101
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Rorsman P, Ashcroft FM. Pancreatic β-Cell Electrical Activity and Insulin Secretion: Of Mice and Men. Physiol Rev 2018; 98:117-214. [PMID: 29212789 PMCID: PMC5866358 DOI: 10.1152/physrev.00008.2017] [Citation(s) in RCA: 445] [Impact Index Per Article: 74.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2017] [Revised: 05/30/2017] [Accepted: 06/18/2017] [Indexed: 12/14/2022] Open
Abstract
The pancreatic β-cell plays a key role in glucose homeostasis by secreting insulin, the only hormone capable of lowering the blood glucose concentration. Impaired insulin secretion results in the chronic hyperglycemia that characterizes type 2 diabetes (T2DM), which currently afflicts >450 million people worldwide. The healthy β-cell acts as a glucose sensor matching its output to the circulating glucose concentration. It does so via metabolically induced changes in electrical activity, which culminate in an increase in the cytoplasmic Ca2+ concentration and initiation of Ca2+-dependent exocytosis of insulin-containing secretory granules. Here, we review recent advances in our understanding of the β-cell transcriptome, electrical activity, and insulin exocytosis. We highlight salient differences between mouse and human β-cells, provide models of how the different ion channels contribute to their electrical activity and insulin secretion, and conclude by discussing how these processes become perturbed in T2DM.
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Affiliation(s)
- Patrik Rorsman
- Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Churchill Hospital, Oxford, United Kingdom; Department of Neuroscience and Physiology, Metabolic Research Unit, Göteborg, Sweden; and Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
| | - Frances M Ashcroft
- Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Churchill Hospital, Oxford, United Kingdom; Department of Neuroscience and Physiology, Metabolic Research Unit, Göteborg, Sweden; and Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
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102
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Gosak M, Stožer A, Markovič R, Dolenšek J, Perc M, Rupnik MS, Marhl M. Critical and Supercritical Spatiotemporal Calcium Dynamics in Beta Cells. Front Physiol 2017; 8:1106. [PMID: 29312008 PMCID: PMC5743929 DOI: 10.3389/fphys.2017.01106] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2017] [Accepted: 12/14/2017] [Indexed: 01/12/2023] Open
Abstract
A coordinated functioning of beta cells within pancreatic islets is mediated by oscillatory membrane depolarization and subsequent changes in cytoplasmic calcium concentration. While gap junctions allow for intraislet information exchange, beta cells within islets form complex syncytia that are intrinsically nonlinear and highly heterogeneous. To study spatiotemporal calcium dynamics within these syncytia, we make use of computational modeling and confocal high-speed functional multicellular imaging. We show that model predictions are in good agreement with experimental data, especially if a high degree of heterogeneity in the intercellular coupling term is assumed. In particular, during the first few minutes after stimulation, the probability distribution of calcium wave sizes is characterized by a power law, thus indicating critical behavior. After this period, the dynamics changes qualitatively such that the number of global intercellular calcium events increases to the point where the behavior becomes supercritical. To better mimic normal in vivo conditions, we compare the described behavior during supraphysiological non-oscillatory stimulation with the behavior during exposure to a slightly lower and oscillatory glucose challenge. In the case of this protocol, we observe only critical behavior in both experiment and model. Our results indicate that the loss of oscillatory changes, along with the rise in plasma glucose observed in diabetes, could be associated with a switch to supercritical calcium dynamics and loss of beta cell functionality.
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Affiliation(s)
- Marko Gosak
- Faculty of Medicine, Institute of Physiology, University of Maribor, Maribor, Slovenia
- Faculty of Natural Sciences and Mathematics, University of Maribor, Maribor, Slovenia
| | - Andraž Stožer
- Faculty of Medicine, Institute of Physiology, University of Maribor, Maribor, Slovenia
| | - Rene Markovič
- Faculty of Natural Sciences and Mathematics, University of Maribor, Maribor, Slovenia
- Faculty of Education, University of Maribor, Maribor, Slovenia
- Faculty of Energy Technology, University of Maribor, Krško, Slovenia
| | - Jurij Dolenšek
- Faculty of Medicine, Institute of Physiology, University of Maribor, Maribor, Slovenia
| | - Matjaž Perc
- Faculty of Natural Sciences and Mathematics, University of Maribor, Maribor, Slovenia
- Center for Applied Mathematics and Theoretical Physics, University of Maribor, Maribor, Slovenia
- Complexity Science Hub, Vienna, Austria
| | - Marjan S. Rupnik
- Faculty of Medicine, Institute of Physiology, University of Maribor, Maribor, Slovenia
- Institute of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Marko Marhl
- Faculty of Natural Sciences and Mathematics, University of Maribor, Maribor, Slovenia
- Faculty of Education, University of Maribor, Maribor, Slovenia
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103
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GLP-1 response to sequential mixed meals: influence of insulin resistance. Clin Sci (Lond) 2017; 131:2901-2910. [PMID: 29097626 DOI: 10.1042/cs20171409] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2017] [Revised: 10/26/2017] [Accepted: 11/01/2017] [Indexed: 12/25/2022]
Abstract
Previous work has shown that potentiation of insulin release is impaired in non-diabetic insulin resistance; we tested the hypothesis that this defect may be related to altered glucagon-like peptide-1 (GLP-1) release. On consecutive days, 82 non-diabetic individuals, classified as insulin sensitive (IS, n=41) or insulin resistant (IR, n=41) by the euglycaemic clamp, were given two sequential mixed meals with standard (75 g, LCD) or double (150 g, HCD) carbohydrate content. Plasma glucose, insulin, C-peptide, non-esterified fatty acids (NEFA) and GLP-1 concentrations were measured; β-cell function (glucose sensitivity and potentiation) was resolved by mathematical modelling. Fasting GLP-1 levels were higher in IR than IS (by 15%, P=0.006), and reciprocally related to insulin sensitivity after adjustment for sex, age, fat mass, fasting glucose or insulin concentrations. Mean postprandial GLP-1 responses were tightly correlated with fasting GLP-1, were higher for the second than the first meal, and higher in IR than IS subjects but only with LCD. In contrast, incremental GLP-1 responses were higher during (i) the second than the first meal, (ii) on HCD than LCD, and (iii) significantly smaller in IR than IS independently of meal and load. Potentiation of insulin release was markedly reduced in IR vs IS across meal and carbohydrate loading. In the whole dataset, incremental GLP-1 was directly related to potentiation, and both were inversely related to mean NEFA concentrations. We conclude that (a) raised GLP-1 tone may be inherently linked with a reduced GLP-1 response and (b) defective post-meal GLP-1 response may be one mechanism for impaired potentiation of insulin release in insulin resistance.
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104
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Westacott MJ, Ludin NWF, Benninger RKP. Spatially Organized β-Cell Subpopulations Control Electrical Dynamics across Islets of Langerhans. Biophys J 2017; 113:1093-1108. [PMID: 28877492 DOI: 10.1016/j.bpj.2017.07.021] [Citation(s) in RCA: 67] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2017] [Revised: 07/21/2017] [Accepted: 07/31/2017] [Indexed: 10/18/2022] Open
Abstract
Understanding how heterogeneous cells within a multicellular system interact and affect overall function is difficult without a means of perturbing individual cells or subpopulations. Here we apply optogenetics to understand how subpopulations of β-cells control the overall [Ca2+]i response and insulin secretion dynamics of the islets of Langerhans. We spatiotemporally perturbed electrical activity in β-cells of channelrhodopsin2-expressing islets, mapped the [Ca2+]i response, and correlated this with the cellular metabolic activity and an in silico electrophysiology model. We discovered organized regions of metabolic activity across the islet, and these affect the way in which β-cells electrically interact. Specific regions acted as pacemakers by initiating calcium wave propagation. Our findings reveal the functional architecture of the islet, and show how distinct subpopulations of cells can disproportionality affect function. These results also suggest ways in which other neuroendocrine systems can be regulated, and demonstrate how optogenetic tools can discern their functional architecture.
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Affiliation(s)
| | - Nurin W F Ludin
- Department of Bioengineering, University of Colorado, Aurora, Colorado
| | - Richard K P Benninger
- Department of Bioengineering, University of Colorado, Aurora, Colorado; Barbara Davis Center for Diabetes, University of Colorado, Aurora, Colorado.
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105
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Skelin Klemen M, Dolenšek J, Slak Rupnik M, Stožer A. The triggering pathway to insulin secretion: Functional similarities and differences between the human and the mouse β cells and their translational relevance. Islets 2017; 9:109-139. [PMID: 28662366 PMCID: PMC5710702 DOI: 10.1080/19382014.2017.1342022] [Citation(s) in RCA: 71] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
In β cells, stimulation by metabolic, hormonal, neuronal, and pharmacological factors is coupled to secretion of insulin through different intracellular signaling pathways. Our knowledge about the molecular machinery supporting these pathways and the patterns of signals it generates comes mostly from rodent models, especially the laboratory mouse. The increased availability of human islets for research during the last few decades has yielded new insights into the specifics in signaling pathways leading to insulin secretion in humans. In this review, we follow the most central triggering pathway to insulin secretion from its very beginning when glucose enters the β cell to the calcium oscillations it produces to trigger fusion of insulin containing granules with the plasma membrane. Along the way, we describe the crucial building blocks that contribute to the flow of information and focus on their functional role in mice and humans and on their translational implications.
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Affiliation(s)
- Maša Skelin Klemen
- Institute of Physiology, Faculty of Medicine, University of Maribor, Maribor, Slovenia
| | - Jurij Dolenšek
- Institute of Physiology, Faculty of Medicine, University of Maribor, Maribor, Slovenia
| | - Marjan Slak Rupnik
- Institute of Physiology, Faculty of Medicine, University of Maribor, Maribor, Slovenia
- Institute of Physiology; Center for Physiology and Pharmacology; Medical University of Vienna; Vienna, Austria
| | - Andraž Stožer
- Institute of Physiology, Faculty of Medicine, University of Maribor, Maribor, Slovenia
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106
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Avrahami D, Wang YJ, Klochendler A, Dor Y, Glaser B, Kaestner KH. β-Cells are not uniform after all-Novel insights into molecular heterogeneity of insulin-secreting cells. Diabetes Obes Metab 2017; 19 Suppl 1:147-152. [PMID: 28880481 PMCID: PMC5659199 DOI: 10.1111/dom.13019] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/06/2017] [Revised: 05/19/2017] [Accepted: 05/22/2017] [Indexed: 01/02/2023]
Abstract
While the β-cells of the endocrine pancreas are defined as cells with high levels of insulin production and tight stimulus-secretion coupling, the existence of functional heterogeneity among them has been known for decades. Recent advances in molecular technologies, in particular single-cell profiling on both the protein and messenger RNA level, have uncovered that β-cells exist in several antigenically and molecularly definable states. Using antibodies to cell surface markers or multidimensional clustering of β-cells using more than 20 protein markers by mass cytometry, 4 distinct groups of β-cells could be differentiated. However, whether these states represent permanent cell lineages or are readily interconvertible from one group to another remains to be determined. Nevertheless, future analysis of the pathogenesis of type 1 and type 2 diabetes will certainly benefit from a growing appreciation of β-cell heterogeneity. Here, we aim to summarize concisely the recent advances in the field and their possible impact on our understanding of β-cell physiology and pathophysiology.
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Affiliation(s)
- Dana Avrahami
- Endocrinology and Metabolism Service, Department of Internal Medicine, Hadassah-Hebrew University Medical Center, Jerusalem, Israel
| | - Yue J. Wang
- Department of Genetics and Institute for Diabetes, Obesity, and Metabolism, Perelman School of Medicine, University of Pennsylvania, Philadelphia, USA
| | - Agnes Klochendler
- Department of Developmental Biology and Cancer Research, The Institute for Medical Research Israel-Canada, The Hebrew University-Hadassah Medical School, Jerusalem, Israel
| | - Yuval Dor
- Department of Developmental Biology and Cancer Research, The Institute for Medical Research Israel-Canada, The Hebrew University-Hadassah Medical School, Jerusalem, Israel
| | - Benjamin Glaser
- Endocrinology and Metabolism Service, Department of Internal Medicine, Hadassah-Hebrew University Medical Center, Jerusalem, Israel
| | - Klaus H. Kaestner
- Department of Genetics and Institute for Diabetes, Obesity, and Metabolism, Perelman School of Medicine, University of Pennsylvania, Philadelphia, USA
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107
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Rutter GA, Hodson DJ, Chabosseau P, Haythorne E, Pullen TJ, Leclerc I. Local and regional control of calcium dynamics in the pancreatic islet. Diabetes Obes Metab 2017; 19 Suppl 1:30-41. [PMID: 28466490 DOI: 10.1111/dom.12990] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/21/2017] [Revised: 04/19/2017] [Accepted: 04/24/2017] [Indexed: 12/31/2022]
Abstract
Ca2+ is the key intracellular regulator of insulin secretion, acting in the β-cell as the ultimate trigger for exocytosis. In response to high glucose, ATP-sensitive K+ channel closure and plasma membrane depolarization engage a sophisticated machinery to drive pulsatile cytosolic Ca2+ changes. Voltage-gated Ca2+ channels, Ca2+ -activated K+ channels and Na+ /Ca2+ exchange all play important roles. The use of targeted Ca2+ probes has revealed that during each cytosolic Ca2+ pulse, uptake of Ca2+ by mitochondria, endoplasmic reticulum (ER), secretory granules and lysosomes fine-tune cytosolic Ca2+ dynamics and control organellar function. For example, changes in the expression of the Ca2+ -binding protein Sorcin appear to provide a link between ER Ca2+ levels and ER stress, affecting β-cell function and survival. Across the islet, intercellular communication between highly interconnected "hubs," which act as pacemaker β-cells, and subservient "followers," ensures efficient insulin secretion. Loss of connectivity is seen after the deletion of genes associated with type 2 diabetes (T2D) and follows metabolic and inflammatory insults that characterize this disease. Hubs, which typically comprise ~1%-10% of total β-cells, are repurposed for their specialized role by expression of high glucokinase (Gck) but lower Pdx1 and Nkx6.1 levels. Single cell-omics are poised to provide a deeper understanding of the nature of these cells and of the networks through which they communicate. New insights into the control of both the intra- and intercellular Ca2+ dynamics may thus shed light on T2D pathology and provide novel opportunities for therapy.
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Affiliation(s)
- Guy A Rutter
- Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, and the Imperial Pancreatic Islet Biology and Diabetes Consortium, Hammersmith Hospital, Imperial College London, London, UK
| | - David J Hodson
- Institute of Metabolism and Systems Research (IMSR), University of Birmingham, Edgbaston, UK
- Centre for Endocrinology, Diabetes and Metabolism, Birmingham Health Partners, COMPARE University of Birmingham and University of Nottingham Midlands, Birmingham, UK
| | - Pauline Chabosseau
- Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, and the Imperial Pancreatic Islet Biology and Diabetes Consortium, Hammersmith Hospital, Imperial College London, London, UK
| | - Elizabeth Haythorne
- Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, and the Imperial Pancreatic Islet Biology and Diabetes Consortium, Hammersmith Hospital, Imperial College London, London, UK
| | - Timothy J Pullen
- Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, and the Imperial Pancreatic Islet Biology and Diabetes Consortium, Hammersmith Hospital, Imperial College London, London, UK
| | - Isabelle Leclerc
- Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, and the Imperial Pancreatic Islet Biology and Diabetes Consortium, Hammersmith Hospital, Imperial College London, London, UK
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108
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Westacott MJ, Farnsworth NL, St Clair JR, Poffenberger G, Heintz A, Ludin NW, Hart NJ, Powers AC, Benninger RKP. Age-Dependent Decline in the Coordinated [Ca 2+] and Insulin Secretory Dynamics in Human Pancreatic Islets. Diabetes 2017; 66:2436-2445. [PMID: 28588099 PMCID: PMC5566297 DOI: 10.2337/db17-0137] [Citation(s) in RCA: 53] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/01/2017] [Accepted: 05/30/2017] [Indexed: 12/25/2022]
Abstract
Aging is associated with increased risk for type 2 diabetes, resulting from reduced insulin sensitivity and secretion. Reduced insulin secretion can result from reduced proliferative capacity and reduced islet function. Mechanisms underlying altered β-cell function in aging are poorly understood in mouse and human islets, and the impact of aging on intraislet communication has not been characterized. Here, we examine how β-cell [Ca2+] and electrical communication are impacted during aging in mouse and human islets. Islets from human donors and from mice were studied using [Ca2+] imaging, static and perifusion insulin secretion assays, and gap junction permeability measurements. In human islets, [Ca2+] dynamics were coordinated within distinct subregions of the islet, invariant with islet size. There was a marked decline in the coordination of [Ca2+] dynamics, gap junction coupling, and insulin secretion dynamics with age. These age-dependent declines were reversed by pharmacological gap junction activation. These results show that human islet function declines with aging, which can reduce insulin action and may contribute to increased risk of type 2 diabetes.
