251
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Chavey C, Lazennec G, Lagarrigue S, Clapé C, Iankova I, Teyssier J, Annicotte JS, Schmidt J, Mataki C, Yamamoto H, Sanches R, Guma A, Stich V, Vitkova M, Jardin-Watelet B, Renard E, Strieter R, Tuthill A, Hotamisligil GS, Vidal-Puig A, Zorzano A, Langin D, Fajas L. CXC ligand 5 is an adipose-tissue derived factor that links obesity to insulin resistance. Cell Metab 2009; 9:339-49. [PMID: 19356715 PMCID: PMC2804846 DOI: 10.1016/j.cmet.2009.03.002] [Citation(s) in RCA: 136] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/18/2008] [Revised: 01/21/2009] [Accepted: 03/05/2009] [Indexed: 12/31/2022]
Abstract
We show here high levels of expression and secretion of the chemokine CXC ligand 5 (CXCL5) in the macrophage fraction of white adipose tissue (WAT). Moreover, we find that CXCL5 is dramatically increased in serum of human obese compared to lean subjects. Conversely, CXCL5 concentration is decreased in obese subjects after a weight reduction program, or in obese non-insulin-resistant, compared to insulin-resistant, subjects. Most importantly we demonstrate that treatment with recombinant CXCL5 blocks insulin-stimulated glucose uptake in muscle in mice. CXCL5 blocks insulin signaling by activating the Jak2/STAT5/SOCS2 pathway. Finally, by treating obese, insulin-resistant mice with either anti-CXCL5 neutralizing antibodies or antagonists of CXCR2, which is the CXCL5 receptor, we demonstrate that CXCL5 mediates insulin resistance. Furthermore CXCR2-/- mice are protected against obesity-induced insulin resistance. Taken together, these results show that secretion of CXCL5 by WAT resident macrophages represents a link between obesity, inflammation, and insulin resistance.
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Affiliation(s)
- Carine Chavey
- INSERM U834, U896, U834, CRLC Val d'Aurelle, Univ Montpellier 1, F-34295, France
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252
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Frühbeck G, Sesma P, Burrell MA. PRDM16: the interconvertible adipo-myocyte switch. Trends Cell Biol 2009; 19:141-6. [PMID: 19285866 DOI: 10.1016/j.tcb.2009.01.007] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2008] [Revised: 01/12/2009] [Accepted: 01/13/2009] [Indexed: 12/16/2022]
Abstract
Both brown and white adipocytes were previously considered to be derived from the same precursor cell, despite being histologically and functionally different. However, a recent study shows that overexpression of the transcriptional regulator positive regulatory domain containing 16 (PRDM16) determines the development of brown adipocytes from a progenitor that expresses myoblast markers. Surprisingly, loss of PRDM16 from these precursors does not lead to white adipocyte differentiation. Thus, PRDM16 controls a bidirectional cell fate switch between skeletal myoblasts and brown adipocytes.
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Affiliation(s)
- Gema Frühbeck
- Department of Endocrinology and Metabolic Research Laboratory, Clínica Universitaria, University of Navarra, Pamplona, Spain.
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253
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Cellular and molecular effects of n-3 polyunsaturated fatty acids on adipose tissue biology and metabolism. Clin Sci (Lond) 2009; 116:1-16. [PMID: 19037880 DOI: 10.1042/cs20070456] [Citation(s) in RCA: 205] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Adipose tissue and its secreted products, adipokines, have a major role in the development of obesity-associated metabolic derangements including Type 2 diabetes. Conversely, obesity and its metabolic sequelae may be counteracted by modulating metabolism and secretory functions of adipose tissue. LC-PUFAs (long-chain polyunsaturated fatty acids) of the n-3 series, namely DHA (docosahexaenoic acid; C(22:6n-3)) and EPA (eicosapentaenoic acid; C(20:5n-3)), exert numerous beneficial effects, such as improvements in lipid metabolism and prevention of obesity and diabetes, which partially result from the metabolic action of n-3 LC-PUFAs in adipose tissue. Recent studies highlight the importance of mitochondria in adipose tissue for the maintenance of systemic insulin sensitivity. For instance, both n-3 LC-PUFAs and the antidiabetic drugs TZDs (thiazolidinediones) induce mitochondrial biogenesis and beta-oxidation. The activation of this 'metabolic switch' in adipocytes leads to a decrease in adiposity. Both n-3 LC-PUFAs and TZDs ameliorate a low-grade inflammation of adipose tissue associated with obesity and induce changes in the pattern of secreted adipokines, resulting in improved systemic insulin sensitivity. In contrast with TZDs, which act as agonists of PPARgamma (peroxisome-proliferator-activated receptor-gamma) and promote differentiation of adipocytes and adipose tissue growth, n-3 LC-PUFAs affect fat cells by different mechanisms, including the transcription factors PPARalpha and PPARdelta. Some of the effects of n-3 LC-PUFAs on adipose tissue depend on their active metabolites, especially eicosanoids. Thus treatments affecting adipose tissue by multiple mechanisms, such as combining n-3 LC-PUFAs with either caloric restriction or antidiabetic/anti-obesity drugs, should be explored.
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254
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Sutherland LN, Bomhof MR, Capozzi LC, Basaraba SAU, Wright DC. Exercise and adrenaline increase PGC-1{alpha} mRNA expression in rat adipose tissue. J Physiol 2009; 587:1607-17. [PMID: 19221126 DOI: 10.1113/jphysiol.2008.165464] [Citation(s) in RCA: 159] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
The purpose of the present investigation was to explore the effects of exercise and adrenaline on the mRNA expression of PGC-1alpha, a master regulator of mitochondrial biogenesis, in rat abdominal adipose tissue. We hypothesized that (1) exercise training would increase PGC-1alpha mRNA expression in association with increases in mitochondrial marker enzymes, (2) adrenaline would increase PGC-1alpha mRNA expression and (3) the effect of exercise on PGC-1alpha mRNA expression in white adipose tissue would be attenuated by a beta-blocker. Two hours of daily swim training for 4 weeks led to increases in mitochondrial marker proteins and PGC-1alpha mRNA expression in epididymal and retroperitoneal fat depots. Additionally, a single 2 h bout of exercise led to increases in PGC-1alpha mRNA expression immediately following exercise cessation. Adrenaline treatment of adipose tissue organ cultures led to dose-dependent increases in PGC-1alpha mRNA expression. A supra-physiological concentration of adrenaline increased PGC-1alpha mRNA expression in epididymal but not retroperitoneal adipose tissue. beta-Blockade attenuated the effects of an acute bout of exercise on PGC-1alpha mRNA expression in epididymal but not retroperitoneal fat pads. In summary, this is the first investigation to demonstrate that exercise training, an acute bout of exercise and adrenaline all increase PGC-1alpha mRNA expression in rat white adipose tissue. Furthermore it would appear that increases in circulating catecholamine levels may be one potential mechanism mediating exercise induced increases in PGC-1alpha mRNA expression in rat abdominal adipose tissue.
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255
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Festuccia WT, Blanchard PG, Turcotte V, Laplante M, Sariahmetoglu M, Brindley DN, Richard D, Deshaies Y. The PPARgamma agonist rosiglitazone enhances rat brown adipose tissue lipogenesis from glucose without altering glucose uptake. Am J Physiol Regul Integr Comp Physiol 2009; 296:R1327-35. [PMID: 19211718 DOI: 10.1152/ajpregu.91012.2008] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
We investigated the mechanisms whereby peroxisome proliferator-activated receptor-gamma (PPARgamma) agonism affects glucose and lipid metabolism in brown adipose tissue (BAT) by studying the impact of PPARgamma activation on BAT glucose uptake and metabolism, lipogenesis, and mRNA levels plus activities of enzymes involved in triacylglycerol (TAG) synthesis. Interscapular BAT of rats treated or not with rosiglitazone (15 mg*kg(-1).day(-1), 7 days) was evaluated in vivo for glucose uptake and lipogenesis and in vitro for glucose metabolism, gene expression, and activities of glycerolphosphate acyltransferase (GPAT), phosphatidate phosphatase-1 (PAP or lipin-1), and diacylglycerol acyltransferase (DGAT). Rosiglitazone increased BAT mass without affecting whole tissue glucose uptake. BAT glycogen content (-80%), its synthesis from glucose (-50%), and mRNA levels of UDP-glucose pyrophosphorylase (-40%), which generates UDP-linked glucose for glycogen synthesis, were all reduced by rosiglitazone. In contrast, BAT TAG-glycerol synthesis in vivo and glucose incorporation into TAG-glycerol in vitro were stimulated by the agonist along with the activities and mRNA levels of glycerol 3-phosphate-generating phosphoenolpyruvate carboxykinase and glycerokinase. Furthermore, rosiglitazone markedly increased the activities of GPAT and DGAT but not those of lipin-1-mediated PAP-1, enzymes involved in the sequential acylation of glycerol 3-phosphate and TAG synthesis. Because an adequate supply of fatty acids is essential for BAT nonshivering thermogenesis, the enhanced ability of BAT to synthesize TAG under PPARgamma activation may constitute an important mechanism by which lipid substrates are stored in preparation for an eventual thermogenic activation.
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Affiliation(s)
- William T Festuccia
- Laval Hospital Research Centre and Department of Anatomy and Physiology, Faculty of Medicine, Laval University, Quebec, QC, Canada G1V 4G5
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256
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Gong Z, Huang C, Sheng X, Zhang Y, Li Q, Wang MW, Peng L, Zang YQ. The role of tanshinone IIA in the treatment of obesity through peroxisome proliferator-activated receptor gamma antagonism. Endocrinology 2009; 150:104-13. [PMID: 18818299 DOI: 10.1210/en.2008-0322] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Peroxisome proliferator-activated receptor (PPAR) gamma is a nuclear receptor that coordinates carbohydrate and lipid metabolism, and is a therapeutic target for type 2 diabetes. Tanshinone IIA (Tan) is a lipophilic diterpene that is widely used to treat cardiovascular diseases in traditional Chinese medicine, and has recently been found to reduce body weight and lower blood lipids. However, its underlying mechanism of antiadipogenic effects remains unknown. Here, we report that Tan inhibits 3T3-L1 preadipocyte differentiation and transcriptional activities of full-length PPARgamma and PPARgamma ligand-binding domains. The effects of Tan are mediated through its property as a natural antagonist of PPARgamma (dissociation constant of an inhibitor value, 2.562 +/- 0.711 microm). Tan treatment reduced adipose mass and body weight, improved glucose tolerance, and lowered the low-density lipoprotein to high-density lipoprotein ratio without changing the food intake in a high-fat diet-induced obese animal model. Our results suggest that the combined properties of Tan in adipogenesis, glucose tolerance, lipogenesis, and cardiovascular protection are beneficial for treating diabetic patients with complex metabolic conditions, in which modulating a single target is often not sufficient to achieve the desired effect.
