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Ding J, Nguyen AT, Lohman K, Hensley MT, Parker D, Hou L, Taylor J, Voora D, Sawyer JK, Boudyguina E, Bancks MP, Bertoni A, Pankow JS, Rotter JI, Goodarzi MO, Tracy RP, Murdoch DM, Duprez D, Rich SS, Psaty BM, Siscovick D, Newgard CB, Herrington D, Hoeschele I, Shea S, Stein JH, Patel M, Post W, Jacobs D, Parks JS, Liu Y. LXR signaling pathways link cholesterol metabolism with risk for prediabetes and diabetes. J Clin Invest 2024; 134:e173278. [PMID: 38747290 PMCID: PMC11093600 DOI: 10.1172/jci173278] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2023] [Accepted: 03/20/2024] [Indexed: 05/19/2024] Open
Abstract
BACKGROUNDPreclinical studies suggest that cholesterol accumulation leads to insulin resistance. We previously reported that alterations in a monocyte cholesterol metabolism transcriptional network (CMTN) - suggestive of cellular cholesterol accumulation - were cross-sectionally associated with obesity and type 2 diabetes (T2D). Here, we sought to determine whether the CMTN alterations independently predict incident prediabetes/T2D risk, and correlate with cellular cholesterol accumulation.METHODSMonocyte mRNA expression of 11 CMTN genes was quantified among 934 Multi-Ethnic Study of Atherosclerosis (MESA) participants free of prediabetes/T2D; cellular cholesterol was measured in a subset of 24 monocyte samples.RESULTSDuring a median 6-year follow-up, lower expression of 3 highly correlated LXR target genes - ABCG1 and ABCA1 (cholesterol efflux) and MYLIP (cholesterol uptake suppression) - and not other CMTN genes, was significantly associated with higher risk of incident prediabetes/T2D. Lower expression of the LXR target genes correlated with higher cellular cholesterol levels (e.g., 47% of variance in cellular total cholesterol explained by ABCG1 expression). Further, adding the LXR target genes to overweight/obesity and other known predictors significantly improved prediction of incident prediabetes/T2D.CONCLUSIONThese data suggest that the aberrant LXR/ABCG1-ABCA1-MYLIP pathway (LAAMP) is a major T2D risk factor and support a potential role for aberrant LAAMP and cellular cholesterol accumulation in diabetogenesis.FUNDINGThe MESA Epigenomics and Transcriptomics Studies were funded by NIH grants 1R01HL101250, 1RF1AG054474, R01HL126477, R01DK101921, and R01HL135009. This work was supported by funding from NIDDK R01DK103531 and NHLBI R01HL119962.
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Affiliation(s)
- Jingzhong Ding
- Department of Internal Medicine, Wake Forest School of Medicine, Winston-Salem, North Carolina, USA
| | | | - Kurt Lohman
- Department of Medicine, Division of Cardiology, and
| | | | - Daniel Parker
- Department of Medicine, Division of Geriatrics, Duke University, Durham, North Carolina, USA
| | - Li Hou
- Department of Medicine, Division of Cardiology, and
| | - Jackson Taylor
- Department of Biological, Geological, and Environmental Sciences, Cleveland State University, Cleveland, Ohio, USA
| | - Deepak Voora
- Department of Medicine, Division of Cardiology, and
| | - Janet K. Sawyer
- Department of Internal Medicine, Wake Forest School of Medicine, Winston-Salem, North Carolina, USA
| | - Elena Boudyguina
- Department of Internal Medicine, Wake Forest School of Medicine, Winston-Salem, North Carolina, USA
| | - Michael P. Bancks
- Department of Epidemiology and Prevention, Wake Forest School of Medicine, Winston-Salem, North Carolina, USA
| | - Alain Bertoni
- Department of Internal Medicine, Wake Forest School of Medicine, Winston-Salem, North Carolina, USA
| | - James S. Pankow
- Division of Epidemiology and Community Health, University of Minnesota, Minneapolis, Minnesota, USA
| | - Jerome I. Rotter
- The Institute for Translational Genomics and Population Sciences, Department of Pediatrics, The Lundquist Institute for Biomedical Innovation at Harbor-UCLA Medical Center, Torrance, California, USA
| | - Mark O. Goodarzi
- Division of Endocrinology, Diabetes and Metabolism, Cedars-Sinai Medical Center, Los Angeles, California, USA
| | - Russell P. Tracy
- Department of Pathology and Laboratory Medicine, University of Vermont, Burlington, Vermont, USA
| | - David M. Murdoch
- Department of Medicine, Division of Pulmonary, Allergy, and Critical Care Medicine, Duke University, Durham, North Carolina, USA
| | - Daniel Duprez
- Cardiovascular Division, Department of Medicine, University of Minnesota, Minneapolis, Minnesota, USA
| | - Stephen S. Rich
- Center for Public Health Genomics, University of Virginia, Charlottesville, Virginia, USA
| | - Bruce M. Psaty
- Cardiovascular Health Research Unit, Departments of Medicine, Epidemiology, and Health Systems and Population Health, University of Washington, Seattle, Washington, USA
| | | | - Christopher B. Newgard
- Department of Pharmacology and Cancer Biology, Duke University, Durham, North Carolina, USA
| | - David Herrington
- Department of Internal Medicine, Wake Forest School of Medicine, Winston-Salem, North Carolina, USA
| | - Ina Hoeschele
- Fralin Life Sciences Institute, Virginia Tech, Blacksburg, Virginia, USA
| | - Steven Shea
- Department of Medicine, Columbia University, New York, New York, USA
| | - James H. Stein
- School of Medicine and Public Health, University of Wisconsin, Madison, Wisconsin, USA
| | - Manesh Patel
- Department of Medicine, Division of Cardiology, and
| | - Wendy Post
- Division of Cardiology, Department of Medicine, Johns Hopkins University, Baltimore, Maryland, USA
| | - David Jacobs
- Division of Epidemiology and Community Health, University of Minnesota, Minneapolis, Minnesota, USA
| | - John S. Parks
- Department of Internal Medicine, Wake Forest School of Medicine, Winston-Salem, North Carolina, USA
| | - Yongmei Liu
- Department of Medicine, Division of Cardiology, and
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2
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Kuwabara R, Qin T, Alberto Llacua L, Hu S, Boekschoten MV, de Haan BJ, Smink AM, de Vos P. Extracellular matrix inclusion in immunoisolating alginate-based microcapsules promotes longevity, reduces fibrosis, and supports function of islet allografts in vivo. Acta Biomater 2023; 158:151-162. [PMID: 36610609 DOI: 10.1016/j.actbio.2022.12.068] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2022] [Revised: 12/14/2022] [Accepted: 12/28/2022] [Indexed: 01/06/2023]
Abstract
Immunoisolation of pancreatic-islets in alginate-microcapsules is applied to treat diabetes. However, long-term islet function is limited, which might be due to damaged and lack of contact with pancreatic extracellular matrix (ECM) components. Herein we investigated the impact of collagen IV combined with laminin sequences, either RGD, LRE, or PDSGR, on graft-survival of microencapsulated bioluminescent islets in vivo. Collagen IV with RGD had the most pronounced effect. It enhanced after 8-week implantation in immune-incompetent mice the bioluminescence of allogeneic islets by 3.2-fold, oxygen consumption rate by 14.3-fold and glucose-induced insulin release by 9.6-fold. Transcriptomics demonstrated that ECM enhanced canonical pathways involving insulin-secretion and that it suppressed pathways related to inflammation and hypoxic stress. Also, 5.8-fold fewer capsules were affected by fibrosis. In a subsequent longevity study in immune-competent mice, microencapsulated allografts containing collagen IV and RGD had a 2.4-fold higher functionality in the first week after implantation and remained at least 2.1-fold higher during the study. Islets in microcapsules containing collagen IV and RGD survived 211 ± 24.1 days while controls survived 125 ± 19.7 days. Our findings provide in vivo evidence for the efficacy of supplementing immunoisolating devices with specific ECM components to enhance functionality and longevity of islet-grafts in vivo. STATEMENT OF SIGNIFICANCE: Limitations in duration of survival of immunoisolated pancreatic islet grafts is a major obstacle for application of the technology to treat diabetes. Accumulating evidence supports that incorporation of extracellular matrix (ECM) molecules in the capsules enhances longevity of pancreatic islets. After selection of the most efficacious laminin sequence in vitro, we show in vivo that inclusion of collagen IV and RGD in alginate-based microcapsules enhances survival, insulin secretion function, and mitochondrial function. It also suppresses fibrosis by lowering proinflammatory cytokines secretion. Moreover, transcriptomic analysis shows that ECM-inclusion promotes insulin-secretion related pathways and attenuates inflammation and hypoxic stress related pathways in islets. We show that inclusion of ECM in immunoisolating devices is a promising strategy to promote long-term survival of islet-grafts.
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Affiliation(s)
- Rei Kuwabara
- Section Immunoendocrinology, Division of Medical Biology, Department of Pathology and Medical Biology, University of Groningen, and University Medical Center Groningen, Hanzeplein 1, EA 11, Groningen 9713 GZ, the Netherlands; Department of Biomaterials, Graduate School of Biomedical and Health Sciences, Hiroshima University, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8553, Japan
| | - Tian Qin
- Section Immunoendocrinology, Division of Medical Biology, Department of Pathology and Medical Biology, University of Groningen, and University Medical Center Groningen, Hanzeplein 1, EA 11, Groningen 9713 GZ, the Netherlands.
| | - L Alberto Llacua
- Section Immunoendocrinology, Division of Medical Biology, Department of Pathology and Medical Biology, University of Groningen, and University Medical Center Groningen, Hanzeplein 1, EA 11, Groningen 9713 GZ, the Netherlands
| | - Shuxian Hu
- Section Immunoendocrinology, Division of Medical Biology, Department of Pathology and Medical Biology, University of Groningen, and University Medical Center Groningen, Hanzeplein 1, EA 11, Groningen 9713 GZ, the Netherlands
| | - Mark V Boekschoten
- Nutrition, Metabolism and Genomics Group, Division of Human Nutrition and Health, Wageningen University, Stippeneng 4, Wageningen 6708 WE, the Netherlands
| | - Bart J de Haan
- Section Immunoendocrinology, Division of Medical Biology, Department of Pathology and Medical Biology, University of Groningen, and University Medical Center Groningen, Hanzeplein 1, EA 11, Groningen 9713 GZ, the Netherlands
| | - Alexandra M Smink
- Section Immunoendocrinology, Division of Medical Biology, Department of Pathology and Medical Biology, University of Groningen, and University Medical Center Groningen, Hanzeplein 1, EA 11, Groningen 9713 GZ, the Netherlands
| | - Paul de Vos
- Section Immunoendocrinology, Division of Medical Biology, Department of Pathology and Medical Biology, University of Groningen, and University Medical Center Groningen, Hanzeplein 1, EA 11, Groningen 9713 GZ, the Netherlands
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Cholesterol Redistribution in Pancreatic β-Cells: A Flexible Path to Regulate Insulin Secretion. Biomolecules 2023; 13:biom13020224. [PMID: 36830593 PMCID: PMC9953638 DOI: 10.3390/biom13020224] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2022] [Revised: 01/17/2023] [Accepted: 01/21/2023] [Indexed: 01/26/2023] Open
Abstract
Pancreatic β-cells, by secreting insulin, play a key role in the control of glucose homeostasis, and their dysfunction is the basis of diabetes development. The metabolic milieu created by high blood glucose and lipids is known to play a role in this process. In the last decades, cholesterol has attracted significant attention, not only because it critically controls β-cell function but also because it is the target of lipid-lowering therapies proposed for preventing the cardiovascular complications in diabetes. Despite the remarkable progress, understanding the molecular mechanisms responsible for cholesterol-mediated β-cell function remains an open and attractive area of investigation. Studies indicate that β-cells not only regulate the total cholesterol level but also its redistribution within organelles, a process mediated by vesicular and non-vesicular transport. The aim of this review is to summarize the most current view of how cholesterol homeostasis is maintained in pancreatic β-cells and to provide new insights on the mechanisms by which cholesterol is dynamically distributed among organelles to preserve their functionality. While cholesterol may affect virtually any activity of the β-cell, the intent of this review is to focus on early steps of insulin synthesis and secretion, an area still largely unexplored.
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4
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Yoshihara E. Adapting Physiology in Functional Human Islet Organogenesis. Front Cell Dev Biol 2022; 10:854604. [PMID: 35557947 PMCID: PMC9086403 DOI: 10.3389/fcell.2022.854604] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2022] [Accepted: 03/22/2022] [Indexed: 01/07/2023] Open
Abstract
Generation of three-dimensional (3D)-structured functional human islets is expected to be an alternative cell source for cadaveric human islet transplantation for the treatment of insulin-dependent diabetes. Human pluripotent stem cells (hPSCs), such as human embryonic stem cells (hESCs) and human induced pluripotent stem cells (hiPSCs), offer infinite resources for newly synthesized human islets. Recent advancements in hPSCs technology have enabled direct differentiation to human islet-like clusters, which can sense glucose and secrete insulin, and those islet clusters can ameliorate diabetes when transplanted into rodents or non-human primates (NHPs). However, the generated hPSC-derived human islet-like clusters are functionally immature compared with primary human islets. There remains a challenge to establish a technology to create fully functional human islets in vitro, which are functionally and transcriptionally indistinguishable from cadaveric human islets. Understanding the complex differentiation and maturation pathway is necessary to generate fully functional human islets for a tremendous supply of high-quality human islets with less batch-to-batch difference for millions of patients. In this review, I summarized the current progress in the generation of 3D-structured human islets from pluripotent stem cells and discussed the importance of adapting physiology for in vitro functional human islet organogenesis and possible improvements with environmental cues.
