Investigating mechanisms underlying diabetes associated with exocrine pancreas diseases

Summary Exocrine pancreas diseases like chronic pancreatitis (CP) and pancreatic ductal adenocarcinoma (PDAC) can engender type 3c diabetes mellitus (T3cD: also called pancreatogenic diabetes), a form of human diabetes that is distinct, but shares some features of type 1 and 2 diabetes. It is increasingly recognized that T3cD likely represents a substantial fraction of all diabetes in some populations, but the cellular, genetic and signaling basis of T3cD are poorly understood. To address this knowledge 'gap' we created a tissue procurement workflow focused on CP patients, and investigated primary islets from these subjects. We found evidence for deranged gene expression in islet alpha cells and excessive glucagon secretion, preceding overt T3cD. Other analysis suggests that a combination of increased pro- inflammatory and reduced anti-inflammatory signaling may lead to dysregulated incretin signaling in alpha cells. Thus, we postulate that CP could promote early stages of T3cD by impairing alpha cell regulation. To test this, we propose in Aim 1 to study gene regulation and electrophysiology in primary human islet cells procured from subjects with CP and CP with prediabetes, and to test the hypothesis that incretin-regulated glucagon secretion is enhanced in prediabetes. In Aim 2 we will use modern multiplexed imaging methods (CODEX) and in vitro islet studies to test the hypothesis that specific inflammatory signaling pathways in CP alter alpha cell gene regulation and function, leading to excessive glucagon secretion. Together, our studies could identify mechanisms of alpha cell dysfunction that occur very early in the development of T3cD. Development of T3cD in CP is thought to presage PDAC; thus, our work could strongly influence work on identifying biomarkers of PDAC at stages when surgery and other therapeutics can be applied with curative intent.