Cerebrospinal fluid lactate and glutamine are reduced in multiple sclerosis

Proliferating Astrocytes in Primary Culture Do Not Depend upon Mitochondrial Respiratory Complex I Activity or Oxidative Phosphorylation

Understanding the role of astrocytes in the development of the nervous system and neurodegenerative disorders implies a necessary knowledge of the oxidative metabolism of proliferating astrocytes. The electron flux through mitochondrial respiratory complexes and oxidative phosphorylation may impact the growth and viability of these astrocytes. Here, we aimed at assessing to which extent mitochondrial oxidative metabolism is required for astrocyte survival and proliferation. Primary astrocytes from the neonatal mouse cortex were cultured in a physiologically relevant medium with the addition of piericidin A or oligomycin at concentrations that fully inhibit complex I-linked respiration and ATP synthase, respectively. The presence of these mitochondrial inhibitors for up to 6 days in a culture medium elicited only minor effects on astrocyte growth. Moreover, neither the morphology nor the proportion of glial fibrillary acidic protein-positive astrocytes in culture was affected by piericidin A or oligomycin. Metabolic characterization of the astrocytes showed a relevant glycolytic metabolism under basal conditions, despite functional oxidative phosphorylation and large spare respiratory capacity. Our data suggest that astrocytes in primary culture can sustainably proliferate when their energy metabolism relies only on aerobic glycolysis since their growth and survival do not require electron flux through respiratory complex I or oxidative phosphorylation.

Metabolomics detects clinically silent neuroinflammatory lesions earlier than neurofilament-light chain in a focal multiple sclerosis animal model

Background

Despite widespread searches, there are currently no validated biofluid markers for the detection of subclinical neuroinflammation in multiple sclerosis (MS). The dynamic nature of human metabolism in response to changes in homeostasis, as measured by metabolomics, may allow early identification of clinically silent neuroinflammation. Using the delayed-type hypersensitivity (DTH) MS rat model, we investigated the serum and cerebrospinal fluid (CSF) metabolomics profiles and neurofilament-light chain (NfL) levels, as a putative marker of neuroaxonal damage, arising from focal, clinically silent neuroinflammatory brain lesions and their discriminatory abilities to distinguish DTH animals from controls.

Methods

¹H nuclear magnetic resonance (NMR) spectroscopy metabolomics and NfL measurements were performed on serum and CSF at days 12, 28 and 60 after DTH lesion initiation. Supervised multivariate analyses were used to determine metabolomics differences between DTH animals and controls. Immunohistochemistry was used to assess the extent of neuroinflammation and tissue damage.

Results

Serum and CSF metabolomics perturbations were detectable in DTH animals (vs. controls) at all time points, with the greatest change occurring at the earliest time point (day 12) when the neuroinflammatory response was most intense (mean predictive accuracy [SD]—serum: 80.6 [10.7]%, p < 0.0001; CSF: 69.3 [13.5]%, p < 0.0001). The top discriminatory metabolites at day 12 (serum: allantoin, cytidine; CSF: glutamine, glucose) were all reduced in DTH animals compared to controls, and correlated with histological markers of neuroinflammation, particularly astrogliosis (Pearson coefficient, r—allantoin: r = − 0.562, p = 0.004; glutamine: r = − 0.528, p = 0.008). Serum and CSF NfL levels did not distinguish DTH animals from controls at day 12, rather, significant differences were observed at day 28 (mean [SEM]—serum: 38.5 [4.8] vs. 17.4 [2.6] pg/mL, p = 0.002; CSF: 1312.0 [379.1] vs. 475.8 [74.7] pg/mL, p = 0.027). Neither serum nor CSF NfL levels correlated with markers of neuroinflammation; serum NfL did, however, correlate strongly with axonal loss (r = 0.641, p = 0.001), but CSF NfL did not (p = 0.137).

Conclusions

While NfL levels were elevated later in the pathogenesis of the DTH lesion, serum and CSF metabolomics were able to detect early, clinically silent neuroinflammation and are likely to present sensitive biomarkers for the assessment of subclinical disease activity in patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-022-02614-8.

The potential roles of amino acids and their major derivatives in the management of multiple sclerosis

Recently, we reviewed the important role of carbohydrates and lipids metabolism in different clinical aspects of multiple sclerosis (MS) disease. In the current paper, we aimed to review the contribution of amino acids and their major derivatives to different clinical outcomes of the disease, including etiology, pathogenesis, diagnosis, prognosis, and treatment. In this line, Thr (threonine), Phe (phenylalanine), Glu (glutamate), Trp (tryptophan), and Sero (serotonin) are the main examples of biomolecules that have been suggested for MS therapy. It has been concluded that different amino acids and their derivatives might be considered prominent tools for the clinical management of MS disease.

