1601
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Abstract
Obesity induces an insulin-resistant state in adipose tissue, liver, and muscle and is a strong risk factor for the development of type 2 diabetes mellitus. Insulin resistance in the setting of obesity results from a combination of altered functions of insulin target cells and the accumulation of macrophages that secrete proinflammatory mediators. At the molecular level, insulin resistance is promoted by a transition in macrophage polarization from an alternative M2 activation state maintained by STAT6 and PPARs to a classical M1 activation state driven by NF-kappaB, AP1, and other signal-dependent transcription factors that play crucial roles in innate immunity. Strategies focused on inhibiting the inflammation/insulin resistance axis that otherwise preserve essential innate immune functions may hold promise for therapeutic intervention.
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Affiliation(s)
- Jerrold M Olefsky
- Department of Medicine, University of California-San Diego, La Jolla, CA 92093-0651, USA.
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1602
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Lu C, Kumar PA, Fan Y, Sperling MA, Menon RK. A novel effect of growth hormone on macrophage modulates macrophage-dependent adipocyte differentiation. Endocrinology 2010; 151:2189-99. [PMID: 20185763 PMCID: PMC2869256 DOI: 10.1210/en.2009-1194] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
The GH receptor (GHR) is expressed on macrophages. However, the precise role of GH in regulation of macrophage function is unclear. We hypothesized that soluble factors including cytokines produced by macrophages in a GH-dependent manner regulate adipogenesis. We confirmed expression and functional integrity of the GHR in the J774A.1 macrophage cells. Conditioned medium (CM) from macrophages inhibited adipogenesis in a 3T3-L1 adipogenesis assay. CM from GH-treated macrophages decreased the inhibitory effect of CM from macrophages on adipogenesis. This effect on preadipocyte differentiation was active only during the first (early) phase of adipocyte differentiation. CM from stromal vascular compartment macrophages of mice with macrophage-specific deletion of the GHR exhibited more inhibitory effect on 3T3-L1 preadipocyte differentiation compared with CM from stromal vascular compartment macrophages of control mice, indicating that intact GH action in primary macrophages also increases preadipocyte differentiation. GH did not increase IGF-1 expression in macrophages. PCR array analysis identified IL-1beta as a candidate cytokine whose expression was altered by GH in macrophages. Levels of IL-1beta mRNA and protein were significantly decreased in GH-treated J774A.1 macrophages. Nuclear factor-kappaB stimulates IL-1beta gene expression, and GH induced a significant decrease in the levels of phosphorylated nuclear factor-kappaB in macrophages. IL-1beta is a known inhibitor of adipogenesis, and these results support GH-dependent down-regulation of macrophage IL-1beta expression as one mechanism for the observed increase in adipogenesis with CM from GH-treated macrophages. We conclude that GH decreases secretion of IL-1beta by the macrophage and thus in a paracrine manner increases adipocyte differentiation. These results provide a novel mechanism for GH's actions in the control of adipogenesis.
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Affiliation(s)
- Chunxia Lu
- Department of Pediatrics, University of Michigan Medical School, Ann Arbor, Michigan 48109-0718, USA
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1603
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Lynch RM, Naswa S, Rogers GL, Kania SA, Das S, Chesler EJ, Saxton AM, Langston MA, Voy BH. Identifying genetic loci and spleen gene coexpression networks underlying immunophenotypes in BXD recombinant inbred mice. Physiol Genomics 2010; 41:244-53. [PMID: 20179155 PMCID: PMC4073992 DOI: 10.1152/physiolgenomics.00020.2010] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2010] [Accepted: 02/22/2010] [Indexed: 01/20/2023] Open
Abstract
The immune system plays a pivotal role in the susceptibility to and progression of a variety of diseases. Due to a strong genetic basis, heritable differences in immune function may contribute to differential disease susceptibility between individuals. Genetic reference populations, such as the BXD (C57BL/6J × DBA/2J) panel of recombinant inbred (RI) mouse strains, provide unique models through which to integrate baseline phenotypes in healthy individuals with heritable risk for disease because of the ability to combine data collected from these populations across both multiple studies and time. We performed basic immunophenotyping (e.g., percentage of circulating B and T lymphocytes and CD4(+) and CD8(+) T cell subpopulations) in peripheral blood of healthy mice from 41 BXD RI strains to define the immunophenotypic variation in this strain panel and to characterize the genetic architecture that underlies these traits. Significant QTL models that explained the majority (50-77%) of phenotypic variance were derived for each trait and for the T:B cell and CD4(+):CD8(+) ratios. Combining QTL mapping with spleen gene expression data uncovered two quantitative trait transcripts, Ptprk and Acp1, as candidates for heritable differences in the relative abundance of helper and cytotoxic T cells. These data will be valuable in extracting genetic correlates of the immune system in the BXD panel. In addition, they will be a useful resource for prospective, phenotype-driven model selection to test hypotheses about differential disease or environmental susceptibility between individuals with baseline differences in the composition of the immune system.
