Vitamin K-dependent Factors Research Articles

Role of Vitamin K-Dependent Factors Protein S and GAS6 and TAM Receptors in SARS-CoV-2 Infection and COVID-19-Associated Immunothrombosis.

The vitamin K-dependent factors protein S (PROS1) and growth-arrest-specific gene 6 (GAS6) and their tyrosine kinase receptors TYRO3, AXL, and MERTK, the TAM subfamily of receptor tyrosine kinases (RTK), are key regulators of inflammation and vascular response to damage. TAM signaling, which has largely studied in the immune system and in cancer, has been involved in coagulation-related pathologies. Because of these established biological functions, the GAS6-PROS1/TAM system is postulated to play an important role in SARS-CoV-2 infection and progression complications. The participation of the TAM system in vascular function and pathology has been previously reported. However, in the context of COVID-19, the role of TAMs could provide new clues in virus-host interplay with important consequences in the way that we understand this pathology. From the viral mimicry used by SARS-CoV-2 to infect cells, to the immunothrombosis that is associated with respiratory failure in COVID-19 patients, TAM signaling seems to be involved at different stages of the disease. TAM targeting is becoming an interesting biomedical strategy, which is useful for COVID-19 treatment now, but also for other viral and inflammatory diseases in the future.

Multiplexed measurement of variant abundance and activity reveals VKOR topology, active site and human variant impact.

Vitamin K epoxide reductase (VKOR) drives the vitamin K cycle, activating vitamin K-dependent blood clotting factors. VKOR is also the target of the widely used anticoagulant drug, warfarin. Despite VKOR's pivotal role in coagulation, its structure and active site remain poorly understood. In addition, VKOR variants can cause vitamin K-dependent clotting factor deficiency or alter warfarin response. Here, we used multiplexed, sequencing-based assays to measure the effects of 2,695 VKOR missense variants on abundance and 697 variants on activity in cultured human cells. The large-scale functional data, along with an evolutionary coupling analysis, supports a four transmembrane domain topology, with variants in transmembrane domains exhibiting strongly deleterious effects on abundance and activity. Functionally constrained regions of the protein define the active site, and we find that, of four conserved cysteines putatively critical for function, only three are absolutely required. Finally, 25% of human VKOR missense variants show reduced abundance or activity, possibly conferring warfarin sensitivity or causing disease.

Subacute administration of Astaxanthin inhibits vitamin K-dependent clotting factors in rats.

This study investigated the effect of Astaxanthin (ASTX) on levels and activities of the clotting factors in control rats. Untreated or ASTX-treated rats (10mg/kg, dissolved in DMSO) were used in this study. ASTX treatment was conducted for 10days daily. ASTX significantly decreased the platelet count and prolonged values of prothrombin and activated partial thromboplastin time (PT and aPTT, respectively). Besides, it significantly reduced serum levels of vitamin K and the plasma activities and hepatic expression of vitamin K-dependent factors (FII, FVII, FIX, and FX) without altering the activities or levels of all other clotting factors nor plasma levels of fibrinogen or von Willebrand Factor. These effects were associated with a reduction in serum and fecal levels of cholesterol and triglycerides and lower serum levels of LDL-c. In conclusion, ASTX exerts an in vivo hypocoagulant effects mediated by the inhibition of vitamin K-dependent factors. PRACTICAL APPLICATIONS: The findings presented here are the first that show the ability of Astaxanthin (ASTX) to inhibit coagulation in rats by suppressing the circulatory levels of Vitamin K and decrease the synthesis and release of all Vitamin-K dependent factor (FII, FVII, FIX, and FX). Since some synthetic anti-coagulants had side effects, these findings may illustrate ASTX as a natural anti-coagulant with fewer side effects that require further investigation in more clinical trials. Besides, awareness should be established for those individuals with some bleeding disorders who are being treated with ASTX for other beneficial effects.

