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Regazzoni L. State of the Art in the Development of Human Serum Carnosinase Inhibitors. Molecules 2024; 29:2488. [PMID: 38893364 PMCID: PMC11173852 DOI: 10.3390/molecules29112488] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2024] [Revised: 05/22/2024] [Accepted: 05/24/2024] [Indexed: 06/21/2024] Open
Abstract
Human serum carnosinase is an enzyme that operates the preferential hydrolysis of dipeptides with a C-terminus histidine. Only higher primates excrete such an enzyme in serum and cerebrospinal fluid. In humans, the serum hydrolytic rate has high interindividual variability owing to gene polymorphism, although age, gender, diet, and also diseases and surgical interventions can modify serum activity. Human genetic diseases with altered carnosinase activity have been identified and associated with neurological disorders and age-related cognitive decline. On the contrary, low peripheral carnosinase activity has been associated with kidney protection, especially in diabetic nephropathy. Therefore, serum carnosinase is a druggable target for the development of selective inhibitors. However, only one molecule (i.e., carnostatine) has been discovered with the purpose of developing serum carnosinase inhibitors. Bestatin is the only inhibitor reported other than carnostatine, although its activity is not selective towards serum carnosinase. Herein, we present a review of the most critical findings on human serum carnosinase, including enzyme expression, localization and substrate selectivity, along with factors affecting the hydrolytic activity, its implication in human diseases and the properties of known inhibitors of the enzyme.
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Affiliation(s)
- Luca Regazzoni
- Department of Pharmaceutical Sciences, University of Milan, Via Mangiagalli 25, 20133 Milan, Italy
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2
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Abstract
Metabolomic profiling is an emerging technology in the clinical setting with immediate diagnostic potential for the population of patients with Inborn Errors of Metabolism. We present the metabolomics profile of two ABAT deficiency patients both pre- and posttreatment with flumazenil. ABAT deficiency, also known as GABA-transaminase deficiency, is caused by recessive mutations in the gene ABAT and leads to encephalopathy of variable severity with hypersomnolence, hypotonia, hypomyelination, and seizures. Through metabolomics screening of multiple patient tissues, we identify 2-pyrrolidinone as a biomarker for GABA that is informative in plasma, urine, and CSF. These data will enable noninvasive diagnostic testing for the population of patients with disorders of GABA metabolism.
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Casado M, Molero M, Sierra C, García-Cazorla A, Ormazabal A, Artuch R. Analysis of cerebrospinal fluid γ-aminobutyric acid by capillary electrophoresis with laser-induced fluorescence detection. Electrophoresis 2014; 35:1181-7. [PMID: 24338894 DOI: 10.1002/elps.201300261] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2013] [Revised: 12/03/2013] [Accepted: 12/09/2013] [Indexed: 01/04/2023]
Abstract
The measurement of γ-aminobutyric acid (GABA) is suitable for investigating various neurological disorders. In this study, a sensitive and selective method for free GABA quantification in cerebrospinal fluid (CSF) has been standardised. This method is based on CE with LIF detection using 4-fluoro-7-nitrobenzo-2-oxa-1,3-diazole (NBD-F) as a derivatisating agent. The reaction conditions (NBD-F concentration, pH, temperature and reaction time) and the electrophoretic parameters (run buffer composition and pH and separation voltage) were optimised to obtain the maximum derivatisation efficiency and electrophoretic resolution. The best resolution was obtained using 200 mM sodium borate, 10 mM SDS, 8.5 mM β-CD, pH 10 and 20 kV voltage. The method was linear in the concentration range of 2.5-1000 nM with good inter- and intra-assay precision values. The effects of CSF handling on free GABA concentrations were also evaluated. Our results show that the time delay between CSF collection and freezing strongly increases the CSF GABA values. Age-related reference values were established in 55 paediatric controls. The influence of antiepileptic therapy on free CSF GABA was studied in 38 neuropaediatric patients. Significantly, higher GABA values were obtained in patients taking valproic acid or vigabatrin therapy, which are antiepileptic drugs that modulate GABA metabolism.
