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Kajani S, Laker RC, Ratkova E, Will S, Rhodes CJ. Hepatic glucagon action: beyond glucose mobilization. Physiol Rev 2024; 104:1021-1060. [PMID: 38300523 DOI: 10.1152/physrev.00028.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2023] [Revised: 01/10/2024] [Accepted: 01/11/2024] [Indexed: 02/02/2024] Open
Abstract
Glucagon's ability to promote hepatic glucose production has been known for over a century, with initial observations touting this hormone as a diabetogenic agent. However, glucagon receptor agonism [when balanced with an incretin, including glucagon-like peptide 1 (GLP-1) to dampen glucose excursions] is now being developed as a promising therapeutic target in the treatment of metabolic diseases, like metabolic dysfunction-associated steatotic disease/metabolic dysfunction-associated steatohepatitis (MASLD/MASH), and may also have benefit for obesity and chronic kidney disease. Conventionally regarded as the opposing tag-team partner of the anabolic mediator insulin, glucagon is gradually emerging as more than just a "catabolic hormone." Glucagon action on glucose homeostasis within the liver has been well characterized. However, growing evidence, in part thanks to new and sensitive "omics" technologies, has implicated glucagon as more than just a "glucose liberator." Elucidation of glucagon's capacity to increase fatty acid oxidation while attenuating endogenous lipid synthesis speaks to the dichotomous nature of the hormone. Furthermore, glucagon action is not limited to just glucose homeostasis and lipid metabolism, as traditionally reported. Glucagon plays key regulatory roles in hepatic amino acid and ketone body metabolism, as well as mitochondrial turnover and function, indicating broader glucagon signaling consequences for metabolic homeostasis mediated by the liver. Here we examine the broadening role of glucagon signaling within the hepatocyte and question the current dogma, to appreciate glucagon as more than just that "catabolic hormone."
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Affiliation(s)
- Sarina Kajani
- Early Cardiovascular, Renal and Metabolism, Biopharmaceuticals R&D, AstraZeneca, Gaithersburg, Maryland, United States
| | - Rhianna C Laker
- Early Cardiovascular, Renal and Metabolism, Biopharmaceuticals R&D, AstraZeneca, Gaithersburg, Maryland, United States
| | - Ekaterina Ratkova
- Early Cardiovascular, Renal and Metabolism, Biopharmaceuticals R&D, AstraZeneca, Mölndal, Sweden
| | - Sarah Will
- Early Cardiovascular, Renal and Metabolism, Biopharmaceuticals R&D, AstraZeneca, Gaithersburg, Maryland, United States
| | - Christopher J Rhodes
- Early Cardiovascular, Renal and Metabolism, Biopharmaceuticals R&D, AstraZeneca, Gaithersburg, Maryland, United States
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2
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Estes SK, Shiota C, O'Brien TP, Printz RL, Shiota M. The impact of glucagon to support postabsorptive glucose flux and glycemia in healthy rats and its attenuation in male Zucker diabetic fatty rats. Am J Physiol Endocrinol Metab 2024; 326:E308-E325. [PMID: 38265288 DOI: 10.1152/ajpendo.00192.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/26/2023] [Revised: 01/19/2024] [Accepted: 01/19/2024] [Indexed: 01/25/2024]
Abstract
Hyperglucagonemia is a hallmark of type 2 diabetes (T2DM), yet the role of elevated plasma glucagon (P-GCG) to promote excessive postabsorptive glucose production and contribute to hyperglycemia in patients with this disease remains debatable. We investigated the acute action of P-GCG to safeguard/support postabsorptive endogenous glucose production (EGP) and euglycemia in healthy Zucker control lean (ZCL) rats. Using male Zucker diabetic fatty (ZDF) rats that exhibit the typical metabolic disorders of human T2DM, such as excessive EGP, hyperglycemia, hyperinsulinemia, and hyperglucagonemia, we examined the ability of hyperglucagonemia to promote greater rates of postabsorptive EGP and hyperglycemia. Euglycemic or hyperglycemic basal insulin (INS-BC) and glucagon (GCG-BC) clamps were performed in the absence or during an acute setting of glucagon deficiency (GCG-DF, ∼10% of basal), either alone or in combination with insulin deficiency (INS-DF, ∼10% of basal). Glucose appearance, disappearance, and cycling rates were measured using [2-3H] and [3-3H]-glucose. In ZCL rats, GCG-DF reduced the levels of hepatic cyclic AMP, EGP, and plasma glucose (PG) by 50%, 32%, and 50%, respectively. EGP fell in the presence GCG-DF and INS-BC, but under GCG-DF and INS-DF, EGP and PG increased two- and threefold, respectively. GCG-DF revealed the hyperglucagonemia present in ZDF rats lacked the ability to regulate hepatic intracellular cyclic AMP levels and glucose flux, since EGP and PG levels fell by only 10%. We conclude that the liver in T2DM suffers from resistance to all three major regulatory factors, glucagon, insulin, and glucose, thus leading to a loss of metabolic flexibility.NEW & NOTEWORTHY In postabsorptive state, basal plasma insulin (P-INS) and plasma glucose (PG) act dominantly to increase hepatic glucose cycling and reduce endogenous glucose production (EGP) and PG in healthy rats, which is only counteracted by the acute action of basal plasma glucagon (P-GCG) to support EGP and euglycemia. Hyperglucagonemia, a hallmark of type 2 diabetes (T2DM) present in Zucker diabetic fatty (ZDF) rats, is not the primary mediator of hyperglycemia and high EGP as commonly thought; instead, the liver is resistant to glucagon as well as insulin and glucose.
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Affiliation(s)
- Shanea K Estes
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee, United States
| | - Chiyo Shiota
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee, United States
| | - Tracy P O'Brien
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee, United States
| | - Richard L Printz
- Department of Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee, United States
| | - Masakazu Shiota
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee, United States
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3
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Himuro M, Wakabayashi Y, Taguchi T, Katahira T, Suzuki L, Iida H, Ogihara T, Nishida Y, Sasaki S, Lynn FC, Hiraoka Y, Oshima S, Okamoto R, Fujitani Y, Watada H, Miyatsuka T. Novel time-resolved reporter mouse reveals spatial and transcriptional heterogeneity during alpha cell differentiation. Diabetologia 2024; 67:156-169. [PMID: 37870650 DOI: 10.1007/s00125-023-06028-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/28/2023] [Accepted: 08/25/2023] [Indexed: 10/24/2023]
Abstract
AIMS/HYPOTHESIS Glucagon-expressing pancreatic alpha cells have attracted much attention for their plasticity to transdifferentiate into insulin-producing beta cells; however, it remains unclear precisely when, and from where, alpha cells emerge and what regulates alpha cell fate. We therefore explored the spatial and transcriptional heterogeneity of alpha cell differentiation using a novel time-resolved reporter system. METHODS We established the mouse model, 'Gcg-Timer', in which newly generated alpha cells can be distinguished from more-differentiated cells by their fluorescence. Fluorescence imaging and transcriptome analysis were performed with Gcg-Timer mice during the embryonic and postnatal stages. RESULTS Fluorescence imaging and flow cytometry demonstrated that green fluorescence-dominant cells were present in Gcg-Timer mice at the embryonic and neonatal stages but not after 1 week of age, suggesting that alpha cell neogenesis occurs during embryogenesis and early neonatal stages under physiological conditions. Transcriptome analysis of Gcg-Timer embryos revealed that the mRNAs related to angiogenesis were enriched in newly generated alpha cells. Histological analysis revealed that some alpha cells arise close to the pancreatic ducts, whereas the others arise away from the ducts and adjacent to the blood vessels. Notably, when the glucagon signal was suppressed by genetic ablation or by chemicals, such as neutralising glucagon antibody, green-dominant cells emerged again in adult mice. CONCLUSIONS/INTERPRETATION Novel time-resolved analysis with Gcg-Timer reporter mice uncovered spatiotemporal features of alpha cell neogenesis that will enhance our understanding of cellular identity and plasticity within the islets. DATA AVAILABILITY Raw and processed RNA sequencing data for this study has been deposited in the Gene Expression Omnibus under accession number GSE229090.
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Affiliation(s)
- Miwa Himuro
- Department of Metabolism and Endocrinology, Juntendo University Graduate School of Medicine, Tokyo, Japan
| | - Yuka Wakabayashi
- Department of Metabolism and Endocrinology, Juntendo University Graduate School of Medicine, Tokyo, Japan
| | - Tomomi Taguchi
- Department of Endocrinology, Diabetes and Metabolism, Kitasato University School of Medicine, Sagamihara, Japan
| | - Takehiro Katahira
- Department of Metabolism and Endocrinology, Juntendo University Graduate School of Medicine, Tokyo, Japan
| | - Luka Suzuki
- Department of Metabolism and Endocrinology, Juntendo University Graduate School of Medicine, Tokyo, Japan
| | - Hitoshi Iida
- Department of Metabolism and Endocrinology, Juntendo University Graduate School of Medicine, Tokyo, Japan
| | - Takeshi Ogihara
- Department of Metabolism and Endocrinology, Juntendo University Graduate School of Medicine, Tokyo, Japan
| | - Yuya Nishida
- Department of Metabolism and Endocrinology, Juntendo University Graduate School of Medicine, Tokyo, Japan
| | - Shugo Sasaki
- Diabetes Research Group, BC Children's Hospital Research Institute, Vancouver, BC, Canada
- Department of Metabolic Medicine, Osaka University Graduate School of Medicine, Osaka, Japan
| | - Francis C Lynn
- Diabetes Research Group, BC Children's Hospital Research Institute, Vancouver, BC, Canada
| | - Yuichi Hiraoka
- Laboratory of Genome Editing for Biomedical Research, Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan
| | - Shigeru Oshima
- Department of Gastroenterology and Hepatology, Tokyo Medical and Dental University, Tokyo, Japan
| | - Ryuichi Okamoto
- Department of Gastroenterology and Hepatology, Tokyo Medical and Dental University, Tokyo, Japan
| | - Yoshio Fujitani
- Laboratory of Developmental Biology & Metabolism, Institute for Molecular & Cellular Regulation, Gunma University, Maebashi, Japan
| | - Hirotaka Watada
- Department of Metabolism and Endocrinology, Juntendo University Graduate School of Medicine, Tokyo, Japan.
- Center for Identification of Diabetic Therapeutic Targets, Juntendo University Graduate School of Medicine, Tokyo, Japan.
| | - Takeshi Miyatsuka
- Department of Metabolism and Endocrinology, Juntendo University Graduate School of Medicine, Tokyo, Japan.
- Department of Endocrinology, Diabetes and Metabolism, Kitasato University School of Medicine, Sagamihara, Japan.
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4
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Liu T, Khanal S, Hertslet GD, Lamichhane R. Single-molecule analysis reveals that a glucagon-bound extracellular domain of the glucagon receptor is dynamic. J Biol Chem 2023; 299:105160. [PMID: 37586587 PMCID: PMC10514447 DOI: 10.1016/j.jbc.2023.105160] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2023] [Revised: 08/07/2023] [Accepted: 08/10/2023] [Indexed: 08/18/2023] Open
Abstract
Dynamic information is vital to understanding the activation mechanism of G protein-coupled receptors (GPCRs). Despite the availability of high-resolution structures of different conformational states, the dynamics of those states at the molecular level are poorly understood. Here, we used total internal reflection fluorescence microscopy to study the extracellular domain (ECD) of the glucagon receptor (GCGR), a class B family GPCR that controls glucose homeostasis. Single-molecule fluorescence resonance energy transfer was used to observe the ECD dynamics of GCGR molecules expressed and purified from mammalian cells. We observed that for apo-GCGR, the ECD is dynamic and spent time predominantly in a closed conformation. In the presence of glucagon, the ECD is wide open and also shows more dynamic behavior than apo-GCGR, a finding that was not previously reported. These results suggest that both apo-GCGR and glucagon-bound GCGRs show reversible opening and closing of the ECD with respect to the seven-transmembrane (7TM) domain. This work demonstrates a molecular approach to visualizing the dynamics of the GCGR ECD and provides a foundation for understanding the conformational changes underlying GPCR activation, which is critical in the development of new therapeutics.
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Affiliation(s)
- Ting Liu
- Department of Biochemistry & Cellular and Molecular Biology, College of Arts & Sciences, University of Tennessee, Knoxville, Tennessee, USA
| | - Susmita Khanal
- Department of Biochemistry & Cellular and Molecular Biology, College of Arts & Sciences, University of Tennessee, Knoxville, Tennessee, USA
| | - Gillian D Hertslet
- Department of Biochemistry & Cellular and Molecular Biology, College of Arts & Sciences, University of Tennessee, Knoxville, Tennessee, USA
| | - Rajan Lamichhane
- Department of Biochemistry & Cellular and Molecular Biology, College of Arts & Sciences, University of Tennessee, Knoxville, Tennessee, USA.
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5
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Viloria K, Nasteska D, Ast J, Hasib A, Cuozzo F, Heising S, Briant LJB, Hewison M, Hodson DJ. GC-Globulin/Vitamin D-Binding Protein Is Required for Pancreatic α-Cell Adaptation to Metabolic Stress. Diabetes 2023; 72:275-289. [PMID: 36445949 DOI: 10.2337/db22-0326] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/06/2022] [Accepted: 11/14/2022] [Indexed: 12/02/2022]
Abstract
GC-globulin (GC), or vitamin D-binding protein, is a multifunctional protein involved in the transport of circulating vitamin 25(OH)D and fatty acids, as well as actin scavenging. In the pancreatic islets, the gene encoding GC, GC/Gc, is highly localized to glucagon-secreting α-cells. Despite this, the role of GC in α-cell function is poorly understood. We previously showed that GC is essential for α-cell morphology, electrical activity, and glucagon secretion. We now show that loss of GC exacerbates α-cell failure during metabolic stress. High-fat diet-fed GC-/- mice have basal hyperglucagonemia, which is associated with decreased α-cell size, impaired glucagon secretion and Ca2+ fluxes, and changes in glucose-dependent F-actin remodelling. Impairments in glucagon secretion can be rescued using exogenous GC to replenish α-cell GC levels, increase glucagon granule area, and restore the F-actin cytoskeleton. Lastly, GC levels decrease in α-cells of donors with type 2 diabetes, which is associated with changes in α-cell mass, morphology, and glucagon expression. Together, these data demonstrate an important role for GC in α-cell adaptation to metabolic stress.
