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Duarte JMN. Challenges of Investigating Compartmentalized Brain Energy Metabolism Using Nuclear Magnetic Resonance Spectroscopy in vivo. Neurochem Res 2025; 50:73. [PMID: 39754627 PMCID: PMC11700056 DOI: 10.1007/s11064-024-04324-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2024] [Revised: 12/16/2024] [Accepted: 12/17/2024] [Indexed: 01/06/2025]
Abstract
Brain function requires continuous energy supply. Thus, unraveling brain metabolic regulation is critical not only for our basic understanding of overall brain function, but also for the cellular basis of functional neuroimaging techniques. While it is known that brain energy metabolism is exquisitely compartmentalized between astrocytes and neurons, the metabolic and neuro-energetic basis of brain activity is far from fully understood. 1H nuclear magnetic resonance (NMR) spectroscopy has been widely used to detect variations in metabolite levels, including glutamate and GABA, while 13C NMR spectroscopy has been employed to study metabolic compartmentation and to determine metabolic rates coupled brain activity, focusing mainly on the component corresponding to excitatory glutamatergic neurotransmission. The rates of oxidative metabolism in neurons and astrocytes are both associated with the rate of the glutamate-glutamine cycle between neurons and astrocytes. However, any possible correlation between energy metabolism pathways and the inhibitory GABAergic neurotransmission rate in the living brain remains to be experimentally demonstrated. That is due to low GABA levels, and the consequent challenge of determining GABAergic rates in a non-invasive manner. This brief review surveys the state-of-the-art analyses of energy metabolism in neurons and astrocytes contributing to glutamate and GABA synthesis using 13C NMR spectroscopy in vivo, and identifies limitations that need to be overcome in future studies.
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Affiliation(s)
- João M N Duarte
- Department of Experimental Medical Science, Faculty of Medicine, Lund University, Lund, Sweden.
- Wallenberg Centre for Molecular Medicine, Lund University, Lund, Sweden.
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De Paula GC, Aldana BI, Battistella R, Fernández-Calle R, Bjure A, Lundgaard I, Deierborg T, Duarte JMN. Extracellular vesicles released from microglia after palmitate exposure impact brain function. J Neuroinflammation 2024; 21:173. [PMID: 39014461 PMCID: PMC11253458 DOI: 10.1186/s12974-024-03168-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2024] [Accepted: 07/09/2024] [Indexed: 07/18/2024] Open
Abstract
Dietary patterns that include an excess of foods rich in saturated fat are associated with brain dysfunction. Although microgliosis has been proposed to play a key role in the development of brain dysfunction in diet-induced obesity (DIO), neuroinflammation with cytokine over-expression is not always observed. Thus, mechanisms by which microglia contribute to brain impairment in DIO are uncertain. Using the BV2 cell model, we investigated the gliosis profile of microglia exposed to palmitate (200 µmol/L), a saturated fatty acid abundant in high-fat diet and in the brain of obese individuals. We observed that microglia respond to a 24-hour palmitate exposure with increased proliferation, and with a metabolic network rearrangement that favors energy production from glycolysis rather than oxidative metabolism, despite stimulated mitochondria biogenesis. In addition, while palmitate did not induce increased cytokine expression, it modified the protein cargo of released extracellular vesicles (EVs). When administered intra-cerebroventricularly to mice, EVs secreted from palmitate-exposed microglia in vitro led to memory impairment, depression-like behavior, and glucose intolerance, when compared to mice receiving EVs from vehicle-treated microglia. We conclude that microglia exposed to palmitate can mediate brain dysfunction through the cargo of shed EVs.
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Affiliation(s)
- Gabriela C De Paula
- Department of Experimental Medical Science (EMV), Faculty of Medicine, Lund University, Sölvegatan 19, BMC C11, Lund, 221 84, Sweden
- Wallenberg Centre for Molecular Medicine, Lund University, Lund, Sweden
| | - Blanca I Aldana
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Roberta Battistella
- Department of Experimental Medical Science (EMV), Faculty of Medicine, Lund University, Sölvegatan 19, BMC C11, Lund, 221 84, Sweden
- Wallenberg Centre for Molecular Medicine, Lund University, Lund, Sweden
| | - Rosalía Fernández-Calle
- Department of Experimental Medical Science (EMV), Faculty of Medicine, Lund University, Sölvegatan 19, BMC C11, Lund, 221 84, Sweden
| | - Andreas Bjure
- Department of Experimental Medical Science (EMV), Faculty of Medicine, Lund University, Sölvegatan 19, BMC C11, Lund, 221 84, Sweden
| | - Iben Lundgaard
- Department of Experimental Medical Science (EMV), Faculty of Medicine, Lund University, Sölvegatan 19, BMC C11, Lund, 221 84, Sweden
- Wallenberg Centre for Molecular Medicine, Lund University, Lund, Sweden
| | - Tomas Deierborg
- Department of Experimental Medical Science (EMV), Faculty of Medicine, Lund University, Sölvegatan 19, BMC C11, Lund, 221 84, Sweden
- Wallenberg Centre for Molecular Medicine, Lund University, Lund, Sweden
| | - João M N Duarte
- Department of Experimental Medical Science (EMV), Faculty of Medicine, Lund University, Sölvegatan 19, BMC C11, Lund, 221 84, Sweden.
- Wallenberg Centre for Molecular Medicine, Lund University, Lund, Sweden.
