FMT significantly attenuates intestinal microbial metabolic disorders in PD mice, reduces intestinal inflammation and barrier disruption, attenuates BBB damage, reduces nigrostriatal microglia and astrocyte activation, inhibits neuroinflammation, and reduces gut and brain TLR4/TNF-α signaling pathway components, thereby protecting dopaminergic neurons and increasing striatal dopamine and 5-HT content [142, 196, 301]. Here, TLR4 is linked to Parkinson disease.