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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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Dienel GA, Schousboe A, McKenna MC, Rothman DL. A tribute to Leif Hertz: The historical context of his pioneering studies of the roles of astrocytes in brain energy metabolism, neurotransmission, cognitive functions, and pharmacology identifies important, unresolved topics for future studies. J Neurochem 2024; 168:461-495. [PMID: 36928655 DOI: 10.1111/jnc.15812] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2023] [Revised: 03/10/2023] [Accepted: 03/13/2023] [Indexed: 03/18/2023]
Abstract
Leif Hertz, M.D., D.Sc. (honōris causā) (1930-2018), was one of the original and noteworthy participants in the International Conference on Brain Energy Metabolism (ICBEM) series since its inception in 1993. The biennial ICBEM conferences are organized by neuroscientists interested in energetics and metabolism underlying neural functions; they have had a high impact on conceptual and experimental advances in these fields and on promoting collaborative interactions among neuroscientists. Leif made major contributions to ICBEM discussions and understanding of metabolic and signaling characteristics of astrocytes and their roles in brain function. His studies ranged from uptake of K+ from extracellular fluid and its stimulation of astrocytic respiration, identification, and regulation of enzymes specifically or preferentially expressed in astrocytes in the glutamate-glutamine cycle of excitatory neurotransmission, a requirement for astrocytic glycogenolysis for fueling K+ uptake, involvement of glycogen in memory consolidation in the chick, and pharmacology of astrocytes. This tribute to Leif Hertz highlights his major discoveries, the high impact of his work on astrocyte-neuron interactions, and his unparalleled influence on understanding the cellular basis of brain energy metabolism. His work over six decades has helped integrate the roles of astrocytes into neurotransmission where oxidative and glycogenolytic metabolism during neurotransmitter glutamate turnover are key aspects of astrocytic energetics. Leif recognized that brain astrocytic metabolism is greatly underestimated unless the volume fraction of astrocytes is taken into account. Adjustment for pathway rates expressed per gram tissue for volume fraction indicates that astrocytes have much higher oxidative rates than neurons and astrocytic glycogen concentrations and glycogenolytic rates during sensory stimulation in vivo are similar to those in resting and exercising muscle, respectively. These novel insights are typical of Leif's astute contributions to the energy metabolism field, and his publications have identified unresolved topics that provide the neuroscience community with challenges and opportunities for future research.
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Affiliation(s)
- Gerald A Dienel
- Department of Neurology, University of Arkansas for Medical Sciences, Little Rock, Arkansas, 72205, USA
- Department of Cell Biology and Physiology, University of New Mexico, Albuquerque, New Mexico, 87131, USA
| | - Arne Schousboe
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, 2100, Denmark
| | - Mary C McKenna
- Department of Pediatrics and Program in Neuroscience, University of Maryland School of Medicine, Baltimore, Maryland, 21201, USA
| | - Douglas L Rothman
- Department of Radiology, Magnetic Resonance Research Center (MRRC), Yale University, New Haven, Connecticut, 06520, USA
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Gondáš E, Kráľová Trančíková A, Šofranko J, Majerová P, Lučanský V, Dohál M, Kováč A, Murín R. The presence of pyruvate carboxylase in the human brain and its role in the survival of cultured human astrocytes. Physiol Res 2023; 72:403-414. [PMID: 37449752 PMCID: PMC10669001 DOI: 10.33549/physiolres.935026] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2022] [Accepted: 02/28/2023] [Indexed: 08/26/2023] Open
Abstract
Pyruvate carboxylase (PC) is a mitochondrial, biotin-containing enzyme catalyzing the ATP-dependent synthesis of oxaloacetate from pyruvate and bicarbonate, with a critical anaplerotic role in sustaining the brain metabolism. Based on the studies performed on animal models, PC expression was assigned to be glia-specific. To study PC distribution among human neural cells, we probed the cultured human astrocytes and brain sections with antibodies against PC. Additionally, we tested the importance of PC for the viability of cultured human astrocytes by applying the PC inhibitor 3-chloropropane-1,2-diol (CPD). Our results establish the expression of PC in mitochondria of human astrocytes in culture and brain tissue and also into a subpopulation of the neurons in situ. CPD negatively affected the viability of astrocytes in culture, which could be partially reversed by supplementing media with malate, 2-oxoglutarate, citrate, or pyruvate. The provided data estimates PC expression in human astrocytes and neurons in human brain parenchyma. Furthermore, the enzymatic activity of PC is vital for sustaining the viability of cultured astrocytes.
