Myelin Fat Facts: An Overview of Lipids and Fatty Acid Metabolism

Lipid dysregulation and delirium in older adults: A review of the current evidence and future directions

Delirium is a complex medical condition marked by acute episodes of cognitive dysfunction and behavioral disturbances, with a multifaceted etiology and challenging management across various clinical settings. Older adults, particularly in postoperative contexts, are at increased risk of developing delirium. Despite extensive research, a single underlying pathophysiological mechanism for delirium remains elusive. However, emerging evidence suggests a correlation between lipid dysregulation and delirium development in elderly patients, especially in postoperative settings. This connection has led to proposed treatments targeting dyslipidemia and associated neuroinflammatory effects in acute-phase delirium. This review aims to synthesize current literature on the relationship between lipid dysregulation and delirium in older adults, highlighting the need for further research into specific neurolipidome constituents and age-related lipid profile changes, potentially uncovering novel therapeutic strategies for delirium.

Enhanced brain myelination and cognitive development in young children associated with milk fat globule membrane (MFGM) intake: a temporal cohort study

Myelination is an important neurodevelopmental process that facilitates efficient brain messaging and connectivity, and contributes to the emergence and refinement of cognitive skills and abilities. Healthy maturation of the myelinated white matter requires coordinated delivery of key nutritional building blocks, including short and long-chain polyunsaturated fatty acids, phospholipids, and sphingolipids. While many of these nutrients are amply supplied by breastmilk, they may not be present in sufficient quantity in infant formula milk. Milk fat globule membrane (MFGM) is a rich source of phospholipids, including sphingomyelin and has been associated with improved cognitive development in infants and children when added to infant formula. To determine if added bovine MFGM is also associated with improved myelination, this study used myelin-sensitive MRI to compare myelination trends in healthy infants and toddlers, 0-2 years of age, who received the same branded infant formula with and without added bovine MFGM in two temporal cohorts: Without Added MFGM between 2010 and 2017; and With Added MFGM between 2018-2020. Concurrent with imaging, cognitive development was assessed using the Mullen Scales of Early Learning (MSEL). Matched for important demographic and socioeconomic characteristics, we found that children who received infant formula with added MFGM showed improved myelination in motor-related areas (motor cortices, internal capsule, and cerebellum) and improved MSEL gross and fine motor scores. No significant differences in verbal or overall cognitive ability scores were noted. These results support the importance of phospholipids, sphingolipids, and sphingomyelin in promoting brain myelination and cognitive development.

Role of saturated fatty acid metabolism in posttranslational modifications of the Tau protein

The relationship between metabolic alterations induced by the consumption of a high-fat diet (HFD) and the risk of developing neurodegenerative diseases such as Alzheimer's disease (AD) has been extensively studied. In particular, the induction of neuronal insulin resistance, endoplasmic reticulum stress, and the production of reactive oxygen species by chronic exposure to high concentrations of saturated fatty acids (sFAs), such as palmitic acid (PA), have been proposed as the cellular and molecular mechanisms underlying cognitive decline. Lipid metabolism affects many processes critical for cellular homeostasis. However, questions remain as to whether neuronal exposure to high sFA levels contributes to the onset and progression of AD features, and how their metabolism plays a role in this process. Therefore, the aim of this work is to review the accumulated evidence for the potential mechanisms by which the neuronal metabolism of sFAs affects signaling pathways that may induce biochemical changes in the AD hallmark protein Tau, ultimately promoting its aggregation and the subsequent generation of neurofibrillary tangles. In particular, the data presented here provide evidence that PA-dependent metabolic stress results in an imbalance in the activities of protein kinases and deacetylases that potentially contribute to the post-translational modifications (PTMs) of Tau.

Elucidating molecular lipid perturbations in trigeminal neuralgia using cerebrospinal fluid lipidomics

Trigeminal neuralgia (TN) is a neuropathic facial pain disorder characterized by severe stabbing pain along the trigeminal nerve. While its pathogenesis remains unclear, nerve demyelination and inflammation are likely involved. Current research has primarily focused on various blood-based omics approaches, which do not fully capture the lipid alterations occurring during TN progression in brain. In contrast, our study is the first to investigate cerebrospinal fluid (CSF) lipidomic profiles in TN patients, aiming to elucidate potential disease mechanisms. CSF samples were collected from 22 TN patients and 18 healthy controls, followed by untargeted lipidomic analysis using high-performance liquid chromatography coupled to quadrupole time-of-flight mass spectrometry. A pipeline for lipid identification and relative quantification, combined with statistical analysis, revealed 188 lipid species across 21 classes. We found significant upregulation of Cer-NPs, LPCs, PCs, TGs, and OxTGs in TN patients, while stigmasterol hexoside was downregulated. Moderate correlations were observed between lipid species and clinical parameters. These findings highlight considerable CSF lipidome alterations in TN, suggesting roles for nerve demyelination, neuroinflammation, and pain sensitization in its pathogenesis. Our study provides novel insights into lipid targets that may offer therapeutic potential for managing TN.

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.

Purifying selection of the lysosomal enzymes arylsulfatase A and beta-galactocerebrosidase and their evolutionary impact on myelin integrity

The myelin is responsible for providing stability to the axons of the nerve cells, but above all, to improve transmission speed of the nerve impulse in vertebrates. Over 70% of the myelin sheath is composed of lipids and the remaining portion by approximately 2,000 proteins. The myelin sheath has been constantly evolving, and it is known that unusually high concentrations of galactosylceramide (GalCer) and its sulfated form play a major role in the biophysical properties of the myelin. To gain insights of the evolutionary role of GalCer, we have studied two lysosomal enzymes involved in GalCer degradation, arylsulfatase A (ARSA) and galactocerebrosidase (GALC). Deficiency of ARSA or GALC causes demyelinating disorders. We conducted phylogenetic analyses of 105 ARSA and 110 GALC orthologs representing more than 600 million years ago of evolution. We examined i) low values of the ratio of nonsynonymous to synonymous nucleotide-substitution rates (dN/dS) indicating purifying selection and ii) negative selection of amino acids located in the active site preventing pathogenic mutations. Gene structure analyses showed evidence of rearrangement with gain and loss of exons while there were conserved regions mainly located around the active site. We also found a limited number of sites under positive selection pressure that do not cause alterations to the overall protein structure. Our results indicate that ARSA and GALC have been highly conserved during the evolutionary process to maintain the metabolism of GalCer, which is essential for the integrity of the white matter in vertebrate species.

ACSL3 is a promising therapeutic target for alleviating anxiety and depression in Alzheimer's disease

Alzheimer's disease (AD), the leading cause of dementia, affects over 55 million people worldwide and is often accompanied by depression and anxiety. Both significantly impact patients' quality of life and impose substantial societal and economic burdens on healthcare systems. Identifying the complex regulatory mechanisms that contribute to the psychological and emotional deficits in AD will provide promising therapeutic targets. Biosynthesis of omega-3 (ω3) and omega-6 fatty acids (ω6-FA) through long-chain acyl-CoA synthetases (ACSL) is crucial for cell function and survival. This is due to ω3/6-FA's imperative role in modulating the plasma membrane, energy production, and inflammation. While ACSL dysfunction is known to cause heart, liver, and kidney diseases, the role of ACSL in pathological conditions in the central nervous system (e.g., depression and anxiety) remains largely unexplored. The impact of ACSLs on AD-related depression and anxiety was investigated in a mouse model of Alzheimer's disease (3xTg-AD). ACSL3 levels were significantly reduced in the hippocampus of aged 3xTg-AD mice (via capillary-based immunoassay). This reduction in ACAL3 was closely associated with increased depression and anxiety-like behavior (via forced swim, tail suspension, elevated plus maze, and sucrose preference test). Upregulation of ACSL3 via adenovirus in aged 3xTg-AD mice led to increased protein levels of brain-derived neurotrophic factor (BDNF) and vascular endothelial growth factor C (VEGF-C) (via brain histology, capillary-based immunoassay), resulting in alleviation of depression and anxiety symptoms. The present study highlights a novel neuroprotective role of ACSL3 in the brain. Targeting ACSL3 will offer an innovative approach for treating AD-related depression and anxiety.

