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Wasana Jayaweera S, Surano S, Pettersson N, Oskarsson E, Lettius L, Gharibyan AL, Anan I, Olofsson A. Mechanisms of Transthyretin Inhibition of IAPP Amyloid Formation. Biomolecules 2021; 11:biom11030411. [PMID: 33802170 PMCID: PMC8001701 DOI: 10.3390/biom11030411] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2021] [Accepted: 03/04/2021] [Indexed: 12/18/2022] Open
Abstract
Amyloid-formation by the islet amyloid polypeptide (IAPP), produced by the β-cells in the human pancreas, has been associated with the development of type II diabetes mellitus (T2DM). The human plasma-protein transthyretin (TTR), a well-known amyloid-inhibiting protein, is interestingly also expressed within the IAPP producing β-cells. In the present study, we have characterized the ability of TTR to interfere with IAPP amyloid-formation, both in terms of its intrinsic stability as well as with regard to the effect of TTR-stabilizing drugs. The results show that TTR can prolong the lag-phase as well as impair elongation in the course of IAPP-amyloid formation. We also show that the interfering ability correlates inversely with the thermodynamic stability of TTR, while no such correlation was observed as a function of kinetic stability. Furthermore, we demonstrate that the ability of TTR to interfere is maintained also at the low pH environment within the IAPP-containing granules of the pancreatic β-cells. However, at both neutral and low pH, the addition of TTR-stabilizing drugs partly impaired its efficacy. Taken together, these results expose mechanisms of TTR-mediated inhibition of IAPP amyloid-formation and highlights a potential therapeutic target to prevent the onset of T2DM.
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Affiliation(s)
- Sanduni Wasana Jayaweera
- Department of Medical Biochemistry and Biophysics, Umeå University, 901 87 Umeå, Sweden; (S.W.J.); (S.S.); (N.P.); (E.O.); (L.L.); (A.L.G.)
| | - Solmaz Surano
- Department of Medical Biochemistry and Biophysics, Umeå University, 901 87 Umeå, Sweden; (S.W.J.); (S.S.); (N.P.); (E.O.); (L.L.); (A.L.G.)
| | - Nina Pettersson
- Department of Medical Biochemistry and Biophysics, Umeå University, 901 87 Umeå, Sweden; (S.W.J.); (S.S.); (N.P.); (E.O.); (L.L.); (A.L.G.)
| | - Elvira Oskarsson
- Department of Medical Biochemistry and Biophysics, Umeå University, 901 87 Umeå, Sweden; (S.W.J.); (S.S.); (N.P.); (E.O.); (L.L.); (A.L.G.)
| | - Lovisa Lettius
- Department of Medical Biochemistry and Biophysics, Umeå University, 901 87 Umeå, Sweden; (S.W.J.); (S.S.); (N.P.); (E.O.); (L.L.); (A.L.G.)
| | - Anna L. Gharibyan
- Department of Medical Biochemistry and Biophysics, Umeå University, 901 87 Umeå, Sweden; (S.W.J.); (S.S.); (N.P.); (E.O.); (L.L.); (A.L.G.)
| | - Intissar Anan
- Wallenberg Centre for Molecular Medicine, Umeå University, 901 87 Umeå, Sweden;
| | - Anders Olofsson
- Department of Medical Biochemistry and Biophysics, Umeå University, 901 87 Umeå, Sweden; (S.W.J.); (S.S.); (N.P.); (E.O.); (L.L.); (A.L.G.)
- Correspondence: ; Tel.: +46-70-354-3301
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Magrì A, Tabbì G, Di Natale G, La Mendola D, Pietropaolo A, Zoroddu MA, Peana M, Rizzarelli E. Zinc Interactions with a Soluble Mutated Rat Amylin to Mimic Whole Human Amylin: An Experimental and Simulation Approach to Understand Stoichiometry, Speciation and Coordination of the Metal Complexes. Chemistry 2020; 26:13072-13084. [DOI: 10.1002/chem.202002114] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2020] [Revised: 05/29/2020] [Indexed: 01/27/2023]
Affiliation(s)
- Antonio Magrì
- Consiglio Nazionale delle Ricerche Istituto di Cristallografia Via P. Gaifami 18 95126 Catania Italy
| | - Giovanni Tabbì
- Consiglio Nazionale delle Ricerche Istituto di Cristallografia Via P. Gaifami 18 95126 Catania Italy
| | - Giuseppe Di Natale
- Consiglio Nazionale delle Ricerche Istituto di Cristallografia Via P. Gaifami 18 95126 Catania Italy
| | - Diego La Mendola
- Dipartimento di Farmacia Università di Pisa Via Bonanno Pisano, 6 56126 Pisa Italy
- Consorzio Interuniversitario di Ricerca in Chimica dei, Metalli nei Sistemi Biologici (CIRCMSB) Via Celso Ulpiani 27 70126 Bari Italy
| | - Adriana Pietropaolo
- Dipartimento di Scienze della Salute Università “Magna Graecia” di Catanzaro Campus Universitario, Viale Europa 88100 Catanzaro Italy
| | | | - Massimiliano Peana
- Dipartimento di Chimica e Farmacia University of Sassari Via Vienna 2 07100 Sassari Italy
| | - Enrico Rizzarelli
- Consiglio Nazionale delle Ricerche Istituto di Cristallografia Via P. Gaifami 18 95126 Catania Italy
- Consorzio Interuniversitario di Ricerca in Chimica dei, Metalli nei Sistemi Biologici (CIRCMSB) Via Celso Ulpiani 27 70126 Bari Italy
- Dipartimento di Scienze Chimiche Università degli Studi di Catania Viale A. Doria 6 95125 Catania Italy
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3
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IAPP/amylin and β-cell failure: implication of the risk factors of type 2 diabetes. Diabetol Int 2018; 9:143-157. [PMID: 30603362 DOI: 10.1007/s13340-018-0347-1] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/08/2017] [Accepted: 01/21/2018] [Indexed: 12/12/2022]
Abstract
In type 2 diabetes (T2D), the most significant pathological change in pancreatic islets is amyloid deposits, of which a major component is islet amyloid polypeptide (IAPP), also called amylin. IAPP is expressed in β-cells and co-secreted with insulin. Together with the inhibitory effects of synthetic human IAPP (hIAPP) on insulin secretion, our studies, using hIAPP transgenic mice, in which glucose-stimulated insulin secretion was moderately reduced without amyloid deposit, and hIAPP gene-transfected β-cell lines, in which insulin secretion was markedly impaired without amyloid, predicted that soluble hIAPP-related molecules would exert cytotoxicity on β-cells. Human IAPP is one of the most aggregation-prone peptides that interact with cell membranes. While it is widely reported that soluble hIAPP oligomers promote cytotoxicity, this is still a hypothesis since the mechanisms are not yet fully defined. Several hIAPP transgenic mouse models did not develop diabetes; however, in models with backgrounds characterized for diabetic phenotypes, β-cell function and glucose tolerance did worsen, compared to those in non-transgenic models with similar backgrounds. Together with these findings, many studies on metabolic and molecular disorders induced by risk factors of T2D suggest that in T2D subjects, toxic IAPP oligomers accumulate in β-cells, impair their function, and reduce mass through disruption of cell membranes, resulting in β-cell failure. IAPP might be central to β-cell failure in T2D. Anti-amyloid aggregation therapeutics will be developed to create treatments with more durable and beneficial effects on β-cell function.
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4
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Raleigh D, Zhang X, Hastoy B, Clark A. The β-cell assassin: IAPP cytotoxicity. J Mol Endocrinol 2017; 59:R121-R140. [PMID: 28811318 DOI: 10.1530/jme-17-0105] [Citation(s) in RCA: 93] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/02/2017] [Accepted: 08/15/2017] [Indexed: 12/28/2022]
Abstract
Islet amyloid polypeptide (IAPP) forms cytotoxic oligomers and amyloid fibrils in islets in type 2 diabetes (T2DM). The causal factors for amyloid formation are largely unknown. Mechanisms of molecular folding and assembly of human IAPP (hIAPP) into β-sheets, oligomers and fibrils have been assessed by detailed biophysical studies of hIAPP and non-fibrillogenic, rodent IAPP (rIAPP); cytotoxicity is associated with the early phases (oligomers/multimers) of fibrillogenesis. Interaction with synthetic membranes promotes β-sheet assembly possibly via a transient α-helical molecular conformation. Cellular hIAPP cytotoxicity can be activated from intracellular or extracellular sites. In transgenic rodents overexpressing hIAPP, intracellular pro-apoptotic signals can be generated at different points in β-cell protein synthesis. Increased cellular trafficking of proIAPP, failure of the unfolded protein response (UPR) or excess trafficking of misfolded peptide via the degradation pathways can induce apoptosis; these data indicate that defects in intracellular handling of hIAPP can induce cytotoxicity. However, there is no evidence for IAPP overexpression in T2DM. Extracellular amyloidosis is directly related to the degree of β-cell apoptosis in islets in T2DM. IAPP fragments, fibrils and multimers interact with membranes causing disruption in vivo and in vitro These findings support a role for extracellular IAPP in β-sheet conformation in cytotoxicity. Inhibitors of fibrillogenesis are useful tools to determine the aberrant mechanisms that result in hIAPP molecular refolding and islet amyloidosis. However, currently, their role as therapeutic agents remains uncertain.
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Affiliation(s)
- Daniel Raleigh
- Department of ChemistryStony Brook University, Stony Brook, New York, USA
- Research Department of Structural and Molecule BiologyUniversity College London, London, UK
| | - Xiaoxue Zhang
- Department of ChemistryStony Brook University, Stony Brook, New York, USA
| | - Benoît Hastoy
- Oxford Centre for Diabetes Endocrinology and MetabolismUniversity of Oxford, Oxford, UK
| | - Anne Clark
- Oxford Centre for Diabetes Endocrinology and MetabolismUniversity of Oxford, Oxford, UK
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5
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Abstract
The finding of islet inflammation in type 2 diabetes (T2D) and its involvement in β cell dysfunction has further highlighted the significance of inflammation in metabolic diseases. The number of intra-islet macrophages is increased in T2D, and these cells are the main source of proinflammatory cytokines within islets. Multiple human studies of T2D have shown that targeting islet inflammation has the potential to be an effective therapeutic strategy. In this Review we provide an overview of the cellular and molecular mechanisms by which islet inflammation develops and causes β cell dysfunction. We also emphasize the regulation and roles of macrophage polarity shift within islets in the context of T2D pathology and β cell health, which may have broad translational implications for therapeutics aimed at improving islet function.