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Affiliation(s)
- Mercedes Casado
- Department of Clinical Biochemistry and Neuropaediatrics, Hospital Sant Joan de Déu-CIBERER-ISCIII, Barcelona, Spain; Department of Biochemistry and Molecular Biology, UAB, Barcelona, Spain
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4
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Abstract
Cortical excitability reflects a balance between excitation and inhibition. Glutamate is the main excitatory and GABA the main inhibitory neurotransmitter in the mammalian cortex. Changes in glutamate and GABA metabolism may play important roles in the control of cortical excitability. Glutamate is the metabolic precursor of GABA, which can be recycled through the tricarboxylic acid cycle to synthesize glutamate. GABA synthesis is unique among neurotransmitters, having two separate isoforms of the rate-controlling enzyme, glutamic acid decarboxylase. The need for two separate genes on two chromosomes to control GABA synthesis is unexplained. Two metabolites of GABA are present in uniquely high concentrations in the human brain. Homocarnosine and pyrrolidinone have a major impact on GABA metabolism in the human brain. Both of these GABA metabolites have anticonvulsant properties and can have a major impact on cortical excitability.
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Affiliation(s)
- Ognen A C Petroff
- Department of Neurology, Yale University, New Haven, Connecticut 06520-8018, USA
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5
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Abstract
Diagnostic testing for genetically determined metabolic disease has for many years relied heavily on the use of generalized screening tests that analyze groups of related compounds in easily accessible peripheral fluids such as plasma and urine. Organic acid profiles in urine and amino acid analysis in plasma are two of the most commonly requested tests; these, together with other protocols that examine peripheral fluids, have been and continue to be invaluable tools. There is, however, an emerging realization that many metabolic encephalopathies do not arise secondary to peripheral metabolic changes but rather have their origins within the central nervous system. In these cases, testing of peripheral fluids might be uninformative. This review is designed to examine the role of cerebrospinal fluid analyses in the investigation of infants and children with undefined encephalopathies. The aims are to review the conditions in which measurement of metabolites in cerebrospinal fluid is critical if a diagnosis is to be made, and to emphasize that considerable forethought is often required to ensure correct collection and handling of cerebrospinal fluid. Thus, fidelity of the diagnostic analytic procedures is maintained. This review will help the pediatric neurologist establish practical diagnostic guidelines that in turn will help in the recognition of recently described conditions. Those conditions can, in general, be identified only after specialized cerebrospinal fluid testing.
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Affiliation(s)
- K Hyland
- Department of Neurochemistry, Institute of Metabolic Disease, Baylor University Medical Center, Dallas, TX 75226, USA.
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Petroff OA, Hyder F, Collins T, Mattson RH, Rothman DL. Acute effects of vigabatrin on brain GABA and homocarnosine in patients with complex partial seizures. Epilepsia 1999; 40:958-64. [PMID: 10403220 DOI: 10.1111/j.1528-1157.1999.tb00803.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
PURPOSE The acute, subacute, and chronic effects of vigabatrin (VGB) were studied in patients with refractory complex partial seizures. VGB increases human brain gamma-aminobutyric acid (GABA) and the related metabolites, homocarnosine and 2-pyrrolidinone. METHODS In vivo measurements of GABA and homocarnosine were made of a 14-cc volume in the occipital cortex by using 1H spectroscopy with a 2.1-Tesla magnetic resonance spectrometer and an 8-cm surface coil. Six patients (three women) were studied serially during the initiation and maintenance of VGB as adjunct therapy. RESULTS The first, 3 g dose of VGB increased brain GABA by 2.0 micromol/g within 81 min of oral administration. After 2 h, median edited GABA remained essentially the same for 2 days. The response to the second, 3-g dose of VGB given at 48 h was considerably less than that to the first dose, with a median increase of 0.5 micromol/g within 72 min. After 2-3 months, rechallenging patients taking 1.5-g VGB twice daily with 6 g increased GABA by 0.4 micromol/g within 87 min. Homocarnosine increased more gradually than GABA to above-normal levels after a week of VGB therapy. CONCLUSIONS VGB promptly elevates brain GABA and presumably offers partial protection against further seizures within hours of the first oral dose. Once-a-day dosing is sufficient to increase GABA. Patients may be expected to experience the effects of increased homocarnosine within 1 week.
