Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0028754 (obesity)
 124,988 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Macrophage migration inhibitory factor (MIF) has been rediscovered as a proinflammatory cytokine, pituitary hormone, and glucocorticoid-induced immunoregulator. A survey of tissue distribution revealed that MIF expression is not limited to T lymphocytes, but exists in several other tissues; however, its presence in adipose tissue has never been investigated. In this study, we examined the expression of MIF in adipose tissue using the rat epididymal fat pad and murine 3T3-L1 adipocytes. Northern and Western blot analyses revealed the expression of MIF mRNA and MIF protein, respectively, in both the fat pad and the adipocyte cell line. In immunohistochemistry, a positive staining reaction with an anti-rat MIF antibody was detected largely in the cytosol of adipocytes of the epididymal fat pad. To examine the production and release of MIF by adipocytes, we examined its content in the culture medium of the 3T3-L1 adipocytes. The results showed that MIF content was 1.6 +/- 0.48 ng/ml (mean +/- SD) after 24 hr culture, and the content was increased up to 9.7 +/- 2.8 ng/ml by stimulation with TNF-alpha (50 nM). Since TNF-alpha produced in adipocytes is known to induce insulin resistance, the results suggest the possibility that MIF plays an important role in the mechanism of insulin resistance often observed in obesity and diabetes via regulation of TNF-alpha expression.
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PMID:Identification of macrophage migration inhibitory factor in adipose tissue and its induction by tumor necrosis factor-alpha. 919 42

Macrophage migration inhibitory factor (MIF) has been rediscovered as a proinflammatory cytokine, pituitary hormone, and glucocorticoid-induced immunoregulator. We have recently identified the expression of MIF in adipocytes and found that tumor necrosis factor (TNF)-alpha stimulates its secretion from 3T3-L1 adipocytes. Since adipocytes are regarded as a potential source of various biologically active substances, we examined in more detail the effect of TNF-alpha on MIF expression in 3T3-L1 adipocytes in the present study. We found that TNF-alpha induced MIF mRNA in dose- and time-dependent manners. After stimulation with TNF-alpha, the amount of intracellular MIF protein was unchanged or slightly decreased, concomitant with increased release of this protein into the extracellular space. This observation indicates that TNF-alpha stimulates MIF secretion from the constitutively expressed intracellular pool of 3T3-L1 adipocytes and promotes de novo synthesis of MIF. From evaluation of the mechanism of MIF gene expression, we found that tyrosine kinase inhibitors, either genistein or herbimycin A, suppressed the MIF mRNA induction by TNF-alpha. The results suggest the possibility that upregulation of MIF mRNA expression by TNF-alpha is mediated by a tyrosine kinase-dependent pathway. Taken together, the present observations shed light on the role of MIF in the metabolism of obesity and diabetes.
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PMID:Tumor necrosis factor-alpha regulates the gene expression of macrophage migration inhibitory factor through tyrosine kinase-dependent pathway in 3T3-L1 adipocytes. 953 68

Macrophage migration inhibitory factor (MIF) was the first T-cell-derived soluble lymphokine to be identified. It was originally found to inhibit the migration of macrophages and activate them at inflammatory loci. During the past few years, however, previously unrecognized properties of MIF have been discovered. It also functions, for example, as a pituitary hormone, glucocorticoid-induced immunomodulator and isomerase. We cloned rat MIF cDNA and reported that the nucleotide sequence of the cDNA predicts a protein consisting of 114 amino acids. Northern blot analysis indicated that the MIF mRNA was expressed in a wide variety of organs, including the brain, kidney, and liver. Following this, we demonstrated definitively that MIF was expressed in a variety of cells, suggesting its involvement in various biological events such as wound healing, atopic dermatitis, and, possibly, diabetes/obesity. Furthermore, we elucidated its physicochemical properties, including the tertiary structures of both human and rat MIF. These tertiary structures showed that this protein forms a homotrimer with each monomer consisting of two beta/alpha/beta motifs, thus resembling 5-carboxymethyl-2-hydroxymuconate isomerase and d-dopachrome tautomerase. From the available data on MIF, including ours, it is considered that the protein is associated not only with immune responses but also with cell growth and differentiation during wound repair and carcinogenesis. Thus, MIF could become a major target protein in a variety of pathophysiological states and anti-MIF antibodies and antagonists could be applied therapeutically in the clinical situation for treatment of various diseases. Bearing this in mind, this review discusses the role of MIF, considering its gene and protein structures as well as its pathophysiological functions in various organs and disease states, finally considering perspectives for the future.
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PMID:Novel pathophysiological aspects of macrophage migration inhibitory factor (review). 985 38

