1
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Fadzeyeva E, Locatelli CA, Trzaskalski NA, Nguyen MA, Capozzi ME, Vulesevic B, Morrow NM, Ghorbani P, Hanson AA, Lorenzen-Schmidt I, Doyle MA, Seymour R, Varin EM, Fullerton MD, Campbell JE, Mulvihill EE. Pancreas-derived DPP4 is not essential for glucose homeostasis under metabolic stress. iScience 2023; 26:106748. [PMID: 37216093 PMCID: PMC10192926 DOI: 10.1016/j.isci.2023.106748] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2022] [Revised: 03/09/2023] [Accepted: 04/21/2023] [Indexed: 05/24/2023] Open
Abstract
Mice systemically lacking dipeptidyl peptidase-4 (DPP4) have improved islet health, glucoregulation, and reduced obesity with high-fat diet (HFD) feeding compared to wild-type mice. Some, but not all, of this improvement can be linked to the loss of DPP4 in endothelial cells (ECs), pointing to the contribution of non-EC types. The importance of intra-islet signaling mediated by α to β cell communication is becoming increasingly clear; thus, our objective was to determine if β cell DPP4 regulates insulin secretion and glucose tolerance in HFD-fed mice by regulating the local concentrations of insulinotropic peptides. Using β cell double incretin receptor knockout mice, β cell- and pancreas-specific Dpp4-/- mice, we reveal that β cell incretin receptors are necessary for DPP4 inhibitor effects. However, although β cell DPP4 modestly contributes to high glucose (16.7 mM)-stimulated insulin secretion in isolated islets, it does not regulate whole-body glucose homeostasis.
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Affiliation(s)
- Evgenia Fadzeyeva
- The University of Ottawa, Faculty of Medicine, Department of Biochemistry, Microbiology and Immunology, Ottawa, ON K1H 8M5, Canada
- The University of Ottawa Heart Institute, 40 Ruskin Street, Ottawa, ON K1Y4W7, Canada
| | - Cassandra A.A. Locatelli
- The University of Ottawa, Faculty of Medicine, Department of Biochemistry, Microbiology and Immunology, Ottawa, ON K1H 8M5, Canada
- The University of Ottawa Heart Institute, 40 Ruskin Street, Ottawa, ON K1Y4W7, Canada
| | - Natasha A. Trzaskalski
- The University of Ottawa, Faculty of Medicine, Department of Biochemistry, Microbiology and Immunology, Ottawa, ON K1H 8M5, Canada
- The University of Ottawa Heart Institute, 40 Ruskin Street, Ottawa, ON K1Y4W7, Canada
| | - My-Anh Nguyen
- The University of Ottawa, Faculty of Medicine, Department of Biochemistry, Microbiology and Immunology, Ottawa, ON K1H 8M5, Canada
- The University of Ottawa Heart Institute, 40 Ruskin Street, Ottawa, ON K1Y4W7, Canada
| | - Megan E. Capozzi
- Duke Molecular Physiology Institute, 300 North Duke Street, Durham, NC 27701, USA
| | - Branka Vulesevic
- The University of Ottawa, Faculty of Medicine, Department of Biochemistry, Microbiology and Immunology, Ottawa, ON K1H 8M5, Canada
- The University of Ottawa Heart Institute, 40 Ruskin Street, Ottawa, ON K1Y4W7, Canada
| | - Nadya M. Morrow
- The University of Ottawa, Faculty of Medicine, Department of Biochemistry, Microbiology and Immunology, Ottawa, ON K1H 8M5, Canada
- The University of Ottawa Heart Institute, 40 Ruskin Street, Ottawa, ON K1Y4W7, Canada
| | - Peyman Ghorbani
