ABSTRACTS CURCUMA LONGA

Br J Anaesth. 2013 May 29. [Epub ahead of print]

Antinociceptive curcuminoid, KMS4034, effects on inflammatory and neuropathic pain likely via modulating TRPV1 in mice. Lee JY, Shin TJ, Choi JM, Seo KS, Kim HJ, Yoon TG, Lee YS, Han H, Chung HJ, Oh Y, Jung SJ, Shin KJ.

Source

Department of Dental Anesthesiology and Dental Research Institute, School of Dentistry, Seoul National University, Seoul, Republic of Korea.

Abstract

BACKGROUND:

/st>Curcumin, the active ingredient of turmeric (Curcuma longa), has a wide range of beneficial effects including anti-inflammation and analgesia. However, poor bioavailability of curcumin hinders its clinical application. To overcome this limitation, we modified the structure of curcumin and synthesized new derivatives with favourable pharmacokinetic profiles. Recently, curcumin has been shown to have an antagonizing effect on transient receptor potential vanilloid type 1 (TRPV1) ion channels. We investigated the antinociceptive activity of KMS4034 which had the most favourable pharmacokinetics among the tested curcumin derivatives.

METHODS:

/st>To evaluate the mechanism of the antinociceptive effects of KMS4034, capsaicin (ICAP)- and heat (Iheat)-induced currents in TRPV1 expressing HEK293 cells were observed after the application of KMS4034. Nociceptive behavioural measurement using the hot-plate test, formalin test, and chronic constriction injury (CCI) model were evaluated in mice. Also, calcitonin gene-related peptide (CGRP) was stained immunohistochemically in the L4/5 dorsal horns in mice with neuropathic pain.

RESULTS:

/st>ICAP (P

Cytokine Research Laboratory, Department of Experimental Therapeutics, The University of Texas MD Anderson Cancer Center, Houston, Texas.

Abstract

Because tumor necrosis factors (TNFs) are major mediators of inflammation and inflammation-related diseases, the United States Food and Drug Administration (FDA) has approved blockers of the cytokine, TNF-, which include chimeric TNF antibody (Infliximab), humanized TNF- antibody (Humira), and soluble TNF receptor-II (Enbrel). TNF blockers are now being used for the treatment of osteoarthritis, inflammatory bowel disease, psoriasis, and ankylosis at a total cumulative market value of more than $20 billion/year. Besides being expensive ($15,000-20,000/person/year), these drugs must be injected and have enough adverse effects to be given a black label warning by the FDA. In the current report, we describe an alternative, curcumin (diferuloylmethane), a component of turmeric (Curcuma longa) that is very inexpensive, orally bioavailable, and highly safe in humans, yet can block TNF- action and production in in vitro models, in animal models, and in humans. In addition, we provide evidence for curcumin's activities against all of the diseases for which TNF blockers are being used. Mechanisms by which curcumin inhibits the production and the cell signaling pathways activated by this cytokine are also discussed. With health care costs and safety being major issues today, this golden spice may help provide the solution.

Altern Med Rev. 2009 Jun;14(2):141-53.

Anti-inflammatory properties of curcumin, a major constituent of Curcuma longa: a review of preclinical and clinical research. Jurenka JS.

Source

Thorne Research, Inc. jjurenka@thorne.com

Erratum in

Altern Med Rev. 2009 Sep;14(3):277.

Abstract

Curcuma longa (turmeric) has a long history of use in Ayurvedic medicine as a treatment for inflammatory conditions. Turmeric constituents include the three curcuminoids: curcumin (diferuloylmethane; the primary constituent and the one responsible for its vibrant yellow color), demethoxycurcumin, and bisdemethoxycurcumin, as well as volatile oils (tumerone, atlantone, and zingiberone), sugars, proteins, and resins. While numerous pharmacological activities, including antioxidant and antimicrobial properties, have been attributed to curcumin, this article focuses on curcumin's anti-inflammatory properties and its use for inflammatory conditions. Curcumin's effect on cancer (from an anti-inflammatory perspective) will also be discussed; however, an exhaustive review of its many anticancer mechanisms is outside the scope of this article. Research has shown curcumin to be a highly pleiotropic molecule capable of interacting with numerous molecular targets involved in inflammation. Based on early cell culture and animal research, clinical trials indicate curcumin may have potential as a therapeutic agent in diseases such as inflammatory bowel disease, pancreatitis, arthritis, and chronic anterior uveitis, as well as certain types of cancer. Because of curcumin's rapid plasma clearance and conjugation, its therapeutic usefulness has been somewhat limited, leading researchers to investigate the benefits of complexing curcumin with other substances to increase systemic bioavailability. Numerous in-progress clinical trials should provide an even deeper understanding of the mechanisms and therapeutic potential of curcumin.