Drug-Induced Cognitive Impairment

Drug-induced cognitive impairment (DICI) is a well-established, yet under-recognised, complication of many types of pharmacological treatment. While there is a large body of scientific literature on DICI, most papers are about drug-induced dementia in the elderly and one specific drug class. However, DICI also comprises subclinical symptoms, domain-specific forms of cognitive impairment as well as mild cognitive impairment (MCI), and delirium. Even mild forms of DICI, if not recognised as such, can have deleterious and life-long consequences. In addition, DICI also occurs in younger adults and in children, and has been reported with many different drug classes. The aim of this review is to raise awareness of DICI by providing an overview on the type(s) and symptoms of observed DICI and the suspected underlying mechanism(s) for various drug classes: antiseizure medications, antidepressants, antiparkinsonian drugs, antipsychotics, lithium, benzodiazepines/Z-drugs, opioids, first-generation antihistamines, drugs for urinary incontinence, proton pump inhibitors, glucocorticoids, NSAIDs, statins, antihypertensives, and chemotherapeutic agents.

Exercise Delays Brain Ageing Through Muscle-Brain Crosstalk

Ageing is often accompanied by cognitive decline and an increased risk of dementia. Exercise is a powerful tool for slowing brain ageing and enhancing cognitive function, as well as alleviating depression, improving sleep, and promoting overall well-being. The connection between exercise and healthy brain ageing is particularly intriguing, with exercise-induced pathways playing key roles. This review explores the link between exercise and brain health, focusing on how skeletal muscle influences the brain through muscle-brain crosstalk. We examine the interaction between the brain with well-known myokines, including brain-derived neurotrophic factor, macrophage colony-stimulating factor, vascular endothelial growth factor and cathepsin B. Neuroinflammation accumulates in the ageing brain and leads to cognitive decline, impaired motor skills and increased susceptibility to neurodegenerative diseases. Finally, we examine the evidence on the effects of exercise on neuronal myelination in the central nervous system, a crucial factor in maintaining brain health throughout the lifespan.

Regional analysis of myelin basic protein across postnatal brain development of C57BL/6J mice

Healthy brain development hinges on proper myelination, with disruption contributing to a wide array of neurological disorders. Immunohistochemical analysis of myelin basic protein (MBP) is a fundamental technique for investigating myelination and related disorders. However, despite decades of MBP research, detailed accounts of normal MBP progression in the developing mouse brain have been lacking. This study aims to address this gap by providing a detailed spatiotemporal account of MBP distribution across 13 developmental ages from postnatal day 2 to 60. We used an optimized immunohistochemistry protocol to overcome the challenges of myelin's unique lipid-rich composition, enabling more consistent staining across diverse brain structures and developmental stages, offering a robust baseline for typical myelination patterns, and enabling comparisons with pathological models. To support and potentially accelerate research into myelination disorders, we have made >1,400 high-resolution micrographs accessible online under the Creative Commons license.

Human brain tissue with MOGHE carrying somatic SLC35A2 variants reveal aberrant protein expression and protein loss in the white matter

Mild Malformation of Cortical Development with Oligodendroglial Hyperplasia in Epilepsy (MOGHE) is a recently described disease entity primarily affecting young children with drug-resistant epilepsy, mainly affecting the frontal lobe. The condition is histopathologically defined by focal lesions with patchy areas of increased oligodendroglial cell density at the grey-white matter boundary and heterotopic neurons in the white matter. Approximately half of the individuals with MOGHE carry brain somatic variants in the SLC35A2 gene, which affects the UDP-galactose transporter and thus sphingolipid glycosylation. To investigate the impact of SLC35A2 variants on protein expression, we analysed MOGHE brain tissue with and without SLC35A2 mosaicism, distinguishing missense from nonsense variants. We developed an antibody targeting the N-terminus of the SLC35A2 galactose transporter and applied it for immunofluorescence (IF) analyses in a MOGHE cohort comprising 59 genetically tested individuals selected from three centres in Germany. The cohort included 13 individuals with SLC35A2 missense variants and 15 with SLC35A2 nonsense variants. Our findings confirm the localisation of the SLC35A2 protein in the Golgi apparatus of all neuroepithelial cell types as well as within Golgi outposts along oligodendroglial processes. The protein distribution was altered in MOGHE samples dependent on the SLC35A2 variant and its allelic frequency. Western blot and IF analyses revealed a significant SLC35A2 reduction in MOGHE tissues carrying nonsense variants. Ultrastructural analyses from three MOGHE samples demonstrated hypomyelination in regions with increased oligodendroglial cell densities, regardless of the harbouring of SLC35A2 variants. Notably, this hypomyelination pattern decreased with age. These results suggested a role for the SLC35A2 protein in the pathogenesis of MOGHE and indicated the presence of additional myelin-associated pathomechanisms in those individuals who do not carry a pathogenic SLC35A2 variant.

Fundamental origins of neural tube defects with a basis in genetics and nutrition

Neural tube defects (NTDs) are leading congenital malformations. Its global prevalence is one in 1000 pregnancies and it has high morbidity and mortality. It has multiple risk factors like genetic errors and environmental stressors like maternal malnutrition and in utero exposure to pollutants like chemicals. The genetic program determines neural tube development based on timely expression of many genes involved in developmental signaling pathways like BMP, PCP and SHH. BMP expression defines ectoderm. SOX represses BMP in ectoderm and convertes to the neuroectoderm. Subsequently, PCP molecules define the tissue patterning for convergent-extension, a critical step in neural tube genesis. Further, SHH sets spatial patterning of the neural tube. Nutrients are the essential major environmental input for embryogenesis. But it may also carry risk factors. Malnutrition, especially folate deficiency, during embryogenesis is a major cause for NTDs. Folate is integral in the One Carbon metabolic pathway. Its deficiency and error in the pathway are implicated in NTDs. Folate supplementation alone is insufficient to prevent NTDs. Thus, a comprehensive understanding of the various risk factors is necessary to strategize reduction of NTDs. We review the current knowledge of various risk factors, like genetic, metabolic, nutritional, and drugs causing NTDs and discuss the steps required to identify them in the early embryogenesis to avoid NTDs.

Nutritional Psychology: Review the Interplay Between Nutrition and Mental Health

Nutritional psychology is a burgeoning field that examines the intricate relationship between nutrition and mental health. This concept, its historical development, and its current significance in understanding the complex interplay between diet and psychological well-being are explored in this article. The influence of various nutrients on mental health, the role of dietary patterns, and the impact of nutrition on specific mental disorders are examined. Highlighted are the potential mechanisms underlying the nutrition-mental health connection, and the implications for clinical practice and public health interventions are discussed. The discussion in this article underscores the importance of considering nutrition as essential in mental health promotion and treatment.

Development and preclinical evaluation of an endonasal Raman spectroscopy probe for transsphenoidal pituitary adenoma surgery

Significance

For most patients with pituitary adenomas, surgical resection represents a viable therapeutic option, particularly in cases with endocrine symptoms or local mass effects. Diagnostic imaging, including MRI and computed tomography, is employed clinically to plan pituitary adenoma surgery. However, these methods cannot provide surgical guidance information in real time to improve resection rates and reduce risks of damage to normal tissue during tumor debulking.

Aim

Here, we present the development of a handheld Raman spectroscopy system that can be seamlessly integrated with transsphenoidal surgery workflows to allow live discrimination of all normal intracranial anatomical structures, including the pituitary gland, and potentially tissue abnormalities such as adenomas.

Approach

A fiber-optic probe was developed with a form factor compatible with endoscopic systems for endonasal surgeries. The instrument was evaluated in an ex vivo experimental protocol designed to assess its ability to distinguish normal intracranial structures. A total of 274 in situ spectroscopic measurements were acquired from six lamb heads, targeting key anatomical structures encountered in surgery. Support vector machine models were developed to classify tissue types based on their spectral signatures.

Results

Binary classification models successfully distinguished the pituitary gland from other tissue structures with a sensitivity and a specificity of 100%. In addition, a four-class predictive model enabled > 95 % accuracy in situ discrimination of four structures of most importance during pituitary adenoma tumor resection, i.e., the pituitary gland, the sella turcica (ST) bone, the optic chiasm, and the ST dura mater.

Conclusions

This work sets the stage for the clinical deployment of Raman spectroscopy as an intraoperative real-time decision support system during transsphenoidal surgery, with future work focused on clinical integration and the generalization of the approach to include the detection of tissue abnormalities, such as pituitary adenomas.

T2/FLAIR mismatch and diffusion restriction as novel pathophysiological markers in MRI evaluation of central tegmental tract hyperintensity in pediatric patients

INTRODUCTION

Central tegmental tract hyperintensity (CTTH) on T2-weighted imaging is an uncommon neuroimaging finding in pediatric patients with unclear clinical significance. CTTH may represent either a physiological or pathological process. This study evaluates the relationship between CTTH and MRI sequences (FLAIR, DWI) to explore its diagnostic value.

