1
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Barros LF, Ruminot I, Sotelo-Hitschfeld T, Lerchundi R, Fernández-Moncada I. Metabolic Recruitment in Brain Tissue. Annu Rev Physiol 2023; 85:115-135. [PMID: 36270291 DOI: 10.1146/annurev-physiol-021422-091035] [Citation(s) in RCA: 17] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Information processing imposes urgent metabolic demands on neurons, which have negligible energy stores and restricted access to fuel. Here, we discuss metabolic recruitment, the tissue-level phenomenon whereby active neurons harvest resources from their surroundings. The primary event is the neuronal release of K+ that mirrors workload. Astrocytes sense K+ in exquisite fashion thanks to their unique coexpression of NBCe1 and α2β2 Na+/K+ ATPase, and within seconds switch to Crabtree metabolism, involving GLUT1, aerobic glycolysis, transient suppression of mitochondrial respiration, and lactate export. The lactate surge serves as a secondary recruiter by inhibiting glucose consumption in distant cells. Additional recruiters are glutamate, nitric oxide, and ammonium, which signal over different spatiotemporal domains. The net outcome of these events is that more glucose, lactate, and oxygen are made available. Metabolic recruitment works alongside neurovascular coupling and various averaging strategies to support the inordinate dynamic range of individual neurons.
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Affiliation(s)
- L F Barros
- Centro de Estudios Científicos (CECs), Valdivia, Chile; .,Facultad de Medicina y Ciencia, Universidad San Sebastián, Valdivia, Chile;
| | - I Ruminot
- Centro de Estudios Científicos (CECs), Valdivia, Chile; .,Facultad de Medicina y Ciencia, Universidad San Sebastián, Valdivia, Chile;
| | - T Sotelo-Hitschfeld
- Department of Neuronal Control of Metabolism, Max Planck Institute for Metabolism Research, Cologne, Germany
| | - R Lerchundi
- Commissariat à l'Energie Atomique et aux Energies Alternatives (CEA), MIRCen, Fontenay-aux-Roses, France
| | - I Fernández-Moncada
- NeuroCentre Magendie, INSERM U1215, University of Bordeaux, Bordeaux, France
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2
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Köhler S, Winkler U, Junge T, Lippmann K, Eilers J, Hirrlinger J. Gray and white matter astrocytes differ in basal metabolism but respond similarly to neuronal activity. Glia 2023; 71:229-244. [PMID: 36063073 DOI: 10.1002/glia.24268] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2022] [Revised: 07/12/2022] [Accepted: 08/22/2022] [Indexed: 11/10/2022]
Abstract
Astrocytes are a heterogeneous population of glial cells in the brain, which adapt their properties to the requirements of the local environment. Two major groups of astrocytes are protoplasmic astrocytes residing in gray matter as well as fibrous astrocytes of white matter. Here, we compared the energy metabolism of astrocytes in the cortex and corpus callosum as representative gray matter and white matter regions, in acute brain slices taking advantage of genetically encoded fluorescent nanosensors for the NADH/NAD+ redox ratio and for ATP. Astrocytes of the corpus callosum presented a more reduced basal NADH/NAD+ redox ratio, and a lower cytosolic concentration of ATP compared to cortical astrocytes. In cortical astrocytes, the neurotransmitter glutamate and increased extracellular concentrations of K+ , typical correlates of neuronal activity, induced a more reduced NADH/NAD+ redox ratio. While application of glutamate decreased [ATP], K+ as well as the combination of glutamate and K+ resulted in an increase of ATP levels. Strikingly, a very similar regulation of metabolism by K+ and glutamate was observed in astrocytes in the corpus callosum. Finally, strong intrinsic neuronal activity provoked by application of bicuculline and withdrawal of Mg2+ caused a shift of the NADH/NAD+ redox ratio to a more reduced state as well as a slight reduction of [ATP] in gray and white matter astrocytes. In summary, the metabolism of astrocytes in cortex and corpus callosum shows distinct basal properties, but qualitatively similar responses to neuronal activity, probably reflecting the different environment and requirements of these brain regions.
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Affiliation(s)
- Susanne Köhler
- Faculty of Medicine, Carl-Ludwig-Institute for Physiology, Leipzig University, Leipzig, Germany
| | - Ulrike Winkler
- Faculty of Medicine, Carl-Ludwig-Institute for Physiology, Leipzig University, Leipzig, Germany
| | - Tabea Junge
- Faculty of Medicine, Carl-Ludwig-Institute for Physiology, Leipzig University, Leipzig, Germany
| | - Kristina Lippmann
- Faculty of Medicine, Carl-Ludwig-Institute for Physiology, Leipzig University, Leipzig, Germany
| | - Jens Eilers
- Faculty of Medicine, Carl-Ludwig-Institute for Physiology, Leipzig University, Leipzig, Germany
| | - Johannes Hirrlinger
- Faculty of Medicine, Carl-Ludwig-Institute for Physiology, Leipzig University, Leipzig, Germany.,Department of Neurogenetics, Max-Planck-Institute for Multidisciplinary Sciences, Göttingen, Germany
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3
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Yao M, Hao Y, Wang T, Xie M, Li H, Feng J, Feng L, Ma D. A review of stress-induced hyperglycaemia in the context of acute ischaemic stroke: Definition, underlying mechanisms, and the status of insulin therapy. Front Neurol 2023; 14:1149671. [PMID: 37025208 PMCID: PMC10070880 DOI: 10.3389/fneur.2023.1149671] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2023] [Accepted: 02/21/2023] [Indexed: 04/08/2023] Open
Abstract
The transient elevation of blood glucose produced following acute ischaemic stroke (AIS) has been described as stress-induced hyperglycaemia (SIH). SIH is common even in patients with AIS who have no previous diagnosis of diabetes mellitus. Elevated blood glucose levels during admission and hospitalization are strongly associated with enlarged infarct size and adverse prognosis in AIS patients. However, insulin-intensive glucose control therapy defined by admission blood glucose for SIH has not achieved the desired results, and new treatment ideas are urgently required. First, we explore the various definitions of SIH in the context of AIS and their predictive value in adverse outcomes. Then, we briefly discuss the mechanisms by which SIH arises, describing the dual effects of elevated glucose levels on the central nervous system. Finally, although preclinical studies support lowering blood glucose levels using insulin, the clinical outcomes of intensive glucose control are not promising. We discuss the reasons for this phenomenon.
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Affiliation(s)
- Mengyue Yao
- Department of Neurology and Neuroscience Centre, The First Hospital of Jilin University, Changchun, Jilin, China
| | - Yulei Hao
- Department of Neurology and Neuroscience Centre, The First Hospital of Jilin University, Changchun, Jilin, China
| | - Tian Wang
- Department of Neurology and Neuroscience Centre, The First Hospital of Jilin University, Changchun, Jilin, China
| | - Meizhen Xie
- Department of Neurology and Neuroscience Centre, The First Hospital of Jilin University, Changchun, Jilin, China
| | - Hui Li
- Department of Neurology and Neuroscience Centre, The First Hospital of Jilin University, Changchun, Jilin, China
| | - Jiachun Feng
- Department of Neurology and Neuroscience Centre, The First Hospital of Jilin University, Changchun, Jilin, China
| | - Liangshu Feng
- Stroke Centre, Department of Neurology, The First Hospital of Jilin University, Changchun, Jilin, China
- Liangshu Feng
| | - Di Ma
- Department of Neurology and Neuroscience Centre, The First Hospital of Jilin University, Changchun, Jilin, China
- *Correspondence: Di Ma
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4
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Tan C, Li L, Han J, Xu K, Liu X. A new strategy for osteoarthritis therapy: Inhibition of glycolysis. Front Pharmacol 2022; 13:1057229. [PMID: 36438808 PMCID: PMC9685317 DOI: 10.3389/fphar.2022.1057229] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2022] [Accepted: 10/27/2022] [Indexed: 11/12/2022] Open
Abstract
Osteoarthritis (OA) is a common degenerative disease of the joints. It is primarily caused by age, obesity, mechanical damage, genetics, and other factors, leading to cartilage degradation, synovial inflammation, and subchondral sclerosis with osteophyte formation. Many recent studies have reported that glycolysis disorders are related lead to OA. There is a close relationship between glycolysis and OA. Because of their hypoxic environment, chondrocytes are highly dependent on glycolysis, their primary energy source for chondrocytes. Glycolysis plays a vital role in OA development. In this paper, we comprehensively summarized the abnormal expression of related glycolytic enzymes in OA, including Hexokinase 2 (HK2), Pyruvate kinase 2 (PKM2), Phosphofructokinase-2/fructose-2, 6-Bisphosphatase 3 (PFKFB3), lactate dehydrogenase A (LDHA), and discussed the potential application of glycolysis in treating OA. Finally, the natural products that can regulate the glycolytic pathway were summarized. Targeting glucose transporters and rate-limiting enzymes to glycolysis may play an essential role in treating OA.
