Moreover, butyrate intervention significantly suppressed the expression of inflammatory genes (Il1b, Il6, and Tnfa) in both gut and brain and ameliorated cognitive function (MWM test), depressive behavior (FS and splash tests), and anxiety (NC, and MB tests) in mice subjected to old FMT and effectively restored to their baseline states (Figure 5, G–M). Here, IL6 is linked to Anxiety.