Standardized dynamic glucose testing reveals donor-dependent heterogeneity in human islet function

Glucose-stimulated insulin secretion (GSIS) testing of isolated islets of Langerhans is crucial for assessing β-cell function, yet protocol variability complicates result interpretation. This study investigated insulin secretion heterogeneity across 576 donors and examined the influence of donor characteristics on secretory responses. We compared static incubation (n = 408) and dynamic perifusion (n = 168) techniques using standardized glucose stimulation protocols (3 vs 15 mM). While both methods showed comparable stimulation indices (r² = 0.652), dynamic perifusion uniquely captured temporal secretion patterns and revealed greater dynamic range in insulin responses. Notably, dynamic perifusion, with insulin content normalization, revealed a 22-fold variation in stimulation index across donors. Body mass index (BMI) and HbA1c significantly influenced basal insulin secretion, particularly in donors with glucose intolerance and type 2 diabetes (T2D) (HbA1c ≥ 6.5%). Cluster analysis identified two distinct groups based on age, BMI/body surface area (BSA), and HbA1c, which strongly predicted insulin secretion patterns, whereas donor sex had no measurable impact. This large-scale study demonstrates the superiority of standardized perifusion over static incubation for resolving islet glucose responses. By capturing dynamic secretion profiles, perifusion reveals substantial donor heterogeneity, primarily driven by BMI and HbA1c through their effects on basal insulin secretion.