379 results on '"Jonas, Jean-Christophe"'
Search Results
202. Influence of cell number on the characteristics and synchrony of Ca2+oscillations in clusters of mouse pancreatic islet cells
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Jonkers, Françoise C., Jonas, Jean‐Christophe, Gilon, Patrick, and Henquin, Jean‐Claude
- Abstract
1The cytoplasmic Ca2+concentration ([Ca2+]i) was measured in single cells and cell clusters of different sizes prepared from mouse pancreatic islets.2During stimulation with 15 mM glucose, 20 % of isolated cells were inert, whereas 80 % showed [Ca2+]ioscillations of variable amplitude, duration and frequency. Spectral analysis identified a major frequency of 0.14 min−1and a less prominent one of 0.27 min−1.3In contrast, practically all clusters (2–50 cells) responded to glucose, and no inert cells were identified within the clusters. As compared to single cells, mean [Ca2+]iwas more elevated, [Ca2+]ioscillations were more regular and their major frequency was slightly higher (but reached a plateau at ≈0.25 min−1). In some cells and clusters, faster oscillations occurred on top of the slow ones, between them or randomly.4Image analysis revealed that the regular [Ca2+]ioscillations were well synchronized between all cells of the clusters. Even when the Ca2+response was irregular, slow and fast [Ca2+]ioscillations induced by glucose were also synchronous in all cells.5In contrast, [Ca2+]ioscillations resulting from mobilization of intracellular Ca2+by acetylcholine were restricted to certain cells only and were not synchronized.6Heptanol and 18α‐glycyrrhetinic acid, two agents widely used to block gap junctions, altered glucose‐induced Ca2+oscillations, but control experiments showed that they also exerted effects other than a selective uncoupling of the cells.7The results support theoretical models predicting an increased regularity of glucose‐dependent oscillatory events in clusters as compared to isolated islet cells, but contradict the proposal that the frequency of the oscillations increases with the number of coupled cells. Islet cell clusters function better as electrical than biochemical syncytia. This may explain the co‐ordination of [Ca2+]ioscillations driven by depolarization‐dependent Ca2+influx during glucose stimulation.
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- 1999
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203. Potential role of the early response gene c-myc in beta-cell adaptation to changes in glucose concentration.
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Jonas, Jean-Christophe, Jonas, J C, Laybutt, R, Steil, G M, Trivedi, N, Weir, G C, and Henquin, J C
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GENES , *PANCREATIC beta cells , *RNA metabolism , *PHYSIOLOGICAL adaptation , *ANIMAL experimentation , *CELL culture , *COMPARATIVE studies , *DOSE-effect relationship in pharmacology , *ISLANDS of Langerhans , *RESEARCH methodology , *MEDICAL cooperation , *POLYMERASE chain reaction , *PROTEINS , *RATS , *RESEARCH , *RNA , *TRANSCRIPTION factors , *DNA-binding proteins , *EVALUATION research , *REVERSE transcriptase polymerase chain reaction , *PHYSIOLOGY - Abstract
Examines the role of response gene c-myc in pancreatic beta-cell adaptation to glucose concentration changes. Factors affecting the loss of beta-cell differentiation; Effect of chronic hyperglycemia on beta-cell function; Increase of island of Langerhans c-myc-to-TATA box binding protein.
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- 2001
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204. Dual EPR measurement of oxygen consumption and superoxide production : principle and applications
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d'Hose, Donatienne, UCL - SSS/LDRI - Louvain Drug Research Institute, UCL - Faculté de pharmacie et des sciences biomédicales, Gallez, Bernard, Jordan, Bénédicte, Sonveaux, Pierre, Feron, Olivier, Jonas, Jean-Christophe, Hardy, Micael, and Mouithys-Mickalad, Ange
- Abstract
A growing body of evidence indicates that mitochondria play a key role in many disorders as well as in cancer progression and response to treatment. Next to being the main cellular energy generator through respiration, mitochondria are also the major producer of superoxide and other downstream reactive oxygen species in the cell. In this thesis, we aimed to develop an integrated electron paramagnetic resonance (EPR) toolbox enabling the assessment of mitochondrial (dys)function by measuring the oxygen consumption rate and superoxide production in a same cellular or mitochondrial preparation. This EPR toolbox was used for the benefit of two different projects: discovering potential radiosensitizers in anticancer therapy (like statins) and assessing the impact of agents such as Boscalid and Bixafen, which are succinate dehydrogenase inhibitors (SDHI), on the mitochondrial function of human cells. (BIFA - Sciences biomédicales et pharmaceutiques) -- UCL, 2021
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- 2021
205. Investigating the platelet metabolic, AMPK-ACC signaling in Coronary Artery Disease
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shakeel kautbally, UCL - SSS/IREC/CARD - Pôle de recherche cardiovasculaire, UCL - Faculté de médecine et médecine dentaire, Jonas, Jean-Christophe, Vanoverschelde, Jean-Louis, Vancraeynest, David, Dessy, Chantal, Coulie, Pierre, Beauloye, Christophe, and Horman, Sandrine
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Platelets ,AMP-activated protein kinase ,Lipidomics ,Coronary Artery Disease ,Acetyl-CoA Carboxylase - Abstract
Platelets are central actors in atherosclerosis and atherothrombosis. Stimulation of the AMP-activated protein kinase (AMPK) leads to phosphorylation and inhibition of acetyl-CoA carboxylase (ACC), the first committed enzyme for the de novo fatty acids synthesis in cells, including platelets. Given the impact of atherogenic environment on platelets, we hypothesized that AMPK-ACC signaling is activated in coronary artery disease (CAD) patients. The ACCTHEROMA trial (NCT03034148) reveals platelet ACC phosphorylation (phosphoACC) as a promising marker for risk stratification in suspected CAD patients. It identifies high-risk patients and correlates with severity of coronary artery calcification. The triglycerides/high-density lipoprotein cholesterol ratio is strongly associated with increased phosphoACC, a metabolic signature of the platelet-atherogenic lipid interplay in CAD patients. Phosphorylation and inhibition of ACC impacts platelet lipid content by down-regulating triglyceride lipid species, which in turn may affect platelet functions. (MED - Sciences médicales) -- UCL, 2019
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- 2019
206. Influence des acides gras libres sur la fonction et la survie des cellules de la lignée ostéogénique et rôle de la lipotoxicité dans la pathogénie de l’ostéonécrose de la tête fémorale
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Gillet, Céline, Rasschaert, Joanne, Gangji, Valérie, Lebrun, Philippe, Body, Jean-Jacques, Communi, Didier, Moreno Reyes, Mario Rodrigo, Jonas, Jean-Christophe JJC, Serteyn, Didier, and Hardouin, Pierre
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adipocyte médullaire ,Métabolisme - Abstract
L’os est un tissu dynamique, en remodelage constant grâce à un processus finement régulé impliquant des facteurs locaux et systémiques. Un déséquilibre entre la formation et la résorption osseuses, assurées respectivement par les ostéoblastes et les ostéoclastes, conduit à une altération de la microarchitecture de l’os, une augmentation du risque de fracture, et à l’apparition de pathologies telles que l’ostéonécrose et l’ostéoporose. Ces deux maladies ont pour caractéristiques communes une diminution du nombre de cellules stromales mésenchymateuses (MSC), les progéniteurs des ostéoblastes, et des anomalies fonctionnelles des MSC et des cellules ostéoblastiques (Ob). De surcroit, elles présentent toutes deux une accumulation d’adipocytes au sein de la moelle osseuse. De récentes publications suggèrent que cette accumulation d’adipocytes médullaires pourrait avoir des conséquences délétères sur la physiologie des cellules ostéoformatrices et de leurs progéniteurs, partageant ce même microenvironnement osseux. Une relation inverse entre l’excès d’adiposité médullaire et la masse osseuse est en effet aujourd’hui clairement établie. Par son importante activité sécrétrice de cytokines et d’adipokines ainsi que sa capacité à stocker et libérer des acides gras libres (AGL), l’adipocyte médullaire est capable de modifier la composition du microenvironnement osseux, et ainsi d’influencer le métabolisme et la fonction des cellules avoisinantes, et notamment des cellules osseuses. Afin d’étudier l’influence des AGL sur la survie et la fonction des cellules ostéogéniques, nous avons utilisé un AGL saturé, le palmitate (Palm ;C16 :0) et un AGL monoinsaturé, l’oléate (Ole ;C18 :1), tous deux étant particulièrement abondants dans l’organisme et l’alimentation de l’homme et couramment utilisés dans les études de lipotoxicité. Dans un premier temps, nous avons travaillé sur des MSC isolées de la moelle osseuse de sujets sains (HV-MSC), qui ont éventuellement été différenciées en Ob. Nous avons démontré que l’exposition de ces cellules à des concentrations physiologiques de Palm entraîne une cytotoxicité dose-et temps-dépendante, via l’initiation d’un stress du réticulum endoplasmique (RE) et l’activation des voies ERK et NFκB. En outre, l’AGL saturé induit un état pro-inflammatoire en augmentant l’expression du toll-like receptor 4 et la production des interleukines (IL) 6 et 8. Nous avons montré que les Ob présentent une sensibilité accrue au Palm, associée à une exacerbation du stress du RE et de la réponse pro-inflammatoire. L’Ole n’a pas d’effet délétère sur les MSC et les Ob, et de surcroit, il bloque les différentes voies activées par le Palm, neutralisant ainsi totalement la lipotoxicité induite par l’AGL saturé. Nous avons démontré par ailleurs que l’AGL monoinsaturé favorise l’estérification et le stockage du Palm dans des gouttelettes lipidiques, contrant ainsi ses effets délétères. Nous avons ensuite étudié les effets de ces deux AGL, sur des MSC isolées de patients atteints d’ostéonécrose de la tête fémorale (ON-MSC), comparativement aux HV-MSC. Lors de la procédure d’isolation des MSC, nous avons conservé le surnageant obtenu après la première centrifugation (bone marrow supernatant fluid, BMSF) pour une analyse de sa composition lipidique, celle du sérum étant réalisée en parallèle. Nous avons démontré que l’exposition au Palm favorise la différenciation des MSC vers la lignée adipogénique, au détriment du phénotype ostéoblastique. De plus, nous avons observé que les ON-MSC possèdent une capacité de différenciation adipogénique supérieure à celles des HV-MSC.D’autre part, nos résultats ont montré que les ON-MSC sont plus sensibles à la lipotoxicité que les HV-MSC, cette hypersensibilité étant associée à un dérèglement de plusieurs mécanismes cellulaires impliqués dans la survie ou les processus de protection cellulaire :le niveau d’activation basal de la voie ERK est supérieur à celui des HV-MSC et la régulation de l’expression génique des enzymes stearoyl-CoA desaturase 1 (SCD1) et carnitine palmitoyl transferase 1 (CPT1), favorisant respectivement la désaturation des AGL saturés et leur β-oxydation mitochondriale, est altérée dans les ON-MSC. Par ailleurs, dans ces cellules, la production des cytokines IL-6 et IL-8 est triplée par rapport à celle des HV-MSC.La caractérisation du profil lipidique du sérum n’a pas mis en évidence de différence significative entre les sujets sains et ostéonécrotiques. Cependant, de profondes modifications du contenu en AGL du BMSF ont été observées, montrant un enrichissement important en acide palmitique, palmitoléique, oléique, vaccénique et linoléique chez les sujets ostéonécrotiques. Ces modifications reflètent un changement du microenvironnement osseux chez ces patients qui pourrait être lié à l’activité sécrétrice des adipocytes médullaires et altérer le fonctionnement des cellules voisines.L’ensemble de nos travaux suggère qu’au sein du microenvironnement osseux, l’accumulation d’adipocytes médullaires pourrait avoir un effet délétère sur les cellules responsables de la formation osseuse, notamment via la libération d’AGL. Ces AGL étant cytotoxiques pour les cellules ostéoformatrices mais bénéfiques pour les cellules responsables de la résorption osseuse, ils pourraient favoriser un déséquilibre du remodelage osseux. En lien avec ces observations, nos résultats obtenus avec les ON-MSC suggèrent également que la lipotoxicité pourrait participer aux mécanismes pathogéniques qui initient et/ou entretiennent l’ostéonécrose., Doctorat en Sciences biomédicales et pharmaceutiques (Médecine), info:eu-repo/semantics/nonPublished
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- 2017
207. Dynamic changes of oxygenation in wound healing in mice diabetic models monitored by Electron Paramagnetic Resonance (EPR) oximetry
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Desmet, Céline, UCL - SSS/LDRI - Louvain Drug Research Institute, UCL - Faculté de pharmacie et des sciences biomédicales, Gallez, Bernard, Levêque, Philippe, Feron, Olivier, Jordan, Bénédicte, Jonas, Jean-Christophe, Vandeleene, Bernard, Germonpré, Peter, and Frapart, Yves-Michel
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Electron Paramagnetic Resonance ,Oxygen ,Diabetes ,Wound healing ,EPR ,Oximetry - Abstract
Oxygen is essential in wound healing and hypoxia is described as a major cause of wound healing impairment. Tissue oxygenation is an important parameter in the clinical management of chronic wounds such as diabetic ulcers. But until now, no techniques are able to perform absolute, non-invasive and repeated measurements of oxygenation directly in a tissue. Electron Paramagnetic Resonance (EPR) oximetry is a technique that allows this kind of measurements, but was never applied in the context of diabetic wound healing. The aim of the thesis was the implementation of EPR oximetry to follow diabetic wound oxygenation variations. The first part of the thesis consisted in the validation of the technique to measure wound oxygenation. Then, the use of EPR oximetry as a biomarker of treatment response in diabetic wounds was assessed. L’oxygène est essentiel à la cicatrisation des plaies et l’hypoxie est décrite comme une cause majeure de problèmes de cicatrisation. L’oxygénation tissulaire est un paramètre important dans la gestion clinique des plaies chroniques comme les ulcères diabétiques. Mais jusqu’à présent, aucune technique n’est capable de réaliser une mesure absolue, non-invasive et répétée de l’oxygénation directement dans un tissu. L’oxymétrie par Résonance Paramagnétique Electronique (RPE) est une technique qui permet de réaliser ce type de mesures mais n’a jamais été appliquée dans le contexte de cicatrisation de plaies diabétiques. Le but de la thèse était d’implémenter l’oxymétrie RPE pour suivre les variations en oxygénation dans les plaies diabétiques. La première partie de la thèse a consisté en la validation de la technique pour mesurer l’oxygénation dans les plaies. Ensuite, l’utilisation de l’oxymétrie RPE comme biomarqueur de réponse à un traitement dans les plaies diabétiques a été évaluée. (BIFA - Sciences biomédicales et pharmaceutiques) -- UCL, 2017
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- 2017
208. The role of activating transcription factor 3 in mouse skeletal muscle
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Fernandez Verdejo, Rodrigo, UCL - SSS/IONS - Institute of NeuroScience, UCL - Faculté des sciences de la motricité, Francaux , Marc, Lemaigre, Frédéric, Deldicque, Louise, Thonnard, Jean-Louis, Thissen, Jean-Paul, Jonas, Jean-Christophe, Pilegaard, Henriette, and Demoulin, Jean-Baptiste
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Inflammation ,Phenotype ,Macrophages ,Training ,Cytokines ,Electrical pulse stimulation ,Microarray ,Chemokines ,Exercise - Abstract