Contribution of Metabolomics to Multiple Sclerosis Diagnosis, Prognosis and Treatment

Metabolomics-based technologies map in vivo biochemical changes that may be used as early indicators of pathological abnormalities prior to the development of clinical symptoms in neurological conditions. Metabolomics may also reveal biochemical pathways implicated in tissue dysfunction and damage and thus assist in the development of novel targeted therapeutics for neuroinflammation and neurodegeneration. Metabolomics holds promise as a non-invasive, high-throughput and cost-effective tool for early diagnosis, follow-up and monitoring of treatment response in multiple sclerosis (MS), in combination with clinical and imaging measures. In this review, we offer evidence in support of the potential of metabolomics as a biomarker and drug discovery tool in MS. We also use pathway analysis of metabolites that are described as potential biomarkers in the literature of MS biofluids to identify the most promising molecules and upstream regulators, and show novel, still unexplored metabolic pathways, whose investigation may open novel avenues of research.

Reactive Astrocytes: Critical Players in the Development of Chronic Pain

Chronic pain is associated with long term plasticity of nociceptive pathways in the central nervous system. Astrocytes can profoundly affect synaptic function and increasing evidence has highlighted how altered astrocyte activity may contribute to the pathogenesis of chronic pain. In response to injury, astrocytes undergo a shift in form and function known as reactive astrogliosis, which affects their release of cytokines and gliotransmitters. These neuromodulatory substances have been implicated in driving the persistent changes in central nociceptive activity. Astrocytes also release lactate which neurons can use to produce energy during synaptic plasticity. Furthermore, recent research has provided insight into lactate's emerging role as a signaling molecule in the central nervous system, which may be involved in directly modulating neuronal and astrocytic activity. In this review, we present evidence for the involvement of astrocyte-derived tumor necrosis factor alpha in pain-associated plasticity, in addition to research suggesting the potential involvement of gliotransmitters D-serine and adenosine-5'-triphosphate. We also discuss work implicating astrocyte-neuron metabolic coupling, and the possible role of lactate, which has been sparsely studied in the context of chronic pain, in supporting pathological changes in central nociceptive activity.

Mitochondrial dysfunction and serum lactate as a biomarker for the progression and disability in MS and its correlation with the radiological findings

Objective: To study the serum lactate level in MS and to explore its correlation with the progression and disability in multiple sclerosis (MS), and the important role of mitochondrial dysfunction in the pathogenesis of MS.Methods: This case-control study included 80 participants, involved 50 MS patients and 30 normal healthy controls. Detailed history taking, complete neurological examination, and clinical evaluation of the disability using the Expanded Disability Status Scale (EDSS) were done for all patients. Level of serum lactate was measured in both groups and was correlated with EDSS, MS subtypes, MRI brain, and MRS findings.Results: Serum lactate in MS patients was about three and half times higher than serum lactate levels of healthy controls (22.87 ± 5.92 mg/dl versus 6.39 ± 0.9 6.39 ± 0.91, p < 0.001). Importantly, serum lactate values were increased in MS cases with a progressive course compared with MS cases with RR course. Also, there were linearly correlations linking serum lactate levels and the duration of MS (r = 0.342, P = 0.015), relapses numbers (r = 0.335, P = 0.022), and EDSS (r = 0.483, P < 0.001). Also, there were strong positive correlations between serum lactate and Lipid/Lactate (r = 0.461, P = 0.001), periventricular lesion (r = 0.453, P = 0.005), and moderate positive correlations between serum lactate and juxtacortical lesion (r = 0.351, P = 0.02), and infratentorial lesion (r = 0.355, P = 0.02).Conclusion: Measurement of serum lactate may be helpful in MS and this supports the hypothesis of the critical role of mitochondrial dysfunction and axonal damage in MS.Registration of Clinical Trial Research: ClinicalTrials.gov ID: NCT04210960.

An emerging potential of metabolomics in multiple sclerosis: a comprehensive overview

Multiple sclerosis (MS) is an inflammatory demyelinating disease of the nervous system that primarily affects young adults. Although the exact etiology of the disease remains obscure, it is clear that alterations in the metabolome contribute to this process. As such, defining a reliable and disease-specific metabolome has tremendous potential as a diagnostic and therapeutic strategy for MS. Here, we provide an overview of studies aimed at identifying the role of metabolomics in MS. These offer new insights into disease pathophysiology and the contributions of metabolic pathways to this process, identify unique markers indicative of treatment responses, and demonstrate the therapeutic effects of drug-like metabolites in cellular and animal models of MS. By and large, the commonly perturbed pathways in MS and its preclinical model include lipid metabolism involving alpha-linoleic acid pathway, nucleotide metabolism, amino acid metabolism, tricarboxylic acid cycle, d-ornithine and d-arginine pathways with collective role in signaling and energy supply. The metabolomics studies suggest that metabolic profiling of MS patient samples may uncover biomarkers that will advance our understanding of disease pathogenesis and progression, reduce delays and mistakes in diagnosis, monitor the course of disease, and detect better drug targets, all of which will improve early therapeutic interventions and improve evaluation of response to these treatments.

