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Zhou Y, Eid T, Hassel B, Danbolt NC. Novel aspects of glutamine synthetase in ammonia homeostasis. Neurochem Int 2020; 140:104809. [DOI: 10.1016/j.neuint.2020.104809] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2020] [Revised: 07/08/2020] [Accepted: 07/09/2020] [Indexed: 02/07/2023]
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Oyarzabal A, Marin-Valencia I. Synaptic energy metabolism and neuronal excitability, in sickness and health. J Inherit Metab Dis 2019; 42:220-236. [PMID: 30734319 DOI: 10.1002/jimd.12071] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/29/2018] [Revised: 01/06/2019] [Accepted: 01/30/2019] [Indexed: 12/11/2022]
Abstract
Most of the energy produced in the brain is dedicated to supporting synaptic transmission. Glucose is the main fuel, providing energy and carbon skeletons to the cells that execute and support synaptic function: neurons and astrocytes, respectively. It is unclear, however, how glucose is provided to and used by these cells under different levels of synaptic activity. It is even more unclear how diseases that impair glucose uptake and oxidation in the brain alter metabolism in neurons and astrocytes, disrupt synaptic activity, and cause neurological dysfunction, of which seizures are one of the most common clinical manifestations. Poor mechanistic understanding of diseases involving synaptic energy metabolism has prevented the expansion of therapeutic options, which, in most cases, are limited to symptomatic treatments. To shed light on the intersections between metabolism, synaptic transmission, and neuronal excitability, we briefly review current knowledge of compartmentalized metabolism in neurons and astrocytes, the biochemical pathways that fuel synaptic transmission at resting and active states, and the mechanisms by which disorders of brain glucose metabolism disrupt neuronal excitability and synaptic function and cause neurological disease in the form of epilepsy.
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Affiliation(s)
- Alfonso Oyarzabal
- Synaptic Metabolism Laboratory, Department of Neurology, Hospital Sant Joan de Deu, Barcelona, Spain
| | - Isaac Marin-Valencia
- Laboratory of Developmental Neurobiology, The Rockefeller University, New York, New York
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Astrocytic pyruvate carboxylation: Status after 35 years. J Neurosci Res 2019; 97:890-896. [DOI: 10.1002/jnr.24402] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2018] [Revised: 01/11/2019] [Accepted: 02/05/2019] [Indexed: 12/24/2022]
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Dienel GA. Lack of appropriate stoichiometry: Strong evidence against an energetically important astrocyte-neuron lactate shuttle in brain. J Neurosci Res 2017; 95:2103-2125. [PMID: 28151548 DOI: 10.1002/jnr.24015] [Citation(s) in RCA: 115] [Impact Index Per Article: 16.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2016] [Revised: 11/28/2016] [Accepted: 12/16/2016] [Indexed: 12/22/2022]
Abstract
Glutamate-stimulated aerobic glycolysis in astrocytes coupled with lactate shuttling to neurons where it can be oxidized was proposed as a mechanism to couple excitatory neuronal activity with glucose utilization (CMRglc ) during brain activation. From the outset, this model was not viable because it did not fulfill critical stoichiometric requirements: (i) Calculated glycolytic rates and measured lactate release rates were discordant in cultured astrocytes. (ii) Lactate oxidation requires oxygen consumption, but the oxygen-glucose index (OGI, calculated as CMRO2 /CMRglc ) fell during activation in human brain, and the small rise in CMRO2 could not fully support oxidation of lactate produced by disproportionate increases in CMRglc . (iii) Labeled products of glucose metabolism are not retained in activated rat brain, indicating rapid release of a highly labeled, diffusible metabolite identified as lactate, thereby explaining the CMRglc -CMRO2 mismatch. Additional independent lines of evidence against lactate shuttling include the following: astrocytic oxidation of glutamate after its uptake can help "pay" for its uptake without stimulating glycolysis; blockade of glutamate receptors during activation in vivo prevents upregulation of metabolism and lactate release without impairing glutamate uptake; blockade of β-adrenergic receptors prevents the fall in OGI in activated human and rat brain while allowing glutamate uptake; and neurons upregulate glucose utilization in vivo and in vitro under many stimulatory conditions. Studies in immature cultured cells are not appropriate models for lactate shuttling in adult brain because of their incomplete development of metabolic capability and astrocyte-neuron interactions. Astrocyte-neuron lactate shuttling does not make large, metabolically significant contributions to energetics of brain activation. © 2017 Wiley Periodicals, Inc.
