Abstract Myostatin ( MSTN ) is a member of the transforming growth factor-β superfamily of cytokines and is a negative regulator of skeletal muscle mass. Compared with MSTN +/+ mice, the extensor digitorum longus muscles of MSTN −/− mice exhibit hypertrophy, hyperplasia, and greater maximum isometric force production (F o ), but decreased specific maximum isometric force (sF o ; F o normalized by muscle cross-sectional area). The reason for the reduction in sF o was not known. Studies in myotubes indicate that inhibiting myostatin may increase muscle mass by decreasing the expression of the E3 ubiquitin ligase atrogin-1, which could impact the force-generating capacity and size of muscle fibers. To gain a greater understanding of the influence of myostatin on muscle contractility, we determined the impact of myostatin deficiency on the contractility of permeabilized muscle fibers and on the levels of atrogin-1 and ubiquitinated myosin heavy chain in whole muscle. We hypothesized that single fibers from MSTN −/− mice have a greater F o , but no difference in sF o , and a decrease in atrogin-1 and ubiquitin-tagged myosin heavy chain levels. The results indicated that fibers from MSTN −/− mice have a greater cross-sectional area, but do not have a greater F o and have a sF o that is significantly lower than fibers from MSTN +/+ mice. The extensor digitorum longus muscles from MSTN −/− mice also have reduced levels of atrogin-1 and ubiquitinated myosin heavy chain. These findings suggest that myostatin inhibition in otherwise healthy muscle increases the size of muscle fibers and decreases atrogin-1 levels, but does not increase the force production of individual muscle fibers. growth differentiating factor-8 permeabilized muscle fiber contractility atrogin-1 muscle atrophy F-box Copyright © 2011 the American Physiological Society
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Decreased specific force and power production of muscle fibers from myostatin-deficient mice are associated with a suppression of protein degradation
Mendias, Christopher L.; Kayupov, Erdan; Bradley, Joshua R.; Brooks, Susan V.; Claflin, Dennis R.
Follow Journal of Applied Physiology
, Volume 111 (1): 185
The American Physiological Society – Jul 1, 2011
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