GCG and Alzheimer disease: Various analogs of glucagon-like peptide-1 (GLP-1) have been examined for their potential in AD and PD, including those that activate receptors for a single type of incretin [single incretin receptor agonists—exenatide, liraglutide, lixisenatide, and semaglutide (SEM)] and those that activate receptors for both types of incretins (dual incretin receptor agonists—Peptide 19, DA4-JC, DA5-CH, DA3-CH) [12,13,14,15,16].