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Affiliation(s)
- Gerald A Dienel
- Department of Neurology, University of Arkansas for Medical Sciences, Little Rock, Arkansas, and Department of Cell Biology and Physiology, University of New Mexico, Albuquerque, New Mexico
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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: 36] [Impact Index Per Article: 3.0] [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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Schousboe A. Studies of Brain Metabolism: A Historical Perspective. NEURAL METABOLISM IN VIVO 2012. [DOI: 10.1007/978-1-4614-1788-0_31] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
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McKenna MC. The glutamate-glutamine cycle is not stoichiometric: fates of glutamate in brain. J Neurosci Res 2008; 85:3347-58. [PMID: 17847118 DOI: 10.1002/jnr.21444] [Citation(s) in RCA: 283] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Although glutamate is usually thought of as the major excitatory neurotransmitter in brain, it is important to note that glutamate has many other fates in brain, including oxidation for energy, incorporation into proteins, and formation of glutamine, gamma-aminobutyric acid (GABA), and glutathione. The compartmentation of glutamate in brain cells is complex and modulated by the presence and concentration of glutamate per se as well as by other metabolites. Both astrocytes and neurons distinguish between exogenous glutamate and glutamate formed endogenously from glutamine via glutaminase. There is evidence of multiple subcellular compartments of glutamate within both neurons and astrocytes, and the carbon skeleton of glutamate can be derived from other amino acids and many energy substrates including glucose, lactate, and 3-hydroxybutyrate. Both astrocytes and neurons utilize glutamate, albeit for cell-specific metabolic fates. Glutamate is readily formed in neurons from glutamine synthesized in astrocytes, released into the extracellular space, and taken up by neurons. However, the glutamate-glutamine cycle is not a stoichiometric cycle but rather an open pathway that interfaces with many other metabolic pathways to varying extents depending on cellular requirements and priorities.
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Affiliation(s)
- Mary C McKenna
- Department of Pediatrics, University of Maryland School of Medicine, Baltimore, MD 21201, USA.
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Affiliation(s)
- H Bachelard
- M.R. Centre, Department of Physics, University of Nottingham, England
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Badar-Goffer RS, Bachelard HS, Morris PG. Cerebral metabolism of acetate and glucose studied by 13C-n.m.r. spectroscopy. A technique for investigating metabolic compartmentation in the brain. Biochem J 1990; 266:133-9. [PMID: 1968742 PMCID: PMC1131106 DOI: 10.1042/bj2660133] [Citation(s) in RCA: 209] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The time courses of incorporation of 13C from 13C-labelled glucose or acetate into cerebral amino acids (glutamate, glutamine and 4-aminobutyrate) and lactate were monitored by using 13C-n.m.r. spectroscopy. When [1-13C]glucose was used as precursor the C-2 of 4-aminobutyrate was more highly labelled than the analogous C-4 of glutamate, whereas no label was observed in glutamine. A similar pattern was observed with [2-13C]glucose: the C-1 of 4-aminobutyrate was more highly labelled than the analogous C-5 of glutamate. Again, no labelling of glutamine was detected. In contrast, [2-13C]acetate labelled the C-4 of glutamine and the C-2 of 4-aminobutyrate more highly than the C-4 of glutamate; [1-13C]acetate also labelled the C-1 and C-5 positions of glutamine more than the analogous positions of glutamate. These results are consistent with earlier patterns reported from the use of 14C-labelled precursors that led to the concept of compartmentation of neuronal and glial metabolism and now provide the possibility of distinguishing differential effects of metabolic perturbations on the two pools simultaneously. An unexpected observation was that citrate is more highly labelled from acetate than from glucose.