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Affiliation(s)
- Eiji Yoshihara
- Lundquist Institute for Biomedical Innovation at Harbor-UCLA Medical Center, Torrance, CA, United States.,David Geffen School of Medicine at University of California, Los Angeles, CA, United States
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5
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Interplay between Fatty Acid Binding Protein 4, Fetuin-A, Retinol Binding Protein 4 and Thyroid Function in Metabolic Dysregulation. Metabolites 2022; 12:metabo12040300. [PMID: 35448487 PMCID: PMC9026429 DOI: 10.3390/metabo12040300] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2022] [Revised: 03/24/2022] [Accepted: 03/27/2022] [Indexed: 12/22/2022] Open
Abstract
Signalling between the tissues integrating synthesis, transformation and utilization of energy substrates and their regulatory hormonal axes play a substantial role in the development of metabolic disorders. Interactions between cytokines, particularly liver derived hepatokines and adipokines, secreted from adipose tissue, constitute one of major areas of current research devoted to metabolic dysregulation. The thyroid exerts crucial influence on the maintenance of basal metabolic rate, thermogenesis, carbohydrate and lipid metabolism, while its dysfunction promotes the development of metabolic disorders. In this review, we discuss the interplay between three adipokines: fatty acid binding protein type 4, fetuin-A, retinol binding protein type 4 and thyroid hormones, that shed a new light onto mechanisms underlying atherosclerosis, cardiovascular complications, obesity, insulin resistance and diabetes accompanying thyroid dysfunction. Furthermore, we summarize clinical findings on those cytokines in the course of thyroid disorders.
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6
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Lewandowski CT, Laham MS, Thatcher GR. Remembering your A, B, C's: Alzheimer's disease and ABCA1. Acta Pharm Sin B 2022; 12:995-1018. [PMID: 35530134 PMCID: PMC9072248 DOI: 10.1016/j.apsb.2022.01.011] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2021] [Revised: 12/27/2021] [Accepted: 01/07/2022] [Indexed: 12/24/2022] Open
Abstract
The function of ATP binding cassette protein A1 (ABCA1) is central to cholesterol mobilization. Reduced ABCA1 expression or activity is implicated in Alzheimer's disease (AD) and other disorders. Therapeutic approaches to boost ABCA1 activity have yet to be translated successfully to the clinic. The risk factors for AD development and progression, including comorbid disorders such as type 2 diabetes and cardiovascular disease, highlight the intersection of cholesterol transport and inflammation. Upregulation of ABCA1 can positively impact APOE lipidation, insulin sensitivity, peripheral vascular and blood–brain barrier integrity, and anti-inflammatory signaling. Various strategies towards ABCA1-boosting compounds have been described, with a bias toward nuclear hormone receptor (NHR) agonists. These agonists display beneficial preclinical effects; however, important side effects have limited development. In particular, ligands that bind liver X receptor (LXR), the primary NHR that controls ABCA1 expression, have shown positive effects in AD mouse models; however, lipogenesis and unwanted increases in triglyceride production are often observed. The longstanding approach, focusing on LXRβ vs. LXRα selectivity, is over-simplistic and has failed. Novel approaches such as phenotypic screening may lead to small molecule NHR modulators that elevate ABCA1 function without inducing lipogenesis and are clinically translatable.
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7
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Kiesel VA, Sheeley MP, Coleman MF, Cotul EK, Donkin SS, Hursting SD, Wendt MK, Teegarden D. Pyruvate carboxylase and cancer progression. Cancer Metab 2021; 9:20. [PMID: 33931119 PMCID: PMC8088034 DOI: 10.1186/s40170-021-00256-7] [Citation(s) in RCA: 36] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2020] [Accepted: 04/04/2021] [Indexed: 01/17/2023] Open
Abstract
Pyruvate carboxylase (PC) is a mitochondrial enzyme that catalyzes the ATP-dependent carboxylation of pyruvate to oxaloacetate (OAA), serving to replenish the tricarboxylic acid (TCA) cycle. In nonmalignant tissue, PC plays an essential role in controlling whole-body energetics through regulation of gluconeogenesis in the liver, synthesis of fatty acids in adipocytes, and insulin secretion in pancreatic β cells. In breast cancer, PC activity is linked to pulmonary metastasis, potentially by providing the ability to utilize glucose, fatty acids, and glutamine metabolism as needed under varying conditions as cells metastasize. PC enzymatic activity appears to be of particular importance in cancer cells that are unable to utilize glutamine for anaplerosis. Moreover, PC activity also plays a role in lipid metabolism and protection from oxidative stress in cancer cells. Thus, PC activity may be essential to link energy substrate utilization with cancer progression and to enable the metabolic flexibility necessary for cell resilience to changing and adverse conditions during the metastatic process.
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Affiliation(s)
- Violet A Kiesel
- Department of Nutrition Sciences, Purdue University, West Lafayette, IN, 47907, USA
| | - Madeline P Sheeley
- Department of Nutrition Sciences, Purdue University, West Lafayette, IN, 47907, USA
| | - Michael F Coleman
- Department of Nutrition, University of North Carolina at Chapel Hill, Chapel Hill, USA
| | - Eylem Kulkoyluoglu Cotul
- Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, USA
| | - Shawn S Donkin
- Department of Animal Science, Purdue University, West Lafayette, USA
| | - Stephen D Hursting
- Department of Nutrition, University of North Carolina at Chapel Hill, Chapel Hill, USA
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, USA
| | - Michael K Wendt
- Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, USA
| | - Dorothy Teegarden
- Department of Nutrition Sciences, Purdue University, West Lafayette, IN, 47907, USA.
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8
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Rehman SU, Schallschmidt T, Rasche A, Knebel B, Stermann T, Altenhofen D, Herwig R, Schürmann A, Chadt A, Al-Hasani H. Alternative exon splicing and differential expression in pancreatic islets reveals candidate genes and pathways implicated in early diabetes development. Mamm Genome 2021; 32:153-172. [PMID: 33880624 PMCID: PMC8128753 DOI: 10.1007/s00335-021-09869-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2020] [Accepted: 04/03/2021] [Indexed: 12/29/2022]
Abstract
Type 2 diabetes (T2D) has a strong genetic component. Most of the gene variants driving the pathogenesis of T2D seem to target pancreatic β-cell function. To identify novel gene variants acting at early stage of the disease, we analyzed whole transcriptome data to identify differential expression (DE) and alternative exon splicing (AS) transcripts in pancreatic islets collected from two metabolically diverse mouse strains at 6 weeks of age after three weeks of high-fat-diet intervention. Our analysis revealed 1218 DE and 436 AS genes in islets from NZO/Hl vs C3HeB/FeJ. Whereas some of the revealed genes present well-established markers for β-cell failure, such as Cd36 or Aldh1a3, we identified numerous DE/AS genes that have not been described in context with β-cell function before. The gene Lgals2, previously associated with human T2D development, was DE as well as AS and localizes in a quantitative trait locus (QTL) for blood glucose on Chr.15 that we reported recently in our N2(NZOxC3H) population. In addition, pathway enrichment analysis of DE and AS genes showed an overlap of only half of the revealed pathways, indicating that DE and AS in large parts influence different pathways in T2D development. PPARG and adipogenesis pathways, two well-established metabolic pathways, were overrepresented for both DE and AS genes, probably as an adaptive mechanism to cope for increased cellular stress. Our results provide guidance for the identification of novel T2D candidate genes and demonstrate the presence of numerous AS transcripts possibly involved in islet function and maintenance of glucose homeostasis.
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Affiliation(s)
- Sayeed Ur Rehman
- Institute for Clinical Biochemistry and Pathobiochemistry, German Diabetes Center (DDZ), Leibniz Center for Diabetes Research at Heinrich Heine University, Medical Faculty, Duesseldorf, Germany.,German Center for Diabetes Research (DZD), München-Neuherberg, Germany.,Department of Biochemistry, School of Chemical and Life Sciences, Jamia Hamdard, New Delhi, 110062, India
| | - Tanja Schallschmidt
- Institute for Clinical Biochemistry and Pathobiochemistry, German Diabetes Center (DDZ), Leibniz Center for Diabetes Research at Heinrich Heine University, Medical Faculty, Duesseldorf, Germany.,German Center for Diabetes Research (DZD), München-Neuherberg, Germany
| | - Axel Rasche
- Department of Computational Molecular Biology, Max Planck Institute for Molecular Genetics, Berlin, Germany
| | - Birgit Knebel
- Institute for Clinical Biochemistry and Pathobiochemistry, German Diabetes Center (DDZ), Leibniz Center for Diabetes Research at Heinrich Heine University, Medical Faculty, Duesseldorf, Germany.,German Center for Diabetes Research (DZD), München-Neuherberg, Germany
| | - Torben Stermann
- Institute for Clinical Biochemistry and Pathobiochemistry, German Diabetes Center (DDZ), Leibniz Center for Diabetes Research at Heinrich Heine University, Medical Faculty, Duesseldorf, Germany.,German Center for Diabetes Research (DZD), München-Neuherberg, Germany
| | - Delsi Altenhofen
- Institute for Clinical Biochemistry and Pathobiochemistry, German Diabetes Center (DDZ), Leibniz Center for Diabetes Research at Heinrich Heine University, Medical Faculty, Duesseldorf, Germany.,German Center for Diabetes Research (DZD), München-Neuherberg, Germany
| | - Ralf Herwig
- Department of Computational Molecular Biology, Max Planck Institute for Molecular Genetics, Berlin, Germany
| | - Annette Schürmann
- German Center for Diabetes Research (DZD), München-Neuherberg, Germany.,German Institute of Human Nutrition, Potsdam, Germany
| | - Alexandra Chadt
- Institute for Clinical Biochemistry and Pathobiochemistry, German Diabetes Center (DDZ), Leibniz Center for Diabetes Research at Heinrich Heine University, Medical Faculty, Duesseldorf, Germany.,German Center for Diabetes Research (DZD), München-Neuherberg, Germany
| | - Hadi Al-Hasani
- Institute for Clinical Biochemistry and Pathobiochemistry, German Diabetes Center (DDZ), Leibniz Center for Diabetes Research at Heinrich Heine University, Medical Faculty, Duesseldorf, Germany. .,German Center for Diabetes Research (DZD), München-Neuherberg, Germany.
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9
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Essaouiba A, Okitsu T, Jellali R, Shinohara M, Danoy M, Tauran Y, Legallais C, Sakai Y, Leclerc E. Microwell-based pancreas-on-chip model enhances genes expression and functionality of rat islets of Langerhans. Mol Cell Endocrinol 2020; 514:110892. [PMID: 32531418 DOI: 10.1016/j.mce.2020.110892] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/03/2020] [Revised: 05/18/2020] [Accepted: 06/03/2020] [Indexed: 12/18/2022]
Abstract
Organ-on-chip technology is a promising tool for investigating physiological in vitro responses in drug screening development, and in advanced disease models. Within this framework, we investigated the behavior of rat islets of Langerhans in an organ-on-chip model. The islets were trapped by sedimentation in a biochip with a microstructure based on microwells, and perfused for 5 days of culture. The live/dead assay confirmed the high viability of the islets in the biochip cultures. The microfluidic culture leads to upregulation of mRNA levels of important pancreatic islet genes: Ins1, App, Insr, Gcgr, Reg3a and Neurod. Furthermore, insulin and glucagon secretion were higher in the biochips compared to the Petri conditions after 5 days of culture. We also confirmed glucose-induced insulin secretion in biochips via high and low glucose stimulations leading to high/low insulin secretion. The high responsiveness of the pancreatic islets to glucagon-like peptide 1 (GLP-1) stimulation in the biochips was reflected by the upregulation of mRNA levels of Gcgr, Reg3a, Neurog3, Ins1, Ins2, Stt and Glp-1r and by increased insulin secretion. The results obtained highlighted the functionality of the islets in the biochips and illustrated the potential of our pancreas-on-chip model for future pancreatic disease modeling and anti-diabetic drugs screening.
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Affiliation(s)
- Amal Essaouiba
- Université de technologie de Compiègne, CNRS, Biomechanics and Bioengineering, Centre de recherche Royallieu, CS 60319, 60203, Compiègne Cedex, France; CNRS UMI 2820, Laboratory for Integrated Micro Mechatronic Systems, Institute of Industrial Science, University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo, 153-8505, Japan
| | - Teru Okitsu
- Institute of Industrial Science, University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo, 153-8505, Japan
| | - Rachid Jellali
- Université de technologie de Compiègne, CNRS, Biomechanics and Bioengineering, Centre de recherche Royallieu, CS 60319, 60203, Compiègne Cedex, France.
| | - Marie Shinohara
- Department of Chemical Engineering, Faculty of Engineering, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
| | - Mathieu Danoy
- CNRS UMI 2820, Laboratory for Integrated Micro Mechatronic Systems, Institute of Industrial Science, University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo, 153-8505, Japan
| | - Yannick Tauran
- Université Claude Bernard Lyon 1, Laboratoire des Multimatériaux et Interfaces, UMR CNRS 5615, F-69622, Villeurbanne, France
| | - Cécile Legallais
- Université de technologie de Compiègne, CNRS, Biomechanics and Bioengineering, Centre de recherche Royallieu, CS 60319, 60203, Compiègne Cedex, France
| | - Yasuyuki Sakai
- Department of Chemical Engineering, Faculty of Engineering, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
| | - Eric Leclerc
- Université de technologie de Compiègne, CNRS, Biomechanics and Bioengineering, Centre de recherche Royallieu, CS 60319, 60203, Compiègne Cedex, France; CNRS UMI 2820, Laboratory for Integrated Micro Mechatronic Systems, Institute of Industrial Science, University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo, 153-8505, Japan.