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Affiliation(s)
- E Gondáš
- Department of Medical Biochemistry, Jessenius Faculty of Medicine in Martin, Comenius University in Bratislava, Martin, Slovak Republic.
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Expression of 3-Methylcrotonyl-CoA Carboxylase in Brain Tumors and Capability to Catabolize Leucine by Human Neural Cancer Cells. Cancers (Basel) 2022; 14:cancers14030585. [PMID: 35158853 PMCID: PMC8833481 DOI: 10.3390/cancers14030585] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2021] [Revised: 01/20/2022] [Accepted: 01/21/2022] [Indexed: 02/04/2023] Open
Abstract
Leucine is an essential, ketogenic amino acid with proteinogenic, metabolic, and signaling roles. It is readily imported from the bloodstream into the brain parenchyma. Therefore, it could serve as a putative substrate that is complementing glucose for sustaining the metabolic needs of brain tumor cells. Here, we investigated the ability of cultured human cancer cells to metabolize leucine. Indeed, cancer cells dispose of leucine from their environment and enrich their media with the metabolite 2-oxoisocaproate. The enrichment of the culture media with a high level of leucine stimulated the production of 3-hydroxybutyrate. When 13C6-leucine was offered, it led to an increased appearance of the heavier citrate isotope with a molar mass greater by two units in the culture media. The expression of 3-methylcrotonyl-CoA carboxylase (MCC), an enzyme characteristic for the irreversible part of the leucine catabolic pathway, was detected in cultured cancer cells and human tumor samples by immunoprobing methods. Our results demonstrate that these cancer cells can catabolize leucine and furnish its carbon atoms into the tricarboxylic acid (TCA) cycle. Furthermore, the release of 3-hydroxybutyrate and citrate by cancer cells suggests their capability to exchange these metabolites with their milieu and the capability to participate in their metabolism. This indicates that leucine could be an additional substrate for cancer cell metabolism in the brain parenchyma. In this way, leucine could potentially contribute to the synthesis of metabolites such as lipids, which require the withdrawal of citrate from the TCA cycle.
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Rose J, Brian C, Pappa A, Panayiotidis MI, Franco R. Mitochondrial Metabolism in Astrocytes Regulates Brain Bioenergetics, Neurotransmission and Redox Balance. Front Neurosci 2020; 14:536682. [PMID: 33224019 PMCID: PMC7674659 DOI: 10.3389/fnins.2020.536682] [Citation(s) in RCA: 78] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2020] [Accepted: 10/14/2020] [Indexed: 01/17/2023] Open
Abstract
In the brain, mitochondrial metabolism has been largely associated with energy production, and its dysfunction is linked to neuronal cell loss. However, the functional role of mitochondria in glial cells has been poorly studied. Recent reports have demonstrated unequivocally that astrocytes do not require mitochondria to meet their bioenergetics demands. Then, the question remaining is, what is the functional role of mitochondria in astrocytes? In this work, we review current evidence demonstrating that mitochondrial central carbon metabolism in astrocytes regulates overall brain bioenergetics, neurotransmitter homeostasis and redox balance. Emphasis is placed in detailing carbon source utilization (glucose and fatty acids), anaplerotic inputs and cataplerotic outputs, as well as carbon shuttles to neurons, which highlight the metabolic specialization of astrocytic mitochondria and its relevance to brain function.
