Increased level of N-acetylaspartylglutamate (NAAG) in the CSF of a patient with Pelizaeus-Merzbacher-like disease due to mutation in the GJA12 gene

Autosomal recessive Pelizaeus-Merzbacher-like disease 1 (PMLD1) is a hypomyelinating disorder of the central nervous system (CNS) with virtually identical phenotype to Pelizaeus-Merzbacher disease (PMD). PMLD1 is caused by mutations in GJA12 gene, PMD is due to mutations in PLP1 gene. Elevated levels of N-acetylaspartylglutamate (NAAG), the most abundant peptide neuromodulator in the human brain, have been recently reported in cerebral spinal fluid (CSF) of patients with PMD. Using capillary electrophoresis, we analyzed for the first time, the CSF from a girl with PMLD1 and detected high concentrations of NAAG. This finding confirms the hypothesis that NAAG may be involved in myelination-related processes and can be considered as a useful diagnostic marker not only for patients with the PLP1 related disorder, but also in those with Pelizaeus-Merzbacher like hypomyelinating disease due to other defined genetic causes, such as PMLD1.

Free amino acid and dipeptide changes in the body fluids from Alzheimer's disease subjects

Our aim was to determine changes in free amino acid (FAA) and dipeptide (DP) concentrations in probable Alzheimer's disease (pAD) subjects compared with control (CT) subjects using liquid chromatography and electrospray ionization tandem mass spectrometry (LCMS2). We recruited gender- and age-matched study participants based on neurological and neuropsychological assessments. We measured FAAs and DPs in cerebrospinal fluid (CSF), plasma and urine using LCMS2 with selected reaction monitoring (SRM). Imidazole-containing FAAs (histidine, methyl-histidine), catecholamines (L-DOPA and dopamine), citrulline, ornithine, glycine and antioxidant DPs (carnosine and anserine) accounted for the major changes between CT and pAD. Carnosine levels were significantly lower in pAD (328.4 +/- 91.31 nmol/dl) than in CT plasma (654.23 +/- 100.61 nmol/dl). In contrast, L-DOPA levels were higher in pAD (1400.84 +/- 253.68) than CT (513.10 +/- 121.61 nmol/dl) plasma. These data underscore the importance of FAA and DP metabolism in the pathogenesis of AD. Since our data show changes in antioxidants, neurotransmitters and their precursors, or FAA associated with urea metabolism in pAD compared with CT, we propose that manipulation of these metabolic pathways may be important in preventing AD progression.

Quantification of free amino acids and dipeptides using isotope dilution liquid chromatography and electrospray ionization tandem mass spectrometry

Our aim was to develop a liquid chromatography and electrospray ionization tandem mass spectrometry (LCMS2) method to measure free amino acid (FAA) and dipeptide (DP) concentrations in biological fluids. We synthesized chloroformate derivatives of FAA and DP, identified the major precursor ions and used LCMS2 to obtain the most intense product ions. Using serial dilutions of unlabeled and labeled standards ([2H3]-L-Dopa, homoarginine, homophenylalanine, [15N]-Glutamine and [2H3]-methionine), we observed linear relationships in MS response that we used to calculate the amounts of FAA and DP in biological samples. This method is sensitive with a limit of detection (LOD) for most of the FAAs and DPs tested in the 0.05-1 pmol range and is linear over 3-5 orders of magnitude when many metabolites were measured simultaneously. Reproducibility and between run or daily variations were <10% for most FAAs and DPs. We applied this method to human samples and quantitatively measured 21 FAAs and 2 DPs in 200 microl CSF, 31 FAAs and 6 DPs in 100 microl plasma, and 23 FAAs and 5 DPs in 200 microl urine. These data demonstrate the potential for using LCMS2 to discover changes in FAA and DP metabolic pathways that occur during disease pathogenesis.

Severe hypomyelination associated with increased levels of N-acetylaspartylglutamate in CSF

BACKGROUND

Two unrelated girls had early onset of nystagmus and epilepsy, absent psychomotor development, and almost complete absence of myelin on cerebral MRI. The clinical features and MR images of both patients resembled the connatal form of Pelizaeus-Merzbacher disease (PMD), which is an X-linked recessive disorder caused by duplications or mutations of the proteolipid protein gene (PLP).

OBJECTIVE

To define a unique neurometabolic disorder with failure of myelination.

METHOD

S AND RESULTS: 1H-NMR of CSF in both girls was performed repeatedly, and both showed highly elevated concentrations of N-acetylaspartylglutamate (NAAG). The coding sequence of the gene coding for glutamate carboxypeptidase II, which converts NAAG to N-acetylaspartate (NAA) and glutamate, was entirely sequenced but revealed no mutations. Even though both patients are girls, the authors sequenced the PLP gene and found no abnormality.

