1
|
Sue N, Thai LM, Saito A, Boyer CK, Fordham AM, Yan C, Davenport A, Tao J, Bensellam M, Cantley J, Shi YC, Stephens SB, Imaizumi K, Biden TJ. Independent activation of CREB3L2 by glucose fills a regulatory gap in mouse β-cells by co-ordinating insulin biosynthesis with secretory granule formation. Mol Metab 2024; 79:101845. [PMID: 38013154 PMCID: PMC10755490 DOI: 10.1016/j.molmet.2023.101845] [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: 06/13/2023] [Revised: 11/22/2023] [Accepted: 11/23/2023] [Indexed: 11/29/2023] Open
Abstract
OBJECTIVE Although individual steps have been characterized, there is little understanding of the overall process whereby glucose co-ordinates the biosynthesis of insulin with its export out of the endoplasmic reticulum (ER) and incorporation into insulin secretory granules (ISGs). Here we investigate a role for the transcription factor CREB3L2 in this context. METHODS MIN6 cells and mouse islets were analysed by immunoblotting after treatment with glucose, fatty acids, thapsigargin and various inhibitors. Knockdown of CREB3L2 was achieved using si or sh constructs by transfection, or viral delivery. In vivo metabolic phenotyping was conducted after deletion of CREB3L2 in β-cells of adult mice using Ins1-CreER+. Islets were isolated for RNAseq and assays of glucose-stimulated insulin secretion (GSIS). Trafficking was monitored in islet monolayers using a GFP-tagged proinsulin construct that allows for synchronised release from the ER. RESULTS With a Km ≈3.5 mM, glucose rapidly (T1/2 0.9 h) increased full length (FL) CREB3L2 followed by a slower rise (T1/2 2.5 h) in its transcriptionally-active cleavage product, P60 CREB3L2. Glucose stimulation repressed the ER stress marker, CHOP, and this was partially reverted by knockdown of CREB3L2. Activation of CREB3L2 by glucose was not due to ER stress, however, but a combination of O-GlcNAcylation, which impaired proteasomal degradation of FL-CREB3L2, and mTORC1 stimulation, which enhanced its conversion to P60. cAMP generation also activated CREB3L2, but independently of glucose. Deletion of CREB3L2 inhibited GSIS ex vivo and, following a high-fat diet (HFD), impaired glucose tolerance and insulin secretion in vivo. RNAseq revealed that CREB3L2 regulated genes controlling trafficking to-and-from the Golgi, as well as a broader cohort associated with β-cell compensation during a HFD. Although post-Golgi trafficking appeared intact, knockdown of CREB3L2 impaired the generation of both nascent ISGs and proinsulin condensates in the Golgi, implying a defect in ER export of proinsulin and/or its processing in the Golgi. CONCLUSION The stimulation of CREB3L2 by glucose defines a novel, rapid and direct mechanism for co-ordinating the synthesis, packaging and storage of insulin, thereby minimizing ER overload and optimizing β-cell function under conditions of high secretory demand. Upregulation of CREB3L2 also potentially contributes to the benefits of GLP1 agonism and might in itself constitute a novel means of treating β-cell failure.
Collapse
Affiliation(s)
- Nancy Sue
- Garvan Institute of Medical Research, 384 Victoria St, Darlinghurst, NSW 2010, Australia
| | - Le May Thai
- Garvan Institute of Medical Research, 384 Victoria St, Darlinghurst, NSW 2010, Australia
| | - Atsushi Saito
- Department of Biochemistry, Institute of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan
| | - Cierra K Boyer
- Fraternal Order of Eagles Diabetes Research Center, Department of Internal Medicine, University of Iowa, Iowa City, IA 52246, USA
| | - Ashleigh M Fordham
- Garvan Institute of Medical Research, 384 Victoria St, Darlinghurst, NSW 2010, Australia
| | - Chenxu Yan
- Garvan Institute of Medical Research, 384 Victoria St, Darlinghurst, NSW 2010, Australia
| | - Aimee Davenport
- Garvan Institute of Medical Research, 384 Victoria St, Darlinghurst, NSW 2010, Australia
| | - Jiang Tao
- Garvan Institute of Medical Research, 384 Victoria St, Darlinghurst, NSW 2010, Australia
| | - Mohammed Bensellam
- Garvan Institute of Medical Research, 384 Victoria St, Darlinghurst, NSW 2010, Australia
| | - James Cantley
- Garvan Institute of Medical Research, 384 Victoria St, Darlinghurst, NSW 2010, Australia
| | - Yan-Chuan Shi
- Garvan Institute of Medical Research, 384 Victoria St, Darlinghurst, NSW 2010, Australia; St Vincent's Clinical School, Faculty of Medicine, The University of New South Wales, Sydney, Australia
| | - Samuel B Stephens
- Fraternal Order of Eagles Diabetes Research Center, Department of Internal Medicine, University of Iowa, Iowa City, IA 52246, USA
| | - Kazunori Imaizumi
- Department of Biochemistry, Institute of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan
| | - Trevor J Biden
- Garvan Institute of Medical Research, 384 Victoria St, Darlinghurst, NSW 2010, Australia; St Vincent's Clinical School, Faculty of Medicine, The University of New South Wales, Sydney, Australia.
| |
Collapse
|
2
|
Krzyzosiak A, Pitera AP, Bertolotti A. An Overview of Methods for Detecting eIF2α Phosphorylation and the Integrated Stress Response. Methods Mol Biol 2022; 2428:3-18. [PMID: 35171470 DOI: 10.1007/978-1-0716-1975-9_1] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Phosphorylation of the translation initiation factor eIF2α is an adaptive signaling event that is essential for cell and organismal survival from yeast to humans. It is central to the integrated stress response (ISR) that maintains cellular homeostasis in the face of threats ranging from viral infection, amino acid, oxygen, and heme deprivation to the accumulation of misfolded proteins in the endoplasmic reticulum. Phosphorylation of eIF2α has broad physiological, pathological, and therapeutic relevance. However, despite more than two decades of research and growing pharmacological interest, phosphorylation of eIF2α remains difficult to detect and quantify, because of its transient nature and because substoichiometric amounts of this modification are sufficient to profoundly reshape cellular physiology. This review aims to provide a roadmap for facilitating a robust evaluation of eIF2α phosphorylation and its downstream consequences in cells and organisms.
Collapse
|
3
|
Bulfoni M, Bouyioukos C, Zakaria A, Nigon F, Rapone R, Del Maestro L, Ait-Si-Ali S, Scharfmann R, Cosson B. Glucose controls co-translation of structurally related mRNAs via the mTOR and eIF2 pathways in human pancreatic beta cells. Front Endocrinol (Lausanne) 2022; 13:949097. [PMID: 35992129 PMCID: PMC9388909 DOI: 10.3389/fendo.2022.949097] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/20/2022] [Accepted: 07/11/2022] [Indexed: 11/13/2022] Open
Abstract
Pancreatic beta cell response to glucose is critical for the maintenance of normoglycemia. A strong transcriptional response was classically described in rodent models but, interestingly, not in human cells. In this study, we exposed human pancreatic beta cells to an increased concentration of glucose and analysed at a global level the mRNAs steady state levels and their translationalability. Polysome profiling analysis showed an early acute increase in protein synthesis and a specific translation regulation of more than 400 mRNAs, independently of their transcriptional regulation. We clustered the co-regulated mRNAs according to their behaviour in translation in response to glucose and discovered common structural and sequence mRNA features. Among them mTOR- and eIF2-sensitive elements have a predominant role to increase mostly the translation of mRNAs encoding for proteins of the translational machinery. Furthermore, we show that mTOR and eIF2α pathways are independently regulated in response to glucose, participating to a translational reshaping to adapt beta cell metabolism. The early acute increase in the translation machinery components prepare the beta cell for further protein demand due to glucose-mediated metabolism changes.
