Regenerating 1 and 3b Gene Expression in the Pancreas of Type 2 Diabetic Goto-Kakizaki (GK) Rats

International audienceRegenerating (REG) proteins are associated with islet development, b-cell damage, diabetes and pancreatitis. Particularly, REG-1 and REG-3-beta are involved in cell growth/survival and/or inflammation and the Reg1 promoter contains interleukin-6 (IL-6)-responsive elements. We showed by transcriptome analysis that islets of Goto-Kakizaki (GK) rats, a model of spontaneous type 2 diabetes, overexpress Reg1, 3a, 3b and 3c, vs Wistar islets. Goto-Kakizaki rat islets also exhibit increased cytokine/chemokine expression/release, particularly IL-6. Here we analyzed Reg1 and Reg3b expression and REG-1 immuno-localization in the GK rat pancreas in relationship with inflammation. Isolated pancreatic islets and acinar tissue from male adult Wistar and diabetic GK rats were used for quantitative RT-PCR analysis. REG-1 immunohistochemistry was performed on paraffin sections with a monoclonal anti-rat REG-1 antibody. Islet cytokine/chemokine release was measured after 48 h-culture. Islet macrophage-positive area was quantified on cryostat sections using anti-CD68 and major histocompatibility complex (MHC) class II antibodies. Pancreatic exocrine-to-endocrine Reg1 and Reg3b mRNA ratios were markedly increased in Wistar vs GK rats. Conversely, both genes were upregulated in isolated GK rat islets. These findings were unexpected, because Reg genes are expressed in the pancreatic acinar tissue. However, we observed REG-1 protein labeling in acinar peri-ductal tissue close to islets and around large, often disorganized, GK rat islets, which may retain acinar cells due to their irregular shape. These large islets also showed peri-islet macrophage infiltration and increased release of various cytokines/ chemokines, particularly IL-6. Thus, IL-6 might potentially trigger acinar REG-1 expression and secretion in the vicinity of large diabetic GK rat islets. This increased acinar REG-1 expression might reflect an adaptive though unsuccessful response to deleterious microenvironment

Fetal pancreatic b-cell growth and insulin-like growth factors relationship in undernourished rats

Resumen del trabajo presentado al 38th EASD Annual Meeting of the European Association for the Study of Diabetes, celebrado en Budapest (Humgria) del 1 al 5 de septiembre de 2002.[Background and Aims] We have previously shown that Wistar fetuses from protein- caloric undernourished pregnant rats (U) at 21 days post coitum (dpc) exhibit increased β cell-mass. This alteration is correlated with increased insulinemia and total pancreatic insulin content, a pattern reminiscent to that reported in infants of mild diabetic mothers. Both Insulinlike Growth Factor (IGF)-I and -2 are essential players for growth and development during the fetal period. The aim of the present study was to investigate in the U fetuses at 21 dpc: 1) serum IGFs levels, 2) IGFs gene expression in the liver and pancreas, and 3) in vitro mitogenic effect of IGFs in isolated fetal islets using BrdU labelling index (LI). All values were compared to those in Wi star control fetuses (C). [Methods] Serum concentrations of IGF-I and IGF-2 were measured by radioimmuno assay and radioreceptor assay respectively. RNase protection assay was performed using RNA from pancreas and liver to evaluate IGFs or IGFBPs gene expression in both tissues. [Results] Similar serum IGF-I and-2levels were observed in U and C. IGF-I and IGF-2 mRNAs were detected in liver and pancreas of both C and U fetuses. Despite being decreased in the liver, IGF-l mRNA level was increased in U pancreases as compared to C. Concerning IGF-2 gene expression it was diminished in U pancreas while being normal in the liver as compared to C. No difference in IGFBP-I, -2 and -3 mRNA levels was detected in U liver when compared to C. However, gene expression of IGFBP-2 was increased and that of IGFBP-3 was decreased in U pancreases. Finally, the in vitro study showed a normal BrdU LI in U isolated fetal islets under basal conditions while it was found significantly increased twice in response to both IGF-I and IGF-2 (lOOng/ml) as compared to fetal C islets. [Conclusion] Our data suggest that in U fetuses at 21 dpc: I) the increased β-cell mass can be related to the stimulation of replicative β-cell response due to locally increased IGF-I in the pancreas 2) such IGF-I action is perhaps favored by an enhanced IGFBP-2 gene expression in pancreas, and 3) at variance with previous reports in several models of decreased intrapancreatic IGF-2 expression in fetuses, the low IGF-2 mRNA level as it is observed in the present U model does not correlate with a decreased β-cell growth.Peer Reviewe