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Abstract
Gamma-aminobutyric acid (GABA) is the most important inhibitory transmitter, quantitatively, in the CNS. Evidence exists that decreased GABAergic neurotransmission may play a role in some forms of epilepsy. Consequently, manipulating the GABA system may be a therapeutic possibility in the treatment of this disease. Inhibition of the major GABA degrading enzyme, GABA-transaminase (GABA-T), seems to be the most promising approach. Currently, 2 antiepileptic drugs, valproate (VPA) and vigabatrin, gamma-vinyl GABA (GVG), are available, which are supposed to inhibit the degradation of GABA. Both drugs cause an increase in the total concentration of GABA in the brain, but to a different extent. VPA produces a moderate elevation, which seems to be the result of a marked increase in the transmitter-related GABA pool, while the pronounced elevation in GABA concentration observed during treatment with GVG seems to be caused mainly by an increase in the non-transmitter-related (glial) GABA pool. In order to investigate this apparently differential influence of VPA and GVG on the GABA system, a number of studies were undertaken in selectively cultured astrocytes and neurons from mice. For both drugs neuronal GABA-T proved far more sensitive with regard to inhibition than glial GABA-T. In order to obtain a more direct measure of a potential GABAergic mechanism of action of VPA and GVG, synaptic release of endogenous GABA was determined after culturing neurons in the presence of clinically relevant concentrations of the drugs. GVG caused a significant increase in GABA release, even at concentrations as low as 25 microM. For VPA only the highest of the investigated concentrations (300 microM) augmented GABA release. It is concluded that the antiepileptic effect of GVG seems to be caused by a direct GABAergic mechanism of action. For VPA an influence on the GABA system may play a role in the antiepileptic effect of the drug. However, the lack of definite data on human brain levels of VPA after chronic treatment, combined with evidence that VPA exhibits a number of other effects that may be relevant for its antiepileptic properties, makes the interpretation of a GABAergic mechanism of action difficult. Controlled clinical trials have been increasingly applied within all areas of medicine. In 1982 a survey of the literature identified 29 studies of antiepileptic drugs, where the design involved randomization, the double-blind principle and a statistical analysis of the results.(ABSTRACT TRUNCATED AT 400 WORDS)
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Affiliation(s)
- L Gram
- University Clinic of Neurology, Hvidovre Hospital, Copenhagen, Denmark
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Vezzani A, Ungerstedt U, French ED, Schwarcz R. In vivo brain dialysis of amino acids and simultaneous EEG measurements following intrahippocampal quinolinic acid injection: evidence for a dissociation between neurochemical changes and seizures. J Neurochem 1985; 45:335-44. [PMID: 3159848 DOI: 10.1111/j.1471-4159.1985.tb03993.x] [Citation(s) in RCA: 85] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The extracellular content of taurine, glutamate, glutamine, and glycine was measured by the novel method of brain dialysis in the acute phases following an intrahippocampal injection of the excitotoxic convulsant brain metabolite quinolinic acid (QUIN). Using bilaterally implanted depth electrodes physically combined with hollow fibers for dialysis, it was possible to collect continuously brain perfusates while simultaneously monitoring brain activity in the unanesthetized rat. In separate animals, hippocampal amino acid tissue levels were measured 2 h after an intracerebral injection of a convulsant dose (156 nmol) of QUIN. When compared with those in animals receiving the nonconvulsant decarboxylation product of QUIN, nicotinic acid, no differences in tissue levels were detected. In contrast, the same dose of QUIN caused a selective increase (2.24-fold) in taurine levels in perfusates from the injected hippocampus. These changes were apparent prior to the onset of electrographic seizures and did not occur in the contralateral hippocampus where seizure activity was equally severe. Thus, increases in extracellular taurine, triggered by the presence of QUIN in the hippocampus, may reflect a selective tissue response to the neurotoxic (rather than the convulsant) effects of this excitotoxin.
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Abstract
Glutamine synthetase activity was measured in seven brain areas post-mortem from control patients, and those with Huntington's disease. The activity of the enzyme was reduced in the frontal and temporal cortex, putamen and cerebellum, but not in the hippocampus, thalamus or olivary nucleus. The results do not suggest a generalised deficiency of glutamine synthetase in Huntington's disease. However, as this enzyme is localised to astrocytic cells, the reduction in activity in areas of neuronal devastation, where the ration of astrocytes to neurones is increased, may reflect a greater functional deficit. The enzyme plays a crucial role in cerebral ammonia assimilation and its inhibition in laboratory animals is known to produce neuronal toxicity. A reduction in its activity in Huntington's disease may well contribute to the neuronal pathology in certain areas.
