The impact of cholecystokinin on pancreatic beta-cell survival through paracrine and pharmacologic signaling

Diabetes affects nearly 1 in 4 Veterans receiving care from the VA. Reduced b-cell mass and increased b-cell apoptosis are key to the pathophysiology of both type 1 and type 2 diabetes. Therefore, identifying factors that can protect from b-cell apoptosis will meet a critical therapeutic need in the prevention and treatment of diabetes

in Veterans. Compensatory responses in b-cells allow adaptation to the stress of obesity, insulin resistance and inflammation and can help preserve b-cell mass and prevent progression to diabetes. Our laboratory has dis- covered that the hormone cholecystokinin (CCK) is produced in the pancreatic islet in response to metabolic

stress and can promote b-cell survival. Further, we find that CCK receptor (CCKR) agonist treatment of human islets can significantly improve b-cell survival, supporting substantial translational relevance. The long-term goal of my research program is to identify novel pathways critical in the preservation of b-cell mass. The overall

objective of this application is to determine how CCK expression and CCK receptor signaling impact islet home- ostasis and b-cell survival. The central hypothesis is that CCK promotes functional b-cell survival. CCK-express- ing islet cells may have reduced b-cell maturity, yet are critical to promote survival of neighboring b-cells through

paracrine signaling. To achieve the objective, three interconnected Specific Aims are proposed. In Aim 1, we will identify the regulators of b-cell CCK expression in mouse and human islets under conditions of hyperglycemia and cellular stress using both targeted and untargeted approaches. Preliminary evidence support the hypothesis

that GLP-1, cAMP, and glucose all contribute to CCK expression. In Aim 2, we will determine how CCK expres- sion impacts islet cell identity, function and survival. We will use innovative experimental techniques, including lineage-tracing mouse models, droplet-assisted RNA targeting single cell sequencing, and live cell imaging to

characterize and determine the impact of CCK-expressing cells in the islet. In Aim 3 we will investigate how short-term incubation of human islets with CCKR agonists alters gene transcription and signaling pathways to promote sustained b-cell survival. Additionally, we will determine the impact of CCK pretreatment on early human

islet graft survival after transplantation. Taken together our work supports the innovative concept of an intra-islet signaling network whereby the non-classic hormone CCK promotes b-cell survival. As human islets have very different characteristics than mouse islet, examining the role of CCK specifically in human islets is of critical

importance to translation of our findings to diabetes therapies. These studies will contribute to our fundamental understanding of how b-cells respond to metabolic stress, as we propose that “de-differentiation” of a subpopu- lation of b-cells will in fact allow production of non-canonical hormones that promote b-cell survival. This contri-

bution is significant as it will advance knowledge of both adaptive and therapeutic mechanisms of functional b- cell survival, allowing development of targeted therapies with maximal efficacy and minimal side effects.