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Affiliation(s)
| | | | | | - Kang Xu
- *Correspondence: Kang Xu, ; Xianqiong Liu,
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5
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San Martín A, Arce-Molina R, Aburto C, Baeza-Lehnert F, Barros LF, Contreras-Baeza Y, Pinilla A, Ruminot I, Rauseo D, Sandoval PY. Visualizing physiological parameters in cells and tissues using genetically encoded indicators for metabolites. Free Radic Biol Med 2022; 182:34-58. [PMID: 35183660 DOI: 10.1016/j.freeradbiomed.2022.02.012] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/10/2022] [Revised: 02/08/2022] [Accepted: 02/10/2022] [Indexed: 02/07/2023]
Abstract
The study of metabolism is undergoing a renaissance. Since the year 2002, over 50 genetically-encoded fluorescent indicators (GEFIs) have been introduced, capable of monitoring metabolites with high spatial/temporal resolution using fluorescence microscopy. Indicators are fusion proteins that change their fluorescence upon binding a specific metabolite. There are indicators for sugars, monocarboxylates, Krebs cycle intermediates, amino acids, cofactors, and energy nucleotides. They permit monitoring relative levels, concentrations, and fluxes in living systems. At a minimum they report relative levels and, in some cases, absolute concentrations may be obtained by performing ad hoc calibration protocols. Proper data collection, processing, and interpretation are critical to take full advantage of these new tools. This review offers a survey of the metabolic indicators that have been validated in mammalian systems. Minimally invasive, these indicators have been instrumental for the purposes of confirmation, rebuttal and discovery. We envision that this powerful technology will foster metabolic physiology.
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Affiliation(s)
- A San Martín
- Centro de Estudios Científicos (CECs), Valdivia, Chile.
| | - R Arce-Molina
- Centro de Estudios Científicos (CECs), Valdivia, Chile
| | - C Aburto
- Centro de Estudios Científicos (CECs), Valdivia, Chile; Universidad Austral de Chile, Valdivia, Chile
| | | | - L F Barros
- Centro de Estudios Científicos (CECs), Valdivia, Chile
| | - Y Contreras-Baeza
- Centro de Estudios Científicos (CECs), Valdivia, Chile; Universidad Austral de Chile, Valdivia, Chile
| | - A Pinilla
- Centro de Estudios Científicos (CECs), Valdivia, Chile; Universidad Austral de Chile, Valdivia, Chile
| | - I Ruminot
- Centro de Estudios Científicos (CECs), Valdivia, Chile
| | - D Rauseo
- Centro de Estudios Científicos (CECs), Valdivia, Chile; Universidad Austral de Chile, Valdivia, Chile
| | - P Y Sandoval
- Centro de Estudios Científicos (CECs), Valdivia, Chile
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6
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Horvat A, Muhič M, Smolič T, Begić E, Zorec R, Kreft M, Vardjan N. Ca 2+ as the prime trigger of aerobic glycolysis in astrocytes. Cell Calcium 2021; 95:102368. [PMID: 33621899 DOI: 10.1016/j.ceca.2021.102368] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2020] [Revised: 02/05/2021] [Accepted: 02/08/2021] [Indexed: 12/17/2022]
Abstract
Astroglial aerobic glycolysis, a process during which d-glucose is converted to l-lactate, a brain fuel and signal, is regulated by the plasmalemmal receptors, including adrenergic receptors (ARs) and purinergic receptors (PRs), modulating intracellular Ca2+ and cAMP signals. However, the extent to which the two signals regulate astroglial aerobic glycolysis is poorly understood. By using agonists to stimulate intracellular α1-/β-AR-mediated Ca2+/cAMP signals, β-AR-mediated cAMP and P2R-mediated Ca2+ signals and genetically encoded fluorescence resonance energy transfer-based glucose and lactate nanosensors in combination with real-time microscopy, we show that intracellular Ca2+, but not cAMP, initiates a robust increase in the concentration of intracellular free d-glucose ([glc]i) and l-lactate ([lac]i), both depending on extracellular d-glucose, suggesting Ca2+-triggered glucose uptake and aerobic glycolysis in astrocytes. When the glycogen shunt, a process of glycogen remodelling, was inhibited, the α1-/β-AR-mediated increases in [glc]i and [lac]i were reduced by ∼65 % and ∼30 %, respectively, indicating that at least ∼30 % of the utilization of d-glucose is linked to glycogen remodelling and aerobic glycolysis. Additional activation of β-AR/cAMP signals aided to α1-/β-AR-triggered [lac]i increase, whereas the [glc]i increase was unaltered. Taken together, an increase in intracellular Ca2+ is the prime mechanism of augmented aerobic glycolysis in astrocytes, while cAMP has only a moderate role. The results provide novel information on the signals regulating brain metabolism and open new avenues to explore whether astroglial Ca2+ signals are dysregulated and contribute to neuropathologies with impaired brain metabolism.
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Affiliation(s)
- Anemari Horvat
- Laboratory of Neuroendocrinology - Molecular Cell Physiology, Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia; Laboratory of Cell Engineering, Celica Biomedical, Ljubljana, Slovenia
| | - Marko Muhič
- Laboratory of Neuroendocrinology - Molecular Cell Physiology, Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia
| | - Tina Smolič
- Laboratory of Neuroendocrinology - Molecular Cell Physiology, Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia
| | - Ena Begić
- Laboratory of Neuroendocrinology - Molecular Cell Physiology, Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia
| | - Robert Zorec
- Laboratory of Neuroendocrinology - Molecular Cell Physiology, Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia; Laboratory of Cell Engineering, Celica Biomedical, Ljubljana, Slovenia
| | - Marko Kreft
- Laboratory of Neuroendocrinology - Molecular Cell Physiology, Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia; Laboratory of Cell Engineering, Celica Biomedical, Ljubljana, Slovenia; Department of Biology, Biotechnical Faculty, University of Ljubljana, Ljubljana, Slovenia
| | - Nina Vardjan
- Laboratory of Neuroendocrinology - Molecular Cell Physiology, Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia; Laboratory of Cell Engineering, Celica Biomedical, Ljubljana, Slovenia.