CONCLUSIONS

NAAG is an abundant peptide neurotransmitter whose exact role is unclear. NAAG is implicated in two cases of unresolved severe CNS disorder. Its elevated concentration in CSF may be the biochemical hallmark for a novel neurometabolic disorder. The cause of its accumulation is still unclear.

The gamma-secretase inhibitor N-[N-(3,5-difluorophenacetyl)-L-alanyl]-S-phenylglycine t-butyl ester reduces A beta levels in vivo in plasma and cerebrospinal fluid in young (plaque-free) and aged (plaque-bearing) Tg2576 mice

Acute, s.c. administration of a gamma-secretase inhibitor, N-[N-(3,5-difluorophenacetyl)-l-alanyl]-S-phenylglycine t-butyl ester (DAPT), to young PDAPP mice dose dependently decreases cortical amyloid-beta (A beta). The present studies replicated these findings in Tg2576 mice and examined further whether DAPT would reduce cerebrospinal fluid (CSF) A beta comparably in young (plaque-free) and aged (plaque-bearing) mice. In the first study, vehicle or DAPT (10, 30, or 100 mg/kg s.c.) administered to young Tg2576 mice (6 months old) dose dependently reduced A beta peptide levels in the cortex as seen previously in the PDAPP mice. Additionally, a dose-dependent decrease in plasma A beta levels was evident. The same dosing regime was applied next to aged mice (17 months old) to assess A beta changes in the CSF in addition to plasma and brains. DAPT dose dependently reduced A beta levels in the CSF and plasma, but not in the brain wherein A beta levels were 400 to 500 times higher than those in young mice, consistent with a large pool of A beta extracted from amyloid deposits. In subsequent studies, effects of oral DAPT (100 or 200 mg/kg) were examined concurrently in young and aged mice. DAPT reduced A beta levels in CSF and plasma to a similar extent at both ages. In contrast, DAPT reduced brain A beta levels primarily in young mice, with minimal effects in aged mice. These results demonstrate that A beta levels in CSF and plasma decrease dose dependently after gamma-secretase inhibition, and this response is not affected by amyloid plaque burden. We conclude that CSF and plasma A beta may offer a clinically applicable, mechanism-based biomarker for inhibitors of A beta production.

N(epsilon)-(gamma-L-glutamyl)-L-lysine (GGEL) is increased in cerebrospinal fluid of patients with Huntington's disease

Pathological-length polyglutamine (Q(n)) expansions, such as those that occur in the huntingtin protein (htt) in Huntington's disease (HD), are excellent substrates for tissue transglutaminase in vitro, and transglutaminase activity is increased in post-mortem HD brain. However, direct evidence for the participation of tissue transglutaminase (or other transglutaminases) in HD patients in vivo is scarce. We now report that levels of N(epsilon)-(gamma-L-glutamyl)-L-lysine (GGEL)--a 'marker' isodipeptide produced by the transglutaminase reaction--are elevated in the CSF of HD patients (708 +/- 41 pmol/mL, SEM, n = 36) vs. control CSF (228 +/- 36, n = 27); p < 0.0001. These data support the hypothesis that transglutaminase activity is increased in HD brain in vivo.

N(epsilon)(gamma-glutamyl)lysine in cerebrospinal fluid marks Alzheimer type and vascular dementia

N(epsilon)(gamma-glutamyl)lysine isodipeptide is released from the breakdown of proteins cross-linked by transglutaminase enzymes. Transglutaminase activation is a marker of apoptosis and elevated isodipeptide concentrations in body fluids might correlate with the intensity of apoptotic cell turnover. The concentration of N(epsilon)(gamma-glutamyl)lysine was measured in the cerebrospinal fluid (CSF) of patients with probable Alzheimer's disease (n = 14) and vascular type dementia (n = 11) and compared with not demented surgical controls (n = 17). Baseline levels of 26-62 nM/l (mean 37.9 +/- 8.7 SD) free isodipeptide were detected in control patients. CSF isodipeptide levels showed significant elevation in vascular (mean 95.6 +/- 45.1 SD) as well as Alzheimer patients (176.6 +/- 77.1 SD). Isodipeptide concentrations above 120 nM/l were 72% specific and 77% sensitive to Alzheimer's dementia, although the difference between the two dementias was statistically insignificant (p > 0.05). Determination of CSF N(epsilon)(gamma-glutamyl)lysine isodipeptide concentration offers a novel method for measurement of neurodegeneration in primary and mixed dementias.

