Plasminogen activator inhibitor 1 (PAI-1) activity is increased in patients with non-insulin-dependent diabetes mellitus (NIDDM) and may contribute to their excess risk of cardiovascular disease. We examined the determinants of PAI-1 activity in 146 NIDDM subjects by using specific assays of insulin and intact and des-31,32-proinsulin and measures of insulin resistance, relating these measurements to serum lipids, hypoglycemic therapy, and a common 4G/5G polymorphism in the promoter region of the PAI-1 gene. Subjects were treated with insulin, sulfonylurea, sulfonylurea plus metformin, metformin, and diet alone. In the whole group, PAI-1 activity correlated significantly with serum triglycerides (r = 0.39, P < 0.001), specific insulin (r = 0.29, P < 0.001), intact proinsulin (r = 0.24, P = 0.004), and des-31,32-proinsulin (r = 0.30, P < 0.001) and in subjects not on insulin (n = 110), with insulin sensitivity (r = −0.42, P < 0.001). There was a significant difference in PAI-1 activity among the three genotypic groups (P = 0.016); subjects with the genotype 4G/4G had PAI-1 levels one-third higher than those with the 5G/5G genotype. In the 4G/4G group, PAI-1 activity correlated significantly with triglyceride levels (r = 0.65, P < 0.0001). There was no significant difference in PAI-1 activity in the different treatment groups despite a significant difference in concentrations of intact and des-31,32-proinsulin. In a multiple regression model, insulin sensitivity and the interaction between PAI-1 4G/5G genotype and triglyceride were the strongest determinants of PAI-1 activity.In conclusion, in this sample of NIDDM subjects, the influence of triglyceride on PAI-1 seems to be genotype dependent, and this interaction is a major determinant of PAI-1 activity.

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