Platelet activation in diabetic microangiopathy.

Platelet activation and hyperreactivity are known to be associated with a rapid development and progression of diabetic angiopathy. The present study attempts to clarify whether IDDM patients without diabetic complications have an increased platelet activation and whether in vivo platelet activation is altered in the presence of diabetic microangiopathy. Platelet activation was assessed by flow cytometry analysis in 50 healthy controls (c) and in 41 patients with insulin-dependent diabetes mellitus (IDDM type 1) who were screened for diabetic complications. Sixteen of these patients (0) showed no evidence of microangiopathic organ lesions as assessed by an established standard battery of clinical tests, whereas the other 25 patients had diabetes derived microvascular complications (dmc). Patients with macroangiopathy were ruled out. Platelet activation was evaluated by flow cytometric detection of four activation-dependent platelet surface markers (lysosomal GP53, thrombospondin, P-selectin and ligand-induced binding site-1 of GPIIb-IIIa). A higher percentage of thrombospondin-positive platelets was detected in the IDDM patients without complications: 8.6 +/- 0.9% (0) vs 6.1 +/- 0.4% (c) vs 5.4 +/- 0.4% (dmc), P < 0.05, respectively. A decrease in GP53-, P-selectin-, and LIBS-1-positive platelets was observed in the IDDM group with dmc: for GP53 17.4 +/- 1.0% (dmc) vs 23.4 +/- 1.0% (c), P < 0.05; for P-selectin 5.5 +/- 0.6% (dmc) vs 8.0+/-0.7% (c), P < 0.01 and for LIBS-1 8.3 +/- 0.9% (dmc) vs 15.8 +/- 1.3% (c), P < 0.01. No differences in these markers were found in controls and IDDM patients without complications. In addition, no correlations were found between the glucose metabolism and platelet activation. These findings indicate (i) that the platelet system is pre-activated in IDDM , and (ii) that an increased consumption of activated platelet may occur in the vessels of IDDM patients with diabetic microangiopathy.