Roles of autophagy in slow-twitch skeletal muscle

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To evaluate the role of autophagy in skeletal muscle atrophy, we subjected skeletal muscle specific Atg7 deficient(Atg7 KO) mice to denervation, a model of skeletal muscle atrophy. Soleus muscle, a slow-twitch skeletal muscle, from Atg7 KO mice maintained muscle mass, while Soleus muscle from control mice, and first-twitch muscles from both wild type and Atg7 KO mice were atrophied. In the denervated Soleus muscles from Atg7 KO mice, the reduction of mitochondrial activity, the accumulation of oxidative stress and the accumulation of Parkin in mitochondria were observed. Parkin participates for mitochondrial quality control(Parkin mediated mitophagy). To confirm whether Parkin mediated mitophagy is involved in the restoration of denervation atrophy in Atg7 KO Soleus muscle, we subjected Parkin deficient(Parkin KO) mice to denervation. Like Atg7 KO Soleus, denervated Soleus muscles from Parkin KO mice maintained muscle mass. These results indicate that Parkin mediated mitophagy is involved in denervation atrophy in slow-twitch skeletal muscles.