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Lee J, Ustione A, Wilkerson EM, Balakrishnan R, Thurmond DC, Goldfarb D, Piston DW. Insulin-Independent Regulation of Type 1 Diabetes via Brown Adipocyte-Secreted Proteins and the Novel Glucagon Regulator Nidogen-2. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.08.30.610490. [PMID: 39257771 PMCID: PMC11383990 DOI: 10.1101/2024.08.30.610490] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/12/2024]
Abstract
Current treatments for type 1 diabetes (T1D) focus on insulin replacement. We demonstrate the therapeutic potential of a secreted protein fraction from embryonic brown adipose tissue (BAT), independent of insulin. The large molecular weight secreted fraction mediates insulin receptor-dependent recovery of euglycemia in a T1D animal model, nonobese diabetic (NOD) mice, by suppressing glucagon secretion. This fraction also promotes white adipocyte differentiation and browning, maintains healthy BAT, and enhances glucose uptake in adipose tissue, skeletal muscle, and liver. From this fraction, we identify nidogen-2 as a critical BAT-secreted protein that reverses hyperglycemia in NOD mice, inhibits glucagon secretion from pancreatic α-cells, and mimics other actions of the entire secreted fraction. These findings confirm that BAT transplants affect physiology and demonstrate that BAT-secreted peptides represent a novel therapeutic approach to diabetes management. Furthermore, our research reveals a novel signaling role for nidogen-2, beyond its traditional classification as an extracellular matrix protein. HIGHLIGHTS The large molecular weight brown adipocyte-secreted protein fraction suppresses glucagon secretion and normalizes glycemia in mouse models of type 1 diabetes (T1D), independent of insulin, offering a novel therapeutic strategy for disease management.Nidogen-2, a critical component of this fraction, is identified as an inhibitor of glucagon secretion in pancreatic α-cells by regulating intracellular messenger activities.The large-secreted protein fraction prevents T1D-related whitening of brown adipose tissue, promotes adipocyte differentiation, and enhances browning of inguinal white adipose tissue.This fraction enhances glucose uptake in adipose tissue, skeletal muscle, and liver through an insulin receptor-dependent pathway.
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Noguchi GM, Castillo VC, Donaldson CJ, Flisher MR, Momen AT, Saghatelian A, Huising MO. Urocortin 3 contributes to paracrine inhibition of islet alpha cells in mice. J Endocrinol 2024; 261:e240018. [PMID: 38593829 PMCID: PMC11095665 DOI: 10.1530/joe-24-0018] [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: 01/18/2024] [Accepted: 04/08/2024] [Indexed: 04/11/2024]
Abstract
Pancreatic alpha cell activity and glucagon secretion lower as glucose levels increase. While part of the decrease is regulated by glucose itself, paracrine signaling by their neighboring beta and delta cells also plays an important role. Somatostatin from delta cells is an important local inhibitor of alpha cells at high glucose. Additionally, urocortin 3 (UCN3) is a hormone that is co-released from beta cells with insulin and acts locally to potentiate somatostatin secretion from delta cells. UCN3 thus inhibits insulin secretion via a negative feedback loop with delta cells, but its role with respect to alpha cells and glucagon secretion is not understood. We hypothesize that the somatostatin-driven glucagon inhibition at high glucose is regulated in part by UCN3 from beta cells. Here, we use a combination of live functional Ca2+ and cAMP imaging as well as direct glucagon secretion measurement, all from alpha cells in intact mouse islets, to determine the contributions of UCN3 to alpha cell behavior. Exogenous UCN3 treatment decreased alpha cell Ca2+ and cAMP levels and inhibited glucagon release. Blocking endogenous UCN3 signaling increased alpha cell Ca2+ by 26.8 ± 7.6%, but this did not result in increased glucagon release at high glucose. Furthermore, constitutive deletion of Ucn3 did not increase Ca2+ activity or glucagon secretion relative to controls. UCN3 is thus capable of inhibiting mouse alpha cells, but, given the subtle effects of endogenous UCN3 signaling on alpha cells, we propose that UCN3-driven somatostatin may serve to regulate local paracrine glucagon levels in the islet instead of inhibiting gross systemic glucagon release.
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Affiliation(s)
- Glyn M. Noguchi
- Department of Neurobiology, Physiology & Behavior, University of California Davis, Davis, CA, USA
| | - Vincent C. Castillo
- Department of Neurobiology, Physiology & Behavior, University of California Davis, Davis, CA, USA
| | | | - Marcus R. Flisher
- Department of Neurobiology, Physiology & Behavior, University of California Davis, Davis, CA, USA
| | - Ariana T. Momen
- Department of Neurobiology, Physiology & Behavior, University of California Davis, Davis, CA, USA
| | | | - Mark O. Huising
- Department of Neurobiology, Physiology & Behavior, University of California Davis, Davis, CA, USA
- Department of Physiology & Membrane Biology, University of California Davis, Davis, CA, USA
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3
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Guo T, Zhang H, Luo Y, Yang X, Wang L, Zhang G. Global Trends and Frontier in Research on Pancreatic Alpha Cells: A Bibliometric Analysis from 2013 to 2023. CLIN INVEST MED 2024; 47:23-39. [PMID: 38958477 DOI: 10.3138/cim-2024-2744] [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] [Indexed: 07/04/2024]
Abstract
PURPOSE Over the past 20 years, much of the research on diabetes has focused on pancreatic beta cells. In the last 10 years, interest in the important role of pancreatic alpha cells in the pathogenesis of diabetes, which had previously received little attention, has grown. We aimed to summarize and visualize the hotspot and development trends of pancreatic alpha cells through bibliometric analysis and to provide research direction and future ideas for the treatment of diabetes and other islet-related diseases. METHODS We used two scientometric software packages (CiteSpace 6.1.R6 and VOSviewer1.6.18) to visualize the information and connection of countries, institutions, authors, and keywords in this field. RESULTS A total of 532 publications, published in 752 institutions in 46 countries and regions, were included in this analysis. The United States showed the highest output, accounting for 39.3% of the total number of published papers. The most active institution was Vanderbilt University, and the authors with highest productivity came from Ulster University. In recent years, research hotspots have concentrated on transdifferentiation, gene expression, and GLP-1 regulatory function. Visualization analysis shows that research hotspots mainly focus on clinical diseases as well as physiological and pathological mechanisms and related biochemical indicators. CONCLUSIONS This study provides a review and summary of the literature on pancreatic alpha cells through bibliometric and visual methods and shows research hotspot and development trends, which can guide future directions for research.
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Affiliation(s)
- Teng Guo
- Department of Endocrinology, Xiyuan Hospital, China Academy of Chinese Medical Sciences, Beijing, China
- Graduate School, Beijing University of Chinese Medicine, Beijing, China
| | - Haoling Zhang
- Institute of Clinical Pharmacology, Xiyuan Hospital, China Academy of Chinese Medical Sciences, Beijing, China
| | - Yunpeng Luo
- Department of Endocrinology, Xiyuan Hospital, China Academy of Chinese Medical Sciences, Beijing, China
- Graduate School, Beijing University of Chinese Medicine, Beijing, China
| | - Xi Yang
- Department of Endocrinology, Xiyuan Hospital, China Academy of Chinese Medical Sciences, Beijing, China
- Graduate School, Beijing University of Chinese Medicine, Beijing, China
| | - Lidan Wang
- Department of Endocrinology, Xiyuan Hospital, China Academy of Chinese Medical Sciences, Beijing, China
| | - Guangde Zhang
- Department of Endocrinology, Xiyuan Hospital, China Academy of Chinese Medical Sciences, Beijing, China
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Acreman S, Ma J, Denwood G, Gao R, Tarasov A, Rorsman P, Zhang Q. The endoplasmic reticulum plays a key role in α-cell intracellular Ca 2+ dynamics and glucose-regulated glucagon secretion in mouse islets. iScience 2024; 27:109665. [PMID: 38646167 PMCID: PMC11033163 DOI: 10.1016/j.isci.2024.109665] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2023] [Revised: 02/13/2024] [Accepted: 04/02/2024] [Indexed: 04/23/2024] Open
Abstract
Glucagon is secreted by pancreatic α-cells to counteract hypoglycaemia. How glucose regulates glucagon secretion remains unclear. Here, using mouse islets, we studied the role of transmembrane and endoplasmic reticulum (ER) Ca2+ on intrinsic α-cell glucagon secretion. Blocking isradipine-sensitive L-type voltage-gated Ca2+ (Cav) channels abolished α-cell electrical activity but had little impact on its cytosolic Ca2+ oscillations or low-glucose-stimulated glucagon secretion. In contrast, depleting ER Ca2+ with cyclopiazonic acid or blocking ER Ca2+-releasing ryanodine receptors abolished α-cell glucose sensitivity and low-glucose-stimulated glucagon secretion. ER Ca2+ mobilization in α-cells is regulated by intracellular ATP and likely to be coupled to Ca2+ influx through P/Q-type Cav channels. ω-Agatoxin IVA blocked α-cell ER Ca2+ release and cell exocytosis, but had no additive effect on glucagon secretion when combined with ryanodine. We conclude that glucose regulates glucagon secretion through the control of ER Ca2+ mobilization, a mechanism that can be independent of α-cell electrical activity.
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Affiliation(s)
- Samuel Acreman
- Oxford Centre for Diabetes, Endocrinology and Metabolism, Radcliffe Department of Medicine, University of Oxford, Oxford OX3 7LE, UK
- Institute of Neuroscience and Physiology, Department of Physiology, Metabolic Research Unit, Sahlgrenska Academy, University of Gothenburg, Box 430, S-405 30 Gothenburg, Sweden
| | - Jinfang Ma
- Oxford Centre for Diabetes, Endocrinology and Metabolism, Radcliffe Department of Medicine, University of Oxford, Oxford OX3 7LE, UK
- Department of Endocrinology and Metabolism, West China Hospital, Sichuan University, Chengdu, China
| | - Geoffrey Denwood
- Oxford Centre for Diabetes, Endocrinology and Metabolism, Radcliffe Department of Medicine, University of Oxford, Oxford OX3 7LE, UK
| | - Rui Gao
- Oxford Centre for Diabetes, Endocrinology and Metabolism, Radcliffe Department of Medicine, University of Oxford, Oxford OX3 7LE, UK
| | - Andrei Tarasov
- Oxford Centre for Diabetes, Endocrinology and Metabolism, Radcliffe Department of Medicine, University of Oxford, Oxford OX3 7LE, UK
- Biomedical Sciences Research Institute, School of Biomedical Sciences, Ulster University, Coleraine, Northern Ireland, UK
| | - Patrik Rorsman
- Oxford Centre for Diabetes, Endocrinology and Metabolism, Radcliffe Department of Medicine, University of Oxford, Oxford OX3 7LE, UK
- Institute of Neuroscience and Physiology, Department of Physiology, Metabolic Research Unit, Sahlgrenska Academy, University of Gothenburg, Box 430, S-405 30 Gothenburg, Sweden
- Biomedical Sciences Research Institute, School of Biomedical Sciences, Ulster University, Coleraine, Northern Ireland, UK
| | - Quan Zhang
- Oxford Centre for Diabetes, Endocrinology and Metabolism, Radcliffe Department of Medicine, University of Oxford, Oxford OX3 7LE, UK
- CNC - Center for Neuroscience and Cell Biology, CIBB - Centre for Innovative Biomedicine and Biotechnology, University of Coimbra, Coimbra, Portugal
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5
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Deng J, Luo K, Xia C, Zhu Y, Xiang Z, Zhu B, Tang X, Zhang T, Shi L, Lyu X, Chen J. Phytochemical composition of Tibetan tea fermented by Eurotium cristatum and its effects on type 1 diabetes mice and gut microbiota. Heliyon 2024; 10:e27145. [PMID: 38468973 PMCID: PMC10926077 DOI: 10.1016/j.heliyon.2024.e27145] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2023] [Revised: 02/14/2024] [Accepted: 02/25/2024] [Indexed: 03/13/2024] Open
Abstract
"Golden-flower" Tibetan tea (GTT) is an innovative dark tea fermented via fungus Eurotium cristatum. To study GTT effects on alleviating the symptoms of type 1 diabetes mellitus (T1DM), GTT's extract (GTTE) was prepared. GTTE chemical compositions were analyzed via HPLC, pyrolysis-gas chromatography-mass (Py-GC-MS) spectrometry analysis, and chemistry analyses. GTTE effects on T1DM were explored on T1DM mice model induced by streptozotocin (STZ). GTTE was composed mainly of tea pigment theabrownin (TB) (49.18%), with high percentages of polysaccharide (16.93%), protein (10.15%), polyphenols (13.90%), amino acids (5.89%), caffeine (1.83%), and flavonoids (0.67%). Py-GC-MS results exhibited that GTTE constituted of phenols, lipids, sugars, and proteins. GTTE attenuated T1DM conditions of mice, relieved their liver and pancreatic injury, restored damaged islet cells, decreased oxidative stress by increasing superoxide dismutase (SOD) and catalase (CAT) levels, modulated cytokine expression leading to the decreasing pro-inflammatory cytokines TNF-α and IL-6, increased anti-inflammatory cytokines IL-4 to improve inflammatory responses, and optimized gut microbiota composition and structure based on high-throughput 16S rDNA sequencing, suggesting multi-channel anti-diabetes mechanisms.
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Affiliation(s)
- Junlin Deng
- Institute of Agro-Products Processing Science and Technology, Institute of Food Nutrition and Health, Sichuan Academy of Agricultural Sciences, Chengdu, 610066, China
| | - Kebin Luo
- Institute of Agro-Products Processing Science and Technology, Institute of Food Nutrition and Health, Sichuan Academy of Agricultural Sciences, Chengdu, 610066, China
- Department of Nutrition and Food Hygiene, West China School of Public Health and West China Fourth Hospital, Sichuan University, Chengdu, 610041, China
| | - Chen Xia
- Institute of Agro-Products Processing Science and Technology, Institute of Food Nutrition and Health, Sichuan Academy of Agricultural Sciences, Chengdu, 610066, China
| | - Yongqing Zhu
- Institute of Agro-Products Processing Science and Technology, Institute of Food Nutrition and Health, Sichuan Academy of Agricultural Sciences, Chengdu, 610066, China
| | - Zhuoya Xiang
- Institute of Agro-Products Processing Science and Technology, Institute of Food Nutrition and Health, Sichuan Academy of Agricultural Sciences, Chengdu, 610066, China
| | - Boyu Zhu
- Institute of Agro-Products Processing Science and Technology, Institute of Food Nutrition and Health, Sichuan Academy of Agricultural Sciences, Chengdu, 610066, China
| | - Xiaobo Tang
- Tea Research Institute, Sichuan Academy of Agricultural Sciences, Chengdu, 610066, China
| | - Ting Zhang
- Tea Research Institute, Sichuan Academy of Agricultural Sciences, Chengdu, 610066, China
| | - Liugang Shi
- Yazhou Hengtai Tea Industry Co. LTD, Sichuan, Ya'an, 625100, China
| | - Xiaohua Lyu
- Department of Nutrition and Food Hygiene, West China School of Public Health and West China Fourth Hospital, Sichuan University, Chengdu, 610041, China
| | - Jian Chen
- Institute of Agro-Products Processing Science and Technology, Institute of Food Nutrition and Health, Sichuan Academy of Agricultural Sciences, Chengdu, 610066, China
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6
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Subramanian V, Bagger JI, Harihar V, Holst JJ, Knop FK, Villsbøll T. An extended minimal model of OGTT: estimation of α- and β-cell dysfunction, insulin resistance, and the incretin effect. Am J Physiol Endocrinol Metab 2024; 326:E182-E205. [PMID: 38088864 PMCID: PMC11193523 DOI: 10.1152/ajpendo.00278.2023] [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: 08/28/2023] [Revised: 11/27/2023] [Accepted: 12/07/2023] [Indexed: 12/20/2023]
Abstract
Loss of insulin sensitivity, α- and β-cell dysfunction, and impairment in incretin effect have all been implicated in the pathophysiology of type 2 diabetes (T2D). Parsimonious mathematical models are useful in quantifying parameters related to the pathophysiology of T2D. Here, we extend the minimum model developed to describe the glucose-insulin-glucagon dynamics in the isoglycemic intravenous glucose infusion (IIGI) experiment to the oral glucose tolerance test (OGTT). The extended model describes glucose and hormone dynamics in OGTT including the contribution of the incretin hormones, glucose-dependent insulinotropic polypeptide (GIP), and glucagon-like peptide-1 (GLP-1), to insulin secretion. A new function describing glucose arrival from the gut is introduced. The model is fitted to OGTT data from eight individuals with T2D and eight weight-matched controls (CS) without diabetes to obtain parameters related to insulin sensitivity, β- and α-cell function. The parameters, i.e., measures of insulin sensitivity, a1, suppression of glucagon secretion, k1, magnitude of glucagon secretion, γ2, and incretin-dependent insulin secretion, γ3, were found to be different between CS and T2D with P values < 0.002, <0.017, <0.009, <0.004, respectively. A new rubric for estimating the incretin effect directly from modeling the OGTT is presented. The average incretin effect correlated well with the experimentally determined incretin effect with a Spearman rank test correlation coefficient of 0.67 (P < 0.012). The average incretin effect was found to be different between CS and T2D (P < 0.032). The developed model is shown to be effective in quantifying the factors relevant to T2D pathophysiology.NEW & NOTEWORTHY A new extended model of oral glucose tolerance test (OGTT) has been developed that includes glucagon dynamics and incretin contribution to insulin secretion. The model allows the estimation of parameters related to α- and β-cell dysfunction, insulin sensitivity, and incretin action. A new function describing the influx of glucose from the gut has been introduced. A new rubric for estimating the incretin effect directly from the OGTT experiment has been developed. The effect of glucose dose was also investigated.
