Meal-induced platelet activation in Type 2 diabetes mellitus: effects of treatment with repaglinide and glibenclamide.

AIMS: To compare the effects of treatment with repaglinide and glibenclamide on platelet function and endothelial markers in patients with Type 2 diabetes mellitus, before and after a standardized meal. METHODS: Fifteen patients with Type 2 diabetes were investigated on three occasions: at baseline without oral hypoglycaemic drug treatment, and after 6 weeks' treatment with repaglinide or glibenclamide, respectively, in an open randomized cross-over study. Agonist-induced platelet P-selectin expression and platelet aggregation, urinary thromboxane, soluble P-selectin, von Willebrand factor (VWF), soluble E-selectin, intercellular adhesion molecule (ICAM-1) and C-reactive protein (CRP) were measured. In addition, pre-meal data were compared with non-diabetic control subjects (n = 15), matched for sex, age and BMI. RESULTS: Adenosine diphosphate (ADP)-induced platelet P-selectin expression increased post-meal in Type 2 diabetic patients both at baseline and after treatment with repaglinide and glibenclamide (P < 0.01 for all; repeated measures anova). Repaglinide treatment reduced fasting ADP-induced P-selectin expression compared with baseline (P = 0.01), but did not influence meal-induced platelet hyper-reactivity (P = 0.32). No significant anti-platelet effects of glibenclamide treatment were found. Plasma concentrations of VWF and ICAM-1 were elevated in patients with Type 2 diabetes compared with control subjects (P < 0.05 for both) and were reduced during treatment with repaglinide (P < 0.01 for both) but did not change during glibenclamide treatment. CONCLUSIONS: The post-meal state is associated with enhanced platelet reactivity in patients with Type 2 diabetes mellitus. Pre-meal treatment with repaglinide or glibenclamide does not inhibit postprandial platelet activation, but repaglinide treatment is associated with attenuated platelet and endothelial activity in the fasting state.

Enhanced P-selectin expression and increased soluble CD40 Ligand in patients with Type 1 diabetes mellitus and microangiopathy: evidence for platelet hyperactivity and chronic inflammation.

AIMS/HYPOTHESIS: Platelet activation, endothelial dysfunction and inflammation may be involved in early stages of diabetic microangiopathy. We therefore investigated patients with Type 1 diabetes mellitus, without ( n=19) and with ( n=20) microangiopathy, matched for glycaemic control and duration of disease, and matched with healthy control subjects ( n=27). METHODS: Platelet activation was measured as platelet P-selectin expression using whole blood flow cytometry and as soluble P-selectin by immunoassay. Von Willebrand factor antigen in plasma, serum soluble E-selectin, CD40 ligand (sCD40L) and C-reactive protein (CRP) served as markers for endothelial function and inflammation. RESULTS: Thrombin-induced platelet P-selectin expression was enhanced, and soluble P-selectin and sCD40L concentrations were increased in patients with microangiopathy compared with the control subjects ( p<0.01 for both) and with patients without microangiopathy ( p<0.05 for P-selectin expression and sP-selectin), whereas all three parameters were similar in patients without microangiopathy and in the control subjects. CRP and soluble E-selectin were increased in patients with microangiopathy, compared with the control subjects ( p<0.01 and p<0.05), whereas von Willebrand factor did not differ between the groups. CONCLUSIONS/INTERPRETATION: Microangiopathy in Type 1 diabetes is associated with platelet hyperactivity, endothelial dysfunction and low-grade inflammation, indicating an increased risk for cardiovascular disease.

Enhanced leukocyte-platelet cross-talk in Type 1 diabetes mellitus: relationship to microangiopathy.

BACKGROUND: Platelets and leukocytes may influence each others' function, i.e. platelet-leukocyte cross-talk. Diabetes mellitus (DM) is associated with platelet and leukocyte dysfunction. OBJECTIVE: To evaluate platelet-leukocyte cross-talk, and if this might contribute to platelet and leukocyte dysfunction and microangiopathy in DM patients. PATIENTS AND METHODS: We evaluated platelet and leukocyte function, and cross-talk between these cells in Type 1 DM patients without (n = 19) and with (n = 20) microangiopathy, and healthy subjects (n = 27), using whole blood flow cytometry. Platelet-leukocyte cross-talk was studied in hirudinized whole blood incubated at 37 degrees C with stirring. RESULTS: Basal single platelet P-selectin and leukocyte CD11b expression were similar in DM patients and healthy subjects, whilst circulating platelet-leukocyte aggregates and plasma elastase levels were elevated in DM patients. The thromboxane A2 analog U46619 (3 x 10(-7) m) induced more marked increases of platelet P-selectin expression and platelet-leukocyte aggregation in DM patients than in healthy subjects. The leukocyte-specific agonist N-formyl-methionyl-leucyl-phenylalanine (fMLP) (10(-7) m) induced more marked CD11b expression in DM patients with microangiopathy, compared with healthy subjects. Platelet-leukocyte cross-talk induced by U46619 (10(-6) m) showed no difference between DM patients and healthy subjects. fMLP (10(-6) m) evoked marked leukocyte activation, which subsequently caused mild platelet P-selectin expression. This leukocyte-platelet cross-talk was more pronounced in DM patients than in healthy subjects. Furthermore, enhanced leukocyte-platelet cross-talk was correlated to platelet hyperreactivity among DM patients with microangiopathy only. CONCLUSIONS: Type 1 DM is associated with platelet and leukocyte hyperactivity, and enhanced leukocyte-platelet cross-talk, which may contribute to platelet hyperactivity and the microvascular complications seen in Type 1 DM.

