IGF1 and sarcopenia: Mammalian target of rapamycin complex 1 regulates protein synthesis by integrating many intracellular signals for degradation.[34] As mentioned above, one of the reasons why sarcopenia occurs is reduced muscle synthesis; insulin-like growth factor-1 activates the intracellular signaling pathway of phosphatidylinositol 3-kinase and protein kinase B and further activates downstream mammalian target of rapamycin, which enhances protein synthesis.[35–37]