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The Potential to Fight Obesity with Adipogenesis Modulating Compounds. Int J Mol Sci 2022; 23:ijms23042299. [PMID: 35216415 PMCID: PMC8879274 DOI: 10.3390/ijms23042299] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2021] [Revised: 02/06/2022] [Accepted: 02/11/2022] [Indexed: 02/06/2023] Open
Abstract
Obesity is an increasingly severe public health problem, which brings huge social and economic burdens. Increased body adiposity in obesity is not only tightly associated with type 2 diabetes, but also significantly increases the risks of other chronic diseases including cardiovascular diseases, fatty liver diseases and cancers. Adipogenesis describes the process of the differentiation and maturation of adipocytes, which accumulate in distributed adipose tissue at various sites in the body. The major functions of white adipocytes are to store energy as fat during periods when energy intake exceeds expenditure and to mobilize this stored fuel when energy expenditure exceeds intake. Brown/beige adipocytes contribute to non-shivering thermogenesis upon cold exposure and adrenergic stimulation, and thereby promote energy consumption. The imbalance of energy intake and expenditure causes obesity. Recent interest in epigenetics and signaling pathways has utilized small molecule tools aimed at modifying obesity-specific gene expression. In this review, we discuss compounds with adipogenesis-related signaling pathways and epigenetic modulating properties that have been identified as potential therapeutic agents which cast some light on the future treatment of obesity.
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Vohra MS, Ahmad B, Serpell CJ, Parhar IS, Wong EH. Murine in vitro cellular models to better understand adipogenesis and its potential applications. Differentiation 2020; 115:62-84. [PMID: 32891960 DOI: 10.1016/j.diff.2020.08.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2020] [Revised: 08/08/2020] [Accepted: 08/13/2020] [Indexed: 02/07/2023]
Abstract
Adipogenesis has been extensively studied using in vitro models of cellular differentiation, enabling long-term regulation of fat cell metabolism in human adipose tissue (AT) material. Many studies promote the idea that manipulation of this process could potentially reduce the prevalence of obesity and its related diseases. It has now become essential to understand the molecular basis of fat cell development to tackle this pandemic disease, by identifying therapeutic targets and new biomarkers. This review explores murine cell models and their applications for study of the adipogenic differentiation process in vitro. We focus on the benefits and limitations of different cell line models to aid in interpreting data and selecting a good cell line model for successful understanding of adipose biology.
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Affiliation(s)
- Muhammad Sufyan Vohra
- School of Medicine, Faculty of Health and Medical Sciences, Taylor's University Lakeside Campus, 47500, Subang Jaya, Selangor Darul Ehsan, Malaysia.
| | - Bilal Ahmad
- School of Biosciences, Faculty of Health and Medical Sciences, Taylor's University Lakeside Campus, 47500, Subang Jaya, Selangor Darul Ehsan, Malaysia.
| | - Christopher J Serpell
- School of Physical Sciences, Ingram Building, University of Kent, Canterbury, Kent, CT2 7NH, United Kingdom.
| | - Ishwar S Parhar
- Brain Research Institute, Jeffery Cheah School of Medicine and Health Sciences, Monash University, Bandar Sunway, PJ 47500, Selangor, Malaysia.
| | - Eng Hwa Wong
- School of Medicine, Faculty of Health and Medical Sciences, Taylor's University Lakeside Campus, 47500, Subang Jaya, Selangor Darul Ehsan, Malaysia.
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Onogi Y, Khalil AEMM, Ussar S. Identification and characterization of adipose surface epitopes. Biochem J 2020; 477:2509-2541. [PMID: 32648930 PMCID: PMC7360119 DOI: 10.1042/bcj20190462] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2020] [Revised: 06/11/2020] [Accepted: 06/12/2020] [Indexed: 12/14/2022]
Abstract
Adipose tissue is a central regulator of metabolism and an important pharmacological target to treat the metabolic consequences of obesity, such as insulin resistance and dyslipidemia. Among the various cellular compartments, the adipocyte cell surface is especially appealing as a drug target as it contains various proteins that when activated or inhibited promote adipocyte health, change its endocrine function and eventually maintain or restore whole-body insulin sensitivity. In addition, cell surface proteins are readily accessible by various drug classes. However, targeting individual cell surface proteins in adipocytes has been difficult due to important functions of these proteins outside adipose tissue, raising various safety concerns. Thus, one of the biggest challenges is the lack of adipose selective surface proteins and/or targeting reagents. Here, we discuss several receptor families with an important function in adipogenesis and mature adipocytes to highlight the complexity at the cell surface and illustrate the problems with identifying adipose selective proteins. We then discuss that, while no unique adipocyte surface protein might exist, how splicing, posttranslational modifications as well as protein/protein interactions can create enormous diversity at the cell surface that vastly expands the space of potentially unique epitopes and how these selective epitopes can be identified and targeted.
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Affiliation(s)
- Yasuhiro Onogi
- RG Adipocytes and Metabolism, Institute for Diabetes and Obesity, Helmholtz Diabetes Center, Helmholtz Zentrum München, German Research Center for Environmental Health GmbH, 85764 Neuherberg, Germany
- German Center for Diabetes Research (DZD), 85764 Neuherberg, Germany
| | - Ahmed Elagamy Mohamed Mahmoud Khalil
- RG Adipocytes and Metabolism, Institute for Diabetes and Obesity, Helmholtz Diabetes Center, Helmholtz Zentrum München, German Research Center for Environmental Health GmbH, 85764 Neuherberg, Germany
- German Center for Diabetes Research (DZD), 85764 Neuherberg, Germany
| | - Siegfried Ussar
- RG Adipocytes and Metabolism, Institute for Diabetes and Obesity, Helmholtz Diabetes Center, Helmholtz Zentrum München, German Research Center for Environmental Health GmbH, 85764 Neuherberg, Germany
- German Center for Diabetes Research (DZD), 85764 Neuherberg, Germany
- Department of Medicine, Technische Universität München, Munich, Germany
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Abstract
Propose Obesity is a fast growing epidemic worldwide. During obesity, the increase in adipose tissue mass arise from two different mechanisms, namely, hyperplasia and hypertrophy. Hyperplasia which is the increase in adipocyte number is characteristic of severe obese patients. Recently, there has been much interest in targeting adipogenesis as therapeutic strategy against obesity. Flavonoids have been shown to regulate several pathways and affect a number of molecular targets during specific stages of adipocyte development. Methods Presently, we provide a review of key studies evaluating the effects of dietary flavonoids in different stages of adipocyte development with a particular emphasis on the investigations that explore the underlying mechanisms of action of these compounds in human or animal cell lines as well as animal models. Results Flavonoids have been shown to regulate several pathways and affect a number of molecular targets during specific stages of adipocyte development. Although most of the studies reveal anti-adipogenic effect of flavonoids, some flavonoids demonstrated proadipogenic effect in mesenchymal stem cells or preadipocytes. Conclusion The anti-adipogenic effect of flavonoids is mainly via their effect on regulation of several pathways such as induction of apoptosis, suppression of key adipogenic transcription factors, activation of AMPK and Wnt pathways, inhibition of clonal expansion, and cell-cycle arrest.
