APP and Alzheimer disease: Although Aβ40 and Aβ42 peptides are generally the most abundant, other peptides such as Aβ34, Aβ37, Aβ38 and Aβ43 have also been recently recognized as having a role in modulation of AD onset and progression or as possible biomarkers for disease-associated APP and Aβ dyshomeostasis [3, 8, 18, 46, 57].