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Yoo HS, Moss KO, Cockrum MA, Woo W, Napoli JL. Energy status regulates levels of the RAR/RXR ligand 9-cis-retinoic acid in mammalian tissues: Glucose reduces its synthesis in β-cells. J Biol Chem 2023; 299:105255. [PMID: 37714463 PMCID: PMC10582780 DOI: 10.1016/j.jbc.2023.105255] [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: 08/05/2023] [Revised: 09/01/2023] [Accepted: 09/10/2023] [Indexed: 09/17/2023] Open
Abstract
9-cis-retinoic acid (9cRA) binds retinoic acid receptors (RAR) and retinoid X receptors (RXR) with nanomolar affinities, in contrast to all-trans-retinoic acid (atRA), which binds only RAR with nanomolar affinities. RXR heterodimerize with type II nuclear receptors, including RAR, to regulate a vast gene array. Despite much effort, 9cRA has not been identified as an endogenous retinoid, other than in pancreas. By revising tissue analysis methods, 9cRA quantification by liquid chromatography-tandem mass spectrometry becomes possible in all mouse tissues analyzed. 9cRA occurs in concentrations similar to or greater than atRA. Fasting increases 9cRA in white and brown adipose, brain and pancreas, while increasing atRA in white adipose, liver and pancreas. 9cRA supports FoxO1 actions in pancreas β-cells and counteracts glucose actions that lead to glucotoxicity; in part by inducing Atg7 mRNA, which encodes the key enzyme essential for autophagy. Glucose suppresses 9cRA biosynthesis in the β-cell lines 832/13 and MIN6. Glucose reduces 9cRA biosynthesis in 832/13 cells by inhibiting Rdh5 transcription, unconnected to insulin, through cAMP and Akt, and inhibiting FoxO1. Through adapting tissue specifically to fasting, 9cRA would act independent of atRA. Widespread occurrence of 9cRA in vivo, and its self-sufficient adaptation to energy status, provides new perspectives into regulation of energy balance, attenuation of insulin and glucose actions, regulation of type II nuclear receptors, and retinoid biology.
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Affiliation(s)
- Hong Sik Yoo
- Department of Nutritional Sciences and Toxicology, Graduate Program in Metabolic Biology, University of California, Berkeley, Berkeley, California, USA
| | - Kristin Obrochta Moss
- Department of Nutritional Sciences and Toxicology, Graduate Program in Metabolic Biology, University of California, Berkeley, Berkeley, California, USA
| | - Michael A Cockrum
- Department of Nutritional Sciences and Toxicology, Graduate Program in Metabolic Biology, University of California, Berkeley, Berkeley, California, USA
| | - Wonsik Woo
- Department of Nutritional Sciences and Toxicology, Graduate Program in Metabolic Biology, University of California, Berkeley, Berkeley, California, USA
| | - Joseph L Napoli
- Department of Nutritional Sciences and Toxicology, Graduate Program in Metabolic Biology, University of California, Berkeley, Berkeley, California, USA.
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Keller DM, Perez IG. Dual regulation of miR-375 and CREM genes in pancreatic beta cells. Islets 2022; 14:139-148. [PMID: 35377267 PMCID: PMC8986308 DOI: 10.1080/19382014.2022.2060688] [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] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
Abstract
MicroRNA-375 (miR-375) is upregulated in the islets of some diabetics and is correlated with poor outcome. Previous work in our laboratory showed that cyclic adenosine monophosphate (cAMP) reduces miR-375 expression and could provide a way to restore normal miR-375 levels, however the transcription repression mechanism is unknown. Using a chromatin immunoprecipitation assay we show that cAMP response element modulator (CREM) binds to the miR-375 promoter 3-fold above background and we find that CREM represses transcription from the miR-375 promoter 1.8-fold. While investigating miR-375 target genes we discovered that several microRNA:mRNA target prediction algorithms listed human CREM as a target gene of miR-375. The predicted binding site is conserved in primates but not in other species. We found that indeed miR-375 binds to the predicted site on human CREM and represses translation of a green fluorescent protein reporter gene by 30%. These findings suggest a primate-specific double-negative feedback loop, a mechanism that would keep these important β-cell regulators in check.
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Affiliation(s)
- David M. Keller
- Department of Biological Sciences, California State University Chico, Chico, CA, USA
- CONTACT David M. Keller Department of Biological Sciences, California State University, Chico, 900 W. 1st St, Chico, CA95929 linkedin.com/in/keller-david-6529485b
| | - Isis G. Perez
- Department of Biological Sciences, California State University Chico, Chico, CA, USA
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The Mystery of Diabetic Cardiomyopathy: From Early Concepts and Underlying Mechanisms to Novel Therapeutic Possibilities. Int J Mol Sci 2021; 22:ijms22115973. [PMID: 34205870 PMCID: PMC8198766 DOI: 10.3390/ijms22115973] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2021] [Revised: 05/26/2021] [Accepted: 05/30/2021] [Indexed: 02/07/2023] Open
Abstract
Diabetic patients are predisposed to diabetic cardiomyopathy, a specific form of cardiomyopathy which is characterized by the development of myocardial fibrosis, cardiomyocyte hypertrophy, and apoptosis that develops independently of concomitant macrovascular and microvascular diabetic complications. Its pathophysiology is multifactorial and poorly understood and no specific therapeutic guideline has yet been established. Diabetic cardiomyopathy is a challenging diagnosis, made after excluding other potential entities, treated with different pharmacotherapeutic agents targeting various pathophysiological pathways that need yet to be unraveled. It has great clinical importance as diabetes is a disease with pandemic proportions. This review focuses on the potential mechanisms contributing to this entity, diagnostic options, as well as on potential therapeutic interventions taking in consideration their clinical feasibility and limitations in everyday practice. Besides conventional therapies, we discuss novel therapeutic possibilities that have not yet been translated into clinical practice.
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Wan S, Zhang J, Chen X, Lang J, Li L, Chen F, Tian L, Meng Y, Yu X. MicroRNA-17-92 Regulates Beta-Cell Restoration After Streptozotocin Treatment. Front Endocrinol (Lausanne) 2020; 11:9. [PMID: 32038500 PMCID: PMC6989481 DOI: 10.3389/fendo.2020.00009] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/05/2019] [Accepted: 01/07/2020] [Indexed: 02/05/2023] Open
Abstract
Objective: To clarify the role and mechanism of miR-17-92 cluster in islet beta-cell repair after streptozotocin intervention. Methods: Genetically engineered mice (miR-17-92βKO) and control RIP-Cre mice were intraperitoneally injected with multiple low dose streptozotocin. Body weight, random blood glucose (RBG), fasting blood glucose, and intraperitoneal glucose tolerance test (IPGTT) were monitored regularly. Mice were sacrificed for histological analysis 8 weeks later. Morphological changes of pancreas islets, quantity, quality, apoptosis, and proliferation of beta-cells were measured. Islets from four groups were isolated. MiRNA and mRNA were extracted and quantified. Results:MiR-17-92βKO mice showed dramatically elevated fasting blood glucose and impaired glucose tolerance after streptozotocin treatment in contrast to control mice, the reason of which is reduced beta-cell number and total mass resulting from reduced proliferation, enhanced apoptosis of beta-cells. Genes related to cell proliferation and insulin transcription repression were significantly elevated in miR-17-92βKO mice treated with streptozotocin. Furthermore, genes involved in DNA biosynthesis and damage repair were dramatically increased in miR-17-92βKO mice with streptozotocin treatment. Conclusion: Collectively, our results demonstrate that homozygous deletion of miR-17-92 cluster in mouse pancreatic beta-cells promotes the development of experimental diabetes, indicating that miR-17-92 cluster may be positively related to beta-cells restoration and adaptation after streptozotocin-induced damage.
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Affiliation(s)
- Shan Wan
- Laboratory of Endocrinology and Metabolism, Department of Endocrinology, National Clinical Research Center for Geriatrics, West China Hospital, Sichuan University, Chengdu, China
| | - Jie Zhang
- Histology and Imaging Platform, Core Facility of West China Hospital, Sichuan University, Chengdu, China
| | - Xiang Chen
- Laboratory of Endocrinology and Metabolism, Department of Endocrinology, National Clinical Research Center for Geriatrics, West China Hospital, Sichuan University, Chengdu, China
| | - Jiangli Lang
- Laboratory of Endocrinology and Metabolism, Department of Endocrinology, National Clinical Research Center for Geriatrics, West China Hospital, Sichuan University, Chengdu, China
| | - Li Li
- Histology and Imaging Platform, Core Facility of West China Hospital, Sichuan University, Chengdu, China
| | - Fei Chen
- Histology and Imaging Platform, Core Facility of West China Hospital, Sichuan University, Chengdu, China
| | - Li Tian
- Laboratory of Endocrinology and Metabolism, Department of Endocrinology, National Clinical Research Center for Geriatrics, West China Hospital, Sichuan University, Chengdu, China
| | - Yang Meng
- Laboratory of Endocrinology and Metabolism, Department of Endocrinology, National Clinical Research Center for Geriatrics, West China Hospital, Sichuan University, Chengdu, China
- Department of Orthopedics, West China Hospital, Sichuan University, Chengdu, China
| | - Xijie Yu
- Laboratory of Endocrinology and Metabolism, Department of Endocrinology, National Clinical Research Center for Geriatrics, West China Hospital, Sichuan University, Chengdu, China
- *Correspondence: Xijie Yu ;
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Enhanced expression of β cell Ca V3.1 channels impairs insulin release and glucose homeostasis. Proc Natl Acad Sci U S A 2019; 117:448-453. [PMID: 31871187 PMCID: PMC6955371 DOI: 10.1073/pnas.1908691117] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
We reveal that increased expression of CaV3.1 channels in rat islets selectively impairs first-phase glucose-stimulated insulin secretion. This deterioration is recapitulated in human islets. Its causal role in diabetes development is clearly manifested in an in vivo diabetic model. Mechanistically, this is due to reduction of phosphorylated FoxO1 in the cytoplasm, elevated FoxO1 nuclear retention, and decreased syntaxin 1A, SNAP-25, and synaptotagmin III in a CaV3.1 channel- and calcineurin-dependent manner. Our findings suggest that elevated expression of CaV3.1 channels in pancreatic islets drives FoxO1-mediated down-regulation of exocytotic proteins resulting in the diabetic phenotypes of impaired insulin secretion and aberrant glucose homeostasis. This causal connection pinpoints β cell CaV3.1 channels as a potential druggable target for antidiabetes therapy. Voltage-gated calcium 3.1 (CaV3.1) channels are absent in healthy mouse β cells and mediate minor T-type Ca2+ currents in healthy rat and human β cells but become evident under diabetic conditions. Whether more active CaV3.1 channels affect insulin secretion and glucose homeostasis remains enigmatic. We addressed this question by enhancing de novo expression of β cell CaV3.1 channels and exploring the consequent impacts on dynamic insulin secretion and glucose homeostasis as well as underlying molecular mechanisms with a series of in vitro and in vivo approaches. We now demonstrate that a recombinant adenovirus encoding enhanced green fluorescent protein–CaV3.1 subunit (Ad-EGFP-CaV3.1) efficiently transduced rat and human islets as well as dispersed islet cells. The resulting CaV3.1 channels conducted typical T-type Ca2+ currents, leading to an enhanced basal cytosolic-free Ca2+ concentration ([Ca2+]i). Ad-EGFP-CaV3.1-transduced islets released significantly less insulin under both the basal and first phases following glucose stimulation and could no longer normalize hyperglycemia in recipient rats rendered diabetic by streptozotocin treatment. Furthermore, Ad-EGFP-CaV3.1 transduction reduced phosphorylated FoxO1 in the cytoplasm of INS-1E cells, elevated FoxO1 nuclear retention, and decreased syntaxin 1A, SNAP-25, and synaptotagmin III. These effects were prevented by inhibiting CaV3.1 channels or the Ca2+-dependent phosphatase calcineurin. Enhanced expression of β cell CaV3.1 channels therefore impairs insulin release and glucose homeostasis by means of initial excessive Ca2+ influx, subsequent activation of calcineurin, consequent dephosphorylation and nuclear retention of FoxO1, and eventual FoxO1-mediated down-regulation of β cell exocytotic proteins. The present work thus suggests an elevated expression of CaV3.1 channels plays a significant role in diabetes pathogenesis.
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Abstract
Heart failure and related morbidity and mortality are increasing at an alarming rate, in large part, because of increases in aging, obesity, and diabetes mellitus. The clinical outcomes associated with heart failure are considerably worse for patients with diabetes mellitus than for those without diabetes mellitus. In people with diabetes mellitus, the presence of myocardial dysfunction in the absence of overt clinical coronary artery disease, valvular disease, and other conventional cardiovascular risk factors, such as hypertension and dyslipidemia, has led to the descriptive terminology, diabetic cardiomyopathy. The prevalence of diabetic cardiomyopathy is increasing in parallel with the increase in diabetes mellitus. Diabetic cardiomyopathy is initially characterized by myocardial fibrosis, dysfunctional remodeling, and associated diastolic dysfunction, later by systolic dysfunction, and eventually by clinical heart failure. Impaired cardiac insulin metabolic signaling, mitochondrial dysfunction, increases in oxidative stress, reduced nitric oxide bioavailability, elevations in advanced glycation end products and collagen-based cardiomyocyte and extracellular matrix stiffness, impaired mitochondrial and cardiomyocyte calcium handling, inflammation, renin-angiotensin-aldosterone system activation, cardiac autonomic neuropathy, endoplasmic reticulum stress, microvascular dysfunction, and a myriad of cardiac metabolic abnormalities have all been implicated in the development and progression of diabetic cardiomyopathy. Molecular mechanisms linked to the underlying pathophysiological changes include abnormalities in AMP-activated protein kinase, peroxisome proliferator-activated receptors, O-linked N-acetylglucosamine, protein kinase C, microRNA, and exosome pathways. The aim of this review is to provide a contemporary view of these instigators of diabetic cardiomyopathy, as well as mechanistically based strategies for the prevention and treatment of diabetic cardiomyopathy.
