1
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Kang BS, Choi BY, Kho AR, Lee SH, Hong DK, Park MK, Lee SH, Lee CJ, Yang HW, Woo SY, Park SW, Kim DY, Park JB, Chung WS, Suh SW. Effects of Pyruvate Kinase M2 (PKM2) Gene Deletion on Astrocyte-Specific Glycolysis and Global Cerebral Ischemia-Induced Neuronal Death. Antioxidants (Basel) 2023; 12:491. [PMID: 36830049 PMCID: PMC9952809 DOI: 10.3390/antiox12020491] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2022] [Revised: 02/04/2023] [Accepted: 02/14/2023] [Indexed: 02/17/2023] Open
Abstract
Ischemic stroke is caused by insufficient blood flow to the brain. Astrocytes have a role in bidirectionally converting pyruvate, generated via glycolysis, into lactate and then supplying it to neurons through astrocyte-neuron lactate shuttle (ANLS). Pyruvate kinase M2 (PKM2) is an enzyme that dephosphorylates phosphoenolpyruvate to pyruvate during glycolysis in astrocytes. We hypothesized that a reduction in lactate supply in astrocyte PKM2 gene deletion exacerbates neuronal death. Mice harboring a PKM2 gene deletion were established by administering tamoxifen to Aldh1l1-CreERT2; PKM2f/f mice. Upon development of global cerebral ischemia, mice were immediately injected with sodium l-lactate (250 mg/kg, i.p.). To verify our hypothesis, we compared oxidative damage, microtubule disruption, ANLS disruption, and neuronal death between the gene deletion and control subjects. We observed that PKM2 gene deletion increases the degree of neuronal damage and impairment of lactate metabolism in the hippocampal region after GCI. The lactate administration groups showed significantly reduced neuronal death and increases in neuron survival and cognitive function. We found that lactate supply via the ANLS in astrocytes plays a crucial role in maintaining energy metabolism in neurons. Lactate administration may have potential as a therapeutic tool to prevent neuronal damage following ischemic stroke.
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Affiliation(s)
- Beom-Seok Kang
- Department of Physiology, College of Medicine, Hallym University, Chuncheon 24252, Republic of Korea
| | - Bo-Young Choi
- Department of Physical Education, Hallym University, Chuncheon 24252, Republic of Korea
- Institute of Sport Science, Hallym University, Chuncheon 24252, Republic of Korea
| | - A-Ra Kho
- Neuroregeneration and Stem Cell Programs, Institute for Cell Engineering, College of Medicine, Johns Hopkins University School, Baltimore, MD 21205, USA
- Department of Neurology, College of Medicine, Johns Hopkins University School, Baltimore, MD 21205, USA
| | - Song-Hee Lee
- Department of Physiology, College of Medicine, Hallym University, Chuncheon 24252, Republic of Korea
| | - Dae-Ki Hong
- Department of Pathology and Laboratory Medicine, College of Medicine, Emory University School, Atlanta, GA 30322, USA
| | - Min-Kyu Park
- Department of Physiology, College of Medicine, Hallym University, Chuncheon 24252, Republic of Korea
| | - Si-Hyun Lee
- Department of Physiology, College of Medicine, Hallym University, Chuncheon 24252, Republic of Korea
| | - Chang-Juhn Lee
- Department of Physiology, College of Medicine, Hallym University, Chuncheon 24252, Republic of Korea
| | - Hyeun-Wook Yang
- Department of Physiology, College of Medicine, Hallym University, Chuncheon 24252, Republic of Korea
| | - Seo-Young Woo
- Department of Physiology, College of Medicine, Hallym University, Chuncheon 24252, Republic of Korea
| | - Se-Wan Park
- Department of Physiology, College of Medicine, Hallym University, Chuncheon 24252, Republic of Korea
| | - Dong-Yeon Kim
- Department of Physiology, College of Medicine, Hallym University, Chuncheon 24252, Republic of Korea
| | - Jae-Bong Park
- Department of Biochemistry, College of Medicine, Chuncheon 24252, Republic of Korea
| | - Won-Suk Chung
- Department of Biological Sciences and KAIST Stem Cell Center, Korea Advanced Institute of Science and Technology, Daejeon 34051, Republic of Korea
| | - Sang-Won Suh
- Department of Physiology, College of Medicine, Hallym University, Chuncheon 24252, Republic of Korea
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2
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Sifat AE, Nozohouri S, Archie SR, Chowdhury EA, Abbruscato TJ. Brain Energy Metabolism in Ischemic Stroke: Effects of Smoking and Diabetes. Int J Mol Sci 2022; 23:ijms23158512. [PMID: 35955647 PMCID: PMC9369264 DOI: 10.3390/ijms23158512] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2022] [Revised: 07/28/2022] [Accepted: 07/29/2022] [Indexed: 02/06/2023] Open
Abstract
Proper regulation of energy metabolism in the brain is crucial for maintaining brain activity in physiological and different pathophysiological conditions. Ischemic stroke has a complex pathophysiology which includes perturbations in the brain energy metabolism processes which can contribute to worsening of brain injury and stroke outcome. Smoking and diabetes are common risk factors and comorbid conditions for ischemic stroke which have also been associated with disruptions in brain energy metabolism. Simultaneous presence of these conditions may further alter energy metabolism in the brain leading to a poor clinical prognosis after an ischemic stroke event. In this review, we discuss the possible effects of smoking and/or diabetes on brain glucose utilization and mitochondrial energy metabolism which, when present concurrently, may exacerbate energy metabolism in the ischemic brain. More research is needed to investigate brain glucose utilization and mitochondrial oxidative metabolism in ischemic stroke in the presence of smoking and/or diabetes, which would provide further insights on the pathophysiology of these comorbid conditions and facilitate the development of therapeutic interventions.
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3
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Rich LR, Ransom BR, Brown AM. Energy Metabolism in Mouse Sciatic Nerve A Fibres during Increased Energy Demand. Metabolites 2022; 12:metabo12060505. [PMID: 35736438 PMCID: PMC9227381 DOI: 10.3390/metabo12060505] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2022] [Revised: 05/29/2022] [Accepted: 05/30/2022] [Indexed: 11/16/2022] Open
Abstract
The ability of sciatic nerve A fibres to conduct action potentials relies on an adequate supply of energy substrate, usually glucose, to maintain necessary ion gradients. Under our ex vivo experimental conditions, the absence of exogenously applied glucose triggers Schwann cell glycogen metabolism to lactate, which is transported to axons to fuel metabolism, with loss of the compound action potential (CAP) signalling glycogen exhaustion. The CAP failure is accelerated if tissue energy demand is increased by high-frequency stimulation (HFS) or by blocking lactate uptake into axons using cinnemate (CIN). Imposing HFS caused CAP failure in nerves perfused with 10 mM glucose, but increasing glucose to 30 mM fully supported the CAP and promoted glycogen storage. A combination of glucose and lactate supported the CAP more fully than either substrate alone, indicating the nerve is capable of simultaneously metabolising each substrate. CAP loss resulting from exposure to glucose-free artificial cerebrospinal fluid (aCSF) could be fully reversed in the absence of glycogen by addition of glucose or lactate when minimally stimulated, but imposing HFS resulted in only partial CAP recovery. The delayed onset of CAP recovery coincided with the release of lactate by Schwann cells, suggesting that functional Schwann cells are a prerequisite for CAP recovery.
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Affiliation(s)
- Laura R. Rich
- School of Life Sciences, University of Nottingham, Nottingham NG7 2UH, UK;
| | - Bruce R. Ransom
- Department of Neurology, School of Medicine, University of Washington, Seattle, WA 98195, USA;
- Department of Neuroscience, City University of Hong Kong, Hong Kong
| | - Angus M. Brown
- School of Life Sciences, University of Nottingham, Nottingham NG7 2UH, UK;
- Department of Neurology, School of Medicine, University of Washington, Seattle, WA 98195, USA;
- Correspondence: ; Tel.: +0115-823-0173
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4
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Gyawali A, Kang YS. Transport Alteration of 4-Phenyl Butyric Acid Mediated by a Sodium- and Proton-Coupled Monocarboxylic Acid Transporter System in ALS Model Cell Lines (NSC-34) Under Inflammatory States. J Pharm Sci 2020; 110:1374-1384. [PMID: 33098824 DOI: 10.1016/j.xphs.2020.10.030] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2020] [Revised: 10/16/2020] [Accepted: 10/18/2020] [Indexed: 12/20/2022]
Abstract
4-Phenyl butyric acid (PBA) has histone deacetylase inhibitory and neuroprotective effects. We aimed to examine the transport alteration activity of PBA in control (WT) and disease (MT) model cell lines of an amyotrophic lateral sclerosis (ALS) model. The transport characteristics of PBA were examined uptake rates and mRNA expression levels in NSC-34 cell lines. PBA uptake was pH, sodium, and concentration dependent. The Km and Vmax values for PBA uptake in the MT were more than two-fold higher than those in the WT. The presence of monocarboxylic acids (MA) and inhibitors of MA transporter (MCT) inhibited the uptake of PBA. PBA showed competitive inhibition in the presence of MAs in both cell lines. SiRNA transfection studies showed that PBA can be transported to NSC-34 cell lines through sodium-coupled MCT1. TNF-α and H2O2 increased, but LPS and glutamate reduced the uptake rate after the pretreatment of the MT cell lines. SMCT1 mRNA expression levels, in the presence of oxidative stress inducing agents, showed consistent results with the uptake results. These results demonstrate that PBA can be transported to the ALS model NSC-34 cell lines by sodium- and proton-coupled MCTs, and MA plays a vital role in the prevention of neurodegenerative diseases.
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Affiliation(s)
- Asmita Gyawali
- College of Pharmacy and Drug Information Research Institute, Sookmyung Women's University, Seoul, Republic of Korea
| | - Young-Sook Kang
- College of Pharmacy and Drug Information Research Institute, Sookmyung Women's University, Seoul, Republic of Korea.
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5
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Rich LR, Harris W, Brown AM. The Role of Brain Glycogen in Supporting Physiological Function. Front Neurosci 2019; 13:1176. [PMID: 31749677 PMCID: PMC6842925 DOI: 10.3389/fnins.2019.01176] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2019] [Accepted: 10/17/2019] [Indexed: 01/08/2023] Open
Abstract
Glycogen is present in the mammalian brain but occurs at concentrations so low it is unlikely to act as a conventional energy reserve. Glycogen has the intriguing feature of being located exclusively in astrocytes, but its presence benefits neurones, suggesting that glycogen is metabolized to a conduit that is transported between the glia and neural elements. In the rodent optic nerve model glycogen supports axon conduction in the form of lactate to supplement axonal metabolism during aglycemia, hypoglycemia and during periods of increased energy demand under normoglycemic conditions. In the hippocampus glycogen plays a vital role in supplying the neurones with lactate during memory formation. The physiological processes that glycogen supports, such as learning and memory, imply an inclusive and vital role in supporting physiological brain functions.
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Affiliation(s)
- Laura R Rich
- School of Life Sciences, University of Nottingham, Nottingham, United Kingdom
| | - William Harris
- School of Life Sciences, University of Nottingham, Nottingham, United Kingdom
| | - Angus M Brown
- School of Life Sciences, University of Nottingham, Nottingham, United Kingdom.,Department of Neurology, University of Washington, Seattle, WA, United States
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6
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Aspatwar A, Tolvanen MEE, Schneider HP, Becker HM, Narkilahti S, Parkkila S, Deitmer JW. Catalytically inactive carbonic anhydrase-related proteins enhance transport of lactate by MCT1. FEBS Open Bio 2019; 9:1204-1211. [PMID: 31033227 PMCID: PMC6609565 DOI: 10.1002/2211-5463.12647] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2018] [Revised: 03/22/2019] [Accepted: 04/26/2019] [Indexed: 11/12/2022] Open
Abstract
Carbonic anhydrases (CA) catalyze the reversible hydration of CO2 to protons and bicarbonate and thereby play a fundamental role in the epithelial acid/base transport mechanisms serving fluid secretion and absorption for whole‐body acid/base regulation. The three carbonic anhydrase‐related proteins (CARPs) VIII, X, and XI, however, are catalytically inactive. Previous work has shown that some CA isoforms noncatalytically enhance lactate transport through various monocarboxylate transporters (MCT). Therefore, we examined whether the catalytically inactive CARPs play a role in lactate transport. Here, we report that CARP VIII, X, and XI enhance transport activity of the MCT MCT1 when coexpressed in Xenopus oocytes, as evidenced by the rate of rise in intracellular H+ concentration detected using ion‐sensitive microelectrodes. Based on previous studies, we suggest that CARPs may function as a ‘proton antenna’ for MCT1, to drive proton‐coupled lactate transport across the cell membrane.
