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Vaňková M, Vejražková D, Lukášová P, Včelák J, Chocholová D, Bendlová B. Age-Related Changes in Proinsulin Processing in Normoglycemic Individuals. Physiol Res 2023; 72:S389-S397. [PMID: 38116775 DOI: 10.33549/physiolres.935181] [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: 01/05/2024] Open
Abstract
In order to understand the pathological changes associated with glucose homeostasis in old age, it is necessary to know the natural changes in the processing of proinsulin to mature insulin. While there is abundant information about insulin production and function in diabetics, the situation in healthy adults and the elderly has surprisingly rarely been investigated. The aim of the study was to determine how proinsulin secretion changes in individuals with normal glucose tolerance during the process of natural aging. A total of 761 individuals (539 women, 222 men) aged 18-90 years with normal fasting glycemia (less than 5.6 mmol/l) were divided into five groups according to age. Body composition and levels of fasting blood glucose, proinsulin, insulin, and C-peptide were determined, and the ratios of proinsulin to both insulin and C-peptide were calculated. The homeostasis model of ?-cell function (HOMA F) and peripheral insulin resistance (HOMA R) were calculated. The effect of age was assessed using an ANOVA model consisting of the factors sex, age, and sex × age interaction. Statgraphics Centurion v. XVIII statistical software was used. Glycemia, insulin, C-peptide and HOMA R increased in both sexes up to 75 years. On the contrary, proinsulin levels as well as proinsulin/insulin and proinsulin/C-peptide ratios decreased with age up to 75 years. In normoglycemic and normotolerant people, both women and men, the aging process is associated with decreased insulin sensitivity compensated by potentiation of insulin production. In older age, there is also a gradual decrease in circulating proinsulin, which can be explained by its more efficient processing into active insulin by matured healthy beta cells.
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Affiliation(s)
- M Vaňková
- Institute of Endocrinology, Prague, Czech Republic, Faculty of Science, Charles University, Prague, Czech Republic
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2
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Urbanczyk M, Jeyagaran A, Zbinden A, Lu CE, Marzi J, Kuhlburger L, Nahnsen S, Layland SL, Duffy G, Schenke-Layland K. Decorin improves human pancreatic β-cell function and regulates ECM expression in vitro. Matrix Biol 2023; 115:160-183. [PMID: 36592738 DOI: 10.1016/j.matbio.2022.12.005] [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: 09/21/2022] [Revised: 12/23/2022] [Accepted: 12/29/2022] [Indexed: 01/01/2023]
Abstract
Transplantation of islets of Langerhans is a promising alternative treatment strategy in severe cases of type 1 diabetes mellitus; however, the success rate is limited by the survival rate of the cells post-transplantation. Restoration of the native pancreatic niche during transplantation potentially can help to improve cell viability and function. Here, we assessed for the first time the regulatory role of the small leucine-rich proteoglycan decorin (DCN) in insulin secretion in human β-cells, and its impact on pancreatic extracellular matrix (ECM) protein expression in vitro. In depth analyses utilizing next-generation sequencing as well as Raman microspectroscopy and Raman imaging identified pathways related to glucose metabolism to be upregulated in DCN-treated cells, including oxidative phosphorylation within the mitochondria as well as proteins and lipids of the endoplasmic reticulum. We further showed the effectiveness of DCN in a transplantation setting by treating collagen type 1-encapsulated β-cell-containing pseudo-islets with DCN. Taken together, in this study, we demonstrate the potential of DCN to improve the function of insulin-secreting β-cells while reducing the expression of ECM proteins affiliated with fibrotic capsule formation, making DCN a highly promising therapeutic agent for islet transplantation.
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Affiliation(s)
- Max Urbanczyk
- Institute of Biomedical Engineering, Department for Medical Technologies and Regenerative Medicine, Eberhard Karls University Tübingen, Silcherstr. 7/1, Tübingen 72076, Germany
| | - Abiramy Jeyagaran
- Institute of Biomedical Engineering, Department for Medical Technologies and Regenerative Medicine, Eberhard Karls University Tübingen, Silcherstr. 7/1, Tübingen 72076, Germany; NMI Natural and Medical Sciences Institute at the University of Tübingen, Reutlingen, Germany
| | - Aline Zbinden
- Institute of Biomedical Engineering, Department for Medical Technologies and Regenerative Medicine, Eberhard Karls University Tübingen, Silcherstr. 7/1, Tübingen 72076, Germany; Department of Immunology, Leiden University Medical Center Leiden, ZA 2333, the Netherlands
| | - Chuan-En Lu
- Institute of Biomedical Engineering, Department for Medical Technologies and Regenerative Medicine, Eberhard Karls University Tübingen, Silcherstr. 7/1, Tübingen 72076, Germany
| | - Julia Marzi
- Institute of Biomedical Engineering, Department for Medical Technologies and Regenerative Medicine, Eberhard Karls University Tübingen, Silcherstr. 7/1, Tübingen 72076, Germany; NMI Natural and Medical Sciences Institute at the University of Tübingen, Reutlingen, Germany; Cluster of Excellence iFIT (EXC 2180) "Image-Guided and Functionally Instructed Tumor Therapies", Eberhard Karls University Tübingen, Tübingen, Germany
| | - Laurence Kuhlburger
- Quantitative Biology Center (QBiC), Eberhard Karls University of Tübingen, Tübingen, Germany; Biomedical Data Science, Department of Computer Science, Eberhard Karls University Tübingen, Tübingen, Germany
| | - Sven Nahnsen
- Quantitative Biology Center (QBiC), Eberhard Karls University of Tübingen, Tübingen, Germany; Biomedical Data Science, Department of Computer Science, Eberhard Karls University Tübingen, Tübingen, Germany
| | - Shannon L Layland
- Institute of Biomedical Engineering, Department for Medical Technologies and Regenerative Medicine, Eberhard Karls University Tübingen, Silcherstr. 7/1, Tübingen 72076, Germany; Department of Women's Health, Eberhard Karls University Tübingen, Tübingen, Germany
| | - Garry Duffy
- Discipline of Anatomy and the Regenerative Medicine Institute, School of Medicine, College of Medicine Nursing and Health Sciences, National University of Ireland Galway, Ireland; Science Foundation Ireland (SFI) Centre for Research in Advanced Materials for Biomedical Engineering (AMBER), Trinity College Dublin & National University of Ireland Galway, Galway, Ireland
| | - Katja Schenke-Layland
- Institute of Biomedical Engineering, Department for Medical Technologies and Regenerative Medicine, Eberhard Karls University Tübingen, Silcherstr. 7/1, Tübingen 72076, Germany; NMI Natural and Medical Sciences Institute at the University of Tübingen, Reutlingen, Germany; Cluster of Excellence iFIT (EXC 2180) "Image-Guided and Functionally Instructed Tumor Therapies", Eberhard Karls University Tübingen, Tübingen, Germany.