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Affiliation(s)
- Zhenwei Gong
- Key Laboratory of Nutrition and Metabolism, Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Graduate School of Chinese Academy of Sciences, Chinese Academy of Sciences, Shanghai, China
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257
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Laurencikiene J, Stenson BM, Arvidsson Nordström E, Agustsson T, Langin D, Isaksson B, Permert J, Rydén M, Arner P. Evidence for an Important Role of CIDEA in Human Cancer Cachexia. Cancer Res 2008; 68:9247-54. [DOI: 10.1158/0008-5472.can-08-1343] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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258
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Shen JJ, Huang L, Li L, Jorgez C, Matzuk MM, Brown CW. Deficiency of growth differentiation factor 3 protects against diet-induced obesity by selectively acting on white adipose. Mol Endocrinol 2008; 23:113-23. [PMID: 19008465 DOI: 10.1210/me.2007-0322] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Growth differentiation factor 3 (GDF3) is a member of the TGFbeta superfamily. White adipose is one of the tissues in which Gdf3 is expressed, and it is the only tissue in which expression increases in response to high-fat diet. We generated Gdf3-/- mice, which were indistinguishable from wild-type mice and had normal weight curves on regular diet. However, on high-fat diet Gdf3-/- mice were resistant to the obesity that normally develops in wild-type mice. Herein we investigate the physiological and molecular mechanisms that underlie this protection from diet-induced obesity and demonstrate that GDF3 deficiency selectively affects white adipose through its influence on basal metabolic rates. Our results are consistent with a role for GDF3 in adipose tissue, with consequential effects on energy expenditure that ultimately impact adiposity.
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Affiliation(s)
- Joseph J Shen
- Children's Hospital of Central California, Madera, CA 93636, USA
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259
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Sutherland LN, Capozzi LC, Turchinsky NJ, Bell RC, Wright DC. Time course of high-fat diet-induced reductions in adipose tissue mitochondrial proteins: potential mechanisms and the relationship to glucose intolerance. Am J Physiol Endocrinol Metab 2008; 295:E1076-83. [PMID: 18780775 DOI: 10.1152/ajpendo.90408.2008] [Citation(s) in RCA: 102] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Increasing evidence suggests that reduced adipose tissue mitochondrial content is associated with the pathogenesis of type 2 diabetes. These investigations have utilized severely insulin-resistant rodent models. Thus, it is difficult to ascertain the potential mechanisms that initiate these changes and whether reductions in adipose mitochondria are an initiating event in the development of impaired glucose homeostasis. Thus, we sought to determine the time course of high-fat diet-induced reductions of mitochondrial content in epididymal adipose tissue in relation to changes in purported mediators of mitochondrial biogenesis and the development of impaired glucose homeostasis. Male Wistar rats were fed a high-fat diet ( approximately 59% of kcals from fat) for 2, 4, or 6 wk. Six weeks of high-fat feeding resulted in reductions in CORE I, COX IV, cytochrome c, HSP60, relative mtDNA copy number, and PGC-1alpha expression. These changes were not associated with decreases in eNOS and AMPK or increases in markers of oxidative stress. Interestingly, ex vivo treatment of adipose tissue cultures with palmitate led to decreases in PGC-1alpha expression and COX IV and CORE I protein content as observed in vivo. Thus, the high-fat diet-induced reductions in adipose tissue mitochondrial proteins may be mediated by increases in plasma fatty acids. Importantly, reductions in adipose tissue mitochondrial content occurred after the development of impaired glucose homeostasis. Thus, reductions in adipose tissue mitochondrial proteins are most likely not a causal event in the development of impaired glucose homeostasis.
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260
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Up-regulation of mitochondrial activity and acquirement of brown adipose tissue-like property in the white adipose tissue of fsp27 deficient mice. PLoS One 2008; 3:e2890. [PMID: 18682832 PMCID: PMC2483355 DOI: 10.1371/journal.pone.0002890] [Citation(s) in RCA: 197] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2008] [Accepted: 07/08/2008] [Indexed: 12/12/2022] Open
Abstract
Fsp27, a member of the Cide family proteins, was shown to localize to lipid droplet and promote lipid storage in adipocytes. We aimed to understand the biological role of Fsp27 in regulating adipose tissue differentiation, insulin sensitivity and energy balance. Fsp27−/− mice and Fsp27/lep double deficient mice were generated and we examined the adiposity, whole body metabolism, BAT and WAT morphology, insulin sensitivity, mitochondrial activity, and gene expression changes in these mouse strains. Furthermore, we isolated mouse embryonic fibroblasts (MEFs) from wildtype and Fsp27−/− mice, followed by their differentiation into adipocytes in vitro. We found that Fsp27 is expressed in both brown adipose tissue (BAT) and white adipose tissue (WAT) and its levels were significantly elevated in the WAT and liver of leptin-deficient ob/ob mice. Fsp27−/− mice had increased energy expenditure, lower levels of plasma triglycerides and free fatty acids. Furthermore, Fsp27−/−and Fsp27/lep double-deficient mice are resistant to diet-induced obesity and display increased insulin sensitivity. Moreover, white adipocytes in Fsp27−/− mice have reduced triglycerides accumulation and smaller lipid droplets, while levels of mitochondrial proteins, mitochondrial size and activity are dramatically increased. We further demonstrated that BAT-specific genes and key metabolic controlling factors such as FoxC2, PPAR and PGC1α were all markedly upregulated. In contrast, factors inhibiting BAT differentiation such as Rb, p107 and RIP140 were down-regulated in the WAT of Fsp27−/− mice. Remarkably, Fsp27−/− MEFs differentiated in vitro show many brown adipocyte characteristics in the presence of the thyroid hormone triiodothyronine (T3). Our data thus suggest that Fsp27 acts as a novel regulator in vivo to control WAT identity, mitochondrial activity and insulin sensitivity.
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261
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Cowell RM, Blake KR, Inoue T, Russell JW. Regulation of PGC-1alpha and PGC-1alpha-responsive genes with forskolin-induced Schwann cell differentiation. Neurosci Lett 2008; 439:269-74. [PMID: 18538475 PMCID: PMC2587443 DOI: 10.1016/j.neulet.2008.04.104] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2008] [Revised: 04/23/2008] [Accepted: 04/30/2008] [Indexed: 02/07/2023]
Abstract
Recent evidence indicates that mitochondrial homeostasis is critical for myelination and maintenance of peripheral nerve function. Mice lacking the metabolic transcriptional coactivator peroxisome proliferator activated receptor gamma coactivator 1alpha (PGC-1alpha) show reductions in expression of myelin-related proteins and exhibit myelin-associated lesions, so we identified PGC-1alpha target genes in Schwann cells (SCs) in vitro to determine potential roles for PGC-1alpha in glia and tested whether PGC-1alpha was sufficient for SC differentiation and myelination. Forskolin-induced differentiation was associated with an upregulation of PGC-1alpha mRNA and protein, and while overexpression of PGC-1alpha upregulated genes such as manganese superoxide dismutase and estrogen-related receptor alpha, it was not sufficient for induction of differentiation. Both PGC-1alpha overexpression and forskolin exposure caused an increase in the mitochondrial fusion-related protein mitofusin 1. These studies suggest that PGC-1alpha might be a potential target to promote mitochondrial stability during differentiation and myelination.
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Affiliation(s)
- Rita M. Cowell
- Department of Psychiatry, University of Alabama, Birmingham, Alabama 35294, USA
- Department of Neurology, University of Michigan, Ann Arbor, Michigan 48109, USA
| | - Kathryn R. Blake
- Department of Neurology, University of Michigan, Ann Arbor, Michigan 48109, USA
| | - Tatsuya Inoue
- Department of Neurology, University of Maryland and Baltimore VA, Baltimore, MD 21201
| | - James W. Russell
- Department of Neurology, University of Maryland and Baltimore VA, Baltimore, MD 21201
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262
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Kajimura S, Seale P, Tomaru T, Erdjument-Bromage H, Cooper MP, Ruas JL, Chin S, Tempst P, Lazar MA, Spiegelman BM. Regulation of the brown and white fat gene programs through a PRDM16/CtBP transcriptional complex. Genes Dev 2008; 22:1397-409. [PMID: 18483224 DOI: 10.1101/gad.1666108] [Citation(s) in RCA: 343] [Impact Index Per Article: 21.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Brown fat is a specialized tissue that can dissipate energy and counteract obesity through a pattern of gene expression that greatly increases mitochondrial content and uncoupled respiration. PRDM16 is a zinc-finger protein that controls brown fat determination by stimulating brown fat-selective gene expression, while suppressing the expression of genes selective for white fat cells. To determine the mechanisms regulating this switching of gene programs, we purified native PRDM16 protein complexes from fat cells. We show here that the PRDM16 transcriptional holocompex contains C-terminal-binding protein-1 (CtBP-1) and CtBP-2, and this direct interaction selectively mediates the repression of white fat genes. This repression occurs through recruiting a PRDM16/CtBP complex onto the promoters of white fat-specific genes such as resistin, and is abolished in the genetic absence of CtBP-1 and CtBP-2. In turn, recruitment of PPAR-gamma-coactivator-1alpha (PGC-1alpha) and PGC-1beta to the PRDM16 complex displaces CtBP, allowing this complex to powerfully activate brown fat genes, such as PGC-1alpha itself. These data show that the regulated docking of the CtBP proteins on PRDM16 controls the brown and white fat-selective gene programs.
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Affiliation(s)
- Shingo Kajimura
- Dana-Farber Cancer Institute and the Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115, USA
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263
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Hemmeryckx B, van Bree R, Van Hoef B, Vercruysse L, Lijnen HR, Verhaeghe J. Adverse adipose phenotype and hyperinsulinemia in gravid mice deficient in placental growth factor. Endocrinology 2008; 149:2176-83. [PMID: 18258676 DOI: 10.1210/en.2007-1272] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Pregnancy-induced metabolic changes are regulated by signals from an expanded adipose organ. Placental growth factor (PlGF), acting through vascular endothelial growth factor receptor-1, may be among those signals. There is a steep rise in circulating PlGF during normal pregnancy, which is repressed in gravidas who develop preeclampsia. PlGF-deficiency in mice impairs adipose vascularization and development. Here we studied young-adult PlGF-deficient (PlGF(-/-)) and wild-type mice on a high-fat diet in the nongravid state and at embryonic day (E) 13.5 or E18.5 of gestation. Litter size and weight were normal, but E18.5 placentas were smaller in PlGF(-/-) pregnancies. PlGF(-/-) mice showed altered intraadipose dynamics, with the following: 1) less blood vessels and fewer brown, uncoupling protein (UCP)-1-positive, adipocytes in white sc and perigonadal fat compartments and 2) white adipocyte hypertrophy. The mRNA expression of beta(3)-adrenergic receptors, peroxisome proliferator-activated receptor-gamma coactivator-1alpha, and UCP-1 was decreased accordingly. Moreover, PlGF(-/-) mice showed hyperinsulinemia. Pregnancy-associated changes were largely comparable in PlGF(-/-) and wild-type dams. They included expanded sc fat compartments and adipocyte hypertrophy, whereas adipose expression of key angiogenesis/adipogenesis (vascular endothelial growth factor receptor-1, peroxisome proliferator-activated receptor-gamma(2)) and thermogenesis (beta(3)-adrenergic receptors, peroxisome proliferator-activated receptor-gamma coactivator-1alpha, and UCP-1) genes was down-regulated; circulating insulin levels gradually increased during pregnancy. In conclusion, reduced adipose vascularization in PlGF(-/-) mice impairs adaptive thermogenesis in favor of energy storage, thereby promoting insulin resistance and hyperinsulinemia. Pregnancy adds to these changes by PlGF-independent mechanisms. Disturbed intraadipose dynamics is a novel mechanism to explain metabolic changes in late pregnancy in general and preeclamptic pregnancy in particular.