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Affiliation(s)
- Ashok Aspatwar
- Faculty of Medicine and Health Technology, Tampere University, Finland
| | | | | | - Holger M Becker
- Division of General Zoology, FB Biologie, TU Kaiserslautern, Germany
| | | | - Seppo Parkkila
- Faculty of Medicine and Health Technology, Tampere University, Finland
| | - Joachim W Deitmer
- Division of General Zoology, FB Biologie, TU Kaiserslautern, Germany
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7
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Al-Khawaga S, AlRayahi J, Khan F, Saraswathi S, Hasnah R, Haris B, Mohammed I, Abdelalim EM, Hussain K. A SLC16A1 Mutation in an Infant With Ketoacidosis and Neuroimaging Assessment: Expanding the Clinical Spectrum of MCT1 Deficiency. Front Pediatr 2019; 7:299. [PMID: 31380330 PMCID: PMC6657212 DOI: 10.3389/fped.2019.00299] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/26/2018] [Accepted: 07/04/2019] [Indexed: 01/01/2023] Open
Abstract
The solute carrier family 16 member 1 (SLC16A1) gene encodes for monocarboxylate transporter 1 (MCT1) that mediates the movement of monocarboxylates, such as lactate and pyruvate across cell membranes. Inactivating recessive homozygous or heterozygous mutations in the SLC16A1 gene were described in patients with recurrent ketoacidosis and hypoglycemia, a potentially lethal condition. In the brain where MCT1 is highly localized around axons and oligodendrocytes, glucose is the most crucial energy substrate while lactate is an alternative substrate. MCT1 mutation or reduced expression leads to neuronal loss due to axonal degeneration in an animal model. Herein, we describe a 28 months old female patient who presented with the first hypoglycemic attack associated with ketoacidosis starting at the age of 3 days old. Whole exome sequencing (WES) performed at 6 months of age revealed a c.218delG mutation in exon 3 in the SLC16A1 gene. The variant is expected to result in loss of normal MCT1 function. Our patient is amongst the youngest presenting with MCT1 deficiency. A detailed neuroimaging assessment performed at 18 months of age revealed a complex white and gray matter disease, with heterotopia. The threshold of blood glucose to circumvent neurological sequelae cannot be set because it is patient-specific, nevertheless, neurodevelopmental follow up is recommended in this patient. Further functional studies will be required to understand the role of the MCT1 in key tissues such as the central nervous system (CNS), liver, muscle and ketone body metabolism. Our case suggests possible neurological sequelae that could be associated with MCT1 deficiency, an observation that could facilitate the initiation of appropriate neurodevelopmental follow up in such patients.
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Affiliation(s)
- Sara Al-Khawaga
- College of Health and Life Sciences, Hamad Bin Khalifa University, Qatar Foundation, Education City, Doha, Qatar.,Division of Endocrinology, Department of Pediatric Medicine, Sidra Medicine, Doha, Qatar.,Diabetes Research Center, Qatar Biomedical Research Institute, Hamad Bin Khalifa University, Qatar Foundation, Doha, Qatar
| | - Jehan AlRayahi
- Division of Neuroradiology, Diagnostic Imaging, Sidra Medicine, Doha, Qatar
| | - Faiyaz Khan
- Division of Endocrinology, Department of Pediatric Medicine, Sidra Medicine, Doha, Qatar
| | - Saras Saraswathi
- Division of Endocrinology, Department of Pediatric Medicine, Sidra Medicine, Doha, Qatar
| | - Reem Hasnah
- Division of Endocrinology, Department of Pediatric Medicine, Sidra Medicine, Doha, Qatar
| | - Basma Haris
- Division of Endocrinology, Department of Pediatric Medicine, Sidra Medicine, Doha, Qatar
| | - Idris Mohammed
- College of Health and Life Sciences, Hamad Bin Khalifa University, Qatar Foundation, Education City, Doha, Qatar.,Division of Endocrinology, Department of Pediatric Medicine, Sidra Medicine, Doha, Qatar
| | - Essam M Abdelalim
- College of Health and Life Sciences, Hamad Bin Khalifa University, Qatar Foundation, Education City, Doha, Qatar.,Diabetes Research Center, Qatar Biomedical Research Institute, Hamad Bin Khalifa University, Qatar Foundation, Doha, Qatar
| | - Khalid Hussain
- Division of Endocrinology, Department of Pediatric Medicine, Sidra Medicine, Doha, Qatar
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8
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Barros LF, Bolaños JP, Bonvento G, Bouzier-Sore AK, Brown A, Hirrlinger J, Kasparov S, Kirchhoff F, Murphy AN, Pellerin L, Robinson MB, Weber B. Current technical approaches to brain energy metabolism. Glia 2018; 66:1138-1159. [PMID: 29110344 PMCID: PMC5903992 DOI: 10.1002/glia.23248] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2017] [Revised: 09/14/2017] [Accepted: 10/04/2017] [Indexed: 12/19/2022]
Abstract
Neuroscience is a technology-driven discipline and brain energy metabolism is no exception. Once satisfied with mapping metabolic pathways at organ level, we are now looking to learn what it is exactly that metabolic enzymes and transporters do and when, where do they reside, how are they regulated, and how do they relate to the specific functions of neurons, glial cells, and their subcellular domains and organelles, in different areas of the brain. Moreover, we aim to quantify the fluxes of metabolites within and between cells. Energy metabolism is not just a necessity for proper cell function and viability but plays specific roles in higher brain functions such as memory processing and behavior, whose mechanisms need to be understood at all hierarchical levels, from isolated proteins to whole subjects, in both health and disease. To this aim, the field takes advantage of diverse disciplines including anatomy, histology, physiology, biochemistry, bioenergetics, cellular biology, molecular biology, developmental biology, neurology, and mathematical modeling. This article presents a well-referenced synopsis of the technical side of brain energy metabolism research. Detail and jargon are avoided whenever possible and emphasis is given to comparative strengths, limitations, and weaknesses, information that is often not available in regular articles.
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Affiliation(s)
- L Felipe Barros
- Centro de Estudios Científicos (CECs), Valdivia, 5110466, Chile
| | - Juan P Bolaños
- Instituto de Biologia Funcional y Genomica-CSIC, Universidad de Salamanca, CIBERFES, Salamanca, 37007, Spain
| | - Gilles Bonvento
- Commissariat à l'Energie Atomique et aux Energies Alternatives (CEA), Département de la Recherche Fondamentale (DRF), Institut de Biologie François Jacob, Molecular Imaging Research Center (MIRCen), CNRS UMR 9199, Université Paris-Sud, Université Paris-Saclay, Fontenay-aux-Roses, France
| | - Anne-Karine Bouzier-Sore
- Centre de Résonance Magnétique des Systèmes Biologiques UMR 5536, CNRS-Université Bordeaux 146 rue Léo-Saignat, Bordeaux, France
| | - Angus Brown
- School of Life Sciences, University of Nottingham, Nottingham, United Kingdom
| | - Johannes Hirrlinger
- Carl Ludwig Institute of Physiology, University of Leipzig, Liebigstr. 27, D-04103, Leipzig, Germany
- Department of Neurogenetics, Max-Planck-Institute for Experimental Medicine, Hermann-Rein-Str. 3, Göttingen, D-37075, Germany
| | - Sergey Kasparov
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, University Walk, BS8 1TD, United Kingdom
- Baltic Federal University, Kalinigrad, Russian Federation
| | - Frank Kirchhoff
- Molecular Physiology, Center for Integrative Physiology and Molecular Medicine, University of Saarland, Building 48, Homburg, 66421, Germany
| | - Anne N Murphy
- Department of Pharmacology, University of California, San Diego, La Jolla, CA, 92093
| | - Luc Pellerin
- Département de Physiologie, 7 rue du Bugnon, Lausanne, CH1005, Switzerland
| | - Michael B Robinson
- Department of Pediatrics, and Department of Systems Pharmacology and Translational Therapeutics, Children's Hospital of Philadelphia Research Institute, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Bruno Weber
- Institute of Pharmacology and Toxicology, University of Zurich, Zurich, Switzerland
- Neuroscience Center Zurich, Zurich, Switzerland
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9
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Ambient but not local lactate underlies neuronal tolerance to prolonged glucose deprivation. PLoS One 2018; 13:e0195520. [PMID: 29617444 PMCID: PMC5884621 DOI: 10.1371/journal.pone.0195520] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2018] [Accepted: 03/23/2018] [Indexed: 11/19/2022] Open
Abstract
Neurons require a nearly constant supply of ATP. Glucose is the predominant source of brain ATP, but the direct effects of prolonged glucose deprivation on neuronal viability and function remain unclear. In sparse rat hippocampal microcultures, neurons were surprisingly resilient to 16 h glucose removal in the absence of secondary excitotoxicity. Neuronal survival and synaptic transmission were unaffected by prolonged removal of exogenous glucose. Inhibition of lactate transport decreased microculture neuronal survival during concurrent glucose deprivation, suggesting that endogenously released lactate is important for tolerance to glucose deprivation. Tandem depolarization and glucose deprivation also reduced neuronal survival, and trace glucose concentrations afforded neuroprotection. Mass cultures, in contrast to microcultures, were insensitive to depolarizing glucose deprivation, a difference attributable to increased extracellular lactate levels. Removal of local astrocyte support did not reduce survival in response to glucose deprivation or alter evoked excitatory transmission, suggesting that on-demand, local lactate shuttling is not necessary for neuronal tolerance to prolonged glucose removal. Taken together, these data suggest that endogenously produced lactate available globally in the extracellular milieu sustains neurons in the absence of glucose. A better understanding of resilience mechanisms in reduced preparations could lead to therapeutic strategies aimed to bolster these mechanisms in vulnerable neuronal populations.
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10
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Mason S. Lactate Shuttles in Neuroenergetics-Homeostasis, Allostasis and Beyond. Front Neurosci 2017; 11:43. [PMID: 28210209 PMCID: PMC5288365 DOI: 10.3389/fnins.2017.00043] [Citation(s) in RCA: 132] [Impact Index Per Article: 18.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2016] [Accepted: 01/20/2017] [Indexed: 12/19/2022] Open
Abstract
Understanding brain energy metabolism—neuroenergetics—is becoming increasingly important as it can be identified repeatedly as the source of neurological perturbations. Within the scientific community we are seeing a shift in paradigms from the traditional neurocentric view to that of a more dynamic, integrated one where astrocytes are no longer considered as being just supportive, and activated microglia have a profound influence. Lactate is emerging as the “good guy,” contrasting its classical “bad guy” position in the now superseded medical literature. This review begins with the evolution of the concept of “lactate shuttles”; goes on to the recent shift in ideas regarding normal neuroenergetics (homeostasis)—specifically, the astrocyte–neuron lactate shuttle; and progresses to covering the metabolic implications whereby homeostasis is lost—a state of allostasis, and the function of microglia. The role of lactate, as a substrate and shuttle, is reviewed in light of allostatic stress, and beyond—in an acute state of allostatic stress in terms of physical brain trauma, and reflected upon with respect to persistent stress as allostatic overload—neurodegenerative diseases. Finally, the recently proposed astrocyte–microglia lactate shuttle is discussed in terms of chronic neuroinflammatory infectious diseases, using tuberculous meningitis as an example. The novelty extended by this review is that the directionality of lactate, as shuttles in the brain, in neuropathophysiological states is emerging as crucial in neuroenergetics.
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Affiliation(s)
- Shayne Mason
- Centre for Human Metabolomics, North-West University Potchefstroom, South Africa
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11
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Abstract
The historically neurocentric view of astrocytes as Styrofoam cushioning that rigidly clad neurons within the brain parenchyma has been superseded in the past 30 years by an increasing appreciation of the myriad roles astrocytes contribute to supporting physiological brain function. It is widely recognized that the continuous support provided by astrocytes, from prenatal development to maturity, is vital for neuronal function. Indeed, the numerous and diverse roles furnished by astrocytes contrasts with the vital but restricted transmission of action potentials that is the neuron's primary role. An emerging role for astrocytes is that of providing energy substrate in the form of glycogen-derived lactate to neurons. This role was established during periods of limited glucose availability but has been extended to encompass one of the most important physiological brain functions, learning and memory. In this context glycogen metabolism is integral to the consolidation of learning into long-term retention of memories, a process vital to the higher functioning of the human brain.