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3
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Miranda MA, Macias-Velasco JF, Lawson HA. Pancreatic β-cell heterogeneity in health and diabetes: classes, sources, and subtypes. Am J Physiol Endocrinol Metab 2021; 320:E716-E731. [PMID: 33586491 PMCID: PMC8238131 DOI: 10.1152/ajpendo.00649.2020] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Pancreatic β-cells perform glucose-stimulated insulin secretion, a process at the center of type 2 diabetes etiology. Efforts to understand how β-cells behave in healthy and stressful conditions have revealed a wide degree of morphological, functional, and transcriptional heterogeneity. Sources of heterogeneity include β-cell topography, developmental origin, maturation state, and stress response. Advances in sequencing and imaging technologies have led to the identification of β-cell subtypes, which play distinct roles in the islet niche. This review examines β-cell heterogeneity from morphological, functional, and transcriptional perspectives, and considers the relevance of topography, maturation, development, and stress response. It also discusses how these factors have been used to identify β-cell subtypes, and how heterogeneity is impacted by diabetes. We examine open questions in the field and discuss recent technological innovations that could advance understanding of β-cell heterogeneity in health and disease.
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Affiliation(s)
- Mario A Miranda
- Department of Genetics, Washington University School of Medicine, Saint Louis, Missouri
| | - Juan F Macias-Velasco
- Department of Genetics, Washington University School of Medicine, Saint Louis, Missouri
| | - Heather A Lawson
- Department of Genetics, Washington University School of Medicine, Saint Louis, Missouri
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4
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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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5
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Herlea-Pana O, Eeda V, Undi RB, Lim HY, Wang W. Pharmacological Inhibition of Inositol-Requiring Enzyme 1α RNase Activity Protects Pancreatic Beta Cell and Improves Diabetic Condition in Insulin Mutation-Induced Diabetes. Front Endocrinol (Lausanne) 2021; 12:749879. [PMID: 34675883 PMCID: PMC8524045 DOI: 10.3389/fendo.2021.749879] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/30/2021] [Accepted: 09/20/2021] [Indexed: 12/25/2022] Open
Abstract
β-cell ER stress plays an important role in β-cell dysfunction and death during the pathogenesis of diabetes. Proinsulin misfolding is regarded as one of the primary initiating factors of ER stress and unfolded protein response (UPR) activation in β-cells. Here, we found that the ER stress sensor inositol-requiring enzyme 1α (IRE1α) was activated in the Akita mice, a mouse model of mutant insulin gene-induced diabetes of youth (MIDY), a monogenic diabetes. Normalization of IRE1α RNase hyperactivity by pharmacological inhibitors significantly ameliorated the hyperglycemic conditions and increased serum insulin levels in Akita mice. These benefits were accompanied by a concomitant protection of functional β-cell mass, as shown by the suppression of β-cell apoptosis, increase in mature insulin production and reduction of proinsulin level. At the molecular level, we observed that the expression of genes associated with β-cell identity and function was significantly up-regulated and ER stress and its associated inflammation and oxidative stress were suppressed in islets from Akita mice treated with IRE1α RNase inhibitors. This study provides the evidence of the in vivo efficacy of IRE1α RNase inhibitors in Akita mice, pointing to the possibility of targeting IRE1α RNase as a therapeutic direction for the treatment of diabetes.
