Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0022116 (ischemia)
 91,303 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

All cells must maintain a high ratio of cellular ATP:ADP to survive. Because of the adenylate kinase reaction (2ADP <--> ATP + AMP), AMP rises whenever the ATP:ADP ratio falls, and a high cellular ratio of AMP:ATP is a signal that the energy status of the cell is compromised. The AMP-activated protein kinase (AMPK) is the downstream component of a protein kinase cascade that is switched on by a rise in the AMP:ATP ratio, via a complex mechanism that results in an exquisitely sensitive system. AMPK is switched on by cellular stresses that either interfere with ATP production (e.g. hypoxia, glucose deprivation, or ischemia) or by stresses that increase ATP consumption (e.g. muscle contraction). It is also activated by hormones that act via Gq-coupled receptors, and by leptin and adiponectin, via mechanisms that remain unclear. Once activated, the system switches on catabolic pathways that generate ATP, while switching off ATP-consuming processes that are not essential for short-term cell survival, such as the synthesis of lipids, carbohydrates, and proteins. The AMPK cascade is the probable target for the antidiabetic drug metformin, and current indications are that it is responsible for many of the beneficial effects of exercise in the treatment and prevention of type 2 diabetes and the metabolic syndrome.
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PMID:Minireview: the AMP-activated protein kinase cascade: the key sensor of cellular energy status. 1296 15

Obesity is a risk factor for the development of cardiovascular diseases that are associated with impaired angiogenesis. Adiponectin is an adipocyte-specific adipocytokine with anti-atherogenic and anti-diabetic properties, and its plasma levels are reduced in association with obesity-linked diseases. Here, we investigated whether adiponectin regulates angiogenesis in response to tissue ischemia using adiponectin knock-out (KO) mice. Angiogenic repair of ischemic hind limbs was impaired in adiponectin-KO mice compared with wild-type (WT) mice as evaluated by laser Doppler flow method and capillary density analyses. Adenovirus-mediated supplement of adiponectin accelerated angiogenic repair in both adiponectin-KO and WT mice. Intramuscular injection of an adenovirus encoding dominant-negative AMP-activated kinase diminished the improvement in limb perfusion seen in WT mice and abolished the adiponectin-induced enhancement of perfusion. These data indicate that adiponectin can function to stimulate angiogenesis in response to ischemic stress by promoting AMP-activated kinase signaling. Therefore, adiponectin may be useful in the treatment for obesity-related vascular deficiency diseases.
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PMID:Adiponectin stimulates angiogenesis in response to tissue ischemia through stimulation of amp-activated protein kinase signaling. 1512 26

Obesity-related disorders are associated with the development of ischemic heart disease. Adiponectin is a circulating adipose-derived cytokine that is downregulated in obese individuals and after myocardial infarction. Here, we examine the role of adiponectin in myocardial remodeling in response to acute injury. Ischemia-reperfusion in adiponectin-deficient (APN-KO) mice resulted in increased myocardial infarct size, myocardial apoptosis and tumor necrosis factor (TNF)-alpha expression compared with wild-type mice. Administration of adiponectin diminished infarct size, apoptosis and TNF-alpha production in both APN-KO and wild-type mice. In cultured cardiac cells, adiponectin inhibited apoptosis and TNF-alpha production. Dominant negative AMP-activated protein kinase (AMPK) reversed the inhibitory effects of adiponectin on apoptosis but had no effect on the suppressive effect of adiponectin on TNF-alpha production. Adiponectin induced cyclooxygenase (COX)-2-dependent synthesis of prostaglandin E(2) in cardiac cells, and COX-2 inhibition reversed the inhibitory effects of adiponectin on TNF-alpha production and infarct size. These data suggest that adiponectin protects the heart from ischemia-reperfusion injury through both AMPK- and COX-2-dependent mechanisms.
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PMID:Adiponectin protects against myocardial ischemia-reperfusion injury through AMPK- and COX-2-dependent mechanisms. 1621 Oct 35

Obesity-related disorders are closely associated with the pathogenesis of cardiovascular disease. Adiponectin is a circulating adipose tissue-derived hormone that is down-regulated in obese individuals. Hypoadiponectinemia has been identified as an independent risk factor for type 2 diabetes, coronary artery disease, and hypertension, and experimental studies show that adiponectin plays a protective role in the development of insulin resistance, atherosclerosis, and inflammation. More recent findings have shown that adiponectin directly affects signaling in myocardial cells and exerts beneficial actions on the heart after pressure overload and ischemia-reperfusion injury. This review focuses on the role of adiponectin in the regulation of myocardial remodeling and acute cardiac injury.
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PMID:Cardioprotection by adiponectin. 1678 46