Fat-soluble vitamin deficiency and subsequent coagulopathy in a cat with exocrine pancreatic insufficiency

This report describes the clinical signs, diagnostic findings and treatment of a female spayed Domestic Shorthair with exocrine pancreatic insufficiency (EPI) who presented in shock due to severe gastrointestinal haemorrhage...

Thrombophilia Screening in Adults Is Not Predictive of a Thrombotic Event after Bipulmonary Lung Transplantation

Introduction: The incidence of venous thrombotic event (VTE ) after lung tansplantation was recently evaluated to approximately 44 % in a large series of patients (Neto et al., Transplantation. 2018; 102: 681). Cystic fibrosis (CF) is a devastating chronic inflammatory disease caused by a mutation in the gene encoding cystic fibrosis transmembrane regulator (CFTR), which is a chloride channel in epithelia cell membranes. Coagulation balance in patient with CF is complexed since there is both a decrease in vitamin K-dependent factor but also an excess of physiological inhibitors deficiencies. Lung fibrosis was also sometimes associated to a higher thrombotic risk. Aim: To analyse whether thrombin generation assay (TGA), which takes in account both pro-and anticoagulant factors, or the activity of soluble tissue factor (TFa) are able to discriminate the thrombotic risk of patients after bipulmonary lung transplantation (BLT) and are better discriminant than classical thrombophilia screening test [prothrombin time (PT), activated partial thromboplastin time (APTT), antithrombin (AT), protein C (PC) S (PS), Z (PZ) fibrinogen (FG) and FVIII levels (FVIIIc) measurements]. Methods: Thrombophilia screening (including TGT in the presence or absence of thrombomodulin (TM) and TFa quantification) was performed for 166 consecutive patients before BLT. Patients were divided in 3 categories : 100 with CF, 43 with chronic obstructive pulmonary disease (COPD) and 23 with idiopathic pulmonary fibrosis (IPF). Among them, 91 (51 with CF, 28 with COPD and 12 with IF) were transplanted. Proven VTE (positive duplex ultrasound) during the first trimester was registered. Results: Because of a defect in lipophilic vitamin absorption, prothrombin time below 70 % and a significant higher proportion of PZ deficiency was observed in patients with CF, in comparison to COPD. The frequency of AT, PC and PS were not significantly different between the 3 groups of patients. Because the chronic pulmonary contamination of the lung by bacteria, the frequency of elevated fibrinogen levels were significantly higher in patients with CF as compared to COPD and IPF groups (table 1). Median TFa values were significantly higher (p < 0.05) in patients with CF (median 0.24 pg/mL, range 0.1 - 7.7) than in patients with COPD (median 0.1 pg/ml, range 0.1 - 0.63). FTa was also elevated (median 0.24, range 0.1 - 6.15) in patients with IPF. Time to Peak (tt-Peak) was significantly shorter in patients with CF as compared to COPD or IPF, even in the presence of thrombomodulin (TM). MRI were higher in patients with CF than in patients with COPD or IPF, even in the presence of TM. Peak was higher in patients with CF as compared to patients with COPD (p < 0.05). In the presence of TM, Endogenous prothrombin potential (ETP) was significantly higher in patients with CF as compared to patients with COPD, and the ratio ETP/ETP with TM was higher in patients with CF as compared to patients with COPD or IPF, indicating a defective PC pathway in patients with CF (table 2). Among the 91 patients with BLT, a VTE was evidenced in 25 (27.5%) patients, with a similar frequency between the 3 groups (33.3 % in CF, 14.7 in COPD, 33.3 % in IPF, not significant). We analysed separately patients with CF from patients with COPD or IPF, since there were differences between coagulation parameters tested in patients with CF. Only APTT ratio was significantly lower (p < 0.01) in patients with CF who had a VTE (1.04) than in patients without VTE (1.12). No difference in the different parameters tested was evidenced in patients with COPD and IPF Conclusion: Even if TGA and TFa clearly evidence a more prothrombotic phenotype in patients with CF than in patients with COPD or IPF, thrombophilia screening before BLT fail to identify patients with a high post-operative thrombotic risk. Disclosures No relevant conflicts of interest to declare.

