Moreover, as marketed GLP-1 analogs to treat T2DM are well-tolerated and rarely cause hypoglycemia, clinical trials have been undertaken to investigate the therapeutic effects of exendin-4 or liraglutide on Alzheimer’s disease (Egefjord et al., 2012; Gejl et al., 2016), and Parkinson’s disease patients (Aviles-Olmos et al., 2013; Athauda et al., 2017), and continue to be evaluated. Here, GCG is linked to Parkinson disease.