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Erthal LCS, Marques AF, Almeida FCL, Melo GLM, Carvalho CM, Palmieri LC, Cabral KMS, Fontes GN, Lima LMTR. Regulation of the assembly and amyloid aggregation of murine amylin by zinc. Biophys Chem 2016; 218:58-70. [PMID: 27693831 DOI: 10.1016/j.bpc.2016.09.008] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2016] [Revised: 09/10/2016] [Accepted: 09/17/2016] [Indexed: 11/17/2022]
Abstract
The secretory granule of the pancreatic β-cells is a zinc-rich environment copopulated with the hormones amylin and insulin. The human amylin is shown to interact with zinc ions with major contribution from the single histidine residue, which is absent in amylin from other species such as cat, rhesus and rodents. We report here the interaction of murine amylin with zinc ions in vitro. The self-assembly of murine amylin is tightly regulated by zinc and pH. Ion mobility mass spectrometry revealed zinc interaction with monomers and oligomers. Nuclear magnetic resonance confirms the binding of zinc to murine amylin. The aggregation process of murine amylin into amyloid fibrils is accelerated by zinc. Collectively these data suggest a general role of zinc in the modulation of amylin variants oligomerization and amyloid fibril formation.
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Affiliation(s)
- Luiza C S Erthal
- School of Pharmacy, Federal University of Rio de Janeiro - UFRJ, CCS, Bss24, Ilha do Fundão, 21941-590 Rio de Janeiro, Brazil
| | - Adriana F Marques
- School of Pharmacy, Federal University of Rio de Janeiro - UFRJ, CCS, Bss24, Ilha do Fundão, 21941-590 Rio de Janeiro, Brazil
| | - Fábio C L Almeida
- School of Pharmacy, Federal University of Rio de Janeiro - UFRJ, CCS, Bss24, Ilha do Fundão, 21941-590 Rio de Janeiro, Brazil
| | - Gustavo L M Melo
- School of Pharmacy, Federal University of Rio de Janeiro - UFRJ, CCS, Bss24, Ilha do Fundão, 21941-590 Rio de Janeiro, Brazil
| | - Camila M Carvalho
- School of Pharmacy, Federal University of Rio de Janeiro - UFRJ, CCS, Bss24, Ilha do Fundão, 21941-590 Rio de Janeiro, Brazil
| | - Leonardo C Palmieri
- School of Pharmacy, Federal University of Rio de Janeiro - UFRJ, CCS, Bss24, Ilha do Fundão, 21941-590 Rio de Janeiro, Brazil
| | - Katia M S Cabral
- School of Pharmacy, Federal University of Rio de Janeiro - UFRJ, CCS, Bss24, Ilha do Fundão, 21941-590 Rio de Janeiro, Brazil
| | - Giselle N Fontes
- Laboratory for Macromolecules (LAMAC-DIMAV), Brazilian National Institute of Metrology, Quality and Technology - INMETRO, Av. N. Sa. das Graças, 50 - Xerém, Duque de Caxias-RJ, 25250-020 Rio de Janeiro, Brazil
| | - Luís Maurício T R Lima
- School of Pharmacy, Federal University of Rio de Janeiro - UFRJ, CCS, Bss24, Ilha do Fundão, 21941-590 Rio de Janeiro, Brazil; Laboratory for Macromolecules (LAMAC-DIMAV), Brazilian National Institute of Metrology, Quality and Technology - INMETRO, Av. N. Sa. das Graças, 50 - Xerém, Duque de Caxias-RJ, 25250-020 Rio de Janeiro, Brazil; National Institute of Science and Technology for Structural Biology and Bioimaging (INBEB-INCT), Federal University of Rio de Janeiro, Rio de Janeiro 21941-590, Brazil.
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7
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He J, Dai J, Li J, Peng X, Niemi AJ. Aspects of structural landscape of human islet amyloid polypeptide. J Chem Phys 2015; 142:045102. [PMID: 25638009 DOI: 10.1063/1.4905586] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
The human islet amyloid polypeptide (hIAPP) co-operates with insulin to maintain glycemic balance. It also constitutes the amyloid plaques that aggregate in the pancreas of type-II diabetic patients. We have performed extensive in silico investigations to analyse the structural landscape of monomeric hIAPP, which is presumed to be intrinsically disordered. For this, we construct from first principles a highly predictive energy function that describes a monomeric hIAPP observed in a nuclear magnetic resonance experiment, as a local energy minimum. We subject our theoretical model of hIAPP to repeated heating and cooling simulations, back and forth between a high temperature regime where the conformation resembles a random walker and a low temperature limit where no thermal motions prevail. We find that the final low temperature conformations display a high level of degeneracy, in a manner which is fully in line with the presumed intrinsically disordered character of hIAPP. In particular, we identify an isolated family of α-helical conformations that might cause the transition to amyloidosis, by nucleation.
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Affiliation(s)
- Jianfeng He
- School of Physics, Beijing Institute of Technology, Beijing 100081, People's Republic of China
| | - Jin Dai
- School of Physics, Beijing Institute of Technology, Beijing 100081, People's Republic of China
| | - Jing Li
- Institute of Biopharmaceutical Research, Yangtze River Pharmaceutical Group Beijing Haiyan Pharmaceutical Co., Ltd, Beijing 102206, China
| | - Xubiao Peng
- Department of Physics and Astronomy, Uppsala University, P.O. Box 803, S-75108 Uppsala, Sweden
| | - Antti J Niemi
- School of Physics, Beijing Institute of Technology, Beijing 100081, People's Republic of China
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8
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Zhang S, Liu H, Chuang CL, Li X, Au M, Zhang L, Phillips ARJ, Scott DW, Cooper GJS. The pathogenic mechanism of diabetes varies with the degree of overexpression and oligomerization of human amylin in the pancreatic islet β cells. FASEB J 2014; 28:5083-96. [PMID: 25138158 DOI: 10.1096/fj.14-251744] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
The aggregation of human amylin (hA) to form cytotoxic structures has been closely associated with the causation of type 2 diabetes. We sought to advance understanding of how altered expression and aggregation of hA might link β-cell degeneration with diabetes onset and progression, by comparing phenotypes between homozygous and hemizygous hA-transgenic mice. The homozygous mice displayed elevated islet hA that correlated positively with measures of oligomer formation (r=0.91; P<0.0001). They also developed hyperinsulinemia with transient insulin resistance during the prediabetes stage and then underwent rapid β-cell loss, culminating in severe juvenile-onset diabetes. The prediabetes stage was prolonged in the hemizygous mice, wherein β-cell dysfunction and extensive oligomer formation occurred in adulthood at a much later stage, when hA levels were lower (r=-0.60; P<0.0001). This is the first report to show that hA-evoked diabetes is associated with age, insulin resistance, progressive islet dysfunction, and β-cell apoptosis, which interact variably to cause the different diabetes syndromes. The various levels of hA elevation cause different extents of oligomer formation in the disease stages, thus eliciting early- or adult-onset diabetes syndromes, reminiscent of type 1 and 2 diabetes, respectively. Thus, the hA-evoked diabetes phenotypes differ substantively according to degree of amylin overproduction. These findings are relevant to the understanding of the pathogenesis and the development of experimental therapeutics for diabetes.
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Affiliation(s)
- Shaoping Zhang
- The School of Biological Sciences and The Maurice Wilkins Centre for Molecular BioDiscovery, Faculty of Science, University of Auckland, Auckland, New Zealand
| | - Hong Liu
- The School of Biological Sciences and
| | | | | | - Maggie Au
- The School of Biological Sciences and
| | - Lin Zhang
- The School of Biological Sciences and
| | - Anthony R J Phillips
- The School of Biological Sciences and The Maurice Wilkins Centre for Molecular BioDiscovery, Faculty of Science, University of Auckland, Auckland, New Zealand
| | | | - Garth J S Cooper
- The School of Biological Sciences and The Maurice Wilkins Centre for Molecular BioDiscovery, Faculty of Science, University of Auckland, Auckland, New Zealand Centre for Advanced Discovery and Experimental Therapeutics, Central Manchester University Hospitals National Health Service (NHS) Foundation Trust, Manchester, UK; and Centre for Endocrinology and Diabetes, Institute of Human Development, Faculty of Medical and Human Sciences, Manchester Academic Health Sciences Centre, The University of Manchester, Manchester, UK
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B-cell translocation gene 2 positively regulates GLP-1-stimulated insulin secretion via induction of PDX-1 in pancreatic β-cells. Exp Mol Med 2013; 45:e25. [PMID: 23703573 PMCID: PMC3674408 DOI: 10.1038/emm.2013.47] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Glucagon-like peptide-1 (GLP-1) is a potent glucoincretin hormone and an important agent for the treatment of type 2 diabetes. Here we demonstrate that B-cell translocation gene 2 (BTG2) is a crucial regulator in GLP-1-induced insulin gene expression and insulin secretion via upregulation of pancreatic duodenal homeobox-1 (PDX-1) in pancreatic β-cells. GLP-1 treatment significantly increased BTG2, PDX-1 and insulin gene expression in pancreatic β-cells. Notably, adenovirus-mediated overexpression of BTG2 significantly elevated insulin secretion, as well as insulin and PDX-1 gene expression. Physical interaction studies showed that BTG2 is associated with increased PDX-1 occupancy on the insulin gene promoter via a direct interaction with PDX-1. Exendin-4 (Ex-4), a GLP-1 agonist, and GLP-1 in pancreatic β-cells increased insulin secretion through the BTG2–PDX-1–insulin pathway, which was blocked by endogenous BTG2 knockdown using a BTG2 small interfering RNA knockdown system. Finally, we revealed that Ex-4 and GLP-1 significantly elevated insulin secretion via upregulation of the BTG2–PDX-1 axis in pancreatic islets, and this phenomenon was abolished by endogenous BTG2 knockdown. Collectively, our current study provides a novel molecular mechanism by which GLP-1 positively regulates insulin gene expression via BTG2, suggesting that BTG2 has a key function in insulin secretion in pancreatic β-cells.