The use of prophylaxis in the treatment of rare bleeding disorders

Rare bleeding disorders (RBDs) are a heterogeneous group of coagulation factor deficiencies that include fibrinogen, prothrombin, α2-antiplasmin, plasminogen activator inhibitor-1, and factors II, V, V/VIII, VII, X, XI and XIII. The incidence varies based upon the disorder and typically ranges from 1 in 500,000 to 1 per million population. Symptoms vary with the disorder and residual level of the clotting factor, and can range from relatively minor such as epistaxis, to life threatening, such as intracranial hemorrhage. Rapid treatment of bleeding episodes in individuals with severe bleeding phenotypes is essential to preserve life or limb and to prevent long-term sequelae; therapeutic options depend on the deficiency and range from plasma-derived (eg, fresh frozen plasma, prothrombin complex concentrates, factor X concentrate) to highly purified and recombinant single factor concentrates. The rarity of these disorders limits the feasibility of conventional prospective clinical trials; instead, clinicians rely upon registries, published case reports/series and experience to guide treatment. In some disorders, long-term prophylactic therapy is administered in response to the bleeding phenotype in an individual patient or based on the known natural history and severity of the deficiency. Intermittent prophylaxis, surrounding surgery, pregnancy, labor, and menstruation may be required to prevent or control excessive bleeding. This review summarizes therapeutic options, guidelines, recommendations and observations from the published literature for long-term, surgical, gynecological, and obstetric prophylaxis in deficiencies of fibrinogen; prothrombin; factors II, V, V/VIII, VII, X, XI and XIII; combined vitamin-K dependent factors; α2-antiplasmin; and plasminogen activator inhibitor 1. Platelet disorders including Glanzmann's thrombasthenia and Bernard-Soulier syndrome are also addressed.

Association of apolipoproteins C-I, C-II, C-III and E with coagulation markers and venous thromboembolism risk.

PurposeApolipoproteins C-I, C-II, C-III and E have been associated with risk of arterial thrombotic diseases. We investigated whether these apolipoproteins have prothrombotic properties and are associated with risk of venous thromboembolism (VTE).Patients and methodsA total of 127 VTE patients and 299 controls were randomly selected from the Multiple Environmental and Genetic Assessment of Risk Factors for Venous Thrombosis study (1999–2004), in the Netherlands. The apolipoproteins were quantified using mass spectrometry (LC/MS/MS), and their levels were analyzed as continuous variable (per SD increase).ResultsIn controls, increases in levels of apolipoproteins were associated with increases in levels of vitamin K-dependent factors, factor XI, antithrombin and clot lysis time. Additionally, increasing apolipoproteins C-III and E levels were associated with higher factor VIII and von Willebrand factor levels. Levels of C-reactive protein were not associated with any apolipoprotein. The age- and sex-adjusted odds ratios of apolipoproteins E, C-III, CII and CI to the risk of venous thrombosis were 1.21 (95% CI, 0.98–1.49), 1.19 (95% CI, 0.99–1.44), 1.24 (95% CI, 0.95–1.61) and 1.06 (95% CI, 0.87–1.30) per SD increase, respectively. These odds ratios did not attenuate after adjustments for statin use, estrogen use, BMI, alcohol use, and self-reported diabetes.ConclusionsLevels of apolipoproteins C-I, C-II, C-III and E are associated with those of several coagulation factors. However, whether these apolipoproteins are also associated with an increased risk of VTE remains to be established.

