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Age-related differences in lean mass, protein synthesis and skeletal muscle markers of proteolysis after bed rest and exercise rehabilitation.
- Source :
-
The Journal of physiology [J Physiol] 2015 Sep 15; Vol. 593 (18), pp. 4259-73. Date of Electronic Publication: 2015 Jul 31. - Publication Year :
- 2015
-
Abstract
- Bed rest-induced muscle loss and impaired muscle recovery may contribute to age-related sarcopenia. It is unknown if there are age-related differences in muscle mass and muscle anabolic and catabolic responses to bed rest. A secondary objective was to determine if rehabilitation could reverse bed rest responses. Nine older and fourteen young adults participated in a 5-day bed rest challenge (BED REST). This was followed by 8 weeks of high intensity resistance exercise (REHAB). Leg lean mass (via dual-energy X-ray absorptiometry; DXA) and strength were determined. Muscle biopsies were collected during a constant stable isotope infusion in the postabsorptive state and after essential amino acid (EAA) ingestion on three occasions: before (PRE), after bed rest and after rehabilitation. Samples were assessed for protein synthesis, mTORC1 signalling, REDD1/2 expression and molecular markers related to muscle proteolysis (MURF1, MAFBX, AMPKα, LC3II/I, Beclin1). We found that leg lean mass and strength decreased in older but not younger adults after bedrest (P < 0.05) and was restored after rehabilitation. EAA-induced mTORC1 signalling and protein synthesis increased before bed rest in both age groups (P < 0.05). Although both groups had blunted mTORC1 signalling, increased REDD2 and MURF1 mRNA after bedrest, only older adults had reduced EAA-induced protein synthesis rates and increased MAFBX mRNA, p-AMPKα and the LC3II/I ratio (P < 0.05). We conclude that older adults are more susceptible than young persons to muscle loss after short-term bed rest. This may be partially explained by a combined suppression of protein synthesis and a marginal increase in proteolytic markers. Finally, rehabilitation restored bed rest-induced deficits in lean mass and strength in older adults.<br /> (© 2015 The Authors. The Journal of Physiology © 2015 The Physiological Society.)
- Subjects :
- AMP-Activated Protein Kinases metabolism
Adult
Aged
Aging metabolism
Amino Acids, Essential metabolism
Bed Rest methods
Exercise Therapy methods
Female
Humans
Male
Microtubule-Associated Proteins metabolism
Muscle Proteins metabolism
Proteolysis
RNA, Messenger metabolism
Thinness metabolism
Tripartite Motif Proteins
Ubiquitin-Protein Ligases metabolism
Young Adult
Aging pathology
Biomarkers metabolism
Exercise physiology
Muscle, Skeletal metabolism
Muscle, Skeletal physiology
Protein Biosynthesis physiology
Thinness physiopathology
Subjects
Details
- Language :
- English
- ISSN :
- 1469-7793
- Volume :
- 593
- Issue :
- 18
- Database :
- MEDLINE
- Journal :
- The Journal of physiology
- Publication Type :
- Academic Journal
- Accession number :
- 26173027
- Full Text :
- https://doi.org/10.1113/JP270699