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Affiliation(s)
- Katrina Viloria
- Institute of Metabolism and Systems Research (IMSR), and Centre of Membrane Proteins and Receptors (COMPARE), University of Birmingham, Birmingham, U.K
- Centre for Endocrinology, Diabetes and Metabolism, Birmingham Health Partners, Birmingham, U.K
| | - Daniela Nasteska
- Institute of Metabolism and Systems Research (IMSR), and Centre of Membrane Proteins and Receptors (COMPARE), University of Birmingham, Birmingham, U.K
- Centre for Endocrinology, Diabetes and Metabolism, Birmingham Health Partners, Birmingham, U.K
| | - Julia Ast
- Institute of Metabolism and Systems Research (IMSR), and Centre of Membrane Proteins and Receptors (COMPARE), University of Birmingham, Birmingham, U.K
- Centre for Endocrinology, Diabetes and Metabolism, Birmingham Health Partners, Birmingham, U.K
| | - Annie Hasib
- Institute of Metabolism and Systems Research (IMSR), and Centre of Membrane Proteins and Receptors (COMPARE), University of Birmingham, Birmingham, U.K
- Centre for Endocrinology, Diabetes and Metabolism, Birmingham Health Partners, Birmingham, U.K
| | - Federica Cuozzo
- Institute of Metabolism and Systems Research (IMSR), and Centre of Membrane Proteins and Receptors (COMPARE), University of Birmingham, Birmingham, U.K
- Centre for Endocrinology, Diabetes and Metabolism, Birmingham Health Partners, Birmingham, U.K
| | - Silke Heising
- Institute of Metabolism and Systems Research (IMSR), and Centre of Membrane Proteins and Receptors (COMPARE), University of Birmingham, Birmingham, U.K
- Centre for Endocrinology, Diabetes and Metabolism, Birmingham Health Partners, Birmingham, U.K
| | - Linford J B Briant
- Oxford Centre for Diabetes, Endocrinology and Metabolism (OCDEM), National Institute for Health Research (NIHR) Oxford Biomedical Research Centre, Churchill Hospital, Radcliffe Department of Medicine, University of Oxford, Oxford, U.K
| | - Martin Hewison
- Institute of Metabolism and Systems Research (IMSR), and Centre of Membrane Proteins and Receptors (COMPARE), University of Birmingham, Birmingham, U.K
- Centre for Endocrinology, Diabetes and Metabolism, Birmingham Health Partners, Birmingham, U.K
| | - David J Hodson
- Institute of Metabolism and Systems Research (IMSR), and Centre of Membrane Proteins and Receptors (COMPARE), University of Birmingham, Birmingham, U.K
- Centre for Endocrinology, Diabetes and Metabolism, Birmingham Health Partners, Birmingham, U.K
- Oxford Centre for Diabetes, Endocrinology and Metabolism (OCDEM), National Institute for Health Research (NIHR) Oxford Biomedical Research Centre, Churchill Hospital, Radcliffe Department of Medicine, University of Oxford, Oxford, U.K
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6
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Tellez K, Hang Y, Gu X, Chang CA, Stein RW, Kim SK. In vivo studies of glucagon secretion by human islets transplanted in mice. Nat Metab 2020; 2:547-557. [PMID: 32694729 PMCID: PMC7739959 DOI: 10.1038/s42255-020-0213-x] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/05/2019] [Accepted: 04/24/2020] [Indexed: 02/06/2023]
Abstract
Little is known about regulated glucagon secretion by human islet α-cells compared to insulin secretion from β-cells, despite conclusive evidence of dysfunction in both cell types in diabetes mellitus. Distinct insulins in humans and mice permit in vivo studies of human β-cell regulation after human islet transplantation in immunocompromised mice, whereas identical glucagon sequences prevent analogous in vivo measures of glucagon output from human α-cells. Here, we use CRISPR-Cas9 editing to remove glucagon codons 2-29 in immunocompromised NSG mice, preserving the production of other proglucagon-derived hormones. Glucagon knockout NSG (GKO-NSG) mice have metabolic, liver and pancreatic phenotypes associated with glucagon-signalling deficits that revert after transplantation of human islets from non-diabetic donors. Glucagon hypersecretion by transplanted islets from donors with type 2 diabetes revealed islet-intrinsic defects. We suggest that GKO-NSG mice provide an unprecedented resource to investigate human α-cell regulation in vivo.
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Affiliation(s)
- Krissie Tellez
- Department of Developmental Biology, Stanford University School of Medicine, Stanford, CA, USA
| | - Yan Hang
- Department of Developmental Biology, Stanford University School of Medicine, Stanford, CA, USA
- Stanford Diabetes Research Center, Stanford University School of Medicine, Stanford, CA, USA
| | - Xueying Gu
- Department of Developmental Biology, Stanford University School of Medicine, Stanford, CA, USA
| | - Charles A Chang
- Department of Developmental Biology, Stanford University School of Medicine, Stanford, CA, USA
| | - Roland W Stein
- Department of Molecular Physiology and Biophysics, Vanderbilt University Medical Center, Nashville, TN, USA
- Department of Cell and Developmental Biology, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Seung K Kim
- Department of Developmental Biology, Stanford University School of Medicine, Stanford, CA, USA.
- Stanford Diabetes Research Center, Stanford University School of Medicine, Stanford, CA, USA.
- Department of Medicine (Endocrinology Division), Stanford University School of Medicine, Stanford, CA, USA.
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7
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Perry RJ, Zhang D, Guerra MT, Brill AL, Goedeke L, Nasiri AR, Rabin-Court A, Wang Y, Peng L, Dufour S, Zhang Y, Zhang XM, Butrico GM, Toussaint K, Nozaki Y, Cline GW, Petersen KF, Nathanson MH, Ehrlich BE, Shulman GI. Glucagon stimulates gluconeogenesis by INSP3R1-mediated hepatic lipolysis. Nature 2020; 579:279-283. [PMID: 32132708 PMCID: PMC7101062 DOI: 10.1038/s41586-020-2074-6] [Citation(s) in RCA: 87] [Impact Index Per Article: 21.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2018] [Accepted: 01/15/2020] [Indexed: 11/09/2022]
Abstract
While it is well-established that alterations in the portal vein insulin/glucagon ratio play a major role in causing dysregulated hepatic glucose metabolism in type 2 diabetes (T2D)1–3, the mechanisms by which glucagon alters hepatic glucose production and mitochondrial oxidation remain poorly understood. Here we show that glucagon stimulates hepatic gluconeogenesis by increasing hepatic adipose triglyceride lipase activity, intrahepatic lipolysis, hepatic acetyl-CoA content, and pyruvate carboxylase flux, while also increasing mitochondrial fat oxidation, mediated by stimulation of the inositol triphosphate receptor-1 (InsP3R-I). Chronic physiological increases in plasma glucagon concentrations increased mitochondrial hepatic fat oxidation and reversed diet-induced hepatic steatosis and insulin resistance in rats and mice; however, the effect of chronic glucagon treatment to reverse hepatic steatosis and glucose intolerance was abrogated in InsP3R-I knockout mice. These results provide new insights into glucagon biology and suggest that InsP3R-I may be a novel therapeutic target to reverse nonalcoholic fatty liver disease and T2D.
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Affiliation(s)
- Rachel J Perry
- Department of Internal Medicine, Yale School of Medicine, New Haven, CT, USA.,Department of Cellular and Molecular Physiology, Yale School of Medicine, New Haven, CT, USA
| | - Dongyan Zhang
- Department of Internal Medicine, Yale School of Medicine, New Haven, CT, USA
| | - Mateus T Guerra
- Department of Internal Medicine, Yale School of Medicine, New Haven, CT, USA
| | - Allison L Brill
- Department of Cellular and Molecular Physiology, Yale School of Medicine, New Haven, CT, USA
| | - Leigh Goedeke
- Department of Internal Medicine, Yale School of Medicine, New Haven, CT, USA
| | - Ali R Nasiri
- Department of Internal Medicine, Yale School of Medicine, New Haven, CT, USA
| | - Aviva Rabin-Court
- Department of Internal Medicine, Yale School of Medicine, New Haven, CT, USA
| | - Yongliang Wang
- Department of Internal Medicine, Yale School of Medicine, New Haven, CT, USA
| | - Liang Peng
- Department of Internal Medicine, Yale School of Medicine, New Haven, CT, USA
| | - Sylvie Dufour
- Department of Internal Medicine, Yale School of Medicine, New Haven, CT, USA
| | - Ye Zhang
- Department of Internal Medicine, Yale School of Medicine, New Haven, CT, USA
| | - Xian-Man Zhang
- Department of Internal Medicine, Yale School of Medicine, New Haven, CT, USA
| | - Gina M Butrico
- Department of Internal Medicine, Yale School of Medicine, New Haven, CT, USA
| | - Keshia Toussaint
- Department of Internal Medicine, Yale School of Medicine, New Haven, CT, USA
| | - Yuichi Nozaki
- Department of Internal Medicine, Yale School of Medicine, New Haven, CT, USA
| | - Gary W Cline
- Department of Internal Medicine, Yale School of Medicine, New Haven, CT, USA
| | - Kitt Falk Petersen
- Department of Internal Medicine, Yale School of Medicine, New Haven, CT, USA
| | - Michael H Nathanson
- Department of Internal Medicine, Yale School of Medicine, New Haven, CT, USA
| | - Barbara E Ehrlich
- Department of Cellular and Molecular Physiology, Yale School of Medicine, New Haven, CT, USA.,Department of Pharmacology, Yale School of Medicine, New Haven, CT, USA
| | - Gerald I Shulman
- Department of Internal Medicine, Yale School of Medicine, New Haven, CT, USA. .,Department of Cellular and Molecular Physiology, Yale School of Medicine, New Haven, CT, USA.
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8
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Kleinert M, Sachs S, Habegger KM, Hofmann SM, Müller TD. Glucagon Regulation of Energy Expenditure. Int J Mol Sci 2019; 20:ijms20215407. [PMID: 31671603 PMCID: PMC6862306 DOI: 10.3390/ijms20215407] [Citation(s) in RCA: 53] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2019] [Revised: 10/23/2019] [Accepted: 10/24/2019] [Indexed: 02/07/2023] Open
Abstract
Glucagon's ability to increase energy expenditure has been known for more than 60 years, yet the mechanisms underlining glucagon's thermogenic effect still remain largely elusive. Over the last years, significant efforts were directed to unravel the physiological and cellular underpinnings of how glucagon regulates energy expenditure. In this review, we summarize the current knowledge on how glucagon regulates systems metabolism with a special emphasis on its acute and chronic thermogenic effects.
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Affiliation(s)
- Maximilian Kleinert
- Institute for Diabetes and Obesity, Helmholtz Diabetes Center at Helmholtz Centre Munich, Ingolstädter Landstraße 1, 85764 Oberschleißheim, Germany.
- Section of Molecular Physiology, Department of Nutrition, Exercise and Sports, University of Copenhagen, 2100 Copenhagen, Denmark.
| | - Stephan Sachs
- Institute for Diabetes and Obesity, Helmholtz Diabetes Center at Helmholtz Centre Munich, Ingolstädter Landstraße 1, 85764 Oberschleißheim, Germany.
- Division of Metabolic Diseases, Technische Universität München, 85740 Munich, Germany.
| | - Kirk M Habegger
- Department of Medicine-Endocrinology and Comprehensive Diabetes Center, Diabetes and Metabolism, University of Alabama at Birmingham, Birmingham, AL 35899, USA.
| | - Susanna M Hofmann
- Institute for Diabetes and Regeneration, Helmholtz Diabetes Center at Helmholtz Zentrum München, German Research Center for Environmental Health (GmbH), 85764 Neuherberg, Germany.
- German Center for Diabetes Research (DZD), 85764 Neuherberg, Germany.
- Medizinische Klinik und Poliklinik IV, Klinikum der LMU, 80336 München, Germany.
| | - Timo D Müller
- Institute for Diabetes and Obesity, Helmholtz Diabetes Center at Helmholtz Centre Munich, Ingolstädter Landstraße 1, 85764 Oberschleißheim, Germany.
- German Center for Diabetes Research (DZD), 85764 Neuherberg, Germany.
- Department of Pharmacology and Experimental Therapy, Institute of Experimental and Clinical Pharmacology and Toxicology, Eberhard Karls University Hospitals and Clinics, 72076 Tübingen, Germany.
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9
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Abstract
PURPOSE OF REVIEW Glucagon is known as a key hormone in the control of glucose and amino acid metabolism. Critical illness is hallmarked by a profound alteration in glucose and amino acid metabolism, accompanied by muscle wasting and hypoaminoacidemia. Here we review novel insights in glucagon (patho)physiology and discuss the recently discovered role of glucagon in controlling amino acid metabolism during critical illness. RECENT FINDINGS The role of glucagon in glucose metabolism is much more complex than originally anticipated, and glucagon has shown to be a key player in amino acid metabolism. During critical illness, the contribution of glucagon in bringing about hyperglycemia appeared to be quite limited, whereas increased glucagon availability seems to contribute importantly to the typical hypoaminoacidemia via stimulating hepatic amino acid breakdown, without affecting muscle wasting. Providing amino acids further increases hepatic amino acid breakdown, mediated by a further increase in glucagon. SUMMARY Glucagon plays a crucial role in amino acid metabolism during critical illness, with an apparent feedback loop between glucagon and circulating amino acids. Indeed, elevated glucagon may, to a large extent, be responsible for the hypoaminoacidemia in the critically ill and infusing amino acids increases glucagon-driven amino acid breakdown in the liver. These novel insights further question the rationale for amino acid administration during critical illness.
