Sphingolipid Catabolism and Glycerophospholipid Levels Are Altered in Erythrocytes and Plasma from Multiple Sclerosis Patients

Identification of lipid metabolism-related gene markers and construction of a diagnostic model for multiple sclerosis: An integrated analysis by bioinformatics and machine learning

BACKGROUND

Multiple sclerosis (MS) is an autoimmune inflammatory disorder that causes neurological disability. Dysregulated lipid metabolism contributes to the pathogenesis of MS. This study aimed to identify lipid metabolism-related gene markers and construct a diagnostic model for MS.

METHODS

Gene expression profiles for MS were obtained from the Gene Expression Omnibus database. Differentially expressed lipid metabolism-related genes (LMRGs) were identified and performed functional enrichment analysis. Least absolute shrinkage and selection operator (LASSO), random forest (RF), and protein-protein interaction (PPI) analysis were employed to screen hub genes. The predictive power of hub genes was evaluated using receiver operating characteristic (ROC) curves. We developed an artificial neural network (ANN) model and validated its performance in three test sets. Immune cell infiltration analysis, Gene set enrichment analysis, and ceRNA network construction were performed to explore the role of lipid metabolism in the pathogenesis of MS. Drugs prediction and molecular docking were utilized to identify potential therapeutic drugs.

RESULTS

We identified 40 differentially expressed LMRGs, with significant enrichment in Arachidonic acid metabolism, Steroid hormone biosynthesis, Fatty acid elongation, and Sphingolipid metabolism. AKR1C3, NFKB1, and ABCA1 were identified as gene markers for MS, and their expression was upregulated in the MS group. The areas under the ROC curve (AUCs) for AKR1C3, NFKB1, and ABCA1 in the training set were 0.779, 0.703, and 0.726, respectively. The ANN model exhibited good discriminative ability in both the training and test sets, achieving an AUC of 0.826 on the training set and AUC values of 0.822, 0.890, and 0.833 on the test sets. Gamma.delta.T.cell, Natural.killer.T.cell, Plasmacytoid.dendritic.cell, Regulatory.T.cell, and Type.1.T.helper.cell were highly expressed in the MS group. A ceRNA network showed a complex regulatory interplay involving hub genes. Luteolin, isoflavone, and thalidomide had good binding affinities to the hub genes.

CONCLUSION

Our study emphasized the crucial role of lipid metabolism in MS, identifing AKR1C3, NFKB1, and ABCA1 as gene markers. The ANN model exhibited good performance on both the training and testing sets. These findings offer valuable insights into the molecular mechanisms underlying MS, and establish a scientific foundation for future research.

Higher dietary nitrate intake is associated with lower likelihood of first clinical diagnosis of central nervous system demyelination in Australian women

Dietary nitrate is a precursor to nitric oxide, for which plausible mechanisms exist for both beneficial and detrimental influences in first clinical diagnosis of central nervous system demyelination (FCD), a common precursor to the diagnosis of multiple sclerosis (MS). Whether dietary nitrate has any role in FCD onset is unclear. We tested associations between nitrate intake from food sources (plant, vegetable, animal, processed meat, and unprocessed meat) and likelihood of FCD. We used data from the Ausimmune Study (264 cases, 474 controls) and logistic regression with full propensity score matching. In females, higher nitrate intake from plant-based foods (odds ratio [OR] per 60 mg/day = 0.50; 95 % confidence interval [CI] 0.31, 0.81; p = <0.01) and vegetables (OR per 60 mg/day = 0.39; 95 % CI 0.22, 0.70; p = <0.01), but not other sources, was statistically significantly associated with lower likelihood of FCD. In males, no associations were found between any source of nitrate intake and likelihood of FCD. Our results support further research to explore a possible beneficial role for plant-derived nitrate in people at higher risk of MS.

Role of dietary and nutritional interventions in ceramide-associated diseases

Ceramides are important intermediates in sphingolipid metabolism and serve as signaling molecules with independent biological significance. Elevated cellular and circulating ceramide levels are consistently associated with pathological conditions including cardiometabolic diseases, neurological diseases, autoimmune diseases, and cancers. Although pharmacological inhibition of ceramide formation often protects against these diseases in animal models, pharmacological modulation of ceramides in humans remains impractical. Dietary interventions including the Mediterranean diet, lacto-ovo-vegetarian diet, calorie-restricted diet, restriction of dairy product consumption, and dietary supplementation with polyunsaturated fatty acids, dietary fibers, and polyphenols, all have beneficial effects on modulating ceramide levels. Mechanistic insights into these interventions are discussed. This article reviews the relationships between ceramides and disease pathogenesis, with a focus on dietary intervention as a viable strategy for lowering the concentration of circulating ceramides.

