101
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Feingold KR, Shigenaga JK, Kazemi MR, McDonald CM, Patzek SM, Cross AS, Moser A, Grunfeld C. Mechanisms of triglyceride accumulation in activated macrophages. J Leukoc Biol 2012; 92:829-39. [PMID: 22753953 DOI: 10.1189/jlb.1111537] [Citation(s) in RCA: 175] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
LPS treatment of macrophages induces TG accumulation, which is accentuated by TG-rich lipoproteins or FFA. We defined pathways altered during macrophage activation that contribute to TG accumulation. Glucose uptake increased with activation, accompanied by increased GLUT1. Oxidation of glucose markedly decreased, whereas incorporation of glucose-derived carbon into FA and sterols increased. Macrophage activation also increased uptake of FFA, associated with an increase in CD36. Oxidation of FA was markedly reduced, whereas the incorporation of FA into TGs increased, associated with increased GPAT3 and DGAT2. Additionally, macrophage activation decreased TG lipolysis; however, expression of ATGL or HSL was not altered. Macrophage activation altered gene expression similarly when incubated with exogenous FA or AcLDL. Whereas activation with ligands of TLR2 (zymosan), TLR3 (poly I:C), or TLR4 (LPS) induced alterations in macrophage gene expression, leading to TG accumulation, treatment of macrophages with cytokines had minimal effects. Thus, activation of TLRs leads to accumulation of TG in macrophages by multiple pathways that may have beneficial effects in host defense but could contribute to the accelerated atherosclerosis in chronic infections and inflammatory diseases.
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Affiliation(s)
- Kenneth R Feingold
- Metabolism Section, Department of Veterans Affairs Medical Center, University of California, San Francisco, San Francisco, CA, USA.
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102
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Aflaki E, Doddapattar P, Radović B, Povoden S, Kolb D, Vujić N, Wegscheider M, Koefeler H, Hornemann T, Graier WF, Malli R, Madeo F, Kratky D. C16 ceramide is crucial for triacylglycerol-induced apoptosis in macrophages. Cell Death Dis 2012; 3:e280. [PMID: 22419109 PMCID: PMC3317349 DOI: 10.1038/cddis.2012.17] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2012] [Revised: 02/02/2012] [Accepted: 02/07/2012] [Indexed: 12/12/2022]
Abstract
Triacylglycerol (TG) accumulation caused by adipose triglyceride lipase (ATGL) deficiency or very low-density lipoprotein (VLDL) loading of wild-type (Wt) macrophages results in mitochondrial-mediated apoptosis. This phenotype is correlated to depletion of Ca(2+) from the endoplasmic reticulum (ER), an event known to induce the unfolded protein response (UPR). Here, we show that ER stress in TG-rich macrophages activates the UPR, resulting in increased abundance of the chaperone GRP78/BiP, the induction of pancreatic ER kinase-like ER kinase, phosphorylation and activation of eukaryotic translation initiation factor 2A, the translocation of activating transcription factor (ATF)4 and ATF6 to the nucleus and the induction of the cell death executor CCAAT/enhancer-binding protein homologous protein. C16:0 ceramide concentrations were increased in Atgl-/- and VLDL-loaded Wt macrophages. Overexpression of ceramide synthases was sufficient to induce mitochondrial apoptosis in Wt macrophages. In accordance, inhibition of ceramide synthases in Atgl-/- macrophages by fumonisin B1 (FB1) resulted in specific inhibition of C16:0 ceramide, whereas intracellular TG concentrations remained high. Although the UPR was still activated in Atgl-/- macrophages, FB1 treatment rescued Atgl-/- macrophages from mitochondrial dysfunction and programmed cell death. We conclude that C16:0 ceramide elicits apoptosis in Atgl-/- macrophages by activation of the mitochondrial apoptosis pathway.
