Journal
JOURNAL OF APPLIED PHYSIOLOGY
Volume 104, Issue 5, Pages 1452-1461Publisher
AMER PHYSIOLOGICAL SOC
DOI: 10.1152/japplphysiol.00021.2008
Keywords
sarcopenia; mammalian target of rapamycin; AMPK; weight lifting
Categories
Funding
- NIAMS NIH HHS [R01 AR 049877, R01 AR049877, R01 AR049877-04] Funding Source: Medline
- NIA NIH HHS [P30 AG024832, P30 AG 024832, R01 AG 018311, R01 AG018311-10, R01 AG018311, P30 AG024832-04] Funding Source: Medline
- NICHD NIH HHS [T32 HD007539, T32 HD007539-08, K12 HD055929] Funding Source: Medline
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Skeletal muscle loss during aging leads to an increased risk of falls, fractures, and eventually loss of independence. Resistance exercise is a useful intervention to prevent sarcopenia; however, the muscle protein synthesis (MPS) response to resistance exercise is less in elderly compared with young subjects. On the other hand, essential amino acids (EAA) increase MPS equally in both young and old subjects when sufficient EAA is ingested. We hypothesized that EAA ingestion following a bout of resistance exercise would stimulate anabolic signaling and MPS similarly between young and old men. Each subject ingested 20 g of EAA 1 h following leg resistance exercise. Muscle biopsies were obtained before and 1, 3, and 6 h after exercise to measure the rate of MPS and signaling pathways that regulate translation initiation. MPS increased early in young (1-3 h postexercise) and later in old (3-6 h postexercise). At 1 h postexercise, ERK1/2 MNK1 phosphorylation increased and eIF2 alpha phosphorylation decreased only in the young. mTOR signaling (mTOR, S6K1, 4E-BP1, eEF2) was similar between groups at all time points, but MNK1 phosphorylation was lower at 3 h and AMP-activated protein kinase-alpha (AMPK alpha) phosphorylation was higher in old 1-3 h postexercise. We conclude that the acute MPS response after resistance exercise and EAA ingestion is similar between young and old men; however, the response is delayed with aging. Unresponsive ERK1/2 signaling and AMPK activation in old muscle may be playing a role in the delayed activation of MPS. Notwithstanding, the combination of resistance exercise and EAA ingestion should be a useful strategy to combat sarcopenia.
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