Journal
JOURNAL OF ANIMAL SCIENCE
Volume 89, Issue 7, Pages 2004-2016Publisher
OXFORD UNIV PRESS INC
DOI: 10.2527/jas.2010-3400
Keywords
amino acid; leucine; muscle; newborn; pig; translation initiation
Categories
Funding
- European Federation of Animal Science (EAAP, Rome, Italy)
- Pfizer Animal Health (Kalamazoo, MI)
- Elanco Animal Health (Greenfield, IN)
- Journal of Animal Science
- American Society of Animal Science
- NIH [R01 AR-44474]
- USDA/ARS [58-6250-6-001]
- Ajinomoto Amino Acid Research Program
Ask authors/readers for more resources
The postprandial increases in AA and insulin independently stimulate protein synthesis in skeletal muscle of piglets. Leucine is an important mediator of the response to AA. We have shown that the postprandial increase in leucine, but not isoleucine or valine, acutely stimulates muscle protein synthesis in piglets. Leucine increases muscle protein synthesis by modulating the activation of mammalian target of rapamycin (mTOR) complex 1 and signaling components of translation initiation. Leucine increases the phosphorylation of mTOR, 70-kDa ribosomal protein S6 kinase-1, eukaryotic initiation factor (eIF) 4E-binding protein-1, and eIF4G; decreases eIF2 alpha phosphorylation; and increases the association of eIF4E with eIF4G. However, leucine does not affect the upstream activators of mTOR, that is, protein kinase B, adenosine monophosphate-activated protein kinase, and tuberous sclerosis complex 1/2, or the activation of translation elongation regulator, eukaryotic elongation factor 2. The action of leucine can be replicated by a-ketoisocaproate but not by norleucine. Interference by rapamycin with the raptor-mTOR interaction blocks leucine-induced muscle protein synthesis. The acute leucine-induced stimulation of muscle protein synthesis is not maintained for prolonged periods, despite continued activation of mTOR signaling, because circulating AA fall as they are utilized for protein synthesis. However, when circulating AA concentrations are maintained, the leucine-induced stimulation of muscle protein synthesis is maintained for prolonged periods. Thus, leucine acts as a nutrient signal to stimulate translation initiation, but whether this translates into a prolonged increase in protein synthesis depends on the sustained availability of all AA.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available