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Affiliation(s)
- E Aflaki
- Institute of Molecular Biology and Biochemistry, Center of Molecular Medicine, Medical University of Graz, Harrachgasse 21, 8010 Graz, Austria
- National Human Genome Research Institute/NIH Molecular Neurogenetics Section, 35 Convent Drive, Bethesda, MD, USA
| | - P Doddapattar
- Institute of Molecular Biology and Biochemistry, Center of Molecular Medicine, Medical University of Graz, Harrachgasse 21, 8010 Graz, Austria
| | - B Radović
- Institute of Molecular Biology and Biochemistry, Center of Molecular Medicine, Medical University of Graz, Harrachgasse 21, 8010 Graz, Austria
| | - S Povoden
- Institute of Molecular Biology and Biochemistry, Center of Molecular Medicine, Medical University of Graz, Harrachgasse 21, 8010 Graz, Austria
| | - D Kolb
- Institute of Cell Biology, Histology and Embryology, Medical University of Graz, Harrachgasse 21, 8010 Graz, Austria
- Center for Medical Research, Medical University of Graz, Stiftingtalstrasse 24, 8010 Graz, Austria
| | - N Vujić
- Institute of Molecular Biology and Biochemistry, Center of Molecular Medicine, Medical University of Graz, Harrachgasse 21, 8010 Graz, Austria
| | - M Wegscheider
- Institute of Molecular Biology and Biochemistry, Center of Molecular Medicine, Medical University of Graz, Harrachgasse 21, 8010 Graz, Austria
| | - H Koefeler
- Institute of Cell Biology, Histology and Embryology, Medical University of Graz, Harrachgasse 21, 8010 Graz, Austria
| | - T Hornemann
- Institute of Clinical Chemistry, University of Zurich, Rämistrasse 100, 8091 Zürich, Switzerland
| | - W F Graier
- Institute of Molecular Biology and Biochemistry, Center of Molecular Medicine, Medical University of Graz, Harrachgasse 21, 8010 Graz, Austria
| | - R Malli
- Institute of Molecular Biology and Biochemistry, Center of Molecular Medicine, Medical University of Graz, Harrachgasse 21, 8010 Graz, Austria
| | - F Madeo
- Institute of Molecular Biosciences, University of Graz, Humboldtstrasse 50, 8010 Graz, Austria
| | - D Kratky
- Institute of Molecular Biology and Biochemistry, Center of Molecular Medicine, Medical University of Graz, Harrachgasse 21, 8010 Graz, Austria
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103
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Zechner R, Zimmermann R, Eichmann TO, Kohlwein SD, Haemmerle G, Lass A, Madeo F. FAT SIGNALS--lipases and lipolysis in lipid metabolism and signaling. Cell Metab 2012; 15:279-91. [PMID: 22405066 PMCID: PMC3314979 DOI: 10.1016/j.cmet.2011.12.018] [Citation(s) in RCA: 793] [Impact Index Per Article: 66.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/07/2011] [Revised: 11/18/2011] [Accepted: 12/07/2011] [Indexed: 12/01/2022]
Abstract
Lipolysis is defined as the catabolism of triacylglycerols stored in cellular lipid droplets. Recent discoveries of essential lipolytic enzymes and characterization of numerous regulatory proteins and mechanisms have fundamentally changed our perception of lipolysis and its impact on cellular metabolism. New findings that lipolytic products and intermediates participate in cellular signaling processes and that "lipolytic signaling" is particularly important in many nonadipose tissues unveil a previously underappreciated aspect of lipolysis, which may be relevant for human disease.
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Affiliation(s)
- Rudolf Zechner
- Institute of Molecular Biosciences, University of Graz, Austria.
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104
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Chandak PG, Obrowsky S, Radovic B, Doddapattar P, Aflaki E, Kratzer A, Doshi LS, Povoden S, Ahammer H, Hoefler G, Levak-Frank S, Kratky D. Lack of acyl-CoA:diacylglycerol acyltransferase 1 reduces intestinal cholesterol absorption and attenuates atherosclerosis in apolipoprotein E knockout mice. BIOCHIMICA ET BIOPHYSICA ACTA 2011; 1811:1011-20. [PMID: 21924378 PMCID: PMC3223411 DOI: 10.1016/j.bbalip.2011.08.010] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/07/2011] [Revised: 07/28/2011] [Accepted: 08/15/2011] [Indexed: 12/30/2022]
Abstract
Triacylglycerols (TG) are the major storage molecules of metabolic energy and fatty acids in several tissues. The final step in TG biosynthesis is catalyzed by acyl-CoA:diacylglycerol acyltransferase (DGAT) enzymes. Lack of whole body DGAT1 is associated with reduced lipid-induced inflammation. Since one major component of atherosclerosis is chronic inflammation we hypothesized that DGAT1 deficiency might ameliorate atherosclerotic lesion development. We therefore crossbred Apolipoprotein E-deficient (ApoE(-/-)) mice with Dgat1(-/-) mice. ApoE(-/-) and ApoE(-/-)Dgat1(-/-) mice were fed Western-type diet (WTD) for 9weeks and thereafter examined for plaque formation. The mean atherosclerotic lesion area was substantially reduced in ApoE(-/-)Dgat1(-/-) compared with ApoE(-/-) mice in en face and aortic valve section analyses. The reduced lesion size was associated with decreased cholesterol uptake and absorption by the intestine, reduced plasma TG and cholesterol concentrations and increased cholesterol efflux from macrophages. The expression of adhesion molecules was reduced in aortas of ApoE(-/-)Dgat1(-/-) mice, which might be the reason for less migration capacities of monocytes and macrophages and the observed decreased amount of macrophages within the plaques. From our results we conclude that the lack of DGAT1 is atheroprotective, implicating an additional application of DGAT1 inhibitors with regard to maintaining cholesterol homeostasis and attenuating atherosclerosis.
