Relation between lipolysis and glycolysis during ischemia in the isolated rat heart (original) (raw)
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Basic Research in Cardiology, 1989
We studied lipolysis in the isolated rat heart, measured as glycerol release during anoxia, low-flow ischemia and subsequent reperfusion. It was found that the rate of lipolysis was enhanced during ischemia/anoxia while the llpase activities in tissue extracts involved in the myocardial lipolysis and the amount of triglycerides were not affected. This indicates the dominant occurrence of a lipolysisreesterification principle in ischemic and anoxic tissue. A common observation of ischemiaJanoxia is an increase in the tissue NADH/NAD + ratio. Therefore we investigated the effect of lactate and malate, both of which enhance the tissue redox state on myocardial lipolysis. Perfusion in the presence of lactate (10 raM) and malate (10 raM) both stimulated myocardial lipolysis by about five times. This suggests that the rate of reesterification of product fatty acids to triglycerides, which is determined by the NADFI/NAD + ratio, because of the increased formation of glycerol 3-phosphate from dihydroxy acetone phosphate, plays an important role in the regulation of lipolysis. The existence of triglyceridefatty acid-triglyceride cycle is discussed.
Inhibition of glucose phosphorylation by fatty acids in the perfused rat heart
FEBS Letters, 1988
The flux of glucose entering the glycolytic pathway under various metabolic conditions has been indirectly monitored in the Langendorff perfused rat heart using 31P-NMR spectroscopy. By totally inhibiting (> 95%) glyceraldehyde-3-phosphate dehydrogenase with low concentrations of iodoacetic acid (0.2 mM) in the perfusion medium, active glycolysis results in the accumulation of sugar phosphate species (fructose 1,6_bisphosphate, dihydroxyacetone phosphate, and glyceraldehyde 3-phosphate) which can be observed in the slP-NMR spectrum. Using this technique, it has been shown that butyrate (10 mM) in the perfusion medium decreases the flux through the initial steps of the glycolytic pathway by at least 6-fold and that both glucose phosphorylation and glycogenolysis are inhibited. Upon total global ischemia in the presence of both glucose and butyrate, the glycolysis rate is stimulated approx. lOO-fold.
Circulation, 2005
Background-It is believed that increasing cardiac glucose metabolism in the setting of ischemia and reperfusion is protective because of the resulting decrease in fatty acid oxidation, which improves cardiac efficiency and increases glucose oxidation relative to glycolysis; however, these conclusions are based primarily on studies in which glucose is the only carbohydrate provided. The goal of this study was to examine the effect of stimulating myocardial carbohydrate use either by increasing glucose and insulin levels or by using dichloroacetate on the response to ischemia and reperfusion in hearts perfused with physiological concentrations of lactate and pyruvate plus glucose and fatty acids. Methods and Results-Metabolic fluxes were determined in hearts from male Sprague-Dawley rats perfused with 13 C-labeled substrates using 13 C/ 1 H-NMR isotopomer analysis after 30 minutes of low-flow ischemia (0.3 mL/min) and 60 minutes of reperfusion. Measurements were made under control conditions: 5 mmol/L glucose, 1 mmol/L lactate, 0.1 mmol/L pyruvate, 0.3 mmol/L palmitate, and 50 U/mL insulin plus dichloroacetate 5 mmol/L or glucose and insulin increased to 30 mmol/L and 1000 U/mL, respectively. Dichloroacetate increased carbohydrate oxidation and the ratio of glucose oxidation to glycolysis but did not improve functional recovery or cardiac efficiency; however, elevated glucose and insulin levels improved functional recovery and cardiac efficiency but did not increase carbohydrate oxidation or the ratio of glucose oxidation to glycolysis. Conclusions-These data support the notion that increasing myocardial glucose use is beneficial in the setting of ischemia and reperfusion; however, the protective effect appears not to be mediated by shifting the balance between carbohydrate and fatty acid oxidation.