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Affiliation(s)
- Jordan Rose
- Redox Biology Center, University of Nebraska-Lincoln, Lincoln, NE, United States.,School of Veterinary Medicine and Biomedical Sciences, University of Nebraska-Lincoln, Lincoln, NE, United States
| | - Christian Brian
- Redox Biology Center, University of Nebraska-Lincoln, Lincoln, NE, United States.,School of Veterinary Medicine and Biomedical Sciences, University of Nebraska-Lincoln, Lincoln, NE, United States
| | - Aglaia Pappa
- Department of Molecular Biology and Genetics, Democritus University of Thrace, Alexandroupolis, Greece
| | - Mihalis I Panayiotidis
- Department of Electron Microscopy & Molecular Pathology, Cyprus Institute of Neurology & Genetics, Nicosia, Cyprus
| | - Rodrigo Franco
- Redox Biology Center, University of Nebraska-Lincoln, Lincoln, NE, United States.,School of Veterinary Medicine and Biomedical Sciences, University of Nebraska-Lincoln, Lincoln, NE, United States
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González-Regueiro J, la Tijera MHD, Moreno-Alcántar R, Torre A. Pathophysiology of hepatic encephalopathy and future treatment options. REVISTA DE GASTROENTEROLOGÍA DE MÉXICO (ENGLISH EDITION) 2019. [DOI: 10.1016/j.rgmxen.2019.05.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/26/2022] Open
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González-Regueiro JA, Higuera-de la Tijera MF, Moreno-Alcántar R, Torre A. Pathophysiology of hepatic encephalopathy and future treatment options. REVISTA DE GASTROENTEROLOGIA DE MEXICO (ENGLISH) 2019; 84:195-203. [PMID: 31014748 DOI: 10.1016/j.rgmx.2019.02.004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/30/2018] [Revised: 01/28/2019] [Accepted: 02/18/2019] [Indexed: 06/09/2023]
Abstract
Understanding of the pathophysiology of hepatic encephalopathy has conditioned new treatment options. Ammonia detoxification in hepatic encephalopathy is regulated by two enzymes: glutaminase or glutamine synthetase. The first produces ammonia and the second detoxifies the ammonia, which is why treatments are aimed at glutaminase inhibition or glutamine synthetase activation. At present, we know that both enzymes are found not only in the liver, but also in the muscle, intestine, kidney, and brain. Therefore, current treatments can be directed at each enzyme at different sites. Awareness of those potential treatment sites makes different options of approach possible in the patient with hepatic encephalopathy, and each approach should be personalized.
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Affiliation(s)
- J A González-Regueiro
- Departamento de Gastroenterología, Instituto Nacional de Ciencias Médicas y Nutrición «Salvador Zubirán», Ciudad de México, México
| | | | - R Moreno-Alcántar
- Departamento de Gastroenterología, Centro Médico Nacional Siglo XXI, Ciudad de México, México
| | - A Torre
- Departamento de Gastroenterología, Instituto Nacional de Ciencias Médicas y Nutrición «Salvador Zubirán», Ciudad de México, México; Unidad de Hepatología y Trasplante Hepático, Departamento de Gastroenterología, Instituto Nacional de Ciencias Médicas y Nutrición «Salvador Zubirán», Ciudad de México, México.