Epigallocatechin gallate (EGCG), a bioactive polyphenol in green tea, may augment metabolic and vascular actions of insulin. Therefore, we investigated effects of EGCG treatment to simultaneously improve cardiovascular and metabolic function in spontaneously hypertensive rats (SHR; model of metabolic syndrome with hypertension, insulin resistance, and overweight). In acute studies, EGCG (1-100 microM) elicited dose-dependent vasodilation in mesenteric vascular beds (MVB) isolated from SHR ex vivo that was inhibitable by N(omega)-nitro-L-arginine methyl ester (L-NAME; nitric oxide synthase antagonist) or wortmannin [phosphatidylinositol (PI) 3-kinase inhibitor]. In chronic studies, 9-wk-old SHR were treated by gavage for 3 wk with EGCG (200 mg.kg(-1).day(-1)), enalapril (30 mg.kg(-1).day(-1)), or vehicle. A separate group of SHR receiving L-NAME (80 mg/l in drinking water) was treated for 3 wk with either EGCG or vehicle. Vasodilator actions of insulin were significantly improved in MVB from EGCG- or enalapril-treated SHR (when compared with vehicle-treated SHR). Both EGCG and enalapril therapy significantly lowered systolic blood pressure (SBP) in SHR. EGCG therapy of SHR significantly reduced infarct size and improved cardiac function in Langendorff-perfused hearts exposed to ischemia-reperfusion (I/R) injury. In SHR given L-NAME, beneficial effects of EGCG on SBP and I/R were not observed. Both enalapril and EGCG treatment of SHR improved insulin sensitivity and raised plasma adiponectin levels. We conclude that acute actions of EGCG to stimulate production of nitric oxide from endothelium using PI 3-kinase-dependent pathways may explain, in part, beneficial effects of EGCG therapy to simultaneously improve metabolic and cardiovascular pathophysiology in SHR. These findings may be relevant to understanding potential benefits of green tea consumption in patients with the metabolic syndrome.
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PMID:EGCG, a green tea polyphenol, improves endothelial function and insulin sensitivity, reduces blood pressure, and protects against myocardial I/R injury in SHR. 1722 56

Transient reduction in coronary perfusion pressure in the isolated mouse heart increases microvascular resistance (paradoxical vasoconstriction) by an endothelium-mediated mechanism. To assess the presence and extent of paradoxical vasoconstriction in hearts from normal and diabetic rats and to determine whether increased heme oxygenase (HO)-1 expression and HO activity, using cobalt protoporphyrin (CoPP), attenuates coronary microvascular response, male Wistar rats were rendered diabetic with nicotinamide/streptozotocin for 2 wk and either CoPP or vehicle was administered by intraperitoneal injection weekly for 3 wk (0.5 mg/100 g body wt). The isolated beating nonworking heart was submitted to transient low perfusion pressure (20 mmHg), and coronary resistance (CR) was measured. During low perfusion pressure, CR increased and was associated with increased lactate release. In diabetic rats, CR was higher, HO-1 expression and endothelial nitric oxide synthase were downregulated, and inducible nitric oxide synthase and O(2)(-) were upregulated. After 3 wk of CoPP treatment, HO activity was significantly increased in the heart. Upregulation of HO-1 expression and HO activity by CoPP resulted in the abolition of paradoxical vasoconstriction and a reduction in oxidative ischemic damage. In addition, there was a marked increase in serum adiponectin. Elevated HO-1 expression was associated with increased expression of cardiac endothelial nitric oxide synthase, B-cell leukemia/lymphoma extra long, and phospho activator protein kinase levels and decreased levels of inducible nitric oxide synthase and malondialdehyde. These results suggest a critical role for HO-1 in microvascular tone control and myocardial protection during ischemia in both normal and mildly diabetic rats through the modulation of constitutive and inducible nitric oxide synthase expression and activity, and an increase in serum adiponectin.
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PMID:Beneficial effect of heme oxygenase-1 expression on myocardial ischemia-reperfusion involves an increase in adiponectin in mildly diabetic rats. 1790 3