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Affiliation(s)
- Prakash G. Chandak
- Institute of Molecular Biology and Biochemistry, Center of Molecular Medicine, Medical University of Graz, Harrachgasse 21, 8010 Graz, Austria
| | - Sascha Obrowsky
- Institute of Molecular Biology and Biochemistry, Center of Molecular Medicine, Medical University of Graz, Harrachgasse 21, 8010 Graz, Austria
| | - Branislav Radovic
- Institute of Molecular Biology and Biochemistry, Center of Molecular Medicine, Medical University of Graz, Harrachgasse 21, 8010 Graz, Austria
| | - Prakash Doddapattar
- Institute of Molecular Biology and Biochemistry, Center of Molecular Medicine, Medical University of Graz, Harrachgasse 21, 8010 Graz, Austria
| | - Elma Aflaki
- Institute of Molecular Biology and Biochemistry, Center of Molecular Medicine, Medical University of Graz, Harrachgasse 21, 8010 Graz, Austria
| | - Adelheid Kratzer
- Institute of Molecular Biology and Biochemistry, Center of Molecular Medicine, Medical University of Graz, Harrachgasse 21, 8010 Graz, Austria
| | - Lalit S. Doshi
- Institute of Molecular Biology and Biochemistry, Center of Molecular Medicine, Medical University of Graz, Harrachgasse 21, 8010 Graz, Austria
| | - Silvia Povoden
- Institute of Molecular Biology and Biochemistry, Center of Molecular Medicine, Medical University of Graz, Harrachgasse 21, 8010 Graz, Austria
| | - Helmut Ahammer
- Institute of Biophysics, Medical University of Graz, Harrachgasse 21, 8010 Graz, Austria
| | - Gerald Hoefler
- Institute of Pathology, Medical University of Graz, Auenbruggerplatz 25, 8036 Graz, Austria
| | - Sanja Levak-Frank
- Institute of Molecular Biology and Biochemistry, Center of Molecular Medicine, Medical University of Graz, Harrachgasse 21, 8010 Graz, Austria
| | - Dagmar Kratky
- Institute of Molecular Biology and Biochemistry, Center of Molecular Medicine, Medical University of Graz, Harrachgasse 21, 8010 Graz, Austria,Corresponding author. Tel.: + 43 3163807543.
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105
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Miranda DA, Koves TR, Gross DA, Chadt A, Al-Hasani H, Cline GW, Schwartz GJ, Muoio DM, Silver DL. Re-patterning of skeletal muscle energy metabolism by fat storage-inducing transmembrane protein 2. J Biol Chem 2011; 286:42188-42199. [PMID: 22002063 DOI: 10.1074/jbc.m111.297127] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Triacylglyceride stored in cytosolic lipid droplets (LDs) constitutes a major energy reservoir in most eukaryotes. The regulated turnover of triacylglyceride in LDs provides fatty acids for mitochondrial β-oxidation and ATP generation in physiological states of high demand for energy. The mechanisms for the formation of LDs in conditions of energy excess are not entirely understood. Fat storage-inducing transmembrane protein 2 (FIT2/FITM2) is the anciently conserved member of the fat storage-inducing transmembrane family of proteins implicated to be important in the formation of LDs, but its role in energy metabolism has not been tested. Here, we report that expression of FIT2 in mouse skeletal muscle had profound effects on muscle energy metabolism. Mice with skeletal muscle-specific overexpression of FIT2 (CKF2) had significantly increased intramyocellular triacylglyceride and complete protection from high fat diet-induced weight gain due to increased energy expenditure. Mass spectrometry-based metabolite profiling suggested that CKF2 skeletal muscle had increased oxidation of branched chain amino acids but decreased oxidation of fatty acids. Glucose was primarily utilized in CKF2 muscle for synthesis of the glycerol backbone of triacylglyceride and not for glycogen production. CKF2 muscle was ATP-deficient and had activated AMP kinase. Together, these studies indicate that FIT2 expression in skeletal muscle plays an unexpected function in regulating muscle energy metabolism and indicates an important role for lipid droplet formation in this process.