GLUT-4 (glucose transporter) receptor, tumor necrosis factor-alpha (TNF-alpha), interleukins-6 (IL-6), daf-genes and PPARs (peroxisomal proliferation activator receptors) play a role in the development of insulin resistance syndrome and associated conditions. But, the exact interaction between these molecules/factors and the mechanism(s) by which they produce insulin resistance syndrome is not clear. I propose that a defect in the activity of the enzymes Delta6 and Delta5 desaturases that are essential for the formation of long chain metabolites of essential fatty acids, linoleic acid and alpha-linolenic acid, is a factor in the development of insulin resistance syndrome. Long chain polyunsaturated fatty acids (LCPUFAs) increase cell membrane fluidity and enhance the number of insulin receptors and the affinity of insulin to its receptors; suppress TNF-alpha, IL-6, macrophage migration inhibitory factor (MIF) and leptin synthesis; increase the number of GLUT-4 receptors, serve as endogenous ligands of PPARs, modify lipolysis, and regulate the balance between pro- and anti-oxidants, and thus, play a critical role in the pathogenesis of insulin resistance. In the nematode, Caenorhabditis elegans, the protein encoded by daf-2 is 35% identical to the human insulin receptor; daf-7 codes a transforming growth factor-beta (TGF-beta) type signal and daf-16 enhances superoxide dismutase (SOD) expression. Melatonin has anti-oxidant actions similar to daf-16, TGF-beta and SOD. Calorie restriction enhances the activity of Delta6 and Delta5 desaturases, melatonin production, decreases daf-2 signaling, free radical generation, and augments anti-oxidant defenses that may explain the beneficial effect of diet control in the management of obesity, insulin resistance, and type II diabetes mellitus. These evidences suggest that the activities of Delta6 and Delta5 enzymes play a critical role in the expression and regulation of GLUT-4, TNF-alpha, IL-6, MIF, daf-genes, melatonin, and leptin by modulating the synthesis and tissue concentrations of LCPUFAs. Caloric restriction delays ageing by activating Sir 2 deacetylase in yeast, and expression of Sir 2 (SIRT1) in human cells. Both insulin and insulin-like growth factor-1 (IGF-1) attenuated this response. SIRT1 sequesters the proapoptotic factor Bax, prevents stress-induced apoptosis of cells, and thus, prolongs survival. In addition, SIRT1 repressed PPAR-gamma, and overexpression of SIRT1 attenuated adipogenesis, and upregulation of SIRT in differentiated fat cells triggered lipolysis and loss of fat, events that are known to attenuate insulin resistance and prolong life span. It remains to be seen whether LCPUFAs have a regulatory role in SIRT1 expression and control Sir 2 deacetylase activity. Thus, calorie restriction or reduced food intake has a role not only in the pathobiology of insulin resistance, but also in other associated conditions such as obesity, type II diabetes mellitus, ageing, and longevity.
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PMID:A defect in the activity of Delta6 and Delta5 desaturases may be a factor predisposing to the development of insulin resistance syndrome. 1585 Jul 15

White adipose tissue (WAT) is now recognized as a major endocrine and secretory organ, releasing a wide range of protein factors and signals termed adipokines - in addition to fatty acids and other lipid moieties. A paradigm shift came with the discovery of leptin, a pleiotropic hormone which is a critical signal to the hypothalamus in the control of appetite and energy balance. A number of adipokines, including adiponectin, tumour necrosis factor-alpha, interleukin (IL)-1beta, IL-6, IL-8, IL-10, monocyte chemoattractant protein-1, macrophage migration inhibitory factor, nerve growth factor, vascular endothelial growth factor, plasminogen activator inhibitor-1 and haptoglobin, are linked to inflammation and the inflammatory response. Obesity is characterized by a state of mild inflammation, and the expression and release of inflammation-related adipokines generally rises as adipose tissue expands; a notable exception is adiponectin, with its anti-inflammatory action, the levels of which fall. WAT may be the main site of inflammation in obesity, increased circulating levels of inflammatory markers reflecting spillover from an 'inflamed' tissue, leading to the obesity-associated pathologies of type 2 diabetes and the metabolic syndrome. From the wide range of adipokines now identified, it is evident that WAT is highly integrated into overall physiological regulation, involving extensive crosstalk with other organs and multiple metabolic systems. Whether major changes in adipokine production in obesity, particularly of those factors linked to inflammation, are unique to this condition, or are a feature of all situations in which there are substantial increases in adipose mass (such as pregnancy, and pre-hibernatory and pre-migratory fattening) requires consideration.
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PMID:Endocrine and signalling role of adipose tissue: new perspectives on fat. 1602 20