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Affiliation(s)
- Guanghong Jia
- From the Diabetes and Cardiovascular Research Center (G.J., J.R.S.) and Department of Medical Pharmacology and Physiology (M.A.H., J.R.S.), University of Missouri School of Medicine, Columbia; Dalton Cardiovascular Research Center, University of Missouri, Columbia (M.A.H., J.R.S.); and Research Service, Truman Memorial Veterans Hospital, Columbia, MO (G.J., J.R.S.)
| | - Michael A Hill
- From the Diabetes and Cardiovascular Research Center (G.J., J.R.S.) and Department of Medical Pharmacology and Physiology (M.A.H., J.R.S.), University of Missouri School of Medicine, Columbia; Dalton Cardiovascular Research Center, University of Missouri, Columbia (M.A.H., J.R.S.); and Research Service, Truman Memorial Veterans Hospital, Columbia, MO (G.J., J.R.S.)
| | - James R Sowers
- From the Diabetes and Cardiovascular Research Center (G.J., J.R.S.) and Department of Medical Pharmacology and Physiology (M.A.H., J.R.S.), University of Missouri School of Medicine, Columbia; Dalton Cardiovascular Research Center, University of Missouri, Columbia (M.A.H., J.R.S.); and Research Service, Truman Memorial Veterans Hospital, Columbia, MO (G.J., J.R.S.).
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Bensellam M, Jonas JC, Laybutt DR. Mechanisms of β-cell dedifferentiation in diabetes: recent findings and future research directions. J Endocrinol 2018; 236:R109-R143. [PMID: 29203573 DOI: 10.1530/joe-17-0516] [Citation(s) in RCA: 149] [Impact Index Per Article: 24.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/13/2017] [Accepted: 12/04/2017] [Indexed: 12/13/2022]
Abstract
Like all the cells of an organism, pancreatic β-cells originate from embryonic stem cells through a complex cellular process termed differentiation. Differentiation involves the coordinated and tightly controlled activation/repression of specific effectors and gene clusters in a time-dependent fashion thereby giving rise to particular morphological and functional cellular features. Interestingly, cellular differentiation is not a unidirectional process. Indeed, growing evidence suggests that under certain conditions, mature β-cells can lose, to various degrees, their differentiated phenotype and cellular identity and regress to a less differentiated or a precursor-like state. This concept is termed dedifferentiation and has been proposed, besides cell death, as a contributing factor to the loss of functional β-cell mass in diabetes. β-cell dedifferentiation involves: (1) the downregulation of β-cell-enriched genes, including key transcription factors, insulin, glucose metabolism genes, protein processing and secretory pathway genes; (2) the concomitant upregulation of genes suppressed or expressed at very low levels in normal β-cells, the β-cell forbidden genes; and (3) the likely upregulation of progenitor cell genes. These alterations lead to phenotypic reconfiguration of β-cells and ultimately defective insulin secretion. While the major role of glucotoxicity in β-cell dedifferentiation is well established, the precise mechanisms involved are still under investigation. This review highlights the identified molecular mechanisms implicated in β-cell dedifferentiation including oxidative stress, endoplasmic reticulum (ER) stress, inflammation and hypoxia. It discusses the role of Foxo1, Myc and inhibitor of differentiation proteins and underscores the emerging role of non-coding RNAs. Finally, it proposes a novel hypothesis of β-cell dedifferentiation as a potential adaptive mechanism to escape cell death under stress conditions.
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Affiliation(s)
- Mohammed Bensellam
- Garvan Institute of Medical ResearchSydney, New South Wales, Australia
- Université Catholique de LouvainInstitut de Recherche Expérimentale et Clinique, Pôle d'Endocrinologie, Diabète et Nutrition, Brussels, Belgium
| | - Jean-Christophe Jonas
- Université Catholique de LouvainInstitut de Recherche Expérimentale et Clinique, Pôle d'Endocrinologie, Diabète et Nutrition, Brussels, Belgium
| | - D Ross Laybutt
- Garvan Institute of Medical ResearchSydney, New South Wales, Australia
- St Vincent's Clinical SchoolUNSW Sydney, Sydney, New South Wales, Australia
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8
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Eliasson L. The small RNA miR-375 - a pancreatic islet abundant miRNA with multiple roles in endocrine beta cell function. Mol Cell Endocrinol 2017; 456:95-101. [PMID: 28254488 DOI: 10.1016/j.mce.2017.02.043] [Citation(s) in RCA: 61] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/13/2017] [Revised: 02/20/2017] [Accepted: 02/26/2017] [Indexed: 12/21/2022]
Abstract
The pathophysiology of diabetes is complex and recent research put focus on the pancreatic islets of Langerhans and the insulin-secreting beta cells as central in the development of the disease. MicroRNAs (miRNAs), the small non-coding RNAs regulating post-transcriptional gene expression, are significant regulators of beta cell function. One of the most abundant miRNAs in the islets is miR-375. This review focus on the role of miR-375 in beta cell function, including effects in development and differentiation, proliferation and regulation of insulin secretion. It also discusses the regulation of miR-375 expression, miR-375 as a potential circulating biomarker in type 1 and type 2 diabetes, and the need for the beta cell to keep expression of miR-375 within optimal levels. The summed picture of miR-375 is a miRNA with multiple functions with importance in the formation of beta cell identity, control of beta cell mass and regulation of insulin secretion.
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Affiliation(s)
- Lena Eliasson
- Unit of Islet Cell Exocytosis, Lund University Diabetes Centre, Department of Clinical Sciences in Malmö, Lund University, CRC, SUS Malmö, Malmö, Sweden.
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Barbati SA, Colussi C, Bacci L, Aiello A, Re A, Stigliano E, Isidori AM, Grassi C, Pontecorvi A, Farsetti A, Gaetano C, Nanni S. Transcription Factor CREM Mediates High Glucose Response in Cardiomyocytes and in a Male Mouse Model of Prolonged Hyperglycemia. Endocrinology 2017; 158:2391-2405. [PMID: 28368536 DOI: 10.1210/en.2016-1960] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/22/2016] [Accepted: 03/16/2017] [Indexed: 01/31/2023]
Abstract
This study aims at investigating the epigenetic landscape of cardiomyocytes exposed to elevated glucose levels. High glucose (30 mM) for 72 hours determined some epigenetic changes in mouse HL-1 and rat differentiated H9C2 cardiomyocytes including upregulation of class I and III histone deacetylase protein levels and activity, inhibition of histone acetylase p300 activity, increase in histone H3 lysine 27 trimethylation, and reduction in H3 lysine 9 acetylation. Gene expression analysis focused on cardiotoxicity revealed that high glucose induced markers associated with tissue damage, fibrosis, and cardiac remodeling such as Nexilin (NEXN), versican, cyclic adenosine 5'-monophosphate-responsive element modulator (CREM), and adrenoceptor α2A (ADRA2). Notably, the transcription factor CREM was found to be important in the regulation of cardiotoxicity-associated genes as assessed by specific small interfering RNA and chromatin immunoprecipitation experiments. In CD1 mice, made hyperglycemic by streptozotoicin (STZ) injection, cardiac structural alterations were evident at 6 months after STZ treatment and were associated with a significant increase of H3 lysine 27 trimethylation and reduction of H3 lysine 9 acetylation. Consistently, NEXN, CREM, and ADRA2 expression was significantly induced at the RNA and protein levels. Confocal microscopy analysis of NEXN localization showed this protein irregularly distributed along the sarcomeres in the heart of hyperglycemic mice. This evidence suggested a structural alteration of cardiac Z-disk with potential consequences on contractility. In conclusion, high glucose may alter the epigenetic landscape of cardiac cells. Sildenafil, restoring guanosine 3', 5'-cyclic monophosphate levels, counteracted the increase of CREM and NEXN, providing a protective effect in the presence of hyperglycemia.
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Affiliation(s)
- Saviana A Barbati
- Institute of Human Physiology, Università Cattolica di Roma, 00168 Rome, Italy
- Institute of Medical Pathology, Università Cattolica di Roma, 00168 Rome, Italy
| | - Claudia Colussi
- Institute of Medical Pathology, Università Cattolica di Roma, 00168 Rome, Italy
- Institute of Cell Biology and Neurobiology, National Research Council, 00143 Rome, Italy
| | - Lorenza Bacci
- Institute of Medical Pathology, Università Cattolica di Roma, 00168 Rome, Italy
| | - Aurora Aiello
- Institute of Medical Pathology, Università Cattolica di Roma, 00168 Rome, Italy
- Institute of Cell Biology and Neurobiology, National Research Council, 00143 Rome, Italy
| | - Agnese Re
- Institute of Cell Biology and Neurobiology, National Research Council, 00143 Rome, Italy
| | - Egidio Stigliano
- Department of Histopathology, Università Cattolica di Roma, 00168 Rome, Italy
| | - Andrea M Isidori
- Department of Experimental Medicine, "Sapienza" University, 00161 Rome, Italy
| | - Claudio Grassi
- Institute of Human Physiology, Università Cattolica di Roma, 00168 Rome, Italy
| | - Alfredo Pontecorvi
- Institute of Medical Pathology, Università Cattolica di Roma, 00168 Rome, Italy
| | - Antonella Farsetti
- Institute of Cell Biology and Neurobiology, National Research Council, 00143 Rome, Italy
- Medicine Clinic III, Goethe University Frankfurt, 60590 Frankfurt am Main, Germany
| | - Carlo Gaetano
- Medicine Clinic III, Division of Cardiovascular Epigenetics, Goethe University Frankfurt, 60590 Frankfurt am Main, Germany
| | - Simona Nanni
- Institute of Medical Pathology, Università Cattolica di Roma, 00168 Rome, Italy
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Brajkovic S, Ferdaoussi M, Pawlowski V, Ezanno H, Plaisance V, Zmuda E, Hai T, Annicotte JS, Waeber G, Abderrahmani A. Islet Brain 1 Protects Insulin Producing Cells against Lipotoxicity. J Diabetes Res 2016; 2016:9158562. [PMID: 26665154 PMCID: PMC4655268 DOI: 10.1155/2016/9158562] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/06/2015] [Accepted: 03/06/2015] [Indexed: 01/09/2023] Open
Abstract
Chronic intake of saturated free fatty acids is associated with diabetes and may contribute to the impairment of functional beta cell mass. Mitogen activated protein kinase 8 interacting protein 1 also called islet brain 1 (IB1) is a candidate gene for diabetes that is required for beta cell survival and glucose-induced insulin secretion (GSIS). In this study we investigated whether IB1 expression is required for preserving beta cell survival and function in response to palmitate. Chronic exposure of MIN6 and isolated rat islets cells to palmitate led to reduction of the IB1 mRNA and protein content. Diminution of IB1 mRNA and protein level relied on the inducible cAMP early repressor activity and proteasome-mediated degradation, respectively. Suppression of IB1 level mimicked the harmful effects of palmitate on the beta cell survival and GSIS. Conversely, ectopic expression of IB1 counteracted the deleterious effects of palmitate on the beta cell survival and insulin secretion. These findings highlight the importance in preserving the IB1 content for protecting beta cell against lipotoxicity in diabetes.
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Affiliation(s)
- Saška Brajkovic
- Service of Internal Medicine, Centre Hospitalier Universitaire Vaudois and University of Lausanne, 1011 Lausanne, Switzerland
- University of Lille, European Genomic Institute for Diabetes (EGID) FR 3508, UMR CNRS 8199, Faculty of Medicine West, 1 place de Verdun, 59045 Lille, France
| | - Mourad Ferdaoussi
- Service of Internal Medicine, Centre Hospitalier Universitaire Vaudois and University of Lausanne, 1011 Lausanne, Switzerland
- University of Lille, European Genomic Institute for Diabetes (EGID) FR 3508, UMR CNRS 8199, Faculty of Medicine West, 1 place de Verdun, 59045 Lille, France
- Department of Pharmacology and the Alberta Diabetes Institute, University of Alberta, Edmonton, AB, Canada
| | - Valérie Pawlowski
- University of Lille, European Genomic Institute for Diabetes (EGID) FR 3508, UMR CNRS 8199, Faculty of Medicine West, 1 place de Verdun, 59045 Lille, France
- University of Lille, EGID FR 3508, Department of Endocrine Surgery, Lille University Hospital, UMR INSERM 1190, Lille, France
| | - Hélène Ezanno
- University of Lille, European Genomic Institute for Diabetes (EGID) FR 3508, UMR CNRS 8199, Faculty of Medicine West, 1 place de Verdun, 59045 Lille, France
| | - Valérie Plaisance
- University of Lille, European Genomic Institute for Diabetes (EGID) FR 3508, UMR CNRS 8199, Faculty of Medicine West, 1 place de Verdun, 59045 Lille, France
| | - Erik Zmuda
- Department of Molecular and Cellular Biochemistry, Ohio State University, 1060 Carmack Road, Columbus, OH, USA
| | - Tsonwin Hai
- Department of Molecular and Cellular Biochemistry, Ohio State University, 1060 Carmack Road, Columbus, OH, USA
| | - Jean-Sébastien Annicotte
- University of Lille, European Genomic Institute for Diabetes (EGID) FR 3508, UMR CNRS 8199, Faculty of Medicine West, 1 place de Verdun, 59045 Lille, France
| | - Gérard Waeber
- Service of Internal Medicine, Centre Hospitalier Universitaire Vaudois and University of Lausanne, 1011 Lausanne, Switzerland
| | - Amar Abderrahmani
- University of Lille, European Genomic Institute for Diabetes (EGID) FR 3508, UMR CNRS 8199, Faculty of Medicine West, 1 place de Verdun, 59045 Lille, France
- *Amar Abderrahmani:
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Ljubicic S, Bezzi P, Brajkovic S, Nesca V, Guay C, Ohbayashi N, Fukuda M, Abderrhamani A, Regazzi R. The GTPase Rab37 Participates in the Control of Insulin Exocytosis. PLoS One 2013; 8:e68255. [PMID: 23826383 PMCID: PMC3694898 DOI: 10.1371/journal.pone.0068255] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2013] [Accepted: 05/27/2013] [Indexed: 01/04/2023] Open
Abstract
Rab37 belongs to a subclass of Rab GTPases regulating exocytosis, including also Rab3a and Rab27a. Proteomic studies indicate that Rab37 is associated with insulin-containing large dense core granules of pancreatic β-cells. In agreement with these observations, we detected Rab37 in extracts of β-cell lines and human pancreatic islets and confirmed by confocal microscopy the localization of the GTPase on insulin-containing secretory granules. We found that, as is the case for Rab3a and Rab27a, reduction of Rab37 levels by RNA interference leads to impairment in glucose-induced insulin secretion and to a decrease in the number of granules in close apposition to the plasma membrane. Pull-down experiments revealed that, despite similar functional effects, Rab37 does not interact with known Rab3a or Rab27a effectors and is likely to operate through a different mechanism. Exposure of insulin-secreting cells to proinflammatory cytokines, fatty acids or oxidized low-density lipoproteins, mimicking physiopathological conditions that favor the development of diabetes, resulted in a decrease in Rab37 expression. Our data identify Rab37 as an additional component of the machinery governing exocytosis of β-cells and suggest that impaired expression of this GTPase may contribute to defective insulin release in pre-diabetic and diabetic conditions.