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Udayasankar J, Zraika S, Aston-Mourney K, Subramanian SL, Brooks-Worrell BM, Taborsky GJ, Hull RL. Rosiglitazone treatment does not decrease amyloid deposition in transplanted islets from transgenic mice expressing human islet amyloid polypeptide. Transplant Proc 2012; 45:574-9. [PMID: 23267797 DOI: 10.1016/j.transproceed.2012.05.079] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2012] [Accepted: 05/04/2012] [Indexed: 12/17/2022]
Abstract
In human islet transplantation, insulin independence decreases over time. We previously showed that amyloid deposition following transplantation of islets from human islet amyloid polypeptide (hIAPP) transgenic mice resulted in ß-cell loss and that rosiglitazone treatment decreased islet amyloid deposition and preserved ß-cell area in the endogenous pancreas of hIAPP transgenic mice. Thus, we sought to determine if rosiglitazone treatment decreases islet amyloid deposition and the associated ß-cell loss after islet transplantation. Streptozocin-diabetic mice were transplanted with 100 islets from hIAPP transgenic (T) mice or nontransgenic (NT) littermates under the kidney capsule and received either rosiglitazone (R) in drinking water or plain drinking water (C). The resultant groups (NTC [n = 11], NTR [n = 9], TC [n = 14], and TR [n = 10]) were followed for 12 weeks after which the graft was removed and processed for histology. Amyloid was detected in nearly all T islet grafts (TC = 13/14, TR = 10/10) but not in NT grafts. Rosiglitazone did not alter amyloid deposition (% graft area occupied by amyloid; TC: 2.15 ± 0.7, TR: 1.72 ± 0.66; P = .86). % ß-cell/graft area was decreased in the TC grafts compared to NTC (56.2 ± 3.1 vs 73.8 ± 1.4; P < .0001) but was not different between TC and TR groups (56.2 ± 3.1 vs 61.0 ± 2.9; P = .34). Plasma glucose levels before and after transplantation did not differ between NTC and TC groups and rosiglitazone did not affect plasma glucose levels post-islet transplantation. Rosiglitazone did not decrease amyloid deposition in hIAPP transgenic islet grafts. Therefore, rosiglitazone treatment of recipients of amyloid forming islets may not improve transplantation outcomes.
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Affiliation(s)
- J Udayasankar
- Division of Metabolism, Endocrinology and Nutrition, VA Puget Sound Health Care System and University of Washington, Seattle, Washington 98108, USA
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Westermark GT, Westermark P. Localized amyloids important in diseases outside the brain - lessons from the islets of Langerhans and the thoracic aorta. FEBS J 2011; 278:3918-29. [DOI: 10.1111/j.1742-4658.2011.08298.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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12
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Wei L, Jiang P, Xu W, Li H, Zhang H, Yan L, Chan-Park MB, Liu XW, Tang K, Mu Y, Pervushin K. The molecular basis of distinct aggregation pathways of islet amyloid polypeptide. J Biol Chem 2011; 286:6291-300. [PMID: 21148563 PMCID: PMC3057848 DOI: 10.1074/jbc.m110.166678] [Citation(s) in RCA: 96] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2010] [Revised: 12/09/2010] [Indexed: 11/06/2022] Open
Abstract
Abnormal aggregation of islet amyloid polypeptide (IAPP) into amyloid fibrils is a hallmark of type 2 diabetes. In this study, we investigated the initial oligomerization and subsequent addition of monomers to growing aggregates of human IAPP at the residue-specific level using NMR, atomic force microscopy, mass spectroscopy, and computational simulations. We found that in solution IAPPs rapidly associate into transient low-order oligomers such as dimers and trimers via interactions between histidine 18 and tyrosine 37. This initial event is proceeded by slow aggregation into higher-order spherical oligomers and elongated fibrils. In these two morphologically distinct types of aggregates IAPPs adopt structures with markedly different residual flexibility. Here we show that the anti-amyloidogenic compound resveratrol inhibits oligomerization and amyloid formation via binding to histidine 18, supporting the finding that this residue is crucial for on-pathway oligomer formation.
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Affiliation(s)
- Lei Wei
- From the Schools of Biological Sciences
| | | | - Weixin Xu
- From the Schools of Biological Sciences
| | - Hai Li
- Materials Science and Engineering
| | | | | | | | - Xue-Wei Liu
- Physical and Mathematical Sciences, Nanyang Technological University, Singapore 639798
| | - Kai Tang
- From the Schools of Biological Sciences
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Abstract
Gut microbiota is an assortment of microorganisms inhabiting the length and width of the mammalian gastrointestinal tract. The composition of this microbial community is host specific, evolving throughout an individual's lifetime and susceptible to both exogenous and endogenous modifications. Recent renewed interest in the structure and function of this "organ" has illuminated its central position in health and disease. The microbiota is intimately involved in numerous aspects of normal host physiology, from nutritional status to behavior and stress response. Additionally, they can be a central or a contributing cause of many diseases, affecting both near and far organ systems. The overall balance in the composition of the gut microbial community, as well as the presence or absence of key species capable of effecting specific responses, is important in ensuring homeostasis or lack thereof at the intestinal mucosa and beyond. The mechanisms through which microbiota exerts its beneficial or detrimental influences remain largely undefined, but include elaboration of signaling molecules and recognition of bacterial epitopes by both intestinal epithelial and mucosal immune cells. The advances in modeling and analysis of gut microbiota will further our knowledge of their role in health and disease, allowing customization of existing and future therapeutic and prophylactic modalities.
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Affiliation(s)
- Inna Sekirov
- Michael Smith Laboratories, Department of Microbiology and Immunology, The University of British Columbia, Vancouver, British Columbia, Canada
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14
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Cooper GJS, Aitken JF, Zhang S. Is type 2 diabetes an amyloidosis and does it really matter (to patients)? Diabetologia 2010; 53:1011-6. [PMID: 20229094 DOI: 10.1007/s00125-010-1715-y] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/08/2010] [Accepted: 02/10/2010] [Indexed: 12/17/2022]
Affiliation(s)
- G J S Cooper
- School of Biological Sciences, and Maurice Wilkins Centre of Excellence for Molecular Biodiscovery, Faculty of Science, University of Auckland, Auckland, New Zealand.
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Cao P, Meng F, Abedini A, Raleigh DP. The ability of rodent islet amyloid polypeptide to inhibit amyloid formation by human islet amyloid polypeptide has important implications for the mechanism of amyloid formation and the design of inhibitors. Biochemistry 2010; 49:872-81. [PMID: 20028124 DOI: 10.1021/bi901751b] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Islet amyloid polypeptide (IAPP) is a 37-residue polypeptide hormone that is responsible for islet amyloid formation in type II diabetes. Human IAPP is extremely amyloidogenic, while rat IAPP and mouse IAPP do not form amyloid in vitro or in vivo. Rat IAPP and mouse IAPP have identical primary sequences, but differ from the human polypeptide at six positions, five of which are localized between residues 20 and 29. The ability of rat IAPP to inhibit amyloid formation by human IAPP was tested, and the rat peptide was found to be an effective inhibitor. Thioflavin-T fluorescence-monitored kinetic experiments, transmission electron microscopy, and circular dichroism showed that rat IAPP lengthened the lag phase for amyloid formation by human IAPP, slowed the growth rate, reduced the amount of amyloid fibrils produced in a dose-dependent manner, and altered the morphology of the fibrils. The inhibition of human IAPP amyloid formation by rat IAPP can be rationalized by a model that postulates formation of an early helical intermediate during amyloid formation where the helical region is localized to the N-terminal region of IAPP. The model predicts that proline mutations in the putative helical region should lead to ineffective inhibitors as should mutations that alter the peptide-peptide interaction interface. We confirmed this by testing the ability of A13P and F15D point mutants of rat IAPP to inhibit amyloid formation by human IAPP. Both these mutants were noticeably less effective inhibitors than wild-type rat IAPP. The implications for inhibitor design are discussed.
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Affiliation(s)
- Ping Cao
- Department of Chemistry, State University of New York, Stony Brook, New York 11794-3400, USA
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Buxbaum JN. Animal models of human amyloidoses: are transgenic mice worth the time and trouble? FEBS Lett 2009; 583:2663-73. [PMID: 19627988 DOI: 10.1016/j.febslet.2009.07.031] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2009] [Revised: 07/15/2009] [Accepted: 07/15/2009] [Indexed: 02/05/2023]
Abstract
The amyloidoses are the prototype gain of toxic function protein misfolding diseases. As such, several naturally occurring animal models and their inducible variants provided some of the first insights into these disorders of protein aggregation. With greater analytic knowledge and the increasing flexibility of transgenic and gene knockout technology, new models have been generated allowing the interrogation of phenomena that have not been approachable in more reductionist systems, i.e. behavioral readouts in the neurodegenerative diseases, interactions among organ systems in the transthyretin amyloidoses and taking pre-clinical therapeutic trials beyond cell culture. The current review describes the features of both transgenic and non-transgenic models and discusses issues that appear to be unresolved even when viewed in their organismal context.
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Affiliation(s)
- Joel N Buxbaum
- Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, CA 92037, USA.
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17
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Garin I, Martinez R, de las Heras J, Perez-Nanclares G, Castano L, Perez de Nanclares G. Mutations in MAFA and IAPP are not a common cause of monogenic diabetes. Diabet Med 2009; 26:746-8. [PMID: 19573128 DOI: 10.1111/j.1464-5491.2009.02758.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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18
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Wiltzius JJW, Sievers SA, Sawaya MR, Eisenberg D. Atomic structures of IAPP (amylin) fusions suggest a mechanism for fibrillation and the role of insulin in the process. Protein Sci 2009; 18:1521-30. [PMID: 19475663 PMCID: PMC2775219 DOI: 10.1002/pro.145] [Citation(s) in RCA: 179] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Islet Amyloid Polypeptide (IAPP or amylin) is a peptide hormone produced and stored in the beta-islet cells of the pancreas along with insulin. IAPP readily forms amyloid fibrils in vitro, and the deposition of fibrillar IAPP has been correlated with the pathology of type II diabetes. The mechanism of the conversion that IAPP undergoes from soluble to fibrillar forms has been unclear. By chaperoning IAPP through fusion to maltose binding protein, we find that IAPP can adopt a alpha-helical structure at residues 8-18 and 22-27 and that molecules of IAPP dimerize. Mutational analysis suggests that this dimerization is on the pathway to fibrillation. The structure suggests how IAPP may heterodimerize with insulin, which we confirmed by protein crosslinking. Taken together, these experiments suggest the helical dimerization of IAPP accelerates fibril formation and that insulin impedes fibrillation by blocking the IAPP dimerization interface.