METHODS

We retrospectively analyzed 3462 pediatric brain MRI scans conducted between July 2011 and January 2022, identifying 104 patients with bilateral CTTH. DWI, FLAIR sequences, and follow-up scans were visually assessed for T2/FLAIR mismatch and diffusion restriction. Clinical data were obtained from electronic patient records. Statistical analysis was performed using SPSS, with significance set at p < .05.

RESULTS

A total of 104 pediatric patients with CTTH were included, ranging from 1 month to 16 years old (mean age: 31.34 months). Epilepsy, metabolic diseases, and cerebral palsy were the most common clinical diagnoses. Diffusion restriction was observed in 40.8% of patients, while 39.6% had FLAIR hyperintensity. T2/FLAIR mismatch, defined for the first time in CTTH, was found in 60.4% of patients. A significant correlation was found between T2/FLAIR mismatch and clinical diagnoses (p = .020), as well as between diffusion restriction and T2/FLAIR mismatch (p = .017).

CONCLUSION

CTTH in pediatric patients may arise from two distinct processes: a transient, developmental phenomenon or a pathological process marked by irreversible myelin degeneration. T2/FLAIR mismatch and diffusion restriction provide valuable diagnostic markers, offering insights into the severity and chronicity of CTTH. Further studies are needed to validate these findings and their clinical implications.

Therapeutic potential of pranlukast against cuprizone-induced inflammatory demyelination and sensory impairment in mice: Comparison with fingolimod

Inflammatory demyelination is present in debilitating diseases such as Multiple Sclerosis (MS). Several drugs are available for MS treatment, with fingolimod as a first-line oral option in the United States. However, a cure has yet to be established, and therapeutic failures are common, highlighting the need for continued research into new pharmacological targets. Pranlukast has shown positive effects on myelination in cell cultures and after LPC-induced demyelination in mice, but it is not yet part of the therapeutic arsenal for this disease. This study investigates pranlukast's effect on demyelination protection in an MS animal model, compared to fingolimod. For this purpose, young adult Swiss mice were treated for five weeks with a 0.2 % cuprizone diet and received daily intraperitoneal injections of pranlukast (0.1 mg/kg), fingolimod (1 mg/kg), or vehicle. Pranlukast treatment, like fingolimod, partially preserved sensory function in the tactile sensitivity test. Both treatments partially preserved myelin basic protein (MBP) levels, but only fingolimod preserved lipids and myelinated fibers in the corpus callosum (CC) at all g-ratio ranges. Cuprizone and Pranlukast groups presented more microglia/macrophages in the CC, but fewer presenting reactive microglia/macrophages and less NOS2 staining in pranlukast-treated when compared to the cuprizone group, while fingolimod treatment prevented the increase in Iba1 in the CC. In summary, this study demonstrated that pranlukast is a good candidate as a novel drug for use in conditions of inflammatory demyelination, such as MS, by restoring function through modulation of the inflammatory environment.

Regulation of CNS Lipids by Protease Activated Receptor 1

Disruptions in the metabolism of cholesterol and other lipids are strongly implicated in the pathogenesis of neurological disease. The CNS is highly enriched in cholesterol, which is primarily synthesized de novo. Cholesterol synthesis is also rate limiting for myelin regeneration. Given that knockout of the thrombin receptor (Protease Activated Receptor 1 (PAR1)) accelerates myelin regeneration, here we sought to determine the potential regulatory actions of PAR1 in CNS cholesterol and lipid metabolism in the intact adult CNS and during myelin regeneration. We present quantitative PCR and RNAseq evidence from murine spinal cords at the peak of myelination and in adulthood showing PAR1 knockout is associated with increased gene expression for cholesterol biosynthesis (Hmgcs1, Hmgcr, Sqle, and Dhcr7), lipid transport (ApoE, Abca1, and Ldlr), and intracellular processing (Lcat, Npc1, and Npc2) at one or more time points examined. An upregulation of genes involved in the synthesis of other lipids enriched in the myelin membrane, specifically Fa2h, Ugt8a, and Gal3st1, was also observed in PAR1 knockouts. Transcription factors essential for lipid and cholesterol production (Srebf1 and Srebf2) were also increased in PAR1 knockout spinal cords at the postnatal day 21 peak of myelination and at day 45. GC-MS and LC-MS quantification of lipids demonstrated coordinate increases in the abundance of select cholesterol and lipid species in the spinal cords of PAR1 knockout mice, including enrichment of esterified cholesterol, together with sphingomyelins and sphingolipids. Co-localization of the SREBP1 and SREBP2 transcription factors, as well as HMGCS1, a rate-limiting enzyme in cholesterol biosynthesis, to glia during remyelination post-lysolecithin or cuprizone-mediated demyelination showed a prominent regulatory role for PAR1 in Olig2+ oligodendrocytes. PAR1 knockouts also demonstrated elevated levels of SREBP2 in more mature GST3+ oligodendrocytes and SREBP1 in GFAP+ astrocytes during remyelination post-lysolecithin. These findings demonstrate novel roles for PAR1 as a regulator of CNS cholesterol and lipid metabolism and its potential as a therapeutic target to increase cholesterol availability to improve myelin regeneration.

Cerebellar lipid dysregulation in SCA3: A comparative study in patients and mice

Spinocerebellar ataxia type 3 (SCA3) is the most common dominantly inherited ataxia and belongs to the family of nine diseases caused by a polyglutamine expansion in the disease-causing protein. In SCA3, a polyglutamine expansion in ATXN3 causes neuron loss in disease-vulnerable brain regions, resulting in progressive loss of coordination and ultimately death. There are no disease-modifying or preventative treatments for this uniformly fatal disorder. Recent studies demonstrate prominent white matter atrophy and microstructural alterations in disease-vulnerable brain regions of SCA3 patients and mouse models. However, the major constituent of white matter - lipids - remains understudied in SCA3. In this study, we conducted the first unbiased investigation of brain lipids in SCA3, focusing on the disease-vulnerable cerebellum of SCA3 postmortem patients and mouse models. Liquid chromatography-mass spectrometry uncovered widespread lipid reductions in patients with SCA3. Lipid downregulation was recapitulated in early- to mid-stage mouse models of SCA3, including transgenic YACQ84 and Knock-in Q300 mice. End-stage Knock-in Q300 mice displayed a progressive reduction in lipid content, highlighting targets that could benefit from early therapeutic intervention. In contrast, Atxn3-Knock-out mice showed mild lipid upregulation, emphasizing a toxic gain-of-function mechanism underlying lipid downregulation in SCA3. We conclude that lipids are significantly altered in SCA3 and establish a platform for continued exploration of lipids in disease through interactive data visualization websites. Pronounced reductions in myelin-enriched lipids suggest that lipid dysregulation could underlie white matter atrophy in SCA3. This study establishes the basis for future work elucidating the mechanistic, biomarker, and therapeutic potential of lipids in SCA3.

Therapeutic potential of siRNA PMP22-SQ nanoparticles for Charcot-Marie-Tooth 1A neuropathy in rodents and non-human primates

Small interfering RNA (siRNA) has shown promising results for the treatment of Charcot-Marie-Tooth disease 1A (CMT1A) caused by overexpression of peripheral myelin protein (PMP22), leading to myelin dysfunction and axonal damage. Recently, we developed siRNA PMP22-squalene (SQ) nanoparticles (NPs) for intravenous use. Three consecutive injections of siRNA PMP22-SQ NPs at a cumulative dose of 1.5 mg/kg restored motor function in C61 transgenic mouse models. Pharmacokinetic studies showed a long half-life of antisense siRNA PMP22 in the sciatic nerve, and spinal cord, indicating targeted release potential. We further assessed the efficiency and safety of siRNA PMP22-SQ NPs in two healthy male non-human primates (Macaca fascicularis) after administering four escalating doses (0.1, 0.5, 2.5 and 4.5 mg/kg at one week interval). Interestingly, the siRNA PMP22-SQ NPs reduced PMP22 mRNA expression by approximately 70 % and probably induced an early-stage hereditary neuropathy with pressure palsies (HNPP)-like condition in two normal NHP. No preliminary toxicity was observed in organs or blood parameters of the two NHPs. Interestingly, the nerve conduction velocity decreased after the third injection of siRNA PMP22-SQ NPS. These results demonstrate the therapeutic potential of siRNA PMP22-SQ NPs, supporting advancement to further pre-clinical testing.

