Sulfated Fucooligosaccharides Ameliorated Neuroinflammation in D‑Galactose-Induced Aging Model Mice via the Gut–Brain Axis

This study was aimed to reveal the neuroprotective effect of sulfated fucooligosaccharides (FOS) in an aging mouse model induced by d-galactose. The results showed that FOS treatment ameliorated inflammation, improved behavioral decline in memory and cognition, and exerted neuroprotective effects. FOS reduced microglia activation by decreasing the expression of P38 mitogen-activated protein kinase (P38 MAPK), cyclic-AMP response binding protein (CREB), cyclooxygenase-2 (COX-2), and prostaglandin E2 (PGE2). In addition, FOS improved intestinal mucosal barrier damage and reduced the release of lipopolysaccharide. FOS increased the diversity of the gut flora and promoted a significant enrichment of the Akkermansia genus. FOS also increased the butyric acid level and reduced the expression of histone deacetylase 3 (HDAC3), Toll-like receptor 4 (TLR4), and nuclear factor kappa-B (NF-κB). Fecal microbiota transplantation from the FOS-treated mice showed a similar effect to FOS treatment in inhibiting neuroinflammation and reduced d-galactose-induced cognitive dysfunction. The results suggested that FOS supplementation ameliorated d-galactose-induced neuron damage and exerted neuroprotective effects through the gut–brain axis.