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Affiliation(s)
| | | | | | - David Eisenberg
- *Correspondence to: David Eisenberg, Howard Hughes Medical Institute, UCLA-DOE Institute of Genomics and Proteomics, Los Angeles, California 90095-1570
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19
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Andrews ME, Inayathullah NM, Jayakumar R, Malar EJP. Conformational polymorphism and cellular toxicity of IAPP and beta AP domains. J Struct Biol 2009; 166:116-25. [PMID: 19374013 DOI: 10.1016/j.jsb.2008.12.011] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The principal component of the amyloid deposits in Alzheimer's disease is the beta-amyloid polypeptide, while in type II diabetes the deposits consist primarily of Islet amyloid polypeptide. These amyloid forming polypeptides consist of highly polymorphic domains, which take different conformations including random coil, helical and beta strand depending upon the microenvironment. We have studied major fibril-forming components of IAPP and beta AP and demonstrated that conformational polymorphism of these peptides in different microenvironments correlate with cellular toxicity and proteasomal inhibitory activity. On treating with trifluoroethanol (TFE) the peptide fragments undergo structural transition from a random coil to a helical conformation. Even though these domains share the same gross amyloid structural characteristic, their proteasomal activities differ. We found that even the tetrapeptides have significant proteasomal inhibitory activity indicating that the amyloid formation is involved in the enhanced life of the smaller aggregates of full-length and fragment peptides, which could explain the toxicity of these sequences.
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Affiliation(s)
- Maneesha E Andrews
- Bio Organic Laboratory, Central Leather Research Institute, Adyar, Chennai 600 020, India
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20
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Udayasankar J, Kodama K, Hull RL, Zraika S, Aston-Mourney K, Subramanian SL, Tong J, Faulenbach MV, Vidal J, Kahn SE. Amyloid formation results in recurrence of hyperglycaemia following transplantation of human IAPP transgenic mouse islets. Diabetologia 2009; 52:145-53. [PMID: 19002432 PMCID: PMC4950742 DOI: 10.1007/s00125-008-1185-7] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/18/2008] [Accepted: 09/26/2008] [Indexed: 10/21/2022]
Abstract
AIMS/HYPOTHESIS Islet transplantation is a potential cure for diabetes; however, rates of graft failure remain high. The aim of the present study was to determine whether amyloid deposition is associated with reduced beta cell volume in islet grafts and the recurrence of hyperglycaemia following islet transplantation. METHODS We transplanted a streptozotocin-induced mouse model of diabetes with 100 islets from human IAPP (which encodes islet amyloid polypeptide) transgenic mice that have the propensity to form islet amyloid (n = 8-12) or from non-transgenic mice that do not develop amyloid (n = 6-10) in sets of studies that lasted 1 or 6 weeks. RESULTS Plasma glucose levels before and for 1 week after transplantation were similar in mice that received transgenic or non-transgenic islets, and at that time amyloid was detected in all transgenic grafts and, as expected, in none of the non-transgenic grafts. However, over the 6 weeks following transplantation, plasma glucose levels increased in transgenic but remained stable in non-transgenic islet graft recipients (p < 0.05). At 6 weeks, amyloid was present in 92% of the transgenic grafts and in none of the non-transgenic grafts. Beta cell volume was reduced by 30% (p < 0.05), beta cell apoptosis was twofold higher (p < 0.05), and beta cell replication was reduced by 50% (p < 0.001) in transgenic vs non-transgenic grafts. In summary, amyloid deposition in islet grafts occurs prior to the recurrence of hyperglycaemia and its accumulation over time is associated with beta cell loss. CONCLUSIONS/INTERPRETATION Islet amyloid formation may explain, in part, the non-immune loss of beta cells and recurrence of hyperglycaemia following clinical islet transplantation.
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Affiliation(s)
- J Udayasankar
- VA Puget Sound Health Care System 151, Seattle, WA 98108, USA
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21
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Wong WP, Scott DW, Chuang CL, Zhang S, Liu H, Ferreira A, Saafi EL, Choong YS, Cooper GJ. Spontaneous diabetes in hemizygous human amylin transgenic mice that developed neither islet amyloid nor peripheral insulin resistance. Diabetes 2008; 57:2737-44. [PMID: 18633116 PMCID: PMC2551684 DOI: 10.2337/db06-1755] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/29/2006] [Accepted: 06/30/2008] [Indexed: 01/09/2023]
Abstract
OBJECTIVES We sought to 1) Determine whether soluble-misfolded amylin or insoluble-fibrillar amylin may cause or result from diabetes in human amylin transgenic mice and 2) determine the role, if any, that insulin resistance might play in these processes. RESEARCH DESIGN AND METHODS We characterized the phenotypes of independent transgenic mouse lines that display pancreas-specific expression of human amylin or a nonaggregating homolog, [(25,28,29)Pro]human amylin, in an FVB/n background. RESULTS Diabetes occurred in hemizygous human amylin transgenic mice from 6 weeks after birth. Glucose tolerance was impaired during the mid- and end-diabetic phases, in which progressive beta-cell loss paralleled decreasing pancreatic and plasma insulin and amylin. Peripheral insulin resistance was absent because glucose uptake rates were equivalent in isolated soleus muscles from transgenic and control animals. Even in advanced diabetes, islets lacked amyloid deposits. In islets from nontransgenic mice, glucagon and somatostatin cells were present mainly at the periphery and insulin cells were mainly in the core; in contrast, all three cell types were distributed throughout the islet in transgenic animals. [(25,28,29)Pro]human amylin transgenic mice developed neither beta-cell degeneration nor glucose intolerance. CONCLUSIONS Overexpression of fibrillogenic human amylin in these human amylin transgenic mice caused beta-cell degeneration and diabetes through mechanisms independent from both peripheral insulin resistance and islet amyloid. These findings are consistent with beta-cell death evoked by misfolded but soluble cytotoxic species, such as those formed by human amylin in vitro.
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Affiliation(s)
- Winifred P.S. Wong
- School of Biological Sciences, Faculty of Science, University of Auckland, Auckland, New Zealand
| | - David W. Scott
- School of Biological Sciences, Faculty of Science, University of Auckland, Auckland, New Zealand
| | - Chia-Lin Chuang
- School of Biological Sciences, Faculty of Science, University of Auckland, Auckland, New Zealand
| | - Shaoping Zhang
- School of Biological Sciences, Faculty of Science, University of Auckland, Auckland, New Zealand
- Maurice Wilkins Centre for Molecular Biodiscovery, University of Auckland, Auckland, New Zealand
| | - Hong Liu
- School of Biological Sciences, Faculty of Science, University of Auckland, Auckland, New Zealand
| | - Athena Ferreira
- School of Biological Sciences, Faculty of Science, University of Auckland, Auckland, New Zealand
| | - Etuate L. Saafi
- School of Biological Sciences, Faculty of Science, University of Auckland, Auckland, New Zealand
| | - Yee Soon Choong
- School of Biological Sciences, Faculty of Science, University of Auckland, Auckland, New Zealand
| | - Garth J.S. Cooper
- School of Biological Sciences, Faculty of Science, University of Auckland, Auckland, New Zealand
- Maurice Wilkins Centre for Molecular Biodiscovery, University of Auckland, Auckland, New Zealand
- MRC Immunochemistry Unit, Department of Biochemistry, University of Oxford, Oxford, U.K
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22
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Knight JD, Williamson JA, Miranker AD. Interaction of membrane-bound islet amyloid polypeptide with soluble and crystalline insulin. Protein Sci 2008; 17:1850-6. [PMID: 18765820 DOI: 10.1110/ps.036350.108] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
Islet amyloid polypeptide (IAPP, also known as amylin) is the major protein component of pancreatic amyloid fibers in type II diabetes and is normally cosecreted with insulin from the beta-cells of the pancreas. IAPP forms amyloid fibrils rapidly at concentrations well below those found in vivo, yet progression of type II diabetes occurs over many years. Insulin, a known inhibitor of IAPP fibrillogenesis, exists as a dense crystalline or near-crystalline core in the secretory vesicle, while IAPP localizes to the region between the crystal and the secretory vesicle membrane. In vitro, IAPP fibrillogenesis is both accelerated by lipid membranes and inhibited by monomeric insulin. In this work, we investigate insulin-IAPP-lipid interactions in vitro under conditions chosen to approximate native secretory vesicle physiology and the amyloid disease state. The effect of insulin on IAPP fibrillogenesis is investigated using fluorescence spectrometry. Additionally, interactions of IAPP and lipids with crystalline insulin are studied using fluorescence microscopy. We find that, while soluble states of insulin and IAPP do not interact significantly, large assemblies of either insulin (crystals) or IAPP (fibers) can lead to stable IAPP-insulin interactions. The results raise the possibility of multiple physiological interactions between these two beta-cell hormones.
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Affiliation(s)
- Jefferson D Knight
- Department of Pharmacology, Yale University, New Haven, Connecticut 06520-8066, USA
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23
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Wiltzius JJW, Sievers SA, Sawaya MR, Cascio D, Popov D, Riekel C, Eisenberg D. Atomic structure of the cross-beta spine of islet amyloid polypeptide (amylin). Protein Sci 2008; 17:1467-74. [PMID: 18556473 DOI: 10.1110/ps.036509.108] [Citation(s) in RCA: 283] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Human islet amyloid polypeptide (IAPP or amylin) is a 37-residue hormone found as fibrillar deposits in pancreatic extracts of nearly all type II diabetics. Although the cellular toxicity of IAPP has been established, the structure of the fibrillar form found in these deposits is unknown. Here we have crystallized two segments from IAPP, which themselves form amyloid-like fibrils. The atomic structures of these two segments, NNFGAIL and SSTNVG, were determined, and form the basis of a model for the most commonly observed, full-length IAPP polymorph.