Int J Biochem Cell Biol. 2009 Jan;41(1):40-59. doi: 10.1016/j.biocel.2008.06.010. Epub 2008 Jul 9.

Potential therapeutic effects of curcumin, the anti-inflammatory agent, against neurodegenerative, cardiovascular, pulmonary, metabolic, autoimmune and neoplastic diseases. Aggarwal BB, Harikumar KB.

Source

Department of Experimental Therapeutics, The University of Texas M. D. Anderson Cancer Center, Houston, TX, USA. aggarwal@mdanderson.org

Abstract

Although safe in most cases, ancient treatments are ignored because neither their active component nor their molecular targets are well defined. This is not the case, however, with curcumin, a yellow-pigment substance and component of turmeric (Curcuma longa), which was identified more than a century ago. For centuries it has been known that turmeric exhibits anti-inflammatory activity, but extensive research performed within the past two decades has shown that this activity of turmeric is due to curcumin (diferuloylmethane). This agent has been shown to regulate numerous transcription factors, cytokines, protein kinases, adhesion molecules, redox status and enzymes that have been linked to inflammation. The process of inflammation has been shown to play a major role in most chronic illnesses, including neurodegenerative, cardiovascular, pulmonary, metabolic, autoimmune and neoplastic diseases. In the current review, we provide evidence for the potential role of curcumin in the prevention and treatment of various proinflammatory chronic diseases. These features, combined with the pharmacological safety and negligible cost, render curcumin an attractive agent to explore further.

Curr Drug Targets. 2011 Mar 1;12(3):332-47.

The targets of curcumin. Zhou H, Beevers CS, Huang S.

Source

Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, 1501 Kings Highway, Shreveport, LA 71130-3932, USA.

Abstract

Curcumin (diferuloylmethane), an orange-yellow component of turmeric or curry powder, is a polyphenol natural product isolated from the rhizome of the plant Curcuma longa. For centuries, curcumin has been used in some medicinal preparation or used as a food-coloring agent. In recent years, extensive in vitro and in vivo studies suggested curcumin has anticancer, antiviral, antiarthritic, anti-amyloid, antioxidant, and anti-inflammatory properties. The underlying mechanisms of these effects are diverse and appear to involve the regulation of various molecular targets, including transcription factors (such as nuclear factor-kB), growth factors (such as vascular endothelial cell growth factor), inflammatory cytokines (such as tumor necrosis factor, interleukin 1

and interleukin 6), protein kinases (such as mammalian target of rapamycin, mitogen-activated protein kinases, and Akt) and other enzymes (such as cyclooxygenase 2 and 5 lipoxygenase). Thus, due to its efficacy and regulation of multiple targets, as well as its safety for human use, curcumin has received considerable interest as a potential therapeutic agent for the prevention and/or treatment of various malignant diseases, arthritis, allergies, Alzheimer's disease, and other inflammatory illnesses. This review summarizes various in vitro and in vivo pharmacological aspects of curcumin as well as the underlying action mechanisms. The recently identified molecular targets and signaling pathways modulated by curcumin are also discussed here.

Trends Pharmacol Sci. 2009 Feb;30(2):85-94. doi: 10.1016/j.tips.2008.11.002. Epub 2008 Dec 26.

Pharmacological basis for the role of curcumin in chronic diseases: an age-old spice with modern targets. Aggarwal BB, Sung B.

