MAPT and diabetes mellitus: Multiple mechanisms may lead to cognitive impairment and involve cellular injury from β-amyloid (Aβ), tau, excitotoxicity, metabotropic receptors, lipid dysfunction, mitochondrial damage, acetylcholine loss, astrocytic cell injury, oxidative stress, heavy metal disease, and cellular metabolic dysfunction with diabetes mellitus (DM) [3,4,8,14,27,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54].