N-acetylaspartic acid (NAA) and N-acetylaspartylglutamic acid (NAAG) in human ventricular, subarachnoid, and lumbar cerebrospinal fluid

N-Acetylaspartic and N-acetylaspartylglutamic acid concentrations in human ventricular, subarachnoid and lumbar cerebrospinal fluid were measured by combined gas chromatography-mass spectrometry using selected ion monitoring with deuterated internal standards. N-Acetylaspartate concentrations were in the range 55, 9, and 1 microM, respectively; N-acetylaspartylglutamate concentrations in the same fluids were in the range 8, 3 and 4 microM, respectively. There did not appear to be any difference in lumbar fluid concentrations of either compound between control subjects, schizophrenic patients, Alzheimer's disease patients and a pooled group of patients with neurological degeneration. Ventricular concentrations of both compounds were greatly increased in deceased patients suggesting that maintenance of their intracellular concentrations is probably energy dependent. The concentrations of these compounds in lumbar cerebrospinal fluid from living, and ventricular cerebrospinal fluid from deceased subjects were weakly correlated with one another. In lumbar fluid neither compound appeared to be correlated with age. Analysis of serially collected lumbar samples from two subjects showed a weak concentration gradient for both compounds. Neither antipsychotic medication nor the acid transport inhibitor probenecid had any effect on lumbar concentrations of either compound. Attempts to use anion exchange high pressure liquid chromatography with UV detection for measurement of the low concentrations of N-acetylaspartate found in cerebrospinal fluid from living subjects were unsuccessful.

N-acetylaspartylglutamate in Canavan disease: an adverse effector?

We measured N-acetylaspartate and its precursor/product N-acetylaspartylglutamate (NAAG) in urine of patients with Canavan disease using capillary zone electrophoresis. Abnormal levels of NAAG were found in 32 of 43 patients examined. Elevated NAAG was also present in the CSF of one patient. Given that NAAG may interfere with N-methyl-D-aspartate receptor function, the occurrence of high levels of NAAG in patients' urine conceivably represents a participating factor in the pathogenesis of Canavan disease.

CONCLUSION

The biochemical role of N-acetylaspartylglutamate and its relationship to glutamatergic function may be relevant to the pathogenesis of Canavan disease.

Markers of glutamatergic neurotransmission and oxidative stress associated with tardive dyskinesia

OBJECTIVE

Tardive dyskinesia is a movement disorder affecting 20%-40% of patients treated chronically with neuroleptic drugs. The dopamine supersensitivity hypothesis cannot account for the time course of tardive dyskinesia or for the persistence of tardive dyskinesia and the associated structural changes after neuroleptics are discontinued. The authors hypothesized that neuroleptics enhance striatal glutamatergic neurotransmission by blocking presynaptic dopamine receptors, which causes neuronal damage as a consequence of oxidative stress.

METHOD

CSF was obtained from 20 patients with schizophrenia, 11 of whom had tardive dyskinesia. Markers for oxidative stress, including superoxide dismutase, lipid hydroperoxide, and protein carbonyl groups, and markers for excitatory neurotransmission, including N-acetylaspartate, N-acetylaspartylglutamate, aspartate, and glutamate, were measured in the CSF specimens. Patients were also rated for tardive dyskinesia symptoms with the Abnormal Involuntary Movement Scale.

RESULTS

Tardive dyskinesia patients had significantly higher concentrations of N-acetylaspartate, N-acetylaspartylglutamate, and aspartate in their CSF than patients without tardive dyskinesia when age and neuroleptic dose were controlled for. The significance of the higher levels of protein-oxidized products associated with tardive dyskinesia did not pass Bonferroni correction, however. Tardive dyskinesia symptoms correlated positively with markers of excitatory neurotransmission and protein carbonyl group and negatively with CSF superoxide dismutase activity.

CONCLUSIONS

These findings suggest that there are elevated levels of oxidative stress and glutamatergic neurotransmission in tardive dyskinesia, both of which may be relevant to the pathophysiology of tardive dyskinesia.

gamma-Glutamylglutamine and taurine concentrations are decreased in the cerebrospinal fluid of drug-naive patients with schizophrenic disorders

HPLC and gas chromatography-mass spectrometry analyses of 18 amino acids, N-acetylaspartate, N-acetylaspartylglutamate, and 5-hydroxyindoleacetic acid, derived from serotonin, and homovanillic acid, derived from dopamine, were performed in CSF collected from a group of patients with schizophrenia who either had been drug free for at least 1 year (n = 5) or were drug naive for psychotropic drugs (n = 21) and in 15 control subjects. Significant differences were found only for taurine (15% lower in the patients) and isoleucine (7% higher). A number of unidentified substances were detected, one of which proved to be markedly reduced (16%) among the schizophrenic patients. Liquid chromatography-mass spectrometry with continuous flow-fast atom bombardment interface allowed us to identify this substance as gamma-glutamylglutamine. The decreased level of gamma-glutamylglutamine may reflect a deficiency in the gamma-glutamyltransferase system, a system probably involved in glutamate uptake, or a deficiency in glutamine, an important precursor of releasable glutamate. Although glutamate was nonsignificantly reduced in the patients, it was one of the five substances (including gamma-glutamylglutamine) that were necessary for the best discrimination between the schizophrenic patients and the controls. These findings support the notion that the glutamatergic system is affected in schizophrenic disorders. In addition, they underscore the need to apply rigid bioanalytical techniques and use drug-naive patients to gain in-depth information on the pathophysiology of brain disorders such as schizophrenia.

