Longitudinal whole-brain N-acetylaspartate concentration in healthy adults

N-Acetylaspartate Drives Oligodendroglial Differentiation via Histone Deacetylase Activation

An unmet clinical goal in demyelinating pathologies is to restore the myelin sheath prior to neural degeneration. N-acetylaspartate (NAA) is an acetylated derivative form of aspartate, abundant in the healthy brain but severely reduced during traumatic brain injury and in patients with neurodegenerative pathologies. How extracellular NAA variations impact the remyelination process and, thereby, the ability of oligodendrocytes to remyelinate axons remains unexplored. Here, we evaluated the remyelination properties of the oligodendroglial (OL) mouse cell line Oli-neuM under different concentrations of NAA using a combination of biochemical, qPCR, immunofluorescence assays, and in vitro engagement tests, at NAA doses compatible with those observed in healthy brains and during brain injury. We observed that oligodendroglia cells respond to decreasing levels of NAA by stimulating differentiation and promoting gene expression of myelin proteins in a temporally regulated manner. Low doses of NAA potently stimulate Oli-neuM to engage with synthetic axons. Furthermore, we show a concentration-dependent expression of specific histone deacetylases essential for MBP gene expression under NAA or Clobetasol treatment. These data are consistent with the idea that oligodendrocytes respond to lowering the NAA concentration by activating the remyelination process via deacetylase activation.

Copper Modulates Mitochondrial Oxidative Phosphorylation to Enhance Dermal Papilla Cells Proliferation in Rex Rabbits

Copper (Cu) is an important coenzyme factor in cell signaling, such as cytochrome c oxidase (Complex IV). Metabolism plays an important role in regulating the fate of mammalian cells. The aim of this study is to experimentally investigate the effect of copper on cell metabolism in the dermal papilla cells of the Rex rabbit. In this study, Cu promoted proliferation of dermal papilla cells (p = 0.0008) while also increasing levels of cellular CIII, CIV, Complex IV and ATP. Moreover, fifty metabolites that were significantly different between Cu and controls were identified as potential biomarkers of Cu stimulation. Copper-stimulated cells had altered levels of arachidonic acid derivatives, S-glutamic acid, and citric acid, which were primarily linked to two different pathways: arachidonic acid metabolism (p < 0.0001) and alanine, aspartate and glutamate metabolism (p = 0.0003). The addition of Cu can increase the proliferation of Rex rabbit dermal papilla cells. Increased levels of ubiquinol-cytochrome c reductase complex core protein 2 (CIII) and cytochrome c oxidase subunit 1 (CIV) were associated with the increased levels of cellular cytochrome c oxidase (Complex IV) and adenosine triphosphate (ATP). In a word, copper promotes cell proliferation by maintaining the function of the cellular mitochondrial electron transport chain (ETC) pathway.

N-acetyl l-aspartate and Triacetin modulate tumor suppressor MicroRNA and class I and II HDAC gene expression induce apoptosis in Glioblastoma cancer cells in vitro

Glioblastoma multiforme (GBM), grade IV glioma and is aggressive, malignant primary brain cancer. Altered expression and activity of epigenetic proteins such as histone deacetylases (HDACs) are involved in GBM metastasis. Also, acetates are important to brain metabolites that regulate cell proliferation and apoptosis. Here, we have examined the effect of the acetates on the cell-cycle. U87MG cancer cells treated with N-acetyl l-aspartate (NAA) and sodium acetate have exhibited G1 phase cell-cycle arrest whereas U87MG cells treated with Triacetin (TA), and potassium acetate has induced G2/M cell cycle arrest. We have observed inhibition of histone deacetylase (HDAC) mRNA levels in acetate treated U87MG cells. Interestingly, acetates-treated U87MG cells have shown a significant reduction in the mRNA level of class II HDACs than class I HDACs. Acetate treated cells have exhibited an enhanced expression of various microRNAs such as miR-15b, miR-92, miR-101, miR-155, miR-199, miR-200, miR-223, miR-16, and miR-17 that are involved in the inhibition of cancer cell proliferation, invasion, migration, and angiogenesis. Further, these acetate molecules regulate genes involved in mammalian target of rapamycin complex 2 (mTORC2) such as mammalian stress-activated protein kinase-interacting protein (mSIN1), protein observed with Rictor 2 (Protor 2), and protein kinase C α (PKCα). The present study reveals the possible involvement of the mTORC2 complex during acetate-mediated HDAC inhibition, as well as microRNA modulation. Furthermore, molecular modeling studies were employed to understand the binding mode of these acetate molecules to mTOR, Rapamycin-insensitive companion of mammalian target of rapamycin (Rictor), and HDAC-8 proteins. Thus in this study, we have identified the pivotal role of acetates in the modulation of mTOR complex, epigenetic genes and provide structural as well as functional insights that will help in future drug discovery against GBM cancer therapy.