Exercise has anti-inflammatory properties useful to prevent and treat some chronic diseases. The expression of activating transcription factor 3 (ATF3) increases in skeletal muscle after exercise. In many tissues, ATF3 regulates the inflammatory response. Whether ATF3 contributes to the anti-inflammatory properties of exercise in skeletal muscle was unknown. To understand the role of ATF3 in skeletal muscle, we used a mutant mouse model unable to express ATF3 (ATF3-KO). We found that the expression of some inflammation-related genes was higher in ATF3-KO than control mice postexercise. ATF3-KO mice also had an impaired molecular adaptation to training in skeletal muscle. Our data suggest ATF3 is an important regulator of the inflammation postexercise, which could influence training adaptation in skeletal muscle. Since inflammation is involved in the pathogenesis of many diseases, the identification of ATF3 as an exercise-induced anti-inflammatory factor is relevant for future studies. (MOTR - Sciences de la motricité) -- UCL, 2017
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- 2017
209. Metabolic plasticity in cancer cells : involvement in the processes of proliferation and response to radiotherapy
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De Preter, Géraldine, UCL - SSS/LDRI - Louvain Drug Research Institute, UCL - Faculté de pharmacie et des sciences biomédicales, Gallez, Bernard, Sonveaux, Pierre, Jordan, Bénédicte, Jonas, Jean-Christophe, Delzenne, Nathalie, Fendt, Sarah-Maria, and Rossignol, Rodrigue
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Radiotherapy ,Dichloroacetate ,Bioenergetics ,Hypoxia ,Cancer - Abstract
While pioneering studies suggested that enhanced glycolysis, a hallmark of cancer, was caused by an irreversible impairment in mitochondrial respiration, more recent data reported functional mitochondrial activity in many cancer cells. In this thesis, we thus intended to investigate whether metabolic modulations could improve the therapeutic outcome of cancer. We found that dichloroacetate, a new clinically tested compound, induced a switch of glycolytic cancer cells to a more oxidative phenotype, and decreased tumor cell proliferation through a decrease in the activity of the pentose phosphate pathway. In a second part of this work, we investigated whether targeting mitochondrial respiration with H2S, the last gaseous transmitter identified in mammals, improved tumor response to radiotherapy. By rapidly alleviating hypoxia inside solid tumors, the single injection of a H2S donor increased the radioresponse of cancer in mice. Overall, our thesis work emphasizes the ability of cancer cells to remodel their energetic metabolism in response to external stimuli and supports that both glycolysis and oxidative phosphorylation are attractive targets for cancer therapy. (BIFA - Sciences biomédicales et pharmaceutiques) -- UCL, 2016
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- 2016
210. Novel insights into the development of hormone resistance phenotype of prostate cancer cells
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Boutin, Benoît, UCL - SSS/IONS/CEMO-Pôle Cellulaire et moléculaire, UCL - Faculté de pharmacie et des sciences biomédicales, Gailly, Philippe, Tajeddine, Nicolas, Brichard, Sonia, Buc Calderon, Pedro, Courtoy, Pierre, Jonas, Jean-Christophe, Parys, Jan, and Prevarskaya, Natacha
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Prostate cancer ,Calcium homeostasis ,Androgen independence ,Autophagy ,Cell survival - Abstract
Prostate cancer (PCa) is the most frequent cancer in men above the age of 50 years. Despite radical prostatectomy or radiation therapy as primary treatment, 15-30% of patients will develop an advanced or metastatic cancer requiring systemic therapies. Reference treatment of advanced PCa relies on pharmacological or surgical androgen deprivation therapy. However, despite initial efficacy of androgen deprivation (AD), the tumor inevitably adapts to low testosterone environment and becomes hormone refractory (HRPCa). A better understanding of the mechanisms of androgen independence is necessary to improve the management of HRPCa. Although autophagy confers chemoresistance in some cancers, its role in the development of HRPCa remained unknown. We found that AD or treatment with the anti-androgen bicalutamide promoted autophagy in HRPCa-derived LNCaP cells. This effect was associated with an inhibition of the PI3K/Akt/mTOR pathway and with a disruption of the complex formed by androgen receptor and the regulatory subunit of PI3K p85. Moreover, genetic or pharmacological inhibition of autophagy restored AD-dependent cell death indicating that autophagy is a protective mechanism against AD in HRPCa cells. Besides, in these same cells, we also observed different modifications of Ca2+ homeostasis after androgen withdrawal among which a reduction of the ER Ca2+ content. We discovered that the [Ca2+]ER decrease was due to the presence of IP3R1 made leakier by their phosphorylation by PKA inhibitor H89 or permeant TAT-peptide containing the Ser-1716 consensus phosphorylation sequence sensitized LNCaP cells to AD, suggesting that [Ca2+]ER can control HRPCa cells resistance to AD. Therefore, we identified two distinct mechanisms by which HRPCa-derived cells manage to overcome cell death that they face in the absence of androgenic stimulation. We hope that these findings will help to device new therapeutic strategies to circumvent hormone independence of advanced PCa. (BIFA - Sciences biomédicales et pharmaceutiques) -- UCL, 2015
- Published
- 2015
211. Glucose et stress oxydatif dans les cellules beta pancréatiques : rôle du zinc et des métallothionéines
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Duprez, Jessica, UCL - SSS/IREC/EDIN - Pôle d'endocrinologie, diabète et nutrition, UCL - Faculté de pharmacie et des sciences biomédicales, Jonas, Jean-Christophe, Brichard, Sonia, Sempoux, Christine, Buc Calderon, Pedro, Jacquemin, Patrick, Knoops, Bernard, and Maechler, Pierre
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cellules beta ,zinc ,stress oxydatif ,glucose ,métallothionéines - Abstract
Glucose stimulation of insulin secretion by pancreatic β cells is essential to maintain glucose homeostasis. In addition to this short-term effect, glucose is also important to maintain β cell survival and differentiated phenotype. Indeed, both chronic hypo- and hyper-glycemia alter β-cell gene expression, survival and function. Similarly, in vitro, rat β-cell gene expression, function and survival are optimally preserved by culture in the presence of 10 mM glucose (G10) and markedly impaired by culture in either lower (2 or 5 mmol/l glucose, G2 or G5) or higher (30 mmol/l glucose, G30) glucose concentrations. It therefore seems that glucose stimulation exerts beneficial effects on β cell function and survival between G2 and G10 and a deleterious effect on these parameters between G10 and G30. The precise molecular mechanisms behind such phenotypical plasticity are poorly understood, but they could involve an increase in oxidative stress. Indeed, mRNA levels of oxidative stress-response genes like Metallothionein 1a/2a (Mt1a/2a), Heme oxygenase 1 (Hmox1) or c-Mycfollow an asymmetric V-shaped profile similar to that of β cell dysfunction and apoptosis. We therefore hypothesized that extreme glucose concentrations increases oxidative stress in β cells. In a first study, we developed a method to measure the β cell redox status in our experimental conditions. Our results showed that mt-HyPer, besides its expected sensitivity to H2O2, was also highly pH-sensitive. As glucose stimulation increases mitochondrial pH in β cells, that probe could not be used in our experimental model. In contrast, the fluorescence ratio of mt-roGFP1, which measures the thiol/disulfide equilibrium, was only slightly affected by pH. Using that probe, we demonstrated that mitochondrial thiol oxidation in rat β cells reversibly increases when glucose is lowered from 10 to 2 mmol/l. In contrast, acutely increasing glucose concentration from 10 to 30 mmol/l did not increase mt-roGFP1 oxidation in β cell. In a second study, I first demonstrated that 18 to 24h culture of rat islet cell clusters in the présence of G5 or G30 vs. G10 increases mitochondrial glutathione oxidation, thereby confirming our initial hypothesis. I also tested the effect of ZnCl2, a potent inducer of Mt1a, on β cell alterations induced by prolonged exposure to low and high glucose concentrations. My results show that addition of 50μM ZnCl2partially reduced mt-roGFP oxidation after 18-24h culture in G5, and tended to do so after culture in G30.Addition of 100μM ZnCl2also significantly decreased late β-cell apoptosis after prolonged culture in G5 or G30. Theses protective effects of ZnCl2 did not correct β cell dysfunction induced by culture in G5 and G30. In a third study, using islets from Mt1/2 knock-out mice, I wanted to determine the role of MT1/2 on the beneficial effects of Zn2+. I also wanted to test whether the deficiency in Mt1/2 increases β cell apoptosis and mitochondrial glutathione oxidation induced by culture in a low glucose concentration. In contrast with what I observed in rat islets, ZnCl2, despite increasing Mt1expression, did not protect wild-type mouse islets from apoptosis induced by culture in a low glucose concentration, thereby preventing me from studying the role of MT1/2 expression in this effect. Moreover, deficiency in Mt1/2 in mouse islets did not increase apoptosis induced by culture in a low glucose concentration. These results help us to understand the molecular mechanisms underlying the plasticity of the β cell phenotype and may help in the development of new therapeutic strategies for T2D. (BIFA - Sciences biomédicales et pharmaceutiques) -- UCL, 2013
- Published
- 2013
212. MicroRNAs and downstream Adipokines regulated by Adiponectin in vivo are novel targets for controlling adipose tissue inflammation
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Ge, Qian, UCL - SSS/IREC/EDIN - Pôle d'endocrinologie, diabète et nutrition, Brichard, Sonia, Thissen, Jean-Paul, Jonas, Jean-Christophe, Leclercq, Isabelle, Delzenne, Nathalie, Burcelin, Remy, and Holvoet, Paul
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Inflammation ,animal structures ,Adipocyte ,Adipokine ,MicroRNA ,Adiponectin ,Obesity ,Stromal-vascular cells ,hormones, hormone substitutes, and hormone antagonists ,Secretome - Abstract
Adipose tissue (AT) has been recognized as an active secretory organ, which releases a number of bioactive peptides, collectively named adipokines. They play a central role in energy and vascular homeostasis as well as in immunity. Dysregulation of adipokines triggers the development of a low-grade pro-inflammatory state, which is considered to build the common soil for the development of obesity-linked disorders. Thus, resetting the immunological balance in obese AT is a fundamental therapeutic strategy for the metabolic syndrome. ApN has emerged as a master regulator of immune/inflammatory homeostasis. Yet, the autocrine/paracrine effects of ApN on AT inflammation have been poorly investigated. We have previously generated a transgenic mouse model allowing persistent and moderate overexpression of ApN (ApN-Overex) specifically in white AT. I therefore took advantage of this unique model to unravel the effects of ApN on AT secretory function. I confirmed that ApN regulated in vivo the secretion of downstream adipokines, decreasing those with pro-inflammatory properties, while enhancing those with anti-inflammatory effects. These changes were specific: they occurred before the emergence of any metabolic confounding factors (such as improvement of insulin action or decrease of fat mass). Moreover, a reverse profile of expression was observed for most adipokines in ApN-knockout (ApN-KO) mice. Thus ApN induced in vivo a shift of the immune balance in AT toward a less inflammatory phenotype. Moreover, this shift induced by ApN was associated with reduced activity of NF-κB and Extracellular Signal-Regulated kinases (ERK1/2), as well as increased activity/expression of AMPK in AT. MicroRNAs (miRNAs) are small non-coding RNAs that control gene expression by inducing target mRNA degradation or blocking translation. Deregulation of miRNAs is closely associated with obesity-related metabolic disorders. I therefore used the same ApN-Overex mice to investigate whether miRNAs regulated by ApN contribute to the anti-inflammatory effects of ApN in AT and whether these miRNAs represent novel mechanisms for controlling AT inflammation. Four miRNAs were modified in AT of ApN-Overex mice. Expression of miR532-5p and miR1983 was down-regulated, while that of miR883b-5p and miR1934 was up-regulated. miR883b-5p was identified by computational analysis as being involved in inflammatory pathways. By using gain-of or loss-of function approaches, I further validated that miR883b-5p repressed the lipopolysaccharide (LPS) facilitator, LPS-binding protein (LBP) in 3T3-F442A cells. miR883b-5p blockade also abolished the protective effects of ApN on induction of pro-inflammatory adipokines. These data were recapitulated in de novo AT (formed from engineered 3T3-F442A preadipocytes transplanted in nude mice) where miR883b-5p silencing induced LBP production and tissue inflammation. Eventually, miR883b-5p expression was down-regulated in AT of obese subjects, concomitantly with reduced ApN expression. Altogether, these data suggest that miR883b-5p may be an important mediator of the anti-inflammatory action of ApN in adipocytes. These newly identified downstream adipokines and miRNAs may open new therapeutic perspectives for the management of metabolic syndrome. (SBIM 3) -- UCL, 2012
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- 2012
213. Transdifferentiation of pancreatic duct cells to β-cells in absence of the transcription factor HNF6
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Heinen, Eric, UCL - BIFA - Sciences biomédicales et pharmaceutiques, Jacquemin, Patrick, Lemaigre, Frédéric, Vikkula, Miikka, Herrera, Pedro, Heimberg, Harry, Hermans, Emmanuel, Jonas, Jean-Christophe, and Tissir, Fadel
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Duct cell ,Transdifferentiation ,Insulin ,Lineage tracing ,Pancreas ,β-cell - Abstract
A promising way to cure diabetes is to implant in vitro produced β-cells, or to induce β-cell regeneration in vivo. Multiple attempts have been made to coax different cell types into β-cells. One of these cell types is the pancreatic duct cell, but its potential as a β-cell precursor remains unclear. In this work we examine the plasticity of duct cells in mice deficient for Hepatocyte Nuclear Factor 6 (HNF6), a transcriptional regulator of pancreatic cell differentiation. In hnf6-/- mice, the number of β-cells is reduced at birth, yet it subsequently undergoes a partial recovery. We show in these mice that a postnatalβ-cell neogenesis occurs. Neogenesis neither results from a higher proliferation rate of mature β-cells nor from delayed differentiation of β-cell precursors. The presence of transition cells that co-express insulin and duct markers, as well as genetic lineage tracing, indicate that duct cells transdifferentiate postnatally to β-cells in hnf6-/- mice. Therefore, our results provide evidence that in the absence of the transcription factor HNF6, duct cells have the potential to generate β-cells. This suggests new strategies for the production of β-cells from duct cells. (SBIM 3) -- UCL, 2010
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- 2010
214. Transistors Electrochimiques Organiques (OECTs) : nouveaux capteurs pour l’analyse de l’activité électrique des micro-organes pancréatiques
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ABARKAN, Myriam, Lang, Jochen, Nadjar, Agnès, Malliaras, George, Nüsse, Oliver, Frick, Andreas, and Jonas, Jean-Christophe
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Cellule α. cellule β ,Îlot pancréatique ,Électrophysiologie ,Matrice de microélectrodes ou MEA ,Transistor électrochimique organique ou OECT ,Biocapteur
215. Transcriptome analysis of islets from diabetes-resistant and diabetes-prone obese mice reveals novel gene regulatory networks involved in beta-cell compensation and failure.