Collapse
Affiliation(s)
- Manuel Bulfoni
- Université Paris Cité, CNRS, Epigenetics and Cell Fate, Paris, France
| | - Costas Bouyioukos
- Université Paris Cité, CNRS, Epigenetics and Cell Fate, Paris, France
| | - Albatoul Zakaria
- Université Paris Cité, Institut Cochin, INSERM, CNRS, Paris, France
| | - Fabienne Nigon
- Université Paris Cité, CNRS, Epigenetics and Cell Fate, Paris, France
| | - Roberta Rapone
- Université Paris Cité, CNRS, Epigenetics and Cell Fate, Paris, France
| | | | | | | | - Bertrand Cosson
- Université Paris Cité, CNRS, Epigenetics and Cell Fate, Paris, France
- *Correspondence: Bertrand Cosson,
| |
Collapse
|
4
|
Cioffi F, Adam RHI, Broersen K. Molecular Mechanisms and Genetics of Oxidative Stress in Alzheimer's Disease. J Alzheimers Dis 2020; 72:981-1017. [PMID: 31744008 PMCID: PMC6971833 DOI: 10.3233/jad-190863] [Citation(s) in RCA: 102] [Impact Index Per Article: 25.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Alzheimer’s disease is the most common neurodegenerative disorder that can cause dementia in elderly over 60 years of age. One of the disease hallmarks is oxidative stress which interconnects with other processes such as amyloid-β deposition, tau hyperphosphorylation, and tangle formation. This review discusses current thoughts on molecular mechanisms that may relate oxidative stress to Alzheimer’s disease and identifies genetic factors observed from in vitro, in vivo, and clinical studies that may be associated with Alzheimer’s disease-related oxidative stress.
Collapse
Affiliation(s)
- Federica Cioffi
- Nanobiophysics Group, Technical Medical Centre, Faculty of Science and Technology, University of Twente, Enschede, The Netherlands
| | - Rayan Hassan Ibrahim Adam
- Nanobiophysics Group, Technical Medical Centre, Faculty of Science and Technology, University of Twente, Enschede, The Netherlands
| | - Kerensa Broersen
- Applied Stem Cell Technologies, Technical Medical Centre, Faculty of Science and Technology, University of Twente, Enschede, The Netherlands
| |
Collapse
|
5
|
Grieco GE, Brusco N, Licata G, Nigi L, Formichi C, Dotta F, Sebastiani G. Targeting microRNAs as a Therapeutic Strategy to Reduce Oxidative Stress in Diabetes. Int J Mol Sci 2019; 20:ijms20246358. [PMID: 31861156 PMCID: PMC6940935 DOI: 10.3390/ijms20246358] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2019] [Revised: 12/09/2019] [Accepted: 12/15/2019] [Indexed: 02/06/2023] Open
Abstract
Diabetes mellitus is a group of heterogeneous metabolic disorders characterized by chronic hyperglycaemia as a consequence of pancreatic β cell loss and/or dysfunction, also caused by oxidative stress. The molecular mechanisms involved inβ cell dysfunction and in response to oxidative stress are also regulated by microRNAs (miRNAs). miRNAs are a class of negative gene regulators, which modulate pathologic mechanisms occurring in diabetes and its complications. Although several pharmacological therapies specifically targeting miRNAs have already been developed and brought to the clinic, most previous miRNA-based drug delivery methods were unable to target a specific miRNA in a single cell type or tissue, leading to important off-target effects. In order to overcome these issues, aptamers and nanoparticles have been described as non-cytotoxic vehicles for miRNA-based drug delivery. These approaches could represent an innovative way to specifically target and modulate miRNAs involved in oxidative stress in diabetes and its complications. Therefore, the aims of this review are: (i) to report the role of miRNAs involved in oxidative stress in diabetes as promising therapeutic targets; (ii) to shed light onto the new delivery strategies developed to modulate the expression of miRNAs in diseases.
Collapse
Affiliation(s)
- Giuseppina Emanuela Grieco
- Diabetes Unit, Department of Medicine, Surgery and Neurosciences, University of Siena, V.le Bracci, 16, 53100 Siena, Italy; (G.E.G.); (N.B.); (G.L.); (L.N.); (C.F.); (G.S.)
- Fondazione Umberto Di Mario ONLUS c/o Toscana Life Sciences, 53100 Siena, Italy
| | - Noemi Brusco
- Diabetes Unit, Department of Medicine, Surgery and Neurosciences, University of Siena, V.le Bracci, 16, 53100 Siena, Italy; (G.E.G.); (N.B.); (G.L.); (L.N.); (C.F.); (G.S.)
- Fondazione Umberto Di Mario ONLUS c/o Toscana Life Sciences, 53100 Siena, Italy
| | - Giada Licata
- Diabetes Unit, Department of Medicine, Surgery and Neurosciences, University of Siena, V.le Bracci, 16, 53100 Siena, Italy; (G.E.G.); (N.B.); (G.L.); (L.N.); (C.F.); (G.S.)
- Fondazione Umberto Di Mario ONLUS c/o Toscana Life Sciences, 53100 Siena, Italy
| | - Laura Nigi
- Diabetes Unit, Department of Medicine, Surgery and Neurosciences, University of Siena, V.le Bracci, 16, 53100 Siena, Italy; (G.E.G.); (N.B.); (G.L.); (L.N.); (C.F.); (G.S.)
- Fondazione Umberto Di Mario ONLUS c/o Toscana Life Sciences, 53100 Siena, Italy
- UO Diabetologia, Azienda Ospedaliera Universitaria Senese, 53100 Siena, Italy
| | - Caterina Formichi
- Diabetes Unit, Department of Medicine, Surgery and Neurosciences, University of Siena, V.le Bracci, 16, 53100 Siena, Italy; (G.E.G.); (N.B.); (G.L.); (L.N.); (C.F.); (G.S.)
- Fondazione Umberto Di Mario ONLUS c/o Toscana Life Sciences, 53100 Siena, Italy
- UO Diabetologia, Azienda Ospedaliera Universitaria Senese, 53100 Siena, Italy
| | - Francesco Dotta
- Diabetes Unit, Department of Medicine, Surgery and Neurosciences, University of Siena, V.le Bracci, 16, 53100 Siena, Italy; (G.E.G.); (N.B.); (G.L.); (L.N.); (C.F.); (G.S.)
- Fondazione Umberto Di Mario ONLUS c/o Toscana Life Sciences, 53100 Siena, Italy
- UO Diabetologia, Azienda Ospedaliera Universitaria Senese, 53100 Siena, Italy
- Correspondence: ; Tel.: +39-0577-586269
| | - Guido Sebastiani
- Diabetes Unit, Department of Medicine, Surgery and Neurosciences, University of Siena, V.le Bracci, 16, 53100 Siena, Italy; (G.E.G.); (N.B.); (G.L.); (L.N.); (C.F.); (G.S.)
- Fondazione Umberto Di Mario ONLUS c/o Toscana Life Sciences, 53100 Siena, Italy
| |
Collapse
|
6
|
Razik Farrag A, Nassar M, El-Khayat Z, Hussein J, Ahmed Mohammed N, Medhat D, El-Gendy AEN, Elshamy A. Heteroxenia Ghardaqensis Extract Protects Against DNA Damage in Streptozotocin-Induced Experimental Diabetes. ACTA ACUST UNITED AC 2019. [DOI: 10.13005/bpj/1615] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
DNA damage is correlated to type-2 diabetes mellitus (T2DM) and its complications via oxidative stress. This study aimed to evaluate the anti-diabetic effect of Heteroxenia ghardaqensis extract on streptozotocin (STZ) induced-diabetes and how far can this extract attenuate DNA damage in this model. Forty male albino rats (160-180 g) were used in this study and divided into four groups: control, diabetic, diabetic rats received H. ghardaqensis extract (30 mg/kg body weight/day) orally for four weeks and diabetic rats received H. ghardaqensis extract (60 mg/kg body weight/day) orally for four weeks. After the experimental period, fasting blood sugar and serum cholesterol were determined. Urinary 8-hydroxyguanosine (8-OHdG) as a marker of DNA damage was estimated by reversed phase (HPLC). Liver and kidney nitic oxide (NO) and malondialdehyde (MDA) were estimated. Pancreatic tissues were histopathologicaly examined. Our results suggested that diabetes mellitus is accompanied by elevation of DNA damage that enhances the tendency to mutagens and reduce the efficacy of DNA repair. H. ghardaqensis extract appeared to be effective against the oxidative stress induced by STZ which may be due to sesquiterpenoids and diterpenes compounds that scavenge free radicals and increase the antioxidant enzymes as appeared in attenuation of DNA damage.
