Brain cholesterol: long secret life behind a barrier

Coenzyme Q10 deficiency disrupts lipid metabolism by altering cholesterol homeostasis in neurons

Coenzyme Q10 (CoQ10) is a critical component of the mitochondrial respiratory chain. CoQ10 deficiencies cause a variety of clinical syndromes, often involving encephalopathies. The heterogeneity of clinical manifestations implies different pathomechanisms, reflecting CoQ10 involvement in several biological processes. One such process is cholesterol homeostasis, since CoQ10 is synthesized through the mevalonate pathway, which also produces cholesterol. To elucidate the role of lipid dysfunction in the pathogenesis of CoQ10 deficiency, we investigated lipid metabolism in human CoQ10 deficient iPSCs-derived neurons, and in SH-SY5Y neurons after pharmacological manipulation of the mevalonate pathway. We show that CoQ10 deficiency causes alterations in cholesterol homeostasis, fatty acids oxidation, phospholipids and sphingolipids synthesis in neurons. These alterations depend on the molecular defect, and on the residual CoQ10 levels. Our results imply that CoQ10 deficiencies can induce pathology by altering lipid homeostasis and the composition of cellular membranes. These findings provide further understanding of the mechanisms underlying CoQ10 deficiency and point to potential novel therapeutic targets.

Molecular dynamics study of stiffness and rupture of axonal membranes

Diffuse axonal injury (DAI), characterized by widespread damage to axons throughout the brain, represents one of the most devastating and difficult-to-treat forms of traumatic brain injury. Different theories exist about the mechanism of DAI, among which one hypothesis states that membrane poration of the axons initiates DAI. To investigate the hypothesis, molecular models of axonal membranes, incorporating 25 different lipids distributed asymmetrically in the leaflets, were developed using a coarse-grain description and simulated using molecular dynamics techniques. Different protein concentrations were embedded inside the lipid bilayer to describe the different sub-cellular parts in myelinated and unmyelinated axons. The models were investigated in equilibration and under deformation to characterize the structural and mechanical properties of the membranes, and comparisons were made with other subcellular parts, particularly myelin. Employing a bottom-top approach, the results were coupled with a finite element model representing the axon at the cell level. The results indicate that pore formation in the node-of-Ranvier occurs at a lower rupture strain compared to other axolemma parts, whereas myelin poration exhibits the highest rupture strains among the investigated models. The observed rupture strain for the node-of-Ranvier aligns with experimental studies, indicating a threshold for injury at axonal strains exceeding 10-13 % depending on the strain rate. The results indicate that the hypothesis suggesting mechanoporation triggers axonal injury cannot be dismissed, as this phenomenon occurs within the threshold of axonal injury.

Lipid metabolism, remodelling and intercellular transfer in the CNS

Lipid metabolism encompasses the catabolism and anabolism of lipids, and is fundamental for the maintenance of cellular homeostasis, particularly within the lipid-rich CNS. Increasing evidence further underscores the importance of lipid remodelling and transfer within and between glial cells and neurons as key orchestrators of CNS lipid homeostasis. In this Review, we summarize and discuss the complex landscape of processes involved in lipid metabolism, remodelling and intercellular transfer in the CNS. Highlighted are key pathways, including those mediating lipid (and lipid droplet) biogenesis and breakdown, lipid oxidation and phospholipid metabolism, as well as cell-cell lipid transfer mediated via lipoproteins, extracellular vesicles and tunnelling nanotubes. We further explore how the dysregulation of these pathways contributes to the onset and progression of neurodegenerative diseases, and examine the homeostatic and pathogenic impacts of environment, diet and lifestyle on CNS lipid metabolism.

Statin is associated with higher cortical thickness in early Alzheimer's disease

BACKGROUND

The brain is the most cholesterol-rich organ, essential for myelination and neuronal function. Statins, widely used to lower cholesterol, cross the blood-brain barrier and may impact brain cholesterol synthesis. Despite their widespread use, the effects of statins on cortical regions relevant to Alzheimer's disease (AD) are not well understood. This study aimed to compare cortical thickness between statin-exposed and statin-unexposed older adults and evaluate the potential neuroprotective effects of statins.

METHODS

Data were obtained from the Alzheimer's Disease Neuroimaging Initiative (ADNI). The sample included 193 healthy controls (HC), 485 individuals with mild cognitive impairment (MCI), and 169 individuals with Alzheimer's disease (AD). Participants were categorized as statin users if they had used statins for at least two years. MRI data were processed using FreeSurfer software to estimate cortical thickness in 64 regions of interest. ANCOVA models assessed the association between statin use and cortical thickness at baseline, and linear mixed models evaluated longitudinal changes.

RESULTS

Statin use was associated with increased cortical thickness in multiple brain regions across HC, MCI, and AD participants. In HC, statin users had greater thickness in the right lateral occipital, left middle temporal, and left parahippocampal regions. MCI participants exhibited additional increases in the right cuneus, right posterior cingulate, and left superior temporal cortex. In AD, statin users had higher thickness in the right cuneus and right superior parietal lobule. Longitudinal analysis revealed no statin-related differences in cortical thickness changes among HC and AD groups, but in MCI, statins slowed cortical thinning in the left medial orbitofrontal cortex.

CONCLUSION

Statin use is associated with greater cortical thickness in older adults, particularly in those with MCI. These findings suggest that statins may have neuroprotective effects, potentially mitigating neurodegenerative changes in early cognitive decline. Further research with larger cohorts and longer follow-up periods is needed to confirm these findings and understand the mechanisms involved.

The Cross-Talk Between the Peripheral and Brain Cholesterol Metabolisms

Cholesterol is an essential element for the development and normal function of the central nervous system. While peripheral cholesterol is influenced by liver metabolism and diet, brain cholesterol metabolism takes place in an isolated system due to the impermeability of the blood-brain barrier (BBB). However, cross-talk occurs between the brain and periphery, specifically through metabolites such as oxysterols that play key roles in regulating cholesterol balance. Several neurodegenerative conditions such as Alzheimer's disease or Parkinson's disease are considered to be affected by the loss of this balance. Also, the treatment of hypercholesterolemia needs to consider these discrete interferences between brain and peripheral cholesterol and the possible implications of each therapeutic approach. This is particularly important because of 27-hydroxycholesterol and 24-hydroxycholesterol, which can cross the BBB and are involved in cholesterol metabolism. This paper examines the metabolic pathways of cholesterol metabolism in the brain and periphery and focuses on the complex cross-talk between these metabolisms. Also, we emphasize the regulatory role of the BBB and the need for an integrated approach to cholesterol management.

Abnormal blood biomarkers and trajectories of depressive symptoms among Chinese middle-aged and older adults

OBJECTIVE

Although previous studies have demonstrated allostatic load (AL) predicts depressive symptoms, few studies have considered the association between AL and trajectories of depressive symptoms. This study aims to systematically examine the associations of abnormal blood biomarkers in the three biological systems with trajectories of depressive symptoms.

METHODS

A total of 6251 participants aged 45+ from the China Health and Retirement Longitudinal Study (CHARLS). Depressive symptoms were assessed using the 10-item Center for Epidemiological Studies Depression Scale (CESD-10) in five visits (waves 2011, 2013, 2015, 2018, and 2020). Biomarkers in three biological systems were evaluated based on standard criteria, including C-reactive protein in the inflammation system; systolic and diastolic blood pressures in the cardiovascular system; and high-density lipoprotein cholesterol (HDLC), total cholesterol/HDL-C ratio, and glycosylated hemoglobin (HbA1c) in the metabolic system. The trajectories of depressive symptoms were measured using group-based trajectory modelling (GBTM). Multinomial logistic regression models were conducted to examine the association between the number of abnormal biological systems and trajectories of depressive symptoms.

RESULTS

Four different trajectories of depressive symptoms were identified: mild (44.22 %), moderate (42.09 %), increasing (9.39 %), and severe (4.30 %). Compared to participants with normal values of biomarkers in all three systems, those with abnormal values of biomarkers in three systems had a 2.26-fold risk of developing the severe depressive symptoms trajectory.

CONCLUSIONS

Our findings highlight the importance of monitoring multiple biological systems to prevent long-term accelerated severe depressive symptoms trajectory.

Genetic insights of lipid metabolism and lipid-lowering drugs with Lewy body dementia risk: Evidence from Mendelian randomization

BACKGROUND

Lewy body dementia (LBD) is the second common dementia, with unclear mechanisms and limited treatment options. Dyslipidemia has been implicated in LBD, but the role of lipid-lowering drugs remains underexplored. This study aims to investigate the association between lipid traits, drug targets, and LBD risk using Mendelian Randomization (MR) analysis.