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Affiliation(s)
- Vijaya Subramanian
- Institute for Computational Medicine, Johns Hopkins University, Baltimore, Maryland, United States
| | - Jonatan I Bagger
- Center for Clinical Metabolic Research, Gentofte Hospital, University of Copenhagen, Hellerup, Denmark
- Novo Nordisk Foundation Center for Basic Metabolic Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
- Clinical Research, Steno Diabetes Center Copenhagen, Herlev, Denmark
| | - Vinayak Harihar
- Department of Biophysics, Johns Hopkins University, Baltimore, Maryland, United States
- Biophysics Graduate Group, University of California, Berkeley, California, United States
| | - Jens J Holst
- Novo Nordisk Foundation Center for Basic Metabolic Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Filip K Knop
- Center for Clinical Metabolic Research, Gentofte Hospital, University of Copenhagen, Hellerup, Denmark
- Novo Nordisk Foundation Center for Basic Metabolic Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
- Clinical Research, Steno Diabetes Center Copenhagen, Herlev, Denmark
- Department of Clinical Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Tina Villsbøll
- Center for Clinical Metabolic Research, Gentofte Hospital, University of Copenhagen, Hellerup, Denmark
- Clinical Research, Steno Diabetes Center Copenhagen, Herlev, Denmark
- Department of Clinical Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
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7
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Asadi F, Gunawardana SC, Dolle RE, Piston DW. An orally available compound suppresses glucagon hypersecretion and normalizes hyperglycemia in type 1 diabetes. JCI Insight 2024; 9:e172626. [PMID: 38258903 PMCID: PMC10906223 DOI: 10.1172/jci.insight.172626] [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: 05/31/2023] [Accepted: 12/05/2023] [Indexed: 01/24/2024] Open
Abstract
Suppression of glucagon hypersecretion can normalize hyperglycemia during type 1 diabetes (T1D). Activating erythropoietin-producing human hepatocellular receptor type-A4 (EphA4) on α cells reduced glucagon hypersecretion from dispersed α cells and T1D islets from both human donor and mouse models. We synthesized a high-affinity small molecule agonist for the EphA4 receptor, WCDD301, which showed robust plasma and liver microsome metabolic stability in both mouse and human preparations. In islets and dispersed islet cells from nondiabetic and T1D human donors, WCDD301 reduced glucagon secretion comparable to the natural EphA4 ligand, Ephrin-A5. In diabetic NOD and streptozotocin-treated mice, once-daily oral administration of WCDD301 formulated with a time-release excipient reduced plasma glucagon and normalized blood glucose for more than 3 months. These results suggest that targeting the α cell EphA4 receptor by sustained release of WCDD301 is a promising pharmacologic pathway for normalizing hyperglycemia in patients with T1D.
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Affiliation(s)
| | | | - Roland E. Dolle
- Center for Drug Discovery, Washington University School of Medicine, St. Louis, Missouri, USA
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8
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Haddad D, Dsouza VS, Al-Mulla F, Al Madhoun A. New-Generation Glucokinase Activators: Potential Game-Changers in Type 2 Diabetes Treatment. Int J Mol Sci 2024; 25:571. [PMID: 38203742 PMCID: PMC10779250 DOI: 10.3390/ijms25010571] [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: 11/23/2023] [Revised: 12/28/2023] [Accepted: 12/28/2023] [Indexed: 01/12/2024] Open
Abstract
Achieving glycemic control and sustaining functional pancreatic β-cell activity remains an unmet medical need in the treatment of type 2 diabetes mellitus (T2DM). Glucokinase activators (GKAs) constitute a class of anti-diabetic drugs designed to regulate blood sugar levels and enhance β-cell function in patients with diabetes. A significant progression in GKA development is underway to address the limitations of earlier generations. Dorzagliatin, a dual-acting GKA, targets both the liver and pancreas and has successfully completed two phase III trials, demonstrating favorable results in diabetes treatment. The hepato-selective GKA, TTP399, emerges as a strong contender, displaying clinically noteworthy outcomes with minimal adverse effects. This paper seeks to review the current literature, delve into the mechanisms of action of these new-generation GKAs, and assess their efficacy and safety in treating T2DM based on published preclinical studies and recent clinical trials.
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Affiliation(s)
- Dania Haddad
- Genetics and Bioinformatics Department, Dasman Diabetes Institute, Dasman 15462, Kuwait; (D.H.); (V.S.D.); (F.A.-M.)
| | - Vanessa Sybil Dsouza
- Genetics and Bioinformatics Department, Dasman Diabetes Institute, Dasman 15462, Kuwait; (D.H.); (V.S.D.); (F.A.-M.)
| | - Fahd Al-Mulla
- Genetics and Bioinformatics Department, Dasman Diabetes Institute, Dasman 15462, Kuwait; (D.H.); (V.S.D.); (F.A.-M.)
| | - Ashraf Al Madhoun
- Genetics and Bioinformatics Department, Dasman Diabetes Institute, Dasman 15462, Kuwait; (D.H.); (V.S.D.); (F.A.-M.)
- Animal and Imaging Core Facilities, Dasman Diabetes Institute, Dasman 15462, Kuwait
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9
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Park J, Hall C, Hubbard B, LaMoia T, Gaspar R, Nasiri A, Li F, Zhang H, Kim J, Haeusler RA, Accili D, Shulman GI, Yu H, Choi E. MAD2-Dependent Insulin Receptor Endocytosis Regulates Metabolic Homeostasis. Diabetes 2023; 72:1781-1794. [PMID: 37725942 PMCID: PMC10658066 DOI: 10.2337/db23-0314] [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: 04/24/2023] [Accepted: 09/12/2023] [Indexed: 09/21/2023]
Abstract
Insulin activates insulin receptor (IR) signaling and subsequently triggers IR endocytosis to attenuate signaling. Cell division regulators MAD2, BUBR1, and p31comet promote IR endocytosis on insulin stimulation. Here, we show that genetic ablation of the IR-MAD2 interaction in mice delays IR endocytosis, increases IR levels, and prolongs insulin action at the cell surface. This in turn causes a defect in insulin clearance and increases circulating insulin levels, unexpectedly increasing glucagon levels, which alters glucose metabolism modestly. Disruption of the IR-MAD2 interaction increases serum fatty acid concentrations and hepatic fat accumulation in fasted male mice. Furthermore, disruption of the IR-MAD2 interaction distinctly changes metabolic and transcriptomic profiles in the liver and adipose tissues. Our findings establish the function of cell division regulators in insulin signaling and provide insights into the metabolic functions of IR endocytosis. ARTICLE HIGHLIGHTS The physiological role of IR endocytosis in insulin sensitivity remains unclear. Disruption of the IR-MAD2 interaction delays IR endocytosis and prolongs insulin signaling. IR-MAD2 controls insulin clearance and glucose metabolism. IR-MAD2 maintains energy homeostasis.
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Affiliation(s)
- Junhee Park
- Department of Pathology and Cell Biology, Vagelos College of Physicians and Surgeons, Columbia University, New York, NY
| | - Catherine Hall
- Department of Pathology and Cell Biology, Vagelos College of Physicians and Surgeons, Columbia University, New York, NY
| | - Brandon Hubbard
- Departments of Internal Medicine and Cellular and Molecular Physiology, Yale School of Medicine, New Haven, CT
| | - Traci LaMoia
- Departments of Internal Medicine and Cellular and Molecular Physiology, Yale School of Medicine, New Haven, CT
| | - Rafael Gaspar
- Departments of Internal Medicine and Cellular and Molecular Physiology, Yale School of Medicine, New Haven, CT
| | - Ali Nasiri
- Departments of Internal Medicine and Cellular and Molecular Physiology, Yale School of Medicine, New Haven, CT
| | - Fang Li
- Cardiometabolic Genomics Program, Division of Cardiology, Department of Medicine, Columbia University Irving Medical Center, New York, NY
| | - Hanrui Zhang
- Cardiometabolic Genomics Program, Division of Cardiology, Department of Medicine, Columbia University Irving Medical Center, New York, NY
| | - Jiyeon Kim
- Department of Urology and Department of Cellular and Molecular Physiology, Yale School of Medicine, New Haven, CT
| | - Rebecca A Haeusler
- Department of Pathology and Cell Biology, Vagelos College of Physicians and Surgeons, Columbia University, New York, NY
- Naomi Berrie Diabetes Center, Columbia University, New York, NY
- Department of Medicine, Vagelos College of Physicians and Surgeons, Columbia University, New York, NY
| | - Domenico Accili
- Naomi Berrie Diabetes Center, Columbia University, New York, NY
- Department of Medicine, Vagelos College of Physicians and Surgeons, Columbia University, New York, NY
| | - Gerald I Shulman
- Departments of Internal Medicine and Cellular and Molecular Physiology, Yale School of Medicine, New Haven, CT
| | - Hongtao Yu
- School of Life Sciences, Westlake University, Hangzhou, Zhejiang Province, China
| | - Eunhee Choi
- Department of Pathology and Cell Biology, Vagelos College of Physicians and Surgeons, Columbia University, New York, NY
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Armour SL, Frueh A, Chibalina MV, Dou H, Argemi-Muntadas L, Hamilton A, Katzilieris-Petras G, Carmeliet P, Davies B, Moritz T, Eliasson L, Rorsman P, Knudsen JG. Glucose Controls Glucagon Secretion by Regulating Fatty Acid Oxidation in Pancreatic α-Cells. Diabetes 2023; 72:1446-1459. [PMID: 37494670 PMCID: PMC10545563 DOI: 10.2337/db23-0056] [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: 01/19/2023] [Accepted: 07/16/2023] [Indexed: 07/28/2023]
Abstract
Whole-body glucose homeostasis is coordinated through secretion of glucagon and insulin from pancreatic islets. When glucose is low, glucagon is released from α-cells to stimulate hepatic glucose production. However, the mechanisms that regulate glucagon secretion from pancreatic α-cells remain unclear. Here we show that in α-cells, the interaction between fatty acid oxidation and glucose metabolism controls glucagon secretion. The glucose-dependent inhibition of glucagon secretion relies on pyruvate dehydrogenase and carnitine palmitoyl transferase 1a activity and lowering of mitochondrial fatty acid oxidation by increases in glucose. This results in reduced intracellular ATP and leads to membrane repolarization and inhibition of glucagon secretion. These findings provide a new framework for the metabolic regulation of the α-cell, where regulation of fatty acid oxidation by glucose accounts for the stimulation and inhibition of glucagon secretion. ARTICLE HIGHLIGHTS It has become clear that dysregulation of glucagon secretion and α-cell function plays an important role in the development of diabetes, but we do not know how glucagon secretion is regulated. Here we asked whether glucose inhibits fatty acid oxidation in α-cells to regulate glucagon secretion. We found that fatty acid oxidation is required for the inhibitory effects of glucose on glucagon secretion through reductions in ATP. These findings provide a new framework for the regulation of glucagon secretion by glucose.
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Affiliation(s)
- Sarah L. Armour
- Section for Cell Biology and Physiology, Department of Biology, University of Copenhagen, Copenhagen, Denmark
| | - Alexander Frueh
- Section for Cell Biology and Physiology, Department of Biology, University of Copenhagen, Copenhagen, Denmark
| | - Margarita V. Chibalina
- Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Churchill Hospital, Oxford, U.K
| | - Haiqiang Dou
- Department of Physiology, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Lidia Argemi-Muntadas
- Novo Nordisk Foundation Center for Basic Metabolic Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Alexander Hamilton
- Section for Cell Biology and Physiology, Department of Biology, University of Copenhagen, Copenhagen, Denmark
- Department of Clinical Sciences in Malmö, Islet Cell Exocytosis, Lund University Diabetes Centre, Lund University, Malmö, Sweden
| | - Georgios Katzilieris-Petras
- Section for Cell Biology and Physiology, Department of Biology, University of Copenhagen, Copenhagen, Denmark
| | - Peter Carmeliet
- Laboratory of Angiogenesis and Vascular Metabolism, Centre for Cancer Biology, Vlaams Instituut voor Biotechnologie (VIB), Department of Oncology, Leuven Cancer Institute, Katholieke Universiteit Leuven, Leuven, Belgium
- Laboratory of Angiogenesis and Vascular Heterogeneity, Department of Biomedicine, Aarhus University, Aarhus, Denmark
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangdong, People’s Republic of China
| | - Benjamin Davies
- Wellcome Centre for Human Genetics, University of Oxford, Oxford, U.K
| | - Thomas Moritz
- Novo Nordisk Foundation Center for Basic Metabolic Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Lena Eliasson
- Department of Clinical Sciences in Malmö, Islet Cell Exocytosis, Lund University Diabetes Centre, Lund University, Malmö, Sweden
| | - Patrik Rorsman
- Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Churchill Hospital, Oxford, U.K
- Department of Physiology, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Jakob G. Knudsen
- Section for Cell Biology and Physiology, Department of Biology, University of Copenhagen, Copenhagen, Denmark
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11
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Safarzad M, Jazi MS, Kiaei M, Asadi J. Lower serum zinc level is associated with higher fasting insulin in type 2 diabetes mellitus (T2DM) and relates with disturbed glucagon suppression response in male patients. Prim Care Diabetes 2023; 17:493-498. [PMID: 37391316 DOI: 10.1016/j.pcd.2023.05.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/17/2023] [Revised: 05/29/2023] [Accepted: 05/30/2023] [Indexed: 07/02/2023]
Abstract
AIMS Zinc ion can play critical role in glycemic control in diabetes mellitus (DM), contributing to both insulin synthesis and secretion. In this study, we aimed to investigate the level of zinc in diabetic patients and its association with glycemic parameters, insulin, and glucagon level. METHODS 112 individuals (59 cases of type 2DM and 53 non-diabetic controls) were included in this study. Biochemical parameters (FBG, 2hpp, HbA1C), and zinc level in the serum were measured using colorimetric assays. Insulin and glucagon were measured by ELISA method. HOMA-IR, HOMA-B, reciprocal HOMA-B, and Quicki indices were calculated using appropriate formula. For further analysis, patients were divided into two groups: high (>135.5 μg/dl) and low (<135.5 μg/dl) zinc. Glucagon suppression was considered yes if 2hpp glucagon < fasting glucagon. RESULTS Our results showed that serum Zn level in type 2 DM patients was lower than control (P value=0.02). Patients with lower Zn had higher fasting insulin (P value=0.006) and higher β-cell activity index (HOMA-B, p value=0.02), however fasting glucagon and parameters of hyperglycemia (FBG, 2hpp, Hba1C) were not different. Moreover, insulin sensitivity and resistance indices (Quicki, HOMA-IR,1/HOMA-IR) showed non-significantly improved status in high Zn group. We found non-significant association between glucagon suppression and Zn level in both genders (N = 39, p value = 0.07), however, it was significant in males (N = 14, p value = 0.02). CONCLUSION Altogether, our results indicated reduced serum Zn in type 2DM can exacerbate hyperinsulinemia and glucagon suppression (only significant in the male), highlighting its importance in type 2DM control.