Multinuclear absolute magnetic resonance thermometry

Non-invasive measurement of absolute temperature is important for proper characterization of various pathologies and for evaluation of thermal dose during interventional procedures. The proton (hydrogen nucleus) magnetic resonance (MR) frequency shift method can be used to map relative temperature changes. However, spatiotemporal variations in the main magnetic field and the lack of local internal frequency reference challenge the determination of absolute temperature. Here, we introduce a multinuclear method for absolute MR thermometry, based on the fact that the hydrogen and sodium nuclei exhibit a unique and distinct characteristic frequency dependence with temperature and with electrolyte concentration. A one-to-one mapping between the precession frequency difference of the two nuclei and absolute temperature is demonstrated. Proof-of-concept experiments were conducted in aqueous solutions with different NaCl concentrations, in agarose gel samples, and in freshly excised ex vivo mouse tissues. One-dimensional chemical shift imaging experiments also demonstrated excellent agreement with infrared measurements.

Increasing N-acetylaspartate in the Brain during Postnatal Myelination Does Not Cause the CNS Pathologies of Canavan Disease

Canavan disease is caused by mutations in the gene encoding aspartoacylase (ASPA), a deacetylase that catabolizes N-acetylaspartate (NAA). The precise involvement of elevated NAA in the pathogenesis of Canavan disease is an ongoing debate. In the present study, we tested the effects of elevated NAA in the brain during postnatal development. Mice were administered high doses of the hydrophobic methyl ester of NAA (M-NAA) twice daily starting on day 7 after birth. This treatment increased NAA levels in the brain to those observed in the brains of Nur7 mice, an established model of Canavan disease. We evaluated various serological parameters, oxidative stress, inflammatory and neurodegeneration markers and the results showed that there were no pathological alterations in any measure with increased brain NAA levels. We examined oxidative stress markers, malondialdehyde content (indicator of lipid peroxidation), expression of NADPH oxidase and nuclear translocation of the stress-responsive transcription factor nuclear factor (erythroid-derived 2)-like 2 (NRF-2) in brain. We also examined additional pathological markers by immunohistochemistry and the expression of activated caspase-3 and interleukin-6 by Western blot. None of the markers were increased in the brains of M-NAA treated mice, and no vacuoles were observed in any brain region. These results show that ASPA expression prevents the pathologies associated with excessive NAA concentrations in the brain during postnatal myelination. We hypothesize that the pathogenesis of Canavan disease involves not only disrupted NAA metabolism, but also excessive NAA related signaling processes in oligodendrocytes that have not been fully determined and we discuss some of the potential mechanisms.

Biochemistry of the cingulate cortex in autism: An MR spectroscopy study

Neuroimaging studies have uncovered structural and functional alterations in the cingulate cortex in individuals with autism spectrum disorders (ASD). Such abnormalities may underlie neurochemical imbalance. In order to characterize the neurochemical profile, the current study examined the concentration of brain metabolites in dorsal ACC (dACC) and posterior cingulate cortex (PCC) in high-functioning adults with ASD. Twenty high-functioning adults with ASD and 20 age-and-IQ-matched typically developing (TD) peers participated in this Proton magnetic resonance spectroscopy (1H-MRS) study. LCModel was used in analyzing the spectra to measure the levels of N-Acetyl aspartate (NAA), choline (Cho), creatine (Cr), and glutamate/glutamine (Glx) in dACC and PCC. Groups were compared using means for the ratio of each metabolite to their respective Cr levels as well as on absolute internal-water-referenced measures of each metabolite. There was a significant increase in Cho in PCC for ASD adults, with a marginal increase in dACC. A reduction in NAA/Cr in dACC was found in ASD participants, compared to their TD peers. No significant differences in Glx/Cr or Cho/Cr were found in dACC. There were no statistically significant group differences in the absolute concentration of NAA, Cr, Glx, or NAA/Cr, Cho/Cr, and Glx/Cr in the PCC. Differences in the metabolic properties of dACC compared to PCC were also found. Results of this study provide evidence for possible cellular and metabolic differences in the dACC and PCC in adults with ASD. This may suggest neuronal dysfunction in these regions and may contribute to the neuropathology of ASD. Autism Res 2016, 9: 643-657. © 2015 International Society for Autism Research, Wiley Periodicals, Inc.

