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Mirasierra M, Fernández-Pérez A, Lizarbe B, Keiran N, Ruiz-Cañas L, Casarejos MJ, Cerdán S, Vendrell J, Fernández-Veledo S, Vallejo M. Alx3 deficiency disrupts energy homeostasis, alters body composition, and impairs hypothalamic regulation of food intake. Cell Mol Life Sci 2024; 81:343. [PMID: 39129011 PMCID: PMC11335267 DOI: 10.1007/s00018-024-05384-z] [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: 07/10/2023] [Revised: 07/03/2024] [Accepted: 07/27/2024] [Indexed: 08/13/2024]
Abstract
The coordination of food intake, energy storage, and expenditure involves complex interactions between hypothalamic neurons and peripheral tissues including pancreatic islets, adipocytes, muscle, and liver. Previous research shows that deficiency of the transcription factor Alx3 alters pancreatic islet-dependent glucose homeostasis. In this study we carried out a comprehensive assessment of metabolic alterations in Alx3 deficiency. We report that Alx3-deficient mice exhibit decreased food intake without changes in body weight, along with reduced energy expenditure and altered respiratory exchange ratio. Magnetic resonance imaging reveals increased adiposity and decreased muscle mass, which was associated with markers of motor and sympathetic denervation. By contrast, Alx3-deficient mice on a high-fat diet show attenuated weight gain and improved insulin sensitivity, compared to control mice. Gene expression analysis demonstrates altered lipogenic and lipolytic gene profiles. In wild type mice Alx3 is expressed in hypothalamic arcuate nucleus neurons, but not in major peripheral metabolic organs. Functional diffusion-weighted magnetic resonance imaging reveals selective hypothalamic responses to fasting in the arcuate nucleus of Alx3-deficient mice. Additionally, altered expression of proopiomelanocortin and melanocortin-3 receptor mRNA in the hypothalamus suggests impaired regulation of feeding behavior. This study highlights the crucial role for Alx3 in governing food intake, energy homeostasis, and metabolic nutrient partitioning, thereby influencing body mass composition.
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Affiliation(s)
- Mercedes Mirasierra
- Instituto de Investigaciones Biomédicas Sols-Morreale, Consejo Superior de Investigaciones Científicas/Universidad Autónoma de Madrid, Madrid, Spain
- Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas CIBERDEM, Instituto de Salud Carlos III, Madrid, Spain
| | - Antonio Fernández-Pérez
- Instituto de Investigaciones Biomédicas Sols-Morreale, Consejo Superior de Investigaciones Científicas/Universidad Autónoma de Madrid, Madrid, Spain
- Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas CIBERDEM, Instituto de Salud Carlos III, Madrid, Spain
- Centro para el Desarrollo Tecnológico e Industrial (CDTI), Madrid, Spain
| | - Blanca Lizarbe
- Instituto de Investigaciones Biomédicas Sols-Morreale, Consejo Superior de Investigaciones Científicas/Universidad Autónoma de Madrid, Madrid, Spain
- Department of Biochemistry, Universidad Autónoma de Madrid, Madrid, Spain
| | - Noelia Keiran
- Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas CIBERDEM, Instituto de Salud Carlos III, Madrid, Spain
- Department of Endocrinology and Nutrition, Research Unit, Institut d'Investigació Sanitària Pere Virgili (IISPV) - Hospital Universitari de Tarragona Joan XXIII, Universitat Rovira i Virgili, Tarragona, Spain
| | - Laura Ruiz-Cañas
- Instituto de Investigaciones Biomédicas Sols-Morreale, Consejo Superior de Investigaciones Científicas/Universidad Autónoma de Madrid, Madrid, Spain
- Chronic Diseases and Cancer Area 3, Instituto Ramón y Cajal de Investigaciones Sanitarias (IRYCIS), Madrid, Spain
| | - María José Casarejos
- Neuropharmacology Laboratory, Neurobiology Department, Hospital Universitario Ramón y Cajal, Instituto Ramón y Cajal de Investigaciones Sanitarias (IRYCIS), Madrid, Spain
| | - Sebastián Cerdán
- Instituto de Investigaciones Biomédicas Sols-Morreale, Consejo Superior de Investigaciones Científicas/Universidad Autónoma de Madrid, Madrid, Spain
| | - Joan Vendrell
- Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas CIBERDEM, Instituto de Salud Carlos III, Madrid, Spain
- Department of Endocrinology and Nutrition, Research Unit, Institut d'Investigació Sanitària Pere Virgili (IISPV) - Hospital Universitari de Tarragona Joan XXIII, Universitat Rovira i Virgili, Tarragona, Spain
| | - Sonia Fernández-Veledo
- Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas CIBERDEM, Instituto de Salud Carlos III, Madrid, Spain
- Department of Endocrinology and Nutrition, Research Unit, Institut d'Investigació Sanitària Pere Virgili (IISPV) - Hospital Universitari de Tarragona Joan XXIII, Universitat Rovira i Virgili, Tarragona, Spain
| | - Mario Vallejo
- Instituto de Investigaciones Biomédicas Sols-Morreale, Consejo Superior de Investigaciones Científicas/Universidad Autónoma de Madrid, Madrid, Spain.
- Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas CIBERDEM, Instituto de Salud Carlos III, Madrid, Spain.
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2
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D'Addio F, Maestroni A, Assi E, Ben Nasr M, Amabile G, Usuelli V, Loretelli C, Bertuzzi F, Antonioli B, Cardarelli F, El Essawy B, Solini A, Gerling IC, Bianchi C, Becchi G, Mazzucchelli S, Corradi D, Fadini GP, Foschi D, Markmann JF, Orsi E, Škrha J, Camboni MG, Abdi R, James Shapiro AM, Folli F, Ludvigsson J, Del Prato S, Zuccotti G, Fiorina P. The IGFBP3/TMEM219 pathway regulates beta cell homeostasis. Nat Commun 2022; 13:684. [PMID: 35115561 PMCID: PMC8813914 DOI: 10.1038/s41467-022-28360-2] [Citation(s) in RCA: 20] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2020] [Accepted: 01/14/2022] [Indexed: 12/12/2022] Open
Abstract
Loss of pancreatic beta cells is a central feature of type 1 (T1D) and type 2 (T2D) diabetes, but a therapeutic strategy to preserve beta cell mass remains to be established. Here we show that the death receptor TMEM219 is expressed on pancreatic beta cells and that signaling through its ligand insulin-like growth factor binding protein 3 (IGFBP3) leads to beta cell loss and dysfunction. Increased peripheral IGFBP3 was observed in established and at-risk T1D/T2D patients and was confirmed in T1D/T2D preclinical models, suggesting that dysfunctional IGFBP3/TMEM219 signaling is associated with abnormalities in beta cells homeostasis. In vitro and in vivo short-term IGFBP3/TMEM219 inhibition and TMEM219 genetic ablation preserved beta cells and prevented/delayed diabetes onset, while long-term IGFBP3/TMEM219 blockade allowed for beta cell expansion. Interestingly, in several patients' cohorts restoration of appropriate IGFBP3 levels was associated with improved beta cell function. The IGFBP3/TMEM219 pathway is thus shown to be a physiological regulator of beta cell homeostasis and is also demonstrated to be disrupted in T1D/T2D. IGFBP3/TMEM219 targeting may therefore serve as a therapeutic option in diabetes.
