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Savic I. MRS Shows Regionally Increased Glutamate Levels among Patients with Exhaustion Syndrome Due to Occupational Stress. Cereb Cortex 2020; 30:3759-3770. [PMID: 32195540 DOI: 10.1093/cercor/bhz340] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2019] [Revised: 12/17/2019] [Indexed: 12/21/2022] Open
Abstract
Despite the rapid increase of reports of exhaustion syndrome (ES) due to daily occupational stress, the mechanisms underlying ES are unknown. We used voxel-based 1H-MR spectroscopy to examine the potential role of glutamate in this condition. The levels of glutamate were found to be elevated among ES patients (n = 30, 16 females) compared with controls (n = 31, 15 females). Notably, this increase was detected only in the anterior cingulate and mesial prefrontal cortex (ACC/mPFC), and the glutamate levels were linearly correlated with the degree of perceived stress. Furthermore, there was a sex by group interaction, as the glutamate elevation was present only in female patients. Female but not male ES patients also showed an increase in N-acetyl aspartate (NAA) levels in the amygdala. No group differences were detected in glutamine concentration (also measured). These data show the key role of glutamate in stress-related neuronal signaling and the specific roles of the amygdala and ACC/mPFC. The data extend previous reports about the neurochemical basis of stress and identify a potential neural marker and mediator of ES due to occupational stress. The observation of specific sex differences provides a tentative explanation to the well-known female predominance in stress-related psychopathology.
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Affiliation(s)
- Ivanka Savic
- Department of Women's and Children's Health, Karolinska Institutet, Karolinska University Hospital, SE-171 76 Stockholm, Sweden.,Department of Neurology, Karolinska University Hospital, SE-171 76 Stockholm, Sweden.,Department of Neurology, UCLA, Los Angeles, CA 90095-1769, USA
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2
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Amaral AI, Hadera MG, Tavares JM, Kotter MRN, Sonnewald U. Characterization of glucose-related metabolic pathways in differentiated rat oligodendrocyte lineage cells. Glia 2016; 64:21-34. [PMID: 26352325 PMCID: PMC4832329 DOI: 10.1002/glia.22900] [Citation(s) in RCA: 64] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2015] [Accepted: 07/22/2015] [Indexed: 12/24/2022]
Abstract
Although oligodendrocytes constitute a significant proportion of cells in the central nervous system (CNS), little is known about their intermediary metabolism. We have, therefore, characterized metabolic functions of primary oligodendrocyte precursor cell cultures at late stages of differentiation using isotope-labelled metabolites. We report that differentiated oligodendrocyte lineage cells avidly metabolize glucose in the cytosol and pyruvate derived from glucose in the mitochondria. The labelling patterns of metabolites obtained after incubation with [1,2-(13)C]glucose demonstrated that the pentose phosphate pathway (PPP) is highly active in oligodendrocytes (approximately 10% of glucose is metabolized via the PPP as indicated by labelling patterns in phosphoenolpyruvate). Mass spectrometry and magnetic resonance spectroscopy analyses of metabolites after incubation of cells with [1-(13)C]lactate or [1,2-(13)C]glucose, respectively, demonstrated that anaplerotic pyruvate carboxylation, which was thought to be exclusive to astrocytes, is also active in oligodendrocytes. Using [1,2-(13)C]acetate, we show that oligodendrocytes convert acetate into acetyl CoA which is metabolized in the tricarboxylic acid cycle. Analysis of labelling patterns of alanine after incubation of cells with [1,2-(13)C]acetate and [1,2-(13)C]glucose showed catabolic oxidation of malate or oxaloacetate. In conclusion, we report that oligodendrocyte lineage cells at late differentiation stages are metabolically highly active cells that are likely to contribute considerably to the metabolic activity of the CNS.
