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Rae CD, Baur JA, Borges K, Dienel G, Díaz-García CM, Douglass SR, Drew K, Duarte JMN, Duran J, Kann O, Kristian T, Lee-Liu D, Lindquist BE, McNay EC, Robinson MB, Rothman DL, Rowlands BD, Ryan TA, Scafidi J, Scafidi S, Shuttleworth CW, Swanson RA, Uruk G, Vardjan N, Zorec R, McKenna MC. Brain energy metabolism: A roadmap for future research. J Neurochem 2024; 168:910-954. [PMID: 38183680 PMCID: PMC11102343 DOI: 10.1111/jnc.16032] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2023] [Revised: 11/29/2023] [Accepted: 12/05/2023] [Indexed: 01/08/2024]
Abstract
Although we have learned much about how the brain fuels its functions over the last decades, there remains much still to discover in an organ that is so complex. This article lays out major gaps in our knowledge of interrelationships between brain metabolism and brain function, including biochemical, cellular, and subcellular aspects of functional metabolism and its imaging in adult brain, as well as during development, aging, and disease. The focus is on unknowns in metabolism of major brain substrates and associated transporters, the roles of insulin and of lipid droplets, the emerging role of metabolism in microglia, mysteries about the major brain cofactor and signaling molecule NAD+, as well as unsolved problems underlying brain metabolism in pathologies such as traumatic brain injury, epilepsy, and metabolic downregulation during hibernation. It describes our current level of understanding of these facets of brain energy metabolism as well as a roadmap for future research.
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Affiliation(s)
- Caroline D. Rae
- School of Psychology, The University of New South Wales, NSW 2052 & Neuroscience Research Australia, Randwick, New South Wales, Australia
| | - Joseph A. Baur
- Department of Physiology and Institute for Diabetes, Obesity and Metabolism, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Karin Borges
- School of Biomedical Sciences, Faculty of Medicine, The University of Queensland, St Lucia, QLD, Australia
| | - Gerald Dienel
- Department of Neurology, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA
- Department of Cell Biology and Physiology, University of New Mexico School of Medicine, Albuquerque, New Mexico, USA
| | - Carlos Manlio Díaz-García
- Department of Biochemistry and Molecular Biology, Center for Geroscience and Healthy Brain Aging, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, USA
| | | | - Kelly Drew
- Center for Transformative Research in Metabolism, Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, Alaska, USA
| | - João M. N. Duarte
- Department of Experimental Medical Science, Faculty of Medicine, Lund University, Lund, & Wallenberg Centre for Molecular Medicine, Lund University, Lund, Sweden
| | - Jordi Duran
- Institut Químic de Sarrià (IQS), Universitat Ramon Llull (URL), Barcelona, Spain
- Institute for Bioengineering of Catalonia (IBEC), The Barcelona Institute of Science and Technology, Barcelona, Spain
| | - Oliver Kann
- Institute of Physiology and Pathophysiology, University of Heidelberg, D-69120; Interdisciplinary Center for Neurosciences (IZN), University of Heidelberg, Heidelberg, Germany
| | - Tibor Kristian
- Veterans Affairs Maryland Health Center System, Baltimore, Maryland, USA
- Department of Anesthesiology and the Center for Shock, Trauma, and Anesthesiology Research (S.T.A.R.), University of Maryland School of Medicine, Baltimore, Maryland, USA
| | - Dasfne Lee-Liu
- Facultad de Medicina y Ciencia, Universidad San Sebastián, Santiago, Región Metropolitana, Chile
| | - Britta E. Lindquist
- Department of Neurology, Division of Neurocritical Care, Gladstone Institute of Neurological Disease, University of California at San Francisco, San Francisco, California, USA
| | - Ewan C. McNay
- Behavioral Neuroscience, University at Albany, Albany, New York, USA
| | - Michael B. Robinson
- Departments of Pediatrics and System Pharmacology & Translational Therapeutics, Children’s Hospital of Philadelphia, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Douglas L. Rothman
- Magnetic Resonance Research Center and Departments of Radiology and Biomedical Engineering, Yale University, New Haven, Connecticut, USA
| | - Benjamin D. Rowlands
- School of Chemistry, Faculty of Science, The University of Sydney, Sydney, New South Wales, Australia
| | - Timothy A. Ryan
- Department of Biochemistry, Weill Cornell Medicine, New York, New York, USA
| | - Joseph Scafidi
- Department of Neurology, Kennedy Krieger Institute, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Susanna Scafidi
- Anesthesiology & Critical Care Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - C. William Shuttleworth
- Department of Neurosciences, University of New Mexico School of Medicine Albuquerque, Albuquerque, New Mexico, USA
| | - Raymond A. Swanson
- Department of Neurology, University of California, San Francisco, and San Francisco Veterans Affairs Medical Center, San Francisco, California, USA
| | - Gökhan Uruk
- Department of Neurology, University of California, San Francisco, and San Francisco Veterans Affairs Medical Center, San Francisco, California, USA
| | - Nina Vardjan
- Laboratory of Cell Engineering, Celica Biomedical, Ljubljana, Slovenia
- Laboratory of Neuroendocrinology—Molecular Cell Physiology, Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia
| | - Robert Zorec
- Laboratory of Cell Engineering, Celica Biomedical, Ljubljana, Slovenia
- Laboratory of Neuroendocrinology—Molecular Cell Physiology, Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia
| | - Mary C. McKenna
- Department of Pediatrics and Program in Neuroscience, University of Maryland School of Medicine, Baltimore, Maryland, USA
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Dong W, Rawat ES, Stephanopoulos G, Abu-Remaileh M. Isotope tracing in health and disease. Curr Opin Biotechnol 2022; 76:102739. [PMID: 35738210 PMCID: PMC9555185 DOI: 10.1016/j.copbio.2022.102739] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2022] [Revised: 04/16/2022] [Accepted: 04/27/2022] [Indexed: 11/16/2022]
Abstract
Biochemical characterization of metabolism provides molecular insights for understanding biology in health and disease. Over the past decades, metabolic perturbations have been implicated in cancer, neurodegeneration, and diabetes, among others. Isotope tracing is a technique that allows tracking of labeled atoms within metabolites through biochemical reactions. This technique has become an integral component of the contemporary metabolic research. Isotope tracing measures substrate contribution to downstream metabolites and indicates its utilization in cellular metabolic networks. In addition, isotopic labeling data are necessary for quantitative metabolic flux analysis. Here, we review recent work utilizing metabolic tracing to study health and disease, and highlight its application to interrogate subcellular, intercellular, and in vivo metabolism. We further discuss the current challenges and opportunities to expand the utility of isotope tracing to new research areas.
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Affiliation(s)
- Wentao Dong
- Department of Chemical Engineering, Stanford University, Stanford, CA 94305, USA; Department of Genetics, Stanford University, Stanford, CA 94305, USA; The Institute for Chemistry, Engineering & Medicine for Human Health (ChEM-H), Stanford University, Stanford, CA 94305, USA; Aligning Science Across Parkinson's (ASAP) Collaborative Research Network, Chevy Chase, MD 20815, USA
| | - Eshaan S Rawat
- Department of Chemical Engineering, Stanford University, Stanford, CA 94305, USA; Department of Genetics, Stanford University, Stanford, CA 94305, USA; The Institute for Chemistry, Engineering & Medicine for Human Health (ChEM-H), Stanford University, Stanford, CA 94305, USA; Aligning Science Across Parkinson's (ASAP) Collaborative Research Network, Chevy Chase, MD 20815, USA
| | - Gregory Stephanopoulos
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
| | - Monther Abu-Remaileh
- Department of Chemical Engineering, Stanford University, Stanford, CA 94305, USA; Department of Genetics, Stanford University, Stanford, CA 94305, USA; The Institute for Chemistry, Engineering & Medicine for Human Health (ChEM-H), Stanford University, Stanford, CA 94305, USA; Aligning Science Across Parkinson's (ASAP) Collaborative Research Network, Chevy Chase, MD 20815, USA.