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10
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Design, synthesis, and effects of novel phenylpyrimidines as glucagon receptor antagonists. Bioorg Med Chem 2018; 26:5701-5710. [PMID: 30366787 DOI: 10.1016/j.bmc.2018.10.013] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2018] [Revised: 10/16/2018] [Accepted: 10/18/2018] [Indexed: 11/20/2022]
Abstract
The hormone glucagon increases blood glucose levels through increasing hepatic glucose output. In diabetic patients, dysregulation of glucagon secretion contributes to hyperglycemia. Thus, the inhibition of glucagon receptor is one target for the treatment of hyperglycemia in type 2 diabetes. Here we designed and synthesized a series of small molecules based on phenylpyrimidine. Of these, the compound (R)-7a most significantly decreased the glucagon-induced cAMP production and glucagon-induced glucose production during in vitro and in vivo assays. In addition, (R)-7a showed good efficacy in glucagon challenge tests and lowered blood glucose levels in diabetic db/db mice. Our results suggest that the compound (R)-7a could be a potential glucose-lowering agent for treating type 2 diabetes.
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11
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Zhang Y, Thai K, Jin T, Woo M, Gilbert RE. SIRT1 activation attenuates α cell hyperplasia, hyperglucagonaemia and hyperglycaemia in STZ-diabetic mice. Sci Rep 2018; 8:13972. [PMID: 30228292 PMCID: PMC6143559 DOI: 10.1038/s41598-018-32351-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2018] [Accepted: 09/04/2018] [Indexed: 12/19/2022] Open
Abstract
The NAD+-dependent lysine deacetylase, Sirtuin 1 (SIRT1), plays a central role in metabolic regulation. With type 1 diabetes a disease that is characterised by metabolic dysregulation, we sought to assess the impact of SIRT1 activation in experimental, streptozotocin (STZ)-induced diabetes. CD1 mice with and without STZ-induced diabetes were randomized to receive the SIRT1 activating compound, SRT3025, or vehicle over 20 weeks. Vehicle treated STZ-CD1 mice developed severe hyperglycaemia with near-absent circulating insulin and widespread beta cell loss in association with hyperglucagonaemia and expanded islet alpha cell mass. Without affecting ß-cell mass or circulating insulin, diabetic mice that received SRT3025 had substantially improved glycaemic control with greatly reduced islet α cell mass and lower plasma glucagon concentrations. Consistent with reduced glucagon abundance, the diabetes-associated overexpression of key gluconeogenic enzymes, glucose-6-phosphatase and PEPCK were also lowered by SRT3025. Incubating cultured α cells with SRT3025 diminished their glucagon secretion and proliferative activity in association with a reduction in the α cell associated transcription factor, Aristaless Related Homeobox (Arx). By reducing the paradoxical increase in glucagon, SIRT1 activation may offer a new, α-cell centric approach to the treatment of type 1 diabetes.
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Affiliation(s)
- Yanling Zhang
- St. Michael's Hospital, Keenan Research Centre, Li Ka Shing Knowledge Institute, Toronto, M5B 1W8, Canada
| | - Kerri Thai
- St. Michael's Hospital, Keenan Research Centre, Li Ka Shing Knowledge Institute, Toronto, M5B 1W8, Canada
| | - Tianru Jin
- Toronto General Hospital Research Institute (TGHRI), Toronto, ON, M5G 2C4, Canada
| | - Minna Woo
- Toronto General Hospital Research Institute (TGHRI), Toronto, ON, M5G 2C4, Canada
| | - Richard E Gilbert
- St. Michael's Hospital, Keenan Research Centre, Li Ka Shing Knowledge Institute, Toronto, M5B 1W8, Canada.
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12
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Wewer Albrechtsen NJ. Glucagon receptor signaling in metabolic diseases. Peptides 2018; 100:42-47. [PMID: 29412830 DOI: 10.1016/j.peptides.2017.11.016] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/27/2017] [Revised: 11/23/2017] [Accepted: 11/24/2017] [Indexed: 01/25/2023]
Abstract
Glucagon is a peptide hormone secreted from the pancreatic alpha cells in response to hypoglycemia but in some patients with type 2 diabetes a paradoxical hypersecretion results from the intake of glucose. In rodent, antagonizing the actions of glucagon have been shown to be effective for lowering blood glucose levels and this has recently have been solidified in patients with type 2 diabetes. Although the reported increases of liver enzymes, hyperglucagonemia, and alpha cell hyperplasia resulting from glucagon receptor antagonism may potentially limit the clinical applicability of glucagon receptor antagonists, they may serve as an instrumental toolbox for delineating the physiology of glucagon. Agonizing glucagon receptor signaling may be relevant, in particular when combined with glucagon-like peptide-1 receptor analogues in the perspective of body weight lowering therapy. Here, we will focus on new conceptual aspects of glucagon biology and how this may led to new diagnostics and treatment of metabolic diseases.
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Affiliation(s)
- Nicolai J Wewer Albrechtsen
- Department of Biomedical Sciences, Novo Nordisk Foundation Center for Basic Metabolic Research, and the Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3B, 2200, Copenhagen, Denmark.
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13
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Kim K, Ryu D, Dongiovanni P, Ozcan L, Nayak S, Ueberheide B, Valenti L, Auwerx J, Pajvani UB. Degradation of PHLPP2 by KCTD17, via a Glucagon-Dependent Pathway, Promotes Hepatic Steatosis. Gastroenterology 2017; 153:1568-1580.e10. [PMID: 28859855 PMCID: PMC5705280 DOI: 10.1053/j.gastro.2017.08.039] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/19/2017] [Revised: 08/22/2017] [Accepted: 08/23/2017] [Indexed: 12/16/2022]
Abstract
BACKGROUND & AIMS Obesity-induced nonalcoholic fatty liver disease (NAFLD) develops, in part, via excess insulin-stimulated hepatic de novo lipogenesis, which increases, paradoxically, in patients with obesity-induced insulin resistance. Pleckstrin homology domain leucine-rich repeat protein phosphatase 2 (PHLPP2) terminates insulin signaling by dephosphorylating Akt; levels of PHLPP2 are reduced in livers from obese mice. We investigated whether loss of hepatic PHLPP2 is sufficient to induce fatty liver in mice, mechanisms of PHLPP2 degradation in fatty liver, and expression of genes that regulate PHLPP2 in livers of patients with NAFLD. METHODS C57BL/6J mice (controls), obese db/db mice, and mice with liver-specific deletion of PHLPP2 (L-PHLPP2) fed either normal chow or high-fat diet (HFD) were analyzed for metabolic phenotypes, including glucose tolerance and hepatic steatosis. PHLPP2-deficient primary hepatocytes or CRISPR/Cas9-mediated PHLPP2-knockout hepatoma cells were analyzed for insulin signaling and gene expression. We performed mass spectrometry analyses of liver tissues from C57BL/6J mice transduced with Ad-HA-Flag-PHLPP2 to identify posttranslational modifications to PHLPP2 and proteins that interact with PHLPP2. We measured levels of mRNAs by quantitative reverse transcription polymerase chain reaction in liver biopsies from patients with varying degrees of hepatic steatosis. RESULTS PHLPP2-knockout hepatoma cells and hepatocytes from L-PHLPP2 mice showed normal initiation of insulin signaling, but prolonged insulin action. Chow-fed L-PHLPP2 mice had normal glucose tolerance but hepatic steatosis. In HFD-fed C57BL/6J or db/db obese mice, endogenous PHLPP2 was degraded by glucagon and PKA-dependent phosphorylation of PHLPP2 (at Ser1119 and Ser1210), which led to PHLPP2 binding to potassium channel tetramerization domain containing 17 (KCTD17), a substrate-adaptor for Cul3-RING ubiquitin ligases. Levels of KCTD17 mRNA were increased in livers of HFD-fed C57BL/6J or db/db obese mice and in liver biopsies patients with NAFLD, compared with liver tissues from healthy control mice or patients without steatosis. Knockdown of KCTD17 with small hairpin RNA in primary hepatocytes increased PHLPP2 protein but not Phlpp2 mRNA, indicating that KCTD17 mediates PHLPP2 degradation. KCTD17 knockdown in obese mice prevented PHLPP2 degradation and decreased expression of lipogenic genes. CONCLUSIONS In mouse models of obesity, we found that PHLPP2 degradation induced lipogenesis without affecting gluconeogenesis. KCTD17, which is up-regulated in liver tissues of obese mice and patients with NAFLD, binds to phosphorylated PHLPP2 to target it for ubiquitin-mediated degradation; this increases expression of genes that regulate lipogenesis to promote hepatic steatosis. Inhibitors of this pathway might be developed for treatment of patients with NAFLD.
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Affiliation(s)
- KyeongJin Kim
- Department of Medicine, Columbia University, New York, NY 10032, USA
| | - Dongryeol Ryu
- Laboratory of Integrative and Systems Physiology, École Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland,Department of Korean Medical Science, School of Korean Medicine and Healthy-Aging Korean Medical Research Center, Pusan National University, Republic of Korea
| | - Paola Dongiovanni
- Internal Medicine and Metabolic Diseases, Fondazione IRCCS Ca’ Granda Ospedale Maggiore Policlinico, DEPT, Università degli Studi di Milano, Milano, Italy
| | - Lale Ozcan
- Department of Medicine, Columbia University, New York, NY 10032, USA
| | - Shruti Nayak
- Proteomics Laboratory, Division of Advanced Research and Technologies, New York University School of Medicine
| | - Beatrix Ueberheide
- Proteomics Laboratory, Division of Advanced Research and Technologies, New York University School of Medicine,Department of Biochemistry and Molecular Pharmacology, New York University Langone Medical Center
| | - Luca Valenti
- Internal Medicine and Metabolic Diseases, Fondazione IRCCS Ca’ Granda Ospedale Maggiore Policlinico, DEPT, Università degli Studi di Milano, Milano, Italy
| | - Johan Auwerx
- Laboratory of Integrative and Systems Physiology, École Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland
| | - Utpal B. Pajvani
- Department of Medicine, Columbia University, New York, NY 10032, USA
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14
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Thiessen SE, Derde S, Derese I, Dufour T, Vega CA, Langouche L, Goossens C, Peersman N, Vermeersch P, Vander Perre S, Holst JJ, Wouters PJ, Vanhorebeek I, Van den Berghe G. Role of Glucagon in Catabolism and Muscle Wasting of Critical Illness and Modulation by Nutrition. Am J Respir Crit Care Med 2017; 196:1131-1143. [PMID: 28475354 DOI: 10.1164/rccm.201702-0354oc] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
RATIONALE Critical illness is hallmarked by muscle wasting and disturbances in glucose, lipid, and amino acid homeostasis. Circulating concentrations of glucagon, a catabolic hormone that affects these metabolic pathways, are elevated during critical illness. Insight in the nutritional regulation of glucagon and its metabolic role during critical illness is lacking. OBJECTIVES To evaluate whether macronutrient infusion can suppress plasma glucagon during critical illness and study the role of illness-induced glucagon abundance in the disturbed glucose, lipid, and amino acid homeostasis and in muscle wasting during critical illness. METHODS In human and mouse studies, we infused macronutrients and manipulated glucagon availability up and down to investigate its acute and chronic metabolic role during critical illness. MEASUREMENTS AND MAIN RESULTS In critically ill patients, infusing glucose with insulin did not lower glucagon, whereas parenteral nutrition containing amino acids increased glucagon. In critically ill mice, infusion of amino acids increased glucagon and up-regulated markers of hepatic amino acid catabolism without affecting muscle wasting. Immunoneutralizing glucagon in critically ill mice only transiently affected glucose and lipid metabolism, did not affect muscle wasting, but drastically suppressed markers of hepatic amino acid catabolism and reversed the illness-induced hypoaminoacidemia. CONCLUSIONS These data suggest that elevated glucagon availability during critical illness increases hepatic amino acid catabolism, explaining the illness-induced hypoaminoacidemia, without affecting muscle wasting and without a sustained impact on blood glucose. Furthermore, amino acid infusion likely results in a further breakdown of amino acids in the liver, mediated by increased glucagon, without preventing muscle wasting. Clinical trial registered with www.clinicaltrials.gov (NCT 00512122).
