**Molecular Mechanisms Controlling Skeletal Muscle Mass**

Kunihiro Sakuma and Akihiko Yamaguchi

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/60876

#### **Abstract**

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The interplay between multiple signaling pathways regulates the maintenance of skeletal muscle. Under physiological conditions, a network of interconnected signals serves to coordinate hypertrophic and atrophic inputs, culminating in a delicate balance between muscle protein synthesis and proteolysis. Loss of skeletal muscle mass, termed "atrophy," is a diagnostic feature of cachexia such as cancer, heart disease, and chronic obstructive pulmonary disease. Recent studies have further defined the pathways leading to gain and loss of skeletal muscle as well as the signaling events that induce post-injury regeneration. In this review, we summarize the relevant recent literature demonstrating these previously undiscovered mediators governing anabolism and catabolism of skeletal muscle.

**Keywords:** Skeletal muscle, hypertrophy, atrophy, mTOR, autophagy, myostatin
