Microbiota-mediated enhancement of the chondroprotective effects of epimedium polysaccharides: Insights from fermentation and zebrafish models.

The health benefits of dietary polysaccharides as functional macromolecules have attracted increasing attention, yet their digestive fate, fermentability, and biological relevance after microbial transformation remain incompletely understood. In the present study, we systematically investigated the gastrointestinal digestion resistance, gut microbial fermentation behavior, and chondroprotective potential of Epimedium polysaccharides (EPs). Simulated salivary-gastrointestinal digestion demonstrated that EPs exhibited high resistance to enzymatic hydrolysis, indicating that a substantial proportion of EPs may resist upper gastrointestinal digestion and become available for microbial transformation in the colon. In vitro fecal fermentation revealed that EPs underwent substantial microbial transformation, accompanied by marked polysaccharide degradation, progressive acidification of the fermentation system, and dynamic production of short-chain fatty acids (SCFAs), including acetate, propionate, and butyrate. Microbial community analysis showed time-dependent alterations in bacterial composition during fermentation, including changes in carbohydrate-utilizing bacterial taxa. The biological significance of fermentation-associated transformation was further evaluated using zebrafish models of cartilage development and chemically induced cartilage injury. Fermented EPs exhibited substantially enhanced chondroprotective activity compared with unfermented EPs, with the 6 h-fermented sample showing the strongest effects among the tested fermentation stages. Although the SCFAs mixture partially reproduced the protective effects, its efficacy was lower than that of fermented EPs, suggesting that SCFAs may contribute to, but do not fully account for, the enhanced bioactivity. Furthermore, cellular evaluation using an H2O2-induced chondrocyte injury model demonstrated that 6 h-fermented EPs promoted extracellular matrix synthesis and suppressed cartilage degradation-associated responses, providing preliminary mechanistic insights into their chondroprotective effects. Collectively, this study demonstrates that gut microbial fermentation enhances the biological activity of Epimedium polysaccharides and highlights the contribution of fermentation-associated transformation, accompanied by microbial metabolite production and community changes, to their cartilage-protective potential. These findings provide new insights into the functional potential of plant-derived polysaccharides in the context of joint and musculoskeletal health.