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Lewandowski ED. Metabolic flux in the driver's seat during cardiac health and disease. J Mol Cell Cardiol 2023; 182:15-24. [PMID: 37451081 PMCID: PMC10529670 DOI: 10.1016/j.yjmcc.2023.07.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/17/2023] [Revised: 06/16/2023] [Accepted: 07/06/2023] [Indexed: 07/18/2023]
Abstract
Cardiac function is a dynamic process that must adjust efficiently to the immediate demands of physical state and activity. So too, the metabolic support of cardiac function is a dynamic process that must respond, in time, to the demands of cardiac function and viability. Flux through metabolic pathways provides chemical energy and generates signaling molecules that regulate activity among intracellular compartments to meet these demands. Thus, flux through metabolic pathways provides a dynamic mode of support of cardiomyocytes during physiological and pathophysiological challenges. Any inability of metabolic flux to keep pace with the demands of the cardiomyocyte results in progressive dysfunction that contributes to cardiac disease. Thus, the priority in maintaining and regulating flux through metabolic pathways in the cardiomyocyte cannot be understated. Great potential exists in current efforts to elucidate metabolic mechanisms as therapeutic targets for the diseased heart. As a consequence, detecting metabolic flux in the functioning myocardium of the heart, under normal and diseased conditions, is essential in elucidating the metabolic basis of contractile dysfunction. As a companion to the 2022 ISHR Research Achievement Award lecture, this review examines the use and applications of stable isotope kinetics to quantify metabolic flux through intermediary pathways and the exchange and transport of intermediates across the mitochondrial membrane and sarcolemma of intact functioning hearts in determining how these intracellular events are coordinated to support cardiac function and health. Finally, this work reviews recently demonstrated metabolic defects in diseased hearts and the potential for metabolic alleviation of heart disease.
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Affiliation(s)
- E Douglas Lewandowski
- Department of Internal Medicine and Davis Heart and Lung Research Institute, The Ohio State University College of Medicine, Columbus, OH, United States of America.
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Simões RV, Cabañas ME, Loreiro C, Illa M, Crispi F, Gratacós E. Assessment of prenatal cerebral and cardiac metabolic changes in a rabbit model of fetal growth restriction based on 13C-labelled substrate infusions and ex vivo multinuclear HRMAS. PLoS One 2018; 13:e0208784. [PMID: 30589837 PMCID: PMC6307735 DOI: 10.1371/journal.pone.0208784] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2017] [Accepted: 11/25/2018] [Indexed: 01/11/2023] Open
Abstract
BACKGROUND We have used a previously reported rabbit model of fetal growth restriction (FGR), reproducing perinatal neurodevelopmental and cardiovascular impairments, to investigate the main relative changes in cerebral and cardiac metabolism of term FGR fetuses during nutrient infusion. METHODS FGR was induced in 9 pregnant New Zealand rabbits at 25 days of gestation: one horn used as FGR, by partial ligation of uteroplacental vessels, and the contralateral as control (appropriate for gestation age, AGA). At 30 days of gestation, fasted mothers under anesthesia were infused i.v. with 1-13C-glucose (4 mothers), 2-13C-acetate (3 mothers), or not infused (2 mothers). Fetal brain and heart samples were quickly harvested and frozen down. Brain cortex and heart apex regions from 30 fetuses were studied ex vivo by HRMAS at 4°C, acquiring multinuclear 1D and 2D spectra. The data were processed, quantified by peak deconvolution or integration, and normalized to sample weight. RESULTS Most of the total 13C-labeling reaching the fetal brains/hearts (80-90%) was incorporated to alanine and lactate (cytosol), and to the glutamine-glutamate pool (mitochondria). Acetate-derived lactate (Lac C2C3) had a slower turnover in FGR brains (~ -20%). In FGR hearts, mitochondrial turnover of acetate-derived glutamine (Gln C4) was slower (-23%) and there was a stronger accumulation of phospholipid breakdown products (glycerophosphoethanolamine and glycerophosphocholine, +50%), resembling the profile of non-infused control hearts. CONCLUSIONS Our results indicate specific functional changes in cerebral and cardiac metabolism of FGR fetuses under nutrient infusion, suggesting glial impairment and restricted mitochondrial metabolism concomitant with slower cell membrane turnover in cardiomyocytes, respectively. These prenatal metabolic changes underlie neurodevelopmental and cardiovascular problems observed in this FGR model and in clinical patients, paving the way for future studies aimed at evaluating metabolic function postnatally and in response to stress and/or treatment.
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Affiliation(s)
- Rui V. Simões
- Fetal i+d Fetal Medicine Reseach Center, BCNatal—Barcelona Center for Maternal-Fetal and Neonatal Medicine (Hospital Clínic and Hospital Sant Joan de Déu), ICGON, IDIBAPS, University of Barcelona, Centre for Biomedical Research on Rare Diseases (CIBER-ER), Barcelona, SPAIN
- * E-mail:
| | - Miquel E. Cabañas
- Servei de Resonància Magnètica Nuclear, Universitat Autònoma de Barcelona (UAB), SPAIN
| | - Carla Loreiro
- Fetal i+d Fetal Medicine Reseach Center, BCNatal—Barcelona Center for Maternal-Fetal and Neonatal Medicine (Hospital Clínic and Hospital Sant Joan de Déu), ICGON, IDIBAPS, University of Barcelona, Centre for Biomedical Research on Rare Diseases (CIBER-ER), Barcelona, SPAIN
| | - Miriam Illa
- Fetal i+d Fetal Medicine Reseach Center, BCNatal—Barcelona Center for Maternal-Fetal and Neonatal Medicine (Hospital Clínic and Hospital Sant Joan de Déu), ICGON, IDIBAPS, University of Barcelona, Centre for Biomedical Research on Rare Diseases (CIBER-ER), Barcelona, SPAIN
| | - Fatima Crispi
- Fetal i+d Fetal Medicine Reseach Center, BCNatal—Barcelona Center for Maternal-Fetal and Neonatal Medicine (Hospital Clínic and Hospital Sant Joan de Déu), ICGON, IDIBAPS, University of Barcelona, Centre for Biomedical Research on Rare Diseases (CIBER-ER), Barcelona, SPAIN
| | - Eduard Gratacós
- Fetal i+d Fetal Medicine Reseach Center, BCNatal—Barcelona Center for Maternal-Fetal and Neonatal Medicine (Hospital Clínic and Hospital Sant Joan de Déu), ICGON, IDIBAPS, University of Barcelona, Centre for Biomedical Research on Rare Diseases (CIBER-ER), Barcelona, SPAIN
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Abstract
The heart is a biological pump that converts chemical to mechanical energy. This process of energy conversion is highly regulated to the extent that energy substrate metabolism matches energy use for contraction on a beat-to-beat basis. The biochemistry of cardiac metabolism includes the biochemistry of energy transfer, metabolic regulation, and transcriptional, translational as well as posttranslational control of enzymatic activities. Pathways of energy substrate metabolism in the heart are complex and dynamic, but all of them conform to the First Law of Thermodynamics. The perspectives expand on the overall idea that cardiac metabolism is inextricably linked to both physiology and molecular biology of the heart. The article ends with an outlook on emerging concepts of cardiac metabolism based on new molecular models and new analytical tools. © 2016 American Physiological Society. Compr Physiol 6:1675-1699, 2016.
