Autophagy is required to maintain muscle mass

Area of Science:

• Cellular Biology
• Muscle Physiology
• Molecular Biology

Background:

• The ubiquitin-proteasome and autophagy-lysosome pathways are key for cellular waste removal.
• Both pathways are regulated by FoxO transcription factors in skeletal muscle, and their overactivation leads to muscle wasting.
• While autophagy alterations are noted in myopathies, its specific function in skeletal muscle requires clarification via loss-of-function studies.

Purpose of the Study:

• To investigate the specific role of autophagy in skeletal muscle maintenance and function.
• To determine the consequences of impaired autophagy in muscle tissue.

Main Methods:

• Muscle-specific deletion of the autophagy gene Atg7 in mice.
• Analysis of muscle mass, force production, and ultrastructure in Atg7-deficient muscles.
• Assessment of autophagy inhibition effects under conditions of denervation and fasting.

Main Results:

• Muscle-specific Atg7 deletion led to significant muscle atrophy and age-dependent force decline.
• Atg7 null muscles exhibited accumulation of damaged mitochondria, sarcoplasmic reticulum distension, and sarcomere disorganization.
• Impaired autophagy worsened muscle loss during denervation and fasting, confirming its importance in muscle preservation.
• Aberrant concentric membranous structures were observed in Atg7-deficient muscle fibers.

Conclusions:

• Autophagy flux is essential for preserving skeletal muscle mass and myofiber integrity.
• Defective autophagy contributes to myofiber degeneration and weakness in muscle disorders characterized by mitochondrial and other inclusions.
• Targeting autophagy may offer therapeutic potential for certain myopathies.