Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0011860 (type 2 diabetes)
 57,723 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The vascular actions of insulin may contribute to the increase in glucose uptake by skeletal muscle. We have recently shown that when capillary recruitment by insulin is blocked in vivo, an acute state of insulin resistance is induced. Another agent that may have vascular effects is the inflammatory cytokine tumor necrosis factor-alpha (TNF-alpha), which has been reported to play an important role in the insulin resistance of obesity, type 2 diabetes, and sepsis in both animals and humans. Thus, in the present study, we have investigated the effect of an intravenous 3-h TNF treatment (0.5 microg x h(1) x kg(-1)) in control and euglycemic-hyperinsulinemic-clamped (10 mU x min(-1) x kg(-1) for 2 h) anesthetized rats. Hind-leg glucose uptake, muscle uptake of 2-deoxyglucose (2-DG), femoral blood flow (FBF), vascular resistance (VR), and capillary recruitment as measured by metabolism of infused 1-methylxanthine (1-MX) were assessed. Insulin alone caused a significant (P < 0.05) increase in FBF (1.7-fold) and capillary recruitment (2.5-fold), with a significant decrease in VR. In addition, hind-leg glucose uptake was increased (fourfold), as was 2-DG uptake in the soleus and plantaris muscles. TNF completely prevented the insulin-mediated changes in FBF, VR, and capillary recruitment and significantly reduced (P < 0.05) the insulin-mediated increase in total hind-leg glucose uptake (by 61%) and muscle 2-DG uptake (by at least 50%). TNF alone had no significant effect on any of these variables. It is concluded that acute administration in vivo of TNF completely blocks the hemodynamic actions of insulin on rat skeletal muscle vasculature and blocks approximately half of the glucose uptake by muscle. It remains to be determined whether these two effects are interdependent.
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PMID:Acute impairment of insulin-mediated capillary recruitment and glucose uptake in rat skeletal muscle in vivo by TNF-alpha. 1107 58

Insulin resistance is a common feature of obesity and predisposes the affected individuals to a variety of diseases, including hypertension, dyslipidemias, cardiovascular problems and type 2 diabetes mellitus. However, the molecular mechanisms underlying abnormal insulin action and these other pathological states are not well understood. We have been focusing on cytokines, particularly TNFalpha and fatty acid binding proteins, as potential sites to study the molecular basis of these disorders. The role of TNFalpha in insulin resistance and other pathologies associated with obesity, have been examined in several experimental systems including obese mice with homozygous null mutations at the TNFalpha or TNF receptor loci. Analysis of these animals demonstrated that the genetic absence of TNF signaling in obesity: (i) significantly improves insulin receptor signaling capacity and consequently insulin sensitivity; (ii) prevents brown adipose tissue atrophy and beta3-adrenoreceptor deficiency and improves thermo-adaptive responses, (iii) decreases the elevated PAI-1 and TGFbeta production; and (iv) lowers hyperlipidemia and hyperleptinemia. Hence, abnormal TNFalpha action in adipocytes disturbs many aspects of metabolic homeostasis in obesity.
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PMID:Molecular mechanisms of insulin resistance and the role of the adipocyte. 1112 35

Gangliosides are known as modulators of transmembrane signaling by regulating various receptor functions. We have found that insulin resistance induced by tumor necrosis factor-alpha (TNF-alpha) in 3T3-L1 adipocytes was accompanied by increased GM3 ganglioside expression caused by elevating GM3 synthase activity and its mRNA. We also demonstrated that TNF-alpha simultaneously produced insulin resistance by uncoupling insulin receptor activity toward insulin receptor substrate-1 (IRS-1) and suppressing insulin-sensitive glucose transport. Pharmacological depletion of GM3 in adipocytes by an inhibitor of glucosylceramide synthase prevented the TNF-alpha-induced defect in insulin-dependent tyrosine phosphorylation of IRS-1 and also counteracted the TNF-alpha-induced serine phosphorylation of IRS-1. Moreover, when the adipocytes were incubated with exogenous GM3, suppression of tyrosine phosphorylation of insulin receptor and IRS-1 and glucose uptake in response to insulin stimulation was observed, demonstrating that GM3 itself is able to mimic the effects of TNF on insulin signaling. We used the obese Zucker fa/fa rat and ob/ob mouse, which are known to overproduce TNF-alpha mRNA in adipose tissues, as typical models of insulin resistance. We found that the levels of GM3 synthase mRNA in adipose tissues of these animals were significantly higher than in their lean counterparts. Taken together, the increased synthesis of cellular GM3 by TNF may participate in the pathological conditions of insulin resistance in type 2 diabetes.
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PMID:Ganglioside GM3 participates in the pathological conditions of insulin resistance. 1170 32