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Affiliation(s)
- Matthew J Westacott
- Department of Bioengineering, University of Colorado, Anschutz Medical Campus, Aurora, CO
| | - Nikki L Farnsworth
- Barbara Davis Center for Diabetes, University of Colorado, Anschutz Medical Campus, Aurora, CO
| | - Joshua R St Clair
- Department of Bioengineering, University of Colorado, Anschutz Medical Campus, Aurora, CO
| | - Greg Poffenberger
- Division of Diabetes, Endocrinology, and Metabolism, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN
- Department of Molecular Physiology and Biophysics, Vanderbilt University Medical Center, Nashville, TN
- VA Tennessee Valley Healthcare System, Nashville, TN
| | - Audrey Heintz
- Department of Bioengineering, University of Colorado, Anschutz Medical Campus, Aurora, CO
| | - Nurin W Ludin
- Department of Bioengineering, University of Colorado, Anschutz Medical Campus, Aurora, CO
| | - Nathaniel J Hart
- Division of Diabetes, Endocrinology, and Metabolism, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN
| | - Alvin C Powers
- Division of Diabetes, Endocrinology, and Metabolism, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN
- Department of Molecular Physiology and Biophysics, Vanderbilt University Medical Center, Nashville, TN
- VA Tennessee Valley Healthcare System, Nashville, TN
| | - Richard K P Benninger
- Department of Bioengineering, University of Colorado, Anschutz Medical Campus, Aurora, CO
- Barbara Davis Center for Diabetes, University of Colorado, Anschutz Medical Campus, Aurora, CO
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109
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Botfield HF, Uldall MS, Westgate CSJ, Mitchell JL, Hagen SM, Gonzalez AM, Hodson DJ, Jensen RH, Sinclair AJ. A glucagon-like peptide-1 receptor agonist reduces intracranial pressure in a rat model of hydrocephalus. Sci Transl Med 2017; 9:eaan0972. [PMID: 28835515 DOI: 10.1126/scitranslmed.aan0972] [Citation(s) in RCA: 58] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2016] [Revised: 03/03/2017] [Accepted: 08/02/2017] [Indexed: 12/13/2022]
Abstract
Current therapies for reducing raised intracranial pressure (ICP) under conditions such as idiopathic intracranial hypertension or hydrocephalus have limited efficacy and tolerability. Thus, there is a pressing need to identify alternative drugs. Glucagon-like peptide-1 receptor (GLP-1R) agonists are used to treat diabetes and promote weight loss but have also been shown to affect fluid homeostasis in the kidney. We investigated whether exendin-4, a GLP-1R agonist, is able to modulate cerebrospinal fluid (CSF) secretion at the choroid plexus and subsequently reduce ICP in rats. We used tissue sections and cell cultures to demonstrate expression of GLP-1R in the choroid plexus and its activation by exendin-4, an effect blocked by the GLP-1R antagonist exendin 9-39. Acute treatment with exendin-4 reduced Na+- and K+-dependent adenosine triphosphatase activity, a key regulator of CSF secretion, in cell cultures. Finally, we demonstrated that administration of exendin-4 to female rats with raised ICP (hydrocephalic) resulted in a GLP-1R-mediated reduction in ICP. These findings suggest that GLP-1R agonists can reduce ICP in rodents. Repurposing existing GLP-1R agonist drugs may be a useful therapeutic strategy for treating raised ICP.
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Affiliation(s)
- Hannah F Botfield
- Institute of Metabolism and Systems Research, University of Birmingham, Edgbaston B15 2TT, UK
- Centre for Endocrinology, Diabetes and Metabolism, Birmingham Health Partners, Birmingham B15 2TH, UK
| | - Maria S Uldall
- Danish Headache Center, Clinic of Neurology, Rigshospitalet-Glostrup, University of Copenhagen, Nordre Ringvej 69, 2600 Glostrup, Denmark
| | - Connar S J Westgate
- Institute of Metabolism and Systems Research, University of Birmingham, Edgbaston B15 2TT, UK
- Centre for Endocrinology, Diabetes and Metabolism, Birmingham Health Partners, Birmingham B15 2TH, UK
| | - James L Mitchell
- Institute of Metabolism and Systems Research, University of Birmingham, Edgbaston B15 2TT, UK
- Centre for Endocrinology, Diabetes and Metabolism, Birmingham Health Partners, Birmingham B15 2TH, UK
- Department of Neurology, University Hospitals Birmingham NHS Foundation Trust, Birmingham B15 2TH, UK
| | - Snorre M Hagen
- Danish Headache Center, Clinic of Neurology, Rigshospitalet-Glostrup, University of Copenhagen, Nordre Ringvej 69, 2600 Glostrup, Denmark
| | - Ana Maria Gonzalez
- Institute of Inflammation and Ageing, University of Birmingham, Edgbaston B15 2TT, UK
| | - David J Hodson
- Institute of Metabolism and Systems Research, University of Birmingham, Edgbaston B15 2TT, UK
- Centre for Endocrinology, Diabetes and Metabolism, Birmingham Health Partners, Birmingham B15 2TH, UK
- Centre of Membrane Proteins and Receptors (COMPARE), University of Birmingham and University of Nottingham, Midlands, UK
| | - Rigmor H Jensen
- Danish Headache Center, Clinic of Neurology, Rigshospitalet-Glostrup, University of Copenhagen, Nordre Ringvej 69, 2600 Glostrup, Denmark
| | - Alexandra J Sinclair
- Institute of Metabolism and Systems Research, University of Birmingham, Edgbaston B15 2TT, UK.
- Centre for Endocrinology, Diabetes and Metabolism, Birmingham Health Partners, Birmingham B15 2TH, UK
- Department of Neurology, University Hospitals Birmingham NHS Foundation Trust, Birmingham B15 2TH, UK
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110
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Daraio T, Bombek LK, Gosak M, Valladolid-Acebes I, Klemen MS, Refai E, Berggren PO, Brismar K, Rupnik MS, Bark C. SNAP-25b-deficiency increases insulin secretion and changes spatiotemporal profile of Ca 2+oscillations in β cell networks. Sci Rep 2017; 7:7744. [PMID: 28798351 PMCID: PMC5552776 DOI: 10.1038/s41598-017-08082-y] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2017] [Accepted: 07/04/2017] [Indexed: 01/02/2023] Open
Abstract
SNAP-25 is a protein of the core SNARE complex mediating stimulus-dependent release of insulin from pancreatic β cells. The protein exists as two alternatively spliced isoforms, SNAP-25a and SNAP-25b, differing in 9 out of 206 amino acids, yet their specific roles in pancreatic β cells remain unclear. We explored the effect of SNAP-25b-deficiency on glucose-stimulated insulin release in islets and found increased secretion both in vivo and in vitro. However, slow photo-release of caged Ca2+ in β cells within pancreatic slices showed no significant differences in Ca2+-sensitivity, amplitude or rate of exocytosis between SNAP-25b-deficient and wild-type littermates. Therefore, we next investigated if Ca2+ handling was affected in glucose-stimulated β cells using intracellular Ca2+-imaging and found premature activation and delayed termination of [Ca2+]i elevations. These findings were accompanied by less synchronized Ca2+-oscillations and hence more segregated functional β cell networks in SNAP-25b-deficient mice. Islet gross morphology and architecture were maintained in mutant mice, although sex specific compensatory changes were observed. Thus, our study proposes that SNAP-25b in pancreatic β cells, except for participating in the core SNARE complex, is necessary for accurate regulation of Ca2+-dynamics.
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Affiliation(s)
- Teresa Daraio
- The Rolf Luft Research Center for Diabetes and Endocrinology, Department of Molecular Medicine and Surgery, Karolinska Institutet, 171 76, Stockholm, Sweden
| | - Lidija Križančić Bombek
- Institute of Physiology, Faculty of Medicine, University of Maribor, SI-2000, Maribor, Slovenia
| | - Marko Gosak
- Institute of Physiology, Faculty of Medicine, University of Maribor, SI-2000, Maribor, Slovenia.,Department of Physics, Faculty of Natural Sciences and Mathematics, University of Maribor, SI-2000, Maribor, Slovenia
| | - Ismael Valladolid-Acebes
- The Rolf Luft Research Center for Diabetes and Endocrinology, Department of Molecular Medicine and Surgery, Karolinska Institutet, 171 76, Stockholm, Sweden
| | - Maša Skelin Klemen
- Institute of Physiology, Faculty of Medicine, University of Maribor, SI-2000, Maribor, Slovenia
| | - Essam Refai
- The Rolf Luft Research Center for Diabetes and Endocrinology, Department of Molecular Medicine and Surgery, Karolinska Institutet, 171 76, Stockholm, Sweden
| | - Per-Olof Berggren
- The Rolf Luft Research Center for Diabetes and Endocrinology, Department of Molecular Medicine and Surgery, Karolinska Institutet, 171 76, Stockholm, Sweden
| | - Kerstin Brismar
- The Rolf Luft Research Center for Diabetes and Endocrinology, Department of Molecular Medicine and Surgery, Karolinska Institutet, 171 76, Stockholm, Sweden
| | - Marjan Slak Rupnik
- Institute of Physiology, Faculty of Medicine, University of Maribor, SI-2000, Maribor, Slovenia. .,Center for Physiology and Pharmacology, Medical University of Vienna, A-1090, Vienna, Austria.
| | - Christina Bark
- The Rolf Luft Research Center for Diabetes and Endocrinology, Department of Molecular Medicine and Surgery, Karolinska Institutet, 171 76, Stockholm, Sweden.
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111
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Avrahami D, Klochendler A, Dor Y, Glaser B. Beta cell heterogeneity: an evolving concept. Diabetologia 2017; 60:1363-1369. [PMID: 28597073 PMCID: PMC5554543 DOI: 10.1007/s00125-017-4326-z] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/28/2017] [Accepted: 05/02/2017] [Indexed: 10/19/2022]
Abstract
Beta cells are primarily defined by their ability to produce insulin and secrete it in response to appropriate stimuli. It has been known for some time, however, that beta cells are not functionally identical to each other and that the rates of insulin synthesis and release differ from cell to cell, although the functional significance of this variability remains unclear. Recent studies have used heterogeneous gene expression to isolate and evaluate different subpopulations of beta cells and to demonstrate alterations in these subpopulations in diabetes. In the last few years, novel technologies have emerged that permit the detailed evaluation of the proteome (e.g. time-of-flight mass spectroscopy, [CyTOF]) and transcriptome (e.g. massively parallel RNA sequencing) at the single-cell level, and tools for single beta cell metabolomics and epigenomics are quickly maturing. The first wave of single beta cell proteome and transcriptome studies were published in 2016, giving a glimpse into the power, but also the limitations, of these approaches. Despite this progress, it remains unclear if the observed heterogeneity of beta cells represents stable, distinct beta cell types or, alternatively, highly dynamic beta cell states. Here we provide a concise overview of recent developments in the emerging field of beta cell heterogeneity and the implications for our understanding of beta cell biology and pathology.
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Affiliation(s)
- Dana Avrahami
- Endocrinology and Metabolism Service, Department of Internal Medicine, Hadassah-Hebrew University Medical Center, POB 12000, 91120, Jerusalem, Israel
| | - Agnes Klochendler
- Department of Developmental Biology and Cancer Research, The Institute for Medical Research Israel-Canada, Hebrew University-Hadassah Medical School, Jerusalem, Israel
| | - Yuval Dor
- Department of Developmental Biology and Cancer Research, The Institute for Medical Research Israel-Canada, Hebrew University-Hadassah Medical School, Jerusalem, Israel
| | - Benjamin Glaser
- Endocrinology and Metabolism Service, Department of Internal Medicine, Hadassah-Hebrew University Medical Center, POB 12000, 91120, Jerusalem, Israel.
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112
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Carrano AC, Mulas F, Zeng C, Sander M. Interrogating islets in health and disease with single-cell technologies. Mol Metab 2017; 6:991-1001. [PMID: 28951823 PMCID: PMC5605723 DOI: 10.1016/j.molmet.2017.04.012] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/18/2017] [Revised: 04/10/2017] [Accepted: 04/11/2017] [Indexed: 02/07/2023] Open
Abstract
BACKGROUND Blood glucose levels are tightly controlled by the coordinated actions of hormone-producing endocrine cells that reside in pancreatic islets. Islet cell malfunction underlies diabetes development and progression. Due to the cellular heterogeneity within islets, it has been challenging to uncover how specific islet cells contribute to glucose homeostasis and diabetes pathogenesis. Recent advances in single-cell technologies and computational methods have opened up new avenues to resolve islet heterogeneity and study islet cell states in health and disease. SCOPE OF REVIEW In the past year, a multitude of studies have been published that used single-cell approaches to interrogate the transcriptome and proteome of the different islet cell types. Here, we summarize the conclusions of these studies, as well as discuss the technologies used and the challenges faced with computational analysis of single-cell data from islet studies. MAJOR CONCLUSIONS By analyzing single islet cells from rodents and humans at different ages and disease states, the studies reviewed here have provided new insight into endocrine cell function and facilitated a high resolution molecular characterization of poorly understood processes, including regeneration, maturation, and diabetes pathogenesis. Gene expression programs and pathways identified in these studies pave the way for the discovery of new targets and approaches to prevent, monitor, and treat diabetes.
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Affiliation(s)
- Andrea C Carrano
- Departments of Pediatrics and Cellular & Molecular Medicine, Pediatric Diabetes Research Center, University of California, San Diego, 2880 Torrey Pines Scenic Drive, La Jolla, CA 92037, USA
| | - Francesca Mulas
- Departments of Pediatrics and Cellular & Molecular Medicine, Pediatric Diabetes Research Center, University of California, San Diego, 2880 Torrey Pines Scenic Drive, La Jolla, CA 92037, USA
| | - Chun Zeng
- Departments of Pediatrics and Cellular & Molecular Medicine, Pediatric Diabetes Research Center, University of California, San Diego, 2880 Torrey Pines Scenic Drive, La Jolla, CA 92037, USA
| | - Maike Sander
- Departments of Pediatrics and Cellular & Molecular Medicine, Pediatric Diabetes Research Center, University of California, San Diego, 2880 Torrey Pines Scenic Drive, La Jolla, CA 92037, USA
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113
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Grasset E, Puel A, Charpentier J, Collet X, Christensen JE, Tercé F, Burcelin R. A Specific Gut Microbiota Dysbiosis of Type 2 Diabetic Mice Induces GLP-1 Resistance through an Enteric NO-Dependent and Gut-Brain Axis Mechanism. Cell Metab 2017; 25:1075-1090.e5. [PMID: 28467926 DOI: 10.1016/j.cmet.2017.04.013] [Citation(s) in RCA: 154] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/25/2016] [Revised: 02/01/2017] [Accepted: 04/13/2017] [Indexed: 12/22/2022]
Abstract
Glucagon-like peptide-1 (GLP-1)-based therapies control glycemia in type 2 diabetic (T2D) patients. However, in some patients the treatment must be discontinued, defining a state of GLP-1 resistance. In animal models we identified a specific set of ileum bacteria impairing the GLP-1-activated gut-brain axis for the control of insulin secretion and gastric emptying. Using prediction algorithms, we identified bacterial pathways related to amino acid metabolism and transport system modules associated to GLP-1 resistance. The conventionalization of germ-free mice demonstrated their role in enteric neuron biology and the gut-brain-periphery axis. Altogether, insulin secretion and gastric emptying require functional GLP-1 receptor and neuronal nitric oxide synthase in the enteric nervous system within a eubiotic gut microbiota environment. Our data open a novel route to improve GLP-1-based therapies.
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Affiliation(s)
- Estelle Grasset
- Institut National de la Santé et de la Recherche Médicale (INSERM), 31024 Toulouse, France; Université Paul Sabatier (UPS), Unité Mixte de Recherche (UMR) 1048, Institut des Maladies Métaboliques et Cardiovasculaires (I2MC), Team 2: Intestinal Risk Factors, Diabetes, Dyslipidemia, Heart Failure, F-31432 Toulouse, Cedex 4, France
| | - Anthony Puel
- Institut National de la Santé et de la Recherche Médicale (INSERM), 31024 Toulouse, France; Université Paul Sabatier (UPS), Unité Mixte de Recherche (UMR) 1048, Institut des Maladies Métaboliques et Cardiovasculaires (I2MC), Team 2: Intestinal Risk Factors, Diabetes, Dyslipidemia, Heart Failure, F-31432 Toulouse, Cedex 4, France
| | - Julie Charpentier
- Institut National de la Santé et de la Recherche Médicale (INSERM), 31024 Toulouse, France; Université Paul Sabatier (UPS), Unité Mixte de Recherche (UMR) 1048, Institut des Maladies Métaboliques et Cardiovasculaires (I2MC), Team 2: Intestinal Risk Factors, Diabetes, Dyslipidemia, Heart Failure, F-31432 Toulouse, Cedex 4, France
| | - Xavier Collet
- Institut National de la Santé et de la Recherche Médicale (INSERM), 31024 Toulouse, France; Université Paul Sabatier (UPS), Unité Mixte de Recherche (UMR) 1048, Institut des Maladies Métaboliques et Cardiovasculaires (I2MC), Team 2: Intestinal Risk Factors, Diabetes, Dyslipidemia, Heart Failure, F-31432 Toulouse, Cedex 4, France
| | - Jeffrey E Christensen
- Institut National de la Santé et de la Recherche Médicale (INSERM), 31024 Toulouse, France; Université Paul Sabatier (UPS), Unité Mixte de Recherche (UMR) 1048, Institut des Maladies Métaboliques et Cardiovasculaires (I2MC), Team 2: Intestinal Risk Factors, Diabetes, Dyslipidemia, Heart Failure, F-31432 Toulouse, Cedex 4, France
| | - François Tercé
- Institut National de la Santé et de la Recherche Médicale (INSERM), 31024 Toulouse, France; Université Paul Sabatier (UPS), Unité Mixte de Recherche (UMR) 1048, Institut des Maladies Métaboliques et Cardiovasculaires (I2MC), Team 2: Intestinal Risk Factors, Diabetes, Dyslipidemia, Heart Failure, F-31432 Toulouse, Cedex 4, France
| | - Rémy Burcelin
- Institut National de la Santé et de la Recherche Médicale (INSERM), 31024 Toulouse, France; Université Paul Sabatier (UPS), Unité Mixte de Recherche (UMR) 1048, Institut des Maladies Métaboliques et Cardiovasculaires (I2MC), Team 2: Intestinal Risk Factors, Diabetes, Dyslipidemia, Heart Failure, F-31432 Toulouse, Cedex 4, France.