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10
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Maczewsky J, Kaiser J, Krippeit-Drews P, Drews G. Approved LXR agonists exert unspecific effects on pancreatic β-cell function. Endocrine 2020; 68:526-535. [PMID: 32146655 PMCID: PMC7308254 DOI: 10.1007/s12020-020-02241-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/16/2019] [Accepted: 02/24/2020] [Indexed: 12/20/2022]
Abstract
Novel agonists of the nuclear liver-X-receptor (LXR) are designed to treat metabolic disorders or cancer. The rationale to develop these new drugs is based on promising results with established LXR agonist like T0901317 and GW3965. LXRα and LXRβ are expressed in β-cells, and expression is increased by T0901317. The aim of the present study was to evaluate whether effects of these drugs on β-cell function are specific and reliably linked to LXR activation. T0901317 and GW3965, widely used as specific LXR agonists, show rapid, non-genomic effects on stimulus-secretion coupling of mouse pancreatic β-cells at low µM concentrations. T0901317 lowered the cytosolic Ca2+ concentration, reduced or completely inhibited action potentials, and decreased insulin secretion. GW3965 exerted similar effects on insulin secretion. T0901317 affected the production of reactive oxygen species and ATP. The involvement of the classical nuclear LXRs in T0901317- and GW3965-mediated effects in β-cells could be ruled out using LXRα, LXRβ and double knockout mice. Our results strongly suggest that LXR agonists, that are considered to be specific for this receptor, interfere with mitochondrial metabolism and metabolism-independent processes in β-cells. Thus, it is indispensable to test novel LXR agonists accompanying to ongoing clinical trials for acute and chronic effects on cell function in cellular systems and/or animal models lacking classical LXRs.
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Affiliation(s)
- Jonas Maczewsky
- Institute of Pharmacy, Department of Pharmacology, University of Tübingen, Auf der Morgenstelle 8, 72076, Tübingen, Germany
| | - Julia Kaiser
- Institute of Pharmacy, Department of Pharmacology, University of Tübingen, Auf der Morgenstelle 8, 72076, Tübingen, Germany
| | - Peter Krippeit-Drews
- Institute of Pharmacy, Department of Pharmacology, University of Tübingen, Auf der Morgenstelle 8, 72076, Tübingen, Germany
| | - Gisela Drews
- Institute of Pharmacy, Department of Pharmacology, University of Tübingen, Auf der Morgenstelle 8, 72076, Tübingen, Germany.
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11
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Shen L, Gu Y, Qiu Y, Cheng T, Nie A, Cui C, Fu C, Li T, Li X, Fu L, Wang Y, Ni Q, Wang Q, Wang W, Feng B. Atorvastatin Targets the Islet Mevalonate Pathway to Dysregulate mTOR Signaling and Reduce β-Cell Functional Mass. Diabetes 2020; 69:48-59. [PMID: 31649162 DOI: 10.2337/db19-0178] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/20/2019] [Accepted: 10/14/2019] [Indexed: 11/13/2022]
Abstract
Statins are cholesterol-lowering agents that increase the incidence of diabetes and impair glucose tolerance via their detrimental effects on nonhepatic tissues, such as pancreatic islets, but the underlying mechanism has not been determined. In atorvastatin (ator)-treated high-fat diet-fed mice, we found reduced pancreatic β-cell size and β-cell mass, fewer mature insulin granules, and reduced insulin secretion and glucose tolerance. Transcriptome profiling of primary pancreatic islets showed that ator inhibited the expression of pancreatic transcription factor, mechanistic target of rapamycin (mTOR) signaling, and small G protein (sGP) genes. Supplementation of the mevalonate pathway intermediate geranylgeranyl pyrophosphate (GGPP), which is produced by 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase, significantly restored the attenuated mTOR activity, v-maf musculoaponeurotic fibrosarcoma oncogene homolog A (MafA) expression, and β-cell function after ator, lovastatin, rosuvastatin, and fluvastatin treatment; this effect was potentially mediated by sGP prenylation. Rab5a, the sGP in pancreatic islets most affected by ator treatment, was found to positively regulate mTOR signaling and β-cell function. Rab5a knockdown mimicked the effect of ator treatment on β-cells. Thus, ator impairs β-cell function by regulating sGPs, for example, Rab5a, which subsequently attenuates islet mTOR signaling and reduces functional β-cell mass. GGPP supplementation could constitute a new approach for preventing statin-induced hyperglycemia.
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Affiliation(s)
- Linyan Shen
- Department of Metabolism and Endocrinology, Shanghai East Hospital, Tongji University School of Medicine, Shanghai, China
| | - Yanyun Gu
- National Research Centre for Endocrine and Metabolic Diseases, Shanghai Institute for Endocrine and Metabolic Diseases, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Yixuan Qiu
- National Research Centre for Endocrine and Metabolic Diseases, Shanghai Institute for Endocrine and Metabolic Diseases, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Tingting Cheng
- Department of Metabolism and Endocrinology, Shanghai East Hospital, Tongji University School of Medicine, Shanghai, China
| | - Aifang Nie
- National Research Centre for Endocrine and Metabolic Diseases, Shanghai Institute for Endocrine and Metabolic Diseases, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Canqi Cui
- National Research Centre for Endocrine and Metabolic Diseases, Shanghai Institute for Endocrine and Metabolic Diseases, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Chenyang Fu
- National Research Centre for Endocrine and Metabolic Diseases, Shanghai Institute for Endocrine and Metabolic Diseases, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Tingting Li
- National Research Centre for Endocrine and Metabolic Diseases, Shanghai Institute for Endocrine and Metabolic Diseases, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Xuelin Li
- National Research Centre for Endocrine and Metabolic Diseases, Shanghai Institute for Endocrine and Metabolic Diseases, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Lihong Fu
- National Research Centre for Endocrine and Metabolic Diseases, Shanghai Institute for Endocrine and Metabolic Diseases, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Yanqiu Wang
- National Research Centre for Endocrine and Metabolic Diseases, Shanghai Institute for Endocrine and Metabolic Diseases, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Qicheng Ni
- National Research Centre for Endocrine and Metabolic Diseases, Shanghai Institute for Endocrine and Metabolic Diseases, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Qidi Wang
- National Research Centre for Endocrine and Metabolic Diseases, Shanghai Institute for Endocrine and Metabolic Diseases, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Weiqing Wang
- National Research Centre for Endocrine and Metabolic Diseases, Shanghai Institute for Endocrine and Metabolic Diseases, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Bo Feng
- Department of Metabolism and Endocrinology, Shanghai East Hospital, Tongji University School of Medicine, Shanghai, China
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12
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Pu S, Wu X, Yang X, Zhang Y, Dai Y, Zhang Y, Wu X, Liu Y, Cui X, Jin H, Cao J, Li R, Cai J, Cao Q, Hu L, Gao Y. The Therapeutic Role of Xenobiotic Nuclear Receptors Against Metabolic Syndrome. Curr Drug Metab 2019; 20:15-22. [PMID: 29886826 DOI: 10.2174/1389200219666180611083155] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2018] [Revised: 04/05/2018] [Accepted: 05/29/2018] [Indexed: 02/07/2023]
Abstract
BACKGROUND Diabetes, with an increased prevalence and various progressive complications, has become a significant global health challenge. The concrete mechanisms responsible for the development of diabetes still remain incompletely unknown, although substantial researches have been conducted to search for the effective therapeutic targets. This review aims to reveal the novel roles of Xenobiotic Nuclear Receptors (XNRs), including the Peroxisome Proliferator-Activated Receptor (PPAR), the Farnesoid X Receptor (FXR), the Liver X Receptor (LXR), the Pregnane X Receptor (PXR) and the Constitutive Androstane Receptor (CAR), in the development of diabetes and provide potential strategies for research and treatment of metabolic diseases. METHODS We retrieved a large number of original data about these five XNRs and organized to focus on their recently discovered functions in diabetes and its complications. RESULTS Increasing evidences have suggested that PPAR, FXR, LXR ,PXR and CAR are involved in the development of diabetes and its complications through different mechanisms, including the regulation of glucose and lipid metabolism, insulin and inflammation response and related others. CONCLUSION PPAR, FXR, LXR, PXR, and CAR, as the receptors for numerous natural or synthetic compounds, may be the most effective therapeutic targets in the treatment of metabolic diseases.
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Affiliation(s)
- Shuqi Pu
- PI-WEI Institute, Guangzhou University of Chinese Medicine, Guangzhou, China
| | - Xiaojie Wu
- Department of Immunology, Binzhou Medical University, Yantai, China
| | - Xiaoying Yang
- Jiangsu Key Laboratory of Immunity and Metabolism, Department of Pathogen Biology and Immunology and Laboratory of Infection and Immunity, Xuzhou Medical University, Xuzhou, China
| | - Yunzhan Zhang
- PI-WEI Institute, Guangzhou University of Chinese Medicine, Guangzhou, China
| | - Yunkai Dai
- PI-WEI Institute, Guangzhou University of Chinese Medicine, Guangzhou, China
| | - Yueling Zhang
- Department of Operating Theatre, Binzhou People's Hospital, Binzhou, China
| | - Xiaoting Wu
- Department of Operating Theatre, Binzhou People's Hospital, Binzhou, China
| | - Yan Liu
- Department of Immunology, Binzhou Medical University, Yantai, China
| | - Xiaona Cui
- Jiangsu Key Laboratory of Brain Disease Bioinformation, Research Center for Biochemistry and Molecular Biology, Xuzhou Medical University, Xuzhou, China
| | - Haiyong Jin
- Department of Otolaryngology, the Second Affiliated Hospital & Yuying Children's Hospital of Wenzhou Medical University, Wenzhou, China
| | - Jianhong Cao
- PI-WEI Institute, Guangzhou University of Chinese Medicine, Guangzhou, China
| | - Ruliu Li
- PI-WEI Institute, Guangzhou University of Chinese Medicine, Guangzhou, China
| | - Jiazhong Cai
- PI-WEI Institute, Guangzhou University of Chinese Medicine, Guangzhou, China
| | - Qizhi Cao
- Department of Immunology, Binzhou Medical University, Yantai, China
| | - Ling Hu
- PI-WEI Institute, Guangzhou University of Chinese Medicine, Guangzhou, China
| | - Yong Gao
- PI-WEI Institute, Guangzhou University of Chinese Medicine, Guangzhou, China
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13
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Hwang HJ, Jang HJ, Cocco L, Suh PG. The regulation of insulin secretion via phosphoinositide-specific phospholipase Cβ signaling. Adv Biol Regul 2019; 71:10-18. [PMID: 30293894 DOI: 10.1016/j.jbior.2018.09.011] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2018] [Revised: 09/17/2018] [Accepted: 09/17/2018] [Indexed: 06/08/2023]
Abstract
Phospholipase Cβ (PLCβ) is a membrane-associated enzyme activated by membrane receptors, especially G-protein coupled receptors (GPCRs). It propagates intracellular signaling by mediating phospholipid metabolism and generating key second messengers, such as inositol triphosphate and diacylglycerol, leading to intracellular Ca2+ mobilization and activation of kinases, such as protein kinases C. In pancreatic β-cells, PLCβ-mediated signaling activated by various factors, such as free fatty acids and neuronal and hormonal ligands, has been confirmed as being involved in the regulation of insulin secretion, and PLCβs have been regarded as essential mediators for augmenting insulin secretion. In this review, we describe the physiological function of PLCβs in the regulation of glucose-stimulated insulin secretion and discuss emerging data on GPCR/PLCβ signaling that is being developed as a target for the treatment of diabetes mellitus.
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Affiliation(s)
- Hyeon-Jeong Hwang
- School of Life Sciences, Ulsan National Institute of Science and Technology, Ulsan, Republic of Korea
| | - Hyun-Jun Jang
- School of Life Sciences, Ulsan National Institute of Science and Technology, Ulsan, Republic of Korea
| | - Lucio Cocco
- Cellular Signaling Laboratory, Department of Biomedical Sciences, University of Bologna, Via Irnerio, 48, I-40126, Bologna, Italy
| | - Pann-Ghill Suh
- School of Life Sciences, Ulsan National Institute of Science and Technology, Ulsan, Republic of Korea.
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14
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Pappa E, Vastardis H, Mermelekas G, Gerasimidi-Vazeou A, Zoidakis J, Vougas K. Saliva Proteomics Analysis Offers Insights on Type 1 Diabetes Pathology in a Pediatric Population. Front Physiol 2018; 9:444. [PMID: 29755368 PMCID: PMC5932525 DOI: 10.3389/fphys.2018.00444] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2018] [Accepted: 04/10/2018] [Indexed: 12/13/2022] Open
Abstract
The composition of the salivary proteome is affected by pathological conditions. We analyzed by high resolution mass spectrometry approaches saliva samples collected from children and adolescents with type 1 diabetes and healthy controls. The list of more than 2000 high confidence protein identifications constitutes a comprehensive characterization of the salivary proteome. Patients with good glycemic regulation and healthy individuals have comparable proteomic profiles. In contrast, a significant number of differentially expressed proteins were identified in the saliva of patients with poor glycemic regulation compared to patients with good glycemic control and healthy children. These proteins are involved in biological processes relevant to diabetic pathology such as endothelial damage and inflammation. Moreover, a putative preventive therapeutic approach was identified based on bioinformatic analysis of the deregulated salivary proteins. Thus, thorough characterization of saliva proteins in diabetic pediatric patients established a connection between molecular changes and disease pathology. This proteomic and bioinformatic approach highlights the potential of salivary diagnostics in diabetes pathology and opens the way for preventive treatment of the disease.