White adipose tissue (WAT) is a major endocrine and secretory organ, which releases a wide range of protein signals and factors termed adipokines. A number of adipokines, including leptin, adiponectin, tumour necrosis factor alpha, IL-1beta (interleukin 1beta), IL-6, monocyte chemotactic protein-1, macrophage migration inhibitory factor, nerve growth factor, vascular endothelial growth factor, plasminogen activator inhibitor 1 and haptoglobin, are linked to inflammation and the inflammatory response. Obesity is characterized by a state of chronic mild inflammation, with raised circulating levels of inflammatory markers and the expression and release of inflammation-related adipokines generally rises as adipose tissue expands (adiponectin, which has anti-inflammatory action is an exception). The elevated production of inflammation-related adipokines is increasingly considered to be important in the development of diseases linked to obesity, particularly Type II diabetes and the metabolic syndrome. WAT is involved in extensive cross-talk with other organs and multiple metabolic systems through the various adipokines.
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PMID:Signalling role of adipose tissue: adipokines and inflammation in obesity. 1624 49

The white adipose tissue, especially of humans, is now recognized as the central player in the mild inflammatory state that is characteristic of obesity. The question is how the increased accumulation of lipid seen in obesity causes an inflammatory state and how this is linked to the hypertension and type 2 diabetes that accompanies obesity. Once it was thought that adipose tissue was primarily a reservoir for excess calories that were stored in the adipocytes as triacylglycerols. In times of caloric deprivation these stored lipids were mobilized as free fatty acids and the insulin resistance of obesity was attributed to free fatty acids. It is now clear that in humans the expansion of adipose tissue seen in obesity results in more blood vessels, more connective tissue fibroblasts, and especially more macrophages. There is an enhanced secretion of some interleukins and inflammatory cytokines in adipose tissue of the obese as well as increased circulating levels of many cytokines. The central theme of this chapter is that human adipose tissue is a potent source of inflammatory interleukins plus other cytokines and that the majority of this release is due to the nonfat cells in the adipose tissue except for leptin and adiponectin that are primarily secreted by adipocytes. Human adipocytes secrete at least as much plasminogen activator inhibitor-1 (PAI-1), MCP-1, interleukin-8 (IL-8), and IL-6 in vitro as they do leptin but the nonfat cells of adipose tissue secrete even more of these proteins. The secretion of leptin, on the other hand, by the nonfat cells is negligible. The amount of serum amyloid A proteins 1 & 2 (SAA 1 & 2), haptoglobin, nerve growth factor (NGF), macrophage migration inhibitory factor (MIF), and PAI-1 secreted by the adipocytes derived from a gram of adipose tissue is 144%, 75%, 72%, 37%, and 23%, respectively, of that by the nonfat cells derived from the same amount of human adipose tissue. However, the release of IL-8, MCP-1, vascular endothelial growth factor (VEGF), TGF-beta1, IL-6, PGE(2), TNF-alpha, cathepsin S, hepatocyte growth factor (HGF), IL-1beta, IL-10, resistin, C-reactive protein (CRP), and interleukin-1 receptor antagonist (IL-1Ra) by adipocytes is less than 12% of that by the nonfat cells present in human adipose tissue. Obesity markedly elevates the total release of TNF-alpha, IL-6, and IL-8 by adipose tissue but only that of TNF-alpha is enhanced in adipocytes. However, on a quantitative basis the vast majority of the TNF-alpha comes from the nonfat cells. Visceral adipose tissue also releases more VEGF, resistin, IL-6, PAI-1, TGF-beta1, IL-8, and IL-10 per gram of tissue than does abdominal subcutaneous adipose tissue. In conclusion, there is an increasing recognition that adipose tissue is an endocrine organ that secretes leptin and adiponectin along with a host of other paracrine and endocrine factors in addition to free fatty acids.
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PMID:Release of interleukins and other inflammatory cytokines by human adipose tissue is enhanced in obesity and primarily due to the nonfat cells. 1702 26