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114
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Carlessi R, Keane KN, Mamotte C, Newsholme P. Nutrient regulation of β-cell function: what do islet cell/animal studies tell us? Eur J Clin Nutr 2017; 71:890-895. [DOI: 10.1038/ejcn.2017.49] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2017] [Accepted: 03/15/2017] [Indexed: 12/18/2022]
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115
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Mitchell RK, Nguyen-Tu MS, Chabosseau P, Callingham RM, Pullen TJ, Cheung R, Leclerc I, Hodson DJ, Rutter GA. The transcription factor Pax6 is required for pancreatic β cell identity, glucose-regulated ATP synthesis, and Ca 2+ dynamics in adult mice. J Biol Chem 2017; 292:8892-8906. [PMID: 28377501 PMCID: PMC5448123 DOI: 10.1074/jbc.m117.784629] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2017] [Revised: 04/03/2017] [Indexed: 12/20/2022] Open
Abstract
Heterozygous mutations in the human paired box gene PAX6 lead to impaired glucose tolerance. Although embryonic deletion of the Pax6 gene in mice leads to loss of most pancreatic islet cell types, the functional consequences of Pax6 loss in adults are poorly defined. Here we developed a mouse line in which Pax6 was selectively inactivated in β cells by crossing animals with floxed Pax6 alleles to mice expressing the inducible Pdx1CreERT transgene. Pax6 deficiency, achieved by tamoxifen injection, caused progressive hyperglycemia. Although β cell mass was preserved 8 days post-injection, total insulin content and insulin:chromogranin A immunoreactivity were reduced by ∼60%, and glucose-stimulated insulin secretion was eliminated. RNA sequencing and quantitative real-time PCR analyses revealed that, although the expression of key β cell genes, including Ins2, Slc30a8, MafA, Slc2a2, G6pc2, and Glp1r, was reduced after Pax6 deletion, that of several genes that are usually selectively repressed (“disallowed”) in β cells, including Slc16a1, was increased. Assessed in intact islets, glucose-induced ATP:ADP increases were significantly reduced (p < 0.05) in βPax6KO versus control β cells, and the former displayed attenuated increases in cytosolic Ca2+. Unexpectedly, glucose-induced increases in intercellular connectivity were enhanced after Pax6 deletion, consistent with increases in the expression of the glucose sensor glucokinase, but decreases in that of two transcription factors usually expressed in fully differentiated β-cells, Pdx1 and Nkx6.1, were observed in islet “hub” cells. These results indicate that Pax6 is required for the functional identity of adult β cells. Furthermore, deficiencies in β cell glucose sensing are likely to contribute to defective insulin secretion in human carriers of PAX6 mutations.
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Affiliation(s)
- Ryan K Mitchell
- From the Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology, and Metabolism, Imperial College London, Du Cane Road, London W12 0NN, United Kingdom
| | - Marie-Sophie Nguyen-Tu
- From the Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology, and Metabolism, Imperial College London, Du Cane Road, London W12 0NN, United Kingdom
| | - Pauline Chabosseau
- From the Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology, and Metabolism, Imperial College London, Du Cane Road, London W12 0NN, United Kingdom
| | - Rebecca M Callingham
- From the Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology, and Metabolism, Imperial College London, Du Cane Road, London W12 0NN, United Kingdom
| | - Timothy J Pullen
- From the Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology, and Metabolism, Imperial College London, Du Cane Road, London W12 0NN, United Kingdom
| | - Rebecca Cheung
- From the Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology, and Metabolism, Imperial College London, Du Cane Road, London W12 0NN, United Kingdom
| | - Isabelle Leclerc
- From the Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology, and Metabolism, Imperial College London, Du Cane Road, London W12 0NN, United Kingdom
| | - David J Hodson
- From the Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology, and Metabolism, Imperial College London, Du Cane Road, London W12 0NN, United Kingdom, .,the Institute of Metabolism and Systems Research and Centre of Membrane Proteins and Receptors, University of Birmingham, Edgbaston B15 2TT, United Kingdom, and.,the Centre for Endocrinology, Diabetes, and Metabolism, Birmingham Health Partners, Birmingham B15 2TH, United Kingdom
| | - Guy A Rutter
- From the Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology, and Metabolism, Imperial College London, Du Cane Road, London W12 0NN, United Kingdom,
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116
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Martinez-Sanchez A, Rutter GA, Latreille M. MiRNAs in β-Cell Development, Identity, and Disease. Front Genet 2017; 7:226. [PMID: 28123396 PMCID: PMC5225124 DOI: 10.3389/fgene.2016.00226] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2016] [Accepted: 12/21/2016] [Indexed: 12/22/2022] Open
Abstract
Pancreatic β-cells regulate glucose metabolism by secreting insulin, which in turn stimulates the utilization or storage of the sugar by peripheral tissues. Insulin insufficiency and a prolonged period of insulin resistance are usually the core components of type 2 diabetes (T2D). Although, decreased insulin levels in T2D have long been attributed to a decrease in β-cell function and/or mass, this model has recently been refined with the recognition that a loss of β-cell “identity” and dedifferentiation also contribute to the decline in insulin production. MicroRNAs (miRNAs) are key regulatory molecules that display tissue-specific expression patterns and maintain the differentiated state of somatic cells. During the past few years, great strides have been made in understanding how miRNA circuits impact β-cell identity. Here, we review current knowledge on the role of miRNAs in regulating the acquisition of the β-cell fate during development and in maintaining mature β-cell identity and function during stress situations such as obesity, pregnancy, aging, or diabetes. We also discuss how miRNA function could be harnessed to improve our ability to generate β-cells for replacement therapy for T2D.
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Affiliation(s)
- Aida Martinez-Sanchez
- Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Imperial College London London, UK
| | - Guy A Rutter
- Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Imperial College London London, UK
| | - Mathieu Latreille
- Cellular Identity and Metabolism Group, MRC London Institute of Medical SciencesLondon, UK; Institute of Clinical Sciences, Faculty of Medicine, Imperial College LondonLondon, UK
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117
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Shimoda M, Miyoshi-Takai M, Irie S, Tanabe A, Obata A, Okauchi S, Hirukawa H, Kimura T, Kohara K, Kamei S, Mune T, Kaku K, Kaneto H. Inadequate Triglyceride Management Worsens the Durability of Dipeptidyl Peptidase-4 Inhibitor in Subjects with Type 2 Diabetes Mellitus. J Diabetes Res 2017; 2017:5856475. [PMID: 28626771 PMCID: PMC5463141 DOI: 10.1155/2017/5856475] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Dipeptidyl peptidase-4 (DPP-4) inhibitors are often used all over the world and exert various beneficial effects including glucose-lowering effect in many subjects with type 2 diabetes. It is poorly understood, however, which factors are closely related with the durability of glucose-lowering effect by DPP-4 inhibitor. In this study, we examined retrospectively which factors could mainly influence the durability of DPP-4 inhibitor. We enrolled 212 participants with type 2 diabetes to whom DPP-4 inhibitor was administered for over 1 year without an addition or increase of other hypoglycemic agents. Age and baseline HbA1c level were significantly higher in the effective group than those in the ineffective group. The effective group had a tendency of smaller amounts of weight change, average total cholesterol, and average triglyceride compared with the ineffective group. Multiple logistic regression analysis showed that average triglyceride and baseline HbA1c were independent predictors associated with the durability of DPP-4 inhibitor. Moreover, an average triglyceride level contributed to the durability of DPP-4 inhibitor in the obese group (BMI ≥ 25 kg/m2) but not in the nonobese group (BMI < 25 kg/m2). These results suggest the importance of strict triglyceride management to maintain the durability of glucose-lowering effect by DPP-4 inhibitor, especially in obese subjects with type 2 diabetes.
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Affiliation(s)
- Masashi Shimoda
- Division of Diabetes, Metabolism and Endocrinology, Kawasaki Medical School, 577 Matsushima, Kurashiki 701-0192, Japan
- *Masashi Shimoda:
| | - Maiko Miyoshi-Takai
- Division of General Internal Medicine 1, Kawasaki Medical School, 577 Matsushima, Kurashiki 701-0192, Japan
| | - Shintaro Irie
- Division of Diabetes, Metabolism and Endocrinology, Kawasaki Medical School, 577 Matsushima, Kurashiki 701-0192, Japan
| | - Akihito Tanabe
- Division of Diabetes, Metabolism and Endocrinology, Kawasaki Medical School, 577 Matsushima, Kurashiki 701-0192, Japan
| | - Atsushi Obata
- Division of Diabetes, Metabolism and Endocrinology, Kawasaki Medical School, 577 Matsushima, Kurashiki 701-0192, Japan
| | - Seizo Okauchi
- Division of Diabetes, Metabolism and Endocrinology, Kawasaki Medical School, 577 Matsushima, Kurashiki 701-0192, Japan
| | - Hidenori Hirukawa
- Division of Diabetes, Metabolism and Endocrinology, Kawasaki Medical School, 577 Matsushima, Kurashiki 701-0192, Japan
| | - Tomohiko Kimura
- Division of Diabetes, Metabolism and Endocrinology, Kawasaki Medical School, 577 Matsushima, Kurashiki 701-0192, Japan
| | - Kenji Kohara
- Division of Diabetes, Metabolism and Endocrinology, Kawasaki Medical School, 577 Matsushima, Kurashiki 701-0192, Japan
| | - Shinji Kamei
- Division of Diabetes, Metabolism and Endocrinology, Kawasaki Medical School, 577 Matsushima, Kurashiki 701-0192, Japan
| | - Tomoatsu Mune
- Division of Diabetes, Metabolism and Endocrinology, Kawasaki Medical School, 577 Matsushima, Kurashiki 701-0192, Japan
| | - Kohei Kaku
- Division of General Internal Medicine 1, Kawasaki Medical School, 577 Matsushima, Kurashiki 701-0192, Japan
| | - Hideaki Kaneto
- Division of Diabetes, Metabolism and Endocrinology, Kawasaki Medical School, 577 Matsushima, Kurashiki 701-0192, Japan
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118
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Abstract
In light of the emerging diabetes epidemic, new experimental approaches in islet research are needed to elucidate the mechanisms behind pancreatic islet dysfunction and to facilitate the development of more effective therapies. Optogenetics has created numerous new experimental tools enabling us to gain insights into processes little was known about before. The spatial and temporal precision that it can achieve is also attractive for studying the cells of the pancreatic islet and we set out to explore the possibilities of this technology for our purposes. We here describe how to use the islets of an "optogenetic beta-cell" mouse line in islet batch incubations and Ca(2+) imaging experiments. This protocol enables light-induced insulin release and provides an all-optical solution to control and measure intracellular Ca(2+) levels in pancreatic beta-cells. The technique is easy to set up and provides a useful tool for controlling the activity of distinct islet cell populations.
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Affiliation(s)
- Thomas M Reinbothe
- Department of Physiology, University of Gothenburg, Box 432, Medicinaregatan 11-13, 40530, Gothenburg, Sweden.
| | - Inês G Mollet
- Department of Clinical Sciences, Malmö, Lund University Diabetes Centre, Lund University, Malmö, Sweden
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119
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Notary AM, Westacott MJ, Hraha TH, Pozzoli M, Benninger RKP. Decreases in Gap Junction Coupling Recovers Ca2+ and Insulin Secretion in Neonatal Diabetes Mellitus, Dependent on Beta Cell Heterogeneity and Noise. PLoS Comput Biol 2016; 12:e1005116. [PMID: 27681078 PMCID: PMC5040430 DOI: 10.1371/journal.pcbi.1005116] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2016] [Accepted: 08/23/2016] [Indexed: 11/29/2022] Open
Abstract
Diabetes is caused by dysfunction to β-cells in the islets of Langerhans, disrupting insulin secretion and glucose homeostasis. Gap junction-mediated electrical coupling between β-cells in the islet plays a major role in coordinating a pulsatile secretory response at elevated glucose and suppressing insulin secretion at basal glucose. Previously, we demonstrated that a critical number of inexcitable cells can rapidly suppress the overall islet response, as a result of gap junction coupling. This was demonstrated in a murine model of Neonatal Diabetes Mellitus (NDM) involving expression of ATP-insensitive KATP channels, and by a multi-cellular computational model of islet electrical activity. Here we examined the mechanisms by which gap junction coupling contributes to islet dysfunction in NDM. We first verified the computational model against [Ca2+] and insulin secretion measurements in islets expressing ATP-insensitive KATP channels under different levels of gap junction coupling. We then applied this model to predict how different KATP channel mutations found in NDM suppress [Ca2+], and the role of gap junction coupling in this suppression. We further extended the model to account for stochastic noise and insulin secretion dynamics. We found experimentally and in the islet model that reductions in gap junction coupling allow progressively greater glucose-stimulated [Ca2+] and insulin secretion following expression of ATP-insensitive KATP channels. The model demonstrated good correspondence between suppression of [Ca2+] and clinical presentation of different NDM mutations. Significant recoveries in [Ca2+] and insulin secretion were predicted for many mutations upon reductions in gap junction coupling, where stochastic noise played a significant role in the recoveries. These findings provide new understanding how the islet functions as a multicellular system and for the role of gap junction channels in exacerbating the effects of decreased cellular excitability. They further suggest novel therapeutic options for NDM and other monogenic forms of diabetes. Diabetes is a disease reaching a global epidemic, which results from dysfunction to the islets of Langerhans in the pancreas and their ability to secrete the hormone insulin to regulate glucose homeostasis. Islets are multicellular structures that show extensive coupling between heterogeneous cellular units; and central to the causes of diabetes is a dysfunction to these cellular units and their interactions. Understanding the inter-relationship between structure and function is challenging in biological systems, but is crucial to the cause of disease and discovering therapeutic targets. With the goal of further characterizing the islet of Langerhans and its excitable behavior, we examined the role of important channels in the islet where dysfunction is linked to or causes diabetes. Advances in our ability to computationally model perturbations in physiological systems has allowed for the testing of hypothesis quickly, in systems that are not experimentally accessible. Using an experimentally validated model and modeling human mutations, we discover that monogenic forms of diabetes may be remedied by a reduction in electrical coupling between cells; either alone or in conjunction with pharmacological intervention. Knowledge of biological systems in general is also helped by these findings, in that small changes to cellular elements may lead to major disruptions in the overall system. This may then be overcome by allowing the system components to function independently in the presence of dysfunction to individual cells.
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Affiliation(s)
- Aleena M. Notary
- Department of Bioengineering, University of Colorado, Anschutz Medical campus, Aurora, Colorado, United States of America
| | - Matthew J. Westacott
- Department of Bioengineering, University of Colorado, Anschutz Medical campus, Aurora, Colorado, United States of America
| | - Thomas H. Hraha
- Department of Bioengineering, University of Colorado, Anschutz Medical campus, Aurora, Colorado, United States of America
| | - Marina Pozzoli
- Department of Bioengineering, University of Colorado, Anschutz Medical campus, Aurora, Colorado, United States of America
| | - Richard K. P. Benninger
- Department of Bioengineering, University of Colorado, Anschutz Medical campus, Aurora, Colorado, United States of America
- Barbara Davis Center for Diabetes, University of Colorado, Anschutz Medical campus, Aurora, Colorado, United States of America
- * E-mail:
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120
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Johnston NR, Mitchell RK, Haythorne E, Pessoa MP, Semplici F, Ferrer J, Piemonti L, Marchetti P, Bugliani M, Bosco D, Berishvili E, Duncanson P, Watkinson M, Broichhagen J, Trauner D, Rutter GA, Hodson DJ. Beta Cell Hubs Dictate Pancreatic Islet Responses to Glucose. Cell Metab 2016; 24:389-401. [PMID: 27452146 PMCID: PMC5031557 DOI: 10.1016/j.cmet.2016.06.020] [Citation(s) in RCA: 314] [Impact Index Per Article: 39.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/16/2015] [Revised: 05/17/2016] [Accepted: 06/23/2016] [Indexed: 12/02/2022]
Abstract
The arrangement of β cells within islets of Langerhans is critical for insulin release through the generation of rhythmic activity. A privileged role for individual β cells in orchestrating these responses has long been suspected, but not directly demonstrated. We show here that the β cell population in situ is operationally heterogeneous. Mapping of islet functional architecture revealed the presence of hub cells with pacemaker properties, which remain stable over recording periods of 2 to 3 hr. Using a dual optogenetic/photopharmacological strategy, silencing of hubs abolished coordinated islet responses to glucose, whereas specific stimulation restored communication patterns. Hubs were metabolically adapted and targeted by both pro-inflammatory and glucolipotoxic insults to induce widespread β cell dysfunction. Thus, the islet is wired by hubs, whose failure may contribute to type 2 diabetes mellitus.