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Sahoo S, S. B. Pharmacogenomic assessment of herbal drugs in affective disorders. Biomed Pharmacother 2019; 109:1148-1162. [DOI: 10.1016/j.biopha.2018.10.135] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2018] [Revised: 10/20/2018] [Accepted: 10/21/2018] [Indexed: 12/14/2022] Open
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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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Westergaard N, Waagepetersen HS, Belhage B, Schousboe A. Citrate, a Ubiquitous Key Metabolite with Regulatory Function in the CNS. Neurochem Res 2017; 42:1583-1588. [DOI: 10.1007/s11064-016-2159-7] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2016] [Revised: 12/16/2016] [Accepted: 12/19/2016] [Indexed: 11/30/2022]
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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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Rogatzki MJ, Ferguson BS, Goodwin ML, Gladden LB. Lactate is always the end product of glycolysis. Front Neurosci 2015; 9:22. [PMID: 25774123 PMCID: PMC4343186 DOI: 10.3389/fnins.2015.00022] [Citation(s) in RCA: 225] [Impact Index Per Article: 25.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2014] [Accepted: 01/13/2015] [Indexed: 12/22/2022] Open
Abstract
Through much of the history of metabolism, lactate (La−) has been considered merely a dead-end waste product during periods of dysoxia. Congruently, the end product of glycolysis has been viewed dichotomously: pyruvate in the presence of adequate oxygenation, La− in the absence of adequate oxygenation. In contrast, given the near-equilibrium nature of the lactate dehydrogenase (LDH) reaction and that LDH has a much higher activity than the putative regulatory enzymes of the glycolytic and oxidative pathways, we contend that La− is always the end product of glycolysis. Cellular La− accumulation, as opposed to flux, is dependent on (1) the rate of glycolysis, (2) oxidative enzyme activity, (3) cellular O2 level, and (4) the net rate of La− transport into (influx) or out of (efflux) the cell. For intracellular metabolism, we reintroduce the Cytosol-to-Mitochondria Lactate Shuttle. Our proposition, analogous to the phosphocreatine shuttle, purports that pyruvate, NAD+, NADH, and La− are held uniformly near equilibrium throughout the cell cytosol due to the high activity of LDH. La− is always the end product of glycolysis and represents the primary diffusing species capable of spatially linking glycolysis to oxidative phosphorylation.
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Affiliation(s)
- Matthew J Rogatzki
- Department of Health and Human Performance, University of Wisconsin-Platteville Platteville, WI, USA
| | - Brian S Ferguson
- Department of Biomedical Sciences, University of Missouri Columbia, MO, USA
| | - Matthew L Goodwin
- Department of Orthopaedics, and Huntsman Cancer Institute, University of Utah Salt Lake City, UT, USA
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Abstract
Human adults produce around 1000 mmol of ammonia daily. Some is reutilized in biosynthesis. The remainder is waste and neurotoxic. Eventually most is excreted in urine as urea, together with ammonia used as a buffer. In extrahepatic tissues, ammonia is incorporated into nontoxic glutamine and released into blood. Large amounts are metabolized by the kidneys and small intestine. In the intestine, this yields ammonia, which is sequestered in portal blood and transported to the liver for ureagenesis, and citrulline, which is converted to arginine by the kidneys. The amazing developments in NMR imaging and spectroscopy and molecular biology have confirmed concepts derived from early studies in animals and cell cultures. The processes involved are exquisitely tuned. When they are faulty, ammonia accumulates. Severe acute hyperammonemia causes a rapidly progressive, often fatal, encephalopathy with brain edema. Chronic milder hyperammonemia causes a neuropsychiatric illness. Survivors of severe neonatal hyperammonemia have structural brain damage. Proposed explanations for brain edema are an increase in astrocyte osmolality, generally attributed to glutamine accumulation, and cytotoxic oxidative/nitrosative damage. However, ammonia neurotoxicity is multifactorial, with disturbances also in neurotransmitters, energy production, anaplerosis, cerebral blood flow, potassium, and sodium. Around 90% of hyperammonemic patients have liver disease. Inherited defects are rare. They are being recognized increasingly in adults. Deficiencies of urea cycle enzymes, citrin, and pyruvate carboxylase demonstrate the roles of isolated pathways in ammonia metabolism. Phenylbutyrate is used routinely to treat inherited urea cycle disorders, and its use for hepatic encephalopathy is under investigation.
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Affiliation(s)
- Valerie Walker
- Department of Clinical Biochemistry, University Hospital Southampton NHS Foundation Trust, Southampton, United Kingdom.