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Affiliation(s)
- Rachel M Lynch
- Systems Genetics Group, Oak Ridge National Laboratory, Oak Ridge
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1604
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Abstract
Atherosclerosis and related cardiovascular diseases represent one of the greatest threats to human health worldwide. Despite important progress in prevention and treatment, these conditions still account for one third of all deaths annually. Often presented together with obesity, insulin resistance and type 2 diabetes, these chronic diseases are strongly influenced by pathways that lie at the interface of chronic inflammation and nutrient metabolism. Here I discuss recent advances in the study of endoplasmic reticulum stress as one mechanism that links immune response with nutrient sensing in the pathogenesis of atherosclerosis and its complications.
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Affiliation(s)
- Gökhan S Hotamisligil
- Department of Genetics, and the Broad Institute of Massachusetts Institute of Technology and Harvard, Harvard School of Public Health, Boston, Massachusetts, USA.
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1605
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Microbial induction of vascular pathology in the CNS. J Neuroimmune Pharmacol 2010; 5:370-86. [PMID: 20401700 DOI: 10.1007/s11481-010-9208-9] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2009] [Accepted: 03/10/2010] [Indexed: 12/31/2022]
Abstract
The central nervous system (CNS) is a finely tuned organ that participates in nearly every aspect of our day-to-day function. Neurons lie at the core of this functional unit and maintain an active dialogue with one another as well as their fellow CNS residents (e.g. astrocytes, oligodendrocytes, microglia). Because of this complex dialogue, it is essential that the CNS milieu be tightly regulated in order to permit uninterrupted and efficient neural chemistry. This is accomplished in part by anatomical barriers that segregate vascular components from the cerebral spinal fluid (CSF) and brain parenchyma. These barriers impede entry of noxious materials and enable the CNS to maintain requisite protein and ionic balances for constant electrochemical signaling. Under homeostatic conditions, the CNS is protected by the presence of specialized endothelium/epithelium, the blood brain barrier (BBB), and the blood-CSF barrier. However, following CNS infection these protective barriers can be comprised, sometimes resulting in severe neurological complications triggered by an imbalance or blockage of neural chemistry. In some instances, these disruptions are severe enough to be fatal. This review focuses on a selection of microbes (both viruses and parasites) that compromise vascular barriers and induce neurological complications upon gaining access to the CNS. Emphasis is placed on CNS diseases that result from a pathogenic interplay between host immune defenses and the invading microbe.
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1606
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Adaptive control of innate immunity. Immunol Lett 2010; 131:107-12. [PMID: 20394777 DOI: 10.1016/j.imlet.2010.04.002] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2010] [Revised: 03/30/2010] [Accepted: 04/03/2010] [Indexed: 02/07/2023]
Abstract
The mechanisms by which the immune system responds to an infection or disease depend on a complex interplay between the elements of innate and adaptive immunity. While most of the focus so far has been on the innate instruction of the adaptive immune responses, considerable evidence now suggests an equally important adaptive control of the innate immunity. Several studies yield new insights into how the adaptive immunity by initiating an antigen-specific response can compensate, suppress and activate innate responses at the site of tissue antigen. Here we discuss recent advances in our understanding of the adaptive control of immune effector functions in various pathological and physiological conditions.
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1607
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Solinas G, Karin M. JNK1 and IKKbeta: molecular links between obesity and metabolic dysfunction. FASEB J 2010; 24:2596-611. [PMID: 20371626 DOI: 10.1096/fj.09-151340] [Citation(s) in RCA: 240] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Inflammation is thought to underlie the pathogenesis of many chronic diseases. It is now established that obesity results in a state of chronic low-grade inflammation thought to contribute to several metabolic disorders, including insulin resistance and pancreatic islet dysfunction. The protein kinases JNK1 and IKKbeta have been found to serve as critical molecular links between obesity, metabolic inflammation, and disorders of glucose homeostasis. The precise mechanisms of these linkages are still being investigated. However, as we discuss here, JNK1 and IKKbeta are activated by almost all forms of metabolic stress that have been implicated in insulin resistance or islet dysfunction. Furthermore, both JNK1 and IKKbeta are critically involved in the promotion of diet-induced obesity, metabolic inflammation, insulin resistance, and beta-cell dysfunction. Understanding the molecular mechanisms by which JNK1 and IKKbeta mediate obesity-induced metabolic stress is likely to be of importance for the development of new treatments for a variety of obesity-associated diseases.
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Affiliation(s)
- Giovanni Solinas
- Laboratory of Metabolic Stress Biology, Department of Medicine, Physiology, University of Fribourg, Chemin du Musée 5, CH-1700 Fribourg, Switzerland.
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1608
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Abstract
The endoplasmic reticulum (ER) is the major site in the cell for protein folding and trafficking and is central to many cellular functions. Failure of the ER's adaptive capacity results in activation of the unfolded protein response (UPR), which intersects with many different inflammatory and stress signaling pathways. These pathways are also critical in chronic metabolic diseases such as obesity, insulin resistance, and type 2 diabetes. The ER and related signaling networks are emerging as a potential site for the intersection of inflammation and metabolic disease.