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7
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Pötzsch A, Zocher S, Bernas SN, Leiter O, Rünker AE, Kempermann G. L-lactate exerts a pro-proliferative effect on adult hippocampal precursor cells in vitro. iScience 2021; 24:102126. [PMID: 33659884 PMCID: PMC7895751 DOI: 10.1016/j.isci.2021.102126] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2019] [Revised: 06/05/2020] [Accepted: 01/27/2021] [Indexed: 12/20/2022] Open
Abstract
L-lactate has energetic and signaling properties, and its availability is modulated by activity-dependent stimuli, which also regulate adult hippocampal neurogenesis. Studying the effects of L-lactate on neural precursor cells (NPCs) in vitro, we found that L-lactate is pro-proliferative and that this effect is dependent on the active lactate transport by monocarboxylate transporters. Increased proliferation was not linked to amplified mitochondrial respiration. Instead, L-lactate deviated glucose metabolism to the pentose phosphate pathway, indicated by increased glucose-6-phosphate dehydrogenase activity while glycolysis decreased. Knockout of Hcar1 revealed that the pro-proliferative effect of L-lactate was not dependent on receptor activity although phosphorylation of ERK1/2 and Akt was increased following L-lactate treatment. Together, we show that availability of L-lactate is linked to the proliferative potential of NPCs and add evidence to the hypothesis that lactate influences cellular homeostatic processes in the adult brain, specifically in the context of adult hippocampal neurogenesis. L-lactate increases NPC proliferation in an MCT-dependent manner The pro-proliferative effect of L-lactate is independent of HCAR1 signaling L-lactate decreases glycolysis in favor of pentose phosphate pathway activity L-lactate treatment leads to a transient increase in Akt and ERK1/2 phosphorylation
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Affiliation(s)
- Alexandra Pötzsch
- German Center for Neurodegenerative Diseases (DZNE) Dresden, Dresden, Germany.,CRTD - Center for Regenerative Therapies Dresden, Technische Universität Dresden, Dresden, Germany
| | - Sara Zocher
- German Center for Neurodegenerative Diseases (DZNE) Dresden, Dresden, Germany.,CRTD - Center for Regenerative Therapies Dresden, Technische Universität Dresden, Dresden, Germany
| | - Stefanie N Bernas
- German Center for Neurodegenerative Diseases (DZNE) Dresden, Dresden, Germany.,CRTD - Center for Regenerative Therapies Dresden, Technische Universität Dresden, Dresden, Germany
| | - Odette Leiter
- CRTD - Center for Regenerative Therapies Dresden, Technische Universität Dresden, Dresden, Germany
| | - Annette E Rünker
- German Center for Neurodegenerative Diseases (DZNE) Dresden, Dresden, Germany.,CRTD - Center for Regenerative Therapies Dresden, Technische Universität Dresden, Dresden, Germany
| | - Gerd Kempermann
- German Center for Neurodegenerative Diseases (DZNE) Dresden, Dresden, Germany.,CRTD - Center for Regenerative Therapies Dresden, Technische Universität Dresden, Dresden, Germany
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8
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Köhler S, Schmidt H, Fülle P, Hirrlinger J, Winkler U. A Dual Nanosensor Approach to Determine the Cytosolic Concentration of ATP in Astrocytes. Front Cell Neurosci 2020; 14:565921. [PMID: 33192312 PMCID: PMC7530325 DOI: 10.3389/fncel.2020.565921] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2020] [Accepted: 08/26/2020] [Indexed: 11/17/2022] Open
Abstract
Adenosine triphosphate (ATP) is the central energy carrier of all cells and knowledge on the dynamics of the concentration of ATP ([ATP]) provides important insights into the energetic state of a cell. Several genetically encoded fluorescent nanosensors for ATP were developed, which allow following the cytosolic [ATP] at high spatial and temporal resolution using fluorescence microscopy. However, to calibrate the fluorescent signal to [ATP] has remained challenging. To estimate basal cytosolic [ATP] ([ATP]0) in astrocytes, we here took advantage of two ATP nanosensors of the ATeam-family (ATeam1.03; ATeam1.03YEMK) with different affinities for ATP. Altering [ATP] by external stimuli resulted in characteristic pairs of signal changes of both nanosensors, which depend on [ATP]0. Using this dual nanosensor strategy and epifluorescence microscopy, [ATP]0 was estimated to be around 1.5 mM in primary cultures of cortical astrocytes from mice. Furthermore, in astrocytes in acutely isolated cortical slices from mice expressing both nanosensors after stereotactic injection of AAV-vectors, 2-photon microscopy revealed [ATP]0 of 0.7 mM to 1.3 mM. Finally, the change in [ATP] induced in the cytosol of cultured cortical astrocytes by application of azide, glutamate, and an increased extracellular concentration of K+ were calculated as −0.50 mM, −0.16 mM, and 0.07 mM, respectively. In summary, the dual nanosensor approach adds another option for determining the concentration of [ATP] to the increasing toolbox of fluorescent nanosensors for metabolites. This approach can also be applied to other metabolites when two sensors with different binding properties are available.
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Affiliation(s)
- Susanne Köhler
- Carl-Ludwig-Institute for Physiology, Faculty of Medicine, University Leipzig, Leipzig, Germany
| | - Hartmut Schmidt
- Carl-Ludwig-Institute for Physiology, Faculty of Medicine, University Leipzig, Leipzig, Germany
| | - Paula Fülle
- Carl-Ludwig-Institute for Physiology, Faculty of Medicine, University Leipzig, Leipzig, Germany.,Wilhelm-Ostwald-Schule, Gymnasium der Stadt Leipzig, Leipzig, Germany
| | - Johannes Hirrlinger
- Carl-Ludwig-Institute for Physiology, Faculty of Medicine, University Leipzig, Leipzig, Germany.,Department of Neurogenetics, Max-Planck-Institute for Experimental Medicine, Göttingen, Germany
| | - Ulrike Winkler
- Carl-Ludwig-Institute for Physiology, Faculty of Medicine, University Leipzig, Leipzig, Germany
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9
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Lactate induces synapse-specific potentiation on CA3 pyramidal cells of rat hippocampus. PLoS One 2020; 15:e0242309. [PMID: 33180836 PMCID: PMC7660554 DOI: 10.1371/journal.pone.0242309] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2020] [Accepted: 10/31/2020] [Indexed: 02/07/2023] Open
Abstract
Neuronal activity within the physiologic range stimulates lactate production that, via metabolic pathways or operating through an array of G-protein-coupled receptors, regulates intrinsic excitability and synaptic transmission. The recent discovery that lactate exerts a tight control of ion channels, neurotransmitter release, and synaptic plasticity-related intracellular signaling cascades opens up the possibility that lactate regulates synaptic potentiation at central synapses. Here, we demonstrate that extracellular lactate (1–2 mM) induces glutamatergic potentiation on the recurrent collateral synapses of hippocampal CA3 pyramidal cells. This potentiation is independent of lactate transport and further metabolism, but requires activation of NMDA receptors, postsynaptic calcium accumulation, and activation of a G-protein-coupled receptor sensitive to cholera toxin. Furthermore, perfusion of 3,5- dihydroxybenzoic acid, a lactate receptor agonist, mimics this form of synaptic potentiation. The transduction mechanism underlying this novel form of synaptic plasticity requires G-protein βγ subunits, inositol-1,4,5-trisphosphate 3-kinase, PKC, and CaMKII. Activation of these signaling cascades is compartmentalized in a synapse-specific manner since lactate does not induce potentiation at the mossy fiber synapses of CA3 pyramidal cells. Consistent with this synapse-specific potentiation, lactate increases the output discharge of CA3 neurons when recurrent collaterals are repeatedly activated during lactate perfusion. This study provides new insights into the cellular mechanisms by which lactate, acting via a membrane receptor, contributes to the memory formation process.
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10
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Fluid Brain Glycolysis: Limits, Speed, Location, Moonlighting, and the Fates of Glycogen and Lactate. Neurochem Res 2020; 45:1328-1334. [DOI: 10.1007/s11064-020-03005-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2019] [Revised: 02/26/2020] [Accepted: 02/28/2020] [Indexed: 01/08/2023]
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11
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Barros LF, Ruminot I, San Martín A, Lerchundi R, Fernández-Moncada I, Baeza-Lehnert F. Aerobic Glycolysis in the Brain: Warburg and Crabtree Contra Pasteur. Neurochem Res 2020; 46:15-22. [PMID: 31981059 DOI: 10.1007/s11064-020-02964-w] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2019] [Revised: 01/10/2020] [Accepted: 01/16/2020] [Indexed: 12/20/2022]
Abstract
Information processing is onerous. Curiously, active brain tissue does not fully oxidize glucose and instead generates a local surplus of lactate, a phenomenon termed aerobic glycolysis. Why engage in inefficient ATP production by glycolysis when energy demand is highest and oxygen is plentiful? Aerobic glycolysis is associated to classic biochemical effects known by the names of Pasteur, Warburg and Crabtree. Here we discuss these three interdependent phenomena in brain cells, in light of high-resolution data of neuronal and astrocytic metabolism in culture, tissue slices and in vivo, acquired with genetically-encoded fluorescent sensors. These sensors are synthetic proteins that can be targeted to specific cell types and subcellular compartments, which change their fluorescence in response to variations in metabolite concentration. A major site of acute aerobic glycolysis is the astrocyte. In this cell, a Crabtree effect triggered by K+ coincides with a Warburg effect mediated by NO, superimposed on a slower longer-lasting Warburg effect caused by glutamate and possibly by NH4+. The compounded outcome is that more fuel (lactate) and more oxygen are made available to neurons, on demand. Meanwhile neurons consume both glucose and lactate, maintaining a strict balance between glycolysis and respiration, commanded by the Na+ pump. We conclude that activity-dependent Warburg and Crabtree effects in brain tissue, and the resulting aerobic glycolysis, do not reflect inefficient energy generation but the marshalling of astrocytes for the purpose of neuronal ATP generation. It remains to be seen whether neurons contribute to aerobic glycolysis under physiological conditions.