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Affiliation(s)
- Heinrich Taegtmeyer
- Division of Cardiology, Department of Internal Medicine, McGovern Medical School at The University of Texas Health Science Center at Houston
| | - Truong Lam
- Division of Cardiology, Department of Internal Medicine, McGovern Medical School at The University of Texas Health Science Center at Houston
| | - Giovanni Davogustto
- Division of Cardiology, Department of Internal Medicine, McGovern Medical School at The University of Texas Health Science Center at Houston
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Taegtmeyer H, Young ME, Lopaschuk GD, Abel ED, Brunengraber H, Darley-Usmar V, Des Rosiers C, Gerszten R, Glatz JF, Griffin JL, Gropler RJ, Holzhuetter HG, Kizer JR, Lewandowski ED, Malloy CR, Neubauer S, Peterson LR, Portman MA, Recchia FA, Van Eyk JE, Wang TJ. Assessing Cardiac Metabolism: A Scientific Statement From the American Heart Association. Circ Res 2016; 118:1659-701. [PMID: 27012580 DOI: 10.1161/res.0000000000000097] [Citation(s) in RCA: 185] [Impact Index Per Article: 23.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
In a complex system of interrelated reactions, the heart converts chemical energy to mechanical energy. Energy transfer is achieved through coordinated activation of enzymes, ion channels, and contractile elements, as well as structural and membrane proteins. The heart's needs for energy are difficult to overestimate. At a time when the cardiovascular research community is discovering a plethora of new molecular methods to assess cardiac metabolism, the methods remain scattered in the literature. The present statement on "Assessing Cardiac Metabolism" seeks to provide a collective and curated resource on methods and models used to investigate established and emerging aspects of cardiac metabolism. Some of those methods are refinements of classic biochemical tools, whereas most others are recent additions from the powerful tools of molecular biology. The aim of this statement is to be useful to many and to do justice to a dynamic field of great complexity.
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Goldenberg JR, Wang X, Lewandowski ED. Acyl CoA synthetase-1 links facilitated long chain fatty acid uptake to intracellular metabolic trafficking differently in hearts of male versus female mice. J Mol Cell Cardiol 2016; 94:1-9. [PMID: 26995156 DOI: 10.1016/j.yjmcc.2016.03.006] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/22/2016] [Revised: 03/14/2016] [Accepted: 03/15/2016] [Indexed: 12/18/2022]
Abstract
RATIONALE Acyl CoA synthetase-1 (ACSL1) is localized at intracellular membranes, notably the mitochondrial membrane. ACSL1 and female sex are suggested to indirectly facilitate lipid availability to the heart and other organs. However, such mechanisms in intact, functioning myocardium remain unexplored, and roles of ACSL1 and sex in the uptake and trafficking of fats are poorly understood. OBJECTIVE To determine the potential for ACSL1 and sex-dependent differences in metabolic trapping and trafficking effects of long-chain fatty acids (LCFA) within cardiomyocytes of intact hearts. METHODS AND RESULTS (13)C NMR of intact, beating mouse hearts, supplied (13)C palmitate, revealed 44% faster trans-sarcolemmal uptake of LCFA in male hearts overexpressing ACSL1 (MHC-ACSL1) than in non-transgenic (NTG) males (p<0.05). Acyl CoA content was elevated by ACSL1 overexpression, 404% in males and 164% in female, relative to NTG. Despite similar ACSL1 content, NTG females displayed faster LCFA uptake kinetics compared to NTG males, which was reversed by ovariectomy. NTG female LCFA uptake rates were similar to those in ACSL1 males and ACSL1 females. ACSL1 and female sex hormones both accelerated LCFA uptake without affecting triglyceride content or turnover. ACSL1 hearts contained elevated ceramide, particularly C22 ceramide in both sexes and specifically, C24 in males. ACSL1 also induced lower content of fatty acid transporter-6 (FATP6) indicating cooperative regulation with ACSL1. Surprisingly, ACSL1 overexpression did not increase mitochondrial oxidation of exogenous palmitate, which actually dropped in female ACSL1 hearts. CONCLUSIONS ACSL1-mediated metabolic trapping of exogenous LCFA accelerates LCFA uptake rates, albeit to a lesser extent in females, which distinctly affects LCFA trafficking to acyl intermediates but not triglyceride storage or mitochondrial oxidation and is affected by female sex hormones.
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Affiliation(s)
- Joseph R Goldenberg
- Center for Cardiovascular Research, University of Illinois College of Medicine at Chicago, 909 South Wolcott Avenue, Chicago, IL 60612, USA; Department of Physiology and Biophysics, University of Illinois College of Medicine at Chicago, 835 South Wolcott Avenue, Chicago, IL 60612, USA
| | - Xuerong Wang
- Center for Cardiovascular Research, University of Illinois College of Medicine at Chicago, 909 South Wolcott Avenue, Chicago, IL 60612, USA
| | - E Douglas Lewandowski
- Center for Cardiovascular Research, University of Illinois College of Medicine at Chicago, 909 South Wolcott Avenue, Chicago, IL 60612, USA; Department of Physiology and Biophysics, University of Illinois College of Medicine at Chicago, 835 South Wolcott Avenue, Chicago, IL 60612, USA; Sanford Burnham Prebys Medical Discovery Institute, 6400 Sanger Road, Orlando, FL 32827, USA.
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Lu M, Atthe B, Mateescu GD, Flask CA, Yu X. Assessing mitochondrial respiration in isolated hearts using (17)O MRS. NMR IN BIOMEDICINE 2012; 25:883-9. [PMID: 22161858 PMCID: PMC3522750 DOI: 10.1002/nbm.1807] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2011] [Revised: 09/10/2011] [Accepted: 09/26/2011] [Indexed: 05/04/2023]
Abstract
The application of (17)O MRI and MRS for the evaluation of cardiac mitochondrial function has been limited because of the challenge of detecting metabolic H(2)(17)O in the vast background of naturally abundant H(2)(17)O. In this study, we have developed a direct (17)O MRS approach to examine the feasibility and sensitivity of detecting metabolically produced H(2)(17)O in isolated rat hearts perfused with (17)O(2)-enriched Krebs-Henseleit buffer containing normal (1.5 mm) and high (2.5 mm) calcium (Ca(2+)) concentrations to induce high workload. Consistent with increased workload at high Ca(2+) concentration, the measured myocardial oxygen consumption rate (MVO(2)) increased by 82%. Dynamic (17)O MRS showed an accelerated increase in the H(2)(17)O signal at high Ca(2+) concentration, suggesting increased mitochondrial production of H(2)(17)O in concordance with the increased workload. A compartment model was developed to describe the kinetics of H(2)(17)O production as a function of MVO(2). The myocardial (17)O(2) consumption rate (MV(17)O(2) was determined by least-squares fitting of the model to the NMR-measured H(2)(17)O concentration. Consistent with the measured MVO(2), the model-determined MV(17)O(2) showed a 92% increase at high Ca(2+) concentration. The increase in metabolic activity at high workload allowed the balance between ATP production and utilization to be maintained, leading to a similar phosphocreatine to ATP ratio. These results demonstrate that dynamic (17)O MRS can provide a valuable tool for the detection of an altered metabolic rate associated with a change in cardiac workload.
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Affiliation(s)
- Ming Lu
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, USA
- Case Center for Imaging Research, Case Western Reserve University, Cleveland, OH, USA
| | - Bharath Atthe
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, USA
- Case Center for Imaging Research, Case Western Reserve University, Cleveland, OH, USA
| | - Gheorghe D. Mateescu
- Case Center for Imaging Research, Case Western Reserve University, Cleveland, OH, USA
- Department of Radiology, Case Western Reserve University, Cleveland, OH, USA
- Department of Chemistry, Case Western Reserve University, Cleveland, OH, USA
| | - Chris A. Flask
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, USA
- Case Center for Imaging Research, Case Western Reserve University, Cleveland, OH, USA
- Department of Radiology, Case Western Reserve University, Cleveland, OH, USA
| | - Xin Yu
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, USA
- Case Center for Imaging Research, Case Western Reserve University, Cleveland, OH, USA
- Department of Radiology, Case Western Reserve University, Cleveland, OH, USA
- Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, OH, USA
- Correspondence to: X. Yu, Wickenden 430, 10900 Euclid Avenue, Cleveland, OH 44106, USA.
