Is insulin resistance atherogenic? A review of the evidence.

Several factors that increase the risk of cardiovascular disease tend to cluster together in the same individual. Insulin resistance is believed to be a pathophysiological disturbance that underlies many of the risk factors. Whether insulin resistance per se is a cardiovascular risk factor is uncertain. Insulin resistance of myocardial muscle has been documented both in patients with type 2 diabetes and in nondiabetic subjects with angiographically proven coronary artery disease. In addition, in diabetic patients there is a mismatch between the redistribution of blood flow and glucose uptake during insulinization. Finally, the endothelial dysfunction and the hyperinsulinemia that accompany insulin resistance may adversely affect myocardial function. The evidence from epidemiological studies or clinical trials is, however, mixed. In at least one recent prospective study in patients with congestive heart failure, insulin resistance was an independent predictor of cardiac death. Conclusive proof would require a prospective study in which insulin resistance is measured directly and adequate account is taken of the classical cardiovascular risk factors.