Discovery of serum APOD as an early sarcopenia biomarker in older adults with low muscle mass: a cross-sectional proteomic and transcriptomic investigation

Background: a cross-sectional study. Methods: In this cross-sectional study, serum samples from 50 older adults (25 with early sarcopenia and 25 healthy controls) were analyzed. In the discovery cohort (10 per group), proteomic sequencing was performed to identify differentially expressed proteins (DEPs). Candidate biomarker were subsequently validated using enzyme-linked immunosorbent assay (ELISA) in an independent validation cohort (15 per group). Furthermore, bioinformatics analyses, including functional enrichment and diagnostic evaluation, were conducted to elucidate the potential role of the identified targets. Results: in the modulation of key pathways, including the activation of the PI3K-Akt signaling pathway and the suppression of pathways related to cardiovascular function, suggesting its potential role in the metabolic dysregulation characteristic of early muscle decline. Conclusion: This study identifies and validates serum APOD as a biomarker associated with early sarcopenia, characterized by significantly elevated levels and demonstrating promising discriminative capacity at the group level between affected individuals and healthy controls.