Concentration Of N-acetylaspartic Acid Research Articles

Body mass and cardiorespiratory fitness are associated with altered brain metabolism.

Magnetic Resonance Spectroscopy provides measures of brain chemistry that are sensitive to cardiorespiratory fitness and body composition. The concentration of N-acetyl aspartic acid (NAA) is of interest because it is a marker of neuronal integrity. The ratio of NAA to creatine, a standard reference metabolite, has been shown to correlate with measures of both cardiorespiratory fitness and body composition. However, previous studies have explored these effects in isolation, making it impossible to know which of these highly correlated measures drive the correlations with NAA/Cr. As a result, the mechanisms underlying their association remain to be established. We therefore conducted a comprehensive study to investigate the relative contributions of cardiorespiratory fitness and percent body fat in predicting NAA/Cr. We demonstrate that NAA/Cr in white matter is correlated with percent body fat, and that this relationship largely subsumes the correlation of NAA/Cr with cardiorespiratory fitness. These results underscore the association of body composition with axonal integrity and suggests that this relationship drives the association of NAA/Cr with physical fitness in young adults.

A quantitative analysis of (1)H-MR spectroscopy at 3.0 T of three brain regions from childhood to middle age.

To study age-related metabolic changes in different brain regions. Point-resolved spectroscopy (repetition time/echo time = 2000 ms/30 ms) was performed in the left and right hippocampus, the left thalamus and the left centrum semiovale of 80 healthy subjects (37 females and 43 males aged 7-64 years). Analysis of covariance and linear regression were used for statistical analysis. Both metabolite concentration ratios with respect to total creatine (tCr) and absolute metabolite concentrations were included for analysis. Ins (myo-inositol)/tCr (p < 0.001) and absolute Ins concentration (p = 0.031) were significantly increased with age after adolescence. NAA (N-acetylaspartic acid)/tCr (p < 0.001) and absolute NAA concentration (p = 0.010) significantly declined with age after adolescence. Age-related increase of Ins and decline of NAA are found in all three regions, especially at the hippocampus, indicating possible gliosis in the ageing brain. We could use NAA/tCr and Ins/tCr as an indicator to estimate the neurons-to-glial cells ratio at the thalamus. This may be an index to distinguish normal tissues from gliosis.

32.: Baseline peri-infarct N-acetylaspartic acid concentration correlates with subsequent white matter atrophy after ischaemic stroke

Longitudinal changes in cerebral volume have been described in ischaemic stroke and may correlate with long-term outcome. We tested the hypothesis that baseline peri-infarct concentration of the neuronal metabolite N-acetylaspartic acid (NAA) correlates with subsequent cerebral volume change after stroke. Patients with supratentorial ischaemic stroke underwent 3 Tesla MRI within 1 week and at 1 and 3 months from onset. Structural imaging involved a T1-weighted axial magnetization prepared rapid gradient echo (1 mm slices, repetition time 1.9 s, echo time 2.82 ms). NAA estimation was performed at baseline using single-voxel spectroscopy (3 × 3 × 3 cm voxels, echo time 30 ms) with the voxel placed in the peri-infarct region determined by visual assessment of the diffusion-weighted image. Quantitative spectroscopic analysis was performed in LCmodel. Cerebral volume change was determined between the 1 and 3 month scans due to the effects of oedema on baseline scans. Grey and white matter volume, normalised for head size, were determined using SIENAX (part of FSL). The result was validated using Freesurfer. Fifteen patients were included in the analysis. Mean age was 69 years (interwquartile range [IQR] 62–78). Median baseline National Institutes of Health Stroke Scale score was 10 (IQR 5–14). Mean peri-infarct NAA concentration was 6.2 mM (IQR 5.1–7.6) versus 7.0 mM (IQR 6.0–8.0) in the contralateral hemisphere (p

Canavan disease: clinical features and recent advances in research.

