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Abstract
SIGNIFICANCE NAD+ and NADP+ are important cosubstrates in redox reactions and participate in regulatory networks operating in adjustment of metabolic pathways. Moreover, NAD+ is a cosubstrate in post-translational modification of proteins and is involved in DNA repair. NADPH is indispensable for reductive syntheses and the redox chemistry involved in attaining and maintaining correct protein conformation. Recent Advances: Within a couple of decades, a wealth of information has been gathered on NAD(H)+/NADP(H) redox imaging, regulatory role of redox potential in assembly of spatial protein structures, and the role of ADP-ribosylation of regulatory proteins affecting both gene expression and metabolism. All these have a bearing also on disease, healthy aging, and longevity. CRITICAL ISSUES Knowledge of the signal propagation pathways of NAD+-dependent post-translational modifications is still fragmentary for explaining the mechanism of cellular stress effects and nutritional state on these actions. Evaluation of the cosubstrate and regulator roles of NAD(H) and NADP(H) still suffers from some controversies in experimental data. FUTURE DIRECTIONS Activating or inhibiting interventions in NAD+-dependent protein modifications for medical purposes has shown promise, but restraining tumor growth by inhibiting DNA repair in tumors by means of interference in sirtuins is still in the early stage. The same is true for the use of this technology in improving health and healthy aging. New genetically encoded specific NAD and NADP probes are expected to modernize the research on redox biology.
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Affiliation(s)
- Ilmo E Hassinen
- Faculty of Biochemistry and Molecular Medicine, University of Oulu, Oulu, Finland
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2
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Mallet RT, Olivencia-Yurvati AH, Bünger R. Pyruvate enhancement of cardiac performance: Cellular mechanisms and clinical application. Exp Biol Med (Maywood) 2017; 243:198-210. [PMID: 29154687 DOI: 10.1177/1535370217743919] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Cardiac contractile function is adenosine-5'-triphosphate (ATP)-intensive, and the myocardium's high demand for oxygen and energy substrates leaves it acutely vulnerable to interruptions in its blood supply. The myriad cardioprotective properties of the natural intermediary metabolite pyruvate make it a potentially powerful intervention against the complex injury cascade ignited by myocardial ischemia-reperfusion. A readily oxidized metabolic substrate, pyruvate augments myocardial free energy of ATP hydrolysis to a greater extent than the physiological fuels glucose, lactate and fatty acids, particularly when it is provided at supra-physiological plasma concentrations. Pyruvate also exerts antioxidant effects by detoxifying reactive oxygen and nitrogen intermediates, and by increasing nicotinamide adenine dinucleotide phosphate reduced form (NADPH) production to maintain glutathione redox state. These enhancements of free energy and antioxidant defenses combine to augment sarcoplasmic reticular Ca2+ release and re-uptake central to cardiac mechanical performance and to restore β-adrenergic signaling of ischemically stunned myocardium. By minimizing Ca2+ mismanagement and oxidative stress, pyruvate suppresses inflammation in post-ischemic myocardium. Thus, pyruvate administration stabilized cardiac performance, augmented free energy of ATP hydrolysis and glutathione redox systems, and/or quelled inflammation in a porcine model of cardiopulmonary bypass, a canine model of cardiac arrest-resuscitation, and a caprine model of hypovolemia and hindlimb ischemia-reperfusion. Pyruvate's myriad benefits in preclinical models provide the mechanistic framework for its clinical application as metabolic support for myocardium at risk. Phase one trials have demonstrated pyruvate's safety and efficacy for intravenous resuscitation for septic shock, intracoronary infusion for heart failure and as a component of cardioplegia for cardiopulmonary bypass. The favorable outcomes of these trials, which argue for expanded, phase three investigations of pyruvate therapy, mirror findings in isolated, perfused hearts, underscoring the pivotal role of preclinical research in identifying clinical interventions for cardiovascular diseases. Impact statement This article reviews pyruvate's cardioprotective properties as an energy-yielding metabolic fuel, antioxidant and anti-inflammatory agent in mammalian myocardium. Preclinical research has shown these properties make pyruvate a powerful intervention to curb the complex injury cascade ignited by ischemia and reperfusion. In ischemically stunned isolated hearts and in large mammal models of cardiopulmonary bypass, cardiac arrest-resuscitation and hypovolemia, intracoronary pyruvate supports recovery of myocardial contractile function, intracellular Ca2+ homeostasis and free energy of ATP hydrolysis, and its antioxidant actions restore β-adrenergic signaling and suppress inflammation. The first clinical trials of pyruvate for cardiopulmonary bypass, fluid resuscitation and intracoronary intervention for congestive heart failure have been reported. Receiver operating characteristic analyses show remarkable concordance between pyruvate's beneficial functional and metabolic effects in isolated, perfused hearts and in patients recovering from cardiopulmonary bypass in which they received pyruvate- vs. L-lactate-fortified cardioplegia. This research exemplifies the translation of mechanism-oriented preclinical studies to clinical application and outcomes.
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Affiliation(s)
- Robert T Mallet
- 1 Department of Integrative Physiology and Anatomy, University of North Texas Health Science Center, Fort Worth, TX 76107-2699, USA
| | - Albert H Olivencia-Yurvati
- 1 Department of Integrative Physiology and Anatomy, University of North Texas Health Science Center, Fort Worth, TX 76107-2699, USA.,2 Department of Medical Education, University of North Texas Health Science Center, Fort Worth, TX 76107-2699, USA
| | - Rolf Bünger
- 3 Emeritus Member of the American Physiological Society, McLean, VA 22101, USA
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3
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Badia MB, Mans R, Lis AV, Tronconi MA, Arias CL, Maurino VG, Andreo CS, Drincovich MF, van Maris AJA, Gerrard Wheeler MC. Specific Arabidopsis thaliana malic enzyme isoforms can provide anaplerotic pyruvate carboxylation function in Saccharomyces cerevisiae. FEBS J 2017; 284:654-665. [PMID: 28075062 DOI: 10.1111/febs.14013] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2016] [Revised: 01/04/2017] [Accepted: 01/05/2017] [Indexed: 11/29/2022]
Abstract
NAD(P)-malic enzyme (NAD(P)-ME) catalyzes the reversible oxidative decarboxylation of malate to pyruvate, CO2 , and NAD(P)H and is present as a multigene family in Arabidopsis thaliana. The carboxylation reaction catalyzed by purified recombinant Arabidopsis NADP-ME proteins is faster than those reported for other animal or plant isoforms. In contrast, no carboxylation activity could be detected in vitro for the NAD-dependent counterparts. In order to further investigate their putative carboxylating role in vivo, Arabidopsis NAD(P)-ME isoforms, as well as the NADP-ME2del2 (with a decreased ability to carboxylate pyruvate) and NADP-ME2R115A (lacking fumarate activation) versions, were functionally expressed in the cytosol of pyruvate carboxylase-negative (Pyc- ) Saccharomyces cerevisiae strains. The heterologous expression of NADP-ME1, NADP-ME2 (and its mutant proteins), and NADP-ME3 restored the growth of Pyc- S. cerevisiae on glucose, and this capacity was dependent on the availability of CO2 . On the other hand, NADP-ME4, NAD-ME1, and NAD-ME2 could not rescue the Pyc- strains from C4 auxotrophy. NADP-ME carboxylation activity could be measured in leaf crude extracts of knockout and overexpressing Arabidopsis lines with modified levels of NADP-ME, where this activity was correlated with the amount of NADP-ME2 transcript. These results indicate that specific A. thaliana NADP-ME isoforms are able to play an anaplerotic role in vivo and provide a basis for the study on the carboxylating activity of NADP-ME, which may contribute to the synthesis of C4 compounds and redox shuttling in plant cells.
