Stat3 activation links a C/EBPδ to myostatin pathway to stimulate loss of muscle mass

Area of Science:

• Biochemistry
• Physiology
• Molecular Biology

Background:

• Catabolic conditions, such as chronic kidney disease (CKD), lead to muscle mass loss through incompletely understood mechanisms.
• Activated Signal Transducer and Activator of Transcription 3 (Stat3) was observed in muscle biopsies of CKD patients, suggesting its potential role in initiating muscle wasting.

Purpose of the Study:

• To investigate the role of activated Stat3 in initiating muscle wasting in catabolic conditions.
• To elucidate the molecular pathway through which Stat3 activation leads to muscle loss.

Main Methods:

• Generation of muscle-specific Stat3 knockout (KO) mice.
• Utilizing small-molecule inhibitors of Stat3 activation.
• Employing CCAAT/enhancer-binding protein δ (C/EBPδ) KO mice and C2C12 myotubes with C/EBPδ or myostatin knockdown.
• Analysis of muscle and body weights in disease models.
• Verification of molecular markers in human CKD patient muscle biopsies.

Main Results:

• Muscle-specific Stat3 KO mice exhibited suppressed body and muscle weight loss in CKD and acute diabetes models.
• A Stat3-inhibiting small molecule replicated these protective effects, indicating translational potential.
• The study identified a pathway where p-Stat3 stimulates C/EBPδ, which in turn upregulates myostatin, a negative regulator of muscle growth.
• C/EBPδ KO improved survival rates in CKD mice.
• Elevated levels of p-Stat3, C/EBPδ, and myostatin were confirmed in the muscles of CKD patients.

Conclusions:

• Activated Stat3 is a key initiator of muscle wasting in catabolic states like CKD.
• The identified Stat3-C/EBPδ-myostatin pathway represents a potential therapeutic target for preventing muscle wasting.
• Targeting this pathway could offer novel strategies for managing muscle loss in CKD and other catabolic conditions.