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Affiliation(s)
- Eftychia Pappa
- Department of Operative Dentistry, School of Dentistry, National and Kapodistrian University of Athens, Athens, Greece
| | - Heleni Vastardis
- Department of Orthodontics, School of Dentistry, National and Kapodistrian University of Athens, Athens, Greece
| | - George Mermelekas
- Proteomics Laboratory, Foundation of Biomedical Research of the Academy of Athens, Athens, Greece
| | | | - Jerome Zoidakis
- Proteomics Laboratory, Foundation of Biomedical Research of the Academy of Athens, Athens, Greece
| | - Konstantinos Vougas
- Proteomics Laboratory, Foundation of Biomedical Research of the Academy of Athens, Athens, Greece
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15
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Hiebl V, Ladurner A, Latkolik S, Dirsch VM. Natural products as modulators of the nuclear receptors and metabolic sensors LXR, FXR and RXR. Biotechnol Adv 2018; 36:1657-1698. [PMID: 29548878 DOI: 10.1016/j.biotechadv.2018.03.003] [Citation(s) in RCA: 88] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2017] [Revised: 03/02/2018] [Accepted: 03/08/2018] [Indexed: 01/25/2023]
Abstract
Nuclear receptors (NRs) represent attractive targets for the treatment of metabolic syndrome-related diseases. In addition, natural products are an interesting pool of potential ligands since they have been refined under evolutionary pressure to interact with proteins or other biological targets. This review aims to briefly summarize current basic knowledge regarding the liver X (LXR) and farnesoid X receptors (FXR) that form permissive heterodimers with retinoid X receptors (RXR). Natural product-based ligands for these receptors are summarized and the potential of LXR, FXR and RXR as targets in precision medicine is discussed.
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Affiliation(s)
- Verena Hiebl
- University of Vienna, Department of Pharmacognosy, Althanstrasse 14, 1090 Vienna, Austria
| | - Angela Ladurner
- University of Vienna, Department of Pharmacognosy, Althanstrasse 14, 1090 Vienna, Austria.
| | - Simone Latkolik
- University of Vienna, Department of Pharmacognosy, Althanstrasse 14, 1090 Vienna, Austria
| | - Verena M Dirsch
- University of Vienna, Department of Pharmacognosy, Althanstrasse 14, 1090 Vienna, Austria
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16
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Farb TB, Adeva M, Beauchamp TJ, Cabrera O, Coates DA, Meredith TD, Droz BA, Efanov A, Ficorilli JV, Gackenheimer SL, Martinez-Grau MA, Molero V, Ruano G, Statnick MA, Suter TM, Syed SK, Toledo MA, Willard FS, Zhou X, Bokvist KB, Barrett DG. Regulation of Endogenous (Male) Rodent GLP-1 Secretion and Human Islet Insulin Secretion by Antagonism of Somatostatin Receptor 5. Endocrinology 2017; 158:3859-3873. [PMID: 28938487 DOI: 10.1210/en.2017-00639] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/17/2017] [Accepted: 09/06/2017] [Indexed: 12/25/2022]
Abstract
Incretin and insulin responses to nutrient loads are suppressed in persons with diabetes, resulting in decreased glycemic control. Agents including sulfonylureas and dipeptidyl peptidase-4 inhibitors (DPP4i) partially reverse these effects and provide therapeutic benefit; however, their modes of action limit efficacy. Because somatostatin (SST) has been shown to suppress insulin and glucagonlike peptide-1 (GLP-1) secretion through the Gi-coupled SST receptor 5 (SSTR5) isoform in vitro, antagonism of SSTR5 may improve glycemic control via intervention in both pathways. Here, we show that a potent and selective SSTR5 antagonist reverses the blunting effects of SST on insulin secretion from isolated human islets, and demonstrate that SSTR5 antagonism affords increased levels of systemic GLP-1 in vivo. Knocking out Sstr5 in mice provided a similar increase in systemic GLP-1 levels, which were not increased further by treatment with the antagonist. Treatment of mice with the SSTR5 antagonist in combination with a DPP4i resulted in increases in systemic GLP-1 levels that were more than additive and resulted in greater glycemic control compared with either agent alone. In isolated human islets, the SSTR5 antagonist completely reversed the inhibitory effect of exogenous SST-14 on insulin secretion. Taken together, these data suggest that SSTR5 antagonism should increase circulating GLP-1 levels and stimulate insulin secretion (directly and via GLP-1) in humans, improving glycemic control in patients with diabetes.
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Affiliation(s)
- Thomas B Farb
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana 46285
| | - Marta Adeva
- Centro de Investigacion Lilly, Eli Lilly and Company, 28108-Alcobendas, Madrid, Spain
| | - Thomas J Beauchamp
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana 46285
| | - Over Cabrera
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana 46285
| | - David A Coates
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana 46285
| | | | - Brian A Droz
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana 46285
| | - Alexander Efanov
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana 46285
| | - James V Ficorilli
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana 46285
| | | | - Maria A Martinez-Grau
- Centro de Investigacion Lilly, Eli Lilly and Company, 28108-Alcobendas, Madrid, Spain
| | - Victoriano Molero
- Centro de Investigacion Lilly, Eli Lilly and Company, 28108-Alcobendas, Madrid, Spain
| | - Gema Ruano
- Centro de Investigacion Lilly, Eli Lilly and Company, 28108-Alcobendas, Madrid, Spain
| | - Michael A Statnick
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana 46285
| | - Todd M Suter
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana 46285
| | - Samreen K Syed
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana 46285
| | - Miguel A Toledo
- Centro de Investigacion Lilly, Eli Lilly and Company, 28108-Alcobendas, Madrid, Spain
| | - Francis S Willard
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana 46285
| | - Xin Zhou
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana 46285
| | - Krister B Bokvist
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana 46285
| | - David G Barrett
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana 46285
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17
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Lai C, Cheng H, Lin C, Huang S, Chen T, Chung C, Chang C, Wang H, Chuu C. Activation of liver X receptor suppresses angiogenesis
via
induction of ApoD. FASEB J 2017; 31:5568-5576. [DOI: 10.1096/fj.201700374r] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2017] [Accepted: 08/07/2017] [Indexed: 01/25/2023]
Affiliation(s)
- Chih‐Jen Lai
- Institute of Cellular and System MedicineNational Health Research Institutes Miaoli Taiwan
- Institute of BiotechnologyNational Tsing Hua University Hsinchu Taiwan
| | - Hsu‐Chen Cheng
- Department of Life SciencesNational Chung Hsing University Taichung Taiwan
| | - Ching‐Yu Lin
- Institute of Cellular and System MedicineNational Health Research Institutes Miaoli Taiwan
| | - Shih‐Han Huang
- Institute of Cellular and System MedicineNational Health Research Institutes Miaoli Taiwan
- Department of Life SciencesNational Central University Taoyuan Taiwan
| | - Ting‐Huan Chen
- Institute of Cellular and System MedicineNational Health Research Institutes Miaoli Taiwan
- Institute of BiotechnologyNational Tsing Hua University Hsinchu Taiwan
| | - Chi‐Jung Chung
- Department of Health Risk ManagementChina Medical University Taichung Taiwan
| | - Chung‐Ho Chang
- Institute of Cellular and System MedicineNational Health Research Institutes Miaoli Taiwan
- Department of Internal MedicineChanghua Christian Hospital Changhua Taiwan
| | - Horng‐Dar Wang
- Institute of BiotechnologyNational Tsing Hua University Hsinchu Taiwan
| | - Chih‐Pin Chuu
- Institute of Cellular and System MedicineNational Health Research Institutes Miaoli Taiwan
- Biotechnology CenterNational Chung Hsing University Taichung Taiwan
- Graduate Institute of Basic Medical ScienceChina Medical University Taichung Taiwan
- Graduate Program for AgingChina Medical University Taichung Taiwan
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18
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Maczewsky J, Sikimic J, Bauer C, Krippeit-Drews P, Wolke C, Lendeckel U, Barthlen W, Drews G. The LXR Ligand T0901317 Acutely Inhibits Insulin Secretion by Affecting Mitochondrial Metabolism. Endocrinology 2017; 158:2145-2154. [PMID: 28449117 DOI: 10.1210/en.2016-1941] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/15/2016] [Accepted: 04/20/2017] [Indexed: 12/15/2022]
Abstract
The role of liver X receptor (LXR) in pancreatic β-cell physiology and pathophysiology is still unclear. It has been postulated that chronic LXR activation in β-cells induces lipotoxicity, a key step in the development of β-cell dysfunction, which accompanies type 2 diabetes mellitus. In most of these studies, the LXR ligand T0901317 has been administered chronically in the micromolar range to study the significance of LXR activation. In the current study, we have evaluated acute effects of T0901317 on stimulus-secretion coupling of β-cells. We found that 10 µM T0901317 completely suppressed oscillations of the cytosolic Ca2+ concentration induced by 15 mM glucose. Obviously, this effect was due to inhibition of mitochondrial metabolism. T0901317 markedly depolarized the mitochondrial membrane potential, thus inhibiting adenosine triphosphate (ATP) production and reducing the cytosolic ATP concentration. This led in turn to a huge increase in KATP current and hyperpolarization of the cell membrane potential. Eventually, T0901317 inhibited glucose-induced insulin secretion. These effects were rapid in on-set and not compatible with the activation of a nuclear receptor. In vivo, T0901317 acutely increased the blood glucose concentration after intraperitoneal application. In summary, these data clearly demonstrate that T0901317 exerts acute effects on stimulus-secretion coupling. This observation questions the chronic use of T0901317 and limits the interpretation of results obtained under these experimental conditions.
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Affiliation(s)
- Jonas Maczewsky
- Institute of Pharmacy, Department of Pharmacology, University of Tübingen, 72076 Tübingen, Germany
| | - Jelena Sikimic
- Institute of Pharmacy, Department of Pharmacology, University of Tübingen, 72076 Tübingen, Germany
| | - Cita Bauer
- Institute of Pharmacy, Department of Pharmacology, University of Tübingen, 72076 Tübingen, Germany
| | - Peter Krippeit-Drews
- Institute of Pharmacy, Department of Pharmacology, University of Tübingen, 72076 Tübingen, Germany
| | - Carmen Wolke
- Institute of Medical Biochemistry and Molecular Biology, University Medicine Greifswald, 17475 Greifswald, Germany
| | - Uwe Lendeckel
- Institute of Medical Biochemistry and Molecular Biology, University Medicine Greifswald, 17475 Greifswald, Germany
| | - Winfried Barthlen
- Department of Pediatric Surgery, University Medicine Greifswald, 17475 Greifswald, Germany
| | - Gisela Drews
- Institute of Pharmacy, Department of Pharmacology, University of Tübingen, 72076 Tübingen, Germany
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19
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Athanason MG, Ratliff WA, Chaput D, MarElia CB, Kuehl MN, Stevens SM, Burkhardt BR. Quantitative proteomic profiling reveals hepatic lipogenesis and liver X receptor activation in the PANDER transgenic model. Mol Cell Endocrinol 2016; 436:41-9. [PMID: 27394190 PMCID: PMC5789791 DOI: 10.1016/j.mce.2016.07.009] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/25/2016] [Revised: 06/06/2016] [Accepted: 07/05/2016] [Indexed: 12/21/2022]
Abstract
PANcreatic-DERived factor (PANDER) is a member of a superfamily of FAM3 proteins modulating glycemic levels by metabolic regulation of the liver and pancreas. The precise PANDER-induced hepatic signaling mechanism is still being elucidated and has been very complex due to the pleiotropic nature of this novel hormone. Our PANDER transgenic (PANTG) mouse displays a selective hepatic insulin resistant (SHIR) phenotype whereby insulin signaling is blunted yet lipogenesis is increased, a phenomena observed in type 2 diabetes. To examine the complex PANDER-induced mechanism of SHIR, we utilized quantitative mass spectrometry-based proteomic analysis using Stable Isotope Labeling by Amino Acids in Cell Culture (SILAC) to reveal the global hepatic proteome differences within the PANTG under the metabolic states of fasting, fed and insulin-stimulated conditions. Proteomic analysis identified lipid metabolism as one of the top cellular functions differentially altered in all metabolic states. Differentially expressed proteins within the PANTG having a lipid metabolic role included ACC, ACLY, CD36, CYP7A1, FASN and SCD1. Central to the differentially expressed proteins involved in lipid metabolism was the predicted activation of the liver X receptor (LXR) pathway. Western analysis validated the increased hepatic expression of LXRα along with LXR-directed targets such as FASN and CYP7A1 within the PANTG liver. Furthermore, recombinant PANDER was capable of inducing LXR promoter activity in-vitro as determined by luciferase reporter assays. Taken together, PANDER strongly impacts hepatic lipid metabolism across metabolic states and may induce a SHIR phenotype via the LXR pathway.
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Affiliation(s)
- Mark G Athanason
- Department of Cell Biology, Microbiology and Molecular Biology, University of South Florida, 4202 East Fowler Avenue, BSF 206, Tampa, FL 33620, USA
| | - Whitney A Ratliff
- Department of Cell Biology, Microbiology and Molecular Biology, University of South Florida, 4202 East Fowler Avenue, BSF 206, Tampa, FL 33620, USA
| | - Dale Chaput
- Department of Cell Biology, Microbiology and Molecular Biology, University of South Florida, 4202 East Fowler Avenue, BSF 206, Tampa, FL 33620, USA
| | - Catherine B MarElia
- Department of Cell Biology, Microbiology and Molecular Biology, University of South Florida, 4202 East Fowler Avenue, BSF 206, Tampa, FL 33620, USA
| | - Melanie N Kuehl
- Department of Cell Biology, Microbiology and Molecular Biology, University of South Florida, 4202 East Fowler Avenue, BSF 206, Tampa, FL 33620, USA
| | - Stanley M Stevens
- Department of Cell Biology, Microbiology and Molecular Biology, University of South Florida, 4202 East Fowler Avenue, BSF 206, Tampa, FL 33620, USA
| | - Brant R Burkhardt
- Department of Cell Biology, Microbiology and Molecular Biology, University of South Florida, 4202 East Fowler Avenue, BSF 206, Tampa, FL 33620, USA.