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Affiliation(s)
- Ana I. Amaral
- Anne McLaren LaboratoryWellcome Trust‐Medical Research Council Cambridge Stem Cell Institute and Department of Clinical Neurosciences, University of CambridgeCambridgeCB2 0SZUnited Kingdom
| | - Mussie G. Hadera
- Department of Neuroscience, Faculty of MedicineNorwegian University of Science and TechnologyTrondheim7491Norway
| | - Joana M. Tavares
- Anne McLaren LaboratoryWellcome Trust‐Medical Research Council Cambridge Stem Cell Institute and Department of Clinical Neurosciences, University of CambridgeCambridgeCB2 0SZUnited Kingdom
| | - Mark R. N. Kotter
- Anne McLaren LaboratoryWellcome Trust‐Medical Research Council Cambridge Stem Cell Institute and Department of Clinical Neurosciences, University of CambridgeCambridgeCB2 0SZUnited Kingdom
| | - Ursula Sonnewald
- Department of Neuroscience, Faculty of MedicineNorwegian University of Science and TechnologyTrondheim7491Norway
- Department of Drug Design and Pharmacology, Faculty of Health and Medical SciencesUniversity of CopenhagenCopenhagen2100Denmark
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Gebril HM, Avula B, Wang YH, Khan IA, Jekabsons MB. (13)C metabolic flux analysis in neurons utilizing a model that accounts for hexose phosphate recycling within the pentose phosphate pathway. Neurochem Int 2015; 93:26-39. [PMID: 26723542 DOI: 10.1016/j.neuint.2015.12.008] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2015] [Revised: 12/16/2015] [Accepted: 12/18/2015] [Indexed: 11/25/2022]
Abstract
Glycolysis, mitochondrial substrate oxidation, and the pentose phosphate pathway (PPP) are critical for neuronal bioenergetics and oxidation-reduction homeostasis, but quantitating their fluxes remains challenging, especially when processes such as hexose phosphate (i.e., glucose/fructose-6-phosphate) recycling in the PPP are considered. A hexose phosphate recycling model was developed which exploited the rates of glucose consumption, lactate production, and mitochondrial respiration to infer fluxes through the major glucose consuming pathways of adherent cerebellar granule neurons by replicating [(13)C]lactate labeling from metabolism of [1,2-(13)C2]glucose. Flux calculations were predicated on a steady-state system with reactions having known stoichiometries and carbon atom transitions. Non-oxidative PPP activity and consequent hexose phosphate recycling, as well as pyruvate production by cytoplasmic malic enzyme, were optimized by the model and found to account for 28 ± 2% and 7.7 ± 0.2% of hexose phosphate and pyruvate labeling, respectively. From the resulting fluxes, 52 ± 6% of glucose was metabolized by glycolysis, compared to 19 ± 2% by the combined oxidative/non-oxidative pentose cycle that allows for hexose phosphate recycling, and 29 ± 8% by the combined oxidative PPP/de novo nucleotide synthesis reactions. By extension, 62 ± 6% of glucose was converted to pyruvate, the metabolism of which resulted in 16 ± 1% of glucose oxidized by mitochondria and 46 ± 6% exported as lactate. The results indicate a surprisingly high proportion of glucose utilized by the pentose cycle and the reactions synthesizing nucleotides, and exported as lactate. While the in vitro conditions to which the neurons were exposed (high glucose, no lactate or other exogenous substrates) limit extrapolating these results to the in vivo state, the approach provides a means of assessing a number of metabolic fluxes within the context of hexose phosphate recycling in the PPP from a minimal set of measurements.
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Affiliation(s)
- Hoda M Gebril
- Department of Biology, Shoemaker Hall, University of Mississippi, University, MS 38677, USA.
| | - Bharathi Avula
- National Center for Natural Products Research, School of Pharmacy, University of Mississippi, University, MS 38677, USA.
| | - Yan-Hong Wang
- National Center for Natural Products Research, School of Pharmacy, University of Mississippi, University, MS 38677, USA.
| | - Ikhlas A Khan
- Department of Biomedical Sciences and National Center for Natural Products Research, School of Pharmacy, University of Mississippi, University, MS 38677, USA.
| | - Mika B Jekabsons
- Department of Biology, Shoemaker Hall, University of Mississippi, University, MS 38677, USA.
