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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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2
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Vaidya MV, Zhang B, Hong D, Brown R, Batsios G, Viswanath P, Paska J, Wulf G, Grant AK, Ronen SM, Larson PEZ. A 13C/ 31P surface coil to visualize metabolism and energetics in the rodent brain at 3 Tesla. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2022; 343:107286. [PMID: 36075133 PMCID: PMC9721620 DOI: 10.1016/j.jmr.2022.107286] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/20/2022] [Revised: 08/04/2022] [Accepted: 08/24/2022] [Indexed: 06/15/2023]
Abstract
PURPOSE We constructed a 13C/31P surface coil at 3 T for studying cancer metabolism and bioenergetics. In a single scan session, hyperpolarized 13C-pyruvate MRS and 31P MRS was carried out for a healthy rat brain. METHODS All experiments were carried out at 3 Tesla. The multinuclear surface coil was designed as two coplanar loops each tuned to either the 13C or 31P operating frequency with an LCC trap on the 13C loop. A commercial volume proton coil was used for anatomical localization and B0 shimming. Single tuned coils operating at either the 13C or 31P frequency were built to evaluate the relative performance of the multinuclear coil. Coil performance metrics consisted of measuring Q factor ratio, calculating system input power using a single-pulse acquisition, and acquiring SNR and flip angle maps using 2D CSI sequences. To observe in vivo spectra, a bolus of hyperpolarized [1-13C] pyruvate was administered via tail vein. In vivo13C and endogenous 31P spectra were obtained in a single scan session using 1D slice selective acquisitions. RESULTS When compared with single tuned surface coils, the multinuclear coil performance showed a decrease in Q factor ratio, SNR, and transmit efficiency. Flip angle maps showed adequate flip angles within the phantom when the transmit voltage was set using an external phantom. Results show good detection of 13C labeled lactate, alanine, and bicarbonate in addition to ATP from 31P MRS. CONCLUSIONS The coil enables obtaining complementary information within a scan session, thus reducing the number of trials and minimizing biological variability for studies of metabolism and bioenergetics.
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Affiliation(s)
- Manushka V Vaidya
- Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, CA, USA.
| | - Bei Zhang
- Advanced Imaging Research Center, UT Southwestern Medical Center, Dallas, TX, USA
| | - DongHyun Hong
- Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, CA, USA
| | - Ryan Brown
- Center for Advanced Imaging Innovation and Research, and Center for Biomedical Imaging, Department of Radiology, New York University School of Medicine, New York, NY, USA
| | - Georgios Batsios
- Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, CA, USA
| | - Pavithra Viswanath
- Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, CA, USA
| | - Jan Paska
- Center for Advanced Imaging Innovation and Research, and Center for Biomedical Imaging, Department of Radiology, New York University School of Medicine, New York, NY, USA
| | - Gerburg Wulf
- Department of Hematology-Oncology, Beth Israel Deaconess Medical Center, Boston, MA, USA
| | - Aaron K Grant
- Department of Radiology, Beth Israel Deaconess Medical Center, Boston, MA, USA
| | - Sabrina M Ronen
- Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, CA, USA
| | - Peder E Z Larson
- Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, CA, USA
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Lundquist J, Horstmann B, Pestov D, Ozgur U, Avrutin V, Topsakal E. Energy-Efficient, On-Demand Activation of Biosensor Arrays for Long-Term Continuous Health Monitoring. BIOSENSORS 2022; 12:bios12050358. [PMID: 35624659 PMCID: PMC9138492 DOI: 10.3390/bios12050358] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/13/2022] [Revised: 05/19/2022] [Accepted: 05/19/2022] [Indexed: 11/16/2022]
Abstract
Wearable biosensors for continuous health monitoring, particularly those used for glucose detection, have a limited operational lifetime due to biodegradation and fouling. As a result, patients must change sensors frequently, increasing cost and patient discomfort. Arrays of multiple sensors, where the individual devices can be activated on demand, increase overall operational longevity, thereby reducing cost and improving patient outcomes. This work demonstrates the feasibility of this approach via decomposition of combustible nitrocellulose membranes that protect the individual sensors from exposure to bioanalytes using a current pulse. Metal contacts, connected by graphene-loaded PEDOT:PSS polymer on the surface of the membrane, deliver the required energy to decompose the membrane. Nitrocellulose membranes with a thickness of less than 1 µm consistently transfer on to polydimethylsiloxane (PDMS) wells. An electrical energy as low as 68 mJ has been shown to suffice for membrane decomposition.
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Affiliation(s)
- Jonathan Lundquist
- Department of Electrical and Computer Engineering, College of Engineering, Virginia Commonwealth University, 907 Floyd Ave, Richmond, VA 23284, USA; (J.L.); (B.H.); (U.O.); (E.T.)
| | - Benjamin Horstmann
- Department of Electrical and Computer Engineering, College of Engineering, Virginia Commonwealth University, 907 Floyd Ave, Richmond, VA 23284, USA; (J.L.); (B.H.); (U.O.); (E.T.)
| | - Dmitry Pestov
- Nanomaterials Core Characterization Facility, College of Engineering, Virginia Commonwealth University, 907 Floyd Ave, Richmond, VA 23284, USA;
| | - Umit Ozgur
- Department of Electrical and Computer Engineering, College of Engineering, Virginia Commonwealth University, 907 Floyd Ave, Richmond, VA 23284, USA; (J.L.); (B.H.); (U.O.); (E.T.)
| | - Vitaliy Avrutin
- Department of Electrical and Computer Engineering, College of Engineering, Virginia Commonwealth University, 907 Floyd Ave, Richmond, VA 23284, USA; (J.L.); (B.H.); (U.O.); (E.T.)
- Correspondence: ; Tel.: +1-804-828-0181
| | - Erdem Topsakal
- Department of Electrical and Computer Engineering, College of Engineering, Virginia Commonwealth University, 907 Floyd Ave, Richmond, VA 23284, USA; (J.L.); (B.H.); (U.O.); (E.T.)
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Bastiaansen JA, Cheng T, Lei H, Gruetter R, Comment A. Direct noninvasive estimation of myocardial tricarboxylic acid cycle flux in vivo using hyperpolarized 13C magnetic resonance. J Mol Cell Cardiol 2015; 87:129-37. [DOI: 10.1016/j.yjmcc.2015.08.012] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/14/2015] [Revised: 07/27/2015] [Accepted: 08/12/2015] [Indexed: 11/28/2022]
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Facile fabrication of 3D layer-by-layer graphene-gold nanorod hybrid architecture for hydrogen peroxide based electrochemical biosensor. SENSING AND BIO-SENSING RESEARCH 2015. [DOI: 10.1016/j.sbsr.2014.10.008] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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Taguchi M, Ptitsyn A, McLamore ES, Claussen JC. Nanomaterial-mediated Biosensors for Monitoring Glucose. J Diabetes Sci Technol 2014; 8:403-411. [PMID: 24876594 PMCID: PMC4455391 DOI: 10.1177/1932296814522799] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Real-time monitoring of physiological glucose transport is crucial for gaining new understanding of diabetes. Many techniques and equipment currently exist for measuring glucose, but these techniques are limited by complexity of the measurement, requirement of bulky equipment, and low temporal/spatial resolution. The development of various types of biosensors (eg, electrochemical, optical sensors) for laboratory and/or clinical applications will provide new insights into the cause(s) and possible treatments of diabetes. State-of-the-art biosensors are improved by incorporating catalytic nanomaterials such as carbon nanotubes, graphene, electrospun nanofibers, and quantum dots. These nanomaterials greatly enhance biosensor performance, namely sensitivity, response time, and limit of detection. A wide range of new biosensors that incorporate nanomaterials such as lab-on-chip and nanosensor devices are currently being developed for in vivo and in vitro glucose sensing. These real-time monitoring tools represent a powerful diagnostic and monitoring tool for measuring glucose in diabetes research and point of care diagnostics. However, concerns over the possible toxicity of some nanomaterials limit the application of these devices for in vivo sensing. This review provides a general overview of the state of the art in nanomaterial-mediated biosensors for in vivo and in vitro glucose sensing, and discusses some of the challenges associated with nanomaterial toxicity.