Metabolomic Biomarkers of Multiple Sclerosis: A Systematic Review

Background

Magnetic resonance imaging (MRI), cerebrospinal fluid (CSF) analysis, and the McDonald’s clinical criteria are currently utilized tools in diagnosing multiple sclerosis. However, a more conclusive, consistent, and efficient way of diagnosing multiple sclerosis (MS) is yet to be discovered. A potential biomarker, discovered using advances in high-throughput sequencing such as nuclear magnetic resonance (NMR) spectroscopy and other “Omics”-based techniques, may make diagnosis and prognosis more reliable resulting in a more personalized and targeted treatment regime and improved outcomes. The aim of this review was to systematically search the literature for potential biomarkers from any bodily fluid that could consistently and accurately diagnose MS and/or indicate disease progression.

Methods

A systematic literature review of EMBASE, PubMed (MEDLINE), The Cochrane Library, and CINAHL databases produced over a thousand potential studies. Inclusion criteria stated studies with potential biomarker outcomes for people with MS were to be included in the review. Studies were limited to those with human participants who had a clinically defined diagnosis of MS and published in English, with no limit placed on date of publication or the type of bodily fluid sampled.

Results

A total of 1,805 studies were recorded from the literature search. A total of 1,760 studies were removed based on their abstract, with a further 18 removed after considering the full text. A total of 30 studies were considered relevant and had their data retrieved and analyzed. Due to the heterogeneity of focus and results from the refined studies, a narrative synthesis was favored.

Conclusion

Several promising candidate biomarkers suitable for clinical application in MS have been studied. It is recommended follow-up studies with larger sample sizes be completed on several potential biomarkers.

The role of glial-neuronal metabolic cooperation in modulating progression of multiple sclerosis and neuropathic pain

While the etiology of multiple sclerosis (MS) remains unclear, research from the clinic and preclinical models identified the essential role of inflammation and demyelination in the pathogenesis of MS. Current treatments focused on anti-inflammatory processes are effective against acute episodes and relapsing-remitting MS, but patients still move on to develop secondary progressive MS. MS progression is associated with activation of microglia and astrocytes, and importantly, metabolic dysfunction leading to neuronal death. Neuronal death also contributes to chronic neuropathic pain. Metabolic support of neurons by glia may play central roles in preventing progression of MS and chronic neuropathic pain. Here, we review mechanisms of metabolic cooperation between glia and neurons and outline future perspectives exploring metabolic support of neurons by glia.

Evaluation of serum arsenic and its effects on antioxidant alterations in relapsing-remitting multiple sclerosis patients

BACKGROUND

Environmental factors that are involved in the development of autoimmune diseases include bacteria, viruses, and xenobiotics such as chemicals, drugs, and metals. Regarding the metals, a number of studies have demonstrated that oxidative stress is one of the well-directed pathways of arsenic-induced tissue damages. This study was designed to explore the serum concentrations of arsenic and its correlation with markers associated with oxidative stress in relapsing-remitting MS (RRMS) patients.

METHODS

This case-controlled study comprised 50 patients with RRMS and 50 healthy subjects. Serum arsenic levels, total antioxidant potential, malondialdehyde (MDA), and lactate levels were measured.

RESULTS

The arsenic value, MDA, and lactate levels were elevated meaningfully while FRAP level significantly was decreased in RRMS patients with respect to healthy subjects (P <0.05). Furthermore, arsenic serum levels were positively correlated with serum concentrations of MDA and lactate. In contrast, serum levels were negatively correlated to FRAP values in RRMS patients.

CONCLUSION

Taken together, the association between arsenic level and oxidative stress parameters supports the hypothesis that high serum arsenic levels may play a critical role in the pathogenesis of MS progression.

CSF profile in primary progressive multiple sclerosis: Re-exploring the basics

Objective

The aim of this study was to report the basic cerebrospinal fluid (CSF) profile in patients with primary progressive multiple sclerosis (PPMS).

Methods

The results of CSF analysis from 254 patients with PPMS were collected at four university hospitals in Germany. Routine CSF parameters and different indices of intrathecal immunoglobulin synthesis were evaluated. We assessed possible correlations between the various CSF parameters and the expanded disability status scale (EDSS) both at the time of lumbar puncture and during the course of the disease.

Results

The median cell count and albumin concentration in the CSF did not deviate from normal values. The CSF-serum albumin-quotient (Q_ALB) was elevated in 29.6% of the patients, while intrathecal immunoglobulin G (IgG) oligoclonal bands (OCBs) were detected in 91.1% of the patients. CSF-lactate levels as well as local IgM- and IgA-synthesis were correlated with the yearly disease progression rate, as assessed by EDSS.