The vitamin K-dependent factor, protein S, regulates brain neural stem cell migration and phagocytic activities towards glioma cells

Malignant gliomas are the most common primary brain tumors. Due to both their invasive nature and resistance to multimodal treatments, these tumors have a very high percentage of recurrence leading in most cases to a rapid fatal outcome. Recent data demonstrated that neural stem/progenitor cells possess an inherent ability to migrate towards glioma cells, track them in the brain and reduce their growth. However, mechanisms involved in these processes have not been explored in-depth.In the present report, we investigated interactions between glioma cells and neural stem/progenitor cells derived from the subventricular zone, the major brain stem cell niche. Our data show that neural stem/progenitor cells are attracted by cultured glioma-derived factors. Using multiple approaches, we demonstrate for the first time that the vitamin K-dependent factor protein S produced by glioma cells is involved in tumor tropism through a mechanism involving the tyrosine kinase receptor Tyro3 that, in turn, is expressed by neural stem/progenitor cells.Neural stem/progenitor cells decrease the growth of both glioma cell cultures and clonogenic population. Cultured neural stem/progenitor cells also engulf, by phagocytosis, apoptotic glioma cell-derived fragments and this mechanism depends on the exposure of phosphatidylserine eat-me signal and is stimulated by protein S.The disclosure of a role of protein S/Tyro3 axis in neural stem/progenitor cell tumor-tropism and the demonstration of a phagocytic activity of neural stem/progenitor cells towards dead glioma cells that is regulated by protein S open up new perspectives for both stem cell biology and brain physiopathology.

Contemporary Reversal of Oral Anticoagulation in Intracerebral Hemorrhage.

Author(s): Bower, Matthew M; Sweidan, Alexander J; Shafie, Mohammad; Atallah, Steven; Groysman, Leonid I; Yu, Wengui

Management of rare coagulation disorders in 2018

Rare bleeding disorders (RBDs) comprise inherited deficiencies of factors I (fibrinogen), II (prothrombin), V, VII, X, XI, and XIII as well as combined factor V + VIII and vitamin K-dependent factors. They represent 3–5% of all congenital bleeding disorders and are usually transmitted as autosomal recessive traits. These disorders often manifest during childhood and have varied clinical presentations from mucocutaneous bleeding to life-threatening symptoms such as central nervous system and gastrointestinal bleeding. Bleeding manifestations generally vary within the same RBD and may also vary from 1 RBD to the other. Laboratory diagnosis is based on coagulation screening tests and specific factor assays, with molecular techniques providing diagnostic accuracy and enabling prenatal counseling. The approach to treatment of bleeding episodes and invasive procedures needs to be individualized and depends on the severity, frequency and procedure-related risk of bleeding. The first line of treatment of RBDs is replacement of the deficient factor, using specific plasma-derived or recombinant products and using fresh frozen plasma or cryoprecipitate when specific products are not available or in resource-limited countries. Prophylaxis may be considered in individuals with recurrent serious bleeding and especially after life-threatening bleeding episodes. Novel no-replacement strategies promoting hemostasis by through different mechanisms need to be studied in RBDs as alternative therapeutic options.

Bioengineering of rFVIIa Biopharmaceutical and Structure Characterization for Biosimilarity Assessment.

Eptacog alfa (NovoSeven®) is a vitamin K-dependent recombinant Factor VIIa produced by genetic engineering from baby hamster kidney (BHK) cells as a single peptide chain of 406 residues. After activation, it consists of a light chain (LC) of 152 amino and a heavy chain (HC) of 254 amino acids. Recombinant FVIIa undergoes many post-translational modifications (PTMs). The first ten glutamic acids of the N-terminal moiety are γ-carboxylated, Asn145 and Asn322 are N-glycosylated, and Ser52 and Ser60 are O-glycosylated. A head-to-head biosimilarity study was conducted for the originator and the first biosimilar AryoSeven™ to evaluate comparable bioengineering. Physicochemical properties were analyzed based on mass spectrometry, including intact mass, PTMs and higher-order structure. Both biotherapeutics exhibit a batch-to-batch variability in their N-glycan profiles. N-Glycopeptide analysis with UHPLC-QTOF-MSE confirmed N-glycosylation sites as well as two different O-glycopeptide sites. Ser60 was found to be O-fucosylated and Ser52 had O-glucose or O-glucose-(xylose)1,2 motifs as glycan variants. Ion mobility spectrometry (TWIMS) and NMR spectroscopy data affirm close similarity of the higher-order structure of both biologicals. Potency of the biodrugs was analyzed by a coagulation assay demonstrating comparable bioactivity. Consequently, careful process optimization led to a stable production process of the biopharmaceuticals.