Source

Cytokine Research Laboratory, Department of Experimental Therapeutics, University of Texas M. D. Anderson Cancer Center, Houston, TX 77030, USA. aggarwal@mdanderson.org

Abstract

Curcumin (diferuloylmethane), a yellow pigment in the spice turmeric (also called curry powder), has been used for centuries as a treatment for inflammatory diseases. Extensive research within the past two decades has shown that curcumin mediates its anti-inflammatory effects through the downregulation of inflammatory transcription factors (such as nuclear factor kappaB), enzymes (such as cyclooxygenase 2 and 5 lipoxygenase) and cytokines (such as tumor necrosis factor, interleukin 1 and interleukin 6). Because of the crucial role of inflammation in most chronic diseases, the potential of curcumin has been examined in neoplastic, neurological, cardiovascular, pulmonary and metabolic diseases. The pharmacodynamics and pharmacokinetics of curcumin have been examined in animals and in humans. Various pharmacological aspects of curcumin in vitro and in vivo are discussed in detail here.

Adv Exp Med Biol. 2007;595:1-75.

Curcumin: the Indian solid gold. Aggarwal BB, Sundaram C, Malani N, Ichikawa H.

Source

Department of Experimental Therapeutics, The University of Texas M.D. Anderson Cancer Center, Houston, TX 77030, USA. aggarwal@mdanderson.org

Abstract

Turmeric, derived from the plant Curcuma longa, is a gold-colored spice commonly used in the Indian subcontinent, not only for health care but also for the preservation of food and as a yellow dye for textiles. Curcumin, which gives the yellow color to turmeric, was first isolated almost two centuries ago, and its structure as diferuloylmethane was determined in 1910. Since the time of Ayurveda (1900 Bc) numerous therapeutic activities have been assigned to turmeric for a wide variety of diseases and conditions, including those of the skin, pulmonary, and gastrointestinal systems, aches, pains, wounds, sprains, and liver disorders. Extensive research within the last half century has proven that most of these activities, once associated with turmeric, are due to curcumin. Curcumin has been shown to exhibit antioxidant, anti-inflammatory, antiviral, antibacterial, antifungal, and anticancer activities and thus has a potential against various malignant diseases, diabetes, allergies, arthritis, Alzheimer's disease, and other chronic illnesses. These effects are mediated through the regulation of various transcription factors, growth factors,

inflammatory cytokines, protein kinases, and other enzymes. Curcumin exhibits activities similar to recently discovered tumor necrosis factor blockers (e.g., HUMIRA, REMICADE, and ENBREL), a vascular endothelial cell growth factor blocker (e.g., AVASTIN), human epidermal growth factor receptor blockers (e.g., ERBITUX, ERLOTINIB, and GEFTINIB), and a HER2 blocker (e.g., HERCEPTIN). Considering the recent scientific bandwagon that multitargeted therapy is better than monotargeted therapy for most diseases, curcumin can be considered an ideal "Spice for Life".

Adv Exp Med Biol. 2007;595:213-26.

Regulation of COX and LOX by curcumin. Rao CV.

Source

Hematology-Oncology Section, University of Oklahoma Cancer Institute, Oklahoma City 73104, USA. cv-rao@ouhsc.edu

Abstract

Turmeric (Curcuma longa) is extensively used as a household remedy for various diseases. For the last few decades, work has been done to establish the biological activities and pharmacological actions of curcumin, the principle constituent of turmeric. Curcumin has proven to be beneficial in the prevention and treatment of a number of inflammatory diseases due to its anti-inflammatory activity. Arachidonic acid-derived lipid mediators that are intimately involved in inflammation are biosynthesized by pathways dependent on cyclooxygenase (COX) and lipoxygenase (LOX) enzymes. The role of LOX and COX isoforms, particularly COX-2, in the inflammation has been well established. At cellular and molecular levels, curcumin has been shown to regulate a number of signaling pathways, including the eicosanoid pathway involving COX and LOX. A number of studies have been conducted that support curcumin-mediated regulation of COX and LOX pathways, which is an important mechanism by which curcumin prevents a number of disease processes, including the cancer. The specific regulation of 5-LOX and COX-2 by curcumin is not fully established; however, existing evidence indicates that curcumin regulates LOX and COX-2 predominately at the transcriptional level and, to a certain extent, the posttranslational level. Thus, the curcumin-selective transcriptional regulatory action of COX-2, and dual COX/LOX inhibitory potential of this naturally occurring agent provides distinctive advantages over synthetic COX/LOX inhibitors, such as nonsteroidal anti-inflammatory drugs. In this review, we discuss evidence that supports the regulation of COX and LOX enzymes by curcumin as the key mechanism for its beneficial effects in preventing various inflammatory diseases.

