N-Acetylaspartate in the CNS: from neurodiagnostics to neurobiology

Integrative metabolomics and transcriptomics analysis of hippocampus reveals taurine metabolism and sphingolipid metabolism dysregulation associated with sleep deprivation-induced memory impairment

Sleep plays a crucial role in restoring and repairing the body, consolidating memory, regulating emotions, maintaining metabolic and so on. Sleep deprivation is known to impair cognitive functions. In this study, we investigated the mechanisms underlying memory impairment induced by sleep deprivation through a combined metabolomic and transcriptomic analysis of hippocampus. Eight-week-old mice were selected as the study subjects and the sleep deprivation chamber was used to establish a sleep deprivation model. Novel object recognition tests (NOR), and Y-maze tests were used to assess the behavioral outcomes in mice. The hippocampus were extracted and studied using the untargeted metabolomics or transcriptomics high-throughput sequencing method. An integrative analysis was conducted to elucidate the metabolic and genetic changes. Behavioral tests showed that sleep-deprived mice exhibited memory impairment. Metabolomic analysis identified 84 differentially expressed metabolites (DEMs), including 12 under the positive ion mode and 72 under the negative ion mode. The analysis revealed that sleep deprivation caused abnormalities in several metabolic pathways, with particularly pronounced effects observed in glycerophospholipid metabolism, linoieic acid metabolism, alanine, aspartate, glutamate metabolism, taurine and hypotaurine metabolism, and purine metabolism. While transcriptomic analysis releaved 97 differentially expressed genes (DEGs) (51 were down-regulated and 46 were up-regulated DEGs). Integrative analysis of the metabolomic and transcriptomic identified profiles showed that sleep deprivation may regulate taurine and hypotaurine metabolism and sphingolipid metabolism, there by influencing memory. Our results prompt severe metabolic disturbances occur in the hippocampus with sleep deprivation in mice, which can provide a basis for the mechanism research.

Molecular neuroimaging of ovarian steroid effects on the female brain: A systematic review of human non-clinical studies

Molecular neuroimaging is a powerful tool for studying ovarian steroid effects on the brain. We systematically reviewed non-clinical studies of female reproductive transitions, ovarian suppression, or estradiol (E2) and/or progesterone (P4) administration. Most studies used ≤3T [1H]MRS to study neurometabolites or PET imaging of glucose metabolism and serotoninergic activity. Results suggest ovarian steroids dynamically influence neurometabolic activity and serotonin neurotransmission. Elevated E2, whether during the late follicular phase or with postmenopausal administration, enhanced glucose-related metabolic activity and excitatory serotonin signaling, while low postmenopausal E2 may shift metabolism away from glucose for energy production. Rising P4, whether during the luteal phase or with postmenopausal administration, attenuated regional energy storage potential and glucose metabolism, while amplifying excitatory serotonin signaling. The perinatal transition was less studied, mostly with [1H]MRS, and showed non-significant or transient effects. Studies examining outcomes related to neuroprotection, neuroinflammation, and hormone receptor density were limited. We highlight the need for further molecular neuroimaging, including multimodal approaches, to systematically characterize ovarian steroid targets and their molecular context. Advances in MRS and PET offer opportunities to study ovarian steroid effects on neuroplasticity, mitochondrial function, neuroprotection, and neuroinflammation, and there is a need for continued robust prospective longitudinal and experimental studies.

Alterations in cerebral perfusion and substrate metabolism in type 2 diabetes: interactions with APOE-ε4

AIMS/HYPOTHESIS

Epidemiological studies indicate that type 2 diabetes increases the risk for Alzheimer's disease. Alterations in cerebral metabolism have been proposed as a potential mechanism underlying this association. A better understanding of these metabolic changes may elucidate potential pathways linking type 2 diabetes to Alzheimer's disease. The aim of the current exploratory study was to investigate whether cerebral metabolism, including glucose and fatty acid uptake as well as cerebral blood flow, is altered in individuals with type 2 diabetes compared with both overweight individuals and lean control individuals.

METHODS

This exploratory study included 38 participants (ten with type 2 diabetes, 13 overweight individuals and 15 lean control individuals). Brain metabolism was assessed using multiple imaging techniques: [18F]fluorodeoxyglucose and [18F]fluoro-6-thiaheptadecanoic acid positron emission tomography for glucose and fatty acid uptake; arterial spin-labelling MRI for cerebral perfusion; and 1H-magnetic resonance spectroscopy for specific metabolites. Neurodegeneration markers were evaluated from lumbar puncture samples. Group comparisons were assessed using one-way ANOVA and unpaired t tests, and correlations were assessed with linear regression.

RESULTS

Individuals with type 2 diabetes exhibited lower cerebral glucose uptake compared with both lean and overweight groups (p<0.01). Cerebral perfusion was reduced in both participants with type 2 diabetes and overweight participants relative to lean control participants (p<0.01). Both glucose uptake and perfusion correlated negatively with HOMA-IR, insulin and HbA1c levels (p<0.001-p<0.05). White matter fatty acid uptake was elevated in the diabetes group compared with the lean group (p<0.05). Post hoc analyses revealed that lean APOE-ε4 carriers had increased fatty acid uptake in the entire brain relative to lean non-carriers. Among non-carriers of APOE-ε4, those with type 2 diabetes showed higher fatty acid uptake than lean control individuals (p<0.01-p<0.05), and this uptake correlated positively with HOMA-IR, insulin and HbA1c levels (p<0.05).

CONCLUSIONS/INTERPRETATION

Type 2 diabetes was associated with decreased cerebral perfusion and glucose uptake but increased fatty acid uptake in white matter. The elevated fatty acid uptake observed both in individuals with type 2 diabetes and in APOE-ε4 carriers suggests a common metabolic dysfunction for these Alzheimer's disease risk factors and suggests that targeting cerebral metabolic dysfunction, particularly fatty acid metabolism, could be a potential strategy for reducing the risk for neurodegeneration in individuals with type 2 diabetes.

"Advances in biomarker discovery and diagnostics for alzheimer's disease"

BACKGROUND

Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by intracellular neurofibrillary tangles with tau protein and extracellular β-amyloid plaques. Early and accurate diagnosis is crucial for effective treatment and management.

OBJECTIVE

The purpose of this review is to investigate new technologies that improve diagnostic accuracy while looking at the current diagnostic criteria for AD, such as clinical evaluations, cognitive testing, and biomarker-based techniques.

METHODS

A thorough review of the literature was done in order to assess both conventional and contemporary diagnostic methods. Multimodal strategies integrating clinical, imaging, and biochemical evaluations were emphasised. The promise of current developments in biomarker discovery was also examined, including mass spectrometry and artificial intelligence.

RESULTS

Current diagnostic approaches include cerebrospinal fluid (CSF) biomarkers, imaging tools (MRI, PET), cognitive tests, and new blood-based markers. Integrating these technologies into multimodal diagnostic procedures enhances diagnostic accuracy and distinguishes dementia from other conditions. New technologies that hold promise for improving biomarker identification and diagnostic reliability include mass spectrometry and artificial intelligence.

CONCLUSION

Advancements in AD diagnostics underscore the need for accessible, minimally invasive, and cost-effective techniques to facilitate early detection and intervention. The integration of novel technologies with traditional methods may significantly enhance the accuracy and feasibility of AD diagnosis.

Magnetic resonance imaging and spectroscopy in hypomyelinating leukodystrophy

Recent advancements in molecular biology and radiology have led to the identification of several new leukodystrophies. A key diagnostic feature of leukodystrophies is the increased white matter signal intensity observed on T2-weighted magnetic resonance (MR) images. Leukodystrophies are typically classified into two main categories: hypomyelinating leukodystrophies (HLD) and other forms, including demyelinating leukodystrophies. HLD is characterized by a primary defect in myelin due to genetic variants that affect structural myelin proteins, oligodendrocyte transcription factors, RNA translation, and lysosomal proteins. Radiologically, HLD tends to show less pronounced white matter hyperintensity on T2-weighted images than demyelinating leukodystrophies. A definitive diagnosis can often be made by identifying abnormalities in regions beyond the white matter, such as the basal ganglia or cerebellum, or through the presence of characteristic clinical symptoms. N-acetylaspartate, a neuroaxonal marker observed on MR spectroscopy, is typically reduced in many neurological conditions, but N-acetylaspartate levels often remain normal in HLD, which is considered a distinctive feature of this disorder. This article provides an overview of the latest imaging findings and clinical features associated with HLD.

Proton Magnetic Resonance Spectroscopy for Pediatric Neuroimaging: Key Concepts for Practice

Magnetic resonance spectroscopy (MRS) of the brain provides the clinician an in vivo neurochemical assessment within the clinical magnetic resonance imaging setting. This information can yield specificity when addressing questions pertaining to brain health and metabolism while characterizing disease and injury, evaluating treatment response, and prognosticating outcome. Proton MRS techniques can be useful in narrowing the diagnostic differential and capturing time-sensitive information for the continually developing pediatric brain. This paper provides a review of key proton MRS topics relevant for usage in pediatric populations. We discuss magnetic field strength, pediatric-sized head coils, water suppression techniques, localization pulse sequences, post-processing methods, analysis, and interpretation. These elements all require special consideration, particularly for the immature brain. We introduce the fundamentals of spectral editing. Finally, we present illustrative examples employing proton MRS in clinical practice to begin to synthesize these concepts into practical application.

