Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.11.31 (AMP-activated protein kinase)
 13,065 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Adiponectin (Ad) is a hormone secreted by adipocytes that regulates energy homeostasis and glucose and lipid metabolism. However, the signaling pathways that mediate the metabolic effects of Ad remain poorly identified. Here we show that phosphorylation and activation of the 5'-AMP-activated protein kinase (AMPK) are stimulated with globular and full-length Ad in skeletal muscle and only with full-length Ad in the liver. In parallel with its activation of AMPK, Ad stimulates phosphorylation of acetyl coenzyme A carboxylase (ACC), fatty-acid oxidation, glucose uptake and lactate production in myocytes, phosphorylation of ACC and reduction of molecules involved in gluconeogenesis in the liver, and reduction of glucose levels in vivo. Blocking AMPK activation by dominant-negative mutant inhibits each of these effects, indicating that stimulation of glucose utilization and fatty-acid oxidation by Ad occurs through activation of AMPK. Our data may provide a novel paradigm that an adipocyte-derived antidiabetic hormone, Ad, activates AMPK, thereby directly regulating glucose metabolism and insulin sensitivity in vitro and in vivo.
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PMID:Adiponectin stimulates glucose utilization and fatty-acid oxidation by activating AMP-activated protein kinase. 1236 7

Adiponectin is an abundant adipocyte-derived plasma protein with anti-atherosclerotic and insulin-sensitizing properties that suppresses hepatic glucose production and enhances glucose uptake into skeletal muscle. To characterize the potential effects of adiponectin on glucose uptake into adipose cells, we incubated isolated epididymal rat adipocytes with the globular domain of recombinant adiponectin purified from an E. coli expression system. Globular adiponectin increased glucose uptake in adipocytes without stimulating tyrosine phosphorylation of the insulin receptor or insulin receptor substrate-1, and without enhancing phosphorylation of Akt on Ser-473. Globular adiponectin further enhanced insulin-stimulated glucose uptake at submaximal insulin concentrations and reversed the inhibitory effect of tumor necrosis factor-alpha on insulin-stimulated glucose uptake. Cellular treatment with globular adiponectin increased the Thr-172 phosphorylation and catalytic activity of AMP-activated protein kinase and enhanced the Ser-79 phosphorylation of acetyl CoA carboxylase, an enzyme downstream of AMP kinase in adipose cells. Inhibition of AMP kinase activation using two pharmacological inhibitors (adenine 9-beta-D-arabinofuranoside and compound C) completely abrogated the increase in glucose uptake stimulated by globular adiponectin, indicating that AMP kinase is integrally involved in the adiponectin signal transduction pathway. Coupled with recent evidence that the effects of adiponectin are mediated via AMP kinase activation in liver and skeletal muscle, the findings reported here provide an important mechanistic link in the signaling effects of adiponectin in diverse metabolically responsive tissues.
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PMID:Involvement of AMP-activated protein kinase in glucose uptake stimulated by the globular domain of adiponectin in primary rat adipocytes. 1276 44

Adiponectin is an insulin-sensitizing hormone whose blood concentration is reduced in obesity and type 2 diabetes. Administration of recombinant adiponectin in rodents increases glucose uptake and increases fat oxidation in muscle, reduces fatty acid uptake and hepatic glucose production in liver, and improves whole body insulin resistance. The exact receptor and signaling systems are unknown, however, recent studies suggest adiponectin activates AMPK, a putative master metabolic regulator. Thus, excitement surrounds the potential for adiponectin, or a homologue of adiponectin, as pharamacotherapy agents for patients suffering from the metabolic syndrome and more particularly for individuals with insulin resistance and type 2 diabetes.
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PMID:The insulin-sensitizing role of the fat derived hormone adiponectin. 1276 32

Adiponectin is an adipocyte-derived hormone, which has been shown to play important roles in the regulation of glucose and lipid metabolism. Eight mutations in human adiponectin have been reported, some of which were significantly related to diabetes and hypoadiponectinemia, but the molecular mechanisms of decreased plasma levels and impaired action of adiponectin mutants were not clarified. Adiponectin structurally belongs to the complement 1q family and is known to form a characteristic homomultimer. Herein, we demonstrated that simple SDS-PAGE under non-reducing and non-heat-denaturing conditions clearly separates multimer species of adiponectin. Adiponectin in human or mouse serum and adiponectin expressed in NIH-3T3 or Escherichia coli formed a wide range of multimers from trimers to high molecular weight (HMW) multimers. A disulfide bond through an amino-terminal cysteine was required for the formation of multimers larger than a trimer. An amino-terminal Cys-Ser mutation, which could not form multimers larger than a trimer, abrogated the effect of adiponectin on the AMP-activated protein kinase pathway in hepatocytes. Among human adiponectin mutations, G84R and G90S mutants, which are associated with diabetes and hypoadiponectinemia, did not form HMW multimers. R112C and I164T mutants, which are associated with hypoadiponectinemia, did not assemble into trimers, resulting in impaired secretion from the cell. These data suggested impaired multimerization and/or the consequent impaired secretion to be among the causes of a diabetic phenotype or hypoadiponectinemia in subjects having these mutations. In conclusion, not only total concentrations, but also multimer distribution should always be considered in the interpretation of plasma adiponectin levels in health as well as various disease states.
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PMID:Impaired multimerization of human adiponectin mutants associated with diabetes. Molecular structure and multimer formation of adiponectin. 1287 98