Conclusion

We present the results of the hitherto largest and most detailed CSF biomarker profile in a cohort of 254 patients with PPMS. As reported previously, OCBs are the most sensitive marker for intrathecal IgG synthesis. CSF-lactate concentrations are positively correlated with the progression rate, which might suggest that mitochondrial dysfunction plays a relevant role in PPMS. The negative correlation between intrathecally produced IgM and IgA and disease progression may indicate their hitherto unexplored protective role.

Age-Related 1H NMR Characterization of Cerebrospinal Fluid in Newborn and Young Healthy Piglets

When it comes to neuroscience, pigs represent an important animal model due to their resemblance with humans’ brains for several patterns including anatomy and developmental stages. Cerebrospinal fluid (CSF) is a relatively easy-to-collect specimen that can provide important information about neurological health and function, proving its importance as both a diagnostic and biomedical monitoring tool. Consequently, it would be of high scientific interest and value to obtain more standard physiological information regarding its composition and dynamics for both swine pathology and the refinement of experimental protocols. Recently, proton nuclear magnetic resonance (¹H NMR) spectroscopy has been applied in order to analyze the metabolomic profile of this biological fluid, and results showed the technique to be highly reproducible and reliable. The aim of the present study was to investigate in both qualitative and quantitative manner the composition of Cerebrospinal Fluid harvested form healthy newborn (5 days old-P5) and young (30-P30 and 50-P50 days old) piglets using ¹H NMR Spectroscopy, and to analyze any possible difference in metabolites concentration between age groups, related to age and Blood-Brain-Barrier maturation. On each of the analyzed samples, 30 molecules could be observed above their limit of quantification, accounting for 95–98% of the total area of the spectra. The concentrations of adenine, tyrosine, leucine, valine, 3-hydroxyvalerate, 3-methyl-2-oxovalerate were found to decrease between P05 and P50, while the concentrations of glutamine, creatinine, methanol, trimethylamine and myo-inositol were found to increase. The P05-P30 comparison was also significant for glutamine, creatinine, adenine, tyrosine, leucine, valine, 3-hydroxyisovalerate, 3-methyl-2-oxovalerate, while for the P30-P50 comparison we found significant differences for glutamine, myo-inositol, leucine and trimethylamine. None of these molecules showed at P30 concentrations outside the P05 –P50 range.

Cerebrospinal fluid lactate is associated with multiple sclerosis disease progression

BACKGROUND

Altered cerebrospinal fluid (CSF) levels of lactate have been described in neurodegenerative diseases and related to mitochondrial dysfunction and neuronal degeneration. We investigated the relationship between CSF lactate levels, disease severity, and biomarkers associated with neuroaxonal damage in patients with multiple sclerosis (MS).

METHODS

One-hundred eighteen subjects with relapsing-remitting multiple sclerosis (RRMS) were included, along with one-hundred fifty seven matched controls. CSF levels of lactate, tau protein, and neurofilament light were detected at the time of diagnosis. Patients were followed-up for a mean of 5 years. Progression index (PI), multiple sclerosis severity scale (MSSS), and Bayesian risk estimate for multiple sclerosis (BREMS) were assessed as clinical measures of disease severity and progression. Differences between groups and correlation between CSF lactate, disease severity and CSF biomarkers of neuronal damage were explored.

RESULTS

CSF lactate was higher in RRMS patients compared to controls. A negative correlation was found between lactate levels and disease duration. Patients with higher CSF lactate concentration had significantly higher PI, MSSS, and BREMS scores at long-term follow-up. Furthermore, CSF lactate correlated positively and significantly with CSF levels of both tau protein and neurofilament light protein.

CONCLUSIONS

Measurement of CSF lactate may be helpful, in conjunction with other biomarkers of tissue damage, as an early predictor of disease severity in RRMS patients. A better understanding of the alterations of mitochondrial metabolic pathways associated to RRMS severity may pave the way to new therapeutic targets to contrast axonal damage and disease severity.

The Glutamine Transporters and Their Role in the Glutamate/GABA-Glutamine Cycle

Glutamine is a key amino acid in the CNS, playing an important role in the glutamate/GABA-glutamine cycle (GGC). In the GGC, glutamine is transferred from astrocytes to neurons, where it will replenish the inhibitory and excitatory neurotransmitter pools. Different transporters participate in this neural communication, i.e., the transporters responsible for glutamine efflux from astrocytes and influx into the neurons, such as the members of the SNAT, LAT, y⁺LAT, and ASC families of transporters. The SNAT family consists of the transporter isoforms SNAT3 and SNAT5 that are related to efflux from the astrocytic compartment, and SNAT1 and SNAT2 that are associated with glutamine uptake into the neuronal compartment. The isoforms SNAT7 and SNAT8 do not have their role completely understood, but they likely also participate in the GGC. The isoforms LAT2 and y⁺LAT2 facilitate the exchange of neutral amino acids and cationic amino acids (y⁺LAT2 isoform) and have been associated with glutamine efflux from astrocytes. ASCT2 is a Na⁺-dependent antiporter, the participation of which in the GGC also remains to be better characterized. All these isoforms are tightly regulated by transcriptional and translational mechanisms, which are induced by several determinants such as amino acid deprivation, hormones, pH, and the activity of different signaling pathways. Dysfunctional glutamine transporter activity has been associated with the pathophysiological mechanisms of certain neurologic diseases, such as Hepatic Encephalopathy and Manganism. However, there might also be other neuropathological conditions associated with an altered GGC, in which glutamine transporters are dysfunctional. Hence, it appears to be of critical importance that the physiological and pathological aspects of glutamine transporters are thoroughly investigated.

