IAPP and early-onset autosomal dominant Alzheimer disease: For example, the fibril aggregates of α-synuclein (α-Syn), islet amyloid polypeptide (IAPP), and amyloid beta (Aβ) peptide are involved in Parkinson’s disease (PD) [6], type II diabetes (T2D) [7], and Alzheimer’s disease (AD) [8], respectively.