Sarcopenia, frailty and type 2 diabetes mellitus (Review).

Skeletal muscle is the largest and most energy‑consuming organ in the human body, which plays an important role in energy metabolism and glucose uptake. There is a notable decrease in glucose uptake in the skeletal muscle of patients with type 2 diabetes mellitus (DM). Endurance exercise can reduce hyperglycemia and improve insulin resistance in patients with type 2 DM. Insulin exerts a variety of effects, many of which are mediated by Akt, including increasing glucose uptake, promoting glycogen synthesis and inhibiting glycogen degradation, increasing free fatty acid uptake, increasing protein synthesis, promoting muscle hypertrophy and inhibiting protein degradation. Skeletal muscle mass progressively declines with aging, resulting in loss of muscle strength and physical function. Sarcopenia is a syndrome characterized by loss of skeletal muscle mass and muscle weakness or loss of physical function, and frailty is another syndrome that has received great interest in recent years. Decreased organ function results in vulnerability to external stress. Frailty is associated with falls, fractures and hospitalization; however, there is the reversibility of returning to a healthy state with appropriate interventions. Frailty is classified into three subgroups: Physical frailty, social frailty and cognitive frailty, whereby sarcopenia is the main component of physical frailty. The present review discusses the associations between sarcopenia, frailty and type 2 DM based on current evidence.