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Mangano RM, Schwarcz R. Huntington's disease. Glutamate and aspartate metabolism in blood platelets. J Neurol Sci 1982; 53:489-500. [PMID: 6121842 DOI: 10.1016/0022-510x(82)90245-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
The metabolism of two excitatory amino acids, glutamate and aspartate, was determined in human blood platelets because of their hypothetical involvement in the etiology of the heritable neurodegenerative disorder, Huntington's disease (HD). The specific activities of the two acids and their amides, glutamine and asparagine, constitute markers for the efficiency of the enzymatic cascades originating from [3H]acetate and [14C]glucose, respectively. Results demonstrate that both precursors are converted by temperature-dependent processes, thus indicating the presence, in platelets, of all glycolytic and tricarboxylic acid cycle enzymes necessary for the biosynthesis of glutamate and aspartate. No differences between normal and HD platelets were found in any of the specific activities investigated. A genetic defect in any of these enzymes is therefore not likely to underlie HD neuropathology.
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Krespan B, Berl S, Nicklas WJ. Alteration in neuronal-glial metabolism of glutamate by the neurotoxin kainic acid. J Neurochem 1982; 38:509-18. [PMID: 6125571 DOI: 10.1111/j.1471-4159.1982.tb08657.x] [Citation(s) in RCA: 64] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
The effect of the excitotoxin kainic acid on glutamate and glutamine metabolism was studied in cerebellar slices incubated with D-[2-14C]glucose, [U-14C]gamma-aminobutyric acid, [3H]acetate, [U-14C]glutamate, and [U-14C]glutamine as precursors. Kainic acid (1 mM) strongly inhibited the labeling of glutamine relative to that of glutamate from all precursors except [2-14C]glucose and [U-14C]glutamine. Kainic acid did not inhibit glutamine synthetase directly. The data indicate that in the cerebellum kainic acid inhibits the synthesis of glutamine from the small pool of glutamate that is thought to be associated with glial cells. Kainic acid also markedly stimulated the efflux of glutamate from cerebellar slices and this release was not sensitive to tetrodotoxin. Kainic acid stimulated efflux of both glucose- and acetate-labeled glutamate. In contrast, veratridine released glucose-labeled glutamate preferentially via a tetrodotoxin-sensitive mechanism. Kainic acid did not release [U-14C]glutamate from synaptosomal fractions. These results suggest that the bulk of the glutamate released from cerebellar slices by kainic acid comes from nonsynaptic pools.
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Silverman M, Vinay P, Shinobu L, Gougoux A, Lemieux G. Luminal and antiluminal transport of glutamine in dog kidney: effect of metabolic acidosis. Kidney Int 1981; 20:359-65. [PMID: 7300126 DOI: 10.1038/ki.1981.147] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
We have studied the luminal acid antiluminal transport of glutamine and glutamate with the pulse injection multiple indicator dilution technique in normal dogs and in dogs with acute and chronic acidosis. The single-pass experiments yield estimates of unidirectional influx at each nephron surface. The kidney of normal dogs extracts 57% of the arterial glutamine load; 23% of this extraction is due to luminal reabsorption and 34% to antiluminal uptake from the peritubular circulation. After the total net extraction by the kidney is determined from arteriovenous differences and blood flow measurements, in normal dogs, the net antiluminal flux is calculated to be negative, indicating that at least part of the glutamine reabsorbed is returned to the renal venous circulation across the antiluminal membrane. In acutely acidotic dogs, the situation is similar, but a 30% to 40% fall in renal hemodynamics (blood flow and GFR) is observed with secondary reduction in luminal and antiluminal uptake. In chronically acidotic dogs, the unidirectional luminal and antiluminal uptakes of glutamine are similar to that observed in normal animals, but the calculated efflux across the antiluminal membrane is drastically reduced. These findings suggest that (l) a cellular transport mechanism for glutamine exists at the antiluminal pole of the renal tubule and dominates the luminal uptake process in normal animals; (2) cellular transport of glutamine (luminal and antiluminal) does not play a role in the renal adaptation to metabolic acidosis; (3) the intrarenal utilization of glutamine acts as a metabolic sink for this amino acid, which in turn regulates its net uptake by the kidney; and (4) the total uptake of glutamine limits ammoniagenesis in this species.