- The University of Ottawa, Faculty of Medicine, Department of Biochemistry, Microbiology and Immunology, Ottawa, ON K1H 8M5, Canada
| | - Antonio A. Hanson
- The University of Ottawa, Faculty of Medicine, Department of Biochemistry, Microbiology and Immunology, Ottawa, ON K1H 8M5, Canada
- The University of Ottawa Heart Institute, 40 Ruskin Street, Ottawa, ON K1Y4W7, Canada
| | - Ilka Lorenzen-Schmidt
- The University of Ottawa Heart Institute, 40 Ruskin Street, Ottawa, ON K1Y4W7, Canada
| | - Mary-Anne Doyle
- Division of Endocrinology & Metabolism, Department of Medicine, University of Ottawa, Ottawa, ON K1H 8L6, Canada
| | - Richard Seymour
- The University of Ottawa Heart Institute, 40 Ruskin Street, Ottawa, ON K1Y4W7, Canada
| | - Elodie M. Varin
- Lunenfeld Tanenbaum Research Institute, Toronto, ON M5G 1X5, Canada
| | - Morgan D. Fullerton
- The University of Ottawa, Faculty of Medicine, Department of Biochemistry, Microbiology and Immunology, Ottawa, ON K1H 8M5, Canada
- Centre for Infection, Immunity and Inflammation, Ottawa, ON K1H 8M5, Canada
| | - Jonathan E. Campbell
- Duke Molecular Physiology Institute, 300 North Duke Street, Durham, NC 27701, USA
| | - Erin E. Mulvihill
- The University of Ottawa, Faculty of Medicine, Department of Biochemistry, Microbiology and Immunology, Ottawa, ON K1H 8M5, Canada
- The University of Ottawa Heart Institute, 40 Ruskin Street, Ottawa, ON K1Y4W7, Canada
- Centre for Infection, Immunity and Inflammation, Ottawa, ON K1H 8M5, Canada
- Montreal Diabetes Research Group, Montreal, QC H2X 0A9, Canada
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2
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Teitelman G. Abnormal Expression of an Insulin Synthesizing Enzyme in Islets of Adult Autoantibody Positive Donors. J Histochem Cytochem 2022; 70:695-706. [PMID: 36341551 PMCID: PMC9660365 DOI: 10.1369/00221554221138368] [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: 08/24/2022] [Accepted: 10/17/2022] [Indexed: 11/07/2022] Open
Abstract
The observation that the two active forms of proprotein convertase 1/3 (PC1/3) were differentially expressed in beta cells of normal islets raised the possibility that this heterogeneity is lost during type 1 diabetes (T1D) progression. To test this hypothesis, the expression of the convertase was evaluated by confocal microscopy in sections of human pancreas of autoantibody positive (AA+) and T1D donors and compared with that of control. Islets of T1D pancreas were comprised of beta cells expressing either low or high PC1/3 levels and all islets of a pancreatic section contained only one beta cell type. Pancreata of AA+ donors contained either of these two classes of islets intermixed with normal islets comprised of beta cells with heterogeneous PC1/3 expression. This alteration affected the expression of proinsulin and insulin, which in most AA+ and T1D donors were lower than in controls. The present results indicate that the heterogeneity of PC1/3 expression is lost in all beta cells in a subset islets of AA+ donors and in all islets of T1D donors. These findings suggest that the heterogeneity of PC1/3 expression is a biomarker of human beta cell health and that its loss coincides with the initial stages of T1D.