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Olsen GM, Sonnewald U. Glutamate: Where does it come from and where does it go? Neurochem Int 2015; 88:47-52. [DOI: 10.1016/j.neuint.2014.11.006] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2014] [Revised: 10/30/2014] [Accepted: 11/03/2014] [Indexed: 11/15/2022]
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Calvetti D, Somersalo E. Ménage à trois: the role of neurotransmitters in the energy metabolism of astrocytes, glutamatergic, and GABAergic neurons. J Cereb Blood Flow Metab 2012; 32:1472-83. [PMID: 22472605 PMCID: PMC3421085 DOI: 10.1038/jcbfm.2012.31] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
This work is a computational study based on a new detailed metabolic network model comprising well-mixed compartments representing separate cytosol and mitochondria of astrocytes, glutamatergic and gamma aminobutyric acid (GABA)ergic neurons, communicating through an extracellular space compartment and fed by arterial blood flow. Our steady-state analysis assumes statistical mass balance of both carbons and amino groups. The study is based on Bayesian flux balance analysis, which uses Markov chain Monte Carlo sampling techniques and provides a quantitative description of steady states when the two exchangers aspartate-glutamate carrier (AGC1) and oxoglutarate carrier (OGC) in the malate-aspartate shuttle in astrocyte are not in equilibrium, as recent studies suggest. It also highlights the importance of anaplerotic reactions, pyruvate carboxylase in astrocyte and malic enzyme in neurons, for neurotransmitter synthesis and recycling. The model is unbiased with respect to the glucose partitioning between cell types, and shows that determining the partitioning cannot be done by stoichiometric constraints alone. Furthermore, the intercellular lactate trafficking is found to depend directly on glucose partitioning, suggesting that a steady state may support different scenarios. At inhibitory steady state, characterized by high rate of GABA release, there is elevated oxidative activity in astrocyte, not in response to specific energetic needs.
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Affiliation(s)
- Daniela Calvetti
- Department of Mathematics and Cognitive Science, Case Western Reserve University, Cleveland, Ohio 44106, USA.
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Fan TWM, Tan J, McKinney MM, Lane AN. Stable Isotope Resolved Metabolomics Analysis of Ribonucleotide and RNA Metabolism in Human Lung Cancer Cells. Metabolomics 2012; 8:517-527. [PMID: 26146495 PMCID: PMC4486296 DOI: 10.1007/s11306-011-0337-9] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
We have developed a simple NMR-based method to determine the turnover of nucleotides and incorporation into RNA by stable isotope resolved metabolomics (SIRM) in A549 lung cancer cells. This method requires no chemical degradation of the nucleotides or chromatography. During cell growth, the free ribonucleotide pool is rapidly replaced by de novo synthesized nucleotides. Using [U-13C]-glucose and [U-13C,15N]-glutamine as tracers, we showed that virtually all of the carbons in the nucleotide riboses were derived from glucose, whereas glutamine was preferentially utilized over glucose for pyrimidine ring biosynthesis, via the synthesis of Asp through the Krebs cycle. Incorporation of the glutamine amido nitrogen into the N3 and N9 positions of the purine rings was also demonstrated by proton-detected 15N NMR. The incorporation of 13C from glucose into total RNA was measured and shown to be a major sink for the nucleotides during cell proliferation. This method was applied to determine the metabolic action of an anti-cancer selenium agent (methylseleninic acid or MSA) on A549 cells. We found that MSA inhibited nucleotide turnover and incorporation into RNA, implicating an important role of nucleotide metabolism in the toxic action of MSA on cancer cells.
