Regional myocardial blood flow and glucose utilization during fasting and physiological hyperinsulinemia in humans

We investigated the effect of insulin on total and regional myocardial blood flow (MBF) and glucose uptake (MGU) in healthy subjects (50 ± 5 yr) by means of positron emission tomography (PET) with oxygen-15-labeled water (H₂¹⁵O) and fluorine-18 labeled fluorodeoxyglucose (¹⁸FDG) before and during physiological hyperinsulinemia (40 mU·min^-1·m^-2). Twelve male subjects were included in the study. During hyperinsulinemia, MBF increased from 0.91 ± 0.28 to 1.01 ± 0.31 ml·min^-1·g^-1 (n = 7 patients, P = 0.05; n = 112 regions, P < 0.005). Intersubject variability ranged from -3.0 to +41%. MGU increased from 0.11 ± 0.08 (n = 5) to 0.56 ± 0.08 μmol·min^-1·g^-1 (P < 0.0001, n = 7). MBF and insulin-mediated MGU were higher in the septum and anterior and lateral wall along short-axis regions of the heart. During hyperinsulinemia, MBF was also higher in the apex and midventricle compared with the base. MBF and MGU were positively correlated before (r = 0.66, P < 0.0001) and during hyperinsulinemia (r = 0.24, P < 0.05). These results provide evidence that insulin stimulates MBF in normal human hearts and appears to involve mainly those regions of the heart where insulin-mediated MGU is higher. Furthermore, regional distribution of insulin-stimulated MBF and MGU does not appear to be uniform across the left ventricular wall of healthy subjects.