Spontaneous diabetes mellitus in transgenic mice expressing human islet amyloid polypeptide.

The islet in non-insulin-dependent diabetes mellitus (NIDDM) is characterized by loss of beta cells and large local deposits of amyloid derived from the 37-amino acid protein, islet amyloid polypeptide (IAPP). We have hypothesized that IAPP amyloid forms intracellularly causing beta-cell destruction under conditions of high rates of expression. To test this we developed a homozygous transgenic mouse model with high rates of expression of human IAPP. Male transgenic mice spontaneously developed diabetes mellitus by 8 weeks of age, which was associated with selective beta-cell death and impaired insulin secretion. Small intra- and extracellular amorphous IAPP aggregates were present in islets of transgenic mice during the development of diabetes mellitus. However, IAPP derived amyloid deposits were found in only a minority of islets at approximately 20 weeks of age, notably after development of diabetes mellitus in male transgenic mice. Approximately 20% of female transgenic mice spontaneously developed diabetes mellitus at 30+ weeks of age, when beta-cell degeneration and both amorphous and amyloid deposits of IAPP were present. We conclude that overexpression of human IAPP causes beta-cell death, impaired insulin secretion, and diabetes mellitus. Large deposits of IAPP derived amyloid do not appear to be important in this cytotoxicity, but early, small amorphous intra- and extracellular aggregates of human IAPP were consistently present at the time of beta-cell death and therefore may be the most cytotoxic form of IAPP.

Rola fosfodiesterazy 3B w regulacji sekrecji insuliny u szczura (Rattus norvegicus Berkenhout)

Wydział Biologii

Why human islets die? analysis of death signaling pathways during isolation and following cytokine treatments