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Schoolwerth A, LaNoue K. The role of microcompartmentation in the regulation of glutamate metabolism by rat kidney mitochondria. J Biol Chem 1980. [DOI: 10.1016/s0021-9258(19)85713-7] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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Nicklàs WJ, Nunez R, Berl S, Duvoisin R. Neuronal-glial contributions to transmitter amino acid metabolism: studies with kainic acid-induced lesions of rat striatum. J Neurochem 1979; 33:839-44. [PMID: 39980 DOI: 10.1111/j.1471-4159.1979.tb09913.x] [Citation(s) in RCA: 63] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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Patel MS, Owen OE. The metabolism of leucine by developing rat brain: effect of leucine and 2-oxo-4-methylvalerate on lipid synthesis from glucose and ketone bodies. J Neurochem 1978; 30:775-82. [PMID: 650218 DOI: 10.1111/j.1471-4159.1978.tb10784.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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Minchin MC. Compartmentation of amino acid metabolism in small slices of rat spinal cord and cerebral cortex. Brain Res 1977; 127:302-6. [PMID: 861763 DOI: 10.1016/0006-8993(77)90545-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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Patel MS, Owen OE, Raefsky C. Effect of methylmalonate on ketone body metabolism in developing rat brain. Life Sci 1976; 19:41-7. [PMID: 940434 DOI: 10.1016/0024-3205(76)90372-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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Patel MS, Owen OE. Lipogenesis from ketone bodies in rat brain. Evidence for conversion of acetoacetate into acetyl-coenzyme A in the cytosol. Biochem J 1976; 156:603-7. [PMID: 949342 PMCID: PMC1163794 DOI: 10.1042/bj1560603] [Citation(s) in RCA: 62] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The metabolism of acetoacetate via a proposed cytosolic pathway in brain of 1-week-old rats was investigated. (-)-Hydroxycitrate, an inhibitor of ATP citrate lyase, markedly inhibited the incorporation of carbon from labelled glucose and 3-hydroxybutyrate into cerebral lipids, but had no effect on the incorporation of labelled acetate and acetoacetate into brain lipids. Similarly, n-butylmalonate and benzene-1,2,3-tricarboxylate inhibited the incorporation of labelled 3-hydroxybutyrate but not of acetoacetate into cerebral lipids. These inhibitors had no effect on the oxidation to 14CO2 of the labelled substrates used. (-)-Hydroxycitrate decreased the incorporation of 3H from 3H2O into cerebral lipids by slices metabolizing either glucose or 3-hydroxybutyrate, but not in the presence of acetoacetate. (-)-Hydroxycitrate also differentially inhibited the incorporation of [2-14C]-leucine and [U-14C]leucine into cerebral lipids. The data show that, although the acetyl moiety of acetyl-CoA generated in brain mitochondria is largely translocated as citrate from these organelles to the cytosol, a cytosolic pathway exists by which acetoacetate is converted directly into acetyl-COA in this cellular compartment.