Protocolized warfarin reversal with 4-factor prothrombin complex concentrate versus 3-factor prothrombin complex concentrate with recombinant factor VIIa

IntroductionLife-threatening bleeding can complicate warfarin therapy. Rapid anticoagulant reversal via replacement of vitamin-K dependent clotting factors is essential for hemostasis. We compare two methods of rapid factor replacement for warfarin reversal. MethodsA retrospective cohort study of warfarin-treated patients experiencing life-threatening bleeding who received a reversal protocol comprised of 4F PCC or 3F PCC and rFVIIa was performed. Demographic, clinical and anticoagulant reversal information, and all adverse events attributed to warfarin reversal were recorded. Results195 patients were included in final analysis. While baseline demographics were similar between groups, the 3F-PCC group had a longer ICU LOS and higher in-hospital mortality (p < .01, .01).Pre-reversal INR was similar between both groups, but post-reversal INR was significantly lower in the 3F-PCC group, 0.8 versus 1.3 (p < .01). Significantly more patients experienced thromboembolic complications in the 3F-PCC group than the 4F-PCC group (p < .01). Receipt of rFVIIa was significantly associated with thromboembolic complications. DiscussionA 4F PCC reversal strategy is efficacious in INR reversal and provides lower thromboembolic risk as compared to 3F PCC with rFVIIa.

Coagulation Testing in the Core Laboratory.

Primary hemostasis begins with endothelial injury. VWF, produced by endothelial cells, binds to platelets and links them to subendothelial collagen. Platelet-derived ADP and thromboxane activate non-adhered platelets via their GPIIb/IIIa receptors, allowing these platelets to participate in platelet aggregation. Secondary hemostasis is initiated with the binding of factor VII to extravascular tissue factor (TF). Factors II, VII, IX and X are vitamin K-dependent factors. The role of vitamin K is to assist in the addition of gamma carboxylate groups to glutamic acids in the "GLA" domains of these factors.In vitro the intrinsic pathway is initiated when fresh whole blood is placed in a glass tube. The negative charge of the glass initiates the "contact pathway" where FXII is activated and then FXIa cleaves FIX to FIXa. The extrinsic pathway is triggered when tissue factor, phospholipid and calcium are added to plasma anticoagulated with citrate. In vitro, FVII is activated to FVIIa, and TF-FVIIa preferentially converts FX to FXa activating the common pathway.The prothrombin time is commonly used to monitor warfarin anticoagulant therapy. To correct for differences in reagent and instrument, the international normalized ratio was developed to improve standardization of PT reporting globally. The activated partial thromboplastin time (aPTT) is used to evaluate the intrinsic and common pathways of coagulation. The aPTT is useful clinically as a screening test for inherited and acquired factor deficiencies as well as to monitor unfractionated heparin therapy although the anti-Xa assay is now the preferred measure of the effects of unfractionated heparin. The Clauss assay is the most commonly performed fibrinogen assay and uses diluted plasma where clotting is initiated with a high concentration of reagent thrombin.The mixing study assists in the assessment of an abnormally prolonged PT or aPTT. An equal volume of citrated patient plasma is mixed with normal pooled plasma and the PT or aPTT are repeated on the 1:1 mix. Factor activity assays are most commonly performed as a one-stage assay. The patient's citrated plasma is diluted and mixed 1-to-1 with a single factor-deficient substrate plasma. A PT or aPTT is performed on the above mix, depending on the factor being tested.Factor inhibitors are antibodies that are most commonly diagnosed in male patients with severe hemophilia A (FVIII deficiency) where they are induced by factor replacement therapy.Factor inhibitors can also appear in the form of spontaneous autoantibodies in both male and female individuals who were previously well. This is an autoimmune condition called "acquired hemophilia."Most coagulation laboratories can measure the plasma concentration of VWF protein (VWF antigen) by an immunoturbidimetric technique. Testing the functional activity of VWF, utilizes the drug ristocetin.The state of multimerization of VWF is important and is assessed by electrophoresis on agarose gels. Type 2a and 2b VWD are associated with the lack of intermediate- and high molecular weight multimers.The antiphospholipid syndrome (APLS) is an acquired autoimmune phenomenon associated with an increased incidence of both venous and arterial thromboses, as well as fetal loss. Typically, there is a paradoxical prolongation of the aPTT in the absence of any clinical features of bleeding. This is the so-called "lupus anticoagulant (LA) effect." The laboratory definition of the APLS requires the presence of either a "lupus anticoagulant" or a persistent titer of antiphospholipid antibodies.There are now 2 broad classes of direct-acting oral anticoagulants (DOACs): [1] The oral direct thrombin inhibitors (DTIs) such as dabigatran; and [2] The oral direct factor Xa inhibitors such as rivaroxaban and apixaban. The PT and aPTT are variably affected by the DOACs and are generally unhelpful in monitoring their concentrations. Most importantly, a normal PT or aPTT does NOT exclude the presence of any of the DOACs.