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Affiliation(s)
- Teresa W-M. Fan
- Department of Chemistry, University of Louisville, 2210 S. Brook St, Rm 348 John W. Shumaker Research, Building, Louisville, KY 40292, USA
- Center for Regulatory Environmental Analytical Metabolomics, 2210 S. Brook St., Louisville, KY 40292, USA
- JG Brown Cancer Center, Clinical Translational Research Building, 505 S. Hancock St., Louisville, KY 40202, USA
| | - Jinlian Tan
- JG Brown Cancer Center, Clinical Translational Research Building, 505 S. Hancock St., Louisville, KY 40202, USA
| | - Martin M. McKinney
- Department of Medicine, Clinical Translational Research Building, 505 S. Hancock St., Louisville, KY 40202, USA
| | - Andrew N. Lane
- Department of Chemistry, University of Louisville, 2210 S. Brook St, Rm 348 John W. Shumaker Research, Building, Louisville, KY 40292, USA
- Center for Regulatory Environmental Analytical Metabolomics, 2210 S. Brook St., Louisville, KY 40292, USA
- JG Brown Cancer Center, Clinical Translational Research Building, 505 S. Hancock St., Louisville, KY 40202, USA
- Department of Medicine, Clinical Translational Research Building, 505 S. Hancock St., Louisville, KY 40202, USA
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7
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Kreft M, Bak LK, Waagepetersen HS, Schousboe A. Aspects of astrocyte energy metabolism, amino acid neurotransmitter homoeostasis and metabolic compartmentation. ASN Neuro 2012; 4:e00086. [PMID: 22435484 PMCID: PMC3338196 DOI: 10.1042/an20120007] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2012] [Revised: 03/06/2012] [Accepted: 03/21/2012] [Indexed: 02/08/2023] Open
Abstract
Astrocytes are key players in brain function; they are intimately involved in neuronal signalling processes and their metabolism is tightly coupled to that of neurons. In the present review, we will be concerned with a discussion of aspects of astrocyte metabolism, including energy-generating pathways and amino acid homoeostasis. A discussion of the impact that uptake of neurotransmitter glutamate may have on these pathways is included along with a section on metabolic compartmentation.
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Key Words
- amino acid
- astrocyte
- compartmentation
- energy
- metabolism
- α-kg, α-ketoglutarate
- aat, aspartate aminotransferase
- cfp, cyan fluorescence protein
- dab, diaminobenzidine
- fret, fluorescence resonance energy transfer
- [glc]i, intracellular glucose concentration
- gaba, γ-aminobutyric acid
- gaba-t, gaba aminotransferase
- gdh, glutamate dehydrogenase
- glut, glucose transporter
- gp, glycogen phosphorylase
- gs, glutamine synthetase
- gsk3, gs kinase 3
- pag, phosphate-activated glutaminase
- pi3k, phosphoinositide 3-kinase
- pkc, protein kinase c
- tca, tricarboxylic acid
- yfp, yellow fluorescence protein
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Affiliation(s)
- Marko Kreft
- *LNMCP, Institute of Pathophysiology, Faculty of Medicine and CPAE, Department of Biology, Biotechnical Faculty, University of Ljubljana and Celica Biomedical Center, Slovenia
| | - Lasse K Bak
- †Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, 2100, Copenhagen, Denmark
| | - Helle S Waagepetersen
- †Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, 2100, Copenhagen, Denmark
| | - Arne Schousboe
- †Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, 2100, Copenhagen, Denmark
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Merle M, Franconi JM. Brain Metabolic Compartmentalization, Metabolism Modeling, and Cerebral Activity-Metabolism Relationship. NEURAL METABOLISM IN VIVO 2012. [DOI: 10.1007/978-1-4614-1788-0_33] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
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9