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Chan JY, Bensellam M, Lin RCY, Liang C, Lee K, Jonas JC, and Laybutt DR
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- Animals, Diabetes Mellitus, Experimental genetics, Diabetes Mellitus, Experimental metabolism, Diabetes Mellitus, Type 2 genetics, Diabetes Mellitus, Type 2 metabolism, Insulin Secretion, Insulin-Secreting Cells metabolism, Male, Mice, Mice, Obese, Diabetes Mellitus, Experimental pathology, Diabetes Mellitus, Type 2 pathology, Gene Expression Regulation, Gene Regulatory Networks, Insulin-Secreting Cells pathology, Obesity physiopathology, Transcriptome
- Abstract
The mechanisms underpinning beta-cell compensation for obesity-associated insulin resistance and beta-cell failure in type 2 diabetes remain poorly understood. We used a large-scale strategy to determine the time-dependent transcriptomic changes in islets of diabetes-prone db/db and diabetes-resistant ob/ob mice at 6 and 16 weeks of age. Differentially expressed genes were subjected to cluster, gene ontology, pathway and gene set enrichment analyses. A distinctive gene expression pattern was observed in 16 week db/db islets in comparison to the other groups with alterations in transcriptional regulators of islet cell identity, upregulation of glucose/lipid metabolism, and various stress response genes, and downregulation of specific amino acid transport and metabolism genes. In contrast, ob/ob islets displayed a coordinated downregulation of metabolic and stress response genes at 6 weeks of age, suggestive of a preemptive reconfiguration in these islets to lower the threshold of metabolic activation in response to increased insulin demand thereby preserving beta-cell function and preventing cellular stress. In addition, amino acid transport and metabolism genes were upregulated in ob/ob islets, suggesting an important role of glutamate metabolism in beta-cell compensation. Gene set enrichment analysis of differentially expressed genes identified the enrichment of binding motifs for transcription factors, FOXO4, NFATC1, and MAZ. siRNA-mediated knockdown of these genes in MIN6 cells altered cell death, insulin secretion, and stress gene expression. In conclusion, these data revealed novel gene regulatory networks involved in beta-cell compensation and failure. Preemptive metabolic reconfiguration in diabetes-resistant islets may dampen metabolic activation and cellular stress during obesity., (© 2021 Federation of American Societies for Experimental Biology.)
- Published
- 2021
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216. Emerging Roles of Metallothioneins in Beta Cell Pathophysiology: Beyond and Above Metal Homeostasis and Antioxidant Response.
- Author
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Bensellam M, Laybutt DR, and Jonas JC
- Abstract
Metallothioneins (MTs) are low molecular weight, cysteine-rich, metal-binding proteins whose precise biological roles have not been fully characterized. Existing evidence implicated MTs in heavy metal detoxification, metal ion homeostasis and antioxidant defense. MTs were thus categorized as protective effectors that contribute to cellular homeostasis and survival. This view has, however, been challenged by emerging evidence in different medical fields revealing novel pathophysiological roles of MTs, including inflammatory bowel disease, neurodegenerative disorders, carcinogenesis and diabetes. In the present focused review, we discuss the evidence for the role of MTs in pancreatic beta-cell biology and insulin secretion. We highlight the pattern of specific isoforms of MT gene expression in rodents and human beta-cells. We then discuss the mechanisms involved in the regulation of MTs in islets under physiological and pathological conditions, particularly type 2 diabetes, and analyze the evidence revealing adaptive and negative roles of MTs in beta-cells and the potential mechanisms involved. Finally, we underscore the unsettled questions in the field and propose some future research directions.
- Published
- 2021
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217. Inhibition of aquaporin-1 prevents myocardial remodeling by blocking the transmembrane transport of hydrogen peroxide.
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Montiel V, Bella R, Michel LYM, Esfahani H, De Mulder D, Robinson EL, Deglasse JP, Tiburcy M, Chow PH, Jonas JC, Gilon P, Steinhorn B, Michel T, Beauloye C, Bertrand L, Farah C, Dei Zotti F, Debaix H, Bouzin C, Brusa D, Horman S, Vanoverschelde JL, Bergmann O, Gilis D, Rooman M, Ghigo A, Geninatti-Crich S, Yool A, Zimmermann WH, Roderick HL, Devuyst O, and Balligand JL
- Subjects
- Animals, Humans, Hydrogen Peroxide metabolism, Mice, Myocardium metabolism, Myocytes, Cardiac metabolism, Aquaporin 1, Induced Pluripotent Stem Cells metabolism
- Abstract
Pathological remodeling of the myocardium has long been known to involve oxidant signaling, but strategies using systemic antioxidants have generally failed to prevent it. We sought to identify key regulators of oxidant-mediated cardiac hypertrophy amenable to targeted pharmacological therapy. Specific isoforms of the aquaporin water channels have been implicated in oxidant sensing, but their role in heart muscle is unknown. RNA sequencing from human cardiac myocytes revealed that the archetypal AQP1 is a major isoform. AQP1 expression correlates with the severity of hypertrophic remodeling in patients with aortic stenosis. The AQP1 channel was detected at the plasma membrane of human and mouse cardiac myocytes from hypertrophic hearts, where it colocalized with NADPH oxidase-2 and caveolin-3. We show that hydrogen peroxide (H
2 O2 ), produced extracellularly, is necessary for the hypertrophic response of isolated cardiac myocytes and that AQP1 facilitates the transmembrane transport of H2 O2 through its water pore, resulting in activation of oxidant-sensitive kinases in cardiac myocytes. Structural analysis of the amino acid residues lining the water pore of AQP1 supports its permeation by H2 O2 Deletion of Aqp1 or selective blockade of the AQP1 intrasubunit pore inhibited H2 O2 transport in mouse and human cells and rescued the myocyte hypertrophy in human induced pluripotent stem cell-derived engineered heart muscle. Treatment of mice with a clinically approved AQP1 inhibitor, Bacopaside, attenuated cardiac hypertrophy. We conclude that cardiac hypertrophy is mediated by the transmembrane transport of H2 O2 by the water channel AQP1 and that inhibitors of AQP1 represent new possibilities for treating hypertrophic cardiomyopathies., (Copyright © 2020 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.)- Published
- 2020
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218. Aspalathin Protects Insulin-Producing β Cells against Glucotoxicity and Oxidative Stress-Induced Cell Death.
- Author
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Moens C, Bensellam M, Himpe E, Muller CJF, Jonas JC, and Bouwens L
- Subjects
- Animals, Cell Death drug effects, Cells, Cultured, Chalcones administration & dosage, Dose-Response Relationship, Drug, Gene Expression Regulation drug effects, Glucose toxicity, Heme Oxygenase (Decyclizing) genetics, Hydrogen Peroxide toxicity, Male, Oxidative Stress genetics, Rats, Wistar, Streptozocin toxicity, Chalcones pharmacology, Insulin-Secreting Cells drug effects, Oxidative Stress drug effects, Protective Agents pharmacology
- Abstract
Scope: Aspalathin, the main polyphenolic phytochemical of rooibos (Aspalathus linearis), has been attributed with health promoting properties, including a glucose lowering effect that can prove interesting for application as nutraceutical or therapeutic in (pre-)diabetics. Preservation of β cell mass in the pancreas is considered a key issue for diabetes prevention or treatment, therefore the aim is to investigate whether aspalathin also has β cell cytoprotective potential., Methods and Results: Rat pancreatic islets and the β cell line Insulinoma 1E (INS1E) are studied in vitro after exposure to various cytotoxic agents, namely streptozotocin (STZ), hydrogen peroxide, or chronic high glucose. The effect of aspalathin on cell survival and apoptosis is studied. Expression of relevant cytoprotective genes is analyzed by qRT-PCR and proteins by Western blot. Aspalathin is found to protect β cells against cytotoxicity and apoptosis. This is associated with increased translocation of nuclear factor erythroid 2-related factor 2 (NRF2) and expression of its antioxidant target genes heme oxygenase 1 (Hmox1), NAD(P)H quinone dehydrogenase 1 (Nqo-1), and superoxide dismutase 1 (Sod1)., Conclusion: It is proposed that aspalathin protects β cells against glucotoxicity and oxidative stress by increasing the expression of NRF2-regulated antioxidant enzymes. This indicates that aspalathin is an interesting β cell cytoprotectant., (© 2020 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)
- Published
- 2020
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219. Editorial Overview: "Islet Biology in Type 2 Diabetes".
- Author
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Gaisano HY, Jonas JC, and Gloyn AL
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- Humans, Obesity, Diabetes Mellitus, Type 2, Islets of Langerhans
- Published
- 2020
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220. Nutrient Metabolism, Subcellular Redox State, and Oxidative Stress in Pancreatic Islets and β-Cells.
- Author
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Roma LP and Jonas JC
- Subjects
- Animals, Antioxidants metabolism, Diabetes Mellitus, Type 2 metabolism, Endoplasmic Reticulum metabolism, Fluorescent Dyes, Glucose metabolism, Humans, Hydrogen Peroxide metabolism, Insulin Secretion, Mitochondria metabolism, Nutrients metabolism, Nutrients toxicity, Oxidation-Reduction, Peroxisomes metabolism, Reactive Oxygen Species metabolism, Signal Transduction, Superoxide Dismutase metabolism, Cell Compartmentation, Insulin-Secreting Cells cytology, Insulin-Secreting Cells metabolism, Islets of Langerhans cytology, Islets of Langerhans metabolism, Oxidative Stress
- Abstract
Insulin-secreting pancreatic β-cells play a critical role in blood glucose homeostasis and the development of type 2 diabetes (T2D) in the context of insulin resistance. Based on data obtained at the whole cell level using poorly specific chemical probes, reactive oxygen species (ROS) such as superoxide and hydrogen peroxide have been proposed to contribute to the stimulation of insulin secretion by nutrients (positive role) and to the alterations of cell survival and secretory function in T2D (negative role). This raised the controversial hypothesis that any attempt to decrease β-cell oxidative stress and apoptosis in T2D would further impair insulin secretion. Over the last decade, the development of genetically-encoded redox probes that can be targeted to cellular compartments of interest and are specific of redox couples allowed the evaluation of short- and long-term effects of nutrients on β-cell redox changes at the subcellular level. The data indicated that the nutrient regulation of β-cell redox signaling and ROS toxicity is far more complex than previously thought and that the subcellular compartmentation of these processes cannot be neglected when evaluating the mechanisms of ROS production or the efficacy of antioxidant enzymes and antioxidant drugs under glucolipotoxic conditions and in T2D. In this review, we present what is currently known about the compartmentation of redox homeostatic systems and tools to investigate it. We then review data about the effects of nutrients on β-cell subcellular redox state under normal conditions and in the context of T2D and discuss challenges and opportunities in the field., (Copyright © 2019 Elsevier Ltd. All rights reserved.)
- Published
- 2020
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221. Exenatide induces frataxin expression and improves mitochondrial function in Friedreich ataxia.