Sleep duration and efficiency moderate the effects of prenatal and childhood ambient pollutant exposure on global white matter microstructural integrity in adolescence

Background

Air pollution is a ubiquitous neurotoxicant associated with alterations in structural connectivity. Good habitual sleep may be an important protective lifestyle factor due to its involvement in the brain waste clearance and its bidirectional relationship with immune function. Wearable multisensory devices may provide more objective measures of sleep quantity and quality. We investigated whether sleep duration and efficiency moderated the relationship between prenatal and childhood pollutant exposure and whole-brain white matter microstructural integrity at ages 10-13 years.

Methods

We used multi-shell diffusion-weighted imaging data collected on 3T MRI scanners and objective sleep data collected with Fitbit Charge 2 from the 2-year follow-up visit for 2178 subjects in the Adolescent Brain Cognitive Development Study®. White matter tracts were identified using a probabilistic atlas. Restriction spectrum imaging was performed to extract restricted normalized isotropic (RNI) and directional (RND) signal fraction parameters for all white matter tracts, then averaged to calculate global measures. Sleep duration was calculated by summing the time spent in each sleep stage; sleep efficiency was calculated by dividing sleep duration by time spent in bed. Using an ensemble-based modeling approach, air pollution concentrations of PM2.5, NO2, and O3 were assigned to each child's residential addresses during the prenatal period (9-month average before birthdate) as well as at ages 9-10 years. Multi-pollutant linear mixed effects models assessed the associations between global RNI and RND and sleep-by-pollutant interactions, adjusting for appropriate covariates.

Results

Sleep duration interacted with childhood NO2 exposure and sleep efficiency interacted with prenatal O3 exposure to affect RND at ages 10-13 years. Longer sleep duration and higher sleep efficiency in the context of higher pollutant exposure was associated with lower RND compared to those with similar pollutant exposure but shorter sleep duration and lower sleep efficiency.

Conclusions

Low-level air pollution poses a risk to brain health in youth, and healthy sleep duration and efficiency may increase resilience to its harmful effects on white matter microstructural integrity. Future studies should evaluate the generalizability of these results in more diverse cohorts as well as utilize longitudinal data to understand how sleep may impact brain health trajectories in the context of pollution over time.

Sphingomyelin Inhibits Hydrolytic Activity of Heterodimeric PLA2 in Model Myelin Membranes: Pharmacological Relevance

In this work, the heterodimeric phospholipase A2, HDP-2, from viper venom was investigated for its hydrolytic activity in model myelin membranes as well as for its effects on intermembrane exchange of phospholipids (studied by phosphorescence quenching) and on phospholipid polymorphism (studied by 1H-NMR spectroscopy) to understand the role of sphingomyelin (SM) in the demyelination of nerve fibers. By using well-validated in vitro approaches, we show that the presence of SM in model myelin membranes leads to a significant inhibition of the hydrolytic activity of HDP-2, decreased intermembrane phospholipid exchange, and reduced phospholipid polymorphism. Using AutoDock software, we show that the NHδ+ group of the sphingosine backbone of SM binds to Tyr22(C=Opbδ-) of HDP-2 via a hydrogen bond which keeps only the polar head of SM inside the HDP-2's active center and positions the sn-2 acyl ester bond away from the active center, thus making it unlikely to hydrolyze the alkyl chains at the sn-2 position. This observation strongly suggests that SM inhibits the catalytic activity of HDP-2 by blocking access to other phospholipids to the active center of the enzyme. Should this observation be verified in further studies, it would offer a tantalizing opportunity for developing effective pharmaceuticals to stop the demyelination of nerve fibers by aberrant PLA2s with overt activity - as observed in brain degenerative diseases - by inhibiting SM hydrolysis and/or facilitating SM synthesis in the myelin sheath membrane.

Palm oil as part of a high-fat diet: advances and challenges, or possible risks of pathology?

Nutritional status disorders have the most significant impact on the development of cardiovascular and oncologic diseases; therefore, the interest in the study of palm oil as among the leading components of nutrition has been increasing. The data examined in this review were sourced from the Scopus, SCIE (Web of Science), PubMed and PubMed Central, MEDLINE, CAPlus/SciFinder, and Embase databases; experts in the field; bibliographies; and abstracts from review analyses from the past 15 years. This review summarizes recent research data focusing on the quantitative and qualitative composition of nutrition of modern humans; concepts of the relationship between high-fat diets and disorders of insulin functioning and transport and metabolism of fatty acids; analyses of data regarding the palmitic acid (16:0) to oleic acid (18:1) ratio; and the effect of diet based on palm oil consumption on cardiovascular risk factors and lipid and lipoprotein levels. Several studies suggest a potential vector contributing to the transmission of maternal, high-fat-diet-induced, addictive-like behaviors and obesogenic phenotypes across generations. The relationship between cholesterol accumulation in lysosomes that may lead to lysosome dysfunction and inhibition of the autophagy process is analyzed, as is the progression of inflammatory diseases, atherosclerosis, nonalcoholic liver inflammation, and obesity with associated complications. Data are discussed from analyses of differences between rodent models and human population studies in the investigated different effects of palm oil consumption as a high-fat diet component. A conclusion is reached that the results cannot be generalized in human population studies because no similar effects were observed. Although there are numerous published reports, more studies are necessary to elucidate the complex regulatory mechanisms in digestive and nutrition processes, because there are great differences in lipoprotein profiles between rodents and humans, which makes it difficult to reproduce the pathology of many diseases caused by different types of the high-fat diet.

Visualization of Efavirenz-Induced Lipid Alterations in the Mouse Brain Using MALDI Mass Spectrometry Imaging

This article highlights experimental procedures and troubleshooting tips for the utilization of matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI MSI) methods for detecting and visualizing lipid alterations in the mouse brain tissue in response to efavirenz (EFV) treatment. To investigate drug-induced adverse effects, it is becoming increasingly important to understand the spatial alterations of lipid molecules in the target organs. EFV is a non-nucleoside reverse transcriptase inhibitor commonly used for HIV treatment in combination with other antiretrovirals. Importantly, EFV is a drug that is included in the World Health Organization's list of essential medications. However, EFV is known to be associated with neurotoxicity. To date, the mechanisms underlying EFV-induced neurotoxicity have not been fully elucidated. Therefore, it is important to gain understanding of the effect of EFV on the brain. It is known that the brain is composed of different neuroanatomical regions that are abundant in lipids. Described here is the use of a chemical imaging strategy, MALDI MSI, to detect, identify, and visualize the spatial localization of several lipid species across the brain tissue sections along with their alterations in response to EFV treatment. The set of protocols consists of three major parts: lipid detection, identification, and tissue imaging. Lipid detection includes testing different chemical matrices and how they facilitate the detection of analytes, which is then followed by identification. Collision-induced dissociation is employed to verify the identity of the lipid molecules. Lastly, tissue imaging experiments are performed to generate the spatial localization profiles of the lipids. The protocols described in this article can be employed to spatially visualize alterations in the lipid molecules in response to drug treatment. © 2025 Wiley Periodicals LLC. Basic Protocol 1: MALDI mass spectrometry (MALDI MS) profiling experiments for detection of lipids Basic Protocol 2: MALDI MS imaging of lipid molecules in mouse brain tissues Basic Protocol 3: MALDI MS data processing and analysis.

Exertional Exhaustion (Post-Exertional Malaise, PEM) Evaluated by the Effects of Exercise on Cerebrospinal Fluid Metabolomics-Lipidomics and Serine Pathway in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome

Post-exertional malaise (PEM) is a defining condition of myalgic encephalomyelitis (ME/CFS). The concept requires that a provocation causes disabling limitation of cognitive and functional effort ("fatigue") that does not respond to rest. Cerebrospinal fluid was examined as a proxy for brain metabolite and lipid flux and to provide objective evidence of pathophysiological dysfunction. Two cohorts of ME/CFS and sedentary control subjects had lumbar punctures at baseline (non-exercise) or after submaximal exercise (post-exercise). Cerebrospinal fluid metabolites and lipids were quantified by targeted Biocrates mass spectrometry methods. Significant differences between ME/CFS and control, non-exercise vs. post-exercise, and by gender were examined by multivariate general linear regression and Bayesian regression methods. Differences were found at baseline between ME/CFS and control groups indicating disease-related pathologies, and between non-exercise and post-exercise groups implicating PEM-related pathologies. A new, novel finding was elevated serine and its derivatives sarcosine and phospholipids with a decrease in 5-methyltetrahydrofolate (5MTHF), which suggests general dysfunction of folate and one-carbon metabolism in ME/CFS. Exercise led to consumption of lipids in ME/CFS and controls while metabolites were consumed in ME/CFS but generated in controls. In general, the frequentist and Bayesian analyses generated complementary but not identical sets of analytes that matched the metabolic modules and pathway analysis. Cerebrospinal fluid is unique because it samples the choroid plexus, brain interstitial fluid, and cells of the brain parenchyma. The quantitative outcomes were placed into the context of the cell danger response hypothesis to explain shifts in serine and phospholipid synthesis; folate and one-carbon metabolism that affect sarcosine, creatine, purines, and thymidylate; aromatic and anaplerotic amino acids; glucose, TCA cycle, trans-aconitate, and coenzyme A in energy metabolism; and vitamin activities that may be altered by exertion. The metabolic and phospholipid profiles suggest the additional hypothesis that white matter dysfunction may contribute to the cognitive dysfunction in ME/CFS.