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Obel LF, Andersen KMH, Bak LK, Schousboe A, Waagepetersen HS. Effects of adrenergic agents on intracellular Ca2+ homeostasis and metabolism of glucose in astrocytes with an emphasis on pyruvate carboxylation, oxidative decarboxylation and recycling: implications for glutamate neurotransmission and excitotoxicity. Neurotox Res 2011; 21:405-17. [PMID: 22194159 DOI: 10.1007/s12640-011-9296-1] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2011] [Revised: 11/17/2011] [Accepted: 11/29/2011] [Indexed: 12/26/2022]
Abstract
Glucose and glycogen are essential sources of energy for maintaining glutamate homeostasis as well as glutamatergic neurotransmission. The metabolism of glycogen, the location of which is confined to astrocytes, is affected by norepinephrine (NE), and hence, adrenergic signaling in the astrocyte might affect glutamate homeostasis with implications for excitatory neurotransmission and possibly excitotoxic neurodegeneration. In order to study this putative correlation, cultured astrocytes were incubated with 2.5 mM [U-(13)C]glucose in the presence and absence of NE as a time course for 1 h. Employing mass spectrometry, labeling in intracellular metabolites was determined. Moreover, the involvement of Ca(2+) in the noradrenergic response was studied. In unstimulated astrocytes, the labeling pattern of glutamate, aspartate, malate and citrate confirmed important roles for pyruvate carboxylation and oxidative decarboxylation in astrocytic glucose metabolism. Importantly, pyruvate carboxylation was best visualized at 10 min of incubation. The abundance and pattern of labeling in lactate and alanine indicated not only an extensive activity of malic enzyme (initial step for pyruvate recycling) but also a high degree of compartmentalization of the pyruvate pool. Stimulating with 1 μM NE had no effect on labeling patterns and glycogen metabolism, whereas 100 μM NE increased glutamate labeling and decreased labeling in alanine, the latter supposedly due to dilution from degradation of non-labeled glycogen. It is suggested that further experiments uncovering the correlation between adrenergic and glutamatergic pathways should be performed in order to gain further insight into the role of astrocytes in brain function and dysfunction, the latter including excitotoxicity.
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Affiliation(s)
- Linea F Obel
- Department of Pharmacology and Pharmacotherapy, Faculty of Pharmaceutical Sciences, University of Copenhagen, 2 Universitetsparken, 2100 Copenhagen, Denmark
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Rat brain slices oxidize glucose at high rates: a (13)C NMR study. Neurochem Int 2011; 59:1145-54. [PMID: 22067134 DOI: 10.1016/j.neuint.2011.10.009] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2011] [Revised: 10/11/2011] [Accepted: 10/21/2011] [Indexed: 11/24/2022]
Abstract
Since glucose is the main cerebral substrate, we have characterized the metabolism of various (13)C glucose isotopomers in rat brain slices. For this, we have used our cellular metabolomic approach that combines enzymatic and carbon 13 NMR techniques with mathematical models of metabolic pathways. We identified the fate and the pathways of the conversion of glucose carbons into various products (pyruvate, lactate, alanine, aspartate, glutamate, GABA, glutamine and CO(2)) and determined absolute fluxes through pathways of glucose metabolism. After 60 min of incubation, lactate and CO(2) were the main end-products of the metabolism of glucose which was avidly metabolized by the slices. Lactate was also used at high rates by the slices and mainly converted into CO(2). High values of flux through pyruvate carboxylase, which were similar with glucose and lactate as substrate, were observed. The addition of glutamine, but not of acetate, stimulated pyruvate carboxylation, the conversion of glutamate into succinate and fluxes through succinate dehydrogenase, malic enzyme, glutamine synthetase and aspartate aminotransferase. It is concluded that, unlike brain cells in culture, and consistent with high fluxes through PDH and enzymes of the tricarboxylic acid cycle, rat brain slices oxidized both glucose and lactate at high rates.