Transport and metabolism of glutathione isopropyl ester in cerebrospinal fluid

The transport of glutathione (GSH) or glutathione isopropyl ester (GSH isopropyl ester) to the cerebrospinal fluid (CSF) in rats was estimated by levels of GSH or GSH isopropyl ester and their metabolites in CSF 30 min after the intravenous administration of GSH or GSH isopropyl ester (300 mg/kg). Although the CSF uptake of GSH isopropyl ester was almost equal to that of GSH as evidenced by about a two-fold increase in the amount of non-protein sulfhydryl groups in CSF, the sum of GSH isopropyl ester and GSH concentrations in the CSF after GSH isopropyl ester treatment was increased by 32% compared with saline-treated controls. On the other hand, treatment with GSH had no significant increase in GSH levels in CSF but increased its metabolite levels, such as cysteinyl-glycine and cysteine. GSH isopropyl ester was less metabolized than GSH. GSH isopropyl ester had low affinity to purified gamma-glutamyl transpeptidase, a key enzyme for metabolism of GSH in the choroid plexus, supporting the finding that GSH isopropyl ester is more stable than GSH in CSF. These results are compatible with our previous report (Yamamoto et al. (1993) showing that the protective action of GSH isopropyl ester against cerebral ischemia was greater than that of GSH in rats. GSH isopropyl ester may be a useful agent which protects the brain from the damage associated with oxygen-related toxicities by increasing GSH levels in the CSF.

Reversal of experimental autoimmune encephalomyelitis with a hydroxamate inhibitor of matrix metalloproteases

Gelatinases, belonging to the matrix metalloproteases, contribute to tissue destruction in inflammatory demyelinating disorders of the central nervous system such as multiple sclerosis. We used experimental autoimmune encephalomyelitis (EAE) as an animal model to evaluate the effect of a hydroxamate matrix metalloprotease inhibitor (GM 6001) on inflammatory demyelination. A single dose of the inhibitor, given intraperitoneally, provided sufficient levels in the cerebrospinal fluid of animals with EAE to induce at least a partial inhibition of the gelatinase activity in the cerebrospinal fluid. When administered daily either from the time of disease induction or from the onset of clinical signs, GM 6001 suppressed the development or reversed clinical EAE in a dose-dependent way, respectively. Animals returned to the same clinical course as the nontreated group after cessation of treatment. Animals treated from the onset of clinical signs had normal permeability of the blood-brain barrier, compared with the enhanced permeability in nontreated animals. These results indicate that matrix metalloprotease inhibition can reverse ongoing EAE. This effect appears to be mediated mainly through restoration of the damaged blood-brain barrier in the inflammatory phase of the disease, since, the degree of demyelination and inflammation did not differ between the treatment groups.

Abnormal acidic amino acids and N-acetylaspartylglutamate in hereditary canine motoneuron disease

Hereditary canine spinal muscular atrophy (HCSMA) is a lower motor neuron disease found in Brittany Spaniels that shares clinical and pathological features with human amyotrophic lateral sclerosis (ALS). Since acidic excitatory amino acids and the neuropeptide N-acetyl-aspartyl-glutamate (NAAG) are reduced in spinal cord and cerebral cortex in ALS, the levels of these substances were measured in nervous tissue in Brittany Spaniels heterozygous and homozygous for HCSMA. Significant reductions in the levels of endogenous aspartate, glutamate, N-acetylaspartate (NAA), and NAAG were found in the spinal cord in homozygous but not heterozygous HCSMA. In contrast, the activity of N-acetylated-alpha-linked-amino dipeptidase (NAALADase), an enzyme that cleaves NAAG into NAA and Glu, was significantly increased. None of these parameters was affected in the motor cortex or occipital cortex. Since NAA and NAAG are highly concentrated in motoneurons, they may play a role in the pathogenesis of motor neuron disease.

Analysis of human beta-endorphin 28-31 (melanotropin potentiating factor) and analogues by high-performance liquid chromatography of their 9-fluorenylmethoxycarbonyl derivatives

A method is described for the determination of sub-picomole amounts of Lys-Lys-Gly-Glu [the C-terminal tetrapeptide sequence of human beta-endorphin, referred to as melanotropin potentiating factor (MPF)], a putative neurotrophic agent. Attempts to raise antibodies to the peptide were not successful and we have therefore developed a method based on the fluorescence of its 9-fluorenylmethyl chloroformate (FMOC) derivative which provides a sensitivity comparable to that of radioimmunoassay. Standard solutions, cerebrospinal fluid or central nervous tissue extracts are first treated with FMOC-Cl. The resulting mixture of FMOC-peptides is then subjected to high-performance liquid chromatography (HPLC) and quantified using a fluorescence monitor. By this procedure, MPF and related peptides can be analysed from one sample in a single HPLC run. The method was also applied to determine the rate of release into a phosphate-buffered saline medium of a metabolically stable analogue of MPF from a slow-release formulation of the compound.