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Affiliation(s)
- Laura Rich
- 1 School of Life Sciences, University of Nottingham, Nottingham, UK
| | - Angus M Brown
- 1 School of Life Sciences, University of Nottingham, Nottingham, UK.,2 Department of Neurology, School of Medicine, University of Washington, Seattle, WA, USA
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12
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Mason S, Reinecke CJ, Kulik W, van Cruchten A, Solomons R, van Furth AMT. Cerebrospinal fluid in tuberculous meningitis exhibits only the L-enantiomer of lactic acid. BMC Infect Dis 2016; 16:251. [PMID: 27267176 PMCID: PMC4897924 DOI: 10.1186/s12879-016-1597-9] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2015] [Accepted: 05/27/2016] [Indexed: 11/17/2022] Open
Abstract
Background The defining feature of the cerebrospinal fluid (CSF) collected from infants and children with tuberculous meningitis (TBM), derived from an earlier untargeted nuclear magnetic resonance (NMR) metabolomics study, was highly elevated lactic acid. Undetermined was the contribution from host response (L-lactic acid) or of microbial origin (D-lactic acid), which was set out to be determined in this study. Methods In this follow-up study, we used targeted ultra-performance liquid chromatography–electrospray ionization–tandem mass spectrometry (UPLC–ESI–MS/MS) to determine the ratio of the L and D enantiomers of lactic acid in these CSF samples. Results Here we report for the first time that the lactic acid observed in the CSF of confirmed TBM cases was in the L-form and solely a response from the host to the infection, with no contribution from any bacteria. The significance of elevated lactic acid in TBM appears to be that it is a crucial energy substrate, used preferentially over glucose by microglia, and exhibits neuroprotective capabilities. Conclusion These results provide experimental evidence to support our conceptual astrocyte–microglia lactate shuttle model formulated from our previous NMR-based metabolomics study — highlighting the fact that lactic acid plays an important role in neuroinflammatory diseases such as TBM. Furthermore, this study reinforces our belief that the determination of enantiomers of metabolites corresponding to infectious diseases is of critical importance in substantiating the clinical significance of disease markers. Electronic supplementary material The online version of this article (doi:10.1186/s12879-016-1597-9) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Shayne Mason
- Centre for Human Metabolomics, Faculty of Natural Sciences, North-West University (Potchefstroom Campus), Private Bag X6001, Potchefstroom, 2531, South Africa.
| | - Carolus J Reinecke
- Centre for Human Metabolomics, Faculty of Natural Sciences, North-West University (Potchefstroom Campus), Private Bag X6001, Potchefstroom, 2531, South Africa
| | - Willem Kulik
- Laboratory Genetic Metabolic Diseases, Department of Clinical Chemistry, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| | - Arno van Cruchten
- Laboratory Genetic Metabolic Diseases, Department of Clinical Chemistry, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| | - Regan Solomons
- Department of Paediatrics and Child Health, Faculty of Medicine and Health Sciences, Stellenbosch University, PO Box 19063, Tygerberg, 7505, South Africa
| | - A Marceline Tutu van Furth
- Department of Paediatric Infectious Diseases-Immunology and Rheumatology, Vrije Universiteit Medical Centre, De Boelelaan 1117, 1081HV, Amsterdam, The Netherlands
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13
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Hong S, Ahn JY, Cho GS, Kim IH, Cho JH, Ahn JH, Park JH, Won MH, Chen BH, Shin BN, Tae HJ, Park SM, Cho JH, Choi SY, Lee JC. Monocarboxylate transporter 4 plays a significant role in the neuroprotective mechanism of ischemic preconditioning in transient cerebral ischemia. Neural Regen Res 2015; 10:1604-11. [PMID: 26692857 PMCID: PMC4660753 DOI: 10.4103/1673-5374.167757] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Monocarboxylate transporters (MCTs), which carry monocarboxylates such as lactate across biological membranes, have been associated with cerebral ischemia/reperfusion process. In this study, we studied the effect of ischemic preconditioning (IPC) on MCT4 immunoreactivity after 5 minutes of transient cerebral ischemia in the gerbil. Animals were randomly designated to four groups (sham-operated group, ischemia only group, IPC + sham-operated group and IPC + ischemia group). A serious loss of neuron was found in the stratum pyramidale of the hippocampal CA1 region (CA1), not CA2/3, of the ischemia-only group at 5 days post-ischemia; however, in the IPC + ischemia groups, neurons in the stratum pyramidale of the CA1 were well protected. Weak MCT4 immunoreactivity was found in the stratum pyramidale of the CA1 in the sham-operated group. MCT4 immunoreactivity in the stratum pyramidale began to decrease at 2 days post-ischemia and was hardly detected at 5 days post-ischemia; at this time point, MCT4 immunoreactivity was newly expressed in astrocytes. In the IPC + sham-operated group, MCT4 immunoreactivity in the stratum pyramidale of the CA1 was increased compared with the sham-operated group, and, in the IPC + ischemia group, MCT4 immunoreactivity was also increased in the stratum pyramidale compared with the ischemia only group. Briefly, present findings show that IPC apparently protected CA1 pyramidal neurons and increased or maintained MCT4 expression in the stratum pyramidale of the CA1 after transient cerebral ischemia. Our findings suggest that MCT4 appears to play a significant role in the neuroprotective mechanism of IPC in the gerbil with transient cerebral ischemia.
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Affiliation(s)
- Seongkweon Hong
- Department of Surgery, School of Medicine, Kangwon National University, Chuncheon, South Korea
| | - Ji Yun Ahn
- Department of Emergency Medicine, Sacred Heart Hospital, College of Medicine, Hallym University, Anyang, South Korea ; Department of Emergency Medicine, School of Medicine, Kangwon National University, Chuncheon, South Korea
| | - Geum-Sil Cho
- Department of Neuroscience, College of Medicine, Korea University, Seoul, South Korea
| | - In Hye Kim
- Department of Neurobiology, School of Medicine, Kangwon National University, Chuncheon, South Korea
| | - Jeong Hwi Cho
- Department of Neurobiology, School of Medicine, Kangwon National University, Chuncheon, South Korea
| | - Ji Hyeon Ahn
- Department of Neurobiology, School of Medicine, Kangwon National University, Chuncheon, South Korea
| | - Joon Ha Park
- Department of Neurobiology, School of Medicine, Kangwon National University, Chuncheon, South Korea
| | - Moo-Ho Won
- Department of Neurobiology, School of Medicine, Kangwon National University, Chuncheon, South Korea
| | - Bai Hui Chen
- Department of Physiology, College of Medicine, Hallym University, Chuncheon, South Korea
| | - Bich-Na Shin
- Department of Physiology, College of Medicine, Hallym University, Chuncheon, South Korea
| | - Hyun-Jin Tae
- Department of Biomedical Science, Research Institute of Bioscience and Biotechnology, Hallym University, Chuncheon, South Korea
| | - Seung Min Park
- Department of Emergency Medicine, Sacred Heart Hospital, College of Medicine, Hallym University, Anyang, South Korea ; Department of Emergency Medicine, School of Medicine, Kangwon National University, Chuncheon, South Korea
| | - Jun Hwi Cho
- Department of Emergency Medicine, School of Medicine, Kangwon National University, Chuncheon, South Korea
| | - Soo Young Choi
- Department of Biomedical Science, Research Institute of Bioscience and Biotechnology, Hallym University, Chuncheon, South Korea
| | - Jae-Chul Lee
- Department of Neurobiology, School of Medicine, Kangwon National University, Chuncheon, South Korea
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14
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Quintard H, Patet C, Zerlauth JB, Suys T, Bouzat P, Pellerin L, Meuli R, Magistretti PJ, Oddo M. Improvement of Neuroenergetics by Hypertonic Lactate Therapy in Patients with Traumatic Brain Injury Is Dependent on Baseline Cerebral Lactate/Pyruvate Ratio. J Neurotrauma 2015; 33:681-7. [PMID: 26421521 PMCID: PMC4827289 DOI: 10.1089/neu.2015.4057] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Energy dysfunction is associated with worse prognosis after traumatic brain injury (TBI). Recent data suggest that hypertonic sodium lactate infusion (HL) improves energy metabolism after TBI. Here, we specifically examined whether the efficacy of HL (3h infusion, 30–40 μmol/kg/min) in improving brain energetics (using cerebral microdialysis [CMD] glucose as a main therapeutic end-point) was dependent on baseline cerebral metabolic state (assessed by CMD lactate/pyruvate ratio [LPR]) and cerebral blood flow (CBF, measured with perfusion computed tomography [PCT]). Using a prospective cohort of 24 severe TBI patients, we found CMD glucose increase during HL was significant only in the subgroup of patients with elevated CMD LPR >25 (n = 13; +0.13 [95% confidence interval (CI) 0.08–0.19] mmol/L, p < 0.001; vs. +0.04 [–0.05–0.13] in those with normal LPR, p = 0.33, mixed-effects model). In contrast, CMD glucose increase was independent from baseline CBF (coefficient +0.13 [0.04–0.21] mmol/L when global CBF was <32.5 mL/100 g/min vs. +0.09 [0.04–0.14] mmol/L at normal CBF, both p < 0.005) and systemic glucose. Our data suggest that improvement of brain energetics upon HL seems predominantly dependent on baseline cerebral metabolic state and support the concept that CMD LPR – rather than CBF – could be used as a diagnostic indication for systemic lactate supplementation following TBI.
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Affiliation(s)
- Hervé Quintard
- 1 Department of Intensive Care Medicine, Neuroscience Critical Care Research Group, Centre Hospitalier Universitaire Vaudois (CHUV), Lausanne University Hospital , Lausanne, Switzerland .,2 Department of Anesthesia and Intensive Care, Nice University Hospital , Nice, France
| | - Camille Patet
- 1 Department of Intensive Care Medicine, Neuroscience Critical Care Research Group, Centre Hospitalier Universitaire Vaudois (CHUV), Lausanne University Hospital , Lausanne, Switzerland
| | - Jean-Baptiste Zerlauth
- 3 Department of Medical Radiology, Centre Hospitalier Universitaire Vaudois (CHUV), Lausanne University Hospital , Lausanne, Switzerland
| | - Tamarah Suys
- 1 Department of Intensive Care Medicine, Neuroscience Critical Care Research Group, Centre Hospitalier Universitaire Vaudois (CHUV), Lausanne University Hospital , Lausanne, Switzerland
| | - Pierre Bouzat
- 1 Department of Intensive Care Medicine, Neuroscience Critical Care Research Group, Centre Hospitalier Universitaire Vaudois (CHUV), Lausanne University Hospital , Lausanne, Switzerland .,4 Department of Anesthesia and Intensive Care, Grenoble University Hospital , Grenoble, France
| | - Luc Pellerin
- 5 Institute of Physiology, University of Lausanne , Lausanne, Switzerland
| | - Reto Meuli
- 3 Department of Medical Radiology, Centre Hospitalier Universitaire Vaudois (CHUV), Lausanne University Hospital , Lausanne, Switzerland
| | - Pierre J Magistretti
- 6 Division of Biological and Environmental Sciences and Engineering, King Abdullah University of Science and Technology (KAUST) , Thuwal, Kingdom of Saudi Arabia .,7 Centre de Neurosciences Psychiatriques, Department of Psychiatry, Centre Hospitalier Universitaire Vaudois (CHUV), Lausanne University Hospital , Lausanne, Switzerland .,8 Laboratory of Neuroenergetics and Cellular Dynamics, Brain Mind Institute , Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Mauro Oddo
- 1 Department of Intensive Care Medicine, Neuroscience Critical Care Research Group, Centre Hospitalier Universitaire Vaudois (CHUV), Lausanne University Hospital , Lausanne, Switzerland
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15
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Brown AM, Ransom BR. Astrocyte glycogen as an emergency fuel under conditions of glucose deprivation or intense neural activity. Metab Brain Dis 2015; 30:233-9. [PMID: 25037166 DOI: 10.1007/s11011-014-9588-2] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/25/2014] [Accepted: 06/30/2014] [Indexed: 10/24/2022]
Abstract
Energy metabolism in the brain is a complex process that is incompletely understood. Although glucose is agreed as the main energy support of the brain, the role of glucose is not clear, which has led to controversies that can be summarized as follows: the fate of glucose, once it enters the brain is unclear. It is not known the form in which glucose enters the cells (neurons and glia) within the brain, nor the degree of metabolic shuttling of glucose derived metabolites between cells, with a key limitation in our knowledge being the extent of oxidative metabolism, and how increased tissue activity alters this. Glycogen is present within the brain and is derived from glucose. Glycogen is stored in astrocytes and acts to provide short-term delivery of substrates to neural elements, although it may also contribute an important component to astrocyte metabolism. The roles played by glycogen awaits further study, but to date its most important role is in supporting neural elements during increased firing activity, where signaling molecules, proposed to be elevated interstitial K(+), indicative of elevated neural firing rates, activate glycogen phosphorylase leading to increased production of glycogen derived substrate.