Accumulating evidence suggests that the pathophysiology of diabetes is analogous to chronic inflammatory states. Circulating levels of inflammatory cytokines such as IL-6 and tumor necrosis factor alpha (TNFalpha) are increased in both type 1 and type 2 diabetes. TNFalpha plays an important role in the pathogenesis of insulin resistance in type 2 diabetes. However, the reason for this increase remains unclear. Levels of the dicarbonyl methylglyoxal (MGO) are elevated in diabetic plasma and MGO-modified bovine serum albumin (MGO-BSA) can trigger cellular uptake of TNF. Therefore we tested the hypothesis that MGO-modified proteins may cause TNFalpha secretion in macrophage-like RAW 264.7 cells. Treatment of cells with MGO-BSA induced TNFalpha release in a dose-dependent manner. MGO-modified ribonuclease A and chicken egg ovalbumin had similar effects. Cotreatment of cells with antioxidant reagent N-acetylcysteine (NAC) inhibited MGO-BSA-induced TNFalpha secretion. MGO-BSA stimulated the simultaneous activation of p44/42 and p38 mitogen-activated protein kinase. PD98059, a selective MEK inhibitor, inhibited MGO-BSA-induced TNFalpha release as well as ERK phosphorylation. Pretreatment of cells with NAC also resulted in inhibition of MGO-BSA-induced ERK phosphorylation. MGO-BSA induced dose-dependent NFkappaB activation as shown by electrophoresis mobility shift assay. The MGO-BSA-induced NFkappaB activation was prevented in the presence of PD98059, NAC, and parthenolide, a selective inhibitor of NFkappaB. Furthermore, the NFkappaB inhibitor parthenolide suppressed MGO-BSA-induced TNFalpha secretion. Confocal microscopy using dichlorofluorescein to demonstrate intracellular reactive oxygen species (ROS) showed that MGO-BSA produced more ROS compared with native BSA. MGO-BSA could also stimulate protein kinase C (PKC) translocation to the cell membrane, considered a key signaling pathway in diabetes. However, there was no evidence that PKC was involved in TNFalpha release based on inhibition by calphostin C and staurosporine. Our findings suggest that the presence of chronically elevated levels of MGO-modified bovine serum albumin may contribute to elevated levels of TNFalpha in diabetes.
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PMID:Methylglyoxal-bovine serum albumin stimulates tumor necrosis factor alpha secretion in RAW 264.7 cells through activation of mitogen-activating protein kinase, nuclear factor kappaB and intracellular reactive oxygen species formation. 1250 94

Obesity and type 2 diabetes are associated strongly with NAFLD. It is not clear if one of these conditions causes the others, or if all are consequences of another process. Although NAFLD is known to occur in overly lean individuals, which indicates that excessive adiposity is not required for the development of NAFLD, the severities of insulin resistance and NAFLD tend to parallel each other, and the greatest prevalence of type 2 diabetes occurs in patients with NAFLD and cirrhosis. This observation suggests that insulin resistance and NAFLD may be related pathogenically. Experiments in mice demonstrate that insulin resistance and NAFLD result from a chronic inflammatory state that is characterized by increased levels of TNF alpha. The mechanisms that drive this chronic inflammation are unknown but might involve the oxidative stress that develops during fatty acid metabolism or when products from intestinal bacteria escape into the mesenteric blood to trigger a sustained hepatic inflammatory cytokine response in genetically susceptible individuals, promoting a positive feedback loop that reinforces insulin resistance and inflammation. This hypothesis is supported by some animal and human studies; however, more research is needed to evaluate this theory. Additional studies also are required to determine the benefits of treatments that interrupt this pathogenic cascade at various points. Preliminary work in animal and human studies suggests that diverse strategies that inhibit production of TNF alpha and improve insulin resistance also ameliorate NAFLD.
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PMID:The liver in obesity and type 2 diabetes mellitus. 1251 96