Automated precolumn fluorescence labelling by carbodiimide activation of N-acetylaspartate and N-acetylaspartylglutamate applied to an HPLC brain tissue analysis

An automated method is described to couple carboxyl-containing metabolites to the fluorophore 2-aminoanthracene in aqueous solution (containing 75% methanol) in the presence of N,N-dicyclohexylcarbodiimide. The reaction was optimized for N-acetylaspartate (N-Ac-Asp) and N-acetylaspartylglutamate (N-Ac-Asp-Glu). The reactions occurred within 5 min at room temperature in the presence of 0.5-2 mM HCl. At concentrations of electrolytes exceeding 10 mM the coupling reaction became suboptimal. Derivatization was performed in a commercial precolumn derivatization unit. Additional tubing was needed to provide the reagents prior to reversed-phase HPLC and fluorescence detection. The assay is linear over at least three orders of magnitude; as little as 1 pmol could reproducibly be assayed in 100 micrograms wet weight brain tissue extracted with a mixture of methanol and 4 mM HCl (9:1, v/v). N-Ac-Asp and N-Ac-Asp-Glu levels in several brain regions and spinal cord were similar to those so far reported. The compounds could not be detected in peripheral tissue. The advantages, prospects and limitations of the present approach over existing methods to estimate water-soluble carboxylic acids is discussed.

Effects of [N-(L-(1-carboxy-2-phenyl)ethyl]-L-phenylalanyl-beta-alanine (SCH32615), a neutral endopeptidase (enkephalinase) inhibitor, on levels of enkephalin, encrypted enkephalins and substance P in cerebrospinal fluid and plasma of primates

In halothane-anesthetized and -ventilated cynomologus macaque monkeys, the effects of administering vehicle (n = 3) or the neutral endopeptidase inhibitor N-[L-(1-carboxy-2-phenyl)ethyl]-L-phenylalanyl-beta-alanine (16 mg/kg, n = 5; or 100 mg/kg, n = 3, intravenously) was examined. Cisternal CSF aliquots were examined by radioimmunoassay: 1) for Met enkephalin; 2) after trypsin and carboxypeptidase B treatment for encrypted enkephalin (X-ENK); 3) for substance P; and 4) for unmetabolized drug. Similar measures were carried out in femoral artery and femoral venous plasma, except that substance P was not assayed. In CSF, prior to drug, low, but measurable levels of enkephalin (61 pg/ml), X-ENK (285 pg/ml) and substance P (16 pg/ml) were observed. Vehicle-injected animals showed no change from baseline levels over a 4-hr sampling period in either plasma or CSF levels. In contrast, following 16 mg/kg, in CSF, there was a significant 9-fold increase in MET and 11-fold increase in X-ENK at 30 min. CSF-substance P levels rose also by a factor of 2, with the peak effect observed at 60 min. All levels displayed a significant reduction by 4 hr. There was no statistical difference between the maximum effects observed with either the 16- or 100-mg/kg dose. Plasma peptide levels of enkephalin and X-ENK were not altered by drug. CSF displayed significant drug levels by 30 min, which were between 0.1 and 1% of levels observed concurrently in plasma.(ABSTRACT TRUNCATED AT 250 WORDS)

gamma-Glutamylglutamine identified in plasma and cerebrospinal fluid from hyperammonaemic patients

gamma-Glutamylglutamine has been identified in plasma and cerebrospinal fluid. Preparative high voltage electrophoresis was used to isolate the compound from two to three ml of sample. Analysis of archival material from eight patients with urea cycle disorders showed that plasma gamma-glutamylglutamine was 20-214 mumol/l when the plasma glutamine was greater than 1,000 mumol/l and that the relationship was strongly positive (P less than 0.0005). Plasma gamma-glutamylglutamine concentration was also raised in one patient with secondary hyperammonaemia, but not in three other cases, one of whom had a plasma glutamine of 10,000 mumol/l. Cerebrospinal fluid from the last patient contained 97 mumol/l of gamma-glutamylglutamine. Samples of cerebrospinal fluid from two patients with urea cycle disorders were available and the gamma-glutamylglutamine levels were 203 and 313 mumol/l. gamma-Glutamylglutamine and 5-oxoproline concentrations were not significantly increased in urine from any of these patients.