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Affiliation(s)
- Angus M Brown
- School of Life Sciences, Queens Medical Centre, University of Nottingham, Nottingham, NG7-2UH, UK,
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16
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Deitmer JW, Theparambil SM, Ruminot I, Becker HM. The role of membrane acid/base transporters and carbonic anhydrases for cellular pH and metabolic processes. Front Neurosci 2015; 8:430. [PMID: 25601823 PMCID: PMC4283522 DOI: 10.3389/fnins.2014.00430] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2014] [Accepted: 12/09/2014] [Indexed: 11/17/2022] Open
Affiliation(s)
- Joachim W Deitmer
- General Zoology, FB Biology, University of Kaiserslautern Kaiserslautern, Germany
| | | | - Iván Ruminot
- General Zoology, FB Biology, University of Kaiserslautern Kaiserslautern, Germany
| | - Holger M Becker
- Zoology/Membrane Transport, FB Biology, University of Kaiserslautern Kaiserslautern, Germany
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17
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Galow LV, Schneider J, Lewen A, Ta TT, Papageorgiou IE, Kann O. Energy substrates that fuel fast neuronal network oscillations. Front Neurosci 2014; 8:398. [PMID: 25538552 PMCID: PMC4256998 DOI: 10.3389/fnins.2014.00398] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2014] [Accepted: 11/18/2014] [Indexed: 01/03/2023] Open
Abstract
Fast neuronal network oscillations in the gamma-frequency band (30–−100 Hz) provide a fundamental mechanism of complex neuronal information processing in the hippocampus and neocortex of mammals. Gamma oscillations have been implicated in higher brain functions such as sensory perception, motor activity, and memory formation. The oscillations emerge from precise synapse interactions between excitatory principal neurons such as pyramidal cells and inhibitory GABAergic interneurons, and they are associated with high energy expenditure. However, both energy substrates and metabolic pathways that are capable to power cortical gamma oscillations have been less defined. Here, we investigated the energy sources fueling persistent gamma oscillations in the CA3 subfield of organotypic hippocampal slice cultures of the rat. This preparation permits superior oxygen supply as well as fast application of glucose, glycolytic metabolites or drugs such as glycogen phosphorylase inhibitor during extracellular recordings of the local field potential. Our findings are: (i) gamma oscillations persist in the presence of glucose (10 mmol/L) for greater than 60 min in slice cultures while (ii) lowering glucose levels (2.5 mmol/L) significantly reduces the amplitude of the oscillation. (iii) Gamma oscillations are absent at low concentration of lactate (2 mmol/L). (iv) Gamma oscillations persist at high concentration (20 mmol/L) of either lactate or pyruvate, albeit showing significant reductions in the amplitude. (v) The breakdown of glycogen significantly delays the decay of gamma oscillations during glucose deprivation. However, when glucose is present, the turnover of glycogen is not essential to sustain gamma oscillations. Our study shows that fast neuronal network oscillations can be fueled by different energy-rich substrates, with glucose being most effective.
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Affiliation(s)
- Lukas V Galow
- Institute of Physiology and Pathophysiology and Interdisciplinary Center for Neurosciences (IZN), University of Heidelberg Heidelberg, Germany
| | - Justus Schneider
- Institute of Physiology and Pathophysiology and Interdisciplinary Center for Neurosciences (IZN), University of Heidelberg Heidelberg, Germany
| | - Andrea Lewen
- Institute of Physiology and Pathophysiology and Interdisciplinary Center for Neurosciences (IZN), University of Heidelberg Heidelberg, Germany
| | - Thuy-Truc Ta
- Institute of Physiology and Pathophysiology and Interdisciplinary Center for Neurosciences (IZN), University of Heidelberg Heidelberg, Germany
| | - Ismini E Papageorgiou
- Institute of Physiology and Pathophysiology and Interdisciplinary Center for Neurosciences (IZN), University of Heidelberg Heidelberg, Germany
| | - Oliver Kann
- Institute of Physiology and Pathophysiology and Interdisciplinary Center for Neurosciences (IZN), University of Heidelberg Heidelberg, Germany
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18
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Stobart JL, Anderson CM. Multifunctional role of astrocytes as gatekeepers of neuronal energy supply. Front Cell Neurosci 2013; 7:38. [PMID: 23596393 PMCID: PMC3622037 DOI: 10.3389/fncel.2013.00038] [Citation(s) in RCA: 171] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2013] [Accepted: 03/26/2013] [Indexed: 01/01/2023] Open
Abstract
Dynamic adjustments to neuronal energy supply in response to synaptic activity are critical for neuronal function. Glial cells known as astrocytes have processes that ensheath most central synapses and express G-protein-coupled neurotransmitter receptors and transporters that respond to neuronal activity. Astrocytes also release substrates for neuronal oxidative phosphorylation and have processes that terminate on the surface of brain arterioles and can influence vascular smooth muscle tone and local blood flow. Membrane receptor or transporter-mediated effects of glutamate represent a convergence point of astrocyte influence on neuronal bioenergetics. Astrocytic glutamate uptake drives glycolysis and subsequent shuttling of lactate from astrocytes to neurons for oxidative metabolism. Astrocytes also convert synaptically reclaimed glutamate to glutamine, which is returned to neurons for glutamate salvage or oxidation. Finally, astrocytes store brain energy currency in the form of glycogen, which can be mobilized to produce lactate for neuronal oxidative phosphorylation in response to glutamatergic neurotransmission. These mechanisms couple synaptically driven astrocytic responses to glutamate with release of energy substrates back to neurons to match demand with supply. In addition, astrocytes directly influence the tone of penetrating brain arterioles in response to glutamatergic neurotransmission, coordinating dynamic regulation of local blood flow. We will describe the role of astrocytes in neurometabolic and neurovascular coupling in detail and discuss, in turn, how astrocyte dysfunction may contribute to neuronal bioenergetic deficit and neurodegeneration. Understanding the role of astrocytes as a hub for neurometabolic and neurovascular coupling mechanisms is a critical underpinning for therapeutic development in a broad range of neurodegenerative disorders characterized by chronic generalized brain ischemia and brain microvascular dysfunction.
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Affiliation(s)
- Jillian L Stobart
- Division of Neurodegenerative Disorders, Department of Pharmacology and Therapeutics, St. Boniface Hospital Research, University of Manitoba Winnipeg, MB, Canada ; Department of Nuclear Medicine, Institute of Pharmacology and Toxicology, University of Zürich Zürich, Switzerland
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19
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Hyun DH, Kim J, Moon C, Lim CJ, de Cabo R, Mattson MP. The plasma membrane redox enzyme NQO1 sustains cellular energetics and protects human neuroblastoma cells against metabolic and proteotoxic stress. AGE (DORDRECHT, NETHERLANDS) 2012; 34:359-370. [PMID: 21487704 PMCID: PMC3312640 DOI: 10.1007/s11357-011-9245-1] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2011] [Accepted: 03/23/2011] [Indexed: 05/30/2023]
Abstract
The plasma membrane redox system (PMRS) of nicotinamide adenine dinucleotide (NADH)-related enzymes plays a key role in the maintenance of cellular energetics. During the aging process, neural cells are particularly sensitive to impaired energy metabolism and oxidative damage, but the involvement of the PMRS in these processes is unknown. Here, we used human neuroblastoma cells with either elevated or reduced levels of the PMRS enzyme NADH-quinone oxidoreductase 1 (NQO1) to investigate how the PMRS regulates neuronal stress responses. Cells with elevated NQO1 levels were more resistant to death induced by 2-deoxyglucose, potassium cyanide (energetic stress), and lactacystin (proteotoxic stress), but were not protected from being killed by H(2)O(2) and serum withdrawal. The NAD(+)(an oxidized form of NADH)/NADH ratio was maintained at a significantly higher level in cells overexpressing NQO1, consistent with enhanced levels of NQO1 activity. Levels of the neuroprotective transcription factors nuclear factor kappa-light-chain-enhancer of activated B cells and nuclear factor (erythroid-derived 2)-like 2, and the protein chaperone HSP70 were elevated in cells overexpressing NQO1. Cells in which NQO1 levels were decreased by RNA interference exhibited increased vulnerability to death induced by 2-deoxyglucose and lactacystin. Thus, a higher NAD(+)/NADH ratio and activation of adaptive stress response pathways are enhanced by the PMRS in neuroblastoma cells, enabling them to maintain redox homeostasis under conditions of energetic and proteotoxic stress. These findings have implications for the development of therapeutic interventions for neural tumors and neurodegenerative conditions.
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Affiliation(s)
- Dong-Hoon Hyun
- Division of Life and Pharmaceutical Sciences, Department of Life Science, Ewha Womans University, Seoul, South Korea.
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20
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21
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Reinert KC, Gao W, Chen G, Wang X, Peng YP, Ebner TJ. Cellular and metabolic origins of flavoprotein autofluorescence in the cerebellar cortex in vivo. CEREBELLUM (LONDON, ENGLAND) 2011; 10:585-99. [PMID: 21503591 PMCID: PMC4126810 DOI: 10.1007/s12311-011-0278-x] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Flavoprotein autofluorescence imaging, an intrinsic mitochondrial signal, has proven useful for monitoring neuronal activity. In the cerebellar cortex, parallel fiber stimulation evokes a beam-like response consisting of an initial, short-duration increase in fluorescence (on-beam light phase) followed by a longer duration decrease (on-beam dark phase). Also evoked are parasagittal bands of decreased fluorescence due to molecular layer inhibition. Previous work suggests that the on-beam light phase is due to oxidative metabolism in neurons. The present study further investigated the metabolic and cellular origins of the flavoprotein signal in vivo, testing the hypotheses that the dark phase is mediated by glia activation and the inhibitory bands reflect decreased flavoprotein oxidation and increased glycolysis in neurons. Blocking postsynaptic ionotropic and metabotropic glutamate receptors abolished the on-beam light phase and the parasagittal bands without altering the on-beam dark phase. Adding glutamate transporter blockers reduced the dark phase. Replacing glucose with lactate (or pyruvate) or adding lactate to the bathing media abolished the on-beam dark phase and reduced the inhibitory bands without affecting the light phase. Blocking monocarboxylate transporters eliminated the on-beam dark phase and increased the light phase. These results confirm that the on-beam light phase is due primarily to increased oxidative metabolism in neurons. They also show that the on-beam dark phase involves activation of glycolysis in glia resulting in the generation of lactate that is transferred to neurons. Oxidative savings in neurons contributes to the decrease in fluorescence characterizing the inhibitory bands. These findings provide strong in vivo support for the astrocyte-neuron lactate shuttle hypothesis.
