Structure-functional changes in eNAMPT at high concentrations mediate mouse and human beta cell dysfunction in type 2 diabetes

Sophie R Sayers; Rebecca L Beavil; Nicholas H F Fine; Guo C Huang; Pratik Choudhary; Kamila J Pacholarz; Perdita E Barran; Sam Butterworth; Charlotte E Mills; J Kennedy Cruickshank; Marta P Silvestre; Sally D Poppitt; Anne-Thea McGill; Gareth G Lavery; David J Hodson; Paul W Caton

doi:10.1007/s00125-019-05029-y

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Structure-functional changes in eNAMPT at high concentrations mediate mouse and human beta cell dysfunction in type 2 diabetes

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Structure-functional changes in eNAMPT at high concentrations mediate mouse and human beta cell dysfunction in type 2 diabetes

Sophie R Sayers, Rebecca L Beavil, Nicholas H F Fine, Guo C Huang, Pratik Choudhary, Kamila J Pacholarz, Perdita E Barran, Sam Butterworth, Charlotte E Mills, J Kennedy Cruickshank, …

Diabetologia, Vol.63(2), pp.313-323

02/2020

DOI: https://doi.org/10.1007/s00125-019-05029-y

PMCID: PMC6946736

PMID: 31732790

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Abstract

Cytokines - metabolism

Humans

Cells, Cultured

Immunoblotting

Male

Structure-Activity Relationship

Diabetes Mellitus, Type 2 - metabolism

Reverse Transcriptase Polymerase Chain Reaction

Glucagon - blood

Diabetes Mellitus, Type 2 - blood

Insulin Secretion - physiology

Insulin-Secreting Cells - metabolism

Animals

Diabetes Mellitus, Type 2 - physiopathology

Somatostatin - blood

Nicotinamide Phosphoribosyltransferase - metabolism

Mass Spectrometry

Glucagon - metabolism

Mice

Somatostatin - metabolism

Nicotinamide Phosphoribosyltransferase - blood

Cytokines - blood

Progressive decline in functional beta cell mass is central to the development of type 2 diabetes. Elevated serum levels of extracellular nicotinamide phosphoribosyltransferase (eNAMPT) are associated with beta cell failure in type 2 diabetes and eNAMPT immuno-neutralisation improves glucose tolerance in mouse models of diabetes. Despite this, the effects of eNAMPT on functional beta cell mass are poorly elucidated, with some studies having separately reported beta cell-protective effects of eNAMPT. eNAMPT exists in structurally and functionally distinct monomeric and dimeric forms. Dimerisation is essential for the NAD-biosynthetic capacity of NAMPT. Monomeric eNAMPT does not possess NAD-biosynthetic capacity and may exert distinct NAD-independent effects. This study aimed to fully characterise the structure-functional effects of eNAMPT on pancreatic beta cell functional mass and to relate these to beta cell failure in type 2 diabetes. CD-1 mice and serum from obese humans who were without diabetes, with impaired fasting glucose (IFG) or with type 2 diabetes (from the Body Fat, Surgery and Hormone [BodyFatS&H] study) or with or at risk of developing type 2 diabetes (from the VaSera trial) were used in this study. We generated recombinant wild-type and monomeric eNAMPT to explore the effects of eNAMPT on functional beta cell mass in isolated mouse and human islets. Beta cell function was determined by static and dynamic insulin secretion and intracellular calcium microfluorimetry. NAD-biosynthetic capacity of eNAMPT was assessed by colorimetric and fluorescent assays and by native mass spectrometry. Islet cell number was determined by immunohistochemical staining for insulin, glucagon and somatostatin, with islet apoptosis determined by caspase 3/7 activity. Markers of inflammation and beta cell identity were determined by quantitative reverse transcription PCR. Total, monomeric and dimeric eNAMPT and nicotinamide mononucleotide (NMN) were evaluated by ELISA, western blot and fluorometric assay using serum from non-diabetic, glucose intolerant and type 2 diabetic individuals. eNAMPT exerts bimodal and concentration- and structure-functional-dependent effects on beta cell functional mass. At low physiological concentrations (~1 ng/ml), as seen in serum from humans without diabetes, eNAMPT enhances beta cell function through NAD-dependent mechanisms, consistent with eNAMPT being present as a dimer. However, as eNAMPT concentrations rise to ~5 ng/ml, as in type 2 diabetes, eNAMPT begins to adopt a monomeric form and mediates beta cell dysfunction, reduced beta cell identity and number, increased alpha cell number and increased apoptosis, through NAD-independent proinflammatory mechanisms. We have characterised a novel mechanism of beta cell dysfunction in type 2 diabetes. At low physiological levels, eNAMPT exists in dimer form and maintains beta cell function and identity through NAD-dependent mechanisms. However, as eNAMPT levels rise, as in type 2 diabetes, structure-functional changes occur resulting in marked elevation of monomeric eNAMPT, which induces a diabetic phenotype in pancreatic islets. Strategies to selectively target monomeric eNAMPT could represent promising therapeutic strategies for the treatment of type 2 diabetes.

