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dos Santos C, Karagiannopoulos A, Rafacho A, Perfilyev A, Eliasson L, Ling C, Bacos K. Glucocorticoids and glucolipotoxicity alter the DNA methylome and function of human EndoC-βH1 cells. Life Sci 2022; 307:120854. [DOI: 10.1016/j.lfs.2022.120854] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2022] [Revised: 07/20/2022] [Accepted: 07/27/2022] [Indexed: 10/16/2022]
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Yoshihara E. Adapting Physiology in Functional Human Islet Organogenesis. Front Cell Dev Biol 2022; 10:854604. [PMID: 35557947 PMCID: PMC9086403 DOI: 10.3389/fcell.2022.854604] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2022] [Accepted: 03/22/2022] [Indexed: 01/07/2023] Open
Abstract
Generation of three-dimensional (3D)-structured functional human islets is expected to be an alternative cell source for cadaveric human islet transplantation for the treatment of insulin-dependent diabetes. Human pluripotent stem cells (hPSCs), such as human embryonic stem cells (hESCs) and human induced pluripotent stem cells (hiPSCs), offer infinite resources for newly synthesized human islets. Recent advancements in hPSCs technology have enabled direct differentiation to human islet-like clusters, which can sense glucose and secrete insulin, and those islet clusters can ameliorate diabetes when transplanted into rodents or non-human primates (NHPs). However, the generated hPSC-derived human islet-like clusters are functionally immature compared with primary human islets. There remains a challenge to establish a technology to create fully functional human islets in vitro, which are functionally and transcriptionally indistinguishable from cadaveric human islets. Understanding the complex differentiation and maturation pathway is necessary to generate fully functional human islets for a tremendous supply of high-quality human islets with less batch-to-batch difference for millions of patients. In this review, I summarized the current progress in the generation of 3D-structured human islets from pluripotent stem cells and discussed the importance of adapting physiology for in vitro functional human islet organogenesis and possible improvements with environmental cues.
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Affiliation(s)
- Eiji Yoshihara
- Lundquist Institute for Biomedical Innovation at Harbor-UCLA Medical Center, Torrance, CA, United States.,David Geffen School of Medicine at University of California, Los Angeles, CA, United States
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Brix JM, Tura A, Herz CT, Feder A, Krzizek EC, Parzer V, Pacini G, Ludvik B. The Association of Cortisol Excretion with Weight and Metabolic Parameters in Nondiabetic Patients with Morbid Obesity. Obes Facts 2021; 14:510-519. [PMID: 34496367 PMCID: PMC8546449 DOI: 10.1159/000517766] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/23/2021] [Accepted: 05/28/2021] [Indexed: 11/19/2022] Open
Abstract
INTRODUCTION Cortisol is involved in the regulation of gluconeogenesis and glucose utilization. In morbid obesity (MO), the association of cortisol excretion with metabolic parameters is not well-characterized. In our study, we evaluated cortisol excretion in nondiabetic subjects with MO and its effect on glucose metabolism. METHODS We included 1,249 nondiabetic patients with MO (79.8% females, mean BMI 44.9 ± 6.5 kg/m2, mean age 38 ± 11 years). Anthropometric data and cardiovascular risk factors were assessed, and an oral glucose tolerance test for calculation of insulin resistance was performed. Cortisol excretion was assessed on 2 consecutive days (24 h urine specimens). RESULTS Regarding cortisol excretion, patients were divided into 3 tertiles (urinary cortisol ≤51.6, >51.6 and <117.6, and ≥117.6 μg/24 h, respectively). Patients in the highest tertile were younger (p = 0.003), more obese (BMI: p = 0.040), had lower diastolic blood pressure ([DBP]; p = 0.012), lower total (p = 0.032) and LDL cholesterol (p = 0.021), fasting (p = 0.049) and 2-h glycemia (p = 0.028), 2-h insulinemia (p = 0.020), and HbA1c (p < 0.001), and a higher estimated glomerular filtration rate (eGFR) (p < 0.001). The glucose (p < 0.001) and insulin (p = 0.011) area under the curve (AUC) were also lower. Urinary cortisol excretion adjusted for age, sex, and eGFR was positively correlated with body weight (BW, beta = 0.076, p = 0.004) and overall glucose tolerance (oral disposition index, beta = 0.090, p = 0.011), and negatively with HbA1c (beta = -0.179, p < 0.001), 2-h glycemia (beta = -0.075, p = 0.032), AUC glucose (beta = -0.103, p = 0.002), and DBP (beta = -0.139, p < 0.001). HbA1c, BW, and DBP remained significant after multivariable analysis. DISCUSSION/CONCLUSION Despite being more obese, patients with higher cortisol excretion have a more favorable metabolic profile. These results deserve further attention regarding the respective mechanisms.
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Affiliation(s)
- Johanna Maria Brix
- Department of Medicine I, Klinik Landstraße, Vienna, Austria
- Karl Landsteiner Institute for Obesity and Metabolic Disorders, Vienna, Austria
- *Johanna Maria Brix,
| | - Andrea Tura
- CNR Institute of Neuroscience, Metabolix Unit, Padova, Italy
| | - Carsten Thilo Herz
- Department of Medicine III, Division for Nephrology and Dialysis, Medical University Vienna, Vienna, Austria
| | - Astrid Feder
- Department of Medicine I, Klinik Landstraße, Vienna, Austria
- Karl Landsteiner Institute for Obesity and Metabolic Disorders, Vienna, Austria
| | - Eva-Christina Krzizek
- Department of Medicine I, Klinik Landstraße, Vienna, Austria
- Karl Landsteiner Institute for Obesity and Metabolic Disorders, Vienna, Austria
| | - Verena Parzer
- Department of Medicine I, Klinik Landstraße, Vienna, Austria
| | - Giovanni Pacini
- CNR Institute of Neuroscience, Metabolix Unit, Padova, Italy
| | - Bernhard Ludvik
- Department of Medicine I, Klinik Landstraße, Vienna, Austria
- Karl Landsteiner Institute for Obesity and Metabolic Disorders, Vienna, Austria
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Templeman NM, Mehran AE, Johnson JD. Hyper-Variability in Circulating Insulin, High Fat Feeding Outcomes, and Effects of Reducing Ins2 Dosage in Male Ins1-Null Mice in a Specific Pathogen-Free Facility. PLoS One 2016; 11:e0153280. [PMID: 27055260 PMCID: PMC4824531 DOI: 10.1371/journal.pone.0153280] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2015] [Accepted: 03/25/2016] [Indexed: 12/31/2022] Open
Abstract
Insulin is an essential hormone with key roles in energy homeostasis and body composition. Mice and rats, unlike other mammals, have two insulin genes: the rodent-specific Ins1 gene and the ancestral Ins2 gene. The relationships between insulin gene dosage and obesity has previously been explored in male and female Ins2-/- mice with full or reduced Ins1 dosage, as well as in female Ins1-/- mice with full or partial Ins2 dosage. We report herein unexpected hyper-variability in Ins1-null male mice, with respect to their circulating insulin levels and to the physiological effects of modulating Ins2 gene dosage. Two large cohorts of Ins1-/-:Ins2+/- mice and their Ins1-/-:Ins2+/+ littermates were fed chow diet or high fat diet (HFD) from weaning, and housed in specific pathogen-free conditions. Cohort A and cohort B were studied one year apart. Contrary to female mice from the same litters, inactivating one Ins2 allele on the complete Ins1-null background did not consistently cause a reduction of circulating insulin in male mice, on either diet. In cohort A, all HFD-fed males showed an equivalent degree of insulin hypersecretion and weight gain, regardless of Ins2 dosage. In cohort B the effects of HFD appeared generally diminished, and cohort B Ins1-/-:Ins2+/- males showed decreased insulin levels and body mass compared to Ins1-/-:Ins2+/+ littermates, on both diets. Although experimental conditions were consistent between cohorts, we found that HFD-fed Ins1-/-:Ins2+/- mice with lower insulin levels had increased corticosterone. Collectively, these observations highlight the phenotypic characteristics that change in association with differences in circulating insulin and Ins2 gene dosage, particularly in male mice.
