Decreased In Situ Insulin Receptor Dephosphorylation in Hyperglycemia-Induced Insulin Resistance in Rat Adipocytes

Tang, Shangguo; Le-Tien, Hoang; Goldstein, Barry J.; Shin, Phillip; Lai, Robert; Fantus, I. George

doi:10.2337/diabetes.50.1.83

Cited by 33 publications

(28 citation statements)

References 72 publications

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“…However, in this model of insulin resistance, we have recently found that IR-related PTP activity is diminished rather than elevated (77). These findings are in agreement with other in vitro (78) and in vivo (79,80) studies demonstrating that hyperglycemiainduced insulin resistance is not associated with increased IR Tyr dephosphorylation or PTP activity.…”

Section: Discussionsupporting

confidence: 80%

Enhanced Sensitivity of Insulin-resistant Adipocytes to Vanadate Is Associated with Oxidative Stress and Decreased Reduction of Vanadate (+5) to Vanadyl (+4)

Ennis²,

Lai

et al. 2001

Journal of Biological Chemistry

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104

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Vanadate (sodium orthovanadate), an inhibitor of phosphotyrosine phosphatases (PTPs), mimics many of the metabolic actions of insulin in vitro and in vivo. The potential of vanadate to stimulate glucose transport independent of the early steps in insulin signaling prompted us to test its effectiveness in an in vitro model of insulin resistance. In primary rat adipocytes cultured for 18 h in the presence of high glucose (15 mM) and insulin (10 ؊7 M), sensitivity to insulin-stimulated glucose transport was decreased. In contrast, there was a paradoxical enhanced sensitivity to vanadate of the insulinresistant cells (EC 50 for control, 325 ؎ 7.5 M; EC 50 for insulin-resistant, 171 ؎ 32 M; p < 0.002). Enhanced sensitivity was also present for vanadate stimulation of insulin receptor kinase activity and autophosphorylation and Akt/protein kinase B Ser-473 phosphorylation consistent with more effective PTP inhibition in the resistant cells. Investigation of this phenomenon revealed that 1) depletion of GSH with buthionine sulfoximine reproduced the enhanced sensitivity to vanadate while preincubation of resistant cells with N-acetylcysteine (NAC) prevented it, 2) intracellular GSH was decreased in resistant cells and normalized by NAC, 3) exposure to high glucose and insulin induced an increase in reactive oxygen species, which was prevented by NAC, 4) EPR (electron paramagnetic resonance) spectroscopy showed a decreased amount of vanadyl (؉4) in resistant and buthionine sulfoximine-treated cells, which correlated with decreased GSH and increased vanadate sensitivity, while total vanadium uptake was not altered, and 5) inhibition of recombinant PTP1B in vitro was more sensitive to vanadate (؉5) than vanadyl (؉4). In conclusion, the parodoxical increased sensitivity to vanadate in hyperglycemia-induced insulin resistant adipocytes is due to oxidative stress and decreased reduction of vanadate (؉5) to vanadyl (؉4). Thus, sensitivity of PTP inhibition and glucose transport to vanadate is regulated by cellular redox state.

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Section: Discussionsupporting

confidence: 80%

Enhanced Sensitivity of Insulin-resistant Adipocytes to Vanadate Is Associated with Oxidative Stress and Decreased Reduction of Vanadate (+5) to Vanadyl (+4)

Ennis²,

Lai

et al. 2001

Journal of Biological Chemistry

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104

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“…Isolation of epididymal fat pads. Male Sprague-Dawley rats or male mice were killed, epididymal fat pads were removed, and adipocytes were isolated as described (18). After collagenase digestion, adipocytes were filtered through 20-mesh and washed three times with 3% BSA-Krebs-Ringer bicarbonate HEPES buffer (118 mmol/l NaCl, 5 mmol/l KCl, 1.2 mmol/l MgSO 4 , 2.5 mmol/l CaCl 2 , 1.2 mmol/l KH 2 PO 4 , 5 mmol/l NaHCO 3 , 30 mmol/l HEPES, and 1 mmol/l pyruvate, pH 7.4).…”

Section: Methodsmentioning

confidence: 99%

“…Isolated adipocytes were incubated with various concentrations of bradykinin and/or NO inhibitors/scavengers/ donors for the times indicated. Basal and insulin-stimulated (100 nmol/l for 30 min at 37°C) rates of glucose uptake were assayed as described (18). Western blotting.…”

Section: -Deoxy-d-[mentioning

confidence: 99%

Bradykinin Augments Insulin-Stimulated Glucose Transport in Rat Adipocytes via Endothelial Nitric Oxide Synthase–Mediated Inhibition of Jun NH2-Terminal Kinase

