Lack of Activation of Mitophagy during Endurance Exercise in Human.
Level 3 - non-randomized controlled study
Small crossover physiological study measuring biochemical surrogates without specified randomization
PubMed 28272266 · doi:10.1249/MSS.0000000000001256
What was done
Seven trained athletes completed a 2-hour cycling bout at 70% VO2peak in both fed and fasted states. Muscle biopsies from the vastus lateralis were taken at baseline, pre-exercise, immediately post-exercise, and 1 hour post-exercise. Researchers evaluated markers of mitophagy, mitochondrial biogenesis, fission, and fusion using RT-qPCR and Western blotting of whole muscle and isolated mitochondrial fractions.
What was found
Mitochondrial fraction levels of mitophagy markers LC3bII and p62/SQSTM1 were unchanged after exercise in both nutritional states. The LC3bII/LC3bI ratio decreased immediately post-exercise only in the fasted state (P = 0.019). Fission marker phospho-DRP1 in the mitochondrial fraction increased immediately and 1 hour post-exercise exclusively in the fed state. Expression of fission and mitophagy genes (Drp1, Bnip3, Bnip3L) and proteins (Fis1, BNIP3) increased after exercise in the fed state (P < 0.05). Mitogenesis markers (PGC1a, Tfam, Hsp60 mRNA) increased in both conditions, but to a greater extent in the fed state.
Why it matters
The study demonstrates that acute endurance exercise does not immediately stimulate mitochondrial clearance via mitophagy in human skeletal muscle, though feeding facilitates mitochondrial fission and upregulates preparatory mitophagy transcripts.
Limits
The study is constrained by a very small sample size (n = 7) of trained athletes, limiting generalizability. Mitophagy was assessed solely via indirect surrogate protein and transcript markers up to 1 hour post-exercise, leaving delayed mitophagy activation unmeasured. The abstract does not state whether the fed and fasted conditions were randomized.
Cited by
- context At least one human study found that vigorous-intensity aerobic exercise enhances markers of mitophagy.