FBXO32 and Atrophy: To elucidate the mechanism of muscle atrophy in mice injected with IS, we first evaluated atrophy related gene expression associated with classic ubiquitin–proteasome pathways, such as myostatin and atrogenes (atrogin-1, and MuRF-1), which are involved in the pathomechanism of skeletal muscle atrophy in sarcopenia45.