Abstract
Exercise-preconditioning attenuates muscle atrophy due to hindlimb suspension (HS). However, the molecular mechanism by which exercise-preconditioning exerts these effects remains poorly understood. The present study investigated whether exercise-preconditioning attenuates HS-induced muscle atrophy via inhibition of the ubiquitin-proteasome pathway and whether heat shock protein (HSP) mediates this inhibition in rat soleus muscle.
Rats were randomized to the following groups: 2-wk HS, treadmill running before 2-wk HS, and aged-matched control. HS-induced atrophy was associated with increased proteolysis (decreased myofibrillar protein), upregulation of components of the ubiquitin-proteasome pathway (ubiquitin ligase E3 mRNA activity) and downregulation of HSP72 mRNA in the soleus muscle. However, exercise-preconditioning attenuated HS-induced atrophy and reduced ubiquitin ligase E3 mRNA. Furthermore, exercise-preconditioning did not decrease HSP72 mRNA.
These findings suggest that exercise-preconditioning attenuates HS-induced atrophy through muscle-specific inhibition of the ubiquitin-proteasome pathway, and is an effective countermeasure to muscle atrophy induced by HS.