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Liang X, Martyniuk CJ, Cheng G, Zha J, Wang Z. Pyruvate carboxylase as a sensitive protein biomarker for exogenous steroid chemicals. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2014; 189:184-193. [PMID: 24681510 DOI: 10.1016/j.envpol.2014.03.006] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2013] [Revised: 03/03/2014] [Accepted: 03/06/2014] [Indexed: 06/03/2023]
Abstract
Assessing protein responses to endocrine disrupting chemicals is critical for understanding the mechanisms of chemical action and for the assessment of hazards. In this study, the response of the liver proteome of male rare minnows (Gobiocypris rarus) treated with 17β-estradiol (E2) and females treated with 17α-methyltestosterone (MT) were analyzed. A total of 23 and 24 proteins were identified with differential expression in response to E2 and MT, respectively. Pyruvate carboxylase (PC) was the only common differentially expressed protein in both males and females after E2- and MT-treatments. The mRNA as well as the protein levels of PC were significantly down-regulated compared with that of the controls (p < 0.05). Our results suggest that endocrine disruptors interfere with genes and proteins of the TCA cycle and PC may be a sensitive biomarker of exposure to exogenous steroid chemicals in the liver of fish.
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Affiliation(s)
- Xuefang Liang
- State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, 18 Shuangqing Road, Haidian District, Beijing 100085, China
| | - Christopher J Martyniuk
- Canadian Rivers Institute, Department of Biology, University of New Brunswick, Saint John, New Brunswick, Canada E2L 4L5
| | - Gang Cheng
- Key Lab for Biotechnology of National Commission for Nationalities, College of Life Science, South Central University for Nationalities, Wuhan 430074, China
| | - Jinmiao Zha
- State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, 18 Shuangqing Road, Haidian District, Beijing 100085, China.
| | - Zijian Wang
- State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, 18 Shuangqing Road, Haidian District, Beijing 100085, China.
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Lietzan AD, St. Maurice M. Functionally diverse biotin-dependent enzymes with oxaloacetate decarboxylase activity. Arch Biochem Biophys 2014; 544:75-86. [DOI: 10.1016/j.abb.2013.10.014] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2013] [Revised: 10/15/2013] [Accepted: 10/18/2013] [Indexed: 12/31/2022]
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Amaral AI, Meisingset TW, Kotter MR, Sonnewald U. Metabolic aspects of neuron-oligodendrocyte-astrocyte interactions. Front Endocrinol (Lausanne) 2013; 4:54. [PMID: 23717302 PMCID: PMC3651962 DOI: 10.3389/fendo.2013.00054] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/12/2013] [Accepted: 04/24/2013] [Indexed: 11/26/2022] Open
Abstract
Whereas astrocytes have been in the limelight of scientific interest in brain energy metabolism for a while, oligodendrocytes are still waiting for a place on the metabolic stage. We propose to term the interaction of oligodendrocytes with astrocytes and neurons: NOA (neuron-oligodendrocyte-astrocyte) interactions. One of the reasons to find out more about metabolic interactions between oligodendrocytes, neurons, and astrocytes is to establish markers of healthy oligodendrocyte metabolism that could be used for the diagnosis and assessment of white matter disease. The vesicular release of glutamate in the white matter has received considerable attention in the past. Oligodendrocyte lineage cells express glutamate receptors and glutamate toxicity has been implicated in diseases affecting oligodendrocytes such as hypoxic-ischaemic encephalopathy, inflammatory diseases and trauma. As oligodendrocyte precursor cells vividly react to injury it is also important to establish whether cells recruited into damaged areas are able to regenerate lost myelin sheaths or whether astrocytic scarring occurs. It is therefore important to consider metabolic aspects of astrocytes and oligodendrocytes separately. The present review summarizes the limited evidence available on metabolic cycles in oligodendrocytes and so hopes to stimulate further research interests in this important field.
