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)

Tumour necrosis factor-alpha (TNF) is a pleiotropic cytokine involved in many metabolic responses in both normal and pathophysiological states. In spite of the fact that this cytokine (also known as "cachectin") has been related to many of the metabolic abnormalities associated with cachexia, recent studies suggest that TNF may also have a central role in obesity modulating energy expenditure, fat deposition and insulin resistance. This review deals with the role of TNF in the control of fat mass and obesity.
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PMID:Tumour necrosis factor, a key role in obesity? 1037 Nov 92

Tumour necrosis factor-alpha (TNF-alpha) plays a key role in orchestrating the complex events involved in inflammation and immunity. Accordingly, TNF-alpha has been implicated in a wide range of autoimmune and infectious diseases, but also in conditions such as obesity and insulin resistance. The regulation of TNF-alpha expression in man is indicated to be partly genetically determined. We therefore screened a 1263 bp section of the proximal promoter of the TNF-alpha gene for common genetic variants affecting the transcriptional activity of the gene. Here we report the characterization of a common functional polymorphism in the promoter region of the TNF-alpha gene, a C-->A substitution at position -863. Electromobility shift assays provided evidence for a distinct difference in the binding of monocytic and hepatic nuclear factors to the -863C and -863A alleles. The rare -863A allele was associated with 31% lower transcriptional activity ( P < 0.001) in chloramphenicol acetyltransferase (CAT) reporter gene studies in human hepatoblastoma (HepG2) cells, indicating that the-863C/A polymorphism influences the basal rate of transcription of the TNF-alpha gene in vitro. Allele frequencies were 0.83/0.17 amongst 254 apparently healthy men of Swedish origin, aged 35-50 years. In 156 men, the -863C/A polymorphism was associated with the serum TNF-alpha concentration, carriers of the rare A allele having a significantly lower TNF-alpha level ( P < 0.05). It is concluded that the common-863C/A polymorphism in the promoter region of the TNF-alpha gene is functional in vitro in monocytic and hepatic cells and influences the serum TNF-alpha concentration in vivo in healthy middle-aged men.
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PMID:A common functional polymorphism (C-->A substitution at position -863) in the promoter region of the tumour necrosis factor-alpha (TNF-alpha) gene associated with reduced circulating levels of TNF-alpha. 1040 Sep 91

1. Insulin resistance has been highlighted as a common causal factor for hypertension, hyperlipidaemia, diabetes mellitus and obesity, all of which are recognized to occur simultaneously, and a distinct clinical entity is defined as 'multiple risk factor syndrome'. 2. Recently, a new class of antidiabetic agents, thiazolidinediones (TZD) has been developed and has been shown to improve insulin resistance by binding and activating a nuclear receptor, peroxisome proliferator-activated receptor (PPAR) gamma. 3. cDNA of rat PPAR gamma 1 and gamma 2 were cloned and gene regulation of PPAR gamma in rat mature adipocytes was examined. Hydrogen peroxide, an oxygen radical, which is recognized to be the common intracellular signal for multiple risk factors, potently down-regulated PPAR gamma mRNA expression in rat mature adipocytes. 4. Tumour necrosis factor (TNF)-alpha, which is considered to play a role in obesity-induced non-insulin-dependent diabetes mellitus and to augment oxidative stress, also suppressed PPAR gamma expression. 5. Thiazolidinediones dose-dependently recovered TNF-alpha-induced down-regulation of PPAR gamma mRNA expression. 6. The modulation of PPAR gamma expression by TZD can be one mechanism for the improvement of insulin resistance by TZD. 7. Vascular tone and remodelling are controlled by several vasoactive autocrine/paracrine factors produced by endothelial cells in response to several vascular injury stimuli, including hypertension. The PPAR gamma gene transcript was detected in cultured endothelial cells. 8. The administration of TZD stimulated the endothelial secretion of type-C natriuretic peptide, which is one of the natriuretic peptide family and is demonstrated by us to act as a novel endothelium-derived relaxing peptide. 9. Concomitantly, TZD significantly suppressed the secretion of endothelin, a potent endothelium-derived vasoconstricting peptide. 10. Thiazolidinediones can affect vascular tone and growth by modulating the production of endothelium-derived vasoactive substances to influence occurrence and progression of hypertension and atherosclerosis.
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PMID:Hypertension and insulin resistance: role of peroxisome proliferator-activated receptor gamma. 1040 88

