[Aging-related frailty and sarcopenia. Frailty/sarcopenia and insulin/IGF-1 signaling.].

Insulin and IGF-1 share many of the downstream molecules involved in the signal transduction, and cooperatively maintain volume of skeletal muscle. Along with aging, however, insulin/IGF-1 signaling is impaired, mainly due to insulin resistance and lowered IGF-1 levels, which is thought to promote the development of sarcopenia, and thus they are among the promising therapeutic targets. It is also known that sarcopenia is associated with the development of frailty, one of the phenomena of systemic aging. Actually insulin/IGF-1 signaling is known to affect longevity in lower organisms, but in humans, little is known about roles of the signaling in the development of frailty, and further investigation is needed.