Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P05231 (interleukin-6)
 23,907 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Obesity is a complex syndrome that involves defective signaling by a number of different factors that regulate appetite and energy homeostasis. Treatment with exogenous leptin reverses hyperphagia and obesity in ob/ob mice, which have a mutation that causes leptin deficiency, proving the importance of this factor and its receptors in the obesity syndrome. Cells with leptin receptors have been identified outside of the appetite regulatory centers in the brain. Thus leptin has peripheral targets. Because macrophages express signaling-competent leptin receptors, these cells may be altered during chronic leptin deficiency. Consistent with this concept, the present study identifies several phenotypic abnormalities in macrophages from ob/ob mice, including decreased steady-state levels of uncoupling protein-2 mRNA, increased mitochondrial production of superoxide and hydrogen peroxide, constitutive activation of CCAAT enhancer binding protein (C/EBP)-beta, an oxidant-sensitive transcription factor, increased expression of interleukin-6 and cyclooxygenase (COX)-2, two C/EBP-beta target genes, and increased COX-2-dependent production of PGE2. Given the importance of macrophages in the general regulation of inflammation and immunity, these alterations in macrophage function may contribute to obesity-related pathophysiology.
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PMID:Phenotypic abnormalities in macrophages from leptin-deficient, obese mice. 995 Jul 66

We determined whether the physiologic changes that accompany food intake or sympathetic activation by beta-adrenergic stimulation result in alterations in the secretion of leptin, tumor necrosis factor-alpha (TNF alpha), or interleukin-6 (IL-6) by serially sampling sc abdominal adipose interstitial fluid by open-flow microperfusion before and after a standardized meal and in response to isoproterenol (1 micromol/L) delivered locally. Post cibum IL-6 rose up to 5-fold, whereas leptin and TNF alpha secretion did not change; TNF alpha, but not IL-6, correlated positively with indices of lipolysis. Isoproterenol-induced lipolysis was accompanied by a transient 40% reduction in leptin and a parallel 85% elevation of TNF alpha concentration, whereas IL-6 levels did not change; again, TNF alpha correlated positively with lipolysis. These data show that secretion of some, but not all, metabolically relevant polypeptides by adipose tissue is modulated within a short time frame by food or stress stimuli, suggesting a role of these peptides in local autocrine/paracrine or distant endocrine effects on fat metabolism. TNF alpha's close correlation with lipolysis suggests that this cytokine participates in a local positive autocrine feedback loop, potentiating lipolysis and inhibiting insulin's antilipolytic actions. The regulations of adipose leptin, TNF alpha, and IL-6 secretion seem distinct from each other and different in the fed vs. fasting state.
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PMID:The differential effect of food intake and beta-adrenergic stimulation on adipose-derived hormones and cytokines in man. 1037 21

This study assessed glucose tolerance, insulin sensitivity and lipid parameters in HIV-infected patients presenting with lipodystrophy during HAART including protease inhibitors. Fourteen consecutive patients from Rothschild Hospital treated with HAART and presenting with marked facial lipoatrophy were evaluated. A 75 g oral glucose tolerance test (OGTT) with measurement of plasma glucose, insulin, proinsulin and free fatty acids at T0, 30, 60, 90 and 120 min was performed. Lipid parameters (triglycerides, cholesterol, apolipoproteins A1 and B) were studied as well as nutritional and inflammatory markers (albumin, prealbumin, transferrin, haptoglobin, orosomucoid, C-reactive protein), endocrine and cytokine parameters (thyrotropin, cortisol, leptin, interleukin-6), HIV viral load and CD4-lymphocyte count. These patients were compared with 20 non-lipodystrophic protease inhibitor-treated patients. The measurements performed during OGTT showed that among the 14 lipodystrophic patients, 11 (79%) presented with diabetes (5 patients) or normal glucose tolerance but with insulin resistance (6 patients). This frequency was strikingly different in the group of nonlipodystrophic patients, which included only 4 (20%) presenting with diabetes (1 patient), or impaired glucose tolerance (2 patients), or normal glucose tolerance but with insulin resistance (1 patient). Hypertriglyceridaemia was present in 11 lipodystrophic (79%) versus 7 nonlipodystrophic patients (35%). Nutritional and endocrine measurements were normal. An abnormal processing of proinsulin to insulin was excluded. Thus, lipodystrophy during HAART was associated with diabetes, insulin resistance and hypertriglyceridaemia. Diabetes, diagnosed by basal and/or 120 min-OGTT glycaemia, seems more frequent than previously described. The therapeutic consequences of these results deserve evaluation in clinical trials.
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PMID:Diabetes, insulin resistance and dyslipidaemia in lipodystrophic HIV-infected patients on highly active antiretroviral therapy (HAART). 1049 91