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Affiliation(s)
- Gökhan S Hotamisligil
- Department of Genetics and Complex Diseases, Broad Institute of Harvard and MIT, Harvard School of Public Health, Boston, MA 02115, USA.
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1609
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Suganami T, Ogawa Y. Adipose tissue macrophages: their role in adipose tissue remodeling. J Leukoc Biol 2010; 88:33-9. [PMID: 20360405 DOI: 10.1189/jlb.0210072] [Citation(s) in RCA: 299] [Impact Index Per Article: 21.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The adipose tissue secretes a large number of bioactive substances, adipocytokines, which may be involved in a variety of physiologic and pathologic processes. Unbalanced production of pro- and anti-inflammatory adipocytokines seen in visceral fat obesity contributes critically to the development of the metabolic syndrome. Evidence has accumulated indicating that obesity is associated with a state of chronic, low-grade inflammation, suggesting that inflammation may be a potential mechanism, whereby obesity leads to insulin resistance. Indeed, obese adipose tissue is characterized by adipocyte hypertrophy, followed by increased angiogenesis, immune cell infiltration, extracellular matrix overproduction, and thus, increased production of proinflammatory adipocytokines during the progression of chronic inflammation. The dynamic change found in the adipose tissue can be referred to as "adipose tissue remodeling," in which stromal cells change dramatically in number and cell type during the course of obesity. Among stromal cells, infiltration of macrophages in the adipose tissue precedes the development of insulin resistance in animal models, suggesting that they are crucial for obesity-related adipose tissue inflammation. We have demonstrated that a paracrine loop involving saturated fatty acids and TNF-alpha derived from adipocytes and macrophages, respectively, aggravates obesity-induced adipose tissue inflammation. Notably, saturated fatty acids, which are released from hypertrophied adipocytes via the macrophage-induced lipolysis, serve as a naturally occurring ligand for TLR4 complex, thereby activating macrophages. Understanding the molecular mechanism underlying adipose tissue remodeling may lead to the identification of novel, therapeutic strategies to prevent or treat obesity-induced adipose tissue inflammation.
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Affiliation(s)
- Takayoshi Suganami
- Department of Molecular Medicine and Metabolism, Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan
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1610
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Li P, Lu M, Nguyen MTA, Bae EJ, Chapman J, Feng D, Hawkins M, Pessin JE, Sears DD, Nguyen AK, Amidi A, Watkins SM, Nguyen U, Olefsky JM. Functional heterogeneity of CD11c-positive adipose tissue macrophages in diet-induced obese mice. J Biol Chem 2010; 285:15333-15345. [PMID: 20308074 DOI: 10.1074/jbc.m110.100263] [Citation(s) in RCA: 192] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Obesity represents a state of chronic, low grade inflammation and is associated with infiltration of increased numbers of adipose tissue macrophages (ATMs). Diet-induced obesity leads to an increase in non-inflammatory M1-like ATMs displaying the CD11c surface marker. We assessed the function of CD11c-positive ATMs when insulin resistant high fat diet (HFD) mice become insulin-sensitive after switching from HFD to normal chow (NC). HFD mice rapidly become insulin-sensitive in all major insulin-target tissues, including muscle, liver, and adipose tissue, after the diet switch. In adipose tissue the CD11c-positive macrophages remain constant in number despite the presence of insulin sensitivity, but these macrophages now assume a new phenotype in which they no longer exhibit increased inflammatory pathway markers. Adipose tissue markers of apoptosis and necrosis were elevated on HFD and remain high after the HFD --> NC diet switch. Furthermore, ATM accumulation preceded detectable adipocyte necrosis at the early phase of HFD. Together, these results indicate that 1) CD11c-positive M1-like ATMs can exhibit phenotypic plasticity and that the polarization of these cells between inflammatory and non-inflammatory states is well correlated to the presence of absence of insulin resistance, and 2) adipocyte necrosis and apoptosis can be dissociated from ATM accumulation.
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Affiliation(s)
- Pingping Li
- Division of Endocrinology and Metabolism, Department of Medicine, University of California, San Diego, La Jolla, California 92093-0673
| | - Min Lu
- Division of Endocrinology and Metabolism, Department of Medicine, University of California, San Diego, La Jolla, California 92093-0673
| | - M T Audrey Nguyen
- Division of Endocrinology and Metabolism, Department of Medicine, University of California, San Diego, La Jolla, California 92093-0673
| | - Eun Ju Bae
- Division of Endocrinology and Metabolism, Department of Medicine, University of California, San Diego, La Jolla, California 92093-0673
| | | | - Daorong Feng
- Department of Medicine, Albert Einstein College of Medicine, Bronx, New York 10461
| | - Meredith Hawkins
- Department of Medicine, Albert Einstein College of Medicine, Bronx, New York 10461
| | - Jeffrey E Pessin
- Department of Medicine, Albert Einstein College of Medicine, Bronx, New York 10461
| | - Dorothy D Sears
- Division of Endocrinology and Metabolism, Department of Medicine, University of California, San Diego, La Jolla, California 92093-0673
| | - Anh-Khoi Nguyen
- Division of Endocrinology and Metabolism, Department of Medicine, University of California, San Diego, La Jolla, California 92093-0673
| | - Arezou Amidi
- Division of Endocrinology and Metabolism, Department of Medicine, University of California, San Diego, La Jolla, California 92093-0673
| | | | - UyenThao Nguyen
- Lipomics Technologies, Inc., West Sacramento, California 95691
| | - Jerrold M Olefsky
- Division of Endocrinology and Metabolism, Department of Medicine, University of California, San Diego, La Jolla, California 92093-0673.