Tumour necrosis factor-alpha (TNF-alpha), secreted by cells of the macrophage-monocyte lineage, has a well established role in inflammation and host-defence. The more recent discovery that adipocytes also secrete TNF-alpha has led to a substantial body of research implicating this molecule in the insulin resistance of obesity. However, little is known about the normal regulation of TNF-alpha release from human adipose tissue. In particular, it is not known whether adipocyte production of TNF-alpha is responsive to similar or different molecular regulators than those relevant to macrophages. TNF-alpha release from cultured human adipose tissue and isolated adipocytes was examined using an ELISA. Insulin, cortisol or the thiazolidinedione, BRL 49653, did not have a significant effect on TNF-alpha release from adipose tissue or isolated adipocytes. In contrast, lipopolysaccharide (LPS), a major stimulus of TNF-alpha protein production in monocytes and macrophages, resulted in a fivefold stimulation of TNF-alpha release from human adipose tissue. Significant stimulation of TNF-alpha release was also seen from isolated adipocytes, indicating that the increase in TNF-alpha release from adipose tissue in the presence of LPS is unlikely to be entirely attributable to contaminating monocytes or macrophages. Consistent with this observation was the finding that mRNA for CD14, a known cellular receptor for LPS, is expressed in human adipocytes. The increase in TNF-alpha protein release in response to LPS was blocked by an inhibitor of the matrix metalloproteinase responsible for the cleavage of the membrane-bound proform of TNF-alpha, indicating that this release represented regulated secretion and was not due to cell lysis. In conclusion, the regulation of TNF-alpha protein release from human adipose tissue and isolated adipocytes appears to be similar to its regulation in cell types more traditionally implicated in host defence. The production by the adipocyte of a range of molecules involved in host defence-TNF-alpha, factors D, B and C3, interleukin-6, and macrophage colony-stimulating factor--suggest that this cell type may make a significant contribution to innate immunity.
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PMID:Regulation of tumour necrosis factor-alpha release from human adipose tissue in vitro. 1049 4

Visceral fat accumulation often accompanies various complications, such as insulin resistance, hypertension, dyslipidemia and atherosclerosis. Adipose tissue has been found to secrete various biologically active adipocytokines including free fatty acids. Accumulation of visceral fat increases the portal free fatty acids concentration to cause insulin resistance and dyslipidemia. Tumor necrosis alpha (TNF alpha) deteriorates insulin resistance in obesity. The levels of plasminogen activator inhibitor(PAI)-1 increase and plasma adiponectin concentration decreases in obesity leading to the development of vascular disease. The finding of genes specifically expressed in visceral fat and new adipocytokines should facilitate clarification of the mechanism for the development and complications of visceral fat accumulation.
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PMID:[Molecular mechanism in the development of the complications associated with obesity--the physiological and pathological role of adipocytokines]. 1126 96

Tumour necrosis factor alpha (TNF-alpha), acting as a modulator of gene expression in adipocytes, has been linked to the development of insulin resistance and obesity. The aim of this study was to investigate whether the A/G variation at position -308 in the TNF-alpha promoter influences the body weight, insulin resistance, and postprandial lipaemia in Polish Caucasians. One hundred twenty one subjects, 38 men and 83 women, representing 40 obese families, were genotyped by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). TNF-1 (GG) and TNF-2 (GA and AA) allele carriers were compared with respect to body mass index, fat/lean body mass composition, waist-to-hip ratio, as well as fasting lipids, glucose, leptin, and insulin fasting, and during the oral glucose tolerance test (4 points within 2 hours) and oral lipid tolerance test (OLTT; 5 points within 8 hours). The insulin sensitivity indices HOMA-IR (homeostasis model assessment of insulin resistance), ISI-COMP (whole body insulin sensitivity index), ISI-HOMA (hepatic insulin sensitivity), and DELTA (early secretory response to an oral glucose load) were calculated. We detected 64 GG, 56 GA, and 1 AA genotypes. Significant increases of insulin resistance parameters in obese female TNF-2 allele carriers were observed (significantly increased HOMA-IR and decreased ISI-HOMA, ISI-composite). The male TNF-2 carriers were characterised by significantly increased levels of triglyceride and free fatty acids during OLTT as well as fasting glucose. The A/G variation at position -308 in the promoter region of the TNF-alpha gene could be an important genetic factor predisposing to insulin resistance in obese women and increased levels of glucose, triglyceride, and free fatty acids in men.
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PMID:The TNF-alpha gene NcoI polymorphism at position -308 of the promoter influences insulin resistance, and increases serum triglycerides after postprandial lipaemia in familiar obesity. 1274 94

