Furthermore, exendin-4 can stimulate the cyclic adenosine monophosphate/protein kinase A (cAMP-PKA) pathway by activating GLP-1R, which then increases the level of non-phosphorylated β-catenin to stimulate the Wnt/β-catenin/NeuroD1 pathway and inhibits the activity of GSK-3β, ultimately decreasing the hyperphosphorylation of AD-associated tau proteins regulated by GSK-3β (Kang et al., 2023). Here, MAPT is linked to Alzheimer disease.