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Ampofo E, Nalbach L, Menger MD, Laschke MW. Regulatory Mechanisms of Somatostatin Expression. Int J Mol Sci 2020; 21:ijms21114170. [PMID: 32545257 PMCID: PMC7312888 DOI: 10.3390/ijms21114170] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2020] [Revised: 06/07/2020] [Accepted: 06/09/2020] [Indexed: 12/17/2022] Open
Abstract
Somatostatin is a peptide hormone, which most commonly is produced by endocrine cells and the central nervous system. In mammals, somatostatin originates from pre-prosomatostatin and is processed to a shorter form, i.e., somatostatin-14, and a longer form, i.e., somatostatin-28. The two peptides repress growth hormone secretion and are involved in the regulation of glucagon and insulin synthesis in the pancreas. In recent years, the processing and secretion of somatostatin have been studied intensively. However, little attention has been paid to the regulatory mechanisms that control its expression. This review provides an up-to-date overview of these mechanisms. In particular, it focuses on the role of enhancers and silencers within the promoter region as well as on the binding of modulatory transcription factors to these elements. Moreover, it addresses extracellular factors, which trigger key signaling pathways, leading to an enhanced somatostatin expression in health and disease.
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Affiliation(s)
- Emmanuel Ampofo
- Correspondence: ; Tel.: +49-6841-162-6561; Fax: +49-6841-162-6553
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Nicolaides NC, Kanaka-Gantenbein C, Papadopoulou-Marketou N, Sertedaki A, Chrousos GP, Papassotiriou I. Emerging technologies in pediatrics: the paradigm of neonatal diabetes mellitus. Crit Rev Clin Lab Sci 2020; 57:522-531. [PMID: 32356495 DOI: 10.1080/10408363.2020.1752141] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
In the era of precision medicine, the tremendous progress in next-generation sequencing technologies has allowed the identification of an ever-increasing number of genes associated with known Mendelian disorders. Neonatal diabetes mellitus is a rare, genetically heterogeneous endocrine disorder diagnosed before 6 months of age. It may occur alone or in the context of genetic syndromes. Neonatal diabetes mellitus has been linked with genetic defects in at least 26 genes to date. Novel mutations in these disease-causing genes are being reported, giving us a better knowledge of the molecular events that occur upon insulin biosynthesis and secretion from the pancreatic β-cell. Of great importance, some of the identified genes encode proteins that can be therapeutically targeted by drugs per os, leading to transitioning from insulin to sulfonylureas. In this review, we provide an overview of pancreatic β-cell physiology, present the clinical manifestations and the genetic causes of the different forms of neonatal diabetes, and discuss the application of next-generation sequencing methods in the diagnosis and therapeutic management of neonatal diabetes and on research in this area.
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Affiliation(s)
- Nicolas C Nicolaides
- Division of Endocrinology, Metabolism and Diabetes, First Department of Pediatrics, National and Kapodistrian University of Athens Medical School, "Aghia Sophia" Children's Hospital, Athens, Greece.,Division of Endocrinology and Metabolism, Center of Clinical, Experimental Surgery and Translational Research, Biomedical Research Foundation of the Academy of Athens, Athens, Greece.,University Research Institute of Maternal and Child Health and Precision Medicine, National and Kapodistrian University of Athens Medical School, Athens, Greece
| | - Christina Kanaka-Gantenbein
- Division of Endocrinology, Metabolism and Diabetes, First Department of Pediatrics, National and Kapodistrian University of Athens Medical School, "Aghia Sophia" Children's Hospital, Athens, Greece
| | - Nektaria Papadopoulou-Marketou
- Division of Endocrinology, Metabolism and Diabetes, First Department of Pediatrics, National and Kapodistrian University of Athens Medical School, "Aghia Sophia" Children's Hospital, Athens, Greece
| | - Amalia Sertedaki
- Division of Endocrinology, Metabolism and Diabetes, First Department of Pediatrics, National and Kapodistrian University of Athens Medical School, "Aghia Sophia" Children's Hospital, Athens, Greece
| | - George P Chrousos
- Division of Endocrinology, Metabolism and Diabetes, First Department of Pediatrics, National and Kapodistrian University of Athens Medical School, "Aghia Sophia" Children's Hospital, Athens, Greece.,Division of Endocrinology and Metabolism, Center of Clinical, Experimental Surgery and Translational Research, Biomedical Research Foundation of the Academy of Athens, Athens, Greece.,University Research Institute of Maternal and Child Health and Precision Medicine, National and Kapodistrian University of Athens Medical School, Athens, Greece
| | - Ioannis Papassotiriou