Acetate supplementation as a means of inducing glioblastoma stem-like cell growth arrest

Glioblastoma (GBM), the most common primary adult malignant brain tumor, is associated with a poor prognosis due, in part, to tumor recurrence mediated by chemotherapy and radiation resistant glioma stem-like cells (GSCs). The metabolic and epigenetic state of GSCs differs from their non-GSC counterparts, with GSCs exhibiting greater glycolytic metabolism and global hypoacetylation. However, little attention has been focused on the potential use of acetate supplementation as a therapeutic approach. N-acetyl-l-aspartate (NAA), the primary storage form of brain acetate, and aspartoacylase (ASPA), the enzyme responsible for NAA catalysis, are significantly reduced in GBM tumors. We recently demonstrated that NAA supplementation is not an appropriate therapeutic approach since it increases GSC proliferation and pursued an alternative acetate source. The FDA approved food additive Triacetin (glyceryl triacetate, GTA) has been safely used for acetate supplementation therapy in Canavan disease, a leukodystrophy due to ASPA mutation. This study characterized the effects of GTA on the proliferation and differentiation of six primary GBM-derived GSCs relative to established U87 and U251 GBM cell lines, normal human cerebral cortical astrocytes, and murine neural stem cells. GTA reduced proliferation of GSCs greater than established GBM lines. Moreover, GTA reduced growth of the more aggressive mesenchymal GSCs greater than proneural GSCs. Although sodium acetate induced a dose-dependent reduction of GSC growth, it also reduced cell viability. GTA-mediated growth inhibition was not associated with differentiation, but increased protein acetylation. These data suggest that GTA-mediated acetate supplementation is a novel therapeutic strategy to inhibit GSC growth.

Automated whole-brain N-acetylaspartate proton MRS quantification

Concentration of the neuronal marker, N-acetylaspartate (NAA), a quantitative metric for the health and density of neurons, is currently obtained by integration of the manually defined peak in whole-head proton ((1) H)-MRS. Our goal was to develop a full spectral modeling approach for the automatic estimation of the whole-brain NAA concentration (WBNAA) and to compare the performance of this approach with a manual frequency-range peak integration approach previously employed. MRI and whole-head (1) H-MRS from 18 healthy young adults were examined. Non-localized, whole-head (1) H-MRS obtained at 3 T yielded the NAA peak area through both manually defined frequency-range integration and the new, full spectral simulation. The NAA peak area was converted into an absolute amount with phantom replacement and normalized for brain volume (segmented from T1 -weighted MRI) to yield WBNAA. A paired-sample t test was used to compare the means of the WBNAA paradigms and a likelihood ratio test used to compare their coefficients of variation. While the between-subject WBNAA means were nearly identical (12.8 ± 2.5 mm for integration, 12.8 ± 1.4 mm for spectral modeling), the latter's standard deviation was significantly smaller (by ~50%, p = 0.026). The within-subject variability was 11.7% (±1.3 mm) for integration versus 7.0% (±0.8 mm) for spectral modeling, i.e., a 40% improvement. The (quantifiable) quality of the modeling approach was high, as reflected by Cramer-Rao lower bounds below 0.1% and vanishingly small (experimental - fitted) residuals. Modeling of the whole-head (1) H-MRS increases WBNAA quantification reliability by reducing its variability, its susceptibility to operator bias and baseline roll, and by providing quality-control feedback. Together, these enhance the usefulness of the technique for monitoring the diffuse progression and treatment response of neurological disorders.

Longitudinal absolute metabolite quantification of white and gray matter regions in healthy controls using proton MR spectroscopic imaging

The purpose of this study was to evaluate quality parameters, metabolite concentrations and concentration ratios, and to investigate the reproducibility of quantitative proton magnetic resonance spectroscopic imaging ((1)H-MRSI) of selected white and gray matter regions of healthy adults. 2D-quantitative short-TE (1)H-MRSI spectra were obtained at 1.5T from the healthy human brain. Subjects (n = 12) were scanned twice with an interval of six months. Absolute metabolite concentrations were obtained based on coil loading, taking into account differences in sensitivity of the phased-array head coil. Spectral quality parameters, absolute metabolite concentrations, concentration ratios, and their reproducibility were determined and compared between time-points using a repeated measures general linear model. The quality of the spectra of selected brain areas was good, as determined by a mean spectral linewidth between 4.8 and 7.3 Hz (depending on the region). No significant differences between the two time-points were observed for spectral quality, concentrations, or concentration ratios. The mean intrasubject coefficient of variation (CoV) varied between 4.0 and 8.5% for total N-acetylaspartate, 7.2 and 10.8% for total creatine, 5.9 and 9.8% for myo-inositol, and 8.0 and 13.3% for choline, and remained below 20% for glutamate. CoV was generally lower when concentration ratios were considered. The study shows that longitudinal quantitative short-TE (1)H-MRSI generates reproducible absolute metabolite concentrations in healthy human white and gray matter. This may serve as a background for longitudinal clinical studies in adult patients.