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Ma J, Pinho MC, Harrison CE, Chen J, Sun C, Hackett EP, Liticker J, Ratnakar J, Reed GD, Chen AP, Sherry AD, Malloy CR, Wright SM, Madden CJ, Park JM. Dynamic 13 C MR spectroscopy as an alternative to imaging for assessing cerebral metabolism using hyperpolarized pyruvate in humans. Magn Reson Med 2022; 87:1136-1149. [PMID: 34687086 PMCID: PMC8776582 DOI: 10.1002/mrm.29049] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2021] [Revised: 09/01/2021] [Accepted: 09/29/2021] [Indexed: 11/10/2022]
Abstract
PURPOSE This study is to investigate time-resolved 13 C MR spectroscopy (MRS) as an alternative to imaging for assessing pyruvate metabolism using hyperpolarized (HP) [1-13 C]pyruvate in the human brain. METHODS Time-resolved 13 C spectra were acquired from four axial brain slices of healthy human participants (n = 4) after a bolus injection of HP [1-13 C]pyruvate. 13 C MRS with low flip-angle excitations and a multichannel 13 C/1 H dual-frequency radiofrequency (RF) coil were exploited for reliable and unperturbed assessment of HP pyruvate metabolism. Slice-wise areas under the curve (AUCs) of 13 C-metabolites were measured and kinetic analysis was performed to estimate the production rates of lactate and HCO3- . Linear regression analysis between brain volumes and HP signals was performed. Region-focused pyruvate metabolism was estimated using coil-wise 13 C reconstruction. Reproducibility of HP pyruvate exams was presented by performing two consecutive injections with a 45-minutes interval. RESULTS [1-13 C]Lactate relative to the total 13 C signal (tC) was 0.21-0.24 in all slices. [13 C] HCO3- /tC was 0.065-0.091. Apparent conversion rate constants from pyruvate to lactate and HCO3- were calculated as 0.014-0.018 s-1 and 0.0043-0.0056 s-1 , respectively. Pyruvate/tC and lactate/tC were in moderate linear relationships with fractional gray matter volume within each slice. White matter presented poor linear regression fit with HP signals, and moderate correlations of the fractional cerebrospinal fluid volume with pyruvate/tC and lactate/tC were measured. Measured HP signals were comparable between two consecutive exams with HP [1-13 C]pyruvate. CONCLUSIONS Dynamic MRS in combination with multichannel RF coils is an affordable and reliable alternative to imaging methods in investigating cerebral metabolism using HP [1-13 C]pyruvate.
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Affiliation(s)
- Junjie Ma
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Marco C. Pinho
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, TX, USA,Department of Radiology, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Crystal E. Harrison
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Jun Chen
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Chenhao Sun
- Department of Electrical and Computer Engineering, Texas A & M, College Station, TX, USA
| | - Edward P. Hackett
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Jeff Liticker
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - James Ratnakar
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | | | | | - A. Dean Sherry
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, TX, USA,Department of Biochemistry and Chemical Biology, University of Texas Dallas, Richardson, TX, USA
| | - Craig R. Malloy
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, TX, USA,Department of Radiology, University of Texas Southwestern Medical Center, Dallas, TX, USA,Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Steven M. Wright
- Department of Electrical and Computer Engineering, Texas A & M, College Station, TX, USA
| | - Christopher J. Madden
- Department of Neurological Surgery, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Jae Mo Park
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, TX, USA,Department of Radiology, University of Texas Southwestern Medical Center, Dallas, TX, USA,Department of Electrical and Computer Engineering, University of Texas Dallas, Richardson, TX, USA,Correspondence to: Jae Mo Park, Ph.D., 5323 Harry Hines Blvd. Dallas, Texas 75390-8568, , Tel: +1-214-645-7206, Fax: +1-214-645-2744
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4
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Stachowicz K, Bobula B, Kusek M, Lenda T, Tokarski K. Evidence for the interaction of COX-2 with mGluR5 in the regulation of EAAT1 and EAAT3 protein levels in the mouse hippocampus. The influence of oxidative stress mechanisms. Brain Res 2021; 1771:147660. [PMID: 34529964 DOI: 10.1016/j.brainres.2021.147660] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2021] [Revised: 08/17/2021] [Accepted: 09/07/2021] [Indexed: 12/29/2022]
Abstract
Since we found that inhibition of cyclooxygenase-2 (COX-2) with concomitant application of a metabotropic glutamate receptor subtype 5 (mGluR5) antagonist (MTEP) down-regulates mGluR7 in the hippocampus (HC) and changes behavior of mice, our team decided to investigate the mechanism responsible for the observed changes. The amino acid glutamate (Glu) is a major excitatory neurotransmitter in the brain. Glu uptake is regulated by excitatory amino acid transporters (EAAT). There are five transporters with documented expression in neurons and glia in the central nervous system (CNS). EAATs, maintain the correct transmission of the Glu signal and prevent its toxic accumulation by removing Glu from the synapse. It has been documented that the toxic level of Glu is one of the main causes of mental and cognitive abnormalities. Given the above mechanisms involved in the functioning of the Glu synapse, we hypothesized modification of Glu uptake, involving EAATs as the cause of the observed changes. This study investigated the level of selected EAATs in the HC after chronic treatment with mGluR5 antagonist MTEP, NS398, and their combination using Western blot. Concomitant MTEP treatment with NS398 or a single administration of the above causes changes in LTP and modulation of EAAT levels in mouse HC. As EAATs are cellular markers of oxidative stress mechanisms, the E. coli lipopolysaccharide (LPS) challenge was performed. The modified Barnes maze test (MBM) revealed alterations in the mouse spatial learning abilities. This study reports an interaction between the mGluR5 and COX-2 in the HC, with EAAT1 and EAAT3 involvement.
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Affiliation(s)
- Katarzyna Stachowicz
- Department of Neurobiology, Maj Institute of Pharmacology, Polish Academy of Sciences, Smętna 12, 31-343 Kraków, Poland.
| | - Bartosz Bobula
- Department of Physiology, Maj Institute of Pharmacology, Polish Academy of Sciences, Smętna 12, 31-343 Kraków, Poland
| | - Magdalena Kusek
- Department of Physiology, Maj Institute of Pharmacology, Polish Academy of Sciences, Smętna 12, 31-343 Kraków, Poland
| | - Tomasz Lenda
- Department of Neuro- and Psychopharmacology, Maj Institute of Pharmacology, Polish Academy of Sciences, Smętna 12, 31-343 Kraków, Poland
| | - Krzysztof Tokarski
- Department of Physiology, Maj Institute of Pharmacology, Polish Academy of Sciences, Smętna 12, 31-343 Kraków, Poland
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Kiesel VA, Sheeley MP, Coleman MF, Cotul EK, Donkin SS, Hursting SD, Wendt MK, Teegarden D. Pyruvate carboxylase and cancer progression. Cancer Metab 2021; 9:20. [PMID: 33931119 PMCID: PMC8088034 DOI: 10.1186/s40170-021-00256-7] [Citation(s) in RCA: 36] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2020] [Accepted: 04/04/2021] [Indexed: 01/17/2023] Open
Abstract
Pyruvate carboxylase (PC) is a mitochondrial enzyme that catalyzes the ATP-dependent carboxylation of pyruvate to oxaloacetate (OAA), serving to replenish the tricarboxylic acid (TCA) cycle. In nonmalignant tissue, PC plays an essential role in controlling whole-body energetics through regulation of gluconeogenesis in the liver, synthesis of fatty acids in adipocytes, and insulin secretion in pancreatic β cells. In breast cancer, PC activity is linked to pulmonary metastasis, potentially by providing the ability to utilize glucose, fatty acids, and glutamine metabolism as needed under varying conditions as cells metastasize. PC enzymatic activity appears to be of particular importance in cancer cells that are unable to utilize glutamine for anaplerosis. Moreover, PC activity also plays a role in lipid metabolism and protection from oxidative stress in cancer cells. Thus, PC activity may be essential to link energy substrate utilization with cancer progression and to enable the metabolic flexibility necessary for cell resilience to changing and adverse conditions during the metastatic process.