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Kudej RK, Fasano M, Zhao X, Lopaschuk GD, Fischer SK, Vatner DE, Vatner SF, Lewandowski ED. Second window of preconditioning normalizes palmitate use for oxidation and improves function during low-flow ischaemia. Cardiovasc Res 2011; 92:394-400. [PMID: 21835931 DOI: 10.1093/cvr/cvr215] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
AIMS Although a major mechanism for cardioprotection is altered metabolism, little is known regarding metabolic changes in ischaemic preconditioning and subsequent ischaemia. Our objective was to examine the effects of the second window of preconditioning (SWOP), the delayed phase of preconditioning against infarction and stunning, on long-chain free fatty acid (LCFA) oxidation during ischaemia in chronically instrumented, conscious pigs. METHODS AND RESULTS We studied three groups: (i) normal baseline perfusion (n = 5); (ii) coronary artery stenosis (CAS; n = 5); (iii) CAS 24 h following 2 × 10 min coronary occlusions and 10 min reperfusion (n = 7). Ischaemia was induced by a left anterior descending (LAD) stenosis (40% flow reduction) for 90 min, dropping systolic wall thickening by 72%. LCFA oxidation was assessed following LAD infusion of (13)C palmitate, i.e. during control or stenosis, by in vitro nuclear magnetic resonance of the sampled myocardium. Stenosis reduced subendocardial blood flow subendocardially, but not subepicardial, yet induced transmural reductions in LCFA oxidation and increased non-oxidative glycolysis. During stenosis, preconditioned hearts showed normalized contributions of LCFA to oxidative ATP synthesis, despite increased lactate accumulation. SWOP induced a shift towards LCFA oxidation during stenosis, despite increased malonyl-CoA, and marked protection of contractile function with a significant improvement in systolic wall thickening. CONCLUSION Thus, the second window of preconditioning normalized oxidative metabolism of LCFA during subsequent ischaemia despite elevated non-oxidative glycolysis and malonyl-CoA and was linked to protection of regional contractile function resulting in improved mechanical performance. Interestingly, the metabolic responses occurred transmurally while ischaemia was restricted solely to the subendocardium.
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Affiliation(s)
- Raymond K Kudej
- Department of Cell Biology and Molecular Medicine, University of Medicine and Dentistry of New Jersey, New Jersey Medical School, Newark, NJ, USA
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8
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Pound KM, Arteaga GM, Fasano M, Wilder T, Fischer SK, Warren CM, Wende AR, Farjah M, Abel ED, Solaro RJ, Lewandowski ED. Expression of slow skeletal TnI in adult mouse hearts confers metabolic protection to ischemia. J Mol Cell Cardiol 2011; 51:236-43. [PMID: 21640727 DOI: 10.1016/j.yjmcc.2011.05.014] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/04/2011] [Revised: 04/26/2011] [Accepted: 05/14/2011] [Indexed: 12/30/2022]
Abstract
Changes in metabolic and myofilament phenotypes coincide in developing hearts. Posttranslational modification of sarcomere proteins influences contractility, affecting the energetic cost of contraction. However, metabolic adaptations to sarcomeric phenotypes are not well understood, particularly during pathophysiological stress. This study explored metabolic adaptations to expression of the fetal, slow skeletal muscle troponin I (ssTnI). Hearts expressing ssTnI exhibited no significant ATP loss during 5 min of global ischemia, while non-transgenic littermates (NTG) showed continual ATP loss. At 7 min ischemia TG-ssTnI hearts retained 80±12% of ATP versus 49±6% in NTG (P<0.05). Hearts expressing ssTnI also had increased AMPK phosphorylation. The mechanism of ATP preservation was augmented glycolysis. Glycolytic end products (lactate and alanine) were 38% higher in TG-ssTnI than NTG at 2 min and 27% higher at 5 min. This additional glycolysis was supported exclusively by exogenous glucose, and not glycogen. Thus, expression of a fetal myofilament protein in adult mouse hearts induced elevated anaerobic ATP production during ischemia via metabolic adaptations consistent with the resistance to hypoxia of fetal hearts. The general findings hold important relevance to both our current understanding of the association between metabolic and contractile phenotypes and the potential for invoking cardioprotective mechanisms against ischemic stress. This article is part of a Special Issue entitled "Possible Editorial".
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Affiliation(s)
- Kayla M Pound
- Program in Integrative Cardiac Metabolism, Center for Cardiovascular Research and Department of Physiology and Biophysics, University of Illinois at Chicago, College of Medicine, Chicago, IL 60612, USA
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The use of magnetic resonance methods in translational cardiovascular research. J Cardiovasc Transl Res 2009; 2:39-47. [PMID: 20559968 DOI: 10.1007/s12265-008-9084-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/17/2008] [Accepted: 12/12/2008] [Indexed: 10/21/2022]
Abstract
Magnetic resonance methods are widely applicable to research questions posed in translational cardiovascular studies. The main intent of this review was to offer the cardiovascular translational research scientist a "menu" of magnetic resonance (MR) approaches that can be applied to answering research questions posed in a variety of experimental situations including those involving the use of human subjects. Obviously, this menu is not comprehensive and many other topics could have been selected for emphasis. However, we hope that the material presented encompasses a broad enough slice of the field to stimulate thinking about the possible applications of MR methods to specific research questions.
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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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Balaban RS, Bose S, French SA, Territo PR. Role of calcium in metabolic signaling between cardiac sarcoplasmic reticulum and mitochondria in vitro. Am J Physiol Cell Physiol 2003; 284:C285-93. [PMID: 12529248 DOI: 10.1152/ajpcell.00129.2002] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The role of Ca(2+) as a cytosolic signaling molecule between porcine cardiac sarcoplasmic reticulum (SR) ATPase and mitochondrial ATP production was evaluated in vitro. The Ca(2+) sensitivity of these processes was determined individually and in a reconstituted system with SR and mitochondria in a 0.5:1 protein-to-cytochrome aa(3) ratio. The half-maximal concentration (K(1/2)) of SR ATPase was 335 nM Ca(2+). The ATP synthesis dependence was similar with a K(1/2) of 243 nM for dehydrogenases and 114 nM for overall ATP production. In the reconstituted system, Ca(2+) increased thapsigargin-sensitive ATP production (maximum approximately 5-fold) with minimal changes in mitochondrial reduced nicotinamide adenine dinucleotide (NADH). NADH concentration remained stable despite graded increases in NADH turnover induced over a wide range of Ca(2+) concentrations (0 to approximately 500 nM). These data are consistent with a balanced activation of SR ATPase and mitochondrial ATP synthesis by Ca(2+) that contributes to a homeostasis of energy metabolism metabolites. It is suggested that this balanced activation by cytosolic Ca(2+) is partially responsible for the minimal alteration in energy metabolism intermediates that occurs with changes in cardiac workload in vivo.
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Affiliation(s)
- Robert S Balaban
- Laboratory of Cardiac Energetics, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892-1061, USA.
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Lewandowski ED. Cardiac carbon 13 magnetic resonance spectroscopy: on the horizon or over the rainbow? J Nucl Cardiol 2002; 9:419-28. [PMID: 12161719 DOI: 10.1067/mnc.2002.125811] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
- E Douglas Lewandowski
- Program in Integrative Cardiac Metabolism, Department of Physiology and Biophysics, University of Illinois, Chicago, IL 60612, USA.
