1
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Rachakonda V, Gabbert C, Raina A, Li H, Malik S, DeLany JP, Behari J. Stratification of risk of death in severe acute alcoholic hepatitis using a panel of adipokines and cytokines. Alcohol Clin Exp Res 2015; 38:2712-21. [PMID: 25421508 DOI: 10.1111/acer.12558] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2014] [Accepted: 08/29/2014] [Indexed: 12/17/2022]
Abstract
BACKGROUND Dysregulated adipose tissue metabolism has been implicated in the pathogenesis of alcoholic liver disease in murine models. We aimed to characterize serum markers of adipose tissue metabolism and inflammation in patients with severe acute alcoholic hepatitis (AAH) and determine their utility to predict survival in severe AAH. METHODS A prospective, case-control study design was used. Seventy-six patients hospitalized with severe AAH and 25 ambulatory patients with alcoholic cirrhosis as controls were included. Serum samples were collected for biochemical analyses. Patients were followed for 180 days after enrollment to determine the survival. RESULTS AAH patients exhibited higher serum glycerol and free fatty acid levels, suggesting enhanced adipose tissue triglyceride hydrolysis. Patients with AAH demonstrated a distinct serum lipidomic profile compared with alcoholic cirrhosis but not in systemic and adipose-specific insulin resistance. AAH patients had higher serum resistin and plasmin activation inhibitor-1 levels, while serum leptin was decreased. Serum levels of the prolipolytic cytokines tumor necrosis factor-α (TNF-α), interleukin (IL)-6, IL-8, and IL-15 were significantly higher in AAH patients. Only 53% of AAH patients survived 180 days after admission, while all cirrhotic patients were alive at the end of the study period. Among patients with severe AAH, white blood cell count, hemoglobin, resistin, IL-6 and TNF-α were associated with 180-day survival, and all 5 markers demonstrated accuracy by area under receiver-operator curve analysis. Serum IL-6 levels ≥38.66 pg/ml most precisely identified deaths in severe AAH. Patients with IL-6 ≥ 38.66 pg/ml had significantly decreased mean survival compared to those with lower levels. CONCLUSIONS AAH patients demonstrate evidence of increased adipose tissue lipolysis and altered serum lipidomic profile compared with alcoholic cirrhosis patients. IL-6 may be a useful biomarker to risk stratify severe AAH patients at the highest risk of mortality.
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Affiliation(s)
- Vikrant Rachakonda
- Division of Gastroenterology, Hepatology, and Nutrition, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
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2
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Wu MV, Bikopoulos G, Hung S, Ceddia RB. Thermogenic capacity is antagonistically regulated in classical brown and white subcutaneous fat depots by high fat diet and endurance training in rats: impact on whole-body energy expenditure. J Biol Chem 2014; 289:34129-40. [PMID: 25344623 DOI: 10.1074/jbc.m114.591008] [Citation(s) in RCA: 133] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
This study investigated the regulation of thermogenic capacity in classical brown adipose tissue (BAT) and subcutaneous inguinal (SC Ing) white adipose tissue (WAT) and how it affects whole-body energy expenditure in sedentary and endurance-trained rats fed ad libitum either low fat or high fat (HF) diets. Analysis of tissue mass, PGC-1α and UCP-1 content, the presence of multilocular adipocytes, and palmitate oxidation revealed that a HF diet increased the thermogenic capacity of the interscapular and aortic brown adipose tissues, whereas exercise markedly suppressed it. Conversely, exercise induced browning of the SC Ing WAT. This effect was attenuated by a HF diet. Endurance training neither affected skeletal muscle FNDC5 content nor circulating irisin, but it increased FNDC5 content in SC Ing WAT. This suggests that locally produced FNDC5 rather than circulating irisin mediated the exercise-induced browning effect on this fat tissue. Importantly, despite reducing the thermogenic capacity of classical BAT, exercise increased whole-body energy expenditure during the dark cycle. Therefore, browning of subcutaneous WAT likely exerted a compensatory effect and raised whole-body energy expenditure in endurance-trained rats. Based on these novel findings, we propose that exercise-induced browning of the subcutaneous WAT provides an alternative mechanism that reduces thermogenic capacity in core areas and increases it in peripheral body regions. This could allow the organism to adjust its metabolic rate to accommodate diet-induced thermogenesis while simultaneously coping with the stress of chronically increased heat production through exercise.