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Affiliation(s)
- Jed J W Wiltzius
- Howard Hughes Medical Institute, UCLA-DOE Institute for Genomics and Proteomics, Los Angeles, California 90095-1570, USA
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24
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25
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Masiello P. Animal models of type 2 diabetes with reduced pancreatic beta-cell mass. Int J Biochem Cell Biol 2005; 38:873-93. [PMID: 16253543 DOI: 10.1016/j.biocel.2005.09.007] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2005] [Revised: 09/02/2005] [Accepted: 09/08/2005] [Indexed: 12/31/2022]
Abstract
Type 2 diabetes is increasingly viewed as a disease of insulin deficiency due not only to intrinsic pancreatic beta-cell dysfunction but also to reduction of beta-cell mass. It is likely that, in diabetes-prone subjects, the regulated beta-cell turnover that adapts cell mass to body's insulin requirements is impaired, presumably on a genetic basis. We still have a limited knowledge of how and when this derangement occurs and what might be the most effective therapeutic strategy to preserve beta-cell mass. The animal models of type 2 diabetes with reduced beta-cell mass described in this review can be extremely helpful (a) to have insight into the mechanisms underlying the defective growth or accelerated loss of beta-cells leading to the beta-cell mass reduction; (b) to investigate in prospective studies the mechanisms of compensatory adaptation and subsequent failure of a reduced beta-cell mass. Furthermore, these models are of invaluable importance to test the effectiveness of potential therapeutic agents that either stimulate beta-cell growth or inhibit beta-cell death.
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Affiliation(s)
- Pellegrino Masiello
- Dipartimento di Patologia Sperimentale, Biotecnologie Mediche, Infettivologia ed Epidemiologia, University of Pisa, Scuola Medica, Italy.
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26
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Hull RL, Watts MR, Kodama K, Shen ZP, Utzschneider KM, Carr DB, Vidal J, Kahn SE. Genetic background determines the extent of islet amyloid formation in human islet amyloid polypeptide transgenic mice. Am J Physiol Endocrinol Metab 2005; 289:E703-9. [PMID: 15899941 DOI: 10.1152/ajpendo.00471.2004] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Genetic background is important in determining susceptibility to metabolic abnormalities such as insulin resistance and beta-cell dysfunction. Islet amyloid is associated with reduced beta-cell mass and function and develops in the majority of our C57BL/6J x DBA/2J (F(1)) male human islet amyloid polypeptide (hIAPP) transgenic mice after 1 yr of increased fat feeding. To determine the relative contribution of each parental strain, C57BL/6J (BL6) and DBA/2J (DBA2), to islet amyloid formation, we studied male hIAPP mice on each background strain (BL6, n = 13; and DBA2 n = 11) and C57BL/6J x DBA/2J F(1) mice (n = 17) on a 9% (wt/wt) fat diet for 1 yr. At the end of 12 mo, islet amyloid deposition was quantified from thioflavin S-stained pancreas sections. The majority of mice in all groups developed islet amyloid (BL6: 91%, F(1): 76%, DBA2: 100%). However, the prevalence (%amyloid-positive islets; BL6: 14 +/- 3%, F(1): 44 +/- 8%, DBA2: 49 +/- 9%, P < 0.05) and severity (%islet area occupied by amyloid; BL6: 0.03 +/- 0.01%, F(1): 9.2 +/- 2.9%, DBA2: 5.7 +/- 2.3%, p < or = 0.01) were significantly lower in BL6 than F(1) and DBA2 mice. Increased islet amyloid severity was negatively correlated with insulin-positive area per islet, in F(1) (r(2) = 0.75, P < 0.001) and DBA2 (r(2) = 0.87, P < 0.001) mice but not BL6 mice (r(2) = 0.07). In summary, the extent of islet amyloid formation in hIAPP transgenic mice is determined by background strain, with mice expressing DBA/2J genes (F(1) and DBA2 mice) being more susceptible to amyloid deposition that replaces beta-cell mass. These findings underscore the importance of genetic and environmental factors in studying metabolic disease.
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Affiliation(s)
- Rebecca L Hull
- Division of Metabolism, Endocrinology, and Nutrition, Veterans Affairs Puget Sound Health Care System, University of Washington, Seattle, WA 98108, USA.
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27
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Muff R, Born W, Lutz TA, Fischer JA. Biological importance of the peptides of the calcitonin family as revealed by disruption and transfer of corresponding genes. Peptides 2004; 25:2027-38. [PMID: 15501537 DOI: 10.1016/j.peptides.2004.08.007] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/11/2004] [Accepted: 08/11/2004] [Indexed: 10/26/2022]
Abstract
The hormone calcitonin (CT) of thyroid C-cell origin, the neuropeptides alpha- and beta-calcitonin gene-related peptide (CGRP), the widely expressed hormone and tissue factor adrenomedullin (AM), and amylin (AMY) that is co-produced with insulin in pancreatic beta-cells, are structurally related peptides. They have in common six or seven amino acid ring structures, linked by disulfide bridges between cysteine residues, and amidated carboxyl termini that are both required for biological activity. The actions of the peptides in vivo have traditionally been studied after intravenous and intracerebroventricular administration. As a result, CT lowers serum calcium and reduces pain perception. alpha- and beta CGRP and AM are highly potent vasodilatory peptides. AMY inhibits food intake through its action in the area postrema of the brain. Physiological actions of the peptides summarized in the present review have been defined through gene knockout and overexpression strategies.
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Affiliation(s)
- Roman Muff
- Department of Orthopedic Surgery, Research Laboratory for Calcium Metabolism, University of Zurich, Balgrist University Hospital, Forchstrasse 340, 8008 Zurich, Switzerland.
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28
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Clark A, Nilsson MR. Islet amyloid: a complication of islet dysfunction or an aetiological factor in Type 2 diabetes? Diabetologia 2004; 47:157-69. [PMID: 14722650 DOI: 10.1007/s00125-003-1304-4] [Citation(s) in RCA: 149] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/04/2003] [Revised: 11/04/2003] [Indexed: 12/30/2022]
Abstract
The role of islet amyloidosis in the onset and progression of Type 2 diabetes remains obscure. Islet amyloid polypeptide is a 37 amino-acid, beta-cell peptide which is co-stored and co-released with insulin. Human islet amyloid polypeptide refolds to a beta-conformation and oligomerises to form insoluble fibrils; proline substitutions in rodent islet amyloid polypeptide prevent this molecular transition. Pro-islet amyloid polypeptide (67 amino acids in man) is processed in secretory granules. Refolding of islet amyloid polypeptide may be prevented by intragranular heterodimer formation with insulin (but not proinsulin). Diabetes-associated abnormal proinsulin processing could contribute to de-stabilisation of granular islet amyloid polypeptide. Increased pro-islet amyloid polypeptide secretion as a consequence of islet dysfunction could promote fibrillogenesis; the propeptide forms fibrils and binds to basement membrane glycosamino-glycans. Islet amyloid polypeptide gene polymorphisms are not universally associated with Type 2 diabetes. Transgenic mice expressing human islet amyloid polypeptide gene have increased islet amyloid polypeptide concentrations but develop islet amyloid only against a background of obesity and/or high fat diet. In transgenic mice, obese monkeys and cats, initially small perivascular deposits progressively increase to occupy 80% islet mass; the severity of amyloidosis in animal models is related to the onset of hyperglycaemia, suggesting that islet amyloid and the associated destruction of islet cells cause diabetes. In human diabetes, islet amyloid can affect less than 1% or up to 80% of islets indicating that islet amyloidosis largely results from diabetes-related pathologies and is not an aetiological factor for hyperglycaemia. However, the associated progressive beta-cell destruction leads to severe islet dysfunction and insulin requirement.
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Affiliation(s)
- A Clark
- Diabetes Research Laboratories, Oxford Centre for Diabetes, Endocrinology and Metabolism, Churchill Hospital, Oxford, UK.
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29
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Bennett RG, Hamel FG, Duckworth WC. An insulin-degrading enzyme inhibitor decreases amylin degradation, increases amylin-induced cytotoxicity, and increases amyloid formation in insulinoma cell cultures. Diabetes 2003; 52:2315-20. [PMID: 12941771 DOI: 10.2337/diabetes.52.9.2315] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Amylin (islet amyloid polypeptide) is the chief component of the islet amyloid found in type 2 diabetes, and amylin fibril precursors may be cytotoxic to pancreatic beta-cells. Little is known about the prevention of amylin aggregation. We investigated the role of insulin-degrading enzyme (IDE) in amylin degradation, amyloid deposition, and cytotoxicity in RIN-m5F insulinoma cells. Human (125)I-labeled amylin degradation was inhibited by 46 and 65% with the addition of 100 nmol/l human amylin or insulin, respectively. (125)I-labeled insulin degradation was inhibited with 100 nmol/l human amylin, rat amylin, and insulin (by 50, 50, and 73%, respectively). The IDE inhibitor bacitracin inhibited amylin degradation by 78% and insulin degradation by 100%. Amyloid staining by Congo red fluorescence was detectable at 100 nmol/l amylin and was pronounced at 1,000 nmol/l amylin treatment for 48 h. Bacitracin treatment markedly increased staining at all amylin concentrations. Bacitracin with amylin caused a dramatic decrease in cell viability compared with amylin alone (68 and 25%, respectively, at 10 nmol/l amylin). In summary, RIN-m5F cells degraded both amylin and insulin through a common proteolytic pathway. IDE inhibition by bacitracin impaired amylin degradation, increased amyloid formation, and increased amylin-induced cytotoxicity, suggesting a role for IDE in amylin clearance and the prevention of amylin aggregation.
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Affiliation(s)
- Robert G Bennett
- Department of Internal Medicine, University of Nebraska Medical Center, and Veterans Affairs Medical Center, Omaha, Nebraska 68105, USA.
