21 results on '"Heimberg, Harry"'
Search Results
2. Semi-automated digital measurement as the method of choice for beta cell mass analysis.
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Coppens, Violette, Leuckx, Gunter, Heremans, Yves, Staels, Willem, Verdonck, Yannick, Baeyens, Luc, De Leu, Nico, and Heimberg, Harry
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PANCREATIC beta cells ,CELL differentiation ,CELL proliferation ,CELL size ,DIGITAL image processing - Abstract
Pancreas injury by partial duct ligation (PDL) activates beta cell differentiation and proliferation in adult mouse pancreas but remains controversial regarding the anticipated increase in beta cell volume. Several reports unable to show beta cell volume augmentation in PDL pancreas used automated digital image analysis software. We hypothesized that fully automatic beta cell morphometry without manual micrograph artifact remediation introduces bias and therefore might be responsible for reported discrepancies and controversy. However, our present results prove that standard digital image processing with automatic thresholding is sufficiently robust albeit less sensitive and less adequate to demonstrate a significant increase in beta cell volume in PDL versus Sham-operated pancreas. We therefore conclude that other confounding factors such as quality of surgery, selection of samples based on relative abundance of the transcription factor Neurogenin 3 (Ngn3) and tissue processing give rise to inter-laboratory inconsistencies in beta cell volume quantification in PDL pancreas. [ABSTRACT FROM AUTHOR]
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- 2018
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3. Inhibition of Cdk5 Promotes β-Cell Differentiation From Ductal Progenitors.
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Ka-Cheuk Liu, Leuckx, Gunter, Daisuke Sakano, Seymour, Philip A., Mattsson, Charlotte L., Rautio, Linn, Staels, Willem, Verdonck, Yannick, Serup, Palle, Shoen Kume, Heimberg, Harry, Andersson, Olov, Liu, Ka-Cheuk, Sakano, Daisuke, and Kume, Shoen
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PANCREATIC beta cells ,TREATMENT of diabetes ,NOTCH signaling pathway ,LABORATORY zebrafish ,LABORATORY mice ,FISH metabolism ,PROTEIN metabolism ,ANIMAL experimentation ,ANIMALS ,CELL differentiation ,CELLULAR signal transduction ,FISHES ,INSECT larvae ,ISLANDS of Langerhans ,PANCREATIC duct ,POLYMERASE chain reaction ,PROTEINS ,RESEARCH funding ,STEM cells ,TRANSFERASES ,SEQUENCE analysis ,GENOTYPES ,PHYSIOLOGY - Abstract
Inhibition of notch signaling is known to induce differentiation of endocrine cells in zebrafish and mouse. After performing an unbiased in vivo screen of ∼2,200 small molecules in zebrafish, we identified an inhibitor of Cdk5 (roscovitine), which potentiated the formation of β-cells along the intrapancreatic duct during concurrent inhibition of notch signaling. We confirmed and characterized the effect with a more selective Cdk5 inhibitor, (R)-DRF053, which specifically increased the number of duct-derived β-cells without affecting their proliferation. By duct-specific overexpression of the endogenous Cdk5 inhibitors Cdk5rap1 or Cdkal1 (which previously have been linked to diabetes in genome-wide association studies), as well as deleting cdk5, we validated the role of chemical Cdk5 inhibition in β-cell differentiation by genetic means. Moreover, the cdk5 mutant zebrafish displayed an increased number of β-cells independently of inhibition of notch signaling, in both the basal state and during β-cell regeneration. Importantly, the effect of Cdk5 inhibition to promote β-cell formation was conserved in mouse embryonic pancreatic explants, adult mice with pancreatic ductal ligation injury, and human induced pluripotent stem (iPS) cells. Thus, we have revealed a previously unknown role of Cdk5 as an endogenous suppressor of β-cell differentiation and thereby further highlighted its importance in diabetes. [ABSTRACT FROM AUTHOR]
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- 2018
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4. Pancreas and gallbladder agenesis in a newborn with semilobar holoprosencephaly, a case report.
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Hilbrands, Robert, Keymolen, Kathelijn, Michotte, Alex, Marichal, Miriam, Cools, Filip, Goossens, Anieta, Veld, Peter In't, De Schepper, Jean, Hattersley, Andrew, and Heimberg, Harry
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HUMAN abnormalities ,DIABETES ,TRANSCRIPTION factors ,PANCREATIC beta cells ,HOLOPROSENCEPHALY - Abstract
Background: Pancreatic agenesis is an extremely rare cause of neonatal diabetes mellitus and has enabled the discovery of several key transcription factors essential for normal pancreas and beta cell development. Case presentation: We report a case of a Caucasian female with complete pancreatic agenesis occurring together with semilobar holoprosencephaly (HPE), a more common brain developmental disorder. Clinical findings were later confirmed by autopsy, which also identified agenesis of the gallbladder. Although the sequences of a selected set of genes related to pancreas agenesis or HPE were wild-type, the patient's phenotype suggests a genetic defect that emerges early in embryonic development of brain, gallbladder and pancreas. Conclusions: Developmental defects of the pancreas and brain can occur together. Identifying the genetic defect may identify a novel key regulator in beta cell development. [ABSTRACT FROM AUTHOR]
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- 2017
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5. Estrogen Receptor α Regulates β-Cell Formation During Pancreas Development and Following Injury.