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MESH Headings
- Adult
- Animals
- Cells, Cultured
- Diabetes Mellitus, Type 1/genetics
- Diabetes Mellitus, Type 1/metabolism
- Diabetes Mellitus, Type 1/pathology
- Diabetes Mellitus, Type 2/genetics
- Diabetes Mellitus, Type 2/metabolism
- Diabetes Mellitus, Type 2/pathology
- Female
- Gene Expression Regulation
- Homeostasis/genetics
- Humans
- Immunoblotting
- Insulin-Like Growth Factor Binding Protein 3/genetics
- Insulin-Like Growth Factor Binding Protein 3/metabolism
- Insulin-Secreting Cells/metabolism
- Male
- Membrane Proteins/genetics
- Membrane Proteins/metabolism
- Mice, Inbred C57BL
- Mice, Inbred NOD
- Mice, Knockout
- Mice, Transgenic
- Middle Aged
- Reverse Transcriptase Polymerase Chain Reaction
- Signal Transduction/genetics
- Mice
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Affiliation(s)
- Francesca D'Addio
- International Center for T1D, Pediatric Clinical Research Center Romeo ed Enrica Invernizzi, DIBIC, Università di Milano, Milan, Italy
| | - Anna Maestroni
- International Center for T1D, Pediatric Clinical Research Center Romeo ed Enrica Invernizzi, DIBIC, Università di Milano, Milan, Italy
| | - Emma Assi
- International Center for T1D, Pediatric Clinical Research Center Romeo ed Enrica Invernizzi, DIBIC, Università di Milano, Milan, Italy
| | - Moufida Ben Nasr
- International Center for T1D, Pediatric Clinical Research Center Romeo ed Enrica Invernizzi, DIBIC, Università di Milano, Milan, Italy
- Nephrology Division, Boston Children's Hospital and Transplantation Research Center, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA
| | | | - Vera Usuelli
- International Center for T1D, Pediatric Clinical Research Center Romeo ed Enrica Invernizzi, DIBIC, Università di Milano, Milan, Italy
- Nephrology Division, Boston Children's Hospital and Transplantation Research Center, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA
| | - Cristian Loretelli
- International Center for T1D, Pediatric Clinical Research Center Romeo ed Enrica Invernizzi, DIBIC, Università di Milano, Milan, Italy
| | - Federico Bertuzzi
- Diabetology Unit, ASST Grande Ospedale Metropolitano Niguarda, Milan, Italy
| | - Barbara Antonioli
- Diabetology Unit, ASST Grande Ospedale Metropolitano Niguarda, Milan, Italy
| | | | - Basset El Essawy
- Transplantation Research Center, Nephrology Division, Brigham and Women's Hospital, Boston, MA, USA
- Medicine, Al-Azhar University, Cairo, Egypt
| | - Anna Solini
- Department of Surgical, Medical and Molecular Pathology and Critical Care Medicine, University of Pisa, Pisa, Italy
| | - Ivan C Gerling
- Department of Medicine, University of Tennessee, Memphis, TN, USA
| | - Cristina Bianchi
- Section of Diabetes and Metabolic Disease, Department of Clinical and Experimental Medicine, University of Pisa and Azienda Ospedaliero-Universitaria Pisana, Pisa, Italy
| | - Gabriella Becchi
- Department of Medicine and Surgery, Unit of Pathology, University of Parma, Parma, Italy
| | - Serena Mazzucchelli
- International Center for T1D, Pediatric Clinical Research Center Romeo ed Enrica Invernizzi, DIBIC, Università di Milano, Milan, Italy
| | - Domenico Corradi
- Department of Medicine and Surgery, Unit of Pathology, University of Parma, Parma, Italy
| | | | - Diego Foschi
- General Surgery, DIBIC, L. Sacco Hospital, Università di Milano, Milan, Italy
| | - James F Markmann
- Division of Transplantation, Department of Surgery, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
| | - Emanuela Orsi
- Diabetes Service, Endocrinology and Metabolic Diseases Unit, IRCCS Cà Granda - Ospedale Maggiore Policlinico Foundation, Milan, Italy
| | - Jan Škrha
- 3rd Department of Internal Medicine, Charles University, First Faculty of Medicine, Prague, Czech Republic
| | | | - Reza Abdi
- Transplantation Research Center, Nephrology Division, Brigham and Women's Hospital, Boston, MA, USA
| | - A M James Shapiro
- Clinical Islet Transplant Program, Alberta Diabetes Institute, University of Alberta, Edmonton, AB, Canada
| | - Franco Folli
- Endocrinology and Metabolism, Department of Health Science, Università di Milano, ASST Santi Paolo e Carlo, Milan, Italy
| | - Johnny Ludvigsson
- Crown Princess Victoria Children´s Hospital and Div of Pediatrics, Dept of Biomedical and Clinical Sciences, Linköping University, Linköping, Sweden
| | - Stefano Del Prato
- Section of Diabetes and Metabolic Disease, Department of Clinical and Experimental Medicine, University of Pisa and Azienda Ospedaliero-Universitaria Pisana, Pisa, Italy
| | - Gianvincenzo Zuccotti
- Pediatric Clinical Research Center Romeo ed Enrica Invernizzi, DIBIC, Università di Milano and Department of Pediatrics, Buzzi Children's Hospital, Milan, Italy
| | - Paolo Fiorina
- International Center for T1D, Pediatric Clinical Research Center Romeo ed Enrica Invernizzi, DIBIC, Università di Milano, Milan, Italy.
