Interactions of catecholamines and GABA+ in cognitive control: Insights from EEG and 1H-MRS

Catecholamines and amino acid transmitter systems are known to interact, the exact links and their impact on cognitive control functions have however remained unclear. Using a multi-modal imaging approach combining EEG and proton-magnetic resonance spectroscopy (1H-MRS), we investigated the effect of different degrees of pharmacological catecholaminergic enhancement onto theta band activity (TBA) as a measure of interference control during response inhibition and execution. It was central to our study to evaluate the predictive impact of in-vivo baseline GABA+ concentrations in the striatum, the anterior cingulate cortex (ACC) and the supplemental motor area (SMA) of healthy adults under varying degrees of methylphenidate (MPH) stimulation. We provide evidence for a predictive interrelation of baseline GABA+ concentrations in cognitive control relevant brain areas onto task-induced TBA during response control stimulated with MPH. Baseline GABA+ concentrations in the ACC, the striatum, and the SMA had a differential impact on predicting interference control-related TBA in response execution trials. GABA+ concentrations in the ACC appeared to be specifically important for TBA modulations when the cognitive effort needed for interference control was high - that is when no prior task experience exists, or in the absence of catecholaminergic enhancement with MPH. The study highlights the predictive role of baseline GABA+ concentrations in key brain areas influencing cognitive control and responsiveness to catecholaminergic enhancement, particularly in high-effort scenarios.

The effectiveness of vortioxetine on neurobiochemical metabolites and cognitive of major depressive disorders patients: A 8-week follow-up study

OBJECTIVE

Vortioxetine has been shown to improve cognitive performance in people with depression. This study will look at the changes in neurobiochemical metabolites that occur when vortioxetine improves cognitive performance in MDD patients, with the goal of determining the neuroimaging mechanism through which vortioxetine improves cognitive function.

METHODS

30 depressed patients and 30 demographically matched healthy controls (HC) underwent MCCB cognitive assessment and 1H-MRS. After 8 weeks of vortioxetine medication, MCCB and 1H-MRS tests were retested in the MDD group. Before and after therapy, changes in cognitive performance, NAA/Cr, and Cho/Cr were examined in the MDD group.

RESULTS

Compared with the HC group, the MDD group had significant reduced in verbal learning, social cognition, and total cognition (all p < 0.05). And the MDD group had lower NAA/Cr in Right thalamus and Left PFC; the Cho/Cr in Right thalamus was lower than HC; the Cho/Cr in Left ACC had significantly increase (all p < 0.05). The MDD group showed significant improvements in the areas of verbal learning, attention/alertness, and total cognitive function before and after Vortioxetine treatment (all p < 0.05). The NAA/Cr ratio of the right PFC before and after treatment (t = 2.338, p = 0.026) showed significant changes.

CONCLUSIONS

Vortioxetine can enhance not just the depression symptoms of MDD patients in the initial period, but also their verbal learning, social cognition, and general cognitive capacities after 8 weeks of treatment. Furthermore, vortioxetine has been shown to enhance cognitive function in MDD patients by altering NAA/Cr and Cho/Cr levels in the frontal-thalamic-ACC.

Greater Choline-Containing Compounds and Myo-inositol in Treatment-Resistant Versus Responsive Schizophrenia: A 1H-Magnetic Resonance Spectroscopy Meta-analysis

BACKGROUND

The neurobiology of treatment-resistant schizophrenia (TRS) is poorly understood, and meta-analytic consensus regarding magnetic resonance spectroscopic profiles of glutamate, choline-containing compounds, myo-inositol, and other metabolites in the condition is lacking.

METHODS

In this meta-analysis, we examined published findings for N-acetylaspartate, choline-containing compounds (phosphocholine+glycerophosphocholine), myo-inositol, creatine+phosphocreatine, glutamate, and glutamate+glutamine in the anterior cingulate cortex and dorsal striatum in people with TRS versus non-TRS as well as TRS versus healthy control participants (HCs) and TRS versus ultra TRS (i.e., TRS with clozapine resistance). A MEDLINE search revealed 9 articles including 239 people with pooled TRS and ultra TRS, 59 with ultra TRS, 175 with non-TRS, and 153 (HCs) that met meta-analytic criteria.

RESULTS

Significant effects included higher anterior cingulate cortex phosphocholine+glycerophosphocholine and myo-inositol in the pooled TRS and ultra TRS group than in both the non-TRS group and HCs as well as higher dorsal striatal phosphocholine+glycerophosphocholine in ultra TRS versus HCs, but no differences in other regional metabolites.

CONCLUSIONS

The observed metabolite profile in TRS (higher phosphocholine+glycerophosphocholine and myo-inositol signal) is consistent with the hypothesis that TRS has a neuroinflammatory component, although this meta-analysis is not a critical test of that hypothesis. A similar profile is seen in healthy aging, which is known to involve increased neuroinflammation and glial activation. Because the overall number of datasets was low, however, results should be considered preliminary and highlight the need for additional studies of brain metabolites in TRS and their possible association with inflammatory processes.

Multiparametric MR Evaluation of the Photoperiodic Regulation of Hypothalamic Structures in Sheep

Most organisms on earth, humans included, have developed strategies to cope with environmental day-night and seasonal cycles to survive. For most of them, their physiological and behavioral functions, including the reproductive function, are synchronized with the annual changes of day length, to ensure winter survival and subsequent reproductive success in the following spring. Sheep are sensitive to photoperiod, which also regulates natural adult neurogenesis in their hypothalamus. We postulate that the ovine model represents a good alternative to study the functional and metabolic changes occurring in response to photoperiodic changes in hypothalamic structures of the brain. Here, the impact of the photoperiod on the neurovascular coupling and the metabolism of the hypothalamic structures was investigated at 3T using BOLD fMRI, perfusion-MRI and proton magnetic resonance spectroscopy (1H-MRS). A longitudinal study involving 8 ewes was conducted during long days (LD) and short days (SD) revealing significant BOLD, rCBV and metabolic changes in hypothalamic structures of the ewe brain between LD and SD. More specifically, the transition between LD and SD revealed negative BOLD responses to hypercapnia at the beginning of SD period followed by significant increases in BOLD, rCBV, Glx and tNAA concentrations towards the end of the SD period. These observations suggest longitudinal mechanisms promoting the proliferation and differentiation of neural stem cells within the hypothalamic niche of breeding ewes. We conclude that multiparametric MRI studies including 1H-MRS could be promising non-invasive translational techniques to investigate the existence of natural adult neurogenesis in-vivo in gyrencephalic brains.

Assessment of neurotransmitter imbalances within the anterior cingulate cortex in women with primary dysmenorrhea: An initial proton magnetic resonance spectroscopy study

PURPOSE

The neural pathophysiology underlying primary dysmenorrhea (PDM), which leads to poor mode and changes in central pain modulatory systems, remains largely unknown. The objective of this study was to investigate the changes in glutamate/glutamine (Glx) and gamma-aminobutyric acid (GABA+) levels within anterior cingulate cortex (ACC), and their associations with clinical indicators in PDM women.

METHODS

Using 3 T proton magnetic resonance spectroscopy (1H-MRS), we acquired and compared ACC-Glx and ACC-GABA+ levels in PDMs (N = 41) and age- and education-matched healthy controls (HCs) (N = 39) during both the menstrual and periovulatory phases, and between menstrual and periovulatory phases within each group. Total creatine (Cr referencing) level was used as an endogenous reference. The correlations of ACC-neurotransmitter levels with clinical characteristics and the correlations of ACC-Glx with ACC-GABA+ levels in the two groups were analyzed.

