GCG and Parkinson disease: GLP-1 is known to have neuroprotective properties that are disease-modifying in models of PD (Bertilsson et al., 2008; Kim et al., 2009; Li et al., 2009, 2020; Yun et al., 2018; Fang et al., 2020; Salles et al., 2020; Zhang et al., 2020; Wang et al., 2021).