Modification of Soluble Dietary Fiber from Millet by Selenylation and Its Immune-Enhancing Activity

Abstract

The immune activity of polysaccharides increases after structural modification, whereas the structure of dietary fiber is similar to that of polysaccharides, and research on the chemical modification of dietary fiber is lacking. Therefore, in this study, we used soluble dietary fiber from millet to chelate metal selenium ions, named the selenium-enriched additive (SDF-Se), and investigated its effects on macrophages and natural killer (NK) cells in vitro. The results showed that SDF-Se could activate RAW 264.7 cells through NF-κB and mitogen-activated protein kinase (MAPK) signaling and promote the accumulation of the reactive oxygen species, thereby increasing the levels of TNF-α, IL-6, and IL-10 and releasing numerous NO molecules. Furthermore, SDF-Se treatment induced NK cells to secrete cytokines (IFN-γ and TNF-α), cytoplasmic granules (granzyme-B), surface-activating receptors (NKp44), and increased CD56 and CD107a expressions, which promote NK cell cytotoxic responses. These results suggest that SDF-Se can promote macrophage and NK cell activation and be used as a potent immunostimulant.