Abnormal excitatory amino acid metabolism in amyotrophic lateral sclerosis

Recently, the excitatory amino acid neurotransmitter glutamate was implicated in the pathogenesis of a variety of chronic degenerative neurological diseases in humans and animals. This report describes abnormalities in excitatory amino acids in the central nervous system of 18 patients with amyotrophic lateral sclerosis (ALS). The concentration of the excitatory amino acids glutamate and aspartate in the cerebrospinal fluid were increased significantly (p less than 0.01) by 100 to 200% in patients with ALS. Similarly, the concentrations of the excitatory neuropeptide N-acetyl-aspartyl glutamate and its metabolite, N-acetyl-aspartate, were elevated twofold to threefold in the cerebrospinal fluid from the patients. There was no relationship between amino acid concentrations and duration of disease, clinical impairment, or patient age. In the ventral horns of the cervical region of the spinal cord, the level of N-acetyl-aspartyl glutamate and N-acetyl-aspartate was decreased by 60% (p less than 0.05) and 40% (p less than 0.05), respectively, in 8 patients with ALS. Choline acetyltransferase activity was also diminished by 35% in the ventral horn consistent with motor neuron loss. We conclude that excitatory amino acid metabolism is altered in patients with ALS. Based on neurodegenerative disease models, these changes may play a role in motor neuron loss in ALS.

Inhibitory and excitatory amino acids in cerebrospinal fluid of chronic epileptic patients

We studied the levels of excitatory and inhibitory amino acids in the cerebrospinal fluid (CSF) of 28 epileptic patients (24 with partial type seizures, 4 with primary generalized seizures) and 12 controls. The levels of aspartate were 63% (p less than 0.01), glutamine 129% (p less than 0.001), and homocarnosine 127% (p less than 0.005) that of controls. The concentrations of glutamate, asparagine, total GABA, free GABA, taurine, and glycine did not differ between epileptic patients and controls. Patients with partial epilepsy had a pattern of amino acids in CSF similar to that in patients with primary generalized seizures. In the present study we did not observe increased excitation or decreased inhibition in the seizure-active brains of epileptics, as far as the CSF levels of amino acids reflect their levels in the brain.

Cerebrospinal fluid parameters in healthy volunteers during serial lumbar punctures

Lumbar punctures were performed on four occasions over a 5-day period (8:30 a.m. on days 1, 3, and 5; 2:30 p.m. on day 2) on 10 normal volunteers (five of each sex; mean age, 27.7 years) to assess, with repeated sampling, the day-to-day variation of selected CSF parameters. Two subjects abstained from the lumbar puncture on day 5 due to headache after the third puncture. Lumbar CSF was analyzed for concentrations of free and total gamma-aminobutyric acid (GABA), homocarnosine, homovanillic acid (HVA), 5-hydroxyindoleacetic acid (5-HIAA), total protein, albumin, and immunoglobulin (Ig)G. No significant concentration differences were found between the afternoon and next morning samples. No differences were found in concentrations of free GABA, total GABA, homocarnosine, 5-HIAA, or albumin across the study. In contrast, HVA concentrations significantly increased by day 5, whereas total protein and IgG decreased during the study. The most likely explanation for these changes involves the known concentration gradients in the CSF column.

Levels of total gamma-aminobutyric acid (GABA), free GABA and homocarnosine in cerebrospinal fluid of epileptic patients before and during gamma-vinyl-GABA (vigabatrin) treatment

Levels of total gamma-aminobutyric acid (TGABA), free GABA (FGABA), and homocarnosine (HC) were studied in CSF taken from 12 controls and 28 patients with drug-refractory epilepsy before and during 7 months of gamma-vinyl-GABA (GVG) administration. At baseline TGABA and FGABA in CSF of epileptic patients did not differ from that of the controls. In epileptic patients HC was 127% of that in controls. During GVG treatment TGABA was 283%, FGABA 197%, and HC 310% of the levels at baseline in the same patients. The patients who had over 50% reduction in seizure frequency during GVG (responders, 46% of the study population) at baseline had higher TGABA and HC in CSF than patients with less than 50% reduction in seizures (non-responders). During GVG the responders and nonresponders had similar levels of different GABAergic markers. The present study shows that in man GVG treatment effectively suppresses seizures in nearly half of the epileptic patients who had previously been drug-refractory. The elevated levels of GABAergic markers in CSF are not, however, necessarily related to good seizure control during GVG.

Effects of single doses of vigabatrin on CSF concentrations of GABA, homocarnosine, homovanillic acid and 5-hydroxyindoleacetic acid in patients with complex partial epilepsy

Vigabatrin, as a single oral dose of 50 mg/kg, was administered to 11 patients with drug-refractory complex partial epilepsy. Serial lumbar punctures were performed prior to and 5 times within the first week following treatment. Cerebrospinal fluid (CSF) concentrations of total GABA, free GABA, homocarnosine, homovanillic acid (HVA), 5-hydroxyindoleacetic acid (5-HIAA) and vigabatrin were determined as well as blood vigabatrin levels. CSF GABA, homocarnosine, HVA and 5-HIAA concentrations increased by 6 h after the single dose and remained elevated for up to 5-7 days. In contrast, CSF and blood vigabatrin levels were maximal within the first 24 h and were no longer detectable thereafter. Hence, these results are consistent with vigabatrin acting as an irreversible inhibitor of GABA-transaminase and suggest that it may also increase biogenic amine turnover.

