TY - JOUR T1 - Differential Effects of Prostaglandin E<sub>2</sub> Production and Signaling through the Prostaglandin EP3 Receptor on Human Beta-cell Compensation JF - bioRxiv DO - 10.1101/670000 SP - 670000 AU - Nathan A. Truchan AU - Harpreet K. Sandhu AU - Rachel J. Fenske AU - Renee Buchanan AU - Jackson Moeller AU - Austin Reuter AU - Jeff Harrington AU - Michelle E. Kimple Y1 - 2019/01/01 UR - http://biorxiv.org/content/early/2019/06/13/670000.abstract N2 - Objective Signaling through Prostaglandin E3 Receptor (EP3), a G protein-coupled receptor for E series prostaglandins such as prostaglandin E2 (PGE2), has been linked to the beta-cell dysfunction and loss of beta-cell mass in type 2 diabetes (T2D). In the beta-cell, EP3 is specifically coupled to the unique cAMP-inhibitory G protein, Gz. Divergent effects of EP3 agonists and antagonists or Gαz loss on beta-cell function, replication, and survival depending on whether islets are isolated from mice or humans in the lean and healthy, type 1 diabetic, or T2D state suggest a divergence in biological effects downstream of EP3/Gαz dependent on the physiological milieu in which the islets reside.Methods We determined the expression of a number of genes in the EP3/Gαz signaling pathway; PGE2 production pathway; and the beta-cell metabolic, proliferative, and survival responses to insulin resistance and its corresponding metabolic and inflammatory derangements in a panel of 80 islet preparations from non-diabetic human organ donors spanning a BMI range of approximately 20-45. In a subset of islet preparations, we also performed glucose-stimulated insulin secretion assays with and without the addition of an EP3 agonist, L798,106, and a glucagon-like peptide 1 receptor agonist, exendin-4, allowing us to compare the gene expression profile of each islet preparation with its (1) total islet insulin content (2), functional responses to glucose and incretin hormones, and (3) intrinsic influence of endogenous EP3 signaling in regulating these functional responses. We also transduced two independent islet preparations from three human organ donors with adenoviruses encoding human Gαz or a GFP control in order to determine the impact of Gαz hyperactivity (a mimic of the T2D state) on human islet insulin content and functional response to glucose.Results In contrast to results from islets isolated from T2D mice and human organ donors, where PGE2-mediated EP3 signaling actively contributes to beta-cell dysfunction, PGE2 production and EP3 expression appeared positively associated with various measurements of functional beta-cell compensation. While Gαz mRNA expression was negatively associated with islet insulin content, that of each of the Gαz-sensitive adenylate cyclase (AC) isoforms were positively associated with BMI and cyclin A1 mRNA expression, suggesting increased expression of AC1, AC5, and AC6 is a compensatory mechanism to augment beta-cell mass. Human islets over-expressing Gαz via adenoviral transduction had reduced islet insulin content and secretion of insulin in response to stimulatory glucose as a percent of content, consistent with the effects of hyperactivation of Gαz by PGE2/EP3 signaling observed in islets exposed to the T2D physiological milieu.Conclusions Our work sheds light on critical mechanisms in the human beta-cell compensatory response, before the progression to frank T2D. ER -