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Affiliation(s)
- Mariana Beatriz Badia
- Centro de Estudios Fotosintéticos y Bioquímicos (CEFOBI), Universidad Nacional de Rosario, Argentina
| | - Robert Mans
- Department of Biotechnology, Delft University of Technology, The Netherlands
| | - Alicia V Lis
- Department of Biotechnology, Delft University of Technology, The Netherlands.,Biochemical Engineering Institute, Saarland University, Saarbrücken, Germany
| | - Marcos Ariel Tronconi
- Centro de Estudios Fotosintéticos y Bioquímicos (CEFOBI), Universidad Nacional de Rosario, Argentina
| | - Cintia Lucía Arias
- Centro de Estudios Fotosintéticos y Bioquímicos (CEFOBI), Universidad Nacional de Rosario, Argentina
| | - Verónica Graciela Maurino
- Plant Molecular Physiology and Biotechnology Group, Institute of Developmental and Molecular Biology of Plants, Cluster of Excellence on Plant Sciences (CEPLAS), Heinrich-Heine-Universität, Düsseldorf, Germany
| | - Carlos Santiago Andreo
- Centro de Estudios Fotosintéticos y Bioquímicos (CEFOBI), Universidad Nacional de Rosario, Argentina
| | - María Fabiana Drincovich
- Centro de Estudios Fotosintéticos y Bioquímicos (CEFOBI), Universidad Nacional de Rosario, Argentina
| | - Antonius J A van Maris
- Department of Biotechnology, Delft University of Technology, The Netherlands.,Division of Industrial Biotechnology, School of Biotechnology, KTH Royal Institute of Technology, AlbaNova University Center, Stockholm, Sweden
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4
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Bar-Even A. Formate Assimilation: The Metabolic Architecture of Natural and Synthetic Pathways. Biochemistry 2016; 55:3851-63. [PMID: 27348189 DOI: 10.1021/acs.biochem.6b00495] [Citation(s) in RCA: 94] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Formate may become an ideal mediator between the physicochemical and biological realms, as it can be produced efficiently from multiple available sources, such as electricity and biomass, and serve as one of the simplest organic compounds for providing both carbon and energy to living cells. However, limiting the realization of formate as a microbial feedstock is the low diversity of formate-fixing enzymes and thereby the small number of naturally occurring formate-assimilation pathways. Here, the natural enzymes and pathways supporting formate assimilation are presented and discussed together with proposed synthetic routes that could permit growth on formate via existing as well as novel formate-fixing reactions. By considering such synthetic routes, the diversity of metabolic solutions for formate assimilation can be expanded dramatically, such that different host organisms, cultivation conditions, and desired products could be matched with the most suitable pathway. Astute application of old and new formate-assimilation pathways may thus become a cornerstone in the development of sustainable strategies for microbial production of value-added chemicals.
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Affiliation(s)
- Arren Bar-Even
- Max Planck Institute of Molecular Plant Physiology , Am Mühlenberg 1, 14476 Potsdam-Golm, Germany
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5
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Goncalves RLS, Quinlan CL, Perevoshchikova IV, Hey-Mogensen M, Brand MD. Sites of superoxide and hydrogen peroxide production by muscle mitochondria assessed ex vivo under conditions mimicking rest and exercise. J Biol Chem 2014; 290:209-27. [PMID: 25389297 DOI: 10.1074/jbc.m114.619072] [Citation(s) in RCA: 232] [Impact Index Per Article: 23.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
The sites and rates of mitochondrial production of superoxide and H2O2 in vivo are not yet defined. At least 10 different mitochondrial sites can generate these species. Each site has a different maximum capacity (e.g. the outer quinol site in complex III (site IIIQo) has a very high capacity in rat skeletal muscle mitochondria, whereas the flavin site in complex I (site IF) has a very low capacity). The maximum capacities can greatly exceed the actual rates observed in the absence of electron transport chain inhibitors, so maximum capacities are a poor guide to actual rates. Here, we use new approaches to measure the rates at which different mitochondrial sites produce superoxide/H2O2 using isolated muscle mitochondria incubated in media mimicking the cytoplasmic substrate and effector mix of skeletal muscle during rest and exercise. We find that four or five sites dominate during rest in this ex vivo system. Remarkably, the quinol site in complex I (site IQ) and the flavin site in complex II (site IIF) each account for about a quarter of the total measured rate of H2O2 production. Site IF, site IIIQo, and perhaps site EF in the β-oxidation pathway account for most of the remainder. Under conditions mimicking mild and intense aerobic exercise, total production is much less, and the low capacity site IF dominates. These results give novel insights into which mitochondrial sites may produce superoxide/H2O2 in vivo.
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Affiliation(s)
| | - Casey L Quinlan
- From the Buck Institute for Research on Aging, Novato, California 94945
| | | | | | - Martin D Brand
- From the Buck Institute for Research on Aging, Novato, California 94945
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6
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Purmal C, Kucejova B, Sherry AD, Burgess SC, Malloy CR, Merritt ME. Propionate stimulates pyruvate oxidation in the presence of acetate. Am J Physiol Heart Circ Physiol 2014; 307:H1134-41. [PMID: 25320331 DOI: 10.1152/ajpheart.00407.2014] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Flux through pyruvate dehydrogenase (PDH) in the heart may be reduced by various forms of injury to the myocardium, or by oxidation of alternative substrates in normal heart tissue. It is important to distinguish these two mechanisms because imaging of flux through PDH based on the appearance of hyperpolarized (HP) [(13)C]bicarbonate derived from HP [1-(13)C]pyruvate has been proposed as a method for identifying viable myocardium. The efficacy of propionate for increasing PDH flux in the setting of PDH inhibition by an alternative substrate was studied using isotopomer analysis paired with exams using HP [1-(13)C]pyruvate. Hearts from C57/bl6 mice were supplied with acetate (2 mM) and glucose (8.25 mM). (13)C NMR spectra were acquired in a cryogenically cooled probe at 14.1 Tesla. After addition of hyperpolarized [1-(13)C]pyruvate, (13)C NMR signals from lactate, alanine, malate, and aspartate were easily detected, in addition to small signals from bicarbonate and CO2. The addition of propionate (2 mM) increased appearance of HP [(13)C]bicarbonate >30-fold without change in O2 consumption. Isotopomer analysis of extracts from the freeze-clamped hearts indicated that acetate was the preferred substrate for energy production, glucose contribution to energy production was minimal, and anaplerosis was stimulated in the presence of propionate. Under conditions where production of acetyl-CoA is dominated by the availability of an alternative substrate, acetate, propionate markedly stimulated PDH flux as detected by the appearance of hyperpolarized [(13)C]bicarbonate from metabolism of hyperpolarized [1-(13)C]pyruvate.