Neurometabolite Changes After Transcranial Photobiomodulation in Major Depressive Disorder: A Randomized Controlled Trial Investigating Dose-Dependent Effects

Background: Transcranial photobiomodulation (t-PBM) is a promising non-invasive therapy for Major Depressive Disorder (MDD). MDD is associated with altered brain metabolism, including changes in N-acetylaspartate (NAA), choline (Cho), and creatine (Cr). This study assessed the effects of varying t-PBM doses on neurometabolite levels in the dorsolateral prefrontal cortex (dlPFC) and their correlations with clinical outcomes. Methods: In this randomized, sham-controlled, cross-over study, 33 adults with MDD received one session of t-PBM at low, medium, and high doses and a sham treatment. Proton magnetic resonance spectroscopy (1H-MRS) measured NAA, Cho, and Cr pre- and post-treatment. Clinical outcomes were assessed using the Montgomery-Åsberg Depression Rating Scale (MADRS) and the Symptoms of Depression Questionnaire (SDQ). Statistical analyses included paired t-tests or Wilcoxon signed-rank tests for neurometabolite changes, and linear mixed-effects regression models for t-PBM dose, neurometabolites, and time effects. Results: NAA levels increased significantly (7.52 ± 0.777 to 8.12 ± 1.05 mmol/L for one session; 7.36 ± 0.85 to 7.85 ± 0.68 mmol/L across all sessions); however, these changes were not associated with specific t-PBM doses or sham. No significant changes were observed for Cho and Cr levels. Positive correlations were found between Cho levels and MADRS scores (r = 0.59, p = 0.017), and negative correlations between Cr levels and SDQ scores at the medium dose (r = -0.91, p = 0.011). Conclusions: While NAA levels increased, and correlations between neurometabolites and clinical outcomes were observed, these findings do not suggest a specific effect of t-PBM. Larger randomized controlled trials with optimized dosing protocols, extended follow-up, and advanced spectroscopy are needed to clarify the neurometabolic therapeutic potential of t-PBM in MDD.

Comparisons of metabolites and gut microbiota profiles for both young and middle-aged APPSwe/PS1De9 mice

The research focused on exploring the differences and relationships between gut microbiota and metabolites at various stages of Alzheimer's disease (AD), specifically using APP/PS1 mice at the ages of 6 months and 10 months. To assess metabolites in serum and cortex, and to evaluate gut microbiota profiles in cecal content, UPLC-MS/MS and 16S rRNA sequencing techniques were utilized, respectively. Findings indicated that, in comparison to younger mice, serum concentrations of L-Leucine, thymine, and Glucosamine 6-phosphate were lower, whereas levels of Sorbitol and Palmitic acid were higher. Furthermore, measurements of the ACE and Chao1 indices significantly declined in the older cohort. At the phylum level, the relative abundance of Bacteroidetes showed a decline, while there was an increase in Actinobacteria and TM7 bacteria among the middle-aged subjects. The novelty of this study is we found there were notable alterations in both gut microbiota and metabolites within serum and cortex when comparing young and older APP/PS1 mice, emphasizing the important connections between metabolites and gut microbiota throughout the progression of AD. These results indicate that manipulating metabolites and gut flora may serve as a vital strategy for the prevention and management of AD.

Impact of intraamniotic inflammation on tryptophan metabolism in the placenta-fetal brain axis in rats

In brief

Intrauterine inflammation disrupts tryptophan metabolism in both the placenta and the fetal brain, leading to a shift toward neurotoxic metabolites. These findings highlight the critical role of placental function in neurodevelopment and suggest that inflammation-induced metabolic changes may contribute to neurodevelopmental disorders.

Abstract

The placenta plays a crucial role beyond nutrient transfer, acting as a dynamic endocrine organ that significantly influences maternal physiology and fetal development. It responds rapidly to even slight changes in the in utero environment to promote fetal survival. Disruptions in placental function are increasingly recognized as key contributors to the origins of neurodevelopmental disorders. In this study, we employed advanced technology to induce intrauterine inflammation through ultrasound-guided administration of LPS into gestational sacs. We then evaluated its effects on the gene expression of enzymes involved in TRP metabolism and conducted a comprehensive LC/MS analysis of the metabolome in the placenta and fetal brain of Wistar rats. Our results show that intraamniotic injection of LPS induces a robust inflammatory response leading to significant alterations in TRP metabolism, including downregulation of tryptophan hydroxylase (TPH) in the placenta, resulting in a decrease in serotonin (5-HT) levels. Similarly, in the fetal brain, exposure to LPS led to reduced Tph expression and increased monoamine oxidase expression, suggesting a decrease in 5-HT synthesis and an increase in its degradation. Furthermore, an upregulation of the kynurenine pathway was observed in both the placenta and fetal brain. Moreover, we detected a shift toward neurotoxicity, evidenced by an imbalance between neuroprotective and neurotoxic metabolites, including decreased levels of kynurenic acid and upregulation of kynurenine monooxygenase in the fetal brain. In conclusion, our findings reveal significant alterations in TRP metabolism following intrauterine inflammation, potentially contributing to neurodevelopmental disorders.

Aeromedical evacuation-relevant hypobaria following traumatic brain injury in rats contributes to cerebral blood flow depression, altered neurochemistry and increased neuroinflammation

Aircraft cabins are routinely pressurized to the equivalent of 8000 ft altitude. Exposure of lab animals to aeromedical evacuation relevant hypobaria after traumatic brain injury worsens neurological outcomes, which is paradoxically exacerbated by hyperoxia. This study tested the hypothesis that exposure of rats to hypobaria following cortical impact reduces cerebral blood flow, increases neuroinflammation, and alters brain neurochemistry. Rats were exposed to simulated ground (normobaric) or air (hypobaric 8000 ft) transport, under normoxia or hyperoxia, 24 hr after trauma. Hypobaria exposure resulted in lower cerebral blood flow to the contralateral cortex and bilateral thalamus during flight and increased delayed cortical inflammation (ED1 immunoreactivity) at 14 days post injury. Impacted rats exposed to hypobaria had higher cortical creatine levels compared rats maintained at sea level. Exposure to the combination of hyperoxia and hypobaria resulted in the greatest reduction in cortical blood flow and total creatine during flight which persisted up to two weeks. In conclusion, hypoperfusion during hypobaria exposure could contribute to worsening of neuroinflammation and neurochemical imbalances. The presence of excessive O2 during hypobaria results in long-term suppression of cerebral blood flow, indicating that supplemental O2 should be titrated during hypobaria to maintain normoxia.

Cytotoxic and metabolic effects of organic extracts from airborne fine particulate matter (PM2.5) in neuronal cells

Airborne fine particulate matter (PM2.5) has been linked to neurological diseases, but its cellular and metabolic effects remain incompletely understood. This study assessed the cytotoxic and metabolic impact of PM2.5 samples from São Paulo, Brazil, on SH-SY5Y neuroblastoma cells. Even at low toxicity levels (IC10-IC30), PM2.5 organic extracts induced apoptosis, increased TNF-α secretion, and triggered moderate oxidative responses. Metabolomic analyses revealed a downregulation of energy-producing pathways, including glycolysis and the TCA cycle, along with decreased ATP and phosphocreatine levels. Compensatory adaptations were evident, such as increased proline oxidation, lipid accumulation, and activation of the creatine-phosphocreatine system. One-carbon metabolism was also affected, with changes suggesting suppression of the folate and methionine cycles. Elevated glutathione levels indicated an enhanced antioxidant response. These findings highlight how PM2.5 disrupts neuronal energy homeostasis and redox balance, offering new insights into the cellular mechanisms of air pollution-related neurotoxicity.

Brain Metabolite Profiles are Associated with Selective Neuronal Vulnerability and Underlying Mechanisms in Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a lethal neurological syndrome accompanied by selective degeneration of somatic motor neurons and neurochemistry alterations. Nevertheless, eye movement's nuclei are relatively spared from ALS damage. This survey was to probe metabolite changes in the primary motor cortex (PMC) and interstitial nucleus of Cajal (INC) of ALS patients using proton magnetic resonance spectroscopy (1H-MRS). In this case-control study, 20 patients with ALS and 20 healthy controls underwent 1.5 T MRI and multivoxel 1H-MRS. 1H-MRS spectra to determine metabolite profiles including tNAA, mIns, tCr, tCho, and also tNAA/tCr, tNAA/tCho, and mIns/tNAA metabolite ratios from the PMC and INC were quantified via a point resolved spectroscopy pulse (PRESS) sequence in two groups. Further, the associations between 1H-MRS markers with forced vital capacity (FVC), ALS functional rating scale (ALSFRS-R), and disease progression rate (ΔFS) were investigated. In the PMC, tNAA and tNAA/tCr were significantly lower in ALS patients than the healthy controls, but mIns and mIns/tNAA were significantly greater in these patients (p < 0.05). In the INC, tCho and mIns concentrations, and mIns/tNAA ratio were significantly increased (p < 0.05) in ALS patients, while tNAA and tNAA/tCr ratio did not show significant discriminations between the two groups (p > 0.05). The PMC tNAA/Cr ratio is associated with ALSFRS-R (p = 0.001, r = 0.71), FVC (p = 0.03, r = 0.58), and ΔFS (p = 0.01, r = -0.33). The mIns/tNAA ratio in PMC is also associated with ΔFS (p = 0.02, r = 0.41). In the INC, tCho concentrations (p = 0.04, r = -0.54) and mIns/tNAA ratio (p = 0.02, r = -0.38) were negatively associated with ALSFRS-R and positively correlated with ΔFS (p = 0.01, r = 0.33) and (p = 0.001, r = 0.61), respectively. The study suggests that neurochemistry changes in ALS patients' brains are linked to selective neuronal vulnerability and the underlying pathophysiology of the disease.

Targeted and Non-Targeted Metabolomic Evaluation of Cerebrospinal Fluid in Early Phase Schizophrenia: A Pilot Study from the Hopkins First Episode Psychosis Project

(1) Background: The lack of reliable biomarkers remains a significant barrier to improving outcomes for patients with schizophrenia. While metabolomic analyses of blood, urine, and feces have been explored, results have been inconsistent. Compared to peripheral compartments, cerebrospinal fluid (CSF) more closely reflects the chemical composition of brain extracellular fluid. Given that brain dysregulation may be more pronounced during the first episode of psychosis (FEP), we hypothesized that metabolomic analysis of CSF from FEP patients could reveal disease-associated biomarkers. (2) Methods: We recruited 15 patients within 24 months of psychosis onset (DSM-4 criteria) and 14 control participants through the Johns Hopkins Schizophrenia Center. CSF samples were analyzed using both non-targeted and targeted liquid chromatography-mass spectrometry. (3) Results: The non-targeted analysis identified lower levels of N-acetylneuraminic acid and N-acetyl-L-aspartic acid in the FEP group, while levels of uric acid were elevated. The targeted analysis focused on indolic and phenolic molecules previously linked to neuropsychiatric disorders. Notably, L-phenylalanine and 4-hydroxycinnamic acid levels were lower in the FEP group, and this difference remained significant after adjusting for age and sex. However, none of the significant differences in analyte levels between the groups survived an adjustment for multiple comparisons. (4) Conclusions: Our intriguing but preliminary associations align with results from other investigational approaches and highlight potential CSF analytes that warrant further study in larger samples.

