IGF1 and muscle atrophy: Skeletal muscle atrophy is known to be closely associated with the inactivation of anabolic-related mammalian target of rapamycin (mTOR) signal transduction and with activation of the catabolic-related muscle RING-finger protein-1 (MuRF-1) and Muscle Atrophy F-box gene (MAFbx1) axis, both of which are major protein metabolism targets located downstream of the insulin-like growth factor 1 (IGF-1)/insulin receptor substrates (IRSs) signaling pathway [12, 13].