Fig. 2

Relationship between the degree of nigrostriatal lesion and diet. A TH⁺ cell count in substantia nigra (SN) of sham- and 6-OHDA-lesioned mice fed either CTRL diet or HFD (CTRL diet: n = 14, HFD: n = 11). Data are expressed as percentage of remaining ipsilateral TH⁺ cells of contralateral mean TH⁺ cell count of the sham/CTRL diet group. The cut-off value between the moderate lesion and severe lesion was 18.6% of TH + remaining cells. Two-tailed Student’s t-test: n.s. not significant. B Linear regression analysis between the percentage of remaining TH⁺ cells and HOMA-IR in HFD-fed mice. The cut-off value for insulin resistance was 0.82 separating severely and moderately lesioned mice and corresponding to 18.6% remaining TH + cells. C TH⁺ cell count in SN depicted in the sham, moderate, and severe lesion groups fed either CTRL diet or HFD. Data are expressed as percentage of remaining ipsilateral TH⁺ cells of contralateral mean TH⁺ cell count of the sham/CTRL diet group. D Striatal TH⁺ and E striatal DAT⁺ fiber density of the sham, moderate, and severe lesion groups, fed either CTRL diet or HFD. Data are expressed as percentage of remaining ipsilateral TH⁺ or DAT⁺ fiber density of contralateral mean TH⁺ or DAT⁺ fiber density of the sham/CTRL diet group. F Representative brightfield images showing different degrees of dopaminergic neuron loss in SN in CTRL diet and HFD groups. G, H Representative brightfield images showing striatal TH⁺ and DAT⁺ fiber density in CTRL diet and HFD groups, respectively. Sham (CTRL diet: n = 5, HFD: n = 4), moderate lesion (CTRL diet: n = 3, HFD: n = 3), severe lesion (CTRL diet: n = 6, HFD: n = 4). Two-way ANOVA: **p < 0.01, ***p < 0.001, ****p < 0.0001; n.s. not significant. Scale bar 200 μm. DAT dopamine transporter, TH tyrosine hydroxylase, CTRL diet control diet, HFD high-fat diet