METHODS

We performed univariable and multivariable MR analyses to evaluate the causal effects of lipid traits on the risk of LBD. Then, drug-target MR analysis and subtype analysis were conducted to evaluate the effects of lipid-lowering therapies on LBD.

RESULTS

In univariable MR, genetically predicted low-density lipoprotein cholesterol (LDL-C) and remnant cholesterol (RC) levels were associated with an increased risk of LBD. Mediation analysis suggested a potential interaction between LDL-C and RC in influencing LBD risk. Drug-target MR analysis identified significant associations between genetically proxied inhibition of ANGPTL3, CETP, and HMGCR and LBD risk.

CONCLUSION

This MR analysis provided evidence that elevated LDL-C and RC may increase the risk of LBD. Additionally, targeting ANGPTL3, CETP, and HMGCR may represent potential therapeutic strategies for the prevention or treatment of LBD.

Targeting intracellular autophagic process for the treatment of post-stroke ischemia/reperfusion injury

Cerebral ischemia/reperfusion (I/R) injury is an important pathophysiological condition of ischemic stroke that involves a variety of physiological and pathological cell death pathways, including autophagy, apoptosis, necroptosis, and phagoptosis, among which autophagy is the most studied. We have reviewed studies published in the past 5 years regarding the association between autophagy and cerebral I/R injury. To the best of our knowledge, this is the first review article summarizing potential candidates targeting autophagic pathways in the treatment of I/R injury post ischemic stroke. The findings of this review may help to better understand the pathogenesis and mechanisms of I/R events and bridge the gap between basic and translational research that may lead to the development of novel therapeutic approaches for I/R injury.

Cellular senescence induced by cholesterol accumulation is mediated by lysosomal ABCA1 in APOE4 and AD

BACKGROUND

Cellular senescence, a hallmark of aging, has been implicated in Alzheimer's disease (AD) pathogenesis. Cholesterol accumulation is known to drive cellular senescence; however, its underlying mechanisms are not fully understood. ATP-binding cassette transporter A1 (ABCA1) plays an important role in cholesterol homeostasis, and its expression and trafficking are altered in APOE4 and AD models. However, the role of ABCA1 trafficking in cellular senescence associated with APOE4 and AD remains unclear.

METHODS

We examined the association between cellular senescence and ABCA1 expression in human postmortem brain samples using transcriptomic, histological, and biochemical analyses. Unbiased proteomic screening was performed to identify the proteins that mediate cellular ABCA1 trafficking. We created ABCA1 knock out cell lines and mouse models to validate the role of ABCA1 in cholesterol-induced mTORC1 activation and senescence. Additionally, we used APOE4-TR mice and induced pluripotent stem cell (iPSC) models to explore cholesterol-ABCA1-senescence pathways.

RESULTS

Transcriptomic profiling of the human dorsolateral prefrontal cortex from the Religious Order Study/Memory Aging Project (ROSMAP) cohort revealed the upregulation of cellular senescence transcriptome signatures in AD, which correlated with ABCA1 expression and oxysterol levels. Immunofluorescence and immunoblotting analyses confirmed increased lipofuscin-stained lipids and ABCA1 expression in AD brains and an association with mTOR phosphorylation. Discovery proteomics identified caveolin-1, a sensor of cellular cholesterol accumulation, as a key promoter of ABCA1 endolysosomal trafficking. Greater caveolin-1 expression was observed in APOE4-TR mouse models and AD human brains. Oxysterol induced mTORC1 activation and senescence were regulated by ABCA1 lysosomal trapping. Treatment of APOE4-TR mice with cyclodextrin reduced brain oxysterol levels, ABCA1 lysosome trapping, mTORC1 activation, and attenuated senescence and neuroinflammation markers. In human iPSC-derived astrocytes, the reduction of cholesterol by cyclodextrin attenuated inflammatory responses.

CONCLUSIONS

Oxysterol accumulation in APOE4 and AD induced ABCA1 and caveolin-1 expression, contributing to lysosomal dysfunction and increased cellular senescence markers. This study provides novel insights into how cholesterol metabolism accelerates features of brain cellular senescence pathway and identifies therapeutic targets to mitigate these processes.

C/EBPβ in Alzheimer's disease: An integrative regulator of pathological mechanisms

Alzheimer's disease (AD) stands as one of the most prevalent neurodegenerative disorders, characterized by a progressive decline in cognitive function, neuroinflammation, amyloid-beta (Aβ) plaques, and neurofibrillary tangles (NFTs). With the global aging population, the incidence of AD continues to rise, yet current therapeutic strategies remain limited in their ability to significantly alleviate cognitive impairments. Therefore, a deeper understanding of the molecular mechanisms underlying AD is imperative for the development of more effective treatments. In recent years, the transcription factor C/EBPβ has emerged as a pivotal regulator in several pathological processes of AD, including neuroinflammation, lipid metabolism, Aβ processing, and tau phosphorylation. Through intricate post-translational modifications, C/EBPβ modulates these processes and may influence the progression of AD on multiple fronts. This review systematically explores the multifaceted roles of C/EBPβ in the pathogenesis of AD, delving into its crucial involvement in neuroinflammation, Aβ production, tau pathology, and lipid metabolism dysregulation. Furthermore, we critically assess therapeutic strategies targeting C/EBPβ, examining the challenges and opportunities in regulating this factor. By synthesizing the latest research findings, we offer a more comprehensive understanding of the role of C/EBPβ in AD and discuss its potential as a therapeutic intervention target.

Targeted Therapies: The Role of Monoclonal Antibodies in Disease Management

Monoclonal antibodies (mAbs) are a key class of biotherapeutic medicines used to treat a wide range of diseases, such as cancer, infectious diseases, autoimmune disorders, cardiovascular diseases, and hemophilia. They can be engineered for greater effectiveness and specific applications while maintaining their structural elements for immune targeting. Traditional immunoglobulin treatments have limited therapeutic uses and various adverse effects. That makes mAbs show rapid growth in the pharmaceutical market, with over 250 mAbs in clinical studies. Although mAbs offer higher specificity, they are less effective against complex antigens. They have become essential in treating diseases with limited medical options, providing innovative solutions that improve patients' quality of life through increasing survival rates, shortening the length of stay in hospitals with an improved treatment outcome, and reducing side effects. This review outlines the mechanisms, applications, and advancements of mAbs, highlighting their transformative role in modern medicine and their potential to shape future therapeutic interventions.

Cholesterol Metabolism in CNS Diseases: The Potential of SREBP2 and LXR as Therapeutic Targets

The brain is the organ with the highest cholesterol content in the body. Cholesterol in the brain plays a crucial role in maintaining the integrity of synapses and myelin sheaths to ensure normal brain function. Disruptions in cholesterol metabolism are closely associated with various central nervous system (CNS) diseases, including Alzheimer's disease (AD), Huntington's disease (HD), and multiple sclerosis (MS). In this review, we explore the synthesis, regulation, transport, and functional roles of cholesterol in the CNS. We discuss in detail the associations between cholesterol homeostasis imbalance and CNS diseases including AD, HD, and MS, highlighting the significant role of cholesterol metabolism abnormalities in the development of these diseases. Sterol regulatory element binding protein-2 (SREBP2) and liver X receptor (LXR) are two critical transcription factors that play central roles in cholesterol synthesis and reverse transport, respectively. Their cooperative interaction finely tunes the balance of brain cholesterol metabolism, presenting potential therapeutic value for preventing and treating CNS diseases. We particularly emphasize the alterations in SREBP2 and LXR under pathological conditions and their impacts on disease progression. This review summarizes current therapeutic agents targeting these two pathways, with the hope of broadening the perspectives of CNS drug developers and encouraging further study into SREBP2 and LXR-related therapies for CNS diseases.

Lipids shape brain function through ion channel and receptor modulations: physiological mechanisms and clinical perspectives

Lipids represent the most abundant molecular type in the brain, with a fat content of ∼60% of the dry brain weight in humans. Despite this fact, little attention has been paid to circumscribe the dynamic role of lipids in brain function and disease. Membrane lipids such as cholesterol, phosphoinositide, sphingolipids, arachidonic acid, and endocannabinoids finely regulate both synaptic receptors and ion channels that ensure critical neural functions. After a brief introduction on brain lipids and their respective properties, we review here their role in regulating synaptic function and ion channel activity, action potential propagation, neuronal development, and functional plasticity and their contribution in the development of neurological and neuropsychiatric diseases. We also provide possible directions for future research on lipid function in brain plasticity and diseases.