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Affiliation(s)
- Violet A Kiesel
- Department of Nutrition Sciences, Purdue University, West Lafayette, IN, 47907, USA
| | - Madeline P Sheeley
- Department of Nutrition Sciences, Purdue University, West Lafayette, IN, 47907, USA
| | - Michael F Coleman
- Department of Nutrition, University of North Carolina at Chapel Hill, Chapel Hill, USA
| | - Eylem Kulkoyluoglu Cotul
- Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, USA
| | - Shawn S Donkin
- Department of Animal Science, Purdue University, West Lafayette, USA
| | - Stephen D Hursting
- Department of Nutrition, University of North Carolina at Chapel Hill, Chapel Hill, USA
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, USA
| | - Michael K Wendt
- Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, USA
| | - Dorothy Teegarden
- Department of Nutrition Sciences, Purdue University, West Lafayette, IN, 47907, USA.
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6
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Kathuria A, Lopez-Lengowski K, Vater M, McPhie D, Cohen BM, Karmacharya R. Transcriptome analysis and functional characterization of cerebral organoids in bipolar disorder. Genome Med 2020; 12:34. [PMID: 32306996 PMCID: PMC7168850 DOI: 10.1186/s13073-020-00733-6] [Citation(s) in RCA: 58] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2019] [Accepted: 04/02/2020] [Indexed: 02/06/2023] Open
Abstract
Background Reprogramming human induced pluripotent stem cells (iPSCs) from somatic cells and generating three-dimensional brain organoids from these iPSCs provide access to live human neuronal tissue with disease-specific genetic backgrounds. Methods Cerebral organoids were generated from iPSCs of eight bipolar disorder (BPI) patients and eight healthy control individuals. RNA-seq experiments were undertaken using RNA isolated from the cerebral organoids. Functional activity in the cerebral organoids was studied using microelectrode arrays. Results RNA-seq data comparing gene expression profiles in the cerebral organoids showed downregulation of pathways involved in cell adhesion, neurodevelopment, and synaptic biology in bipolar disorder along with upregulation of genes involved in immune signaling. The central hub in the network analysis was neurocan (NCAN), which is located in a locus with evidence for genome-wide significant association in BPI. Gene ontology analyses suggested deficits related to endoplasmic reticulum biology in BPI, which was supported by cellular characterization of ER–mitochondria interactions. Functional studies with microelectrode arrays revealed specific deficits in response to stimulation and depolarization in BPI cerebral organoids. Conclusions Our studies in cerebral organoids from bipolar disorder showed dysregulation in genes involved in cell adhesion, immune signaling, and endoplasmic reticulum biology; implicated a central role for the GWAS hit NCAN in the biology of BPI; and showed evidence of deficits in neurotransmission.
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Affiliation(s)
- Annie Kathuria
- Center for Genomic Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA.,Chemical Biology Program, Broad Institute of MIT & Harvard, Cambridge, MA, USA.,Department of Psychiatry, Harvard Medical School, Boston, MA, USA
| | - Kara Lopez-Lengowski
- Center for Genomic Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA.,Chemical Biology Program, Broad Institute of MIT & Harvard, Cambridge, MA, USA
| | - Magdalena Vater
- Center for Genomic Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA.,Chemical Biology Program, Broad Institute of MIT & Harvard, Cambridge, MA, USA.,Department of Psychiatry, Harvard Medical School, Boston, MA, USA
| | - Donna McPhie
- Department of Psychiatry, Harvard Medical School, Boston, MA, USA.,Schizophrenia and Bipolar Disorder Program, McLean Hospital, Belmont, MA, USA
| | - Bruce M Cohen
- Department of Psychiatry, Harvard Medical School, Boston, MA, USA.,Schizophrenia and Bipolar Disorder Program, McLean Hospital, Belmont, MA, USA
| | - Rakesh Karmacharya
- Center for Genomic Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA. .,Chemical Biology Program, Broad Institute of MIT & Harvard, Cambridge, MA, USA. .,Department of Psychiatry, Harvard Medical School, Boston, MA, USA. .,Schizophrenia and Bipolar Disorder Program, McLean Hospital, Belmont, MA, USA. .,Program in Neuroscience, Harvard University, Cambridge, MA, USA. .,Program in Chemical Biology, Harvard University, Cambridge, MA, USA. .,Harvard Stem Cell Institute, Cambridge, MA, USA.
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7
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Robinson MB, Lee ML, DaSilva S. Glutamate Transporters and Mitochondria: Signaling, Co-compartmentalization, Functional Coupling, and Future Directions. Neurochem Res 2020; 45:526-540. [PMID: 32002773 DOI: 10.1007/s11064-020-02974-8] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2019] [Revised: 01/21/2020] [Accepted: 01/22/2020] [Indexed: 12/12/2022]
Abstract
In addition to being an amino acid that is incorporated into proteins, glutamate is the most abundant neurotransmitter in the mammalian CNS, the precursor for the inhibitory neurotransmitter γ-aminobutyric acid, and one metabolic step from the tricarboxylic acid cycle intermediate α-ketoglutarate. Extracellular glutamate is cleared by a family of Na+-dependent transporters. These transporters are variably expressed by all cell types in the nervous system, but the bulk of clearance is into astrocytes. GLT-1 and GLAST (also called EAAT2 and EAAT1) mediate this activity and are extremely abundant proteins with their expression enriched in fine astrocyte processes. In this review, we will focus on three topics related to these astrocytic glutamate transporters. First, these transporters co-transport three Na+ ions and a H+ with each molecule of glutamate and counter-transport one K+; they are also coupled to a Cl- conductance. The movement of Na+ is sufficient to cause profound astrocytic depolarization, and the movement of H+ is linked to astrocytic acidification. In addition, the movement of Na+ can trigger the activation of Na+ co-transporters (e.g. Na+-Ca2+ exchangers). We will describe the ways in which these ionic movements have been linked as signals to brain function and/or metabolism. Second, these transporters co-compartmentalize with mitochondria, potentially providing a mechanism to supply glutamate to mitochondria as a source of fuel for the brain. We will provide an overview of the proteins involved, discuss the evidence that glutamate is oxidized, and then highlight some of the un-resolved issues related to glutamate oxidation. Finally, we will review evidence that ischemic insults (stroke or oxygen/glucose deprivation) cause changes in these astrocytic mitochondria and discuss the ways in which these changes have been linked to glutamate transport, glutamate transport-dependent signaling, and altered glutamate metabolism. We conclude with a broader summary of some of the unresolved issues.