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Affiliation(s)
- Mahdieh Safarzad
- Metabolic Disorders Research Center, Golestan University of Medical Sciences, Gorgan, Iran
| | - Marie Saghaeian Jazi
- Metabolic Disorders Research Center, Golestan University of Medical Sciences, Gorgan, Iran; Stem Cell Research Center, Golestan University of Medical Sciences, Gorgan, Iran.
| | - Mohammadreza Kiaei
- Laboratory Sciences Research Center, Golestan University of Medical Sciences, Gorgan, Iran
| | - Jahanbakhsh Asadi
- Metabolic Disorders Research Center, Golestan University of Medical Sciences, Gorgan, Iran
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12
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Knuth ER, Foster HR, Jin E, Merrins MJ. Leucine suppresses glucagon secretion from pancreatic islets by directly modulating α-cell cAMP. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.07.31.551113. [PMID: 37577685 PMCID: PMC10418066 DOI: 10.1101/2023.07.31.551113] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/15/2023]
Abstract
Objective Pancreatic islets are nutrient sensors that regulate organismal blood glucose homeostasis. Glucagon release from the pancreatic α-cell is important under fasted, fed, and hypoglycemic conditions, yet metabolic regulation of α-cells remains poorly understood. Here, we identified a previously unexplored role for physiological levels of leucine, which is classically regarded as a β-cell fuel, in the intrinsic regulation of α-cell glucagon release. Methods GcgCreERT:CAMPER and GcgCreERT:GCaMP6s mice were generated to perform dynamic, high-throughput functional measurements of α-cell cAMP and Ca2+ within the intact islet. Islet perifusion assays were used for simultaneous, time-resolved measurements of glucagon and insulin release from mouse and human islets. The effects of leucine were compared with glucose and the mitochondrial fuels 2-aminobicyclo(2,2,1)heptane-2-carboxylic acid (BCH, non-metabolized leucine analog that activates glutamate dehydrogenase), α-ketoisocaproate (KIC, leucine metabolite), and methyl-succinate (complex II fuel). CYN154806 (Sstr2 antagonist), diazoxide (KATP activator, which prevents Ca2+-dependent exocytosis from α, β, and δ-cells), and dispersed α-cells were used to inhibit islet paracrine signaling and identify α-cell intrinsic effects. Results Mimicking the effect of glucose, leucine strongly suppressed amino acid-stimulated glucagon secretion. Mechanistically, leucine dose-dependently reduced α-cell cAMP at physiological concentrations, with an IC50 of 57, 440, and 1162 μM at 2, 6, and 10 mM glucose, without affecting α-cell Ca2+. Leucine also reduced α-cell cAMP in islets treated with Sstr2 antagonist or diazoxide, as well as dispersed α-cells, indicating an α-cell intrinsic effect. The effect of leucine was matched by KIC and the glutamate dehydrogenase activator BCH, but not methyl-succinate, indicating a dependence on mitochondrial anaplerosis. Glucose, which stimulates anaplerosis via pyruvate carboxylase, had the same suppressive effect on α-cell cAMP but with lower potency. Similarly to mouse islets, leucine suppressed glucagon secretion from human islets under hypoglycemic conditions. Conclusions These findings highlight an important role for physiological levels of leucine in the metabolic regulation of α-cell cAMP and glucagon secretion. Leucine functions primarily through an α-cell intrinsic effect that is dependent on glutamate dehydrogenase, in addition to the well-established α-cell regulation by β/δ-cell paracrine signaling. Our results suggest that mitochondrial anaplerosis-cataplerosis facilitates the glucagonostatic effect of both leucine and glucose, which cooperatively suppress α-cell tone by reducing cAMP.
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Affiliation(s)
- Emily R. Knuth
- Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Wisconsin-Madison, Madison, WI 53705, USA
| | - Hannah R. Foster
- Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Wisconsin-Madison, Madison, WI 53705, USA
| | - Erli Jin
- Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Wisconsin-Madison, Madison, WI 53705, USA
| | - Matthew J. Merrins
- Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Wisconsin-Madison, Madison, WI 53705, USA
- William S. Middleton Memorial Veterans Hospital, Madison, WI 53705, USA
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13
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Brown A, Tzanakakis ES. Mathematical modeling clarifies the paracrine roles of insulin and glucagon on the glucose-stimulated hormonal secretion of pancreatic alpha- and beta-cells. Front Endocrinol (Lausanne) 2023; 14:1212749. [PMID: 37645413 PMCID: PMC10461634 DOI: 10.3389/fendo.2023.1212749] [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: 04/27/2023] [Accepted: 07/21/2023] [Indexed: 08/31/2023] Open
Abstract
Introduction Blood sugar homeostasis relies largely on the action of pancreatic islet hormones, particularly insulin and glucagon. In a prototypical fashion, glucagon is released upon hypoglycemia to elevate glucose by acting on the liver while elevated glucose induces the secretion of insulin which leads to sugar uptake by peripheral tissues. This simplified view of glucagon and insulin does not consider the paracrine roles of the two hormones modulating the response to glucose of α- and β-cells. In particular, glucose-stimulated glucagon secretion by isolated α-cells exhibits a Hill-function pattern, while experiments with intact pancreatic islets suggest a 'U'-shaped response. Methods To this end, a framework was developed based on first principles and coupled to experimental studies capturing the glucose-induced response of pancreatic α- and β-cells influenced by the two hormones. The model predicts both the transient and steady-state profiles of secreted insulin and glucagon, including the typical biphasic response of normal β-cells to hyperglycemia. Results and discussion The results underscore insulin activity as a differentiating factor of the glucagon secretion from whole islets vs. isolated α-cells, and highlight the importance of experimental conditions in interpreting the behavior of islet cells in vitro. The model also reproduces the hyperglucagonemia, which is experienced by diabetes patients, and it is linked to a failure of insulin to inhibit α-cell activity. The framework described here is amenable to the inclusion of additional islet cell types and extrapancreatic tissue cells simulating multi-organ systems. The study expands our understanding of the interplay of insulin and glucagon for pancreas function in normal and pathological conditions.
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Affiliation(s)
- Aedan Brown
- Department of Chemical and Biological Engineering, Tufts University, Medford, MA, United States
| | - Emmanuel S. Tzanakakis
- Department of Chemical and Biological Engineering, Tufts University, Medford, MA, United States
- Genetics, Molecular and Cellular Biology, Tufts University, Boston, MA, United States
- Pharmacology and Drug Development, Tufts University, Boston, MA, United States
- Clinical and Translational Science Institute, Tufts University, Boston, MA, United States
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14
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Asadi F, Dhanvantari S. Misrouting of glucagon and stathmin-2 towards lysosomal system of α-cells in glucagon hypersecretion of diabetes. Islets 2022; 14:40-57. [PMID: 34923907 PMCID: PMC8726656 DOI: 10.1080/19382014.2021.2011550] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
Glucagon hypersecretion from the pancreatic α-cell is a characteristic sign of diabetes, which exacerbates fasting hyperglycemia. Thus, targeting glucagon secretion from α-cells may be a promising approach for combating hyperglucagonemia. We have recently identified stathmin-2 as an α-cell protein that regulates glucagon secretion by directing glucagon toward the endolysosomal system in αTC1-6 cells. We hypothesized that disruption of Stmn2-mediated trafficking of glucagon to the endolysosomes in diabetes contributes to hyperglucagonemia. In isolated islets from male mice treated with streptozotocin (STZ), glucagon secretion and cellular content were augmented, but cellular Stmn2 levels were reduced (p < .01), as measured by both ELISA and immunofluorescence intensity. Using confocal immunofluorescence microscopy, the colocalization of glucagon and Stmn2 in Lamp2A+ lysosomes was dramatically reduced (p < .001) in islets from diabetic mice, and the colocalization of Stmn2, but not glucagon, with the late endosome marker, Rab7, significantly (p < .01) increased. Further studies were conducted in αTC1-6 cells cultured in media containing high glucose (16.7 mM) for 2 weeks to mimic glucagon hypersecretion of diabetes. Surprisingly, treatment of αTC1-6 cells with the lysosomal inhibitor bafilomycin A1 reduced K+-induced glucagon secretion, suggesting that high glucose may induce glucagon secretion from another lysosomal compartment. Both glucagon and Stmn2 co-localized with Lamp1, which marks secretory lysosomes, in cells cultured in high glucose. We propose that, in addition to enhanced trafficking and secretion through the regulated secretory pathway, the hyperglucagonemia of diabetes may also be due to re-routing of glucagon from the degradative Lamp2A+ lysosome toward the secretory Lamp1+ lysosome.
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Affiliation(s)
- Farzad Asadi
- Department of Pathology and Laboratory Medicine, Schulich School of Medicine & Dentistry, Western University, London, ON, Canada
| | - Savita Dhanvantari
- Department of Pathology and Laboratory Medicine, Schulich School of Medicine & Dentistry, Western University, London, ON, Canada
- Department of Medical Biophysics, Western University, London, ON, Canada
- Metabolism & Diabetes and Imaging Programs, Lawson Health Research Institute, London, ON, Canada
- CONTACT Savita Dhanvantari Lawson Health Research Institute, PO Box 5777, Stn B, London, ONN6A 4V2, Canada
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15
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Panzer JK, Tamayo A, Caicedo A. Restoring glutamate receptor signaling in pancreatic alpha cells rescues glucagon responses in type 1 diabetes. Cell Rep 2022; 41:111792. [PMID: 36516761 DOI: 10.1016/j.celrep.2022.111792] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2022] [Revised: 05/19/2022] [Accepted: 11/16/2022] [Indexed: 12/15/2022] Open
Abstract
Glucagon secretion from pancreatic alpha cells is crucial to prevent hypoglycemia. People with type 1 diabetes lose this glucoregulatory mechanism and are susceptible to dangerous hypoglycemia for reasons still unclear. Here we determine that alpha cells in living pancreas slices from donors with type 1 diabetes do not mount an adequate glucagon response and cannot activate the positive autocrine feedback mediated by AMPA/kainate glutamate receptors. This feedback is required to elicit full glucagon responses in the healthy state. Reactivating residual AMPA/kainate receptor function with positive allosteric modulators restores glucagon secretion in human slices from donors with type 1 diabetes as well as glucose counterregulation in non-obese diabetic mice. Our study thus identifies a defect in autocrine signaling that contributes to alpha cell failure. The use of positive allosteric modulators of AMPA/kainate receptors overcomes this deficiency and prevents hypoglycemia, an effect that could be used to improve the management of diabetes.
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Affiliation(s)
- Julia K Panzer
- Division of Endocrinology, Diabetes, and Metabolism, Department of Medicine, University of Miami Miller School of Medicine, Miami, FL 33136, USA.
| | - Alejandro Tamayo
- Division of Endocrinology, Diabetes, and Metabolism, Department of Medicine, University of Miami Miller School of Medicine, Miami, FL 33136, USA
| | - Alejandro Caicedo
- Division of Endocrinology, Diabetes, and Metabolism, Department of Medicine, University of Miami Miller School of Medicine, Miami, FL 33136, USA.
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16
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Ng XW, Chung YH, Asadi F, Kong C, Ustione A, Piston DW. RhoA as a Signaling Hub Controlling Glucagon Secretion From Pancreatic α-Cells. Diabetes 2022; 71:2384-2394. [PMID: 35904939 PMCID: PMC9630081 DOI: 10.2337/db21-1010] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/18/2021] [Accepted: 07/26/2022] [Indexed: 11/13/2022]
Abstract
Glucagon hypersecretion from pancreatic islet α-cells exacerbates hyperglycemia in type 1 diabetes (T1D) and type 2 diabetes. Still, the underlying mechanistic pathways that regulate glucagon secretion remain controversial. Among the three complementary main mechanisms (intrinsic, paracrine, and juxtacrine) proposed to regulate glucagon release from α-cells, juxtacrine interactions are the least studied. It is known that tonic stimulation of α-cell EphA receptors by ephrin-A ligands (EphA forward signaling) inhibits glucagon secretion in mouse and human islets and restores glucose inhibition of glucagon secretion in sorted mouse α-cells, and these effects correlate with increased F-actin density. Here, we elucidate the downstream target of EphA signaling in α-cells. We demonstrate that RhoA, a Rho family GTPase, plays a key role in this pathway. Pharmacological inhibition of RhoA disrupts glucose inhibition of glucagon secretion in islets and decreases cortical F-actin density in dispersed α-cells and α-cells in intact islets. Quantitative FRET biosensor imaging shows that increased RhoA activity follows directly from EphA stimulation. We show that in addition to modulating F-actin density, EphA forward signaling and RhoA activity affect α-cell Ca2+ activity in a novel mechanistic pathway. Finally, we show that stimulating EphA forward signaling restores glucose inhibition of glucagon secretion from human T1D donor islets.
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Affiliation(s)
| | | | | | | | | | - David W. Piston
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO
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17
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Capozzi ME, D'Alessio DA, Campbell JE. The past, present, and future physiology and pharmacology of glucagon. Cell Metab 2022; 34:1654-1674. [PMID: 36323234 PMCID: PMC9641554 DOI: 10.1016/j.cmet.2022.10.001] [Citation(s) in RCA: 26] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/21/2022] [Revised: 08/23/2022] [Accepted: 09/30/2022] [Indexed: 11/07/2022]
Abstract
The evolution of glucagon has seen the transition from an impurity in the preparation of insulin to the development of glucagon receptor agonists for use in type 1 diabetes. In type 2 diabetes, glucagon receptor antagonists have been explored to reduce glycemia thought to be induced by hyperglucagonemia. However, the catabolic actions of glucagon are currently being leveraged to target the rise in obesity that paralleled that of diabetes, bringing the pharmacology of glucagon full circle. During this evolution, the physiological importance of glucagon advanced beyond the control of hepatic glucose production, incorporating critical roles for glucagon to regulate both lipid and amino acid metabolism. Thus, it is unsurprising that the study of glucagon has left several paradoxes that make it difficult to distill this hormone down to a simplified action. Here, we describe the history of glucagon from the past to the present and suggest some direction to the future of this field.
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Affiliation(s)
- Megan E Capozzi
- Duke Molecular Physiology Institute, Duke University Medical Center, Durham, NC 27701, USA
| | - David A D'Alessio
- Duke Molecular Physiology Institute, Duke University Medical Center, Durham, NC 27701, USA; Department of Medicine, Endocrinology Division, Duke University Medical Center, Durham, NC 27701, USA
| | - Jonathan E Campbell
- Duke Molecular Physiology Institute, Duke University Medical Center, Durham, NC 27701, USA; Department of Medicine, Endocrinology Division, Duke University Medical Center, Durham, NC 27701, USA; Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC 27701, USA.
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18
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Ren H, Li Y, Han C, Yu Y, Shi B, Peng X, Zhang T, Wu S, Yang X, Kim S, Chen L, Tang C. Pancreatic α and β cells are globally phase-locked. Nat Commun 2022; 13:3721. [PMID: 35764654 PMCID: PMC9240067 DOI: 10.1038/s41467-022-31373-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2021] [Accepted: 06/15/2022] [Indexed: 11/25/2022] Open
Abstract
The Ca2+ modulated pulsatile glucagon and insulin secretions by pancreatic α and β cells play a crucial role in glucose homeostasis. However, how α and β cells coordinate to produce various Ca2+ oscillation patterns is still elusive. Using a microfluidic device and transgenic mice, we recorded Ca2+ signals from islet α and β cells, and observed heterogeneous Ca2+ oscillation patterns intrinsic to each islet. After a brief period of glucose stimulation, α and β cells’ oscillations were globally phase-locked. While the activation of α cells displayed a fixed time delay of ~20 s to that of β cells, β cells activated with a tunable period. Moreover, islet α cell number correlated with oscillation frequency. We built a mathematical model of islet Ca2+ oscillation incorporating paracrine interactions, which quantitatively agreed with the experimental data. Our study highlights the importance of cell-cell interaction in generating stable but tunable islet oscillation patterns. The Ca2+ modulated pulsatile glucagon and insulin secretions by pancreatic α and β cells are critical in glucose homeostasis. Here the authors show that the Ca2+ oscillations of α and β cells are phase-locked, and that the oscillation pattern is tuned by paracrine interactions between α and β cells.
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Affiliation(s)
- Huixia Ren
- Center for Quantitative Biology, Peking University, Beijing, 100871, China.,Peking-Tsinghua Center for Life Sciences, Peking University, Beijing, 100871, China
| | - Yanjun Li
- Center for Quantitative Biology, Peking University, Beijing, 100871, China.,Institute of Molecular Medicine, School of Future Technology, National Biomedical Imaging Center, Peking University, Beijing, 100871, China
| | - Chengsheng Han
- Institute of Molecular Medicine, School of Future Technology, National Biomedical Imaging Center, Peking University, Beijing, 100871, China
| | - Yi Yu
- Center for Quantitative Biology, Peking University, Beijing, 100871, China
| | - Bowen Shi
- Peking-Tsinghua Center for Life Sciences, Peking University, Beijing, 100871, China
| | - Xiaohong Peng
- Institute of Molecular Medicine, School of Future Technology, National Biomedical Imaging Center, Peking University, Beijing, 100871, China
| | - Tianming Zhang
- Yuanpei College, Peking University, Beijing, 100871, China
| | - Shufang Wu
- Center for Quantitative Biology, Peking University, Beijing, 100871, China
| | - Xiaojing Yang
- Center for Quantitative Biology, Peking University, Beijing, 100871, China.,Peking-Tsinghua Center for Life Sciences, Peking University, Beijing, 100871, China
| | - Sneppen Kim
- Niels Bohr Institute, University of Copenhagen, 2100, Copenhagen, Denmark
| | - Liangyi Chen
- Peking-Tsinghua Center for Life Sciences, Peking University, Beijing, 100871, China. .,Institute of Molecular Medicine, School of Future Technology, National Biomedical Imaging Center, Peking University, Beijing, 100871, China.
| | - Chao Tang
- Center for Quantitative Biology, Peking University, Beijing, 100871, China. .,Peking-Tsinghua Center for Life Sciences, Peking University, Beijing, 100871, China.
