The effects of hyperglycaemia on thrombin-activatable fibrinolysis inhibitor

Epidemiological studies have shown a strong association between type 2 diabetes mellitus and cardiovascular diseases, and hypofibrinolysis may contribute to this phenomenon. The aim of this study was to determine the effect of hyperglycaemia on thrombin-activatable fibrinolysis inhibitor (TAR). Hyperglycaemia was mimicked in vitro by incubation of TAFI with glyceraldehyde and in vivo by hyperglycaemic clamping of healthy volunteers. The effects of long-term hyperglycaemia in vivo on TAR were investigated by comparing TAFI from poorly regulated and tightly regulated patients with type 2 diabetes. In vitro glycated TAR showed an altered migration pattern on SDS-PAGE due to aggregation. Glycated TAFI showed decreased activity after activation by thrombin-thrombomodulin in a glyceraldehyde-dose-dependent manner and a reduced anti-fibrinolytic potential. In vivo, no differences in TAR parameters were found after hyperglycaemic clamping of healthy volunteers and between tightly and poorly regulated patients with type 2 diabetes. Moreover, TAR purified from poorly regulated and tightly regulated patients with type 2 diabetes migrated similarly on SDS-PAGE, indicating little or no glycation of the protein. Despite the deleterious effects of glycation of TAR in vitro on its function,TAFI was neither affected by hyperglycaemic clamping, nor by long-term hyperglycaemia in patients with type 2 diabetes. This is in contrast to fibrinolytic factors as plasminogen-activator inhibitor I and tissue-type plasminogen activator, which are affected. We therefore hypothesise that a normally functioning TAR under hyperglycaemic conditions may tip the haemostatic balance towards hypofibrinolysis, which may contribute to the development of cardiovascular diseases in type 2 diabetic patients.