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Affiliation(s)
- Oana Herlea-Pana
- Department of Medicine, Division of Endocrinology, Harold Hamm Diabetes Center, Oklahoma City, OK, United States
| | - Venkateswararao Eeda
- Department of Medicine, Division of Endocrinology, Harold Hamm Diabetes Center, Oklahoma City, OK, United States
| | - Ram Babu Undi
- Department of Physiology, Harold Hamm Diabetes Center, The University of Oklahoma Health Science Center, Oklahoma City, OK, United States
| | - Hui-Ying Lim
- Department of Physiology, Harold Hamm Diabetes Center, The University of Oklahoma Health Science Center, Oklahoma City, OK, United States
| | - Weidong Wang
- Department of Medicine, Division of Endocrinology, Harold Hamm Diabetes Center, Oklahoma City, OK, United States
- *Correspondence: Weidong Wang, , orcid.org/0000-0003-3619-0953
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Sun J, Xiong Y, Li X, Haataja L, Chen W, Mir SA, Lv L, Madley R, Larkin D, Anjum A, Dhayalan B, Rege N, Wickramasinghe NP, Weiss MA, Itkin-Ansari P, Kaufman RJ, Ostrov DA, Arvan P, Liu M. Role of Proinsulin Self-Association in Mutant INS Gene-Induced Diabetes of Youth. Diabetes 2020; 69:954-964. [PMID: 32139596 PMCID: PMC7171958 DOI: 10.2337/db19-1106] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/06/2019] [Accepted: 02/22/2020] [Indexed: 02/06/2023]
Abstract
Abnormal interactions between misfolded mutant and wild-type (WT) proinsulin (PI) in the endoplasmic reticulum (ER) drive the molecular pathogenesis of mutant INS gene-induced diabetes of youth (MIDY). How these abnormal interactions are initiated remains unknown. Normally, PI-WT dimerizes in the ER. Here, we suggest that the normal PI-PI contact surface, involving the B-chain, contributes to dominant-negative effects of misfolded MIDY mutants. Specifically, we find that PI B-chain tyrosine-16 (Tyr-B16), which is a key residue in normal PI dimerization, helps confer dominant-negative behavior of MIDY mutant PI-C(A7)Y. Substitutions of Tyr-B16 with either Ala, Asp, or Pro in PI-C(A7)Y decrease the abnormal interactions between the MIDY mutant and PI-WT, rescuing PI-WT export, limiting ER stress, and increasing insulin production in β-cells and human islets. This study reveals the first evidence indicating that noncovalent PI-PI contact initiates dominant-negative behavior of misfolded PI, pointing to a novel therapeutic target to enhance PI-WT export and increase insulin production.
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Affiliation(s)
- Jinhong Sun
- Division of Metabolism, Endocrinology and Diabetes, University of Michigan Medical School, Ann Arbor, MI
| | - Yi Xiong
- Division of Metabolism, Endocrinology and Diabetes, University of Michigan Medical School, Ann Arbor, MI
| | - Xin Li
- Department of Endocrinology and Metabolism, Tianjin Medical University General Hospital, Tianjin, China
| | - Leena Haataja
- Division of Metabolism, Endocrinology and Diabetes, University of Michigan Medical School, Ann Arbor, MI
| | - Wei Chen
- Division of Metabolism, Endocrinology and Diabetes, University of Michigan Medical School, Ann Arbor, MI
- Beijing Institute of Pharmacology and Toxicology, Beijing, China
| | - Saiful A Mir
- Development, Aging and Regeneration Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA
| | - Li Lv
- Department of Endocrinology and Metabolism, Tianjin Medical University General Hospital, Tianjin, China
| | - Rachel Madley
- Division of Metabolism, Endocrinology and Diabetes, University of Michigan Medical School, Ann Arbor, MI
| | - Dennis Larkin
- Division of Metabolism, Endocrinology and Diabetes, University of Michigan Medical School, Ann Arbor, MI
| | - Arfah Anjum
- Division of Metabolism, Endocrinology and Diabetes, University of Michigan Medical School, Ann Arbor, MI
| | - Balamurugan Dhayalan
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN
| | - Nischay Rege
- Department of Biochemistry, Case Western Reserve University, Cleveland, OH
| | | | - Michael A Weiss
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN
| | - Pamela Itkin-Ansari
- Development, Aging and Regeneration Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA
- Department of Pediatrics, University of California, San Diego, La Jolla, CA
| | - Randal J Kaufman
- Degenerative Diseases Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA
| | - David A Ostrov
- Department of Pathology, Immunology and Laboratory Medicine, University of Florida College of Medicine, Gainesville, FL
| | - Peter Arvan
- Division of Metabolism, Endocrinology and Diabetes, University of Michigan Medical School, Ann Arbor, MI
| | - Ming Liu
- Division of Metabolism, Endocrinology and Diabetes, University of Michigan Medical School, Ann Arbor, MI
- Department of Endocrinology and Metabolism, Tianjin Medical University General Hospital, Tianjin, China
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7
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Arunagiri A, Haataja L, Pottekat A, Pamenan F, Kim S, Zeltser LM, Paton AW, Paton JC, Tsai B, Itkin-Ansari P, Kaufman RJ, Liu M, Arvan P. Proinsulin misfolding is an early event in the progression to type 2 diabetes. eLife 2019; 8:44532. [PMID: 31184302 PMCID: PMC6559786 DOI: 10.7554/elife.44532] [Citation(s) in RCA: 81] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2018] [Accepted: 04/09/2019] [Indexed: 02/06/2023] Open
Abstract
Biosynthesis of insulin – critical to metabolic homeostasis – begins with folding of the proinsulin precursor, including formation of three evolutionarily conserved intramolecular disulfide bonds. Remarkably, normal pancreatic islets contain a subset of proinsulin molecules bearing at least one free cysteine thiol. In human (or rodent) islets with a perturbed endoplasmic reticulum folding environment, non-native proinsulin enters intermolecular disulfide-linked complexes. In genetically obese mice with otherwise wild-type islets, disulfide-linked complexes of proinsulin are more abundant, and leptin receptor-deficient mice, the further increase of such complexes tracks with the onset of islet insulin deficiency and diabetes. Proinsulin-Cys(B19) and Cys(A20) are necessary and sufficient for the formation of proinsulin disulfide-linked complexes; indeed, proinsulin Cys(B19)-Cys(B19) covalent homodimers resist reductive dissociation, highlighting a structural basis for aberrant proinsulin complex formation. We conclude that increased proinsulin misfolding via disulfide-linked complexes is an early event associated with prediabetes that worsens with ß-cell dysfunction in type two diabetes. Our body fine-tunes the amount of sugar in our blood thanks to specialized ‘beta cells’ in the pancreas, which can release a hormone called insulin. To produce insulin, the beta cells first need to build an early version of the molecule – known as proinsulin – inside a cellular compartment called the endoplasmic reticulum. This process involves the formation of internal staples that keep the molecule of proinsulin folded correctly. Individuals developing type 2 diabetes have spikes of sugar in their blood, and so their bodies often respond by trying to make large amounts of insulin. After a while, the beta cells can fail to keep up, which brings on the full-blown disease. However, scientists have discovered that early in type 2 diabetes, the endoplasmic reticulum of beta cells can already show signs of stress; yet, the exact causes of this early damage are still unknown. To investigate this, Arunagiri et al. looked into whether proinsulin folds correctly during the earliest stages of type 2 diabetes. Biochemical experiments showed that even healthy beta cells contained some misfolded proinsulin molecules, where the molecular staples that should fold proinsulin internally were instead abnormally linking proinsulin molecules together. Further work revealed that the misfolded proinsulin was accumulating inside the endoplasmic reticulum. Finally, obese mice that were in the earliest stages of type 2 diabetes had the highest levels of abnormal proinsulin in their beta cells. Overall, the work by Arunagiri et al. suggests that large amounts of proinsulin molecules stapling themselves to each other in the endoplasmic reticulum of beta cells could be an early hallmark of the disease, and could make it get worse. A separate study by Jang et al. also shows that a protein that limits the misfolding of proinsulin is key to maintain successful insulin production in animals eating a Western-style, high fat diet. Hundreds of millions of people around the world have type 2 diabetes, and this number is rising quickly. Detecting and then fixing early problems associated with the condition may help to stop the disease in its track.