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19
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Honzawa N, Fujimoto K, Kobayashi M, Kohno D, Kikuchi O, Yokota-Hashimoto H, Wada E, Ikeuchi Y, Tabei Y, Dorn GW, Utsunomiya K, Nishimura R, Kitamura T. Protein Kinase C (Pkc)-δ Mediates Arginine-Induced Glucagon Secretion in Pancreatic α-Cells. Int J Mol Sci 2022; 23:4003. [PMID: 35409362 PMCID: PMC8999522 DOI: 10.3390/ijms23074003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2022] [Revised: 03/28/2022] [Accepted: 04/01/2022] [Indexed: 02/04/2023] Open
Abstract
The pathophysiology of type 2 diabetes involves insulin and glucagon. Protein kinase C (Pkc)-δ, a serine-threonine kinase, is ubiquitously expressed and involved in regulating cell death and proliferation. However, the role of Pkcδ in regulating glucagon secretion in pancreatic α-cells remains unclear. Therefore, this study aimed to elucidate the physiological role of Pkcδ in glucagon secretion from pancreatic α-cells. Glucagon secretions were investigated in Pkcδ-knockdown InR1G9 cells and pancreatic α-cell-specific Pkcδ-knockout (αPkcδKO) mice. Knockdown of Pkcδ in the glucagon-secreting cell line InR1G9 cells reduced glucagon secretion. The basic amino acid arginine enhances glucagon secretion via voltage-dependent calcium channels (VDCC). Furthermore, we showed that arginine increased Pkcδ phosphorylation at Thr505, which is critical for Pkcδ activation. Interestingly, the knockdown of Pkcδ in InR1G9 cells reduced arginine-induced glucagon secretion. Moreover, arginine-induced glucagon secretions were decreased in αPkcδKO mice and islets from αPkcδKO mice. Pkcδ is essential for arginine-induced glucagon secretion in pancreatic α-cells. Therefore, this study may contribute to the elucidation of the molecular mechanism of amino acid-induced glucagon secretion and the development of novel antidiabetic drugs targeting Pkcδ and glucagon.
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Affiliation(s)
- Norikiyo Honzawa
- Division of Diabetes, Metabolism and Endocrinology, Department of Internal Medicine, Jikei University School of Medicine, 3-25-8 Nishishinbashi, Minato-ku, Tokyo 105-8461, Japan; (N.H.); (K.U.); (R.N.)
- Metabolic Signal Research Center, Institute for Molecular and Cellular Regulation, Gunma University, 3-39-15 Showa-machi, Maebashi 371-8512, Japan; (M.K.); (D.K.); (O.K.); (H.Y.-H.); (E.W.); (Y.I.); (Y.T.)
| | - Kei Fujimoto
- Division of Diabetes, Metabolism and Endocrinology, Department of Internal Medicine, Jikei University Daisan Hospital, 4-11-1, Izumihoncho, Komae-shi, Tokyo 201-8601, Japan
| | - Masaki Kobayashi
- Metabolic Signal Research Center, Institute for Molecular and Cellular Regulation, Gunma University, 3-39-15 Showa-machi, Maebashi 371-8512, Japan; (M.K.); (D.K.); (O.K.); (H.Y.-H.); (E.W.); (Y.I.); (Y.T.)
| | - Daisuke Kohno
- Metabolic Signal Research Center, Institute for Molecular and Cellular Regulation, Gunma University, 3-39-15 Showa-machi, Maebashi 371-8512, Japan; (M.K.); (D.K.); (O.K.); (H.Y.-H.); (E.W.); (Y.I.); (Y.T.)
| | - Osamu Kikuchi
- Metabolic Signal Research Center, Institute for Molecular and Cellular Regulation, Gunma University, 3-39-15 Showa-machi, Maebashi 371-8512, Japan; (M.K.); (D.K.); (O.K.); (H.Y.-H.); (E.W.); (Y.I.); (Y.T.)
| | - Hiromi Yokota-Hashimoto
- Metabolic Signal Research Center, Institute for Molecular and Cellular Regulation, Gunma University, 3-39-15 Showa-machi, Maebashi 371-8512, Japan; (M.K.); (D.K.); (O.K.); (H.Y.-H.); (E.W.); (Y.I.); (Y.T.)
| | - Eri Wada
- Metabolic Signal Research Center, Institute for Molecular and Cellular Regulation, Gunma University, 3-39-15 Showa-machi, Maebashi 371-8512, Japan; (M.K.); (D.K.); (O.K.); (H.Y.-H.); (E.W.); (Y.I.); (Y.T.)
| | - Yuichi Ikeuchi
- Metabolic Signal Research Center, Institute for Molecular and Cellular Regulation, Gunma University, 3-39-15 Showa-machi, Maebashi 371-8512, Japan; (M.K.); (D.K.); (O.K.); (H.Y.-H.); (E.W.); (Y.I.); (Y.T.)
| | - Yoko Tabei
- Metabolic Signal Research Center, Institute for Molecular and Cellular Regulation, Gunma University, 3-39-15 Showa-machi, Maebashi 371-8512, Japan; (M.K.); (D.K.); (O.K.); (H.Y.-H.); (E.W.); (Y.I.); (Y.T.)
| | - Gerald W. Dorn
- Center for Pharmacogenomics, Division of Cardiology, Department of Internal Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA;
| | - Kazunori Utsunomiya
- Division of Diabetes, Metabolism and Endocrinology, Department of Internal Medicine, Jikei University School of Medicine, 3-25-8 Nishishinbashi, Minato-ku, Tokyo 105-8461, Japan; (N.H.); (K.U.); (R.N.)
| | - Rimei Nishimura
- Division of Diabetes, Metabolism and Endocrinology, Department of Internal Medicine, Jikei University School of Medicine, 3-25-8 Nishishinbashi, Minato-ku, Tokyo 105-8461, Japan; (N.H.); (K.U.); (R.N.)
| | - Tadahiro Kitamura
- Metabolic Signal Research Center, Institute for Molecular and Cellular Regulation, Gunma University, 3-39-15 Showa-machi, Maebashi 371-8512, Japan; (M.K.); (D.K.); (O.K.); (H.Y.-H.); (E.W.); (Y.I.); (Y.T.)
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20
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Singh B, Khattab F, Gilon P. Glucose inhibits glucagon secretion by decreasing [Ca2+]c and by reducing the efficacy of Ca2+ on exocytosis via somatostatin-dependent and independent mechanisms. Mol Metab 2022; 61:101495. [PMID: 35421610 PMCID: PMC9065434 DOI: 10.1016/j.molmet.2022.101495] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/23/2021] [Revised: 03/15/2022] [Accepted: 04/04/2022] [Indexed: 11/15/2022] Open
Abstract
Objective Methods Results Conclusions Glucose modulates [Ca2+]c in α-cells within islets but not in dispersed α-cells. In α-cells within islets, it decreases [Ca2+]c independently of their KATP channels. It decreases α-cell [Ca2+]c partly via somatostatin. All glucose-induced [Ca2+]c changes trigger parallel changes in glucagon release. Glucose also decreases the efficacy of Ca2+ on exocytosis (attenuating pathway).
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Affiliation(s)
- Bilal Singh
- Université Catholique de Louvain, Institut de Recherche Expérimentale et Clinique, Pôle d'Endocrinologie, Diabète et Nutrition, Brussels, Belgium
| | - Firas Khattab
- Université Catholique de Louvain, Institut de Recherche Expérimentale et Clinique, Pôle d'Endocrinologie, Diabète et Nutrition, Brussels, Belgium
| | - Patrick Gilon
- Université Catholique de Louvain, Institut de Recherche Expérimentale et Clinique, Pôle d'Endocrinologie, Diabète et Nutrition, Brussels, Belgium.
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21
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Dai XQ, Camunas-Soler J, Briant LJB, Dos Santos T, Spigelman AF, Walker EM, Arrojo E Drigo R, Bautista A, Jones RC, Avrahami D, Lyon J, Nie A, Smith N, Zhang Y, Johnson J, Manning Fox JE, Michelakis ED, Light PE, Kaestner KH, Kim SK, Rorsman P, Stein RW, Quake SR, MacDonald PE. Heterogenous impairment of α cell function in type 2 diabetes is linked to cell maturation state. Cell Metab 2022; 34:256-268.e5. [PMID: 35108513 PMCID: PMC8852281 DOI: 10.1016/j.cmet.2021.12.021] [Citation(s) in RCA: 34] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/09/2021] [Revised: 10/08/2021] [Accepted: 12/22/2021] [Indexed: 02/03/2023]
Abstract
In diabetes, glucagon secretion from pancreatic α cells is dysregulated. The underlying mechanisms, and whether dysfunction occurs uniformly among cells, remain unclear. We examined α cells from human donors and mice using electrophysiological, transcriptomic, and computational approaches. Rising glucose suppresses α cell exocytosis by reducing P/Q-type Ca2+ channel activity, and this is disrupted in type 2 diabetes (T2D). Upon high-fat feeding of mice, α cells shift toward a "β cell-like" electrophysiological profile in concert with indications of impaired identity. In human α cells we identified links between cell membrane properties and cell surface signaling receptors, mitochondrial respiratory chain complex assembly, and cell maturation. Cell-type classification using machine learning of electrophysiology data demonstrated a heterogenous loss of "electrophysiologic identity" in α cells from donors with type 2 diabetes. Indeed, a subset of α cells with impaired exocytosis is defined by an enrichment in progenitor and lineage markers and upregulation of an immature transcriptomic phenotype, suggesting important links between α cell maturation state and dysfunction.
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Affiliation(s)
- Xiao-Qing Dai
- Department of Pharmacology, University of Alberta, Edmonton, AB T6G2R3, Canada; Alberta Diabetes Institute, University of Alberta, Edmonton, AB T6G2R3, Canada
| | - Joan Camunas-Soler
- Department of Bioengineering, Stanford University, Stanford, CA 94305, USA; Chan Zuckerberg Biohub, San Francisco, CA 94518, USA
| | - Linford J B Briant
- Oxford Centre for Diabetes, Endocrinology and Metabolism, Radcliffe Department of Medicine, Churchill Hospital, Oxford OX3 7LE, UK
| | - Theodore Dos Santos
- Department of Pharmacology, University of Alberta, Edmonton, AB T6G2R3, Canada; Alberta Diabetes Institute, University of Alberta, Edmonton, AB T6G2R3, Canada
| | - Aliya F Spigelman
- Department of Pharmacology, University of Alberta, Edmonton, AB T6G2R3, Canada; Alberta Diabetes Institute, University of Alberta, Edmonton, AB T6G2R3, Canada
| | - Emily M Walker
- Department of Internal Medicine, University of Michigan, Ann Arbor, MI 48105, USA
| | - Rafael Arrojo E Drigo
- Department of Molecular Physiology and Biophysics, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Austin Bautista
- Alberta Diabetes Institute, University of Alberta, Edmonton, AB T6G2R3, Canada
| | - Robert C Jones
- Department of Bioengineering, Stanford University, Stanford, CA 94305, USA
| | - Dana Avrahami
- Endocrinology and Metabolism Department, Hadassah-Hebrew University Medical Centre, Jerusalem, Israel
| | - James Lyon
- Alberta Diabetes Institute, University of Alberta, Edmonton, AB T6G2R3, Canada
| | - Aifang Nie
- Department of Pharmacology, University of Alberta, Edmonton, AB T6G2R3, Canada; Alberta Diabetes Institute, University of Alberta, Edmonton, AB T6G2R3, Canada
| | - Nancy Smith
- Department of Pharmacology, University of Alberta, Edmonton, AB T6G2R3, Canada; Alberta Diabetes Institute, University of Alberta, Edmonton, AB T6G2R3, Canada
| | - Yongneng Zhang
- Department of Medicine, University of Alberta, Edmonton, AB T6G2R3, Canada
| | - Janyne Johnson
- Department of Pharmacology, University of Alberta, Edmonton, AB T6G2R3, Canada; Alberta Diabetes Institute, University of Alberta, Edmonton, AB T6G2R3, Canada
| | - Jocelyn E Manning Fox
- Department of Pharmacology, University of Alberta, Edmonton, AB T6G2R3, Canada; Alberta Diabetes Institute, University of Alberta, Edmonton, AB T6G2R3, Canada
| | | | - Peter E Light
- Department of Pharmacology, University of Alberta, Edmonton, AB T6G2R3, Canada; Alberta Diabetes Institute, University of Alberta, Edmonton, AB T6G2R3, Canada
| | - Klaus H Kaestner
- Department of Genetics and Institute for Diabetes, Obesity and Metabolism, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Seung K Kim
- Department of Developmental Biology, Stanford University School of Medicine, Stanford, CA 94305, USA; Stanford Diabetes Research Center, Stanford University, Stanford, CA 94305, USA
| | - Patrik Rorsman
- Oxford Centre for Diabetes, Endocrinology and Metabolism, Radcliffe Department of Medicine, Churchill Hospital, Oxford OX3 7LE, UK
| | - Roland W Stein
- Department of Molecular Physiology and Biophysics, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Stephen R Quake
- Department of Bioengineering, Stanford University, Stanford, CA 94305, USA; Chan Zuckerberg Biohub, San Francisco, CA 94518, USA; Department of Applied Physics, Stanford University, Stanford, CA 94305, USA
| | - Patrick E MacDonald
- Department of Pharmacology, University of Alberta, Edmonton, AB T6G2R3, Canada; Alberta Diabetes Institute, University of Alberta, Edmonton, AB T6G2R3, Canada.
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22
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Holter MM, Saikia M, Cummings BP. Alpha-cell paracrine signaling in the regulation of beta-cell insulin secretion. Front Endocrinol (Lausanne) 2022; 13:934775. [PMID: 35957816 PMCID: PMC9360487 DOI: 10.3389/fendo.2022.934775] [Citation(s) in RCA: 19] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/03/2022] [Accepted: 06/28/2022] [Indexed: 01/14/2023] Open
Abstract
As an incretin hormone, glucagon-like peptide 1 (GLP-1) lowers blood glucose levels by enhancing glucose-stimulated insulin secretion from pancreatic beta-cells. Therapies targeting the GLP-1 receptor (GLP-1R) use the classical incretin model as a physiological framework in which GLP-1 secreted from enteroendocrine L-cells acts on the beta-cell GLP-1R. However, this model has come into question, as evidence demonstrating local, intra-islet GLP-1 production has advanced the competing hypothesis that the incretin activity of GLP-1 may reflect paracrine signaling of GLP-1 from alpha-cells on GLP-1Rs on beta-cells. Additionally, recent studies suggest that alpha-cell-derived glucagon can serve as an additional, albeit less potent, ligand for the beta-cell GLP-1R, thereby expanding the role of alpha-cells beyond that of a counterregulatory cell type. Efforts to understand the role of the alpha-cell in the regulation of islet function have revealed both transcriptional and functional heterogeneity within the alpha-cell population. Further analysis of this heterogeneity suggests that functionally distinct alpha-cell subpopulations display alterations in islet hormone profile. Thus, the role of the alpha-cell in glucose homeostasis has evolved in recent years, such that alpha-cell to beta-cell communication now presents a critical axis regulating the functional capacity of beta-cells. Herein, we describe and integrate recent advances in our understanding of the impact of alpha-cell paracrine signaling on insulin secretory dynamics and how this intra-islet crosstalk more broadly contributes to whole-body glucose regulation in health and under metabolic stress. Moreover, we explore how these conceptual changes in our understanding of intra-islet GLP-1 biology may impact our understanding of the mechanisms of incretin-based therapeutics.
