Transcriptional and functional profiling reveals a dynamic continuum of beta-cell activation states

A central question is whether beta-cells respond uniformly to glucose. Using phospho-S6 as an activation marker, this study shows that beta-cells are recruited sequentially as glucose concentrations increase. Recruitment is spatially organized, with high-threshold cells predominantly located in the islet core. Transcriptomic profiling indicates functional heterogeneity among beta-cells. A low-threshold subset is characterized by enhanced stress resilience necessary for sustained secretion. An intermediate subset, enriched for calcium-signaling and vesicle-excitatory genes, modulates postprandial glucose excursions. The high-threshold subset specializes in high-capacity protein synthesis and insulin secretion to manage glucose peaks. Single-cell RNA sequencing reveals that these functional subsets form a continuous spectrum rather than discrete subpopulations. This division of labor is adaptable; under high-fat diet-induced metabolic demand, islets undergo remodeling with a global reduction in activation thresholds and a shift toward high-capacity profiles. Collectively, these findings identify a beta-cell hierarchy that balances metabolic resilience with secretory demand to maintain glucose homeostasis.