Collapse
Affiliation(s)
| | - Mahmoud Nassar
- Natural Compounds Chemistry, National Research Centre, Cairo, Egypt
| | | | - Jihan Hussein
- Medical Biochemistry, National Research Centre, Cairo, Egypt
| | | | - Dalia Medhat
- Medical Biochemistry, National Research Centre, Cairo, Egypt
| | - Abd El-Nasser El-Gendy
- Medicinal and Aromatic Plants Research Department, National Research Centre, Cairo, Egypt
| | | |
Collapse
|
7
|
Rodríguez-Comas J, Moreno-Asso A, Moreno-Vedia J, Martín M, Castaño C, Marzà-Florensa A, Bofill-De Ros X, Mir-Coll J, Montané J, Fillat C, Gasa R, Novials A, Servitja JM. Stress-Induced MicroRNA-708 Impairs β-Cell Function and Growth. Diabetes 2017; 66:3029-3040. [PMID: 28970284 DOI: 10.2337/db16-1569] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/19/2016] [Accepted: 09/24/2017] [Indexed: 11/13/2022]
Abstract
The pancreatic β-cell transcriptome is highly sensitive to external signals such as glucose oscillations and stress cues. MicroRNAs (miRNAs) have emerged as key factors in gene expression regulation. Here, we aimed to identify miRNAs that are modulated by glucose in mouse pancreatic islets. We identified miR-708 as the most upregulated miRNA in islets cultured at low glucose concentrations, a setting that triggers a strong stress response. miR-708 was also potently upregulated by triggering endoplasmic reticulum (ER) stress with thapsigargin and in islets of ob/ob mice. Low-glucose induction of miR-708 was blocked by treatment with the chemical chaperone 4-phenylbutyrate, uncovering the involvement of ER stress in this response. An integrative analysis identified neuronatin (Nnat) as a potential glucose-regulated target of miR-708. Indeed, Nnat expression was inversely correlated with miR-708 in islets cultured at different glucose concentrations and in ob/ob mouse islets and was reduced after miR-708 overexpression. Consistent with the role of Nnat in the secretory function of β-cells, miR-708 overexpression impaired glucose-stimulated insulin secretion (GSIS), which was recovered by NNAT overexpression. Moreover, miR-708 inhibition recovered GSIS in islets cultured at low glucose. Finally, miR-708 overexpression suppressed β-cell proliferation and induced β-cell apoptosis. Collectively, our results provide a novel mechanism of glucose regulation of β-cell function and growth by repressing stress-induced miR-708.
Collapse
Affiliation(s)
- Júlia Rodríguez-Comas
- Diabetes and Obesity Research Laboratory, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain
| | - Alba Moreno-Asso
- Diabetes and Obesity Research Laboratory, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain
- Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas (CIBERDEM), Barcelona, Spain
| | - Juan Moreno-Vedia
- Diabetes and Obesity Research Laboratory, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain
| | - Mercè Martín
- Diabetes and Obesity Research Laboratory, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain
| | - Carlos Castaño
- Diabetes and Obesity Research Laboratory, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain
- Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas (CIBERDEM), Barcelona, Spain
| | - Anna Marzà-Florensa
- Diabetes and Obesity Research Laboratory, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain
| | - Xavier Bofill-De Ros
- Gene Therapy and Cancer Laboratory, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain
- Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Barcelona, Spain
| | - Joan Mir-Coll
- Diabetes and Obesity Research Laboratory, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain
- Department of Medicine, University of Barcelona, Barcelona, Spain
| | - Joel Montané
- Diabetes and Obesity Research Laboratory, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain
- Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas (CIBERDEM), Barcelona, Spain
| | - Cristina Fillat
- Gene Therapy and Cancer Laboratory, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain
- Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Barcelona, Spain
| | - Rosa Gasa
- Diabetes and Obesity Research Laboratory, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain
- Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas (CIBERDEM), Barcelona, Spain
| | - Anna Novials
- Diabetes and Obesity Research Laboratory, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain
- Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas (CIBERDEM), Barcelona, Spain
| | - Joan-Marc Servitja
- Diabetes and Obesity Research Laboratory, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain
- Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas (CIBERDEM), Barcelona, Spain
| |
Collapse
|
8
|
Gillespie AL, Pan X, Marco-Ramell A, Meharg C, Green BD. Detailed characterisation of STC-1 cells and the pGIP/Neo sub-clone suggests the incretin hormones are translationally regulated. Peptides 2017; 96:20-30. [PMID: 28870797 DOI: 10.1016/j.peptides.2017.08.010] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/05/2017] [Revised: 07/10/2017] [Accepted: 08/28/2017] [Indexed: 12/25/2022]
Abstract
STC-1 is a heterogeneous plurihormonal cell line producing several prominent gut peptide hormones. pGIP/Neo is a genetically selected sub-clone of STC-1 with augmented levels of glucose-dependent insulinotropic peptide (GIP). Morphometric parameters, hormone concentrations, mRNA transcripts, hormone immunocytochemistry and nutrient utilisation/production of these two cell lines were compared. Proglucagon-derived peptides (Glucagon-like peptide-1 (GLP-1) and - 2(GLP-2)) were lower in sub-clone cells than progenitor cells. High Content Analysis found altered intracellular GLP-1, GIP, cholecystokinin (CCK) and peptide YY (PYY) levels and differing hormone co-localisation. The proportion pGIP/Neo cells containing GIP immunoreactivity (82%) was greater than STC-1 (65%), as were the proportion with 'GIP only', 'GLP-1+GIP' or 'GIP+PYY' immunoreactivity. Most surprisingly mRNA transcripts of the proglucagon and GIP genes were inversely correlated to the levels of their translated peptides. This strongly suggests that proglucagon and GIP are encoded on 'translationally regulated genes' - a characteristic possessed by other endocrine hormones. Metabolomic profiling revealed differences in cellular nutrient utilisation/production and that under normal culture conditions both cell lines exhibit signs of overflow metabolism. These studies provide an insight into the metabolism and properties of these valuable cells, suggesting for the first time that incretin hormone genes are translationally regulated.
Collapse
Affiliation(s)
- Anna L Gillespie
- Institute for Global Food Security (IGFS), Queen's University Belfast, United Kingdom
| | - Xiaobei Pan
- Institute for Global Food Security (IGFS), Queen's University Belfast, United Kingdom
| | - Anna Marco-Ramell
- Biomarkers and Nutrimetabolomics Group, University of Barcelona, Spain
| | - Caroline Meharg
- Institute for Global Food Security (IGFS), Queen's University Belfast, United Kingdom
| | - Brian D Green
- Institute for Global Food Security (IGFS), Queen's University Belfast, United Kingdom.
| |
Collapse
|
9
|
Figueroa-García MDC, Espinosa-García MT, Martinez-Montes F, Palomar-Morales M, Mejía-Zepeda R. Even a Chronic Mild Hyperglycemia Affects Membrane Fluidity and Lipoperoxidation in Placental Mitochondria in Wistar Rats. PLoS One 2015; 10:e0143778. [PMID: 26630275 PMCID: PMC4667935 DOI: 10.1371/journal.pone.0143778] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2015] [Accepted: 11/09/2015] [Indexed: 11/19/2022] Open
Abstract
It is known the deleterious effects of diabetes on embryos, but the effects of diabetes on placenta and its mitochondria are still not well known. In this work we generated a mild hyperglycemia model in female wistar rats by intraperitoneal injection of streptozotocin in 48 hours-old rats. The sexual maturity onset of the female rats was delayed around 6–7 weeks and at 16 weeks-old they were mated, and sacrificed at day 19th of pregnancy. In placental total tissue and isolated mitochondria, the fatty acids composition was analyzed by gas chromatography, and lipoperoxidation was measured by thiobarbituric acid reactive substances. Membrane fluidity in mitochondria was measured with the excimer forming probe dipyrenylpropane and mitochondrial function was measured with a Clark-type electrode. The results show that even a chronic mild hyperglycemia increases lipoperoxidation and decreases mitochondrial function in placenta. Simultaneously, placental fatty acids metabolism in total tissue is modified but in a different way than in placental mitochondria. Whereas the chronic mild hyperglycemia induced a decrease in unsaturated to saturated fatty acids ratio (U/S) in placental total tissue, the ratio increased in placental mitochondria. The measurements of membrane fluidity showed that fluidity of placenta mitochondrial membranes increased with hyperglycemia, showing consistency with the fatty acids composition through the U/S index. The thermotropic characteristics of mitochondrial membranes were changed, showing lower transition temperature and activation energies. All of these data together demonstrate that even a chronic mild hyperglycemia during pregnancy of early reproductive Wistar rats, generates an increment of lipoperoxidation, an increase of placental mitochondrial membrane fluidity apparently derived from changes in fatty acids composition and consequently, mitochondrial malfunction.