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Affiliation(s)
- Marlena M. Holter
- Department of Biomedical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY, United States
- *Correspondence: Marlena M. Holter,
| | - Mridusmita Saikia
- Department of Biomedical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY, United States
- Nancy E. and Peter C. Meinig School of Biomedical Engineering, Cornell University, Ithaca, NY, United States
| | - Bethany P. Cummings
- School of Medicine, Department of Surgery, Center for Alimentary and Metabolic Sciences, University of California, Davis, Sacramento, CA, United States
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23
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Benninger RKP, Kravets V. The physiological role of β-cell heterogeneity in pancreatic islet function. Nat Rev Endocrinol 2022; 18:9-22. [PMID: 34667280 PMCID: PMC8915749 DOI: 10.1038/s41574-021-00568-0] [Citation(s) in RCA: 55] [Impact Index Per Article: 27.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 09/07/2021] [Indexed: 01/03/2023]
Abstract
Endocrine cells within the pancreatic islets of Langerhans are heterogeneous in terms of transcriptional profile, protein expression and the regulation of hormone release. Even though this heterogeneity has long been appreciated, only within the past 5 years have detailed molecular analyses led to an improved understanding of its basis. Although we are beginning to recognize why some subpopulations of endocrine cells are phenotypically different to others, arguably the most important consideration is how this heterogeneity affects the regulation of hormone release to control the homeostasis of glucose and other energy-rich nutrients. The focus of this Review is the description of how endocrine cell heterogeneity (and principally that of insulin-secreting β-cells) affects the regulation of hormone secretion within the islets of Langerhans. This discussion includes an overview of the functional characteristics of the different islet cell subpopulations and describes how they can communicate to influence islet function under basal and glucose-stimulated conditions. We further discuss how changes to the specific islet cell subpopulations or their numbers might underlie islet dysfunction in type 2 diabetes mellitus. We conclude with a discussion of several key open questions regarding the physiological role of islet cell heterogeneity.
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Affiliation(s)
- Richard K P Benninger
- Department of Bioengineering, University of Colorado Anschutz Medical Campus, Aurora, CO, USA.
- Barbara Davis Center for Diabetes, University of Colorado Anschutz Medical Campus, Aurora, CO, USA.
| | - Vira Kravets
- Department of Bioengineering, University of Colorado Anschutz Medical Campus, Aurora, CO, USA.
- Barbara Davis Center for Diabetes, University of Colorado Anschutz Medical Campus, Aurora, CO, USA.
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24
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Martins-Oliveira M, Tavares I, Goadsby PJ. Was it something I ate? Understanding the bidirectional interaction of migraine and appetite neural circuits. Brain Res 2021; 1770:147629. [PMID: 34428465 DOI: 10.1016/j.brainres.2021.147629] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2021] [Revised: 08/16/2021] [Accepted: 08/17/2021] [Indexed: 12/18/2022]
Abstract
Migraine attacks can involve changes of appetite: while fasting or skipping meals are often reported triggers in susceptible individuals, hunger or food craving are reported in the premonitory phase. Over the last decade, there has been a growing interest and recognition of the importance of studying these overlapping fields of neuroscience, which has led to novel findings. The data suggest additional studies are needed to unravel key neurobiological mechanisms underlying the bidirectional interaction between migraine and appetite. Herein, we review information about the metabolic migraine phenotype and explore migraine therapeutic targets that have a strong input on appetite neuronal circuits, including the calcitonin gene-related peptide (CGRP), the pituitary adenylate cyclase-activating polypeptide (PACAP) and the orexins. Furthermore, we focus on potential therapeutic peptide targets that are involved in regulation of feeding and play a role in migraine pathophysiology, such as neuropeptide Y, insulin, glucagon and leptin. We then examine the orexigenic - anorexigenic circuit feedback loop and explore glucose metabolism disturbances. Additionally, it is proposed a different perspective on the most reported feeding-related trigger - skipping meals - as well as a link between contrasting feeding behaviors (skipping meals vs food craving). Our review aims to increase awareness of migraine through the lens of appetite neurobiology in order to improve our understanding of the earlier phase of migraine, encourage better studies and cross-disciplinary collaborations, and provide novel migraine-specific therapeutic opportunities.
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Affiliation(s)
- Margarida Martins-Oliveira
- Headache Group, Wolfson Centre for Age-Related Disease, Institute of Psychiatry, Psychology and Neuroscience, King's College London, UK; Nutrition and Metabolism Department, NOVA Medical School, Faculdade de Ciências Médicas de Lisboa, Universidade Nova de Lisboa, Campo Mártires da Pátria 130, 1169-056 Lisbon, Portugal.
| | - Isaura Tavares
- Department of Biomedicine, Unit of Experimental Biology, Faculty of Medicine, University of Porto, Alameda Prof. Hernâni Monteiro, 4200-319 Porto, Portugal; Institute of Investigation and Innovation in Health (i3S), University of Porto, Portugal.
| | - Peter J Goadsby
- Headache Group, Wolfson Centre for Age-Related Disease, Institute of Psychiatry, Psychology and Neuroscience, King's College London, UK; Department of Neurology, University of California, Los Angeles, Los Angeles, CA, USA.
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25
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Asadi F, Dhanvantari S. Pathways of Glucagon Secretion and Trafficking in the Pancreatic Alpha Cell: Novel Pathways, Proteins, and Targets for Hyperglucagonemia. Front Endocrinol (Lausanne) 2021; 12:726368. [PMID: 34659118 PMCID: PMC8511682 DOI: 10.3389/fendo.2021.726368] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/16/2021] [Accepted: 09/13/2021] [Indexed: 12/15/2022] Open
Abstract
Patients with diabetes mellitus exhibit hyperglucagonemia, or excess glucagon secretion, which may be the underlying cause of the hyperglycemia of diabetes. Defective alpha cell secretory responses to glucose and paracrine effectors in both Type 1 and Type 2 diabetes may drive the development of hyperglucagonemia. Therefore, uncovering the mechanisms that regulate glucagon secretion from the pancreatic alpha cell is critical for developing improved treatments for diabetes. In this review, we focus on aspects of alpha cell biology for possible mechanisms for alpha cell dysfunction in diabetes: proglucagon processing, intrinsic and paracrine control of glucagon secretion, secretory granule dynamics, and alterations in intracellular trafficking. We explore possible clues gleaned from these studies in how inhibition of glucagon secretion can be targeted as a treatment for diabetes mellitus.
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Affiliation(s)
- Farzad Asadi
- Department of Pathology and Laboratory Medicine, Western University, London, ON, Canada
- Program in Metabolism and Diabetes, Lawson Health Research Institute, London, ON, Canada
| | - Savita Dhanvantari
- Department of Pathology and Laboratory Medicine, Western University, London, ON, Canada
- Program in Metabolism and Diabetes, Lawson Health Research Institute, London, ON, Canada
- Imaging Research Program, Lawson Health Research Institute, London, ON, Canada
- Department of Medical Biophysics, Western University, London, ON, Canada
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26
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Bisgaard Bengtsen M, Møller N. Mini-review: Glucagon responses in type 1 diabetes - a matter of complexity. Physiol Rep 2021; 9:e15009. [PMID: 34405569 PMCID: PMC8371343 DOI: 10.14814/phy2.15009] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2021] [Accepted: 07/29/2021] [Indexed: 12/14/2022] Open
Abstract
In recent years the role of altered alpha cell function and glucagon secretion in type 1 diabetes has attracted scientific attention. It is well established that glucagon responses to hypoglycemia are absent in type 1 diabetes, but more uncertain whether it is intact following other physiological and metabolic stimuli compared with nondiabetic individuals. The aim of this review is to (i) summarize current knowledge on glucagon responses during hypoglycemia in normal physiology and type 1 diabetes, and (ii) review human in vivo studies investigating glucagon responses after other stimuli in individuals with type 1 diabetes and nondiabetic individuals. Available data suggest that in type 1 diabetes the absence of glucagon secretion after hypoglycemia is irreversible. This is a scenario specific to hypoglycemia, since other stimuli, including administration of amino acids, insulin withdrawal, lipopolysaccharide exposure and exercise lead to substantial glucagon responses though attenuated compared to nondiabetic individuals in head-to-head studies. The derailed glucagon secretion is not confined to hypoglycemia as individuals with type 1 diabetes, as opposed to nondiabetic individuals display glucagon hypersecretion after meals, thereby potentially contributing to insulin resistance. The complexity of these phenomena may relate to activation of distinct regulatory pathways controlling glucagon secretion i.e., intra-islet paracrine signaling, direct and autonomic nervous signaling.
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Affiliation(s)
- Mads Bisgaard Bengtsen
- Department of Endocrinology and Internal MedicineAarhus University HospitalAarhusDenmark
- Department of Internal MedicineRegional Hospital HorsensHorsensDenmark
| | - Niels Møller
- Department of Endocrinology and Internal MedicineAarhus University HospitalAarhusDenmark
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27
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Ng XW, Chung YH, Piston DW. Intercellular Communication in the Islet of Langerhans in Health and Disease. Compr Physiol 2021; 11:2191-2225. [PMID: 34190340 PMCID: PMC8985231 DOI: 10.1002/cphy.c200026] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Blood glucose homeostasis requires proper function of pancreatic islets, which secrete insulin, glucagon, and somatostatin from the β-, α-, and δ-cells, respectively. Each islet cell type is equipped with intrinsic mechanisms for glucose sensing and secretory actions, but these intrinsic mechanisms alone cannot explain the observed secretory profiles from intact islets. Regulation of secretion involves interconnected mechanisms among and between islet cell types. Islet cells lose their normal functional signatures and secretory behaviors upon dispersal as compared to intact islets and in vivo. In dispersed islet cells, the glucose response of insulin secretion is attenuated from that seen from whole islets, coordinated oscillations in membrane potential and intracellular Ca2+ activity, as well as the two-phase insulin secretion profile, are missing, and glucagon secretion displays higher basal secretion profile and a reverse glucose-dependent response from that of intact islets. These observations highlight the critical roles of intercellular communication within the pancreatic islet, and how these communication pathways are crucial for proper hormonal and nonhormonal secretion and glucose homeostasis. Further, misregulated secretions of islet secretory products that arise from defective intercellular islet communication are implicated in diabetes. Intercellular communication within the islet environment comprises multiple mechanisms, including electrical synapses from gap junctional coupling, paracrine interactions among neighboring cells, and direct cell-to-cell contacts in the form of juxtacrine signaling. In this article, we describe the various mechanisms that contribute to proper islet function for each islet cell type and how intercellular islet communications are coordinated among the same and different islet cell types. © 2021 American Physiological Society. Compr Physiol 11:2191-2225, 2021.
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Affiliation(s)
- Xue W Ng
- Department of Cell Biology and Physiology, Washington University, St Louis, Missouri, USA
| | - Yong H Chung
- Department of Cell Biology and Physiology, Washington University, St Louis, Missouri, USA
| | - David W Piston
- Department of Cell Biology and Physiology, Washington University, St Louis, Missouri, USA
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28
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Singh B, Khattab F, Chae H, Desmet L, Herrera PL, Gilon P. K ATP channel blockers control glucagon secretion by distinct mechanisms: A direct stimulation of α-cells involving a [Ca 2+] c rise and an indirect inhibition mediated by somatostatin. Mol Metab 2021; 53:101268. [PMID: 34118477 PMCID: PMC8274344 DOI: 10.1016/j.molmet.2021.101268] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/13/2021] [Revised: 05/10/2021] [Accepted: 06/03/2021] [Indexed: 02/06/2023] Open
Abstract
Objective Glucagon is secreted by pancreatic α-cells in response to hypoglycemia and its hyperglycemic effect helps to restore normal blood glucose. Insulin and somatostatin (SST) secretions from β- and δ-cells, respectively, are stimulated by glucose by mechanisms involving an inhibition of their ATP-sensitive K+ (KATP) channels, leading to an increase in [Ca2+]c that triggers exocytosis. Drugs that close KATP channels, such as sulfonylureas, are used to stimulate insulin release in type 2 diabetic patients. α-cells also express KATP channels. However, the mechanisms by which sulfonylureas control glucagon secretion are still largely debated and were addressed in the present study. In particular, we studied the effects of KATP channel blockers on α-cell [Ca2+]c and glucagon secretion in the presence of a low (1 mM) or a high (15 mM) glucose concentration and evaluated the role of SST in these effects. Methods Using a transgenic mouse model expressing the Ca2+-sensitive fluorescent protein, GCaMP6f, specifically in α-cells, we measured [Ca2+]c in α-cells either dispersed or within whole islets (by confocal microscopy). By measuring [Ca2+]c in α-cells within islets and glucagon secretion using the same perifusion protocols, we tested whether glucagon secretion correlated with changes in [Ca2+]c in response to sulfonylureas. We studied the role of SST in the effects of sulfonylureas using multiple approaches including genetic ablation of SST, or application of SST-14 and SST receptor antagonists. Results Application of the sulfonylureas, tolbutamide, or gliclazide, to a medium containing 1 mM or 15 mM glucose increased [Ca2+]c in α-cells by a direct effect as in β-cells. At low glucose, sulfonylureas inhibited glucagon secretion of islets despite the rise in α-cell [Ca2+]c that they triggered. This glucagonostatic effect was indirect and attributed to SST because, in the islets of SST-knockout mice, sulfonylureas induced a stimulation of glucagon secretion which correlated with an increase in α-cell [Ca2+]c. Experiments with exogenous SST-14 and SST receptor antagonists indicated that the glucagonostatic effect of sulfonylureas mainly resulted from an inhibition of the efficacy of cytosolic Ca2+ on exocytosis. Although SST-14 was also able to inhibit glucagon secretion by decreasing α-cell [Ca2+]c, no decrease in [Ca2+]c occurred during sulfonylurea application because it was largely counterbalanced by the direct stimulatory effect of these drugs on α-cell [Ca2+]c. At high glucose, i.e., in conditions where glucagon release was already low, sulfonylureas stimulated glucagon secretion because their direct stimulatory effect on α-cells exceeded the indirect effect by SST. Our results also indicated that, unexpectedly, SST-14 poorly decreased the efficacy of Ca2+ on exocytosis in β-cells. Conclusions Sulfonylureas exert two opposite actions on α-cells: a direct stimulation as in β-cells and an indirect inhibition by SST. This suggests that any alteration of SST paracrine influence, as described in diabetes, will modify the effect of sulfonylureas on glucagon release. In addition, we suggest that δ-cells inhibit α-cells more efficiently than β-cells. KATP channel blockers control glucagon secretion by two mechanisms. The first one is the direct stimulation of α-cell by a [Ca2+]c rise, as in β-cells. The second one is an indirect inhibition mediated by δ-cells releasing somatostatin. Somatostatin mainly reduces the efficacy of Ca2+ on exocytosis in α-cells. Somatostatin more potently inhibits glucagon than insulin secretion.
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Affiliation(s)
- Bilal Singh
- Université Catholique de Louvain, Institut de Recherche Expérimentale et Clinique, Pôle d'Endocrinologie, Diabète et Nutrition, Brussels, Belgium
| | - Firas Khattab
- Université Catholique de Louvain, Institut de Recherche Expérimentale et Clinique, Pôle d'Endocrinologie, Diabète et Nutrition, Brussels, Belgium
| | - Heeyoung Chae
- Université Catholique de Louvain, Institut de Recherche Expérimentale et Clinique, Pôle d'Endocrinologie, Diabète et Nutrition, Brussels, Belgium
| | - Lieven Desmet
- Université Catholique de Louvain, SMCS, Louvain Institute of Data Analysis and Modeling in economics and statistics, Louvain-la-Neuve, Belgium
| | - Pedro L Herrera
- Department of Genetic Medicine and Development, Faculty of Medicine, University of Geneva, Geneva, Switzerland
| | - Patrick Gilon
- Université Catholique de Louvain, Institut de Recherche Expérimentale et Clinique, Pôle d'Endocrinologie, Diabète et Nutrition, Brussels, Belgium.
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29
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Ghazvini Zadeh EH, Huang Z, Xia J, Li D, Davidson HW, Li WH. ZIGIR, a Granule-Specific Zn 2+ Indicator, Reveals Human Islet α Cell Heterogeneity. Cell Rep 2021; 32:107904. [PMID: 32668245 DOI: 10.1016/j.celrep.2020.107904] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2019] [Revised: 05/04/2020] [Accepted: 06/23/2020] [Indexed: 02/07/2023] Open
Abstract
Numerous mammalian cells contain abundant Zn2+ in their secretory granules, yet available Zn2+ sensors lack the desired specificity and sensitivity for imaging granular Zn2+. We developed a fluorescent zinc granule indicator, ZIGIR, that possesses numerous desired properties for live cell imaging, including >100-fold fluorescence enhancement, membrane permeability, and selective enrichment to acidic granules. The combined advantages endow ZIGIR with superior sensitivity and specificity for imaging granular Zn2+. ZIGIR enables separation of heterogenous β cells based on their insulin content and sorting of mouse islets into pure α cells and β cells. In human islets, ZIGIR facilitates sorting of endocrine cells into highly enriched α cells and β cells, reveals unexpectedly high Zn2+ activity in the somatostatin granule of some δ cells, and uncovers variation in the glucagon content among human α cells. We expect broad applications of ZIGIR for studying Zn2+ biology and Zn2+-rich secretory granules and for engineering β cells with high insulin content for treating diabetes.
