Frailty of the elderly in orthopaedic surgery and body composition changes: the musculoskeletal crosstalk through irisin

In recent years, scientific interest has been developed towards irisin, a novel molecule of the family of myokines, which is directly involved in body mass composition balance, chronic diseases susceptibility and physiologic resilience to stressful events, including surgery. In the context of musculoskeletal disease, the role of this molecule has been associated to the balance of lean and fatty mass, and the production of irisin is subordinated to a healthy lifestyle and exercise. The mechanism of action of irisin on tissues is complex, and several studies described the molecular pathways in animal model and human subjects. In particular, in adipose cells, the key-role of irisin is to stimulate the differentiation of white adipose tissue to brown adipose tissue, through the action on the uncoupling protein 1. Furthermore, in the bony tissue, irisin stimulates osteogenesis through expression of Sost and Opn genes. These features make irisin a suitable molecule to use as a biomarker of the overall musculoskeletal health of the elderly, before undergoing orthopaedic surgery. Further research on this topic should be carried out to highlight the possible clinical role and predictive value of irisin in a multidisciplinary approach to the elderly before musculoskeletal surgery.