Multi-Omic characterization of the effects of Ocrelizumab in patients with relapsing-remitting multiple sclerosis

The study examined changes in the plasma proteome, metabolome, and lipidome of N = 14 patients with relapsing-remitting multiple sclerosis (RRMS) initiating treatment with ocrelizumab, assayed at baseline, 6 months, and 12 months. Analyses of >4000 circulating biomarkers identified depletion of B-cell associated proteins as the early effect observed following ocrelizumab (OCR) initiation, accompanied by the reduction in plasma abundance of cytokines and cytotoxic proteins, markers of neuronaxonal damage, and biologically active lipids including ceramides and lysophospholipids, at 6 months. B-cell depletion was accompanied by decreases in B-cell receptor and cytokine signaling but a pronounced increase in circulating plasma B-cell activating factor (BAFF). This was followed by an upregulation of a number of signaling and metabolic pathways at 12 months. Patients with higher baseline brain MRI lesion load demonstrated both higher levels of cytotoxic and structural proteins in plasma at baseline and more pronounced biomarker change trajectories over time. Digital cytometry identified a putative increase in myeloid cells and a pro-inflammatory subset of T-cells. Therapeutic effects of ocrelizumab extend beyond CD20-mediated B-cell lysis and implicate metabolic reprogramming, juxtaposing the early normalization of immune activation, cytokine signaling and metabolite and lipid turnover in periphery with changes in the dynamics of immune cell activation or composition. We identify BAFF increase following CD20 depletion as a tentative compensatory mechanism that contributes to the reconstitution of targeted B-cells, necessitating further research.

The metabolic response of HepG2 cells to extracellular vesicles derived from Raphanus sativus L. var. caudatus Alef microgreens probed by chemometrics-assisted LC-MS/MS analysis

Extracellular vesicles (EVs) derived from Thai rat-tailed radish (Raphanus sativus L. var. caudatus Alef) microgreens were previously reported as novel bioactive bioparticles against cancer. This study aimed to investigate the metabolic disruption associated with the antiproliferative effect against HepG2 liver cancer cells, a representative of metabolizing cells and tissue. In this study, the neutral red uptake assay was performed to screen for the antiproliferative effect and determine the cytotoxic concentrations of EVs against HepG2 cells. An untargeted approach to cellular metabolomics was conducted using liquid chromatography coupled with the high-resolution mass spectrometry system with multivariate and univariate analyses to determine the metabolic changes of HepG2 liver cancer cells after EV treatment. EVs showed an antiproliferative effect in HepG2 cells with a half-maximal inhibitory concentration (IC50) of 685.5 ± 26.4 and 139.7 ± 4.2 μg/ml at 24 and 48 h, respectively. In the metabolomics study, 163 metabolites were annotated, with 61 significantly altered metabolites. Among these significant metabolites, 18 were related to glycerophospholipid metabolism. Phosphatidylcholine-the important lipid building blocks for cell membranes, lipid mediators for cell proliferation, and immunosuppressive signaling-was mainly decreased by EV treatment. The alteration of cellular phospholipids in cancer was discussed. This finding suggested the possible mechanism of anticancer action of EVs by disrupting phospholipid metabolism and survival signaling in cancer cells. Further studies should be made to confirm EVs' potential as single and combination therapy in vivo to reduce cancer resistance. This may close the gap between in vitro study and clinical setting.

Recent Advances in Metabolomics and Lipidomics Studies in Human and Animal Models of Multiple Sclerosis

Multiple sclerosis (MS) is a neurodegenerative and inflammatory disease of the central nervous system (CNS) that leads to a loss of myelin. There are three main types of MS: relapsing-remitting MS (RRMS) and primary and secondary progressive disease (PPMS, SPMS). The differentiation in the pathogenesis of these two latter courses is still unclear. The underlying mechanisms of MS are yet to be elucidated, and the treatment relies on immune-modifying agents. Recently, lipidomics and metabolomics studies using human biofluids, mainly plasma and cerebrospinal fluid (CSF), have suggested an important role of lipids and metabolites in the pathophysiology of MS. In this review, the results from studies on metabolomics and lipidomics analyses performed on biological samples of MS patients and MS-like animal models are presented and analyzed. Based on the collected findings, the biochemical pathways in human and animal cohorts involved were investigated and biological mechanisms and the potential role they have in MS are discussed. Limitations and challenges of metabolomics and lipidomics approaches are presented while concluding that metabolomics and lipidomics may provide a more holistic approach and provide biomarkers for early diagnosis of MS disease.

