Activation of autophagy in human skeletal muscle is dependent on exercise intensity and AMPK activation.
Level 3 - non-randomized controlled study
Controlled human physiological study with non-randomized or unspecified allocation
PubMed 25957282 · doi:10.1096/fj.14-267187
What was done
Twenty-three well-trained athletes were divided into control (n = 8), low-intensity (LI, n = 8), and high-intensity (HI, n = 7) exercise groups and completed fed and fasting sessions. Vastus lateralis muscle biopsies were taken before, immediately after, and 1 h after a 2-hour cycling bout to evaluate autophagy markers, gene expression, and AMPK signaling.
What was found
Phosphorylation of ULK1(Ser317) was higher after exercise (P < 0.001). In both fed and fasted states, LC3bII protein level and LC3bII/I were decreased after LI and HI (P < 0.05), while p62/SQSTM1 decreased only 1 h after HI (P < 0.05). HI exercise, but not LI, increased mRNA levels of LC3b, p62/SQSTM1, GabarapL1, and Cathepsin L. Phosphorylation of AMPKα(Thr172) and ACC(Ser79) was higher after HI (P < 0.001). Baseline values, absolute effect sizes, and measures of variance were not reported in the abstract.
Why it matters
The findings indicate that exercise intensity, mediated through AMPK activation, is more critical than nutritional fasting status for driving complete autophagic flux and transcriptional activation in human skeletal muscle.
Limits
The sample size was small (total n = 23 across three groups) and restricted to well-trained athletes. Randomization was not specified in the abstract. Clinical outcomes were not measured, relying solely on acute muscle biopsy biochemical markers.
Cited by
- supports High-intensity exercise stimulates skeletal muscle autophagy more potently than an overnight fast.