(1)H-NMR analysis provides a metabolomic profile of patients with multiple sclerosis

Objective:

To investigate the metabolomic profiles of patients with multiple sclerosis (MS) and to define the metabolic pathways potentially related to MS pathogenesis.

Methods:

Plasma samples from 73 patients with MS (therapy-free for at least 90 days) and 88 healthy controls (HC) were analyzed by ¹H-NMR spectroscopy. Data analysis was conducted with principal components analysis followed by a supervised analysis (orthogonal partial least squares discriminant analysis [OPLS-DA]). The metabolites were identified and quantified using Chenomx software, and the receiver operating characteristic (ROC) curves were calculated.

Results:

The model obtained with the OPLS-DA identified predictive metabolic differences between the patients with MS and HC (R2X = 0.615, R2Y = 0.619, Q2 = 0.476; p < 0.001). The differential metabolites included glucose, 5-OH-tryptophan, and tryptophan, which were lower in the MS group, and 3-OH-butyrate, acetoacetate, acetone, alanine, and choline, which were higher in the MS group. The suitability of the model was evaluated using an external set of samples. The values returned by the model were used to build the corresponding ROC curve (area under the curve of 0.98).

Conclusion:

NMR metabolomic analysis was able to discriminate different metabolic profiles in patients with MS compared with HC. With the exception of choline, the main metabolic changes could be connected to 2 different metabolic pathways: tryptophan metabolism and energy metabolism. Metabolomics appears to represent a promising noninvasive approach for the study of MS.

Metabolomic profiling in multiple sclerosis: insights into biomarkers and pathogenesis

Metabolomics enables the provision of sensitive bio-markers of disease. We performed 800 MHz 1H-nuclear magnetic resonance (NMR) spectroscopic analyses of cerebrospinal fluid (CSF) specimens to identify biomarkers of multiple sclerosis (MS), yielding reproducible detection of 15 metabolites from MS ( n=15) and non-MS ( n=17) patients. Mean levels of choline, myo-inositol and threonate were increased, whereas 3-hydroxybutyrate, citrate, phenylalanine, 2-hydroxyisovalerate and mannose were decreased in MS-derived CSF ( p<0.05), suggesting alterations to energy and phospholipid metabolism. Multivariate hierarchal cluster analysis indicated a high correlation within the metabolite profiles, significantly clustering samples into the two clinical groups, which was corroborated using principal components analysis. CSF metabolomics have the capacity to yield quantitative biomarkers and insights into the pathogenesis of MS.

Determination of metabolic organic acids in cerebrospinal fluid by microchip electrophoresis

A new MCE method for the determination of oxalic, citric, glycolic, lactic, and 2- and 3-hydroxybutyric acids, indicators of some metabolic and neurological diseases, in cerebrospinal fluid (CSF) was developed. MCE separations were performed on a PMMA microchip with coupled channels at lower pH (5.5) to prevent proteins interference. A double charged counter-ion, BIS-TRIS propane, was very effective in resolving the studied organic acids. The limits of detection (S/N = 3) ranging from 0.1 to 1.6 μM were obtained with the aid of contact conductivity detector implemented directly on the microchip. RSDs for migration time and peak area of organic acids in artificial and CSF samples were <0.8 and <9.7%, respectively. Recoveries of organic acids in untreated CSF samples on the microchip varied from 91 to 104%. Elimination of chloride interference, a major anionic constituent of CSF, has been reached by two approaches: (i) the use of coupled channels microchip in a column switching mode when approximately 97-99% of chloride was removed electrophoretically in the first separation channel and (ii) the implementation of micro-SPE with silver-form resin prior to the MCE analysis, which selectively removed chloride from undeproteinized CSF samples.