Plasma levels of C-reactive protein, interleukin-6, tumor necrosis factor-alpha, and lipid peroxides are high whereas those of endothelial nitric oxide are low in insulin resistance, obesity, type 2 diabetes mellitus, hypertension, hyperlipidemias, metabolic syndrome X, and Alzheimer's disease suggesting that these diseases are characterized by low-grade systemic inflammation. Recent studies showed that the plasma and tissue activities of enzymes butyrylcholinesterase and acetylcholinesterase are elevated in patients with Alzheimer's disease, and diabetes mellitus, hypertension, insulin resistance, and hyperlipidemia. As a result of this increase in the activities of enzymes acetylcholinesterase and butyrylcholinesterase, the plasma and tissue levels of acetylcholine (ACh) will be low. The "cholinergic anti-inflammatory pathway" mediated by acetylcholine acts by inhibiting the production of tumor necrosis factor, interleukin-1, macrophage migration inhibitory factor, and high mobility group box-1 and suppresses the activation of nuclear factor-kappa B expression. ACh is a neurotransmitter and regulates the levels and activities of serotonin, dopamine and other neuropeptides and thus, modulates both immune response and neurotransmission. Hence, both acetylcholinesterase and butyrylcholinesterase by inactivating acetylcholine may enhance inflammation. This suggests that increased plasma and tissue activities of acetylcholinesterase and butyrylcholinesterase seen in various clinical conditions could serve as a marker of low-grade systemic inflammation.
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PMID:Acetylcholinesterase and butyrylcholinesterase as possible markers of low-grade systemic inflammation. 1804 45

White adipose tissue is a key endocrine and secretory organ, releasing multiple adipokines, many of which are linked to inflammation and immunity. During the expansion of adipose tissue mass in obesity there is a major inflammatory response in the tissue with increased expression and release of inflammation-related adipokines, including IL-6, leptin, monocyte chemoattractant protein-1 and TNF-alpha, together with decreased adiponectin production. We proposed in 2004 (Trayhurn & Wood, Br J Nutr 92, 347-355) that inflammation in adipose tissue in obesity is a response to hypoxia in enlarged adipocytes distant from the vasculature. Hypoxia has now been directly demonstrated in adipose tissue of several obese mouse models (ob/ob, KKAy, diet-induced) and molecular studies indicate that the level of the hypoxia-inducible transcription factor, hypoxia-inducible factor-1 alpha, is increased, as is expression of the hypoxia-sensitive marker gene, GLUT1. Cell- culture studies on murine and human adipocytes show that hypoxia (induced by low O2 or chemically) leads to stimulation of the expression and secretion of a number of inflammation-related adipokines, including angiopoietin-like protein 4, IL-6, leptin, macrophage migration inhibitory factor and vascular endothelial growth factor. Hypoxia also stimulates the inflammatory response of macrophages and inhibits adipocyte differentiation from preadipocytes. GLUT1 gene expression, protein level and glucose transport by human adipocytes are markedly increased by hypoxia, indicating that low O2 tension stimulates glucose utilisation. It is suggested that hypoxia has a pervasive effect on adipocyte metabolism and on overall adipose tissue function, underpinning the inflammatory response in the tissue in obesity and the subsequent development of obesity-associated diseases, particularly type 2 diabetes and the metabolic syndrome.
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PMID:Hypoxia in adipose tissue: a basis for the dysregulation of tissue function in obesity? 1838 4

Obesity is a condition in which adipose tissue mass is expanded. Increases in both adipocyte size and number contribute to enlargement of adipose tissue. The increase in cell number is thought to be caused by proliferation and differentiation of preadipocytes. Macrophage migration inhibitory factor (MIF) is expressed in adipocytes, and intracellular MIF content is increased during adipogenesis. Therefore, we hypothesized that MIF is associated with adipocyte biology during adipogenesis and focused on the influence of MIF on adipogenesis. To examine the effects of MIF on adipocytes, MIF expression in 3T3-L1 preadipocytes was inhibited by RNA interference, and cell differentiation was induced by standard procedures. The triglyceride content of MIF small interfering RNA (siRNA)-transfected 3T3-L1 cells was smaller than that of nonspecific siRNA-transfected cells. In addition, MIF knockdown apparently abrogated increases in adiponectin mRNA levels during differentiation. Gene expression of peroxisome proliferator-activated receptor (PPAR)gamma, CCAAT/enhancer binding protein (C/EBP)alpha, and C/EBPdelta decreased with MIF siRNA transfection, but C/EBPbeta expression increased. Cell number and incorporation of 5-bromo-2-deoxyuridine into cells decreased from 1-3 d and from 14-20 h, respectively, after induction of differentiation in MIF siRNA-transfected cells, thus suggesting that MIF siRNA inhibits mitotic clonal expansion. Taken together, these results indicated that MIF regulates differentiation of 3T3-L1 preadipocytes, at least partially, through inhibition of mitotic clonal expansion and/or C/EBPdelta expression.
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PMID:Knockdown of macrophage migration inhibitory factor disrupts adipogenesis in 3T3-L1 cells. 1870 34


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