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Tsiloulis T, Watt MJ. Exercise and the Regulation of Adipose Tissue Metabolism. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2015; 135:175-201. [PMID: 26477915 DOI: 10.1016/bs.pmbts.2015.06.016] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Adipose tissue is a major regulator of metabolism in health and disease. The prominent roles of adipose tissue are to sequester fatty acids in times of energy excess and to release fatty acids via the process of lipolysis during times of high-energy demand, such as exercise. The fatty acids released during lipolysis are utilized by skeletal muscle to produce adenosine triphosphate to prevent fatigue during prolonged exercise. Lipolysis is controlled by a complex interplay between neuro-humoral regulators, intracellular signaling networks, phosphorylation events involving protein kinase A, translocation of proteins within the cell, and protein-protein interactions. Herein, we describe in detail the cellular and molecular regulation of lipolysis and how these processes are altered by acute exercise. We also explore the processes that underpin adipocyte adaptation to endurance exercise training, with particular focus on epigenetic modifications, control by microRNAs and mitochondrial adaptations. Finally, we examine recent literature describing how exercise might influence the conversion of traditional white adipose tissue to high energy-consuming "brown-like" adipocytes and the implications that this has on whole-body energy balance.
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Affiliation(s)
- Thomas Tsiloulis
- Biology of Lipid Metabolism Laboratory, Department of Physiology, Monash University, Clayton, Victoria, Australia
| | - Matthew J Watt
- Biology of Lipid Metabolism Laboratory, Department of Physiology, Monash University, Clayton, Victoria, Australia.
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202
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Yang RM, Liu F, He ZD, Ji M, Chu XX, Kang ZY, Cai DY, Gao NN. Anti-obesity effect of total phenylpropanoid glycosides from Ligustrum robustum Blume in fatty diet-fed mice via up-regulating leptin. JOURNAL OF ETHNOPHARMACOLOGY 2015; 169:459-465. [PMID: 25576894 DOI: 10.1016/j.jep.2014.12.066] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/06/2014] [Revised: 09/22/2014] [Accepted: 12/29/2014] [Indexed: 06/04/2023]
Abstract
ETHNOPHARMACOLOGICAL RELEVANCE In Chinese folk medicine, the leaves of Ligustrum robustum Blume (LR) were commonly used in the treatment of obesity and hyperlipidemia. This study aimed to evaluate the anti-obesity effect and mechanisms of total phenylpropanoid glycosides from Ligustrum robustum Blume (LRTPG) in fatty diet-fed C57BL/6J mice. MATERIALS AND METHODS C57BL/6J mice were divided randomly into 6 groups, i.e., control, model, positive (Orlistat 0.12g/kg), and LRTPG at three dosages (0.3, 0.6 or 1.2g/kg), respectively. Control mice were fed with standard diet; the others were fed with fatty diet. After 4 weeks׳ modeling, therapy mice were intragastrically administrated with positive drug or LRTPG for 5 weeks, respectively. Pharmacodynamic effects including body weight, fat weight, Lee׳s index, serum lipid levels, morphological changes and adipocyte area ratio were evaluated. The mechanisms were explored as the factors related to lipids metabolism in gene expressions by real-time PCR, and assured as the protein level of differential gene by Western blotting. RESULTS The anti-obesity effects of LRTPG in all treated mice were shown as decreased body weight, fat mass, Lee׳s index, total cholesterol (TC) level, and adipocyte area. The mechanisms were demonstrated as elevated mRNA and protein levels of adipose leptin, and consequently decreasing mRNA of adipose acyl coenzyme A: diacylglycerol acyltransferase (DGAT) with increasing mRNA of hepatic cholesterol 7α-hydroxylase (CYP7A1), which led to inhibition of triglyceride (TG) synthesis and promotion of cholesterol catabolism. CONCLUSIONS The anti-obesity effect of LRTPG in fatty diet-fed mice was related to the up-regulation of leptin, which may provide scientific evidence supporting the traditional usage of LR on obesity in China.
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Affiliation(s)
- Run-mei Yang
- Institute of Medicinal Plant Development, Chinese Academy of Medical Sciences, Peking Union Medical College, Beijing 100193, China
| | - Fang Liu
- Institute of Medicinal Plant Development, Chinese Academy of Medical Sciences, Peking Union Medical College, Beijing 100193, China
| | - Zhen-dan He
- Department of Pharmacy, School of Medicine, Shenzhen University, Shenzhen 518060, China
| | - Min Ji
- Institute of Medicinal Plant Development, Chinese Academy of Medical Sciences, Peking Union Medical College, Beijing 100193, China
| | - Xin-xin Chu
- Institute of Medicinal Plant Development, Chinese Academy of Medical Sciences, Peking Union Medical College, Beijing 100193, China
| | - Zhuo-ying Kang
- Institute of Medicinal Plant Development, Chinese Academy of Medical Sciences, Peking Union Medical College, Beijing 100193, China
| | - Da-yong Cai
- Institute of Medicinal Plant Development, Chinese Academy of Medical Sciences, Peking Union Medical College, Beijing 100193, China.
| | - Nan-nan Gao
- Institute of Medicinal Plant Development, Chinese Academy of Medical Sciences, Peking Union Medical College, Beijing 100193, China.
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203
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Rabacchi C, Pisciotta L, Cefalù AB, Noto D, Fresa R, Tarugi P, Averna M, Bertolini S, Calandra S. Spectrum of mutations of the LPL gene identified in Italy in patients with severe hypertriglyceridemia. Atherosclerosis 2015; 241:79-86. [DOI: 10.1016/j.atherosclerosis.2015.04.815] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/15/2015] [Revised: 04/24/2015] [Accepted: 04/26/2015] [Indexed: 12/20/2022]
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205
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Robey RB, Weisz J, Kuemmerle NB, Salzberg AC, Berg A, Brown DG, Kubik L, Palorini R, Al-Mulla F, Al-Temaimi R, Colacci A, Mondello C, Raju J, Woodrick J, Scovassi AI, Singh N, Vaccari M, Roy R, Forte S, Memeo L, Salem HK, Amedei A, Hamid RA, Williams GP, Lowe L, Meyer J, Martin FL, Bisson WH, Chiaradonna F, Ryan EP. Metabolic reprogramming and dysregulated metabolism: cause, consequence and/or enabler of environmental carcinogenesis? Carcinogenesis 2015; 36 Suppl 1:S203-31. [PMID: 26106140 PMCID: PMC4565609 DOI: 10.1093/carcin/bgv037] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2014] [Revised: 02/21/2015] [Accepted: 02/24/2015] [Indexed: 12/20/2022] Open
Abstract
Environmental contributions to cancer development are widely accepted, but only a fraction of all pertinent exposures have probably been identified. Traditional toxicological approaches to the problem have largely focused on the effects of individual agents at singular endpoints. As such, they have incompletely addressed both the pro-carcinogenic contributions of environmentally relevant low-dose chemical mixtures and the fact that exposures can influence multiple cancer-associated endpoints over varying timescales. Of these endpoints, dysregulated metabolism is one of the most common and recognizable features of cancer, but its specific roles in exposure-associated cancer development remain poorly understood. Most studies have focused on discrete aspects of cancer metabolism and have incompletely considered both its dynamic integrated nature and the complex controlling influences of substrate availability, external trophic signals and environmental conditions. Emerging high throughput approaches to environmental risk assessment also do not directly address the metabolic causes or consequences of changes in gene expression. As such, there is a compelling need to establish common or complementary frameworks for further exploration that experimentally and conceptually consider the gestalt of cancer metabolism and its causal relationships to both carcinogenesis and the development of other cancer hallmarks. A literature review to identify environmentally relevant exposures unambiguously linked to both cancer development and dysregulated metabolism suggests major gaps in our understanding of exposure-associated carcinogenesis and metabolic reprogramming. Although limited evidence exists to support primary causal roles for metabolism in carcinogenesis, the universality of altered cancer metabolism underscores its fundamental biological importance, and multiple pleiomorphic, even dichotomous, roles for metabolism in promoting, antagonizing or otherwise enabling the development and selection of cancer are suggested.