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Affiliation(s)
- Michael B Robinson
- Departments of Pediatrics and Systems Pharmacology & Translational Therapeutics, Children's Hospital of Philadelphia, University of Pennsylvania, 502N, Abramson Pediatric Research Building, 3615 Civic Center Boulevard, Philadelphia, PA, 19104-4318, USA.
| | - Meredith L Lee
- Departments of Pediatrics and Systems Pharmacology & Translational Therapeutics, Children's Hospital of Philadelphia, University of Pennsylvania, 502N, Abramson Pediatric Research Building, 3615 Civic Center Boulevard, Philadelphia, PA, 19104-4318, USA
| | - Sabrina DaSilva
- Departments of Pediatrics and Systems Pharmacology & Translational Therapeutics, Children's Hospital of Philadelphia, University of Pennsylvania, 502N, Abramson Pediatric Research Building, 3615 Civic Center Boulevard, Philadelphia, PA, 19104-4318, USA
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8
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In Vivo Microdialysis of Endogenous and 13C-labeled TCA Metabolites in Rat Brain: Reversible and Persistent Effects of Mitochondrial Inhibition and Transient Cerebral Ischemia. Metabolites 2019; 9:metabo9100204. [PMID: 31569792 PMCID: PMC6835622 DOI: 10.3390/metabo9100204] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2019] [Revised: 09/24/2019] [Accepted: 09/25/2019] [Indexed: 11/17/2022] Open
Abstract
Cerebral micro-dialysis allows continuous sampling of extracellular metabolites, including glucose, lactate and pyruvate. Transient ischemic events cause a rapid drop in glucose and a rise in lactate levels. Following such events, the lactate/pyruvate (L/P) ratio may remain elevated for a prolonged period of time. In neurointensive care clinics, this ratio is considered a metabolic marker of ischemia and/or mitochondrial dysfunction. Here we propose a novel, sensitive microdialysis liquid chromatography-mass spectrometry (LC-MS) approach to monitor mitochondrial dysfunction in living brain using perfusion with 13C-labeled succinate and analysis of 13C-labeled tricarboxylic acid cycle (TCA) intermediates. This approach was evaluated in rat brain using malonate-perfusion (10-50 mM) and endothelin-1 (ET-1)-induced transient cerebral ischemia. In the malonate model, the expected changes upon inhibition of succinate dehydrogenase (SDH) were observed, i.e., an increase in endogenous succinate and decreases in fumaric acid and malic acid. The inhibition was further elaborated by incorporation of 13C into specific TCA intermediates from 13C-labeled succinate. In the ET-1 model, increases in non-labeled TCA metabolites (reflecting release of intracellular compounds) and decreases in 13C-labeled TCA metabolites (reflecting inhibition of de novo synthesis) were observed. The analysis of 13C incorporation provides further layers of information to identify metabolic disturbances in experimental models and neuro-intensive care patients.
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9
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Astrocytic pyruvate carboxylation: Status after 35 years. J Neurosci Res 2019; 97:890-896. [DOI: 10.1002/jnr.24402] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2018] [Revised: 01/11/2019] [Accepted: 02/05/2019] [Indexed: 12/24/2022]
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10
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Lizarbe B, Cherix A, Duarte JMN, Cardinaux JR, Gruetter R. High-fat diet consumption alters energy metabolism in the mouse hypothalamus. Int J Obes (Lond) 2018; 43:1295-1304. [PMID: 30301962 DOI: 10.1038/s41366-018-0224-9] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/21/2018] [Revised: 08/14/2018] [Accepted: 08/29/2018] [Indexed: 12/15/2022]
Abstract
BACKGROUND/OBJECTIVES High-fat diet consumption is known to trigger an inflammatory response in the hypothalamus, which has been characterized by an initial expression of pro-inflammatory genes followed by hypothalamic astrocytosis, microgliosis, and the appearance of neuronal injury markers. The specific effects of high-fat diet on hypothalamic energy metabolism and neurotransmission are however not yet known and have not been investigated before. SUBJECTS/METHODS We used 1H and 13C magnetic resonance spectroscopy (MRS) and immunofluorescence techniques to evaluate in vivo the consequences of high-saturated fat diet administration to mice, and explored the effects on hypothalamic metabolism in three mouse cohorts at different time points for up to 4 months. RESULTS We found that high-fat diet increases significantly the hypothalamic levels of glucose (P < 0.001), osmolytes (P < 0.001), and neurotransmitters (P < 0.05) from 2 months of diet, and alters the rates of metabolic (P < 0.05) and neurotransmission fluxes (P < 0.001), and the contribution of non-glycolytic substrates to hypothalamic metabolism (P < 0.05) after 10 weeks of high-fat feeding. CONCLUSIONS/INTERPRETATION We report changes that reveal a high-fat diet-induced alteration of hypothalamic metabolism and neurotransmission that is quantifiable by 1H and 13C MRS in vivo, and present the first evidence of the extension of the inflammation pathology to a localized metabolic imbalance.
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Affiliation(s)
- Blanca Lizarbe
- Laboratory of Functional and Metabolic Imaging (LIFMET), Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland.
| | - Antoine Cherix
- Laboratory of Functional and Metabolic Imaging (LIFMET), Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
| | - João M N Duarte
- Laboratory of Functional and Metabolic Imaging (LIFMET), Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland.,Department of Experimental Medical Science, Faculty of Medicine, Lund University, Lund, Sweden.,Wallenberg Centre for Molecular Medicine, Lund University, Lund, Sweden
| | - Jean-René Cardinaux
- Center for Psychiatric Neuroscience (CNP), Centre Hospitalier Universitaire Vaudois (CHUV), Lausanne, Switzerland
| | - Rolf Gruetter
- Laboratory of Functional and Metabolic Imaging (LIFMET), Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland.,Department of Radiology, University of Geneva, Geneva, Switzerland.,Department of Radiology, University of Lausanne, Lausanne, Switzerland
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11
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Oligodendrocytes: Development, Physiology and Glucose Metabolism. ADVANCES IN NEUROBIOLOGY 2018; 13:275-294. [PMID: 27885633 DOI: 10.1007/978-3-319-45096-4_10] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The glutamate-glutamine cycle is an outstanding example of how essential neuronal-glial interactions are for brain function. For several decades, this and other metabolic cycles in the brain have only included neurons and astrocytes but not oligodendrocytes, the myelinating cells of the central nervous system (CNS). Recent data revealed that oligodendrocytes are highly metabolically active cells in the brain and, therefore, should not be ignored. Using 13C-labelled glucose in combination with nuclear magnetic resonance spectroscopy (MRS) and/or mass spectrometry (MS) it is possible to characterize metabolic functions in primary oligodendrocyte cultures. Mature rat oligodendrocytes avidly metabolize glucose in the cytosol and pyruvate derived from glucose in mitochondria. Moreover, they seem to have the ability of performing anaplerosis from pyruvate, which might enable them to synthesize metabolites de novo and transfer them to neighbouring cells. All these original findings highlight the importance of investigating oligodendrocyte metabolism separately from that of astrocytes and neurons to be able to discern the roles played by the individual partners. This is of particular importance in the white matter where the number of oligodendrocytes is considerable. The present book chapter provides some background on oligodendrocyte biology and physiology and summarizes the not very extensive information published on glucose metabolism in oligodendrocytes.