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Affiliation(s)
- Gladys Teitelman
- Department of Cell Biology, SUNY Downstate Health
Sciences University, Brooklyn, NY
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3
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Liu QR, Zhu M, Zhang P, Mazucanti CH, Huang NS, Lang DL, Chen Q, Auluck P, Marenco S, O'Connell JF, Ferrucci L, Chia CW, Egan JM. Novel Human Insulin Isoforms and Cα-Peptide Product in Islets of Langerhans and Choroid Plexus. Diabetes 2021; 70:2947-2956. [PMID: 34649926 PMCID: PMC8660980 DOI: 10.2337/db21-0198] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/05/2021] [Accepted: 09/07/2021] [Indexed: 11/26/2022]
Abstract
Human insulin (INS) gene diverged from the ancestral genes of invertebrate and mammalian species millions of years ago. We previously found that mouse insulin gene (Ins2) isoforms are expressed in brain choroid plexus (ChP) epithelium cells, where insulin secretion is regulated by serotonin and not by glucose. We further compared human INS isoform expression in postmortem ChP and islets of Langerhans. We uncovered novel INS upstream open reading frame isoforms and their protein products. In addition, we found a novel alternatively spliced isoform that translates to a 74-amino acid (AA) proinsulin containing a shorter 19-AA C-peptide sequence, herein designated Cα-peptide. The middle portion of the conventional C-peptide contains β-sheet (GQVEL) and hairpin (GGGPG) motifs that are not present in Cα-peptide. Islet amyloid polypeptide (IAPP) is not expressed in ChP, and its amyloid formation was inhibited in vitro more efficiently by Cα-peptide than by C-peptide. Of clinical relevance, the ratio of the 74-AA proinsulin to proconvertase-processed Cα-peptide was significantly increased in islets from type 2 diabetes mellitus autopsy donors. Intriguingly, 100 years after the discovery of insulin, we found that INS isoforms are present in ChP from insulin-deficient autopsy donors.
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Affiliation(s)
- Qing-Rong Liu
- Diabetes Section, Intramural Research Program, National Institute on Aging, National Institutes of Health, Baltimore, MD
| | - Min Zhu
- Longitudinal Study Section, Intramural Research Program, National Institute on Aging, National Institutes of Health, Baltimore, MD
| | - Pingbo Zhang
- Longitudinal Study Section, Intramural Research Program, National Institute on Aging, National Institutes of Health, Baltimore, MD
| | - Caio H Mazucanti
- Diabetes Section, Intramural Research Program, National Institute on Aging, National Institutes of Health, Baltimore, MD
| | - Nicholas S Huang
- Diabetes Section, Intramural Research Program, National Institute on Aging, National Institutes of Health, Baltimore, MD
| | - Doyle L Lang
- Diabetes Section, Intramural Research Program, National Institute on Aging, National Institutes of Health, Baltimore, MD
| | - Qinghua Chen
- Diabetes Section, Intramural Research Program, National Institute on Aging, National Institutes of Health, Baltimore, MD
| | - Pavan Auluck
- Human Brain Collection Core, Intramural Research Program, National Institute of Mental Health, National Institutes of Health, Bethesda, MD
| | - Stefano Marenco
- Human Brain Collection Core, Intramural Research Program, National Institute of Mental Health, National Institutes of Health, Bethesda, MD
| | - Jennifer F O'Connell
- Diabetes Section, Intramural Research Program, National Institute on Aging, National Institutes of Health, Baltimore, MD
| | - Luigi Ferrucci
- Longitudinal Study Section, Intramural Research Program, National Institute on Aging, National Institutes of Health, Baltimore, MD
| | - Chee W Chia
- Diabetes Section, Intramural Research Program, National Institute on Aging, National Institutes of Health, Baltimore, MD
| | - Josephine M Egan
- Diabetes Section, Intramural Research Program, National Institute on Aging, National Institutes of Health, Baltimore, MD
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4
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Yau B, Hocking S, Andrikopoulos S, Kebede MA. Targeting the insulin granule for modulation of insulin exocytosis. Biochem Pharmacol 2021; 194:114821. [PMID: 34748819 DOI: 10.1016/j.bcp.2021.114821] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2021] [Revised: 10/29/2021] [Accepted: 11/02/2021] [Indexed: 02/08/2023]
Abstract
The pancreatic β-cells control insulin secretion in the body to regulate glucose homeostasis, and β-cell stress and dysfunction is characteristic of Type 2 Diabetes. Pharmacological targeting of the β-cell to increase insulin secretion is typically utilised, however, extended use of common drugs such as sulfonylureas are known to result in secondary failure. Moreover, there is evidence they may induce β-cell failure in the long term. Within β-cells, insulin secretory granules (ISG) serve as compartments to store, process and traffic insulin for exocytosis. There is now growing evidence that ISG exist in multiple populations, distinct in their protein composition, motility, age, and capacity for secretion. In this review, we discuss the implications of a heterogenous ISG population in β-cells and highlight the need for more understanding into how unique ISG populations may be targeted in anti-diabetic therapies.