RESULTS

Compared to HCs or the periovulatory phase, PDMs exhibited significantly increased ACC-Glx levels (p < 0.05) during the menstrual phase. Positive correlations between GABA+ and Glx levels (r = 0.385, p = 0.025) were found in PDMs during the menstrual phase. ACC-GABA+ levels were associated with self-rating distress scale (SDS) scores (GABA+/Cr: r = 0.369, p = 0.045) and pain catastrophizing scale (PCS) scores (GABA+/Cr: r = 0.373, p = 0.042) in PDM group in only the menstrual phase.

CONCLUSION

Our study represents the first report of ACC-GABA+/Glx imbalances in PDMs during the menstrual phase, which may underlie the mechanisms mediating depression and painful catastrophic symptoms.

Neurometabolite changes in response to antidepressant medication: A systematic review of 1H-MRS findings

Selective serotonin reuptake inhibitors (SSRIs), serotonin and noradrenaline reuptake inhibitors (SNRIs), and (es)ketamine are used to treat major depressive disorder (MDD). These different types of medication may involve common neural pathways related to glutamatergic and GABAergic neurotransmitter systems, both of which have been implicated in MDD pathology. We conducted a systematic review of pharmacological proton Magnetic Resonance Spectroscopy (1H-MRS) studies in healthy volunteers and individuals with MDD to explore the potential impact of these medications on glutamatergic and GABAergic systems. We searched PubMed, Web of Science and Embase and included randomized controlled trials or cohort studies, which assessed the effects of SSRIs, SNRIs, or (es)ketamine on glutamate, glutamine, Glx or GABA using single-voxel 1H-MRS or Magnetic Resonance Spectroscopic Imaging (MRSI). Additionally, studies were included when they used a field strength > 1.5 T, and when a comparison of metabolite levels between antidepressant treatment and placebo or baseline with post-medication metabolite levels was done. We excluded animal studies, duplicate publications, or articles with 1H-MRS data already described in another included article. Twenty-nine studies were included in this review. Fifteen studies investigated the effect of administration or treatment with SSRIs or SNRIs, and fourteen studies investigated the effect of (es)ketamine on glutamatergic and GABAergic metabolite levels. Studies on SSRIs and SNRIs were highly variable, generally underpowered, and yielded no consistent findings across brain regions or specific populations. Although studies on (es)ketamine were also highly variable, some demonstrated an increase in glutamate levels in the anterior cingulate cortex in a time-dependent manner after administration. Our findings highlight the need for standardized study and acquisition protocols. Additionally, measuring metabolites dynamically over time or combining 1H-MRS with whole brain functional imaging techniques could provide valuable insights into the effects of these medications on glutamate and GABAergic neurometabolism.

The association between peripheral inflammation, brain glutamate and antipsychotic response in Schizophrenia: Data from the STRATA collaboration

Glutamate and increased inflammation have been separately implicated in the pathophysiology of schizophrenia and the extent of clinical response to antipsychotic treatment. Despite the mechanistic links between pro-inflammatory and glutamatergic pathways, the relationships between peripheral inflammatory markers and brain glutamate in schizophrenia have not yet been investigated. In this study, we tested the hypothesis that peripheral levels of pro-inflammatory cytokines would be positively associated with brain glutamate levels in schizophrenia. Secondary analyses determined whether this relationship differed according to antipsychotic treatment response. The sample consisted of 79 patients with schizophrenia, of whom 40 were rated as antipsychotic responders and 39 as antipsychotic non-responders. Brain glutamate levels were assessed in the anterior cingulate cortex (ACC) and caudate using proton magnetic resonance spectroscopy (1H-MRS) and blood samples were collected for cytokine assay on the same study visit (IL-6, IL-8, IL-10, TNF- α and IFN-γ). Across the whole patient sample, there was a positive relationship between interferon-gamma (IFN-γ) and caudate glutamate levels (r = 0.31, p = 0.02). In the antipsychotic non-responsive group only, there was a positive relationship between interleukin-8 (IL-8) and caudate glutamate (r = 0.46, p = 0.01). These findings provide evidence to link specific peripheral inflammatory markers and caudate glutamate in schizophrenia and may suggest that this relationship is most marked in patients who show a poor response to antipsychotic treatment.

Medial Frontal Cortex GABA Concentrations in Psychosis Spectrum and Mood Disorders: A Meta-analysis of Proton Magnetic Resonance Spectroscopy Studies

BACKGROUND

Abnormalities of GABAergic (gamma-aminobutyric acidergic) systems may play a role in schizophrenia and mood disorders. Magnetic resonance spectroscopy allows for noninvasive in vivo quantification of GABA; however, studies of GABA in schizophrenia have yielded inconsistent findings. This may stem from grouping together disparate voxels from functionally heterogeneous regions.

METHODS

We searched PubMed for magnetic resonance spectroscopy studies of GABA in the medial frontal cortex (MFC) in patients with schizophrenia, bipolar disorder, and depression and in individuals meeting criteria for ultra-high risk for psychosis. Voxel placements were classified as rostral-, rostral-mid-, mid-, or posterior MFC, and meta-analyses were conducted for each group for each subregion.

RESULTS

Of 341 screened articles, 23 studies of schizophrenia, 6 studies of bipolar disorder, 20 studies of depression, and 7 studies of ultra-high risk met the inclusion criteria. Meta-analysis revealed lower mid- (standardized mean difference [SMD] = -0.28, 95% CI, -0.48 to -0.07, p < .01) and posterior (SMD = -0.29, 95% CI, -0.49 to -0.09, p < .01) MFC GABA in schizophrenia and increased rostral MFC GABA in bipolar disorder (SMD = 0.76, 95% CI, 0.25 to -1.25, p < .01). In depression, reduced rostral MFC GABA (SMD = -0.36, 95% CI, -0.64 to -0.08, p = .01) did not survive correction for multiple comparisons. We found no evidence for GABA differences in individuals at ultra-high risk for psychosis.

CONCLUSIONS

While limited by small numbers of published studies, these results substantiate the relevance of GABA in the pathophysiology of psychosis spectrum and mood disorders and underline the importance of voxel placement.

Neurofunctional correlates of glutamate and GABA imbalance in psychosis: A systematic review

Glutamatergic and GABAergic dysfunction are implicated in the pathophysiology of schizophrenia. Previous work has shown relationships between glutamate, GABA, and brain activity in healthy volunteers. We conducted a systematic review to evaluate whether these relationships are disrupted in psychosis. Primary outcomes were the relationship between metabolite levels and fMRI BOLD response in psychosis relative to healthy volunteers. 17 case-control studies met inclusion criteria (594 patients and 538 healthy volunteers). Replicated findings included that in psychosis, positive associations between ACC glutamate levels and brain activity are reduced during resting state conditions and increased during cognitive control tasks, and negative relationships between GABA and local activation in the ACC are reduced. There was evidence that antipsychotic medication may alter the relationship between glutamate levels and brain activity. Emerging literature is providing insights into disrupted relationships between neurometabolites and brain activity in psychosis. Future studies determining a link to clinical variables may develop this approach for biomarker applications, including development or targeting novel therapeutics.