JPEN J Parenter Enteral Nutr. 2006 Jan-Feb;30(1):45-51.

Curcumin, an atoxic antioxidant and natural NFkappaB, cyclooxygenase-2, lipooxygenase, and inducible nitric oxide synthase inhibitor: a shield against acute and chronic diseases. Bengmark S.

Source

Institute of Hepatology, University College, London Medical School, London, United Kingdom. s.bengmark@ucl.ac.uk

Abstract

BACKGROUND:

The world suffers a tsunami of chronic diseases, and a typhoon of acute illnesses, many of which are associated with the inappropriate or exaggerated activation of genes involved in inflammation. Finding therapeutic agents which can modulate the inflammatory reaction is the highest priority in medical research today. Drugs developed by the pharmaceutical industry have thus far been associated with toxicity and side effects, which is why natural substances are of increasing interest.

METHODS:

A literature search (PubMed) showed almost 1500 papers dealing with curcumin, most from recent years. All available abstracts were read. Approximately 300 full papers were reviewed.

RESULTS:

Curcumin, a component of turmeric, has been shown to be non-toxic, to have antioxidant activity, and to inhibit such mediators of inflammation as NFkappaB, cyclooxygenase-2 (COX-2), lipooxygenase (LOX), and inducible nitric oxide synthase (iNOS). Significant preventive and/or curative effects have been observed in experimental animal models of a number of diseases, including arteriosclerosis, cancer, diabetes, respiratory, hepatic, pancreatic, intestinal and gastric diseases, neurodegenerative and eye diseases.

CONCLUSIONS:

Turmeric, an approved food additive, or its component curcumin, has shown surprisingly beneficial effects in experimental studies of acute and chronic diseases characterized by an exaggerated inflammatory reaction. There is ample evidence to support its clinical use, both as a prevention and a treatment. Several natural substances have greater antioxidant effects than conventional vitamins, including various polyphenols, flavonoids and curcumenoids. Natural substances are worth further exploration both experimentally and clinically.

Adv Exp Med Biol. 2007;595:105-25.

Antioxidant and anti-inflammatory properties of curcumin. Menon VP, Sudheer AR.

Source

Department of Biochemistry & Center for Micronutrient Research, Annamalai University, Tamilnadu, India. biocmr@sify.com

Abstract

Curcumin, a yellow pigment from Curcuma longa, is a major component of turmeric and is commonly used as a spice and food-coloring agent. It is also used as a cosmetic and in some medical preparations. The desirable preventive or putative therapeutic properties of curcumin have also been considered to be associated with its antioxidant and anti-inflammatory properties. Because free-radical-mediated peroxidation of membrane lipids and oxidative damage of DNA and proteins are believed to be associated with a variety of chronic pathological complications such as cancer, atherosclerosis, and neurodegenerative diseases, curcumin is thought to play a vital role against these pathological conditions. The anti-inflammatory effect of curcumin is most likely mediated through its ability to inhibit cyclooxygenase-2 (COX-2), lipoxygenase (LOX), and inducible nitric oxide synthase (iNOS). COX-2, LOX, and iNOS are important enzymes that mediate inflammatory processes. Improper upregulation of COX-2 and/or iNOS has been associated with the pathophysiology of certain types of human cancer as well as inflammatory disorders. Because inflammation is closely linked to tumor promotion, curcumin with its potent anti-inflammatory property is anticipated to exert chemopreventive effects on carcinogenesis. Hence, the past few decades have witnessed intense research devoted to the antioxidant and anti-inflammatory properties of curcumin. In this review, we describe both antioxidant and anti-inflammatory properties of curcumin, the mode of action of curcumin, and its therapeutic usage against different pathological conditions.