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Affiliation(s)
- Diego A Miranda
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York 10461
| | - Timothy R Koves
- Sarah W. Stedman Nutrition and Metabolism Center, Department of Medicine, Duke University, Durham, North Carolina 27704
| | - David A Gross
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York 10461
| | - Alexandra Chadt
- Institute for Clinical Biochemistry and Pathobiochemistry, German Diabetes Center, 40225 Dusseldorf, Germany
| | - Hadi Al-Hasani
- Institute for Clinical Biochemistry and Pathobiochemistry, German Diabetes Center, 40225 Dusseldorf, Germany
| | - Gary W Cline
- Diabetes Endocrinology Research Center, Yale University School of Medicine, New Haven, Connecticut 06520
| | - Gary J Schwartz
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York 10461; Department of Medicine, Albert Einstein College of Medicine, Bronx, New York 10461
| | - Deborah M Muoio
- Sarah W. Stedman Nutrition and Metabolism Center, Department of Medicine, Duke University, Durham, North Carolina 27704
| | - David L Silver
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York 10461.
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106
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Ueno N, Taketomi Y, Yamamoto K, Hirabayashi T, Kamei D, Kita Y, Shimizu T, Shinzawa K, Tsujimoto Y, Ikeda K, Taguchi R, Murakami M. Analysis of two major intracellular phospholipases A(2) (PLA(2)) in mast cells reveals crucial contribution of cytosolic PLA(2)α, not Ca(2+)-independent PLA(2)β, to lipid mobilization in proximal mast cells and distal fibroblasts. J Biol Chem 2011; 286:37249-63. [PMID: 21880721 DOI: 10.1074/jbc.m111.290312] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Mast cells release a variety of mediators, including arachidonic acid (AA) metabolites, to regulate allergy, inflammation, and host defense, and their differentiation and maturation within extravascular microenvironments depend on the stromal cytokine stem cell factor. Mouse mast cells express two major intracellular phospholipases A(2) (PLA(2)s), namely group IVA cytosolic PLA(2) (cPLA(2)α) and group VIA Ca(2+)-independent PLA(2) (iPLA(2)β), and the role of cPLA(2)α in eicosanoid synthesis by mast cells has been well documented. Lipidomic analyses of mouse bone marrow-derived mast cells (BMMCs) lacking cPLA(2)α (Pla2g4a(-/-)) or iPLA(2)β (Pla2g6(-/-)) revealed that phospholipids with AA were selectively hydrolyzed by cPLA(2)α, not by iPLA(2)β, during FcεRI-mediated activation and even during fibroblast-dependent maturation. Neither FcεRI-dependent effector functions nor maturation-driven phospholipid remodeling was impaired in Pla2g6(-/-) BMMCs. Although BMMCs did not produce prostaglandin E(2) (PGE(2)), the AA released by cPLA(2)α from BMMCs during maturation was converted to PGE(2) by microsomal PGE synthase-1 (mPGES-1) in cocultured fibroblasts, and accordingly, Pla2g4a(-/-) BMMCs promoted microenvironmental PGE(2) synthesis less efficiently than wild-type BMMCs both in vitro and in vivo. Mice deficient in mPGES-1 (Ptges(-/-)) had an augmented local anaphylactic response. These results suggest that cPLA(2)α in mast cells is functionally coupled, through the AA transfer mechanism, with stromal mPGES-1 to provide anti-anaphylactic PGE(2). Although iPLA(2)β is partially responsible for PGE(2) production by macrophages and dendritic cells, it is dispensable for mast cell maturation and function.
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Affiliation(s)
- Noriko Ueno
- Lipid Metabolism Project, Tokyo Metropolitan Institute of Medical Science, 2-1-6 Kamikitazawa, Setagaya-ku, Tokyo 256-8506, Japan
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107
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Lee JY, Cha KH, Chae BJ, Ohh SJ. Supplementation of Either Conjugated Linoleic Acid or γ-linolenic Acid with or without Carnitine to Pig Diet Affect Flavor of Pork and Neutrophil Phagocytosis. JOURNAL OF ANIMAL SCIENCE AND TECHNOLOGY 2011. [DOI: 10.5187/jast.2011.53.3.237] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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108
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Impaired Rho GTPase activation abrogates cell polarization and migration in macrophages with defective lipolysis. Cell Mol Life Sci 2011; 68:3933-47. [PMID: 21533980 PMCID: PMC3214256 DOI: 10.1007/s00018-011-0688-4] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2010] [Revised: 03/22/2011] [Accepted: 04/07/2011] [Indexed: 11/23/2022]
Abstract
Infiltration of monocytes and macrophages into the site of inflammation is critical in the progression of inflammatory diseases such as atherosclerosis. Cell migration is dependent on the continuous organization of the actin cytoskeleton, which is regulated by members of the small Rho GTPase family (RhoA, Cdc42, Rac) that are also important for the regulation of signal transduction pathways. We have recently reported on reduced plaque formation in an atherosclerotic mouse model transplanted with bone marrow from adipose triglyceride lipase-deficient (Atgl−/−) mice. Here we provide evidence that defective lipolysis in macrophages lacking ATGL, the major enzyme responsible for triacylglycerol hydrolysis, favors an anti-inflammatory M2-like macrophage phenotype. Our data implicate an as yet unrecognized principle that insufficient lipolysis influences macrophage polarization and actin polymerization, resulting in impaired macrophage migration. Sustained phosphorylation of focal adhesion kinase [due to inactivation of its phosphatase by elevated levels of reactive oxygen species (ROS)] results in defective Cdc42, Rac1 and RhoA activation and in increased and sustained activation of Rac2. Inhibition of ROS production restores the migratory capacity of Atgl−/− macrophages. Since monocyte and macrophage migration are a prerequisite for infiltrating the arterial wall, our results provide a molecular link between lipolysis and the development of atherosclerosis.
