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J Physiol. 2015 Sep 15;593(18):4275-84. doi: 10.1113/JP271219.

Rapamycin does not prevent increases in myofibrillar or mitochondrial protein synthesis following endurance exercise.

Author information

1
School of Sport, Exercise and Rehabilitation Sciences, University of Birmingham, Birmingham, UK.
2
Neurobiology, Physiology and Behaviour, University of California, Davis, CA, USA.
3
Department of Orthopaedic Surgery and Biomedical Sciences Graduate Program, University of California, San Diego, CA, USA.
4
School of Sport, University of Stirling, Stirling, UK.
5
Department of Kinesiology, McMaster University, Hamilton, ON, CA.

Abstract

The present study aimed to investigate the role of the mechanistic target of rapamycin complex 1 (mTORC1) in the regulation of myofibrillar (MyoPS) and mitochondrial (MitoPS) protein synthesis following endurance exercise. Forty-two female C57BL/6 mice performed 1 h of treadmill running (18 m min(-1) ; 5° grade), 1 h after i.p. administration of rapamycin (1.5 mg · kg(-1) ) or vehicle. To quantify skeletal muscle protein fractional synthesis rates, a flooding dose (50 mg · kg(-1) ) of l-[ring-(13) C6 ]phenylalanine was administered via i.p. injection. Blood and gastrocnemius muscle were collected in non-exercised control mice, as well as at 0.5, 3 and 6 h after completing exercise (n = 4 per time point). Skeletal muscle MyoPS and MitoPS were determined by measuring isotope incorporation in their respective protein pools. Activation of the mTORC1-signalling cascade was measured via direct kinase activity assay and immunoblotting, whereas genes related to mitochondrial biogenesis were measured via a quantitative RT-PCR. MyoPS increased rapidly in the vehicle group post-exercise and remained elevated for 6 h, whereas this response was transiently blunted (30 min post-exercise) by rapamycin. By contrast, MitoPS was unaffected by rapamycin, and was increased over the entire post-exercise recovery period in both groups (P < 0.05). Despite rapid increases in both MyoPS and MitoPS, mTORC1 activation was suppressed in both groups post-exercise for the entire 6 h recovery period. Peroxisome proliferator activated receptor-γ coactivator-1α, pyruvate dehydrogenase kinase 4 and mitochondrial transcription factor A mRNA increased post-exercise (P < 0.05) and this response was augmented by rapamycin (P < 0.05). Collectively, these data suggest that endurance exercise stimulates MyoPS and MitoPS in skeletal muscle independently of mTORC1 activation.

PMID:
26227152
PMCID:
PMC4594297
DOI:
10.1113/JP271219
[Indexed for MEDLINE]
Free PMC Article

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