Amylin at the crossroads of type 2 diabetes and neurodegenerative diseases.

Type 2 diabetes (T2D) is traditionally viewed as a metabolic disease centered on insulin resistance and β-cell failure. However, growing evidence supports its reclassification as a systemic proteinopathy, in which the aggregation of amylin (islet amyloid polypeptide, IAPP) emerges as a key pathogenic event. In this review, we examine the shift toward an IAPP-centric model of disease, highlighting how IAPP misfolding and aggregation drive β-cell dysfunction independently of, and in parallel with, metabolic stress. We integrate recent advances in the structural biology of IAPP to provide a mechanistic framework for its cytotoxicity. IAPP aggregation disrupts cellular homeostasis through membrane damage, proteostasis imbalance, mitochondrial dysfunction, oxidative and ER stress, and inflammation, ultimately leading to progressive β-cell loss. Beyond the pancreas, we position IAPP as a molecular bridge between peripheral metabolic stress and neurodegeneration. Through prion-like cross-seeding, IAPP interacts with Aβ, tau, α-synuclein, and PrP, linking T2D as a major risk factor for neurodegenerative disorders such as Alzheimer's and Parkinson's diseases. We review emerging therapeutic strategies, including long-acting non-fibrillating analogues that suppress endogenous secretion, cross-amyloid inhibitors, conformation-specific immunotherapies, and synthetic chaperones. Finally, we discuss structure-based and AI-driven diffusion models as tools to design binders that selectively mask the amyloidogenic core while preserving the homeostatic function of IAPP. Given the projected magnitude of T2D, targeting the IAPP-neurodegeneration axis through early detection and midlife intervention is essential to mitigating the impending socioeconomic impact of combined metabolic and cognitive decline.