Angiotensin II type 2 receptor regulates the development of pancreatic endocrine cells in mouse embryos

Abstract

Background: We previously identified a local renin-angiotensin system (RAS) regulating the differentiation of an isolated population of human pancreatic progenitor cells. Major RAS components that regulate organogenesis have been also described in embryos; however, it is not known whether a local RAS is present in the fetal pancreas. We now hypothesize that angiotensin II type 1 (AT 1 ) and type 2 (AT 2 ) receptors are expressed in mouse embryonic pancreas and involved in regulating endocrine cell development. Results: Differential expression of AT 1 and AT 2 receptors was observed in the mouse pancreata in late embryogenesis. Systemic AT 2 , but not AT 1 , receptor blockade during the second transition in pancreatic development (from embryonic day 12.0 onward) reduced the b-cell to a-cell ratio of the neonate islets, impaired their insulin secretory function and the glucose tolerance of the pups. Studies with pancreas explants ex vivo revealed regulation by AT 2 receptors of the differentiation of pancreatic progenitors into insulin-producing cells and of the proliferation of the differentiated cell, actions that did not result from reduced angiogenesis as a secondary effect of AT 2 receptor antagonism. Conclusions: These data revealed an AT 2 receptor-mediated mechanism regulating pancreatic endocrine cell development in vivo. Developmental Dynamics 243:415-427, 2014. V C 2013 Wiley Periodicals, Inc.Key words: renin-angiotensin system; fetal pancreas; islet; insulin Key findings:Differential expression of AT 1 and AT 2 receptors was identified in mouse pancreas during pancreatic development. AT 2 receptor, but not AT 1 receptor, blockade during the second transition stage of pancreatic development altered islet cell composition and impaired both insulin secretory function of neonatal islets and glucose tolerance of the pups. Pancreas explants ex vivo data showed that AT 2 receptors were essential for the differentiation of pancreatic progenitors into insulin producing cells, as well as for proliferation of the differentiated cells. No evidence was found to suggest that AT 2 receptor regulation of b-cell development is a secondary effect of angiotensin II-induced vascular endothelial growth factor-driven angiogenesis.

ACE2 deficiency shifts energy metabolism towards glucose utilization

“…This would be a phenotypic imprint on β-cell structure, or function, that is not reversed by RAAS blockade. Certainly, ACE2 and AT receptors are expressed in mouse embryonic pancreas and may be involved in regulating endocrine cell development [27]. Indeed, overexpression of ACE2 can reduce β-cell dysfunction [7,28].…”

The ACE2/Ang-(1-7)/Mas Axis Regulates the Development of Pancreatic Endocrine Cells in Mouse Embryos

“…Protocols for islet isolation from neonatal mouse pancreata were modified from previously reported protocols developed in our laboratory [ 22 , 23 ]. In brief, the dissected pancreata from five neonatal mice from each treatment group were pooled together for islet isolation.…”

“…GSIS measurements from pancreatic islets were evaluated as described in detail previously [ 22 , 23 ]. Approximately 20 neonatal islets were collected from each group and pre-incubated in Krebs-Ringer bicarbonate buffer (KRBB) containing 1.6 mM D-glucose (Sigma-Aldrich) for 1h to normalize the basal insulin-secreting status before being incubated in KRBB buffer with 1.6 mM D-glucose for 1h after which the buffer was collected; the islets were then incubated for an additional hour with fresh KRBB buffer containing 16.7 mM D-glucose to determine the stimulated level of insulin secretion.…”

“…Glucose tolerance was tested in 3–4 weeks old pups with an IPGTT as described previously [ 23 ] with minor modifications. Briefly, the pups were fasted for 16 h before being given intraperitoneal injections of glucose dissolved in saline (1 g/kg body weight).…”

“…Islet β-cell area was assessed by determining the proportion of area occupied by Alexa Fluor 488 or 568 labeling within each islet using Leica Qwin image analysis software (Leica Microsystems), as described previously [ 22 , 23 ]. At least five islets from each experimental group and islets isolated from at least five different mother mice were chosen randomly for analysis.…”