Gut Microbiota Metabolite, Trimethylamine N-Oxide, Aggravates Cognitive Impairment in Cerebral Ischemia–Reperfusion Injury

Purpose: Cerebral ischemia–reperfusion injury (CIRI) causes neuronal inflammation, oxidative stress, and cognitive impairment. We hypothesized that gut microbiota dysbiosis exacerbates post-ischemic cognitive deficits, with trimethylamine N-oxide (TMAO) acting as a potential mediator. Methods: In the primary experiment, mice received an antibiotic cocktail for 28 days to induce gut dysbiosis prior to bilateral common carotid artery occlusion (BCCAO), a model of CIRI (n = 12 per group). Gut microbial composition was analyzed using 16S rRNA sequencing, and cognitive function was assessed with the Morris water maze. Functional enrichment analyses (Kyoto Encyclopedia of Genes and Genomes and Clusters of Orthologous Groups) and microbiota–metabolite database mapping were used to identify candidate metabolites. In a separate validation cohort (n = 6 per group), TMAO (6.5 mg/day) was administered intraperitoneally for 7 days before BCCAO. Results: Antibiotic treatment markedly altered microbial diversity and composition, characterized by an expansion of Proteobacteria and a reduction in Lactobacillus. Bioinformatic analyses identified TMAO, a metabolite associated with Proteobacteria/Enterobacteria, as a potential mediator. Mice with antibiotic-induced dysbiosis subjected to CIRI exhibited impaired spatial memory, as indicated by fewer platform crossings and reduced time spent in the target quadrant. Similarly, TMAO pretreatment reproduced these cognitive deficits in BCCAO mice. Conclusion: Antibiotic-induced gut dysbiosis appears to exacerbate CIRI-related cognitive impairment, at least in part through elevated TMAO levels. These findings highlight a potential microbiota–metabolite axis as a target for therapeutic intervention.