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Garcia-Serrano AM, Vieira JPP, Fleischhart V, Duarte JMN. Taurine and N-acetylcysteine treatments prevent memory impairment and metabolite profile alterations in the hippocampus of high-fat diet-fed female mice. Nutr Neurosci 2023; 26:1090-1102. [PMID: 36222315 DOI: 10.1080/1028415x.2022.2131062] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Background: Obesity constitutes a risk factor for cognitive impairment. In rodent models, long-term exposure to obesogenic diets leads to hippocampal taurine accumulation. Since taurine has putative cyto-protective effects, hippocampal taurine accumulation in obese and diabetic models might constitute a counteracting response to metabolic stress. Objective: We tested the hypothesis that treatment with taurine or with N-acetylcysteine (NAC), which provides cysteine for the synthesis of taurine and glutathione, prevent high-fat diet (HFD)-associated hippocampal alterations and memory impairment. Methods: Female mice were fed either a regular diet or HFD. Some mice had access to 3%(w/v) taurine or 3%(w/v) NAC in the drinking water. After 2 months, magnetic resonance spectroscopy (MRS) was used to measure metabolite profiles. Memory was assessed in novel object and novel location recognition tests. Results: HFD feeding caused memory impairment in both tests, and reduced concentration of lactate, phosphocreatine-to-creatine ratio, and the neuronal marker N-acetylaspartate in the hippocampus. Taurine and NAC prevented HFD-induced memory impairment and N-acetylaspartate reduction. NAC, but not taurine, prevented the reduction of lactate and phosphocreatine-to-creatine ratio. MRS revealed NAC/taurine-induced increase of hippocampal glutamate and GABA levels. Conclusion: NAC and taurine can prevent memory impairment, while only NAC prevents alterations of metabolite concentrations in HFD-exposed female mice.
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Affiliation(s)
- Alba M Garcia-Serrano
- Faculty of Medicine, Department of Experimental Medical Science, Lund University, Lund, Sweden
- Wallenberg Centre for Molecular Medicine, Lund University, Lund, Sweden
| | - Joao P P Vieira
- Faculty of Medicine, Department of Experimental Medical Science, Lund University, Lund, Sweden
- Wallenberg Centre for Molecular Medicine, Lund University, Lund, Sweden
| | - Veronika Fleischhart
- Faculty of Medicine, Department of Experimental Medical Science, Lund University, Lund, Sweden
- Wallenberg Centre for Molecular Medicine, Lund University, Lund, Sweden
| | - João M N Duarte
- Faculty of Medicine, Department of Experimental Medical Science, Lund University, Lund, Sweden
- Wallenberg Centre for Molecular Medicine, Lund University, Lund, Sweden
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Effects of Chronic Caffeine Consumption on Synaptic Function, Metabolism and Adenosine Modulation in Different Brain Areas. Biomolecules 2023; 13:biom13010106. [PMID: 36671491 PMCID: PMC9855869 DOI: 10.3390/biom13010106] [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: 11/28/2022] [Revised: 12/28/2022] [Accepted: 12/30/2022] [Indexed: 01/06/2023] Open
Abstract
Adenosine receptors mainly control synaptic function, and excessive activation of adenosine receptors may worsen the onset of many neurological disorders. Accordingly, the regular intake of moderate doses of caffeine antagonizes adenosine receptors and affords robust neuroprotection. Although caffeine intake alters brain functional connectivity and multi-omics analyses indicate that caffeine intake modifies synaptic and metabolic processes, it is unclear how caffeine intake affects behavior, synaptic plasticity and its modulation by adenosine. We now report that male mice drinking caffeinated water (0.3 g/L) for 2 weeks were behaviorally indistinguishable (locomotion, mood, memory) from control mice (drinking water) and displayed superimposable synaptic plasticity (long-term potentiation) in different brain areas (hippocampus, prefrontal cortex, amygdala). Moreover, there was a general preservation of the efficiency of adenosine A1 and A2A receptors to control synaptic transmission and plasticity, although there was a tendency for lower levels of endogenous adenosine ensuring A1 receptor-mediated inhibition. In spite of similar behavioral and neurophysiological function, caffeine intake increased the energy charge and redox state of cortical synaptosomes. This increased metabolic competence likely involved a putative increase in the glycolytic rate in synapses and a prospective greater astrocyte-synapse lactate shuttling. It was concluded that caffeine intake does not trigger evident alterations of behavior or of synaptic plasticity but increases the metabolic competence of synapses, which might be related with the previously described better ability of animals consuming caffeine to cope with deleterious stimuli triggering brain dysfunction.
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Soares AF, Nissen JD, Garcia‐Serrano AM, Nussbaum SS, Waagepetersen HS, Duarte JMN. Glycogen metabolism is impaired in the brain of male type 2 diabetic Goto‐Kakizaki rats. J Neurosci Res 2019; 97:1004-1017. [DOI: 10.1002/jnr.24437] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2018] [Revised: 04/15/2019] [Accepted: 04/15/2019] [Indexed: 12/19/2022]
Affiliation(s)
- Ana Francisca Soares
- Laboratory for Functional and Metabolic Imaging École Polytechnique Fédérale de Lausanne Lausanne Switzerland
| | - Jakob D. Nissen
- Faculty of Health and Medical Sciences, Department of Drug Design and Pharmacology University of Copenhagen Copenhagen Denmark
| | - Alba M. Garcia‐Serrano
- Faculty of Medicine, Department of Experimental Medical Science Lund University Lund Sweden
- Wallenberg Centre for Molecular Medicine Lund University Lund Sweden
| | - Sakura S. Nussbaum
- Laboratory for Functional and Metabolic Imaging École Polytechnique Fédérale de Lausanne Lausanne Switzerland
| | - Helle S. Waagepetersen
