Hyperlipidemia and hemostatic system.

Abstract

The plasma levels of blood coagulation and fibrinolytic factors and the serum levels of lipids were measured in 62 subjects (22 normolipidemia and 40 hyperlipidemia) to investigate whether hyperlipidemia may affect the hemostatic system. Prothrombin, factors VII, IX and X were elevated in hyperlipidemic patients. The positive correlations were found between factors VII, IX and X, and triglyceride. The significant correlations were also found between VII and IX, and total cholesterol. Plasma levels of thrombin-antithrombin III complex (TAT), which reflects activation of coagulation system, were slightly but significantly higher in type IIb hyperlipidemia, although they were within normal range. Plasma levels of active plasminogen activator inhibitor (PAI) in type IIb and IV were significantly higher than in normals. A significant correlation was found between active PAI and triglyceride (r = 0.76, p < 0.0001). After the administration of fat emulsion to 18 patients with various diseases, which induced artificial hypertriglyceridemia, PAI levels as well as triglyceride levels significantly increased. These results suggest that hypertriglyceridemia may increase the synthesis and/or release of PAI, inducing a hypofibrinolytic condition, which could lead to thrombosis. It has been established that lipoprotein (a) [Lp(a)], which has a molecular structure homology to plasminogen, impairs fibrinolysis by its competitive inhibition of adsorption of plasminogen to vascular endothelial surface and/or fibrin. We assayed plasma levels of Lp(a) and parameters of blood coagulation and fibrinolysis in 168 patients with type II diabetes mellitus and 48 normal controls. In the diabetics, the levels of Lp(a) as well as levels of tissue-type plasminogen activator (t-PA) antigen and PAI activity were significantly higher than normal controls. Furthermore, it was shown that Lp(a) had a weakly negative correlation with t-PA antigen in the diabetics. These results suggest that an elevated level of Lp(a) may decrease release of t-PA, although the underlying mechanism remains unsolved.