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Yixing Yuchi, Ying Cai, Legein, Bart, De Groef, Sofie, Leuckx, Gunter, Coppens, Violette, Van Overmeire, Eva, Staels, Willem, De Leu, Nico, Martens, Geert, Van Ginderachter, Jo A., Heimberg, Harry, and de Casteele, Mark Van
- Subjects
ESTROGEN receptors ,PANCREATIC beta cells ,CELLULAR therapy ,ESTRADIOL ,DIABETES - Abstract
Identifying pathways for β-cell generation is essential for cell therapy in diabetes. We investigated the potential of 17β-estradiol (E
2 ) and estrogen receptor (ER) signaling for stimulating β-cell generation during embryonic development and in the severely injured adult pancreas. E2 concentration, ER activity, and number of ERα transcripts were enhanced in the pancreas injured by partial duct ligation (PDL) along with nuclear localization of ERα in β-cells. PDL-induced proliferation of β-cells depended on aromatase activity. The activation of Neurogenin3 (Ngn3) gene expression and β-cell growth in PDL pancreas were impaired when ERα was turned off chemically or genetically (ERα-/- ), whereas in situ delivery of E2 promoted β-cell formation. In the embryonic pancreas, β-cell replication, number of Ngn3+progenitor cells, and expression of key transcription factors of the endocrine lineage were decreased by ERα inactivation. The current study reveals that E2 and ERα signaling can drive β-cell replication and formation in mouse pancreas. [ABSTRACT FROM AUTHOR]- Published
- 2015
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6. Partial Duct Ligation: β-Cell Proliferation and Beyond.
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Van de Casteele, Mark, Leuckx, Gunter, Ying Cai, Yixing Yuchi, Coppens, Violette, De Groef, Sofie, Van Gassen, Naomi, Baeyens, Luc, Heremans, Yves, Wright, Christopher V. E., and Heimberg, Harry
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PANCREATIC beta cells ,CELL proliferation ,PANCREAS ,TAMOXIFEN ,CYTOLOGICAL research - Abstract
The article discusses research on the correlation between β-cell proliferation and partial duct ligation (PDL) pancreas. Topics discussed include the use of the cell ablation paradigm to study the replacement of the endogenous β-cell pool, the minority seeding of β-cells, and the tamoxifen (TAM)-induced labeling methods. Also mentioned are PSL as a pancreatic injury, β-cell formation in PDL pancreas, and β-cell neogenesis.
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- 2014
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7. Clusters of Conserved Beta Cell Marker Genes for Assessment of Beta Cell Phenotype.
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Martens, Geert A., Jiang, Lei, Hellemans, Karine H., Stangé, Geert, Heimberg, Harry, Nielsen, Finn C., Sand, Olivier, Van Helden, Jacques, Gorus, Frans K., and Pipeleers, Daniel G.
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PANCREATIC beta cells ,CLUSTER analysis (Statistics) ,BIOMARKERS ,PHENOTYPES ,GENE expression ,CELL differentiation ,TRANSCRIPTION factors - Abstract
Background and Methodology: The aim of this study was to establish a gene expression blueprint of pancreatic beta cells conserved from rodents to humans and to evaluate its applicability to assess shifts in the beta cell differentiated state. Genome-wide mRNA expression profiles of isolated beta cells were compared to those of a large panel of other tissue and cell types, and transcripts with beta cell-abundant and -selective expression were identified. Iteration of this analysis in mouse, rat and human tissues generated a panel of conserved beta cell biomarkers. This panel was then used to compare isolated versus laser capture microdissected beta cells, monitor adaptations of the beta cell phenotype to fasting, and retrieve possible conserved transcriptional regulators. Principal Findings: A panel of 332 conserved beta cell biomarker genes was found to discriminate both isolated and laser capture microdissected beta cells from all other examined cell types. Of all conserved beta cell-markers, 15% were strongly beta cell-selective and functionally associated to hormone processing, 15% were shared with neuronal cells and associated to regulated synaptic vesicle transport and 30% with immune plus gut mucosal tissues reflecting active protein synthesis. Fasting specifically down-regulated the latter cluster, but preserved the neuronal and strongly beta cellselective traits, indicating preserved differentiated state. Analysis of consensus binding site enrichment indicated major roles of CREB/ATF and various nutrient- or redox-regulated transcription factors in maintenance of differentiated beta cell phenotype. Conclusions: Conserved beta cell marker genes contain major gene clusters defined by their beta cell selectivity or by their additional abundance in either neural cells or in immune plus gut mucosal cells. This panel can be used as a template to identify changes in the differentiated state of beta cells. [ABSTRACT FROM AUTHOR]
- Published
- 2011
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8. Beta Cells within Single Human Islets Originate from Multiple Progenitors.
