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 Eselectin, 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. [Diabetologia (2004) 47:537-540]

Summary. Background: Platelets and leukocytes may in¯u-ence 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¯ow cytometry. Platelet± leukocyte cross-talk was studied in hirudinized whole blood incubated at 37 8C with stirring. Results: Basal single platelet P-selectin and leukocyte CD11b expression were similar in DM patients and healthy subjects, whilst circulating platelet±leu-kocyte aggregates and plasma elastase levels were elevated in DM patients. The thromboxane A 2 analog U46619 (3 Â 10 À7 M) induced more marked increases of platelet P-selectin expression and platelet±leukocyte aggregation in DM patients than in healthy subjects. The leukocyte-speci®c agonist N-formylmethionyl-leucyl-phenylalanine (fMLP) (10 À7 M) induced more marked CD11b expression in DM patients with microangiopathy, compared with healthy subjects. Platelet±leukocyte cross-talk induced by U46619 (10 À6 M) showed no difference between DM patients and healthy subjects. fMLP (10 À6 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.

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.