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Affiliation(s)
- Kenneth C. Reinert
- Department of Neurobiology, University of Pittsburgh, Pittsburgh, PA 15261, USA
| | - Wangcai Gao
- Department of Neuroscience, University of Minnesota, Lions Research Building, Room 421, 2001 Sixth St. S.E., Minneapolis, MN 55455, USA
| | - Gang Chen
- Department of Neuroscience, University of Minnesota, Lions Research Building, Room 421, 2001 Sixth St. S.E., Minneapolis, MN 55455, USA
| | - Xinming Wang
- Department of Neuroscience, University of Minnesota, Lions Research Building, Room 421, 2001 Sixth St. S.E., Minneapolis, MN 55455, USA
| | - Yu-Ping Peng
- Nantong University, Nantong, Jiangsu 226001, People’s Republic of China
| | - Timothy J. Ebner
- Department of Neuroscience, University of Minnesota, Lions Research Building, Room 421, 2001 Sixth St. S.E., Minneapolis, MN 55455, USA,
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22
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Pyruvate incubation enhances glycogen stores and sustains neuronal function during subsequent glucose deprivation. Neurobiol Dis 2011; 45:177-87. [PMID: 21854850 DOI: 10.1016/j.nbd.2011.08.002] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2011] [Revised: 07/11/2011] [Accepted: 08/03/2011] [Indexed: 11/23/2022] Open
Abstract
The use of energy substrates, such as lactate and pyruvate, has been shown to improve synaptic function when administered during glucose deprivation. In the present study, we investigated whether prolonged incubation with monocarboxylate (pyruvate or lactate) prior rather than during glucose deprivation can also sustain synaptic and metabolic function. Pyruvate pre-incubation(3-4h) significantly prolonged (>25 min) the tolerance of rat hippocampal slices to delayed glucose deprivation compared to control and lactate pre-incubated slices, as revealed by field excitatory post synaptic potentials (fEPSPs); pre-incubation with pyruvate also reduced the marked decrease in NAD(P)H fluorescence resulting from glucose deprivation. Moreover, pyruvate exposure led to the enhancement of glycogen stores with time, compared to glucose alone (12 μmol/g tissue at 4h vs. 3.5 μmol/g tissue). Prolonged resistance to glucose deprivation following exogenous pyruvate incubation was prevented by glycogenolysis inhibitors, suggesting that enhanced glycogen mediates the delay in synaptic activity failure. The application of an adenosine A1 receptor antagonist enhanced glycogen utilization and prolonged the time to synaptic failure, further confirming this hypothesis of the importance of glycogen. Moreover, tissue levels of ATP were also significantly maintained during glucose deprivation in pyruvate pretreated slices compared to control and lactate. In summary, these experiments indicate that pyruvate exposure prior to glucose deprivation significantly increased the energy buffering capacity of hippocampal slices, particularly by enhancing internal glycogen stores, delaying synaptic failure during glucose deprivation by maintaining ATP levels, and minimizing the decrease in the levels of NAD(P)H.
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Allaman I, Fiumelli H, Magistretti PJ, Martin JL. Fluoxetine regulates the expression of neurotrophic/growth factors and glucose metabolism in astrocytes. Psychopharmacology (Berl) 2011; 216:75-84. [PMID: 21301813 DOI: 10.1007/s00213-011-2190-y] [Citation(s) in RCA: 149] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/07/2010] [Accepted: 01/17/2011] [Indexed: 02/08/2023]
Abstract
RATIONALE The pharmacological actions of most antidepressants are ascribed to the modulation of serotonergic and/or noradrenergic transmission in the brain. During therapeutic treatment for major depression, fluoxetine, one of the most commonly prescribed selective serotonin reuptake inhibitor (SSRI) antidepressants, accumulates in the brain, suggesting that fluoxetine may interact with additional targets. In this context, there is increasing evidence that astrocytes are involved in the pathophysiology of major depression. OBJECTIVES The aim of this study was to examine the effects of fluoxetine on the expression of neurotrophic/growth factors that have antidepressant properties and on glucose metabolism in cultured cortical astrocytes. RESULTS Treatment of astrocytes with fluoxetine and paroxetine, another SSRI antidepressant, upregulated brain-derived neurotrophic factor (BDNF), vascular endothelial growth factor (VEGF), and VGF mRNA expression. In contrast, the tricyclic antidepressants desipramine and imipramine did not affect the expression of these neurotrophic/growth factors. Analysis of the effects of fluoxetine on glucose metabolism revealed that fluoxetine reduces glycogen levels and increases glucose utilization and lactate release by astrocytes. Similar data were obtained with paroxetine, whereas imipramine and desipramine did not regulate glucose metabolism in this glial cell population. Our results also indicate that the effects of fluoxetine and paroxetine on glucose utilization, lactate release, and expression of BDNF, VEGF, and VGF are not mediated by serotonin-dependent mechanisms. CONCLUSIONS These data suggest that, by increasing the expression of specific astrocyte-derived neurotrophic factors and lactate release from astrocytes, fluoxetine may contribute to normalize the trophic and metabolic support to neurons in major depression.
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Affiliation(s)
- Igor Allaman
- Laboratory of Neuroenergetics and Cellular Dynamics, Brain Mind Institute, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, CH-1015, Switzerland
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24
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Acosta ML, Shin YS, Ready S, Fletcher EL, Christie DL, Kalloniatis M. Retinal metabolic state of the proline-23-histidine rat model of retinitis pigmentosa. Am J Physiol Cell Physiol 2009; 298:C764-74. [PMID: 20032515 DOI: 10.1152/ajpcell.00253.2009] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We determined the metabolic changes that precede cell death in the dystrophic proline-23-histidine (P23H) line 3 (P23H-3) rat retina compared with the normal Sprague-Dawley (SD) rat retina. Metabolite levels and metabolic enzymes were analyzed early in development and during the early stages of degeneration in the P23H-3 retina. Control and degenerating retinas showed an age-dependent change in metabolite levels and enzymatic activity, particularly around the time when phototransduction was activated. However, lactate dehydrogenase (LDH) activity was significantly higher in P23H-3 than SD retina before the onset of photoreceptor death. The creatine/phosphocreatine system did not contribute to the increase in ATP, because phosphocreatine levels, creatine kinase, and expression of the creatine transporter remained constant. However, Na(+)-K(+)-ATPase and Mg(2+)-Ca(2+)-ATPase activities were increased in the developing P23H-3 retina. Therefore, photoreceptor apoptosis in the P23H-3 retina occurs in an environment of increased LDH, ATPase activity, and higher-than-normal ATP levels. We tested the effect of metabolic challenge to the retina by inhibiting monocarboxylate transport with alpha-cyano-4-hydroxycinnamic acid or systemically administering the phosphodiesterase inhibitor sildenafil. Secondary to monocarboxylate transport inhibition, the P23H-3 retina did not demonstrate alterations in metabolic activity. However, administration of sildenafil significantly reduced LDH activity in the P23H-3 retina and increased the number of terminal deoxynucleotidyl transferase biotin-dUPT nick end-labeled photoreceptor cells. Photoreceptor cells with a rhodopsin mutation display an increase in apoptotic markers secondary to inhibition of a phototransduction enzyme (phosphodiesterase), suggesting increased susceptibility to altered cation entry.
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Affiliation(s)
- Monica L Acosta
- Department of Optometry and Vision Science, University of Auckland, Auckland, New Zealand
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25
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Abstract
Astrocytes are the main neural cell type responsible for the maintenance of brain homeostasis. They form highly organized anatomical domains that are interconnected into extensive networks. These features, along with the expression of a wide array of receptors, transporters, and ion channels, ideally position them to sense and dynamically modulate neuronal activity. Astrocytes cooperate with neurons on several levels, including neurotransmitter trafficking and recycling, ion homeostasis, energy metabolism, and defense against oxidative stress. The critical dependence of neurons upon their constant support confers astrocytes with intrinsic neuroprotective properties which are discussed here. Conversely, pathogenic stimuli may disturb astrocytic function, thus compromising neuronal functionality and viability. Using neuroinflammation, Alzheimer's disease, and hepatic encephalopathy as examples, we discuss how astrocytic defense mechanisms may be overwhelmed in pathological conditions, contributing to disease progression.
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Affiliation(s)
- Mireille Bélanger
- Laboratory of Neuroenergetics and Cellular Dynamics, Brain Mind Institute, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
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26
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Glucose and lactate supply to the synapse. ACTA ACUST UNITED AC 2009; 63:149-59. [PMID: 19879896 DOI: 10.1016/j.brainresrev.2009.10.002] [Citation(s) in RCA: 119] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2009] [Revised: 10/19/2009] [Accepted: 10/25/2009] [Indexed: 11/23/2022]
Abstract
The main source of energy for the mammalian brain is glucose, and the main sink of energy in the mammalian brain is the neuron, so the conventional view of brain energy metabolism is that glucose is consumed preferentially in neurons. But between glucose and the production of energy are several steps that do not necessarily take place in the same cell. An alternative model has been proposed that states that glucose preferentially taken by astrocytes, is degraded to lactate and then exported into neurons to be oxidized. Short of definitive data, opinions about the relative merits of these competing models are divided, making it a very exciting field of research. Furthermore, growing evidence suggests that lactate acts as a signaling molecule, involved in Na(+) sensing, glucosensing, and in coupling neuronal and glial activity to the modulation of vascular tone. In the present review, we discuss possible dynamics of glucose and lactate in excitatory synaptic regions, focusing on the transporters that catalyze the movement of these molecules.
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Izumi Y, Zorumski CF. Glial-neuronal interactions underlying fructose utilization in rat hippocampal slices. Neuroscience 2009; 161:847-54. [PMID: 19362122 DOI: 10.1016/j.neuroscience.2009.04.008] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2008] [Revised: 03/18/2009] [Accepted: 04/04/2009] [Indexed: 12/21/2022]
Abstract
Although fructose is commonly used as a sweetener, its effects on brain function are unclear. Using rat hippocampal slices, we found that fructose and mannose, like pyruvate, preserve ATP levels during 3-h of glucose deprivation. Similarly, fructose and mannose restored synaptic potentials (excitatory postsynaptic potential, EPSPs) depressed during glucose deprivation. However, restoration of synaptic responses was slow and only partial with fructose. EPSPs supported by mannose were inhibited by cytochalasin B (CCB), a glucose transport inhibitor, but were not inhibited by alpha-cyano-4-hydroxycinnamate (4-CIN), a monocarboxylate transport inhibitor, indicating that neurons use mannose via glucose transporters. In contrast, both CCB and 4-CIN depressed EPSPs supported by fructose, suggesting that fructose may be taken up by non-neuronal cells through CCB sensitive hexose transporters and metabolized to a monocarboxylate for subsequent use during neuronal respiration. Supporting this possibility, 20 minutes of oxygen deprivation in the presence of fructose resulted in functional and morphological deterioration whereas oxygen deprivation in the presence of glucose or mannose had minimal toxic effects. These results indicate that neuronal fructose utilization differs from glucose and mannose and likely involves release of monocarboxylates from glia.
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Affiliation(s)
- Y Izumi
- Department of Psychiatry, Washington University School of Medicine, St. Louis, MO 63110, USA.
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28
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Ichai C, Armando G, Orban JC, Berthier F, Rami L, Samat-Long C, Grimaud D, Leverve X. Sodium lactate versus mannitol in the treatment of intracranial hypertensive episodes in severe traumatic brain-injured patients. Intensive Care Med 2008; 35:471-9. [PMID: 18807008 DOI: 10.1007/s00134-008-1283-5] [Citation(s) in RCA: 126] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2008] [Accepted: 08/19/2008] [Indexed: 10/21/2022]
Abstract
OBJECTIVES Traumatic brain injury (TBI) is still a major cause of mortality and morbidity. Recent trials have failed to demonstrate a beneficial outcome from therapeutic treatments such as corticosteroids, hypothermia and hypertonic saline. We investigated the effect of a new hyperosmolar solution based on sodium lactate in controlling raised intracranial pressure (ICP). DESIGN AND SETTING Prospective open randomized study in an adult ICU. PATIENTS Thirty-four patients with isolated severe TBI (Glasgow Coma Scale <or= 8) and intracranial hypertension were allocated to receive equally hyperosmolar and isovolumic therapy, consisting of either mannitol or sodium lactate. Rescue therapy by crossover to the alternative treatment was indicated when ICP could not be controlled. The primary endpoint was efficacy in lowering ICP after 4 h, with a secondary endpoint of the percentage of successfully treated episodes of intracranial hypertension. The analysis was performed with both intention-to-treat and actual treatments provided. MEASUREMENTS AND RESULTS Compared to mannitol, the effect of the lactate solution on ICP was significantly more pronounced (7 vs. 4 mmHg, P = 0.016), more prolonged (fourth-hour-ICP decrease: -5.9 +/- 1 vs. -3.2 +/- 0.9 mmHg, P = 0.009) and more frequently successful (90.4 vs. 70.4%, P = 0.053). CONCLUSION Acute infusion of a sodium lactate-based hyperosmolar solution is effective in treating intracranial hypertension following traumatic brain injury. This effect is significantly more pronounced than that of an equivalent osmotic load of mannitol. Additionally, in this specific group of patients, long-term outcome was better in terms of GOS in those receiving as compared to mannitol. Larger trials are warranted to confirm our findings.
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Affiliation(s)
- Carole Ichai
- Faculté de Médecine and CHU de Nice, Service de Réanimation, Hôpital Saint-Roch, Nice Cedex 1, France.
