The complex interplay between T2DM and AD encompasses various factors such as insulin resistance, inflammation, oxidative stress (OS), glutamate kinase 3β, insulin growth factor signaling, Aβ production from amyloid precursor protein (APP), NFT formation, and acetylcholine esterase activity regulation due to common pathways across type 1 diabetes mellitus (T1DM), T2DM, and AD. This evidence concerns the gene APP and Alzheimer disease.