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Affiliation(s)
- R Brooks Robey
- Research and Development Service, Veterans Affairs Medical Center, White River Junction, VT 05009, USA, Departments of Medicine and of Physiology and Neurobiology, Geisel School of Medicine at Dartmouth, Dartmouth College, Hanover, NH 03756, USA,
| | - Judith Weisz
- Departments of Gynecology and Pathology, Pennsylvania State University College of Medicine, Hershey, PA 17033, USA
| | - Nancy B Kuemmerle
- Research and Development Service, Veterans Affairs Medical Center, White River Junction, VT 05009, USA, Departments of Medicine and of
| | - Anna C Salzberg
- Departments of Gynecology and Pathology, Pennsylvania State University College of Medicine, Hershey, PA 17033, USA
| | - Arthur Berg
- Departments of Gynecology and Pathology, Pennsylvania State University College of Medicine, Hershey, PA 17033, USA
| | - Dustin G Brown
- Department of Environmental and Radiological Health Sciences, Colorado State University/Colorado School of Public Health, Fort Collins, CO 80523, USA
| | - Laura Kubik
- Nicholas School of the Environment, Duke University, Durham, NC 27708, USA
| | - Roberta Palorini
- Department of Biotechnology and Biosciences, University of Milano-Bicocca, Milan, 20126, Italy, SYSBIO Center for Systems Biology, Department of Biotechnology and Biosciences, University of Milano-Bicocca, Milan 20126, Italy
| | - Fahd Al-Mulla
- Department of Pathology, Kuwait University, Safat 13110, Kuwait
| | | | - Annamaria Colacci
- Center for Environmental Carcinogenesis and Risk Assessment, Environmental Protection and Health Prevention Agency, Bologna, 40126, Italy
| | - Chiara Mondello
- Institute of Molecular Genetics, National Research Council, Pavia 27100, Italy
| | - Jayadev Raju
- Toxicology Research Division, Bureau of Chemical Safety Food Directorate, Health Products and Food Branch Health Canada, Ottawa, Ontario K1A0K9, Canada
| | - Jordan Woodrick
- Molecular Oncology Program, Lombardi Comprehensive Cancer Center, Georgetown University Medical Center, Washington, DC, 20057 USA
| | - A Ivana Scovassi
- Institute of Molecular Genetics, National Research Council, Pavia 27100, Italy
| | - Neetu Singh
- Advanced Molecular Science Research Centre, King George's Medical University, Lucknow Uttar Pradesh 226003, India
| | - Monica Vaccari
- Center for Environmental Carcinogenesis and Risk Assessment, Environmental Protection and Health Prevention Agency, Bologna, 40126, Italy
| | - Rabindra Roy
- Molecular Oncology Program, Lombardi Comprehensive Cancer Center, Georgetown University Medical Center, Washington, DC, 20057 USA
| | - Stefano Forte
- Mediterranean Institute of Oncology, Viagrande 95029, Italy
| | - Lorenzo Memeo
- Mediterranean Institute of Oncology, Viagrande 95029, Italy
| | - Hosni K Salem
- Urology Department, kasr Al-Ainy School of Medicine, Cairo University, El Manial, Cairo, 12515, Egypt
| | - Amedeo Amedei
- Department of Experimental and Clinical Medicine, University of Firenze, Firenze, 50134, Italy
| | - Roslida A Hamid
- Faculty of Medicine and Health Sciences, Universiti Putra Malaysia, Serdang, Selangor 43400, Malaysia
| | - Graeme P Williams
- Department of Molecular Medicine, University of Reading, Reading RG6 6UB, UK
| | - Leroy Lowe
- Centre for Biophotonics, LEC, Lancaster University, Bailrigg, Lancaster LA1 4YQ, UK, Getting to Know Cancer, Truro, Nova Scotia B2N 1X5, Canada, and
| | - Joel Meyer
- Nicholas School of the Environment, Duke University, Durham, NC 27708, USA
| | - Francis L Martin
- Centre for Biophotonics, LEC, Lancaster University, Bailrigg, Lancaster LA1 4YQ, UK
| | - William H Bisson
- Environmental and Molecular Toxicology, Environmental Health Science Center, Oregon State University, Corvallis, OR 97331, USA
| | - Ferdinando Chiaradonna
- Department of Biotechnology and Biosciences, University of Milano-Bicocca, Milan, 20126, Italy, SYSBIO Center for Systems Biology, Department of Biotechnology and Biosciences, University of Milano-Bicocca, Milan 20126, Italy
| | - Elizabeth P Ryan
- Department of Environmental and Radiological Health Sciences, Colorado State University/Colorado School of Public Health, Fort Collins, CO 80523, USA
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206
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Neess D, Bek S, Engelsby H, Gallego SF, Færgeman NJ. Long-chain acyl-CoA esters in metabolism and signaling: Role of acyl-CoA binding proteins. Prog Lipid Res 2015; 59:1-25. [PMID: 25898985 DOI: 10.1016/j.plipres.2015.04.001] [Citation(s) in RCA: 115] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2015] [Revised: 03/11/2015] [Accepted: 04/09/2015] [Indexed: 02/03/2023]
Abstract
Long-chain fatty acyl-CoA esters are key intermediates in numerous lipid metabolic pathways, and recognized as important cellular signaling molecules. The intracellular flux and regulatory properties of acyl-CoA esters have been proposed to be coordinated by acyl-CoA-binding domain containing proteins (ACBDs). The ACBDs, which comprise a highly conserved multigene family of intracellular lipid-binding proteins, are found in all eukaryotes and ubiquitously expressed in all metazoan tissues, with distinct expression patterns for individual ACBDs. The ACBDs are involved in numerous intracellular processes including fatty acid-, glycerolipid- and glycerophospholipid biosynthesis, β-oxidation, cellular differentiation and proliferation as well as in the regulation of numerous enzyme activities. Little is known about the specific roles of the ACBDs in the regulation of these processes, however, recent studies have gained further insights into their in vivo functions and provided further evidence for ACBD-specific functions in cellular signaling and lipid metabolic pathways. This review summarizes the structural and functional properties of the various ACBDs, with special emphasis on the function of ACBD1, commonly known as ACBP.
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Affiliation(s)
- Ditte Neess
- Villum Center for Bioanalytical Sciences, Department of Biochemistry and Molecular Biology, University of Southern Denmark, DK-5230 Odense M, Denmark
| | - Signe Bek
- Villum Center for Bioanalytical Sciences, Department of Biochemistry and Molecular Biology, University of Southern Denmark, DK-5230 Odense M, Denmark
| | - Hanne Engelsby
- Villum Center for Bioanalytical Sciences, Department of Biochemistry and Molecular Biology, University of Southern Denmark, DK-5230 Odense M, Denmark
| | - Sandra F Gallego
- Villum Center for Bioanalytical Sciences, Department of Biochemistry and Molecular Biology, University of Southern Denmark, DK-5230 Odense M, Denmark
| | - Nils J Færgeman
- Villum Center for Bioanalytical Sciences, Department of Biochemistry and Molecular Biology, University of Southern Denmark, DK-5230 Odense M, Denmark.
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207
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Guijas C, Rodríguez JP, Rubio JM, Balboa MA, Balsinde J. Phospholipase A2 regulation of lipid droplet formation. Biochim Biophys Acta Mol Cell Biol Lipids 2015; 1841:1661-71. [PMID: 25450448 DOI: 10.1016/j.bbalip.2014.10.004] [Citation(s) in RCA: 67] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2014] [Revised: 10/02/2014] [Accepted: 10/14/2014] [Indexed: 02/07/2023]
Abstract
The classical regard of lipid droplets as mere static energy-storage organelles has evolved dramatically. Nowadays these organelles are known to participate in key processes of cell homeostasis, and their abnormal regulation is linked to several disorders including metabolic diseases (diabetes, obesity, atherosclerosis or hepatic steatosis), inflammatory responses in leukocytes, cancer development and neurodegenerative diseases. Hence, the importance of unraveling the cell mechanisms controlling lipid droplet biosynthesis, homeostasis and degradation seems evident Phospholipase A2s, a family of enzymes whose common feature is to hydrolyze the fatty acid present at the sn-2 position of phospholipids, play pivotal roles in cell signaling and inflammation. These enzymes have recently emerged as key regulators of lipid droplet homeostasis, regulating their formation at different levels. This review summarizes recent results on the roles that various phospholipase A2 forms play in the regulation of lipid droplet biogenesis under different conditions. These roles expand the already wide range of functions that these enzymes play in cell physiology and pathophysiology.
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208
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Reimund M, Larsson M, Kovrov O, Kasvandik S, Olivecrona G, Lookene A. Evidence for Two Distinct Binding Sites for Lipoprotein Lipase on Glycosylphosphatidylinositol-anchored High Density Lipoprotein-binding Protein 1 (GPIHBP1). J Biol Chem 2015; 290:13919-34. [PMID: 25873395 DOI: 10.1074/jbc.m114.634626] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2014] [Indexed: 01/20/2023] Open
Abstract
GPIHBP1 is an endothelial membrane protein that transports lipoprotein lipase (LPL) from the subendothelial space to the luminal side of the capillary endothelium. Here, we provide evidence that two regions of GPIHBP1, the acidic N-terminal domain and the central Ly6 domain, interact with LPL as two distinct binding sites. This conclusion is based on comparative binding studies performed with a peptide corresponding to the N-terminal domain of GPIHBP1, the Ly6 domain of GPIHBP1, wild type GPIHBP1, and the Ly6 domain mutant GPIHBP1 Q114P. Although LPL and the N-terminal domain formed a tight but short lived complex, characterized by fast on- and off-rates, the complex between LPL and the Ly6 domain formed more slowly and persisted for a longer time. Unlike the interaction of LPL with the Ly6 domain, the interaction of LPL with the N-terminal domain was significantly weakened by salt. The Q114P mutant bound LPL similarly to the N-terminal domain of GPIHBP1. Heparin dissociated LPL from the N-terminal domain, and partially from wild type GPIHBP1, but was unable to elute the enzyme from the Ly6 domain. When LPL was in complex with the acidic peptide corresponding to the N-terminal domain of GPIHBP1, the enzyme retained its affinity for the Ly6 domain. Furthermore, LPL that was bound to the N-terminal domain interacted with lipoproteins, whereas LPL bound to the Ly6 domain did not. In summary, our data suggest that the two domains of GPIHBP1 interact independently with LPL and that the functionality of LPL depends on its localization on GPIHBP1.
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Affiliation(s)
- Mart Reimund
- From the Department of Chemistry, Tallinn University of Technology, Tallinn 12618, Estonia
| | - Mikael Larsson
- the Department of Medical Biosciences, Umeå University, SE-901 87 Umeå, Sweden, and
| | - Oleg Kovrov
- the Department of Medical Biosciences, Umeå University, SE-901 87 Umeå, Sweden, and
| | - Sergo Kasvandik
- the Institute of Technology, University of Tartu, Tartu 50411, Estonia
| | - Gunilla Olivecrona
- the Department of Medical Biosciences, Umeå University, SE-901 87 Umeå, Sweden, and
| | - Aivar Lookene
- From the Department of Chemistry, Tallinn University of Technology, Tallinn 12618, Estonia,
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209
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Affiliation(s)
- Sara N Vallerie
- From the Department of Medicine, Division of Metabolism, Endocrinology and Nutrition (S.N.V., K.E.B.), and Department of Pathology (K.E.B.), Diabetes and Obesity Center of Excellence, University of Washington School of Medicine, Seattle, WA
| | - Karin E Bornfeldt
- From the Department of Medicine, Division of Metabolism, Endocrinology and Nutrition (S.N.V., K.E.B.), and Department of Pathology (K.E.B.), Diabetes and Obesity Center of Excellence, University of Washington School of Medicine, Seattle, WA.