Canavan disease (CD) is a genetic neurodegenerative leukodystrophy that results in the spongy degeneration of white matter in the brain. CD is characterized by mutations in the gene encoding aspartoacylase (ASPA), the substrate enzyme that hydrolyzes N-acetylaspartic acid (NAA) to acetate and aspartate. Elevated NAA and subsequent deficiency in acetate associated with this disease cause progressive neurological symptoms, such as macrocephaly, visuocognitive dysfunction, and psychomotor delay. The prevalence of CD is higher among Ashkenazi Jewish people, and several types of mutations have been reported in the gene coding ASPA. Highly elevated NAA is more specific to CD than other leukodystrophies, and an examination of urinary NAA concentration is useful for diagnosing CD. Many researchers are now examining the mechanisms responsible for white matter degeneration or dysmyelination in CD using mouse models, and several persuasive hypotheses have been suggested for the pathophysiology of CD. One is that NAA serves as a water pump; consequently, a disorder in NAA catabolism leads to astrocytic edema. Another hypothesis is that the hydrolyzation of NAA in oligodendrocytes is essential for myelin synthesis through the supply of acetate. Although there is currently no curative therapy for CD, dietary supplements are candidates that may retard the progression of the symptoms associated with CD. Furthermore, gene therapies using viral vectors have been investigated using rat models. These therapies have been found to be tolerable with no severe long-term adverse effects, reduce the elevated NAA in the brain, and may be applied to humans in the future.

Abstract T P73: Peri Infarct N-Acetylaspartic Acid Predicts White Matter Atrophy After Ischemic Stroke

Objective: Cerebral volume changes post stroke have recently been described and may correlate with clinical outcome. We aimed to determine whether peri infarct measurement of the neuronal marker N-Acetylaspartic acid (NAA) on Magnetic Resonance Spectroscopy (MRS) predicts progressive cerebral volume change after stroke. Methods: 11 patients (7 male) with supratentorial ischemic stroke underwent serial MRI within 1 week of onset, and at 1 and 3 months. Imaging was performed on a 3T Siemens Trio scanner. Structural imaging utilized a T1-weighted axial MPRAGE acquisition (1mm slices, TR1.9sec, TE2.82msec). NAA estimation was performed at the baseline scan using single voxel MRS (TE30msec, 3x3x3cm voxels). The voxel was placed in the peri infarct region as determined by assessment of the diffusion weighted image. Quantitative MRS analysis was performed using LCmodel using water referencing. Brain tissue volume, normalized for subject head size, was estimated with SIENAX, part of FSL. Due to anticipated effects of edema on initial cerebral volume, changes in grey, white and total brain volume were assessed as percentage change between the 1 and 3 month scans. Results: Mean age was 71yr (IQR 62-79yr). Median baseline NIHSS was 11 (IQR 6-14). Mean baseline grey, white and total brain volume were 713ml (IQR 683-749), 731mL (IQR 721-747) and 1444mL (IQR 1384-1503) respectively. There was a significant correlation between age and baseline grey matter volume (r2=0.73, p=0.001) and total brain volume (r2=0.74, p=0.001). Mean peri infarct NAA concentration was 6.2mM (SD 1.3) compared with 7.0mM (SD 1.2) in the contralateral hemisphere (p=0.09, paired t-test). Mean percentage grey, white and total brain volume changes were 1.2% (IQR -1.8-4.1), 0.4% (IQR -2.2-3.7) and 0.8% (IRQ -1.0-2.6) respectively. There was a significant correlation between baseline NAA in the peri infarct region and change in white matter volume between the 1 and 3 month time points (r2=0.26, p=0.008). Conclusions: Estimation of the neuronal marker NAA using MRS may signify varying degrees of neuronal damage after stroke which may correlate with the severity of axonal degeneration and subsequent white matter volume changes. Further validation and correlation with clinical outcomes is required.