Exploring Human Brain Metabolism via Genome-Scale Metabolic Modeling with Highlights on Multiple Sclerosis

Cerebral dysfunctions give rise to a wide range of neurological diseases due to the structural and functional complexity of the human brain stemming from the interactive cellular metabolism of its specific cells, including neurons and glial cells. In parallel with advances in isolation and measurement technologies, genome-scale metabolic models (GEMs) have become a powerful tool in the studies of systems biology to provide critical insights into the understanding of sophisticated eukaryotic systems. In this study, brain cell-specific GEMs were reconstructed for neurons, astrocytes, microglia, oligodendrocytes, and oligodendrocyte precursor cells by integrating single-cell RNA-seq data and global Human1 via a task-driven integrative network inference for tissues (tINIT) algorithm. Then, intercellular reactions among neurons, astrocytes, microglia, and oligodendrocytes were added to generate a combined brain model, iHumanBrain2690. This brain network was used in the prediction of metabolic alterations in glucose, ketone bodies, oxygen change, and reporter metabolites. Glucose supplementation increased the subsystems' activities in glycolysis, and ketone bodies elevated those in the TCA cycle and oxidative phosphorylation. Reporter metabolite analysis identified L-carnitine and arachidonate as the top reporter metabolites in gray and white matter microglia in multiple sclerosis (MS), respectively. Carbamoyl-phosphate was found to be the top reporter metabolite in primary progressive MS. Taken together, single and integrated iHumanBrain2690 metabolic networks help us elucidate complex metabolism in brain physiology and homeostasis in health and disease.

Gut dysbiosis as a driver of neuroinflammation in attention-deficit/hyperactivity disorder: A review of current evidence

There is mounting evidence for the involvement of the immune system, neuroinflammation and disturbed gut microbiota, or dysbiosis, in attention-deficit/hyperactivity disorder (ADHD). Gut dysbiosis is strongly implicated in many physical, autoimmune, neurological, and neuropsychiatric conditions, however knowledge of its particular pathogenic role in ADHD is sparse. As such, this narrative review examines and synthesizes the available evidence related to inflammation, dysbiosis, and neural processes in ADHD. Minimal differences in microbiota diversity measures between cases and controls were found, however many relative abundance differences were observed at all classification levels (phylum to strain). Compositional differences of taxa important to key gut-brain axis pathways, in particular Bacteroides species and Faecalibacterium, may contribute to inflammation, brain functioning differences, and symptoms, in ADHD. We have identified one possible model of ADHD etiopathogenesis involving systemic inflammation, an impaired blood-brain barrier, and neural disturbances as downstream consequences of gut dysbiosis. Nevertheless, studies conducted to date have varied degrees of methodological rigour and involve diverse participant characteristics and analytical techniques, highlighting a need for additional research.

Metabolic Reprogramming in Primary Microglial Cell and Extracellular Vesicle Triggered by Aβ Exposure

Microglia, key immune cells in the brain, play a pivotal role in brain homeostasis and immune responses. Emerging evidence suggests their critical involvement in Alzheimer's disease (AD) pathogenesis and propagation. The propagation of AD pathology is related to the extracellular matrix of microglia, including extracellular vesicles (EV). Recently, microglia-derived EVs are implicated in inflammatory processes and neuronal death. This study aimed to extensively profile and propose the metabolic role of microglial EVs in AD. Accordingly, we determined the significant alterations of the EV metabolome associated with the metabolites in primary microglial cells. Aβ exposure induced significant metabolic alteration of 39, 18, and 28 metabolites in microglial cells, cultured media, and EVs, respectively. Aβ exposure triggered common alteration of key metabolic pathways between microglial cells and EVs, including purine, amino acid, and fatty acid metabolisms. While most of the common metabolites showed the same directional changes among the microglial system, N-acetyl aspartic acid displayed the opposite directional change in EVs. N-acetyl aspartic acid decreased 2.3-fold and twofold in microglial cells and media, respectively, but increased 3.5-fold in EVs under Aβ exposure. Moreover, mediation analysis proposed key EV metabolites that were directly affected by the metabolic dysregulation of Aβ-exposed microglial cells. The up-regulation of cysteic acid in EVs was mediated by up-regulated IMP in microglial cells. The down-regulation of 1-16:0-lysoPE in EVs was mediated by stearoyl-L-carnitine in microglial cells. Our study sheds new light on the role of microglia and EVs in neurodegenerative diseases, offering promising avenues for future therapeutic interventions.

Substrate translocation and inhibition in human dicarboxylate transporter NaDC3

The human high-affinity sodium-dicarboxylate cotransporter (NaDC3) imports various substrates into the cell as tricarboxylate acid cycle intermediates, lipid biosynthesis precursors and signaling molecules. Understanding the cellular signaling process and developing inhibitors require knowledge of the structural basis of the dicarboxylate specificity and inhibition mechanism of NaDC3. To this end, we determined the cryo-electron microscopy structures of NaDC3 in various dimers, revealing the protomer in three conformations: outward-open Co, outward-occluded Coo and inward-open Ci. A dicarboxylate is first bound and recognized in Co and how the substrate interacts with NaDC3 in Coo likely helps to further determine the substrate specificity. A phenylalanine from the scaffold domain interacts with the bound dicarboxylate in the Coo state and modulates the kinetic barrier to the transport domain movement. Structural comparison of an inhibitor-bound structure of NaDC3 to that of the sodium-dependent citrate transporter suggests ways for making an inhibitor that is specific for NaDC3.

Imbalanced Brain Neurochemicals in Long COVID and ME/CFS: A Preliminary Study Using MRI

PURPOSE

Long COVID and myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) patients experience multiple complex symptoms, potentially linked to imbalances in brain neurochemicals. This study aims to measure brain neurochemical levels in long COVID and ME/CFS patients as well as healthy controls to investigate associations with severity measures.

METHODS

Magnetic resonance spectroscopy data were acquired with a 3T Prisma magnetic resonance imaging scanner (Siemens Healthcare, Erlangen, Germany). We measured absolute levels of brain neurochemicals in the posterior cingulate cortex in long COVID (n = 17), ME/CFS (n = 17), and healthy controls (n = 10) using Osprey software. The statistical analyses were performed using SPSS version 29 (IBM, Armonk, NY). Age and sex were included as nuisance covariates.

RESULTS

Glutamate levels were significantly higher in patients with long COVID (P = .02) and ME/CFS (P = .017) than in healthy controls. No significant difference was found between the 2 patient cohorts. Additionally, N-acetyl-aspartate levels were significantly higher in long COVID patients (P = .012). Importantly, brain neurochemical levels were associated with self-reported severity measures in long COVID and ME/CFS.

CONCLUSION

Our study identified significantly elevated glutamate and N-acetyl-aspartate levels in long COVID and ME/CFS patients compared with healthy controls. No significant differences in brain neurochemicals were observed between the 2 patient cohorts, suggesting a potential overlap in their underlying pathology. These findings suggest that imbalanced neurochemicals contribute to the complex symptoms experienced by long COVID and ME/CFS patients.

1H Nuclear Magnetic Resonance (NMR)-Based Metabolic Changes in Nucleus Accumbens and Medial Prefrontal Cortex Following Administration of Morphine in Mice

INTRODUCTION

It is well known that opiate addiction is a neurobiological disease associated with dysregulation of multiple neurotransmitters and neurochemicals. Previous ex-vivo 1H nuclear magnetic resonance (NMR) studies have yielded mixed findings concerning opiate-induced neurometabolic changes at key reward-addiction sites. Whether such changes reflect the conditions in a live animal remains unknown. The present study was therefore designed to fill this knowledge gap by determining the effects of morphine-induced neurometabolic changes under in-vivo conditions.

METHODS

In-vivo 1H NMR spectroscopy (SA Instruments, Stony Brook, NY) was used to measure neurochemical changes in nucleus accumbens (NAc) and medial prefrontal cortex (mPFC) of mice, subjected to twice-daily injections of morphine (10 mg kg-1 s.c.) for five days.

RESULTS

Morphine induced significant changes in the concentrations of a number of metabolites in both mPFC and NAc. The glutamine component of the glutamine-glutamate-GABA excitatory-inhibitory cycle, increased in both mPFC and NAc. Significant increase in glutamate was also observed at mPFC, but not in NAc. The phosphocreatine, marker for energy metabolism, and the N-acetylaspartate marker for neuronal viability and energy metabolism decreased significantly in both mPFC and NAc. Glycerophosphocholine + phosphocholine, markers for cell membrane integrity, increased significantly in both NAc and mPFC after morphine. The antioxidant neurometabolites taurine and glutathione increased significantly in NAc; however, taurine decreased, and glutathione was unchanged in mPFC after morphine. Inositol, a marker for neuroinflammation, increased significantly in NAc.

CONCLUSION

The present study is the first in-vivo 1H NMR spectroscopy in mice to demonstrate morphine-induced dysregulation of multiple metabolites and neurochemicals within the reward-addiction neurocircuitry.