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12
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Achanta LB, Rowlands BD, Thomas DS, Housley GD, Rae CD. β-Hydroxybutyrate Boosts Mitochondrial and Neuronal Metabolism but is not Preferred Over Glucose Under Activated Conditions. Neurochem Res 2017; 42:1710-1723. [DOI: 10.1007/s11064-017-2228-6] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2017] [Revised: 03/06/2017] [Accepted: 03/09/2017] [Indexed: 12/21/2022]
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13
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McNair LF, Kornfelt R, Walls AB, Andersen JV, Aldana BI, Nissen JD, Schousboe A, Waagepetersen HS. Metabolic Characterization of Acutely Isolated Hippocampal and Cerebral Cortical Slices Using [U-13C]Glucose and [1,2-13C]Acetate as Substrates. Neurochem Res 2016; 42:810-826. [DOI: 10.1007/s11064-016-2116-5] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2016] [Revised: 11/11/2016] [Accepted: 11/16/2016] [Indexed: 12/21/2022]
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14
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Shijo K, Sutton RL, Ghavim SS, Harris NG, Bartnik-Olson BL. Metabolic fate of glucose in rats with traumatic brain injury and pyruvate or glucose treatments: A NMR spectroscopy study. Neurochem Int 2016; 102:66-78. [PMID: 27919624 DOI: 10.1016/j.neuint.2016.11.014] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2016] [Revised: 11/30/2016] [Accepted: 11/30/2016] [Indexed: 12/27/2022]
Abstract
Administration of sodium pyruvate (SP; 9.08 μmol/kg, i.p.), ethyl pyruvate (EP; 0.34 μmol/kg, i.p.) or glucose (GLC; 11.1 μmol/kg, i.p.) to rats after unilateral controlled cortical impact (CCI) injury has been reported to reduce neuronal loss and improve cerebral metabolism. In the present study these doses of each fuel or 8% saline (SAL; 5.47 nmoles/kg) were administered immediately and at 1, 3, 6 and 23 h post-CCI. At 24 h all CCI groups and non-treated Sham injury controls were infused with [1,2 13C] glucose for 68 min 13C nuclear magnetic resonance (NMR) spectra were obtained from cortex + hippocampus tissues from left (injured) and right (contralateral) hemispheres. All three fuels increased lactate labeling to a similar degree in the injured hemisphere. The amount of lactate labeled via the pentose phosphate and pyruvate recycling (PPP + PR) pathway increased in CCI-SAL and was not improved by SP, EP, and GLC treatments. Oxidative metabolism, as assessed by glutamate labeling, was reduced in CCI-SAL animals. The greatest improvement in oxidative metabolism was observed in animals treated with SP and fewer improvements after EP or GLC treatments. Compared to SAL, all three fuels restored glutamate and glutamine labeling via pyruvate carboxylase (PC), suggesting improved astrocyte metabolism following fuel treatment. Only SP treatments restored the amount of [4 13C] glutamate labeled by the PPP + PR pathway to sham levels. Milder injury effects in the contralateral hemisphere appear normalized by either SP or EP treatments, as increases in the total pool of 13C lactate and labeling of lactate in glycolysis, or decreases in the ratio of PC/PDH labeling of glutamine, were found only for CCI-SAL and CCI-GLC groups compared to Sham. The doses of SP, EP and GLC examined in this study all enhanced lactate labeling and restored astrocyte-specific PC activity but differentially affected neuronal metabolism after CCI injury. The restoration of astrocyte metabolism by all three fuel treatments may partially underlie their abilities to improve cerebral glucose utilization and to reduce neuronal loss following CCI injury.
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Affiliation(s)
- Katsunori Shijo
- Brain Injury Research Center, Department of Neurosurgery, David Geffen School of Medicine at UCLA, Los Angeles, Box 956901, CA, USA.
| | - Richard L Sutton
- Brain Injury Research Center, Department of Neurosurgery, David Geffen School of Medicine at UCLA, Los Angeles, Box 956901, CA, USA.
| | - Sima S Ghavim
- Brain Injury Research Center, Department of Neurosurgery, David Geffen School of Medicine at UCLA, Los Angeles, Box 956901, CA, USA.
| | - Neil G Harris
- Brain Injury Research Center, Department of Neurosurgery, David Geffen School of Medicine at UCLA, Los Angeles, Box 956901, CA, USA.
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15
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Amoedo ND, Punzi G, Obre E, Lacombe D, De Grassi A, Pierri CL, Rossignol R. AGC1/2, the mitochondrial aspartate-glutamate carriers. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2016; 1863:2394-412. [PMID: 27132995 DOI: 10.1016/j.bbamcr.2016.04.011] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 01/15/2016] [Revised: 03/28/2016] [Accepted: 04/08/2016] [Indexed: 10/21/2022]
Abstract
In this review we discuss the structure and functions of the aspartate/glutamate carriers (AGC1-aralar and AGC2-citrin). Those proteins supply the aspartate synthesized within mitochondrial matrix to the cytosol in exchange for glutamate and a proton. A structure of an AGC carrier is not available yet but comparative 3D models were proposed. Moreover, transport assays performed by using the recombinant AGC1 and AGC2, reconstituted into liposome vesicles, allowed to explore the kinetics of those carriers and to reveal their specific transport properties. AGCs participate to a wide range of cellular functions, as the control of mitochondrial respiration, calcium signaling and antioxydant defenses. AGC1 might also play peculiar tissue-specific functions, as it was found to participate to cell-to-cell metabolic symbiosis in the retina. On the other hand, AGC1 is involved in the glutamate-mediated excitotoxicity in neurons and AGC gene or protein alterations were discovered in rare human diseases. Accordingly, a mice model of AGC1 gene knock-out presented with growth delay and generalized tremor, with myelinisation defects. More recently, AGC was proposed to play a crucial role in tumor metabolism as observed from metabolomic studies showing that the asparate exported from the mitochondrion by AGC1 is employed in the regeneration of cytosolic glutathione. Therefore, given the central role of AGCs in cell metabolism and human pathology, drug screening are now being developed to identify pharmacological modulators of those carriers. This article is part of a Special Issue entitled: Mitochondrial Channels edited by Pierre Sonveaux, Pierre Maechler and Jean-Claude Martinou.
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Affiliation(s)
- N D Amoedo
- Univ. Bordeaux, U1211, Bordeaux, France; INSERM, U1211, Bordeaux, France; Instituto de Bioquímica Médica Leopoldo De Meis, UFRJ, Rio de Janeiro, Brazil
| | - G Punzi
- Univ. Bordeaux, U1211, Bordeaux, France; INSERM, U1211, Bordeaux, France; Department of Biosciences, Biotechnologies and Biopharmaceutics, Laboratory of Biochemistry and Molecular Biology, University of Bari
| | - E Obre
- Univ. Bordeaux, U1211, Bordeaux, France; INSERM, U1211, Bordeaux, France
| | - D Lacombe
- Univ. Bordeaux, U1211, Bordeaux, France; INSERM, U1211, Bordeaux, France
| | - A De Grassi
- Department of Biosciences, Biotechnologies and Biopharmaceutics, Laboratory of Biochemistry and Molecular Biology, University of Bari
| | - C L Pierri
- Department of Biosciences, Biotechnologies and Biopharmaceutics, Laboratory of Biochemistry and Molecular Biology, University of Bari.
| | - R Rossignol
- Univ. Bordeaux, U1211, Bordeaux, France; INSERM, U1211, Bordeaux, France.
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16
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Amaral AI, Hadera MG, Tavares JM, Kotter MRN, Sonnewald U. Characterization of glucose-related metabolic pathways in differentiated rat oligodendrocyte lineage cells. Glia 2016; 64:21-34. [PMID: 26352325 PMCID: PMC4832329 DOI: 10.1002/glia.22900] [Citation(s) in RCA: 68] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2015] [Accepted: 07/22/2015] [Indexed: 12/24/2022]
Abstract
Although oligodendrocytes constitute a significant proportion of cells in the central nervous system (CNS), little is known about their intermediary metabolism. We have, therefore, characterized metabolic functions of primary oligodendrocyte precursor cell cultures at late stages of differentiation using isotope-labelled metabolites. We report that differentiated oligodendrocyte lineage cells avidly metabolize glucose in the cytosol and pyruvate derived from glucose in the mitochondria. The labelling patterns of metabolites obtained after incubation with [1,2-(13)C]glucose demonstrated that the pentose phosphate pathway (PPP) is highly active in oligodendrocytes (approximately 10% of glucose is metabolized via the PPP as indicated by labelling patterns in phosphoenolpyruvate). Mass spectrometry and magnetic resonance spectroscopy analyses of metabolites after incubation of cells with [1-(13)C]lactate or [1,2-(13)C]glucose, respectively, demonstrated that anaplerotic pyruvate carboxylation, which was thought to be exclusive to astrocytes, is also active in oligodendrocytes. Using [1,2-(13)C]acetate, we show that oligodendrocytes convert acetate into acetyl CoA which is metabolized in the tricarboxylic acid cycle. Analysis of labelling patterns of alanine after incubation of cells with [1,2-(13)C]acetate and [1,2-(13)C]glucose showed catabolic oxidation of malate or oxaloacetate. In conclusion, we report that oligodendrocyte lineage cells at late differentiation stages are metabolically highly active cells that are likely to contribute considerably to the metabolic activity of the CNS.