Carcinogenesis. 2004 Sep;25(9):1671-9. Epub 2004 Apr 8.

Modulation of arachidonic acid metabolism by curcumin and related beta-diketone derivatives: effects on cytosolic phospholipase A(2), cyclooxygenases and 5-lipoxygenase. Hong J, Bose M, Ju J, Ryu JH, Chen X, Sang S, Lee MJ, Yang CS.

Source

Susan Lehman Cullman Laboratory for Cancer Research, Department of Chemical Biology, Ernest Mario School of Pharmacy, Rutgers, The State University of New Jersey, Piscataway, NJ 08854, USA.

Abstract

Aberrant arachidonic acid metabolism is involved in the inflammatory and carcinogenic processes. In this study, we investigated the effects of curcumin, a naturally occurring chemopreventive agent, and related beta-diketone derivatives on the release of arachidonic acid and its metabolites in the murine macrophage RAW264.7 cells and in HT-29 human colon cancer cells. We also examined their effects on the catalytic activities and protein levels of related enzymes: cytosolic phospholipase A(2) (cPLA(2)), cyclooxygenases (COX) as well as 5-lipoxygenase (5-LOX). At 10 micro M, dibenzoylmethane (DBM), trimethoxydibenzoylmethane (TDM), tetrahydrocurcumin (THC) and curcumin effectively inhibited the release of arachidonic acid and its metabolites in lipopolysaccharide (LPS)-stimulated RAW cells and A23187-stimulated HT-29 cells. Inhibition of phosphorylation of cPLA(2), the activation process of this enzyme, rather than direct inhibition of cPLA(2) activity appears to be involved in the effect of curcumin. All the curcuminoids (10 micro M) potently inhibited the formation of prostaglandin E(2) (PGE(2)) in LPS-stimulated RAW cells. Curcumin (20 micro M) significantly inhibited LPS-induced COX-2 expression; this effect, rather than the catalytic inhibition of COX, may contribute to the decreased PGE(2) formation. Without LPS-stimulation, however, curcumin increased the COX-2 level in the macrophage cells. Studies with isolated ovine COX-1 and COX-2 enzymes showed that the curcuminoids had significantly higher inhibitory effects on the peroxidase activity of COX-1 than that of COX-2. Curcumin and THC potently inhibited the activity of human recombinant 5-LOX, showing estimated IC(50) values of 0.7 and 3 micro M, respectively. The results suggest that curcumin affects arachidonic acid metabolism by blocking the phosphorylation of cPLA(2), decreasing the expression of COX-2 and inhibiting the catalytic activities of 5-LOX. These activities may contribute to the anti-inflammatory and anticarcinogenic actions of curcumin and its analogs.

Mol Cancer Ther. 2006 May;5(5):1371-82.

Synthetic curcuminoids modulate the arachidonic acid metabolism of human platelet 12-lipoxygenase and reduce sprout formation of human endothelial cells. Jankun J, Aleem AM, Malgorzewicz S, Szkudlarek M, Zavodszky MI, Dewitt DL, Feig M, Selman SH, Skrzypczak-Jankun E.

Source

Urology Research Center, Medical University of Ohio, 3065 Arlington, Toledo, OH 43614-5807, USA. jerzy@meduohio.edu

Abstract

Platelet 12-lipoxygenase (P-12-LOX) is overexpressed in different types of cancers, including prostate cancer, and the level of expression is correlated with the grade of this cancer. Arachidonic acid is metabolized by 12-LOX to 12(S)-hydroxyeicosatetraenoic acid [12(S)-HETE], and this biologically active metabolite is involved in prostate cancer progression by modulating cell proliferation in multiple cancer-related pathways inducing angiogenesis and metastasis. Thus, inhibition of P-12-LOX can reduce these two