- Faculty of Health and Medical Sciences, Department of Drug Design and Pharmacology University of Copenhagen Copenhagen Denmark
| | - João M. N. Duarte
- Laboratory for Functional and Metabolic Imaging École Polytechnique Fédérale de Lausanne Lausanne Switzerland
- Faculty of Medicine, Department of Experimental Medical Science Lund University Lund Sweden
- Wallenberg Centre for Molecular Medicine Lund University Lund Sweden
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Jakkamsetti V, Marin-Valencia I, Ma Q, Good LB, Terrill T, Rajasekaran K, Pichumani K, Khemtong C, Hooshyar MA, Sundarrajan C, Patel MS, Bachoo RM, Malloy CR, Pascual JM. Brain metabolism modulates neuronal excitability in a mouse model of pyruvate dehydrogenase deficiency. Sci Transl Med 2019; 11:eaan0457. [PMID: 30787166 PMCID: PMC6637765 DOI: 10.1126/scitranslmed.aan0457] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2017] [Revised: 09/25/2018] [Accepted: 01/31/2019] [Indexed: 12/25/2022]
Abstract
Glucose is the ultimate substrate for most brain activities that use carbon, including synthesis of the neurotransmitters glutamate and γ-aminobutyric acid via mitochondrial tricarboxylic acid (TCA) cycle. Brain metabolism and neuronal excitability are thus interdependent. However, the principles that govern their relationship are not always intuitive because heritable defects of brain glucose metabolism are associated with the paradoxical coexistence, in the same individual, of episodic neuronal hyperexcitation (seizures) with reduced basal cerebral electrical activity. One such prototypic disorder is pyruvate dehydrogenase (PDH) deficiency (PDHD). PDH is central to metabolism because it steers most of the glucose-derived flux into the TCA cycle. To better understand the pathophysiology of PDHD, we generated mice with brain-specific reduced PDH activity that paralleled salient human disease features, including cerebral hypotrophy, decreased amplitude electroencephalogram (EEG), and epilepsy. The mice exhibited reductions in cerebral TCA cycle flux, glutamate content, spontaneous, and electrically evoked in vivo cortical field potentials and gamma EEG oscillation amplitude. Episodic decreases in gamma oscillations preceded most epileptiform discharges, facilitating their prediction. Fast-spiking neuron excitability was decreased in brain slices, contributing to in vivo action potential burst prolongation after whisker pad stimulation. These features were partially reversed after systemic administration of acetate, which augmented cerebral TCA cycle flux, glutamate-dependent synaptic transmission, inhibition and gamma oscillations, and reduced epileptiform discharge duration. Thus, our results suggest that dysfunctional excitability in PDHD is consequent to reduced oxidative flux, which leads to decreased neuronal activation and impaired inhibition, and can be mitigated by an alternative metabolic substrate.
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Affiliation(s)
- Vikram Jakkamsetti
- Rare Brain Disorders Program, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
- Department of Neurology and Neurotherapeutics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Isaac Marin-Valencia
- Rare Brain Disorders Program, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
- Department of Neurology and Neurotherapeutics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
- Laboratory of Developmental Neurobiology, The Rockefeller University, New York, NY 10065, USA
| | - Qian Ma
- Rare Brain Disorders Program, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
- Department of Neurology and Neurotherapeutics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Levi B Good
- Rare Brain Disorders Program, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
- Department of Neurology and Neurotherapeutics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Tyler Terrill
- Rare Brain Disorders Program, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
- Department of Neurology and Neurotherapeutics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Karthik Rajasekaran
- Rare Brain Disorders Program, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
- Department of Neurology and Neurotherapeutics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Kumar Pichumani
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Chalermchai Khemtong
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
- Department of Radiology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - M Ali Hooshyar
- Department of Mathematical Sciences, The University of Texas at Dallas, Richardson, TX 75080, USA
| | - Chandrasekhar Sundarrajan
- Rare Brain Disorders Program, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
- Department of Neurology and Neurotherapeutics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Mulchand S Patel
- Department of Biochemistry, SUNY Buffalo, Buffalo, NY 14203, USA
| | - Robert M Bachoo
- Department of Neurology and Neurotherapeutics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Craig R Malloy
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
- Department of Radiology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Juan M Pascual
- Rare Brain Disorders Program, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
- Department of Neurology and Neurotherapeutics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
- Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
- Eugene McDermott Center for Human Growth & Development / Center for Human Genetics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
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Sonnay S, Poirot J, Just N, Clerc AC, Gruetter R, Rainer G, Duarte JMN. Astrocytic and neuronal oxidative metabolism are coupled to the rate of glutamate-glutamine cycle in the tree shrew visual cortex. Glia 2017; 66:477-491. [DOI: 10.1002/glia.23259] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2017] [Revised: 10/20/2017] [Accepted: 10/24/2017] [Indexed: 01/09/2023]
Affiliation(s)
- Sarah Sonnay
