Epigenetic adaptation of beta cells across lifespan and disease.

Although the prevalence of type 2 diabetes (T2D) increases with age, most adults maintain normoglycaemia despite rising insulin resistance owing to the adaptive capacity of pancreatic beta cells to meet increased metabolic demand. However, persistent insulin resistance can lead to beta cell dysfunction and T2D onset. Here we show the mapping of genome-wide DNA methylation (DNAm) patterns and the epigenomic basis of beta cell adaptations by leveraging cell-type-specific methylome data from the Human Pancreas Analysis Program. In healthy donors, we identify progressive age-related demethylation enriched in cis-regulatory elements at beta cell identity and function genes. By contrast, alpha cells show the opposite trajectory, with subtle, age-related hypermethylation. In T2D beta cells, but not alpha cells, we observed further demethylation compared to healthy controls, underscoring a unique capacity of beta cells to respond to changes in metabolic demand. Together, our findings suggest that DNAm remodelling in healthy beta cells reflects a long-term adaptation to metabolic demand, which, in T2D, is accelerated as part of a compensatory response that ultimately fails under sustained insulin resistance.