Mutation in PRKAG2 encoding the gamma2 subunit of the AMP activated protein kinase (AMPK) cause human cardiomyopathy characterized by hypertrophy, Wolff-Parkinson-White syndrome, conduction system disease and glycogen storage in the myocardium. AMPK is a master metabolic regulator activated by hormones and energy deficient states. A heterotrimer enzyme comprising the catalytic alpha- and regulatory beta-and gamma-subunits was preserved through evolution and is ubiquitously expressed among mammalian tissues. AMPK is activated by AMP and inhibited by ATP that competes for binding to the regulatory sites on the gamma-subunit. Upstream kinases which phosphorylate Thr172 on the catalytic subunit activate the enzyme during exercise, ischemia, in response to sympathetic stimulation and hormones such as leptin and adiponectin. AMPK operates by phosphorylating its target proteins such as Acetyl CoA Carboxylase. Its classic functions include decreased fat synthesis in liver and adipose tissues, increased fatty acid oxidation, stimulating muscle glucose uptake and glycolysis. Altogether, these activities serve to restore the cellular and whole body energy balance. Human mutations which disrupt the nucleotide-binding affinity of the gamma2 subunit lead to loss of inhibition by ATP and inappropriate activate AMPK under resting conditions. As a result, myocytes recruit energy metabolites in excess of demand, causing storage of glycogen. Will AMPK ever emerge as a therapeutic target? Bench experiments suggest its potential in treating diabetes, ischemia and cell cycle regulation but much work is needed until these developments reach the bedside.
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PMID:[AMP-activated protein kinase: how a mistake in energy gauge causes glycogen storage]. 1799 Mar 92

Adiponectin is a circulating cytokine with important cardioprotective effects. Plasma adiponectin levels are significantly reduced in patients with insulin resistance and type II diabetes mellitus and cardiovascular disease. Although adiponectin is primarily synthesized by adipocytes, new studies reveal that adiponectin is secreted by other cell types, including cardiomyocytes. Control of adiponectin gene expression in heart and microvasculature is poorly understood. We investigated the regulation of adiponectin expression by the transcription factor hypoxia inducible factor-1 (HIF-1) and its role in attenuating cardiac reperfusion injury. HIF-1 regulation of adiponectin was examined by isolating and characterizing the murine adiponectin promoter. HIF-1-dependent activation of the murine adiponectin promoter was verified via electrophoretic mobility shift assays, transient transfection assays, and QPCR. We show for the first time that HIF-1 activation via an siRNA-mediated prolyl 4-hydroxylase-2 gene silencing strategy induced adiponectin mRNA expression in murine microvascular endothelium in vitro (17-fold), intact hearts (22-fold, wild type; 5-fold, obese/diabetic) and white adipose tissue (37-fold, wild-type; 9.6-fold, obese/diabetic). HIF-1-induced adiponectin expression was associated with improved myocardial viability in obese/diabetic mice (32% increase) and preservation of left ventricular function (36% increase in rate pressure product). Our studies suggest that local production of adiponectin by cardiomyocytes/microvascular endothelial cells may regulate cardiac function and indicate a novel strategy for protecting diabetic hearts from ischemia/reperfusion injury.
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PMID:Hypoxia inducible factor-1 upregulates adiponectin in diabetic mouse hearts and attenuates post-ischemic injury. 1828 86

The adipose-derived plasma protein, adiponectin (APN), has various protective effects on cardiovascular diseases. In this study, we show that endogenous APN is required for full cyclooxygenase-2 (COX-2) induction by ischemia-reperfusion injury in the heart in vivo. In rat neonatal cardiac myocytes, APN-induced COX-2 expression was reduced by treatment with a sphingosine kinase-1 (SphK-1) inhibitor or siRNA targeting SphK-1. Treatment with a sphingosine-1-phosphate (S1P) receptor antagonist also diminished COX-2 expression in response to APN stimulation. These findings suggest that APN is a physiological regulator of COX-2 signaling in the heart and that this regulation occurs in part via a SphK-1-S1P receptor dependent mechanism in cardiac myocytes.
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PMID:Cyclooxygenase-2 induction by adiponectin is regulated by a sphingosine kinase-1 dependent mechanism in cardiac myocytes. 1833 20

Obesity-linked diseases are associated with suppressed endothelial progenitor cell (EPC) function. Adiponectin is an adipose-derived protein that is downregulated in obese and diabetic subjects. Here, we investigated the effects of adiponectin on EPCs. EPC levels did not increase in adiponectin deficient (APN-KO) in response to hindlimb ischemia. Adenovirus-mediated delivery of adiponectin increased EPC levels in both WT and APN-KO mice. Incubation of human peripheral blood mononuclear cells with adiponectin led to an increase of the number of EPCs. Adiponectin induced EPC differentiation into network structures and served as a chemoattractant in EPC migration assays. These data suggest that hypoadiponectinemia may contribute to the depression of EPC levels that are observed in patients with obesity-related cardiovascular disorders.
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PMID:Adiponectin promotes endothelial progenitor cell number and function. 1842 3


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