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Affiliation(s)
- Michelle V Wu
- From the Muscle Health Research Center, School of Kinesiology and Health Science, York University, Toronto, Ontario M3J 1P3, Canada
| | - George Bikopoulos
- From the Muscle Health Research Center, School of Kinesiology and Health Science, York University, Toronto, Ontario M3J 1P3, Canada
| | - Steven Hung
- From the Muscle Health Research Center, School of Kinesiology and Health Science, York University, Toronto, Ontario M3J 1P3, Canada
| | - Rolando B Ceddia
- From the Muscle Health Research Center, School of Kinesiology and Health Science, York University, Toronto, Ontario M3J 1P3, Canada
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3
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Zhao Y, Ling F, Griffin TM, He T, Towner R, Ruan H, Sun XH. Up-regulation of the Sirtuin 1 (Sirt1) and peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α) genes in white adipose tissue of Id1 protein-deficient mice: implications in the protection against diet and age-induced glucose intolerance. J Biol Chem 2014; 289:29112-22. [PMID: 25190816 DOI: 10.1074/jbc.m114.571679] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Id1, a helix-loop-helix (HLH) protein that inhibits the function of basic HLH E protein transcription factors in lymphoid cells, has been implicated in diet- and age-induced obesity by unknown mechanisms. Here we show that Id1-deficient mice are resistant to a high fat diet- and age-induced obesity, as revealed by reduced weight gain and body fat, increased lipid oxidation, attenuated hepatosteatosis, lower levels of lipid droplets in brown adipose tissue, and smaller white adipocytes after a high fat diet feeding or in aged animals. Id1 deficiency improves glucose tolerance, lowers serum insulin levels, and reduces TNFα gene expression in white adipose tissue. Id1 deficiency also increased expression of Sirtuin 1 and peroxisome proliferator-activated receptor γ coactivator 1α, regulators of mitochondrial biogenesis and energy expenditure, in the white adipose tissue. This effect was accompanied by the elevation of several genes encoding proteins involved in oxidative phosphorylation and fatty acid oxidation, such as cytochrome c, medium-chain acyl-CoA dehydrogenase, and adipocyte protein 2. Moreover, the phenotype for Id1 deficiency was similar to that of mice expressing an E protein dominant-positive construct, ET2, suggesting that the balance between Id and E proteins plays a role in regulating lipid metabolism and insulin sensitivity.
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Affiliation(s)
- Ying Zhao
- From the Program in Immunobiology and Cancer Research
| | - Flora Ling
- From the Program in Immunobiology and Cancer Research, Department of Cell Biology and
| | - Timothy M Griffin
- Program in Free Radical Biology and Aging, and Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104, and
| | - Ting He
- Advanced Magnetic Resonance Center, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma 73104
| | - Rheal Towner
- Advanced Magnetic Resonance Center, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma 73104
| | - Hong Ruan
- Department of Physiology and Biophysics, Rutgers University, Piscataway, New Jersey 08854
| | - Xiao-Hong Sun
- From the Program in Immunobiology and Cancer Research, Department of Cell Biology and
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4
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Rakhshandehroo M, Gijzel SMW, Siersbæk R, Broekema MF, de Haar C, Schipper HS, Boes M, Mandrup S, Kalkhoven E. CD1d-mediated presentation of endogenous lipid antigens by adipocytes requires microsomal triglyceride transfer protein. J Biol Chem 2014; 289:22128-39. [PMID: 24966328 DOI: 10.1074/jbc.m114.551242] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Obesity-induced adipose tissue (AT) dysfunction results in a chronic low-grade inflammation that predisposes to the development of insulin resistance and type 2 diabetes. During the development of obesity, the AT-resident immune cell profile alters to create a pro-inflammatory state. Very recently, CD1d-restricted invariant (i) natural killer T (NKT) cells, a unique subset of lymphocytes that are reactive to so called lipid antigens, were implicated in AT homeostasis. Interestingly, recent data also suggest that human and mouse adipocytes can present such lipid antigens to iNKT cells in a CD1d-dependent fashion, but little is known about the lipid antigen presentation machinery in adipocytes. Here we show that CD1d, as well as the lipid antigen loading machinery genes pro-saposin (Psap), Niemann Pick type C2 (Npc2), α-galactosidase (Gla), are up-regulated in early adipogenesis, and are transcriptionally controlled by CCAAT/enhancer-binding protein (C/EBP)-β and -δ. Moreover, adipocyte-induced Th1 and Th2 cytokine release by iNKT cells also occurred in the absence of exogenous ligands, suggesting the display of endogenous lipid antigen-D1d complexes by 3T3-L1 adipocytes. Furthermore, we identified microsomal triglyceride transfer protein, which we show is also under the transcriptional regulation of C/EBPβ and -δ, as a novel player in the presentation of endogenous lipid antigens by adipocytes. Overall, our findings indicate that adipocytes can function as non-professional lipid antigen presenting cells, which may present an important aspect of adipocyte-immune cell communication in the regulation of whole body energy metabolism and immune homeostasis.