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Scharfmann, Raphaël, Xiangwei Xiao, Heimberg, Harry, Mallet, Jacques, and Ravassard, Philippe
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ISLANDS of Langerhans ,CELL differentiation ,GENETIC transformation ,MORPHOGENESIS ,LABORATORY rodents ,PANCREATIC beta cells ,GENETIC research ,LENTIVIRUSES ,INSULIN - Abstract
Background: In both humans and rodents, glucose homeostasis is controlled by micro-organs called islets of Langerhans composed of beta cells, associated with other endocrine cell types. Most of our understanding of islet cell differentiation and morphogenesis is derived from rodent developmental studies. However, little is known about human islet formation. The lack of adequate experimental models has restricted the study of human pancreatic development to the histological analysis of different stages of pancreatic development. Our objective was to develop a new experimental model to (i) transfer genes into developing human pancreatic cells and (ii) validate gene transfer by defining the clonality of developing human islets. Methods and Findings: In this study, a unique model was developed combining ex vivo organogenesis from human fetal pancreatic tissue and cell type-specific lentivirus-mediated gene transfer. Human pancreatic progenitors were transduced with lentiviruses expressing GFP under the control of an insulin promoter and grafted to severe combined immunodeficient mice, allowing human beta cell differentiation and islet morphogenesis. By performing gene transfer at low multiplicity of infection, we created a chimeric graft with a subpopulation of human beta cells expressing GFP and found both GFPpositive and GFP-negative beta cells within single islets. Conclusion: The detection of both labeled and unlabeled beta cells in single islets demonstrates that beta cells present in a human islet are derived from multiple progenitors thus providing the first dynamic analysis of human islet formation during development. This human transgenic-like tool can be widely used to elucidate dynamic genetic processes in human tissue formation. [ABSTRACT FROM AUTHOR]
- Published
- 2008
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9. Variations in IB1/JIP1 expression regulate susceptibility of beta-cells to cytokine-induced apoptosis irrespective of C-Jun NH2-terminal kinase signaling.
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Ling, Zhidong, de Casteele, Mark Van, Dong, Jing, Heimberg, Harry, Haefliger, Jacques-Antoine, Waeber, Gérard, Schuit, Frans, Pipeleers, Daniel, Van de Casteele, Mark, and Waeber, Gérard
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APOPTOSIS ,INTERLEUKINS ,CYTOKINES ,PANCREATIC beta cells ,PROTEIN metabolism ,ANIMAL experimentation ,CARRIER proteins ,CELL culture ,CELLULAR signal transduction ,COMBINATION drug therapy ,COMPARATIVE studies ,DRUG synergism ,DRUG administration ,GENETIC techniques ,INTERFERONS ,INTERLEUKIN-1 ,ISLANDS of Langerhans ,RESEARCH methodology ,MEDICAL cooperation ,RATS ,RECOMBINANT proteins ,RESEARCH ,TRANSFERASES ,TUMOR necrosis factors ,EVALUATION research ,NUCLEAR proteins ,PHYSIOLOGY - Abstract
We previously reported that interleukin-1β (IL-1β) alone does not cause apoptosis of β-cells, whereas when combined with γ-interferon (IFN-γ) and tumor necrosis factor-α (TNF-α), it exerts a distinct apoptotic effect. Studies in β-cell lines indicated that IL-1β reduced expression of islet brain (IB)-1/JNK interacting protein (JIP)-1, a JNK scaffold protein with antiapoptotic action. We examined whether variations in IB1/JIP-1 expression in purified primary β-cells affect their susceptibility to cytokine-induced apoptosis. Exposure to IL-1β for 24 h decreased cellular IB1/JIP-1 content by 66 ± 17%; this IL-1β effect was maintained in the presence of TNF-α + IFN-γ, which did not influence IB1/JIP-1 levels by themselves. Addition of IL-1β to TNF-α + IFN-γ increased apoptosis from 20 ± 2% to 59 ± 5%. A similar increase in TNF-α + IFN-γ-induced apoptosis was produced by adenoviral expression of antisense IB1/JIP-1 and was not further enhanced by addition of IL-1β, indicating that IL-1β-mediated suppression of IB1/JIP-1 in β-cells increases their susceptibility to cytokine-induced apoptosis. However, adenovirally mediated overexpression of IB1/JIP-1 also potentiated TNF-α + IFN-γ-induced apoptosis, suggesting that the antiapoptotic effect of IB1/JIP-1 depends on well-defined cellular levels. We conclude that the IB1/ JIP-1 level in β-cells can control their susceptibility to apoptosis independent of JNK signaling. [ABSTRACT FROM AUTHOR]
- Published
- 2003
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10. Inhibition of cytokine-induced NF-kappaB activation by adenovirus-mediated expression of a NF-kappaB super-repressor prevents beta-cell apoptosis.
