Effects of exercise in a fed or fasted state on mitochondrial dynamics regulators in the skeletal muscle of recreationally active males.

Abstract

Exercise and nutritional modulation favourably alter mitochondrial quantity and quality in skeletal muscle. Mitochondrial dynamics, the coordination of fission and fusion events, are poised to mediate key aspects of organelle adaptation that arise from exercise. However, the molecular basis by which exercise affects mitochondrial dynamics remains poorly understood. The objective of this work was to further elucidate the signalling response of mitochondrial dynamics regulators to exercise and explore the synergistic potential to combine exercise and nutritional modulation. In a randomized crossover design, eight healthy, recreationally active men (age 25.8 ± 5.3 years, BMI 24.4 ± 1.2 kg/m², ${\dot{V}}_{O_2\mathrm{peak}}$ 39.2 ± 5.7 ml/kg/min) performed a 1-h bout of workload-matched aerobic exercise on a cycle ergometer at 50-70% of W_max, either in a fasted or a fed (i.e., following a carbohydrate rich breakfast) state. Gas exchange was measured throughout, and blood samples were collected intermittently. Vastus lateralis muscle biopsies were collected pre-, post- and 3 h post-exercise. Western blotting was performed on cytosolic and mitochondrial fractions. Fasted exercise was accompanied by increased cytosolic acetyl-CoA carboxylase Ser79 phosphorylation (P ≤ 0.001), an effect not observed in the fed group (P > 0.05). The subcellular location of mitochondrial fission effector dynamin-related protein 1 (DRP1) was unchanged (P > 0.05) following exercise. However, group differences (i.e., Fed vs. Fasted) in DRP1 subcellular localization and phosphorylation at residues Ser616 and Ser637 were observed post-exercise. Substrate availability may potentially influence the mitochondrial dynamics signalling response in skeletal muscle to acute aerobic exercise.