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109
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Chuang HH, Chen PT, Wang WN, Chen YT, Shaw JF. Functional proteomic analysis of rice bran esterases/lipases and characterization of a novel recombinant esterase. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2011; 59:2019-2025. [PMID: 21322560 DOI: 10.1021/jf103972h] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
An esterase from rice ( Oryza sativa ) bran was identified on two-dimensional gel using 4-methylumbelliferyl butyrate as a substrate. The esterase cDNA (870 bp) encoded a 289 amino acid protein (designated OsEST-b) and was expressed in Escherichia coli . The molecular weight of recombinant OsEST-b (rOsEST-b) was 27 kDa, as measured by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Biochemical characterization demonstrated that rOsEST-b was active over a broad temperature range (optimum at 60 °C) and preferred alkaline conditions (optimum at pH 9.0). The rOsEST-b showed maximum activity toward p-nitrophenyl butyrate (C(4)) among various p-nitrophenyl esters (C(4)-C(18)), indicating that rOsEST-b is an esterase for short-chain fatty acids. The kinetic parameters under optimal conditions were K(m) = 27.03 μM, k(cat) = 49 s(-1), and k(cat)/K(m) = 1.81 s(-1) μM(-1). The activity of rOsEST-b was not influenced by ethylenediaminetetraacetic acid, suggesting that it is not a metalloenzyme. The amino acid sequence analysis revealed that OsEST-b had a conserved pentapeptide esterase/lipase motif but that the essential active site serine (GXSXG) was replaced by cysteine (C). These results suggest that OsEST-b is distinct from traditional esterases/lipases and is a novel lipolytic enzyme in rice bran.
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Affiliation(s)
- Hsu-Han Chuang
- Department of Food Science and Biotechnology, National Chung Hsing University , Taichung 402, Taiwan
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110
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Aflaki E, Radović B, Chandak PG, Kolb D, Eisenberg T, Ring J, Fertschai I, Uellen A, Wolinski H, Kohlwein SD, Zechner R, Levak-Frank S, Sattler W, Graier WF, Malli R, Madeo F, Kratky D. Triacylglycerol accumulation activates the mitochondrial apoptosis pathway in macrophages. J Biol Chem 2011; 286:7418-28. [PMID: 21196579 PMCID: PMC3044998 DOI: 10.1074/jbc.m110.175703] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2010] [Revised: 12/19/2010] [Indexed: 12/20/2022] Open
Abstract
Programmed cell death of lipid-laden macrophages is a prominent feature of atherosclerotic lesions and mostly ascribed to accumulation of excess intracellular cholesterol. The present in vitro study investigated whether intracellular triacylglycerol (TG) accumulation could activate a similar apoptotic response in macrophages. To address this question, we utilized peritoneal macrophages isolated from mice lacking adipose triglyceride lipase (ATGL), the major enzyme responsible for TG hydrolysis in multiple tissues. In Atgl(-/-) macrophages, we observed elevated levels of cytosolic Ca(2+) and reactive oxygen species, stimulated cytochrome c release, and nuclear localization of apoptosis-inducing factor. Fragmented mitochondria prior to cell death were indicative of the mitochondrial apoptosis pathway being triggered as a consequence of defective lipolysis. Other typical markers of apoptosis, such as externalization of phosphatidylserine in the plasma membrane, caspase 3 and poly(ADP-ribose) polymerase cleavage, were increased in Atgl(-/-) macrophages. An artificial increase of cellular TG levels by incubating wild-type macrophages with very low density lipoprotein closely mimicked the apoptotic phenotype observed in Atgl(-/-) macrophages. Results obtained during the present study define a novel pathway linking intracellular TG accumulation to mitochondrial dysfunction and programmed cell death in macrophages.