Association between CACNA1C gene rs100737 polymorphism and glutamatergic neurometabolites in bipolar disorder

Abnormalities in Ca²⁺ homeostasis in Bipolar Disorders (BD) have been associated with impairments in glutamatergic receptors and voltage-gated calcium channels. Increased anterior cingulate cortex (ACC) glutamatergic neurometabolites have been consistently disclosed in BD by proton magnetic resonance spectroscopy (¹H-MRS). A single nucleotide polymorphism (SNP) in the CACNA1C gene (rs1006737), which encodes the alpha 1-C subunit of the L-type calcium channel, has been associated with BD and is reported to modulate intra-cellular Ca²⁺. Thus, this study aimed to explore the association of the CACNA1C genotype with ACC glutamatergic metabolites measured by ¹H-MRS in both BD and HC subjects. A total of 194 subjects (121 euthymic BD type I patients and 73 healthy controls (HC) were genotyped for CACNA1C rs1006737, underwent a 3-Tesla ¹H-MRS imaging examination and ACC glutamatergic metabolite were assessed. We found overall increased glutamatergic metabolites in AA carriers in BD. Specifically, higher Glx/Cr was observed in subjects with the AA genotype compared to both AG and GG in the overall sample (BD + HC). Also, female individuals in the BD group with AA genotype were found to have higher Glx/Cr compared to those with other genotypes. CACNA1C AA carriers in use of anticonvulsant medication had higher estimated Glutamine (Glx-Glu) than the other genotypes. Thus, this study suggest an association between calcium channel genetics and increased glutamatergic metabolites in BD, possibly playing a synergic role in intracellular Ca²⁺ overload and excitotoxicity.

Neurometabolic patterns of an "at risk for mental disorders" syndrome involve abnormalities in the thalamus and anterior midcingulate cortex

BACKGROUND

The ultra-high risk (UHR) paradigm allows the investigation of individuals at increased risk of developing psychotic or other mental disorders with the aim of making prevention and early intervention as specific as possible in terms of the individual outcome.

METHODS

Single-session ¹H-/³¹P-Chemical Shift Imaging of thalamus, prefrontal (DLPFC) and anterior midcingulate (aMCC) cortices was applied to 69 UHR patients for psychosis and 61 matched healthy controls. N-acetylaspartate (NAA), glutamate/glutamine complex (Glx), energy (PCr, ATP) and phospholipid metabolites were assessed, analysed by ANOVA (or ANCOVA [with covariates]) and correlated with symptomatology (SCL-90R).

RESULTS

The thalamus showed decreased NAA, inversely correlated with self-rated aggressiveness, as well as increased PCr, and altered phospholipid breakdown. While the aMCC showed a pattern of NAA decrease and PCr increase, the DLPFC showed PCr increase only in the close-to-psychosis patient subgroup. There were no specific findings in transition patients.

CONCLUSION

The results do not support the notion of a specific pre-psychotic neurometabolic pattern, but likely reflect correlates of an "at risk for mental disorders syndrome". This includes disturbed neuronal (mitochondrial) metabolism in the thalamus and aMCC, with emphasis on left-sided structures, and altered PL remodeling across structures.

PET CMRglc mapping and 1H-MRS show altered glucose uptake and neurometabolic profiles in BDL rats

Type C hepatic encephalopathy (HE) is a complex neuropsychiatric disorder occurring as a consequence of chronic liver disease. Alterations in energy metabolism have been suggested in type C HE, but in vivo studies on this matter remain sparse and have reported conflicting results. Here, we propose a novel preclinical ¹⁸F-FDG PET methodology to compute quantitative 3D maps of the regional cerebral metabolic rate of glucose (CMR_glc) from a labelling steady-state PET image of the brain and an image-derived input function. This quantitative approach shows its strength when comparing groups of animals with divergent physiology, such as HE animals. PET CMR_glc maps were registered to an atlas and the mean CMR_glc from the hippocampus and the cerebellum were associated to the corresponding localized ¹H-MR spectroscopy acquisitions. This study provides for the first time local and quantitative information on both brain glucose uptake and neurometabolic profile alterations in a rat model of type C HE. A 2-fold lower brain glucose uptake, concomitant with an increase in brain glutamine and a decrease in the main osmolytes was observed in the hippocampus and in the cerebellum. These novel findings are an important step towards new insights into energy metabolism in the pathophysiology of HE.

Decreased brain GABA levels in patients with migraine without aura: an exploratory proton magnetic resonance spectroscopy study

Increasing neurophysiological studies had revealed that regional excitation-inhibition imbalance in the brain played a key role in the pathogenesis of migraine. This study aimed to explore the alterations in gamma-aminobutyric acid (GABA) and glutamate/glutamine complex (Glx) levels in the anterior cingulate gyrus (ACC) and medial prefrontal lobe (mPFC) of patients with migraine without aura (MWoA) and investigate the correlation between neurotransmitter levels and clinical indicators. A total of 28 patients with MWoA and 28 sex-, age-, and education level-matched healthy controls (HCs) underwent single-voxel proton magnetic resonance spectroscopy scanning at 3.0 Tesla. MEscher-Garwood Point RESolved Spectroscopy (MEGA-PRESS) sequence was performed to acquire the spectral data of GABA and Glx in the ACC and mPFC. The clinical indicators and anxiety-depression states of all participants were assessed. The acquired GABA signal contained the overlapping signals of macromolecules and homocarnosine, hence expressed as GABA+. The creatine (Cr) signal was applied as an endogenous reference. We observed that GABA+/Cr levels were significantly lower in ACC and mPFC of patients with MWoA than of HCs, with no significant difference in Glx levels. Negative correlations between GABA+/Cr levels and attack frequency were found in the ACC and mPFC regions of patients. These results suggested that there might be a close relationship between ACC and mPFC GABAergic neurons abnormalities and the pathophysiological mechanisms of MWoA. It might be beneficial to targeted treatment for patients with MWoA.

Reduced GABA levels in the medial prefrontal cortex are associated with cognitive impairment in patients with NMOSD

BACKGROUND

Cognitive impairment is a symptom present in part of patients with neuromyelitis optica spectrum disorder (NMOSD) and its pathophysiology is unknown. Dysfunction of the GABAergic/glutamatergic pathways involving inhibitory and excitatory neurotransmitters have been implicated in several neurological disorders. This study aimed to investigate the changes in inhibitory gamma-aminobutyric acid (GABA) and excitatory glutamate and glutamine (Glx) neurotransmitter levels and their correlations with cognitive functions in patients with NMOSD.

METHODS

A total of 29 patients with NMOSD and 28 sex-, age-, and education-matched healthy controls (HCs) were included in the study. All participants underwent clinical and cognitive assessments and proton magnetic resonance spectroscopy scanning. Meshcher-Garwood point-resolved spectroscopy was used to measure GABA and Glx levels in the medial prefrontal cortex (mPFC) and left thalamus. Total creatine (tCr) was applied as an internal reference. The GABA and Glx levels in the patient group were compared with those in HCs and correlated with cognitive scores and clinical variables.

RESULTS

Patients with NMOSD showed lower GABA+/tCr levels in the mPFC compared with HCs (P = 0.028). The GABA+/tCr levels in the mPFC were significantly associated with verbal memory performance (r = 0.462, P = 0.027) and overall cognition (r = 0.440, P = 0.035) in the NMOSD group. The GABA+/tCr levels in the left thalamus or Glx/tCr levels in both regions were not significantly different between groups, nor were they related to any cognitive domain in patients with NMOSD (all P values > 0.05).

CONCLUSION

The GABA+ levels in the mPFC decreased and correlated with cognitive dysfunction in patients with NMOSD, suggesting that the changes in regional GABA+ levels might be a potential metabolic feature of cognitive decline in patients with NMOSD.