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Galeffi F, Foster KA, Sadgrove MP, Beaver CJ, Turner DA. Lactate uptake contributes to the NAD(P)H biphasic response and tissue oxygen response during synaptic stimulation in area CA1 of rat hippocampal slices. J Neurochem 2007; 103:2449-61. [PMID: 17931363 DOI: 10.1111/j.1471-4159.2007.04939.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Synaptic train stimulation (10 Hz x 25 s) in hippocampal slices results in a biphasic response of NAD(P)H fluorescence indicating a transient oxidation followed by a prolonged reduction. The response is accompanied by a transient tissue PO(2) decrease indicating enhanced oxygen utilization. The activation of mitochondrial metabolism and/or glycolysis may contribute to the secondary NAD(P)H peak. We investigated whether extracellular lactate uptake via monocarboxylate transporters (MCTs) contributes to the generation of the NAD(P)H response during neuronal activation. We measured the effect of lactate uptake inhibition [using the MCT inhibitor alpha-cyano-4-hydroxycinnamate (4-CIN)] on the NAD(P)H biphasic response, tissue PO(2) response, and field excitatory post-synaptic potential in hippocampal slices during synaptic stimulation in area CA1 (stratum radiatum). The application of 4-CIN (150-250 micromol/L) significantly decreased the reduction phase of the NAD(P)H response. When slices were supplemented with 20 mmol/L lactate in 150-250 micromol/L 4-CIN, the secondary NAD(P)H peak was restored; whereas 20 mmol/L pyruvate supplementation did not produce a recovery. Similarly, the tissue PO(2) response was decreased by MCT inhibition; 20 mmol/L lactate restored this response to control levels at all 4-CIN concentrations. These results indicate that lactate uptake via MCTs contributes significantly to energy metabolism in brain tissue and to the generation of the delayed NAD(P)H peak after synaptic stimulation.
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Affiliation(s)
- Francesca Galeffi
- Neurosurgery, Neurobiology, Duke University Medical Center Research and Surgery Services, Durham VAMC, North Carolina 27710, USA.
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30
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Baker KD, Edwards TM. d-Lactate inhibition of memory in a single trial discrimination avoidance task in the young chick. Neurobiol Learn Mem 2007; 88:269-76. [PMID: 17692538 DOI: 10.1016/j.nlm.2007.06.004] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2007] [Revised: 06/17/2007] [Accepted: 06/19/2007] [Indexed: 11/26/2022]
Abstract
L-Lactate is a metabolite possibly able to meet some neuronal energy demands. However, a clear role for L-lactate in behaviour remains elusive. Administration of the inactive isomer D-lactate (1.75 mM; ic), immediately post-training, resulted in a persistent retention loss from 40 min post-training when used in conjuction with a single trial discrimination avoidance task designed for the young chick. Furthermore, 1mM noradrenaline (ic) administered 20 min post-training overcame the retention loss induced by D-lactate. Although not directly demonstrated in the current study, it is plausible that D-lactate inhibited memory processing by competing with L-lactate for uptake into neurons. The time of onset of the retention loss induced by D-lactate is in accord with findings where the action of noradrenaline is inhibited. The successful challenge of D-lactate inhibition by a high concentration of noradrenaline may suggest a relationship by some unidentified mechanism.
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Affiliation(s)
- K D Baker
- School of Psychology, Psychiatry and Psychological Medicine, Monash University, 3800 Vic., Australia
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31
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Wang X, Takata T, Sakurai T, Yokono K. Different effects of monocarboxylates on neuronal survival and beta-amyloid toxicity. Eur J Neurosci 2007; 26:2142-50. [PMID: 17908170 DOI: 10.1111/j.1460-9568.2007.05853.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Glucose is a principal metabolic fuel in the central nervous system, but, when glucose is unavailable, the brain can utilize alternative metabolic substrates such as monocarboxylates to sustain brain functions. This study examined whether the replacement of glucose with monocarboxylates (particularly pyruvate and lactate) had an equivalent effect of glucose on neuronal survival in rat hippocampal organotypic slice cultures, or ameliorate the neurotoxicity induced by amyloid beta-peptide (Abeta). The possible mechanism was also explored. We found that pyruvate and lactate alone increased cell death in the hippocampal slice cultures at 24 and 48 h. Supplementation of glucose-containing culture media and Abeta-treated culture media with pyruvate, but not lactate, attenuated cell death as strong as with trolox, known as a reactive oxygen species scavenger, and niacinamide, an NAD(+) precursor, and this protective effect was reversed by alpha-cyano-4-hydroxycinnamic acid. Pyruvate significantly increased the aconitase activity and the NAD(+) levels in the hippocampal slices in the presence of Abeta, but did not maintain the ATP levels. Our results indicate that pyruvate and lactate alone cannot replace glucose as an alternative energy source to preserve the neuronal viability in the hippocampal slice cultures. Pyruvate, in the presence of glucose, improves neuronal survival in the hippocampal slice cultures and also protects neurons against Abeta-induced cell death in which mitochondrial NAD(P) redox status may play a central role.
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Affiliation(s)
- Xiaonan Wang
- Department of Internal and Geriatric Medicine, Kobe University Graduate School of Medicine, Kobe 650-0017, Japan
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32
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Bergersen LH. Is lactate food for neurons? Comparison of monocarboxylate transporter subtypes in brain and muscle. Neuroscience 2007; 145:11-9. [PMID: 17218064 DOI: 10.1016/j.neuroscience.2006.11.062] [Citation(s) in RCA: 168] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2006] [Revised: 11/08/2006] [Accepted: 11/21/2006] [Indexed: 10/23/2022]
Abstract
Intercellular monocarboxylate transport is important, particularly in tissues with high energy demands, such as brain and muscle. In skeletal muscle, it is well established that glycolytic fast twitch muscle fibers produce lactate, which is transported out of the cell through the monocarboxylate transporter (MCT) 4. Lactate is then taken up and oxidized by the oxidative slow twitch muscle fibers, which express MCT1. In the brain it is still questioned whether lactate produced in astrocytes is taken up and oxidized by neurons upon activation. Several studies have reported that astrocytes express MCT4, whereas neurons express MCT2. By comparing the localizations of MCTs in oxidative and glycolytic compartments I here give support to the idea that there is a lactate shuttle in the brain similar to that in muscle. This conclusion is based on studies in rodents using high resolution immunocytochemical methods at the light and electron microscopical levels.
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Affiliation(s)
- L H Bergersen
- Centre for Molecular Biology and Neuroscience, and Department of Anatomy, IBM, University of Oslo, Domus Medica, Room 1293, Songsvannsveien 9, POB 1105 Blindern, N-0317 Oslo, Norway.
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Abstract
The brain contains glycogen but at low concentration compared with liver and muscle. In the adult brain, glycogen is found predominantly in astrocytes. Astrocyte glycogen content is modulated by a number of factors including some neurotransmitters and ambient glucose concentration. Compelling evidence indicates that astrocyte glycogen breaks down during hypoglycemia to lactate that is transferred to adjacent neurons or axons where it is used aerobically as fuel. In the case of CNS white matter, this source of energy can extend axon function for 20 min or longer. Likewise, during periods of intense neural activity when energy demand exceeds glucose supply, astrocyte glycogen is degraded to lactate, a portion of which is transferred to axons for fuel. Astrocyte glycogen, therefore, offers some protection against hypoglycemic neural injury and ensures that neurons and axons can maintain their function during very intense periods of activation. These emerging principles about the roles of astrocyte glycogen contradict the long held belief that this metabolic pool has little or no functional significance.
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Affiliation(s)
- Angus M Brown
- School of Biomedical Sciences, Queens Medical Centre, University of Nottingham, Nottingham, NG7 2UH, United Kingdom
- Department of Neurology, University of Washington, Seattle, Washington, USA
| | - Bruce R Ransom
- School of Biomedical Sciences, Queens Medical Centre, University of Nottingham, Nottingham, NG7 2UH, United Kingdom
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Bak LK, Schousboe A, Sonnewald U, Waagepetersen HS. Glucose is necessary to maintain neurotransmitter homeostasis during synaptic activity in cultured glutamatergic neurons. J Cereb Blood Flow Metab 2006; 26:1285-97. [PMID: 16467783 DOI: 10.1038/sj.jcbfm.9600281] [Citation(s) in RCA: 132] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Glucose is the primary energy substrate for the adult mammalian brain. However, lactate produced within the brain might be able to serve this purpose in neurons. In the present study, the relative significance of glucose and lactate as substrates to maintain neurotransmitter homeostasis was investigated. Cultured cerebellar (primarily glutamatergic) neurons were superfused in medium containing [U-13C]glucose (2.5 mmol/L) and lactate (1 or 5 mmol/L) or glucose (2.5 mmol/L) and [U-13C]lactate (1 mmol/L), and exposed to pulses of N-methyl-D-aspartate (300 micromol/L), leading to synaptic activity including vesicular release. The incorporation of 13C label into intracellular lactate, alanine, succinate, glutamate, and aspartate was determined by mass spectrometry. The metabolism of [U-13C]lactate under non-depolarizing conditions was high compared with that of [U-13C]glucose; however, it decreased significantly during induced depolarization. In contrast, at both concentrations of extracellular lactate, the metabolism of [U-13C]glucose was increased during neuronal depolarization. The role of glucose and lactate as energy substrates during vesicular release as well as transporter-mediated influx and efflux of glutamate was examined using preloaded D-[3H]aspartate as a glutamate tracer and DL-threo-beta-benzyloxyaspartate to inhibit glutamate transporters. The results suggest that glucose is essential to prevent depolarization-induced reversal of the transporter (efflux), whereas vesicular release was unaffected by the choice of substrate. In conclusion, the present study shows that glucose is a necessary substrate to maintain neurotransmitter homeostasis during synaptic activity and that synaptic activity does not induce an upregulation of lactate metabolism in glutamatergic neurons.
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Affiliation(s)
- Lasse K Bak
- Department of Pharmacology and Pharmacotherapy, Danish University of Pharmaceutical Sciences, Copenhagen, Denmark
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35
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Tarasenko AS, Linetska MV, Storchak LG, Himmelreich NH. Effectiveness of extracellular lactate/pyruvate for sustaining synaptic vesicle proton gradient generation and vesicular accumulation of GABA. J Neurochem 2006; 99:787-96. [PMID: 16836653 DOI: 10.1111/j.1471-4159.2006.04109.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The effects of extracellular monocarboxylates pyruvate and lactate on membrane potentials, acidification and neurotransmitter filling of synaptic vesicles were investigated in experiments with rat brain synaptosomes using [(3)H]GABA and fluorescent dyes, potential-sensitive rhodamine 6G and pH-sensitive acridine orange. In experiments investigating accumulation of acridine orange in synaptic vesicles within the synaptosomes, monocarboxylates, similarly to glucose, ensured generation of the vesicle proton gradient by available and recycled vesicles, and pyruvate demonstrated the highest efficacy. An increase in the level of proton gradient correlated with enhanced accumulation of [(3)H]GABA in synaptic vesicles and resulted in enlarged exocytosis and attenuated the transporter-mediated [(3)H]GABA release. Pyruvate added to glucose-contained medium caused more active binding of rhodamine 6G by synaptosomes that reflected mitochondrial membrane hyperpolarization, and this intensification of nerve terminal energy metabolism resulted in an increase in total ATP content by approximately 25%. Pyruvate also prolonged the state of metabolic competence of nerve terminal preparations, keeping the mitochondrial potential and synaptic vesicle proton gradient at steady levels over a long period of time. Thus, besides glucose, the extracellular monocarboxylates pyruvate and lactate can provide sufficient support of energy-dependent processes in isolated nerve terminals, allowing effective functioning of neurotransmitter release and reuptake systems.
