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PMID |
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9493493
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The aetiology of insulin resistance is likely to be multifactorial, but the present review focuses on candidate post-receptor mechanisms of insulin resistance, particularly protein kinase C (PKC), and the metabolic and genetic significance of beta3-adrenoceptors (beta3-AR) in adipose tissue. 2.
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2 |
9493493
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Multiple lines of evidence suggest that isoform-selective activation of PKC phosphorylates and down-regulates one or more substrates involved in glucose transport and metabolism (e.g. glycogen synthase and the insulin receptor) and recent studies have shown increased expression of calcium-independent isozymes (PKC-epsilon and PKC-theta) in the membrane fraction of skeletal muscle in fructose- and fat-fed rat models of insulin resistance.
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3 |
9493493
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New pharmacological approaches to NIDDM and obesity have focused on insulin-sensitizing agents (e.g. troglitazone), beta3-AR agonists, anti-lipolytic drugs (e.g. the adenosine A1 receptor agonist GR79236) and selective inhibitors of PKC isoforms (e.g. the inhibitor of PKC-beta LY333531).
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4 |
9726238
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Because retinal ischemia is known to increase intracellular adenosine levels, which subsequently regulate hypoxia-inducible genes, such as vascular endothelial growth factor and erythropoietin, the role of adenosine and its receptor-mediated pathways has also been evaluated.
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5 |
9726238
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N6-Cyclopentyl adenosine (adenosine A1 receptor agonist, Kd = 1 nmol/l) did not affect GLUT1 mRNA expression at concentrations up to 1 micromol/l, while 2-p-(2-carboxyethyl)-phenethyl-amino-5'-N-ethylcarboxamidoadenosine and 5'-(N-ethylcalboxamido)-adenosine (adenosine A2 receptor [A2R] agonists, Kd = 15 and 16 nmol/l, respectively) increased mRNA levels at concentrations as low as 10 nmol/l.
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6 |
9726238
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The adenosine A2a receptor antagonist 8-(3-chlorostyryl)caffeine (CSC) (Kd = 100 nmol/l for A2R) inhibited hypoxia-stimulated GLUT1 mRNA expression by 40 +/- 8% at 100 nmo/l.
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7 |
9726238
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A protein kinase A (PKA) inhibitor (H89, 20 micromol/l) suppressed hypoxia-induced GLUT1 mRNA expression by 42 +/- 9% (P < 0.01).
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8 |
10615945
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Role of adenosine in insulin-stimulated release of leptin from isolated white adipocytes of Wistar rats.
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9 |
10615945
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Leptin, the ob gene product that can decrease caloric intake and increase energy expenditure, is functionally released by insulin from adipose tissue.
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10 |
10615945
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The present study investigated the role of adenosine in the release of leptin by insulin in isolated rat white adipocytes.
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11 |
10615945
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Release of leptin, measured by radioimmunoassay, from insulin-stimulated samples was seen after 30 min.
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12 |
10615945
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Adenosine deaminase, at concentrations sufficient to metabolize endogenous adenosine, decreased insulin-stimulated leptin release.
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13 |
10615945
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Also, the insulin-stimulated leptin release was completely blocked by the adenosine A1 receptor antagonist 8-cyclopentyl-1,3-dipropylxanthine (DPCPX).
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14 |
10615945
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In the presence of U73312, a specific inhibitor of phospholipase C (PLC), CPA-stimulated leptin secretion from adipocytes was reduced in a concentration-dependent manner, but it was not affected by U73343, the negative control for U73312.
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10615945
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Moreover, chelerythrine and GF 109203X diminished the CPA-stimulated leptin secretion at concentrations sufficient to inhibit protein kinase C (PKC).
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16 |
10615945
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These results suggest that, in isolated white adipocytes, the released adenosine acts as a helper and/or a positive regulator for insulin in the release of leptin via an activation of adenosine A1 receptors that involves the PLC-PKC pathway.
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17 |
11593763
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To examine the role of the adenosine A1 receptor in glucose regulation in the absence of insulin, the present study investigated the changes of plasma glucose in male streptozotocin-induced diabetic rats (STZ-diabetic rats) using dipyridamole to increase endogenous adenosine and N6-cyclopentyladenosine (CPA) to activate the adenosine A1 receptor.
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18 |
18979526
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Modulation of insulin release by adenosine A1 receptor agonists and antagonists in INS-1 cells: the possible contribution of 86Rb+ efflux and 45Ca2+ uptake.
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19 |
19552053
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Adenosine (100, 200 and 500 mg/kg, ip) produced significant reversal of responses to thermal and chemical stimuli in diabetic rats. 8-Cyclopentyl-1, 3-dipropylxanthine (DPCPX 1 mg/kg, ip), an adenosine A1-receptor antagonist, but not 3,7-dimethyl-1-propargylxanthine (DMPX 1 mg/kg, ip), an adenosine A2A-receptor antagonist, reversed the protective effect of adenosine.
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20 |
23283998
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Accordingly, the changes in their functions were investigated in control and 2-wk streptozotocin-diabetic rats after intrarenal infusion of the ANG II AT1 receptor antagonist candesartan, the adenosine A1 receptor antagonist 8-cyclopentyl-1,3-dipropylxanthine (DPCPX), or their combination.
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21 |
23700520
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Adenosine A1 receptor-deficient mice develop a phenotype of insulin resistance and grow fat.
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22 |
23700520
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This commentary further explores possible pathophysiological mechanisms with emphasis on the roles of the adipokines resistin, retinol-binding protein 4, adiponectin and the function of the gastric hormone ghrelin in adenosine mediated central regulation of energy balance.
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