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Patel MS, Owen OE. Effect of hyperphenylalaninaemia on lipid synthesis from ketone bodies by rat brain. Biochem J 1976; 154:319-25. [PMID: 938453 PMCID: PMC1172713 DOI: 10.1042/bj1540319] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The effect of hyperphenylalaninaemia on the metabolism of ketone bodies in vivo and in vitro by developing rat brain was investigated. The incorporation in vivo of [14C]acetoacetate into cerebral lipids was decreased by both chronic (for 3 days) and acute (for 6h) hyperphenylalaninaemia induced by injecting phenylalanine into 1-week-old rats. In studies in vitro it was observed that the incorporation of the radioactivity from [14C]acetoacetate and 3-hydroxy[14C]butyrate into cerebral lipids was inhibited by phenyl-pyruvate, but not by phenylalanine. Phenylpyruvate also inhibited the incorporation of 3H from 3H2O into lipids by brain slices metabolizing either 3-hydroxybutyrate or acetoacetate in the presence of glucose. These findings suggest that the decrease in the incorporation in vivo of [14C]acetoacetate into cerebral lipids in hyperphenylalaninaemic rats is most likely caused by phenylpyruvate and not by phenylalanine. Phenylpyruvate as well as phenylalanine had no inhibitory effects on ketone-body-catabolizing enzymes, namely 3-hydroxybutyrate dehydrogenase, 3-oxo acid CoA-transferase and acetoacetyl-CoA thiolase, in rat brain. Phenylpyruvate but not phenylalanine inhibited the activity of the 2-oxoglutarate dehydrogenase complex from rat and human brain. These findings suggest that the metabolism of ketone bodies is impaired in brains of untreated phenylketonuric patients, and in turn may contribute to the diminution of mental development and function associated with phenylketonuria.
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Rose MS, Lock EA, Smith LL, Wyatt I. Paraquat accumulation: tissue and species specificity. Biochem Pharmacol 1976; 25:419-23. [PMID: 820354 DOI: 10.1016/0006-2952(76)90344-0] [Citation(s) in RCA: 175] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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Lajtha A, Banay-Schwartz M. The usefulness of studies in vitro for understanding cerebral metabolite transport in vivo. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1976; 69:415-34. [PMID: 941744 DOI: 10.1007/978-1-4684-3264-0_31] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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Patel MS, Johnson CA, Rajan R, Owen OE. The metabolism of ketone bodies in developing human brain: development of ketone-body-utilizing enzymes and ketone bodies as precursors for lipid synthesis. J Neurochem 1975; 25:905-8. [PMID: 1206409 DOI: 10.1111/j.1471-4159.1975.tb04428.x] [Citation(s) in RCA: 68] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
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Neidle A, Kandera J, Lajtha A. Compartmentation and exchangeability of brain amino acids: evidence from studies of transport into tissue slices. Arch Biochem Biophys 1975; 169:397-405. [PMID: 1180557 DOI: 10.1016/0003-9861(75)90181-2] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
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Mukherji B, Kashiki Y, Ohyanagi H, Sloviter HA. Metabolism of ethanol and acetaldehyde by the isolated perfused rat brain. J Neurochem 1975. [DOI: 10.1111/j.1471-4159.1975.tb03881.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Clarke DD, Greenfield S, Dicker E, Tirri LJ, Ronan EJ. A relationship of N-acetylaspartate biosynthesis to neuronal protein synthesis. J Neurochem 1975; 24:479-85. [PMID: 1113123 DOI: 10.1111/j.1471-4159.1975.tb07665.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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Hertz L, Schousboe A. Ion and energy metabolism of the brain at the cellular level. INTERNATIONAL REVIEW OF NEUROBIOLOGY 1975; 18:141-211. [PMID: 128532 DOI: 10.1016/s0074-7742(08)60035-5] [Citation(s) in RCA: 101] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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Weiss B, Stiller RL. Dibutyryl cyclic adenosine 3',5-monophosphate and brain lipid metabolism. Lipids 1974; 9:514-9. [PMID: 4371698 DOI: 10.1007/bf02532498] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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Nicklas WJ, Berl S, Clarke DD. Interaction of catecholamine and amino acid metabolism in brain: effect of pargyline and L-dopa. J Neurochem 1974; 23:149-57. [PMID: 4852502 DOI: 10.1111/j.1471-4159.1974.tb06929.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