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Affiliation(s)
- Natalie R Johnston
- Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Imperial College London, London W12 0NN, UK
| | - Ryan K Mitchell
- Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Imperial College London, London W12 0NN, UK
| | - Elizabeth Haythorne
- Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Imperial College London, London W12 0NN, UK
| | - Maria Paiva Pessoa
- Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Imperial College London, London W12 0NN, UK
| | - Francesca Semplici
- Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Imperial College London, London W12 0NN, UK
| | - Jorge Ferrer
- Beta Cell Genome Regulation Lab, Department of Medicine, Imperial College London, London W12 0NN, UK
| | - Lorenzo Piemonti
- Diabetes Research Institute (HSR-DRI), San Raffaele Scientific Institute, Via Olgettina 60, 20132 Milan, Italy
| | - Piero Marchetti
- Department of Clinical and Experimental Medicine, Islet Cell Laboratory, University of Pisa, 56126 Pisa, Italy
| | - Marco Bugliani
- Department of Clinical and Experimental Medicine, Islet Cell Laboratory, University of Pisa, 56126 Pisa, Italy
| | - Domenico Bosco
- Cell Isolation and Transplantation Center, Department of Surgery, Geneva University Hospitals and University of Geneva, 1205 Geneva, Switzerland
| | - Ekaterine Berishvili
- Cell Isolation and Transplantation Center, Department of Surgery, Geneva University Hospitals and University of Geneva, 1205 Geneva, Switzerland
| | - Philip Duncanson
- School of Biological and Chemical Sciences, Queen Mary University of London, Mile End Road, London E1 4NS, UK
| | - Michael Watkinson
- School of Biological and Chemical Sciences, Queen Mary University of London, Mile End Road, London E1 4NS, UK
| | - Johannes Broichhagen
- Department of Chemistry, Ludwig-Maximilians-Universität München, and Munich Center for Integrated Protein Science, Butenandtstrasse 5-13, 81377 München, Germany
| | - Dirk Trauner
- Department of Chemistry, Ludwig-Maximilians-Universität München, and Munich Center for Integrated Protein Science, Butenandtstrasse 5-13, 81377 München, Germany
| | - Guy A Rutter
- Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Imperial College London, London W12 0NN, UK.
| | - David J Hodson
- Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Imperial College London, London W12 0NN, UK; Institute of Metabolism and Systems Research (IMSR) and Centre of Membrane Proteins and Receptors (COMPARE), University of Birmingham, Birmingham B15 2TT, UK; Centre for Endocrinology, Diabetes and Metabolism, Birmingham Health Partners, Birmingham B15 2TH, UK.
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121
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Mehta ZB, Fine N, Pullen TJ, Cane MC, Hu M, Chabosseau P, Meur G, Velayos-Baeza A, Monaco AP, Marselli L, Marchetti P, Rutter GA. Changes in the expression of the type 2 diabetes-associated gene VPS13C in the β-cell are associated with glucose intolerance in humans and mice. Am J Physiol Endocrinol Metab 2016; 311:E488-507. [PMID: 27329800 PMCID: PMC5005967 DOI: 10.1152/ajpendo.00074.2016] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/26/2016] [Accepted: 06/20/2016] [Indexed: 12/31/2022]
Abstract
Single nucleotide polymorphisms (SNPs) close to the VPS13C, C2CD4A and C2CD4B genes on chromosome 15q are associated with impaired fasting glucose and increased risk of type 2 diabetes. eQTL analysis revealed an association between possession of risk (C) alleles at a previously implicated causal SNP, rs7163757, and lowered VPS13C and C2CD4A levels in islets from female (n = 40, P < 0.041) but not from male subjects. Explored using promoter-reporter assays in β-cells and other cell lines, the risk variant at rs7163757 lowered enhancer activity. Mice deleted for Vps13c selectively in the β-cell were generated by crossing animals bearing a floxed allele at exon 1 to mice expressing Cre recombinase under Ins1 promoter control (Ins1Cre). Whereas Vps13c(fl/fl):Ins1Cre (βVps13cKO) mice displayed normal weight gain compared with control littermates, deletion of Vps13c had little effect on glucose tolerance. Pancreatic histology revealed no significant change in β-cell mass in KO mice vs. controls, and glucose-stimulated insulin secretion from isolated islets was not altered in vitro between control and βVps13cKO mice. However, a tendency was observed in female null mice for lower insulin levels and β-cell function (HOMA-B) in vivo. Furthermore, glucose-stimulated increases in intracellular free Ca(2+) were significantly increased in islets from female KO mice, suggesting impaired Ca(2+) sensitivity of the secretory machinery. The present data thus provide evidence for a limited role for changes in VPS13C expression in conferring altered disease risk at this locus, particularly in females, and suggest that C2CD4A may also be involved.
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Affiliation(s)
- Zenobia B Mehta
- Section of Cell Biology and Functional Genomics, Imperial College London, London, United Kingdom
| | - Nicholas Fine
- Section of Cell Biology and Functional Genomics, Imperial College London, London, United Kingdom
| | - Timothy J Pullen
- Section of Cell Biology and Functional Genomics, Imperial College London, London, United Kingdom
| | - Matthew C Cane
- Section of Cell Biology and Functional Genomics, Imperial College London, London, United Kingdom
| | - Ming Hu
- Section of Cell Biology and Functional Genomics, Imperial College London, London, United Kingdom
| | - Pauline Chabosseau
- Section of Cell Biology and Functional Genomics, Imperial College London, London, United Kingdom
| | - Gargi Meur
- Section of Cell Biology and Functional Genomics, Imperial College London, London, United Kingdom
| | | | - Anthony P Monaco
- Wellcome Trust Centre for Human Genetics, Oxford, United Kingdom; and
| | - Lorella Marselli
- Department of Clinical and Experimental Medicine, University of Pisa, Pisa, Italy
| | - Piero Marchetti
- Department of Clinical and Experimental Medicine, University of Pisa, Pisa, Italy
| | - Guy A Rutter
- Section of Cell Biology and Functional Genomics, Imperial College London, London, United Kingdom;
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Tanabe A, Kaneto H, Kamei S, Hirukawa H, Shimoda M, Kimura T, Obata A, Okauchi S, Tatsumi F, Kohara K, Mune T, Kaku K. Clinical effects of liraglutide are possibly influenced by hypertriglyceridemia and remaining pancreatic β-cell function in subjects with type 2 diabetes mellitus. J Diabetes Complications 2016; 30:1201-3. [PMID: 27220544 DOI: 10.1016/j.jdiacomp.2016.04.005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/22/2016] [Revised: 04/05/2016] [Accepted: 04/08/2016] [Indexed: 12/25/2022]
Abstract
We searched for factors influencing the clinical effects of GLP-1 analogue liraglutide in subjects with type 2 diabetes. Multivariate analyses showed that hypertriglyceridemia and baseline HbA1c levels were independent predictors for the efficacy of liraglutide and that CPR index was an independent predictor for the durability of liraglutide.
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Affiliation(s)
- Akihito Tanabe
- Division of Diabetes, Endocrinology and Metabolism, Kawasaki Medical School
| | - Hideaki Kaneto
- Division of Diabetes, Endocrinology and Metabolism, Kawasaki Medical School
| | - Shinji Kamei
- Division of Diabetes, Endocrinology and Metabolism, Kawasaki Medical School.
| | - Hidenori Hirukawa
- Division of Diabetes, Endocrinology and Metabolism, Kawasaki Medical School
| | - Masashi Shimoda
- Division of Diabetes, Endocrinology and Metabolism, Kawasaki Medical School
| | - Tomohiko Kimura
- Division of Diabetes, Endocrinology and Metabolism, Kawasaki Medical School
| | - Atsushi Obata
- Division of Diabetes, Endocrinology and Metabolism, Kawasaki Medical School
| | - Seizo Okauchi
- Division of Diabetes, Endocrinology and Metabolism, Kawasaki Medical School
| | - Fuminori Tatsumi
- Division of Diabetes, Endocrinology and Metabolism, Kawasaki Medical School
| | - Kenji Kohara
- Division of Diabetes, Endocrinology and Metabolism, Kawasaki Medical School
| | - Tomoatsu Mune
- Division of Diabetes, Endocrinology and Metabolism, Kawasaki Medical School
| | - Kohei Kaku
- Division of Diabetes, Endocrinology and Metabolism, Kawasaki Medical School
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Lu H, Hao L, Li S, Lin S, Lv L, Chen Y, Cui H, Zi T, Chu X, Na L, Sun C. Elevated circulating stearic acid leads to a major lipotoxic effect on mouse pancreatic beta cells in hyperlipidaemia via a miR-34a-5p-mediated PERK/p53-dependent pathway. Diabetologia 2016; 59:1247-57. [PMID: 26969487 DOI: 10.1007/s00125-016-3900-0] [Citation(s) in RCA: 53] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/08/2015] [Accepted: 01/25/2016] [Indexed: 01/15/2023]
Abstract
AIMS/HYPOTHESIS Serum stearic acid (C18:0) is elevated in individuals with hyperlipidaemia and type 2 diabetes. However, the lipotoxicity induced by increased stearic acid in beta cells has not been well described. This study aimed to examine the adverse effects of stearic acid on beta cells and the potential mechanisms through which these are mediated. METHODS Three groups of C57BL/6 mice were fed a normal diet or a high-stearic-acid/high-palmitic-acid diet for 24 weeks, respectively. The microRNA (miR) profiles of islets were determined by microarray screening. Islet injury was detected with co-staining using the TUNEL assay and insulin labelling. A lentiviral vector expressing anti-miRNA-34a-5p oligonucleotide (AMO-34a-5p) was injected into mice via an intraductal pancreatic route. RESULTS In both mouse islets and cultured rat insulinoma INS-1 cells, stearic acid exhibited a stronger lipotoxic role than other fatty acids, owing to repression of B cell CLL/lymphoma 2 (BCL-2) and BCL-2-like 2 (BCL-W) by stearic acid stimulation of miR-34a-5p. The stearic-acid-induced lipotoxicity and reduction in insulin secretion were alleviated by AMO-34a-5p. Further investigations in INS-1 cells revealed that p53 was involved in stearic-acid-induced elevation of miR-34a-5p, owing in part to activation of protein kinase-like endoplasmic reticulum kinase (PERK). Conversely, silencing PERK alleviated stearic-acid-induced p53, miR-34a-5p and lipotoxicity. CONCLUSIONS/INTERPRETATION These findings provide new insight for understanding the molecular mechanisms underlying not only the deleterious impact of stearic-acid-induced lipotoxicity but also apoptosis in beta cells and progression to type 2 diabetes.
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Affiliation(s)
- Huimin Lu
- Department of Nutrition and Food Hygiene, Public Health College, Harbin Medical University, 157 Baojian Road, Nangang District, Harbin, Hei Longjiang Province, 150081, People's Republic of China
| | - Liuyi Hao
- Department of Nutrition and Food Hygiene, Public Health College, Harbin Medical University, 157 Baojian Road, Nangang District, Harbin, Hei Longjiang Province, 150081, People's Republic of China
| | - Songtao Li
- Department of Nutrition and Food Hygiene, Public Health College, Harbin Medical University, 157 Baojian Road, Nangang District, Harbin, Hei Longjiang Province, 150081, People's Republic of China
| | - Song Lin
- Department of Nutrition and Food Hygiene, Public Health College, Harbin Medical University, 157 Baojian Road, Nangang District, Harbin, Hei Longjiang Province, 150081, People's Republic of China
| | - Lin Lv
- Department of Nutrition and Food Hygiene, Public Health College, Harbin Medical University, 157 Baojian Road, Nangang District, Harbin, Hei Longjiang Province, 150081, People's Republic of China
| | - Yang Chen
- Department of Nutrition and Food Hygiene, Public Health College, Harbin Medical University, 157 Baojian Road, Nangang District, Harbin, Hei Longjiang Province, 150081, People's Republic of China
| | - Hongli Cui
- Department of Nutrition and Food Hygiene, Public Health College, Harbin Medical University, 157 Baojian Road, Nangang District, Harbin, Hei Longjiang Province, 150081, People's Republic of China
| | - Tianqi Zi
- Department of Nutrition and Food Hygiene, Public Health College, Harbin Medical University, 157 Baojian Road, Nangang District, Harbin, Hei Longjiang Province, 150081, People's Republic of China
| | - Xia Chu
- Department of Nutrition and Food Hygiene, Public Health College, Harbin Medical University, 157 Baojian Road, Nangang District, Harbin, Hei Longjiang Province, 150081, People's Republic of China
| | - Lixin Na
- Department of Nutrition and Food Hygiene, Public Health College, Harbin Medical University, 157 Baojian Road, Nangang District, Harbin, Hei Longjiang Province, 150081, People's Republic of China.
| | - Changhao Sun
- Department of Nutrition and Food Hygiene, Public Health College, Harbin Medical University, 157 Baojian Road, Nangang District, Harbin, Hei Longjiang Province, 150081, People's Republic of China.
- Research Institute of Food, Nutrition and Health, Sino-Russian Medical Research Center, Harbin Medical University, Harbin, People's Republic of China.
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Tracking Dynamic Gap Junctional Coupling in Live Cells by Local Photoactivation and Fluorescence Imaging. Methods Mol Biol 2016. [PMID: 27207295 DOI: 10.1007/978-1-4939-3664-9_13] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
Abstract
Intercellular communication through gap junction channels is crucial for maintaining cell homeostasis and synchronizing physiological functions of tissues and organs. In this chapter, we present a noninvasive fluorescence imaging assay termed LAMP (local activation of a molecular fluorescent probe) that consists of the following steps: loading cells with a caged and cell permeable coumarin probe (NPE-HCCC2/AM), locally photolyzing the caged coumarin in one or a subpopulation of coupled cells, monitoring cell-cell dye transfer by digital fluorescence microscopy, and post-acquisition analysis to quantify the rate of junction dye transfer using Fick's equation. The LAMP assay can be conveniently carried out in fully intact cells to assess the extent and degree of cell coupling, and is compatible with other fluorophores emitting at different wavelengths to allow multicolor imaging. Moreover, by carrying out multiple photo-activations in a coupled cell pair, LAMP assay can track changes in cell coupling strength between coupled cells, hence providing a powerful method for investigating the regulation of junctional coupling by cellular biochemical changes.
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125
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Marmugi A, Parnis J, Chen X, Carmichael L, Hardy J, Mannan N, Marchetti P, Piemonti L, Bosco D, Johnson P, Shapiro JAM, Cruciani-Guglielmacci C, Magnan C, Ibberson M, Thorens B, Valdivia HH, Rutter GA, Leclerc I. Sorcin Links Pancreatic β-Cell Lipotoxicity to ER Ca2+ Stores. Diabetes 2016; 65:1009-21. [PMID: 26822088 PMCID: PMC4806657 DOI: 10.2337/db15-1334] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/25/2015] [Accepted: 01/18/2016] [Indexed: 01/02/2023]
Abstract
Preserving β-cell function during the development of obesity and insulin resistance would limit the worldwide epidemic of type 2 diabetes. Endoplasmic reticulum (ER) calcium (Ca(2+)) depletion induced by saturated free fatty acids and cytokines causes β-cell ER stress and apoptosis, but the molecular mechanisms behind these phenomena are still poorly understood. Here, we demonstrate that palmitate-induced sorcin downregulation and subsequent increases in glucose-6-phosphatase catalytic subunit-2 (G6PC2) levels contribute to lipotoxicity. Sorcin is a calcium sensor protein involved in maintaining ER Ca(2+) by inhibiting ryanodine receptor activity and playing a role in terminating Ca(2+)-induced Ca(2+) release. G6PC2, a genome-wide association study gene associated with fasting blood glucose, is a negative regulator of glucose-stimulated insulin secretion (GSIS). High-fat feeding in mice and chronic exposure of human islets to palmitate decreases endogenous sorcin expression while levels of G6PC2 mRNA increase. Sorcin-null mice are glucose intolerant, with markedly impaired GSIS and increased expression of G6pc2 Under high-fat diet, mice overexpressing sorcin in the β-cell display improved glucose tolerance, fasting blood glucose, and GSIS, whereas G6PC2 levels are decreased and cytosolic and ER Ca(2+) are increased in transgenic islets. Sorcin may thus provide a target for intervention in type 2 diabetes.
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Affiliation(s)
- Alice Marmugi
- Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology & Metabolism, Department of Medicine, Imperial College London, London, U.K
| | - Julia Parnis
- Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology & Metabolism, Department of Medicine, Imperial College London, London, U.K
| | - Xi Chen
- Center for Arrhythmia Research, University of Michigan, Ann Arbor, MI
| | - LeAnne Carmichael
- Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology & Metabolism, Department of Medicine, Imperial College London, London, U.K
| | - Julie Hardy
- Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology & Metabolism, Department of Medicine, Imperial College London, London, U.K
| | - Naila Mannan
- Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology & Metabolism, Department of Medicine, Imperial College London, London, U.K
| | - Piero Marchetti
- Department of Endocrinology and Metabolism, University of Pisa, Pisa, Italy
| | - Lorenzo Piemonti
- Diabetes Research Institute (HSR-DRI), San Raffaele Scientific Institute, Milan, Italy
| | - Domenico Bosco
- Cell Isolation and Transplantation Center, Department of Surgery, Geneva University Hospitals and University of Geneva, Geneva, Switzerland
| | - Paul Johnson
- Nuffield Department of Surgical Sciences, University of Oxford, Oxford, U.K
| | - James A M Shapiro
- Clinical Islet Laboratory and Clinical Islet Transplant Program, University of Alberta, Edmonton, Alberta, Canada
| | | | - Christophe Magnan
- Unit of Functional and Adaptive Biology, Paris Diderot University-Paris 7, Paris, France
| | - Mark Ibberson
- Vital-IT Group, SIB Swiss Institute of Bioinformatics, Lausanne, Switzerland
| | - Bernard Thorens
- Center for Integrative Genomics, University of Lausanne, Lausanne, Switzerland
| | - Héctor H Valdivia
- Center for Arrhythmia Research, University of Michigan, Ann Arbor, MI
| | - Guy A Rutter
- Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology & Metabolism, Department of Medicine, Imperial College London, London, U.K.
| | - Isabelle Leclerc
- Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology & Metabolism, Department of Medicine, Imperial College London, London, U.K.