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Affiliation(s)
- Bianca Hemmeryckx
- Department of Obstetrics and Gynecology, Health Canpus Gasthuisberg, Katholieke Universiteit Leuven, 3000 Leuven, Belgium
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264
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Crowe S, Turpin SM, Ke F, Kemp BE, Watt MJ. Metabolic remodeling in adipocytes promotes ciliary neurotrophic factor-mediated fat loss in obesity. Endocrinology 2008; 149:2546-56. [PMID: 18276754 DOI: 10.1210/en.2007-1447] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Obesity is characterized by an expanded adipose tissue mass, and reversing obesity reduces the risk of insulin resistance and cardiovascular disease. Ciliary neurotrophic factor (CNTF) reverses obesity by promoting the preferential loss of white adipose tissue. We evaluated the cellular and molecular mechanisms by which CNTF regulates adiposity. Obese mice fed a high-fat diet were treated with saline or recombinant CNTF for 10 d, and adipose tissue was removed for analysis. Another group fed a high-fat diet was pair fed to CNTF mice. In separate experiments, 3T3-L1 adipocytes were treated with CNTF to examine metabolic responses and signaling. CNTF reduced adipose mass that resulted from reductions in adipocyte area and triglyceride content. CNTF treatment did not affect lipolysis but resulted in decreases in fat esterification and lipogenesis and enhanced fatty acid oxidation. The enhanced fat oxidation was associated with the expression of peroxisome proliferator-activated receptor coactivator-1alpha (PGC1alpha) and nuclear respiratory factor 1 and increases in oxidative phosphorylation subunits and mitochondrial biogenesis as determined by electron microscopy. Studies in cultured adipocytes revealed that CNTF activates p38 MAPK and AMP-activated protein kinase. Inhibiting p38 activation prevented the CNTF-induced increase in PGC1alpha but not AMP-activated protein kinase activation. Diminished food intake with pair feeding induced similar decreases in fat mass, but this was related to increased expression of uncoupling protein 1. We conclude that CNTF reprograms adipose tissue to promote mitochondrial biogenesis, enhancing oxidative capacity and reducing lipogenic capacity, thereby resulting in triglyceride loss.
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Affiliation(s)
- Seamus Crowe
- St. Vincent's Institute of Medical Research and the Department of Medicine, The University of Melbourne, Fitzroy, Victoria 3065, Australia
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265
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The transcriptional co-activator PGC-1alpha up regulates apelin in human and mouse adipocytes. ACTA ACUST UNITED AC 2008; 150:33-7. [PMID: 18501443 DOI: 10.1016/j.regpep.2008.04.003] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2007] [Revised: 03/13/2008] [Accepted: 04/08/2008] [Indexed: 11/24/2022]
Abstract
By using pangenomic microarray, we identified apelin as a unique adipokine up regulated by the transcriptional co-activator peroxisome proliferator-activated receptor gamma (PPARgamma) co-activator 1alpha (PGC-1alpha) in human white adipocytes. We investigated its regulation in vitro and in vivo. Overexpression of PGC-1alpha by adenovirus in human adipocytes induces apelin expression and secretion. Pharmacological induction of cAMP, an upstream regulator of endogenous PGC-1alpha expression, up regulates apelin gene expression and also apelin secretion in human and mice adipocytes. Moreover, during cold exposure in mice, a physiological situation known to induce both cAMP and PGC-1alpha, apelin expression in adipocytes and plasma levels were increased. This is the first demonstration that PGC-1alpha is involved in the regulation of an adipokine gene expression and release.
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266
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Hammarstedt A, Pihlajamäki J, Graham TE, Kainulainen S, Kahn BB, Laakso M, Smith U. High circulating levels of RBP4 and mRNA levels of aP2, PGC-1alpha and UCP-2 predict improvement in insulin sensitivity following pioglitazone treatment of drug-naïve type 2 diabetic subjects. J Intern Med 2008; 263:440-9. [PMID: 18324929 PMCID: PMC2676866 DOI: 10.1111/j.1365-2796.2007.01914.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
CONTEXT High levels of circulating retinol-binding protein 4 (RBP4) and baseline expression of adipogenic genes correlate with subsequent improvement in insulin sensitivity following Thiazolidinedione (TZD) treatment. OBJECTIVE The aim was to identify baseline characteristics and early changes related to TZD treatment that could predict a good treatment response. DESIGN Subjects were examined with oral glucose tolerance test, intravenous glucose tolerance test, hyperinsulinaemic euglycaemic clamp, body composition and standard blood sampling at baseline and after 4 and 12 weeks treatment. Subcutaneous adipose tissue biopsies were taken from the abdominal region at baseline, after 3 days and 4 weeks treatment to examine the gene expression profile. SETTING Research laboratory in a University hospital. PARTICIPANTS Ten newly diagnosed and previously untreated type 2 diabetic subjects were treated with pioglitazone for 3 months. MAIN OUTCOME MEASURES Baseline characteristics and early changes related to TZD treatment that could predict the response after 3 months. RESULTS Pioglitazone improved insulin sensitivity after 4 weeks combined with lower glucose and insulin levels without any change in BMI. It was accompanied by lower circulating resistin and plasminogen activator inhibitor-1 levels rapidly increased levels of circulating total and high molecular weight adiponectin as well as adiponectin and adipocyte fatty acid-binding protein (aP2) mRNA expression in the adipose tissue. High levels of circulating RBP4 at baseline and adipose tissue expression of aP2, proliferator-activated receptor-gamma coactivator 1 alpha (PGC-1alpha) and uncoupling protein 2 (UCP-2) predicted a good treatment response measured as improvement in insulin-stimulated whole-body glucose uptake after 3 months. CONCLUSIONS Circulating levels of RBP4 as an index of insulin sensitivity and mRNA levels of adipogenic genes correlate with the subsequent improvement in insulin sensitivity following TZD treatment.
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Affiliation(s)
- A Hammarstedt
- The Lundberg Laboratory for Diabetes Research, Department of Molecular and Clinical Medicine/Diabetes, The Sahlgrenska Academy at Göteborg University, Göteborg, Sweden.
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267
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Frayn KN, Langin D, Karpe F. Fatty acid-induced mitochondrial uncoupling in adipocytes is not a promising target for treatment of insulin resistance unless adipocyte oxidative capacity is increased. Diabetologia 2008; 51:394-7. [PMID: 18097647 DOI: 10.1007/s00125-007-0901-z] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/24/2007] [Accepted: 10/25/2007] [Indexed: 11/30/2022]
Abstract
The release of fatty acids from white adipose tissue is regulated at several levels. We have examined the suggestion that fatty acid release might be diminished by upregulation of mitochondrial fatty acid oxidation in the adipocyte, through increasing mitochondrial uncoupling. The intrinsic oxidative capacity of white adipose tissue is low, and older studies suggest that there is little fatty acid oxidation in white adipocytes, human or rodent. We have examined data on fatty acid metabolism and O(2) consumption in human white adipose tissue in vivo, and conclude that increasing fatty acid oxidation within the oxidative capacity of the tissue would produce only small changes (a few percent) in fatty acid release. The major locus of control of fatty acid release beyond the stimulation of lipolysis is the pathway of fatty acid esterification, already probably targeted by the thiazolidinedione insulin-sensitising agents. An alternative approach would be to upregulate the mitochondrial capacity of the adipocyte. We review proof-of-concept studies in which the phenotype of the white adipocyte has been changed to resemble that of the brown adipocyte by expression of peroxisome proliferator-activated receptor coactivator-1alpha. This increases oxidative capacity and also leads to fatty acid retention through upregulation of glycerol-3-phosphate production, and hence increased fatty acid re-esterification. We conclude that prevention or treatment of insulin resistance through alteration of adipocyte fatty acid handling will require more than a simple alteration of the activity of mitochondrial beta-oxidation within normal limits.
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Affiliation(s)
- K N Frayn
- Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Churchill Hospital, Oxford OX3 7LJ, UK
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268
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Abstract
After a long history of relative neglect by the scientific community, white adipose tissue is finally emerging as a central component of body homeostasis. Indeed, the explosion of obesity statistics worldwide encouraged the study of adipose tissue and the complications of increased adiposity, such as insulin resistance, type 2 diabetes, and accelerated vascular disease. Far beyond merely furnishing free fatty acids from triglyceride depots, a growing list of fat tissue-derived mediators has increased the understanding of the regulatory role of adipose tissue in metabolic control. Recently, inflammation within the obese adipose tissue has surfaced as another important link of obesity to its undesirable metabolic consequences.
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Affiliation(s)
- Viviane Zorzanelli Rocha
- Division of Cardiovascular Medicine, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts 02115, USA.
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269
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Medina-Gomez G, Gray S, Vidal-Puig A. Adipogenesis and lipotoxicity: role of peroxisome proliferator-activated receptor gamma (PPARgamma) and PPARgammacoactivator-1 (PGC1). Public Health Nutr 2008; 10:1132-7. [PMID: 17903321 DOI: 10.1017/s1368980007000614] [Citation(s) in RCA: 132] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Obesity is characterised by an increase in the adipose deposits, resulting from an imbalance between food intake and energy expenditure. When expansion of the adipose tissue reaches its maximum limit, as in obesity, fat accumulates in non-adipose tissues such as liver, heart, muscle and pancreas, developing a toxic response known as lipotoxicity, a condition that promotes the development of insulin resistance and other metabolic complications. Thus, the lipotoxic state may contribute to the increased risk of insulin resistance, diabetes, fatty liver and cardiovascular complications associated with obesity. We are interested in studying adipose tissue, specifically how mechanisms of adipogenesis and remodelling of adipose tissue, in terms of size and function of the adipocytes, could be considered a strategy to increase the capacity for lipid storage and prevent lipotoxicity. The peroxisome proliferator-activated receptors (PPARs) are a family of transcription factors that regulate energy balance by promoting either energy deposition or energy dissipation. Under normal physiological conditions, PPARgamma is mainly expressed in adipose tissue and regulates diverse functions such as the development of fat cells and their capacity to store lipids. The generation of PPARgamma knockout mice, either tissue specific or isoform specific, has provided new models to study PPARgamma's role in adipose tissue differentiation and function and have highlighted the essential role of PPARgamma in adipogenesis and lipogenesis.A second strategy to prevent lipotoxicity is to increase the capacity of tissues to oxidise fatty acids. PPARgammacoactivator-1alpha is a coactivator of PPARgamma that induces the expression of genes that promote the differentiation of preadipocytes to brown adipocytes. Recently, it has been implicated in increasing the oxidation of fatty acids via increasing mitochondrial capacity and function, making this co-factor a key candidate for the treatment of lipotoxicity.
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Affiliation(s)
- Gema Medina-Gomez
- Department of Clinical Biochemistry and Medicine, University of Cambridge, Box 232, Addenbrooke's Hospital, Hills Road, Cambridge CB2 2QR, UK.
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270
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Bansode RR, Huang W, Roy SK, Mehta M, Mehta KD. Protein Kinase Cβ Deficiency Increases Fatty Acid Oxidation and Reduces Fat Storage. J Biol Chem 2008; 283:231-236. [DOI: 10.1074/jbc.m707268200] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
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271
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Senocak FS, Si Y, Moya C, Russell WK, Russell DH, Lee K, Jayaraman A. Effect of uncoupling protein-1 expression on 3T3-L1 adipocyte gene expression. FEBS Lett 2007; 581:5865-71. [PMID: 18061577 DOI: 10.1016/j.febslet.2007.11.064] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2007] [Revised: 11/01/2007] [Accepted: 11/21/2007] [Indexed: 12/24/2022]
Abstract
The mitochondrial respiratory uncoupling protein 1 (UCP1) partially uncouples substrate oxidation and oxidative phosphorylation to promote the dissipation of cellular biochemical energy as heat in brown adipose tissue. We have recently shown that expression of UCP1 in 3T3-L1 white adipocytes reduces the accumulation of triglycerides. Here, we investigated the molecular basis underlying UCP1 expression in 3T3-L1 adipocytes. Gene expression data showed that forced UCP1 expression down-regulated several energy metabolism pathways; but ATP levels were constant. A metabolic flux analysis model was used to reflect the gene expression changes onto metabolic processes and concordance was observed in the down-regulation of energy consuming pathways. Our data suggest that adipocytes respond to long-term mitochondrial uncoupling by minimizing ATP utilization.
