In accordance with previous studies discovering the damage to the intestinal barrier in PD patients or PD animals [17,60], we observed decreased TJ protein expression in the distal colon, as well as increased content of diamine oxidase (DAO) and d-lactate (D-LA) in serum after MPTP administration, implying the dysfunction of the intestinal barrier in PD mice. The gene discussed is DAO; the disease is Parkinson disease.