In conclusion, the current study indicated that OCN could ameliorate motor deficits and dopaminergic neuronal loss in PD mice, modulating gut microbiome and increasing propionate level could constitute an underlying mechanism responsible for the neuroprotective effects of OCN in PD, and that FFAR3 in the ENS might mediate the neuroprotective effect of propionate in PD. This evidence concerns the gene FFAR3 and Parkinson disease.