Glucose requirement for postischemic recovery of perfused working heart
European Journal of Biochemistry, 1990
The quantitative importance of glycolysis in cardiomyocyte reenergization and contractile recovery was examined in postischemic, preload-controlled, isolated working guinea pig hearts. A 25-min global but low-flow ischemia with concurrent norepinephrine infusion to exhaust cellular glycogen stores was followed by a 15-min reperfusion. With 5 mM pyruvate as sole reperfusion substrate, severe contractile failure developed despite normal sarcolemmal pyruvate transport rate and high intracellular pyruvate concentrations near 2 mM. Reperfusion dysfunction was characterized by a low cytosolic phosphorylation potential ([ATP]/([ADP][P,]) due to accumulations of inorganic phosphate (Pi) and lactate. In contrast, with 5 mM glucose plus pyruvate as substrates, but not with glucose as sole substrate, reperfusion phosphorylation potential and function recovered to near normal. During the critical ischemia-reperfusion transition at 30 s reperfusion the cytosolic creatine kinase appeared displaced from equilibrium, regardless of the substrate supply. When under these conditions glucose and pyruvate were coinfused, glycolytic flux was near maximum, the glyceraldehyde-3-phosphate dehydrogenase13phosphoglycerate kinase reaction was enhanced, accumulation of Pi was attenuated, ATP content was slightly increased, and adenosine release was low. Thus, glucose prevented deterioration of the phosphorylation potential to levels incompatible with reperfusion recovery. Immediate energetic support due to maximum glycolytic ATP production and enhancement of the glyceraldehyde-3-phosphate dehydrogenase/3-phosphoglycerate kinase reaction appeared to act in concert to prevent detrimental collapse of [ATP]/([ADP][P,]) during creatine kinase dysfunction in the ischemia-reperfusion transition. Dichloroacetate (2 mM) plus glucose stimulated glycolysis but failed fully to reenergize the reperfused heart; conversely, 10 mM 2-deoxyglucose plus pyruvate inhibited glycolysis and produced virtually instantaneous de-energization during reperfusion. The following conclusions were reached. (1) A functional glycolysis is required to prevent energetic and contractile collapse of the low-flow ischemic or reperfused heart (2). Glucose stabilization of energetics in pyruvate-perfused hearts is due in part to intensification of glyceraldehyde-3-phosphate dehydrogenase/3-phosphoglycerate kinase activity.
Free fatty acids, but not ketone bodies, protect diabetic rat hearts during low-flow ischemia
American journal of physiology. Heart and circulatory physiology, 2001
To determine whether the effects of fatty acids on the diabetic heart during ischemia involve altered glycolytic ATP and proton production, we measured energetics and intracellular pH (pH(i)) by using (31)P NMR spectroscopy plus [2-(3)H]glucose uptake in isolated rat hearts. Hearts from 7-wk streptozotocin diabetic and control rats, perfused with buffer containing 11 mM glucose, with or without 1.2 mM palmitate or the ketone bodies, 4 mM beta-hydroxybutyrate plus 1 mM acetoacetate, were subjected to 32 min of low-flow (0.3 ml x g wet wt(-1) x min(-1)) ischemia, followed by 32 min of reperfusion. In control rat hearts, neither palmitate nor ketone bodies altered the recovery of contractile function. Diabetic rat hearts perfused with glucose alone or with ketone bodies, had functional recoveries 50% lower than those of the control hearts, but palmitate restored recovery to control levels. In a parallel group with the functional recoveries, palmitate prevented the 54% faster loss of AT...
The Journal of Physiological Sciences, 2011
The effects of ischemic-postconditioning (IPOC) on functional recovery and cell viability of ischemic-reperfused hearts from fed and fasted rats were studied in relation to triacylglycerol and glycogen mobilization, ATP content, glucose-6-phosphate dehydrogenase activity and reduced/oxidized glutathione (GSH/GSSG). Oxidative damage was estimated by measuring thiobarbituric acid reactive substances (TBARS). IPOC improved contractile recovery and cell viability in the fed but attenuated them in the fasted hearts. In both groups ischemia lowered glycogen. IPOC further reduced it. Triacylglycerol remained unchanged during ischemia-reperfusion in both groups, but triacylglycerol mobilization was activated by IPOC in the fasted group. ATP was increased by IPOC in the fed hearts, but lowered in the fasted ones, which appeared to be associated with the rates of ATP synthesis in isolated mitochondria. In the fed hearts IPOC raised glucose-6phosphate dehydrogenase activity and GSH/GSSG, and lowered TBARS. These results suggest that IPOC effects are associated with changes in the ATP supply, mobilization of energy sources and glutathione antioxidant ratio.