Glutamate, GABA and NAA in treatment-resistant schizophrenia: A systematic review of the effect of clozapine and group differences between clozapine-responders and non-responders

Treatment-resistance in patients with schizophrenia is a major obstacle for improving outcome in patients, especially in those not gaining from clozapine. Novel research implies that glutamatergic and GABAergic abnormalities may be present in treatment-resistant patients, and preclinical research suggests that clozapine affects the GABAergic system. Moreover, clozapine may have a neuroprotective role. To investigate these issues, we conducted a systematic review to evaluate the relationship between clozapine and in vivo measures of gamma-aminobutyric acid (GABA), glutamate (glu), and N-acetylaspartate (NAA) brain levels in treatment- and ultra-treatment-resistant schizophrenia patients (TRS and UTRS). Following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, we included three longitudinal and six cross sectional studies utilizing proton magnetic resonance spectroscopy (H-MRS) that explored brain metabolite levels in clozapine-treated patients. Findings were limited by a small number of studies and definite conclusions cannot be drawn, but the present studies may imply that clozapine reduces glutamate levels in striatal but not cortical areas, whereas glutamatergic metabolites and GABA levels may be increased in ACC in the combined group of TRS and UTRS. Clozapine may also increase NAA in cortical areas. Importantly, this review highlights the need for further clinical studies investigating the effect of clozapine on brain levels of glutamate, GABA, and NAA as well as metabolite group differences in patients with UTRS compared with TRS.

ATP-sensitive potassium channels alter glycolytic flux to modulate cortical activity and sleep

Metabolism plays a key role in the maintenance of sleep/wake states. Brain lactate fluctuations are a biomarker of sleep/wake transitions, where increased interstitial fluid (ISF) lactate levels are associated with wakefulness and decreased ISF lactate is required for sleep. ATP-sensitive potassium (KATP) channels couple glucose-lactate metabolism with excitability. Using mice lacking KATP channel activity (e.g., Kir6.2-/- mice), we explored how changes in glucose utilization affect cortical electroencephalography (EEG) activity and sleep/wake homeostasis. In the brain, Kir6.2-/- mice shunt glucose toward glycolysis, reducing neurotransmitter biosynthesis and dampening cortical EEG activity. Kir6.2-/- mice spent more time awake at the onset of the light period due to altered ISF lactate dynamics. Together, we show that Kir6.2-KATP channels act as metabolic sensors to gate arousal by maintaining the metabolic stability of sleep/wake states and providing the metabolic flexibility to transition between states.

Non-targeted Metabolomics Reveals the Potential Role of MFSD8 in Metabolism in Human Endothelial Cells

The major facilitator superfamily domain containing 8 (MFSD8) belongs to an orphan transporter protein expressed in a wide range of tissues. Nevertheless, the specific role of MFSD8 in human health and disease remains unknown. This study aimed to evaluate the role of MFSD8 protein on metabolic function using untargeted metabolomics analysis in human umbilical vein endothelial cells (HUVECs). HUVECs overexpressing MFSD8 were subjected to metabolomics analysis to evaluate changes in endogenous small molecules using LC-MS/MS analysis. In the positive scan mode, 634 metabolites from 1583 compounds were identified. In the negative scan mode, 169 metabolites from 405 compounds were identified. According to the established criteria for identifying differential metabolites, 96 metabolites exhibited significant differences between the MFSD8 and Vector groups. Among them, 62 metabolites were found to be up-regulated, whereas 34 metabolites were classified as down-regulated. Bioinformatics pipeline analysis revealed three common metabolic pathways, including arginine biosynthesis, beta-alanine metabolism, and pyrimidine metabolism, were found under the positive and negative scan modes. The semi-quantitative analysis was conducted on the differential metabolites, revealing that overexpression of MFSD8 resulted in increased levels of L-citrulline, L-aspartic acid, ornithine, N-acetyl-l-aspartic acid, L-histidine, beta-alanine metabolites and exhibited decreased levels of cytidine. The findings of our study indicated that MFSD8 had the most significant role in arginine biosynthesis, beta-alanine metabolism, and pyrimidine metabolism pathways within endothelial cells. The metabolomics data provide new insights into studying potential features of MFSD8 protein in the future.

Glutamate/GABA/glutamine ratios in intact and ischemia reperfusion challenged rat brain subregions, the effect of ischemic preconditioning

The proper function of the brain is entirely dependent on intact neurotransmission, where glutamate (Glu) and γ-aminobutyric acid (GABA) are the two most present neurotransmitters. Maintenance of these neurotransmitters pools is strictly relying on the de novo synthesis of glutamine in astrocytes. Cerebral ischemic events disrupt the balance in uptake and re-synthesis, altering Glu, GABA, and glutamine (Gln) levels. We focused on the determining of the ratios of glutamate, GABA and glutamine in the brain of rats in the intact state, the early changes and temporal development of changes towards the recovery after disruption of balance by global cerebral ischemia. Animals underwent 15 min of global cerebral ischemia, and changes in Glu/GABA/Gln ratios in the hippocampus, cortex, and cerebellum were assessed at 3 h, 24 h, and 72 h post-reperfusion using high-resolution NMR. Ischemic preconditioning was also used to induce tolerance. In an intact rat brain, glutamate level was about twice that of glutamine in all substructures, about sevenfold compared to GABA in the hippocampus and cortex, and almost eightfold compared to GABA in the cerebellum. There were three to four times as much glutamine compared to GABA. After severe cerebral ischemia, Glu/Gln as well as GABA/Gln ratios extensively dropped in early reperfusion (3 h) and gradually increased in 72 h reperfusion time, however, only the Glu/Gln ratio recovered to the level of controls. Glu/GABA ratio remained in all three reperfusion times over the level of control animals. We observed a decrease in glutathione NMR peak in brain tissue homogenates after ischemia. The obtained data suggest the accelerated accumulation of intraparenchymal glutamate after ischemia, which was even more pronounced in the preconditioned animals three days after an ischemic event. The postischemic GABA level restoration did not achieve the level before ischemia in 72 h reperfusion, which could be one of the limiting factors in the complete postischemic GABA transmission recovery. Presented data may be of advantage not only when comparing glutamate and GABA homeostasis and neurotransmission, but also for glutamine reserve display as neurotransmitter precursor and ammonia transfer buffer in glutamate/GABA/glutamine cycle within the intact brain substructures as well after ischemic insult in rats.

Diminished lactate utilization in LDHB-deficient neurons leads to impaired long-term memory retention

Neurons' high energy demands for processing, transmitting, and storing information in the brain necessitate efficient energy metabolism to maintain normal neuronal function. The astrocyte-neuron lactate shuttle (ANLS) hypothesis suggests neurons preferentially use lactate from astrocytes over glucose for energy. This study investigated lactate dehydrogenase B (LDHB), which preferentially converts lactate to pyruvate, in neuronal energy metabolism and cognitive function. LDHB-deficient neurons showed reduced lactate-driven energy metabolism in culture, while LDHB-deficient brains accumulated lactate, both indicating decreased lactate utilization. This reduced lactate utilization was correlated with impaired long-term memory in LDHB-deficient mice, while short-term memory remained unaffected and overall neuropathology was only mildly disturbed. Unexpectedly, LDHB-deficient neurons maintain stable energy metabolism under physiological glucose conditions, indicating the presence of lactate dehydrogenase (LDH) activity in LDHB-deficient neurons. The observation of lactate dehydrogenase A (LDHA), which preferentially converts pyruvate to lactate but can also catalyze the reverse reaction less efficiently, in LDHB-deficient neurons may explain their stable energy metabolism and reduced lactate utilization. This study challenges the established concept of strict LDH isoform compartmentalization in brain cells, questioning the exclusive presence of LDHB in neurons and suggesting a more flexible neuronal metabolic profile than previously assumed by the ANSL hypothesis.

[Analysis of ischemic stroke biomarkers based on non-targeted metabolomics]

Biomarkers for ischemic stroke (IS) are yet to fulfill clinical requirements. This study used non-targeted metabolomics to investigate differential metabolites and metabolic pathways in plasma and brain tissue following IS, with the aim of identifying new potential biomarkers and therapeutic targets. Twelve Tibetan miniature pigs were randomly assigned to a model- or sham-operation group. An electrocoagulation-based anterior temporal approach was employed to occlude the middle cerebral artery, thereby creating a model for IS. Plasma and brain tissue samples were collected 36 h post-surgery and analyzed using liquid chromatography-mass spectrometry. Principal component and partial least squares discriminant analyses were used to screen for differential metabolites and exclude exogenous metabolites at p<0.05. Compounds were classified according to the HMDB (Human Metabolome Database), and subjected to KEGG (Kyoto Encyclopedia of Genes and Genomes) pathway and VIP (variable importance in projection) analyses. Plasma metabolomics revealed that 86 metabolites were upregulated while 149 were downregulated, with (Z)-3-oxo-2-(2-pentenyl)-1-cyclopentylacetic acid, trans-cinnamic acid and cinnamoylglycine determined to be significant metabolites. Fifty-eight differential metabolites were upregulated in brain tissue and 53 were downregulated, with 2,3-dihydroflavon-3-ol, guanidinoacetic acid (GAA), N-acetyl-D-tryptophan, oxidized glutathione, 2-hydroxyquinoline, and N-acetyl-L-aspartate (NAA) identified as significant metabolites. Organic acids and derivatives, lipids and lipid-like molecules, organoheterocyclic compounds, and organic oxygen compounds were found to be common compound categories among the top five types of compound in both plasma and brain tissue. Common metabolic pathways in plasma and brain tissue include amino acid metabolism, digestive system, cancer overview, and lipid metabolism pathways, with the (Z)-3-oxo-2-(2-pentenyl)-1-cyclopentylacetic acid, GAA, oxidized glutathione, and NAA metabolites serving as potential biomarkers. This study provides a theoretical foundation for the early screening and development of clinical treatment strategies for IS.

Multimodal associations between posterior hippocampus glutamate metabolism, visual cortex connectivity, and intrusive trauma reexperiencing symptoms

Objective

Hippocampal dysfunction is implicated in posttraumatic stress disorder (PTSD), particularly intrusive reexperiencing symptoms, and may be mediated by glutamatergic excitotoxicity. Markers of glutamate dysfunction (higher glutamate to N-acetyl aspartate levels; Glu/NAA) in the hippocampus (HPC) have been linked to reexperiencing symptoms. However, the HPC demonstrates heterogeneity along its anterior-posterior axis, with different functional connectivity patterns and PTSD symptom associations, motivating investigations into glutamate metabolism in anterior and posterior HPC subregions (a/pHPC).