A Joint Model for Vitamin K-Dependent Clotting Factors and Anticoagulation Proteins.

Warfarin acts by inhibiting the reduction of vitamin K (VK) to its active form, thereby decreasing the production of VK-dependent coagulation proteins. The aim of this research is to develop a joint model for the VK-dependent clotting factors II, VII, IX and X, and the anticoagulation proteins, proteins C and S, during warfarin initiation. Data from 18 patients with atrial fibrillation who had warfarin therapy initiated were available for analysis. Nine blood samples were collected from each subject at baseline, and at 1-5, 8, 15 and 29days after warfarin initiation and assayed for factors II, VII, IX and X, and proteins C and S. Warfarin concentration-time data were not available. The coagulation proteins data were modelled in a stepwise manner using NONMEM® Version 7.2. In the first stage, each of the coagulation proteins was modelled independently using a kinetic-pharmacodynamic model. In the subsequent step, the six kinetic-pharmacodynamic models were combined into a single joint model. One patient was administered VK and was excluded from the analysis. Each kinetic-pharmacodynamic model consisted of two parts: (1) a common one-compartment pharmacokinetic model with first-order absorption and elimination for warfarin; and (2) an inhibitory E max model linked to a turnover model for coagulation proteins. In the joint model, an unexpected pharmacodynamic lag was identified and the estimated degradation half-life of VK-dependent coagulation proteins were in agreement with previously published values. The model provided an adequate fit to the observed data. The joint model represents the first work to quantify the influence of warfarin on all six VK-dependent coagulation proteins simultaneously. Future work will expand the model to predict the influence of exogenously administered VK on the time course of clotting factor concentrations after warfarin overdose and during perioperative warfarin reversal procedures.

Autosomal recessive inherited bleeding disorders in Pakistan: a cross-sectional study from selected regions

BackgroundAutosomal recessive bleeding disorders (ARBDs) include deficiencies of clotting factors I, II, V, VII, X, XI, XIII, vitamin K dependent clotting factors, combined factor V & VIII, Von Willebrand Disease (vWD) type 3, Glanzmann’s thrombasthenia (GT) and Bernard–Soulier syndrome. Patients with primary bleeding disorders from all the major provincial capitals of Pakistan were screened for ARBDs. Prothrombin (PT), activated partial thromboplastin time (APTT), bleeding time (BT) and fibrinogen levels were measured. Cases with isolated prolonged APTT were tested for factors VIII and IX using factor assays This was followed by FXI:C level assessment in cases with normal FVIII and FIX levels. vWD was screened in patients with low FVIII levels. Factors II, V and X were tested in patients with simultaneous prolongation of PT and APTT. Peripheral blood film examination and platelet aggregation studies were performed to assess platelet disorders. Urea clot solubility testing was done to detect Factor XIII levels where platelet function tests were normal. Descriptive analysis was done using SPSS version 16.ResultsOf the 429 suspected bleeding disorder patients, 148 (35%) were diagnosed with hemophilia A and 211 (49.1%) patients had ARBDs. 70 patients (16.3%) remained undiagnosed. Out of 211 patients with ARBD; 95 (33.8%) had vWD type 3. Fibrinogen deficiency was found in 34 patients (12%), GT in 27 (9.6%), factor XIII deficiency in 13 (4.6%), factor VII deficiency in 12 (4.3%), factor V deficiency in 9 (3.2%). Eight patients (2.8%) had vitamin K-dependent clotting factor deficiency, Bernard–Soulier syndrome was diagnosed in seven patients (2.5%), factor X deficiency in 2 (0.7%), factor II deficiency in 2 (0.7%), factor XI deficiency and combined factor V and VIII deficiency in 1 (0.4%) patient each.ConclusionvWD type 3 was the most common ARBD found in our sample of patients in Pakistan, followed by fibrinogen deficiency and GT in respective order.

