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Bian H, Shao X, Cai W, Fu H. Understanding the Reversible Binding of a Multichain Protein-Protein Complex through Free-Energy Calculations. J Phys Chem B 2024; 128:3598-3604. [PMID: 38574232 DOI: 10.1021/acs.jpcb.4c00519] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/06/2024]
Abstract
We demonstrate that the binding affinity of a multichain protein-protein complex, insulin dimer, can be accurately predicted using a streamlined route of standard binding free-energy calculations. We find that chains A and C, which do not interact directly during binding, stabilize the insulin monomer structures and reduce the binding affinity of the two monomers, therefore enabling their reversible association. Notably, we confirm that although classical methods can estimate the binding affinity of the insulin dimer, conventional molecular dynamics, enhanced sampling algorithms, and classical geometrical routes of binding free-energy calculations may not fully capture certain aspects of the role played by the noninteracting chains in the binding dynamics. Therefore, this study not only elucidates the role of noninteracting chains in the reversible binding of the insulin dimer but also offers a methodological guide for investigating the reversible binding of multichain protein-protein complexes utilizing streamlined free-energy calculations.
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Affiliation(s)
- Hengwei Bian
- Research Center for Analytical Sciences, Tianjin Key Laboratory of Biosensing and Molecular Recognition, State Key Laboratory of Medicinal Chemical Biology, College of Chemistry, Nankai University, Tianjin 300071, China
- Haihe Laboratory of Sustainable Chemical Transformations, Tianjin 300192, China
| | - Xueguang Shao
- Research Center for Analytical Sciences, Tianjin Key Laboratory of Biosensing and Molecular Recognition, State Key Laboratory of Medicinal Chemical Biology, College of Chemistry, Nankai University, Tianjin 300071, China
- Haihe Laboratory of Sustainable Chemical Transformations, Tianjin 300192, China
- School of Materials Science and Engineering, Smart Sensing Interdisciplinary Science Center, Nankai University, Tianjin 300350, China
| | - Wensheng Cai
- Research Center for Analytical Sciences, Tianjin Key Laboratory of Biosensing and Molecular Recognition, State Key Laboratory of Medicinal Chemical Biology, College of Chemistry, Nankai University, Tianjin 300071, China
- Haihe Laboratory of Sustainable Chemical Transformations, Tianjin 300192, China
- School of Materials Science and Engineering, Smart Sensing Interdisciplinary Science Center, Nankai University, Tianjin 300350, China
| | - Haohao Fu
- Research Center for Analytical Sciences, Tianjin Key Laboratory of Biosensing and Molecular Recognition, State Key Laboratory of Medicinal Chemical Biology, College of Chemistry, Nankai University, Tianjin 300071, China
- Haihe Laboratory of Sustainable Chemical Transformations, Tianjin 300192, China
- School of Materials Science and Engineering, Smart Sensing Interdisciplinary Science Center, Nankai University, Tianjin 300350, China
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2
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Arunagiri A, Alam M, Haataja L, Draz H, Alasad B, Samy P, Sadique N, Tong Y, Cai Y, Shakeri H, Fantuzzi F, Ibrahim H, Jang I, Sidarala V, Soleimanpour SA, Satin LS, Otonkoski T, Cnop M, Itkin‐Ansari P, Kaufman RJ, Liu M, Arvan P. Proinsulin folding and trafficking defects trigger a common pathological disturbance of endoplasmic reticulum homeostasis. Protein Sci 2024; 33:e4949. [PMID: 38511500 PMCID: PMC10955614 DOI: 10.1002/pro.4949] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2023] [Revised: 01/23/2024] [Accepted: 02/14/2024] [Indexed: 03/22/2024]
Abstract
Primary defects in folding of mutant proinsulin can cause dominant-negative proinsulin accumulation in the endoplasmic reticulum (ER), impaired anterograde proinsulin trafficking, perturbed ER homeostasis, diminished insulin production, and β-cell dysfunction. Conversely, if primary impairment of ER-to-Golgi trafficking (which also perturbs ER homeostasis) drives misfolding of nonmutant proinsulin-this might suggest bi-directional entry into a common pathological phenotype (proinsulin misfolding, perturbed ER homeostasis, and deficient ER export of proinsulin) that can culminate in diminished insulin storage and diabetes. Here, we've challenged β-cells with conditions that impair ER-to-Golgi trafficking, and devised an accurate means to assess the relative abundance of distinct folded/misfolded forms of proinsulin using a novel nonreducing SDS-PAGE/immunoblotting protocol. We confirm abundant proinsulin misfolding upon introduction of a diabetogenic INS mutation, or in the islets of db/db mice. Whereas blockade of proinsulin trafficking in Golgi/post-Golgi compartments results in intracellular accumulation of properly-folded proinsulin (bearing native disulfide bonds), impairment of ER-to-Golgi trafficking (regardless whether such impairment is achieved by genetic or pharmacologic means) results in decreased native proinsulin with more misfolded proinsulin. Remarkably, reversible ER-to-Golgi transport defects (such as treatment with brefeldin A or cellular energy depletion) upon reversal quickly restore the ER folding environment, resulting in the disappearance of pre-existing misfolded proinsulin while preserving proinsulin bearing native disulfide bonds. Thus, proper homeostatic balance of ER-to-Golgi trafficking is linked to a more favorable proinsulin folding (as well as trafficking) outcome.
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Affiliation(s)
- Anoop Arunagiri
- Division of Metabolism, Endocrinology & DiabetesUniversity of Michigan Medical CenterAnn ArborMichiganUSA
| | - Maroof Alam
- Division of Metabolism, Endocrinology & DiabetesUniversity of Michigan Medical CenterAnn ArborMichiganUSA
| | - Leena Haataja
- Division of Metabolism, Endocrinology & DiabetesUniversity of Michigan Medical CenterAnn ArborMichiganUSA
| | - Hassan Draz
- Division of Metabolism, Endocrinology & DiabetesUniversity of Michigan Medical CenterAnn ArborMichiganUSA
| | - Bashiyer Alasad
- Division of Metabolism, Endocrinology & DiabetesUniversity of Michigan Medical CenterAnn ArborMichiganUSA
| | - Praveen Samy
- Division of Metabolism, Endocrinology & DiabetesUniversity of Michigan Medical CenterAnn ArborMichiganUSA
| | - Nadeed Sadique
- Division of Metabolism, Endocrinology & DiabetesUniversity of Michigan Medical CenterAnn ArborMichiganUSA
| | - Yue Tong
- ULB Center for Diabetes Research, Medical Faculty; and Division of EndocrinologyErasmus Hospital, Universite Libre de BruxellesBrusselsBelgium
| | - Ying Cai
- ULB Center for Diabetes Research, Medical Faculty; and Division of EndocrinologyErasmus Hospital, Universite Libre de BruxellesBrusselsBelgium
| | - Hadis Shakeri
- ULB Center for Diabetes Research, Medical Faculty; and Division of EndocrinologyErasmus Hospital, Universite Libre de BruxellesBrusselsBelgium
| | - Federica Fantuzzi
- ULB Center for Diabetes Research, Medical Faculty; and Division of EndocrinologyErasmus Hospital, Universite Libre de BruxellesBrusselsBelgium
| | - Hazem Ibrahim
- Stem Cells and Metabolism Research Program, Faculty of MedicineUniversity of HelsinkiHelsinkiFinland
| | - Insook Jang
- Degenerative Diseases ProgramCenter for Genetic Disorders and Aging Research, Sanford Burnham Prebys Medical Discovery InstituteLa JollaCaliforniaUSA
| | - Vaibhav Sidarala
- Division of Metabolism, Endocrinology & DiabetesUniversity of Michigan Medical CenterAnn ArborMichiganUSA
| | - Scott A. Soleimanpour
- Division of Metabolism, Endocrinology & DiabetesUniversity of Michigan Medical CenterAnn ArborMichiganUSA
| | - Leslie S. Satin
- Department of PharmacologyUniversity of Michigan Medical SchoolAnn ArborMichiganUSA
| | - Timo Otonkoski
- Stem Cells and Metabolism Research Program, Faculty of MedicineUniversity of HelsinkiHelsinkiFinland
| | - Miriam Cnop
- ULB Center for Diabetes Research, Medical Faculty; and Division of EndocrinologyErasmus Hospital, Universite Libre de BruxellesBrusselsBelgium
| | - Pamela Itkin‐Ansari
- Development, Aging and Regeneration ProgramCenter for Genetic Disorders and Aging Research, Sanford Burnham Prebys Medical Discovery InstituteLa JollaCaliforniaUSA
| | - Randal J. Kaufman
- Degenerative Diseases ProgramCenter for Genetic Disorders and Aging Research, Sanford Burnham Prebys Medical Discovery InstituteLa JollaCaliforniaUSA
| | - Ming Liu
- Department of Endocrinology and MetabolismTianjin Medical University General HospitalTianjinChina
| | - Peter Arvan
- Division of Metabolism, Endocrinology & DiabetesUniversity of Michigan Medical CenterAnn ArborMichiganUSA
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3
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Campelo F, Tian M, von Blume J. Rediscovering the intricacies of secretory granule biogenesis. Curr Opin Cell Biol 2023; 85:102231. [PMID: 37657367 DOI: 10.1016/j.ceb.2023.102231] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2023] [Revised: 08/01/2023] [Accepted: 08/07/2023] [Indexed: 09/03/2023]
Abstract
Regulated secretion, an essential cellular process, relies on secretory granules (SGs) for the controlled release of a diverse range of cargo molecules, including proteins, peptides, hormones, enzymes, and neurotransmitters. SG biogenesis encompasses cargo selection, sorting, packaging, and trafficking, with the trans-Golgi Network (TGN) playing a central role. Research in the last three decades has revealed significant components required for SG biogenesis; however, no cargo receptor transferring granule cargo from the TGN to immature SGs (ISGs) has yet been identified. Consequently, recent research has devoted significant attention to studying receptor-independent cargo sorting mechanisms, shedding new light on the complexities of regulated secretion. Understanding the underlying molecular and biophysical mechanisms behind cargo sorting into ISGs holds great promise for advancing our knowledge of cellular communication and disease mechanisms.
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Affiliation(s)
- Felix Campelo
- ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, 08860, Castelldefels, Barcelona, Spain
| | - Meng Tian
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA
| | - Julia von Blume
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA.
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Ghaedi K, Ghasempour D, Jowshan M, Zheng M, Ghobadi S, Jafari A. Effect of zinc supplementation in the management of type 2 diabetes: A grading of recommendations assessment, development, and evaluation-assessed, dose-response meta-analysis of randomized controlled trials. Crit Rev Food Sci Nutr 2023:1-12. [PMID: 37183697 DOI: 10.1080/10408398.2023.2209802] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
The question of whether zinc supplementation may improve cardio-metabolic health in patients with type 2 diabetes mellitus (T2DM) remains controversial and require further evaluation. This study aimed to summarize the effectiveness of oral zinc supplementation in improving cardio-metabolic risk markers in people with T2DM. We searched PubMed, Scopus, and Web of Science from inception to April 2023, for randomized controlled trials (RCTs). RCTs of type 2 diabetic adults (aged ≥18 years) comparing zinc supplementation with placebo were included. We excluded studies if not randomized, involved co-supplementation, and were conducted in children or pregnant women. Glycemic indices, lipid profiles, blood pressure, anthropometric measure, c-reactive protein (CRP), creatinine, and serum zinc were extracted. Certainty of evidence was assessed using the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) methods. We used a random-effect model to perform the dose-response analysis. Effect sizes were presented as mean difference (MD) and 95% confidence interval (CI). 22 studies (n = 1442 participants) were included. The certainty of the evidence was rated as moderate to high. Zinc supplementation significantly reduced glycemic indices: including two-hour postprandial glucose (2hpp) (mean difference (MD): -34.34 mg/dl; 95%CI: -51.61∼ -17.07), fast blood sugar (FBS) (MD: -23.32 mg/dl; 95% CI: -33.81∼ -12.83), and hemoglobin A1c (HbA1c) (MD: -0.47; 95% CI: -0.71∼ -0.23). Zinc had a favorable effect on lipid profiles low-density lipoprotein (LDL) (MD: -10.76 mg/dl; CI: -17.79∼-3.73), triglyceride (TG) (MD: -18.23 mg/dl; CI: -32.81∼-3.65), total cholesterol (TC) (MD: -12.74 mg/dl; CI: -21.68∼-3.80), VLDL (MD: -5.39 mg/dl; CI: -7.35∼-3.43) and high-density lipoprotein (HDL) (MD: 4.04 mg/dl; CI: 0.96 ∼ 7.12). Systolic blood pressure (SBP) (MD): -3.64 mmHg; 95% CI: -6.77∼ -0.52), weight (MD: 1.00 kg; 95% CI: 0.34∼1.66), CRP (MD: -3.37 mg/l, 95% CI: -4.05∼ -2.70), and serum zinc (MD: 15.38 µg/dl; 95% CI: 10.74∼ 20.02) changed to a statistically significant extent with zinc supplementation. There was also a linear association between additional 10 mg/d zinc treatment with FBS, HbA1c, HDL, LDL, TG, TC, and serum zinc. A non-linear dose-response gradient was seen for FBS, HDL, and SBP (p < 0.05). Egger's test showed no substantial publication bias. Our findings strongly suggest a potential beneficial effect of zinc supplementation on type 2 diabetic patients. Further high-quality research is needed to determine the optimal form, dosage, and duration of zinc supplementation for this population.