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Oh JD, Kim ES, Lee HK, Song KD. Effect of a c-MYC Gene Polymorphism (g.3350G>C) on Meat Quality Traits in Berkshire. ASIAN-AUSTRALASIAN JOURNAL OF ANIMAL SCIENCES 2015; 28:1545-50. [PMID: 26580277 PMCID: PMC4647093 DOI: 10.5713/ajas.15.0425] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/14/2015] [Revised: 05/17/2015] [Accepted: 08/14/2015] [Indexed: 01/17/2023]
Abstract
c-MYC (v-myelocytomatosis viral oncogene homologue) is a transcription factor that plays important role in many biological process including cell growth and differentiation, such as myogenesis and adipogenesis. In this study, we aimed to detect MYC gene polymorphisms, their genotype frequencies and to determine associations between these polymorphisms and meat quality traits in Berkshire pigs. We identified a single nucleotide polymorphism (SNP) in intron 2 of MYC gene by Sanger sequencing, i.e., g.3350G>C (rs321898326), that is only found in Berkshire pigs, but not in other breeds including Duroc, Landrace, and Yorkshire pigs that were used in this study. Genotypes of total 378 Berkshire pigs (138 sows and 240 boars) were determined using Hha I restriction enzyme digestion after polymerase chain reaction. Observed allele frequencies of GG, GC, and CC genotypes were 0.399, 0.508, and 0.093 respectively. Statistical analysis indicated that the g.3350G>C polymorphism was significantly associated with pH45min and cooking loss (p<0.05), suggesting that g.3350G>C SNP can be used for pre-selection of pH45min and cooking loss traits in Berkshire pigs.
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Affiliation(s)
| | - E. S. Kim
- Department of Animal Science, Iowa State University, Ames, IA 50011,
USA
| | | | - K. D. Song
- Department of Animal Science, Iowa State University, Ames, IA 50011,
USA
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Perotti V, Baldassari P, Molla A, Vegetti C, Bersani I, Maurichi A, Santinami M, Anichini A, Mortarini R. NFATc2 is an intrinsic regulator of melanoma dedifferentiation. Oncogene 2015; 35:2862-72. [DOI: 10.1038/onc.2015.355] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2015] [Accepted: 08/04/2015] [Indexed: 12/20/2022]
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Curcumin and diabetes: a systematic review. EVIDENCE-BASED COMPLEMENTARY AND ALTERNATIVE MEDICINE 2013; 2013:636053. [PMID: 24348712 PMCID: PMC3857752 DOI: 10.1155/2013/636053] [Citation(s) in RCA: 158] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/04/2013] [Revised: 08/30/2013] [Accepted: 09/12/2013] [Indexed: 12/20/2022]
Abstract
Turmeric (Curcuma longa), a rhizomatous herbaceous perennial plant of the ginger family, has been used for the treatment of diabetes in Ayurvedic and traditional Chinese medicine. The active component of turmeric, curcumin, has caught attention as a potential treatment for diabetes and its complications primarily because it is a relatively safe and inexpensive drug that reduces glycemia and hyperlipidemia in rodent models of diabetes. Here, we review the recent literature on the applications of curcumin for glycemia and diabetes-related liver disorders, adipocyte dysfunction, neuropathy, nephropathy, vascular diseases, pancreatic disorders, and other complications, and we also discuss its antioxidant and anti-inflammatory properties. The applications of additional curcuminoid compounds for diabetes prevention and treatment are also included in this paper. Finally, we mention the approaches that are currently being sought to generate a "super curcumin" through improvement of the bioavailability to bring this promising natural product to the forefront of diabetes therapeutics.
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Qadir AS, Lee HL, Baek KH, Park HJ, Woo KM, Ryoo HM, Baek JH. Msx2 is required for TNF-α-induced canonical Wnt signaling in 3T3-L1 preadipocytes. Biochem Biophys Res Commun 2011; 408:399-404. [DOI: 10.1016/j.bbrc.2011.04.029] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2011] [Accepted: 04/06/2011] [Indexed: 10/18/2022]
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Ahn J, Lee H, Kim S, Ha T. Curcumin-induced suppression of adipogenic differentiation is accompanied by activation of Wnt/β-catenin signaling. Am J Physiol Cell Physiol 2010; 298:C1510-6. [DOI: 10.1152/ajpcell.00369.2009] [Citation(s) in RCA: 188] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Curcumin, a polyphenol found in the rhizomes of Curcuma longa , improves obesity-associated inflammation and diabetes in obese mice. Curcumin also suppresses adipocyte differentiation, although the underlying mechanism remains unclear. Here, we used 3T3-L1 cells to investigate the details of the mechanism underlying the anti-adipogenic effects of curcumin. Curcumin inhibited mitogen-activated protein kinase (MAPK) (ERK, JNK, and p38) phosphorylation that was associated with differentiation of 3T3-L1 cells into adipocytes. During differentiation, curcumin also restored nuclear translocation of the integral Wnt signaling component β-catenin in a dose-dependent manner. In parallel, curcumin reduced differentiation-stimulated expression of CK1α, GSK-3β, and Axin, components of the destruction complex targeting β-catenin. Accordingly, quantitative PCR analysis revealed that curcumin inhibited the mRNA expression of AP2 (mature adipocyte marker) and increased the mRNA expression of Wnt10b, Fz2 (Wnt direct receptor), and LRP5 (Wnt coreceptor). Curcumin also increased mRNA levels of c-Myc and cyclin D1, well-known Wnt targets. These results suggest that the Wnt signaling pathway participates in curcumin-induced suppression of adipogenesis in 3T3-L1 cells.