APOEε4 alters ApoE and Fabp7 in frontal cortex white matter in prodromal Alzheimer's disease

The ApoE ε4 allele (APOEε4) is a major genetic risk factor for sporadic Alzheimer's disease (AD) and is linked to demyelination and cognitive decline. However, its effects on the lipid transporters apolipoprotein E (ApoE) and fatty acid-binding protein 7 (Fabp7), which are crucial for the maintenance of myelin in white matter (WM) during the progression of AD remain underexplored. To evaluate the effects of APOEε4 on ApoE, Fabp7 and myelin in the WM of the frontal cortex (FC), we examined individuals carrying one ε4 allele that came to autopsy with a premortem clinical diagnosis of no cognitive impairment (NCI), mild cognitive impairment (MCI) and mild to moderate AD compared with non-carrier counterparts. ApoE, Fabp7 and Olig2 immunostaining was used to visualize cells, whereas myelin basic protein (MBP) immunocytochemistry and luxol fast blue (LFB) histochemistry of myelin in the WM of the FC were combined with quantitative morphometry. We observed increased numbers of ApoE-positive astrocytes in the WM of both NCI and MCI APOEε4 carriers compared with non-carriers, whereas Fabp7-positive cells were elevated only in AD. Conversely, Olig2 cell counts and MBP immunostaining decreased in MCI APOEε4 carriers compared to non-carriers, while LFB levels were higher in NCI APOEε4 carriers compared to non-carriers. Although no correlations were found between ApoE, Fabp7, and cognitive status, LFB measurements were positively correlated with perceptual speed, global cognition, and visuospatial scores in APOEε4 carriers across clinical groups. The present findings suggest that the ε4 allele compromises FC myelin homeostasis by disrupting the lipid transporters ApoE, Fabp7 and myelination early in the onset of AD. These data support targeting cellular components related to WM integrity as possible treatments for AD.

Myelin ensheathment and drug responses of oligodendrocytes are modulated by stiffness of artificial axons

Myelination is a key biological process wherein glial cells such as oligodendrocytes wrap myelin around neuronal axons, forming an insulative sheath that accelerates signal propagation down the axon. A major obstacle to understanding myelination is the challenge of visualizing and reproducibly quantifying this inherently three-dimensional process in vitro. To this end, we previously developed artificial axons (AAs), a biocompatible platform consisting of 3D-printed hydrogel-based axon mimics designed to more closely recapitulate the micrometer-scale diameter and sub-kilopascal mechanical stiffness of biological axons. First, we present our platform for fabricating AAs with tunable axon diameter, stiffness, and inter-axonal spacing. Second, we demonstrate that increasing the Young's modulus E or stiffness of polymer comprising the AAs increases the extent of myelin ensheathment by rat oligodendrocytes. Third, we demonstrate that the responses of oligodendrocytes to pro-myelinating compounds are also dependent on axon stiffness, which can affect compounds efficacy and the relative ranking. These results reinforce the importance of studying myelination in mechanically representative environments, and highlight the importance of considering biophysical cues when conducting drug screening studies.

Endogenous histidine peptides are physiological antioxidants that prevent oligodendrocyte cell death and myelin loss in vivo

Histidine dipeptides (HDs) are synthesized in brain oligodendrocytes by carnosine synthase (carns1), but their role is unknown. Using metabolomics and in vivo experiments with both constitutive and oligodendrocyte-selective carns1-KO mouse models, we found that HDs are critical for oligodendrocyte survival and protect against oxidative stress. Carns1-KO mouse models had lower numbers of mature oligodendrocytes, increased lipid peroxidation, and behavioral changes. Cuprizone administration, which increases reactive oxygen species in vivo, resulted in higher oligodendrocyte death, demyelination, axonal alterations, and oxidative damage in the corpus callosum of carns1-KO mice. Gliosis and oxidative damage by cuprizone were prevented by pretreatment with the antioxidant N-acetylcysteine. NADPH levels were increased threefold in the brains of carns1-KO mice as an antioxidant response to oxidative stress through acceleration of the pentose phosphate pathway (PPP). This was due to overexpression of glucose-6-phosphate dehydrogenase, the rate-limiting enzyme of the PPP. Likewise, expression of NAD kinase, the biosynthetic enzyme for NADP+, and NAMPT, which replenishes the NAD+ pool, was higher in carns1-KO mice brains than in controls. Our observations suggest that HDs cell-autonomously protect oligodendrocytes from oxidative stress, with implications for demyelinating diseases.

Transcription factor 7-like 2 (TCF7l2) regulates CNS myelination separating from its role in upstream oligodendrocyte differentiation

Oligodendrocyte progenitor cells (OPCs) differentiation into oligodendrocytes (OLs) and subsequent myelination are two closely coordinated yet differentially regulated steps for myelin formation and repair in the CNS. Previously thought as an inhibitory factor by activating Wnt/beta-catenin signaling, we and others have demonstrated that the Transcription factor 7-like 2 (TCF7l2) promotes OL differentiation independent of Wnt/beta-catenin signaling activation. However, it remains elusive if TCF7l2 directly controls CNS myelination separating from its role in upstream oligodendrocyte differentiation. This is partially because of the lack of genetic animal models that could tease out CNS myelination from upstream OL differentiation. Here, we report that constitutively depleting TCF7l2 transiently inhibited oligodendrocyte differentiation during early postnatal development, but it impaired CNS myelination in the long term in adult mice. Using time-conditional and developmental-stage-specific genetic approaches, we further showed that depleting TCF7l2 in already differentiated OLs did not impact myelin protein gene expression nor oligodendroglial populations, instead, it perturbed CNS myelination in the adult. Therefore, our data convincingly demonstrate the crucial role of TCF7l2 in regulating CNS myelination independent of its role in upstream oligodendrocyte differentiation.

Machine learning for refining interpretation of magnetic resonance imaging scans in the management of multiple sclerosis: a narrative review

Multiple sclerosis (MS) is an autoimmune disease of the brain and spinal cord with both inflammatory and neurodegenerative features. Although advances in imaging techniques, particularly magnetic resonance imaging (MRI), have improved the process of diagnosis, its cause is unknown, a cure remains elusive and the evidence base to guide treatment is lacking. Computational techniques like machine learning (ML) have started to be used to understand MS. Published MS MRI-based computational studies can be divided into five categories: automated diagnosis; differentiation between lesion types and/or MS stages; differential diagnosis; monitoring and predicting disease progression; and synthetic MRI dataset generation. Collectively, these approaches show promise in assisting with MS diagnosis, monitoring of disease activity and prediction of future progression, all potentially contributing to disease management. Analysis quality using ML is highly dependent on the dataset size and variability used for training. Wider public access would mean larger datasets for experimentation, resulting in higher-quality analysis, permitting for more conclusive research. This narrative review provides an outline of the fundamentals of MS pathology and pathogenesis, diagnostic techniques and data types in computational analysis, as well as collating literature pertaining to the application of computational techniques to MRI towards developing a better understanding of MS.

The role of ATP citrate lyase in myelin formation and maintenance

Formation of myelin by Schwann cells is tightly coupled to peripheral nervous system development and is important for neuronal function and long-term maintenance. Perturbation of myelin causes a number of specific disorders that are among the most prevalent diseases affecting the nervous system. Schwann cells synthesize myelin lipids de novo rather than relying on uptake of circulating lipids, yet one unresolved matter is how acetyl CoA, a central metabolite in lipid formation is generated during myelin formation and maintenance. Recent studies have shown that glucose-derived acetyl CoA itself is not required for myelination. However, the importance of mitochondrially-derived acetyl CoA has never been tested for myelination in vivo. Therefore, we have developed a Schwann cell-specific knockout of the ATP citrate lyase (Acly) gene to determine the importance of mitochondrial metabolism to supply acetyl CoA in nerve development. Intriguingly, the ACLY pathway is important for myelin maintenance rather than myelin formation. In addition, ACLY is required to maintain expression of a myelin-associated gene program and to inhibit activation of the latent Schwann cell injury program.