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Affiliation(s)
- L Felipe Barros
- Centro de Estudios Científicos-CECs, 5110466, Valdivia, Chile.
| | - Iván Ruminot
- Centro de Estudios Científicos-CECs, 5110466, Valdivia, Chile
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12
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Heterogeneity of Astrocytes in Grey and White Matter. Neurochem Res 2019; 46:3-14. [PMID: 31797158 DOI: 10.1007/s11064-019-02926-x] [Citation(s) in RCA: 53] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2019] [Revised: 11/21/2019] [Accepted: 11/28/2019] [Indexed: 02/07/2023]
Abstract
Astrocytes are a diverse and heterogeneous type of glial cells. The major task of grey and white matter areas in the brain are computation of information at neuronal synapses and propagation of action potentials along axons, respectively, resulting in diverse demands for astrocytes. Adapting their function to the requirements in the local environment, astrocytes differ in morphology, gene expression, metabolism, and many other properties. Here we review the differential properties of protoplasmic astrocytes of grey matter and fibrous astrocytes located in white matter in respect to glutamate and energy metabolism, to their function at the blood-brain interface and to coupling via gap junctions. Finally, we discuss how this astrocytic heterogeneity might contribute to the different susceptibility of grey and white matter to ischemic insults.
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13
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Kaushik DK, Bhattacharya A, Mirzaei R, Rawji KS, Ahn Y, Rho JM, Yong VW. Enhanced glycolytic metabolism supports transmigration of brain-infiltrating macrophages in multiple sclerosis. J Clin Invest 2019; 129:3277-3292. [PMID: 31112527 DOI: 10.1172/jci124012] [Citation(s) in RCA: 59] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The migration of leukocytes into the CNS drives the neuropathology of multiple sclerosis (MS). This penetration likely utilizes energy resources that remain to be defined. Using the experimental autoimmune encephalomyelitis (EAE) model of MS, we determined that macrophages within the perivascular cuff of post-capillary venules are highly glycolytic as manifested by strong expression of lactate dehydrogenase A (LDHA) that converts pyruvate to lactate. These macrophages expressed prominent levels of monocarboxylate transporter-4 (MCT-4) specialized in secreting lactate from glycolytic cells. The functional relevance of glycolysis was confirmed by siRNA-mediated knockdown of LDHA and MCT-4, which decreased lactate secretion and macrophage transmigration. MCT-4 was in turn regulated by EMMPRIN (CD147) as determined through co-expression/co-immunoprecipitation studies, and siRNA-mediated EMMPRIN silencing. The functional relevance of MCT-4/EMMPRIN interaction was affirmed by lower macrophage transmigration in culture using the MCT-4 inhibitor, α-cyano-4-hydroxy-cinnamic acid (CHCA), a cinnamon derivative. CHCA also reduced leukocyte infiltration and the clinical severity of EAE. Relevance to MS was corroborated by the strong expression of MCT-4, EMMPRIN and LDHA in perivascular macrophages in MS brains. These results detail the metabolism of macrophages for transmigration from perivascular cuffs into the CNS parenchyma and identifies CHCA and diet as potential modulators of neuro-inflammation in MS.
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Affiliation(s)
| | | | - Reza Mirzaei
- Hotchkiss Brain Institute.,Department of Clinical Neurosciences
| | - Khalil S Rawji
- Hotchkiss Brain Institute.,Department of Clinical Neurosciences
| | - Younghee Ahn
- Alberta Children's Hospital Research Institute.,Department of Pediatrics, and
| | - Jong M Rho
- Alberta Children's Hospital Research Institute.,Department of Pediatrics, and.,Department of Physiology and Pharmacology, University of Calgary, Calgary, Alberta, Canada
| | - V Wee Yong
- Hotchkiss Brain Institute.,Department of Clinical Neurosciences
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14
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Gonçalves CA, Rodrigues L, Bobermin LD, Zanotto C, Vizuete A, Quincozes-Santos A, Souza DO, Leite MC. Glycolysis-Derived Compounds From Astrocytes That Modulate Synaptic Communication. Front Neurosci 2019; 12:1035. [PMID: 30728759 PMCID: PMC6351787 DOI: 10.3389/fnins.2018.01035] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2018] [Accepted: 12/20/2018] [Indexed: 12/14/2022] Open
Abstract
Based on the concept of the tripartite synapse, we have reviewed the role of glucose-derived compounds in glycolytic pathways in astroglial cells. Glucose provides energy and substrate replenishment for brain activity, such as glutamate and lipid synthesis. In addition, glucose metabolism in the astroglial cytoplasm results in products such as lactate, methylglyoxal, and glutathione, which modulate receptors and channels in neurons. Glucose has four potential destinations in neural cells, and it is possible to propose a crossroads in “X” that can be used to describe these four destinations. Glucose-6P can be used either for glycogen synthesis or the pentose phosphate pathway on the left and right arms of the X, respectively. Fructose-6P continues through the glycolysis pathway until pyruvate is formed but can also act as the initial compound in the hexosamine pathway, representing the left and right legs of the X, respectively. We describe each glucose destination and its regulation, indicating the products of these pathways and how they can affect synaptic communication. Extracellular L-lactate, either generated from glucose or from glycogen, binds to HCAR1, a specific receptor that is abundantly localized in perivascular and post-synaptic membranes and regulates synaptic plasticity. Methylglyoxal, a product of a deviation of glycolysis, and its derivative D-lactate are also released by astrocytes and bind to GABAA receptors and HCAR1, respectively. Glutathione, in addition to its antioxidant role, also binds to ionotropic glutamate receptors in the synaptic cleft. Finally, we examined the hexosamine pathway and evaluated the effect of GlcNAc-modification on key proteins that regulate the other glucose destinations.
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Affiliation(s)
- Carlos-Alberto Gonçalves
- Department of Biochemistry, Federal University of Rio Grande do Sul (UFRGS), Porto Alegre, Brazil
| | - Letícia Rodrigues
- Department of Biochemistry, Federal University of Rio Grande do Sul (UFRGS), Porto Alegre, Brazil
| | - Larissa D Bobermin
- Department of Biochemistry, Federal University of Rio Grande do Sul (UFRGS), Porto Alegre, Brazil
| | - Caroline Zanotto
- Department of Biochemistry, Federal University of Rio Grande do Sul (UFRGS), Porto Alegre, Brazil
| | - Adriana Vizuete
- Department of Biochemistry, Federal University of Rio Grande do Sul (UFRGS), Porto Alegre, Brazil
| | - André Quincozes-Santos
- Department of Biochemistry, Federal University of Rio Grande do Sul (UFRGS), Porto Alegre, Brazil
| | - Diogo O Souza
- Department of Biochemistry, Federal University of Rio Grande do Sul (UFRGS), Porto Alegre, Brazil
| | - Marina C Leite
- Department of Biochemistry, Federal University of Rio Grande do Sul (UFRGS), Porto Alegre, Brazil
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15
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Schurr A. Glycolysis Paradigm Shift Dictates a Reevaluation of Glucose and Oxygen Metabolic Rates of Activated Neural Tissue. Front Neurosci 2018; 12:700. [PMID: 30364172 PMCID: PMC6192285 DOI: 10.3389/fnins.2018.00700] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2018] [Accepted: 09/18/2018] [Indexed: 01/31/2023] Open
Abstract
In 1988 two seminal studies were published, both instigating controversy. One concluded that “the energy needs of activated neural tissue are minimal, being fulfilled via the glycolytic pathway alone,” a conclusion based on the observation that neural activation increased glucose consumption, which was not accompanied by a corresponding increase in oxygen consumption (Fox et al., 1988). The second demonstrated that neural tissue function can be supported exclusively by lactate as the energy substrate (Schurr et al., 1988). While both studies continue to have their supporters and detractors, the present review attempts to clarify the issues responsible for the persistence of the controversies they have provoked and offer a possible rationalization. The concept that lactate rather than pyruvate, is the glycolytic end-product, both aerobically and anaerobically, and thus the real mitochondrial oxidative substrate, has gained a greater acceptance over the years. The idea of glycolysis as the sole ATP supplier for neural activation (glucose → lactate + 2ATP) continues to be controversial. Lactate oxidative utilization by activated neural tissue could explain the mismatch between glucose and oxygen consumption and resolve the existing disagreements among users of imaging methods to measure the metabolic rates of the two energy metabolic substrates. The postulate that the energy necessary for active neural tissue is supplied by glycolysis alone stems from the original aerobic glycolysis paradigm. Accordingly, glucose consumption is accompanied by oxygen consumption at 1–6 ratio. Since Fox et al. (1988) observed only a minimal if non-existent oxygen consumption compared to glucose consumption, their conclusion make sense. Nevertheless, considering (a) the shift in the paradigm of glycolysis (glucose → lactate; lactate + O2 + mitochondria → pyruvate → TCA cycle → CO2 + H2O + 17ATP); (b) that one mole of lactate oxidation requires only 50% of the amount of oxygen necessary for the oxidation of one mole of glucose; and (c) that lactate, as a mitochondrial substrate, is over eight times more efficient at ATP production than glucose as a glycolytic substrate, suggest that future studies of cerebral metabolic rates of activated neural tissue should include along with the measurements of CMRO2 and CMRglucose the measurement of CMRlactate.