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Affiliation(s)
- Nicole M Templeman
- Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, British Columbia, Canada
| | - Arya E Mehran
- Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, British Columbia, Canada
| | - James D Johnson
- Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, British Columbia, Canada
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Regulation of Glucose Homeostasis by Glucocorticoids. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2015. [PMID: 26215992 DOI: 10.1007/978-1-4939-2895-8_5] [Citation(s) in RCA: 357] [Impact Index Per Article: 39.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Glucocorticoids are steroid hormones that regulate multiple aspects of glucose homeostasis. Glucocorticoids promote gluconeogenesis in liver, whereas in skeletal muscle and white adipose tissue they decrease glucose uptake and utilization by antagonizing insulin response. Therefore, excess glucocorticoid exposure causes hyperglycemia and insulin resistance. Glucocorticoids also regulate glycogen metabolism. In liver, glucocorticoids increase glycogen storage, whereas in skeletal muscle they play a permissive role for catecholamine-induced glycogenolysis and/or inhibit insulin-stimulated glycogen synthesis. Moreover, glucocorticoids modulate the function of pancreatic α and β cells to regulate the secretion of glucagon and insulin, two hormones that play a pivotal role in the regulation of blood glucose levels. Overall, the major glucocorticoid effect on glucose homeostasis is to preserve plasma glucose for brain during stress, as transiently raising blood glucose is important to promote maximal brain function. In this chapter we will discuss the current understanding of the mechanisms underlying different aspects of glucocorticoid-regulated mammalian glucose homeostasis.
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Valtat B, Riveline JP, Zhang P, Singh-Estivalet A, Armanet M, Venteclef N, Besseiche A, Kelly DP, Tronche F, Ferré P, Gautier JF, Bréant B, Blondeau B. Fetal PGC-1α overexpression programs adult pancreatic β-cell dysfunction. Diabetes 2013; 62:1206-16. [PMID: 23274887 PMCID: PMC3609553 DOI: 10.2337/db12-0314] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Adult β-cell dysfunction, a hallmark of type 2 diabetes, can be programmed by adverse fetal environment. We have shown that fetal glucocorticoids (GCs) participate in this programming through inhibition of β-cell development. Here we have investigated the molecular mechanisms underlying this regulation. We showed that GCs stimulate the expression of peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α), a coregulator of the GCs receptor (GR), and that the overexpression of PGC-1α represses genes important for β-cell development and function. More precisely, PGC-1α inhibited the expression of the key β-cell transcription factor pancreatic duodenal homeobox 1 (Pdx1). This repression required the GR and was mediated through binding of a GR/PGC-1α complex to the Pdx1 promoter. To explore PGC-1α function, we generated mice with inducible β-cell PGC-1α overexpression. Mice overexpressing PGC-1α exhibited at adult age impaired glucose tolerance associated with reduced insulin secretion, decreased β-cell mass, and β-cell hypotrophy. Interestingly, PGC-1α expression in fetal life only was sufficient to impair adult β-cell function whereas β-cell PGC-1α overexpression from adult age had no consequence on β-cell function. Altogether, our results demonstrate that the GR and PGC-1α participate in the fetal programming of adult β-cell function through inhibition of Pdx1 expression.
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Affiliation(s)
- Bérengère Valtat
- INSERM, UMRS 872, Cordeliers Research Center, Paris, France
- Université Pierre et Marie Curie, Paris, France
| | - Jean-Pierre Riveline
- INSERM, UMRS 872, Cordeliers Research Center, Paris, France
- Université Pierre et Marie Curie, Paris, France
| | - Ping Zhang
- INSERM, UMRS 872, Cordeliers Research Center, Paris, France
- Université Pierre et Marie Curie, Paris, France
| | - Amrit Singh-Estivalet
- INSERM, UMRS 872, Cordeliers Research Center, Paris, France
- Université Pierre et Marie Curie, Paris, France
| | - Mathieu Armanet
- INSERM, UMRS 872, Cordeliers Research Center, Paris, France
- Université Pierre et Marie Curie, Paris, France
- Cell Therapy Unit, Hôpital Saint-Louis, Assistance Publique Hôpitaux de Paris, Paris, France
| | - Nicolas Venteclef
- INSERM, UMRS 872, Cordeliers Research Center, Paris, France
- Université Pierre et Marie Curie, Paris, France
| | - Adrien Besseiche
- INSERM, UMRS 872, Cordeliers Research Center, Paris, France
- Université Pierre et Marie Curie, Paris, France
| | - Daniel P. Kelly
- Sanford-Burnham Medical Research Institute, Orlando, Florida
| | - François Tronche
- Université Pierre et Marie Curie, Paris, France
- CNRS UMR INSERM 952-CNRS 7224, Paris, France
| | - Pascal Ferré
- INSERM, UMRS 872, Cordeliers Research Center, Paris, France
- Université Pierre et Marie Curie, Paris, France
| | - Jean-François Gautier
- INSERM, UMRS 872, Cordeliers Research Center, Paris, France
- Université Pierre et Marie Curie, Paris, France
- Department of Diabetes and Endocrinology, Hôpital Saint-Louis, Assistance Publique Hôpitaux de Paris, Paris, France
- Université Paris Diderot, Paris, France
| | - Bernadette Bréant
- INSERM, UMRS 872, Cordeliers Research Center, Paris, France
- Université Pierre et Marie Curie, Paris, France
| | - Bertrand Blondeau
- INSERM, UMRS 872, Cordeliers Research Center, Paris, France
- Université Pierre et Marie Curie, Paris, France
- Corresponding author: Bertrand Blondeau,
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Reich E, Tamary A, Sionov RV, Melloul D. Involvement of thioredoxin-interacting protein (TXNIP) in glucocorticoid-mediated beta cell death. Diabetologia 2012; 55:1048-57. [PMID: 22246375 DOI: 10.1007/s00125-011-2422-z] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/27/2011] [Accepted: 11/07/2011] [Indexed: 11/29/2022]
Abstract
