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OR24-4 Targeting Hyperglucagonemia Reverses Glucagon Resistance

Elevation of glucagon levels and increase in alpha-cell mass are associated with states of hyperglycemia in diabetes. A better understanding of the molecular mechanisms governing glucagon secretion could have major implications in understanding abnormal responses to hypoglycemia in diabetic patients...

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Autores principales: Bernal-Mizrachi, Ernesto, Kramer, Nadejda Bozadjieva, Gittes, George, Lubaczeuski, Camila
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Oxford University Press 2022
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Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9624587/
http://dx.doi.org/10.1210/jendso/bvac150.732
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author Bernal-Mizrachi, Ernesto
Kramer, Nadejda Bozadjieva
Gittes, George
Lubaczeuski, Camila
author_facet Bernal-Mizrachi, Ernesto
Kramer, Nadejda Bozadjieva
Gittes, George
Lubaczeuski, Camila
author_sort Bernal-Mizrachi, Ernesto
collection PubMed
description Elevation of glucagon levels and increase in alpha-cell mass are associated with states of hyperglycemia in diabetes. A better understanding of the molecular mechanisms governing glucagon secretion could have major implications in understanding abnormal responses to hypoglycemia in diabetic patients and provide novel avenues for diabetes management. Stimulation of glucagon secretion in hypoglycemia, or by amino acids, induces hepatic glucose production via cellular mechanisms including suppression of glycogenesis and glycolysis and stimulation of glycogenolysis and gluconeogenesis. The close link between amino acids and the alpha-cell is highlighted by the liver–alpha-cell axis. This axis was identified by the major increase in alpha-cell hyperplasia and hyperglucagonemia in models of reduced glucagon action in hepatocytes genetically or pharmacologically by treatment with glucagon receptor antagonists, which was subsequently attributed to the dramatic rise in amino acids. Induction of mTORC1 by constitutive genetic deletion of TSC2 in alpha-cells (aTSC2KO) recapitulated the effects of chronic hyperaminoacidemia with increases in alpha-cell mass and chronic hyperglucagonemia indicating that mTORC1 mediates amino acids signals in alpha-cells. However, the effects of acute versus chronic induction of alpha-cell mTORC1 signaling on these outcomes have not been explored. Using mice with doxycycline induction of Rheb (activator of mTORC1 signaling) (aRhebTg) and inducible Cre-mediated deletion of the mTORC1 inhibitor, TSC2, in alpha-cells (iaTSC2KO), we showed that induction of hyperglucagonemia is associated with two phases: Acute phase characterized by impaired glucose tolerance because of increased gluconeogenesis and glucose output by the liver. And a chronic phase, characterized by normalization of glucose tolerance due to downregulation of the hepatic glucagon receptor (Gcgr), Pepck, and some genes involved in amino acid metabolism and urea production. Importantly, the consequences of chronic hyperglucagonemia were reversible after normalization of glucagon levels by turning off alpha-cell Rheb expression. These studies uncovered the acute versus chronic effects of hyperglucagonemia on glucose homeostasis and further demonstrate that glucagon resistance is a reversible process. These observations provide insight into the impact of glucagon in the pathogenesis of hyperglycemia and the physiological effects of administration of dual GLP1/Glucagon receptor agonists. Presentation: Monday, June 13, 2022 11:45 a.m. - 12:00 p.m.
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spelling pubmed-96245872022-11-14 OR24-4 Targeting Hyperglucagonemia Reverses Glucagon Resistance Bernal-Mizrachi, Ernesto Kramer, Nadejda Bozadjieva Gittes, George Lubaczeuski, Camila J Endocr Soc Diabetes & Glucose Metabolism Elevation of glucagon levels and increase in alpha-cell mass are associated with states of hyperglycemia in diabetes. A better understanding of the molecular mechanisms governing glucagon secretion could have major implications in understanding abnormal responses to hypoglycemia in diabetic patients and provide novel avenues for diabetes management. Stimulation of glucagon secretion in hypoglycemia, or by amino acids, induces hepatic glucose production via cellular mechanisms including suppression of glycogenesis and glycolysis and stimulation of glycogenolysis and gluconeogenesis. The close link between amino acids and the alpha-cell is highlighted by the liver–alpha-cell axis. This axis was identified by the major increase in alpha-cell hyperplasia and hyperglucagonemia in models of reduced glucagon action in hepatocytes genetically or pharmacologically by treatment with glucagon receptor antagonists, which was subsequently attributed to the dramatic rise in amino acids. Induction of mTORC1 by constitutive genetic deletion of TSC2 in alpha-cells (aTSC2KO) recapitulated the effects of chronic hyperaminoacidemia with increases in alpha-cell mass and chronic hyperglucagonemia indicating that mTORC1 mediates amino acids signals in alpha-cells. However, the effects of acute versus chronic induction of alpha-cell mTORC1 signaling on these outcomes have not been explored. Using mice with doxycycline induction of Rheb (activator of mTORC1 signaling) (aRhebTg) and inducible Cre-mediated deletion of the mTORC1 inhibitor, TSC2, in alpha-cells (iaTSC2KO), we showed that induction of hyperglucagonemia is associated with two phases: Acute phase characterized by impaired glucose tolerance because of increased gluconeogenesis and glucose output by the liver. And a chronic phase, characterized by normalization of glucose tolerance due to downregulation of the hepatic glucagon receptor (Gcgr), Pepck, and some genes involved in amino acid metabolism and urea production. Importantly, the consequences of chronic hyperglucagonemia were reversible after normalization of glucagon levels by turning off alpha-cell Rheb expression. These studies uncovered the acute versus chronic effects of hyperglucagonemia on glucose homeostasis and further demonstrate that glucagon resistance is a reversible process. These observations provide insight into the impact of glucagon in the pathogenesis of hyperglycemia and the physiological effects of administration of dual GLP1/Glucagon receptor agonists. Presentation: Monday, June 13, 2022 11:45 a.m. - 12:00 p.m. Oxford University Press 2022-11-01 /pmc/articles/PMC9624587/ http://dx.doi.org/10.1210/jendso/bvac150.732 Text en © The Author(s) 2022. Published by Oxford University Press on behalf of the Endocrine Society. https://creativecommons.org/licenses/by-nc-nd/4.0/This is an Open Access article distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs licence (https://creativecommons.org/licenses/by-nc-nd/4.0/), which permits non-commercial reproduction and distribution of the work, in any medium, provided the original work is not altered or transformed in any way, and that the work is properly cited. For commercial re-use, please contact journals.permissions@oup.com
spellingShingle Diabetes & Glucose Metabolism
Bernal-Mizrachi, Ernesto
Kramer, Nadejda Bozadjieva
Gittes, George
Lubaczeuski, Camila
OR24-4 Targeting Hyperglucagonemia Reverses Glucagon Resistance
title OR24-4 Targeting Hyperglucagonemia Reverses Glucagon Resistance
title_full OR24-4 Targeting Hyperglucagonemia Reverses Glucagon Resistance
title_fullStr OR24-4 Targeting Hyperglucagonemia Reverses Glucagon Resistance
title_full_unstemmed OR24-4 Targeting Hyperglucagonemia Reverses Glucagon Resistance
title_short OR24-4 Targeting Hyperglucagonemia Reverses Glucagon Resistance
title_sort or24-4 targeting hyperglucagonemia reverses glucagon resistance
topic Diabetes & Glucose Metabolism
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9624587/
http://dx.doi.org/10.1210/jendso/bvac150.732
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