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Affiliation(s)
- Avital Schurr
- Department of Anesthesiology and Perioperative Medicine, School of Medicine, University of Louisville, Louisville, KY, United States
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16
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Köhler S, Winkler U, Sicker M, Hirrlinger J. NBCe1 mediates the regulation of the NADH/NAD + redox state in cortical astrocytes by neuronal signals. Glia 2018; 66:2233-2245. [PMID: 30208253 DOI: 10.1002/glia.23504] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2018] [Revised: 06/19/2018] [Accepted: 06/25/2018] [Indexed: 12/20/2022]
Abstract
Astrocytes are a glial cell type, which is indispensable for brain energy metabolism. Within cells, the NADH/NAD+ redox state is a crucial node in metabolism connecting catabolic pathways to oxidative phosphorylation and ATP production in mitochondria. To characterize the dynamics of the intracellular NADH/NAD+ redox state in cortical astrocytes Peredox, a genetically encoded sensor for the NADH/NAD+ redox state, was expressed in cultured cortical astrocytes as well as in cortical astrocytes in acutely isolated brain slices. Calibration of the sensor in cultured astrocytes revealed a mean basal cytosolic NADH/NAD+ redox ratio of about 0.01; however, with a broad distribution and heterogeneity in the cell population, which was mirrored by a heterogeneous basal cellular concentration of lactate. Inhibition of glucose uptake decreased the NADH/NAD+ redox state while inhibition of lactate dehydrogenase or of lactate release resulted in an increase in the NADH/NAD+ redox ratio. Furthermore, the NADH/NAD+ redox state was regulated by the extracellular concentration of K+ , and application of the neurotransmitters ATP or glutamate increased the NADH/NAD+ redox state dependent on purinergic receptors and glutamate uptake, respectively. This regulation by K+ , ATP, and glutamate involved NBCe1 mediated sodium-bicarbonate transport. These results demonstrate that the NADH/NAD+ redox state in astrocytes is a metabolic node regulated by neuronal signals reflecting physiological activity, most likely contributing to adjust astrocytic metabolism to energy demand of the brain.
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Affiliation(s)
- Susanne Köhler
- Faculty of Medicine, Carl-Ludwig-Institute for Physiology, University of Leipzig, Leipzig, Germany
| | - Ulrike Winkler
- Faculty of Medicine, Carl-Ludwig-Institute for Physiology, University of Leipzig, Leipzig, Germany
| | - Marit Sicker
- Faculty of Medicine, Carl-Ludwig-Institute for Physiology, University of Leipzig, Leipzig, Germany
| | - Johannes Hirrlinger
- Faculty of Medicine, Carl-Ludwig-Institute for Physiology, University of Leipzig, Leipzig, Germany.,Department of Neurogenetics, Max-Planck-Institute for Experimental Medicine, Göttingen, Germany
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17
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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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18
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Winkler U, Seim P, Enzbrenner Y, Köhler S, Sicker M, Hirrlinger J. Activity-dependent modulation of intracellular ATP in cultured cortical astrocytes. J Neurosci Res 2017; 95:2172-2181. [PMID: 28151554 DOI: 10.1002/jnr.24020] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2016] [Revised: 12/15/2016] [Accepted: 12/21/2016] [Indexed: 01/21/2023]
Abstract
Brain function is absolutely dependent on an appropriate supply of energy. A shortfall in supply-as occurs, for instance, following stroke-can lead rapidly to irreversible damage to this vital organ. While the consequences of pathophysiological energy depletion have been well documented, much less is known about the physiological energy dynamics of brain cells, although changes in the intracellular concentration of adenosine triphosphate (ATP), the major energy carrier of cells, have been postulated to contribute to cellular signaling. To address this issue more closely, we have investigated intracellular ATP in cultured primary cortical astrocytes by time-lapse microscopy using a genetically encoded fluorescent sensor for ATP. The cytosolic ATP sensor signal decreased after application of the neurotransmitter glutamate in a manner dependent on both glutamate concentration and glutamate transporter activity, but independent of glutamate receptors. The application of dopamine did not affect ATP levels within astrocytes. These results confirm that intracellular ATP levels in astrocytes do indeed respond to changes in physiological activity and pave the way for further studies addressing factors that affect regulation of ATP. © 2017 Wiley Periodicals, Inc.
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Affiliation(s)
- Ulrike Winkler
- Carl-Ludwig-Institute for Physiology, Faculty of Medicine, University of Leipzig, Leipzig, Germany
| | - Pauline Seim
- Carl-Ludwig-Institute for Physiology, Faculty of Medicine, University of Leipzig, Leipzig, Germany
| | - Yvonne Enzbrenner
- Carl-Ludwig-Institute for Physiology, Faculty of Medicine, University of Leipzig, Leipzig, Germany
| | - Susanne Köhler
- Carl-Ludwig-Institute for Physiology, Faculty of Medicine, University of Leipzig, Leipzig, Germany
| | - Marit Sicker
- Carl-Ludwig-Institute for Physiology, Faculty of Medicine, University of Leipzig, Leipzig, Germany
| | - Johannes Hirrlinger
- Carl-Ludwig-Institute for Physiology, Faculty of Medicine, University of Leipzig, Leipzig, Germany.,Department of Neurogenetics, Max Planck Institute for Experimental Medicine, Göttingen, Germany
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19
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Béland-Millar A, Larcher J, Courtemanche J, Yuan T, Messier C. Effects of Systemic Metabolic Fuels on Glucose and Lactate Levels in the Brain Extracellular Compartment of the Mouse. Front Neurosci 2017; 11:7. [PMID: 28154523 PMCID: PMC5243849 DOI: 10.3389/fnins.2017.00007] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2016] [Accepted: 01/04/2017] [Indexed: 01/11/2023] Open
Abstract
Classic neuroenergetic research has emphasized the role of glucose, its transport and its metabolism in sustaining normal neural function leading to the textbook statement that it is the necessary and sole metabolic fuel of the mammalian brain. New evidence, including the Astrocyte-to-Neuron Lactate Shuttle hypothesis, suggests that the brain can use other metabolic substrates. To further study that possibility, we examined the effect of intraperitoneally administered metabolic fuels (glucose, fructose, lactate, pyruvate, ß-hydroxybutyrate, and galactose), and insulin, on blood, and extracellular brain levels of glucose and lactate in the adult male CD1 mouse. Primary motor cortex extracellular levels of glucose and lactate were monitored in freely moving mice with the use of electrochemical electrodes. Blood concentration of these same metabolites were obtained by tail vein sampling and measured with glucose and lactate meters. Blood and extracellular fluctuations of glucose and lactate were monitored for a 2-h period. We found that the systemic injections of glucose, fructose, lactate, pyruvate, and ß-hydroxybutyrate increased blood lactate levels. Apart for a small transitory rise in brain extracellular lactate levels, the main effect of the systemic injection of glucose, fructose, lactate, pyruvate, and ß-hydroxybutyrate was an increase in brain extracellular glucose levels. Systemic galactose injections produced a small rise in blood glucose and lactate but almost no change in brain extracellular lactate and glucose. Systemic insulin injections led to a decrease in blood glucose and a small rise in blood lactate; however brain extracellular glucose and lactate monotonically decreased at the same rate. Our results support the concept that the brain is able to use alternative fuels and the current experiments suggest some of the mechanisms involved.
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Affiliation(s)
| | - Jeremy Larcher
- School of Psychology, University of Ottawa Ottawa, ON, Canada
| | | | - Tina Yuan
- School of Psychology, University of Ottawa Ottawa, ON, Canada
| | - Claude Messier
- School of Psychology, University of Ottawa Ottawa, ON, Canada
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20
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Patet C, Suys T, Carteron L, Oddo M. Cerebral Lactate Metabolism After Traumatic Brain Injury. Curr Neurol Neurosci Rep 2016; 16:31. [PMID: 26898683 DOI: 10.1007/s11910-016-0638-5] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Cerebral energy dysfunction has emerged as an important determinant of prognosis following traumatic brain injury (TBI). A number of studies using cerebral microdialysis, positron emission tomography, and jugular bulb oximetry to explore cerebral metabolism in patients with TBI have demonstrated a critical decrease in the availability of the main energy substrate of brain cells (i.e., glucose). Energy dysfunction induces adaptations of cerebral metabolism that include the utilization of alternative energy resources that the brain constitutively has, such as lactate. Two decades of experimental and human investigations have convincingly shown that lactate stands as a major actor of cerebral metabolism. Glutamate-induced activation of glycolysis stimulates lactate production from glucose in astrocytes, with subsequent lactate transfer to neurons (astrocyte-neuron lactate shuttle). Lactate is not only used as an extra energy substrate but also acts as a signaling molecule and regulator of systemic and brain glucose use in the cerebral circulation. In animal models of brain injury (e.g., TBI, stroke), supplementation with exogenous lactate exerts significant neuroprotection. Here, we summarize the main clinical studies showing the pivotal role of lactate and cerebral lactate metabolism after TBI. We also review pilot interventional studies that examined exogenous lactate supplementation in patients with TBI and found hypertonic lactate infusions had several beneficial properties on the injured brain, including decrease of brain edema, improvement of neuroenergetics via a "cerebral glucose-sparing effect," and increase of cerebral blood flow. Hypertonic lactate represents a promising area of therapeutic investigation; however, larger studies are needed to further examine mechanisms of action and impact on outcome.