Neuroprotective Efficacy of Phytoconstituents of Methanolic Shoots Extract of Calligonum polygonoides L. in Hypercholesterolemia-associated Neurodegenerations

BACKGROUND

Small molecule phytocompounds can potentially ameliorate degenerative changes in cerebral tissues. Thus, the current study aimed to evaluate the neuroprotective efficacy of phytocompounds of methanolic shoots extract of Calligonum polygonoides L. (MSECP) in hypercholesterolemia-associated neurodegenerations.

METHODS

Phytochemical screening of the extract was made by LCMS/MS and validated by a repository of the chemical library. The hypercholesterolemia was induced through the intraperitoneal administration of poloxamer-407 with a high-fat diet. The in silico assessments were accomplished by following the molecular docking, ADME and molecular dynamics. MMPBSA and PCA (Principal Component Analysis) analyzed the molecular dynamics simulations. Consequently, in-vivo studies were examined by lipid metabolism, free radical scavenging capabilities and histopathology of brain tissues (cortex and hippocampus).

RESULTS

22 leading phytocompounds were exhibited in the test extract, as revealed by LCMS/ MS scrutiny. Molecular docking evaluated significant interactions of apigenin triacetate with target proteins (HMGCR (HMG-CoA reductase), (AChE-Acetylcholinesterase) and (BuChE- Butyrylcholinesterase). Molecular dynamics examined the interactions through assessments of the radius of gyration, RSMD, RSMF and SASA at 100 ns, which were further analyzed by MMPBSA (Molecular Mechanics Poisson-Boltzmann) and PCA (Principal Component Analysis). Accordingly, the treatment of test extract caused significant alterations in lipid profile, dyslipidemia indices, antioxidant levels and histopathology of brain tissues.

CONCLUSION

It can be concluded that apigenin triacetate is a potent phytoconstituent of MSEPC and can interact with HMGCR, AChE, and BuChE, which resulted in improved hypercholesterolemia along with neuroprotective ameliorations in the cortex and hippocampus.

Role of cholesterol in modulating brain hyperexcitability

Cholesterol is a critical molecule in the central nervous system, and imbalances in the synthesis and metabolism of brain cholesterol can result in a range of pathologies, including those related to hyperexcitability. The impact of cholesterol on disorders of epilepsy and developmental and epileptic encephalopathies is an area of growing interest. Cholesterol cannot cross the blood-brain barrier, and thus the brain synthesizes and metabolizes its own pool of cholesterol. The primary metabolic enzyme for brain cholesterol is cholesterol 24-hydroxylase (CH24H), which metabolizes cholesterol into 24S-hydroxycholesterol (24HC). Dysregulation of CH24H and 24HC can affect neuronal excitability through a range of mechanisms. 24HC is a positive allosteric modulator of N-methyl-D-aspartate (NMDA) receptors and can increase glutamate release via tumor necrosis factor-α-dependent pathways. Increasing cholesterol metabolism can lead to dysfunction of excitatory amino acid transporter 2 and impair glutamate reuptake. Finally, overstimulation of NMDA receptors can further activate metabolism of cholesterol, leading to a vicious cycle of overactivation. All of these mechanisms increase extracellular glutamate and can lead to hyperexcitability. For these reasons, the cholesterol pathway represents a new potential mechanistic target for antiseizure medications. CH24H inhibition has been shown to decrease seizure behavior and improve survival in multiple animal models of epilepsy and could be a promising new mechanism of action for the treatment of neuronal hyperexcitability and developmental and epileptic encephalopathies.

Biological Functions and Clinical Significance of the ABCG1 Transporter

ATP-binding cassette (ABC) transporters are a large family of proteins that transport various substances across cell membranes using energy from ATP hydrolysis. ATP-binding cassette sub-family G member 1 (ABCG1) is a member of the ABCG subfamily of transporters and performs many important functions, such as the export of cholesterol and some other lipids across the membranes of various cells. Cholesterol transport is the mechanism that links metabolism and the innate immune system. Due to its lipid transport function, ABCG1 may contribute to the prevention of atherosclerosis and is involved in the functioning of the lung, pancreas, and other organs and systems. However, the full clinical significance of ABCG1 is still unknown and is a promising area for future research.

Impaired Cerebrospinal Fluid Lipoprotein-Mediated Cholesterol Delivery to Neurons in Alzheimer's Disease

In the central nervous system, apolipoprotein (APO) E-containing high-density lipoprotein (HDL)-like particles mediate the transport of glial-derived cholesterol to neurons, which is essential for neuronal membrane remodeling and maintenance of the myelin sheath. Despite this, the role of HDL-like cholesterol trafficking on Alzheimer's disease (AD) pathogenesis remains poorly understood. We aimed to examine cholesterol transport via HDL-like particles in cerebrospinal fluid (CSF) of AD patients compared to control individuals. Additionally, we explored the ability of reconstituted HDL containing different APOE isoforms to regulate cholesterol transport. We evaluated the capacity of CSF HDL-like particles to facilitate radiolabeled unesterified cholesterol efflux from A172 human glioblastoma astrocytes and to deliver cholesterol to SH-SY5Y human neuronal cells. The HDL-like proteome in the AD and control groups was analyzed by liquid chromatography-mass spectrometry (LC-MS/MS). Reconstituted HDL nanoparticles were prepared by combining phospholipids and cholesterol with human APOE3 or APOE4, followed by radiolabeling with unesterified cholesterol. Our results showed that cholesterol efflux from astrocytes to CSF were similar between AD patients and controls, both under baseline conditions and after activation of ATP-binding cassette transporters A1 and G1. However, CSF HDL-like particle-mediated neuronal cholesterol uptake was significantly reduced in the AD group. LC-MS/MS analysis identified 775 proteins associated with HDL-like particles in both groups, with no major alterations in proteins linked to cholesterol metabolism. However, 27 proteins involved in non-cholesterol-related processes were differentially expressed. Notably, synthetic reconstituted HDL particles containing APOE4 exhibited reduced capacity to deliver cholesterol to neurons compared to those with APOE3. These findings indicate that CSF HDL-like particles from patients with AD demonstrate impaired cholesterol delivery to neurons. Our study highlights APOE4 as a critical contributor to abnormal neuronal cholesterol uptake in AD pathophysiology.

Neuroinflammation in Alzheimer disease

Increasing evidence points to a pivotal role of immune processes in the pathogenesis of Alzheimer disease, which is the most prevalent neurodegenerative and dementia-causing disease of our time. Multiple lines of information provided by experimental, epidemiological, neuropathological and genetic studies suggest a pathological role for innate and adaptive immune activation in this disease. Here, we review the cell types and pathological mechanisms involved in disease development as well as the influence of genetics and lifestyle factors. Given the decade-long preclinical stage of Alzheimer disease, these mechanisms and their interactions are driving forces behind the spread and progression of the disease. The identification of treatment opportunities will require a precise understanding of the cells and mechanisms involved as well as a clear definition of their temporal and topographical nature. We will also discuss new therapeutic strategies for targeting neuroinflammation, which are now entering the clinic and showing promise for patients.

Non-canonical pathways associated to Amyloid beta and tau protein dyshomeostasis in Alzheimer's disease: A narrative review

Alzheimer's Disease (AD) is the most common form of dementia among elderly people. This disease imposes a significant burden on the healthcare system, society, and economy due to the increasing global aging population. Current trials with drugs or bioactive compounds aimed at reducing cerebral Amyloid beta (Aβ) plaques and tau protein neurofibrillary tangles, which are the two main hallmarks of this devastating neurodegenerative disease, have not provided significant results in terms of their neuropathological outcomes nor met the expected clinical end-points. Ageing, genetic and environmental risk factors, along with different clinical symptoms suggest that AD is a complex and heterogeneous disorder with multiple interconnected pathological pathways rather than a single disease entity. In the present review, we highlight and discuss various non-canonical, Aβ-independent mechanisms, like gliosis, unhealthy dietary intake, lipid and sugar signaling, and cerebrovascular damage that contribute to the onset and development of AD. We emphasize that challenging the traditional "amyloid cascade hypothesis" may improve our understanding of this age-related complex syndrome and help fight the progressive cognitive decline in AD.