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O'Donnell JM, Alpert NM, White LT, Lewandowski ED. Coupling of mitochondrial fatty acid uptake to oxidative flux in the intact heart. Biophys J 2002; 82:11-8. [PMID: 11751291 PMCID: PMC1302444 DOI: 10.1016/s0006-3495(02)75369-1] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
The coordination of long chain fatty acid (LCFA) transport across the mitochondrial membrane (V(PAL)) with subsequent oxidation rate through beta-oxidation and the tricarboxylic acid (TCA) cycle (V(tca)) has been difficult to characterize in the intact heart. Kinetic analysis of dynamic (13)C-NMR distinguished these flux rates in isolated rabbit hearts. Hearts were perfused in a 9.4 T magnet with either 0.5 mM [2,4,6,8,10,12,14,16-(13)C(8)] palmitate (n = 4), or 0.5 mM (13)C-labeled palmitate plus 0.08 mM unlabeled butyrate (n = 4). Butyrate is a short chain fatty acid (SCFA) that bypasses the LCFA transporters of mitochondria. In hearts oxidizing palmitate alone, the ratio of V(TCA) to V(PAL) was 8:1. This is consistent with one molecule of palmitate yielding eight molecules of acetyl-CoA for the subsequent oxidation through the TCA cycle. Addition of butyrate elevated this ratio; V(TCA)/V(PAL) = 12:1 due to an SCFA-induced increase in V(TCA) of 43% (p < 0.05). However, SCFA oxidation did not significantly reduce palmitate transport into the mitochondria: V(PAL) = 1.0 +/- 0.2 micromol/min/g dw with palmitate alone versus 0.9 +/- 0.1 with palmitate plus butyrate. Thus, the products of beta-oxidation are preferentially channeled to the TCA cycle, away from mitochondrial efflux via carnitine acetyltransferase.
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Affiliation(s)
- J Michael O'Donnell
- Program in Integrative Cardiac Metabolism, Department of Physiology and Biophysics, University of Illinois at Chicago, Chicago, Illinois 60612-7342, USA
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Blüml S, Moreno-Torres A, Ross BD. [1-13C]glucose MRS in chronic hepatic encephalopathy in man. Magn Reson Med 2001; 45:981-93. [PMID: 11378875 DOI: 10.1002/mrm.1131] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
[1-13C]-labeled glucose was infused intravenously in a single dose of 0.2 g/kg body weight over 15 min in six patients with chronic hepatic encephalopathy, and three controls. Serial 13C MR spectra of the brain were acquired. Patients exhibited the following characteristics relative to normal controls: 1) Cerebral glutamine concentration was increased (12.6 +/- 3.8 vs. 6.5 +/- 1.9 mmol/kg, P < 0.006) and glutamate was reduced (8.2 +/- 1.0 vs. 9.9 +/- 0.6 mmol/kg, P < 0.02). 2) 13C incorporation into glutamate C4 and C2 positions was reduced in patients (80 min after start of infusion C4: 0.43 +/- 0.09 vs. 0.84 +/- 0.15 mmol/kg, P < 0.001; C2: 0.20 +/- 0.03 vs. 0.45 +/- 0.07 mmol/kg, P < 0.0001). 3) 13C incorporation into bicarbonate was delayed (90 +/- 21 vs. 40 +/- 10 min, P < 0.003), and the time interval between detection of glutamate C4 and C2 labeling was longer in patients (22 +/- 8 vs. 12 +/- 3 min, P < 0.03). 4) Glutamate C2 turnover time was reduced in chronic hepatic encephalopathy (17.1 +/- 6.8 vs. 49.6 +/- 8.7 min, P < 0.0002). 5) 13C accumulation into glutamine C2 relative to its substrate glutamate C2 increased progressively with the severity of clinical symptoms (r = 0.96, P < 0.01). These data indicate disturbed neurotransmitter glutamate/glutamine cycling and reduced glucose oxidation in chronic hepatic encephalopathy. [1-13C] glucose MRS provides novel insights into disease progression and the pathophysiology of chronic hepatic encephalopathy.
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Affiliation(s)
- S Blüml
- Huntington Medical Research Institutes, Pasadena, California 91105, USA.
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16
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Jeffrey FM, Reshetov A, Storey CJ, Carvalho RA, Sherry AD, Malloy CR. Use of a single (13)C NMR resonance of glutamate for measuring oxygen consumption in tissue. THE AMERICAN JOURNAL OF PHYSIOLOGY 1999; 277:E1111-21. [PMID: 10600802 DOI: 10.1152/ajpendo.1999.277.6.e1111] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
A kinetic model of the citric acid cycle for calculating oxygen consumption from (13)C nuclear magnetic resonance (NMR) multiplet data has been developed. Measured oxygen consumption (MVO(2)) was compared with MVO(2) predicted by the model with (13)C NMR data obtained from rat hearts perfused with glucose and either [2-(13)C]acetate or [3-(13)C]pyruvate. The accuracy of MVO(2) measured from three subsets of NMR data was compared: glutamate C-4 and C-3 resonance areas; the doublet C4D34 (expressed as a fraction of C-4 area); and C-4 and C-3 areas plus several multiplets of C-2, C-3, and C-4. MVO(2) determined by set 2 (C4D34 only) gave the same degree of accuracy as set 3 (complete data); both were superior to set 1 (C-4 and C-3 areas). Analysis of the latter suffers from the correlation between citric acid cycle flux and exchange between alpha-ketoglutarate and glutamate, resulting in greater error in estimating MVO(2). Analysis of C4D34 is less influenced by correlation between parameters, and this single measurement provides the best opportunity for a noninvasive measurement of oxygen consumption.
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Affiliation(s)
- F M Jeffrey
- Department of Radiology, The Mary Nell and Ralph B. Rogers Magnetic Resonance Center, University of Texas Southwestern Medical Center, Dallas, Texas 75235-9085, USA.
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17
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van Beek JH, van Mil HG, King RB, de Kanter FJ, Alders DJ, Bussemaker J. A (13)C NMR double-labeling method to quantitate local myocardial O(2) consumption using frozen tissue samples. THE AMERICAN JOURNAL OF PHYSIOLOGY 1999; 277:H1630-40. [PMID: 10516204 DOI: 10.1152/ajpheart.1999.277.4.h1630] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Measurement of local myocardial O(2) consumption (VO(2)) has been problematic but is needed to investigate the heterogeneity of aerobic metabolism. The goal of the present investigation was to develop a method to measure local VO(2) using small frozen myocardial samples, suitable for determining VO(2) profiles. In 26 isolated rabbit hearts, 1.5 mmol/l [2-(13)C]acetate was infused for 4 min, followed by 1.5 min of [1,2-(13)C]acetate. The left ventricular (LV) free wall was then quickly frozen. High-resolution (13)C-NMR spectra were measured from extracts taken from 2- to 3-mm thick transmural layer samples. The multiplet intensities of glutamate were analyzed with a computer model allowing simultaneous estimation of the absolute flux through the tricarboxylic acid cycle and the fractional contribution of acetate to acetyl CoA formation from which local VO(2) was calculated. The (13)C-derived VO(2) in the LV free wall was linearly related to "gold standard" VO(2) from coronary venous O(2) electrode measurements in the same region (r = 0.932, n = 22, P < 0.0001, slope 1.05) for control and lowered metabolic rates. The ratio of subendocardial to subepicardial VO(2) was 1.52 +/- 0.19 (SE, significantly >1, P < 0.025). Local myocardial VO(2) can now be quantitated with this new (13)C method to determine profiles of aerobic energy metabolism.
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Affiliation(s)
- J H van Beek
- Laboratory for Physiology, Vrije Universiteit, 1081 BT Amsterdam, The Netherlands.
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18
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Angelos MG, Torres CA, Rath DP, Zhu H, Beckley PD, Robitaille PM. In-vivo myocardial substrate alteration during perfused ventricular fibrillation. Acad Emerg Med 1999; 6:581-7. [PMID: 10386674 DOI: 10.1111/j.1553-2712.1999.tb00409.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
OBJECTIVES Earlier work suggests the in-vivo heart alters its substrate utilization as a function of cardiac work. Previous work has also demonstrated the high oxygen requirements of the heart during ventricular fibrillation (VF). The authors hypothesized that myocardial substrate utilization during VF with perfusion is similar to the normal beating heart under conditions of increased workload. METHODS Myocardial substrate selection was studied in the in-vivo porcine myocardium using 13carbon nuclear magnetic resonance (13C NMR) under conditions of increased cardiac work (dobutamine group) and VF with extracorporeal perfusion (VF group). Once the animal preparation was completed, metabolic steady state was achieved with the infusion of unlabeled acetate into the left anterior descending (LAD) coronary artery. The infused substrate was then changed to [2-13C] acetate and glutamate pool labeling was monitored by 13C NMR. The glutamate C4 resonance areas at baseline and after intervention of either increased workload (dobutamine group) or perfused VF (VF group) were compared within groups using paired t-tests. RESULTS Baseline aortic and great cardiac vein lactates, glucose levels, blood gases, hemoglobin levels, and temperatures were similar between groups. In both groups, there was a significant decrease from baseline in the labeling of C4 glutamate peaks (dobutamine group: 20.2+/-14.9 vs 84.7+/-32.7, p = 0.002; and VF group: 49.8+/-24.4 vs 83.9+/-24.4, p = 0.02), indicating selection against acetate oxidation in favor of other endogenous substrates. CONCLUSIONS In the in-vivo heart, despite the absence of functional contractions, changes in substrate utilization during perfused VF are similar to changes that occur with increased workload in the normal beating heart.
