GABA, glutamatergic dynamics and BOLD contrast assessed concurrently using functional MRS during a cognitive task

A recurring issue in functional neuroimaging is how to link task-driven haemodynamic blood oxygen level dependent functional MRI (BOLD-fMRI) responses to underlying neurochemistry at the synaptic level. Glutamate and γ-aminobutyric acid (GABA), the major excitatory and inhibitory neurotransmitters respectively, are typically measured with MRS sequences separately from fMRI, in the absence of a task. The present study aims to resolve this disconnect, developing acquisition and processing techniques to simultaneously assess GABA, glutamate and glutamine (Glx) and BOLD in relation to a cognitive task, at 3 T. Healthy subjects (N = 81) performed a cognitive task (Eriksen flanker), which was presented visually in a task-OFF, task-ON block design, with individual event onset timing jittered with respect to the MRS readout. fMRS data were acquired from the medial anterior cingulate cortex during task performance, using an adapted MEGA-PRESS implementation incorporating unsuppressed water-reference signals at a regular interval. These allowed for continuous assessment of BOLD activation, through T2 *-related changes in water linewidth. BOLD-fMRI data were additionally acquired. A novel linear model was used to extract modelled metabolite spectra associated with discrete functional stimuli, building on well established processing and quantification tools. Behavioural outcomes from the flanker task, and activation patterns from the BOLD-fMRI sequence, were as expected from the literature. BOLD response assessed through fMRS showed a significant correlation with fMRI, specific to the fMRS-targeted region of interest; fMRS-assessed BOLD additionally correlated with lengthening of response time in the incongruent flanker condition. While no significant task-related changes were observed for GABA+, a significant increase in measured Glx levels (~8.8%) was found between task-OFF and task-ON periods. These findings verify the efficacy of our protocol and analysis pipelines for the simultaneous assessment of metabolite dynamics and BOLD. As well as establishing a robust basis for further work using these techniques, we also identify a number of clear directions for further refinement in future studies.

The developmental trajectory of 1H-MRS brain metabolites from childhood to adulthood

Human brain development is ongoing throughout childhood, with for example, myelination of nerve fibers and refinement of synaptic connections continuing until early adulthood. 1H-Magnetic Resonance Spectroscopy (1H-MRS) can be used to quantify the concentrations of endogenous metabolites (e.g. glutamate and γ -aminobutyric acid (GABA)) in the human brain in vivo and so can provide valuable, tractable insight into the biochemical processes that support postnatal neurodevelopment. This can feasibly provide new insight into and aid the management of neurodevelopmental disorders by providing chemical markers of atypical development. This study aims to characterize the normative developmental trajectory of various brain metabolites, as measured by 1H-MRS from a midline posterior parietal voxel. We find significant non-linear trajectories for GABA+ (GABA plus macromolecules), Glx (glutamate + glutamine), total choline (tCho) and total creatine (tCr) concentrations. Glx and GABA+ concentrations steeply decrease across childhood, with more stable trajectories across early adulthood. tCr and tCho concentrations increase from childhood to early adulthood. Total N-acetyl aspartate (tNAA) and Myo-Inositol (mI) concentrations are relatively stable across development. Trajectories likely reflect fundamental neurodevelopmental processes (including local circuit refinement) which occur from childhood to early adulthood and can be associated with cognitive development; we find GABA+ concentrations significantly positively correlate with recognition memory scores.

Linewidth-related bias in modelled concentration estimates from GABA-edited 1H-MRS

J-difference-edited MRS is widely used to study GABA in the human brain. Editing for low-concentration target molecules (such as GABA) typically exhibits lower signal-to-noise ratio (SNR) than conventional non-edited MRS, varying with acquisition region, volume and duration. Moreover, spectral lineshape may be influenced by age-, pathology-, or brain-region-specific effects of metabolite T2, or by task-related blood-oxygen level dependent (BOLD) changes in functional MRS contexts. Differences in both SNR and lineshape may have systematic effects on concentration estimates derived from spectral modelling. The present study characterises the impact of lineshape and SNR on GABA+ estimates from different modelling algorithms: FSL-MRS, Gannet, LCModel, Osprey, spant and Tarquin. Publicly available multi-site GABA-edited data (222 healthy subjects from 20 sites; conventional MEGA-PRESS editing; TE = 68 ms) were pre-processed with a standardised pipeline, then filtered to apply controlled levels of Lorentzian and Gaussian linebroadening and SNR reduction. Increased Lorentzian linewidth was associated with a 2-5% decrease in GABA+ estimates per Hz, observed consistently (albeit to varying degrees) across datasets and most algorithms. Weaker, often opposing effects were observed for Gaussian linebroadening. Variations are likely caused by differing baseline parametrization and lineshape constraints between models. Effects of linewidth on other metabolites (e.g., Glx and tCr) varied, suggesting that a linewidth confound may persist after scaling to an internal reference. These findings indicate a potentially significant confound for studies where linewidth may differ systematically between groups or experimental conditions, e.g. due to T2 differences between brain regions, age, or pathology, or varying T2* due to BOLD-related changes. We conclude that linewidth effects need to be rigorously considered during experimental design and data processing, for example by incorporating linewidth into statistical analysis of modelling outcomes or development of appropriate lineshape matching algorithms.