- Laboratory for Functional and Metabolic Imaging (LIFMET); Ecole Polytechnique Fédérale de Lausanne (EPFL); Lausanne Switzerland
| | - Jordan Poirot
- Department of Medicine, Visual Cognition Laboratory; University of Fribourg; Fribourg Switzerland
| | | | - Anne-Catherine Clerc
- Laboratory for Functional and Metabolic Imaging (LIFMET); Ecole Polytechnique Fédérale de Lausanne (EPFL); Lausanne Switzerland
| | - Rolf Gruetter
- Laboratory for Functional and Metabolic Imaging (LIFMET); Ecole Polytechnique Fédérale de Lausanne (EPFL); Lausanne Switzerland
- Department of Radiology; University de Lausanne; Lausanne Switzerland
- Department of Radiology; University de Geneva; Geneva Switzerland
| | - Gregor Rainer
- Department of Medicine, Visual Cognition Laboratory; University of Fribourg; Fribourg Switzerland
| | - João M. N. Duarte
- Laboratory for Functional and Metabolic Imaging (LIFMET); Ecole Polytechnique Fédérale de Lausanne (EPFL); Lausanne Switzerland
- Department of Experimental Medical Science, Faculty of Medicine; Lund University; Lund Sweden
- Wallenberg Centre for Molecular Medicine, Lund University; Lund Sweden
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Girault FM, Sonnay S, Gruetter R, Duarte JMN. Alterations of Brain Energy Metabolism in Type 2 Diabetic Goto-Kakizaki Rats Measured In Vivo by 13C Magnetic Resonance Spectroscopy. Neurotox Res 2017; 36:268-278. [DOI: 10.1007/s12640-017-9821-y] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2017] [Revised: 08/21/2017] [Accepted: 09/20/2017] [Indexed: 12/11/2022]
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Sonnay S, Duarte JMN, Just N, Gruetter R. Energy metabolism in the rat cortex under thiopental anaesthesia measured In Vivo by 13 C MRS. J Neurosci Res 2017; 95:2297-2306. [PMID: 28316083 DOI: 10.1002/jnr.24032] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2016] [Revised: 01/05/2017] [Accepted: 01/16/2017] [Indexed: 01/05/2023]
Abstract
Barbiturates, commonly used as general anaesthetics, depress neuronal activity and thus cerebral metabolism. Moreover, they are likely to disrupt the metabolic support of astrocytes to neurons, as well as the uptake of nutrients from circulation. By employing 13 C magnetic resonance spectroscopy (MRS) in vivo at high magnetic field, we characterized neuronal and astrocytic pathways of energy metabolism in the rat cortex under thiopental anaesthesia. The neuronal tricarboxylic acid (TCA) cycle rate was 0.46 ± 0.02 µmol/g/min, and the rate of the glutamate-glutamine cycle was 0.09 ± 0.02 µmol/g/min. In astrocytes, the TCA cycle rate was 0.16 ± 0.02 µmol/g/min, accounting for a quarter of whole brain glucose oxidation, pyruvate carboxylase rate was 0.02 ± 0.01 µmol/g/min, and glutamine synthetase was 0.12 ± 0.01 µmol/g/min. Relative to previous experiments under light α-chloralose anaesthesia, thiopental reduced oxidative metabolism in neurons and even more so in astrocytes. Interestingly, total oxidative metabolism in the cortex under thiopental anaesthesia surpassed the rate of pyruvate production by glycolysis, indicating substantial utilisation of substrates other than glucose, likely plasma lactate. © 2017 Wiley Periodicals, Inc.
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Affiliation(s)
- Sarah Sonnay
- Laboratory for Functional and Metabolic Imaging, École Polytechnique Fédérale Lausanne, Switzerland
| | - João M N Duarte
- Laboratory for Functional and Metabolic Imaging, École Polytechnique Fédérale Lausanne, Switzerland
| | - Nathalie Just
- Centre d'Imagerie Biomédicale - Animal and Technology Core, Lausanne, Switzerland
| | - Rolf Gruetter
- Laboratory for Functional and Metabolic Imaging, École Polytechnique Fédérale Lausanne, Switzerland.,Department of Radiology, University of Geneva, Switzerland.,Department of Radiology, University of Lausanne, Switzerland
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McNair LF, Kornfelt R, Walls AB, Andersen JV, Aldana BI, Nissen JD, Schousboe A, Waagepetersen HS. Metabolic Characterization of Acutely Isolated Hippocampal and Cerebral Cortical Slices Using [U-13C]Glucose and [1,2-13C]Acetate as Substrates. Neurochem Res 2016; 42:810-826. [DOI: 10.1007/s11064-016-2116-5] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2016] [Revised: 11/11/2016] [Accepted: 11/16/2016] [Indexed: 12/21/2022]
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Sonnay S, Duarte JM, Just N, Gruetter R. Compartmentalised energy metabolism supporting glutamatergic neurotransmission in response to increased activity in the rat cerebral cortex: A 13C MRS study in vivo at 14.1 T. J Cereb Blood Flow Metab 2016; 36:928-40. [PMID: 26823472 PMCID: PMC4853840 DOI: 10.1177/0271678x16629482] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/15/2015] [Accepted: 01/06/2016] [Indexed: 12/20/2022]
Abstract
Many tissues exhibit metabolic compartmentation. In the brain, while there is no doubt on the importance of functional compartmentation between neurons and glial cells, there is still debate on the specific regulation of pathways of energy metabolism at different activity levels. Using (13)C magnetic resonance spectroscopy (MRS) in vivo, we determined fluxes of energy metabolism in the rat cortex under α-chloralose anaesthesia at rest and during electrical stimulation of the paws. Compared to resting metabolism, the stimulated rat cortex exhibited increased glutamate-glutamine cycle (+67 nmol/g/min, +95%, P < 0.001) and tricarboxylic (TCA) cycle rate in both neurons (+62 nmol/g/min, +12%, P < 0.001) and astrocytes (+68 nmol/g/min, +22%, P = 0.072). A minor, non-significant modification of the flux through pyruvate carboxylase was observed during stimulation (+5 nmol/g/min, +8%). Altogether, this increase in metabolism amounted to a 15% (67 nmol/g/min, P < 0.001) increase in CMRglc(ox), i.e. the oxidative fraction of the cerebral metabolic rate of glucose. In conclusion, stimulation of the glutamate-glutamine cycle under α-chloralose anaesthesia is associated to similar enhancement of neuronal and glial oxidative metabolism.