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210
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JCL Roundtable: Hypertriglyceridemia due to defects in lipoprotein lipase function. J Clin Lipidol 2015; 9:274-80. [PMID: 26073384 DOI: 10.1016/j.jacl.2015.03.009] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2015] [Accepted: 03/31/2015] [Indexed: 01/11/2023]
Abstract
In this Roundtable, our intent is to discuss those rare genetic disorders that impair the function of lipoprotein lipase. These cause severe hypertriglyceridemia that appears in early childhood with Mendelian inheritance and usually with full penetrance in a recessive pattern. Dr Ira Goldberg from New York University School of Medicine and Dr Stephen Young from the University of California, Los Angeles have agreed to answer my questions about this topic. Both have done fundamental work in recent years that has markedly altered our views on lipoprotein lipase function. I am going to start by asking them to give us a brief history of this enzyme system as a clinical entity.
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211
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Savonen R, Hiden M, Hultin M, Zechner R, Levak-Frank S, Olivecrona G, Olivecrona T. The tissue distribution of lipoprotein lipase determines where chylomicrons bind. J Lipid Res 2015; 56:588-598. [PMID: 25589507 DOI: 10.1194/jlr.m056028] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
To determine the role of LPL for binding of lipoproteins to the vascular endothelium, and for the distribution of lipids from lipoproteins, four lines of induced mutant mice were used. Rat chylomicrons labeled in vivo with [(14)C]oleic acid (primarily in TGs, providing a tracer for lipolysis) and [(3)H]retinol (primarily in ester form, providing a tracer for the core lipids) were injected. TG label was cleared more rapidly than core label. There were no differences between the mouse lines in the rate at which core label was cleared. Two minutes after injection, about 5% of the core label, and hence chylomicron particles, were in the heart of WT mice. In mice that expressed LPL only in skeletal muscle, and had much reduced levels of LPL in the heart, binding of chylomicrons was reduced to 1%, whereas in mice that expressed LPL only in the heart, the binding was increased to over 10%. The same patterns of distribution were evident at 20 min when most of the label had been cleared. Thus, the amount of LPL expressed in muscle and heart governed both the binding of chylomicron particles and the assimilation of chylomicron lipids in the tissue.
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Affiliation(s)
- Roger Savonen
- Department of Medical Biosciences, Physiological Chemistry, Umeå University, Umeå, Sweden
| | - Michaela Hiden
- Institut für Medizinische Biochemie, Abteilung für Molekülarbiologie, Karl Franzens Universität, Graz, Austria
| | - Magnus Hultin
- Department of Medical Biosciences, Physiological Chemistry, Umeå University, Umeå, Sweden
| | - Rudolf Zechner
- Institut für Medizinische Biochemie, Abteilung für Molekülarbiologie, Karl Franzens Universität, Graz, Austria
| | - Sanja Levak-Frank
- Department of Medical Biosciences, Physiological Chemistry, Umeå University, Umeå, Sweden
| | - Gunilla Olivecrona
- Department of Medical Biosciences, Physiological Chemistry, Umeå University, Umeå, Sweden
| | - Thomas Olivecrona
- Department of Medical Biosciences, Physiological Chemistry, Umeå University, Umeå, Sweden.
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212
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Abstract
The liver is an essential metabolic organ, and its metabolic function is controlled by insulin and other metabolic hormones. Glucose is converted into pyruvate through glycolysis in the cytoplasm, and pyruvate is subsequently oxidized in the mitochondria to generate ATP through the TCA cycle and oxidative phosphorylation. In the fed state, glycolytic products are used to synthesize fatty acids through de novo lipogenesis. Long-chain fatty acids are incorporated into triacylglycerol, phospholipids, and/or cholesterol esters in hepatocytes. These complex lipids are stored in lipid droplets and membrane structures, or secreted into the circulation as very low-density lipoprotein particles. In the fasted state, the liver secretes glucose through both glycogenolysis and gluconeogenesis. During pronged fasting, hepatic gluconeogenesis is the primary source for endogenous glucose production. Fasting also promotes lipolysis in adipose tissue, resulting in release of nonesterified fatty acids which are converted into ketone bodies in hepatic mitochondria though β-oxidation and ketogenesis. Ketone bodies provide a metabolic fuel for extrahepatic tissues. Liver energy metabolism is tightly regulated by neuronal and hormonal signals. The sympathetic system stimulates, whereas the parasympathetic system suppresses, hepatic gluconeogenesis. Insulin stimulates glycolysis and lipogenesis but suppresses gluconeogenesis, and glucagon counteracts insulin action. Numerous transcription factors and coactivators, including CREB, FOXO1, ChREBP, SREBP, PGC-1α, and CRTC2, control the expression of the enzymes which catalyze key steps of metabolic pathways, thus controlling liver energy metabolism. Aberrant energy metabolism in the liver promotes insulin resistance, diabetes, and nonalcoholic fatty liver diseases.
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Affiliation(s)
- Liangyou Rui
- Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan
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213
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Kleberg K, Nielsen LL, Stuhr-Hansen N, Nielsen J, Hansen HS. Evaluation of the immediate vascular stability of lipoprotein lipase-generated 2-monoacylglycerol in mice. Biofactors 2014; 40:596-602. [PMID: 25359532 DOI: 10.1002/biof.1189] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/18/2014] [Accepted: 10/14/2014] [Indexed: 11/07/2022]
Abstract
2-Monoacylglycerols are gaining increasing interest as signaling lipids, beyond endocannabinoids, for example, as ligands for the receptor GPR119 and as mediators of insulin secretion. In the vascular system, they are formed by the action of lipoprotein lipase (LPL); however, their further disposition is unclear. Assuming similar affinity for uptake and incorporation into tissues of 2-oleoylglycerol and 2-oleylglyceryl ether, we have synthesized a (3)H-labeled 2-ether analog of triolein (labeled in alkyl group) and compared its disposition with (14)C-labeled triolein (labeled in glycerol) 20 min after intravenous coadministration in a ratio of 1:1 to mice. We found that peripheral tissues and the liver in particular are able to take up 2-monoacylglycerols as seen from (3)H uptake. In muscle and adipose tissue, 2-monoacylglycerols are probably further hydrolyzed as seen by an increased (3)H/(14)C ratio, whereas in the liver and the heart, data suggest that they are also subjected to re-esterification to triacylglycerol, as seen by an unchanged (3)H/(14)C ratio in the lipid fraction of the tissues. Our findings suggest that LPL-generated 2-monoacylglycerol is likely to be stable in the vascular system and thus have a potential to circulate or at least exert effects in tissues where it may be locally produced.
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Affiliation(s)
- Karen Kleberg
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
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214
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Fuchs CD, Claudel T, Trauner M. Role of metabolic lipases and lipolytic metabolites in the pathogenesis of NAFLD. Trends Endocrinol Metab 2014; 25:576-85. [PMID: 25183341 DOI: 10.1016/j.tem.2014.08.001] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/12/2014] [Revised: 08/06/2014] [Accepted: 08/06/2014] [Indexed: 12/12/2022]
Abstract
Non-alcoholic fatty liver disease (NAFLD) is the most frequent chronic liver disease in Western countries, ranging from simple steatosis to steatohepatitis, cirrhosis, and hepatocellular cancer. Although the mechanisms underlying disease progression are incompletely understood, lipotoxic events in the liver resulting in inflammation and fibrosis appear to be central. Free fatty acids and their metabolites are potentially lipotoxic mediators triggering liver injury, suggesting a central role for metabolic lipases. These enzymes are major players in lipid partitioning between tissues and within cells, and provide ligands for nuclear receptors (NRs). We discuss the potential role of intracellular lipases and their lipolytic products in NAFLD. Because tissue-specific modulation of lipases is currently impossible, targeting NRs with ligands may open novel therapeutic perspectives.
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Affiliation(s)
- Claudia D Fuchs
- Hans Popper Laboratory of Molecular Hepatology, Division of Gastroenterology and Hepatology, Department of Internal Medicine III, Medical University of Vienna, Vienna, Austria
| | - Thierry Claudel
- Hans Popper Laboratory of Molecular Hepatology, Division of Gastroenterology and Hepatology, Department of Internal Medicine III, Medical University of Vienna, Vienna, Austria
| | - Michael Trauner
- Hans Popper Laboratory of Molecular Hepatology, Division of Gastroenterology and Hepatology, Department of Internal Medicine III, Medical University of Vienna, Vienna, Austria.
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215
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Joffin N, Jaubert AM, Durant S, Bastin J, De Bandt JP, Cynober L, Moinard C, Coumoul X, Forest C, Noirez P. Citrulline reduces glyceroneogenesis and induces fatty acid release in visceral adipose tissue from overweight rats. Mol Nutr Food Res 2014; 58:2320-30. [PMID: 25271764 DOI: 10.1002/mnfr.201400507] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2014] [Revised: 09/15/2014] [Accepted: 09/21/2014] [Indexed: 12/21/2022]
Abstract
SCOPE High-fat diet (HFD) increases visceral adipose tissue (AT). Our aim was to evaluate whether citrulline (CIT) affected nonesterified fatty acid (NEFA) metabolism in AT from HFD-fed rats. METHODS AND RESULTS Rats were fed for 8 weeks with either a control diet (CD) or HFD. Retroperitoneal AT explants were exposed to 2.5 mmol/L CIT for 24 h. We analyzed lipolysis, beta-oxidation, glyceroneogenesis, and the expression of the key associated enzymes. CIT doubled NEFA release selectively in HFD AT. Phosphorylation of hormone-sensitive lipase was upregulated 50 and 100% by CIT in CD and HFD AT, respectively. Under CIT, beta-oxidation increased similarly whatever the diet, whereas glyceroneogenesis, which permits NEFA re-esterification, was downregulated 50 and 80% in CD and HFD AT, respectively. In the latter, the important decrease in re-esterification probably explains the rise of NEFA release. A pretreatment with the nitric oxide synthase inhibitor N ω-nitro-l-arginine methyl ester abolished CIT effects. CONCLUSION These results demonstrate direct lipolytic and antiglyceroneogenic effects of CIT on CD and HFD AT. The selective CIT-mediated NEFA release from HFD AT was probably the consequence of the drastic decrease in glyceroneogenesis and nitric oxide was a mediator of CIT effects. These results provide evidence for a direct action of CIT on AT to reduce overweight.