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Affiliation(s)
- Steven E Thiessen
- 1 Clinical Division and Laboratory of Intensive Care Medicine, Department of Cellular and Molecular Medicine, and
| | - Sarah Derde
- 1 Clinical Division and Laboratory of Intensive Care Medicine, Department of Cellular and Molecular Medicine, and
| | - Inge Derese
- 1 Clinical Division and Laboratory of Intensive Care Medicine, Department of Cellular and Molecular Medicine, and
| | - Thomas Dufour
- 1 Clinical Division and Laboratory of Intensive Care Medicine, Department of Cellular and Molecular Medicine, and
| | - Chloé Albert Vega
- 1 Clinical Division and Laboratory of Intensive Care Medicine, Department of Cellular and Molecular Medicine, and
| | - Lies Langouche
- 1 Clinical Division and Laboratory of Intensive Care Medicine, Department of Cellular and Molecular Medicine, and
| | - Chloë Goossens
- 1 Clinical Division and Laboratory of Intensive Care Medicine, Department of Cellular and Molecular Medicine, and
| | - Nele Peersman
- 2 Department of Laboratory Medicine, KU Leuven, Leuven, Belgium; and
| | - Pieter Vermeersch
- 2 Department of Laboratory Medicine, KU Leuven, Leuven, Belgium; and
| | - Sarah Vander Perre
- 1 Clinical Division and Laboratory of Intensive Care Medicine, Department of Cellular and Molecular Medicine, and
| | - Jens J Holst
- 3 Novo Nordisk Foundation Center for Basic Metabolic Research and.,4 Department of Biomedical Sciences, Panum Institute, University of Copenhagen, Copenhagen, Denmark
| | - Pieter J Wouters
- 1 Clinical Division and Laboratory of Intensive Care Medicine, Department of Cellular and Molecular Medicine, and
| | - Ilse Vanhorebeek
- 1 Clinical Division and Laboratory of Intensive Care Medicine, Department of Cellular and Molecular Medicine, and
| | - Greet Van den Berghe
- 1 Clinical Division and Laboratory of Intensive Care Medicine, Department of Cellular and Molecular Medicine, and
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15
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Scheen AJ, Paquot N, Lefèbvre PJ. Investigational glucagon receptor antagonists in Phase I and II clinical trials for diabetes. Expert Opin Investig Drugs 2017; 26:1373-1389. [PMID: 29052441 DOI: 10.1080/13543784.2017.1395020] [Citation(s) in RCA: 58] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
INTRODUCTION Despite type 2 diabetes (T2D) being recognized as a bihormonal pancreatic disease, current therapies are mainly focusing on insulin, while targeting glucagon has been long dismissed. However, glucagon receptor (GCGr) antagonists are currently investigated in clinical trials. Area covered: Following a brief description of the rationale for antagonizing GCGr in T2D, lessons from GCGr knock-out mice and pharmacological means to antagonize GCGr, a detailed description of the main results obtained with GCGr antagonists in Phase I-II clinical trials is provided. The development of several small molecules has been discontinued, while new ones are currently considered as well as innovative approaches such as monoclonal antibodies or antisense oligonucleotides inhibiting GCGr gene expression. Their potential benefits but also limitations are discussed. Expert opinion: The proof-of-concept that antagonizing GCGr improves glucose control in T2D has been confirmed in humans. Nevertheless, some adverse events led to stopping the development of some of these GCGr antagonists. New approaches seem to have a better benefit/risk balance, although none has progressed to Phase III clinical trials so far. Pharmacotherapy of T2D is becoming a highly competitive field so that GCGr antagonists should provide clear advantages over numerous existing glucose-lowering medications before eventually reaching clinical practice.
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Affiliation(s)
- André J Scheen
- a Division of Clinical Pharmacology , Center for Interdisciplinary Research on Medicines (CIRM), University of Liège , Belgium.,b Division of Diabetes, Nutrition and Metabolic Disorders, Department of Medicine , CHU , Liège , Belgium
| | - Nicolas Paquot
- b Division of Diabetes, Nutrition and Metabolic Disorders, Department of Medicine , CHU , Liège , Belgium
| | - Pierre J Lefèbvre
- b Division of Diabetes, Nutrition and Metabolic Disorders, Department of Medicine , CHU , Liège , Belgium
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16
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Neumann UH, Ho JSS, Chen S, Tam YYC, Cullis PR, Kieffer TJ. Lipid nanoparticle delivery of glucagon receptor siRNA improves glucose homeostasis in mouse models of diabetes. Mol Metab 2017; 6:1161-1172. [PMID: 29031717 PMCID: PMC5641600 DOI: 10.1016/j.molmet.2017.06.012] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/14/2017] [Revised: 06/17/2017] [Accepted: 06/19/2017] [Indexed: 12/15/2022] Open
Abstract
Objective Hyperglucagonemia is present in many forms of diabetes and contributes to hyperglycemia, and glucagon suppression can ameliorate diabetes in mice. Leptin, a glucagon suppressor, can also reverse diabetes in rodents. Lipid nanoparticle (LNP) delivery of small interfering RNA (siRNA) effectively targets the liver and is in clinical trials for the treatment of various diseases. We compared the effectiveness of glucagon receptor (Gcgr)-siRNA delivered via LNPs to leptin in two mouse models of diabetes. Methods Gcgr siRNA encapsulated into LNPs or leptin was administered to mice with diabetes due to injection of the β-cell toxin streptozotocin (STZ) alone or combined with high fat diet (HFD/STZ). Results In STZ-diabetic mice, a single injection of Gcgr siRNA lowered blood glucose levels for 3 weeks, improved glucose tolerance, and normalized plasma ketones levels, while leptin therapy normalized blood glucose levels, oral glucose tolerance, and plasma ketones, and suppressed lipid metabolism. In contrast, in HFD/STZ-diabetic mice, Gcgr siRNA lowered blood glucose levels for 2 months, improved oral glucose tolerance, and reduced HbA1c, while leptin had no beneficial effects. Conclusions While leptin may be more effective than Gcgr siRNA at normalizing both glucose and lipid metabolism in STZ diabetes, Gcgr siRNA is more effective at reducing blood glucose levels in HFD/STZ diabetes. Gcgr siRNA improves glucose metabolism but not lipid metabolism in STZ diabetic mice. Leptin improves both glucose and lipid metabolism in STZ diabetic mice. Gcgr siRNA improves glucose metabolism in HFD/STZ diabetic mice. Leptin does not improve glucose metabolism in HFD/STZ diabetic mice.
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Affiliation(s)
- Ursula H Neumann
- Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, British Columbia, V6T 1Z3, Canada
| | - Jessica S S Ho
- Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, British Columbia, V6T 1Z3, Canada
| | - Sam Chen
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, British Columbia, V6T 1Z3, Canada
| | - Yuen Yi C Tam
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, British Columbia, V6T 1Z3, Canada
| | - Pieter R Cullis
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, British Columbia, V6T 1Z3, Canada
| | - Timothy J Kieffer
- Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, British Columbia, V6T 1Z3, Canada; Department of Surgery, University of British Columbia, Vancouver, British Columbia, V6T 1Z3, Canada.
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17
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D'souza AM, Neumann UH, Glavas MM, Kieffer TJ. The glucoregulatory actions of leptin. Mol Metab 2017; 6:1052-1065. [PMID: 28951828 PMCID: PMC5605734 DOI: 10.1016/j.molmet.2017.04.011] [Citation(s) in RCA: 114] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/06/2017] [Revised: 04/18/2017] [Accepted: 04/24/2017] [Indexed: 12/28/2022] Open
Abstract
Background The hormone leptin is an important regulator of metabolic homeostasis, able to inhibit food intake and increase energy expenditure. Leptin can also independently lower blood glucose levels, particularly in hyperglycemic models of leptin or insulin deficiency. Despite significant efforts and relevance to diabetes, the mechanisms by which leptin acts to regulate blood glucose levels are not fully understood. Scope of review Here we assess literature relevant to the glucose lowering effects of leptin. Leptin receptors are widely expressed in multiple cell types, and we describe both peripheral and central effects of leptin that may be involved in lowering blood glucose. In addition, we summarize the potential clinical application of leptin in regulating glucose homeostasis. Major conclusions Leptin exerts a plethora of metabolic effects on various tissues including suppressing production of glucagon and corticosterone, increasing glucose uptake, and inhibiting hepatic glucose output. A more in-depth understanding of the mechanisms of the glucose-lowering actions of leptin may reveal new strategies to treat metabolic disorders.
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Affiliation(s)
- Anna M D'souza
- Department of Cellular and Physiological Sciences, University of British Columbia, 2350 Health Sciences Mall, Vancouver, British Columbia V6T 1Z3, Canada
| | - Ursula H Neumann
- Department of Cellular and Physiological Sciences, University of British Columbia, 2350 Health Sciences Mall, Vancouver, British Columbia V6T 1Z3, Canada
| | - Maria M Glavas
- Department of Cellular and Physiological Sciences, University of British Columbia, 2350 Health Sciences Mall, Vancouver, British Columbia V6T 1Z3, Canada
| | - Timothy J Kieffer
- Department of Cellular and Physiological Sciences, University of British Columbia, 2350 Health Sciences Mall, Vancouver, British Columbia V6T 1Z3, Canada.,Department of Surgery, University of British Columbia, 2350 Health Sciences Mall, Vancouver, British Columbia V6T 1Z3, Canada
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18
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Agrawal S, Gupta Y. Comment on Kazda et al. Evaluation of Efficacy and Safety of the Glucagon Receptor Antagonist LY2409021 in Patients With Type 2 Diabetes: 12- and 24-Week Phase 2 Studies. Diabetes Care 2016;39:1241-1249. Diabetes Care 2016; 39:e198. [PMID: 27926897 DOI: 10.2337/dc16-1340] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Affiliation(s)
- Sweety Agrawal
- Department of Endocrinology & Metabolism, All India Institute of Medical Sciences, New Delhi, India
| | - Yashdeep Gupta
- Department of Endocrinology & Metabolism, All India Institute of Medical Sciences, New Delhi, India
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19
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Rines AK, Sharabi K, Tavares CDJ, Puigserver P. Targeting hepatic glucose metabolism in the treatment of type 2 diabetes. Nat Rev Drug Discov 2016; 15:786-804. [PMID: 27516169 DOI: 10.1038/nrd.2016.151] [Citation(s) in RCA: 222] [Impact Index Per Article: 27.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Type 2 diabetes mellitus is characterized by the dysregulation of glucose homeostasis, resulting in hyperglycaemia. Although current diabetes treatments have exhibited some success in lowering blood glucose levels, their effect is not always sustained and their use may be associated with undesirable side effects, such as hypoglycaemia. Novel antidiabetic drugs, which may be used in combination with existing therapies, are therefore needed. The potential of specifically targeting the liver to normalize blood glucose levels has not been fully exploited. Here, we review the molecular mechanisms controlling hepatic gluconeogenesis and glycogen storage, and assess the prospect of therapeutically targeting associated pathways to treat type 2 diabetes.
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Affiliation(s)
- Amy K Rines
- Department of Cancer Biology, Dana-Farber Cancer Institute, and Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115, USA
| | - Kfir Sharabi
- Department of Cancer Biology, Dana-Farber Cancer Institute, and Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115, USA
| | - Clint D J Tavares
- Department of Cancer Biology, Dana-Farber Cancer Institute, and Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115, USA
| | - Pere Puigserver
- Department of Cancer Biology, Dana-Farber Cancer Institute, and Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115, USA
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20
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Damond N, Thorel F, Moyers JS, Charron MJ, Vuguin PM, Powers AC, Herrera PL. Blockade of glucagon signaling prevents or reverses diabetes onset only if residual β-cells persist. eLife 2016; 5. [PMID: 27092792 PMCID: PMC4871705 DOI: 10.7554/elife.13828] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2015] [Accepted: 04/07/2016] [Indexed: 12/15/2022] Open
Abstract
Glucagon secretion dysregulation in diabetes fosters hyperglycemia. Recent studies report that mice lacking glucagon receptor (Gcgr-/-) do not develop diabetes following streptozotocin (STZ)-mediated ablation of insulin-producing β-cells. Here, we show that diabetes prevention in STZ-treated Gcgr-/- animals requires remnant insulin action originating from spared residual β-cells: these mice indeed became hyperglycemic after insulin receptor blockade. Accordingly, Gcgr-/- mice developed hyperglycemia after induction of a more complete, diphtheria toxin (DT)-induced β-cell loss, a situation of near-absolute insulin deficiency similar to type 1 diabetes. In addition, glucagon deficiency did not impair the natural capacity of α-cells to reprogram into insulin production after extreme β-cell loss. α-to-β-cell conversion was improved in Gcgr-/- mice as a consequence of α-cell hyperplasia. Collectively, these results indicate that glucagon antagonism could i) be a useful adjuvant therapy in diabetes only when residual insulin action persists, and ii) help devising future β-cell regeneration therapies relying upon α-cell reprogramming. DOI:http://dx.doi.org/10.7554/eLife.13828.001 After meals, digested food causes sugar to accumulate in the blood. This triggers the release of the hormone insulin from beta cells in the pancreas, which allows liver cells, muscle cells and fat cells to use and store the sugar for energy. Other cells in the pancreas, called alpha cells, release a hormone called glucagon that counteracts the effects of insulin by telling the liver to release sugar into the bloodstream. The balance between the activity of insulin and glucagon keeps blood sugar levels steady. Diabetes results from the body being unable to produce enough insulin or respond to the insulin that is produced, which results in sugar accumulating in the blood. Diabetes also increases the production of glucagon, which further increases blood sugar levels. Recently, some researchers have reported that mice that lack the receptor proteins through which glucagon works do not develop diabetes, even when they are treated with a drug called streptozotocin that wipes out most of their beta cells. This suggests that the high blood sugar levels seen in diabetes result from an excess of glucagon, and not a lack of insulin. Drugs that block the action of glucagon have been found to reduce the symptoms of mild diabetes in mice and are now being tested in humans. However, it is less clear whether this treatment has any benefits in animals with more severe diabetes. Streptozotocin destroys most of a mouse’s beta cells but a significant fraction of them persist, while a different system relying on diphtheria toxin destroys more than 99% of these cells. Damond et al. have now found that treating mice that lack glucagon receptors with diphtheria toxin causes the mice to develop severe diabetes. Mice that lacked glucagon receptors that had been treated with streptozotocin also developed diabetes after they had been treated with an insulin-blocking drug. Further experiments showed that blocking glucagon receptors in typical mice with diabetes reduces blood sugar, but only if there is some insulin left in their bodies. Damond et al. also found that the glucagon receptor-lacking mice have more alpha cells, which have the ability to convert into insulin-producing cells after the widespread destruction of beta cells. Together, the experiments suggest that blocking glucagon could be a useful treatment for diabetes, but only in individuals who still have some insulin-producing cells. Such treatment would help reduce the release of sugar from the liver and increase the production of insulin in converted alpha cells in the pancreas. Damond et al. are now investigating how alpha cells convert into beta cells, with the aim of learning how to make beta cells regenerate more efficiently. DOI:http://dx.doi.org/10.7554/eLife.13828.002
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Affiliation(s)
- Nicolas Damond
- Department of Genetic Medicine and Development of the Faculty of Medicine, University of Geneva, Geneva, Switzerland.,Institute of Genetics and Genomics in Geneva, University of Geneva, Geneva, Switzerland.,Centre facultaire du diabète, University of Geneva, Geneva, Switzerland
| | - Fabrizio Thorel
- Department of Genetic Medicine and Development of the Faculty of Medicine, University of Geneva, Geneva, Switzerland.,Institute of Genetics and Genomics in Geneva, University of Geneva, Geneva, Switzerland.,Centre facultaire du diabète, University of Geneva, Geneva, Switzerland
| | - Julie S Moyers
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, United States
| | - Maureen J Charron
- Departments of Biochemistry, Medicine, and Obstetrics & Gynecology and Women's Health, Albert Einstein College of Medicine, Bronx, United States
| | - Patricia M Vuguin
- Pediatric Endocrinology, Women's and Childrens Health, College of Physicians & Surgeons, Columbia University, New York, United States
| | - Alvin C Powers
- Division of Diabetes, Endocrinology & Metabolism, Department of Medicine, Department of Molecular Physiology, Vanderbilt University, Nashville, United States.,VA Tennessee Valley Healthcare System, Nashville, United States
| | - Pedro L Herrera
- Department of Genetic Medicine and Development of the Faculty of Medicine, University of Geneva, Geneva, Switzerland.,Institute of Genetics and Genomics in Geneva, University of Geneva, Geneva, Switzerland.,Centre facultaire du diabète, University of Geneva, Geneva, Switzerland
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Abstract
OBJECTIVE There is general recognition that insulin and glucagon are the main hormones involved in the pathophysiology of diabetes, but the role of glucagon in diabetes is complex and in some circumstances controversial. The increasing appreciation of the role of glucagon in currently used hypoglycemic agents and the ongoing development of glucagon-targeted therapies underscores glucagon's important contribution in optimizing diabetes management. The current review provides a background on glucagon physiology and pathophysiology and an update for investigators, endocrinologists, and other healthcare providers on glucagon-modulating therapies. METHODS A literature review was conducted utilizing published literature in PubMed and AccessMedicine including the years 1922-2015 using the following key words: glucagon, bihormonal, diabetes mellitus, glucagon antagonists, glucagon-targeted therapies. RESULTS Glucagon is a counterregulatory hormone that promotes hepatic glucose production, thus preventing hypoglycemia in normal physiology. In patients with diabetes mellitus, glucagon secretion may be unregulated, which contributes to problems with glucose homeostasis. Several of the most effective therapies for diabetes have been found to suppress glucagon secretion or action, which may contribute to their success. Additionally, glucagon-specific targeted therapies, such as glucagon receptor antagonists, are being studied at a basic and clinical level. CONCLUSION Glucagon plays an important role in contributing to hyperglycemia in patients with diabetes. Utilizing hypoglycemic agents that decrease glucagon secretion or inhibit glucagon action can help improve glycemic control, making these agents a valuable resource in diabetes therapy.