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Affiliation(s)
- Belinda Yau
- School of Medical Sciences, Faculty of Medicine and Health, University of Sydney, Camperdown, NSW, Australia; Charles Perkins Centre, The University of Sydney, Camperdown, NSW, Australia.
| | - Samantha Hocking
- Charles Perkins Centre, The University of Sydney, Camperdown, NSW, Australia; Central Clinical School, Faculty of Medicine and Health and Department of Endocrinology Royal Prince Alfred Hospital, NSW, Australia
| | | | - Melkam A Kebede
- School of Medical Sciences, Faculty of Medicine and Health, University of Sydney, Camperdown, NSW, Australia; Charles Perkins Centre, The University of Sydney, Camperdown, NSW, Australia
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5
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Kahn SE, Chen YC, Esser N, Taylor AJ, van Raalte DH, Zraika S, Verchere CB. The β Cell in Diabetes: Integrating Biomarkers With Functional Measures. Endocr Rev 2021; 42:528-583. [PMID: 34180979 PMCID: PMC9115372 DOI: 10.1210/endrev/bnab021] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/12/2021] [Indexed: 02/08/2023]
Abstract
The pathogenesis of hyperglycemia observed in most forms of diabetes is intimately tied to the islet β cell. Impairments in propeptide processing and secretory function, along with the loss of these vital cells, is demonstrable not only in those in whom the diagnosis is established but typically also in individuals who are at increased risk of developing the disease. Biomarkers are used to inform on the state of a biological process, pathological condition, or response to an intervention and are increasingly being used for predicting, diagnosing, and prognosticating disease. They are also proving to be of use in the different forms of diabetes in both research and clinical settings. This review focuses on the β cell, addressing the potential utility of genetic markers, circulating molecules, immune cell phenotyping, and imaging approaches as biomarkers of cellular function and loss of this critical cell. Further, we consider how these biomarkers complement the more long-established, dynamic, and often complex measurements of β-cell secretory function that themselves could be considered biomarkers.
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Affiliation(s)
- Steven E Kahn
- Division of Metabolism, Endocrinology and Nutrition, Department of Medicine, VA Puget Sound Health Care System and University of Washington, Seattle, 98108 WA, USA
| | - Yi-Chun Chen
- BC Children's Hospital Research Institute and Centre for Molecular Medicine and Therapeutics, Vancouver, BC, V5Z 4H4, Canada.,Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, BC, V5Z 4H4, Canada.,Department of Surgery, University of British Columbia, Vancouver, BC, V5Z 4H4, Canada
| | - Nathalie Esser
- Division of Metabolism, Endocrinology and Nutrition, Department of Medicine, VA Puget Sound Health Care System and University of Washington, Seattle, 98108 WA, USA
| | - Austin J Taylor
- BC Children's Hospital Research Institute and Centre for Molecular Medicine and Therapeutics, Vancouver, BC, V5Z 4H4, Canada.,Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, BC, V5Z 4H4, Canada.,Department of Surgery, University of British Columbia, Vancouver, BC, V5Z 4H4, Canada
| | - Daniël H van Raalte
- Department of Internal Medicine, Amsterdam University Medical Center (UMC), Vrije Universiteit (VU) University Medical Center, 1007 MB Amsterdam, The Netherlands.,Department of Experimental Vascular Medicine, Amsterdam University Medical Center (UMC), Academic Medical Center, 1007 MB Amsterdam, The Netherlands
| | - Sakeneh Zraika
- Division of Metabolism, Endocrinology and Nutrition, Department of Medicine, VA Puget Sound Health Care System and University of Washington, Seattle, 98108 WA, USA
| | - C Bruce Verchere
- BC Children's Hospital Research Institute and Centre for Molecular Medicine and Therapeutics, Vancouver, BC, V5Z 4H4, Canada.,Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, BC, V5Z 4H4, Canada.,Department of Surgery, University of British Columbia, Vancouver, BC, V5Z 4H4, Canada
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6