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Johnson JL. An analysis of the compartmentation and proximo-distal convection of the clutamate-glutamine system in the dorsal sensory neuron: comparison with the motoneuron and cerebral cortex. Brain Res 1974; 67:489-502. [PMID: 4470437 DOI: 10.1016/0006-8993(74)90497-1] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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Curtis DR, Johnston GA. Amino acid transmitters in the mammalian central nervous system. ERGEBNISSE DER PHYSIOLOGIE, BIOLOGISCHEN CHEMIE UND EXPERIMENTELLEN PHARMAKOLOGIE 1974; 69:97-188. [PMID: 4151806 DOI: 10.1007/3-540-06498-2_3] [Citation(s) in RCA: 124] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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Nicklas WJ, Berl S. In vivo studies on the effect of 6-hydroxydopamine on amino acid metabolism in brain. Brain Res 1973; 61:343-56. [PMID: 4359223 DOI: 10.1016/0006-8993(73)90538-6] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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Graafmans WD. The influence of carbon dioxide on morphogenesis in Penicillium isariiforme. ARCHIV FUR MIKROBIOLOGIE 1973; 91:67-76. [PMID: 4711458 DOI: 10.1007/bf00409539] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
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Nicklas WJ, Puszkin S, Berl S. Effect of vinblastine and colchicine on uptake and release of putative transmitters by synaptosomes and on brain actomyosin-like protein. J Neurochem 1973; 20:109-21. [PMID: 4347043 DOI: 10.1111/j.1471-4159.1973.tb12109.x] [Citation(s) in RCA: 80] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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Santini M, Berl S. Effects of reserpine and monoamine oxidase inhibition on the levels of amino acids in sensory ganglia, sympathetic ganglia and spinal cord. Brain Res 1972; 47:167-76. [PMID: 4641266 DOI: 10.1016/0006-8993(72)90260-0] [Citation(s) in RCA: 42] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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Benjamin AM, Quastel JH. Locations of amino acids in brain slices from the rat. Tetrodotoxin-sensitive release of amino acids. Biochem J 1972; 128:631-46. [PMID: 4634833 PMCID: PMC1173815 DOI: 10.1042/bj1280631] [Citation(s) in RCA: 227] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
1. Amino acids, particularly glutamate, gamma-aminobutyrate, aspartate and glycine, were released from rat brain slices on incubation with protoveratrine (especially in a Ca(2+)-deficient medium) or with ouabain or in the absence of glucose. Release was partially or wholly suppressed by tetrodotoxin. 2. Tetrodotoxin did not affect the release of glutamine under various incubation conditions, nor did protoveratrine accelerate it. 3. Protoveratrine caused an increased rate of formation of glutamine in incubated brain slices. 4. Increased K(+) in the incubation medium caused release of gamma-aminobutyrate, the process being partly suppressed by tetrodotoxin. 5. Incubation of brain slices in a glucose-free medium led to increased production of aspartate and to diminished tissue contents of glutamates, glutamine and glycine. 6. Use of tetrodotoxin to suppress the release of amino acids from neurons in slices caused by the joint action of protoveratrine and ouabain (the latter being added to diminish reuptake of amino acids), it was shown that the major pools of glutamate, aspartate, glycine, serine and probably gamma-aminobutyrate are in the neurons. 7. The major pool of glutamine lies not in the neurons but in the glia. 8. The tricarboxylic cycle inhibitors, fluoroacetate and malonate, exerted different effects on amino acid contents in, and on amino acid release from, brain slices incubated in the presence of protoveratrine. Fluoroacetate (3mm) diminished the content of glutamine, increased that of glutamate and gamma-aminobutyrate and did not affect respiration. Malonate (2mm) diminished aspartate and gamma-aminobutyrate content, suppressed respiration and did not affect glutamine content. It is suggested that malonate acts mainly on the neurons, and that fluoroacetate acts mainly on the glia, at the concentrations quoted. 9. Glutamine was more effective than glutamate as a precursor of gamma-aminobutyrate. 10. It is suggested that glutamate released from neurons is partly taken up by glia and converted there into glutamine. This is returned to the neurons where it is hydrolysed and converted into glutamate and gamma-aminobutyrate.
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Cheng SC, Nakamura R. Metabolism related to the tricarboxylic acid cycle in rat brain slices. Observations on CO 2 fixation and metabolic compartmentation. Brain Res 1972; 38:355-70. [PMID: 5028531 DOI: 10.1016/0006-8993(72)90718-4] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
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Mushahwar IK, Koeppe RE. Incorporation of label from(1- 14 C)ethanol into the glutamate-glutamine pools of rat brain in vivo. Biochem J 1972; 126:467-9. [PMID: 5075261 PMCID: PMC1178401 DOI: 10.1042/bj1260467] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Glutamate and glutamine were isolated from the brains of rats given [1-(14)C]ethanol by three different routes of injection with and without carrier ethanol or acetate. Without exception, the specific radioactivity of brain glutamine was 3- to 5-fold that of brain glutamate. The route of injection had no consistent effect on the results. These results indicate that small amounts of ethanol are oxidized by rat brain in the compartment responsible for the so-called ;small metabolic pool' of brain glutamate.