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30
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Hull RL, Andrikopoulos S, Verchere CB, Vidal J, Wang F, Cnop M, Prigeon RL, Kahn SE. Increased dietary fat promotes islet amyloid formation and beta-cell secretory dysfunction in a transgenic mouse model of islet amyloid. Diabetes 2003; 52:372-9. [PMID: 12540610 DOI: 10.2337/diabetes.52.2.372] [Citation(s) in RCA: 91] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Transgenic mice expressing the amyloidogenic human islet amyloid polypeptide (hIAPP) in their islet beta-cells are a model of islet amyloid formation as it occurs in type 2 diabetes. Our hIAPP transgenic mice developed islet amyloid when fed a breeder chow but not regular chow. Because the breeder chow contained increased amounts of fat, we hypothesized that increased dietary fat enhances islet amyloid formation. To test this hypothesis, we fed male hIAPP transgenic and nontransgenic control mice diets containing 15% (low fat), 30% (medium fat), or 45% (high fat) of calories derived from fat for 12 months, and we measured islet amyloid, islet endocrine cell composition, and beta-cell function. Increased dietary fat in hIAPP transgenic mice was associated with a dose-dependent increase in both the prevalence (percentage of islets containing amyloid deposits; 34 +/- 8, 45 +/- 8, and 58 +/- 10%, P < 0.05) and severity (percentage of islet area occupied by amyloid; 0.8 +/- 0.5, 1.0 +/- 0.5, and 4.6 +/- 2.5%, P = 0.05) of islet amyloid. In addition, in these hIAPP transgenic mice, there was a dose-dependent decrease in the proportion of islet area comprising beta-cells, with no significant change in islet size. In contrast, nontransgenic mice adapted to diet-induced obesity by increasing their islet size more than twofold. Increased dietary fat was associated with impaired insulin secretion in hIAPP transgenic (P = 0.05) but not nontransgenic mice. In summary, dietary fat enhances both the prevalence and severity of islet amyloid and leads to beta-cell loss and impaired insulin secretion. Because both morphologic and functional defects are present in hIAPP transgenic mice, this would suggest that the effect of dietary fat to enhance islet amyloid formation might play a role in the pathogenesis of the islet lesion of type 2 diabetes in humans.
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Affiliation(s)
- Rebecca L Hull
- Division of Metabolism, Endocrinology and Nutrition, Department of Medicine, VA Puget Sound Health Care System and University of Washington, Seattle 98108, USA.
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31
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Ma Z, Westermark GT. Effects of Free Fatty Acid on Polymerization of Islet Amyloid Polypeptide (IAPP) In Vitro and on Amyloid Fibril Formation in Cultivated Isolated Islets of Transgenic Mice Overexpressing Human IAPP. Mol Med 2002. [DOI: 10.1007/bf03402092] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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32
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Cooper GJS. Amylin and Related Proteins: Physiology and Pathophysiology. Compr Physiol 2001. [DOI: 10.1002/cphy.cp070210] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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33
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Jaikaran ET, Clark A. Islet amyloid and type 2 diabetes: from molecular misfolding to islet pathophysiology. BIOCHIMICA ET BIOPHYSICA ACTA 2001; 1537:179-203. [PMID: 11731221 DOI: 10.1016/s0925-4439(01)00078-3] [Citation(s) in RCA: 223] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Islet amyloid polypeptide (IAPP, amylin) is secreted from pancreatic islet beta-cells and converted to amyloid deposits in type 2 diabetes. Conversion from soluble monomer, IAPP 1-37, to beta-sheet fibrils involves changes in the molecular conformation, cellular biochemistry and diabetes-related factors. In addition to the recognised amyloidogenic region, human IAPP (hIAPP) 20-29, the peptides human or rat IAPP 30-37 and 8-20, assume beta-conformation and form fibrils. These three amyloidogenic regions of hIAPP can be modelled as a folding intermediate with an intramolecular beta-sheet. A hypothesis is proposed for co-secretion of proIAPP with proinsulin in diabetes and formation of a 'nidus' adjacent to islet capillaries for subsequent accumulation of secreted IAPP to form the deposit. Although intracellular fibrils have been identified in experimental systems, extracellular deposition predominates in animal models and man. Extensive fibril accumulations replace islet cells. The molecular species of IAPP that is cytotoxic remains controversial. However, since fibrils form invaginations in cell membranes, small non-toxic IAPP fibrillar or amorphous accumulations could affect beta-cell stimulus-secretion coupling. The level of production of hIAPP is important but not a primary factor in islet amyloidosis; there is little evidence for inappropriate IAPP hypersecretion in type 2 diabetes and amyloid formation is generated in transgenic mice overexpressing the gene for human IAPP only against a background of obesity. Animal models of islet amyloidosis suggest that diabetes is induced by the deposits whereas in man, fibril formation appears to result from diabetes-associated islet dysfunction. Islet secretory failure results from progressive amyloidosis which provides a target for new therapeutic interventions.
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Affiliation(s)
- E T Jaikaran
- Diabetes Research Laboratories, Oxford Centre for Diabetes, Endocrinology and Metabolism, Radcliffe Infirmary, Woodstock Road, Oxford, UK
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34
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Wang F, Hull RL, Vidal J, Cnop M, Kahn SE. Islet amyloid develops diffusely throughout the pancreas before becoming severe and replacing endocrine cells. Diabetes 2001; 50:2514-20. [PMID: 11679429 DOI: 10.2337/diabetes.50.11.2514] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Islet amyloid occurs in >90% of type 2 diabetic patients and may play a role in the pathogenesis of this disease. To determine whether islet amyloid occurs diffusely throughout the pancreas, whether it affects islets equally, and whether it decreases islet endocrine cells, we characterized islet amyloidosis by computerized fluorescence microscopy in transgenic mice that develop typical islet amyloid. These mice produce the unique amyloidogenic component of human islet amyloid, human islet amyloid polypeptide (hIAPP). The prevalence of amyloid (number of islets containing amyloid/total number of islets x 100) and the severity of amyloid (Sigmaamyloid area/Sigmaislet area x 100) were found to be uniform throughout the pancreas. Furthermore, a high prevalence of amyloid was observed in islets when the severity of amyloid was only 1.5% of the islet area, suggesting a diffuse distribution of amyloid from the very early stages of islet amyloidosis. In 12 hIAPP transgenic mice with an amyloid severity of 9.6 +/- 3.4%, the proportion of islets composed of beta- and delta-cells was reduced in the transgenic mice compared with 6 nontransgenic mice that do not develop amyloid (beta-cells: 62.9 +/- 3.1% vs. 75.5 +/- 0.9%, P = 0.02; delta-cells: 2.8 +/- 0.5% vs. 4.4 +/- 0.4%, P = 0.05), whereas the proportion of islets composed of alpha-cells did not significantly differ between the two groups of mice. In the individual islets in these transgenic mice, amyloid severity was inversely correlated with beta-cell, (r = -0.59, P < 0.0001), alpha-cell (r = -0.32, P < 0.0001), and delta-cell (r = -0.25, P < 0.0001) areas. In conclusion, islet amyloidosis occurs uniformly throughout the pancreas, affecting all islets before becoming severe. A reduction in islet endocrine mass starts at this early stage of islet amyloid development and progresses as amyloid mass increases.
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Affiliation(s)
- F Wang
- Division of Metabolism, Endocrinology and Nutrition, Department of Medicine, Veterans Affairs Puget Sound Health Care System and University of Washington, Seattle, Washington 98108, USA
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Xue B, Zemel MB. Agouti signaling protein stimulates islet amyloid polypeptide (amylin) secretion in pancreatic beta-cells. Exp Biol Med (Maywood) 2001; 226:565-9. [PMID: 11395927 DOI: 10.1177/153537020122600609] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Ectopic overexpression of the murine agouti gene results in yellow coat color, obesity, hyperinsulinemia, and type II diabetes. We have shown the human homologue of agouti (agouti signaling protein; ASP) to regulate human adipocyte metabolism and lipid storage via a Ca(2+)-dependent mechanism. We have also demonstrated agouti expression in human pancreas, and that ASP stimulates insulin release via a similar Ca(2+)-dependent mechanism. Plasma amylin is also elevated in agouti mutant mice. Amylin is cosecreted with insulin from beta-cells, and overexpression of human amylin in beta-cells in yellow agouti mutant mice resulted in accelerated pancreatic amyloid deposition, severely impaired beta-cell function, and a diabetic phenotype. We report here that ASP stimulates amylin release in both the HIT-T15 beta-cell line and human pancreatic islets in the presence of a wide range of glucose concentrations (0-16.7 mmol/L), similar to its effect on insulin release; this effect was blocked by 30 mumol/L nitrendipine, confirming a Ca(2+)-dependent mechanism. Accordingly, ASP stimulation of amylin release may serve as a compensatory system to regulate blood glucose in yellow agouti mutants.
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Affiliation(s)
- B Xue
- Department of Nutrition, University of Tennessee, 1215 West Cumberland Avenue, Room 229, Knoxville TN 37996-1900, USA
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36
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Westermark GT, Gebre-Medhin S, Steiner DF, Westermark P. Islet Amyloid Development in a Mouse Strain Lacking Endogenous Islet Amyloid Polypeptide (IAPP) but Expressing Human IAPP. Mol Med 2000. [DOI: 10.1007/bf03402051] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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Abstract
A pathological feature of Type 2 diabetes is deposits in the pancreatic islets primarily composed of amylin (islet amyloid polypeptide). Although much attention has been paid to the expression and secretion of amylin, little is known about the enzymes involved in amylin turnover. Recent reports suggest that insulin-degrading enzyme (IDE) may have specificity for amyloidogenic proteins, and therefore we sought to determine whether amylin is an IDE substrate. Amylin-degrading activity co-purified with IDE from rat muscle through several chromatographic steps. Metalloproteinase inhibitors inactivated amylin-degrading activity with a pattern consistent with the enzymatic properties of IDE, whereas inhibitors of acid and serine proteases, calpains, and the proteasome were ineffective. Amylin degradation was inhibited by insulin in a dose-dependent manner, whereas insulin degradation was inhibited by amylin. Other substrates of IDE such as atrial natriuretic peptide and glucagon also competitively inhibited amylin degradation. Radiolabeled amylin and insulin were both covalently cross-linked to a protein of 110 kDa, and the binding was competitively inhibited by either unlabeled insulin or amylin. Finally, a monoclonal anti-IDE antibody immunoprecipitated both insulin- and amylin-degrading activities. The data strongly suggest that IDE is an amylin-degrading enzyme and plays an important role in the clearance of amylin and the prevention of islet amyloid formation.
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Affiliation(s)
- R G Bennett
- Medical Research Service, Omaha Veterans Affairs Medical Center and Department of Internal Medicine, University of Nebraska Medical Center, Omaha, Nebraska 68105, USA.
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Affiliation(s)
- J W Höppener
- Department of Internal Medicine, University Medical Center, Utrecht, The Netherlands.