Fat tissue is a significant source of endogenous tumor necrosis factor alpha (TNFalpha), the pluripotent cytokine that plays an important role as a mediator of the peripheral insulin resistance found in obesity. The majority of evidence for this role of TNFalpha is from studies in animal models of obesity. To explore further the role of TNFalpha in the pathogenesis of obesity-related insulin resistance in humans, we compared plasma levels of TNFalpha and the other main endocrine cytokine, interleukin-6 ([IL-6] both measured by enzyme-linked immunosorbent assay), in 26 obese women (body mass index [BMI] > 30 kg/m2) and 13 female controls (BMI < 26 kg/m2) without a history of recent or active infection. Glucose and insulin levels were measured at 0, 1, and 2 hours after a 75-g oral glucose load. There was no significant difference in plasma TNFalpha or IL-6 levels between obese and non-obese subjects overall (2.10 +/- 0.19 v 1.65 +/- 0.18 pg/mL and 2.06 +/- 0.29 v 1.50 +/- 0.17 pg/mL, respectively). However, TNFalpha levels were significantly elevated in obese subjects with a 2-hour glucose level more than 140 mg/dL (n = 8) compared with the other obese subjects (n = 18) and the non-obese controls (2.88 +/- 0.46 v 1.75 +/- 0.10 and 1.65 +/- 0.18 pg/mL, respectively, P < .01). Furthermore, the TNFalpha level correlated significantly with the waist to hip ratio ([WHR] r = .53, P < .01) and fasting and post-oral glucose tolerance test (OGTT) insulin levels (r = .47, P < .02), but not with the BMI, and was higher in obese women with a WHR more than 0.90 (n = 14) in comparison to those with a WHR less than 0.90 (n = 12, 2.47 +/- 0.29 v 1.66 +/- 0.18 pg/mL, respectively, P < .03). The corresponding plasma leptin level was significantly higher in obese women versus the control group (41.6 +/- 2.5 v22.3 +/- 2.9 ng/mL, P < .001) and was related to the BMI (r = .60, P < .01) but not to TNFalpha or the WHR. There were no significant differences in the corresponding IL-6 concentration between groups, and IL-6 did not correlate with TNFalpha, leptin, BMI, WHR, or insulin levels. In conclusion, circulating TNFalpha levels are higher in abdominal obesity compared with peripheral obesity, and may contribute to the insulin resistance that more commonly complicates the former pattern of fat distribution.
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PMID:Circulating tumor necrosis factor alpha concentrations are higher in abdominal versus peripheral obesity. 1053

Tumour invasion and trophoblastic invasion share the same biochemical mediators: the matrix metalloproteinases (MMP) and their inhibitors. In contrast to tumour invasion of a host tissue, trophoblastic invasion during implantation and placentation is stringently controlled both in tissue localization and developmental stage. The factors responsible for these important regulatory processes are unknown, but in-vitro studies point to endometrial cytokines and growth factors as possible candidates. Here we examined the possibility that interleukin-6 (IL-6), a trophoblastic and endometrial cytokine, represents such a regulatory factor. Purified first trimester cytotrophoblastic cells (CTB) were cultured for 4 days in presence or absence of increasing concentrations of IL-6. MMP-2 and MMP-9 bioactivity (zymography) and immunoactivity were measured in the culture supernatants together with total human chorionic gonadotrophin (HCG), fetal fibronectin (FFN) and leptin. IL-6 did not change the cytotrophoblastic secretion of FFN or total HCG. In contrast, this cytokine induced a dose-dependent stimulation of the leptin secretion and increased the activity, but not the immunoreactivity, of MMP-9 and MMP-2. These results indicate that IL-6 could be considered as an endometrio-trophoblastic regulator of cytotrophoblastic gelatinases.
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PMID:Effects of interleukin-6 (IL-6) on cytotrophoblastic cells. 1054 68

