Postprandial changes in the phospholipid composition of circulating microparticles are not associated with coagulation activation

Introduction

Evidence is present that the phospholipid composition of circulating cell-derived microparticles (MP) affects coagulation in vivo, and that postprandial metabolic alterations may be associated with hypercoagulable state. Our objective was to investigate whether postprandial metabolic responses affect the phospholipid composition of MP, and whether such changes are associated with coagulation activation.

Materials and Methods

Twelve healthy males were studied twice and randomly received two consecutive meals or remained fasted. Blood was collected before and at 2, 4, 6 and 8 h following breakfast. Plasma concentrations of prothrombin-F_1 + 2 and thrombin-antithrombin-complexes were measured. Numbers and cellular origin of MP were determined by flowcytometry. The phospholipid composition of MP was determined by hpTLC. In vitro procoagulant activity of MP was studied by fibrin generation.

Results

During the meal visit, plasma glucose, triglyceride and insulin levels increased, compared to baseline and the fasting visit (all P < 0.05). Postprandially, the total numbers of MP increased in time compared to the fasting visit (P < 0.05). Erythrocyte-derived MP increased (6-fold) during the meal visit, but remained constant on the fasting day (P < 0.001). On the meal versus fasting day circulating MP contained increased phosphatidylcholine (P < 0.05) and decreased sphingomyelin (P < 0.05) amounts. The amount of phosphatidylserine did not change. Concentrations of plasma F_1 + 2 and thrombin-antithrombin were similar on both days, as was the ability of MP to generate fibrin in vitro.

Conclusion

Although numbers, cellular origin and phospholipid composition of MP alter during exposure to two consecutive meals in healthy subjects, this does not lead to changes in the coagulation activation in vivo.     

Circulating platelet-derived microparticles and endothelium-derived microparticles may be a potential cause of microthrombosis in patients with osteonecrosis of the femoral head

Introduction

To test the hypothesis that the platelet microparticle (PMP) and endothelial microparticle (EMP) may contribute to the hypercoagulability associated with microvascular thrombosis in patients with nontraumatc osteonecrosis of the femoral head (ONFH).

Materials and methods

The study comprised 46 patients who had been diagnosed with ONFH and 20 control subjects. The plasma was ultracentrifuged, and then PMPs and EMPs were examined by the flow cytometry. The thrombotic and fibrinolytic disorders were investigated.

Results

The numbers of PMPs expressing P-selectin and CD42a and EMPs expressing E-selectin and CD31 in the ONFH patients were significantly higher than those in the controls (P < 0.001). The number of MPs was correlated with the level of the serum C-reactive protein (CRP) (r = 0.661, P < 0.001), but there was a poor correlation between the MPs counts and the risk factors for ONFH (P > 0.05). The mean levels PAI-1, F1 + 2, and TAT were higher in the patients with ONFH than in the controls (P < 0.05).

Conclusions

The elevated numbers of PMPs and EMPs may contribute to hypercoagulability in the ONFH patients. This may provide important pathophysiological insights into the hypercoagulability associated with nontraumatic ONFH and have implications for pharmacological prevention and treatment of ONFH.     

Comparison of a direct Factor Xa inhibitor, edoxaban, with dalteparin and ximelagatran: A randomised controlled trial in healthy elderly adults

Introduction

Edoxaban (the free base of DU-176b) is a new, oral direct Factor Xa inhibitor. This is the first study to compare the hemostatic response to edoxaban, ximelagatran, and dalteparin in healthy, elderly adults.

Materials and Methods

In this open-label, active-controlled clinical trial, 40 adults (65-75 years), were randomised to: oral edoxaban (60 mg, twice-daily, 7 doses), subcutaneous dalteparin (5000 IU, once-daily, 4 doses), oral ximelagatran (24 mg, twice-daily, 7 doses) or no drug. Blood samples were taken before, and 1.5, 4, 12, 24, 72, 84, 96, 108, 120, and 144 hours after, the first dose. The primary outcomes were changes in thrombin-antithrombin complex, prothrombin fragment 1 + 2 and D-dimer, and adverse events. Additional biomarkers of coagulation, and endothelial cell and platelet activation were compared (ANOVA).

Results

All subjects completed the study. Inhibition of thrombin generation lag time, peak, and constant velocity index were significantly greater, and extended for a longer period of time, following edoxaban administration, compared with dalteparin. We found that the traditional assay for anti-FXa activity was not appropriate for the new anticoagulants. Biomarker changes following edoxaban administration (including prolongation of prothrombin time) reflected inhibition of Factor Xa; there was no effect on platelet, tissue factor or endothelial activation. There were no clinically significant changes in primary outcomes. No serious adverse events were reported.

Conclusion

Oral administration of edoxaban resulted in effective Factor Xa and TG inhibition, and was well-tolerated. Studies are needed to confirm edoxaban (60 mg daily) use in clinical practice.

Sponsorship

Daiichi Sankyo Pharma Development.     

Coagulation activation and ultrasound characteristics in patients with carotid artery disease

Introduction

Elevated levels of markers for thrombin activation are associated with plaque echogenicity and degree of stenosis in patients with carotid artery stenosis. The Activated Protein C-Protein C Inhibitor (APC-PCI) complex reflects activation of the Protein C system and is a measure of thrombin generation. The aim of the present study was to examine APC-PCI complex in patients undergoing thrombendartherectomy for carotid artery stenosis, and to relate the findings to clinical characteristics and plaque morphology as determined by ultrasound.

