Determinants of disuse-induced skeletal muscle atrophy: exercise and nutrition c

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J Nutr Sci Vitaminol (Tokyo). 2006 Aug;52(4):233-47.

Determinants of disuse-induced skeletal muscle atrophy: exercise and

nutrition countermeasures to prevent protein loss.

Bajotto G, Shimomura Y.

Department of Materials Science and Engineering, Shikumi College,

Nagoya Institute of' Technology, Gokiso-cho, Showa-ku, Nagoya 466-8

555, Japan.

Muscle atrophy results from a variety of conditions such as disease

states, neuromuscular injuries, disuse, and aging. Absence of

gravitational loading during spaceflight or long-term bed rest

predisposes humans to undergo substantial loss of muscle mass and,

consequently, become unfit and/or unhealthy.

Disuse- or inactivity-induced skeletal muscle protein loss takes

place by differential modulation of proteolytic and synthetic

systems. Transcriptional, translational, and posttranslational

events are involved in the regulation of protein synthesis and

degradation in myofibers, and these regulatory events are known to

be responsive to contractile activity.

However, regardless of the numerous studies which have been

performed, the intracellular signals that mediate skeletal muscle

wasting due to muscular disuse are not completely comprehended.

Understanding the triggers of atrophy and the mechanisms that

regulate protein loss in unloaded muscles may lead to the

development of effective countermeasures such as exercise and

dietary intervention. The objective of the present review is to

provide a window into the molecular processes that underlie skeletal

muscle remodeling and to examine what we know about exercise and

nutrition countermeasures designed to minimize muscle atrophy.