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Ramzy A, Kieffer TJ. Altered islet prohormone processing: A cause or consequence of diabetes? Physiol Rev 2021; 102:155-208. [PMID: 34280055 DOI: 10.1152/physrev.00008.2021] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Peptide hormones are first produced as larger precursor prohormones that require endoproteolytic cleavage to liberate the mature hormones. A structurally conserved but functionally distinct family of nine prohormone convertase enzymes (PCs) are responsible for cleavage of protein precursors of which PC1/3 and PC2 are known to be exclusive to neuroendocrine cells and responsible for prohormone cleavage. Differential expression of PCs within tissues define prohormone processing; whereas glucagon is the major product liberated from proglucagon via PC2 in pancreatic α-cells, proglucagon is preferentially processed by PC1/3 in intestinal L cells to produce glucagon-like peptides 1 and 2 (GLP-1, GLP-2). Beyond our understanding of processing of islet prohormones in healthy islets, there is convincing evidence that proinsulin, proIAPP, and proglucagon processing is altered during prediabetes and diabetes. There is predictive value of elevated circulating proinsulin or proinsulin : C-peptide ratio for progression to type 2 diabetes and elevated proinsulin or proinsulin : C-peptide is predictive for development of type 1 diabetes in at risk groups. After onset of diabetes, patients have elevated circulating proinsulin and proIAPP and proinsulin may be an autoantigen in type 1 diabetes. Further, preclinical studies reveal that α-cells have altered proglucagon processing during diabetes leading to increased GLP-1 production. We conclude that despite strong associative data, current evidence is inconclusive on the potential causal role of impaired prohormone processing in diabetes, and suggest that future work should focus on resolving the question of whether altered prohormone processing is a causal driver or merely a consequence of diabetes pathology.
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Affiliation(s)
- Adam Ramzy
- Laboratory of Molecular and Cellular Medicine, Department of Cellular and Physiological Sciences, Life Sciences Institute, University of British Columbia, Vancouver, BC, Canada
| | - Timothy J Kieffer
- Laboratory of Molecular and Cellular Medicine, Department of Cellular and Physiological Sciences, Life Sciences Institute, University of British Columbia, Vancouver, BC, Canada.,Department of Surgery, University of British Columbia, Vancouver, BC, Canada.,School of Biomedical Engineering, University of British Columbia, Vancouver, BC, Canada
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7
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Apaolaza PS, Petropoulou PI, Rodriguez-Calvo T. Whole-Slide Image Analysis of Human Pancreas Samples to Elucidate the Immunopathogenesis of Type 1 Diabetes Using the QuPath Software. Front Mol Biosci 2021; 8:689799. [PMID: 34179094 PMCID: PMC8226255 DOI: 10.3389/fmolb.2021.689799] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2021] [Accepted: 05/18/2021] [Indexed: 12/25/2022] Open
Abstract
Type 1 diabetes is a chronic disease of the pancreas characterized by the loss of insulin-producing beta cells. Access to human pancreas samples for research purposes has been historically limited, restricting pathological analyses to animal models. However, intrinsic differences between animals and humans have made clinical translation very challenging. Recently, human pancreas samples have become available through several biobanks worldwide, and this has opened numerous opportunities for scientific discovery. In addition, the use of new imaging technologies has unraveled many mysteries of the human pancreas not merely in the presence of disease, but also in physiological conditions. Nowadays, multiplex immunofluorescence protocols as well as sophisticated image analysis tools can be employed. Here, we described the use of QuPath—an open-source platform for image analysis—for the investigation of human pancreas samples. We demonstrate that QuPath can be adequately used to analyze whole-slide images with the aim of identifying the islets of Langerhans and define their cellular composition as well as other basic morphological characteristics. In addition, we show that QuPath can identify immune cell populations in the exocrine tissue and islets of Langerhans, accurately localizing and quantifying immune infiltrates in the pancreas. Therefore, we present a tool and analysis pipeline that allows for the accurate characterization of the human pancreas, enabling the study of the anatomical and physiological changes underlying pancreatic diseases such as type 1 diabetes. The standardization and implementation of these analysis tools is of critical importance to understand disease pathogenesis, and may be informative for the design of new therapies aimed at preserving beta cell function and halting the inflammation caused by the immune attack.