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Li Y, Jing C, Tang X, Chen Y, Han X, Zhu Y. LXR activation causes G1/S arrest through inhibiting SKP2 expression in MIN6 pancreatic beta cells. Endocrine 2016; 53:689-700. [PMID: 27071658 DOI: 10.1007/s12020-016-0915-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/20/2015] [Accepted: 03/02/2016] [Indexed: 11/24/2022]
Abstract
Liver X receptors (LXRs) are nuclear hormone receptors with central roles in lipid homeostasis. We previously showed that LXR activation induced aberrant lipid metabolism and G1 cell cycle arrest in pancreatic beta cells. In this study, we aimed to identify the molecular target of LXR causing G1 arrest. LXR activation was induced by its agonist, T0901317. A series of luciferase reporters of truncated Skp2 promoter were analyzed in MIN6 cells. mRNA and protein levels of SKP2 and P27 were detected. Flow cytometry assay was used to determine the cell cycle distribution. MTT assay was used to evaluate cell viability. LXR activation increased cell distribution in G1 phase and lipid accumulation. Since dominant-negative Srebp1c could clear the deposited lipid rather than recover the G1 arrest, we identified S-phase kinase-associated protein 2 (Skp2) as a potential target gene of LXR. In deed, LXR activation significantly inhibited Skp2 gene expression and protein amount. We also observed that the luciferase activity of Skp2 promoter was suppressed by T0901317 and the potential LXR regulatory site was narrowed down to a region of nt -289 to -38. Silencing Lxrα and Lxrβ rescued SKP2 protein level and recovered the cellular growth repressed by LXR activation. Moreover, SKP2 overabundance reduced P27 protein level by promoting its degradation, consequently overcame the G1 arrest caused by T0901317. Our findings demonstrate that transrepressing Skp2 expression by LXR activation resulted in defective SKP2-mediated P27 degradation and inhibitory cell growth in beta cells.
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Affiliation(s)
- Yating Li
- Key Laboratory of Human Functional Genomics of Jiangsu Province, Department of Biochemistry and Molecular Biology, Nanjing Medical University, 140 Hanzhong Road, Nanjing, 210029, People's Republic of China
| | - Changwen Jing
- Key Laboratory of Human Functional Genomics of Jiangsu Province, Department of Biochemistry and Molecular Biology, Nanjing Medical University, 140 Hanzhong Road, Nanjing, 210029, People's Republic of China
| | - Xinyi Tang
- Key Laboratory of Human Functional Genomics of Jiangsu Province, Department of Biochemistry and Molecular Biology, Nanjing Medical University, 140 Hanzhong Road, Nanjing, 210029, People's Republic of China
| | - Yuanyuan Chen
- Key Laboratory of Human Functional Genomics of Jiangsu Province, Department of Biochemistry and Molecular Biology, Nanjing Medical University, 140 Hanzhong Road, Nanjing, 210029, People's Republic of China
| | - Xiao Han
- Key Laboratory of Human Functional Genomics of Jiangsu Province, Department of Biochemistry and Molecular Biology, Nanjing Medical University, 140 Hanzhong Road, Nanjing, 210029, People's Republic of China
| | - Yunxia Zhu
- Key Laboratory of Human Functional Genomics of Jiangsu Province, Department of Biochemistry and Molecular Biology, Nanjing Medical University, 140 Hanzhong Road, Nanjing, 210029, People's Republic of China.
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Wortham M, Sander M. Mechanisms of β-cell functional adaptation to changes in workload. Diabetes Obes Metab 2016; 18 Suppl 1:78-86. [PMID: 27615135 PMCID: PMC5021190 DOI: 10.1111/dom.12729] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/08/2016] [Accepted: 05/09/2016] [Indexed: 11/28/2022]
Abstract
Insulin secretion must be tightly coupled to nutritional state to maintain blood glucose homeostasis. To this end, pancreatic β-cells sense and respond to changes in metabolic conditions, thereby anticipating insulin demands for a given physiological context. This is achieved in part through adjustments of nutrient metabolism, which is controlled at several levels including allosteric regulation, post-translational modifications, and altered expression of metabolic enzymes. In this review, we discuss mechanisms of β-cell metabolic and functional adaptation in the context of two physiological states that alter glucose-stimulated insulin secretion: fasting and insulin resistance. We review current knowledge of metabolic changes that occur in the β-cell during adaptation and specifically discuss transcriptional mechanisms that underlie β-cell adaptation. A more comprehensive understanding of how β-cells adapt to changes in nutrient state could identify mechanisms to be co-opted for therapeutically modulating insulin secretion in metabolic disease.
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Affiliation(s)
- M Wortham
- Departments of Pediatrics and Cellular and Molecular Medicine, Pediatric Diabetes Research Center, University of California San Diego, La Jolla
| | - M Sander
- Departments of Pediatrics and Cellular and Molecular Medicine, Pediatric Diabetes Research Center, University of California San Diego, La Jolla.
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Once and for all, LXRα and LXRβ are gatekeepers of the endocrine system. Mol Aspects Med 2016; 49:31-46. [DOI: 10.1016/j.mam.2016.04.001] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2015] [Revised: 03/08/2016] [Accepted: 04/10/2016] [Indexed: 01/08/2023]
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Abstract
The mechanisms or causes of pancreatic β-cell death as well as impaired insulin secretion, which are the principal events of diabetic etiopathology, are largely unknown. Diabetic complications are known to be associated with abnormal plasma lipid profile, mainly elevated level of cholesterol and free fatty acids. However, in recent years, elevated plasma cholesterol has been implicated as a primary modulator of pancreatic β-cell functions as well as death. High-cholesterol diet in animal models or excess cholesterol in pancreatic β-cell causes transporter desensitization and results in morphometric changes in insulin granules. Moreover, cholesterol is also held responsible to cause oxidative stress, mitochondrial dysfunction, and activation of proapoptotic markers leading to β-cell death. The present review focuses on the pathways and molecularevents that occur in the β-cell under the influence of excess cholesterol that hampers the basal physiology of the cell leading to the progression of diabetes.
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Emerging role of liver X receptors in cardiac pathophysiology and heart failure. Basic Res Cardiol 2015; 111:3. [PMID: 26611207 PMCID: PMC4661180 DOI: 10.1007/s00395-015-0520-7] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/11/2015] [Accepted: 11/03/2015] [Indexed: 01/09/2023]
Abstract
Liver X receptors (LXRs) are master regulators of metabolism and have been studied for their pharmacological potential in vascular and metabolic disease. Besides their established role in metabolic homeostasis and disease, there is mounting evidence to suggest that LXRs may exert direct beneficial effects in the heart. Here, we aim to provide a conceptual framework to explain the broad mode of action of LXRs and how LXR signaling may be an important local and systemic target for the treatment of heart failure. We discuss the potential role of LXRs in systemic conditions associated with heart failure, such as hypertension, diabetes, and renal and vascular disease. Further, we expound on recent data that implicate a direct role for LXR activation in the heart, for its impact on cardiomyocyte damage and loss due to ischemia, and effects on cardiac hypertrophy, fibrosis, and myocardial metabolism. Taken together, the accumulating evidence supports the notion that LXRs may represent a novel therapeutic target for the treatment of heart failure.
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25
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Gao M, Zhang C, Ma Y, Liu D. Cold Exposure Improves the Anti-diabetic Effect of T0901317 in Streptozotocin-Induced Diabetic Mice. AAPS JOURNAL 2015; 17:700-10. [PMID: 25739819 DOI: 10.1208/s12248-015-9746-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/29/2014] [Accepted: 02/22/2015] [Indexed: 01/11/2023]
Abstract
Activation of liver X receptors (LXRs) can improve glucose tolerance in insulin-independent diabetes, however, whether similar effects can be achieved in insulin-dependent diabetes remains unclear. Here, we evaluated the anti-diabetic activity of T0901317, a potent agonist of LXRs, in diabetic mice induced by streptozotocin, and our data demonstrate that T0901317 is most effective when combined with cold treatment of animals. Treatment with T0901317 improved glucose tolerance of diabetic mice, which was associated with repressed expression of key genes involved in hepatic gluconeogenesis such as Pepck and G6p. Combined treatment by T0901317 and cold exposure reduced transcription of gluconeogenic genes to similar levels. Intriguingly, combined treatment greatly increased expression of Ucp1, Cidea, Dio2, and Elvol3 predominantly in the inguinal white adipose tissue, consequently leading to browning of this fat pad, and resulting in further improvement of glucose tolerance which was associated with increased protein levels of UCP1 and GLUT4. Collectively, these results suggest that browning of white adipose tissue via cold exposure in combination with activation of liver X receptors is an alternative and effective strategy to manage insulin-dependent diabetes.
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Affiliation(s)
- Mingming Gao
- Department of Pharmaceutical and Biomedical Sciences, College of Pharmacy, University of Georgia, 450 Pharmacy South, 250 West Green Street, Athens, Georgia, 30602, USA
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26
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Bindesbøll C, Fan Q, Nørgaard RC, MacPherson L, Ruan HB, Wu J, Pedersen TÅ, Steffensen KR, Yang X, Matthews J, Mandrup S, Nebb HI, Grønning-Wang LM. Liver X receptor regulates hepatic nuclear O-GlcNAc signaling and carbohydrate responsive element-binding protein activity. J Lipid Res 2015; 56:771-85. [PMID: 25724563 DOI: 10.1194/jlr.m049130] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Liver X receptor (LXR)α and LXRβ play key roles in hepatic de novo lipogenesis through their regulation of lipogenic genes, including sterol regulatory element-binding protein (SREBP)-1c and carbohydrate responsive element-binding protein (ChREBP). LXRs activate lipogenic gene transcription in response to feeding, which is believed to be mediated by insulin. We have previously shown that LXRs are targets for glucose-hexosamine-derived O-linked β-N-acetylglucosamine (O-GlcNAc) modification enhancing their ability to regulate SREBP-1c promoter activity in vitro. To elucidate insulin-independent effects of feeding on LXR-mediated lipogenic gene expression in vivo, we subjected control and streptozotocin-treated LXRα/β(+/+) and LXRα/β(-/-) mice to a fasting-refeeding regime. We show that under hyperglycemic and hypoinsulinemic conditions, LXRs maintain their ability to upregulate the expression of glycolytic and lipogenic enzymes, including glucokinase (GK), SREBP-1c, ChREBPα, and the newly identified shorter isoform ChREBPβ. Furthermore, glucose-dependent increases in LXR/retinoid X receptor-regulated luciferase activity driven by the ChREBPα promoter was mediated, at least in part, by O-GlcNAc transferase (OGT) signaling in Huh7 cells. Moreover, we show that LXR and OGT interact and colocalize in the nucleus and that loss of LXRs profoundly reduced nuclear O-GlcNAc signaling and ChREBPα promoter binding activity in vivo. In summary, our study provides evidence that LXRs act as nutrient and glucose metabolic sensors upstream of ChREBP by modulating GK expression, nuclear O-GlcNAc signaling, and ChREBP expression and activity.
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Affiliation(s)
- Christian Bindesbøll
- Department of Nutrition, Institute of Basic Medical Sciences, University of Oslo, N-0316 Oslo, Norway
| | - Qiong Fan
- Department of Nutrition, Institute of Basic Medical Sciences, University of Oslo, N-0316 Oslo, Norway
| | - Rikke C Nørgaard
- Department of Nutrition, Institute of Basic Medical Sciences, University of Oslo, N-0316 Oslo, Norway
| | - Laura MacPherson
- Department of Pharmacology and Toxicology, University of Toronto, Toronto, Ontario M5S1A8, Canada
| | - Hai-Bin Ruan
- Program in Integrative Cell Signaling and Neurobiology of Metabolism, Yale University School of Medicine, New Haven, CT 06519 Section of Comparative Medicine, Yale University School of Medicine, New Haven, CT 06519
| | - Jing Wu
- Program in Integrative Cell Signaling and Neurobiology of Metabolism, Yale University School of Medicine, New Haven, CT 06519 Section of Comparative Medicine, Yale University School of Medicine, New Haven, CT 06519
| | - Thomas Å Pedersen
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, 5230 Odense M, Denmark
| | - Knut R Steffensen
- Division of Clinical Chemistry Department of Laboratory Medicine, Karolinska Institutet, Karolinska University Hospital Huddinge, C174, SE-141 86 Stockholm, Sweden
| | - Xiaoyong Yang
- Program in Integrative Cell Signaling and Neurobiology of Metabolism, Yale University School of Medicine, New Haven, CT 06519 Section of Comparative Medicine, Yale University School of Medicine, New Haven, CT 06519 Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, CT 06519
| | - Jason Matthews
- Department of Nutrition, Institute of Basic Medical Sciences, University of Oslo, N-0316 Oslo, Norway Department of Pharmacology and Toxicology, University of Toronto, Toronto, Ontario M5S1A8, Canada
| | - Susanne Mandrup
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, 5230 Odense M, Denmark
| | - Hilde I Nebb
- Department of Nutrition, Institute of Basic Medical Sciences, University of Oslo, N-0316 Oslo, Norway
| | - Line M Grønning-Wang
- Department of Nutrition, Institute of Basic Medical Sciences, University of Oslo, N-0316 Oslo, Norway
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27
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Kelder T, Verschuren L, van Ommen B, van Gool AJ, Radonjic M. Network signatures link hepatic effects of anti-diabetic interventions with systemic disease parameters. BMC SYSTEMS BIOLOGY 2014; 8:108. [PMID: 25204982 PMCID: PMC4363943 DOI: 10.1186/s12918-014-0108-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/29/2014] [Accepted: 08/29/2014] [Indexed: 11/10/2022]
Abstract
Background Multifactorial diseases such as type 2 diabetes mellitus (T2DM), are driven by a complex network of interconnected mechanisms that translate to a diverse range of complications at the physiological level. To optimally treat T2DM, pharmacological interventions should, ideally, target key nodes in this network that act as determinants of disease progression. Results We set out to discover key nodes in molecular networks based on the hepatic transcriptome dataset from a preclinical study in obese LDLR-/- mice recently published by Radonjic et al. Here, we focus on comparing efficacy of anti-diabetic dietary (DLI) and two drug treatments, namely PPARA agonist fenofibrate and LXR agonist T0901317. By combining knowledge-based and data-driven networks with a random walks based algorithm, we extracted network signatures that link the DLI and two drug interventions to dyslipidemia-related disease parameters. Conclusions This study identified specific and prioritized sets of key nodes in hepatic molecular networks underlying T2DM, uncovering pathways that are to be modulated by targeted T2DM drug interventions in order to modulate the complex disease phenotype.
