OR12-05 Blunting Of Sympathetic Activation Of Pancreas As A Cause For Hypoglycemic Unawareness In Hypoglycemia Associated Autonomic Failure

Abstract

Abstract Disclosure: K. Thakkar: None. R. Hampton: None. M. Jimenez Gonzalez: None. D. Espinoza: None. S. Stanley: None. Introduction: Hypoglycemia activates the autonomic nervous system to suppress pancreatic insulin and increase glucagon release, restoring blood glucose levels to normal. These effects occur partly via sympathetic innervation of pancreatic islets. Recurrent hypoglycemia leads to a blunted autonomic response known as Hypoglycemia Associated Autonomic Failure (HAAF), which further exacerbates hypoglycemia. The mechanisms underlying HAAF are not well-understood, but changes in pancreatic innervation may contribute. Hypothesis: Decreased activity and remodeling of sympathetic innervation to the pancreas contribute to autonomic dysfunction with repeated hypoglycemia. Methods: To examine pancreatic sympathetic innervation with repeated hypoglycemia, C57Bl6 mice were treated with 0, 1, or 5 episodes (0, 1x, or 5x) of insulin-induced hypoglycemia. Pancreata, sympathetic celiac ganglia, and brains were harvested. Pancreatic tissue was immunostained for insulin, glucagon, and tyrosine hydroxylase (TH), a marker for sympathetic innervation. Samples were then cleared using iDISCO+, imaged, and analyzed using Imaris to examine the 3D distribution of innervation and islets. To determine if pancreatic sympathetic nerve function is altered in HAAF, we used viral delivery to express activating chemogenetic constructs specifically in pancreas-projecting sympathetic nerves. We assessed the effects of chemogenetic activation of pancreatic sympathetic innervation during insulin tolerance testing (ITT) in C57Bl6 mice with or without previous recurrent hypoglycemia. Results: 3D image analyses suggest acute hypoglycemia (1x) upregulates islet glucagon staining intensity. By comparison, recurrent hypoglycemia (5x) ​decreases pancreatic TH+ innervation and may blunt hypoglycemia-induced increases in islet glucagon staining intensity. Chemogenetic activation of pancreas sympathetic nerves in mice with repeated hypoglycemia increased blood glucose during an ITT while activation in mice without previous hypoglycemia did not significantly alter blood glucose. These data suggest reduced activity in pancreatic sympathetic innervation with recurrent hypoglycemia that can be restored by chemogenetic activation. Conclusions: Our data suggest repeated episodes of hypoglycemia may remodel the structure and function of peripheral pancreatic sympathetic innervation as compared to one episode of hypoglycemia. Restoring activity in pancreatic sympathetic innervation may partially reverse the severity of hypoglycemia in HAAF. Staining and analysis of celiac ganglia and sympathetic outflow circuits in the CNS will allow determination of the level at which blunting of sympathetic activation and/or remodeling of innervation occurs. Presentation: Friday, June 16, 2023