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1611
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Affiliation(s)
- Lionel Hebbard
- Storr Liver Unit, Westmead Millennium InstituteThe University of Sydney and Westmead Hospital Westmead, NSW, Australia
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1612
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Affiliation(s)
- Carey N. Lumeng
- Department of Pediatrics and Communicable Diseases, and Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI 48109, USA
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1613
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Iyer A, Fairlie DP, Prins JB, Hammock BD, Brown L. Inflammatory lipid mediators in adipocyte function and obesity. Nat Rev Endocrinol 2010; 6:71-82. [PMID: 20098448 DOI: 10.1038/nrendo.2009.264] [Citation(s) in RCA: 203] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Survival of multicellular organisms depends on their ability to fight infection, metabolize nutrients, and store energy for times of need. Unsurprisingly, therefore, immunoregulatory and metabolic mechanisms interact in human conditions such as obesity. Both infiltrating immunoinflammatory cells and adipocytes play critical roles in the modulation of metabolic homeostasis, so it is important to understand factors that regulate both adipocyte and immune cell function. A currently favored paradigm for obesity-associated metabolic dysfunction is that chronic macronutrient and/or lipid overload (associated with adiposity) induces cellular stress that initiates and perpetuates an inflammatory cycle and pathophysiological signaling of immunoinflammatory cells and adipocytes. Many lipid mediators exert their biological effects by binding to cognate receptors, such as G-protein-coupled receptors and Toll-like receptors. This process is tightly regulated under normal physiological conditions, and any disruption can initiate disease processes. Observations that cellular lipid loading (associated with adiposity) initiates inflammatory events has encouraged studies on the role of lipid mediators. In this review, we speculate that lipid mediators act on important immune receptors to induce low-grade tissue inflammation, which leads to adipocyte and metabolic dysfunction.
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Affiliation(s)
- Abishek Iyer
- School of Biomedical Sciences, The University of Queensland, Brisbane, QLD 4072, Australia
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1614
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Sepe A, Tchkonia T, Thomou T, Zamboni M, Kirkland JL. Aging and regional differences in fat cell progenitors - a mini-review. Gerontology 2010; 57:66-75. [PMID: 20110661 PMCID: PMC3031153 DOI: 10.1159/000279755] [Citation(s) in RCA: 158] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2009] [Accepted: 12/02/2009] [Indexed: 12/14/2022] Open
Abstract
Fat mass and fat tissue distribution change dramatically throughout life. In old age, fat becomes dysfunctional and is redistributed from subcutaneous to intra-abdominal visceral depots as well as other ectopic sites, including bone marrow, muscle and the liver. These changes are associated with increased risk of metabolic syndrome. Fat tissue is a nutrient storage, endocrine and immune organ that undergoes renewal throughout the lifespan. Preadipocytes, which account for 15-50% of cells in fat tissue, give rise to new fat cells. With aging, declines in preadipocyte proliferation and differentiation likely contribute to increased systemic exposure to lipotoxic free fatty acids. Age-related fat tissue inflammation is related to changes that occur in preadipocytes and macrophages in a fat depot-dependent manner. Fat tissue inflammation frequently leads to further reduction in adipogenesis with aging, more lipotoxicity and activation of cellular stress pathways that, in turn, exacerbate inflammatory responses of preadipocytes and immune cells, establishing self-perpetuating cycles that lead to systemic dysfunction. In this review, we will consider how inherent, age-related, depot-dependent alterations in preadipocyte function contribute to age-related fat tissue redistribution and metabolic dysfunction.