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Affiliation(s)
| | - Sanne M W Gijzel
- From the Molecular Cancer Research, Center for Molecular Medicine and
| | - Rasmus Siersbæk
- the Department of Biochemistry and Molecular Biology, University of Southern Denmark, DK-5230 Odense, Denmark
| | | | - Colin de Haar
- the Department of Pediatric Immunology, University Medical Center Utrecht, 3584 CG Utrecht, the Netherlands and
| | - Henk S Schipper
- From the Molecular Cancer Research, Center for Molecular Medicine and the Department of Pediatric Immunology, University Medical Center Utrecht, 3584 CG Utrecht, the Netherlands and
| | - Marianne Boes
- the Department of Pediatric Immunology, University Medical Center Utrecht, 3584 CG Utrecht, the Netherlands and
| | - Susanne Mandrup
- the Department of Biochemistry and Molecular Biology, University of Southern Denmark, DK-5230 Odense, Denmark
| | - Eric Kalkhoven
- From the Molecular Cancer Research, Center for Molecular Medicine and
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5
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Chu DT, Malinowska E, Gawronska-Kozak B, Kozak LP. Expression of adipocyte biomarkers in a primary cell culture models reflects preweaning adipobiology. J Biol Chem 2014; 289:18478-88. [PMID: 24808178 DOI: 10.1074/jbc.m114.555821] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A cohort of genes was selected to characterize the adipogenic phenotype in primary cell cultures from three tissue sources. We compared the quantitative expression of biomarkers in culture relative to their expression in vivo because the mere presence or absence of expression is minimally informative. Although all biomarkers analyzed have biochemical functions in adipocytes, the expression of some of the biomarkers varied enormously in culture relative to their expression in the adult fat tissues in vivo, i.e. inguinal fat for white adipocytes and brite cells, interscapular brown adipose tissue for brown adipocytes, and ear mesenchymal stem cells for white adipocytes from adult mice. We propose that the pattern of expression in vitro does not reflect gene expression in the adult mouse; rather it is predominantly the expression pattern of adipose tissue of the developing mouse between birth and weaning. The variation in gene expression among fat depots in both human and rodent has been an extensively studied phenomenon, and as recently reviewed, it is related to subphenotypes associated with immune function, the inflammatory response, fat depot blood flow, and insulin sensitivity. We suggest that adipose tissue biology in the period from birth to weaning is not just a staging platform for the emergence of adult white fat but that it has properties to serve the unique needs of energy metabolism in the newborn. A case in point is the differentiation of brite cells that occurs during this period followed by their involution immediately following weaning.