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Affiliation(s)
- Sanda Ljubicic
- Department of Fundamental Neurosciences, University of Lausanne, Lausanne, Switzerland
| | - Paola Bezzi
- Department of Fundamental Neurosciences, University of Lausanne, Lausanne, Switzerland
| | - Saska Brajkovic
- EGID FR 3508, INSERM U859, Université de Lille 2, Lille, France
| | - Valeria Nesca
- Department of Fundamental Neurosciences, University of Lausanne, Lausanne, Switzerland
| | - Claudiane Guay
- Department of Fundamental Neurosciences, University of Lausanne, Lausanne, Switzerland
| | - Norihiko Ohbayashi
- Laboratory of Membrane Trafficking Mechanisms, Department of Developmental Biology and Neurosciences, Graduate School of Life Sciences, Tohoku University, Sendai, Japan
| | - Mitsunori Fukuda
- Laboratory of Membrane Trafficking Mechanisms, Department of Developmental Biology and Neurosciences, Graduate School of Life Sciences, Tohoku University, Sendai, Japan
| | | | - Romano Regazzi
- Department of Fundamental Neurosciences, University of Lausanne, Lausanne, Switzerland
- * E-mail:
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12
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Lee YS, Morinaga H, Kim JJ, Lagakos W, Taylor S, Keshwani M, Perkins G, Dong H, Kayali AG, Sweet IR, Olefsky J. The fractalkine/CX3CR1 system regulates β cell function and insulin secretion. Cell 2013; 153:413-25. [PMID: 23582329 DOI: 10.1016/j.cell.2013.03.001] [Citation(s) in RCA: 103] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2012] [Revised: 10/31/2012] [Accepted: 02/25/2013] [Indexed: 02/06/2023]
Abstract
Here, we demonstrate that the fractalkine (FKN)/CX3CR1 system represents a regulatory mechanism for pancreatic islet β cell function and insulin secretion. CX3CR1 knockout (KO) mice exhibited a marked defect in glucose and GLP1-stimulated insulin secretion, and this defect was also observed in vitro in isolated islets from CX3CR1 KO mice. In vivo administration of FKN improved glucose tolerance with an increase in insulin secretion. In vitro treatment of islets with FKN increased intracellular Ca(2+) and potentiated insulin secretion in both mouse and human islets. The KO islets exhibited reduced expression of a set of genes necessary for the fully functional, differentiated β cell state, whereas treatment of wild-type (WT) islets with FKN led to increased expression of these genes. Lastly, expression of FKN in islets was decreased by aging and high-fat diet/obesity, suggesting that decreased FKN/CX3CR1 signaling could be a mechanism underlying β cell dysfunction in type 2 diabetes.
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Affiliation(s)
- Yun Sok Lee
- Department of Medicine, Division of Endocrinology and Metabolism, University of California, San Diego, La Jolla, CA 92093, USA
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13
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Haefliger JA, Rohner-Jeanrenaud F, Caille D, Charollais A, Meda P, Allagnat F. Hyperglycemia downregulates Connexin36 in pancreatic islets via the upregulation of ICER-1/ICER-1γ. J Mol Endocrinol 2013; 51:49-58. [PMID: 23613279 DOI: 10.1530/jme-13-0054] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Channels formed by the gap junction protein Connexin36 (CX36) contribute to the proper control of insulin secretion. We previously demonstrated that chronic exposure to glucose decreases Cx36 levels in insulin-secreting cells in vitro. Here, we investigated whether hyperglycemia also regulates Cx36 in vivo. Using a model of continuous glucose infusion in adult rats, we showed that prolonged (24-48 h) hyperglycemia reduced the Cx36 gene Gjd2 mRNA levels in pancreatic islets. Accordingly, prolonged exposure to high glucose concentrations also reduced the expression and function of Cx36 in the rat insulin-producing INS-1E cell line. The glucose effect was blocked after inhibition of the cAMP/PKA pathway and was associated with an overexpression of the inducible cAMP early repressor ICER-1/ICER-1γ, which binds to a functional cAMP-response element in the promoter of the Cx36 gene Gjd2. The involvement of this repressor was further demonstrated using an antisense strategy of ICER-1 inhibition, which prevented glucose-induced downregulation of Cx36. The data indicate that chronic exposure to glucose alters the in vivo expression of Cx36 by the insulin-producing β-cells through ICER-1/ICER-1γ overexpression. This mechanism may contribute to the reduced glucose sensitivity and altered insulin secretion, which contribute to the pathophysiology of diabetes.
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Affiliation(s)
- Jacques-Antoine Haefliger
- Service of Internal Medicine, Department of Physiology, University Hospital Lausanne, Lausanne, Switzerland
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14
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Bensellam M, Laybutt DR, Jonas JC. The molecular mechanisms of pancreatic β-cell glucotoxicity: recent findings and future research directions. Mol Cell Endocrinol 2012; 364:1-27. [PMID: 22885162 DOI: 10.1016/j.mce.2012.08.003] [Citation(s) in RCA: 206] [Impact Index Per Article: 17.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/30/2012] [Revised: 07/11/2012] [Accepted: 08/01/2012] [Indexed: 02/06/2023]
Abstract
It is well established that regular physiological stimulation by glucose plays a crucial role in the maintenance of the β-cell differentiated phenotype. In contrast, prolonged or repeated exposure to elevated glucose concentrations both in vitro and in vivo exerts deleterious or toxic effects on the β-cell phenotype, a concept termed as glucotoxicity. Evidence indicates that the latter may greatly contribute to the pathogenesis of type 2 diabetes. Through the activation of several mechanisms and signaling pathways, high glucose levels exert deleterious effects on β-cell function and survival and thereby, lead to the worsening of the disease over time. While the role of high glucose-induced β-cell overstimulation, oxidative stress, excessive Unfolded Protein Response (UPR) activation, and loss of differentiation in the alteration of the β-cell phenotype is well ascertained, at least in vitro and in animal models of type 2 diabetes, the role of other mechanisms such as inflammation, O-GlcNacylation, PKC activation, and amyloidogenesis requires further confirmation. On the other hand, protein glycation is an emerging mechanism that may play an important role in the glucotoxic deterioration of the β-cell phenotype. Finally, our recent evidence suggests that hypoxia may also be a new mechanism of β-cell glucotoxicity. Deciphering these molecular mechanisms of β-cell glucotoxicity is a mandatory first step toward the development of therapeutic strategies to protect β-cells and improve the functional β-cell mass in type 2 diabetes.
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Affiliation(s)
- Mohammed Bensellam
- Université catholique de Louvain, Institut de recherche expérimentale et clinique, Pôle d'endocrinologie, diabète et nutrition, Brussels, Belgium
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15
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Keller DM, Clark EA, Goodman RH. Regulation of microRNA-375 by cAMP in pancreatic β-cells. Mol Endocrinol 2012; 26:989-99. [PMID: 22539037 DOI: 10.1210/me.2011-1205] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
MicroRNA-375 (miR-375) is necessary for proper formation of pancreatic islets in vertebrates and is necessary for the development of β-cells in mice, but regulation of miR-375 in these cells is poorly understood. Here, we show that miR-375 is transcriptionally repressed by the cAMP-protein kinase A (PKA) pathway and that this repression is mediated through a block in RNA polymerase II binding to the miR-375 promoter. cAMP analogs that are PKA selective repress miR-375, as do cAMP agonists and the glucagon-like peptide-1 receptor agonist, exendin-4. Repression of the miR-375 precursor occurs rapidly in rat insulinoma INS-1 832/13 cells, within 15 min after cAMP stimulation, although the mature microRNA declines more slowly due to the kinetics of RNA processing. Repression of miR-375 in isolated rat islets by exendin-4 also occurs slowly, after several hours of stimulation. Glucose is another reported antagonist of miR-375 expression, although we demonstrate here that glucose does not target the microRNA through the PKA pathway. As reported previously, miR-375 negatively regulates insulin secretion, and attenuation of miR-375 through the cAMP-PKA pathway may boost the insulin response in pancreatic β-cells.
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Affiliation(s)
- David M Keller
- Department of Biological Sciences, California State University, Chico, CA 95929-0515, USA.
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16
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Pasternak A, Feng Z, de Jesus R, Ye Z, He S, Dobbelaar P, Bradley S, Chicchi GG, Tsao KL, Trusca D, Eiermann GJ, Li C, Feng Y, Wu M, Shao Q, Zhang BB, Nargund R, Mills SG, Howard AD, Yang L, Zhou YP. Stimulation of Glucose-Dependent Insulin Secretion by a Potent, Selective sst3 Antagonist. ACS Med Chem Lett 2012; 3:289-93. [PMID: 24900466 PMCID: PMC4025754 DOI: 10.1021/ml200272z] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2011] [Accepted: 02/13/2012] [Indexed: 12/22/2022] Open
Abstract
This letter provides the first pharmacological proof of principle that the sst3 receptor mediates glucose-stimulated insulin secretion (GSIS) from pancreatic β-cells. To enable these studies, we identified the selective sst3 antagonist (1R,3R)-3-(5-phenyl-1H-imidazol-2-yl)-1-(tetrahydro-2H-pyran-4-yl)-2,3,4,9-tetrahydro-1H-β-carboline (5a), with improved ion channel selectivity and mouse pharmacokinetic properties as compared to previously described tetrahydro-β-carboline imidazole sst3 antagonists. We demonstrated that compound 5a enhances GSIS in pancreatic β-cells and blocks glucose excursion induced by dextrose challenge in ipGTT and OGTT models in mice. Finally, we provided strong evidence that these effects are mechanism-based in an ipGTT study, showing reduction of glucose excursion in wild-type but not sst3 knockout mice. Thus, we have shown that antagonism of sst3 represents a new mechanism with potential in treating type 2 diabetes mellitus.
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Affiliation(s)
| | - Zhe Feng
- Merck Research Laboratories, Rahway, New Jersey 07065, United States
| | - Reynalda de Jesus
- Merck Research Laboratories, Rahway, New Jersey 07065, United States
| | - Zhixiong Ye
- Merck Research Laboratories, Rahway, New Jersey 07065, United States
| | - Shuwen He
- Merck Research Laboratories, Rahway, New Jersey 07065, United States
| | - Peter Dobbelaar
- Merck Research Laboratories, Rahway, New Jersey 07065, United States
| | - Scott
A. Bradley
- Merck Research Laboratories, Rahway, New Jersey 07065, United States
| | - Gary G. Chicchi
- Merck Research Laboratories, Rahway, New Jersey 07065, United States
| | - Kwei-Lan Tsao
- Merck Research Laboratories, Rahway, New Jersey 07065, United States
| | - Dorina Trusca
- Merck Research Laboratories, Rahway, New Jersey 07065, United States
| | | | - Cai Li
- Merck Research Laboratories, Rahway, New Jersey 07065, United States
| | - Yue Feng
- Merck Research Laboratories, Rahway, New Jersey 07065, United States
| | - Margaret Wu
- Merck Research Laboratories, Rahway, New Jersey 07065, United States
| | - Qing Shao
- Merck Research Laboratories, Rahway, New Jersey 07065, United States
| | - Bei B. Zhang
- Merck Research Laboratories, Rahway, New Jersey 07065, United States
| | - Ravi Nargund
- Merck Research Laboratories, Rahway, New Jersey 07065, United States
| | - Sander G. Mills
- Merck Research Laboratories, Rahway, New Jersey 07065, United States
| | - Andrew D. Howard
- Merck Research Laboratories, Rahway, New Jersey 07065, United States
| | - Lihu Yang
- Merck Research Laboratories, Rahway, New Jersey 07065, United States
| | - Yun-Ping Zhou
- Merck Research Laboratories, Rahway, New Jersey 07065, United States
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17
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Cho IS, Jung M, Kwon KS, Moon E, Cho JH, Yoon KH, Kim JW, Lee YD, Kim SS, Suh-Kim H. Deregulation of CREB signaling pathway induced by chronic hyperglycemia downregulates NeuroD transcription. PLoS One 2012; 7:e34860. [PMID: 22509362 PMCID: PMC3318007 DOI: 10.1371/journal.pone.0034860] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2011] [Accepted: 03/08/2012] [Indexed: 01/05/2023] Open
Abstract
CREB mediates the transcriptional effects of glucose and incretin hormones in insulin-target cells and insulin-producing β-cells. Although the inhibition of CREB activity is known to decrease the β-cell mass, it is still unknown what factors inversely alter the CREB signaling pathway in β-cells. Here, we show that β-cell dysfunctions occurring in chronic hyperglycemia are not caused by simple inhibition of CREB activity but rather by the persistent activation of CREB due to decreases in protein phophatase PP2A. When freshly isolated rat pancreatic islets were chronically exposed to 25 mM (high) glucose, the PP2A activity was reduced with a concomitant increase in active pCREB. Brief challenges with 15 mM glucose or 30 µM forskolin after 2 hour fasting further increased the level of pCREB and consequently induced the persistent expression of ICER. The excessively produced ICER was sufficient to repress the transcription of NeuroD, insulin, and SUR1 genes. In contrast, when islets were grown in 5 mM (low) glucose, CREB was transiently activated in response to glucose or forskolin stimuli. Thus, ICER expression was transient and insufficient to repress those target genes. Importantly, overexpression of PP2A reversed the adverse effects of chronic hyperglycemia and successfully restored the transient activation of CREB and ICER. Conversely, depletion of PP2A with siRNA was sufficient to disrupt the negative feedback regulation of CREB and induce hyperglycemic phenotypes even under low glucose conditions. Our findings suggest that the failure of the negative feedback regulation of CREB is the primary cause for β-cell dysfunctions under conditions of pathogenic hyperglycemia, and PP2A can be a novel target for future therapies aiming to protect β-cells mass in the late transitional phase of non-insulin dependent type 2 diabetes (NIDDM).