RESUME Le diabète de type 1 se définit comme un désordre métabolique d'origine auto-immune qui aboutit à la destruction progressive et sélective de la cellule ß-pancréatique sécrétrice d'insuline. Cette maladie représente 10 % des cas de diabète enregistrés dans la population mondiale, et touche les jeunes de moins de 20 ans. Le traitement médical par insulinothérapie corrige le manque d'hormone mais ne prévient pas les nombreuses complications telles que les atteintes cardiaques, neurologiques, rénales, rétiniennes, et les amputations que la maladie provoque. Le remplacement de la cellule ß par transplantation d'îlots de Langerhans est une alternative prometteuse au traitement médical du diabète de type 1. Cependant la greffe d'îlots est encore un traitement expérimental et ne permet pas un contrôle efficace de la glycémie au long terme chez les patients transplantés, et les raisons de cet échec restent mal comprises. L'obstacle immédiat qui se pose est la purification d'un nombre suffisant d'îlots viables et la perte massive de ces îlots dans les premières heures suite à la greffe. Cette tendance presque systématique de la perte fonctionnelle du greffon immédiatement après la transplantation est connue sous le terme de « primary graft non-function » (PNF). En effet, la procédure d'isolement des îlots provoque la destruction des composantes cellulaires et non cellulaires du tissu pancréatique qui jouent un rôle déterminant dans le processus de survie de l'îlot. De plus, la transplantation elle-même expose les cellules à différents stress, notamment le stress par les cytokines inflammatoires qui encourage la mort cellulaire par apoptose et provoque par la suite le rejet de la greffe. L'ensemble de ces mécanismes aboutit a une perte de la masse d'îlot estimée a plus de 60%. Dans ce contexte, nous nous sommes intéressés à définir les voies majeures de stress qui régissent cette perte massive d'îlot par apoptose lors du processus d'isolement et suite à l'exposition immédiate aux cytokines. L'ensemble des résultats obtenus indique que plusieurs voies de signalisation intracellulaire sont recrutées qui s'activent de manière maximale très tôt lors des premières phases de l'isolement. La mise en culture des îlots deux jours permet aux voies activées de revenir aux taux de base. De ce fait nous proposons une stratégie dite de protection qui doit être 1) initiée aussitôt que possible lors de l'isolement des îlots pancréatiques, 2) devrait probablement bloquer l'activation de ces différentes voies de stress mis en évidence lors de notre étude et 3) devrait inclure la mise en culture des îlots purifiés deux jours après l'isolement et avant la transplantation. RESUME LARGE PUBLIC Le diabète est une maladie qui entraîne un taux anormalement élevé de sucre (glucose) dans le sang du à une insuffisance du pancréas endocrine à produire de l'insuline, une hormone qui régule la glycémie (taux de glucose dans le sang). On distingue deux types majeurs de diabètes; le diabète de type 1 ou juvénile ou encore appelé diabète maigre qui se manifeste souvent pendant l'enfance et qui se traduit par une déficience absolue en insuline. Le diabète de type 2 ou diabète gras est le plus fréquent, et touche les sujets de plus de 40 ans qui souffrent d'obésité et qui se traduit par une dysfonction de la cellule ß avec une incapacité à réguler la glycémie malgré la production d'insuline. Dans le diabète de type 1, la destruction de la cellule ß est programmée (apoptose) et est majoritairement provoquée par des médiateurs inflammatoires appelés cytokines qui sont produites localement par des cellules inflammatoires du système immunitaire qui envahissent la cellule ß-pancréatiques. Les cytokines activent différentes voies de signalisation parmi lesquelles on distingue celles des Mitogen-Activated Protein Kinase (MAPKs) composées de trois familles de MAPKs: ERK1/2, p38, et JNK, et la voie NF-κB. Le traitement médical par injections quotidiennes d'insuline permet de contrôler la glycémie mais ne prévient pas les nombreuses complications secondaires liées à cette maladie. La greffe d'îlots de Langerhans est une alternative possible au traitement médical, considérée avantageuse comparée a la greffe du pancréas entier. En effet l'embolisation d'îlots dans le foie par injection intraportale constitue une intervention simple sans complications majeures. Néanmoins la technique de préparation d'îlots altère la fonction endocrine et cause la perte massive d'îlots pancréatiques. De plus, la transplantation elle-même expose la cellule ß à différents stress, notamment le stress par les cytokines inflammatoires qui provoque le rejet de greffon cellulaire. Dans la perspective d'augmenter les rendements des îlots purifiés, nous nous sommes intéressés à définir les voies majeures de stress qui régissent cette perte massive d'îlot lors du processus d'isolement et suite à l'exposition immédiate aux cytokines après transplantation. L'ensemble de ces résultats indique que le stress induit lors de l'isolement des îlots et celui des cytokines recrute différentes voies de signalisation intracellulaire (JNK, p38 et NF-κB) qui s'additionnent entre-elles pour altérer la fonction et la viabilité de l'îlot. De ce fait une stratégie doit être mise en place pour bloquer toute action synergique entre ces différentes voies activées pour améliorer la viabilité et la fonction de la cellule ß lors du greffon cellulaire. SUMMARY Type 1 diabetes mellitus (T1DM) is an autoimmune disease characterized by the progressive and selective destruction of the pancreatic ß-cells that secrete insulin, leading to absolute insulin deficiency. T1DM accounts for about 10% of all diabetes cases, affecting persons younger than 20 years of age. Medical treatment using daily exogenous insulin injection corrects hormone deficiency but does not prevent devastating complications such as heart attack, neuropathy, kidney failure, blindness, and amputation caused by the disease. Pancreatic islet transplantation (PIT) is one strategy that holds promise to cure patients with T1DM, but purified pancreatic islet grafts have failed to maintain long-term glucose homeostasis in human recipients, the reasons for this failure being still poorly understood. There is however a more immediate problem with islet grafting that is dependent upon poor islet recovery from donors and early islet loss following the first hours of grafting. This tendency of islet grafts to fail to function within a short period after transplantation is termed primary graft non-function (PNF). Indeed, the islet isolation procedure itself destroys cellular and non-cellular components of the pancreas that may play a role in supporting islet survival. Further, islet transplantation exposes cells to a variety of stressful stimuli, notably pro-inflammatory cytokines that encourage ß-cell death by apoptosis and lead to early graft failure. Altogether these mechanisms lead to an estimated loss of 60% of the total islet mass. Here, we have mapped the major intracellular stress signaling pathways that may mediate human islet loss by apoptosis during isolation and following cytokine attack. We found that several stress pathways are maximally activated from the earliest stages of the isolation procedure. Culturing islet for two days allow for the activated pathways to return to basal levels. We propose that protective strategies should 1) be initiated as early as possible during isolation of the islets, 2) should probably target the activated stress pathways that we uncovered during our studies and 3) should include culturing islets for two days post-isolation and prior transplantation.

