Background and Objective

Aerobic exercise has a strong effect on skeletal muscle metabolism, in both males and females of all ages. However, the effect of a single bout of aerobic exercise on the regulation of protein balance remains unknown. In the present study, we investigated the effect of a single bout of treadmill-based exercise on the levels of various protein synthesis-related eukaryotic proteins (initiation factor 2a, eukaryotic initiation factor 4E, eukaryotic initiation factor 4E-binding protein 1, and eukaryotic elongation factor 2), breakdown-related proteins (microtubule-associated protein 1 light chain 3 alpha (LC3), autophagy-related 7, and muscle RING-finger protein 1 (MuRF1)), and polyubiquitination in 3-month-old male ICR mice.

Material and Methods

Twenty-four male mice were randomized into four time-point groups; each group of mice was run on a rodent treadmill for 10 min at 10 m/min at a slope of 5° between 7:00 p.m. and 8:00 p.m. for 2 days during the adaptation period. On the third day, exercise was performed for 50 min at a speed of 12.3 m/min; the control mice did not perform any exercise. Gastrocnemius muscles were collected immediately after the mice were sacrificed by cervical dislocation at 0, 3, 6, or 12 hours post-exercise.

Results

Levels of synthesis-related proteins were significantly reduced at 3 and 6 hours into the recovery period,

whereas levels of breakdown-related proteins, including that of the autophagy marker LC3, increased immediately after exercise but not during the recovery period. MuRF1 level was determined in the gastrocnemius muscle to identify the factors involved in this increase. We found that increased MuRF1 levels were associated with an increase in polyubiquitination during the recovery period.

Conclusion

Our results suggest a potential role of optimal time points in muscle protein metabolism during recovery from a single bout of treadmill exercise.