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Title: Structure-functional changes in eNAMPT at high concentrations mediate mouse and human beta cell dysfunction in type 2 diabetes
Creators: Sophie R Sayers (Author) - Diabetes Research Group, Department of Diabetes, School of Life Course Sciences, King's College London, Hodgkin Building, Guy's Campus, London, SE1 1UL, UK
Rebecca L Beavil (Author) - Protein Production Facility, Randall Centre for Cell and Molecular Biophysics, King's College London, London, UK
Nicholas H F Fine (Author) - Centre for Endocrinology, Diabetes and Metabolism, Birmingham Health Partners, Birmingham, UK
Guo C Huang (Author) - Diabetes Research Group, Department of Diabetes, School of Life Course Sciences, King's College London, Hodgkin Building, Guy's Campus, London, SE1 1UL, UK
Pratik Choudhary (Author) - Diabetes Research Group, Department of Diabetes, School of Life Course Sciences, King's College London, Hodgkin Building, Guy's Campus, London, SE1 1UL, UK
Kamila J Pacholarz (Author) - Michael Barber Centre for Collaborative Mass Spectrometry, School of Chemistry, Manchester Institute of Biotechnology, Manchester, UK
Perdita E Barran (Author) - Michael Barber Centre for Collaborative Mass Spectrometry, School of Chemistry, Manchester Institute of Biotechnology, Manchester, UK
Sam Butterworth (Author) - Division of Pharmacy and Optometry, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK
Charlotte E Mills (Author) - Nutrition Research Group, University of Reading, Reading, UK
J Kennedy Cruickshank - Department of Nutritional Sciences, School of Life Course Sciences, King's College London, London, UK
Marta P Silvestre (Author) - Human Nutrition Unit, School of Biological Sciences, University of Auckland, Auckland, New Zealand
Sally D Poppitt (Author) - Human Nutrition Unit, School of Biological Sciences, University of Auckland, Auckland, New Zealand
Anne-Thea McGill (Author) - School of Health & Human Sciences, Southern Cross University, Lismore, NSW, Australia
Gareth G Lavery (Author) - Centre for Endocrinology, Diabetes and Metabolism, Birmingham Health Partners, Birmingham, UK
David J Hodson (Author) - Centre for Endocrinology, Diabetes and Metabolism, Birmingham Health Partners, Birmingham, UK
Paul W Caton (Author) - Department of Nutritional Sciences, School of Life Course Sciences, King's College London, London, UK. paul.w.caton@kcl.ac.uk
Publication Details: Diabetologia, Vol.63(2), pp.313-323
Publisher: Germany
Grant note: Wellcome Trust MC_PC_17164 / Medical Research Council MR/S025618/1 / Medical Research Council MR/N00275X/1 / Medical Research Council
Identifiers: 991012925053002368
Academic Unit: National Centre for Naturopathic Medicine
Language: English
Resource Type: Journal article

Structure-functional changes in eNAMPT at high concentrations mediate mouse and human beta cell dysfunction in type 2 diabetes

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