Cholesterol promotes IFNG mRNA expression in CD4+ effector/memory cells by SGK1 activation

IFNγ-secreting T cells are central for the maintenance of immune surveillance within the central nervous system (CNS). It was previously reported in healthy donors that the T-cell environment in the CNS induces distinct signatures related to cytotoxic capacity, CNS trafficking, tissue adaptation, and lipid homeostasis. These findings suggested that the CNS milieu consisting predominantly of lipids mediated the metabolic conditions leading to IFNγ-secreting brain CD4 T cells. Here, we demonstrate that the supplementation of CD4+CD45RO+CXCR3+ cells with cholesterol modulates their function and increases IFNG expression. The heightened IFNG expression was mediated by the activation of the serum/glucocorticoid-regulated kinase (SGK1). Inhibition of SGK1 by a specific enzymatic inhibitor significantly reduces the expression of IFNG Our results confirm the crucial role of lipids in maintaining T-cell homeostasis and demonstrate a putative role of environmental factors to induce effector responses in CD4+ effector/memory cells. These findings offer potential avenues for further research targeting lipid pathways to modulate inflammatory conditions.

TMAO is involved in sleep deprivation-induced cognitive dysfunction through regulating astrocytic cholesterol metabolism via SREBP2

Sleep deprivation (SD) contributes to cognitive impairment. Astrocytic cholesterol biosynthesis is crucial for brain cholesterol homeostasis and cognitive function. However, the underlying mechanism of astrocytic cholesterol metabolism in SD-induced cognitive impairment has not been fully explored. Trimethylamine N-oxide (TMAO), a product of liver flavin-containing monooxygenase-3 (FMO3), has been shown to be increased in the urine of sleep-deprived humans and implicated with peripheral cholesterol metabolism. Nevertheless, how TMAO affects brain cholesterol metabolism remains unclear. In our study, increased FMO3 and brain TMAO levels were observed in the SD mice, and elevated levels of TMAO were confirmed to lead to SD-induced cognitive dysfunction. In addition, we found that the expression of sterol regulatory element-binding protein 2 (SREBP2) is decreased in the brain of SD mice, resulting in the reduction in brain cholesterol content, which in turn causes synaptic damage. Moreover, we demonstrated that TMAO inhibits the expression of SREBP2. In contrast, FMO3 inhibitor 3,3'-diindolylmethane (DIM) alleviates SD-induced cognitive impairment by targeting the liver-brain axis. In conclusion, our study revealed that the TMAO pathway is involved in memory impairment in SD mice through deregulating astrocytic cholesterol metabolism.

Do Statins Affect Cognitive Health? A Narrative Review and Critical Analysis of the Evidence

PURPOSE OF REVIEW

Statins are the first-line treatment for hypercholesterolemia and play a key role in the prevention of cardiovascular disease (CVD). Current studies report mixed effects of statins on cognitive health, including harmful, neutral, and protective outcomes. However, these ongoing controversies about the potential cognitive adverse effects of statins may compromise their use in CVD prevention. Several factors may influence how statins affect cognition, including the unique cholesterol homeostasis in the brain, the limited permeability of the blood-brain barrier to lipoproteins, and the varying lipophilicity of different statins. This review examines the evidence linking statins to cognitive function and considers the effect of different dosages and treatment durations.

RECENT FINDINGS

Earlier studies suggested cognitive disturbances with statins, but recent evidence does not strongly support a link between statins and cognitive impairment. In fact, observational studies suggest potential neuroprotective benefits, though biases like selection bias, confounding and reverse causation limit definitive conclusions. Two large randomized controlled trials, STAREE and PREVENTABLE, are underway, and their results are expected to address some of these gaps in the literature. Due to insufficient evidence in the current literature, well-designed randomized controlled trials are needed for a better understanding of statins' effects on cognition. More data is needed regarding statin type, dose intensity, and treatment duration, which may affect cognitive outcomes. Future studies are also needed to examine how statins may affect cognition in specific high-risk groups, such as individuals with mild cognitive impairment, diabetes, cardiovascular disease, or chronic kidney disease.

Conserved region of human TDP-43 is structurally similar to membrane binding protein FARP1 and protein chaperons BAG6 and CYP33

Transactive response DNA-binding protein of 43 KDa (TDP-43) is important for RNA metabolism in all animals and in humans is involved in neuromuscular diseases. Full-length TDP-43 is prone to oligomerization and misfolding what renders difficult its characterization. We report that TDP-43 domains are structurally similar to lipid binding protein FARP1 and protein chaperons BAG6 and CYP33. Sequence analysis suggests putative lipid binding sites throughout TDP-43 and in vitro thioflavin T fluorescence assays show that cholesterol and phosphatidylcholine affect fibrillation of recombinant TDP-43 fragments. Our findings suggest that TDP-43 can bind lipids directly and it may contribute to its own chaperoning.

Unveiling the neurolipidome of obsessive-compulsive disorder: A scoping review navigating future diagnostic and therapeutic applications

Obsessive-Compulsive Disorder (OCD) poses a multifaceted challenge in psychiatry, with various subtypes and severities greatly impacting well-being. Recent scientific attention has turned towards lipid metabolism, particularly the neurolipidome, in response to clinical demands for cost-effective diagnostics and therapies. This scoping review integrates recent animal, translational, and clinical studies to explore impaired neurolipid metabolism mechanisms in OCD's pathogenesis, aiming to enhance future diagnostics and therapeutics. Five key neurolipids - endocannabinoids, lipid peroxidation, phospholipids, cholesterol, and fatty acids - were identified as relevant. While the endocannabinoid system shows promise in animal models, its clinical application remains limited. Conversely, lipid peroxidation and disruptions in phospholipid metabolism exhibit significant impacts on OCD's pathophysiology based on robust clinical data. However, the role of cholesterol and fatty acids remains inconclusive. The review emphasises the importance of translational research in linking preclinical findings to real-world applications, highlighting the potential of the neurolipidome as a potential biomarker for OCD detection and monitoring. Further research is essential for advancing OCD understanding and treatment modalities.

Lipid Compositions of Liquid-Ordered and Liquid-Disordered Phases in Ternary Membranes of Sphingomyelin, Cholesterol, and Dioleoylphosphatidylcholine Determined by 2H NMR: Stearoyl-Sphingomyelin Compared with Its Palmitoyl Counterpart

Sphingomyelin (SM) and cholesterol are the major lipids in the signaling platforms of cell membranes, known as lipid rafts. In particular, SM with a stearoyl chain (C18-SM) is abundant in specific tissues such as the brain, the most cholesterol-rich organ, whereas the distribution of palmitoyl (C16)-SM is ubiquitous. Here, we reveal the differences between palmitoyl- and stearoyl-SM in lipid-lipid interactions based on the tie lines obtained from the 2H solid-state NMR spectra of bilayer systems composed of SM/dioleoylphosphatidylcholine/cholesterol 33:33:33 and 40:40:20. Lipid probes carrying position-selective deuterations, 10',10'-d2-SM, 24-d1-cholesterol, and 6″,6″-d2-dioleoyl-phosphatidylcholine, were incorporated into the membranes. 2H NMR peaks from these probes in the membranes directly provide the lipid compositions of the liquid-ordered (Lo) and liquid-disordered (Ld) regions. Without using bulky fluorescent groups, these probes allow us to obtain the end points of the tie lines in a ternary phase diagram based on the lever rule. Consequently, the tie lines of the stearoyl-SM membranes were steeper than those of the palmitoyl-SM membranes, indicating that cholesterol content was higher in the Lo domains of stearoyl-SM, regardless of the total concentration of unsaturated phospholipids. When comparing the content of unsaturated lipids in the Lo domain, the stearoyl-SM membranes had a higher content than palmitoyl-SM membranes. These results revealed that stearoyl-SM is suitable for stabilizing biologically functional microdomains in cholesterol-rich organs, whereas palmitoyl-SM may be better suited for stabilizing domains in tissue membranes with normal cholesterol content. The small but significant differences in the lipid interactions between stearoyl-SM and palmitoyl-SM may be related to the spatiotemporal formation of functional domains in biological environments.

Therapeutic targeting of differentiation-state dependent metabolic vulnerabilities in diffuse midline glioma

H3K27M diffuse midline gliomas (DMG), including diffuse intrinsic pontine gliomas (DIPG), exhibit cellular heterogeneity comprising less-differentiated oligodendrocyte precursors (OPC)-like stem cells and more differentiated astrocyte (AC)-like cells. Here, we establish in vitro models that recapitulate DMG-OPC-like and AC-like phenotypes and perform transcriptomics, metabolomics, and bioenergetic profiling to identify metabolic programs in the different cellular states. We then define strategies to target metabolic vulnerabilities within specific tumor populations. We show that AC-like cells exhibit a mesenchymal phenotype and are sensitized to ferroptotic cell death. In contrast, OPC-like cells upregulate cholesterol biosynthesis, have diminished mitochondrial oxidative phosphorylation (OXPHOS), and are accordingly more sensitive to statins and OXPHOS inhibitors. Additionally, statins and OXPHOS inhibitors show efficacy and extend survival in preclinical orthotopic models established with stem-like H3K27M DMG cells. Together, this study demonstrates that cellular subtypes within DMGs harbor distinct metabolic vulnerabilities that can be uniquely and selectively targeted for therapeutic gain.

