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Tiwari AK, Adhikari A, Mishra LC, Srivastava A. Current Status of Our Understanding for Brain Integrated Functions and its Energetics. Neurochem Res 2022; 47:2499-2512. [PMID: 35689788 DOI: 10.1007/s11064-022-03633-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Revised: 05/07/2022] [Accepted: 05/09/2022] [Indexed: 10/18/2022]
Abstract
Human/animal brain is a unique organ with substantially high metabolism but it contains no energy reserve that is the reason it requires continuous supply of O2 and energy fluxes through CBF. The main source of energy remains glucose as the other biomolecules do not able to cross the blood-brain barrier. The speed of glucose metabolism is heterogeneous throughout the brain. One of the major flux consumption is Neuron-astrocyte cycling of glutamate and glutamine in glutamatergic neurons (approximately 80% of glucose metabolism in brain). The quantification of cellular glucose and other related substrate in resting, activated state can be analyzed through [18 F]FDG -positron-emission tomography (studying CMRglc) and [13 C/31P -MRS: for neuroenergetics & neurotransmitter cycling &31P-MRS: for energy induction & redox state). Merging basic in vitro studies with these techniques will help to develop new treatment paradigms for human brain diseased conditions.
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Affiliation(s)
- Anjani Kumar Tiwari
- Department of Chemistry, Babasaheb Bhimrao Ambedkar University (A Central University), 226025, Lucknow, Uttar Pradesh, India.
| | - Anupriya Adhikari
- Department of Chemistry, Babasaheb Bhimrao Ambedkar University (A Central University), 226025, Lucknow, Uttar Pradesh, India
| | - Lokesh Chandra Mishra
- Department of Zoology, Hansraj College, University of Delhi, North Campus, 110007, Delhi, India
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Dal-Cim T, Martins WC, Thomaz DT, Coelho V, Poluceno GG, Lanznaster D, Vandresen-Filho S, Tasca CI. Neuroprotection Promoted by Guanosine Depends on Glutamine Synthetase and Glutamate Transporters Activity in Hippocampal Slices Subjected to Oxygen/Glucose Deprivation. Neurotox Res 2016; 29:460-8. [PMID: 26858177 DOI: 10.1007/s12640-015-9595-z] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2015] [Revised: 12/02/2015] [Accepted: 12/30/2015] [Indexed: 12/22/2022]
Abstract
Guanosine (GUO) has been shown to act as a neuroprotective agent against glutamatergic excitotoxicity by increasing glutamate uptake and decreasing its release. In this study, a putative effect of GUO action on glutamate transporters activity modulation was assessed in hippocampal slices subjected to oxygen and glucose deprivation (OGD), an in vitro model of brain ischemia. Slices subjected to OGD showed increased excitatory amino acids release (measured by D-[(3)H]aspartate release) that was prevented in the presence of GUO (100 µM). The glutamate transporter blockers, DL-TBOA (10 µM), DHK (100 µM, selective inhibitor of GLT-1), and sulfasalazine (SAS, 250 µM, Xc(-) system inhibitor) decreased OGD-induced D-aspartate release. Interestingly, DHK or DL-TBOA blocked the decrease in glutamate release induced by GUO, whereas SAS did not modify the GUO effect. GUO protected hippocampal slices from cellular damage by modulation of glutamate transporters, however selective blockade of GLT-1 or Xc- system only did not affect this protective action of GUO. OGD decreased hippocampal glutamine synthetase (GS) activity and GUO recovered GS activity to control levels without altering the kinetic parameters of GS activity, thus suggesting GUO does not directly interact with GS. Additionally, the pharmacological inhibition of GS activity with methionine sulfoximine abolished the effect of GUO in reducing D-aspartate release and cellular damage evoked by OGD. Altogether, results in hippocampal slices subjected to OGD show that GUO counteracts the release of excitatory amino acids, stimulates the activity of GS, and decreases the cellular damage by modulation of glutamate transporters activity.
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Affiliation(s)
- Tharine Dal-Cim
- Departamento de Bioquímica, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, Trindade, Florianópolis, SC, 88040-900, Brazil.,Programa de pós-graduação em Neurociências, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, Florianópolis, SC, Brazil
| | - Wagner C Martins
- Departamento de Bioquímica, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, Trindade, Florianópolis, SC, 88040-900, Brazil.,Programa de pós-graduação em Neurociências, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, Florianópolis, SC, Brazil
| | - Daniel T Thomaz
- Departamento de Bioquímica, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, Trindade, Florianópolis, SC, 88040-900, Brazil.,Programa de pós-graduação em Bioquímica, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, Florianópolis, SC, Brazil
| | - Victor Coelho
- Departamento de Bioquímica, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, Trindade, Florianópolis, SC, 88040-900, Brazil
| | - Gabriela Godoy Poluceno
- Departamento de Bioquímica, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, Trindade, Florianópolis, SC, 88040-900, Brazil
| | - Débora Lanznaster
- Departamento de Bioquímica, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, Trindade, Florianópolis, SC, 88040-900, Brazil.,Programa de pós-graduação em Neurociências, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, Florianópolis, SC, Brazil
| | - Samuel Vandresen-Filho
- Departamento de Ciências Básicas em Saúde, Faculdade de Medicina, Universidade Federal de Mato Grosso, Cuiabá, MT, Brazil
| | - Carla I Tasca
- Departamento de Bioquímica, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, Trindade, Florianópolis, SC, 88040-900, Brazil. .,Programa de pós-graduação em Neurociências, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, Florianópolis, SC, Brazil. .,Programa de pós-graduação em Bioquímica, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, Florianópolis, SC, Brazil.