A missense mutation (p.G274R) in gene ASPA causes Canavan disease in a Pakistani family

Canavan disease (OMIM 271900) is an autosomal recessive lethal neurodegenerative disorder characterized by spongy degeneration of the brain. A highly consanguineous Pakistani family with Canavan disease was enrolled on the basis of diagnosis. All the affected individuals have mental retardation, megalocephaly and degradation of motor skills, poor head control, partial vision loss, weakness of the muscles and raised urinary concentration of N-acetyl aspartic acid in the urine. Blood samples were collected from affected as well as normal siblings and processed for DNA purification. Linkage analysis was performed by typing three short tandem repeat markers D17S1583 (7.19cM), D17S1828 (10.02cM) and D17S919 (14.69cM) for an already-reported gene/locus ASPA at chromosome 17p13.2 causing Canavan disease. During linkage analysis, all the affected individuals were homozygous for short tandem repeat markers while the normal siblings were heterozygous showing co-segregation of the disease. Gene ASPA (NM_000049) was undertaken to sequence for mutation analysis. As a result of sequence analysis, we found missense substitution 740A→G (p.G274R) in exon 6 of gene ASPA. To our knowledge, this is the first report about Canavan disease on a Pakistani family.

Determination of N‐acetylaspartic acid concentration in the mouse brain using HPLC with fluorescence detection

The concentration of brain N-acetylaspartic acid (NAA) in mice was determined by high-performance liquid chromatography (HPLC) using fluorescence detection after pre-column derivatization with 4-N,N-dimethylaminosulfonyl-7-N-(2-aminoethyl)amino-2,1,3-benzoxadiazole (DBD-ED). Six different brain parts, namely, the prefrontal cortex, olfactory bulb, nucleus accumbens, striatum, cerebellum and hippocampus, of male C57BL6/J mice, were investigated. The NAA concentration (nmol/mg protein) was highest in the olfactory bulb (58.2 ± 4.0, n = 8) and lowest in the hippocampus (42.8 ± 1.6, n = 8). The proposed HPLC method with fluorescence detection was successfully used to determine the NAA concentration in each investigated brain area.

N-acetylaspartic acid in cerebrospinal fluid of multiple sclerosis patients determined by gas-chromatography-mass spectrometry

BackgroundAxonal degeneration is considered to play a major role in the development of clinical disability in multiple sclerosis (MS). N-AcetylAspartic Acid (NAA) is a neuron-specific marker constantly identified in MR-spectroscopy studies of the normal and MS brain. To our knowledge there are no studies available that evaluated NAA in cerebrospinal fluid (CSF) as a possible marker for disease severity.ObjectiveTo evaluate CSF concentrations of NAA in MS in relation to disease phenotype, clinical measures of disability and MRI markers of disease burden.MethodsNAA concentrations were determined in CSF of 46 patients with MS (26 relapsing remitting (RRMS), 12 secondary progressive (SPMS) and 8 primary progressive (PPMS)). Prior to lumbar puncture, MS-patients underwent MRI and clinical examination, including the Expanded Disability Status Scale (EDSS) and the MS Functional Composite (MSFC). Additionally, CSF concentrations of NAA were determined in 12 patients with other neurological diseases (OND).ResultsMedian CSF NAA concentration was 0.74 (IQR: 0.59-.94) in RRMS , 0.54 (IQR: 0.35-.73) in SPMS and 0.83 μmol/l (IQR: 0.56-.03) in PPMS patients. SPMS patients had a significantly lower NAA concentration than RRMS patients. NAA concentrations correlated with EDSS (r = )0.37, p = 0.016), MSFC (r = 0.41, p = 0.010), normalised brain volume (r = 0.49, p = 0.001), T2 lesion load (r = )0.35, p = 0.021) and black hole lesion load (r = )0.47, p = 0.002). No differences were observed between OND (median: 0.57 IQR: 0.28-.73) and MS patients.ConclusionCSF NAA concentration in MS patients is related to clinical performance and MRI measures of disease burden and may therefore be an important neuron specific marker of disease severity and possibly progression.

