, aortic calcification, and the susceptibility of coronary artery disease as shown in our previous study. Little is known regarding the association of VKORC1 polymorphisms with coronary artery calcification (CAC) and the role of CAC in the association with coronary artery disease (CAD). Due to a natural haplotype block in the VKORC1 gene in Chinese, polymorphism rs2359612 was analyzed in a case-control study and a prospective study. The case-control study included 464 CAD patients with non-calcified plaque (NCP), 562 CAD patients with mixed calcified plaque (MCP), 492 subjects with calcified plaque (CP), and 521 controls. The rs2359612C was only associated with increased risk of MCP, the CAD in the presence of CAC; the odds ratio was 1.397 (95 % CI 1.008-1.937, P < 0.05), which was replicated in the second independent population. On the contrary, a negative correlation was observed between rs2359612 and log-transformed Agatston score, and rs2359612 was negatively associated with the number of calcified vessels. Moreover, in a prospective study including 849 CAD patients undergoing revascularization, rs2359612C predicted a higher incidence of cardiovascular events in MCP subgroup; the relative risk was 1.435 (95 % CI 1.008-2.041, P = 0.045), which was not observed in the NCP subgroup. We conclude that the rs2359612C was associated with a higher risk of CAD in the presence of CAC and a higher incidence of cardiovascular events in CAD patients with CAC, but a lower coronary calcification. VKORC1 polymorphisms may be associated with the endophenotype of CAD, calcification-related atherosclerosis.

Impact of genetic factors (VKORC1, CYP2C9, CYP4F2 and EPHX1) on the anticoagulation response to fluindione

AIM

Genetic variants of the enzyme that metabolizes warfarin, cytochrome P-450 2C9 (CYP2C9) and of a key pharmacologic target of vitamin K antagonists, vitamin K epoxide reductase (VKORC1), contribute to differences in patients' responses to coumarin derivatives. The role of these variants in fluindione response is unknown. Our aim was to assess whether genetic factors contribute to the variability in the response to fluindione.

METHODS

Four hundred sixty-five patients with a venous thromboembolic event treated by fluindione for at least 3 months with a target international normalized ratio (INR) of 2.0 to 3.0 were studied. VKORC1, CYP2C9, CYP4F2 and EPHX1 genotypes were assessed. INR checks, fluindione doses and bleeding events were collected.

RESULTS

VKORC1 genotype had a significant impact on early anticoagulation (INR value ≥2 after the first two intakes) (P < 0.0001), on the time required to reach a first INR within the therapeutic range (P < 0.0001) and on the time to obtain a first INR value > 4 (P= 0.0002). The average daily dose of fluindione during the first period of stability was significantly associated with the VKORC1 genotype: 19.8 mg (±5.5) for VKORC1 CC, 14.7mg (±6.2) for VKORC1 CT and 8.2mg (±2.5) for VKORC1 TT (P < 0.0001). CYP2C9, CYP4F2 and EPHX1 genotypes did not significantly influence the response to fluindione.

CONCLUSIONS

VKORC1 genotype strongly affected anticoagulation induced by fluindione whereas CYP2C9, CYP4F2 and EPHX1 genotypes seemed less determining.

Predictive value of the vitamin K epoxide reductase complex subunit 1 G-1639A and C1173T single nucleotide polymorphisms in retinal vein occlusion

BACKGROUND

  To determine if vitamin K epoxide reductase complex subunit 1 gene polymorphisms have an effect on the risk of having a retinal vein occlusion.

DESIGN

  Case-control study.

PARTICIPANTS

  The study population consisted of 68 patients who were newly diagnosed with retinal vein occlusion and 66 sex-matched controls.

METHODS

  Genomic DNA was extracted from peripheral leukocytes from ethylenediamine tetra-acetic acid-anticoagulated blood. Genotyping of the vitamin K epoxide reductase complex subunit 1 G-1639A (rs 9923231) and C1173T (rs 9934438) single nucleotide polymorphisms was performed using real-time polymerase chain reaction and commercially available kits.

