Two weeks of one-leg immobilization decreases skeletal muscle respiratory capacity equally in young and elderly men

Sep 7, 2014Experimental gerontology

Two weeks of one-leg immobilization reduces muscle breathing ability similarly in young and older men

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Abstract

Elderly men (68±1 years) showed lower protein content of mitochondrial complexes I-V and heat shock protein 70 compared to young men (23±1 years).

Both young and elderly men experienced decreased respiratory capacity and protein content of mitochondrial complexes I, II, IV, V, and mtHSP70 after two weeks of immobilization.
Following six weeks of supervised cycle training, respiratory capacity and protein content of the same mitochondrial complexes increased in both age groups.
No significant differences in respiratory capacity or response to immobilization and training were observed between young and elderly men.
When adjusted for citrate synthase activity, the differences in respiratory capacity related to immobilization and training were not present.
Aging is not linked to a decrease in muscle respiratory capacity despite lower levels of mitochondrial protein content in elderly men.

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Physical inactivity affects human skeletal muscle mitochondrial oxidative capacity but the influence of aging combined with physical inactivity is not known. This study investigates the effect of two weeks of immobilization followed by six weeks of supervised cycle training on muscle oxidative capacity in 17 young (23±1years) and 15 elderly (68±1years) healthy men. We applied high-resolution respirometry in permeabilized fibers from muscle biopsies at inclusion after immobilization and training. Furthermore, protein content of mitochondrial complexes I-V, mitochondrial heat shock protein 70 (mtHSP70) and voltage dependent anion channel (VDAC) were measured in skeletal muscle by Western blotting. The elderly men had lower content of complexes I-V and mtHSP70 but similar respiratory capacity and content of VDAC compared to the young. In both groups the respiratory capacity and protein content of VDAC, mtHSP70 and complexes I, II, IV and V decreased with immobilization and increased with retraining. Moreover, there was no overall difference in the response between the groups. When the intrinsic mitochondrial capacity was evaluated by normalizing respiration to citrate synthase activity, the respiratory differences with immobilization and training disappeared. In conclusion, aging is not associated with a decrease in muscle respiratory capacity in spite of lower complexes I-V and mtHSP70 protein content. Furthermore, immobilization decreased and aerobic training increased the respiratory capacity and protein contents of complexes I-V, mtHSP70 and VDAC similarly in the two groups. This suggests that inactivity and training alter mitochondrial biogenesis equally in young and elderly men.

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Two weeks of one-leg immobilization decreases skeletal muscle respiratory capacity equally in young and elderly men

Abstract

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