Simultaneous Measurement of GABA, Glutathione, and Glutamate-Glutamine in the Thalamus using Edited MR Spectroscopy: Feasibility and Applications in Traumatic Brain Injury

BACKGROUND

MR spectroscopy (MRS) is a noninvasive tool for evaluating biochemical alterations, such as glutamate (Glu)/gamma-aminobutyric acid (GABA) imbalance and depletion of antioxidative glutathione (GSH) after traumatic brain injury (TBI). Thalamus, a critical and vulnerable region post-TBI, is challenging for MRS acquisitions, necessitating optimization to simultaneously measure GABA/Glu and GSH.

PURPOSE

To assess the feasibility and optimize acquisition and processing approaches for simultaneously measuring GABA, Glx (Glu + glutamine (Gln)), and GSH in the thalamus, employing Hadamard encoding and reconstruction of MEscher-GArwood (MEGA)-edited spectroscopy (HERMES).

STUDY TYPE

Prospective.

SUBJECTS

28 control subjects (age: 35.9 ± 15.1 years), and 17 mild TBI (mTBI) patients (age: 32.4 ± 11.3 years).

FIELD STRENGTH/SEQUENCE

3T/T1-weighted magnetization-prepared rapid gradient-echo (MP-RAGE), HERMES.

ASSESSMENT

We evaluated the impact of acquisition with spatial saturation bands and post-processing with spectral alignment on HERMES performance in the thalamus among controls. Within-subject variability was examined in five controls through repeated scans within a week. The HERMES spectra in the posterior cingulate cortex (PCC) of controls were used as a reference for assessing HERMES performance in a reliable target. Furthermore, we compared metabolite levels and fitting quality in the thalamus between mTBI patients and controls.

STATISTICAL TESTS

Unpaired t-tests and within-subject coefficient-of-variation (CV). A P-value <0.05 was deemed significant.

RESULTS

HERMES spectra, acquired with saturation bands and processed with spectral alignment, yielded reliable metabolite measurements in the thalamus. The mean within-subject CV for GABA, Glx, and GSH levels were 18%, 10%, and 16% in the thalamus (7%, 9%, and 16% in the PCC). GABA (3.20 ± 0.60 vs 2.51 ± 0.55, P < 0.01) and Glx (8.69 ± 1.23 vs 7.72 ± 1.19, P = 0.03) levels in the thalamus were significantly higher in mTBI patients than in controls, with GSH (1.27 ± 0.35 vs 1.22 ± 0.28, P = 0.65) levels showing no significant difference.

DATA CONCLUSION

Simultaneous measuring GABA/Glx and GSH using HERMES is feasible in the thalamus, providing valuable insight into TBI.

LEVEL OF EVIDENCE

2 TECHNICAL EFFICACY: Stage 2.

Neurotransmitter levels in the basal ganglia are associated with intracortical circuit activity of the primary motor cortex in healthy humans

BACKGROUND

The basal ganglia are strongly connected to the primary motor cortex (M1) and play a crucial role in movement control. Interestingly, several disorders showing abnormal neurotransmitter levels in basal ganglia also present concomitant anomalies in intracortical function within M1.

OBJECTIVE/HYPOTHESIS

The main aim of this study was to clarify the relationship between neurotransmitter content in the basal ganglia and intracortical function at M1 in healthy individuals. We hypothesized that neurotransmitter content of the basal ganglia would be significant predictors of M1 intracortical function.

METHODS

We combined magnetic resonance spectroscopy (MRS) and transcranial magnetic stimulation (TMS) to test this hypothesis in 20 healthy adults. An extensive TMS battery probing common measures of intracortical, and corticospinal excitability was administered, and GABA and glutamate-glutamine levels were assessed from voxels placed over the basal ganglia and the occipital cortex (control region).

RESULTS

Regression models using metabolite concentration as predictor and TMS metrics as outcome measures showed that glutamate level in the basal ganglia significantly predicted short interval intracortical inhibition (SICI) and intracortical facilitation (ICF), while GABA content did not. No model using metabolite measures from the occipital control voxel was significant.

CONCLUSIONS

Taken together, these results converge with those obtained in clinical populations and suggest that intracortical circuits in human M1 are associated with the neurotransmitter content of connected but distal subcortical structures crucial for motor function.

Subcutaneous deuterated substrate administration in mice: An alternative to tail vein infusion

PURPOSE

Tail-vein catheterization and subsequent in-magnet infusion is a common route of administration of deuterium (2 H)-labeled substrates in small-animal deuterium (D) MR studies. With mice, because of the tail vein's small diameter, this procedure is challenging. It requires considerable personnel training and practice, is prone to failure, and may preclude serial studies. Motivated by the need for an alternative, the time courses for common small-molecule deuterated substrates and downstream metabolites in brain following subcutaneous infusion were determined in mice and are presented herein.

