Insulin resistance affects endothelium-dependent acetylcholine-induced coronary artery response

This study was designed to investigate the relationship between insulin resistance and the acetylcholine-induced endothelium-dependent coronary artery response in patients without angiographically significant atherosclerotic coronary artery disease and to elucidate the pathophysiological significance of insulin resistance in the early stages of coronary atherosclerosis.

Insulin resistance was calculated from fasting plasma glucose and insulin concentration using homeostasis model assessment in 40 patients suspected of having ischaemic heart disease, but without angiographic evidence of atherosclerotic coronary artery disease defined as a discrete stenosis or intimal irregularity. They were selected for an acetylcholine provocation test in both left and right coronary arteries. The homeostasis model assessment level was higher in 16 acetylcholine-positive patients than in 24 acetylcholine-negative patients (1.84+/-1.24 vs 0.72+/-0.62, P<0.01). Comparisons of the percentage change in vessel lumen diameter after the acetylcholine test in each of proximal, mid and distal segments of three coronary arteries among the three groups of low (less than 0.7; n=13), intermediate (0.7 to 1.4; n=13), and high homeostasis model assessment level (more than 1.4; n=14) revealed that a higher level resulted in a worse acetylcholine-induced constrictive response in coronary arteries.

These results suggest that there is an association between high insulin resistance and coronary vascular endothelial cell dysfunction, and that insulin resistance may be an indicator of early stage coronary artery atherosclerosis not detectable by angiography.