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Affiliation(s)
- Anna Sepe
- Department of Biomedical and Surgical Sciences, Division of Geriatrics, University of Verona, Verona, Italy
- Mayo Clinic Robert and Arlene Kogod Center on Aging, Rochester, Minn., USA
| | - Tamara Tchkonia
- Mayo Clinic Robert and Arlene Kogod Center on Aging, Rochester, Minn., USA
| | - Thomas Thomou
- Mayo Clinic Robert and Arlene Kogod Center on Aging, Rochester, Minn., USA
| | - Mauro Zamboni
- Department of Biomedical and Surgical Sciences, Division of Geriatrics, University of Verona, Verona, Italy
| | - James L. Kirkland
- Department of Biomedical and Surgical Sciences, Division of Geriatrics, University of Verona, Verona, Italy
- Mayo Clinic Robert and Arlene Kogod Center on Aging, Rochester, Minn., USA
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1615
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Abstract
Inflammation drives the formation, progression, and rupture of atherosclerotic plaques. Experimental studies have demonstrated that an inflammatory subset of monocytes/macrophages preferentially accumulate in atherosclerotic plaque and produce proinflammatory cytokines. T lymphocytes can contribute to inflammatory processes that promote thrombosis by stimulating production of collagen-degrading proteinases and the potent procoagulant tissue factor. Recent data link obesity, inflammation, and modifiers of atherosclerotic events, a nexus of growing clinical concern given the worldwide increase in the prevalence of obesity. Modulators of inflammation derived from visceral adipose tissue evoke production of acute phase reactants in the liver, implicated in thrombogenesis and clot stability. Additionally, C-reactive protein levels rise with increasing levels of visceral adipose tissue. Adipose tissue in obese mice contains increased numbers of macrophages and T lymphocytes, increased T lymphocyte activation, and increased interferon-gamma (IFN-gamma) expression. IFN-gamma deficiency in mice reduces production of inflammatory cytokines and inflammatory cell accumulation in adipose tissue. Another series of in vitro and in vivo mouse experiments affirmed that adiponectin, an adipocytokine, the plasma levels of which drop with obesity, acts as an endogenous antiinflammatory modulator of both innate and adaptive immunity in atherogenesis. Thus, accumulating experimental evidence supports a key role for inflammation as a link between risk factors for atherosclerosis and the biology that underlies the complications of this disease. The recent JUPITER trial supports the clinical utility of an assessment of inflammatory status in guiding intervention to limit cardiovascular events. Inflammation is thus moving from a theoretical concept to a tool that provides practical clinical utility in risk assessment and targeting of therapy.
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Affiliation(s)
- Peter Libby
- Division of Cardiovascular Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA.
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1616
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Rajsheker S, Manka D, Blomkalns AL, Chatterjee TK, Stoll LL, Weintraub NL. Crosstalk between perivascular adipose tissue and blood vessels. Curr Opin Pharmacol 2010; 10:191-6. [PMID: 20060362 DOI: 10.1016/j.coph.2009.11.005] [Citation(s) in RCA: 130] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2009] [Revised: 11/03/2009] [Accepted: 11/14/2009] [Indexed: 12/21/2022]
Abstract
Crosstalk between cells in the blood vessel wall is vital to normal vascular function and is perturbed in diseases such as atherosclerosis and hypertension. Perivascular adipocytes reside at the adventitial border of blood vessels but until recently were virtually ignored in studies of vascular function. However, perivascular adipocytes have been demonstrated to be powerful endocrine cells capable of responding to metabolic cues and transducing signals to adjacent blood vessels. Accordingly, crosstalk between perivascular adipose tissue (PVAT) and blood vessels is now being intensely examined. Emerging evidence suggests that PVAT regulates vascular function through numerous mechanisms, but evidence to date suggests modulation of three key aspects that are the focus of this review: inflammation, vasoreactivity, and smooth muscle cell proliferation.
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Affiliation(s)
- Srinivas Rajsheker
- Department of Internal Medicine, University of Cincinnati College of Medicine, Cincinnati, OH 45267, United States
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1617
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Abstract
Metabolic and immune-related pathways intersect at numerous levels. Their common regulation is effectuated by several hormonal signaling routes that involve specific nuclear hormone receptors and adipokines. Glucocorticoids and leptin are hormones that play a key role in coordinating energy metabolism and food-seeking behavior during energy deficiency as does the nuclear hormone receptor Peroxisome Proliferator Activated Receptor α (PPARalpha). Importantly, the glucocorticoid, leptin, and PPARalpha signaling routes share a profound role in governing inflammation and other immune-related processes. Using specific examples, this chapter aims at illustrating the interplay between metabolism and immunity/inflammation by discussing common endocrine and transcriptional regulators of metabolism and inflammation and by highlighting the interaction between macrophages and metabolically active cells in liver and adipose tissue. Convergence of metabolic and immune signaling is likely at least partially driven by the evolutionary need during times of food insufficiency to minimize loss of energy to processes that are temporarily nonessential to the survival of the species.
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Affiliation(s)
- Sander Kersten
- Nutrition, Metabolism and Genomics Group, Division of Human Nutrition, Wageningen University, Bomenweg 2, 6703 HD, Wageningen, The Netherlands.
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1618
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Popov Y, Schuppan D. CD8+ T cells drive adipose tissue inflammation--a novel clue for NASH pathogenesis? J Hepatol 2010; 52:130-2. [PMID: 19914729 DOI: 10.1016/j.jhep.2009.10.019] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/07/2009] [Accepted: 10/08/2009] [Indexed: 01/25/2023]
Affiliation(s)
- Yury Popov
- Division of Gastroenterology and Hepatology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215, USA.
