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Query: UMLS:C0018801 (heart failure)
 72,216 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The mammalian heart is normally well oxygenated and anaerobic glycolysis is extremely rare except for the production of extra ATP during extreme exercise like a marathon race. Anaerobic glycolysis plays a role when there is a serious impairment in coronary blood flow such as during heart attack and open heart surgery. The control of glycolysis in ischemic myocardial tissue appears to be extremely complex. During aerobic glycolysis, phosphofructokinase is the most important regulatory enzyme that controls the energy requirements of the cell. Under anaerobic conditions, however, glyceraldehyde-3-phosphate dehydrogenase becomes the key enzyme because it responds promptly to any changes in the essential supply of co-factors for oxidation. The conversion of pyruvate to acetyl CoA (aerobic metabolism) involves a series of chain reactions primarily catalyzed by pyruvate dehydrogenase complex which is situated at the cross roads between both aerobic and anaerobic glycolysis. It is important to remember that substrate utilization is carefully controlled by substrate availability. During aerobic metabolism, control mechanisms using fatty acids, lactate and glucose as energy substrates regulate the rate of ATP production according to energy demand. This precise mechanism is upset during ischemia and post-ischemic reperfusion for reasons discussed in this review. The demand for ATP can no longer be met by its supply because of severely reduced anaerobic glycolysis and significantly inhibited beta-oxidation of fatty acids. The impairment of bioenergetics is discussed in the context of several diseases such as cardiomyopathy, heart failure, diabetes, arrhythmias, cardiac surgery, heart-lung transplantation, and also in aging and oxidative stress. The regulation of energy metabolism in preconditioned heart is also discussed. Finally, methods used to preserve energy in ischemic myocardium are summarized and quantitation of the high-energy phosphates is discussed. This review challenges scientists to discover drugs which will stimulate energy supply during myocardial ischemia.
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PMID:Bioenergetics, ischemic contracture and reperfusion injury. 880 94

Alterations in substrate selection and utilisation are characteristics of heart failure of different etiologies and these changes may be involved in the development of contractile dysfunction. Regulation of pyruvate dehydrogenase (PDH) is crucial in determining the relative contribution of glucose oxidation to energy production; however, the role of PDH in the development of heart failure has not been clarified. In this study, we present a reliable and simple method for assaying both the active and total forms of PDH (PDHa and PDHt respectively) in cardiac tissue, and have compared the effects of pressure overload hypertrophy and diabetes on PDH activity. PDHa and PDHt were measured in extracts of hypertrophied hearts after 5 weeks of pressure overload or in hearts after 7 weeks following induction of diabetes. There was no significant change in PDHt in the hypertrophied group, but the fraction of PDH in the active form significantly decreased from 61+/-1% in controls to 36+/-1% (P<0.05). Following diabetes, there was a decrease in the ratio of PDHa:PDHt from 60+/-3% to 11+/-1% (P<0.0001) and PDHt activity -6.2+/-0.9 to 2.7+/-0.4 micromol/min/g wet weight (P<0.02)]. This study reports for the first time that (i) concomitant with the development of compensated hypertrophy, there is a decrease in the fraction of PDH in the active form; and (ii) in the diabetic heart, there is marked decrease in total PDH activity in addition to a decrease in the fraction of PDH in the active form. These results indicate that myocardial substrate delivery to the mitochondria may be impaired in both hypertrophy and diabetes, which may lead to the energy depleted state observed in heart failure.
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PMID:The effects of hypertrophy and diabetes on cardiac pyruvate dehydrogenase activity. 934 71