Adiponectin is secreted by adipose cells and mimics many metabolic actions of insulin. However, mechanisms by which adiponectin acts are poorly understood. The vascular action of insulin to stimulate endothelial production of nitric oxide (NO), leading to vasodilation and increased blood flow is an important component of insulin-stimulated whole body glucose utilization. Therefore, we hypothesized that adiponectin may also stimulate production of NO in endothelium. Bovine aortic endothelial cells in primary culture loaded with the NO-specific fluorescent dye 4,5-diaminofluorescein diacetate (DAF-2 DA) were treated with lysophosphatidic acid (LPA) (a calcium-releasing agonist) or adiponectin (10 microg/ml bacterially produced full-length adiponectin). LPA treatment increased production of NO by approximately 4-fold. Interestingly, adiponectin treatment significantly increased production of NO by approximately 3-fold. Preincubation of cells with wortmannin (phosphatidylinositol 3-kinase inhibitor) blocked only adiponectin- but not LPA-mediated production of NO. Using phospho-specific antibodies, we observed that either adiponectin or insulin treatment (but not LPA treatment) caused phosphorylation of both Akt at Ser473 and endothelial nitric-oxide synthase (eNOS) at Ser1179 that was inhibitable by wortmannin. We next transfected bovine aortic endothelial cells with dominant-inhibitory mutants of Akt (Akt-AAA) or AMP-activated protein kinase (AMPK) (AMPKK45R). Neither mutant affected production of NO in response to LPA treatment. Importantly, only AMPKK45R, but not Akt-AAA, caused a significant partial inhibition of NO production in response to adiponectin. Moreover, AMPK-K45R inhibited phosphorylation of eNOS at Ser1179 in response to adiponectin but not in response to insulin. We conclude that adiponectin has novel vascular actions to directly stimulate production of NO in endothelial cells using phosphatidylinositol 3-kinase-dependent pathways involving phosphorylation of eNOS at Ser1179 by AMPK. Thus, the effects of adiponectin to augment metabolic actions of insulin in vivo may be due, in part, to vasodilator actions of adiponectin.
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PMID:Adiponectin stimulates production of nitric oxide in vascular endothelial cells. 1294 90

Adiponectin is an adipocyte-specific adipocytokine with anti-atherogenic and anti-diabetic properties. Here, we investigated whether adiponectin regulates angiogenic processes in vitro and in vivo. Adiponectin stimulated the differentiation of human umbilical vein endothelium cells (HUVECs) into capillary-like structures in vitro and functioned as a chemoattractant in migration assays. Adiponectin promoted the phosphorylation of AMP-activated protein kinase (AMPK), protein kinase Akt/protein kinase B, and endothelial nitric oxide synthesis (eNOS) in HUVECs. Transduction with either dominant-negative AMPK or dominant-negative Akt abolished adiponectin-induced eNOS phosphorylation as well as adiponectin-stimulated HUVEC migration and differentiation. Dominant-negative AMPK also inhibited adiponectin-induced Akt phosphorylation, suggesting that AMPK is upstream of Akt. Dominant-negative Akt or the phosphatidylinositol 3-kinase inhibitor LY294002 blocked adiponectin-stimulated Akt and eNOS phosphorylation, migration, and differentiation without altering AMPK phosphorylation. Finally, adiponectin stimulated blood vessel growth in vivo in mouse Matrigel plug implantation and rabbit corneal models of angiogenesis. These data indicate that adiponectin can function to stimulate the new blood vessel growth by promoting cross-talk between AMP-activated protein kinase and Akt signaling within endothelial cells.
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PMID:Adiponectin stimulates angiogenesis by promoting cross-talk between AMP-activated protein kinase and Akt signaling in endothelial cells. 1455 59

Adiponectin is an adipocyte-derived, antiatherogenic protein that is present in serum as three isoforms. Total adiponectin levels are decreased in obese or diabetic humans or animal models. This study was designed to elucidate the relative isoform distribution of adiponectin in human disease states and identify the active form of adiponectin toward vascular endothelial cells. The percentage of high molecular weight form (HMW) per total adiponectin was significantly lower in patients with coronary artery disease than control subjects, whereas the hexamer form was similar and the trimer form was significantly higher. During weight reduction in obese subjects, the HMW form increased and the trimer and hexamer forms decreased. Recombinant adiponectin dose-dependently suppressed apoptosis and caspase-3 activity in human umbilical vein endothelial cells (HUVECs). Transduction with dominant-negative AMP-activated protein kinase (AMPK) abolished the suppressive effect of adiponectin on HUVECs. Gel filtration chromatography was used to separate the adiponectin isoforms, and the antiapoptotic effect toward HUVECs was only observed with the HMW form. These data suggest that HMW adiponectin specifically confers the vascular-protective activities of this adipocytokine. The full text of this article is available online at http://circres.ahajournals.org.
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PMID:Selective suppression of endothelial cell apoptosis by the high molecular weight form of adiponectin. 1475 31

