Abstract 653: Muscle Ring Finger-1 (MuRF1) Expression Shifts Cardiomyocyte Substrate Utilization from Fatty Acids to Glucose

Abstract

Previous work has suggested that MuRF1, a cardiac-specific protein, regulates metabolism by its interactions with proteins that regulate ATP transport, glycolysis, and the electron transport chain. We recently identified that MuRF1 is cardioprotective in ischemia reperfusion injury. In the current study, we investigated the effects of MuRF1 expression on metabolic substrate utilization and found that MuRF1 shifts substrate utilization from fatty acids to glucose in a dose-dependent manner. Isolated neonatal ventricular cardiomyocytes were treated with an adenovirus expressing MuRF1 (Ad.MuRF1) or GFP (Ad.GFP) at a range of 0–25 MOI (Multiplicity Of Infection). 14C-Oleate or 14C-glucose were added to cells for 1 hour and 14C-CO2 release was determined using the CO2-trapping method. Trapped 14CO2 and acid soluble metabolites were used to calculate total fatty acid oxidation. Cardiomyocytes treated with 5–25 MOI Ad.MuRF1 demonstrated a dose dependent decrease in fatty acid oxidation of 10.5 +/− 2.3(5 MOI), 8.5 +/− 1.9 (10 MOI), 6.6 +/− 1.6 (15 MOI), and 5.1 +/− 1.3 (25 MOI) nmol oleate/mg protein/h. Compared with control cardiomyocytes treated with 5–25 MOI Ad.GFP (average of 5–25 MOI=13.5 +/− 0.7 nmol oleate/mg protein/h), this represents a 22.2%– 62.2% decrease in fatty acid oxidation. Inversely, glucose oxidation increased with increasing MuRF1 expression. Cardiomyocytes infected with 25 MOI Ad.MuRF1 oxidized 184% more glucose (28.9 +/− 4.6 nmol glucose/mg protein/h) compared to control cells treated with 25 MOI Ad.GFP (15.7 +/− 1.3 nmol glucose/mg protein/h). Increasing MuRF1 expression resulted in no net gain or loss of calculated ATP production (1699 +/− 157 vs. 1480 +/− 188 nmol ATP/mg protein/h). The co-utilization of glucose and fatty acids as substrates for the production of ATP allows the heart to adapt to both environmental stress and disease. Increasing the relative proportion of glucose oxidation in relationship to fatty acids is a known protective mechanism during cardiac stress, and may represent one mechanism by which MuRF1 is cardioprotective.