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Affiliation(s)
- Kimia Ghaedi
- Student Research Committee, Shiraz University of Medical Sciences, Shiraz, Iran
| | - Dorsa Ghasempour
- Student Research Committee, Shiraz University of Medical Sciences, Shiraz, Iran
| | - Mohammadreza Jowshan
- Department of Clinical Nutrition, School of Nutritional Sciences and Dietetics, Tehran University of Medical Sciences, Tehran, Iran
| | - Miaobing Zheng
- Institute for Physical Activity and Nutrition, School of Exercise and Nutrition Sciences, Deakin University, Melbourne, Victoria, Australia
| | - Saeed Ghobadi
- Institute for Physical Activity and Nutrition, School of Exercise and Nutrition Sciences, Deakin University, Melbourne, Victoria, Australia
| | - Alireza Jafari
- Physiology Research Center, Institute of Neuropharmacology, Kerman University of Medical Sciences, Kerman, Iran
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Limanaqi F, Vicentini C, Saulle I, Clerici M, Biasin M. The role of endoplasmic reticulum aminopeptidases in type 1 diabetes mellitus. Life Sci 2023; 323:121701. [PMID: 37059356 DOI: 10.1016/j.lfs.2023.121701] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2023] [Revised: 04/05/2023] [Accepted: 04/11/2023] [Indexed: 04/16/2023]
Abstract
Type-I diabetes mellitus (T1DM) is generally considered as a chronic, T-cell mediated autoimmune disease. This notwithstanding, both the endogenous characteristics of β-cells, and their response to environmental factors and exogenous inflammatory stimuli are key events in disease progression and exacerbation. As such, T1DM is now recognized as a multifactorial condition, with its onset being influenced by both genetic predisposition and environmental factors, among which, viral infections represent major triggers. In this frame, endoplasmic reticulum aminopeptidase 1 (ERAP1) and 2 (ERAP2) hold center stage. ERAPs represent the main hydrolytic enzymes specialized in trimming of N-terminal antigen peptides to be bound by MHC class I molecules and presented to CD8+ T cells. Thus, abnormalities in ERAPs expression alter the peptide-MHC-I repertoire both quantitatively and qualitatively, fostering both autoimmune and infectious diseases. Although only a few studies succeeded in determining direct associations between ERAPs variants and T1DM susceptibility/outbreak, alterations of ERAPs do impinge on a plethora of biological events which might indeed contribute to the disease development/exacerbation. Beyond abnormal self-antigen peptide trimming, these include preproinsulin processing, nitric oxide (NO) production, ER stress, cytokine responsiveness, and immune cell recruitment/activity. The present review brings together direct and indirect evidence focused on the immunobiological role of ERAPs in T1DM onset and progression, covering both genetic and environmental aspects.
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Affiliation(s)
- Fiona Limanaqi
- Department of Biomedical and Clinical Sciences, University of Milan, Via G.B. Grassi, 20122 Milan, Italy; Department of Pathophysiology and Transplantation, University of Milan, Via Francesco Sforza, 20122 Milan, Italy
| | - Chiara Vicentini
- Department of Biomedical and Clinical Sciences, University of Milan, Via G.B. Grassi, 20122 Milan, Italy
| | - Irma Saulle
- Department of Biomedical and Clinical Sciences, University of Milan, Via G.B. Grassi, 20122 Milan, Italy; Department of Pathophysiology and Transplantation, University of Milan, Via Francesco Sforza, 20122 Milan, Italy
| | - Mario Clerici
- Department of Pathophysiology and Transplantation, University of Milan, Via Francesco Sforza, 20122 Milan, Italy; Don C. Gnocchi Foundation, Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS) Foundation, Via A. Capecelatro 66, 20148 Milan, Italy
| | - Mara Biasin
- Department of Biomedical and Clinical Sciences, University of Milan, Via G.B. Grassi, 20122 Milan, Italy.
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Paldino G, Fierabracci A. Shedding new light on the role of ERAP1 in Type 1 diabetes: A perspective on disease management. Autoimmun Rev 2023; 22:103291. [PMID: 36740089 DOI: 10.1016/j.autrev.2023.103291] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2023] [Accepted: 02/01/2023] [Indexed: 02/05/2023]
Abstract
Type 1 diabetes mellitus (T1D) is a multifactorial organ specific autoimmune disease which originates from the destruction of insulin-producing beta cells within the pancreatic islets by autoreactive CD8+ T lymphocytes. The autoimmune responses are raised against autoantigenic peptides presented in the context of the Major Histocompatibility Complex (MHC) class I molecules. Peptides are generated in the cytoplasm of the beta cell by degradation through the proteasome activity and other proteases. Proteolytic intermediate protein fragments are then vehicled into the endoplasmic reticulum (ER) by transporters associated with antigen processing TAP1 and TAP2. In the ER, Endoplasmic Reticulum Aminopeptidase 1 (ERAP1) and 2 (ERAP2) shape the intermediate proteins to produce the optimal peptide size for loading into the MHC class I molecules. Subsequently complexes are shuttled to the cell surface for antigen presentation. Genome Wide Association Studies (GWAS) have identified different SNPs of ERAP1 associated to several autoimmune diseases and in particular the T1D-related ERAP1 SNP rs30187 encoding for K528R ERAP1. An association between the ER stress and the increased exposure of beta cells to the immune system has been hypothesized to further contribute to the etiopathogenesis. In particular in a recent study by Thomaidou et al. 2020 (doi: https://doi.org/10.2337/db19-0984) the posttranscriptional regulation of ERAP1 is shown to shaping the recognition of the preproinsulin (PPI) signal peptide by cytotoxic T lymphocytes. In the light of foregoing ERAP1 inhibitors could potentially prevent the activation of epitope-specific autoimmune-promoting T cells and their cytokine production; further regulating ERAP1 expression at posttranscriptional level under stress conditions of the beta cells could help to reverse autoimmune process through limiting epitope-presentation to autoreactive T cells. In this article we provide a perspective on the role of ERAP1 as implicated in the pathogenesis of insulin-dependent diabetes mellitus by reviewing studies reported in literature and discussing our own experimental evidence.
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Mendonca A, Thandapani P, Nagarajan P, Venkatesh S, Sundaresan S. Role of microRNAs in regulation of insulin secretion and insulin signaling involved in type 2 diabetes mellitus. J Biosci 2022. [DOI: 10.1007/s12038-022-00295-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
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Rahman MM, Dhar PS, Sumaia, Anika F, Ahmed L, Islam MR, Sultana NA, Cavalu S, Pop O, Rauf A. Exploring the plant-derived bioactive substances as antidiabetic agent: An extensive review. Biomed Pharmacother 2022; 152:113217. [PMID: 35679719 DOI: 10.1016/j.biopha.2022.113217] [Citation(s) in RCA: 42] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2022] [Revised: 05/25/2022] [Accepted: 05/26/2022] [Indexed: 11/24/2022] Open
Abstract
Diabetes mellitus (DM) is a metabolic syndrome. Diabetes has become more common in recent years. Chemically generated drugs are used to lessen the effects of DM and its following repercussions due to unpleasant side effects such as weight gain, gastrointestinal issues, and heart failure. On the other hand, medicinal plants could be a good source of anti-diabetic medications. This article aims to determine any plant matrix's positive potential. Food restriction, physical activity, and the use of antidiabetic plant-derived chemicals are all being promoted as effective ways to manage diabetes because they are less expensive and have fewer or no side effects. This review focuses on antidiabetic plants, along with their bioactive constituent, chemically characterization, and plant-based diets for diabetes management. There is minimal scientific data about the mechanism of action of the plant-based product has been found. The purpose of this article is to highlight anti-diabetic plants and plant-derived bioactive compounds that have anti-diabetic properties. It also provides researchers with data that may be used to build future strategies, such as identifying promising bioactive molecules to make diabetes management easier.
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Affiliation(s)
- Md Mominur Rahman
- Department of Pharmacy, Faculty of Allied Health Sciences, Daffodil International University, Dhaka 1207, Bangladesh
| | - Puja Sutro Dhar
- Department of Pharmacy, Faculty of Allied Health Sciences, Daffodil International University, Dhaka 1207, Bangladesh
| | - Sumaia
- Department of Pharmacy, Faculty of Allied Health Sciences, Daffodil International University, Dhaka 1207, Bangladesh
| | - Fazilatunnesa Anika
- Department of Pharmacy, Faculty of Allied Health Sciences, Daffodil International University, Dhaka 1207, Bangladesh
| | - Limon Ahmed
- Department of Pharmacy, Faculty of Allied Health Sciences, Daffodil International University, Dhaka 1207, Bangladesh
| | - Md Rezaul Islam
- Department of Pharmacy, Faculty of Allied Health Sciences, Daffodil International University, Dhaka 1207, Bangladesh
| | - Nazneen Ahmeda Sultana
- Department of Pharmacy, Faculty of Allied Health Sciences, Daffodil International University, Dhaka 1207, Bangladesh
| | - Simona Cavalu
- Faculty of Medicine and Pharmacy, University of Oradea, P-ta 1 Decembrie 10, 410087 Oradea, Romania
| | - Ovidiu Pop
- Faculty of Medicine and Pharmacy, University of Oradea, P-ta 1 Decembrie 10, 410087 Oradea, Romania.
| | - Abdur Rauf
- Department of Chemistry, University of Swabi, Anbar, Swabi, KPK, Pakistan.
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Attia JR, Holliday E, Weaver N, Peel R, Fleming KC, Hure A, Wiggers J, McEvoy M, Searles A, Reeves P, Ranasinghe P, Jayawardena R, Samman S, Luu J, Rissel C, Acharya S. The effect of zinc supplementation on glucose homeostasis: a randomised double-blind placebo-controlled trial. Acta Diabetol 2022; 59:965-975. [PMID: 35451678 PMCID: PMC9026040 DOI: 10.1007/s00592-022-01888-x] [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: 03/03/2022] [Accepted: 03/30/2022] [Indexed: 11/29/2022]
Abstract
AIMS The burden and health costs of Type 2 Diabetes Mellitus continue to increase globally and prevention strategies in at-risk people need to be explored. Previous work, in both animal models and humans, supports the role of zinc in improving glucose homeostasis. We, therefore, aimed to test the effectiveness of zinc supplementation on glycaemic control in pre-diabetic adults. METHODS We conducted a randomized, double-blind, placebo-controlled trial across 10 General Practitioner (GP) practices in NSW, Australia. The trial is known as Zinc in Preventing the Progression of pre-Diabetes (ZIPPeD)Study. Pre-diabetic (haemoglobin A1c [HbA1c] 5.7-6.4%, 39-46 mmol/mol) men and women (N = 98) were all assigned to a free state government telephone health coaching service (New South Wales Get Healthy Information and Coaching Service) and then randomised to either daily 30 mg zinc gluconate or placebo. Blood tests were collected at baseline, 1, 6 and 12 months for the primary outcomes (HbA1c, fasting blood glucose (FBG)); secondary outcomes included Homeostasis Model Assessment 2 (HOMA 2) parameters, lipids, body weight, height, waist circumference, blood pressure and pulse. RESULTS The baseline-adjusted mean group difference at 6 months, expressed as treatment-placebo, (95% CI) was -0.02 (-0.14, 0.11, p = 0.78) for HbA1c and 0.17 (-0.07, 0.42; p = 0.17) for FBG, neither of which were statistically significant. There were also no significant differences between groups in any of the secondary outcomes. Zinc was well tolerated, and compliance was high (88%). CONCLUSION We believe our results are consistent with other Western clinical trial studies and do not support the use of supplemental zinc in populations with a Western diet. There may still be a role for supplemental zinc in the developing world where diets may be zinc deficient. TRIAL REGISTRATION Australian and New Zealand Clinical Trials Registry, ACTRN12618001120268. Registered on 6 July 2018.
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Affiliation(s)
- John R Attia
- School of Medicine and Public Health, University of Newcastle, New Lambton Heights, Australia.
- Division of Medicine, Hunter New England Local Health District, New Lambton Heights, Australia.
| | - Elizabeth Holliday
- School of Medicine and Public Health, University of Newcastle, New Lambton Heights, Australia
| | - Natasha Weaver
- School of Medicine and Public Health, University of Newcastle, New Lambton Heights, Australia
| | - Roseanne Peel
- School of Medicine and Public Health, University of Newcastle, New Lambton Heights, Australia
| | - Kerry C Fleming
- School of Medicine and Public Health, University of Newcastle, New Lambton Heights, Australia
| | - Alexis Hure
- Diabetes Service and Diabetes Alliance Hunter New England Local Health District, New Lambton Heights, Australia
| | - John Wiggers
- School of Medicine and Public Health, University of Newcastle, New Lambton Heights, Australia
- Hunter New England Local Health District, New Lambton Heights, Australia
| | - Mark McEvoy
- School of Medicine and Public Health, University of Newcastle, New Lambton Heights, Australia
- La Trobe Rural Health School, College of Science, Health and Engineering, La Trobe University, Bendigo, VIC, Australia
| | - Andrew Searles
- Hunter Medical Research Institute, New Lambton Heights, Australia
| | - Penny Reeves
- Hunter Medical Research Institute, New Lambton Heights, Australia
| | | | | | - Samir Samman
- School of Life and Environmental Sciences, University of Sydney, New Lambton Heights, Australia
| | - Judy Luu
- Diabetes Stream, Diabetes Alliance HNELHD, New Lambton Heights, Australia
| | - Chris Rissel
- The University of Sydney, Camperdown, 2050, Australia
| | - Shamasunder Acharya
- Endocrinology and Diabetes Service and Diabetes Alliance Hunter New England Local Health District, New Lambton Heights, Australia
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Cargo receptor Surf4 regulates endoplasmic reticulum export of proinsulin in pancreatic β-cells. Commun Biol 2022; 5:458. [PMID: 35562580 PMCID: PMC9106718 DOI: 10.1038/s42003-022-03417-6] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2021] [Accepted: 04/26/2022] [Indexed: 11/08/2022] Open
Abstract
Insulin is an essential peptide hormone that maintains blood glucose levels. Although the mechanisms underlying insulin exocytosis have been investigated, the mechanism of proinsulin export from the endoplasmic reticulum (ER) remains unclear. Here, we demonstrated that Surf4, a cargo receptor homolog, regulates the ER export of proinsulin via its recruitment to ER exit sites (ERES). Under high-glucose conditions, Surf4 expression was upregulated, and Surf4 proteins mainly localized to the ER at a steady state and accumulated in the ERES, along with proinsulin in rat insulinoma INS-1 cells. Surf4-knockdown resulted in proinsulin retention in the ER and decreased the levels of mature insulin in secretory granules, thereby significantly reducing insulin secretion. Surf4 forms an oligomer and can physically interact with proinsulin and Sec12, essential for COPII vesicle formation. Our findings suggest that Surf4 interacts with proinsulin and delivers it into COPII vesicles for ER export in co-operation with Sec12 and COPII.