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Sonko BJ, Schmitt TC, Guo L, Shi Q, Boros LG, Leakey JEA, Beger RD. Assessment of usnic acid toxicity in rat primary hepatocytes using ¹³C isotopomer distribution analysis of lactate, glutamate and glucose. Food Chem Toxicol 2011; 49:2968-74. [PMID: 21802472 DOI: 10.1016/j.fct.2011.07.047] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2011] [Revised: 07/07/2011] [Accepted: 07/10/2011] [Indexed: 11/19/2022]
Abstract
The lichen metabolite usnic acid (UA) has been promoted as a dietary supplement for weight loss, although cases of hepatotoxicity have been reported. Here we evaluated UA-associated hepatotoxicity in vitro using isolated rat hepatocytes. We measured cell viability and ATP content to evaluate UA induced cytotoxicity and applied (13)C isotopomer distribution measuring techniques to gain a better understanding of glucose metabolism during cytotoxicity. The cells were exposed to 0, 1, 5 or 10 μM UA concentrations for 2, 6 or 24h. Aliquots of media were collected at the end of these time periods and the (13)C mass isotopomer distribution determined for CO(2), lactate, glucose and glutamate. The 1 μM UA exposure did not appear to cause significant change in cell viability compared to controls. However, the 5 and 10 μM UA concentrations significantly reduced cell viability as exposure time increased. Similar results were obtained for ATP depletion experiments. The 1 and 5 μM UA doses suggest increased oxidative phosphorylation. Conversely, oxidative phosphorylation and gluconeogenesis were dramatically inhibited by 10 μM UA. Augmented oxidative phosphorylation at the lower UA concentrations may be an adaptive response by the cells to compensate for diminished mitochondrial function.
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Affiliation(s)
- Bakary J Sonko
- Division of Systems Biology, National Center for Toxicological Research, US FDA, Jefferson, AR 72079, USA
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Abstract
We have determined the time course of [U-(13)C]-glucose utilization and transformations in SCID mice via bolus injection of the tracer in the tail vein. Incorporation of (13)C into metabolites extracted from mouse blood plasma and several tissues (lung, heart, brain, liver, kidney, and skeletal muscle) were profiled by NMR and GC-MS, which helped ascertain optimal sampling times for different target tissues. We found that the time for overall optimal (13)C incorporation into tissue was 15-20 min but with substantial differences in (13)C labeling patterns of various organs that reflected their specific metabolism. Using this stable isotope resolved metabolomics (SIRM) approach, we have compared the (13)C metabolite profile of the lungs in the same mouse with or without an orthotopic lung tumor xenograft established from human PC14PE6 lung adenocarcinoma cells. The (13)C metabolite profile shows considerable differences in [U-(13)C]-glucose transformations between the two lung tissues, demonstrating the feasibility of applying SIRM to investigate metabolic networks of human cancer xenograft in the mouse model.
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Affiliation(s)
- Teresa W.-M. Fan
- Department of Chemistry, University of Louisville, 2210 S. Brook St, Rm 348 John W. Shumaker Research Building, Louisville, KY 40292, USA
- Department of Medicine, James Graham Brown Cancer Center, Clinical Translational Research Building, 505 S. Hancock St., Louisville, KY 40202, USA
- Center for Regulatory Environmental Metabolomics, University of Louisville, 2210 S. Brook St., Louisville, KY 40292, USA
| | - Andrew N. Lane
- Department of Chemistry, University of Louisville, 2210 S. Brook St, Rm 348 John W. Shumaker Research Building, Louisville, KY 40292, USA
- Department of Medicine, James Graham Brown Cancer Center, Clinical Translational Research Building, 505 S. Hancock St., Louisville, KY 40202, USA
- Center for Regulatory Environmental Metabolomics, University of Louisville, 2210 S. Brook St., Louisville, KY 40292, USA
| | - Richard M. Higashi
- Department of Chemistry, University of Louisville, 2210 S. Brook St, Rm 348 John W. Shumaker Research Building, Louisville, KY 40292, USA
- Center for Regulatory Environmental Metabolomics, University of Louisville, 2210 S. Brook St., Louisville, KY 40292, USA
| | - Jun Yan
- Department of Medicine, James Graham Brown Cancer Center, Clinical Translational Research Building, 505 S. Hancock St., Louisville, KY 40202, USA