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Affiliation(s)
- In-Su Cho
- Department of Anatomy, Ajou University, Suwon, South Korea
- Graduate Neuroscience Program, Ajou University, Suwon, South Korea
- BK21, Division of Cell Transformation and Restoration, Ajou University, Suwon, South Korea
| | - Miyoung Jung
- Department of Biological Sciences, Ajou University, Suwon, South Korea
| | - Ki-Sun Kwon
- Aging Research Center, Korea Research Institute of Bioscience and Biotechnology (KRIBB), Daejeon, South Korea
| | - Eunpyo Moon
- Department of Biological Sciences, Ajou University, Suwon, South Korea
| | - Jang-Hyeon Cho
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, Texas, United States of America
| | - Kun-Ho Yoon
- Department of Endocrinology, Catholic University, School of Medicine, Seoul, South Korea
| | - Ji-Won Kim
- Department of Endocrinology, Catholic University, School of Medicine, Seoul, South Korea
| | - Young-Don Lee
- Department of Anatomy, Ajou University, Suwon, South Korea
- Molecular Science and Technology, Ajou University, Suwon, South Korea
- Control for Cell Death Regulating Biodrug, Ajou University, Suwon, South Korea
| | - Sung-Soo Kim
- Department of Anatomy, Ajou University, Suwon, South Korea
- Control for Cell Death Regulating Biodrug, Ajou University, Suwon, South Korea
- * E-mail: (HS-K); (S-SK)
| | - Haeyoung Suh-Kim
- Department of Anatomy, Ajou University, Suwon, South Korea
- Graduate Neuroscience Program, Ajou University, Suwon, South Korea
- BK21, Division of Cell Transformation and Restoration, Ajou University, Suwon, South Korea
- * E-mail: (HS-K); (S-SK)
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18
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Futamura M, Yao J, Li X, Bergeron R, Tran JL, Zycband E, Woods J, Zhu Y, Shao Q, Maruki-Uchida H, Goto-Shimazaki H, Langdon RB, Erion MD, Eiki J, Zhou YP. Chronic treatment with a glucokinase activator delays the onset of hyperglycaemia and preserves beta cell mass in the Zucker diabetic fatty rat. Diabetologia 2012; 55:1071-80. [PMID: 22234649 DOI: 10.1007/s00125-011-2439-3] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/24/2011] [Accepted: 12/02/2011] [Indexed: 01/07/2023]
Abstract
AIMS/HYPOTHESIS Glucokinase activators (GKAs) are currently being developed as new therapies for type 2 diabetes and have been shown to enhance beta cell survival and proliferation in vitro. Here, we report the effects of chronic GKA treatment on the development of hyperglycaemia and beta cell loss in the male Zucker diabetic fatty (ZDF) rat, a model of type 2 diabetes with severe obesity. METHODS Cell protection by GKA was studied in MIN6 and INS-1 cells exposed to hydrogen peroxide. Glucose homeostasis and beta cell mass were evaluated in ZDF rats dosed for 41 days with Cpd-C (a GKA) or glipizide (a sulfonylurea) as food admixtures at doses of approximately 3 and 10 mg kg(-1) day(-1). RESULTS Incubation of MIN6 and INS-1 832/3 insulinoma cell cultures with GKA significantly reduced cell death and impairment of intracellular NADH production caused by exposure to hydrogen peroxide. Progression from prediabetes (normoglycaemia and hyperinsulinaemia) to overt diabetes (hyperglycaemia and hypoinsulinaemia) was significantly delayed in male ZDF rats by in-feed treatment with Cpd-C, but not glipizide. Glucose tolerance, tested in the fifth week of treatment, was also significantly improved by Cpd-C, as was pancreatic insulin content and beta cell area. In a limited immunohistochemical analysis, Cpd-C modestly and significantly enhanced the rate of beta cell proliferation, but not rates of beta cell apoptosis relative to untreated ZDF rats. CONCLUSIONS/INTERPRETATION These findings suggest that chronic activation of glucokinase preserves beta cell mass and delays disease in the ZDF rat, a model of insulin resistance and progressive beta cell failure.
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Affiliation(s)
- M Futamura
- Banyu Tsukuba Research Institute, Okubo, Tsukuba, Ibaraki, Japan
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19
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Favre D, Niederhauser G, Fahmi D, Plaisance V, Brajkovic S, Beeler N, Allagnat F, Haefliger JA, Regazzi R, Waeber G, Abderrahmani A. Role for inducible cAMP early repressor in promoting pancreatic beta cell dysfunction evoked by oxidative stress in human and rat islets. Diabetologia 2011; 54:2337-46. [PMID: 21547497 PMCID: PMC3149674 DOI: 10.1007/s00125-011-2165-x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/15/2010] [Accepted: 04/01/2011] [Indexed: 02/03/2023]
Abstract
AIMS/HYPOTHESIS Pro-atherogenic and pro-oxidant, oxidised LDL trigger adverse effects on pancreatic beta cells, possibly contributing to diabetes progression. Because oxidised LDL diminish the expression of genes regulated by the inducible cAMP early repressor (ICER), we investigated the involvement of this transcription factor and of oxidative stress in beta cell failure elicited by oxidised LDL. METHODS Isolated human and rat islets, and insulin-secreting cells were cultured with human native or oxidised LDL or with hydrogen peroxide. The expression of genes was determined by quantitative real-time PCR and western blotting. Insulin secretion was monitored by EIA kit. Cell apoptosis was determined by scoring cells displaying pycnotic nuclei. RESULTS Exposure of beta cell lines and islets to oxidised LDL, but not to native LDL raised the abundance of ICER. Induction of this repressor by the modified LDL compromised the expression of important beta cell genes, including insulin and anti-apoptotic islet brain 1, as well as of genes coding for key components of the secretory machinery. This led to hampering of insulin production and secretion, and of cell survival. Silencing of this transcription factor by RNA interference restored the expression of its target genes and alleviated beta cell dysfunction and death triggered by oxidised LDL. Induction of ICER was stimulated by oxidative stress, whereas antioxidant treatment with N-acetylcysteine or HDL prevented the rise of ICER elicited by oxidised LDL and restored beta cell functions. CONCLUSIONS/INTERPRETATION Induction of ICER links oxidative stress to beta cell failure caused by oxidised LDL and can be effectively abrogated by antioxidant treatment.
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Affiliation(s)
- D. Favre
- Service of Internal Medicine, CHUV-Hospital, Lausanne, Switzerland
- Department of Cell Biology and Morphology, University of Lausanne, Rue du Bugnon 9, 1005 Lausanne, Switzerland
| | - G. Niederhauser
- Service of Internal Medicine, CHUV-Hospital, Lausanne, Switzerland
- Department of Cell Biology and Morphology, University of Lausanne, Rue du Bugnon 9, 1005 Lausanne, Switzerland
| | - D. Fahmi
- Service of Internal Medicine, CHUV-Hospital, Lausanne, Switzerland
- Department of Cell Biology and Morphology, University of Lausanne, Rue du Bugnon 9, 1005 Lausanne, Switzerland
| | - V. Plaisance
- Service of Internal Medicine, CHUV-Hospital, Lausanne, Switzerland
- Department of Cell Biology and Morphology, University of Lausanne, Rue du Bugnon 9, 1005 Lausanne, Switzerland
| | - S. Brajkovic
- Service of Internal Medicine, CHUV-Hospital, Lausanne, Switzerland
- Department of Cell Biology and Morphology, University of Lausanne, Rue du Bugnon 9, 1005 Lausanne, Switzerland
| | - N. Beeler
- Service of Internal Medicine, CHUV-Hospital, Lausanne, Switzerland
- Department of Cell Biology and Morphology, University of Lausanne, Rue du Bugnon 9, 1005 Lausanne, Switzerland
| | - F. Allagnat
- Service of Internal Medicine, CHUV-Hospital, Lausanne, Switzerland
| | - J. A. Haefliger
- Service of Internal Medicine, CHUV-Hospital, Lausanne, Switzerland
| | - R. Regazzi
- Department of Cell Biology and Morphology, University of Lausanne, Rue du Bugnon 9, 1005 Lausanne, Switzerland
| | - G. Waeber
- Service of Internal Medicine, CHUV-Hospital, Lausanne, Switzerland
| | - A. Abderrahmani
- Service of Internal Medicine, CHUV-Hospital, Lausanne, Switzerland
- Department of Cell Biology and Morphology, University of Lausanne, Rue du Bugnon 9, 1005 Lausanne, Switzerland
- CNRS-UMR-8199, Université Lille Nord de France, UDSL, Lille, France
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20
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Kim SK, Kim NK, Yoon DH, Kim TH, Yang BK, Lee HJ. Gene Expression of Candidate Genes Involved in Fat Metabolism During In vitro Adipogenic Differentiation of Bovine Mesenchymal Stem Cell. JOURNAL OF ANIMAL SCIENCE AND TECHNOLOGY 2010. [DOI: 10.5187/jast.2010.52.4.265] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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21
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El-Assaad W, Joly E, Barbeau A, Sladek R, Buteau J, Maestre I, Pepin E, Zhao S, Iglesias J, Roche E, Prentki M. Glucolipotoxicity alters lipid partitioning and causes mitochondrial dysfunction, cholesterol, and ceramide deposition and reactive oxygen species production in INS832/13 ss-cells. Endocrinology 2010; 151:3061-73. [PMID: 20444946 DOI: 10.1210/en.2009-1238] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Elevated glucose and saturated fatty acids synergize in inducing apoptosis in INS832/13 cells and in human islet cells. In order to gain insight into the molecular mechanism(s) of glucolipotoxicity (Gltox), gene profiling and metabolic analyses were performed in INS832/13 cells cultured at 5 or 20 mm glucose in the absence or presence of palmitate. Expression changes were observed for transcripts involved in mitochondrial, lipid, and glucose metabolism. At 24 h after Gltox, increased expression of lipid partitioning genes suggested a promotion of fatty acid esterification and reduced lipid oxidation/detoxification, whereas changes in the expression of energy metabolism genes suggested mitochondrial dysfunction. These changes were associated with decreased glucose-induced insulin secretion, total insulin content, ATP levels, AMP-kinase activity, mitochondrial membrane potential and fat oxidation, unchanged de novo fatty acid synthesis, and increased reactive oxygen species, cholesterol, ceramide, and triglyceride levels. However, the synergy between elevated glucose and palmitate to cause ss-cell toxicity in term of apoptosis and reduced glucose-induced insulin secretion only correlated with triglyceride and ceramide depositions. Overexpression of endoplasmic reticulum glycerol-3-phosphate acyl transferase to enhance lipid esterification amplified Gltox at intermediate glucose (11 mm), whereas reducing acetyl-coenzyme A carboxylase 1 expression by small interfering RNA to shift lipid partitioning to fat oxidation reduced Gltox. The results suggest that Gltox entails alterations in lipid partitioning, sterol and ceramide accumulation, mitochondrial dysfunction, and reactive oxygen species production, all contributing to altering ss-cell function. The data also suggest that the early promotion of lipid esterification processes is instrumental in the Gltox process.
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Affiliation(s)
- Wissal El-Assaad
- Molecular Nutrition Unit and the Montreal Diabetes Research Center, the Centre de Recherche du Centre Hospitalier de l'Université de Montréal, Montreal, Quebec, Canada H1W 4A4
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22
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Martens GA, Pipeleers D. Glucose, regulator of survival and phenotype of pancreatic beta cells. VITAMINS AND HORMONES 2009; 80:507-39. [PMID: 19251048 DOI: 10.1016/s0083-6729(08)00617-1] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
The key role of glucose in regulating insulin release by the pancreatic beta cell population is not only dependent on acute stimulus-secretion coupling mechanisms but also on more long-term influences on beta cell survival and phenotype. Glucose serves as a major survival factor for beta cells via at least three actions: it prevents an oxidative redox state, it suppresses a mitochondrial apoptotic program that is triggered at reduced mitochondrial metabolic activity and it induces genes needed for the cellular responsiveness to glucose and to growth factors. Glucose-regulated pathways may link protein synthetic and proliferative activities, making glucose a permissive factor for beta cell proliferation, in check with metabolic needs. Conditions of inadequate glucose metabolism in beta cells are not only leading to deregulation of acute secretory responses but should also be considered as causes for increased apoptosis and reduced formation of beta cells, and loss of their normal differentiated state.