Constitutive nitric oxide synthase (cNOS) activity in Langerhans islets from streptozotocin diabetic rats

Nitric oxide synthase activity was measured in Langerhans islets isolated from control and streptozotocin diabetic rats. The activity of the enzyme was linear up to 150 µg of protein from control rats and was optimal at 0.1 µM calcium, when it was measured after 45 min of incubation at 37oC in the presence of 200 µM arginine. Specific activity of the enzyme was 25 x 10-4 nmol [3H]citrulline 45 min-1 mg protein-1. Streptozotocin diabetic rats exhibited less enzyme activity both in total pancreas homogenate and in isolated Langerhans islets when compared to control animals. Nitric oxide synthase activity measured in control and diabetic rats 15 days after the last streptozotocin injection in the second group of animals corresponded only to a constitutive enzyme since it was not inhibited by aminoguanidine in any of the mentioned groups. Hyperglycemia in diabetic rats may be the consequence of impaired insulin release caused at least in part by reduced positive modulation mediated by constitutive nitric oxide synthase activity, which was dramatically reduced in islets severely damaged after streptozotocin treatment.

Alterations of NADPH Oxidase Activity in Rat Pancreatic Islets Induced by a High-Fat Diet

Objective: The aim of this study was to evaluate the effect of a high-fat diet (HFD) on nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity in rat pancreatic islets. We investigated if changes in NADPH oxidase are connected to beta cell dysfunction reported in obese animals. Methods: Male Wistar rats were fed a HFD or control diet for 3 months. DNA fragmentation, insulin secretion, and [U-(14)C] glucose oxidation were examined in isolated pancreatic islets. The oxidative stress markers nitrotyrosine and 4-hydroxy-2-nonenal were assessed by immunohistochemistry. The protein content of gp91(phox) and p47(phox) was evaluated by Western blotting. Production of reactive oxygen species (ROS) was determined by a fluorescence assay using hydroethidine. Results: Occurrence of DNA fragmentation was reduced in pancreatic islets from HFD rats. There were no differences in oxidative stress markers between the groups. Glucose oxidation and insulin secretion were elevated due to high glucose in pancreatic islets from HFD rats. Protein concentrations of p47(phox) and gp91(phox) subunits were reduced and ROS production was diminished in pancreatic islets from HFD rats. Conclusions: The diminished content of NADPH oxidase subunits and ROS concentrations may be associated with increased glucose oxidation and insulin secretion in an attempt to compensate for the peripheral insulin resistance elicited by the HFD.