Atypical MRI Findings in Canavan Disease: A Patient with a Mild Course

Canavan disease is a severe, progressive leukodystrophy with an autosomal recessive inheritance, caused by aspartoacylase (ASPA) deficiency. The characteristic MRI features include diffuse, symmetrical white matter degeneration in the subcortical areas, with bilateral involvement of the globus pallidus. Proton magnetic resonance spectroscopy of the brain shows an increase in the concentration of N-acetylaspartic acid (NAA). The altered NAA metabolism has been traced to mutations in the gene encoding ASPA, located on chromosome 17 (17p13-ter). We present here a patient with a mild form of Canavan disease confirmed with the absent ASPA activity, atypical MRI findings, related to compound heterozygosity for a missense mutation, p.Tyr288Cys, and the known pan-European mutation, the p.Ala305Glu.

High-resolution 1H NMR spectroscopy following experimental brain trauma.

We investigated acute metabolic changes following parasagittal fluid-percussion brain injury in the rat, using high-resolution 1H nuclear magnetic resonance (NMR) spectroscopy. Sixty minutes following brain injury or sham (surgery, no injury) treatment, brains were rapidly removed and the injured and control cortices were isolated (n = 5/group). Isolates of brain cortices were then placed in buffer and studied in a 400-MHz spectrometer with measurements taken every 15 min over a 145-min period. At the initial NMR evaluation (immediately following dissection), we observed significantly lower levels of N-acetyl aspartic acid (NAA) in the injured group compared to the sham group. Surprisingly, a reciprocal increase in the concentration of acetate, a major metabolic product of NAA, was not observed at this timepoint. At subsequent timepoints, a progressive loss of NAA was observed in both injured and sham cortices, presumably due to ischemic conditions of the ex vivo samples. However, this progressive loss of NAA was now accompanied by a commensurate accumulation of acetate. These results suggest that (1) a decrease in the concentration of NAA occurs by 1 h following experimental brain trauma, potentially marking traumatic neural injury; (2) the initial absence of an expected reciprocal increase in acetate concentration may signify rapid utilization of acetate following trauma, potentially for reparative processes; and (3) in contrast to trauma alone, post mortem ischemic conditions may induce an increase in acetate concentrations.

Prenatal detection of Canavan disease (aspartoacylase deficiency) by DNA analysis.

Amniocentesis was performed in four pregnancies at risk for Canavan disease (CD). In all families both parents were of Ashkenazi-Jewish origin and harboured the C854 mutation in the cDNA of the aspartoacylase gene. Using DNA analysis of the amniotic cells, three fetuses were predicted to be non-affected and one fetus was predicted to be affected. The concentration of N-acetylaspartic acid (NAA) in the amniotic fluid was in agreement with these results. In urine samples of the three newborns predicted to be non-affected, the concentration of NAA was normal. Tissues of the aborted fetus were not available. We conclude that DNA analysis is probably a reliable method for prenatal diagnosis of CD.

Decreased brain N-acetylaspartate in Huntington's disease

The concentration of N-acetylaspartic acid (NAA) was measured in perchloric acid extracts of postmortem brain tissue obtained from patients with Huntington's disease and from control subjects. The material in the desalted extracts was resolved on an ion exclusion column and the content of NAA was determined by subsequent fluorometric quantitation of aspartate in hydrolyzates of the resolved NAA. The concentration of NAA in the putamen from patients with Huntington's disease was less than half that of controls (2.74 vs. 6.06 μmol/g wet weight). A smaller but significant reduction was also evident in samples of cerebral cortex from Brodmann area 10 (3.99 vs. 5.29 μmol/g), while the difference in concentrations in the cerebellum was not statistically significant. Though NAA could play a direct role in Huntington's disease, it seems more likely that the changes observed reflect illness or death of neurons, and that it may be feasible to monitor the course of Huntington's disease from NAA determinations. The same tissue extracts were also examined for the presence of d-isomers of amino acids. Only traces were found in NAA, aspartate, or glutamate.