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Affiliation(s)
- Jiyun Ahn
- Food Function Research Center, Korea Food Research Institute, Gyeonggi, Korea
| | - Hyunjung Lee
- Food Function Research Center, Korea Food Research Institute, Gyeonggi, Korea
| | - Suna Kim
- Food Function Research Center, Korea Food Research Institute, Gyeonggi, Korea
| | - Taeyoul Ha
- Food Function Research Center, Korea Food Research Institute, Gyeonggi, Korea
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Atsumi T, Cho YR, Leng L, McDonald C, Yu T, Danton C, Hong EG, Mitchell RA, Metz C, Niwa H, Takeuchi J, Onodera S, Umino T, Yoshioka N, Koike T, Kim JK, Bucala R. The proinflammatory cytokine macrophage migration inhibitory factor regulates glucose metabolism during systemic inflammation. THE JOURNAL OF IMMUNOLOGY 2007; 179:5399-406. [PMID: 17911626 DOI: 10.4049/jimmunol.179.8.5399] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Inflammation provokes significant abnormalities in host metabolism that result from the systemic release of cytokines. An early response of the host is hyperglycemia and resistance to the action of insulin, which progresses over time to increased glucose uptake in peripheral tissue. Although the cytokine TNF-alpha has been shown to exert certain catabolic effects, recent studies suggest that the metabolic actions of TNF-alpha occur by the downstream regulation of additional mediators, such as macrophage migration inhibitory factor (MIF). We investigated the glycemic responses of endotoxemic mice genetically deficient in MIF (MIF(-/-)). In contrast to wild-type mice, MIF(-/-) mice exhibit normal blood glucose and lactate responses following the administration of endotoxin, or TNF-alpha. MIF(-/-) mice also show markedly increased glucose uptake into white adipose tissue in vivo in the endotoxemic state. Treatment of adipocytes with MIF, or anti-MIF mAb, modulates insulin-mediated glucose transport and insulin receptor signal transduction; these effects include the phosphorylation of insulin receptor substrate-1, its association with the p85 regulatory subunit of PI3K, and the downstream phosphorylation of Akt. Genetic MIF deficiency also promotes adipogenesis, which is in accord with a downstream role for MIF in the action of TNF-alpha. These studies support an important role for MIF in host glucose metabolism during sepsis.
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Affiliation(s)
- Toshiya Atsumi
- Graduate School of Medicine, Hokkaido University, Sapporo, Japan
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Abstract
Dyslipidemia and insulin resistance are commonly associated with catabolic or lipodystrophic conditions (such as cancer and sepsis) and with pathological states of nutritional overload (such as obesity-related type 2 diabetes). Two common features of these metabolic disorders are adipose tissue dysfunction and elevated levels of tumour necrosis factor-alpha (TNF-alpha). Herein, we review the multiple actions of this pro-inflammatory adipokine on adipose tissue biology. These include inhibition of carbohydrate metabolism, lipogenesis, adipogenesis and thermogenesis and stimulation of lipolysis. TNF-alpha can also impact the endocrine functions of adipose tissue. Taken together, TNF-alpha contributes to metabolic dysregulation by impairing both adipose tissue function and its ability to store excess fuel. The molecular mechanisms that underlie these actions are discussed.
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Affiliation(s)
- William P Cawthorn
- Institute of Metabolic Science-Metabolic Research Laboratories, University of Cambridge, Addenbrooke's Hospital, Cambridge CB2 0QQ, UK
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Cawthorn WP, Heyd F, Hegyi K, Sethi JK. Tumour necrosis factor-alpha inhibits adipogenesis via a beta-catenin/TCF4(TCF7L2)-dependent pathway. Cell Death Differ 2007; 14:1361-73. [PMID: 17464333 PMCID: PMC4303765 DOI: 10.1038/sj.cdd.4402127] [Citation(s) in RCA: 175] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Tumour necrosis factor-alpha (TNF-alpha), a proinflammatory cytokine, is a potent negative regulator of adipocyte differentiation. However, the mechanism of TNF-alpha-mediated antiadipogenesis remains incompletely understood. In this study, we first confirm that TNF-alpha inhibits adipogenesis of 3T3-L1 preadipocytes by preventing the early induction of the adipogenic transcription factors peroxisome proliferator-activated receptor-gamma (PPARgamma) and CCAAT/enhancer binding protein-alpha (C/EBPalpha). This suppression coincides with enhanced expression of several reported mediators of antiadipogenesis that are also targets of the Wnt/beta-catenin/T-cell factor 4 (TCF4) pathway. Indeed, we found that TNF-alpha enhanced TCF4-dependent transcriptional activity during early antiadipogenesis, and promoted the stabilisation of beta-catenin throughout antiadipogenesis. We analysed the effect of TNF-alpha on adipogenesis in 3T3-L1 cells in which beta-catenin/TCF signalling was impaired, either via stable knockdown of beta-catenin, or by overexpression of dominant-negative TCF4 (dnTCF4). The knockdown of beta-catenin enhanced the adipogenic potential of 3T3-L1 preadipocytes and attenuated TNF-alpha-induced antiadipogenesis. However, beta-catenin knockdown also promoted TNF-alpha-induced apoptosis in these cells. In contrast, overexpression of dnTCF4 prevented TNF-alpha-induced antiadipogenesis but showed no apparent effect on cell survival. Finally, we show that TNF-alpha-induced antiadipogenesis and stabilisation of beta-catenin requires a functional death domain of TNF-alpha receptor 1 (TNFR1). Taken together these data suggest that TNFR1-mediated death domain signals can inhibit adipogenesis via a beta-catenin/TCF4-dependent pathway.
