Values are presented as means ± standard deviation (n = 36). * vs. rest, P < 0.001; # vs. After-exercise, P < 0.01. Glycogen concentrations in the tissues The glycogen concentration in the liver did not differ between the groups at any of the time points P505-15 mouse (Figure 4A). Furthermore, the glycogen concentration in the white gastrocnemius muscle tissue did not differ between the groups at the rest and immediately post-exercise time points; however, this variable was significantly higher in the SP group than in the CON group at the recovery period time point (1 h post-exercise; Figure 4B). In contrast, no

significant between-group differences were observed in the red gastrocnemius muscle tissue (Figure 4C). Figure 4 Changes in the glycogen levels during exercise and after 1 h of exercise. CON: distilled water buy Quisinostat with training, SP: silk peptide-treated with training. A, liver; B, white gastrocnemius muscle tissue; and C, red gastrocnemius muscle tissue at rest, after exercise, and recovery in the CON and SP groups. Values are presented as means ± standard deviations (n = 36). * vs. rest, P < 0.01; # vs. rest and after-exercise, P < 0.05; $ vs. recovery in CON, P < 0.001; ¶ vs.

after-exercise, P < 0.05. Discussion The present study demonstrated that a 2-week regimen of silk peptide (SP) treatment and endurance training could increase the max, whereas endurance training alone had no similar effect. Depsipeptide in vivo A 2-week period of SP treatment also increased fat oxidation during the initial phase of exercise in exercised mice. In human studies, the max test during

graded treadmill exercise is the most commonly used endurance performance measurement [20, 21]. In the present study, max was not changed in the CON group after the 2-week training. Our previous study demonstrated that max was significantly increased by 4 week-training which the intensity was the same with the present study training protocol [16]. Thus, the duration (2 weeks) and/or intensity (75% of VO2 max) seem not to be enough to increase the endurance capacity in the present study. On the other hand, the max was significantly increased after a 2-week period of SP treatment when compared with the same metric before training. A previous study reported that a 30-day SP treatment regimen (800 mg/kg body weight daily) and swimming exercise training increased the maximum swimming time of mice by reducing exercise-induced tissue injuries and energy depletion [13]. In addition, a 44-day SP treatment regimen led to an increased maximum swimming time and decrease in the levels of muscle tissue damage markers such as creatine kinase, aspartate aminotransferase, and lactate dehydrogenase in a dose-dependent (50, 160, and 500 mg/kg) manner after forced swimming exercises [12]. Therefore, it seems that SP treatment can increase the exercise capacity regardless of the type of exercise.