Purification, Characterization, and Localization of Aspartoacylase from Bovine Brain

Canavan disease, an autosomal recessive disorder, is characterized biochemically by N-acetylaspartic aciduria and aspartoacylase (N-acyl-L-aspartate amidohydrolase; EC 3.5.1.15) deficiency. However, the role of aspartoacylase and N-acetylaspartic acid in brain metabolism is unknown. Aspartoacylase has been purified to apparent homogeneity with a specific activity of approximately 19,000-20,000 nmol of aspartate released/mg of protein. The native enzyme is a 58-kDa monomer. The purified aspartoacylase activity is enhanced by divalent cations, nonionic detergents, and dithiothreitol. Low levels of dithiothreitol or beta-mercaptoethanol are required for enzyme stability. Aspartoacylase has a Km of 8.5 x 10(-4) M and a Vmax of 43,000 nmol/min/mg of protein. Inhibition of aspartoacylase by glycyl-L-aspartate and amino derivatives of D-aspartic acid suggests that the carbon backbone of the substrate is primarily involved in its interaction with the active site and that a blocked amino group is essential for the catalytic activity of aspartoacylase. Biochemical and immunocytochemical studies revealed that aspartoacylase is localized to white matter, whereas the N-acetylaspartic acid concentration is threefold higher in gray matter than in white matter. Our studies so far indicate that aspartoacylase is conserved across species during evolution and suggest a significant role for aspartoacylase and N-acetylaspartic acid in normal brain biology.

Stable isotope dilution analysis ofN‐acetylaspartic acid in CSF, blood, urine and amniotic fluid: Accurate postnatal diagnosis and the potential for prenatal diagnosis of canavan disease

A sensitive and selective analytical technique is described for the determination of N-acetylaspartic acid in body fluids using stable isotope dilution in combination with positive chemical ionization mass spectrometry with selected ion monitoring. Control mean and ranges have been established: in urine 19.5 and 6.6-35.4 mumol/mmol creat.; in plasma 0.44 and 0.17-0.81 mumol/L; in cerebrospinal fluid 1.51 and 0.25-2.83 mumol/L; and in amniotic fluid 1.27 and 0.30-2.55 mumol/L. In a patient with Canavan disease, N-acetylaspartic acid concentration was elevated 80-fold in urine and 20-fold in plasma compared to the control means. A subsequent pregnancy of the mother was monitored and the N-acetylaspartic acid concentration in the amniotic fluid was within the control range and a healthy child was born.

N-Acetyl-L-Aspartic acid: A literature review of a compound prominent in 1H-NMR spectroscopic studies of brain

N-acetyl aspartic acid (NAA), discovered in 1956 by Tallan, is the major peak seen in water-suppressed NMR proton (hydrogen) spectroscopy. NAA makes up about one thousandth of the wet weight of human brain and appears to be limited solely to neurons. This compound has been shown to be relatively stable for a period of twenty-four hours post-mortem and the concentration of NAA is not changed by insulin-induced hypoglycemia. MAO inhibitors lower its concentration while reserpine and other drugs increase it. NAA has been implicated in many processes of the nervous system: it may be involved in the regulation of neuronal protein synthesis, myelin production, or the metabolism of several neurotransmitters such as aspartate or N-acetyl-aspartyl-glutamate. It is involved in the neurologic disorder Canavan disease and has grown to be a vital component of in vivo 1H-NMR spectroscopic studies.

N-Acetylaspartic aciduria in a child with a progressive cerebral atrophy

Excessive excretion of N-acetylaspartic acid in urine is reported in a 6-yr-old child with extensive and progressive cerebral atrophy. The concentration in urine was 947–1433 μmol/mmol creatinine (controls, n = 10, 5–21 μmol/mmol creatinine) and the daily excretion approximately 3–4 mmol. In cerebrospinal fluid from the patient the concentration was 611 μmol/l (controls, n = 10, not detectable, detection limit 2.3 μmol/l). The concentration of N-acetylaspartic acid in serum was 7 μmol/l. The low level in serum compared to the high urinary excretion of NAA suggests the possibility that NAA is synthesised in the kidneys in addition to the brain. This patient may cast new light on the functional role of N-acetylaspartic acid in humans.