Incretin hormone action on ß-cells stimulates in parallel two different intracellular cyclic AMP-dependent signaling branches mediated by PKA and EPAC2A. Both pathways contribute towards potentiation of glucose-stimulated insulin secretion (GSIS). However, the overall functional role of EPAC2A in ß-cells as it relates to in vivo glucose homeostasis remains incompletely understood. Therefore, we have examined in vivo GSIS in global EPAC2A knockout mice. Additionally, we have conducted in vitro studies of GSIS and calcium dynamics in isolated EPAC2A-deficient islets. EPAC2A deficiency does not impact glucose-stimulated insulin secretion in mice under basal conditions. However, when mice are exposed to diet-induced insulin resistance, pharmacologic secretagogue stimulation of ß-cells with an incretin hormone glucagon-like peptide-1 analogue or with a Fatty Acid Receptor 1/GPR40 selective activator, EPAC2A is required for the increased ß-cell response to secretory demand. Under these circumstances, EPAC2A is required for potentiating the early dynamic increase in islet calcium levels after glucose stimulation, which is reflected in potentiated first phase insulin secretion. These studies broaden our understanding of EPAC2A function and highlight its significance during increased secretory demand or drive on ß-cells. Our findings advance the rationale for developing EPAC2A selective pharmacologic activators for ß-cell targeted pharmacotherapy in type 2 diabetes mellitus.
- Received October 10, 2012.
- Accepted March 26, 2013.
- © 2013 by the American Diabetes Association.
Readers may use this article as long as the work is properly cited, the use is educational and not for profit, and the work is not altered. See http://creativecommons.org/licenses/by-nc-nd/3.0/ for details.