Abstract: To investigate the mechanism by which ergosterol (Erg) protects against muscle atrophy, this study established a mouse model of dexamethasone (Dex)-induced muscle atrophy. Muscle function was evaluated using histopathology (hematoxylin-eosin staining and immunohistochemistry), grip strength tests, and exhaustive swimming tests. Key targets were selected via network pharmacology, molecular docking, molecular dynamic simulations, and surface plasmon resonance technology. Alterations in the gut microbiota were analyzed using 16S rRNA sequencing and short-chain fatty acid (SCFA) quantification, and the role of the gut microbiota was validated through fecal microbiota transplantation (FMT). The results showed that Erg significantly ameliorated Dex-induced reductions in gastrocnemius muscle mass, muscle strength, and cross-sectional area of muscle fibers, decreased atrogin-1 protein expression and creatine kinase activity, and enhanced total antioxidant capacity and catalase activity. Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis combined with network pharmacology revealed that the peroxisome proliferator-activated receptor (PPAR) signaling pathway was the primary pathway, with PPAR-α identified as the core target in this signaling pathway by protein-protein interaction network screening. Molecular docking and dynamics simulations confirmed a strong binding affinity between Erg and PPAR-α (3.12 × 10 -6 kcal/mol). Furthermore, 16S rRNA sequencing demonstrated that Erg restored gut microbiota diversity, increased the Firmicutes/Bacteroidota ratio, and significantly restored the levels of SCFAs such as acetic and propionic acids. FMT experiments verified that transplantation of the microbiota from Erg-treated mice replicated the aforementioned muscle-protective effects. In conclusion, Erg exerts anti-muscle atrophy effects through a dual mechanism: at the molecular level, it activates the PPAR-α signaling pathway to suppress atrogin-1 expression, optimize energy metabolism, and alleviate oxidative stress; at the microecological level, it reshapes gut microbiota composition, enhances SCFA production, and consequently improves muscle function via the gut-muscle axis. This study provides an experimental basis for the development of sterol-based functional foods and nutritional interventions against muscle atrophy.

Key words: ergosterol; muscle atrophy; peroxisome proliferator activated receptors signaling pathway; short-chain fatty acids; 16S rRNA microbiomics