AIM/HYPOTHESIS Glucocorticoid hormones (GCs) are widely used to treat a variety of inflammatory and immune diseases. However, their long-term administration is associated with adverse metabolic effects, including glucose intolerance and diabetes. Our objective was to elucidate the mechanisms by which GCs affect beta cell survival with a specific emphasis on the role of the thioredoxin-interacting protein (TXNIP) in beta cell apoptosis. METHODS Human and mouse islets, together with MIN6 beta cells, were exposed to dexamethasone (Dex) and apoptosis was assessed by measuring the percentage of sub-G1 cells, the appearance of cleaved caspase-3 or by using a TUNEL assay. Dex-upregulated expression of Txnip mRNA was analysed by real-time PCR, and GC-modulated production and modification of proteins were determined by western blotting. RESULTS We provide evidence that TXNIP, a negative regulator of the antioxidant thioredoxin (TRX), is strongly induced in beta cells by GCs and that its induction is dependent on p38 mitogen-activated protein kinase (MAPK) activation. TXNIP downregulation by RNA interference, overexpression of the radical scavenger TRX1 or elevation of intracellular cAMP levels attenuated the Dex-mediated apoptosis. Dex-induced Txnip expression and beta cell apoptosis are mediated by the glucocorticoid receptor (GR), as the GR antagonist RU486 fully abolishes these effects. CONCLUSIONS/INTERPRETATION Altogether, our data suggest TXNIP as a novel mediator of GC-induced apoptosis in beta cells and further contribute to our understanding of beta cell death pathways.
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Affiliation(s)
- E Reich
- Department of Endocrinology, Hadassah University Hospital, Jerusalem, Israel
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Baxi DB, Singh PK, Vachhrajani KD, Ramachandran AV. Plasticity changes in adult metabolic homeostasis and tissue oxidative stress: neonatal programming by corticosterone and melatonin as deprogrammer. J Matern Fetal Neonatal Med 2011; 25:831-44. [PMID: 21848498 DOI: 10.3109/14767058.2011.599456] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
OBJECTIVE To evaluate the long-term plasticity changes induced by neonatal corticosterone programming on adult metabolic status and the deprogramming effect of melatonin. METHODS Male and female Wistar rats were maintained under standard conditions and when mated females delivered pups, neonates of both sexes were separated and equal number of pups was assigned to lactating mothers. Pups treated with saline, corticosterone or a combination of corticosterone and melatonin from PND 2 to PND 14, were maintained until 120 days of age. Various serum and tissue parameters pertaining to glycaemic regulation, dyslipidemia, hepatic and renal distress and oxidative stress were analyzed in adult rats. RESULTS Neonatal corticosterone exposure induced dyslipidemia, increased fed and fasting glucose levels, insulin resistance, lipid peroxidation, serum levels of insulin, corticosterone and hepatic and renal dysfunction markers and decreased the levels of enzymatic and non-enzymatic antioxidants, relatively more in males. Melatonin proved as an effective deprogrammer of corticosterone induced plasticity changes. CONCLUSIONS Neonatal corticosterone exposure induces long lasting effects on adult physiology and metabolism. Concurrent treatment with melatonin effectively deprograms the changes.
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Affiliation(s)
- Darshee B Baxi
- Division of Metabolic Endocrinology, Department of Zoology, Faculty of Science, The M.S.University of Baroda, Vadodara, Gujarat, India
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Prednisolone-induced beta cell dysfunction is associated with impaired endoplasmic reticulum homeostasis in INS-1E cells. Cell Signal 2011; 23:1708-15. [PMID: 21689745 DOI: 10.1016/j.cellsig.2011.06.002] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2011] [Accepted: 06/06/2011] [Indexed: 12/25/2022]
Abstract
Glucocorticoids (GCs), such as prednisolone (PRED), are widely prescribed anti-inflammatory drugs, but their use may induce glucose intolerance and diabetes. GC-induced beta cell dysfunction contributes to these diabetogenic effects through mechanisms that remain to be elucidated. In this study, we hypothesized that activation of the unfolded protein response (UPR) following endoplasmic reticulum (ER) stress could be one of the underlying mechanisms involved in GC-induced beta cell dysfunction. We report here that PRED did not affect basal insulin release but time-dependently inhibited glucose-stimulated insulin secretion in INS-1E cells. PRED treatment also decreased both PDX1 and insulin expression, leading to a marked reduction in cellular insulin content. These PRED-induced detrimental effects were found to be prevented by prior treatment with the glucocorticoid receptor (GR) antagonist RU486 and associated with activation of two of the three branches of the UPR. Indeed, PRED induced a GR-mediated activation of both ATF6 and IRE1/XBP1 pathways but was found to reduce the phosphorylation of PERK and its downstream substrate eIF2α. These modulations of ER stress pathways were accompanied by upregulation of calpain 10 and increased cleaved caspase 3, indicating that long term exposure to PRED ultimately promotes apoptosis. Taken together, our data suggest that the inhibition of insulin biosynthesis by PRED in the insulin-secreting INS-1E cells results, at least in part, from a GR-mediated impairment in ER homeostasis which may lead to apoptotic cell death.
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Surjit M, Ganti KP, Mukherji A, Ye T, Hua G, Metzger D, Li M, Chambon P. Widespread negative response elements mediate direct repression by agonist-liganded glucocorticoid receptor. Cell 2011; 145:224-41. [PMID: 21496643 DOI: 10.1016/j.cell.2011.03.027] [Citation(s) in RCA: 384] [Impact Index Per Article: 29.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2010] [Revised: 11/18/2010] [Accepted: 03/15/2011] [Indexed: 01/25/2023]
Abstract
The glucocorticoid (GC) receptor (GR), when liganded to GC, activates transcription through direct binding to simple (+)GRE DNA binding sequences (DBS). GC-induced direct repression via GR binding to complex "negative" GREs (nGREs) has been reported. However, GR-mediated transrepression was generally ascribed to indirect "tethered" interaction with other DNA-bound factors. We report that GC-induces direct transrepression via the binding of GR to simple DBS (IR nGREs) unrelated to (+)GRE. These DBS act on agonist-liganded GR, promoting the assembly of cis-acting GR-SMRT/NCoR repressing complexes. IR nGREs are present in over 1000 mouse/human ortholog genes, which are repressed by GC in vivo. Thus variations in the levels of a single ligand can coordinately turn genes on or off depending in their response element DBS, allowing an additional level of regulation in GR signaling. This mechanism suits GR signaling remarkably well, given that adrenal secretion of GC fluctuates in a circadian and stress-related fashion.