- Department of Clinical Biochemistry, "Aghia Sophia" Children's Hospital, Athens, Greece.,IFCC Emerging Technologies Division, Emerging Technologies in Pediatric Laboratory Medicine (C-ETPLM), Milano, Italy
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Protein Kinase CK2-A Putative Target for the Therapy of Diabetes Mellitus? Int J Mol Sci 2019; 20:ijms20184398. [PMID: 31500224 PMCID: PMC6770776 DOI: 10.3390/ijms20184398] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2019] [Revised: 09/04/2019] [Accepted: 09/05/2019] [Indexed: 02/06/2023] Open
Abstract
Since diabetes is a global epidemic, the development of novel therapeutic strategies for the treatment of this disease is of major clinical interest. Diabetes is differentiated in two types: type 1 diabetes mellitus (T1DM) and type 2 diabetes mellitus (T2DM). T1DM arises from an autoimmune destruction of insulin-producing β-cells whereas T2DM is characterized by an insulin resistance, an impaired insulin reaction of the target cells, and/or dysregulated insulin secretion. In the past, a growing number of studies have reported on the important role of the protein kinase CK2 in the regulation of the survival and endocrine function of pancreatic β-cells. In fact, inhibition of CK2 is capable of reducing cytokine-induced loss of β-cells and increases insulin expression as well as secretion by various pathways that are regulated by reversible phosphorylation of proteins. Moreover, CK2 inhibition modulates pathways that are involved in the development of diabetes and prevents signal transduction, leading to late complications such as diabetic retinopathy. Hence, targeting CK2 may represent a novel therapeutic strategy for the treatment of diabetes.
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Abstract
Pancreatic cancers arise through a series of genetic events both inherited and acquired. Inherited genetic changes, both high penetrance and low penetrance, are an important component of pancreatic cancer risk, and may be used to characterize populations who will benefit from early detection. Furthermore, pancreatic cancer patients with inherited mutations may be particularly sensitive to certain targeted agents, providing an opportunity to personalized treatment. Family history of pancreatic cancer is one of the strongest risk factors for the disease, and is associated with an increased risk of caners at other sites, including but not limited to breast, ovarian and colorectal cancer. The goal of this chapter is to discuss the importance of family history of pancreatic cancer, and the known genes that account for a portion of the familial clustering of pancreatic cancer.
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Affiliation(s)
- Fei Chen
- Department of Epidemiology, The Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
| | - Nicholas J Roberts
- Department of Pathology, Department of Oncology, The Sol Goldman Pancreatic Cancer Research Center, The Johns Hopkins Medical Institution, Baltimore, MD, USA
| | - Alison P Klein
- Department of Epidemiology, The Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA; Department of Pathology, Department of Oncology, The Sol Goldman Pancreatic Cancer Research Center, The Johns Hopkins Medical Institution, Baltimore, MD, USA.
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5
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Functional interplay between the transcription factors USF1 and PDX-1 and protein kinase CK2 in pancreatic β-cells. Sci Rep 2017; 7:16367. [PMID: 29180680 PMCID: PMC5703852 DOI: 10.1038/s41598-017-16590-0] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2017] [Accepted: 10/04/2017] [Indexed: 11/22/2022] Open
Abstract
Glucose homeostasis is regulated by insulin, which is produced in the β-cells of the pancreas. The synthesis of insulin is controlled by several transcription factors including PDX-1, USF1 and USF2. Both, PDX-1 and USF1 were identified as substrates for protein kinase CK2. Here, we have analysed the interplay of PDX-1, USF1 and CK2 in the regulation of PDX-1 gene transcription. We found that the PDX-1 promoter is dose-dependently transactivated by PDX-1 and transrepressed by USF1. With increasing glucose concentrations the transrepression of the PDX-1 promoter by USF1 is successively abrogated. PDX-1 binding to its own promoter was not influenced by glucose, whereas USF1 binding to the PDX-1 promoter was reduced. The same effect was observed after inhibition of the protein kinase activity by three different inhibitors or by using a phospho-mutant of USF1. Moreover, phosphorylation of USF1 by CK2 seems to strengthen the interaction between USF1 and PDX-1. Thus, CK2 is a negative regulator of the USF1-dependent PDX-1 transcription. Moreover, upon inhibition of CK2 in primary islets, insulin expression as well as insulin secretion were enhanced without affecting the viability of the cells. Therefore, inhibition of CK2 activity may be a promising approach to stimulate insulin production in pancreatic β-cells.