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Heimberg, Harry, Heremans, Yves, Jobin, Christian, Leemans, Ruth, Cardozo, Alessandra K., Darville, Martine, Eizirik, Decio L., Heimberg, H, Heremans, Y, Jobin, C, Leemans, R, Cardozo, A K, Darville, M, and Eizirik, D L
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CELL death , *PANCREATIC beta cells , *DIABETES , *PATHOLOGY - Abstract
Cytokine-induced beta-cell death is an important event in the pathogenesis of type 1 diabetes. The transcription factor nuclear factor-kappaB (NF-kappaB) is activated by interleukin-1beta (IL-1beta), and its activity promotes the expression of several beta-cell genes, including pro- and anti-apoptotic genes. To elucidate the role of cytokine (IL-1beta + gamma-interferon [IFN-gamma])-induced expression of NF-kappaB in beta-cell apoptosis, rat beta-cells were infected with the recombinant adenovirus AdIkappaB((SA)2), which contained a nondegradable mutant form of inhibitory kappaB (IkappaB((SA)2), with S32A and S36A) that locks NF-kappaB in a cytosolic protein complex, preventing its nuclear action. Expression of IkappaB((SA)2) inhibited cytokine-stimulated nuclear translocation and DNA-binding of NF-kappaB. Cytokine-induced gene expression of several NF-kappaB targets, namely inducible nitric oxide synthase, Fas, and manganese superoxide dismutase, was prevented by AdIkappaB((SA)2), as established by reverse transcriptase-polymerase chain reaction, protein blot, and measurement of nitrite in the medium. Finally, beta-cell survival after IL-1beta + IFN-gamma treatment was significantly improved by IkappaB((SA)2) expression, mostly through inhibition of the apoptotic pathway. Based on these findings, we conclude that NF-kappaB activation, under in vitro conditions, has primarily a pro-apoptotic function in beta-cells. [ABSTRACT FROM AUTHOR]
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- 2001
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11. Towards a Functional Cure for Diabetes Using Stem Cell-Derived Beta Cells: Are We There Yet?
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Bourgeois, Stephanie, Sawatani, Toshiaki, Van Mulders, Annelore, De Leu, Nico, Heremans, Yves, Heimberg, Harry, Cnop, Miriam, and Staels, Willem
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PANCREATIC beta cells ,EMBRYONIC stem cells ,ISLANDS of Langerhans ,HUMAN stem cells ,PLURIPOTENT stem cells ,CELL transplantation ,CELL differentiation - Abstract
Diabetes mellitus is a pandemic metabolic disorder that results from either the autoimmune destruction or the dysfunction of insulin-producing pancreatic beta cells. A promising cure is beta cell replacement through the transplantation of islets of Langerhans. However, donor shortage hinders the widespread implementation of this therapy. Human pluripotent stem cells, including embryonic stem cells and induced pluripotent stem cells, represent an attractive alternative beta cell source for transplantation. Although major advances over the past two decades have led to the generation of stem cell-derived beta-like cells that share many features with genuine beta cells, producing fully mature beta cells remains challenging. Here, we review the current status of beta cell differentiation protocols and highlight specific challenges that are associated with producing mature beta cells. We address the challenges and opportunities that are offered by monogenic forms of diabetes. Finally, we discuss the remaining hurdles for clinical application of stem cell-derived beta cells and the status of ongoing clinical trials. [ABSTRACT FROM AUTHOR]
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- 2021
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12. Boosting Beta-Cell Numbers.
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Heimberg, Harry
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DIABETES , *PANCREATIC acinar cells , *PANCREATIC beta cells , *CYTOGENETICS - Abstract
The article discusses restoration of beta-cells by cell therapy as a potential cure for diabetes mellitus. The authors comment on a study by Zhou and colleagues which reported successful reprogramming of acinar cells into insulin-producing beta cells. Induction of cells by retroviral transduction is discussed. Induced transdifferentiation of acinar cells into beta cells is mentioned. The authors comment on the potential risks involving genetic manipulation during in vivo treatments.
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- 2008
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13. Notch Signaling as Gatekeeper of Rat Acinar-to-β-Cell Conversion in Vitro.
