Comparative study of platelet activation markers in diabetes mellitus patients complicated by cerebrovascular disease

An investigation into the pleiotropic activity of metformin. A glimpse of haemostasis

The most characteristic features of type 2 diabetes mellitus (T2DM) are hyperglycaemia and insulin resistance, however, patients with T2DM are at higher risk of cardiovascular disease (CVD) and atherosclerosis. Diabetes, frequently related to metabolic and vascular impairments, is also associated with thrombosis, increased blood coagulation and an imbalance between coagulation and fibrinolysis. Metformin is the most often used oral glucose-lowering agent; its beneficial properties include lowering insulin resistance, weight reduction and cardioprotection. Available data suggest that the advantageous properties of metformin stem from its favourable effects on endothelium, and anti-oxidative and anti-inflammatory properties. This paper reviews the favourable impact of metformin on endothelial function, with particular emphasis on the release of endogenous molecules modulating the state of the vascular endothelium and coagulation. It also summarizes the present knowledge on the influence of metformin on platelet activity and plasma haemostasis, including clot formation, stabilization and fibrinolysis. Its findings confirm that metformin should constitute first line therapy of T2DM subjects; however, more comprehensive methodical studies are required to discover the full potential of this drug.

Receptor GP IIb/IIIa as an Indicator of Risk in Vascular Events

Type 2 diabetes causes a significant risk of cardiovascular diseases, leading to 70% of deaths in patients with diabetes. The effective treatment of diabetes significantly reduces the risk of requiring the involvement of specialists from various fields of medicine. This research aimed to assess the risk of cardiovascular events based on selected biochemical parameters (glycoprotein [GP] IIb/IIIa, von Willebrand factor [vWf], fibrinogen) and their changes in response to physical exercise. The research group consisted of 52 patients with type 2 diabetes with micro- or macro-angiopathy at a mean age of 63.80 years (8.79). The control group consisted of 50 healthy volunteers (17 women and 33 men) at a mean age of 51.16 years (6.39). All the patients consented to have their venous blood tested to measure complete blood counts. Activated GP IIb/IIIa receptors were labeled and analyzed by flow cytometry. Mean values of vWF factor were higher when compared with the control group (196.59% [80.32%] vs 148.06% [90.34%], respectively). The GP IIb/IIIa receptor expression was much higher in test patients than in the control group (3.91% [2.91%] vs 2.79% [2.51%]). Physical exercise had a positive influence on GP IIb/IIIa receptor expression and vWF, decreasing their baseline percentage values.

Determination of thromboxane formation, soluble CD40L release and thrombopoietin clearance in apheresis platelet concentrates

All deleterious changes in platelet morphology, structure and function that occur in platelet concentrates (PC) during storage are titled as the 'platelet storage lesion'. No single in vitro test currently available is sufficient in assessing these changes of platelet quality. The release of soluble CD40 Ligand (sCD40L), the formation of thromboxane (TXB2) and the thrombopoietin (TPO) clearance reflect different aspects of platelet metabolism and activitiy, and were used to examine platelet quality in apheresis platelet products. At days 1, 3 and 5, in single-donor apheresis platelet products (n = 10) under routine storage conditions, sCD40L (measured by ELISA) and TXB2 (measured by RIA) were determined after platelet stimulation (recalcification and clot formation). TPO (measured by ELISA) was determined after an incubation time of 5 h at 37°C with platelet-rich plasma (adjusted initial TPO concentration of about 500 pg/mL). Results were related to a therapeutic unit (TU = 2 × 10(11) platelets). Immediately after platelet preparation, sCD40L release was 41 ± 7.6 ng/TU, TXB2 formation 1688 ± 374 ng/TU and TPO clearance 1.22 ± 0.32 ng/h/TU. At days 1, 3 and 5, sCD40L was reduced to 89 ± 7%, 71 ± 12% and 57 ± 9%, TXB2 release to 91 ± 6%, 74 ± 12% and 58 ± 9% and TPO clearance to 90 ± 15%, 84 ± 5% and 79 ± 10% of the respective control values. In conclusion, in single-donor apheresis PC, sCD40L release and TXB2 formation as well as TPO clearance by the platelets were dependent on storage duration and reduced to about 60% to 80% of the respective control values after a storage period for 5 days. These findings are in line with literature data, indicating that a loss of platelet functionality of about 30% will occur after 5 days of storage.