Peripheral myelin: From development to maintenance

Peripheral myelin is synthesized by glial cells called Schwann cells (SCs). SC development and differentiation must be tightly regulated to avoid any pathological consequence affecting peripheral nerve function. Neuropathic symptoms can arise from developmental issues in SCs, as well as in adult life through processes affecting mature SCs. In this review we focus on SC differentiation from the immature towards the myelinating and non-myelinating SC stages, defining molecular mechanisms outlining radial sorting, a multi-stepped event essential for immature SC differentiation and myelination. We also describe mechanisms regulating myelin sheath maintenance and SC homeostasis during aging. Finally, we will conclude with some remaining questions in the field of SC biology.

From BBB to PPP: Bioenergetic requirements and challenges for oligodendrocytes in health and disease

Mature myelinating oligodendrocytes, the cells that produce the myelin sheath that insulates axons in the central nervous system, have distinct energetic and metabolic requirements compared to neurons. Neurons require substantial energy to execute action potentials, while the energy needs of oligodendrocytes are directed toward building the lipid-rich components of myelin and supporting neuronal metabolism by transferring glycolytic products to axons as additional fuel. The utilization of energy metabolites in the brain parenchyma is tightly regulated to meet the needs of different cell types. Disruption of the supply of metabolites can lead to stress and oligodendrocyte injury, contributing to various neurological disorders, including some demyelinating diseases. Understanding the physiological properties, structures, and mechanisms involved in oligodendrocyte energy metabolism, as well as the relationship between oligodendrocytes and neighboring cells, is crucial to investigate the underlying pathophysiology caused by metabolic impairment in these disorders. In this review, we describe the particular physiological properties of oligodendrocyte energy metabolism and the response of oligodendrocytes to metabolic stress. We delineate the relationship between oligodendrocytes and other cells in the context of the neurovascular unit, and the regulation of metabolite supply according to energetic needs. We focus on the specific bioenergetic requirements of oligodendrocytes and address the disruption of metabolic energy in demyelinating diseases. We encourage further studies to increase understanding of the significance of metabolic stress on oligodendrocyte injury, to support the development of novel therapeutic approaches for the treatment of demyelinating diseases.

Deciphering the role of sphingosine 1-phosphate in central nervous system myelination and repair

Sphingosine 1-phosphate (S1P) is a bioactive lipid of the sphingolipid family and plays a pivotal role in the mammalian nervous system. Indeed, S1P is a therapeutic target for treating demyelinating diseases such as multiple sclerosis. Being part of an interconnected sphingolipid metabolic network, the amount of S1P available for signalling is equilibrated between its synthetic (sphingosine kinases 1 and 2) and degradative (sphingosine 1-phosphate lyase) enzymes. Once produced, S1P exerts its biological roles via signalling to a family of five G protein-coupled S1P receptors 1-5 (S1PR1-5). Despite significant progress, the precise roles that S1P metabolism and downstream signalling play in regulating myelin formation and repair remain largely opaque and somewhat controversial. Genetic or pharmacological studies adopting various model systems identify that stimulating S1P-S1PR signalling protects myelin-forming oligodendrocytes after central nervous system (CNS) injury and attenuates demyelination in vivo. However, evidence to support its role in remyelination of the mammalian CNS is limited, although blocking S1P synthesis sheds light on the role of endogenous S1P in promoting CNS remyelination. This review focuses on summarising the current understanding of S1P in CNS myelin formation and repair, discussing the complexity of S1P-S1PR interaction and the underlying mechanism by which S1P biosynthesis and signalling regulates oligodendrocyte myelination in the healthy and injured mammalian CNS, raising new questions for future investigation.

Metabolomics study of serum from patients with type 2 diabetes: Peripheral neuropathy could be associated with sphingosine and phospholipid molecules

Abnormal lipid metabolism is one of the risk factors for type 2 diabetes mellitus peripheral neuropathy (DPN). This study aimed to determine the differences in lipid metabolism in patients with type 2 diabetes and DPN and the possible pathogenesis caused by this difference. The participants comprised type 2 diabetes mellitus patients with DPN (N = 60) and healthy controls (N = 20). Blood samples were drawn from the participants in the morning in the fasting state, and then changes in serum lipids were explored using targeted metabolomics on the liquid chromatography-electrospray ionization-tandem mass spectrometry platform. Among the 1768 differentially abundant lipid metabolites, the results of orthogonal partial least squares-discriminant analysis combined with random forest analysis showed that the levels of sphingosine (SPH) (d18:0), carnitine 22:1, lysophosphatidylethanolamine (LPE) (18:0/0:0), LPC (16:0/0:0), lysophosphatidylcholine (LPC) (18:1/0:0), LPC (0:0/18:0) and LPE (0:0/18:1) were significantly different between the two groups. Spearman correlation analysis showed that SPH (d18:0), carnitine 22:1, LPE (18:0/0:0), and LPC (0:0/18:0) levels correlated highly with the patients' electromyography results. Kyoto Encyclopedia of Genes and Genomes pathway annotation and enrichment analysis of 538 differentially abundant lipid metabolites revealed that type 2 diabetes mellitus DPN was related to glycerophospholipid metabolism and glycerol metabolism. Our results further identified the dangerous lipid metabolites associated with DPN and abnormal lipid metabolism. The influence of lipid metabolites such as SPH and phospholipid molecules on DPN development in patients with type 2 diabetes mellitus were suggested and the possible pathogenic pathways were clarified, providing new insights into the clinical risk of DPN in patients with type 2 diabetes mellitus.

White matter lipidome alterations in the schizophrenia brain

Numerous brain imaging studies have reported white matter alterations in schizophrenia, but the lipidome analysis of the corresponding tissue remains incomplete. In this study, we investigated the lipidome composition of six subcortical white matter regions corresponding to major axonal tracks in both control subjects and schizophrenia patients. All six regions exhibited a consistent pattern of quantitative lipidome alterations in schizophrenia, involving myelin-forming and mitochondria associated lipid classes. While alteration levels of myelin-forming lipids, particularly sphingolipids, aligned with the extent of the myelin changes reported in structural brain imaging studies, a significant decrease of mitochondria in the white matter, indicated by the lipidome alterations, was not previously investigated. To verify this effect, we performed lipidome analysis in a larger set of individuals and in the mitochondria-enriched membrane fraction, as well as directly quantified mitochondrial content. Our results suggest a substantial reduction of the mitochondrial quotient accompanied by the imbalance in myelin lipids in schizophrenia white matter.

Circadian Influences on Brain Lipid Metabolism and Neurodegenerative Diseases

Circadian rhythms are intrinsic, 24 h cycles that regulate key physiological, mental, and behavioral processes, including sleep-wake cycles, hormone secretion, and metabolism. These rhythms are controlled by the brain's suprachiasmatic nucleus, which synchronizes with environmental signals, such as light and temperature, and consequently maintains alignment with the day-night cycle. Molecular feedback loops, driven by core circadian "clock genes", such as Clock, Bmal1, Per, and Cry, are essential for rhythmic gene expression; disruptions in these feedback loops are associated with various health issues. Dysregulated lipid metabolism in the brain has been implicated in the pathogenesis of neurological disorders by contributing to oxidative stress, neuroinflammation, and synaptic dysfunction, as observed in conditions such as Alzheimer's and Parkinson's diseases. Disruptions in circadian gene expression have been shown to perturb lipid regulatory mechanisms in the brain, thereby triggering neuroinflammatory responses and oxidative damage. This review synthesizes current insights into the interconnections between circadian rhythms and lipid metabolism, with a focus on their roles in neurological health and disease. It further examines how the desynchronization of circadian genes affects lipid metabolism and explores the potential mechanisms through which disrupted circadian signaling might contribute to the pathophysiology of neurodegenerative disorders.

Hypertension may lead to cognitive dysfunction in older adults via methylmalonic acid: evidence from NHANES 2011-2014 population

BACKGROUND

An enriched understanding is necessary concerning the association between hypertension and cognitive impairment in older adults, particularly regarding the potential underlying mechanisms at a biological level. This study aimed to explore the mediating role of methylmalonic acid (MMA) in the hypertension-cognition link in the older population.