Dietary and genetic influences on hemostasis in a Yup'ik Alaska Native population.

Fish and marine animals are important components of the subsistence diet of Alaska Native people, resulting in a high ω3 PUFA intake. The historical record for circumpolar populations highlights a tendency for facile bleeding, possibly related to ω3 PUFA effects on platelet activation and/or vitamin K-dependent clotting factors. To evaluate these two scenarios in Yup’ik people of southwestern Alaska, we examined the association between dietary ω3 PUFA intake and activities of clotting factor II, V, fibrinogen, PT, INR, PTT, and sP-selectin in 733 study participants, using the nitrogen isotope ratio of red blood cells as a biomarker of ω3 PUFA consumption. sP-selectin alone correlated strongly and inversely with ω3 PUFA consumption. Approximately 36% of study participants exhibited PIVKA-II values above the threshold of 2 ng/ml, indicative of low vitamin K status. To assess genetic influences on vitamin K status, study participants were genotyped for common vitamin K cycle polymorphisms in VKORC1, GGCX and CYP4F2. Only CYP4F2*3 associated significantly with vitamin K status, for both acute (plasma vitamin K) and long-term (PIVKA-II) measures. These findings suggest: (i) a primary association of ω3 PUFAs on platelet activation, as opposed to vitamin K-dependent clotting factor activity, (ii) that reduced CYP4F2 enzyme activity associates with vitamin K status. We conclude that high ω3 PUFA intake promotes an anti-platelet effect and speculate that the high frequency of the CYP4F2*3 allele in Yup’ik people (~45%) evolved in response to a need to conserve body stores of vitamin K due to environmental limitations on its availability.

During warfarin induction, the Fiix‐prothrombin time reflects the anticoagulation level better than the standard prothrombin time

Background The prothrombin time (PT) is equally prolonged by reduction of each of the vitamin K-dependent (VKD) factors (F) II, VII and X. The Fiix-PT is only affected by FII and FX, the main contributors to thrombin generation (TG). Objective To test the hypothesis that variability in warfarin anticoagulation is reduced early during monitoring with the normalized PT-ratio calculated from Fiix-PT (Fiix-International Normalized Ratio [INR]) compared with traditional PT-INR monitoring. Also, that because of its insensitivity to FVII, Fiix-PT more accurately reflects TG when Fiix-INR and PT-INR are discrepant. Methods Samples from Fiix-trial participants monitored with either Fiix-PT or PT were used. VKD coagulation factors and TG were measured in samples from 40 patients during stable anticoagulation and in serial samples obtained from 26 patients during warfarin induction. TG was assessed in relation to selective reduction in single VKD factors. Results During Fiix-warfarin induction full anticoagulation measured as FII or FX activity was achieved at a similar rate to that with PT-warfarin but subsequently stabilized better. Fiix-INR but not PT-INR mirrored total TG during initiation. During induction, FII (R2 = 0.66) and FX (R2 = 0.52) correlated better with TG and with a steeper slope than did FIX (R2 = 0.37) and in particular FVII (R2 = 0.21). In vitro, FII and FX were the main determinants of TG at concentrations observed during VKA anticoagulation, whereas FVII and FIX had little influence. Conclusions Fiix-PT monitoring reduces anticoagulation variability, suggesting that monitoring FVII has a limited role during VKA management. TG is better reflected by Fiix-PT.

