Physical stress as a model to study variations in ADAMTS-13 activity, von Willebrand factor level and platelet activation

Effect of exercise on the plasma vesicular proteome: a methodological study comparing acoustic trapping and centrifugation

Extracellular vesicles (EVs) are a heterogeneous group of actively released vesicles originating from a wide range of cell types. Characterization of these EVs and their proteomes in the human plasma provides a novel approach in clinical diagnostics, as they reflect physiological and pathological states. However, EV isolation is technically challenging with the current methods having several disadvantages, requiring large sample volumes, and resulting in loss of sample and EV integrity. Here, we use an alternative, non-contact method based on a microscale acoustic standing wave technology. Improved coupling of the acoustic resonator increased the EV recovery from 30% in earlier reports to 80%, also displaying long term stability between experiment days. We report a pilot study, with 20 subjects who underwent physical exercise. Plasma samples were obtained before and 1 h after the workout. Acoustic trapping was compared to a standard high-speed centrifugation protocol, and the method was validated by flow cytometry (FCM). To monitor the device stability, the pooled frozen plasma from volunteers was used as an internal control. A key finding from the FCM analysis was a decrease in CD62E+ (E-selectin) EVs 1 h after exercise that was consistent for both methods. Furthermore, we report the first data that analyse differential EV protein expression before and after physical exercise. Olink-based proteomic analysis showed 54 significantly changed proteins in the EV fraction in response to physical exercise, whereas the EV-free plasma proteome only displayed four differentially regulated proteins, thus underlining an important role of these vesicles in cellular communication, and their potential as plasma derived biomarkers. We conclude that acoustic trapping offers a fast and efficient method comparable with high-speed centrifugation protocols. Further, it has the advantage of using smaller sample volumes (12.5 μL) and rapid contact-free separation with higher yield, and can thus pave the way for future clinical EV-based diagnostics.

Effect of ABO blood group on haemostatic parameters in severe haemophilia A patients performing acute moderate-intensity exercise

: The primary objective was to assess the effect of ABO blood group on von Willebrand factor (VWF) rise induced by four bouts of moderate-intensity physical activity, on pharmacokinetics of a B-domain-deleted recombinant FVIII (BDD-rFVIII), and haemostatic parameters in severe haemophilia A patients with a null mutation. The secondary objective was to compare the response to exercise according to infused product type in a subgroup of patients who previously participated to the same exercise protocol, while treated with a full length recombinant FVIII (FL-rFVIII). Twenty patients had two visits (rest and exercise). Blood samples were drawn before administration of BDD-rFVIII and at 6 time points, until 24 h postinfusion. FVIII activity increased transiently by 1.1-fold, but only after the first exercise session, as compared to rest. VWF:Ag and platelet count were significantly elevated after each session. Mean FVIII half-life and thromboelastography measurements were unchanged with exercise. However, 14 participants had a slight variation of FVIII half-life with exercise compared to rest (from -3.42 h to +2.51 h). Seven patients demonstrated a longer FVIII half-life (four with O blood group), whereas the remainders had a reduced half-life (three with O blood group). FVIII half-life correlated with baseline VWF:Ag at rest (r = 0.70, P < 0.001) and with exercise (r = 0.67, P < 0.002). Recovery was different between FL-rFVIII and BDD-rFVIII at rest (P = 0.032), but no significant differences were observed between half-life of products at rest and with exercise. ABO blood group and the type of rFVIII administered did not influence the response to exercise.

Glucose fluctuation and the resultant endothelial injury are correlated with pancreatic β cell dysfunction in patients with coronary artery disease

AIMS

We evaluated whether glucose fluctuation (GF) causes vascular endothelial injury and affects glucometabolic factors during lengthy oral glucose tolerance test (OGTT).

METHODS

We enrolled consecutive 116 patients with coronary artery disease (CAD) who were performed coronary angiography and 4-h OGTT. Blood samples were collected before and 4h after glucose load to measure endothelial injury factor [von Willebrand factor (vWF) and vWF/a disintegrin-like and metalloproteinase with thrombospondin type-1 motifs 13 (ADAMTS-13) ratio]. GF was defined as maximum - minimum blood glucose levels during 4-h OGTT. We estimated the relationship between GF and glucometabolic factors.