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22
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Steenberg VR, Jensen SM, Pedersen J, Madsen AN, Windeløv JA, Holst B, Quistorff B, Poulsen SS, Holst JJ. Acute disruption of glucagon secretion or action does not improve glucose tolerance in an insulin-deficient mouse model of diabetes. Diabetologia 2016; 59:363-70. [PMID: 26537124 DOI: 10.1007/s00125-015-3794-2] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/09/2015] [Accepted: 09/29/2015] [Indexed: 12/25/2022]
Abstract
AIMS/HYPOTHESIS Normal glucose metabolism depends on pancreatic secretion of insulin and glucagon. The bihormonal hypothesis states that while lack of insulin leads to glucose underutilisation, glucagon excess is the principal factor in diabetic glucose overproduction. A recent study reported that streptozotocin-treated glucagon receptor knockout mice have normal glucose tolerance. We investigated the impact of acute disruption of glucagon secretin or action in a mouse model of severe diabetes by three different approaches: (1) alpha cell elimination; (2) glucagon immunoneutralisation; and (3) glucagon receptor antagonism, in order to evaluate the effect of these on glucose tolerance. METHODS Severe diabetes was induced in transgenic and wild-type mice by streptozotocin. Glucose metabolism was investigated using OGTT in transgenic mice with the human diphtheria toxin receptor expressed in proglucagon producing cells allowing for diphtheria toxin (DT)-induced alpha cell ablation and in mice treated with either a specific high affinity glucagon antibody or a specific glucagon receptor antagonist. RESULTS Near-total alpha cell elimination was induced in transgenic mice upon DT administration and resulted in a massive decrease in pancreatic glucagon content. Oral glucose tolerance in diabetic mice was neither affected by glucagon immunoneutralisation, glucagon receptor antagonism, nor alpha cell removal, but did not deteriorate further compared with mice with intact alpha cell mass. CONCLUSIONS/INTERPRETATION Disruption of glucagon action/secretion did not improve glucose tolerance in diabetic mice. Near-total alpha cell elimination may have prevented further deterioration. Our findings support insulin lack as the major factor underlying hyperglycaemia in beta cell-deficient diabetes.
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Affiliation(s)
- Vivi R Steenberg
- Section for Translational Metabolic Physiology, Novo Nordisk Foundation Center for Basic Metabolic Research and Department of Biomedical Sciences, University of Copenhagen, Blegdamsvej 3, building 12.2, DK-2200, Copenhagen, Denmark
| | - Signe M Jensen
- Section for Translational Metabolic Physiology, Novo Nordisk Foundation Center for Basic Metabolic Research and Department of Biomedical Sciences, University of Copenhagen, Blegdamsvej 3, building 12.2, DK-2200, Copenhagen, Denmark
| | - Jens Pedersen
- Section for Translational Metabolic Physiology, Novo Nordisk Foundation Center for Basic Metabolic Research and Department of Biomedical Sciences, University of Copenhagen, Blegdamsvej 3, building 12.2, DK-2200, Copenhagen, Denmark
| | - Andreas N Madsen
- Section for Metabolic Receptology, Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen, Copenhagen, Denmark
| | - Johanne A Windeløv
- Section for Translational Metabolic Physiology, Novo Nordisk Foundation Center for Basic Metabolic Research and Department of Biomedical Sciences, University of Copenhagen, Blegdamsvej 3, building 12.2, DK-2200, Copenhagen, Denmark
| | - Birgitte Holst
- Section for Metabolic Receptology, Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen, Copenhagen, Denmark
| | - Bjørn Quistorff
- Section for Translational Metabolic Physiology, Novo Nordisk Foundation Center for Basic Metabolic Research and Department of Biomedical Sciences, University of Copenhagen, Blegdamsvej 3, building 12.2, DK-2200, Copenhagen, Denmark
| | - Steen S Poulsen
- Section for Translational Metabolic Physiology, Novo Nordisk Foundation Center for Basic Metabolic Research and Department of Biomedical Sciences, University of Copenhagen, Blegdamsvej 3, building 12.2, DK-2200, Copenhagen, Denmark
| | - Jens J Holst
- Section for Translational Metabolic Physiology, Novo Nordisk Foundation Center for Basic Metabolic Research and Department of Biomedical Sciences, University of Copenhagen, Blegdamsvej 3, building 12.2, DK-2200, Copenhagen, Denmark.
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23
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Lefèbvre PJ, Paquot N, Scheen AJ. Inhibiting or antagonizing glucagon: making progress in diabetes care. Diabetes Obes Metab 2015; 17:720-5. [PMID: 25924114 DOI: 10.1111/dom.12480] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/24/2015] [Revised: 04/27/2015] [Accepted: 04/27/2015] [Indexed: 01/07/2023]
Abstract
Absolute or relative hyperglucagonaemia has been recognized for years in all experimental or clinical forms of diabetes. It has been suggested that excess secretion of glucagon by the islet α cells is a direct consequence of intra-islet insulin secretory defects. Recent studies have shown that knockout of the glucagon receptor or administration of a monoclonal specific glucagon receptor antibody make insulin-deficient type 1 diabetic rodents thrive without insulin. These observations suggest that glucagon plays an essential role in the pathophysiology of diabetes and that targeting the α cell and glucagon are innovative approaches in the management of diabetes. Despite active research and identification of promising compounds, no one selective glucagon antagonist is presently used in the treatment of diabetes. Interestingly, besides insulin, several drugs used today in the management of diabetes appear to exert their effects, in part, by inhibiting glucagon secretion (glucagon-like peptide-1 receptor agonists, dipeptidyl peptidase-4 inhibitors, α-glucosidase inhibitors and, possibly, sulphonylureas) or glucagon action (metformin). The potential risks associated with total glucagon suppression include α-cell hyperplasia, increased mass of the pancreas, increased susceptibility to hepatosteatosis and hepatocellular injury and increased risk of hypoglycaemia, and these should be considered in the search and development of new compounds reducing glucagon receptor signalling. More than 40 years after its initial description, hyperglucagonaemia in diabetes can no longer be ignored or minimized, and its correction represents an attractive way to improve diabetes management.
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Affiliation(s)
- P J Lefèbvre
- Division of Diabetes, Nutrition and Metabolic Disorders, Department of Medicine, University of Liège, Liège, Belgium
| | - N Paquot
- Division of Diabetes, Nutrition and Metabolic Disorders, Department of Medicine, University of Liège, Liège, Belgium
| | - A J Scheen
- Division of Diabetes, Nutrition and Metabolic Disorders, Department of Medicine, University of Liège, Liège, Belgium
- Division of Clinical Pharmacology, Department of Medicine, University of Liège, Liège, Belgium
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24
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Filipski KJ. Small molecule glucagon receptor antagonists: a patent review (2011 – 2014). Expert Opin Ther Pat 2015; 25:819-30. [DOI: 10.1517/13543776.2015.1032250] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
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25
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Glucagon receptor antibody completely suppresses type 1 diabetes phenotype without insulin by disrupting a novel diabetogenic pathway. Proc Natl Acad Sci U S A 2015; 112:2503-8. [PMID: 25675519 DOI: 10.1073/pnas.1424934112] [Citation(s) in RCA: 81] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Insulin monotherapy can neither maintain normoglycemia in type 1 diabetes (T1D) nor prevent the long-term damage indicated by elevated glycation products in blood, such as glycated hemoglobin (HbA1c). Here we find that hyperglycemia, when unaccompanied by an acute increase in insulin, enhances itself by paradoxically stimulating hyperglucagonemia. Raising glucose from 5 to 25 mM without insulin enhanced glucagon secretion ∼two- to fivefold in InR1-G9 α cells and ∼18-fold in perfused pancreata from insulin-deficient rats with T1D. Mice with T1D receiving insulin treatment paradoxically exhibited threefold higher plasma glucagon during hyperglycemic surges than during normoglycemic intervals. Blockade of glucagon action with mAb Ac, a glucagon receptor (GCGR) antagonizing antibody, maintained glucose below 100 mg/dL and HbA1c levels below 4% in insulin-deficient mice with T1D. In rodents with T1D, hyperglycemia stimulates glucagon secretion, up-regulating phosphoenolpyruvate carboxykinase and enhancing hyperglycemia. GCGR antagonism in mice with T1D normalizes glucose and HbA1c, even without insulin.
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26
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Kaiser D, Oetjen E. Something old, something new and something very old: drugs for treating type 2 diabetes. Br J Pharmacol 2015; 171:2940-50. [PMID: 24641580 DOI: 10.1111/bph.12624] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2013] [Revised: 01/13/2014] [Accepted: 01/30/2014] [Indexed: 12/28/2022] Open
Abstract
Diabetes mellitus belongs to the most rapidly increasing diseases worldwide. Approximately 90-95% of these patients suffer from type 2 diabetes mellitus, which is characterized by peripheral insulin resistance and the progressive loss of beta-cell function and mass. Considering the complications of this chronic disease, a reliable anti-diabetic treatment is indispensable. An ideal oral anti-diabetic drug should not only correct glucose homeostasis but also preserve or even augment beta-cell function and mass, ameliorate the subclinical inflammation present under insulin-resistant conditions and prevent the macro- and microvascular consequences of diabetes in order to reduce the mortality. Despite the many anti-diabetic drugs already in use, there is an ongoing research for additional drugs, guided by different concepts of the pathogenesis of type 2 diabetes. This review will briefly summarize current oral anti-diabetic drugs. In addition, emerging strategies for the treatment of diabetes will be described, among them the inhibition of glucagon action and anti-inflammatory drugs. Their suitability as 'ideal anti-diabetic drugs' will be discussed.
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Affiliation(s)
- D Kaiser
- Department of Clinical Pharmacology and Toxicology, Cardiovascular Research Center, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
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27
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Lotfy M, Kalasz H, Szalai G, Singh J, Adeghate E. Recent Progress in the Use of Glucagon and Glucagon Receptor Antago-nists in the Treatment of Diabetes Mellitus. THE OPEN MEDICINAL CHEMISTRY JOURNAL 2014; 8:28-35. [PMID: 25674162 PMCID: PMC4321206 DOI: 10.2174/1874104501408010028] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/06/2014] [Revised: 10/08/2014] [Accepted: 10/12/2014] [Indexed: 12/25/2022]
Abstract
Glucagon is an important pancreatic hormone, released into blood circulation by alpha cells of the islet of
Langerhans. Glucagon induces gluconeogenesis and glycogenolysis in hepatocytes, leading to an increase in hepatic glucose
production and subsequently hyperglycemia in susceptible individuals. Hyperglucagonemia is a constant feature in
patients with T2DM. A number of bioactive agents that can block glucagon receptor have been identified. These glucagon
receptor antagonists can reduce the hyperglycemia associated with exogenous glucagon administration in normal as well
as diabetic subjects. Glucagon receptor antagonists include isoserine and beta-alanine derivatives, bicyclic 19-residue peptide
BI-32169, Des-His1-[Glu9] glucagon amide and related compounds, 5-hydroxyalkyl-4-phenylpyridines, N-[3-cano-6-
(1,1 dimethylpropyl)-4,5,6,7-tetrahydro-1-benzothien-2-yl]-2-ethylbutamide, Skyrin and NNC 250926. The absorption,
dosage, catabolism, excretion and medicinal chemistry of these agents are the subject of this review. It emphasizes the
role of glucagon in glucose homeostasis and how it could be applied as a novel tool for the management of diabetes mellitus
by blocking its receptors with either monoclonal antibodies, peptide and non-peptide antagonists or gene knockout
techniques.