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Amirruddin NS, Tan WX, Tan YS, Gardner DSL, Bee YM, Verma CS, Hoon S, Lee KO, Teo AKK. Progressive endoplasmic reticulum stress over time due to human insulin gene mutation contributes to pancreatic beta cell dysfunction. Diabetologia 2021; 64:2534-2549. [PMID: 34448879 DOI: 10.1007/s00125-021-05530-3] [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: 12/11/2020] [Accepted: 05/14/2021] [Indexed: 10/20/2022]
Abstract
AIMS/HYPOTHESIS We studied the effects of heterozygous human INS gene mutations on insulin secretion, endoplasmic reticulum (ER) stress and other mechanisms in both MIN6 and human induced pluripotent stem cells (hiPSC)-derived beta-like cells, as well as the effects of prolonged overexpression of mutant human INS in MIN6 cells. METHODS We modelled the structure of mutant C109Y and G32V proinsulin computationally to examine the in silico effects. We then overexpressed either wild-type (WT), mutant (C109Y or G32V), or both WT and mutant human preproinsulin in MIN6 cells, both transiently and stably over several weeks. We measured the levels of human and rodent insulin secreted, and examined the transcript and protein levels of several ER stress and apoptotic markers. We also reprogrammed human donor fibroblasts heterozygous for the C109Y mutation into hiPSCs and differentiated these into pancreatic beta-like cells, which were subjected to single-cell RNA-sequencing and transcript and protein analyses for ER stress and apoptotic markers. RESULTS The computational modelling studies, and short-term and long-term expression studies in beta cells, revealed the presence of ER stress, organelle changes and insulin processing defects, resulting in a decreased amount of insulin secreted but not the ability to secrete insulin. By 9 weeks of expression of mutant human INS, dominant-negative effects of mutant INS were evident and beta cell insulin secretory capacity declined. INS+/C109Y patient-derived beta-like cells and single-cell RNA-sequencing analyses then revealed compensatory upregulation in genes involved in insulin secretion, processing and inflammatory response. CONCLUSIONS/INTERPRETATION The results provide deeper insights into the mechanisms of beta cell failure during INS mutation-mediated diabetes disease progression. Decreasing spliced X-box binding protein 1 (sXBP1) or inflammatory response could be avenues to restore the function of the remaining WT INS allele.
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Affiliation(s)
- Nur Shabrina Amirruddin
- Stem Cells and Diabetes Laboratory, Institute of Molecular and Cell Biology (IMCB), Agency for Science, Technology and Research (A*STAR), Singapore, Republic of Singapore
- Department of Medicine, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Republic of Singapore
| | - Wei Xuan Tan
- Stem Cells and Diabetes Laboratory, Institute of Molecular and Cell Biology (IMCB), Agency for Science, Technology and Research (A*STAR), Singapore, Republic of Singapore
- Department of Medicine, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Republic of Singapore
| | - Yaw Sing Tan
- Bioinformatics Institute, A*STAR, Singapore, Republic of Singapore
| | - Daphne Su-Lyn Gardner
- Department of Endocrinology, Singapore General Hospital, Singapore, Republic of Singapore
| | - Yong Mong Bee
- Department of Endocrinology, Singapore General Hospital, Singapore, Republic of Singapore
| | - Chandra Shekhar Verma
- Bioinformatics Institute, A*STAR, Singapore, Republic of Singapore
- Department of Biological Sciences, National University of Singapore, Singapore, Republic of Singapore
- School of Biological Sciences, Nanyang Technological University, Singapore, Republic of Singapore
| | - Shawn Hoon
- Molecular Engineering Laboratory, IMCB, A*STAR, Singapore, Republic of Singapore
| | - Kok Onn Lee
- Department of Medicine, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Republic of Singapore
| | - Adrian Kee Keong Teo
- Stem Cells and Diabetes Laboratory, Institute of Molecular and Cell Biology (IMCB), Agency for Science, Technology and Research (A*STAR), Singapore, Republic of Singapore.
- Department of Medicine, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Republic of Singapore.
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Republic of Singapore.
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12
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Dhayalan B, Chatterjee D, Chen YS, Weiss MA. Structural Lessons From the Mutant Proinsulin Syndrome. Front Endocrinol (Lausanne) 2021; 12:754693. [PMID: 34659132 PMCID: PMC8514764 DOI: 10.3389/fendo.2021.754693] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/06/2021] [Accepted: 09/13/2021] [Indexed: 12/30/2022] Open
Abstract
Insight into folding mechanisms of proinsulin has been provided by analysis of dominant diabetes-associated mutations in the human insulin gene (INS). Such mutations cause pancreatic β-cell dysfunction due to toxic misfolding of a mutant proinsulin and impairment in trans of wild-type insulin secretion. Anticipated by the "Akita" mouse (a classical model of monogenic diabetes mellitus; DM), this syndrome illustrates the paradigm endoreticulum (ER) stress leading to intracellular proteotoxicity. Diverse clinical mutations directly or indirectly perturb native disulfide pairing leading to protein misfolding and aberrant aggregation. Although most introduce or remove a cysteine (Cys; leading in either case to an unpaired thiol group), non-Cys-related mutations identify key determinants of folding efficiency. Studies of such mutations suggest that the hormone's evolution has been constrained not only by structure-function relationships, but also by the susceptibility of its single-chain precursor to impaired foldability. An intriguing hypothesis posits that INS overexpression in response to peripheral insulin resistance likewise leads to chronic ER stress and β-cell dysfunction in the natural history of non-syndromic Type 2 DM. Cryptic contributions of conserved residues to folding efficiency, as uncovered by rare genetic variants, define molecular links between biophysical principles and the emerging paradigm of Darwinian medicine: Biosynthesis of proinsulin at the edge of non-foldability provides a key determinant of "diabesity" as a pandemic disease of civilization.
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Affiliation(s)
| | | | | | - Michael A. Weiss
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN, United States
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13
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Germanos M, Gao A, Taper M, Yau B, Kebede MA. Inside the Insulin Secretory Granule. Metabolites 2021; 11:metabo11080515. [PMID: 34436456 PMCID: PMC8401130 DOI: 10.3390/metabo11080515] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2021] [Revised: 08/03/2021] [Accepted: 08/03/2021] [Indexed: 12/19/2022] Open
Abstract
The pancreatic β-cell is purpose-built for the production and secretion of insulin, the only hormone that can remove glucose from the bloodstream. Insulin is kept inside miniature membrane-bound storage compartments known as secretory granules (SGs), and these specialized organelles can readily fuse with the plasma membrane upon cellular stimulation to release insulin. Insulin is synthesized in the endoplasmic reticulum (ER) as a biologically inactive precursor, proinsulin, along with several other proteins that will also become members of the insulin SG. Their coordinated synthesis enables synchronized transit through the ER and Golgi apparatus for congregation at the trans-Golgi network, the initiating site of SG biogenesis. Here, proinsulin and its constituents enter the SG where conditions are optimized for proinsulin processing into insulin and subsequent insulin storage. A healthy β-cell is continually generating SGs to supply insulin in vast excess to what is secreted. Conversely, in type 2 diabetes (T2D), the inability of failing β-cells to secrete may be due to the limited biosynthesis of new insulin. Factors that drive the formation and maturation of SGs and thus the production of insulin are therefore critical for systemic glucose control. Here, we detail the formative hours of the insulin SG from the luminal perspective. We do this by mapping the journey of individual members of the SG as they contribute to its genesis.
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14
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Dhayalan B, Chatterjee D, Chen YS, Weiss MA. Diabetes mellitus due to toxic misfolding of proinsulin variants. Mol Metab 2021:101229. [PMID: 33823319 DOI: 10.1016/j.molmet.2021.101229] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/14/2020] [Revised: 03/10/2021] [Accepted: 03/29/2021] [Indexed: 02/06/2023] Open
Abstract
BACKGROUND Dominant mutations in the human insulin gene (INS) lead to pancreatic β-cell dysfunction and diabetes mellitus (DM) due to toxic misfolding of a mutant proinsulin. Analogous to a classical mouse model of monogenic DM ("Akita"), this syndrome highlights the susceptibility of β-cells to endoreticulum (ER) stress due to protein misfolding and aberrant aggregation. SCOPE OF REVIEW Diverse clinical mutations directly or indirectly perturb native disulfide pairing. Whereas most introduce or remove a cysteine (Cys; leading in either case to an unpaired thiol group), non-Cys-related mutations identify key determinants of folding efficiency. Studies of such mutations suggest that the hormone's evolution has been constrained not only by structure-function relationships but also by the susceptibility of its single-chain precursor to impaired foldability. An intriguing hypothesis posits that INS overexpression in response to peripheral insulin resistance likewise leads to chronic ER stress and β-cell dysfunction in the natural history of nonsyndromic Type 2 DM. MAJOR CONCLUSIONS Cryptic contributions of conserved residues to folding efficiency, as uncovered by rare genetic variants, define molecular links between biophysical principles and the emerging paradigm of Darwinian medicine: Biosynthesis of proinsulin at the edge of nonfoldability provides a key determinant of "diabesity" as a pandemic disease of civilization.
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Affiliation(s)
- Balamurugan Dhayalan
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Deepak Chatterjee
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Yen-Shan Chen
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Michael A Weiss
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN 46202, USA.
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15
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Sexual hormones and diabetes: The impact of estradiol in pancreatic β cell. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2021. [PMID: 33832654 DOI: 10.1016/bs.ircmb.2021.02.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/13/2023]
Abstract
Diabetes is one of the most prevalent metabolic diseases and its incidence is increasing throughout the world. Data from World Health Organization (WHO) point-out that diabetes is a major cause of blindness, kidney failure, heart attacks, stroke and lower limb amputation and estimated 1.6 million deaths were directly caused by it in 2016. Population studies show that the incidence of this disease increases in women after menopause, when the production of estrogen is decreasing in them. Knowing the impact that estrogenic signaling has on insulin-secreting β cells is key to prevention and design of new therapeutic targets. This chapter explores the role of estrogen and their receptors in the regulation of insulin secretion and biosynthesis, proliferation, regeneration and survival in pancreatic β cells. In addition, delves into the genetic animal models developed and its application for the specific study of the different estrogen signaling pathways. Finally, discusses the impact of menopause and hormone replacement therapy on pancreatic β cell function.
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16
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Cottet-Dumoulin D, Lavallard V, Lebreton F, Wassmer CH, Bellofatto K, Parnaud G, Berishvili E, Berney T, Bosco D. Biosynthetic Activity Differs Between Islet Cell Types and in Beta Cells Is Modulated by Glucose and Not by Secretion. Endocrinology 2021; 162:6047597. [PMID: 33367617 PMCID: PMC7940959 DOI: 10.1210/endocr/bqaa239] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/18/2020] [Indexed: 11/19/2022]
Abstract
A correct biosynthetic activity is thought to be essential for the long-term function and survival of islet cells in culture and possibly also after islet transplantation. Compared to the secretory activity, biosynthetic activity has been poorly studied in pancreatic islet cells. Here we aimed to assess biosynthetic activity at the single cell level to investigate if protein synthesis is dependent on secretagogues and increased as a consequence of hormonal secretion. Biosynthetic activity in rat islet cells was studied at the single cell level using O-propargyl-puromycin (OPP) that incorporates into newly translated proteins and chemically ligates to a fluorescent dye by "click" reaction. Heterogeneous biosynthetic activity was observed between the four islet cell types, with delta cells showing the higher relative protein biosynthesis. Beta cells protein biosynthesis was increased in response to glucose while 3-isobutyl-1-methylxanthine and phorbol-12-myristate-13-acetate, 2 drugs known to stimulate insulin secretion, had no similar effect on protein biosynthesis. However, after several hours of secretion, protein biosynthesis remained high even when cells were challenged to basal conditions. These results suggest that mechanisms regulating secretion and biosynthesis in islet cells are different, with glucose directly triggering beta cells protein biosynthesis, independently of insulin secretion. Furthermore, this OPP labeling approach is a promising method to identify newly synthesized proteins under various physiological and pathological conditions.
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Affiliation(s)
- David Cottet-Dumoulin
- Cell Isolation and Transplantation Center, Department of Surgery, Geneva University Hospitals and University of Geneva, Geneva, Switzerland
- Diabetes Center of the Faculty of Medicine, University of Geneva, Geneva, Switzerland
- Correspondence: Domenico Bosco, Cell Isolation and Transplantation Center, Department of Surgery, Geneva University Hospitals and University of Geneva, 1, rue Michel Servet, CH-1211 Genève 4, Switzerland.
| | - Vanessa Lavallard
- Cell Isolation and Transplantation Center, Department of Surgery, Geneva University Hospitals and University of Geneva, Geneva, Switzerland
- Diabetes Center of the Faculty of Medicine, University of Geneva, Geneva, Switzerland
| | - Fanny Lebreton
- Cell Isolation and Transplantation Center, Department of Surgery, Geneva University Hospitals and University of Geneva, Geneva, Switzerland
- Diabetes Center of the Faculty of Medicine, University of Geneva, Geneva, Switzerland
| | - Charles H Wassmer
- Cell Isolation and Transplantation Center, Department of Surgery, Geneva University Hospitals and University of Geneva, Geneva, Switzerland
- Diabetes Center of the Faculty of Medicine, University of Geneva, Geneva, Switzerland
| | - Kevin Bellofatto
- Cell Isolation and Transplantation Center, Department of Surgery, Geneva University Hospitals and University of Geneva, Geneva, Switzerland
- Diabetes Center of the Faculty of Medicine, University of Geneva, Geneva, Switzerland
| | - Géraldine Parnaud
- Cell Isolation and Transplantation Center, Department of Surgery, Geneva University Hospitals and University of Geneva, Geneva, Switzerland
- Diabetes Center of the Faculty of Medicine, University of Geneva, Geneva, Switzerland
| | - Ekaterine Berishvili
- Cell Isolation and Transplantation Center, Department of Surgery, Geneva University Hospitals and University of Geneva, Geneva, Switzerland
- Diabetes Center of the Faculty of Medicine, University of Geneva, Geneva, Switzerland
| | - Thierry Berney
- Cell Isolation and Transplantation Center, Department of Surgery, Geneva University Hospitals and University of Geneva, Geneva, Switzerland
- Diabetes Center of the Faculty of Medicine, University of Geneva, Geneva, Switzerland
| | - Domenico Bosco
- Cell Isolation and Transplantation Center, Department of Surgery, Geneva University Hospitals and University of Geneva, Geneva, Switzerland
- Diabetes Center of the Faculty of Medicine, University of Geneva, Geneva, Switzerland
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17
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Liu M, Huang Y, Xu X, Li X, Alam M, Arunagiri A, Haataja L, Ding L, Wang S, Itkin-Ansari P, Kaufman RJ, Tsai B, Qi L, Arvan P. Normal and defective pathways in biogenesis and maintenance of the insulin storage pool. J Clin Invest 2021; 131:142240. [PMID: 33463547 PMCID: PMC7810482 DOI: 10.1172/jci142240] [Citation(s) in RCA: 33] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Both basal and glucose-stimulated insulin release occur primarily by insulin secretory granule exocytosis from pancreatic β cells, and both are needed to maintain normoglycemia. Loss of insulin-secreting β cells, accompanied by abnormal glucose tolerance, may involve simple exhaustion of insulin reserves (which, by immunostaining, appears as a loss of β cell identity), or β cell dedifferentiation, or β cell death. While various sensing and signaling defects can result in diminished insulin secretion, somewhat less attention has been paid to diabetes risk caused by insufficiency in the biosynthetic generation and maintenance of the total insulin granule storage pool. This Review offers an overview of insulin biosynthesis, beginning with the preproinsulin mRNA (translation and translocation into the ER), proinsulin folding and export from the ER, and delivery via the Golgi complex to secretory granules for conversion to insulin and ultimate hormone storage. All of these steps are needed for generation and maintenance of the total insulin granule pool, and defects in any of these steps may, weakly or strongly, perturb glycemic control. The foregoing considerations have obvious potential relevance to the pathogenesis of type 2 diabetes and some forms of monogenic diabetes; conceivably, several of these concepts might also have implications for β cell failure in type 1 diabetes.
