<scp>UHPLC</scp> – <scp>MS</scp> based metabolomics study of the <scp>ErZhi</scp> formula on skeletal muscle against osteosarcopenia focusing on energy metabolism

BACKGROUND: The ErZhi formula (EZF) exhibits sound therapeutic effects on osteosarcopenia (OS). However, EZF's therapeutic effects on skeletal muscles are rarely reported. This study explored the mechanism of EZF in skeletal muscle during OS by integrating energy metabolism and metabolomics. METHODS: After an ovariectomized rat model was established for 4 weeks, the rats were subjected to a 12-week intervention of EZF and alendronate. The rats' body weight, gastrocnemius muscle mass, degree of myofiber fibrosis, and myofiber cross-sectional area (CSA) were measured to evaluate the pathological state of the gastrocnemius muscle. The mitochondrial membrane potential and reactive oxygen species (ROS) levels were detected to assess mitochondrial function. Then, energy metabolite analysis and metabolomics were performed on the gastrocnemius muscle. RESULTS: Compared to the model group, EZH increased CSA by 5.58% and decreased myofiber fibrosis by 15.11%. Notably, compared to the model group, EZH exhibited a 52.66% increase in mitochondrial membrane potential and a 44.32% reduction in ROS levels. Starch and sucrose metabolism, insulin secretion, insulin resistance, and galactose metabolism were the most significantly affected pathways in energy metabolism. Thirty-five differential metabolites were found in the metabolomics of the gastrocnemius muscle, and EZF could effectively inhibit the sphingolipid metabolism pathway. Correlation analysis identified 13 differential metabolites that were significantly associated with skeletal muscle mass, ROS production, muscle fibrosis, and mitochondrial function, suggesting that these metabolites may play important roles in the progression of skeletal muscle lesions. CONCLUSIONS: EZF alleviates OS by regulating skeletal muscle physiological indicators, mitochondrial function, and energy metabolism.