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1619
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Ohashi K, Parker JL, Ouchi N, Higuchi A, Vita JA, Gokce N, Pedersen AA, Kalthoff C, Tullin S, Sams A, Summer R, Walsh K. Adiponectin promotes macrophage polarization toward an anti-inflammatory phenotype. J Biol Chem 2009; 285:6153-60. [PMID: 20028977 DOI: 10.1074/jbc.m109.088708] [Citation(s) in RCA: 454] [Impact Index Per Article: 30.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
It is established that the adipocyte-derived cytokine adiponectin protects against cardiovascular and metabolic diseases, but the effect of this adipokine on macrophage polarization, an important mediator of disease progression, has never been assessed. We hypothesized that adiponectin modulates macrophage polarization from that resembling a classically activated M1 phenotype to that resembling alternatively-activated M2 cells. Peritoneal macrophages and the stromal vascular fraction (SVF) cells of adipose tissue isolated from adiponectin knock-out mice displayed increased M1 markers, including tumor necrosis factor-alpha, interleukin-6, and monocyte chemoattractant protein-1 and decreased M2 markers, including arginase-1, macrophage galactose N-acetyl-galactosamine specific lectin-1, and interleukin-10. The systemic delivery of adenovirus expressing adiponectin significantly augmented arginase-1 expression in peritoneal macrophages and SVF cells in both wild-type and adiponectin knock-out mice. In culture, the treatment of macrophages with recombinant adiponectin protein led to an increase in the levels of M2 markers and a reduction of reactive oxygen species and reactive oxygen species-related gene expression. Adiponectin also stimulated the expression of M2 markers and attenuated the expression of M1 markers in human monocyte-derived macrophages and SVF cells isolated from human adipose tissue. These data show that adiponectin functions as a regulator of macrophage polarization, and they indicate that conditions of high adiponectin expression may deter metabolic and cardiovascular disease progression by favoring an anti-inflammatory phenotype in macrophages.
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Affiliation(s)
- Koji Ohashi
- Molecular Cardiology/Whitaker Cardiovascular Institute, Boston University School of Medicine, Boston, Massachusetts 02118, USA
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1620
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Surmi BK, Hasty AH. The role of chemokines in recruitment of immune cells to the artery wall and adipose tissue. Vascul Pharmacol 2009; 52:27-36. [PMID: 20026286 DOI: 10.1016/j.vph.2009.12.004] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2009] [Revised: 12/08/2009] [Accepted: 12/13/2009] [Indexed: 01/02/2023]
Abstract
The role of the immune system is to recognize pathogens, tumor cells or dead cells and to react with a very specific and localized response. By taking advantage of a highly sophisticated system of chemokines and chemokine receptors, leukocytes such as neutrophils, macrophages, and T-lymphocytes are targeted to the precise location of inflammation. While this is a beneficial process for acute infection and inflammation, recruitment of immune cells to sites of chronic inflammation can be detrimental. It is becoming clear that these inflammatory cells play a significant role in the initiation and progression of metabolic disorders such as atherosclerosis and insulin resistance by infiltrating the artery wall and adipose tissue (AT), respectively. Data from human studies indicate that elevated plasma levels of chemokines are correlated with these metabolic diseases. Recruitment of macrophages to the artery wall is well known to be one of the first steps in early atherosclerotic lesion formation. Likewise, recruitment of macrophages to AT is thought to contribute to insulin resistance associated with obesity. Based on this knowledge, much recent work in these areas has focused on the role of chemokines in attracting immune cells (monocytes/macrophages in particular) to these 2 sites. Thus, understanding the potential for chemokines to contribute to metabolic disease can help direct studies of chemokines as therapeutic targets. In this article, we will review current literature regarding the role of chemokines in atherosclerosis and obesity-related insulin resistance. We will focus on novel work showing that chemokine secretion from endothelial cells, platelets, and adipocytes can contribute to immune cell recruitment, with a diagram showing the time course of chemokine expression and leukocyte recruitment to AT. We will also highlight a few of the less-commonly known chemokine-chemokine receptor pairs. Finally, we will discuss the potential for chemokines as therapeutic targets for treatment of atherosclerosis and insulin resistance.
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Affiliation(s)
- Bonnie K Surmi
- Department of Molecular Physiology and Biophysics, Vanderbilt University Medical Center, Nashville, TN, USA
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1621
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Abstract
The initial event in atherogenesis is the increased transcytosis of low density lipoprotein, and its subsequent deposition, retention and modification in the subendothelium. It is followed by the infiltration of activated inflammatory cells from the coronary circulation into the arterial wall. There they secrete reactive oxygen species (ROS) and produce oxidized lipoproteins capable of inducing endothelial cell apoptosis, and thereby plaque erosion. Activated T lymphocytes, macrophages and mast cells, accumulate in the eroded plaque where they secrete a variety of proteases capable of inducing degradation of extracellular proteins, thereby rendering the plaques more prone to rupture. This review summarizes the recent advancements in the understanding of the roles of ROS and oxidized lipoproteins in the activation of inflammatory cells and inducing signalling pathways related to cell death and apoptosis. In addition, it presents evidence that this vicious circle between oxidative stress and inflammation does not only occur in the diseased arterial wall, but also in adipose tissues. There, oxidative stress and inflammation impair adipocyte maturation resulting in defective insulin action and adipocytokine signalling. The latter is associated with increased infiltration of inflammatory cells, loss of anti-oxidant protection and cell death in the arterial wall.