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Affiliation(s)
- Fatih S Senocak
- Artie McFerrin Department of Chemical Engineering, Texas A&M University, College Station, TX 77843-3122, United States
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272
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Katic M, Kennedy AR, Leykin I, Norris A, McGettrick A, Gesta S, Russell SJ, Bluher M, Maratos-Flier E, Kahn CR. Mitochondrial gene expression and increased oxidative metabolism: role in increased lifespan of fat-specific insulin receptor knock-out mice. Aging Cell 2007; 6:827-39. [PMID: 18001293 DOI: 10.1111/j.1474-9726.2007.00346.x] [Citation(s) in RCA: 120] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Caloric restriction, leanness and decreased activity of insulin/insulin-like growth factor 1 (IGF-1) receptor signaling are associated with increased longevity in a wide range of organisms from Caenorhabditis elegans to humans. Fat-specific insulin receptor knock-out (FIRKO) mice represent an interesting dichotomy, with leanness and increased lifespan, despite normal or increased food intake. To determine the mechanisms by which a lack of insulin signaling in adipose tissue might exert this effect, we performed physiological and gene expression studies in FIRKO and control mice as they aged. At the whole body level, FIRKO mice demonstrated an increase in basal metabolic rate and respiratory exchange ratio. Analysis of gene expression in white adipose tissue (WAT) of FIRKO mice from 6 to 36 months of age revealed persistently high expression of the nuclear-encoded mitochondrial genes involved in glycolysis, tricarboxylic acid cycle, beta-oxidation and oxidative phosphorylation as compared to expression of the same genes in WAT from controls that showed a tendency to decline in expression with age. These changes in gene expression were correlated with increased cytochrome c and cytochrome c oxidase subunit IV at the protein level, increased citrate synthase activity, increased expression of peroxisome proliferator-activated receptor gamma coactivator 1alpha (PGC-1alpha) and PGC-1beta, and an increase in mitochondrial DNA in WAT of FIRKO mice. Together, these data suggest that maintenance of mitochondrial activity and metabolic rates in adipose tissue may be important contributors to the increased lifespan of the FIRKO mouse.
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Affiliation(s)
- Masa Katic
- Joslin Diabetes Center, One Joslin Place and Department of Medicine, Harvard Medical School, Boston, MA 02215, USA
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273
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Kaaman M, Sparks LM, van Harmelen V, Smith SR, Sjölin E, Dahlman I, Arner P. Strong association between mitochondrial DNA copy number and lipogenesis in human white adipose tissue. Diabetologia 2007; 50:2526-33. [PMID: 17879081 DOI: 10.1007/s00125-007-0818-6] [Citation(s) in RCA: 158] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/02/2007] [Accepted: 08/08/2007] [Indexed: 01/06/2023]
Abstract
AIMS/HYPOTHESIS Recent studies suggest a link between insulin resistance and mitochondrial function in white fat cells. The aim of this study was to evaluate adipocyte mitochondrial DNA (mtDNA) copy number in relation to adipocyte and clinical variables that are related to insulin sensitivity. METHODS We studied a group of 148 healthy volunteers with a large inter-individual variation in BMI. Relative amounts of mtDNA and nuclear DNA were determined by quantitative RT-PCR. The mtDNA:nuclear DNA ratio reflects the tissue concentration of mtDNA per cell. RESULTS The mtDNA copy number was enriched in adipocytes of adipose tissue and decreased slightly by ageing (p = 0.015) and increasing BMI (p = 0.004); however, it was not influenced by sex, energy-restricted diets or marked long-term weight reduction. Adipose mtDNA copy number was not independently related to resting energy expenditure, overall insulin sensitivity or adipocyte lipolysis. However, it showed a strong positive correlation with basal (p = 0.0012) and insulin-stimulated lipogenesis (p < 0.0001) in fat cells, independently of age and BMI, and a weak positive correlation with levels of mRNA from several genes involved in mitochondrial oxidative capacity (r = 0.2-0.3). CONCLUSIONS/INTERPRETATION The mtDNA copy number in human white fat cells is fairly stable within healthy individuals. It is not influenced by sex or weight loss and is not important for overall insulin sensitivity or energy expenditure at rest. However, it is strongly related to adipocyte lipogenesis and weakly to mitochondrial oxidative capacity, suggesting that adipocyte mitochondria are, above all, local regulators.
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Affiliation(s)
- M Kaaman
- Karolinska Institute at Department of Medicine, Huddinge, Karolinska University Hospital, M61, Stockholm, Sweden
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274
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Morganstein DL, Christian M, Turner JJO, Parker MG, White R. Conditionally immortalized white preadipocytes: a novel adipocyte model. J Lipid Res 2007; 49:679-85. [PMID: 18046046 DOI: 10.1194/jlr.d700029-jlr200] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
This study describes a novel approach to generate conditionally immortalized preadipocyte cell lines from white adipose tissue (IMWAT) that can be induced to differentiate into white adipocytes even after expansion in culture. Such adipocytes express markers of white fat such as peroxisome proliferator-activated receptor gamma and aP2 but not brown fat markers, have an intact insulin signaling pathway, and express proinflammatory cytokines. They can be readily transduced with adenoviral vectors, allowing them to be used to investigate the consequences of the depletion of specific adipocyte factors using short hairpin RNA. This approach has been used to study the effect of reduced expression of the nuclear receptor corepressor receptor interacting protein 140 (RIP140), a regulator of adipocyte function. The depletion of RIP140 results in changes in metabolic gene expression that resemble those in adipose tissue of the RIP140 null mouse. Thus, IMWAT cells provide a novel model for adipocytes that are derived from preadipocytes rather than fibroblasts and provide an alternative system to primary preadipocytes for the investigation of adipocyte function.
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Affiliation(s)
- D L Morganstein
- Institute of Reproductive and Developmental Biology, Imperial College London, London W12 0NN, United Kingdom
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275
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White R, Morganstein D, Christian M, Seth A, Herzog B, Parker MG. Role of RIP140 in metabolic tissues: Connections to disease. FEBS Lett 2007; 582:39-45. [DOI: 10.1016/j.febslet.2007.11.017] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2007] [Accepted: 11/06/2007] [Indexed: 01/06/2023]
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276
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Abstract
Understanding the molecular regulation of metabolism will lead to a better understanding of the pathogenesis and treatment of common metabolic conditions, including obesity and diabetes. Nuclear receptors are a family of transcription factors, many of which play major roles in regulating metabolic genes in key tissues. They function by recruiting coregulators to the promoters of metabolic genes that can either activate or repress transcription. This review examines the roles of these coregulators in the control of metabolism in adipose tissue and skeletal muscle, and discusses how they result in coordinated and regulated control of metabolic pathways. In particular, the ligand-dependent recruitment of both coactivators and corepressors has potential implications for the treatment of obesity and diabetes.
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Affiliation(s)
- Daniel L Morganstein
- a Imperial College, Molecular Endocrinology, Institute of Reproductive and Developmental Biology, Imperial College, London, UK.
| | - Malcolm G Parker
- b Imperial College, Molecular Endocrinology, Institute of Reproductive and Developmental Biology, Imperial College, London, UK.
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277
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Abstract
PURPOSE OF REVIEW Thermogenesis is activated at the expense of carbon molecules. Mitochondria play a dominant role in oxidation and parallel heat production since the recovery of oxidation energy is less than perfect. Recent data of mitochondriogenesis and mitochondrial thermogenesis may boost research into certain aspects of obesity. RECENT FINDINGS Recent studies have outlined the unexpected decreased thermogenesis that limits fat loss during prolonged food restriction. Activation of fat oxidation in skeletal muscle remains a strategy against fat accumulation, however. Certain adipose depots have the potential to promote thermogenesis, either using mitochondrial uncoupling protein or independently. Peroxisome proliferator-activated receptor gamma coactivators alpha and ss are important regulators of mitochondria thermogenesis. Brain mitochondria are involved in the control of refeeding after starvation. This dual action of mitochondria inform their role in thermogenesis and energy partitioning. The importance of thyroid hormones in mitochondria thermogenesis is also confirmed. SUMMARY The clinical and research implications of these findings are that the mechanisms inhibiting adaptive thermogenesis during diet restriction should be investigated. An important field of research is the contribution of transcriptional coactivators to adipocyte plasticity since adipocytes have an underestimated ability to oxidise fatty acids in addition to their role in triglyceride storage.
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Affiliation(s)
- Ségolène Gambert
- Biologie des transporteurs mitochondriaux et métabolisme, Université Paris Descartes, CNRS, Paris, France
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278
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Abstract
The development of obesity not only depends on the balance between food intake and caloric utilization but also on the balance between white adipose tissue, which is the primary site of energy storage, and brown adipose tissue, which is specialized for energy expenditure. In addition, some sites of white fat storage in the body are more closely linked than others to the metabolic complications of obesity, such as diabetes. In this Review, we consider how the developmental origins of fat contribute to its physiological, cellular, and molecular heterogeneity and explore how these factors may play a role in the growing epidemic of obesity.
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Affiliation(s)
- Stephane Gesta
- Joslin Diabetes Center, Harvard Medical School, Boston, MA 02215, USA
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279
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Mazzucotelli A, Viguerie N, Tiraby C, Annicotte JS, Mairal A, Klimcakova E, Lepin E, Delmar P, Dejean S, Tavernier G, Lefort C, Hidalgo J, Pineau T, Fajas L, Clément K, Langin D. The transcriptional coactivator peroxisome proliferator activated receptor (PPAR)gamma coactivator-1 alpha and the nuclear receptor PPAR alpha control the expression of glycerol kinase and metabolism genes independently of PPAR gamma activation in human white adipocytes. Diabetes 2007; 56:2467-75. [PMID: 17646210 DOI: 10.2337/db06-1465] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
OBJECTIVE The purpose of this work was to determine the pattern of genes regulated by peroxisome proliferator-activated receptor (PPAR) gamma coactivator 1 alpha (PGC-1 alpha) in human adipocytes and the involvement of PPARalpha and PPARgamma in PGC-1 alpha transcriptional action. RESEARCH DESIGN AND METHODS Primary cultures of human adipocytes were transduced with a PGC-1 alpha adenovirus and treated with PPARgamma and PPARalpha agonists. Variation in gene expression was assessed using pangenomic microarrays and quantitative RT-PCR. To investigate glycerol kinase (GyK), a target of PGC-1 alpha, we measured enzymatic activity and glycerol incorporation into triglycerides. In vivo studies were performed on wild-type and PPARalpha(-/-) mice. The GyK promoter was studied using chromatin immunoprecipitation and promoter reporter gene assays. RESULTS Among the large number of genes regulated by PGC-1 alpha independently of PPARgamma, new targets involved in metabolism included the gene encoding GyK. The induction of GyK by PGC-1 alpha was observed at the levels of mRNA, enzymatic activity, and glycerol incorporation into triglycerides. PPARalpha was also upregulated by PGC-1 alpha. Its activation led to an increase in GyK expression and activity. PPARalpha was shown to bind and activate the GyK promoter. Experiments in mice confirmed the role of PGC-1 alpha and PPARalpha in the regulation of GyK in vivo. CONCLUSIONS This work uncovers novel pathways regulated by PGC-1 alpha and reveals that PPARalpha controls gene expression in human white adipocytes. The induction of GyK by PGC-1 alpha and PPARalpha may promote a futile cycle of triglyceride hydrolysis and fatty acid reesterification.
