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Query: UMLS:C0028754 (obesity)
 124,988 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Hepatic PPARgamma expression is increased in several animal models of diabetes and obesity, and liver-specific overexpression of PPARgamma induces liver steatosis. The aim of this study was to investigate the regulation of PPARgamma expression in primary mouse hepatocytes. PPARgamma2, but not PPARgamma1, was up-regulated by insulin and to a lesser extent by oleic acid. Insulin increased transcription of the PPARgamma2 gene via phosphatidylinositol 3-kinase activation. The PPARgamma agonist, rosiglitazone, increased PPARgamma2 expression, but not PPARgamma1, only in the presence of insulin. Also aP2 mRNA expression was induced by rosiglitazone to a higher degree in the presence of insulin, while acyl-CoA oxidase was increased independently of insulin. In summary, PPARgamma2 is increased in hepatocytes by oleic acid and insulin. These results may help to understand the regulation of PPARgamma expression in liver, which possibly plays a role in the development of liver steatosis.
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PMID:Insulin and oleic acid increase PPARgamma2 expression in cultured mouse hepatocytes. 1636 46

Human embryonic stem (hES) cells are undifferentiated and pluripotent cells that hold great therapeutic potential, but are hampered by our limited knowledge to promote specific cell differentiation. Here we provide the first report of the directed differentiation of hES cells into adipocytes. Embryoid bodies (EBs) derived from hES cells are shown to respond to factors that promote adipogenesis. Differentiated cells were observed that displayed the key features of adipocytes, i.e., expression of specific molecular markers, such as peroxisome proliferator-activated receptor gamma2 (PPARgamma2), adipocyte fatty acid binding protein (aP2) and adiponectin, the secretion of leptin, and the accumulation of lipid droplets in cytoplasm. Taken together, our results demonstrate that adipocytes derived from hES cells in vitro can provide a novel model system to study human adipogenesis and obesity.
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PMID:Derivation of adipocytes from human embryonic stem cells. 1643 22

In adipocytes, suppressor of cytokine signaling (SOCS)3 deficiency increases insulin-stimulated insulin receptor substrate (IRS)-1 and -2 phosphorylation, IRS-associated phosphatidylinositol 3 kinase activity, and insulin-stimulated glucose uptake. Moreover, SOCS3 is required for tumor necrosis factor-alpha full inhibition of insulin-stimulated IRS-1 and -2 phosphorylation, phosphatidylinositol 3 kinase activity, and glucose uptake. Whether SOCS3 also inhibits adipocyte insulin signaling in vivo and whether this action further affects systemic insulin sensitivity is not clear. We therefore generated a transgenic mouse (aP2-SOCS3 mouse) overexpressing SOCS3 in adipose tissue. Overexpression of SOCS3 in adipocytes decreases IRS1 protein levels and subsequent insulin-stimulated IRS-1 and -2 phosphorylation, decreases p85 binding to IRS-1, and leads to decreased insulin-stimulated glucose uptake in adipocytes. This impaired insulin signaling in adipose tissue of aP2-SOCS3 mice causes decreased lipogenesis and blocks insulin's antilipolytic action. However, because of decreased energy partitioning in adipose tissue, aP2-SOCS3 mice are resistant to diet-induced obesity and are protected against systemic insulin resistance caused by a high-fat diet. Therefore, overexpression of SOCS3 in adipocytes causes local adipocyte insulin resistance, but it is not sufficient to cause systemic insulin resistance.
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PMID:Overexpression of suppressor of cytokine signaling 3 in adipose tissue causes local but not systemic insulin resistance. 1650 33

Obesity and the associated pathologies including dyslipidemia, insulin resistance, type 2 diabetes, and cardiovascular disease constitute a major threat to global human health. Yet, the genetic factors that differentially predispose individuals to this cluster of pathologies are unclear. The fatty acid-binding protein aP2 is a cytoplasmic lipid chaperon expressed in adipocytes and macrophages. Mice with aP2 deficiency are partially resistant to obesity-induced insulin resistance and type 2 diabetes, have lower circulating triglycerides, and exhibit marked protection against atherosclerosis. Here, we demonstrate a functionally significant genetic variation at the aP2 locus in humans that results in decreased adipose tissue aP2 expression due to alteration of the CAAT box/enhancer-binding protein binding and reduced transcriptional activity of the aP2 promoter. In population genetic studies with 7,899 participants, individuals that carry this T-87C polymorphism had lower serum triglyceride levels and significantly reduced risk for coronary heart disease and type 2 diabetes compared with subjects homozygous for the WT allele. Taken together, our results indicate that reduction in aP2 activity in humans generate a metabolically favorable phenotype that is similar to aP2 deficiency in experimental models.
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PMID:A genetic variant at the fatty acid-binding protein aP2 locus reduces the risk for hypertriglyceridemia, type 2 diabetes, and cardiovascular disease. 1664 Oct 93