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Affiliation(s)
- Sarah Sonnay
- Laboratory for Functional and Metabolic Imaging, École Polytechnique Fédérale, Lausanne, Switzerland
| | - João Mn Duarte
- Laboratory for Functional and Metabolic Imaging, École Polytechnique Fédérale, Lausanne, Switzerland
| | - Nathalie Just
- Centre d'Imagerie Biomédicale - Animal and Technology Core, Lausanne, Switzerland
| | - Rolf Gruetter
- Laboratory for Functional and Metabolic Imaging, École Polytechnique Fédérale, Lausanne, Switzerland Department of Radiology, University of Geneva, Switzerland Department of Radiology, University of Lausanne, Switzerland
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Dehghani M M, Lanz B, Duarte JMN, Kunz N, Gruetter R. Refined Analysis of Brain Energy Metabolism Using In Vivo Dynamic Enrichment of 13C Multiplets. ASN Neuro 2016; 8:8/2/1759091416632342. [PMID: 26969691 PMCID: PMC4790427 DOI: 10.1177/1759091416632342] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2015] [Accepted: 12/30/2015] [Indexed: 11/18/2022] Open
Abstract
Carbon-13 nuclear magnetic resonance spectroscopy in combination with the infusion of 13C-labeled precursors is a unique approach to study in vivo brain energy metabolism. Incorporating the maximum information available from in vivo localized 13C spectra is of importance to get broader knowledge on cerebral metabolic pathways. Metabolic rates can be quantitatively determined from the rate of 13C incorporation into amino acid neurotransmitters such as glutamate and glutamine using suitable mathematical models. The time course of multiplets arising from 13C-13C coupling between adjacent carbon atoms was expected to provide additional information for metabolic modeling leading to potential improvements in the estimation of metabolic parameters. The aim of the present study was to extend two-compartment neuronal/glial modeling to include dynamics of 13C isotopomers available from fine structure multiplets in 13C spectra of glutamate and glutamine measured in vivo in rats brain at 14.1 T, termed bonded cumomer approach. Incorporating the labeling time courses of 13C multiplets of glutamate and glutamine resulted in elevated precision of the estimated fluxes in rat brain as well as reduced correlations between them.
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Affiliation(s)
- Masoumeh Dehghani M
- Laboratory for Functional and Metabolic Imaging (LIFMET), Ecole Polytechnique Fédérale de Lausanne (EPFL), Switzerland
| | - Bernard Lanz
- Laboratory for Functional and Metabolic Imaging (LIFMET), Ecole Polytechnique Fédérale de Lausanne (EPFL), Switzerland
| | - João M N Duarte
- Laboratory for Functional and Metabolic Imaging (LIFMET), Ecole Polytechnique Fédérale de Lausanne (EPFL), Switzerland Department of Radiology, University of Lausanne, Switzerland
| | - Nicolas Kunz
- CIBM-AIT, Ecole Polytechnique Fédérale de Lausanne, Switzerland
| | - Rolf Gruetter
- Laboratory for Functional and Metabolic Imaging (LIFMET), Ecole Polytechnique Fédérale de Lausanne (EPFL), Switzerland Department of Radiology, University of Lausanne, Switzerland Department of Radiology, University of Geneva, Switzerland
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Duarte JMN, Cunha RA, Carvalho RA. Adenosine A1receptors control the metabolic recovery after hypoxia in rat hippocampal slices. J Neurochem 2016; 136:947-57. [DOI: 10.1111/jnc.13512] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2015] [Revised: 12/07/2015] [Accepted: 12/11/2015] [Indexed: 12/11/2022]
Affiliation(s)
- João M. N. Duarte
- CNC-Center for Neuroscience and Cell Biology; University of Coimbra; Coimbra Portugal
- Faculty of Sciences and Technology; Department of Life Sciences; University of Coimbra; Coimbra Portugal
| | - Rodrigo A. Cunha
- CNC-Center for Neuroscience and Cell Biology; University of Coimbra; Coimbra Portugal
- Faculty of Medicine; University of Coimbra; Coimbra Portugal
| | - Rui A. Carvalho
- CNC-Center for Neuroscience and Cell Biology; University of Coimbra; Coimbra Portugal
- Faculty of Sciences and Technology; Department of Life Sciences; University of Coimbra; Coimbra Portugal
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Valente-Silva P, Lemos C, Köfalvi A, Cunha RA, Jones JG. Ketone bodies effectively compete with glucose for neuronal acetyl-CoA generation in rat hippocampal slices. NMR IN BIOMEDICINE 2015; 28:1111-1116. [PMID: 26174755 DOI: 10.1002/nbm.3355] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/26/2015] [Revised: 06/03/2015] [Accepted: 06/07/2015] [Indexed: 06/04/2023]
Abstract
Ketone bodies can be used for cerebral energy generation in situ, when their availability is increased as during fasting or ingestion of a ketogenic diet. However, it is not known how effectively ketone bodies compete with glucose, lactate, and pyruvate for energy generation in the brain parenchyma. Hence, the contributions of exogenous 5.0 mM [1-(13)C]glucose and 1.0 mM [2-(13)C]lactate + 0.1 mM pyruvate (combined [2-(13)C]lactate + [2-(13)C]pyruvate) to acetyl-CoA production were measured both without and with 5.0 mM [U-(13)C]3-hydroxybutyrate in superfused rat hippocampal slices by (13)C NMR non-steady-state isotopomer analysis of tissue glutamate and GABA. Without [U-(13)C]3-hydroxybutyrate, glucose, combined lactate + pyruvate, and unlabeled endogenous sources contributed (mean ± SEM) 70 ± 7%, 10 ± 2%, and 20 ± 8% of acetyl-CoA, respectively. With [U-(13)C]3-hydroxybutyrate, glucose contributions significantly fell from 70 ± 7% to 21 ± 3% (p < 0.0001), combined lactate + pyruvate and endogenous contributions were unchanged, and [U-(13)C]3-hydroxybutyrate became the major acetyl-CoA contributor (68 ± 3%)--about three-times higher than glucose. A direct analysis of the GABA carbon 2 multiplet revealed that [U-(13)C]3-hydroxybutyrate contributed approximately the same acetyl-CoA fraction as glucose, indicating that it was less avidly oxidized by GABAergic than glutamatergic neurons. The appearance of superfusate lactate derived from glycolysis of [1-(13)C]glucose did not decrease significantly in the presence of 3-hydroxybutyrate, hence total glycolytic flux (Krebs cycle inflow + exogenous lactate formation) was attenuated by 3-hydroxybutyrate. This indicates that, under these conditions, 3-hydroxybutyrate inhibited glycolytic flux upstream of pyruvate kinase.