Control of the Intracellular Redox State by Glucose Participates in the Insulin Secretion Mechanism

Background: Production of reactive oxygen species (ROS) due to chronic exposure to glucose has been associated with impaired beta cell function and diabetes. However, physiologically, beta cells are well equipped to deal with episodic glucose loads, to which they respond with a fine tuned glucose-stimulated insulin secretion (GSIS). In the present study, a systematic investigation in rat pancreatic islets about the changes in the redox environment induced by acute exposure to glucose was carried out. Methodology/Principal Findings: Short term incubations were performed in isolated rat pancreatic islets. Glucose dose- and time-dependently reduced the intracellular ROS content in pancreatic islets as assayed by fluorescence in a confocal microscope. This decrease was due to activation of pentose-phosphate pathway (PPP). Inhibition of PPP blunted the redox control as well as GSIS in a dose-dependent manner. The addition of low doses of ROS scavengers at high glucose concentration acutely improved beta cell function. The ROS scavenger N-acetyl-L-cysteine increased the intracellular calcium response to glucose that was associated with a small decrease in ROS content. Additionally, the presence of the hydrogen peroxide-specific scavenger catalase, in its membrane-permeable form, nearly doubled glucose metabolism. Interestingly, though an increase in GSIS was also observed, this did not match the effect on glucose metabolism. Conclusions: The control of ROS content via PPP activation by glucose importantly contributes to the mechanisms that couple the glucose stimulus to insulin secretion. Moreover, we identified intracellular hydrogen peroxide as an inhibitor of glucose metabolism intrinsic to rat pancreatic islets. These findings suggest that the intracellular adjustment of the redox environment by glucose plays an important role in the mechanism of GSIS.

Induction of Indoleamine 2,3-Dioxygenase by Gene Delivery in Allogeneic Islets Prolongs Allograft Survival

Indoleamine 2,3-dioxygenase (IDO), an enzyme that plays a critical role in fetomaternal tolerance, exerts immunoregulatory functions suppressing T-cell responses. The aims of this study were to promote IDO expression in rat islets using a nonviral gene transfer approach, and to analyze the effect of the in vivo induction of IDO in a model of allogeneic islet transplantation. The IDO cDNA was isolated from rat placenta, subcloned into a plasmid and transfected into rat islets using Lipofectamine. The efficiency of transfection was confirmed by qRT-PCR and functional analysis. The in vivo effect of IDO expression was analyzed in streptozotocin-induced diabetic Lewis rats transplanted with allogeneic islets under the renal capsule. Transplantation of IDO-allogeneic islets reversed diabetes and maintained metabolic control, in contrast to transplantation of allogeneic nontransfected islets, which failed shortly after transplantation in all animals. Graft survival of allograft islets transfected with IDO transplanted without any immunosuppression was superior to that observed in diabetic rats receiving nontransfected islets. These data demonstrated that IDO expression induced in islets by lipofection improved metabolic control of streptozotocin-diabetic rats and prolonged allograft survival.

Rare case of unifocal Langerhans cell histiocytosis in four-month-old child

Langerhans cell histiocytosis (LCH) comprises a group of disorders, the common feature of which is Langerhans cell proliferation. The clinical presentation is highly varied. The severity and prognosis of the disease are dependent on the type and extent of organ involvement. This paper reports a rare case of a four-month-old white male with unifocal LCH limited exclusively to the mandible, discussing the diagnosis, radiographic and immunohistochemical aspects, treatment and monitoring multidisciplinary of the case. (C) 2011 Elsevier Ireland Ltd. All rights reserved.

High doses of dexamethasone induce increased beta-cell proliferation in pancreatic rat islets