Collapse
Affiliation(s)
| | | | | | - Martín Palomar-Morales
- Unidad de Morfología y Función, Facultad de Estudios Superiores Iztacala, UNAM, Tlalnepantla, State of Mexico, Mexico
| | - Ricardo Mejía-Zepeda
- Unidad de Biomedicina, Facultad de Estudios Superiores Iztacala, UNAM, Tlalnepantla, State of Mexico, Mexico
- * E-mail:
| |
Collapse
|
10
|
Sharma RB, O'Donnell AC, Stamateris RE, Ha B, McCloskey KM, Reynolds PR, Arvan P, Alonso LC. Insulin demand regulates β cell number via the unfolded protein response. J Clin Invest 2015; 125:3831-46. [PMID: 26389675 DOI: 10.1172/jci79264] [Citation(s) in RCA: 158] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2014] [Accepted: 08/13/2015] [Indexed: 12/11/2022] Open
Abstract
Although stem cell populations mediate regeneration of rapid turnover tissues, such as skin, blood, and gut, a stem cell reservoir has not been identified for some slower turnover tissues, such as the pancreatic islet. Despite lacking identifiable stem cells, murine pancreatic β cell number expands in response to an increase in insulin demand. Lineage tracing shows that new β cells are generated from proliferation of mature, differentiated β cells; however, the mechanism by which these mature cells sense systemic insulin demand and initiate a proliferative response remains unknown. Here, we identified the β cell unfolded protein response (UPR), which senses insulin production, as a regulator of β cell proliferation. Using genetic and physiologic models, we determined that among the population of β cells, those with an active UPR are more likely to proliferate. Moreover, subthreshold endoplasmic reticulum stress (ER stress) drove insulin demand-induced β cell proliferation, through activation of ATF6. We also confirmed that the UPR regulates proliferation of human β cells, suggesting that therapeutic UPR modulation has potential to expand β cell mass in people at risk for diabetes. Together, this work defines a stem cell-independent model of tissue homeostasis, in which differentiated secretory cells use the UPR sensor to adapt organ size to meet demand.
Collapse
|
11
|
You L, Wang N, Yin D, Wang L, Jin F, Zhu Y, Yuan Q, De W. Downregulation of Long Noncoding RNA Meg3 Affects Insulin Synthesis and Secretion in Mouse Pancreatic Beta Cells. J Cell Physiol 2015; 231:852-62. [PMID: 26313443 DOI: 10.1002/jcp.25175] [Citation(s) in RCA: 113] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2014] [Accepted: 08/25/2015] [Indexed: 12/15/2022]
Affiliation(s)
- LiangHui You
- Department of Biochemistry and Molecular Biology; Nanjing Medical University; Nanjing China
- Nanjing Maternity and Child Health Care Institute; Nanjing Maternity and Child Health Care Hospital Affiliated with Nanjing Medical University; Nanjing China
| | - Ning Wang
- Department of Biochemistry and Molecular Biology; Nanjing Medical University; Nanjing China
| | - DanDan Yin
- Department of Central Laboratory; The Second Affiliated Hospital of Southeast University; Nanjing China
| | - LinTao Wang
- Department of Biochemistry and Molecular Biology; Nanjing Medical University; Nanjing China
| | - FeiYan Jin
- Department of Biochemistry and Molecular Biology; Nanjing Medical University; Nanjing China
| | - YaNan Zhu
- Department of Biochemistry and Molecular Biology; Nanjing Medical University; Nanjing China
| | - QingXin Yuan
- Department of Endocrinology; First Affiliated Hospital of Nanjing Medical University; Nanjing China
| | - Wei De
- Department of Biochemistry and Molecular Biology; Nanjing Medical University; Nanjing China
| |
Collapse
|
12
|
Vasu S, Moffett RC, McClenaghan NH, Flatt PR. Differential molecular and cellular responses of GLP-1 secreting L-cells and pancreatic alpha cells to glucotoxicity and lipotoxicity. Exp Cell Res 2015; 336:100-8. [DOI: 10.1016/j.yexcr.2015.05.022] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2015] [Revised: 05/25/2015] [Accepted: 05/26/2015] [Indexed: 12/25/2022]
|
13
|
Abstract
Recent work has demonstrated the importance of post-transcriptional gene regulation in toxic responses. In the present study, we used two rat models to investigate mRNA translation in the liver following xenobiotic-induced toxicity. By combining polysome profiling with genomic methodologies, we were able to assess global changes in hepatic mRNA translation. Dio3 (iodothyronine deiodinase type III) was identified as a gene that exhibited specific translational repression and had a functional role in a number of relevant canonical pathways. Western blot analysis indicated that this repression led to reduced D3 (the protein expressed by Dio3) levels, enhanced over time and with increased dose. Using Northern blotting techniques and qRT-PCR (quantitative reverse transcription–PCR), we confirmed further that there was no reduction in Dio3 mRNA, suggesting that translational repression of Dio3 is an important determinant of the reduced D3 protein expression following liver damage. Finally, we show that drug-induced hepatotoxicity appears to cause localized disruptions in thyroid hormone levels in the liver and plasma. We suggest that this leads to reduced translation of Dio3 mRNA, which results in decreased D3 production. It may therefore be possible that this is an important mechanism by which the liver can, upon early signs of damage, act rapidly to maintain its own energy equilibrium, thereby avoiding global disruption of the hypothalamic–pituitary–thyroid axis.
Collapse
|
14
|
Moreno-Asso A, Castaño C, Grilli A, Novials A, Servitja JM. Glucose regulation of a cell cycle gene module is selectively lost in mouse pancreatic islets during ageing. Diabetologia 2013; 56:1761-72. [PMID: 23685457 DOI: 10.1007/s00125-013-2930-0] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/19/2012] [Accepted: 04/12/2013] [Indexed: 12/16/2022]
Abstract
AIMS/HYPOTHESIS Transcriptional networks in beta cells are modulated by extracellular signals such as glucose, thereby ensuring beta cell adaptation to systemic insulin demands. Ageing is a main risk factor for type 2 diabetes and has been associated with perturbed expression of genes essential for beta cell function. We aimed to uncover glucose-dependent gene modules in mouse pancreatic islets and investigate how this regulation is affected by ageing. METHODS Global gene expression was assessed in pancreatic islets from young and aged wild-type and Cdkn2a (Ink4a/Arf)-deficient mice exposed to different glucose concentrations. Gene modules were identified by gene ontology and gene set enrichment analysis. RESULTS Gene expression profiling revealed that variations in glucose levels have a widespread and highly dynamic impact on the islet transcriptome. Stimulatory glucose levels induced the expression of highly beta cell-selective genes and repressed the expression of ubiquitous genes involved in stress and antiproliferative responses, and in organelle biogenesis. Interestingly, a module comprising cell cycle genes was significantly induced between non-stimulatory and stimulatory glucose concentrations. Unexpectedly, glucose regulation of gene expression was broadly maintained in islets from old mice. However, glucose induction of mitotic genes was selectively lost in aged islets and was not even restored in the absence of the cell cycle inhibitors p16(INK4a) and p19(ARF), which have been implicated in the restricted proliferative capacity of beta cells with advanced age. CONCLUSIONS/INTERPRETATION Glucose-dependent transcriptional networks in islets are globally conserved during ageing, with the exception of the ability of stimulatory glucose levels to induce a cell cycle gene module.