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Affiliation(s)
- Dinh-Toi Chu
- From the Institute of Animal Reproduction and Food Research, Polish Academy of Sciences, 10-748 Olsztyn, Poland
| | - Elzbieta Malinowska
- From the Institute of Animal Reproduction and Food Research, Polish Academy of Sciences, 10-748 Olsztyn, Poland
| | - Barbara Gawronska-Kozak
- From the Institute of Animal Reproduction and Food Research, Polish Academy of Sciences, 10-748 Olsztyn, Poland
| | - Leslie P Kozak
- From the Institute of Animal Reproduction and Food Research, Polish Academy of Sciences, 10-748 Olsztyn, Poland
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6
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Grant R, Nguyen KY, Ravussin A, Albarado D, Youm YH, Dixit VD. Inactivation of C/ebp homologous protein-driven immune-metabolic interactions exacerbate obesity and adipose tissue leukocytosis. J Biol Chem 2014; 289:14045-55. [PMID: 24662293 DOI: 10.1074/jbc.m113.545921] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Successful adaptation to periods of chronic caloric excess is a highly coordinated event that is critical to the survival and propagation of species. Transcription factor C/ebp homologous protein (Chop) is thought to be an important molecular mediator that integrates nutrient signals to endoplasmic reticulum (ER) stress and innate immune activation. Given that aberrant ER stress response is implicated in inducing metabolic inflammation and insulin resistance, we hypothesized that ER stress target gene Chop integrates immune and metabolic systems to adapt to chronic positive energy balance. Here we report that inactivation of Chop in mice fed a high fat diet led to significant increase in obesity caused by a reduction in energy expenditure without any change in food intake. Importantly, ablation of Chop does not induce metabolically healthy obesity, because Chop-deficient mice fed a high fat diet had increased hepatic steatosis with significantly higher insulin resistance. Quantification of adipose tissue leukocytosis revealed that elimination of Chop during obesity led to substantial increase in number of adipose tissue T and B lymphocytes. In addition, deficiency of Chop led to increase in total number of myeloid subpopulations like neutrophils and F4/80(+) adipose tissue macrophages without any alterations in the frequency of M1- or M2-like adipose tissue macrophages. Further investigation of inflammatory mechanisms revealed that ablation of Chop increases the sensitivity of macrophages to inflammasome-induced activation of IL-β in macrophages. Our findings indicate that regulated expression of Chop during obesity is critical for adaptation to chronic caloric excess and maintenance of energy homeostasis via integration of metabolic and immune systems.
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Affiliation(s)
- Ryan Grant
- From the Pennington Biomedical Research Center, Louisiana State University System, Baton Rouge, Louisiana 70808 and
| | - Kim Y Nguyen
- the Section of Comparative Medicine and Department of Immunobiology, Yale School of Medicine, New Haven, Connecticut 06520
| | - Anthony Ravussin
- the Section of Comparative Medicine and Department of Immunobiology, Yale School of Medicine, New Haven, Connecticut 06520
| | - Diana Albarado
- From the Pennington Biomedical Research Center, Louisiana State University System, Baton Rouge, Louisiana 70808 and
| | - Yun-Hee Youm
- the Section of Comparative Medicine and Department of Immunobiology, Yale School of Medicine, New Haven, Connecticut 06520
| | - Vishwa Deep Dixit
- From the Pennington Biomedical Research Center, Louisiana State University System, Baton Rouge, Louisiana 70808 and the Section of Comparative Medicine and Department of Immunobiology, Yale School of Medicine, New Haven, Connecticut 06520
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7
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Grahn THM, Kaur R, Yin J, Schweiger M, Sharma VM, Lee MJ, Ido Y, Smas CM, Zechner R, Lass A, Puri V. Fat-specific protein 27 (FSP27) interacts with adipose triglyceride lipase (ATGL) to regulate lipolysis and insulin sensitivity in human adipocytes. J Biol Chem 2014; 289:12029-12039. [PMID: 24627478 DOI: 10.1074/jbc.m113.539890] [Citation(s) in RCA: 87] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
In adipocytes, lipolysis is a highly regulated process involving hormonal signals, lipid droplet-associated proteins, and lipases. The discovery of new lipid droplet-associated proteins added complexity to the current model of lipolysis. In this study, we used cultured human adipocytes to demonstrate that fat-specific protein 27 (FSP27), an abundantly expressed protein in adipocytes, regulates both basal and stimulated lipolysis by interacting with adipose triglyceride lipase (ATGL, also called desnutrin or PNPLA2). We identified a core domain of FSP27, amino acids 120-220, that interacts with ATGL to inhibit its lipolytic function and promote triglyceride storage. We also defined the role of FSP27 in free fatty acid-induced insulin resistance in adipocytes. FSP27 depletion in human adipocytes increased lipolysis and inhibited insulin signaling by decreasing AKT phosphorylation. However, reducing lipolysis by either depletion of ATGL or expression of exogenous full-length FSP27 or amino acids 120-220 protected human adipocytes against the adverse effects of free fatty acids on insulin signaling. In embryonic fibroblasts derived from ATGL KO mice, exogenous free fatty acids did not affect insulin sensitivity. Our results demonstrate a crucial role for FSP27-ATGL interactions in regulating lipolysis, triglyceride accumulation, and insulin signaling in human adipocytes.
