European Journal of Applied Physiology

, Volume 114, Issue 4, pp 735–742 | Cite as

Whey protein intake after resistance exercise activates mTOR signaling in a dose-dependent manner in human skeletal muscle

  • Ryo Kakigi
  • Toshinori Yoshihara
  • Hayao Ozaki
  • Yuji Ogura
  • Noriko Ichinoseki-Sekine
  • Hiroyuki Kobayashi
  • Hisashi Naito
Original Article



Protein ingestion after resistance exercise increases muscle protein synthesis (MPS) in a dose-dependent manner. However, the molecular mechanism(s) for the dose-dependency of MPS remains unclear. This study aimed to determine the dose response of mammalian target of rapamycin (mTOR) signaling in muscle with ingestion of protein after resistance exercise.


Fifteen male subjects performed four sets of six unilateral isokinetic concentric knee extensions. Immediately after exercise, eight subjects consumed water only. The other seven subjects, in a randomized-order crossover design, took either a 10 [3.6 g essential amino acids (EAA)] or 20 g (7.1 g EAA) solution of whey protein. Muscle biopsies from the vastus lateralis muscle were taken 30 min before and 1 h after resistance exercise. Phosphorylation of Akt (Ser473), mTOR (Ser2448), 4E-BP1 (Thr37/46), and S6K1 (Thr389) was measured by western blotting.


Concentric knee extension exercise alone did not increase phosphorylation of Akt and mTOR 1 h after exercise, but ingesting protein after exercise significantly increased the phosphorylation of Akt and mTOR in a dose-dependent manner (P < 0.05). 4E-BP1 phosphorylation significantly decreased after resistance exercise (P < 0.05), but subjects who took 10 or 20 g of protein after exercise showed increased 4E-BP1 from post-exercise dephosphorylation (P < 0.05). S6K1 phosphorylation significantly increased after resistance exercise (P < 0.05), and 20 g of protein further increased S6K1 phosphorylation compared with ingestion of 10 g (P < 0.05).


These findings suggest that whey protein intake after resistance exercise activates mTOR signaling in a dose-dependent manner in untrained men.


Mammalian target of rapamycin Whey hydrolysate Concentric contraction Muscle protein synthesis 



Protein kinase B


Essential amino acids


Eukaryotic initiation factor


Mammalian target of rapamycin


Myosin heavy chain


Muscle protein breakdown


Muscle protein synthesis


Ribosomal protein S6 kinase 1



This study was supported by the MEXT-Supported Program for the Juntendo University, and a Grant-in Aid for Scientific Research B (No. 21300238 to HN, and No. 24700703 to RK) from the Ministry of Education, Culture, Sports, Science, and Technology of Japan. We thank the research subjects for their invaluable contribution to this study.

Conflict of interest

The authors declare that they have no conflicts of interest.


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Copyright information

© Springer-Verlag Berlin Heidelberg 2013

Authors and Affiliations

  • Ryo Kakigi
    • 1
    • 2
  • Toshinori Yoshihara
    • 3
  • Hayao Ozaki
    • 3
  • Yuji Ogura
    • 4
  • Noriko Ichinoseki-Sekine
    • 1
    • 3
  • Hiroyuki Kobayashi
    • 5
  • Hisashi Naito
    • 1
    • 3
  1. 1.Institute of Health and Sports Science & MedicineJuntendo UniversityInzaiJapan
  2. 2.Department of PhysiologyJuntendo University School of MedicineTokyoJapan
  3. 3.Department of Exercise Physiology, Graduate School of Health and Sports ScienceJuntendo UniversityInzaiJapan
  4. 4.Department of PhysiologySt Marianna University School of MedicineKawasakiJapan
  5. 5.Department of General MedicineMito Medical Center, Tsukuba University HospitalMitoJapan

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