Molecular insights into human soleus muscle atrophy development: long-term dry immersion effects on the transcriptomic profile and post-translational signaling.

Muscle disuse results in complex signaling alterations followed by structural and functional changes, such as atrophy, force decrease and slow-to-fast fiber-type shift. Little is known about human skeletal muscle signaling alterations under long-term muscle disuse. In this study, we describe the effects of 21-day dry immersion on human postural soleus muscle. We performed both transcriptomic analysis and Western blots to describe the states of the key signaling pathways regulating soleus muscle fiber size, fiber-type, and metabolism. 21-day dry immersion resulted in both slow-type and fast-type myofibers atrophy, downregulation of rRNA content, and mTOR signaling. 21-day dry immersion also leads to slow-to-fast fiber-type and gene expression shift, upregulation of p-eEF2, p-CaMKII, p-ACC content and downregulation of NFATc1 nuclear content. It also caused massive gene expression alterations associated with calcium signaling, cytoskeletal parameters, and downregulated mitochondrial signaling (including fusion, fission, and marker of mitochondrial density).