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Am J Physiol Regul Integr Comp Physiol. 2011 Nov;301(5):R1400-7. doi: 10.1152/ajpregu.00093.2011. Epub 2011 Sep 7.

Skeletal muscle weakness due to deficiency of CuZn-superoxide dismutase is associated with loss of functional innervation.

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Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan 48109-2200, USA.


An association between oxidative stress and muscle atrophy and weakness in vivo is supported by elevated oxidative damage and accelerated loss of muscle mass and force with aging in CuZn-superoxide dismutase-deficient (Sod1(-/-)) mice. The purpose was to determine the basis for low specific force (N/cm(2)) of gastrocnemius muscles in Sod1(-/-) mice and establish the extent to which structural and functional changes in muscles of Sod1(-/-) mice resemble those associated with normal aging. We tested the hypothesis that muscle weakness in Sod1(-/-) mice is due to functionally denervated fibers by comparing forces during nerve and direct muscle stimulation. No differences were observed for wild-type mice at any age in the forces generated in response to nerve and muscle stimulation. Nerve- and muscle-stimulated forces were also not different for 4-wk-old Sod1(-/-) mice, whereas, for 8- and 20-mo-old mice, forces during muscle stimulation were 16 and 30% greater, respectively, than those obtained using nerve stimulation. In addition to functional evidence of denervation with aging, fiber number was not different for Sod1(-/-) and wild-type mice at 4 wk, but 50% lower for Sod1(-/-) mice by 20 mo, and denervated motor end plates were prevalent in Sod1(-/-) mice at both 8 and 20 mo and in WT mice by 28 mo. The data suggest ongoing denervation in muscles of Sod1(-/-) mice that results in fiber loss and muscle atrophy. Moreover, the findings support using Sod1(-/-) mice to explore mechanistic links between oxidative stress and the progression of deficits in muscle structure and function.

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