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Affiliation(s)
- WP Cawthorn
- Department of Clinical Biochemistry, Addenbrooke’s Hospital, University of Cambridge, Cambridge, UK
| | - F Heyd
- Department of Clinical Biochemistry, Addenbrooke’s Hospital, University of Cambridge, Cambridge, UK
| | - K Hegyi
- Department of Clinical Biochemistry, Addenbrooke’s Hospital, University of Cambridge, Cambridge, UK
| | - JK Sethi
- Department of Clinical Biochemistry, Addenbrooke’s Hospital, University of Cambridge, Cambridge, UK
- Corresponding author: JK Sethi, Department of Clinical Biochemistry, University of Cambridge, Addenbrooke’s Hospital, Box 232, Hills Road, Cambridge CB2 2QR, UK. Tel: + 44 1223 762633; Fax: + 44 1223 330598;
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Celis JE, Moreira JMA, Cabezón T, Gromov P, Friis E, Rank F, Gromova I. Identification of extracellular and intracellular signaling components of the mammary adipose tissue and its interstitial fluid in high risk breast cancer patients: toward dissecting the molecular circuitry of epithelial-adipocyte stromal cell interactions. Mol Cell Proteomics 2005; 4:492-522. [PMID: 15695426 DOI: 10.1074/mcp.m500030-mcp200] [Citation(s) in RCA: 184] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
It has become clear that growth and progression of breast tumor cells not only depend on their malignant potential but also on factors present in the tumor microenvironment. Of the cell types that constitute the mammary stroma, the adipocytes are perhaps the least well studied despite the fact that they represent one of the most prominent cell types surrounding the breast tumor cells. There is compelling evidence demonstrating a role for the mammary fat pad in mammary gland development, and some studies have revealed the ability of fat tissue to augment the growth and ability to metastasize of mammary carcinoma cells. Very little is known, however, about which factors adipocytes produce that may orchestrate these actions and how this may come about. In an effort to shed some light on these questions, we present here a detailed proteomic analysis, using two-dimensional gel-based technology, mass spectrometry, immunoblotting, and antibody arrays, of adipose cells and interstitial fluid of fresh fat tissue samples collected from sites topologically distant from the tumors of high risk breast cancer patients that underwent mastectomy and that were not treated prior to surgery. A total of 359 unique proteins were identified, including numerous signaling molecules, hormones, cytokines, and growth factors, involved in a variety of biological processes such as signal transduction and cell communication; energy metabolism; protein metabolism; cell growth and/or maintenance; immune response; transport; regulation of nucleobase, nucleoside, and nucleic acid metabolism; and apoptosis. Apart from providing a comprehensive overview of the mammary fat proteome and its interstitial fluid, the results offer some insight as to the role of adipocytes in the breast tumor microenvironment and provide a first glance of their molecular cellular circuitry. In addition, the results open new possibilities to the study of obesity, which has a strong association with type 2 diabetes, hypertension, and coronary heart disease.
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Affiliation(s)
- Julio E Celis
- Department of Proteomics in Cancer, Institute of Cancer Biology, Copenhagen University Hospital, DK-2100 Copenhagen, Denmark.
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Nagashima H, Matsumura F. 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD)-induced down-regulation of glucose transporting activities in mouse 3T3-L1 preadipocyte. JOURNAL OF ENVIRONMENTAL SCIENCE AND HEALTH. PART. B, PESTICIDES, FOOD CONTAMINANTS, AND AGRICULTURAL WASTES 2002; 37:1-14. [PMID: 11990355 DOI: 10.1081/pfc-120002893] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The possibility that 3T3-L1 preadipocytes, while the level of its glucose uptake activity is relatively low, may offer a useful tool for studying the cause for 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-induced "lipolytic response" was studied. It was established first, that TCDD causes reduction of glucose uptake, one of the hallmark events of the lipolytic process. Then the function of c-Src was investigated. The antisense c-src oligonucleotide decreased the inhibitory action of TCDD on glucose uptake activity in a sequence specific manner. Since antisense oligonucleotides are known to own their blocking effects to their ability to reduce translation of proteins, Western blotting analysis was performed to verify their effectiveness. As expected, the treatment of pre-adipocytes with antisense c-src oligonucleotide reduced c-Src in a sequence specific manner. The treatment of antisense c-src oligonucleotide alone was sufficient to diminish the inhibitory action of TCDD on glucose uptake activity in 3T3-L1 cells, indicating that c-Src is somehow involved in the action of TCDD. In a similar manner, the contribution of c-Fos was investigated using antisense c-fos oligonucleotide, since c-Fos is known to be one of the most affected proteins by c-Src activation among AP-1 members. The treatment of antisense c-fos oligonucleotide did not block the effect of TCDD on glucose uptake activity in 3T3-L1 cells. Therefore, it is unlikely that c-Fos is very important in the lipolytic signal transduction of TCDD mediated through c-Src. In order to determine the relationship between c-Src and c-Myc in the mitotic signal transduction pathway, the effect of antisense c-myc oligonucleotide was investigated. Basically the same result as antisense c-src oligonucleotide experiment was obtained thereby, suggesting the importance of c-Myc as well as c-Src in the signal transduction of TCDD. To show the effect of antisense c-myc oligonucleotide treatment, the level of c-Myc protein by Western blotting and electrophoretic gel-mobility shift assay was assessed. However, antisense c-myc oligonucleotide treatment increased the activity of c-Myc in a sequence specific manner. This may be the result of cellular compensatory response to the initial suppression of c-Myc by antisense treatment. The observation that antisense c-fos oligonucleotide could not block the effect of TCDD indicates that this preadipocyte model is different from the adipocyte differentiation model.
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Affiliation(s)
- Hitoshi Nagashima
- Department of Environmental Toxicology and the Center for Environmental Health Sciences, University of California, Davis 95616, USA.