Compartmentation of glycolysis and glycogenolysis in the perfused rat heart
NMR in Biomedicine, 2004
Developing methods that can detect compartmentation of metabolic pathways in intact tissues may be important for understanding energy demand and supply. In this study, we investigated compartmentation of glycolysis and glycogenolysis in the isolated perfused rat heart using 13 C NMR isotopomer analysis. Rat hearts previously depleted of myocardial glycogen were perfused with 5.5 mM [U-13 C]glucose plus 50 mU/mL insulin until newly synthesized glycogen recovered to new steady-state levels ( $ 60% of pre-depleted values). After a short wash-out period, the perfusate glucose was then switched to [1-13 C]glucose, and glycolysis and glycogenolysis were stimulated by addition of glucagon (1 mg/ml). A 13 C NMR multiplet analysis of the methyl resonance of lactate provided an estimate of pyruvate derived from glucose vs glycogen while a multiplet analysis of the C4 resonance of glutamate provided an estimate of acetyl-CoA derived from glycolytic pyruvate vs glycogenolytic pyruvate. These two indices were not equivalent and their difference was further magnified in the presence of insulin during the stimulation phase. These combined observations are consistent with functional compartmentation of glycolytic and glycogenolytic enzymes that allows pyruvate generated by these two processes to be distinguished at the level of lactate and acetyl-CoA. Abbreviations used: C3S, singlet component of the methyl carbon resonance of lactate; C3D, doublet component of the methyl carbon resonance of lactate; C4S, singlet component of the carbon-4 resonance of glutamate; C4D34, doublet component of the carbon-4 resonance of glutamate representing spin-spin coupling between carbon-3 and carbon-4; C4D45, doublet component of the carbon-4 resonance of glutamate representing spin-spin coupling between carbon-4 and carbon-5; C4DQ, quartet component of the carbon-4 resonance of glutamate representing spin-spin coupling between carbon-4 and both carbon-3 and carbon-5; [1-13 C]glucose, glucose enriched with 13 C at the C1 carbon; gww, gram wet weight; HR, heart rate; KHB, Krebs-Henseleit bicarbonate; MSD rats, male Sprague-Dawley rats; PDH, pyruvate dehydrogenase complex; TCA cycle, tricarboxylic acid cycle; [U-13 C]glucose, glucose enriched with 13 C in all carbons.
Journal of Molecular and Cellular Cardiology, 1999
We undertook this study to determine if the metabolism of exogenous glucose and glycogen in hypertrophied hearts differed from that in normal hearts during severe ischemia. Thus, rates of glycolysis ( 3 H 2 O production) and oxidation ( 14 CO 2 production) from exogenous glucose and glycogen were measured in isolated working control (n=13) and hypertrophied (n=12) hearts from sham-operated and aortic-banded rats during 40 min of severe low-flow ischemia. Hearts, in which glycogen was prelabelled with [5-3 H]-or [ 14 C]-glucose, were paced and perfused with Krebs-Henseleit solution containing 1.2 m palmitate, 5.5 m [5-3 H]-or [ 14 C]-glucose (different from the isotope used to label glycogen), 0.5 m lactate and 100 U/ml insulin during ischemia. Rates of glycolysis from exogenous glucose (3301±122 v 2467±167 nmol/min/g dry wt, mean±..., P<0.05) and glucose from glycogen (808±27 v 725±21 nmol/ min/g dry wt, P<0.05) were accelerated in hypertrophied hearts compared to control hearts. However, rates of oxidation of exogenous glucose and glucose from glycogen were not significantly different between the two groups. As observed in normoxic non-ischemic hearts, glucose from glycogen was preferentially oxidized compared to exogenous glucose. Additionally, rates of glycogen synthesis (167±7 v 140±9 nmol/min/g dry wt, P<0.05) were increased in hypertrophied hearts compared to control hearts during severe low-flow ischemia indicating that glycogen turnover (i.e. simultaneous synthesis and degradation) was accelerated in the hypertrophied heart. Thus, we demonstrate that glucose utilization and glycogen turnover are accelerated in the hypertrophied heart during severe low-flow ischemia as compared to the normal heart.
The Correlation of Glycogen Metabolism in Rabbit Myocardial Ischemia
Journal of Veterinary Science & Technology, 2015
Ischemia is responsible for several heart injuries, leading to functional disorders and higher mortality in animals. This process is a condition of blood circulatory arrest, leading to hypoxia and an anaerobic glycolysis. In this case, glycogen is fundamental to maintain energy homeostasis, through glycogen synthase kinase 3 (GSK3) regulations. This enzyme is usually involved in cardio protection, as well as several other biological processes. To study glycogen synthase kinase 3β (GSK3β), analyzing the involvement of this enzyme on cardiac system protection to understand its role in energetic metabolism during ischemia and reperfusion. Using the inflow occlusion (IO) application, the circulatory blood to the heart was blocked in adult New Zealand white rabbits. Parameters such hemogasometry as lactate levels were evaluated during the transoperatory period, using CG4+test strips (i-STAT® System). GSK3β transcription and activity analysis was performed by real time qRT-PCR and western blotting respectively, and glycogen quantification was determined enzymatically.GSK3β transcription increased during ischemia, followed by a decrease in glycogen content, suggesting that the consumption of this substrate during ischemia is mediated by GSK3β. Lactate level is highest in ischemia, and the pH value decreased during the same period. The results suggest the importance of GSK3β in the heart metabolic adaptations after ischemia and reperfusion injuries, sustaining glucose anaerobic metabolism through glycogen reserves modulation. The results show that the transcription of GSK3β correlated with cardiac metabolic adaptations after ischemia and reperfusion injuries, sustaining glucose anaerobic metabolism.