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Affiliation(s)
- Ana I. Amaral
- Anne McLaren LaboratoryWellcome Trust‐Medical Research Council Cambridge Stem Cell Institute and Department of Clinical Neurosciences, University of CambridgeCambridgeCB2 0SZUnited Kingdom
| | - Mussie G. Hadera
- Department of Neuroscience, Faculty of MedicineNorwegian University of Science and TechnologyTrondheim7491Norway
| | - Joana M. Tavares
- Anne McLaren LaboratoryWellcome Trust‐Medical Research Council Cambridge Stem Cell Institute and Department of Clinical Neurosciences, University of CambridgeCambridgeCB2 0SZUnited Kingdom
| | - Mark R. N. Kotter
- Anne McLaren LaboratoryWellcome Trust‐Medical Research Council Cambridge Stem Cell Institute and Department of Clinical Neurosciences, University of CambridgeCambridgeCB2 0SZUnited Kingdom
| | - Ursula Sonnewald
- Department of Neuroscience, Faculty of MedicineNorwegian University of Science and TechnologyTrondheim7491Norway
- Department of Drug Design and Pharmacology, Faculty of Health and Medical SciencesUniversity of CopenhagenCopenhagen2100Denmark
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18
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Modification of Astrocyte Metabolism as an Approach to the Treatment of Epilepsy: Triheptanoin and Acetyl-l-Carnitine. Neurochem Res 2015; 41:86-95. [DOI: 10.1007/s11064-015-1728-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2015] [Revised: 09/22/2015] [Accepted: 09/23/2015] [Indexed: 12/30/2022]
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19
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Olsen GM, Sonnewald U. Glutamate: Where does it come from and where does it go? Neurochem Int 2015; 88:47-52. [DOI: 10.1016/j.neuint.2014.11.006] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2014] [Revised: 10/30/2014] [Accepted: 11/03/2014] [Indexed: 11/15/2022]
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20
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Hackett JT, Ueda T. Glutamate Release. Neurochem Res 2015; 40:2443-60. [PMID: 26012367 DOI: 10.1007/s11064-015-1622-1] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2015] [Revised: 05/17/2015] [Accepted: 05/20/2015] [Indexed: 12/18/2022]
Abstract
Our aim was to review the processes of glutamate release from both biochemical and neurophysiological points of view. A large body of evidence now indicates that glutamate is specifically accumulated into synaptic vesicles, which provides strong support for the concept that glutamate is released from synaptic vesicles and is the major excitatory neurotransmitter. Evidence suggests the notion that synaptic vesicles, in order to sustain the neurotransmitter pool of glutamate, are endowed with an efficient mechanism for vesicular filling of glutamate. Glutamate-loaded vesicles undergo removal of Synapsin I by CaM kinase II-mediated phosphorylation, transforming to the release-ready pool. Vesicle docking to and fusion with the presynaptic plasma membrane are thought to be mediated by the SNARE complex. The Ca(2+)-dependent step in exocytosis is proposed to be mediated by synaptotagmin.
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Affiliation(s)
- John T Hackett
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA, 22908-0736, USA
| | - Tetsufumi Ueda
- Molecular and Behavioral Neuroscience Institute, The University of Michigan, 109 Zina Pitcher Place, Ann Arbor, MI, 48109-2200, USA. .,Department of Pharmacology, Medical School, The University of Michigan, Ann Arbor, MI, 48109, USA. .,Department of Psychiatry, Medical School, The University of Michigan, Ann Arbor, MI, 48109, USA.
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21
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Brekke E, Morken TS, Sonnewald U. Glucose metabolism and astrocyte-neuron interactions in the neonatal brain. Neurochem Int 2015; 82:33-41. [PMID: 25684072 DOI: 10.1016/j.neuint.2015.02.002] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2014] [Revised: 02/07/2015] [Accepted: 02/09/2015] [Indexed: 10/24/2022]
Abstract
Glucose is essentially the sole fuel for the adult brain and the mapping of its metabolism has been extensive in the adult but not in the neonatal brain, which is believed to rely mainly on ketone bodies for energy supply. However, glucose is absolutely indispensable for normal development and recent studies have shed light on glycolysis, the pentose phosphate pathway and metabolic interactions between astrocytes and neurons in the 7-day-old rat brain. Appropriately (13)C labeled glucose was used to distinguish between glycolysis and the pentose phosphate pathway during development. Experiments using (13)C labeled acetate provided insight into the GABA-glutamate-glutamine cycle between astrocytes and neurons. It could be shown that in the neonatal brain the part of this cycle that transfers glutamine from astrocytes to neurons is operating efficiently while, in contrast, little glutamate is shuttled from neurons to astrocytes. This lack of glutamate for glutamine synthesis is compensated for by anaplerosis via increased pyruvate carboxylation relative to that in the adult brain. Furthermore, compared to adults, relatively more glucose is prioritized to the pentose phosphate pathway than glycolysis and pyruvate dehydrogenase activity. The reported developmental differences in glucose metabolism and neurotransmitter synthesis may determine the ability of the brain at various ages to resist excitotoxic insults such as hypoxia-ischemia.
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Affiliation(s)
- Eva Brekke
- Department of Neuroscience, Norwegian University of Science and Technology, Trondheim N-7489, Norway; Department of Pediatrics, Division of Pediatrics, Obstetrics and Women's Health, Nordland Hospital Trust, Bodo, Norway
| | - Tora Sund Morken
- Department of Laboratory Medicine, Children's and Women's Health, Norwegian University of Science and Technology (NTNU), Trondheim N-7489, Norway; Department of Ophthalmology, St. Olav's Hospital HF, Trondheim, Norway
| | - Ursula Sonnewald
- Department of Neuroscience, Norwegian University of Science and Technology, Trondheim N-7489, Norway.
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22
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Rowlands BD, Lau CL, Ryall JG, Thomas DS, Klugmann M, Beart PM, Rae CD. Silent information regulator 1 modulator resveratrol increases brain lactate production and inhibits mitochondrial metabolism, whereas SRT1720 increases oxidative metabolism. J Neurosci Res 2015; 93:1147-56. [PMID: 25677687 DOI: 10.1002/jnr.23570] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2014] [Revised: 01/16/2015] [Accepted: 01/16/2015] [Indexed: 12/26/2022]
Abstract
Silent information regulators (SIRTs) have been shown to deacetylate a range of metabolic enzymes, including those in glycolysis and the Krebs cycle, and thus alter their activity. SIRTs require NAD(+) for their activity, linking cellular energy status to enzyme activity. To examine the impact of SIRT1 modulation on oxidative metabolism, this study tests the effect of ligands that are either SIRT-activating compounds (resveratrol and SRT1720) or SIRT inhibitors (EX527) on the metabolism of (13)C-enriched substrates by guinea pig brain cortical tissue slices with (13)C and (1)H nuclear magnetic resonance spectroscopy. Resveratrol increased lactate labeling but decreased incorporation of (13)C into Krebs cycle intermediates, consistent with effects on AMPK and inhibition of the F0/F1-ATPase. By testing with resveratrol that was directly applied to astrocytes with a Seahorse analyzer, increased glycolytic shift and increased mitochondrial proton leak resulting from interactions of resveratrol with the mitochondrial electron transport chain were revealed. SRT1720, by contrast, stimulated incorporation of (13)C into Krebs cycle intermediates and reduced incorporation into lactate, although the inhibitor EX527 paradoxically also increased Krebs cycle (13)C incorporation. In summary, the various SIRT1 modulators show distinct acute effects on oxidative metabolism. The strong effects of resveratrol on the mitochondrial respiratory chain and on glycolysis suggest that caution should be used in attempts to increase bioavailability of this compound in the CNS.