Advances in the cell biology of the trafficking and processing of amyloid precursor protein: impact of familial Alzheimer's disease mutations

The production of neurotoxic amyloid-β peptides (Aβ) is central to the initiation and progression of Alzheimer's disease (AD) and involves sequential cleavage of the amyloid precursor protein (APP) by β- and γ-secretases. APP and the secretases are transmembrane proteins and their co-localisation in the same membrane-bound sub-compartment is necessary for APP cleavage. The intracellular trafficking of APP and the β-secretase, BACE1, is critical in regulating APP processing and Aβ production and has been studied in several cellular systems. Here, we summarise the intracellular distribution and transport of APP and its secretases, and the intracellular location for APP cleavage in non-polarised cells and neuronal models. In addition, we review recent advances on the potential impact of familial AD mutations on APP trafficking and processing. This is critical information in understanding the molecular mechanisms of AD progression and in supporting the development of novel strategies for clinical treatment.

HSP60 chaperone deficiency disrupts the mitochondrial matrix proteome and dysregulates cholesterol synthesis

OBJECTIVE

Mitochondrial proteostasis is critical for cellular function. The molecular chaperone HSP60 is essential for cell function and dysregulation of HSP60 expression has been implicated in cancer and diabetes. The few reported patients carrying HSP60 gene variants show neurodevelopmental delay and brain hypomyelination. Hsp60 interacts with more than 260 mitochondrial proteins but the mitochondrial proteins and functions affected by HSP60 deficiency are poorly characterized.

METHODS

We studied two model systems for HSP60 deficiency: (1) engineered HEK cells carrying an inducible dominant negative HSP60 mutant protein, (2) zebrafish HSP60 knockout larvae. Both systems were analyzed by RNASeq, proteomics, and targeted metabolomics, and several functional assays relevant for the respective model. In addition, skin fibroblasts from patients with disease-associated HSP60 variants were analyzed by proteomics.

RESULTS

We show that HSP60 deficiency leads to a differentially downregulated mitochondrial matrix proteome, transcriptional activation of stress responses, and dysregulated cholesterol biosynthesis. This leads to lipid accumulation in zebrafish knockout larvae.

CONCLUSIONS

Our data provide a compendium of the effects of HSP60 deficiency on the mitochondrial matrix proteome. We show that HSP60 is a master regulator and modulator of mitochondrial functions and metabolic pathways. HSP60 dysfunction also affects cellular metabolism and disrupts the integrated stress response. The effect on cholesterol synthesis explains the effect of HSP60 dysfunction on myelination observed in patients carrying genetic variants of HSP60.

LDL Exposure Disrupts Mitochondrial Function and Dynamics in a Hippocampal Neuronal Cell Line

Hypercholesterolemia has been associated with cognitive dysfunction and neurodegenerative diseases. Moreover, this metabolic condition disrupts the blood-brain barrier, allowing low-density lipoprotein (LDL) to enter the central nervous system. Thus, we investigated the effects of LDL exposure on mitochondrial function in a mouse hippocampal neuronal cell line (HT-22). HT-22 cells were exposed to human LDL (50 and 300 μg/mL) for 24 h. After this, intracellular lipid droplet (LD) content, cell viability, cell death, and mitochondrial parameters were assessed. We found that the higher LDL concentration increases LD content compared with control. Both concentrations increased the number of Annexin V-positive cells, indicating apoptosis. Moreover, in mitochondrial parameters, the LDL exposure on hippocampal neuronal cell line leads to a decrease in mitochondrial complexes I and II activities in both concentrations tested and a reduction in Mitotracker™ Red fluorescence and Mitotracker™ Red and Mitotracker™ Green ratio in the higher concentration, indicating mitochondrial impairment. The LDL incubation induces mitochondrial superoxide production and decreases superoxide dismutase activity in the lower concentration in HT-22 cells. Finally, LDL exposure increases the expression of genes associated with mitochondrial fusion (OPA1 and mitofusin 2) in the lower concentration. In conclusion, our findings suggest that LDL exposure induces mitochondrial dysfunction and modulates mitochondrial dynamics in the hippocampal neuronal cells.

Autophagic degradation of DHCR7 activates AKT3 and promotes sevoflurane-induced hippocampal neuroinflammation in neonatal mice

Repeated sevoflurane exposure in neonatal mice triggers neuroinflammation with detrimental effects on cognitive function. Yet, the mechanism of the sevoflurane-induced cytokine response is largely unknown. In this study, we reveal that 3-MA, an autophagy inhibitor, attenuated the sevoflurane-induced neuroinflammation and cognitive dysfunction, including the decreased freezing time and fewer platform crossings, in the neonate mice. 3-Methyladenine (3-MA) suppressed sevoflurane-induced expression of interleukin-6 and tumor necrosis factor-alpha in vitro. Moreover, sevoflurane activates IRF3, facilitating cytokine transcription in an AKT3-dependent manner. Mechanistically, sevoflurane-induced autophagic degradation of dehydrocholesterol-reductase-7 (DHCR7) resulted in accumulations of its substrate 7-dehydrocholesterol (7-DHC), mimicking the effect of sevoflurane on AKT3 activation and IRF3-driven cytokine expression. 3-MA significantly reversed sevoflurane-induced DHCR7 degradation, AKT phosphorylation, IRF3 activation, and the accumulation of 7-DHC in the hippocampal CA1 region. These findings pave the way for additional investigations aimed at developing novel strategies to mitigate postoperative cognitive impairment in pediatric patients.

Emerging Roles of Bile Acids and TGR5 in the Central Nervous System: Molecular Functions and Therapeutic Implications

Bile acids (BAs) are cholesterol derivatives synthesized in the liver and released into the digestive tract to facilitate lipid uptake during the digestion process. Most of these BAs are reabsorbed and recycled back to the liver. Some of these BAs progress to other tissues through the bloodstream. The presence of BAs in the central nervous system (CNS) has been related to their capacity to cross the blood-brain barrier (BBB) from the systemic circulation. However, the expression of enzymes and receptors involved in their synthesis and signaling, respectively, support the hypothesis that there is an endogenous source of BAs with a specific function in the CNS. Over the last decades, BAs have been tested as treatments for many CNS pathologies, with beneficial effects. Although they were initially reported as neuroprotective substances, they are also known to reduce inflammatory processes. Most of these effects have been related to the activation of the Takeda G protein-coupled receptor 5 (TGR5). This review addresses the new challenges that face BA research for neuroscience, focusing on their molecular functions. We discuss their endogenous and exogenous sources in the CNS, their signaling through the TGR5 receptor, and their mechanisms of action as potential therapeutics for neuropathologies.

Genetic Polymorphisms in the HMGCR Gene and Associations with Cognitive Decline in Parkinson's Disease Patients

Parkinson's disease (PD) is a common neurodegenerative disease characterized by motor and non-motor symptoms including cognitive impairment and dementia. The etiopathogenesis of PD, as well as its protective and susceptibility factors, are still elusive. 3-Hydroxy-3-methyglutaryl coenzyme A reductase (HMGCR) is an enzyme regulating cholesterol synthesis. Single-nucleotide polymorphisms (SNPs) in the gene coding HMGCR have recently been correlated with the risk of Alzheimer's disease. Alternative splicing of exon 13 of the HMGCR transcript and its strongly associated HMGCR haplotype 7 (H7: rs17244841, rs3846662, rs17238540) may downregulate protein activity and cholesterol synthesis, with lower low-density lipoprotein cholesterol (LDL) levels associated with PD that may affect cognitive abilities. We genotyped three SNPs in the H7 HMGCR gene in 306 PD patients divided into three groups-without cognitive decline, with mild cognitive impairment (MCI), and with PD dementia-and in 242 healthy participants. A correlation between the rs17238540 genotype and PD susceptibility as well as a minor association between rs3846662 and cognitive status in PD patients was observed; however, the two-sided analysis of these groups did not reveal any significance. We observed a statistically significant elevated high-density lipoprotein cholesterol (HDL) plasma level in the minor allele carriers of rs17238540 and rs17244841 among PD patients. This study should be replicated in a larger population.