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Affiliation(s)
- Anoop Arunagiri
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical School, Ann Arbor, United States
| | - Leena Haataja
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical School, Ann Arbor, United States
| | - Anita Pottekat
- Degenerative Diseases Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, United States
| | - Fawnnie Pamenan
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical School, Ann Arbor, United States
| | - Soohyun Kim
- Department of Biomedical Science and Technology, Konkuk University, Gwangjin-gu, Republic of Korea
| | - Lori M Zeltser
- Department of Pathology and Cell Biology, Naomi Berrie Diabetes Center, Columbia University, New York, United States
| | - Adrienne W Paton
- Research Centre for Infectious Diseases, Department of Molecular and Biomedical Science, University of Adelaide, Adelaide, Australia
| | - James C Paton
- Research Centre for Infectious Diseases, Department of Molecular and Biomedical Science, University of Adelaide, Adelaide, Australia
| | - Billy Tsai
- Department of Cell and Developmental Biology, University of Michigan, Ann Arbor, United States
| | - Pamela Itkin-Ansari
- Development, Aging and Regeneration Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, United States
| | - Randal J Kaufman
- Degenerative Diseases Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, United States
| | - Ming Liu
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical School, Ann Arbor, United States.,Department of Endocrinology and Metabolism, Tianjin Medical University, Tianjin, China
| | - Peter Arvan
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical School, Ann Arbor, United States
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8
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Wei X, Zhu D, Feng C, Chen G, Mao X, Wang Q, Wang J, Liu C. Inhibition of peptidyl-prolyl cis-trans isomerase B mediates cyclosporin A-induced apoptosis of islet β cells. Exp Ther Med 2018; 16:3959-3964. [PMID: 30344674 PMCID: PMC6176207 DOI: 10.3892/etm.2018.6706] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2017] [Accepted: 08/29/2018] [Indexed: 12/21/2022] Open
Abstract
Cyclosporin A (CsA) is widely used as an immunosuppressor in the context of organ transplantation or autoimmune disorders. Recent studies have revealed the detrimental effects of CsA on insulin resistance and pancreatic β cell failure; however, the molecular mechanisms are unknown. The present study sought to confirm the associations between CsA and β cell failure, and to investigate the roles of proinsulin folding and endoplasmic reticulum (ER) stress in CsA-induced β cell failure. The viability of MIN6 cells treated with CsA was evaluated with MTT assay. Expression levels of insulin, peptidyl-prolyl cis-trans isomerase B (PPIB), cleaved caspase-3, phospho-protein kinase R (PKR)-like endoplasmic reticulum kinase (p-PERK), PKR-like endoplasmic reticulum kinase (PERK), binding immunoglobulin protein (BIP), and C/EBP homologous protein (CHOP) were detected via reducing western blot assay. Non-reducing western blot analysis was performed to examine the expression of misfolded proinsulin peptides. The proliferation of MIN6 cells was not inhibited by CsA at concentrations <1 µmol/l. CsA treatment resulted in the decreased expression of insulin and PPIB; however, it also increased the phosphorylation of PERK, and upregulated the expression of PERK, BIP, CHOP and cleaved caspase-3. The results indicated that CsA could induce pancreatic β cell dysfunction and the potential mechanism underlying this phenomenon may be PPIB-associated proinsulin misfolding, which in turn induces ER stress in β cells.