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Affiliation(s)
- Maarten Hulsmans
- Atherosclerosis and Metabolism Unit, Department of Cardiovascular Diseases, Katholieke Universiteit Leuven, Belgium
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1622
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Hulsmans M, Holvoet P. The vicious circle between oxidative stress and inflammation in atherosclerosis. FASEB J 2009; 25:2515-27. [PMID: 19968738 DOI: 10.1096/fj.11-181149] [Citation(s) in RCA: 171] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The initial event in atherogenesis is the increased transcytosis of low density lipoprotein, and its subsequent deposition, retention and modification in the subendothelium. It is followed by the infiltration of activated inflammatory cells from the coronary circulation into the arterial wall. There they secrete reactive oxygen species (ROS) and produce oxidized lipoproteins capable of inducing endothelial cell apoptosis, and thereby plaque erosion. Activated T lymphocytes, macrophages and mast cells, accumulate in the eroded plaque where they secrete a variety of proteases capable of inducing degradation of extracellular proteins, thereby rendering the plaques more prone to rupture. This review summarizes the recent advancements in the understanding of the roles of ROS and oxidized lipoproteins in the activation of inflammatory cells and inducing signalling pathways related to cell death and apoptosis. In addition, it presents evidence that this vicious circle between oxidative stress and inflammation does not only occur in the diseased arterial wall, but also in adipose tissues. There, oxidative stress and inflammation impair adipocyte maturation resulting in defective insulin action and adipocytokine signalling. The latter is associated with increased infiltration of inflammatory cells, loss of anti-oxidant protection and cell death in the arterial wall.
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Affiliation(s)
- Maarten Hulsmans
- Atherosclerosis and Metabolism Unit, Department of Cardiovascular Diseases, Katholieke Universiteit Leuven, Belgium
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1623
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Ohmura K, Ishimori N, Ohmura Y, Tokuhara S, Nozawa A, Horii S, Andoh Y, Fujii S, Iwabuchi K, Onoé K, Tsutsui H. Natural killer T cells are involved in adipose tissues inflammation and glucose intolerance in diet-induced obese mice. Arterioscler Thromb Vasc Biol 2009; 30:193-9. [PMID: 19910631 DOI: 10.1161/atvbaha.109.198614] [Citation(s) in RCA: 168] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
BACKGROUND Macrophage and lymphocyte infiltration in adipose tissue may contribute to the pathogenesis of obesity-mediated metabolic disorders. Natural killer T (NKT) cells, which integrate proinflammatory cytokines, have been demonstrated in the atherosclerotic lesions and in visceral adipose tissue. OBJECTIVE To determine whether NKT cells are involved in glucose intolerance and adipose tissue inflammation in diet-induced obese mice. METHODS AND RESULTS Male beta(2)-microglobulin knockout (KO) mice lacking NKT cells and C57BL/6J (wild-type) mice were fed with a high-fat diet (HFD) for 13 weeks [corrected]. Body weight and visceral obesity were comparable between wild-type and KO mice. However, macrophage infiltration was reduced in adipose tissue and glucose intolerance was significantly ameliorated in KO mice. To further confirm that NKT cells are involved in these abnormalities, alpha-galactosylceramide, 0.1 microg/g body weight, which specifically activates NKT cells, was administered after 13 weeks of HFD feeding. alpha-Galactosylceramide significantly exacerbated glucose intolerance and macrophage infiltration as well as cytokine gene expression in adipose tissue. CONCLUSIONS NKT cells play a crucial role in the development of adipose tissue inflammation and glucose intolerance in diet-induced obesity.
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Affiliation(s)
- Kazue Ohmura
- Department of Cardiovascular Medicine, Hokkaido University Graduate School of Medicine, Sapporo 060-8638, Japan
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1624
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Wu H, Perrard XD, Wang Q, Perrard JL, Polsani VR, Jones PH, Smith CW, Ballantyne CM. CD11c expression in adipose tissue and blood and its role in diet-induced obesity. Arterioscler Thromb Vasc Biol 2009; 30:186-92. [PMID: 19910635 DOI: 10.1161/atvbaha.109.198044] [Citation(s) in RCA: 113] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
OBJECTIVE To examine CD11c, a beta(2)-integrin, on adipose tissue (AT) leukocytes and blood monocytes and its role in diet-induced obesity. METHODS AND RESULTS High-fat diet-induced obese C57BL/6 mice, CD11c-deficient mice, and obese humans were studied. CD11c, leukocytes, and chemokines/cytokines were examined in AT and/or blood by flow cytometry, RNase protection assay, quantitative polymerase chain reaction, or enzyme-linked immunosorbent assay. Obese C57BL/6 mice had increased CD11c in AT and blood compared with lean controls. CD11c messenger RNA positively correlated with monocyte chemoattractant protein 1 in human visceral AT. Obese humans with metabolic syndrome had a higher CD11c level on blood monocytes compared with lean humans. Low-fat diet-induced weight loss reduced blood monocyte CD11c in obese mice and humans. Mouse and human monocyte CD11c levels and mouse AT CD11c messenger RNA correlated with insulin resistance. CD11c deficiency in mice did not alter weight gain but decreased inflammation, evidenced by a lower T-cell number and reduced levels of major histocompatibility complex class II, C-C chemokine ligand 2 (CCL5), CCL4, and interferon gamma in AT, and ameliorated insulin resistance and glucose intolerance associated with diet-induced obesity. CONCLUSIONS Diet-induced obesity increased CD11c in both AT and blood in mice and humans. CD11c plays an important role in T-cell accumulation and activation in AT, and contributes to insulin resistance associated with obesity.
