ESRRA and Atrophy: In states of physical inactivity and in diseases associated with muscle atrophy and mitochondrial dysfunction (e.g., amyotrophic lateral sclerosis and Duchene muscular dystrophy), where skeletal muscle PGC-1α and ERRα are reduced [39], PERM1 expression is also reduced [12,13,21], and PERM1 protein degradation is accelerated [25].