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Affiliation(s)
- Camille Patet
- Neuroscience Critical Care Research Group, Department of Intensive Care Medicine, CHUV - Lausanne University Hospital, Rue du Bugnon 46, BH 08.623, 1011, Lausanne, Switzerland
| | - Tamarah Suys
- Neuroscience Critical Care Research Group, Department of Intensive Care Medicine, CHUV - Lausanne University Hospital, Rue du Bugnon 46, BH 08.623, 1011, Lausanne, Switzerland
| | - Laurent Carteron
- Neuroscience Critical Care Research Group, Department of Intensive Care Medicine, CHUV - Lausanne University Hospital, Rue du Bugnon 46, BH 08.623, 1011, Lausanne, Switzerland
| | - Mauro Oddo
- Neuroscience Critical Care Research Group, Department of Intensive Care Medicine, CHUV - Lausanne University Hospital, Rue du Bugnon 46, BH 08.623, 1011, Lausanne, Switzerland.
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21
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Bolaños JP. Bioenergetics and redox adaptations of astrocytes to neuronal activity. J Neurochem 2016; 139 Suppl 2:115-125. [PMID: 26968531 PMCID: PMC5018236 DOI: 10.1111/jnc.13486] [Citation(s) in RCA: 181] [Impact Index Per Article: 22.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2015] [Revised: 11/19/2015] [Accepted: 11/23/2015] [Indexed: 12/14/2022]
Abstract
Neuronal activity is a high‐energy demanding process recruiting all neural cells that adapt their metabolism to sustain the energy and redox balance of neurons. During neurotransmission, synaptic cleft glutamate activates its receptors in neurons and in astrocytes, before being taken up by astrocytes through energy costly transporters. In astrocytes, the energy requirement for glutamate influx is likely to be met by glycolysis. To enable this, astrocytes are constitutively glycolytic, robustly expressing 6‐phosphofructo‐2‐kinase/fructose‐2,6‐bisphosphatase‐3 (PFKFB3), an enzyme that is negligibly present in neurons by continuous degradation because of the ubiquitin‐proteasome pathway via anaphase‐promoting complex/cyclosome (APC)‐Cdh1. Additional factors contributing to the glycolytic frame of astrocytes may include 5′‐AMP‐activated protein kinase (AMPK), hypoxia‐inducible factor‐1 (HIF‐1), pyruvate kinase muscle isoform‐2 (PKM2), pyruvate dehydrogenase kinase‐4 (PDK4), lactate dehydrogenase‐B, or monocarboxylate transporter‐4 (MCT4). Neurotransmission‐associated messengers, such as nitric oxide or ammonium, stimulate lactate release from astrocytes. Astrocyte‐derived glycolytic lactate thus sustains the energy needs of neurons, which in contrast to astrocytes mainly rely on oxidative phosphorylation. Neuronal activity unavoidably triggers reactive oxygen species, but the antioxidant defense of neurons is weak; hence, they use glucose for oxidation through the pentose‐phosphate pathway to preserve the redox status. Furthermore, neural activity is coupled with erythroid‐derived erythroid‐derived 2‐like 2 (Nrf2) mediated transcriptional activation of antioxidant genes in astrocytes, which boost the de novo glutathione biosynthesis in neighbor neurons. Thus, the bioenergetics and redox programs of astrocytes are adapted to sustain neuronal activity and survival. Developing therapeutic strategies to interfere with these pathways may be useful to combat neurological diseases.
Our current knowledge on brain's management of bioenergetics and redox requirements associated with neural activity is herein revisited. The astrocyte‐neuronal lactate shuttle (ANLS) explains the energy needs of neurotransmission. Furthermore, neurotransmission unavoidably triggers increased mitochondrial reactive oxygen species in neurons. By coupling glutamatergic activity with transcriptional activation of antioxidant genes, astrocytes provide neurons with neuroprotective glutathione through an astrocyte‐neuronal glutathione shuttle (ANGS).
This article is part of the60th Anniversary special issue.
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Affiliation(s)
- Juan P Bolaños
- Institute of Functional Biology and Genomics (IBFG), University of Salamanca-CSIC-IBSAL, Salamanca, Spain.
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22
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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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23
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Abstract
Excitatory synaptic transmission is accompanied by a local surge in interstitial lactate that occurs despite adequate oxygen availability, a puzzling phenomenon termed aerobic glycolysis. In addition to its role as an energy substrate, recent studies have shown that lactate modulates neuronal excitability acting through various targets, including NMDA receptors and G-protein-coupled receptors specific for lactate, but little is known about the cellular and molecular mechanisms responsible for the increase in interstitial lactate. Using a panel of genetically encoded fluorescence nanosensors for energy metabolites, we show here that mouse astrocytes in culture, in cortical slices, and in vivo maintain a steady-state reservoir of lactate. The reservoir was released to the extracellular space immediately after exposure of astrocytes to a physiological rise in extracellular K(+) or cell depolarization. Cell-attached patch-clamp analysis of cultured astrocytes revealed a 37 pS lactate-permeable ion channel activated by cell depolarization. The channel was modulated by lactate itself, resulting in a positive feedback loop for lactate release. A rapid fall in intracellular lactate levels was also observed in cortical astrocytes of anesthetized mice in response to local field stimulation. The existence of an astrocytic lactate reservoir and its quick mobilization via an ion channel in response to a neuronal cue provides fresh support to lactate roles in neuronal fueling and in gliotransmission.
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24
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Currais A. Ageing and inflammation - A central role for mitochondria in brain health and disease. Ageing Res Rev 2015; 21:30-42. [PMID: 25684584 DOI: 10.1016/j.arr.2015.02.001] [Citation(s) in RCA: 68] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2014] [Revised: 01/29/2015] [Accepted: 02/02/2015] [Indexed: 02/08/2023]
Abstract
To develop successful therapies that prevent or treat neurodegenerative diseases requires an understanding of the upstream events. Ageing is by far the greatest risk factor for most of these diseases, and to clarify their causes will require an understanding of the process of ageing itself. Starting with the question Why do we age as individual organisms, but the line of pluripotent embryonic stem cells and germ cells carried by individuals and transmitted to descendants is immortal? this review discusses how the process of cellular differentiation leads to the accumulation of biological imperfections with ageing, and how these imperfections may be the cause of chronic inflammatory responses to stress that undermine cellular function. Both differentiation and inflammation involve drastic metabolic changes associated with alterations in mitochondrial dynamics that shift the balance between aerobic glycolysis and oxidative phosphorylation. With ageing, mitochondrial dysfunction can be both the cause and consequence of inflammatory processes and elicit metabolic adaptations that might be either protective or become progressively detrimental. It is argued here that an understanding of the relationship between metabolism, differentiation and inflammation is essential to understand the pathological mechanisms governing brain health and disease during ageing.