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Affiliation(s)
- O A Petroff
- Department of Neurology, Yale University, New Haven, Connecticut 06520-8018, USA
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7
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Podell M, Hadjiconstantinou M. Low Concentrations of Cerebrospinal Fluid GABA Correlate to a Reduced Response to Phenobarbital Therapy in Primary Canine Epilepsy. J Vet Intern Med 1999. [DOI: 10.1111/j.1939-1676.1999.tb01135.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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Petroff OA, Mattson RH, Behar KL, Hyder F, Rothman DL. Vigabatrin increases human brain homocarnosine and improves seizure control. Ann Neurol 1998; 44:948-52. [PMID: 9851440 DOI: 10.1002/ana.410440614] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Homocarnosine, a dipeptide of gamma-aminobutyric acid (GABA) and histidine, is thought to be an inhibitory neuromodulator synthesized in subclasses of GABAergic neurons. Homocarnosine is present in human brain in greater amounts (0.4-1.0 micromol/g) than in other animals. The antiepileptic drug vigabatrin increases human cerebrospinal fluid homocarnosine linearly with daily dose. By using 1H nuclear magnetic resonance spectroscopy, serial occipital lobe GABA and homocarnosine concentrations were measured in 11 patients started on vigabatrin. Daily low-dose (2 g) vigabatrin increased both homocarnosine and GABA. Larger doses of vigabatrin (4 g) further increased homocarnosine but changed GABA levels minimally. Seizure control improved with increasing homocarnosine and GABA concentrations. Patients whose seizure control improved with the addition of vigabatrin had higher mean homocarnosine, but the same mean GABA concentrations, than those whose seizure control did not improve. Increased homocarnosine may contribute to improved seizure control.
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Affiliation(s)
- O A Petroff
- Department of Neurology, Yale University, New Haven, CT 06520-8018, USA
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9
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Bergquist J, Vona MJ, Stiller CO, O'Connor WT, Falkenberg T, Ekman R. Capillary electrophoresis with laser-induced fluorescence detection: a sensitive method for monitoring extracellular concentrations of amino acids in the periaqueductal grey matter. J Neurosci Methods 1996; 65:33-42. [PMID: 8815306 DOI: 10.1016/0165-0270(95)00141-7] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The use of capillary electrophoresis with laser-induced fluorescence detection (CE-LIF) for the analysis of microdialysate samples from the periaqueductal grey matter (PAG) of freely moving rats is described. By employing 3-(4-carboxybenzoyl)-2-quinoline-carboxaldehyde (CBQCA) as a derivatization agent, we simultaneously monitored the concentrations of 8 amino acids (arginine, glutamine, valine, gamma-amino-n-butyric acid (GABA), alanine, glycine, glutamate, and aspartate), with nanomolar and subnanomolar detection limits. Two of the amino acids (GABA and glutamate) were analysed in parallel by conventional high-performance liquid chromatography (HPLC) in order to directly compare the two analytical methods. Other CE methods for analysis of microdialysate have been previously described, and this improved method offers greater sensitivity, ease of use, and the possibility to monitor several amino acids simultaneously. By using this technique together with an optimised form of microdialysis technique, the tiny sample consumption and the improved detection limits permit the detection of fast and transient transmitter changes.
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Affiliation(s)
- J Bergquist
- Department of Psychiatry and Neurochemistry, Göteborg University, Mölndal Hospital, Sweden.