Acetate supplementation induces growth arrest of NG2/PDGFRα-positive oligodendroglioma-derived tumor-initiating cells

Cancer is associated with globally hypoacetylated chromatin and considerable attention has recently been focused on epigenetic therapies. N-acetyl-L-aspartate (NAA), the primary storage form of acetate in the brain, and aspartoacylase (ASPA), the enzyme responsible for NAA catalysis to generate acetate and ultimately acetyl-Coenzyme A for histone acetylation, are reduced in oligodendroglioma. The short chain triglyceride glyceryl triacetate (GTA), which increases histone acetylation and inhibits histone deacetylase expression, has been safely used for acetate supplementation in Canavan disease, a leukodystrophy due to ASPA mutation. We demonstrate that GTA induces cytostatic G₀ growth arrest of oligodendroglioma-derived cells in vitro, without affecting normal cells. Sodium acetate, at doses comparable to that generated by complete GTA catalysis, but not glycerol also promoted growth arrest, whereas long chain triglycerides promoted cell growth. To begin to elucidate its mechanism of action, the effects of GTA on ASPA and acetyl-CoA synthetase protein levels and differentiation of established human oligodendroglioma cells (HOG and Hs683) and primary tumor-derived oligodendroglioma cells that exhibit some features of cancer stem cells (grade II OG33 and grade III OG35) relative to an oligodendrocyte progenitor line (Oli-Neu) were examined. The nuclear localization of ASPA and acetyl-CoA synthetase-1 in untreated cells was regulated during the cell cycle. GTA-mediated growth arrest was not associated with apoptosis or differentiation, but increased expression of acetylated proteins. Thus, GTA-mediated acetate supplementation may provide a safe, novel epigenetic therapy to reduce the growth of oligodendroglioma cells without affecting normal neural stem or oligodendrocyte progenitor cell proliferation or differentiation.

Triacetin-based acetate supplementation as a chemotherapeutic adjuvant therapy in glioma

Cancer is associated with epigenetic (i.e., histone hypoacetylation) and metabolic (i.e., aerobic glycolysis) alterations. Levels of N-acetyl-L-aspartate (NAA), the primary storage form of acetate in the brain, and aspartoacylase (ASPA), the enzyme responsible for NAA catalysis to generate acetate, are reduced in glioma; yet, few studies have investigated acetate as a potential therapeutic agent. This preclinical study sought to test the efficacy of the food additive Triacetin (glyceryl triacetate, GTA) as a novel therapy to increase acetate bioavailability in glioma cells. The growth-inhibitory effects of GTA, compared to the histone deacetylase inhibitor Vorinostat (SAHA), were assessed in established human glioma cell lines (HOG and Hs683 oligodendroglioma, U87 and U251 glioblastoma) and primary tumor-derived glioma stem-like cells (GSCs), relative to an oligodendrocyte progenitor line (Oli-Neu), normal astrocytes, and neural stem cells (NSCs) in vitro. GTA was also tested as a chemotherapeutic adjuvant with temozolomide (TMZ) in orthotopically grafted GSCs. GTA-induced cytostatic growth arrest in vitro comparable to Vorinostat, but, unlike Vorinostat, GTA did not alter astrocyte growth and promoted NSC expansion. GTA alone increased survival of mice engrafted with glioblastoma GSCs and potentiated TMZ to extend survival longer than TMZ alone. GTA was most effective on GSCs with a mesenchymal cell phenotype. Given that GTA has been chronically administered safely to infants with Canavan disease, a leukodystrophy due to ASPA mutation, GTA-mediated acetate supplementation may provide a novel, safe chemotherapeutic adjuvant to reduce the growth of glioma tumors, most notably the more rapidly proliferating, glycolytic and hypoacetylated mesenchymal glioma tumors.

Metabolic changes in patients with aneurysmal subarachnoid hemorrhage apart from perfusion deficits: neuronal mitochondrial injury?

BACKGROUND AND PURPOSE

Neuronal damage in aSAH apart from perfusion deficits has been widely discussed. We aimed to test if cerebral injury occurs in aSAH independently from visible perfusion deficit by measuring cerebral metabolites in patients with aSAH without infarction or impaired perfusion.