Adipocytes secrete a variety of bioactive molecules that affect the insulin sensitivity of other tissues. We now show that the abundance of monocyte chemoattractant protein-1 (MCP-1) mRNA in adipose tissue and the plasma concentration of MCP-1 were increased both in genetically obese diabetic (db/db) mice and in WT mice with obesity induced by a high-fat diet. Mice engineered to express an MCP-1 transgene in adipose tissue under the control of the aP2 gene promoter exhibited insulin resistance, macrophage infiltration into adipose tissue, and increased hepatic triglyceride content. Furthermore, insulin resistance, hepatic steatosis, and macrophage accumulation in adipose tissue induced by a high-fat diet were reduced extensively in MCP-1 homozygous KO mice compared with WT animals. Finally, acute expression of a dominant-negative mutant of MCP-1 ameliorated insulin resistance in db/db mice and in WT mice fed a high-fat diet. These findings suggest that an increase in MCP-1 expression in adipose tissue contributes to the macrophage infiltration into this tissue, insulin resistance, and hepatic steatosis associated with obesity in mice.
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PMID:MCP-1 contributes to macrophage infiltration into adipose tissue, insulin resistance, and hepatic steatosis in obesity. 1669 Dec 91

Peroxisome proliferator-activated receptor gamma (PPARgamma) has been reported to play an important role to regulate adiposity and insulin sensitivity. It is not clear whether antagonism of PPARgamma using a synthetic ligand has significant effects on adipose tissue weight and glucose metabolism in vivo. The aim of this study is to examine the effects of a synthetic PPARgamma antagonist (GW9662) on adiposity and glycemic control in high-fat (HF) diet-fed mice. First the properties of GW9662 as a PPARgamma antagonist were estimated in vitro. GW9662 displaced [(3)H]rosiglitazone from PPARgamma with K(i) values of 13nM, indicating that the affinity of GW9662 for PPARgamma was higher than that of rosiglitazone (110nM). GW9662 had no effect on PPARgamma transactivation in cells expressing human PPARgamma. Treatment of 3T3-L1 preadipocytes with GW9662 did not increase aP2 expression or [(14)C]acetic acid uptake. GW9662 did not recruit transcriptional cofactors to PPARgamma. Limited trypsin digestion of the human PPARgamma/GW9662 complex showed patterns of digestion distinct from those of rosiglitazone. This suggests that the binding characteristics between GW9662 and PPARgamma are different from those of rosiglitazone. Treatment of HF diet-fed mice with GW9662 revealed that this compound prevented HF diet-induced obesity without affecting food intake. GW9662 suppressed any increase in the amount of visceral adipose tissue, but it did not change HF diet-induced glucose intolerance. These data indicate that antagonism of PPARgamma using a synthetic ligand suppresses the increased adiposity observed in HF diet-induced obesity, and that a PPARgamma antagonist could possibly be developed as an anti-obesity drug.
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PMID:Antagonism of peroxisome proliferator-activated receptor gamma prevents high-fat diet-induced obesity in vivo. 1669 51

Adiponectin (ApN) is an adipokine whose expression and plasma levels are inversely related to obesity and insulin-resistant states. The in vivo effects of a chronic expression of exogenous ApN restricted to adipose tissue are unclear. Moreover, the regulatory effects of ApN on its own expression and on that of its receptors are still unknown. In this study, we generated transgenic (Tg) mice with moderate expression of exogenous ApN targeted to adipose tissue (native full-length ApN being placed under control of the adipocyte promoter aP2). After a transient overexpression of ApN in young pups, we intriguingly observed a reduction of ApN mRNA levels and protein content in fat depots, together with a decrease of circulating ApN in adult mice. As a result, the phenotype of these adult mice included glucose intolerance, insulin resistance, and increased adiposity. Reduced expression of ApN in fat tissue was associated with diminished expression of uncoupling protein 2 involved in energy dissipation, and higher expression of fatty acid synthase, a key enzyme of lipogenesis, and of TNFalpha implicated in insulin resistance. Concomitantly, the expression of the ApN receptor AdipoR2 that mediates action of full-length ApN was downregulated, while that of AdipoR1 was unaffected. In agreement with the in vivo studies, recombinant ApN added to the culture medium of 3T3-F442A adipocytes caused a decrease in AdipoR2 and ApN mRNA levels. This treatment did not affect the expression of AdipoR1. Eventually, we demonstrated a contrario that AdipoR2 (but not R1) was specifically upregulated in fat of ApN(-/-) mice. Our in vivo and in vitro data provide evidence for a novel regulatory feedback loop by which ApN downregulates its own production and the expression of its AdipoR2 receptor.
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PMID:Adiponectin downregulates its own production and the expression of its AdipoR2 receptor in transgenic mice. 1672 74