Hemostasis, bleeding and thrombosis in liver disease

The presence of cirrhosis poses an increased risk of both thrombosis and bleeding in individuals with chronic liver disease. This duality is a result of a dynamic disequilibrium between procoagulant and anticoagulant states in individuals with cirrhosis. The mechanism of this imbalance in cirrhosis remains unclear. It is known that the progression of cirrhosis leads to decreased synthetic function and a concurrent lack of natural anticoagulants. Other proposed mechanisms contributing to this hemostatic imbalance include decreased platelet production, increased platelet destruction from hypersplenism, decreased synthesis of Vitamin K-dependent and independent clotting factors and anticoagulant factors, and alterations in purinergic signaling pathways. Given the current state of flux in our understanding of bleeding and thrombophilia in cirrhosis, the recommendations for treatment of these conditions are still evolving. We provide a current update on the proposed pathophysiology of altered hemostasis and thrombophilia in cirrhosis. We discuss recent studies in portal vein thrombosis (PVT) and venous thromboembolism (VTE), which are the common thrombotic consequences of cirrhosis, resulting in substantive morbidity and mortality. To address these, we discuss new prophylactic interventions and current treatment options to manage the heightened risk of thrombosis in cirrhosis, while limiting hemorrhagic complications.

Reversing vitamin K antagonists: making the old new again.

Vitamin K antagonists (VKAs) are commonly used for the prevention and treatment of thrombotic disorders. The response to VKAs is highly variable due to their specific interaction with the vitamin K cycle, and hence interference with hepatic synthesis of vitamin K-dependent coagulation factors. Monitoring the anticoagulant effect of VKAs by assessing the patient's international normalized ratio (INR) is essential because complications are closely related to the intensity of anticoagulation. Treatment with VKAs contains a substantial risk of bleeding with a high case fatality rate. Reversal of VKAs is required in case of bleeding or a supratherapeutic INR, but also prior to high-risk surgery or interventions. Choice of methods to reverse VKAs depends on whether or not the patient is bleeding or is in need of an urgent procedure, and has to be based on the pharmacokinetic and pharmacodynamic properties of the VKA. Reversal strategies include withholding the VKA, administration of vitamin K1, and substitution of vitamin K-dependent procoagulant factors, and need to be combined with measures according to general bleeding management.

Uniparental disomy causes deficiencies of vitamin K‐dependent proteins

Background Inherited deficiency of all vitamin K-dependent coagulant factors (VKCFD) is a rare autosomal recessive disorder caused by mutations in the γ-glutamyl carboxylase gene (GGCX) or the vitamin K epoxide reductase gene (VKORC1), with great heterogeneity in terms of both clinical presentation and response to treatment. Objective To characterize the molecular basis of VKCFD in a Spanish family. Methods and Results Sequencing of candidate genes, comparative genomic hybridization and massive sequencing identified a new mechanism causing VKCFD in the proband. Uniparental disomy (UPD) of chromosome 2 caused homozygosity of a mutation (c.44-1G>A) resulting in aberrant GGCX splicing. This change contributed to absent expression of the mRNA coding for the full-length protein, and to four-fold overexpression of the smaller mRNA isoform lacking exon 2 (Δ2GGCX). Δ2GGCX might be responsible for two unexpected clinical observations in the patient: (i) increased plasma osteocalcin levels following vitamin K1 supplementation; and (ii) a mild non-bleeding phenotype. Conclusions Our study identifies a new autosomal disease, VKCFD1, caused by UPD. These data suggest that the Δ2GGCX isoform may retain enzymatic activity, and strongly encourage the evaluation of both hepatic and non-hepatic vitamin K-dependent proteins to assess differing responses to vitamin K supplementation in VKCFD patients.