Serum irisin level is independent of sarcopenia and related muscle parameters in older adults

Accumulating evidence indicates that irisin, a myokine consisting of 112 amino acids, protects against muscle wasting in an autocrine manner; however, its impact on human muscle metabolism is still inconclusive. In this cross-sectional study, we aimed to investigate whether circulating irisin could be a potential biomarker reflecting muscle health in older adults.Comprehensive assessment of muscle mass; muscle function, including grip strength, gait speed, chair stand test, and short physical performance battery (SPPB); and muscle quality was performed in 143 older adults who visited outpatient geriatrics and endocrinology clinics. Sarcopenia was defined using the Asian-specific cutoff value. Blood samples were also collected to determine serum irisin concentration which was measured using enzyme immunoassay.The serum irisin level was not significantly different according to the status of sarcopenia, low muscle mass, weak muscle strength, poor physical performance, and poor muscle quality, before or after adjustment for age, sex, appendicular skeletal muscle (ASM), and body mass index. Consistently, the association of circulating irisin level with sarcopenia-related parameters (skeletal muscle index, grip strength, gait speed, chair stand test, SPPB, and grip strength/body weight or ASM) was not evident in any adjustment models.Despite the clear implication of irisin's involvement in muscle metabolism based on experimental research, we did not observe a definite association between its serum level and clinical muscle parameters in humans. These results suggest that the blood irisin level may not accurately predict the risk of sarcopenia in older adults.