MAPT and diabetes mellitus: The most promising early biomarkers to predict and/or early detect neurodegenerative and neurovascular complications in diabetes include C-reactive protein (CRP), microRNAs (miRNAs), paraoxonase 1 (PON-1), tau protein, β-amyloid, glycogen synthase kinase 3β (GSK-3β), phosphoinositide 3-kinases (PI3K), amylin, dopamine, gamma-glutamyl transferase (GGT), various growth factors and homocysteine.