Platelet function abnormalities in qualified whole-blood donors: effects of medication and recent food intake

BACKGROUND AND OBJECTIVES

Platelet function abnormalities have been reported in blood donors who have not consumed aspirin. Our objective was to identify factors other than aspirin that may contribute to impaired platelet function in qualified volunteer blood donors.

MATERIALS AND METHODS

Blood samples were obtained from 24 donors following routine blood donation. Donors completed a study questionnaire that included questions about recent food consumption, medication and medical history. Platelet activation was measured using monoclonal antibodies and flow cytometry. CD62P expression and PAC-1 binding on platelets were used as indicators of platelet activation. Platelet function was measured on a platelet function analyser (PFA-100) using both collagen/epinephrine (cEPI) and collagen/ADP (cADP) cartridges.

RESULTS

Fifty-four per cent of donors (13 of 24) had normal platelet function. Thirty-eight per cent (nine of 24) had prolonged cEPI closure times, of whom four (17%) had no cEPI closure (> 300 seconds). No closure was associated with aspirin use (two donors) or chocolate consumption (two donors) before donation. Two donors (8%) had either a shortened cEPI or cADP closure time.

CONCLUSIONS

Platelet dysfunction in qualified blood donors is underestimated. Platelet function screening can identify donors with diet-related platelet dysfunction or with poor recollection of aspirin use.

Helicobacter pylori seropositivity is associated with enhanced platelet activation in patients with intermittent claudication

OBJECTIVE

Patients with intermittent claudication have a significantly increased risk of mortality from cardiovascular and cerebrovascular causes. Helicobacter pylori infection and abnormal platelet function have been shown to be associated with atherosclerosis as well as with acute ischemic events. The aim of this study was to assess for the first time the relation between H pylori serology status, platelet activation, and endothelial injury in patients with intermittent claudication. Design of study : A prospective observational study of 125 patients with intermittent claudication suitable for angioplasty was conducted at the Vascular Unit of the Aberdeen Royal Infirmary. Main outcome measures Main outcome measures were (1) H pylori serology using ELISA kit for immunoglobulin G antibody to H pylori and (2) whole blood flow cytometric analysis of resting platelet P-selectin expression and fibrinogen binding as measures of platelet activation. Results are presented as platelet percentage. von Wildebrand factor levels were measured using ELISA as a marker of endothelial injury. Carstair deprivation scores were calculated for all patients.

RESULTS

H pylori serology was positive in 62 patients (49.6%), negative in 56 (44.8%) and equivocal in 7 (5.6%). Median P-selectin expression was significantly increased in H pylori-positive patients compared with seronegative patients (0.815 vs 0.65; P =.039). Median platelet fibrinogen binding was higher in seropositive patients, but this failed to reach statistical significance (2.135 vs 1.85%; P =.11). There was no difference in von Wildebrand factor levels between the two groups (P =.51). There was no difference in socioeconomic status between the two groups.

CONCLUSION

Patients with intermittent claudication who are H pylori positive show enhanced platelet activation that does not appear to be mediated by means of endothelial cell injury.

Improved metabolic control decreases platelet activation markers in patients with type-2 diabetes

BACKGROUND

Cardiovascular disease is associated with platelet dysfunction in patients with diabetes. Hyperglycaemia is known as an independent risk factor for micro- and macrovascular complications, and improvement of metabolic control has shown beneficial effects on diabetic late complications. Our study attempts to clarify the effect of improved metabolic control on platelet activation markers in patients with type-2 diabetes.

MATERIALS AND METHODS

Thirty patients were studied at baseline and 3 months after improvement of metabolic control and compared with an age-matched nondiabetic control group. Platelet activation markers (CD31, CD36, CD49b, CD62P and CD63) were assessed by flow cytometry analysis.

RESULTS

Significantly more activated platelets were detected in patients with diabetes compared with controls. After 3 months' improvement of metabolic control, a significant decline of all platelet activation markers except CD36 was noted. Furthermore a significant correlation between CD62P, CD63 and HbA(1c) levels was observed.

CONCLUSIONS

We conclude therefore that improvement of metabolic control has a beneficial effect on platelet activation. This may have an implication in the pathogenesis of vascular disease in patients with type-2 diabetes.

Mechanisms involved in platelet hyperactivation and platelet-endothelium interrelationships in diabetes mellitus

This article discusses the recent findings about the mechanisms involved in platelet hyperactivation in diabetes mellitus. Particular attention is focused on the advances pertaining to 1) new features of platelet activation; 2) the role of calcium fluxes; 3) the role of glucose, insulin, and insulin resistance; 4) the role of nitric oxide; and 5) the role of endothelium.