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Affiliation(s)
- Elma Aflaki
- From the Institute of Molecular Biology and Biochemistry, Center of Molecular Medicine, Medical University of Graz, Harrachgasse 21, 8010 Graz, Austria and
| | - Branislav Radović
- From the Institute of Molecular Biology and Biochemistry, Center of Molecular Medicine, Medical University of Graz, Harrachgasse 21, 8010 Graz, Austria and
| | - Prakash G. Chandak
- From the Institute of Molecular Biology and Biochemistry, Center of Molecular Medicine, Medical University of Graz, Harrachgasse 21, 8010 Graz, Austria and
| | - Dagmar Kolb
- From the Institute of Molecular Biology and Biochemistry, Center of Molecular Medicine, Medical University of Graz, Harrachgasse 21, 8010 Graz, Austria and
- the Institute of Molecular Biosciences, University of Graz, Heinrichstrasse 31A/Humboldtstrasse 50, 8010 Graz, Austria
| | - Tobias Eisenberg
- the Institute of Molecular Biosciences, University of Graz, Heinrichstrasse 31A/Humboldtstrasse 50, 8010 Graz, Austria
| | - Julia Ring
- the Institute of Molecular Biosciences, University of Graz, Heinrichstrasse 31A/Humboldtstrasse 50, 8010 Graz, Austria
| | - Ismene Fertschai
- From the Institute of Molecular Biology and Biochemistry, Center of Molecular Medicine, Medical University of Graz, Harrachgasse 21, 8010 Graz, Austria and
| | - Andreas Uellen
- From the Institute of Molecular Biology and Biochemistry, Center of Molecular Medicine, Medical University of Graz, Harrachgasse 21, 8010 Graz, Austria and
| | - Heimo Wolinski
- the Institute of Molecular Biosciences, University of Graz, Heinrichstrasse 31A/Humboldtstrasse 50, 8010 Graz, Austria
| | - Sepp-Dieter Kohlwein
- the Institute of Molecular Biosciences, University of Graz, Heinrichstrasse 31A/Humboldtstrasse 50, 8010 Graz, Austria
| | - Rudolf Zechner
- the Institute of Molecular Biosciences, University of Graz, Heinrichstrasse 31A/Humboldtstrasse 50, 8010 Graz, Austria
| | - Sanja Levak-Frank
- From the Institute of Molecular Biology and Biochemistry, Center of Molecular Medicine, Medical University of Graz, Harrachgasse 21, 8010 Graz, Austria and
| | - Wolfgang Sattler
- From the Institute of Molecular Biology and Biochemistry, Center of Molecular Medicine, Medical University of Graz, Harrachgasse 21, 8010 Graz, Austria and
| | - Wolfgang F. Graier
- From the Institute of Molecular Biology and Biochemistry, Center of Molecular Medicine, Medical University of Graz, Harrachgasse 21, 8010 Graz, Austria and
| | - Roland Malli
- From the Institute of Molecular Biology and Biochemistry, Center of Molecular Medicine, Medical University of Graz, Harrachgasse 21, 8010 Graz, Austria and
| | - Frank Madeo
- the Institute of Molecular Biosciences, University of Graz, Heinrichstrasse 31A/Humboldtstrasse 50, 8010 Graz, Austria
| | - Dagmar Kratky
- From the Institute of Molecular Biology and Biochemistry, Center of Molecular Medicine, Medical University of Graz, Harrachgasse 21, 8010 Graz, Austria and
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111
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Fujimoto T, Parton RG. Not just fat: the structure and function of the lipid droplet. Cold Spring Harb Perspect Biol 2011; 3:cshperspect.a004838. [PMID: 21421923 DOI: 10.1101/cshperspect.a004838] [Citation(s) in RCA: 335] [Impact Index Per Article: 25.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Lipid droplets (LDs) are independent organelles that are composed of a lipid ester core and a surface phospholipid monolayer. Recent studies have revealed many new proteins, functions, and phenomena associated with LDs. In addition, a number of diseases related to LDs are beginning to be understood at the molecular level. It is now clear that LDs are not an inert store of excess lipids but are dynamically engaged in various cellular functions, some of which are not directly related to lipid metabolism. Compared to conventional membrane organelles, there are still many uncertainties concerning the molecular architecture of LDs and how each function is placed in a structural context. Recent findings and remaining questions are discussed.
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Affiliation(s)
- Toyoshi Fujimoto
- Department of Anatomy and Molecular Cell Biology, Nagoya University Graduate School of Medicine, Japan.