Methods

121 symptomatic trauma-exposed adults (93 female) with current trauma reexperiencing symptoms completed magnetic resonance spectroscopy and resting-state functional magnetic resonance imaging to examine the regional specificity of HPC Glu/NAA associations with reexperiencing, and the link to a/pHPC functional connectivity. PTSD symptoms were assessed with the Clinician-Administered PTSD Scale for DSM-5.

Results

Reexperiencing symptom severity was associated with greater Glu/NAA in the pHPC, but not aHPC. pHPC Glu/NAA was further linked to stronger functional connectivity between the pHPC and visual cortex (VC), which in turn correlated with more severe reexperiencing symptoms. This strengthened pHPC-VC connectivity explained the shared variance between pHPC Glu/NAA and reexperiencing severity, suggesting dysregulated glutamate metabolism in the pHPC may contribute to reexperiencing symptoms through functional connectivity with the VC.

Conclusions

These findings replicate prior work linking HPC Glu/NAA to trauma reexperiencing symptoms and provide novel evidence this association may be specific to the pHPC and mediated by its functional connectivity with the VC. This multimodal investigation supports translational models of glutamatergic dysfunction in trauma-related disorders and highlights new targets for pharmacological and neuromodulatory interventions.

COSIME: Cooperative multi-view integration and Scalable and Interpretable Model Explainer

Single-omics approaches often provide a limited view of complex biological systems, whereas multiomics integration offers a more comprehensive understanding by combining diverse data views. However, integrating heterogeneous data types and interpreting the intricate relationships between biological features-both within and across different data views-remains a bottleneck. To address these challenges, we introduce COSIME (Cooperative Multi-view Integration and Scalable Interpretable Model Explainer). COSIME uses backpropagation of Learnable Optimal Transport (LOT) to deep neural networks, enabling the learning of latent features from multiple views to predict disease phenotypes. In addition, COSIME incorporates Monte Carlo sampling to efficiently estimate Shapley values and Shapley-Taylor indices, enabling the assessment of both feature importance and their pairwise interactions-synergistically or antagonistically-in predicting disease phenotypes. We applied COSIME to both simulated data and real-world datasets, including single-cell transcriptomics, single-cell spatial transcriptomics, epigenomics, and metabolomics, specifically for Alzheimer's disease-related phenotypes. Our results demonstrate that COSIME significantly improves prediction performance while offering enhanced interpretability of feature relationships. For example, we identified that synergistic interactions between microglia and astrocyte genes associated with AD are more likely to be active at the edges of the middle temporal gyrus as indicated by spatial locations. Finally, COSIME is open-source and available for general use.

Effects of Acute Stress on Metabolic Interactions Related to the Tricarboxylic Acid (TCA) Cycle in the Left Hippocampus of Mice

BACKGROUND/OBJECTIVES

The acute stress response affects brain metabolites closely linked to the tricarboxylic acid (TCA) cycle. This response involves time-dependent changes in hormones and neurotransmitters, which contribute to resilience and the ability to adapt to acute stress while maintaining homeostasis. This physiological mechanism of metabolic dynamics, combined with time-series analysis, has prompted the development of new methods to observe the relationship between TCA cycle-related brain metabolites. This study aimed to observe the acute stress response through metabolic interactions using time-series proton magnetic resonance spectroscopy (1H-MRS) in the left hippocampus of mice.

METHODS

In this study, 4-week-old male C57BL/6N mice (n = 24) were divided into control (n = 12) and acute stress groups (n = 12). Acute stress was induced through a 2 h restraint protocol. Time-series 1H-MRS data were obtained on the left hippocampus of both groups using a 9.4 T 1H-MRS scanner. Time-series MRS data were quantified using LCModel, and significant metabolic interactions were identified through Spearman correlation analysis, a one-tailed sign test, and false discovery rate correction.

RESULTS

No significant metabolic correlation coefficient was observed in the control group. However, in the acute stress group, glutathione (GSH) and N-acetyl aspartate (NAA) showed a significant positive correlation over time, with a high correlation coefficient exceeding 0.5.

CONCLUSIONS

Temporal measurement of GSH and NAA, combined with correlation analysis, offers a comprehensive understanding for the metabolic dynamics during acute stress. This approach emphasizes their distinct roles and interdependence in the progression of oxidative stress, mitochondrial function, and the maintenance of physiological homeostasis.

Assessing the Relationship of Brain Metabolites to Cortical Thickness and Dementia Symptoms in Adults with Down Syndrome: A Pilot Study

BACKGROUND/OBJECTIVES

Those with the genetic disorder Down syndrome are at high risk of developing Alzheimer's disease. Previous work shows group differences in magnetic resonance spectroscopy metabolite measures in adults with Down syndrome who have Alzheimer's disease-related dementia compared to those who do not. In this pilot study, we assess relationships between metabolites and measures related to dementia status in a sample of adults with Down syndrome.

METHODS

Seventeen adults with Down syndrome were scanned using a 3 tesla MRI scanner. Magnetic resonance spectroscopy scans focused on the hippocampus and dorsal lateral prefrontal cortex. Metabolites of interest, including myo-inositol and N-acetyl-aspartate, were correlated with scores on the Dementia Questionnaire for People with Learning Disabilities, cortical thickness, and a measure of cognitive ability. In addition, cortical thickness was compared to an age- and sex-matched cohort of 17 previously scanned adults without Down syndrome.

RESULTS

Metabolite measures were not significantly related to cognitive/behavioral measures or to cortical thickness in this small cohort. Participants with Down syndrome showed widespread increases in cortical thickness compared to controls, even after accounting for potential differences in grey matter/white matter contrast.

CONCLUSIONS

Metabolite values were not related to two continuous measures that have previously been associated with dementia status in those with Down syndrome.

Targeting purine metabolism-related enzymes for therapeutic intervention: A review from molecular mechanism to therapeutic breakthrough

Purines are ancient metabolites with established and emerging metabolic and non-metabolic signaling attributes. The expression of purine metabolism-related genes is frequently activated in human malignancies, correlating with increased cancer aggressiveness and chemoresistance. Importantly, under certain stimulating conditions, the purine biosynthetic enzymes can assemble into a metabolon called "purinosomes" to enhance purine flux. Current evidence suggests that purine flux is regulated by a complex circuit that encompasses transcriptional, post-translational, metabolic, and association-dependent regulatory mechanisms. Furthermore, purines within the tumor microenvironment modulate cancer immunity through signaling mediated by purinergic receptors. The deregulation of purine metabolism has significant metabolic consequences, particularly hyperuricemia. Herbal-based therapeutics have emerged as valuable pharmacological interventions for the treatment of hyperuricemia by inhibiting the activity of hepatic XOD, modulating the expression of renal urate transporters, and suppressing inflammatory responses. This review summarizes recent advancements in the understanding of purine metabolism in clinically relevant malignancies and metabolic disorders. Additionally, we discuss the role of herbal interventions and the interaction between the host and gut microbiota in the regulation of purine homeostasis. This information will fuel the innovation of therapeutic strategies that target the disease-associated rewiring of purine metabolism for therapeutic applications.

Characterization of a natural model of adult mice with different rate of aging

Aging is a heterogeneous process, so individuals of the same age may be aging at a different rate. A natural model of premature aging in mice have been proposed based on the poor response to the T-maze. Those that take longer to cross the intersection are known as Prematurely Aging Mice (PAM), while those that show an exceptional response are known as Exceptional non-PAM (E-NPAM), being the rest non-PAM (NPAM). Although many aspects of PAM and E-NPAM have been described, some aspects of their brain aging have not been studied. Similarly, it is known that PAM, NPAM and E-NPAM show a different rate of aging and longevity, but the differences between these three groups in behavior, immune function and oxidative-inflammatory state are unknown. The present study aims to deepen the study of brain aging in PAM and E-NPAM, and to study the differences in behavior, immunity, and oxidative-inflammatory state of peritoneal leukocytes between PAM, NPAM and E-NPAM. Results show deteriorated brains in PAM. Moreover, NPAM show an oxidative state similar to E-NPAM, an anxiety similar to PAM, and an intermediate immunity and lifespan between PAM and E-NPAM. In conclusion, immune function seems to be more associated with the longevity achieved.

Non-invasive metabolic biomarkers in initial cognitive impairment in patients with diabetes: A systematic review and meta-analysis

AIM

Diabetic cognitive impairment (DCI), considered one of the most severe and commonly overlooked complications of diabetes, has shown inconsistent findings regarding the metabolic profiles in DCI patients. This systematic review and meta-analysis aimed to identify dysregulated metabolites as potential biomarkers for early DCI, providing valuable insights into the underlying pathophysiological mechanisms.

MATERIALS AND METHODS

A systematic search of four databases, namely PubMed, Embase, Web of Science and Cochrane, was conducted up to March 2024. Subsequently, a qualitative review of clinical studies was performed followed by a meta-analysis of metabolite markers. Finally, the sources of heterogeneity were explored through subgroup and sensitivity analyses.

RESULTS

A total of 774 unique publications involving 4357 participants and the identification of multiple metabolites were retrieved. Of these, 13 clinical studies reported metabolite differences between the DCI and control groups. Meta-analysis was conducted for six brain metabolites and two metabolite ratios. The results revealed a significant increase in myo-inositol (MI) concentration and decreases in glutamate (Glu), Glx (glutamate and glutamine) and N-acetylaspartate/creatine (NAA/Cr) ratios in DCI, which have been identified as the most sensitive metabolic biomarkers for evaluating DCI progression. Notably, brain metabolic changes associated with cognitive impairment are more pronounced in type 2 diabetes mellitus than in type 1 diabetes mellitus, and the hippocampus emerged as the most sensitive brain region regarding metabolic changes associated with DCI.

CONCLUSIONS

Our results suggest that MI, Glu, and Glx concentrations and NAA/Cr ratios within the hippocampus may serve as metabolic biomarkers for patients with early-stage DCI.