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126
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Sayers SR, Reimann F, Gribble FM, Parker H, Zac-Varghese S, Bloom SR, Foretz M, Viollet B, Rutter GA. Proglucagon Promoter Cre-Mediated AMPK Deletion in Mice Increases Circulating GLP-1 Levels and Oral Glucose Tolerance. PLoS One 2016; 11:e0149549. [PMID: 27010458 PMCID: PMC4806996 DOI: 10.1371/journal.pone.0149549] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2015] [Accepted: 02/02/2016] [Indexed: 01/04/2023] Open
Abstract
BACKGROUND Enteroendocrine L-cells synthesise and release the gut hormone glucagon-like peptide-1 (GLP-1) in response to food transit. Deletion of the tumour suppressor kinase LKB1 from proglucagon-expressing cells leads to the generation of intestinal polyps but no change in circulating GLP-1 levels. Here, we explore the role of the downstream kinase AMP-activated protein kinase (AMPK) in these cells. METHOD Loss of AMPK from proglucagon-expressing cells was achieved using a preproglucagon promoter-driven Cre (iGluCre) to catalyse recombination of floxed alleles of AMPKα1 and α2. Oral and intraperitoneal glucose tolerance were measured using standard protocols. L-cell mass was measured by immunocytochemistry. Hormone and peptide levels were measured by electrochemical-based luminescence detection or radioimmunoassay. RESULTS Recombination with iGluCre led to efficient deletion of AMPK from intestinal L- and pancreatic alpha-cells. In contrast to mice rendered null for LKB1 using the same strategy, mice deleted for AMPK displayed an increase (WT: 0.05 ± 0.01, KO: 0.09±0.02%, p<0.01) in L-cell mass and elevated plasma fasting (WT: 5.62 ± 0.800 pg/ml, KO: 14.5 ± 1.870, p<0.01) and fed (WT: 15.7 ± 1.48pg/ml, KO: 22.0 ± 6.62, p<0.01) GLP-1 levels. Oral, but not intraperitoneal, glucose tolerance was significantly improved by AMPK deletion, whilst insulin and glucagon levels were unchanged despite an increase in alpha to beta cell ratio (WT: 0.23 ± 0.02, KO: 0.33 ± 0.03, p<0.01). CONCLUSION AMPK restricts L-cell growth and GLP-1 secretion to suppress glucose tolerance. Targeted inhibition of AMPK in L-cells may thus provide a new therapeutic strategy in some forms of type 2 diabetes.
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Affiliation(s)
- Sophie R. Sayers
- Department of Cell Biology and Functional Genomics, Imperial College London, London, W12 ONN, United Kingdom
| | - Frank Reimann
- Wellcome Trust - MRC Institute of Metabolic Science, University of Cambridge, Hills Road, Cambridge, CB2 0QQ, United Kingdom
| | - Fiona M. Gribble
- Wellcome Trust - MRC Institute of Metabolic Science, University of Cambridge, Hills Road, Cambridge, CB2 0QQ, United Kingdom
| | - Helen Parker
- Wellcome Trust - MRC Institute of Metabolic Science, University of Cambridge, Hills Road, Cambridge, CB2 0QQ, United Kingdom
| | - Sagen Zac-Varghese
- Department of Investigative Medicine, Imperial College London, London, W12 ONN, United Kingdom
| | - Stephen R. Bloom
- Department of Investigative Medicine, Imperial College London, London, W12 ONN, United Kingdom
| | - Marc Foretz
- INSERM, U1016, Institut Cochin, 75014 Paris, France
- CNRS, UMR8104, 75014 Paris, France
- Université Paris Descartes, Sorbonne Paris Cité, 75014 Paris, France
| | - Benoit Viollet
- INSERM, U1016, Institut Cochin, 75014 Paris, France
- CNRS, UMR8104, 75014 Paris, France
- Université Paris Descartes, Sorbonne Paris Cité, 75014 Paris, France
| | - Guy A. Rutter
- Department of Cell Biology and Functional Genomics, Imperial College London, London, W12 ONN, United Kingdom
- * E-mail:
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Seillier M, Pouyet L, N'Guessan P, Nollet M, Capo F, Guillaumond F, Peyta L, Dumas JF, Varrault A, Bertrand G, Bonnafous S, Tran A, Meur G, Marchetti P, Ravier MA, Dalle S, Gual P, Muller D, Rutter GA, Servais S, Iovanna JL, Carrier A. Defects in mitophagy promote redox-driven metabolic syndrome in the absence of TP53INP1. EMBO Mol Med 2016; 7:802-18. [PMID: 25828351 PMCID: PMC4459819 DOI: 10.15252/emmm.201404318] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The metabolic syndrome covers metabolic abnormalities including obesity and type 2 diabetes (T2D). T2D is characterized by insulin resistance resulting from both environmental and genetic factors. A genome-wide association study (GWAS) published in 2010 identified TP53INP1 as a new T2D susceptibility locus, but a pathological mechanism was not identified. In this work, we show that mice lacking TP53INP1 are prone to redox-driven obesity and insulin resistance. Furthermore, we demonstrate that the reactive oxygen species increase in TP53INP1-deficient cells results from accumulation of defective mitochondria associated with impaired PINK/PARKIN mitophagy. This chronic oxidative stress also favors accumulation of lipid droplets. Taken together, our data provide evidence that the GWAS-identified TP53INP1 gene prevents metabolic syndrome, through a mechanism involving prevention of oxidative stress by mitochondrial homeostasis regulation. In conclusion, this study highlights TP53INP1 as a molecular regulator of redox-driven metabolic syndrome and provides a new preclinical mouse model for metabolic syndrome clinical research.
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Affiliation(s)
- Marion Seillier
- Inserm, U1068, CRCM, Marseille, France Institut Paoli-Calmettes, Marseille, France Aix-Marseille Université, Marseille, France CNRS, UMR7258, CRCM, Marseille, France
| | - Laurent Pouyet
- Inserm, U1068, CRCM, Marseille, France Institut Paoli-Calmettes, Marseille, France Aix-Marseille Université, Marseille, France CNRS, UMR7258, CRCM, Marseille, France
| | - Prudence N'Guessan
- Inserm, U1068, CRCM, Marseille, France Institut Paoli-Calmettes, Marseille, France Aix-Marseille Université, Marseille, France CNRS, UMR7258, CRCM, Marseille, France
| | - Marie Nollet
- Inserm, U1068, CRCM, Marseille, France Institut Paoli-Calmettes, Marseille, France Aix-Marseille Université, Marseille, France CNRS, UMR7258, CRCM, Marseille, France
| | - Florence Capo
- Inserm, U1068, CRCM, Marseille, France Institut Paoli-Calmettes, Marseille, France Aix-Marseille Université, Marseille, France CNRS, UMR7258, CRCM, Marseille, France
| | - Fabienne Guillaumond
- Inserm, U1068, CRCM, Marseille, France Institut Paoli-Calmettes, Marseille, France Aix-Marseille Université, Marseille, France CNRS, UMR7258, CRCM, Marseille, France
| | - Laure Peyta
- Inserm, U1069 Nutrition, Croissance et Cancer (N2C), Tours, France
| | | | - Annie Varrault
- CNRS, UMR5203, Inserm, U661 Universités de Montpellier 1 & 2, IGF, Montpellier, France
| | - Gyslaine Bertrand
- CNRS, UMR5203, Inserm, U661 Universités de Montpellier 1 & 2, IGF, Montpellier, France
| | - Stéphanie Bonnafous
- Inserm, U1065, C3M Team 8 "Hepatic Complications in Obesity", Nice, France Université de Nice-Sophia-Antipolis, Nice, France Centre Hospitalier Universitaire de Nice, Pôle Digestif Hôpital L'Archet, Nice, France
| | - Albert Tran
- Inserm, U1065, C3M Team 8 "Hepatic Complications in Obesity", Nice, France Université de Nice-Sophia-Antipolis, Nice, France Centre Hospitalier Universitaire de Nice, Pôle Digestif Hôpital L'Archet, Nice, France
| | - Gargi Meur
- Cell Biology, Department of Medicine, Imperial College, London, UK
| | - Piero Marchetti
- Islet Cell Laboratory, University of Pisa - Cisanello Hospital, Pisa, Italy
| | - Magalie A Ravier
- CNRS, UMR5203, Inserm, U661 Universités de Montpellier 1 & 2, IGF, Montpellier, France
| | - Stéphane Dalle
- CNRS, UMR5203, Inserm, U661 Universités de Montpellier 1 & 2, IGF, Montpellier, France
| | - Philippe Gual
- Inserm, U1065, C3M Team 8 "Hepatic Complications in Obesity", Nice, France Université de Nice-Sophia-Antipolis, Nice, France Centre Hospitalier Universitaire de Nice, Pôle Digestif Hôpital L'Archet, Nice, France
| | - Dany Muller
- CNRS, UMR5203, Inserm, U661 Universités de Montpellier 1 & 2, IGF, Montpellier, France
| | - Guy A Rutter
- Cell Biology, Department of Medicine, Imperial College, London, UK
| | - Stéphane Servais
- Inserm, U1069 Nutrition, Croissance et Cancer (N2C), Tours, France
| | - Juan L Iovanna
- Inserm, U1068, CRCM, Marseille, France Institut Paoli-Calmettes, Marseille, France Aix-Marseille Université, Marseille, France CNRS, UMR7258, CRCM, Marseille, France
| | - Alice Carrier
- Inserm, U1068, CRCM, Marseille, France Institut Paoli-Calmettes, Marseille, France Aix-Marseille Université, Marseille, France CNRS, UMR7258, CRCM, Marseille, France
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Farnsworth NL, Walter RL, Hemmati A, Westacott MJ, Benninger RKP. Low Level Pro-inflammatory Cytokines Decrease Connexin36 Gap Junction Coupling in Mouse and Human Islets through Nitric Oxide-mediated Protein Kinase Cδ. J Biol Chem 2016; 291:3184-96. [PMID: 26668311 PMCID: PMC4751367 DOI: 10.1074/jbc.m115.679506] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2015] [Revised: 12/07/2015] [Indexed: 11/06/2022] Open
Abstract
Pro-inflammatory cytokines contribute to the decline in islet function during the development of diabetes. Cytokines can disrupt insulin secretion and calcium dynamics; however, the mechanisms underlying this are poorly understood. Connexin36 gap junctions coordinate glucose-induced calcium oscillations and pulsatile insulin secretion across the islet. Loss of gap junction coupling disrupts these dynamics, similar to that observed during the development of diabetes. This study investigates the mechanisms by which pro-inflammatory cytokines mediate gap junction coupling. Specifically, as cytokine-induced NO can activate PKCδ, we aimed to understand the role of PKCδ in modulating cytokine-induced changes in gap junction coupling. Isolated mouse and human islets were treated with varying levels of a cytokine mixture containing TNF-α, IL-1β, and IFN-γ. Islet dysfunction was measured by insulin secretion, calcium dynamics, and gap junction coupling. Modulators of PKCδ and NO were applied to determine their respective roles in modulating gap junction coupling. High levels of cytokines caused cell death and decreased insulin secretion. Low levels of cytokine treatment disrupted calcium dynamics and decreased gap junction coupling, in the absence of disruptions to insulin secretion. Decreases in gap junction coupling were dependent on NO-regulated PKCδ, and altered membrane organization of connexin36. This study defines several mechanisms underlying the disruption to gap junction coupling under conditions associated with the development of diabetes. These mechanisms will allow for greater understanding of islet dysfunction and suggest ways to ameliorate this dysfunction during the development of diabetes.
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Affiliation(s)
- Nikki L Farnsworth
- From the Barbara Davis Center for Childhood Diabetes, Department of Bioengineering, University of Colorado, Anschutz Medical Campus, Aurora, Colorado 80045
| | - Rachelle L Walter
- Department of Bioengineering, University of Colorado, Anschutz Medical Campus, Aurora, Colorado 80045
| | - Alireza Hemmati
- Department of Bioengineering, University of Colorado, Anschutz Medical Campus, Aurora, Colorado 80045
| | - Matthew J Westacott
- Department of Bioengineering, University of Colorado, Anschutz Medical Campus, Aurora, Colorado 80045
| | - Richard K P Benninger
- From the Barbara Davis Center for Childhood Diabetes, Department of Bioengineering, University of Colorado, Anschutz Medical Campus, Aurora, Colorado 80045
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Palanker Musselman L, Fink JL, Baranski TJ. CoA protects against the deleterious effects of caloric overload in Drosophila. J Lipid Res 2016; 57:380-7. [PMID: 26805007 DOI: 10.1194/jlr.m062976] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2015] [Indexed: 01/30/2023] Open
Abstract
We developed a Drosophila model of T2D in which high sugar (HS) feeding leads to insulin resistance. In this model, adipose TG storage is protective against fatty acid toxicity and diabetes. Initial biochemical and gene expression studies suggested that deficiency in CoA might underlie reduced TG synthesis in animals during chronic HS feeding. Focusing on the Drosophila fat body (FB), which is specialized for TG storage and lipolysis, we undertook a series of experiments to test the hypothesis that CoA could protect against the deleterious effects of caloric overload. Quantitative metabolomics revealed a reduction in substrate availability for CoA synthesis in the face of an HS diet. Further reducing CoA synthetic capacity by expressing FB-specific RNAi targeting pantothenate kinase (PK orfumble) or phosphopantothenoylcysteine synthase (PPCS) exacerbated HS-diet-induced accumulation of FFAs. Dietary supplementation with pantothenic acid (vitamin B5, a precursor of CoA) was able to ameliorate HS-diet-induced FFA accumulation and hyperglycemia while increasing TG synthesis. Taken together, our data support a model where free CoA is required to support fatty acid esterification and to protect against the toxicity of HS diets.
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Affiliation(s)
- Laura Palanker Musselman
- Division of Endocrinology, Metabolism, and Lipid Research, Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110
| | - Jill L Fink
- Division of Endocrinology, Metabolism, and Lipid Research, Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110
| | - Thomas J Baranski
- Division of Endocrinology, Metabolism, and Lipid Research, Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110
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130
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Cane MC, Parrington J, Rorsman P, Galione A, Rutter GA. The two pore channel TPC2 is dispensable in pancreatic β-cells for normal Ca²⁺ dynamics and insulin secretion. Cell Calcium 2015; 59:32-40. [PMID: 26769314 PMCID: PMC4751975 DOI: 10.1016/j.ceca.2015.12.004] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2015] [Revised: 12/08/2015] [Accepted: 12/21/2015] [Indexed: 12/21/2022]
Abstract
Ca(2+) signals are central to the stimulation of insulin secretion from pancreatic β-cells by glucose and other agents, including glucagon-like peptide-1 (GLP-1). Whilst Ca(2+) influx through voltage-gated Ca(2+) channels on the plasma membrane is a key trigger for glucose-stimulated secretion, mobilisation of Ca(2+) from acidic stores has been implicated in the control of more localised Ca(2+) changes and membrane potential. Nicotinic acid adenine dinucleotide phosphate (NAADP), generated in β-cells in response to high glucose, is a potent mobiliser of these stores, and has been proposed to act through two pore channels (TPC1 and TPC2, murine gene names Tpcn1 and Tpcn2). Whilst the role of TPC1 in the control of Ca(2+) mobilisation and insulin secretion was recently confirmed, conflicting data exist for TPC2. Here, we used the selective and efficient deleter strain, Ins1Cre to achieve β-cell selective deletion of the Tpcn2 gene in mice. βTpcn2 KO mice displayed normal intraperitoneal and oral glucose tolerance, and glucose-stimulated Ca(2+) dynamics and insulin secretion from islets were similarly normal. GLP-1-induced Ca(2+) increases involved an increase in oscillation frequency from 4.35 to 4.84 per minute (p=0.04) at 8mM glucose, and this increase was unaffected by the absence of Tpcn2. The current data thus indicate that TPC2 is not absolutely required for normal glucose- or incretin-stimulated insulin secretion from the β-cell. Our findings suggest that TPC1, whose expression tended to increase in Tpcn2 null islets, might be sufficient to support normal Ca(2+) dynamics in response to stimulation by nutrients or incretins.
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Affiliation(s)
- Matthew C Cane
- Section of Cell Biology and Functional Genomics, Imperial College London, Du Cane Road, W12 0NN London, UK
| | - John Parrington
- Department of Pharmacology, University of Oxford, Mansfield Road, OX1 3QT, UK
| | - Patrik Rorsman
- The Oxford Centre for Diabetes, Endocrinology and Metabolism, Churchill Hospital, Oxford OX3 7LJ, UK
| | - Antony Galione
- Department of Pharmacology, University of Oxford, Mansfield Road, OX1 3QT, UK
| | - Guy A Rutter
- Section of Cell Biology and Functional Genomics, Imperial College London, Du Cane Road, W12 0NN London, UK.