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Affiliation(s)
- Colin Purmal
- School of Medicine, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Blanka Kucejova
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, Texas
| | - A Dean Sherry
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, Texas; Department of Radiology, University of Texas Southwestern Medical Center, Dallas, Texas; Department of Chemistry, University of Texas at Dallas, Richardson, Texas; and
| | - Shawn C Burgess
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, Texas; Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Craig R Malloy
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, Texas; Department of Radiology, University of Texas Southwestern Medical Center, Dallas, Texas; Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas; Veterans Affairs North Texas Healthcare System, Dallas, Texas
| | - Matthew E Merritt
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, Texas; Department of Chemistry, University of Texas at Dallas, Richardson, Texas; and
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Thermodynamic constraints shape the structure of carbon fixation pathways. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2012; 1817:1646-59. [PMID: 22609686 DOI: 10.1016/j.bbabio.2012.05.002] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Received: 03/27/2012] [Revised: 05/07/2012] [Accepted: 05/09/2012] [Indexed: 11/27/2022]
Abstract
Thermodynamics impose a major constraint on the structure of metabolic pathways. Here, we use carbon fixation pathways to demonstrate how thermodynamics shape the structure of pathways and determine the cellular resources they consume. We analyze the energetic profile of prototypical reactions and show that each reaction type displays a characteristic change in Gibbs energy. Specifically, although carbon fixation pathways display a considerable structural variability, they are all energetically constrained by two types of reactions: carboxylation and carboxyl reduction. In fact, all adenosine triphosphate (ATP) molecules consumed by carbon fixation pathways - with a single exception - are used, directly or indirectly, to power one of these unfavorable reactions. When an indirect coupling is employed, the energy released by ATP hydrolysis is used to establish another chemical bond with high energy of hydrolysis, e.g. a thioester. This bond is cleaved by a downstream enzyme to energize an unfavorable reaction. Notably, many pathways exhibit reduced ATP requirement as they couple unfavorable carboxylation or carboxyl reduction reactions to exergonic reactions other than ATP hydrolysis. In the most extreme example, the reductive acetyl coenzyme A (acetyl-CoA) pathway bypasses almost all ATP-consuming reactions. On the other hand, the reductive pentose phosphate pathway appears to be the least ATP-efficient because it is the only carbon fixation pathway that invests ATP in metabolic aims other than carboxylation and carboxyl reduction. Altogether, our analysis indicates that basic thermodynamic considerations accurately predict the resource investment required to support a metabolic pathway and further identifies biochemical mechanisms that can decrease this requirement.
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Des Rosiers C, Labarthe F, Lloyd SG, Chatham JC. Cardiac anaplerosis in health and disease: food for thought. Cardiovasc Res 2011; 90:210-9. [PMID: 21398307 DOI: 10.1093/cvr/cvr055] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
There has been a resurgence of interest for the field of cardiac metabolism catalysed by the increased need for new therapeutic targets for patients with heart failure. The primary focus of research in this area to date has been on the impact of substrate selection for oxidative energy metabolism; however, anaplerotic metabolism also has significant interest for its potential cardioprotective role. Anaplerosis refers to metabolic pathways that replenish the citric acid cycle intermediates, which are essential to energy metabolism; however, our understanding of the role and regulation of this process in the heart, particularly under pathophysiological conditions, is very limited. Therefore, the goal of this article is to provide a foundation for future directions of research on cardiac anaplerosis and heart disease. We include an overview of anaplerotic metabolism, a critical evaluation of current methods available for its quantitation in the intact heart, and a discussion of its role and regulation both in health and disease as it is currently understood based mostly on animal studies. We also consider genetic diseases affecting anaplerotic pathways in humans and acute intervention studies with anaplerotic substrates in the clinics. Finally, as future perspectives, we will share our thoughts about potential benefits and practical considerations on modalities of interventions targeting anaplerosis in heart disease, including heart failure.
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Affiliation(s)
- Christine Des Rosiers
- Department of Nutrition, Montreal Heart Institute and Université de Montréal, Montreal, QC, Canada H3C 3J7.
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Anaplerotic role for cytosolic malic enzyme in engineered Saccharomyces cerevisiae strains. Appl Environ Microbiol 2010; 77:732-8. [PMID: 21131518 DOI: 10.1128/aem.02132-10] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Malic enzyme catalyzes the reversible oxidative decarboxylation of malate to pyruvate and CO(2). The Saccharomyces cerevisiae MAE1 gene encodes a mitochondrial malic enzyme whose proposed physiological roles are related to the oxidative, malate-decarboxylating reaction. Hitherto, the inability of pyruvate carboxylase-negative (Pyc(-)) S. cerevisiae strains to grow on glucose suggested that Mae1p cannot act as a pyruvate-carboxylating, anaplerotic enzyme. In this study, relocation of malic enzyme to the cytosol and creation of thermodynamically favorable conditions for pyruvate carboxylation by metabolic engineering, process design, and adaptive evolution, enabled malic enzyme to act as the sole anaplerotic enzyme in S. cerevisiae. The Escherichia coli NADH-dependent sfcA malic enzyme was expressed in a Pyc(-) S. cerevisiae background. When PDC2, a transcriptional regulator of pyruvate decarboxylase genes, was deleted to increase intracellular pyruvate levels and cells were grown under a CO(2) atmosphere to favor carboxylation, adaptive evolution yielded a strain that grew on glucose (specific growth rate, 0.06 ± 0.01 h(-1)). Growth of the evolved strain was enabled by a single point mutation (Asp336Gly) that switched the cofactor preference of E. coli malic enzyme from NADH to NADPH. Consistently, cytosolic relocalization of the native Mae1p, which can use both NADH and NADPH, in a pyc1,2Δ pdc2Δ strain grown under a CO(2) atmosphere, also enabled slow-growth on glucose. Although growth rates of these strains are still low, the higher ATP efficiency of carboxylation via malic enzyme, compared to the pyruvate carboxylase pathway, may contribute to metabolic engineering of S. cerevisiae for anaerobic, high-yield C(4)-dicarboxylic acid production.