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15
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Liu H, Lo CR, Jones BE, Pradhan Z, Srinivasan A, Valentino KL, Stockert RJ, Czaja MJ. Inhibition of c-Myc expression sensitizes hepatocytes to tumor necrosis factor-induced apoptosis and necrosis. J Biol Chem 2000; 275:40155-62. [PMID: 11016920 DOI: 10.1074/jbc.m001565200] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
The typical proliferative response of hepatocytes to tumor necrosis factor (TNF) can be converted to a cytotoxic one by transcriptional arrest. Although NF-kappaB activation is critical for hepatocyte resistance to TNF toxicity, the contribution of other TNF-inducible transcription factors remains unknown. To determine the function of c-Myc in hepatocyte sensitivity to TNF, stable transfectants of the rat hepatocyte cell line RALA255-10G containing sense and antisense c-myc expression vectors were isolated with increased (S-Myc cells) and decreased (AN-Myc cells) c-Myc transcriptional activity. While S-Myc cells proliferated in response to TNF treatment, AN-Myc cells underwent 32% cell death within 6 h. Fluorescent microscopic studies indicated that TNF induced apoptosis and necrosis in AN-Myc cells. Cell death was associated with DNA hypoploidy and poly(ADP-ribose) polymerase cleavage but occurred in the absence of detectable caspase-3, -7, or -8 activation. TNF-induced, AN-Myc cell death was dependent on Fas-associated protein with death domain and partially blocked by caspase inhibitors. AN-Myc cells had decreased levels of NF-kappaB transcriptional activity, but S-Myc cells maintained resistance to TNF despite NF-kappaB inactivation, suggesting that c-Myc and NF-kappaB independently mediate TNF resistance. Thus, in the absence of sufficient c-Myc expression, hepatocytes are sensitized to TNF-induced apoptosis and necrosis. These findings demonstrate that hepatocyte resistance to TNF is regulated by multiple transcriptional activators.
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Affiliation(s)
- H Liu
- Department of Medicine and Marion Bessin Liver Research Center, Albert Einstein College of Medicine, Bronx, New York 10461, USA
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Trouba KJ, Wauson EM, Vorce RL. Sodium arsenite inhibits terminal differentiation of murine C3H 10T1/2 preadipocytes. Toxicol Appl Pharmacol 2000; 168:25-35. [PMID: 11000097 DOI: 10.1006/taap.2000.9012] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Cancer represents an imbalance between cell proliferation and differentiation, two processes that are coordinately and antagonistically regulated. Aberrant cell proliferation is considered to be an important etiological factor in the development of arsenic-induced cancer, suggesting that arsenic also dysregulates differentiation. Based on evidence that arsenic modulates mitogenic events that antagonize the process of differentiation, this study addresses the hypothesis that sodium arsenite inhibits insulin/dexamethasone-induced differentiation of C3H 10T1/2 preadipocytes; it was further postulated that arsenic-treated cells retain mitogenic responsiveness under differentiating conditions. To test this hypothesis, the differentiation capacity of C3H 10T1/2 preadipocytes was examined in control cells and cells treated with sodium arsenite. Differentiation was assessed morphologically and quantified by Oil Red-O staining of accumulated lipids. The effect of long-term arsenic exposure on mitogenic competence was quantified by flow cytometry, [(3)H]thymidine incorporation, and cell counting under conditions favorable for adipocyte differentiation. Results indicate that arsenic inhibits morphological differentiation of wild-type C3H 10T1/2 preadipocytes. Short-term arsenic exposure inhibits differentiation in a dose-dependent manner, with arsenic concentrations > or = 3 microM producing a significant inhibition of dexamethasone/insulin-induced lipid accumulation. Furthermore, arsenic-treated cells exhibit an accentuated response to mitogenic stimulation under differentiating conditions. These data suggest that arsenic exposure results in the inhibition of cellular programming required for terminal differentiation of C3H 10T1/2 preadipocytes and that cells acquire mitogenic hyperresponsiveness. The ability of arsenic to dysregulate the balance between proliferation and differentiation is proposed to be one mechanism by which this metalloid causes cancer in humans.
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Affiliation(s)
- K J Trouba
- Department of Pharmacology, University of Nebraska Medical Center, Omaha, Nebraska 68198-6260, USA
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Tao H, Umek RM. C/EBPalpha is required to maintain postmitotic growth arrest in adipocytes. DNA Cell Biol 2000; 19:9-18. [PMID: 10668787 DOI: 10.1089/104454900314663] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Terminal differentiation is often coupled with irreversible loss of proliferative potential. The CCAAT enhancer binding protein alpha (C/EBPalpha) preferentially accumulates in postmitotic, differentiated 3T3-L1 adipocytes but declines during tumor necrosis factor alpha (TNFalpha)-induced dedifferentiation. We have discovered that this decline in C/EBPalpha correlates with an increased mitotic growth potential. In order to further investigate the antimitotic activity of C/EBPalpha, we introduced antisense C/EBPalpha RNA into 3T3-L1 cells to block endogenous C/EBPalpha expression. When treated according to the standard differentiation protocol, stable cells lines harboring antisense C/EBPalpha RNA did not differentiate into fat-laden adipocytes, consistent with previous findings (Lin F, Lane MD, Genes Dev 1992;6:533-544). We found that these undifferentiated cells expressing antisense-C/EBPalpha can reenter the cell cycle after mitogenic stimulation at a time in development when parental 3T3-L1 cells cannot. Moreover, the expression profiles of the growth-arrest-associated genes gas1 and gas2 revealed that the antisense C/EBPalpha-expressing cells withdrew from the cell cycle after the period of clonal expansion but failed to progress to the state of least proliferative potential characteristic of terminally differentiated adipocytes.
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Affiliation(s)
- H Tao
- Department of Biology, University of Virginia, Charlottesville 22903, USA.
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18
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Reiner BG, Moser G, Geldermann H, Dzapo V. Associations between the c-myc proto-oncogene and carcass quality traits in the pig: evidence for epistasis with the Ryr1-gene. J Anim Breed Genet 1999. [DOI: 10.1046/j.1439-0388.1999.00200.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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19
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Reiner G, Hecht W, Leeb T, Brenig B, Robic A, Dzapo V. Isolation and characterization of the porcine c-myc proto-oncogene and chromosomal assignment to SSC 4p13. Anim Genet 1999; 30:204-6. [PMID: 10442983 DOI: 10.1046/j.1365-2052.1999.00447.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The proto-oncogene c-myc codes for a nuclear phosphoprotein, a transcription factor composed of the typical basic/helix-loop-helix/leucine zipper domains. Its expression is coupled to a multitude of physiological processes and regulated by a variety of hormones, growth factors, cytokines, lymphokines and the nutritional status, development and differentiation. Its key roles have been characterized, e.g. in adipogenesis, myogenesis and folliculogenesis. We have isolated and sequenced a 6.4-kb genomic fragment encoding the porcine c-myc proto-oncogene. The gene shows the typical c-myc structure with three exons, three putative promoters and a deduced protein of 439 amino acids. The porcine c-myc was mapped to chromosome 4p13 by screening of a porcine-rodent hybrid cell panel.