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Affiliation(s)
- Nolwenn Joffin
- Université Paris Descartes, Sorbonne Paris Cité, France; Institut National de la Santé et de la Recherche Médicale UMR-S 1124, Faculté des Sciences Fondamentales et Biomédicales, Pharmacologie Toxicologie et Signalisation Cellulaire, Paris, France
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Picco R, Tomasella A, Fogolari F, Brancolini C. Transcriptomic analysis unveils correlations between regulative apoptotic caspases and genes of cholesterol homeostasis in human brain. PLoS One 2014; 9:e110610. [PMID: 25330190 PMCID: PMC4199739 DOI: 10.1371/journal.pone.0110610] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2014] [Accepted: 09/23/2014] [Indexed: 01/09/2023] Open
Abstract
Regulative circuits controlling expression of genes involved in the same biological processes are frequently interconnected. These circuits operate to coordinate the expression of multiple genes and also to compensate dysfunctions in specific elements of the network. Caspases are cysteine-proteases with key roles in the execution phase of apoptosis. Silencing of caspase-2 expression in cultured glioblastoma cells allows the up-regulation of a limited number of genes, among which some are related to cholesterol homeostasis. Lysosomal Acid Lipase A (LIPA) was up-regulated in two different cell lines in response to caspase-2 down-regulation and cells silenced for caspase-2 exhibit reduced cholesterol staining in the lipid droplets. We expanded this observation by large-scale analysis of mRNA expression. All caspases were analyzed in terms of co-expression in comparison with 166 genes involved in cholesterol homeostasis. In the brain, hierarchical clustering has revealed that the expression of regulative apoptotic caspases (CASP2, CASP8 CASP9, CASP10) and of the inflammatory CASP1 is linked to several genes involved in cholesterol homeostasis. These correlations resulted in altered GBM (Glioblastoma Multiforme), in particular for CASP1. We have also demonstrated that these correlations are tissue specific being reduced (CASP9 and CASP10) or different (CASP2) in the liver. For some caspases (CASP1, CASP6 and CASP7) these correlations could be related to brain aging.
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Affiliation(s)
- Raffaella Picco
- Department of Medical and Biological Sciences, Università degli Studi di Udine, Udine, Italy
| | - Andrea Tomasella
- Department of Medical and Biological Sciences, Università degli Studi di Udine, Udine, Italy
| | - Federico Fogolari
- Department of Medical and Biological Sciences, Università degli Studi di Udine, Udine, Italy
| | - Claudio Brancolini
- Department of Medical and Biological Sciences, Università degli Studi di Udine, Udine, Italy
- * E-mail:
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217
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Buonuomo PS, Bartuli A, Rabacchi C, Bertolini S, Calandra S. A 3-day-old neonate with severe hypertriglyceridemia from novel mutations of the GPIHBP1 gene. J Clin Lipidol 2014; 9:265-70. [PMID: 25911085 DOI: 10.1016/j.jacl.2014.10.003] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2014] [Revised: 10/01/2014] [Accepted: 10/06/2014] [Indexed: 12/16/2022]
Abstract
BACKGROUND Familial chylomicronemia is a genetic defect of the intravascular lipolysis of triglyceride (TG)-rich lipoproteins. Intravascular lipolysis involves the TG-hydrolase lipoprotein lipase (LPL) as well as other factors such as apolipoprotein CII and apolipoprotein AV (activators of LPL), GPIHBP1 (the molecular platform required for LPL activity on endothelial surface), and LMF1 (a factor required for intracellular formation of active LPL). METHODS We sequenced the familial chylomicronemia candidate genes in a neonate with chylomicronemia. RESULTS A 3-day-old newborn was found to have chylomicronemia (plasma TG 18.8 mmol/L, 1.667 mg/dL). The discontinuation of breastfeeding for 24 hours reduced plasma TG to 2.3 mmol/L (201 mg/dL), whereas its resumption induced a sharp TG increase (7.9 mmol/L, 690 mg/dL). The child was switched to a low-fat diet, which was effective in maintaining TG level below 3.5 mmol/L (294 mg/dL) during the first months of life. The child was found to be a compound heterozygous for 2 novel mutations in GPIHBP1 gene. The first mutation was a 9-bp deletion and 4-bp insertion in exon 2, causing a frameshift that abolished the canonical termination codon TGA. The predicted translation product of the mutant messenger RNA is a peptide that contains 51 amino acids of the N-terminal end of the wild-type protein followed by 252 novel amino acids. The second mutation was a nucleotide change (c.319T>C), causing an amino acid substitution p.(Ser107Pro) predicted in silico to be damaging. CONCLUSIONS GPIHBP1 mutations should be considered in neonates with chylomicronemia negative for mutations in LPL gene.
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Affiliation(s)
| | - Andrea Bartuli
- Rare Diseases and Medical Genetics, Bambino Gesù Children Hospital, Rome, Italy
| | - Claudio Rabacchi
- Department of Life Sciences, University of Modena and Reggio Emilia, Modena, Italy
| | - Stefano Bertolini
- Department of Internal Medicine, University of Genova, Genova, Italy
| | - Sebastiano Calandra
- Department of Biomedical, Metabolic and Neural Sciences, University of Modena and Reggio Emilia, Modena, Italy.
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Yen CLE, Nelson DW, Yen MI. Intestinal triacylglycerol synthesis in fat absorption and systemic energy metabolism. J Lipid Res 2014; 56:489-501. [PMID: 25231105 DOI: 10.1194/jlr.r052902] [Citation(s) in RCA: 89] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The intestine plays a prominent role in the biosynthesis of triacylglycerol (triglyceride; TAG). Digested dietary TAG is repackaged in the intestine to form the hydrophobic core of chylomicrons, which deliver metabolic fuels, essential fatty acids, and other lipid-soluble nutrients to the peripheral tissues. By controlling the flux of dietary fat into the circulation, intestinal TAG synthesis can greatly impact systemic metabolism. Genes encoding many of the enzymes involved in TAG synthesis have been identified. Among TAG synthesis enzymes, acyl-CoA:monoacylglycerol acyltransferase 2 and acyl-CoA:diacylglycerol acyltransferase (DGAT)1 are highly expressed in the intestine. Their physiological functions have been examined in the context of whole organisms using genetically engineered mice and, in the case of DGAT1, specific inhibitors. An emerging theme from recent findings is that limiting the rate of TAG synthesis in the intestine can modulate gut hormone secretion, lipid metabolism, and systemic energy balance. The underlying mechanisms and their implications for humans are yet to be explored. Pharmacological inhibition of TAG hydrolysis in the intestinal lumen has been employed to combat obesity and associated disorders with modest efficacy and unwanted side effects. The therapeutic potential of inhibiting specific enzymes involved in intestinal TAG synthesis warrants further investigation.
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Affiliation(s)
- Chi-Liang Eric Yen
- Department of Nutritional Sciences, University of Wisconsin-Madison, Madison, WI 53706.
| | - David W Nelson
- Department of Nutritional Sciences, University of Wisconsin-Madison, Madison, WI 53706
| | - Mei-I Yen
- Department of Nutritional Sciences, University of Wisconsin-Madison, Madison, WI 53706
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219
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Mao HZ, Ehrhardt N, Bedoya C, Gomez JA, DeZwaan-McCabe D, Mungrue IN, Kaufman RJ, Rutkowski DT, Péterfy M. Lipase maturation factor 1 (lmf1) is induced by endoplasmic reticulum stress through activating transcription factor 6α (Atf6α) signaling. J Biol Chem 2014; 289:24417-27. [PMID: 25035425 PMCID: PMC4148868 DOI: 10.1074/jbc.m114.588764] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2014] [Indexed: 11/06/2022] Open
Abstract
Lipase maturation factor 1 (Lmf1) is a critical determinant of plasma lipid metabolism, as demonstrated by severe hypertriglyceridemia associated with its mutations in mice and human subjects. Lmf1 is a chaperone localized to the endoplasmic reticulum (ER) and required for the post-translational maturation and activation of several vascular lipases. Despite its importance in plasma lipid homeostasis, the regulation of Lmf1 remains unexplored. We report here that Lmf1 expression is induced by ER stress in various cell lines and in tunicamycin (TM)-injected mice. Using genetic deficiencies in mouse embryonic fibroblasts and mouse liver, we identified the Atf6α arm of the unfolded protein response as being responsible for the up-regulation of Lmf1 in ER stress. Experiments with luciferase reporter constructs indicated that ER stress activates the Lmf1 promoter through a GC-rich DNA sequence 264 bp upstream of the transcriptional start site. We demonstrated that Atf6α is sufficient to induce the Lmf1 promoter in the absence of ER stress, and this effect is mediated by the TM-responsive cis-regulatory element. Conversely, Atf6α deficiency induced by genetic ablation or a dominant-negative form of Atf6α abolished TM stimulation of the Lmf1 promoter. In conclusion, our results indicate that Lmf1 is an unfolded protein response target gene, and Atf6α signaling is sufficient and necessary for activation of the Lmf1 promoter. Importantly, the induction of Lmf1 by ER stress appears to be a general phenomenon not restricted to lipase-expressing cells, which suggests a lipase-independent cellular role for this protein in ER homeostasis.