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Affiliation(s)
- Thomas Kelder
- TNO, Research Group Microbiology & Systems Biology, Zeist, The Netherlands. .,Current address: EdgeLeap B.V, Utrecht, The Netherlands.
| | - Lars Verschuren
- TNO, Research Group Microbiology & Systems Biology, Zeist, The Netherlands.
| | - Ben van Ommen
- TNO, Research Group Microbiology & Systems Biology, Zeist, The Netherlands.
| | - Alain J van Gool
- TNO, Research Group Microbiology & Systems Biology, Zeist, The Netherlands. .,Department of Laboratory Medicine, Radboud University Nijmegen Medical Center, Nijmegen, The Netherlands. .,Faculty of Physics, Mathematics and Informatics, Radboud University Nijmegen, Nijmegen, The Netherlands.
| | - Marijana Radonjic
- TNO, Research Group Microbiology & Systems Biology, Zeist, The Netherlands. .,Current address: EdgeLeap B.V, Utrecht, The Netherlands.
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28
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Bays HE. Lowering low-density lipoprotein cholesterol levels in patients with type 2 diabetes mellitus. Int J Gen Med 2014; 7:355-64. [PMID: 25045281 PMCID: PMC4094576 DOI: 10.2147/ijgm.s65148] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Type 2 diabetes mellitus (T2DM) is characterized by hyperglycemia, insulin resistance, and/or progressive loss of β-cell function. T2DM patients are at increased risk of micro- and macrovascular disease, and are often considered as representing an atherosclerotic coronary heart disease (CHD) risk equivalent. Interventions directed at glucose and lipid level control in T2DM patients may reduce micro- and macrovascular disease. The optimal T2DM agent is one that lowers glucose levels with limited risk for hypoglycemia, and with no clinical trial evidence of worsening CHD risk. Lipid-altering drugs should preferably reduce low-density lipoprotein cholesterol and apolipoprotein B (apo B) and have evidence that the mechanism of action reduces CHD risk. Statins reduce low-density lipoprotein cholesterol and apo B and have evidence of improving CHD outcomes, and are thus first-line therapy for the treatment of hypercholesterolemia. In patients who do not achieve optimal lipid levels with statin therapy, or who are intolerant to statin therapy, add-on therapy or alternative therapies may be indicated. Additional available agents to treat hypercholesterolemic patients with T2DM include bile acid sequestrants, fibrates, niacin, and ezetimibe. This review discusses the use of these alternative agents to treat hypercholesterolemia in patients with T2DM, either as monotherapy or in combination with statin therapy.
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Affiliation(s)
- Harold E Bays
- Louisville Metabolic and Atherosclerosis Research Center, Louisville, KY, USA
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29
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Ding L, Pang S, Sun Y, Tian Y, Yu L, Dang N. Coordinated Actions of FXR and LXR in Metabolism: From Pathogenesis to Pharmacological Targets for Type 2 Diabetes. Int J Endocrinol 2014; 2014:751859. [PMID: 24872814 PMCID: PMC4020365 DOI: 10.1155/2014/751859] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/02/2014] [Accepted: 04/09/2014] [Indexed: 12/13/2022] Open
Abstract
Type 2 diabetes (T2D) is the most prevalent metabolic disease, and many people are suffering from its complications driven by hyperglycaemia and dyslipidaemia. Nuclear receptors (NRs) are ligand-inducible transcription factors that mediate changes to metabolic pathways within the body. As metabolic regulators, the farnesoid X receptor (FXR) and the liver X receptor (LXR) play key roles in the pathogenesis of T2D, which remains to be clarified in detail. Here we review the recent progress concerning the physiological and pathophysiological roles of FXRs and LXRs in the regulation of bile acid, lipid and glucose metabolism and the implications in T2D, taking into account that these two nuclear receptors are potential pharmaceutical targets for the treatment of T2D and its complications.
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Affiliation(s)
- Lin Ding
- Endocrinology Department, Jinan Central Hospital Affiliated to Shandong University, No. 105 Jiefang Road, Jinan, Shandong 250013, China
| | - Shuguang Pang
- Endocrinology Department, Jinan Central Hospital Affiliated to Shandong University, No. 105 Jiefang Road, Jinan, Shandong 250013, China
- *Shuguang Pang:
| | - Yongmei Sun
- Endocrinology Department, Jinan Central Hospital Affiliated to Shandong University, No. 105 Jiefang Road, Jinan, Shandong 250013, China
| | - Yuling Tian
- Endocrinology Department, Jinan Central Hospital Affiliated to Shandong University, No. 105 Jiefang Road, Jinan, Shandong 250013, China
| | - Li Yu
- Endocrinology Department, Jinan Central Hospital Affiliated to Shandong University, No. 105 Jiefang Road, Jinan, Shandong 250013, China
| | - Ningning Dang
- Endocrinology Department, Jinan Central Hospital Affiliated to Shandong University, No. 105 Jiefang Road, Jinan, Shandong 250013, China
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Beaven SW, Matveyenko A, Wroblewski K, Chao L, Wilpitz D, Hsu TW, Lentz J, Drew B, Hevener AL, Tontonoz P. Reciprocal regulation of hepatic and adipose lipogenesis by liver X receptors in obesity and insulin resistance. Cell Metab 2013; 18:106-17. [PMID: 23823481 PMCID: PMC4089509 DOI: 10.1016/j.cmet.2013.04.021] [Citation(s) in RCA: 108] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/08/2012] [Revised: 03/28/2013] [Accepted: 04/26/2013] [Indexed: 12/25/2022]
Abstract
Liver X receptors (LXRs) regulate lipogenesis and inflammation, but their contribution to the metabolic syndrome is unclear. We show that LXRs modulate key aspects of the metabolic syndrome in mice. LXRαβ-deficient-ob/ob (LOKO) mice remain obese but show reduced hepatic steatosis and improved insulin sensitivity compared to ob/ob mice. Impaired hepatic lipogenesis in LOKO mice is accompanied by reciprocal increases in adipose lipid storage, reflecting tissue-selective effects on the SREBP, PPARγ, and ChREBP lipogenic pathways. LXRs are essential for obesity-driven SREBP-1c and ChREBP activity in liver, but not fat. Furthermore, loss of LXRs in obesity promotes adipose PPARγ and ChREBP-β activity, leading to improved insulin sensitivity. LOKO mice also exhibit defects in β cell mass and proliferation despite improved insulin sensitivity. Our data suggest that sterol sensing by LXRs in obesity is critically linked with lipid and glucose homeostasis and provide insight into the complex relationships between LXR and insulin signaling.
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Affiliation(s)
- Simon W Beaven
- Howard Hughes Medical Institute and Department of Pathology and Laboratory Medicine, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA
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31
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Zhang C, Suckow AT, Chessler SD. Altered pancreatic islet function and morphology in mice lacking the Beta-cell surface protein neuroligin-2. PLoS One 2013; 8:e65711. [PMID: 23776533 PMCID: PMC3679192 DOI: 10.1371/journal.pone.0065711] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2012] [Accepted: 05/03/2013] [Indexed: 11/24/2022] Open
Abstract
Neuroligin-2 is a transmembrane, cell-surface protein originally identified as an inhibitory synapse-associated protein in the central nervous system. Neuroligin-2 is also present on the pancreatic beta-cell surface, and there it engages in transcellular interactions that drive functional maturation of the insulin secretory machinery; these are necessary for normal insulin secretion. The effects of neuroligin-2 deficiency on brain and neuronal function and morphology and on behavior and coordination have been extensively characterized using neuroligin-2 knockout mice. The effects of absent neuroligin-2 expression on islet development and function, however, are unknown. Here, to help test whether neuroligin-2 is necessary for normal islet development, we characterized islet morphology in mice lacking neuroligin-2. To test whether–as predicted by our earlier co-culture studies–absence of neuroligin-2 impairs beta cell function, we compared glucose-stimulated insulin secretion by islets from mutant and wild-type mice. Our results show that while islets from neuroligin-2-deficient mice do not to appear to differ architecturally from wild-type islets, they are smaller, fewer in number, and contain beta cells with lower insulin content. Evaluation of transcript levels suggests that upregulation of neuroligin-1 helps compensate for loss of neuroligin-2. Surprisingly, under both basal and stimulating glucose levels, isolated islets from the knockout mice secreted more of their intracellular insulin content. Rat islets with shRNA-mediated neuroligin-2 knockdown also exhibited increased insulin secretion. Neurexin transcript levels were lower in the knockout mice and, consistent with our prior finding that neurexin is a key constituent of the insulin granule docking machinery, insulin granule docking was reduced. These results indicate that neuroligin-2 is not necessary for the formation of pancreatic islets but that neuroligin-2 influences islet size and number. Neuroligin-2–perhaps through its effects on the expression and/or activity of its binding partner neurexin–promotes insulin granule docking, a known constraint on insulin secretion.
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Affiliation(s)
- Charles Zhang
- Department of Medicine, University of California Irvine, School of Medicine, Irvine, California, United States of America
| | - Arthur T. Suckow
- Pediatric Diabetes Research Center, University of California San Diego, La Jolla, California, United States of America
| | - Steven D. Chessler
- Department of Medicine, University of California Irvine, School of Medicine, Irvine, California, United States of America
- * E-mail:
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Cermenati G, Brioschi E, Abbiati F, Melcangi RC, Caruso D, Mitro N. Liver X receptors, nervous system, and lipid metabolism. J Endocrinol Invest 2013; 36:435-43. [PMID: 23609963 DOI: 10.3275/8941] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Lipids in the nervous system are represented by cholesterol and phospholipids as constituents of cell membranes and, in particular, of myelin. Therefore, lipids are finely regulated to guarantee physiological functions. In the central nervous system, cholesterol is locally synthesized due to the presence of the blood brain barrier. In the peripheral nervous system cholesterol is either up-taken by lipoproteins and/or produced by de novo biosynthesis. Defects in lipid homeostasis in these tissues lead to structural and functional changes that often result in different pathological conditions depending on the affected pathways (i.e. cholesterol biosynthesis, cholesterol efflux, fatty acid biosynthesis etc.). Alterations in cholesterol metabolism in the central nervous system are linked to several disorders such as Alzheimer's disease, Huntington disease, Parkinson disease, Multiple sclerosis, Smith-Lemli-Opitz syndrome, Niemann-Pick type C disease, and glioblastoma. In the peripheral nervous system changes in lipid metabolism are associated with the development of peripheral neuropathy that may be caused by metabolic disorders, injuries, therapeutics, and autoimmune diseases. Transcription factors, such as the Liver X receptors (LXR), regulate both cholesterol and fatty acid metabolism in several tissues including the nervous system. In the last few years several studies elucidated the biology of LXR in the nervous system due to the availability of knock-out mice and the development of synthetic ligands. Here, we review a survey of the literature focused on the central and peripheral nervous system and in physiological and pathological settings with particular attention to the roles played by LXR in both districts.
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Affiliation(s)
- G Cermenati
- Department of Pharmacological and Biomolecular Sciences, University of Milan, Via Balzaretti 9, Milan, Italy
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33
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Hectors TLM, Vanparys C, Pereira-Fernandes A, Martens GA, Blust R. Evaluation of the INS-1 832/13 cell line as a beta-cell based screening system to assess pollutant effects on beta-cell function. PLoS One 2013; 8:e60030. [PMID: 23555872 PMCID: PMC3605429 DOI: 10.1371/journal.pone.0060030] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2012] [Accepted: 02/22/2013] [Indexed: 01/15/2023] Open
Abstract
Environmental pollutants have recently emerged as potential risk factors for metabolic diseases, urging systematic investigation of pollutant effects on metabolic disease processes. To enable risk assessment of these so-called metabolic disruptors the use of stable, robust and well-defined cell based screening systems has recently been encouraged. Since beta-cell (dys)functionality is central in diabetes pathophysiology, the need to develop beta-cell based pollutant screening systems is evident. In this context, the present research evaluated the strengths and weaknesses of the INS-1 832/13 pancreatic beta-cell line as diabetogenic pollutant screening system with a focus on beta-cell function. After optimization of exposure conditions, positive (exendin-4, glibenclamide) and negative (diazoxide) control compounds for acute insulin secretion responses were tested and those with the most profound effects were selected to allow potency estimations and ranking of pollutants. This was followed by a first explorative screening of acute bisphenol A and bis(2-ethylhexyl)phthalate effects. The same approach was applied for chronic exposures, focusing primarily on evaluation of acknowledged chronic stimulators (diazoxide, T0901317, exendin-4) or inhibitors (glibenclamide) of insulin secretion responses to select the most responsive ones for use as control compounds in a chronic pollutant testing framework. Our results showed that INS-1 832/13 cells responded conform previous observations regarding acute effects of control compounds on insulin secretion, while bisphenol A and bis(2-ethylhexyl)phthalate had limited acute effects. Furthermore, chronic exposure to known beta-cell reactive compounds resulted in deviating insulin secretion and insulin content profiles compared to previous reports. In conclusion, this INS-1 subclone appears to lack certain characteristics needed to respond appropriately to acute pollutant exposure or long term exposure to known beta-cell reactive compounds and thus seems to be, in our setting, inadequate as a diabetogenic pollutant screening system.
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Affiliation(s)
- Tine L M Hectors
- Systemic Physiological and Ecotoxicological Research, Department of Biology, University of Antwerp, Antwerp, Belgium.