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Affiliation(s)
- M G Angelos
- Department of Emergency Medicine, The Ohio State University, Columbus 43210-1270, USA.
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19
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van Beek JH, Csont T, de Kanter FJ, Bussemaker J. Simple model analysis of 13C NMR spectra to measure oxygen consumption using frozen tissue samples. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1999; 454:475-85. [PMID: 9889927 DOI: 10.1007/978-1-4615-4863-8_58] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- J H van Beek
- Department of Chemistry, Vrije Universiteit, Amsterdam, The Netherlands.
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20
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Sherry AD, Zhao P, Wiethoff AJ, Jeffrey FM, Malloy CR. Effects of aminooxyacetate on glutamate compartmentation and TCA cycle kinetics in rat hearts. THE AMERICAN JOURNAL OF PHYSIOLOGY 1998; 274:H591-9. [PMID: 9486263 DOI: 10.1152/ajpheart.1998.274.2.h591] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The nonspecific transaminase inhibitor aminooxyacetate (AOA) has multiple influences on the dynamics of 13C appearance in glutamate in rat hearts as measured by 13C nuclear magnetic resonance (NMR) without altering O2 consumption or tricarboxylic acid (TCA) cycle flux. These include the following: 1) a reduced rate of 13C enrichment at glutamate C3 and C4; 2) a near coalescence of the C3 and C4 fractional enrichment curves; 3) a dramatic alteration in the time-dependent evolution of the glutamate C4 multiplets, C4S and C4D34; and 4) a decrease in the NMR visibility of glutamate. A fit of the 13C fractional enrichment curves of glutamate C4 and C3 in the absence of inhibitor to a kinetic model of the TCA cycle gave values for transaminase flux of 7.5 mumol.min-1.g dry wt-1 and TCA cycle flux of 7.5 mumol.min-1.g dry wt-1, thereby confirming reports by others that the kinetics of 13C enrichment of glutamate C3 and C4 in heart tissue is significantly affected by flux through reactions other than TCA cycle. The 13C fractional enrichment data collected in the presence of 0.5 mM AOA could not be fitted using this same kinetic model. However, kinetic simulations demonstrated that the time-dependent changes in C4S and C4D34 are only consistent with a 10-fold reduction in the size of intermediate pools undergoing rapid turnover in the TCA cycle. We conclude that inhibition of glutamic-oxalacetic transaminase by AOA effectively reduces the size of the alpha-ketoglutarate pool in rapid exchange with the TCA cycle. Our data indicate that changes in glutamate multiplet areas in the 13C NMR spectra of heart (as demonstrated by glutamate C4S and C4D34) are more sensitive to alterations in metabolic pool sizes in exchange with the TCA cycle than are measurements of 13C fractional enrichment at glutamate C3 and C4.
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Affiliation(s)
- A D Sherry
- Mary Nell and Ralph B. Rogers Magnetic Resonance Center, Department of Radiology, University of Texas Southwestern Medical Center, Dallas 75235-9085, USA
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21
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O'Donnell JM, Doumen C, LaNoue KF, White LT, Yu X, Alpert NM, Lewandowski ED. Dehydrogenase regulation of metabolite oxidation and efflux from mitochondria in intact hearts. THE AMERICAN JOURNAL OF PHYSIOLOGY 1998; 274:H467-76. [PMID: 9486249 DOI: 10.1152/ajpheart.1998.274.2.h467] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
To test how alpha-ketoglutarate dehydrogenase (alpha-KGDH) activity influences the balance between oxidative flux and transmitochondrial metabolite exchange, we monitored these rates in isolated mitochondria and in perfused rabbit hearts at an altered kinetics (Km) of alpha-KGDH for alpha-ketoglutarate (alpha-KG). In isolated mitochondria, relative Km dropped from 0.23 mM at pH = 7.2 to 0.10 mM at pH 6.8 (P < 0.05), and alpha-KG efflux decreased from 126 to 95 nmol.min-1.mg-1. In intact hearts, Km was reduced with low intracellular pH, while matching control workload and respiratory rate with increased Ca2+ (pHi = 7.20, perfusate CaCl2 = 1.5 mM; pHi = 6.89, perfusate CaCl2 = 3 +/- 1 mM). Sequential 13C nuclear magnetic resonance spectra from hearts oxidizing [2-13C]acetate provided tricarboxylic acid cycle flux and the exchange rate between alpha-KG and cytosolic glutamate (F1). Tricarboxylic acid cycle flux was 10 mumol.min-1.g-1 in both groups, but F1 fell from a control of 9.3 +/- 0.6 to 2.8 +/- 0.4 mumol.min-1.g-1 at low Km. The results indicate that increased activity of alpha-KGDH occurs at the expense of alpha-KG efflux during support of normal workloads.
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Affiliation(s)
- J M O'Donnell
- Nuclear Magnetic Resonance Center, Massachusetts General Hospital, Harvard Medical School, Boston 02129, USA
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22
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Rath DP, Zhu H, Tong X, Jiang Z, Hamlin RL, Robitaille PM. Dynamic 13C NMR analysis of pyruvate and lactate oxidation in the in vivo canine myocardium: evidence of reduced utilization with increased work. Magn Reson Med 1997; 38:896-906. [PMID: 9402190 DOI: 10.1002/mrm.1910380608] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
In this work, substrate selection was monitored in the left ventricle of the canine myocardium by following pyruvate and lactate oxidation under in vivo conditions at basal and elevated workloads. These studies were conducted in the open chest model using dynamic 13C NMR techniques in the presence and absence of dichloroacetic acid (DCA), a well-known activator of pyruvate dehydrogenase (PDH). Following the infusion of (3-(13)C) pyruvate or (3-(13)C) lactate into the left anterior descending artery, highly variable 13C enrichments of glutamate, alanine, aspartate, and citrate were noted under low (RPP < 14,500 mmHg/min), intermediate (RPP = 15,000-25,000 mmHg/min), and high (RPP > 25,500 mmHg/min) rate pressure products (RPP). At low workloads, the myocardium typically oxidized the infused (3-(13)C) pyruvate or (3-(13)C) lactate and incorporated the labeled carbon into the glutamate pool as expected. However, in a few notable instances (n = 3), 13C-enriched pyruvate and lactate were unable to label the glutamate pool under in vivo conditions even at the lowest RPPs, indicating a lack of selection for these substrates by the tricarboxylic acid (TCA) cycle. Nonetheless, the levels of glutamate C4 enrichment observed at low workloads could usually be enhanced by infusion of DCA. Importantly, 13C NMR extract analysis revealed that (3-(13)C) pyruvate or (3-(13)C) lactate labeling of the glutamate pool was reduced (< 20%) at high workloads in spite of increased DCA concentrations.