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Affiliation(s)
- Benjamin D Rowlands
- Neuroscience Research Australia, Randwick, New South Wales, Australia.,Department of Physiology and Translational Neuroscience Facility, School of Medical Sciences, The University of New South Wales, Randwick, New South Wales, Australia
| | - Chew Ling Lau
- Florey Institute of Neuroscience and Mental Health, The University of Melbourne, Parkville, Victoria, Australia
| | - James G Ryall
- Stem Cell Metabolism and Regenerative Medicine Group, Basic and Clinical Myology Laboratory, Department of Physiology, The University of Melbourne, Parkville, Victoria, Australia
| | - Donald S Thomas
- Mark Wainwright Analytical Centre, The University of New South Wales, Randwick, New South Wales, Australia
| | - Matthias Klugmann
- Department of Physiology and Translational Neuroscience Facility, School of Medical Sciences, The University of New South Wales, Randwick, New South Wales, Australia
| | - Philip M Beart
- Florey Institute of Neuroscience and Mental Health, The University of Melbourne, Parkville, Victoria, Australia
| | - Caroline D Rae
- Neuroscience Research Australia, Randwick, New South Wales, Australia.,Department of Physiology and Translational Neuroscience Facility, School of Medical Sciences, The University of New South Wales, Randwick, New South Wales, Australia
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23
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Marx MC, Billups D, Billups B. Maintaining the presynaptic glutamate supply for excitatory neurotransmission. J Neurosci Res 2015; 93:1031-44. [PMID: 25648608 DOI: 10.1002/jnr.23561] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2014] [Revised: 01/04/2015] [Accepted: 01/05/2015] [Indexed: 01/09/2023]
Abstract
Glutamate released from synapses during excitatory neurotransmission must be rapidly recycled to maintain neuronal communication. This review evaluates data from physiological experiments at hippocampal CA3 to CA1 synapses and the calyx of Held synapse in the brainstem to analyze quantitatively the rates of release and resupply of glutamate required to sustain neurotransmission. We calculate that, without efficient recycling, the presynaptic glutamate supply will be exhausted within about a minute of normal synaptic activity. We also discuss replenishment of the presynaptic pool by diffusion from the soma, direct uptake of glutamate back into the presynaptic terminal, and uptake of glutamate precursor molecules. Diffusion of glutamate from the soma is calculated to be fast enough to resupply presynaptic glutamate in the hippocampus but not at the calyx of Held. However, because the somatic cytoplasm will also quickly run out of glutamate and synapses can function continually even if the presynaptic axon is severed, mechanisms other than diffusion must be present to resupply glutamate for release. Direct presynaptic uptake of glutamate is not present at the calyx of Held but may play a role in glutamate recycling in the hippocampus. Alternatively, glutamine or tricarboxylic acid cycle intermediates released from glia can serve as a precursor for glutamate in synaptic terminals, and we calculate that the magnitude of presynaptic glutamine uptake is sufficient to supply enough glutamate to sustain neurotransmission. The nature of these mechanisms, their relative abundance, and the co-ordination between them remain areas of intensive investigation.
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Affiliation(s)
- Mari-Carmen Marx
- Eccles Institute of Neuroscience, The John Curtin School of Medical Research, The Australian National University, Canberra, Australian Capital Territory, Australia
| | - Daniela Billups
- Eccles Institute of Neuroscience, The John Curtin School of Medical Research, The Australian National University, Canberra, Australian Capital Territory, Australia
| | - Brian Billups
- Eccles Institute of Neuroscience, The John Curtin School of Medical Research, The Australian National University, Canberra, Australian Capital Territory, Australia
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24
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Sonnewald U. Glutamate synthesis has to be matched by its degradation - where do all the carbons go? J Neurochem 2014; 131:399-406. [PMID: 24989463 DOI: 10.1111/jnc.12812] [Citation(s) in RCA: 125] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2014] [Revised: 06/24/2014] [Accepted: 06/28/2014] [Indexed: 01/11/2023]
Abstract
The central process in energy production is the oxidation of acetyl-CoA to CO2 by the tricarboxylic acid (TCA, Krebs, citric acid) cycle. However, this cycle functions also as a biosynthetic pathway from which intermediates leave to be converted primarily to glutamate, GABA, glutamine and aspartate and to a smaller extent to glucose derivatives and fatty acids in the brain. When TCA cycle ketoacids are removed, they must be replaced to permit the continued function of this essential pathway, by a process termed anaplerosis. Since the TCA cycle cannot act as a carbon sink, anaplerosis must be coupled with cataplerosis; the exit of intermediates from the TCA cycle. The role of anaplerotic reactions for cellular metabolism in the brain has been studied extensively. However, the coupling of this process with cataplerosis and the roles that both pathways play in the regulation of amino acid, glucose, and fatty acid homeostasis have not been emphasized. The concept of a linkage between anaplerosis and cataplerosis should be underscored, because the balance between these two processes is essential. The hypothesis that cataplerosis in the brain is achieved by exporting the lactate generated from the TCA cycle intermediates into the blood and perivascular area is presented. This shifts the generally accepted paradigm of lactate generation as simply derived from glycolysis to that of oxidation and might present an alternative explanation for aerobic glycolysis. Intermediates leave the tricarboxylic acid cycle and must be replaced by a process termed anaplerosis that must be coupled to cataplerosis. We hypothesize that cataplerosis is achieved by exporting the lactate generated from the cycle into the blood and perivascular area. This shifts the paradigm of lactate generation as solely derived from glycolysis to that of oxidation and might present an alternative explanation for aerobic glycolysis.
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Affiliation(s)
- Ursula Sonnewald
- Department of Neuroscience, Faculty of Medicine, Norwegian University of Science and Technology (NTNU), Trondheim, Norway
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25
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Rodrigues TB, Valette J, Bouzier-Sore AK. (13)C NMR spectroscopy applications to brain energy metabolism. FRONTIERS IN NEUROENERGETICS 2013; 5:9. [PMID: 24367329 PMCID: PMC3856424 DOI: 10.3389/fnene.2013.00009] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/31/2013] [Accepted: 11/15/2013] [Indexed: 12/31/2022]
Abstract
(13)C nuclear magnetic resonance (NMR) spectroscopy is the method of choice for studying brain metabolism. Indeed, the most convincing data obtained to decipher metabolic exchanges between neurons and astrocytes have been obtained using this technique, thus illustrating its power. It may be difficult for non-specialists, however, to grasp thefull implication of data presented in articles written by spectroscopists. The aim of the review is, therefore, to provide a fundamental understanding of this topic to facilitate the non-specialists in their reading of this literature. In the first part of this review, we present the metabolic fate of (13)C-labeled substrates in the brain in a detailed way, including an overview of some general neurochemical principles. We also address and compare the various spectroscopic strategies that can be used to study brain metabolism. Then, we provide an overview of the (13)C NMR experiments performed to analyze both intracellular and intercellular metabolic fluxes. More particularly, the role of lactate as a potential energy substrate for neurons is discussed in the light of (13)C NMR data. Finally, new perspectives and applications offered by (13)C hyperpolarization are described.
