The Effects of Insulin on the Cardiovascular System

Abstract

Numerous epidemiologic studies have now shown that insulin levels correlate with the development of cardiovascular disease after correction for other confounding variables. These findings leave open the possibility that excess circulating insulin is a risk factor that may have some predictive value in cardiovascular disease. Several years ago it was noted that low risk populations for ischemic heart disease have lower ambient insulin levels and insulin responses to glucose are higher in countries where the rate of ischemic heart disease is high (19,18). A number of large prospective studies where insulin levels were measured have now confirmed the relationship of insulin to cardiovascular disease. For example, in the Helsinki Policeman Study (13) those men in the highest quintile for fasting and post-glucose insulin levels had the highest incidence of ischemic heart disease, including myocardial infarction. Other studies such as the Busselton Study (22) in Australia and the Paris Civil Servants Study (5) have supported this relationship. In healthy, normotensive Italian factory workers, divided as having normal and high insulin levels, the hyperinsulinemic group had higher mean triglycerides and blood pressure and lower HDL cholesterol than the normoinsulinemic group (23). Thus, in the general population subjects with normal glucose tolerance and no evidence of diabetes, but with hyperinsulinemia, have an increased risk for ischemic heart disease and accompanying higher levels of other risk factors for ischemic cardiovascular disease.