- Nephrology Division, Boston Children's Hospital and Transplantation Research Center, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA.
- Division of Endocrinology, ASST Fatebenefratelli-Sacco, Milan, Italy.
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Arcones AC, Vila-Bedmar R, Mirasierra M, Cruces-Sande M, Vallejo M, Jones B, Tomas A, Mayor F, Murga C. GRK2 regulates GLP-1R-mediated early phase insulin secretion in vivo. BMC Biol 2021; 19:40. [PMID: 33658023 PMCID: PMC7931601 DOI: 10.1186/s12915-021-00966-w] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2020] [Accepted: 01/22/2021] [Indexed: 12/12/2022] Open
Abstract
BACKGROUND Insulin secretion from the pancreatic β-cell is finely modulated by different signals to allow an adequate control of glucose homeostasis. Incretin hormones such as glucagon-like peptide-1 (GLP-1) act as key physiological potentiators of insulin release through binding to the G protein-coupled receptor GLP-1R. Another key regulator of insulin signaling is the Ser/Thr kinase G protein-coupled receptor kinase 2 (GRK2). However, whether GRK2 affects insulin secretion or if GRK2 can control incretin actions in vivo remains to be analyzed. RESULTS Using GRK2 hemizygous mice, isolated pancreatic islets, and model β-cell lines, we have uncovered a relevant physiological role for GRK2 as a regulator of incretin-mediated insulin secretion in vivo. Feeding, oral glucose gavage, or administration of GLP-1R agonists in animals with reduced GRK2 levels (GRK2+/- mice) resulted in enhanced early phase insulin release without affecting late phase secretion. In contrast, intraperitoneal glucose-induced insulin release was not affected. This effect was recapitulated in isolated islets and correlated with the increased size or priming efficacy of the readily releasable pool (RRP) of insulin granules that was observed in GRK2+/- mice. Using nanoBRET in β-cell lines, we found that stimulation of GLP-1R promoted GRK2 association to this receptor and that GRK2 protein and kinase activity were required for subsequent β-arrestin recruitment. CONCLUSIONS Overall, our data suggest that GRK2 is an important negative modulator of GLP-1R-mediated insulin secretion and that GRK2-interfering strategies may favor β-cell insulin secretion specifically during the early phase, an effect that may carry interesting therapeutic applications.
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Affiliation(s)
- Alba C Arcones
- Departamento de Biología Molecular and Centro de Biología Molecular Severo Ochoa (CBMSO) UAM-CSIC; Instituto de Investigación Sanitaria Hospital Universitario La Princesa; CIBER de Enfermedades Cardiovasculares (CIBERCV), UNIVERSIDAD AUTONOMA DE MADRID and Instituto de Salud Carlos III, Madrid, Spain
| | - Rocío Vila-Bedmar
- Departamento de Ciencias Básicas de la Salud, Facultad de Ciencias de la Salud, Universidad Rey Juan Carlos (URJC), Madrid, Spain
| | - Mercedes Mirasierra
- Instituto de Investigaciones Biomédicas Alberto Sols (CSIC-UAM); Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (Ciberdem), Madrid, Spain
| | - Marta Cruces-Sande
- Departamento de Biología Molecular and Centro de Biología Molecular Severo Ochoa (CBMSO) UAM-CSIC; Instituto de Investigación Sanitaria Hospital Universitario La Princesa; CIBER de Enfermedades Cardiovasculares (CIBERCV), UNIVERSIDAD AUTONOMA DE MADRID and Instituto de Salud Carlos III, Madrid, Spain
| | - Mario Vallejo
- Instituto de Investigaciones Biomédicas Alberto Sols (CSIC-UAM); Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (Ciberdem), Madrid, Spain
| | - Ben Jones
- Section of Investigative Medicine, Imperial College London, London, W12 0NN, UK
| | - Alejandra Tomas
- Section of Cell Biology and Functional Genomics, Imperial College London, London, W12 0NN, UK
| | - Federico Mayor
- Departamento de Biología Molecular and Centro de Biología Molecular Severo Ochoa (CBMSO) UAM-CSIC; Instituto de Investigación Sanitaria Hospital Universitario La Princesa; CIBER de Enfermedades Cardiovasculares (CIBERCV), UNIVERSIDAD AUTONOMA DE MADRID and Instituto de Salud Carlos III, Madrid, Spain.
