ABSTRACT
BACKGROUND: Strategies to minimize ischemic damage during heart transplantation (HTX) by donation after circulatory death (DCD) are warranted because the inevitable ischemic injury linked to DCD HTX deteriorates mitochondrial respiratory capacity and ultimately graft quality. This study aimed to examine the myocardial mitochondrial function during DCD HTX with hypothermic oxygenated machine perfusion (HOPE) and compare the effect of normothermic regional perfusion (NRP) with that of direct procurement and perfusion (DPP). METHODS: A porcine DCD HTX model was used with hearts subjected to either DPP (nâ =â 6) or NRP (nâ =â 7) followed by HOPE and orthotopic HTX. Mitochondrial respiratory function was analyzed by high-resolution respirometry in left ventricle biopsies at baseline, after 180 min of HOPE, and after 60 min of reperfusion post-HTX. RESULTS: Mitochondrial oxidative phosphorylation (Pâ =â 0.0008), respiratory control ratio (Pâ =â 0.04), and coupling efficiency (Pâ =â 0.04) declined during DCD HTX. Fatty acid oxidation was preserved after 3 h of HOPE with a modest, statistically nonsignificant decline after reperfusion (Pâ =â 0.2). Oxidative phosphorylation was inversely correlated with troponin-T levels (râ =â -0.70, Pâ =â 0.0004). No statistically significant difference in mitochondrial respiratory capacity was observed between participants exposed to NRP and DPP. CONCLUSIONS: Mitochondrial respiratory capacity declined gradually throughout the course of DCD HTX and correlated with the degree of myocardial damage. Following HOPE, the extent of mitochondrial deterioration was comparable between NRP and DPP.
ABSTRACT
Sodium-glucose cotransporter 2 (SGLT2) inhibition reduces cardiovascular morbidity and mortality in individuals with type 2 diabetes. Beneficial effects have been attributed to increased ketogenesis, reduced cardiac fatty acid oxidation, and diminished cardiac oxygen consumption. We therefore studied whether SGLT2 inhibition altered cardiac oxidative substrate consumption, efficiency, and perfusion. Thirteen individuals with type 2 diabetes were studied after 4 weeks' treatment with empagliflozin and placebo in a randomized, double-blind, placebo-controlled crossover study. Myocardial palmitate and glucose uptake were measured with 11C-palmitate and 18F-fluorodeoxyglucose positron emission tomography (PET)/computed tomography (CT). Oxygen consumption and myocardial external efficiency (MEE) were measured with 11C-acetate PET/CT. Resting and adenosine stress myocardial blood flow (MBF) and myocardial flow reserve (MFR) were measured using 15O-H2O PET/CT. Empagliflozin did not affect myocardial free fatty acids (FFAs) uptake but reduced myocardial glucose uptake by 57% (P < 0.001). Empagliflozin did not change myocardial oxygen consumption or MEE. Empagliflozin reduced resting MBF by 13% (P < 0.01), but did not significantly affect stress MBF or MFR. In conclusion, SGLT2 inhibition did not affect myocardial FFA uptake, but channeled myocardial substrate utilization from glucose toward other sources and reduced resting MBF. However, the observed metabolic and hemodynamic changes were modest and most likely contribute only partially to the cardioprotective effect of SGLT2 inhibition.