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23
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Plaisance V, Perret V, Favre D, Abderrahmani A, Yang JY, Widmann C, Regazzi R. Role of the transcriptional factor C/EBPbeta in free fatty acid-elicited beta-cell failure. Mol Cell Endocrinol 2009; 305:47-55. [PMID: 19133313 DOI: 10.1016/j.mce.2008.12.005] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/04/2008] [Accepted: 12/04/2008] [Indexed: 01/09/2023]
Abstract
Fatty acids can favour the development of Type 2 diabetes by reducing insulin secretion and inducing apoptosis of pancreatic beta-cells. Here, we show that sustained exposure of the beta-cell line MIN6 or of isolated pancreatic islets to the most abundant circulating fatty acid palmitate increases the level of C/EBPbeta, an insulin transcriptional repressor. In contrast, two unsaturated fatty acids, oleate and linoleate were without effect. The induction of C/EBPbeta elicited by palmitate was prevented by inhibiting the ERK1/2 MAP kinase pathway or by reducing mitochondrial fatty acid oxidation with an inhibitor of Carnitine Palmitoyl Transferase-1. Overexpression of C/EBPbeta mimicked the detrimental effects of palmitate and resulted in a drastic reduction in insulin promoter activity, impairment in the capacity to respond to secretory stimuli and an increase in apoptosis. Our data suggest a potential involvement of C/EBPbeta as mediator of the deleterious effects of unsaturated free fatty acids on beta-cell function.
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Affiliation(s)
- Valérie Plaisance
- Department of Cell Biology and Morphology, Faculty of Biology and Medicine, University of Lausanne, Rue du Bugnon 9, 1005 Lausanne, Switzerland
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24
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Bensellam M, Van Lommel L, Overbergh L, Schuit FC, Jonas JC. Cluster analysis of rat pancreatic islet gene mRNA levels after culture in low-, intermediate- and high-glucose concentrations. Diabetologia 2009; 52:463-76. [PMID: 19165461 DOI: 10.1007/s00125-008-1245-z] [Citation(s) in RCA: 84] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/06/2008] [Accepted: 11/19/2008] [Indexed: 10/21/2022]
Abstract
AIMS/HYPOTHESIS Survival and function of insulin-secreting pancreatic beta cells are markedly altered by changes in nutrient availability. In vitro, culture in 10 rather than 2 mmol/l glucose improves rodent beta cell survival and function, whereas glucose concentrations above 10 mmol/l are deleterious. METHODS To identify the mechanisms of such beta cell plasticity, we tested the effects of 18 h culture at 2, 5, 10 and 30 mmol/l glucose on the transcriptome of rat islets pre-cultured for 1 week at 10 mmol/l glucose using Affymetrix Rat 230 2.0 arrays. RESULTS Culture in either 2-5 or 30 mmol/l instead of 10 mmol/l glucose markedly impaired beta cell function, while little affecting cell survival. Of about 16,000 probe-sets reliably detected in islets, some 5,000 were significantly up- or downregulated at least 1.4-fold by glucose. Analysis of these probe-sets with GeneCluster software identified ten mRNA profiles with unidirectional up- or downregulation between 2 and 10, 2 and 30, 5 and 10, 5 and 30 or 10 and 30 mmol/l glucose. It also identified eight complex V-shaped or inverse V-shaped profiles with a nadir or peak level of expression in 5 or 10 mmol/l glucose. Analysis of genes belonging to these various clusters using Onto-express and GenMAPP software revealed several signalling and metabolic pathways that may contribute to induction of beta cell dysfunction and apoptosis after culture in low- or high- vs intermediate-glucose concentration. CONCLUSIONS/INTERPRETATION We have identified 18 distinct mRNA profiles of glucose-induced changes in islet gene mRNA levels that should help understand the mechanisms by which glucose affects beta cell survival and function under states of chronic hypo- or hyperglycaemia.
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Affiliation(s)
- M Bensellam
- Unit of Endocrinology and Metabolism, Faculty of Medicine, Université catholique de Louvain, Avenue Hippocrate 55 (UCL5530), 1200, Brussels, Belgium
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Kirino Y, Sato Y, Kamimoto T, Kawazoe K, Minakuchi K, Nakahori Y. Interrelationship of dipeptidyl peptidase IV (DPP4) with the development of diabetes, dyslipidaemia and nephropathy: a streptozotocin-induced model using wild-type and DPP4-deficient rats. J Endocrinol 2009; 200:53-61. [PMID: 18931022 DOI: 10.1677/joe-08-0424] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
We examined the role of dipeptidyl peptidase IV (DPP4) in the development of diabetes, dyslipidaemia and renal dysfunction induced by streptozotocin (STZ). F344/DuCrlCrlj rats, which lack DPP4 activity, and wild-type rats were treated with STZ. Plasma DPP4 activity and biochemical parameters were measured until 42 days after STZ treatment. At the end of the experiment, renal function and DPP4 expressions of the kidney, liver, pancreas and adipose tissues were determined. Increases in blood glucose, cholesterol and triglycerides were evoked by STZ in both rat strains; however, the onset of hyperglycaemia was delayed in DPP4-deficient rats as compared with wild-type rats. By contrast, more severe dyslipidaemia was observed in DPP4-deficient rats than in wild-type rats after STZ treatment. Plasma DPP4 activity increased progressively with time after STZ treatment in wild-type rats. The kidney of wild-type rats showed decreased DPP4 activity with increased Dpp4 mRNA after STZ treatment. In addition, kidney weight, serum creatinine and excreted amounts of urinary protein, glucose and DPP4 enzyme were enhanced by STZ. DPP4-deficient rats showed increased serum creatinine in accordance with decreased creatinine clearance as compared with wild-type rats after STZ treatment. In conclusion, plasma DPP4 activity increased after STZ treatment, positively correlating to blood glucose. DPP4-deficient rats were resistant to developing diabetes, while susceptible to dyslipidaemia and reduction of glomerular filtration rate by STZ. DPP4 activation may be responsible for hyperglycaemia, lipid metabolism and preservation of renal function.
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Affiliation(s)
- Yasushi Kirino
- Department of Human Genetics and Public Health, Institute of Health Biosciences, The University of Tokushima Graduate School, The University of Tokushima, Kuramoto-Cho, Tokushima, Japan
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Pipeleers D, Chintinne M, Denys B, Martens G, Keymeulen B, Gorus F. Restoring a functional beta-cell mass in diabetes. Diabetes Obes Metab 2008; 10 Suppl 4:54-62. [PMID: 18834433 DOI: 10.1111/j.1463-1326.2008.00941.x] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Type 1 and type 2 diabetes have often been presented as disease forms that profoundly differ in the presence and pathogenic significance of a reduced beta-cell mass. We review evidence indicating that the beta-cell mass in type 1 diabetes is usually not decreased by at least 90% at clinical onset, and remains often detectable for years after diagnosis at age above 15 years. Clinical and experimental evidence also exists for a reduced beta-cell mass in type 2 diabetes where it can be the cause for and/or the consequence of dysregulated beta-cell functions. With beta-cell mass defined as number of beta-cells, these views face the limitation of insufficient data and methods for human organs. Because beta-cells can occur under different phenotypes that vary with age and with environmental conditions, we propose to use the term functional beta-cell mass as an assessment of a beta-cell population by the number of beta-cells and their phenotype or functional state. Assays exist to measure functional beta-cell mass in isolated preparations. We selected a glucose-clamp test to evaluate functional beta-cell mass in type 1 patients at clinical onset and in type 1 recipients following intraportal islet cell transplantation. Comparison of the data with those in non-diabetic controls helps targeting and monitoring of therapeutic interventions.
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Affiliation(s)
- D Pipeleers
- Diabetes Research Center, Brussels Free University-VUB, JDRF Center for Beta Cell Therapy in Diabetes, Brussels, Belgium.
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Higai K, Tsukada M, Moriya Y, Azuma Y, Matsumoto K. Prolonged high glucose suppresses phorbol 12-myristate 13-acetate and ionomycin-induced interleukin-2 mRNA expression in Jurkat cells. Biochim Biophys Acta Gen Subj 2008; 1790:8-15. [PMID: 18992303 DOI: 10.1016/j.bbagen.2008.10.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2008] [Revised: 09/29/2008] [Accepted: 10/03/2008] [Indexed: 01/13/2023]
Abstract
BACKGROUND The disturbance of immunological responses is a complication of diabetes mellitus. METHODS AND RESULTS We cultured Jurkat cells in 11.1 (normal) and 22.2 mmol/l (high) glucose for 12 weeks and stimulated them with 10 nmol/l phorbol 12-myristate 13-acetate (PMA) and 500 nmol/l ionomycin. RT-PCR revealed that induced interleukin (IL)-2 mRNA expression levels were suppressed in high glucose cultures compared to those in normal glucose. Promoter activities of IL-2, nuclear factor of activated T cells (NFAT), and activator protein-1 (AP-1), after 6 h stimulation with PMA and ionomycin, gradually decreased in high glucose cultures to approximately 20% of those in normal glucose at 12 weeks. The prolonged culture in high glucose increased inducible cAMP early repressor (ICER) II mRNA and protein levels, and overexpression of ICER II dose-dependently suppressed promoter activities of IL-2, NFAT, and AP-1. Moreover, ICER II mRNA expression was transiently induced by stimulation with PMA and ionomycin in normal glucose cultures; however, with high glucose, the induction disappeared. CONCLUSION These results indicate that ICER II protein accumulates during prolonged culture in high glucose and suppresses IL-2 mRNA expression in Jurkat cells.
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Affiliation(s)
- Koji Higai
- Department of Clinical Chemistry, School of Pharmaceutical Sciences, Toho University Miyama 2-2-1, Funabashi, Chiba 247-8510, Japan.
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28
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Tan CP, Feng Y, Zhou YP, Eiermann GJ, Petrov A, Zhou C, Lin S, Salituro G, Meinke P, Mosley R, Akiyama TE, Einstein M, Kumar S, Berger JP, Mills SG, Thornberry NA, Yang L, Howard AD. Selective small-molecule agonists of G protein-coupled receptor 40 promote glucose-dependent insulin secretion and reduce blood glucose in mice. Diabetes 2008; 57:2211-9. [PMID: 18477808 PMCID: PMC2494688 DOI: 10.2337/db08-0130] [Citation(s) in RCA: 145] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
OBJECTIVE Acute activation of G protein-coupled receptor 40 (GPR40) by free fatty acids (FFAs) or synthetic GPR40 agonists enhances insulin secretion. However, it is still a matter of debate whether activation of GPR40 would be beneficial for the treatment of type 2 diabetes, since chronic exposure to FFAs impairs islet function. We sought to evaluate the specific role of GPR40 in islets and its potential as a therapeutic target using compounds that specifically activate GPR40. RESEARCH DESIGN AND METHODS We developed a series of GPR40-selective small-molecule agonists and studied their acute and chronic effects on glucose-dependent insulin secretion (GDIS) in isolated islets, as well as effects on blood glucose levels during intraperitoneal glucose tolerance tests in wild-type and GPR40 knockout mice (GPR40(-/-)). RESULTS Small-molecule GPR40 agonists significantly enhanced GDIS in isolated islets and improved glucose tolerance in wild-type mice but not in GPR40(-/-) mice. While a 72-h exposure to FFAs in tissue culture significantly impaired GDIS in islets from both wild-type and GPR40(-/-) mice, similar exposure to the GPR40 agonist did not impair GDIS in islets from wild-type mice. Furthermore, the GPR40 agonist enhanced insulin secretion in perfused pancreata from neonatal streptozotocin-induced diabetic rats and improved glucose levels in mice with high-fat diet-induced obesity acutely and chronically. CONCLUSIONS GPR40 does not mediate the chronic toxic effects of FFAs on islet function. Pharmacological activation of GPR40 may potentiate GDIS in humans and be beneficial for overall glucose control in patients with type 2 diabetes.
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MESH Headings
- Animals
- Animals, Newborn
- Blood Glucose/metabolism
- CHO Cells
- Cell Line
- Cricetinae
- Cricetulus
- Diabetes Mellitus, Experimental/blood
- Diabetes Mellitus, Experimental/metabolism
- Diabetes Mellitus, Experimental/pathology
- Dietary Fats/administration & dosage
- Fatty Acids/pharmacology
- Fatty Acids, Nonesterified/pharmacology
- Female
- Humans
- In Vitro Techniques
- Inositol 1,4,5-Trisphosphate/metabolism
- Insulin/blood
- Insulin/metabolism
- Insulin Secretion
- Islets of Langerhans/drug effects
- Islets of Langerhans/metabolism
- Male
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Obesity/blood
- Obesity/etiology
- Obesity/metabolism
- Pregnancy
- Rats
- Rats, Wistar
- Receptors, G-Protein-Coupled/agonists
- Receptors, G-Protein-Coupled/genetics
- Receptors, G-Protein-Coupled/physiology
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Affiliation(s)
- Carina P Tan
- Department of Metabolic Disorders-Diabetes, Merck Research Laboratories, Rahway, New Jersey, USA
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Nino-Fong R, Collins T, Chan C. Nutrigenomics, beta-cell function and type 2 diabetes. Curr Genomics 2008; 8:1-29. [PMID: 18645625 PMCID: PMC2474685 DOI: 10.2174/138920207780076947] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2006] [Revised: 08/12/2006] [Accepted: 10/13/2006] [Indexed: 01/15/2023] Open
Abstract
INTRODUCTION The present investigation was designed to investigate the accuracy and precision of lactate measurement obtained with contemporary biosensors (Chiron Diagnostics, Nova Biomedical) and standard enzymatic photometric procedures (Sigma Diagnostics, Abbott Laboratories, Analyticon). MATERIALS AND METHODS Measurements were performed in vitro before and after the stepwise addition of 1 molar sodium lactate solution to samples of fresh frozen plasma to systematically achieve lactate concentrations of up to 20 mmol/l. RESULTS Precision of the methods investigated varied between 1% and 7%, accuracy ranged between 2% and -33% with the variability being lowest in the Sigma photometric procedure (6%) and more than 13% in both biosensor methods. CONCLUSION Biosensors for lactate measurement provide adequate accuracy in mean with the limitation of highly variable results. A true lactate value of 6 mmol/l was found to be presented between 4.4 and 7.6 mmol/l or even with higher difference. Biosensors and standard enzymatic photometric procedures are only limited comparable because the differences between paired determinations presented to be several mmol. The advantage of biosensors is the complete lack of preanalytical sample preparation which appeared to be the major limitation of standard photometry methods.
