Repetitive restriction of muscle blood flow enhances mTOR signaling pathways in a rat model
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.
KeywordsBlood flow restriction Mammalian target of rapamycin (mTOR) Microvascular pO2 Muscle atrophy Myostatin p70 S6-kinase Rat skeletal muscle Hypoxia
Restriction of muscle blood flow
Repetitive restriction of muscle blood flow
Microvascular oxygen pressure
Mammalian target of rapamycin
Extracellular signal-regulated kinase 1/2
Forkhead box O3A
Muscle ring finger-1
Vascular endothelial growth factor
Dr. Yoshiaki Sato is an inventor of low-load resistance training with blood flow restriction, so-called Kaatsu training, and the owner of KAATSU Japan Co. Ltd. This work was supported by JSPS KAKENHI Grant Number 24300189 (to T.N.) and 25750288 (to T.Y.). This study was previously presented, in part, in abstract form at the Scientific Sessions, American Heart Association 2013 (Dallas, Texas, USA, 2013/11/16-11/20).
Compliance with ethical standards
Conflict of interest
There is no conflict of interests to disclose.
- 4.Wilkinson SB, Phillips SM, Atherton PJ, Patel R, Yarasheski KE, Tarnopolsky MA, Rennie MJ (2008) Differential effects of resistance and endurance exercise in the fed state on signalling molecule phosphorylation and protein synthesis in human muscle. J Physiol 586(Pt 15):3701–3717CrossRefPubMedPubMedCentralGoogle Scholar
- 5.Takano H, Morita T, Iida H, Asada K, Kato M, Uno K, Hirose K, Matsumoto A, Takenaka K, Hirata Y, Eto F, Nagai R, Sato Y, Nakajima T (2005) Hemodynamic and hormonal responses to a short-term low-intensity resistance exercise with the reduction of muscle blood flow. Eur J Appl Physiol 95:65–73CrossRefPubMedGoogle Scholar
- 19.Iida H, Kurano M, Takano H, Kubota N, Morita T, Meguro K, Sato Y, Abe T, Yamazaki Y, Uno K, Takenaka K, Hirose K, Nakajima T (2007) Hemodynamic and neurohumoral responses to the restriction of femoral blood flow by KAATSU in healthy subjects. Eur J Appl Physiol 100:275–285CrossRefPubMedGoogle Scholar
- 21.Navé BT, Ouwens M, Withers DJ, Alessi DR, Shepherd PR (1999) Mammalian target of rapamycin is a direct target for protein kinase B: identification of a convergence point for opposing effects of insulin and amino-acid deficiency on protein translation. Biochem J 344:427–431CrossRefPubMedPubMedCentralGoogle Scholar
- 36.Bodine SC, Stitt TN, Gonzalez M, Kline WO, Stover GL, Bauerlein R, Zlotchenko E, Scrimgeour A, Lawrence JC, Glass DJ, Yancopoulos GD (2001) Akt/mTOR pathway is a crucial regulator of skeletal muscle hypertrophy and can prevent muscle atrophy in vivo. Nat Cell Biol 3:1014–1019CrossRefPubMedGoogle Scholar