Summary
A significant relationship has been described between plasminogen activator inhibitor-1
(PAI-1) and plasma insulin concentrations. However, most radioimmunoassays (RIA) substantially
overestimate plasma insulin concentrations because of cross reaction with proinsulin-like
molecules and it has been proposed that proinsulin-like molecules may be important
determinants of PAI-1 activity. We measured fasting plasma immunoreactive insulin
by conventional RIA, fasting plasma insulin (EIMA) by specific two site immuno-enzymometric
assay, and intact proinsulin and des-31,32-proinsulin by two site immunoradiometric
assay (IRMA) in 74 (50 nondiabetic and 24 diabetic) subjects who had survived a myocardial
infarction between 6 and 24 months previously. In univariate analysis, PAI-1 activity
correlated with serum triglycerides (rs=0.43; p <0.0001), insulin sensitivity (rs = -0.30; p = 0.004), and immunoreactive insulin (rs = 0.45; p <0.0001). However, the relationship between PAI-1 activity and plasma specific
insulin (IEMA) was weaker (rs = 0.24; p = 0.019) than those with intact proinsulin (rs = 0.53; p <0.0001) and des-31,32-proinsulin (rs = 0.54; p <0.0001) despite the low concentrations of these proinsulin-like molecules.
In multiple regression analysis, only des-31,32-proinsulin (p = 0.001) and serum triglycerides
(p = 0.013) were significant determinants of PAI-1 activity. In conclusion, these
results suggest that proinsulin-like molecules and serum triglycerides are important
determinants of PAI-1 activity in survivors of myocardial infarction.