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39
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Goldsbury C, Goldie K, Pellaud J, Seelig J, Frey P, Müller SA, Kistler J, Cooper GJ, Aebi U. Amyloid fibril formation from full-length and fragments of amylin. J Struct Biol 2000; 130:352-62. [PMID: 10940238 DOI: 10.1006/jsbi.2000.4268] [Citation(s) in RCA: 271] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Amyloiddeposits of fibrillar human amylin (hA) in the pancreas may be a causative factor in type-2 diabetes. A detailed comparison of in vitro fibril formation by full-length hA(1-37) versus fragments of this peptide-hA(8-37) and hA(20-29)-is presented. Circular dichroism spectroscopy revealed that fibril formation was accompanied by a conformational change: random coil to beta-sheet/alpha-helical structure. Fibril morphologies were visualized by electron microscopy and displayed a remarkable diversity. hA(20-29) formed flat ribbons consisting of numerous 3. 6-nm-wide protofibrils. In contrast, hA(1-37) and hA(8-37) formed polymorphic higher order fibrils by lateral association and/or coiling together of 5.0-nm-wide protofibril subunits. For full-length hA(1-37), the predominant fibril type contained three protofibrils and for hA(8-37), the predominant type contained two protofibrils. Polymerization was also monitored with the thioflavin-T binding assay, which revealed different kinetics of assembly for hA(1-37) and hA(8-37) fibrils. hA(20-29) fibrils did not bind thioflavin-T. Together the results demonstrate that the N-terminal region of the hA peptide influences the relative frequencies of the various higher order fibril types and thereby the overall kinetics of fibril formation. Furthermore, while residues 20-29 contribute to the fibrils' beta-sheet core, the flanking C- and N-terminal regions of the hA peptide determine the interactions involved in the formation of higher order coiled polymorphic superstructures.
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Affiliation(s)
- C Goldsbury
- Department of Biophysical Chemistry, M. E. Müller Institute for Structural Biology, Basel, Switzerland
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40
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Macfarlane WM, Campbell SC, Elrick LJ, Oates V, Bermano G, Lindley KJ, Aynsley-Green A, Dunne MJ, James RF, Docherty K. Glucose regulates islet amyloid polypeptide gene transcription in a PDX1- and calcium-dependent manner. J Biol Chem 2000; 275:15330-5. [PMID: 10748090 DOI: 10.1074/jbc.m908045199] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Islet amyloid polypeptide (IAPP) and insulin are expressed in the beta-cells of the islets of Langerhans. They are co-secreted in response to changes in glucose concentration, and their mRNA levels are also regulated by glucose. The promoters of both genes share similar cis-acting sequence elements, and both bind the homeodomain transcription factor PDX1, which plays an important role in the regulation of the insulin promoter and insulin mRNA levels by glucose. Here we examine the role of PDX1 in the regulation of the human IAPP promoter by glucose. The experiments were facilitated by the availability of a human beta-cell line (NES2Y) that lacks PDX1. NES2Y cells also lack operational K(ATP) channels, resulting in a loss of control of calcium signaling. We have previously used these cells to show that glucose regulation of the insulin gene is dependent on PDX1, but not calcium. In the mouse beta-cell line Min6, glucose (16 mm) stimulated a 3.5-4-fold increase in the activity of a -222 to +450 IAPP promoter construct compared with values observed in 0.5 mm glucose. In NES2Y cells, glucose failed to stimulate transcriptional activation of the IAPP promoter. Overexpression of PDX1 in NES2Y cells failed to reinstate glucose-responsive control of the IAPP promoter. Glucose effects on the IAPP promoter were observed only in the presence of PDX1 when normal calcium signaling was restored by overexpression of the two K(ATP) channel subunits SUR1 and Kir6.2. The importance of calcium was further emphasized by an experiment in which glucose-stimulated IAPP promoter activity was inhibited by the calcium channel blocker verapamil (50 microm). Verapamil was further shown to inhibit the stimulatory effect of glucose on IAPP mRNA levels. These results demonstrate that like the insulin promoter, glucose regulation of the IAPP promoter is dependent on the activity of PDX1, but unlike the insulin promoter, it additionally requires the activity of another, as yet uncharacterized factor(s), the activity of which is calcium-dependent.
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Affiliation(s)
- W M Macfarlane
- Department of Molecular and Cell Biology, University of Aberdeen, Institute of Medical Sciences, Foresterhill, Aberdeen AB25 2ZD, United Kingdom
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41
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Westermark G, Westermark P, Eizirik DL, Hellerström C, Fox N, Steiner DF, Andersson A. Differences in amyloid deposition in islets of transgenic mice expressing human islet amyloid polypeptide versus human islets implanted into nude mice. Metabolism 1999; 48:448-54. [PMID: 10206436 DOI: 10.1016/s0026-0495(99)90102-6] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Islet amyloid polypeptide (IAPP)-derived amyloid is frequently deposited in the islets of Langerhans in patients with chronic non-insulin-dependent diabetes mellitus (NIDDM). When human islets were implanted under the renal capsule in nude mice, amyloid occurred in 73% of the grafts within 2 weeks. In this study, we compare the deposition of amyloid in islets from a transgenic mouse strain expressing human IAPP (hIAPP) and in normal human islets after implantation in nude mice. The implantations were performed as follows: (1) nondiabetic recipients were given islets from transgenic mice alone, (2) human islets were implanted in the upper pole of the kidney and islets from transgenic mice were implanted in the lower pole of the kidney, (3) grafts containing a mixture of human and transgenic islets were implanted, and (4) transgenic islets and islets from nontransgenic littermates were implanted in therapeutic numbers into recipients made diabetic by a single injection of alloxan prior to implantation. The implants were removed after various periods from 4 days to 8 weeks. The implants were either fixed in Formalin, stained for amyloid, and viewed in polarized light, or processed for immunoelectron microscopy and studied after immunolabeling with specific antibodies against IAPP. We found that the course of amyloid deposition differed significantly between human islets and hIAPP-expressing mouse islets. In human islets, amyloid was mainly deposited intracellularly and only small amounts of amyloid were found extracellularly. In contrast, in islets from transgenic mice, amyloid was exclusively deposited extracellularly and deposition in this site was preceded by an aggregation of immunoreactive material along the basement membrane. These findings point to separate mechanisms for amyloid formation in these two models.
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Affiliation(s)
- G Westermark
- Division of Molecular and Immunological Pathology, Linköping University, Sweden
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de Koning EJ, van den Brand JJ, Mott VL, Chargé SB, Hansen BC, Bodkin NL, Morris JF, Clark A. Macrophages and pancreatic islet amyloidosis. Amyloid 1998; 5:247-54. [PMID: 10036582 DOI: 10.3109/13506129809007297] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Islet amyloid formed from islet amyloid polypeptide (IAPP, amylin) is found in spontaneously diabetic monkeys and cats. Islet amyloidosis is progressive, apparently irreversible and is associated with destruction of insulin-secreting cells. The role of macrophages in the destruction and removal of islet amyloid is unknown. Therefore, the presence and morphology of macrophages were determined by electron and quantitative light microscopy in islets of diabetic and nondiabetic man and monkeys and in transgenic mice expressing the gene for human IAPP. Tissue macrophages were present in all pancreatic sections and tissue distribution was similar in exocrine and endocrine areas. There was no difference in macrophage density in amyloidotic and amyloid-free islets in monkeys and man. Macrophage density was similar in islets of transgenic mice expressing human IAPP which do not contain amyloid in vivo but in which fibrils are formed in vitro following islet isolation compared to islets from mice expressing rat IAPP which is not amyloidogenic. IAPP amyloid fibrils were visible by electron microscopy in lysosomes of pancreatic macrophages in man, monkeys and human IAPP transgenic mice. Thus, human IAPP is internalised but inefficiently degraded by tissue macrophages. Diabetes-associated amyloidosis is not associated with visible recruitment of macrophages for removal of amyloid or islet debris.
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Affiliation(s)
- E J de Koning
- Diabetes Research Laboratories, Radcliffe Infirmary, Oxford, UK
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43
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Gebre-Medhin S, Mulder H, Pekny M, Westermark G, Törnell J, Westermark P, Sundler F, Ahrén B, Betsholtz C. Increased insulin secretion and glucose tolerance in mice lacking islet amyloid polypeptide (amylin). Biochem Biophys Res Commun 1998; 250:271-7. [PMID: 9753619 DOI: 10.1006/bbrc.1998.9308] [Citation(s) in RCA: 128] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Islet amyloid polypeptide (IAPP or amylin) is costored and cosecreted with insulin and may regulate insulin secretion and blood glucose handling. However, the role and importance of endogenous IAPP in the regulation of insulin release and glucose homeostasis have been controversial. Here we report on the generation and phenotypic analysis of IAPP-deficient mice. These mice have normal, or near to normal, basal levels of circulating insulin and glucose. However, following glucose administration, IAPP-deficient males presented increased insulin responses paralleled with a more rapid blood glucose elimination compared to wild-type controls. Blood glucose elimination was also found to be enhanced in IAPP-deficient females, but the insulin response in this gender did not differ from controls. In a transgenic rescue experiment, using an insulin-promoter human-IAPP fusion gene, insulin responses and blood glucose elimination were reversed in IAPP-deficient males, whereas the female phenotype appeared unaffected. Our results provide the first firm evidence of a physiological role for endogenous IAPP and indicate that IAPP, apparently in a gender-dependent manner, limits the degree of glucose-induced insulin secretion and the rate of blood glucose elimination.
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Affiliation(s)
- S Gebre-Medhin
- Department of Medical Biochemistry, Göteborg University, Sweden.