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Affiliation(s)
- Milan Surjit
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, CNRS UMR7104, Inserm U964, Université de Strasbourg, Collège de France, Illkirch, 67404, France
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Beck IME, Vanden Berghe W, Vermeulen L, Yamamoto KR, Haegeman G, De Bosscher K. Crosstalk in inflammation: the interplay of glucocorticoid receptor-based mechanisms and kinases and phosphatases. Endocr Rev 2009; 30:830-82. [PMID: 19890091 PMCID: PMC2818158 DOI: 10.1210/er.2009-0013] [Citation(s) in RCA: 221] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/31/2009] [Accepted: 08/18/2009] [Indexed: 12/20/2022]
Abstract
Glucocorticoids (GCs) are steroidal ligands for the GC receptor (GR), which can function as a ligand-activated transcription factor. These steroidal ligands and derivatives thereof are the first line of treatment in a vast array of inflammatory diseases. However, due to the general surge of side effects associated with long-term use of GCs and the potential problem of GC resistance in some patients, the scientific world continues to search for a better understanding of the GC-mediated antiinflammatory mechanisms. The reversible phosphomodification of various mediators in the inflammatory process plays a key role in modulating and fine-tuning the sensitivity, longevity, and intensity of the inflammatory response. As such, the antiinflammatory GCs can modulate the activity and/or expression of various kinases and phosphatases, thus affecting the signaling efficacy toward the propagation of proinflammatory gene expression and proinflammatory gene mRNA stability. Conversely, phosphorylation of GR can affect GR ligand- and DNA-binding affinity, mobility, and cofactor recruitment, culminating in altered transactivation and transrepression capabilities of GR, and consequently leading to a modified antiinflammatory potential. Recently, new roles for kinases and phosphatases have been described in GR-based antiinflammatory mechanisms. Moreover, kinase inhibitors have become increasingly important as antiinflammatory tools, not only for research but also for therapeutic purposes. In light of these developments, we aim to illuminate the integrated interplay between GR signaling and its correlating kinases and phosphatases in the context of the clinically important combat of inflammation, giving attention to implications on GC-mediated side effects and therapy resistance.
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Affiliation(s)
- Ilse M E Beck
- Laboratory of Eukaryotic Gene Expression and Signal Transduction, K.L. Ledeganckstraat 35, B-9000 Gent, Belgium
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Kim JW, You YH, Ham DS, Cho JH, Ko SH, Song KH, Son HY, Suh-Kim H, Lee IK, Yoon KH. Suppression of peroxisome proliferator-activated receptor gamma-coactivator-1alpha normalizes the glucolipotoxicity-induced decreased BETA2/NeuroD gene transcription and improved glucose tolerance in diabetic rats. Endocrinology 2009; 150:4074-83. [PMID: 19520786 DOI: 10.1210/en.2009-0241] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Peroxisome proliferator-activated receptor gamma-coactivator-1alpha (PGC-1alpha) is significantly elevated in the islets of animal models of diabetes. However, the molecular mechanism has not been clarified. We investigated whether the suppression of PGC-1alpha expression protects against beta-cell dysfunction in vivo and determined the mechanism of action of PGC-1alpha in beta-cells. The studies were performed in glucolipotixicity-induced primary rat islets and INS-1 cells. In vitro and in vivo approaches using adenoviruses were used to evaluate the role of PGC-1alpha in glucolipotoxicity-associated beta-cell dysfunction. The expression of PGC-1alpha in cultured beta-cells increased gradually with glucolipotoxicity. The overexpression of PGC-1alpha also suppressed the expression of the insulin and beta-cell E-box transcription factor (BETA2/NeuroD) genes, which was reversed by PGC-1alpha small interfering RNA (siRNA). BETA2/NeuroD, p300-enhanced BETA2/NeuroD, and insulin transcriptional activities were significantly suppressed by Ad-PGC-1alpha but were rescued by Ad-siPGC-1alpha. PGC-1alpha binding at the glucocorticoid receptor site on the BETA2/NeuroD promoter increased in the presence of PGC-1alpha. Ad-siPGC-1alpha injection through the celiac arteries of 90% pancreatectomized diabetic rats improved their glucose tolerance and maintained their fasting insulin levels. The suppression of PGC-1alpha expression protects the glucolipotoxicity-induced beta-cell dysfunction in vivo and in vitro. A better understanding of the functions of molecules such as PGC-1alpha, which play key roles in intracellular fuel regulation, could herald a new era of the treatment of patients with type 2 diabetes mellitus by providing protection from glucolipotoxicity, which is an important cause of the development and progression of the disease.
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Affiliation(s)
- Ji-Won Kim
- Department of Internal Medicine, The Catholic University of Korea, Kangnam St Mary's Hospital, Seoul 137-040, Korea
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Rogoff D, Ryder JW, Black K, Yan Z, Burgess SC, McMillan DR, White PC. Abnormalities of glucose homeostasis and the hypothalamic-pituitary-adrenal axis in mice lacking hexose-6-phosphate dehydrogenase. Endocrinology 2007; 148:5072-80. [PMID: 17656460 DOI: 10.1210/en.2007-0593] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Hexose-6-phosphate dehydrogenase (EC 1.1.1.47) catalyzes the conversion of glucose 6-phosphate to 6-phosphogluconolactone within the lumen of the endoplasmic reticulum, thereby generating reduced nicotinamide adenine dinucleotide phosphate. Reduced nicotinamide adenine dinucleotide phosphate is a necessary cofactor for the reductase activity of 11beta-hydroxysteroid dehydrogenase type 1 (EC 1.1.1.146), which converts hormonally inactive cortisone to active cortisol (in rodents, 11-dehydrocorticosterone to corticosterone). Mice with targeted inactivation of hexose-6-phosphate dehydrogenase lack 11beta-hydroxysteroid dehydrogenase type 1 reductase activity, whereas dehydrogenase activity (corticosterone to 11-dehydrocorticosterone) is increased. We now report that both glucose output and glucose use are abnormal in these mice. Mutant mice have fasting hypoglycemia. In mutant primary hepatocytes, glucose output does not increase normally in response to glucagon. Mutant animals have lower hepatic glycogen content when fed and cannot mobilize it normally when fasting. As assessed by RT-PCR, responses of hepatic enzymes to fasting are blunted; enzymes involved in gluconeogenesis (phosphoenolpyruvate carboxykinase, tyrosine aminotransferase) are not appropriately up-regulated, and expression of glucokinase, an enzyme required for glycolysis, is not suppressed. Corticosterone has attenuated effects on expression of these enzymes in cultured mutant primary hepatocytes. Mutant mice have increased sensitivity to insulin, as assessed by homeostatic model assessment values and by increased glucose uptake by the muscle. The hypothalamic-pituitary-adrenal axis is also abnormal. Circulating ACTH, deoxycorticosterone, and corticosterone levels are increased in mutant animals, suggesting decreased negative feedback on the hypothalamic-pituitary-adrenal axis. Comparison with other animal models of adrenal insufficiency suggests that many of the observed abnormalities can be explained by blunted intracellular corticosterone actions, despite elevated circulating levels of this hormone.
