Role of apelin as a biomarker in functional recovery and post-stroke-associated sarcopenia: insights from rehabilitation therapy

Background Skeletal muscles play critical roles in mobility, respiratory function, and metabolic regulation by releasing myokines. Age-related sarcopenia, characterized by the loss of muscle mass and function, exacerbates health outcomes, including disability and mortality. Stroke survivors are particularly vulnerable to muscle wasting, known as stroke-related sarcopenia, which affects their recovery and quality of life. This study aimed to investigate the effects of rehabilitation on apelin expression, clinical outcomes, and psychosocial well-being in stroke survivors. Methods This single-center observational study enrolled 23 patients with stroke who underwent rehabilitation. Outcome measures included apelin concentration using enzyme-linked immunosorbent assay, cytokine profiling, skeletal muscle index (SMI), phase angle, grip strength, balance, functional scores (Modified Barthel Index, Berg Balance Scale), and psychosocial measures (SF-12, Fatigue Severity Scale). Data were collected at baseline and discharge after 4–6 weeks of rehabilitation. Results Apelin levels increased significantly after rehabilitation (46.81–59.23 ng/mL, p < 0.001) and correlated with improved SMI (6.67–7.11 kg/m 2 , p = 0.0035) and functional outcomes ( p < 0.001). Significant changes in the cytokine profiles highlighted exercise-induced anti-inflammatory responses. Psychosocial assessments revealed reduced fatigue and improved quality of life ( p < 0.001). Conclusion Stroke patient rehabilitation enhanced apelin expression, skeletal muscle mass, and functional recovery. Therefore, apelin may serve as a biomarker to monitor muscle health and rehabilitation outcomes.