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Affiliation(s)
- Paula Valente-Silva
- CNC-Center for Neurosciences and Cell Biology, University of Coimbra, Portugal
| | - Cristina Lemos
- CNC-Center for Neurosciences and Cell Biology, University of Coimbra, Portugal
| | - Attila Köfalvi
- CNC-Center for Neurosciences and Cell Biology, University of Coimbra, Portugal
| | - Rodrigo A Cunha
- CNC-Center for Neurosciences and Cell Biology, University of Coimbra, Portugal
- Faculty of Medicine, University of Coimbra, Portugal
| | - John G Jones
- CNC-Center for Neurosciences and Cell Biology, University of Coimbra, Portugal
- APDP-Portuguese Diabetes Association, Lisbon, Portugal
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15
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Duarte JMN, Girault FM, Gruetter R. Brain energy metabolism measured by (13)C magnetic resonance spectroscopy in vivo upon infusion of [3-(13)C]lactate. J Neurosci Res 2014; 93:1009-18. [PMID: 25522255 DOI: 10.1002/jnr.23531] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2014] [Revised: 11/06/2014] [Accepted: 11/10/2014] [Indexed: 11/11/2022]
Abstract
The brain uses lactate produced by glycolysis as an energy source. How lactate originated from the blood stream is used to fuel brain metabolism is not clear. The current study measures brain metabolic fluxes and estimates the amount of pyruvate that becomes labeled in glial and neuronal compartments upon infusion of [3-(13)C]lactate. For that, labeling incorporation into carbons of glutamate and glutamine was measured by (13)C magnetic resonance spectroscopy at 14.1 T and analyzed with a two-compartment model of brain metabolism to estimate rates of mitochondrial oxidation, glial pyruvate carboxylation, and the glutamate-glutamine cycle as well as pyruvate fractional enrichments. Extracerebral lactate at supraphysiological levels contributes at least two-fold more to replenish the neuronal than the glial pyruvate pools. The rates of mitochondrial oxidation in neurons and glia, pyruvate carboxylase, and glutamate-glutamine cycles were similar to those estimated by administration of (13)C-enriched glucose, the main fuel of brain energy metabolism. These results are in agreement with primary utilization of exogenous lactate in neurons rather than astrocytes.
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Affiliation(s)
- João M N Duarte
- Laboratory for Functional and Metabolic Imaging, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
| | - Freya-Merret Girault
- Laboratory for Functional and Metabolic Imaging, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
| | - Rolf Gruetter
- Laboratory for Functional and Metabolic Imaging, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland.,Department of Radiology, University of Lausanne, Lausanne, Switzerland.,Department of Radiology, University of Geneva, Geneva, Switzerland
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16
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Jeffrey FM, Marin-Valencia I, Good LB, Shestov AA, Henry PG, Pascual JM, Malloy CR. Modeling of brain metabolism and pyruvate compartmentation using (13)C NMR in vivo: caution required. J Cereb Blood Flow Metab 2013; 33:1160-7. [PMID: 23652627 PMCID: PMC3734769 DOI: 10.1038/jcbfm.2013.67] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/03/2012] [Revised: 04/01/2013] [Accepted: 04/03/2013] [Indexed: 01/30/2023]
Abstract
Two variants of a widely used two-compartment model were prepared for fitting the time course of [1,6-(13)C2]glucose metabolism in rat brain. Features common to most models were included, but in one model the enrichment of the substrates entering the glia and neuronal citric acid cycles was allowed to differ. Furthermore, the models included the capacity to analyze multiplets arising from (13)C spin-spin coupling, known to improve parameter estimates in heart. Data analyzed were from a literature report providing time courses of [1,6-(13)C2]glucose metabolism. Four analyses were used, two comparing the effect of different pyruvate enrichment in glia and neurons, and two for determining the effect of multiplets present in the data. When fit independently, the enrichment in glial pyruvate was less than in neurons. In the absence of multiplets, fit quality and parameter values were typical of those in the literature, whereas the multiplet curves were not modeled well. This prompted the use of robust statistical analysis (the Kolmogorov-Smirnov test of goodness of fit) to determine whether individual curves were modeled appropriately. At least 50% of the curves in each experiment were considered poorly fit. It was concluded that the model does not include all metabolic features required to analyze the data.
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Affiliation(s)
- F Mark Jeffrey
- Advanced Imaging Research Center, The University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA.
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17
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Duarte JMN, Gruetter R. Glutamatergic and GABAergic energy metabolism measured in the rat brain by 13
C NMR spectroscopy at 14.1 T. J Neurochem 2013; 126:579-90. [DOI: 10.1111/jnc.12333] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2013] [Revised: 06/05/2013] [Accepted: 06/06/2013] [Indexed: 12/11/2022]
Affiliation(s)
- João M. N. Duarte
- Laboratory for Functional and Metabolic Imaging; École Polytechnique Fédérale de Lausanne; Lausanne Switzerland
- Department of Radiology; University of Lausanne; Lausanne Switzerland
| | - Rolf Gruetter
- Laboratory for Functional and Metabolic Imaging; École Polytechnique Fédérale de Lausanne; Lausanne Switzerland
- Department of Radiology; University of Lausanne; Lausanne Switzerland
- Department of Radiology; University of Geneva; Geneva Switzerland
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18
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Cudalbu C, Lanz B, Duarte JMN, Morgenthaler FD, Pilloud Y, Mlynárik V, Gruetter R. Cerebral glutamine metabolism under hyperammonemia determined in vivo by localized (1)H and (15)N NMR spectroscopy. J Cereb Blood Flow Metab 2012; 32:696-708. [PMID: 22167234 PMCID: PMC3318147 DOI: 10.1038/jcbfm.2011.173] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Brain glutamine synthetase (GS) is an integral part of the glutamate-glutamine cycle and occurs in the glial compartment. In vivo Magnetic Resonance Spectroscopy (MRS) allows noninvasive measurements of the concentrations and synthesis rates of metabolites. (15)N MRS is an alternative approach to (13)C MRS. Incorporation of labeled (15)N from ammonia in cerebral glutamine allows to measure several metabolic reactions related to nitrogen metabolism, including the glutamate-glutamine cycle. To measure (15)N incorporation into the position 5N of glutamine and position 2N of glutamate and glutamine, we developed a novel (15)N pulse sequence to simultaneously detect, for the first time, [5-(15)N]Gln and [2-(15)N]Gln+Glu in vivo in the rat brain. In addition, we also measured for the first time in the same experiment localized (1)H spectra for a direct measurement of the net glutamine accumulation. Mathematical modeling of (1)H and (15)N MRS data allowed to reduce the number of assumptions and provided reliable determination of GS (0.30±0.050 μmol/g per minute), apparent neurotransmission (0.26±0.030 μmol/g per minute), glutamate dehydrogenase (0.029±0.002 μmol/g per minute), and net glutamine accumulation (0.033±0.001 μmol/g per minute). These results showed an increase of GS and net glutamine accumulation under hyperammonemia, supporting the concept of their implication in cerebral ammonia detoxification.