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Marzioni M, Germani U, Agostinelli L, Bedogni G, Saccomanno S, Marini F, Bellentani S, Barbera C, De Minicis S, Rychlicki C, Santinelli A, Ferretti M, Di Maira PV, Baroni GS, Benedetti A, Caletti G, Lorenzini I, Fusaroli P. PDX-1 mRNA expression in endoscopic ultrasound-guided fine needle cytoaspirate: perspectives in the diagnosis of pancreatic cancer. Dig Liver Dis 2015; 47:138-43. [PMID: 25454709 DOI: 10.1016/j.dld.2014.10.010] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/16/2014] [Revised: 10/03/2014] [Accepted: 10/10/2014] [Indexed: 02/06/2023]
Abstract
BACKGROUND AND AIMS Endoscopic ultrasound-guided fine needle aspiration is routinely used in the diagnostic work up of pancreatic cancer but has a low sensitivity. Studies showed that Pancreatic Duodenal Homeobox-1 (PDX-1) is expressed in pancreatic cancer, which is associated with a worse prognosis. We aimed to verify whether the assessment of PDX-1 in endoscopic ultrasound-guided fine needle aspiration samples may be helpful for the diagnosis of pancreatic cancer. METHODS mRNA of 54 pancreatic cancer and 25 cystic lesions was extracted. PDX-1 expression was assessed by Real-Time PCR. RESULTS In all but two patients with pancreatic cancer, PDX-1 was expressed and was found positive in 7 patients with pancreatic cancer in which cytology was negative. The positivity was associated with a probability of 0.98 (95% CI 0.90-1.00) of having cancer and the negativity with one of 0.08 (95% CI 0.01-0.27). The probability of cancer rose to 1.00 (95% CI 0.97-1.00) for patients positive to both PDX-1 and cytology and fell to 0.0 (95% CI 0.00-0.15) in patients negative for both. CONCLUSIONS PDX-1mRNA is detectable in samples of pancreatic cancer. Its quantification may be helpful to improve the diagnosis of pancreatic cancer.
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Affiliation(s)
- Marco Marzioni
- Clinic of Gastroenterology and Hepatology, Università Politecnica delle Marche, Ancona, Italy.
| | - Ugo Germani
- Division of Gastroenterology, Azienda Ospedaliero Universitaria "Ospedali Riuniti", Ancona, Italy
| | - Laura Agostinelli
- Clinic of Gastroenterology and Hepatology, Università Politecnica delle Marche, Ancona, Italy
| | | | - Stefania Saccomanno
- Clinic of Gastroenterology and Hepatology, Università Politecnica delle Marche, Ancona, Italy
| | - Francesco Marini
- Division of Gastroenterology, Azienda Ospedaliero Universitaria "Ospedali Riuniti", Ancona, Italy
| | - Stefano Bellentani
- Servizio di Gastroenterologia - Ospedale "Ramazzini" Carpi, Modena, Italy
| | - Carmelo Barbera
- Servizio di Gastroenterologia - Ospedale "Ramazzini" Carpi, Modena, Italy
| | - Samuele De Minicis
- Clinic of Gastroenterology and Hepatology, Università Politecnica delle Marche, Ancona, Italy
| | - Chiara Rychlicki
- Clinic of Gastroenterology and Hepatology, Università Politecnica delle Marche, Ancona, Italy
| | - Alfredo Santinelli
- Institute of Pathologic Anatomy, Università Politecnica delle Marche, Ancona, Italy
| | - Maurizio Ferretti
- Division of Cytopathology, Azienda Ospedaliero Universitaria "Ospedali Riuniti", Ancona, Italy
| | | | | | - Antonio Benedetti
- Clinic of Gastroenterology and Hepatology, Università Politecnica delle Marche, Ancona, Italy
| | - Giancarlo Caletti
- Division of Cytopathology, Azienda Ospedaliero Universitaria "Ospedali Riuniti", Ancona, Italy
| | - Ivano Lorenzini
- Division of Gastroenterology, Azienda Ospedaliero Universitaria "Ospedali Riuniti", Ancona, Italy
| | - Pietro Fusaroli