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131
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Mitchell RK, Hu M, Chabosseau PL, Cane MC, Meur G, Bellomo EA, Carzaniga R, Collinson LM, Li WH, Hodson DJ, Rutter GA. Molecular Genetic Regulation of Slc30a8/ZnT8 Reveals a Positive Association With Glucose Tolerance. Mol Endocrinol 2015; 30:77-91. [PMID: 26584158 PMCID: PMC4995240 DOI: 10.1210/me.2015-1227] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Zinc transporter 8 (ZnT8), encoded by SLC30A8, is chiefly expressed within pancreatic islet cells, where it mediates zinc (Zn2+) uptake into secretory granules. Although a common nonsynonymous polymorphism (R325W), which lowers activity, is associated with increased type 2 diabetes (T2D) risk, rare inactivating mutations in SLC30A8 have been reported to protect against T2D. Here, we generate and characterize new mouse models to explore the impact on glucose homeostasis of graded changes in ZnT8 activity in the β-cell. Firstly, Slc30a8 was deleted highly selectively in these cells using the novel deleter strain, Ins1Cre. The resultant Ins1CreZnT8KO mice displayed significant (P < .05) impairments in glucose tolerance at 10 weeks of age vs littermate controls, and glucose-induced increases in circulating insulin were inhibited in vivo. Although insulin release from Ins1CreZnT8KO islets was normal, Zn2+ release was severely impaired. Conversely, transgenic ZnT8Tg mice, overexpressing the transporter inducibly in the adult β-cell using an insulin promoter-dependent Tet-On system, showed significant (P < .01) improvements in glucose tolerance compared with control animals. Glucose-induced insulin secretion from ZnT8Tg islets was severely impaired, whereas Zn2+ release was significantly enhanced. Our findings demonstrate that glucose homeostasis in the mouse improves as β-cell ZnT8 activity increases, and remarkably, these changes track Zn2+ rather than insulin release in vitro. Activation of ZnT8 in β-cells might therefore provide the basis of a novel approach to treating T2D.
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Affiliation(s)
- Ryan K Mitchell
- Section of Cell Biology and Functional Genomics (R.K.M., M.H., P.L.C., M.C.C., G.M., E.A.B., D.J.H., G.A.R.), Division of Diabetes, Endocrinology and Metabolism, Imperial Centre for Translational and Experimental Medicine, Imperial College London, London W12 0NN, United Kingdom; Electron Microscopy Unit (R.C., L.M.C.), Francis Crick Institute, Lincoln's Inn Fields, London WC2A 3LY, United Kingdom; and Department of Cell Biology and Biochemistry (W.-H.L.), The University of Texas Southwestern Medical Center, Dallas, Texas 75390
| | - Ming Hu
- Section of Cell Biology and Functional Genomics (R.K.M., M.H., P.L.C., M.C.C., G.M., E.A.B., D.J.H., G.A.R.), Division of Diabetes, Endocrinology and Metabolism, Imperial Centre for Translational and Experimental Medicine, Imperial College London, London W12 0NN, United Kingdom; Electron Microscopy Unit (R.C., L.M.C.), Francis Crick Institute, Lincoln's Inn Fields, London WC2A 3LY, United Kingdom; and Department of Cell Biology and Biochemistry (W.-H.L.), The University of Texas Southwestern Medical Center, Dallas, Texas 75390
| | - Pauline L Chabosseau
- Section of Cell Biology and Functional Genomics (R.K.M., M.H., P.L.C., M.C.C., G.M., E.A.B., D.J.H., G.A.R.), Division of Diabetes, Endocrinology and Metabolism, Imperial Centre for Translational and Experimental Medicine, Imperial College London, London W12 0NN, United Kingdom; Electron Microscopy Unit (R.C., L.M.C.), Francis Crick Institute, Lincoln's Inn Fields, London WC2A 3LY, United Kingdom; and Department of Cell Biology and Biochemistry (W.-H.L.), The University of Texas Southwestern Medical Center, Dallas, Texas 75390
| | - Matthew C Cane
- Section of Cell Biology and Functional Genomics (R.K.M., M.H., P.L.C., M.C.C., G.M., E.A.B., D.J.H., G.A.R.), Division of Diabetes, Endocrinology and Metabolism, Imperial Centre for Translational and Experimental Medicine, Imperial College London, London W12 0NN, United Kingdom; Electron Microscopy Unit (R.C., L.M.C.), Francis Crick Institute, Lincoln's Inn Fields, London WC2A 3LY, United Kingdom; and Department of Cell Biology and Biochemistry (W.-H.L.), The University of Texas Southwestern Medical Center, Dallas, Texas 75390
| | - Gargi Meur
- Section of Cell Biology and Functional Genomics (R.K.M., M.H., P.L.C., M.C.C., G.M., E.A.B., D.J.H., G.A.R.), Division of Diabetes, Endocrinology and Metabolism, Imperial Centre for Translational and Experimental Medicine, Imperial College London, London W12 0NN, United Kingdom; Electron Microscopy Unit (R.C., L.M.C.), Francis Crick Institute, Lincoln's Inn Fields, London WC2A 3LY, United Kingdom; and Department of Cell Biology and Biochemistry (W.-H.L.), The University of Texas Southwestern Medical Center, Dallas, Texas 75390
| | - Elisa A Bellomo
- Section of Cell Biology and Functional Genomics (R.K.M., M.H., P.L.C., M.C.C., G.M., E.A.B., D.J.H., G.A.R.), Division of Diabetes, Endocrinology and Metabolism, Imperial Centre for Translational and Experimental Medicine, Imperial College London, London W12 0NN, United Kingdom; Electron Microscopy Unit (R.C., L.M.C.), Francis Crick Institute, Lincoln's Inn Fields, London WC2A 3LY, United Kingdom; and Department of Cell Biology and Biochemistry (W.-H.L.), The University of Texas Southwestern Medical Center, Dallas, Texas 75390
| | - Raffaella Carzaniga
- Section of Cell Biology and Functional Genomics (R.K.M., M.H., P.L.C., M.C.C., G.M., E.A.B., D.J.H., G.A.R.), Division of Diabetes, Endocrinology and Metabolism, Imperial Centre for Translational and Experimental Medicine, Imperial College London, London W12 0NN, United Kingdom; Electron Microscopy Unit (R.C., L.M.C.), Francis Crick Institute, Lincoln's Inn Fields, London WC2A 3LY, United Kingdom; and Department of Cell Biology and Biochemistry (W.-H.L.), The University of Texas Southwestern Medical Center, Dallas, Texas 75390
| | - Lucy M Collinson
- Section of Cell Biology and Functional Genomics (R.K.M., M.H., P.L.C., M.C.C., G.M., E.A.B., D.J.H., G.A.R.), Division of Diabetes, Endocrinology and Metabolism, Imperial Centre for Translational and Experimental Medicine, Imperial College London, London W12 0NN, United Kingdom; Electron Microscopy Unit (R.C., L.M.C.), Francis Crick Institute, Lincoln's Inn Fields, London WC2A 3LY, United Kingdom; and Department of Cell Biology and Biochemistry (W.-H.L.), The University of Texas Southwestern Medical Center, Dallas, Texas 75390
| | - Wen-Hong Li
- Section of Cell Biology and Functional Genomics (R.K.M., M.H., P.L.C., M.C.C., G.M., E.A.B., D.J.H., G.A.R.), Division of Diabetes, Endocrinology and Metabolism, Imperial Centre for Translational and Experimental Medicine, Imperial College London, London W12 0NN, United Kingdom; Electron Microscopy Unit (R.C., L.M.C.), Francis Crick Institute, Lincoln's Inn Fields, London WC2A 3LY, United Kingdom; and Department of Cell Biology and Biochemistry (W.-H.L.), The University of Texas Southwestern Medical Center, Dallas, Texas 75390
| | - David J Hodson
- Section of Cell Biology and Functional Genomics (R.K.M., M.H., P.L.C., M.C.C., G.M., E.A.B., D.J.H., G.A.R.), Division of Diabetes, Endocrinology and Metabolism, Imperial Centre for Translational and Experimental Medicine, Imperial College London, London W12 0NN, United Kingdom; Electron Microscopy Unit (R.C., L.M.C.), Francis Crick Institute, Lincoln's Inn Fields, London WC2A 3LY, United Kingdom; and Department of Cell Biology and Biochemistry (W.-H.L.), The University of Texas Southwestern Medical Center, Dallas, Texas 75390
| | - Guy A Rutter
- Section of Cell Biology and Functional Genomics (R.K.M., M.H., P.L.C., M.C.C., G.M., E.A.B., D.J.H., G.A.R.), Division of Diabetes, Endocrinology and Metabolism, Imperial Centre for Translational and Experimental Medicine, Imperial College London, London W12 0NN, United Kingdom; Electron Microscopy Unit (R.C., L.M.C.), Francis Crick Institute, Lincoln's Inn Fields, London WC2A 3LY, United Kingdom; and Department of Cell Biology and Biochemistry (W.-H.L.), The University of Texas Southwestern Medical Center, Dallas, Texas 75390
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Broichhagen J, Podewin T, Meyer-Berg H, von Ohlen Y, Johnston NR, Jones BJ, Bloom SR, Rutter GA, Hoffmann-Röder A, Hodson DJ, Trauner D. Optical Control of Insulin Secretion Using an Incretin Switch. Angew Chem Int Ed Engl 2015; 54:15565-9. [PMID: 26585495 PMCID: PMC4736448 DOI: 10.1002/anie.201506384] [Citation(s) in RCA: 69] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2015] [Revised: 08/11/2015] [Indexed: 12/30/2022]
Abstract
Incretin mimetics are set to become a mainstay of type 2 diabetes treatment. By acting on the pancreas and brain, they potentiate insulin secretion and induce weight loss to preserve normoglycemia. Despite this, incretin therapy has been associated with off-target effects, including nausea and gastrointestinal disturbance. A novel photoswitchable incretin mimetic based upon the specific glucagon-like peptide-1 receptor (GLP-1R) agonist liraglutide was designed, synthesized, and tested. This peptidic compound, termed LirAzo, possesses an azobenzene photoresponsive element, affording isomer-biased GLP-1R signaling as a result of differential activation of second messenger pathways in response to light. While the trans isomer primarily engages calcium influx, the cis isomer favors cAMP generation. LirAzo thus allows optical control of insulin secretion and cell survival.
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Affiliation(s)
- Johannes Broichhagen
- LMU Munich, Department of Chemistry and Centre for Integrated Protein Science (CIPSM), Butenandtstrasse 5-13, 81377 Munich (Germany)
| | - Tom Podewin
- LMU Munich, Department of Chemistry and Centre for Integrated Protein Science (CIPSM), Butenandtstrasse 5-13, 81377 Munich (Germany)
| | - Helena Meyer-Berg
- LMU Munich, Department of Chemistry and Centre for Integrated Protein Science (CIPSM), Butenandtstrasse 5-13, 81377 Munich (Germany)
| | - Yorrick von Ohlen
- Imperial College London, Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Hammersmith Hospital, Du Cane Road, London W12 0NN (UK)
| | - Natalie R Johnston
- Imperial College London, Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Hammersmith Hospital, Du Cane Road, London W12 0NN (UK)
| | - Ben J Jones
- Imperial College London, Section of Investigative Medicine, Division of Diabetes, Endocrinology and Metabolism, Hammersmith Hospital, Du Cane Road, London W12 0NN (UK)
| | - Stephen R Bloom
- Imperial College London, Section of Investigative Medicine, Division of Diabetes, Endocrinology and Metabolism, Hammersmith Hospital, Du Cane Road, London W12 0NN (UK)
| | - Guy A Rutter
- Imperial College London, Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Hammersmith Hospital, Du Cane Road, London W12 0NN (UK)
| | - Anja Hoffmann-Röder
- LMU Munich, Department of Chemistry and Centre for Integrated Protein Science (CIPSM), Butenandtstrasse 5-13, 81377 Munich (Germany).
| | - David J Hodson
- Imperial College London, Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Hammersmith Hospital, Du Cane Road, London W12 0NN (UK).
| | - Dirk Trauner
- LMU Munich, Department of Chemistry and Centre for Integrated Protein Science (CIPSM), Butenandtstrasse 5-13, 81377 Munich (Germany).
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133
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Broichhagen J, Podewin T, Meyer-Berg H, von Ohlen Y, Johnston NR, Jones BJ, Bloom SR, Rutter GA, Hoffmann-Röder A, Hodson DJ, Trauner D. Optische Kontrolle der Insulinsekretion mit einem Inkretinschalter. Angew Chem Int Ed Engl 2015. [DOI: 10.1002/ange.201506384] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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134
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Abstract
The pancreas produces enzymes with a digestive function and hormones with a metabolic function, which are produced by distinct cell types of acini and islets, respectively. Within these units, secretory cells coordinate their functioning by exchanging information via signals that flow in the intercellular spaces and are generated either at distance (several neural and hormonal inputs) or nearby the pancreatic cells themselves (inputs mediated by membrane ionic-specific channels and by ionic- and metabolite-permeant pannexin channels and connexin "hemichannels"). Pancreatic secretory cells further interact via the extracellular matrix of the pancreas (inputs mediated by integrins) and directly with neighboring cells, by mechanisms that do not require extracellular mediators (inputs mediated by gap and tight junction channels). Here, we review the expression and function of the connexins and pannexins that are expressed by the main secretory cells of the exocrine and endocrine pancreatic cells. Available data show that the patterns of expression of these proteins differ in acini and islets, supporting distinct functions in the physiological secretion of pancreatic enzymes and hormones. Circumstantial evidence further suggests that alterations in the signaling provided by these proteins are involved in pancreatic diseases.
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135
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Bouillon R, Drucker DJ, Ferrannini E, Grinspoon S, Rosen CJ, Zimmet P. The past 10 years-new hormones, new functions, new endocrine organs. Nat Rev Endocrinol 2015; 11:681-6. [PMID: 26323661 DOI: 10.1038/nrendo.2015.142] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Since the publication of the first issue of this journal in November 2005, our understanding of the endocrine system has evolved, with the identification of novel hormones and novel endocrine roles for previously identified molecules. Here, we have asked six of our Advisory Board Members to comment on how these insights have led to the recognition that many organs and tissues that were not widely considered part of the classic endocrine system in the past have important endocrine functions.
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Affiliation(s)
- Roger Bouillon
- Clinical and Experimental Endocrinology, KU Leuven, Herestraat 49 ON1, Box 902, 3000 Leuven, Belgium
| | - Daniel J Drucker
- Mount Sinai Hospital, Lunenfeld-Tanenbaum Research Institute, 600 University Avenue, TCP5-1004 MailBox 39, Toronto, ON M5G 1X5, Canada
| | - Ele Ferrannini
- University of Pisa, Department of Internal Medicine, Via Roma 67, Pisa, PI 56100, Italy
| | - Steven Grinspoon
- Harvard Medical School, MGH Program in Nutritional Metabolism, 5 Longfellow Place, Room 207, Boston, MA 02114, USA
| | - Clifford J Rosen
- Maine Medical Center Research Institute, 81 Research Drive, Scarborough, ME 04074, USA
| | - Paul Zimmet
- Baker IDI Heart and Diabetes Institute, Epidemiology &Clinical Diabetes, 99 Commercial Road, Melbourne, VIC 3004, Australia
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136
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Dolenšek J, Špelič D, Skelin Klemen M, Žalik B, Gosak M, Slak Rupnik M, Stožer A. Membrane Potential and Calcium Dynamics in Beta Cells from Mouse Pancreas Tissue Slices: Theory, Experimentation, and Analysis. SENSORS 2015; 15:27393-419. [PMID: 26516866 PMCID: PMC4701238 DOI: 10.3390/s151127393] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/28/2015] [Revised: 10/11/2015] [Accepted: 10/14/2015] [Indexed: 12/17/2022]
Abstract
Beta cells in the pancreatic islets of Langerhans are precise biological sensors for glucose and play a central role in balancing the organism between catabolic and anabolic needs. A hallmark of the beta cell response to glucose are oscillatory changes of membrane potential that are tightly coupled with oscillatory changes in intracellular calcium concentration which, in turn, elicit oscillations of insulin secretion. Both membrane potential and calcium changes spread from one beta cell to the other in a wave-like manner. In order to assess the properties of the abovementioned responses to physiological and pathological stimuli, the main challenge remains how to effectively measure membrane potential and calcium changes at the same time with high spatial and temporal resolution, and also in as many cells as possible. To date, the most wide-spread approach has employed the electrophysiological patch-clamp method to monitor membrane potential changes. Inherently, this technique has many advantages, such as a direct contact with the cell and a high temporal resolution. However, it allows one to assess information from a single cell only. In some instances, this technique has been used in conjunction with CCD camera-based imaging, offering the opportunity to simultaneously monitor membrane potential and calcium changes, but not in the same cells and not with a reliable cellular or subcellular spatial resolution. Recently, a novel family of highly-sensitive membrane potential reporter dyes in combination with high temporal and spatial confocal calcium imaging allows for simultaneously detecting membrane potential and calcium changes in many cells at a time. Since the signals yielded from both types of reporter dyes are inherently noisy, we have developed complex methods of data denoising that permit for visualization and pixel-wise analysis of signals. Combining the experimental approach of high-resolution imaging with the advanced analysis of noisy data enables novel physiological insights and reassessment of current concepts in unprecedented detail.
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Affiliation(s)
- Jurij Dolenšek
- Institute of Physiology, Faculty of Medicine, University of Maribor, SI-2000 Maribor, Slovenia; E-Mails: (J.D.); (M.S.K.); (M.G.); (M.S.R.)
| | - Denis Špelič
- Faculty of Electrical Engineering and Computer Science, University of Maribor, SI-2000 Maribor, Slovenia; E-Mails: (D.Š.); (B.Ž.)
| | - Maša Skelin Klemen
- Institute of Physiology, Faculty of Medicine, University of Maribor, SI-2000 Maribor, Slovenia; E-Mails: (J.D.); (M.S.K.); (M.G.); (M.S.R.)
| | - Borut Žalik
- Faculty of Electrical Engineering and Computer Science, University of Maribor, SI-2000 Maribor, Slovenia; E-Mails: (D.Š.); (B.Ž.)
- Center for Open Innovation and Research, Core@UM, University of Maribor, SI-2000 Maribor, Slovenia
| | - Marko Gosak
- Institute of Physiology, Faculty of Medicine, University of Maribor, SI-2000 Maribor, Slovenia; E-Mails: (J.D.); (M.S.K.); (M.G.); (M.S.R.)
