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 ofmyokines, which is directly involved in body mass composition balance, chronic diseases susceptibility andphysiologic resilience to stressful events, including surgery. In the context of musculoskeletal disease, therole of this molecule has been associated to the balance of lean and fatty mass, and the production of irisin issubordinated to a healthy lifestyle and exercise. The mechanism of action of irisin on tissues is complex, andseveral studies described the molecular pathways in animal model and human subjects. In particular, inadipose cells, the key-role of irisin is to stimulate the differentiation of white adipose tissue to brown adiposetissue, through the action on the uncoupling protein 1. Furthermore, in the bony tissue, irisin stimulatesosteogenesis through expression of Sost and Opn genes. These features make irisin a suitable molecule to useas 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 predictivevalue of irisin in a multidisciplinary approach to the elderly before musculoskeletal surgery.