Acute hyperglycemia and acute hyperinsulinemia decrease plasma fibrinolytic activity and increase plasminogen activator inhibitor type 1 in the rat

Decreased plasma fibrinolysis may contribute to accelerated atherothrombosis in diabetes. To observe whether hyperglycemia and hyperinsulinemia, common findings in type 2 diabetes, acutely affect plasma fibrinolysis in vivo, we evaluated plasma fibrinolysis (lysis of fibrin plates, free PAI-1 activity and t-PA activity) in the rat after a hyperglycemic euinsulinemic clamp (n=8), an euglycemic hyperinsulinemic clamp (n=7) or a saline infusion (n=15). Plasma fibrinolytic activity was sharply reduced after both the hyperglycemic and hyperinsulinemic clamps as compared to the respective controls (mean lysis areas on the fibrin plate, 139±21 vs. 323±30 mm², p<0.001; 78±27 vs. 312±27 mm² p<0.001, respectively). Plasma PAI-1 activity was greater after both hyperglycemic and hyperinsulinemic clamps as compared to saline infusion (6.6±2.6 vs. 1.6±0.6 IU/ml, p<0.001; 26±4 vs. 1.3±0.7 IU/ml, p<0.0001, respectively). Plasma t-PA activity was significantly reduced both after the hyperglycemic 0.36±0.15 vs. 2.17±0.18 IU/ml in controls, p<0.001) and the hyperinsulinemic vs. (0.3±0.1 vs. 2.3±0.3 IU/ml in control, p<0.001) clamps. These data show that in vivo both acute hyperglycemia and acute hyperinsulinemia can decrease plasma fibrinolytic potential and that this is due to increased plasma PAI-1 and decreased free t-PA activities.