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Gélinas R, Labarthe F, Bouchard B, Mc Duff J, Charron G, Young ME, Des Rosiers C. Alterations in carbohydrate metabolism and its regulation in PPARalpha null mouse hearts. Am J Physiol Heart Circ Physiol 2008; 294:H1571-80. [PMID: 18223187 DOI: 10.1152/ajpheart.01340.2007] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Although a shift from fatty acids (FAs) to carbohydrates (CHOs) is considered beneficial for the diseased heart, it is unclear why subjects with FA beta-oxidation defects are prone to cardiac decompensation under stress conditions. The present study investigated potential alterations in the myocardial utilization of CHOs for energy production and anaplerosis in 12-wk-old peroxisome proliferator-activating receptor-alpha (PPARalpha) null mice (a model of FA beta-oxidation defects). Carbon-13 methodology was used to assess substrate flux through energy-yielding pathways in hearts perfused ex vivo at two workloads with a physiological substrate mixture mimicking the fed state, and real-time RT-quantitative polymerase chain reaction was used to document the expression of selected metabolic genes. When compared with that from control C57BL/6 mice, isolated working hearts from PPARalpha null mice displayed an impaired capacity to withstand a rise in preload (mimicking an increased venous return as it occurs during exercise) as reflected by a 20% decline in the aortic flow rate. At the metabolic level, beyond the expected shift from FA (5-fold down) to CHO (1.5-fold up; P < 0.001) at both preloads, PPARalpha null hearts also displayed 1) a significantly greater contribution of exogenous lactate and glucose and/or glycogen (2-fold up) to endogenous pyruvate formation, whereas that of exogenous pyruvate remained unchanged and 2) marginal alterations in citric acid cycle-related parameters. The lactate production rate was the only measured parameter that was affected differently by preloads in control and PPARalpha null mouse hearts, suggesting a restricted reserve for the latter hearts to enhance glycolysis when the energy demand is increased. Alterations in the expression of some glycolysis-related genes suggest potential mechanisms involved in this defective CHO metabolism. Collectively, our data highlight the importance of metabolic alterations in CHO metabolism associated with FA oxidation defects as a factor that may predispose the heart to decompensation under stress conditions even in the fed state.
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Affiliation(s)
- Roselle Gélinas
- Montreal Heart Inst. Research Center, 5350, Montreal, Quebec, Canada H1T 1C8
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Kasumov T, Cendrowski AV, David F, Jobbins KA, Anderson VE, Brunengraber H. Mass isotopomer study of anaplerosis from propionate in the perfused rat heart. Arch Biochem Biophys 2007; 463:110-7. [PMID: 17418801 PMCID: PMC2047339 DOI: 10.1016/j.abb.2007.02.022] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2007] [Accepted: 02/13/2007] [Indexed: 11/29/2022]
Abstract
Anaplerosis from propionate was investigated in rat hearts perfused with 0-2mM [(13)C(3)]propionate and physiological concentrations of glucose, lactate, and pyruvate. The data show that when the concentration of [(13)C(3)]propionate was raised from 0 to 2mM, total anaplerosis increased from 5% to 16% of the turnover of citric acid cycle intermediates. Then, [(13)C(3)]propionate abolished anaplerosis from endogenous substrates, glucose, lactate, and pyruvate. Also, while the contents of propionyl-CoA and methylmalonyl-CoA increased with [(13)C(3)]propionate concentration, the content of succinyl-CoA decreased, presumably via activation of succinyl-CoA hydrolysis by a decrease in free CoA. Under our conditions, [(13)C(3)]propionate was a purely anaplerotic substrate since there was no labeling of mitochondrial acetyl-CoA, reflected by the labeling of the acetyl moiety of citrate.
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Affiliation(s)
- Takhar Kasumov
- Department of Nutrition, Case Western Reserve University, Cleveland OH 44106
| | | | - France David
- Department of Nutrition, Case Western Reserve University, Cleveland OH 44106
| | - Kathryn A. Jobbins
- Department of Nutrition, Case Western Reserve University, Cleveland OH 44106
| | - Vernon E. Anderson
- Department of Biochemistry, Case Western Reserve University, Cleveland OH 44106
| | - Henri Brunengraber
- Department of Nutrition, Case Western Reserve University, Cleveland OH 44106
- * To whom correspondence should be addressed: Department of Nutrition, Case Western Reserve University, School of Medicine - WG 48, 10900 Euclid Avenue, Cleveland OH 44106-4954. Tel: (216)368-6429; E-mail:
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Popova T, Pinheiro de Carvalho MAA, Matasova L, Medvedeva L. Regulation of mitochondrial NADP-isocitrate dehydrogenase in rat heart during ischemia. Mol Cell Biochem 2006; 294:97-105. [PMID: 16823514 DOI: 10.1007/s11010-006-9249-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2005] [Accepted: 05/16/2006] [Indexed: 11/27/2022]
Abstract
The changes in the regulation of at mitochondrial NADP-isocitrate dehydrogenase (NADP-ICDH) in a rat heart during have been analysed. Increase of enzyme activity in the cytosol and mitochondria of the heart ischemia was detected. Catalytic properties of the mitochondrial NADP-ICDH at norm and pathology have been compared on homogeneous enzyme preparations. Enzyme from the normoxic and ischemic heart showed the same electrophoretical mobility and molecular mass. Enzyme isolated from the ischemic heart mitochondria demonstrated higher activation energy and lower thermal stability. NADP-isocitrate dehydrogenase at the normoxic and ischemic conditions exhibited different Km for substrates and regulatory behaviour in relation to ATP, ADP, 2-oxoglutarate, citrate, malate, reduced and oxidised glutathione. The inhibitory effect of the Fe2+ and H2O2 mixture associated with the generation of hydroxyl radicals was lower in the ischemic enzyme. We hypothesise that the specific features of regulation behaviour of NADP-ICDH from the ischemic tissues permits the enzyme to supply NADPH to the glutathione reductase/glutathione peroxidase system.