Dissociation of focal and large-scale inhibitory functions in the older adults: A multimodal MRI study

BACKGROUND

The decline of inhibitory in cognitive aging is linked to reduced cognitive and mental capacities in older adults. However, this decline often shows inconsistent clinical presentations, suggesting varied impacts on different inhibition-related tasks. Inhibitory control, a multifaceted construct, involves various types of inhibition. Understanding these components is crucial for comprehending how aging affects inhibitory functions. Our research investigates the influences of aging on large-scale and focal-scale inhibitory and examines the relationship with brain markers.

METHODS

We examined the impact of aging on inhibitory in 18 younger (20-35 years) and 17 older adults (65-85 years) using focal and large-scale inhibition tasks. The Gabor task assessed focal-scale inhibition, while the Stop Signal Task (SST) evaluated large-scale inhibition. Participants underwent neuropsychological assessments and MRI scans, including magnetic resonance spectroscopy (MRS) and structural and resting fMRI.

RESULTS

Older adults exhibited a marked decline in inhibitory function, with slower SST responses indicating compromised large-scale inhibition. Conversely, the Gabor task showed no significant age-related changes. MRS findings revealed decreased levels of GABA, glutamate, glutamine, and NAA in the pre-SMA, correlating with observed large-scale inhibition in older adults. Additionally, pre-SMA seed-based functional connectivity analysis showed reduced brain network connections in older adults, potentially contributing to inhibitory control deficits.

CONCLUSIONS

Our study elucidates the differential effects of aging on inhibitory functions. While large-scale inhibition is more vulnerable to aging, focal-scale inhibition is relatively preserved. These findings highlight the importance of targeted cognitive interventions and underscore the necessity of a multifaceted approach in aging research.

Contribution of Magnetic Resonance Imaging Studies to the Understanding of Cerebral Malaria Pathogenesis

Cerebral malaria (CM), the most lethal clinical syndrome of Plasmodium falciparum infection, mostly affects children under 5 in sub-Saharan Africa. CM is characterized by seizures and impaired consciousness that lead to death in 15-20% of cases if treated quickly, but it is completely fatal when untreated. Brain magnetic resonance imaging (MRI) is an invaluable source of information on the pathophysiology of brain damage, but, due to limited access to scanners in endemic regions, only until very recently have case reports of CM patients studied with advanced MRI methods been published. The murine model of experimental cerebral malaria (ECM) shares many common features with the human disease and has been extensively used to study the pathogenic mechanisms of the neurological syndrome. In vivo MRI studies on this model, the first of which was published in 2005, have contributed to a better understanding of brain lesion formation in CM and identified disease markers that were confirmed by MRI studies published from 2013 onwards in pediatric patients from endemic areas. In this review, we recapitulate the main findings and critically discuss the contributions of MRI studies in the ECM model to the understanding of human CM.

N-acetylaspartate mitigates pro-inflammatory responses in microglial cells by intersecting lipid metabolism and acetylation processes

BACKGROUND

Microglia play a crucial role in brain development and repair by facilitating processes such as synaptic pruning and debris clearance. They can be activated in response to various stimuli, leading to either pro-inflammatory or anti-inflammatory responses associated with specific metabolic alterations. The imbalances between microglia activation states contribute to chronic neuroinflammation, a hallmark of neurodegenerative diseases. N-acetylaspartate (NAA) is a brain metabolite predominantly produced by neurons and is crucial for central nervous system health. Alterations in NAA metabolism are observed in disorders such as Multiple Sclerosis and Canavan disease. While NAA's role in oligodendrocytes and astrocytes has been investigated, its impact on microglial function remains less understood.

METHODS

The murine BV2 microglial cell line and primary microglia were used as experimental models. Cells were treated with exogenous NAA and stimulated with LPS/IFN-γ to reproduce the pro-inflammatory phenomenon. HPLC and immunofluorescence analysis were used to study lipid metabolism following NAA treatment. Automated fluorescence microscopy was used to analyze phagocytic activity. The effects on the pro-inflammatory response were evaluated by analysis of protein/mRNA expression and ChIP assay of typical inflammatory markers.

RESULTS

NAA treatment promotes an increase in both lipid synthesis and degradation, and enhances the phagocytic activity of BV2 cells, thus fostering surveillant microglia characteristics. Importantly, NAA decreases the pro-inflammatory state induced by LPS/IFN-γ via the activation of histone deacetylases (HDACs). These findings were validated in primary microglial cells, highlighting the impact on cellular metabolism and inflammatory responses.

CONCLUSIONS

The study highlighted the role of NAA in reinforcing the oxidative metabolism of surveillant microglial cells and, most importantly, in buffering the inflammatory processes characterizing reactive microglia. These results suggest that the decreased levels of NAA observed in neurodegenerative disorders can contribute to chronic neuroinflammation.

Neuronal viability/astrocyte activity ratio in the dorsolateral prefrontal cortex as a biomarker of Alzheimer's dementia: a proton magnetic resonance spectroscopy study

N-acetyl-aspartate (NAA) and myo-inositol (mI) are neurometabolites reflecting neuronal viability and astrocyte activity, respectively. These are quantified using proton magnetic resonance spectroscopy (1H-MRS) and may be biomarkers for Alzheimer's disease dementia (AD). Our objectives were: 1) Compare dorsolateral prefrontal cortex (DLPFC) NAA and mI levels between AD and cognitively healthy control participants (HC) 2) assess if NAA/mI ratio can distinguish groups, and 3) explore the relationship between metabolites and cognition. The study included 64 participants over 55, 41 with AD. Bilateral DLPFC NAA and mI levels were quantified using 3 T 1H-MRS and normalized to H2O. NAA and NAA/mI ratio were lower in AD vs. HC. mI was unchanged. The NAA/mI ratio at a cut-off value of 1.69 showed 59% sensitivity and 87% specificity at distinguishing AD from HC. NAA was associated positively with cognition. In conclusion, DLPFC metabolite changes suggest altered mitochondrial function in AD. NAA/mI ratio shows good specificity in distinguishing AD from HC, suggesting its role in complementing other biomarkers. Future studies should evaluate NAA/mI ratio with other disease specific biomarkers.

Metabolic Profile of Cerebellum in Posterior Fossa Tumor Survivors: Correlation With Memory Impairment

AIMS

The cerebellum is a key structure in working and procedural memory. The aim of the present prospective exploratory study was to investigate, the metabolic characteristics of the cerebellum in posterior fossa tumor (PFT) survivors using 3D proton magnetic resonance spectroscopy imaging (3D MRSI), to determine whether metabolites could be useful biomarkers of memory impairment.

MATERIALS AND METHODS

Sixty participants were included in the IMPALA study, divided into three groups: 22 irradiated PFT, 17 nonirradiated PFT, and 21 healthy controls matched with irradiated PFT for age, sex, and handedness. PFT survivors were treated at least 5 years ago, either by surgery or a combination of surgery, chemotherapy, and radiotherapy. All participants underwent working and procedural memory tests and multimodal MRI including a 3D MRSI sequence. N-acetylaspartate (NAA), choline (Cho), creatine (Cr), and lactate (Lac) metabolite values were extracted from the cerebellum for comparisons between groups, correlations with neurocognitive test scores, and radiotherapy doses.

RESULTS

Median (range) age at neurocognitive tests was 18 (7-26) years. Median Cho, Cr, NAA, and Lac values, and the ratio of NAA to the sum of metabolites were significantly lower for PFT survivors than for healthy controls (p < 0.05). Scores on working and procedural memory tests were significantly lower for PFT survivors (p < 0.004) and correlated with median and maximum Cho and NAA values (0.28

CONCLUSION

Results revealed changes in cerebellar metabolic values in PFT survivors that were closely correlated with memory deficits, suggesting that some metabolites could be used as markers of cognitive decline, but this will require validation on a larger sample size.

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Key Words

• Cerebellum
• Memory
• Metabolic
• Paediatric posterior fossa tumor
• Radiotherapy
• Spectroscopy imaging

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MESH Headings

• Humans
• Female
• Male
• Cerebellum/metabolism
• Cerebellum/radiation effects
• Cerebellum/diagnostic imaging
• Adult
• Infratentorial Neoplasms/metabolism
• Prospective Studies
• Memory Disorders/etiology
• Memory Disorders/metabolism
• Cancer Survivors
• Young Adult
• Adolescent
• Case-Control Studies
• Metabolome
• Choline/metabolism

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Affiliation(s)

F Tensaouti Radiation Oncology Department, Oncopole Claudius Regaud- Institut Universitaire du Cancer de Toulouse-Oncopole, Toulouse, France; ToNIC, Toulouse NeuroImaging Center, Université de Toulouse, Inserm, UPS, France.
N Courbière ToNIC, Toulouse NeuroImaging Center, Université de Toulouse, Inserm, UPS, France
B Cabarrou Biostatistics & Health Data Science Unit, Oncopole Claudius Regaud/Institut Universitaire du Cancer de Toulouse - Oncopôle, Toulouse, France
L Pollidoro ToNIC, Toulouse NeuroImaging Center, Université de Toulouse, Inserm, UPS, France
M Roques Radiology Department, Toulouse University Hospital, Toulouse, France
A Sévely Radiology Department, Toulouse University Hospital, Toulouse, France
P Péran ToNIC, Toulouse NeuroImaging Center, Université de Toulouse, Inserm, UPS, France
E Baudou ToNIC, Toulouse NeuroImaging Center, Université de Toulouse, Inserm, UPS, France; Pediatric Neurology Department, Children's Hospital, Toulouse University Hospital, Toulouse, France
A Laprie Radiation Oncology Department, Oncopole Claudius Regaud- Institut Universitaire du Cancer de Toulouse-Oncopole, Toulouse, France; ToNIC, Toulouse NeuroImaging Center, Université de Toulouse, Inserm, UPS, France

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Diffusion magnetic resonance spectroscopy captures microglial reactivity related to gut-derived systemic lipopolysaccharide: A preliminary study

Neuroinflammation is a key component underlying multiple neurological disorders, yet non-invasive and cost-effective assessment of in vivo neuroinflammatory processes in the central nervous system remains challenging. Diffusion weighted magnetic resonance spectroscopy (dMRS) has shown promise in addressing these challenges by measuring diffusivity properties of different neurometabolites, which can reflect cell-specific morphologies. Prior work has demonstrated dMRS utility in capturing microglial reactivity in the context of lipopolysaccharide (LPS) challenges and serious neurological disorders, detected as changes of microglial metabolite diffusivity properties. However, the extent to which such dMRS metrics are capable of detecting subtler and more nuanced levels of neuroinflammation in populations without overt neuropathology is unknown. Here we examined the relationship between intrinsic, gut-derived levels of systemic LPS and dMRS-based apparent diffusion coefficients (ADC) of choline, creatine, and N-acetylaspartate (NAA) in two brain regions: the thalamus and the corona radiata. Higher plasma LPS concentrations were significantly associated with increased ADC of choline and NAA in the thalamic region, with no such relationships observed in the corona radiata for any of the metabolites examined. As such, dMRS may have the sensitivity to measure microglial reactivity across populations with highly variable levels of neuroinflammation, and holds promising potential for widespread applications in both research and clinical settings.

