Fig. 8

The interplay between the microbiota and the gut-brain axis in high-fat and fiber-deficient diet (HFFD) and β-glucan intervention. Gut microbiota contributes to regulating the gut-brain axis and maintaining health, while its alteration (decrease of Bacteroidetes and microbial diversity) due to HFFD is related to obesity and its adverse consequences on cognition (Steps 1–5). A β-glucan supplementation is thought to increase Bacteroidetes and gut microbiota (1), thereby, contribute to gut mucus and epithelial integrity and immune homeostasis (2); this attenuates the translocation of components of Gram-negative bacteria (3), which decreases the peripheral inflammatory tone and inhibits activation of microglia to neuroinflammation (4) and synapse engulfment in the CNS (5). Therefore, the supplement of β-glucan beneficially impacts on cognition, via restoration of gut microbiota and its regulatory role in the gut-brain axis