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Affiliation(s)
- Tatiana Popova
- Department of Analytical and Medical Biochemistry and Microbiology, Voronezh State University, 394006 Voronezh, Russia
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Gustavsson N, Larsson-Nyrén G, Lindström P. Pancreatic beta cells from db/db mice show cell-specific [Ca2+]i and NADH responses to glucose but not to alpha-ketoisocaproic acid. Pancreas 2005; 31:242-50. [PMID: 16163056 DOI: 10.1097/01.mpa.0000175891.58918.c8] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/10/2022]
Abstract
OBJECTIVE We recently showed that timing and magnitude of the glucose-induced cytoplasmic calcium [Ca2+]i response are reproducible and specific for the individual beta cell. We now wanted to identify which step(s) of stimulus-secretion coupling determine the cell specificity of the [Ca2+]i response and whether cell specificity is lost in beta-cells from diabetic animals. Besides glucose, we studied the effects of glyceraldehyde, a glycolytic intermediate, and alpha-ketoisocaproic acid (KIC), a mitochondrial substrate. METHODS Early [Ca2+]i changes were studied stimulations in fura-2-labeled dispersed beta cells from lean, ob/ob, and db/db mice. Lag time and peak height were compared during 2 consecutive stimulations with the same stimulator. Nicotinamide adenine dinucleotide (NADH) responses to glucose and KIC were studied as a measure of metabolic flux. RESULTS Both glyceraldehyde and KIC induced cell-specific temporal responses in lean mouse beta cells with a correlation between lag times for [Ca2+]i rise during the first and second stimulation. Beta cells from ob/ob and db/db mice showed cell-specific temporal [Ca2+]i responses to glucose and glyceraldehyde but not to KIC. Glucose induced cell-specific NADH responses in all 3 models, but KIC did so only in lean mouse [beta] cells. CONCLUSIONS A cell-specific response may be induced at several steps of beta-cell stimulus-secretion coupling. Mitochondrial metabolism generates a cell-specific response in normal beta cells but not in db/db and ob/ob mouse beta cells.
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Affiliation(s)
- Natalia Gustavsson
- Department of Integrative Medical Biology, Section for Histology and Cell Biology, Umeå University, Umeå, Sweden.
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Ala-Rämi A, Ylihautala M, Ingman P, Hassinen IE. Influence of calcium-induced workload transitions and fatty acid supply on myocardial substrate selection. Metabolism 2005; 54:410-20. [PMID: 15736122 DOI: 10.1016/j.metabol.2004.09.004] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Because of differences in energy yield and oxygen demand, the selection of oxidative fuels is important in the hypoxic or ischemic heart muscle. The aim of the present study was to clarify the contradictions observed in the effects of workload and fatty acid supply on myocardial fuel preference in isolated perfused rat hearts. Nuclear magnetic resonance spectroscopy combined with the administration of substrates labeled with the stable isotope carbon 13 and isotopomer analysis of glutamate labeling offers an opportunity to simultaneously measure metabolic fluxes in pathways feeding into the tricarboxylic acid (TCA) cycle. The work output was modulated by changes in extracellular calcium. In the presence of 5 mmol/L glucose, 0.5 mmol/L octanoate in the perfusate dominated the oxidative metabolism, and workload had little effect on the ratio of glucose to fatty acid utilization. This was the case even when the octanoate concentration was lowered to 50 micromol/L. The relative rate of replenishment of the TCA cycle intermediates was higher at a low workload. The redox state of flavoproteins in the intact heart was monitored fluorometrically to obtain an estimate of the mitochondrial reduced/oxidized nicotinamide-adenine dinucleotide ratio (NADH/NAD ratio) for assessment of the dominant level of regulation of cell respiration, and the myoglobin spectrum was simultaneously monitored to evaluate the oxygenation status of the myocardium. Commencement of octanoate infusion (50 micromol/L or 0.5 mmol/L) caused a large but transient reduction of mitochondrial NAD and, conversely, its cessation elicited NADH oxidation and rebound reduction. During glucose oxidation, an increase in workload led to oxidation of the mitochondrial NADH, but this effect was much smaller in the presence of 50 micromol/L octanoate and absent in the presence of 0.5 mmol/L. This indicates that strong control of oxygen consumption during glucose oxidation is exerted in the mitochondrial respiratory chain, whereas equal control during fatty acid oxidation is exerted within the metabolic pathway upstream from the respiratory chain. It is concluded that when a medium-chain fatty acid is available, myocardial workload and energy consumption have little influence on fuel preference and glucose oxidation remains suppressed.
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Affiliation(s)
- Antti Ala-Rämi
- Department of Medical Biochemistry and Molecular Biology, University of Oulu, FIN-90014 Oulu, Finland
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Vincent G, Bouchard B, Khairallah M, Des Rosiers C. Differential modulation of citrate synthesis and release by fatty acids in perfused working rat hearts. Am J Physiol Heart Circ Physiol 2004; 286:H257-66. [PMID: 12933348 DOI: 10.1152/ajpheart.00717.2003] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The objective of this study was to test the effect of increasing fatty acid concentrations on substrate fluxes through pathways leading to citrate synthesis and release in the heart. This was accomplished using semirecirculating work-performing rat hearts perfused with substrate mixtures mimicking the in situ milieu (5.5 mM glucose, 8 nM insulin, 1 mM lactate, 0.2 mM pyruvate, and 0.4 mM oleate-albumin) and 13C methods. Raising the fatty acid concentration from 0.4 to 1 mM with long-chain oleate or medium-chain octanoate resulted in a lowering ( approximately 20%) of cardiac output and efficiency with unaltered O2 consumption. At the metabolic level, beyond the expected effects of high fatty acid levels on the contribution of pyruvate decarboxylation (reduced >3-fold) and beta-oxidation (enhanced approximately 3-fold) to citrate synthesis, there was also a 2.4-fold lowering of anaplerotic pyruvate carboxylation. Despite the dual inhibitory effect of high fatty acids on pyruvate decarboxylation and carboxylation, tissue citrate levels were twofold higher, but citrate release rates remained unchanged at 11-14 nmol/min, representing <0.5% of citric acid cycle flux. A similar trend was observed for most metabolic parameters after oleate or octanoate addition. Together, these results emphasize a differential modulation of anaplerotic pyruvate carboxylation and citrate release in the heart by fatty acids. We interpret the lack of effects of high fatty acid concentrations on citrate release rates as suggesting that, under physiological conditions, this process is maximal, probably limited by the activity of its mitochondrial or plasma membrane transporter. Limited citrate release at high fatty acid concentrations may have important consequences for the heart's fuel metabolism and function.
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Affiliation(s)
- Genevieve Vincent
- Department of Biochemistry, Université de Montréal, Montréal, Quebéc, Canada H2L 4M1
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16
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Comte B, Vincent G, Bouchard B, Benderdour M, Des Rosiers C. Reverse flux through cardiac NADP(+)-isocitrate dehydrogenase under normoxia and ischemia. Am J Physiol Heart Circ Physiol 2002; 283:H1505-14. [PMID: 12234803 DOI: 10.1152/ajpheart.00287.2002] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Little is known about the role of mitochondrial NADP(+)-isocitrate dehydrogenase (NADP(+)-ICDH) in the heart, where this enzyme shows its highest expression and activity. We tested the hypothesis that in the heart, NADP(+)-ICDH operates in the reverse direction of the citric acid cycle (CAC) and thereby may contribute to the fine regulation of CAC activity (Sazanov and Jackson, FEBS Lett 344: 109-116, 1994). We documented a reverse flux through this enzyme in rat hearts perfused with the medium-chain fatty acid octanoate using [U-(13)C(5)]glutamate and mass isotopomer analysis of tissue citrate (Comte et al., J Biol Chem 272: 26117-26124, 1997). In this study, we assessed the significance of our previous finding by perfusing hearts with long-chain fatty acids and tested the effects of changes in O(2) supply. We showed that under all of these conditions citrate was enriched in an isotopomer containing five (13)C atoms. This isotopomer can only be explained by substrate flux through reversal of the NADP(+)-ICDH reaction, which is evaluated at 3-7% of flux through citrate synthase. Small variations in reversal fluxes induced by low-flow ischemia that mimicked hibernation occurred despite major changes in contractile function and O(2) consumption of the heart as well as citrate and succinate release rates and tissue levels. Our data show a reverse flux through NADP(+)-ICDH and support its hypothesized role in the fine regulation of CAC activity in the normoxic and O(2)-deprived heart.
