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Karger G, Berger J, Dringen R. Modulation of Cellular Levels of Adenosine Phosphates and Creatine Phosphate in Cultured Primary Astrocytes. Neurochem Res 2024; 49:402-414. [PMID: 37855866 PMCID: PMC10787699 DOI: 10.1007/s11064-023-04039-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2023] [Revised: 09/19/2023] [Accepted: 09/22/2023] [Indexed: 10/20/2023]
Abstract
Adenosine triphosphate (ATP) is the main energy currency of all cells, while creatine phosphate (CrP) is considered as a buffer of high energy-bond phosphate that facilitates rapid regeneration of ATP from adenosine diphosphate (ADP). Astrocyte-rich primary cultures contain ATP, ADP and adenosine monophosphate (AMP) in average specific contents of 36.0 ± 6.4 nmol/mg, 2.9 ± 2.1 nmol/mg and 1.7 ± 2.1 nmol/mg, respectively, which establish an adenylate energy charge of 0.92 ± 0.04. The average specific cellular CrP level was found to be 25.9 ± 10.8 nmol/mg and the CrP/ATP ratio was 0.74 ± 0.28. The specific cellular CrP content, but not the ATP content, declined with the age of the culture. Absence of fetal calf serum for 24 h caused a partial loss in the cellular contents of both CrP and ATP, while application of creatine for 24 h doubled the cellular CrP content and the CrP/ATP ratio, but did not affect ATP levels. In glucose-deprived astrocytes, the high cellular ATP and CrP contents were rapidly depleted within minutes after application of the glycolysis inhibitor 2-deoxyglucose and the respiratory chain inhibitor antimycin A. For those conditions, the decline in CrP levels always preceded that of ATP contents. In contrast, incubation of glucose-fed astrocytes for up to 30 min with antimycin A had little effect on the high cellular ATP content, while the CrP level was significantly lowered. These data demonstrate the importance of cellular CrP for maintaining a high cellular ATP content in astrocytes during episodes of impaired ATP regeneration.
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Affiliation(s)
- Gabriele Karger
- Faculty 2 (Biology/Chemistry), Centre for Biomolecular Interactions Bremen, University of Bremen, P.O. Box 330440, 28334, Bremen, Germany
- Centre for Environmental Research and Sustainable Technologies, University of Bremen, Bremen, Germany
| | - Julius Berger
- Faculty 2 (Biology/Chemistry), Centre for Biomolecular Interactions Bremen, University of Bremen, P.O. Box 330440, 28334, Bremen, Germany
| | - Ralf Dringen
- Faculty 2 (Biology/Chemistry), Centre for Biomolecular Interactions Bremen, University of Bremen, P.O. Box 330440, 28334, Bremen, Germany.
- Centre for Environmental Research and Sustainable Technologies, University of Bremen, Bremen, Germany.
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2
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He W, Wu G. Metabolism of Amino Acids in the Brain and Their Roles in Regulating Food Intake. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2020; 1265:167-185. [PMID: 32761576 DOI: 10.1007/978-3-030-45328-2_10] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Amino acids (AAs) and their metabolites play an important role in neurological health and function. They are not only the building blocks of protein but are also neurotransmitters. In the brain, glutamate and aspartate are the major excitatory neurotransmitters, whereas γ-aminobutyrate (GABA, a metabolite of glutamate) and glycine are the major inhibitory neurotransmitters. Nitric oxide (NO, a metabolite of arginine), H2S (a metabolite of cysteine), serotonin (a metabolite of tryptophan) and histamine (a metabolite of histidine), as well as dopamine and norepinephrine (metabolites of tyrosine) are neurotransmitters to modulate synaptic plasticity, neuronal activity, learning, motor control, motivational behavior, emotion, and executive function. Concentrations of glutamine (a precursor of glutamate and aspartate), branched-chain AAs (precursors of glutamate, glutamine and aspartate), L-serine (a precursor of glycine and D-serine), methionine and phenylalanine in plasma are capable of affecting neurotransmission through the syntheses of glutamate, aspartate, and glycine, as well as the competitive transport of tryptophan and tyrosine across from the blood-brain barrier. Adequate consumption of AAs is crucial to maintain their concentrations and the production of neurotransmitters in the central nervous system. Thus, the content and balance of AAs in diets have a profound impact on food intake by animals. Knowledge of AA transport and metabolism in the brain is beneficial for improving the health and well-being of humans and animals.
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Affiliation(s)
- Wenliang He
- Department of Animal Science, Texas A&M University, College Station, TX, USA
| | - Guoyao Wu
- Department of Animal Science, Texas A&M University, College Station, TX, USA.
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3
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Skoczen A, Setkowicz Z, Janeczko K, Sandt C, Borondics F, Chwiej J. The influence of high fat diets with different ketogenic ratios on the hippocampal accumulation of creatine - FTIR microspectroscopy study. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2017; 184:13-22. [PMID: 28477512 DOI: 10.1016/j.saa.2017.04.085] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/06/2017] [Revised: 04/12/2017] [Accepted: 04/30/2017] [Indexed: 06/07/2023]
Abstract
The main purpose of this study was the determination and comparison of anomalies in creatine (Cr) accumulation occurring within CA3 and DG areas of hippocampal formation as a result of two high-fat, carbohydrate-restricted ketogenic diets (KD) with different ketogenic ratio (KR). To reach this goal, Fourier transformed infrared microspectroscopy with synchrotron radiation source (SRFTIR microspectroscopy) was applied for chemical mapping of creatine absorption bands, occurring around 1304, 1398 and 2800 cm-1. The samples were taken from three groups of experimental animals: control group (N) fed with standard laboratory diet, KD1 and KD2 groups fed with high-fat diets with KR 5:1 and 9:1 respectively. Additionally, the possible influence on the phosphocreatine (PhCr, the high energetic form of creatine) content was evaluated by comparative analysis of chemical maps obtained for creatine and for compounds containing phosphate groups which manifest in the spectra at the wavenumbers of around 1240 and 1080 cm-1. Our results showed that KD2 strongly modifies the frequency of Cr inclusions in both analyzed hippocampal areas. Statistical analysis, performed with Mann-Whitney U test revealed increased accumulation of Cr within CA3 and DG areas of KD2 fed rats compared to both normal rats and KD1 experimental group. Moreover, KD2 diet may modify the frequency of PhCr deposits as well as the PhCr to Cr ratio.
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Affiliation(s)
- A Skoczen
- AGH University of Science and Technology, Faculty of Physics and Applied Computer Science, Krakow, Poland.
| | - Z Setkowicz
- Jagiellonian University, Institute of Zoology, Krakow, Poland
| | - K Janeczko
- Jagiellonian University, Institute of Zoology, Krakow, Poland
| | | | | | - J Chwiej
- AGH University of Science and Technology, Faculty of Physics and Applied Computer Science, Krakow, Poland
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Bhowmick R, Subramanian A, Sarkar RR. Exploring the differences in metabolic behavior of astrocyte and glioblastoma: a flux balance analysis approach. SYSTEMS AND SYNTHETIC BIOLOGY 2015; 9:159-177. [PMID: 28392849 DOI: 10.1007/s11693-015-9183-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2015] [Revised: 09/08/2015] [Accepted: 10/05/2015] [Indexed: 12/21/2022]
Abstract
Brain cancers demonstrate a complex metabolic behavior so as to adapt the external hypoxic environment and internal stress generated by reactive oxygen species. To survive in these stringent conditions, glioblastoma cells develop an antagonistic metabolic phenotype as compared to their predecessors, the astrocytes, thereby quenching the resources expected for nourishing the neurons. The complexity and cumulative effect of the large scale metabolic functioning of glioblastoma is mostly unexplored. In this study, we reconstruct a metabolic network comprising of pathways that are known to be deregulated in glioblastoma cells as compared to the astrocytes. The network, consisted of 147 genes encoding for enzymes performing 247 reactions distributed across five distinct model compartments, was then studied using constrained-based modeling approach by recreating the scenarios for astrocytes and glioblastoma, and validated with available experimental evidences. From our analysis, we predict that glycine requirement of the astrocytes are mostly fulfilled by the internal glycine-serine metabolism, whereas glioblastoma cells demand an external uptake of glycine to utilize it for glutathione production. Also, cystine and glucose were identified to be the major contributors to glioblastoma growth. We also proposed an extensive set of single and double lethal reaction knockouts, which were further perturbed to ascertain their role as probable chemotherapeutic targets. These simulation results suggested that, apart from targeting the reactions of central carbon metabolism, knockout of reactions belonging to the glycine-serine metabolism effectively reduce glioblastoma growth. The combinatorial targeting of glycine transporter with any other reaction belonging to glycine-serine metabolism proved lethal to glioblastoma growth.
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Affiliation(s)
- Rupa Bhowmick
- Chemical Engineering and Process Development, CSIR-National Chemical Laboratory, Pune, Maharashtra 411008 India
| | - Abhishek Subramanian
- Chemical Engineering and Process Development, CSIR-National Chemical Laboratory, Pune, Maharashtra 411008 India.,Academy of Scientific and Innovative Research (AcSIR), CSIR-NCL Campus, Pune, 411008 India
| | - Ram Rup Sarkar
- Chemical Engineering and Process Development, CSIR-National Chemical Laboratory, Pune, Maharashtra 411008 India.,Academy of Scientific and Innovative Research (AcSIR), CSIR-NCL Campus, Pune, 411008 India
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Westhaus A, Blumrich EM, Dringen R. The Antidiabetic Drug Metformin Stimulates Glycolytic Lactate Production in Cultured Primary Rat Astrocytes. Neurochem Res 2015; 42:294-305. [PMID: 26433380 DOI: 10.1007/s11064-015-1733-8] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2015] [Revised: 09/25/2015] [Accepted: 09/26/2015] [Indexed: 12/11/2022]
Abstract
Metformin is the most frequently used drug for the treatment of type 2 diabetes in humans. However, only little is known about effects of metformin on brain metabolism. To investigate potential metabolic consequences of an exposure of brain cells to metformin, we incubated rat astrocyte-rich primary cultures with this compound. Metformin in concentrations of up to 30 mM did not acutely compromise the viability of astrocytes, but caused a time- and concentration-dependent increase in cellular glucose consumption and lactate production. For acute incubations in the hour range, the presence of 10 mM metformin doubled the glycolytic flux, while already 1 mM metformin doubled glycolytic flux during incubation for 24 h. In addition to metformin, also other guanidino compounds increased astrocytic lactate production. After 4 h of incubation, half-maximal stimulation of glycolysis was observed for metformin, guanidine and phenformin at concentrations of around 3 mM, 3 mM and 30 µM, respectively. The acute stimulation of glycolytic lactate production by metformin was persistent after removal of extracellular metformin and was also observed, if glucose was absent from the incubation medium or replaced by other hexoses. The metformin-induced stimulation of glycolytic flux was not prevented by compound C, an inhibitor of AMP-dependent protein kinase, nor was it additive to the stimulation of glycolytic flux caused by respiratory chain inhibitors. These data demonstrate that the antidiabetic drug metformin has the potential to strongly activate glycolytic lactate production in brain astrocytes.
