Hypofibrinolysis in diabetes: a therapeutic target for the reduction of cardiovascular risk

An enhanced thrombotic environment and premature atherosclerosis are key factors for the increased cardiovascular risk in diabetes. The occlusive vascular thrombus, formed secondary to interactions between platelets and coagulation proteins, is composed of a skeleton of fibrin fibres with cellular elements embedded in this network. Diabetes is characterised by quantitative and qualitative changes in coagulation proteins, which collectively increase resistance to fibrinolysis, consequently augmenting thrombosis risk. Current long-term therapies to prevent arterial occlusion in diabetes are focussed on anti-platelet agents, a strategy that fails to address the contribution of coagulation proteins to the enhanced thrombotic milieu. Moreover, antiplatelet treatment is associated with bleeding complications, particularly with newer agents and more aggressive combination therapies, questioning the safety of this approach. Therefore, to safely control thrombosis risk in diabetes, an alternative approach is required with the fibrin network representing a credible therapeutic target. In the current review, we address diabetes-specific mechanistic pathways responsible for hypofibrinolysis including the role of clot structure, defects in the fibrinolytic system and increased incorporation of anti-fibrinolytic proteins into the clot. Future anti-thrombotic therapeutic options are discussed with special emphasis on the potential advantages of modulating incorporation of the anti-fibrinolytic proteins into fibrin networks. This latter approach carries theoretical advantages, including specificity for diabetes, ability to target a particular protein with a possible favourable risk of bleeding. The development of alternative treatment strategies to better control residual thrombosis risk in diabetes will help to reduce vascular events, which remain the main cause of mortality in this condition

Omecamtiv mecarbil in chronic heart failure with reduced ejection fraction, GALACTIC‐HF: baseline characteristics and comparison with contemporary clinical trials

Aims: The safety and efficacy of the novel selective cardiac myosin activator, omecamtiv mecarbil, in patients with heart failure with reduced ejection fraction (HFrEF) is tested in the Global Approach to Lowering Adverse Cardiac outcomes Through Improving Contractility in Heart Failure (GALACTIC‐HF) trial. Here we describe the baseline characteristics of participants in GALACTIC‐HF and how these compare with other contemporary trials. Methods and Results: Adults with established HFrEF, New York Heart Association functional class (NYHA) ≥ II, EF ≤35%, elevated natriuretic peptides and either current hospitalization for HF or history of hospitalization/ emergency department visit for HF within a year were randomized to either placebo or omecamtiv mecarbil (pharmacokinetic‐guided dosing: 25, 37.5 or 50 mg bid). 8256 patients [male (79%), non‐white (22%), mean age 65 years] were enrolled with a mean EF 27%, ischemic etiology in 54%, NYHA II 53% and III/IV 47%, and median NT‐proBNP 1971 pg/mL. HF therapies at baseline were among the most effectively employed in contemporary HF trials. GALACTIC‐HF randomized patients representative of recent HF registries and trials with substantial numbers of patients also having characteristics understudied in previous trials including more from North America (n = 1386), enrolled as inpatients (n = 2084), systolic blood pressure < 100 mmHg (n = 1127), estimated glomerular filtration rate < 30 mL/min/1.73 m2 (n = 528), and treated with sacubitril‐valsartan at baseline (n = 1594). Conclusions: GALACTIC‐HF enrolled a well‐treated, high‐risk population from both inpatient and outpatient settings, which will provide a definitive evaluation of the efficacy and safety of this novel therapy, as well as informing its potential future implementation

Predictors of neutrophil extracellular traps markers in type 2 diabetes mellitus: associations with a prothrombotic state and hypofibrinolysis

Abstract Background Type 2 diabetes mellitus (T2DM) is associated with a hypercoagulable state and increased neutrophil extracellular traps formation (NETosis). We investigated predictors of NETosis and cell death markers in circulating blood and their association with a prothrombotic state in T2DM. Methods In a cross-sectional study involving 113 T2DM patients aged 63.7 ± 8.2 years, we investigated citrullinated histone H3 (H3Cit), cell-free deoxyribonucleic acid (cfDNA), myeloperoxidase, neutrophil elastase, and inflammation markers, along with thrombin generation (TG), plasma clot lysis time (CLT), clot permeability (Ks) and fibrinolysis inhibitors. Results On multivariate logistic regression analysis adjusted for age and gender, predictors of high H3Cit (≥ 7.36 ng/mL, upper quartile) were: glycated hemoglobin (HbA1c) ≥ 7.0% and interleukin-6. Interleukin-6 was also found to be a predictor of high cfDNA (≥ 2.84 µg/mL, upper quartile) along with glucose. Citrullinated histone H3 and cfDNA correlated positively with CLT and inversely with Ks, while TG associated solely with cfDNA. These associations were not seen with myeloperoxidase and neutrophil elastase. Patients with previous myocardial infarction (n = 21, 18.6%) had higher H3Cit (+108%, p < 0.001) and cfDNA (+45%, p = 0.022). On multivariable analysis adjusted for potential confounders, H3Cit and cfDNA, along with plasminogen activator inhibitor-1 and concomitant cardiovascular disease, were predictors of CLT. Citrullinated histone H3 alone was a predictor of Ks and only cfDNA was a predictor of peak thrombin generated. Conclusions In T2DM, NETosis detectable in circulating blood is associated with inflammatory state and a prothrombotic state, especially hypofibrinolysis

Factor XIIIa-dependent retention of red blood cells in clots is mediated by fibrin α-chain crosslinking

Factor XIII(a) [FXIII(a)] stabilizes clots and increases resistance to fibrinolysis and mechanical disruption. FXIIIa also mediates red blood cell (RBC) retention in contracting clots and determines venous thrombus size, suggesting FXIII(a) is a potential target for reducing thrombosis. However, the mechanism by which FXIIIa retains RBCs in clots is unknown. We determined the effect of FXIII(a) on human and murine clot weight and composition. Real-time microscopy revealed extensiveRBCloss from clots formed in the absence of FXIIIa activity, and RBCs exhibited transient deformation as they exited the clots. Fibrin band-shift assays and flow cytometry did not reveal crosslinking of fibrin or FXIIIa substrates to RBCs, suggesting FXIIIa does not crosslink RBCs directly to the clot. RBCs were retained in clots from mice deficient in α2-antiplasmin, thrombin-activatable fibrinolysis inhibitor, or fibronectin, indicating RBC retention does not depend on these FXIIIa substrates. RBC retention in clots was positively correlated with fibrin network density; however, FXIIIa inhibition reduced RBC retention at all network densities. FXIIIa inhibition reduced RBC retention in clots formed with fibrinogen that lacks γ-chain crosslinking sites, but not in clots that lack α-chain crosslinking sites. Moreover, FXIIIa inhibitor concentrations that primarily block α-, but not γ-, chain crosslinking decreased RBC retention in clots. These data indicate FXIIIa-dependent retention of RBCs in clots is mediated by fibrin α-chain crosslinking. These findings expose a newly recognized, essential role for fibrin crosslinking during whole blood clot formation and consolidation and establish FXIIIa activity as a key determinant of thrombus composition and size