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Affiliation(s)
- Ana I. Amaral
- Anne McLaren Laboratory for Regenerative Medicine, Wellcome Trust and Medical Research Council Cambridge Stem Cell Institute, Department of Clinical Neurosciences, University of CambridgeCambridge, UK
| | - Tore W. Meisingset
- Department of Neuroscience, Faculty of Medicine, Norwegian University of Science and TechnologyTrondheim, Norway
| | - Mark R. Kotter
- Anne McLaren Laboratory for Regenerative Medicine, Wellcome Trust and Medical Research Council Cambridge Stem Cell Institute, Department of Clinical Neurosciences, University of CambridgeCambridge, UK
| | - Ursula Sonnewald
- Department of Neuroscience, Faculty of Medicine, Norwegian University of Science and TechnologyTrondheim, Norway
- *Correspondence: Ursula Sonnewald, Department of Neuroscience, Faculty of Medicine, Norwegian University of Science and Technology, PO Box 8905, MTFS, 7491 Trondheim, Norway. e-mail:
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Grondona JM, Granados-Durán P, Fernández-Llebrez P, López-Ávalos MD. A simple method to obtain pure cultures of multiciliated ependymal cells from adult rodents. Histochem Cell Biol 2012; 139:205-20. [PMID: 22878526 DOI: 10.1007/s00418-012-1008-2] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/25/2012] [Indexed: 11/25/2022]
Abstract
Ependymal cells form an epithelium lining the ventricular cavities of the vertebrate brain. Numerous methods to obtain primary culture ependymal cells have been developed. Most of them use foetal or neonatal rat brain and the few that utilize adult brain hardly achieve purity. Here, we describe a simple and novel method to obtain a pure non-adherent ependymal cell culture from explants of the striatal and septal walls of the lateral ventricles. The combination of a low incubation temperature followed by a gentle enzymatic digestion allows the detachment of most of the ependymal cells from the ventricular wall in a period of 6 h. Along with ependymal cells, a low percentage (less than 6 %) of non-ependymal cells also detaches. However, they do not survive under two restrictive culture conditions: (1) a simple medium (alpha-MEM with glucose) without any supplement; and (2) a low density of 1 cell/µl. This purification method strategy does not require cell labelling with antibodies and cell sorting, which makes it a simpler and cheaper procedure than other methods previously described. After a period of 48 h, only ependymal cells survive such conditions, revealing the remarkable survival capacity of ependymal cells. Ependymal cells can be maintained in culture for up to 7-10 days, with the best survival rates obtained in Neurobasal supplemented with B27 among the tested media. After 7 days in culture, ependymal cells lose most of the cilia and therefore the mobility, while acquiring radial glial cell markers (GFAP, BLBP, GLAST). This interesting fact might indicate a reprogramming of the cell identity.
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Affiliation(s)
- J M Grondona
- Departamento de Biología Celular, Genética y Fisiología, Facultad de Ciencias, Campus de Teatinos, Universidad de Málaga, 29071 Málaga, Spain.
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DiNuzzo M, Mangia S, Maraviglia B, Giove F. Glycogenolysis in astrocytes supports blood-borne glucose channeling not glycogen-derived lactate shuttling to neurons: evidence from mathematical modeling. J Cereb Blood Flow Metab 2010; 30:1895-904. [PMID: 20827264 PMCID: PMC3002884 DOI: 10.1038/jcbfm.2010.151] [Citation(s) in RCA: 86] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
In this article, we examined theoretically the role of human cerebral glycogen in buffering the metabolic requirement of a 360-second brain stimulation, expanding our previous modeling study of neurometabolic coupling. We found that glycogen synthesis and degradation affects the relative amount of glucose taken up by neurons versus astrocytes. Under conditions of 175:115 mmol/L (∼1.5:1) neuronal versus astrocytic activation-induced Na(+) influx ratio, ∼12% of astrocytic glycogen is mobilized. This results in the rapid increase of intracellular glucose-6-phosphate level on stimulation and nearly 40% mean decrease of glucose flow through hexokinase (HK) in astrocytes via product inhibition. The suppression of astrocytic glucose phosphorylation, in turn, favors the channeling of glucose from interstitium to nearby activated neurons, without a critical effect on the concurrent intercellular lactate trafficking. Under conditions of increased neuronal versus astrocytic activation-induced Na(+) influx ratio to 190:65 mmol/L (∼3:1), glycogen is not significantly degraded and blood glucose is primarily taken up by neurons. These results support a role for astrocytic glycogen in preserving extracellular glucose for neuronal utilization, rather than providing lactate to neurons as is commonly accepted by the current 'thinking paradigm'. This might be critical in subcellular domains during functional conditions associated with fast energetic demands.
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Affiliation(s)
- Mauro DiNuzzo
- Dipartimento di Fisica, Sapienza Università di Roma, Rome, Italy.