METHODS

Three 2 H-labeled substrates-[6,6-2 H2 ]glucose, [2 H3 ]acetate, and [3,4,4,4-2 H4 ]beta-hydroxybutyrate-and 2 H2 O were administered to mice in-magnet via subcutaneous catheter. Brain time courses of the substrates and downstream metabolites (and semi-heavy water) were determined via single-voxel DMRS.

RESULTS

Subcutaneous catheter placement and substrate administration was readily accomplished with limited personnel training. Substrates reached pseudo-steady state in brain within ∼30-40 min of bolus infusion. Time constants characterizing the appearance in brain of deuterated substrates or semi-heavy water following 2 H2 O administration were similar (∼15 min).

CONCLUSION

Administration of deuterated substrates via subcutaneous catheter for in vivo DMRS experiments with mice is robust, requires limited personnel training, and enables substantial dosing. It is suitable for metabolic studies where pseudo-steady state substrate administration/accumulation is sufficient. It is particularly advantageous for serial longitudinal studies over an extended period because it avoids inevitable damage to the tail vein following multiple catheterizations.

Magnetic resonance spectroscopy and auditory brain-stem response audiometry as predictors of bilirubin-induced neurologic dysfunction in full-term jaundiced neonates

The purpose of this research was to define the functions of MRS and ABR as predictors of bilirubin-induced neurologic dysfunction (BIND) in full-term neonates who required intervention (phototherapy and/or exchange transfusion). This prospective cohort study was done at the NICU of Tanta University Hospitals over a 2-year duration. Fifty-six full-term neonates with pathological unconjugated hyperbilirubinemia were divided according to MRS and ABR findings into 2 groups: group (1) included 26 cases with mild acute bilirubin encephalopathy (BIND-M score 1-4). Group (2) included 30 cases with neonatal hyperbilirubinemia only. In addition, 20 healthy neonates with similar ages were employed as the controls. When compared to group 2 and the control group, group 1's peak-area ratios of NAA/Cr and NAA/Cho were found to be significantly reduced (P < 0.05). As compared to group 2 and the control group, group 1's Lac/Cr ratio was significantly greater (P < 0.05), but the differences were not significant for group 2 when compared to the control group. Waves III and V peak latencies, I-III, and I-V interpeak intervals were significantly prolonged in group 1 in comparison to group 2 and controls (P < 0.05) with no significant difference between group 2 and control group.   Conclusion: When the symptoms of ABE are mild and MRI does not show any evident abnormalities, MRS and ABR are helpful in differentiating individuals with ABE from patients with neonatal hyperbilirubinemia.    Trial registration:  ClinicalTrials.gov , Identifier: NCT06018012. What is Known: • MRS can be used as a diagnostic and prognostic tool for the differential diagnosis of patients with acute bilirubin encephalopathy, from patients with neonatal hyperbilirubinemia What is New: • ABR is a useful diagnostic and prognostic tool in the care and management of neonates with significantly raised bilirubin. It can be used as early predictor of acute bilirubin encephalopathy in the earliest stage of auditory damage caused by bilirubin.

Peripheral and central biomarkers associated with inflammation in antipsychotic naïve first episode psychosis: Pilot studies

BACKGROUND

Elevated serum pro-inflammatory molecules have been reported in early psychosis. What is not known is whether peripheral inflammatory biomarkers are associated with CNS biomarkers. In the brain, release of pro-inflammatory molecules by microglial hyperactivity may lead to neuronal apoptosis seen in neurodegenerative disorders and account for loss of brain tissue observed in psychotic disorders. Neurochemical changes, including elevated glutamate levels, are also associated with neuroinflammation, present in early psychosis and change with antipsychotic treatment.

METHODS

Antipsychotic naïve patients with first episode psychosis (FEP) were studied as part of a collaborative project of neuroinflammation. In Study 1 we explored associations between plasma inflammatory molecules and neurometabolites in the dorsal caudate using magnetic resonance spectroscopy (1H-MRS) in N = 13 FEP participants. Study 2 examined the relationship between inflammatory molecules in the Plasma and CSF in N = 20 FEP participants.

RESULTS

In Study 1, the proinflammatory chemokine MDC/CCL22 and IL10 were significantly positively correlated with Glutamate and Glx (glutamate + glutamine) levels in the dorsal caudate. In Study 2, plasma inflammatory molecules (MIP1β/CCL4, MCP1/CCL2, Eotaxin-1/CCL11 and TNFα) were significantly correlated with CSF MIP1β/CCL4, IL10, MCP1/CCL2 and Fractalkine/CX3CL1 and symptoms ratings.

DISCUSSION

Plasma inflammatory biomarkers are elevated in early psychosis, associated with neurochemical markers as well as CSF inflammatory molecules found in neurodegenerative disorders. Future studies are needed that combine both peripheral and central biomarkers in both FEP and HC to better understand a potential neuroinflammatory subtype of psychosis likely to respond to targeted interventions.