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Affiliation(s)
- D P Rath
- Department of Radiology, The Ohio State University, Columbus, USA
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23
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Yu X, Alpert NM, Lewandowski ED. Modeling enrichment kinetics from dynamic 13C-NMR spectra: theoretical analysis and practical considerations. THE AMERICAN JOURNAL OF PHYSIOLOGY 1997; 272:C2037-48. [PMID: 9227433 DOI: 10.1152/ajpcell.1997.272.6.c2037] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Measurements of oxidative metabolism in the heart from dynamic 13C nuclear magnetic resonance (NMR) spectroscopy rely on 13C turnover in the NMR-detectable glutamate pool. A kinetic model was developed for the analysis of isotope turnover to determine tricarboxylic acid cycle flux (VTCA) and the interconversion rate between alpha-ketoglutarate and glutamate (F1) by fitting the model to NMR data of glutamate enrichment. The results of data fitting are highly reproducible when the noise level is within 10%, making this model applicable to single or grouped experiments. The values for VTCA and F1 were unchanged whether obtained from least-squares fitting of the model to mean experimental enrichment data with standard deviations in the cost function (VTCA = 10.52 mumol.min-1.g dry wt-1, F1 = 10.67 mumol.min-1.g dry wt-1) or to the individual enrichment values for each heart with the NMR noise level in the cost function (VTCA = 10.67 mumol.min-1.g dry wt-1, F1 = 10.18 mumol.min-1.g dry wt-1). Computer simulation and theoretical analysis indicate that glutamate enrichment kinetics are insensitive to the fractional enrichment of acetyl-CoA and changes in small intermediate pools (< 1 mumol/g dry wt). Therefore, high-resolution NMR analysis of tissue extracts and biochemical assays for intermediates at low concentrations are unnecessary. However, a high correlation between VTCA and F1 exists, as anticipated from competition for alpha-ketoglutarate, which indicates the utility of introducing independent experimental constraints into the data fitting for accurate quantification.
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Affiliation(s)
- X Yu
- Nuclear Magnetic Resonance Center, Massachusetts General Hospital, Boston, USA
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24
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Tran-Dinh S, Hoerter JA, Mateo P, Bouet F, Herve M. A simple mathematical model and practical approach for evaluating citric acid cycle fluxes in perfused rat hearts by 13C-NMR and 1H-NMR spectroscopy. EUROPEAN JOURNAL OF BIOCHEMISTRY 1997; 245:497-504. [PMID: 9151985 DOI: 10.1111/j.1432-1033.1997.t01-2-00497.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
We propose a simple mathematical model and a practical approach for evaluating the flux constant and the absolute value of flux in the citric acid cycle in perfused organs by 13C-NMR and 1H-NMR spectroscopy. We demonstrate that 13C-NMR glutamate spectra are independent of the relative sizes of the mitochondrial and cytosolic compartments and the exchange rates of glutamates, unless there is a difference in 13C chemical shifts of glutamate carbons between the two compartments. Wistar rat hearts (five beating and four KCl-arrested hearts) were aerobically perfused with 100% enriched [2-(13)C]acetate and the kinetics of glutamate carbon labeling from perchloric acid extracts were studied at various perfusion times. Under our experimental conditions, the citric acid cycle flux constant, which represents the fraction of glutamate in exchange with the citric acid cycle per unit time, is about 0.350 +/- 0.003 min(-1) for beating hearts and 0.0741 +/- 0.004 min(-1) for KCl-arrested hearts. The absolute values of the citric acid flux for beating hearts and for KCl-arrested hearts are 1.06 +/- 0.06 micromol x min(-1) x mg(-1) and 0.21 +/- 0.02 micromol x min(-1) x g(-1), respectively. The fraction of unlabeled acetate determined from the proton signal of the methyl group is small and essentially the same in beating and arrested hearts (7.4 +/- 1.7% and 8.8 +/- 2.1%, respectively). Thus, the large difference in the Glu C2/C4 between beating and arrested hearts is not due to the important contribution from anaplerotic sources in arrested hearts but simply to a substantial difference in citric acid cycle fluxes. Our model fits the experimental data well, indicating a fast exchange between 2-oxoglutarate and glutamate in the mitochondria of rat hearts. Analysis of the flux constant, calculated from the half-time of glutamate C4 labeling given in the literature, allows for a comparison of the citric acid flux for various working conditions in different animal species.
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Affiliation(s)
- S Tran-Dinh
- Département de Biologie Cellulaire et Moléculaire, CEN Saclay, Gif-sur-Yvette, France
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25
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Wei H, Merkle H, Xu Y, Ellermann J, Sipprell K, Uğurbil K. Detection of 13C-labeled metabolites in the in vivo canine heart by B1 insensitive heteronuclear coherent polarization transfer and comparison of signal enhancement with NOE. Magn Reson Med 1997; 37:327-30. [PMID: 9055219 DOI: 10.1002/mrm.1910370303] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
A recently developed adiabatic coherent polarization transfer enhancement technique [H. Merkle, H. Wei, M. Garwood, K. Uğurbil. J. Magn. Reson, 99, 480-494 (1992)] was employed to perform 13C spectroscopy in the intact canine heart in vivo during [2-13C]-acetate infusion into the left descending coronary artery, the results were compared with 13C spectra obtained with conventionally employed nuclear Overhauser enhancement. The results demonstrate that both methods can be performed by using surface coils to obtain in vivo 13C spectra and that coherent polarization transfer provides better enhancement than NOE for [2-13C]-acetate but not for short T2 compounds.
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Affiliation(s)
- H Wei
- Department of Radiology, University of Minnesota Medical School, Minneapolis 55455, USA
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26
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Reed MK, Barak C, Malloy CR, Maniscalco SP, Jessen ME. Effects of glutamate and aspartate on myocardial substrate oxidation during potassium arrest. J Thorac Cardiovasc Surg 1996; 112:1651-60. [PMID: 8975857 DOI: 10.1016/s0022-5223(96)70024-7] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
OBJECTIVES A recent report (J Clin Invest 1993;92:831-9) found no effect of glutamate plus aspartate on metabolic pathways in the heart, but the experimental conditions did not model clinical cardioplegia. The purpose of this study was to determine the effects of glutamate and aspartate on metabolic pathways feeding the citric acid cycle during cardioplegic arrest in the presence of physiologic substrates. METHODS Isolated rat hearts were supplied with fatty acids, lactate, pyruvate, glucose, and acetoacetate in physiologic concentrations. These substrates were enriched with 13C, which allowed a complete analysis of substrate oxidation by 13C-nuclear magnetic resonance spectroscopy in one experiment. Three groups of hearts were studied: arrest with potassium cardioplegic solution, arrest with cardioplegic solution supplemented with glutamate and aspartate (both in concentrations of 13 mmol/L), and a control group without cardioplegic arrest. RESULTS In potassium-arrested hearts, the contributions of fatty acids and lactate to acetyl coenzyme A were reduced, and acetoacetate was the preferred substrate for oxidation in the citric acid cycle. The addition of aspartate and glutamate in the presence of cardioplegic arrest did not further alter patterns of substrate utilization substantially, although acetoacetate use was somewhat lower than with simple cardioplegic arrest. When [U-13C]glutamate (13 mmol/L) and [U-13C]aspartate (13 mmol/L) were supplied as the only compounds labeled with 13C, little enrichment in citric acid cycle intermediates could be detected. CONCLUSIONS Glutamate and aspartate when added to potassium cardioplegic solutions have relatively minor effects on citric acid cycle metabolism.
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Affiliation(s)
- M K Reed
- Department of Surgery, University of Texas Southwestern Medical Center at Dallas 75235-8879, USA
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27
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Szczepaniak L, Babcock EE, Malloy CR, Sherry AD. Oxidation of acetate in rabbit skeletal muscle: detection by 13C NMR spectroscopy in vivo. Magn Reson Med 1996; 36:451-7. [PMID: 8875417 DOI: 10.1002/mrm.1910360318] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The results of a proton-decoupled and Overhauser-enhanced 13C NMR study of acetate metabolism in skeletal muscle are reported. [2-13C]Acetate was infused intravenously over 2 h into anesthetized rabbits, and skeletal muscle in the lateral thigh was monitored by 13C NMR spectroscopy at 4.7 T. Stable 13C enrichment in carbons 2, 3, and 4 of glutamate was observed at the end of the infusion, and the half-time for enrichment was 17 min for glutamate C4 and 50 min for glutamate C2 and C3. The contribution of exogenous acetate to acetylcoenzyme A was nearly equal in skeletal muscle and heart in vivo (83-87%, measured in tissue extracts), comparable with earlier perfused heart studies in which acetate was the sole available substrate. Although relative flux through the combined anaplerotic pathways (relative to citric acid cycle flux) was higher in quiescent skeletal muscle (28%) compared with hearts (3%) from the same animals, actual anaplerotic flux was estimated to be substantially higher in heart than in skeletal muscle after correcting for differences in citric acid cycle flux in the two tissues.