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10
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Jackson MC, Scollard DM, Mack RJ, Lenney JF. Localization of a novel pathway for the liberation of GABA in the human CNS. Brain Res Bull 1994; 33:379-85. [PMID: 8124577 DOI: 10.1016/0361-9230(94)90280-1] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Serum carnosinase is a dipeptidase, which is synthesized in human brain, where it hydrolyzes homocarnosine to release free GABA. Immunohistochemical procedures were used to demonstrate the presence of this enzyme in several layers of the retina and in certain neuronal tracts of the cerebral cortex, cerebellar cortex, olfactory bulb, hippocampus, and in disseminated tracts presumably from the internal capsule, interspersed among the basal ganglia. The enzyme was also present in the epithelial cells of the choroid plexus and in corpora amylacea, which were seen in many regions of the CNS. Homocarnosine was localized either in the same tracts or in nearby neurons. For example, the Purkinje cells of the cerebellar cortex contained homocarnosine, whereas serum carnosinase was localized in adjacent neuronal projections apparently originating from outside the cerebellar cortex and having probable synaptic contact with the Purkinje cells. These findings suggest that in addition to glutamate decarboxylation, a second metabolic reaction for the formation of free GABA exists in specific neuronal tracts of the human CNS where GABA is released from homocarnosine by the action of serum carnosinase.
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Affiliation(s)
- M C Jackson
- Department of Pharmacology, University of Hawaii School of Medicine, Leahi Hospital, Honolulu 96816
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11
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Kok RM, Howells DW, van den Heuvel CC, Guérand WS, Thompson GN, Jakobs C. Stable isotope dilution analysis of GABA in CSF using simple solvent extraction and electron-capture negative-ion mass fragmentography. J Inherit Metab Dis 1993; 16:508-12. [PMID: 7541876 DOI: 10.1007/bf00711667] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Affiliation(s)
- R M Kok
- Department of Pediatrics, Free University Hospital, Amsterdam, The Netherlands
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12
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Schechter PJ, Sjoerdsma A. Clinical relevance of measuring GABA concentrations in cerebrospinal fluid. Neurochem Res 1990; 15:419-23. [PMID: 2201926 DOI: 10.1007/bf00969927] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Determination of GABA concentrations in human cerebrospinal fluid can be used to assess GABAergic activity in the central nervous system. As CSF free GABA concentrations may vary with age, sex, CSF fraction, and collection and storage conditions, careful attention to these factors are necessary to allow interpretation of results. Longitudinal studies to investigate the influence of pharmacological agents on CSF GABA have proven especially useful to define clinical biochemical activity and have been utilized to attribute the anti-epileptic action of vigabatrin, a selective inhibitor of GABA-transaminase, to its effects on brain GABA metabolism.
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13
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Affiliation(s)
- B Francois
- Dr L Willems Institute, Diepenbeek, Belgium
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14
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Jaeken J, Casaer P, Haegele KD, Schechter PJ. Review: Normal and abnormal central nervous system GABA metabolism in childhood. J Inherit Metab Dis 1990; 13:793-801. [PMID: 2079831 DOI: 10.1007/bf01800202] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The metabolism and function of central nervous system GABA is briefly reviewed. Hereditary disorders of the GABA metabolism presenting in childhood are discussed with particular emphasis on the recently identified succinic semialdehyde dehydrogenase deficiency and GABA-transaminase deficiency, and on diseases associated with low CSF GABA which await further unravelling. Low CSF GABA concentrations are not always associated with convulsions. A separate section is devoted to the CSF as a tool in the diagnosis of these disorders. Finally, we present a few diagnostic and therapeutic guidelines.
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Affiliation(s)
- J Jaeken
- Department of Paediatrics, University of Leuven, Belgium
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15
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Gerrits GP, Trijbels FJ, Monnens LA, Gabreëls FJ, De Abreu RA, Theeuwes AG, van Raay-Selten B. Reference values for amino acids in cerebrospinal fluid of children determined using ion-exchange chromatography with fluorimetric detection. Clin Chim Acta 1989; 182:271-80. [PMID: 2766551 DOI: 10.1016/0009-8981(89)90104-6] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
One thousand specimens of CSF were collected from subjects ranging in age from newborn to 18 yr, who were undergoing a diagnostic lumbar puncture. Sixty-two samples were judged retrospectively as being suitable for calculating reference age-related values. The analyses were performed by an amino acid analyser using ion-exchange chromatography with fluorimetric detection giving a tenfold increase in sensitivity, thereby enhancing the diagnostic capabilities. As many as 36 known compounds could be detected, additionally 10 we could not identify. In children older than 3 yr nine of the identified compounds showed age-dependency. We found 22 amino acids to be significantly higher in infants younger than 1 yr, with only gamma-aminobutyric acid being significantly lower in infants. Alpha-aminoadipic acid showed a sex difference, being slightly higher in girls.
