MON-569 Cholecystokinin Expression in Islets Under Hyperglycemic Stress

Abstract Disclosure: M.C. Mulcahy: None. H. Von Ruden: None. A. Deepak: None. R. Modhurima: None. D.B. Davis: None. Background: Although cholecystokinin (CCK) is a canonical gut hormone, it is produced and secreted from pancreatic islets. Our group has demonstrated that islets secrete CCK in response to metabolic stressors, such as hyperglycemia, which prevents beta cell apoptosis. Previous work demonstrated that Cck is expressed in beta cells but has not characterized if its production results in dedifferentiation, a known consequence of beta cell dysfunction. The goal of this study is to determine the location and the characteristics of islet cells that express Cck under metabolic stress in order to understand the hormone’s role on beta cell dedifferentiation. We hypothesized that Cck expression would be greatest in dedifferentiated beta cells. Methods: We generated triple transgenic mice using Rosa26-H2BmCherry with Ins1-Cre driver and Cck-eGFP (LTCCK). This genetic makeup allows for lineage-tracing of beta cells through mCherry labeling and visualization with GFP where Cck is expressed. In combination with immunofluorescent staining of Ucn3, this facilitates the quantification of dedifferentiated beta cells, Cck expressing cells, and their overlap. To determine the relationship between beta cell dedifferentiation and Cck expression, we treated mice with insulin receptor antagonist (S961) for one week to induce hyperglycemic stress. Pancreata were dissected, fixed, and mounted on slides, then stained for GFP and Ucn3. We evaluated Cck expression, beta cell lineage, and Ucn3 expression as a marker of differentiated beta cells in confocal images using FIJI. Results: We successfully induced expression of Cck by S961 treatment in 6.4% of islet cells. Cck expression was not exclusive to beta cells. We discovered that Cck-eGFP positive cells were enriched in dedifferentiated beta cells (19.3% of mCherry+, Ucn3- cells) compared to mature beta cells (7.7% of mCherry+, Ucn3+ cells). However, Cck-eGFP negative cells were more abundant than Cck-eGFP positive cells in both populations. There was evidence of Ucn3+/mCherry-/Cck-eGFP- cells (13% of total cells), suggesting there could be evidence of transdifferentiation or incomplete lineage tracing of beta cells in this model. Conclusion:Cck expression is induced by metabolic stress in islets and occurs in both beta and non-beta cells. Based on our finding that few Cck positive cells were dedifferentiated beta cells, it is unlikely that CCK production results in beta cell dedifferentiation as the mechanism to protect from apoptosis. Further analysis will examine spatial relationships to determine if paracrine action of CCK may impart benefits to neighboring cells. Presentation: Monday, July 14, 2025