Exercise Training Improves Age-Related Myocardial Metabolic Derangement: Proton Magnetic Resonance Spectroscopy Study in the Rat Model

Background and Objectives: The objective of this study was to determine whether long-term exercise training will improve age-related cardiac metabolic derangement using proton magnetic resonance (MR) spectroscopy. Materials and Methods: Young and old male Fischer 344 rats were assigned to sedentary controls groups {young control (YC) group-3 months of age: YC, n=10; old control (OC) group-22 months of age: OC, n=10}, and an exercise training group (OT, n=5). After 12-week of treadmill exercise training, MR spectroscopy at 4.7 T was performed to assess myocardial energy metabolism: measurements of myocardial creatine-to-water ratio (Scr/Sw) were performed using the XWIN-NMR software. Results: Exercise capacity was 14.7 minutes greater in OT than that in OC (20.1${\pm}$1.9 minutes in OT, 5.4${\pm}$2.3 minutes in OC; p<0.001). The 12-week exercise training rendered the old rats a maximum exercise capacity matching that of untrained YC rats (17.9${\pm}$1.5 minutes in YC, 20.1${\pm}$1.9 minutes in OT; p>0.05). The creatine-to-water ratios in the interventricular septa of YC did not differ significantly from that of OT (0.00131${\pm}$0.00025 vs. 0.00127${\pm}$0.00031; p=0.37). However, OC showed significant reduction in creatine-to-water ratio compared to OT (0.00096${\pm}$0.00025 vs. 0.00127${\pm}$0.00031; p<0.001). Mean total creatine concentrations in the myocardium were similar between YC and OT (13.3 ${\pm}$3.6 vs. 11.5${\pm}$4.1 mmol/kg wet weight; p=0.29). In contrast, the mean total creatine concentration of OC was significantly reduced compared to OT (6.8${\pm}$3.2 vs. 11.5${\pm}$4.1 mmol/kg wet weight; p=0.03). Conclusion: Our findings suggest that long-term exercise training in old rats induced prevention of age-related deterioration in myocardial metabolism.