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Affiliation(s)
- Tan Hooi Min Grahn
- Section of Endocrinology, Diabetes, and Nutrition, Department of Medicine, Boston University School of Medicine, Boston, Massachusetts 02118
| | - Rajween Kaur
- Section of Endocrinology, Diabetes, and Nutrition, Department of Medicine, Boston University School of Medicine, Boston, Massachusetts 02118
| | - Jun Yin
- Section of Endocrinology, Diabetes, and Nutrition, Department of Medicine, Boston University School of Medicine, Boston, Massachusetts 02118
| | - Martina Schweiger
- Institute of Molecular Biosciences, University of Graz, Heinrichstrasse 31, A-8010 Graz
| | - Vishva Mitra Sharma
- Section of Endocrinology, Diabetes, and Nutrition, Department of Medicine, Boston University School of Medicine, Boston, Massachusetts 02118
| | - Mi-Jeong Lee
- Section of Endocrinology, Diabetes, and Nutrition, Department of Medicine, Boston University School of Medicine, Boston, Massachusetts 02118
| | - Yasuo Ido
- Section of Endocrinology, Diabetes, and Nutrition, Department of Medicine, Boston University School of Medicine, Boston, Massachusetts 02118
| | - Cynthia M Smas
- Department of Biochemistry and Cancer Biology, University of Toledo College of Medicine, Toledo, Ohio 43614
| | - Rudolf Zechner
- Institute of Molecular Biosciences, University of Graz, Heinrichstrasse 31, A-8010 Graz
| | - Achim Lass
- Institute of Molecular Biosciences, University of Graz, Heinrichstrasse 31, A-8010 Graz
| | - Vishwajeet Puri
- Section of Endocrinology, Diabetes, and Nutrition, Department of Medicine, Boston University School of Medicine, Boston, Massachusetts 02118.
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8
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Pessentheiner AR, Pelzmann HJ, Walenta E, Schweiger M, Groschner LN, Graier WF, Kolb D, Uno K, Miyazaki T, Nitta A, Rieder D, Prokesch A, Bogner-Strauss JG. NAT8L (N-acetyltransferase 8-like) accelerates lipid turnover and increases energy expenditure in brown adipocytes. J Biol Chem 2013; 288:36040-51. [PMID: 24155240 PMCID: PMC3861652 DOI: 10.1074/jbc.m113.491324] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
NAT8L (N-acetyltransferase 8-like) catalyzes the formation of N-acetylaspartate (NAA) from acetyl-CoA and aspartate. In the brain, NAA delivers the acetate moiety for synthesis of acetyl-CoA that is further used for fatty acid generation. However, its function in other tissues remained elusive. Here, we show for the first time that Nat8l is highly expressed in adipose tissues and murine and human adipogenic cell lines and is localized in the mitochondria of brown adipocytes. Stable overexpression of Nat8l in immortalized brown adipogenic cells strongly increases glucose incorporation into neutral lipids, accompanied by increased lipolysis, indicating an accelerated lipid turnover. Additionally, mitochondrial mass and number as well as oxygen consumption are elevated upon Nat8l overexpression. Concordantly, expression levels of brown marker genes, such as Prdm16, Cidea, Pgc1α, Pparα, and particularly UCP1, are markedly elevated in these cells. Treatment with a PPARα antagonist indicates that the increase in UCP1 expression and oxygen consumption is PPARα-dependent. Nat8l knockdown in brown adipocytes has no impact on cellular triglyceride content, lipogenesis, or oxygen consumption, but lipolysis and brown marker gene expression are increased; the latter is also observed in BAT of Nat8l-KO mice. Interestingly, the expression of ATP-citrate lyase is increased in Nat8l-silenced adipocytes and BAT of Nat8l-KO mice, indicating a compensatory mechanism to sustain the acetyl-CoA pool once Nat8l levels are reduced. Taken together, our data show that Nat8l impacts on the brown adipogenic phenotype and suggests the existence of the NAT8L-driven NAA metabolism as a novel pathway to provide cytosolic acetyl-CoA for lipid synthesis in adipocytes.