Signal Transducer and Activator of Transcription 3 (STAT3) is a transcription factor that acts as an intracellular signalling molecule after receptor activation by several cytokines, e.g., interleukin-6, leptin and ciliary neurotrophic factor. We have investigated the localization of STAT3 in the rat central nervous system and dorsal root ganglia. Light microscopic immunohistochemistry showed that STAT3-like immunoreactivity (STAT3-LI) was present in the nucleus and cytoplasm of neurons. STAT3-LI was seen both in cell bodies and in proximal and distal dendrites. Many structures involved in motor functions, such as the ventral horn of the spinal cord, the motor cranial nerve nuclei, the red nucleus and the Purkinje cells of the cerebellum showed STAT3-LI. STAT3-LI was also present in many regions involved in autonomic regulation, such as the intermediolateral cell column of the spinal cord, the nucleus of the solitary tract, the dorsal motor nucleus of the vagus nerve, the area postrema, the locus coeruleus, the Barrington's nucleus and the arcuate, the lateral, the dorsomedial, the ventromedial, and the paraventricular hypothalamic nuclei. Other structures showing STAT3-LI were the dorsal root ganglia, the thalamus (the anterodorsal and paraventricular nucleus), the cerebral neocortex (layer 5) and the olfactory bulb. The wide distribution of STAT3-LI in the nervous system is consistent with reports of cytokine actions in the brain, but the present findings further suggest novel roles for STAT3 in mediating influences of cytokines on specific neuronal circuits regulating motor, sensory and autonomic functions.
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PMID:Distribution of the transcription factor signal transducer and activator of transcription 3 in the rat central nervous system and dorsal root ganglia. 1062 14

Sleep apnea and associated daytime sleepiness and fatigue are common manifestations of mainly obese middle-aged men. The onset of sleep apnea peaks in middle age, and its morbid and mortal sequelae include complications from accidents and cardiovascular events. The pathophysiology of sleep apnea remains obscure. The purpose of this study was to test three separate, albeit closely related, hypotheses. 1) Does sleep apnea contribute to the previously reported changes of plasma cytokine (tumor necrosis factor-alpha and interleukin-6) and leptin levels independently of obesity? 2) Among obese patients, is it generalized or visceral obesity that predisposes to sleep apnea? 3) Is apnea a factor independent from obesity in the development of insulin resistance? Obese middle-aged men with sleep apnea were first compared with nonapneic age- and body mass index (BMI)-matched obese and age-matched lean men. All subjects were monitored in the sleep laboratory for 4 consecutive nights. We obtained simultaneous indexes of sleep, sleep stages, and sleep apnea, including apnea/hypopnea index and percent minimum oxygen saturation. The sleep apneic men had higher plasma concentrations of the adipose tissue-derived hormone, leptin, and of the inflammatory, fatigue-causing, and insulin resistance-producing cytokines tumor necrosis factor-alpha and interleukin-6 than nonapneic obese men, who had intermediate values, or lean men, who had the lowest values. Because these findings suggested that sleep apneics might have a higher degree of insulin resistance than the BMI-matched controls, we studied groups of sleep-apneic obese and age- and BMI-matched nonapneic controls in whom we obtained computed tomographic scan measures of total, sc, and visceral abdominal fat, and additional biochemical indexes of insulin resistance, including fasting plasma glucose and insulin. The sleep apnea patients had a significantly greater amount of visceral fat compared to obese controls (<0.05) and indexes of sleep disordered breathing were positively correlated with visceral fat, but not with BMI or total or sc fat. Furthermore, the biochemical data confirmed a higher degree of insulin resistance in the group of apneics than in BMI-matched nonapneic controls. We conclude that there is a strong independent association among sleep apnea, visceral obesity, insulin resistance and hypercytokinemia, which may contribute to the pathological manifestations and somatic sequelae of this condition.
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PMID:Sleep apnea and daytime sleepiness and fatigue: relation to visceral obesity, insulin resistance, and hypercytokinemia. 1072 86