The aim of the present study was to define the cellular mechanisms underlying changes in K+ channel function in the failing heart after myocardial infarction. Rats with left coronary artery ligation were prepared and allowed to recover for 16 wk before study. Animals with chronic infarction exhibited marked cardiac hypertrophy and signs of heart failure, as indicated by a nearly twofold increase in heart weight- and lung weight-to-body weight ratios, respectively, compared with time-matched controls. Cardiac hypertrophy was also evident by a 49% increase in whole cell capacitance of isolated left ventricular myocytes (P < 0.05). Voltage-clamp experiments revealed that the maximum density of the Ca(2+)-independent, transient outward current (I.t.o.), measured at +60 mV, was 42% less in myocytes from infarcted hearts than in myocytes from control hearts (P < 0.05), whereas the inward rectifier current (IK1) density was not different between groups. The reduced Ito density in the infarcted group was reversed, however, in 4-5 h by treatment with exogenous dichloroacetate or pyruvate, both activators of pyruvate dehydrogenase. Moreover, control myocytes incubated for 6 h in the presence of an inhibitor of pyruvate dehydrogenase, 3-bromopyruvate, exhibited a concentration-dependent decrease in Ito density compared with untreated cells. The present data demonstrate that Ito density is reversibly decreased in surviving myocytes from infarcted hearts and suggest that mechanisms related to glucose metabolism via pyruvate dehydrogenase may be involved. These postinfarction changes in myocyte Ito channel function may relate to impaired contractility and arrhythmogenesis, which are characteristic of the intact, failing heart.
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PMID:Altered K+ current of ventricular myocytes in rats with chronic myocardial infarction. 945 75

Rapid ventricular pacing in dogs results in a low output cardiomyopathic state which is similar to idiopathic dilated cardiomyopathy in man. However, the pathophysiological mechanisms which cause this failure following pacing are unknown. Five dogs underwent rapid ventricular pacing. Hearts were stimulated at 245 beats per min (bpm) for four weeks and then reduced to 190 bpm to stabilize the failure. Six unoperated dogs were used as controls. This paper compares the two-dimensional gel electrophoresis (2-DE) protein patterns of left ventricular samples from the paced myocardium with the control dogs. Changes in protein expression were analyzed qualitatively and semi-quantitatively. In the paced dog samples 69 protein spots were significantly altered of which 42 were decreased and 27 were elevated. One qualitative change was observed: elongation factor Tu was present only the control hearts. Of these proteins, 20 have been identified by a combination of N-terminal protein microsequencing, peptide mass profiling by mass spectrometry, amino acid compositional analysis, and by comparison with databases of canine and human ventricular proteins. Ten of these are associated with mitochondria and energy production, including: pyruvate dehydrogenase E1 component, isocitrate dehydrogenase subunit alpha, HSP60 and HSP70, creatine kinase M and fatty acid binding protein. The cytoskeletal protein desmin was detected in reduced quantities and a spot corresponding to a fragment of desmin was increased. These results indicate that the development of heart failure in the paced dog involves alterations in mitochondrial energy production, the cytoskeleton and calcium activation.
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PMID:Protein changes observed in pacing-induced heart failure using two-dimensional electrophoresis. 974 64

This paper reviews the model of the control of mitochondrial substrate oxidation by Ca2+ ions. The mechanism is the activation by Ca2+ of four mitochondrial dehydrogenases, viz. glycerol 3-phosphate dehydrogenase, the pyruvate dehydrogenase multienzyme complex (PDH), NAD-linked isocitrate dehydrogenase (NAD-IDH) and 2-oxoglutarate dehydrogenase (OGDH). This results in the increase, or near-maintenance, of mitochondrial NADH/NAD ratios in the activated state, depending upon the tissue and the degree of 'downstream' activation by Ca2+, likely at the level of the F1Fo ATPase. Higher values of the redox span of the respiratory chain allow for greatly increased fluxes through oxidative phosphorylation with a minimal drop in protonmotive force and phosphorylation potential. As PDH, NAD-IDH and OGDH are all located within the inner mitochondrial membrane, it is changes in matrix free Ca2+ [Ca2+]m which act as a signal to these activities. In this article, we review recent work in which [Ca2+]m is measured in cells and tissues, using different techniques, with special emphasis on the question of the degree of damping of [Ca2+]m relative to changes in cytosol free Ca2+ in cells with rapid transients in cytosol Ca2+, e.g. cardiac myocytes. Further, we put forward the point of view that the failure of mitochondrial energy transduction to keep pace with cellular energy needs in some forms of heart failure may involve a failure of [Ca2+]m to be raised adequately to allow the activation of the dehydrogenases. We present new data to show that this is so in cardiac myocytes isolated from animals suffering from chronic, streptozocin-induced diabetes. This raises the possibility of therapy based upon partial inhibition of mitochondrial Ca2+ efflux pathways, thereby raising [Ca2+]m at a given, time-average value of cytosol free Ca+2.
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PMID:Role of mitochondrial calcium transport in the control of substrate oxidation. 974 30