Multi-omics and pharmacological characterization of patient-derived glioma cell lines

Glioblastoma (GBM) is the most common brain tumor and remains incurable. Primary GBM cultures are widely used tools for drug screening, but there is a lack of genomic and pharmacological characterization for these primary GBM cultures. Here, we collect 50 patient-derived glioma cell (PDGC) lines and characterize them by whole genome sequencing, RNA sequencing, and drug response screening. We identify three molecular subtypes among PDGCs: mesenchymal (MES), proneural (PN), and oxidative phosphorylation (OXPHOS). Drug response profiling reveals that PN subtype PDGCs are sensitive to tyrosine kinase inhibitors, whereas OXPHOS subtype PDGCs are sensitive to histone deacetylase inhibitors, oxidative phosphorylation inhibitors, and HMG-CoA reductase inhibitors. PN and OXPHOS subtype PDGCs stably form tumors in vivo upon intracranial transplantation into immunodeficient mice, whereas most MES subtype PDGCs fail to form tumors in vivo. In addition, PDGCs cultured by serum-free medium, especially long-passage PDGCs, carry MYC/MYCN amplification, which is rare in GBM patients. Our study provides a valuable resource for understanding primary glioma cell cultures and clinical translation and highlights the problems of serum-free PDGC culture systems that cannot be ignored.

Aggregation Behavior of Amyloid Beta Peptide Depends Upon the Membrane Lipid Composition

Protein aggregation plays a crucial role in the development of several neurodegenerative diseases. It is important to understand the aggregation process for the detection of the onset of these diseases. Alzheimer's Disease (AD) is one of the most prevalent neurodegenerative diseases caused by the aggregation of Aβ-40 and Aβ-42 peptides. The smaller oligomers lead to the formation of protein plaque at the neural membranes leading to memory loss and other disorders. Interestingly, aggregation takes place at the neural membranes, therefore the membrane composition seems to play an important role in the aggregation process. Despite a large number of literatures on the effect of lipid composition on protein aggregation, there are very few concise reviews that highlight the role of membrane composition in protein aggregation. In this review, we have discussed the implication of membrane composition on the aggregation of amyloid beta peptide with a special emphasis on cholesterol. We have further discussed the role of the degree of unsaturation of fatty acids and the participation of apolipoprotein E4 (ApoE4) in the onset of AD.

Cholesterol imbalance and neurotransmission defects in neurodegeneration

The brain contains the highest concentration of cholesterol in the human body, which emphasizes the importance of cholesterol in brain physiology. Cholesterol is involved in neurogenesis and synaptogenesis, and age-related reductions in cholesterol levels can lead to synaptic loss and impaired synaptic plasticity, which potentially contribute to neurodegeneration. The maintenance of cholesterol homeostasis in the neuronal plasma membrane is essential for normal brain function, and imbalances in cholesterol distribution are associated with various neurodegenerative disorders, including Alzheimer's disease, Parkinson's disease, and Huntington's disease. This review aims to explore the molecular and pathological mechanisms by which cholesterol imbalance can lead to neurotransmission defects and neurodegeneration, focusing on four key mechanisms: (1) synaptic dysfunction, (2) alterations in membrane structure and protein clustering, (3) oligomers of amyloid beta (Aβ) protein, and (4) α-synuclein aggregation.

Statins during Anticoagulation for Emergency Life-Threatening Venous Thromboembolism: A Review

Venous thromboembolism (VTE) is the leading cause of morbidity and death worldwide, after cancer and cardiovascular diseases. VTE is defined to include pulmonary embolism (PE) and/or deep vein thrombosis (DVT). Approximately 25% of PE patients experience sudden death as an initial symptom of VTE, and between 10% and 30% of patients die within the first month after diagnosis. Currently, the only drugs approved for the treatment of both acute and chronic VTE are vitamin K antagonists (VKAs) and direct oral anticoagulants (DOACs). However, their effectiveness is limited due to their associated risk of bleeding. Ideally, therapy should be able to treat VTE and limit the risk of VTE recurrence without increasing the risk of bleeding. Several studies have shown that the use of statins during anticoagulation for VTE reduces the risk of death and VTE recurrence. However, to date, there are conflicting data on the impact of statins during anticoagulation for VTE. A biological protective function of statins during anticoagulation has also been reported. Statins affect D-dimer levels; tissue factor (TF) gene expression; and VIII, VII, and Von Willebrand clotting factors-the major clotting factors they are able to affect. However, the usefulness of statins for the treatment and prevention of VTE is currently under debate, and they should not be substituted for guideline-recommended VTE prophylaxis or anticoagulation treatment. In this review of the literature, we illustrate the advances on this topic, including data on the role of statins in primary VTE prevention and secondary VTE prevention, related biological mechanisms, the risk of bleeding during their use, and their ability to reduce the risk of death.

Comparative Analysis of Right vs. Left Radial Access in Percutaneous Coronary Intervention: Impact on Silent Cerebral Ischemia

Background and Objectives: Silent cerebral ischemia (SCI) is defined as a condition that can be detected by biochemical markers or cranial imaging methods but does not produce clinical symptom. This study aims both to compare the frequency of SCI in PCIs performed with right transradial access and left transradial access and to evaluate the influencing factors. Materials and Methods: A prospective, single-center study included 197 patients undergoing PCI via transradial access between November 2020 and July 2022. The patients were categorized into right radial and left radial groups. Neuron-specific enolase (NSE) values were measured and recorded before and 18 h after the procedure. A post-procedure NSE level higher than 20 ng/dL was defined as SCI. Results: SCI occurred in 60 of the 197 patients. NSE elevation was observed in 37.4% (n = 37) of the right radial group and in 23.5% (n = 23) of the left radial group (p = 0.032). Patients with SCI had higher rates of smoking (p = 0.043), presence of subclavian tortuosity (p = 0.027), and HbA1c (p = 0.031). In the multivariate logistic regression analysis, the level of EF (ejection fraction) (OR: 0.958 95% CI 0.920-0.998, p = 0.039), right radial preference (OR: 2.104 95% CI 1.102-3.995 p = 0.023), and smoking (OR: 2.088 95% CI 1.105-3.944, p = 0.023) were observed as independent variables of NSE elevation. Conclusions: Our findings suggest that PCI via right radial access poses a greater risk of SCI compared to left radial access. Anatomical considerations and technical challenges associated with right radial procedures and factors such as smoking and low ejection fraction contribute to this elevated risk.

High-Density Lipoprotein Correlates with Cognitive Functioning in Schizophrenic Women

(1) Background: Schizophrenia is a chronic and progressive neuropsychiatric illness. Apart from positive and negative symptoms, 98% of the population diagnosed with schizophrenia have impaired cognitive functioning, which significantly influences the quality of life. The correlation between lipids and cognitive functioning has been well established. Our study aimed to investigate correlations between cognitive functions, the severity of schizophrenia symptoms, and lipid profiles. (2) Methods: Fifty-two women diagnosed with schizophrenia participated in this study. Cognitive functioning was measured using the Wisconsin Card Sorting Test (WCST). The Positive and Negative Symptom Scale (PANSS) was used. The serum lipid profile, including low-density lipoproteins (LDLs), high-density lipoproteins (HDLs), and triglycerides was measured. (3) Results: Better cognitive functions were associated with normal HDL levels, while low HDL levels correlated with worse WSCT scores. Only the PANSS negative subscale showed a correlation with HDL levels. Correlations with chronicity of schizophrenia and the patient's age with poorer cognitive functions, but not with symptom severity, were detected. Early/late age at onset did not influence WSCT scores. (4) Conclusions: Our results suggest high HDL levels might be a protective factor against cognitive impairment. The influences of age and illness duration also play a vital role in cognitive performance.

Relationships of brain cholesterol and cholesterol biosynthetic enzymes to Alzheimer's pathology and dementia in the CFAS population-derived neuropathology cohort

Altered cholesterol metabolism is implicated in brain ageing and Alzheimer's disease. We examined whether key genes regulating cholesterol metabolism and levels of brain cholesterol are altered in dementia and Alzheimer's disease neuropathological change (ADNC). Temporal cortex (n = 99) was obtained from the Cognitive Function and Ageing Study. Expression of the cholesterol biosynthesis rate-limiting enzyme HMG-CoA reductase (HMGCR) and its regulator, SREBP2, were detected using immunohistochemistry. Expression of HMGCR, SREBP2, CYP46A1 and ABCA1 were quantified by qPCR in samples enriched for astrocyte and neuronal RNA following laser-capture microdissection. Total cortical cholesterol was measured using the Amplex Red assay. HMGCR and SREBP2 proteins were predominantly expressed in pyramidal neurones, and in glia. Neuronal HMGCR did not vary with ADNC, oxidative stress, neuroinflammation or dementia status. Expression of HMGCR neuronal mRNA decreased with ADNC (p = 0.022) and increased with neuronal DNA damage (p = 0.049), whilst SREBP2 increased with ADNC (p = 0.005). High or moderate tertiles for cholesterol levels were associated with increased dementia risk (OR 1.44, 1.58). APOE ε4 allele was not associated with cortical cholesterol levels. ADNC is associated with gene expression changes that may impair cholesterol biosynthesis in neurones but not astrocytes, whilst levels of cortical cholesterol show a weak relationship to dementia status.

