T2DM is characterized by aggregates of the peptide amylin in insulin-secreting pancreatic β-cells; AD results from the extracellular amyloid aggregation of the Aβ peptide (mostly Aβ1–42) in senile and neuritic plaques and the intracellular aggregation into neurofibrillary tangles of tau protein; these aggregates are found in specific brain areas, notably the hippocampus and the pre-frontal cortex. This evidence concerns the gene MAPT and Alzheimer disease.