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Affiliation(s)
- G Reiner
- Institute for Animal Breeding and Genetics, University of Giessen, Germany
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20
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Haraguchi K, Shimura H, Ikeda M, Endo T, Onaya T. Effects of cytokines on expression of thyrotropin receptor mRNA in rat preadipocytes. Thyroid 1998; 8:687-92. [PMID: 9737365 DOI: 10.1089/thy.1998.8.687] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Cultured rat preadipocytes express thyrotropin receptor (TSHR) during their differentiation. To evaluate the effects of inflammatory cytokines on the expression of TSHR in cultured rat preadipocytes, we cultured those cells in the presence of recombinant human tumor necrosis factor (rhTNF)-alpha, recombinant human interferon (rhIFN)-gamma, and human transforming growth factor (hTGF)-beta1. The effects on the level of TSHR mRNA and signal transduction were evaluated. Addition to the medium of 1 ng/mL TNF-alpha, 1 ng/mL rhIFN-gamma, and 1 ng/mL hTGF-beta1 during the differentiation of rat preadipocytes inhibited the expression of TSHR mRNA. The decrease in TSHR mRNA was accompanied by a decrease in TSH-stimulated cyclic adenosine monophosphate (cAMP) production. Histochemical analysis showed that these cytokines inhibited the morphological differentiation of the cells. These cytokines also decreased the expression of mRNA for such fat-specific proteins as lipoprotein lipase and aP2. Results indicate that the loss of expression and function of the TSHR is closely related to the inhibition of differentiation. This confirms the close relation between the expression of the TSHR and the differentiation of the rat preadipocytes.
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Affiliation(s)
- K Haraguchi
- Third Department of Internal Medicine, Yamanashi Medical University, Tamaho, Japan
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21
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Abstract
The adipocyte plays a critical role in energy balance. Adipose tissue growth involves an increase in adipocyte size and the formation of new adipocytes from precursor cells. For the last 20 years, the cellular and molecular mechanisms of adipocyte differentiation have been extensively studied using preadipocyte culture systems. Committed preadipocytes undergo growth arrest and subsequent terminal differentiation into adipocytes. This is accompanied by a dramatic increase in expression of adipocyte genes including adipocyte fatty acid binding protein and lipid-metabolizing enzymes. Characterization of regulatory regions of adipose-specific genes has led to the identification of the transcription factors peroxisome proliferator-activated receptor-gamma (PPAR-gamma) and CCAAT/enhancer binding protein (C/EBP), which play a key role in the complex transcriptional cascade during adipocyte differentiation. Growth and differentiation of preadipocytes is controlled by communication between individual cells or between cells and the extracellular environment. Various hormones and growth factors that affect adipocyte differentiation in a positive or negative manner have been identified. In addition, components involved in cell-cell or cell-matrix interactions such as preadipocyte factor-1 and extracellular matrix proteins are also pivotal in regulating the differentiation process. Identification of these molecules has yielded clues to the biochemical pathways that ultimately result in transcriptional activation via PPAR-gamma and C/EBP. Studies on the regulation of the these transcription factors and the mode of action of various agents that influence adipocyte differentiation will reveal the physiological and pathophysiological mechanisms underlying adipose tissue development.
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Affiliation(s)
- F M Gregoire
- Department of Nutritional Sciences, University of California, Berkeley, USA
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22
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Knittel T, Müller L, Saile B, Ramadori G. Effect of tumour necrosis factor-alpha on proliferation, activation and protein synthesis of rat hepatic stellate cells. J Hepatol 1997; 27:1067-80. [PMID: 9453433 DOI: 10.1016/s0168-8278(97)80151-1] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
BACKGROUND/AIMS Hepatic stellate cells represent the principal matrix-synthesising cells of damaged liver and are targets of a number of cytokines currently under investigation. The study analyses the effects of tumour necrosis factor-alpha and interferon-gamma on proliferation, "activation" and protein synthesis of hepatic stellate cells. METHODS Primary cultures of hepatic stellate cells were exposed to tumour necrosis factor-alpha and interferon-gamma. Cell proliferation was studied by 3H-thymidine and bromo-deoxy-uridine incorporation. Protein synthesis was analysed using immunoprecipitation, Western- and Northern blotting techniques. RESULTS Proliferation of hepatic stellate cells was reduced by tumor necrosis factor-alpha and interferon-gamma, while "activation" of hepatic stellate cells as assessed by expression of smooth muscle alpha-actin and of TGF-beta/activin type I receptor was induced by tumour necrosis factor-alpha but downregulated by interferon-gamma. Tumour necrosis factor-alpha increased the synthesis of distinct extracellular matrix proteins, particularly of fibronectin and tenascin, but decreased collagen type III expression. In contrast, interferon-gamma reduced the synthesis of all connective tissue proteins tested. Among the protease inhibitors, interferon-gamma induced C1-esterase inhibitor synthesis, while tumour necrosis factor-alpha stimulated plasminogen activator inhibitor type 1 production. CONCLUSIONS Tumour necrosis factor-alpha and interferon-gamma decrease proliferation of hepatic stellate cells, while "activation" of hepatic stellate cells and synthesis of proteins involved in matrix metabolism are regulated in a differential, cytokine-specific manner, suggesting that both cytokines play an important role in liver repair.
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Affiliation(s)
- T Knittel
- Department of Internal Medicine, University of Göttingen, Germany
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23
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Lacasa D, Garcia E, Henriot D, Agli B, Giudicelli Y. Site-related specificities of the control by androgenic status of adipogenesis and mitogen-activated protein kinase cascade/c-fos signaling pathways in rat preadipocytes. Endocrinology 1997; 138:3181-6. [PMID: 9231766 DOI: 10.1210/endo.138.8.5290] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
In rats, castration induces a complete defective adipose conversion of preadipocytes from the epididymal fat depots (Lacasa, D., B. Agli, D. Noynarol, and Y. Giudicelli, 1995, Endocrine 3: 789-793). The aim of this study was to establish the eventual site-specificity of this effect as well as the mechanisms involved. Therefore, the influence of androgenic status on the Fos protein induction and the Raf/mitogen-activated protein (MAP) kinase kinase (MEK)MAP cascade, which are all required for adipose conversion of preadipocytes, was compared in proliferating and differentiated preadipocytes from femoral sc and deep intraabdominal (epididymal and perirenal) fat depots. In epididymal and perirenal proliferating preadipocytes, increased proliferation due to castration is associated with increased MAP kinase activity. However, higher immunoreactive levels of the upstream activators of MAP kinase, Raf-1 and MEK, were observed only in epididymal cells. Moreover, in vivo testosterone treatment corrected the effects of castration on Raf-1 but not on MEK and MAP kinase. MAP kinase activity was decreased during the course of adipogenesis. In differentiated cells, MAP kinase activity showed variations according to the anatomical origin of preadipocytes but not to the androgenic status. In contrast, MEK and Raf-1 immunoreactive levels were both sensitive to androgenic status but were differently affected depending on cell origin. Finally, the defective adipogenesis seen in epididymal preadipocytes from castrated rats was associated with reduced Fos protein induction in these cells, an alteration which was partly corrected by testosterone-treatment. Taken together, these results suggest that androgenic status affects adipogenesis from deep intraabdominal preadipocytes through alterations of some components of the MAP kinase cascade/Fos signaling pathways.