Cardiodepressant effects of tumor necrosis factor-alpha (TNF-alpha have been documented in numerous experimental settings in vivo and in vitro. In vivo administration of TNF-alpha mimicks the cardiovascular pattern of sepsis including septic cardiomyopathy. Serum levels of TNF-alpha were found to be elevated both in sepsis and in numerous non-septic heart disorders. Although an involvement of TNF-alpha in the pathogenesis of septic cardiomyopathy seems likely, presently no definite conclusion can be drawn with regard to the role of TNF-alpha in chronic heart failure. The origin and trigger mechanisms for the release of TNF-alpha in heart failure are a matter of debate, endotoxin (LPS) from intestinal translocation in venous congestion being one possible player. The negative inotropic impact of TNF-alpha is frequently ascribed to the induction of inducible nitric oxide (NO) synthase (iNOS). Results from in vitro studies rather suggest a complex interaction of TNF-alpha with the heart, with pleiotropic effects on cardiomyocyte performance, including an induction of iNOS at higher TNF-alpha concentrations, but NO-independent cardiodepression at low, pathophysiologically more relevant concentrations. TNF-alpha effects on the heart also vary with regard to the kinetics of the process: rapidly occuring cardiodepressant effects include a release of sphingosine and a suppression of the calcium transient, while chronic administration of TNF-alpha was shown to depress the synthesis of precursors for the phosphoinositide pathway and inhibit pyruvate dehydrogenase activity and mitochondrial function. Whether secondary cytokines induced by TNF-alpha in cardiomyocytes contribute to cardiodepression or whether apoptotic signals activated by TNF-alpha are involved in the cardiodepressive pathways is presently unknown.
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PMID:Cardiodepression by tumor necrosis factor-alpha. 988 17

We report a new type of fatal mitochondrial disorder caused by selective deficiency of mitochondrial ATP synthase (ATPase). A hypotrophic newborn from a consanguineous marriage presented severe lactic acidosis, cardiomegaly and hepatomegaly and died from heart failure after 2 days. The activity of oligomycin-sensitive ATPase was only 31-34% of the control, both in muscle and heart, but the activities of cytochrome c oxidase, citrate synthase and pyruvate dehydrogenase were normal. Electrophoretic and western blot analysis revealed selective reduction of ATPase complex but normal levels of the respiratory chain complexes I, III and IV. The same selective deficiency of ATPase was found in cultured skin fibroblasts which showed similar decreases in ATPase content, ATPase hydrolytic activity and level of substrate-dependent ATP synthesis (20-25, 18 and 29-33% of the control, respectively). Pulse-chase labelling of patient fibroblasts revealed low incorporation of [(35)S]methionine into assembled ATPase complexes, but increased incorporation into immunoprecipitated ATPase subunit beta, which had a very short half-life. In contrast, no difference was found in the size and subunit composition of the assembled and newly produced ATPase complex. Transmitochondrial cybrids prepared from enucleated fibroblasts of the patient and rho degrees cells derived from 143B. TK(-)human osteosarcoma cells fully restored the ATPase activity, ATP synthesis and ATPase content, when compared with control cybrids. Likewise, the pattern of [(35)S]methionine labelling of ATPase was found to be normal in patient cybrids. We conclude that the generalized deficiency of mitochondrial ATPase described is of nuclear origin and is caused by altered biosynthesis of the enzyme.
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PMID:A novel deficiency of mitochondrial ATPase of nuclear origin. 1048 64

