Effect of non-insulin-dependent diabetes mellitus on myocardial insulin responsiveness in patients with ischemic heart disease

Background-Patients with non-insulin-dependent diabetes mellitus (NIDDM) ex hibit poor clinical outcomes from myocardial ischemia. This may reflect an impairment in their cardiac insulin-response system. Methods and Results-We used AV balance and intracoronary infusion technique s to compare the intrinsic cardiac responsiveness to insulin in 26 coronary disease patients with (n=13) and without (n=13) NIDDM, During fasting, NID DM hearts demonstrated lower fractional extraction of glucose from arterial plasma than controls (1.0 +/-0.5% versus 2.1 +/-0.5%, P<0.05) despite high er circulating insulin levels (26<plus/minus>5 versus 13 +/-4 muU (.) mL, P <0,05). This was compensated for by higher circulating glucose levels, so t hat net cardiac glucose uptake in the 2 groups was equivalent (5.2<plus/min us>1.1 versus 5.3 +/-1.1 mu mol (.) min). Intracoronary insulin infusion pr oduced an approximate to3-fold increase in fractional extraction and net up take of glucose across the heart in both groups (to 3.7 +/-0.4% and 18.3 +/ -3.5 mu mol (.) min in NIDDM and to 5.4 +/-0.7% and 17.7 +/-4.3 mu mol (.) min in controls) accompanied by an approximate to 30% increase in net lacta te uptake, suggesting preserved insulin action on both glucose uptake and g lucose oxidation in the NIDDM heart, In nondiabetics, insulin consistently increased coronary blood flow, but this effect was absent in NIDDM. Conclusions-In contrast to their peripheral tissues and coronary vasculatur e, the myocardium of patients with NIDDM expresses a competent insulin-resp onse system with respect to glucose metabolism. This suggests that insulin resistance is mediated at the level of individual organs and that different mechanisms are involved in muscle and vascular tissue.