High serum insulin concentrations in relation to other cardiovascular risk factors in macrovascular disease of type 2 diabetes.

In normal, nondiabetic man, a link between hyperinsulinaemia and coronary heart disease (CHD) has been suggested by recent population surveys. The present study reports on hyperinsulinaemia as associated with macrovascular (coronary, peripheral, and carotid artery) disease in 323 non-selected NIDDs (type 2 diabetics) and 178 age and sex matched controls. Both among the 58% of diabetics and 38% of nondiabetics with large vessel disease fasting serum C-peptide was significantly elevated (p less than 0.001) as compared to subjects without. Analysing nondiabetics and non insulin treated NIDDs (n = 154) according to quintiles of fasting C-peptide, significantly more patients with macrovascular disease in general and CHD in particular were found in the upper two quintiles (p less than 0.01). In addition, insulin treated NIDDs (n = 169) with macroangiopathy exhibited higher daily insulin requirement and fasting free insulin concentrations (p less than 0.01) than those without. The association of hyperinsulinaemia--whether endogenous or exogenous--with large vessel disease appeared to be independent from age, relative weight, and actual fasting blood glucose. There were, however, significant interrelations of fasting C-peptide with fasting triglycerides and--inversely--with HDL cholesterol and HbA1 in the diabetics. These results point to a role of hyperinsulinaemia also in macrovascular disease of diabetic patients, i.e. NIDDs, as previously observed in nondiabetics. Metabolic compensation of NIDDs should probably the accomplished at the lowest possible blood insulin concentration, regardless whether insulin affects large vessels by direct or indirect means.