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Affiliation(s)
- Masashige Taguchi
- Agricultural and Biological Engineering Department, University of Florida, Gainesville, FL, USA
| | - Andre Ptitsyn
- Whitney Laboratory for Marine Biosciences, University of Florida, St. Augustine, FL, USA
| | - Eric S McLamore
- Agricultural and Biological Engineering Department, University of Florida, Gainesville, FL, USA
| | - Jonathan C Claussen
- US Naval Research Laboratory, Center for Bio-Molecular Science and Engineering, Washington, DC, USA College of Science, George Mason University, Fairfax, VA, USA
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Hettling H, Alders DJC, Heringa J, Binsl TW, Groeneveld ABJ, van Beek JHGM. Computational estimation of tricarboxylic acid cycle fluxes using noisy NMR data from cardiac biopsies. BMC SYSTEMS BIOLOGY 2013; 7:82. [PMID: 23965343 PMCID: PMC3765389 DOI: 10.1186/1752-0509-7-82] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/31/2013] [Accepted: 08/15/2013] [Indexed: 11/16/2022]
Abstract
Background The aerobic energy metabolism of cardiac muscle cells is of major importance for the contractile function of the heart. Because energy metabolism is very heterogeneously distributed in heart tissue, especially during coronary disease, a method to quantify metabolic fluxes in small tissue samples is desirable. Taking tissue biopsies after infusion of substrates labeled with stable carbon isotopes makes this possible in animal experiments. However, the appreciable noise level in NMR spectra of extracted tissue samples makes computational estimation of metabolic fluxes challenging and a good method to define confidence regions was not yet available. Results Here we present a computational analysis method for nuclear magnetic resonance (NMR) measurements of tricarboxylic acid (TCA) cycle metabolites. The method was validated using measurements on extracts of single tissue biopsies taken from porcine heart in vivo. Isotopic enrichment of glutamate was measured by NMR spectroscopy in tissue samples taken at a single time point after the timed infusion of 13C labeled substrates for the TCA cycle. The NMR intensities for glutamate were analyzed with a computational model describing carbon transitions in the TCA cycle and carbon exchange with amino acids. The model dynamics depended on five flux parameters, which were optimized to fit the NMR measurements. To determine confidence regions for the estimated fluxes, we used the Metropolis-Hastings algorithm for Markov chain Monte Carlo (MCMC) sampling to generate extensive ensembles of feasible flux combinations that describe the data within measurement precision limits. To validate our method, we compared myocardial oxygen consumption calculated from the TCA cycle flux with in vivo blood gas measurements for 38 hearts under several experimental conditions, e.g. during coronary artery narrowing. Conclusions Despite the appreciable NMR noise level, the oxygen consumption in the tissue samples, estimated from the NMR spectra, correlates with blood-gas oxygen uptake measurements for the whole heart. The MCMC method provides confidence regions for the estimated metabolic fluxes in single cardiac biopsies, taking the quantified measurement noise level and the nonlinear dependencies between parameters fully into account.
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Affiliation(s)
- Hannes Hettling
- Centre for Integrative Bioinformatics (IBIVU), Vrije Universiteit Amsterdam, de Boelelaan 1081A, 1081 HV Amsterdam, The Netherlands.
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Shi J, McLamore ES, Porterfield DM. Nanomaterial based self-referencing microbiosensors for cell and tissue physiology research. Biosens Bioelectron 2013; 40:127-34. [PMID: 22889647 PMCID: PMC3604890 DOI: 10.1016/j.bios.2012.06.059] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2012] [Revised: 06/23/2012] [Accepted: 06/25/2012] [Indexed: 12/11/2022]
Abstract
Physiological studies require sensitive tools to directly quantify transport kinetics in the cell/tissue spatial domain under physiological conditions. Although biosensors are capable of measuring concentration, their applications in physiological studies are limited due to the relatively low sensitivity, excessive drift/noise, and inability to quantify analyte transport. Nanomaterials significantly improve the electrochemical transduction of microelectrodes, and make the construction of highly sensitive microbiosensors possible. Furthermore, a novel biosensor modality, self-referencing (SR), enables direct measurement of real-time flux and drift/noise subtraction. SR microbiosensors based on nanomaterials have been used to measure the real-time analyte transport in several cell/tissue studies coupled with various stimulators/inhibitors. These studies include: glucose uptake in pancreatic β cells, cancer cells, muscle tissues, intestinal tissues and P. Aeruginosa biofilms; glutamate flux near neuronal cells; and endogenous indole-3-acetic acid flux near the surface of Zea mays roots. Results from the SR studies provide important insights into cancer, diabetes, nutrition, neurophysiology, environmental and plant physiology studies under dynamic physiological conditions, demonstrating that the SR microbiosensors are an extremely valuable tool for physiology research.
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Affiliation(s)
- Jin Shi
- Birck-Bindley Physiological Sensing Facility, Purdue University, United States
- Department of Agricultural & Biological Engineering, Purdue University, United States
| | - Eric S. McLamore
- Department of Agricultural & Biological Engineering, University of Florida, United States
| | - D. Marshall Porterfield
- Birck-Bindley Physiological Sensing Facility, Purdue University, United States
- Department of Agricultural & Biological Engineering, Purdue University, United States
- Department of Horticulture and Landscape Architecture, Purdue University, United States
- Weldon School of Biomedical Engineering, Purdue University, United States
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Akki A, Gupta A, Weiss RG. Magnetic resonance imaging and spectroscopy of the murine cardiovascular system. Am J Physiol Heart Circ Physiol 2013; 304:H633-48. [PMID: 23292717 DOI: 10.1152/ajpheart.00771.2011] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Magnetic resonance imaging (MRI) has emerged as a powerful and reliable tool to noninvasively study the cardiovascular system in clinical practice. Because transgenic mouse models have assumed a critical role in cardiovascular research, technological advances in MRI have been extended to mice over the last decade. These have provided critical insights into cardiac and vascular morphology, function, and physiology/pathophysiology in many murine models of heart disease. Furthermore, magnetic resonance spectroscopy (MRS) has allowed the nondestructive study of myocardial metabolism in both isolated hearts and in intact mice. This article reviews the current techniques and important pathophysiological insights from the application of MRI/MRS technology to murine models of cardiovascular disease.
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Affiliation(s)
- Ashwin Akki
- Division of Cardiology, Department of Medicine, and Division of Magnetic Resonance Research, Department of Radiology, The Johns Hopkins University, School of Medicine, Baltimore, MD, USA
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Shestov AA, Mancuso A, Leeper DB, Glickson JD. Metabolic network analysis of DB1 melanoma cells: how much energy is derived from aerobic glycolysis? ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2013; 765:265-271. [PMID: 22879043 DOI: 10.1007/978-1-4614-4989-8_37] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
A network model has been developed for analysis of tumor glucose metabolism from (13)C MRS isotope exchange kinetic data. Data were obtained from DB1 melanoma cells grown on polystyrene microcarrier beads contained in a 20-mm diameter perfusion chamber in a 9.4 T Varian NMR spectrometer; the cells were perfused with 26 mM [1,6-(13)C(2)]glucose under normoxic conditions and 37°C and monitored by (13)C NMR spectroscopy for 6 h. The model consists of ∼150 differential equations in the cumomer formalism describing glucose and lactate transport, glycolysis, TCA cycle, pyruvate cycling, the pentose shunt, lactate dehydrogenase, the malate-aspartate and glycerophosphate shuttles, and various anaplerotic pathways. The rate of oxygen consumption (CMRO(2)) was measured polarographically by monitoring differences in pO(2). The model was validated by excellent agreement between model predicted and experimentally measured values of CMRO(2) and glutamate pool size. Assuming a P/O ratio of 2.5 for NADH and 1.5 for FADH2, ATP production was estimated as 46% glycolytic and 54% mitochondrial based on average values of CMRO(2) and glycolytic flux (two experiments).
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Affiliation(s)
- A A Shestov
- CMRR, Department of Radiology, University of Minnesota Medical School, Minneapolis, MN, USA
| | - A Mancuso
- Department of Radiology, University of Pennsylvania, Perelman School of Medicine, 626 Chatsworth Dr.Ambler, Philadelphia, PA, 19002, USA.,Abramson Comprehensive Cancer Center, Perelman School of Medicine, Philadelphia, PA, USA
| | - D B Leeper
- Department of Radiation Oncology, Thomas Jefferson University, Philadelphia, PA, USA
| | - J D Glickson
- Department of Radiology, University of Pennsylvania, Perelman School of Medicine, 626 Chatsworth Dr.Ambler, Philadelphia, PA, 19002, USA.
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Sugimoto M, Kawakami M, Robert M, Soga T, Tomita M. Bioinformatics Tools for Mass Spectroscopy-Based Metabolomic Data Processing and Analysis. Curr Bioinform 2012; 7:96-108. [PMID: 22438836 PMCID: PMC3299976 DOI: 10.2174/157489312799304431] [Citation(s) in RCA: 189] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2011] [Revised: 10/25/2011] [Accepted: 12/07/2011] [Indexed: 01/04/2023]
Abstract
Biological systems are increasingly being studied in a holistic manner, using omics approaches, to provide quantitative and qualitative descriptions of the diverse collection of cellular components. Among the omics approaches, metabolomics, which deals with the quantitative global profiling of small molecules or metabolites, is being used extensively to explore the dynamic response of living systems, such as organelles, cells, tissues, organs and whole organisms, under diverse physiological and pathological conditions. This technology is now used routinely in a number of applications, including basic and clinical research, agriculture, microbiology, food science, nutrition, pharmaceutical research, environmental science and the development of biofuels. Of the multiple analytical platforms available to perform such analyses, nuclear magnetic resonance and mass spectrometry have come to dominate, owing to the high resolution and large datasets that can be generated with these techniques. The large multidimensional datasets that result from such studies must be processed and analyzed to render this data meaningful. Thus, bioinformatics tools are essential for the efficient processing of huge datasets, the characterization of the detected signals, and to align multiple datasets and their features. This paper provides a state-of-the-art overview of the data processing tools available, and reviews a collection of recent reports on the topic. Data conversion, pre-processing, alignment, normalization and statistical analysis are introduced, with their advantages and disadvantages, and comparisons are made to guide the reader.