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Affiliation(s)
- Tiago B. Rodrigues
- Cancer Research UK Cambridge Institute and Department of Biochemistry, University of CambridgeCambridge, UK
| | - Julien Valette
- Commissariat à l’Energie Atomique, Institut d’Imagerie Biomédicale, Molecular Imaging Research CenterFontenay-Aux-Roses, France
| | - Anne-Karine Bouzier-Sore
- Centre de Résonance Magnétique des Systèmes Biologiques, UMR 5536, Université Bordeaux Segalen - Centre National de la Recherche ScientifiqueBordeaux, France
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26
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Hadera MG, Smeland OB, McDonald TS, Tan KN, Sonnewald U, Borges K. Triheptanoin partially restores levels of tricarboxylic acid cycle intermediates in the mouse pilocarpine model of epilepsy. J Neurochem 2013; 129:107-19. [PMID: 24236946 DOI: 10.1111/jnc.12610] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2013] [Revised: 10/31/2013] [Accepted: 11/07/2013] [Indexed: 11/30/2022]
Abstract
Triheptanoin, the triglyceride of heptanoate, is anticonvulsant in various epilepsy models. It is thought to improve energy metabolism in the epileptic brain by re-filling the tricarboxylic acid (TCA) cycle with C4-intermediates (anaplerosis). Here, we injected mice with [1,2-(13) C]glucose 3.5-4 weeks after pilocarpine-induced status epilepticus (SE) fed either a control or triheptanoin diet. Amounts of metabolites and incorporations of (13) C were determined in extracts of cerebral cortices and hippocampal formation and enzyme activity and mRNA expression were quantified. The percentage enrichment with two (13) C atoms in malate, citrate, succinate, and GABA was reduced in hippocampal formation of control-fed SE compared with control mice. Except for succinate, these reductions were not found in triheptanoin-fed SE mice, indicating that triheptanoin prevented a decrease of TCA cycle capacity. Compared to those on control diet, triheptanoin-fed SE mice showed few changes in most other metabolite levels and their (13) C labeling. Reduced pyruvate carboxylase mRNA and enzyme activity in forebrains and decreased [2,3-(13) C]aspartate amounts in cortex suggest a pyruvate carboxylation independent source of C-4 TCA cycle intermediates. Most likely anaplerosis was kept unchanged by carboxylation of propionyl-CoA derived from heptanoate. Further studies are proposed to fully understand triheptanoin's effects on neuroglial metabolism and interaction.
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Affiliation(s)
- Mussie G Hadera
- Department of Neuroscience, Faculty of Medicine, Norwegian University of Science and Technology, Trondheim, Norway
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Dobolyi A, Ostergaard E, Bagó AG, Dóczi T, Palkovits M, Gál A, Molnár MJ, Adam-Vizi V, Chinopoulos C. Exclusive neuronal expression of SUCLA2 in the human brain. Brain Struct Funct 2013; 220:135-51. [PMID: 24085565 DOI: 10.1007/s00429-013-0643-2] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2013] [Accepted: 09/18/2013] [Indexed: 11/24/2022]
Abstract
SUCLA2 encodes the ATP-forming β subunit (A-SUCL-β) of succinyl-CoA ligase, an enzyme of the citric acid cycle. Mutations in SUCLA2 lead to a mitochondrial disorder manifesting as encephalomyopathy with dystonia, deafness and lesions in the basal ganglia. Despite the distinct brain pathology associated with SUCLA2 mutations, the precise localization of SUCLA2 protein has never been investigated. Here, we show that immunoreactivity of A-SUCL-β in surgical human cortical tissue samples was present exclusively in neurons, identified by their morphology and visualized by double labeling with a fluorescent Nissl dye. A-SUCL-β immunoreactivity co-localized >99 % with that of the d subunit of the mitochondrial F0-F1 ATP synthase. Specificity of the anti-A-SUCL-β antiserum was verified by the absence of labeling in fibroblasts from a patient with a complete deletion of SUCLA2. A-SUCL-β immunoreactivity was absent in glial cells, identified by antibodies directed against the glial markers GFAP and S100. Furthermore, in situ hybridization histochemistry demonstrated that SUCLA2 mRNA was present in Nissl-labeled neurons but not glial cells labeled with S100. Immunoreactivity of the GTP-forming β subunit (G-SUCL-β) encoded by SUCLG2, or in situ hybridization histochemistry for SUCLG2 mRNA could not be demonstrated in either neurons or astrocytes. Western blotting of post mortem brain samples revealed minor G-SUCL-β immunoreactivity that was, however, not upregulated in samples obtained from diabetic versus non-diabetic patients, as has been described for murine brain. Our work establishes that SUCLA2 is expressed exclusively in neurons in the human cerebral cortex.
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Affiliation(s)
- Arpád Dobolyi
- Department of Anatomy, Histology and Embryology, Semmelweis University, Budapest, 1094, Hungary
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Zhang N, Li BQ, Gao S, Ruan JS, Cai YD. Computational prediction and analysis of protein γ-carboxylation sites based on a random forest method. MOLECULAR BIOSYSTEMS 2012; 8:2946-55. [PMID: 22918520 DOI: 10.1039/c2mb25185j] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The glutamate γ-carboxylation plays a pivotal part in a number of important human diseases. However, traditional protein γ-carboxylation site detection by experimental approaches are often laborious and time-consuming. In this study, we initiated an attempt for the computational prediction of protein γ-carboxylation sites. We developed a new method for predicting the γ-carboxylation sites based on a Random Forest method. As a result, 90.44% accuracy and 0.7739 MCC value were obtained for the training dataset, and 89.83% accuracy and 0.7448 MCC value for the testing dataset. Our method considered several features including sequence conservation, residual disorder, secondary structures, solvent accessibility, physicochemical/biochemical properties and amino acid occurrence frequencies. By means of the feature selection algorithm, an optimal set of 327 features were selected; these features were considered as the ones that contributed significantly to the prediction of protein γ-carboxylation sites. Analysis of the optimal feature set indicated several important factors in determining the γ-carboxylation and a possible consensus sequence of the γ-carboxylation recognition site (γ-CRS) was suggested. These may shed some light on the in-depth understanding of the mechanisms of γ-carboxylation, providing guidelines for experimental validation.
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Affiliation(s)
- Ning Zhang
- Department of Biomedical Engineering Tianjin University, Tianjin Key Lab of BME Measurement, Tianjin, 300072, PR China
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Borges K, Sonnewald U. Triheptanoin--a medium chain triglyceride with odd chain fatty acids: a new anaplerotic anticonvulsant treatment? Epilepsy Res 2011; 100:239-44. [PMID: 21855298 DOI: 10.1016/j.eplepsyres.2011.05.023] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2011] [Revised: 05/16/2011] [Accepted: 05/25/2011] [Indexed: 01/30/2023]
Abstract
The triglyceride of heptanoate (C7 fatty acid), triheptanoin, is a tasteless oil used to treat rare metabolic disorders in USA and France. Heptanoate is metabolized by β-oxidation to provide propionyl-CoA, which after carboxylation can produce succinyl-CoA, resulting in anaplerosis - the refilling of the tricarboxylic acid cycle. Heptanoate is also metabolized by the liver to the C5 ketones, β-ketopentanoate and/or β-hydroxypentanoate, which are released into the blood and thought to enter the brain via monocarboxylate transporters. Oral triheptanoin has recently been discovered to be reproducibly anticonvulsant in acute and chronic mouse seizures models. However, current knowledge on alterations of brain metabolism after triheptanoin administration and anaplerosis via propionyl-CoA carboxylation in the brain is limited. This review outlines triheptanoin's unique anticonvulsant profile and its clinical potential for the treatment of medically refractory epilepsy. Anaplerosis as a therapeutic approach for the treatment of epilepsy is discussed. More research is needed to elucidate the anticonvulsant mechanism of triheptanoin and to reveal its clinical potential for the treatment of epilepsy and other disorders of the brain.
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Affiliation(s)
- Karin Borges
- Department of Pharmacology, School of Biomedical Sciences, The University of Queensland, St Lucia, QLD, Australia.
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Nasrallah FA, Balcar VJ, Rae CD. Activity-dependent γ-aminobutyric acid release controls brain cortical tissue slice metabolism. J Neurosci Res 2011; 89:1935-45. [DOI: 10.1002/jnr.22649] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2010] [Revised: 02/15/2011] [Accepted: 03/01/2011] [Indexed: 12/16/2022]
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