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Affiliation(s)
- Hui Z Mao
- From the Medical Genetics Research Institute and
| | | | - Candy Bedoya
- Department of Biomedical Sciences, Cedars-Sinai Medical Center, Los Angeles, California 90048
| | - Javier A Gomez
- Department of Anatomy and Cell Biology and Department of Internal Medicine, University of Iowa Carver College of Medicine, Iowa City, Iowa 52242
| | - Diane DeZwaan-McCabe
- Department of Anatomy and Cell Biology and Department of Internal Medicine, University of Iowa Carver College of Medicine, Iowa City, Iowa 52242
| | - Imran N Mungrue
- the Department of Pharmacology and Experimental Therapeutics, Louisiana State University School of Medicine, New Orleans, Louisiana 70112
| | - Randal J Kaufman
- Degenerative Disease Research, Sanford-Burnham Medical Research Institute, La Jolla, California 92037, and
| | - D Thomas Rutkowski
- Department of Anatomy and Cell Biology and Department of Internal Medicine, University of Iowa Carver College of Medicine, Iowa City, Iowa 52242
| | - Miklós Péterfy
- From the Medical Genetics Research Institute and Department of Biomedical Sciences, Cedars-Sinai Medical Center, Los Angeles, California 90048, the Department of Medicine, David Geffen School of Medicine at the University of California, Los Angeles, California 90095
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220
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Turlo K, Leung CS, Seo JJ, Goulbourne CN, Adeyo O, Gin P, Voss C, Bensadoun A, Fong LG, Young SG, Beigneux AP. Equivalent binding of wild-type lipoprotein lipase (LPL) and S447X-LPL to GPIHBP1, the endothelial cell LPL transporter. BIOCHIMICA ET BIOPHYSICA ACTA 2014; 1841:963-9. [PMID: 24704550 PMCID: PMC4212522 DOI: 10.1016/j.bbalip.2014.03.011] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/04/2013] [Revised: 03/18/2014] [Accepted: 03/27/2014] [Indexed: 02/05/2023]
Abstract
The S447X polymorphism in lipoprotein lipase (LPL), which shortens LPL by two amino acids, is associated with low plasma triglyceride levels and reduced risk for coronary heart disease. S447X carriers have higher LPL levels in the pre- and post-heparin plasma, raising the possibility that the S447X polymorphism leads to higher LPL levels within capillaries. One potential explanation for increased amounts of LPL in capillaries would be more avid binding of S447X-LPL to GPIHBP1 (the protein that binds LPL dimers and shuttles them to the capillary lumen). This explanation seems plausible because sequences within the carboxyl terminus of LPL are known to mediate LPL binding to GPIHBP1. To assess the impact of the S447X polymorphism on LPL binding to GPIHBP1, we compared the ability of internally tagged versions of wild-type LPL (WT-LPL) and S447X-LPL to bind to GPIHBP1 in both cell-based and cell-free binding assays. In the cell-based assay, we compared the binding of WT-LPL and S447X-LPL to GPIHBP1 on the surface of cultured cells. This assay revealed no differences in the binding of WT-LPL and S447X-LPL to GPIHBP1. In the cell-free assay, we compared the binding of internally tagged WT-LPL and S447X-LPL to soluble GPIHBP1 immobilized on agarose beads. Again, no differences in the binding of WT-LPL and S447X-LPL to GPIHBP1 were observed. We conclude that increased binding of S447X-LPL to GPIHBP1 is unlikely to be the explanation for more efficient lipolysis and lower plasma triglyceride levels in S447X carriers.
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Affiliation(s)
- Kirsten Turlo
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, United States
| | - Calvin S Leung
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, United States
| | - Jane J Seo
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, United States
| | - Chris N Goulbourne
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, United States
| | - Oludotun Adeyo
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, United States
| | - Peter Gin
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, United States
| | - Constance Voss
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, United States
| | - André Bensadoun
- Division of Nutritional Science, Cornell University, Ithaca, NY 14853, United States
| | - Loren G Fong
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, United States
| | - Stephen G Young
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, United States; Department of Human Genetics, University of California, Los Angeles, CA 90095, United States.
| | - Anne P Beigneux
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, United States.
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221
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Kleberg K, Hassing HA, Hansen HS. Classical endocannabinoid-like compounds and their regulation by nutrients. Biofactors 2014; 40:363-72. [PMID: 24677570 DOI: 10.1002/biof.1158] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/06/2014] [Accepted: 01/07/2014] [Indexed: 11/08/2022]
Abstract
Endocannabinoid-like compounds are structurally related to the true endocannabinoids but do not contain highly unsaturated fatty acids, and they do not bind the cannabinoid receptors. The classical endocannabinoid-like compounds include N-acylethanolamines and 2-monoacylglycerols, and their structural resemblance to the endocannabinoids makes them players in the endocannabinoid system, where they can interfere with the actions of the true endocannabinoids, because they in several cases engage the same synthesizing and degrading enzymes. In addition they have pharmacological actions of their own, which are particularly interesting in a nutritional and metabolic context. Exogenously supplied oleoylethanolamide, palmitoylethanolamide, and linoleoylethanolamide have anorexic effects, and the endogenous formation of these N-acylethanolamines in the small intestine may serve an important role in regulating food intake, through signaling via PPARα and the vagus nerve to the brain appetite center. A chronic high-fat diet will decrease intestinal levels of these anorectic N-acylethanolamines and this may contribute to the hyperphagic effect of high-fat diet; 2-monoacylglycerols mediate endocrine responses in the small intestine; probably trough activation of GPR119 on enteroendocrine cells, and diet-derived 2-monoacylglycerols, for example, 2-oleoylglycerol and 2-palmitoylglycerol might be important for intestinal fat sensing. Whether these 2-monoacylglycerols have signaling functions in other tissues is unclear at present.
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Affiliation(s)
- Karen Kleberg
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark
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222
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Larsson M, Caraballo R, Ericsson M, Lookene A, Enquist PA, Elofsson M, Nilsson SK, Olivecrona G. Identification of a small molecule that stabilizes lipoprotein lipase in vitro and lowers triglycerides in vivo. Biochem Biophys Res Commun 2014; 450:1063-9. [DOI: 10.1016/j.bbrc.2014.06.114] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2014] [Accepted: 06/23/2014] [Indexed: 01/04/2023]
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223
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Jiang H, Favaro E, Goulbourne CN, Rakowska PD, Hughes GM, Ryadnov MG, Fong LG, Young SG, Ferguson DJP, Harris AL, Grovenor CRM. Stable isotope imaging of biological samples with high resolution secondary ion mass spectrometry and complementary techniques. Methods 2014; 68:317-24. [PMID: 24556558 PMCID: PMC4222523 DOI: 10.1016/j.ymeth.2014.02.012] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2013] [Revised: 01/07/2014] [Accepted: 02/06/2014] [Indexed: 02/07/2023] Open
Abstract
Stable isotopes are ideal labels for studying biological processes because they have little or no effect on the biochemical properties of target molecules. The NanoSIMS is a tool that can image the distribution of stable isotope labels with up to 50 nm spatial resolution and with good quantitation. This combination of features has enabled several groups to undertake significant experiments on biological problems in the last decade. Combining the NanoSIMS with other imaging techniques also enables us to obtain not only chemical information but also the structural information needed to understand biological processes. This article describes the methodologies that we have developed to correlate atomic force microscopy and backscattered electron imaging with NanoSIMS experiments to illustrate the imaging of stable isotopes at molecular, cellular, and tissue scales. Our studies make it possible to address 3 biological problems: (1) the interaction of antimicrobial peptides with membranes; (2) glutamine metabolism in cancer cells; and (3) lipoprotein interactions in different tissues.
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Affiliation(s)
- H Jiang
- Materials Department, Oxford University, Oxford, UK.
