[Pathogenic role of hyperinsulinism in macroangiopathy. Epidemiological data]

Abstract

The hypothesis of the atherogenic role of endogenous insulin was based on a series of epidemiological studies. Several large-scale prospective studies have demonstrated that diabetes constitutes an independent risk factor for cardiovascular disease. However, neither the duration of diabetes nor the blood glucose level appear to be predictive of the incidence of a cardiovascular accident. More recent prospective studies (Finland, Australia, Paris) in non-diabetic men have shown that hyperinsulinemia, while fasting or after glucose stimulation, constitutes a risk factor for fatal myocardial infarction, but they failed to show whether diabetes or the blood glucose level constituted a risk factor for the disease. Cross-sectional studies have provided similar results. Insulin resistance affects the majority of non-insulin-dependent diabetics and glucose-intolerant patients. It has also been observed in 25 percent of non-obese subjects with a normal glucose tolerance test. Associated hyperinsulinemia prevents the development of diabetes, but diabetes appears when the beta-cell function is altered and can no longer maintain this hyperinsulinemia. However, hyperinsulinemia is not devoid of cardiovascular consequences. Insulin resistance and hyperinsulinemia are also observed in patients with essential hypertension: a correlation between plasma insulin and blood pressure has been reported. These data, together with other experimental arguments, suggest that excessive endogenous insulin may participate in the rise in blood pressure. Furthermore, hypertensive patients have a high risk of coronary heart disease and this risk is not significantly decreased by anti-hypertensive treatments. This is probably related to the presence of other metabolic risk factors associated with insulin resistance: hyperinsulinemia, glucose intolerance, hypertriglyceridemia, decreased HDL cholesterol. These metabolic disorders have been grouped together under the term "syndrome X". All of these risk factors are probably also involved in the development of coronary heart disease in general population. In conclusion, epidemiological studies now suggest that insulin resistance and hyperinsulinemia increase the risk of hypertension and coronary heart disease. A great many experimental studies support this hypothesis. Lastly, it can be proposed that the increased cardiovascular risk in non-insulin-dependent diabetics is related to the fact that they belong to a larger group of insulin-resistant subjects. The management of diabetes, hypertension, and all of the metabolic abnormalities would appear to be the only way of reducing the incidence of cardiovascular disease.