Glutamate and GABA levels in the anterior cingulate cortex in treatment resistant first episode psychosis patients

BACKGROUND

Around 30 % of schizophrenia patients do not respond sufficiently to conventional antipsychotic treatment. Glutamate and γ-aminobutyric acid (GABA) may be implicated in treatment resistant (TR) patients. Some data indicate that TR patients show increased glutamate levels compared to responders, but findings are inconclusive and limited in the early disease stage. Furthermore, the two neurotransmitters have rarely been assessed in conjunction. We therefore aimed to investigate the role of GABA+ and glutamate in first episode TR patients and explore whether these neurometabolites could be potential predictive markers for TR schizophrenia.

STUDY DESIGN

We used proton magnetic resonance spectroscopy (MRS) to assess glutamate + glutamine (Glx) and GABA including macromolecules (GABA+) in the anterior cingulate cortex (ACC) of 58 first episode psychosis patients. At six months follow-up treatment response was determined and in a subgroup of 33 patients a follow-up MRS scan was acquired.

STUDY RESULTS

Glx and GABA+ levels were not significantly different between TR patients and responders at baseline and the levels did not change at six months follow-up. The groups differed in voxel fractions, which could have influenced our results even though we corrected for these differences.

CONCLUSIONS

Our findings do not provide evidence that ACC Glx or GABA+ levels are potential biomarkers for TR in first episode psychosis. Future research needs to take in to account voxel fractions and report potential differences. Comparison with previous literature suggests that illness duration, clozapine responsiveness and medication effects may partly explain the heterogeneous results on Glx and GABA+ levels in TR.

In Vitro MRS of Cells Treated with Trastuzumab at 1.5 Tesla

The aim of the study was to investigate the effect of Trastuzumab on the MCF-7 and CRL-2314 breast cancer cell lines. Additionally, an attempt was made to optimize magnetic resonance spectroscopy (MRS) for cell culture studies, with particular emphasis on the impact of treatment with Trastuzumab. The research materials included MCF-7 and CRL-2314 breast cancer cell lines. The study examined the response of these cell lines to treatment with Trastuzumab. The clinical magnetic resonance imaging (MRI) system, OPTIMA MR360 manufactured by GEMS, with a magnetic field induction of 1.5 T, was used. Due to the nature of the tested objects, their size and shape, it was necessary to design and manufacture additional receiving coils. They were used to image the tested cell cultures and record the spectroscopic signal. The spectra obtained by MRS were confirmed by NMR using a 300 MHz NMR Fourier 300 with the TopSpin 3.1 system from Bruker. The designed receiving coils allowed for conducting experiments with the cell lines in a satisfactory manner. These tests would not be possible using factory-delivered coils due to their parameters and the size of the test objects, whose volume did not exceed 1 mL. MRS studies revealed an increase in the metabolite at 1.9 ppm, which indicates the induction of histone acetylation. Changes in histone acetylation play a very important role in both cell development and differentiation processes. The use of Trastuzumab therapy in breast cancer cells increases the levels of acetylated histones. MRS studies and spectra obtained from the 300 MHz NMR system are consistent with the specificity inherent in both systems.

The Lack of Alterations in Metabolites in the Medial Prefrontal Cortex and Amygdala, but Their Associations with Autistic Traits, Empathy, and Personality Traits in Adults with Autism Spectrum Disorder: A Preliminary Study

Proton magnetic resonance spectroscopy (1H-MRS) has shown inconsistent alterations in brain metabolites of adults with autism spectrum disorder (ASD). We investigated brain metabolites in the medial prefrontal cortex and amygdala of 24 drug-naive adults with ASD and no intellectual disability and 24 non-ASD control subjects, using 3 T 1H-MRS. Adults with ASD showed no significant differences from control in glutamate, glutamate plus glutamine, N-acetylaspartate, glycerophosphorylcholine plus phosphorylcholine, creatine plus phosphocreatine, or myo-inositol in either region. However, ASD subjects did show significant correlations of localized brain metabolites with autistic traits, empathy deficits, and personality traits using the Autism-Spectrum Quotient, Questionnaire of Cognitive and Affective Empathy, Interpersonal Reactivity Index, and NEO Personality Inventory-Revised. These findings should be taken as preliminary or exploratory.

Baseline GABA+ levels in areas associated with sensorimotor control predict initial and long-term motor learning progress