| | - E Favaro
- Weatherall Institute of Molecular Medicine, Oxford University, Oxford, UK
| | - C N Goulbourne
- Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, USA
| | - P D Rakowska
- National Physical Laboratory, Teddington, UK; Department of Chemistry, University College London, London, UK
| | - G M Hughes
- Materials Department, Oxford University, Oxford, UK
| | - M G Ryadnov
- National Physical Laboratory, Teddington, UK; School of Physics and Astronomy, University of Edinburgh, Edinburgh, UK
| | - L G Fong
- Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, USA
| | - S G Young
- Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, USA; Department of Human Genetics, University of California Los Angeles, Los Angeles, USA
| | - D J P Ferguson
- Nuffield Department of Clinical Laboratory Science, University of Oxford, John Radcliffe Hospital, Oxford, UK
| | - A L Harris
- Weatherall Institute of Molecular Medicine, Oxford University, Oxford, UK
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Joffin N, Jaubert AM, Durant S, Bastin J, De Bandt JP, Cynober L, Moinard C, Forest C, Noirez P. Citrulline induces fatty acid release selectively in visceral adipose tissue from old rats. Mol Nutr Food Res 2014; 58:1765-75. [DOI: 10.1002/mnfr.201400053] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2014] [Revised: 04/11/2014] [Accepted: 04/14/2014] [Indexed: 12/17/2022]
Affiliation(s)
- Nolwenn Joffin
- Université Paris Descartes; Sorbonne Paris Cité France
- Institut National de la Santé et de la Recherche Médicale UMR-S 1124; Faculté des Sciences Fondamentales et Biomédicales; Pharmacologie Toxicologie et Signalisation Cellulaire; Paris France
| | - Anne-Marie Jaubert
- Institut National de la Santé et de la Recherche Médicale UMR-S 1124; Faculté des Sciences Fondamentales et Biomédicales; Pharmacologie Toxicologie et Signalisation Cellulaire; Paris France
- Département de Biochimie et de Biologie Moléculaire; Faculté de Médecine Paris-Ile de France-Ouest; Université de Versailles Saint-Quentin en Yvelines; Versailles France
| | - Sylvie Durant
- Université Paris Descartes; Sorbonne Paris Cité France
- Institut National de la Santé et de la Recherche Médicale UMR-S 1124; Faculté des Sciences Fondamentales et Biomédicales; Pharmacologie Toxicologie et Signalisation Cellulaire; Paris France
| | - Jean Bastin
- Université Paris Descartes; Sorbonne Paris Cité France
- Institut National de la Santé et de la Recherche Médicale UMR-S 1124; Faculté des Sciences Fondamentales et Biomédicales; Pharmacologie Toxicologie et Signalisation Cellulaire; Paris France
| | - Jean-Pascal De Bandt
- Université Paris Descartes; Sorbonne Paris Cité France
- Laboratoire de Biologie de la Nutrition; Faculté des Sciences Pharmaceutiques et Biologiques; Paris France
- Service de Biochimie, Hôpital Cochin; Assistance Publique Hôpitaux de Paris; Paris France
| | - Luc Cynober
- Université Paris Descartes; Sorbonne Paris Cité France
- Laboratoire de Biologie de la Nutrition; Faculté des Sciences Pharmaceutiques et Biologiques; Paris France
- Service de Biochimie, Hôpital Cochin; Assistance Publique Hôpitaux de Paris; Paris France
| | - Christophe Moinard
- Université Paris Descartes; Sorbonne Paris Cité France
- Laboratoire de Biologie de la Nutrition; Faculté des Sciences Pharmaceutiques et Biologiques; Paris France
| | - Claude Forest
- Université Paris Descartes; Sorbonne Paris Cité France
- Institut National de la Santé et de la Recherche Médicale UMR-S 1124; Faculté des Sciences Fondamentales et Biomédicales; Pharmacologie Toxicologie et Signalisation Cellulaire; Paris France
| | - Philippe Noirez
- Université Paris Descartes; Sorbonne Paris Cité France
- Institut de Recherche Biomédicale et d’Epidémiologie du Sport; Paris France
- UFR des Sciences et Techniques des Activités Physiques et Sportives; Paris France
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225
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Ilias I, Vassiliadi DA, Theodorakopoulou M, Boutati E, Maratou E, Mitrou P, Nikitas N, Apollonatou S, Dimitriadis G, Armaganidis A, Dimopoulou I. Adipose tissue lipolysis and circulating lipids in acute and subacute critical illness: effects of shock and treatment. J Crit Care 2014; 29:1130.e5-9. [PMID: 25012960 DOI: 10.1016/j.jcrc.2014.06.003] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2014] [Revised: 05/26/2014] [Accepted: 06/01/2014] [Indexed: 02/08/2023]
Abstract
PURPOSE The purpose of this study is to assess lipid metabolism at the tissue level in critically ill subjects. MATERIALS AND METHODS We studied 182 patients with systemic inflammatory response syndrome/severe sepsis or shock during the acute (day 1) and subacute phase of critical illness (day 6). All subjects had a tissue microdialysis (MD) catheter placed in femoral adipose tissue upon admission to the intensive care unit (ICU). Plasma cholesterol, high-density lipoprotein, low-density lipoprotein, free fatty acids (FFAs), triglyceride, and MD glycerol (GLYC) were measured on days 1 and 6 in the ICU. RESULTS On admission, 56% of the patients had increased levels (>200 μmol/L) of MD GLYC. Patients with shock displayed more pronounced subcutaneous tissue lipolysis and more profound derangements of circulating lipids vs patients without shock (but no appreciable differences in FFA levels). Furthermore, in patients with shock during the acute period, there were positive, albeit weak, correlations of subcutaneous tissue lipolysis (MD GLYC), plasma FFAs (r=0.260; P=.01), and norepinephrine's dose (r=0.230; P=.01), whereas during the subacute phase, MD GLY levels were higher in patients receiving glucocorticoids (344.7±276.0 μmol/L vs 252.2±158.4 μmol/L; P=.03). CONCLUSIONS Subcutaneous tissue lipolysis is only one of the many determinants of plasma FFAs. Routinely applied therapeutic modalities in the ICU interfere with adipose tissue metabolism.
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Affiliation(s)
- I Ilias
- Endocrine Department, E. Venizelou Hospital, Athens, Greece.
| | - D A Vassiliadi
- Second Department of Internal Medicine, National and Kapodistrian University of Athens, Attikon University Hospital, Athens, Greece
| | - M Theodorakopoulou
- Second Department of Critical Care Medicine, National and Kapodistrian University of Athens, Attikon University Hospital, Athens, Greece
| | - E Boutati
- Second Department of Internal Medicine, National and Kapodistrian University of Athens, Attikon University Hospital, Athens, Greece
| | - E Maratou
- Second Department of Internal Medicine, National and Kapodistrian University of Athens, Attikon University Hospital, Athens, Greece
| | - P Mitrou
- Second Department of Internal Medicine, National and Kapodistrian University of Athens, Attikon University Hospital, Athens, Greece
| | - N Nikitas
- Second Department of Critical Care Medicine, National and Kapodistrian University of Athens, Attikon University Hospital, Athens, Greece
| | - S Apollonatou
- Second Department of Internal Medicine, National and Kapodistrian University of Athens, Attikon University Hospital, Athens, Greece
| | - G Dimitriadis
- Second Department of Internal Medicine, National and Kapodistrian University of Athens, Attikon University Hospital, Athens, Greece
| | - A Armaganidis
- Second Department of Critical Care Medicine, National and Kapodistrian University of Athens, Attikon University Hospital, Athens, Greece
| | - I Dimopoulou
- Second Department of Critical Care Medicine, National and Kapodistrian University of Athens, Attikon University Hospital, Athens, Greece
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Abstract
In adipocytes the hydrolysis of TAG to produce fatty acids and glycerol under fasting conditions or times of elevated energy demands is tightly regulated by neuroendocrine signals, resulting in the activation of lipolytic enzymes. Among the classic regulators of lipolysis, adrenergic stimulation and the insulin-mediated control of lipid mobilisation are the best known. Initially, hormone-sensitive lipase (HSL) was thought to be the rate-limiting enzyme of the first lipolytic step, while we now know that adipocyte TAG lipase is the key enzyme for lipolysis initiation. Pivotal, previously unsuspected components have also been identified at the protective interface of the lipid droplet surface and in the signalling pathways that control lipolysis. Perilipin, comparative gene identification-58 (CGI-58) and other proteins of the lipid droplet surface are currently known to be key regulators of the lipolytic machinery, protecting or exposing the TAG core of the droplet to lipases. The neuroendocrine control of lipolysis is prototypically exerted by catecholaminergic stimulation and insulin-induced suppression, both of which affect cyclic AMP levels and hence the protein kinase A-mediated phosphorylation of HSL and perilipin. Interestingly, in recent decades adipose tissue has been shown to secrete a large number of adipokines, which exert direct effects on lipolysis, while adipocytes reportedly express a wide range of receptors for signals involved in lipid mobilisation. Recently recognised mediators of lipolysis include some adipokines, structural membrane proteins, atrial natriuretic peptides, AMP-activated protein kinase and mitogen-activated protein kinase. Lipolysis needs to be reanalysed from the broader perspective of its specific physiological or pathological context since basal or stimulated lipolytic rates occur under diverse conditions and by different mechanisms.
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227
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Abstract
In addition to their roles in normal cell physiology, endocytic processes play a key role in many diseases. In this review, three diseases are discussed as examples of the role of endocytic processes in disease. The uptake of cholesterol via LDL is central to our understanding of atherosclerosis, and the study of this disease led to many of the key breakthroughs in understanding receptor-mediated endocytosis. Alzheimer's disease is a growing burden as the population ages. Endosomes and lysosomes play important but only partially understood roles in both the formation and the degradation of the amyloid fibrils that are associated with Alzheimer's disease. Inherited lysosomal storage diseases are individually rare, but collectively they affect many individuals. Recent advances are leading to improved enzyme replacement therapy and are also leading to small-molecule drugs to treat some of these diseases.
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Affiliation(s)
- Frederick R Maxfield
- Department of Biochemistry, Weill Cornell Medical College, New York, New York 10065
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228
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Type 1 hyperlipoproteinemia due to a novel deletion of exons 3 and 4 in the GPIHBP1 gene. Atherosclerosis 2014; 234:30-3. [DOI: 10.1016/j.atherosclerosis.2014.02.005] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/20/2013] [Revised: 01/23/2014] [Accepted: 02/06/2014] [Indexed: 11/22/2022]
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229
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Abstract
The endothelium is often viewed solely as the barrier that prevents the penetration of circulating lipoproteins into the arterial wall. However, recent research has demonstrated that the endothelium has an important part in regulating circulating fatty acids and lipoproteins, and is in turn affected by these lipids/lipoproteins in ways that appear to have important repercussions for atherosclerosis. Thus, a number of potentially toxic lipids are produced during lipolysis of lipoproteins at the endothelial cell surface. Catabolism of triglyceride-rich lipoproteins creates free fatty acids that are readily taken up by endothelial cells, and, likely through the action of acyl-CoA synthetases, exacerbate inflammatory processes. In this article, we review how the endothelium participates in lipoprotein metabolism, how lipids alter endothelial functions, and how lipids are internalized, processed, and transported into the subendothelial space. Finally, we address the many endothelial changes that might promote atherogenesis, especially in the setting of diabetes.
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Affiliation(s)
- Ira J Goldberg
- Department of Medicine, Division of Preventive Medicine & Nutrition, Columbia University College of Physicians and Surgeons, 630 West 168th Street, New York, NY, 10032, USA,
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230
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Kersten S. Physiological regulation of lipoprotein lipase. Biochim Biophys Acta Mol Cell Biol Lipids 2014; 1841:919-33. [PMID: 24721265 DOI: 10.1016/j.bbalip.2014.03.013] [Citation(s) in RCA: 347] [Impact Index Per Article: 34.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2014] [Revised: 03/27/2014] [Accepted: 03/30/2014] [Indexed: 01/01/2023]
Abstract
The enzyme lipoprotein lipase (LPL), originally identified as the clearing factor lipase, hydrolyzes triglycerides present in the triglyceride-rich lipoproteins VLDL and chylomicrons. LPL is primarily expressed in tissues that oxidize or store fatty acids in large quantities such as the heart, skeletal muscle, brown adipose tissue and white adipose tissue. Upon production by the underlying parenchymal cells, LPL is transported and attached to the capillary endothelium by the protein GPIHBP1. Because LPL is rate limiting for plasma triglyceride clearance and tissue uptake of fatty acids, the activity of LPL is carefully controlled to adjust fatty acid uptake to the requirements of the underlying tissue via multiple mechanisms at the transcriptional and post-translational level. Although various stimuli influence LPL gene transcription, it is now evident that most of the physiological variation in LPL activity, such as during fasting and exercise, appears to be driven via post-translational mechanisms by extracellular proteins. These proteins can be divided into two main groups: the liver-derived apolipoproteins APOC1, APOC2, APOC3, APOA5, and APOE, and the angiopoietin-like proteins ANGPTL3, ANGPTL4 and ANGPTL8, which have a broader expression profile. This review will summarize the available literature on the regulation of LPL activity in various tissues, with an emphasis on the response to diverse physiological stimuli.