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Affiliation(s)
- Adrian Westhaus
- Centre for Biomolecular Interactions Bremen, University of Bremen, PO. Box 330440, 28334, Bremen, Germany
| | - Eva Maria Blumrich
- Centre for Biomolecular Interactions Bremen, University of Bremen, PO. Box 330440, 28334, Bremen, Germany.,Centre for Environmental Research and Sustainable Technology, Leobener Strasse, 28359, Bremen, Germany
| | - Ralf Dringen
- Centre for Biomolecular Interactions Bremen, University of Bremen, PO. Box 330440, 28334, Bremen, Germany. .,Centre for Environmental Research and Sustainable Technology, Leobener Strasse, 28359, Bremen, Germany.
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van de Kamp JM, Mancini GM, Salomons GS. X-linked creatine transporter deficiency: clinical aspects and pathophysiology. J Inherit Metab Dis 2014; 37:715-33. [PMID: 24789340 DOI: 10.1007/s10545-014-9713-8] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/04/2014] [Revised: 03/27/2014] [Accepted: 04/01/2014] [Indexed: 12/22/2022]
Abstract
Creatine transporter deficiency was discovered in 2001 as an X-linked cause of intellectual disability characterized by cerebral creatine deficiency. This review describes the current knowledge regarding creatine metabolism, the creatine transporter and the clinical aspects of creatine transporter deficiency. The condition mainly affects the brain while other creatine requiring organs, such as the muscles, are relatively spared. Recent studies have provided strong evidence that creatine synthesis also occurs in the brain, leading to the intriguing question of why cerebral creatine is deficient in creatine transporter deficiency. The possible mechanisms explaining the cerebral creatine deficiency are discussed. The creatine transporter knockout mouse provides a good model to study the disease. Over the past years several treatment options have been explored but no treatment has been proven effective. Understanding the pathogenesis of creatine transporter deficiency is of paramount importance in the development of an effective treatment.
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MESH Headings
- Amino Acid Metabolism, Inborn Errors/diagnosis
- Amino Acid Metabolism, Inborn Errors/drug therapy
- Amino Acid Metabolism, Inborn Errors/genetics
- Amino Acid Metabolism, Inborn Errors/pathology
- Animals
- Brain Diseases, Metabolic, Inborn/complications
- Brain Diseases, Metabolic, Inborn/genetics
- Brain Diseases, Metabolic, Inborn/physiopathology
- Creatine/deficiency
- Creatine/genetics
- Genetic Diseases, X-Linked/genetics
- Humans
- Intellectual Disability/etiology
- Intellectual Disability/genetics
- Membrane Transport Proteins/deficiency
- Membrane Transport Proteins/genetics
- Mental Retardation, X-Linked/complications
- Mental Retardation, X-Linked/genetics
- Mental Retardation, X-Linked/physiopathology
- Mice
- Plasma Membrane Neurotransmitter Transport Proteins/deficiency
- Plasma Membrane Neurotransmitter Transport Proteins/genetics
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Affiliation(s)
- Jiddeke M van de Kamp
- Department of Clinical Genetics, VU University Medical Center, P.O. Box 7057, 1007 MB, Amsterdam, The Netherlands,
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Rae CD. A Guide to the Metabolic Pathways and Function of Metabolites Observed in Human Brain 1H Magnetic Resonance Spectra. Neurochem Res 2013; 39:1-36. [PMID: 24258018 DOI: 10.1007/s11064-013-1199-5] [Citation(s) in RCA: 327] [Impact Index Per Article: 29.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2013] [Revised: 11/08/2013] [Accepted: 11/11/2013] [Indexed: 12/20/2022]
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Hattingen E, Delic O, Franz K, Pilatus U, Raab P, Lanfermann H, Gerlach R. 1H MRSI and progression-free survival in patients with WHO grades II and III gliomas. Neurol Res 2013; 32:593-602. [DOI: 10.1179/016164109x12478302362770] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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Li Y, Lupo JM, Parvataneni R, Lamborn KR, Cha S, Chang SM, Nelson SJ. Survival analysis in patients with newly diagnosed glioblastoma using pre- and postradiotherapy MR spectroscopic imaging. Neuro Oncol 2013; 15:607-17. [PMID: 23393206 DOI: 10.1093/neuonc/nos334] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
BACKGROUND The objective of this study was to examine the predictive value of parameters of 3D (1)H magnetic resonance spectroscopic imaging (MRSI) prior to treatment with radiation/chemotherapy (baseline) and at a postradiation 2-month follow-up (F2mo) in relationship to 6-month progression-free survival (PFS6) and overall survival (OS). METHODS Sixty-four patients with newly diagnosed glioblastoma multiforme (GBM) being treated with radiation and concurrent chemotherapy were involved in this study. Evaluated were metabolite indices and metabolite ratios. Logistic linear regression and Cox proportional hazards models were utilized to evaluate PFS6 and OS, respectively. These analyses were adjusted by age and MR scanner field strength (1.5 T or 3 T). Stepwise regression was performed to determine a subset of the most relevant variables. RESULTS Associated with shorter PFS6 were a decrease in the ratio of N-acetyl aspartate to choline-containing compounds (NAA/Cho) in the region with a Cho-to-NAA index (CNI) >3 at baseline and an increase of the CNI within elevated CNI regions (>2) at F2mo. Patients with higher normalized lipid and lactate at either time point had significantly worse OS. Patients who had larger volumes with abnormal CNI at F2mo had worse PFS6 and OS. CONCLUSIONS Our study found more 3D MRSI parameters that predicted PFS6 and OS for patients with GBM than did anatomic, diffusion, or perfusion imaging, which were previously evaluated in the same population of patients.
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Affiliation(s)
- Yan Li
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, CA, USA.
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Zhang Y, Lv SJ, Yan H, Wang L, Liang GP, Wan QX, Peng X. Effects of glycine supplementation on myocardial damage and cardiac function after severe burn. Burns 2012; 39:729-35. [PMID: 23036846 DOI: 10.1016/j.burns.2012.09.006] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2012] [Revised: 08/06/2012] [Accepted: 09/05/2012] [Indexed: 10/27/2022]
Abstract
BACKGROUND Glycine has been shown to participate in protection from hypoxia/reoxygenation injury. However, the cardioprotective effect of glycine after burn remains unclear. This study aimed to explore the protective effect of glycine on myocardial damage in severely burned rats. METHODS Seventy-two Wistar rats were randomly divided into three groups: normal controls (C), burned controls (B), and glycine-treated (G). Groups B and G were given a 30% total body surface area full-thickness burn. Group G was administered 1.5 g/(kg d) glycine and group B was given the same dose of alanine via intragastric administration for 3d. Serum creatine kinase (CK), lactate dehydrogenase (LDH), aspartate transaminase (AST), and blood lactate, as well as myocardial ATP and glutathione (GSH) content, were measured. Cardiac contractile function and histopathological changes were analyzed at 12, 24, 48, and 72 hours. RESULTS Serum CK, LDH, AST, and blood lactate increased, while myocardial ATP and GSH content decreased in both burned groups. Compared with group B, the levels of CK, LDH, and AST significantly decreased, whereas blood lactate as well as myocardial ATP and GSH content increased in group G. Moreover, cardiac contractile function inhibition and myocardial histopathological damage in group G significantly decreased compared with group B. CONCLUSION Myocardial histological structure and function were damaged significantly after burn. Glycine is beneficial to myocardial preservation by improving cardiomyocyte energy metabolism and increasing ATP and GSH abundance.
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Affiliation(s)
- Yong Zhang
- State Key Laboratory of Trauma, Burns and Combined Injury, Institute of Burns of PLA, Southwest Hospital, Third Military Medical University, Chongqing 400038, PR China
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Neuropsychological profile and clinical effects of arginine treatment in children with creatine transport deficiency. Orphanet J Rare Dis 2012; 7:43. [PMID: 22713831 PMCID: PMC3526552 DOI: 10.1186/1750-1172-7-43] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2011] [Accepted: 02/27/2012] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND SLC6A8, an X-linked gene, encodes the creatine transporter (CRTR) and its mutations lead to cerebral creatine (Cr) deficiency which results in mental retardation, speech and language delay, autistic-like behaviour and epilepsy (CRTR-D, OMIM 300352). CRTR-D represents the most frequent Cr metabolism disorder but, differently from Cr synthesis defects, that are partially reversible by oral Cr supplementation, does not respond to Cr treatment even if precociously administrated. The precursors of Cr are the non-essential amino acids Glycine (Gly) and Arginine (Arg), which have their own transporters at the brain-blood barrier level and, therefore, their supplementation appears an attractive and feasible therapeutic option aimed at stimulating Cr endogenous synthesis and, in this way, at overcoming the block of Cr transport within the brain. However, until now the effects of Arg and/or Gly supplementation on Cr brain levels and behaviour have been controversial. METHODS In this study five Italian male patients affected by CRTR-D were supplemented with oral L-Arg at a dosage of 300 mg/kg/day divided into 3 doses, for 24-36 months. Biochemical and plasmatic amino acids examinations and thyroid hormone dosages were periodically performed. Moreover, Proton and Phosphorus Magnetic Resonance Spectroscopy (MRS) was monitored during follow-up in concurrence with neuropsychological evaluations. RESULTS During L-Arg treatment a clinical improvement in motor skills and to a lesser extent in communication and attention was observed. In addition, all patients had a reduction in the number and frequency of epileptic seizures. Daily living skills appeared also to be positively influenced by L-Arg treatment. Moreover, Total Cr and especially PhosphoCr, evaluated by proton and phosphorus spectroscopy, showed a mild increase, although well below the normal range. CONCLUSION This study provides information to support the effectiveness of L-Arg supplement treatment in CTRT-D patients; in fact the syndromic pattern of cognitive and linguistic deficit presented by CRTR-D patients was partially altered by L-Arg supplementation especially at a qualitative clinical level. Oral L-Arg may represent not only a protective factor towards a further cognitive decline, but can lead to the acquisition of new skills.
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Carducci C, Carducci C, Santagata S, Adriano E, Artiola C, Thellung S, Gatta E, Robello M, Florio T, Antonozzi I, Leuzzi V, Balestrino M. In vitro study of uptake and synthesis of creatine and its precursors by cerebellar granule cells and astrocytes suggests some hypotheses on the physiopathology of the inherited disorders of creatine metabolism. BMC Neurosci 2012; 13:41. [PMID: 22536786 PMCID: PMC3355046 DOI: 10.1186/1471-2202-13-41] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2011] [Accepted: 04/26/2012] [Indexed: 10/28/2022] Open
Abstract
BACKGROUND The discovery of the inherited disorders of creatine (Cr) synthesis and transport in the last few years disclosed the importance of blood Cr supply for the normal functioning of the brain. These putatively rare diseases share a common pathogenetic mechanism (the depletion of brain Cr) and similar phenotypes characterized by mental retardation, language disturbances, seizures and movement disorders. In the effort to improve our knowledge on the mechanisms regulating Cr pool inside the nervous tissue, Cr transport and synthesis and related gene transcripts were explored in primary cultures of rat cerebellar granule cells and astrocytes. METHODS Cr uptake and synthesis were explored in vitro by incubating monotypic primary cultures of rat type I astrocytes and cerebellar granule cells with: a) D3-Creatine (D3Cr) and D3Cr plus β-guanidinopropionate (GPA, an inhibitor of Cr transporter), and b) labelled precursors of Guanidinoacetate (GAA) and Cr (Arginine, Arg; Glycine, Gly). Intracellular D3Cr and labelled GAA and Cr were assessed by ESI-MS/MS. Creatine transporter (CT1), L-arginine:glycine amidinotransferase (AGAT), and S-adenosylmethionine:guanidinoacetate N-methyltransferase (GAMT) gene expression was assessed in the same cells by real time PCR. RESULTS D3Cr signal was extremely high in cells incubated with this isotope (labelled/unlabelled Cr ratio reached about 10 and 122, respectively in cerebellar granule cells and astrocytes) and was reduced by GPA. Labelled Arg and Gly were taken up by the cells and incorporated in GAA, whose concentration paralleled that of these precursors both in the extracellular medium and inside the cells (astrocytes). In contrast, the increase of labelled Cr was relatively much more limited since labelled Cr after precursors' supplementation did not exceed 2,7% (cerebellar granule cells) and 21% (astrocytes) of unlabelled Cr. Finally, AGAT, GAMT and SLC6A8 were expressed in both kind of cells. CONCLUSIONS Our results confirm that both neurons and astrocytes have the capability to synthesize and uptake Cr, and suggest that at least in vitro intracellular Cr can increase to a much greater extent through uptake than through de novo synthesis. Our results are compatible with the clinical observations that when the Cr transporter is defective, intracellular Cr is absent despite the brain should be able to synthesize it. Further research is needed to fully understand to what extent our results reflect the in vivo situation.