High-density lipoprotein (HDL) has significant anti-atherogenic properties, whereas the underlying mechanisms are complex and have not been completely elucidated. Adipocytes produce a variety of adipokines with cardiovascular effects. The dysregulated secretion of adipokines by adipocytes may contribute to the increased risk of atherosclerosis associated with obesity. Clinical evidences indicate that higher plasma HDL-C levels are associated with a favourable adipokines secretion profile, suggesting that HDL might improve the dysregulated adipokines secretion. HDL may diminish lipid accumulation in adipocytes through phosphorylation of PPARgamma and inhibition of aP2 expression, which possibly account for the favourable effects of HDL on adipokines secretion. Therefore, we hypothesize that HDL might exert several beneficial effects on adipocytes, which may relate to its anti-atherogenic properties.
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PMID:The beneficial effects of high-density lipoprotein on adipocytes may relate to its anti-atherogenic properties. 1679 54

Fatty acid-binding proteins (FABPs) are cytosolic fatty acid chaperones that play a critical role in systemic regulation of lipid and glucose metabolism. In animals lacking the adipocyte/macrophage FABP isoforms aP2 and mal1, there is strong protection against diet-induced obesity, insulin resistance, type 2 diabetes, fatty liver disease, and hypercholesterolemic atherosclerosis. On high-fat diet, FABP-deficient mice also exhibit enhanced muscle AMP-activated kinase (AMPK) and reduced liver stearoyl-CoA desaturase-1 (SCD-1) activities. Here, we performed a cross between aP2(-/-), mal1(-/-), and leptin-deficient (ob/ob) mice to elucidate the role of leptin action on the metabolic phenotype of aP2-mal1 deficiency. The extent of obesity in the ob/ob-aP2-mal1(-/-) mice was comparable with ob/ob mice. However, despite severe obesity, ob/ob-aP2-mal1(-/-) mice remained euglycemic and demonstrated improved peripheral insulin sensitivity. There was also a striking protection from liver fatty infiltration in the ob/ob-aP2-mal1(-/-) mice with strong suppression of SCD-1 activity. On the other hand, the enhanced muscle AMPK activity in aP2-mal1(-/-) mice was lost in the ob/ob background. These results indicated that both decreased body weight and enhanced muscle AMPK activity in aP2-mal1(-/-) mice are potentially leptin dependent but improved systemic insulin sensitivity and protection from liver fatty infiltration are largely unrelated to leptin action and that insulin-sensitizing effects of FABP deficiency are, at least in part, independent of its effects on total-body adiposity.
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PMID:Regulation of metabolic responses by adipocyte/macrophage Fatty Acid-binding proteins in leptin-deficient mice. 1680 58

Resistin is secreted from adipocytes, and high circulating levels have been associated with obesity and insulin resistance. To investigate whether resistin could exert autocrine effects in adipocytes, we expressed resistin gene in 3T3-L1 fibroblasts using a lentiviral vector, and selected several stably-transduced cell lines under blasticidin selection. We observed that 3T3-L1 adipocytes expressing resistin have a decreased gene expression for related transcriptional factors (CCAAT/enhancer binding protein alpha(C/EBPalpha), peroxisome proliferator-activated receptor gamma (PPARgamma), and adipocyte lipid binding protein (ALBP/aP2) which is one of target genes for the PPARgamma during adipocyte differentiation,. Overexpression of resistin increased the levels of three proinflammatory cytokines, tumor necrosis factor alpha (TNFalpha), interleukin 6 (IL-6) and monocyte chemoattractant protein-1 (MCP-1), which play important roles for insulin resistance, glucose and lipid metabolisms during adipogenesis. Furthermore, overexpressing resistin in adipocytes inhibits glucose transport 4 (GLUT4) activity and its gene expression, reducing insulin's ability for glucose uptake by 30%. In conclusion, resistin overexpression in stably transduced 3T3-L1 cells resulted in: 1) Attenuation of programmed gene expression responsible for adipogenesis; 2) Increase in expression of proinflammatory cytokines; 3) Decrease in insulin responsiveness of the glucose transport system. These data suggest a new role for resistin as an autocrine/paracrine factor affecting inflammation and insulin sensitivity in adipose tissue.
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PMID:Proinflammatory cytokine production and insulin sensitivity regulated by overexpression of resistin in 3T3-L1 adipocytes. 1685 42


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