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. 2011 Aug;66(8):835-41.
doi: 10.1093/gerona/glr088. Epub 2011 Jun 9.

Myosin heavy chain plasticity in aging skeletal muscle with aerobic exercise training

Adam R Konopka  1 , Todd A Trappe, Bozena Jemiolo, Scott W Trappe, Matthew P Harber
Affiliations

Myosin heavy chain plasticity in aging skeletal muscle with aerobic exercise training

Adam R Konopka et al. J Gerontol A Biol Sci Med Sci. 2011 Aug.

Abstract

To assess myosin heavy chain (MHC) plasticity in aging skeletal muscle with aerobic exercise training, MHC composition was measured at the messenger RNA (mRNA) level and protein level in mixed-muscle homogenates and single myofibers. Muscle samples were obtained from eight nonexercising women (70 ± 2 years) before and after 12 weeks of training (20-45 minutes of cycle exercise per session at 60%-80% heart rate reserve, three to four sessions per week). Training elevated MHC I mRNA (p < .10) and protein (p < .05) in mixed-muscle (54% ± 4% to 61% ± 2%) and single myofibers (42% ± 4% to 52% ± 3%). The increase in MHC I protein was positively correlated (p < .05) with improvements in whole muscle power. Training resulted in a general downregulation of MHC IIa and IIx at the mRNA and protein levels. The training-induced increase in MHC I protein and mRNA demonstrates the maintenance of skeletal muscle plasticity with aging. Furthermore, these data suggest that a shift toward an oxidative MHC phenotype may be beneficial for metabolic and functional health in older individuals.

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Figures

Figure 1.
Figure 1.
(A) MHC mRNA, (B) mixed-muscle homogenate composition (H-MHC), and (C) single-fiber distribution (SF-MHC) within skeletal muscle of older women pre- and postaerobic exercise training. Hybrids in (C) signify the collective representation of all hybrid fibers (I/IIa and IIa/IIx). Data are presented in mean ± SE. *p < .05, †p < .10 compared with Pre.
Figure 2.
Figure 2.
Correlation between the absolute change in whole muscle knee extensor power with the change of myosin heavy chain (MHC) I content in (A) the mixed-muscle homogenate and (B) individual myofibers, with aerobic exercise training in older women (R2 = .78 and .92 respectively, p < .05).
Figure 3.
Figure 3.
The inverse relationship between the percent change of myosin heavy chain (MHC) I and MHC IIa single-fiber distribution (SF-MHC) after aerobic exercise training in older women (R2 = .92, p < .05).
See this image and copyright information in PMC

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