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Affiliation(s)
- Masahiro Sugimoto
- Institute for Advanced Biosciences, Keio University, Tsuruoka, Yamagata 997-0017, Japan
- Systems Biology Program, Graduate School of Media and Governance, Keio University, Fujisawa, Kanagawa 252-8520, Japan
- Graduate School of Medicine and Faculty of Medicine Kyoto University, Yoshida-Konoe-cho, Sakyo-ku, Kyoto 606-8501, Japan
| | - Masato Kawakami
- Institute for Advanced Biosciences, Keio University, Tsuruoka, Yamagata 997-0017, Japan
- Department of Environment and Information Studies, Keio University, Fujisawa, Kanagawa 252-8520, Japan
| | - Martin Robert
- Institute for Advanced Biosciences, Keio University, Tsuruoka, Yamagata 997-0017, Japan
- Systems Biology Program, Graduate School of Media and Governance, Keio University, Fujisawa, Kanagawa 252-8520, Japan
| | - Tomoyoshi Soga
- Institute for Advanced Biosciences, Keio University, Tsuruoka, Yamagata 997-0017, Japan
- Department of Environment and Information Studies, Keio University, Fujisawa, Kanagawa 252-8520, Japan
| | - Masaru Tomita
- Institute for Advanced Biosciences, Keio University, Tsuruoka, Yamagata 997-0017, Japan
- Department of Environment and Information Studies, Keio University, Fujisawa, Kanagawa 252-8520, Japan
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Shi J, Cha TG, Claussen JC, Diggs AR, Choi JH, Porterfield DM. Microbiosensors based on DNA modified single-walled carbon nanotube and Pt black nanocomposites. Analyst 2011; 136:4916-24. [PMID: 21858297 DOI: 10.1039/c1an15179g] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Glucose and ATP biosensors have important applications in diagnostics and research. Biosensors based on conventional materials suffer from low sensitivity and low spatial resolution. Our previous work has shown that combining single-walled carbon nanotubes (SWCNTs) with Pt nanoparticles can significantly enhance the performance of electrochemical biosensors. The immobilization of SWCNTs on biosensors remains challenging due to the aqueous insolubility originating from van der Waals forces. In this study, we used single-stranded DNA (ssDNA) to modify SWCNTs to increase solubility in water. This allowed us to explore new schemes of combining ssDNA-SWCNT and Pt black in aqueous media systems. The result is a nanocomposite with enhanced biosensor performance. The surface morphology, electroactive surface area, and electrocatalytic performance of different fabrication protocols were studied and compared. The ssDNA-SWCNT/Pt black nanocomposite constructed by a layered scheme proved most effective in terms of biosensor activity. The key feature of this protocol is the exploitation of ssDNA-SWCNTs as molecular templates for Pt black electrodeposition. The glucose and ATP microbiosensors fabricated on this platform exhibited high sensitivity (817.3 nA/mM and 45.6 nA/mM, respectively), wide linear range (up to 7 mM and 510 μM), low limit of detection (1 μM and 2 μM) and desirable selectivity. This work is significant to biosensor development because this is the first demonstration of ssDNA-SWCNT/Pt black nanocomposite as a platform for constructing both single-enzyme and multi-enzyme biosensors for physiological applications.
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Affiliation(s)
- Jin Shi
- Physiological Sensing Facility, Purdue University, West Lafayette, IN 47907-2057, USA
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Shi J, McLamore ES, Jaroch D, Claussen JC, Mirmira RG, Rickus JL, Porterfield DM. Oscillatory glucose flux in INS 1 pancreatic β cells: a self-referencing microbiosensor study. Anal Biochem 2010; 411:185-93. [PMID: 21167120 DOI: 10.1016/j.ab.2010.12.019] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2010] [Revised: 12/08/2010] [Accepted: 12/10/2010] [Indexed: 12/27/2022]
Abstract
Signaling and insulin secretion in β cells have been reported to demonstrate oscillatory modes, with abnormal oscillations associated with type 2 diabetes. We investigated cellular glucose influx in β cells with a self-referencing (SR) microbiosensor based on nanomaterials with enhanced performance. Dose-response analyses with glucose and metabolic inhibition studies were used to study oscillatory patterns and transporter kinetics. For the first time, we report a stable and regular oscillatory uptake of glucose (averaged period 2.9±0.6 min), which corresponds well with an oscillator model. This oscillatory behavior is part of the feedback control pathway involving oxygen, cytosolic Ca(2+)/ATP, and insulin secretion (periodicity approximately 3 min). Glucose stimulation experiments show that the net Michaelis-Menten constant (6.1±1.5 mM) is in between GLUT2 and GLUT9. Phloretin inhibition experiments show an EC(50) value of 28±1.6 μM phloretin for class I GLUT proteins and a concentration of 40±0.6 μM phloretin caused maximum inhibition with residual nonoscillating flux, suggesting that the transporters not inhibited by phloretin are likely responsible for the remaining nonoscillatory uptake, and that impaired uptake via GLUT2 may be the cause of the oscillation loss in type 2 diabetes. Transporter studies using the SR microbiosensor will contribute to diabetes research and therapy development by exploring the nature of oscillatory transport mechanisms.
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Affiliation(s)
- Jin Shi
- Physiological Sensing Facility, 1203 W. State Street, Purdue University, West Lafayette, IN 47907-2057, USA
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McLamore ES, Shi J, Jaroch D, Claussen JC, Uchida A, Jiang Y, Zhang W, Donkin SS, Banks MK, Buhman KK, Teegarden D, Rickus JL, Porterfield DM. A self referencing platinum nanoparticle decorated enzyme-based microbiosensor for real time measurement of physiological glucose transport. Biosens Bioelectron 2010; 26:2237-45. [PMID: 20965716 DOI: 10.1016/j.bios.2010.09.041] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2010] [Revised: 08/31/2010] [Accepted: 09/21/2010] [Indexed: 10/19/2022]
Abstract
Glucose is the central molecule in many biochemical pathways, and numerous approaches have been developed for fabricating micro biosensors designed to measure glucose concentration in/near cells and/or tissues. An inherent problem for microsensors used in physiological studies is a low signal-to-noise ratio, which is further complicated by concentration drift due to the metabolic activity of cells. A microsensor technique designed to filter extraneous electrical noise and provide direct quantification of active membrane transport is known as self-referencing. Self-referencing involves oscillation of a single microsensor via computer-controlled stepper motors within a stable gradient formed near cells/tissues (i.e., within the concentration boundary layer). The non-invasive technique provides direct measurement of trans-membrane (or trans-tissue) analyte flux. A glucose micro biosensor was fabricated using deposition of nanomaterials (platinum black, multiwalled carbon nanotubes, Nafion) and glucose oxidase on a platinum/iridium microelectrode. The highly sensitive/selective biosensor was used in the self-referencing modality for cell/tissue physiological transport studies. Detailed analysis of signal drift/noise filtering via phase sensitive detection (including a post-measurement analytical technique) are provided. Using this highly sensitive technique, physiological glucose uptake is demonstrated in a wide range of metabolic and pharmacological studies. Use of this technique is demonstrated for cancer cell physiology, bioenergetics, diabetes, and microbial biofilm physiology. This robust and versatile biosensor technique will provide much insight into biological transport in biomedical, environmental, and agricultural research applications.
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Affiliation(s)
- E S McLamore
- Bindley Bioscience Center, Physiological Sensing Facility, Purdue University, 1203 W, State Street, West Lafayette, IN, USA
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Mancuso A, Sharfstein ST, Tucker SN, Clark DS, Blanch HW. Examination of primary metabolic pathways in a murine hybridoma with carbon-13 nuclear magnetic resonance spectroscopy. Biotechnol Bioeng 2009; 44:563-85. [PMID: 18618793 DOI: 10.1002/bit.260440504] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Primary metabolism of a murine hybridoma was probed with (13)C nuclear magnetic resonance (NMR) spectroscopy. Cells cultured in a hollow fiber bioreactor were serially infused with [1-(13)C] glucose, [2-(13)C] glucose, and [3-(13)C] glutamine. In vivo spectroscopy of the culture was used in conjunction with off-line spectroscopy of the medium to determine the intracellular concentration of several metabolic intermediates and to determine fluxes for primary metabolic pathways. Intracellular concentrations of pyruvate and alanine were very high relative to levels observed in normal quiescent mammalian cells. Estimates made from labeling patterns in lactate indicate that 76% of pyruvate is derived directly from glycolysis; some is also derived from the malate shunt, the pyruvate/melate shuttle associated with lipid synthesis and the pentose phosphate pathway. The rate of formation of pyruvate from the pentose phosphate pathway was estimated to be 4% of that from glycolysis; This value is a lower limit and the actual value may be higher. Incorporation of pyruvate into the tricarboxylic acid (TCA) cycle appears to occur through only pyruvate dehydrogenase; no pyruvate carboxylase activity was detected. The malate shunt rate was approximately equal to the rate of glutamine uptake. The rate of incorporation of glucosederived acetyl-CoA into lipids was 4% of the glucose uptake rate. The TCA cycle rate between isocitrate and alpha-ketoglutarate was 110% of the glutamine uptake rate.
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Affiliation(s)
- A Mancuso
- Department of Chemical Engineering, University of California, Berkeley, CA 94720, USA
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Wiczer BM, Bernlohr DA. A novel role for fatty acid transport protein 1 in the regulation of tricarboxylic acid cycle and mitochondrial function in 3T3-L1 adipocytes. J Lipid Res 2009; 50:2502-13. [PMID: 19535819 DOI: 10.1194/jlr.m900218-jlr200] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Fatty acid transport proteins (FATPs) are integral membrane acyl-CoA synthetases implicated in adipocyte fatty acid influx and esterification. Whereas some FATP1 translocates to the plasma membrane in response to insulin, the majority of FATP1 remains within intracellular structures and bioinformatic and immunofluorescence analysis of FATP1 suggests the protein primarily resides in the mitochondrion. To evaluate potential roles for FATP1 in mitochondrial metabolism, we used a proteomic approach following immunoprecipitation of endogenous FATP1 from 3T3-L1 adipocytes and identified mitochondrial 2-oxoglutarate dehydrogenase. To assess the functional consequence of the interaction, purified FATP1 was reconstituted into phospholipid-containing vesicles and its effect on 2-oxoglutarate dehydrogenase activity evaluated. FATP1 enhanced the activity of 2-oxoglutarate dehydrogenase independently of its acyl-CoA synthetase activity whereas silencing of FATP1 in 3T3-L1 adipocytes resulted in decreased activity of 2-oxoglutarate dehydrogenase. FATP1 silenced 3T3-L1 adipocytes exhibited decreased tricarboxylic acid cycle activity, increased cellular NAD(+)/NADH, increased fatty acid oxidation, and increased lactate production indicative of altered mitochondrial energy metabolism. These results reveal a novel role for FATP1 as a regulator of tricarboxylic acid cycle activity and mitochondrial function.
