Evaluation of the blood coagulation mechanism and platelet aggregation in individuals with mechanical or biological heart prostheses

Vitamin K: A vital micronutrient with the cardioprotective potential against diabetes-associated complications

Cardiovascular disease (CVD) remains the leading cause of mortality in patients with type 2 diabetes (T2D). The conventional therapies seem to offer minimal long-term cardioprotection against diabetes-related complications in patients living with T2D. There is a growing interest in understanding the therapeutic effects of food-derived bioactive compounds in protecting or managing these metabolic diseases. This includes uncovering the therapeutic potential of fat-soluble micronutrients such as vitamin K, which are abundantly found in green leafy vegetables. We searched the major electronic databases including PubMed, Web of Sciences, Scopus, Google Scholar and Science direct. The search retrieved randomized clinical trials and preclinical studies, reporting on the impact of vitamin K on CVD-related complications in T2D. The current review updates clinical evidence on the therapeutic benefits of vitamin K by attenuating CVD-risk factors such as blood lipid profiles, blood pressure, as well as markers of oxidative stress and inflammation in patients with T2D. Importantly, the summarized preclinical evidence provides a unique perspective into the pathophysiological mechanisms that could be targeted by vitamin K in the primary prevention of T2D-related complications. Lastly, this review further explores the controversies related to the cardioprotective effects of vitamin K, and also provides the basic information such as the source and bioavailability profile of this micronutrient is covered to highlight its therapeutic potential.

The prophylactic effects of vitamin K supplementation on coagulopathies associated with type 2 diabetes mellitus: A protocol for a systematic review and meta-analysis

BACKGROUND

The impact of vitamin K in ameliorating diabetes-associated complications, especially those linked with platelet activation and coagulation remains unclear. The current study aims to systematically explore and discuss the available evidence on the impact of vitamin K on the diabetes-cardiovascular disease (CVD)-associated complications.

METHODS

A systematic review of studies published on the MEDLINE (PubMed), EMBASE, and Google Scholar electronic database will be conducted. The review will include studies published from inception until May 25, 2020, reporting on the effect of vitamin K on CVD-related markers, especially coagulation factors and platelet activation in type 2 diabetes mellitus. Before the full-text screening, all studies will be screened by title, abstract, and keywords. The Downs and Black checklist will be used to assess the quality of the studies. Additionally, the Cochrane collaboration tool will also be used to evaluate the risk of bias across the included studies. Kappa Cohen's calculator will be used to assess the level of agreement between the authors.

DISCUSSIONS

This systematic review will not require ethical approval, and the results will be distributed through conference and peer-reviewed publications. Our results will assist current and future research scientists on the potential use of vitamin K as a protective therapy against CVD-related complications.

SYSTEMATIC REVIEW REGISTRATION

This protocol is registered on the International Prospective Register of Systematic Reviews (PROSPERO) registration number: CRD42020151667.

Inherited thrombophilia in mechanical valve malfunction

Mechanical valve malfunction due to thrombosis is an important and life-threatening complication in patients with prosthetic valves. Our study was performed to determine the prevalence of thrombophilia genes among patients with acute thrombosis of the mechanical pulmonary valves despite acceptable anticoagulation levels. In this cross-sectional comparative study thirthy two consecutive patients with acute thrombosis of pulmonary mechanical valve who had international normalized ratio (INR) levels for prothrombin time of at least 2 at the time of presentation and in the preceding three months were enrolled and the prevalence rates of thrombophilia factor genes among them was assessed. The results showed that 24 patients (75%) had thrombophilia gene mutations. The affected patients had mutations in one gene in 37.5% of cases, two genes in 31.3%, and three genes in 6.3%. Prevalence rate of Factor V Leiden (FVL), prothrombin (PTH), Plasminogen activator inhibitor-1 (PAI-I), Methylenetetrahydrofolate Reductase (MTHFR), and endothelial protein C receptor (EPCR) gene mutations was 3.1%, 6.3%, 50%, 37.5%, and 25%, respectively. In our study the prevalence of thrombophilia factor gene mutations of patients with acute thrombosis of pulmonary valve was higher than that reported in the general population.