Increased plasma fibrin gel porosity in patients with Type I diabetes during continuous subcutaneous insulin infusion.

BACKGROUND: Patients with Type 1 diabetes have a tighter plasma fibrin gel structure, to which impaired glycemic control might contribute. Improved glycemic control can be achieved with continuous subcutaneous insulin infusion (CSII). OBJECTIVES: The aim of the present study was to investigate the effect of CSII on plasma fibrin gel properties and circulating markers of inflammatory activity in patients with Type 1 diabetes. PATIENTS AND METHODS: Twenty-eight patients were investigated before and after 4-6 months' treatment with CSII. Fibrin gel structure formed in vitro from plasma samples was investigated by liquid permeation of hydrated fibrin gel networks. P-fibrinogen was analyzed by a syneresis method. Comparisons were made between patients with improved (> 0.5%) and unchanged (< 0.5%) glucosylated hemoglobin (HbA1c) during CSII. RESULTS: Eighteen patients showed improved and 10 patients unchanged HbA1c during CSII. P-fibrinogen, high sensitive C-reactive protein and serum amyloid A-antigen were not significantly changed, while fibrin gel permeability (Ks) and fiber mass-length ratio ( micro ) increased in both groups (P < 0.02). P-insulin and triglycerides decreased (P < 0.05) in both groups, while reductions of total cholesterol and intercellular adhesion molecule-1 were seen only in patients with improved HbA(1c) (P < 0.05). Absolute changes in Ks were inversely correlated to changes in plasma fibrinogen (r = 0.50; P < 0.01) and in LDL-cholesterol (r = 0.46; P < 0.05). CONCLUSIONS: Treatment with CSII in patients with Type 1 diabetes is associated with increased plasma fibrin gel porosity. Slight attenuation of the inflammatory activity was also observed. The changes in fibrin gel porosity seem to be mainly mediated by changes in plasma fibrinogen and blood lipids, and are probably secondary to improved insulin sensitivity.

Insulin enhances platelet activation in vitro.

Diabetes mellitus is associated with an increased risk of atherothrombotic complications. There is accumulating evidence of platelet hyperreactivity in diabetes, which may be of importance in the pathogenesis of diabetic vascular complications. Platelets possess insulin receptors, but their physiological relevance is not clear, and data on insulin effects on platelet function in the literature are less than consistent. We therefore investigated the influence of insulin on platelet activation in vitro. Fasting blood samples were collected in 20 healthy males, using citrate or hirudin as anticoagulants. Platelet activation was measured as platelet P-selectin expression and fibrinogen binding using whole blood flow cytometry in unstimulated and adenosine diphosphate (ADP) stimulated samples, incubated with 0-10000 microU/ml insulin for 20 min. The effect of insulin (30 or 300 microU/ml, incubated for 3 min) on platelet aggregation was studied using Born aggregometry in platelet-rich plasma (PRP). Insulin enhanced platelet fibrinogen binding more than P-selectin expression in unstimulated and ADP stimulated samples (P<.001 by analysis of variance [ANOVA]; n=20). Insulin (30 or 300 microU/ml) also enhanced ADP-induced platelet aggregation in PRP (P<.01 or P<.001; n=14). The platelet activating effect of insulin was verified in hirudinized samples (n=12), indicating that it was not dependent on unphysiologically low extracellular calcium concentrations. Thus, insulin enhances platelet activation in vitro, independently of extracellular calcium concentrations. Beneficial effects of insulin treatment on platelet function in vivo are probably related to improved metabolic control, rather than to direct platelet stabilizing effects.

Acute hyperglycemia increases soluble P-selectin in male patients with mild diabetes mellitus.

The aim of this study was to examine if acute hyperglycemia (an oral glucose tolerance test) activates platelet function, endothelial cells or thrombin generation in diabetic patients and healthy controls. Eleven males with mild type II diabetes mellitus and 11 healthy male volunteers, matched for age and body mass index, were investigated before and after the glucose load. Soluble P-selectin, von Willebrand factor antigen and markers of thrombin generation in plasma were determined by immunoassays, and platelet P-selectin expression (unstimulated and agonist-stimulated) by flow cytometry in whole blood. Acute hyperglycemia elevated plasma soluble P-selectin from 32.5 to 50.9 ng/ml in the diabetic group (P = 0.05) but not in the controls (from 27.3 to 28.8 ng/ml; P = 0.6). Also, soluble P-selectin levels were higher in patients with diabetes than in healthy controls during hyperglycemia, but not in the fasting state. Adenosine diphosphate- and thrombin-induced platelet P-selectin expression was slightly, but significantly, decreased by the glucose load, whereas platelet P-selectin expression in unstimulated samples was not affected. Plasma levels of von Willebrand factor and thrombin generation were similar in patients and controls, and were not altered by hyperglycemia. In conclusion, we found that acute hyperglycemia elevates soluble P-selectin in plasma in males with mild type II diabetes mellitus. Our observation of unaltered plasma levels of the endothelial marker von Willebrand factor is in agreement with platelets being the main source of P-selectin released into plasma following hyperglycemia. Thus, platelets in individuals with type II diabetes may be more susceptible to hyperglycemia than platelets in non-diabetic individuals.