Homocarnosinosis: influence of dietary restriction of histidine

Homocarnosinosis, an inherited disorder, is characterized by an elevated level of the dipeptide homocarnosine (Hca) in the CSF and the brain and, in addition, by carnosinuria and serum carnosinase deficiency. In three children with homocarnosinosis the biochemical aberration co-exists with paraplegia, retinitis pigmentosa, and a progressive mental deficiency. In the mother, however, only the biochemical aberration was present without clinical symptoms. In order to study whether this elevated level of Hca and increased excretion of carnosine (Car) could be reduced towards normal, a dietary regiment with restriction of histidine (His) was maintained for nearly 2 1/2 years for two of the patients, 33 and 39 years old, with homocarnosinosis associated with neurological symptoms. His was reduced by about 90% in the CSF, in the plasma and in the urine. Within 5-6 months CSF Hca was reduced by about 70%, and urinary Car by 22 and 42%. The clinical neurological symptoms, however, did not alter significantly together with these biochemical changes.

[Determination of dipeptidyl aminopeptidase activities in the cerebrospinal fluid]

The investigation of enzyme activity in cerebrospinal fluid has been without relevant results for laboratories analysing spinal fluid. For neurochemical purposes, it is interesting that the Substance P is convered by Depeptidyl-aminopeptidase IV (DP IV), liberating dipeptides. The hydrolysis of nitroanilids of the form Xaa-Pro-NHNp in cerebrospinal fluid was analysed using them as peptidases substrates. Finally a method for measuring the activity was proposed.

Total GABA and homocarnosine in CSF as indices of brain GABA concentrations

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.

Brain function estimated from the ratio of glutamine to homocarnosine levels in cerebrospinal fluid

The ratio of glutamine to homocarnosine (G/H ratio) in CSF of children with meningeal pathology or convulsions was measured and the following results were obtained. 1. The mean G/H ratio of normal subjects was 83.0 +/- 41.4. 2. The mean G/H ratios of the patients with bacterial meningitis and meningeal leukemia were 115.9 +/- 81.9 and 115.2 +/- 49.2, respectively. Significant differences were found between those in normal subjects and these diseases. 3. The mean G/H ratio of the patients with viral meningitis was 80.0 +/- 35.1 and no significant difference was found between normal subjects and these patients. 4. The mean G/H ratios in the patients with controlled versus uncontrolled epilepsy were 130.9 +/- 67.1 and 74.8 +/- 49.4, respectively. A significant difference was found between normal subjects and the patients with controlled epilepsy. 5. The mean G/H ratio in the patients with febrile convulsions was 46.5 +/- 6.3. A significant difference was found between normal subjects and these patients. These data suggest that a high G/H ratio in CSF may indicate the excited state of the brain.

Homocarnosine levels in cerebrospinal fluid of patients with infantile spasms under ACTH therapy

The alteration of homocarnosine (dipeptide of GABA and histidine) levels in cerebrospinal fluid (CSF) was studied on 8 cases with infantile spasms under ACTH therapy. CSF was obtained by lumbar puncture before and during ACTH therapy. Homocarnosine was determined by the amino acid autoanalyzer. The attacks of infantile spasms were well controlled in all 8 cases by ACTH therapy. Homocarnosine levels in cerebrospinal fluid of each case decreased from 1.09 to 0.55, 0.92 to 0.41, 1.23 to 0.90, 0.79 to 0.49, 1.06 to 0.75, 1.06 to 0.89, 0.84 to 0.33 and 2.17 to 0.97 mumol/dl, respectively. The decrease of homocarnosine in CSF were 49.5%, 55.4%, 26.8%, 38.0%, 29.2%, 16.0%, 60.7% and 55.3%, respectively. This finding suggests that the decrease of homocarnosine in CSF may be related to the disappearance of attacks of infantile spasms.

Concentration gradients of free and total gamma-aminobutyric acid and homocarnosine in human CSF: comparison of suboccipital and lumbar sampling

Concentrations of free and total gamma-aminobutyric acid (GABA) and homocarnosine were determined in sequential aliquots of the first 30 ml of CSF obtained by lumbar puncture in five patients. Rostrocaudal gradients were calculated and compared to gradients estimated by determining concentrations of these substances in CSF obtained by simultaneous suboccipital and lumbar punctures in four more patients. In the lumbar fractions study, rostrocaudal mean gradients of 0.36, 36, and 21 pmol/ml for free GABA, total GABA, and homocarnosine, respectively, were calculated. In the suboccipital/lumbar study, gradients of 0.33, 30, and 24 pmol/ml for free GABA, total GABA, and homocarnosine, respectively, were estimated. These results indicate that valid comparison of CSF concentrations of these substances is restricted to similar fractions and suggest that in CSF the substances originate largely from brain rather than from peripheral sources.