Interictal pontine metabolism in migraine without aura patients: A 3 Tesla proton magnetic resonance spectroscopy study

In the pons, glutamatergic mechanisms are involved in regulating inhibitory descending pain modulation, serotoninergic neurotransmission as well as modulating the sensory transmission of the trigeminovascular system. Migraine involves altered pontine activation and structural changes, while biochemical, genetic and clinical evidence suggests that altered interictal pontine glutamate levels may be an important pathophysiological feature of migraine abetting to attack initiation. Migraine without aura patients were scanned outside attacks using a proton magnetic resonance spectroscopy protocol optimized for the pons at 3 Tesla. The measurements were performed on two separate days to increase accuracy and compared to similar repeated measurements in healthy controls. We found that interictal glutamate (i.e. Glx) levels in the pons of migraine patients (n = 33) were not different from healthy controls (n = 16) (p = 0.098), while total creatine levels were markedly increased in patients (9%, p = 0.009). There was no correlation of glutamate or total creatine levels to migraine frequency, days since the last attack, usual pain intensity of attacks or disease duration. In conclusion, migraine is not associated with altered interictal pontine glutamate levels. However, the novel finding of increased total creatine levels suggests that disequilibrium in the pontine energy metabolism could be an important feature of migraine pathophysiology.

Altered brain creatine cycle metabolites in bipolar I disorder with childhood abuse: A 1H magnetic resonance spectroscopy study

BACKGROUND

Childhood abuse (CA) is a risk factor for a number of psychiatric disorders and has been associated with higher risk of developing bipolar disorders (BD). CA in BD has been associated with more severe clinical outcomes, but the neurobiological explanation for this is unknown. Few studies have explored in vivo measurement of brain metabolites using proton magnetic resonance spectroscopy (¹H-MRS) in CA and no studies have investigated the association of CA severity with brain neurometabolites in BD.

OBJECTIVE

To investigate whether CA severity is associated with changes in anterior cingulate cortex (ACC) neurometabolite profile in BD and HC subjects.

METHODS

Fifty-nine BD I euthymic patients and fifty-nine HC subjects were assessed using the Childhood Trauma Questionnaire (CTQ) and underwent a 3-Tesla ¹H-MRS scan. Severity of childhood abuse (physical, sexual and emotional) and its association with levels of brain metabolites was analyzed within each group.

RESULTS

BD patients had higher total scores on the CTQ and higher severity rates of sexual and physical abuse compared to HC subjects. Greater severity of physical and sexual abuse was associated with increased ACC PCr level and lower Cr/PCr ratio in the BD group only.

CONCLUSION

Sexual and physical abuse in BD patients, but not in HC subjects, appeared to be associated with creatine metabolism in the ACC, which can influence neuronal mitochondrial energy production. Further studies should investigate whether this is the mechanism underlying the association between CA and worse clinical outcomes in BD.

Glutamate in the Dorsolateral Prefrontal Cortex in Patients With Schizophrenia: A Meta-analysis of 1H-Magnetic Resonance Spectroscopy Studies

BACKGROUND

To date, there is no systematic overview of glutamate in the dorsolateral prefrontal cortex (DLPFC) of patients with schizophrenia. Here, we meta-analyzed case-control studies of high-field proton magnetic resonance spectroscopy (¹H-MRS) investigating glutamate in DLPFC. Additionally, we estimated variance ratios to investigate homo/heterogeneity.

METHODS

Preregistration of the study was performed on September 20, 2019. The predefined literature search on PubMed comprised articles with search terms (magnetic resonance spectroscopy OR MRS) AND (glutamate OR glut∗ OR GLX) AND (schizophrenia OR psychosis OR schizophren∗). Meta-analyses with a fixed- and random-effects model with inverse variance method, DerSimonian-Laird estimator for τ², and Cohen's d were calculated. For differences in variability, we calculated a random-effects model for measures of variance ratios. The primary study outcome was the difference in glutamate in the DLPFC in cases versus controls. Secondary outcomes were differences in variability.

RESULTS

The quantitative analysis comprised 429 cases and 365 controls. Overall, we found no group difference (d = 0.03 [95% confidence interval (CI), -0.20 to 0.26], z = 0.28, p = .78). Sensitivity analysis revealed an effect for medication status (Q = 8.35, p = .039), i.e., increased glutamate in antipsychotic-naïve patients (d = 0.46 [95% CI, 0.08 to 0.84], z = 2.37, p = .018). Concerning variance ratios, we found an effect of medication status (Q = 16.95, p < .001) due to lower coefficient of variation ratio (CVR) in medication-naïve patients (logCVR = -0.49 [95% CI, -0.78 to -0.20], z = -3.33, p < .001). In studies with medicated patients, we found higher CVR (logCVR = 0.22 [95% CI, 0.06 to 0.39], z = 2.67; p = .008).

CONCLUSIONS

We carefully interpret the higher levels and lower variability in cortical glutamate in antipsychotic-naïve patients as a possible key factor resulting from a putative allostatic mechanism. We conclude that care has to be taken when evaluating metabolite levels in clinical samples in which medication might confound findings.

Changes in skeletal muscle diffusion parameters owing to intramyocellular lipid

INTRODUCTION

Several studies investigated the changes in diffusion of water molecules in skeletal muscle cells of lifestyle-related-disease patients who performed a hybrid training (HYBT) for six months. They reported that the apparent diffusion coefficient (ADC) and all diffusion eigenvalues (λ₁, λ₂, and λ₃) increased after the HYBT, owing to the enlargement of the intramyocellular diffusion space (intracellular space) caused by the muscular hypertrophy. We assumed that the HYBT promoted metabolism of the whole skeletal muscle including lipids, which reduced the amount of intramyocellular lipid (IMCL), and led to a secondary enlargement of the diffusion space in the skeletal muscle cells. However, the IMCL has to be a diffusion limiting factor in order to verify this hypothesis. Until now, there is no report on whether IMCL is a diffusion limiting factor for water molecules. The objective of this study was to examine whether the IMCL is a diffusion limiting factor in skeletal muscle cells.

MATERIALS AND METHODS

We performed a three-dimensional quantification of the IMCL in triceps surae muscles of lifestyle-related-disease patients and healthy volunteers. In addition, we measured the ADC in the volume of interest (VOI), diffusion anisotropy (FA), and diffusion eigenvalues (λ₁, λ₂, and λ₃), and evaluated the correlations between these diffusion parameters and IMCL.

RESULTS

The results showed that the amount of IMCL was positively and negatively correlated with the FA and λ₃, respectively, in lifestyle-related-disease patients. In addition, there was a weak negative correlation between IMCL and ADC, λ₁, and λ₂. There was no correlation between the amount of IMCL and diffusion parameters of healthy volunteers.

DISCUSSION

Above a certain amount, the IMCL correlates with the diffusion parameters. A higher amount of IMCL leads to smaller diffusion eigenvalues. This result suggested that IMCL possibility of influencing diffusion of water molecules in skeletal muscle cells. However, in order for the influence of IMCL to be reflected in the diffusion eigenvalues, it was needed large amount of IMCL existed, and we thought that the influence was smaller than the influence by the already reported cell membrane.

Cerebral Glutamate and Gamma-Aminobutyric Acid Levels in Individuals at Ultra-high Risk for Psychosis and the Association With Clinical Symptoms and Cognition

BACKGROUND

Studies examining glutamate or gamma-aminobutyric acid (GABA) in ultra-high risk for psychosis (UHR) and the association with pathophysiology and cognition have shown conflicting results. We aimed to determine whether perturbed glutamate and GABA levels in the anterior cingulate cortex and glutamate levels in the left thalamus were present in UHR individuals and to investigate associations between metabolite levels and clinical symptoms and cognition.

