Autophagy response to acute high-intensity interval training and moderate-intensity continuous training is dissimilar in skeletal muscle and peripheral blood mononuclear cells and is influenced by sex

Autophagy is an evolutionary conserved cellular degradation system that underlies the positive effects of exercise. Currently, few human data exist investigating the autophagic response to exercise including the response to high-intensity interval training (HIIT), response in divergent tissues, and if sex differences exist. The purpose of this study was to investigate the autophagy response in skeletal muscle and peripheral blood mononuclear cells (PBMCs) following an acute bout of HIIT and moderate-intensity continuous training (MICT) with treadmill running in males and females. Using a crossover design, ten recreationally-active males (n = 5; 25.2 & PLUSMN; 1.1 yrs) and females (n = 5; 21.6 & PLUSMN; 3.6 yrs) performed a bout of MICT (60 min at 55% of max velocity [Vmax]]) and HIIT (12 bouts of 1 min at 100% Vmax and 1 min at 3 miles per hour) in a fasted state separated by & GE; 72 h. Muscle biopsy samples from the vastus lateralis and PBMCs were collected pre- and 3 h post-exercise and analyzed for differences in protein expression of LC3I, LC3II, and p62 via western blot analysis. Expression of LC3II:LC3I was significantly different from pre-exercise 3 h post-exercise in MICT in skeletal muscle (64.3 & PLUSMN; 47.3%; p = 0.024). A significant time effect was found for p62 3 h post-exercise compared to pre-exercise (135.23 & PLUSMN; 84.6%; p = 0.043) in skeletal muscle. No differences in markers of autophagy were observed in PBMCs. When sexes were analyzed separately there was a condition x time x sex interaction in LC3II (p = 0.007) and LC3II:LC3I (p = 0.043) in PBMCs. Post hoc analyses revealed a difference in LC3II pre vs. 3 h post exercise in males, but not females, in both HIIT (144.2 & PLUSMN; 89.7%; p = 0.024) and MICT (61.8 & PLUSMN; 36.1%; p = 0.043). Our findings show that HIIT results in changes in markers of autophagy and that the exercise-induced autophagy response varies in tissues and between sexes.