INS and diabetes mellitus: Additionally, basic research has demonstrated that mice with brain IR show impaired dopamine transport function (Sharma and Taliyan, 2018), and MPTP-modeled mice show impaired insulin signaling in the substantia nigra (Bousquet et al., 2012; Kao et al., 2019), with diabetes and PD sharing common pathway damage (Labandeira et al., 2022).