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Affiliation(s)
- Daniela Rogoff
- University of Texas Southwestern Medical Center, 5223 Harry Hines Boulevard, Dallas, TX 75390-9063, USA
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14
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Jang WG, Kim EJ, Park KG, Park YB, Choi HS, Kim HJ, Kim YD, Kim KS, Lee KU, Lee IK. Glucocorticoid receptor mediated repression of human insulin gene expression is regulated by PGC-1α. Biochem Biophys Res Commun 2007; 352:716-21. [PMID: 17150186 DOI: 10.1016/j.bbrc.2006.11.074] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2006] [Accepted: 11/15/2006] [Indexed: 11/20/2022]
Abstract
Transcriptional regulation of the insulin gene plays a critical role in maintenance of pancreatic beta cell function in response to various stimuli. Here, we used INS-1 cells to test the hypothesis that PGC-1alpha regulates human insulin gene transcription by modulating glucocorticoid (GR) binding to the insulin gene promoter. Analysis of the human insulin promoter region revealed that the suppressive region regulated by GR and PGC-1alpha is localized from -362 to -257 bp. To locate the GR binding site in the human insulin promoter region, EMSAs were performed with candidate GR binding sequences and confirmed that a palindromic region (Palin, -284 to -274 bp) specifically interacts with GR. We also found that the Palin-binding activity of GR is increased in the presence of PGC-1alpha. These findings suggest that PGC-1alpha elevates the binding of GR to Palin and thereby enhances the GR-mediated inhibition of human insulin transcription.
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Affiliation(s)
- Won Gu Jang
- Department of Genetic Engineering, Kyungpook National University, Daegu, Republic of Korea
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15
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Gesina E, Tronche F, Herrera P, Duchene B, Tales W, Czernichow P, Breant B. Dissecting the role of glucocorticoids on pancreas development. Diabetes 2004; 53:2322-9. [PMID: 15331541 DOI: 10.2337/diabetes.53.9.2322] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
To determine whether glucocorticoids are involved in pancreas development, glucocorticoid treatment of rat pancreatic buds in vitro was combined with the analysis of transgenic mice lacking the glucocorticoid receptor (GR) in specific pancreatic cells. In vitro treatment of embryonic pancreata with dexamethasone, a glucocorticoid agonist, induced a decrease of insulin-expressing cell numbers and a doubling of acinar cell area, indicating that glucocorticoids favored acinar differentiation; in line with this, expression of Pdx-1, Pax-6, and Nkx6.1 was downregulated, whereas the mRNA levels of Ptf1-p48 and Hes-1 were increased. The selective inactivation of the GR gene in insulin-expressing beta-cells in mice (using a RIP-Cre transgene) had no measurable consequences on beta- or alpha-cell mass, whereas the absence of GR in the expression domain of Pdx-1 (Pdx-Cre transgene) led to a twofold increased beta-cell mass, with increased islet numbers and size but normal alpha-cell mass in adults. These results demonstrate that glucocorticoids play an important role in pancreatic beta-cell lineage, acting before hormone gene expression onset and possibly also modulating the balance between endocrine and exocrine cell differentiation.
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Affiliation(s)
- Emilie Gesina
- INSERM U457, Hôpital Robert Debré, Paris F 75019, France
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16
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Bledsoe RK, Stewart EL, Pearce KH. Structure and function of the glucocorticoid receptor ligand binding domain. VITAMINS AND HORMONES 2004; 68:49-91. [PMID: 15193451 DOI: 10.1016/s0083-6729(04)68002-2] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
After binding to an activating ligand, such as corticosteroid, the glucocorticoid receptor (GR) performs an impressive array of functions ranging from nuclear translocation, oligomerization, cofactor/kinase/transcription factor association, and DNA binding. One of the central functions of the receptor is to regulate gene expression, an activity triggered by ligand binding. In this role, GR acts as an adapter molecule by encoding the ligand's message within the structural flexibility of the ligand binding domain (LBD). The purpose of this review is to discuss the many structural and functional features of the GR LBD in light of recent successful biochemical and crystallographic studies. Progress in this area of research promises to reveal new strategies and insights allowing for the design of novel drugs to treat inflammatory diseases, diabetic conditions, steroid resistance, and cancers.
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Affiliation(s)
- Randy K Bledsoe
- Department of Gene Expression and Protein Biochemistry, Discovery Research, GlaxoSmithKline, Research Triangle Park, North Carolina 27709, USA
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17
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Blondeau B, Lesage J, Czernichow P, Dupouy JP, Bréant B. Glucocorticoids impair fetal beta-cell development in rats. Am J Physiol Endocrinol Metab 2001; 281:E592-9. [PMID: 11500315 DOI: 10.1152/ajpendo.2001.281.3.e592] [Citation(s) in RCA: 90] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In rats, poor fetal growth due to maternal food restriction during pregnancy is associated with decreased beta-cell mass at birth and glucose intolerance in adulthood. Overexposure to glucocorticoids in utero can induce intrauterine growth retardation in humans and animals and subsequent glucose intolerance in rodents. The aims of this study were to investigate whether glucocorticoid overexposure mediates the effect of undernutrition on beta-cell mass and to study their potential role in normally nourished rats. Undernutrition significantly increased maternal and fetal corticosterone levels. Twenty-one-day-old fetuses with undernutrition showed growth retardation and decreased pancreatic insulin content; adrenalectomy and subcutaneous corticosterone implants in their dams prevented the maternal corticosterone increase and restored fetal beta-cell mass. In fetuses with normal nutrition, fetal corticosterone levels were negatively correlated to fetal weight and insulin content; fetal beta-cell mass increased from 355 +/- 48 microg in sham to 516 +/- 160 microg after maternal adrenalectomy; inhibition of steroid production by metyrapone induced a further increase to 757 +/- 125 microg. Our data support the new concept of a negative role of glucocorticoids in fetal beta-cell development.
