Proinsulin and Insulin Sensitivity as Predictors of Type 2 Diabetes Mellitus and Coronary Heart Disease : Clinical Epidemiological Studies with up to 27 Years of Follow-Up

Abstract: Defects in insulin secretion and insulin action are the major abnormalities in the development of Type 2 diabetes. Hyperinsulinemia is a risk marker for Type 2 diabetes and according to some, but not in all studies also for coronary heart disease (CHD). Conventional insulin assays measure immunoreactive insulin including proinsulin-like molecules. Proinsulin and insulin measured by specific methods, insulin sensitivity measured by the euglycemic insulin clamp and early insulin response after a glucose challenge give more detailed information and may be better estimates of true risk for Type 2 diabetes and CHD. This study examined relationships between proinsulin, insulin, insulin secretion and insulin sensitivity for the development of Type 2 diabetes and CHD. The investigation of the prognostic significance of proinsulin and insulin for the development of Type 2 diabetes and CHD was performed in prospective studies of 50-year and 70-year-old men in a population-based cohort. The results indicated, that increased proinsulin concentrations, was a marker of increased risk for Type 2 diabetes independent of measurements of insulin secretion and insulin sensitivity whereas insulin was not. Proinsulin was shown to be a predictor for CHD mortality and morbidity, respectively, independent of conventional risk factors, whereas insulin was not. Insulin sensitivity measured by the gold standard euglycemic insulin clamp at age 70 was a predictor of CHD morbidity, independently of established risk factors.In summary, these data provide evidence that an increased concentration of proinsulin and not an elevated plasma insulin level per se, that constitutes the association with Type 2 diabetes and CHD and that insulin resistance per se, is associated with CHD risk.