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112
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Meilin E, Aviram M, Hayek T. Insulin increases macrophage triglyceride accumulation under diabetic conditions through the down regulation of hormone sensitive lipase and adipose triglyceride lipase. Biofactors 2011; 37:95-103. [PMID: 21344529 DOI: 10.1002/biof.144] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/12/2010] [Accepted: 12/19/2010] [Indexed: 12/17/2022]
Abstract
Diabetes mellitus (DM) is a major risk factor for the development of atherosclerosis, and high-serum levels of insulin are strongly associated with type 2 DM. Atherosclerosis is characterized by lipid-laden macrophage foam cell formations, which contain substantial amount of cholesterol and triglycerides (TG). This study analyzed for the first time, the effects of insulin on TG metabolism in macrophages under normal and diabetic conditions. Mouse peritoneal macrophages from C57BL6 mice were cultured under normal (5 mM) or high (diabetic condition, 25 mM) glucose concentration, with or without insulin, followed by the assessment of TGs metabolism in these cells. Under diabetic condition, insulin increased TG accumulation in macrophages by 100%, decreased cellular TG degradation by 21%, and increased C-reactive protein levels in macrophages by 83%. Insulin decreased hormone-sensitive lipase mRNA and protein expression by 28 and 60%, respectively, and adipose TG lipase (ATGL) protein expression by 36%, with no significant reduction in ATGL mRNA levels. The inhibition of insulin-mediated phosphorylation, and the addition of cyclic adenosine 3'5'-monoposphate, abolished the insulin-mediated inhibition of TGs degradation in cells. Insulin increases macrophage TGs accumulation only under diabetic conditions, suggesting that impaired glycemic control in diabetic patients treated with insulin may contribute to foam cell formations and enhanced inflammation in macrophages.
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Affiliation(s)
- Edna Meilin
- The Lipid Research Laboratory, Technion, Faculty of Medicine, The Rappaport Family Institute for Research in the Medical Science, Rambam Medical Center, Haifa, Israel
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113
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Abstract
The lipid droplet (LD), an organelle that exists ubiquitously in various organisms, from bacteria to mammals, has attracted much attention from both medical and cell biology fields. The LD in white adipocytes is often treated as the prototype LD, but is rather a special example, considering that its size, intracellular localization and molecular composition are vastly different from those of non-adipocyte LDs. These differences confer distinct properties on adipocyte and non-adipocyte LDs. In this article, we address the current understanding of LDs by discussing the differences between adipocyte and non-adipocyte LDs.
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Affiliation(s)
- Michitaka Suzuki
- Department of Anatomy and Molecular Cell Biology, Nagoya University Graduate School of Medicine, Nagoya 466-8550, Japan
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De Naeyer H, Ouwens DM, Van Nieuwenhove Y, Pattyn P, ‘t Hart LM, Kaufman JM, Sell H, Eckel J, Cuvelier C, Taes YE, Ruige JB. Combined gene and protein expression of hormone-sensitive lipase and adipose triglyceride lipase, mitochondrial content, and adipocyte size in subcutaneous and visceral adipose tissue of morbidly obese men. Obes Facts 2011; 4:407-16. [PMID: 22166762 PMCID: PMC6450043 DOI: 10.1159/000333445] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
AIMS Lipotoxicity in obesity might be a failure of adipocytes to respond sufficiently adequate to persistent energy surplus. To evaluate the role of lipolytic enzymes or mitochondria in lipotoxicity, we studied expression levels of genes and proteins involved in lipolysis and mitochondrial DNA (mtDNA) content. METHODS As differences in lipid metabolism between men and women are extremely complex, we recruited only men (lean and morbidly obese) and collected subcutaneous and visceral adipose tissue during abdominal surgery for real-time PCR gene expression, protein expression, and microscopic study. RESULTS Although mRNA levels of hormone-sensitive lipase (HSL) and adipose triglyceride lipase (ATGL) were increased in visceral adipose tissue of morbidly obese men, this was not paralleled by alterations in protein expression and phosphorylation of HSL and ATGL. mtDNA content of visceral adipose tissue was increased in morbidly obese men as compared to lean controls (p < 0.013). Positive correlations were observed between visceral adipocyte size and serum triacylglycerol (r = 0.6, p < 0.007) as well as between visceral adipocyte size and CRP (r = 0.6, p < 0.009) in analyses performed separately in obese men. CONCLUSION Lipotoxicity of morbidly obese men might be related to the quantitative impact of the visceral fat depot rather than to important dysregulation of involved lipolytic enzymes or adipocyte mitochondria.