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Affiliation(s)
- Paola S Apaolaza
- Institute of Diabetes Research, Helmholtz Diabetes Center at Helmholtz Zentrum München, Munich, Germany.,German Center for Diabetes Research (DZD), Helmholtz Zentrum Munich, Munich, Germany
| | - Peristera-Ioanna Petropoulou
- Institute of Diabetes Research, Helmholtz Diabetes Center at Helmholtz Zentrum München, Munich, Germany.,German Center for Diabetes Research (DZD), Helmholtz Zentrum Munich, Munich, Germany
| | - Teresa Rodriguez-Calvo
- Institute of Diabetes Research, Helmholtz Diabetes Center at Helmholtz Zentrum München, Munich, Germany.,German Center for Diabetes Research (DZD), Helmholtz Zentrum Munich, Munich, Germany
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8
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Sanchez Caballero L, Gorgogietas V, Arroyo MN, Igoillo-Esteve M. Molecular mechanisms of β-cell dysfunction and death in monogenic forms of diabetes. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2021; 359:139-256. [PMID: 33832649 DOI: 10.1016/bs.ircmb.2021.02.005] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Monogenetic forms of diabetes represent 1%-5% of all diabetes cases and are caused by mutations in a single gene. These mutations, that affect genes involved in pancreatic β-cell development, function and survival, or insulin regulation, may be dominant or recessive, inherited or de novo. Most patients with monogenic diabetes are very commonly misdiagnosed as having type 1 or type 2 diabetes. The severity of their symptoms depends on the nature of the mutation, the function of the affected gene and, in some cases, the influence of additional genetic or environmental factors that modulate severity and penetrance. In some patients, diabetes is accompanied by other syndromic features such as deafness, blindness, microcephaly, liver and intestinal defects, among others. The age of diabetes onset may also vary from neonatal until early adulthood manifestations. Since the different mutations result in diverse clinical presentations, patients usually need different treatments that range from just diet and exercise, to the requirement of exogenous insulin or other hypoglycemic drugs, e.g., sulfonylureas or glucagon-like peptide 1 analogs to control their glycemia. As a consequence, awareness and correct diagnosis are crucial for the proper management and treatment of monogenic diabetes patients. In this chapter, we describe mutations causing different monogenic forms of diabetes associated with inadequate pancreas development or impaired β-cell function and survival, and discuss the molecular mechanisms involved in β-cell demise.
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Affiliation(s)
- Laura Sanchez Caballero
- ULB Center for Diabetes Research (UCDR), Université Libre de Bruxelles, Brussels, Belgium. http://www.ucdr.be/
| | - Vyron Gorgogietas
- ULB Center for Diabetes Research (UCDR), Université Libre de Bruxelles, Brussels, Belgium. http://www.ucdr.be/
| | - Maria Nicol Arroyo
- ULB Center for Diabetes Research (UCDR), Université Libre de Bruxelles, Brussels, Belgium. http://www.ucdr.be/
| | - Mariana Igoillo-Esteve
- ULB Center for Diabetes Research (UCDR), Université Libre de Bruxelles, Brussels, Belgium. http://www.ucdr.be/.