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Affiliation(s)
- Anne Mazzucotelli
- Institut National de la Santé et de la Recherche Médicale (INSERM) U858, Obesity Research Laboratory, Toulouse, F-31432, France
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280
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Abstract
PPARγ is an important transcription factor in the process of adipocyte recruitment and differentiation. Its relevance in vivo has been clearly observed using genetically modified animal models with different degrees of PPARγ function impairment. These animals showed defects in white and brown adipose tissue development and plasticity. Also, the use of PPARγ synthetic activators provided pharmacological evidence for the role of PPARγ as a modulator of adipose tissue plasticity and function. Aside from its well-established role in white adipocyte differentiation, PPARγ also plays a role in brown adipocyte differentiation. Specifically, in brown adipocytes, PPARγ promotes the transcription of genes involved in thermogenesis, such as mitochondrial uncoupling protein (UCP) 1, resulting in enhanced noradrenaline-dependent thermogenesis. PPARγ may also promote the acquirement of a 'brown' phenotype by mature white adipocytes.
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Affiliation(s)
- Edoardo Dalla Nora
- a University of Ferrara, Department of Clinical and Experimental Medicine, Section of Internal Medicine, Gerontology and Geriatric, Via Savonarola 9, 44100, Ferrara, Italy.
| | - Sarah L Gray
- b University of British Columbia, Department of Cellular and Physiological Sciences, Vancouver, 2350 Health Sciences Mall, V6T 1Z3 Canada.
| | - Antonio Vidal-Puig
- c University of Cambridge, Department of Clinical Biochemistry, Addenbrooke's Hospital, Hills Rd., Cambridge, CB2 2QR, UK.
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281
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Seale P, Kajimura S, Yang W, Chin S, Rohas L, Uldry M, Tavernier G, Langin D, Spiegelman BM. Transcriptional control of brown fat determination by PRDM16. Cell Metab 2007; 6:38-54. [PMID: 17618855 PMCID: PMC2564846 DOI: 10.1016/j.cmet.2007.06.001] [Citation(s) in RCA: 886] [Impact Index Per Article: 52.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/06/2007] [Revised: 05/03/2007] [Accepted: 06/11/2007] [Indexed: 01/15/2023]
Abstract
Brown fat cells are specialized to dissipate energy and can counteract obesity; however, the transcriptional basis of their determination is largely unknown. We show here that the zinc-finger protein PRDM16 is highly enriched in brown fat cells compared to white fat cells. When expressed in white fat cell progenitors, PRDM16 activates a robust brown fat phenotype including induction of PGC-1alpha, UCP1, and type 2 deiodinase (Dio2) expression and a remarkable increase in uncoupled respiration. Transgenic expression of PRDM16 at physiological levels in white fat depots stimulates the formation of brown fat cells. Depletion of PRDM16 through shRNA expression in brown fat cells causes a near total loss of the brown characteristics. PRDM16 activates brown fat cell identity at least in part by simultaneously activating PGC-1alpha and PGC-1beta through direct protein binding. These data indicate that PRDM16 can control the determination of brown fat fate.
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MESH Headings
- 3T3-L1 Cells
- Adipocytes
- Adipocytes, Brown/metabolism
- Adipocytes, White/metabolism
- Adipose Tissue, Brown/metabolism
- Adipose Tissue, White/metabolism
- Animals
- Blotting, Western
- COS Cells
- Cell Differentiation
- Cell Respiration
- Cells, Cultured
- Chlorocebus aethiops
- DNA-Binding Proteins/physiology
- Electrophoretic Mobility Shift Assay
- Fibroblasts
- Gene Expression Regulation
- Genes, Reporter
- Iodide Peroxidase/genetics
- Iodide Peroxidase/metabolism
- Ion Channels/genetics
- Ion Channels/metabolism
- Male
- Mice
- Mice, Inbred C3H
- Mice, Inbred C57BL
- Mice, Knockout
- Mice, Transgenic
- Mitochondria
- Mitochondrial Proteins/genetics
- Mitochondrial Proteins/metabolism
- Oxygen Consumption
- Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha
- Phenotype
- Reverse Transcriptase Polymerase Chain Reaction
- Trans-Activators/genetics
- Trans-Activators/metabolism
- Transcription Factors/genetics
- Transcription Factors/physiology
- Transcription, Genetic
- Uncoupling Protein 1
- Iodothyronine Deiodinase Type II
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Affiliation(s)
- Patrick Seale
- Dana-Farber Cancer Institute and the Department of Cell Biology, Harvard Medical School 1 Jimmy Fund Way, Boston, MA 02115
| | - Shingo Kajimura
- Dana-Farber Cancer Institute and the Department of Cell Biology, Harvard Medical School 1 Jimmy Fund Way, Boston, MA 02115
| | - Wenli Yang
- Dana-Farber Cancer Institute and the Department of Cell Biology, Harvard Medical School 1 Jimmy Fund Way, Boston, MA 02115
| | - Sherry Chin
- Dana-Farber Cancer Institute and the Department of Cell Biology, Harvard Medical School 1 Jimmy Fund Way, Boston, MA 02115
| | - Lindsay Rohas
- Dana-Farber Cancer Institute and the Department of Cell Biology, Harvard Medical School 1 Jimmy Fund Way, Boston, MA 02115
| | - Marc Uldry
- Dana-Farber Cancer Institute and the Department of Cell Biology, Harvard Medical School 1 Jimmy Fund Way, Boston, MA 02115
| | - Geneviève Tavernier
- Inserm, U858, Rangueil Institute of Molecular Medicine, Obesity Research Laboratory, Toulouse, F-31432 France
- Paul Sabatier University, Louis Bugnard Institute, IFR31, Toulouse, F-31432 France
| | - Dominique Langin
- Inserm, U858, Rangueil Institute of Molecular Medicine, Obesity Research Laboratory, Toulouse, F-31432 France
- Paul Sabatier University, Louis Bugnard Institute, IFR31, Toulouse, F-31432 France
- CHU de Toulouse, Laboratory of Clinical Biochemistry, Biology Institute of Purpan, Toulouse, F-31059 France
| | - Bruce M. Spiegelman
- Dana-Farber Cancer Institute and the Department of Cell Biology, Harvard Medical School 1 Jimmy Fund Way, Boston, MA 02115
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282
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Debevec D, Christian M, Morganstein D, Seth A, Herzog B, Parker M, White R. Receptor interacting protein 140 regulates expression of uncoupling protein 1 in adipocytes through specific peroxisome proliferator activated receptor isoforms and estrogen-related receptor alpha. Mol Endocrinol 2007; 21:1581-92. [PMID: 17456798 PMCID: PMC2072047 DOI: 10.1210/me.2007-0103] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Expression of uncoupling protein 1 (Ucp1) mRNA is elevated in differentiated adipocytes derived from brown or white adipose tissue devoid of the nuclear receptor corepressor receptor interacting protein 140 (RIP140). Increased expression is mediated in part by the recruitment of peroxisome proliferator activated receptors alpha and gamma, together with estrogen-related receptor alpha, which functions through a novel binding site on the Ucp1 enhancer. This demonstrates that regulation of Ucp1 expression in the absence of RIP140 involves derepression of at least three different nuclear receptors. The ability to increase expression of Ucp1 by beta-adrenergic signaling is independent of RIP140, as shown by the action of the beta(3)-adrenergic agonist CL 316,243 to stimulate expression in both brown and white adipocytes in the presence and absence of the corepressor. Therefore, the expression of this metabolic uncoupling protein in adipose cells is regulated by inhibition as well as activation of distinct signaling pathways.
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MESH Headings
- Adaptor Proteins, Signal Transducing/deficiency
- Adaptor Proteins, Signal Transducing/genetics
- Adaptor Proteins, Signal Transducing/metabolism
- Adipocytes/metabolism
- Adipose Tissue, Brown/metabolism
- Animals
- Base Sequence
- Binding Sites/genetics
- Cells, Cultured
- DNA Primers/genetics
- Enhancer Elements, Genetic
- Gene Expression Regulation
- In Vitro Techniques
- Ion Channels/genetics
- Mice
- Mice, Knockout
- Mitochondrial Proteins/genetics
- Nuclear Proteins/deficiency
- Nuclear Proteins/genetics
- Nuclear Proteins/metabolism
- Nuclear Receptor Interacting Protein 1
- PPAR alpha/metabolism
- PPAR gamma/metabolism
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- Receptors, Adrenergic, beta-3/metabolism
- Receptors, Estrogen/metabolism
- Signal Transduction
- Transcriptional Activation
- Uncoupling Protein 1
- ERRalpha Estrogen-Related Receptor
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Affiliation(s)
- Darja Debevec
- Institute of Reproductive and Developmental Biology, Imperial College London, London W12 0NN, United Kingdom
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283
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284
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Vitkova M, Klimcakova E, Kovacikova M, Valle C, Moro C, Polak J, Hanacek J, Capel F, Viguerie N, Richterova B, Bajzova M, Hejnova J, Stich V, Langin D. Plasma levels and adipose tissue messenger ribonucleic acid expression of retinol-binding protein 4 are reduced during calorie restriction in obese subjects but are not related to diet-induced changes in insulin sensitivity. J Clin Endocrinol Metab 2007; 92:2330-5. [PMID: 17405846 DOI: 10.1210/jc.2006-2668] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
CONTEXT Retinol-binding protein 4 (RBP4) may play a role in the development of insulin resistance. OBJECTIVE We investigated whether RBP4 adipose tissue mRNA expression and plasma level are related to insulin sensitivity during a diet-induced weight loss. DESIGN, SETTING, PATIENTS, AND INTERVENTION Obese women followed a dietary intervention composed of a 4-wk very low-calorie diet (VLCD), a 2-month low-calorie diet, and 3-4 months of a weight maintenance (WM) phase. MAIN OUTCOME MEASURES Clinical investigation was performed before and at the end of each phase. Insulin sensitivity was assessed with the euglycemic hyperinsulinemic clamp. Adipose tissue mRNA and plasma levels of RBP4 were determined using reverse transcription-quantitative PCR and ELISA, respectively. RESULTS Weight and fat mass decreased during VLCD and were stabilized during WM. Glucose disposal rate increased during VLCD and remained elevated thereafter. Plasma levels of RBP4 decreased after VLCD and, although increasing at subsequent phases, remained lower than prediet values. Adipose tissue mRNA levels were diminished after VLCD, and increased during low-calorie diet and WM to reach basal values. Basal RBP4 levels or diet-induced variations of RBP4 were not different in lean women and two groups of obese women with high- and low-insulin sensitivity. CONCLUSIONS Severe calorie restriction promotes a reduction in adipose tissue and plasma levels of RBP4. The study does not bring evidence for a role for RBP4 in the regulation of diet-induced changes in insulin sensitivity.