METHODS

We included 122 UHR individuals and 60 healthy control subjects. Participants underwent proton magnetic resonance spectroscopy to estimate glutamate and GABA levels and undertook clinical and cognitive assessments.

RESULTS

We found no differences in metabolite levels between UHR individuals and healthy control subjects. In UHR individuals, we found negative correlations in the anterior cingulate cortex between the composite of glutamate and glutamine (Glx) and the Comprehensive Assessment of At-Risk Mental States composite score (p = .04) and between GABA and alogia (p = .01); positive associations in the anterior cingulate cortex between glutamate (p = .01) and Glx (p = .01) and spatial working memory and between glutamate (p = .04), Glx (p = .04), and GABA (p = .02) and set-shifting; and a positive association in the thalamus between glutamate and attention (p = .04). No associations between metabolites and clinical or cognitive scores were found in the healthy control subjects.

CONCLUSIONS

An association between glutamate and GABA levels and clinical symptoms and cognition found only in UHR individuals suggests a loss of the normal relationship between metabolite levels and cognitive function. Longitudinal studies with investigation of clinical and cognitive outcome and the association with baseline levels of glutamate and GABA could illuminate whether glutamatergic and GABAergic dysfunction predicts clinical outcome.

Association of Cortical Glutamate and Working Memory Activation in Patients With Schizophrenia: A Multimodal Proton Magnetic Resonance Spectroscopy and Functional Magnetic Resonance Imaging Study

BACKGROUND

Cognitive deficits such as working memory (WM) impairment are core features of schizophrenia. One candidate marker for the integrity of synaptic neurotransmission necessary for cognitive processes is glutamate. It is frequently postulated that antipsychotic medication possibly alters functional mechanisms in the living brain. We tested in vivo for group differences in activation of the dorsolateral prefrontal cortex (DLPFC) during WM performance and the association with glutamate concentration in DLPFC depending on medication status.

METHODS

A total of 90 subjects (35 control subjects, 36 medicated patients, and 19 unmedicated patients) contributed magnetic resonance spectroscopy data. We estimated glutamate in left DLPFC. Subjects performed an n-back WM task (2-back vs. 0-back) during functional magnetic resonance imaging, and local activation in left DLPFC was measured. For analysis of association with medication status, we calculated linear regression models including an interaction effect with group.

RESULTS

Medicated and unmedicated patients with schizophrenia showed impaired performance. We found significantly reduced WM activation in left DLPFC in medicated patients and a trendwise reduction in unmedicated patients as compared with control subjects. We found no group difference in local glutamate concentration. However, we found differential effects of medication status on the association between local glutamate concentration and WM activation in left DLPFC, with a positive association in unmedicated patients but not in medicated patients.

CONCLUSIONS

We provide evidence that WM-dependent activation is associated with glutamate concentration in unmedicated patients with schizophrenia. Our finding points to putative allostatic changes that affect the functioning of the brain and might be altered through medication.

Influence of muscarinic M1 receptor antagonism on brain choline levels and functional connectivity in medication-free subjects with psychosis: A placebo controlled, cross-over study

An increasing number of studies implicate the muscarinic cholinergic system in cognitive dysfunction associated with psychosis. This study examined the effect of muscarinic M₁ receptor modulation on anterior cingulate cortex (ACC) and striatal choline concentrations and the relation with cognitive performance, as well as functional connectivity of cognitive networks. Thirty medication-free subjects with a psychosis spectrum disorder and 30 gender, age and IQ-matched healthy control subjects underwent ¹H-proton magnetic resonance spectroscopy (¹H-MRS) twice, once after placebo and once after a single dose of biperiden (M₁ receptor antagonist, 4 mg). A subset of 19 psychotic subjects and 28 controls underwent resting-state functional magnetic resonance imaging (rs-fMRI) as well. No significant differences were found in ACC and striatal choline levels, nor in functional connectivity, between the two groups after placebo. Moreover, M₁ antagonism did not significantly affect choline levels or functional connectivity. No correlations were found between choline levels and cognition as well as psychotic symptoms. Our findings do not support an association between the cholinergic system and cognition and psychotic symptoms. However, the lack of group differences in choline concentrations and functional connectivity, both after biperiden and placebo, may indicate that there were no severe cholinergic abnormalities present in our sample.

Predicting conversion from mild cognitive impairment to Alzheimer's disease using brain 1H-MRS and volumetric changes: A two- year retrospective follow-up study

This study investigated the ability of magnetic resonance spectroscopy (¹H-MRS) of posterior cingulate cortex (PCC) and brain volumetry to predict the progression from mild cognitive impairment (MCI) to Alzheimer's Disease (AD) on the basis of clinical classification at 2 years follow-up. Thirty-eight MCI patients, eighteen healthy older adults and twenty-three AD patients were included in this study. All participants underwent a brain-MR protocol (1.5 T GE scanner) including high-resolution T1-weighted volumetric sequence (isotropic 1mm³). Voxel-wise differences in brain volumetry were evaluated using FreeSurfer software and all volumes were normalized by the total intracranial volume (TIV). Careful localization of ¹H-MRS volume of PCC was performed and data were processed with the LCModel program. MCI patients underwent a complete neuropsychological assessment at baseline and were clinically re-evaluated after a mean of 28 months; twenty-six MCI patients (68.4%) converted to AD and twelve remained stable.

At baseline these two MCI subgroups did not differ in the global cognitive level (Mini Mental State Examination, MMSE) or in any of the other cognitive domains; the NAA/ mI ratio in the PCC was able to differentiate MCI converters from those MCI that did not develop AD (p = 0.022) with a level of accuracy (AUC area) of 0.779. A significantly reduced volume of parahippocampal gyrus (p = 0.010) and fusiform gyrus (p = 0.026) were found in the converter MCI subgroup compared to the stable MCI subgroup. The combined use of both N- acetyl-aspartate (NAA)/myo-Inositol (mI) ratio and volume of parahippocampal gyrus, increases the overall accuracy (AUC = 0.910) in predicting the conversion to AD two years before the development of clinical symptoms. Additional longitudinal studies with a broader representative sample of MCI patients and longer follow-up might be helpful to confirm these results and to elucidate the role of each parameter in predicting the possible progression to AD, and also to all the other non-AD dementia subtypes.

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Alterations of NAA/ml ratio in the PCC show high accuracy in predicting the progression to AD.

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Volume reduction of parahippocampal and fusiform gyrus are able to distinguish stable from converter MCI.

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The combined use of both NAA/mI ratio and volume of parahippocampal gyrus increases the accuracy.

Glutamatergic Neurometabolite Levels in Patients With Ultra-Treatment-Resistant Schizophrenia: A Cross-Sectional 3T Proton Magnetic Resonance Spectroscopy Study

BACKGROUND

In terms of antipsychotic treatment response, patients with schizophrenia can be classified into three groups: 1) treatment resistant to both non-clozapine (non-CLZ) antipsychotics and CLZ (ultra-treatment-resistant schizophrenia [URS]), 2) treatment resistant to non-CLZ antipsychotics but CLZ-responsive schizophrenia [non-URS]), and 3) responsive to first-line antipsychotics (non-treatment-resistant schizophrenia). This study aimed to compare glutamatergic neurometabolite levels among these three patient groups and healthy control subjects using proton magnetic resonance spectroscopy.