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Chambers TW, Daly TP, Hockley A, Brown AM. Contribution of glycogen in supporting axon conduction in the peripheral and central nervous systems: the role of lactate. Front Neurosci 2014; 8:378. [PMID: 25505379 PMCID: PMC4243571 DOI: 10.3389/fnins.2014.00378] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2014] [Accepted: 11/05/2014] [Indexed: 11/25/2022] Open
Abstract
The role of glycogen in the central nervous system is intimately linked with the glycolytic pathway. Glycogen is synthesized from glucose, the primary substrate for glycolysis, and degraded to glucose-6-phosphate. The metabolic cost of shunting glucose via glycogen exceeds that of simple phosphorylation of glucose to glucose-6-phosphate by hexokinase; thus, there must be a metabolic advantage in utilizing this shunt pathway. The dogmatic view of glycogen as a storage depot persists, based on initial descriptions of glycogen supporting neural function in the face of aglycemia. The variable latency to conduction failure, dependent upon tissue glycogen levels, provided convincing evidence of the role played by glycogen in supporting neural function. Glycogen is located predominantly in astrocytes in the central nervous system, thus for glycogen to benefit neural elements, intercellular metabolic communication must exist in the form of astrocyte to neuron substrate transfer. Experimental evidence supports a model where glycogen is metabolized to lactate in astrocytes, with cellular expression of monocarboxylate transporters and enzymes appropriately located for lactate shuttling between astrocytes and neural elements, where lactate acts as a substrate for oxidative metabolism. Biosensor recordings have demonstrated a significant steady concentration of lactate present on the periphery of both central white matter and peripheral nerve under unstimulated baseline conditions, indicating continuous cellular efflux of lactate to the interstitium. The existence of this lactate pool argues we must reexamine the "on demand" shuttling of lactate between cellular elements, and suggests continuous lactate efflux surplus to immediate neural requirements.
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Affiliation(s)
- Tom W. Chambers
- School of Life Sciences, Queen's Medical Centre, University of NottinghamNottingham, UK
| | - Timothy P. Daly
- School of Life Sciences, Queen's Medical Centre, University of NottinghamNottingham, UK
| | - Adam Hockley
- School of Life Sciences, Queen's Medical Centre, University of NottinghamNottingham, UK
| | - Angus M. Brown
- School of Life Sciences, Queen's Medical Centre, University of NottinghamNottingham, UK
- Department of Neurology, University of WashingtonSeattle, WA, USA
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26
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Hirrlinger J, Nave KA. Adapting brain metabolism to myelination and long-range signal transduction. Glia 2014; 62:1749-61. [DOI: 10.1002/glia.22737] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2013] [Revised: 07/23/2014] [Accepted: 07/23/2014] [Indexed: 12/24/2022]
Affiliation(s)
- Johannes Hirrlinger
- Department of Neurogenetics; Max-Planck-Institute for Experimental Medicine; Göttingen Germany
- Carl-Ludwig-Institute for Physiology, Faculty of Medicine, University of Leipzig; Leipzig Germany
| | - Klaus-Armin Nave
- Department of Neurogenetics; Max-Planck-Institute for Experimental Medicine; Göttingen Germany
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27
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Laureys G, Valentino M, Demol F, Zammit C, Muscat R, Cambron M, Kooijman R, De Keyser J. β₂-adrenergic receptors protect axons during energetic stress but do not influence basal glio-axonal lactate shuttling in mouse white matter. Neuroscience 2014; 277:367-74. [PMID: 25064060 DOI: 10.1016/j.neuroscience.2014.07.022] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2014] [Revised: 06/30/2014] [Accepted: 07/16/2014] [Indexed: 10/25/2022]
Abstract
In vitro studies have demonstrated that β2-adrenergic receptor activation stimulates glycogen degradation in astrocytes, generating lactate as a potential energy source for neurons. Using in vivo microdialysis in mouse cerebellar white matter we demonstrate continuous axonal lactate uptake and glial-axonal metabolic coupling of glutamate/lactate exchange. However, this physiological lactate production was not influenced by activation (clenbuterol) or blocking (ICI 118551) of β2-adrenergic receptors. In two-photon imaging experiments on ex vivo mouse corpus callosum subjected to aglycemia, β2-adrenergic activation rescued axons, whereas inhibition of axonal lactate uptake by α-cyano-4-hydroxycinnamic acid (4-CIN) was associated with severe axonal loss. Our results suggest that axonal protective effects of glial β2-adrenergic receptor activation are not mediated by enhanced lactate production.
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Affiliation(s)
- G Laureys
- Department of Neurology, University Hospital Brussels, Center for Neurosciences, Vrije Universiteit Brussel, Laarbeeklaan 101, 1090 Brussels, Belgium.
| | - M Valentino
- Department of Physiology and Biochemistry, Faculty of Medicine & Surgery, University of Malta, Msida MSD 2080, Malta
| | - F Demol
- Department of Neurology, University Hospital Brussels, Center for Neurosciences, Vrije Universiteit Brussel, Laarbeeklaan 101, 1090 Brussels, Belgium
| | - C Zammit
- Department of Anatomy, Faculty of Medicine & Surgery, University of Malta, Msida MSD 2080, Malta
| | - R Muscat
- Department of Physiology and Biochemistry, Faculty of Medicine & Surgery, University of Malta, Msida MSD 2080, Malta
| | - M Cambron
- Department of Neurology, University Hospital Brussels, Center for Neurosciences, Vrije Universiteit Brussel, Laarbeeklaan 101, 1090 Brussels, Belgium
| | - R Kooijman
- Experimental Pharmacology, Center for Neurosciences, Vrije Universiteit Brussel, Laarbeeklaan 103, 1090 Brussels, Belgium
| | - J De Keyser
- Department of Neurology, University Hospital Brussels, Center for Neurosciences, Vrije Universiteit Brussel, Laarbeeklaan 101, 1090 Brussels, Belgium; Department of Neurology, University Medical Center Groningen, Groningen, The Netherlands
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28
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San Martín A, Sotelo-Hitschfeld T, Lerchundi R, Fernández-Moncada I, Ceballo S, Valdebenito R, Baeza-Lehnert F, Alegría K, Contreras-Baeza Y, Garrido-Gerter P, Romero-Gómez I, Barros LF. Single-cell imaging tools for brain energy metabolism: a review. NEUROPHOTONICS 2014; 1:011004. [PMID: 26157964 PMCID: PMC4478754 DOI: 10.1117/1.nph.1.1.011004] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2014] [Revised: 04/09/2014] [Accepted: 04/10/2014] [Indexed: 05/03/2023]
Abstract
Neurophotonics comes to light at a time in which advances in microscopy and improved calcium reporters are paving the way toward high-resolution functional mapping of the brain. This review relates to a parallel revolution in metabolism. We argue that metabolism needs to be approached both in vitro and in vivo, and that it does not just exist as a low-level platform but is also a relevant player in information processing. In recent years, genetically encoded fluorescent nanosensors have been introduced to measure glucose, glutamate, ATP, NADH, lactate, and pyruvate in mammalian cells. Reporting relative metabolite levels, absolute concentrations, and metabolic fluxes, these sensors are instrumental for the discovery of new molecular mechanisms. Sensors continue to be developed, which together with a continued improvement in protein expression strategies and new imaging technologies, herald an exciting era of high-resolution characterization of metabolism in the brain and other organs.
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Affiliation(s)
- Alejandro San Martín
- Centro de Estudios Científicos, Arturo Prat 514, Valdivia, 5110466, Chile
- Universidad Austral de Chile, Valdivia, Chile
| | - Tamara Sotelo-Hitschfeld
- Centro de Estudios Científicos, Arturo Prat 514, Valdivia, 5110466, Chile
- Universidad Austral de Chile, Valdivia, Chile
| | - Rodrigo Lerchundi
- Centro de Estudios Científicos, Arturo Prat 514, Valdivia, 5110466, Chile
- Universidad Austral de Chile, Valdivia, Chile
| | - Ignacio Fernández-Moncada
- Centro de Estudios Científicos, Arturo Prat 514, Valdivia, 5110466, Chile
- Universidad Austral de Chile, Valdivia, Chile
| | - Sebastian Ceballo
- Centro de Estudios Científicos, Arturo Prat 514, Valdivia, 5110466, Chile
| | - Rocío Valdebenito
- Centro de Estudios Científicos, Arturo Prat 514, Valdivia, 5110466, Chile
| | | | - Karin Alegría
- Centro de Estudios Científicos, Arturo Prat 514, Valdivia, 5110466, Chile
| | - Yasna Contreras-Baeza
- Centro de Estudios Científicos, Arturo Prat 514, Valdivia, 5110466, Chile
- Universidad Austral de Chile, Valdivia, Chile
| | - Pamela Garrido-Gerter
- Centro de Estudios Científicos, Arturo Prat 514, Valdivia, 5110466, Chile
- Universidad Austral de Chile, Valdivia, Chile
| | - Ignacio Romero-Gómez
- Centro de Estudios Científicos, Arturo Prat 514, Valdivia, 5110466, Chile
- Universidad Austral de Chile, Valdivia, Chile
| | - L. Felipe Barros
- Centro de Estudios Científicos, Arturo Prat 514, Valdivia, 5110466, Chile
- Address all correspondence to: L. Felipe Barros, E-mail:
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29
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Rosafio K, Pellerin L. Oxygen tension controls the expression of the monocarboxylate transporter MCT4 in cultured mouse cortical astrocytes via a hypoxia-inducible factor-1α-mediated transcriptional regulation. Glia 2013; 62:477-90. [PMID: 24375723 DOI: 10.1002/glia.22618] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2013] [Revised: 11/29/2013] [Accepted: 12/06/2013] [Indexed: 12/13/2022]
Abstract
The monocarboxylate transporter MCT4 is a high capacity carrier important for lactate release from highly glycolytic cells. In the central nervous system, MCT4 is predominantly expressed by astrocytes. Surprisingly, MCT4 expression in cultured astrocytes is low, suggesting that a physiological characteristic, not met in culture conditions, is necessary. Here we demonstrate that reducing oxygen concentration from 21% to either 1 or 0% restored in a concentration-dependent manner the expression of MCT4 at the mRNA and protein levels in cultured astrocytes. This effect was specific for MCT4 since the expression of MCT1, the other astrocytic monocarboxylate transporter present in vitro, was not altered in such conditions. MCT4 expression was shown to be controlled by the transcription factor hypoxia-inducible factor-1α (HIF-1α) since under low oxygen levels, transfecting astrocyte cultures with a siRNA targeting HIF-1α largely prevented MCT4 induction. Moreover, the prolyl hydroxylase inhibitor dimethyloxalylglycine (DMOG) induced MCT4 expression in astrocytes cultured in presence of 21% oxygen. In parallel, glycolytic activity was enhanced by exposure to 1% oxygen as demonstrated by the increased lactate release, an effect dependent on MCT4 expression. Finally, MCT4 expression was found to be necessary for astrocyte survival when exposed for a prolonged period to 1% oxygen. These data suggest that a major determinant of astrocyte MCT4 expression in vivo is likely the oxygen tension. This could be relevant in areas of high neuronal activity and oxygen consumption, favouring astrocytic lactate supply to neurons. Moreover, it could also play an important role for neuronal recovery after an ischemic episode.