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Affiliation(s)
- Brian M Wiczer
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN, USA
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Golman K, Petersson JS, Magnusson P, Johansson E, Akeson P, Chai CM, Hansson G, Månsson S. Cardiac metabolism measured noninvasively by hyperpolarized 13C MRI. Magn Reson Med 2008; 59:1005-13. [PMID: 18429038 DOI: 10.1002/mrm.21460] [Citation(s) in RCA: 163] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Pyruvate is included in the energy production of the heart muscle and is metabolized into lactate, alanine, and CO(2) in equilibrium with HCO(3) (-). The aim of this study was to evaluate the feasibility of using (13)C hyperpolarization enhanced MRI to monitor pyruvate metabolism in the heart during an ischemic episode. The left circumflex artery of pigs (4 months, male, 29-34 kg) was occluded for 15 or 45 min followed by 2 hr of reperfusion. Pigs were examined by (13)C chemical shift imaging following intravenous injection of 1-(13)C pyruvate. (13)C chemical shift MR imaging was used in order to visualize the local concentrations of the metabolites. After a 15-min occlusion (no infarct) the bicarbonate signal level in the affected area was reduced (25-44%) compared with the normal myocardium. Alanine signal level was normal. After a 45-min occlusion (infarction) the bicarbonate signal was almost absent (0.2-11%) and the alanine signal was reduced (27-51%). Due to image-folding artifacts the data obtained for lactate were inconclusive. These studies demonstrate that cardiac metabolic imaging with hyperpolarized 1-(13)C-pyruvate is feasible. The changes in concentrations of the metabolites within a minute after injection can be detected and metabolic maps constructed.
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Affiliation(s)
- Klaes Golman
- GE Healthcare, Bio Sciences, Medeon, Malmö, Sweden
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18
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Beyond aerobic glycolysis: transformed cells can engage in glutamine metabolism that exceeds the requirement for protein and nucleotide synthesis. Proc Natl Acad Sci U S A 2007; 104:19345-50. [PMID: 18032601 DOI: 10.1073/pnas.0709747104] [Citation(s) in RCA: 1873] [Impact Index Per Article: 110.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Tumor cell proliferation requires rapid synthesis of macromolecules including lipids, proteins, and nucleotides. Many tumor cells exhibit rapid glucose consumption, with most of the glucose-derived carbon being secreted as lactate despite abundant oxygen availability (the Warburg effect). Here, we used 13C NMR spectroscopy to examine the metabolism of glioblastoma cells exhibiting aerobic glycolysis. In these cells, the tricarboxylic acid (TCA) cycle was active but was characterized by an efflux of substrates for use in biosynthetic pathways, particularly fatty acid synthesis. The success of this synthetic activity depends on activation of pathways to generate reductive power (NADPH) and to restore oxaloacetate for continued TCA cycle function (anaplerosis). Surprisingly, both these needs were met by a high rate of glutamine metabolism. First, conversion of glutamine to lactate (glutaminolysis) was rapid enough to produce sufficient NADPH to support fatty acid synthesis. Second, despite substantial mitochondrial pyruvate metabolism, pyruvate carboxylation was suppressed, and anaplerotic oxaloacetate was derived from glutamine. Glutamine catabolism was accompanied by secretion of alanine and ammonia, such that most of the amino groups from glutamine were lost from the cell rather than incorporated into other molecules. These data demonstrate that transformed cells exhibit a high rate of glutamine consumption that cannot be explained by the nitrogen demand imposed by nucleotide synthesis or maintenance of nonessential amino acid pools. Rather, glutamine metabolism provides a carbon source that facilitates the cell's ability to use glucose-derived carbon and TCA cycle intermediates as biosynthetic precursors.
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Mancuso A, Beardsley NJ, Wehrli S, Pickup S, Matschinsky FM, Glickson JD. Real-time detection of 13C NMR labeling kinetics in perfused EMT6 mouse mammary tumor cells and betaHC9 mouse insulinomas. Biotechnol Bioeng 2005; 87:835-48. [PMID: 15334410 DOI: 10.1002/bit.20191] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
A method was developed for obtaining high signal-to-noise 13C NMR spectra of intracellular compounds in metabolically active cultured cells. The method allows TCA cycle labeling kinetics to be determined in real time without significant oxygen transport limitations. Cells were immobilized on the surface of nonporous microcarriers that were either uncoated or coated with polypeptides and used in a 12-cm3 packed bed. The methods were tested with two EMT6 mouse mammary tumor cell lines, one strongly adherent and the other moderately adherent, and a weakly adherent mouse insulinoma line (betaHC9). For both EMT6 lines, NTP and oxygen consumption measurements indicated that the number of cells in the spectrometer ranged from 6 x 10(8) to 1 x 10(9). During infusion of [1-13C]glucose, labeling in C-4 glutamate (indicative of flux into the first half of the TCA cycle) could be detected with 15-min resolution. However, labeling for C-3 and C-2 glutamate (indicative of complete TCA cycle activity) was fivefold lower and difficult to quantify. To increase TCA cycle labeling, cells were infused with medium containing [1,6-13C2]glucose. A 2.5-fold increase was observed in C-4 glutamate labeling and C-3 and C-2 glutamate labeling could be monitored with 30-min resolution. Citrate synthase activity was indirectly detected in real time, as [3,4-13C2]glutamate was formed from [2-13C]oxaloacetate and [2-13C]acetate (of acetyl-CoA). Cell mass levels observed with betaHC9 cells were somewhat lower. However, the 13C S/N was sufficient to allow real-time monitoring of the response of intracellular metabolite labeling to a step change in glucose and a combined glutamine/serum pulse.
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Affiliation(s)
- A Mancuso
- Department of Radiology/6069, B6 Blockley Hall, 423 Guardian Drive, Philadelphia, Pennsylvania 19104-6021, USA.
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Ross-Ascuitto NT, Joyce JJ, Hasan AZMA, Ascuitto RJ. Performance of the chronically hypoxic young rabbit heart. Pediatr Cardiol 2004; 25:397-405. [PMID: 14743303 DOI: 10.1007/s00246-003-0429-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Hearts isolated from 30 rabbits, raised from birth to approximately 5 weeks of age under either hypoxic (FIO2, 0.10) or normoxic (FIO2, 0.21) conditions, underwent retrograde aortic perfusion using a non-recirculating, well-oxygenated crystalloid solution. The left ventricular end diastolic pressure was initially set at approximately 5 mmHg. Aerobic performance was studied by measuring peak systolic pressure (PSP), coronary flow, glucose oxidation, and oxygen consumption. Anaerobic function was assessed by determining time for the onset of contracture (TOC) in the presence of zero coronary flow. Hypoxic vs normoxic hearts (mean+/-SEM): heart rate, 197+/-6 vs 190+/-5 beats per minute; PSP, 136+/-4* vs 108+/-4 mmHg; dP/dt(max), 2294+/-125* vs 1549+/-144 mmHg/sec; relaxation time constant (Tau), 26.9+/-1.1* vs 41.6+/-4.8 msec; (-) dP/dt(max), 1422+/-43* vs 1001+/-63 mmHg/sec; coronary flow, 86.3+/-4.2* vs 59.9+/-2.9 ml/min/g(dry); glucose oxidation, 3511+/-118* vs 2979+/-233 nmol/min/g(dry); oxygen consumption, 28.2+/-1.4* vs 22.7+/-1.4 micromol/min/g(dry); and TOC, 11.8+/-1.2* vs 22.9+/-2.2 min (*p < 0.05). Hearts isolated from young rabbits, exposed to hypoxia from birth, exhibited enhanced ventricular systolic and diastolic mechanical function, elevated coronary flow, retained capacity for aerobic metabolism, and a shorter TOC compared to their normoxic counterparts.
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Affiliation(s)
- N T Ross-Ascuitto
- Department of Pediatric Cardiology, Tulane University School of Medicine, New Orleans, LA 70112, USA.
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21
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Forder JR, Pohost GM. Cardiovascular nuclear magnetic resonance: basic and clinical applications. J Clin Invest 2003. [DOI: 10.1172/jci200318868] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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Forder JR, Pohost GM. Cardiovascular nuclear magnetic resonance: basic and clinical applications. J Clin Invest 2003; 111:1630-9. [PMID: 12782663 PMCID: PMC156119 DOI: 10.1172/jci18868] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Affiliation(s)
- John R Forder
- Division of Cardiovascular Medicine, Keck School of Medicine, The University of Southern California, Los Angeles, California 90033, USA
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Jagasia D, McNulty PH. Diabetes mellitus and heart failure. CONGESTIVE HEART FAILURE (GREENWICH, CONN.) 2003; 9:133-9; quiz 140-1. [PMID: 12826771 DOI: 10.1111/j.1527-5299.2002.00901.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Type 2 diabetes mellitus substantially increases the lifetime risk of both developing and dying from heart failure. While this appears to be explained in part by the well-known association of diabetes with hypertension, dyslipidemia, and coronary atherosclerosis, additional pathophysiologic mechanisms linking type 2 diabetes and heart failure have recently been suggested. These include the potentially adverse effects of hyperglycemia on endothelial function and redox state, effects of excess circulating glucose and fatty acids on cardiomyocyte ultrastructure, intracellular signaling and gene expression, and the possibility that diabetes may impair recruitment of the myocardial insulin-responsive glucose transport system in response to ischemia. Because many of these putative pathophysiologic mechanisms should be amenable to normalization of the diabetic metabolic milieu, strategies designed to more carefully control circulating levels of glucose and fatty acids might conceivably delay or prevent the development of heart failure.