The 1H NMR profile of healthy dog cerebrospinal fluid

The availability of data for reference values in cerebrospinal fluid for healthy humans is limited due to obvious practical and ethical issues. The variability of reported values for metabolites in human cerebrospinal fluid is quite large. Dogs present great similarities with humans, including in cases of central nervous system pathologies. The paper presents the first study on healthy dog cerebrospinal fluid metabolomic profile using ¹H NMR spectroscopy. A number of 13 metabolites have been identified and quantified from cerebrospinal fluid collected from a group of 10 mix breed healthy dogs. The biological variability as resulting from the relative standard deviation of the physiological concentrations of the identified metabolites had a mean of 18.20% (range between 9.3% and 44.8%). The reported concentrations for metabolites may be used as normal reference values. The homogeneity of the obtained results and the low biologic variability show that the ¹H NMR analysis of the dog’s cerebrospinal fluid is reliable in designing and interpreting clinical and therapeutic trials in dogs with central nervous system pathologies.

Axonal damage in multiple sclerosis

Multiple sclerosis is a debilitating disease of the central nervous system that has been characteristically classified as an immune-mediated destruction of myelin, the protective coating on nerve fibers. Although the mechanisms responsible for the immune attack to central nervous system myelin have been the subject of intense investigation, more recent studies have focused on the neurodegenerative component, which is cause of clinical disability in young adults and appears to be only partially controlled by immunomodulatory therapies. Here, we review distinct, but not mutually exclusive, mechanisms of pathogenesis of axonal damage in multiple sclerosis patients that are either consequent to long-term demyelination or independent from it. We propose that the complexity of axonal degeneration and the heterogeneity of the underlying pathogenetic mechanisms should be taken into consideration for the design of targeted therapeutic intervention.

High-resolution nuclear magnetic resonance spectroscopic study of metabolites in the cerebrospinal fluid of patients with cervical myelopathy and lumbar radiculopathy

There have been few reports describing substances related to oxidative and intermediary metabolism in the cerebrospinal fluid (CSF) in patients with spinal degenerative disorders. This study investigated whether the concentrations of metabolites in the CSF differed between patients with spinal degenerative disorders and controls, and whether the concentrations of these metabolites correlated with the severity of symptoms. CSF samples were obtained from 30 patients with cervical myelopathy (Group M), 30 patients with lumbar radiculopathy (Group R), and 10 volunteers (control). Metabolites in these CSF samples were measured by nuclear magnetic resonance spectroscopy. There were no differences in the concentrations of lactate, alanine, acetate, glutamate, pyruvate, or citrate between Groups M and R, between Group M and the control, or between Group R and the control. In Group M, neither symptom duration nor the Japanese Orthopaedic Association score correlated with the concentration of any metabolite. In Group R, the symptom duration positively correlated with the concentration of lactate, glutamate, and citrate in CSF. The duration of nerve root block showed a negative correlation with the concentrations of acetate in CSF of the patients in Group R. In patients with lumbar radiculopathy, there is a possibility of increased aerobic metabolic activity or decreased gluconeogenic activity in patients with shorter symptom duration, and increased aerobic metabolic activity in patients with severe inflammation around a nerve root.

Cerebrospinal fluid evidence of increased extra-mitochondrial glucose metabolism implicates mitochondrial dysfunction in multiple sclerosis disease progression

In contrast to relapse, the mechanisms of multiple sclerosis (MS) disease progression are less understood and appear not to be exclusively inflammatory in nature. In this pilot study we investigated the relationship between disturbed CNS energy metabolism and MS disease progression. We tested the hypothesis that cerebrospinal fluid (CSF) concentrations of sorbitol, fructose, and lactate, all metabolites of extra-mitochondrial glucose metabolism, would be elevated in secondary progressive (SP) MS patients and would be associated with worsening neurologic disability. We measured metabolite concentrations by gas chromatographic/mass spectrometric and enzymatic methods in archived CSF samples from 85 MS patients [31 relapsing-remitting (RR) and 54 SP patients] and 18 healthy controls. We found that concentrations of all three metabolites, but not concentrations of glucose or myoinositol, were significantly increased in CSF from SP and, to a lesser degree, RR patients, compared to controls. Furthermore, CSF concentrations of sorbitol and fructose (polyol pathway metabolites), but not lactate (anaerobic glycolysis metabolite), correlated positively and significantly with Expanded Disability Status Scale (EDSS) score, an index of neurologic disability in MS patients. We conclude that extra-mitochondrial glucose metabolism is increased in MS patients and is associated with disease progression evidenced by increasing EDSS score. As extra-mitochondrial glucose metabolism increases with impaired mitochondrial metabolism of glucose, these findings implicate mitochondrial dysfunction in the pathogenesis of MS disease progression. CSF metabolic profiling may be useful in clarifying the role of mitochondrial pathology in progression and in targeting and monitoring therapies for disease progression that aim to preserve or boost mitochondrial glucose metabolism.

Inflammatory multiple-sclerosis plaques generate characteristic metabolic profiles in cerebrospinal fluid

Background

Multiple sclerosis (MS), an inflammatory disease of the central nervous system, manifests itself in numerous forms and stages. A number of brain metabolic alterations have been reported for MS patients vs. control subjects. However, metabolite profiles of cerebrospinal fluid (CSF) are not consistent among the published MS studies, most probably due to variations in the patient cohorts studied. We undertook the first investigation of highly homogeneous MS patient cohorts to determine characteristic effects of inflammatory MS plaques on the CSF metabolome, including only patients with clinically isolated syndrome (CIS) with or without inflammatory brain plaques, and controls.