Collapse
Affiliation(s)
- A Moreno-Asso
- Institut d'Investigacions Biomèdiques August Pi i Sunyer, Centre Esther Koplowitz, Barcelona, Spain
| | | | | | | | | |
Collapse
|
15
|
Vasu S, McClenaghan NH, McCluskey JT, Flatt PR. Cellular responses of novel human pancreatic β-cell line, 1.1B4 to hyperglycemia. Islets 2013; 5:170-7. [PMID: 23985558 DOI: 10.4161/isl.26184] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The novel human-derived pancreatic β-cell line, 1.1B4 exhibits insulin secretion and β-cell enriched gene expression. Recent investigations of the cellular responses of this novel cell line to lipotoxicity and cytokine toxicity revealed similarities to primary human β cells. The current study has investigated the responses of 1.1B4 cells to chronic 48 and 72 h exposure to hyperglycemia to probe mechanisms of human β-cell dysfunction and cell death. Exposure to 25 mM glucose significantly reduced insulin content (p<0.05) and glucokinase activity (p<0.01) after 72 h. Basal insulin release was unaffected but acute secretory response to 16.7 mM glucose was impaired (p<0.05). Insulin release stimulated by alanine, GLP-1, KCl, elevated Ca (2+) and forskolin was also markedly reduced after exposure to hyperglycemia (p<0.001). In addition, PDX1 protein expression was reduced by 58% by high glucose (p<0.05). Effects of hyperglycemia on secretory function were accompanied by decreased mRNA expression of INS, GCK, PCSK1, PCSK2, PPP3CB, GJA1, ABCC8, and KCNJ11. In contrast, exposure to hyperglycemia upregulated the transcription of GPX1, an antioxidant enzyme involved in detoxification of hydrogen peroxide and HSPA4, a molecular chaperone involved in ER stress response. Hyperglycemia-induced DNA damage was demonstrated by increased % tail DNA and olive tail moment, assessed by comet assay. Hyperglycemia-induced apoptosis was evident from increased activity of caspase 3/7 and decreased BCL2 protein. These observations reveal significant changes in cellular responses and gene expression in novel human pancreatic 1.1B4 β cells exposed to hyperglycemia, illustrating the usefulness of this novel human-derived cell line for studying human β-cell biology and diabetes.
Collapse
Affiliation(s)
- Srividya Vasu
- SAAD Centre for Pharmacy and Diabetes; University of Ulster; Coleraine, Northern Ireland, UK
| | | | | | | |
Collapse
|
16
|
Jiang XY, Lu DB, Jiang YZ, Zhou LN, Cheng LQ, Chen B. PGC-1α prevents apoptosis in adipose-derived stem cells by reducing reactive oxygen species production in a diabetic microenvironment. Diabetes Res Clin Pract 2013; 100:368-75. [PMID: 23618552 DOI: 10.1016/j.diabres.2013.03.036] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/29/2013] [Revised: 03/12/2013] [Accepted: 03/28/2013] [Indexed: 11/30/2022]
Abstract
AIMS To examine whether overexpression of peroxisome proliferator activated receptor-gamma coactivator-1 alpha (PGC-1α) can prevent apoptosis in adipose-derived stem cells (ASCs) by reducing reactive oxygen species (ROS) production and enhancing mitochondrial function in a diabetic environment. METHODS After the isolation, expansion and characterisation of rat ASCs, we overexpressed PGC-1α in ASCs using an adenoviral vector encoding green fluorescent protein (GFP) or PGC-1α and tested the apoptotic effect under conditions of high glucose, hypoxia and serum deprivation. The production of intracellular ROS and mitochondrial ROS was evaluated using dihydroethidium and CM-H2XRos fluorescent probes. RESULTS Under conditions of high glucose, hypoxia and serum deprivation, the overexpression of PGC-1α in ASCs decreased apoptosis and led to an increased survival rate. The ASCs modified with PGC-1α produced lower intracellular and mitochondrial ROS. The mitochondrial morphology and structure in the PGC-1α-ASC group remained relatively complete compared with the control group. CONCLUSIONS These results reveal a crucial protective role for PGC-1α in the treatment of diabetes mellitus and its complications using stem cells therapy.
Collapse
Affiliation(s)
- Xiao-Yan Jiang
- Department of Endocrinology, Southwest Hospital, Third Military Medical University, Chongqing 400038, China
| | | | | | | | | | | |
Collapse
|
17
|
Chan JY, Luzuriaga J, Bensellam M, Biden TJ, Laybutt DR. Failure of the adaptive unfolded protein response in islets of obese mice is linked with abnormalities in β-cell gene expression and progression to diabetes. Diabetes 2013; 62:1557-68. [PMID: 23274897 PMCID: PMC3636637 DOI: 10.2337/db12-0701] [Citation(s) in RCA: 89] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
The normal β-cell response to obesity-associated insulin resistance is hypersecretion of insulin. Type 2 diabetes develops in subjects with β-cells that are susceptible to failure. Here, we investigated the time-dependent gene expression changes in islets of diabetes-prone db/db and diabetes-resistant ob/ob mice. The expressions of adaptive unfolded protein response (UPR) genes were progressively induced in islets of ob/ob mice, whereas they declined in diabetic db/db mice. Genes important for β-cell function and maintenance of the islet phenotype were reduced with time in db/db mice, whereas they were preserved in ob/ob mice. Inflammation and antioxidant genes displayed time-dependent upregulation in db/db islets but were unchanged in ob/ob islets. Treatment of db/db mouse islets with the chemical chaperone 4-phenylbutyric acid partially restored the changes in several β-cell function genes and transcription factors but did not affect inflammation or antioxidant gene expression. These data suggest that the maintenance (or suppression) of the adaptive UPR is associated with β-cell compensation (or failure) in obese mice. Inflammation, oxidative stress, and a progressive loss of β-cell differentiation accompany diabetes progression. The ability to maintain the adaptive UPR in islets may protect against the gene expression changes that underlie diabetes development in obese mice.
Collapse
|
18
|
Bensellam M, Laybutt DR, Jonas JC. The molecular mechanisms of pancreatic β-cell glucotoxicity: recent findings and future research directions. Mol Cell Endocrinol 2012; 364:1-27. [PMID: 22885162 DOI: 10.1016/j.mce.2012.08.003] [Citation(s) in RCA: 208] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/30/2012] [Revised: 07/11/2012] [Accepted: 08/01/2012] [Indexed: 02/06/2023]
Abstract
It is well established that regular physiological stimulation by glucose plays a crucial role in the maintenance of the β-cell differentiated phenotype. In contrast, prolonged or repeated exposure to elevated glucose concentrations both in vitro and in vivo exerts deleterious or toxic effects on the β-cell phenotype, a concept termed as glucotoxicity. Evidence indicates that the latter may greatly contribute to the pathogenesis of type 2 diabetes. Through the activation of several mechanisms and signaling pathways, high glucose levels exert deleterious effects on β-cell function and survival and thereby, lead to the worsening of the disease over time. While the role of high glucose-induced β-cell overstimulation, oxidative stress, excessive Unfolded Protein Response (UPR) activation, and loss of differentiation in the alteration of the β-cell phenotype is well ascertained, at least in vitro and in animal models of type 2 diabetes, the role of other mechanisms such as inflammation, O-GlcNacylation, PKC activation, and amyloidogenesis requires further confirmation. On the other hand, protein glycation is an emerging mechanism that may play an important role in the glucotoxic deterioration of the β-cell phenotype. Finally, our recent evidence suggests that hypoxia may also be a new mechanism of β-cell glucotoxicity. Deciphering these molecular mechanisms of β-cell glucotoxicity is a mandatory first step toward the development of therapeutic strategies to protect β-cells and improve the functional β-cell mass in type 2 diabetes.