MATERIALS AND METHODS

We performed 3T MR imaging including (1)H-MR spectroscopy, DWI, and MR perfusion in 58 patients with aSAH and 11 age-matched and sex-matched control patients with incidental aneurysm. We compared changes of NAA, Cho, Glx, Lac, and Cr between all patients with aSAH and controls, between patients with and without visible perfusion deficit or infarction and controls, and between patients with and without visible perfusion deficit or infarction by using the Wilcoxon signed-rank test.

RESULTS

We found that NAA significantly (P < .005) decreased in all patients with aSAH. Cho was significantly increased in all patients compared with controls (P < .05). In patients without impaired perfusion or infarction, Glx was significantly decreased compared with both controls (P = .005) and patients with impaired perfusion or infarction (P = .006).

CONCLUSIONS

The significant decrease of NAA and Glx in patients with aSAH but without impaired perfusion or infarction strongly suggests global metabolic changes independent from visible perfusion deficits that might reflect neuronal mitochondrial injury. Further, impaired perfusion in aSAH seems to induce additional metabolic changes from increasing neuronal stress that might, to some extent, mask the global metabolic changes.

Association between change in normal appearing white matter metabolites and intrathecal inflammation in natalizumab-treated multiple sclerosis

Background

Multiple sclerosis (MS) is associated not only with focal inflammatory lesions but also diffuse pathology in the central nervous system (CNS). Since there is no firm association between the amount of focal inflammatory lesions and disease severity, diffuse pathology in normal appearing white matter (NAWM) may be crucial for disease progression. Immunomodulating treatments for MS reduce the number of focal lesions, but possible effects on diffuse white matter pathology are less studied. Furthermore, it is not known whether intrathecal levels of inflammatory or neurodegenerative markers are associated with development of pathology in NAWM.

Methods

Quantitative proton magnetic resonance spectroscopy (¹H-MRS) was used to investigate NAWM in 27 patients with relapsing MS before and after one year of treatment with natalizumab as well as NAWM in 20 healthy controls at baseline. Changes in ¹H-MRS metabolite concentrations during treatment were also correlated with a panel of intrathecal markers of inflammation and neurodegeneration in 24 of these 27 patients.

Results

The group levels of ¹H-MRS metabolite concentrations were unchanged pre-to posttreatment, but a pattern of high magnitude correlation coefficients (r = 0.43–0.67, p<0.0005–0.03) were found between changes in individual metabolite concentrations (total creatine and total choline) and levels of pro-inflammatory markers (IL-1β and CXCL8).

Conclusions

Despite a clinical improvement and a global decrease in levels of inflammatory markers in cerebrospinal fluid during treatment, high levels of pro-inflammatory CXCL8 and IL-1β were associated with an increase in ¹H-MRS metabolites indicative of continued gliosis development and membrane turnover in NAWM.

Two-year serial whole-brain N-acetyl-L-aspartate in patients with relapsing-remitting multiple sclerosis

OBJECTIVES

To test the hypotheses that 1) patients with relapsing-remitting multiple sclerosis (RR-MS) exhibit a quantifiable decline in their whole-brain concentration of the neural marker N-acetyl-L-aspartate (WBNAA), that is 2) more sensitive than clinical changes and 3) may provide a practical outcome measure for proof-of-concept and larger phase III clinical trials.

METHODS

Nineteen patients (5 men and 14 women) with clinically definite RR-MS, who were 33 ± 5 years old (mean ± SD), had a disease duration of 47 ± 28 months, and had a median Expanded Disability Status Scale (EDSS) score of 1.0 (range 0-5.5), underwent MRI and proton magnetic resonance spectroscopy ((1)H-MRS) semiannually for 2 years (5 time points). Eight matched control subjects underwent the protocol annually (3 time points). Their global N-acetyl-L-aspartate (1)H-MRS signal was converted into absolute amounts by phantom replacement and into WBNAA by dividing with the brain parenchymal volume, V(B), from MRI segmentation.

RESULTS

The baseline WBNAA of the patients (10.5 ± 1.7 mM) was significantly lower than that of the controls (12.3 ± 1.3 mM; p < 0.002) and declined significantly (5%/year, p < 0.002) vs that for the controls who did not show a decline (0.4%/year, p > 0.7). Likewise, V(B) values of the patients also declined significantly (0.5%/year, p < 0.0001), whereas those of the controls did not (0.2%/year, p = 0.08). The mean EDSS score of the patients increased insignificantly from 1.0 to 1.5 (range 0-6.0) and did not correlate with V(B) or WBNAA.

CONCLUSIONS

WBNAA of patients with RR-MS declined significantly at both the group and individual levels over a 2-year time period common in clinical trials. Because of the small sample sizes required to establish power, WBNAA can be incorporated into future studies.