processes. Several lipoxygenase inhibitors are known, including plant and mammalian lipoxygenases, but only a few of them are known inhibitors of P-12-LOX. Curcumin is one of these lipoxygenase inhibitors. Using a homology model of the three-dimensional structure of human P-12-LOX, we did computational docking of synthetic curcuminoids (curcumin derivatives) to identify inhibitors superior to curcumin. Docking of the known inhibitors curcumin and NDGA to P-12-LOX was used to optimize the docking protocol for the system in study. Over 75% of the compounds of interest were successfully docked into the active site of P-12-LOX, many of them sharing similar binding modes. Curcuminoids that did not dock into the active site did not inhibit P-12-LOX. From a set of the curcuminoids that were successfully docked and selected for testing, two were found to inhibit human lipoxygenase better than curcumin. False-positive curcuminoids showed high LogP (theoretical) values, indicating poor water solubility, a possible reason for lack of inhibitory activity or/and nonrealistic binding. Additionally, the curcuminoids inhibiting P-12-LOX were tested for their ability to reduce sprout formation of endothelial cells (in vitro model of angiogenesis). We found that only curcuminoids inhibiting human P-12-LOX and the known inhibitor NDGA reduced sprout formation. Only limited inhibition of sprout formation at approximately IC(50) concentrations has been seen. At IC(50), a substantial amount of 12-HETE can be produced by lipoxygenase, providing a stimulus for angiogenic sprouting of endothelial cells. Increasing the concentration of lipoxygenase inhibitors above IC(50), thus decreasing the concentration of 12(S)-HETE produced, greatly reduced sprout formation for all inhibitors tested. This universal event for all tested lipoxygenase inhibitors suggests that the inhibition of sprout formation was most likely due to the inhibition of human P-12-LOX but not other cancer-related pathways.

Biofactors. 2013 Jan-Feb;39(1):69-77. doi: 10.1002/biof.1066. Epub 2012 Dec 22.

Curcumin in inflammatory diseases. Shehzad A, Rehman G, Lee YS.

Source

School of Life Sciences, College of Natural Sciences, Kyungpook National University, Daegu 702-701, Korea.

Abstract

Curcumin (diferuloylmethane), a yellow coloring agent extracted from turmeric is also used as a remedy for the treatment and prevention of inflammatory diseases. Acute and chronic inflammation is a major factor in the progression of obesity, type II diabetes, arthritis, pancreatitis, cardiovascular, neurodegenerative and metabolic diseases, as well as certain types of cancer. Turmeric has a long history of use in Ayurvedic medicine for the treatment of inflammatory disorders. Recent studies on the efficacy and therapeutic applicability of turmeric have suggested that the active ingredient of tumeric is curcumin. Further, compelling evidence has shown that curcumin has the ability to inhibit inflammatory cell proliferation, invasion, and angiogenesis through multiple molecular targets and mechanisms of action. Curcumin is safe, non-toxic, and mediates its anti-inflammatory effects through the down-regulation of inflammatory transcription factors, cytokines, redox status, protein kinases, and enzymes that all promote inflammation. In addition, curcumin induces apoptosis through mitochondrial and receptor-mediated pathways, as well as activation of caspase cascades. In the current study, the anti-inflammatory effects of curcumin were evaluated relative to various chronic inflammatory diseases. Based on the available pharmacological data obtained from in vitro and in vivo research, as well as clinical trials, an opportunity exists to translate curcumin into clinics for the prevention of inflammatory diseases in the near future.

Biofactors. 2013 Jan-Feb;39(1):78-87. doi: 10.1002/biof.1074. Epub 2013 Jan 22.

Curcumin and obesity. Bradford PG.

Source

Department of Pharmacology and Toxicology, School of Medicine and Biomedical Sciences, State University of New York at Buffalo, Buffalo, NY 14214-3000, USA. pgb@buffalo.edu