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Affiliation(s)
- Mohamed Lotfy
- Department of Biology, College of Science, United Arab Emirates University; School of Forensic and Investigative Sciences, University of Central Lancashire, Preston PR1 2HE, England, UK; National Research Centre, Hormones Department, Cairo, Egypt
| | - Huba Kalasz
- Department of Pharmacology and Pharmacotherapy, Semmelweis University, Budapest, Hungary
| | - Gyorgy Szalai
- ENT Department, St. Janos Hospital, Budapest, Hungary
| | - Jaipaul Singh
- School of Forensic and Investigative Sciences and School of Pharmacy and Biomedical Science, University of Central Lancashire, Preston PR1 2HE, England, UK
| | - Ernest Adeghate
- Department of Anatomy, College of Medicine & Health Sciences, United Arab Emirates University, Al Ain, United Ar-ab Emirates
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28
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Barnes TM, Otero YF, Elliott AD, Locke AD, Malabanan CM, Coldren AG, Brissova M, Piston DW, McGuinness OP. Interleukin-6 amplifies glucagon secretion: coordinated control via the brain and pancreas. Am J Physiol Endocrinol Metab 2014; 307:E896-905. [PMID: 25205821 PMCID: PMC4233256 DOI: 10.1152/ajpendo.00343.2014] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Inappropriate glucagon secretion contributes to hyperglycemia in inflammatory disease. Previous work implicates the proinflammatory cytokine interleukin-6 (IL-6) in glucagon secretion. IL-6-KO mice have a blunted glucagon response to lipopolysaccharide (LPS) that is restored by intravenous replacement of IL-6. Given that IL-6 has previously been demonstrated to have a transcriptional (i.e., slow) effect on glucagon secretion from islets, we hypothesized that the rapid increase in glucagon following LPS occurred by a faster mechanism, such as by action within the brain. Using chronically catheterized conscious mice, we have demonstrated that central IL-6 stimulates glucagon secretion uniquely in the presence of an accompanying stressor (hypoglycemia or LPS). Contrary to our hypothesis, however, we found that IL-6 amplifies glucagon secretion in two ways; IL-6 not only stimulates glucagon secretion via the brain but also by direct action on islets. Interestingly, IL-6 augments glucagon secretion from both sites only in the presence of an accompanying stressor (such as epinephrine). Given that both adrenergic tone and plasma IL-6 are elevated in multiple inflammatory diseases, the interactions of the IL-6 and catecholaminergic signaling pathways in regulating GCG secretion may contribute to our present understanding of these diseases.
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Affiliation(s)
- Tammy M Barnes
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Yolanda F Otero
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Amicia D Elliott
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Alicia D Locke
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Carlo M Malabanan
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Anastasia G Coldren
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Marcela Brissova
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - David W Piston
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Owen P McGuinness
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee
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29
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Ahrén B, Gautier JF, Berria R, Stager W, Aronson R, Bailey CJ. Pronounced reduction of postprandial glucagon by lixisenatide: a meta-analysis of randomized clinical trials. Diabetes Obes Metab 2014; 16:861-8. [PMID: 24641271 DOI: 10.1111/dom.12290] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/12/2013] [Revised: 12/19/2013] [Accepted: 03/11/2014] [Indexed: 01/03/2023]
Abstract
AIM Glucagon-like peptide-1 (GLP-1) receptor agonists improve islet function and delay gastric emptying in patients with type 2 diabetes mellitus (T2DM). This meta-analysis aimed to investigate the effects of the once-daily prandial GLP-1 receptor agonist lixisenatide on postprandial plasma glucose (PPG), glucagon and insulin levels. METHODS Six randomized, placebo-controlled studies of lixisenatide 20 µg once daily were included in this analysis: lixisenatide as monotherapy (GetGoal-Mono), as add-on to oral antidiabetic drugs (OADs; GetGoal-M, GetGoal-S) or in combination with basal insulin (GetGoal-L, GetGoal-Duo-1 and GetGoal-L-Asia). Change in 2-h PPG and glucose excursion were evaluated across six studies. Change in 2-h glucagon and postprandial insulin were evaluated across two studies. A meta-analysis was performed on least square (LS) mean estimates obtained from analysis of covariance (ANCOVA)-based linear regression. RESULTS Lixisenatide significantly reduced 2-h PPG from baseline (LS mean difference vs. placebo: -4.9 mmol/l, p < 0.001) and glucose excursion (LS mean difference vs. placebo: -4.5 mmol/l, p < 0.001). As measured in two studies, lixisenatide also reduced postprandial glucagon (LS mean difference vs. placebo: -19.0 ng/l, p < 0.001) and insulin (LS mean difference vs. placebo: -64.8 pmol/l, p < 0.001). There was a stronger correlation between 2-h postprandial glucagon and 2-h PPG with lixisenatide than with placebo. CONCLUSIONS Lixisenatide significantly reduced 2-h PPG and glucose excursion together with a marked reduction in postprandial glucagon and insulin; thus, lixisenatide appears to have biological effects on blood glucose that are independent of increased insulin secretion. These effects may be, in part, attributed to reduced glucagon secretion.
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Affiliation(s)
- B Ahrén
- Department of Clinical Sciences, Lund University, Lund, Sweden
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30
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DeFronzo RA, Triplitt CL, Abdul-Ghani M, Cersosimo E. Novel Agents for the Treatment of Type 2 Diabetes. Diabetes Spectr 2014; 27:100-12. [PMID: 26246766 PMCID: PMC4522879 DOI: 10.2337/diaspect.27.2.100] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
In Brief Impaired insulin secretion, increased hepatic glucose production, and decreased peripheral glucose utilization are the core defects responsible for the development and progression of type 2 diabetes. However, the pathophysiology of this disease also includes adipocyte insulin resistance (increased lipolysis), reduced incretin secretion/sensitivity, increased glucagon secretion, enhanced renal glucose reabsorption, and brain insulin resistance/neurotransmitter dysfunction. Although current diabetes management focuses on lowering blood glucose, the goal of therapy should be to delay disease progression and eventual treatment failure. Recent innovative treatment approaches target the multiple pathophysiological defects present in type 2 diabetes. Optimal management should include early initiation of combination therapy using multiple drugs with different mechanisms of action. This review examines novel therapeutic options that hold particular promise.
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31
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Tudurí E, Denroche HC, Kara JA, Asadi A, Fox JK, Kieffer TJ. Partial ablation of leptin signaling in mouse pancreatic α-cells does not alter either glucose or lipid homeostasis. Am J Physiol Endocrinol Metab 2014; 306:E748-55. [PMID: 24473435 DOI: 10.1152/ajpendo.00681.2013] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The role of glucagon in the pathological condition of diabetes is gaining interest, and it has been recently reported that its action is essential for hyperglycemia to occur. Glucagon levels, which are elevated in some diabetic models, are reduced following leptin therapy. Likewise, hyperglycemia is corrected in type 1 diabetic mice treated with leptin, although the mechanisms have not been fully determined. A direct inhibitory effect of leptin on mouse and human α-cells has been demonstrated at the levels of electrical activity, calcium signaling, and glucagon secretion. In the present study we employed the Cre-loxP strategy to generate Lepr(flox/flox) Gcg-cre mice, which specifically lack leptin receptors in glucagon-secreting α-cells, to determine whether leptin resistance in α-cells contributes to hyperglucagonemia, and also whether leptin action in α-cells is required to improve glycemia in type 1 diabetes with leptin therapy. Immunohistochemical analysis of pancreas sections revealed Cre-mediated recombination in ∼ 43% of the α-cells. We observed that in vivo Lepr(flox/flox) Gcg-cre mice display normal glucose and lipid homeostasis. In addition, leptin administration in streptozotocin-induced diabetic Lepr(flox/flox) Gcg-cre mice restored euglycemia similarly to control mice. These findings suggest that loss of leptin receptor signaling in close to one-half of α-cells does not alter glucose metabolism in vivo, nor is it sufficient to prevent the therapeutic action of leptin in type 1 diabetes.
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MESH Headings
- Animals
- Cells, Cultured
- Diabetes Mellitus, Experimental/drug therapy
- Diabetes Mellitus, Experimental/genetics
- Diabetes Mellitus, Experimental/metabolism
- Diabetes Mellitus, Type 1/drug therapy
- Diabetes Mellitus, Type 1/genetics
- Diabetes Mellitus, Type 1/metabolism
- Female
- Gene Deletion
- Glucagon-Secreting Cells/metabolism
- Glucose/metabolism
- Homeostasis/genetics
- Leptin/metabolism
- Leptin/therapeutic use
- Lipid Metabolism/genetics
- Mice
- Mice, Inbred C57BL
- Mice, Transgenic
- Receptors, Leptin/genetics
- Receptors, Leptin/metabolism
- Signal Transduction/genetics
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Affiliation(s)
- Eva Tudurí
- Department of Cellular and Physiological Sciences, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia, Canada; and
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32
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Guo S. Insulin signaling, resistance, and the metabolic syndrome: insights from mouse models into disease mechanisms. J Endocrinol 2014; 220:T1-T23. [PMID: 24281010 PMCID: PMC4087161 DOI: 10.1530/joe-13-0327] [Citation(s) in RCA: 326] [Impact Index Per Article: 32.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Insulin resistance is a major underlying mechanism responsible for the 'metabolic syndrome', which is also known as insulin resistance syndrome. The incidence of the metabolic syndrome is increasing at an alarming rate, becoming a major public and clinical problem worldwide. The metabolic syndrome is represented by a group of interrelated disorders, including obesity, hyperglycemia, hyperlipidemia, and hypertension. It is also a significant risk factor for cardiovascular disease and increased morbidity and mortality. Animal studies have demonstrated that insulin and its signaling cascade normally control cell growth, metabolism, and survival through the activation of MAPKs and activation of phosphatidylinositide-3-kinase (PI3K), in which the activation of PI3K associated with insulin receptor substrate 1 (IRS1) and IRS2 and subsequent Akt→Foxo1 phosphorylation cascade has a central role in the control of nutrient homeostasis and organ survival. The inactivation of Akt and activation of Foxo1, through the suppression IRS1 and IRS2 in different organs following hyperinsulinemia, metabolic inflammation, and overnutrition, may act as the underlying mechanisms for the metabolic syndrome in humans. Targeting the IRS→Akt→Foxo1 signaling cascade will probably provide a strategy for therapeutic intervention in the treatment of type 2 diabetes and its complications. This review discusses the basis of insulin signaling, insulin resistance in different mouse models, and how a deficiency of insulin signaling components in different organs contributes to the features of the metabolic syndrome. Emphasis is placed on the role of IRS1, IRS2, and associated signaling pathways that are coupled to Akt and the forkhead/winged helix transcription factor Foxo1.
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Affiliation(s)
- Shaodong Guo
- Division of Molecular Cardiology, Department of Medicine, College of Medicine, Texas A&M University Health Science Center, Scott & White, Central Texas Veterans Health Care System, 1901 South 1st Street, Bldg. 205, Temple, Texas 76504, USA
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33
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Li XC, Zhuo JL. Current insights and new perspectives on the roles of hyperglucagonemia in non-insulin-dependent type 2 diabetes. Curr Hypertens Rep 2013; 15:522-30. [PMID: 23996678 PMCID: PMC3810031 DOI: 10.1007/s11906-013-0383-y] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Type 2 diabetes is well recognized as a noninsulin-dependent diabetic disease. Clinical evidence indicates that the level of circulating insulin may be normal, subnormal, and even elevated in type 2 diabetic patients. Unlike type 1 diabetes, the key problem for type 2 diabetes is not due to the absolute deficiency of insulin secretion, but because the body is no longer sensitive to insulin. Thus, insulin resistance is increased and the sensitivity to insulin is reset, so increasing levels of insulin are required to maintain body glucose and metabolic homeostasis. How insulin resistance is increased and what factors contribute to its development in type 2 diabetes remain incompletely understood. Overemphasis of insulin deficiency alone may be too simplistic for us to understand how type 2 diabetes is developed and should be treated, since glucose metabolism and homeostasis are tightly controlled by both insulin and glucagon. Insulin acts as a YIN factor to lower blood glucose level by increasing cellular glucose uptake, whereas glucagon acts as a YANG factor to counter the action of insulin by increasing glucose production. Furthermore, other humoral factors other than insulin and glucagon may also directly or indirectly contribute to increased insulin resistance and the development of hyperglycemia. The purpose of this article is to briefly review recently published animal and human studies in this field, and provide new insights and perspectives on recent debates as to whether hyperglucagonemia and/or glucagon receptors should be targeted to treat insulin resistance and target organ injury in type 2 diabetes.
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Affiliation(s)
- Xiao C Li
- Laboratory of Receptor and Signal Transduction, Department of Pharmacology & Toxicology, University of Mississippi Medical Center, Jackson, MS, 39216, USA
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34
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Vater A, Sell S, Kaczmarek P, Maasch C, Buchner K, Pruszynska-Oszmalek E, Kolodziejski P, Purschke WG, Nowak KW, Strowski MZ, Klussmann S. A mixed mirror-image DNA/RNA aptamer inhibits glucagon and acutely improves glucose tolerance in models of type 1 and type 2 diabetes. J Biol Chem 2013; 288:21136-21147. [PMID: 23744070 PMCID: PMC3774380 DOI: 10.1074/jbc.m112.444414] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2012] [Revised: 06/04/2013] [Indexed: 11/23/2022] Open
Abstract
Excessive secretion of glucagon, a functional insulin antagonist, significantly contributes to hyperglycemia in type 1 and type 2 diabetes. Accordingly, immunoneutralization of glucagon or genetic deletion of the glucagon receptor improved glucose homeostasis in animal models of diabetes. Despite this strong evidence, agents that selectively interfere with endogenous glucagon have not been implemented in clinical practice yet. We report the discovery of mirror-image DNA-aptamers (Spiegelmer®) that bind and inhibit glucagon. The affinity of the best binding DNA oligonucleotide was remarkably increased (>25-fold) by the introduction of oxygen atoms at selected 2'-positions through deoxyribo- to ribonucleotide exchanges resulting in a mixed DNA/RNA-Spiegelmer (NOX-G15) that binds glucagon with a Kd of 3 nm. NOX-G15 shows no cross-reactivity with related peptides such as glucagon-like peptide-1, glucagon-like peptide-2, gastric-inhibitory peptide, and prepro-vasoactive intestinal peptide. In vitro, NOX-G15 inhibits glucagon-stimulated cAMP production in CHO cells overexpressing the human glucagon receptor with an IC50 of 3.4 nm. A single injection of NOX-G15 ameliorated glucose excursions in intraperitoneal glucose tolerance tests in mice with streptozotocin-induced (type 1) diabetes and in a non-genetic mouse model of type 2 diabetes. In conclusion, the data suggest NOX-G15 as a therapeutic candidate with the potential to acutely attenuate hyperglycemia in type 1 and type 2 diabetes.