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Affiliation(s)
- Ming Liu
- Department of Endocrinology and Metabolism, Tianjin Medical University General Hospital, Tianjin, China
| | - Yumeng Huang
- Department of Endocrinology and Metabolism, Tianjin Medical University General Hospital, Tianjin, China
- Division of Metabolism, Endocrinology and Diabetes, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Xiaoxi Xu
- Department of Endocrinology and Metabolism, Tianjin Medical University General Hospital, Tianjin, China
- Division of Metabolism, Endocrinology and Diabetes, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Xin Li
- Department of Endocrinology and Metabolism, Tianjin Medical University General Hospital, Tianjin, China
| | - Maroof Alam
- Division of Metabolism, Endocrinology and Diabetes, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Anoop Arunagiri
- Division of Metabolism, Endocrinology and Diabetes, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Leena Haataja
- Division of Metabolism, Endocrinology and Diabetes, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Li Ding
- Department of Endocrinology and Metabolism, Tianjin Medical University General Hospital, Tianjin, China
| | - Shusen Wang
- Organ Transplant Center, Tianjin First Central Hospital, Tianjin, China
| | | | - Randal J. Kaufman
- Degenerative Diseases Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California, USA
| | - Billy Tsai
- Department of Cell and Developmental Biology, and
| | - Ling Qi
- Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Peter Arvan
- Division of Metabolism, Endocrinology and Diabetes, University of Michigan Medical School, Ann Arbor, Michigan, USA
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18
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Insulin granule biogenesis and exocytosis. Cell Mol Life Sci 2020; 78:1957-1970. [PMID: 33146746 PMCID: PMC7966131 DOI: 10.1007/s00018-020-03688-4] [Citation(s) in RCA: 48] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2020] [Revised: 09/11/2020] [Accepted: 10/19/2020] [Indexed: 02/06/2023]
Abstract
Insulin is produced by pancreatic β-cells, and once released to the blood, the hormone stimulates glucose uptake and suppresses glucose production. Defects in both the availability and action of insulin lead to elevated plasma glucose levels and are major hallmarks of type-2 diabetes. Insulin is stored in secretory granules that form at the trans-Golgi network. The granules undergo extensive modifications en route to their release sites at the plasma membrane, including changes in both protein and lipid composition of the granule membrane and lumen. In parallel, the insulin molecules also undergo extensive modifications that render the hormone biologically active. In this review, we summarize current understanding of insulin secretory granule biogenesis, maturation, transport, docking, priming and eventual fusion with the plasma membrane. We discuss how different pools of granules form and how these pools contribute to insulin secretion under different conditions. We also highlight the role of the β-cell in the development of type-2 diabetes and discuss how dysregulation of one or several steps in the insulin granule life cycle may contribute to disease development or progression.
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19
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Thomaidou S, Kracht MJL, van der Slik A, Laban S, de Koning EJ, Carlotti F, Hoeben RC, Roep BO, Zaldumbide A. β-Cell Stress Shapes CTL Immune Recognition of Preproinsulin Signal Peptide by Posttranscriptional Regulation of Endoplasmic Reticulum Aminopeptidase 1. Diabetes 2020; 69:670-680. [PMID: 31896552 DOI: 10.2337/db19-0984] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/02/2019] [Accepted: 12/28/2019] [Indexed: 11/13/2022]
Abstract
The signal peptide of preproinsulin is a major source for HLA class I autoantigen epitopes implicated in CD8 T cell (CTL)-mediated β-cell destruction in type 1 diabetes (T1D). Among them, the 10-mer epitope located at the C-terminal end of the signal peptide was found to be the most prevalent in patients with recent-onset T1D. While the combined action of signal peptide peptidase and endoplasmic reticulum (ER) aminopeptidase 1 (ERAP1) is required for processing of the signal peptide, the mechanisms controlling signal peptide trimming and the contribution of the T1D inflammatory milieu on these mechanisms are unknown. Here, we show in human β-cells that ER stress regulates ERAP1 gene expression at posttranscriptional level via the IRE1α/miR-17-5p axis and demonstrate that inhibition of the IRE1α activity impairs processing of preproinsulin signal peptide antigen and its recognition by specific autoreactive CTLs during inflammation. These results underscore the impact of ER stress in the increased visibility of β-cells to the immune system and position the IRE1α/miR-17 pathway as a central component in β-cell destruction processes and as a potential target for the treatment of autoimmune T1D.
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Affiliation(s)
- Sofia Thomaidou
- Department of Cell and Chemical Biology, Leiden University Medical Center, Leiden, the Netherlands
| | - Maria J L Kracht
- Department of Cell and Chemical Biology, Leiden University Medical Center, Leiden, the Netherlands
| | - Arno van der Slik
- Department of Cell and Chemical Biology, Leiden University Medical Center, Leiden, the Netherlands
- Department of Immunohematology and Blood Transfusion, Leiden University Medical Center, Leiden, the Netherlands
| | - Sandra Laban
- Department of Immunohematology and Blood Transfusion, Leiden University Medical Center, Leiden, the Netherlands
| | - Eelco J de Koning
- Department of Internal Medicine, Leiden University Medical Center, Leiden, the Netherlands
| | - Francoise Carlotti
- Department of Internal Medicine, Leiden University Medical Center, Leiden, the Netherlands
| | - Rob C Hoeben
- Department of Cell and Chemical Biology, Leiden University Medical Center, Leiden, the Netherlands
| | - Bart O Roep
- Department of Immunohematology and Blood Transfusion, Leiden University Medical Center, Leiden, the Netherlands
- Department of Diabetes Immunology, Diabetes & Metabolism Research Institute, City of Hope, Duarte, CA
| | - Arnaud Zaldumbide
- Department of Cell and Chemical Biology, Leiden University Medical Center, Leiden, the Netherlands
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20
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Mao R, Chen Y, Chi Z, Wang Y. Insulin and its single-chain analogue. Appl Microbiol Biotechnol 2019; 103:8737-8751. [PMID: 31637493 DOI: 10.1007/s00253-019-10170-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2019] [Revised: 10/02/2019] [Accepted: 10/08/2019] [Indexed: 12/26/2022]
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21
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Perego C, Da Dalt L, Pirillo A, Galli A, Catapano AL, Norata GD. Cholesterol metabolism, pancreatic β-cell function and diabetes. Biochim Biophys Acta Mol Basis Dis 2019; 1865:2149-2156. [DOI: 10.1016/j.bbadis.2019.04.012] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2018] [Revised: 12/20/2018] [Accepted: 01/06/2019] [Indexed: 12/11/2022]
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22
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Peel R, Hure A, Wiggers J, McEvoy M, Holliday E, Searles A, Reeves P, Ranasinghe P, Jayawardena R, Samman S, Acharya S, Luu J, Rissel C, Attia J. Zinc in Preventing the Progression of pre-Diabetes (ZIPPeD Study) - study protocol for a randomised placebo-controlled trial in Australia. Trials 2019; 20:219. [PMID: 30992081 PMCID: PMC6466783 DOI: 10.1186/s13063-019-3317-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2018] [Accepted: 03/21/2019] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Diabetes is increasing in incidence, morbidity and treatment costs globally, hence prevention strategies need to be explored. Animal studies and some human data have shown that zinc can improve glycaemic control, but the impact of this effect in a pre-diabetic population remains uncertain. This study is designed to investigate whether zinc gluconate and lifestyle coaching can improve glucose handling and ultimately reduce diabetes incidence in an at-risk pre-diabetic population in Australia. METHODS/DESIGN The study will be a randomised, placebo-controlled, double-blind clinical trial. The study will be conducted at the Hunter New England Local Health District New South Wales (NSW), Australia. Pre-diabetic (haemoglobin A1c [HbA1c] 5.7-6.4) male and female participants (n = 410) aged 40-70 years will be recruited through the Diabetes Alliance Network, a collaboration of diabetes specialists and general practitioner practices. All participants will be given routine care to encourage healthy lifestyle changes using a telephone coaching service (Get Healthy Information and Coaching Service, NSW Health) and then randomised to receive a supplement, either zinc gluconate (equivalent to 30 mg of elemental zinc) or placebo of identical appearance for 12 months. The identity of the supplements will be blinded to both research personnel and the participants. Participants will be asked to complete medical, lifestyle and dietary surveys and will have baseline and final visits at their general practitioner practice. Primary outcomes will be HbA1c and insulin sensitivity collected at baseline and at 1, 6 and 12 months; secondary outcomes will include fasting blood glucose, fasting cholesterol, blood pressure and body mass index. The primary efficacy endpoint will be judged at 6 months. DISCUSSION This study will generate new evidence about the potential for health coaching, with or without zinc supplementation, to improve glucose handling and ultimately to reduce progression from pre-diabetes to diabetes. TRIAL REGISTRATION Australian and New Zealand Clinical Trials Registry, ACTRN12618001120268 . Registered on 6 July 2018.
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Affiliation(s)
- Roseanne Peel
- School of Medicine and Public Health, The University of Newcastle, Callaghan, NSW, Australia
| | - Alexis Hure
- School of Medicine and Public Health, The University of Newcastle, Callaghan, NSW, Australia
| | - John Wiggers
- School of Medicine and Public Health, The University of Newcastle, Callaghan, NSW, Australia.,Health Research and Translation and Population Health, Hunter New England Local Health District, New Lambton, NSW, Australia
| | - Mark McEvoy
- School of Medicine and Public Health, The University of Newcastle, Callaghan, NSW, Australia
| | - Elizabeth Holliday
- School of Medicine and Public Health, The University of Newcastle, Callaghan, NSW, Australia
| | - Andrew Searles
- School of Medicine and Public Health, The University of Newcastle, Callaghan, NSW, Australia.,Hunter Medical Research Institute, Newcastle, NSW, Australia
| | - Penny Reeves
- School of Medicine and Public Health, The University of Newcastle, Callaghan, NSW, Australia.,Hunter Medical Research Institute, Newcastle, NSW, Australia
| | - Priyanga Ranasinghe
- Department of Pharmacology, Faculty of Medicine, University of Colombo, Colombo, Sri Lanka
| | - Ranil Jayawardena
- Department of Pharmacology, Faculty of Medicine, University of Colombo, Colombo, Sri Lanka.,Department of Physiology Faculty of Medicine, University of Colombo, Colombo, Sri Lanka
| | - Samir Samman
- School of Life and Environmental Sciences, University of Sydney, Sydney, NSW, Australia
| | - Shamasunder Acharya
- Division of Medicine, Hunter New England Local Health District, New Lambton, NSW, Australia.,Diabetes Alliance, Hunter New England Local Health District, New Lambton, NSW, Australia
| | - Judy Luu
- Division of Medicine, Hunter New England Local Health District, New Lambton, NSW, Australia.,Diabetes Alliance, Hunter New England Local Health District, New Lambton, NSW, Australia
| | - Chris Rissel
- The NSW Office of Preventive Health, South Western Sydney Local Health District, Liverpool Hospital, Liverpool, NSW, Australia
| | - John Attia
- School of Medicine and Public Health, The University of Newcastle, Callaghan, NSW, Australia. .,Division of Medicine, Hunter New England Local Health District, New Lambton, NSW, Australia.
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23
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Jafarnejad S, Mahboobi S, McFarland LV, Taghizadeh M, Rahimi F. Meta-Analysis: Effects of Zinc Supplementation Alone or with Multi-Nutrients, on Glucose Control and Lipid Levels in Patients with Type 2 Diabetes. Prev Nutr Food Sci 2019; 24:8-23. [PMID: 31008092 PMCID: PMC6456233 DOI: 10.3746/pnf.2019.24.1.8] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2018] [Accepted: 11/07/2018] [Indexed: 01/08/2023] Open
Abstract
The present study aims to assess the effects of zinc supplementation on metabolic parameters in patients with type 2 diabetes. A literature search was conducted in PubMedTM, Google ScholarTM, and ScopusTM up to March 2018. Twenty randomized controlled trials met the predefined inclusion criteria and were included in the meta-analysis. Weighted mean difference (WMD) with 95% confidence intervals (CIs) were calculated for net changes in glycemic indices including fasting blood glucose (FBG) and hemoglobin A1c (HbA1c), and in lipid markers including total cholesterol (TC), triglyceride (TG), low-density lipoprotein cholesterol (LDL-c), and high density lipoprotein cholesterol (HDL-c). Subgroup analyses were performed based on intervention and study quality. Compared to controls, zinc supplementation significantly reduced the concentrations of both FBG and HbA1c (FBG WMD: −19.66 mg/dL, 95% CI: −33.71, −5.62; HbA1c WMD: −0.43 mg/dL, 95% CI: −0.80, −0.07). The pooled estimate showed a significant decrease in serum TC and LDL-c, and increase in serum HDL-c levels in treatment group compared with the control group (TC WMD: −18.51 mg/dL, 95% CI: −21.36, −15.66; LDL-c WMD: −4.80 mg/dL, 95% CI: −6.07, −3.53; HDL-c WMD: 1.45 mg/dL, 95% CI: 1.40, 1.51). Subgroup analysis of “no co-supplement” intervention demonstrated significant differences for mean changes in HDL-c and FBG levels, whereas subgroup analysis of high quality studies showed significant differences for mean changes of LDL-c, HDL-c, and FBG levels. Results suggested that zinc supplementation reduces FBG, HbA1c and LDL-c levels and increases HDL-C levels; however, these changes were related to intervention and quality of studies.