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Affiliation(s)
- B Blondeau
- Institut National de la Santé et de la Recherche Médicale Unité 457, Hôpital Robert Debré, 48 boulevard Sérurier, 75019 Paris, France
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18
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Morimoto S, Fernandez-Mejia C, Romero-Navarro G, Morales-Peza N, Díaz-Sánchez V. Testosterone effect on insulin content, messenger ribonucleic acid levels, promoter activity, and secretion in the rat. Endocrinology 2001; 142:1442-7. [PMID: 11250923 DOI: 10.1210/endo.142.4.8069] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Coexistence of hyperinsulinemia and hyperandrogenism in women has been frequently described. Most of the studies addressing this issue have focused on the mechanisms by which insulin produces hyperandrogenism. In the present study, we analyzed the effects of testosterone in vivo and in vitro upon insulin gene expression and release in the rat. Our studies demonstrate that testosterone increases insulin messenger RNA (mRNA) levels in vitro as well as in vivo. In both prepuberal and intact adult rats, serum testosterone concentrations were positively correlated with insulin mRNA levels and insulin concentration in serum. Testosterone deprivation after gonadectomy decreased both insulin gene expression and serum insulin concentration. Insulin mRNA levels were partially restored after 3 days of testosterone administration and serum insulin was 80% and 27% above baseline values at 5 and 7 days posttreatment. Primary cultured pancreatic islets treated with the sexual steroid increased about 80% insulin mRNA, as well as protein, and release. In transfected islets, testosterone increased the activity of the -410 bp rat insulin promoter I by 154%. These data demonstrate that testosterone has a direct effect upon pancreatic islet function by favoring insulin gene expression and release.
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Affiliation(s)
- S Morimoto
- Department of Reproductive Biology, National Institute of Medical Sciences and Nutrition Salvador Zubiran, National University of México, Tlalpan 14000, D.F. México City, México
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19
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Jeong IK, Oh SH, Kim BJ, Chung JH, Min YK, Lee MS, Lee MK, Kim KW. The effects of dexamethasone on insulin release and biosynthesis are dependent on the dose and duration of treatment. Diabetes Res Clin Pract 2001; 51:163-71. [PMID: 11269888 DOI: 10.1016/s0168-8227(00)00229-1] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Complex results concerning the effect of glucocorticoids on insulin secretion have been reported. The aim of this study is to clarify the direct effects of glucocorticoids on pancreatic islets and to determine whether the effect of glucocorticoids on insulin biosynthesis or release is dependent on the dose and duration of treatment with glucocorticoid. Studies on insulin secretion and biosynthesis were performed with different concentrations (0, 1, 10, 100 nmol/l) and durations (1 and 6 h) of treatment with dexamethasone (dexa) in rat pancreatic islets. (1) One nmol/l dexa had no inhibitory effect on insulin secretion and biosynthesis. Ten and 100 nmol/l had an inhibitory effect on insulin secretion, which was mainly due to suppression of the first phase of insulin secretion. (2) Insulin content was significantly increased regardless of the concentration in 1-h treated islets. However, insulin content was markedly diminished with 100 nmol/l dexa in 6-h treated islets. (3) The preproinsulin mRNA expression of 6-h treated islets was suppressed in a dose-dependent manner. Our data revealed that, in the condition of short-term and low-dose glucocorticoid exposure, insulin secretion and biosynthesis are not affected. The secretory process of insulin seems to be the initial step of the inhibitory action of glucocorticoid. Both insulin release and biosynthesis are inhibited by chronic exposure to high dose dexamethasone. It can be concluded that glucocorticoid might be involved in the multisteps of insulin release and biosynthesis.
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Affiliation(s)
- I K Jeong
- Division of Endocrinology and Metabolism, Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, 50 Ilwon-dong, Kangnam-ku, Seoul 135-230, South Korea
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20
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Viswanath RL, Rose SD, Swift GH, MacDonald RJ. A binary mechanism for the selective action of a pancreatic beta -cell transcriptional silencer. J Biol Chem 2000; 275:40273-81. [PMID: 10995768 DOI: 10.1074/jbc.m007021200] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The pancreatic elastase I gene (ELA1) is selectively transcribed to high levels in pancreatic acinar cells. Pancreatic specificity is imparted by a 100-base pair enhancer that activates transcription in beta-cells of the islets of Langerhans as well as in acinar cells. Adjacent to the enhancer is a silencer that renders transcription specific to acinar cells by selectively suppressing the inherent beta-cell activity of the enhancer. We show that the selective repression of beta-cell transcription is due neither to a beta-cell specific activity of the silencer nor to selective interference with beta-cell-specific transcriptional activators acting on the enhancer. Rather, the silencer is effective in both pancreatic endocrine and acinar cell types against all low and moderate strength enhancers and promoters tested. The silencer appears to act in a binary manner by reducing the probability that a promoter will be active without affecting the rate of transcription from active promoters. We propose that the ELA1 silencer is a weak off switch capable of inactivating enhancer/promoter combinations whose strength is below a threshold level but ineffective against stronger enhancer/promoters. The apparent cell-specific effects on the ELA1 enhancer appear due to the ability of the silencer to inactivate the weak beta-cell activity of the enhancer but not the stronger acinar cell activity.
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Affiliation(s)
- R L Viswanath
- Department of Molecular Biology, the University of Texas Southwestern Medical Center, Dallas, Texas 75235-9148, USA
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21
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Bramblett DE, Huang HP, Tsai MJ. Pancreatic islet development. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 1999; 47:255-315. [PMID: 10582089 DOI: 10.1016/s1054-3589(08)60114-3] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Affiliation(s)
- D E Bramblett
- Department of Cell Biology, Baylor College of Medicine, Houston, Texas 77030, USA
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22
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Wordinger RJ, Clark AF. Effects of glucocorticoids on the trabecular meshwork: towards a better understanding of glaucoma. Prog Retin Eye Res 1999; 18:629-67. [PMID: 10438153 DOI: 10.1016/s1350-9462(98)00035-4] [Citation(s) in RCA: 163] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Glucocorticoid effects on the human trabecular meshwork can be used as a model system in which to study glaucomatous damage to the trabecular meshwork. One of the most important risk factors for glaucoma is an elevated intraocular pressure. The administration of glucocorticoids also can cause elevated intraocular pressure in some individuals. In addition, there is suggestive evidence linking glucocorticoids with the development of glaucoma. Glucocorticoids cause multiple effects on the human trabecular meshwork including changes in extracellular matrix metabolism, organisation of the cytoskeleton, and changes in gene expression and cell function. New discoveries on the molecular mechanisms of glucocorticoid receptor action provide new opportunities to study the possible role of this receptor in the development of glaucoma. For example, alternate spliced forms of the glucocorticoid receptor, glucocorticoid receptor response element half-sites, numerous modulatory factors, and direct effects of nuclear transcription factors have been recently described. Other recent information has shown that the new glaucoma gene (GLC1A/myocilin) is induced in the human trabecular meshwork by glucocorticoids. Although the exact function of myocilin is currently unknown, it offers the opportunity to dissect the molecular pathways regulating aqueous humor outflow. Future challenges include determining (1) which glucocorticoid effects in the human trabecular meshwork are responsible for elevated intraocular pressure; and (2) the significance of these findings to the development of glaucoma.
