These include improvements in glucose metabolism, reductions in oxidative stress, preservation of blood–brain barrier integrity, modulation of inflammatory responses, and beneficial impacts on mitochondrial function and amyloid-beta and tau pathology, all of which contribute to their neuroprotective potential in patients with type 2 diabetes mellitus (T2DM) and cognitive decline (Figure 2). This evidence concerns the gene MAPT and type 2 diabetes mellitus.