Maternal prenatal immune activation associated with brain tissue microstructure and metabolite concentrations in newborn infants

Few human studies have assessed the association of prenatal maternal immune activation (MIA) with measures of brain development and psychiatric risk in newborn offspring. Our goal was to identify the effects of MIA during the 2nd and 3rd trimesters of pregnancy on newborn measures of brain metabolite concentrations, tissue microstructure, and motor development. This was a prospective longitudinal cohort study conducted with nulliparous pregnant women who were aged 14 to 19 years and recruited in their 2nd trimester, as well as their children who were followed through 14 months of age. MIA was indexed by maternal interleukin-6 (IL-6) and C-reactive protein (CRP) in both trimesters of pregnancy. Primary outcomes included: (1) newborn brain metabolite concentrations as ratios to creatine (N-acetylaspartate (NAA)/creatine (Cr) and choline (Cho)/Cr) measured using Magnetic Resonance Spectroscopy; (2) newborn fractional anisotropy and mean diffusivity, measured using Diffusion Tensor Imaging; and (3) indices of motor development, assessed prenatally and postnatally at ages 4- and 14-months. Maternal IL-6 and CRP levels associated significantly with both metabolites in the putamen, thalamus, insula, and the internal capsule. Maternal IL-6 associated significantly with fractional anisotropy in the putamen, caudate, thalamus, insula, and precuneus, and with mean diffusivity in the inferior parietal and middle temporal gyrus. CRP associated significantly with fractional anisotropy in the thalamus, insula, and putamen. Significant associations were found in common regions across imaging modalities, though the direction of associations differed by immune marker. In addition, both maternal IL-6 and CRP (in both trimesters) prenatally associated significantly with offspring motor development at 4- and 14-months of age. The left thalamus mediated effects of IL-6 on postnatal motor development. These findings demonstrate that levels of MIA in mid- to late pregnancy in a generally healthy sample associate with tissue characteristics in newborn brain regions that primarily support motor integration and coordination, as well as behavioral regulation. Those brain effects may contribute to differences in motor development.

Diffuse white matter pathology in multiple sclerosis during treatment with dimethyl fumarate-An observational study of changes in normal-appearing white matter using proton magnetic resonance spectroscopy

BACKGROUND

Multiple sclerosis (MS) is an inflammatory demyelinating disease with neurodegenerative features causing risk for neurologic irreversible disability over time. Examination of normal-appearing white matter (NAWM) changes in MS by proton magnetic resonance spectroscopy (1H-MRS), may detect diffuse white matter pathology that is associated with neurodegeneration.

METHODS

In this observational study of in total twenty-six patients with MS, starting treatment with dimethyl fumarate (DMF), we measured the absolute concentration of metabolites in periventricular NAWM using 1H-MRS at baseline and after one and three years of treatment. Metabolite concentrations were analyzed both cross-sectionally, in relation to 10 controls and longitudinally in relation to disease activity.

RESULTS

Patients with MS had higher concentrations of myo-inositol (mIns) in NAWM at baseline compared with controls (mean 5.98 ± 1.37 (SD) and 4.32 ± 1.16 (SD), p<0.01, independent samples t-test). The disease duration was inversely correlated with concentrations of total N-acetylaspartate and N-acetylaspartylglutamate (tNA) (r = -0.62, p<0.01) in NAWM as well as positively to the ratio of mIns and tNA (r = 0.51, p = 0.03). Metabolite concentrations during one-year (n = 19) and three-years (n = 11) follow-up were generally stable. The dropouts were caused by treatment switch after one year, mainly due to new MRI activity. Cross-sectional analyses showed that there was an inverse correlation between concentrations of tNA and mIns at both baseline and at 1 and 3-years follow-up (r = -0.44 to -0.65, p = 0.04 to 0.004). Metabolite concentrations were stable during 1-year follow-up independently of disease activity.

CONCLUSIONS

Higher concentrations of the astrogliosis marker mIns in MS compared to controls, the inverse relation between MS disease duration and the neuroaxonal integrity marker tNA, as well as the consistent inverse relation between these two metabolites during follow-up, showed that non-lesional white matter pathology is present in this cohort of MS patients in early disease stages. However, metabolite concentrations during follow-up were generally stable and did not reflect differences in disease activity among patients.

Metabolic changes assessed by 1H MR spectroscopy in the corpus callosum of post-COVID patients

OBJECTIVE

Many patients with long COVID experience neurological and psychological symptoms. Signal abnormalities on MR images in the corpus callosum have been reported. Knowledge about the metabolic profile in the splenium of the corpus callosum (CCS) may contribute to a better understanding of the pathophysiology of long COVID.

MATERIALS AND METHODS

Eighty-one subjects underwent proton MR spectroscopy examination. The metabolic concentrations of total N-acetylaspartate (NAA), choline-containing compounds (Cho), total creatine (Cr), myo-inositol (mI), and NAA/Cho in the CCS were statistically compared in the group of patients containing 58 subjects with positive IgG COVID-19 antibodies or positive SARS-CoV-2 qPCR test at least two months before the MR and the group of healthy controls containing 23 subjects with negative IgG antibodies.

RESULTS

An age-dependent effect of SARS-CoV-2 on Cho concentrations in the CCS has been observed. Considering the subjective threshold of age = 40 years, older patients showed significantly increased Cho concentrations in the CCS than older healthy controls (p = 0.02). NAA, Cr, and mI were unchanged. All metabolite concentrations in the CCS of younger post-COVID-19 patients remained unaffected by SARS-CoV-2. Cho did not show any difference between symptomatic and asymptomatic patients (p = 0.91).

DISCUSSION

Our results suggest that SARS-CoV-2 disproportionately increases Cho concentration in the CCS among older post-COVID-19 patients compared to younger ones. The observed changes in Cho may be related to the microstructural reorganization in the CCS also reported in diffusion measurements rather than increased membrane turnover. These changes do not seem to be related to neuropsychological problems of the post-COVID-19 patients. Further metabolic studies are recommended to confirm these observations.

Terra incognita of glial cell dynamics in the etiology of leukodystrophies: Broadening disease and therapeutic perspectives

Neuroglial cells, also known as glia, are primarily characterized as auxiliary cells within the central nervous system (CNS). The recent findings have shed light on their significance in numerous physiological processes and their involvement in various neurological disorders. Leukodystrophies encompass an array of rare and hereditary neurodegenerative conditions that were initially characterized by the deficiency, aberration, or degradation of myelin sheath within CNS. The primary cellular populations that experience significant alterations are astrocytes, oligodendrocytes and microglia. These glial cells are either structurally or metabolically impaired due to inherent cellular dysfunction. Alternatively, they may fall victim to the accumulation of harmful by-products resulting from metabolic disturbances. In either situation, the possible replacement of glial cells through the utilization of implanted tissue or stem cell-derived human neural or glial progenitor cells hold great promise as a therapeutic strategy for both the restoration of structural integrity through remyelination and the amelioration of metabolic deficiencies. Various emerging treatment strategies like stem cell therapy, ex-vivo gene therapy, infusion of adeno-associated virus vectors, emerging RNA-based therapies as well as long-term therapies have demonstrated success in pre-clinical studies and show promise for rapid clinical translation. Here, we addressed various leukodystrophies in a comprehensive and detailed manner as well as provide prospective therapeutic interventions that are being considered for clinical trials. Further, we aim to emphasize the crucial role of different glial cells in the pathogenesis of leukodystrophies. By doing so, we hope to advance our understanding of the disease, elucidate underlying mechanisms, and facilitate the development of potential treatment interventions.

Altered brain metabolites in male nonhuman primate offspring exposed to maternal immune activation

Converging data show that exposure to maternal immune activation (MIA) in utero alters brain development in animals and increases the risk of neurodevelopmental disorders in humans. A recently developed non-human primate MIA model affords opportunities for studies with uniquely strong translational relevance to human neurodevelopment. The current longitudinal study used 1H-MRS to investigate the developmental trajectory of prefrontal cortex metabolites in male rhesus monkey offspring of dams (n = 14) exposed to a modified form of the inflammatory viral mimic, polyinosinic:polycytidylic acid (Poly IC), in the late first trimester. Brain metabolites in these animals were compared to offspring of dams that received saline (n = 10) or no injection (n = 4). N-acetylaspartate (NAA), glutamate, creatine, choline, myo-inositol, taurine, and glutathione were estimated from PRESS and MEGA-PRESS acquisitions obtained at 6, 12, 24, 36, and 45 months of age. Prior investigations of this cohort reported reduced frontal cortical gray and white matter and subtle cognitive impairments in MIA offspring. We hypothesized that the MIA-induced neurodevelopmental changes would extend to abnormal brain metabolite levels, which would be associated with the observed cognitive impairments. Prefrontal NAA was significantly higher in the MIA offspring across all ages (p < 0.001) and was associated with better performance on the two cognitive measures most sensitive to impairment in the MIA animals (both p < 0.05). Myo-inositol was significantly lower across all ages in MIA offspring but was not associated with cognitive performance. Taurine was elevated in MIA offspring at 36 and 45 months. Glutathione did not differ between groups. MIA exposure in male non-human primates is associated with altered prefrontal cortex metabolites during childhood and adolescence. A positive association between elevated NAA and cognitive performance suggests the hypothesis that elevated NAA throughout these developmental stages reflects a protective or resilience-related process in MIA-exposed offspring. The potential relevance of these findings to human neurodevelopmental disorders is discussed.