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Affiliation(s)
- G P Gerrits
- Department of Pediatrics, University of Nijmegen, The Netherlands
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16
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Abstract
1. Upon oral administration vigabatrin is rapidly absorbed. Plasma elimination half-life ranges between 5 and 7 h in normal volunteers. Vigabatrin is eliminated primarily via the kidneys with about 65% of the administered dose found unchanged in the urine within 24 h. Kinetics are dose-linear within the range of usual therapeutic doses. 2. At therapeutic doses in man vigabatrin produces dose-related increases in CSF concentrations of free and total GABA, homocarnosine (the GABA-histidine dipeptide) and beta-alanine. These biochemical changes are consistent with an inhibition of GABA-transaminase activity in brain. 3. Thus, with systemic availability upon oral administration and biochemical activity in the CNS, the prerequisites for potential uses of vigabatrin in neurological disorders have been demonstrated in clinical pharmacological studies.
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17
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Haegele KD, Schwartz JJ, Schoun J, Schmitt AH, Schechter PJ. 2-Pyrrolidinone in human cerebrospinal fluid: a major constituent of total gamma-aminobutyric acid. J Neurochem 1987; 49:1402-6. [PMID: 3668531 DOI: 10.1111/j.1471-4159.1987.tb01006.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
2-Pyrrolidinone, the lactam of gamma-aminobutyric acid (GABA), is identified as the major constituent of total GABA in human CSF. Structural elucidation was done by mass spectrometry. In lumbar CSF of four patients, 2-pyrrolidinone represented about 54% of GABA found after acid hydrolysis, thus accounting for essentially all of the hitherto unknown GABA fraction in CSF.
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Affiliation(s)
- K D Haegele
- Merrell Dow Research Institute, Strasbourg, France
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18
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Bonnet AM, Tell G, Schechter PJ, Grove J, Saint-Hilaire MH, De Smet Y, Agid Y. Cerebrospinal fluid GABA and homocarnosine concentrations in patients with Friedreich's ataxia, Parkinson's disease, and Huntington's chorea. Mov Disord 1987; 2:117-23. [PMID: 2973560 DOI: 10.1002/mds.870020206] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Free and total gamma-aminobutyric acid (GABA) and homocarnosine concentrations were measured in the lumbar cerebrospinal fluid (CSF) of patients with Friedreich's ataxia, Huntington's chorea, and Parkinson's disease (with and without levodopa treatment), and compared with those determined in control subjects. Values found in Friedreich's ataxia or Parkinson's disease were not significantly different from those in controls. Unexpectedly, in Huntington patients, known to have a characteristic decrease in GABA concentrations in specific brain areas, CSF concentrations of total GABA and homocarnosine were significantly higher, whereas free GABA was not different from controls. These findings indicate that the measurement of CSF GABA and homocarnosine in patients with CNS degenerative diseases should be interpreted cautiously.
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Affiliation(s)
- A M Bonnet
- Clinique de Neurologie et de Neuropsychologie, INSERM (U 289), Hopital de la Salpétrière, Paris, France
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19
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Rapid gas chromatographic—mass spectrometric quantitation of γ-aminobutyric acid in biological specimens. ACTA ACUST UNITED AC 1985. [DOI: 10.1016/0378-4347(85)80003-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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20
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Ferraro TN, Hare TA. Triple-column ion-exchange physiological amino acid analysis with fluorescent detection: baseline characterization of human cerebrospinal fluid. Anal Biochem 1984; 143:82-94. [PMID: 6528999 DOI: 10.1016/0003-2697(84)90561-x] [Citation(s) in RCA: 36] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
A highly resolving triple-column amino acid analyzer with fluorometric detection is described. The reliability of this technique was evaluated and it was used in a baseline investigation of amino acids and related compounds in human cerebrospinal fluid (CSF). The procedure employs three distinct ion-exchange columns to elute the acidic, neutral, and basic amino acids, respectively. Each column is run isocratically with lithium citrate buffers designed to provide overlapping elution profiles. Studies using CSF collected under strictly controlled conditions documented nanomolar concentrations of aspartate, gamma-aminobutyric acid (GABA), beta-alanine, 1-methylhistidine, and 3-methylhistidine, as well as low levels of glutamate, methyllysine, and ammonia. In addition, other common amino acids were also quantified. Chromatograms of CSF from all three systems (acidic, neutral, and basic) exhibited numerous uncharacterized compounds emphasizing the resolution and sensitivity of the analytical procedure. In vitro stability studies revealed that levels of aspartate, glutamate, GABA, homocarnosine, and ammonia are subject to significant change when CSF is maintained at room temperature for various periods of time up to 24 h. It is concluded that the valid and accurate measurement of CSF amino compounds, especially the neurotransmitter amino acids, requires a highly specific and sensitive assay procedure as well as strict control of CSF manipulation in vitro.