Materials and Methods

Blood was obtained from 125 patients (39 female, median age 71 years) with carotid artery stenosis admitted from September 2005 to May 2007. The APC-PCI complex was measured using a sandwich immunofluorometric method and compared to an age- and sex-matched healthy control-group. Clinical and demographic characteristics, routine laboratory markers and ultrasound characteristics were analysed using univariate and multivariate analysis.

Results

APC-PCI complex concentration was significantly increased in patients with carotid artery stenosis (median 0.21 µg/L; 10th to 90th percentile 0.15-0.36) compared to a healthy control-group (0.19 µg/L; 0.11-0.31; P = .009). There was no significant difference in APC-PCI-values between asymptomatic (n = 48) and symptomatic (n = 77) patients with carotid artery stenosis (0.22 vs. 0.20 µg/L; p = 0.626). Patients with minor stroke (n = 31) had a higher median APC-PCI-concentration (0.27 µg/L; 0.15-0.63) than patients with amaurosis fugax (0.19 µg/L; 0.15-0.36) or transient ischemic attack (0.21 µg/L; 0.12-0.36) (p = 0.016). No association was found between APC-PCI-values and the degrees of carotid artery stenosis or the time from the latest neurological symptoms to blood sampling. Patients with echolucent plaques had significantly lower APC-PCI concentrations (0.20 µg/L; 0.14-0.35 vs. 0.24 µg/L; 0.15-0.60; p = 0.043), according to the Gray-Weale classification.

Conclusions

Patients with carotid artery disease exhibit increased concentrations of APC-PCI compared to a healthy control-group, particularly those patients with echogenic plaques, who have significantly higher APC-PCI levels than patients with echolucent plaques.     

Inflammatory and thrombotic markers in patients with ST-elevation myocardial infarction treated with thrombolysis and early PCI: A NORDISTEMI substudy

Introduction

Both pharmacological and invasive treatment might influence the inflammatory and pro-thrombotic responses observed in acute ST-elevation myocardial infarction (STEMI). We aimed to study whether circulating levels of inflammatory and pro-thrombotic markers differ in STEMI patients treated with early angioplasty compared to standard therapy following thrombolysis. Furthermore, we wanted to study if levels of markers were related to infarct size.

Materials and Methods

This was a substudy of the NORwegian study on DIstrict treatment of ST-Elevation Myocardial Infarction (NORDISTEMI), in which STEMI patients treated with thrombolysis were randomized to early invasive or standard therapy. Fasting blood samples were collected in the morning 3 days and 3 months after onset of STEMI. Commercially available ELISA methods were used for determination of inflammatory and pro-thrombotic markers. Infarct size was assessed by SPECT after 3 months.

Results

246 patients were included in this substudy. At 3 days, levels of prothrombin fragment 1 + 2 and D-dimer were higher in the early invasive compared to the standard treatment group, whereas levels of soluble CD40 ligand were lower (p < 0.01 for all). No other differences between groups were found in any of the measured markers. Significant, although weak correlations were found between Day 3 levels of C-reactive protein, interleukin-6, prothrombin fragment 1 + 2 and D-dimer, and infarct size assessed by SPECT after 3 months.

Conclusions

An early invasive strategy following thrombolysis for STEMI was associated with higher subacute levels of D-dimer and prothrombin fragment 1 + 2, and lower levels of soluble CD40 ligand than standard treatment. Further studies are needed to establish the relation between these changes and clinical outcome.The NORDISTEMI was registered at www.clinicaltrials.gov, NCT00161005.     

Women with unexplained recurrent pregnancy loss do not have evidence of an underlying prothrombotic state: Experience with calibrated automated thrombography and rotational thromboelastometry

Introduction

Where unexplained recurrent pregnancy loss (RPL) is attributed to an underlying maternal prothrombotic state, empirical prophylactic anticoagulation may be recommended.

Materials and Methods

In the present study we used calibrated automated thrombography and rotational thromboelastometry to determine the procoagulant potential of these women as a rationale for anticoagulation. Fifty women with ≥ three consecutive unexplained losses prior to 14 weeks’ gestation or one loss after this time were compared with forty-one parous women with no miscarriages. Exclusion criteria included antiphospholipid syndrome, inherited thrombophilia and prior venous thromboembolism. Thrombin generation in platelet poor plasma and whole blood thromboelastometry was performed outside pregnancy to determine the presence or not of an underlying prothrombotic state.

Results

Peak thrombin and endogenous thrombin potential were not significantly increased in subjects relative to controls. The use of low tissue factor (1 pM) to better reflect physiological conditions and assay modification to better assess the protein C pathway (5 pM in the presence of thrombomodulin) provided no additional discrimination. Consistent results were shown with thromboelastometry; mean parameters were equivalent between subjects and controls.

Conclusions

These data demonstrate that global coagulation assays provide no evidence of an underlying hypercoagulable state in women with unexplained RPL; this is in keeping with the results of recent randomised controlled trials and strengthens the evidence base against use of anticoagulants in this setting.