Collapse
Affiliation(s)
- Mohammed Bensellam
- Université catholique de Louvain, Institut de recherche expérimentale et clinique, Pôle d'endocrinologie, diabète et nutrition, Brussels, Belgium
| | | | | |
Collapse
|
19
|
Moore CE, Omikorede O, Gomez E, Willars GB, Herbert TP. PERK activation at low glucose concentration is mediated by SERCA pump inhibition and confers preemptive cytoprotection to pancreatic β-cells. Mol Endocrinol 2010; 25:315-26. [PMID: 21193559 PMCID: PMC3070211 DOI: 10.1210/me.2010-0309] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
A decrease in the ATP/energy status of the cell in response to a decrease in glucose concentration results in SERCA pump inhibition, the efflux of Ca2+ from the ER and the activation of PERK, which plays an important role in both pancreatic β-cell function and survival. Protein kinase R-like ER kinase (PERK) is activated at physiologically low glucose concentrations in pancreatic β-cells. However, the molecular mechanisms by which PERK is activated under these conditions and its role in β-cell function are poorly understood. In this report, we investigated, in dispersed rat islets of Langerhans and mouse insulinoma-6 (MIN6) cells, the relationship between extracellular glucose concentration, the free endoplasmic reticulum (ER) calcium concentration ([Ca2+]ER) measured directly using an ER targeted fluorescence resonance energy transfer-based calcium sensor, and the activation of PERK. We found that a decrease in glucose concentration leads to a concentration-dependent reduction in [Ca2+]ER that parallels the activation of PERK and the phosphorylation of its substrate eukaryotic initiation factor-2α. We provide evidence that this decrease in [Ca2+]ER is caused by a decrease in sarcoplasmic/ER Ca2+-ATPase pump activity mediated by a reduction in the energy status of the cell. Importantly, we also report that PERK-dependent eukaryotic initiation factor-2α phosphorylation at low glucose concentration plays a significant role in 1) the regulation of both proinsulin and global protein synthesis, 2) cell viability, and 3) conferring preemptive cytoprotection against ER stress. Taken together, these results provide evidence that a decrease in the ATP/energy status of the cell in response to a decrease in glucose concentration results in sarcoplasmic/ER Ca2+-ATPase pump inhibition, the efflux of Ca2+ from the ER, and the activation of PERK, which plays an important role in both pancreatic β-cell function and survival.
Collapse
Affiliation(s)
- Claire E Moore
- Department of Cell Physiology and Pharmacology, The Henry Wellcome Building, University of Leicester, University Road, Leicester LE1 9HN, United Kingdom
| | | | | | | | | |
Collapse
|
20
|
Cavener DR, Gupta S, McGrath BC. PERK in beta cell biology and insulin biogenesis. Trends Endocrinol Metab 2010; 21:714-21. [PMID: 20850340 PMCID: PMC2991375 DOI: 10.1016/j.tem.2010.08.005] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/16/2010] [Revised: 08/17/2010] [Accepted: 08/18/2010] [Indexed: 11/17/2022]
Abstract
PERK (EIF2AK3) was originally discovered as a major component of the unfolded protein response (UPR). PERK deficiency results in permanent neonatal diabetes, which was initially thought to be caused by a failure to regulate ER stress in insulin-secreting beta cells, culminating in beta cell death. However, subsequent studies found that low beta cell mass was a result of reduced cell proliferation, rather than increased apoptosis. Genetic and cellular studies of Perk-deficient beta cells showed that PERK was crucially required for ER functions including proinsulin trafficking and quality control, unrelated to the ER stress pathway. Under normal physiological conditions, changes in ER calcium levels, mediated by glucose and other insulin secretagogues, regulate PERK activity for the purpose of controlling insulin biogenesis.
Collapse
Affiliation(s)
- Douglas R Cavener
- Department of Biology, Center for Cellular Dynamics, Pennsylvania State University, University Park, PA 16802, USA.
| | | | | |
Collapse
|
21
|
Keene JD. Minireview: global regulation and dynamics of ribonucleic Acid. Endocrinology 2010; 151:1391-7. [PMID: 20332203 PMCID: PMC2850242 DOI: 10.1210/en.2009-1250] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/22/2009] [Accepted: 12/29/2009] [Indexed: 01/09/2023]
Abstract
Gene expression starts with transcription and is followed by multiple posttranscriptional processes that carry out the splicing, capping, polyadenylation, and export of each mRNA. Interest in posttranscriptional regulation has increased recently with explosive discoveries of large numbers of noncoding RNAs such as microRNAs, yet posttranscriptional processes depend largely on the functions of RNA-binding proteins as well. Glucocorticoid nuclear receptors are classical examples of environmentally reactive activators and repressors of transcription, but there has also been a significant increase in studies of the role of posttranscriptional regulation in endocrine responses, including insulin and insulin receptors, and parathyroid hormone as well as other hormonal responses, at the levels of RNA stability and translation. On the global level, the transcriptome is defined as the total RNA complement of the genome, and thereby, represents the accumulated levels of all expressed RNAs, because they are each being produced and eventually degraded in either the nucleus or the cytoplasm. In addition to RNA turnover, the many underlying posttranscriptional layers noted above that follow from the transcriptome function within a dynamic ribonucleoprotein (RNP) environment of global RNA-protein and RNA-RNA interactions. With the exception of the spliceosome and the ribosome, thousands of heterodispersed RNP complexes wherein RNAs are dynamically processed, trafficked, and exchanged are heterogeneous in size and composition, thus providing significant challenges to their investigation. Among the diverse RNPs that show dynamic features in the cytoplasm are processing bodies and stress granules as well as a large number of smaller heterogeneous RNPs distributed throughout the cell. Although the localization of functionally related RNAs within these RNPs are responsive to developmental and environmental signals, recent studies have begun to elucidate the global RNA components of RNPs that are dynamically coordinated in response to these signals. Among the factors that have been found to affect coordinated RNA regulation are developmental signals and treatments with small molecule drugs, hormones, and toxins, but this field is just beginning to understand the role of RNA dynamics in these responses.
Collapse
Affiliation(s)
- Jack D Keene
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina 27710, USA.
| |
Collapse
|
22
|
Bisio A, Nasti S, Jordan JJ, Gargiulo S, Pastorino L, Provenzani A, Quattrone A, Queirolo P, Bianchi-Scarrà G, Ghiorzo P, Inga A. Functional analysis of CDKN2A/p16INK4a 5'-UTR variants predisposing to melanoma. Hum Mol Genet 2010; 19:1479-91. [PMID: 20093296 DOI: 10.1093/hmg/ddq022] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Germline CDKN2A mutations are observed in 20-50% of melanoma-prone families. We identified melanoma patients that were heterozygous for non-coding germline variants in the 5'-UTR of CDKN2A (c.-21C > T; c.-25C > T&c.-180G > A; c.-56G > T; c.-67G > C) and examined their impact on the p16(INK4a) 5'-UTR activity using two luciferase-based reporter vectors that differ in basal transcription level and that were transfected into the melanoma-derived WM266-4 and in the breast cancer-derived MCF7 cells. The wild-type 5'-UTR sequence, containing a reported SNP (c.-33G > C) and a known melanoma-predisposing mutation (c.-34G > T), was included as controls. Results revealed that the variants at -21 and -34 severely reduced the reporter activity. The variants at -56 and at -25&-180 exhibited a milder impact, while results with c.-67G > C were dependent on the plasmid type. Quantification of the luciferase mRNA indicated that the effects of the variants were mainly post-transcriptional. Using a bicistronic dual-luciferase reporter plasmid, we confirmed that c.-21C > T and c.-34G > T had a severe negative impact in both cell lines. We also applied a polysomal profiling technique to samples heterozygous for the 5'-UTR variants, including patient-derived lymphoblasts. Analysis of allelic imbalance indicated that in addition to the c.-21C > T variant, the c.-56T > G and c.-67G > C variants also reduced mRNA translation efficiency. Overall, our results suggest that the c.-21C > T sequence variant is a melanoma-predisposing mutation. The c.-25C > T&c.-180G > A and particularly the c.-56G > T variants showed a range of intermediate functional defects in the different assays, and were not observed in the control population. We propose that these variants should be considered as potential mutations.
Collapse
Affiliation(s)
- Alessandra Bisio
- Unit of Molecular Mutagenesis and DNA Repair, National Institute for Cancer Research IST, 16132 Genoa, Italy
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
23
|
Exercise and possible molecular mechanisms of protection from vascular disease and diabetes: the central role of ROS and nitric oxide. Clin Sci (Lond) 2009; 118:341-9. [PMID: 19922417 DOI: 10.1042/cs20090433] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
It is now widely accepted that hypertension and endothelial dysfunction are associated with an insulin-resistant state and thus with the development of T2DM (Type 2 diabetes mellitus). Insulin signalling is impaired in target cells and tissues, indicating that common molecular signals are involved. The free radical NO* regulates cell metabolism, insulin signalling and secretion, vascular tone, neurotransmission and immune system function. NO* synthesis is essential for vasodilation, the maintenance of blood pressure and glucose uptake and, thus, if levels of NO* are decreased, insulin resistance and hypertension will result. Decreased blood levels of insulin, increased AngII (angiotensin II), hyperhomocysteinaemia, increased ADMA (asymmetric omega-NG,NG-dimethylarginine) and low plasma L-arginine are all conditions likely to decrease NO* production and which are associated with diabetes and cardiovascular disease. We suggest in the present article that the widely reported beneficial effects of exercise in the improvement of metabolic and cardiovascular health are mediated by enhancing the flux of muscle- and kidney-derived amino acids to pancreatic and vascular endothelial cells aiding the intracellular production of NO*, therefore resulting in normalization of insulin secretion, vascular tone and insulin sensitivity. Exercise may also have an impact on AngII and ADMA signalling and the production of pro- and anti-inflammatory cytokines in muscle, so reducing the progression and development of vascular disease and diabetes. NO* synthesis will be increased during exercise in the vascular endothelial cells so promoting blood flow. We suggest that exercise may promote improvements in health due to positive metabolic and cytokine-mediated effects.