- Author
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Igoillo-Esteve M, Oliveira AF, Cosentino C, Fantuzzi F, Demarez C, Toivonen S, Hu A, Chintawar S, Lopes M, Pachera N, Cai Y, Abdulkarim B, Rai M, Marselli L, Marchetti P, Tariq M, Jonas JC, Boscolo M, Pandolfo M, Eizirik DL, and Cnop M
- Subjects
- Adolescent, Adult, Aged, Animals, Brain pathology, Cerebellum pathology, Disease Models, Animal, Exenatide therapeutic use, Female, Friedreich Ataxia genetics, Friedreich Ataxia metabolism, Ganglia, Spinal pathology, Gene Knock-In Techniques, Glucagon-Like Peptide 1 analogs & derivatives, Glucagon-Like Peptide 1 metabolism, Humans, Insulin metabolism, Insulin-Secreting Cells metabolism, Iron metabolism, Male, Mice, Mice, Knockout, Middle Aged, Oxidative Stress, Reactive Oxygen Species metabolism, Trinucleotide Repeat Expansion, Young Adult, Frataxin, Exenatide pharmacology, Friedreich Ataxia drug therapy, Gene Expression Regulation drug effects, Iron-Binding Proteins genetics, Iron-Binding Proteins metabolism, Mitochondria metabolism
- Abstract
Friedreich ataxia is an autosomal recessive neurodegenerative disease associated with a high diabetes prevalence. No treatment is available to prevent or delay disease progression. Friedreich ataxia is caused by intronic GAA trinucleotide repeat expansions in the frataxin-encoding FXN gene that reduce frataxin expression, impair iron-sulfur cluster biogenesis, cause oxidative stress, and result in mitochondrial dysfunction and apoptosis. Here we examined the metabolic, neuroprotective, and frataxin-inducing effects of glucagon-like peptide-1 (GLP-1) analogs in in vivo and in vitro models and in patients with Friedreich ataxia. The GLP-1 analog exenatide improved glucose homeostasis of frataxin-deficient mice through enhanced insulin content and secretion in pancreatic β cells. Exenatide induced frataxin and iron-sulfur cluster-containing proteins in β cells and brain and was protective to sensory neurons in dorsal root ganglia. GLP-1 analogs also induced frataxin expression, reduced oxidative stress, and improved mitochondrial function in Friedreich ataxia patients' induced pluripotent stem cell-derived β cells and sensory neurons. The frataxin-inducing effect of exenatide was confirmed in a pilot trial in Friedreich ataxia patients, showing modest frataxin induction in platelets over a 5-week treatment course. Taken together, GLP-1 analogs improve mitochondrial function in frataxin-deficient cells and induce frataxin expression. Our findings identify incretin receptors as a therapeutic target in Friedreich ataxia.
- Published
- 2020
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222. Metallothionein 1 negatively regulates glucose-stimulated insulin secretion and is differentially expressed in conditions of beta cell compensation and failure in mice and humans.
- Author
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Bensellam M, Shi YC, Chan JY, Laybutt DR, Chae H, Abou-Samra M, Pappas EG, Thomas HE, Gilon P, and Jonas JC
- Subjects
- Acrylates, Animals, Cell Line, Diabetes Mellitus, Type 2 genetics, Diet, High-Fat, Female, Gene Expression, Glucose Tolerance Test, Humans, Insulin blood, Insulin Secretion drug effects, Islets of Langerhans drug effects, Islets of Langerhans metabolism, Metallothionein genetics, Mice, Obesity genetics, Obesity metabolism, Phenyl Ethers, Prediabetic State genetics, Prediabetic State metabolism, Blood Glucose metabolism, Diabetes Mellitus, Type 2 metabolism, Glucose pharmacology, Insulin Secretion physiology, Insulin-Secreting Cells metabolism, Metallothionein metabolism
- Abstract
Aims/hypothesis: The mechanisms responsible for beta cell compensation in obesity and for beta cell failure in type 2 diabetes are poorly defined. The mRNA levels of several metallothionein (MT) genes are upregulated in islets from individuals with type 2 diabetes, but their role in beta cells is not clear. Here we examined: (1) the temporal changes of islet Mt1 and Mt2 gene expression in mouse models of beta cell compensation and failure; and (2) the role of Mt1 and Mt2 in beta cell function and glucose homeostasis in mice., Methods: Mt1 and Mt2 expression was assessed in islets from: (1) control lean (chow diet-fed) and diet-induced obese (high-fat diet-fed for 6 weeks) mice; (2) mouse models of diabetes (db/db mice) at 6 weeks old (prediabetes) and 16 weeks old (after diabetes onset) and age-matched db/+ (control) mice; and (3) obese non-diabetic ob/ob mice (16-week-old) and age-matched ob/+ (control) mice. MT1E, MT1X and MT2A expression was assessed in islets from humans with and without type 2 diabetes. Mt1-Mt2 double-knockout (KO) mice, transgenic mice overexpressing Mt1 under the control of its natural promoter (Tg-Mt1) and corresponding control mice were also studied. In MIN6 cells, MT1 and MT2 were inhibited by small interfering RNAs. mRNA levels were assessed by real-time RT-PCR, plasma insulin and islet MT levels by ELISA, glucose tolerance by i.p. glucose tolerance tests and overnight fasting-1 h refeeding tests, insulin tolerance by i.p. insulin tolerance tests, insulin secretion by RIA, cytosolic free Ca
2+ concentration with Fura-2 leakage resistant (Fura-2 LR), cytosolic free Zn2+ concentration with Fluozin-3, and NAD(P)H by autofluorescence., Results: Mt1 and Mt2 mRNA levels were reduced in islets of murine models of beta cell compensation, whereas they were increased in diabetic db/db mice. In humans, MT1X mRNA levels were significantly upregulated in islets from individuals with type 2 diabetes in comparison with non-diabetic donors, while MT1E and MT2A mRNA levels were unchanged. Ex vivo, islet Mt1 and Mt2 mRNA and MT1 and MT2 protein levels were downregulated after culture with glucose at 10-30 mmol/l vs 2-5 mmol/l, in association with increased insulin secretion. In human islets, mRNA levels of MT1E, MT1X and MT2A were downregulated by stimulation with physiological and supraphysiological levels of glucose. In comparison with wild-type (WT) mice, Mt1-Mt2 double-KO mice displayed improved glucose tolerance in association with increased insulin levels and enhanced insulin release from isolated islets. In contrast, isolated islets from Tg-Mt1 mice displayed impaired glucose-stimulated insulin secretion (GSIS). In both Mt1-Mt2 double-KO and Tg-Mt1 models, the changes in GSIS occurred despite similar islet insulin content, rises in cytosolic free Ca2+ concentration and NAD(P)H levels, or intracellular Zn2+ concentration vs WT mice. In MIN6 cells, knockdown of MT1 but not MT2 potentiated GSIS, suggesting that Mt1 rather than Mt2 affects beta cell function., Conclusions/interpretation: These findings implicate Mt1 as a negative regulator of insulin secretion. The downregulation of Mt1 is associated with beta cell compensation in obesity, whereas increased Mt1 accompanies beta cell failure and type 2 diabetes.- Published
- 2019
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223. Phlda3 regulates beta cell survival during stress.
- Author
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Bensellam M, Chan JY, Lee K, Joglekar MV, Hardikar AA, Loudovaris T, Thomas HE, Jonas JC, and Laybutt DR
- Subjects
- Animals, Antioxidants pharmacology, Cell Death drug effects, Cell Line, Cell Survival drug effects, Cytokines pharmacology, Cytoprotection drug effects, Endoplasmic Reticulum Chaperone BiP, Endoplasmic Reticulum Stress drug effects, Female, Humans, Insulin-Secreting Cells drug effects, Mice, Inbred C57BL, Mice, Inbred NOD, Models, Biological, NF-kappa B metabolism, Nuclear Proteins genetics, Oxidative Stress drug effects, Palmitic Acid pharmacology, RNA, Messenger genetics, RNA, Messenger metabolism, Thapsigargin pharmacology, Unfolded Protein Response drug effects, Up-Regulation drug effects, Up-Regulation genetics, X-Box Binding Protein 1 metabolism, Insulin-Secreting Cells cytology, Insulin-Secreting Cells metabolism, Nuclear Proteins metabolism, Stress, Physiological drug effects
- Abstract
The loss of functional beta cell mass characterises all forms of diabetes. Beta cells are highly susceptible to stress, including cytokine, endoplasmic reticulum (ER) and oxidative stress. This study examined the role of pleckstrin homology-like, domain family A, member 3 (Phlda3) in beta cell survival under stress conditions and the regulatory basis. We found that the mRNA levels of Phlda3 were markedly upregulated in vivo in the islets of diabetic humans and mice. In vitro, exposure of MIN6 cells or islets to cytokines, palmitate, thapsigargin or ribose upregulated Phlda3 mRNA and protein levels, concurrent with the induction of ER stress (Ddit3 and Trb3) and antioxidant (Hmox1) genes. Furthermore, H
2 O2 treatment markedly increased PHLDA3 immunostaining in human islets. Phlda3 expression was differentially regulated by adaptive (Xbp1) and apoptotic (Ddit3) unfolded protein response (UPR) mediators. siRNA-mediated knockdown of Xbp1 inhibited the induction of Phlda3 by cytokines and palmitate, whereas knockdown of Ddit3 upregulated Phlda3. Moreover, knockdown of Phlda3 potentiated cytokine-induced apoptosis in association with upregulation of inflammatory genes (iNos, IL1β and IκBα) and NFκB phosphorylation and downregulation of antioxidant (Gpx1 and Srxn1) and adaptive UPR (Xbp1, Hspa5 and Fkbp11) genes. Knockdown of Phlda3 also potentiated apoptosis under oxidative stress conditions induced by ribose treatment. These findings suggest that Phlda3 is crucial for beta cell survival under stress conditions. Phlda3 regulates the cytokine, oxidative and ER stress responses in beta cells via the repression of inflammatory gene expression and the maintenance of antioxidant and adaptive UPR gene expression. Phlda3 may promote beta cell survival in diabetes.- Published
- 2019
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224. Glucose Acutely Reduces Cytosolic and Mitochondrial H 2 O 2 in Rat Pancreatic Beta Cells.
- Author
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Deglasse JP, Roma LP, Pastor-Flores D, Gilon P, Dick TP, and Jonas JC
- Subjects
- Animals, Cytosol metabolism, Glucose metabolism, Hydrogen Peroxide metabolism, Insulin-Secreting Cells metabolism, Male, Mitochondria metabolism, Oxidation-Reduction, Rats, Rats, Wistar, Cytosol drug effects, Glucose pharmacology, Hydrogen Peroxide antagonists & inhibitors, Insulin-Secreting Cells drug effects, Mitochondria drug effects
- Abstract
Aims: Whether H
2 O2 contributes to the glucose-dependent stimulation of insulin secretion (GSIS) by pancreatic β cells is highly controversial. We used two H2 O2 -sensitive probes, roGFP2-Orp1 (reduction/oxidation-sensitive enhanced green fluorescent protein fused to oxidant receptor peroxidase 1) and HyPer (hydrogen peroxide sensor) with its pH-control SypHer, to test the acute effects of glucose, monomethyl succinate, leucine with glutamine, and α-ketoisocaproate on β cell cytosolic and mitochondrial H2 O2 concentrations. We then tested the effects of low H2 O2 and menadione concentrations on insulin secretion. Results: RoGFP2-Orp1 was more sensitive than HyPer to H2 O2 (response at 2-5 vs. 10 μ M ) and less pH-sensitive. Under control conditions, stimulation with glucose reduced mitochondrial roGFP2-Orp1 oxidation without affecting cytosolic roGFP2-Orp1 and HyPer fluorescence ratios, except for the pH-dependent effects on HyPer. However, stimulation with glucose decreased the oxidation of both cytosolic probes by 15 μ M exogenous H2 O2 . The glucose effects were not affected by overexpression of catalase, mitochondrial catalase, or superoxide dismutase 1 and 2. They followed the increase in NAD(P)H autofluorescence, were maximal at 5 m M glucose in the cytosol and 10 m M glucose in the mitochondria, and were partly mimicked by the other nutrients. Exogenous H2 O2 (1-15 μ M ) did not affect insulin secretion. By contrast, menadione (1-5 μ M ) did not increase basal insulin secretion but reduced the stimulation of insulin secretion by 20 m M glucose. Innovation: Subcellular changes in β cell H2 O2 levels are better monitored with roGFP2-Orp1 than HyPer/SypHer. Nutrients acutely lower mitochondrial H2 O2 levels in β cells and promote degradation of exogenously supplied H2 O2 in both cytosolic and mitochondrial compartments. Conclusion: The GSIS occurs independently of a detectable increase in β cell cytosolic or mitochondrial H2 O2 levels.- Published
- 2019
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225. Pancreatic β-cell tRNA hypomethylation and fragmentation link TRMT10A deficiency with diabetes.
- Author
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Cosentino C, Toivonen S, Diaz Villamil E, Atta M, Ravanat JL, Demine S, Schiavo AA, Pachera N, Deglasse JP, Jonas JC, Balboa D, Otonkoski T, Pearson ER, Marchetti P, Eizirik DL, Cnop M, and Igoillo-Esteve M
- Subjects
- Aged, Animals, Apoptosis genetics, Cell Death genetics, Cell Differentiation genetics, Cells, Cultured, DNA Fragmentation, Diabetes Mellitus metabolism, Genetic Linkage, Humans, Induced Pluripotent Stem Cells physiology, Insulin-Secreting Cells physiology, Methyltransferases deficiency, Methyltransferases metabolism, Middle Aged, Mutation, Rats, DNA Methylation, Diabetes Mellitus genetics, Insulin-Secreting Cells metabolism, Methyltransferases genetics, RNA, Transfer metabolism
- Abstract
Transfer RNAs (tRNAs) are non-coding RNA molecules essential for protein synthesis. Post-transcriptionally they are heavily modified to improve their function, folding and stability. Intronic polymorphisms in CDKAL1, a tRNA methylthiotransferase, are associated with increased type 2 diabetes risk. Loss-of-function mutations in TRMT10A, a tRNA methyltransferase, are a monogenic cause of early onset diabetes and microcephaly. Here we confirm the role of TRMT10A as a guanosine 9 tRNA methyltransferase, and identify tRNAGln and tRNAiMeth as two of its targets. Using RNA interference and induced pluripotent stem cell-derived pancreatic β-like cells from healthy controls and TRMT10A-deficient patients we demonstrate that TRMT10A deficiency induces oxidative stress and triggers the intrinsic pathway of apoptosis in β-cells. We show that tRNA guanosine 9 hypomethylation leads to tRNAGln fragmentation and that 5'-tRNAGln fragments mediate TRMT10A deficiency-induced β-cell death. This study unmasks tRNA hypomethylation and fragmentation as a hitherto unknown mechanism of pancreatic β-cell demise relevant to monogenic and polygenic forms of diabetes.
- Published
- 2018
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226. Somatostatin Is Only Partly Required for the Glucagonostatic Effect of Glucose but Is Necessary for the Glucagonostatic Effect of K ATP Channel Blockers.