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Affiliation(s)
- Dinesh Jagasia
- Division of Cardiology, University of Iowa, Iowa City, IA, USA
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Eynan M, Knubuvetz T, Meiri U, Navon G, Gerstenblith G, Bromberg Z, Hasin Y, Horowitz M. Heat acclimation-induced elevated glycogen, glycolysis, and low thyroxine improve heart ischemic tolerance. J Appl Physiol (1985) 2002; 93:2095-104. [PMID: 12391086 DOI: 10.1152/japplphysiol.00304.2002] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Based on our observations of energy sparing in heat-acclimated (AC) rat hearts, we investigated whether changes in preischemic glycogen level, glycolytic rate, and plasma thyroxine level mediate cardioprotection induced in these hearts during ischemia-reperfusion insults. Control (C) (24 degrees C), AC (34 degrees C, 30 days), acclimated-euthyroid (34 degrees C + 3 ng/ml l-thyroxine), and control hypothyroid (24 degrees C + 0.02% 6-n-propyl-2-thiouracil) groups were studied. Preischemic glycogen was higher in AC than in C hearts [39.0 +/- 8.5 vs. 19.2 +/- 4.2 (SE) micromol glucose/g wet wt; P < 0.0006], and the lactate produced vs. glycogen level during total ischemia ((13)C-NMR spectroscopy) was markedly slower (AC: -0.82x, r = 0.98 vs. C: -4.7x, r = 0.9). Time to onset of ischemic contracture was lengthened, and the fraction of hearts experiencing ischemic contracture was lowered. Pulse pressure recovery was improved in AC compared with C animals before, but not after, absolute sodium iodoacetate-induced glycolysis inhibition. Acclimated-euthyroid hearts exhibited decreased ischemic tolerance, whereas induced hypothyroidism in C improved cardiotolerance. Thus higher preischemic glycogen and slowed glycolysis are associated with hypothyroidism and are likely important mediators of the improved ischemic tolerance exhibited by AC hearts.
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Affiliation(s)
- Mirit Eynan
- Division of Physiology, Hadassah Schools of Dental Medicine and Medicine, The Hebrew University, Jerusalem 91120, Israel
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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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McNulty PH, Ettinger SM, Gilchrist IC, Kozak M, Chambers CE. Cardiovascular implications of insulin resistance and non-insulin-dependent diabetes mellitus. J Cardiothorac Vasc Anesth 2001; 15:768-77. [PMID: 11748532 DOI: 10.1053/jcan.2001.28338] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- P H McNulty
- Section of Cardiology, Penn State College of Medicine, H-047, PO Box 850, Hershey, PA 17033, USA.
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Zehr KJ, Wong CY, Chin B, Ravert HT, Dannals RF, Hruban RH, Wong DF, Baumgartner WA. Comparison of myocardial oxygen consumption using 11C acetate positron emission tomography scanning in a working and non-working heart transplant model. Eur J Cardiothorac Surg 2001; 19:74-81. [PMID: 11163564 DOI: 10.1016/s1010-7940(00)00611-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/18/2022] Open
Abstract
OBJECTIVE In acute cardiac rejection, changes in myocardial oxygen consumption occur; non-invasive detection of these metabolic changes would have obvious clinical utility. In the classic cervical, heterotopic, canine, transplant model, the heart is non-working. It has a low myocardial oxygen consumption. Creation of a working model with normal myocardial oxygen consumption would enhance validity of non-human studies. METHODS Clearance of 11C acetate was determined by positron emission tomography (PET) scanning and compared with myocardial oxygen consumption in normal and transplanted canine hearts. Donor hearts from mongrel dogs (2.5-3 kg; n=4) were transplanted into the neck of adult beagles (12-15 kg; n=4), no immunosuppression was given. Two non-working hearts were modified to eject only coronary flow via the right ventricle. In two hearts, a novel working model was created with aortic regurgitation to load the left ventricle. Working and non-working hearts underwent PET scanning on post-operative days 2 and 4. Normal dog hearts (n=2) and native hearts of transplanted dogs (n=3) were used to validate the scanning technique. Coronary sinus and aortic oxygen saturation data along with myocardial blood flow (radiolabeled microspheres) confirmed that clearance of 11C acetate in normal and transplanted hearts followed a bi-exponential model. RESULTS Myocardial oxygen consumption was correlated with the rate constant of 11C acetate rapid phase clearance (r=0.91) in normal and transplanted hearts. The working hearts had increased myocardial oxygen consumption compared to non-working hearts. CONCLUSIONS This study (1) introduces a model of a working heterotopic cardiac transplantation with near-normal oxygen consumption; and (2) demonstrates that regional myocardial oxygen consumption in transplanted hearts can be detected by 11C acetate PET.
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Affiliation(s)
- K J Zehr
- Department of Cardiac Surgery, Johns Hopkins Medical Institution, MD 21287, Baltimore, USA.
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Herve M, Buffin-Meyer B, Bouet F, Son TD. Detection of modifications in the glucose metabolism induced by genetic mutations in Saccharomyces cerevisiae by 13C- and H-NMR spectroscopy. EUROPEAN JOURNAL OF BIOCHEMISTRY 2000; 267:3337-44. [PMID: 10824121 DOI: 10.1046/j.1432-1327.2000.01365.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
NMR spectroscopy may offer a suitable technique to characterize the glucose metabolism in response to genetic mutations in cells. The effects of various genetic modifications in Saccharomyces cerevisiae yeast were investigated using 13C- and 1H-NMR spectroscopy associated with biochemical techniques. Cells were incubated with [1-13C]glucose in order to study glucose consumption and the formation of various end-products (ethanol, trehalose, glycerol, glutamate and amino acids) as a function of time. Two types of genetic modifications were studied in S. cerevisiae. A genetic modification deleted the N-terminal part of the TFC7 protein which is the smallest subunit (tau55) of the TFIIIC transcription factor. One secondary effect of this mutation was a large deletion of mitochondrial DNA giving the rho-phenotype. The other genetic modification corresponded to the disruption of the HUF gene; the mutated cells were rho+ like the reference strain. Both mutations increase the glycolysis rate and glycerol synthesis and decrease trehalose production. The most modified cells, which contain both TFC7 deletion and HUF gene disruption, utilize glucose in the most extreme manner as in these cells the largest production of the two glycolytic products (ethanol and glycerol) and the smallest trehalose formation occur. The HUF gene disruption serves as a positive modulator of glycolysis and respiration. However, the TFC7 deletion, associated with the phenotype rho-, induces the most damage in the cellular function, dramatically altering the behaviour of the Krebs cycle. The cycle becomes blocked at the level of 2-oxoglutarate, detected by a characteristic pattern of the 13C-NMR glutamate spectra. These NMR spectra corroborate the phenotypic data, the rho-phenotype corresponding to deletions of mitochondria DNA which block all mitochondria protein synthesis and render the cells unable to derive energy from respiration. Moreover, as a consequence of the Krebs cycle blocking, alanine formation is also observed.
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Affiliation(s)
- M Herve
- Section de Biophysique des Protéines et des Membranes, Département de Biologie Cellulaire et Moléculaire, CEN Saclay, Gif-sur-Yvette, France.
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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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30
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Comte B, Vincent G, Bouchard B, Des Rosiers C. Probing the origin of acetyl-CoA and oxaloacetate entering the citric acid cycle from the 13C labeling of citrate released by perfused rat hearts. J Biol Chem 1997; 272:26117-24. [PMID: 9334176 DOI: 10.1074/jbc.272.42.26117] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
We present a strategy for simultaneous assessment of the relative contributions of anaplerotic pyruvate carboxylation, pyruvate decarboxylation, and fatty acid oxidation to citrate formation in the perfused rat heart. This requires perfusing with a mix of 13C-substrates and determining the 13C labeling pattern of a single metabolite, citrate, by gas chromatography-mass spectrometry. The mass isotopomer distributions of the oxaloacetate and acetyl moieties of citrate allow calculation of the flux ratios: (pyruvate carboxylation)/(pyruvate decarboxylation), (pyruvate carboxylation)/(citrate synthesis), (pyruvate decarboxylation)/(citrate synthesis) (pyruvate carboxylation)/(fatty acid oxidation), and (pyruvate decarboxylation)/(fatty acid oxidation). Calculations, based on precursor-product relationship, are independent of pool size. The utility of our method was demonstrated for hearts perfused under normoxia with [U-13C3](lactate + pyruvate) and [1-13C]octanoate under steady-state conditions. Under these conditions, effluent and tissue citrate were similarly enriched in all 13C mass isotopomers. The use of effluent citrate instead of tissue citrate allows probing substrate fluxes through the various reactions non-invasively in the intact heart. The methodology should also be applicable to hearts perfused with other 13C-substrates, such as 1-13C-labeled long chain fatty acid, and under various conditions, provided that assumptions on which equations are developed are valid.
