White kidney bean episperm polysaccharides improve cognitive impairment in D-galactose-induced aging mice via modulation of oxidative stress, neuroinflammation, and the gut-brain axis.

White kidney bean (Phaseolus vulgaris L.) episperm is an abundant by-product of legume processing that contains a distinct class of non-digestible polysaccharides with high resistance to small intestinal hydrolysis. These features confer unique fermentability and the potential to modulate gut microbial ecology. Given emerging links between age-related cognitive decline, oxidative stress, inflammation, and gut microbiota dysbiosis, whether dietary white kidney bean episperm polysaccharides (WKBEP) could alleviate cognitive impairment in a D-galactose-induced aging mouse model was investigated. WKBEP supplementation significantly improved spatial learning and memory. It also preserved hippocampal neuronal morphology. These effects were associated with enhanced antioxidant capacity, attenuation of neuroinflammatory signaling, and suppression of apoptosis-related markers. In parallel, WKBEP reshaped gut microbial composition and increased the production of short-chain fatty acids. Collectively, these findings highlight WKBEP as a promising functional dietary fiber and provide a mechanistic basis for its potential application in mitigating aging-associated cognitive decline.