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Baeyens, Luc, Bonné, Stefan, Bos, Tomas, Rooman, Ilse, Peleman, Cindy, Lahoutte, Tony, German, Michael, Heimberg, Harry, and Bouwens, Luc
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NOTCH genes ,CELLULAR signal transduction ,PANCREATIC acinar cells ,PANCREATIC beta cells ,LABORATORY rats ,EPIDERMAL growth factor ,CELLULAR therapy - Abstract
Background & Aims: Exocrine acinar cells in the pancreas are highly differentiated cells that retain a remarkable degree of plasticity. After isolation and an initial phase of dedifferentiation in vitro, rodent acinar cells can convert to endocrine β-cells when cultured in the presence of appropriate factors. The mechanisms regulating this phenotypic conversion are largely unknown. Methods: Using rat acinar cell cultures, we studied the role of Notch signaling in a model of acinar-to-β-cell conversion. Results: We report a novel lectin-based cell labeling method to demonstrate the acinar origin of newly formed insulin-expressing β-cells. This method allows for specific tracing of the acinar cells. We demonstrate that growth factor-induced conversion of adult acinar cells to β-cells is negatively regulated by Notch1 signaling. Activated Notch1 signaling prevents the reexpression of the proendocrine transcription factor Neurogenin-3, the key regulator of endocrine development in the embryonic pancreas. Interfering with Notch1 signaling allows modulating the acinar cell susceptibility to the differentiation-inducing factors. Its inhibition significantly improves β-cell neoformation with approximately 30% of acinar cells that convert to β-cells. The newly formed β-cells mature when transplanted ectopically and are capable of restoring normal blood glycemia in diabetic recipients. Conclusions: We report for the first time an efficient way to reprogram one third of the acinar cells to β-cells by adult cell type conversion. This could find application in cell replacement therapy of type 1 diabetes, provided that it can be translated from rodent to human models. [Copyright &y& Elsevier]
- Published
- 2009
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14. In vitro reprogramming of pancreatic alpha cells towards a beta cell phenotype following ectopic HNF4α expression.
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Sangan, Caroline B., Jover, Ramiro, Heimberg, Harry, and Tosh, David
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ORGAN donors , *PANCREATIC beta cells , *REGENERATION (Biology) , *HEPATOCYTE nuclear factors , *PHENOTYPES , *PROTEIN expression , *IN vitro studies - Abstract
There is currently a shortage of organ donors available for pancreatic beta cell transplantation into diabetic patients. An alternative source of beta cells is pre-existing pancreatic cells. While we know that beta cells can arise directly from alpha cells during pancreatic regeneration we do not understand the molecular basis for the switch in phenotype. The aim of the present study was to investigate if hepatocyte nuclear factor 4 alpha (HNF4α), a transcription factor essential for a normal beta cell phenotype, could induce the reprogramming of alpha cells towards potential beta cells. We utilised an in vitro model of pancreatic alpha cells, the murine αTC1-9 cell line. We initially characterised the αTC1-9 cell line before and following adenovirus-mediated ectopic expression of HNF4α. We analysed the phenotype at transcript and protein level and assessed its glucose-responsiveness. Ectopic HNF4α expression in the αTC1-9 cell line induced a change in morphology (1.7-fold increase in size), suppressed glucagon expression, induced key beta cell-specific markers (insulin, C-peptide, glucokinase, GLUT2 and Pax4) and pancreatic polypeptide (PP) and enabled the cells to secrete insulin in a glucose-regulated manner. In conclusion, HNF4α reprograms alpha cells to beta-like cells. [ABSTRACT FROM AUTHOR]
- Published
- 2015
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15. Pancreatic beta-cells: From generation to regeneration
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Collombat, Patrick, Xu, Xiaobo, Heimberg, Harry, and Mansouri, Ahmed
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PANCREATIC beta cells , *LANGERHANS cells , *HOMEOSTASIS , *DIABETES , *MORPHOGENESIS , *REGENERATION (Biology) , *LABORATORY mice , *STEM cells - Abstract
Abstract: The pancreas is composed of two main compartments consisting of endocrine and exocrine tissues. The majority of the organ is exocrine and responsible for the synthesis of digestive enzymes and for their transport via an intricate ductal system into the duodenum. The endocrine tissue represents less than 2% of the organ and is organized into functional units called islets of Langerhans, comprising alpha-, beta-, delta-, epsilon- and PP-cells, producing the hormones glucagon, insulin, somatostatin, ghrelin and pancreatic polypeptide (PP), respectively. Insulin-producing beta-cells play a central role in the control of the glucose homeostasis. Accordingly, absolute or relative deficiency in beta-cells may ultimately lead to type 1 and/or type 2 diabetes, respectively. One major goal of diabetes research is therefore to understand the molecular mechanisms controlling the development of beta-cells during pancreas morphogenesis, but also those underlying the regeneration of adult injured pancreas, and assess their significance for future cell-based therapy. In this review, we will therefore present new insights into beta-cell development with focus on beta-cell regeneration. [ABSTRACT FROM AUTHOR]