1H-MRS reveals abnormal energy metabolism and excitatory-inhibitory imbalance in a chronic migraine-like state induced by nitroglycerin in mice

BACKGROUND

Chronic migraine is closely related to the dysregulation of neurochemical substances in the brain, with metabolic imbalance being one of the proposed causes of chronic migraine. This study aims to evaluate the metabolic changes between energy metabolism and excitatory and inhibitory neurotransmitters in key brain regions of mice with chronic migraine-like state and to uncover the dysfunctional pathways of migraine.

METHODS

A chronic migraine-like state mouse model was established by repeated administration of nitroglycerin (NTG). We used von Frey filaments to assess the mechanical thresholds of the hind paw and periorbital in wild-type and familial hemiplegic migraine type 2 mice. After the experiments, tissue was collected from five brain regions: the somatosensory cortex (SSP), hippocampus, thalamus (TH), hypothalamus, and the spinal trigeminal nucleus caudalis (TNC). Proton magnetic resonance spectroscopy (1H-MRS) was employed to study the changes in brain metabolites associated with migraine, aiming to explore the mechanisms underlying metabolic imbalance in chronic migraine-like state.

RESULTS

In NTG-induced chronic migraine-like state model, we observed a significant reduction in energy metabolism during central sensitization, an increase in excitatory neurotransmitters such as glutamate, and a tendency for inhibitory neurotransmitters like GABA to decrease. The TNC and thalamus were the most affected regions. Furthermore, the consistency of N-acetylaspartate levels highlighted the importance of the TNC-TH-SSP pathway in the ascending nociceptive transmission of migraine.

CONCLUSION

Abnormal energy metabolism and neurotransmitter imbalance in the brain region of NTG-induced chronic migraine-like state model are crucial mechanisms contributing to the chronicity of migraine.

N-acetylaspartate promotes glycolytic-to-oxidative fiber-type switch and resistance to atrophic stimuli in myotubes

N-acetylaspartate (NAA) is a neuronal metabolite that can be extruded in extracellular fluids and whose blood concentration increases in several neurodegenerative disorders, including amyotrophic lateral sclerosis (ALS). Aspartoacylase (ASPA) is the enzyme responsible for NAA breakdown. It is abundantly expressed in skeletal muscle and most other human tissues, but the role of NAA catabolism in the periphery is largely neglected. Here we demonstrate that NAA treatment of differentiated C2C12 muscle cells increases lipid turnover, mitochondrial biogenesis and oxidative metabolism at the expense of glycolysis. These effects were ascribed to NAA catabolism, as CRISPR/Cas9 ASPA KO cells are insensitive to NAA administration. Moreover, the metabolic switch induced by NAA was associated with an augmented resistance to atrophic stimuli. Consistently with in vitro results, SOD1-G93A ALS mice show an increase in ASPA levels in those muscles undergoing the glycolytic to oxidative switch during the disease course. The impact of NAA on the metabolism and resistance capability of myotubes supports a role for this metabolite in the phenotypical adaptations of skeletal muscle in neuromuscular disorders.

Understanding Proton Magnetic Resonance Spectroscopy Neurochemical Changes Using Alzheimer's Disease Biofluid, PET, Postmortem Pathology Biomarkers, and APOE Genotype

In vivo proton (1H) magnetic resonance spectroscopy (MRS) is a powerful non-invasive method that can measure Alzheimer's disease (AD)-related neuropathological alterations at the molecular level. AD biomarkers include amyloid-beta (Aβ) plaques and hyperphosphorylated tau neurofibrillary tangles. These biomarkers can be detected via postmortem analysis but also in living individuals through positron emission tomography (PET) or biofluid biomarkers of Aβ and tau. This review offers an overview of biochemical abnormalities detected by 1H MRS within the biologically defined AD spectrum. It includes a summary of earlier studies that explored the association of 1H MRS metabolites with biofluid, PET, and postmortem AD biomarkers and examined how apolipoprotein e4 allele carrier status influences brain biochemistry. Studying these associations is crucial for understanding how AD pathology affects brain homeostasis throughout the AD continuum and may eventually facilitate the development of potential novel therapeutic approaches.

Gender-related alterations of serum trace elements and neurometabolism in the anterior cingulate cortex of patients with major depressive disorder

BACKGROUND

It is widely known that sex differences have a significant impact on patients with major depressive disorder (MDD). This study aims to evaluate the sex-related connection between serum trace elements and changes in neurometabolism in the anterior cingulate cortex (ACC) of MDD patients.

METHODS

109 untreated MDD patients and 59 healthy controls underwent proton magnetic resonance spectroscopy (1H-MRS) under resting conditions. We measured metabolic ratios in the ACC from both sides. Additionally, venous blood samples were taken from all participants to detect calcium (Ca), phosphorus, magnesium (Mg), copper (Cu), ceruloplasmin (CER), zinc (Zn), and iron (Fe) levels. We performed association and interaction analyses to explore the connections between the disease and gender.

RESULTS

In individuals with MDD, the Cu/Zn ratio increased, while the levels of Mg, CER, Zn and Fe decreased. Male MDD patients had lower Cu levels, while female patients had an increased Cu/Zn ratio. We observed significant gender differences in Cu, CER and the Cu/Zn ratio in MDD. Male patients showed a reduced N-acetyl aspartate (NAA)/phosphocreatine + creatine (PCr + Cr) ratio in the left ACC. The NAA/PCr + Cr ratio decreased in the right ACC in patients with MDD. In the left ACC of male MDD patients, the Cu/Zn ratio was inversely related to the NAA/PCr + Cr ratio, and Fe levels were negatively associated with the GPC + PC/PCr + Cr ratio.

CONCLUSIONS

Our findings highlight gender-specific changes in Cu homeostasis among male MDD patients. The Cu/Zn ratio and Fe levels in male MDD patients were significantly linked to neurometabolic alterations in the ACC.

Changes in the medial prefrontal cortex metabolites after 6 months of medication therapy for patients with bipolar disorder: A 1H-MRS study

AIMS

The study aimed to assess brain metabolite differences in the medial prefrontal cortex (mPFC) between acute and euthymic episodes of bipolar disorder (BD) with both mania and depression over a 6-month medication treatment period.

METHODS

We utilized 1H-MRS technology to assess the metabolite levels in 53 individuals with BD (32 in depressive phase, 21 in manic phase) and 34 healthy controls (HCs) at baseline. After 6 months of medication treatment, 40 subjects underwent a follow-up scan in euthymic state. Metabolite levels, including N-acetyl aspartate (NAA), glutamate (Glu), and Glutamine (Gln), were measured in the mPFC.

RESULTS

Patients experiencing depressive and manic episodes exhibited a notable reduction in NAA/Cr + PCr ratios at baseline compared to healthy controls (p = 0.004; p = 0.006) in baseline, compared with HCs. Over the 6-month follow-up period, the manic group displayed a significant decrease in Gln/Cr + PCr compared to the initial acute phase (p = 0.03). No significant alterations were found in depressed group between baseline and follow-up.

CONCLUSION

This study suggests that NAA/Cr + PCr ratios and Gln/Cr + PCr ratios in the mPFC may be associated with manic and depressive episodes, implicating that Gln and NAA might be useful biomarkers for distinguishing mood phases in BD and elucidating its mechanisms.

Chromosome-level genome assembly of a deep-sea Venus flytrap sea anemone sheds light upon adaptations to an extremely oligotrophic environment

The Venus flytrap sea anemone Actinoscyphia liui inhabits the nutrient-limited deep ocean in the tropical western Pacific. Compared with most other sea anemones, it has undergone a distinct modification of body shape similar to that of the botanic flytrap. However, the molecular mechanism by which such a peculiar sea anemone adapts to a deep-sea oligotrophic environment is unknown. Here, we report the chromosomal-level genome of A. liui constructed from PacBio and Hi-C data. The assembled genome is 522 Mb in size and exhibits a continuous scaffold N50 of 58.4 Mb. Different from most other sea anemones, which typically possess 14-18 chromosomes per haplotype, A. liui has only 11. The reduced number of chromosomes is associated with chromosome fusion, which likely represents an adaptive strategy to economize energy in oligotrophic deep-sea environments. Comparative analysis with other deep-sea sea anemones revealed adaptive evolution in genes related to cellular autophagy (TMBIM6, SESN1, SCOCB and RPTOR) and mitochondrial energy metabolism (MDH1B and KAD2), which may aid in A. liui coping with severe food scarcity. Meanwhile, the genome has undergone at least two rounds of expansion in gene families associated with fast synaptic transmission, facilitating rapid responses to water currents and prey. Positive selection was detected on putative phosphorylation sites of muscle contraction-related proteins, possibly further improving feeding efficiency. Overall, the present study provides insights into the molecular adaptation to deep-sea oligotrophic environments and sheds light upon potential effects of a novel morphology on the evolution of Cnidaria.

Metabolic coupling between glutamate and N-acetylaspartate in the human brain

A metabolic coupling between glutamate and N-acetylaspartate measured by in vivo magnetic resonance spectroscopy has been recently reported in the literature with inconsistent findings. In this study, confounders originating from Pearson's spurious correlation of ratios and spectral correlation due to overlapping magnetic resonance spectroscopy signals of glutamate and N-acetylaspartate were practically eliminated to facilitate the determination of any metabolic link between glutamate and N-acetylaspartate in the human brain using in vivo magnetic resonance spectroscopy. In both occipital and medial prefrontal cortices of healthy individuals, correlations between glutamate and N-acetylaspartate were found to be insignificant. Our results do not lend support to a recent hypothesis that N-acetylaspartate serves as a significant reservoir for the rapid replenishment of glutamate during signaling or stress.