- Division of Gastroenterology and Digestive Endoscopy, Università degli Studi di Bologna, Castel San Pietro Terme Hospital, Castel San Pietro Terme, Italy
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Abstract
Neonatal diabetes mellitus (NDM) is the term commonly used to describe diabetes with onset before 6 months-of-age. It occurs in approximately one out of every 100,000-300,000 live births. Although this term encompasses diabetes of any etiology, it is recognized that NDM diagnosed before 6 months-of-age is most often monogenic in nature. Clinically, NDM subgroups include transient (TNDM) and permanent NDM (PNDM), as well as syndromic cases of NDM. TNDM often develops within the first few weeks of life and remits by a few months of age. However, relapse occurs in 50% of cases, typically in adolescence or adulthood. TNDM is most frequently caused by abnormalities in the imprinted region of chromosome 6q24, leading to overexpression of paternally derived genes. Mutations in KCNJ11 and ABCC8, encoding the two subunits of the adenosine triphosphate-sensitive potassium channel on the β-cell membrane, can cause TNDM, but more often result in PNDM. NDM as a result of mutations in KCNJ11 and ABCC8 often responds to sulfonylureas, allowing transition from insulin therapy. Mutations in other genes important to β-cell function and regulation, and in the insulin gene itself, also cause NDM. In 40% of NDM cases, the genetic cause remains unknown. Correctly identifying monogenic NDM has important implications for appropriate treatment, expected disease course and associated conditions, and genetic testing for at-risk family members. Early recognition of monogenic NDM allows for the implementation of appropriate therapy, leading to improved outcomes and potential societal cost savings. (J Diabetes Invest, doi:10.1111/j.2040-1124.2011.00106.x, 2011).
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Affiliation(s)
| | | | - Graeme I Bell
- Medicine, Section of Adult and Pediatric Endocrinology, Diabetes and Metabolism, The University of Chicago, Chicago, Illinois, USA
| | - Louis H Philipson
- Departments of Pediatrics
- Medicine, Section of Adult and Pediatric Endocrinology, Diabetes and Metabolism, The University of Chicago, Chicago, Illinois, USA
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Balentine CJ, Berger DH, Liu SH, Chen C, Nemunaitis J, Brunicardi FC. Defining the cancer master switch. World J Surg 2011; 35:1738-45. [PMID: 21286716 DOI: 10.1007/s00268-010-0941-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
BACKGROUND Recent research has focused on signaling cascades and their interactions yielding considerable insight into which genetic pathways are targeted and how they tend to be altered in tumors. Therapeutic interventions now can be designed based on the knowledge of pathways vital to tumor growth and survival. These critical targets for intervention, master switches for cancer, are termed so because the tumor attempts to "flip the switch" in a way that promotes its survival, whereas molecular therapy aims to "switch off" signals important for tumor-related processes. METHODS Literature review. CONCLUSIONS Defining useful targets for therapy depends on identifying pathways that are crucial for tumor growth, survival, and metastasis. Because not all signaling cascades are created equal, selecting master switches or targets for intervention needs to be done in a systematic fashion. This discussion proposes a set of criteria to define what it means to be a cancer master switch and provides examples to illustrate their application.