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Manyam BV, Tremblay RD. Free and conjugated GABA in human cerebrospinal fluid: effect of degenerative neurologic diseases and isoniazid. Brain Res 1984; 307:217-23. [PMID: 6235893 DOI: 10.1016/0006-8993(84)90475-x] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
gamma-Aminobutyric acid (GABA) was measured in CSF as such and following acid hydrolysis by the ion-exchange/fluorometric method. The conjugated GABA level was obtained by subtracting the free GABA level from the total GABA level. Results showed that at room temperature, while the free GABA level increased, the level of conjugated GABA decreased in a linear fashion during the first 24 h (r = -0.974; P less than 0.001). Aging and CSF conjugated GABA levels were inversely correlated (r = -0.613; P less than 0.05). Unlike free GABA levels, the levels of conjugated GABA were not altered in Huntington's disease, Parkinson's disease, cerebellar ataxias, dementias, epilepsy and multiple sclerosis compared to controls. In patients with Huntington's disease, on administration of isoniazid at 900 mg/day, along with pyridoxine at 100 mg/day, a 4-fold increase of both free (P less than 0.005) and conjugated GABA (P less than 0.0025) was seen. The results indicate that while total GABAergic peptides are not altered in several of the neurologic diseases studied, drugs such as isoniazid and/or pyridoxine can significantly elevate both free and conjugated GABA levels in human CSF.
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22
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Lenney JF, Peppers SC, Kucera CM, Sjaastad O. Homocarnosinosis: lack of serum carnosinase is the defect probably responsible for elevated brain and CSF homocarnosine. Clin Chim Acta 1983; 132:157-65. [PMID: 6616870 DOI: 10.1016/0009-8981(83)90243-7] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Patients afflicted with homocarnosinosis have elevated concentrations of homocarnosine in brain and CSF. It has been reported that they lack brain homocarnosinase. However, we have found that these patients are deficient in serum carnosinase, a dipeptidase which hydrolyzes homocarnosine about 5% as rapidly as it splits carnosine. Homocarnosinase could not be detected in normal human brain extracts after isoelectric focusing or DEAE-cellulose column chromatography. The ability of brain extracts to hydrolyze homocarnosine thus appears to be attributable solely to the serum carnosinase which is present because of serum trapped in the brain sample. Preliminary data indicate that homocarnosinase is probably not present in 13 other human tissues. Normal CSF contained serum carnosinase, whereas the CSF of a homocarnosinosis patient was lacking this enzyme. Thus it appears that the elevated concentrations of homocarnosine in the CSF of homocarnosinosis patients are attributable to serum carnosinase deficiency.
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23
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Palfreyman MG, Huot S, Grove J. Total GABA and homocarnosine in CSF as indices of brain GABA concentrations. Neurosci Lett 1983; 35:161-6. [PMID: 6856194 DOI: 10.1016/0304-3940(83)90544-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Treatment of rats with gamma-vinyl-GABA, an inhibitor of GABA-transaminase, caused a dose- and time-related increase in brain GABA concentrations concomitant with increases in the concentrations of total GABA and homocarnosine in the CSF. At 18 h after treatment both CSF parameters correlated significantly with brain GABA concentrations. However, only total GABA in CSF accurately reflected brain GABA concentrations as a function of time after treatment and is therefore the preferred index.
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