RESULTS

vWV and vWF/ADAMTS-13 ratio were significantly correlated with GF during 4-h OGTT. GF was significantly correlated with homeostasis model to assess insulin resistance (HOMA-IR) (R=0.262), Matsuda index (R=-0.405), insulinogenic index (R=-0.336), HbA1c (R=0.281) and disposition index (R=-0.672). When dividing patients into impaired and preserved category groups according to the average value of GF (122mg/dL), adjusted to age, sex, HOMA-β, insulinogenic index, HOMA-IR, Matsuda index and HbA1c, disposition index was an independent risk factor for impaired GF [odds ratio (95% confidence interval): 2.87 (1.70-4.83), P<0.001].

CONCLUSION

Pancreatic β cell dysfunction is associated with GF and causes endothelial injury in CAD patients.

Preserved Expression of mRNA Coding von Willebrand Factor-Cleaving Protease ADAMTS13 by Selenite and Activated Protein C

In sepsis, the severity-dependent decrease of von Willebrand factor (VWF)-inactivating protease, a disintegrin and metalloproteinase with thrombospondin motifs 13 (ADAMTS13), results in platelet aggregation and consumption, leading to sepsis-associated thrombotic microangiopathy (TMA) and organ failure. Previous reports assessing its functional deficiency have pinpointed involvement of autoantibodies or mutations to propagate thrombotic thrombocytopenic purpura (TTP). However, mechanisms of acquired ADAMTS13 deficiency during host response remain unclear. To enhance understanding of ADAMTS13 deficiency in sepsis, we evaluated changes in expression of mRNA coding ADAMTS13 during septic conditions using primary cellular sources of the protease. We hypothesized that proinflammatory cytokines and constituents of serum from septic patients affect the transcriptional level of ADAMTS13 in vitro, and previously recommended therapeutic agents as adjunctive therapy for sepsis interact therewith. Cultured hepatic stellate cells (HSCs), endothelial cells (HMEC) and human precision-cut liver slices as an ex vivo model were stimulated with sepsis prototypic cytokines, bacterial endotoxin and pooled serum obtained from septic patients. Stimulation resulted in a significant decrease in ADAMTS13 mRNA between 10% and 80% of basal transcriptional rates. Costimulation of selenite or recombinant activated protein C (APC) with serum prevented ADAMTS13 decrease in HSCs and increased ADAMTS13 transcripts in HMEC. In archived clinical samples, the activity of ADAMTS13 in septic patients treated with APC (n = 5) increased with an accompanying decrease in VWF propeptide as surrogate for improved endothelial function. In conclusion, proinflammatory conditions of sepsis repress mRNA coding ADAMTS13 and the ameliorating effect by selenite and APC may support the concept for identification of beneficial mechanisms triggered by these drugs at a molecular level.

Performance related factors are the main determinants of the von Willebrand factor response to exhaustive physical exercise

Background

Physical stress triggers the endothelium to release von Willebrand Factor (VWF) from the Weibel Palade bodies. Since VWF is a risk factor for arterial thrombosis, it is of great interest to discover determinants of VWF response to physical stress. We aimed to determine the main mediators of the VWF increase by exhaustive physical exercise.

Methods

105 healthy individuals (18–35 years) were included in this study. Each participant performed an incremental exhaustive exercise test on a cycle ergometer. Respiratory gas exchange measurements were obtained while cardiac function was continuously monitored. Blood was collected at baseline and directly after exhaustion. VWF antigen (VWF:Ag) levels, VWF collagen binding (VWF:CB) levels, ADAMTS13 activity and common variations in Syntaxin Binding Protein-5 (STXBP5, rs1039084 and rs9399599), Syntaxin-2 (STX2, rs7978987) and VWF (promoter, rs7965413) were determined.

Results

The median VWF:Ag level at baseline was 0.94 IU/mL [IQR 0.8–1.1] and increased with 47% [IQR 25–73] after exhaustive exercise to a median maximum VWF:Ag of 1.38 IU/mL [IQR 1.1–1.8] (p<0.0001). VWF:CB levels and ADAMTS13 activity both also increased after exhaustive exercise (median increase 43% and 12%, both p<0.0001). The strongest determinants of the VWF:Ag level increase are performance related (p<0.0001). We observed a gender difference in VWF:Ag response to exercise (females 1.2 IU/mL; males 1.7 IU/mL, p = 0.001), which was associated by a difference in performance. Genetic variations in STXBP5, STX2 and the VWF promoter were not associated with VWF:Ag levels at baseline nor with the VWF:Ag increase.