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Affiliation(s)
- Sander Kersten
- Nutrition, Metabolism and Genomics Group, Division of Human Nutrition, Wageningen University, Bomenweg 2, 6703HD Wageningen, The Netherlands
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231
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Abstract
There has been an upsurge of interest in the adipocyte coincident with the onset of the obesity epidemic and the realization that adipose tissue plays a major role in the regulation of metabolic function. The past few years, in particular, have seen significant changes in the way that we classify adipocytes and how we view adipose development and differentiation. We have new perspective on the roles played by adipocytes in a variety of homeostatic processes and on the mechanisms used by adipocytes to communicate with other tissues. Finally, there has been significant progress in understanding how these relationships are altered during metabolic disease and how they might be manipulated to restore metabolic health.
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Affiliation(s)
- Evan D Rosen
- Division of Endocrinology, Beth Israel Deaconess Medical Center, Boston, MA 02215, USA; Departments of Genetics and Cell Biology, Harvard Medical School, Boston, MA 02215, USA; Broad Institute of Harvard and MIT, Cambridge, MA 02142, USA.
| | - Bruce M Spiegelman
- Departments of Genetics and Cell Biology, Harvard Medical School, Boston, MA 02215, USA; Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA 02115, USA.
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232
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Dijk W, Kersten S. Regulation of lipoprotein lipase by Angptl4. Trends Endocrinol Metab 2014; 25:146-55. [PMID: 24397894 DOI: 10.1016/j.tem.2013.12.005] [Citation(s) in RCA: 140] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/01/2013] [Revised: 11/30/2013] [Accepted: 12/02/2013] [Indexed: 02/07/2023]
Abstract
Triglyceride (TG)-rich chylomicrons and very low density lipoproteins (VLDL) distribute fatty acids (FA) to various tissues by interacting with the enzyme lipoprotein lipase (LPL). The protein angiopoietin-like 4 (Angptl4) is under sensitive transcriptional control by FA and the FA-activated peroxisome proliferator activated receptors (PPARs), and its tissue expression largely overlaps with that of LPL. Growing evidence indicates that Angptl4 mediates the physiological fluctuations in LPL activity, including the decrease in adipose tissue LPL activity during fasting. This review focuses on the major ambiguities concerning the mechanism of LPL inhibition by Angptl4, as well as on the physiological role of Angptl4 in lipid metabolism, highlighting its function in a variety of tissues, and uses this information to make suggestions for further research.
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Affiliation(s)
- Wieneke Dijk
- Nutrition, Metabolism, and Genomics group, Wageningen University, Bomenweg 2, 6703 HD Wageningen, The Netherlands
| | - Sander Kersten
- Nutrition, Metabolism, and Genomics group, Wageningen University, Bomenweg 2, 6703 HD Wageningen, The Netherlands.
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233
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Lafontan M. Adipose tissue and adipocyte dysregulation. DIABETES & METABOLISM 2014; 40:16-28. [DOI: 10.1016/j.diabet.2013.08.002] [Citation(s) in RCA: 115] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/19/2013] [Accepted: 08/25/2013] [Indexed: 12/19/2022]
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234
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Mehrotra D, Wu J, Papangeli I, Chun HJ. Endothelium as a gatekeeper of fatty acid transport. Trends Endocrinol Metab 2014; 25:99-106. [PMID: 24315207 PMCID: PMC3946743 DOI: 10.1016/j.tem.2013.11.001] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/11/2013] [Revised: 11/04/2013] [Accepted: 11/05/2013] [Indexed: 12/13/2022]
Abstract
The endothelium transcends all clinical disciplines and is crucial to the function of every organ system. A critical, but poorly understood, role of the endothelium is its ability to control the transport of energy supply according to organ needs. Fatty acids (FAs) in particular represent a key energy source that is utilized by a number of tissues, but utilization must be tightly regulated to avoid potentially deleterious consequences of excess accumulation, including insulin resistance. Recent studies have identified important endothelial signaling mechanisms, involving vascular endothelial growth factor-B, peroxisome proliferator-activated receptor-γ, and apelin, that mediate endothelial regulation of FA transport. In this review, we discuss the mechanisms by which these signaling pathways regulate this key endothelial function.
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Affiliation(s)
- Devi Mehrotra
- Yale Cardiovascular Research Center, Section of Cardiovascular Medicine, Department of Internal Medicine, Yale University School of Medicine, New Haven, CT 06511, USA
| | - Jingxia Wu
- Yale Cardiovascular Research Center, Section of Cardiovascular Medicine, Department of Internal Medicine, Yale University School of Medicine, New Haven, CT 06511, USA
| | - Irinna Papangeli
- Yale Cardiovascular Research Center, Section of Cardiovascular Medicine, Department of Internal Medicine, Yale University School of Medicine, New Haven, CT 06511, USA
| | - Hyung J Chun
- Yale Cardiovascular Research Center, Section of Cardiovascular Medicine, Department of Internal Medicine, Yale University School of Medicine, New Haven, CT 06511, USA.
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235
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de Haan W, Bhattacharjee A, Ruddle P, Kang MH, Hayden MR. ABCA1 in adipocytes regulates adipose tissue lipid content, glucose tolerance, and insulin sensitivity. J Lipid Res 2014; 55:516-23. [PMID: 24443560 DOI: 10.1194/jlr.m045294] [Citation(s) in RCA: 73] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Adipose tissue contains one of the largest reservoirs of cholesterol in the body. Adipocyte dysfunction in obesity is associated with intracellular cholesterol accumulation, and alterations in cholesterol homeostasis have been shown to alter glucose metabolism in cultured adipocytes. ABCA1 plays a major role in cholesterol efflux, suggesting a role for ABCA1 in maintaining cholesterol homeostasis in the adipocyte. However, the impact of adipocyte ABCA1 on adipose tissue function and glucose metabolism is unknown. Our aim was to determine the impact of adipocyte ABCA1 on adipocyte lipid metabolism, body weight, and glucose metabolism in vivo. To address this, we used mice lacking ABCA1 specifically in adipocytes (ABCA1(-ad/-ad)). When fed a high-fat, high-cholesterol diet, ABCA1(-ad/-ad) mice showed increased cholesterol and triglyceride stores in adipose tissue, developed enlarged fat pads, and had increased body weight. Associated with these phenotypic changes, we observed significant changes in the expression of genes involved in cholesterol and glucose homeostasis, including ldlr, abcg1, glut-4, adiponectin, and leptin. ABCA1(-ad/-ad) mice also demonstrated impaired glucose tolerance, lower insulin sensitivity, and decreased insulin secretion. We conclude that ABCA1 in adipocytes influences adipocyte lipid metabolism, body weight, and whole-body glucose homeostasis.
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Affiliation(s)
- Willeke de Haan
- Centre for Molecular Medicine and Therapeutics, University of British Columbia, Vancouver, BC, Canada
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236
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Yang J, Liu X, Zhang Q, Jiang L. Identification and quantitative mRNA analysis of a novel splice variant of GPIHBP1 in dairy cattle. J Anim Sci Biotechnol 2014; 5:50. [PMID: 25810903 PMCID: PMC4373091 DOI: 10.1186/2049-1891-5-50] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2014] [Accepted: 10/20/2014] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Identification of functional genes affecting milk production traits is very crucial for improving breeding efficiency in dairy cattle. Many potential candidate genes have been identified through our previous genome wide association study (GWAS). Of these, GPIHBP1 is an important novel candidate gene for milk production traits. However, the mRNA structure of the bovine GPIHBP1 gene is not fully determined up to now. RESULTS In this study, we identified a novel alternatively splice transcript variant (X5) which leads to a 31 bp insertion in exon 3 and also confirmed the other four existed transcripts (X1, X2, X3 and X4) of the bovine GPIHBP1 gene. We showed that transcript X5 with a 31 bp insertion and transcript X1 with an 8 bp deletion might have tremendous effect on the protein function and structure of GPIHBP1, respectively. With semi-quantitative PCR and quantitative real-time RT-PCR, we found that the mRNA expression of GPIHBP1, GPIHBP1-X1 and GPIHBP1-X5 in mammary gland of lactating cows were much higher than that in other tissues. CONCLUSIONS Our study reports a novel alternative splicing of GPIHBP1 in bovine for the first time and provide useful information for the further functional analyses of GPIHBP1 in dairy cattle.
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Affiliation(s)
- Jie Yang
- National Engineering Laboratory for Animal Breeding; Key Laboratory of Animal Genetics, Breeding and Reproduction, Ministry of Agriculture of China; College of Animal Science and Technology, China Agricultural University, Beijing, 100193 China
| | - Xuan Liu
- National Engineering Laboratory for Animal Breeding; Key Laboratory of Animal Genetics, Breeding and Reproduction, Ministry of Agriculture of China; College of Animal Science and Technology, China Agricultural University, Beijing, 100193 China
| | - Qin Zhang
- National Engineering Laboratory for Animal Breeding; Key Laboratory of Animal Genetics, Breeding and Reproduction, Ministry of Agriculture of China; College of Animal Science and Technology, China Agricultural University, Beijing, 100193 China
| | - Li Jiang
- National Engineering Laboratory for Animal Breeding; Key Laboratory of Animal Genetics, Breeding and Reproduction, Ministry of Agriculture of China; College of Animal Science and Technology, China Agricultural University, Beijing, 100193 China
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237
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Abstract
Lipid droplets are intracellular organelles that are found in most cells, where they have fundamental roles in metabolism. They function prominently in storing oil-based reserves of metabolic energy and components of membrane lipids. Lipid droplets are the dispersed phase of an oil-in-water emulsion in the aqueous cytosol of cells, and the importance of basic biophysical principles of emulsions for lipid droplet biology is now being appreciated. Because of their unique architecture, with an interface between the dispersed oil phase and the aqueous cytosol, specific mechanisms underlie their formation, growth and shrinkage. Such mechanisms enable cells to use emulsified oil when the demands for metabolic energy or membrane synthesis change. The regulation of the composition of the phospholipid surfactants at the surface of lipid droplets is crucial for lipid droplet homeostasis and protein targeting to their surfaces.