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Affiliation(s)
- Blandine Comte
- Department of Nutrition, University of Montreal, Quebec H3C 3J7, Canada
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17
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Iizuka K, Nakajima H, Namba M, Miyagawa JI, Miyazaki J, Hanafusa T, Matsuzawa Y. Metabolic consequence of long-term exposure of pancreatic beta cells to free fatty acid with special reference to glucose insensitivity. BIOCHIMICA ET BIOPHYSICA ACTA 2002; 1586:23-31. [PMID: 11781146 DOI: 10.1016/s0925-4439(01)00082-5] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Long-term exposure of the pancreatic beta cells to free fatty acid (FFA) reportedly inhibits glucose-stimulated insulin secretion. We here studied the impact of FFA on glucose and lipid metabolism in pancreatic beta cells with special reference to insulin secretion. Pancreatic beta-cell line MIN6 was exposed to various concentrations of palmitate for 3 days. Glucose-stimulated insulin secretion and insulin content were decreased corresponding to the concentration of the palmitate exposed. Glycolytic flux and ATP synthesis was unchanged, but pyruvate-stimulated change in NAD(P)H concentration was decreased. Pyruvate carboxylase was decreased at the protein level, which was restored by the removal of palmitate or the inhibition of beta-oxidation. Intracellular content of triglyceride and FFA were elevated, beta-oxidation was increased, and de novo lipogenesis from glucose was decreased. NADPH content and citrate output into the medium, which reflected pyruvate malate shuttle flux, were decreased, but malic enzyme activity was unaffected. The malic enzyme inhibitor alone inhibited insulin response to glucose. In conclusion, long-term exposure of FFA to beta cells inhibits glucose-stimulated insulin secretion via the decreased NADPH contents due to the inhibition of pyruvate carboxylase and malate pyruvate shuttle flux.
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Affiliation(s)
- Katsumi Iizuka
- Department of Internal Medicine, Graduate School of Medicine, Osaka University, Suita, Japan
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18
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Panchal AR, Comte B, Huang H, Dudar B, Roth B, Chandler M, Des Rosiers C, Brunengraber H, Stanley WC. Acute hibernation decreases myocardial pyruvate carboxylation and citrate release. Am J Physiol Heart Circ Physiol 2001; 281:H1613-20. [PMID: 11557551 DOI: 10.1152/ajpheart.2001.281.4.h1613] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In the well-perfused heart, pyruvate carboxylation accounts for 3-6% of the citric acid cycle (CAC) flux, and CAC carbon is lost via citrate release. We investigated the effects of an acute reduction in coronary flow on these processes and on the tissue content of CAC intermediates. Measurements were made in an open-chest anesthetized swine model. Left anterior descending coronary artery blood flow was controlled by a extracorporeal perfusion circuit, and flow was decreased by 40% for 80 min to induce myocardial hibernation (n = 8). An intracoronary infusion of [U-(13)C(3)]lactate and [U-(13)C(3)]pyruvate was given to measure the entry of pyruvate into the CAC through pyruvate carboxylation from the (13)C-labeled isotopomers of CAC intermediates. Compared with normal coronary flow, myocardial hibernation resulted in parallel decreases of 65% and 79% in pyruvate carboxylation and net citrate release by the myocardium, respectively, and maintenance of the CAC intermediate content. Elevation of the arterial pyruvate concentration by 1 mM had no effect. Thus a 40% decrease in coronary blood flow resulted in a concomitant decrease in pyruvate carboxylation and citrate release as well as maintenance of the CAC intermediates.
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Affiliation(s)
- A R Panchal
- Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, Ohio 44106-4970, USA
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Panchal AR, Comte B, Huang H, Kerwin T, Darvish A, des Rosiers C, Brunengraber H, Stanley WC. Partitioning of pyruvate between oxidation and anaplerosis in swine hearts. Am J Physiol Heart Circ Physiol 2000; 279:H2390-8. [PMID: 11045976 DOI: 10.1152/ajpheart.2000.279.5.h2390] [Citation(s) in RCA: 68] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The goal of this study was to measure flux through pyruvate carboxylation and decarboxylation in the heart in vivo. These rates were measured in the anterior wall of normal anesthetized swine hearts by infusing [U-(13)C(3)]lactate and/or [U-(13)C(3)] pyruvate into the left anterior descending (LAD) coronary artery. After 1 h, the tissue was freeze-clamped and analyzed by gas chromatography-mass spectrometry for the mass isotopomer distribution of citrate and its oxaloacetate moiety. LAD blood pyruvate and lactate enrichments and concentrations were constant after 15 min of infusion. Under near-normal physiological concentrations of lactate and pyruvate, pyruvate carboxylation and decarboxylation accounted for 4.7 +/- 0.3 and 41.5 +/- 2.0% of citrate formation, respectively. Similar relative fluxes were found when arterial pyruvate was raised from 0.2 to 1.1 mM. Addition of 1 mM octanoate to 1 mM pyruvate inhibited pyruvate decarboxylation by 93% without affecting carboxylation. The absence of M1 and M2 pyruvate demonstrated net irreversible pyruvate carboxylation. Under our experimental conditions we found that pyruvate carboxylation in the in vivo heart accounts for at least 3-6% of the citric acid cycle flux despite considerable variation in the flux through pyruvate decarboxylation.
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Affiliation(s)
- A R Panchal
- Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, Ohio 44106-4970, USA
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20
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Voegele RT, Mitsch MJ, Finan TM. Characterization of two members of a novel malic enzyme class. BIOCHIMICA ET BIOPHYSICA ACTA 1999; 1432:275-85. [PMID: 10407149 DOI: 10.1016/s0167-4838(99)00112-0] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The Gram-negative bacterium Rhizobium meliloti contains two distinct malic enzymes. We report the purification of the two isozymes to homogeneity, and their in vitro characterization. Both enzymes exhibit unusually high subunit molecular weights of about 82 kDa. The NAD(P)(+) specific malic enzyme [EC 1.1.1.39] exhibits positive co-operativity with respect to malate, but Michaelis-Menten type behavior with respect to the co-factors NAD(+) or NADP(+). The enzyme is subject to substrate inhibition, and shows allosteric regulation by acetyl-CoA, an effect that has so far only been described for some NADP(+) dependent malic enzymes. Its activity is positively regulated by succinate and fumarate. In contrast to the NAD(P)(+) specific malic enzyme, the NADP(+) dependent malic enzyme [EC 1.1.1.40] shows Michaelis-Menten type behavior with respect to malate and NADP(+). Apart from product inhibition, the enzyme is not subjected to any regulatory mechanism. Neither reductive carboxylation of pyruvate, nor decarboxylation of oxaloacetate, could be detected for either malic enzyme. Our characterization of the two R. meliloti malic enzymes therefore suggests a number of features uncharacteristic for malic enzymes described so far.