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Affiliation(s)
- Michaela Vitkova
- Institut National de la Santé et de la Recherche Médicale Université Paul Sabatier U858, IFR31, BP 84225, 31432 Toulouse Cedex 4, France
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285
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Cowell RM, Blake KR, Russell JW. Localization of the transcriptional coactivator PGC-1alpha to GABAergic neurons during maturation of the rat brain. J Comp Neurol 2007; 502:1-18. [PMID: 17335037 DOI: 10.1002/cne.21211] [Citation(s) in RCA: 91] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The transcriptional coactivator peroxisome proliferator activated receptor gamma coactivator 1alpha (PGC-1alpha) can activate a number of transcription factors to regulate mitochondrial biogenesis and cell-specific responses to cold, fasting, and exercise. Recent studies indicate that PGC-1alpha knockout mice exhibit behavioral abnormalities and progressive vacuolization in various brain regions. To investigate the roles for PGC-1alpha in the nervous system, we evaluated the temporal and cell-specific expression of PGC-1alpha in the normal developing rat brain. Western blot of whole brain homogenates with a PGC-1alpha-specific antibody revealed that PGC-1alpha protein was most abundant in the embryonic and early postnatal forebrain and cerebellum. Using quantitative reverse-transcriptase polymerase chain reaction (RT-PCR), we determined that PGC-1alpha mRNA expression increased most markedly between postnatal days 3 (P3) and 14 in the cortex, striatum, and hippocampus. Immunohistochemical and immunofluorescence analyses of brain tissue indicated that while PGC-1alpha was found in most neuronal populations from embryonic day 15 to P3, it was specifically concentrated in GABAergic populations from P3 to adulthood. Interestingly, PGC-1alpha colocalized with the developmentally regulated chemoattractant reelin in the cortex and hippocampus, and the survival-promoting transcription factor myocyte enhancing factor 2 was highly concentrated in GABAergic populations in the striatum and cerebellum at times of PGC-1alpha expression. These results implicate PGC-1alpha as a regulator of metabolism and/or survival in GABAergic neurons during a phase of mitochondrial and synaptic changes in the developing brain and suggest that PGC-1alpha may be a good target for increasing metabolism in GABAergic populations in neurodevelopmental and neurodegenerative disorders.
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Affiliation(s)
- Rita Marie Cowell
- Department of Psychiatry, University of Alabama, Birmingham, Alabama 35294, USA
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286
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Nisoli E, Clementi E, Carruba MO, Moncada S. Defective mitochondrial biogenesis: a hallmark of the high cardiovascular risk in the metabolic syndrome? Circ Res 2007; 100:795-806. [PMID: 17395885 DOI: 10.1161/01.res.0000259591.97107.6c] [Citation(s) in RCA: 185] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The metabolic syndrome is a group of risk factors of metabolic origin that are accompanied by increased risk for type 2 diabetes mellitus and cardiovascular disease. These risk factors include atherogenic dyslipidemia, elevated blood pressure and plasma glucose, and a prothrombotic and proinflammatory state. The condition is progressive and is exacerbated by physical inactivity, advancing age, hormonal imbalance, and genetic predisposition. The metabolic syndrome is a particularly challenging clinical condition because its complex molecular basis is still largely undefined. Impaired cell metabolism has, however, been suggested as a relevant pathophysiological process underlying several clinical features of the syndrome. In particular, defective oxidative metabolism seems to be involved in visceral fat gain and in the development of insulin resistance in skeletal muscle. This suggests that mitochondrial function may be impaired in the metabolic syndrome and, thus, in the consequent cardiovascular disease. We have recently found that mitochondrial biogenesis and function are enhanced by nitric oxide in various cell types and tissues, including cardiac muscle. Increasing evidence suggests that this mediator acts as a metabolic sensor in cardiomyocytes. This implies that a defective production of nitric oxide might be linked to dysfunction of the cardiomyocyte metabolism. Here we summarize some recent findings and propose a hypothesis for the high cardiovascular risk linked to the metabolic syndrome.
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Affiliation(s)
- Enzo Nisoli
- Department of Pharmacology, Chemotherapy and Medical Toxicology, School of Medicine, Milan University, Milan, Italy.
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287
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Timmons JA, Wennmalm K, Larsson O, Walden TB, Lassmann T, Petrovic N, Hamilton DL, Gimeno RE, Wahlestedt C, Baar K, Nedergaard J, Cannon B. Myogenic gene expression signature establishes that brown and white adipocytes originate from distinct cell lineages. Proc Natl Acad Sci U S A 2007; 104:4401-6. [PMID: 17360536 PMCID: PMC1810328 DOI: 10.1073/pnas.0610615104] [Citation(s) in RCA: 522] [Impact Index Per Article: 30.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Attainment of a brown adipocyte cell phenotype in white adipocytes, with their abundant mitochondria and increased energy expenditure potential, is a legitimate strategy for combating obesity. The unique transcriptional regulators of the primary brown adipocyte phenotype are unknown, limiting our ability to promote brown adipogenesis over white. In the present work, we used microarray analysis strategies to study primary preadipocytes, and we made the striking discovery that brown preadipocytes demonstrate a myogenic transcriptional signature, whereas both brown and white primary preadipocytes demonstrate signatures distinct from those found in immortalized adipogenic models. We found a plausible SIRT1-related transcriptional signature during brown adipocyte differentiation that may contribute to silencing the myogenic signature. In contrast to brown preadipocytes or skeletal muscle cells, white preadipocytes express Tcf21, a transcription factor that has been shown to suppress myogenesis and nuclear receptor activity. In addition, we identified a number of developmental genes that are differentially expressed between brown and white preadipocytes and that have recently been implicated in human obesity. The interlinkage between the myocyte and the brown preadipocyte confirms the distinct origin for brown versus white adipose tissue and also represents a plausible explanation as to why brown adipocytes ultimately specialize in lipid catabolism rather than storage, much like oxidative skeletal muscle tissue.
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Affiliation(s)
- James A. Timmons
- *Wenner–Gren Institute, Arrhenius Laboratories, Stockholm University, SE-106 91 Stockholm, Sweden
- School of Life Sciences, Heriot–Watt University, Edinburgh EH14 4AS, Scotland
- Center for Genomics and Bioinformatics, Berzelius Väg 35, Karolinska Institutet, SE-171 77 Stockholm, Sweden
- To whom correspondence may be addressed at:
School of Life Sciences, John Muir Building, Heriot–Watt University, Edinburgh EH14 4AS, Scotland. E-mail:
| | - Kristian Wennmalm
- Center for Genomics and Bioinformatics, Berzelius Väg 35, Karolinska Institutet, SE-171 77 Stockholm, Sweden
| | - Ola Larsson
- Center for Genomics and Bioinformatics, Berzelius Väg 35, Karolinska Institutet, SE-171 77 Stockholm, Sweden
| | - Tomas B. Walden
- *Wenner–Gren Institute, Arrhenius Laboratories, Stockholm University, SE-106 91 Stockholm, Sweden
- School of Life Sciences, Heriot–Watt University, Edinburgh EH14 4AS, Scotland
| | - Timo Lassmann
- Center for Genomics and Bioinformatics, Berzelius Väg 35, Karolinska Institutet, SE-171 77 Stockholm, Sweden
| | - Natasa Petrovic
- *Wenner–Gren Institute, Arrhenius Laboratories, Stockholm University, SE-106 91 Stockholm, Sweden
- Center for Genomics and Bioinformatics, Berzelius Väg 35, Karolinska Institutet, SE-171 77 Stockholm, Sweden
| | - D. Lee Hamilton
- Division of Molecular Physiology, University of Dundee, Dundee DD1 5EH, Scotland; and
| | - Ruth E. Gimeno
- Millennium Pharmaceuticals, Inc., 40 Landsdowne Street, Cambridge, MA 02139
| | - Claes Wahlestedt
- Center for Genomics and Bioinformatics, Berzelius Väg 35, Karolinska Institutet, SE-171 77 Stockholm, Sweden
| | - Keith Baar
- Division of Molecular Physiology, University of Dundee, Dundee DD1 5EH, Scotland; and
| | - Jan Nedergaard
- *Wenner–Gren Institute, Arrhenius Laboratories, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Barbara Cannon
- *Wenner–Gren Institute, Arrhenius Laboratories, Stockholm University, SE-106 91 Stockholm, Sweden
- School of Life Sciences, Heriot–Watt University, Edinburgh EH14 4AS, Scotland
- To whom correspondence may be addressed at:
Wenner–Gren Institute, Arrhenius Laboratories, Stockholm University, SE-106 91 Stockholm, Sweden. E-mail:
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288
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Bour S, Daviaud D, Gres S, Lefort C, Prévot D, Zorzano A, Wabitsch M, Saulnier-Blache JS, Valet P, Carpéné C. Adipogenesis-related increase of semicarbazide-sensitive amine oxidase and monoamine oxidase in human adipocytes. Biochimie 2007; 89:916-25. [PMID: 17400359 DOI: 10.1016/j.biochi.2007.02.013] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2006] [Accepted: 02/16/2007] [Indexed: 02/08/2023]
Abstract
A strong induction of semicarbazide-sensitive amine oxidase (SSAO) has previously been reported during murine preadipocyte lineage differentiation but it remains unknown whether this emergence also occurs during adipogenesis in man. Our aim was to compare SSAO and monoamine oxidase (MAO) expression during in vitro differentiation of human preadipocytes and in adipose and stroma-vascular fractions of human fat depots. A human preadipocyte cell strain from a patient with Simpson-Golabi-Behmel syndrome was first used to follow amine oxidase expression during in vitro differentiation. Then, human preadipocytes isolated from subcutaneous adipose tissues were cultured under conditions promoting ex vivo adipose differentiation and tested for MAO and SSAO expression. Lastly, human adipose tissue was separated into mature adipocyte and stroma-vascular fractions for analyses of MAO and SSAO at mRNA, protein and activity levels. Both SSAO and MAO were increased from undifferentiated preadipocytes to lipid-laden cells in all the models: 3T3-F442A and 3T3-L1 murine lineages, human SGBS cell strain or human preadipocytes in primary culture. In human subcutaneous adipose tissue, the adipocyte-enriched fraction exhibited seven-fold higher amine oxidase activity and contained three- to seven-fold higher levels of mRNAs encoded by MAO-A, MAO-B, AOC3 and AOC2 genes than the stroma-vascular fraction. MAO-A and AOC3 genes accounted for the majority of their respective MAO and SSAO activities in human adipose tissue. Most of the SSAO and MAO found in adipose tissue originated from mature adipocytes. Although the mechanism and role of adipogenesis-related increase in amine oxidase expression remain to be established, the resulting elevated levels of amine oxidase activities found in human adipocytes may be of potential interest for therapeutic intervention in obesity.
