Hyperinsulinemia predicts low tissue plasminogen activator activity in a healthy population: the Northern Sweden MONICA Study.

Fibrinogen levels predict atherothrombotic disease, and impaired fibrinolysis has been proposed as a risk factor for myocardial infarction. Fibrinolysis is mainly dependent on the activity of tissue plasminogen activator (tPA) and its inhibitor plasminogen activator inhibitor type-1 (PAI-1). Oral glucose tolerance tests were performed in 318 randomly selected healthy men and 324 women aged 25 to 64 years. tPA activity was strongly predicted by fasting insulin in both univariate analysis (r = -.37 and -.34 in men and women, respectively) and multivariate analysis with age, anthropometric measurements, lipids, and blood pressure included. Fasting insulin was the strongest predictor of PAI-1 activity (r = .49 and .51). In women, the influence of fasting insulin level on tPA and PAI-1 activity was consistently stronger after than before menopause, and a threshold effect was seen with distinctly lower fibrinolytic activity in the highest quartile of insulin (> 7.0 mU/L). In men, the relation between insulin and fibrinolytic variables was linear. Fibrinogen levels were not related to insulin or glucose levels after adjustment for age and other risk factors in a multiple regression. Subjects with previously unknown diabetes or impaired glucose tolerance tended to have elevated fibrinogen and PAI-1 activity and decreased tPA activity. Our data support previous findings of a strong correlation between insulin and PAI-1 activity in small highly selected groups, and extend them to randomly selected population samples. The strong inverse relation between endogenous insulin levels and tPA activity has not previously been demonstrated in a healthy population.