Characterization of Purified Mulberry Leaf Glycoprotein and Its Immunoregulatory Effect on Cyclophosphamide-Treated Mice.

Mulberry leaf protein is a potentially functional food component and health care agent with antioxidant and anti-inflammatory properties. However, its composition, immunoregulatory effects, and gut microbial regulatory effects are unclear. Herein, ultra-filtrated and gel-fractionated mulberry leaf protein (GUMP) was characterized. Its effects on cyclophosphamide-induced immunosuppressed mice were further investigated. The results indicated that GUMP is a glycoprotein mainly containing glucose, arabinose, and mannose with 9.23% total sugar content. Its secondary structure is mainly β-sheet. LC-MS/MS analysis showed that GUMP closely matched with a 16.7 kDa mannose-binding lectin and a 52.7 kDa Rubisco's large subunit. GUMP intervention significantly improved serous TNF-α, IL-6, and IL-2 contents; increased serum immunoglobulins (IgA and IgG) levels; and reversed splenic damage prominently. Moreover, GUMP administration increased fecal shot-chain fatty acid concentration and up-regulated the relative abundance of Odoribacter , which was positively correlated with SCFAs and cytokine contents. Overall, GUMP alleviated immunosuppression through the integrated modulation of the gut microbiota and immune response. Therefore, GUMP could be a promising dietary supplement to help maintain gut health.