Besides GLP1 receptor agonist, other oral glucose lowering drugs such as metformin, thiazolidinediones and DPP-4 inhibitors, as well as insulin have been tested in preclinical models or in small clinical studies and proven to be effective in the treatment of PD (Pang et al. 2016; Svenningsson et al. 2016; Novak et al. 2019; Brauer et al. 2020; Wang et al. 2024). Here, DPP4 is linked to Parkinson disease.