Atractylodes macrocephala Koidz., a traditional Chinese medicine known for "strengthening the spleen and replenishing qi", has been recognized for its gastrointestinal protective and immunomodulatory properties, suggesting a potential role in gut-brain axis regulation. This study investigated the protective effect and underlying mechanism of a purified inulin-type polysaccharide from Atractylodes macrocephala, AMP1-1, against weightlessness-induced cognitive impairment via the microbiota-gut-brain axis. Using a tail-suspension rat model to simulate microgravity, we assessed: (i) cognitive function through behavioral tests; (ii) neuroinflammation and barrier integrity through histological staining, ELISA, and Western blot; and (iii) gut microbiota composition through 16S rDNA sequencing and metabolomics analysis. Fecal microbiota transplantation (FMT) and butyrate supplementation were employed to validate the causal contributions of gut microbiota and their metabolites. AMP1-1 administration significantly improved cognitive performance, inhibited hippocampal neuroinflammation via the TLR4/MyD88/NF-κB pathway, and enhanced the integrity of both intestinal and blood-brain barriers in suspended rats. It also reshaped the gut microbiota structure, elevated fecal butyrate levels, and reduced systemic lipopolysaccharide (LPS). FMT from AMP1-1-treated donors replicated the cognitive and barrier-protective effects in recipient rats, and butyrate supplementation similarly alleviated neuroinflammation and cognitive deficits. These findings demonstrate that AMP1-1 alleviates weightlessness-induced cognitive impairment by modulating the gut microbiota to promote butyrate production, thereby restoring gut and brain barriers, suppressing peripheral and central inflammation, and inhibiting the hippocampal TLR4/MyD88/NF-κB pathway. AMP1-1 emerges as a promising prebiotic-like agent for preventing neuroinflammation-related cognitive decline under microgravity conditions.