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Affiliation(s)
- A S Tarasenko
- Department of Neurochemistry, Palladin Institute of Biochemistry, National Academy of Sciences of Ukraine, Kiev, Ukraine
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36
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Homola A, Zoremba N, Slais K, Kuhlen R, Syková E. Changes in diffusion parameters, energy-related metabolites and glutamate in the rat cortex after transient hypoxia/ischemia. Neurosci Lett 2006; 404:137-42. [PMID: 16759801 DOI: 10.1016/j.neulet.2006.05.028] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2006] [Revised: 05/12/2006] [Accepted: 05/14/2006] [Indexed: 11/29/2022]
Abstract
It has been shown that global anoxia leads to dramatic changes in the diffusion properties of the extracellular space (ECS). In this study, we investigated how changes in ECS volume and geometry in the rat somatosensory cortex during and after transient hypoxia/ischemia correlate with extracellular concentrations of energy-related metabolites and glutamate. Adult male Wistar rats (n = 12) were anesthetized and subjected to hypoxia/ischemia for 30 min (ventilation with 10% oxygen and unilateral carotid artery occlusion). The ECS diffusion parameters, volume fraction and tortuosity, were determined from concentration-time profiles of tetramethylammonium applied by iontophoresis. Concentrations of lactate, glucose, pyruvate and glutamate in the extracellular fluid (ECF) were monitored by microdialysis (n = 9). During hypoxia/ischemia, the ECS volume fraction decreased from initial values of 0.19 +/- 0.03 (mean +/- S.E.M.) to 0.07 +/- 0.01 and tortuosity increased from 1.57 +/- 0.01 to 1.88 +/- 0.03. During reperfusion the volume fraction returned to control values within 20 min and then increased to 0.23 +/- 0.01, while tortuosity only returned to original values (1.53 +/- 0.06). The concentrations of lactate and glutamate, and the lactate/pyruvate ratio, substantially increased during hypoxia/ischemia, followed by continuous recovery during reperfusion. The glucose concentration decreased rapidly during hypoxia/ischemia with a subsequent return to control values within 20 min of reperfusion. We conclude that transient hypoxia/ischemia causes similar changes in ECS diffusion parameters as does global anoxia and that the time course of the reduction in ECS volume fraction correlates with the increase of extracellular concentration of glutamate. The decrease in the ECS volume fraction can therefore contribute to an increased accumulation of toxic metabolites, which may aggravate functional deficits and lead to damage of the central nervous system (CNS).
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Affiliation(s)
- Ales Homola
- Department of Neuroscience and Centre for Cell Therapy and Tissue Repair, 2nd Medical Faculty, Prague, Czech Republic
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Leegsma-Vogt G, Venema K, Brouwer N, Gramsbergen JB, Copray S, Korf J. Quantitative on-line monitoring of cellular glucose and lactate metabolism in vitro with slow perfusion. Anal Chem 2006; 76:5431-5. [PMID: 15362903 DOI: 10.1021/ac040057u] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
An on-line in vitro perfusion technique is described that allows the continuous quantification of cellular glucose metabolism in vitro. Using biosensor technology, we measure glucose and lactate metabolism at a minute-to-minute time resolution for periods up to several days. The application of our perfusion-detection technique for in vitro monitoring is demonstrated in a wide variety of cells, including primary neuronal and astroglia cultures, yeast cells, and human lymphocytes. The method shows that variations in oxygen delivery or exposure to a noncompetitive pseudosubstrate (here 2-deoxyglucose) affects normal glucose metabolism. The innovative advantage of the present system is that, in contrast to other devices including a recently described system, metabolism per cell can be quantified. The potential of in vitro on-line monitoring is discussed for application in studying normal and abnormal metabolism, toxic and nontoxic drug effects, and human tissue biopsies.
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Affiliation(s)
- Gea Leegsma-Vogt
- Department of Psychiatry, Section Biological Psychiatry, University of Groningen, Groningen, The Netherlands
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Becker HM, Hirnet D, Fecher-Trost C, Sültemeyer D, Deitmer JW. Transport Activity of MCT1 Expressed in Xenopus Oocytes Is Increased by Interaction with Carbonic Anhydrase. J Biol Chem 2005; 280:39882-9. [PMID: 16174776 DOI: 10.1074/jbc.m503081200] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Injection of carbonic anhydrase isoform II (CA) into Xenopus frog oocytes increased the rate of H+ flux via the rat monocarboxylate transporter isoform 1 (MCT1) expressed in the oocytes. MCT1 activity was assessed by changes of intracellular H+ concentration measured by pH-selective microelectrodes during application of lactate. CA-induced augmentation of the rate of H+ flux mediated by MCT1 was not inhibited by ethoxyzolamide (10 microM) and did not depend on the presence of added CO2/HCO3- but was suppressed by injection of an antibody against CA. Deleting the C terminus of the MCT1 greatly reduced its transport rate and removed transport facilitation by CA. Injected CA accelerated the CO2/HCO3(-)-induced acidification severalfold, which was blocked by ethoxyzolamide and was independent of MCT1 expression. Mass spectrometry confirmed activity of CA as injected into the frog oocytes. With pulldown assays we demonstrated a specific binding of CA to MCT1 that was not attributed to the C terminus of MCT1. Our results suggest that CA enhances MCT1 transport activity, independent of its enzymatic reaction center, presumably by binding to MCT1.
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Affiliation(s)
- Holger M Becker
- Abteilungen, Allgemeine Zoologie, Fachbereich Biologie, Technische Universität Kaiserslautern, D-67653 Kaiserslautern, Germany
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Tekkök SB, Brown AM, Westenbroek R, Pellerin L, Ransom BR. Transfer of glycogen-derived lactate from astrocytes to axons via specific monocarboxylate transporters supports mouse optic nerve activity. J Neurosci Res 2005; 81:644-52. [PMID: 16015619 DOI: 10.1002/jnr.20573] [Citation(s) in RCA: 170] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
It is hypothesized that L-lactate derived from astrocyte glycogen sustains axon excitability in mouse optic nerve (MON). This theory was tested by using a competitive antagonist of L-lactate transport and immunocytochemistry to determine whether transport proteins are appropriately distributed in adult MON. L-lactate sustained the compound action potential (CAP), indicating that exogenous L-lactate was an effective energy substrate. During 60 min of aglycemia, the CAP persisted for 30 min, surviving on a glycogen-derived substrate (probably lactate), before failing. After failing, the CAP could be partially rescued by restoring 10 mM glucose or 20 mM L-lactate. Aglycemia in the presence of 20 mM D-lactate, a metabolically inert but transportable monocarboxylate, resulted in accelerated CAP decline compared with aglycemia alone, suggesting that D-lactate blocked the axonal uptake of glycogen-derived L-lactate, speeding the onset of energy failure and loss of the CAP. The CAP was maintained for up to 2 hr when exposed to 20% of normal bath glucose (i.e., 2 mM). To test whether glycogen-derived L-lactate "supplemented" available glucose (2 mM) in supporting metabolism, L-lactate uptake into axons was reduced by the competitive inhibitor D-lactate. Indeed, in the presence of 20 mM D-lactate, the CAP was lost more rapidly in MONs bathed in 2 mM glucose artificial cerebrospinal fluid. Immunocytochemical staining demonstrated cell-specific expression of monocarboxylate transporter (MCT) subtypes, localizing MCT2 predominantly to axons and MCT1 predominantly to astrocytes, supporting the idea that L-lactate is released from astrocytes and taken up by axons as an energy source for sustaining axon excitability.
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Affiliation(s)
- Selva Baltan Tekkök
- Department of Neurology, University of Washington School of Medicine, Seattle, Washington, USA
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Lin T, Koustova E, Chen H, Rhee PM, Kirkpatrick J, Alam HB. Energy Substrate-Supplemented Resuscitation Affects Brain Monocarboxylate Transporter Levels and Gliosis in a Rat Model of Hemorrhagic Shock. ACTA ACUST UNITED AC 2005; 59:1191-202; discussion 1202. [PMID: 16385299 DOI: 10.1097/01.ta.0000188646.86995.9d] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
BACKGROUND Monocarboxylate (MC)-supplemented resuscitation has been shown to attenuate cellular injury after hemorrhagic shock. However, little is known about its effect on the central nervous system. The brain can use MCs such as lactate, pyruvate, and beta-hydroxybutyrate as energy substrates. The transit of MCs into the central nervous system is facilitated by the monocarboxylate transporters (MCTs), and their blockage can exacerbate neuronal damage. We examined the expression of MCT1 and markers specific for activation of astroglia and microglia in the brains of rats subjected to hemorrhagic shock and resuscitation. The hypothesis was that resuscitation with MC-based fluids would be accompanied by MCT1 up-regulation and glial response. METHODS Rats (n = 30) were subjected to volume-controlled hemorrhage. Test groups included: sham, no resuscitation, resuscitation with normal saline, resuscitation with racemic lactated Ringer's solution, resuscitation with pyruvate Ringer's solution, and resuscitation with beta-hydroxybutyrate-containing ketone Ringer's solution. Plasma levels of MC were measured serially. The brains were investigated using GFAP, CD11b, CD43, MCT1, and GLUT1 immunohistochemistry. RESULTS Rats resuscitated with MC-containing fluids had increased levels of MCT1 in brain endothelial cells and neuropil compared with sham rats. Enhanced staining was localized to the choroid plexus, astrocytic end feet, and white matter structures. None of the resuscitation treatment induced astrocytic hyperplasia, and pyruvate Ringer's solution and ketone Ringer's solution resuscitation led to hypertrophy of astrocytes. CONCLUSION In hemorrhagic shock, resuscitation with MC-based fluids increased brain MCT1 level and led to activation of astrocytes. Enhanced MC trafficking could be an essential route for energy supply to neurons under adverse circulatory conditions.
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Affiliation(s)
- Tom Lin
- Department of Surgery, Uniformed Services University of the Health Sciences, Bethesda, Maryland, USA
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Pellerin L. How astrocytes feed hungry neurons. Mol Neurobiol 2005; 32:59-72. [PMID: 16077184 DOI: 10.1385/mn:32:1:059] [Citation(s) in RCA: 99] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2004] [Accepted: 12/17/2004] [Indexed: 11/11/2022]
Abstract
For years glucose was thought to constitute the sole energy substrate for neurons; it was believed to be directly provided to neurons via the extracellular space by the cerebral circulation. It was recently proposed that in addition to glucose, neurons might rely on lactate to sustain their activity. Therefore, it was demonstrated that lactate is a preferred oxidative substrate for neurons not only in vitro but also in vivo. Moreover, the presence of specific monocarboxylate transporters on neurons as well as on astrocytes is consistent with the hypothesis of a transfer of lactate from astrocytes to neurons. Evidence has been provided for a mechanism whereby astrocytes respond to glutamatergic activity by enhancing their glycolytic activity, resulting in increased lactate release. This is accomplished via the uptake of glutamate by glial glutamate transporters, leading to activation of the Na+/K+ ATPase and a stimulation of astrocytic glycolysis. Several recent observations obtained both in vitro and in vivo with different approaches have reinforced this view of brain energetics. Such an understanding might be critically important, not only because it forms the basis of some classical functional brain imaging techniques but also because several neurodegenerative diseases exhibit diverse alterations in energy metabolism.
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Affiliation(s)
- Luc Pellerin
- Département de Physiologie, Université de Lausanne, Switzerland.
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Ogawa M, Watabe H, Teramoto N, Miyake Y, Hayashi T, Iida H, Murata T, Magata Y. Understanding of cerebral energy metabolism by dynamic living brain slice imaging system with [18F]FDG. Neurosci Res 2005; 52:357-61. [PMID: 15904986 DOI: 10.1016/j.neures.2005.04.007] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2005] [Revised: 04/11/2005] [Accepted: 04/18/2005] [Indexed: 11/27/2022]
Abstract
Recently, lactate has been receiving great attention as an energy substrate in the brain. In this study, the role of lactate was evaluated by "bioradiography" system with 2-deoxy-2-[(18)F]fluoro-d-glucose ([(18)F]FDG), which is a positron emitting radiotracer for glucose uptake quantification. "Bioradiography" is the dynamic living tissue slice imaging system for positron-emitter labeled compounds. We investigated the brain energy metabolism under resting state and neural activated conditions induced by KCl addition. The monocarboxylate transporter inhibitor, alpha-cyano-4-hydroxycinnamate (4-CIN), had no effect on [(18)F]FDG uptake rate in rat brain slices before KCl addition. On the other hand, addition of 4-CIN induced larger [(18)F]FDG uptake rates under the activated condition in comparison with the control condition. Because neurons cannot utilize lactate under the 4-CIN loaded conditions, this indicates that activated neurons consume lactate as an energy substrate. The lactate concentration in the incubation medium was increased with KCl treatment in both groups and the extent was slightly greater in 4-CIN group. These results suggested that: (1) the brain mainly uses glucose, not lactate, as an energy substrate in resting state; (2) when neuron is stimulated, excess amounts of lactate might be produced in astrocytes and the lactate is mobilized as an energy substrate.