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Affiliation(s)
- Claudia Carducci
- Department of Experimental Medicine, La Sapienza Università di Roma, Viale del Policlinico 155, Rome 00161, Italy
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Thelwall PE, Simpson NE, Rabbani ZN, Clark MD, Pourdeyhimi R, Macdonald JM, Blackband SJ, Gamcsik MP. In vivo MR studies of glycine and glutathione metabolism in a rat mammary tumor. NMR IN BIOMEDICINE 2012; 25:271-278. [PMID: 21751272 PMCID: PMC3193887 DOI: 10.1002/nbm.1745] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/23/2010] [Revised: 04/12/2011] [Accepted: 04/14/2011] [Indexed: 05/31/2023]
Abstract
The metabolism of glycine into glutathione was monitored noninvasively in vivo in intact rat mammary adenocarcinomas (R3230Ac) by MRI and MRS. Metabolism was tracked by following the isotope label from intravenously infused [2-(13)C]-glycine into the glycinyl residue of glutathione. Signals from [2-(13)C]-glycine and γ-glutamylcysteinyl-[2-(13)C]-glycine ((13)C-glutathione) were detected by nonlocalized (13)C spectroscopy, as these resonances are distinct from background signals. In addition, using spectroscopic imaging methods, heterogeneity in the in vivo tumor distribution of glutathione was observed. In vivo spectroscopy also detected isotope incorporation from [2-(13)C]-glycine into both the 2- and 3-carbons of serine. Analyses of tumor tissue extracts showed single- and multiple-label incorporation from [2-(13)C]-glycine into serine from metabolism through the serine hydroxymethyltransferase and glycine cleavage system pathways. Mass spectrometric analysis of extracts also showed that isotope-labeled serine is further metabolized via the trans-sulfuration pathway, as (13)C isotope labels appear in both the glycinyl and cysteinyl residues of glutathione. Our studies demonstrate the use of MRI and MRS for the monitoring of tumor metabolic processes central to oxidative stress defense.
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Affiliation(s)
- Peter E. Thelwall
- Newcastle Magnetic Resonance Centre, Campus for Ageing and Vitality, Newcastle University, Newcastle upon Tyne, UK
| | - Nicholas E. Simpson
- Department of Medicine, Division of Endocrinology, University of Florida, Gainesville, FL, USA
| | - Zahid N. Rabbani
- Department of Radiation Oncology, Duke University Medical Center, Durham, NC
| | - M. Daniel Clark
- Department of Neuroscience, University of Florida, Gainesville, FL, USA
| | - Roxana Pourdeyhimi
- Joint Department of Biomedical Engineering, University of North Carolina, Chapel Hill and North Carolina State University, Raleigh, NC, USA
| | - Jeffrey M. Macdonald
- Joint Department of Biomedical Engineering, University of North Carolina, Chapel Hill and North Carolina State University, Raleigh, NC, USA
| | | | - Michael P. Gamcsik
- Joint Department of Biomedical Engineering, University of North Carolina, Chapel Hill and North Carolina State University, Raleigh, NC, USA
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O'Neill J, Piacentini JC, Chang S, Levitt JG, Rozenman M, Bergman L, Salamon N, Alger JR, McCracken JT. MRSI correlates of cognitive-behavioral therapy in pediatric obsessive-compulsive disorder. Prog Neuropsychopharmacol Biol Psychiatry 2012; 36:161-8. [PMID: 21983143 PMCID: PMC4344316 DOI: 10.1016/j.pnpbp.2011.09.007] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/25/2011] [Revised: 09/02/2011] [Accepted: 09/08/2011] [Indexed: 01/01/2023]
Abstract
BACKGROUND The brain mechanisms of cognitive-behavioral therapy (CBT), a highly effective treatment for pediatric obsessive-compulsive disorder (OCD), are unknown. Neuroimaging in adult OCD indicates that CBT is associated with metabolic changes in striatum, thalamus, and anterior cingulate cortex. We therefore probed putative metabolic effects of CBT on these brain structures in pediatric OCD using proton magnetic resonance spectroscopic imaging (1H MRSI). METHOD Five unmedicated OCD patients (4 ♀, 13.5±2.8) and 9 healthy controls (7 ♀, 13.0±2.5) underwent MRSI (1.5 T, repetition-time/echo-time=1500/30 ms) of bilateral putamen, thalamus and pregenual anterior cingulate cortex (pACC). Patients were rescanned after 12 weeks of exposure-based CBT. The Children's Yale-Brown Obsessive-Compulsive Scale (CY-BOCS) of OCD symptoms was administered before and after CBT. RESULTS Four of 5 patients responded to CBT (mean 32.8% CY-BOCS reduction). Multiple metabolite effects emerged. Pre-CBT, N-acetyl-aspartate+N-acetyl-aspartyl-glutamate (tNAA) in left pregenual anterior cingulate cortex (pACC) was 55.5% higher in patients than controls. Post-CBT, tNAA (15.0%) and Cr (23.9%) in left pACC decreased and choline compounds (Cho) in right thalamus increased (10.6%) in all 5 patients. In left thalamus, lower pre-CBT tNAA, glutamate+glutamine (Glx), and myo-inositol (mI) predicted greater post-CBT drop in CY-BOCS (r=0.98) and CY-BOCS decrease correlated with increased Cho. CONCLUSIONS Interpretations are offered in terms of the Glutamatergic Hypothesis of Pediatric OCD. Similar to 18FDG-PET in adults, objectively measurable regional MRSI metabolites may indicate pediatric OCD and predict its response to CBT.
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Affiliation(s)
- Joseph O'Neill
- Division of Child & Adolescent Psychiatry, Semel Institute for Neurosciences, Department of Radiological Sciences, UCLA School of Medicine, Los Angeles, CA 90024-1759, United States.
| | - John C. Piacentini
- Division of Child & Adolescent Psychiatry, Semel Institute for Neurosciences, UCLA School of Medicine, Los Angeles, California
| | - Susanna Chang
- Division of Child & Adolescent Psychiatry, Semel Institute for Neurosciences, UCLA School of Medicine, Los Angeles, California
| | - Jennifer G. Levitt
- Division of Child & Adolescent Psychiatry, Semel Institute for Neurosciences, UCLA School of Medicine, Los Angeles, California
| | - Michelle Rozenman
- Division of Child & Adolescent Psychiatry, Semel Institute for Neurosciences, UCLA School of Medicine, Los Angeles, California
| | - Lindsey Bergman
- Division of Child & Adolescent Psychiatry, Semel Institute for Neurosciences, UCLA School of Medicine, Los Angeles, California
| | - Noriko Salamon
- Department of Radiological Sciences, UCLA School of Medicine, Los Angeles, California
| | - Jeffry R. Alger
- Department of Neurology, UCLA School of Medicine, Los Angeles, California
| | - James T. McCracken
- Division of Child & Adolescent Psychiatry, Semel Institute for Neurosciences, UCLA School of Medicine, Los Angeles, California
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Blasel S, Pilatus U, Magerkurth J, von Stauffenberg M, Vronski D, Mueller M, Woeckel L, Hattingen E. Metabolic gray matter changes of adolescents with anorexia nervosa in combined MR proton and phosphorus spectroscopy. Neuroradiology 2012; 54:753-64. [PMID: 22210349 DOI: 10.1007/s00234-011-1001-9] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2011] [Accepted: 12/15/2011] [Indexed: 11/29/2022]
Abstract
INTRODUCTION There are hints for changes in phospholipid membrane metabolism and structure in the brain of adolescents with anorexia nervosa (AN) using either proton ((1)H) or phosphorus ((31)P) magnetic resonance spectroscopic imaging (MRSI). We aimed to specify these pathological metabolite changes by combining both methods with additional focus on the neuronal metabolites glutamate (Glu) and N-acetyl-l-aspartate (NAA). METHODS Twenty-one female patients (mean 14.4 ± 1.9 years) and 29 female controls (mean 16 ± 1.6 years) underwent (1)H and (31)P MRSI at 3 T applied to the centrum semiovale including the anterior cingulate cortex. We assessed gray matter (GM) and white matter (WM) metabolite concentration changes of the frontal and parietal brain measuring choline(Cho)- and ethanolamine(Eth)-containing compounds, Glutamate (Glu) and glutamine (Gln) and their sum (Glx), myoinositol, NAA, and high-energy phosphates. RESULTS For (1)H MRSI, a clear discrimination between GM and WM concentrations was possible, showing an increase of Glx (p < 0.001), NAA (frontal p < 0.05), pooled creatine (tCr) (p < 0.001), and choline (tCho) (p < 0.05) in the GM of AN patients. The lipid catabolites glycerophosphocholine (p < 0.07) and glycerophosphoethanolamine (p < 0.03) were increased in the parietal region. CONCLUSIONS Significant changes in GM metabolite concentrations were observed in AN possibly triggered by elevated excitotoxin Glu. Increased tCho may indicate modifications of membrane phospholipids due to increased catabolism in the parietal region. Since no significant changes in phosphorylated choline compounds were found for the frontal region, the tCho increase in this region may hint to fluidity changes.
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Affiliation(s)
- Stella Blasel
- Institute of Neuroradiology, University of Frankfurt, Schleusenweg 2-16, 60528 Frankfurt, Germany.
