3113-LB: Loss of ß-Cell Heterogeneity due to Glucolipotoxicity-Induced Metabolic Stress

Introduction and Objective: β-cell heterogeneity is essential for islet function, yet loss of resilient subpopulations contributes to dysfunction under metabolic stress. While female islets exhibit greater resilience, the mechanisms underlying this sexual dimorphism remain unclear. Here, we aimed to define the molecular identity of a c-Fos+ β-cell subpopulation -where c-Fos, an immediate early gene (IEG), marks activated cells- and investigate how glucolipotoxicity (GLT) disrupts heterogeneity in a sex-dependent manner. Methods: We used the FosTRAP2;Ai14 mouse model (n=6/sex) to identify c-Fos+ β-cells. GLT conditions were applied (25 mM glucose, 100 µM palmitate, 48 h). Cell survival, granularity, and signaling were assessed via flow cytometry and Luxendin-647 staining. Glycolytic activity was measured using FLIM in n=17 cells. RNA-seq was performed to profile gene expression in c-Fos+ cells. Results: Female islets harbored a higher baseline proportion of c-Fos+ cells than males (2±1% vs. 0.4±0.3%, p<0.01). Under GLT, the c-Fos+ population expanded to 8% in females compared to 1.2% in males, with a significantly greater absolute increase in females (p<0.05). c-Fos+ cells were highly stress-resistant, showing lower death rates independent of sex or treatment. Granularity was reduced, and signaling differed by sex: GLP-1 receptor staining (Luxendin-647 gMFI) decreased in male c-Fos+ cells under GLT but increased in females. RNA-seq revealed enrichment in metabolic regulators (Hk1, Pfkp), consistent with FLIM data showing higher glycolytic activity under low glucose, supporting a protective metabolic adaptation. Conclusion: Together, these findings indicate that sexual dimorphism in β-cell resilience is driven by distinct patterns of heterogeneity. Female islets maintain a larger, more adaptable c-Fos+ subpopulation that survives chronic stress through glycolytic and signaling adaptation, providing a mechanistic basis for the superior durability of the female endocrine pancreas. Disclosure A. Gresch: None. T. Gaia Pedraza: None. R.K. Benninger: None. Funding NIH /NIDDK (R01 DK102950 and R01 DK106412), Ludeman Family Center for Women's Health Research (Seed grant 2025)