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Affiliation(s)
- Xiao Wei
- Department of Endocrinology, Affiliated Hospital of Integrated Traditional Chinese and Western Medicine, Nanjing University of Chinese Medicine, Nanjing, Jiangsu 210028, P.R. China
| | - Dan Zhu
- Department of Endocrinology, Jiangdu People's Hospital of Yangzhou, Yangzhou, Jiangsu 225200, P.R. China
| | - Chenchen Feng
- Central Laboratory, Jiangsu Province Blood Center, Nanjing, Jiangsu 210042, P.R. China
| | - Guofang Chen
- Department of Endocrinology, Affiliated Hospital of Integrated Traditional Chinese and Western Medicine, Nanjing University of Chinese Medicine, Nanjing, Jiangsu 210028, P.R. China
| | - Xiaodong Mao
- Department of Endocrinology, Affiliated Hospital of Integrated Traditional Chinese and Western Medicine, Nanjing University of Chinese Medicine, Nanjing, Jiangsu 210028, P.R. China
| | - Qifeng Wang
- Department of Endocrinology, Affiliated Hospital of Integrated Traditional Chinese and Western Medicine, Nanjing University of Chinese Medicine, Nanjing, Jiangsu 210028, P.R. China
| | - Jie Wang
- Department of Endocrinology, Affiliated Hospital of Integrated Traditional Chinese and Western Medicine, Nanjing University of Chinese Medicine, Nanjing, Jiangsu 210028, P.R. China
| | - Chao Liu
- Department of Endocrinology, Affiliated Hospital of Integrated Traditional Chinese and Western Medicine, Nanjing University of Chinese Medicine, Nanjing, Jiangsu 210028, P.R. China
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9
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Xin Y, Dominguez Gutierrez G, Okamoto H, Kim J, Lee AH, Adler C, Ni M, Yancopoulos GD, Murphy AJ, Gromada J. Pseudotime Ordering of Single Human β-Cells Reveals States of Insulin Production and Unfolded Protein Response. Diabetes 2018; 67:1783-1794. [PMID: 29950394 DOI: 10.2337/db18-0365] [Citation(s) in RCA: 117] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/29/2018] [Accepted: 06/09/2018] [Indexed: 11/13/2022]
Abstract
Proinsulin is a misfolding-prone protein, making its biosynthesis in the endoplasmic reticulum (ER) a stressful event. Pancreatic β-cells overcome ER stress by activating the unfolded protein response (UPR) and reducing insulin production. This suggests that β-cells transition between periods of high insulin biosynthesis and UPR-mediated recovery from cellular stress. We now report the pseudotime ordering of single β-cells from humans without diabetes detected by large-scale RNA sequencing. We identified major states with 1) low UPR and low insulin gene expression, 2) low UPR and high insulin gene expression, or 3) high UPR and low insulin gene expression. The latter state was enriched for proliferating cells. Stressed human β-cells do not dedifferentiate and show little propensity for apoptosis. These data suggest that human β-cells transition between states with high rates of biosynthesis to fulfill the body's insulin requirements to maintain normal blood glucose levels and UPR-mediated recovery from ER stress due to high insulin production.
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Affiliation(s)
- Yurong Xin
- Regeneron Pharmaceuticals, Tarrytown, NY
| | | | | | | | | | | | - Min Ni
- Regeneron Pharmaceuticals, Tarrytown, NY
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Liu M, Weiss MA, Arunagiri A, Yong J, Rege N, Sun J, Haataja L, Kaufman RJ, Arvan P. Biosynthesis, structure, and folding of the insulin precursor protein. Diabetes Obes Metab 2018; 20 Suppl 2:28-50. [PMID: 30230185 PMCID: PMC6463291 DOI: 10.1111/dom.13378] [Citation(s) in RCA: 124] [Impact Index Per Article: 20.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/25/2018] [Revised: 05/04/2018] [Accepted: 05/23/2018] [Indexed: 02/06/2023]
Abstract
Insulin synthesis in pancreatic β-cells is initiated as preproinsulin. Prevailing glucose concentrations, which oscillate pre- and postprandially, exert major dynamic variation in preproinsulin biosynthesis. Accompanying upregulated translation of the insulin precursor includes elements of the endoplasmic reticulum (ER) translocation apparatus linked to successful orientation of the signal peptide, translocation and signal peptide cleavage of preproinsulin-all of which are necessary to initiate the pathway of proper proinsulin folding. Evolutionary pressures on the primary structure of proinsulin itself have preserved the efficiency of folding ("foldability"), and remarkably, these evolutionary pressures are distinct from those protecting the ultimate biological activity of insulin. Proinsulin foldability is manifest in the ER, in which the local environment is designed to assist in the overall load of proinsulin folding and to favour its disulphide bond formation (while limiting misfolding), all of which is closely tuned to ER stress response pathways that have complex (beneficial, as well as potentially damaging) effects on pancreatic β-cells. Proinsulin misfolding may occur as a consequence of exuberant proinsulin biosynthetic load in the ER, proinsulin coding sequence mutations, or genetic predispositions that lead to an altered ER folding environment. Proinsulin misfolding is a phenotype that is very much linked to deficient insulin production and diabetes, as is seen in a variety of contexts: rodent models bearing proinsulin-misfolding mutants, human patients with Mutant INS-gene-induced Diabetes of Youth (MIDY), animal models and human patients bearing mutations in critical ER resident proteins, and, quite possibly, in more common variety type 2 diabetes.
