Do determinants of platelet function co-segregate with genetic markers of type 1 diabetes mellitus?

This study examined the significance of selected parameters of primary haemostasis to discriminate between relatives of children with insulin-dependent diabetes mellitus (IDDM). Platelet function, including markers of spontaneous and agonist-induced platelet activation (CD62), platelet consumption (microparticles) and clumping (aggregates), as well as selected parameters of the fibrinolytic system (t-PA and PAI-1), were studied in IDDM children ( n = 45), their parents ( n = 65), siblings ( n = 17) and unrelated healthy controls ( n = 51). The fraction of activated platelets circulating in whole blood amounted to 4.3 +/- 2.1% in IDDM children, and significantly exceeded the level found in parents (1.3 +/- 0.7%, P < 0.002), siblings (1.2 +/- 1.0%, P < 0.002), and controls (1.2 +/- 0.6%, P < 0.002). Furthermore, an enhanced formation of platelet microparticles was observed in the IDDM group, both in resting platelets and also when platelets were stimulated with thrombin. Significantly decreased total PAI-1 occurred in IDDM children ( P < 0.02 versus parents); also slightly lowered active PAI-1 and t-PA antigen were noticed in IDDM subjects compared to other groups, however, the differences were not statistically significant. To assess dissimilarities between the groups of subjects we applied the forward stepwise model of discriminant function analysis, which included platelet flow cytometry parameters. The best separation and the highest discrepancy (expressed as the so called squared Mahalanobis distances, d ) was M revealed between controls and IDDM patients ( P < < 0.0001) and between controls and parents ( P < < 0.0001). The values of d found between IDDM children and their siblings (P < 0.001), as well as parents ( P < 0.01), were M of much lower significance. The finding that the control group, representing unrelated subjects, remains particularly well separated from the other groups, more or less clustered together, implies the possible involvement of genetic factor(s) which might potentially affect platelet activation and reactivity. In addition, the distinguished distribution of HLA DQAI(52) and HLA DQBI(57) genotypes in the groups further validates the suspicion that the altered platelet function and response in diabetes might be associated with some independent genetic factor(s), and is not likely to result from HLA DQAI(52) and HLA DQBI(57) impact.