1. Electrical remodelling of the ventricle is a common pathogenic feature of cardiovascular disease states that lead to heart failure. Experimental data suggest this change in electrophysiological phenotype is largely due to downregulation of K(+) channels involved in repolarization of the action potential. 2. Voltage-clamp studies of the transient outward current (I(to)) in diabetic cardiomyopathy support a metabolic mechanism for K(+) channel downregulation. In particular, I(to) density is significantly increased in diabetic rat isolated ventricular myocytes treated in vitro with insulin or agents that activate pyruvate dehydrogenase. Recent data suggest this mechanism is not limited to diabetic conditions, because metabolic stimuli that upregulate I(to) in diabetic rat myocytes act similarly in non- diabetic models of heart failure. 3. Depressed I(to) channel activity is also reversed by experimental conditions that increase myocyte levels of reduced glutathione, indicating that oxidative stress is involved in electrical remodelling. Moreover, upregulation of I(to) density by activators of glucose utilization is blocked by inhibitors of glutathione metabolism, supporting the premise that there is a functional link between glucose utilization and the glutathione system. 4. Electrophysiological studies of diabetic and non-diabetic disease conditions affecting the heart suggest I(to) channels are regulated by a redox-sensitive mechanism, where glucose utilization plays an essential role in maintaining a normally reduced state of the myocyte. This hypothesis has implications for clinical approaches aimed at reversing pathogenic electrical remodelling in a variety of cardiovascular disease states.
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PMID:A metabolic mechanism for cardiac K+ channel remodelling. 1190 72

The incidence of diabetes mellitus is becoming progressively more frequent. The majority of diabetic patients will develop cardiovascular complications, among which coronary artery disease and diabetic cardiomyopathy are the most frequent and insidious. Apart from a meticulous metabolic control of diabetes, cardiac and vascular complications should be aggressively treated using the usual drugs at present effectively employed for their treatment in the general population. Additionally, the possibility of modifying cardiac substrate metabolism of the diabetic heart appears particularly attractive. Specifically, the possibility of increasing glucose metabolism rate and, accordingly, reducing free fatty acid oxidation, appears to be a very attractive therapeutic approach. Indeed, among traditional pharmacological tools, there is growing evidence that specific metabolically active drugs, the so-called partial free fatty acid inhibitors, of which the most studied is trimetazidine, will play an increasing role in the treatment of diabetic patients with coronary artery disease and cardiomyopathy. The property of these drugs is to facilitate myocardial utilization of glucose instead of free fatty acids which, in the context of ischemic and dysfunctional myocardial cells, appears to be deleterious. Similarly to other compounds that stimulate pyruvate dehydrogenase activity thereby facilitating glucose oxidation and inhibiting free fatty acid oxidation, such as dichloroacetate, trimetazidine has been shown to improve left ventricular function in diabetic patients with heart failure. Prospective studies in large clinical trials would produce more objective and definitive insights into the specific value of these new therapeutic concepts in the treatment of diabetic patients with cardiac diseases.
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PMID:[Heart disease and diabetes: from pathophysiology to therapeutic options]. 1507 72

Free fatty acid (FFA) oxidation is depressed in severe heart failure due to reduced activity of mitochondrial fatty acid oxidation enzymes. It is unknown whether the concomitant enhancement in cardiac glucose use is a consequence of reduced FFA oxidation, or also due to potentiation of the carbohydrate oxidative pathway. FFA and glucose oxidation rates were measured in vivo in 9 normal dogs and 9 dogs with pacing-induced heart failure by infusing (3)H-oleate and (14)C-glucose. FFA oxidation was lower (39 +/- 9 vs. 73 +/- 5 nmol min(-1) g(-1)), while glucose oxidation was higher (42 +/- 8 vs. 17 +/- 6 nmol min(-1) g(-1)) in failing compared to normal hearts (P < 0.05). At the end of the in vivo experiment, clamp-frozen biopsies were harvested from the left ventricle. Messenger RNAs encoding for proteins involved in both glucose and fatty acid metabolism, and for citrate synthase, were significantly reduced. Protein expression of GLUT-1 and GLUT-4, and GLUT-4 translocation to the sarcolemma showed no significant differences between the two groups despite a significant reduction in mRNAs with heart failure. GAPDH mRNA, protein expression, and activity were all reduced. The E2 subunit of pyruvate dehydrogenase was decreased both at the mRNA and protein level, with no effect on either fractional or maximal activity. In conclusion, we found either no changes or moderate downregulation of key enzymes of the carbohydrate metabolism in failing hearts, which suggests that the increase in glucose oxidation in vivo was principally due to impaired FFA oxidation and that the maximal myocardial capacity to obtain energy from substrate is globally depressed.
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PMID:Paradoxical downregulation of the glucose oxidation pathway despite enhanced flux in severe heart failure. 1508 16


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