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Abstract
In vitro and in vivo studies have shown that glutamate can be oxidized for energy by brain astrocytes. The ability to harvest the energy from glutamate provides astrocytes with a mechanism to offset the high ATP cost of the uptake of glutamate from the synaptic cleft. This brief review focuses on oxidative metabolism of glutamate by astrocytes, the specific pathways involved in the complete oxidation of glutamate and the energy provided by each reaction.
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Affiliation(s)
- Mary C. McKenna
- Department of Pediatrics and Program in Neuroscience, University of Maryland School of Medicine, Baltimore, MD, USA
- *Correspondence: Mary C. McKenna, Department of Pediatrics and Program in Neuroscience, University of Maryland School of Medicine, 655 West Baltimore Street, Room 13-019 BRB, Baltimore, MD 21201, USA e-mail:
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McKenna MC. Substrate competition studies demonstrate oxidative metabolism of glucose, glutamate, glutamine, lactate and 3-hydroxybutyrate in cortical astrocytes from rat brain. Neurochem Res 2012; 37:2613-26. [PMID: 23079895 DOI: 10.1007/s11064-012-0901-3] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2012] [Revised: 10/01/2012] [Accepted: 10/03/2012] [Indexed: 01/14/2023]
Abstract
It is well established that astrocytes can utilize many substrates to support oxidative energy metabolism; however, use of energy substrates in the presence of other substrates, as would occur in vivo, has not been systematically evaluated. Substrate competition studies were used to determine changes in the rates of (14)CO(2) production since little is known about the interaction of energy substrates in astrocytes. The rates of (14)CO(2) production from 1 mM D-[6-(14)C]glucose, L-[U-(14)C]glutamate, L-[U-(14)C]glutamine, D-3-hydroxy[3-(14)C]butyrate, L-[U-(14)C]lactate and L-[U-(14)C]malate by primary cultures of astrocytes from rat brain were determined to be 1.17 ± 0.19, 85.30 ± 12.25, 28.04 ± 2.84, 13.55 ± 4.56, 14.84 ± 2.40 and 5.20 ± 1.20 nmol/h/mg protein (mean ± SEM), respectively. The rate of (14)CO(2) production from glutamate oxidation was higher than that of the other substrates Addition of unlabeled glutamate significantly decreased the rates of (14)CO(2) production from all other substrates studied; however, glutamate oxidation was not altered by the addition of any of the other substrates. The rate of (14)CO(2) production of glutamine was decreased by glutamate, but not altered by other substrates. The rate of (14)CO(2) production from glucose was significantly decreased by the addition of unlabeled glutamate, glutamine or lactate, but not by 3-hydroxybutyrate or malate. Addition of unlabeled glucose did not significantly alter the (14)CO(2) production from any other substrate. (14)CO(2) production from lactate was decreased by the addition of unlabeled glutamine or glutamate and increased by addition of malate. The (14)CO(2) production from malate was decreased by the addition of unlabeled glutamate or lactate, but was not altered by the other substrates. The substrate utilization for oxidative energy metabolism in astrocytes is very different than the profile previously reported for synaptic terminals. These studies demonstrate the potential use of multiple substrates including glucose, glutamate, glutamine, lactate and 3-hydroxybutyrate as energy substrates for astrocytes. The data also provide evidence of interactions of substrates and multiple compartments of TCA cycle activity in cultured astrocytes.
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Affiliation(s)
- Mary C McKenna
- Department of Pediatrics and Program in Neuroscience, University of Maryland School of Medicine, Baltimore, MD, USA.
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Ribeiro LC, Quincozes-Santos A, Leite MC, Abib RT, Kleinkauf-Rocha J, Biasibetti R, Rotta LN, Wofchuk ST, Perry MLS, Gonçalves CA, Gottfried C. Caloric restriction increases hippocampal glutamate uptake and glutamine synthetase activity in Wistar rats. Neurosci Res 2009; 64:330-4. [PMID: 19376166 DOI: 10.1016/j.neures.2009.04.004] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2009] [Revised: 03/29/2009] [Accepted: 04/06/2009] [Indexed: 11/26/2022]
Abstract
Recent studies indicate that caloric restriction (CR) protects the central nervous system from several pathological conditions. The impairment of astroglial cell function, including glutamate uptake, glutamine synthetase (GS) activity and S100B secretion, may contribute to the progression of neurological disorders. The present study aimed to evaluate hippocampal astrocytic changes in response to CR diet, measuring astroglial parameters, such as glutamate uptake, GS activity and the immunocontent of GFAP and S100B. Blood biochemical parameters were also analyzed. Rats (60-day old) were fed ad libitum or on CR diets for 12 weeks. CR-fed rats showed approximately 16% less body weight gain than control rats. The CR diet was able to induce a significant increase in glutamate uptake (23%) and in GS activity (26%). There were no statistically significant differences in the immunocontent of either GFAP or S100B. In summary, the present study indicates that CR also modulates astrocyte functions by increasing glutamate uptake and GS activity, suggesting that CR might exert its neuroprotective effects against brain illness by modulation of astrocytic functions.
