title: The order of concurrent endurance and resistance exercise modifies mTOR signaling and protein synthesis in rat skeletal muscle.
abstract: Concurrent training, a combination of endurance (EE) and resistance exercise (RE) performed in succession, may compromise the muscle hypertrophic adaptations induced by RE alone. However, little is known about the molecular signaling interactions underlying the changes in skeletal muscle adaptation during concurrent training. Here, we used an animal model to investigate whether EE before or after RE affects the molecular signaling associated with muscle protein synthesis, specifically the interaction between RE-induced mammalian target of rapamycin complex 1 (mTORC1) signaling and EE-induced AMP-activated protein kinase (AMPK) signaling. Male Sprague-Dawley rats were divided into five groups: an EE group (treadmill, 25 m/min, 60 min), an RE group (maximum isometric contraction via percutaneous electrical stimulation for 3 × 10 s, 5 sets), an EE before RE group, an EE after RE group, and a nonexercise control group. Phosphorylation of p70S6K, a marker of mTORC1 activity, was significantly increased 3 h after RE in both the EE before RE and EE after RE groups, but the increase was smaller in latter. Furthermore, protein synthesis was greatly increased 6 h after RE in the EE before RE group. Increases in the phosphorylation of AMPK and Raptor were observed only in the EE after RE group. Akt and mTOR phosphorylation were increased in both groups, with no between-group differences. Our results suggest that the last bout of exercise dictates the molecular responses and that mTORC1 signaling induced by any prior bout of RE may be downregulated by a subsequent bout of EE.
authors.affiliation: Faculty of Sport and Health Science, Ritsumeikan University, Kusatsu, Shiga, Japan; The Research Organization of Science and Technology, Ritsumeikan University, Kusatsu, Shiga, Japan; ogasawara@idaten.c.u-tokyo.ac.jp.
authors.forename: Riki
authors.initials: R
authors.lastname: Ogasawara
authors.affiliation: Faculty of Sport and Health Science, Ritsumeikan University, Kusatsu, Shiga, Japan; Ritsumeikan Global Innovation Research Organization, Ritsumeikan University, Kusatsu, Shiga, Japan; and.
authors.forename: Koji
authors.initials: K
authors.lastname: Sato
authors.affiliation: Faculty of Sport and Health Science, Ritsumeikan University, Kusatsu, Shiga, Japan;
authors.forename: Kenji
authors.initials: K
authors.lastname: Matsutani
authors.affiliation: Graduate School of Health and Sport Science, Nippon Sport Science University, Tokyo, Japan.
authors.forename: Koichi
authors.initials: K
authors.lastname: Nakazato
authors.affiliation: Faculty of Sport and Health Science, Ritsumeikan University, Kusatsu, Shiga, Japan;
authors.forename: Satoshi
authors.initials: S
authors.lastname: Fujita
mesh_terms: D000818:Animals; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism*; D010766:Phosphorylation; D010805:Physical Conditioning, Animal / Q000379:methods / Q000502:physiology*; D010807:Physical Endurance / Q000502:physiology*; D014176:Protein Biosynthesis; D051381:Rats; D017207:Rats, Sprague-Dawley; D055070:Resistance Training; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000378:metabolism; D015398:Signal Transduction; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism*
chemical_list: C546843:mTOR protein, mouse; D038762:Ribosomal Protein S6 Kinases, 70-kDa; D058570:TOR Serine-Threonine Kinases
keywords: adenosine 5′-monophosphate-activated protein kinase; concurrent exercise; endurance exercise; mammalian target of rapamycin complex 1; resistance exercise