Methodology/Principal Findings

CSF obtained by lumbar puncture was analyzed by proton magnetic resonance spectroscopy. 27 metabolites were quantified. Differences between groups of control subjects (n = 10), CIS patients with (n = 21) and without (n = 12) inflammatory plaques were evaluated by univariate statistics and principal component analysis (PCA). Seven metabolites showed statistically significant inter-group differences (p<0.05). Interestingly, a significant increase in β-hydroxyisobutyrate (BHIB) was detected in CIS with vs. without active plaques, but not when comparing either CIS group with control subjects. Moreover, a significant correlation was found, for the first time, between CSF lactate concentration and the number of inflammatory MS brain plaques. In contrast, fructose concentrations were equally enhanced in CIS with or without active plaques. PCA based on all 27 metabolites yielded group-specific clusters.

Conclusions/Significance

CSF metabolic profiles suggest a close link between MS plaque activity in CIS patients on the one hand and organic-acid metabolism on the other. Our detection of increased BHIB levels points to a hitherto unsuspected role for this compound in MS with active plaques, and serves as a basis for further investigation. The metabolic effects described in our study are crucial elements in the explanation of biochemical mechanisms involved in specific MS manifestations.

Analytical strategies in metabonomics

To perform metabonomics investigations, it is necessary to generate comprehensive metabolite profiles for complex samples such as biofluids and tissue/tissue extracts. Analytical technologies that can be used to achieve this aim are constantly evolving, and new developments are changing the way in which such profiles' metabolite profiles can be generated. Here, the utility of various analytical techniques for global metabolite profiling, such as, e.g., 1H NMR, MS, HPLC-MS, and GC-MS, are explored and compared.

Cerebrospinal fluid from patients with dementia contains increased amounts of an unknown factor

Increased levels of an unidentified peak have been found in cerebrospinal fluid (CSF) from patients with Alzheimer's disease or vascular dementia compared to the level in healthy controls using proton magnetic resonance spectroscopy. No increase was found in patients with amyotrophic lateral sclerosis. Reexamination of spectra from a study published previously (Gårseth et al. [2000] J. Neurosci. Res. 60:779-782), however, shows that this peak was also elevated significantly in CSF from patients with Huntington's disease compared to that in controls. The level in patients with Parkinson's disease, where dementia develops in up to 40% of patients, was not elevated significantly compared to that in controls. To the best of our knowledge, this peak has not yet been identified and we therefore find it appropriate to temporarily designate the name "dementia associated factor" (DAF), although there is as yet no certainty that this substance is specific for these conditions. Apart from a significantly increased level of glutamine in CSF from patients with vascular dementia compared to that in controls, no other significant difference was found for any other metabolite measured in the patient groups using proton magnetic resonance spectroscopy.

Astrocytic beta2-adrenergic receptors and multiple sclerosis

Despite intensive research, the cause and a cure of multiple sclerosis (MS) have remained elusive and many aspects of the pathogenesis are not understood. Immunohistochemical experiments have shown that astrocytic beta(2)-adrenergic receptors are lost in MS. Because norepinephrine mediates important supportive and protective actions of astrocytes via activation of these beta(2)-adrenergic receptors, we postulate that this abnormality may play a prominent role in the pathogenesis of MS. First, it may allow astrocytes to act as facultative antigen-presenting cells, thereby initiating T-cell mediated inflammatory responses that lead to the characteristic demyelinated lesions. Second, it may contribute to inflammatory injury by stimulating the production of nitric oxide and proinflammatory cytokines, and reducing glutamate uptake. Third, it may lead to apoptosis of oligodendrocytes by reducing the astrocytic production of trophic factors, including neuregulin, nerve growth factor and brain-derived neurotrophic factor. Fourth, it may impair astrocytic glycogenolysis, which supplies energy to axons, and this may represent a mechanism underlying axonal degeneration that is hold responsible for the progressive chronic disability.

Nanoprobe NMR spectroscopy and in vivo microdialysis: new analytical methods to study brain neurochemistry

Nuclear magnetic resonance (NMR) spectroscopy was used to study the chemical composition of cerebrospinal fluid (CSF) microdialysate from the rat brain. In vivo microdialysis techniques were used in several brain regions including the frontal cortex, amygdala, striatum, nucleus accumbens and third ventricle and dialysate samples (20microl) were subsequently analyzed by one and two-dimensional 1H NMR experiments using a Varian nanoprobe. Neurochemical resonances were assigned on the basis of published chemical shifts [Lindon et al., Ann. Rep. NMR Spectrosc. 38 (1999) 1-88], correlation experiments and addition of standard compounds. Glucose, lactate, formate, pyruvate, creatinine, gamma-hydroxybutyrate, acetate, glutamate, glycine, tyrosine, isoleucine, leucine, alanine and choline were some of the neurochemicals unambiguously assigned. Additional studies in the frontal cortex showed that amino acids such as glutamate, alanine and isoleucine were sensitive to local tetrodotoxin (TTX) infusion. The NMR spectra were also subjected to multivariate statistical methods to compare the different brain regions examined. To our knowledge, the present experiments are the first to describe the combination of nanoprobe NMR technology with in vivo microdialysis for the analysis of brain neurochemistry in freely-moving rats.