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Affiliation(s)
- Ebrahim H Ghazvini Zadeh
- Departments of Cell Biology and Biochemistry, University of Texas Southwestern Medical Center, 6000 Harry Hines Blvd., Dallas, TX 75390-9039, USA
| | - ZhiJiang Huang
- Departments of Cell Biology and Biochemistry, University of Texas Southwestern Medical Center, 6000 Harry Hines Blvd., Dallas, TX 75390-9039, USA
| | - Jing Xia
- Departments of Cell Biology and Biochemistry, University of Texas Southwestern Medical Center, 6000 Harry Hines Blvd., Dallas, TX 75390-9039, USA; Department of Biological Sciences, The University of Texas at Dallas, Richardson, TX, USA
| | - Daliang Li
- Departments of Cell Biology and Biochemistry, University of Texas Southwestern Medical Center, 6000 Harry Hines Blvd., Dallas, TX 75390-9039, USA
| | - Howard W Davidson
- Barbara Davis Center for Diabetes, University of Colorado Denver Anschutz Medical Campus, Aurora, CO 80045, USA
| | - Wen-Hong Li
- Departments of Cell Biology and Biochemistry, University of Texas Southwestern Medical Center, 6000 Harry Hines Blvd., Dallas, TX 75390-9039, USA.
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30
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Marunaka Y, Yagi K. Essential requirement of complex number for oscillatory phenomenon in intracellular trafficking process. Comput Struct Biotechnol J 2021; 19:2990-3005. [PMID: 34136098 PMCID: PMC8176294 DOI: 10.1016/j.csbj.2021.04.053] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2021] [Revised: 04/20/2021] [Accepted: 04/20/2021] [Indexed: 11/23/2022] Open
Abstract
Intracellular protein trafficking processes consisting of three intracellular states are described by three differential equations. To solve the equations, a quadratic equation is required, and its roots are generally real or complex. The purpose of the present study is to clarify the meanings of roots of real and complex numbers. To clarify the point, we define that: 1) ‘kI’ is the insertion rate from an insertion state trafficking to the plasma membrane state; 2) ‘kE’, the endocytotic rate from the plasma membrane state trafficking to a recycling state; 3) ‘kR’, the recycling rate from the recycling state trafficking to the insertion state. Amounts of proteins in three states are expressed as αelt+βemt+γ with α,β,γ = constant and l and m are roots of a quadratic equation, r2+kI+kE+kRr+kIkE+kIkR+kEkR=0. When l and m are real kI2+kE2+kR2>2kIkE+kEkR+kRkI, amounts of proteins in three states shows no oscillatory change but a monotonic change after a transient increase (or decrease); when l and m are complex kI2+kE2+kR2<2kIkE+kEkR+kRkI, amounts of proteins in three states are expressed as αelt+βemt+γ=2g2+h2sinbt+σeat+γ (α, β, l, m = complex and γ,a,b,g,h,σ = real: α,β = conjugate each other; l,m = conjugate each other), showing an oscillatory change with time. The frequency of oscillatory change appearance is evaluated to be 60% at random combinations of three trafficking rates, kI, kE and kR. The present study indicates that complex numbers have an essentially important meaning in appearance of oscillatory phenomena in bodily and cellular function.
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Affiliation(s)
- Yoshinori Marunaka
- Medical Research Institute, Kyoto Industrial Health Association, Nakagyo-ku, Kyoto 604-8472, Japan
- Research Center for Drug Discovery and Pharmaceutical Development Science, Research Organization of Science and Technology, Ritsumeikan University, Kusatsu 525-8577, Japan
- Department of Molecular Cell Physiology, Kyoto Prefectural University of Medicine, Kamigyo-ku, Kyoto 802-8566, Japan
- Corresponding authors at: Medical Research Institute, Kyoto Industrial Health Association, General Incorporated Foundation, 67 Kitatsuboi-cho, Nishino-kyo, Nakagyo-ku, Kyoto 604-8472, Japan.
| | - Katsumi Yagi
- Medical Research Institute, Kyoto Industrial Health Association, Nakagyo-ku, Kyoto 604-8472, Japan
- Luis Pasteur Center for Medical Research, Sakyo-ku, Kyoto 606-8225, Japan
- Corresponding authors at: Medical Research Institute, Kyoto Industrial Health Association, General Incorporated Foundation, 67 Kitatsuboi-cho, Nishino-kyo, Nakagyo-ku, Kyoto 604-8472, Japan.
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Takatani T, Shirakawa J, Shibue K, Gupta MK, Kim H, Lu S, Hu J, White MF, Kennedy RT, Kulkarni RN. Insulin receptor substrate 1, but not IRS2, plays a dominant role in regulating pancreatic alpha cell function in mice. J Biol Chem 2021; 296:100646. [PMID: 33839150 PMCID: PMC8131928 DOI: 10.1016/j.jbc.2021.100646] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2021] [Revised: 03/24/2021] [Accepted: 04/07/2021] [Indexed: 11/29/2022] Open
Abstract
Dysregulated glucagon secretion deteriorates glycemic control in type 1 and type 2 diabetes. Although insulin is known to regulate glucagon secretion via its cognate receptor (insulin receptor, INSR) in pancreatic alpha cells, the role of downstream proteins and signaling pathways underlying insulin's activities are not fully defined. Using in vivo (knockout) and in vitro (knockdown) studies targeting insulin receptor substrate (IRS) proteins, we compared the relative roles of IRS1 and IRS2 in regulating alpha cell function. Alpha cell-specific IRS1-knockout mice exhibited glucose intolerance and inappropriate glucagon suppression during glucose tolerance tests. In contrast, alpha cell-specific IRS2-knockout animals manifested normal glucose tolerance and suppression of glucagon secretion after glucose administration. Alpha cell lines with stable IRS1 knockdown could not repress glucagon mRNA expression and exhibited a reduction in phosphorylation of AKT Ser/Thr kinase (AKT, at Ser-473 and Thr-308). AlphaIRS1KD cells also displayed suppressed global protein translation, including reduced glucagon expression, impaired cytoplasmic Ca2+ response, and mitochondrial dysfunction. This was supported by the identification of novel IRS1-specific downstream target genes, Trpc3 and Cartpt, that are associated with glucagon regulation in alpha cells. These results provide evidence that IRS1, rather than IRS2, is a dominant regulator of pancreatic alpha cell function.
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Affiliation(s)
- Tomozumi Takatani
- Islet Cell and Regenerative Biology, Joslin Diabetes Center, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA; Department of Pediatrics, Graduate School of Medicine, Chiba University, Chiba, Japan
| | - Jun Shirakawa
- Laboratory of Diabetes and Metabolic Disorders, Institute for Molecular and Cellular Regulation (IMCR), Gunma University, Gunma, Japan
| | - Kimitaka Shibue
- Islet Cell and Regenerative Biology, Joslin Diabetes Center, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - Manoj K Gupta
- Islet Cell and Regenerative Biology, Joslin Diabetes Center, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA; Cell Therapy Translational Engine (CTTE), Takeda Pharmaceuticals, Cambridge, Massachusetts, USA
| | - Hyunki Kim
- Islet Cell and Regenerative Biology, Joslin Diabetes Center, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - Shusheng Lu
- Departments of Chemistry and Pharmacology, University of Michigan, Ann Arbor, Michigan, USA
| | - Jiang Hu
- Islet Cell and Regenerative Biology, Joslin Diabetes Center, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - Morris F White
- Department of Pediatrics, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - Robert T Kennedy
- Departments of Chemistry and Pharmacology, University of Michigan, Ann Arbor, Michigan, USA
| | - Rohit N Kulkarni
- Islet Cell and Regenerative Biology, Joslin Diabetes Center, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA; Harvard Stem Cell Institute, Harvard Medical School, Boston, Massachusetts, USA.
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Jo S, Xu G, Jing G, Chen J, Shalev A. Human Glucagon Expression Is under the Control of miR-320a. Endocrinology 2021; 162:6052618. [PMID: 33367814 PMCID: PMC7814302 DOI: 10.1210/endocr/bqaa238] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/23/2020] [Indexed: 11/19/2022]
Abstract
Increased glucagon is a hallmark of diabetes and leads to worsening of the hyperglycemia, but the molecular mechanisms causing it are still unknown. We therefore investigated the possibility that microRNAs might be involved in the regulation of glucagon. Indeed, analysis of the glucagon 3' untranslated region (UTR) revealed potential binding sites for miR-320a, and using luciferase reporter assays we found that miR-320a directly targets the 3' UTRs of human and rodent glucagon. In addition, endogenous glucagon mRNA and protein expression as well as glucagon secretion were reduced in response to miR-320a overexpression, whereas inhibition of miR-320a upregulated glucagon expression. Interestingly, miR-320a expression was decreased by high glucose, and this was associated with an increase in glucagon expression in human islets and mouse αTC1-6 cells. Moreover, miR-320a overexpression completely blunted these effects. Importantly, miR-320a was also significantly downregulated in human islets of subjects with type 2 diabetes and this was accompanied by increased glucagon expression. Thus, our data suggest that glucose-induced downregulation of miR-320a may contribute to the paradoxical increase in glucagon observed in type 2 diabetes and reveal for the first time that glucagon expression is under the control by a microRNA providing novel insight into the abnormal regulation of glucagon in diabetes.
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Affiliation(s)
- SeongHo Jo
- Comprehensive Diabetes Center and Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Guanlan Xu
- Comprehensive Diabetes Center and Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Gu Jing
- Comprehensive Diabetes Center and Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Junqin Chen
- Comprehensive Diabetes Center and Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Anath Shalev
- Comprehensive Diabetes Center and Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Alabama at Birmingham, Birmingham, AL, USA
- Correspondence: Anath Shalev, MD, Professor and Director, Comprehensive Diabetes Center, University of Alabama at Birmingham, 1825 University Blvd, SHELBY Bldg 1206, Birmingham, AL 35294-2182, USA.
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Yabe SG, Fukuda S, Nishida J, Takeda F, Nashiro K, Okochi H. Efficient induction of pancreatic alpha cells from human induced pluripotent stem cells by controlling the timing for BMP antagonism and activation of retinoic acid signaling. PLoS One 2021; 16:e0245204. [PMID: 33428669 PMCID: PMC7799802 DOI: 10.1371/journal.pone.0245204] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2020] [Accepted: 12/23/2020] [Indexed: 01/15/2023] Open
Abstract
Diabetes mellitus is caused by breakdown of blood glucose homeostasis, which is maintained by an exquisite balance between insulin and glucagon produced respectively by pancreatic beta cells and alpha cells. However, little is known about the mechanism of inducing glucagon secretion from human alpha cells. Many methods for generating pancreatic beta cells from human pluripotent stem cells (hPSCs) have been reported, but only two papers have reported generation of pancreatic alpha cells from hPSCs. Because NKX6.1 has been suggested as a very important gene for determining cell fate between pancreatic beta and alpha cells, we searched for the factors affecting expression of NKX6.1 in our beta cell differentiation protocols. We found that BMP antagonism and activation of retinoic acid signaling at stage 2 (from definitive endoderm to primitive gut tube) effectively suppressed NKX6.1 expression at later stages. Using two different hPSCs lines, treatment with BMP signaling inhibitor (LDN193189) and retinoic acid agonist (EC23) at Stage 2 reduced NKX6.1 expression and allowed differentiation of almost all cells into pancreatic alpha cells in vivo after transplantation under a kidney capsule. Our study demonstrated that the cell fate of pancreatic cells can be controlled by adjusting the expression level of NKX6.1 with proper timing of BMP antagonism and activation of retinoic acid signaling during the pancreatic differentiation process. Our method is useful for efficient induction of pancreatic alpha cells from hPSCs.
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Affiliation(s)
- Shigeharu G Yabe
- Department of Regenerative Medicine, Research Institute, National Center for Global Health and Medicine, Tokyo, Japan
| | - Satsuki Fukuda
- Department of Regenerative Medicine, Research Institute, National Center for Global Health and Medicine, Tokyo, Japan
| | - Junko Nishida
- Department of Regenerative Medicine, Research Institute, National Center for Global Health and Medicine, Tokyo, Japan
| | - Fujie Takeda
- Department of Regenerative Medicine, Research Institute, National Center for Global Health and Medicine, Tokyo, Japan
| | - Kiyoko Nashiro
- Department of Regenerative Medicine, Research Institute, National Center for Global Health and Medicine, Tokyo, Japan
| | - Hitoshi Okochi
- Department of Regenerative Medicine, Research Institute, National Center for Global Health and Medicine, Tokyo, Japan
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Campbell JE, Newgard CB. Mechanisms controlling pancreatic islet cell function in insulin secretion. Nat Rev Mol Cell Biol 2021; 22:142-158. [PMID: 33398164 DOI: 10.1038/s41580-020-00317-7] [Citation(s) in RCA: 255] [Impact Index Per Article: 85.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/19/2020] [Indexed: 02/07/2023]
Abstract
Metabolic homeostasis in mammals is tightly regulated by the complementary actions of insulin and glucagon. The secretion of these hormones from pancreatic β-cells and α-cells, respectively, is controlled by metabolic, endocrine, and paracrine regulatory mechanisms and is essential for the control of blood levels of glucose. The deregulation of these mechanisms leads to various pathologies, most notably type 2 diabetes, which is driven by the combined lesions of impaired insulin action and a loss of the normal insulin secretion response to glucose. Glucose stimulates insulin secretion from β-cells in a bi-modal fashion, and new insights about the underlying mechanisms, particularly relating to the second or amplifying phase of this secretory response, have been recently gained. Other recent work highlights the importance of α-cell-produced proglucagon-derived peptides, incretin hormones from the gastrointestinal tract and other dietary components, including certain amino acids and fatty acids, in priming and potentiation of the β-cell glucose response. These advances provide a new perspective for the understanding of the β-cell failure that triggers type 2 diabetes.
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Affiliation(s)
- Jonathan E Campbell
- Sarah W. Stedman Nutrition and Metabolism Center and Duke Molecular Physiology Institute, Duke University Medical Center, Durham, NC, USA.,Department of Medicine, Endocrinology and Metabolism Division, Duke University Medical Center, Durham, NC, USA.,Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC, USA
| | - Christopher B Newgard
- Sarah W. Stedman Nutrition and Metabolism Center and Duke Molecular Physiology Institute, Duke University Medical Center, Durham, NC, USA. .,Department of Medicine, Endocrinology and Metabolism Division, Duke University Medical Center, Durham, NC, USA. .,Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC, USA.
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González-Vélez V, Piron A, Dupont G. Calcium Oscillations in Pancreatic α-cells Rely on Noise and ATP-Driven Changes in Membrane Electrical Activity. Front Physiol 2020; 11:602844. [PMID: 33281631 PMCID: PMC7705205 DOI: 10.3389/fphys.2020.602844] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2020] [Accepted: 10/28/2020] [Indexed: 11/13/2022] Open
Abstract
In pancreatic α-cells, intracellular Ca2+ ([Ca2+]i) acts as a trigger for secretion of glucagon, a hormone that plays a key role in blood glucose homeostasis. Intracellular Ca2+ dynamics in these cells are governed by the electrical activity of voltage-gated ion channels, among which ATP-sensitive K+ (KATP) channels play a crucial role. In the majority of α-cells, the global Ca2+ response to lowering external glucose occurs in the form of oscillations that are much slower than electrical activity. These Ca2+ oscillations are highly variable as far as inter-spike intervals, shapes and amplitudes are concerned. Such observations suggest that Ca2+ dynamics in α-cells are much influenced by noise. Actually, each Ca2+ increase corresponds to multiple cycles of opening/closing of voltage gated Ca2+ channels that abruptly become silent, before the occurrence of another burst of activity a few tens of seconds later. The mechanism responsible for this intermittent activity is currently unknown. In this work, we used computational modeling to investigate the mechanism of cytosolic Ca2+ oscillations in α-cells. Given the limited population of KATP channels in this cell type, we hypothesized that the stochastic activity of these channels could play a key role in the sporadic character of the action potentials. To test this assumption, we extended a previously proposed model of the α-cells electrical activity (Diderichsen and Göpel, 2006) to take Ca2+ dynamics into account. Including molecular noise on the basis of a Langevin type description as well as realistic dynamics of opening and closing of KATP channels, we found that stochasticity at the level of the activity of this channel is on its own not able to produce Ca2+ oscillations with a time scale of a few tens of seconds. However, when taking into account the intimate relation between Ca2+ and ATP changes together with the intrinsic noise at the level of the KATP channels, simulations displayed Ca2+ oscillations that are compatible with experimental observations. We analyzed the detailed mechanism and used computational simulations to identify the factors that can affect Ca2+ oscillations in α-cells.