Computational investigation of potential dosing schedules for a switch of medication from warfarin to rivaroxaban-an oral, direct Factor Xa inhibitor

The long-lasting anticoagulant effect of vitamin K antagonists can be problematic in cases of adverse drug reactions or when patients are switched to another anticoagulant therapy. The objective of this study was to examine in silico the anticoagulant effect of rivaroxaban, an oral, direct Factor Xa inhibitor, combined with the residual effect of discontinued warfarin. Our simulations were based on the recommended anticoagulant dosing regimen for stroke prevention in patients with atrial fibrillation. The effects of the combination of discontinued warfarin plus rivaroxaban were simulated using an extended version of a previously validated blood coagulation computer model. A strong synergistic effect of the two distinct mechanisms of action was observed in the first 2–3 days after warfarin discontinuation; thereafter, the effect was close to additive. Nomograms for the introduction of rivaroxaban therapy after warfarin discontinuation were derived for Caucasian and Japanese patients using safety and efficacy criteria described previously, together with the coagulation model. The findings of our study provide a mechanistic pharmacologic rationale for dosing schedules during the therapy switch from warfarin to rivaroxaban and support the switching strategies as outlined in the Summary of Product Characteristics and Prescribing Information for rivaroxaban.

Evaluation of the efficacy and safety of rivaroxaban using a computer model for blood coagulation

Rivaroxaban is an oral, direct Factor Xa inhibitor approved in the European Union and several other countries for the prevention of venous thromboembolism in adult patients undergoing elective hip or knee replacement surgery and is in advanced clinical development for the treatment of thromboembolic disorders. Its mechanism of action is antithrombin independent and differs from that of other anticoagulants, such as warfarin (a vitamin K antagonist), enoxaparin (an indirect thrombin/Factor Xa inhibitor) and dabigatran (a direct thrombin inhibitor). A blood coagulation computer model has been developed, based on several published models and preclinical and clinical data. Unlike previous models, the current model takes into account both the intrinsic and extrinsic pathways of the coagulation cascade, and possesses some unique features, including a blood flow component and a portfolio of drug action mechanisms. This study aimed to use the model to compare the mechanism of action of rivaroxaban with that of warfarin, and to evaluate the efficacy and safety of different rivaroxaban doses with other anticoagulants included in the model. Rather than reproducing known standard clinical measurements, such as the prothrombin time and activated partial thromboplastin time clotting tests, the anticoagulant benchmarking was based on a simulation of physiologically plausible clotting scenarios. Compared with warfarin, rivaroxaban showed a favourable sensitivity for tissue factor concentration inducing clotting, and a steep concentration–effect relationship, rapidly flattening towards higher inhibitor concentrations, both suggesting a broad therapeutic window. The predicted dosing window is highly accordant with the final dose recommendation based upon extensive clinical studies.

Exploratory study on the reversal of warfarin with rFVIIa in healthy subjects

The use of warfarin has a well-known bleeding risk. Recombinant activated factor VII (rFVIIa) is a non–plasma-derived, rapid-acting, and rapidly infused potential treatment. This randomized, single-center, placebo-controlled, double-blinded, dose-escalation, exploratory phase 1 trial assessed safety and effects of rFVIIa in reversing warfarin-induced changes in bleeding and coagulation parameters, using a punch biopsy–induced bleeding model in healthy subjects. The effects of warfarin (experiment 1) and rFVIIa (5-80 μg/kg; experiment 2) were evaluated. Outcomes were bleeding duration, blood loss, coagulation parameters, and safety. Warfarin treatment significantly increased bleeding duration and blood loss from pretreatment (experiment 1, 12 subjects). However, these parameters after rFVIIa treatment were not significantly different from placebo (experiment 2, 85 subjects). Mean activated partial thromboplastin time, prothrombin time, and international normalized ratio were reduced from warfarin-elevated levels. rFVIIa (80 μg/kg) significantly reversed warfarin effects on all thromboelastography parameters, compared with placebo (P < .05), and returned the thrombin generation speed to baseline. There were no thromboembolic or serious adverse events. In this exploratory trial, the reversal of warfarin effects was observed in the thromboelastography, thrombin generation, and clotting assays. However, this reversal did not translate to improvements in the bleeding model parameters evaluated in the punch biopsy model. Trial registration is exempt (phase 1).