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Affiliation(s)
- Katia Rosafio
- Département de Physiologie, Université de Lausanne, Lausanne, Switzerland
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30
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Metabolic signaling by lactate in the brain. Trends Neurosci 2013; 36:396-404. [DOI: 10.1016/j.tins.2013.04.002] [Citation(s) in RCA: 220] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2013] [Revised: 03/31/2013] [Accepted: 04/01/2013] [Indexed: 01/27/2023]
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31
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Barros LF, San Martín A, Sotelo-Hitschfeld T, Lerchundi R, Fernández-Moncada I, Ruminot I, Gutiérrez R, Valdebenito R, Ceballo S, Alegría K, Baeza-Lehnert F, Espinoza D. Small is fast: astrocytic glucose and lactate metabolism at cellular resolution. Front Cell Neurosci 2013; 7:27. [PMID: 23526722 PMCID: PMC3605549 DOI: 10.3389/fncel.2013.00027] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2013] [Accepted: 03/03/2013] [Indexed: 12/28/2022] Open
Abstract
Brain tissue is highly dynamic in terms of electrical activity and energy demand. Relevant energy metabolites have turnover times ranging from milliseconds to seconds and are rapidly exchanged between cells and within cells. Until recently these fast metabolic events were inaccessible, because standard isotopic techniques require use of populations of cells and/or involve integration times of tens of minutes. Thanks to fluorescent probes and recently available genetically-encoded optical nanosensors, this Technology Report shows how it is now possible to monitor the concentration of metabolites in real-time and in single cells. In combination with ad hoc inhibitor-stop protocols, these probes have revealed a key role for K+ in the acute stimulation of astrocytic glycolysis by synaptic activity. They have also permitted detection of the Warburg effect in single cancer cells. Genetically-encoded nanosensors currently exist for glucose, lactate, NADH and ATP, and it is envisaged that other metabolite nanosensors will soon be available. These optical tools together with improved expression systems and in vivo imaging, herald an exciting era of single-cell metabolic analysis.
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Affiliation(s)
- L F Barros
- Centro de Estudios Científicos Valdivia, Chile
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32
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Álvarez Z, Mateos-Timoneda MA, Hyroššová P, Castaño O, Planell JA, Perales JC, Engel E, Alcántara S. The effect of the composition of PLA films and lactate release on glial and neuronal maturation and the maintenance of the neuronal progenitor niche. Biomaterials 2013; 34:2221-33. [DOI: 10.1016/j.biomaterials.2012.12.001] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2012] [Accepted: 12/09/2012] [Indexed: 12/12/2022]
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33
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San Martín A, Ceballo S, Ruminot I, Lerchundi R, Frommer WB, Barros LF. A genetically encoded FRET lactate sensor and its use to detect the Warburg effect in single cancer cells. PLoS One 2013; 8:e57712. [PMID: 23469056 PMCID: PMC3582500 DOI: 10.1371/journal.pone.0057712] [Citation(s) in RCA: 241] [Impact Index Per Article: 21.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2012] [Accepted: 01/24/2013] [Indexed: 11/18/2022] Open
Abstract
Lactate is shuttled between and inside cells, playing metabolic and signaling roles in healthy tissues. Lactate is also a harbinger of altered metabolism and participates in the pathogenesis of inflammation, hypoxia/ischemia, neurodegeneration and cancer. Many tumor cells show high rates of lactate production in the presence of oxygen, a phenomenon known as the Warburg effect, which has diagnostic and possibly therapeutic implications. In this article we introduce Laconic, a genetically-encoded Forster Resonance Energy Transfer (FRET)-based lactate sensor designed on the bacterial transcription factor LldR. Laconic quantified lactate from 1 µM to 10 mM and was not affected by glucose, pyruvate, acetate, betahydroxybutyrate, glutamate, citrate, α-ketoglutarate, succinate, malate or oxalacetate at concentrations found in mammalian cytosol. Expressed in astrocytes, HEK cells and T98G glioma cells, the sensor allowed dynamic estimation of lactate levels in single cells. Used in combination with a blocker of the monocarboxylate transporter MCT, the sensor was capable of discriminating whether a cell is a net lactate producer or a net lactate consumer. Application of the MCT-block protocol showed that the basal rate of lactate production is 3–5 fold higher in T98G glioma cells than in normal astrocytes. In contrast, the rate of lactate accumulation in response to mitochondrial inhibition with sodium azide was 10 times lower in glioma than in astrocytes, consistent with defective tumor metabolism. A ratio between the rate of lactate production and the rate of azide-induced lactate accumulation, which can be estimated reversibly and in single cells, was identified as a highly sensitive parameter of the Warburg effect, with values of 4.1 ± 0.5 for T98G glioma cells and 0.07 ± 0.007 for astrocytes. In summary, this article describes a genetically-encoded sensor for lactate and its use to measure lactate concentration, lactate flux, and the Warburg effect in single mammalian cells.
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Brain energy metabolism in glutamate-receptor activation and excitotoxicity: role for APC/C-Cdh1 in the balance glycolysis/pentose phosphate pathway. Neurochem Int 2013; 62:750-6. [PMID: 23416042 DOI: 10.1016/j.neuint.2013.02.005] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2012] [Revised: 01/25/2013] [Accepted: 02/03/2013] [Indexed: 02/07/2023]
Abstract
Recent advances in the field of brain energy metabolism strongly suggest that glutamate receptor-mediated neurotransmission is coupled with molecular signals that switch-on glucose utilization pathways to meet the high energetic requirements of neurons. Failure to adequately coordinate energy supply for neurotransmission ultimately results in a positive amplifying loop of receptor over-activation leading to neuronal death, a process known as excitotoxicity. In this review, we revisited current concepts in excitotoxic mechanisms, their involvement in energy substrate utilization, and the signaling pathways that coordinate both processes. In particular, we have focused on the novel role played by the E3 ubiquitin ligase, anaphase-promoting complex/cyclosome (APC/C)-Cdh1, in cell metabolism. Our laboratory identified 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase-3 (PFKFB3) -a key glycolytic-promoting enzyme- as an APC/C-Cdh1 substrate. Interestingly, APC/C-Cdh1 activity is inhibited by over-activation of glutamate receptors through a Ca(2+)-mediated mechanism. Furthermore, by inhibiting APC/C-Cdh1 activity, glutamate-receptors activation promotes PFKFB3 stabilization, leading to increased glycolysis and decreased pentose-phosphate pathway activity. This causes a loss in neuronal ability to regenerate glutathione, triggering oxidative stress and delayed excitotoxicity. Further investigation is critical to identify novel molecules responsible for the coupling of energy metabolism with glutamatergic neurotransmission and excitotoxicity, as well as to help developing new therapeutic strategies against neurodegeneration.
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