Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.11.11 (AMPK)
 12,425 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

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

Obesity, a state of increased adipose tissue mass, is a major cause for type 2 diabetes, hyperlipidemia, and hypertension, resulting in clustering of risk factors for atherosclerosis. Heterozygous PPARgamma knockout mice and KKA(y) mice administered with a PPARgamma antagonist were protected from high-fat diet-induced adipocyte hypertrophy and insulin resistance. Moderate reduction of PPARgamma activity prevented adipocyte hypertrophy, thereby diminution of TNFalpha, resistin, and FFA and upregulation of adiponectin and leptin. These alterations led to reduction of tissue TG content in muscle/liver, thereby ameliorating insulin resistance. Insulin resistance in the lipoatrophic mice and KKA(y) mice were ameliorated by replenishment of adiponectin. Moreover, adiponectin transgenic mice ameliorated insulin resistance and diabetes, but not the obesity of ob/ob mice. Furthermore, targeted disruption of the adiponectin gene caused moderate insulin resistance and glucose intolerance. In muscle, adiponectin activated AMP kinase and PPARgamma pathways, thereby increasing beta-oxidation of lipids, leading to decreased TG content, which ameliorated muscle insulin resistance. In the liver, adiponectin also activated AMPK, thereby downregulating PEPCK and G6Pase, leading to decreased glucose output from the liver. In conclusion, PPARgamma plays a central role in the regulation of adipocyte hypertrophy and insulin sensitivity. The upregulation of the adiponectin pathway by PPARgamma may play a role in the increased insulin sensitivity of heterozygous PPARgamma knockout mice, and activation of adiponectin pathway may provide novel therapeutic strategies for obesity-linked disorders such as type 2 diabetes and metabolic syndrome.
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PMID:[The mechanisms by which PPARgamma and adiponectin regulate glucose and lipid metabolism]. 1450 Nov 64

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

Metabolic syndrome is thought to result from obesity and obesity-linked insulin resistance. Obesity in adulthood is characterized by adipocyte hypertrophy. Adipose tissue participates in the regulation of energy homeostasis as an important endocrine organ that secretes a number of biologically active "adipokines."Heterozygous peroxisome proliferator-activated receptor-gamma knockout mice were protected from high-fat diet induced obesity, adipocyte hypertrophy, and insulin resistance. Systematic gene profiling analysis of these mice revealed that adiponectin/Acrp30 was overexpressed. Functional analyses including generation of adiponectin transgenic or knockout mice have revealed that adiponectin serves as an insulin-sensitizing adipokine. In fact, obesity-linked down-regulation of adiponectin was a mechanism whereby obesity could cause insulin resistance and diabetes. Recently, we have cloned adiponectin receptors in the skeletal muscle (AdipoR1) and liver (AdipoR2), which appear to comprise a novel cell-surface receptor family. We showed that AdipoR1 and AdipoR2 serve as receptors for globular and full-length adiponectin and mediate increased AMP-activated protein kinase, peroxisome proliferator-activated receptor-alpha ligand activities, and glucose uptake and fatty-acid oxidation by adiponectin. Obesity decreased expression levels of AdipoR1/R2, thereby reducing adiponectin sensitivity, which finally leads to insulin resistance, the so-called "vicious cycle." Most recently, we showed that osmotin, which is a ligand for the yeast homolog of AdipoR (PHO36), activated AMPK via AdipoR in C2C12 myocytes. This may facilitate efficient development of adiponectin receptor agonists. Adiponectin receptor agonists and adiponectin sensitizers should serve as versatile treatment strategies for obesity-linked diseases such as diabetes and metabolic syndrome.
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PMID:Adiponectin and adiponectin receptors. 1589 98

We show that Topiramate (TPM) treatment normalizes whole body insulin sensitivity in high-fat diet (HFD)-fed male Wistar rats. Thus drug treatment markedly lowered glucose and insulin levels during glucose tolerance tests and caused increased insulin sensitization in adipose and muscle tissues as assessed by euglycemic clamp studies. The insulin-stimulated glucose disposal rate increased twofold (indicating enhanced muscle insulin sensitivity), and suppression of circulating FFAs increased by 200 to 300%, consistent with increased adipose tissue insulin sensitivity. There were no effects of TPM on hepatic insulin sensitivity in these TPM-treated HFD-fed rats. In addition, TPM administration resulted in a three- to fourfold increase in circulating levels of total and high-molecular-weight (HMW) adiponectin (Acrp30). Western blot analysis revealed normal AMPK (Thr(172)) phosphorylation in liver with a twofold increased phospho-AMPK in skeletal muscle in TPM-treated rats. In conclusion, 1) TPM treatment prevents overall insulin resistance in HFD male Wistar rats; 2) drug treatment improved insulin sensitivity in skeletal muscle and adipose tissue associated with enhanced AMPK phosphorylation; and 3) the tissue "specific" effects are associated with increased serum levels of adiponectin, particularly the HMW component.
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PMID:Topiramate treatment causes skeletal muscle insulin sensitization and increased Acrp30 secretion in high-fat-fed male Wistar rats. 1603 65

