MAPT and Alzheimer disease: AD, Alzheimer’s disease; Apo, Apolipoprotein; BBB, Blood-brain barrier; CMA, Chaperone-mediated autophagy; CNS, Central nervous system; CSF, Cerebrospinal fluid; DLB, Dementia with Lewy bodies; HDL, High-density lipoproteins; kDa, Kilodalton; LBs, Lewy bodies; LDL, Low-density lipoproteins; MAPK, Mitogen-activated protein kinases; MAPT, Microtubule-associated protein tau; MW, Molecular weight; PD, Parkinson’s disease; PEA, β-Phenylethylamine; PP2A, Protein phosphatase 2A; ROS, Reactive oxygen species; SN, Substantia nigra; TH, Tyrosine hydroxylase; VLDL, Very-low-density lipoproteins