- Center for Open Innovation and Research, Core@UM, University of Maribor, SI-2000 Maribor, Slovenia
- Department of Physics, Faculty of Natural Sciences and Mathematics, University of Maribor, SI-2000 Maribor, Slovenia
| | - Marjan Slak Rupnik
- Institute of Physiology, Faculty of Medicine, University of Maribor, SI-2000 Maribor, Slovenia; E-Mails: (J.D.); (M.S.K.); (M.G.); (M.S.R.)
- Center for Open Innovation and Research, Core@UM, University of Maribor, SI-2000 Maribor, Slovenia
- Center for Physiology and Pharmacology, Medical University of Vienna, A-1090 Vienna, Austria
| | - Andraž Stožer
- Institute of Physiology, Faculty of Medicine, University of Maribor, SI-2000 Maribor, Slovenia; E-Mails: (J.D.); (M.S.K.); (M.G.); (M.S.R.)
- Center for Open Innovation and Research, Core@UM, University of Maribor, SI-2000 Maribor, Slovenia
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +386-2-2345843
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137
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Loppini A, Braun M, Filippi S, Pedersen MG. Mathematical modeling of gap junction coupling and electrical activity in human β-cells. Phys Biol 2015; 12:066002. [PMID: 26403477 DOI: 10.1088/1478-3975/12/6/066002] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Coordinated insulin secretion is controlled by electrical coupling of pancreatic β-cells due to connexin-36 gap junctions. Gap junction coupling not only synchronizes the heterogeneous β-cell population, but can also modify the electrical behavior of the cells. These phenomena have been widely studied with mathematical models based on data from mouse β-cells. However, it is now known that human β-cell electrophysiology shows important differences to its rodent counterpart, and although human pancreatic islets express connexin-36 and show evidence of β-cell coupling, these aspects have been little investigated in human β-cells. Here we investigate theoretically, the gap junction coupling strength required for synchronizing electrical activity in a small cluster of cells simulated with a recent mathematical model of human β-cell electrophysiology. We find a lower limit for the coupling strength of approximately 20 pS (i.e., normalized to cell size, ∼2 pS pF(-1)) below which spiking electrical activity is asynchronous. To confront this theoretical lower bound with data, we use our model to estimate from an experimental patch clamp recording that the coupling strength is approximately 100-200 pS (10-20 pS pF(-1)), similar to previous estimates in mouse β-cells. We then investigate the role of gap junction coupling in synchronizing and modifying other forms of electrical activity in human β-cell clusters. We find that electrical coupling can prolong the period of rapid bursting electrical activity, and synchronize metabolically driven slow bursting, in particular when the metabolic oscillators are in phase. Our results show that realistic coupling conductances are sufficient to promote synchrony in small clusters of human β-cells as observed experimentally, and provide motivation for further detailed studies of electrical coupling in human pancreatic islets.
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Affiliation(s)
- Alessandro Loppini
- Nonlinear Physics and Mathematical Modeling Laboratory, University Campus Bio-Medico, I-00128, Rome, Italy
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138
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Yesildag B, Bock T, Herrmanns K, Wollscheid B, Stoffel M. Kin of IRRE-like Protein 2 Is a Phosphorylated Glycoprotein That Regulates Basal Insulin Secretion. J Biol Chem 2015; 290:25891-906. [PMID: 26324709 DOI: 10.1074/jbc.m115.684704] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2015] [Indexed: 12/17/2022] Open
Abstract
Direct interactions among pancreatic β-cells via cell surface proteins inhibit basal and enhance stimulated insulin secretion. Here, we functionally and biochemically characterized Kirrel2, an immunoglobulin superfamily protein with β-cell-specific expression in the pancreas. Our results show that Kirrel2 is a phosphorylated glycoprotein that co-localizes and interacts with the adherens junction proteins E-cadherin and β-catenin in MIN6 cells. We further demonstrate that the phosphosites Tyr(595-596) are functionally relevant for the regulation of Kirrel2 stability and localization. Analysis of the extracellular and intracellular domains of Kirrel2 revealed that it is cleaved and shed from MIN6 cells and that the remaining membrane spanning cytoplasmic domain is processed by γ-secretase complex. Kirrel2 knockdown with RNA interference in MIN6 cells and ablation of Kirrel2 from mice with genetic deletion resulted in increased basal insulin secretion from β-cells, with no immediate influence on stimulated insulin secretion, total insulin content, or whole body glucose metabolism. Our results show that in pancreatic β-cells Kirrel2 localizes to adherens junctions, is regulated by multiple post-translational events, including glycosylation, extracellular cleavage, and phosphorylation, and engages in the regulation of basal insulin secretion.
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Affiliation(s)
- Burcak Yesildag
- From the Department of Biology, Institute of Molecular Health Sciences, Swiss Federal Institute of Technology (ETH) Zurich, Otto-Stern-Weg 7, 8093 Zurich
| | - Thomas Bock
- the Department of Health Sciences and Technology, Institute of Molecular Systems Biology, Swiss Federal Institute of Technology Zurich, Auguste-Piccard-Hof 1, 8093 Zurich, and
| | - Karolin Herrmanns
- From the Department of Biology, Institute of Molecular Health Sciences, Swiss Federal Institute of Technology (ETH) Zurich, Otto-Stern-Weg 7, 8093 Zurich
| | - Bernd Wollscheid
- the Department of Health Sciences and Technology, Institute of Molecular Systems Biology, Swiss Federal Institute of Technology Zurich, Auguste-Piccard-Hof 1, 8093 Zurich, and
| | - Markus Stoffel
- From the Department of Biology, Institute of Molecular Health Sciences, Swiss Federal Institute of Technology (ETH) Zurich, Otto-Stern-Weg 7, 8093 Zurich, the Department of Health Sciences and Technology, Institute of Molecular Systems Biology, Swiss Federal Institute of Technology Zurich, Auguste-Piccard-Hof 1, 8093 Zurich, and the Faculty of Medicine, University of Zurich, 8091 Zurich, Switzerland
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Striegel DA, Hara M, Periwal V. The Beta Cell in Its Cluster: Stochastic Graphs of Beta Cell Connectivity in the Islets of Langerhans. PLoS Comput Biol 2015; 11:e1004423. [PMID: 26266953 PMCID: PMC4534467 DOI: 10.1371/journal.pcbi.1004423] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2014] [Accepted: 07/02/2015] [Indexed: 12/25/2022] Open
Abstract
Pancreatic islets of Langerhans consist of endocrine cells, primarily α, β and δ cells, which secrete glucagon, insulin, and somatostatin, respectively, to regulate plasma glucose. β cells form irregular locally connected clusters within islets that act in concert to secrete insulin upon glucose stimulation. Due to the central functional significance of this local connectivity in the placement of β cells in an islet, it is important to characterize it quantitatively. However, quantification of the seemingly stochastic cytoarchitecture of β cells in an islet requires mathematical methods that can capture topological connectivity in the entire β-cell population in an islet. Graph theory provides such a framework. Using large-scale imaging data for thousands of islets containing hundreds of thousands of cells in human organ donor pancreata, we show that quantitative graph characteristics differ between control and type 2 diabetic islets. Further insight into the processes that shape and maintain this architecture is obtained by formulating a stochastic theory of β-cell rearrangement in whole islets, just as the normal equilibrium distribution of the Ornstein-Uhlenbeck process can be viewed as the result of the interplay between a random walk and a linear restoring force. Requiring that rearrangements maintain the observed quantitative topological graph characteristics strongly constrained possible processes. Our results suggest that β-cell rearrangement is dependent on its connectivity in order to maintain an optimal cluster size in both normal and T2D islets. High or low blood glucose levels are detrimental to human health. The hormone-secreting cells primarily responsible for maintaining glucose at physiologically appropriate levels are embedded in small clusters within the pancreas, the so-called islets of Langerhans. These islets have an irregular arrangement of cells, β cells that secrete insulin, α cells that secrete glucagon, and other cells with less well-understood functions. While the arrangement of β cells is irregular, these cells need to be touching for the islet to respond to glucose with insulin secretion. We first use a mathematical formalism called graph theory to show that cell arrangements in islets from diabetic and control donors are significantly different. The question we then address is: Is there some set of moves of islet cells that will preserve the observed arrangement? The aim is to gain insight into the biological processes by which islets are formed and maintained. We find moves on β-cell graphs that leave the same significant aspects of cell arrangements unchanged. These moves turn out to be severely restricted, and suggest that β cells may prefer to move from larger clusters but can move to a cluster of any size, possibly to maximize their exposure to blood vessels.
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Affiliation(s)
- Deborah A. Striegel
- Laboratory of Biological Modeling, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Manami Hara
- Department of Medicine, University of Chicago, Chicago, Illinois, United States of America
| | - Vipul Periwal
- Laboratory of Biological Modeling, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
- * E-mail:
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140
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DeFronzo RA, Ferrannini E, Groop L, Henry RR, Herman WH, Holst JJ, Hu FB, Kahn CR, Raz I, Shulman GI, Simonson DC, Testa MA, Weiss R. Type 2 diabetes mellitus. Nat Rev Dis Primers 2015; 1:15019. [PMID: 27189025 DOI: 10.1038/nrdp.2015.19] [Citation(s) in RCA: 1057] [Impact Index Per Article: 117.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Type 2 diabetes mellitus (T2DM) is an expanding global health problem, closely linked to the epidemic of obesity. Individuals with T2DM are at high risk for both microvascular complications (including retinopathy, nephropathy and neuropathy) and macrovascular complications (such as cardiovascular comorbidities), owing to hyperglycaemia and individual components of the insulin resistance (metabolic) syndrome. Environmental factors (for example, obesity, an unhealthy diet and physical inactivity) and genetic factors contribute to the multiple pathophysiological disturbances that are responsible for impaired glucose homeostasis in T2DM. Insulin resistance and impaired insulin secretion remain the core defects in T2DM, but at least six other pathophysiological abnormalities contribute to the dysregulation of glucose metabolism. The multiple pathogenetic disturbances present in T2DM dictate that multiple antidiabetic agents, used in combination, will be required to maintain normoglycaemia. The treatment must not only be effective and safe but also improve the quality of life. Several novel medications are in development, but the greatest need is for agents that enhance insulin sensitivity, halt the progressive pancreatic β-cell failure that is characteristic of T2DM and prevent or reverse the microvascular complications. For an illustrated summary of this Primer, visit: http://go.nature.com/V2eGfN.
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Affiliation(s)
- Ralph A DeFronzo
- Diabetes Division, Department of Medicine, University of Texas Health Science Center, South Texas Veterans Health Care System and Texas Diabetes Institute, 701 S. Zarzamoro, San Antonio, Texas 78207, USA
| | | | - Leif Groop
- Department of Clinical Science Malmoe, Diabetes &Endocrinology, Lund University Diabetes Centre, Lund, Sweden
| | - Robert R Henry
- University of California, San Diego, Section of Diabetes, Endocrinology &Metabolism, Center for Metabolic Research, VA San Diego Healthcare System, San Diego, California, USA
| | | | | | - Frank B Hu
- Department of Nutrition, Harvard T.H. Chan School of Public Health and Department of Epidemiology, Harvard T.H. Chan School of Public Health and Channing Division of Network Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - C Ronald Kahn
- Harvard Medical School and Joslin Diabetes Center, Boston, Massachusetts, USA
| | - Itamar Raz
- Diabetes Unit, Division of Internal Medicine, Hadassah Hebrew University Hospital, Jerusalem, Israel
| | - Gerald I Shulman
- Howard Hughes Medical Institute and the Departments of Internal Medicine and Cellular &Molecular Physiology, Yale University School of Medicine, New Haven, Connecticut, USA
| | - Donald C Simonson
- Division of Endocrinology, Diabetes and Hypertension, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - Marcia A Testa
- Department of Biostatistics, Harvard T.H. Chan School of Public Health, Boston, Massachusetts, USA
| | - Ram Weiss
- Department of Human Metabolism and Nutrition, Braun School of Public Health, Hebrew University, Jerusalem, Israel
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141
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Li D, Huang Z, Chen S, Hu Z, Li WH. GLP-1 Receptor Mediated Targeting of a Fluorescent Zn(2+) Sensor to Beta Cell Surface for Imaging Insulin/Zn(2+) Release. Bioconjug Chem 2015; 26:1443-50. [PMID: 26121325 DOI: 10.1021/acs.bioconjchem.5b00332] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The pancreatic islet beta cell plays an essential role in maintaining the normal blood glucose level by releasing insulin. Loss of functional beta cell mass leads to diabetes—a disease affecting ∼9% of the population worldwide. There has been great interest and intense effort in developing imaging probes for monitoring islet beta cells, and glucagon-like peptide-1 receptor (GLP-1R) has emerged as a valuable biomarker for targeting beta cells. However, efforts thus far in GLP-1R mediated beta cell labeling and imaging has largely, if not exclusively, focused on developing imaging probes for monitoring beta cell mass, and few studies have investigated imaging beta cell function (insulin release) through GLP-1R. We now report the design and synthesis of a bioconjugate, ZIMIR-Ex4(9-39), that consists of a fluorescent Zn(2+) sensor and a truncated exendin 4 peptide for imaging insulin/Zn(2+) release in islet beta cells. In vitro, the conjugate bound to Zn(2+) with high affinity and displayed a robust fluorescence enhancement upon Zn(2+) chelation. When added to beta cells at submicromolar concentration, ZIMIR-Ex4(9-39) rapidly labeled cell surface in minutes to report the dynamics of insulin/Zn(2+) release with high spatiotemporal resolution. Future explorations of this approach may lead to probes for tracking beta cell function using different imaging modalities.
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Affiliation(s)
- Daliang Li
- †Departments of Cell Biology and of Biochemistry, ‡Children's Medical Center Research Institute, University of Texas Southwestern Medical Center, 6000 Harry Hines Boulevard, Dallas, Texas 75390-9039, United States
| | - ZhiJiang Huang
- †Departments of Cell Biology and of Biochemistry, ‡Children's Medical Center Research Institute, University of Texas Southwestern Medical Center, 6000 Harry Hines Boulevard, Dallas, Texas 75390-9039, United States
| | - Shiuhwei Chen
- †Departments of Cell Biology and of Biochemistry, ‡Children's Medical Center Research Institute, University of Texas Southwestern Medical Center, 6000 Harry Hines Boulevard, Dallas, Texas 75390-9039, United States
| | - Zeping Hu
- †Departments of Cell Biology and of Biochemistry, ‡Children's Medical Center Research Institute, University of Texas Southwestern Medical Center, 6000 Harry Hines Boulevard, Dallas, Texas 75390-9039, United States
| | - Wen-hong Li
- †Departments of Cell Biology and of Biochemistry, ‡Children's Medical Center Research Institute, University of Texas Southwestern Medical Center, 6000 Harry Hines Boulevard, Dallas, Texas 75390-9039, United States
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142
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Swisa A, Granot Z, Tamarina N, Sayers S, Bardeesy N, Philipson L, Hodson DJ, Wikstrom JD, Rutter GA, Leibowitz G, Glaser B, Dor Y. Loss of Liver Kinase B1 (LKB1) in Beta Cells Enhances Glucose-stimulated Insulin Secretion Despite Profound Mitochondrial Defects. J Biol Chem 2015; 290:20934-20946. [PMID: 26139601 PMCID: PMC4543653 DOI: 10.1074/jbc.m115.639237] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2015] [Indexed: 12/25/2022] Open
Abstract
The tumor suppressor liver kinase B1 (LKB1) is an important regulator of pancreatic β cell biology. LKB1-dependent phosphorylation of distinct AMPK (adenosine monophosphate-activated protein kinase) family members determines proper β cell polarity and restricts β cell size, total β cell mass, and glucose-stimulated insulin secretion (GSIS). However, the full spectrum of LKB1 effects and the mechanisms involved in the secretory phenotype remain incompletely understood. We report here that in the absence of LKB1 in β cells, GSIS is dramatically and persistently improved. The enhancement is seen both in vivo and in vitro and cannot be explained by altered cell polarity, increased β cell number, or increased insulin content. Increased secretion does require membrane depolarization and calcium influx but appears to rely mostly on a distal step in the secretion pathway. Surprisingly, enhanced GSIS is seen despite profound defects in mitochondrial structure and function in LKB1-deficient β cells, expected to greatly diminish insulin secretion via the classic triggering pathway. Thus LKB1 is essential for mitochondrial homeostasis in β cells and in parallel is a powerful negative regulator of insulin secretion. This study shows that β cells can be manipulated to enhance GSIS to supra-normal levels even in the face of defective mitochondria and without deterioration over months.