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Cohen HP LIN S. The effect of diethyl- -fluoroglutarate on phosphates and glutamate in slices of rabbit cerebral cortex. J Neurochem 1972; 19:513-23. [PMID: 5010093 DOI: 10.1111/j.1471-4159.1972.tb01361.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
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Berl S, Clarke DD. Effects of LI + on the metabolism in brain of glutamate, glutamine, aspartate and GABA from (1- 14 C)acetate in vitro. Brain Res 1972; 36:203-13. [PMID: 5008380 DOI: 10.1016/0006-8993(72)90776-7] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
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Wherrett JR, Tower DB. Glutamyl, aspartyl and amide moieties of cerebral proteins: metabolic aspects in vitro. J Neurochem 1971; 18:1027-42. [PMID: 5567896 DOI: 10.1111/j.1471-4159.1971.tb12032.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
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Nicklas WJ, Clark JB, Williamson JR. Metabolism of rat brain mitochondria. Studies on the potassium ion-stimulated oxidation of pyruvate. Biochem J 1971; 123:83-95. [PMID: 5128666 PMCID: PMC1176902 DOI: 10.1042/bj1230083] [Citation(s) in RCA: 42] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
1. Rat brain-cortex mitochondria were incubated in media containing 1, 5 or 100mm-K(+) in the presence of ADP, uncoupler (FCCP, carbonyl cyanide p-trifluoro-methoxyphenylhydrazone) or valinomycin while metabolizing pyruvate and malate, or acetylcarnitine and malate or glutamate and malate as substrates. Both the uptake of oxygen and disappearance of substrate were measured under these conditions. 2. With pyruvate and malate as substrate in the presence of both ADP and valinomycin, both the uptake of oxygen and disappearance of pyruvate increased markedly on increasing the K(+) content of the incubation medium from 5 to 100mm-K(+). However, in the presence of uncoupler (FCCP), although the oxygen uptake doubled little change was observed in the rate of disappearance of pyruvate on increasing the K(+) concentration. 3. Only small changes in uptake of substrate and oxygen were observed in the presence of ADP, uncoupler (FCCP) or valinomycin on increasing the K(+) concentration when acetylcarnitine+malate or glutamate+malate were used as substrates by brain mitochondria. 4. Further, increasing the K(+) concentration from 1 to 20mm when rat brain mitochondria were oxidizing a mixture of pyruvate and glutamate in the presence of malate and ADP caused a 30% increase in the respiration rate, 50% increase in the rate of disappearance of pyruvate and an 80% decrease in the rate of disappearance of glutamate. 5. Investigation of the redox state of the cytochromes and the nicotinamide nucleotides in various conditions with either pyruvate or acetylcarnitine as substrates suggested that the specific stimulation of metabolism of pyruvate by K(+) could not be explained by a general stimulation of the electron-transport system. 6. Low-amplitude high-energy swelling of rat brain mitochondria was investigated in both Na(+)- and K(+)-containing media. Swelling of brain mitochondria was much greater in the Na(+)-containing medium and in this medium, the addition of Mg(2+) caused a partial reversal of swelling together with an 85% decrease in the rate of utilization of pyruvate. However, in the K(+)-containing medium, the addition of Mg(2+), although also causing a reversal of swelling, did not affect the rate of disappearance of pyruvate. 7. Measurements of the ATP, NADH/NAD(+) and acetyl-CoA/CoA contents were made under various conditions and no evidence that K(+) concentrations affected these parameters was obtained. 8. The results are discussed in relationship to the physiological significance of the stimulation of pyruvate metabolism by K(+) in rat brain mitochondria. It is proposed that K(+) causes its effects by a direct stimulation of the pyruvate dehydrogenase complex.
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