Peroxisome proliferator-activated receptor gamma thiazolidinedione agonists increase glucose metabolism in astrocytes

Activation of peroxisome proliferator-activated receptors (PPARs) can regulate brain physiology and provide protection in models of neurological disease; however, neither their exact targets nor mechanisms of action in brain are known. In many cells, PPAR gamma agonists increase glucose uptake and metabolism. Because astrocytes store glucose and provide lactate to neurons on demand, we tested effects of PPAR gamma agonists on astroglial glucose metabolism. Incubation of cortical astrocytes with the PPAR gamma thiazolidinedione (TZD) agonist pioglitazone (Pio) significantly increased glucose consumption in a time- and dose-dependent manner, with maximal increase of 36% observed after 4 h in 30 microm Pio. Pio increased 2-deoxy-glucose uptake because of increased flux through the type 1 glucose transporter. However, at this time point Pio did not increase type 1 glucose transporter expression, nor were its effects blocked by transcriptional or translational inhibitors. Pio also increased astrocyte lactate production as soon as 3 h after incubation. These effects were replicated by other TZDs; however, the order of efficacy (troglitazone > pioglitazone > rosiglitazone) suggests that effects were not mediated via PPAR gamma activation. TZDs increased astrocyte cAMP levels, and their glucose modifying effects were reduced by protein kinase A inhibitors. TZDs inhibited state III respiration in isolated brain mitochondria, whereas in astrocytes they caused mitochondrial membrane hyperpolarization. Pio protected astrocytes against hypoglycemia-induced cell death. Finally, glucose uptake was modified in brain sections prepared from Pio-fed rats. These results demonstrate that TZDs modify astrocyte metabolism and mitochondrial function, which could be beneficial in neurological conditions where glucose availability is reduced.

Proton magnetic resonance spectroscopy of cerebrospinal fluid in neurodegenerative disease: indication of glial energy impairment in Huntington chorea, but not Parkinson disease

Metabolite levels in cerebrospinal fluid from patients with Parkinson disease or Huntington chorea were compared with the levels in healthy controls using proton magnetic resonance spectroscopy. No significant differences were found for any metabolite measured in cerebrospinal fluid from patients with Parkinson disease compared to controls. Slight but significantly reduced levels of both lactate and citrate, however, were found in cerebrospinal fluid from patients with Huntington chorea compared to controls. This suggests possible impairment of both glycolysis and tricarboxylic acid cycle function. The reduction in lactate found in the present study may reflect neuronal loss. The decrease in citrate supports the theory of mitochondrial dysfunction in the brain of patients with Huntington chorea, but also suggests that there may be an important astrocytic component in this disease. If so, it would certainly have implications for neuronal function.

Elevated serum and CSF levels of soluble CD30 during clinical remission in multiple sclerosis

OBJECTIVE

To ascertain the presence of the Th2 response in MS patients by evaluating the level of soluble (s) CD30 across the clinical spectrum of MS and during relapse and remission.

BACKGROUND

MS is considered a T-cell-mediated disorder with the immune attack dominated by a Thl cytokine response. Elevated levels of sCD30 have been associated with CD4+ cells that secrete Th2-type cytokines.

METHODS

Levels of sCD30 were determined in the serum and CSF of patients with primary progressive MS, secondary progressive MS, relapsing-remitting MS (RRMS), both in relapse and remission, and in patients with other inflammatory neurologic disease (IND) and noninflammatory neurologic disease (NIND). None of the patients were on immunomodulatory treatment.

RESULTS

Higher serum levels of sCD30 were detected in all MS subgroups and IND patients compared with NIND patients. RRMS patients in remission had significantly higher levels than those in relapse (median, 45.7 U/mL versus 18.3 U/mL; p = 0.04). Significantly higher CSF levels were also found in all groups, except those with RRMS in relapse compared with NIND patients. Again, RRMS patients in remission had higher CSF sCD30 levels compared with those in relapse (median, 4.0 U/mL versus 3.0 U/mL; p = 0.08).

CONCLUSIONS

Serum and CSF levels of sCD30 are increased in MS, particularly during remission. The results provide additional evidence for the presence of a Th2 response and indicate that sCD30 may be of value as a marker of lesion resolution.