- Published
- 2010
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16. Adiponectin-mediated stimulation of AMP-activated protein kinase (AMPK) in pancreatic beta cells
- Author
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Huypens, Peter, Moens, Karen, Heimberg, Harry, Ling, Zhidong, Pipeleers, Daniël, and Van de Casteele, Mark
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ISLANDS of Langerhans , *PANCREATIC beta cells , *ENDOCRINE diseases , *ISOPENTENOIDS - Abstract
Abstract: The adipocyte-derived hormone adiponectin was recently shown to stimulate glucose-utilization and to increase fatty acid oxidation in liver and muscle. The effects were ascribed to adiponectin-receptor mediated activation of the key metabolic regulator AMP-activated protein kinase (AMPK). In pancreatic beta cells, AMPK-activation is known to affect cellular function. We therefore investigated a possible adiponectin-induced activation of AMPK in beta cells. RT-PCR analysis confirmed the expression of adiponectin receptor subtypes 1 and 2 in rat beta cells and showed their expression in insulin-secreting MIN6 cells. Culture with physiological concentrations (2.5 μg/ml) of globular adiponectin was found to increase the phosphorylation of both AMPK and acetylcoA carboxylase (ACC) in these cell types. Like the pharmacological AMPK activator 5-amino-imidazole-4-carboxamide-riboside (AICAR), adiponectin activated AMPK in beta cells and MIN6 cells. In short-term incubations of MIN6 cells with either adiponectin (2.5 μg/ml) or AICAR (1 mM), the flux of glucose-carbon to acyl CoA/cholesterol biosynthetic intermediates was reduced. We conclude that adiponectin induces an activation of AMPK in beta cells, which inhibits their cataplerosis of glucose-carbon to lipids. [Copyright &y& Elsevier]
- Published
- 2005
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17. The Ectopic Expression of Pax4 in the Mouse Pancreas Converts Progenitor Cells into α and Subsequently β Cells
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Collombat, Patrick, Xu, Xiaobo, Ravassard, Philippe, Sosa-Pineda, Beatriz, Dussaud, Sébastien, Billestrup, Nils, Madsen, Ole D., Serup, Palle, Heimberg, Harry, and Mansouri, Ahmed
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GENE expression , *PANCREAS , *PROMOTERS (Genetics) , *GLUCAGON , *CELL differentiation , *DIABETES , *PANCREATIC beta cells , *LABORATORY mice - Abstract
Summary: We have previously reported that the loss of Arx and/or Pax4 gene activity leads to a shift in the fate of the different endocrine cell subtypes in the mouse pancreas, without affecting the total endocrine cell numbers. Here, we conditionally and ectopically express Pax4 using different cell-specific promoters and demonstrate that Pax4 forces endocrine precursor cells, as well as mature α cells, to adopt a β cell destiny. This results in a glucagon deficiency that provokes a compensatory and continuous glucagon+ cell neogenesis requiring the re-expression of the proendocrine gene Ngn3. However, the newly formed α cells fail to correct the hypoglucagonemia since they subsequently acquire a β cell phenotype upon Pax4 ectopic expression. Notably, this cycle of neogenesis and redifferentiation caused by ectopic expression of Pax4 in α cells is capable of restoring a functional β cell mass and curing diabetes in animals that have been chemically depleted of β cells. [ABSTRACT FROM AUTHOR]
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- 2009
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18. Akt activation protects pancreatic beta cells from AMPK-mediated death through stimulation of mTOR
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Cai, Ying, Wang, Qidi, Ling, Zhidong, Pipeleers, Daniel, McDermott, Paul, Pende, Mario, Heimberg, Harry, and Van de Casteele, Mark
- Subjects
- *
GREEN fluorescent protein , *PANCREATIC beta cells , *CELL death , *ENDOCRINE diseases - Abstract
Abstract: Sustained activation of AMP-activated protein kinase (AMPK) induces apoptosis in several cell types. In pancreatic beta cells this occurs under glucose limitation, or in the presence of the pharmacological AMPK activator 5-aminoimidazole-4-carboxamide-riboside (AICAR). It is unknown whether Akt activation can counteract AMPK-mediated apoptosis, nor whether mTOR activation downstream of Akt mediates any survival signal in these conditions. We report that expression of a constitutively active form of Akt increases mTOR activity and prevents apoptosis upon AMPK activation. Akt-mediated survival was inhibited by rapamycin. Expression of a constitutively active form of the mTOR target ribosomal protein S6 kinase (S6K) or of translation factor eIF4E reduced apoptosis by glucose limitation, and co-expression of S6K and eIF4E protected beta cells to the same extent as active Akt. The protective effects of active Akt and S6K were associated with increased cellular protein synthesis activity. It is concluded that Akt stimulation of mTOR and subsequent activation of the targets by which mTOR affects protein translation are required and sufficient mechanisms for Akt-mediated survival of beta cells undergoing sustained AMPK activation. [Copyright &y& Elsevier]