METHODS

Glutamate and glutamate+glutamine levels were assessed in the caudate, the dorsal anterior cingulate cortex (dACC), and the dorsolateral prefrontal cortex using 3T proton magnetic resonance spectroscopy (point-resolved spectroscopy, echo time = 35 ms). Glutamatergic neurometabolite levels were compared between the groups.

RESULTS

A total of 100 participants were included, consisting of 26 patients with URS, 27 patients with non-URS, 21 patients with non-treatment-resistant schizophrenia, and 26 healthy control subjects. Group differences were detected in ACC glutamate+glutamine levels (F_3,96 = 2.93, p = .038); patients with URS showed higher dACC glutamate+glutamine levels than healthy control subjects (p = .038). There were no group differences in the caudate or dorsolateral prefrontal cortex.

CONCLUSIONS

Taken together with previous studies that demonstrated higher ACC glutamate levels in patients with treatment-resistant schizophrenia, this study suggests that higher levels of ACC glutamatergic metabolites may be among the shared biological characteristics of treatment resistance to antipsychotics, including CLZ.

Proton magnetic resonance spectroscopic imaging of gray and white matter in bipolar-I and schizophrenia

BACKGROUND

Glutamine plus glutamate (Glx), as well as N-acetylaspartate compounds, (NAAc), a marker of neuronal viability, are quantified with proton magnetic resonance spectroscopy (¹H-MRS) and have been reported altered in psychotic disorders. However, few studies have compared these neurometabolites in bipolar disorder and schizophrenia.

METHODS

Used ¹H-MRS imaging from an axial supraventricular slab of gray matter (GM; medial-frontal and medial-parietal) and white matter (WM; bilateral-frontal and bilateral-parietal) voxels. Bipolar-I with history of psychosis (N = 43), schizophrenia (N = 41) and healthy controls (HC; N = 45) were studied (age range: 17-65).

RESULTS

Amongst younger (age ≤40 years-median split) bipolar-I vs HC subjects Glx was increased (p < 0.001), while NAAc was reduced in WM (p < 0.001). In GM, NAAc (p < 0.001) and myo-inositol (p = 0.002) were reduced. Amongst older bipolar-I (vs HC) in WM regions we found reductions in: NAAc (p < 0.001), glycerophospho-choline + phospho-choline (p < 0.001), creatine + phospho-creatine (p < 0.001) and myo-inositol (p < 0.001); in GM only Glx was increased (p < 0.005). Contrasts between bipolar-I and schizophrenia produced fewer results: amongst younger subjects, reduced NAAc (p < 0.001) in WM and lower myo-inositol in GM (p = 0.04) in bipolar-I vs schizophrenia. In the older patients, bipolar-I had lower GM NAAc (p = 0.009) than schizophrenia.

LIMITATIONS

First, differential exposure to antipsychotic and mood stabilizing medication across the groups. Second, differences in substance use histories among the groups. Third, neglect of peripheral and ventral cortical and subcortical regions. Finally, limited power to detect bipolar/schizophrenia differences.

CONCLUSIONS

Chronically-treated bipolar-I have increased Glx and reduced NAAc, suggestive of neuronal dysfunction. The NAAc reductions are more severe in bipolar-I than in schizophrenia patients.

The impact of acute and short-term methamphetamine abstinence on brain metabolites: A proton magnetic resonance spectroscopy chemical shift imaging study

BACKGROUND

Abuse of methamphetamine (MA) is a global health concern. Previous ¹H-MRS studies have found that, with methamphetamine abstinence (MAA), there are changes in n-acetyl-aspartate (NAA/Cr), myo-inositol (mI/Cr), choline (Cho/Cr and Cho/NAA), and glutamate with glutamine (Glx) metabolites. Limited studies have investigated the effect of acute MAA, and acute-to-short-term MAA on brain metabolites.

METHODS

Adults with chronic MA dependence (n = 31) and healthy controls (n = 22) were recruited. Two-dimensional chemical shift ¹H-MRS imaging (TR2000 ms, TE30 ms) slice was performed and included voxels in bilateral anterior-cingulate (ACC), frontal-white-matter (FWM), and dorsolateral-prefrontal-cortices (DLPFC). Control participants were scanned once. The MA group was scanned twice, with acute (1.5 ± 0.6 weeks, n = 31) and short-term MAA (5.1 ± 0.8 weeks, n = 22). The change in ¹H-MRS metabolites over time (n = 19) was also investigated. Standard ¹H-MRS metabolites are reported relative to Cr + PCr.

RESULTS

Acute MAA showed lower n-acetyl-aspartate (NAA) and n-acetyl-aspartate with n-acetyl-aspartyl-glutamate (NAA + NAAG) in left DLPFC, and glycerophosphocholine with phosphocholine (GPC + PCh) in left FWM. Short-term MAA showed lower NAA + NAAG and higher myo-inositol (mI) in right ACC, lower NAA and NAA + NAAG in the left DLPFC, and lower GPC + PCh in left FWM. Over time, MAA showed decreased NAA and NAA + NAAG and increased mI in right ACC, decreased NAA and NAA + NAAG in right FWM, and decreased in mI in left FWM.

CONCLUSION

In acute MAA, there was damage to the integrity of neuronal tissue, which was enhanced with short-term MAA. From acute to short-term MAA, activation of neuroinflammatory processes are suggested. This is the first ¹H-MRS study to report the development of neuroinflammation with loss of neuronal integrity in MAA.

Reduced insulin sensitivity may be related to less striatal glutamate: An 1H-MRS study in healthy non-obese humans

Levels of striatal dopamine (DA) may be positively correlated with levels of striatal glutamate (Glu). While reduced insulin sensitivity (%S) has been associated with reduced striatal DA levels in healthy non-obese persons, whether reduced %S is also associated with reduced striatal Glu levels has not yet been established. Using ¹H-MRS, we measured levels of several neurometabolites in the striatum and dorsolateral prefrontal cortex (DLPFC) of seventeen healthy non-obese persons (9 female, mean age: 28.35 ± 9.53). Insulin sensitivity was estimated for each subject from fasting plasma glucose and insulin using the Homeostasis Model Assessment II. We hypothesized that %S would be positively related with levels of Glu and Glu + glutamine (Glx) in the striatum. Exploratory analyses were also conducted between other fasting markers of metabolic health and neurometabolites measured with ¹H-MRS. In the right striatum, %S was positively correlated with levels of Glu (r(15) = .49, p = .04) and Glx (r(15) = .50, p = .04). In the left striatum, there was a trend positive correlation between %S and Glu (r(15) = .46, p = .06), but not Glx levels (r(15) = .20, p = .44). The relationships between %S and striatal Glu levels remained after controlling for age, sex, and BMI (right: r(12) = .73, β = .52, t = 2.55, p = .03; left: (r(12) = .63, β = .53, t = 2.25, p = .04) These preliminary findings suggest that %S may be related to markers of glutamatergic functioning in the striatum of healthy non-obese persons. These findings warrant replication in larger samples and extension into neuropsychiatric populations where altered striatal DA, Glu, and %S are implicated.

Prefrontal glutamatergic emotion regulation is disturbed in cluster B and C personality disorders - A combined 1H/31P-MR spectroscopic study

BACKGROUND

Personality disorders (PD) belong to the most common and most serious mental disorders as regards social dysfunction, inability to work, occurrence of comorbidity and suicidal risk. PDs also crucially influence the incidence, clinical course and treatment response of mental disorders with high suicidal risk, such as depression or substance abuse. One key issue of PD concerns the regulation of emotions.

