Independent association of type 2 diabetes and coronary artery disease with myocardial insulin resistance

Clustering of classical cardiovascular risk factors is insufficient to account for the excess coronary artery disease (CAD) of patients with diabetes, and chronic hyperglycemia and insulin resistance (IR) are obvious culprits. Whole-body and skeletal muscle IR is characteristic of patients with type 2 diabetes, but whether it extends to the normally contracting cardiac muscle is controversial. We investigated whether type 2 diabetes is associated with myocardial IR independent of CAD in a case-control series (n = 55) of male nondiabetic and diabetic (type 2 and type 1) patients with or without angiographically documented CAD. Baseline blood flow (¹⁵O-water) and insulin-stimulated glucose uptake (¹⁸F-fluoro-deoxyglucose) during euglycemic (5.6 mmol/l), physiological hyperinsulinemia (40 mU·min^-1·m^-2 insulin clamp) were measured by positron emission tomography in skeletal muscle and normally contracting myocardium. Skeletal muscle glucose uptake was reduced in association with both CAD and type 2 diabetes. In regions with normal baseline perfusion, insulin-mediated myocardial glucose uptake was reduced in non-CAD type 2 diabetic (0.36 ± 0.14 μmol·min^-1·g^-1) and nondiabetic CAD patients (0.44 ± 0.15 μmol·min^-1·g^-1) in comparison with healthy control subjects (0.61 ± 0.08) or with non-CAD type 1 diabetic patients (0.80 ± 0.13; P < 0.001 for both CAD and diabetes). Neither basal skeletal muscle nor basal myocardial blood flow differed across groups; both skeletal muscle and myocardial IR were directly related to whole-body IR. We conclude that type 2 diabetes is specifically associated with myocardial IR that is independent of and nonadditive with angiographic CAD and proportional to skeletal muscle and whole-body IR.