Rafacho A, Cestari TM, Taboga SR, Boschero AC, Bosqueiro JR. High doses of dexamethasone induce increased beta-cell proliferation in pancreatic rat islets. Am J Physiol Endocrinol Metab 296: E681-E689, 2009. First published January 21, 2009; doi:10.1152/ajpendo.90931.2008.-Activation of insulin signaling and cell cycle intermediates is required for adult beta-cell proliferation. Here, we report a model to study beta-cell proliferation in living rats by administering three different doses of dexamethasone (0.1, 0.5, and 1.0 mg/kg ip, DEX 0.1, DEX 0.5, and DEX 1.0, respectively) for 5 days. Insulin sensitivity, insulin secretion, and histomorphometric data were investigated. Western blotting was used to analyze the levels of proteins related to the control of beta-cell growth. DEX 1.0 rats, which present moderate hyperglycemia and marked hyperinsulinemia, exhibited a 5.1-fold increase in beta-cell proliferation and an increase (17%) in beta-cell size, with significant increase in beta-cell mass, compared with control rats. The hyperinsulinemic but euglycemic DEX 0.5 rats also showed a significant 3.6-fold increase in beta-cell proliferation. However, DEX 0.1 rats, which exhibited the lowest degree of insulin resistance, compensate for insulin demand by improving only islet function. Activation of the insulin receptor substrate 2/phosphatidylinositol 3-kinase/serine-threoninekinase/ribosomalprotein S6 kinase pathway, as well as protein retinoblastoma in islets from DEX 1.0 and DEX 0.5, but not in DEX 0.1, rats was also observed. Therefore, increasing doses of dexamethasone induce three different degrees of insulin requirement in living rats, serving as a model to investigate compensatory beta-cell alterations. Augmented beta-cell mass involves beta-cell hyperplasia and, to a lower extent, beta-cell hypertrophy. We suggest that alterations in circulating insulin and, to a lesser extent, glucose levels could be the major stimuli for beta-cell proliferation in the dexamethasone-induced insulin resistance.

Biotic and Abiotic factors in the distribution of resident fish species : a case study from two islets and an adjacent shoreline in Terceira Island, Azores, Portugal

XV European Congress of Ichthyology, Porto, Portugal, 7 Sep - 11 Sep, 2015.

Hyperglycemia downregulates Connexin36 in pancreatic islets via the upregulation of ICER-1/ICER-1γ.

Channels formed by the gap junction protein Connexin36 (CX36) contribute to the proper control of insulin secretion. We previously demonstrated that chronic exposure to glucose decreases Cx36 levels in insulin-secreting cells in vitro. Here, we investigated whether hyperglycemia also regulates Cx36 in vivo. Using a model of continuous glucose infusion in adult rats, we showed that prolonged (24-48 h) hyperglycemia reduced the Cx36 gene Gjd2 mRNA levels in pancreatic islets. Accordingly, prolonged exposure to high glucose concentrations also reduced the expression and function of Cx36 in the rat insulin-producing INS-1E cell line. The glucose effect was blocked after inhibition of the cAMP/PKA pathway and was associated with an overexpression of the inducible cAMP early repressor ICER-1/ICER-1γ, which binds to a functional cAMP-response element in the promoter of the Cx36 gene Gjd2. The involvement of this repressor was further demonstrated using an antisense strategy of ICER-1 inhibition, which prevented glucose-induced downregulation of Cx36. The data indicate that chronic exposure to glucose alters the in vivo expression of Cx36 by the insulin-producing β-cells through ICER-1/ICER-1γ overexpression. This mechanism may contribute to the reduced glucose sensitivity and altered insulin secretion, which contribute to the pathophysiology of diabetes.

Effectiveness of cladribine therapy in patients with pulmonary Langerhans cell histiocytosis.

