Circulating Musclin is associated with skeletal muscle function and subclinical cardiac dysfunction in patients with cancer

Background and Purpose Musclin (osteocrin) is a skeletal muscle‐derived peptide that has been implicated in cardioprotective signalling pathways. Its relevance in cancer patients, who frequently experience muscle wasting and cardiotoxicity, remains unclear. This study aimed to determine whether circulating Musclin levels reflect functional capacity and cardiovascular risk in a cardio‐oncology population. Experimental Approach We prospectively evaluated circulating Musclin levels in cancer patients ( n = 69) undergoing standardised cardiovascular assessment during oncologic therapy. Echocardiographic measures of cardiac function, anthropometric and functional indices of muscle integrity, oncologic stage and clinical outcomes were analysed to identify associations with Musclin exposure over time. Key Results Lower circulating Musclin levels were associated with a reduced survival probability in exploratory analyses (log‐rank P = 0.046), decreased physical performance (hand grip strength), and features of advanced malignancy. Patients with higher cumulative Musclin levels showed significantly better cardiac functional parameters (global longitudinal strain) ( P = 0.031). Musclin serum concentrations also reflected indicators of skeletal muscle function that were not captured by weight‐based metrics. Conclusion and Implications Circulating Musclin may reveal information on skeletal muscle integrity and subclinical cardiac dysfunction, identifying cancer patients at increased functional and prognostic risk. These findings support Musclin as a biologically plausible and clinically relevant biomarker at the interface of muscle–heart signalling.