Loss of Sugar Detection by GLUT2 Affects Glucose Homeostasis in Mice

International audienceBACKGROUND: Mammals must sense the amount of sugar available to them and respond appropriately. For many years attention has focused on intracellular glucose sensing derived from glucose metabolism. Here, we studied the detection of extracellular glucose concentrations in vivo by invalidating the transduction pathway downstream from the transporter-detector GLUT2 and measured the physiological impact of this pathway. METHODOLOGY/PRINCIPAL FINDINGS: We produced mice that ubiquitously express the largest cytoplasmic loop of GLUT2, blocking glucose-mediated gene expression in vitro without affecting glucose metabolism. Impairment of GLUT2-mediated sugar detection transiently protected transgenic mice against starvation and streptozotocin-induced diabetes, suggesting that both low- and high-glucose concentrations were not detected. Transgenic mice favored lipid oxidation, and oral glucose was slowly cleared from blood due to low insulin production, despite massive urinary glucose excretion. Kidney adaptation was characterized by a lower rate of glucose reabsorption, whereas pancreatic adaptation was associated with a larger number of small islets. CONCLUSIONS/SIGNIFICANCE: Molecular invalidation of sugar sensing in GLUT2-loop transgenic mice changed multiple aspects of glucose homeostasis, highlighting by a top-down approach, the role of membrane glucose receptors as potential therapeutic targets

Desensibilisation de la celule B au glucose. Etude dans 3 modeles de diabete non insulino-dependant chez le rat

SIGLEINIST T 74118 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Localisation de GLUT2 dans l'intestin et son rôle physiopathologique dans la détection des sucres contrôlant la sécrétion de GLP-1

Ce travail porte sur la localisation du transporteur/détecteur de sucres GLUT2 dans l intestin et son rôle physiopathologique dans la détection des sucres contrôlant la sécrétion du Glucagon-Like Peptide-1 (GLP-1). Nous montrons que chez l Homme obèse et insulinorésistant, GLUT2 est anormalement localisé à la membrane apicale de l entérocyte malgré les conditions de jeûne, suggérant une altération du trafic intracellulaire de ce transporteur. La localisation de GLUT2 au pôle apical de l entérocyte pourrait constituer un marqueur de la résistance à l insuline. Le GLP-1 est une hormone sécrétée par les cellules L de l intestin notamment en réponse aux sucres alimentaires. Nos résultats obtenus avec le modèle de souris transgénique invalidée pour la détection des sucres par GLUT2 révèlent l importance de la fonction de détecteur de GLUT2 pour la sécrétion de GLP-1. Chez l Homme obèse, la présence de GLUT2 au pôle apical des cellules L entéroendocrines suggère une détection des sucres directement par la cellule L pour la sécrétion de GLP-1. Enfin, la caractérisation des cellules L entéroendocrines dans des biopsies jéjunales de sujets massivement obèses montre un nombre accru et une forme atypique de ces cellules dans 10% des sujets étudiés. Nos résultats suggèrent un impact de l obésité et de l environnement nutritionnel sur la modulation du nombre et/ou de la forme des cellules L chez l Homme. Ainsi, par sa localisation apicale dans l entérocyte et dans les cellules L entéroendocrines chez l Homme, et par son rôle dans la sécrétion de GLP-1 en réponse au glucose, GLUT2 pourrait constituer une cible thérapeutique dans le traitement de l obésité et/ou du diabète.PARIS-BIUP (751062107) / SudocPARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