- Author
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Lai BK, Chae H, Gómez-Ruiz A, Cheng P, Gallo P, Antoine N, Beauloye C, Jonas JC, Seghers V, Seino S, and Gilon P
- Subjects
- Animals, Islets of Langerhans drug effects, Islets of Langerhans metabolism, Mice, Mice, Knockout, Pancreas drug effects, Somatostatin genetics, Glucagon metabolism, Glucose pharmacology, KATP Channels antagonists & inhibitors, Pancreas metabolism, Potassium Channel Blockers pharmacology, Somatostatin metabolism
- Abstract
The mechanisms of control of glucagon secretion are largely debated. In particular, the paracrine role of somatostatin (SST) is unclear. We studied its role in the control of glucagon secretion by glucose and K
ATP channel blockers, using perifused islets and the in situ perfused pancreas. The involvement of SST was evaluated by comparing glucagon release of control tissue or tissue without paracrine influence of SST (pertussis toxin-treated islets, or islets or pancreas from Sst-/- mice). We show that removal of the paracrine influence of SST suppresses the ability of KATP channel blockers or KATP channel ablation to inhibit glucagon release, suggesting that in control islets, the glucagonostatic effect of KATP channel blockers/ablation is fully mediated by SST. By contrast, the glucagonostatic effect of glucose in control islets is mainly independent of SST for low glucose concentrations (0-7 mmol/L) but starts to involve SST for high concentrations of the sugar (15-30 mmol/L). This demonstrates that the glucagonostatic effect of glucose only partially depends on SST. Real-time quantitative PCR and pharmacological experiments indicate that the glucagonostatic effect of SST is mediated by two types of SST receptors, SSTR2 and SSTR3. These results suggest that alterations of the paracrine influence of SST will affect glucagon release., (© 2018 by the American Diabetes Association.)- Published
- 2018
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227. Glucolipotoxic conditions induce β-cell iron import, cytosolic ROS formation and apoptosis.
- Author
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Hansen JB, Dos Santos LRB, Liu Y, Prentice KJ, Teudt F, Tonnesen M, Jonas JC, Wheeler MB, and Mandrup-Poulsen T
- Subjects
- Animals, Biological Transport physiology, Diabetes Mellitus, Type 2 metabolism, Mice, Apoptosis physiology, Cytosol metabolism, Insulin-Secreting Cells metabolism, Iron metabolism, Reactive Oxygen Species metabolism
- Abstract
Type 2 diabetes (T2D) arises when the pancreatic beta-cell fails to compensate for increased insulin needs due to insulin resistance. Glucolipotoxicity (GLT) has been proposed to induce beta-cell dysfunction in T2D by formation of reactive oxygen species (ROS). Here, we examined if modeling glucolipotoxic conditions by high glucose-high free fatty acid (FFA) exposure (GLT) regulates beta-cell iron transport, by increasing the cytosolic labile iron pool (LIP). In isolated mouse islets, the GLT-induced increase in the LIP catalyzed cytosolic ROS formation and induced apoptosis. We show that GLT-induced ROS production is regulated by an increased LIP associated with elevated expression of genes regulating iron import. Using pharmacological and transgenic approaches, we show that iron reduction and decreased iron import protects from GLT-induced ROS production, prevents impairment of the mitochondrial membrane potential (MMP) and inhibits apoptosis. This study identifies a novel pathway underlying GLT-induced apoptosis involving increased iron import, generation of hydroxyl radicals from hydrogen peroxide through the Fenton reaction in the cytosolic compartment associated with dissipation of the MMP and beta-cell apoptosis., (© 2018 Society for Endocrinology.)
- Published
- 2018
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228. Mechanisms of β-cell dedifferentiation in diabetes: recent findings and future research directions.
- Author
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Bensellam M, Jonas JC, and Laybutt DR
- Subjects
- Animals, Cell Death physiology, Cell Differentiation, Diabetes Mellitus pathology, Diabetes Mellitus physiopathology, Humans, Insulin-Secreting Cells pathology, Stem Cells physiology, Biomedical Research trends, Cell Dedifferentiation physiology, Diabetes Mellitus etiology, Endocrinology trends, Insulin-Secreting Cells physiology
- 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., (© 2018 Society for Endocrinology.)
- Published
- 2018
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229. Biomarkers of tumour redox status in response to modulations of glutathione and thioredoxin antioxidant pathways.
- Author
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Kengen J, Deglasse JP, Neveu MA, Mignion L, Desmet C, Gourgue F, Jonas JC, Gallez B, and Jordan BF
- Subjects
- Animals, Biomarkers analysis, Cell Line, Tumor, Female, Humans, Mice, Oxidation-Reduction, Xenograft Model Antitumor Assays, Breast Neoplasms metabolism, Glutathione drug effects, Oxidative Stress, Thioredoxins antagonists & inhibitors, Uterine Cervical Neoplasms metabolism
- Abstract
The ability of certain cancer cells to maintain a highly reduced intracellular environment is correlated with aggressiveness and drug resistance. Since the glutathione (GSH) and thioredoxin (TRX) systems cooperate to a tight regulation of ROS in cell physiology, and to a stimulation of tumour initiation and progression, modulation of the GSH and TRX pathways are emerging as new potential targets in cancer. In vivo methods to assess changes in tumour redox status are critically needed to assess the relevance of redox-targeted agents. The current study assesses in vitro and in vivo biomarkers of tumour redox status in response to treatments targeting the GSH and TRX pathways, by comparing cytosolic and mitochondrial redox nitroxide electron paramagnetic resonance (EPR) probes, and cross-validation with redox dynamic fluorescent measurement. For that purpose, the effect of the GSH modulator buthionine sulfoximine (BSO) and of the TRX reductase inhibitor auranofin were measured in vitro using both cytosolic and mitochondrial EPR and roGFP probes in breast and cervical cancer cells. In vivo, mice bearing breast or cervical cancer xenografts were treated with the GSH or TRX modulators and monitored using the mito-TEMPO spin probe. Our data highlight the importance of using mitochondria-targeted spin probes to assess changes in tumour redox status induced by redox modulators. Further in vivo validation of the mito-tempo spin probe with alternative in vivo methods should be considered, yet the spin probe used in vivo in xenografts demonstrated sensitivity to the redox status modulators.
- Published
- 2018
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230. NNT reverse mode of operation mediates glucose control of mitochondrial NADPH and glutathione redox state in mouse pancreatic β-cells.
- Author
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Santos LRB, Muller C, de Souza AH, Takahashi HK, Spégel P, Sweet IR, Chae H, Mulder H, and Jonas JC
- Subjects
- Animals, Calcium metabolism, Cells, Cultured, Exocytosis, Female, Insulin metabolism, Mice, Mice, Inbred C57BL, Mitochondrial Proteins genetics, Mitochondrial Proteins metabolism, NADP Transhydrogenase, AB-Specific genetics, Oxidation-Reduction, Glucose metabolism, Glutathione metabolism, Insulin-Secreting Cells metabolism, NADP metabolism, NADP Transhydrogenase, AB-Specific metabolism
- Abstract
Objective: The glucose stimulation of insulin secretion (GSIS) by pancreatic β-cells critically depends on increased production of metabolic coupling factors, including NADPH. Nicotinamide nucleotide transhydrogenase (NNT) typically produces NADPH at the expense of NADH and ΔpH in energized mitochondria. Its spontaneous inactivation in C57BL/6J mice was previously shown to alter ATP production, Ca
2+ influx, and GSIS, thereby leading to glucose intolerance. Here, we tested the role of NNT in the glucose regulation of mitochondrial NADPH and glutathione redox state and reinvestigated its role in GSIS coupling events in mouse pancreatic islets., Methods: Islets were isolated from female C57BL/6J mice (J-islets), which lack functional NNT, and genetically close C57BL/6N mice (N-islets). Wild-type mouse NNT was expressed in J-islets by adenoviral infection. Mitochondrial and cytosolic glutathione oxidation was measured with glutaredoxin 1-fused roGFP2 probes targeted or not to the mitochondrial matrix. NADPH and NADH redox state was measured biochemically. Insulin secretion and upstream coupling events were measured under dynamic or static conditions by standard procedures., Results: NNT is largely responsible for the acute glucose-induced rise in islet NADPH/NADP+ ratio and decrease in mitochondrial glutathione oxidation, with a small impact on cytosolic glutathione. However, contrary to current views on NNT in β-cells, these effects resulted from a glucose-dependent reduction in NADPH consumption by NNT reverse mode of operation, rather than from a stimulation of its forward mode of operation. Accordingly, the lack of NNT in J-islets decreased their sensitivity to exogenous H2 O2 at non-stimulating glucose. Surprisingly, the lack of NNT did not alter the glucose-stimulation of Ca2+ influx and upstream mitochondrial events, but it markedly reduced both phases of GSIS by altering Ca2+ -induced exocytosis and its metabolic amplification., Conclusion: These results drastically modify current views on NNT operation and mitochondrial function in pancreatic β-cells.- Published
- 2017
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231. NADPH oxidase-2 does not contribute to β-cell glucotoxicity in cultured pancreatic islets from C57BL/6J mice.
- Author
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de Souza AH, Santos LRB, Roma LP, Bensellam M, Carpinelli AR, and Jonas JC
- Subjects
- Animals, Apoptosis drug effects, Cell Survival drug effects, Cytosol metabolism, Glucose Transporter Type 2 genetics, Glucose Transporter Type 2 metabolism, Glutaredoxins metabolism, Glutathione metabolism, Green Fluorescent Proteins metabolism, Heme Oxygenase-1 genetics, Heme Oxygenase-1 metabolism, Insulin metabolism, Insulin Secretion, Insulin-Secreting Cells drug effects, Male, Mice, Inbred C57BL, Mice, Knockout, NADPH Oxidase 2 deficiency, Oxidation-Reduction, RNA, Messenger genetics, RNA, Messenger metabolism, Sulfhydryl Compounds metabolism, Tissue Culture Techniques, Glucose toxicity, Insulin-Secreting Cells enzymology, Insulin-Secreting Cells pathology, NADPH Oxidase 2 metabolism
- Abstract
High glucose-induced oxidative stress and increased NADPH oxidase-2 (NOX2) activity may contribute to the progressive decline of the functional β-cell mass in type 2 diabetes. To test that hypothesis, we characterized, in islets from male NOX2 knockout (NOX2-KO) and wild-type (WT) C57BL/6J mice cultured for up to 3 weeks at 10 or 30 mmol/l glucose (G10 or G30), the in vitro effects of glucose on cytosolic oxidative stress using probes sensing glutathione oxidation (GRX1-roGFP2), thiol oxidation (roGFP1) or H
2 O2 (roGFP2-Orp1), on β-cell stimulus-secretion coupling events and on β-cell apoptosis. After 1-2 days of culture in G10, the glucose stimulation of insulin secretion (GSIS) was ∼1.7-fold higher in NOX2-KO vs. WT islets at 20-30 mmol/l glucose despite similar rises in NAD(P)H and intracellular calcium concentration ([Ca2+ ]i ) and no differences in cytosolic GRX1-roGFP2 oxidation. After long-term culture at G10, roGFP1 and roGFP2-Orp1 oxidation and β-cell apoptosis remained low, and the glucose-induced rises in NAD(P)H, [Ca2+ ]i and GSIS were similarly preserved in both islet types. After prolonged culture at G30, roGFP1 and roGFP2-Orp1 oxidation increased in parallel with β-cell apoptosis, the glucose sensitivity of the NADPH, [Ca2+ ]i and insulin secretion responses increased, the maximal [Ca2+ ]i response decreased, but maximal GSIS was preserved. These responses were almost identical in both islet types. In conclusion, NOX2 is a negative regulator of maximal GSIS in C57BL/6J mouse islets, but it does not detectably contribute to the in vitro glucotoxic induction of cytosolic oxidative stress and alterations of β-cell survival and function., (Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.)- Published
- 2017
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232. Hypoxia reduces ER-to-Golgi protein trafficking and increases cell death by inhibiting the adaptive unfolded protein response in mouse beta cells.
- Author
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Bensellam M, Maxwell EL, Chan JY, Luzuriaga J, West PK, Jonas JC, Gunton JE, and Laybutt DR
- Subjects
- Animals, Apoptosis genetics, Apoptosis physiology, Cell Death physiology, Cell Line, Diabetes Mellitus, Type 2 metabolism, Endoplasmic Reticulum Chaperone BiP, Heat-Shock Proteins genetics, Heat-Shock Proteins metabolism, Mice, Mice, Inbred C57BL, Protein Transport physiology, Real-Time Polymerase Chain Reaction, Reverse Transcriptase Polymerase Chain Reaction, Transcription Factor CHOP genetics, Transcription Factor CHOP metabolism, Unfolded Protein Response physiology, Endoplasmic Reticulum metabolism, Golgi Apparatus metabolism, Insulin-Secreting Cells metabolism
- Abstract
Aims/hypothesis: Hypoxia may contribute to beta cell failure in type 2 diabetes and islet transplantation. The adaptive unfolded protein response (UPR) is required for endoplasmic reticulum (ER) homeostasis. Here we investigated whether or not hypoxia regulates the UPR in beta cells and the role the adaptive UPR plays during hypoxic stress., Methods: Mouse islets and MIN6 cells were exposed to various oxygen (O2) tensions. DNA-damage inducible transcript 3 (DDIT3), hypoxia-inducible transcription factor (HIF)1α and HSPA5 were knocked down using small interfering (si)RNA; Hspa5 was also overexpressed. db/db mice were used., Results: Hypoxia-response genes were upregulated in vivo in the islets of diabetic, but not prediabetic, db/db mice. In isolated mouse islets and MIN6 cells, O2 deprivation (1-5% vs 20%; 4-24 h) markedly reduced the expression of adaptive UPR genes, including Hspa5, Hsp90b1, Fkbp11 and spliced Xbp1. Coatomer protein complex genes (Copa, Cope, Copg [also known as Copg1], Copz1 and Copz2) and ER-to-Golgi protein trafficking were also reduced, whereas apoptotic genes (Ddit3, Atf3 and Trb3 [also known as Trib3]), c-Jun N-terminal kinase (JNK) phosphorylation and cell death were increased. Inhibition of JNK, but not HIF1α, restored adaptive UPR gene expression and ER-to-Golgi protein trafficking while protecting against apoptotic genes and cell death following hypoxia. DDIT3 knockdown delayed the loss of the adaptive UPR and partially protected against hypoxia-induced cell death. The latter response was prevented by HSPA5 knockdown. Finally, Hspa5 overexpression significantly protected against hypoxia-induced cell death., Conclusions/interpretation: Hypoxia inhibits the adaptive UPR in beta cells via JNK and DDIT3 activation, but independently of HIF1α. Downregulation of the adaptive UPR contributes to reduced ER-to-Golgi protein trafficking and increased beta cell death during hypoxic stress.