Collapse
|
24
|
Jonas JC, Bensellam M, Duprez J, Elouil H, Guiot Y, Pascal SMA. Glucose regulation of islet stress responses and beta-cell failure in type 2 diabetes. Diabetes Obes Metab 2009; 11 Suppl 4:65-81. [PMID: 19817790 DOI: 10.1111/j.1463-1326.2009.01112.x] [Citation(s) in RCA: 100] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Pancreatic beta-cells exposed to high glucose concentrations display altered gene expression, function, survival and growth that may contribute to the slow deterioration of the functional beta-cell mass in type 2 diabetes. These glucotoxic alterations may result from various types of stress imposed by the hyperglycaemic environment, including oxidative stress, endoplasmic reticulum stress, cytokine-induced apoptosis and hypoxia. The glucose regulation of oxidative stress-response and integrated stress-response genes in cultured rat islets follows an asymmetric V-shaped profile parallel to that of beta-cell apoptosis, with a large increase at low glucose and a moderate increase at high vs. intermediate glucose concentrations. These observations suggest that both types of stress could play a role in the alteration of the functional beta-cell mass under states of prolonged hypoglycaemia and hyperglycaemia. In addition, beta-cell demise under glucotoxic conditions may also result from beta-cell hypoxia and, in vivo, from their exposure to inflammatory cytokines released locally by non-endocrine islet cells. A better understanding of the relative contribution of each type of stress to beta-cell glucotoxicity and of their pathophysiological cause in vivo may lead to new therapeutic strategies to prevent the slow deterioration of the functional beta-cell mass in glucose intolerant and type 2 diabetic patients.
Collapse
Affiliation(s)
- J C Jonas
- Université catholique de Louvain, Brussels, Belgium.
| | | | | | | | | | | |
Collapse
|
25
|
Mandl J, Mészáros T, Bánhegyi G, Hunyady L, Csala M. Endoplasmic reticulum: nutrient sensor in physiology and pathology. Trends Endocrinol Metab 2009; 20:194-201. [PMID: 19349192 DOI: 10.1016/j.tem.2009.01.003] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/02/2008] [Revised: 01/08/2009] [Accepted: 01/09/2009] [Indexed: 12/23/2022]
Abstract
The endoplasmic reticulum (ER) is a metabolic organelle and an ideal nutrient sensor. In response to hypoglycemia, hyperglycemia or fatty acid overload, the ER triggers the unfolded protein response, which represses protein synthesis, alters insulin responsiveness and favors apoptosis. In addition, the ER affects steroid hormone activation and autophagy. The primary aim of these responses is to adjust the metabolism to environmental changes. Failure of the ER to adapt to changes in nutrient availability can result in a pathological transition in ER functions, as observed in cases of obesity-related diseases. This review highlights the recent evidence that the ER has a prominent role in cellular adaptation, as well as in the pathomechanism of type 2 diabetes.
Collapse
Affiliation(s)
- József Mandl
- Department of Medical Chemistry, Molecular Biology and Pathobiochemistry, Semmelweis University, Budapest, Hungary.
| | | | | | | | | |
Collapse
|
26
|
Bensellam M, Van Lommel L, Overbergh L, Schuit FC, Jonas JC. Cluster analysis of rat pancreatic islet gene mRNA levels after culture in low-, intermediate- and high-glucose concentrations. Diabetologia 2009; 52:463-76. [PMID: 19165461 DOI: 10.1007/s00125-008-1245-z] [Citation(s) in RCA: 84] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/06/2008] [Accepted: 11/19/2008] [Indexed: 10/21/2022]
Abstract
AIMS/HYPOTHESIS Survival and function of insulin-secreting pancreatic beta cells are markedly altered by changes in nutrient availability. In vitro, culture in 10 rather than 2 mmol/l glucose improves rodent beta cell survival and function, whereas glucose concentrations above 10 mmol/l are deleterious. METHODS To identify the mechanisms of such beta cell plasticity, we tested the effects of 18 h culture at 2, 5, 10 and 30 mmol/l glucose on the transcriptome of rat islets pre-cultured for 1 week at 10 mmol/l glucose using Affymetrix Rat 230 2.0 arrays. RESULTS Culture in either 2-5 or 30 mmol/l instead of 10 mmol/l glucose markedly impaired beta cell function, while little affecting cell survival. Of about 16,000 probe-sets reliably detected in islets, some 5,000 were significantly up- or downregulated at least 1.4-fold by glucose. Analysis of these probe-sets with GeneCluster software identified ten mRNA profiles with unidirectional up- or downregulation between 2 and 10, 2 and 30, 5 and 10, 5 and 30 or 10 and 30 mmol/l glucose. It also identified eight complex V-shaped or inverse V-shaped profiles with a nadir or peak level of expression in 5 or 10 mmol/l glucose. Analysis of genes belonging to these various clusters using Onto-express and GenMAPP software revealed several signalling and metabolic pathways that may contribute to induction of beta cell dysfunction and apoptosis after culture in low- or high- vs intermediate-glucose concentration. CONCLUSIONS/INTERPRETATION We have identified 18 distinct mRNA profiles of glucose-induced changes in islet gene mRNA levels that should help understand the mechanisms by which glucose affects beta cell survival and function under states of chronic hypo- or hyperglycaemia.
Collapse
Affiliation(s)
- M Bensellam
- Unit of Endocrinology and Metabolism, Faculty of Medicine, Université catholique de Louvain, Avenue Hippocrate 55 (UCL5530), 1200, Brussels, Belgium
| | | | | | | | | |
Collapse
|
27
|
Simone S, Gorin Y, Velagapudi C, Abboud HE, Habib SL. Mechanism of oxidative DNA damage in diabetes: tuberin inactivation and downregulation of DNA repair enzyme 8-oxo-7,8-dihydro-2'-deoxyguanosine-DNA glycosylase. Diabetes 2008; 57:2626-36. [PMID: 18599524 PMCID: PMC2551671 DOI: 10.2337/db07-1579] [Citation(s) in RCA: 96] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/08/2007] [Accepted: 06/26/2008] [Indexed: 12/29/2022]
Abstract
OBJECTIVE To investigate potential mechanisms of oxidative DNA damage in a rat model of type 1 diabetes and in murine proximal tubular epithelial cells and primary culture of rat proximal tubular epithelial cells. RESEARCH DESIGN AND METHODS Phosphorylation of Akt and tuberin, 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) levels, and 8-oxoG-DNA glycosylase (OGG1) expression were measured in kidney cortical tissue of control and type 1 diabetic animals and in proximal tubular cells incubated with normal or high glucose. RESULTS In the renal cortex of diabetic rats, the increase in Akt phosphorylation is associated with enhanced phosphorylation of tuberin, decreased OGG1 protein expression, and 8-oxodG accumulation. Exposure of proximal tubular epithelial cells to high glucose causes a rapid increase in reactive oxygen species (ROS) generation that correlates with the increase in Akt and tuberin phosphorylation. High glucose also resulted in downregulation of OGG1 protein expression, paralleling its effect on Akt and tuberin. Inhibition of phosphatidylinositol 3-kinase/Akt significantly reduced high glucose-induced tuberin phosphorylation and restored OGG1 expression. Hydrogen peroxide stimulates Akt and tuberin phosphorylation and decreases OGG1 protein expression. The antioxidant N-acetylcysteine significantly inhibited ROS generation, Akt/protein kinase B, and tuberin phosphorylation and resulted in deceased 8-oxodG accumulation and upregulation of OGG1 protein expression. CONCLUSIONS Hyperglycemia in type 1 diabetes and treatment of proximal tubular epithelial cells with high glucose leads to phosphorylation/inactivation of tuberin and downregulation of OGG1 via a redox-dependent activation of Akt in renal tubular epithelial cells. This signaling cascade provides a mechanism of oxidative stress-mediated DNA damage in diabetes.