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Affiliation(s)
- Ming Liu
- Department of Endocrinology and Metabolism, Tianjin Medical University General Hospital, Tianjin, China 300052
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical School, Ann Arbor 48105 MI USA
| | - Michael A. Weiss
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis 46202 IN USA
- Department of Biochemistry, Case-Western Reserve University, Cleveland 44016 OH USA
| | - Anoop Arunagiri
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical School, Ann Arbor 48105 MI USA
| | - Jing Yong
- Degenerative Diseases Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA 92307 USA
| | - Nischay Rege
- Department of Biochemistry, Case-Western Reserve University, Cleveland 44016 OH USA
| | - Jinhong Sun
- Department of Endocrinology and Metabolism, Tianjin Medical University General Hospital, Tianjin, China 300052
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical School, Ann Arbor 48105 MI USA
| | - Leena Haataja
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical School, Ann Arbor 48105 MI USA
| | - Randal J. Kaufman
- Degenerative Diseases Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA 92307 USA
| | - Peter Arvan
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical School, Ann Arbor 48105 MI USA
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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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Tang W, Yuan Q, Xu B, Osei K, Wang J. Exenatide substantially improves proinsulin conversion and cell survival that augment Ins2 +/Akita beta cell function. Mol Cell Endocrinol 2017; 439:297-307. [PMID: 27658750 DOI: 10.1016/j.mce.2016.09.015] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/18/2016] [Revised: 09/16/2016] [Accepted: 09/16/2016] [Indexed: 02/06/2023]
Abstract
Proinsulin folding imperfections cause extensive beta-cell defects known in diabetes. Here, we investigated whether exenatide can alleviate such defects in proinsulin conversion, beta-cell survival, and insulin secretion, in the Ins2+/Akita beta-cells that have a spontaneous mutation (Cys 96 Tyr) in the insulin 2 gene caused dominant negative misfolding problem. 15 or 120 min exenatide administration substantially improves glucose-stimulated insulin secretion, marked in the secreted insulin levels and proinsulin/insulin ratio. This improvement is mainly due to enhanced conversion of proinsulin to insulin, having nothing to do with the prohormone convertase PC1/3 and PC2 levels. The 15 min improvement is calcium-independent. The 120 min improvement is linked to calcium and/or cAMP dependent mechanisms. This efficacy is validated during longer treatment and in Akita islets. Exenatide improves Ins2+/Akita beta-cell survival and Akita mouse's glucose tolerance. The results suggest a potential of incretin mimetics in alleviating defective proinsulin conversion and other proinsulin misfolding consequences.
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Affiliation(s)
- Wei Tang
- Department of Endocrinology, Jiangsu Province Geriatric Institute Islet Cell Senescence and Function Research Laboratory, Jiangsu Province Official Hospital, 65 Jiangsu Road, Nanjing 210024, China.
| | - Qingxin Yuan
- Department of Endocrinology, First Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu 210029, China
| | - Bo Xu
- State Key Laboratory of Reproductive Medicine, Institute of Toxicology, Nanjing Medical University, Nanjing 211166, China
| | - Kwame Osei
- Division of Endocrinology, Diabetes, and Metabolism, Department of Internal Medicine, The Ohio State University, Columbus, OH 43210, USA
| | - Jie Wang
- Division of Endocrinology, Diabetes, and Metabolism, Department of Internal Medicine, The Ohio State University, Columbus, OH 43210, USA; Division of Endocrinology, Jiangsu Province Hospital on Integration of Chinese and Western Medicine, Nanjing University of Chinese and Western Medicine, Nanjing, Jiangsu 210028, China.
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13
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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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Wang L, Liu Y, Yang J, Zhao H, Ke J, Tian Q, Zhang L, Wen J, Wei R, Hong T. GLP-1 analog liraglutide enhances proinsulin processing in pancreatic β-cells via a PKA-dependent pathway. Endocrinology 2014; 155:3817-28. [PMID: 25051441 DOI: 10.1210/en.2014-1218] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Hyperproinsulinemia has gained increasing attention in the development of type 2 diabetes. Clinical studies have demonstrated that glucagon-like peptide-1 (GLP-1)-based therapies significantly decrease plasma proinsulin/insulin ratio in patients with type 2 diabetes. However, the underlying mechanism remains unclear. Prohormone convertase (PC)-1/3 and PC2 are primarily responsible for processing proinsulin to insulin in pancreatic β-cells. We have recently reported that Pax6 mutation down-regulated PC1/3 and PC2 expression, resulting in defective proinsulin processing in Pax6 heterozygous mutant (Pax6(m/+)) mice. In this study, we investigated whether and how liraglutide, a novel GLP-1 analog, modulated proinsulin processing. Our results showed that liraglutide significantly up-regulated PC1/3 expression and decreased the proinsulin to insulin ratio in both Pax6(m/+) and db/db diabetic mice. In the cultured mouse pancreatic β-cell line, Min6, liraglutide stimulated PC1/3 and PC2 expression and lowered the proinsulin to insulin ratio in a dose- and time-dependent manner. Moreover, the beneficial effects of liraglutide on PC1/3 and PC2 expression and proinsulin processing were dependent on the GLP-1 receptor-mediated cAMP/protein kinase A signaling pathway. The same mechanism was recapitulated in isolated mouse islets. In conclusion, liraglutide enhanced PC1/3- and PC2-dependent proinsulin processing in pancreatic β-cells through the activation of the GLP-1 receptor/cAMP/protein kinase A signaling pathway. Our study provides a new mechanism for improvement of pancreatic β-cell function by the GLP-1-based therapy.