Beard

et al. 2006

Diabetes

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An increase in bradykinin has been suggested to contribute to the enhanced insulin sensitivity observed in the presence of ACE inhibitors. To investigate a potential direct, nonvascular effect on an insulin target tissue, the effect of bradykinin on glucose uptake and insulin signaling was studied in primary rat adipocytes. Whereas basal glucose uptake was not altered, bradykinin augmented insulinstimulated glucose uptake twofold, which was blocked by HOE-140, a bradykinin B 2 receptor antagonist. The bradykinin effect on glucose uptake was nitric oxide (NO) dependent, mimicked by NO donors and absent in adipocytes from endothelial NO synthase ؊/؊ mice. Investigation of insulin signaling revealed that bradykinin enhanced insulin receptor substrate-1 (IRS-1) Tyr phosphorylation, Akt/protein kinase B phosphorylation, and GLUT4 translocation. In contrast, insulin-stimulated extracellular signal-regulated kinase1/2 and Jun NH 2 -terminal kinase (JNK) activation were decreased in the presence of bradykinin, accompanied by decreased IRS-1 Ser 307 phosphorylation. Furthermore, bradykinin did not enhance insulin action in the presence of the JNK inhibitor, SP-600125, or in adipocytes from JNK1 ؊/؊ mice. These data indicate that bradykinin enhances insulin sensitivity in adipocytes via an NO-dependent pathway that acts by modulating the feedback inhibition of insulin signaling at the level of IRS-1. Diabetes

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“…Normalization of mitochondrial reactive oxygen species by a number of different approaches prevents these phenomena (2). In adipocytes, Tang and colleagues (3) have shown that a combination of hyperglycemia and hyperinsulinemia results in reduced insulin-stimulated glucose uptake that was in part because of reduced insulin receptor dephosphorylation.…”

mentioning

confidence: 99%

“…Measurement of [1][2][3] H]2-Deoxyglucose Uptake-Assay of [ 3 H]2-deoxyglucose uptake was performed as described previously (8). Briefly, the cells were glucose starved for 30 min.…”

mentioning

confidence: 99%

The Hyperglycemia-induced Inflammatory Response in Adipocytes

Lin

Berg

Iyengar

et al. 2005

Journal of Biological Chemistry

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436

298

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Hyperglycemia is a major independent risk factor for diabetic macrovascular disease. The consequences of exposure of endothelial cells to hyperglycemia are well established. However, little is known about how adipocytes respond to both acute as well as chronic exposure to physiological levels of hyperglycemia. Here, we analyze adipocytes exposed to hyperglycemia both in vitro as well as in vivo. Comparing cells differentiated at 4 mM to cells differentiated at 25 mM glucose (the standard differentiation protocol) reveals severe insulin resistance in cells exposed to 25 mM glucose. A global assessment of transcriptional changes shows an up-regulation of a number of mitochondrial proteins. Exposure to hyperglycemia is associated with a significant induction of reactive oxygen species (ROS), both in vitro as well as in vivo in adipocytes isolated from streptozotocin-treated hyperglycemic mice. Furthermore, hyperglycemia for a few hours in a clamped setting will trigger the induction of a pro-inflammatory response in adipose tissue from rats that can effectively be reduced by co-infusion of N-acetylcysteine (NAC). ROS levels in 3T3-L1 adipocytes can be reduced significantly with pharmacological agents that lower the mitochondrial membrane potential, or by overexpression of uncoupling protein 1 or superoxide dismutase. In parallel with ROS, interleukin-6 secretion from adipocytes is significantly reduced. On the other hand, treatments that lead to a hyperpolarization of the mitochondrial membrane, such as overexpression of the mitochondrial dicarboxylate carrier result in increased ROS formation and decreased insulin sensitivity, even under normoglycemic conditions. Combined, these results highlight the importance ROS production in adipocytes and the associated insulin resistance and inflammatory response.Many genetic and environmental factors can lead to the development of insulin resistance. Once a degree of insulin resistance is established, decreased glucose tolerance arises and occasional bouts of hyperglycemia ensue. Hyperglycemia can in turn cause a further deterioration of insulin sensitivity in a number of tissues, such as the vascular endothelium, muscle, and adipocytes (1).In the vascular endothelium, hyperglycemia has been shown to activate protein kinase C isoforms, give rise to increased levels of glucose-derived advanced glycation end products, and to cause an increased glucose flux through the aldose reductase pathway. Normalization of mitochondrial reactive oxygen species by a number of different approaches prevents these phenomena (2). In adipocytes, Tang and colleagues (3) have shown that a combination of hyperglycemia and hyperinsulinemia results in reduced insulin-stimulated glucose uptake that was in part because of reduced insulin receptor dephosphorylation.Gagnon and Sorisky (4) have previously assessed the effects of low and high glucose levels on 3T3-L1 adipocytes and reported effects on insulin-mediated IRS-1 1 phosphorylation and associated phosphatidylinositol kinase activity. Lu and coll...

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Decreased In Situ Insulin Receptor Dephosphorylation in Hyperglycemia-Induced Insulin Resistance in Rat Adipocytes

Cited by 33 publications

References 72 publications

Enhanced Sensitivity of Insulin-resistant Adipocytes to Vanadate Is Associated with Oxidative Stress and Decreased Reduction of Vanadate (+5) to Vanadyl (+4)

Enhanced Sensitivity of Insulin-resistant Adipocytes to Vanadate Is Associated with Oxidative Stress and Decreased Reduction of Vanadate (+5) to Vanadyl (+4)

Bradykinin Augments Insulin-Stimulated Glucose Transport in Rat Adipocytes via Endothelial Nitric Oxide Synthase–Mediated Inhibition of Jun NH2-Terminal Kinase

The Hyperglycemia-induced Inflammatory Response in Adipocytes

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