Collapse
Affiliation(s)
- Simona Simone
- George O'Brien Kidney Research Center, Department of Medicine, Division of Nephrology, University of Texas Health Science Center, San Antonio, Texas
- Department of Emergency and Transplantation, University of Bari, Policlinico, Bari, Italy
| | - Yves Gorin
- George O'Brien Kidney Research Center, Department of Medicine, Division of Nephrology, University of Texas Health Science Center, San Antonio, Texas
| | - Chakradhar Velagapudi
- George O'Brien Kidney Research Center, Department of Medicine, Division of Nephrology, University of Texas Health Science Center, San Antonio, Texas
| | - Hanna E. Abboud
- George O'Brien Kidney Research Center, Department of Medicine, Division of Nephrology, University of Texas Health Science Center, San Antonio, Texas
- South Texas Veterans Healthcare System, Geriatric Research, Education, and Clinical Center, San Antonio, Texas
| | - Samy L. Habib
- George O'Brien Kidney Research Center, Department of Medicine, Division of Nephrology, University of Texas Health Science Center, San Antonio, Texas
- South Texas Veterans Healthcare System, Geriatric Research, Education, and Clinical Center, San Antonio, Texas
| |
Collapse
|
28
|
Abstract
Post-transcriptional regulation of gene expression plays important roles in diverse cellular processes such as development, metabolism and cancer progression. Whereas many classical studies explored the mechanistics and physiological impact on specific mRNA substrates, the recent development of genome-wide analysis tools enables the study of post-transcriptional gene regulation on a global scale. Importantly, these studies revealed distinct programs of RNA regulation, suggesting a complex and versatile post-transcriptional regulatory network. This network is controlled by specific RNA-binding proteins and/or non-coding RNAs, which bind to specific sequence or structural elements in the RNAs and thereby regulate subsets of mRNAs that partly encode functionally related proteins. It will be a future challenge to link the spectra of targets for RNA-binding proteins to post-transcriptional regulatory programs and to reveal its physiological implications.
Collapse
|
29
|
A decrease in cellular energy status stimulates PERK-dependent eIF2alpha phosphorylation and regulates protein synthesis in pancreatic beta-cells. Biochem J 2008; 410:485-93. [PMID: 18052927 DOI: 10.1042/bj20071367] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
In the present study, we demonstrate that, in pancreatic beta-cells, eIF2alpha (eukaryotic initiation factor 2alpha) phosphorylation in response to a decrease in glucose concentration is primarily mediated by the activation of PERK [PKR (protein kinase RNA activated)-like endoplasmic reticulum kinase]. We provide evidence that this increase in PERK activity is evoked by a decrease in the energy status of the cell via a potentially novel mechanism that is independent of IRE1 (inositol requiring enzyme 1) activation and the accumulation of unfolded nascent proteins within the endoplasmic reticulum. The inhibition of eIF2alpha phosphorylation in glucose-deprived cells by the overexpression of dominant-negative PERK or an N-terminal truncation mutant of GADD34 (growth-arrest and DNA-damage-inducible protein 34) leads to a 53% increase in the rate of total protein synthesis. Polysome analysis revealed that this coincides with an increase in the amplitude but not the number of ribosomes per mRNA, indicating that eIF2alpha dephosphorylation mobilizes hitherto untranslated mRNAs on to polysomes. In summary, we show that PERK is activated at low glucose concentrations in response to a decrease in energy status and that this plays an important role in glucose-regulated protein synthesis in pancreatic beta-cells.
Collapse
|
30
|
Abstract
To ensure cellular survival to ER (endoplasmic reticulum) stress, PERK [PKR (double-stranded-RNA-dependent protein kinase)-like ER kinase], an ER transmembrane kinase, is activated as part of the unfolded protein response. PERK is highly expressed in pancreatic beta-cells and is essential in the beta-cell's development, differentiation and function. However, chronic activation of PERK can induce cell death, and its activation has been implicated in both Type 1 and Type 2 diabetes. This short review aims to provide an insight into our current understanding of the role of PERK in the life and death of the beta-cell.
Collapse
|
31
|
Elouil H, Bensellam M, Guiot Y, Vander Mierde D, Pascal SMA, Schuit FC, Jonas JC. Acute nutrient regulation of the unfolded protein response and integrated stress response in cultured rat pancreatic islets. Diabetologia 2007; 50:1442-52. [PMID: 17497122 DOI: 10.1007/s00125-007-0674-4] [Citation(s) in RCA: 114] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/06/2006] [Accepted: 03/05/2007] [Indexed: 01/19/2023]
Abstract
AIMS/HYPOTHESIS Inadequate chaperone function relative to client protein load in the endoplasmic reticulum triggers an adaptive unfolded protein response (UPR), including the integrated stress response (ISR), the latter being also activated by other types of stresses. It is well established that pancreatic beta cells, which synthesise and secrete insulin upon nutrient stimulation, are markedly affected by pathological disruption or excessive activation of the UPR. However, whether and how physiological nutrient stimulation affects the beta cell UPR has been little investigated. MATERIALS AND METHODS We compared the effects of increasing glucose concentrations and of endoplasmic reticulum Ca(2+) emptying with thapsigargin on the UPR (X-box binding protein [Xbp1] mRNA splicing and XBP1/activating transcription factor [ATF] 6-target gene expression) and ISR (eukaryotic translation initiation factor 2A phosphorylation, ATF4 protein levels and target gene expression) in isolated rat islets. RESULTS Thapsigargin strongly increased both UPR and ISR. In comparison, glucose moderately increased the UPR between 5 and 30 mmol/l, but exerted complex effects on the ISR as follows: (1) marked reduction between 2 and 10 mmol/l; (2) moderate increase parallel to the UPR between 10 and 30 mmol/l. These glucose effects occurred within 2 h, were mimicked by other metabolic substrates, but were independent of changes in Ca(2+) influx or insulin secretion. Remarkably, attenuating the glucose stimulation of protein synthesis with a low concentration of cycloheximide prevented UPR activation but not ISR reduction by high glucose. CONCLUSIONS/INTERPRETATION Nutrient stimulation acutely activates rat islet UPR in a manner dependent on protein synthesis, while exerting complex effects on the ISR. These effects may contribute to nutrient-induced maintenance of the beta cell phenotype.
Collapse
Affiliation(s)
- H Elouil
- Unit of Endocrinology and Metabolism, Faculty of Medicine, Université Catholique de Louvain, Avenue Hippocrate, 55 (UCL 55.30), 1200, Brussels, Belgium
| | | | | | | | | | | | | |
Collapse
|
32
|
Newsholme P, Haber EP, Hirabara SM, Rebelato ELO, Procopio J, Morgan D, Oliveira-Emilio HC, Carpinelli AR, Curi R. Diabetes associated cell stress and dysfunction: role of mitochondrial and non-mitochondrial ROS production and activity. J Physiol 2007; 583:9-24. [PMID: 17584843 PMCID: PMC2277225 DOI: 10.1113/jphysiol.2007.135871] [Citation(s) in RCA: 459] [Impact Index Per Article: 27.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
It is now widely accepted, given the current weight of experimental evidence, that reactive oxygen species (ROS) contribute to cell and tissue dysfunction and damage caused by glucolipotoxicity in diabetes. The source of ROS in the insulin secreting pancreatic beta-cells and in the cells which are targets for insulin action has been considered to be the mitochondrial electron transport chain. While this source is undoubtably important, we provide additional information and evidence for NADPH oxidase-dependent generation of ROS both in pancreatic beta-cells and in insulin sensitive cells. While mitochondrial ROS generation may be important for regulation of mitochondrial uncoupling protein (UCP) activity and thus disruption of cellular energy metabolism, the NADPH oxidase associated ROS may alter parameters of signal transduction, insulin secretion, insulin action and cell proliferation or cell death. Thus NADPH oxidase may be a useful target for intervention strategies based on reversing the negative impact of glucolipotoxicity in diabetes.
Collapse
Affiliation(s)
- P Newsholme
- School of Biomolecular and Biomedical Science, Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Belfield, Dublin 4, Ireland.
| | | | | | | | | | | | | | | | | |
Collapse
|