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44
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van Rossum D, Hanisch UK, Quirion R. Neuroanatomical localization, pharmacological characterization and functions of CGRP, related peptides and their receptors. Neurosci Biobehav Rev 1997; 21:649-78. [PMID: 9353797 DOI: 10.1016/s0149-7634(96)00023-1] [Citation(s) in RCA: 381] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Calcitonin generelated peptide (CGRP) is a neuropeptide discovered by a molecular approach over 10 years ago. More recently, islet amyloid polypeptide or amylin, and adrenomedullin were isolated from human insulinoma and pheochromocytoma respectively, and revealed between 25 and 50% sequence homology with CGRP. This review discusses findings on the anatomical distributions of CGRP mRNA, CGRP-like immunoreactivity and receptors in the central nervous system, as well as the potential physiological roles for CGRP. The anatomical distribution and biological activities of amylin and adrenomedullin are also presented. Based upon the differential biological activity of various CGRP analogs, the CGRP receptors have been classified in two major classes, namely the CGRP1 and CGRP2 subtypes. A third subtype has also been proposed (e.g. in the nucleus accumbens) as it does not share the pharmacological properties of the other two classes. The anatomical distribution and the pharmacological characteristics of amylin binding sites in the rat brain are different from those reported for CGRP but share several similarities with the salmon calcitonin receptors. The receptors identified thus far for CGRP and related peptides belong to the G protein-coupled receptor superfamily. Indeed, modulation of adenylate cyclase activity following receptor activation has been reported for CGRP, amylin and adrenomedullin. Furthermore, the binding affinity of CGRP and related peptides is modulated by nucleotides such as GTP. The cloning of various calcitonin and most recently of CGRP1 and adrenomedullin receptors was reported and revealed structural similarities but also significant differences to other members of the G protein-coupled receptors. They may thus form a new subfamily. The cloning of the amylin receptor(s) as well as of the other putative CGRP receptor subtype(s) are still awaited. Finally, a broad variety of biological activities has been described for CGRP-like peptides. These include vasodilation, nociception, glucose uptake and the stimulation of glycolysis in skeletal muscles. These effects may thus suggest their potential role and therapeutic applications in migraine, subarachnoid haemorrhage, diabetes and pain-related mechanisms, among other disorders.
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Affiliation(s)
- D van Rossum
- Department of Pharmacology, McGill University, Douglas Hospital Research Centre, Verdun, Québec, Canada
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45
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Janson J, Soeller WC, Roche PC, Nelson RT, Torchia AJ, Kreutter DK, Butler PC. Spontaneous diabetes mellitus in transgenic mice expressing human islet amyloid polypeptide. Proc Natl Acad Sci U S A 1996; 93:7283-8. [PMID: 8692984 PMCID: PMC38975 DOI: 10.1073/pnas.93.14.7283] [Citation(s) in RCA: 252] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
The islet in non-insulin-dependent diabetes mellitus (NIDDM) is characterized by loss of beta cells and large local deposits of amyloid derived from the 37-amino acid protein, islet amyloid polypeptide (IAPP). We have hypothesized that IAPP amyloid forms intracellularly causing beta-cell destruction under conditions of high rates of expression. To test this we developed a homozygous transgenic mouse model with high rates of expression of human IAPP. Male transgenic mice spontaneously developed diabetes mellitus by 8 weeks of age, which was associated with selective beta-cell death and impaired insulin secretion. Small intra- and extracellular amorphous IAPP aggregates were present in islets of transgenic mice during the development of diabetes mellitus. However, IAPP derived amyloid deposits were found in only a minority of islets at approximately 20 weeks of age, notably after development of diabetes mellitus in male transgenic mice. Approximately 20% of female transgenic mice spontaneously developed diabetes mellitus at 30+ weeks of age, when beta-cell degeneration and both amorphous and amyloid deposits of IAPP were present. We conclude that overexpression of human IAPP causes beta-cell death, impaired insulin secretion, and diabetes mellitus. Large deposits of IAPP derived amyloid do not appear to be important in this cytotoxicity, but early, small amorphous intra- and extracellular aggregates of human IAPP were consistently present at the time of beta-cell death and therefore may be the most cytotoxic form of IAPP.
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Affiliation(s)
- J Janson
- Endocrine Research Unit, Mayo Clinic, Rochester, MN 55905, USA
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Verchere CB, D'Alessio DA, Palmiter RD, Weir GC, Bonner-Weir S, Baskin DG, Kahn SE. Islet amyloid formation associated with hyperglycemia in transgenic mice with pancreatic beta cell expression of human islet amyloid polypeptide. Proc Natl Acad Sci U S A 1996; 93:3492-6. [PMID: 8622964 PMCID: PMC39637 DOI: 10.1073/pnas.93.8.3492] [Citation(s) in RCA: 201] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Pancreatic islet amyloid deposits are a characteristic pathologic feature of non-insulin-dependent diabetes mellitus and contain islet amyloid polypeptide (IAPP; amylin). We used transgenic mice that express human IAPP in pancreatic beta cells to explore the potential role of islet amyloid in the pathogenesis of non-insulin-dependent diabetes mellitus. Extensive amyloid deposits were observed in the pancreatic islets of approximately 80% of male transgenic mice > 13 months of age. Islet amyloid deposits were rarely observed in female transgenic mice (11%) and were never seen in nontransgenic animals. Ultrastructural analysis revealed that these deposits were composed of human IAPP-immunoreactive fibrils that accumulated between beta cells and islet capillaries. Strikingly, approximately half of the mice with islet amyloid deposits were hyperglycemic (plasma glucose > 11 mM). In younger (6- to 9-month-old) male transgenic mice, islet amyloid deposits were less commonly observed but were always associated with severe hyperglycemia (plasma glucose > 22 mM). These data indicate that expression of human IAPP in beta cells predisposes male mice to the development of islet amyloid and hyperglycemia. The frequent concordance of islet amyloid with hyperglycemia in these mice suggests an interdependence of these two conditions and supports the hypothesis that islet amyloid may play a role in the development of hyperglycemia.
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Affiliation(s)
- C B Verchere
- Division of Metabolism, Endocrinology and Nutrition, Department of Medicine, Howard Hughes Medical Institute, University of Washington, Seattle 98195, USA
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47
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Oosterwijk C, Höppener JW, van Hulst KL, Lips CJ. Pancreatic islet amyloid formation in patients with noninsulin-dependent diabetes mellitus. Implication for therapeutic strategy. INTERNATIONAL JOURNAL OF PANCREATOLOGY : OFFICIAL JOURNAL OF THE INTERNATIONAL ASSOCIATION OF PANCREATOLOGY 1995; 18:7-14. [PMID: 7594773 DOI: 10.1007/bf02825416] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Islet amyloid polypeptide (IAPP or amylin) is the main component of pancreatic islet amyloid found in the vast majority of patients with noninsulin-dependent (Type-2) diabetes mellitus (NIDDM). IAPP may also act as a hormone that antagonizes the effects of insulin on peripheral tissues, but the results with IAPP overproducing transgenic mice and other recent findings indicate that IAPP overproduction is unlikely to induce peripheral insulin resistance in NIDDM. However, IAPP may contribute to the progression of NIDDM by impairing beta-cell function via islet amyloid formation. This may be initiated by locally elevated IAPP concentrations, induced by insulin-resistance-associated beta-cell hyperactivity. In order to improve therapeutic results, we propose strategies to inhibit IAPP production and islet amyloid formation during the pathogenesis of NIDDM.
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Affiliation(s)
- C Oosterwijk
- Department of Internal Medicine, Utrecht University Hospital, The Netherlands
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48
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Westermark G, Arora MB, Fox N, Carroll R, Chan SJ, Westermark P, Steiner DF. Amyloid Formation in Response to β Cell Stress Occurs In Vitro, but Not In Vivo, in Islets of Transgenic Mice Expressing Human Islet Amyloid Polypeptide. Mol Med 1995. [DOI: 10.1007/bf03401591] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022] Open
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Abstract
Cats are one of the few species that develop a form of diabetes mellitus that is clinically and histologically analogous to human type 2 diabetes mellitus. Figure 9 summarizes the etiologic factors thought to be involved in the development of feline and human type 2 diabetes. The main metabolic characteristics of type 2 diabetes mellitus are impaired insulin secretion and resistance to the action of insulin in its target tissues. Impaired beta cell function occurs before histologic changes become evident. The characteristic histologic finding in cats with type 2 diabetes is deposition of amyloid in pancreatic islets. Amyloid deposition occurs before the onset of clinical signs, but does not seem to be the primary defect. Pancreatic amyloid is derived form the recently discovered pancreatic hormone amylin. Amylin is synthesized in pancreatic beta cells, and is co-stored and co-secreted with insulin. Amylin has been postulated to be involved in the pathogenesis of feline diabetes mellitus both through its metabolic effects, which include inhibition of insulin secretion and induction of insulin resistance, and via progressive amyloid deposition and beta cell degeneration. Increased amylin concentration has been documented intracellularly in cats with impaired glucose tolerance and in the plasma of diabetic cats, and supports the hypothesis that amylin is involved in the pathogenesis of type 2 diabetes. Obesity is a common finding in diabetic felines and is a contributing factor to the insulin resistance present in type 2 diabetes. Clinical signs of diabetes develop once total insulin secretion decreases to 20% to 25% of normal levels. Many diabetic cats have been treated successfully with oral hypoglycemics, but 50% to 70% of diabetic cats are insulin dependent. Based on histologic evidence, this is the result of extensive amyloid deposition and subsequent beta cell degeneration, rather than autoimmune destruction of pancreatic beta cells associated with type 1 diabetes. Alternative ways of treating type 2 diabetes currently are being investigated. Amylin antagonists recently have been proposed as a novel treatment to reverse the deleterious effects of excessive amylin concentrations. The gastrointestinal hormone glucagon-like peptide-1 may also prove useful in treating diabetic cats, because of its stimulatory effect on insulin secretion and synthesis, and the absence of significant hypoglycemic effect.
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Affiliation(s)
- T A Lutz
- Institute of Veterinary Physiology, University of Zůrich, Switzerland
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50
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Westermark P, Eizirik DL, Pipeleers DG, Hellerström C, Andersson A. Rapid deposition of amyloid in human islets transplanted into nude mice. Diabetologia 1995; 38:543-9. [PMID: 7489836 DOI: 10.1007/bf00400722] [Citation(s) in RCA: 74] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Human islets of Langerhans were transplanted to the subcapsular space of the kidneys of nude mice which were either normoglycaemic or made diabetic with alloxan. After 2 weeks, the transplants were processed for light and electron microscopical analyses. In all transplants, islet amyloid polypeptide (IAPP)-positive cells were found with highest frequency in normoglycaemic animals. IAPP-positive amyloid was seen in 16 out of 22 transplants (73%), either by polarisation microscopy after Congo red staining or by immune electron microscopy. At variance with previous findings of amyloid deposits exclusively in the extracellular space of islets of non-insulin-dependent diabetic patients, the grafted islets contained intracellular amyloid deposits as well. There was no clear difference in occurrence of amyloid between diabetic and non-diabetic animals. The present study indicates that human islets transplanted into nude mice very soon present IAPP-positive amyloid deposits. This technique may provide a valuable model for studies of the pathogenesis of islet amyloid and its impact on islet cell function.
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Affiliation(s)
- P Westermark
- Department of Pathology, Linköping University, Sweden
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