Adiponectin is thought to play a decisive role in the relationships among obesity, insulin resistance and cardiovascular risk. This study investigated whether cardiomyocytes synthesize and secrete adiponectin, and the effects of this hormone on cardiac cells. RT-PCR showed that mouse, rat and human cardiomyocytes produced mRNA for adiponectin and adiponectin receptors 1 and 2. Immunohistochemistry confirmed the presence of adiponectin in the cytoplasm of cultured cardiomyocytes, and radioimmunoassay showed that these cells secreted adiponectin into the culture medium. Exogenous adiponectin enhanced glucose and fatty acid uptake and induced AMPK phosphorylation in cultured cardiomyocytes. Our results demonstrate that adiponectin is synthesized and secreted by isolated murine and human cardiomyocytes, and suggest that the local production of this hormone by cardiomyocytes could be involved in the regulation of cardiac metabolism and function.
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PMID:Adiponectin is synthesized and secreted by human and murine cardiomyocytes. 1614 Feb 97

Hepatic gluconeogenesis plays a key role in the maintenance of glucose homeostasis. The hormone glucagon stimulates this process, whereas insulin and adiponectin are inhibitory. In a recent report, Koo et al identify the transcriptional regulator TORC2 (Transducer of Regulated CREB activity 2) as a pivotal component of the gluconeogenic program.1 Both insulin and AMPK increase the phosphorylation of TORC2, while glucagon suppresses it. This in turn regulates the nuclear/cytoplasmic shuttling of TORC2 and its ability to transactivate gluconeogenic genes. Thus, TORC2 might serve as a gluconeogenic "molecular switch" that senses hormones and cellular energy status.
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PMID:More TORC for the gluconeogenic engine. 1647 85

Most rodent models of insulin resistance are accompanied by decreased circulating adiponectin levels. Adiponectin treatment improves the metabolic phenotype by increasing fatty acid oxidation in skeletal muscle and suppressing hepatic glucose production. Muscle IGF-I receptor (IGF-IR)-lysine-arginine (MKR) mice expressing dominant-negative mutant IGF-IRs in skeletal muscle are diabetic with insulin resistance in muscle, liver, and adipose tissue. Adiponectin levels are elevated in MKR mice, suggesting an unusual discordance between insulin resistance and adiponectin responsiveness. Therefore, we investigated the metabolic actions of adiponectin in MKR mice. MKR and ob/ob mice were treated both acutely (28 microg/g) and chronically (for 2 wk) with full-length adiponectin. Acute hypoglycemic effects of adiponectin were evident only in ob/ob mice but not in MKR mice. Chronic adiponectin treatment significantly improved both insulin sensitivity and glucose tolerance in ob/ob but not in MKR mice. Adiponectin receptor mRNA levels and adiponectin-stimulated phosphorylation of AMPK in skeletal muscle and liver were similar among MKR, wild-type, and ob/ob mice. Thus MKR mice are adiponectin resistant despite normal expression of adiponectin receptors and normal AMPK phosphorylation in muscle and liver. MKR mice may be a useful model for dissecting relationships between insulin resistance and adiponectin action in regulation of glucose homeostasis.
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PMID:MKR mice are resistant to the metabolic actions of both insulin and adiponectin: discordance between insulin resistance and adiponectin responsiveness. 1650 4

Adipose tissue is an active endocrine organ producing a variety of cytokines and chemokines, which may be involved in the deregulation of glucose and lipid homeostasis as well as in the inflammatory state observed in obesity. We have shown previously that differentiated human adipocytes secrete a variety of cytokines which are able to induce skeletal muscle insulin resistance. However, the regulation of these factors by anti-diabetic drugs has remained mainly undefined. Secretion of IL-6, IL-8, MIP-1alpha/beta, and MCP-1 by adipocytes was found to be downregulated by adiponectin. In parallel to adiponectin, the AMPK activator AICAR also decreased the secretion of most of the measured cytokines including IL-6 and MIP-1alpha/beta but not IL-8. In contrast, the thiazolidinedione troglitazone only slightly reduced cytokine secretion despite increasing the phosphorylation of AMPK. In conclusion, we show that adipocyte secretion is strongly inhibited by the anti-diabetic adipocyte hormone adiponectin, an effect that can also be mimicked by the AMPK activator AICAR. However, the PPARgamma agonist troglitazone is much less effective in reducing cytokine secretion.
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PMID:Cytokine secretion by human adipocytes is differentially regulated by adiponectin, AICAR, and troglitazone. 1656 50

The LKB1-->AMPK cascade is switched on by metabolic stresses that either inhibit ATP production (e.g. hypoxia, hypoglycaemia) or that accelerate ATP consumption (e.g. muscle contraction). Any decline in cellular energy status is accompanied by a rise in the cellular AMP: ATP ratio, and this activates AMPK by a complex and sensitive mechanism involving antagonistic binding of the nucleotides to two sites on the regulatory gamma subunits of AMPK. Once activated by metabolic stress, AMPK activates catabolic pathways that generate ATP, while inhibiting cell growth and biosynthesis and other processes that consume ATP. While the AMPK system probably evolved in single-celled eukaryotes to maintain energy balance at the cellular level, in multicellular organisms its role has become adapted so that it is also involved in maintaining whole body energy balance. Thus, it is regulated by hormones and cytokines, especially the adipokines leptin and adiponectin, increasing whole body energy expenditure while regulating food intake. Some hormones may activate AMPK by an LKB1-independent mechanism involving Ca2+/calmodulin dependent protein kinase kinases. Low levels of activation of AMPK are likely to play a role in the current global rise in obesity and Type 2 diabetes, and AMPK is the target for the widely used antidiabetic drug metformin.
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PMID:AMP-activated protein kinase--development of the energy sensor concept. 1664


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