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Pancreatic Duodenal Homeobox-1 de novo expression drives cholangiocyte neuroendocrine-like transdifferentiation. J Hepatol 2010; 53:663-70. [PMID: 20621380 DOI: 10.1016/j.jhep.2010.04.022] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/25/2009] [Revised: 04/10/2010] [Accepted: 04/12/2010] [Indexed: 12/25/2022]
Abstract
BACKGROUND & AIMS Reactive cholangiocytes acquire a neuroendocrine-like phenotype, with synthesis and local release of neuropeptides and hormones. The mechanism that drives such phenotypical changes is still undefined. Pancreatic Duodenal Homeobox-1 (PDX-1) is a transcription factor required for pancreatic development, that sustains pancreatic beta-cell response to injury and insulin synthesis. PDX-1 induces neuroendocrine-like transition of pancreatic ductal cells. Cholangiocyte response to injury is modulated by Glucagon-Like Peptide-1 Receptor (GLP-1R), which, in the pancreas, activates PDX-1. We wanted to verify whether PDX-1 plays any role in cholangiocyte neuroendocrine-like transdifferentiation in response to injury. METHODS PDX-1 expression was assessed in cholangiocytes from normal and one week bile duct ligated (BDL) rats. Changes in PDX-1 expression and activation upon GLP-1R activation were then assayed. The effects of the lack of PDX-1 in cholangiocytes were studied in vitro by siRNA and in vivo by the employment of PDX-1-deficient (+/-) mice. RESULTS BDL but not normal cholangiocytes express PDX-1. GLP-1R activation elicits, in a PI3K-dependent fashion, PDX-1 expression, together with its nuclear translocation. In vitro, GLP-1R-induced increases in VEGF and IGF-1 mRNA expression were blunted in cells with PDX-1 siRNA. In vivo, the VEGF and IGF-1 mRNA expression in the liver after one week BDL was markedly reduced in PDX-1-deficient mice, together with reduced bile duct mass. CONCLUSIONS In response to injury, reactive cholangiocytes de novo express PDX-1, the activation of which allows cholangiocytes to synthesize IGF-1 and VEGF. These findings suggest that PDX-1 drives the acquisition of the neuroendocrine-like phenotype by cholangiocytes in response to cholestatic injury.
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Abstract
Production and secretion of insulin from the β-cells of the pancreas is very crucial in maintaining normoglycaemia. This is achieved by tight regulation of insulin synthesis and exocytosis from the β-cells in response to changes in blood glucose levels. The synthesis of insulin is regulated by blood glucose levels at the transcriptional and post-transcriptional levels. Although many transcription factors have been implicated in the regulation of insulin gene transcription, three β-cell-specific transcriptional regulators, Pdx-1 (pancreatic and duodenal homeobox-1), NeuroD1 (neurogenic differentiation 1) and MafA (V-maf musculoaponeurotic fibrosarcoma oncogene homologue A), have been demonstrated to play a crucial role in glucose induction of insulin gene transcription and pancreatic β-cell function. These three transcription factors activate insulin gene expression in a co-ordinated and synergistic manner in response to increasing glucose levels. It has been shown that changes in glucose concentrations modulate the function of these β-cell transcription factors at multiple levels. These include changes in expression levels, subcellular localization, DNA-binding activity, transactivation capability and interaction with other proteins. Furthermore, all three transcription factors are able to induce insulin gene expression when expressed in non-β-cells, including liver and intestinal cells. The present review summarizes the recent findings on how glucose modulates the function of the β-cell transcription factors Pdx-1, NeuroD1 and MafA, and thereby tightly regulates insulin synthesis in accordance with blood glucose levels.
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Niu X, Perakakis N, Laubner K, Limbert C, Stahl T, Brendel MD, Bretzel RG, Seufert J, Päth G. Human Krüppel-like factor 11 inhibits human proinsulin promoter activity in pancreatic beta cells. Diabetologia 2007; 50:1433-41. [PMID: 17479246 DOI: 10.1007/s00125-007-0667-3] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/07/2006] [Accepted: 02/26/2007] [Indexed: 10/23/2022]
Abstract
AIMS/HYPOTHESIS The Krüppel-like factor 11 (KLF11; TIEG2), a pancreas-enriched Sp1-like transcription factor, is a known negative regulator of pancreatic exocrine cell growth. A recent study indicated KLF11-induced activation of the human proinsulin promoter (hInsP). MATERIALS AND METHODS We investigated the functional role of KLF11 in pancreatic beta cells. RESULTS Endogenous KLF11 mRNA expression was found in whole rat pancreas, human pancreatic islets and INS-1E beta cells and was profoundly reduced by high glucose in INS-1E. Cotransfections of INS-1E and beta-TC3 beta cells with a human (h)KLF11 expression plasmid and an hInsP-driven reporter plasmid resulted in a substantial dose-dependent and glucose-independent inhibition of proinsulin promoter activity. 5'-deletion of hInsP demonstrated that hKLF11 acts via DNA sequences upstream of -173 and requires the beta cell-specific transcription machinery, since hKLF11-mediated inhibition of promoter activity was abolished in HEK293 cells. Besides a previously described GC box, we further identified a CACCC box within the hInsP, both putative KLF11-binding motifs. Electrophoretic mobility shift analysis (EMSA) verified binding of in vitro translated hKLF11 to the GC box, but neither hKLF11-induced inhibition nor basal hInsP activity was altered by mutation or 5'-deletion of the GC box. In contrast, CACCC box mutation substantially reduced basal promoter activity and partially diminished hKLF11 inhibition, although binding of in vitro translated hKLF11 to the CACCC box could not be verified by EMSA. CONCLUSIONS/INTERPRETATION In rodent beta cell lines, we demonstrate hKLF11overexpression-mediated inhibition [corrected] of human proinsulin gene expression and characterise a prominent role for the CACCC box in maintaining basal proinsulin promoter activity.