Synaptic plasticity relies on the balance between excitation and inhibition in the brain. As the primary inhibitory and excitatory neurotransmitters, gamma-aminobutyric acid (GABA) and glutamate (Glu), play critical roles in synaptic plasticity and learning. However, the role of these neurometabolites in motor learning is still unclear. Furthermore, it remains to be investigated which neurometabolite levels from the regions composing the sensorimotor network predict future learning outcome. Here, we studied the role of baseline neurometabolite levels in four task-related brain areas during different stages of motor skill learning under two different feedback (FB) conditions. Fifty-one healthy participants were trained on a bimanual motor task over 5 days while receiving either concurrent augmented visual FB (CA-VFB group, N = 25) or terminal intrinsic visual FB (TA-VFB group, N = 26) of their performance. Additionally, MRS-measured baseline GABA+ (GABA + macromolecules) and Glx (Glu + glutamine) levels were measured in the primary motor cortex (M1), primary somatosensory cortex (S1), dorsolateral prefrontal cortex (DLPFC), and medial temporal cortex (MT/V5). Behaviorally, our results revealed that the CA-VFB group outperformed the TA-VFB group during task performance in the presence of augmented VFB, while the TA-VFB group outperformed the CA-VFB group in the absence of augmented FB. Moreover, baseline M1 GABA+ levels positively predicted and DLPFC GABA+ levels negatively predicted both initial and long-term motor learning progress in the TA-VFB group. In contrast, baseline S1 GABA+ levels positively predicted initial and long-term motor learning progress in the CA-VFB group. Glx levels did not predict learning progress. Together, these findings suggest that baseline GABA+ levels predict motor learning capability, yet depending on the FB training conditions afforded to the participants.

The diagnostic challenge of lack of choline level elevation on 1H-MR spectroscopy in grade II-III gliomas

The accurate diagnosis of brain tumour is very important in modern neuro-oncology medicine. Magnetic resonance spectroscopy (MRS) is supposed to be a promising tool for detecting cancerous lesions. However, the interpretation of MRS data is complicated by the fact that not all cancerous lesions exhibit elevated choline (Cho) levels. The main goal of our study was to investigate the lack of Cho lesion /Cho ref elevation in the population of grade II-III gliomas. 89 cases of gliomas grade II and III were used for the retrospective analysis - glioma (astrocytoma or oligodendroglioma) grade II (74 out of 89 cases [83%]) and III (15 out of 89 cases [17%]) underwent conventional MRI extended by MRS before treatment. Histopathological diagnosis was obtained either by biopsy or surgical resection. Gliomas were classified to the group of no-choline elevation when the ratio of choline measured within the tumour (Cho lesion ) to choline from NABT (Cho ref ) were equal to or lower than 1. Significant differences were observed between ratios of Cho lesion /Cr lesion calculated for no-choline elevation and glial tumour groups as well as in the NAA lesion /Cr lesion ratio between the no-choline elevation group and glial tumour group. With consistent data concerning choline level elevation and slightly lower NAA value, the Cho lesion /NAA lesion ratio is significantly higher in the WHO II glial tumour group compared to the no-choline elevation cases ( p < 0.000). In the current study the results demonstrated possibility of lack of choline elevation in patients with grade II-III gliomas, so it is important to remember that the lack of elevated choline levels does not exclude neoplastic lesion.

The Trajectory of Prefrontal GABA levels in Initially Antipsychotic-Naïve Patients with Psychosis during Two Years Treatment and associations with Striatal Cerebral Blood Flow and Outcome

BACKGROUND

Gamma-aminobutyric acid (GABA)-ergic function in the prefrontal cortex seems dysfunctional in first-episode patients with psychosis, but the impact of longer-term treatment and relation to clinical outcomes as well as striatal activity are unknown.

METHODS

Longitudinal study of 39 antipsychotic-naïve and benzodiazepine-free patients with psychosis (22.4 ± 5.4 years, 64% females) and 54 matched healthy controls (HCs) (22.2 ± 4.3 years, 61% females) followed-up after six weeks (28 patients, 51 HCs), six months (17 patients, 47 HCs), and two years (21 patients, 43 HCs). GABA levels in dorsal anterior cingulate cortex (dACC) and striatal resting cerebral blood flow (rCBF) were assessed on a 3T MR scanner at all visits.

RESULTS

GABA levels in dACC were significantly lower in patients at baseline and after six weeks, but not after six months and two years. Analyses of groups separately revealed decreased GABA levels after two years in HCs but stable levels in patients. Treatment increased striatal rCBF after six weeks and six months but not after two years. GABA levels were negatively associated with striatal rCBF in both groups at all visits. Last, lower baseline GABA levels in patients were related to less functional improvement after two years.

CONCLUSIONS

The findings suggest a different trajectory of GABA levels and striatal perfusion in first-episode patients over two years of antipsychotic treatment compared with HCs and indicate a downregulatory role of prefrontal GABAergic function on striatum. Moreover, abnormally low prefrontal GABA level at illness onset may be a marker for a more severe prognosis.

Automated High-Order Shimming for Neuroimaging Studies

B0 inhomogeneity presents a significant challenge in MRI and MR spectroscopy, particularly at high-field strengths, leading to image distortion, signal loss, and spectral broadening. Existing high-order shimming methods can alleviate these issues but often require time-consuming and subjective manual selection of regions of interest (ROIs). To address this, we proposed an automated high-order shimming (autoHOS) method, incorporating deep-learning-based brain extraction and image-based high-order shimming. This approach performs automated real-time brain extraction to define the ROI of the field map to be used in the shimming algorithm. The shimming performance of autoHOS was assessed through in vivo echo-planar imaging (EPI) and spectroscopic studies at both 3T and 7T field strengths. AutoHOS outperforms linear shimming and manual high-order shimming, enhancing both the image and spectral quality by reducing the EPI image distortion and narrowing the MRS spectral lineshapes. Therefore, autoHOS demonstrated a significant improvement in correcting B0 inhomogeneity while eliminating the need for additional user interaction.