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Valayannopoulos V, Boddaert N, Chabli A, Barbier V, Desguerre I, Philippe A, Afenjar A, Mazzuca M, Cheillan D, Munnich A, de Keyzer Y, Jakobs C, Salomons GS, de Lonlay P. Treatment by oral creatine, L-arginine and L-glycine in six severely affected patients with creatine transporter defect. J Inherit Metab Dis 2012; 35:151-7. [PMID: 21660517 DOI: 10.1007/s10545-011-9358-9] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/07/2011] [Revised: 05/11/2011] [Accepted: 05/25/2011] [Indexed: 11/24/2022]
Abstract
BACKGROUND X-linked cerebral creatine deficiency is caused by the deficiency of the creatine transporter (CTP) encoded by the SLC6A8 gene. PATIENTS AND METHODS We report here a series of six patients with severe CTP deficiency, four males and two females; clinical presentations include mild to severe mental retardation (6/6), associated with psychiatric symptoms (5/6: autistic behaviour, chronic hallucinatory psychosis), seizures (2/6) and muscular symptoms (2/4 males). Diagnosis was suspected upon elevated urinary creatine/creatinine (except in one of the female patients) and on a markedly decreased creatine peak on magnetic resonance spectroscopy (MRS). Diagnosis was confirmed by molecular analysis that identified four novel mutations not reported so far, including a mutation found twice in two male patients. All patients were treated successively and according to the same protocol by creatine alone then combined to its precursors, L-glycine and L-arginine for 42 months. RESULTS AND CONCLUSION In our patients, creatine supplementation alone or with its precursors L-glycine and L-arginine showed benefit only in the muscular symptoms of the disease and no improvement in the cognitive and psychiatric manifestations and did not modify brain creatine content on MRS of male and female CTP deficient patients. New treatment strategies are required including creatine derivatives transported independently from CTP or using alternative pathways and transporters.
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Affiliation(s)
- Vassili Valayannopoulos
- Reference Center for Inherited Metabolic Disorders (MaMEA), Necker-Enfants Malades Hospital, Paris Descartes University, 149 Rue de Sèvres, 75743 Paris Cedex, France.
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17
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van de Kamp JM, Pouwels PJW, Aarsen FK, ten Hoopen LW, Knol DL, de Klerk JB, de Coo IF, Huijmans JGM, Jakobs C, van der Knaap MS, Salomons GS, Mancini GMS. Long-term follow-up and treatment in nine boys with X-linked creatine transporter defect. J Inherit Metab Dis 2012; 35:141-9. [PMID: 21556832 PMCID: PMC3249187 DOI: 10.1007/s10545-011-9345-1] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/03/2011] [Revised: 04/05/2011] [Accepted: 04/19/2011] [Indexed: 10/26/2022]
Abstract
The creatine transporter (CRTR) defect is a recently discovered cause of X-linked intellectual disability for which treatment options have been explored. Creatine monotherapy has not proved effective, and the effect of treatment with L-arginine is still controversial. Nine boys between 8 months and 10 years old with molecularly confirmed CRTR defect were followed with repeated (1)H-MRS and neuropsychological assessments during 4-6 years of combination treatment with creatine monohydrate, L-arginine, and glycine. Treatment did not lead to a significant increase in cerebral creatine content as observed with H(1)-MRS. After an initial improvement in locomotor and personal-social IQ subscales, no lasting clinical improvement was recorded. Additionally, we noticed an age-related decline in IQ subscales in boys affected with the CRTR defect.
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Affiliation(s)
- Jiddeke M van de Kamp
- Department of Clinical Genetics, VU University Medical Center, PO Box 7057, 1007 MB, Amsterdam, The Netherlands.
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Le-Corronc H, Rigo JM, Branchereau P, Legendre P. GABA(A) receptor and glycine receptor activation by paracrine/autocrine release of endogenous agonists: more than a simple communication pathway. Mol Neurobiol 2011; 44:28-52. [PMID: 21547557 DOI: 10.1007/s12035-011-8185-1] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2011] [Accepted: 04/14/2011] [Indexed: 02/04/2023]
Abstract
It is a common and widely accepted assumption that glycine and GABA are the main inhibitory transmitters in the central nervous system (CNS). But, in the past 20 years, several studies have clearly demonstrated that these amino acids can also be excitatory in the immature central nervous system. In addition, it is now established that both GABA receptors (GABARs) and glycine receptors (GlyRs) can be located extrasynaptically and can be activated by paracrine release of endogenous agonists, such as GABA, glycine, and taurine. Recently, non-synaptic release of GABA, glycine, and taurine gained further attention with increasing evidence suggesting a developmental role of these neurotransmitters in neuronal network formation before and during synaptogenesis. This review summarizes recent knowledge about the non-synaptic activation of GABA(A)Rs and GlyRs, both in developing and adult CNS. We first present studies that reveal the functional specialization of both non-synaptic GABA(A)Rs and GlyRs and we discuss the neuronal versus non-neuronal origin of the paracrine release of GABA(A)R and GlyR agonists. We then discuss the proposed non-synaptic release mechanisms and/or pathways for GABA, glycine, and taurine. Finally, we summarize recent data about the various roles of non-synaptic GABAergic and glycinergic systems during the development of neuronal networks and in the adult.
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Affiliation(s)
- Herve Le-Corronc
- Institut National de la Santé et de la Recherche Médicale, U952, Centre National de la Recherche Scientifique, UMR 7224, Université Pierre et Marie Curie, 9 quai Saint Bernard, Paris, Ile de France, France
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Braissant O, Henry H, Béard E, Uldry J. Creatine deficiency syndromes and the importance of creatine synthesis in the brain. Amino Acids 2011; 40:1315-24. [DOI: 10.1007/s00726-011-0852-z] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2010] [Accepted: 11/25/2010] [Indexed: 10/18/2022]
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20
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Kim DW, Yeo SI, Ryu HJ, Kim JE, Song HK, Kwon OS, Choi SY, Kang TC. Effects of creatine and β-guanidinopropionic acid and alterations in creatine transporter and creatine kinases expression in acute seizure and chronic epilepsy models. BMC Neurosci 2010; 11:141. [PMID: 20979657 PMCID: PMC2978220 DOI: 10.1186/1471-2202-11-141] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2010] [Accepted: 10/28/2010] [Indexed: 11/12/2022] Open
Abstract
Background In order to confirm the roles of creatine (Cr) in epilepsy, we investigated the anti-convulsive effects of Cr, creatine transporter (CRT) and creatine kinases (CKs) against chemical-induced acute seizure activity and chronic epileptic seizure activity. Results Two hr after pilocarpine (PILO)-seizure induction, ubiquitous mitochondrial CK (uMtCK) immunoreactivity was unaltered as compared to control level. However, brain-type cytoplasm CK (BCK) immunoreactivity was decreased to 70% of control level. CRT immunoreactivity was decreased to 60% of control level. Following Cr or Tat-CK treatment, uMtCK or CRT immunoreactivity was unaffected, while BCK immunoreactivity in Cr treated group was increased to 3.6-fold of control levels. β-Guanidinopropionic acid (GPA, a competitive CRT inhibitor) reduced BCK and CRT expression. In addition, Cr and tat-BCK treatment delayed the beginning of seizure activity after PILO injection. However, GPA treatment induced spontaneous seizure activity without PILO treatment. In chronic epilepsy rats, both uMtCK and CRT immunoreactivities were reduced in the hippocampus. In contrast, BCK immunoreactivity was similar to that observed in control animals. Cr-, GPA and tat-BCK treatment could not change EEG. Conclusion Cr/CK circuit may play an important role in sustaining or exacerbating acute seizure activity, but not chronic epileptic discharge.
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Affiliation(s)
- Dae Won Kim
- Department of Biomedical Sciences, College of Life Science, Hallym University, Chunchon Kangwon-Do 200-702, Republic of Korea
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Béard E, Braissant O. Synthesis and transport of creatine in the CNS: importance for cerebral functions. J Neurochem 2010; 115:297-313. [DOI: 10.1111/j.1471-4159.2010.06935.x] [Citation(s) in RCA: 118] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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22
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Braissant O, Béard E, Torrent C, Henry H. Dissociation of AGAT, GAMT and SLC6A8 in CNS: Relevance to creatine deficiency syndromes. Neurobiol Dis 2010; 37:423-33. [DOI: 10.1016/j.nbd.2009.10.022] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2009] [Revised: 10/15/2009] [Accepted: 10/22/2009] [Indexed: 10/20/2022] Open
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Rae C. RE: Magnetic resonance spectroscopy of the brain: review of metabolites and clinical applications. Clin Radiol 2009; 64:1042-3. [DOI: 10.1016/j.crad.2009.06.003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2009] [Accepted: 06/02/2009] [Indexed: 12/01/2022]
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24
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Kuiper JWP, van Horssen R, Oerlemans F, Peters W, van Dommelen MMT, te Lindert MM, ten Hagen TLM, Janssen E, Fransen JAM, Wieringa B. Local ATP generation by brain-type creatine kinase (CK-B) facilitates cell motility. PLoS One 2009; 4:e5030. [PMID: 19333390 PMCID: PMC2659440 DOI: 10.1371/journal.pone.0005030] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2009] [Accepted: 03/03/2009] [Indexed: 01/01/2023] Open
Abstract
Background Creatine Kinases (CK) catalyze the reversible transfer of high-energy phosphate groups between ATP and phosphocreatine, thereby playing a storage and distribution role in cellular energetics. Brain-type CK (CK-B) deficiency is coupled to loss of function in neural cell circuits, altered bone-remodeling by osteoclasts and complement-mediated phagocytotic activity of macrophages, processes sharing dependency on actomyosin dynamics. Methodology/Principal Findings Here, we provide evidence for direct coupling between CK-B and actomyosin activities in cortical microdomains of astrocytes and fibroblasts during spreading and migration. CK-B transiently accumulates in membrane ruffles and ablation of CK-B activity affects spreading and migration performance. Complementation experiments in CK-B-deficient fibroblasts, using new strategies to force protein relocalization from cytosol to cortical sites at membranes, confirmed the contribution of compartmentalized CK-B to cell morphogenetic dynamics. Conclusion/Significance Our results provide evidence that local cytoskeletal dynamics during cell motility is coupled to on-site availability of ATP generated by CK-B.