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Affiliation(s)
- Sandy Bour
- U858 INSERM, I2MR, IFR 31, CHU Rangueil, BP 84225, 31432 Toulouse Cedex 4, France
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289
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Lelliott CJ, Medina-Gomez G, Petrovic N, Kis A, Feldmann HM, Bjursell M, Parker N, Curtis K, Campbell M, Hu P, Zhang D, Litwin SE, Zaha VG, Fountain KT, Boudina S, Jimenez-Linan M, Blount M, Lopez M, Meirhaeghe A, Bohlooly-Y M, Storlien L, Strömstedt M, Snaith M, Orešič M, Abel ED, Cannon B, Vidal-Puig A. Ablation of PGC-1beta results in defective mitochondrial activity, thermogenesis, hepatic function, and cardiac performance. PLoS Biol 2007; 4:e369. [PMID: 17090215 PMCID: PMC1634886 DOI: 10.1371/journal.pbio.0040369] [Citation(s) in RCA: 225] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2006] [Accepted: 09/05/2006] [Indexed: 01/20/2023] Open
Abstract
The transcriptional coactivator peroxisome proliferator-activated receptor-gamma coactivator-1β (PGC-1β) has been implicated in important metabolic processes. A mouse lacking PGC-1β (PGC1βKO) was generated and phenotyped using physiological, molecular, and bioinformatic approaches. PGC1βKO mice are generally viable and metabolically healthy. Using systems biology, we identified a general defect in the expression of genes involved in mitochondrial function and, specifically, the electron transport chain. This defect correlated with reduced mitochondrial volume fraction in soleus muscle and heart, but not brown adipose tissue (BAT). Under ambient temperature conditions, PGC-1β ablation was partially compensated by up-regulation of PGC-1α in BAT and white adipose tissue (WAT) that lead to increased thermogenesis, reduced body weight, and reduced fat mass. Despite their decreased fat mass, PGC1βKO mice had hypertrophic adipocytes in WAT. The thermogenic role of PGC-1β was identified in thermoneutral and cold-adapted conditions by inadequate responses to norepinephrine injection. Furthermore, PGC1βKO hearts showed a blunted chronotropic response to dobutamine stimulation, and isolated soleus muscle fibres from PGC1βKO mice have impaired mitochondrial function. Lack of PGC-1β also impaired hepatic lipid metabolism in response to acute high fat dietary loads, resulting in hepatic steatosis and reduced lipoprotein-associated triglyceride and cholesterol content. Altogether, our data suggest that PGC-1β plays a general role in controlling basal mitochondrial function and also participates in tissue-specific adaptive responses during metabolic stress. The authors conduct an in-depth analysis of a PGC-1β knockout mouse; these animals posses specific defects in basal mitochondrial function and adaptation to metabolic stress.
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Affiliation(s)
- Christopher J Lelliott
- Department of Clinical Biochemistry, University of Cambridge, Cambridge, United Kingdom
- AstraZeneca R&D, Mölndal, Sweden
| | - Gema Medina-Gomez
- Department of Clinical Biochemistry, University of Cambridge, Cambridge, United Kingdom
| | - Natasa Petrovic
- The Wenner-Gren Institute, Stockholm University, Stockholm, Sweden
| | - Adrienn Kis
- Department of Clinical Biochemistry, University of Cambridge, Cambridge, United Kingdom
| | | | | | - Nadeene Parker
- Department of Clinical Biochemistry, University of Cambridge, Cambridge, United Kingdom
| | - Keira Curtis
- Department of Clinical Biochemistry, University of Cambridge, Cambridge, United Kingdom
| | - Mark Campbell
- Department of Clinical Biochemistry, University of Cambridge, Cambridge, United Kingdom
| | - Ping Hu
- Division of Cardiology, University of Utah, Salt Lake City, Utah, United States of America
| | - Dongfang Zhang
- Division of Cardiology, University of Utah, Salt Lake City, Utah, United States of America
| | - Sheldon E Litwin
- Division of Cardiology, University of Utah, Salt Lake City, Utah, United States of America
| | - Vlad G Zaha
- Division of Endocrinology, Metabolism, and Diabetes and Program in Human Molecular Biology and Genetics, University of Utah, Salt Lake City, Utah, United States of America
| | - Kimberly T Fountain
- Division of Endocrinology, Metabolism, and Diabetes and Program in Human Molecular Biology and Genetics, University of Utah, Salt Lake City, Utah, United States of America
| | - Sihem Boudina
- Division of Endocrinology, Metabolism, and Diabetes and Program in Human Molecular Biology and Genetics, University of Utah, Salt Lake City, Utah, United States of America
| | | | - Margaret Blount
- Department of Clinical Biochemistry, University of Cambridge, Cambridge, United Kingdom
| | - Miguel Lopez
- Department of Clinical Biochemistry, University of Cambridge, Cambridge, United Kingdom
| | | | | | | | | | | | - Matej Orešič
- VTT Technical Research Centre of Finland, Espoo, Finland
| | - E. Dale Abel
- Division of Endocrinology, Metabolism, and Diabetes and Program in Human Molecular Biology and Genetics, University of Utah, Salt Lake City, Utah, United States of America
| | - Barbara Cannon
- The Wenner-Gren Institute, Stockholm University, Stockholm, Sweden
| | - Antonio Vidal-Puig
- Department of Clinical Biochemistry, University of Cambridge, Cambridge, United Kingdom
- * To whom correspondence should be addressed. E-mail:
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290
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Fürnsinn C, Willson TM, Brunmair B. Peroxisome proliferator-activated receptor-delta, a regulator of oxidative capacity, fuel switching and cholesterol transport. Diabetologia 2007; 50:8-17. [PMID: 17119917 DOI: 10.1007/s00125-006-0492-0] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/06/2006] [Accepted: 08/16/2006] [Indexed: 12/14/2022]
Abstract
Synthetic agonists of peroxisome proliferator-activated receptor (PPAR)-delta have shown a promising pharmacological profile in preclinical models of metabolic and cardiovascular disease. At present, the pharmaceutical development of these drugs exploits the potential to raise plasma HDL-cholesterol in animals and their insulin-sensitising and glucose-lowering properties. PPAR-delta agonists have also proven to be powerful research tools that have provided insights into the role of fatty acid metabolism in human physiology and disease. Activation of PPAR-delta induces the expression of genes important for cellular fatty acid combustion and an associated increase in whole-body lipid dissipation. The predominant target tissue in this regard is skeletal muscle, in which PPAR-delta activation regulates the oxidative capacity of the mitochondrial apparatus, switches fuel preference from glucose to fatty acids, and reduces triacylglycerol storage. These changes counter the characteristic derangements of insulin- resistant skeletal muscle but resemble the metabolic adaptation to regular physical exercise. Apart from effects on fuel turnover, there is evidence for direct antiatherogenic properties, because PPAR-delta activation increases cholesterol export and represses inflammatory gene expression in macrophages and atherosclerotic lesions. Whereas conclusions about the full potential of PPAR-delta as a drug target await the result of large scale clinical testing, ongoing investigation of this nuclear receptor has greatly improved our knowledge of the physiological regulation of whole-body fuel turnover and the interdependence of mitochondrial function and insulin sensitivity.
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Affiliation(s)
- C Fürnsinn
- Department of Medicine III, Division of Endocrinology and Metabolism, Medical University of Vienna, Vienna, Austria.
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291
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Handschin C, Spiegelman BM. Peroxisome proliferator-activated receptor gamma coactivator 1 coactivators, energy homeostasis, and metabolism. Endocr Rev 2006; 27:728-35. [PMID: 17018837 DOI: 10.1210/er.2006-0037] [Citation(s) in RCA: 864] [Impact Index Per Article: 48.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Many biological programs are regulated at the transcriptional level. This is generally achieved by the concerted actions of several transcription factors. Recent findings have shown that, in many cases, transcriptional coactivators coordinate the overall regulation of the biological programs. One of the best-studied examples of coactivator control of metabolic pathways is the peroxisome proliferator-activated receptor coactivator 1 (PGC-1) family. These proteins are strong activators of mitochondrial function and are thus dominant regulators of oxidative metabolism in a variety of tissues. The PGC-1 coactivators themselves are subject to powerful regulation at the transcriptional and posttranslational levels. Recent studies have elucidated the function of the PGC-1 coactivators in different tissues and have highlighted the implications of PGC-1 dysregulation in diseases such as diabetes, obesity, cardiomyopathy, or neurodegeneration.
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Affiliation(s)
- Christophe Handschin
- Dana-Farber Cancer Institute and Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115, USA
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292
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The role of brown adipose tissue in human obesity. Nutr Metab Cardiovasc Dis 2006; 16:569-74. [PMID: 17113764 DOI: 10.1016/j.numecd.2006.07.009] [Citation(s) in RCA: 104] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/16/2006] [Accepted: 07/18/2006] [Indexed: 11/24/2022]
Abstract
It is widely accepted that newborn humans are provided with brown adipose tissue (BAT) and that adult humans lack, or have only a small amount, of it. Therefore the physiological role of BAT in humans is debated. It is quite clear that BAT in rodents has an important role in the prevention and therapy of obesity and diabetes and specific drugs can induce BAT development in adult animals. New concepts regarding the biology of adipose tissues in mammals have been developed during the last years leading to the hope for the development of BAT in human adults as a new challenge for the treatment of obesity and related diseases. These new concepts are basic to understanding the above-proposed therapeutic strategy and are the concept of the adipose organ and the concept of transdifferentiation. In this paper these new concepts will be explained together with a review of available scientific data on human BAT.
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293
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Mercader J, Ribot J, Murano I, Felipe F, Cinti S, Bonet ML, Palou A. Remodeling of white adipose tissue after retinoic acid administration in mice. Endocrinology 2006; 147:5325-32. [PMID: 16840543 DOI: 10.1210/en.2006-0760] [Citation(s) in RCA: 178] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
A reduced brown adipose phenotype in white adipose tissue (WAT) may contribute to obesity and type 2 diabetes in humans. Retinoic acid, the carboxylic form of vitamin A, triggers in rodents a reduction of body weight and adiposity and an increased expression of uncoupling proteins in brown adipose tissue and skeletal muscle. In this study, we investigated possible remodeling effects of all-trans retinoic acid (ATRA) in WAT depots. Changes in the expression of genes related to thermogenesis and fatty acid oxidation and levels of phosphorylated retinoblastoma protein were analyzed in WAT depots of adult NMRI male mice acutely injected with ATRA or vehicle, together with biometric and blood parameters. Body fat loss after ATRA treatment was unaccompanied by any increase in circulating nonesterified fatty acids or ketone bodies and accompanied by increased rectal temperature. The treatment triggered an up-regulation of the mRNA levels of uncoupling proteins 1 and 2, peroxisome proliferator-activated receptor gamma coactivator-1alpha, peroxisome proliferator-activated receptor alpha, muscle- and liver-type carnitine palmitoyltransferase 1, and subunit II of cytochrome oxidase in different WAT depots. Levels of phosphorylated retinoblastoma protein in WAT depots were increased after ATRA treatment. Adipocyte size was reduced, and the number of multilocular adipocytes was increased in inguinal WAT of ATRA-treated mice. The results indicate that ATRA favors the acquisition of brown adipose tissue-like properties in WAT. Understanding the mechanisms and effectors involved in the remodeling of WAT can contribute to new avenues of prevention and treatment of obesity and type 2 diabetes.
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Affiliation(s)
- Josep Mercader
- Laboratory of Molecular Biology, Nutrition and Biotechnology, University of the Balearic Islands, 07122 Palma de Mallorca, Spain
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294
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Bing C, Russell S, Becket E, Pope M, Tisdale MJ, Trayhurn P, Jenkins JR. Adipose atrophy in cancer cachexia: morphologic and molecular analysis of adipose tissue in tumour-bearing mice. Br J Cancer 2006; 95:1028-37. [PMID: 17047651 PMCID: PMC2360696 DOI: 10.1038/sj.bjc.6603360] [Citation(s) in RCA: 114] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Extensive loss of adipose tissue is a hallmark of cancer cachexia but the cellular and molecular basis remains unclear. This study has examined morphologic and molecular characteristics of white adipose tissue in mice bearing a cachexia-inducing tumour, MAC16. Adipose tissue from tumour-bearing mice contained shrunken adipocytes that were heterogeneous in size. Increased fibrosis was evident by strong collagen-fibril staining in the tissue matrix. Ultrastructure of 'slimmed' adipocytes revealed severe delipidation and modifications in cell membrane conformation. There were major reductions in mRNA levels of adipogenic transcription factors including CCAAT/enhancer binding protein alpha (C/EBPalpha), CCAAT/enhancer binding protein beta, peroxisome proliferator-activated receptor gamma, and sterol regulatory element binding protein-1c (SREBP-1c) in adipose tissue, which was accompanied by reduced protein content of C/EBPalpha and SREBP-1. mRNA levels of SREBP-1c targets, fatty acid synthase, acetyl CoA carboxylase, stearoyl CoA desaturase 1 and glycerol-3-phosphate acyl transferase, also fell as did glucose transporter-4 and leptin. In contrast, mRNA levels of peroxisome proliferators-activated receptor gamma coactivator-1alpha and uncoupling protein-2 were increased in white fat of tumour-bearing mice. These results suggest that the tumour-induced impairment in the formation and lipid storing capacity of adipose tissue occurs in mice with cancer cachexia.