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Amaral AI, Teixeira AP, Sonnewald U, Alves PM. Estimation of intracellular fluxes in cerebellar neurons after hypoglycemia: Importance of the pyruvate recycling pathway and glutamine oxidation. J Neurosci Res 2011; 89:700-10. [DOI: 10.1002/jnr.22571] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2010] [Revised: 11/02/2010] [Accepted: 11/05/2010] [Indexed: 11/06/2022]
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Meisingset TW, Risa Ø, Brenner M, Messing A, Sonnewald U. Alteration of glial-neuronal metabolic interactions in a mouse model of Alexander disease. Glia 2010; 58:1228-34. [PMID: 20544858 DOI: 10.1002/glia.21003] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Alexander disease is a rare and usually fatal neurological disorder characterized by the abundant presence of protein aggregates in astrocytes. Most cases result from dominant missense de novo mutations in the gene encoding glial fibrillary acidic protein (GFAP), but how these mutations lead to aggregate formation and compromise function is not known. A transgenic mouse line (Tg73.7) over-expressing human GFAP produces astrocytic aggregates indistinguishable from those seen in the human disease, making them a model of this disorder. To investigate possible metabolic changes associated with Alexander disease Tg73.7 mice and controls were injected simultaneously with [1-(13)C]glucose to analyze neuronal metabolism and [1,2-(13)C]acetate to monitor astrocytic metabolism. Brain extracts were analyzed by (1)H magnetic resonance spectroscopy (MRS) to quantify amounts of several key metabolites, and by (13)C MRS to analyze amino acid neurotransmitter metabolism. In the cerebral cortex, reduced utilization of [1,2-(13)C]acetate was observed for synthesis of glutamine, glutamate, and GABA, and the concentration of the marker for neuronal mitochondrial metabolism, N-acetylaspartate (NAA) was decreased. This indicates impaired astrocytic and neuronal metabolism and decreased transfer of glutamine from astrocytes to neurons compared with control mice. In the cerebellum, glutamine and GABA content and labeling from [1-(13)C]glucose were increased. Evidence for brain edema was found in the increased amount of water and of the osmoregulators myo-inositol and taurine. It can be concluded that astrocyte-neuronal interactions were altered differently in distinct regions.
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Affiliation(s)
- Tore Wergeland Meisingset
- Department of Neuroscience, Norwegian University of Science and Technology (NTNU), N-7489 Trondheim, Norway
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15
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Meierhans R, Béchir M, Ludwig S, Sommerfeld J, Brandi G, Haberthür C, Stocker R, Stover JF. Brain metabolism is significantly impaired at blood glucose below 6 mM and brain glucose below 1 mM in patients with severe traumatic brain injury. Crit Care 2010; 14:R13. [PMID: 20141631 PMCID: PMC2875528 DOI: 10.1186/cc8869] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2009] [Revised: 12/20/2009] [Accepted: 02/08/2010] [Indexed: 12/25/2022] Open
Abstract
INTRODUCTION The optimal blood glucose target following severe traumatic brain injury (TBI) must be defined. Cerebral microdialysis was used to investigate the influence of arterial blood and brain glucose on cerebral glucose, lactate, pyruvate, glutamate, and calculated indices of downstream metabolism. METHODS In twenty TBI patients, microdialysis catheters inserted in the edematous frontal lobe were dialyzed at 1 microl/min, collecting samples at 60 minute intervals. Occult metabolic alterations were determined by calculating the lactate- pyruvate (L/P), lactate- glucose (L/Glc), and lactate- glutamate (L/Glu) ratios. RESULTS Brain glucose was influenced by arterial blood glucose. Elevated L/P and L/Glc were significantly reduced at brain glucose above 1 mM, reaching lowest values at blood and brain glucose levels between 6-9 mM (P < 0.001). Lowest cerebral glutamate was measured at brain glucose 3-5 mM with a significant increase at brain glucose below 3 mM and above 6 mM. While L/Glu was significantly increased at low brain glucose levels, it was significantly decreased at brain glucose above 5 mM (P < 0.001). Insulin administration increased brain glutamate at low brain glucose, but prevented increase in L/Glu. CONCLUSIONS Arterial blood glucose levels appear to be optimal at 6-9 mM. While low brain glucose levels below 1 mM are detrimental, elevated brain glucose are to be targeted despite increased brain glutamate at brain glucose >5 mM. Pathogenity of elevated glutamate appears to be relativized by L/Glu and suggests to exclude insulin- induced brain injury.