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Affiliation(s)
- D Lacasa
- Service de Biochimie, INSERM CJF 94-02, Faculté de Medecine Paris-Ouest, Université René Descartes (Paris V) and Centre Hospitalier de Poissy, France
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24
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Xing H, Northrop JP, Grove JR, Kilpatrick KE, Su JL, Ringold GM. TNF alpha-mediated inhibition and reversal of adipocyte differentiation is accompanied by suppressed expression of PPARgamma without effects on Pref-1 expression. Endocrinology 1997; 138:2776-83. [PMID: 9202217 DOI: 10.1210/endo.138.7.5242] [Citation(s) in RCA: 113] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Tumor necrosis factor alpha (TNF alpha) is a polypeptide hormone with pleiotropic effects on cellular proliferation and differentiation. To investigate how TNF alpha inhibits and reverses adipocyte differentiation, we studied the expression of two factors involved in the adipocyte differentiation process. Peroxisome proliferator-activated receptor gamma (PPARgamma) is a positive regulator of adipogenesis, whereas preadipocyte factor 1 (Pref-1) inhibits adipocyte differentiation. The expression patterns of both PPARgamma and Pref-1 change during early stages of adipocyte differentiation. Decreased expression of Pref-1 and increased expression of PPARgamma occur 1 day and 2 days, respectively, after 3T3-L1 cells reach confluence. During TNF alpha-mediated inhibition of adipocyte differentiation, PPARgamma messenger RNA (mRNA) expression stays at low levels. In contrast, TNF alpha treatment has no effect on the normal decrease in Pref-1 gene expression that occurs during adipogenesis. We observed that certain cytokine and growth factors [such as TNF alpha, basic fibroblast growth factor, transforming growth factor beta, and protein kinase C-activating agents plus calcium ionophore], when added to differentiated adipocytes, cause rapid down-regulation of PPARgamma mRNA expression with concomitant decrease in adipocyte-specific gene expression but fail to increase Pref-1 mRNA expression. Moreover, addition of TNF alpha to fully differentiated adipocytes results in the rapid disappearance of PPARgamma protein expression and the rapid loss of PPARgamma DNA-binding activity. Therefore, Pref-1 seems to function as a nonreversible molecular checkpoint whose expression is insensitive to TNF alpha-generated signals, whereas PPARgamma expression remains sensitive to TNF alpha at all stages of the adipogenesis program. Our results support the notion that dedifferentiated adipocytes and preadipocytes are not identical, though they share many similar morphological and gene expression patterns.
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Affiliation(s)
- H Xing
- Affymax Research Institute, Santa Clara, California 95051, USA.
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25
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Köster R, Blatt LM, Streubert M, Zietz C, Hermeking H, Brysch W, Stürzl M. Consensus-interferon and platelet-derived growth factor adversely regulate proliferation and migration of Kaposi's sarcoma cells by control of c-myc expression. THE AMERICAN JOURNAL OF PATHOLOGY 1996; 149:1871-85. [PMID: 8952524 PMCID: PMC1865356] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Platelet-derived growth factor-B (PDGF-B) is a potent paracrine-acting mitogen in Kaposi's sarcoma (KS) lesions. Interferon-alpha is widely used for clinical treatment of KS. Here we show that platelet-derived growth factor-B activates proliferation and migration of cultivated AIDS-KS spindle cells whereas interferon-alpha acts as an inhibitor. At the molecular level, these opposite activities of platelet-derived growth factor-B and interferon-alpha converged onto the adverse regulation of the c-myc gene expression. Platelet-derived growth factor-B induced c-myc mRNA and protein synthesis in cultivated AIDS-KS spindle cells whereas interferon-alpha inhibited these processes. Using c-myc-specific phoshothioate antisense oligodeoxynucleotides, we demonstrated that down-regulation of c-myc expression is sufficient to inhibit proliferation and migration of KS spindle cells in vitro. This indicated that c-Myc protein may be an important regulatory molecule of KS spindle cell proliferation and migration. High amounts of the c-Myc protein were detected in the nuclei of KS spindle cells in histological sections of AIDS-KS biopsies. This suggested that the c-myc gene may also regulate proliferation and migration of AIDS-KS spindle cells in vivo. In this case, c-myc may play an important role in the focus of major pathogenic and therapeutic pathways of KS.
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Affiliation(s)
- R Köster
- Abteilung Virusforschung, Max-Planck-Institut für Biochemie, Martinsried, Germany
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26
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Lacasa D, Agli B, Moynard D, Giudicelli Y. Evidence for a regional-specific control of rat preadipocyte proliferation and differentiation by the androgenic status. Endocrine 1995; 3:789-93. [PMID: 21153122 DOI: 10.1007/bf02935682] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/06/1995] [Accepted: 08/15/1995] [Indexed: 10/21/2022]
Abstract
In the rat, castration induces a decreased weight of fat depots. One possible explanation for these alterations could be that the capacities of preadipocytes to proliferate and differentiate are reduced by castration. Considering the regional specification of adipose tissue metabolism, these capacities and their eventual modulation by the androgenic status were presently compared in cultured preadipocytes from rat subcutaneous (SC) and epididymal fat depots.In epididymal preadipocytes, castration induced an increase in their proliferative capacity and conversely, a decrease in their adipogenesis.In vivo treatment by testosterone reversed the proliferative alteration but not the defective adipogenesis caused by castration.In vitro, no direct effect of testosterone on the proliferative capacities of epididymal preadipocytes could be observed suggesting that testosterone acts indirectly or needs the presence of other cofactors, such as insulin, dexamethasone and growth hormone. Surprisingly, testosterone partly counteracted the inhibitory effect of growth hormone on preadipocyte differentiation.In contrast to these observations, SC preadipocytes were completely insensitive to the androgenic status in terms of proliferation and differentiation.This study showing site-specific effects of castration on preadipocyte proliferation and differentiation suggests that part of the decreased fatness induced by castration in the rat is related to the modulatory effect of androgenic status on adipogenesis in some deep fat depots.