Abstract

Turmeric has been long recognized for its anti-inflammatory and health-promoting properties. Curcumin is one of the principal anti-inflammatory and healthful components of turmeric comprising 2-8% of most turmeric preparations. Experimental evidence supports the activity of curcumin in promoting weight loss and reducing the incidence of obesity-related diseases. With the discovery that obesity is characterized by chronic low-grade metabolic inflammation, phytochemicals like curcumin which have anti-inflammatory activity are being intensely investigated. Recent scientific research reveals that curcumin directly interacts with white adipose tissue to suppress chronic inflammation. In adipose tissue, curcumin inhibits macrophage infiltration and nuclear factor B (NF-B) activation induced by inflammatory agents. Curcumin reduces the expression of the potent proinflammatory adipokines tumor necrosis factor- (TNF), monocyte chemoattractant protein-1 (MCP-1), and plasminogen activator inhibitor type-1 (PAI-1), and it induces the expression of adiponectin, the principal anti-inflammatory agent secreted by adipocytes. Curcumin also has effects to inhibit adipocyte differentiation and to promote antioxidant activities. Through these diverse mechanisms curcumin reduces obesity and curtails the adverse health effects of obesity.

Eur Cytokine Netw. 2006 Mar;17(1):4-12.

Recent advances in the relationship between obesity, inflammation, and insulin resistance. Bastard JP, Maachi M, Lagathu C, Kim MJ, Caron M, Vidal H, Capeau J, Feve B.

Source

Inserm U680, Facult de Mdecine Pierre et Marie Curie, site Saint-Antoine, Universit Pierre et Marie Curie, Paris 6 et Service de Biochimie et Hormonologie, Hpital Tenon, AP-HP, 75970 Paris cedex 20, France. jean-philippe.bastard@tnn.ap-hop-paris.fr

Abstract

It now appears that, in most obese patients, obesity is associated with a low-grade inflammation of white adipose tissue (WAT) resulting from chronic activation of the innate immune system and which can subsequently lead to insulin resistance, impaired glucose tolerance and even diabetes. WAT is the physiological site of energy storage as lipids. In addition, it has been more recently recognized as an active participant in numerous physiological and pathophysiological processes. In obesity, WAT is characterized by an increased production and secretion of a wide range of inflammatory molecules including TNF-alpha and interleukin-6 (IL-6), which may have local effects on WAT physiology but also systemic effects on other organs. Recent data indicate that obese WAT is infiltrated by macrophages, which may be a major source of locally-produced pro-inflammatory cytokines. Interestingly, weight loss is associated with a reduction in the macrophage infiltration of WAT and an improvement of the inflammatory profile of gene expression. Several factors derived not only from adipocytes but also from infiltrated macrophages probably contribute to the pathogenesis of insulin resistance. Most of them are overproduced during obesity, including leptin, TNF-alpha, IL-6 and resistin. Conversely, expression and plasma levels of adiponectin, an insulin-sensitising effector, are down-regulated during obesity. Leptin could modulate TNF-alpha production and macrophage activation. TNF-alpha is overproduced in adipose tissue of several rodent models of obesity and has an important role in the pathogenesis of insulin resistance in these species. However, its actual involvement in glucose metabolism disorders in humans remains controversial. IL-6 production by human adipose tissue increases during obesity. It may induce hepatic CRP synthesis and may promote the onset of cardiovascular complications. Both TNF-alpha and IL-6 can alter insulin sensitivity by triggering different key steps in the insulin signalling pathway. In rodents, resistin can induce insulin resistance, while its implication in the control of insulin sensitivity is still a matter of debate in humans. Adiponectin is highly expressed in WAT, and circulating adiponectin levels are decreased in subjects with obesity-related insulin resistance, type 2 diabetes and coronary heart disease. Adiponectin inhibits liver neoglucogenesis and promotes fatty acid oxidation in skeletal muscle. In addition, adiponectin counteracts the pro-inflammatory effects of TNF-alpha on the arterial wall and probably protects against the development of arteriosclerosis. In obesity, the pro-inflammatory effects of cytokines through intracellular signalling pathways involve the NF-kappaB and JNK systems. Genetic or pharmacological manipulations of these effectors of the inflammatory response have been shown to modulate insulin sensitivity in different animal models. In humans, it has been suggested that

the improved glucose tolerance observed in the presence of thiazolidinediones or statins is likely related to their anti-inflammatory properties. Thus, it can be considered that obesity corresponds to a sub-clinical inflammatory condition that promotes the production of pro-inflammatory factors involved in the pathogenesis of insulin resistance.