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Naik A, Belič A, Zanger UM, Rozman D. Molecular Interactions between NAFLD and Xenobiotic Metabolism. Front Genet 2013; 4:2. [PMID: 23346097 PMCID: PMC3550596 DOI: 10.3389/fgene.2013.00002] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2012] [Accepted: 01/03/2013] [Indexed: 01/01/2023] Open
Abstract
Non-alcoholic fatty liver disease (NAFLD), the hepatic manifestation of the metabolic syndrome, is a complex multifactorial disease characterized by metabolic deregulations that include accumulation of lipids in the liver, lipotoxicity, and insulin resistance. The progression of NAFLD to non-alcoholic steatohepatitis and cirrhosis, and ultimately to carcinomas, is governed by interplay of pro-inflammatory pathways, oxidative stress, as well as fibrogenic and apoptotic cues. As the liver is the major organ of biotransformation, deregulations in hepatic signaling pathways have effects on both, xenobiotic and endobiotic metabolism. Several major nuclear receptors involved in the transcription and regulation of phase I and II drug metabolizing enzymes and transporters also have endobiotic ligands including several lipids. Hence, hepatic lipid accumulation in steatosis and NAFLD, which leads to deregulated activation patterns of nuclear receptors, may result in altered drug metabolism capacity in NAFLD patients. On the other hand, genetic and association studies have indicated that a malfunction in drug metabolism can affect the prevalence and severity of NAFLD. This review focuses on the complex interplay between NAFLD pathogenesis and drug metabolism. A better understanding of these relationships is a prerequisite for developing improved drug dosing algorithms for the pharmacotherapy of patients with different stages of NAFLD.
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Affiliation(s)
- Adviti Naik
- Faculty of Computer Sciences and Informatics, University of Ljubljana Ljubljana, Slovenia
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Welters HJ, El Ouaamari A, Kawamori D, Meyer J, Hu J, Smith DM, Kulkarni RN. Rosiglitazone promotes PPARγ-dependent and -independent alterations in gene expression in mouse islets. Endocrinology 2012; 153:4593-9. [PMID: 22807489 PMCID: PMC3512010 DOI: 10.1210/en.2012-1243] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The glitazone class of insulin-sensitizing agents act, in part, by the activation of peroxisome proliferator-activated receptor (PPAR)-γ in adipocytes. However, it is unclear whether the expression of PPARγ in the islets is essential for their potential β-cell-sparing properties. To investigate the in vivo effects of rosiglitazone on β-cell biology, we used an inducible, pancreatic and duodenal homeobox-1 enhancer element-driven, Cre recombinase to knockout PPARγ expression specifically in adult β-cells (PPARgKO). Subjecting the PPARgKO mice to a chow diet led to virtually undetectable changes in glucose or insulin sensitivity, which was paralleled by minimal changes in islet gene expression. Similarly, challenging the mutant mice with a high-fat diet and treatment with rosiglitazone did not alter insulin sensitivity, glucose-stimulated insulin secretion, islet size, or proliferation in the knockout mice despite PPARγ-dependent and -independent changes in islet gene expression. These data suggest that PPARγ expression in the β-cells is unlikely to be directly essential for normal β-cell function or the insulin-sensitizing actions of rosiglitazone.
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Affiliation(s)
- Hannah J Welters
- Peninsula College of Medicine and Dentistry, University of Exeter, Exeter EX2 5DW, United Kingdom.
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Kang J, Rivest S. Lipid metabolism and neuroinflammation in Alzheimer's disease: a role for liver X receptors. Endocr Rev 2012; 33:715-46. [PMID: 22766509 DOI: 10.1210/er.2011-1049] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Liver X receptors (LXR) are nuclear receptors that have emerged as key regulators of lipid metabolism. In addition to their functions as cholesterol sensors, LXR have also been found to regulate inflammatory responses in macrophages. Alzheimer's disease (AD) is a neurodegenerative disease characterized by a progressive cognitive decline associated with inflammation. Evidence indicates that the initiation and progression of AD is linked to aberrant cholesterol metabolism and inflammation. Activation of LXR can regulate neuroinflammation and decrease amyloid-β peptide accumulation. Here, we highlight the role of LXR in orchestrating lipid homeostasis and neuroinflammation in the brain. In addition, diabetes mellitus is also briefly discussed as a significant risk factor for AD because of the appearing beneficial effects of LXR on glucose homeostasis. The ability of LXR to attenuate AD pathology makes them potential therapeutic targets for this neurodegenerative disease.
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Affiliation(s)
- Jihong Kang
- Department of Physiology and Pathophysiology and Key Laboratory of Molecular Cardiovascular Sciences, State Education Ministry, Peking University Health Science Center, Beijing 100191, China
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Meng ZX, Yin Y, Lv JH, Sha M, Lin Y, Gao L, Zhu YX, Sun YJ, Han X. Aberrant activation of liver X receptors impairs pancreatic beta cell function through upregulation of sterol regulatory element-binding protein 1c in mouse islets and rodent cell lines. Diabetologia 2012; 55:1733-44. [PMID: 22415588 DOI: 10.1007/s00125-012-2516-2] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/27/2011] [Accepted: 02/10/2012] [Indexed: 10/28/2022]
Abstract
AIMS/HYPOTHESIS Liver X receptors (LXR) are important transcriptional regulators of lipid and glucose metabolism. Our previous report demonstrated that LXR activation inhibited pancreatic beta cell proliferation through cell cycle arrest. Here we explore the role of LXR activation in beta cell insulin secretion and the underlying mechanism that might be involved. METHODS Mouse pancreatic islets or insulin-secreting MIN6 cells were exposed to the LXR agonist, T0901317, and insulin secretion, glucose and fatty acid oxidation, and lipogenic gene expression were assessed. The unsaturated fatty acid eicosapentaenoic acid and the dominant negative sterol regulatory element binding protein 1c (SREBP1c) were used to inhibit endogenous SREBP1c and evaluate the involvement of SREBP1c in beta cell dysfunction induced by LXR activation. RESULTS Treatment with the LXR agonist decreased beta cell glucose sensitivity and impaired glucose-stimulated insulin secretion in vivo and in vitro. This was accompanied by derangements of beta cell glucose oxygen consumption, glucose oxidation, ATP production and intracellular voltage-gated calcium channel flux. LXR activation also regulated the expression of lipid metabolism-related genes such as Fas, Acc (also known as Acaca) and Cpt1a, and led to intracellular lipid accumulation. Further studies revealed that inhibition of SREBP1c abolished LXR activation-induced lipid accumulation and improved beta cell glucose metabolism, ATP production and insulin secretion. CONCLUSIONS/INTERPRETATION Our data reveal that aberrant activation of LXR reproduced the phenomenon of beta cell dysfunction in the development of type 2 diabetes in vitro and in vivo. Upregulation of SREBP1c production and the lipotoxicity mediated by it played a central role in this process.
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Affiliation(s)
- Z X Meng
- Department of Biochemistry and Molecular Biology, Key Laboratory of Human Functional Genomics of Jiangsu Province, Nanjing Medical University, 140 Hanzhong Road, Nanjing 210029, People's Republic of China
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Prentki M, Madiraju SRM. Glycerolipid/free fatty acid cycle and islet β-cell function in health, obesity and diabetes. Mol Cell Endocrinol 2012; 353:88-100. [PMID: 22108437 DOI: 10.1016/j.mce.2011.11.004] [Citation(s) in RCA: 109] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/15/2011] [Revised: 11/07/2011] [Accepted: 11/07/2011] [Indexed: 12/16/2022]
Abstract
Pancreatic β-cells secrete insulin in response to fluctuations in blood fuel concentrations, in particular glucose and fatty acids. However, chronic fuel surfeit can overwhelm the metabolic, signaling and secretory capacity of the β-cell leading to its dysfunction and death - often referred to as glucolipotoxicity. In β-cells and many other cells, glucose and lipid metabolic pathways converge into a glycerolipid/free fatty acid (GL/FFA) cycle, which is driven by the substrates, glycerol-3-phosphate and fatty acyl-CoA, derived from glucose and fatty acids, respectively. Although the overall operation of GL/FFA cycle, consisting of lipolysis and lipogenesis, is "futile" in terms of energy expenditure, this metabolic cycle likely plays an indispensable role for various β-cell functions, in particular insulin secretion and excess fuel detoxification. In this review, we discuss the significance of GL/FFA cycle in the β-cell, its regulation and role in generating essential metabolic signals that participate in the lipid amplification arm of glucose stimulated insulin secretion and in β-cell growth. We propose the novel concept that the lipolytic segment of GL/FFA cycle is instrumental in producing signals for insulin secretion, whereas, the lipogenic segment generates signals relevant for β-cell survival/death and growth/proliferation.
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Affiliation(s)
- Marc Prentki
- Departments of Nutrition and Biochemistry, University of Montreal, Montreal Diabetes Research Center, CR-CHUM, Technopôle Angus, 2901, Montreal, Canada QC H1W 4A4.
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Transcriptional integration of metabolism by the nuclear sterol-activated receptors LXR and FXR. Nat Rev Mol Cell Biol 2012; 13:213-24. [PMID: 22414897 DOI: 10.1038/nrm3312] [Citation(s) in RCA: 545] [Impact Index Per Article: 45.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Nuclear receptors are integrators of hormonal and nutritional signals, mediating changes to metabolic pathways within the body. Given that modulation of lipid and glucose metabolism has been linked to diseases including type 2 diabetes, obesity and atherosclerosis, a greater understanding of pathways that regulate metabolism in physiology and disease is crucial. The liver X receptors (LXRs) and the farnesoid X receptors (FXRs) are activated by oxysterols and bile acids, respectively. Mounting evidence indicates that these nuclear receptors have essential roles, not only in the regulation of cholesterol and bile acid metabolism but also in the integration of sterol, fatty acid and glucose metabolism.
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Turban S, Liu X, Ramage L, Webster SP, Walker BR, Dunbar DR, Mullins JJ, Seckl JR, Morton NM. Optimal elevation of β-cell 11β-hydroxysteroid dehydrogenase type 1 is a compensatory mechanism that prevents high-fat diet-induced β-cell failure. Diabetes 2012; 61:642-52. [PMID: 22315313 PMCID: PMC3282808 DOI: 10.2337/db11-1054] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Type 2 diabetes ultimately results from pancreatic β-cell failure. Abnormally elevated intracellular regeneration of glucocorticoids by the enzyme 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) in fat or liver may underlie pathophysiological aspects of the metabolic syndrome. Elevated 11β-HSD1 is also found in pancreatic islets of obese/diabetic rodents and is hypothesized to suppress insulin secretion and promote diabetes. To define the direct impact of elevated pancreatic β-cell 11β-HSD1 on insulin secretion, we generated β-cell-specific, 11β-HSD1-overexpressing (MIP-HSD1) mice on a strain background prone to β-cell failure. Unexpectedly, MIP-HSD1(tg/+) mice exhibited a reversal of high fat-induced β-cell failure through augmentation of the number and intrinsic function of small islets in association with induction of heat shock, protein kinase A, and extracellular signal-related kinase and p21 signaling pathways. 11β-HSD1(-/-) mice showed mild β-cell impairment that was offset by improved glucose tolerance. The benefit of higher β-cell 11β-HSD1 exhibited a threshold because homozygous MIP-HSD1(tg/tg) mice and diabetic Lep(db/db) mice with markedly elevated β-cell 11β-HSD1 levels had impaired basal β-cell function. Optimal elevation of β-cell 11β-HSD1 represents a novel biological mechanism supporting compensatory insulin hypersecretion rather than exacerbating metabolic disease. These findings have immediate significance for current therapeutic strategies for type 2 diabetes.
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Affiliation(s)
- Sophie Turban
- Molecular Metabolism Group, University of Edinburgh/British Heart Foundation Centre for Cardiovascular Science, Queen’s Medical Research Institute, University of Edinburgh, Edinburgh, U.K
| | - Xiaoxia Liu
- Molecular Metabolism Group, University of Edinburgh/British Heart Foundation Centre for Cardiovascular Science, Queen’s Medical Research Institute, University of Edinburgh, Edinburgh, U.K
| | - Lynne Ramage
- Molecular Metabolism Group, University of Edinburgh/British Heart Foundation Centre for Cardiovascular Science, Queen’s Medical Research Institute, University of Edinburgh, Edinburgh, U.K
| | - Scott P. Webster
- Endocrinology Unit, University of Edinburgh/British Heart Foundation Centre for Cardiovascular Science, Queen’s Medical Research Institute, University of Edinburgh, Edinburgh, U.K
| | - Brian R. Walker
- Endocrinology Unit, University of Edinburgh/British Heart Foundation Centre for Cardiovascular Science, Queen’s Medical Research Institute, University of Edinburgh, Edinburgh, U.K
| | - Donald R. Dunbar
- Bioinformatics Core, University of Edinburgh/British Heart Foundation Centre for Cardiovascular Science, Queen’s Medical Research Institute, University of Edinburgh, Edinburgh, U.K
| | - John J. Mullins
- Molecular Physiology, University of Edinburgh/British Heart Foundation Centre for Cardiovascular Science, Queen’s Medical Research Institute, University of Edinburgh, Edinburgh, U.K
| | - Jonathan R. Seckl
- Endocrinology Unit, University of Edinburgh/British Heart Foundation Centre for Cardiovascular Science, Queen’s Medical Research Institute, University of Edinburgh, Edinburgh, U.K
| | - Nicholas M. Morton
- Molecular Metabolism Group, University of Edinburgh/British Heart Foundation Centre for Cardiovascular Science, Queen’s Medical Research Institute, University of Edinburgh, Edinburgh, U.K
- Corresponding author: Nicholas M. Morton,
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ElAli A, Hermann DM. Liver X receptor activation enhances blood-brain barrier integrity in the ischemic brain and increases the abundance of ATP-binding cassette transporters ABCB1 and ABCC1 on brain capillary cells. Brain Pathol 2011; 22:175-87. [PMID: 21767321 DOI: 10.1111/j.1750-3639.2011.00517.x] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
The blood-brain barrier (BBB) consists of dense contacts between endothelial cells, the tight junctions, which are complemented by membrane-bound transporters belonging to the ATP-binding cassette (ABC) transporter family. Liver X receptors (LXR) have previously been shown to stabilize the integrity of atherosclerotic noncerebral arteries. Their effects on ischemic cerebral vessels are still unknown. By delivering LXR agonists, T0901317 and GW3965, to mice submitted to 30 minutes intraluminal middle cerebral artery occlusion, we show that LXR activation reduces brain swelling and decreases BBB permeability by upregulating LXR's target calpastatin that deactivates calpain-1/2, stabilizing p120 catenin. p120 catenin specifically interacts with RhoA and Cdc42, inactivating the former and overactivating the latter, thus restoring the postischemic expression, phosphorylation and interaction of the tight junction proteins occludin and zona occludens-1. Moreover, LXR activation deactivates matrix metalloproteases-2/9 and inhibits microvascular apoptosis by deactivating JNK1/2 and caspase-3. In addition to the cholesterol transporters ABCA1 and ABCG1, which have previously been shown to be upregulated by LXR in noncerebral vessels, LXR activation increases the abundance of the drug transporters ABCB1 and ABCC1 on ischemic brain capillaries, as we further show. That LXR activation promotes endothelial integrity in different ways makes this receptor attractive as target for stroke therapies.
