Abstract

The scientific evidence regarding the use of plant-derived extracts to alleviate exercise-induced muscle damage in horses remains limited. Mulberry leaf flavonoids (MLFs) are the primary bioactive constituents of a traditional medicinal plant and are potent antioxidants. The aim of this study was to investigate the protective effects of MLFs against exercise-induced muscle damage. In this study, twelve Mongolian horses were used in a 3 × 3 Latin square design to investigate the protective effects of MLFs. Our results showed that high-intensity exercise negatively impacted the immune status, metabolic state, myofibrillar structure, and antioxidant capacity of the horses. Conversely, MLFs significantly reduced blood levels of white blood cells (WBC), monocytes (MON), aspartate aminotransferase (AST), creatine kinase (CK), and malondialdehyde (MDA) across various exercise distances and during recovery. Simultaneously, MLFs increased serum glutathione peroxidase (GPx), superoxide dismutase (SOD), and total antioxidant capacity (T-AOC). Mechanistically, transcriptomic analysis revealed that dietary MLFs upregulated genes associated with myofibrillar structural proteins (MYOZ2, MYOM3), the antioxidant defense system (GPX3, SOD3), and skeletal muscle satellite cell proliferation and differentiation (MYOD1, MRF6). Furthermore, quantitative proteomics indicated the enrichment of the PI3K-Akt and TGF-β signaling pathways, as well as ECM–receptor interactions, suggesting their potential involvement in regulating protein metabolism and facilitating myofibrillar restoration. Overall, MLFs effectively alleviated inflammation, metabolic disorder, and exercise-induced muscle damage. Under the tested conditions, a daily dosage of 10 g MLFs provided superior protective effects.

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