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United States Department of Agriculture

Agricultural Research Service

Research Project: NUTRITION, EXERCISE PHYSIOLOGY, AND SARCOPENIA Title: Effects of chronic overload on muscle hypertrophy and mTOR signaling in adult and aged rats

Authors
item Chale-Rush, Angela -
item Morris, Evan -
item Kendall, Tracee -
item Brooks, Naomi -
item Fielding, Roger -

Submitted to: Journal of Gerontology Biological Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 8, 2009
Publication Date: December 1, 2009
Citation: Chale-Rush, A., Morris, E.P., Kendall, T., Brooks, N.E., Fielding, R.A. 2009. Effects of chronic overload on muscle hypertrophy and mTOR signaling in adult and aged rats. Journal of Gerontology Biological Science. 64(12):1232-1239.

Interpretive Summary: This study compared how the activation of specific proteins in muscle differ in response to exercise in young adult (Y) and aged (O) rats. The proteins of interest are part of signaling pathways important to diseases that affect muscle function as well as in aging because they control muscle size. We examined the effect of 28 days of exercise on two signaling pathways: mammalian target of rapamycin (mTOR) and extracellular signal-regulated kinase (ERK) in Y and O rats subjected to bilateral synergist ablation (SA) of two-thirds of the gastrocnemius muscle or sham surgery (CON). Although plantaris (PLA) muscle hypertrophy was attenuated by aging, mTOR phosphorylation was greater in Y SA and O SA compared to CON. Ribosomal protein S6 (rpS6) phosphorylation was higher in Y SA and O SA compared to CON. Eukaryotic initiation factor 2Be (eIF2Be) phosphorylation was higher in Y SA and O SA compared to CON. These are all signaling proteins, which are activated abd function when phosphorylated. Translational signaling in young adult and aged plantaris muscle is equally responsive to chronic exercise. Thus, exercised muscle from aged animals has the ability to counteract the effects of muscle loss.

Technical Abstract: We examined the effect of 28 days of overload on mammalian target of rapamycin (mTOR) and extracellular signal-regulated kinase (ERK) signaling in young adult (Y; 6 mo old) and aged (O; 30 mo old) Fischer 344 x Brown Norway rats subjected to bilateral synergist ablation (SA) of two-thirds of the gastrocnemius muscle or sham surgery (CON). Although plantaris (PLA) muscle hypertrophy was attenuated by aging, mTOR phosphorylation was 44 % and 35 % greater in Y SA and O SA compared to CON ( p = 0.038). Ribosomal protein S6 (rpS6) phosphorylation was 114 % and 24 % higher in Y SA and O SA compared to CON (p = 0.009). Eukaryotic initiation factor 2Bepsilon (eIF2Bepsilon) phosphorylation was 33 % and 9 % higher in Y SA and O SA compared to CON (p = 0.04). Translational signaling in young adult and aged plantaris muscle is equally responsive to chronic overload.

Last Modified: 11/27/2014
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