Interactions of Serum Amyloid A Proteins with the Blood-Brain Barrier: Implications for Central Nervous System Disease

Serum amyloid A (SAA) proteins are highly conserved lipoproteins that are notoriously involved in the acute phase response and systemic amyloidosis, but their biological functions are incompletely understood. Recent work has shown that SAA proteins can enter the brain by crossing the intact blood-brain barrier (BBB), and that they can impair BBB functions. Once in the central nervous system (CNS), SAA proteins can have both protective and harmful effects, which have important implications for CNS disease. In this review of the thematic series on SAA, we discuss the existing literature that relates SAA to neuroinflammation and CNS disease, and the possible roles of the BBB in these relations.

Characterizing defective lipid metabolism in the lateral septum of mice treated with olanzapine: implications for its side effects

Schizophrenia significantly impacts cognitive and behavioral functions and is primarily treated with second-generation antipsychotics (SGAs) such as olanzapine. Despite their efficacy, these drugs are linked to serious metabolic side effects which can diminish patient compliance, worsen psychiatric symptoms and increase cardiovascular disease risk. This study explores the hypothesis that SGAs affect the molecular determinants of synaptic plasticity and brain activity, particularly focusing on the lateral septum (LS) and its interactions within hypothalamic circuits that regulate feeding and energy expenditure. Utilizing functional ultrasound imaging, RNA sequencing, and weighted gene co-expression network analysis, we identified significant alterations in the functional connection between the hypothalamus and LS, along with changes in gene expression in the LS of mice following prolonged olanzapine exposure. Our analysis revealed a module closely linked to increases in body weight and adiposity, featuring genes primarily involved in lipid metabolism pathways, notably Apoa1, Apoc3, and Apoh. These findings suggest that olanzapine may influence body weight and adiposity through its impact on lipid metabolism-related genes in the LS. Therefore, the neural circuits connecting the LS and LH, along with the accompanying alterations in lipid metabolism, are likely crucial factors contributing to the weight gain and metabolic side effects associated with olanzapine treatment.

Low-Temperature Plasma Pretreatment Enhanced Cholesterol Detection in Brain by Desorption Electrospray Ionization-Mass Spectrometry Imaging

Cholesterol is a primary lipid molecule in the brain that contains one-fourth of the total body cholesterol. Abnormal cholesterol homeostasis is associated with neurodegenerative disorders. Mass spectrometry imaging (MSI) technique is a powerful tool for studying lipidomics and metabolomics. Among the MSI techniques, desorption electrospray ionization-MSI (DESI-MSI) has been used advantageously to study brain lipidomics due to its soft and ambient ionization nature. However, brain cholesterol is poorly ionized. To this end, we have developed a new method for detecting brain cholesterol by DESI-MSI using low-temperature plasma (LTP) pretreatment as an ionization enhancement. In this method, the brain sections were treated with LTP for 1 and 2 min prior to DESI-MSI analyses. Interestingly, the MS signal intensity of cholesterol (at m/z 369.35 [M + H - H2O]+) was more than 2-fold higher in the 1 min LTP-treated brain section compared to the untreated section. In addition, we detected cholesterol, more specifically excluding isomers by targeted-DESI-MSI in multiple reaction monitoring (MRM) mode and similar results were observed: the signal intensity of each cholesterol transition (m/z 369.4 → 95.1, 109.1, 135.1, 147.1, and 161.1) was increased by more than 2-fold due to 1 min LTP treatment. Cholesterol showed characteristic distributions in the fiber tract region, including the corpus callosum and anterior commissure, anterior part of the brain where LTP markedly (p < 0.001) enhanced the cholesterol intensity. In addition, the distributions of some unknown analytes were exclusively detected in the LTP-treated section. Our study revealed LTP pretreatment as a potential strategy to ionize molecules that show poor ionization efficiency in the MSI technique.

Modulation of Brain Cholesterol Metabolism through CYP46A1 Overexpression for Rett Syndrome

Rett syndrome (RTT) is a rare neurodevelopmental disorder caused by mutation in the X-linked gene methyl-CpG-binding protein 2 (Mecp2), a ubiquitously expressed transcriptional regulator. RTT results in mental retardation and developmental regression that affects approximately 1 in 10,000 females. Currently, there is no curative treatment for RTT. Thus, it is crucial to develop new therapeutic approaches for children suffering from RTT. Several studies suggested that RTT is linked with defects in cholesterol homeostasis, but for the first time, therapeutic evaluation is carried out by modulating this pathway. Moreover, AAV-based CYP46A1 overexpression, the enzyme involved in cholesterol pathway, has been demonstrated to be efficient in several neurodegenerative diseases. Based on these data, we strongly believe that CYP46A1 could be a relevant therapeutic target for RTT. Herein, we evaluated the effects of intravenous AAVPHP.eB-hCYP46A1-HA delivery in male and female Mecp2-deficient mice. The applied AAVPHP.eB-hCYP46A1 transduced essential neurons of the central nervous system (CNS). CYP46A1 overexpression alleviates behavioral alterations in both male and female Mecp2 knockout mice and extends the lifespan in Mecp2-deficient males. Several parameters related to cholesterol pathway are improved and correction of mitochondrial activity is demonstrated in treated mice, which highlighted the clear therapeutic benefit of CYP46A1 through the neuroprotection effect. IV delivery of AAVPHP.eB-CYP46A1 is perfectly well tolerated with no inflammation observed in the CNS of the treated mice. Altogether, our results strongly suggest that CYP46A1 is a relevant target and overexpression could alleviate the phenotype of Rett patients.

Transcriptomic profile in carbendazim-induced developmental defects in zebrafish (Danio rerio) embryos/larvae

Carbendazim is a widely used fungicide to protect agricultural and horticultural crops against a wide array of fungal species. Published reports have shown that the wide usage of carbendazim resulted in reprotoxicity, carcinogenicity, immunotoxicity, and developmental toxicity in mammalian models. However, studies related to the developmental toxicity of carbendazim in aquatic organisms are not clear. To address this gap, an attempt was made by exposing zebrafish embryos to carbendazim (800 μg/L) and assessing the phenotypic and transcriptomic profile at different developmental stages [24 hour post fertilization (hpf), 48 hpf, 72 hpf and 96 hpf). At 48 hpf, phenotypic abnormalities such as delay in hatching rate, deformed spinal axial curvature, and pericardial edema were observed in zebrafish larvae over its respective controls. At 72 hpf, exposure of zebrafish embryos exposed to carbendazim resulted in scoliosis; however, unexposed larvae did not exhibit signs of scoliosis. Interestingly, the transcriptomic analysis revealed a total of 1253 DEGs were observed at selected time points, while unique genes at 24 hpf, 48 hpf, 72 hpf and 96 hpf was found to be 76.54 %, 61.14 %, 92.98 %, and 68.28 %, respectively. Functional profiling of downregulated genes revealed altered transcriptomic markers associated with phototransduction (24 hpf and 72 hpf), immune system (48 hpf), and SNARE interactions in the vesicular pathway (96 hpf). Whereas functional profiling of upregulated genes revealed altered transcriptomic markers associated with riboflavin metabolism (24 hpf), basal transcription factors (48 hpf), insulin signaling pathway (72 hpf), and primary bile acid biosynthesis (96 hpf). Taken together, carbendazim-induced developmental toxicity could be ascribed to pleiotropic responses at the molecular level, which in turn might reflect phenotypic abnormalities.