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Affiliation(s)
- Jan W. P. Kuiper
- Department of Cell Biology, Nijmegen Centre for Molecular Life Sciences (NCMLS), Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
| | - Remco van Horssen
- Department of Cell Biology, Nijmegen Centre for Molecular Life Sciences (NCMLS), Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
| | - Frank Oerlemans
- Department of Cell Biology, Nijmegen Centre for Molecular Life Sciences (NCMLS), Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
| | - Wilma Peters
- Department of Cell Biology, Nijmegen Centre for Molecular Life Sciences (NCMLS), Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
| | - Michiel M. T. van Dommelen
- Department of Cell Biology, Nijmegen Centre for Molecular Life Sciences (NCMLS), Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
| | - Mariska M. te Lindert
- Department of Cell Biology, Nijmegen Centre for Molecular Life Sciences (NCMLS), Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
| | | | - Edwin Janssen
- Department of Cell Biology, Nijmegen Centre for Molecular Life Sciences (NCMLS), Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
| | - Jack A. M. Fransen
- Department of Cell Biology, Nijmegen Centre for Molecular Life Sciences (NCMLS), Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
| | - Bé Wieringa
- Department of Cell Biology, Nijmegen Centre for Molecular Life Sciences (NCMLS), Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
- * E-mail:
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Hoffman HE, Jirásková J, Ingr M, Zvelebil M, Konvalinka J. Recombinant human serine racemase: Enzymologic characterization and comparison with its mouse ortholog. Protein Expr Purif 2009; 63:62-7. [DOI: 10.1016/j.pep.2008.09.003] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2008] [Revised: 08/29/2008] [Accepted: 09/04/2008] [Indexed: 10/21/2022]
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Hattingen E, Raab P, Franz K, Lanfermann H, Setzer M, Gerlach R, Zanella FE, Pilatus U. Prognostic value of choline and creatine in WHO grade II gliomas. Neuroradiology 2008; 50:759-67. [DOI: 10.1007/s00234-008-0409-3] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2008] [Accepted: 04/30/2008] [Indexed: 11/29/2022]
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Braissant O, Henry H. AGAT, GAMT and SLC6A8 distribution in the central nervous system, in relation to creatine deficiency syndromes: a review. J Inherit Metab Dis 2008; 31:230-9. [PMID: 18392746 DOI: 10.1007/s10545-008-0826-9] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/30/2007] [Revised: 02/01/2008] [Accepted: 02/05/2008] [Indexed: 11/25/2022]
Abstract
Creatine deficiency syndromes, either due to AGAT, GAMT or SLC6A8 deficiencies, lead to a complete absence, or a very strong decrease, of creatine within the brain, as measured by magnetic resonance spectroscopy. While the mammalian central nervous system (CNS) expresses AGAT, GAMT and SLC6A8, the lack of SLC6A8 in astrocytes around the blood-brain barrier limits the brain capacity to import creatine from the periphery, and suggests that the CNS has to rely mainly on endogenous creatine synthesis through AGAT and GAMT expression. This seems contradictory with SLC6A8 deficiency, which, despite AGAT and GAMT expression, also leads to creatine deficiency in the CNS. We present novel data showing that in cortical grey matter, AGAT and GAMT are expressed in a dissociated way: e.g. only a few cells co-express both genes. This suggests that to allow synthesis of creatine within the CNS, at least for a significant part of it, guanidinoacetate must be transported from AGAT- to GAMT-expressing cells, possibly through SLC6A8. This would explain the creatine deficiency observed in SLC6A8-deficient patients. By bringing together creatine deficiency syndromes, AGAT, GAMT and SLC6A8 distribution in CNS, as well as a synthetic view on creatine and guanidinoacetate levels in the brain, this review presents a comprehensive framework, including new hypotheses, on brain creatine metabolism and transport, both in normal conditions and in case of creatine deficiency.
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Affiliation(s)
- O Braissant
- Inborn Errors of Metabolism, Clinical Chemistry Laboratory, Centre Hospitalier Universitaire Vaudois and University of Lausanne, Lausanne, Switzerland.
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28
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Hattingen E, Raab P, Franz K, Zanella FE, Lanfermann H, Pilatus U. Myo-inositol: a marker of reactive astrogliosis in glial tumors? NMR IN BIOMEDICINE 2008; 21:233-41. [PMID: 17562554 DOI: 10.1002/nbm.1186] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
In a prospective study, two-dimensional (1)H-MRS with TE of 30 ms was performed before surgery in 56 patients with glial brain tumors. Concentrations of myo-inositol (MI), trimethylamine (TMA) and creatine/phosphocreatine (tCr) were evaluated for the whole tumor and scaled to the normal-appearing contralateral brain tissue. To assign changes in MI to specific tissue pathology, the normalized peak and mean concentrations of MI were correlated with TMA and tCr concentrations. TMA is accepted as a marker of proliferating tumor tissue, and tCr might be a marker of reactive astrogliosis. The mean and peak concentrations of MI and tCr correlated positively (r = 0.7), but not the concentrations of MI and TMA. The absolute concentration of MI was significantly increased in all tumor tissues (5.55 +/- 2.92 mM; mean +/- SD) compared with the normal-appearing white matter (4.33 +/- 1.22 mM, p = 0.005), with the highest concentrations for gliomatoses (n = 10) and grade II oligoastrocytomas (n = 3). Significant differences (P = 0.004) between low- and high-grade astrocytomas were found for TMA (1.67 +/- 0.32 mM and 2.65 +/- 0.86 mM, respectively), but not for MI (5.92 +/- 1.98 mM and 5.49 +/- 3.27 mM, respectively). As increased MI and tCr concentrations were found in gliomatosis and other cerebral diseases associated with marked astrogliosis, this process may also be responsible for the observed changes in MI in other glial tumors.
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Affiliation(s)
- Elke Hattingen
- Institute of Neuroradiology, Johann Wolfgang Goethe University of Frankfurt/Main, Germany.
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29
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Chilosi A, Leuzzi V, Battini R, Tosetti M, Ferretti G, Comparini A, Casarano M, Moretti E, Alessandri MG, Bianchi MC, Cioni G. Treatment with L-arginine improves neuropsychological disorders in a child with creatine transporter defect. Neurocase 2008; 14:151-61. [PMID: 18569740 DOI: 10.1080/13554790802060821] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Creatine transporter deficit (CT1) is an inherited metabolic disorder that causes mental retardation, epilepsy, speech, language and behavioral deficits. Until now, no treatment has been proven to be successful for this condition. We describe 1-year follow-up study of a child, aged 9.6 years, with CT1 defect, on oral supplementation with L-arginine, a precursor of creatine synthesis. Under supplementation, he showed a noticeable improvement of neurological, language and behavioral status and an increase of brain creatine and phosphocreatine documented with magnetic resonance spectroscopy. The results suggest that children with CT1 disorder show some residual adaptive plasticity for certain functions even at quite an advanced age. Further trials with higher L-arginine dosages and more protracted treatment are encouraged.
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Affiliation(s)
- Anna Chilosi
- Department of Developmental Neuroscience, IRCCS Stella Maris, Calambrone, Pisa, Italy
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Cakir T, Alsan S, Saybaşili H, Akin A, Ulgen KO. Reconstruction and flux analysis of coupling between metabolic pathways of astrocytes and neurons: application to cerebral hypoxia. Theor Biol Med Model 2007; 4:48. [PMID: 18070347 PMCID: PMC2246127 DOI: 10.1186/1742-4682-4-48] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2007] [Accepted: 12/10/2007] [Indexed: 01/07/2023] Open
Abstract
BACKGROUND It is a daunting task to identify all the metabolic pathways of brain energy metabolism and develop a dynamic simulation environment that will cover a time scale ranging from seconds to hours. To simplify this task and make it more practicable, we undertook stoichiometric modeling of brain energy metabolism with the major aim of including the main interacting pathways in and between astrocytes and neurons. MODEL The constructed model includes central metabolism (glycolysis, pentose phosphate pathway, TCA cycle), lipid metabolism, reactive oxygen species (ROS) detoxification, amino acid metabolism (synthesis and catabolism), the well-known glutamate-glutamine cycle, other coupling reactions between astrocytes and neurons, and neurotransmitter metabolism. This is, to our knowledge, the most comprehensive attempt at stoichiometric modeling of brain metabolism to date in terms of its coverage of a wide range of metabolic pathways. We then attempted to model the basal physiological behaviour and hypoxic behaviour of the brain cells where astrocytes and neurons are tightly coupled. RESULTS The reconstructed stoichiometric reaction model included 217 reactions (184 internal, 33 exchange) and 216 metabolites (183 internal, 33 external) distributed in and between astrocytes and neurons. Flux balance analysis (FBA) techniques were applied to the reconstructed model to elucidate the underlying cellular principles of neuron-astrocyte coupling. Simulation of resting conditions under the constraints of maximization of glutamate/glutamine/GABA cycle fluxes between the two cell types with subsequent minimization of Euclidean norm of fluxes resulted in a flux distribution in accordance with literature-based findings. As a further validation of our model, the effect of oxygen deprivation (hypoxia) on fluxes was simulated using an FBA-derivative approach, known as minimization of metabolic adjustment (MOMA). The results show the power of the constructed model to simulate disease behaviour on the flux level, and its potential to analyze cellular metabolic behaviour in silico. CONCLUSION The predictive power of the constructed model for the key flux distributions, especially central carbon metabolism and glutamate-glutamine cycle fluxes, and its application to hypoxia is promising. The resultant acceptable predictions strengthen the power of such stoichiometric models in the analysis of mammalian cell metabolism.
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Affiliation(s)
- Tunahan Cakir
- Department of Chemical Engineering, Boğaziçi University, 34342, Bebek, Istanbul, Turkey.
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Kalló I, Jekkel C, Hrabovszky E, Jurányi Z, Vida B, Járási A, Wilheim T, Harsing LG, Liposits Z. Immunohistochemical and in situ hybridization studies on glycine transporter 1 after transient ischemia in the rat forebrain. Neurochem Int 2007; 52:799-808. [PMID: 17980459 DOI: 10.1016/j.neuint.2007.09.011] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2007] [Revised: 09/18/2007] [Accepted: 09/20/2007] [Indexed: 01/27/2023]
Abstract
Glycine is a critical factor in ischemia as reduced astrocytic and increased extracellular glycine levels aggravate the neurotoxic effect of glutamate and consequently, increase the extent of brain damage. Extracellular levels of glycine are primarily regulated by the plasma membrane glycine transporter 1. In the present study, we examined the effects of transient ischemia (1 h occlusion of the middle cerebral artery; followed by 0 h, 0.5 h, 1 h, 2 h, 4 h, 24 h or 48 h reperfusion) on immunoreactivity and mRNA expression of glycine transporter 1 in the rat forebrain. In control animals, glycine transporter 1-immunoreactivity was strong in diencephalic and certain telencephalic structures, moderate in the globus pallidus, and rather low in the cortex and striatum. In situ hybridization studies revealed a similar distribution pattern of glycine transporter 1 mRNA expression. One hour occlusion of the middle cerebral artery resulted in a significant decrease in ipsilateral glycine transporter 1-immunoreactivity and mRNA expression in a circumscribed region of the preoptic/hypothalamic area; both the immunoreactivity and mRNA exhibited further reductions with increasing reperfusion time. In contrast, the cerebral cortex and the globus pallidus showed an increase of glycine transporter 1-immunoreactivity after 0.5 h reperfusion; the elevation proved to be transient in the somatosensory cortex and remained sustained in the globus pallidus after longer reperfusion times. Western blot analysis of globus pallidus samples from the ipsilateral side confirmed higher glycine transporter 1 protein levels. These results suggest an elevated expression of the transporter protein facilitating the glial uptake of glycine from the extracellular space. However, glycine transporter 1 mRNA expression was not significantly different in the penumbra regions from the corresponding contralateral sites of the injury. Together, these findings indicate that post-translational mechanisms are of primary importance in elevating glycine transporter 1 protein levels following transient ischemia.
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Affiliation(s)
- Imre Kalló
- Laboratory of Endocrine Neurobiology, Institute of Experimental Medicine, Budapest, Hungary.
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Stockler S, Schutz PW, Salomons GS. Cerebral creatine deficiency syndromes: clinical aspects, treatment and pathophysiology. Subcell Biochem 2007; 46:149-166. [PMID: 18652076 DOI: 10.1007/978-1-4020-6486-9_8] [Citation(s) in RCA: 103] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Cerebral creatine deficiency syndromes (CCDSs) are a group of inborn errors of creatine metabolism comprising two autosomal recessive disorders that affect the biosynthesis of creatine--i.e. arginine:glycine amidinotransferase deficiency (AGAT; MIM 602360) and guanidinoacetate methyltransferase deficiency (GAMT; MIM 601240)--and an X-linked defect that affects the creatine transporter, SLC6A8 deficiency (SLC6A8; MIM 300036). The biochemical hallmarks of these disorders include cerebral creatine deficiency as detected in vivo by 1H magnetic resonance spectroscopy (MRS) of the brain, and specific disturbances in metabolites of creatine metabolism in body fluids. In urine and plasma, abnormal guanidinoacetic acid (GAA) levels are found in AGAT deficiency (reduced GAA) and in GAMT deficiency (increased GAA). In urine of males with SLC6A8 deficiency, an increased creatine/creatinine ratio is detected. The common clinical presentation in CCDS includes mental retardation, expressive speech and language delay, autistic like behaviour and epilepsy. Treatment of the creatine biosynthesis defects has yielded clinical improvement, while for creatine transporter deficiency, successful treatment strategies still need to be discovered. CCDSs may be responsible for a considerable fraction of children and adults affected with mental retardation of unknown etiology. Thus, screening for this group of disorders should be included in the differential diagnosis of this population. In this review, also the importance of CCDSs for the unravelling of the (patho)physiology of cerebral creatine metabolism is discussed.