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238
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Makoveichuk E, Vorrsjö E, Olivecrona T, Olivecrona G. Inactivation of lipoprotein lipase in 3T3-L1 adipocytes by angiopoietin-like protein 4 requires that both proteins have reached the cell surface. Biochem Biophys Res Commun 2013; 441:941-6. [DOI: 10.1016/j.bbrc.2013.11.013] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2013] [Accepted: 11/01/2013] [Indexed: 01/25/2023]
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239
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Abstract
Cardiovascular disease represents the most common cause of death in patients with nonalcoholic fatty liver disease (NAFLD). Patients with NAFLD exhibit an atherogenic dyslipidemia that is characterized by an increased plasma concentration of triglycerides, reduced concentration of high-density lipoprotein (HDL) cholesterol, and low-density lipoprotein (LDL) particles that are smaller and more dense than normal. The pathogenesis of NAFLD-associated atherogenic dyslipidemia is multifaceted, but many aspects are attributable to manifestations of insulin resistance. Here the authors review the structure, function, and metabolism of lipoproteins, which are macromolecular particles of lipids and proteins that transport otherwise insoluble triglyceride and cholesterol molecules within the plasma. They provide a current explanation of the metabolic perturbations that are observed in the setting of insulin resistance. An improved understanding of the pathophysiology of atherogenic dyslipidemia would be expected to guide therapies aimed at reducing morbidity and mortality in patients with NAFLD.
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Affiliation(s)
- Edward Fisher
- Division of Cardiology, Department of Medicine, The Marc and Ruti Bell Program in Vascular Biology, New York University School of Medicine, New York, New York
| | - David Cohen
- Division of Gastroenterology, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts
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240
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Hultin M, Savonen R, Chevreuil O, Olivecrona T. Chylomicron metabolism in rats: kinetic modeling indicates that the particles remain at endothelial sites for minutes. J Lipid Res 2013; 54:2595-605. [PMID: 23922383 DOI: 10.1194/jlr.m032979] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Chylomicrons labeled in vivo with (14)C-oleic acid (primarily in triglycerides, providing a tracer for lipolysis) and (3)H-retinol (primarily in ester form, providing a tracer for the core lipids) were injected into rats. Radioactivity in tissues was followed at a series of times up to 40 min and the data were analyzed by compartmental modeling. For heart-like tissues it was necessary to allow the chylomicrons to enter into a compartment where lipolysis is rapid and then transfer to a second compartment where lipolysis is slower. The particles remained in these compartments for minutes and when they returned to blood they had reduced affinity for binding in the tissue. In contrast, the data for liver could readily be fitted with a single compartment for native and lipolyzed chylomicrons in blood, and there was no need for a pathway back to blood. A composite model was built from the individual tissue models. This whole-body model could simultaneously fit all data for both fed and fasted rats and allowed estimation of fluxes and residence times in the four compartments; native and lipolyzed chylomicrons ("remnants") in blood, and particles in the tissue compartments where lipolysis is rapid and slow, respectively.
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Affiliation(s)
- Magnus Hultin
- Departments of Surgical and Perioperative Sciences, Anaesthesiology and Intensive Care, Umeå University, S-901 87 Umeå, Sweden
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241
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Radner FPW, Fischer J. The important role of epidermal triacylglycerol metabolism for maintenance of the skin permeability barrier function. Biochim Biophys Acta Mol Cell Biol Lipids 2013; 1841:409-15. [PMID: 23928127 DOI: 10.1016/j.bbalip.2013.07.013] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2013] [Revised: 07/22/2013] [Accepted: 07/29/2013] [Indexed: 12/29/2022]
Abstract
Survival in a terrestrial, dry environment necessitates a permeability barrier for regulated permeation of water and electrolytes in the cornified layer of the skin (the stratum corneum) to minimize desiccation of the body. This barrier is formed during cornification and involves a cross-linking of corneocyte proteins as well as an extensive remodeling of lipids. The cleavage of precursor lipids from lamellar bodies by various hydrolytic enzymes generates ceramides, cholesterol, and non-esterified fatty acids for the extracellular lipid lamellae in the stratum corneum. However, the important role of epidermal triacylglycerol (TAG) metabolism during formation of a functional permeability barrier in the skin was only recently discovered. Humans with mutations in the ABHD5/CGI-58 (α/β hydrolase domain containing protein 5, also known as comparative gene identification-58, CGI-58) gene suffer from a defect in TAG catabolism that causes neutral lipid storage disease with ichthyosis. In addition, mice with deficiencies in genes involved in TAG catabolism (Abhd5/Cgi-58 knock-out mice) or TAG synthesis (acyl-CoA:diacylglycerol acyltransferase-2, Dgat2 knock-out mice) also develop severe skin permeability barrier dysfunctions and die soon after birth due to increased dehydration. As a result of these defects in epidermal TAG metabolism, humans and mice lack ω-(O)-acylceramides, which leads to malformation of the cornified lipid envelope of the skin. In healthy skin, this epidermal structure provides an interface for the linkage of lamellar membranes with corneocyte proteins to maintain permeability barrier homeostasis. This review focuses on recent advances in the understanding of biochemical mechanisms involved in epidermal neutral lipid metabolism and the generation of a functional skin permeability barrier. This article is part of a Special Issue entitled The Important Role of Lipids in the Epidermis and their Role in the Formation and Maintenance of the Cutaneous Barrier. Guest Editors: Kenneth R. Feingold and Peter Elias.
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Affiliation(s)
- Franz P W Radner
- Institute for Human Genetics, University Medical Center Freiburg, Freiburg 79106, Germany.
| | - Judith Fischer
- Institute for Human Genetics, University Medical Center Freiburg, Freiburg 79106, Germany
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242
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Gårdsvoll H, Kriegbaum MC, Hertz EP, Alpízar-Alpízar W, Ploug M. The urokinase receptor homolog Haldisin is a novel differentiation marker of stratum granulosum in squamous epithelia. J Histochem Cytochem 2013; 61:802-13. [PMID: 23896969 DOI: 10.1369/0022155413501879] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Several members of the Ly-6/uPAR (LU)-protein domain family are differentially expressed in human squamous epithelia. In some cases, they even play important roles in maintaining skin homeostasis, as exemplified by the secreted single domain member, SLURP-1, the deficiency of which is associated with the development of palmoplantar hyperkeratosis in the congenital skin disorder Mal de Meleda. In the present study, we have characterized a new member of the LU-protein domain family, which we find to be predominantly expressed in the stratum granulosum of human skin, thus resembling the expression of SLURP-1. In accordance with its expression pattern, we denote this protein product, which is encoded by the LYPD5 gene, as Haldisin (human antigen with LU-domains expressed in skin). Two of the five human glycolipid-anchored membrane proteins with multiple LU-domains characterized so far are predominantly confined to squamous epithelia (i.e., C4.4A), to stratum spinosum, and Haldisin to stratum granulosum under normal homeostatic conditions. Whether Haldisin is a prognostic biomarker for certain epithelial malignancies, like C4.4A and SLURP-1, remains to be explored.
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Affiliation(s)
- Henrik Gårdsvoll
- The Finsen Laboratory, Rigshospitalet & Biotech Research and Innovation Centre, Copenhagen Biocenter, Copenhagen, Denmark (HG,MCK,EPH,WAA,MP)
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243
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Bays HE, Toth PP, Kris-Etherton PM, Abate N, Aronne LJ, Brown WV, Gonzalez-Campoy JM, Jones SR, Kumar R, La Forge R, Samuel VT. Obesity, adiposity, and dyslipidemia: a consensus statement from the National Lipid Association. J Clin Lipidol 2013; 7:304-83. [PMID: 23890517 DOI: 10.1016/j.jacl.2013.04.001] [Citation(s) in RCA: 303] [Impact Index Per Article: 27.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2013] [Revised: 04/02/2013] [Accepted: 04/03/2013] [Indexed: 01/04/2023]
Abstract
The term "fat" may refer to lipids as well as the cells and tissue that store lipid (ie, adipocytes and adipose tissue). "Lipid" is derived from "lipos," which refers to animal fat or vegetable oil. Adiposity refers to body fat and is derived from "adipo," referring to fat. Adipocytes and adipose tissue store the greatest amount of body lipids, including triglycerides and free cholesterol. Adipocytes and adipose tissue are active from an endocrine and immune standpoint. Adipocyte hypertrophy and excessive adipose tissue accumulation can promote pathogenic adipocyte and adipose tissue effects (adiposopathy), resulting in abnormal levels of circulating lipids, with dyslipidemia being a major atherosclerotic coronary heart disease risk factor. It is therefore incumbent upon lipidologists to be among the most knowledgeable in the understanding of the relationship between excessive body fat and dyslipidemia. On September 16, 2012, the National Lipid Association held a Consensus Conference with the goal of better defining the effect of adiposity on lipoproteins, how the pathos of excessive body fat (adiposopathy) contributes to dyslipidemia, and how therapies such as appropriate nutrition, increased physical activity, weight-management drugs, and bariatric surgery might be expected to impact dyslipidemia. It is hoped that the information derived from these proceedings will promote a greater appreciation among clinicians of the impact of excess adiposity and its treatment on dyslipidemia and prompt more research on the effects of interventions for improving dyslipidemia and reducing cardiovascular disease risk in overweight and obese patients.
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Affiliation(s)
- Harold E Bays
- Louisville Metabolic and Atherosclerosis Research Center, 3288 Illinois Avenue, Louisville, KY 40213, USA.
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