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Affiliation(s)
- Sadegh Jafarnejad
- Research Center for Biochemistry and Nutrition in Metabolic Diseases, Kashan University of Medical Sciences, Kashan 87137-81147, Iran
| | - Sepideh Mahboobi
- Department of Community Nutrition, Shiraz University of Medical Sciences, Shiraz 71348-14336, Iran
| | - Lynne V McFarland
- Department of Medicinal Chemistry, University of Washington, Seattle, WA 98195-5502, USA
| | - Mohsen Taghizadeh
- Research Center for Biochemistry and Nutrition in Metabolic Diseases, Kashan University of Medical Sciences, Kashan 87137-81147, Iran
| | - Fatemeh Rahimi
- Faculty of Public Health, Kermanshah University of Medical Science, Kermanshah 67158-47141, Iran
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Arunagiri A, Haataja L, Cunningham CN, Shrestha N, Tsai B, Qi L, Liu M, Arvan P. Misfolded proinsulin in the endoplasmic reticulum during development of beta cell failure in diabetes. Ann N Y Acad Sci 2018; 1418:5-19. [PMID: 29377149 DOI: 10.1111/nyas.13531] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2017] [Revised: 09/14/2017] [Accepted: 09/25/2017] [Indexed: 02/06/2023]
Abstract
The endoplasmic reticulum (ER) is broadly distributed throughout the cytoplasm of pancreatic beta cells, and this is where all proinsulin is initially made. Healthy beta cells can synthesize 6000 proinsulin molecules per second. Ordinarily, nascent proinsulin entering the ER rapidly folds via the formation of three evolutionarily conserved disulfide bonds (B7-A7, B19-A20, and A6-A11). A modest amount of proinsulin misfolding, including both intramolecular disulfide mispairing and intermolecular disulfide-linked protein complexes, is a natural by-product of proinsulin biosynthesis, as is the case for many proteins. The steady-state level of misfolded proinsulin-a potential ER stressor-is linked to (1) production rate, (2) ER environment, (3) presence or absence of naturally occurring (mutational) defects in proinsulin, and (4) clearance of misfolded proinsulin molecules. Accumulation of misfolded proinsulin beyond a certain threshold begins to interfere with the normal intracellular transport of bystander proinsulin, leading to diminished insulin production and hyperglycemia, as well as exacerbating ER stress. This is most obvious in mutant INS gene-induced Diabetes of Youth (MIDY; an autosomal dominant disease) but also likely to occur in type 2 diabetes owing to dysregulation in proinsulin synthesis, ER folding environment, or clearance.
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Affiliation(s)
- Anoop Arunagiri
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan, Ann Arbor, Michigan
| | - Leena Haataja
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan, Ann Arbor, Michigan
| | - Corey N Cunningham
- Cellular and Molecular Biology Program, University of Michigan, Ann Arbor, Michigan
| | - Neha Shrestha
- Department of Molecular & Integrative Physiology, University of Michigan, Ann Arbor, Michigan
| | - Billy Tsai
- Department of Cell and Developmental Biology, University of Michigan, Ann Arbor, Michigan
| | - Ling Qi
- Department of Molecular & Integrative Physiology, University of Michigan, Ann Arbor, Michigan
| | - Ming Liu
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan, Ann Arbor, Michigan.,Department of Endocrinology and Metabolism, Tianjin Medical University General Hospital, Tianjin, China
| | - Peter Arvan
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan, Ann Arbor, Michigan
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Li L, Bai S, Sheline CT. hZnT8 (Slc30a8) Transgenic Mice That Overexpress the R325W Polymorph Have Reduced Islet Zn2+ and Proinsulin Levels, Increased Glucose Tolerance After a High-Fat Diet, and Altered Levels of Pancreatic Zinc Binding Proteins. Diabetes 2017; 66:551-559. [PMID: 27899481 PMCID: PMC5248993 DOI: 10.2337/db16-0323] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/09/2016] [Accepted: 11/17/2016] [Indexed: 01/23/2023]
Abstract
Zinc (Zn2+) is involved in both type 1 diabetes (T1DM) and type 2 diabetes (T2DM). The wild-type (WT) form of the β-cell-specific Zn2+ transporter, ZNT8, is linked to T2DM susceptibility. ZnT8 null mice have a mild phenotype with a slight decrease in glucose tolerance, whereas patients with the ZnT8 R325W polymorphism (rs13266634) have decreased proinsulin staining and susceptibility to T2DM. We measured Zn2+, insulin, and proinsulin stainings and performed intraperitoneal glucose tolerance testing in transgenic mice overexpressing hZnT8 WT or hZnT8 R325W fed a normal or high-fat diet. The hZnT8 R325W transgenic line had lower pancreatic [Zn2+]i and proinsulin and higher insulin and glucose tolerance compared with control littermates after 10 weeks of a high-fat diet in male mice. The converse was true for the hZnT8 WT transgenic line, and dietary Zn2+ supplementation also induced glucose intolerance. Finally, pancreatic zinc binding proteins were identified by Zn2+-affinity chromatography and proteomics. Increasing pancreatic Zn2+ (hZnT8WT) induced nucleoside diphosphate kinase B, and Zn2+ reduction (hZnT8RW) induced carboxypeptidase A1. These data suggest that pancreatic Zn2+ and proinsulin levels covary but are inversely variant with insulin or glucose tolerance in the HFD model of T2DM suggesting novel therapeutic targets.
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Affiliation(s)
- Li Li
- Department of Ophthalmology and the Neuroscience Center of Excellence, Louisiana State University Health Sciences Center, New Orleans, LA
| | - Shi Bai
- Department of Ophthalmology and the Neuroscience Center of Excellence, Louisiana State University Health Sciences Center, New Orleans, LA
| | - Christian T Sheline
- Department of Ophthalmology and the Neuroscience Center of Excellence, Louisiana State University Health Sciences Center, New Orleans, LA
- Department of Neurology, Stony Brook University Hospital, Stony Brook, NY
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Simon SF, Taylor CG. Dietary Zinc Supplementation Attenuates Hyperglycemia in db/db Mice. Exp Biol Med (Maywood) 2016; 226:43-51. [PMID: 11368237 DOI: 10.1177/153537020122600107] [Citation(s) in RCA: 128] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Although zinc (Zn) deficiency has been associated with insulin resistance, and altered Zn metabolism (e.g., hyperzincuria, low-normal plasma Zn concentrations) may be present in diabetes, the potential effects of Zn on modulation of insulin action in Type II diabetes have not been established. The objective of this study was to compare the effects of dietary Zn deficiency and Zn supplementation on glycemic control in db/db mice. Weanling db/db mice and lean littermate controls were fed Zn-deficient (3 ppm Zn; dbZD and InZD groups), Zn-adequate control (30 ppm Zn; dbC and InC groups) or Zn-supplemented (300 ppm Zn; dbZS and InZS groups) diets for 6 weeks. Mice were assessed for Zn status, serum and urinary indices of diabetes, and gastrocnemius insulin receptor concentration and tyrosine kinase activity. Fasting serum glucose concentrations were significantly lower in the dbZS group compared with the dbZD group (19.3 ± 2.9 and 27.9 ± 4.1 mM, respectively), whereas the dbC mice had an intermediate value. There was a negative correlation between femur Zn and serum glucose concentrations (r = −0.59 for lean mice, P = 0.007). The dbZS group had higher pancreatic Zn and lower circulating insulin concentrations than dbZC mice. Insulin-stimulated tyrosine kinase activity in gastrocnemius muscle was higher in the db/db genotype, and insulin receptor concentration was not altered. In summary, dietary Zn supplementation attenuated hyperglycemia and hyperinsulinemia in db/db mice, suggesting that the roles of Zn in pancreatic function and peripheral tissue glucose uptake need to be further investigated.
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Affiliation(s)
- S F Simon
- Department of Food and Nutrition, University of Manitoba, Winnipeg, Canada
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Islam MR, Attia J, Ali L, McEvoy M, Selim S, Sibbritt D, Akhter A, Akter S, Peel R, Faruque O, Mona T, Lona H, Milton AH. Zinc supplementation for improving glucose handling in pre-diabetes: A double blind randomized placebo controlled pilot study. Diabetes Res Clin Pract 2016; 115:39-46. [PMID: 27242121 DOI: 10.1016/j.diabres.2016.03.010] [Citation(s) in RCA: 58] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/11/2015] [Revised: 01/31/2016] [Accepted: 03/04/2016] [Indexed: 02/02/2023]
Abstract
AIMS There are a number of studies showing that zinc supplementation may improve glucose handling in people with established diabetes. We sought to investigate whether this zinc-dependent improvement in glucose handling could potentially be harnessed to prevent the progression of pre-diabetes to diabetes. In this double-blind randomized placebo-controlled trial, we determined participants' fasting blood glucose levels, (FBG) and Homeostasis Model Assessment (HOMA) parameters (beta cell function, insulin sensitivity and insulin resistance) at baseline and after 6 months of zinc supplementation. METHODS The Bangladesh Institute of Health Sciences Hospital (BIHS) (Mirpur, Dhaka, Bangladesh) database was used to identify 224 patients with prediabetes, of whom 55 met the inclusion criteria and agreed to participate. The participants were randomized either to the intervention or control group using block randomization. The groups received either 30mg zinc sulphate dispersible tablet or placebo, once daily for six months. RESULTS After six months, the intervention group significantly improved their FBG concentration compared to the placebo group (5.37±0.20mmol/L vs 5.69±0.26, p<0.001) as well as compared to their own baseline (5.37±0.20mmol/L vs 5.8±0.09, p<0.001). Beta cell function, insulin sensitivity and insulin resistance all showed a statistically significant improvement as well. CONCLUSION To our knowledge this is the first trial to show an improvement in glucose handling using HOMA parameters in participants with prediabetes. Larger randomized controlled trials are warranted to confirm these findings and to explore clinical endpoints.
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Affiliation(s)
- Md Rafiqul Islam
- CCEB, School of Medicine and Public Health, The University of Newcastle and Hunter Medical Research Institute, Kookaburra Close, New Lambton Heights, Newcastle, NSW, Australia; Goulburn Valley Health, Shepparton, VIC, Australia; RHAC, the University of Melbourne, Shepparton, VIC 3630, Australia
| | - John Attia
- CCEB, School of Medicine and Public Health, The University of Newcastle and Hunter Medical Research Institute, Kookaburra Close, New Lambton Heights, Newcastle, NSW, Australia
| | - Liaquat Ali
- Bangladesh University of Health Sciences, Mirpur, Dhaka, Bangladesh
| | - Mark McEvoy
- CCEB, School of Medicine and Public Health, The University of Newcastle and Hunter Medical Research Institute, Kookaburra Close, New Lambton Heights, Newcastle, NSW, Australia
| | - Shahjada Selim
- Bangabandhu Sheikh Mujib Medical University, Shahbag, Dhaka, Bangladesh
| | | | | | - Shahnaz Akter
- Institute of Child and Mother Health (ICMH), Demra, Matuail, Dhaka, Bangladesh
| | - Roseanne Peel
- CCEB, School of Medicine and Public Health, The University of Newcastle and Hunter Medical Research Institute, Kookaburra Close, New Lambton Heights, Newcastle, NSW, Australia
| | - Omar Faruque
- Bangladesh University of Health Sciences, Mirpur, Dhaka, Bangladesh
| | - Tazreen Mona
- Centre for Health and Development (CHAD), West Rampura, Dhaka, Bangladesh
| | - Hafiza Lona
- Medical College for Women, Uttara, Dhaka, Bangladesh
| | - Abul Hasnat Milton
- CCEB, School of Medicine and Public Health, The University of Newcastle and Hunter Medical Research Institute, Kookaburra Close, New Lambton Heights, Newcastle, NSW, Australia.
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Haataja L, Manickam N, Soliman A, Tsai B, Liu M, Arvan P. Disulfide Mispairing During Proinsulin Folding in the Endoplasmic Reticulum. Diabetes 2016; 65:1050-60. [PMID: 26822090 PMCID: PMC4806660 DOI: 10.2337/db15-1345] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/27/2015] [Accepted: 01/14/2016] [Indexed: 02/06/2023]
Abstract
Proinsulin folding within the endoplasmic reticulum (ER) remains incompletely understood, but it is clear that in mutant INS gene-induced diabetes of youth (MIDY), progression of the (three) native disulfide bonds of proinsulin becomes derailed, causing insulin deficiency, β-cell ER stress, and onset of diabetes. Herein, we have undertaken a molecular dissection of proinsulin disulfide bond formation, using bioengineered proinsulins that can form only two (or even only one) of the native proinsulin disulfide bonds. In the absence of preexisting proinsulin disulfide pairing, Cys(B19)-Cys(A20) (a major determinant of ER stress response activation and proinsulin stability) preferentially initiates B-A chain disulfide bond formation, whereas Cys(B7)-Cys(A7) can initiate only under oxidizing conditions beyond that existing within the ER of β-cells. Interestingly, formation of these two "interchain" disulfide bonds demonstrates cooperativity, and together, they are sufficient to confer intracellular transport competence to proinsulin. The three most common proinsulin disulfide mispairings in the ER appear to involve Cys(A11)-Cys(A20), Cys(A7)-Cys(A20), and Cys(B19)-Cys(A11), each disrupting the critical Cys(B19)-Cys(A20) pairing. MIDY mutations inhibit Cys(B19)-Cys(A20) formation, but treatment to force oxidation of this disulfide bond improves folding and results in a small but detectable increase of proinsulin export. These data suggest possible therapeutic avenues to ameliorate ER stress and diabetes.
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Affiliation(s)
- Leena Haataja
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical Center, Ann Arbor, MI
| | - Nandini Manickam
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical Center, Ann Arbor, MI
| | - Ann Soliman
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical Center, Ann Arbor, MI
| | - Billy Tsai
- Department of Cell & Developmental Biology, University of Michigan Medical Center, Ann Arbor, MI
| | - Ming Liu
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical Center, Ann Arbor, MI Department of Endocrinology and Metabolism, Tianjin Medical University General Hospital, Tianjin, China
| | - Peter Arvan
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical Center, Ann Arbor, MI
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29
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Imaging trace element distributions in single organelles and subcellular features. Sci Rep 2016; 6:21437. [PMID: 26911251 PMCID: PMC4766485 DOI: 10.1038/srep21437] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2014] [Accepted: 01/15/2016] [Indexed: 12/30/2022] Open
Abstract
The distributions of chemical elements within cells are of prime importance in a wide range of basic and applied biochemical research. An example is the role of the subcellular Zn distribution in Zn homeostasis in insulin producing pancreatic beta cells and the development of type 2 diabetes mellitus. We combined transmission electron microscopy with micro- and nano-synchrotron X-ray fluorescence to image unequivocally for the first time, to the best of our knowledge, the natural elemental distributions, including those of trace elements, in single organelles and other subcellular features. Detected elements include Cl, K, Ca, Co, Ni, Cu, Zn and Cd (which some cells were supplemented with). Cell samples were prepared by a technique that minimally affects the natural elemental concentrations and distributions, and without using fluorescent indicators. It could likely be applied to all cell types and provide new biochemical insights at the single organelle level not available from organelle population level studies.