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Affiliation(s)
- Huaizhu Wu
- Section of Atherosclerosis and Vascular Medicine, Baylor College of Medicine, Houston, Tex 77030, USA
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1625
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McGillicuddy FC, Chiquoine EH, Hinkle CC, Kim RJ, Shah R, Roche HM, Smyth EM, Reilly MP. Interferon gamma attenuates insulin signaling, lipid storage, and differentiation in human adipocytes via activation of the JAK/STAT pathway. J Biol Chem 2009; 284:31936-44. [PMID: 19776010 DOI: 10.1074/jbc.m109.061655] [Citation(s) in RCA: 189] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Recent reports demonstrate T-cell infiltration of adipose tissue in early obesity. We hypothesized that interferon (IFN) gamma, a major T-cell inflammatory cytokine, would attenuate human adipocyte functions and sought to establish signaling mechanisms. Differentiated human adipocytes were treated with IFNgamma +/- pharmacological inhibitors prior to insulin stimulation. [(3)H]Glucose uptake and AKT phosphorylation were assessed as markers of insulin sensitivity. IFNgamma induced sustained loss of insulin-stimulated glucose uptake in human adipocytes, coincident with reduced Akt phosphorylation and down-regulation of the insulin receptor, insulin receptor substrate-1, and GLUT4. Loss of adipocyte triglyceride storage was observed with IFNgamma co-incident with reduced expression of peroxisome proliferator-activated receptor gamma, adiponectin, perilipin, fatty acid synthase, and lipoprotein lipase. Treatment with IFNgamma also blocked differentiation of pre-adipocytes to the mature phenotype. IFNgamma-induced robust STAT1 phosphorylation and SOCS1 mRNA expression, with modest, transient STAT3 phosphorylation and SOCS3 induction. Preincubation with a non-selective JAK inhibitor restored glucose uptake and Akt phosphorylation while completely reversing IFNgamma suppression of adipogenic mRNAs and adipocyte differentiation. Specific inhibition of JAK2 or JAK3 failed to block IFNgamma effects suggesting a predominant role for JAK1-STAT1. We demonstrate that IFNgamma attenuates insulin sensitivity and suppresses differentiation in human adipocytes, an effect most likely mediated via sustained JAK-STAT1 pathway activation.
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Affiliation(s)
- Fiona C McGillicuddy
- Cardiovascular Institute, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104, USA
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1626
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Patsouris D, Neels JG, Fan W, Li PP, Nguyen MTA, Olefsky JM. Glucocorticoids and thiazolidinediones interfere with adipocyte-mediated macrophage chemotaxis and recruitment. J Biol Chem 2009; 284:31223-35. [PMID: 19740750 DOI: 10.1074/jbc.m109.041665] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
The link between intra-abdominal adiposity and type II diabetes has been known for decades, and adipose tissue macrophage (ATM)-associated inflammation has recently been linked to insulin resistance. However, the mechanisms associated with ATM recruitment remain ill defined. Herein, we describe in vitro chemotaxis studies, in which adipocyte conditioned medium was used to stimulate macrophage migration. We demonstrate that tumor necrosis factor alpha and free fatty acids, key inflammatory stimuli involved in obesity-associated autocrine/paracrine inflammatory signaling, stimulate adipocyte expression and secretion of macrophage chemoattractants. Pharmacological studies showed that peroxisome proliferator-activated receptor gamma agonists and glucocorticoids potently inhibit adipocyte- induced recruitment of macrophages. This latter effect was mediated by the glucocorticoid receptor, which led to decreased chemokine secretion and expression. In vivo results were quite comparable; treatment of high fat diet-fed mice with dexamethasone prevented ATM accumulation in epididymal fat. This decrease in ATM was most pronounced for the proinflammatory F4/80(+), CD11b(+), CD11c(+) M-1-like ATM subset. Overall, our results elucidate a beneficial function of peroxisome proliferator-activated receptor gamma activation and glucocorticoid receptor/glucocorticoids in adipose tissue and indicate that pharmacologic prevention of ATM accumulation could be beneficial.
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Affiliation(s)
- David Patsouris
- Division of Endocrinology-Metabolism, Department of Medicine, University of California, San Diego, La Jolla, California 92093, USA
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1627
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Finding the T in fat. Nat Rev Drug Discov 2009. [DOI: 10.1038/nrd2978] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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1628
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Bird L. Finding the T in fat. Nat Rev Immunol 2009. [DOI: 10.1038/nri2630] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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1629
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