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Affiliation(s)
- Cristina Cudalbu
- Laboratory for Functional and Metabolic Imaging, Center for Biomedical Imaging, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland.
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19
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Duarte JMN, Ferreira SG, Carvalho RA, Cunha RA, Köfalvi A. CB₁ receptor activation inhibits neuronal and astrocytic intermediary metabolism in the rat hippocampus. Neurochem Int 2011; 60:1-8. [PMID: 22085448 DOI: 10.1016/j.neuint.2011.10.019] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2011] [Revised: 10/21/2011] [Accepted: 10/31/2011] [Indexed: 01/30/2023]
Abstract
Cannabinoid CB₁ receptor (CB₁R) activation decreases synaptic GABAergic and glutamatergic transmission and it also controls peripheral metabolism. Here we aimed at testing with ¹³C NMR isotopomer analysis whether CB₁Rs could have a local metabolic role in brain areas having high CB₁R density, such as the hippocampus. We labelled hippocampal slices with the tracers [2-¹³C]acetate, which is oxidized in glial cells, and [U-¹³C]glucose, which is metabolized both in glia and neurons, to evaluate metabolic compartmentation between glia and neurons. The synthetic CB₁R agonist WIN55212-2 (1 μM) significantly decreased the metabolism of both [2-¹³C]acetate (-11.6±2.0%) and [U-¹³C]glucose (-11.2±3.4%) in the tricarboxylic acid cycle that contributes to the glutamate pool. WIN55212-2 also significantly decreased the metabolism of [U-¹³C]glucose (-11.7±4.0%) but not that of [2-¹³C]acetate contributing to the pool of GABA. These effects of WIN55212-2 were prevented by the CB₁R antagonist AM251 (500 nM). These results thus suggest that CB₁Rs might be present also in hippocampal astrocytes besides their well-known neuronal localization. Indeed, confocal microscopy analysis revealed the presence of specific CB₁R immunoreactivity in astrocytes and pericytes throughout the hippocampus. In conclusion, CB₁Rs are able to control hippocampal intermediary metabolism in both neuronal and glial compartments, which suggests new alternative mechanisms by which CB₁Rs control cell physiology and afford neuroprotection.
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Affiliation(s)
- João M N Duarte
- Center for Neurosciences and Cell Biology of Coimbra, University of Coimbra, Coimbra, Portugal
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20
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Lund TM, Obel LF, Risa Ø, Sonnewald U. β-Hydroxybutyrate is the preferred substrate for GABA and glutamate synthesis while glucose is indispensable during depolarization in cultured GABAergic neurons. Neurochem Int 2011; 59:309-18. [DOI: 10.1016/j.neuint.2011.06.002] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2011] [Revised: 05/31/2011] [Accepted: 06/03/2011] [Indexed: 11/26/2022]
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21
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Duarte JMN, Lanz B, Gruetter R. Compartmentalized Cerebral Metabolism of [1,6-(13)C]Glucose Determined by in vivo (13)C NMR Spectroscopy at 14.1 T. FRONTIERS IN NEUROENERGETICS 2011; 3:3. [PMID: 21713114 PMCID: PMC3112327 DOI: 10.3389/fnene.2011.00003] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/01/2011] [Accepted: 05/17/2011] [Indexed: 11/13/2022]
Abstract
Cerebral metabolism is compartmentalized between neurons and glia. Although glial glycolysis is thought to largely sustain the energetic requirements of neurotransmission while oxidative metabolism takes place mainly in neurons, this hypothesis is matter of debate. The compartmentalization of cerebral metabolic fluxes can be determined by (13)C nuclear magnetic resonance (NMR) spectroscopy upon infusion of (13)C-enriched compounds, especially glucose. Rats under light α-chloralose anesthesia were infused with [1,6-(13)C]glucose and (13)C enrichment in the brain metabolites was measured by (13)C NMR spectroscopy with high sensitivity and spectral resolution at 14.1 T. This allowed determining (13)C enrichment curves of amino acid carbons with high reproducibility and to reliably estimate cerebral metabolic fluxes (mean error of 8%). We further found that TCA cycle intermediates are not required for flux determination in mathematical models of brain metabolism. Neuronal tricarboxylic acid cycle rate (V(TCA)) and neurotransmission rate (V(NT)) were 0.45 ± 0.01 and 0.11 ± 0.01 μmol/g/min, respectively. Glial V(TCA) was found to be 38 ± 3% of total cerebral oxidative metabolism, accounting for more than half of neuronal oxidative metabolism. Furthermore, glial anaplerotic pyruvate carboxylation rate (V(PC)) was 0.069 ± 0.004 μmol/g/min, i.e., 25 ± 1% of the glial TCA cycle rate. These results support a role of glial cells as active partners of neurons during synaptic transmission beyond glycolytic metabolism.
