INS and sarcopenia: ↑ gastrocnemius and soleus muscle mass; ↓ sarcopenia-related markers (HDAH4, MyoD, myogenin, myostatin, MURF1, Atrogin-1); ↑ MyHC isoforms; ↑ PGC1α; ↑ anti-inflammatory cytokine IL-10; ↓ macrophage infiltration and ↑ insulin sensitivity in gastrocnemius muscle