Ibandronate concomitantly blocks immobilization-induced bone and muscle atrophy

Area of Science:

• Biomedical Science
• Pharmacology
• Cell Biology

Background:

• Immobilization leads to simultaneous bone and muscle volume loss.
• No current drug effectively targets both conditions concurrently.
• Bisphosphonates are known to inhibit bone resorption but their muscle effects are unclear.

Purpose of the Study:

• To investigate the effects of bisphosphonates, specifically ibandronate (IBN), on muscle atrophy.
• To determine if IBN can prevent both bone and muscle loss during immobilization.
• To elucidate the mechanism by which IBN affects muscle cells.

Main Methods:

• In vivo studies using a mouse model of muscle atrophy induced by immobilization.
• In vitro studies using C2C12 myogenic cells subjected to serum starvation.
• Analysis of atrogene expression (Atrogin-1, MuRF1) and protein accumulation.
• Treatment with ibandronate (IBN) and MG132 (ubiquitin/proteasome inhibitor).

Main Results:

• IBN administration significantly inhibited muscle volume reduction and the induction of atrogenes Atrogin-1 and MuRF1 in vivo.
• IBN treatment also prevented immobilization-induced bone loss in vivo.
• In vitro, IBN inhibited serum starvation-induced expression of Atrogin-1, MuRF1, and Smad2/3 accumulation in C2C12 cells.
• IBN's effects on C2C12 cells were blocked by MG132, indicating involvement of the ubiquitin-proteasome system.

Conclusions:

• Skeletal muscle is a direct target of ibandronate (IBN).
• IBN effectively prevents muscle atrophy and bone loss associated with immobilization.
• IBN likely functions through the ubiquitin-proteasome pathway to inhibit muscle wasting.