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Affiliation(s)
- R J Wordinger
- Department of Anatomy and Cell Biology, University of North Texas, Health Science Center, Fort Worth 76107, USA.
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23
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Ren H, Stiles GL. Dexamethasone stimulates human A1 adenosine receptor (A1AR) gene expression through multiple regulatory sites in promoter B. Mol Pharmacol 1999; 55:309-16. [PMID: 9927623 DOI: 10.1124/mol.55.2.309] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The expression of the human A1 adenosine receptor gene is controlled by two promoters, promoters A and B, and they are located 600 base pairs apart. The characteristics of the two promoters differ by the activity of expression, tissue specificity, and the potential regulatory elements around them. Promoter A is more active but its expression is observed only in selected tissues, whereas promoter B is constitutively expressed but at much reduced levels. In Chinese hamster ovary (CHO) cells transiently transfected with plasmids containing either promoter linked to a reporter gene, dexamethasone (dex) can stimulate (or enhance) the expression of promoter B much more effectively than that of promoter A. Mutation and deletion studies on plasmids containing promoter B have shown that the stimulation is mediated through multiple regulatory sites, including a serum response element, AP1, and TATA box. However, a single-glucocorticoid response element monomer-binding site between promoters A and B does not have significant contribution to dex-regulated expression. The interactions between glucocorticoid receptor (GR) and some regulatory sites are probably occurring via this protein (GR) interacting with other DNA-binding proteins because there is no GR DNA-binding sequence in the sites studied. The stimulation can be eliminated by mifepristone, an antagonist of GR, indicating the involvement of GR in gene regulation. In addition, dex treatment also stimulated the expression of A1 adenosine receptors in CHO cells transfected with the plasmids containing contiguous genomic sequences of promoter B or promoters A and B linked to the receptor-coding sequence. When promoter A is active and both promoter A and B are present in a construct, dex treatment induced a much smaller percentage of stimulation.
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Affiliation(s)
- H Ren
- Departments of Medicine and Pharmacology, Duke University Medical Center, Durham, North Carolina, USA
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24
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Insulin Gene Expression. ACTA ACUST UNITED AC 1999. [DOI: 10.1016/s1569-2558(08)60090-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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25
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Subramaniam N, Cairns W, Okret S. Glucocorticoids repress transcription from a negative glucocorticoid response element recognized by two homeodomain-containing proteins, Pbx and Oct-1. J Biol Chem 1998; 273:23567-74. [PMID: 9722596 DOI: 10.1074/jbc.273.36.23567] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Several studies have established that the prolactin (PRL) gene is expressed not only in lactotrophs and somatotrophs of the anterior pituitary but, albeit to a lesser extent, in non-pituitary cells like human thymocytes, decidualized endometrium, mammary glands during lactation, and some human non-pituitary cell lines. Despite the requirement in the pituitary for the pituitary-specific transcription factor Pit-1/GHF-1 for PRL expression, the expression in non-pituitary cells occurs in the absence of Pit-1/GHF-1 and can be repressed by glucocorticoids. This prompted us to investigate the transcription factors in non-pituitary cells which are involved in controlling expression and glucocorticoid repression of a previously characterized negative glucocorticoid response element from the bovine prolactin gene (PRL3 nGRE). Here we have demonstrated that non-pituitary cells (COS-7 and mouse hepatoma Hepa1c1c7 cells) conferred increased expression via the PRL3 nGRE mainly because of the binding of the ubiquitously expressed POU-homeodomain-containing octamer transcription factor-1 (Oct-1) to an AT-rich sequence present in the PRL3 sequence. However, full transcriptional activity required the binding of a second ubiquitously expressed homeodomain-containing protein, Pbx, previously shown to bind cooperatively with several homeotic selector proteins. The Pbx binding site in the PRL3 nGRE, located just upstream of the Oct-1 binding site, showed a strong sequence similarity with known Pbx binding sites and bound Pbx with an affinity similar to that of other established Pbx target sequences. Interestingly, both Oct-1 and Pbx binding to the PRL3 nGRE were found to be required for glucocorticoid repression. Addition of in vitro translated glucocorticoid receptor DNA binding domain to the nuclear extract prevented Oct-1 and Pbx from binding to the PRL element. The involvement of the homeobox protein Pbx in glucocorticoid repression via an nGRE identifies a new role for this protein.
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Affiliation(s)
- N Subramaniam
- Department of Medical Nutrition, Karolinska Institute, Huddinge University Hospital, F60 Novum, S-141 86 Huddinge, Sweden
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26
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Yamaoka T, Idehara C, Yano M, Matsushita T, Yamada T, Ii S, Moritani M, Hata J, Sugino H, Noji S, Itakura M. Hypoplasia of pancreatic islets in transgenic mice expressing activin receptor mutants. J Clin Invest 1998; 102:294-301. [PMID: 9664070 PMCID: PMC508887 DOI: 10.1172/jci2769] [Citation(s) in RCA: 130] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Activin, a member of the TGF-beta superfamily, regulates the growth and differentiation of a variety of cell types. Based on the expression of activin in pancreatic rudiments of rat embryos and stimulation of insulin secretion from adult rat pancreatic islets by activin, activin is implicated in the development and function of islets. To examine the significance of activin signaling in the fetal and postnatal development of islets, transgenic mice expressing a dominant negative form of activin receptor (dn-ActR) or a constitutively active form of activin receptor (ActR-T206D) in islets were generated together with the transgenic mice expressing intact activin receptor (intact ActR) as a negative control. Transgenic mice with both dn-ActR and ActR-T206D showed lower survival rates, smaller islet area, and lower insulin content in the whole pancreas with impaired glucose tolerance when compared with transgenic mice with intact ActR or littermates, but they showed the same alpha cell/beta cell ratios as their littermates. In addition to islet hypoplasia, the insulin response to glucose was severely impaired in dn-ActR transgenic mice. It is suggested that a precisely regulated intensity of activin signaling is necessary for the normal development of islets at the stage before differentiation into alpha and beta cells, and that activin plays a role in the postnatal functional maturation of islet beta cells.