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9
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Teitelman G. Human Islets Contain a Beta Cell Type That Expresses Proinsulin But Not the Enzyme That Converts the Precursor to Insulin. J Histochem Cytochem 2021; 68:691-702. [PMID: 32998631 DOI: 10.1369/0022155420961361] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
In pancreatic beta cells, proinsulin (ProIN) undergoes folding in endoplasmic reticulum/Golgi system and is translocated to secretory vesicles for processing into insulin and C-peptide by the proprotein convertases (PC)1/3 and PC2, and carboxypeptidase E. Human beta cells show significant variation in the level of expression of PC1/3, the critical proconvertase involved in proinsulin processing. To ascertain whether this heterogeneity is correlated with the level of expression of the prohormone and mature hormone, the expression of proinsulin, insulin, and PC1/3 in human beta cells was examined. This analysis identified a human beta cell type that expressed proinsulin but lacked PC1/3 (ProIN+PC1/3-). This beta cell type is absent in rodent islets and is abundant in human islets of adults but scarce in islets from postnatal donors. Human islets also contained a beta cell type that expressed both proinsulin and variable levels of PC1/3 (ProIN+PC1/3+) and a less abundant cell type that lacked proinsulin but expressed the convertase (ProIN-PC1/3+). These cell phenotypes were altered by type 2 diabetes. These data suggest that these three cell types represent different stages of a dynamic process with proinsulin folding in ProIN+PC1/3- cells, proinsulin conversion into insulin in ProIN+PC1/3+cells, and replenishment of the proinsulin content in ProIN-PC1/3+ cells.
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Affiliation(s)
- Gladys Teitelman
- Department of Cell Biology, SUNY Downstate Health Science University, Brooklyn, New York
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10
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Ramzy A, Asadi A, Kieffer TJ. Revisiting Proinsulin Processing: Evidence That Human β-Cells Process Proinsulin With Prohormone Convertase (PC) 1/3 but Not PC2. Diabetes 2020; 69:1451-1462. [PMID: 32291281 DOI: 10.2337/db19-0276] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/13/2019] [Accepted: 04/03/2020] [Indexed: 11/13/2022]
Abstract
Insulin is first produced in pancreatic β-cells as the precursor prohormone proinsulin. Defective proinsulin processing has been implicated in the pathogenesis of both type 1 and type 2 diabetes. Though there is substantial evidence that mouse β-cells process proinsulin using prohormone convertase 1/3 (PC1/3) and then prohormone convertase 2 (PC2), this finding has not been verified in human β-cells. Immunofluorescence with validated antibodies revealed that there was no detectable PC2 immunoreactivity in human β-cells and little PCSK2 mRNA by in situ hybridization. Similarly, rat β-cells were not immunoreactive for PC2. In all histological experiments, PC2 immunoreactivity in neighboring α-cells acted as a positive control. In donors with type 2 diabetes, β-cells had elevated PC2 immunoreactivity, suggesting that aberrant PC2 expression may contribute to impaired proinsulin processing in β-cells of patients with diabetes. To support histological findings using a biochemical approach, human islets were used for pulse-chase experiments. Despite inhibition of PC2 function by temperature blockade, brefeldin A, chloroquine, and multiple inhibitors that blocked production of mature glucagon from proglucagon, β-cells retained the ability to produce mature insulin. Conversely, suppression of PC1/3 blocked processing of proinsulin but not proglucagon. By demonstrating that healthy human β-cells process proinsulin by PC1/3 but not PC2, we suggest that there is a need to revise the long-standing theory of proinsulin processing.
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Affiliation(s)
- Adam Ramzy
- Laboratory of Molecular and Cellular Medicine, Department of Cellular and Physiological Sciences, Life Sciences Institute, The University of British Columbia, Vancouver, British Columbia, Canada
| | - Ali Asadi
- Laboratory of Molecular and Cellular Medicine, Department of Cellular and Physiological Sciences, Life Sciences Institute, The University of British Columbia, Vancouver, British Columbia, Canada
| | - Timothy J Kieffer
- Laboratory of Molecular and Cellular Medicine, Department of Cellular and Physiological Sciences, Life Sciences Institute, The University of British Columbia, Vancouver, British Columbia, Canada
- Department of Surgery, The University of British Columbia, Vancouver, British Columbia, Canada
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