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Affiliation(s)
- Liang Wang
- Department of Endocrinology and Metabolism (L.W., Y.L., J.Y., H.Z., J.K., Q.T., L.Z., R.W., T.H.), Peking University Third Hospital, and Peking University Stem Cell Research Center (J.W., T.H.), Peking University Health Science Center, Beijing 100191, China
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15
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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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16
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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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Wang N, Khan SA, Prabhakar NR, Nanduri J. Impairment of pancreatic β-cell function by chronic intermittent hypoxia. Exp Physiol 2013; 98:1376-85. [PMID: 23709585 PMCID: PMC3756548 DOI: 10.1113/expphysiol.2013.072454] [Citation(s) in RCA: 71] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
NEW FINDINGS What is the central question of this study? Periodic decreases in arterial blood O2 or chronic intermittent hypoxia (CIH) is a hallmark feature of sleep apnoea patients. Despite a large body of clinical evidence linking sleep disordered breathing with apnoeas to diabetes, the causal relationships between CIH and β-cell function and the underlying molecular mechanisms have not been established. What is the main finding and its importance? In a rodent model, we show that mitochondrial oxidative stress generated by CIH leads to pancreatic β-cell dysfunction manifested by augmented basal insulin secretion, insulin resistance, defective proinsulin processing and impaired glucose-stimulated insulin secretion. The results of the present study provide evidence for direct effects of CIH on β-cell function, which may be an underlying molecular mechanism contributing to the development of type 2 diabetes among sleep apnoea patients. Breathing disorders with recurrent apnoea produce periodic decreases in arterial blood O2, i.e. chronic intermittent hypoxia (CIH). Recurrent apnoea patients and CIH-exposed rodents exhibit several co-morbidities, including diabetes. However, the effects of CIH on pancreatic β-cell function are not known. In the present study, we investigated pancreatic β-cell function in C57BL6 mice exposed to 30 days of CIH. Compared with control animals, the CIH-exposed mice exhibited elevated levels of fasting plasma insulin but comparable glucose levels and higher homeostasis model assessment, indicating insulin resistance. Pancreatic β-cell morphology was unaltered in CIH-exposed mice. Insulin content was decreased in CIH-exposed β-cells, and this effect was associated with increased proinsulin levels. The mRNA and protein levels of the enzyme prohormone convertase 1, which converts proinsulin to insulin, were downregulated in CIH-treated islets. More importantly, glucose-stimulated insulin secretion was impaired in CIH-exposed mice and in isolated islets. Mitochondrial levels of reactive oxygen species (ROS) were elevated in CIH-exposed pancreatic islets. Treatment of mice with mito-tempol, a scavenger of mitochondrial ROS, during exposure to CIH prevented the augmented insulin secretion and restored the proinsulin and homeostasis model assessment values to control levels. These results demonstrate that CIH leads to pancreatic β-cell dysfunction, manifested by augmented basal insulin secretion, insulin resistance, defective proinsulin processing, impaired glucose-stimulated insulin secretion and increased mitochondrial ROS, which mediate the effects of CIH on pancreatic β-cell function.
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Affiliation(s)
- Ning Wang
- Institute for Integrative Physiology and Center for Systems Biology of O2 Sensing, Biological Science Division, University of Chicago, Chicago, IL 60615
| | - Shakil A. Khan
- Institute for Integrative Physiology and Center for Systems Biology of O2 Sensing, Biological Science Division, University of Chicago, Chicago, IL 60615
| | - Nanduri R. Prabhakar
- Institute for Integrative Physiology and Center for Systems Biology of O2 Sensing, Biological Science Division, University of Chicago, Chicago, IL 60615
| | - Jayasri Nanduri
- Institute for Integrative Physiology and Center for Systems Biology of O2 Sensing, Biological Science Division, University of Chicago, Chicago, IL 60615
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Wright J, Wang X, Haataja L, Kellogg AP, Lee J, Liu M, Arvan P. Dominant protein interactions that influence the pathogenesis of conformational diseases. J Clin Invest 2013; 123:3124-34. [PMID: 23722904 DOI: 10.1172/jci67260] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2012] [Accepted: 03/28/2013] [Indexed: 02/06/2023] Open
Abstract
Misfolding of exportable proteins can trigger endocrinopathies. For example, misfolding of insulin can result in autosomal dominant mutant INS gene-induced diabetes of youth, and misfolding of thyroglobulin can result in autosomal recessive congenital hypothyroidism with deficient thyroglobulin. Both proinsulin and thyroglobulin normally form homodimers; the mutant versions of both proteins misfold in the ER, triggering ER stress, and, in both cases, heterozygosity creates potential for cross-dimerization between mutant and WT gene products. Here, we investigated these two ER-retained mutant secretory proteins and the selectivity of their interactions with their respective WT counterparts. In both cases and in animal models of these diseases, we found that conditions favoring an increased stoichiometry of mutant gene product dominantly inhibited export of the WT partner, while increased relative level of the WT gene product helped to rescue secretion of the mutant partner. Surprisingly, the bidirectional consequences of secretory blockade and rescue occur simultaneously in the same cells. Thus, in the context of heterozygosity, expression level and stability of WT subunits may be a critical factor influencing the effect of protein misfolding on clinical phenotype. These results offer new insight into dominant as well as recessive inheritance of conformational diseases and offer opportunities for the development of new therapies.
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Affiliation(s)
- Jordan Wright
- Division of Metabolism, Endocrinology and Diabetes, University of Michigan Medical Center, Ann Arbor, Michigan, USA
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Yuan Q, Tang W, Zhang X, Hinson JA, Liu C, Osei K, Wang J. Proinsulin atypical maturation and disposal induces extensive defects in mouse Ins2+/Akita β-cells. PLoS One 2012; 7:e35098. [PMID: 22509386 PMCID: PMC3318013 DOI: 10.1371/journal.pone.0035098] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2011] [Accepted: 03/08/2012] [Indexed: 02/06/2023] Open
Abstract
Because of its low relative folding rate and plentiful manufacture in β-cells, proinsulin maintains a homeostatic balance of natively and plentiful non-natively folded states (i.e., proinsulin homeostasis, PIHO) through the integration of maturation and disposal processes. PIHO is susceptible to genetic and environmental influences, and its disorder has been critically linked to defects in β-cells in diabetes. To explore this hypothesis, we performed polymerase chain reaction (PCR), metabolic-labeling, immunoblotting, and histological studies to clarify what defects result from primary disorder of PIHO in model Ins2+/Akita β-cells. We used T antigen-transformed Ins2+/Akita and control Ins2+/+ β-cells established from Akita and wild-type littermate mice. In Ins2+/Akita β-cells, we found no apparent defect at the transcriptional and translational levels to contribute to reduced cellular content of insulin and its precursor and secreted insulin. Glucose response remained normal in proinsulin biosynthesis but was impaired for insulin secretion. The size and number of mature insulin granules were reduced, but the size/number of endoplasmic reticulum, Golgi, mitochondrion, and lysosome organelles and vacuoles were expanded/increased. Moreover, cell death increased, and severe oxidative stress, which manifested as increased reactive oxygen species, thioredoxin-interacting protein, and protein tyrosine nitration, occurred in Ins2+/Akita β-cells and/or islets. These data show the first clear evidence that primary PIHO imbalance induces severe oxidative stress and impairs glucose-stimulated insulin release and β-cell survival as well as producing other toxic consequences. The defects disclosed/clarified in model Ins2+/Akita β-cells further support a role of the genetic and stress-susceptible PIHO disorder in β-cell failure and diabetes.