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Affiliation(s)
- Mikako Ogawa
- Photon Medical Research Center, Hamamatsu University School of Medicine, Laboratory of Genome Bio-Photonics, 1-20-1 Handayama, Hamamatsu 431-3192, Japan
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43
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Pierre K, Pellerin L. Monocarboxylate transporters in the central nervous system: distribution, regulation and function. J Neurochem 2005; 94:1-14. [PMID: 15953344 DOI: 10.1111/j.1471-4159.2005.03168.x] [Citation(s) in RCA: 472] [Impact Index Per Article: 24.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Monocarboxylate transporters (MCTs) are proton-linked membrane carriers involved in the transport of monocarboxylates such as lactate, pyruvate, as well as ketone bodies. They belong to a larger family of transporters composed of 14 members in mammals based on sequence homologies. MCTs are found in various tissues including the brain where three isoforms, MCT1, MCT2 and MCT4, have been described. Each of these isoforms exhibits a distinct regional and cellular distribution in rodent brain. At the cellular level, MCT1 is expressed by endothelial cells of microvessels, by ependymocytes as well as by astrocytes. MCT4 expression appears to be specific for astrocytes. By contrast, the predominant neuronal monocarboxylate transporter is MCT2. Interestingly, part of MCT2 immunoreactivity is located at postsynaptic sites, suggesting a particular role of monocarboxylates and their transporters in synaptic transmission. In addition to variation in expression during development and upon nutritional modifications, new data indicate that MCT expression is regulated at the translational level by neurotransmitters. Understanding how transport of monocarboxylates is regulated could be of particular importance not only for neuroenergetics but also for areas such as functional brain imaging, regulation of food intake and glucose homeostasis, or for central nervous system disorders such as ischaemia and neurodegenerative diseases.
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Affiliation(s)
- Karin Pierre
- Département de Physiologie, Université de Lausanne, Switzerland
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Abstract
Astrocytes are multifunctional cells that interact with neurons and other astrocytes in signaling and metabolic functions, and their resistance to pathophysiological conditions can help restrict loss of tissue after an ischemic event provided adequate nutrients are supplied to support their requirements. Astrocytes have substantial oxidative capacity and mechanisms to upregulate glycolytic capability when respiration is impaired. An astrocytic enzyme that synthesizes a powerful activator of glycolysis is not present in neurons, endowing astrocytes with the ability to sustain ATP production under restrictive conditions. The monocarboxylic acid transporter (MCT) isoforms predominating in astrocytes are optimized to facilitate very large increases in lactate flux as lactate concentration increases within (1-3 mM) and above (>3 mM) the normal range. In sharp contrast, the major neuronal MCT serves as a barrier to increased transmembrane transport as lactate rises above 1 mM, restricting both entry and efflux. Lactate can serve as fuel during recovery from ischemia but direct evidence that lactate is oxidized by neurons (vs. astrocytes) to maintain synaptic function is lacking. Astrocytes have critical roles in regulation of ionic homeostasis and control of extracellular glutamate levels, and spreading depression associated with ischemia places high demands on energy supplies in astrocytes and contributes to metabolic exhaustion and demise. Disruption of Ca2+ homeostasis, generation of oxygen free radicals and nitric oxide, and mitochondrial depolarization contribute to astrocyte death during and after a metabolic insult. Novel pharmaceutical agents targeted to astrocytes and hyperoxic therapy that restores penumbral oxygen level during energy failure might improve postischemic outcome.
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Affiliation(s)
- Gerald A Dienel
- Department of Neurology, University of Arkansas for Medical Sciences, Little Rock, Arkansas
| | - Leif Hertz
- College of Basic Medical Sciences, China Medical University, Shenyang, People's Republic of China
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Wood JPM, Chidlow G, Graham M, Osborne NN. Energy substrate requirements for survival of rat retinal cells in culture: the importance of glucose and monocarboxylates. J Neurochem 2005; 93:686-97. [PMID: 15836627 DOI: 10.1111/j.1471-4159.2005.03059.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The process of metabolic coupling has been described as a means of providing additional fuel for neurons during periods of intense activity. This process has been suggested to occur in the mammalian retina, but whether retinal neurons can metabolise glial-derived monocarboxylates remains uncertain. The present study therefore sought to define the preferred energy substrates for maintenance of different retinal cells in culture, in order to clarify whether metabolic coupling can potentially occur in this tissue. All cells in rat retinal cultures were detrimentally affected by glucose deprivation. The effect on some neurons, however, could be partially reversed by 5 mm pyruvate or lactate. Furthermore, the glycolytic inhibitor, iodoacetic acid, caused a dose-dependent loss of all retinal cells in culture, whereas the mitochondrial inhibitor, 2,4-dinitrophenol, only led to a decrease in the number of neurons. Finally, inhibition of transporters for glucose or monocarboxylates caused the respective loss of glia or neurons from cultures. These data together demonstrate that, although cells do preferentially metabolise glucose, monocarboxylates such as lactate or pyruvate do play an important role in neuronal maintenance. These data therefore give partial support to the notion that metabolic coupling may occur in the retina.
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Affiliation(s)
- John P M Wood
- Nuffield Laboratory of Ophthalmology, University of Oxford, Oxford, UK.
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Bliss TM, Ip M, Cheng E, Minami M, Pellerin L, Magistretti P, Sapolsky RM. Dual-gene, dual-cell type therapy against an excitotoxic insult by bolstering neuroenergetics. J Neurosci 2005; 24:6202-8. [PMID: 15240812 PMCID: PMC6729663 DOI: 10.1523/jneurosci.0805-04.2004] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Increasing evidence suggests that glutamate activates the generation of lactate from glucose in astrocytes; this lactate is shuttled to neurons that use it as a preferential energy source. We explore this multicellular "lactate shuttle" with a novel dual-cell, dual-gene therapy approach and determine the neuroprotective potential of enhancing this shuttle. Viral vector-driven overexpression of a glucose transporter in glia enhanced glucose uptake, lactate efflux, and the glial capacity to protect neurons from excitotoxicity. In parallel, overexpression of a lactate transporter in neurons enhanced lactate uptake and neuronal resistance to excitotoxicity. Finally, overexpression of both transgenes in the respective cell types provided more protection than either therapy alone, demonstrating that a dual-cell, dual-gene therapy approach gives greater neuroprotection than the conventional single-cell, single-gene strategy.
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Affiliation(s)
- Tonya M Bliss
- Department of Biological Sciences, Stanford University, Stanford, California 94305-5020, USA
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Gramsbergen JB, Skjøth-Rasmussen J, Rasmussen C, Lambertsen KL. On-line monitoring of striatum glucose and lactate in the endothelin-1 rat model of transient focal cerebral ischemia using microdialysis and flow-injection analysis with biosensors. J Neurosci Methods 2004; 140:93-101. [PMID: 15589339 DOI: 10.1016/j.jneumeth.2004.03.027] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2003] [Accepted: 03/29/2004] [Indexed: 11/15/2022]
Abstract
In vivo studies on cerebral glucose and lactate metabolism following a brain insult require fast and sensitive monitoring techniques. Here we report on-line monitoring of ischemic events and metabolic changes following reperfusion in striatum of freely moving rats subjected to endothelin-1 (60-240 pmol) induced, transient focal cerebral ischemia using slow microdialysis (0.5 microl/min), fast sampling (every minute) and flow-injection analysis with biosensors for glucose and lactate. The high-time resolution provides detailed information on lactate rise times and duration of low glucose. In rats, developing large striatal lesions, lactate increased from 1.0 +/- 0.1 to 4.2 +/- 0.7 mM within 37 +/- 1 min, whereas glucose dropped from 0.3 +/- 0.1 mM to below detection levels (<0.05 mM) for a period of 80 +/- 18 min. The lactate increase measured over a 2-h period after endothelin-1 infusion was highly correlated with striatal infarct size. In some rats oscillatory changes are observed which cannot be detected in traditional assays. The here-described monitoring technique applied in a clinically relevant rat model is a sensitive tool to study post-ischemic energy metabolism, effects of therapeutic interventions and its relationship with histological outcome.
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Affiliation(s)
- Jan Bert Gramsbergen
- Anatomy and Neurobiology, Institute of Medical Biology, University of Southern Denmark, Odense, Denmark.
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Reinert M, Schaller B, Widmer HR, Seiler R, Bullock R. Influence of oxygen therapy on glucose-lactate metabolism after diffuse brain injury. J Neurosurg 2004; 101:323-9. [PMID: 15309926 DOI: 10.3171/jns.2004.101.2.0323] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
OBJECT Severe traumatic brain injury (TBI) imposes a huge metabolic load on brain tissue, which can be summarized initially as a state of hypermetabolism and hyperglycolysis. In experiments O2 consumption has been shown to increase early after trauma, especially in the presence of high lactate levels and forced O2 availability. In recent clinical studies the effect of increasing O2 availability on brain metabolism has been analyzed. By their nature, however, clinical trauma models suffer from a heterogeneous injury distribution. The aim of this study was to analyze, in a standardized diffuse brain injury model, the effect of increasing the fraction of inspired O2 on brain glucose and lactate levels, and to compare this effect with the metabolism of the noninjured sham-operated brain. METHODS A diffuse severe TBI model developed by Foda and Maramarou, et al., in which a 420-g weight is dropped from a height of 2 m was used in this study. Forty-one male Wistar rats each weighing approximately 300 g were included. Anesthesized rats were monitored by placing a femoral arterial line for blood pressure and blood was drawn for a blood gas analysis. Two time periods were defined: Period A was defined as preinjury and Period B as postinjury. During Period B two levels of fraction of inspired oxygen (FiO2) were studied: air (FiO2 0.21) and oxygen (FiO2 1). Four groups were studied including sham-operated animals: air-air-sham (AAS); air-O2-sham (AOS); air-air-trauma (AAT); and air-O2-trauma (AOT). In six rats the effect of increasing the FiO2 on serum glucose and lactate was analyzed. During Period B lactate values in the brain determined using microdialysis were significantly lower (p < 0.05) in the AOT group than in the AAT group and glucose values in the brain determined using microdialysis were significantly higher (p < 0.04). No differences were demonstrated in the other groups. Increasing the FiO2 had no significant effect on the serum levels of glucose and lactate. CONCLUSIONS Increasing the FiO2 influences dialysate glucose and lactate levels in injured brain tissue. Using an FiO2 of 1 influences brain metabolism in such a way that lactate is significantly reduced and glucose significantly increased. No changes in dialysate glucose and lactate values were found in the noninjured brain.
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Affiliation(s)
- Michael Reinert
- Department of Neurological Surgery, University of Bern, Inselspital Bern, Switzerland.
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Abstract
The mammalian brain contains glycogen, which is located predominantly in astrocytes, but its function is unclear. A principal role for brain glycogen as an energy reserve, analogous to its role in the periphery, had been universally dismissed based on its relatively low concentration, an assumption apparently reinforced by the limited duration that the brain can function in the absence of glucose. However, during insulin-induced hypoglycaemia, where brain glucose availability is limited, glycogen content falls first in areas with the highest metabolic rate, suggesting that glycogen provides fuel to support brain function during pathological hypoglycaemia. General anaesthesia results in elevated brain glycogen suggesting quiescent neurones allow glycogen accumulation, and as long ago as the 1950s it was shown that brain glycogen accumulates during sleep, is mobilized upon waking, and that sleep deprivation results in region-specific decreases in brain glycogen, implying a supportive functional role for brain glycogen in the conscious, awake brain. Interest in brain glycogen has recently been re-awakened by the first continuous in vivo measurements using NMR spectroscopy, by the general acceptance of metabolic coupling between glia and neurones involving intercellular transfer of energy substrate, and by studies supporting a prominent physiological role for brain glycogen as a provider of supplemental energy substrate during periods of increased tissue energy demand, when ambient normoglycaemic glucose is unable to meet immediate energy requirements.
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Affiliation(s)
- Angus M Brown
- Department of Neurology, University of Washington School of Medicine, Seattle, Washington, USA.
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Pellerin L, Magistretti PJ. Neuroenergetics: calling upon astrocytes to satisfy hungry neurons. Neuroscientist 2004; 10:53-62. [PMID: 14987448 DOI: 10.1177/1073858403260159] [Citation(s) in RCA: 206] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Classical neuroenergetics states that glucose is the exclusive energy substrate of brain cells and its full oxidation provides all the necessary energy to support brain function. Recent data have revealed a more intricate picture in which astrocytes play a key role in supplying lactate as an additional energy substrate in register with glutamatergic activity.
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Affiliation(s)
- Luc Pellerin
- Institut de Physiologie, Université de Lausanne, Switzerland.
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