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Chrast R, Saher G, Nave KA, Verheijen MHG. Lipid metabolism in myelinating glial cells: lessons from human inherited disorders and mouse models. J Lipid Res 2010; 52:419-34. [PMID: 21062955 DOI: 10.1194/jlr.r009761] [Citation(s) in RCA: 206] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The integrity of central and peripheral nervous system myelin is affected in numerous lipid metabolism disorders. This vulnerability was so far mostly attributed to the extraordinarily high level of lipid synthesis that is required for the formation of myelin, and to the relative autonomy in lipid synthesis of myelinating glial cells because of blood barriers shielding the nervous system from circulating lipids. Recent insights from analysis of inherited lipid disorders, especially those with prevailing lipid depletion and from mouse models with glia-specific disruption of lipid metabolism, shed new light on this issue. The particular lipid composition of myelin, the transport of lipid-associated myelin proteins, and the necessity for timely assembly of the myelin sheath all contribute to the observed vulnerability of myelin to perturbed lipid metabolism. Furthermore, the uptake of external lipids may also play a role in the formation of myelin membranes. In addition to an improved understanding of basic myelin biology, these data provide a foundation for future therapeutic interventions aiming at preserving glial cell integrity in metabolic disorders.
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Affiliation(s)
- Roman Chrast
- Department of Medical Genetics, University of Lausanne, Switzerland.
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Reactive astrocytes give neurons less support: implications for Alzheimer's disease. Neurobiol Aging 2010; 33:423.e1-13. [PMID: 21051108 DOI: 10.1016/j.neurobiolaging.2010.09.018] [Citation(s) in RCA: 96] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2010] [Revised: 09/20/2010] [Accepted: 09/20/2010] [Indexed: 11/20/2022]
Abstract
Astrocytes become activated in Alzheimer's disease (AD), contributing to and reinforcing an inflammatory cascade. It is proposed that by transforming from a basal to a reactive state, astrocytes neglect their neurosupportive functions, thus rendering neurons vulnerable to excitotoxicity and oxidative stress. This review considers 3 important astrocytic functions, that when disrupted, can affect neuronal metabolism. These are the uptake of glucose and release of lactate; the uptake of glutamate and release of glutamine; and the uptake of glutathione precursors and release of glutathione. Conditions under which these functions can be manipulated in vitro, as well as examples of possible loss of astrocytic function in AD, are discussed. It is proposed that the targeting of astrocytes with pharmacological agents that are specifically designed to return astrocytes to a quiescent phenotype could represent a fruitful new angle for the therapeutic treatment of AD and other neurodegenerative disorders.
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Marin-Valencia I, Roe CR, Pascual JM. Pyruvate carboxylase deficiency: mechanisms, mimics and anaplerosis. Mol Genet Metab 2010; 101:9-17. [PMID: 20598931 DOI: 10.1016/j.ymgme.2010.05.004] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/26/2010] [Accepted: 05/26/2010] [Indexed: 11/30/2022]
Abstract
Pyruvate carboxylase (PC) is a regulated mitochondrial enzyme that catalyzes the conversion of pyruvate to oxaloacetate, a critical transition that replenishes citric acid cycle intermediates and facilitates other biosynthetic reactions that drive anabolism. Its deficiency causes multiorgan metabolic imbalance that predominantly manifests with lactic acidemia and neurological dysfunction at an early age. Three clinical forms of PC deficiency have been identified: an infantile form (Type A), a severe neonatal form (Type B), and a benign form (Type C), all of which exhibit clinical or biochemical correlates of impaired anaplerosis. There is no effective treatment for these patients and most, except those affected by the benign form, die in early life. We review the physiology of this enzyme and dissect the major clinical, biochemical, and genetic aspects of its dysfunction, emphasizing features that distinguish PC deficiency from other causes of lactic acidemia that render PC deficiency potentially treatable using novel interventions capable of enhancing anaplerosis.
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Affiliation(s)
- Isaac Marin-Valencia
- Department of Neurology, UT Southwestern Medical Center, Dallas, TX 75390-8813, USA
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