title: Repetitive restriction of muscle blood flow enhances mTOR signaling pathways in a rat model.
abstract: Skeletal muscle is a plastic organ that adapts its mass to various stresses by affecting pathways that regulate protein synthesis and degradation. This study investigated the effects of repetitive restriction of muscle blood flow (RRMBF) on microvascular oxygen pressure (PmvO2), mammalian target of rapamycin (mTOR) signaling pathways, and transcripts associated with proteolysis in rat skeletal muscle. Eleven-week-old male Wistar rats under anesthesia underwent six RRMBF consisting of an external compressive force of 100 mmHg for 5 min applied to the proximal portion of the right thigh, each followed by 3 min rest. During RRMBF, PmvO2 was measured by phosphorescence quenching techniques. The total RNA and protein of the tibialis anterior muscle were obtained from control rats, and rats treated with RRMBF 0-6 h after the stimuli. The protein expression and phosphorylation of various signaling proteins were determined by western blotting. The mRNA expression level was measured by real-time RT-PCR analysis. The total muscle weight increased in rats 0 h after RRMBF, but not in rats 1-6 h. During RRMBF, PmvO2 significantly decreased (36.1 ± 5.7 to 5.9 ± 1.7 torr), and recovered at rest period. RRMBF significantly increased phosphorylation of p70 S6-kinase (p70S6k), a downstream target of mTOR, and ribosomal protein S6 1 h after the stimuli. The protein level of REDD1 and phosphorylation of AMPK and MAPKs did not change. The mRNA expression levels of FOXO3a, MuRF-1, and myostatin were not significantly altered. These results suggested that RRMBF significantly decreased PmvO2, and enhanced mTOR signaling pathways in skeletal muscle using a rat model, which may play a role in diminishing muscle atrophy under various conditions in human studies.
authors.affiliation: Department of Cardiovascular Medicine, Dokkyo Medical University and Heart Center, Dokkyo Medical University Hospital, 880 Kitakobayashi, Mibu, Tochigi, 321-0293, Japan. nakat@dokkyomed.ac.jp.
authors.forename: Toshiaki
authors.identifier: http://orcid.org/0000-0001-9545-7529
authors.initials: T
authors.lastname: Nakajima
authors.affiliation: Seirei Christopher University, Shizuoka, Japan.
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Yasuda
authors.affiliation: Department of Engineering Science, Bioscience and Technology Program, University of Electro-Communications, Tokyo, Japan.
authors.forename: Seiichiro
authors.initials: S
authors.lastname: Koide
authors.affiliation: Department of Otolaryngology, University of Tokyo, Tokyo, Japan.
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Yamasoba
authors.affiliation: Department of Cardiovascular Medicine and Research Support Center, Dokkyo Medical Univerasity, Tochigi, Japan.
authors.forename: Syotaro
authors.initials: S
authors.lastname: Obi
authors.affiliation: Department of Cardiovascular Medicine, Dokkyo Medical University and Heart Center, Dokkyo Medical University Hospital, 880 Kitakobayashi, Mibu, Tochigi, 321-0293, Japan.
authors.forename: Shigeru
authors.initials: S
authors.lastname: Toyoda
authors.affiliation: Department of Basic Sciences in Medicine, Kaatsu International University, Battaramulla, Sri Lanka.
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Sato
authors.affiliation: Department of Cardiovascular Medicine, Dokkyo Medical University and Heart Center, Dokkyo Medical University Hospital, 880 Kitakobayashi, Mibu, Tochigi, 321-0293, Japan.
authors.forename: Teruo
authors.initials: T
authors.lastname: Inoue
authors.affiliation: Department of Engineering Science, Bioscience and Technology Program, University of Electro-Communications, Tokyo, Japan.
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Kano
mesh_terms: D000818:Animals; D000860:Hypoxia / Q000378:metabolism*; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism*; D009133:Muscular Atrophy; D010766:Phosphorylation; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D038601:Ribosomal Protein S6 / Q000378:metabolism*; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000378:metabolism*; D015398:Signal Transduction; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism*
chemical_list: D012333:RNA, Messenger; D038601:Ribosomal Protein S6; C546845:mTOR protein, rat; D038762:Ribosomal Protein S6 Kinases, 70-kDa; D058570:TOR Serine-Threonine Kinases
keywords: Blood flow restriction; Hypoxia; Mammalian target of rapamycin (mTOR); Microvascular pO2; Muscle atrophy; Myostatin; Rat skeletal muscle; p70 S6-kinase
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