Menopausal symptoms in midlife Singaporean women: Prevalence rates and associated factors from the Integrated Women's Health Programme (IWHP)

OBJECTIVE

Menopausal symptoms can substantially impact quality of life. We studied somatic, psychological, and urogenital symptoms and their associated factors.

DESIGN

Cross-sectional study of healthy midlife Singaporean women from three major Asian ethnic groups.

METHODS

In 2014-16, women aged 45 to 69 attending well-woman clinics at the National University Hospital Singapore completed the Menopause Rating Scale (MRS). Sociodemographic, reproductive, medical, anthropometric, body composition, and physical performance characteristics were assessed using validated questionnaires and strict protocols. We analysed sub-scales and total scores by median split, and adjusted odds ratios using multivariable logistic regression.

RESULTS

Of the 1054 eligible women, 62.6 % reported at least one moderate to extremely severe symptom. The top five menopausal symptoms were joint and muscle discomfort, sleep problems, vaginal dryness, physical and mental exhaustion, and hot flushes. Higher total scores on the MRS were associated with moderate disability (adjusted odds ratio: 9.80, 95 % confidence interval: 2.88-33.34), poorer self-rated health status (2.18, 1.60-2.97), menstrual irregularity at 25 years (1.63, 1.07-2.49), and slower chair stands (1.49, 1.09-2.03). Age ≥65 (0.54, 0.30-0.94) and a lower level of education (0.45, 0.26-0.76) had significant inverse associations with total MRS score.

CONCLUSIONS

Menopausal symptoms were associated with disability, poorer health status, and weaker lower-body muscle strength. These data add to the limited Asian evidence and raise the profile of this important area of health.

MRI Methods to Visualize and Quantify Adipose Tissue in Health and Disease

MRI is the modality of choice for a vast range of pathologies but also a sensitive probe into human physiology and tissue function. For this reason, several methodologies have been developed and continuously evolve in order to non-invasively monitor underlying phenomena in human adipose tissue that were difficult to assess in the past through visual inspection of standard imaging modalities. To this end, this work describes the imaging methodologies used in medical practice and lists the most important quantitative markers related to adipose tissue physiology and pathology that are currently supporting diagnosis, longitudinal evaluation and patient management decisions. The underlying physical principles and the resulting markers are presented and associated with frequently encountered pathologies in radiology in order to set the frame of the ability of MRI to reveal the complex role of adipose tissue, not as an inert tissue but as an active endocrine organ.

Organic Fluorine Compounds and Their Uses as Molecular MR-Based Temperature Sensors

The interest in fluorinated substances has increased significantly in recent decades due to their diverse properties and possible uses. An important analytical method in this context is NMR spectroscopy, which provides information on the structure as well as on intermolecular interactions or generally on changes in the environment of the nucleus under consideration. A physical quantity that is of great importance in most studies is temperature. However, this is not always easy, e. g. in shielded systems or within an organism. However, the application potential in chemical reactors or in medical diagnosis and therapy is very high and for this reason 13 fluorinated organic compound were chosen for a first 19 F NMR signal temperature sensitivity examination for determination of local temperatures in solution. Polyfluorinated molecules with separate 19 F MR signals are particularly suitable for temperature determination. Those can be serve as internal error-correcting thermometers without the need of a reference substance. Under these conditions, a 19 F MR signal shift of up to 0.03 ppm/K was detectable. Fluorine position and chemical environment were very important for the temperature sensitivity.

Effect of circadian rhythm on NAD and other metabolites in human brain

Nicotinamide Adenine Dinucleotide (NAD) plays a central role in the master circadian clock of the brain (the suprachiasmatic nuclei, SCN) as demonstrated in many model organisms. NAD acts as an enzyme co-factor and substrate and its modulation was found to be tightly regulated to the periodicity of the cycles. However, in human brain, the effect of the circadian rhythm (CR) on the metabolism of the SCN and other brain regions is poorly understood. We conducted a magnetic resonance spectroscopy (MRS) study at a high magnetic field, measuring the occipital brain NAD levels and other metabolites in two different morning and afternoon diurnal states in 25 healthy participants. Salivary cortisol levels were determined to confirm that the experiment was done in two chronologically different physiological conditions, and a behavioral test of risk-taking propensity was administered. Overall, we found that the CR did not significantly affect NAD levels in the occipital brain region. The other brain metabolites measured, including lactate, were not significantly affected by the CR either, except for taurine. The CR did impact risk-taking behavior and salivary cortisol level, confirming that the participants were in two circadian different behavioral and physiological states in the morning and in the afternoon. Measurement of the CR effect on NAD and taurine levels in other brain regions might provide stronger effects.