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Affiliation(s)
- Hélène De Naeyer
- Department of Abdominal Surgery, University Hospital, Ghent, Belgium
- Department of Endocrinology
| | - D. Margriet Ouwens
- German Diabetes Center, Institute for Clinical Biochemistry and Pathobiochemistry, Düsseldorf, Germany
| | | | - Piet Pattyn
- Department of Abdominal Surgery, University Hospital, Ghent, Belgium
| | - Leen M. ‘t Hart
- Molecular Cell Biology and Molecular Epidemiology, Leiden University Center, Leiden, the Netherlands
| | | | - Henrike Sell
- German Diabetes Center, Institute for Clinical Biochemistry and Pathobiochemistry, Düsseldorf, Germany
| | - Juergen Eckel
- German Diabetes Center, Institute for Clinical Biochemistry and Pathobiochemistry, Düsseldorf, Germany
| | - Claude Cuvelier
- Department of Pathology, University Hospital, Ghent, Belgium
| | | | - Johannes B. Ruige
- Department of Endocrinology
- * Department of Endocrinology, Ghent University Hospital, De Pintelaan 185, Building 9 K12, Ghent, Belgium, Tel. +32 9 332-6861, Fax -3897,
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Murakami M, Taketomi Y, Miki Y, Sato H, Hirabayashi T, Yamamoto K. Recent progress in phospholipase A₂ research: from cells to animals to humans. Prog Lipid Res 2010; 50:152-92. [PMID: 21185866 DOI: 10.1016/j.plipres.2010.12.001] [Citation(s) in RCA: 368] [Impact Index Per Article: 26.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Mammalian genomes encode genes for more than 30 phospholipase A₂s (PLA₂s) or related enzymes, which are subdivided into several classes including low-molecular-weight secreted PLA₂s (sPLA₂s), Ca²+-dependent cytosolic PLA₂s (cPLA₂s), Ca²+-independent PLA₂s (iPLA₂s), platelet-activating factor acetylhydrolases (PAF-AHs), lysosomal PLA₂s, and a recently identified adipose-specific PLA. Of these, the intracellular cPLA₂ and iPLA₂ families and the extracellular sPLA₂ family are recognized as the "big three". From a general viewpoint, cPLA₂α (the prototypic cPLA₂ plays a major role in the initiation of arachidonic acid metabolism, the iPLA₂ family contributes to membrane homeostasis and energy metabolism, and the sPLA₂ family affects various biological events by modulating the extracellular phospholipid milieus. The cPLA₂ family evolved along with eicosanoid receptors when vertebrates first appeared, whereas the diverse branching of the iPLA₂ and sPLA₂ families during earlier eukaryote development suggests that they play fundamental roles in life-related processes. During the past decade, data concerning the unexplored roles of various PLA₂ enzymes in pathophysiology have emerged on the basis of studies using knockout and transgenic mice, the use of specific inhibitors, and information obtained from analysis of human diseases caused by mutations in PLA₂ genes. This review focuses on current understanding of the emerging biological functions of PLA₂s and related enzymes.
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Affiliation(s)
- Makoto Murakami
- Lipid Metabolism Project, The Tokyo Metropolitan Institute of Medical Science, 2-1-6 Kamikitazawa, Setagaya-ku, Tokyo 156-8506, Japan.
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116
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Lammers B, Chandak PG, Aflaki E, Van Puijvelde GHM, Radovic B, Hildebrand RB, Meurs I, Out R, Kuiper J, Van Berkel TJC, Kolb D, Haemmerle G, Zechner R, Levak-Frank S, Van Eck M, Kratky D. Macrophage adipose triglyceride lipase deficiency attenuates atherosclerotic lesion development in low-density lipoprotein receptor knockout mice. Arterioscler Thromb Vasc Biol 2010; 31:67-73. [PMID: 21030715 DOI: 10.1161/atvbaha.110.215814] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
OBJECTIVE The consequences of macrophage triglyceride (TG) accumulation on atherosclerosis have not been studied in detail so far. Adipose triglyceride lipase (ATGL) is the rate-limiting enzyme for the initial step in TG hydrolysis. Because ATGL knockout (KO) mice exhibit massive TG accumulation in macrophages, we used ATGL KO mice to study the effects of macrophage TG accumulation on atherogenesis. METHODS AND RESULTS Low-density lipoprotein receptor (LDLr) KO mice were transplanted with bone marrow from ATGL KO (ATGL KO→LDLr KO) or wild-type (WT→LDLr KO) mice and challenged with a Western-type diet for 9 weeks. Despite TG accumulation in ATGL KO macrophages, atherosclerosis in ATGL KO→LDLr KO mice was 43% reduced associated with decreased plasma monocyte chemoattractant protein-1 (MCP-1) and macrophage interleukin-6 concentrations. This coincided with a reduced amount of macrophages, possibly because of a 39% increase in intraplaque apoptosis and a decreased migratory capacity of ATGL KO macrophages. The reduced number of white blood cells might be due to a 36% decreased Lin(-)Sca-1(+)cKit(+) hematopoietic stem cell population. CONCLUSIONS We conclude that the attenuation of atherogenesis in ATGL KO→LDLr KO mice is due to decreased infiltration of less inflammatory macrophages into the arterial wall and increased macrophage apoptosis.
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Affiliation(s)
- Bart Lammers
- Division of Biopharmaceutics, Gorlaeus Laboratories, Einsteinweg 55, 2333CC Leiden, the Netherlands.
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