- Published
- 2016
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233. Glucokinase activation is beneficial or toxic to cultured rat pancreatic islets depending on the prevailing glucose concentration.
- Author
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Roma LP, Duprez J, and Jonas JC
- Subjects
- Animals, Apoptosis drug effects, Cell Survival drug effects, Cells, Cultured, Dose-Response Relationship, Drug, Enzyme Activation drug effects, Enzyme Activation physiology, Islets of Langerhans metabolism, Male, Rats, Rats, Wistar, Glucokinase metabolism, Glucose pharmacology, Islets of Langerhans drug effects, Sulfones pharmacology, Thiazoles pharmacology
- Abstract
In rat pancreatic islets, β-cell gene expression, survival, and subsequent acute glucose stimulation of insulin secretion (GSIS) are optimally preserved by prolonged culture at 10 mM glucose (G10) and markedly altered by culture at G5 or G30. Here, we tested whether pharmacological glucokinase (GK) activation prevents these alterations during culture or improves GSIS after culture. Rat pancreatic islets were cultured 1-7 days at G5, G10, or G30 with or without 3 μM of the GK activator Ro 28-0450 (Ro). After culture, β-cell apoptosis and islet gene mRNA levels were measured, and the acute glucose-induced increase in NAD(P)H autofluorescence, intracellular calcium concentration, and insulin secretion were tested in the absence or presence of Ro. Prolonged culture of rat islets at G5 or G30 instead of G10 triggered β-cell apoptosis and reduced their glucose responsiveness. Addition of Ro during culture differently affected β-cell survival and glucose responsiveness depending on the glucose concentration during culture: it was beneficial to β-cell survival and function at G5, detrimental at G10, and ineffective at G30. In contrast, acute GK activation with Ro increased the glucose sensitivity of islets cultured at G10 but failed at restoring β-cell glucose responsiveness after culture at G5 or G30. We conclude that pharmacological GK activation prevents the alteration of β-cell survival and function by long-term culture at G5 but mimics glucotoxicity when added to G10. The complex effects of glucose on the β-cell phenotype result from changes in glucose metabolism and not from an effect of glucose per se., (Copyright © 2015 the American Physiological Society.)
- Published
- 2015
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234. Unveiling a common mechanism of apoptosis in β-cells and neurons in Friedreich's ataxia.
- Author
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Igoillo-Esteve M, Gurgul-Convey E, Hu A, Romagueira Bichara Dos Santos L, Abdulkarim B, Chintawar S, Marselli L, Marchetti P, Jonas JC, Eizirik DL, Pandolfo M, and Cnop M
- Subjects
- Animals, Cell Line, Diabetes Mellitus etiology, Diabetes Mellitus genetics, Diabetes Mellitus metabolism, Diabetes Mellitus physiopathology, Female, Friedreich Ataxia complications, Friedreich Ataxia genetics, Friedreich Ataxia metabolism, Humans, Insulin-Secreting Cells metabolism, Iron-Binding Proteins genetics, Iron-Binding Proteins metabolism, Male, Middle Aged, Neurons metabolism, Oxidative Stress, Rats, Rats, Wistar, Frataxin, Apoptosis, Friedreich Ataxia physiopathology, Insulin-Secreting Cells cytology, Neurons cytology
- Abstract
Friedreich's ataxia (FRDA) is a neurodegenerative disorder associated with cardiomyopathy and diabetes. Effective therapies for FRDA are an urgent unmet need; there are currently no options to prevent or treat this orphan disease. FRDA is caused by reduced expression of the mitochondrial protein frataxin. We have previously demonstrated that pancreatic β-cell dysfunction and death cause diabetes in FRDA. This is secondary to mitochondrial dysfunction and apoptosis but the underlying molecular mechanisms are not known. Here we show that β-cell demise in frataxin deficiency is the consequence of oxidative stress-mediated activation of the intrinsic pathway of apoptosis. The pro-apoptotic Bcl-2 family members Bad, DP5 and Bim are the key mediators of frataxin deficiency-induced β-cell death. Importantly, the intrinsic pathway of apoptosis is also activated in FRDA patients' induced pluripotent stem cell-derived neurons. Interestingly, cAMP induction normalizes mitochondrial oxidative status and fully prevents activation of the intrinsic pathway of apoptosis in frataxin-deficient β-cells and neurons. This preclinical study suggests that incretin analogs hold potential to prevent/delay both diabetes and neurodegeneration in FRDA., (© The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)
- Published
- 2015
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235. Acute nutrient regulation of the mitochondrial glutathione redox state in pancreatic β-cells.
- Author
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Takahashi HK, Santos LR, Roma LP, Duprez J, Broca C, Wojtusciszyn A, and Jonas JC
- Subjects
- Animals, Calcium metabolism, Catalase metabolism, Cell Nucleus metabolism, Cytosol metabolism, HEK293 Cells, Humans, Hydrogen Peroxide metabolism, Hydrogen-Ion Concentration, Insulin metabolism, Insulin Secretion, Insulin-Secreting Cells drug effects, Mitochondria physiology, NADP metabolism, Oxidation-Reduction, Rats, Reactive Oxygen Species metabolism, Vitamin K 3 metabolism, Glucose pharmacology, Glutathione metabolism, Insulin-Secreting Cells metabolism, Mitochondria drug effects
- Abstract
The glucose stimulation of insulin secretion by pancreatic β-cells depends on increased production of metabolic coupling factors, among which changes in NADPH and ROS (reactive oxygen species) may alter the glutathione redox state (EGSH) and signal through changes in thiol oxidation. However, whether nutrients affect EGSH in β-cell subcellular compartments is unknown. Using redox-sensitive GFP2 fused to glutaredoxin 1 and its mitochondria-targeted form, we studied the acute nutrient regulation of EGSH in the cytosol/nucleus or the mitochondrial matrix of rat islet cells. These probes were mainly expressed in β-cells and reacted to low concentrations of exogenous H2O2 and menadione. Under control conditions, cytosolic/nuclear EGSH was close to -300 mV and unaffected by glucose (from 0 to 30 mM). In comparison, mitochondrial EGSH was less negative and rapidly regulated by glucose and other nutrients, ranging from -280 mV in the absence of glucose to -299 mV in 30 mM glucose. These changes were largely independent from changes in intracellular Ca(2+) concentration and in mitochondrial pH. They were unaffected by overexpression of SOD2 (superoxide dismutase 2) and mitochondria-targeted catalase, but were inversely correlated with changes in NAD(P)H autofluorescence, suggesting that they indirectly resulted from increased NADPH availability rather than from changes in ROS concentration. Interestingly, the opposite regulation of mitochondrial EGSH and NAD(P)H autofluorescence by glucose was also observed in human islets isolated from two donors. In conclusion, the present study demonstrates that glucose and other nutrients acutely reduce mitochondrial, but not cytosolic/nuclear, EGSH in pancreatic β-cells under control conditions.
- Published
- 2014
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236. The islet estrogen receptor-α is induced by hyperglycemia and protects against oxidative stress-induced insulin-deficient diabetes.
- Author
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Kilic G, Alvarez-Mercado AI, Zarrouki B, Opland D, Liew CW, Alonso LC, Myers MG Jr, Jonas JC, Poitout V, Kulkarni RN, and Mauvais-Jarvis F
- Subjects
- Animals, Blotting, Western, Brain drug effects, Brain metabolism, Brain pathology, Diabetes Mellitus, Experimental etiology, Estrogens pharmacology, Female, Immunoenzyme Techniques, Integrases metabolism, Islets of Langerhans drug effects, Islets of Langerhans metabolism, Male, Mice, Mice, Inbred C57BL, Mice, Knockout, RNA, Messenger genetics, Rats, Rats, Wistar, Real-Time Polymerase Chain Reaction, Receptors, G-Protein-Coupled genetics, Reverse Transcriptase Polymerase Chain Reaction, Diabetes Mellitus, Experimental prevention & control, Estrogen Receptor alpha physiology, Hyperglycemia physiopathology, Insulin deficiency, Islets of Langerhans pathology, Oxidative Stress
- Abstract
The female steroid, 17β-estradiol (E2), is important for pancreatic β-cell function and acts via at least three estrogen receptors (ER), ERα, ERβ, and the G-protein coupled ER (GPER). Using a pancreas-specific ERα knockout mouse generated using the Cre-lox-P system and a Pdx1-Cre transgenic line (PERαKO ⁻/⁻), we previously reported that islet ERα suppresses islet glucolipotoxicity and prevents β-cell dysfunction induced by high fat feeding. We also showed that E2 acts via ERα to prevent β-cell apoptosis in vivo. However, the contribution of the islet ERα to β-cell survival in vivo, without the contribution of ERα in other tissues is still unclear. Using the PERαKO ⁻/⁻ mouse, we show that ERα mRNA expression is only decreased by 20% in the arcuate nucleus of the hypothalamus, without a parallel decrease in the VMH, making it a reliable model of pancreas-specific ERα elimination. Following exposure to alloxan-induced oxidative stress in vivo, female and male PERαKO ⁻/⁻ mice exhibited a predisposition to β-cell destruction and insulin deficient diabetes. In male PERαKO ⁻/⁻ mice, exposure to E2 partially prevented alloxan-induced β-cell destruction and diabetes. ERα mRNA expression was induced by hyperglycemia in vivo in islets from young mice as well as in cultured rat islets. The induction of ERα mRNA by hyperglycemia was retained in insulin receptor-deficient β-cells, demonstrating independence from direct insulin regulation. These findings suggest that induction of ERα expression acts to naturally protect β-cells against oxidative injury.
- Published
- 2014
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237. MicroRNAs contribute to compensatory β cell expansion during pregnancy and obesity.
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Jacovetti C, Abderrahmani A, Parnaud G, Jonas JC, Peyot ML, Cornu M, Laybutt R, Meugnier E, Rome S, Thorens B, Prentki M, Bosco D, and Regazzi R
- Subjects
- Animals, Cells, Cultured drug effects, Cells, Cultured metabolism, Cytokines biosynthesis, Cytokines genetics, Estradiol analogs & derivatives, Estradiol pharmacology, Estradiol physiology, Estrogen Antagonists pharmacology, Female, Fulvestrant, Gene Expression Regulation physiology, Glucagon-Like Peptide 1 physiology, Glucagon-Like Peptide-1 Receptor, Islets of Langerhans metabolism, Male, Mice, Mice, Mutant Strains, MicroRNAs biosynthesis, MicroRNAs genetics, Obesity physiopathology, Organ Size drug effects, Postpartum Period metabolism, Pregnancy metabolism, Rats, Rats, Wistar, Receptors, G-Protein-Coupled agonists, Receptors, G-Protein-Coupled biosynthesis, Receptors, G-Protein-Coupled genetics, Receptors, Glucagon agonists, Receptors, Glucagon deficiency, Signal Transduction drug effects, Signal Transduction physiology, Adaptation, Physiological physiology, Insulin Resistance physiology, Islets of Langerhans growth & development, Islets of Langerhans pathology, MicroRNAs physiology, Obesity pathology, Pregnancy physiology
- Abstract
Pregnancy and obesity are frequently associated with diminished insulin sensitivity, which is normally compensated for by an expansion of the functional β cell mass that prevents chronic hyperglycemia and development of diabetes mellitus. The molecular basis underlying compensatory β cell mass expansion is largely unknown. We found in rodents that β cell mass expansion during pregnancy and obesity is associated with changes in the expression of several islet microRNAs, including miR-338-3p. In isolated pancreatic islets, we recapitulated the decreased miR-338-3p level observed in gestation and obesity by activating the G protein-coupled estrogen receptor GPR30 and the glucagon-like peptide 1 (GLP1) receptor. Blockade of miR-338-3p in β cells using specific anti-miR molecules mimicked gene expression changes occurring during β cell mass expansion and resulted in increased proliferation and improved survival both in vitro and in vivo. These findings point to a major role for miR-338-3p in compensatory β cell mass expansion occurring under different insulin resistance states.
- Published
- 2012
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238. HDLs protect pancreatic β-cells against ER stress by restoring protein folding and trafficking.
- Author
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Pétremand J, Puyal J, Chatton JY, Duprez J, Allagnat F, Frias M, James RW, Waeber G, Jonas JC, and Widmann C
- Subjects
- Animals, Apoptosis, Cells, Cultured, Green Fluorescent Proteins metabolism, Humans, Insulin-Secreting Cells cytology, Insulin-Secreting Cells ultrastructure, Insulinoma metabolism, Lipoproteins, HDL genetics, Male, Mice, Mutation, Protein Folding, Protein Transport, Rats, Rats, Wistar, Viral Fusion Proteins metabolism, Endoplasmic Reticulum physiology, Insulin-Secreting Cells metabolism, Lipoproteins, HDL metabolism, Membrane Proteins metabolism, Stress, Physiological physiology
- Abstract
Endoplasmic reticulum (ER) homeostasis alteration contributes to pancreatic β-cell dysfunction and death and favors the development of diabetes. In this study, we demonstrate that HDLs protect β-cells against ER stress induced by thapsigargin, cyclopiazonic acid, palmitate, insulin overexpression, and high glucose concentrations. ER stress marker induction and ER morphology disruption mediated by these stimuli were inhibited by HDLs. Using a temperature-sensitive viral glycoprotein folding mutant, we show that HDLs correct impaired protein trafficking and folding induced by thapsigargin and palmitate. The ability of HDLs to protect β-cells against ER stress was inhibited by brefeldin A, an ER to Golgi trafficking blocker. These results indicate that HDLs restore ER homeostasis in response to ER stress, which is required for their ability to promote β-cell survival. This study identifies a cellular mechanism mediating the beneficial effect of HDLs on β-cells against ER stress-inducing factors.