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Affiliation(s)
- Roman Meierhans
- Surgical Intensive Care, University Hospital Zürich, Rämistrasse 100, 8091 Zürich, Switzerland
| | - Markus Béchir
- Surgical Intensive Care, University Hospital Zürich, Rämistrasse 100, 8091 Zürich, Switzerland
| | - Silke Ludwig
- Surgical Intensive Care, University Hospital Zürich, Rämistrasse 100, 8091 Zürich, Switzerland
| | - Jutta Sommerfeld
- Surgical Intensive Care, University Hospital Zürich, Rämistrasse 100, 8091 Zürich, Switzerland
| | - Giovanna Brandi
- Surgical Intensive Care, University Hospital Zürich, Rämistrasse 100, 8091 Zürich, Switzerland
- Ospedale Maggiore Policlinico Milano, Via Francesco Sforza, 28, I-20122 Milano, Italy
| | - Christoph Haberthür
- Surgical Intensive Care, Luzerner Kantonsspital, 6000 Luzern 16, Switzerland
| | - Reto Stocker
- Surgical Intensive Care, University Hospital Zürich, Rämistrasse 100, 8091 Zürich, Switzerland
| | - John F Stover
- Surgical Intensive Care, University Hospital Zürich, Rämistrasse 100, 8091 Zürich, Switzerland
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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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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: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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Bak LK, Ziemińska E, Waagepetersen HS, Schousboe A, Albrecht J. Metabolism of [U-13C]Glutamine and [U-13C]Glutamate in Isolated Rat Brain Mitochondria Suggests Functional Phosphate-Activated Glutaminase Activity in Matrix. Neurochem Res 2007; 33:273-8. [PMID: 17763943 DOI: 10.1007/s11064-007-9471-1] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2007] [Accepted: 08/06/2007] [Indexed: 11/27/2022]
Abstract
One of the forms of phosphate activated glutaminase (PAG) is associated with the inner mitochondrial membrane. It has been debated whether glutamate formed from glutamine in the reaction catalyzed by PAG has direct access to mitochondrial or cytosolic metabolism. In this study, metabolism of [U-(13)C]glutamine (3 mM) or [U-(13)C]glutamate (10 mM) was investigated in isolated rat brain mitochondria. The presence of a functional tricarboxylic (TCA) cycle in the mitochondria was tested using [U-(13)C]succinate as substrate and extensive labeling in aspartate was seen. Accumulation of glutamine into the mitochondrial matrix was inhibited by histidine (15 mM). Extracts of mitochondria were analyzed for labeling in glutamine, glutamate and aspartate using liquid chromatography-mass spectrometry. Formation of [U-(13)C]glutamate from exogenous [U-(13)C]glutamine was decreased about 50% (P<0.001) in the presence of histidine. In addition, the (13)C-labeled skeleton of [U-(13)C]glutamine was metabolized more vividly in the tricarboxylic acid (TCA) cycle than that from [U-(13)C]glutamate, even though glutamate was labeled to a higher extent in the latter condition. Collectively the results show that transport of glutamine into the mitochondrial matrix may be a prerequisite for deamidation by PAG.
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Affiliation(s)
- Lasse K Bak
- Department of Pharmacology and Pharmacotherapy, Faculty of Pharmaceutical Sciences, University of Copenhagen, 2 Universitetsparken, 2100 Copenhagen, Denmark.
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