MAIN OUTCOME MEASURES

  A full ophthalmological evaluation was performed in each subject, and all subjects were screened for hypertension, hypercholesterolaemia and diabetes. The genotypes of the vitamin K epoxide reductase complex subunit 1 single nucleotide polymorphisms were determined.

RESULTS

  The vitamin K epoxide reductase complex subunit 1 GG and CC genotypes were more frequent (41% vs. 21%; P = 0.021), and the combined GA/AA and CT/CC genotypes were less frequent in patients with retinal vein occlusion than in control subjects. After adjusting for hypertension, age, plasma fibrinogen levels and prevalence of diabetes and hypercholesterolaemia, the GG and CC genotypes were found to be an independent predictor of retinal vein occlusion (B = 2.28; odds ratio = 9.79; P = 0.003; 95% confidence interval: 2.22-43.24).

CONCLUSION

  It was found that subjects with the vitamin K epoxide reductase complex subunit 1 GG and CC genotypes had a higher risk of retinal vein occlusion.

Vitamin K nutrition, metabolism, and requirements: current concepts and future research

In 2001, the US Food and Nutrition Board concluded that there were insufficient data with which to establish a RDA for vitamin K, in large part because of a lack of robust endpoints that reflected adequacy of intake. Knowledge of the relative bioavailability of multiple vitamin K forms was also poor. Since then, stable isotope methodologies have been applied to the assessment of the bioavailability of the major dietary form of vitamin K in its free state and when incorporated into a plant matrix. There is a need for stable isotope studies with enhanced sensitivity to expand knowledge of the bioavailability, absorption, disposition, and metabolism of different molecular forms of vitamin K. Another area for future research stems from evidence that common polymorphisms or haplotypes in certain key genes implicated in vitamin K metabolism might affect nutritional requirements. Thus far, much of this evidence is indirect via effects on warfarin dose requirements. In terms of clinical endpoints, vitamin K deficiency in early infancy continues to be a leading cause of intracranial bleeding even in developed countries and the reasons for its higher prevalence in certain Asian countries has not been solved. There is universal consensus for the need for vitamin K prophylaxis in newborns, but the effectiveness of any vitamin K prophylactic regimen needs to be based on sound nutritional principles. In contrast, there is still a lack of suitable biomarkers or clinical endpoints that can be used to determine vitamin K requirements among adults.

Association of VKORC1 -1639 G>A polymorphism with carotid intima-media thickness in type 2 diabetes mellitus

AIMS

Media calcification is a predictor of cardiovascular mortality in type 2 diabetes mellitus (T2DM). Undercarboxylation of some vitamin K-dependent proteins, due to genetic polymorphisms of VKORC1, can lead to calcification. We examined a potential association between VKORC1 -1639 G>A polymorphism and T2DM and, also, the association of this polymorphism with carotid intima-media thickness (cIMT).

METHODS

VKORC1 -1639 G>A polymorphism was determined in 299 T2DM patients and 328 controls of Caucasian origin using PCR-RFLP. cIMT was measured in a subgroup of 118 T2DM patients.

RESULTS

The frequency of VKORC1 genotypes between diabetic and nondiabetic subjects differed significantly (p=0.01). VKORC1 genotype was associated with T2DM in an adjusted model (OR 1.36, p=0.009). A statistically significant difference was observed in the maximum value of cIMT among different genotypes. VKORC1 -1639 G>A polymorphism was an independent predictor of cIMT (p=0.029) after adjusting for established risk factors.

CONCLUSIONS

The association between VKORC1 -1639 G>A polymorphism and risk of T2DM could be due to the higher prevalence of calcification in T2DM patients. This is supported by the independent association between VKORC1 -1639 G>A polymorphism and maximum cIMT in T2DM patients which is likely due to atherosclerosis characterized by increased calcification.