Type 2 diabetic mellitus (type 2 DM) comprises more than 95% of all Taiwanese patients with DM. Tumor necrosis factor-alpha (TNF-alpha) expression is linked with insulin resistance, and is under strong genetic control. The correlation between TNF promoter genotypes and type 2 DM is still controversial, because discrepancies among different studies exist. Ethnic differences play certain roles in these conflicting results, because the distribution of TNF promoter polymorphisms is different among study subjects with different racial origins. Therefore, we examined the relationship between the incidence of type 2 diabetes in Taiwanese and two polymorphisms of the TNF-alpha promoter region (positions -238 and -308) as well as the correlation between these polymorphisms and the patients' biochemical manifestations. Genomic DNA was extracted from peripheral blood cells of 261 Taiwanese patients with type 2 DM and 189 non-diabetic control study subjects, and their TNF promoter G-238A and G-308A polymorphisms were analyzed by PCR-RFLP analysis. No significant association between TNF-alpha G-238A and G-308A polymorphisms with type 2 diabetic incidence was observed. However, associations between TNF-alpha G-238A and low-density lipoprotein-cholesterol and between G-308A promoter polymorphism and high-fasting plasma glucose levels, using multiple linear regression analysis with adjustment for the subjects' age, sex, body mass index and diabetic status, were found. Our results suggested that though TNF-alpha G-238A and G-308A polymorphisms were not involved in the pathogenesis of type 2 DM, type 2 diabetic patients carrying TNFA-A or TNF-308*2 genotype might be more susceptible to diabetic complications such as atherosclerosis.
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PMID:TNF-alpha polymorphisms and type 2 diabetes mellitus in Taiwanese patients. 1275 58

Our previous results have suggested that genes outside the human leukocyte antigen (HLA) class II locus may affect the phenotype of type 2 diabetic patients from families with both type 1 and type 2 diabetes (mixed type 1/2). To study whether the TNF alpha gene could be such a modifying gene, we studied TNF alpha promoter polymorphisms (G-->A substitution at positions -308 and -238) in relation to HLA-DQB1 genotypes in type 2 patients from mixed type 1/2 families or common type 2 diabetes families as well as in patients with adult-onset type 1 diabetes and control subjects. The TNF alpha(308) AA/AG genotype frequency was increased in adult onset type 1 patients (55%, 69 of 126), but it was similar in type 2 patients from type 1/2 families (35%, 33/93) or common type 2 families (31%, 122 of 395), compared with controls (33%, 95/284; P < 0.0001 vs. type 1). The TNF alpha(308) A and DQB1*02 alleles were in linkage disequilibrium in type 1 patients (Ds = 0.81; P < 0.001 vs. Ds = 0.25 in controls) and type 2 patients from type 1/2 families (Ds = 0.59, P < 0.05 vs. controls) but not in common type 2 patients (Ds = 0.39). The polymorphism was associated with an insulin-deficient phenotype in the type 2 patients from type 1/2 families only together with DQB*02, whereas the common type 2 patients with AA/AG had lower waist to hip ratio [0.92 (0.12) vs. 0.94 (0.11), P = 0.008] and lower fasting C-peptide concentration [0.48 (0.47) vs. 0.62 (0.46) nmol/liter, P = 0.020] than those with GG, independently of the presence of DQB1*02. In conclusion, TNF alpha is unlikely to be the second gene in the HLA area responsible for our previous findings in type 1/2 patients. However, we could show an association between TNF alpha(308) polymorphism and the phenotype of common type 2 diabetes.
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PMID:A combination of human leukocyte antigen DQB1*02 and the tumor necrosis factor alpha promoter G308A polymorphism predisposes to an insulin-deficient phenotype in patients with type 2 diabetes. 1278 86

The adipose tissue plays a fundamental role in maintaining the energy balance in mammals. During periods of high energy intake, the adipocytes store energy in the form of fat (triglycerides), which can be mobilized as free fatty acids during energy deprivation. Adipose tissue can no longer be considered only as a passive tissue that simply stores energy. Some recent discoveries have made it evident that this is a very active endocrine tissue that secretes important molecules related to different processes such as the immune response (TNF alpha) the regulation of food intake and expenditure of energy (leptin, Acrp30/adipoQ) and the vascular function (angiotensin and plasminogen activator inhibitor type 1). Alterations in the growth, development and function of the adipose tissue might therefore be involved in the development of different pathologies such as obesity, insulin resistance and type 2 diabetes, hypertension and atherosclerosis. A deeper understanding of the adipose tissue (morphology, development-adipogenesis, role in the metabolism and in the regulation of body weight, endocrine functions.) is needed for an adequate study of the underlying aspects in the development of obesity.
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PMID:[Adipose tissue: a storage and secretory organ]. 1286 Dec 68

