Fructooligosaccharides and Aspergillus enzymes increase brain GABA and homocarnosine by modulating microbiota in adolescent mice

Recent research suggests that dietary prebiotics, probiotics, or healthy fecal-microbiota transplantation attenuate gut microbiota dysbiosis and ameliorate neurological disorders, in which gut-microbiota-derived γ-aminobutyric acid (GABA) has gained much attention as one of key mediators in the gut-brain axis. Although it is widely accepted that prebiotics and probiotics induce gut and brain GABA production via modulating gut microbiota, only evidence of probiotics has been solidly demonstrated while this evidence of prebiotics is scarce. Here, we demonstrated that prebiotic fructo-oligosaccharides and Aspergillus-derived enzymes elevated gut and brain GABA concentrations by modulating gut microbiota. Interestingly, we found that the prebiotic and enzymes increased a brain-specific dipeptide, homocarnosine. Gut GABA levels were found correlated with brain GABA/homocarnosine levels. Parabateroides, Akkermansia, Muribaculum, Hungatella, Marvinbryantia, Flavonifractor, and Incertae_sedis exhibited a positive correlation with gut GABA and brain GABA/homocarnosine levels, while Blautia, Unclassified_Lachnospiraceae, Colidextribacter, Acetatifactor, Roseburia, Unclassified_Oscillospiraceae, Romboutsia, and Eubacterium_coprostanoligenes exhibited a negative correlation with those levels.