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Affiliation(s)
- Letícia Carina Ribeiro
- Programa de Pós-Graduação em Neurociências, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil
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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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Waagepetersen HS, Hansen GH, Fenger K, Lindsay JG, Gibson G, Schousboe A. Cellular mitochondrial heterogeneity in cultured astrocytes as demonstrated by immunogold labeling of α-ketoglutarate dehydrogenase. Glia 2005; 53:225-31. [PMID: 16206171 DOI: 10.1002/glia.20276] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
In brain cells, various metabolites and metabolic pathways, largely of mitochondrial origin, have been shown to be compartmentalized. Attention has therefore been focused on the possible existence of mitochondrial heterogeneity in the brain at the cellular level. To determine whether mitochondria in cultured cortical and cerebellar astrocytes are heterogeneous at the single cell level, immunogold electron microscopy and an antibody against the alpha-ketoglutarate dehydrogenase component of the alpha-ketoglutarate dehydrogenase complex, a marker enzyme for the tricarboxylic acid (TCA) cycle, were employed. The number of gold particles was counted in the mitochondria of 36 and 42 cells from cultured cerebellar and cortical astrocytes, respectively. A test for random distribution (Poisson distribution) of mitochondria according to the number of gold particles was subsequently performed for every one of the 36 and 42 cells as the ratio variance/mean (= index of dispersion). This should be approximately distributed as chi2/degrees of freedom (df) = n - 1, n = number of mitochondria), if the observations obeyed a Poisson distribution. For 26 of the 36 (cerebellar astrocytes) distributions and for 28 of the 42 (cortical astrocytes) distributions a random distribution had to be rejected. These findings therefore strongly indicate that alpha-ketoglutarate dehydrogenase is heterogeneously distributed in mitochondria within individual astrocytes originating either from cerebellum or cerebral cortex. In conclusion, this study underlines the probability that mitochondrial heterogeneity at the single cell level might be extended to involve other metabolic pathways and metabolites.
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Affiliation(s)
- Helle S Waagepetersen
- Department of Pharmacology, Danish University of Pharmaceutical Sciences, Copenhagen, Denmark
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McKenna MC, Sonnewald U. GABA alters the metabolic fate of [U-13C]glutamate in cultured cortical astrocytes. J Neurosci Res 2004; 79:81-7. [PMID: 15593283 DOI: 10.1002/jnr.20309] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The effect of gamma-aminobutyric acid (GABA) on glutamate metabolism was studied by (13)C-nuclear magnetic resonance (NMR) spectroscopy. Cerebral cortical astrocytes were incubated with 0.5 mM [U-(13)C]glutamate and 5 mM glucose in the presence or absence of 0.2 mM GABA for 2 hr. (13)C-labeled glutamate, glutamine, and aspartate were observed in cell extracts, and (13)C-labeled glutamine and lactate were present in the media. Both uniformly labeled glutamate and [1,2,3-(13)C]glutamate derived from the tricarboxylic acid (TCA) cycle were present in the cells. The consumption of [U-(13)C]glutamate and glucose was unchanged in the presence of GABA; however, the formation of [U-(13)C]lactate and [U-(13)C]aspartate from metabolism of [U-(13)C]glutamate was increased in cells incubated with GABA. The total concentration of aspartate was increased to the same extent as the (13)C-labeled aspartate, suggesting increased entry of [U-(13)C]glutamate into the TCA cycle to allow for the transamination of GABA. Although the concentrations of unlabeled glucose and lactate in the media were unchanged in the presence of GABA, the concentration of alanine was decreased, indicating that there was decreased transamination of the unlabeled pyruvate from glucose metabolism. The amount of [U-(13)C]glutamate converted to [U-(13)C]glutamine and [U-(13)C]lactate was increased in the presence of GABA. However, since the overall consumption of [U-(13)C]glutamate was not different, it can be concluded that the amount of [U-(13)C]glutamate used for energy was decreased. This suggests that exogenous GABA could substitute for glutamate as an energy source for astrocytes. The results indicate that the presence of GABA influences the metabolic fate of both glutamate and glucose in astrocytes, suggesting that fluctuations in the concentration of GABA in normal and pathological conditions can alter the compartmentation of glial metabolism in brain.
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Affiliation(s)
- Mary C McKenna
- Department of Pediatrics, University of Maryland School of Medicine, 655 W. Baltimore Street., Room 10-031, Baltimore, MD 21201, USA.
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