- Published
- 2008
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19. Prolonged culture in low glucose induces apoptosis of rat pancreatic β-cells through induction of c-myc
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Van de Casteele, Mark, Kefas, Benjamin Ate, Cai, Ying, Heimberg, Harry, Scott, Donald K., Henquin, Jean-Claude, Pipeleers, Daniël, and Jonas, Jean-Christophe
- Subjects
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APOPTOSIS , *PANCREATIC beta cells , *GLUCOSE , *RATS - Abstract
Prolonged culture in low-glucose concentrations (⩽5 mM) induces apoptosis in pancreatic β-cells by a poorly defined mechanism. We now show that, in both purified rat β-cells and isolated rat islets, culture in the presence of 3 or 5 mM (G3–G5) instead of 10 mM 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 Ca2+ influx and insulin secretion with diazoxide under control conditions did not stimulate islet c-myc expression nor β-cell apoptosis. In rat β-cells, adenovirus-mediated c-myc overexpression increased their rate of apoptosis, whereas antisense-c-myc expression reduced low-glucose-induced apoptosis by ∼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 β-cell apoptosis by prolonged culture at low glucose partly results from early and sustained induction of β-cell c-myc expression. These effects may be due to sustained restriction in nutrient-derived metabolic signals. [Copyright &y& Elsevier]
- Published
- 2003
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20. Identification et caractérisation des voies de signalisation du stress du réticulum endoplasmique dans la cellule bêta pancréatique
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Pirot, Pierre, Cardozo, Alessandra K, Eizirik, Decio, Lebrun, Philippe, Herchuelz, André, Heimberg, Harry, Vandenabeele, Peter, Robberecht, Patrick, and Blanpain, Cédric
- Subjects
Apoptose ,Langerhans, Cellules bêta des îlots de ,Diabetes ,apoptosis ,Médecine pathologie humaine ,Réticulum endoplasmique ,Pancreatic beta cells ,pancreatic beta cell ,endoplasmic reticulum stress ,T1DM ,Type 1 Diabetes ,Diabète insulinodépendant ,Disciplines biomédicales diverses ,ER stress ,microarray ,Endoplasmic reticulum - Abstract
The endoplasmic reticulum (ER) is the organelle responsible for synthesis and folding of secreted and membranous protein and lipid biosynthesis. It also functions as one of the main cellular calcium stores. Pancreatic beta-cells evolved to produce and secrete insulin upon demand in order to regulate blood glucose homeostasis. In response to increases in serum glucose, insulin synthesis represents nearly 50% of the total protein biosynthesis by beta-cells. This poses an enormous burden on the ER, rendering beta-cells vulnerable to agents that perturb ER function. Alterations of ER homeostasis lead to accumulation of misfolded proteins and activation of an adaptive response named the unfolded protein response (UPR). The UPR is transduced via 3 ER transmembrane proteins, namely PERK, IRE-1 and ATF6. The signaling cascades activated downstream of these proteins: a) induce expression of ER resident chaperones and protein foldases. Increasing the protein folding capacity of the ER; b) attenuate general protein translations which avoids overloading the stressed ER with new proteins; c) upregulate ER-associated degradation (ERAD) genes, which decreases the unfolded protein load of the ER. In severe cases, failure by the UPR to solve the ER stress leads to apoptosis. The mechanisms linking ER stress to apoptosis are still poorly understood, but potential mediators include the transcription factors Chop and ATF3, pro-apoptotic members of the Bcl-2 familly, the caspase 12 and the kinase JNK. Accumulating evidence suggest that ER stress contributes to beta-cell apoptosis in both type 1 and type 2 diabetes. Type 1 diabetes is characterized by a severe insulin deficiency resulting from chronic and progressive destruction of pancreatic beta-cells by the immune system. During this autoimmune assault, beta-cells are exposed to cytokines secreted by the immune cells infiltrating the pancreatic islets. Our group has previously shown that the pro-inflamatory cytokines interleukin-1beta (IL1-beta and interferon-gamma (IFN-gamma), via nitric oxide (NO) formation, downregulate expression and function of the ER Ca2+ pump SERCA2. This depletes beta-cell ER Ca2+ stores, leading to ER stress and apoptosis. Of note, IL1-beta alone triggers ER stress but does not induce beta-cell death, while IFN-gamma neither causes ER stress nor induces beta-cell death. Together, these