FNDC5 and sarcopenia: On the other hand, increased expression and secretion of myokines such as fractalkine, osteoprotegerin, chitinase-3-like protein 1, irisin, and FST by insulin-resistant inflamed human myotubes may represent an autoprotective mechanism counteracting inflammation, insulin resistance, beta cell dysfunction, and sarcopenia (8, 40, 41, 43, 52).