Artifactual increases in the concentration of free GABA in samples of human cerebrospinal fluid are due to degradation of homocarnosine

Samples of untreated human cerebrospinal fluid (CSF) were kept at room temperature (20 +/- 1 degree C) up to 72 h, and changes in gamma-aminobutyric acid (GABA) and homocarnosine contents were measured. The concentration of free GABA increased with time, and concomitantly a similar decrease occurred in the concentration of homocarnosine. Total GABA after hydrolysis (present in human CSF at concentrations of 40-100 times that of free GABA) did not change. After 2 h the increase in CSF GABA for seven subjects ranged from 42 to 244 pmol/ml. The rate of increase in CSF GABA was positively correlated with the initial homocarnosine concentration. Approximately 5% per h of the initial homocarnosine content was degraded during the first 7 h at room temperature; thereafter the rate gradually decreased. No free GABA was formed in CSF frozen at -70 degrees C for 10 days. When this CSF was restored to room temperature, the formation of free GABA from homocarnosine occurred at essentially the same rate as that observed in fresh CSF. These results demonstrate that the well-known artifactual increase in GABA concentration of untreated human CSF depends on the concentration of homocarnosine. The rapidity of this increase (up to 2 pmol/ml/min) could account for disparities among CSF free GABA concentrations previously reported from normal subjects. It is suggested that measurement of concentrations of total GABA in the CSF would provide a better index of human brain GABA concentration than determination of CSF free GABA.

Studies on homocarnosine in cerebrospinal fluid in infancy and childhood. Part II. Homocarnosine levels in cerebrospinal fluid from children with epilepsy, febrile convulsion or meningitis

To clarify the pathophysiological role of homocarnosine in the cerebrospinal fluid (CSF) in children, homocarnosine levels in CSF were determined in patients with epilepsy (32 cases), febrile convulsion (5 cases) and meningitis (42 cases) with a high speed amino acid autoanalyzer (Hitachi Co.). Mean homocarnosine levels in CSF of controlled epileptic children, uncontrolled epileptic children and febrile convulsion cases were 0.61 +/- 0.25 mumol/dl, 1.03 +/- 0.37 mumol/dl and 1.09 +/- 0.04 mumol/dl, respectively. High homocarnosine levels in CSF of children with uncontrolled epilepsy or febrile convulsion may indicate the reduced turnover rate from homocarnosine to GABA. In patients with meningitis, the unconscious states were accompanied by significantly lower homocarnosine levels in CSF (0.39 +/- 0.20 mumol/dl) than those in the patients with clear conscious states (0.9 +/- 0.31 mumol/dl, however, in patients with clear conscious states homocarnosine in CSF were almost the same as those of normal children (0.89 +/- 0.23 mumol/dl). These data suggest that homocarnosine in CSF might be related to the convulsive tendency and consciousness.

Studies on homocarnosine in cerebrospinal fluid in infancy and childhood. Part I. Homocarnosine level in cerebrospinal fluid of normal infants and children

Homocarnosine levels in the cerebrospinal fluid of 49 normal infants and children were determined by a high speed amino acid autoanalyzer (Hitachi Co.). The mean homocarnosine level in cerebrospinal fluid (CSF) of infants and children was 0.75 +/- 0.24 mumol/dl. In infants under 2 years of age, significant correlation between homocarnosine levels in CSF and the gestational age was found (r = 0.79, p less than 0.001). In children from 2 to 8 years of age, homocarnosine levels in CSF were almost constant being independent of the age (mean +/- SD: 0.89 +/- 0.20 mumol/dl). In school children over 9 years of age, significant correlation between homocarnosine levels in CSF and the age was found ( r = -0.68, p less than 0.01).

Homocarnosinosis. 3. Spinal fluid amino acids in familial spastic paraplegia

Increased concentration of CSF homocarnosine has recently been found in a family with spastic paraplegia. CSF homocarnosine was therefore determined in 13 patients from other families with familial spastic paraplegia. Also examined were seven patients from families where the constellation of symptoms and signs was more complex, but also comprised spastic paraplegia, and five patients with non-familial spastic paraplegia. No changes were found in homocarnosine level. In one patient with spastic familial paraplegia clear elevation of threonine in the CSF was found. The affected brother showed no such abnormality. CSF homocarnosine elevation is thus no common denominator in familial spastic paraplegia.