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Affiliation(s)
- C Bing
- Obesity Biology Unit, Division of Metabolic & Cellular Medicine, School of Clinical Sciences, University of Liverpool, Liverpool L69 3GA, UK.
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295
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Laplante M, Festuccia WT, Soucy G, Gélinas Y, Lalonde J, Berger JP, Deshaies Y. Mechanisms of the depot specificity of peroxisome proliferator-activated receptor gamma action on adipose tissue metabolism. Diabetes 2006; 55:2771-8. [PMID: 17003342 DOI: 10.2337/db06-0551] [Citation(s) in RCA: 101] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
In this study, we aimed to establish the mechanisms whereby peroxisome proliferator-activated receptor gamma (PPARgamma) agonism brings about redistribution of fat toward subcutaneous depots and away from visceral fat. In rats treated with the full PPARgamma agonist COOH (30 mg x kg(-1) x day(-1)) for 3 weeks, subcutaneous fat mass was doubled and that of visceral fat was reduced by 30% relative to untreated rats. Uptake of triglyceride-derived nonesterified fatty acids was greatly increased in subcutaneous fat (14-fold) and less so in visceral fat (4-fold), with a concomitant increase, restricted to subcutaneous fat only, in mRNA levels of the uptake-, retention-, and esterification-promoting enzymes lipoprotein lipase, aP2, and diacylglycerol acyltransferase 1. Basal lipolysis and fatty acid recycling were stimulated by COOH in both subcutaneous fat and visceral fat, with no frank quantitative depot specificity. The agonist increased mRNA levels of enzymes of fatty acid oxidation and thermogenesis much more strongly in visceral fat than in subcutaneous fat, concomitantly with a stronger elevation in O2 consumption in the former than in the latter. Mitochondrial biogenesis was stimulated equally in both depots. These findings demonstrate that PPARgamma agonism redistributes fat by stimulating the lipid uptake and esterification potential in subcutaneous fat, which more than compensates for increased O2 consumption; conversely, lipid uptake is minimally altered and energy expenditure is greatly increased in visceral fat, with consequent reduction in fat accumulation.
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Affiliation(s)
- Mathieu Laplante
- Laval Hospital Research Centre, Laval University, Quebec, QC, Canada G1V 4G5
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296
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Hansen JB, Kristiansen K. Regulatory circuits controlling white versus brown adipocyte differentiation. Biochem J 2006; 398:153-68. [PMID: 16898874 PMCID: PMC1550312 DOI: 10.1042/bj20060402] [Citation(s) in RCA: 136] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Adipose tissue is a major endocrine organ that exerts a profound influence on whole-body homoeostasis. Two types of adipose tissue exist in mammals: WAT (white adipose tissue) and BAT (brown adipose tissue). WAT stores energy and is the largest energy reserve in mammals, whereas BAT, expressing UCP1 (uncoupling protein 1), can dissipate energy through adaptive thermogenesis. In rodents, ample evidence supports BAT as an organ counteracting obesity, whereas less is known about the presence and significance of BAT in humans. Despite the different functions of white and brown adipocytes, knowledge of factors differentially influencing the formation of white and brown fat cells is sparse. Here we summarize recent progress in the molecular understanding of white versus brown adipocyte differentiation, including novel insights into transcriptional and signal transduction pathways. Since expression of UCP1 is the hallmark of BAT and a key factor determining energy expenditure, we also review conditions associated with enhanced energy expenditure and UCP1 expression in WAT that may provide information on processes involved in brown adipocyte differentiation.
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Affiliation(s)
- Jacob B Hansen
- Department of Medical Biochemistry and Genetics, the Panum Institute, University of Copenhagen, DK-2200 Copenhagen N, Denmark.
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297
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Debard C, Cozzone D, Ricard N, Vouillarmet J, Disse E, Husson B, Laville M, Vidal H. Short-term activation of peroxysome proliferator-activated receptor beta/delta increases fatty acid oxidation but does not restore insulin action in muscle cells from type 2 diabetic patients. J Mol Med (Berl) 2006; 84:747-52. [PMID: 16897074 DOI: 10.1007/s00109-006-0077-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2005] [Accepted: 03/29/2006] [Indexed: 12/25/2022]
Abstract
Defective fatty acid oxidation in skeletal muscle is one of the possible causes of insulin resistance. Peroxisome proliferator-activated receptor beta activators are strong inducers of fatty acid oxidation. The aim of this study was to verify whether activation of fatty acid oxidation by PPARbeta agonists in human skeletal muscle cells prepared from type 2 diabetic patients could improve the reduced responses to insulin that characterized this cell model. GW0742 (10 nM) significantly increased fatty acid oxidation and oxidative gene expression in myotubes prepared from both healthy subjects and type 2 diabetic patients. In cells from control subjects, incubation with the agonist for 48 h affected neither insulin-induced rate of glycogen synthesis nor the phosphorylation state of protein kinase B (PKB serine 473). Myotubes from type 2 diabetic patients displayed marked reduction in the effects of insulin on glycogen synthesis and on PKB phosphorylation. However, treatment with PPARbeta agonists did not restore these defects. Therefore, these results indicate that induction of fatty acid oxidation with PPARbeta activators during short-term exposition is not sufficient to correct for insulin resistance in muscle cells from type 2 diabetic patients. This suggests that additional studies are needed to better characterize the link between fatty acid oxidation and insulin sensitivity in humans.
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Affiliation(s)
- Cyrille Debard
- INSERM U-449, INRA U-1235, R. Laennec Faculty of Medicine, Human Nutrition Research Center, Claude Bernard-Lyon 1 University, Rue G. Paradin, 69372, Lyon, Cedex 08, France
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298
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Soyal S, Krempler F, Oberkofler H, Patsch W. PGC-1alpha: a potent transcriptional cofactor involved in the pathogenesis of type 2 diabetes. Diabetologia 2006; 49:1477-88. [PMID: 16752166 DOI: 10.1007/s00125-006-0268-6] [Citation(s) in RCA: 97] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/25/2005] [Accepted: 02/03/2006] [Indexed: 12/24/2022]
Abstract
Data derived from several recent studies implicate peroxisome proliferator-activated receptor-gamma coactivator-1alpha (PGC-1alpha) in the pathogenesis of type 2 diabetes. Lacking DNA binding activity itself, PGC-1alpha is a potent, versatile regulator of gene expression that co-ordinates the activation and repression of transcription via protein-protein interactions with specific, as well as more general, factors contained within the basal transcriptional machinery. PGC-1alpha is suggested to play a pivotal role in the control of genetic pathways that result in homeostatic glucose utilisation in liver and muscle, beta cell insulin secretion and mitochondrial biogenesis. This review focuses on the role of PGC-1alpha in glucose metabolism and considers how PGC-1alpha links cellular glucose metabolism, insulin sensitivity and mitochondrial function, and why defects in PGC-1alpha expression and regulation may contribute to the pathophysiology of type 2 diabetes in humans.
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Affiliation(s)
- S Soyal
- Department of Internal Medicine, Krankenhaus Hallein, 5400, Hallein, Austria
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299
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Dahlman I, Forsgren M, Sjögren A, Nordström EA, Kaaman M, Näslund E, Attersand A, Arner P. Downregulation of electron transport chain genes in visceral adipose tissue in type 2 diabetes independent of obesity and possibly involving tumor necrosis factor-alpha. Diabetes 2006; 55:1792-9. [PMID: 16731844 DOI: 10.2337/db05-1421] [Citation(s) in RCA: 145] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Impaired oxidative phosphorylation is suggested as a factor behind insulin resistance of skeletal muscle in type 2 diabetes. The role of oxidative phosphorylation in adipose tissue was elucidated from results of Affymetrix gene profiling in subcutaneous and visceral adipose tissue of eight nonobese healthy, eight obese healthy, and eight obese type 2 diabetic women. Downregulation of several genes in the electron transport chain was the most prominent finding in visceral fat of type 2 diabetic women independent of obesity, but the gene pattern was distinct from that previously reported in skeletal muscle in type 2 diabetes. A similar but much weaker effect was observed in subcutaneous fat. Tumor necrosis factor-alpha (TNF-alpha) is a major factor behind inflammation and insulin resistance in adipose tissue. TNF-alpha treatment decreased mRNA expression of electron transport chain genes and also inhibited fatty acid oxidation when differentiated human preadipocytes were treated with the cytokine for 48 h. Thus, type 2 diabetes is associated with a tissue- and region-specific downregulation of oxidative phosphorylation genes that is independent of obesity and at least in part mediated by TNF-alpha, suggesting that impaired oxidative phosphorylation of visceral adipose tissue has pathogenic importance for development of type 2 diabetes.
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Affiliation(s)
- Ingrid Dahlman
- Department of Medicine, Karolinska University Hospital, Huddinge, SE-141 86 Stockholm, Sweden
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300
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Hondares E, Mora O, Yubero P, Rodriguez de la Concepción M, Iglesias R, Giralt M, Villarroya F. Thiazolidinediones and rexinoids induce peroxisome proliferator-activated receptor-coactivator (PGC)-1alpha gene transcription: an autoregulatory loop controls PGC-1alpha expression in adipocytes via peroxisome proliferator-activated receptor-gamma coactivation. Endocrinology 2006; 147:2829-38. [PMID: 16513826 DOI: 10.1210/en.2006-0070] [Citation(s) in RCA: 147] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Thiazolidinediones (TZDs) are insulin-sensitizing drugs currently used to treat type 2 diabetes. They are activators of peroxisome proliferator-activated receptor (PPAR)-gamma, and adipose tissue constitutes a major site for their biological effects. PPAR coactivator (PGC)-1alpha is a transcriptional coactivator of PPARgamma and other transcription factors. It is involved in the control of mitochondrial biogenesis, and its activity has been linked to insulin sensitization. Here we report that PGC-1alpha gene expression in brown and white adipocytes is a direct target of TZDs via PPARgamma activation. Activators of the retinoid X receptor also induce PGC-1alpha gene expression. This is due to the presence of a PPARgamma-responsive element in the distal region of the PGC-1alpha gene promoter that binds PPARgamma/retinoid X receptor heterodimers. Moreover, there is a positive autoregulatory loop of control of the PGC-1alpha gene through coactivation of PPARgamma responsiveness to TZDs by PGC-1alpha itself. These data indicate that some of the effects of TZDs, especially promotion of mitochondrial biogenesis and oxidative pathways in adipose depots, entail PGC-1alpha up-regulation via enhanced transcription of the PGC-1alpha gene.
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Affiliation(s)
- Elayne Hondares
- Department of Biochemistry and Molecular Biology, University of Barcelona, 08028 Barcelona, Spain
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