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Affiliation(s)
- R T Voegele
- Department of Biology, McMaster University, 1280 Main Street West, Hamilton, Ont. L8S 4K1, Canada
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21
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Hassel B, Ilebekk A, Tønnessen T. Cardiac accumulation of citrate during brief myocardial ischaemia and reperfusion in the pig in vivo. ACTA PHYSIOLOGICA SCANDINAVICA 1998; 164:53-9. [PMID: 9777025 DOI: 10.1046/j.1365-201x.1998.0400e.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Citrate is a key intermediate in energy metabolism and an inhibitor of phosphofructokinase of the glycolytic pathway. During myocardial ischaemia glycolysis is the main source of cardiac ATP. The aim of the present study was to determine if myocardial ischaemia and reperfusion alter cardiac tissue levels of citrate. Open-chest, anaesthetized pigs were subjected to 10 min of regional myocardial ischaemia by occlusion of the left anterior descending coronary artery, with and without reperfusion, and to 10 min of global ischaemia by circulatory arrest. Citrate, amino acids, glucose and NH3 were measured in biopsies. Ischaemia, whether regional or global, caused a 60-70% increase in tissue levels of citrate. During 1 min of reperfusion following regional ischaemia the level of citrate increased 460%, to approximately 600 nmol g-1 wet weight. The level of glutamate decreased by 20-33% (corresponding to 1300-2200 nmol g-1 wet weight), indicating net consumption of this amino acid during ischaemia. The level of aspartate decreased 50% indicating conversion of aspartate to oxaloacetate for the synthesis of citrate. Theoretically, the accumulation of myocardial citrate during brief ischaemia and early reperfusion is large enough to significantly inhibit phosphofructokinase activity and could therefore affect the ability of the myocardium to increase the glycolytic rate in response to ischaemia. This could, however, be partly compensated by the metabolism of myocardial glutamate.
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Affiliation(s)
- B Hassel
- Norwegian Defence Research Establishment, Division for Environmental Toxicology, Kjeller, Norway
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22
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Cohen DM, Bergman RN. Improved estimation of anaplerosis in heart using 13C NMR. THE AMERICAN JOURNAL OF PHYSIOLOGY 1997; 273:E1228-42. [PMID: 9435540 DOI: 10.1152/ajpendo.1997.273.6.e1228] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Anaplerotic enzymes, such as pyruvate carboxylase or malic enzyme, catalyze reactions that fill up the pools of the citric acid cycle (CAC), thereby increasing the total mass of CAC intermediates. Relative anaplerosis (y) denotes the ratio of anaplerotic flux to the flux catalyzed by citrate synthase. We examine conventional methods [C. R. Malloy, A. D. Sherry, and F. M. H. Jeffrey. J. Biol. Chem. 263:6964-6971, 1988; C. R. Malloy, A. D. Sherry, and F. M. H. Jeffrey. Am. J. Physiol. 259 (Heart Circ. Physiol. 28): H987-H995, 1990] of measurement of y using 13C-labeled precursors and analysis of [13C]glutamate labeling by nuclear magnetic resonance (NMR) spectroscopy. Through mathematical analysis and computer simulation, we show that isotopic enrichment of the pool of pyruvate that is substrate for anaplerosis will severely decrease the accuracy of estimates of y made with conventional methods no matter how small the mass of the pool of pyruvate. Suppose that the recycling parameter R denotes the fraction of molecules of pyruvate that contain carbons derived from intermediates of the CAC. Each means of estimation of relative anaplerosis in the peer-reviewed literature assumes that R = O, although this assumption has not been confirmed by experiment. We show that conventional formulas, using either fractional enrichments of carbons or isotopomer analysis, actually estimate at most y.(1 - R) instead of y during administration of [2-13C]acetate and unlabeled pyruvate. Using a new formula for estimation of y, we recalculate values of y from the literature and find them approximately 50% too low. We assume that all anaplerosis is via pyruvate and that the difference in isotopic enrichment between cytosolic and mitochondrial malate is negligible.
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Affiliation(s)
- D M Cohen
- Department of Physiology and Biophysics, University of Southern California School of Medicine, Los Angeles 90033, USA
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Comte B, Vincent G, Bouchard B, Jetté M, Cordeau S, Rosiers CD. A 13C mass isotopomer study of anaplerotic pyruvate carboxylation in perfused rat hearts. J Biol Chem 1997; 272:26125-31. [PMID: 9334177 DOI: 10.1074/jbc.272.42.26125] [Citation(s) in RCA: 69] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Anaplerotic pyruvate carboxylation was examined in hearts perfused with physiological concentrations of glucose, [U-13C3]lactate, and [U-13C3]pyruvate. Also, a fatty acid, [1-13C]octanoate, or ketone bodies were added at concentrations providing acetyl-CoA at a rate resulting in either low or substantial pyruvate decarboxylation. Relative contributions of pyruvate and fatty acids to citrate synthesis were determined from the 13C labeling pattern of effluent citrate by gas chromatography-mass spectrometry (see companion article, Comte, B., Vincent, G., Bouchard, B., and Des Rosiers, C. (1997) J. Biol. Chem. 272, 26117-26124). Precision on flux measurements of anaplerotic pyruvate carboxylation depended on the mix of substrates supplied to the heart. Anaplerotic fluxes were precisely determined under conditions where acetyl-CoA was predominantly supplied by beta-oxidation, as it occurred with 0.2 or 1 mM octanoate. Then, anaplerotic pyruvate carboxylation provided 3-8% of the OAA moiety of citrate and was modulated by concentrations of lactate and pyruvate in the physiological range. Also, the contribution of pyruvate to citrate formation through carboxylation was equal to or greater than through decarboxylation. Furthermore, 13C labeling data on tissue citric acid cycle intermediates and pyruvate suggest that (i) anaplerosis occurs also at succinate and (ii) cataplerotic malate decarboxylation is low. Rather, the presence of citrate in the effluent perfusate of hearts perfused with physiological concentrations of glucose, lactate, and pyruvate and concentrations of octanoate leading to maximal oxidative rates suggests a cataplerotic citrate efflux from mitochondria to cytosol. Taken altogether, our data raise the possibility of a link between pyruvate carboxylation and mitochondrial citrate efflux. In view of the proposed feedback regulation of glycolysis by cytosolic citrate, such a link would support a role of anaplerosis and cataplerosis in metabolic signal transmission between mitochondria and cytosol in the normoxic heart.