METHODS

A total of 2762 adults (age > = 60 years) from the National Health and Nutrition Examination Survey (NHANES) 2011-2014 participated. Cognitive function was assessed using a combination of the Animal Fluency Test (AFT), the Digit Symbol Substitution Test (DSST), and the Consortium to Establish a Registry for Alzheimer's Disease (CERAD) Word List Learning Test. Self-reported hypertension diagnosis, antihypertensive medications use, and blood pressure examinations were used to identify hypertension. Serum MMA (sMMA) levels were collected. Weighted multiple linear regressions and mediation analysis were applied. A subgroup analysis by sex and age was performed.

RESULTS

After adjusting for potential confounding factors, we observed a significant mediating effect of the sMMA level in the hypertension-cognition link, accounting for 11.14% (95% CI 4.09%-14.00%, p < 0.001) of the relationship in older adults. The proportion mediated by the sMMA level in the relationship between hypertension and cognitive function was higher in males (15.23%, 95%CI 1.32%-27.00%, p < 0.001) than in females (6.61%, 95%CI 2.12%-10.00%, p < 0.001). This mediating effect of sMMA was observed only in individuals aged 68 years and older (11.31%, 95%CI 3.80%-16.00%, p < 0.001), with no significant mediation detected in those younger than 68 years.

CONCLUSION

Hypertension may lead to cognitive dysfunction in older adults through MMA. Apart from its role as a biomarker reflecting vitamin B12, MMA may act as an independent neurotoxin capable of inducing brain injury and cognitive impairment. Addressing MMA accumulation, such as through Vitamin B12 supplementation, may have a potential to mitigate hypertension-induced cognitive decline in older adults. Special attention could be paid to hypertensive males with an advanced age (> = 68) to address MMA-related cognitive decline.

Pathology and Treatments of Alzheimer's Disease Based on Considering Changes in Brain Energy Metabolism Due to Type 2 Diabetes

Alzheimer's disease (AD) is a progressive neurodegenerative disorder with cognitive dysfunction, memory decline, and behavioral disturbance, and it is pathologically characterized by the accumulation of amyloid plaques and neurofibrillary tangles in the brain. Although various hypotheses have been proposed to explain the pathogenesis of AD, including the amyloid beta hypothesis, oxidative stress hypothesis, and abnormal phosphorylation of tau proteins, the exact pathogenic mechanisms underlying AD remain largely undefined. Furthermore, effective curative treatments are very limited. Epidemiologic studies provide convincing evidence for a significant association between type 2 diabetes and AD. Here, we showed energy metabolism using glucose, lactate, ketone bodies, and lipids as energy substrates in a normal brain, and changes in such energy metabolism due to type 2 diabetes. We also showed the influences of such altered energy metabolism due to type 2 diabetes on the pathology of AD. Furthermore, we comprehensively searched for risk factors related with type 2 diabetes for AD and showed possible therapeutic interventions based on considering risk factors and altered brain energy metabolism due to type 2 diabetes for the development of AD.

Contribution of gut microbiota to hepatic steatosis following F-53B exposure from the perspective of glucose and fatty acid metabolism

Altered gut microbiota is a pathogenic mechanism of 6:2 Cl-PFESA (F-53B)-induced hepatic steatosis, indicated by correlations between gut microbiota and lipid indices. However, the detailed mechanism remains unknown. In this study, adult zebrafish were exposed to 0.25, 5 and 100 μg/L F-53B for 28 days to explore how microbiota regulate hepatic lipid metabolism from the perspective of glucose and fatty acid metabolism. Results showed glucose and fatty acids were transported from blood into liver after 100 μg/L F-53B exposure, in which glucose was further transformed into acetyl-CoA and fatty acid. The accumulated fatty acids were then converted into triglycerides (TGs), inducing hepatic steatosis. Changes in the abundances of certain gut microbiota contributed to the above processes, which was verified by the fact that the levels of g_Crenobacter, g_Shewanella, and g_Vibrio restored to control levels after Lactobacillus rhamnosus GG intervention, and the levels of their related lipid indicators recovered partially towards the control levels. 0.25 and 5 μg/L F-53B had no effect on the hepatic lipid profile due to the few changed TG synthesis related indicators. Our findings provide novel insights into lipid metabolic disorders caused by F-53B exposure, highlighting the health risks linked to gut microbial dysbiosis.

Subacute combined degeneration from nitrous oxide abuse

Nitrous oxide is an anesthetic medication which can also be recreationally abused in the form of whippet canisters. Its prolonged abuse can interfere with Vitamin B12 metabolism and lead to its functional deficiency. We report a case of a 30-year-old male who presented with generalized weakness and was found to have subacute combined degeneration (SCD) of the spinal cord. His laboratory workup showed low Vitamin B12 with elevated homocysteine and methylmalonic Co-A levels, and further questioning revealed prolonged nitrous oxide abuse. Nitrous oxide causes functional inactivation of methylcobalamin by rendering it unable to function as a coenzyme for methionine synthase enzyme. This leads to the decreased production of methionine and subsequent production of myelin. This case describes nitrous oxide abuse as an important etiology to be considered in patients presenting with weakness and myeloneuropathy and describes important imaging findings.

Myelin Lipid Alterations in Neurodegenerative Diseases: Landscape and Pathogenic Implications

Significance: Lipids, which constitute the highest portion (over 50%) of brain dry mass, are crucial for brain integrity, energy homeostasis, and signaling regulation. Emerging evidence revealed that lipid profile alterations and abnormal lipid metabolism occur during normal aging and in different forms of neurodegenerative diseases. Moreover, increasing genome-wide association studies have validated new targets on lipid-associated pathways involved in disease development. Myelin, the protective sheath surrounding axons, is crucial for efficient neural signaling transduction. As the primary site enriched with lipids, impairments of myelin are increasingly recognized as playing significant and complex roles in various neurodegenerative diseases, beyond simply being secondary effects of neuronal loss. Recent Advances: With advances in the lipidomics field, myelin lipid alterations and their roles in contributing to or reflecting the progression of diseases, including Alzheimer's disease, Parkinson's disease, Huntington's disease, amyotrophic lateral sclerosis, multiple sclerosis, and others, have recently caught great attention. Critical Issues: This review summarizes recent findings of myelin lipid alterations in the five most common neurodegenerative diseases and discusses their implications in disease pathogenesis. Future Directions: By highlighting myelin lipid abnormalities in neurodegenerative diseases, this review aims to encourage further research focused on lipids and the development of new lipid-oriented therapeutic approaches in this area. Antioxid. Redox Signal. 00, 000-000.

Metabolite Associations with Childhood and Juvenile Absence Epilepsy: A Bidirectional Mendelian Randomization Study

Background

The precise involvement of metabolites in the pathogenesis of Childhood absence epilepsy (CAE) and juvenile absence epilepsy (JAE) remains elusive. Consequently, this investigation introduces bidirectional Mendelian randomization (MR) as a tool to explore causality and underlying mechanisms.

Methods

Bidirectional MR analysis was conducted employing a comprehensive set comprising 1091 human blood metabolites and 309 metabolite ratios, systematically probing potential causal associations with JAE and CAE. Genome-wide association study (GWAS) data pertaining to these epileptic conditions were meticulously obtained from the International League Against Epilepsy (ILAE) consortium. Sensitivity analyses were rigorously performed to evaluate for heterogeneity and pleiotropy. Reverse MR analysis was also conducted to verify the direction of causality, and no significant reverse causal relationships were identified.

Results

Following rigorous genetic variant selection, significant associations were identified based on PIVW < .05, PWM < .05, and PMR-Egger < .05 criteria in MR analysis. Only 1 metabolite, (2 or 3)-decaonate levels, exhibited an association with JAE (P = .005, OR=0.987, 95% CI=0.978-0.996). Childhood absence epilepsy was associated with 5 metabolites: X-23648 (P = .012, OR=0.982, 95% CI=0.968-0.996), X-21845 levels (P = .045, OR=1.018, 95% CI=1.001-1.035), 2'-o-methylcytidine (P = .008, OR=0.995, 95% CI=0.991-1.001), 2'-o-methyluridine (P = .007, OR=0.995, 95% CI=0.99-0.999), and spermidine-topyruvate ratio (P = .014, OR=0.973, 95% CI=0.954-0.992). No evidence of reverse causality was found between JAE and CAE and the aforementioned metabolites.

Conclusion

The study establishes causal relationships between the aforementioned 6 metabolites and CAE and JAE. This integration of genomics with metabolism offers novel insights into epilepsy mechanisms and has important implications for screening and prevention.

