Myocardial pre-synaptic sympathetic function correlates with glucose uptake in the failing human heart.

Abstract

We have previously shown that the myocardium of patients with heart failure (HF) is insulin resistant. Chronic beta-adrenergic stimulation has been implicated in insulin resistance in cultured cardiomyocytes in vitro, where sustained noradrenaline stimulation inhibited insulin-modulated glucose uptake. As the failing heart is characterized by increased sympathetic drive, we hypothesized that there is a correlation between pre-synaptic sympathetic function and insulin sensitivity in the myocardium of patients with HF. Eight patients (aged 67 +/- 7 years) with coronary artery disease and left ventricular dysfunction (ejection fraction 44 +/- 10%) underwent function and viability assessment with cardiovascular magnetic resonance. Myocardial glucose utilization (MGU) was measured using positron emission tomography (PET) with (18)F-fluorodeoxyglucose (FDG). Pre-synaptic noradrenaline re-uptake was measured by calculating [(11)C]meta-hydroxy-ephedrine (HED) volume of distribution (V (d)) with PET. Two groups of healthy volunteers served as controls for the FDG (n = 8, aged 52 +/- 4 years, p < 0.01 vs patients) and HED (n = 8, aged 40 +/- 6 years, p < 0.01 vs patients) data. MGU in patients was reduced in both normal remote (0.44 +/- 0.14 micromol.min(-1).g(-1)) and dysfunctional (0.49 +/- 0.14 micromol.min(-1).g(-1)) segments compared with controls (0.61 +/- 0.7 micromol.min(-1).g(-1); p < 0.001 vs both). HED V (d) was reduced in dysfunctional segments of patients (38.9 +/- 21.2 ml.g(-1)) compared with normal segments (52.2 +/- 19.6 ml.g(-1)) and compared with controls (62.7 +/- 11.3 ml.g(-1)). In patients, regional MGU was correlated with HED V (d). The results of this study provide novel evidence of a correlation between cardiac sympathetic function and insulin sensitivity, which may represent one of the mechanisms contributing to insulin resistance in failing human hearts.