| | - Cristina Murga
- Departamento de Biología Molecular and Centro de Biología Molecular Severo Ochoa (CBMSO) UAM-CSIC; Instituto de Investigación Sanitaria Hospital Universitario La Princesa; CIBER de Enfermedades Cardiovasculares (CIBERCV), UNIVERSIDAD AUTONOMA DE MADRID and Instituto de Salud Carlos III, Madrid, Spain.
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4
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Functional interplay between the transcription factors USF1 and PDX-1 and protein kinase CK2 in pancreatic β-cells. Sci Rep 2017; 7:16367. [PMID: 29180680 PMCID: PMC5703852 DOI: 10.1038/s41598-017-16590-0] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2017] [Accepted: 10/04/2017] [Indexed: 11/22/2022] Open
Abstract
Glucose homeostasis is regulated by insulin, which is produced in the β-cells of the pancreas. The synthesis of insulin is controlled by several transcription factors including PDX-1, USF1 and USF2. Both, PDX-1 and USF1 were identified as substrates for protein kinase CK2. Here, we have analysed the interplay of PDX-1, USF1 and CK2 in the regulation of PDX-1 gene transcription. We found that the PDX-1 promoter is dose-dependently transactivated by PDX-1 and transrepressed by USF1. With increasing glucose concentrations the transrepression of the PDX-1 promoter by USF1 is successively abrogated. PDX-1 binding to its own promoter was not influenced by glucose, whereas USF1 binding to the PDX-1 promoter was reduced. The same effect was observed after inhibition of the protein kinase activity by three different inhibitors or by using a phospho-mutant of USF1. Moreover, phosphorylation of USF1 by CK2 seems to strengthen the interaction between USF1 and PDX-1. Thus, CK2 is a negative regulator of the USF1-dependent PDX-1 transcription. Moreover, upon inhibition of CK2 in primary islets, insulin expression as well as insulin secretion were enhanced without affecting the viability of the cells. Therefore, inhibition of CK2 activity may be a promising approach to stimulate insulin production in pancreatic β-cells.
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5
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García-Sanz P, Mirasierra M, Moratalla R, Vallejo M. Embryonic defence mechanisms against glucose-dependent oxidative stress require enhanced expression of Alx3 to prevent malformations during diabetic pregnancy. Sci Rep 2017; 7:389. [PMID: 28341857 PMCID: PMC5428206 DOI: 10.1038/s41598-017-00334-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2016] [Accepted: 02/20/2017] [Indexed: 12/20/2022] Open
Abstract
Oxidative stress constitutes a major cause for increased risk of congenital malformations associated to severe hyperglycaemia during pregnancy. Mutations in the gene encoding the transcription factor ALX3 cause congenital craniofacial and neural tube defects. Since oxidative stress and lack of ALX3 favour excessive embryonic apoptosis, we investigated whether ALX3-deficiency further increases the risk of embryonic damage during gestational hyperglycaemia in mice. We found that congenital malformations associated to ALX3-deficiency are enhanced in diabetic pregnancies. Increased expression of genes encoding oxidative stress-scavenging enzymes in embryos from diabetic mothers was blunted in the absence of ALX3, leading to increased oxidative stress. Levels of ALX3 increased in response to glucose, but ALX3 did not activate oxidative stress defence genes directly. Instead, ALX3 stimulated the transcription of Foxo1, a master regulator of oxidative stress-scavenging genes, by binding to a newly identified binding site located in the Foxo1 promoter. Our data identify ALX3 as an important component of the defence mechanisms against the occurrence of developmental malformations during diabetic gestations, stimulating the expression of oxidative stress-scavenging genes in a glucose-dependent manner via Foxo1 activation. Thus, ALX3 deficiency provides a novel molecular mechanism for developmental defects arising from maternal hyperglycaemia.
