Elevated expression of activins promotes muscle wasting and cachexia

Area of Science:

• Biochemistry
• Molecular Biology
• Physiology

Background:

• Cancer cachexia involves muscle wasting and reduced survival.
• Type IIB activin receptors (ActRIIBs) are implicated in cancer cachexia models.
• Activins, signaling through ActRIIBs, are potent regulators of muscle mass.

Purpose of the Study:

• To investigate if elevated activin signaling alone, without tumor factors, induces cachexia.
• To elucidate the mechanisms by which activin A impacts muscle mass and function.

Main Methods:

• Used recombinant adeno-associated virus serotype 6 (rAAV6) vectors to increase circulating activin A in mice.
• Administered varying doses of rAAV6:activin A to C57BL/6 mice.
• Measured body mass changes, serum activin A levels, and molecular markers of muscle atrophy and synthesis.

Main Results:

• Increased activin A levels caused dose-dependent body mass loss in mice.
• Muscle wasting was linked to increased transcription of atrophy-related ubiquitin ligases.
• Decreased Akt/mTOR-mediated protein synthesis and a profibrotic response were observed.
• Muscle wasting and fibrosis induced by excess activin were fully reversible.

Conclusions:

• Activin A signaling via ActRIIB is sufficient to induce muscle wasting and cachexia-like symptoms.
• Targeting activins presents a potential therapeutic strategy for managing cancer cachexia.
• Reversibility of muscle wasting suggests potential for recovery even after significant loss.