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30
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Vinther TN, Kjeldsen TB, Jensen KJ, Hubálek F. The road to the first, fully active and more stable human insulin variant with an additional disulfide bond. J Pept Sci 2015; 21:797-806. [DOI: 10.1002/psc.2822] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2015] [Revised: 08/14/2015] [Accepted: 08/19/2015] [Indexed: 12/21/2022]
Affiliation(s)
| | | | - Knud J. Jensen
- Faculty of Science, Department of Chemistry; University of Copenhagen; DK-1871 Frederiksberg Denmark
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31
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Byun HR, Choi JA, Koh JY. The role of metallothionein-3 in streptozotocin-induced beta-islet cell death and diabetes in mice. Metallomics 2015; 6:1748-57. [PMID: 25054451 DOI: 10.1039/c4mt00143e] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Metallothionein-3 (Mt3), a zinc (Zn)-regulatory protein mainly expressed in the central nervous system, may contribute to oxidative cell death. In the present study, we examined the possible role of Mt3 in streptozotocin (STZ)-induced islet cell death and consequent hyperglycemia. Quantitative real-time polymerase chain reaction (RT-PCR) confirmed that islet cells expressed Mt3 mRNA. In all cases, wild-type (WT) mice injected with STZ exhibited hyperglycemia 7-21 days later. In stark contrast, all Mt3-null mice remained normoglycemic following STZ injection. STZ treatment increased free Zn levels in islet cells and induced their death in WT mice, but failed to do so in Mt3-null mice. Consistent with this, cultured Mt3-null islet cells exhibited striking resistance to STZ toxicity. Notably, PDE3a (phosphodiesterase 3A) was downregulated in islets of Mt3-null mice compared to those of WT mice, and was not induced by STZ treatment. Moreover, the PDE3 inhibitor cilostazol reduced islet cell death, likely by increasing cAMP levels, further supporting a role for PDE3 in STZ-induced islet cell death. Collectively, these results demonstrate that Mt3 may act through PDE3a to play a key role in Zn dyshomeostasis and cell death in STZ-treated islets.
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Affiliation(s)
- Hyae-Ran Byun
- Neural Injury Research Center, Asan Institute for Life Science, University of Ulsan College of Medicine, Seoul, Korea
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32
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Sun J, Cui J, He Q, Chen Z, Arvan P, Liu M. Proinsulin misfolding and endoplasmic reticulum stress during the development and progression of diabetes. Mol Aspects Med 2015; 42:105-18. [PMID: 25579745 PMCID: PMC4404191 DOI: 10.1016/j.mam.2015.01.001] [Citation(s) in RCA: 119] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2014] [Revised: 12/31/2014] [Accepted: 01/02/2015] [Indexed: 02/06/2023]
Abstract
To maintain copious insulin granule stores in the face of ongoing metabolic demand, pancreatic beta cells must produce large quantities of proinsulin, the insulin precursor. Proinsulin biosynthesis can account for up to 30-50% of total cellular protein synthesis of beta cells. This puts pressure on the beta cell secretory pathway, especially the endoplasmic reticulum (ER), where proinsulin undergoes its initial folding, including the formation of three evolutionarily conserved disulfide bonds. In normal beta cells, up to 20% of newly synthesized proinsulin may fail to reach its native conformation, suggesting that proinsulin is a misfolding-prone protein. Misfolded proinsulin molecules can either be refolded to their native structure or degraded through ER associated degradation (ERAD) and autophagy. These degraded molecules decrease proinsulin yield but do not otherwise compromise beta cell function. However, under certain pathological conditions, proinsulin misfolding increases, exceeding the genetically determined threshold of beta cells to handle the misfolded protein load. This results in accumulation of misfolded proinsulin in the ER - a causal factor leading to beta cell failure and diabetes. In patients with Mutant INS-gene induced diabetes of Youth (MIDY), increased proinsulin misfolding due to insulin gene mutations is the primary defect operating as a "first hit" to beta cells. Additionally, increased proinsulin misfolding can be secondary to an unfavorable ER folding environment due to genetic and/or environmental factors. Under these conditions, increased wild-type proinsulin misfolding becomes a "second hit" to the ER and beta cells, aggravating beta cell failure and diabetes. In this article, we describe our current understanding of the normal proinsulin folding pathway in the ER, and then review existing links between proinsulin misfolding, ER dysfunction, and beta cell failure in the development and progression of type 2, type 1, and some monogenic forms of diabetes.
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Affiliation(s)
- Jinhong Sun
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan, Ann Arbor, MI 48105, USA
| | - Jingqiu Cui
- Department of Endocrinology and Metabolism, Tianjin Medical University General Hospital, Tianjin 300052, China
| | - Qing He
- Department of Endocrinology and Metabolism, Tianjin Medical University General Hospital, Tianjin 300052, China
| | - Zheng Chen
- School of Life Sciences, Northeast Normal University, Changchun, Jilin 130024, China
| | - Peter Arvan
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan, Ann Arbor, MI 48105, USA.
| | - Ming Liu
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan, Ann Arbor, MI 48105, USA; Department of Endocrinology and Metabolism, Tianjin Medical University General Hospital, Tianjin 300052, China.
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Tomasello MF, Sinopoli A, Pappalardo G. On the Environmental Factors Affecting the Structural and Cytotoxic Properties of IAPP Peptides. J Diabetes Res 2015; 2015:918573. [PMID: 26582441 PMCID: PMC4637107 DOI: 10.1155/2015/918573] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/27/2014] [Accepted: 02/05/2015] [Indexed: 12/18/2022] Open
Abstract
Pancreatic islets in type 2 diabetes mellitus (T2DM) patients are characterized by reduced β-cells mass and diffuse extracellular amyloidosis. Amyloid deposition involves the islet amyloid polypeptide (IAPP), a neuropancreatic hormone cosecreted with insulin by β-cells. IAPP is physiologically involved in glucose homeostasis, but it may turn toxic to β-cells owing to its tendency to misfold giving rise to oligomers and fibrils. The process by which the unfolded IAPP starts to self-assemble and the overall factors promoting this conversion are poorly understood. Other open questions are related to the nature of the IAPP toxic species and how exactly β-cells die. Over the last decades, there has been growing consensus about the notion that early molecular assemblies, notably small hIAPP oligomers, are the culprit of β-cells decline. Numerous environmental factors might affect the conformational, aggregation, and cytotoxic properties of IAPP. Herein we review recent progress in the field, focusing on the influences that membranes, pH, and metal ions may have on the conformational conversion and cytotoxicity of full-length IAPP as well as peptide fragments thereof. Current theories proposed for the mechanisms of toxicity will be also summarized together with an outline of the underlying molecular links between IAPP and amyloid beta (Aβ) misfolding.
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Affiliation(s)
| | - Alessandro Sinopoli
- International PhD Program in Translational Biomedicine, University of Catania, Viale A. Doria 6, 95125 Catania, Italy
| | - Giuseppe Pappalardo
- CNR Institute of Biostructures and Bioimaging, Via P. Gaifami 18, 95126 Catania, Italy
- *Giuseppe Pappalardo:
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Liu M, Sun J, Cui J, Chen W, Guo H, Barbetti F, Arvan P. INS-gene mutations: from genetics and beta cell biology to clinical disease. Mol Aspects Med 2014; 42:3-18. [PMID: 25542748 DOI: 10.1016/j.mam.2014.12.001] [Citation(s) in RCA: 91] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2014] [Revised: 12/02/2014] [Accepted: 12/04/2014] [Indexed: 02/06/2023]
Abstract
A growing list of insulin gene mutations causing a new form of monogenic diabetes has drawn increasing attention over the past seven years. The mutations have been identified in the untranslated regions of the insulin gene as well as the coding sequence of preproinsulin including within the signal peptide, insulin B-chain, C-peptide, insulin A-chain, and the proteolytic cleavage sites both for signal peptidase and the prohormone convertases. These mutations affect a variety of different steps of insulin biosynthesis in pancreatic beta cells. Importantly, although many of these mutations cause proinsulin misfolding with early onset autosomal dominant diabetes, some of the mutant alleles appear to engage different cellular and molecular mechanisms that underlie beta cell failure and diabetes. In this article, we review the most recent advances in the field and discuss challenges as well as potential strategies to prevent/delay the development and progression of autosomal dominant diabetes caused by INS-gene mutations. It is worth noting that although diabetes caused by INS gene mutations is rare, increasing evidence suggests that defects in the pathway of insulin biosynthesis may also be involved in the progression of more common types of diabetes. Collectively, the (pre)proinsulin mutants provide insightful molecular models to better understand the pathogenesis of all forms of diabetes in which preproinsulin processing defects, proinsulin misfolding, and ER stress are involved.
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Affiliation(s)
- Ming Liu
- Department of Endocrinology and Metabolism, Tianjin Medical University General Hospital, Tianjin, 300052, China; Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical School, Ann Arbor, MI, 48105, USA.
| | - Jinhong Sun
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical School, Ann Arbor, MI, 48105, USA
| | - Jinqiu Cui
- Department of Endocrinology and Metabolism, Tianjin Medical University General Hospital, Tianjin, 300052, China
| | - Wei Chen
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical School, Ann Arbor, MI, 48105, USA
| | - Huan Guo
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical School, Ann Arbor, MI, 48105, USA
| | - Fabrizio Barbetti
- Department of Experimental Medicine, University of Tor Vergata, Rome and Bambino Gesù Children's Hospital, Rome, Italy
| | - Peter Arvan
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical School, Ann Arbor, MI, 48105, USA.
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Abstract
Zinc is an essential nutrient with tremendous importance for human health, and zinc deficiency is a severe risk factor for increased mortality and morbidity. As abnormal zinc homeostasis causes diabetes, and because the pancreatic β-cell contains the highest zinc content of any known cell type, it is of interest to know how zinc fluxes are controlled in β-cells. The understanding of zinc homeostasis has been boosted by the discovery of multiprotein families of zinc transporters, and one of them - zinc transporter 8 (ZnT8) - is abundantly and specifically expressed in the pancreatic islets of Langerhans. In this review, we discuss the evidence for a physiological role of ZnT8 in the formation of zinc-insulin crystals, the physical form in which most insulin is stored in secretory granules. In addition, we cross-examine this information, collected in genetically modified mouse strains, to the knowledge that genetic variants of the human ZnT8 gene predispose to the onset of type 2 diabetes and that epitopes on the ZnT8 protein trigger autoimmunity in patients with type 1 diabetes. The overall conclusion is that we are still at the dawn of a complete understanding of how zinc homeostasis operates in normal β-cells and how abnormalities lead to β-cell dysfunction and diabetes. (J Diabetes Invest, doi: 10.1111/j.2040-1124.2012.00199.x, 2012).
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Affiliation(s)
- Katleen Lemaire
- Gene Expression Unit, Department of Molecular Cell Biology, KU Leuven, Leuven, Belgium
| | | | - Frans Schuit
- Gene Expression Unit, Department of Molecular Cell Biology, KU Leuven, Leuven, Belgium
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Guo H, Xiong Y, Witkowski P, Cui J, Wang LJ, Sun J, Lara-Lemus R, Haataja L, Hutchison K, Shan SO, Arvan P, Liu M. Inefficient translocation of preproinsulin contributes to pancreatic β cell failure and late-onset diabetes. J Biol Chem 2014; 289:16290-302. [PMID: 24770419 DOI: 10.1074/jbc.m114.562355] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Among the defects in the early events of insulin biosynthesis, proinsulin misfolding and endoplasmic reticulum (ER) stress have drawn increasing attention as causes of β cell failure. However, no studies have yet addressed potential defects at the cytosolic entry point of preproinsulin into the secretory pathway. Here, we provide the first evidence that inefficient translocation of preproinsulin (caused by loss of a positive charge in the n region of its signal sequence) contributes to β cell failure and diabetes. Specifically, we find that, after targeting to the ER membrane, preproinsulin signal peptide (SP) mutants associated with autosomal dominant late-onset diabetes fail to be fully translocated across the ER membrane. The newly synthesized, untranslocated preproinsulin remains strongly associated with the ER membrane, exposing its proinsulin moiety to the cytosol. Rather than accumulating in the ER and inducing ER stress, untranslocated preproinsulin accumulates in a juxtanuclear compartment distinct from the Golgi complex, induces the expression of heat shock protein 70 (HSP70), and promotes β cell death. Restoring an N-terminal positive charge to the mutant preproinsulin SP significantly improves the translocation defect. These findings not only reveal a novel molecular pathogenesis of β cell failure and diabetes but also provide the first evidence of the physiological and pathological significance of the SP n region positive charge of secretory proteins.
