Association between venous thromboembolism-associated genetic variants, coagulation factor levels, and thrombin generation potential.

Recently three large meta-analyses of genome-wide association studies for venous thromboembolism (VTE) identified over 130 genetic variants. However, mechanisms by which newly identified and therefore underexplored VTE-associated genetic variants influence VTE remain unclear. To elucidate the mechanism, we investigated the association between 61 newly identified VTE-associated genetic variants and the levels of coagulation factor (F) VIII, FIX, FXI, and fibrinogen as well as thrombin generation parameters (lag time, peak, endogenous thrombin potential, time-to-peak, and velocity), which are well-known biological traits associated with VTE. This study was conducted on 5341 participants of the Netherlands Epidemiology of Obesity study. The associations between VTE-associated genetic variants and coagulation factor levels and thrombin generation parameters were examined using linear regression analyses, adjusted for age, sex, body mass index, oral contraceptive use, hormone replacement therapy, and menopausal status. Of 61 genetic variants, 33 were associated with one or more of the coagulation factor levels and thrombin generation parameters. Following multiple testing corrections, five genetic variants remained significant, of which MAP1A rs55707100 exhibited the most robust association with thrombin generation parameters and FXI levels (ß = -5.33%, 95% confidence interval: -8.44, -2.22). Our findings shed light on the underlying mechanisms by which these genetic variants influence the risk of VTE.

Thalidomide for the Management of Gastrointestinal Bleeding in a Palliative Care Setting.

BACKGROUND: Palliative care patients frequently present with clinically significant gastrointestinal bleeding. Due to the existence of confounding comorbidities and a remarkably reduced state of general health in many cases, the management of gastrointestinal bleeding in this population is often challenging. SUMMARY: This review summarizes and discusses the role of thalidomide in gastrointestinal bleeding with a special focus on palliative care patients. In addition, an illustrative case report is presented. Thalidomide may be beneficial in gastrointestinal bleeding by exerting antiangiogenic effects. The drug has an acceptable safety profile. Side effects like neurotoxicity may limit its use but can be monitored safely. Due to thalidomide's thrombin generation potential, patients managed with thalidomide-containing regimes should be closely monitored for deep venous thrombosis. Given its teratogenicity, thalidomide should not be administered to women of childbearing potential who are not using adequate contraception. KEY MESSAGE: Physicians caring for patients in a palliative care setting should be aware of thalidomide as an effective therapeutic option when endoscopy fails to find a bleeding source or for those patients who cannot or refuse to undergo endoscopy but present with recurrent or obscure gastrointestinal bleeding.

Impaired glucose metabolism is associated with increased thrombin generation potential in patients undergoing angioplasty and stenting.

BACKGROUND: As a strong platelet agonist on the one hand and key molecule in plasmatic coagulation on the other hand, thrombin connects primary and secondary hemostasis. Thrombin generation potential reflects the individual capacity to generate thrombin, and has been associated with the occurrence of thromboembolic events. In the current study, we sought to identify predictors of thrombin generation potential in patients undergoing angioplasty and stenting for atherosclerotic cardiovascular disease. METHODS: Peak thrombin generation potential and area under the curve (AUC) of thrombin generation potential were determined with a commercially available assay in 315 patients on dual antiplatelet therapy 1 day after percutaneous intervention, and in 100 healthy individuals without cardiovascular disease. RESULTS: Median (interquartile range) peak thrombin generation potential and AUC of thrombin generation potential in the study cohort (n = 315) were significantly higher than in healthy individuals (n = 100) without cardiovascular disease (peak thrombin generation potential: 445.4 nM [354.5-551.8 nM] vs. 174.5 nM [141.2-261.2 nM]; AUC of thrombin generation potential: 5262.7 nM thrombin [4806.6-5756.9 nM thrombin] vs. 3405.2 nM thrombin [3043.6-3747.3 nM thrombin]; both p < 0.001). In patients undergoing angioplasty and stenting, hemoglobin A1c (HbA1c) was the only variable that was independently associated with both, peak thrombin generation potential and AUC of thrombin generation potential (both p ≤ 0.007). In contrast, platelet count and high-sensitivity C-reactive protein were only associated with peak thrombin generation potential, and body mass index and serum creatinine were only associated with AUC of thrombin generation potential after adjustment for covariates by multivariate linear regression analyses (all p < 0.05). Patients with HbA1c ≥ 6% had significantly higher peak thrombin generation potential and AUC of thrombin generation potential than patients with HbA1c < 6% (peak thrombin generation potential: 476.9 nM [385.8-577.9 nM] vs. 423.9 nM [335.8-529.5 nM], p = 0.002; AUC of thrombin generation potential: 5371.8 nM thrombin [4903 - 5899 nM thrombin] vs. 5172.5 nM thrombin [4731.8-5664.7 nM thrombin], p = 0.01). HbA1c ≥ 6% remained independently associated with both parameters of thrombin generation potential after multivariate linear regression analyses (both p ≤ 0.02). CONCLUSIONS: Impaired glucose metabolism is associated with increased thrombin generation potential in patients undergoing angioplasty and stenting for cardiovascular disease.

Platelet-specific markers are associated with monocyte-platelet aggregate formation and thrombin generation potential in advanced atherosclerosis.