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Affiliation(s)
- R Nino-Fong
- Department of Biomedical Sciences, University of Prince Edward Island, Charlottetown, PE C1A 4P3 Canada
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Allagnat F, Alonso F, Martin D, Abderrahmani A, Waeber G, Haefliger JA. ICER-1gamma overexpression drives palmitate-mediated connexin36 down-regulation in insulin-secreting cells. J Biol Chem 2008; 283:5226-34. [PMID: 18073214 DOI: 10.1074/jbc.m708181200] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Channels formed by the gap junction protein connexin36 (Cx36) contribute to the proper control of insulin secretion. We investigated the impact of chronic hyperlipidemia on Cx36 expression in pancreatic beta-cells. Prolonged exposure to the saturated free fatty acid palmitate reduced the expression of Cx36 in several insulin-secreting cell lines and isolated mouse islets. The effect of palmitate was fully blocked upon protein kinase A (PKA) inhibition by H89 and (Rp)-cAMP, indicating that the cAMP/PKA pathway is involved in the control of Cx36 expression. Palmitate treatment led to overexpression of the inducible cAMP early repressor (ICER-1gamma), which bound to a functional cAMP-response element located in the promoter of the CX36 gene. Inhibition of ICER-1gamma overexpression prevented the Cx36 decrease, as well as the palmitate-induced beta-cell secretory dysfunction. Finally, freshly isolated islets from mice undergoing a long term high fat diet expressed reduced Cx36 levels and increased ICER-1gamma levels. Taken together, these data demonstrate that chronic exposure to palmitate inhibits the Cx36 expression through PKA-mediated ICER-1gamma overexpression. This Cx36 down-regulation may contribute to the reduced glucose sensitivity and altered insulin secretion observed during the pre-diabetic stage and in the metabolic syndrome.
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Affiliation(s)
- Florent Allagnat
- Department of Medicine, University Hospital, CHUV-1011 Lausanne, Switzerland
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31
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Dual role of proapoptotic BAD in insulin secretion and beta cell survival. Nat Med 2008; 14:144-53. [PMID: 18223655 DOI: 10.1038/nm1717] [Citation(s) in RCA: 246] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2007] [Accepted: 12/20/2007] [Indexed: 12/25/2022]
Abstract
The proapoptotic BCL-2 family member BAD resides in a glucokinase-containing complex that regulates glucose-driven mitochondrial respiration. Here, we present genetic evidence of a physiologic role for BAD in glucose-stimulated insulin secretion by beta cells. This novel function of BAD is specifically dependent upon the phosphorylation of its BH3 sequence, previously defined as an essential death domain. We highlight the pharmacologic relevance of phosphorylated BAD BH3 by using cell-permeable, hydrocarbon-stapled BAD BH3 helices that target glucokinase, restore glucose-driven mitochondrial respiration and correct the insulin secretory response in Bad-deficient islets. Our studies uncover an alternative target and function for the BAD BH3 domain and emphasize the therapeutic potential of phosphorylated BAD BH3 mimetics in selectively restoring beta cell function. Furthermore, we show that BAD regulates the physiologic adaptation of beta cell mass during high-fat feeding. Our findings provide genetic proof of the bifunctional activities of BAD in both beta cell survival and insulin secretion.
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Lee SH, Park EW, Cho YM, Kim SK, Lee JH, Jeon JT, Lee CS, Im SK, Oh SJ, Thompson JM, Yoon D. Identification of differentially expressed genes related to intramuscular fat development in the early and late fattening stages of hanwoo steers. BMB Rep 2008; 40:757-64. [PMID: 17927910 DOI: 10.5483/bmbrep.2007.40.5.757] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Marbling of cattle meat is dependent on the coordinated expression of multiple genes. Cattle dramatically increase their intramuscular fat content in the longissimus dorsi muscle between 12 and 27 months of age. We used the annealing control primer (ACP)-differential display RT-PCR method to identify differentially expressed genes (DEGs) that may participate in the development of intramuscular fat between early (12 months old) and late fattening stages (27 months old). Using 20 arbitrary ACP primers, we identified and sequenced 14 DEGs. BLAST searches revealed that expression of the MDH, PI4-K, ferritin, ICER, NID-2, WDNMI, telethonin, filamin, and desmin (DES) genes increased while that of GAPD, COP VII, ACTA1, CamK II, and nebulin decreased during the late fattening stage. The results of functional categorization using the Gene Ontology database for 14 known genes indicated that MDH, GAPD, and COP VII are involved in metabolic pathways such as glycolysis and the TCA cycle, whereas telethonin, filamin, nebulin, desmin, and ACTA1 contribute to the muscle contractile apparatus, and PI4-K, CamK II, and ICER have roles in signal transduction pathways regulated by growth factor or hormones. The final three genes, NID-2, WDNMI, and ferritin, are involved in iron transport and extracellular protein inhibition. The expression patterns were confirmed for seven genes (MDH, PI4-K, ferritin, ICER, nebulin, WDNMI, and telethonin) using real-time PCR. We found that the novel transcription repressor ICER gene was highly expressed in the late fattening stage and during bovine preadipocyte differentiation. This information may be helpful in selecting candidate genes that participate in intramuscular fat development in cattle.
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Affiliation(s)
- Seung-Hwan Lee
- Animal Genomics & Bioinformatics Division, National Livestock Research Institute, RDA, Suwon 441-305, Korea
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Inada A, Arai H, Nagai K, Miyazaki JI, Yamada Y, Seino Y, Fukatsu A. Gender difference in ICER Igamma transgenic diabetic mouse. Biosci Biotechnol Biochem 2007; 71:1920-6. [PMID: 17690470 DOI: 10.1271/bbb.70116] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Few studies have been done to examine gender differences in diabetic mouse models. Here we examined a gender difference in Inducible cAMP Early Repressor (ICER) transgenic (Tg) mice, a diabetic mouse model. Longitudinal changes in diabetes and nephropathy were investigated in male and female Tg mice. Both male and female Tg mice developed severe diabetes early in life due to severely impaired insulin synthesis and decreased beta-cell numbers, but only female Tg mice became less hyperglycemic later in life, and most female Tg mice did not develop diabetic nephropathy. Even some female Tg mice that remained hyperglycemic showed less renal expansion than age-matched male Tg mice. Thus the gender difference in the severity of diabetes and diabetic nephropathy was evident with age in this model. This study indicates that sex hormones may play a role in glucose metabolism in diabetic conditions.
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Affiliation(s)
- Akari Inada
- Department of Diabetes and Clinical Nutrition, Kyoto University Graduate School of Medicine, Kyoto, Japan
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Abstract
PURPOSE OF THE REVIEW In addition to its metabolic function, glucose modulates gene expression which is crucial in adapting cells to variations in glycaemia. We summarize recent advances in our understanding of regulation of gene expression by glucose. RECENT FINDINGS In-vivo and in-vitro experiments demonstrated that glucose regulates the transcription of genes encoding not only lipogenic and glycolytic enzymes but also proteins involved in global cell functions. The molecular mechanisms have begun to be elucidated, and the transcription factor carbohydrate responsive element-binding protein has emerged as a key actor, at least in liver. More recently, other candidates have been proposed, such as liver X receptors. In pathological situations, altered glycaemic control, as observed in diabetes mellitus, is associated with increased risk for microvascular and macrovascular complications. Recent findings suggest that changes in gene expression occurring in response to hyperglycaemia represent a novel component of glucotoxicity. SUMMARY Until recently, the direct transcriptional effects of glucose were underestimated, and insulin was considered to be the major regulator of gene expression in response to glycaemic variation. The recent discovery and characterization of transcription factors mediating the glucose response demonstrate that glucose, like fatty acids and other key nutrients, can directly control gene expression.
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Chen J, Jeppesen PB, Nordentoft I, Hermansen K. Stevioside improves pancreatic beta-cell function during glucotoxicity via regulation of acetyl-CoA carboxylase. Am J Physiol Endocrinol Metab 2007; 292:E1906-16. [PMID: 17341549 DOI: 10.1152/ajpendo.00356.2006] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Chronic hyperglycemia is detrimental to pancreatic beta-cells, causing impaired insulin secretion and beta-cell turnover. The characteristic secretory defects are increased basal insulin secretion (BIS) and a selective loss of glucose-stimulated insulin secretion (GSIS). Several recent studies support the view that the acetyl-CoA carboxylase (ACC) plays a pivotal role for GSIS. We have shown that stevioside (SVS) enhances insulin secretion and ACC gene expression. Whether glucotoxicity influences ACC and whether this action can be counteracted by SVS are not known. To investigate this, we exposed isolated mouse islets as well as clonal INS-1E beta-cells for 48 h to 27 or 16.7 mM glucose, respectively. We found that 48-h exposure to high glucose impairs GSIS from mouse islets and INS-1E cells, an effect that is partly counteracted by SVS. The ACC dephosphorylation inhibitor okadaic acid (OKA, 10(-8) M), and 5-aminoimidazole-4-carboxamide-1-beta-d-ribofuranoside (AICAR, 10(-4) M), an activator of 5'-AMP protein kinase that phosphorylates ACC, eliminated the beneficial effect of SVS. 5-Tetrade-cyloxy-2-furancarboxylic acid (TOFA), the specific ACC inhibitor, blocked the effect of SVS as well. During glucotoxity, ACC gene expression, ACC protein, and phosphorylated ACC protein were increased in INS-1E beta-cells. SVS pretreatment further increased ACC gene expression with strikingly elevated ACC activity and increased glucose uptake accompanied by enhanced GSIS. Our studies show that glucose is a potent stimulator of ACC and that SVS to some extent counteracts glucotoxicity via increased ACC activity. SVS possesses the potential to alleviate negative effects of glucotoxicity in beta-cells via a unique mechanism of action.
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Affiliation(s)
- Jianguo Chen
- Department of Endocrinology and Metabolism, C. Aarhus Sygehus THG, Aarhus University Hospital, Tage-Hansens Gade 2, DK-8000 Aarhus C, Denmark.
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Ma Z, Portwood N, Brodin D, Grill V, Björklund A. Effects of diazoxide on gene expression in rat pancreatic islets are largely linked to elevated glucose and potentially serve to enhance beta-cell sensitivity. Diabetes 2007; 56:1095-106. [PMID: 17229937 DOI: 10.2337/db06-0322] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Diazoxide enhances glucose-induced insulin secretion from beta-cells through mechanisms that are not fully elucidated. Here, we used microarray analysis (Affymetrix) to investigate effects of diazoxide. Pancreatic islets were cultured overnight at 27, 11, or 5.5 mmol/l glucose with or without diazoxide. Inclusion of diazoxide upregulated altogether 211 genes (signal log(2) ratio > or =0.5) and downregulated 200 genes (signal log(2) ratio -0.5 or lower), and 92% of diazoxide's effects (up- and downregulation) were observed only after coculture with 11 or 27 mmol/l glucose. We found that 11 mmol/l diazoxide upregulated 97 genes and downregulated 21 genes. Increasing the glucose concentration to 27 mmol/l markedly shifted these proportions toward downregulation (101 genes upregulated and 160 genes downregulated). At 27 mmol/l glucose, most genes downregulated by diazoxide were oppositely affected by glucose (80%). Diazoxide influenced expression of several genes central to beta-cell metabolism. Diazoxide downregulated genes of fatty acid oxidation, upregulated genes of fatty acid synthesis, and downregulated uncoupling protein 2 and lactic acid dehydrogenase. Diazoxide upregulated certain genes known to support beta-cell functionality, such as NKX6.1 and PDX1. Long-term elevated glucose is permissive for most of diazoxide's effects on gene expression, the proportion of effects shifting to downregulation with increasing glucose concentration. Effects of diazoxide on gene expression could serve to enhance beta-cell functionality during continuous hyperglycemia.
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Affiliation(s)
- Zuheng Ma
- Endocrine and Diabetes Unit, Department of Molecular Medicine and Surgery, Karolinska Hospital, Karolinska Institutet, Stockholm, Sweden
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Tsai B, Yue S, Irwin DM. A novel element regulates expression of the proximal human proglucagon promoter in islet cells. Gen Comp Endocrinol 2007; 151:230-9. [PMID: 17324423 DOI: 10.1016/j.ygcen.2007.01.012] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/21/2006] [Revised: 01/15/2007] [Accepted: 01/19/2007] [Indexed: 11/21/2022]
Abstract
The human and rat proglucagon gene proximal promoter regions have differing transcriptional activities in pancreatic islet cell lines, with 300 bases of rat proglucagon 5' flanking sequence being sufficient to support expression in rodent islet cell lines, while the homologous human sequences are transcriptionally silent. To better understand the changes in promoter activity between human and rat we have used a comparative approach and cloned promoters from diverse mammalian species and tested their transcriptional activities. Proglucagon gene proximal promoter regions from species representing three orders of mammals (rodents, artiodactyls, and carnivores) support transcription in rodent islet cell lines, while promoters from primates (human and rhesus monkey), despite significant sequence conservation, failed to drive reporter gene expression. These results suggest that nucleotide changes have occurred to the sequence of the proximal promoter region of the proglucagon gene during the evolution of primates that prevent them from supporting expression in rodent islet cell lines. Using hybrid human-rat proglucagon promoters and site-directed mutagenesis we identified a novel regulatory element in the human proglucagon proximal promoter, located between the G2 and G3 enhancer elements that is responsible for most of the difference in transcriptional activity between the human and rat proximal proglucagon promoters.