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Affiliation(s)
- João M N Duarte
- Center for Biomedical Imaging, Ecole Polytechnique Fédérale de Lausanne Lausanne, Switzerland
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22
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Santiago AR, Garrido MJ, Cristóvão AJ, Duarte JMN, Carvalho RA, Ambrósio AF. Evaluation of the Impact of Diabetes on Retinal Metabolites by NMR Spectroscopy. Curr Eye Res 2010; 35:992-1001. [DOI: 10.3109/02713683.2010.500113] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Affiliation(s)
- A. R. Santiago
- Center for Neuroscience and Cell Biology, Department of Zoology, University of Coimbra, Coimbra, Portugal
- Center of Ophthalmology and Visual Sciences, IBILI, Faculty of Medicine, University of Coimbra, Coimbra, Portugal
| | - M. J. Garrido
- Center for Neuroscience and Cell Biology, Department of Zoology, University of Coimbra, Coimbra, Portugal
| | - A. J. Cristóvão
- Center for Neuroscience and Cell Biology, Department of Zoology, University of Coimbra, Coimbra, Portugal
- Department of Zoology, University of Coimbra, Coimbra, Portugal
| | - J. M. N. Duarte
- Center for Neuroscience and Cell Biology, Institute of Biochemistry, Faculty of Medicine, University of Coimbra, Coimbra, Portugal
| | - R. A. Carvalho
- Center for Neuroscience and Cell Biology, Department of Zoology, University of Coimbra, Coimbra, Portugal
- Department of Life Sciences, Faculty of Sciences and Technology, University of Coimbra, Coimbra, Portugal
| | - A. F. Ambrósio
- Center for Neuroscience and Cell Biology, Department of Zoology, University of Coimbra, Coimbra, Portugal
- Center of Ophthalmology and Visual Sciences, IBILI, Faculty of Medicine, University of Coimbra, Coimbra, Portugal
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Abstract
Development of therapeutic measures to reduce the risk of potentially fatal episodes of hypoglycaemia and thus to achieve the full benefits of intensive insulin therapy in diabetic patients requires a complete understanding of the multi-factorial mechanisms for repeated hypoglycaemia-induced blunting of the sympatho-adrenal response (BSAR). After critical analysis of the hypotheses, this review paper suggests a heuristic theory. This theory suggests two mechanisms for the BSAR, each involving a critical role for the central brain noradrenergic system. Furthermore, this theory also suggests that the lateral hypothalamus (LH) plays an important role in this phenomenon. Within the framework of this theory, explanations for 1) sexual dimorphism in the adrenomedullary response (AR), 2) dissociation in the blunting of the AR and the sympathetic response (SR) and 3) antecedent exercise-induced blunting of the AR are provided. In addition, habituation of orexin-A neurons is suggested to cause defective awakening. Moreover, potential therapeutics measures have been also suggested that will reduce or prevent severe episodes of hypoglycaemia.
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Affiliation(s)
- B Parekh
- Institute of Metabolic Science, University of Cambridge, Cambridge CB2 0QQ, UK.
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Dericioglu N, Garganta CL, Petroff OA, Mendelsohn D, Williamson A. Blockade of GABA synthesis only affects neural excitability under activated conditions in rat hippocampal slices. Neurochem Int 2008; 53:22-32. [PMID: 18534717 PMCID: PMC2535818 DOI: 10.1016/j.neuint.2008.04.006] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2008] [Revised: 04/05/2008] [Accepted: 04/07/2008] [Indexed: 10/22/2022]
Abstract
The primary goal of this study was to establish whether inhibition of GABA synthesis was sufficient to induce network hyperexcitability in a rat hippocampal slice model comparable to that seen with GABA receptor blockade. We used field and intracellular recordings from the CA1 region of rat hippocampal slices to determine the physiological effects of blocking GABA synthesis with the convulsant, 3-mercaptoproprionic acid (MPA). We measured the rate of synthesis of GABA and glutamate in slices using 2-13C-glucose as a label source and liquid chromatography-tandem mass spectrometry. There was little effect of 3.5mM MPA on evoked events under control recording conditions. Tissue excitability was enhanced following a series of stimulus trains; this effect was enhanced when GABA transport was blocked. Evoked inhibitory potentials (IPSPs) failed following repetitive stimulation and MPA. Spontaneous epileptiform activity was seen reliably with elevated extracellular potassium (5mM). GABA synthesis decreased by 49% with MPA alone and 45% with the combination of MPA and excess potassium; GABA content was not substantially altered. Our data indicate: (1) GABAergic inhibition cannot be significantly compromised by MPA without network activation; (2) GABAergic synaptic inhibition is mediated by newly synthesized GABA; (3) there is a depletable pool of GABA that can sustain GABAergic inhibition when synthesis is impaired under basal, but not activated conditions; (4) overt hyperexcitability is only seen when newly synthesized GABA levels are low.
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Affiliation(s)
- Nese Dericioglu
- Department of Neurology, Hacettepe University School of Medicine, Ankara, Turkey
| | | | - Ognen A Petroff
- Department of Neurology, Yale University School of Medicine, New Haven, CT
| | - Dara Mendelsohn
- Department of Neurosurgery, Yale University School of Medicine, New Haven, CT
| | - Anne Williamson
- Department of Neurosurgery, Yale University School of Medicine, New Haven, CT
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25
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Eid T, Williamson A, Lee TSW, Petroff OA, De Lanerolle NC. Glutamate and astrocytes-Key players in human mesial temporal lobe epilepsy? Epilepsia 2008; 49 Suppl 2:42-52. [DOI: 10.1111/j.1528-1167.2008.01492.x] [Citation(s) in RCA: 114] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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26
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Energy substrates to support glutamatergic and GABAergic synaptic function: Role of glycogen, glucose and lactate. Neurotox Res 2007; 12:263-8. [DOI: 10.1007/bf03033909] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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