Structural characterization and the protective effects of green walnut husk polysaccharides by modulating inflammation and gut microbiota for inflammatory bowel disease.

An acidic polysaccharide, designated GWHP, was isolated from the husk of Juglans regia L. (green walnut husk). Its protective activity and anti-inflammatory mechanisms were systematically investigated using lipopolysaccharide (LPS)-induced MODE-K cell model and dextran sulfate sodium (DSS)-induced colitis in mice. Structural characterization revealed that GWHP consisted of galacturonic acid (76.2%), galactose (8.5%), arabinose (7.4%), rhamnose (6.5%), and fucose (1.4%), with an average molecular weight of 108 kDa. GWHP administration significantly enhanced the activities of antioxidant enzymes including GSH-Px, SOD, CAT, while reduced the malondialdehyde accumulation. In LPS-induced MODE-K cells, GWHP efficiently downregulated the secretion of pro-inflammatory cytokines (IL-1β, TNF-α, and IL-6) and promoted the release of the anti-inflammatory cytokine IL-10. In the DSS colitis model, GWHP administration effectively improved colonic physiological indices. Histopathological analysis further verified its dose-dependent efficacy in repairing colonic tissue damage. Furthermore, GWHP rebalanced systemic inflammatory responses by significantly reducing serum pro-inflammatory cytokines levels (TNF-α, IL-1β and IL-6) and upregulating the expression of anti-inflammatory IL-10. In addition, GWHP also rescued gut microbial diversity and community structure, specifically enriching the relative abundance of Lactobacillaceae and inhibiting the growth of opportunistic pathogens in Enterobacteriaceae. Network pharmacology analysis further verified stable binding affinity between GWHP and dopamine receptor D2, providing clues to its underlying molecular mechanism. In conclusion, GWHP can efficiently alleviate intestinal inflammatory injury, maintain gut microbiota homeostasis, and restore intestinal barrier function. These findings suggest that GWHP holds great potential as a natural functional food ingredient or preventive agent for the intervention of inflammatory bowel disease.