The relationships of concentrations of insulin, intact proinsulin and 32-33 split proinsulin with cardiovascular risk factors in type 2 (non-insulin-dependent) diabetic subjects

Abstract

Standard radioimmunoassay for insulin may substantially overestimate levels of insulin because of cross-reaction with other insulin-like molecules. We have measured concentrations of insulin, intact proinsulin and 32-33 split proinsulin using two-site monoclonal antibody based immunoradiometric assays, and of insulin by a standard radioimmunoassay ("immunoreactive insulin") in 51 Type 2 (non-insulin-dependent) diabetic subjects in the fasting state. The relationships of these concentrations were sought with those of total cholesterol, high density lipoprotein cholesterol, low density lipoprotein cholesterol, triglyceride, plasminogen activator inhibitor, blood pressure, and indices of body fat distribution. Significant relationships were apparent between concentrations of "immunoreactive insulin" as measured by standard radioimmunoassay and triglyceride (rs = 0.42, p less than 0.001), total cholesterol (rs = 0.25, p = 0.038), high density lipoprotein cholesterol (rs = -0.30, p = 0.018) and body mass index (rs = 0.30, p = 0.017), but only the relationships with triglyceride (rs = 0.36, p = 0.006) and body mass index (rs = 0.26, p = 0.34) remained significant when concentrations of immunoradiometrically measured insulin were employed. Concentrations of 32-33 split proinsulin, which comprises the major insulin-like molecule in these subjects, correlated positively with triglyceride (rs = 0.33, p = 0.009), total cholesterol (rs = 0.23, p = 0.050), and plasminogen activator inhibitor (rs = 0.26, p = 0.049), and negatively with high density lipoprotein cholesterol (rs = -0.29, p = 0.021).(ABSTRACT TRUNCATED AT 250 WORDS)