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MESH Headings
- Adult
- Amidinotransferases/deficiency
- Animals
- Brain Diseases, Metabolic, Inborn/diagnosis
- Brain Diseases, Metabolic, Inborn/enzymology
- Brain Diseases, Metabolic, Inborn/pathology
- Brain Diseases, Metabolic, Inborn/physiopathology
- Brain Diseases, Metabolic, Inborn/therapy
- Cerebellar Diseases/diagnosis
- Cerebellar Diseases/enzymology
- Cerebellar Diseases/pathology
- Cerebellar Diseases/physiopathology
- Cerebellar Diseases/therapy
- Child
- Child, Preschool
- Creatine/deficiency
- Creatine/metabolism
- Creatinine/metabolism
- Diagnosis, Differential
- Female
- Genetic Diseases, X-Linked/diagnosis
- Genetic Diseases, X-Linked/enzymology
- Genetic Diseases, X-Linked/pathology
- Genetic Diseases, X-Linked/physiopathology
- Genetic Diseases, X-Linked/therapy
- Glycine/analogs & derivatives
- Glycine/metabolism
- Guanidinoacetate N-Methyltransferase/deficiency
- Humans
- Male
- Nerve Tissue Proteins/deficiency
- Plasma Membrane Neurotransmitter Transport Proteins/deficiency
- Syndrome
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Affiliation(s)
- Sylvia Stockler
- Department of Pediatrics, University of British Columbia, Division of Biochemical Diseases, British Columbia Children's Hospital, Vancouver, B.C., V6H 3V4, Canada
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Braissant O, Bachmann C, Henry H. Expression and function of AGAT, GAMT and CT1 in the mammalian brain. Subcell Biochem 2007; 46:67-81. [PMID: 18652072 DOI: 10.1007/978-1-4020-6486-9_4] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
In mammals, creatine is taken up from the diet and can be synthesized endogenously by a two-step mechanism involving the enzymes arginine:glycine amidinotransferase (AGAT) and guanidinoacetate methyltransferase (GAMT). Creatine (Cr) is taken up by cells through a specific transporter, CT1. While the major part of endogenous synthesis of Cr is thought to occur in kidney, pancreas and liver, the brain widely expresses AGAT, GAMT and CT1, both during development and in adulthood. The adult central nervous system (CNS) has a limited capacity to take up Cr from periphery, and seems to rely more on its endogenous Cr synthesis. In contrast, the embryonic CNS might be more dependent on Cr supply from periphery than on endogenous synthesis. This review will focus on the expression and function of AGAT, GAMT and CT1 in the mammalian CNS, both during development and in adulthood. Emphasis will also be placed on their specific roles in the different cell types of the brain, to analyze which brain cells are responsible for the CNS capacity of (i) endogenous Cr synthesis and (ii) Cr uptake from the periphery, and which brain cells are the main Cr consumers. The potential role of CT1 as guanidinoacetate transporter between "AGAT-only" and "GAMT-only" expressing cells will also be explored.
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Affiliation(s)
- Olivier Braissant
- Clinical Chemistry Laboratory, Centre Hospitalier Universitaire Vaudois, CH-1011 Lausanne, Switzerland
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Tachikawa M, Hosoya KI, Ohtsuki S, Terasaki T. A novel relationship between creatine transport at the blood-brain and blood-retinal barriers, creatine biosynthesis, and its use for brain and retinal energy homeostasis. Subcell Biochem 2007; 46:83-98. [PMID: 18652073 DOI: 10.1007/978-1-4020-6486-9_5] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Evidence is increasing that the creatine/phosphocreatine shuttle system plays an essential role in energy homeostasis in the brain and retina to ensure proper development and function. Thus, our understanding of the mechanism of creatine supply and creatine usage in the brain and retina and of creatine supplementation in patients with creatine deficiency syndromes is an important step towards improved therapeutic strategies for brain and retinal disorders. Our recent research provides novel molecular-anatomical evidence that (i) at the blood-brain barrier and the inner blood-retinal barrier, the creatine transporter (CRT/SLC6AS) functions as a major pathway for supplying creatine to the brain and retina, and that (ii) local creatine is preferentially synthesized in the glial cells, e.g., oligodendrocytes, astrocytes, and Müller cells, in the brain and retina. Thus, the blood-brain barrier and inner blood-retinal barrier play important roles not only in supplying energy sources (glucose and lactate), but also in supplying an energy 'buffer' (creatine). These findings lead to the novel insight that the creatine/phosphocreatine shuttle system is based on an intricate relationship between the blood-brain barrier, inner blood-retinal barrier, glia, and neurons (photoreceptor cells) to maintain and ensure energy homeostasis in the brain and retina.
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Affiliation(s)
- Masanori Tachikawa
- Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, Toyama 930-0194, Japan
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35
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Almeida LS, Rosenberg EH, Verhoeven NM, Jakobs C, Salomons GS. Are cerebral creatine deficiency syndromes on the radar screen? FUTURE NEUROLOGY 2006. [DOI: 10.2217/14796708.1.5.637] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Cerebral creatine deficiency syndromes (CCDS) are responsible for a considerable proportion of the population affected with mental retardation. CCDS are caused by either an inborn error of the proteins involved in creatine biosynthesis or in the creatine transporter. Besides mental retardation, the clinical characteristics of CCDS are speech and language delay, epilepsy and features of autism. CCDS can be diagnosed by proton magnetic resonance spectroscopy of the brain and/or by biochemical and molecular analysis. Treatment of the defects in creatine biosynthesis has yielded favorable outcomes, while treatments for creatine transporter deficiency are still under investigation at this time. The relatively large contribution of the CCDS to the monogenic causes of mental retardation emphasizes the importance of including CCDS in the differential diagnosis of mental retardation of unknown etiology. Pathophysiology is not yet unravelled, although it is known that creatine plays an important role in energy storage and transmission. Moreover, in vitro data indicate that creatine acts as a neuromodulator in the brain.
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Affiliation(s)
- Lígia S Almeida
- VU University Medical Center, Department of Clinical Chemistry, Metabolic Unit, De Boelelaan 1117, 1081 HV, Amsterdam, The Netherlands
| | - Efraim H Rosenberg
- VU University Medical Center, Department of Clinical Chemistry, Metabolic Unit, De Boelelaan 1117, 1081 HV Amsterdam, The Netherlands
| | - Nanda M Verhoeven
- VU University Medical Center, Department of Clinical Chemistry, Metabolic Unit, De Boelelaan 1117, 1081 HV Amsterdam, The Netherlands
| | - Cornelis Jakobs
- VU University Medical Center, Department of Clinical Chemistry, Metabolic Unit, De Boelelaan 1117, 1081 HV Amsterdam, The Netherlands
| | - Gajja S Salomons
- VU University Medical Center, Department of Clinical Chemistry, Metabolic Unit, De Boelelaan 1117, 1081 HV Amsterdam, The Netherlands
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36
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Galbraith RA, Furukawa M, Li M. Possible role of creatine concentrations in the brain in regulating appetite and weight. Brain Res 2006; 1101:85-91. [PMID: 16781683 DOI: 10.1016/j.brainres.2006.05.032] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2005] [Revised: 05/01/2006] [Accepted: 05/08/2006] [Indexed: 11/30/2022]
Abstract
Cobaltic protoporphyrin IX (CoPP) is a synthetic heme analog which can elicit profound and prolonged decreases in appetite and body weight in several different animal species. Intracerebroventricular administration of CoPP in rats was found, by differential display and confirmed by Real-Time PCR, to result in an increase in expression of the creatine transporter when compared to vehicle-treated fed or vehicle-treated fasted control animals. In situ hybridization studies showed that creatine transporter mRNA concentrations were increased in several areas of the brain involved in the regulation of food intake, but creatine concentrations were decreased in hypothalamic homogenates in CoPP-treated animals compared to controls. Intracerebroventricular administration of beta-guanidinopropionic acid, a compound known to decrease intracellular creatine concentration by competition for uptake, resulted in decreased food intake and body weight and increased Fos expression in the hypothalamus. Taken together, these findings suggest that creatine concentrations in the brain may play a role in regulating food intake and body weight.
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Affiliation(s)
- Richard A Galbraith
- Department of Medicine, University of Vermont, C209 Given Building, 89 Beaumont Avenue, Burlington, VT 05405, USA.
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37
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Bürklen TS, Schlattner U, Homayouni R, Gough K, Rak M, Szeghalmi A, Wallimann T. The creatine kinase/creatine connection to Alzheimer's disease: CK-inactivation, APP-CK complexes and focal creatine deposits. J Biomed Biotechnol 2006; 2006:35936. [PMID: 17047305 PMCID: PMC1510941 DOI: 10.1155/jbb/2006/35936] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2005] [Revised: 02/28/2006] [Accepted: 02/28/2006] [Indexed: 12/12/2022] Open
Abstract
Cytosolic brain-type creatine kinase (BB-CK), which is coexpressed with ubiquitous mitochondrial uMtCK, is significantly inactivated by oxidation, in Alzheimer's disease (AD) patients. Since CK has been shown to play a fundamental role in cellular energetics of the brain, any disturbance of this enzyme may exasperate the AD disease process. Mutations in amyloid precursor protein (APP) are associated with early onset AD and result in abnormal processing of APP, and accumulation of A beta peptide, the main constituent of amyloid plaques in AD brain. Recent data on a direct interaction between APP and the precursor of uMtCK support an emerging relationship between AD, cellular energy levels and mitochondrial function. In addition, recently discovered creatine (Cr) deposits in the brain of transgenic AD mice, as well as in the hippocampus from AD patients, indicate a direct link between perturbed energy state, Cr metabolism and AD. Here, we review the roles of Cr and Cr-related enzymes and consider the potential value of supplementation with Cr, a potent neuroprotective substance. As a hypothesis, we consider whether Cr, if given at an early time point of the disease, may prevent or delay the course of AD-related neurodegeneration.
