MAPT and type 2 diabetes mellitus: Type 2 diabetes mellitus (T2DM) causes the activation of glycogen synthase kinase 3 beta (GSK3β), amyloid-beta production, low production of adenosine triphosphate (ATP), phosphorylation of tau, impaired mitochondrial function, cognitive impairments, activation of wingless-related integration site/beta catenin (Wnt/β-catenin) pathway, and increased production of free radicals [16].