Conclusions

VWF:Ag levels strongly increase upon exhaustive exercise and this increase is strongly determined by physical fitness level and the intensity of the exercise, while there is no clear effect of genetic variation in STXBP5, STX2 and the VWF promoter.

Quantification of perioperative changes in von Willebrand factor and factor VIII during elective orthopaedic surgery in normal individuals

von Willebrand's disease (VWD) patients undergoing major surgery are prophylactically treated to promote haemostasis. There is variability in perioperative clinical practice; however, most guidelines suggest replacing the deficient factor to a level of 1.0 IU mL(-1) (or 100%). A review of the literature reveals a paucity of well constructed descriptive data quantifying the changes in coagulation that occur in response to surgical stress. The aim of this study was to quantify the changes in haemostatic variables occurring in response to elective orthopaedic surgery in normal individuals. Eligible subjects >18 years of age undergoing total hip or knee replacement were recruited. Blood samples were drawn at five time points: baseline, preoperatively, 30 min after surgical incision, 30 min postoperatively, postoperative day (POD) 1. Analyses included t-tests and repeated measures anova. Overall 30 patients, 21 women and 9 men, with a mean age of 65 were included in the final analysis. All von Willebrand factor (VWF) variables were seen to significantly decrease intraoperatively and increase postoperatively. VWF multimers showed a statistically significant decrease in high molecular weight multimers intraoperatively and an increase postoperatively. On subgroup analysis, age, gender and anaesthesia type were significantly correlated with changes in VWF parameters. Data presented in the current study establish a physiological baseline for VWF parameters in the normal population and demonstrate mean VWF/factor VIII levels greater than 1.0 IU mL(-1) intraoperatively. As such, current management in VWD patients does not appear to mimic the normal physiological response to surgery.

Exercise-induced shear stress is associated with changes in plasma von Willebrand factor in older humans

Shear stress is the frictional force of blood against the endothelium, a stimulus for endothelial activation and the release of von Willebrand factor (vWF). This study tested the hypothesis that the increase in shear stress associated with exercise correlates with plasma vWF. Young (n = 14, 25.7 +/- 5.4 years) and older (n = 13, 65.6 +/- 10.7 years) individuals participated in 30 min of dynamic handgrip exercise at a moderate intensity. Brachial artery diameter and blood flow were measured using ultrasound Doppler and blood samples were collected before, immediately after, and following 30 min of recovery from exercise with plasma levels of vWF. Plasma levels of vWF increased (P < 0.05) by 6 +/- 2% in young individuals and 4 +/- 1% in older individuals immediately after exercise. The change in plasma vWF was linearly correlated with the increase in shear stress during exercise in older individuals (post-exercise: r = 0.78, 30 min recovery: r = 0.77, P < 0.01), but no association was found in the young individuals. These changes in plasma levels of vWF in humans suggest that aging influences endothelial activation and hemostasis.

The effect of exercise on von Willebrand factor and ADAMTS-13 in individuals with type 1 and type 2B von Willebrand disease

BACKGROUND

The effect of exercise on von Willebrand factor (VWF) and ADAMTS-13 levels in individuals with von Willebrand disease (VWD) has never been reported.

OBJECTIVES

The aim was to quantify the effect of a standardized exercise protocol on individuals with type 1 and type 2B VWD.

PATIENTS/METHODS

Thirty individuals from three groups (10 controls, 11 with type 1 VWD and 9 with type 2B VWD) completed the Standard Bruce Protocol Treadmill Test. A bleeding questionnaire was administered and blood tests were performed pre- and immediately postexercise. The groups were well matched for age, gender and body mass index (BMI).

RESULTS

There was a correlation in all groups between the metabolic equivalents (METS) achieved and the degree of change of VWF and FVIII:C levels (P < 0.002, Pearson's correlation). There was a significant postexercise increase in VWF:Ag, VWF:RCo, FVIII:C and activated VWF levels in both the control group and in the type 2B VWD group, but not in the type 1 VWD group. Specific to the type 2B VWD group was an increase in the percentage of high molecular weight multimers (P = 0.022), a decrease in the mean platelet count compared with the other groups (P < 0.001) and an increase in the ADAMTS-13 level (P = 0.001).

CONCLUSIONS

There are significant differences in the effects of exercise on individuals with type 1 and type 2B VWD compared with controls. Further clinical studies are necessary to evaluate exercise as a therapeutic option in VWD.