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Affiliation(s)
- Tanja S. Bürklen
- Institute of Cell Biology, ETH Zurich,
Hönggerberg HPM, 8093 Zurich, Switzerland
| | - Uwe Schlattner
- Institute of Cell Biology, ETH Zurich,
Hönggerberg HPM, 8093 Zurich, Switzerland
- Laboratory of Fundamental and Applied Bioenergetics,
INSERM E0221, Joseph Fourier University, 38041 Grenoble, Cedex 9, France
| | - Ramin Homayouni
- Department of Neurology, University of Tennessee
Health Science Center, Memphis, TN 38163, USA
| | - Kathleen Gough
- Department of Chemistry, University of Manitoba,
Winnipeg, Manitoba, Canada R3T 2N2
| | - Margaret Rak
- Department of Chemistry, University of Manitoba,
Winnipeg, Manitoba, Canada R3T 2N2
| | - Adriana Szeghalmi
- Department of Chemistry, University of Manitoba,
Winnipeg, Manitoba, Canada R3T 2N2
| | - Theo Wallimann
- Institute of Cell Biology, ETH Zurich,
Hönggerberg HPM, 8093 Zurich, Switzerland
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38
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Gallant M, Rak M, Szeghalmi A, Del Bigio MR, Westaway D, Yang J, Julian R, Gough KM. Focally elevated creatine detected in amyloid precursor protein (APP) transgenic mice and Alzheimer disease brain tissue. J Biol Chem 2005; 281:5-8. [PMID: 16267054 DOI: 10.1074/jbc.c500244200] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The creatine/phosphocreatine system, regulated by creatine kinase, plays an important role in maintaining energy balance in the brain. Energy metabolism and the function of creatine kinase are known to be affected in Alzheimer diseased brain and in cells exposed to the beta-amyloid peptide. We used infrared microspectroscopy to examine hippocampal, cortical, and caudal tissue from 21-89-week-old transgenic mice expressing doubly mutant (K670N/M671L and V717F) amyloid precursor protein and displaying robust pathology from an early age. Microcrystalline deposits of creatine, suggestive of perturbed energetic status, were detected by infrared microspectroscopy in all animals with advanced plaque pathology. Relatively large creatine deposits were also found in hippocampal sections from post-mortem Alzheimer diseased human brain, compared with hippocampus from non-demented brain. We therefore speculate that this molecule is a marker of the disease process.
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Affiliation(s)
- Meghan Gallant
- Department of Chemistry, University of Manitoba, Winnipeg, Manitoba R3T 2N2, Canada
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Navarro E, Alonso SJ, Martín FA, Castellano MA. Toxicological and Pharmacological Effects of D-Arginine. Basic Clin Pharmacol Toxicol 2005; 97:149-54. [PMID: 16128908 DOI: 10.1111/j.1742-7843.2005.pto_973110.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
D-Arginine is extensively used in studies on L-arginine/nitric oxide pathway as an inactive form of L-arginine, even in man. In addition, it has previously been reported that this D-amino acid appears to have pharmacological activity. The present work aimed at evaluating the toxicity and pharmacology of D-arginine administered by the intraperitoneally route in albino male mice. Toxicity of D-arginine, alone as well as in the presence of propranolol and betamethasone was evaluated. D-Arginine in mice showed a light toxicity order (DL50: 2800 mg/kg). Previous injection of the beta-adrenoceptor blocker, propranolol (2 mg/kg, intraperitoneally), or betamethasone (0.5 mg/kg, intraperitoneally) produced a decrease in the toxicity of D-arginine (LD50: 3600 mg/kg, 3300 mg/kg, respectively). Also, a neuropharmacological screening of D-arginine using behavioural, neurological, autonomic, barbiturate-induced sleep time and pentylenetetrazole-induced convulsions tests were performed. D-Arginine 700 mg/kg displayed central stimulant properties, whereas a depressant profile was observed at a dose of 1400 mg/kg. In addition, D-arginine 1400 mg/kg produced a potentiation of pentobarbital sleeping time and a marked anticonvulsivant action against pentylenetetrazole.
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Affiliation(s)
- Eduardo Navarro
- Department of Pharmacology, Faculty of Medicine, University of La Laguna, Tenerife, Spain.
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40
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Choi IY, Gruetter R. Dynamic or inert metabolism? Turnover of N-acetyl aspartate and glutathione from D-[1-13C]glucose in the rat brain in vivo. J Neurochem 2005; 91:778-87. [PMID: 15525331 PMCID: PMC1513183 DOI: 10.1111/j.1471-4159.2004.02716.x] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The rate of (13)C-label incorporation into both aspartyl (NAA C3) and acetyl (NAA C6) groups of N-acetyl aspartate (NAA) was simultaneously measured in the rat brain in vivo for up to 19 h of [1-(13)C]glucose infusion (n = 8). Label incorporation was detected in NAA C6 approximately 1.5 h earlier than in NAA C3 because of the delayed labeling of the precursor of NAA C3, aspartate, compared to that of NAA C6, glucose. The time courses of NAA were fitted using a mathematical model assuming synthesis of NAA in one kinetic compartment with the respective precursor pools of aspartate and acetyl coenzyme A (acetyl-CoA). The turnover rates of NAA C6 and C3 were 0.7 +/- 0.1 and 0.6 +/- 0.1 micromol/(g h) with the time constants 14 +/- 2 and 13 +/- 2 h, respectively, with an estimated pool size of 8 micromol/g. The results suggest that complete label turnover of NAA from glucose occurs in approximately 70 h. Several hours after starting the glucose infusion, label incorporation into glutathione (GSH) was also detected. The turnover rate of GSH was 0.06 +/- 0.02 micromol/(g h) with a time constant of 13 +/- 2 h. The estimated pool size of GSH was 0.8 micromol/g, comparable to the cortical glutathione concentration. We conclude that NAA and GSH are completely turned over and that the metabolism is extremely slow (< 0.05% of the glucose metabolic rate).
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Affiliation(s)
- In-Young Choi
- The Nathan Kline Institute, Medical Physics, Orangeburg, New York 10962, USA.
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41
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Nakashima T, Tomi M, Tachikawa M, Watanabe M, Terasaki T, Hosoya KI. Evidence for creatine biosynthesis in Müller glia. Glia 2005; 52:47-52. [PMID: 15892122 DOI: 10.1002/glia.20222] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
In high-energy metabolic tissues like the retina, creatine may play an important role in energy storage and in transmission of phosphate-bound energy substrates. To prove this, we investigated creatine synthesis in Müller glia. We also characterized the localization of the creatine synthetic enzyme, S-adenosyl-L-methionine:N-guanidinoacetate methyltransferase (GAMT) in the retina. Reverse transcription-polymerase chain reaction analysis revealed that L-arginine:glycine amidinotransferase and GAMT mRNAs were expressed in the retina and the Müller cell line, TR-MUL5. [(14)C]Creatine was detected after incubation of isolated rat retina or TR-MUL5 cells with [(14)C]glycine, L-arginine and L-methionine, suggesting creatine synthesis in Müller glia. Western blot analysis also revealed expression of GAMT protein in the rat retina and TR-MUL5 cells. Furthermore, confocal immunofluorescent microscopy of dual-labeled rat retinal sections demonstrated co-localization of GAMT with glutamine synthetase. Taken together, the results of the present study indicate creatine synthesis in Müller glia, implying an important role of creatine in energy metabolism in the retina.
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Affiliation(s)
- Toshihisa Nakashima
- Faculty of Pharmaceutical Sciences, Toyama Medical and Pharmaceutical University, Toyama, Japan
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42
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Brennan L, Hewage C, Malthouse JPG, McBean GJ. Gliotoxins disrupt alanine metabolism and glutathione production in C6 glioma cells: a 13C NMR spectroscopic study. Neurochem Int 2004; 45:1155-65. [PMID: 15380625 DOI: 10.1016/j.neuint.2004.06.012] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2004] [Accepted: 06/23/2004] [Indexed: 11/20/2022]
Abstract
Gliotoxins are a group of amino acids that are toxic to astrocytes, and are substrates of high-affinity sodium-dependent glutamate transporters. In the present study, C6 glioma cells were preincubated for 20 h in the presence of 400 microM L-alpha-aminoadipate, L-serine-O-sulphate, D-aspartate or L-cysteate, as well as in the presence of the poorly transported L-glutamate uptake inhibitor, L-anti-endo-methanopyrrolidine dicarboxylate. In experiments following [3-13C]alanine metabolism, all toxins caused a decreased incorporation of label into glutamate. Production of labelled lactate changed only when cells were incubated in the presence of L-alpha-aminoadipate or L-serine-O-sulphate. Incubation with L-anti-endo-methanopyrrolidine dicarboxylate caused no change in the amount of label incorporated into either glutamate or lactate. When glutathione production was followed using 1 mM [2-13C]glycine, differential effects of the gliotoxins were revealed. Most notably, both L-serine-O-sulphate and L-alpha-aminoadipate caused significant increases in labelling of glutathione. Once again, L-anti-endo-methanopyrrolidine dicarboxylate was without effect. Overall, we have shown that the gliotoxins cause disruption to alanine metabolism and glutathione production in C6 glioma cells, but that there are notable differences in their mechanisms of action. In the absence of any disruption to metabolism by L-anti-endo-methanopyrrolidine dicarboxylate, it is concluded that their mode of action involves more than inhibition of glutamate transport.
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Affiliation(s)
- Lorraine Brennan
- Department of Biochemistry, Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Belfield, Dublin 4, Ireland
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43
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de Souza KB, Feoli AM, Krüger AH, de Souza MR, Perry CT, Rotta LN, Souza DO, Perry MLS. Effects of Undernutrition on Glycine Metabolism in the Cerebellum of Rats. ANNALS OF NUTRITION AND METABOLISM 2004; 48:246-50. [PMID: 15331883 DOI: 10.1159/000080458] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/20/2003] [Accepted: 03/30/2004] [Indexed: 11/19/2022]
Abstract
Undernutrition is a worldwide problem affecting millions of unborn and young children during the most vulnerable stages of brain development. Total restriction of protein during the perinatal period of life can alter the development of the mammalian fetus and have marked repercussions on development of the central nervous system (CNS). The brain is vulnerable to undernutrition with altered morphologic and biochemical maturation, leading to impaired functions. The focus of this study is to investigate [U-14C]glycine metabolism in undernourished rats submitted to pre- and postnatal protein deprivation (diet: 8% protein with and without addition of L-methionine; control group: 25% protein). Although undernutrition produced a reduction in cerebellar weight and alterations in the DNA concentration, the present study shows that glycine metabolism in this structure is partially protected because the undernourished group with L-methionine did not show modifications in glycine metabolism at all ages studied. However, L-methionine deficiency alters glycine metabolism at 7 and 21 days, but in the adult age both undernourished groups presented no differences in oxidation to CO2, conversion to lipids and incorporation into protein from glycine, compared to the control group.