METHODS

Both ¹H-/³¹P-Chemical Shift Imaging (CSI) was applied in a single session to assess neurochemical markers of glutamate function (NAA, Glu) and local energy metabolism (PCr, ATP) in two patient cohorts encompassing 22 cluster B (CB) and 21 cluster C (CC) PD patients, whereby 10 patients of each group were on low-dose antidepressants, and in 60 healthy controls (HC). Non-parametric statistical tests and correlation analyses were performed to assess disease effects on the metabolites and their relation to symptomatology as assessed by SCL-90R self-ratings.

RESULTS

Overall comparison including Bonferroni correction revealed significant differences of Glu across all groups in the dorsolateral prefrontal cortex (DLPFC). The following uncorrected results of pairwise tests were obtained: (i) Glu was bilaterally increased in the DLPFC in CB patients, whereas it was - together with NAA - bilaterally decreased in the DLPFC in CC patients and accompanied by increased PCr in the left DLPFC. (ii) NAA and Glu, accompanied by increased PCr, were significantly decreased in the dorsomedial prefrontal cortex (DMPFC) in CC patients. (iii) NAA was decreased in the right anterior cingulate cortex (ACC) in CB patients, and in the left ACC in CC patients with PCr being increased bilaterally. (iv) No associations were observed between metabolites and psychopathology measures.

CONCLUSION

The observations in the DLPFC may reflect a neurobiochemical correlate of disturbed cognitive control function in CB and CC PD. While the alterations in CB patients suggest increased basal activity, the observed patterns in CC patients likely reflect decreased or inhibited activity. The alterations of NAA and Glu levels in the ACC and DMPFC indirectly support the assumption of disturbed neuronal function in regions involved in social cognition and mentalizing abilities in both CB and CC PD. Further studies should include the investigation of metabolites of neuronal inhibition (GABA) and the examination of treatment effects.

Noninvasive evaluation of radiation-enhanced glioma cells invasiveness by ultra-high-field (1)H-MRS in vitro

INTRODUCTION

Glioma is the most common type of the primary CNS tumor. Radiotherapy is an important treatment measure after surgery. However, its highly invasive character is the main reason of postoperative recurrence. The aim of the study was to probe the correlation between the invasion ability and the metabolite characteristics of glioma cells at the cellular level after irradiation by using 14.7T high-resolution nuclear proton magnetic resonance spectroscopy ((1)H-MRS).

METHODS

To determine the matrix metalloproteinase-2 (MMP-2) activity and metabolite ratios of glioma cells after irradiation with different doses of X-rays, U87 and C6 glioma cells were exposed to X-ray irradiation of 0, 1, 5, 10, and 15Gy. After 20h, the perchloric acid (PCA) extraction method was used to evaluate water-soluble metabolites [choline (Cho), creatine (Cr), and N-acetylaspartate (NAA)], and (1)H-MRS patterns and changes in metabolite ratios were observed in vitro by 14.7T high resolution (1)H-MRS. Matrigel invasion assays and gelatin zymography were performed to test the invasion ability of U87 and C6 glioma cells.

RESULTS

Good MR spectra were obtained from PCA method extracts of U87 and C6 glioma cells. Both radiation-induced MMP-2 activity and the Cho/Cr and Cho/NAA ratios increased after irradiation, and their increase occurred in a dose-dependent manner. The MMP-2 activity and the Cho/Cr and Cho/NAA ratios of glioma cells increased after irradiation up to 10Gy and decreased thereafter. In particular, the Cho/NAA ratio of U87 cells increased from 3.55±0.06 (0Gy) to 9.13±0.30 (10Gy) and then declined to 5.94±0.15 (15Gy). Furthermore, the invasion ability of glioma cells had a strong positive correlation with the Cho/Cr and Cho/NAA ratios. Both the Cho/Cr ratio and the Cho/NAA ratio of U87 glioma cells were highly positively correlated with the number of invading cells in the Matrigel invasion assay. The Pearson's correlation coefficient (r) values of U87 cells were 0.89 (Cho/Cr ratio versus invasion ability) and 0.91 (Cho/NAA ratio versus invasion ability) (P<0.01). C6 cells exhibited similar changes to those of U87 cells.

CONCLUSIONS

In vitro high-resolution (1)H-MRS is useful for detecting glioma invasiveness at the cellular level.

Use of quantitative brain water imaging as concentration reference for J-edited MR spectroscopy of GABA

PURPOSE

To compare two different methods of obtaining the water reference for determination of quantitative water-scaled in vivo concentration estimates of γ-aminobutyric acid (GABA).

METHODS

Water-scaled GABA estimates from localized J-difference edited MR spectroscopy experiments can be computed using standard values for tissue-specific water content and relaxation times. Water content and relaxation may, however, be altered in pathology. This work re-analyzed data from a recent study in healthy controls and patients with minimal (mHE) or grade I (HE 1) hepatic encephalopathy, a disease associated with slight elevation of brain water content. J-difference edited MR spectroscopy data were combined with quantitative brain water measures, which provided individual water density references and T1 relaxation times. Resulting GABA estimates were compared to concentration values obtained using standard tissue-specific water content and relaxation values.

RESULTS

Occipital GABA concentration values obtained from individual water and T1 maps were 1.64±0.35mM in controls, and significantly higher (P<0.01) than in mHE (1.15±0.28mM) and HE 1 patients (1.18±0.09mM). Results from the tissue-dependent approach (1.58±0.30mM (controls), 1.10±0.27mM (mHE) and 1.12±0.12mM (HE 1)) were slightly lower (P<0.05 in each group).

CONCLUSION

Water-scaled in vivo GABA estimates can be obtained with individual water density and T1 relaxation mapping. This approach may be useful for studying GABA levels in pathologies with substantial brain water content or relaxation changes.

Glutamatergic dysfunction linked to energy and membrane lipid metabolism in frontal and anterior cingulate cortices of never treated first-episode schizophrenia patients

BACKGROUND

Glutamatergic dysfunction and altered membrane lipid and energy metabolism have been repeatedly demonstrated in the frontal/prefrontal and anterior cingulate cortex (ACC) in schizophrenia. Though having been already studied in animals, the presumed link between glutamatergic function and structural plasticity has not been investigated directly in the human brain yet. We measured glutamate (Glu), focal energy metabolism, and membrane phospholipid turnover to investigate main pathologies in those key brain regions of schizophrenia.

METHODS

(1)H- and (31)P-Chemical Shift Imaging (CSI) was combined in a single session to assess Glu and markers of energy (PCr, ATP) and membrane lipid (PME, PDE) metabolism in 31 neuroleptic-naïve first acute onset psychosis patients and 31 matched healthy controls. Multivariate analyses of covariance were used to assess disease effects on Glu and to investigate the impact of Glu alterations on phospholipid and energy metabolites.

RESULTS

Glu levels of patients were increased in the frontal and prefrontal cortex bilaterally and in the ACC. Higher Glu was associated with increased left frontal/prefrontal PME and right frontal/prefrontal PDE in patients, which was not observed in healthy controls. In contrast, higher Glu levels were associated with lower PCr or ATP values in the frontal/prefrontal cortex bilaterally and in the right ACC of controls. This was not observed in the right ACC and left frontal/prefrontal cortex of patients.

CONCLUSION

Frontal glutamatergic hyperactivity is disconnected from physiologically regulated energy metabolism and is associated with increased membrane breakdown in right and increased membrane restoration in left frontal and prefrontal cortical regions. As indicated by previous findings, this pathology is likely dynamic during the course of first acute illness and possibly associated with negative symptoms and cognitive impairment. Our findings underline the importance of further research on neuroprotective treatment options during the early acute or even better for the ultra-high risk state of psychotic illness.