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Affiliation(s)
- Virginia González-Vélez
- Department Basic Sciences, Universidad Autónoma Metropolitana-Azcapotzalco, CDMX, Mèxico, Mexico
| | - Anthony Piron
- ULB Center for Diabetes Research, Faculté de Médecine, Université libre de Bruxelles (ULB), Brussels, Belgium.,Interuniversity Institute of Bioinformatics (IB2), Brussels, Belgium
| | - Geneviève Dupont
- Interuniversity Institute of Bioinformatics (IB2), Brussels, Belgium.,Unit of Theoretical Chronobiology, Faculté des Sciences, Université libre de Bruxelles (ULB), Brussels, Belgium
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Sandoval D. Updating the Role of α-Cell Preproglucagon Products on GLP-1 Receptor-Mediated Insulin Secretion. Diabetes 2020; 69:2238-2245. [PMID: 33082272 PMCID: PMC7576561 DOI: 10.2337/dbi19-0027] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/08/2020] [Accepted: 08/10/2020] [Indexed: 02/06/2023]
Abstract
While the field of islet biology has historically focused its attention on understanding β-cell function and the mechanisms by which these cells become dysfunctional with diabetes, there has been a scientific shift toward greater understanding of other endocrine cells of the islet and their paracrine role in regulating the β-cell. In recent years, many questions and new data have come forward regarding the paracrine role of the α-cell and specifically preproglucagon peptides in regulating insulin secretion. The role of intestinally secreted glucagon-like peptide 1 (GLP-1) in regulation of insulin secretion has been questioned, and a physiological role of pancreatic GLP-1 in regulation of insulin secretion has been proposed. In addition, in the last 2 years, a series of studies demonstrated a physiological role for glucagon, acting via the GLP-1 receptor, in paracrine regulation of insulin secretion. Altogether, this work challenges the textbook physiology of both GLP-1 and glucagon and presents a critical paradigm shift for the field. This article addresses these new findings surrounding α-cell preproglucagon products, with a particular focus on GLP-1, in the context of their roles in insulin secretion and consequently glucose metabolism.
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Zaborska KE, Dadi PK, Dickerson MT, Nakhe AY, Thorson AS, Schaub CM, Graff SM, Stanley JE, Kondapavuluru RS, Denton JS, Jacobson DA. Lactate activation of α-cell K ATP channels inhibits glucagon secretion by hyperpolarizing the membrane potential and reducing Ca 2+ entry. Mol Metab 2020; 42:101056. [PMID: 32736089 PMCID: PMC7479281 DOI: 10.1016/j.molmet.2020.101056] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/01/2020] [Revised: 07/17/2020] [Accepted: 07/24/2020] [Indexed: 12/20/2022] Open
Abstract
Objective Elevations in pancreatic α-cell intracellular Ca2+ ([Ca2+]i) lead to glucagon (GCG) secretion. Although glucose inhibits GCG secretion, how lactate and pyruvate control α-cell Ca2+ handling is unknown. Lactate enters cells through monocarboxylate transporters (MCTs) and is also produced during glycolysis by lactate dehydrogenase A (LDHA), an enzyme expressed in α-cells. As lactate activates ATP-sensitive K+ (KATP) channels in cardiomyocytes, lactate may also modulate α-cell KATP. Therefore, this study investigated how lactate signaling controls α-cell Ca2+ handling and GCG secretion. Methods Mouse and human islets were used in combination with confocal microscopy, electrophysiology, GCG immunoassays, and fluorescent thallium flux assays to assess α-cell Ca2+ handling, Vm, KATP currents, and GCG secretion. Results Lactate-inhibited mouse (75 ± 25%) and human (47 ± 9%) α-cell [Ca2+]i fluctuations only under low-glucose conditions (1 mM) but had no effect on β- or δ-cells [Ca2+]i. Glyburide inhibition of KATP channels restored α-cell [Ca2+]i fluctuations in the presence of lactate. Lactate transport into α-cells via MCTs hyperpolarized mouse (14 ± 1 mV) and human (12 ± 1 mV) α-cell Vm and activated KATP channels. Interestingly, pyruvate showed a similar KATP activation profile and α-cell [Ca2+]i inhibition as lactate. Lactate-induced inhibition of α-cell [Ca2+]i influx resulted in reduced GCG secretion in mouse (62 ± 6%) and human (43 ± 13%) islets. Conclusions These data demonstrate for the first time that lactate entry into α-cells through MCTs results in KATP activation, Vm hyperpolarization, reduced [Ca2+]i, and inhibition of GCG secretion. Thus, taken together, these data indicate that lactate either within α-cells and/or elevated in serum could serve as important modulators of α-cell function. Lactate reduces islet α-cell Ca2+ entry under low glucose conditions. Lactate does not alter β- or δ-cell Ca2+ handling under low glucose conditions. Lactate enters islet α-cells through monocarboxylate transporters. Lactate hyperpolarizes islet α-cell membrane potential by activating KATP channels. Lactate reduces mouse and human islet glucagon secretion.
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Affiliation(s)
- Karolina E Zaborska
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN 37232, USA
| | - Prasanna K Dadi
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN 37232, USA
| | - Matthew T Dickerson
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN 37232, USA
| | - Arya Y Nakhe
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN 37232, USA
| | - Ariel S Thorson
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN 37232, USA
| | - Charles M Schaub
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN 37232, USA
| | - Sarah M Graff
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN 37232, USA
| | - Jade E Stanley
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN 37232, USA
| | - Roy S Kondapavuluru
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN 37232, USA
| | - Jerod S Denton
- Department of Pharmacology, Vanderbilt University, Nashville, TN 37232, USA
| | - David A Jacobson
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN 37232, USA.
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Xu SFS, Andersen DB, Izarzugaza JMG, Kuhre RE, Holst JJ. In the rat pancreas, somatostatin tonically inhibits glucagon secretion and is required for glucose-induced inhibition of glucagon secretion. Acta Physiol (Oxf) 2020; 229:e13464. [PMID: 32145704 DOI: 10.1111/apha.13464] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2019] [Revised: 02/28/2020] [Accepted: 03/04/2020] [Indexed: 12/20/2022]
Abstract
AIM It is debated whether the inhibition of glucagon secretion by glucose results from direct effects of glucose on the α-cell (intrinsic regulation) or by paracrine effects exerted by beta- or delta-cell products. METHODS To study this in a more physiological model than isolated islets, we perfused isolated rat pancreases and measured glucagon, insulin and somatostatin secretion in response to graded increases in perfusate glucose concentration (from 3.5 to 4, 5, 6, 7, 8, 10, 12 mmol/L) as well as glucagon responses to blockage/activation of insulin/GABA/somatostatin signalling with or without addition of glucose. RESULTS Glucagon secretion was reduced by about 50% (compared to baseline secretion at 3.5 mmol/L) within minutes after increasing glucose from 4 to 5 mmol/L (P < .01, n = 13). Insulin secretion was increased minimally, but significantly, compared to baseline (3.5 mmol/L) at 4 mmol/L, whereas somatostatin secretion was not significantly increased from baseline until 7 mmol/L. Hereafter secretion of both increased gradually up to 12 mmol/L glucose. Neither recombinant insulin (1 µmol/L), GABA (300 µmol/L) or the insulin-receptor antagonist S961 (at 1 µmol/L) affected basal (3.5 mmol/L) or glucose-induced (5.0 mmol/L) attenuation of glucagon secretion (n = 7-8). Somatostatin-14 attenuated glucagon secretion by ~ 95%, and blockage of somatostatin-receptor (SSTR)-2 or combined blockage of SSTR-2, -3 and -5 by specific antagonists increased glucagon output (at 3.5 mmol/L glucose) and prevented glucose-induced (from 3.5 to 5.0 mmol/L) suppression of secretion. CONCLUSION Somatostatin is a powerful and tonic inhibitor of glucagon secretion from the rat pancreas and is required for glucose to inhibit glucagon secretion.
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Affiliation(s)
- Stella F. S. Xu
- Department of Biomedical Sciences Faculty of Health and Medical Sciences University of Copenhagen Copenhagen Denmark
- Novo Nordisk Foundation Center for Basic Metabolic Research Faculty of Health and Medical Sciences University of Copenhagen Copenhagen Denmark
| | - Daniel B. Andersen
- Department of Biomedical Sciences Faculty of Health and Medical Sciences University of Copenhagen Copenhagen Denmark
- Novo Nordisk Foundation Center for Basic Metabolic Research Faculty of Health and Medical Sciences University of Copenhagen Copenhagen Denmark
| | | | - Rune E. Kuhre
- Department of Biomedical Sciences Faculty of Health and Medical Sciences University of Copenhagen Copenhagen Denmark
- Novo Nordisk Foundation Center for Basic Metabolic Research Faculty of Health and Medical Sciences University of Copenhagen Copenhagen Denmark
| | - Jens J. Holst
- Department of Biomedical Sciences Faculty of Health and Medical Sciences University of Copenhagen Copenhagen Denmark
- Novo Nordisk Foundation Center for Basic Metabolic Research Faculty of Health and Medical Sciences University of Copenhagen Copenhagen Denmark
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Finan B, Capozzi ME, Campbell JE. Repositioning Glucagon Action in the Physiology and Pharmacology of Diabetes. Diabetes 2020; 69:532-541. [PMID: 31178432 PMCID: PMC7085250 DOI: 10.2337/dbi19-0004] [Citation(s) in RCA: 70] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/18/2019] [Accepted: 05/30/2019] [Indexed: 01/03/2023]
Abstract
Glucagon is historically described as the counterregulatory hormone to insulin, induced by fasting/hypoglycemia to raise blood glucose through action mediated in the liver. However, it is becoming clear that the biology of glucagon is much more complex and extends beyond hepatic actions to exert control on glucose metabolism. We discuss the inconsistencies with the canonical view that glucagon is primarily a hyperglycemic agent driven by fasting/hypoglycemia and highlight the recent advances that have reshaped the metabolic role of glucagon. These concepts are placed within the context of both normal physiology and the pathophysiology of disease and then extended to discuss emerging strategies that incorporate glucagon agonism in the pharmacology of treating diabetes.
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Affiliation(s)
- Brian Finan
- Novo Nordisk Research Center, Indianapolis, IN
| | - Megan E Capozzi
- Duke Molecular Physiology Institute, Duke University, Durham, NC
| | - Jonathan E Campbell
- Duke Molecular Physiology Institute, Duke University, Durham, NC
- Division of Endocrinology, Department of Medicine, Duke University, Durham, NC
- Department of Pharmacology and Cancer Biology, Duke University, Durham, NC
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Davis EM, Sandoval DA. Glucagon‐Like Peptide‐1: Actions and Influence on Pancreatic Hormone Function. Compr Physiol 2020; 10:577-595. [DOI: 10.1002/cphy.c190025] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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41
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Grubelnik V, Zmazek J, Markovič R, Gosak M, Marhl M. Modelling of energy-driven switch for glucagon and insulin secretion. J Theor Biol 2020; 493:110213. [PMID: 32109481 DOI: 10.1016/j.jtbi.2020.110213] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2019] [Revised: 02/19/2020] [Accepted: 02/24/2020] [Indexed: 12/14/2022]
Abstract
We present a mathematical model of the energy-driven metabolic switch for glucagon and insulin secretion from pancreatic alpha and beta cells, respectively. The energy status related to hormone secretion is studied for various glucose concentrations. Additionally, the physiological response is studied with regards to the presence of other metabolites, particularly the free-fatty acids. At low glucose, the ATP production in alpha cells is high due to free-fatty acids oxidation in mitochondria, which enables glucagon secretion. When the glucose concentration is elevated above the threshold value, the glucagon secretion is switched off due to the contribution of glycolytic ATP production, representing an "anaerobic switch". On the other hand, during hypoglycemia, the ATP production in beta cells is low, reflecting a "waiting state" for glucose as the main metabolite. When glucose is elevated above the threshold value, the oxidative fate of glucose in mitochondria is the main source of energy required for effective insulin secretion, i.e. the "aerobic switch". Our results show the importance of well-regulated and fine-tuned energetic processes in pancreatic alpha and beta cells required for efficient hormone secretion and hence effective blood glucose regulation. These energetic processes have to be appropriately switched on and off based on the sensing of different metabolites by alpha and beta cells. Our computational results indicate that disturbances in cell energetics (e.g. mitochondrial dysfunction), and dysfunctional metabolite sensing and distribution throughout the cell might be related to pathologies such as metabolic syndrome and diabetes.
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Affiliation(s)
- Vladimir Grubelnik
- Faculty of Electrical Engineering and Computer Science, University of Maribor, Maribor SI-2000, Slovenia
| | - Jan Zmazek
- Faculty of Natural Sciences and Mathematics, University of Maribor, Maribor SI-2000, Slovenia
| | - Rene Markovič
- Faculty of Electrical Engineering and Computer Science, University of Maribor, Maribor SI-2000, Slovenia; Faculty of Natural Sciences and Mathematics, University of Maribor, Maribor SI-2000, Slovenia
| | - Marko Gosak
- Faculty of Natural Sciences and Mathematics, University of Maribor, Maribor SI-2000, Slovenia; Faculty of Medicine, University of Maribor, Maribor SI-2000, Slovenia
| | - Marko Marhl
- Faculty of Natural Sciences and Mathematics, University of Maribor, Maribor SI-2000, Slovenia; Faculty of Medicine, University of Maribor, Maribor SI-2000, Slovenia; Faculty of Education, University of Maribor, Maribor SI-2000, Slovenia.
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Li WH. Functional analysis of islet cells in vitro, in situ, and in vivo. Semin Cell Dev Biol 2020; 103:14-19. [PMID: 32081627 DOI: 10.1016/j.semcdb.2020.02.002] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2019] [Accepted: 02/05/2020] [Indexed: 12/20/2022]
Abstract
The islet of Langerhans contains at least five types of endocrine cells producing distinct hormones. In response to nutrient or neuronal stimulation, islet endocrine cells release biochemicals including peptide hormones to regulate metabolism and to control glucose homeostasis. It is now recognized that malfunction of islet cells, notably insufficient insulin release of β-cells and hypersecretion of glucagon from α-cells, represents a causal event leading to hyperglycemia and frank diabetes, a disease that is increasing at an alarming rate to reach an epidemic level worldwide. Understanding the mechanisms regulating stimulus-secretion coupling and investigating how islet β-cells maintain a robust secretory activity are important topics in islet biology and diabetes research. To facilitate such studies, a number of biological systems and assay platforms have been developed for the functional analysis of islet cells. These technologies have enabled detailed analyses of individual islets at the cellular level, either in vitro, in situ, or in vivo.
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Affiliation(s)
- Wen-Hong Li
- Departments of Cell Biology and of Biochemistry, University of Texas Southwestern Medical Center, 6000 Harry Hines Blvd., Dallas, TX, 75390-9039, United States.
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Gilon P. The Role of α-Cells in Islet Function and Glucose Homeostasis in Health and Type 2 Diabetes. J Mol Biol 2020; 432:1367-1394. [PMID: 31954131 DOI: 10.1016/j.jmb.2020.01.004] [Citation(s) in RCA: 45] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2019] [Revised: 12/23/2019] [Accepted: 01/06/2020] [Indexed: 01/09/2023]
Abstract
Pancreatic α-cells are the major source of glucagon, a hormone that counteracts the hypoglycemic action of insulin and strongly contributes to the correction of acute hypoglycemia. The mechanisms by which glucose controls glucagon secretion are hotly debated, and it is still unclear to what extent this control results from a direct action of glucose on α-cells or is indirectly mediated by β- and/or δ-cells. Besides its hyperglycemic action, glucagon has many other effects, in particular on lipid and amino acid metabolism. Counterintuitively, glucagon seems also required for an optimal insulin secretion in response to glucose by acting on its cognate receptor and, even more importantly, on GLP-1 receptors. Patients with diabetes mellitus display two main alterations of glucagon secretion: a relative hyperglucagonemia that aggravates hyperglycemia, and an impaired glucagon response to hypoglycemia. Under metabolic stress states, such as diabetes, pancreatic α-cells also secrete GLP-1, a glucose-lowering hormone, whereas the gut can produce glucagon. The contribution of extrapancreatic glucagon to the abnormal glucose homeostasis is unclear. Here, I review the possible mechanisms of control of glucagon secretion and the role of α-cells on islet function in healthy state. I discuss the possible causes of the abnormal glucagonemia in diabetes, with particular emphasis on type 2 diabetes, and I briefly comment the current antidiabetic therapies affecting α-cells.
