The Prostaglandin E₂ EP3 Receptor Has Disparate Effects on Islet Insulin Secretion and Content in β-cells in a High Fat Diet-induced Mouse Model of Obesity

Signaling through Prostaglandin E₂ EP3 receptor (EP3) actively contributes to the β-cell dysfunction of type 2 diabetes (T2D). In T2D models, full-body EP3 knockout mice have a significantly worse metabolic phenotype than wild-type controls due to hyperphagia and severe insulin resistance resulting from loss of EP3 in extra-pancreatic tissues, masking any potential beneficial effects of EP3 loss in the β-cell. We hypothesized β-cell-specific EP3 knockout (EP3 βKO) mice would be protected from high-fat diet (HFD)-induced glucose intolerance, phenocopying mice lacking the EP3 effector, Gɑ_z, which is much more limited in its tissue distribution. When fed a HFD for 16 weeks, though, EP3 βKO mice were partially, but not fully, protected from glucose intolerance. Additionally, exendin-4, an analog of the incretin hormone, glucagon-like peptide 1, more strongly potentiated glucose-stimulated insulin secretion in islets from both control diet- and HFD-fed EP3 βKO mice as compared to wild-type controls, with no effect of β-cell-specific EP3 loss on islet insulin content or markers of replication and survival. However, after 26 weeks of diet feeding, islets from both control diet- and HFD-fed EP3 βKO mice secreted significantly less insulin as a percent of content in response to stimulatory glucose, with or without exendin-4, with elevated total insulin content unrelated to markers of β-cell replication and survival, revealing severe β-cell dysfunction. Our results suggest that EP3 serves a critical role in temporally regulating β-cell function along the progression to T2D and that there exist Gɑ_z-independent mechanisms behind its effects.