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Affiliation(s)
- D Lacasa
- Department of Biochemistry, Faculté de Médecine Paris-Ouest, Université René Descartes (Paris V), 78303, Poissy Cedex, France
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27
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Antonson P, Pray MG, Jacobsson A, Xanthopoulos KG. Myc inhibits CCAAT/enhancer-binding protein alpha-gene expression in HIB-1B hibernoma cells through interactions with the core promoter region. EUROPEAN JOURNAL OF BIOCHEMISTRY 1995; 232:397-403. [PMID: 7556187 DOI: 10.1111/j.1432-1033.1995.397zz.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The product of the c-myc proto-oncogene, Myc, has been implicated in the transcriptional regulation of several genes, acting either as an activator or repressor of gene expression. To determine whether Myc is involved in the modulation of the expression of the CCAAT/enhancer-binding protein alpha (C/EBP alpha) gene, we used both stable cell lines overexpressing Myc and transient co-transfection assays. We show that the endogenous C/EBP alpha protein level is repressed in stable cell lines overexpressing Myc. We also show that enforced expression of Myc in mouse hibernoma HIB-1B cells dramatically repressed the expression of C/EBP alpha--promoter-reporter fusion genes. This effect of Myc was mediated through the core promoter region. Mutation of the initiator site could not abolish this affect, indicating that Myc may interact with some component(s) of the basal transcription machinery.
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Affiliation(s)
- P Antonson
- Karolinska Institute, Center for Biotechnology, NOVUM, Huddinge, Sweden
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28
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Affiliation(s)
- C M Smas
- Department of Nutritional Sciences, University of California, Berkeley 94720, USA
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29
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Crescenzi M, Soddu S, Tatò F. Mitotic cycle reactivation in terminally differentiated cells by adenovirus infection. J Cell Physiol 1995; 162:26-35. [PMID: 7814449 DOI: 10.1002/jcp.1041620105] [Citation(s) in RCA: 56] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Different cell types (e.g., neurons, skeletal and heart myocytes, adipocytes, keratinocytes) undergo terminal differentiation, in which acquisition of specialized functions entails definitive withdrawal from the cell cycle. Such cells are distinct from quiescent (reversibly growth-arrested) cells, such as contact-inhibited fibroblasts. Terminally differentiated cells can not be induced to proliferate by means of growth factor stimulation or transduction of cellular oncogenes. An important first step toward defining the molecular basis for such unresponsiveness is to find a practical means to overcome the proliferative block. Furthermore, determining whether terminally differentiated, postmitotic cells still retain a potential competence for proliferation that can be reactivated would have important theoretical and practical implications. To address these questions, we exploited the properties of adenoviruses. These viruses can infect postmitotic cells and express E1A, a powerful activator of proliferation in reversibly growth-arrested cells. We infected terminally differentiated skeletal muscle cells and adipocytes with human adenovirus type 5 or 12, obtaining full reentry into the cell cycle, including DNA synthesis, mitosis, cytokinesis, and extended proliferation. Similar results were obtained with established cell lines and primary cells belonging to several species, from quail to humans. Genetic analysis indicated that the smaller splice product of E1A, E1A 12S, is sufficient to induce cell cycle reactivation in otherwise permanently nonmitotic cells. These results demonstrate that terminally differentiated cells retain proliferative potential and establish adenovirus as a convenient and powerful means to force such cells to reenter the cell cycle.
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Affiliation(s)
- M Crescenzi
- Department of Cellular and Developmental Biology, University of Rome La Sapieza, Italy
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30
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Vassaux G, Négrel R, Ailhaud G, Gaillard D. Proliferation and differentiation of rat adipose precursor cells in chemically defined medium: differential action of anti-adipogenic agents. J Cell Physiol 1994; 161:249-56. [PMID: 7962109 DOI: 10.1002/jcp.1041610209] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Primary rat adipose precursor cells, maintained in the minimal chemically defined medium (ITT medium) able to promote differentiation, have been used to investigate the ability of several agents to modulate their proliferation and their differentiation. Fetuin and fibroblast growth factor (FGF), which exhibited a strong and a weak mitogenic activity, respectively, do not significantly affect the proportion of differentiated cells as indicated by glycerol-3-phosphate dehydrogenase (GPDH) activity values. In contrast, carbaprostacyclin (cPGI2), a stable analogue of prostacyclin, behaves as a true adipogenic factor leading to a 4 to 5-fold increase in GPDH-specific activities with no significant effect on cell growth. Submaxillary gland kallikrein (SMGK), transforming growth factor-beta (TGF-beta) and tumor necrosis factor-alpha (TNF-alpha) behave as growth-promoting agents but at the same time elicit a dose-dependent inhibition of differentiation. Epidermal growth factor (EGF) and prostaglandin F2 alpha (PGF2 alpha) do not show any effect on cell proliferation at concentrations which exert a maximal inhibitory action on differentiation. Upon removal of EGF from the culture medium, complete resumption of differentiation occurs, whereas upon removal of PGF2 alpha or SMGK, complete resumption only takes place when differentiation is triggered by cPGI2. Upon removal of TNF-alpha, a partial resumption of differentiation is observed, whereas no subsequent differentiation is observed upon TGF-beta removal. These results emphasize the adipogenic, nonmitogenic role of cPGI2 and also allow the distinction between the various adipogenic/mitogenic factors which affect adipose cell differentiation.
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Affiliation(s)
- G Vassaux
- Centre de Biochimie (UMR 134 CNRS), Université de Nice-Sophia Antipolis, Faculté des Sciences, France
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