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Affiliation(s)
- Huan Guo
- From the Division of Metabolism, Endocrinology, and Diabetes, University of Michigan Medical School, Ann Arbor, Michigan 48105
| | - Yi Xiong
- From the Division of Metabolism, Endocrinology, and Diabetes, University of Michigan Medical School, Ann Arbor, Michigan 48105
| | - Piotr Witkowski
- the Division of Organ Transplantation, University of Chicago, Chicago, Illinois 60637
| | - Jingqing Cui
- From the Division of Metabolism, Endocrinology, and Diabetes, University of Michigan Medical School, Ann Arbor, Michigan 48105, the Division of Metabolism, Tianjin Medical University General Hospital, Tianjin, China 300052
| | - Ling-jia Wang
- the Division of Organ Transplantation, University of Chicago, Chicago, Illinois 60637
| | - Jinhong Sun
- From the Division of Metabolism, Endocrinology, and Diabetes, University of Michigan Medical School, Ann Arbor, Michigan 48105
| | - Roberto Lara-Lemus
- From the Division of Metabolism, Endocrinology, and Diabetes, University of Michigan Medical School, Ann Arbor, Michigan 48105, the Department of Research in Biochemistry, National Institute of Respiratory Diseases "Ismael Cosío Villegas", Mexico City 14080, Mexico, and
| | - Leena Haataja
- From the Division of Metabolism, Endocrinology, and Diabetes, University of Michigan Medical School, Ann Arbor, Michigan 48105
| | - Kathryn Hutchison
- From the Division of Metabolism, Endocrinology, and Diabetes, University of Michigan Medical School, Ann Arbor, Michigan 48105
| | - Shu-ou Shan
- the Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125
| | - Peter Arvan
- From the Division of Metabolism, Endocrinology, and Diabetes, University of Michigan Medical School, Ann Arbor, Michigan 48105,
| | - Ming Liu
- From the Division of Metabolism, Endocrinology, and Diabetes, University of Michigan Medical School, Ann Arbor, Michigan 48105, the Division of Metabolism, Tianjin Medical University General Hospital, Tianjin, China 300052,
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Guizzetti L, McGirr R, Dhanvantari S. Two dipolar α-helices within hormone-encoding regions of proglucagon are sorting signals to the regulated secretory pathway. J Biol Chem 2014; 289:14968-80. [PMID: 24727476 DOI: 10.1074/jbc.m114.563684] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Proglucagon is expressed in pancreatic α cells, intestinal L cells, and some hypothalamic and brainstem neurons. Tissue-specific processing of proglucagon yields three major peptide hormones as follows: glucagon in the α cells and glucagon-like peptides (GLP)-1 and -2 in the L cells and neurons. Efficient sorting and packaging into the secretory granules of the regulated secretory pathway in each cell type are required for nutrient-regulated secretion of these proglucagon-derived peptides. Our previous work suggested that proglucagon is directed into granules by intrinsic sorting signals after initial processing to glicentin and major proglucagon fragment (McGirr, R., Guizzetti, L., and Dhanvantari, S. (2013) J. Endocrinol. 217, 229-240), leading to the hypothesis that sorting signals may be present in multiple domains. In the present study, we show that the α-helices within glucagon and GLP-1, but not GLP-2, act as sorting signals by efficiently directing a heterologous secretory protein to the regulated secretory pathway. Biophysical characterization of these peptides revealed that glucagon and GLP-1 each encode a nonamphipathic, dipolar α-helix, whereas the helix in GLP-2 is not dipolar. Surprisingly, glicentin and major proglucagon fragment were sorted with different efficiencies, thus providing evidence that proglucagon is first sorted to granules prior to processing. In contrast to many other prohormones in which sorting is directed by ordered prodomains, the sorting determinants of proglucagon lie within the ordered hormone domains of glucagon and GLP-1, illustrating that each prohormone has its own sorting "signature."
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Affiliation(s)
| | - Rebecca McGirr
- the Metabolism/Diabetes and Imaging Programs, Lawson Health Research Institute, London, Ontario N6A 4V2, Canada
| | - Savita Dhanvantari
- From the Departments of Medical Biophysics, the Metabolism/Diabetes and Imaging Programs, Lawson Health Research Institute, London, Ontario N6A 4V2, Canada Pathology, and Medicine, University of Western Ontario, London, Ontario N6A 3K7 and
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Liu M, Wright J, Guo H, Xiong Y, Arvan P. Proinsulin entry and transit through the endoplasmic reticulum in pancreatic beta cells. VITAMINS AND HORMONES 2014; 95:35-62. [PMID: 24559913 DOI: 10.1016/b978-0-12-800174-5.00002-8] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Insulin is an essential hormone for maintaining metabolic homeostasis in the body. To make fully bioactive insulin, pancreatic beta cells initiate synthesis of the insulin precursor, preproinsulin, at the cytosolic side of the endoplasmic reticulum (ER), whereupon it undergoes co- and post-translational translocation across the ER membrane. Preproinsulin is cleaved by signal peptidase to form proinsulin that folds on the luminal side of the ER, forming three evolutionarily conserved disulfide bonds. Properly folded proinsulin forms dimers and exits from the ER, trafficking through Golgi complex into immature secretory granules wherein C-peptide is endoproteolytically excised, allowing fully bioactive two-chain insulin to ultimately be stored in mature granules for insulin secretion. Although insulin biosynthesis has been intensely studied in recent decades, the earliest events, including proinsulin entry and exit from the ER, have been relatively understudied. However, over the past 5 years, more than 20 new insulin gene mutations have been reported to cause a new syndrome termed Mutant INS-gene-induced Diabetes of Youth (MIDY). Although these mutants have not been completely characterized, most of them affect proinsulin entry and exit from the ER. Here, we summarize our current knowledge about the early events of insulin biosynthesis and review recent advances in understanding how defects in these events may lead to pancreatic beta cell failure.
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Affiliation(s)
- Ming Liu
- Division of Metabolism, Endocrinology & Diabetes, The University of Michigan Medical School, Ann Arbor, Michigan, USA; Department of Metabolism, Tianjin Medical University General Hospital, Tianjin, PR China.
| | - Jordan Wright
- Division of Metabolism, Endocrinology & Diabetes, The University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Huan Guo
- Division of Metabolism, Endocrinology & Diabetes, The University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Yi Xiong
- Division of Metabolism, Endocrinology & Diabetes, The University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Peter Arvan
- Division of Metabolism, Endocrinology & Diabetes, The University of Michigan Medical School, Ann Arbor, Michigan, USA.
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Pottekat A, Becker S, Spencer KR, Yates JR, Manning G, Itkin-Ansari P, Balch WE. Insulin biosynthetic interaction network component, TMEM24, facilitates insulin reserve pool release. Cell Rep 2013; 4:921-30. [PMID: 24012759 DOI: 10.1016/j.celrep.2013.07.050] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2013] [Revised: 07/16/2013] [Accepted: 07/31/2013] [Indexed: 12/31/2022] Open
Abstract
Insulin homeostasis in pancreatic β cells is now recognized as a critical element in the progression of obesity and type II diabetes (T2D). Proteins that interact with insulin to direct its sequential synthesis, folding, trafficking, and packaging into reserve granules in order to manage release in response to elevated glucose remain largely unknown. Using a conformation-based approach combined with mass spectrometry, we have generated the insulin biosynthetic interaction network (insulin BIN), a proteomic roadmap in the β cell that describes the sequential interacting partners of insulin along the secretory axis. The insulin BIN revealed an abundant C2 domain-containing transmembrane protein 24 (TMEM24) that manages glucose-stimulated insulin secretion from a reserve pool of granules, a critical event impaired in patients with T2D. The identification of TMEM24 in the context of a comprehensive set of sequential insulin-binding partners provides a molecular description of the insulin secretory pathway in β cells.
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Affiliation(s)
- Anita Pottekat
- Department of Cell and Molecular Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA
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Diabetes mellitus due to the toxic misfolding of proinsulin variants. FEBS Lett 2013; 587:1942-50. [PMID: 23669362 DOI: 10.1016/j.febslet.2013.04.044] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2013] [Revised: 04/29/2013] [Accepted: 04/30/2013] [Indexed: 02/06/2023]
Abstract
Dominant mutations in the human insulin gene can lead to pancreatic β-cell dysfunction and diabetes mellitus due to toxic folding of a mutant proinsulin. Analogous to a classical mouse model (the Akita mouse), this monogenic syndrome highlights the susceptibility of human β-cells to endoreticular stress due to protein misfolding and aberrant aggregation. The clinical mutations directly or indirectly perturb native disulfide pairing. Whereas the majority of mutations introduce or remove a cysteine (leading in either case to an unpaired residue), non-cysteine-related mutations identify key determinants of folding efficiency. Studies of such mutations suggest that the evolution of insulin has been constrained not only by its structure and function, but also by the susceptibility of its single-chain precursor to impaired foldability.
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Islam MR, Arslan I, Attia J, McEvoy M, McElduff P, Basher A, Rahman W, Peel R, Akhter A, Akter S, Vashum KP, Milton AH. Is serum zinc level associated with prediabetes and diabetes?: a cross-sectional study from Bangladesh. PLoS One 2013; 8:e61776. [PMID: 23613929 PMCID: PMC3629219 DOI: 10.1371/journal.pone.0061776] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2012] [Accepted: 03/13/2013] [Indexed: 12/17/2022] Open
Abstract
AIMS To determine serum zinc level and other relevant biological markers in normal, prediabetic and diabetic individuals and their association with Homeostasis Model Assessment (HOMA) parameters. METHODS This cross-sectional study was conducted between March and December 2009. Any patient aged ≥ 30 years attending the medicine outpatient department of a medical university hospital in Dhaka, Bangladesh and who had a blood glucose level ordered by a physician was eligible to participate. RESULTS A total of 280 participants were analysed. On fasting blood sugar results, 51% were normal, 13% had prediabetes and 36% had diabetes. Mean serum zinc level was lowest in prediabetic compared to normal and diabetic participants (mean differences were approximately 65 ppb/L and 33 ppb/L, respectively). In multiple linear regression, serum zinc level was found to be significantly lower in prediabetes than in those with normoglycemia. Beta cell function was significantly lower in prediabetes than normal participants. Adjusted linear regression for HOMA parameters did not show a statistically significant association between serum zinc level, beta cell function (P = 0.07) and insulin resistance (P = 0.08). Low serum zinc accentuated the increase in insulin resistance seen with increasing BMI. CONCLUSION Participants with prediabetes have lower zinc levels than controls and zinc is significantly associated with beta cell function and insulin resistance. Further longitudinal population based studies are warranted and controlled trials would be valuable for establishing whether zinc supplementation in prediabetes could be a useful strategy in preventing progression to Type 2 diabetes.
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Affiliation(s)
- Md. Rafiqul Islam
- Centre for Clinical Epidemiology and Biostatistics (CCEB), School of Medicine and Public Health, The University of Newcastle, New Lambton Heights, New South Wales, Australia
| | - Iqbal Arslan
- Department of Biochemistry, Bangobondhu Sheikh Mujib Medical University (BSMMU), Dhaka, Bangladesh
| | - John Attia
- Centre for Clinical Epidemiology and Biostatistics (CCEB), School of Medicine and Public Health, The University of Newcastle, New Lambton Heights, New South Wales, Australia
| | - Mark McEvoy
- Centre for Clinical Epidemiology and Biostatistics (CCEB), School of Medicine and Public Health, The University of Newcastle, New Lambton Heights, New South Wales, Australia
| | - Patrick McElduff
- Centre for Clinical Epidemiology and Biostatistics (CCEB), School of Medicine and Public Health, The University of Newcastle, New Lambton Heights, New South Wales, Australia
| | - Ariful Basher
- Department of Medicine, Mymensingh Medical College, Ministry of Health and Family Welfare, Government of Bangladesh, Mymensingh, Bangladesh
| | - Waliur Rahman
- Department of Biochemistry, Bangobondhu Sheikh Mujib Medical University (BSMMU), Dhaka, Bangladesh
| | - Roseanne Peel
- Centre for Clinical Epidemiology and Biostatistics (CCEB), School of Medicine and Public Health, The University of Newcastle, New Lambton Heights, New South Wales, Australia
| | - Ayesha Akhter
- Department of Obstetrics and Gynaecology, Tairunnessa Memorial Medical College, Gazipur, Dhaka, Bangladesh
| | - Shahnaz Akter
- Department of Paediatrics, Institute of Child and Mother Health (ICMH), Dhaka, Bangladesh
| | - Khanrin P. Vashum
- Centre for Clinical Epidemiology and Biostatistics (CCEB), School of Medicine and Public Health, The University of Newcastle, New Lambton Heights, New South Wales, Australia
| | - Abul Hasnat Milton
- Centre for Clinical Epidemiology and Biostatistics (CCEB), School of Medicine and Public Health, The University of Newcastle, New Lambton Heights, New South Wales, Australia
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Haataja L, Snapp E, Wright J, Liu M, Hardy AB, Wheeler MB, Markwardt ML, Rizzo M, Arvan P. Proinsulin intermolecular interactions during secretory trafficking in pancreatic β cells. J Biol Chem 2012; 288:1896-906. [PMID: 23223446 DOI: 10.1074/jbc.m112.420018] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Classically, exit from the endoplasmic reticulum (ER) is rate-limiting for secretory protein trafficking because protein folding/assembly occurs there. In this study, we have exploited "hPro-CpepSfGFP," a human proinsulin bearing "superfolder" green fluorescent C-peptide expressed in pancreatic β cells where it is processed to human insulin and CpepSfGFP. Remarkably, steady-state accumulation of hPro-CpepSfGFP and endogenous proinsulin is in the Golgi region, as if final stages of protein folding/assembly were occurring there. The Golgi regional distribution of proinsulin is dynamic, influenced by fasting/refeeding, and increased with β cell zinc deficiency. However, coexpression of ER-entrapped mutant proinsulin-C(A7)Y shifts the steady-state distribution of wild-type proinsulin to the ER. Endogenous proinsulin coprecipitates with hPro-CpepSfGFP and even more so with hProC(A7)Y-CpepSfGFP. Using Cerulean and Venus-tagged proinsulins, we find that both WT-WT and WT-mutant proinsulin pairs exhibit FRET. The data demonstrate that wild-type proinsulin dimerizes within the ER but accumulates at a poorly recognized slow step within the Golgi region, reflecting either slow kinetics of proinsulin hexamerization, steps in formation of nascent secretory granules, or other unknown molecular events. However, in the presence of ongoing misfolding of a subpopulation of proinsulin in β cells, the rate-limiting step in transport of the remaining proinsulin shifts to the ER.
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Affiliation(s)
- Leena Haataja
- Division of Metabolism, Endocrinology, and Diabetes, University of Michigan Medical School, Ann Arbor, Michigan 48105, USA
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El Muayed M, Raja MR, Zhang X, MacRenaris KW, Bhatt S, Chen X, Urbanek M, O'Halloran TV, Lowe WL. Accumulation of cadmium in insulin-producing β cells. Islets 2012; 4:405-16. [PMID: 23466887 PMCID: PMC3605169 DOI: 10.4161/isl.23101] [Citation(s) in RCA: 77] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Evidence suggests that chronic low level cadmium exposure impairs the function of insulin-producing β cells and may be associated with type-2 diabetes mellitus. Herein, we describe the cadmium content in primary human islets and define the uptake kinetics and effects of environmentally relevant cadmium concentrations in cultured β cells. The average cadmium content in islets from 10 non-diabetic human subjects was 29 ± 7 nmol/g protein (range 7 to 72 nmol/g protein). Exposure of the β-cell line MIN6 to CdCl 2 concentrations between 0.1 and 1.0 µmol/L resulted in a dose- and time-dependent uptake of cadmium over 72 h. This uptake resulted in an induction of metallthionein expression, likely enhancing cellular cadmium accumulation. Furthermore, cadmium accumulation resulted in an inhibition of glucose stimulated insulin secretion in MIN6 cells and primary mouse islets. Our results indicate that this impairment in β-cell function is not due to an increase in cell death or due to an increase in oxidative stress. We conclude that mouse β cells accumulate cadmium in a dose- and time-dependent manner over a prolonged time course at environmentally relevant concentrations. This uptake leads to a functional impairment of β-cell function without significant alterations in cell viability, expression of genes important for β-cell function or increase in oxidative stress.