- Published
- 2012
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239. Mechanisms of control of the free Ca2+ concentration in the endoplasmic reticulum of mouse pancreatic β-cells: interplay with cell metabolism and [Ca2+]c and role of SERCA2b and SERCA3.
- Author
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Ravier MA, Daro D, Roma LP, Jonas JC, Cheng-Xue R, Schuit FC, and Gilon P
- Subjects
- Animals, Calcium pharmacology, Diazoxide pharmacology, Endoplasmic Reticulum metabolism, Gene Deletion, Gene Expression Regulation, Genetic Engineering, Glucose pharmacology, Insulin genetics, Insulin metabolism, Insulin-Secreting Cells drug effects, Mice, Mice, Knockout, Promoter Regions, Genetic, Sarcoplasmic Reticulum Calcium-Transporting ATPases genetics, Vasodilator Agents pharmacology, Calcium metabolism, Insulin-Secreting Cells metabolism, Sarcoplasmic Reticulum Calcium-Transporting ATPases metabolism
- Abstract
Objective: Sarco-endoplasmic reticulum Ca(2+)-ATPase 2b (SERCA2b) and SERCA3 pump Ca(2+) in the endoplasmic reticulum (ER) of pancreatic β-cells. We studied their role in the control of the free ER Ca(2+) concentration ([Ca(2+)](ER)) and the role of SERCA3 in the control of insulin secretion and ER stress., Research Design and Methods: β-Cell [Ca(2+)](ER) of SERCA3(+/+) and SERCA3(-/-) mice was monitored with an adenovirus encoding the low Ca(2+)-affinity sensor D4 addressed to the ER (D4ER) under the control of the insulin promoter. Free cytosolic Ca(2+) concentration ([Ca(2+)](c)) and [Ca(2+)](ER) were simultaneously recorded. Insulin secretion and mRNA levels of ER stress genes were studied., Results: Glucose elicited synchronized [Ca(2+)](ER) and [Ca(2+)](c) oscillations. [Ca(2+)](ER) oscillations were smaller in SERCA3(-/-) than in SERCA3(+/+) β-cells. Stimulating cell metabolism with various [glucose] in the presence of diazoxide induced a similar dose-dependent [Ca(2+)](ER) rise in SERCA3(+/+) and SERCA3(-/-) β-cells. In a Ca(2+)-free medium, glucose moderately raised [Ca(2+)](ER) from a highly buffered cytosolic Ca(2+) pool. Increasing [Ca(2+)](c) with high [K] elicited a [Ca(2+)](ER) rise that was larger but more transient in SERCA3(+/+) than SERCA3(-/-) β-cells because of the activation of a Ca(2+) release from the ER in SERCA3(+/+) β-cells. Glucose-induced insulin release was larger in SERCA3(-/-) than SERCA3(+/+) islets. SERCA3 ablation did not induce ER stress., Conclusions: [Ca(2+)](c) and [Ca(2+)](ER) oscillate in phase in response to glucose. Upon [Ca(2+)](c) increase, Ca(2+) is taken up by SERCA2b and SERCA3. Strong Ca(2+) influx triggers a Ca(2+) release from the ER that depends on SERCA3. SERCA3 deficiency neither impairs Ca(2+) uptake by the ER upon cell metabolism acceleration and insulin release nor induces ER stress.
- Published
- 2011
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240. Endoplasmic reticulum accumulation of Kir6.2 without activation of ER stress response in islet cells from adult Sur1 knockout mice.
- Author
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Marhfour I, Jonas JC, Marchandise J, Lefevre A, Rahier J, Sempoux C, and Guiot Y
- Subjects
- ATP-Binding Cassette Transporters genetics, ATP-Binding Cassette Transporters metabolism, Animals, Antibody Specificity immunology, Calreticulin metabolism, Endoplasmic Reticulum genetics, Endoplasmic Reticulum ultrastructure, Gene Expression Regulation, Islets of Langerhans cytology, Islets of Langerhans ultrastructure, Mice, Mice, Inbred C57BL, Mice, Knockout, Oxidative Stress genetics, Potassium Channels, Inwardly Rectifying genetics, Protein Transport, RNA, Messenger genetics, RNA, Messenger metabolism, Receptors, Drug genetics, Receptors, Drug metabolism, Subcellular Fractions metabolism, Sulfonylurea Receptors, Endoplasmic Reticulum metabolism, Islets of Langerhans metabolism, Potassium Channels, Inwardly Rectifying deficiency, Potassium Channels, Inwardly Rectifying metabolism, Receptors, Drug deficiency, Stress, Physiological
- Abstract
Trafficking of pancreatic K(ATP) channels to the plasma membrane critically depends on masking the endoplasmic reticulum (ER) retention signals of the SUR1 and Kir6.2 subunits upon their proper assembly into functional hetero-octamers. When expressed in the absence of the partner protein, each subunit might accumulate in the ER and trigger beta-cell ER stress and oxidative stress. To test this hypothesis, Kir6.2 localisation, ER ultra-structure and ER-stress- and oxidative-stress-response gene mRNA levels were evaluated in pancreatic endocrine cells from adult wild-type (WT) and Sur1 knockout (Sur1 ( -/- )) mice. As previously reported, Kir6.2 was mainly expressed on secretory granules and at the plasma membrane of WT islet cells. In contrast, like the ER chaperone calreticulin, Kir6.2 was primarily localised in the rough endoplasmic reticulum (RER) of Sur1 ( -/- ) islet cells. ER retention of Kir6.2 was demonstrated (electron microscopy) by a significant increase in the length and Kir6.2 density of RER in Sur1 ( -/- ) vs WT islet cells. Despite Kir6.2 retention in RER, Xbp1 mRNA splicing and mRNA levels of preproinsulin and ER-stress-response genes Bip, Edem and Gadd153 were similar in WT and Sur1 ( -/- ) islets. However, mRNA levels of the antioxidant enzymes Sod1, Sod2, Gpx2 and catalase were significantly up-regulated in Sur1 ( -/- ) islets. Sequestration of Kir6.2 in RER of Sur1 ( -/- ) islet cells is thus associated with an increase in RER length and mild oxidative stress without activation of the classical ER stress response.
- Published
- 2010
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241. Effects of c-MYC activation on glucose stimulus-secretion coupling events in mouse pancreatic islets.
- Author
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Pascal SM, Guiot Y, Pelengaris S, Khan M, and Jonas JC
- Subjects
- Animals, Apoptosis drug effects, Apoptosis genetics, Blood Glucose metabolism, Calcium metabolism, Crosses, Genetic, Female, Gene Expression Regulation, Glucose administration & dosage, Hydrogen Peroxide pharmacology, Insulin biosynthesis, Insulin genetics, Insulin metabolism, Insulin-Secreting Cells drug effects, Insulin-Secreting Cells metabolism, Male, Mice, Mice, Inbred C57BL, Mice, Inbred CBA, Mice, Transgenic, Mitochondrial Membranes drug effects, Mitochondrial Membranes physiology, Protein Precursors biosynthesis, Protein Precursors genetics, Proto-Oncogene Proteins c-myc biosynthesis, RNA, Messenger biosynthesis, RNA, Messenger genetics, Tamoxifen pharmacology, Glucose metabolism, Insulin-Secreting Cells physiology, Proto-Oncogene Proteins c-myc genetics
- Abstract
Alteration of pancreatic beta-cell survival and Preproinsulin gene expression by prolonged hyperglycemia may result from increased c-MYC expression. However, it is unclear whether c-MYC effects on beta-cell function are compatible with its proposed role in glucotoxicity. We therefore tested the effects of short-term c-MYC activation on key beta-cell stimulus-secretion coupling events in islets isolated from mice expressing a tamoxifen-switchable form of c-MYC in beta-cells (MycER) and their wild-type littermates. Tamoxifen treatment of wild-type islets did not affect their cell survival, Preproinsulin gene expression, and glucose stimulus-secretion coupling. In contrast, tamoxifen-mediated c-MYC activation for 2-3 days triggered cell apoptosis and decreased Preproinsulin gene expression in MycER islets. These effects were accompanied by mitochondrial membrane hyperpolarization at all glucose concentrations, a higher resting intracellular calcium concentration ([Ca(2+)](i)), and lower glucose-induced [Ca(2+)](i) rise and islet insulin content, leading to a strong reduction of glucose-induced insulin secretion. Compared with these effects, 1-wk culture in 30 mmol/l glucose increased the islet sensitivity to glucose stimulation without reducing the maximal glucose effectiveness or the insulin content. In contrast, overnight exposure to a low H(2)O(2) concentration increased the islet resting [Ca(2+)](i) and reduced the amplitude of the maximal glucose response as in tamoxifen-treated MycER islets. In conclusion, c-MYC activation rapidly stimulates apoptosis, reduces Preproinsulin gene expression and insulin content, and triggers functional alterations of beta-cells that are better mimicked by overnight exposure to a low H(2)O(2) concentration than by prolonged culture in high glucose.
- Published
- 2008
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242. Glucose-induced cytosolic pH changes in beta-cells and insulin secretion are not causally related: studies in islets lacking the Na+/H+ exchangeR NHE1.
- Author
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Stiernet P, Nenquin M, Moulin P, Jonas JC, and Henquin JC
- Subjects
- Animals, Biological Transport, Cation Transport Proteins, Dose-Response Relationship, Drug, Hydrogen-Ion Concentration, Insulin Secretion, Membrane Proteins, Mice, Mice, Inbred C57BL, Models, Biological, Protein Isoforms, Sodium-Hydrogen Exchanger 1, Sodium-Hydrogen Exchangers metabolism, Time Factors, Cytosol metabolism, Glucose metabolism, Insulin metabolism, Insulin-Secreting Cells metabolism
- Abstract
The contribution of Na(+)/H(+) exchange (achieved by NHE proteins) to the regulation of beta-cell cytosolic pH(c), and the role of pH(c) changes in glucose-induced insulin secretion are disputed and were examined here. Using real-time PCR, we identified plasmalemmal NHE1 and intracellular NHE7 as the two most abundant NHE isoforms in mouse islets. We, therefore, compared insulin secretion, cytosolic free Ca(2+) ([Ca(2+)](c)) and pH(c) in islets from normal mice and mice bearing an inactivating mutation of NHE1 (Slc9A1-swe/swe). The experiments were performed in HCO(-)(3)/CO(2) or HEPES/NaOH buffers. PCR and functional approaches showed that NHE1 mutant islets do not express compensatory pH-regulating mechanisms. NHE1 played a greater role than HCO(-)(3)-dependent mechanisms in the correction of an acidification imposed by a pulse of NH(4)Cl. In contrast, basal pH(c) (in low glucose) and the alkalinization produced by high glucose were independent of NHE1. Dimethylamiloride, a classic blocker of Na(+)/H(+) exchange, did not affect pH(c) but increased insulin secretion in NHE1 mutant islets, indicating unspecific effects. In control islets, glucose similarly increased [Ca(2+)](c) and insulin secretion in HCO(-)(3) and HEPES buffer, although pH(c) changed in opposite directions. The amplification of insulin secretion that glucose produces when [Ca(2+)](c) is clamped at an elevated level by KCl was also unrelated to pH(c) and pH(c) changes. All effects of glucose on [Ca(2+)](c) and insulin secretion proved independent of NHE1. In conclusion, NHE1 protects beta-cells against strong acidification, but has no role in stimulus-secretion coupling. The changes in pH(c) produced by glucose involve HCO(-)(3)-dependent mechanisms. Variations in beta-cell pH(c) are not causally related to changes in insulin secretion.
- Published
- 2007
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243. Probe-independent and direct quantification of insulin mRNA and growth hormone mRNA in enriched cell preparations.
- Author
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Van Lommel L, Janssens K, Quintens R, Tsukamoto K, Vander Mierde D, Lemaire K, Denef C, Jonas JC, Martens G, Pipeleers D, and Schuit FC
- Subjects
- Actins genetics, Animals, Biotechnology methods, Energy Intake, Islets of Langerhans physiology, Kinetics, Proinsulin genetics, RNA, Complementary genetics, Rats, Reverse Transcriptase Polymerase Chain Reaction, Insulin genetics, RNA, Messenger genetics
- Abstract
Task division in multicellular organisms ensures that differentiated cell types produce cell-specific proteins that fulfill tasks for the whole organism. In some cases, the encoded mRNA species is so abundant that it represents a sizeable fraction of total mRNA in the cell. In this study, we have used a probe- and primer-free technique to quantify such abundant mRNA species in order to assess regulatory effects of in vitro and in vivo conditions. As a first example, we were able to quantify the regulation of proinsulin mRNA abundance in beta-cells by food intake or by the glucose concentration in tissue culture. The second example of application of this technique is the effect of corticosteroids on growth hormone mRNA in enriched somatrotrophs. It is anticipated that other examples exist in which measurement of very abundant mRNAs in dedicated cells will help to understand biological processes, monitor disease states, or assist biotechnological manufacturing procedures.
- Published
- 2006
- Full Text
- View/download PDF
244. Glucose-induced mixed [Ca2+]c oscillations in mouse beta-cells are controlled by the membrane potential and the SERCA3 Ca2+-ATPase of the endoplasmic reticulum.