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Affiliation(s)
- Patricia García-Sanz
- Instituto de Investigaciones Biomédicas Alberto Sols, Consejo Superior de Investigaciones Científicas (CSIC)/Universidad Autónoma de Madrid, and Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas CIBERDEM, Madrid, Spain.,Instituto Cajal, Consejo Superior de Investigaciones Científicas (CSIC), Madrid, and CIBERNED, Instituto de Salud Carlos III, Madrid, Spain
| | - Mercedes Mirasierra
- Instituto de Investigaciones Biomédicas Alberto Sols, Consejo Superior de Investigaciones Científicas (CSIC)/Universidad Autónoma de Madrid, and Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas CIBERDEM, Madrid, Spain
| | - Rosario Moratalla
- Instituto Cajal, Consejo Superior de Investigaciones Científicas (CSIC), Madrid, and CIBERNED, Instituto de Salud Carlos III, Madrid, Spain
| | - Mario Vallejo
- Instituto de Investigaciones Biomédicas Alberto Sols, Consejo Superior de Investigaciones Científicas (CSIC)/Universidad Autónoma de Madrid, and Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas CIBERDEM, Madrid, Spain.
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Mirasierra M, Vallejo M. Glucose-dependent downregulation of glucagon gene expression mediated by selective interactions between ALX3 and PAX6 in mouse alpha cells. Diabetologia 2016; 59:766-75. [PMID: 26739814 DOI: 10.1007/s00125-015-3849-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/15/2015] [Accepted: 12/07/2015] [Indexed: 12/11/2022]
Abstract
AIMS/HYPOTHESIS The stimulation of glucagon secretion in response to decreased glucose levels has been studied extensively. In contrast, little is known about the regulation of glucagon gene expression in response to fluctuations in glucose concentration. Paired box 6 (PAX6) is a key transcription factor that regulates the glucagon promoter by binding to the G1 and G3 elements. Here, we investigated the role of the transcription factor aristaless-like homeobox 3 (ALX3) as a glucose-dependent modulator of PAX6 activity in alpha cells. METHODS Experiments were performed in wild-type or Alx3-deficient islets and alphaTC1 cells. We used chromatin immunoprecipitations and electrophoretic mobility shift assays for DNA binding, immunoprecipitations and pull-down assays for protein interactions, transfected cells for promoter activity, and small interfering RNA and quantitative RT-PCR for gene expression. RESULTS Elevated glucose concentration resulted in stimulated expression of Alx3 and decreased glucagon gene expression in wild-type islets. In ALX3-deficient islets, basal glucagon levels were non-responsive to changes in glucose concentration. In basal conditions ALX3 bound to the glucagon promoter at G3, but not at G1. ALX3 could form heterodimers with PAX6 that were permissive for binding to G3 but not to G1. Thus, increasing the levels of ALX3 in response to glucose resulted in the sequestration of PAX6 by ALX3 for binding to G1, thus reducing glucagon promoter activation and glucagon gene expression. CONCLUSIONS/INTERPRETATION Glucose-stimulated expression of ALX3 in alpha cells provides a regulatory mechanism for the downregulation of glucagon gene expression by interfering with PAX6-mediated transactivation on the glucagon G1 promoter element.