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Affiliation(s)
- Brian Tsai
- Department of Laboratory Medicine and Pathobiology, University of Toronto, 100 College Street, Toronto, Ont., Canada
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Dubois M, Vacher P, Roger B, Huyghe D, Vandewalle B, Kerr-Conte J, Pattou F, Moustaïd-Moussa N, Lang J. Glucotoxicity inhibits late steps of insulin exocytosis. Endocrinology 2007; 148:1605-14. [PMID: 17204559 DOI: 10.1210/en.2006-1022] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Prolonged exposure of beta-cells to high glucose (glucotoxicity) diminishes insulin secretion in response to glucose and has been linked to altered generation of metabolism-secretion coupling factors. We have investigated whether glucotoxicity may also alter calcium handling and late steps in secretion such as exocytosis. Clonal INS-1E beta-cells cultured at high glucose (20 or 30 mM vs. 5.5 mM) for 72 h exhibited elevated basal intracellular calcium ([Ca2+]i), which was KATP-channel dependent and due to long-term activation of protein kinase A. An increased amplitude and shortened duration of depolarization-evoked rises in [Ca2+]i were apparent. These changes were probably linked to the observed increased filling of intracellular stores and to short-term activation of protein kinase A. Insulin secretion was reduced not only by acute stimulation with either glucose or KCl but more importantly by direct calcium stimulation of permeabilized cells. These findings indicate a defect in the final steps of exocytosis. To confirm this, we measured expression levels of some 30 proteins implicated in trafficking/exocytosis of post-Golgi vesicles. Several proteins required for calcium-induced exocytosis of secretory granules were down-regulated, such as the soluble N-ethylmaleimide-sensitive factor-sensitive factor attachment receptor (SNARE) proteins VAMP-2 [vesicle (v)-SNARE, vesicle-associated membrane protein 2] and syntaxin 1 as well as complexin. VAMP-2 was also reduced in human islets. In contrast, cell immunostaining and expression levels of several fluorescent proteins suggested that other post-trans-Golgi trafficking steps and compartments are preserved and that cells were not degranulated. Thus, these studies indicate that, in addition to known metabolic changes, glucotoxicity impedes generation of signals for secretion and diminishes the efficiency of late steps in exocytosis.
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Affiliation(s)
- Mathilde Dubois
- Université de Bordeaux, Cell Biology Program, and Institut National de la Santé et de la Recherche Médicale E347, Pessac, France
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Hay CW, Ferguson LA, Docherty K. ATF-2 stimulates the human insulin promoter through the conserved CRE2 sequence. ACTA ACUST UNITED AC 2007; 1769:79-91. [PMID: 17337306 DOI: 10.1016/j.bbaexp.2007.01.005] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2006] [Revised: 01/22/2007] [Accepted: 01/22/2007] [Indexed: 01/04/2023]
Abstract
The insulin promoter contains a number of dissimilar cis-acting regulatory elements that bind a range of tissue specific and ubiquitous transcription factors. Of the regulatory elements within the insulin promoter, the cyclic AMP responsive element (CRE) binds by far the most diverse array of transcription factors. Rodent insulin promoters have a single CRE site, whereas there are four CREs within the human insulin gene, of which CRE2 is the only one conserved between species. The aim of this study was to characterise the human CRE2 site and to investigate the effects of the two principal CRE-associated transcription factors; CREB-1 and ATF-2. Co-transfection of INS-1 pancreatic beta-cells with promoter constructs containing the human insulin gene promoter placed upstream of the firefly luciferase reporter gene and expression plasmids for ATF-2 or CREB-1 showed that ATF-2 stimulated transcriptional activity while CREB-1 elicited an inhibitory effect. Mutagenesis of CRE2 diminished the effect of ATF-2 but not that of CREB-1. ATF-2 was shown to bind to the CRE2 site by electrophoretic mobility shift assay and by chromatin immunoprecipitation, while siRNA mediated knockdown of ATF-2 diminished the stimulatory effects of cAMP related signalling on promoter activity. These results suggest that ATF-2 may be a key regulator of the human insulin promoter possibly stimulating activity in response to extracellular signals.
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Affiliation(s)
- Colin W Hay
- School of Medical Sciences, University of Aberdeen, Institute of Medical Sciences, Foresterhill, Aberdeen, AB25 2ZD, UK
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40
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Li X, Zhang L, Meshinchi S, Dias-Leme C, Raffin D, Johnson JD, Treutelaar MK, Burant CF. Islet microvasculature in islet hyperplasia and failure in a model of type 2 diabetes. Diabetes 2006; 55:2965-73. [PMID: 17065332 DOI: 10.2337/db06-0733] [Citation(s) in RCA: 113] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Gene expression profiling of islets from pre-diabetic male Zucker diabetic fatty (ZDF) rats showed increased expression of hypoxia-related genes, prompting investigation of the vascular integrity of the islets. The islet microvasculature was increased approximately twofold in young male ZDF rats by both morphometric analysis and quantifying mRNA levels of endothelial markers. ZDF rats at 12 weeks of age showed a significant reduction in the number of endothelial cells, which was prevented by pretreatment with pioglitazone. Light and electron microscopy of normoglycemic 7-week-old ZDF rats showed thickened endothelial cells with loss of endothelial fenestrations. By 12 weeks of age, there was disruption of the endothelium and intra-islet hemorrhage. Islets from 7- and 12-week-old ZDF rats showed an approximate three- and twofold increase in vascular endothelial growth factor (VEGF)-A mRNA and VEGF protein secretion, respectively, compared with lean controls. Thrombospondin-1 mRNA increased in 7- and 12-week-old rats by 2- and 10-fold, respectively, and was reduced by 50% in 12-week-old rats pretreated with pioglitazone. Islets from young male control rats induced migration of endothelial cells in a collagen matrix only after pretreatment with matrix metalloproteinase (MMP)-9. Islets from 7-week-old ZDF rats showed a fivefold increase in migration score compared with wild-type controls, even without MMP-9 treatment. Islets from 15-week-old ZDF rats did not induce migration; rather, they caused a significant rounding up of the duct-derived cells, suggesting a toxic effect. These data suggest that in the ZDF rat model of type 2 diabetes, an inability of the islet to maintain vascular integrity may contribute to beta-cell failure.
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Affiliation(s)
- Xianquan Li
- University of Michigan Medical Center, Box 0678, 1500 E. Medical Center Dr., Ann Arbor, MI 48109, USA
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41
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Abderrahmani A, Plaisance V, Lovis P, Regazzi R. Mechanisms controlling the expression of the components of the exocytotic apparatus under physiological and pathological conditions. Biochem Soc Trans 2006; 34:696-700. [PMID: 17052177 DOI: 10.1042/bst0340696] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The last decade has witnessed spectacular progress in the identification of the protein apparatus required for exocytosis of neurotransmitters, peptide hormones and other bioactive products. In striking contrast, our knowledge of the mechanisms determining the expression of the components of the secretory machinery has remained rudimentary. Since modifications in secretory functions are associated with several physiological processes and contribute to the development of human pathologies, a better knowledge of the control of the expression of the genes involved in exocytosis is urgently needed. Recent studies have led to the identification of transcription factors and other regulatory molecules such as microRNAs that modulate the cellular level of key controllers of the exocytotic process. These findings furnish a new perspective for understanding how secretory functions can adapt to normal physiological conditions and shed light on the mechanisms involved in the development of important human diseases such as diabetes mellitus characterized by defective release of bioactive compounds.
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Affiliation(s)
- A Abderrahmani
- Department of Internal Medicine, University of Lausanne, Rue du Bugnon 9, 1005 Lausanne, Switzerland
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42
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Mu J, Woods J, Zhou YP, Roy RS, Li Z, Zycband E, Feng Y, Zhu L, Li C, Howard AD, Moller DE, Thornberry NA, Zhang BB. Chronic inhibition of dipeptidyl peptidase-4 with a sitagliptin analog preserves pancreatic beta-cell mass and function in a rodent model of type 2 diabetes. Diabetes 2006; 55:1695-704. [PMID: 16731832 DOI: 10.2337/db05-1602] [Citation(s) in RCA: 384] [Impact Index Per Article: 21.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Inhibitors of dipeptidyl peptidase-4 (DPP-4), a key regulator of the actions of incretin hormones, exert antihyperglycemic effects in type 2 diabetic patients. A major unanswered question concerns the potential ability of DPP-4 inhibition to have beneficial disease-modifying effects, specifically to attenuate loss of pancreatic beta-cell mass and function. Here, we investigated the effects of a potent and selective DPP-4 inhibitor, an analog of sitagliptin (des-fluoro-sitagliptin), on glycemic control and pancreatic beta-cell mass and function in a mouse model with defects in insulin sensitivity and secretion, namely high-fat diet (HFD) streptozotocin (STZ)-induced diabetic mice. Significant and dose-dependent correction of postprandial and fasting hyperglycemia, HbA(1c), and plasma triglyceride and free fatty acid levels were observed in HFD/STZ mice following 2-3 months of chronic therapy. Treatment with des-fluoro-sitagliptin dose dependently increased the number of insulin-positive beta-cells in islets, leading to the normalization of beta-cell mass and beta-cell-to-alpha-cell ratio. In addition, treatment of mice with des-fluoro-sitagliptin, but not glipizide, significantly increased islet insulin content and improved glucose-stimulated insulin secretion in isolated islets. These findings suggest that DPP-4 inhibitors may offer long-lasting efficacy in the treatment of type 2 diabetes by modifying the courses of the disease.
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Affiliation(s)
- James Mu
- Department of Metabolic Disorders, Merck Research Laboratories, P.O. Box 2000, Rahway, NJ 07065, USA
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43
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Wojtal KA, de Vries E, Hoekstra D, van IJzendoorn SC. Efficient trafficking of MDR1/P-glycoprotein to apical canalicular plasma membranes in HepG2 cells requires PKA-RIIalpha anchoring and glucosylceramide. Mol Biol Cell 2006; 17:3638-50. [PMID: 16723498 PMCID: PMC1525225 DOI: 10.1091/mbc.e06-03-0230] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
In hepatocytes, cAMP/PKA activity stimulates the exocytic insertion of apical proteins and lipids and the biogenesis of bile canalicular plasma membranes. Here, we show that the displacement of PKA-RIIalpha from the Golgi apparatus severely delays the trafficking of the bile canalicular protein MDR1 (P-glycoprotein), but not that of MRP2 (cMOAT), DPP IV and 5'NT, to newly formed apical surfaces. In addition, the direct trafficking of de novo synthesized glycosphingolipid analogues from the Golgi apparatus to the apical surface is inhibited. Instead, newly synthesized glucosylceramide analogues are rerouted to the basolateral surface via a vesicular pathway, from where they are subsequently endocytosed and delivered to the apical surface via transcytosis. Treatment of HepG2 cells with the glucosylceramide synthase inhibitor PDMP delays the appearance of MDR1, but not MRP2, DPP IV, and 5'NT at newly formed apical surfaces, implicating glucosylceramide synthesis as an important parameter for the efficient Golgi-to-apical surface transport of MDR1. Neither PKA-RIIalpha displacement nor PDMP inhibited (cAMP-stimulated) apical plasma membrane biogenesis per se, suggesting that other cAMP effectors may play a role in canalicular development. Taken together, our data implicate the involvement of PKA-RIIalpha anchoring in the efficient direct apical targeting of distinct proteins and glycosphingolipids to newly formed apical plasma membrane domains and suggest that rerouting of Golgi-derived glycosphingolipids may underlie the delayed Golgi-to-apical surface transport of MDR1.
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Affiliation(s)
- Kacper A. Wojtal
- Section of Membrane Cell Biology, Department of Cell Biology, University Medical Center Groningen, University of Groningen, 9713 AV Groningen, The Netherlands
| | - Erik de Vries
- Section of Membrane Cell Biology, Department of Cell Biology, University Medical Center Groningen, University of Groningen, 9713 AV Groningen, The Netherlands
| | - Dick Hoekstra
- Section of Membrane Cell Biology, Department of Cell Biology, University Medical Center Groningen, University of Groningen, 9713 AV Groningen, The Netherlands
| | - Sven C.D. van IJzendoorn
- Section of Membrane Cell Biology, Department of Cell Biology, University Medical Center Groningen, University of Groningen, 9713 AV Groningen, The Netherlands
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44
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Herrington J, Zhou YP, Bugianesi RM, Dulski PM, Feng Y, Warren VA, Smith MM, Kohler MG, Garsky VM, Sanchez M, Wagner M, Raphaelli K, Banerjee P, Ahaghotu C, Wunderler D, Priest BT, Mehl JT, Garcia ML, McManus OB, Kaczorowski GJ, Slaughter RS. Blockers of the delayed-rectifier potassium current in pancreatic beta-cells enhance glucose-dependent insulin secretion. Diabetes 2006; 55:1034-42. [PMID: 16567526 DOI: 10.2337/diabetes.55.04.06.db05-0788] [Citation(s) in RCA: 129] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Delayed-rectifier K+ currents (I(DR)) in pancreatic beta-cells are thought to contribute to action potential repolarization and thereby modulate insulin secretion. The voltage-gated K+ channel, K(V)2.1, is expressed in beta-cells, and the biophysical characteristics of heterologously expressed channels are similar to those of I(DR) in rodent beta-cells. A novel peptidyl inhibitor of K(V)2.1/K(V)2.2 channels, guangxitoxin (GxTX)-1 (half-maximal concentration approximately 1 nmol/l), has been purified, characterized, and used to probe the contribution of these channels to beta-cell physiology. In mouse beta-cells, GxTX-1 inhibits 90% of I(DR) and, as for K(V)2.1, shifts the voltage dependence of channel activation to more depolarized potentials, a characteristic of gating-modifier peptides. GxTX-1 broadens the beta-cell action potential, enhances glucose-stimulated intracellular calcium oscillations, and enhances insulin secretion from mouse pancreatic islets in a glucose-dependent manner. These data point to a mechanism for specific enhancement of glucose-dependent insulin secretion by applying blockers of the beta-cell I(DR), which may provide advantages over currently used therapies for the treatment of type 2 diabetes.