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Affiliation(s)
- Avital Swisa
- Department of Developmental Biology and Cancer Research, The Institute for Medical Research Israel-Canada, The Hebrew University-Hadassah Medical School, Jerusalem 91120, Israel
| | - Zvi Granot
- Department of Developmental Biology and Cancer Research, The Institute for Medical Research Israel-Canada, The Hebrew University-Hadassah Medical School, Jerusalem 91120, Israel
| | - Natalia Tamarina
- Department of Medicine, University of Chicago, Chicago, Illinois 60637
| | - Sophie Sayers
- Section of Cell Biology and Functional Genomics, Division of Diabetes Endocrinology and Metabolism, Department of Medicine, Imperial College London, SW7 2AZ, London, United Kingdom
| | - Nabeel Bardeesy
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Boston, Massachusetts 02114
| | - Louis Philipson
- Department of Medicine, University of Chicago, Chicago, Illinois 60637
| | - David J Hodson
- Section of Cell Biology and Functional Genomics, Division of Diabetes Endocrinology and Metabolism, Department of Medicine, Imperial College London, SW7 2AZ, London, United Kingdom
| | - Jakob D Wikstrom
- Endocrinology and Metabolism Service, Department of Internal Medicine, Hadassah-Hebrew University Medical Center, Jerusalem 91120, Israel; Unit of Dermatology and Venereology, Department of Medicine, Karolinska Institutet, Karolinska University Hospital, 171 77 Stockholm, Sweden
| | - Guy A Rutter
- Section of Cell Biology and Functional Genomics, Division of Diabetes Endocrinology and Metabolism, Department of Medicine, Imperial College London, SW7 2AZ, London, United Kingdom
| | - Gil Leibowitz
- Endocrinology and Metabolism Service, Department of Internal Medicine, Hadassah-Hebrew University Medical Center, Jerusalem 91120, Israel
| | - Benjamin Glaser
- Endocrinology and Metabolism Service, Department of Internal Medicine, Hadassah-Hebrew University Medical Center, Jerusalem 91120, Israel
| | - Yuval Dor
- Department of Developmental Biology and Cancer Research, The Institute for Medical Research Israel-Canada, The Hebrew University-Hadassah Medical School, Jerusalem 91120, Israel.
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143
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Gosak M, Stožer A, Markovič R, Dolenšek J, Marhl M, Rupnik MS, Perc M. The relationship between node degree and dissipation rate in networks of diffusively coupled oscillators and its significance for pancreatic beta cells. CHAOS (WOODBURY, N.Y.) 2015; 25:073115. [PMID: 26232966 DOI: 10.1063/1.4926673] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Self-sustained oscillatory dynamics is a motion along a stable limit cycle in the phase space, and it arises in a wide variety of mechanical, electrical, and biological systems. Typically, oscillations are due to a balance between energy dissipation and generation. Their stability depends on the properties of the attractor, in particular, its dissipative characteristics, which in turn determine the flexibility of a given dynamical system. In a network of oscillators, the coupling additionally contributes to the dissipation, and hence affects the robustness of the oscillatory solution. Here, we therefore investigate how a heterogeneous network structure affects the dissipation rate of individual oscillators. First, we show that in a network of diffusively coupled oscillators, the dissipation is a linearly decreasing function of the node degree, and we demonstrate this numerically by calculating the average divergence of coupled Hopf oscillators. Subsequently, we use recordings of intracellular calcium dynamics in pancreatic beta cells in mouse acute tissue slices and the corresponding functional connectivity networks for an experimental verification of the presented theory. We use methods of nonlinear time series analysis to reconstruct the phase space and calculate the sum of Lyapunov exponents. Our analysis reveals a clear tendency of cells with a higher degree, that is, more interconnected cells, having more negative values of divergence, thus confirming our theoretical predictions. We discuss these findings in the context of energetic aspects of signaling in beta cells and potential risks for pathological changes in the tissue.
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Affiliation(s)
- Marko Gosak
- Institute of Physiology, Faculty of Medicine, University of Maribor, SI-2000 Maribor, Slovenia
| | - Andraž Stožer
- Institute of Physiology, Faculty of Medicine, University of Maribor, SI-2000 Maribor, Slovenia
| | - Rene Markovič
- Department of Physics, Faculty of Natural Sciences and Mathematics, University of Maribor, SI-2000 Maribor, Slovenia
| | - Jurij Dolenšek
- Institute of Physiology, Faculty of Medicine, University of Maribor, SI-2000 Maribor, Slovenia
| | - Marko Marhl
- Department of Physics, Faculty of Natural Sciences and Mathematics, University of Maribor, SI-2000 Maribor, Slovenia
| | - Marjan Slak Rupnik
- Institute of Physiology, Faculty of Medicine, University of Maribor, SI-2000 Maribor, Slovenia
| | - Matjaž Perc
- Department of Physics, Faculty of Natural Sciences and Mathematics, University of Maribor, SI-2000 Maribor, Slovenia
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144
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Soedling H, Hodson DJ, Adrianssens AE, Gribble FM, Reimann F, Trapp S, Rutter GA. Limited impact on glucose homeostasis of leptin receptor deletion from insulin- or proglucagon-expressing cells. Mol Metab 2015; 4:619-30. [PMID: 26413468 PMCID: PMC4563029 DOI: 10.1016/j.molmet.2015.06.007] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/02/2015] [Accepted: 06/12/2015] [Indexed: 01/07/2023] Open
Abstract
AIMS/HYPOTHESIS The adipose tissue-derived hormone leptin plays an important role in the maintenance of body weight and glucose homeostasis. Leptin mediates its effects by interaction with leptin receptors (LepRb), which are highly expressed in the hypothalamus and other brain centres, and at lower levels in the periphery. Previous studies have used relatively promiscuous or inefficient Cre deleter strains, respectively, to explore the roles of LepR in pancreatic β and α cells. Here, we use two newly-developed Cre lines to explore the role of leptin signalling in insulin and proglucagon-expressing cells. METHODS Leptin receptor expression was measured in isolated mouse islets and highly-purified islet cells by RNASeq and quantitative RT-PCR. Mice lacking leptin signalling in pancreatic β, or in α and other proglucagon-expressing cells, were generated using Ins1Cre- or iGluCre-mediated recombination respectively of flox'd leptin receptor alleles. In vivo glucose homeostasis, changes in body weight, pancreatic histology and hormone secretion from isolated islets were assessed using standard techniques. RESULTS Leptin receptor mRNA levels were at or below the level of detection in wild-type adult mouse isolated islets and purified cells, and leptin signalling to Stat3 phosphorylation was undetectable. Whereas male mice further deleted for leptin receptors in β cells exhibited no abnormalities in glucose tolerance up to 16 weeks of age, females transiently displayed improved glucose tolerance at 8 weeks (11.2 ± 3.2% decrease in area under curve; p < 0.05), and improved (39.0 ± 13.0%, P < 0.05) glucose-stimulated insulin secretion in vitro. No differences were seen between genotypes in body weight, fasting glucose or β/α cell ratio. Deletion of LepR from α-cells, a minority of β cells, and a subset of proglucagon-expressing cells in the brain, exerted no effects on body weight, glucose or insulin tolerance, nor on pancreatic hormone secretion assessed in vivo and in vitro. CONCLUSIONS/INTERPRETATION The use here of a highly selective Cre recombinase indicates that leptin signalling plays a relatively minor, age- and sex-dependent role in the control of β cell function in the mouse. No in vivo role for leptin receptors on α cells, nor in other proglucagon-expressing cells, was detected in this study.
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Affiliation(s)
- Helen Soedling
- Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Imperial College London, du Cane Road, London W12 0NN, UK
| | - David J Hodson
- Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Imperial College London, du Cane Road, London W12 0NN, UK
| | | | - Fiona M Gribble
- University of Cambridge Metabolic Research Laboratories, Cambridge, UK
| | - Frank Reimann
- University of Cambridge Metabolic Research Laboratories, Cambridge, UK
| | - Stefan Trapp
- Centre for Cardiovascular and Metabolic Neuroscience, Department of Neuroscience, Physiology & Pharmacology, University College London, London, UK
| | - Guy A Rutter
- Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Imperial College London, du Cane Road, London W12 0NN, UK
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145
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Lebreton F, Pirog A, Belouah I, Bosco D, Berney T, Meda P, Bornat Y, Catargi B, Renaud S, Raoux M, Lang J. Slow potentials encode intercellular coupling and insulin demand in pancreatic beta cells. Diabetologia 2015; 58:1291-9. [PMID: 25788295 DOI: 10.1007/s00125-015-3558-z] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/07/2014] [Accepted: 02/23/2015] [Indexed: 11/24/2022]
Abstract
AIMS/HYPOTHESIS Ion fluxes constitute a major integrative signal in beta cells that leads to insulin secretion and regulation of gene expression. Understanding these electrical signals is important for deciphering the endogenous algorithms used by islets to attain homeostasis and for the design of new sensors for monitoring beta cell function. METHODS Mouse and human islets were cultured on multielectrode arrays (MEAs) for 3-13 days. Extracellular electrical activities received on each electrode were continuously amplified and recorded for offline characterisation. RESULTS Differential band-pass filtering of MEA recordings of mouse islets showed two extracellular voltage waveforms: action potentials (lasting 40-60 ms) and very robust slow potentials (SPs, lasting 800-1,500 ms), the latter of which have not been described previously. The frequency of SPs directly correlated with glucose concentration, peaked at 10 mmol/l glucose and was further augmented by picomolar concentrations of glucagon-like peptide-1. SPs required the closure of ATP-dependent potassium channels as they were induced by glucose or glibenclamide but were not elicited by KCl-induced depolarisation. Pharmacological tools and the use of beta cell specific knockout mice showed that SPs reflected cell coupling via connexin 36. Moreover, increasing and decreasing glucose ramps showed hysteresis with reduced glucose sensitivity during the decreasing phase. SPs were also observed in human islets and could be continuously recorded over 24 h. CONCLUSIONS/INTERPRETATION This novel electrical signature reflects the syncytial function of the islets and is specific to beta cells. Moreover, the observed hysteresis provides evidence for an endogenous algorithm naturally present in islets to protect against hypoglycaemia.
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Affiliation(s)
- Fanny Lebreton
- CNRS UMR 5248, Chimie et Biologie des Membranes et Nano-objets, Université de Bordeaux, Batiment B14, Allée Geoffroy St Hilaire, CS90063, 33615, Pessac, France
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146
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Ma RCW, Xu G. Incretin action on bone: An added benefit? J Diabetes Investig 2015; 6:267-8. [PMID: 25969710 PMCID: PMC4420557 DOI: 10.1111/jdi.12273] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/19/2014] [Revised: 07/30/2014] [Accepted: 07/31/2014] [Indexed: 11/27/2022] Open
Affiliation(s)
- Ronald C W Ma
- Department of Medicine and Therapeutics, The Chinese University of Hong Kong Shatin, New Territories ; Hong Kong Institute of Diabetes and Obesity, The Chinese University of Hong Kong Shatin, New Territories
| | - Gang Xu
- Hong Kong Institute of Diabetes and Obesity, The Chinese University of Hong Kong Shatin, New Territories ; School of Chinese Medicine, Hong Kong Baptist University Hong Kong
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147
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Pancreatic β-cell identity, glucose sensing and the control of insulin secretion. Biochem J 2015; 466:203-18. [PMID: 25697093 DOI: 10.1042/bj20141384] [Citation(s) in RCA: 239] [Impact Index Per Article: 26.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Insulin release from pancreatic β-cells is required to maintain normal glucose homoeostasis in man and many other animals. Defective insulin secretion underlies all forms of diabetes mellitus, a disease currently reaching epidemic proportions worldwide. Although the destruction of β-cells is responsible for Type 1 diabetes (T1D), both lowered β-cell mass and loss of secretory function are implicated in Type 2 diabetes (T2D). Emerging results suggest that a functional deficiency, involving de-differentiation of the mature β-cell towards a more progenitor-like state, may be an important driver for impaired secretion in T2D. Conversely, at least in rodents, reprogramming of islet non-β to β-cells appears to occur spontaneously in models of T1D, and may occur in man. In the present paper, we summarize the biochemical properties which define the 'identity' of the mature β-cell as a glucose sensor par excellence. In particular, we discuss the importance of suppressing a group of 11 'disallowed' housekeeping genes, including Ldha and the monocarboxylate transporter Mct1 (Slc16a1), for normal nutrient sensing. We then survey the changes in the expression and/or activity of β-cell-enriched transcription factors, including FOXO1, PDX1, NKX6.1, MAFA and RFX6, as well as non-coding RNAs, which may contribute to β-cell de-differentiation and functional impairment in T2D. The relevance of these observations for the development of new approaches to treat T1D and T2D is considered.
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148
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Li D, Liu L, Li WH. Genetic targeting of a small fluorescent zinc indicator to cell surface for monitoring zinc secretion. ACS Chem Biol 2015; 10:1054-63. [PMID: 25572404 DOI: 10.1021/cb5007536] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Numerous mammalian cells contain Zn2+ in their secretory granules. During secretion, Zn2+ is coreleased with granular cargos into extracellular medium so Zn2+ serves as a convenient surrogate marker for tracking the dynamics of secretion. Fluorescent Zn2+ sensors that can be selectively targeted to cells of interest would be invaluable tools for imaging Zn2+ release in multicellular systems including tissues and live animals. Exploiting the HaloTag labeling technology and using an optimized linker, we have engineered a fluorescent Zn2+ indicator that displayed a 15-fold fluorescence enhancement upon Zn2+ binding while reacting efficiently with a HaloTag enzyme in a cellular environment. Two-color imaging of ZIMIR-HaloTag and a red-emitting calcium indicator in pancreatic islet beta cells demonstrated that photoactivation of a channelrhodopsin was able to induce exocytosis of Zn2+/insulin granules and revealed heterogeneity in secretory activity along the cell membrane that was uncoupled from cellular Ca2+ activity. This integrated photonic approach for imaging and controlling the release of large dense core granules provides exquisite cellular selectivity and should facilitate future studies of stimulus-secretion coupling and paracrine signaling in secretory cells.
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Affiliation(s)
- Daliang Li
- Departments of Cell Biology
and Biochemistry, University of Texas Southwestern Medical Center, 6000
Harry Hines Boulevard, Dallas, Texas 75390-9039, United States
| | - Lin Liu
- Departments of Cell Biology
and Biochemistry, University of Texas Southwestern Medical Center, 6000
Harry Hines Boulevard, Dallas, Texas 75390-9039, United States
| | - Wen-Hong Li
- Departments of Cell Biology
and Biochemistry, University of Texas Southwestern Medical Center, 6000
Harry Hines Boulevard, Dallas, Texas 75390-9039, United States
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149
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Kenty JHR, Melton DA. Testing pancreatic islet function at the single cell level by calcium influx with associated marker expression. PLoS One 2015; 10:e0122044. [PMID: 25853429 PMCID: PMC4390334 DOI: 10.1371/journal.pone.0122044] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2014] [Accepted: 02/09/2015] [Indexed: 01/06/2023] Open
Abstract
Studying the response of islet cells to glucose stimulation is important for understanding cell function in healthy and disease states. Most functional assays are performed on whole islets or cell populations, resulting in averaged observations and loss of information at the single cell level. We demonstrate methods to examine calcium fluxing in individual cells of intact islets in response to multiple glucose challenges. Wild-type mouse islets predominantly contained cells that responded to three (out of three) sequential high glucose challenges, whereas cells of diabetic islets (db/db or NOD) responded less frequently or not at all. Imaged islets were also immunostained for endocrine markers to associate the calcium flux profile of individual cells with gene expression. Wild-type mouse islet cells that robustly fluxed calcium expressed β cell markers (INS/NKX6.1), whereas islet cells that inversely fluxed at low glucose expressed α cell markers (GCG). Diabetic mouse islets showed a higher proportion of dysfunctional β cells that responded poorly to glucose challenges. Most of the failed calcium influx responses in β cells were observed in the second and third high glucose challenges, emphasizing the importance of multiple sequential glucose challenges for assessing the full function of islet cells. Human islet cells were also assessed and showed functional α and β cells. This approach to analyze islet responses to multiple glucose challenges in correlation with gene expression assays expands the understanding of β cell function and the diseased state.
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Affiliation(s)
- Jennifer H. R. Kenty
- Department of Stem Cell and Regenerative Biology, Harvard University, Harvard Stem Cell Institute, Cambridge, Massachusetts, United States of America
| | - Douglas A. Melton
- Department of Stem Cell and Regenerative Biology, Harvard University, Harvard Stem Cell Institute, Cambridge, Massachusetts, United States of America
- * E-mail:
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150
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Tian G, Sol ERM, Xu Y, Shuai H, Tengholm A. Impaired cAMP generation contributes to defective glucose-stimulated insulin secretion after long-term exposure to palmitate. Diabetes 2015; 64:904-15. [PMID: 25281428 DOI: 10.2337/db14-1036] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Chronic palmitate exposure impairs glucose-stimulated insulin secretion and other aspects of β-cell function, but the underlying mechanisms are not known. Using various live-cell fluorescence imaging approaches, we show here that long-term palmitate treatment influences cAMP signaling in pancreatic β-cells. Glucose stimulation of mouse and human β-cells induced oscillations of the subplasma-membrane cAMP concentration, but after 48 h exposure to palmitate, most β-cells failed to increase cAMP in response to glucose. In contrast, GLP-1-triggered cAMP formation and glucose- and depolarization-induced increases in cytoplasmic Ca2+ concentration were unaffected by the fatty acid treatment. Insulin secretion from control β-cells was pulsatile, but the response deteriorated after long-term palmitate exposure. Palmitate-treated mouse islets showed reduced expression of adenylyl cyclase 9, and knockdown of this protein in insulinoma cells reduced the glucose-stimulated cAMP response and insulin secretion. We conclude that impaired glucose-induced generation of cAMP is an important determinant of defective insulin secretion after chronic palmitate exposure.
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Affiliation(s)
- Geng Tian
- Binzhou Medical University, Yantai, Shandong, China Department of Medical Cell Biology, Uppsala University Biomedical Centre, Uppsala, Sweden
| | - E-ri Maria Sol
- Department of Medical Cell Biology, Uppsala University Biomedical Centre, Uppsala, Sweden
| | - Yunjian Xu
- Department of Medical Cell Biology, Uppsala University Biomedical Centre, Uppsala, Sweden
| | - Hongyan Shuai
- Department of Medical Cell Biology, Uppsala University Biomedical Centre, Uppsala, Sweden
| | - Anders Tengholm
- Department of Medical Cell Biology, Uppsala University Biomedical Centre, Uppsala, Sweden
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