Investigating brain alterations in the Dp1Tyb mouse model of Down syndrome

Down syndrome (DS) is one of the most common birth defects and the most prevalent genetic form of intellectual disability. DS arises from trisomy of chromosome 21, but its molecular and pathological consequences are not fully understood. In this study, we compared Dp1Tyb mice, a DS model, against their wild-type (WT) littermates of both sexes to investigate the impact of DS-related genetic abnormalities on the brain phenotype. We performed in vivo whole brain magnetic resonance imaging (MRI) and hippocampal 1H magnetic resonance spectroscopy (MRS) on the animals at 3 months of age. Subsequently, ex vivo MRI scans and histological analyses were conducted post-mortem. Our findings unveiled the following neuroanatomical and biochemical alterations in the Dp1Tyb brains: a smaller surface area and a rounder shape compared to WT brains, with DS males also presenting smaller global brain volume compared with the counterpart WT. Regional volumetric analysis revealed significant changes in 26 out of 72 examined brain regions, including the medial prefrontal cortex and dorsal hippocampus. These alterations were consistently observed in both in vivo and ex vivo imaging data. Additionally, high-resolution ex vivo imaging enabled us to investigate cerebellar layers and hippocampal sub-regions, revealing selective areas of decrease and remodelling in these structures. An analysis of hippocampal metabolites revealed an elevation in glutamine and the glutamine/glutamate ratio in the Dp1Tyb mice compared to controls, suggesting a possible imbalance in the excitation/inhibition ratio. This was accompanied by the decreased levels of taurine. Histological analysis revealed fewer neurons in the hippocampal CA3 and DG layers, along with an increase in astrocytes and microglia. These findings recapitulate multiple neuroanatomical and biochemical features associated with DS, enriching our understanding of the potential connection between chromosome 21 trisomy and the resultant phenotype.

Taurine and N-acetylcysteine treatments prevent memory impairment and metabolite profile alterations in the hippocampus of high-fat diet-fed female mice

Background: Obesity constitutes a risk factor for cognitive impairment. In rodent models, long-term exposure to obesogenic diets leads to hippocampal taurine accumulation. Since taurine has putative cyto-protective effects, hippocampal taurine accumulation in obese and diabetic models might constitute a counteracting response to metabolic stress. Objective: We tested the hypothesis that treatment with taurine or with N-acetylcysteine (NAC), which provides cysteine for the synthesis of taurine and glutathione, prevent high-fat diet (HFD)-associated hippocampal alterations and memory impairment. Methods: Female mice were fed either a regular diet or HFD. Some mice had access to 3%(w/v) taurine or 3%(w/v) NAC in the drinking water. After 2 months, magnetic resonance spectroscopy (MRS) was used to measure metabolite profiles. Memory was assessed in novel object and novel location recognition tests. Results: HFD feeding caused memory impairment in both tests, and reduced concentration of lactate, phosphocreatine-to-creatine ratio, and the neuronal marker N-acetylaspartate in the hippocampus. Taurine and NAC prevented HFD-induced memory impairment and N-acetylaspartate reduction. NAC, but not taurine, prevented the reduction of lactate and phosphocreatine-to-creatine ratio. MRS revealed NAC/taurine-induced increase of hippocampal glutamate and GABA levels. Conclusion: NAC and taurine can prevent memory impairment, while only NAC prevents alterations of metabolite concentrations in HFD-exposed female mice.

Determination of Urban Formaldehyde Emission Ratios in the Shanghai Megacity

We analyzed two data sets of atmospheric formaldehyde (FA) at an urban site in the Shanghai megacity during the summer of 2017 and the winter of 2017/18, with the primary objective of determining the emission ratio of formaldehyde versus carbon monoxide (CO). Through the photochemical age method and the minimum R squared (MRS) method, we derived the summer urban formaldehyde release ratios of 3.37 ppbv (ppmv of CO)-1 and 4.04 ppbv (ppmv of CO)-1, respectively. The error of both estimations is within ±20%, indicating the consistency of the results. We recognized the hourly minimum emission ratios determined from the MRS method to be indicative of actual formaldehyde emission ratios. Similarly, the emission ratio in winter is determined to be 2.10 ppbv (ppmv of CO)-1 utilizing the MRS method. The findings provide significant insights into the potential impact of motor vehicle exhaust on formaldehyde emissions in urban areas. This work demonstrates that the formaldehyde emission ratio determined by the MRS method can be used to represent the emissions of the freshest air mass. Formaldehyde photolysis contributed an average of 9% to the free radical primary reaction rate (P(ROx)) as a single chemical species during the daytime in summer, which was lower than the 11% recorded in winter. Formaldehyde emission reduction positively impacts local ozone production, so models describing ozone formation in Shanghai during summer need to reflect these emissions accurately. Evidence of the crucial catalytic role of formaldehyde in particulate matter formation has been confirmed by recent research. A potentially effective way to decrease the incidence of haze days in autumn and winter in the future is therefore to focus on reducing formaldehyde emissions.