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Affiliation(s)
- Qingxin Yuan
- Division of Endocrinology, Diabetes, and Metabolism, Department of Internal Medicine, The Ohio State University, Columbus, Ohio, United States of America
| | - Wei Tang
- Division of Endocrinology, Diabetes, and Metabolism, Department of Internal Medicine, The Ohio State University, Columbus, Ohio, United States of America
| | - Xiaoping Zhang
- Division of Endocrinology, Diabetes, and Metabolism, Department of Internal Medicine, The Ohio State University, Columbus, Ohio, United States of America
| | - Jack A. Hinson
- Department of Pharmacology and Toxicology, University of Arkansas for Medical Sciences, Little Rock, Arkansas, United States of America
| | - Chao Liu
- Division of Endocrinology, Jiangsu Province Hospital on Integration of Chinese and Western Medicine, Nanjing University of Chinese and Western Medicine, Nanjing, Jiangsu, China
| | - Kwame Osei
- Division of Endocrinology, Diabetes, and Metabolism, Department of Internal Medicine, The Ohio State University, Columbus, Ohio, United States of America
| | - Jie Wang
- Division of Endocrinology, Diabetes, and Metabolism, Department of Internal Medicine, The Ohio State University, Columbus, Ohio, United States of America
- Division of Endocrinology, Jiangsu Province Hospital on Integration of Chinese and Western Medicine, Nanjing University of Chinese and Western Medicine, Nanjing, Jiangsu, China
- * E-mail:
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20
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Zhang X, Degenstein L, Cao Y, Stein J, Osei K, Wang J. β-Cells with relative low HIMP1 overexpression levels in a transgenic mouse line enhance basal insulin production and hypoxia/hypoglycemia tolerance. PLoS One 2012; 7:e34126. [PMID: 22470529 PMCID: PMC3309936 DOI: 10.1371/journal.pone.0034126] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2011] [Accepted: 02/22/2012] [Indexed: 11/19/2022] Open
Abstract
Rodent pancreatic β-cells that naturally lack hypoglycemia/hypoxia inducible mitochondrial protein 1 (HIMP1) are susceptible to hypoglycemia and hypoxia influences. A linkage between the hypoglycemia/hypoxia susceptibility and the lack of HIMP1 is suggested in a recent study using transformed β-cells lines. To further illuminate this linkage, we applied mouse insulin 1 gene promoter (MIP) to control HIMP1-a isoform cDNA and have generated three lines (L1 to L3) of heterozygous HIMP1 transgenic (Tg) mice by breeding of three founders with C57BL/6J mice. In HIMP1-Tg mice/islets, we performed quantitative polymerase chain reaction (PCR), immunoblot, histology, and physiology studies to investigate HIMP1 overexpression and its link to β-cell function/survival and body glucose homeostasis. We found that the HIMP1 level increased steadily in β-cells of L1 to L3 heterozygous HIMP1-Tg mice. HIMP1 overexpression at relatively lower levels in L1 heterozygotes results in a negligible decline in blood glucose concentrations and an insignificant elevation in blood insulin levels, while HIMP1 overexpression at higher levels are toxic, causing hyperglycemia in L2/3 heterozygotes. Follow-up studies in 5-30-week-old L1 heterozygous mice/islets found that HIMP1 overexpression at relatively lower levels in β-cells has enhanced basal insulin biosynthesis, basal insulin secretion, and tolerances to low oxygen/glucose influences. The findings enforced the linkage between the hypoglycemia/hypoxia susceptibility and the lack of HIMP1 in β-cells, and show a potential value of HIMP1 overexpression at relatively lower levels in modulating β-cell function and survival.
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Affiliation(s)
- Xiaoping Zhang
- Department of Internal Medicine, The Ohio State University, Columbus, Ohio, United States of America
| | - Linda Degenstein
- Transgenic Core, The University of Chicago, Chicago, Illinois, United States of America
| | - Yun Cao
- Department of Medicine, The University of Chicago, Chicago, Illinois, United States of America
| | - Jeffrey Stein
- Department of Medicine, The University of Chicago, Chicago, Illinois, United States of America
| | - Kwame Osei
- Department of Internal Medicine, The Ohio State University, Columbus, Ohio, United States of America
| | - Jie Wang
- Department of Internal Medicine, The Ohio State University, Columbus, Ohio, United States of America
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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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Wang J, Osei K. Proinsulin maturation disorder is a contributor to the defect of subsequent conversion to insulin in β-cells. Biochem Biophys Res Commun 2011; 411:150-5. [DOI: 10.1016/j.bbrc.2011.06.119] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2011] [Accepted: 06/17/2011] [Indexed: 11/24/2022]
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