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Affiliation(s)
- L Szczepaniak
- Department of Radiology, Mary Nell and Ralph B. Rogers Magnetic Resonance Center, University of Texas Southwestern Medical Center, Dallas, USA
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28
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Lewandowski ED, Doumen C, White LT, LaNoue KF, Damico LA, Yu X. Multiplet structure of 13C NMR signal from glutamate and direct detection of tricarboxylic acid (TCA) cycle intermediates. Magn Reson Med 1996; 35:149-54. [PMID: 8622576 DOI: 10.1002/mrm.1910350203] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
For the first time, 13C NMR signals are shown from 13C-enriched, low-level tricarboxylic acid (TCA) cycle intermediates from extracts of normal cardiac tissue. As the low tissue content of the key intermediates alpha-ketoglutarate (alpha-KG) and succinate (SUC) in normal, well perfused tissues has until now precluded direct NMR detection from intact tissues and tissue extracts, 13C NMR signal from glutamate has generally been used to infer the isotopomer patterns of intermediates that are in chemical exchange with glutamate. However, the required assumptions regarding intracellular compartmentation for such indirect analysis have not been previously tested, as glutamate is largely cytosolic while the TCA cycle enzymes are located in the mitochondria. Chromatographic isolation of alpha-KG and SUC from heart tissue extracts allowed isotopomer analysis to be performed for comparison with that of glutamate. At steady state, a direct relationship between glutamate and alpha-ketoglutarate isotopomers was found, but succinate isotopomers matched those of glutamate only in hearts that displayed negligible contributions from the oxidation of unlabeled endogenous carbon sources.
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Affiliation(s)
- E D Lewandowski
- NMR Center, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Charlestown 02129, USA
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29
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Poizat C, Grably S, Cuchet P, Keriel C. Relationship between heart function and energy production. A study on isolated rat heart. Arch Physiol Biochem 1996; 104:71-80. [PMID: 8724883 DOI: 10.1076/apab.104.1.71.12874] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The purpose of this study is to determine the relationship between cardiac performance and energy production in isolated rat heart when heart function is modified either by calcium concentration or by oxygen partial pressure (PO2), and to evaluate the relative contribution of glycolytic ATP. Hearts are perfused at a constant 10 ml/min flow and submitted to increasing calcium concentration (0.36 to 1.78 mM free calcium) with maximal PO2 or to graded hypoxia (660 to 52 mmHg) with maximal calcium concentration. Cardiac performance, oxygen consumption (VO2), lactate+pyruvate production are measured. To inhibit glycolysis, perfusions are also carried out with deoxyglucose (2-DG). The plotting of mitochondrial ATP production, as calculated from VO2 vs contractility parameters shows a different relationship when we modify the PO2 or the calcium concentration, whereas the relationship is similar for heart rate. When cardiac performance is related to total ATP production, glycolytic ATP being calculated from lactate+pyruvate production, the difference, although decreased, remains. 2-DG impairs heart function, but with 2-DG the relationship between ATP production and heart function becomes unique. In conclusion, there is an evident difference in the dependence of heart contractility on ATP production according to the factor that limits heart function. The contribution of glycolysis to energy production does not explain all of this difference. Furthermore, such a difference does not exist for heart rate. This raises the question of energy compartmentation in myocardial cells.
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Affiliation(s)
- C Poizat
- Laboratoire de Bioénergétique Fondamentale et Appliquée Université Joseph Fourier, Grenoble, France
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30
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Yu X, White LT, Doumen C, Damico LA, LaNoue KF, Alpert NM, Lewandowski ED. Kinetic analysis of dynamic 13C NMR spectra: metabolic flux, regulation, and compartmentation in hearts. Biophys J 1995; 69:2090-102. [PMID: 8580353 PMCID: PMC1236443 DOI: 10.1016/s0006-3495(95)80080-9] [Citation(s) in RCA: 88] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Control of oxidative metabolism was studied using 13C NMR spectroscopy to detect rate-limiting steps in 13C labeling of glutamate. 13C NMR spectra were acquired every 1 or 2 min from isolated rabbit hearts perfused with either 2.5 mM [2-13C]acetate or 2.5 mM [2-13C]butyrate with or without KCl arrest. Tricarboxylic acid cycle flux (VTCA) and the exchange rate between alpha-ketoglutarate and glutamate (F1) were determined by least-square fitting of a kinetic model to NMR data. Rates were compared to measured kinetics of the cardiac glutamate-oxaloacetate transaminase (GOT). Despite similar oxygen use, hearts oxidizing butyrate instead of acetate showed delayed incorporation of 13C label into glutamate and lower VTCA, because of the influence of beta-oxidation: butyrate = 7.1 +/- 0.2 mumol/min/g dry wt; acetate = 10.1 +/- 0.2; butyrate + KCl = 1.8 +/- 0.1; acetate + KCl = 3.1 +/- 0.1 (mean +/- SD). F1 ranged from a low of 4.4 +/- 1.0 mumol/min/g (butyrate + KCl) to 9.3 +/- 0.6 (acetate), at least 20-fold slower than GOT flux, and proved to be rate limiting for isotope turnover in the glutamate pool. Therefore, dynamic 13C NMR observations were sensitive not only to TCA cycle flux but also to the interconversion between TCA cycle intermediates and glutamate.
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Affiliation(s)
- X Yu
- NMR Center, Massachusetts General Hospital, Boston, USA
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31
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Weiss RG, Stern MD, de Albuquerque CP, Vandegaer K, Chacko VP, Gerstenblith G. Consequences of altered aspartate aminotransferase activity on 13C-glutamate labelling by the tricarboxylic acid cycle in intact rat hearts. BIOCHIMICA ET BIOPHYSICA ACTA 1995; 1243:543-8. [PMID: 7727532 DOI: 10.1016/0304-4165(95)00031-6] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The appearance of 13C label in glutamate has been used to quantify cellular tricarboxylic acid (TCA) cycle activity using 13C-NMR spectroscopy. Glutamate is linked to the TCA cycle by the amino-transferase reactions, however the consequences of alterations in amino-transferase activity on glutamate labelling kinetics, at a constant total tricarboxylic acid cycle activity, have not been investigated. Aspartate amino-transferase activity in [2-13C]acetate-perfused beating rat hearts was found to be similar to total TCA cycle flux in the presence of normal perfusion conditions and was reduced by more than 50% with the subsequent administration of amino-oxyacetic acid (AOA). AOA did not reduce contractile or kinetic measures of total TCA cycle flux, but did slow the 13C labelling of glutamate, in accord with current mathematical predictions. The impact of similar reductions in amino-transferase activity on estimates of total TCA cycle flux derived from several previously reported methods was also evaluated. Because total TCA cycle and the amino-transferase activities both affect the kinetics of 13C-glutamate labelling and because the amino-transferase activities are often unknown under physiologic conditions and can be reduced under pathologic conditions, the calculation of total TCA cycle flux from 13C-NMR data in the future is probably best accomplished either with a sufficiently sophisticated mathematical model that assesses amino-transferase activity or with an empiric model that is relatively insensitive to variations in amino-transferase activity.
