Objective: To investigate the relationship between blood pressure and the plasma fibrinolytic system and to verify whether this association was independent or mediated by one or more potential confounding factor.
Design: A random sample of 94 males aged 38 years subdivided into normotensives, hypertensives and those hypertensives with the highest blood pressure values.
Methods: Overall and regional obesity, blood lipids, fasting and 2-h post-load glucose, C-peptide and insulin levels, and main behavioural variables, including adipose tissue fatty acid composition (an objective index of dietary fat intake), were measured. The plasma fibrinolytic system was evaluated by determining activities and total plasma concentrations of both tissue-type plasminogen activator before and after venous occlusion, and its inhibitor plasminogen activator inhibitor type-1 (PAI-1).
Results: PAI-1 activity was significantly higher in the hypertensives than in the normotensives. PAI-1 antigen tended to parallel PAI-1 activity, and levels of tissue-type plasminogen activator antigen and activity tended to be lower in the hypertensives at baseline and after venous occlusion, but not significantly different from those in the normotensives. The hypertensives also had significantly higher body mass index and body fat content (measured by bio-impedance), increased plasma triglycerides, uric acid, fasting and 2-h glucose, C-peptide and insulin concentrations. In univariate linear regression analysis both systolic and diastolic blood pressures were found to be positively correlated with PAI-1 levels (r = 0.27, P < 0.01, for both). This correlation was maintained after adjustment for total body fat, fasting glucose, fasting insulin concentration or adipose tissue alpha-linolenic acid; however, it was no longer significant after adjustment for plasma 2-h insulin, 2-h C-peptide, 2-h glucose or triglyceride levels. Multivariate regression analysis revealed that only 2-h insulin and triglyceride concentration showed an independent association with PAI-1 levels.
Conclusions: This study confirms that, in 38-year-old males, hypertension is associated with increased PAI-1 activity. It supports the possibility that the relationship between blood pressure and PAI-1 may reflect the overall effect of the insulin resistance syndrome (in particular hyperinsulinaemia and hypertriglyceridaemia) rather than a direct effect of blood pressure on the fibrinolytic system.