Mismatch between insulin-mediated glucose uptake and blood flow in the heart of patients with type II diabetes

AIMS/HYPOTHESIS: We investigated the effect of physiological hyperinsulinaemia on global and regional myocardial blood flow and glucose uptake in five patients with Type II (non-insulin-dependent) diabetes mellitus and seven healthy control subjects. METHODS: Myocardial blood flow was assessed by positron emission tomography with oxygen-15 labelled water (H(2)(15)O) either before or after 1 h of euglycaemic hyperinsulinaemia. Myocardial glucose uptake was assessed by positron emission tomography and fluorine-18 labelled fluorodeoxyglucose ((18)FDG). RESULTS: During hyperinsulinaemia, myocardial blood flow increased from 0.91+/-0.03 to 1.00+/-0.03 ml(.)min(-1.)g(-1) in control subjects ( p<0.005) and from 0.81+/-0.02 to 0.95+/-0.04 ml(.)min(-1.)g(-1) in diabetic patients ( p<0.0005). Corresponding glucose uptakes were 0.56+/-0.01 and 0.36+/-0.02 micro mol(.)min(-1.)g(-1) ( p<0.0001), respectively. During hyperinsulinaemia, the regional distribution of myocardial blood flow and glucose uptake showed higher values in the septum and anterolateral wall (short axis) and in the mid-ventricle (long axis) in control subjects, and insulin action was circumscribed to these regions. In diabetic patients, the regional distribution of glucose uptake was similar; however, insulin-induced increase of myocardial blood flow was mainly directed to the postero-inferior areas (short axis) and to the base (long axis) of the heart, thus cancelling the predominance of the anterior wall observed before insulin administration. CONCLUSION/INTERPRETATION: These results provide evidence that insulin-mediated regulation of global myocardial blood flow is preserved in Type II diabetic patients. In contrast, the regional re-distribution of myocardial blood flow induced by insulin is directed to different target areas when compared with healthy subjects, thereby resulting in a mismatch between blood flow and glucose metabolism.