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MESH Headings
- Animals
- Aptamers, Nucleotide/blood
- Aptamers, Nucleotide/pharmacokinetics
- Aptamers, Nucleotide/pharmacology
- Aptamers, Nucleotide/therapeutic use
- Blood Glucose/metabolism
- Body Weight/drug effects
- CHO Cells
- Cricetinae
- Cricetulus
- Cyclic AMP/biosynthesis
- Diabetes Mellitus, Type 1/blood
- Diabetes Mellitus, Type 1/drug therapy
- Diabetes Mellitus, Type 2/blood
- Diabetes Mellitus, Type 2/drug therapy
- Disease Models, Animal
- Fasting/blood
- Glucagon/antagonists & inhibitors
- Glucagon/metabolism
- Glucose Tolerance Test
- Humans
- Kinetics
- Male
- Mice
- Mice, Inbred BALB C
- RNA/metabolism
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Affiliation(s)
- Axel Vater
- From the NOXXON Pharma AG, Max-Dohrn-Strasse 8-10, 10589 Berlin, Germany
| | - Simone Sell
- From the NOXXON Pharma AG, Max-Dohrn-Strasse 8-10, 10589 Berlin, Germany
| | - Przemyslaw Kaczmarek
- the Department of Animal Physiology and Biochemistry, Poznan University of Life Sciences, 35 Wolynska Street, 60637 Poznan, Poland, and
| | - Christian Maasch
- From the NOXXON Pharma AG, Max-Dohrn-Strasse 8-10, 10589 Berlin, Germany
| | - Klaus Buchner
- From the NOXXON Pharma AG, Max-Dohrn-Strasse 8-10, 10589 Berlin, Germany
| | - Ewa Pruszynska-Oszmalek
- the Department of Animal Physiology and Biochemistry, Poznan University of Life Sciences, 35 Wolynska Street, 60637 Poznan, Poland, and
| | - Pawel Kolodziejski
- the Department of Animal Physiology and Biochemistry, Poznan University of Life Sciences, 35 Wolynska Street, 60637 Poznan, Poland, and
| | - Werner G Purschke
- From the NOXXON Pharma AG, Max-Dohrn-Strasse 8-10, 10589 Berlin, Germany
| | - Krzysztof W Nowak
- the Department of Animal Physiology and Biochemistry, Poznan University of Life Sciences, 35 Wolynska Street, 60637 Poznan, Poland, and
| | - Mathias Z Strowski
- the Department of Hepatology and Gastroenterology and Interdisciplinary Centre of Metabolism: Endocrinology, Diabetes and Metabolism, Charité-Universitätsmedizin Berlin, Augustenburger Platz 1, 13353 Berlin, Germany
| | - Sven Klussmann
- From the NOXXON Pharma AG, Max-Dohrn-Strasse 8-10, 10589 Berlin, Germany,.
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Han S, Akiyama TE, Previs SF, Herath K, Roddy TP, Jensen KK, Guan HP, Murphy BA, McNamara LA, Shen X, Strapps W, Hubbard BK, Pinto S, Li C, Li J. Effects of small interfering RNA-mediated hepatic glucagon receptor inhibition on lipid metabolism in db/db mice. J Lipid Res 2013; 54:2615-22. [PMID: 23828778 DOI: 10.1194/jlr.m035592] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Hepatic glucose overproduction is a major characteristic of type 2 diabetes. Because glucagon is a key regulator for glucose homeostasis, antagonizing the glucagon receptor (GCGR) is a possible therapeutic strategy for the treatment of diabetes mellitus. To study the effect of hepatic GCGR inhibition on the regulation of lipid metabolism, we generated siRNA-mediated GCGR knockdown (si-GCGR) in the db/db mouse. The hepatic knockdown of GCGR markedly reduced plasma glucose levels; however, total plasma cholesterol was increased. The detailed lipid analysis showed an increase in the LDL fraction, and no change in VLDL HDL fractions. Further studies showed that the increase in LDL was the result of over-expression of hepatic lipogenic genes and elevated de novo lipid synthesis. Inhibition of hepatic glucagon signaling via siRNA-mediated GCGR knockdown had an effect on both glucose and lipid metabolism in db/db mice.
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Affiliation(s)
- Seongah Han
- Division of Cardiovascular Disease, Merck Sharp & Dohme Corp., Whitehouse Station, NJ
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Erion DM, Kotas ME, McGlashon J, Yonemitsu S, Hsiao JJ, Nagai Y, Iwasaki T, Murray SF, Bhanot S, Cline GW, Samuel VT, Shulman GI, Gillum MP. cAMP-responsive element-binding protein (CREB)-regulated transcription coactivator 2 (CRTC2) promotes glucagon clearance and hepatic amino acid catabolism to regulate glucose homeostasis. J Biol Chem 2013; 288:16167-76. [PMID: 23595987 DOI: 10.1074/jbc.m113.460246] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
cAMP-responsive element-binding protein (CREB)-regulated transcription coactivator 2 (CRTC2) regulates transcription of gluconeogenic genes by specifying targets for the transcription factor CREB in response to glucagon. We used an antisense oligonucleotide directed against CRTC2 in both normal rodents and in rodent models of increased gluconeogenesis to better understand the role of CRTC2 in metabolic disease. In the context of severe hyperglycemia and elevated hepatic glucose production, CTRC2 knockdown (KD) improved glucose homeostasis by reducing endogenous glucose production. Interestingly, despite the known role of CRTC2 in coordinating gluconeogenic gene expression, CRTC2 KD in a rodent model of type 2 diabetes resulted in surprisingly little alteration of glucose production. However, CRTC2 KD animals had elevated circulating concentrations of glucagon and a ∼80% reduction in glucagon clearance. When this phenomenon was prevented with somatostatin or a glucagon-neutralizing antibody, endogenous glucose production was reduced by CRTC2 KD. Additionally, CRTC2 inhibition resulted in reduced expression of several glucagon-induced pyridoxal 5'-phosphate-dependent enzymes that convert amino acids to gluconeogenic intermediates, suggesting that it may control substrate availability as well as gluconeogenic gene expression. CRTC2 is an important regulator of gluconeogenesis with tremendous impact in models of elevated hepatic glucose production. Surprisingly, it is also part of a previously unidentified negative feedback loop that degrades glucagon and regulates amino acid metabolism to coordinately control glucose homeostasis in vivo.
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Affiliation(s)
- Derek M Erion
- Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut 06536, USA
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Cho YM, Merchant CE, Kieffer TJ. Targeting the glucagon receptor family for diabetes and obesity therapy. Pharmacol Ther 2012; 135:247-78. [DOI: 10.1016/j.pharmthera.2012.05.009] [Citation(s) in RCA: 93] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2012] [Accepted: 05/15/2012] [Indexed: 12/11/2022]
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38
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Xiong Y, Guo J, Candelore MR, Liang R, Miller C, Dallas-Yang Q, Jiang G, McCann PE, Qureshi SA, Tong X, Xu SS, Shang J, Vincent SH, Tota LM, Wright MJ, Yang X, Zhang BB, Tata JR, Parmee ER. Discovery of a novel glucagon receptor antagonist N-[(4-{(1S)-1-[3-(3, 5-dichlorophenyl)-5-(6-methoxynaphthalen-2-yl)-1H-pyrazol-1-yl]ethyl}phenyl)carbonyl]-β-alanine (MK-0893) for the treatment of type II diabetes. J Med Chem 2012; 55:6137-48. [PMID: 22708876 DOI: 10.1021/jm300579z] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A potent, selective glucagon receptor antagonist 9m, N-[(4-{(1S)-1-[3-(3,5-dichlorophenyl)-5-(6-methoxynaphthalen-2-yl)-1H-pyrazol-1-yl]ethyl}phenyl)carbonyl]-β-alanine, was discovered by optimization of a previously identified lead. Compound 9m is a reversible and competitive antagonist with high binding affinity (IC(50) of 6.6 nM) and functional cAMP activity (IC(50) of 15.7 nM). It is selective for glucagon receptor relative to other family B GPCRs, showing IC(50) values of 1020 nM for GIPR, 9200 nM for PAC1, and >10000 nM for GLP-1R, VPAC1, and VPAC2. Compound 9m blunted glucagon-induced glucose elevation in hGCGR mice and rhesus monkeys. It also lowered ambient glucose levels in both acute and chronic mouse models: in hGCGR ob/ob mice it reduced glucose (AUC 0-6 h) by 32% and 39% at 3 and 10 mpk single doses, respectively. In hGCGR mice on a high fat diet, compound 9m at 3, and 10 mpk po in feed lowered blood glucose levels by 89% and 94% at day 10, respectively, relative to the difference between the vehicle control and lean hGCGR mice. On the basis of its favorable biological and DMPK properties, compound 9m (MK-0893) was selected for further preclinical and clinical evaluations.
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Affiliation(s)
- Yusheng Xiong
- Discovery and Preclinical Sciences, Merck Research Laboratories, Rahway, NJ 07065, USA.
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39
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Ozcan L, Wong CC, Li G, Xu T, Pajvani U, Park SKR, Wronska A, Chen BX, Marks AR, Fukamizu A, Backs J, Singer HA, Yates JR, Accili D, Tabas I. Calcium signaling through CaMKII regulates hepatic glucose production in fasting and obesity. Cell Metab 2012; 15:739-51. [PMID: 22503562 PMCID: PMC3348356 DOI: 10.1016/j.cmet.2012.03.002] [Citation(s) in RCA: 163] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/14/2011] [Revised: 01/20/2012] [Accepted: 03/05/2012] [Indexed: 12/31/2022]
Abstract
Hepatic glucose production (HGP) is crucial for glucose homeostasis, but the underlying mechanisms have not been fully elucidated. Here, we show that a calcium-sensing enzyme, CaMKII, is activated in a calcium- and IP3R-dependent manner by cAMP and glucagon in primary hepatocytes and by glucagon and fasting in vivo. Genetic deficiency or inhibition of CaMKII blocks nuclear translocation of FoxO1 by affecting its phosphorylation, impairs fasting- and glucagon/cAMP-induced glycogenolysis and gluconeogenesis, and lowers blood glucose levels, while constitutively active CaMKII has the opposite effects. Importantly, the suppressive effect of CaMKII deficiency on glucose metabolism is abrogated by transduction with constitutively nuclear FoxO1, indicating that the effect of CaMKII deficiency requires nuclear exclusion of FoxO1. This same pathway is also involved in excessive HGP in the setting of obesity. These results reveal a calcium-mediated signaling pathway involved in FoxO1 nuclear localization and hepatic glucose homeostasis.
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Affiliation(s)
- Lale Ozcan
- Department of Medicine, Columbia University, New York, NY 10032, USA
| | - Catherine C.L. Wong
- Department of Chemical Physiology, Scripps Research Institute, La Jolla, CA 92037, USA
| | - Gang Li
- Department of Medicine, Columbia University, New York, NY 10032, USA
| | - Tao Xu
- Department of Chemical Physiology, Scripps Research Institute, La Jolla, CA 92037, USA
| | - Utpal Pajvani
- Department of Medicine, Columbia University, New York, NY 10032, USA
| | - Sung Kyu Robin Park
- Department of Chemical Physiology, Scripps Research Institute, La Jolla, CA 92037, USA
| | - Anetta Wronska
- Department of Physiology & Cellular Biophysics and The Clyde and Helen Wu Center for Molecular Cardiology, Columbia University, New York, NY 10032, USA
| | - Bi-Xing Chen
- Department of Physiology & Cellular Biophysics and The Clyde and Helen Wu Center for Molecular Cardiology, Columbia University, New York, NY 10032, USA
| | - Andrew R. Marks
- Department of Medicine, Columbia University, New York, NY 10032, USA
- Department of Physiology & Cellular Biophysics and The Clyde and Helen Wu Center for Molecular Cardiology, Columbia University, New York, NY 10032, USA
| | - Akiyoshi Fukamizu
- Life Science Center, Tsukuba Advanced Research Alliance, University of Tsukuba, Tsukuba, Japan
| | - Johannes Backs
- Department of Internal Medicine III, University of Heidelberg, Heidelberg, Germany
| | - Harold A. Singer
- Center for Cardiovascular Sciences, Albany Medical College, Albany, NY 12208 USA
| | - John R. Yates
- Department of Chemical Physiology, Scripps Research Institute, La Jolla, CA 92037, USA
| | - Domenico Accili
- Department of Medicine, Columbia University, New York, NY 10032, USA
| | - Ira Tabas
- Department of Medicine, Columbia University, New York, NY 10032, USA
- Department of Physiology & Cellular Biophysics and The Clyde and Helen Wu Center for Molecular Cardiology, Columbia University, New York, NY 10032, USA
- Department of Pathology & Cell Biology, Columbia University, New York, NY 10032, USA
- Correspondence:
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Jamison RA, Stark R, Dong J, Yonemitsu S, Zhang D, Shulman GI, Kibbey RG. Hyperglucagonemia precedes a decline in insulin secretion and causes hyperglycemia in chronically glucose-infused rats. Am J Physiol Endocrinol Metab 2011; 301:E1174-83. [PMID: 21862723 PMCID: PMC3233775 DOI: 10.1152/ajpendo.00175.2011] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Islet damage from glucose toxicity is implicated in the pathogenesis of type 2 diabetes, but the sequence of events leading to islet cell dysfunction and hyperglycemia remains unclear. To examine the early stages of islet pathology resulting from increased basal glucose loads, normal awake rats were infused with glucose continuously for 10 days. Plasma glucose and markers of islet and liver function were monitored throughout the infusion. After initial hyperglycemia, rats adapted to the infusion and maintained euglycemia for approximately 4 days. Continued infusion led to worsening hyperglycemia in just 5% of rats after 6 days, but 69% after 8 days and 89% after 10 days, despite unchanged basal and stimulated plasma insulin and C-peptide concentrations. In contrast, plasma glucagon concentrations increased fivefold. Endogenous glucose production (EGP) was appropriately suppressed after 4 days (2.8 ± 0.7 vs. 6.1 ± 0.4 mg·kg(-1)·min(-1) on day 0, P < 0.001) but tripled between days 4 and 8 (9.9 ± 1.7 mg·kg(-1)·min(-1), P < 0.01). Surprisingly, the increase in EGP was accompanied by increased mitochondrial phosphoenolpyruvate carboxykinase expression with appropriate suppression of the cytosolic isoform. Infusion of anti-glucagon antibodies normalized plasma glucose to levels identical to those on day 4 and ∼300 mg/dl lower than controls. This improved glycemia was associated with a 60% reduction in EGP. These data support the novel concept that glucose toxicity may first manifest as α-cell dysfunction prior to any measurable deficit in insulin secretion. Such hyperglucagonemia could lead to excessive glucose production overwhelming the capacity of the β-cell to maintain glucose homeostasis.
