Lack of Activation of Mitophagy during Endurance Exercise in Human

Purpose: This study aimed to determine whether fission and mitophagy are activated by acute endurance exercise in human skeletal muscle and to investigate if this activation is dependent upon the nutritional state. Methods: Trained athletes (n = 7) cycled for 2 h at 70% V˙O2peak in a fed or fasted state. Vastus lateralis muscle biopsies were obtained at baseline, before, immediately after, and 1 h after exercise. Protein and mRNA markers for mitophagy, mitochondrial biogenesis, fission, and fusion were analyzed using quantitative real-time polymerase chain reaction and Western blot. Results: Fission, assessed by phospho-DRP1Ser616 in the mitochondrial fraction, increased postexercise and 1 h postexercise only in the fed state. LC3bII and p62/SQSTM1 in the mitochondrial fraction were unchanged, whereas the LC3bII/LC3bI ratio was decreased only postexercise in the fasted state (P = 0.019), indicating a reduced mitophagy. Genes implicated in fission and mitophagy, such as Drp1, Bnip3, and Bnip3L, and proteins involved in fission (Fis1) or mitophagy (BNIP3) were all more expressed after exercise in the fed state (P

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