- Author
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Beauvois MC, Merezak C, Jonas JC, Ravier MA, Henquin JC, and Gilon P
- Subjects
- Animals, Insulin metabolism, Insulin Secretion, Islets of Langerhans metabolism, Mice, Reverse Transcriptase Polymerase Chain Reaction, Sarcoplasmic Reticulum Calcium-Transporting ATPases, Calcium Signaling physiology, Calcium-Transporting ATPases metabolism, Endoplasmic Reticulum metabolism, Glucose metabolism, Insulin-Secreting Cells metabolism, Membrane Potentials physiology
- Abstract
Stimulatory concentrations of glucose induce two patterns of cytosolic Ca2+ concentration ([Ca2+]c) oscillations in mouse islets: simple or mixed. In the mixed pattern, rapid oscillations are superimposed on slow ones. In the present study, we examined the role of the membrane potential in the mixed pattern and the impact of this pattern on insulin release. Simultaneous measurement of [Ca2+]c and insulin release from single islets revealed that mixed [Ca2+]c oscillations triggered synchronous oscillations of insulin secretion. Simultaneous recordings of membrane potential in a single beta-cell within an islet and of [Ca2+]c in the whole islet demonstrated that the mixed pattern resulted from compound bursting (i.e., clusters of membrane potential oscillations separated by prolonged silent intervals) that was synchronized in most beta-cells of the islet. Each slow [Ca2+]c increase during mixed oscillations was due to a progressive summation of rapid oscillations. Digital image analysis confirmed the good synchrony between subregions of an islet. By contrast, islets from sarco(endo)plasmic reticulum Ca2+-ATPase isoform 3 (SERCA3)-knockout mice did not display typical mixed [Ca2+]c oscillations in response to glucose. This results from a lack of progressive summation of rapid oscillations and from altered spontaneous electrical activity, i.e., lack of compound bursting, and membrane potential oscillations characterized by lower-frequency but larger-depolarization phases than observed in SERCA3+/+ beta-cells. We conclude that glucose-induced mixed [Ca2+]c oscillations result from compound bursting in all beta-cells of the islet. Disruption of SERCA3 abolishes mixed [Ca2+]c oscillations and augments beta-cell depolarization. This latter observation indicates that the endoplasmic reticulum participates in the control of the beta-cell membrane potential during glucose stimulation.
- Published
- 2006
- Full Text
- View/download PDF
245. Mechanisms of pancreatic beta-cell death in type 1 and type 2 diabetes: many differences, few similarities.
- Author
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Cnop M, Welsh N, Jonas JC, Jörns A, Lenzen S, and Eizirik DL
- Subjects
- Diabetes Mellitus, Type 1 immunology, Diabetes Mellitus, Type 2 immunology, Humans, Interferon-gamma physiology, Interleukin-1 physiology, Models, Biological, Cell Death, Diabetes Mellitus, Type 1 pathology, Diabetes Mellitus, Type 2 pathology, Insulin-Secreting Cells pathology
- 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.
- Published
- 2005
- Full Text
- View/download PDF
246. Induction of adiponectin in skeletal muscle by inflammatory cytokines: in vivo and in vitro studies.
- Author
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Delaigle AM, Jonas JC, Bauche IB, Cornu O, and Brichard SM
- Subjects
- Adiponectin, Animals, Cells, Cultured, Gene Expression drug effects, Gene Expression immunology, Humans, In Vitro Techniques, Lipopolysaccharides pharmacology, Male, Mice, Mice, Inbred Strains, Muscle, Skeletal cytology, Myoblasts cytology, Myoblasts drug effects, RNA, Messenger analysis, Antineoplastic Agents pharmacology, Intercellular Signaling Peptides and Proteins genetics, Interferon-gamma pharmacology, Muscle, Skeletal physiology, Myoblasts physiology, Tumor Necrosis Factor-alpha pharmacology
- Abstract
Adiponectin (ApN) is an adipocytokine that plays a fundamental role in energy homeostasis and counteracting inflammation. We examined whether ApN could be induced in a nonadipose tissue, the skeletal muscle, in vivo, and in cultured myotubes in response to lipopolysaccharides or proinflammatory cytokines. We next explored the underlying mechanisms. In vivo, injection of lipopolysaccharides to mice caused, after 24 h, an approximately 10-fold rise in ApN mRNA abundance and a concomitant 70% increase in ApN levels in tibialis anterior muscle. This ApN induction was reproduced in C2C12 myotubes cultured for 48 h with a proinflammatory cytokine combination, interferon-gamma + TNFalpha. This effect occurred in a time- and dose-dependent manner. Several pieces of evidence suggest that nitric oxide (NO) mediates this up-regulation by cytokines in myotubes or muscle. First, ApN was induced in vitro exclusively in the experimental conditions that stimulated NO production. Second, inducible NO synthase mRNA induction or NO production clearly preceded ApN mRNA induction. Third, preventing NO production by inhibitors of the NO synthases, nitro-L-arginine methyl ester or NG-methyl-L-arginine, suppressed the inductive effect of the cytokines in vitro and in vivo. Finally, ApN mRNA induction by cytokines was reproduced in cultured human myotubes. In conclusion, our data provide evidence that adiponectin is up-regulated in vivo and in vitro in human and rodent myotubes in response to inflammatory stimuli. The underlying mechanisms seem to involve a NO-dependent pathway. This overexpression may be viewed as a local antiinflammatory protection and a way to deliver extra energy supplies during inflammation.
- Published
- 2004
- Full Text
- View/download PDF
247. Atypical Ca2+-induced Ca2+ release from a sarco-endoplasmic reticulum Ca2+-ATPase 3-dependent Ca2+ pool in mouse pancreatic beta-cells.
- Author
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Beauvois MC, Arredouani A, Jonas JC, Rolland JF, Schuit F, Henquin JC, and Gilon P
- Subjects
- Animals, Calcium pharmacology, Calcium-Transporting ATPases deficiency, Calcium-Transporting ATPases genetics, Female, Islets of Langerhans drug effects, Mice, Mice, Inbred C57BL, Mice, Knockout, Mice, Obese, Ryanodine pharmacology, Sarcoplasmic Reticulum Calcium-Transporting ATPases, Calcium metabolism, Calcium-Transporting ATPases biosynthesis, Islets of Langerhans metabolism
- Abstract
The contribution of Ca(2+) release from intracellular stores to the rise in the free cytosolic Ca(2+) concentration ([Ca(2+)](c)) triggered by Ca(2+) influx was investigated in mouse pancreatic beta-cells. Depolarization of beta-cells by 45 mm K(+) (in the presence of 15 mm glucose and 0.1 mm diazoxide) evoked two types of [Ca(2+)](c) responses: a monotonic and sustained elevation; or a sustained elevation superimposed by a transient [Ca(2+)](c) peak (TCP) (40-120 s after the onset of depolarization). Simultaneous measurements of [Ca(2+)](c) and voltage-dependent Ca(2+) current established that the TCP did not result from a larger Ca(2+) current. Abolition of the TCP by thapsigargin and its absence in sarco-endoplasmic reticulum Ca(2+)-ATPase 3 (SERCA3) knockout mice show that it is caused by Ca(2+) mobilization from the endoplasmic reticulum. A TCP could not be evoked by the sole depolarization of beta-cells but required a rise in [Ca(2+)](c) pointing to a Ca(2+)-induced Ca(2+) release (CICR). This CICR did not involve inositol 1,4,5-trisphosphate (IP(3)) receptors (IP(3)Rs) because it was resistant to heparin. Nor did it involve ryanodine receptors (RyRs) because it persisted after blockade of RyRs with ryanodine, and was not mimicked by caffeine, a RyR agonist. Moreover, RyR1 and RyR2 mRNA were not found and RyR3 mRNA was only slightly expressed in purified beta-cells. A CICR could also be detected in a limited number of cells in response to glucose. Our data demonstrate, for the first time in living cells, the existence of an atypical CICR that is independent from the IP(3)R and the RyR. This CICR is prominent in response to a supraphysiological stimulation with high K(+), but plays little role in response to glucose in non-obese mouse pancreatic beta-cells.
- Published
- 2004
- Full Text
- View/download PDF
248. Prolonged culture in low glucose induces apoptosis of rat pancreatic beta-cells through induction of c-myc.
- Author
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Van de Casteele M, Kefas BA, Cai Y, Heimberg H, Scott DK, Henquin JC, Pipeleers D, and Jonas JC
- Subjects
- Animals, Apoptosis drug effects, Cell Culture Techniques methods, Cell Line, Cells, Cultured, Dose-Response Relationship, Drug, Gene Expression Regulation drug effects, Glucose pharmacology, Glutamine pharmacology, Islets of Langerhans drug effects, Leucine pharmacology, Mice, Rats, Apoptosis physiology, Gene Expression Regulation physiology, Glucose metabolism, Insulin metabolism, Islets of Langerhans metabolism, Proto-Oncogene Proteins c-myc metabolism
- Abstract
Prolonged culture in low-glucose concentrations (=5mM) induces apoptosis in pancreatic beta-cells by a poorly defined mechanism. We now show that, in both purified rat beta-cells and isolated rat islets, culture in the presence of 3 or 5mM (G3-G5) instead of 10mM glucose (G10) induces a large increase in c-myc expression before onset of a caspase-dependent apoptosis. These effects were prevented by addition of leucine and glutamine to G3 and G5, and were mimicked by addition of the mitochondrial poison azide to G10. In contrast, inhibition of Ca(2+) influx and insulin secretion with diazoxide under control conditions did not stimulate islet c-myc expression nor beta-cell apoptosis. In rat beta-cells, adenovirus-mediated c-myc overexpression increased their rate of apoptosis, whereas antisense-c-myc expression reduced low-glucose-induced apoptosis by approximately 50%. In the insulin producing MIN6 cell line, apoptosis induction by either low glucose or an activator of AMP-activated protein kinase (AMPK) was associated with c-myc mRNA and protein upregulation. In conclusion, stimulation of beta-cell apoptosis by prolonged culture at low glucose partly results from early and sustained induction of beta-cell c-myc expression. These effects may be due to sustained restriction in nutrient-derived metabolic signals.
- Published
- 2003
- Full Text
- View/download PDF
249. Corticosteroids induce expression of aquaporin-1 and increase transcellular water transport in rat peritoneum.
- Author
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Stoenoiu MS, Ni J, Verkaeren C, Debaix H, Jonas JC, Lameire N, Verbavatz JM, and Devuyst O
- Subjects
- Animals, Aquaporin 1, Endothelium enzymology, Gene Expression drug effects, Male, Nitric Oxide Synthase metabolism, Osmosis drug effects, Peritoneal Dialysis, Rats, Rats, Wistar, Water-Electrolyte Balance drug effects, Aquaporins genetics, Aquaporins metabolism, Dexamethasone pharmacology, Glucocorticoids pharmacology, Peritoneum metabolism, Water metabolism
- Abstract
The water channel aquaporin-1 (AQP1) is the molecular counterpart of the ultrasmall pore responsible for transcellular water permeability during peritoneal dialysis (PD). This water permeability accounts for up to 50% of ultrafiltration (UF) during a hypertonic dwell, and its loss can be a major clinical problem for PD patients. By analogy with the lung, the hypothesis was tested that corticosteroids may increase AQP1 expression in the peritoneal membrane (PM) and improve water permeability and UF in rats. First, the expression and distribution of the glucocorticoid receptor (GR) in the PM and capillary endothelium was documented. Time-course and dose-response analyses showed that a daily IM injection of dexamethasone (1 or 4 mg/kg) for 5 d induced an approximately twofold increase in the expression of AQP1 at the mRNA and protein levels. The GR antagonist RU-486 completely inhibited the dexamethasone effect. The functional counterpart of the increased AQP1 expression was a significant increase in sodium sieving and net UF across the PM, contrasting with a lack of effect on the osmotic gradient and permeability for small solutes. The latter observation reflected the lack of effect of corticosteroids on nitric oxide synthase (NOS) activity and endothelial NOS isoform expression in the PM. In conclusion, corticosteroids induce AQP1 expression in the capillary endothelium of the PM, which is reflected by increased transcellular water permeability and UF. These data emphasize the critical role of AQP1 during PD and suggest that pharmacologic regulation of AQP1 may provide a target for manipulating water permeability across the PM.
- Published
- 2003
- Full Text
- View/download PDF
250. Increased glucose sensitivity of stimulus-secretion coupling in islets from Psammomys obesus after diet induction of diabetes.
- Author
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Pertusa JA, Nesher R, Kaiser N, Cerasi E, Henquin JC, and Jonas JC
- Subjects
- Adenosine Diphosphate metabolism, Adenosine Triphosphate metabolism, Animals, Cells, Cultured, Gerbillinae, Insulin Secretion, Islets of Langerhans drug effects, Kinetics, Male, Membrane Potentials physiology, Mitochondria physiology, NAD metabolism, NADP metabolism, Oxidation-Reduction, Diabetes Mellitus, Experimental physiopathology, Diabetes Mellitus, Type 2 physiopathology, Diet, Glucose pharmacology, Insulin metabolism, Islets of Langerhans metabolism
- Abstract
When fed a high-energy (HE) diet, diabetes-prone (DP) Psammomys obesus develop type 2 diabetes with altered glucose-stimulated insulin secretion (GSIS). Beta-cell stimulus-secretion coupling was investigated in islets isolated from DP P. obesus fed a low-energy (LE) diet (DP-LE) and after 5 days on a HE diet (DP-HE). DP-LE islets cultured overnight in 5 mmol/l glucose displayed glucose dose-dependent increases in NAD(P)H, mitochondrial membrane potential, ATP/(ATP + ADP) ratio, cytosolic calcium concentration ([Ca(2+)](c)), and insulin secretion. In comparison, DP-HE islets cultured overnight in 10 mmol/l glucose were 80% degranulated and displayed an increased sensitivity to glucose at the level of glucose metabolism, [Ca(2+)](c), and insulin secretion. These changes in DP-HE islets were only marginally reversed after culture in 5 mmol/l glucose and were not reproduced in DP-LE islets cultured overnight in 10 mmol/l glucose, except for the 75% degranulation. Diabetes-resistant P. obesus remain normoglycemic on HE diet. Their beta-cell stimulus-secretion coupling was similar to that of DP-LE islets, irrespective of the type of diet. Thus, islets from diabetic P. obesus display an increased sensitivity to glucose at the level of glucose metabolism and a profound beta-cell degranulation, both of which may affect their in vivo GSIS.
- Published
- 2002
- Full Text
- View/download PDF
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