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Affiliation(s)
- X Niu
- Laboratory B9, Division of Endocrinology and Diabetology, Department of Internal Medicine II, University Hospital of Freiburg, 79106, Freiburg, Germany
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Brissova M, Blaha M, Spear C, Nicholson W, Radhika A, Shiota M, Charron MJ, Wright CVE, Powers AC. Reduced PDX-1 expression impairs islet response to insulin resistance and worsens glucose homeostasis. Am J Physiol Endocrinol Metab 2005; 288:E707-14. [PMID: 15562255 DOI: 10.1152/ajpendo.00252.2004] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
In type 2 diabetes mellitus, insulin resistance and an inadequate pancreatic beta-cell response to the demands of insulin resistance lead to impaired insulin secretion and hyperglycemia. Pancreatic duodenal homeodomain-1 (PDX-1), a transcription factor required for normal pancreatic development, also plays a key role in normal insulin secretion by islets. To investigate the role of PDX-1 in islet compensation for insulin resistance, we examined glucose disposal, insulin secretion, and islet cell mass in mice of four different genotypes: wild-type mice, mice with one PDX-1 allele inactivated (PDX-1+/-, resulting in impaired insulin secretion), mice with one GLUT4 allele inactivated (GLUT4+/-, resulting in insulin resistance), and mice heterozygous for both PDX-1 and GLUT4 (GLUT4+/-;PDX-1+/-). The combination of PDX-1 and GLUT4 heterozygosity markedly prolonged glucose clearance. GLUT4+/-;PDX-1+/- mice developed beta-cell hyperplasia but failed to increase their beta-cell insulin content. These results indicate that PDX-1 heterozygosity (approximately 60% of normal protein levels) abrogates the beta-cell's compensatory response to insulin resistance, impairs glucose homeostasis, and may contribute to the pathogenesis of type 2 diabetes.
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Affiliation(s)
- Marcela Brissova
- Department of Medicine, Division of Diabetes, Endocrinology, and Metabolism, 715 PRB, Dept. of Medicine, Vanderbilt University, Nashville, TN 37232, USA
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13
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Abstract
Type 2 diabetes is the result of a progressive impairment of pancreatic beta-cell function in the setting of worsening insulin resistance. Studies in high-risk populations have demonstrated that during progression to diabetes, beta cells have declining function and lose the first phase of insulin secretion, resulting in less than adequate suppression of hepatic glucose production following meals. In addition, oscillations of insulin secretion become unmatched from their normal coupling with glucose. Several mechanisms are thought to be responsible for impaired beta-cell function, including glucose toxicity and lipotoxicity, and potentially contribute to beta-cell loss. Advances in molecular science have elucidated several cytokines and transcription factors possibly implicated in the loss of beta-cell mass. In the past 15 years, clinical trials have given hope for potential therapies that may either delay or prevent the progression to diabetes. Lifestyle modification and pharmaceutical treatment remain the most promising interventions.
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Affiliation(s)
- Jeanne H Steppel
- Joslin Diabetes Center, One Joslin Place, Room 346, Boston, MA 02215, USA
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14
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Melloul D. Transcription Factors in Islet Development and Physiology: Role of PDX-1 in Beta-Cell Function. Ann N Y Acad Sci 2004; 1014:28-37. [PMID: 15153417 DOI: 10.1196/annals.1294.003] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Differentiation of early foregut endoderm into pancreatic endocrine and exocrine cells depends on a cascade of gene activation events controlled by various transcription factors. The first molecular marker identified that specifies the early pancreatic epithelium is the homeodomain-containing transcription factor PDX-1. Its absence in mice and humans during development leads to agenesis of the pancreas. Later, it becomes restricted primarily to beta cells where it regulates the expression of beta cell-specific genes, and, most importantly, mediates the glucose effect on insulin gene transcription. Although exposure of beta cells to high glucose concentrations for relatively short periods stimulates insulin gene expression, chronic exposure has adverse effects on many beta-cell functions, including insulin gene transcription. These events appear to correlate with pdx-1 gene expression and its ability to bind the insulin gene. We consider that loss of PDX-1 function or altered pdx-1 gene expression due to mutations or functional impairment of transcription factors controlling its expression can lead to diabetes.