A novel assay for measuring the free leptin fraction was developed and validated against a chromatographic technique. The assay used acid-ethanol extraction (AEE) for separation of bound/free leptin moieties. The interassay coefficient of variation was 3.9%. The specificity for leptin binding was confirmed by incubation with 1 microg of unlabeled rat leptin that effectively competed with radiolabeled leptin whereas human growth hormone and interleukin-6 were ineffective in competing with radiolabeled leptin binding. Scatchard analysis of competitive binding experiments with rat plasma demonstrated a linear relationship with a binding affinity of 0.3-0.6 x 109 M-1. This novel assay was used to determine if age-related insensitivity to leptin action is secondary to altered serum leptin binding. Rats at various age groups were studied for changes in body adiposity and serum total and free leptin concentrations. Serum free leptin concentrations (ng/ml mean +/- SEM) were significantly increased in 24-month-old rats (5.56 +/- 0. 21) compared with 18-month-old rats (4.76 +/- 0.17) (P < 0.01) despite similar body weight and adiposity of the two age groups. The increase in plasma free leptin concentrations in 12-month-old rats (3.86 +/- 0.28) and 6-month-old rats (2.05 +/- 0.06) relative to 3-month-old rats (1.37 +/- 0.06) (P < 0.001) was out of proportion to the increase in body adiposity in aging rats. It is concluded that aging in rats is associated with relative insensitivity to leptin. This change cannot be attributed to increased plasma binding or to a reduction in the leptin free fraction.
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PMID:Age-related changes in plasma leptin binding activity in rats: A comparison of a simple acid-ethanol precipitation technique with column chromatography. 1096 62

Ciliary neurotrophic factor (CNTF), a cytokine of the interleukin-6 superfamily, has been shown to induce hypophagia and weight loss. Neuropeptide Y (NPY) and orexin are potent orexigenic signals in the hypothalamus. Anorexia, normally seen in response to infection, injury and inflammation, may result from diminished hypothalamic orexigenic signalling caused by persistently elevated cytokines, including CNTF. To test this hypothesis, we first examined the effects of chronic intracerebroventricular (i.c.v.) infusion of CNTF for 6-7 days on food intake and body weight as well as hypothalamic NPY and orexin gene expression in male rats. Subsequently, the effectiveness of NPY replacement to counteract the effects of CNTF by coinfusion of NPY and CNTF was evaluated. Chronic i.c.v. infusion of CNTF (2.5 microg/day) reduced body weight (14.3% vs control) at the end of 7 days. Food intake remained suppressed for 5 days postinfusion and subsequently gradually returned to the control range by day 7. Serum leptin concentrations in these rats were in the same range seen in control rats. Chronic i.c.v. infusion of higher doses of CNTF (5.0 microg/day) produced sustained anorexia and body weight loss (29% vs controls) through the entire duration of the experiment. This severe anorexia was accompanied by markedly suppressed serum leptin concentrations. Furthermore, CNTF infusion alone significantly reduced hypothalamic NPY gene expression (P < 0. 05) without affecting orexin gene expression. As expected, in fusion of NPY alone (18 microg/day) augmented food intake (191.6% over the initial control, P < 0.05) and produced a 25.1% weight gain in conjunction with a 10-fold increase in serum leptin concentrations at the end of the 7-day period. Interestingly, coinfusion of this regimen of NPY with the highly effective anorectic and body reducing effects of CNTF (5.0 microg/day) not only prevented the CNTF-induced anorexia and weight loss, but also normalized serum leptin concentrations and hypothalamic NPY gene expression. These results demonstrate that chronic central infusion to produce a persistent elevation of the cytokine at pathophysiological levels (a situation that may normally manifest during infection, injury and inflammation) produced severe anorexia and weight loss in conjunction with reduction in both serum leptin concentrations and hypothalamic NPY gene expression. Reinstatement of hypothalamic NPY signalling by coinfusion of NPY counteracted these CNTF-induced responses.
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PMID:Neuropeptide Y counteracts the anorectic and weight reducing effects of ciliary neurotropic factor. 1097 7

Leptin, the product of the ob gene, is a pleiotropic molecule that regulates food intake as well as metabolic and endocrine functions. Leptin also plays a regulatory role in immunity, inflammation, and hematopoiesis. Alterations in immune and inflammatory responses are present in leptin- or leptin-receptor-deficient animals, as well as during starvation and malnutrition, two conditions characterized by low levels of circulating leptin. Both leptin and its receptor share structural and functional similarities with the interleukin-6 family of cytokines. Leptin exerts proliferative and antiapoptotic activities in a variety of cell types, including T lymphocytes, leukemia cells, and hematopoietic progenitors. Leptin also affects cytokine production, the activation of monocytes/macrophages, wound healing, angiogenesis, and hematopoiesis. Moreover, leptin production is acutely increased during infection and inflammation. This review focuses on the role of leptin in the modulation of the innate immune response, inflammation, and hematopoiesis.
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PMID:Leptin in the regulation of immunity, inflammation, and hematopoiesis. 1103 63


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