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Affiliation(s)
- B Comte
- Department of Nutrition, University of Montréal, Montréal, Québec H3C 3J7, Canada
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Soares PR, de Albuquerque CP, Chacko VP, Gerstenblith G, Weiss RG. Role of preischemic glycogen depletion in the improvement of postischemic metabolic and contractile recovery of ischemia-preconditioned rat hearts. Circulation 1997; 96:975-83. [PMID: 9264509 DOI: 10.1161/01.cir.96.3.975] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
BACKGROUND Ischemic preconditioning (IPC) attenuates acidosis during prolonged ischemia and improves contractile and metabolic parameters during subsequent reperfusion. Glycogen depletion induced by IPC is proposed as a potential mechanism. METHODS AND RESULTS We studied the influence of manipulations of preischemic glycogen levels (Pre-G, micromol glucose/g wet wt) on contractile and metabolic (via 31P-nuclear magnetic resonance) parameters during 30 minutes of ischemia and recovery in four groups of isovolumic rat hearts: First, control (Con, n=18, mean Pre-G, 21.5+/-0.8); second, after two 5-minute IPC periods (IPC, n=12, Pre-G, 11.3+/-0.7); third, a control group in which Pre-G was depleted by glucose-free, acetate perfusion (Con-LowG, n=9, Pre-G, 7.9+/-1.2); and fourth, an IPC group in which Pre-G was raised by glucose and lactate perfusion such that Pre-G was similar to Con (IPC-HiG, n=11, Pre-G, 20+/-1.4). Manipulation of Pre-G significantly altered the pH fall during 30 minutes of ischemia (Con, 5.76+/-.03, Con-LowG, 6.26+/-.07; IPC-HiG, 5.91+/-.02, IPC, 6.05+/-.09). IPC-HiG hearts had significantly worse metabolic recovery (PCr, 70+/-7 versus 91+/-3% initial; IPC-HiG versus IPC, P<.05) and contractile recovery (end-diastolic pressure, 52+/-5 versus 29+/-5 mm Hg, P<.05) than IPC hearts but better recovery than Con (%PCr, 56+/-6% and end-diastolic pressure, 72+/-6 mm Hg). An ischemic rise in intracellular magnesium occurred and was atttenuated in preconditioned hearts. CONCLUSIONS Pre-G levels before ischemia influence but are not the sole determinants of the extent of acidosis during prolonged ischemia and of metabolic and contractile recovery during reperfusion in control and preconditioned hearts.
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Affiliation(s)
- P R Soares
- Department of Medicine, The Johns Hopkins Hospital, Baltimore, MD 21287-6568, USA
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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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Brunengraber H, Kelleher JK, Des Rosiers C. Applications of mass isotopomer analysis to nutrition research. Annu Rev Nutr 1997; 17:559-96. [PMID: 9240940 DOI: 10.1146/annurev.nutr.17.1.559] [Citation(s) in RCA: 92] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Investigations into regulating metabolic pathways with stable isotopes have, over the past decade, undergone major development with the use of nuclear magnetic resonance and mass spectrometry in studying labeling patterns of newly synthesized biomolecules. In this review, we concentrate on investigations of mass isotopomer distribution (MID) measured by mass spectrometry. We review the applications of MID to analytical problems, in particular the possibility of amplifying the measurement of low isotopic enrichments by incorporating multiple molecules or atoms of a primary analyte into the molecule of a secondary analyte, the MID of which is assayed. We also review new information on the regulation of intermediary metabolism gathered from the analysis of MID patterns of synthesized compounds. Lastly, we review the applications of MID to the synthesis of polymeric molecules, with emphasis on the validity of these techniques. A number of these techniques are applicable to investigations of nutrient metabolism in health and disease.
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Affiliation(s)
- H Brunengraber
- Department of Nutrition, Case Western Reserve University, Cleveland, Ohio 44106, USA.
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Prevention of ischemia-reperfusion injury by metabolic substrate—Mechanisms and surgical implications. Eur Surg 1996. [DOI: 10.1007/bf02616278] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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35
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Weiss RG, de Albuquerque CP, Vandegaer K, Chacko VP, Gerstenblith G. Attenuated glycogenolysis reduces glycolytic catabolite accumulation during ischemia in preconditioned rat hearts. Circ Res 1996; 79:435-46. [PMID: 8781477 DOI: 10.1161/01.res.79.3.435] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Prior transient episodes of ischemia ("ischemic preconditioning") reduce lactate accumulation and attenuate acidosis during a subsequent prolonged ischemic insult. The mechanisms responsible for attenuated glycolytic catabolite accumulation have not been established but may include earlier exhaustion of glycogen stores, slowed glycogenolysis before complete glycogen depletion, and/or inhibition of glycolysis. Simultaneous repeated measures of myocardial glycogen and the rates of glycolysis, glycogenolysis, glucose utilization, and glycolytic ATP production were obtained during total ischemia by 13C nuclear magnetic resonance spectroscopy in control and ischemia-preconditioned isolated rat hearts. Both [13C]glycolytic and [13C]glycogenolytic rates were significantly lower during total ischemia in preconditioned compared with control hearts (0.77 +/- 0.04 versus 1.06 +/- 0.06 mumol/min per gram wet weight [P < .01] for glycolysis and 0.15 +/- 0.07 versus 0.78 +/- 0.12 mumol/ min per gram wet weight [P < .001] for glycogenolysis, respectively, at 2.5 minutes of ischemia). Slowed glycolysis was present even during the early minutes of ischemia, when significant amounts of available [13C]glycogen were still present. Importantly, the reduction in the rate of glycogenolysis was larger and out of proportion to the reduction in glycolysis and occurred despite an increase in glucose utilization in preconditioned hearts (2.23 +/- 0.15 versus 1.5 +/- 0.10 mumol/min per gram wet weight at 1.25 minutes, P < .01). During early ischemia, conversion of glycogen phosphorylase to the a or "active" form was less in preconditioned than in control hearts (29.1 +/- 2.6% versus 41.2 +/- 9.8%, respectively; P < .05). Taken together, these findings demonstrate that ischemic preconditioning significantly depresses glycolytic catabolite accumulation during sustained ischemia not by more severe glycolytic inhibition or exhaustion of glycogen stores but by depressed glycogenolysis from the onset of ischemia.
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Affiliation(s)
- R G Weiss
- Peter Belfer Laboratory, Johns Hopkins Hospital, Baltimore, Md. 21287-6568, USA.
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McNulty PH, Sinusas AJ, Shi CQ, Dione D, Young LH, Cline GC, Shulman GI. Glucose metabolism distal to a critical coronary stenosis in a canine model of low-flow myocardial ischemia. J Clin Invest 1996; 98:62-9. [PMID: 8690805 PMCID: PMC507401 DOI: 10.1172/jci118778] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Myocardial regions perfused through a coronary stenosis may cease contracting, but remain viable. Clinical observations suggest that increased glucose utilization may be an adaptive mechanism in such "hibernating" regions. In this study, we used a combination of 13C-NMR spectroscopy, GC-MS analysis, and tissue biochemical measurements to track glucose through intracellular metabolism in intact dogs infused with [1-13C]glucose during a 3-4-h period of acute ischemic hibernation. During low-flow ischemia [3-13C]alanine enrichment was higher, relative to plasma [1-13C]glucose enrichment, in ischemic than in nonischemic regions of the heart, suggesting a greater contribution of exogenous glucose to glycolytic flux in the ischemic region (approximately 72 vs. approximately 28%, P < 0.01). Both the fraction of glycogen synthase present in the physiologically active glucose-6-phosphate-independent form (46 +/- 10 vs. 9 +/- 6%, P < 0.01) and the rate of incorporation of circulating glucose into glycogen (94 +/- 25 vs. 20 +/- 15 nmol/gram/min, P < 0.01) were also greater in ischemic regions. Measurement of steady state [4-13C)glutamate/[3-13C]alanine enrichment ratios demonstrated that glucose-derived pyruvate supported 26-36% of total tricarboxylic acid cycle flux in all regions, however, indicating no preference for glucose over fat as an oxidative substrate in the ischemic myocardium. Thus during sustained regional low-flow ischemia in vivo, the ischemic myocardium increases its utilization of exogenous glucose as a substrate. Upregulation is restricted to cytosolic utilization pathways, however (glycolysis and glycogen synthesis), and fat continues to be the major source of mitochondrial oxidative substrate.
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Affiliation(s)
- P H McNulty
- Department of Internal Medicine, VA Connecticut Medical Center, New Haven, 06520, USA
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Chatham JC, Forder JR, Glickson JD, Chance EM. Calculation of absolute metabolic flux and the elucidation of the pathways of glutamate labeling in perfused rat heart by 13C NMR spectroscopy and nonlinear least squares analysis. J Biol Chem 1995; 270:7999-8008. [PMID: 7713900 DOI: 10.1074/jbc.270.14.7999] [Citation(s) in RCA: 87] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Absolute metabolic fluxes in isolated perfused hearts have been determined by a nonlinear least squares analysis of glutamate labeling kinetics from [1-13C]glucose, [4-13C]beta-hydroxybutyrate, or [2-13C]acetate using 13C NMR spectroscopy. With glucose as substrate, the malate-aspartate shuttle flux was too slow to account for the reducing equivalents generated by glycolysis and to predict the observed oxygen consumption rate. For acetate and beta-hydroxybutyrate, the malate-aspartate shuttle had to be reversed for the network to agree with the observed oxygen consumption and glutamate labeling. Thus, an additional redox shuttle was required to reoxidize the NADH produced by cytoplasmic malate dehydrogenase. Using this model there was good agreement between the experimentally determined oxygen consumption and glutamate labeling and the calculated values of these parameters from the model for all substrates. The contribution of exogenous substrate to the overall tricarboxylic acid (TCA) cycle flux, 89.6 +/- 6.5% (mean +/- S.D.) as measured in the tissue extracts compared well with 91.4 +/- 4.2% calculated by the model. The ratio of TCA cycle flux to oxygen consumption for acetate, was 2.2 +/- 0.1, indicating that NADH production is principally accounted for by TCA cycle flux. For glucose or beta-hydroxybutyrate, this ratio was 2.9 +/- 0.2, consistent with the existence of other NADH producing reactions (e.g. glycolysis, beta-hydroxybutyrate oxidation).
