APP and Alzheimer disease: Despite the several hypotheses explored to explain the origin of AD, the most accepted ones are the extracellular deposition of Aβ protein, a 40–42-amino acid peptide generated by proteolytic cleavages of the amyloid-protein precursor (APP), and intraneuronal neurofibrillary tangles (NFTs) of hyperphosphorylated tau protein [24,25].