Huangjing Yangji Decoction ameliorates skeletal muscle aging and mitochondrial dysfunction via SIRT1/ATF5-mediated mitochondrial unfolded protein response

• HJYJD ameliorates muscle atrophy and functional decline in aged mice. • HJYJD restores mitochondrial function and reduces oxidative stress. • HJYJD activates UPR mt via the SIRT1/ATF5 pathway. • UPR mt inhibition or SIRT1/ATF5 silencing abolishes HJYJD protective effects. Sarcopenia is a progressive age-associated disorder characterized by the loss of skeletal muscle mass, strength, and function. Mitochondrial dysfunction and impaired proteostasis are central to its pathogenesis, however, effective pharmacological interventions are currently lacking. Huangjing Yangji Decoction (HJYJD), a traditional Chinese medicinal formula, has demonstrated promising clinical benefits in managing age-related muscle atrophy, but its mechanisms remain unclear. This study aimed to investigate the therapeutic effects and underlying mechanisms of HJYJD in alleviating age-related sarcopenia. The chemical constituents of HJYJD were identified using UPLC-Q-TOF/MS. Aged SAMP8 mice and D-galactose-induced C2C12 myoblasts were used to evaluate the therapeutic effects of HJYJD. Behavioral assays, histological analysis, transmission electron microscopy, immunofluorescence, biochemical assays, western blotting, qRT-PCR, and mitochondrial function probes were employed to assess muscle function, myotube differentiation, cellular senescence, oxidative stress, and mitochondrial function. Untargeted metabolomics and transcriptomic sequencing were performed to explore regulatory pathways. Key molecular markers were validated by qRT-PCR, western blotting, and immunofluorescence. Furthermore, the role of the SIRT1/ATF5-mitochondrial unfolded protein response (UPR mt ) signaling axis was explored using siRNA-mediated knockdown and pharmacological inhibition. HJYJD significantly improved muscle mass, strength, coordination, and endurance in sarcopenic mice, and attenuated cellular senescence and muscle atrophy in myotubes. Treatment with HJYJD ameliorated oxidative stress, improved mitochondrial morphology, membrane potential, and ATP production. Multi-omics data revealed that HJYJD modulated key metabolic and protein folding pathways related to mitochondrial function. Mechanistically, HJYJD activated UPR mt , as evidenced by upregulation of ClpP, LONP1, HSP60, and HSP10. These effects were abolished upon UPR mt inhibition. Furthermore, HJYJD promoted the expression of SIRT1 and ATF5, and silencing of SIRT1/ATF5 suppressed UPR mt activation and mitochondrial restoration, indicating that SIRT1/ATF5 mediates HJYJD-induced UPR mt activation. HJYJD alleviates skeletal muscle aging and mitochondrial dysfunction by activating the SIRT1/ATF5-mediated UPR mt pathway. These findings offer novel mechanistic understanding of the therapeutic potential of HJYJD and support its further development as a promising intervention for sarcopenia.