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Affiliation(s)
- Rachel A Jamison
- Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut 06520-8020, USA
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41
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Larqué C, Velasco M, Navarro-Tableros V, Duhne M, Aguirre J, Gutiérrez-Reyes G, Moreno J, Robles-Diaz G, Hong E, Hiriart M. Early endocrine and molecular changes in metabolic syndrome models. IUBMB Life 2011; 63:831-9. [PMID: 21905198 DOI: 10.1002/iub.544] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2011] [Accepted: 07/02/2011] [Indexed: 12/12/2022]
Abstract
The twenty-first century arrived in the middle of a global epidemic of metabolic syndrome (MS) and type 2 diabetes mellitus (DM2). It is generally accepted that an excess of nutrients linked to a low physical activity triggers the problem. However, the molecular features that interact to develop the MS are not clear. In an effort to understand and control them, they have been extensively studied, but this goal has not been achieved yet. Nonhuman animal models have been used to explore diet and genetic factors in which experimental conditions are controlled. For example, only one factor in the diet, such as fats or carbohydrates can be modified to better understand a single change that would be impossible in humans. Most of the studies have been done in rodents. However, it is difficult to directly compare them, because experiments are different in more than one variable; genetic strains, amount, and the type of fat used in the diet and sex. Thus, the only possible criteria of comparison are the relevance of the observed changes. We review different animal models and add some original observations on short-term changes in metabolism and beta cells in our own model of adult Wistar rats that are not especially prone to get fat or develop DM2, treated with 20% sucrose in drinking water. One early change observed in pancreatic beta cells is the increase in GLUT2 expression that is located to the membrane of the cells. This change could partially explain the presence of insulin hypersecretion and hyperinsulinemia in these rats. Understanding early changes that lead to MS and in time to pancreatic islet exhaustion is an important biomedical problem that may contribute to learn how to prevent or even reverse MS, before developing DM2.
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Affiliation(s)
- Carlos Larqué
- Neuroscience Division, Department of Neural Development and Physiology, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico DF, Mexico
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Yu R, Dhall D, Nissen NN, Zhou C, Ren SG. Pancreatic neuroendocrine tumors in glucagon receptor-deficient mice. PLoS One 2011; 6:e23397. [PMID: 21853126 PMCID: PMC3154424 DOI: 10.1371/journal.pone.0023397] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2011] [Accepted: 07/14/2011] [Indexed: 02/06/2023] Open
Abstract
Inhibition of glucagon signaling causes hyperglucagonemia and pancreatic α cell hyperplasia in mice. We have recently demonstrated that a patient with an inactivating glucagon receptor mutation (P86S) also exhibits hyperglucagonemia and pancreatic α cell hyperplasia but further develops pancreatic neuroendocrine tumors (PNETs). To test the hypothesis that defective glucagon signaling causes PNETs, we studied the pancreata of mice deficient in glucagon receptor (Gcgr−/−) from 2 to 12 months, using WT and heterozygous mice as controls. At 2–3 months, Gcgr−/− mice exhibited normal islet morphology but the islets were mostly composed of α cells. At 5–7 months, dysplastic islets were evident in Gcgr−/− mice but absent in WT or heterozygous controls. At 10–12 months, gross PNETs (≥1 mm) were detected in most Gcgr−/− pancreata and micro-PNETs (<1 mm) were found in all (n = 14), whereas the islet morphology remained normal and no PNETs were found in any WT (n = 10) or heterozygous (n = 25) pancreata. Most PNETs in Gcgr−/− mice were glucagonomas, but some were non-functioning. No tumors predominantly expressed insulin, pancreatic polypeptide, or somatostatin, although some harbored focal aggregates of tumor cells expressing one of those hormones. The PNETs in Gcgr−/− mice were well differentiated and occasionally metastasized to the liver. Menin expression was aberrant in most dysplatic islets and PNETs. Vascular endothelial growth factor (VEGF) was overexpressed in PNET cells and its receptor Flk-1 was found in the abundant blood vessels or blood islands inside the tumors. We conclude that defective glucagon signaling causes PNETs in the Gcgr−/− mice, which may be used as a model of human PNETs. Our results further suggest that completely inhibiting glucagon signaling may not be a safe approach to treat diabetes.
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Affiliation(s)
- Run Yu
- Division of Endocrinology, Cedars-Sinai Medical Center, David Geffen School of Medicine at UCLA, Los Angeles, California, United States of America.
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Abstract
In the past century, incidences of chronic metabolic diseases, such as obesity and type II diabetes, have increased dramatically. Obesity and abnormal insulin level are associated with a wide variety of health problems including a markedly increased risk for type II diabetes, fatty liver, hepato-biliary and gallbladder diseases, cardiovascular pathologies, neurodegenerative disorders, asthma and a variety of cancers. The development of therapeutic antibodies has evolved over the past decades into a mainstay of therapeutic options for patients with inflammatory diseases and cancer, while other indication areas such as metabolic diseases have so far only been rarely addressed. Although therapeutic antibodies might have advantages over current type II diabetes treatments like favorable serum half-life and high specificity, their development is also likely to face obstacles. For example the technical feasibility of antibody generation against G protein coupled receptors and transporters is challenging, patient compliance for a likely needle application might be limited, bioavailability in organs involved in the pathogenesis like the brain might be suboptimal and reimbursement issues for high treatment costs have to be taken into account. The current review focuses on the pathogenesis and standard therapeutic approaches as well as antibodies in development and potential antibody targets for type II diabetes.
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Gu W, Winters KA, Motani AS, Komorowski R, Zhang Y, Liu Q, Wu X, Rulifson IC, Sivits G, Graham M, Yan H, Wang P, Moore S, Meng T, Lindberg RA, Véniant MM. Glucagon receptor antagonist-mediated improvements in glycemic control are dependent on functional pancreatic GLP-1 receptor. Am J Physiol Endocrinol Metab 2010; 299:E624-32. [PMID: 20647556 DOI: 10.1152/ajpendo.00102.2010] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Antagonism of the glucagon receptor (GCGR) is associated with increased circulating levels of glucagon-like peptide-1 (GLP-1). To investigate the contribution of GLP-1 to the antidiabetic actions of GCGR antagonism, we administered an anti-GCGR monoclonal antibody (mAb B) to wild-type mice and GLP-1 receptor knockout (GLP-1R KO) mice. Treatment of wild-type mice with mAb B lowered fasting blood glucose, improved glucose tolerance, and enhanced glucose-stimulated insulin secretion during an intraperitoneal glucose tolerance test (ipGTT). In contrast, treatment of GLP-1R KO mice with mAb B had little efficacy during an ipGTT. Furthermore, pretreatment with the GLP-1R antagonist exendin-(9-39) diminished the antihyperglycemic effects of mAb B in wild-type mice. To determine the mechanism whereby mAb B improves glucose tolerance, we generated a monoclonal antibody that specifically antagonizes the human GLP-1R. Using a human islet transplanted mouse model, we demonstrated that pancreatic islet GLP-1R signaling is required for the full efficacy of the GCGR antagonist. To identify the source of the elevated GLP-1 observed in GCGR mAb-treated mice, we measured active GLP-1 content in pancreas and intestine from db/db mice treated with anti-GCGR mAb for 8 wk. Elevated GLP-1 in GCGR mAb-treated mice was predominantly derived from increased pancreatic GLP-1 synthesis and processing. All together, these data show that pancreatic GLP-1 is a significant contributor to the glucose-lowering effects observed in response to GCGR antagonist treatment.
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Affiliation(s)
- Wei Gu
- Dept. of Metabolic Disorders, Amgen Inc., One Amgen Center Dr., Mail Stop 29-1-A, Thousand Oaks, CA 91320, USA.
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Kawamori D, Welters HJ, Kulkarni RN. Molecular Pathways Underlying the Pathogenesis of Pancreatic α-Cell Dysfunction. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2010; 654:421-45. [DOI: 10.1007/978-90-481-3271-3_18] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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46
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beta-cell function in obese-hyperglycemic mice [ob/ob Mice]. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2010; 654:463-77. [PMID: 20217510 DOI: 10.1007/978-90-481-3271-3_20] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
This review summarizes key aspects of what has been learned about the physiology of pancreatic islets and leptin deficiency from studies in obese ob/ob mice. ob/ob Mice lack functional leptin. They are grossly overweight and hyperphagic particularly at young ages and develop severe insulin resistance with hyperglycemia and hyperinsulinemia. ob/ob Mice have large pancreatic islets. The beta-cells respond adequately to most stimuli, and ob/ob mice have been used as a rich source of pancreatic islets with high insulin release capacity. ob/ob Mice can perhaps be described as a model for the prediabetic state. The large capacity for islet growth and insulin release makes ob/ob mice a good model for studies on how beta-cells can cope with prolonged functional stress.
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47
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Prevention of hepatic steatosis and hepatic insulin resistance by knockdown of cAMP response element-binding protein. Cell Metab 2009; 10:499-506. [PMID: 19945407 PMCID: PMC2799933 DOI: 10.1016/j.cmet.2009.10.007] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/17/2008] [Revised: 07/19/2009] [Accepted: 10/14/2009] [Indexed: 12/30/2022]
Abstract
In patients with poorly controlled type 2 diabetes mellitus (T2DM), hepatic insulin resistance and increased gluconeogenesis contribute to fasting and postprandial hyperglycemia. Since cAMP response element-binding protein (CREB) is a key regulator of gluconeogenic gene expression, we hypothesized that decreasing hepatic CREB expression would reduce fasting hyperglycemia in rodent models of T2DM. In order to test this hypothesis, we used a CREB-specific antisense oligonucleotide (ASO) to knock down CREB expression in liver. CREB ASO treatment dramatically reduced fasting plasma glucose concentrations in ZDF rats, ob/ob mice, and an STZ-treated, high-fat-fed rat model of T2DM. Surprisingly, CREB ASO treatment also decreased plasma cholesterol and triglyceride concentrations, as well as hepatic triglyceride content, due to decreases in hepatic lipogenesis. These results suggest that CREB is an attractive therapeutic target for correcting both hepatic insulin resistance and dyslipidemia associated with nonalcoholic fatty liver disease (NAFLD) and T2DM.
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48
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Gu W, Yan H, Winters KA, Komorowski R, Vonderfecht S, Atangan L, Sivits G, Hill D, Yang J, Bi V, Shen Y, Hu S, Boone T, Lindberg RA, Véniant MM. Long-Term Inhibition of the Glucagon Receptor with a Monoclonal Antibody in Mice Causes Sustained Improvement in Glycemic Control, with Reversible α-Cell Hyperplasia and Hyperglucagonemia. J Pharmacol Exp Ther 2009; 331:871-81. [DOI: 10.1124/jpet.109.157685] [Citation(s) in RCA: 84] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
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49
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Moaeen-ud-Din M, Malik N, Guo YL, Ali A, Babar ME. Cortistatin vaccination--a solution to growth hormone deficiency. Med Hypotheses 2009; 73:1053-4. [PMID: 19560289 DOI: 10.1016/j.mehy.2009.05.020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2009] [Revised: 04/17/2009] [Accepted: 05/20/2009] [Indexed: 11/15/2022]
Abstract
Cortistatin and somatostatin are neuropeptides which have inhibitory effects on growth hormone through common five receptors. Although, both have inhibitory effects but, only cortistatin has direct inhibitory effects on growth hormone secretagogue and is more potent inhibitor of growth hormone than somatostatin. This control of growth hormone can be manipulated through immunoneutralization of cortistatin through cortistatin DNA vaccine rather than antibodies application. A DNA vaccine of cortistatin can be produced using recombinant DNA technology in a eukaryotic expression system and will serve as a tool not to only alleviate the growth hormone deficiency problems in human but, can also be used to improve growth rate in farm animals.
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Affiliation(s)
- M Moaeen-ud-Din
- Functional Genomics Lab, University of Veterinary and Animal Sciences, Lahore, Pakistan.
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50
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Grapp M, Teichler S, Kitz J, Dibaj P, Dickel C, Knepel W, Krätzner R. The homeodomain of PAX6 is essential for PAX6-dependent activation of the rat glucagon gene promoter: Evidence for a PH0-like binding that induces an active conformation. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2009; 1789:403-12. [DOI: 10.1016/j.bbagrm.2009.02.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/29/2008] [Revised: 01/23/2009] [Accepted: 02/06/2009] [Indexed: 10/21/2022]
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