cytokines cause beta-cell apoptosis but the mechanisms behind this synergistic effect were unknown.Type 2 diabetes is characterized by both peripheral resistance to insulin, usually as a result of obesity, and deficient insulin secretion secondary to beta cell failure. Obese patients have high levels of circulating free fatty acids (FFA) and several studies have shown that the FFA palmitate induces ER stress and beta-cell apoptosis.In the present work we initially established an experimental model to specifically activate the ER stress response in pancreatic beta-cells. For this purpose, insulinoma cells (INS-1E) or primary rat beta-cells were exposed to the reversible chemical SERCA pump blocker cyclopiazonic acid (CPA). Dose-response and time course experiments determined the best conditions to induce a marked ER stress without excessive cell death (The first goal of the work was to understand the synergistic effects of IL1-beta and IFN-gamma leading to pancreatic beta-cell apoptosis. Our group previously observed, by microarray analysis of primary beta-cells, that IFN-gamma down-regulates mRNAs encoding for some ER chaperones. Against this background, our hypothesis was that IFN-gamma aggravates beta-cell ER stress by decreasing the ability of these cells to mount an adequate UPR. To test this hypothesis, we investigated whether IFN-gamma pre-treatment augments CPA-induced ER stress and beta cell death. The results obtained indicated that IFN-gamma pre-treatment potentiates CPA-induced apoptosis in INS-1E and primary beta-cells. This effect was specific for IFN-gamma since neither IL1-beta nor a low dose CPA pre-treatment potentiated CPA-induced apoptosis in INS-1E cells. These effects of IFN-gamma were mediated via the down regulation of genes involved in beta cell defense against ER stress, including the ER chaperones BiP, Orp150 and Grp94 as well as Sec61, a component of the ERAD pathway. This had functional consequences as evidenced by a decreased basal and CPA-induced activity of a reporter construct for the unfolded protein response element (UPRE) and augmented expression of the pro-apoptotic transcription factor Chop. We next investigated the molecular regulation of the Chop gene in INS-1E cells in response to several pro-apoptotic and ER stress inducing agents, namely cytokines (IL1-beta and IFN-gamma), palmitate, or CPA. Detailed mutagenesis studies of the Chop promoter showed differential regulation of Chop transcription by these compounds. While cytokines (via NO production)- and palmitate-induced Chop expression was mediated via a C/EBP-ATF composite and AP-1 binding sites, CPA induction required the C/EBP-ATF site and the ER stress response element (ERSE). Cytokines, palmitate and CPA induced ATF4 protein expression and further binding to the C/EBP-ATF composite site, as shown by Western blot and EMSA experiments. There was also formation of distinct AP-1 dimers and binding to the AP-1 site after exposure to cytokines or palmitate. \, Doctorat en Sciences biomédicales et pharmaceutiques, info:eu-repo/semantics/nonPublished
- Published
- 2007
21. Derepression of Polycomb targets during pancreatic organogenesis allows insulin-producing beta-cells to adopt a neural gene activity program.
- Author
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van Arensbergen, Joris, García-Hurtado, Javier, Moran, Ignasi, Maestro, Miguel Angel, Xiaobo Xu, de Casteele, Mark Van, Skoudy, Anouchka L., Palassini, Matteo, Heimberg, Harry, and Ferrer, Jorge
- Subjects
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MORPHOGENESIS , *PANCREAS , *PANCREATIC beta cells , *EMBRYONIC stem cells , *CHROMATIN - Abstract
The epigenome changes that underlie cellular differentiation in developing organisms are poorly understood. To gain insights into how pancreatic beta-cells are programmed, we profiled key histone methylations and transcripts in embryonic stem cells, multipotent progenitors of the nascent embryonic pancreas, purified beta-cells, and 10 differentiated tissues. We report that despite their endodermal origin, beta-cells show a transcriptional and active chromatin signature that is most similar to ectoderm-derived neural tissues. In contrast, the beta-cell signature of trimethylated H3K27, a mark of Polycomb-mediated repression, clusters with pancreatic progenitors, acinar cells and liver, consistent with the epigenetic transmission of this mark from endoderm progenitors to their differentiated cellular progeny. We also identified two H3K27 methylation events that arise in the beta-cell lineage after the pancreatic progenitor stage. One is a wave of cell-selective de novo H3K27 trimethylation in non-CpG island genes. Another is the loss of bivalent and H3K27me3-repressed chromatin in a core program of neural developmental regulators that enables a convergence of the gene activity state of beta-cells with that of neural cells. These findings reveal a dynamic regulation of Polycomb repression programs that shape the identity of differentiated beta-cells. [ABSTRACT FROM AUTHOR]
- Published
- 2010
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