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Affiliation(s)
- J C Chatham
- Department of Radiology and Radiological Sciences, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
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38
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Young LH, McNulty PH. Metabolic imaging: what are the challenges? J Nucl Cardiol 1994; 1:213-7. [PMID: 9420689 DOI: 10.1007/bf02984094] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
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40
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Nordback IH, Chacko VP, Cameron JL. Induction of anaerobic glucose metabolism during the development of acute pancreatitis. Ann Surg 1994; 219:248-57. [PMID: 8147606 PMCID: PMC1243132 DOI: 10.1097/00000658-199403000-00004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
OBJECTIVE Studies were performed with the ex vivo perfused canine pancreas preparation to characterize acinar cell metabolism during the development of acute pancreatitis. SUMMARY BACKGROUND DATA Acute pancreatitis can be initiated in the ex vivo perfused canine pancreas preparation by five different stimuli as follows: (1) the infusion of oleic acid (FFA), (2) partial obstruction of the pancreatic duct and secretin stimulation (POSS), (3) a 2-hour ischemic period before perfusion (ISCH 2), (4) a 1-hour ischemic period followed by acetaldehyde infusion (ISCH 1 + AA), and (5) supramaximal stimulation by cerulein (CER-HIGH). In each model, weight gain, edema formation, and hyperamylasemia occur, signifying the development of pancreatitis. Previously, the authors demonstrated that intracellular adenosine triphosphate (ATP) levels decline during the development of pancreatitis in the FFA model but not in the other four models. METHODS The ex vivo perfused canine pancreas preparation was used to study five different stimuli that result in the initiation of acute pancreatitis, as manifested by weight gain, edema formation, and hyperamylasemia during a 4-hour perfusion period. Glucose metabolism (using 13C-labeled glucose) and intracellular pH and ATP levels were monitored by magnetic resonance spectroscopy. Oxygen consumption and pancreatic secretion were measured directly. RESULTS In control preparations, a glucose signal appeared in the 13C-labeled spectra within 15 minutes, and a signal from glycogen appeared at the end of the 4-hour perfusion. In the preparations with an ischemic period (ISCH 2 and ISCH 1 + AA), a lactate signal appeared during the ischemia, disappeared during the early perfusion, and appeared again later during the perfusion as the physiologic injury response of pancreatitis developed. Similarly, in the POSS and CER-HIGH pancreatitis preparations, lactate accumulated in the pancreas during the perfusion period. In these four preparations, the intracellular pH did not differ significantly during the perfusion from that of the control preparations. Oxygen consumption was unchanged during the perfusion in the ISCH 2 and ISCH 1 + AA preparations and increased in the POSS and CER-HIGH preparations. In the FFA pancreatitis preparations, only a trace of glycogen was observed, and the metabolites of glucose were not detected. Intracellular pH and oxygen consumption both dropped significantly during the perfusion. CONCLUSIONS In four of the five acute experimental pancreatitis models, anaerobic glucose metabolism was induced, despite continuous oxygen extraction by the pancreas. This induction of anaerobic glucose metabolism may be important in maintaining normal levels of intracellular ATP early after the induction of pancreatitis because the absence of anaerobic glucose metabolism in the FFA model was associated with a remarkable decrease in intracellular ATP levels and pH. The FFA model of pancreatitis is the most severe of the five models.
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Affiliation(s)
- I H Nordback
- Department of Surgery, Johns Hopkins Medical Institutions, Baltimore, Maryland
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41
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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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42
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Chacko VP, Weiss RG. Intracellular pH determination by 13C-NMR spectroscopy. THE AMERICAN JOURNAL OF PHYSIOLOGY 1993; 264:C755-60. [PMID: 8460678 DOI: 10.1152/ajpcell.1993.264.3.c755] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
A noninvasive method for the determination of pH by the 13C-nuclear magnetic resonance (NMR) chemical shift of the C-3 carbon of sn-glycerol 3-phosphate is described. Nonlinear least-squares analysis of the chemical shift variation of the C-3 resonance of sn-glycerol 3-phosphate with pH at 37 degrees C in solutions and in perchloric acid extracts of tissue yielded a pKa of 6.2, making it a very sensitive indicator of pH in the approximate range of 5-7. Intracellular pH determined by the present 13C-NMR method correlated well with simultaneous measurements of pH by 31P-NMR spectroscopy over a wide range during normal perfusion and ischemic conditions in intact rat hearts. These findings indicate that this approach is particularly suited for quantification of intracellular pH over the physiological range in intact tissues and that observed in ischemic myocardium.
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Affiliation(s)
- V P Chacko
- Department of Radiology, Johns Hopkins University, School of Medicine, Baltimore, Maryland 21287
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43
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Weiss RG, Kalil-Filho R, Herskowitz A, Chacko VP, Litt M, Stern MD, Gerstenblith G. Tricarboxylic acid cycle activity in postischemic rat hearts. Circulation 1993; 87:270-82. [PMID: 8419016 DOI: 10.1161/01.cir.87.1.270] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
BACKGROUND Although myocardial oxidative tricarboxylic acid (TCA) cycle activity and contractile function are closely linked in normal cardiac muscle, their relation during postischemic reperfusion, when contractility often is reduced, is not well defined. METHODS AND RESULTS To test the hypothesis that oxidative TCA cycle flux is reduced in reperfused myocardium with persistent contractile dysfunction, TCA cycle flux was measured by analyzing the time course of sequential myocardial glutamate labeling during 13C-labeled substrate infusion with 13C nuclear magnetic resonance spectroscopy in beating isolated rat hearts at 37 degrees C. Total TCA cycle flux, indexed by both empirical and mathematical modeling analyses of the 13C data, was not reduced but rather increased in hearts reperfused after 17-20 minutes of ischemia (left ventricular pressure, 73 +/- 5% of preischemic values) compared with flux in developed pressure-matched controls (e.g., total flux, 2.5 +/- 0.4 versus 1.6 +/- 0.1 mumol.min-1.g wet wt-1, respectively; p < 0.01). No TCA cycle activity was detectable by 13C nuclear magnetic resonance in hearts reperfused after 40-45 minutes of ischemia, which lacked contractile recovery and had ultrastructural evidence of irreversible injury. CONCLUSIONS These results suggest that TCA cycle activity is not persistently decreased in dysfunctional reperfused myocardium after a brief ischemic episode and therefore cannot account for the reduced contractile function at that time.
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Affiliation(s)
- R G Weiss
- Peter Belfer Laboratory, Division of Cardiology, Johns Hopkins Hospital, Baltimore, Md 21205
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Figueredo VM, Brandes R, Weiner MW, Massie BM, Camacho SA. Cardiac contractile dysfunction during mild coronary flow reductions is due to an altered calcium-pressure relationship in rat hearts. J Clin Invest 1992; 90:1794-802. [PMID: 1430205 PMCID: PMC443238 DOI: 10.1172/jci116054] [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: 12/27/2022] Open
Abstract
Coronary artery stenosis or occlusion results in reduced coronary flow and myocardial contractile depression. At severe flow reductions, increased inorganic phosphate (Pi) and intracellular acidosis clearly play a role in contractile depression. However, during milder flow reductions the mechanism(s) underlying contractile depression are less clear. Previous perfused heart studies demonstrated no change of Pi or pH during mild flow reductions, suggesting that changes of intravascular pressure (garden hose effect) may be the mediator of this contractile depression. Others have reported conflicting results regarding another possible mediator of contractility, the cytosolic free calcium (Cai). To examine the respective roles of Cai, Pi, pH, and vascular pressure in regulating contractility during mild flow reductions, Indo-1 calcium fluorescence and 31P magnetic resonance spectroscopy measurements were performed on Langendorff-perfused rat hearts. Cai and diastolic calcium levels did not change during flow reductions to 50% of control. Pi demonstrated a close relationship with developed pressure and significantly increased from 2.5 +/- 0.3 to 4.2 +/- 0.4 mumol/g dry weight during a 25% flow reduction. pH was unchanged until a 50% flow reduction. Increasing vascular pressure to superphysiological levels resulted in further increases of developed pressure, with no change in Cai. These findings are consistent with the hypothesis that during mild coronary flow reductions, contractile depression is mediated by an altered relationship between Cai and pressure, rather than by decreased Cai. Furthermore, increased Pi and decreased intravascular pressure may be responsible for this altered calcium-pressure relationship during mild coronary flow reductions.