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Affiliation(s)
- Danielle Melloul
- Department of Endocrinology and Metabolism, The Hadassah-Hebrew University Medical Center, Jerusalem, Israel.
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15
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Kajihara M, Sone H, Amemiya M, Katoh Y, Isogai M, Shimano H, Yamada N, Takahashi S. Mouse MafA, homologue of zebrafish somite Maf 1, contributes to the specific transcriptional activity through the insulin promoter. Biochem Biophys Res Commun 2004; 312:831-42. [PMID: 14680841 DOI: 10.1016/j.bbrc.2003.10.196] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2003] [Indexed: 10/26/2022]
Abstract
Large Maf transcription factors, which are members of the basic leucine zipper (b-Zip) superfamily, have been reported to be involved in embryonic development and cell differentiation. Previously, we isolated a novel zebrafish large Maf cDNA, somite Maf1 (SMaf1), which possesses transactivational activity within its N-terminus domain. To elucidate SMaf1 function in mammals, we tried to isolate the mouse homologue of zebrafish SMaf1. We isolated the mouse homologue of zebrafish SMaf1, which is the same molecule as the recently reported MafA. MafA mRNA was detected in formed somites, head neural tube, and liver cells in the embryos. In the adult mouse, MafA transcript was amplified in the brain, lung, spleen, and kidney by RT-PCR. MafA mRNA was also detectable in beta-cell line. Next, we analyzed the transcriptional activity of MafA using rat insulin promoters I and II (RIPI and II), since a part of RIP sequence was similar to the Maf recognition element (MARE) and MafA was expressed in pancreatic beta cells. MafA was able to activate transcription from RIPII, but not RIPI, in a dose dependent manner and the activity was dependent on RIPE3b/C1 sequences. In addition, the amount of MafA protein was regulated by glucose concentration. These results indicate that MafA is the homologue of zebrafish SMaf1 and acts as a transcriptional activator of the insulin gene promoter through the RIPE3b element.
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Affiliation(s)
- Miwako Kajihara
- Department of Internal Medicine, University of Tsukuba, 1-1-1, Tennodai, Tsukuba 305-8575, Japan
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16
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Dunne MJ, Cosgrove KE, Shepherd RM, Aynsley-Green A, Lindley KJ. Hyperinsulinism in Infancy: From Basic Science to Clinical Disease. Physiol Rev 2004; 84:239-75. [PMID: 14715916 DOI: 10.1152/physrev.00022.2003] [Citation(s) in RCA: 184] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Dunne, Mark J., Karen E. Cosgrove, Ruth M. Shepherd, Albert Aynsley-Green, and Keith J. Lindley. Hyperinsulinism in Infancy: From Basic Science to Clinical Disease. Physiol Rev 84: 239–275, 2004; 10.1152/physrev.00022.2003.—Ion channelopathies have now been described in many well-characterized cell types including neurons, myocytes, epithelial cells, and endocrine cells. However, in only a few cases has the relationship between altered ion channel function, cell biology, and clinical disease been defined. Hyperinsulinism in infancy (HI) is a rare, potentially lethal condition of the newborn and early childhood. The causes of HI are varied and numerous, but in almost all cases they share a common target protein, the ATP-sensitive K+channel. From gene defects in ion channel subunits to defects in β-cell metabolism and anaplerosis, this review describes the relationship between pathogenesis and clinical medicine. Until recently, HI was generally considered an orphan disease, but as parallel defects in ion channels, enzymes, and metabolic pathways also give rise to diabetes and impaired insulin release, the HI paradigm has wider implications for more common disorders of the endocrine pancreas and the molecular physiology of ion transport.
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Affiliation(s)
- Mark J Dunne
- Research Division of Physiology and Pharmacology, The School of Biological Sciences, University of Manchester, Manchester, United Kingdom.
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