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Affiliation(s)
- Mercedes Mirasierra
- Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Madrid, Spain
- Instituto de Investigaciones Biomédicas Alberto Sols, Consejo Superior de Investigaciones Científicas/Universidad Autónoma de Madrid (CSIC/UAM), Calle Arturo Duperier 4, 28029, Madrid, Spain
| | - Mario Vallejo
- Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Madrid, Spain.
- Instituto de Investigaciones Biomédicas Alberto Sols, Consejo Superior de Investigaciones Científicas/Universidad Autónoma de Madrid (CSIC/UAM), Calle Arturo Duperier 4, 28029, Madrid, Spain.
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Pdx1 and USF transcription factors co-ordinately regulate Alx3 gene expression in pancreatic β-cells. Biochem J 2014; 463:287-96. [DOI: 10.1042/bj20140643] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
We investigated the transcriptional mechanisms regulating the expression of Alx3 in pancreatic islets. We found that the transcriptional transactivation of Alx3 in β-cells requires the co-operation of the islet-specific homeoprotein Pdx1 with the transcription factors USF1 and USF2.
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8
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Kappen C. Modeling anterior development in mice: diet as modulator of risk for neural tube defects. AMERICAN JOURNAL OF MEDICAL GENETICS. PART C, SEMINARS IN MEDICAL GENETICS 2013; 163C:333-56. [PMID: 24124024 PMCID: PMC4149464 DOI: 10.1002/ajmg.c.31380] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Head morphogenesis is a complex process that is controlled by multiple signaling centers. The most common defects of cranial development are craniofacial defects, such as cleft lip and cleft palate, and neural tube defects, such as anencephaly and encephalocoele in humans. More than 400 genes that contribute to proper neural tube closure have been identified in experimental animals, but only very few causative gene mutations have been identified in humans, supporting the notion that environmental influences are critical. The intrauterine environment is influenced by maternal nutrition, and hence, maternal diet can modulate the risk for cranial and neural tube defects. This article reviews recent progress toward a better understanding of nutrients during pregnancy, with particular focus on mouse models for defective neural tube closure. At least four major patterns of nutrient responses are apparent, suggesting that multiple pathways are involved in the response, and likely in the underlying pathogenesis of the defects. Folic acid has been the most widely studied nutrient, and the diverse responses of the mouse models to folic acid supplementation indicate that folic acid is not universally beneficial, but that the effect is dependent on genetic configuration. If this is the case for other nutrients as well, efforts to prevent neural tube defects with nutritional supplementation may need to become more specifically targeted than previously appreciated. Mouse models are indispensable for a better understanding of nutrient-gene interactions in normal pregnancies, as well as in those affected by metabolic diseases, such as diabetes and obesity.
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9
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Differential configurations involving binding of USF transcription factors and Twist1 regulate Alx3 promoter activity in mesenchymal and pancreatic cells. Biochem J 2013. [PMID: 23181698 DOI: 10.1042/bj20120962] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
During embryonic development, the aristaless-type homeodomain protein Alx3 is expressed in the forehead mesenchyme and contributes to the regulation of craniofacial development. In the adult, Alx3 is expressed in pancreatic islets where it participates in the control of glucose homoeostasis. In the present study, we investigated the transcriptional regulation of Alx3 gene expression in these two cell types. We found that the Alx3 promoter contains two E-box regulatory elements, named EB1 and EB2, that provide binding sites for the basic helix-loop-helix transcription factors Twist1, E47, USF (upstream stimulatory factor) 1 and USF2. In primary mouse embryonic mesenchymal cells isolated from the forehead, EB2 is bound by Twist1, whereas EB1 is bound by USF1 and USF2. Integrity of both EB1 and EB2 is required for Twist1-mediated transactivation of the Alx3 promoter, even though Twist1 does not bind to EB1, indicating that binding of USF1 and USF2 to this element is required for Twist1-dependent Alx3 promoter activity. In contrast, in pancreatic islet insulin-producing cells, the integrity of EB2 is not required for proximal promoter activity. The results of the present study indicate that USF1 and USF2 are important regulatory factors for Alx3 gene expression in different cell types, whereas Twist1 contributes to transcriptional transactivation in mesenchymal, but not in pancreatic, cells.
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