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Affiliation(s)
- Ariane R. Pessentheiner
- From the Institute for Genomics and Bioinformatics, Graz University of Technology, Petergasse 14, 8010 Graz, Austria, ,the Institute of Biochemistry, Graz University of Technology, Petergasse 12, 8010 Graz, Austria
| | - Helmut J. Pelzmann
- From the Institute for Genomics and Bioinformatics, Graz University of Technology, Petergasse 14, 8010 Graz, Austria, ,the Institute of Biochemistry, Graz University of Technology, Petergasse 12, 8010 Graz, Austria
| | - Evelyn Walenta
- From the Institute for Genomics and Bioinformatics, Graz University of Technology, Petergasse 14, 8010 Graz, Austria
| | - Martina Schweiger
- the Institute for Molecular Biosciences, University of Graz, Heinrichstrasse 31, 8010 Graz, Austria
| | | | | | - Dagmar Kolb
- Institute of Cell Biology, Histology, and Embryology, Medical University of Graz, Harrachgasse 21, 8010 Graz, Austria, ,the Core Facility Ultrastructure Analysis, Center for Medical Research, Medical University of Graz, Stiftingtalstrasse 24, 8010 Graz, Austria
| | - Kyosuke Uno
- the Department of Pharmaceutical Therapy and Neuropharmacology, Faculty of Pharmaceutical Sciences, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, 2630 Sugitani, Toyama 930-0194, Japan, and
| | - Toh Miyazaki
- the Department of Pharmaceutical Therapy and Neuropharmacology, Faculty of Pharmaceutical Sciences, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, 2630 Sugitani, Toyama 930-0194, Japan, and
| | - Atsumi Nitta
- the Department of Pharmaceutical Therapy and Neuropharmacology, Faculty of Pharmaceutical Sciences, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, 2630 Sugitani, Toyama 930-0194, Japan, and
| | - Dietmar Rieder
- the Division of Bioinformatics, Biocenter, Innsbruck Medical University, Innrain 80, 6020 Innsbruck, Austria
| | - Andreas Prokesch
- From the Institute for Genomics and Bioinformatics, Graz University of Technology, Petergasse 14, 8010 Graz, Austria, ,the Institute of Biochemistry, Graz University of Technology, Petergasse 12, 8010 Graz, Austria
| | - Juliane G. Bogner-Strauss
- From the Institute for Genomics and Bioinformatics, Graz University of Technology, Petergasse 14, 8010 Graz, Austria, ,the Institute of Biochemistry, Graz University of Technology, Petergasse 12, 8010 Graz, Austria, , To whom correspondence should be addressed: Petersgasse 14/5, 8010 Graz, Austria. Tel.: 43-316-873-5337; E-mail:
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9
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Heckmann BL, Zhang X, Xie X, Saarinen A, Lu X, Yang X, Liu J. Defective adipose lipolysis and altered global energy metabolism in mice with adipose overexpression of the lipolytic inhibitor G0/G1 switch gene 2 (G0S2). J Biol Chem 2013; 289:1905-16. [PMID: 24302733 DOI: 10.1074/jbc.m113.522011] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Biochemical and cell-based studies have identified the G0S2 (G0/G1 switch gene 2) as a selective inhibitor of the key intracellular triacylglycerol hydrolase, adipose triglyceride lipase. To better understand the physiological role of G0S2, we constructed an adipose tissue-specific G0S2 transgenic mouse model. In comparison with wild type animals, the transgenic mice exhibited a significant increase in overall fat mass and a decrease in peripheral triglyceride accumulation. Basal and adrenergically stimulated lipolysis was attenuated in adipose explants isolated from the transgenic mice. Following fasting or injection of a β3-adrenergic agonist, in vivo lipolysis and ketogenesis were decreased in G0S2 transgenic mice when compared with wild type animals. Consequently, adipose overexpression of G0S2 prevented the "switch" of energy substrate from carbohydrates to fatty acids during fasting. Moreover, G0S2 overexpression promoted accumulation of more and larger lipid droplets in brown adipocytes without impacting either mitochondrial morphology or expression of oxidative genes. This phenotypic change was accompanied by defective cold adaptation. Furthermore, feeding with a high fat diet caused a greater gain of both body weight and adiposity in the transgenic mice. The transgenic mice also displayed a decrease in fasting plasma levels of free fatty acid, triglyceride, and insulin as well as improved glucose and insulin tolerance. Cumulatively, these results indicate that fat-specific G0S2 overexpression uncouples adiposity from insulin sensitivity and overall metabolic health through inhibiting adipose lipolysis and decreasing circulating fatty acids.