Electrophysiological and Imaging Biomarkers to Evaluate Exercise Training in Patients with Neuromuscular Disease: A Systematic Review

Exercise therapy as part of the clinical management of patients with neuromuscular diseases (NMDs) is complicated by the limited insights into its efficacy. There is an urgent need for sensitive and non-invasive quantitative muscle biomarkers to monitor the effects of exercise training. Therefore, the objective of this systematic review was to critically appraise and summarize the current evidence for the sensitivity of quantitative, non-invasive biomarkers, based on imaging and electrophysiological techniques, for measuring the effects of physical exercise training. We identified a wide variety of biomarkers, including imaging techniques, i.e., magnetic resonance imaging (MRI) and ultrasound, surface electromyography (sEMG), magnetic resonance spectroscopy (MRS), and near-infrared spectroscopy (NIRS). Imaging biomarkers, such as muscle maximum area and muscle thickness, and EMG biomarkers, such as compound muscle action potential (CMAP) amplitude, detected significant changes in muscle morphology and neural adaptations following resistance training. MRS and NIRS biomarkers, such as initial phosphocreatine recovery rate (V), mitochondrial capacity (Qmax), adenosine phosphate recovery half-time (ADP t1/2), and micromolar changes in deoxygenated hemoglobin and myoglobin concentrations (Δ[deoxy(Hb + Mb)]), detected significant adaptations in oxidative metabolism after endurance training. We also identified biomarkers whose clinical relevance has not yet been assessed due to lack of sufficient study.

Individual Differences in Decision Strategy Relate to Neurochemical Excitability and Cortical Thickness

The speed-accuracy trade-off (SAT), whereby faster decisions increase the likelihood of an error, reflects a cognitive strategy humans must engage in during the performance of almost all daily tasks. To date, computational modeling has implicated the latent decision variable of response caution (thresholds), the amount of evidence required for a decision to be made, in the SAT. Previous imaging has associated frontal regions, notably the left prefrontal cortex and the presupplementary motor area (pre-SMA), with the setting of such caution levels. In addition, causal brain stimulation studies, using transcranial direct current stimulation (tDCS), have indicated that while both of these regions are involved in the SAT, their role appears to be dissociable. tDCS efficacy to impact decision-making processes has previously been linked with neurochemical concentrations and cortical thickness of stimulated regions. However, to date, it is unknown whether these neurophysiological measures predict individual differences in the SAT, and brain stimulation effects on the SAT. Using ultra-high field (7T) imaging, here we report that instruction-based adjustments in caution are associated with both neurochemical excitability (the balance between GABA+ and glutamate) and cortical thickness across a range of frontal regions in both sexes. In addition, cortical thickness, but not neurochemical concentrations, was associated with the efficacy of left prefrontal and superior medial frontal cortex (SMFC) stimulation to modulate performance. Overall, our findings elucidate key neurophysiological predictors, frontal neural excitation, of individual differences in latent psychological processes and the efficacy of stimulation to modulate these.SIGNIFICANCE STATEMENT The speed-accuracy trade-off (SAT), faster decisions increase the likelihood of an error, reflects a cognitive strategy humans must engage in during most daily tasks. The SAT is often investigated by explicitly instructing participants to prioritize speed or accuracy when responding to stimuli. Using ultra-high field (7T) magnetic resonance imaging (MRI), we found that individual differences in the extent to which participants adjust their decision strategies with instruction related to neurochemical excitability (ratio of GABA+ to glutamate) and cortical thickness in the frontal cortex. Moreover, brain stimulation to the left prefrontal cortex and the superior medial frontal cortex (SMFC) modulated performance, with the efficacy specifically related to cortical thickness. This work sheds new light on the neurophysiological basis of decision strategies and brain stimulation.

Basal glutamate in the hippocampus and the dorsolateral prefrontal cortex in schizophrenia: Relationships to cognitive proficiency investigated with structural equation modelling

OBJECTIVES

Schizophrenia is characterised by deficits across multiple cognitive domains and altered glutamate related neuroplasticity. The purpose was to investigate whether glutamate deficits are related to cognition in schizophrenia, and whether glutamate-cognition relationships are different between schizophrenia and controls.

METHODS

Magnetic resonance spectroscopy (MRS) at 3 Tesla was acquired from the dorsolateral prefrontal cortex (dlPFC) and hippocampus in 44 schizophrenia participants and 39 controls during passive viewing visual task. Cognitive performance (working memory, episodic memory, and processing speed) was assessed on a separate session. Group differences in neurochemistry and mediation/moderation effects using structural equation modelling (SEM) were investigated.

RESULTS

Schizophrenia participants showed lower hippocampal glutamate (p = .0044) and myo-Inositol (p = .023) levels, and non-significant dlPFC levels. Schizophrenia participants also demonstrated poorer cognitive performance (p < .0032). SEM-analyses demonstrated no mediation or moderation effects, however, an opposing dlPFC glutamate-processing speed association between groups was observed.

CONCLUSIONS

Hippocampal glutamate deficits in schizophrenia participants are consistent with evidence of reduced neuropil density. Moreover, SEM analyses indicated that hippocampal glutamate deficits in schizophrenia participants as measured during a passive state were not driven by poorer cognitive ability. We suggest that functional MRS may provide a better framework for investigating glutamate-cognition relationships in schizophrenia.