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Affiliation(s)
- T Yamaoka
- Otsuka Department of Clinical and Molecular Nutrition, School of Medicine, The University of Tokushima, Tokushima-city, 770, Japan.
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27
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Ogbourne S, Antalis TM. Transcriptional control and the role of silencers in transcriptional regulation in eukaryotes. Biochem J 1998; 331 ( Pt 1):1-14. [PMID: 9512455 PMCID: PMC1219314 DOI: 10.1042/bj3310001] [Citation(s) in RCA: 169] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Mechanisms controlling transcription and its regulation are fundamental to our understanding of molecular biology and, ultimately, cellular biology. Our knowledge of transcription initiation and integral factors such as RNA polymerase is considerable, and more recently our understanding of the involvement of enhancers and complexes such as holoenzyme and mediator has increased dramatically. However, an understanding of transcriptional repression is also essential for a complete understanding of promoter structure and the regulation of gene expression. Transcriptional repression in eukaryotes is achieved through 'silencers', of which there are two types, namely 'silencer elements' and 'negative regulatory elements' (NREs). Silencer elements are classical, position-independent elements that direct an active repression mechanism, and NREs are position-dependent elements that direct a passive repression mechanism. In addition, 'repressors' are DNA-binding trasncription factors that interact directly with silencers. A review of the recent literature reveals that it is the silencer itself and its context within a given promoter, rather than the interacting repressor, that determines the mechanism of repression. Silencers form an intrinsic part of many eukaryotic promoters and, consequently, knowledge of their interactive role with enchancers and other transcriptional elements is essential for our understanding of gene regulation in eukaryotes.
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Affiliation(s)
- S Ogbourne
- Queensland Cancer Fund Experimental Oncology Program, The Queensland Institute of Medical Research, Brisbane, 4029 Queensland, Australia
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28
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Lauterborn JC, Poulsen FR, Stinis CT, Isackson PJ, Gall CM. Transcript-specific effects of adrenalectomy on seizure-induced BDNF expression in rat hippocampus. BRAIN RESEARCH. MOLECULAR BRAIN RESEARCH 1998; 55:81-91. [PMID: 9645963 DOI: 10.1016/s0169-328x(97)00368-9] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Activity-induced brain-derived neurotrophic factor (BDNF) expression is negatively modulated by circulating adrenal steroids. The rat BDNF gene gives rise to four major transcript forms that each contain a unique 5' exon (I-IV) and a common 3' exon (V) that codes for BDNF protein. Exon-specific in situ hybridization was used to determine if adrenalectomy has differential effects on basal and activity-induced BDNF transcript expression in hippocampus. Adrenalectomy alone had only modest effects on BDNF mRNA levels with slight increases in exon III-containing mRNA with 7-10-day survival and in exon II-containing mRNA with 30-days survival. In the dentate gyrus granule cells, adrenalectomy markedly potentiated increases in exon I and II cRNA labeling, but not increases in exon III and IV cRNA labeling, elicited by one hippocampal afterdischarge. Similarly, for the granule cells and CA1 pyramidal cells, hilus lesion (HL)-induced recurrent limbic seizures elicited greater increases in exon I and II cRNA hybridization in adrenalectomized (ADX) as compared to adrenal-intact rats. In this paradigm, adrenalectomy modestly potentiated the increase in exon III-containing mRNA in CA1 but had no effect on exon IV-containing mRNA content. These results demonstrate that the negative effects of adrenal hormones on activity-induced BDNF expression are by far the greatest for transcripts containing exons I and II. Together with evidence for region-specific transcript expression, these results suggest that the effects of stress on adaptive changes in BDNF signalling will be greatest for neurons that predominantly express transcripts I and II.
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Affiliation(s)
- J C Lauterborn
- Department of Anatomy and Neurobiology, University of California, Irvine 92697-1275, USA
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29
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Myrsén-Axcrona U, Karlsson S, Sundler F, Ahrén B. Dexamethasone induces neuropeptide Y (NPY) expression and impairs insulin release in the insulin-producing cell line RINm5F. Release of NPY and insulin through different pathways. J Biol Chem 1997; 272:10790-6. [PMID: 9099732 DOI: 10.1074/jbc.272.16.10790] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Neuropeptide Y (NPY) occurs in adrenergic as well as in non-adrenergic nerves innervating the islets of Langerhans and inhibits glucose-stimulated insulin secretion. Recently we demonstrated that NPY is expressed within islet beta cells of the rat pancreas following treatment with dexamethasone in vivo. In this study we examined the cellular expression of NPY following dexamethasone treatment of the insulin-producing cell line RINm5F, which under control conditions does not express or release NPY. The cells were cultured with or without dexamethasone (100 nM) for 5 days. Over the 5-day culture period, dexamethasone time dependently induced an increased release of NPY with a concomitant decrease in the release of insulin. Northern blot and in situ hybridization revealed a corresponding time-dependent increase in the amount of NPY transcripts and in the number of cells labeled for NPY mRNA, whereas immunocytochemistry for NPY revealed only a few immunoreactive cells, indicating a rapid release of the formed peptide. Following 5 days of culture with dexamethasone, acute stimulation with D-glyceraldehyde (10 mM) or KCl (20 mM) Ca2+ dependently stimulated the release of insulin. In contrast neither stimulation with D-glyceraldehyde or KCl nor removal of extracellular Ca2+ affected the release of NPY. Furthermore the D-glyceraldehyde- and KCl-induced increase in cytosolic Ca2+, evident in control RINm5F cells, was impaired after dexamethasone treatment. We conclude that RINm5F cells show steroid-sensitive plasticity and express NPY after dexamethasone treatment concomitantly with a decreased insulin secretion and impaired increase in cytosolic Ca2+ upon depolarization with KCl or stimulation with D-glyceraldehyde. We also conclude that NPY and insulin secretion are regulated differently and suggest that the inability of the removal of extracellular Ca2+ to inhibit NPY secretion and the failure of D-glyceraldehyde and KCl to stimulate NPY secretion reflect a constitutive release of this peptide from the cells in contrast to the regulated release of insulin.
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Affiliation(s)
- U Myrsén-Axcrona
- Department of Physiology and Neuroscience, Section of Neuroendocrine Cell Biology, Lund University, 221 85 Lund, Sweden
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