Defining a vitamin A5/X specific deficiency - vitamin A5/X as a critical dietary factor for mental health

A healthy and balanced diet is an important factor to assure a good functioning of the central and peripheral nervous system. Retinoid X receptor (RXR)-mediated signaling was identified as an important mechanism of transmitting major diet-dependent physiological and nutritional signaling such as the control of myelination and dopamine signalling. Recently, vitamin A5/X, mainly present in vegetables as provitamin A5/X, was identified as a new concept of a vitamin which functions as the nutritional precursor for enabling RXR-mediated signaling. The active form of vitamin A5/X, 9-cis-13,14-dehydroretinoic acid (9CDHRA), induces RXR-activation, thereby acting as the central switch for enabling various heterodimer-RXR-signaling cascades involving various partner heterodimers like the fatty acid and eicosanoid receptors/peroxisome proliferator-activated receptors (PPARs), the cholesterol receptors/liver X receptors (LXRs), the vitamin D receptor (VDR), and the vitamin A(1) receptors/retinoic acid receptors (RARs). Thus, nutritional supply of vitamin A5/X might be a general nutritional-dependent switch for enabling this large cascade of hormonal signaling pathways and thus appears important to guarantee an overall organism homeostasis. RXR-mediated signaling was shown to be dependent on vitamin A5/X with direct effects for beneficial physiological and neuro-protective functions mediated systemically or directly in the brain. In summary, through control of dopamine signaling, amyloid β-clearance, neuro-protection and neuro-inflammation, the vitamin A5/X - RXR - RAR - vitamin A(1)-signaling might be "one of" or even "the" critical factor(s) necessary for good mental health, healthy brain aging, as well as for preventing drug addiction and prevention of a large array of nervous system diseases. Likewise, vitamin A5/X - RXR - non-RAR-dependent signaling relevant for myelination/re-myelination and phagocytosis/brain cleanup will contribute to such regulations too. In this review we discuss the basic scientific background, logical connections and nutritional/pharmacological expert recommendations for the nervous system especially considering the ageing brain.

The Intersection of cerebral cholesterol metabolism and Alzheimer's disease: Mechanisms and therapeutic prospects

Alzheimer's disease (AD) is a common neurodegenerative disease in the elderly, the exact pathogenesis of which remains incompletely understood, and effective preventive and therapeutic drugs are currently lacking. Cholesterol plays a vital role in cell membrane formation and neurotransmitter synthesis, and its abnormal metabolism is associated with the onset of AD. With the continuous advancement of imaging techniques and molecular biology methods, researchers can more accurately explore the relationship between cholesterol metabolism and AD. Elevated cholesterol levels may lead to vascular dysfunction, thereby affecting neuronal function. Additionally, abnormal cholesterol metabolism may affect the metabolism of β-amyloid protein, thereby promoting the onset of AD. Brain cholesterol levels are regulated by multiple factors. This review aims to deepen the understanding of the subtle relationship between cholesterol homeostasis and AD, and to introduce the latest advances in cholesterol-regulating AD treatment strategies, thereby inspiring readers to contemplate deeply on this complex relationship. Although there are still many unresolved important issues regarding the risk of brain cholesterol and AD, and some studies may have opposite conclusions, further research is needed to enrich our understanding. However, these findings are expected to deepen our understanding of the pathogenesis of AD and provide important insights for the future development of AD treatment strategies targeting brain cholesterol homeostasis.

Nutritional roles and therapeutic potentials of dietary sphingomyelin in brain diseases

Sphingolipids have recently gained interest as potential players in variety of diseases due to their import roles in human body particularly, the brain. As sphingomyelin is the most common type of sphingolipids, deficits in its distribution to brain cells may contribute to neurological anomalies. However, data is limited regarding the impact of different levels of dietary sphingomyelin intake on neural function especially if this approach can boost cognition and prevent neurological disorders. This review evaluates the effect of dietary sphingomyelin and its metabolites (ceramide and sphingosine-1-phosphate) in animal models and in humans, with a primary focus on its impact on brain health. Additionally, it proposes multiple neuroenhancing effects of sphingomyelin-rich diet. This presents an opportunity to stimulate further research that aims to determine the therapeutic value of dietary sphingomyelin in preventing, improving or slowing the progression of central nervous system disorders.

Obesity during preclinical Alzheimer's disease development exacerbates brain metabolic decline

Alzheimer's disease (AD) is the most common form of dementia. Obesity in middle age increases AD risk and severity, which is alarming given that obesity prevalence peaks at middle age and obesity rates are accelerating worldwide. Midlife, but not late-life obesity increases AD risk, suggesting that this interaction is specific to preclinical AD. AD pathology begins in middle age, with accumulation of amyloid beta (Aβ), hyperphosphorylated tau, metabolic decline, and neuroinflammation occurring decades before cognitive symptoms appear. We used a transcriptomic discovery approach in young adult (6.5 months old) male and female TgF344-AD rats that overexpress mutant human amyloid precursor protein and presenilin-1 and wild-type (WT) controls to determine whether inducing obesity with a high-fat/high-sugar "Western" diet during preclinical AD increases brain metabolic dysfunction in dorsal hippocampus (dHC), a brain region vulnerable to the effects of obesity and early AD. Analyses of dHC gene expression data showed dysregulated mitochondrial and neurotransmission pathways, and up-regulated genes involved in cholesterol synthesis. Western diet amplified the number of genes that were different between AD and WT rats and added pathways involved in noradrenergic signaling, dysregulated inhibition of cholesterol synthesis, and decreased intracellular lipid transporters. Importantly, the Western diet impaired dHC-dependent spatial working memory in AD but not WT rats, confirming that the dietary intervention accelerated cognitive decline. To examine later consequences of early transcriptional dysregulation, we measured dHC monoamine levels in older (13 months old) AD and WT rats of both sexes after long-term chow or Western diet consumption. Norepinephrine (NE) abundance was significantly decreased in AD rats, NE turnover was increased, and the Western diet attenuated the AD-induced increases in turnover. Collectively, these findings indicate obesity during prodromal AD impairs memory, potentiates AD-induced metabolic decline likely leading to an overproduction of cholesterol, and interferes with compensatory increases in NE transmission.

Cholesterol homeostasis confers glioma malignancy triggered by hnRNPA2B1-dependent regulation of SREBP2 and LDLR

BACKGROUND

Dysregulation of cholesterol metabolism is a significant characteristic of glioma, yet the underlying mechanisms are largely unknown. N6-methyladenosine (m6A) modification has been implicated in promoting tumor development and progression. The aim of this study was to determine the key m6A regulatory proteins involved in the progression of glioma, which is potentially associated with the reprogramming of cholesterol homeostasis.

METHODS

Bioinformatics analysis was performed to determine the association of m6A modification with glioma malignancy from The Cancer Genome Atlas and Genotype-Tissue Expression datasets. Glioma stem cell (GSC) self-renewal was determined by tumor sphere formation and bioluminescence image assay. RNA sequencing and lipidomic analysis were performed for cholesterol homeostasis analysis. RNA immunoprecipitation and luciferase reporter assay were performed to determine hnRNPA2B1-dependent regulation of sterol regulatory element-binding protein 2 (SREBP2) and low-density lipoprotein receptor (LDLR) mRNA. The methylation status of hnRNPA2B1 promoter was determined by bioinformatic analysis and methylation-specific PCR assay.

RESULTS

Among the m6A-regulatory proteins, hnRNPA2B1 was demonstrated the most important independent prognostic risk factor for glioma. hnRNPA2B1 ablation exhibited a significant tumor-suppressive effect on glioma cell proliferation, GSC self-renewal and tumorigenesis. hnRNPA2B1 triggers de novo cholesterol synthesis by inducing HMGCR through the stabilization of SREBP2 mRNA. m6A modification of SREBP2 or LDLR mRNA is required for hnRNPA2B1-mediated mRNA stability. The hypomethylation of cg21815882 site on hnRNPA2B1 promoter confers elevated expression of hnRNPA2B1 in glioma tissues. The combination of targeting hnRNPA2B1 and cholesterol metabolism exhibited remarkable antitumor effects, suggesting valuable clinical implications for glioma treatment.

CONCLUSIONS

hnRNPA2B1 facilitates cholesterol uptake and de novo synthesis, thereby contributing to glioma stemness and malignancy.

Serotonin Signaling through Lipid Membranes

Serotonin (5-HT) is a vital modulatory neurotransmitter responsible for regulating most behaviors in the brain. An inefficient 5-HT synaptic function is often linked to various mental disorders. Primarily, membrane proteins controlling the expression and activity of 5-HT synthesis, storage, release, receptor activation, and inactivation are critical to 5-HT signaling in synaptic and extra-synaptic sites. Moreover, these signals represent information transmission across membranes. Although the lipid membrane environment is often viewed as fairly stable, emerging research suggests significant functional lipid-protein interactions with many synaptic 5-HT proteins. These protein-lipid interactions extend to almost all the primary lipid classes that form the plasma membrane. Collectively, these lipid classes and lipid-protein interactions affect 5-HT synaptic efficacy at the synapse. The highly dynamic lipid composition of synaptic membranes suggests that these lipids and their interactions with proteins may contribute to the plasticity of the 5-HT synapse. Therefore, this broader protein-lipid model of the 5-HT synapse necessitates a reconsideration of 5-HT's role in various associated mental disorders.