Failure of insulin producing pancreatic beta-cells is a common characteristic of type 1 (insulin-dependent) and type 2 (insulin non-dependent) diabetes mellitus. Accumulating evidence suggests that programmed cell death (apoptosis) is the main form of beta-cell death in these disorders. The beta-cell is particularly sensitive to apoptotic stimuli due to the inherent features of the specialized beta-cell phenotype. In type 1 diabetes anti-beta-cell autoimmune reactivity delivers the apoptotic signals in the form of inflammatory mediators or T-cell effectors. In type 2 diabetes, the metabolic derangement is associated with production of inflammatory mediators in insulin-sensitive tissues leading elevated levels of circulating inflammatory mediators such as IL-6 and TNF. Further glucose has been suggested to induce beta-cell apoptosis via the induction of beta-cell synthesis of IL-1 which via autocrine action may elicit signalling cascades analogous to those seen in beta-cell destruction in type 1 diabetes. Considering the apparent importance of IL-1-beta signalling in beta-cell failure in both type 1 and type 2 diabetes, we here review the modulatory effect exerted on IL-1signalling by cellular characteristics related to the specialized beta-cell phenotype. We conclude that beta-cell differentiation signals (Pdx-1), glucose metabolism, calcium handling as well as regulation of naturally occurring inhibitors of cytokine signalling contribute to sensitize the beta-cell to apoptotic stimuli. We hypothesize that immunological stimuli in type 1 diabetes and metabolic/inflammatory signals in type 2 diabetes converge on common signalling pathways leading to beta-cell failure and destruction in these two diseases.
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PMID:Apoptotic signal transduction pathways in diabetes. 1455 18

Plasma inflammatory cytokines are elevated in obese subjects as well as in those with type 2 diabetes. This presumably results in systemic insulin resistance, characterized by a pro-atherogenic plasma lipid profile and reduced apolipoprotein AI (apoAI) protein levels. To determine how cytokine-mediated insulin resistance suppresses apoAI gene expression, we investigated the effect of tumor necrosis factor alpha (TNF alpha) and interleukin-1beta (IL-1beta) on apoAI protein, mRNA, and transcriptional activity in the human hepatoma cell line HepG2. ApoAI secretion was suppressed in a dose-dependent manner in HepG2 cells treated with both cytokines. ApoAI protein levels were 2892+/-22.0, 2263+/-117, 2458+/-25.0, 3401+/-152, 2333+/-248, 1520+/-41.5 and 956.0+/-11.0 arbitrary units (AU) in cells treated with 0, 0.3, 1.0, 3.0, 10, 30, and 100 ng/ml TNF alpha, achieving statistical significance in the 30 and 100 ng/ml range (P<0.0009). ApoAI protein levels were 4055+/-360, 3697+/-101, 3347+/-327, 1561+/-33.0, 1581+/-182, 810.0+/-59.5, and 1766+/-717 AU in cells treated with similar doses of IL-1beta, achieving statistical significance within the range of 3-100 ng/ml (P<0.02). ApoAI mRNA levels were suppressed 50.8% in HepG2 cells treated with 30 ng/ml TNF alpha for 24 h (P<0.05), and remained suppressed for up to 96 h. Similarly, treatment of cells with 30 ng/ml IL-1beta for 24 h, resulted in 42.9% reduction in apoAI mRNA levels (P<0.05) and remained suppressed for up to 96 h. In order to determine if the effect of TNF alpha and IL-1beta occurs at the transcriptional level, HepG2 cells were transfected with a chloramphenicol acetyltransferase (CAT) reporter gene plasmid containing the full-length apoAI promoter, and after 24 h, treated with TNF alpha (30 ng/ml), IL-1beta (30 ng/ml), or both cytokines. CAT activity was suppressed by both cytokines (24.0+/-1.9% acetylation in control cells vs. 5.6+/-1.2% (P<0.0004), 10.2+/-1.5% (P<0.0006), and 3.9+/-0.9% acetylation (P<0.0002) in cells treated with TNF alpha, IL-1beta, and the combination of both cytokines, respectively) suggesting that cytokine-mediated suppression occurs at the transcriptional level. Using a series of apoAI deletion constructs, the cytokine response element was mapped between nucleotides -325 and -186 (relative to the transcriptional start site). This region contains a previously identified and characterized cis-element, site A, which binds several different transcription factors. Finally, electrophoretic mobility shift assays (EMSA) showed that TNF alpha treatment of HepG2 cells is associated with reduced nuclear factor binding to site A. These studies suggest that inflammatory cytokines down-regulate apoAI expression at least partly through inhibition of binding of the nuclear factors to site A of the apoAI promoter.
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PMID:Suppression of apolipoprotein AI gene expression in HepG2 cells by TNF alpha and IL-1beta. 1457 9


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