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Affiliation(s)
- Ayman ElAli
- Department of Neurology, University Hospital Essen, Essen, North Rhine-Westphalia, Germany
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Viennois E, Pommier AJC, Mouzat K, Oumeddour A, Hajjaji FZE, Dufour J, Caira F, Volle DH, Baron S, Lobaccaro JMA. Targeting liver X receptors in human health: deadlock or promising trail? Expert Opin Ther Targets 2011; 15:219-32. [DOI: 10.1517/14728222.2011.547853] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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Takebayashi K, Aso Y, Inukai T. Role of bile acid sequestrants in the treatment of type 2 diabetes. World J Diabetes 2010; 1:146-52. [PMID: 21537442 PMCID: PMC3083899 DOI: 10.4239/wjd.v1.i5.146] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/22/2010] [Revised: 08/27/2010] [Accepted: 09/03/2010] [Indexed: 02/05/2023] Open
Abstract
Cholestyramine is a first-generation bile acid sequestrant (BAS) and antihyperlipidemic agent that currently has limited use because of its relatively weak effect on lowering low density-lipoprotein (LDL)-cholesterol (C) and poor tolerability. The current first choice drugs for hyper-LDL-cholesterolemia are 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins) because of their strong LDL-C lowering effects and efficacy in prevention of cardiovascular disease. However, after lowering the target levels of LDL-C in very high risk patients, combination therapy with statins and other antihyperlipidemic drugs may become more important for treatment of hyper-LDL-cholesterolemia. Second-generation BASs such as colesevelam and colestimide have a glucose-lowering effect and improved tolerance, which has led to re-evaluation of their utility in combination with statins or antidiabetic agents.
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Affiliation(s)
- Kohzo Takebayashi
- Kohzo Takebayashi, Yoshimasa Aso, Toshihiko Inukai, Department of Internal Medicine, Dokkyo Medical University Koshigaya Hospital, Koshigaya 343-8555, Japan
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Ketterer C, Müssig K, Machicao F, Stefan N, Fritsche A, Häring HU, Staiger H. Genetic variation within the NR1H2 gene encoding liver X receptor β associates with insulin secretion in subjects at increased risk for type 2 diabetes. J Mol Med (Berl) 2010; 89:75-81. [PMID: 21042792 DOI: 10.1007/s00109-010-0687-1] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2010] [Revised: 08/23/2010] [Accepted: 09/08/2010] [Indexed: 01/17/2023]
Abstract
The liver X receptors (LXRs)-α and -β play a crucial role in control of insulin production and secretion in pancreatic β-cells. We hypothesized that common variants in the NR1H2 and NR1H3 genes, encoding LXR-β and -α, respectively, may alter pancreatic β-cell function. One thousand five hundred seventy-four subjects of European ancestry with elevated risk for type 2 diabetes were genotyped for the two NR1H2 single nucleotide polymorphisms (SNPs) rs2248949 and rs1405655 and for the four NR1H3 SNPs rs11039149, rs3758673, rs12221497 and rs2279238, and association studies with metabolic traits were performed. Metabolic characterization comprised an oral glucose tolerance test (OGTT) in all participants and, in addition, a hyperinsulinemic-euglycemic clamp and an intravenous glucose tolerance test (IVGTT) in subsets. One hundred per cent of common genetic variation (minor allele frequency ≥1%) within the NR1H2 and NR1H3 loci (D' = 1.0; r² ≥ 0.8) were covered by the six chosen tagging SNPs. NR1H2 rs2248949 was nominally associated with OGTT-derived first-phase insulin secretion and proinsulin conversion to insulin and significantly associated with the AUC of insulin levels during the IVGTT (p = 0.007) after adjustment for age, gender, BMI and insulin sensitivity in the dominant model, with the minor allele conferring reduced pancreatic β-cell function to the carriers. In subjects of European ancestry at increased risk for type 2 diabetes, common variation within the NR1H2 gene impaired insulin secretion, which may facilitate the development of type 2 diabetes.
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Affiliation(s)
- Caroline Ketterer
- Division of Endocrinology, Diabetology, Angiology, Nephrology, and Clinical Chemistry, Department of Internal Medicine, Eberhard Karls University Tübingen, German Center for Diabetes Research (DZD), Otfried-Müller-Str. 10, 72076, Tübingen, Germany
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Miyazaki S, Taniguchi H, Moritoh Y, Tashiro F, Yamamoto T, Yamato E, Ikegami H, Ozato K, Miyazaki JI. Nuclear hormone retinoid X receptor (RXR) negatively regulates the glucose-stimulated insulin secretion of pancreatic ß-cells. Diabetes 2010; 59:2854-61. [PMID: 20798333 PMCID: PMC2963544 DOI: 10.2337/db09-1897] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
OBJECTIVE Retinoid X receptors (RXRs) are members of the nuclear hormone receptor superfamily and are thought to be key regulators in differentiation, cellular growth, and gene expression. Although several experiments using pancreatic β-cell lines have shown that the ligands of nuclear hormone receptors modulate insulin secretion, it is not clear whether RXRs have any role in insulin secretion. RESEARCH DESIGN AND METHODS To elucidate the function of RXRs in pancreatic β-cells, we generated a double-transgenic mouse in which a dominant-negative form of RXRβ was inducibly expressed in pancreatic β-cells using the Tet-On system. We also established a pancreatic β-cell line from an insulinoma caused by the β-cell-specific expression of simian virus 40 T antigen in the above transgenic mouse. RESULTS In the transgenic mouse, expression of the dominant-negative RXR enhanced the insulin secretion with high glucose stimulation. In the pancreatic β-cell line, the suppression of RXRs also enhanced glucose-stimulated insulin secretion at a high glucose concentration, while 9-cis-retinoic acid, an RXR agonist, repressed it. High-density oligonucleotide microarray analysis showed that expression of the dominant-negative RXR affected the expression levels of a number of genes, some of which have been implicated in the function and/or differentiation of β-cells. CONCLUSIONS These results suggest that endogenous RXR negatively regulates the glucose-stimulated insulin secretion. Given these findings, we propose that the modulation of endogenous RXR in β-cells may be a new therapeutic approach for improving impaired insulin secretion in type 2 diabetes.
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Affiliation(s)
- Satsuki Miyazaki
- Division of Stem Cell Regulation Research, Osaka University Graduate School of Medicine, Osaka, Japan
| | - Hidenori Taniguchi
- Division of Stem Cell Regulation Research, Osaka University Graduate School of Medicine, Osaka, Japan
| | - Yusuke Moritoh
- Division of Stem Cell Regulation Research, Osaka University Graduate School of Medicine, Osaka, Japan
| | - Fumi Tashiro
- Division of Stem Cell Regulation Research, Osaka University Graduate School of Medicine, Osaka, Japan
| | - Tsunehiko Yamamoto
- Division of Stem Cell Regulation Research, Osaka University Graduate School of Medicine, Osaka, Japan
| | - Eiji Yamato
- Division of Stem Cell Regulation Research, Osaka University Graduate School of Medicine, Osaka, Japan
| | - Hiroshi Ikegami
- Department of Endocrinology, Metabolism and Diabetes, Kinki University School of Medicine, Osaka, Japan
| | - Keiko Ozato
- Section on Molecular Genetics of Immunity, Laboratory of Molecular Growth Regulation, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland
| | - Jun-ichi Miyazaki
- Division of Stem Cell Regulation Research, Osaka University Graduate School of Medicine, Osaka, Japan
- Corresponding author: Jun-ichi Miyazaki,
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Solaas K, Legry V, Retterstol K, Berg PR, Holven KB, Ferrières J, Amouyel P, Lien S, Romeo J, Valtueña J, Widhalm K, Ruiz JR, Dallongeville J, Tonstad S, Rootwelt H, Halvorsen B, Nenseter MS, Birkeland KI, Thorsby PM, Meirhaeghe A, Nebb HI. Suggestive evidence of associations between liver X receptor β polymorphisms with type 2 diabetes mellitus and obesity in three cohort studies: HUNT2 (Norway), MONICA (France) and HELENA (Europe). BMC MEDICAL GENETICS 2010; 11:144. [PMID: 20939869 PMCID: PMC2958901 DOI: 10.1186/1471-2350-11-144] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/11/2010] [Accepted: 10/12/2010] [Indexed: 01/03/2023]
Abstract
BACKGROUND The liver X receptors (LXR) α and β regulate lipid and carbohydrate homeostasis and inflammation. Lxrβ⁻/⁻ mice are glucose intolerant and at the same time lean. We aimed to assess the associations between single nucleotide polymorphisms (SNPs) in LXRβ and risk of type 2 diabetes mellitus (T2DM), obesity and related traits in 3 separate cohort studies. METHODS Twenty LXRβ SNPs were identified by sequencing and genotyped in the HUNT2 adult nested case-control study for T2DM (n = 835 cases/1986 controls). Five tag-SNPs (rs17373080, rs2695121, rs56151148, rs2303044 and rs3219281), covering 99.3% of the entire common genetic variability of the LXRβ gene were identified and genotyped in the French MONICA adult study (n = 2318) and the European adolescent HELENA cross-sectional study (n = 1144). In silico and in vitro functionality studies were performed. RESULTS We identified suggestive or significant associations between rs17373080 and the risk of (i) T2DM in HUNT2 (OR = 0.82, p = 0.03), (ii) obesity in MONICA (OR = 1.26, p = 0.05) and (iii) overweight/obesity in HELENA (OR = 1.59, p = 0.002). An intron 4 SNP (rs28514894, a perfect proxy for rs17373080) could potentially create binding sites for hepatic nuclear factor 4 alpha (HNF4α) and nuclear factor 1 (NF1). The C allele of rs28514894 was associated with ~1.25-fold higher human LXRβ basal promoter activity in vitro. However, no differences between alleles in terms of DNA binding and reporter gene transactivation by HNF4α or NF1 were observed. CONCLUSIONS Our results suggest that rs17373080 in LXRβ is associated with T2DM and obesity, maybe via altered LXRβ expression.
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Affiliation(s)
- Karianne Solaas
- Department of Endocrinology, Oslo University Hospital, Aker, Oslo, Norway
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Yang J, Chi Y, Burkhardt BR, Guan Y, Wolf BA. Leucine metabolism in regulation of insulin secretion from pancreatic beta cells. Nutr Rev 2010; 68:270-9. [PMID: 20500788 DOI: 10.1111/j.1753-4887.2010.00282.x] [Citation(s) in RCA: 138] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Leucine, a branched-chain amino acid that must be supplied in the daily diet, plays an important role in controlling protein synthesis and regulating cell metabolism in various cell types. In pancreatic beta cells, leucine acutely stimulates insulin secretion by serving as both metabolic fuel and allosteric activator of glutamate dehydrogenase to enhance glutaminolysis. Leucine has also been shown to regulate gene transcription and protein synthesis in pancreatic islet beta cells via both mTOR-dependent and -independent pathways at physiological concentrations. Long-term treatment with leucine has been shown to improve insulin secretory dysfunction of human diabetic islets via upregulation of certain key metabolic genes. In vivo, leucine administration improves glycemic control in humans and rodents with type 2 diabetes. This review summarizes and discusses the recent findings regarding the effects of leucine metabolism on pancreatic beta-cell function.
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Affiliation(s)
- Jichun Yang
- Department of Physiology and Pathophysiology, Peking University Diabetes Center, Peking University Health Science Center, Beijing, China.
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Dave VP, Kaul D. Coronary heart disease: Significance of liver X receptor α genomics. World J Cardiol 2010; 2:140-9. [PMID: 21160732 PMCID: PMC2999051 DOI: 10.4330/wjc.v2.i6.140] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/18/2010] [Revised: 06/11/2010] [Accepted: 06/18/2010] [Indexed: 02/06/2023] Open
Abstract
Crosstalk between lipid peroxidation and inflammation is known to be a pathognomonic feature for the development of coronary heart disease (CHD). In this regard ligand activated liver X receptor (LXR)-α has emerged as a key molecular switch by its inherent ability to modulate an array of genes involved in these two fundamental cellular processes. In addition, LXR-α has also been found to play a role in hepatic lipogenesis and innate immunity. Although several lines of evidence in experimental model systems have established the atheroprotective nature of LXR-α, human subjects have been reported to possess a paradoxical situation in which increased blood cellular LXR-α gene expression is always accompanied by increased coronary occlusion. This apparent paradox was resolved recently by the finding that CHD patients possess a deregulated LXR-α transcriptome due to impaired ligand-receptor interaction. This blood cellular mutated LXR-α gene expression correlated specifically with the extent of coronary occlusion and hence need is felt to devise new synthetic ligands that could restore the function of this mutated LXR-α protein in order to modulate genes involved in reverse cholesterol transport and suppression of the inflammatory response leading to the effective treatment of CHD.
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Affiliation(s)
- Vivek Priy Dave
- Vivek Priy Dave, Deepak Kaul, Department of Experimental Medicine and Biotechnology, Post Graduate Institute of Medical Education and Research, Chandigarh 160012, India
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