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Affiliation(s)
- R G Weiss
- Peter Belfer Laboratory, Department of Medicine, Johns Hopkins Hospital, Baltimore, MD 21287-6568, USA
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32
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Cohen DM, Bergman RN. Estimation of TCA cycle flux, aminotransferase flux, and anaplerosis in heart: validation with syntactic model. THE AMERICAN JOURNAL OF PHYSIOLOGY 1995; 268:E397-409. [PMID: 7900786 DOI: 10.1152/ajpendo.1995.268.3.e397] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Weiss et al. (Circ. Res. 70: 392-408, 1992) proposed a model of the citric acid cycle (CAC) in myocytes and a system of 17 differential equations that can be used to describe the changes over time in enrichment of carbons C-2 and C-4 of glutamate under conditions of metabolic steady state. They also proposed an empirical measure (KT) of flux through the CAC, which has been shown to be correlated to O2 consumption in rat hearts perfused with acetate or a mixture of glucose and acetate. We report a new method for estimation of the absolute rate of the flux through the CAC in heart (vTCA), without the numerical solution of differential equations. Unlike KT, our estimate is equal to the rate of flux catalyzed by the alpha-ketoglutarate dehydrogenase complex (vTCA), not merely correlated with it. We also estimate the rate of flux catalyzed by aspartate aminotransferase (vTA) and by NADP(+)-dependent malic enzyme (an anaplerotic reaction). The formula for vTCA during administration of [2-13C]acetate is as follows: vTCA = M[(C-2ssLC-4)/[C-4ss(LC-4-LC-2)]], where C-2ss and C-4ss represent steady-state fractional enrichment, LC-2 and LC-4 represent dominant rate constants of C-2 and C-4 of glutamate, respectively, and M is the sum of concentrations of aspartate, glutamate, and intermediates of the CAC. The assumptions underlying our formula are as follows: 1) metabolic steady state is maintained, 2) exchange of molecules between cytosolic and mitochondrial compartments is rapid, 3) 13C enters pools of the CAC only from acetyl CoA via citrate synthase, 4) [citrate]/[glutamate] < 1 + (vTCA/vTA), and 5) (m-[glutamate])/M < C-2ss/C-4ss.
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Affiliation(s)
- D M Cohen
- Department of Physiology and Biophysics, University of Southern California School of Medicine, Los Angeles 90033
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Pruski J, Ahmad A, Sun L, Robitaille PM. Construction of a 28-mm 1H/13C probe and actively shielded Z-gradient set for operation in a 9.4 T/89 mm magnet. Magn Reson Med 1994; 32:129-32. [PMID: 8084228 DOI: 10.1002/mrm.1910320118] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
In this work, we present a new RF and gradient assembly for operation in a 9.4 Tesla/89 mm magnet. This assembly was designed in order to enable 1H-NMR perfusion studies that are based on proton-observed carbon-edited approaches or gradient selected double quantum coherence. The RF portion of this probe assembly is comprised of a modified Alderman-Grant coil and a saddle coil operating at 400 and 100 MHz, respectively. These coils are surrounded by an actively shielded Z gradient, which also allows for the use of gradient-based water suppression without the need for carbon selection. We demonstrate that this probe can be used to implement gradient selected double quantum coherence experiments resulting in a high degree of water suppression.
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Affiliation(s)
- J Pruski
- Department of Radiology, Ohio State University, Columbus
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34
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Saks VA, Khuchua ZA, Vasilyeva EV, Kuznetsov AV. Metabolic compartmentation and substrate channelling in muscle cells. Role of coupled creatine kinases in in vivo regulation of cellular respiration--a synthesis. Mol Cell Biochem 1994; 133-134:155-92. [PMID: 7808453 DOI: 10.1007/bf01267954] [Citation(s) in RCA: 184] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The published experimental data and existing concepts of cellular regulation of respiration are analyzed. Conventional, simplified considerations of regulatory mechanism by cytoplasmic ADP according to Michaelis-Menten kinetics or by derived parameters such as phosphate potential etc. do not explain relationships between oxygen consumption, workload and metabolic state of the cell. On the other hand, there are abundant data in literature showing microheterogeneity of cytoplasmic space in muscle cells, in particular with respect to ATP (and ADP) due to the structural organization of cell interior, existence of multienzyme complexes and structured water phase. Also very recent experimental data show that the intracellular diffusion of ADP is retarded in cardiomyocytes because of very low permeability of the mitochondrial outer membrane for adenine nucleotides in vivo. Most probably, permeability of the outer mitochondrial membrane porin channels is controlled in the cells in vivo by some intracellular factors which may be connected to cytoskeleton and lost during mitochondrial isolation. All these numerous data show convincingly that cellular metabolism cannot be understood if cell interior is considered as homogenous solution, and it is necessary to use the theories of organized metabolic systems and substrate-product channelling in multienzyme systems to understand metabolic regulation of respiration. One of these systems is the creatine kinase system, which channels high energy phosphates from mitochondria to sites of energy utilization. It is proposed that in muscle cells feed-back signal between contraction and mitochondrial respiration may be conducted by metabolic wave (propagation of oscillations of local concentration of ADP and creatine) through cytoplasmic equilibrium creatine and adenylate kinases and is amplified by coupled creatine kinase reaction in mitochondria. Mitochondrial creatine kinase has experimentally been shown to be a powerful amplifier of regulatory action of weak ADP fluxes due to its coupling to adenine nucleotide translocase. This phenomenon is also carefully analyzed.
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Affiliation(s)
- V A Saks
- Group of Bioenergetics, Cardiology Research Center, Moscow, Russia
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35
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Robitaille PM, Rath DP, Abduljalil AM, O'Donnell JM, Jiang Z, Zhang H, Hamlin RL. Dynamic 13C NMR analysis of oxidative metabolism in the in vivo canine myocardium. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(19)74314-2] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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36
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Abstract
NMR spectroscopy is a powerful and non-invasive technique with which to study cardiac energy metabolism in vivo. This method makes use of the "spin" properties of certain atomic nuclei. The naturally occurring phosphorus nucleus (P-31) is visible by NMR and phosphorus-31 NMR spectra contain signals from the major components of energy metabolism. In vivo, the phosphocreatine to ATP ratio (PCr/ATP) is used as an index of the energy status and viability of the myocardium. However, it is the response of this metabolic index to differing physiological and pharmacological stresses that has helped to elucidate the mechanisms that regulate cellular respiration and to highlight abnormalities in heart failure. As there are many technical difficulties involved with cardiac NMR, 31-phosphorus studies of skeletal muscle have provided an indirect way of studying abnormalities in myocardial metabolism in vivo. One of the unique features of NMR is that it permits in vivo measurements of fluxes through key enzymes in energy metabolism using magnetization transfer. Determination of the rates of energy transfer through the creatine kinase reaction and energy turnover in vivo will provide new insights into the control of energy metabolism in health and disease. Alternatively, carbon-13 NMR can be used to measure fluxes through the different metabolic pathways of synthesis and catabolism following administration of selectively labelled carbon-13 substrates. In conclusion, the non-invasive and versatile nature of NMR spectroscopy makes it an ideal method to assess and evaluate energy metabolism in vivo.
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Affiliation(s)
- A M Seymour
- Department of Cardiothoracic Surgery, National Heart & Lung Institute at Harefield Hospital, Harefield, Middlesex, United Kingdom
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Robitaille PM, Rath DP, Skinner TE, Abduljalil AM, Hamlin RL. Transaminase reaction rates, transport activities and TCA cycle analysis by post-steady state 13C NMR. Magn Reson Med 1993; 30:262-6. [PMID: 8366809 DOI: 10.1002/mrm.1910300218] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
In this work, we present the post-steady state analysis of the TCA cycle and a closed form solution to the rate of label washout from the C4 carbon of glutamic acid through the transaminases and the malate-aspartate shuttle and then through alpha-ketoglutarate dehydrogenase. We demonstrate using a model of this problem that the rate of label washout depends not only on the flux through alpha-ketoglutarate dehydrogenase, but most importantly on the activity of the malate-aspartate shuttle as determined by the forward and reverse fluxes through the transaminases and by the rate of transport of glutamate and alpha-ketoglutarate across the mitochondrial membrane.
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Affiliation(s)
- P M Robitaille
- Department of Medical Biochemistry, Ohio State University, Columbus 43210
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