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Affiliation(s)
- B Comte
- Department of Nutrition, University of Montréal, Montréal, Québec H3C 3J7, Canada
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24
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Hakkola EH, Hiltunen JK. The existence of two mitochondrial isoforms of 2,4-dienoyl-CoA reductase in the rat. EUROPEAN JOURNAL OF BIOCHEMISTRY 1993; 215:199-204. [PMID: 8344281 DOI: 10.1111/j.1432-1033.1993.tb18023.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Isoforms of 2,4-dienoyl-CoA reductase (EC 1.3.1.34), which is the key enzyme in the beta-oxidation of fatty acids with double bonds, have been studied in rat heart and liver. Electrofocusing and adsorption chromatography on hydroxyapatite were used to separate the reductase activity in tissue homogenates into two peaks, one peak in each experiment being identified as the previously purified mitochondrial reductase. The novel activity was partially purified from rat liver by means of ammonium sulphate precipitation, anion-exchange chromatography on DEAE-cellulose (DE-52), hydrophobic chromatography on Phenyl-Sepharose and dye-ligand binding chromatography (Blue Sepharose). Taking into account the contribution of the different reductases to the total activity in rat liver, the overall purification for the novel isoform was 1900-fold. Ultracentrifugation on a sucrose gradient gave an M(r) of 50,000 and size-exclusion chromatography on Superdex 200 an M(r) of 60,000. The antibody against the previously characterised reductase did not cross-react with this novel isoform, but the distribution of the activity peaks in heart and liver tissue, and an electrofocusing experiment with isolated mitochondria, both pointed to a mitochondrial origin. The novel reductase was estimated to account for 80% (50%) of the total reductase activity in rat heart (liver) homogenate measured with 2,4-hexadienoyl-CoA. The present results, together with those previously published, suggest that mammals have at least three reductase isoforms: two in mitochondria and a third one in peroxisomes, but the peroxisomal activity has not been characterised so far.
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Affiliation(s)
- E H Hakkola
- Department of Medical Biochemistry, University of Oulu, Finland
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25
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Russell RR, Taegtmeyer H. Changes in citric acid cycle flux and anaplerosis antedate the functional decline in isolated rat hearts utilizing acetoacetate. J Clin Invest 1991; 87:384-90. [PMID: 1671390 PMCID: PMC295088 DOI: 10.1172/jci115008] [Citation(s) in RCA: 107] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
To determine the temporal relationship between changes in contractile performance and flux through the citric acid cycle in hearts oxidizing acetoacetate, we perfused isolated working rat hearts with either glucose or acetoacetate (both 5 mM) and freeze-clamped the tissue at defined times. After 60 min of perfusion, hearts utilizing acetoacetate exhibited lower systolic and diastolic pressures and lower cardiac outputs. The oxidation of acetoacetate increased the tissue content of 2-oxoglutarate and glutamate and decreased the content of succinyl-CoA suggesting inhibition of citric acid cycle flux through 2-oxoglutarate dehydrogenase. Whereas hearts perfused with either acetoacetate or glucose were similar with respect to their function for the first 20 min, changes in tissue metabolites were already observed within 5 min of perfusion at near-physiological workloads. The addition of lactate or propionate, but not acetate, to hearts oxidizing acetoacetate improved contractile performance, although inhibition of 2-oxoglutarate dehydrogenase was probably not diminished. If lactate or propionate were added, malate and citrate accumulated indicating utilization of anaplerotic pathways for the citric acid cycle. We conclude that a decreased rate of flux through 2-oxoglutarate dehydrogenase in hearts oxidizing acetoacetate precedes, and may be responsible for, contractile failure and is not the result of decreased cardiac work. Further, anaplerosis play an important role in the maintenance of contractile function in hearts utilizing acetoacetate.
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Affiliation(s)
- R R Russell
- Department of Medicine, University of Texas Medical School, Houston 77030
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Humphrey SM, Buckman JE, Holliss DG. Subcellular distribution of energy metabolites in the pre-ischaemic and post-ischaemic perfused working rat heart. EUROPEAN JOURNAL OF BIOCHEMISTRY 1990; 191:755-9. [PMID: 2143988 DOI: 10.1111/j.1432-1033.1990.tb19184.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Isolated working rat hearts were subjected to 20 min of global ischaemia and either 5 min or 15 min of reperfusion. The subcellular distribution of ATP, ADP, AMP, phosphocreatine and Pi were determined before and after ischaemia by the method of non-aqueous tissue fractionation. Ventricular function and the cytosolic, mitochondrial and ATPase-associated compartmentation of metabolites were measured. After 5 min of reperfusion, only 13 +/- 9% of the pre-ischaemic contractile function was restored compared to 67 +/- 8% after 15 min reperfusion. ATP was reduced in all cellular compartments after 5 min of reperfusion but was only decreased from pre-ischaemic values in the cytosolic compartment after 15 min of reperfusion (17.1 +/- 3.9 nmol/mg vs. 4.3 +/- 1.5 nmol/mg total protein; P less than 0.05). The mitochondrial [ATP]/[ADP] was reduced from a normal value of 4.36 to 1.79 after 5 min but recovered to 4.62 after 15 min of reperfusion. Most of the Pi was located in the mitochondria or with the ATPase fraction of the cell, with only 16% of the total Pi free in the cytosol. This study indicates that the capacity of the heart to recover function may be compromised during early reperfusion by a 59% increase in mitochondrial phosphate content and during late reperfusion by a reduced cytosolic/mitochondrial concentration ratio of both ATP (from 0.85 to 0.19) and phosphocreatine (from 3.9 to 1.24).
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Affiliation(s)
- S M Humphrey
- Department of Pathology, University of Auckland School of Medicine, New Zealand
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27
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Sundqvist KE, Hiltunen JK, Hassinen IE. Pyruvate carboxylation in the rat heart. Role of biotin-dependent enzymes. Biochem J 1989; 257:913-6. [PMID: 2930495 PMCID: PMC1135674 DOI: 10.1042/bj2570913] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Pyruvate carboxylation in the isolated perfused rat heart was studied under steady-state conditions. A biotin deficiency resulting in a 90% decrease in myocardial pyruvate carboxylase left the pyruvate carboxylation rate unchanged. Pyruvate carboxylation in heart muscle must therefore take place by means of an enzyme which does not contain biotin. The kinetic properties and mass-action ratio of the NADP-linked malic enzyme in heart muscle can be taken as circumstantial evidence in favour of the role of malic enzyme in pyruvate carboxylation in myocardium.
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Affiliation(s)
- K E Sundqvist
- Department of Medical Biochemistry, University of Oulu, Finland
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