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Affiliation(s)
- Malek El Muayed
- Division of Endocrinology, Metabolism and Molecular Medicine, Northwestern University Feinberg School of Medicine, Chicago, IL, USA.
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Arvan P, Pietropaolo M, Ostrov D, Rhodes CJ. Islet autoantigens: structure, function, localization, and regulation. Cold Spring Harb Perspect Med 2012; 2:cshperspect.a007658. [PMID: 22908193 DOI: 10.1101/cshperspect.a007658] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Islet autoantigens associated with autoimmune type 1 diabetes (T1D) are expressed in pancreatic β cells, although many show wider patterns of expression in the neuroendocrine system. Within pancreatic β cells, every T1D autoantigen is in one way or another linked to the secretory pathway. Together, these autoantigens play diverse roles in glucose regulation, metabolism of biogenic amines, as well as the regulation, formation, and packaging of secretory granules. The mechanism(s) by which immune tolerance to islet-cell antigens is lost during the development of T1D, remains unclear. Antigenic peptide creation for immune presentation may potentially link to the secretory biology of β cells in a number of ways, including proteasomal digestion of misfolded products, exocytosis and endocytosis of cell-surface products, or antigen release from dying β cells during normal or pathological turnover. In this context, we evaluate the biochemical nature and immunogenicity of the major autoantigens in T1D including (pro)insulin, GAD65, ZnT8, IA2, and ICA69.
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Affiliation(s)
- Peter Arvan
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical School, Ann Arbor, MI 48105, USA.
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Sheline CT. Involvement of SIRT1 in Zn 2+, Streptozotocin, Non-Obese Diabetic, and Cytokine-Mediated Toxicities of β-cells. JOURNAL OF DIABETES & METABOLISM 2012; 3:1000193. [PMID: 23565341 PMCID: PMC3615451 DOI: 10.4172/2155-6156.1000193] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Zn2+ toxicity is implicated in pancreatic β-cell death that occurs secondarily to: streptozotocin exposure in vitro; and both autoimmune attack or streptozotocin in vivo models of T1DM. This is demonstrated by reduced β-cell death or diabetic incidence in vitro or in NOD mice after treatment with Zn2+ preferring chelators, pyruvate, nicotinamide, a reduced zinc diet, sirtuin inhibitors, or zinc transporter knockout. These therapeutics are also demonstrated to be efficacious against Zn2+ neurotoxicity. AIMS To determine if the sirtuin pathway is involved in Zn2+-, streptozotocin-, or cytokine-mediated β-cell death in vitro, and streptozotocin-, or NOD induced T1DM in vivo. METHODS Sensitivity of MIN6 cells expressing empty vector, sirtuin protein-1 (SIRT1) or its siRNA, to Zn2+, streptozotocin, or cytokines, and effects on NAD+ levels were determined. Covariance of manipulating SIRT1 levels with diabetic incidence was tested in vivo. RESULTS 1) sirtuin pathway inhibition or SIRT1 knockdown attenuated Zn2+-, STZ-, and cytokine-mediated toxicity and NAD+ loss in β-cells, 2) SIRT1 overexpression potentiated these toxicities, 3) young SIRT1 β-cell transgenic mice have improved glucose tolerance under basal conditions, but upon aging showed increased sensitivity to streptozotocin compared to SIRT1 +/- mice, and 4) SIRT1 +/- mice in an NOD background or exposed to streptozotocin trended toward reduced diabetic incidence and mortality compared to wildtype. CONCLUSIONS These results have implicated SIRT1-mediated NAD+ loss in Zn2+, STZ, or cytokine toxicities of MIN6, and in NOD or streptozotocin T1DM animal models. Modulation of β-cell Zn2+ and NAD+ levels, and the sirtuin pathway could be novel therapeutic targets for T1DM.
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Vinther TN, Norrman M, Strauss HM, Huus K, Schlein M, Pedersen TÅ, Kjeldsen T, Jensen KJ, Hubálek F. Novel covalently linked insulin dimer engineered to investigate the function of insulin dimerization. PLoS One 2012; 7:e30882. [PMID: 22363506 PMCID: PMC3281904 DOI: 10.1371/journal.pone.0030882] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2011] [Accepted: 12/23/2011] [Indexed: 11/18/2022] Open
Abstract
An ingenious system evolved to facilitate insulin binding to the insulin receptor as a monomer and at the same time ensure sufficient stability of insulin during storage. Insulin dimer is the cornerstone of this system. Insulin dimer is relatively weak, which ensures dissociation into monomers in the circulation, and it is stabilized by hexamer formation in the presence of zinc ions during storage in the pancreatic β-cell. Due to the transient nature of insulin dimer, direct investigation of this important form is inherently difficult. To address the relationship between insulin oligomerization and insulin stability and function, we engineered a covalently linked insulin dimer in which two monomers were linked by a disulfide bond. The structure of this covalent dimer was identical to the self-association dimer of human insulin. Importantly, this covalent dimer was capable of further oligomerization to form the structural equivalent of the classical hexamer. The covalently linked dimer neither bound to the insulin receptor, nor induced a metabolic response in vitro. However, it was extremely thermodynamically stable and did not form amyloid fibrils when subjected to mechanical stress, underlining the importance of oligomerization for insulin stability.
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Affiliation(s)
- Tine N. Vinther
- Diabetes Research Unit, Novo Nordisk A/S, Novo Nordisk Park, Måløv, Denmark
- Faculty of Life Sciences, IGM, University of Copenhagen, Frederiksberg, Denmark
| | - Mathias Norrman
- Diabetes Research Unit, Novo Nordisk A/S, Novo Nordisk Park, Måløv, Denmark
| | - Holger M. Strauss
- Diabetes Research Unit, Novo Nordisk A/S, Novo Nordisk Park, Måløv, Denmark
| | - Kasper Huus
- Diabetes Research Unit, Novo Nordisk A/S, Novo Nordisk Park, Måløv, Denmark
| | - Morten Schlein
- Diabetes Research Unit, Novo Nordisk A/S, Novo Nordisk Park, Måløv, Denmark
| | - Thomas Å. Pedersen
- Diabetes Research Unit, Novo Nordisk A/S, Novo Nordisk Park, Måløv, Denmark
| | - Thomas Kjeldsen
- Diabetes Research Unit, Novo Nordisk A/S, Novo Nordisk Park, Måløv, Denmark
| | - Knud J. Jensen
- Faculty of Life Sciences, IGM, University of Copenhagen, Frederiksberg, Denmark
| | - František Hubálek
- Diabetes Research Unit, Novo Nordisk A/S, Novo Nordisk Park, Måløv, Denmark
- * E-mail:
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Substrate-favored lysosomal and proteasomal pathways participate in the normal balance control of insulin precursor maturation and disposal in β-cells. PLoS One 2011; 6:e27647. [PMID: 22102916 PMCID: PMC3213186 DOI: 10.1371/journal.pone.0027647] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2011] [Accepted: 10/21/2011] [Indexed: 11/19/2022] Open
Abstract
Our recent studies have uncovered that aggregation-prone proinsulin preserves a low relative folding rate and maintains a homeostatic balance of natively and non-natively folded states (i.e., proinsulin homeostasis, PIHO) in β-cells as a result of the integration of maturation and disposal processes. Control of precursor maturation and disposal is thus an early regulative mechanism in the insulin production of β-cells. Herein, we show pathways involved in the disposal of endogenous proinsulin at the early secretory pathway. We conducted metabolic-labeling, immunoblotting, and immunohistochemistry studies to examine the effects of selective proteasome and lysosome or autophagy inhibitors on the kinetics of proinsulin and control proteins in various post-translational courses. Our metabolic-labeling studies found that the main lysosomal and ancillary proteasomal pathways participate in the heavy clearance of insulin precursor in mouse islets/β-cells cultured at the mimic physiological glucose concentrations. Further immunoblotting and immunohistochemistry studies in cloned β-cells validated that among secretory proteins, insulin precursor is heavily and preferentially removed. The rapid disposal of a large amount of insulin precursor after translation is achieved mainly through lysosomal autophagy and the subsequent basal disposals are carried out by both lysosomal and proteasomal pathways within a 30 to 60-minute post-translational process. The findings provide the first clear demonstration that lysosomal and proteasomal pathways both play roles in the normal maintenance of PIHO for insulin production, and defined the physiological participation of lysosomal autophagy in the protein quality control at the early secretory pathway of pancreatic β-cells.
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Verhulst PJ, Lintermans A, Janssen S, Loeckx D, Himmelreich U, Buyse J, Tack J, Depoortere I. GPR39, a receptor of the ghrelin receptor family, plays a role in the regulation of glucose homeostasis in a mouse model of early onset diet-induced obesity. J Neuroendocrinol 2011; 23:490-500. [PMID: 21470317 DOI: 10.1111/j.1365-2826.2011.02132.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
GPR39, which may function as a Zn(2+) sensor, is a member of the G protein-coupled receptor family that also includes the receptor for the hunger hormone ghrelin. The down-regulation of GPR39 mRNA in adipose tissue of obese type 2 diabetic patients suggests that GPR39 may contribute to the pathogenesis of the disease. The present study aimed to investigate the role of GPR39 in the regulation of energy balance and glucose homeostasis in wild-type (GPR39(+/+) ) and GPR39 knockout mice (GPR39(-/-) ) with obesity-related type 2 diabetes. GPR39 mRNA levels in adipose tissue of fasted GPR39(+/+) mice fed a high-fat diet (HFD) for 30 weeks were reduced and correlated positively with blood glucose levels. Body weight, fat percentage and energy intake were increased in the HFD group but did not differ between both genotypes. Within the HFD group, blood glucose levels were lower in GPR39(-/-) than in GPR39(+/+) mice, despite significant reductions in prandial plasma insulin levels. The latter may not be a result of changes in β-cell hyperplasia because immunohistochemical staining of pancreata of mice on a HFD showed no differences between genotypes. The lower blood glucose levels may involve alterations in insulin sensitivity as revealed by glucose tolerance tests and respiratory quotient measurements that showed a preference of obese GPR39(-/-) mice for the use of carbohydrates as metabolic fuel. The increase in plasma ghrelin levels in GPR39(-/-) mice fed a HFD may contribute to the alterations in glucose homeostasis, whereas changes in gastric emptying or intestinal Zn(2+) absorption are not involved. The results obtained in the present study suggest that GPR39 plays a role in the pathogenesis of obesity-related type 2 diabetes by affecting the regulation of glucose homeostasis.
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MESH Headings
- Age of Onset
- Animals
- Diabetes Mellitus, Type 2/genetics
- Diabetes Mellitus, Type 2/metabolism
- Diet/adverse effects
- Diet, Atherogenic
- Disease Models, Animal
- Genetic Predisposition to Disease
- Glucose/metabolism
- Homeostasis/genetics
- Male
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Multigene Family/physiology
- Obesity/epidemiology
- Obesity/etiology
- Obesity/genetics
- Obesity/metabolism
- Receptors, G-Protein-Coupled/genetics
- Receptors, G-Protein-Coupled/metabolism
- Receptors, G-Protein-Coupled/physiology
- Receptors, Ghrelin/genetics
- Receptors, Ghrelin/physiology
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Affiliation(s)
- P J Verhulst
- Department of Pathophysiology, Translational Research Center for Gastrointestinal Disorders, Catholic University of Leuven, Leuven, Belgium
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Wang J, Chen Y, Yuan Q, Tang W, Zhang X, Osei K. Control of precursor maturation and disposal is an early regulative mechanism in the normal insulin production of pancreatic β-cells. PLoS One 2011; 6:e19446. [PMID: 21559376 PMCID: PMC3084858 DOI: 10.1371/journal.pone.0019446] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2010] [Accepted: 04/06/2011] [Indexed: 11/22/2022] Open
Abstract
The essential folding and maturation process of proinsulin in β-cells is largely uncharacterized. To analyze this process, we improved approaches to immunoblotting, metabolic labeling, and data analysis used to determine the proportion of monomers and non-monomers and changes in composition of proinsulin in cells. We found the natural occurrence of a large proportion of proinsulin in various non-monomer states, i.e., aggregates, in normal mouse and human β-cells and a striking increase in the proportion of proinsulin non-monomers in Ins2+/Akita mice in response to a mutation (C96Y) in the insulin 2 (Ins2) gene. Proinsulin emerges in monomer and abundant dual-fate non-monomer states during nascent protein synthesis and shows heavy and preferential ATP/redox-sensitive disposal among secretory proteins during early post-translational processes. These findings support the preservation of proinsulin's aggregation-prone nature and low relative folding rate that permits the plentiful production of non-monomer forms with incomplete folding. Thus, in normal mouse/human β-cells, proinsulin's integrated maturation and degradation processes maintain a balance of natively and non-natively folded states, i.e., proinsulin homeostasis (PIHO). Further analysis discovered the high susceptibility of PIHO to cellular energy and calcium changes, endoplasmic reticulum (ER) and reductive/oxidative stress, and insults by thiol reagent and cytokine. These results expose a direct correlation between various extra-/intracellular influences and (a)typical integrations of proinsulin maturation and disposal processes. Overall, our findings demonstrated that the control of precursor maturation and disposal acts as an early regulative mechanism in normal insulin production, and its disorder is crucially linked to β-cell failure and diabetes pathogenesis.
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Affiliation(s)
- Jie Wang
- Department of Internal Medicine, The Ohio State University, Columbus, Ohio, United States of America.
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Bosco MD, Mohanasundaram DM, Drogemuller CJ, Lang CJ, Zalewski PD, Coates PT. Zinc and zinc transporter regulation in pancreatic islets and the potential role of zinc in islet transplantation. Rev Diabet Stud 2011; 7:263-74. [PMID: 21713314 DOI: 10.1900/rds.2010.7.263] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
The critical trace element zinc is essential for normal insulin production, and plays a central role in cellular protection against apoptosis and oxidative stress. The regulation of zinc within the pancreas and β-cells is controlled by the zinc transporter families ZnT and ZIP. Pancreatic islets display wide variability in the occurrence of these molecules. The zinc transporter, ZnT8 is an important target for autoimmunity in type 1 diabetes. Gene polymorphisms of this transporter confer sensitivity for immunosuppressive drugs used in islet transplantation. Understanding the biology of zinc transport within pancreatic islets will provide insight into the mechanisms of β-cell death, and may well reveal new pathways for improvement of diabetes therapy, including islet transplantation. This review discusses the possible roles of zinc in β-cell physiology with a special focus on islet transplantation.
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Affiliation(s)
- Mariea D Bosco
- Central Northern Adelaide Renal and Transplantation Service, Renal and Transplantation Immunology Lab, Royal Adelaide Hospital, South Australia
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