Effet des lipides alimentaires sur l abondance et la fonction des cellules entéroendocrines au cours de l obésité et du diabète de type 2

Le glucagon-like peptide-1 (GLP-1) est une hormone produite par les cellules L endocrines de l intestin. La présence de nutriments dans la lumière intestinale déclenche sa sécrétion. Le GLP-1 exerce différents rôles physiologiques sur l homéostasie énergétique, il a notamment des effets insulinotrope et anorexigène. Au cours de l obésité, une altération de la sécrétion de GLP-1 est rapportée. Certains sujets obèses présentent également un déséquilibre qualitatif de l apport en nutriments. L objectif de ma thèse a été de comprendre comment les lipides alimentaires en excès pouvaient moduler l abondance et la fonction des cellules L entéroendocrines au cours de l obésité, chez l Homme et la souris. Une consommation excessive de lipides chez les sujets obèses, comme un régime hyperlipidique chez la souris, induisent une abondance accrue de cellules L exprimant le GLP-1. Chez la souris, l abondance accrue des cellules L est due à une augmentation de la différenciation terminale des cellules L, ce qui conduit à une augmentation de la sécrétion de GLP-1 en réponse au glucose. De plus, chez l Homme, l obésité morbide provoque une réduction de l abondance des cellules L avec une perte de la fonction sécrétoire de ces cellules. Il existe donc une plasticité intestinale permettant de moduler l abondance des cellules L entéroendocrines en réponse aux lipides alimentaires. La capacité de ces cellules à sécréter le GLP-1 semble quant à elle être influencée par la durée et la sévérité des perturbations métaboliques liées à l obésité.Glucagon-like peptide-1 (GLP-1) is a hormone produced by enteroendocrine L cells. GLP-1 is secreted in response to luminal nutrients. GLP-1 exerts many physiological effects on energy homeostasis, including promoting insulin secretion and suppressing appetite. In obesity, GLP-1 secretion is impaired. Some obese subjects also have an imbalanced nutrient composition of their diet. The aim of my thesis was to investigate how dietary lipids can modulate abundance and function of enteroendocrine cells during obesity, in human subjects and mice. Excessive lipid intake in obese subjects, as high fat diet in mice, increases L cell abundance. In mice, greater L cell abundance relies on an increased terminal L cell differentiation that subsequently induces a rise of glucose-induced GLP-1 secretion. Furthermore, morbid obesity in human subjects seems to reduce L cell abundance and to impair L cell capacity to secrete GLP-1. These results indicate that gut plasticity allows a modulation of enteroendocrine L cell abundance in response to nutrients. The secretion capacity of these cells seems to rely on duration and gravity of metabolic disorders linked to obesity.PARIS-BIUSJ-Biologie recherche (751052107) / SudocSudocFranceF

IGF-2 and development in vitro of a pancreatic embryonic bourgeon in the GK rat, spontaneous diabetes model type 2

National audienc

IGF-2 and development in vitro of a pancreatic embryonic bourgeon in the GK rat, spontaneous diabetes model type 2

National audienc

Enteroendocrine System and Gut Barrier in Metabolic Disorders

International audienceWith the continuous rise in the worldwide prevalence of obesity and type 2 diabetes, developing therapies regulating body weight and glycemia has become a matter of great concern. Among the current treatments, evidence now shows that the use of intestinal hormone analogs (e.g., GLP1 analogs and others) helps to control glycemia and reduces body weight. Indeed, intestinal endocrine cells produce a large variety of hormones regulating metabolism, including appetite, digestion, and glucose homeostasis. Herein, we discuss how the enteroendocrine system is affected by local environmental and metabolic signals. These signals include those arising from unbalanced diet, gut microbiota, and the host metabolic organs and their complex cross-talk with the intestinal barrier integrity

Respective impact of inheritance and environmental programming on beta-cell mass and beta-cell function in the GK model

International audienc