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Affiliation(s)
- V M Figueredo
- Department of Medicine (Cardiology), University of California, San Francisco 94143
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45
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Sherry AD, Malloy CR, Zhao P, Thompson JR. Alterations in substrate utilization in the reperfused myocardium: a direct analysis by 13C NMR. Biochemistry 1992; 31:4833-7. [PMID: 1350466 DOI: 10.1021/bi00135a014] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
An alternative 13C NMR method which allows direct determination of substrate oxidation in tissue for up to three competing 13C-enriched substrates is presented. Oxidation of competing substrates can be measured by 13C NMR spectroscopy under non-steady-state conditions if the relative areas of the glutamate C3 and C4 resonances can be determined. The accuracy of this measurement is limited during brief exposure to 13C-enriched substrates because of the low enrichment in the C3 carbon. The glutamate C4 resonance from a tissue sample which has oxidized a combination of [1,2-13C]acetate (or a uniformly enriched fatty acid mixture) and [3-13C]lactate appears as a nine-line resonance consisting of four multiplet components: a singlet (C4S), two doublets with differing one-bond coupling constants (C4D34 and C4D45), and a quartet (C4Q). It is shown that the sum of the C4S + C4D34 resonance areas versus the C4D45 + C4Q resonance areas directly reports the relative utilization of [3-13C]lactate versus [1,2-13C]acetate, respectively, regardless of citric acid cycle intermediate pool sizes or carbon flux through anaplerotic reactions. We also show that homonuclear 13C decoupling of the glutamate C2 resonance collapses the C3 resonance multiplet into an apparent triplet (actually, a singlet plus a doublet); the relative area of the singlet component reflects the amount of unlabeled acetyl-CoA entering the cycle. The method has been used to determine the contribution of lactate/acetate/glucose to acetyl-CoA in normoxic and reperfused rat hearts.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- A D Sherry
- Department of Chemistry, University of Texas, Dallas, Richardson 75083-0688
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46
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Lewandowski ED. Nuclear magnetic resonance evaluation of metabolic and respiratory support of work load in intact rabbit hearts. Circ Res 1992; 70:576-82. [PMID: 1537093 DOI: 10.1161/01.res.70.3.576] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Pre-steady-state 13C nuclear magnetic resonance (NMR) spectra can provide a nondestructive probe of metabolic events associated with the physiology of intact organs. Therefore, the relation between phosphorylation state and intermediary metabolism in rabbit hearts, oxidizing [2-13C]acetate, was examined with a combination of 31P and 13C NMR. Multiple enrichment of the tissue glutamate pool with 13C as an index of metabolic turnover within the tricarboxylic acid cycle was readily observed as a function of work load. Dynamic changes in pre-steady-state 13C spectra evolved according to work load and correlated closely to respiratory rate in rabbit hearts perfused 1) under normal conditions (n = 7), 2) at basal metabolic rates (20 mM KCl arrest, n = 5), 3) and at heightened contractile state (10(-7) M isoproterenol, n = 7). The ratio of signal intensity arising from the secondary labeling sites within glutamate (C-2 and C-3) to that of the initial labeling site (C-4) reached steady state within 8.5 minutes in isoproterenol-treated hearts versus 18.5 minutes in control hearts. Work load did not affect glutamate concentration or fractional enrichment at the C-4 position, although an unlabeled fraction of glutamate persisted. Arrested hearts displayed slowed evolution of steady-state 13C enrichment with increased contributions from anaplerotic sources for tricarboxylic acid intermediate formation (32%) as compared with control (9%). Thus, the response of mitochondrial dehydrogenase activity to the demands of cardiac performance is likely to influence the recruitment of anabolic sources supplying the tricarboxylic acid cycle.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- E D Lewandowski
- Section of Cardiology, Baylor College of Medicine, Houston, Tex
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Weiss RG, Gloth ST, Kalil-Filho R, Chacko VP, Stern MD, Gerstenblith G. Indexing tricarboxylic acid cycle flux in intact hearts by carbon-13 nuclear magnetic resonance. Circ Res 1992; 70:392-408. [PMID: 1735137 DOI: 10.1161/01.res.70.2.392] [Citation(s) in RCA: 75] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Although the tricarboxylic acid (TCA) cycle is the prime means of carbon metabolism for energy generation in normal myocardium, the noninvasive quantification of TCA cycle flux in intact cardiac tissues is difficult. A novel approach for estimating citric acid cycle flux using 13C nuclear magnetic resonance (NMR) is presented and evaluated experimentally by comparison with measured myocardial oxygen consumption over a wide range of cardiac contractile function in intact, beating rat hearts. Continuous series of 13C NMR spectra, obtained after the introduction of [2-13C]acetate as substrate, quantified the time course of 13C appearance in the carbon positions of myocardial glutamate, which are sequentially enriched via citric acid cycle metabolism. A TCA cycle flux parameter was calculated using the premise that TCA cycle flux is inversely proportional to the time difference between 13C appearance in the C-4 and C-2 positions of glutamate (glutamate delta t50 [minutes]), which are enriched in subsequent "turns" of the TCA cycle. This TCA cycle flux parameter, termed KT, correlated strongly with myocardial oxygen consumption over a range of developed pressures in hearts perfused with 5 mM acetate (r = 0.98, p less than 0.001), as well as in separate studies in hearts perfused with 5 mM glucose and 0.5-0.8 mM acetate (r = 0.94, p less than 0.001). Results of numerical modeling of 13C glutamate kinetics suggest that this TCA cycle flux parameter, KT, is relatively insensitive to changes in metabolite pool sizes that could occur during metabolism of other substrates or during conditions of altered oxygen availability. Additional studies in separate hearts indicated that the time course of 13C appearance in citrate, which is predominantly mitochondrial in the rat heart, is similar to that in glutamate, further supporting the premise that the described 13C NMR parameters reflect mitochondrial citric acid cycle activity in intact cardiac tissues.
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Affiliation(s)
- R G Weiss
- Peter Belfer Laboratory of the Cardiology Division, Department of Medicine, Johns Hopkins Hospital, Baltimore, Md. 21205
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Kaplan O, van Cohen PCM, Cohen JS. NMR Studies of Metabolism of Cells and Perfused Organs. IN-VIVO MAGNETIC RESONANCE SPECTROSCOPY III: IN-VIVO MR SPECTROSCOPY: POTENTIAL AND LIMITATIONS 1992. [DOI: 10.1007/978-3-642-77218-4_1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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Syrota A, Jehenson P. Complementarity of magnetic resonance spectroscopy, positron emission tomography and single photon emission tomography for the in vivo investigation of human cardiac metabolism and neurotransmission. EUROPEAN JOURNAL OF NUCLEAR MEDICINE 1991; 18:897-923. [PMID: 1661237 DOI: 10.1007/bf02258457] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The three techniques allowing the noninvasive study of cardiac metabolism, namely magnetic resonance spectroscopy (MRS), positron emission tomography (PET) and single photon emission computed tomography (SPET), all use external detection with stable or radioactive isotopes. These techniques yield different information. PET is quantitative and very sensitive, and therefore only tracer amounts of molecules need to be injected. It allows neurotransmitters and receptors to be studied and a global view of metabolism (oxygen consumption, glucose and fatty acid utilization) to be obtained. SPET also has good sensitivity, but uses gamma-emitting isotopes of heteroatoms. Their longer half-lives allow follow-up for hours or days. MRS is based on stable elements with high (hydrogen 1, phosphorus 31, fluorine 19...) or low (carbon 13, Deuterium) natural abundance. It has very low sensitivity and only millimolar concentrations of substrates can be detected, but various parts of metabolism can be studied. The in vivo measurement of myocardial concentration of substances has many problems that are common to all three techniques (measurement of the volume, measurement of the quantity of each molecule, resolution, partial volume effect, improvement of the signal-to-noise ratio, movement of the organ). The complementarity of the techniques is illustrated by their applications to the study of cardiac metabolism. For instance, the energy metabolism can be studied by 31P-MRS, which detects the high-energy compounds ATP and phosphocreatine, and 13C-MRS yields information on the tricarboxylic acid cycle activity. PET and SPET allow the utilization of fatty acids, the normal fuels of the heart, to be studied. During ischaemia, PET with 18F-fluorodeoxyglucose (18FDG) can determine the glucose consumption and 1H-MRS shows the increase in lactic acid, reflecting anaerobic glycolysis. Comparison of the use of acetate labelled with 11C for PET or 13C for MRS shows the potentials and limitations of each technique. Myocardial perfusion can be evaluated directly with various PET tracers or indirectly with thallium 201 or various technetium-99m-labelled tracers by SPET. No MRS marker of perfusion is so far clinically available. Mainly SPET and PET are used clinically for the investigation of ischaemic heart disease as well as cardiomyopathies, but some initial results using 31P-MRS are being obtained.
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Affiliation(s)
- A Syrota
- Service Hospitalier Frédéric Joliot, Orsay, France
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50
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Lewandowski ED, Hulbert C. Dynamic changes in 13C NMR spectra of intact hearts under conditions of varied metabolite enrichment. Magn Reson Med 1991; 19:186-90. [PMID: 1675417 DOI: 10.1002/mrm.1910190118] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Dynamic changes in 13C NMR signal from enriched glutamate pools within hearts have been examined under varied conditions of metabolite pool size and fractional enrichment. Relative signal intensities of 13C-enriched glutamate isotope isomers were similar within spectra from both intact hearts and corresponding in vitro samples. The parameters used to assess metabolic activity with 13C NMR proved independent of fractional enrichment and pool size. The data show the importance of acknowledging unlabeled, 13C NMR invisible metabolites.
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Affiliation(s)
- E D Lewandowski
- Section of Cardiology, Baylor College of Medicine, Houston, Texas 77030
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