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Affiliation(s)
- Bradlee L Heckmann
- From the Department of Biochemistry & Molecular Biology, Mayo Clinic, Scottsdale, Arizona 85259
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10
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Tsushima Y, Nishizawa H, Tochino Y, Nakatsuji H, Sekimoto R, Nagao H, Shirakura T, Kato K, Imaizumi K, Takahashi H, Tamura M, Maeda N, Funahashi T, Shimomura I. Uric acid secretion from adipose tissue and its increase in obesity. J Biol Chem 2013; 288:27138-27149. [PMID: 23913681 DOI: 10.1074/jbc.m113.485094] [Citation(s) in RCA: 243] [Impact Index Per Article: 22.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Obesity is often accompanied by hyperuricemia. However, purine metabolism in various tissues, especially regarding uric acid production, has not been fully elucidated. Here we report, using mouse models, that adipose tissue could produce and secrete uric acid through xanthine oxidoreductase (XOR) and that the production was enhanced in obesity. Plasma uric acid was elevated in obese mice and attenuated by administration of the XOR inhibitor febuxostat. Adipose tissue was one of major organs that had abundant expression and activities of XOR, and adipose tissues in obese mice had higher XOR activities than those in control mice. 3T3-L1 and mouse primary mature adipocytes produced and secreted uric acid into culture medium. The secretion was inhibited by febuxostat in a dose-dependent manner or by gene knockdown of XOR. Surgical ischemia in adipose tissue increased local uric acid production and secretion via XOR, with a subsequent increase in circulating uric acid levels. Uric acid secretion from whole adipose tissue was increased in obese mice, and uric acid secretion from 3T3-L1 adipocytes was increased under hypoxia. Our results suggest that purine catabolism in adipose tissue could be enhanced in obesity.
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Affiliation(s)
- Yu Tsushima
- Department of Metabolic Medicine, Graduate School of Medicine, Osaka University, Suita, Osaka 565-0871, Japan; Teijin Institute for Biomedical Research, Teijin Pharma Limited, Hino, Tokyo 191-8512, Japan
| | - Hitoshi Nishizawa
- Department of Metabolic Medicine, Graduate School of Medicine, Osaka University, Suita, Osaka 565-0871, Japan.
| | - Yoshihiro Tochino
- Department of Metabolic Medicine, Graduate School of Medicine, Osaka University, Suita, Osaka 565-0871, Japan
| | - Hideaki Nakatsuji
- Department of Metabolic Medicine, Graduate School of Medicine, Osaka University, Suita, Osaka 565-0871, Japan
| | - Ryohei Sekimoto
- Department of Metabolic Medicine, Graduate School of Medicine, Osaka University, Suita, Osaka 565-0871, Japan
| | - Hirofumi Nagao
- Department of Metabolic Medicine, Graduate School of Medicine, Osaka University, Suita, Osaka 565-0871, Japan
| | - Takashi Shirakura
- Teijin Institute for Biomedical Research, Teijin Pharma Limited, Hino, Tokyo 191-8512, Japan
| | - Kenta Kato
- Teijin Institute for Biomedical Research, Teijin Pharma Limited, Hino, Tokyo 191-8512, Japan
| | | | - Hiroyuki Takahashi
- Teijin Institute for Biomedical Research, Teijin Pharma Limited, Hino, Tokyo 191-8512, Japan
| | - Mizuho Tamura
- Teijin Institute for Biomedical Research, Teijin Pharma Limited, Hino, Tokyo 191-8512, Japan
| | - Norikazu Maeda
- Department of Metabolic Medicine, Graduate School of Medicine, Osaka University, Suita, Osaka 565-0871, Japan
| | - Tohru Funahashi
- Department of Metabolism and Atherosclerosis, Graduate School of Medicine, Osaka University, Suita, Osaka 565-0871, Japan
| | - Iichiro Shimomura
- Department of Metabolic Medicine, Graduate School of Medicine, Osaka University, Suita, Osaka 565-0871, Japan
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