The role of hyperglycaemia-induced alterations of antithrombin III and factor X activation in the thrombin hyperactivity of diabetes mellitus

Factor X concentration and factor X activation, antithrombin III anti-Xa activity and plasma concentration, and fibrinopeptide A were measured in 20 diabetic patients and 20 normal subjects. Although factor X activation (81.3 ± 2.2 vs 97.3 ± 2.1 %, p < 0.01; mean ± SE) and antithrombin III activity (76.5 ± 2.2 vs 96.3 ± 1.8 %, p < 0.01) were reduced in the diabetic patients, fibrinopeptide A concentration was increased (3.7 ± 0.4 vs 1.7 ± 0.2 ng ml−1, p < 0.01). The ratio of factor X activation to antithrombin III anti-factor Xa activity was increased in the diabetic patients (1.10 ± 0.01 vs 1.01 ± 0.02, p < 0.01). Induced hyperglycaemia was able to mimic all these abnormalities, without changing factor X or antithrombin III concentration. The results suggest that in vivo hyperglycaemia produces a decrease of factor X activation, but at the same time increases fibrinopeptide A formation due to a greater decrease of antithrombin III anti-Xa activity.