Insulin resistance is characterized by a peripheral resistance to insulin-mediated glucose uptake, and an hepatic resistance of glucose production to insulin. Insulin resistance in skeletal muscle is of a particular importance, and could be the consequence of an increase in intracellular and circulating fatty acids and triglycerides. Adipose tIssue plays an important role to regulate mobilization and release of fatty acids. Adipose tIssue is an endocrine organ which secretes several factors, including adiponectin. Adiponectin improves insulin sensitivity in skeletal muscle and liver, through a stimulation of fatty acid oxidation and glucose utilization. Thiazolidinediones enhance adiponectin expression and synthesis through PPARgamma, although the precise mechanism remains controversial. AMP-activated protein kinase (AMPK) is the main adiponectin target. Adiponectin, clearly, is a major modulator of glucose and lipid metabolism in insulin-sensitive tIssue and/or regulator of insulin-sensitivity, in obese and/or glucose intolerant subjects, as well as in type 2 diabetes mellitus. Recent works and the links between insulin resistance, adipose tIssue, adiponectin and its PPARgamma-enhanced secretion are reviewed in this paper.
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PMID:[Adiponectin: from adipocyte to skeletal muscle]. 1516 22

Adiponectin (also called AdipoQ, gelatin-binding protein 28, Acrp30) is a novel adipocytokine with important metabolic effects. It is physiologically released from adipose tissue and circulates in serum as a hexamer and larger multimeric structure of high molecular weight. Serum level of the protein correlates with systemic insulin sensitivity. Recently adiponectin receptors AdipoR1 and AdipoR2 have been discovered by expression cloning. AdipoR1 is abundantly expressed in skeletal muscles, whereas AdipoR2 is predominantly expressed in the liver. Marked expression of mRNA for AdipoR1 and AdipoR2 has been lately reported in pancreatic beta cells. Both of the receptors activate AMPK and PPAR alpha metabolic pathways leading to an increase in fatty acid oxidation, glucose uptake and a decreased rate of gluconeogenesis, thus enhancing insulin sensitivity. Moreover effects of adiponectin mimic many metabolic actions of insulin such as augmenting blood flow and glucose disposal in NO-dependent manner. The precise mechanism of regulation of plasma adiponectin level is unknown. Recently the mechanism of transcriptional activation of adiponectin gene via PPAR gamma was described. Its level seems to be decreased by TNFalfa and beta-adrenergic agonists. Furthermore there is increasing evidence that some genetic variants in the adiponectin gene may be associated with its ethnical differences in level as well as its likely clinical consequences. Hipoadiponectynemia is associated with obesity, metabolic syndrome, diabetes type 2, cardiovascular disease, lipodystrophy in AIDS. In patients with chronic renal failure, anorexia nervosa plasma adlponectin level is increased. Weight loss and therapy with thlazolidinediones are proved to enhance endogenous adlponectin production in humans. In summary, the ability of adiponectin to increase insulin sensitivity in conjunction with its anti-inflammatory and antiatherogenic properties have made this novel adipocytokine a promising therapeutic tool for the future, especially in individuals with low plasma levels of adiponectin.
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PMID:[Adiponectin--adipocytokine with a broad clinical spectrum]. 1523 Jan 53

Patients with diabetes and other obesity-linked conditions have increased susceptibility to cardiovascular disorders. The adipocytokine adiponectin is decreased in patients with obesity-linked diseases. Here, we found that pressure overload in adiponectin-deficient mice resulted in enhanced concentric cardiac hypertrophy and increased mortality that was associated with increased extracellular signal-regulated kinase (ERK) and diminished AMP-activated protein kinase (AMPK) signaling in the myocardium. Adenovirus-mediated supplemention of adiponectin attenuated cardiac hypertrophy in response to pressure overload in adiponectin-deficient, wild-type and diabetic db/db mice. In cultures of cardiac myocytes, adiponectin activated AMPK and inhibited agonist-stimulated hypertrophy and ERK activation. Transduction with a dominant-negative form of AMPK reversed these effects, suggesting that adiponectin inhibits hypertrophic signaling in the myocardium through activation of AMPK signaling. Adiponectin may have utility for the treatment of hypertrophic cardiomyopathy associated with diabetes and other obesity-related diseases.
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PMID:Adiponectin-mediated modulation of hypertrophic signals in the heart. 1555 58


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