BackgroundPulmonary Langerhans cell histiocytosis (PLCH) is a rare disorder characterised by granulomatous proliferation of CD1a-positive histiocytes forming granulomas within lung parenchyma, in strong association with tobacco smoking, and which may result in chronic respiratory failure. Smoking cessation is considered to be critical in management, but has variable effects on outcome. No drug therapy has been validated. Cladribine (chlorodeoxyadenosine, 2-CDA) down-regulates histiocyte proliferation and has been successful in curbing multi-system Langerhans cell histiocytosis and isolated PLCH.Methods and patientsWe retrospectively studied 5 patients (aged 37¿55 years, 3 females) with PLCH who received 3 to 4 courses of cladribine therapy as a single agent (0.1 mg/kg per day for 5 consecutive days at monthly intervals). One patient was treated twice because of relapse at 1 year. Progressive pulmonary disease with obstructive ventilatory pattern despite smoking cessation and/or corticosteroid therapy were indications for treatment. Patients were administered oral trimethoprim/sulfamethoxazole and valaciclovir to prevent opportunistic infections. They gave written consent to receive off-label cladribine in the absence of validated treatment.ResultsFunctional class dyspnea improved with cladribine therapy in 4 out of 5 cases, and forced expiratory volume in 1 second (FEV1) increased in all cases by a mean of 387 ml (100¿920 ml), contrasting with a steady decline prior to treatment. Chest high-resolution computed tomography (HRCT) features improved with cladribine therapy in 4 patients. Hemodynamic improvement was observed in 1 patient with pre-capillary pulmonary hypertension. The results suggested a greater treatment effect in subjects with nodular lung lesions and/or thick-walled cysts on chest HRCT, with diffuse hypermetabolism of lung lesions on positron emission tomography (PET)-scan, and with progressive disease despite smoking cessation. Infectious pneumonia developed in 1 patient, with later grade 4 neutrocytopenia but without infection.DiscussionData interpretation was limited by the retrospective, uncontrolled study design and small sample size.ConclusionCladribine as a single agent may be effective therapy in patients with progressive PLCH.

Reduction of connexin36 content by ICER-1 contributes to insulin-secreting cells apoptosis induced by oxidized LDL particles.

Connexin36 (Cx36), a trans-membrane protein that forms gap junctions between insulin-secreting beta-cells in the Langerhans islets, contributes to the proper control of insulin secretion and beta-cell survival. Hypercholesterolemia and pro-atherogenic low density lipoproteins (LDL) contribute to beta-cell dysfunction and apoptosis in the context of Type 2 diabetes. We investigated the impact of LDL-cholesterol on Cx36 levels in beta-cells. As compared to WT mice, the Cx36 content was reduced in islets from hypercholesterolemic ApoE-/- mice. Prolonged exposure to human native (nLDL) or oxidized LDL (oxLDL) particles decreased the expression of Cx36 in insulin secreting cell-lines and isolated rodent islets. Cx36 down-regulation was associated with overexpression of the inducible cAMP early repressor (ICER-1) and the selective disruption of ICER-1 prevented the effects of oxLDL on Cx36 expression. Oil red O staining and Plin1 expression levels suggested that oxLDL were less stored as neutral lipid droplets than nLDL in INS-1E cells. The lipid beta-oxidation inhibitor etomoxir enhanced oxLDL-induced apoptosis whereas the ceramide synthesis inhibitor myriocin partially protected INS-1E cells, suggesting that oxLDL toxicity was due to impaired metabolism of the lipids. ICER-1 and Cx36 expressions were closely correlated with oxLDL toxicity. Cx36 knock-down in INS-1E cells or knock-out in primary islets sensitized beta-cells to oxLDL-induced apoptosis. In contrast, overexpression of Cx36 partially protected INS-1E cells against apoptosis. These data demonstrate that the reduction of Cx36 content in beta-cells by oxLDL particles is mediated by ICER-1 and contributes to oxLDL-induced beta-cell apoptosis.

Multisystem Langerhans' cell histiocytosis (Hand-Schüller-Christian disease) in an adult: a case report and review of the literature.

Langerhans' cell histiocytosis (LCH) is a rare and enigmatic clonal disorder that affects mainly children. It is characterized by single or multiple granulomatous mass lesions composed of cells with the Langerhans' cell phenotype. Clinical presentation and behavior are heterogeneous and can range from a solitary lytic bone lesion (i.e., eosinophilic granuloma) with a favorable course to a fatal disseminated leukaemia-like form, with a wide spectrum of intermediate clinical presentations between these two extremes. Although LCH typically involves the bone, lesions can be found in almost all organs. We are reporting the case of a multisystem LCH in a 47-year-old patient who presented with a panhypopituitarism and diabetes insipidus, and who, 5 years later, developed mandibular, mastoid and femoral lesions. The final diagnosis of LCH was made on mandibular biopsy.