Adipocytes have recently been shown to secrete a variety of bioactive substances called 'adipocytokines', and have been recognized as endocrine cells. Tumour necrosis factor (TNF)-alphaalpha, plasminogen activator inhibitor-1 (PAI-1) and heparin-binding epidermal-growth-factor-like growth factor (HBEGF) are among these adipocytokines, and they contribute to the development of vascular diseases. Visfatin is a visceral fat-specific protein that may be related to the development of obesity-related diseases such as diabetes mellitus and cardiovascular disease. In contrast, adiponectin, an adipose-tissue-specific collagen-like protein, has recently been reported as an important anti-atherogenic and anti-diabetic protein. Adipocytokine secretion may be regulated dynamically by the nutritional state. Visceral fat accumulation leads to dysfunction of adipocytes (including hypersecretion of TNF-alphaalpha, PAI-1 and HBEGF, and hyposecretion of adiponectin), which results in the development of a variety of metabolic and circulatory diseases. In this review, the importance of adipocytokines, including adiponectin, is discussed with respect to cardiovascular disease.
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PMID:White adipose tissue and cardiovascular disease. 1631 Dec 22

Tumour necrosis factor (TNF)alpha is implicated in the relationship between obesity and insulin resistance/ type 2 diabetes. In an effort to understand this association better we (i) profiled gene expression patterns of TNF, TNFR1 and TNFR2 and (ii) investigated the effects of TNF on glucose uptake in isolated adipocytes and adipose tissue explants from omental and subcutaneous depots from lean, overweight and obese individuals. TNF expression correlated with expression of TNFR2, but not TNFR1, and TNF and TNFR2 expression increased in obesity. TNFR1 expression was higher in omental than in subcutaneous adipocytes. Expression levels of TNF or either receptor did not differ between adipocytes from individuals with central and peripheral obesity. TNF only suppressed glucose uptake in insulin-stimulated subcutaneous tissue and this suppression was only observed in tissue from lean subjects. These data support a relationship between the TNF system and body mass index (BMI), but not fat distribution, and suggest depot specificity of the TNF effect on glucose uptake. Furthermore, adipose tissue from obese subjects already appears insulin 'resistant' and this may be a result of the increased TNF levels.
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PMID:TNF and TNF receptor expression and insulin sensitivity in human omental and subcutaneous adipose tissue--influence of BMI and adipose distribution. 1678 78

Tumour necrosis factor alpha (TNFalpha) is a pro-inflammatory cytokine which has been closely linked to obesity and insulin resistance. We present two cases of patients with rheumatoid arthritis (RA) and concomitant diabetes mellitus, who showed a marked decrease of fructosamine levels after initiating therapy with adalimumab, a TNFalpha-blocking agent, for active RA. This finding may implicate that TNFalpha blockade causes better glycaemic control in RA patients with concomitant diabetes, possibly by improving insulin resistance.
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PMID:Decrease of fructosamine levels during treatment with adalimumab in patients with both diabetes and rheumatoid arthritis. 1732 87

Tumour necrosis factor alpha (TNFalpha) induces platelet-activating factor (PAF) synthesis in many inflammatory cells. Here, we investigate the possibility that TNFalpha stimulates PAF synthesis in rat adipocytes and preadipocytes and that phosphoinositide 3-kinase (PI3K) and extracellular signal-regulated kinase 1/2 (ERK1/2) are implicated in this process. Primary cultures were incubated with [3H]lyso-PAF and stimulated by TNFalpha in the presence or absence of wortmannin. We found that, although both cultures synthesized PAF at a similar basal rate, TNFalpha-induced PAF synthesis in adipocytes was 7-fold higher than in preadipocytes. This suggested a maturation of PAF-TNFalpha interrelationship during adipocyte differentiation. Wortmannin enhanced TNFalpha-dependent PAF synthesis in adipocytes but not in preadipocytes, indicating the negative control by PI3K in mature cells. PAF increase was due to the regulation of its biosynthesis since PAF-acetylhydrolase (PAF-AH) activity was TNFalpha- and wortmannin-independent. Our hypothesis is that PAF mediates TNFalpha inflammatory effects in both adipocytes and preadipocytes and that this pathway is enhanced during adipocyte differentiation, a mechanism which is highly active during the development of obesity.
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PMID:TNFalpha is a potent inducer of platelet-activating factor synthesis in adipocytes but not in preadipocytes. Differential regulation by PI3K. 1818 Jan 65


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