Should We Consider Neurodegeneration by Itself or in a Triangulation with Neuroinflammation and Demyelination? The Example of Multiple Sclerosis and Beyond

Neurodegeneration is preeminent in many neurological diseases, and still a major burden we fail to manage in patient's care. Its pathogenesis is complicated, intricate, and far from being completely understood. Taking multiple sclerosis as an example, we propose that neurodegeneration is neither a cause nor a consequence by itself. Mitochondrial dysfunction, leading to energy deficiency and ion imbalance, plays a key role in neurodegeneration, and is partly caused by the oxidative stress generated by microglia and astrocytes. Nodal and paranodal disruption, with or without myelin alteration, is further involved. Myelin loss exposes the axons directly to the inflammatory and oxidative environment. Moreover, oligodendrocytes provide a singular metabolic and trophic support to axons, but do not emerge unscathed from the pathological events, by primary myelin defects and cell apoptosis or secondary to neuroinflammation or axonal damage. Hereby, trophic failure might be an overlooked contributor to neurodegeneration. Thus, a complex interplay between neuroinflammation, demyelination, and neurodegeneration, wherein each is primarily and secondarily involved, might offer a more comprehensive understanding of the pathogenesis and help establishing novel therapeutic strategies for many neurological diseases and beyond.

Global and Regional Sex-Related Differences, Asymmetry, and Peak Age of Brain Myelination in Healthy Adults

Background: The fundamental question of normal brain myelination in human is still poorly understood. Methods: Age-dependent global, regional, and interhemispheric sex-related differences in brain myelination of 42 (19 men, 23 women) healthy adults (19-67 years) were explored using the MRI method of fast macromolecular fraction (MPF) mapping. Results: Higher brain myelination in males compared to females was found in global white matter (WM), most WM tracts, juxtacortical WM regions, and putamen. The largest differences between men and women, exceeding 4%, were observed bilaterally in the frontal juxtacortical WM; angular, inferior occipital, and cuneus WM; external capsule; and inferior and superior fronto-orbital fasciculi. The majority of hemispheric differences in MPF were common to men and women. Sex-specific interhemispheric differences were found in juxtacortical WM; men more often had left-sided asymmetry, while women had right-sided asymmetry. Most regions of deep gray matter (GM), juxtacortical WM, and WM tracts (except for projection pathways) showed a later peak age of myelination in women compared to men, with a difference of 3.5 years on average. Body mass index (BMI) was associated with higher MPF and later peak age of myelination independent of age and sex. Conclusions: MPF mapping showed high sensitivity to assess sex-related differences in normal brain myelination, providing the basis for using this method in clinics.

Plasmalogens Improve Lymphatic Clearance of Amyloid Beta from Mouse Brain and Cognitive Functions

Amyloid beta (Aβ) is a neuronal metabolic product that plays an important role in maintaining brain homeostasis. Normally, intensive brain Aβ formation is accompanied by its effective lymphatic removal. However, the excessive accumulation of brain Aβ is observed with age and during the development of Alzheimer's disease (AD) leading to cognitive impairment and memory deficits. There is emerging evidence that plasmalogens (Pls), as one of the key brain lipids, may be beneficial for AD and cognitive aging. Here, we studied the effects of Pls on cognitive functions and the lymphatic clearance of Aβ from the brain of AD mice and mice of different ages. The results showed that Pls effectively reduce brain Aβ levels and facilitate learning in aged but not old mice. In AD mice, Pls improve the lymphatic clearance of Aβ that is accompanied by an increase in general motor activity and an improvement of the emotional status and learning ability. Thus, these findings suggest that Pls could be a promising candidate for the alternative or concomitant therapy of AD and age-related brain diseases to enhance the lymphatic clearance of Aβ from the brain and cognitive functions.

Disrupting the transmembrane domain interface between PMP22 and MPZ causes peripheral neuropathy

Peripheral Myelin Protein 22 (PMP22) and MPZ are abundant myelin membrane proteins in Schwann cells. The MPZ adhesion protein holds myelin wraps together across the intraperiod line. PMP22 is a tetraspan protein belonging to the Claudin superfamily. Loss of either MPZ or PMP22 causes severe demyelinating Charcot-Marie-Tooth (CMT) peripheral neuropathy, and duplication of PMP22 causes the most common form of CMT, CMT1A. Yet, the molecular functions provided by PMP22 and how its alteration causes CMT are unknown. Here, we find MPZ and PMP22 form a specific complex through interfaces within their transmembrane domains. We also find that the PMP22 A67T patient variant that causes a loss-of-function (hereditary neuropathy with pressure palsies) phenotype maps to this interface, and blocks MPZ association without affecting localization to the plasma membrane or interactions with other proteins. These data define the molecular basis for the MPZ ∼ PMP22 interaction and indicate this complex fulfills an important function in myelinating cells.

All roads lead to cholesterol: Modulating lipid biosynthesis in multiple sclerosis patient-derived models

Studies from Ionescu et al.1 and Clayton et al.2 using multiple sclerosis (MS) patient-derived cell models underscore cholesterol metabolism's role in inflammatory and dysfunctional cell phenotypes in the disease. Inhibiting cholesterol biosynthesis ameliorated critical cellular phenotypes, emphasizing the need to further investigate this pathway as a potential target for MS treatment.

The Link Between Paraquat and Demyelination: A Review of Current Evidence

Paraquat (1,1'-dimethyl-4,4'-bipyridilium dichloride), a widely used bipyridinium herbicide, is known for inducing oxidative stress, leading to extensive cellular toxicity, particularly in the lungs, liver, kidneys, and central nervous system (CNS), and is implicated in fatal poisonings. Due to its biochemical similarities with the neurotoxin 1-methyl-4-phenylpyridinium (MPP+), paraquat has been used as a Parkinson's disease model, although its broader neurotoxic effects suggest the participation of multiple mechanisms. Demyelinating diseases are conditions characterized by damage to the myelin sheath of neurons. They affect the CNS and peripheral nervous system (PNS), resulting in diverse clinical manifestations. In recent years, growing concerns have emerged about the impact of chronic, low-level exposure to herbicides on human health, particularly due to agricultural runoff contaminating drinking water sources and their presence in food. Studies indicate that paraquat may significantly impact myelinating cells, myelin-related gene expression, myelin structure, and cause neuroinflammation, potentially contributing to demyelination. Therefore, demyelination may represent another mechanism of neurotoxicity associated with paraquat, which requires further investigation. This manuscript reviews the potential association between paraquat and demyelination. Understanding this link is crucial for enhancing strategies to minimize exposure and preserve public health.

Copper in Human Health and Disease: A Comprehensive Review

This comprehensive review discusses the crucial role of copper in human health and disease as an essential trace mineral. It emphasizes the significance of copper while addressing potential risks from imbalances in copper levels, be it excessive or inadequate. The review outlines various challenges in copper research, including toxicity concerns, data limitations, metabolic complexities, genetic influences, nutrient interactions, and resource constraints. Despite these challenges, the review identifies specific research areas needing exploration, such as copper homeostasis regulation, transport mechanisms, gut microbiome interactions, immune function, neurodegenerative diseases, cardiovascular health, cancer, fertility, and reproductive health. The purpose of this review is to explore the important role of copper in human health and disease, which highlights the delicate balance required to avoid deficiency or toxicity. For the researchers and scientists, it provides the gaps in the research, so it aims to provide insights that could advance diagnostic and therapeutic strategies across various medical disciplines.

Astrocytic Ephrin-B1 Regulates Oligodendrocyte Development and Myelination

Astrocytes have been implicated in oligodendrocyte development and myelination, however, the mechanisms by which astrocytes regulate oligodendrocytes remain unclear. Our findings suggest a new mechanism that regulates astrocyte-mediated oligodendrocyte development through ephrin-B1 signaling in astrocytes. Using a mouse model, we examined the role of astrocytic ephrin-B1 signaling in oligodendrocyte development by deleting ephrin-B1 specifically in astrocytes during the postnatal days (P)14-P28 period and used mRNA analysis, immunohistochemistry, and mouse behaviors to study its effects on oligodendrocytes and myelination. We found that deletion of astrocytic ephrin-B1 downregulated many genes associated with oligodendrocyte development, myelination, and lipid metabolism in the hippocampus and the corpus callosum. Additionally, we observed a reduced number of oligodendrocytes and impaired myelination in the corpus callosum of astrocyte-specific ephrin-B1 KO mice. Finally, our data show reduced motor strength in these mice exhibiting clasping phenotype and impaired performance in the rotarod test most likely due to impaired myelination. Our studies provide new evidence that astrocytic ephrin-B1 positively regulates oligodendrocyte development and myelination, potentially through astrocyte-oligodendrocyte interactions.