Using TH immunostaining in the nigrostriatal pathway, we found that the percentage of TH-positive cells in the SN of HFD mice was significantly less as compared to that in the controls (Figure 3A) (67.9 ± 1.5% vs. 90.3 ± 1.6%, respectively, p < 0.001), indicating that the HFD could indeed reduce the number of nigral DA neurons, which is the main pathology of PD. Here, TH is linked to Parkinson disease.