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Affiliation(s)
- Patrick Gilon
- Université Catholique de Louvain, Institute of Experimental and Clinical Research, Pole of Endocrinology, Diabetes and Nutrition, Avenue Hippocrate 55 (B1.55.06), Brussels, B-1200, Belgium.
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Asadi F, Dhanvantari S. Stathmin-2 Mediates Glucagon Secretion From Pancreatic α-Cells. Front Endocrinol (Lausanne) 2020; 11:29. [PMID: 32117057 PMCID: PMC7011091 DOI: 10.3389/fendo.2020.00029] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/06/2019] [Accepted: 01/14/2020] [Indexed: 01/26/2023] Open
Abstract
Inhibition of glucagon hypersecretion from pancreatic α-cells is an appealing strategy for the treatment of diabetes. Our hypothesis is that proteins that associate with glucagon within alpha cell secretory granules will regulate glucagon secretion, and may provide druggable targets for controlling abnormal glucagon secretion in diabetes. Recently, we identified a dynamic glucagon interactome within the secretory granules of the α cell line, αTC1-6, and showed that select proteins within the interactome could modulate glucagon secretion. In the present study, we show that one of these interactome proteins, the neuronal protein stathmin-2, is expressed in αTC1-6 cells and in mouse pancreatic alpha cells, and is a novel regulator of glucagon secretion. The secretion of both glucagon and Stmn2 was significantly enhanced in response to 55 mM K+, and immunofluorescence confocal microscopy showed co-localization of stathmin-2 with glucagon and the secretory granule markers chromogranin A and VAMP-2 in αTC1-6 cells. In mouse pancreatic islets, Stathmin-2 co-localized with glucagon, but not with insulin, and co-localized with secretory pathway markers. To show a function for stathmin-2 in regulating glucagon secretion, we showed that siRNA-mediated depletion of stathmin-2 in αTC1-6 cells caused glucagon secretion to become constitutive without any effect on proglucagon mRNA levels, while overexpression of stathmin-2 completely abolished both basal and K+-stimulated glucagon secretion. Overexpression of stathmin-2 increased the localization of glucagon into the endosomal-lysosomal compartment, while depletion of stathmin-2 reduced the endosomal localization of glucagon. Therefore, we describe stathmin-2 as having a novel role as an alpha cell secretory granule protein that modulates glucagon secretion via trafficking through the endosomal-lysosomal system. These findings describe a potential new pathway for the regulation of glucagon secretion, and may have implications for controlling glucagon hypersecretion in diabetes.
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Affiliation(s)
- Farzad Asadi
- Department of Pathology and Laboratory Medicine, Schulich School of Medicine & Dentistry, Western University, London, ON, Canada
| | - Savita Dhanvantari
- Department of Pathology and Laboratory Medicine, Schulich School of Medicine & Dentistry, Western University, London, ON, Canada
- Department of Medical Biophysics, Western University, London, ON, Canada
- Lawson Health Research Institute, London, ON, Canada
- *Correspondence: Savita Dhanvantari
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45
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Bru-Tari E, Oropeza D, Herrera PL. Cell Heterogeneity and Paracrine Interactions in Human Islet Function: A Perspective Focused in β-Cell Regeneration Strategies. Front Endocrinol (Lausanne) 2020; 11:619150. [PMID: 33613453 PMCID: PMC7888438 DOI: 10.3389/fendo.2020.619150] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/19/2020] [Accepted: 12/14/2020] [Indexed: 12/27/2022] Open
Abstract
The β-cell regeneration field has shown a strong knowledge boost in the last 10 years. Pluripotent stem cell differentiation and direct reprogramming from other adult cell types are becoming more tangible long-term diabetes therapies. Newly generated β-like-cells consistently show hallmarks of native β-cells and can restore normoglycemia in diabetic mice in virtually all recent studies. Nonetheless, these cells still show important compromises in insulin secretion, cell metabolism, electrical activity, and overall survival, perhaps due to a lack of signal integration from other islet cells. Mounting data suggest that diabetes is not only a β-cell disease, as the other islet cell types also contribute to its physiopathology. Here, we present an update on the most recent studies of islet cell heterogeneity and paracrine interactions in the context of restoring an integrated islet function to improve β-cell replacement therapies.
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Liu W, Kin T, Ho S, Dorrell C, Campbell SR, Luo P, Chen X. Abnormal regulation of glucagon secretion by human islet alpha cells in the absence of beta cells. EBioMedicine 2019; 50:306-316. [PMID: 31780397 PMCID: PMC6921359 DOI: 10.1016/j.ebiom.2019.11.018] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2018] [Revised: 11/11/2019] [Accepted: 11/11/2019] [Indexed: 02/07/2023] Open
Abstract
BACKGROUND The understanding of the regulation of glucagon secretion by pancreatic islet α-cells remains elusive. We aimed to develop an in vitro model for investigating the function of human α-cells under direct influence of glucose and other potential regulators. METHODS Highly purified human α-cells from islets of deceased donors were re-aggregated in the presence or absence of β-cells in culture, evaluated for glucagon secretion under various treatment conditions, and compared to that of intact human islets and non-sorted islet cell aggregates. FINDINGS The pure human α-cell aggregates maintained proper glucagon secretion capability at low concentrations of glucose, but failed to respond to changes in ambient glucose concentration. Addition of purified β-cells, but not the secreted factors from β-cells at low or high concentrations of glucose, partly restored the responsiveness of α-cells to glucose with regulated glucagon secretion. The EphA stimulator ephrinA5-fc failed to mimic the inhibitory effect of β-cells on glucagon secretion. Glibenclamide inhibited glucagon secretion from islets and the α- and β-mixed cell-aggregates, but not from the α-cell-only aggregates, at 2.0 mM glucose. INTERPRETATION This study validated the use of isolated and then re-aggregated human islet cells for investigating α-cell function and paracrine regulation, and demonstrated the importance of cell-to-cell contact between α- and β-cells on glucagon secretion. Loss of proper β- and α-cell physical interaction in islets likely contributes to the dysregulated glucagon secretion in diabetic patients. Re-aggregated select combinations of human islet cells provide unique platforms for studying islet cell function and regulation.
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Affiliation(s)
- Wei Liu
- Department of Nephropathy, The Second Hospital of Jilin University, 218 Ziquiang Street, Nanguan District, Changchun, Jilin 130041, China; Columbia Center for Translational Immunology, Department of Medicine, Columbia University Medical Center, New York, NY, USA
| | - Tatsuya Kin
- Clinical Islet Laboratory, University of Alberta, Edmonton, Alberta, Canada
| | - Siuhong Ho
- Columbia Center for Translational Immunology, Department of Medicine, Columbia University Medical Center, New York, NY, USA
| | - Craig Dorrell
- Oregon Stem Cell Center, Oregon Health & Science University, Portland, OR, USA
| | - Sean R Campbell
- Columbia Center for Translational Immunology, Department of Medicine, Columbia University Medical Center, New York, NY, USA
| | - Ping Luo
- Department of Nephropathy, The Second Hospital of Jilin University, 218 Ziquiang Street, Nanguan District, Changchun, Jilin 130041, China.
| | - Xiaojuan Chen
- Columbia Center for Translational Immunology, Department of Surgery, Columbia University Medical Center, 650 West 168th Street, BB1701, New York, NY 10032, USA.
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47
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Somvanshi PR, Tomar M, Kareenhalli V. Computational Analysis of Insulin-Glucagon Signalling Network: Implications of Bistability to Metabolic Homeostasis and Disease states. Sci Rep 2019; 9:15298. [PMID: 31653897 PMCID: PMC6814820 DOI: 10.1038/s41598-019-50889-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2019] [Accepted: 09/19/2019] [Indexed: 02/06/2023] Open
Abstract
Insulin and glucagon control plasma macronutrient homeostasis through their signalling network composed of multiple feedback and crosstalk interactions. To understand how these interactions contribute to metabolic homeostasis and disease states, we analysed the steady state response of metabolic regulation (catabolic or anabolic) with respect to structural and input perturbations in the integrated signalling network, for varying levels of plasma glucose. Structural perturbations revealed: the positive feedback of AKT on IRS is responsible for the bistability in anabolic zone (glucose >5.5 mmol); the positive feedback of calcium on cAMP is responsible for ensuring ultrasensitive response in catabolic zone (glucose <4.5 mmol); the crosstalk between AKT and PDE3 is responsible for efficient catabolic response under low glucose condition; the crosstalk between DAG and PKC regulates the span of anabolic bistable region with respect to plasma glucose levels. The macronutrient perturbations revealed: varying plasma amino acids and fatty acids from normal to high levels gradually shifted the bistable response towards higher glucose range, eventually making the response catabolic or unresponsive to increasing glucose levels. The analysis reveals that certain macronutrient composition may be more conducive to homeostasis than others. The network perturbations that may contribute to disease states such as diabetes, obesity and cancer are discussed.
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Affiliation(s)
- Pramod R Somvanshi
- Department of Chemical Engineering, Indian Institute of Technology, Bombay, Powai, Mumbai, India.,Bioengineering Division, John A. Paulson School of Engineering and Applied Science, Harvard University, Cambridge, USA
| | - Manu Tomar
- Department of Chemical Engineering, Indian Institute of Technology, Bombay, Powai, Mumbai, India
| | - Venkatesh Kareenhalli
- Department of Chemical Engineering, Indian Institute of Technology, Bombay, Powai, Mumbai, India.
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48
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Montefusco F, Cortese G, Pedersen MG. Heterogeneous alpha-cell population modeling of glucose-induced inhibition of electrical activity. J Theor Biol 2019; 485:110036. [PMID: 31585105 DOI: 10.1016/j.jtbi.2019.110036] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2019] [Revised: 09/12/2019] [Accepted: 09/28/2019] [Indexed: 12/22/2022]
Abstract
Glucagon release from the pancreatic alpha-cells is regulated by glucose, but the underlying mechanisms are far from understood. It is known that the alpha-cell population is very heterogeneous, but - compared to the insulin-secreting beta-cells - the consequences of this cell-to-cell variation are much less studied. Since the alpha-cells are not electrically coupled, large differences in the single cell responses are to be expected, and this variation may contribute to the confusion regarding the mechanisms of glucose-induced suppression of glucagon release. Using mathematical modeling of alpha-cells with realistic cell-to-cell parameter variation based on recent experimental results, we show that the simulated alpha-cells exhibit great diversity in their electrophysiological behavior. To robustly reproduce experimental recordings from alpha-cell exposed to a rise in glucose levels, we must assume that both intrinsic mechanisms and paracrine signals contribute to glucose-induced changes in electrical activity. Our simulations suggest that the sum of different electrophysiological responses due to alpha-cell heterogeneity is involved in glucose-suppressed glucagon secretion, and that more than one mechanism contribute to control the alpha-cell populations' behavior. Finally, we apply regression analysis to our synthetic alpha-cell population to infer which membrane currents influence electrical activity in alpha-cells at different glucose levels. The results from such statistical modeling suggest possible disturbances underlying defect regulation of alpha-cell electrical behavior in diabetics. Thus, although alpha-cells appear to be inherently complex and heterogeneous as reflected in published data, realistic modeling of the alpha-cells at the population level provides insight into the mechanisms of glucagon release.
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Affiliation(s)
| | - Giuliana Cortese
- Department of Statistical Sciences, University of Padova, Padova, Italy
| | - Morten G Pedersen
- Department of Information Engineering, University of Padova, Padova, Italy; Department of Mathematics "Tullio Levi-Civita", University of Padova, Padova, Italy; Padova Neuroscience Center, University of Padova, Padova, Italy.
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49
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Castiello FR, Tabrizian M. Gold nanoparticle amplification strategies for multiplex SPRi-based immunosensing of human pancreatic islet hormones. Analyst 2019; 144:2541-2549. [PMID: 30864587 DOI: 10.1039/c9an00140a] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
In this work, we demonstrate the potential use of SPRi for secretion-monitoring of pancreatic islets, small micro-organs that regulate glucose homeostasis in the body. In the islets, somatostatin works as a paracrine inhibitor of insulin and glucagon secretion. However, this inhibitory effect is lost in diabetic individuals and little is known about its contribution to the pathology of diabetes. Thus, the simultaneous detection of insulin, glucagon and somatostatin could help understand such communications. Previously, the authors introduced an SPRi biosensor to simultaneously monitor insulin, glucagon and somatostatin using an indirect competitive immunoassay. However, our sensor achieved a relatively high LOD for somatostatin detection (246 nM), the smallest of the three hormones. For this reason, the present work aimed to improve the performance of our SPRi biosensor using gold nanoparticles (GNPs) as a means of ensuring somatostatin detection from a small group of islets. Although GNP amplification is frequently reported in the literature for individual detection of analytes using SPR, studies regarding the optimal strategy in a multiplexed SPR setup are missing. Therefore, with the aim of finding the optimal GNP amplification strategies for multiplex sensing we compared three architectures: (1) GNPs immobilized on the sensor surface, (2) GNPs conjugated with primary antibodies (GNP-Ab1) and (3) GNPs conjugated with a secondary antibody (GNP-Ab2). Among these strategies an immunoassay using GNP-Ab2 conjugates was able to achieve multiplex detection of the three hormones without cross-reactivity and with 9-fold LOD improvement for insulin, 10-fold for glucagon and 200-fold for somatostatin when compared to the SPRi biosensor without GNPs. The present work denotes the first report of the simultaneous detection of such hormones with a sensitivity level comparable to ELISA assays, particularly for somatostatin.
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Affiliation(s)
- F Rafael Castiello
- Biomedical and Biological Engineering Department, McGill University, Montreal, QC, Canada.
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50
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Tudurí E, Glavas MM, Asadi A, Baker RK, Ellis CE, Soukhatcheva G, Philit M, Huynh FK, Johnson JD, Bruce Verchere C, Kieffer TJ. AAV GCG-EGFP, a new tool to identify glucagon-secreting α-cells. Sci Rep 2019; 9:10829. [PMID: 31346189 PMCID: PMC6658537 DOI: 10.1038/s41598-019-46735-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2018] [Accepted: 07/04/2019] [Indexed: 01/07/2023] Open
Abstract
The study of primary glucagon-secreting α-cells is hampered by their low abundance and scattered distribution in rodent pancreatic islets. We have designed a double-stranded adeno-associated virus containing a rat proglucagon promoter (700 bp) driving enhanced green fluorescent protein (AAV GCG-EGFP), to specifically identify α-cells. The administration of AAV GCG-EGFP by intraperitoneal or intraductal injection led to EGFP expression selectively in the α-cell population. AAV GCG-EGFP delivery to mice followed by islet isolation, dispersion and separation by FACS for EGFP resulted in an 86% pure population of α-cells. Furthermore, the administration of AAV GCG-EGFP at various doses to adult wild type mice did not significantly alter body weight, blood glucose, plasma insulin or glucagon levels, glucose tolerance or arginine tolerance. In vitro experiments in transgene positive α-cells demonstrated that EGFP expression did not alter the intracellular Ca2+ pattern in response to glucose or adrenaline. This approach may be useful for studying purified primary α-cells and for the in vivo delivery of other genes selectively to α-cells to further probe their function or to manipulate them for therapeutic purposes.
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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.,Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Madrid, Spain.,Instituto de Investigación, Desarrollo e innovación en Biotecnología Sanitaria de Elche (IDiBE), Elche, Spain
| | - Maria M Glavas
- Department of Cellular and Physiological Sciences, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia, Canada
| | - Ali Asadi
- Department of Cellular and Physiological Sciences, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia, Canada
| | - Robert K Baker
- Department of Cellular and Physiological Sciences, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia, Canada
| | - Cara E Ellis
- Department of Cellular and Physiological Sciences, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia, Canada
| | - Galina Soukhatcheva
- Department of Pathology and Laboratory Medicine, BC Children's Hospital Research Institute, Vancouver, British Columbia, Canada
| | - Marjolaine Philit
- Department of Cellular and Physiological Sciences, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia, Canada
| | - Frank K Huynh
- Department of Cellular and Physiological Sciences, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia, Canada.,Department of Biological Sciences, San Jose State University, San Jose, CA, USA
| | - James D Johnson
- Department of Cellular and Physiological Sciences, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia, Canada.,Department of Surgery, University of British Columbia, Vancouver, British Columbia, Canada
| | - C Bruce Verchere
- Department of Surgery, University of British Columbia, Vancouver, British Columbia, Canada.,Department of Pathology and Laboratory Medicine, BC Children's Hospital Research Institute, Vancouver, British Columbia, Canada
| | - Timothy J Kieffer
- Department of Cellular and Physiological Sciences, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia, Canada. .,Department of Surgery, University of British Columbia, Vancouver, British Columbia, Canada.
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