Platelet activation and thrombin generation are crucial steps in primary and secondary haemostasis. However, both also play major roles in intravascular thrombus formation and therefore in the development of adverse cardiovascular events. In the current study, we first sought to investigate the associations of the platelet biomarkers platelet factor (PF)-4, thrombospondin (TSP)-1, soluble CD40 ligand (sCD40L), and soluble P-selectin (sP-selectin) with each other and with monocyte-platelet aggregate (MPA) formation in 316 patients undergoing angioplasty and stenting. To better understand the interplay between platelet activation and thrombin generation, we subsequently investigated the associations of the platelet biomarkers with thrombin generation potential. The mostly platelet-specific markers PF-4, TSP-1 and sCD40L correlated strongly with each other (all p < 0.001), and the best correlation was observed between PF-4 and TSP-1 (r=0.91). In contrast, sP-selectin, which derives from platelets and endothelial cells, correlated rather poorly with TSP-1 (r=0.12, p=0.04), and did not correlate with PF-4 and sCD40L. While PF-4, TSP-1 and sP-selectin correlated significantly with in vivo MPA formation (all p< 0.001), no such association was found between sCD40L and MPA formation. PF-4, TSP-1 and sCD40L correlated strongly with peak thrombin generation (all p< 0.001) with the best correlation between PF-4 and peak thrombin generation (r=0.55), whereas sP-selectin did not correlate with peak thrombin generation. Likewise, PF-4, TSP-1 and sCD40L correlated significantly with the area under the thrombin generation curve (AUC; all p< 0.01), whereas sP-selectin did not correlate with the AUC. In conclusion, platelet-specific markers are associated with MPA formation and thrombin generation potential in patients with advanced atherosclerosis.

Residual thrombin generation potential is inversely linked to the occurrence of atherothrombotic events in patients with peripheral arterial disease.

BACKGROUND: The serine protease thrombin is the most potent platelet agonist and acts mainly via protease-activated receptors (PAR)-1 and -4. Data linking in vitro thrombin generation potential with PAR-1-mediated platelet activation and adverse events after angioplasty and stenting are missing, so far. MATERIALS AND METHODS: In this prospective cohort study, thrombin generation potential was measured with a commercially available assay in 108 patients undergoing infrainguinal angioplasty and stenting for lower extremity artery disease classified as Rutherford stages of peripheral arterial disease (PAD) 2-3. Thrombin receptor-activating peptide (TRAP)-6-inducible P-selectin expression was determined by flow cytometry. RESULTS: One hundred and four patients entered statistical analysis. Peak thrombin generation potential correlated inversely with TRAP-6-inducible P-selectin (r = -0.2, P < 0.05). Target vessel restenosis or reocclusion (TVR) occurred in 37 patients (35.6%), and the composite atherothrombotic endpoint of myocardial infarction, ischaemic stroke or transient ischaemic attack, and cardiovascular death occurred in seven patients (6.7%) within 2-year follow-up. Peak thrombin generation was similar between patients without and with TVR [465 nM (354-566 nM) vs. 440 nM (355-523 nM), P = 0.6], but significantly lower in patients with the atherothrombotic endpoint than in patients without atherothrombotic events [357 nM (219-389 nM) vs. 463 nM (362-55 nM), P = 0.03]. Further, low thrombin generation potential was associated with an 11.7-fold (95% CI 1.4-97.6; P = 0.02) increased risk of future atherothrombotic events. CONCLUSIONS: Residual thrombin generation potential is inversely correlated with PAR-1-mediated platelet activation and linked to the occurrence of atherothrombotic events in patients with PAD.

Antithrombotic effects of PAR1 and PAR4 antagonists evaluated under flow and static conditions.

INTRODUCTION: Thrombin-mediated activation of human platelets involves the G-protein-coupled protease-activated receptors PAR1 and PAR4. Inhibition of PAR1 and/or PAR4 is thought to modulate platelet activation and subsequent procoagulant reactions. However, the antithrombotic effects of PAR1 and PAR4 antagonism have not been fully elucidated, particularly under flow conditions. MATERIALS AND METHODS: A microchip-based flow chamber system was used to evaluate the influence of SCH79797 (PAR1 antagonist) and YD-3 (PAR4 antagonist) on thrombus formation mediated by collagen and tissue thromboplastin at shear rates simulating those experienced in small- to medium-sized arteries (600s(-1)) and large arteries and small veins (240s(-1)). RESULTS: At a shear rate of 600s(-1), SCH79797 (10µM) efficiently reduced fibrin-rich platelet thrombi and significantly delayed occlusion of the flow chamber capillary (1.44 fold of control; P<0.001). The inhibitory activity of SCH79797 was diminished at 240s(-1). YD-3 (20µM) had no significant effect at either shear rate. The antithrombotic effects of SCH79797 were significantly augmented when combined with aspirin and AR-C66096 (P2Y12 antagonist), but not with YD-3. In contrast, no significant inhibition of tissue factor-induced clot formation under static conditions was observed in blood treated with SCH79797 and YD-3, although thrombin generation in platelet-rich plasma was weakly delayed by these antagonists. CONCLUSIONS: Our results suggest that the antithrombotic activities of PAR1 and/or PAR4 antagonism is influenced by shear conditions as well as by combined platelet inhibition with aspirin and a P2Y12-antagonist.