Nutrient signalling in the regulation of human muscle protein synthesis

Satoshi Fujita, Hans C. Dreyer, Micah J. Drummond, Erin L. Glynn, Jerson G. Cadenas, Fumiaki Yoshizawa, Elena Volpi, Blake Rasmussen

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Abstract

The mammalian target of rapamycin (mTOR) and AMP-activated protein kinase (AMPK) are important nutrient- and energy-sensing and signalling proteins in skeletal muscle. AMPK activation decreases muscle protein synthesis by inhibiting mTOR signalling to regulatory proteins associated with translation initiation and elongation. On the other hand, essential amino acids (leucine in particular) and insulin stimulate mTOR signalling and protein synthesis. We hypothesized that anabolic nutrients would be sensed by both AMPK and mTOR, resulting in an acute and potent stimulation of human skeletal muscle protein synthesis via enhanced translation initiation and elongation. We measured muscle protein synthesis and mTOR-associated upstream and downstream signalling proteins in young male subjects (n = 14) using stable isotopic and immunoblotting techniques. Following a first muscle biopsy, subjects in the 'Nutrition' group ingested a leucine-enriched essential amino acid-carbohydrate mixture (EAC). Subjects in the Control group did not consume nutrients. A second biopsy was obtained 1 h later. Ingestion of EAC significantly increased muscle protein synthesis, modestly reduced AMPK phosphorylation, and increased Akt/PKB (protein kinase B) and mTOR phosphorylation (P < 0.05). mTOR signalling to its downstream effectors (S6 kinase 1 (S6K1) and 4E-binding protein 1 (4E-BP1) phosphorylation status) was also increased (P < 0.05). In addition, eukaryotic elongation factor 2 (eEF2) phosphorylation was significantly reduced (P < 0.05). Protein synthesis and cell signalling (phosphorylation status) was unchanged in the control group (P > 0.05). We conclude that anabolic nutrients alter the phosphorylation status of both AMPK- and mTOR-associated signalling proteins in human muscle, in association with an increase in protein synthesis not only via enhanced translation initiation but also through signalling promoting translation elongation.

Original languageEnglish
Pages (from-to)813-823
Number of pages11
JournalJournal of Physiology
Volume582
Issue number2
DOIs
StatePublished - Jul 2007

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Muscle Proteins
Sirolimus
AMP-Activated Protein Kinases
Food
Essential Amino Acids
Phosphorylation
Proteins
Leucine
Skeletal Muscle
TOR Serine-Threonine Kinases
Carbohydrates
Biopsy
Muscles
Proto-Oncogene Proteins c-akt
Immunoblotting
Eating
Insulin
Control Groups

ASJC Scopus subject areas

  • Physiology

Cite this

Fujita, S., Dreyer, H. C., Drummond, M. J., Glynn, E. L., Cadenas, J. G., Yoshizawa, F., ... Rasmussen, B. (2007). Nutrient signalling in the regulation of human muscle protein synthesis. Journal of Physiology, 582(2), 813-823. https://doi.org/10.1113/jphysiol.2007.134593

Nutrient signalling in the regulation of human muscle protein synthesis. / Fujita, Satoshi; Dreyer, Hans C.; Drummond, Micah J.; Glynn, Erin L.; Cadenas, Jerson G.; Yoshizawa, Fumiaki; Volpi, Elena; Rasmussen, Blake.

In: Journal of Physiology, Vol. 582, No. 2, 07.2007, p. 813-823.

Research output: Contribution to journalArticle

Fujita, S, Dreyer, HC, Drummond, MJ, Glynn, EL, Cadenas, JG, Yoshizawa, F, Volpi, E & Rasmussen, B 2007, 'Nutrient signalling in the regulation of human muscle protein synthesis', Journal of Physiology, vol. 582, no. 2, pp. 813-823. https://doi.org/10.1113/jphysiol.2007.134593
Fujita S, Dreyer HC, Drummond MJ, Glynn EL, Cadenas JG, Yoshizawa F et al. Nutrient signalling in the regulation of human muscle protein synthesis. Journal of Physiology. 2007 Jul;582(2):813-823. https://doi.org/10.1113/jphysiol.2007.134593
Fujita, Satoshi ; Dreyer, Hans C. ; Drummond, Micah J. ; Glynn, Erin L. ; Cadenas, Jerson G. ; Yoshizawa, Fumiaki ; Volpi, Elena ; Rasmussen, Blake. / Nutrient signalling in the regulation of human muscle protein synthesis. In: Journal of Physiology. 2007 ; Vol. 582, No. 2. pp. 813-823.
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