A longitudinal proton magnetic resonance spectroscopy study investigating oxidative stress as a result of alcohol and tobacco use in youth with bipolar disorder

Alcohol and tobacco have been suggested to be "aggravating factors" for neuroprogression in bipolar disorder (BD), however the impact of these substances on the underlying neurobiology is limited. Oxidative stress is a key target for research into neuroprogression in BD and in accordance with this model, our previous cross-sectional studies have found that risky alcohol and tobacco use in BD is associated with increased oxidative stress, investigated via in vivo glutathione (GSH) measured by proton magnetic resonance spectroscopy ((1)H-MRS) in the anterior cingulate cortex (ACC). What remains unknown is whether the negative impact on GSH levels can be modified as a result of limiting alcohol and tobacco use. Thirty BD patients were included in the study. (1)H-MRS and tobacco and alcohol measures were conducted at baseline and follow-up assessments (15.5±4.6 months apart). Pearson׳s correlations were performed between percentage change in GSH concentration and changes in alcohol/tobacco use. Regression analyses were then conducted to further explore the significant correlations. An increase in GSH was associated with a decrease in alcohol consumption (r=-0.381, p<0.05) and frequency of tobacco use (-0.367, p=0.05). Change in alcohol consumption, tobacco use and age were significant predictors of change in GSH concentration (F (3, 26)=3.69, p<0.05). Due to the high comorbidity of alcohol and tobacco use in the sample, the individual effects of these substances on GSH levels could not be determined. This study offers longitudinal evidence that changing risky drinking patterns and tobacco use early in the course of BD is associated with improvements in antioxidant capacity, and therefore may be specific targets for early intervention and prevention of neuroprogression in BD.

Proton magnetic resonance spectroscopy of prefrontal white matter in psychotropic naïve children and adolescents with obsessive-compulsive disorder

Obsessive-compulsive disorder (OCD) has a typical onset during childhood or adolescence. Although recent in-vivo proton magnetic resonance spectroscopy ((1)H-MRS) studies report gray matter metabolite abnormalities in children and adolescents with OCD, there are no existing (1)H-MRS studies that measure white matter (WM) metabolite levels in this population. In the present study, we measured metabolite levels in the left and right prefrontal WM (LPFWM and RPFWM, respectively) of psychotropic-naïve children and adolescents with OCD (LPFWM: N=15, mean age 13.3±2.4 years; right RPFWM: N=14, mean age 13.0±2.3 years) and healthy controls (LPFWM: N=17, mean age 11.8±2.7 years; RPFWM: N=18, mean age 12.2±2.8 years). Spectra were acquired using a 3T single voxel PRESS sequence (1.5×2.0×2.0cm(3)). When age and sex effects were controlled, OCD patients had higher levels of RPFWM choline and N-acetyl-aspartate (NAA). In addition, RPFWM levels of NAA, creatine and myo-inositol were positively and significantly correlated with severity of OCD symptoms. In summary, this is the first published study of WM metabolite levels in children and adolescents with OCD. Our preliminary findings lend further support to the previous findings of WM abnormalities in OCD.

Community-based lifestyle modification programme for non-alcoholic fatty liver disease: a randomized controlled trial

BACKGROUND & AIMS

Healthy lifestyle is the most important management of non-alcoholic fatty liver disease (NAFLD). This study aimed at assessing the efficacy of a community-based lifestyle modification programme in the remission of NAFLD.

METHODS

This was a parallel group, superiority, randomized controlled trial. 154 adults with NAFLD identified during population screening were randomized to participate in a dietitian-led lifestyle modification programme at 2 community centres or receive usual care for 12 months. The primary outcome was remission of NAFLD at month 12 as evidenced by intrahepatic triglyceride content (IHTG) of less than 5% by proton-magnetic resonance spectroscopy.

RESULTS

74 patients in the intervention group and 71 patients in the control group completed all study assessments. In an intention-to-treat analysis of all 154 patients, 64% of the patients in the intervention group and 20% in the control group achieved remission of NAFLD (difference between groups 44%; 95% CI 30-58%; p<0.001). The mean (SD) changes in IHTG from baseline to month 12 were -6.7% (6.1%) in the intervention group and -2.1% (6.4%) in the control group (p<0.001). Body weight decreased by 5.6 (4.4) kg and 0.6 (2.5) kg in the two groups, respectively (p<0.001). While 97% of patients with weight loss of more than 10% had remission of NAFLD, 41% of those with weight loss of 3.0-4.9% could also achieve the primary outcome.

CONCLUSIONS

The community-based lifestyle modification programme is effective in reducing and normalizing liver fat in NAFLD patients.

Glutamatergic correlates of gamma-band oscillatory activity during cognition: a concurrent ER-MRS and EEG study

Frequency specific synchronisation of neuronal firing within the gamma-band (30-70 Hz) appears to be a fundamental correlate of both basic sensory and higher cognitive processing. In-vitro studies suggest that the neurochemical basis of gamma-band oscillatory activity is based on interactions between excitatory (i.e. glutamate) and inhibitory (i.e. GABA) neurotransmitter concentrations. However, the nature of the relationship between excitatory neurotransmitter concentration and changes in gamma band activity in humans remains undetermined. Here, we examine the links between dynamic glutamate concentration and the formation of functional gamma-band oscillatory networks. Using concurrently acquired event-related magnetic resonance spectroscopy and electroencephalography, during a repetition-priming paradigm, we demonstrate an interaction between stimulus type (object vs. abstract pictures) and repetition in evoked gamma-band oscillatory activity, and find that glutamate levels within the lateral occipital cortex, differ in response to these distinct stimulus categories. Importantly, we show that dynamic glutamate levels are related to the amplitude of stimulus evoked gamma-band (but not to beta, alpha or theta or ERP) activity. These results highlight the specific connection between excitatory neurotransmitter concentration and amplitude of oscillatory response, providing a novel insight into the relationship between the neurochemical and neurophysiological processes underlying cognition.

Metabolomic approach to human brain spectroscopy identifies associations between clinical features and the frontal lobe metabolome in multiple sclerosis

Proton magnetic resonance spectroscopy ((1)H-MRS) is capable of noninvasively detecting metabolic changes that occur in the brain tissue in vivo. Its clinical utility has been limited so far, however, by analytic methods that focus on independently evaluated metabolites and require prior knowledge about which metabolites to examine. Here, we applied advanced computational methodologies from the field of metabolomics, specifically partial least squares discriminant analysis and orthogonal partial least squares, to in vivo (1)H-MRS from frontal lobe white matter of 27 patients with relapsing-remitting multiple sclerosis (RRMS) and 14 healthy controls. We chose RRMS, a chronic demyelinating disorder of the central nervous system, because its complex pathology and variable disease course make the need for reliable biomarkers of disease progression more pressing. We show that in vivo MRS data, when analyzed by multivariate statistical methods, can provide reliable, distinct profiles of MRS-detectable metabolites in different patient populations. Specifically, we find that brain tissue in RRMS patients deviates significantly in its metabolic profile from that of healthy controls, even though it appears normal by standard MRI techniques. We also identify, using statistical means, the metabolic signatures of certain clinical features common in RRMS, such as disability score, cognitive impairments, and response to stress. This approach to human in vivo MRS data should promote understanding of the specific metabolic changes accompanying disease pathogenesis, and could provide biomarkers of disease progression that would be useful in clinical trials.