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Affiliation(s)
- James Herrington
- Department of Ion Channels, Merck Research Laboratories, RY80N-C31, P.O. Box 2000, Rahway, NJ 07065-0900, USA.
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45
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Abderrahmani A, Cheviet S, Ferdaoussi M, Coppola T, Waeber G, Regazzi R. ICER induced by hyperglycemia represses the expression of genes essential for insulin exocytosis. EMBO J 2006; 25:977-86. [PMID: 16498408 PMCID: PMC1409716 DOI: 10.1038/sj.emboj.7601008] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2005] [Accepted: 01/26/2006] [Indexed: 12/28/2022] Open
Abstract
The GTPases Rab3a and Rab27a and their effectors Granuphilin/Slp4 and Noc2 are essential regulators of neuroendocrine secretion. Chronic exposure of pancreatic beta-cells to supraphysiological glucose levels decreased selectively the expression of these proteins. This glucotoxic effect was mimicked by cAMP-raising agents and blocked by PKA inhibitors. We demonstrate that the transcriptional repressor ICER, which is induced in a PKA-dependent manner by chronic hyperglycemia and cAMP-raising agents, is responsible for the decline of the four genes. ICER overexpression diminished the level of Granuphilin, Noc2, Rab3a and Rab27a by binding to cAMP responsive elements located in the promoters of these genes and inhibited exocytosis of beta-cells in response to secretagogues. Moreover, the loss in the expression of the genes of the secretory machinery caused by glucose and cAMP-raising agents was prevented by an antisense construct that reduces ICER levels. We propose that induction of inappropriate ICER levels lead to defects in the secretory process of pancreatic beta-cells possibly contributing, in conjunction with other known deleterious effects of hyperglycemia, to defective insulin release in type 2 diabetes.
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Affiliation(s)
- Amar Abderrahmani
- Département de Médecine Interne, Université de Lausanne, Switzerland
- Département de Biologie Cellulaire et de Morphologie, Université de Lausanne, Switzerland
| | - Séverine Cheviet
- Département de Biologie Cellulaire et de Morphologie, Université de Lausanne, Switzerland
| | - Mourad Ferdaoussi
- Département de Médecine Interne, Université de Lausanne, Switzerland
- Département de Biologie Cellulaire et de Morphologie, Université de Lausanne, Switzerland
| | - Thierry Coppola
- Institut de Pharmacologie Moléculaire et Cellulaire, CNRS UMR 6097, Université de Nice, Sophia-Antipolis, Valbonne, France
| | - Gérard Waeber
- Département de Médecine Interne, Université de Lausanne, Switzerland
| | - Romano Regazzi
- Département de Biologie Cellulaire et de Morphologie, Université de Lausanne, Switzerland
- Department of Cell Biology & Morphology, University of Lausanne, Rue du Bugnon 9, 1005 Lausanne, Switzerland. Tel.: +41 21 692 5280; Fax: +41 21 692 5255; E-mail:
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46
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Cnop M, Welsh N, Jonas JC, Jörns A, Lenzen S, Eizirik DL. Mechanisms of pancreatic beta-cell death in type 1 and type 2 diabetes: many differences, few similarities. Diabetes 2005; 54 Suppl 2:S97-107. [PMID: 16306347 DOI: 10.2337/diabetes.54.suppl_2.s97] [Citation(s) in RCA: 1090] [Impact Index Per Article: 57.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Type 1 and type 2 diabetes are characterized by progressive beta-cell failure. Apoptosis is probably the main form of beta-cell death in both forms of the disease. It has been suggested that the mechanisms leading to nutrient- and cytokine-induced beta-cell death in type 2 and type 1 diabetes, respectively, share the activation of a final common pathway involving interleukin (IL)-1beta, nuclear factor (NF)-kappaB, and Fas. We review herein the similarities and differences between the mechanisms of beta-cell death in type 1 and type 2 diabetes. In the insulitis lesion in type 1 diabetes, invading immune cells produce cytokines, such as IL-1beta, tumor necrosis factor (TNF)-alpha, and interferon (IFN)-gamma. IL-1beta and/or TNF-alpha plus IFN-gamma induce beta-cell apoptosis via the activation of beta-cell gene networks under the control of the transcription factors NF-kappaB and STAT-1. NF-kappaB activation leads to production of nitric oxide (NO) and chemokines and depletion of endoplasmic reticulum (ER) calcium. The execution of beta-cell death occurs through activation of mitogen-activated protein kinases, via triggering of ER stress and by the release of mitochondrial death signals. Chronic exposure to elevated levels of glucose and free fatty acids (FFAs) causes beta-cell dysfunction and may induce beta-cell apoptosis in type 2 diabetes. Exposure to high glucose has dual effects, triggering initially "glucose hypersensitization" and later apoptosis, via different mechanisms. High glucose, however, does not induce or activate IL-1beta, NF-kappaB, or inducible nitric oxide synthase in rat or human beta-cells in vitro or in vivo in Psammomys obesus. FFAs may cause beta-cell apoptosis via ER stress, which is NF-kappaB and NO independent. Thus, cytokines and nutrients trigger beta-cell death by fundamentally different mechanisms, namely an NF-kappaB-dependent mechanism that culminates in caspase-3 activation for cytokines and an NF-kappaB-independent mechanism for nutrients. This argues against a unifying hypothesis for the mechanisms of beta-cell death in type 1 and type 2 diabetes and suggests that different approaches will be required to prevent beta-cell death in type 1 and type 2 diabetes.
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Affiliation(s)
- Miriam Cnop
- Laboratory of Experimental Medicine, Faculty of Medicine, Erasmus Hospital, Université Libre de Bruxelles (ULB), Route de Lennik 808, CP-618, 1070 Brussels, Belgium.
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Allagnat F, Martin D, Condorelli DF, Waeber G, Haefliger JA. Glucose represses connexin36 in insulin-secreting cells. J Cell Sci 2005; 118:5335-44. [PMID: 16263767 DOI: 10.1242/jcs.02600] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
The gap-junction protein connexin36 (Cx36) contributes to control the functions of insulin-producing cells. In this study, we investigated whether the expression of Cx36 is regulated by glucose in insulin-producing cells. Glucose caused a significant reduction of Cx36 in insulin-secreting cell lines and freshly isolated pancreatic rat islets. This decrease appeared at the mRNA and the protein levels in a dose- and time-dependent manner. 2-Deoxyglucose partially reproduced the effect of glucose, whereas glucosamine, 3-O-methyl-D-glucose and leucine were ineffective. Moreover, KCl-induced depolarization of beta-cells had no effect on Cx36 expression, indicating that glucose metabolism and ATP production are not mandatory for glucose-induced Cx36 downregulation. Forskolin mimicked the repression of Cx36 by glucose. Glucose or forskolin effects on Cx36 expression were not suppressed by the L-type Ca(2+)-channel blocker nifedipine but were fully blunted by the cAMP-dependent protein kinase (PKA) inhibitor H89. A 4 kb fragment of the human Cx36 promoter was identified and sequenced. Reporter-gene activity driven by various Cx36 promoter fragments indicated that Cx36 repression requires the presence of a highly conserved cAMP responsive element (CRE). Electrophoretic-mobility-shift assays revealed that, in the presence of a high glucose concentration, the binding activity of the repressor CRE-modulator 1 (CREM-1) is enhanced. Taken together, these data provide evidence that glucose represses the expression of Cx36 through the cAMP-PKA pathway, which activates a member of the CRE binding protein family.
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Affiliation(s)
- Florent Allagnat
- Department of Internal Medicine, Laboratory of Molecular Biology 19-135S, University Hospital, CHUV-1011 Lausanne, Switzerland
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48
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Zhou YP, Madjidi A, Wilson ME, Nothhelfer DA, Johnson JH, Palma JF, Schweitzer A, Burant C, Blume JE, Johnson JD. Matrix metalloproteinases contribute to insulin insufficiency in Zucker diabetic fatty rats. Diabetes 2005; 54:2612-9. [PMID: 16123349 DOI: 10.2337/diabetes.54.9.2612] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
To assess the molecular changes associated with pancreatic beta-cell dysfunction occurring during the onset of type 2 diabetes, we profiled pancreatic islet mRNAs from diabetic male and high-fat-fed female Zucker diabetic fatty (ZDF) rats and their nondiabetic lean counterparts on custom islet-specific oligonucleotide arrays. The most prominent changes in both the male and female models of type 2 diabetes were increases in the mRNAs encoding proteases and extracellular matrix components that are associated with tissue remodeling and fibrosis. The mRNAs for metalloproteinase (MMP)-2, -12, and -14 were sharply increased with the onset of islet dysfunction and diabetes. Zymography of islet extracts revealed a concurrent, >10-fold increase in MMP-2 protease activity in islets from 9-week-old male ZDF rats. Treatment of female ZDF rats receiving a diabetogenic diet with PD166793, a broad-spectrum MMP inhibitor, substantially prevented diabetes. The effect of this compound was due in part to marked beta-cell expansion. These studies indicate that MMPs contribute to islet fibrosis and insulin insufficiency in ZDF rats. Class-targeted protease inhibitors should be explored for their potential therapeutic utility in preservation of beta-cell mass in type 2 diabetes.
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Affiliation(s)
- Yun-Ping Zhou
- Metabolex, 3876 Bay Center Place, Hayward, CA 94583, USA
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49
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Inada A, Weir GC, Bonner-Weir S. Induced ICER Iγ down-regulates cyclin A expression and cell proliferation in insulin-producing β cells. Biochem Biophys Res Commun 2005; 329:925-9. [PMID: 15752744 DOI: 10.1016/j.bbrc.2005.02.046] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2005] [Indexed: 10/25/2022]
Abstract
We have previously found that cyclin A expression is markedly reduced in pancreatic beta-cells by cell-specific overexpression of repressor inducible cyclic AMP early repressor (ICER Igamma) in transgenic mice. Here we further examined regulatory effects of ICER Igamma on cyclin A gene expression using Min6 cells, an insulin-producing cell line. The cyclin A promoter luciferase assay showed that ICER Igamma directly repressed cyclin A gene transcription. In addition, upon ICER Igamma overexpression, cyclin A mRNA levels markedly decreased, thereby confirming an inhibitory effect of ICER Igamma on cyclin A expression. Suppression of cyclin A results in inhibition of BrdU incorporation. Under normal culture conditions endogenous cyclin A is abundant in these cells, whereas ICER is hardly detectable. However, serum starvation of Min6 cells induces ICER Igamma expression with a concomitant very low expression level of cyclin A. Cyclin A protein is not expressed unless the cells are in active DNA replication. These results indicate a potentially important anti-proliferative effect of ICER Igamma in pancreatic beta cells. Since ICER Igamma is greatly increased in diabetes as well as in FFA- or high glucose-treated islets, this effect may in part exacerbate diabetes by limiting beta-cell proliferation.
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Affiliation(s)
- Akari Inada
- Section of Islet Transplantation and Cell Biology, Joslin Diabetes Center, Harvard Medical School, Boston, MA 02215, USA
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50
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Kharroubi I, Ladrière L, Cardozo AK, Dogusan Z, Cnop M, Eizirik DL. Free fatty acids and cytokines induce pancreatic beta-cell apoptosis by different mechanisms: role of nuclear factor-kappaB and endoplasmic reticulum stress. Endocrinology 2004; 145:5087-96. [PMID: 15297438 DOI: 10.1210/en.2004-0478] [Citation(s) in RCA: 442] [Impact Index Per Article: 22.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Apoptosis is probably the main form of beta-cell death in both type 1 diabetes mellitus (T1DM) and T2DM. In T1DM, cytokines contribute to beta-cell destruction through nuclear factor-kappaB (NF-kappaB) activation. Previous studies suggested that in T2DM high glucose and free fatty acids (FFAs) are beta-cell toxic also via NF-kappaB activation. The aims of this study were to clarify whether common mechanisms are involved in FFA- and cytokine-induced beta-cell apoptosis and determine whether TNFalpha, an adipocyte-derived cytokine, potentiates FFA toxicity through enhanced NF-kappaB activation. Apoptosis was induced in insulinoma (INS)-1E cells, rat islets, and fluorescence-activated cell sorting-purified beta-cells by oleate, palmitate, and/or cytokines (IL-1beta, interferon-gamma, TNFalpha). Palmitate and IL-1beta induced a similar percentage of apoptosis in INS-1E cells, whereas oleate was less toxic. TNFalpha did not potentiate FFA toxicity in primary beta-cells. The NF-kappaB-dependent genes inducible nitric oxide synthase and monocyte chemoattractant protein-1 were induced by IL-1beta but not by FFAs. Cytokines activated NF-kappaB in INS-1E and beta-cells, but FFAs did not. Moreover, FFAs did not enhance NF-kappaB activation by TNFalpha. Palmitate and oleate induced C/EBP homologous protein, activating transcription factor-4, and immunoglobulin heavy chain binding protein mRNAs, X-box binding protein-1 alternative splicing, and activation of the activating transcription factor-6 promoter in INS-1E cells, suggesting that FFAs trigger an endoplasmic reticulum (ER) stress response. We conclude that apoptosis is the main mode of FFA- and cytokine-induced beta-cell death but the mechanisms involved are different. Whereas cytokines induce NF-kappaB activation and ER stress (secondary to nitric oxide formation), FFAs activate an ER stress response via an NF-kappaB- and nitric oxide-independent mechanism. Our results argue against a unifying hypothesis for the mechanisms of beta-cell death in T1DM and T2DM.
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Affiliation(s)
- Ilham Kharroubi
- Laboratory of Experimental Medicine, Université Libre de Bruxelles, Route de Lennik, 808 CP 618, B-1070 Brussels, Belgium
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