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Affiliation(s)
- Karine B de Souza
- Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde--UFRGS, Porto Alegre, Brazil
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44
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Tachikawa M, Fukaya M, Terasaki T, Ohtsuki S, Watanabe M. Distinct cellular expressions of creatine synthetic enzyme GAMT and creatine kinases uCK-Mi and CK-B suggest a novel neuron-glial relationship for brain energy homeostasis. Eur J Neurosci 2004; 20:144-60. [PMID: 15245487 DOI: 10.1111/j.1460-9568.2004.03478.x] [Citation(s) in RCA: 136] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The creatine/phosphocreatine shuttle system, as catalysed reversibly by creatine kinases, is thought to be essential for the storing and buffering of high phosphate-bound energy in tissues with high energy demand. In the present study, we aimed to clarify the cellular system of creatine biosynthesis and its energy metabolism in the mouse brain by immunohistochemistry for creatine biosynthetic enzyme S-adenosylmethionine:guanidinoacetate N-methyltransferase (GAMT), ubiquitous mitochondrial creatine kinase (uCK-Mi) and brain-type cytoplasmic creatine kinase (CK-B). GAMT was expressed highly in oligodendrocytes and olfactory ensheathing glia and moderately in astrocytes, whereas GAMT was very low in neurons and microglia. By contrast, uCK-Mi was expressed selectively in neurons and localized in their mitochondria in dendrites, cell bodies, axons and terminals. The distinct and almost complementary distribution of GAMT and uCK-Mi suggests that the creatine in neuronal mitochondria is derived not only from the circulation, but also from local glial cells associated with these neuronal elements. By contrast, CK-B was selective to astrocytes among glial populations, and was exclusive to inhibitory neurons among neuronal populations. Interestingly, these cells with high CK-B immunoreactivity are known to be highly resistant to acute energy loss, such as hypoxia and hypoglycemia. Considering that phosphocreatine generates ATP much faster than the processes of glycolysis and oxidative phosphorylation, the highly regulated cellular expressions of creatine biosynthetic and metabolic enzymes suggest that the creatine/phosphocreatine shuttle system plays a role in brain energy homeostasis through a novel neuron-glial relationship.
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Affiliation(s)
- Masanori Tachikawa
- Department of Molecular Biopharmacy and Genetics, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai 980-8578, Japan
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Rae C, Digney AL, McEwan SR, Bates TC. Oral creatine monohydrate supplementation improves brain performance: a double-blind, placebo-controlled, cross-over trial. Proc Biol Sci 2003; 270:2147-50. [PMID: 14561278 PMCID: PMC1691485 DOI: 10.1098/rspb.2003.2492] [Citation(s) in RCA: 132] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Creatine supplementation is in widespread use to enhance sports-fitness performance, and has been trialled successfully in the treatment of neurological, neuromuscular and atherosclerotic disease. Creatine plays a pivotal role in brain energy homeostasis, being a temporal and spatial buffer for cytosolic and mitochondrial pools of the cellular energy currency, adenosine triphosphate and its regulator, adenosine diphosphate. In this work, we tested the hypothesis that oral creatine supplementation (5 g d(-1) for six weeks) would enhance intelligence test scores and working memory performance in 45 young adult, vegetarian subjects in a double-blind, placebo-controlled, cross-over design. Creatine supplementation had a significant positive effect (p < 0.0001) on both working memory (backward digit span) and intelligence (Raven's Advanced Progressive Matrices), both tasks that require speed of processing. These findings underline a dynamic and significant role of brain energy capacity in influencing brain performance.
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Affiliation(s)
- Caroline Rae
- Discipline of Biochemistry, School of Molecular and Microbial Biosciences G08, The University of Sydney, Sydney, NSW 2006, Australia.
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Espinosa-Jeffrey A, Becker-Catania SG, Zhao PM, Cole R, Edmond J, de Vellis J. Selective specification of CNS stem cells into oligodendroglial or neuronal cell lineage: cell culture and transplant studies. J Neurosci Res 2002; 69:810-25. [PMID: 12205675 DOI: 10.1002/jnr.10344] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Neural stem cells (NSCs) were isolated from embryonic day 16 Sprague-Dawley rats and cultured in a novel serum-free stem cell medium that selected for the growth of NSCs and against the growth of GFAP(+) cells (astrocytes). NSCs maintained in culture for extended periods of time retained immunoreactivity for both nestin and PSA-NCAM, two markers characteristic of the stem cell phenotype. Moreover, using an oligodendrocyte (OL) specification medium, NSCs differentiated into OL as evidenced by their morphology and expression of multiple oligodendrocyte/myelin-specific markers. In addition, NSCs are capable of acquiring a neuronal phenotype as evidenced by expressing neuronal markers, such as neurofilament (NF) and NeuN when cultured in a defined medium for neurons indicating that these cells are also a good source of neuroblasts, which could be used to replace neuronal populations in the brain. We also showed successful propagation and differentiation of NSCs into OL after cryostorage, allowing for the later use of stored NSCs. The long-term goal of culturing NSCs and committed oligodendrocyte progenitors (OLP) is to obtain homogeneous populations for transplantation with the goal of remyelinating the myelin-deficient CNS. Our preliminary experiments carried out on normal and myelin deficient rats demonstrate that these cells survive and migrate extensively in both types of hosts. NSCs grafted as such, as well as cells derived from NSCs exposed to selective specification before grafting, are able to differentiate within the host brain. As expected, NSCs are capable of giving rise to astrocytes in a medium favoring this phenotype.
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Affiliation(s)
- Araceli Espinosa-Jeffrey
- UCLA Mental Retardation Research Center and Department of Neurobiology, Los Angeles, California 90095-1759, USA.
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Viola A, Chabrol B, Nicoli F, Confort-Gouny S, Viout P, Cozzone PJ. Magnetic resonance spectroscopy study of glycine pathways in nonketotic hyperglycinemia. Pediatr Res 2002; 52:292-300. [PMID: 12149509 DOI: 10.1203/00006450-200208000-00024] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Nonketotic hyperglycinemia is a life-threatening disorder in neonates characterized by a deficiency of the glycine cleavage system. We report on four cases of the neonatal form of the disease, which were investigated by in vitro(1)H magnetic resonance spectroscopy of blood and cerebrospinal fluid, and in vivo(1)H magnetic resonance spectroscopy of brain. The existence of glycine disposal pathways leading to an increase in lactate in fluids and creatine in fluids and brain was demonstrated. This is the first observation of elevated creatine in brain in nonketotic hyperglycinemia. A recurrent decrease of glutamine and citrate was observed in cerebrospinal fluid, which might be related to abnormal glutamine metabolism in brain. Finally, the cerebral N-acetylaspartate to myo-inositol-glycine ratio was identified as a prognostic indicator of the disease.
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Affiliation(s)
- Angèle Viola
- Center for Magnetic Resonance in Biology and Medicine CRMBM-UMR-CNRS 6612, Faculty of Medicine, Marseille, France
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Gamcsik MP, Dubay GR, Cox BR. Increased rate of glutathione synthesis from cystine in drug-resistant MCF-7 cells. Biochem Pharmacol 2002; 63:843-51. [PMID: 11911835 DOI: 10.1016/s0006-2952(01)00931-5] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The rate of glutathione synthesis was determined in drug-sensitive and -resistant MCF-7 cells by monitoring the rate of label uptake from [3,3'-13C(2)]-cystine using NMR spectroscopy and mass spectrometry. Compared with the wild-type human mammary adenocarcinoma cell line (MCF-7wt), the isotope incorporation rate was increased 1.6-, 2.4-, and 5.3-fold in the etoposide-resistant MCF-7 cell line (MCF-7vp), doxorubicin-resistant MCF-7 cell line (MCF-7adr), and 4-hydroperoxycyclophosphamide-resistant MCF-7 cell line (MCF-7hc), respectively. The increase in glutathione metabolism in the MCF-7hc line correlated with steady-state levels as determined by biochemical assay. In contrast, both the MCF-7vp and MCF-7adr lines showed increased metabolic synthesis of glutathione but displayed lower steady-state levels compared with the MCF-7wt line. The increased synthetic rates of all resistant lines reflected, in part, contributions from the increased activities of both gamma-glutamyltranspeptidase and gamma-glutamylcysteine synthetase. These results emphasize the importance of monitoring glutathione metabolic rates, rather than steady-state levels of enzymes or substrates, for assessing drug resistance.
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Affiliation(s)
- Michael P Gamcsik
- Department of Medicine, Duke Comprehensive Cancer Center, Duke University Medical Center, P.O. Box 3843, MSRB 301, Research Drive, Durham, NC 27710, USA.
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Castellano MA, Rojas-Díaz D, Martín F, Quintero M, Alonso J, Navarro E, González-Mora JL. Opposite effects of low and high doses of arginine on glutamate-induced nitric oxide formation in rat substantia nigra. Neurosci Lett 2001; 314:127-30. [PMID: 11704300 DOI: 10.1016/s0304-3940(01)02295-9] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
L-arginine is a very versatile amino acid that is involved in many important physiological processes such as protein, nitric oxide (NO), agmatine, putrescine, urea, L-ornithine or creatine synthesis and is essential for posttranslational arginylation of protein. The present study was designed to evaluate in vivo the effect of L-arginine on NO production in substantia nigra. In vivo spectroscopic and voltammetric studies were addressed in rats to record modifications in methemoglobin and NO levels under glutamate stimulation. Results showed that, under physiological L-arginine extracellular concentration, the intranigral infusion of glutamate produced an increase in NO levels. When a low dose of L-arginine was co-infused with glutamate, a persistent and higher increase in NO levels was observed. The co-infusion of glutamate with a moderate dose of L-arginine induced drastic and persistent NO production. It was also observed that high doses of either L-arginine or D-arginine inhibit NO production. Subsequently, these data show that L-arginine and D-arginine are involved in a mechanism that inhibits NO production.
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Affiliation(s)
- M A Castellano
- Area de Psicobiología, Facultad de Psicología, Campus de Guajara, Universidad de La Laguna, Tenerife-38205, Canary Islands, Spain.
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Abstract
The biochemistry and physiology of L-arginine have to be reconsidered in the light of the recent discovery that the amino acid is the only substrate of all isoforms of nitric oxide synthase (NOS). Generation of nitric oxide, NO, a versatile molecule in signaling processes and unspecific immune defense, is intertwined with synthesis, catabolism and transport of arginine which thus ultimately participates in the regulation of a fine-tuned balance between normal and pathophysiological consequences of NO production. The complex composition of the brain at the cellular level is reflected in a complex differential distribution of the enzymes of arginine metabolism. Argininosuccinate synthetase (ASS) and argininosuccinate lyase which together can recycle the NOS coproduct L-citrulline to L-arginine are expressed constitutively in neurons, but hardly colocalize with each other or with NOS in the same neuron. Therefore, trafficking of citrulline and arginine between neurons necessitates transport capacities in these cells which are fulfilled by well-described carriers for cationic and neutral amino acids. The mechanism of intercellular exchange of argininosuccinate, a prerequisite also for its proposed function as a neuromodulator, remains to be elucidated. In cultured astrocytes transcription and protein expression of arginine transport system y(+) and of ASS are upregulated concomittantly with immunostimulant-mediated induction of NOS-2. In vivo ASS-immunoreactivity was found in microglial cells in a rat model of brain inflammation and in neurons and glial cells in the brains of Alzheimer patients. Any attempt to estimate the contributions of arginine transport and synthesis to substrate supply for NOS has to consider competition for arginine between NOS and arginase, the latter enzyme being expressed as mitochondrial isoform II in nervous tissue. Generation of NOS inhibitors agmatine and methylarginines is documented for the nervous system. Suboptimal supply of NOS with arginine leads to production of detrimental peroxynitrite which may result in neuronal cell death. Data have been gathered recently which point to a particular role of astrocytes in neural arginine metabolism. Arginine appears to be accumulated in astroglial cells and can be released after stimulation with a variety of signals. It is proposed that an intercellular citrulline-NO cycle is operating in brain with astrocytes storing arginine for the benefit of neighbouring cells in need of the amino acid for a proper synthesis of NO.
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Affiliation(s)
- H Wiesinger
- Physiologisch-Chemisches Institut der Universität, Hoppe-Seyler-Strasse 4, D-72076, Tübingen, Germany.
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