Multi-omics profiling reveals peripheral blood biomarkers of multiple sclerosis: implications for diagnosis and stratification

Background

Multiple sclerosis (MS), a chronic autoimmune disorder marked by demyelination in the central nervous system, is exceptionally uncommon in China, and remains poorly understood in terms of its peripheral blood manifestations.

Methods

We conducted a cohort study comprising 39 MS patients and 40 normal controls (NC). High-dimensional mass cytometry, protein arrays, and targeted metabolomics were utilized to profile immune subsets, proteins, and metabolites in blood. Differences in multi-omics signatures were scrutinized across varying MS subtypes.

Results

Immune profiling demonstrated an elevation in various B cell subsets and monocytes, alongside a reduction in dendritic cells among MS patients. Proteomic data revealed a downregulation in neurotrophic and tissue repair proteins. Metabolomic assessment showed a noted decrease in anti-inflammatory molecules and sphingolipids. Integrated analysis identified distinct molecular patterns distinguishing MS from controls. Additionally, multi-omics differences among different MS subtypes were uncovered. Notably, hippuric acid levels was consistently lower in MS subgroups with greater disease severity.

Conclusion

This study represents the pioneering exploration of multi-omics in Chinese MS patients, presenting a comprehensive view of the peripheral blood changes in MS. Our study underscores the robust capability of multi-omics assessments in identifying peripheral blood biomarkers that delineate the varied clinical presentation, and facilitates future development of biomarkers and targeted therapeutic interventions in MS.

Vitamin C-Dependent Uptake of Non-Heme Iron by Enterocytes, Its Impact on Erythropoiesis and Redox Capacity of Human Erythrocytes

In the small intestine, nutrients from ingested food are absorbed and broken down by enterocytes, which constitute over 95% of the intestinal epithelium. Enterocytes demonstrate diet- and segment-dependent metabolic flexibility, enabling them to take up large amounts of glutamine and glucose to meet their energy needs and transfer these nutrients into the bloodstream. During glycolysis, ATP, lactate, and H+ ions are produced within the enterocytes. Based on extensive but incomplete glutamine oxidation large amounts of alanine or lactate are produced. Lactate, in turn, promotes hypoxia-inducible factor-1α (Hif-1α) activation and Hif-1α-dependent transcription of various proton channels and exchangers, which extrude cytoplasmic H+-ions into the intestinal lumen. In parallel, the vitamin C-dependent and duodenal cytochrome b-mediated conversion of ferric iron into ferrous iron progresses. Finally, the generated electrochemical gradient is utilized by the divalent metal transporter 1 for H+-coupled uptake of non-heme Fe2+-ions. Iron efflux from enterocytes, subsequent binding to the plasma protein transferrin, and systemic distribution supply a wide range of cells with iron, including erythroid precursors essential for erythropoiesis. In this review, we discuss the impact of vitamin C on the redox capacity of human erythrocytes and connect enterocyte function with iron metabolism, highlighting its effects on erythropoiesis.

Mass Spectrometric Imaging of Anionic Phospholipids Desorbed from Human Hippocampal Sections: Discrimination between Temporal and Nontemporal Lobe Epilepsies

Temporal lobe epilepsy (TLE) is one of the most common neurological disorders, often accompanied by hippocampal sclerosis. The molecular processes underlying this epileptogenesis are poorly understood. To examine the lipid profile, 39 fresh frozen sections of the human hippocampus obtained from epilepsy surgery for TLE (n = 14) and non-TLE (control group; n = 25) patients were subjected to desorption electrospray ionization mass spectrometry imaging in the negative ion mode. In contrast to our earlier report that showed striking downregulation of positively charged phospholipids (e.g., phosphatidylcholine and phosphatidylethanolamine, etc.) in the TLE hippocampus, this study finds complementary upregulation of negatively charged phospholipids, notably, phosphatidylserine and phosphatidylglycerol. This result may point to an active metabolic pool in the TLE hippocampus that produces these anionic phospholipids at the expense of the cationic phospholipids. This metabolic shift could be due to the dysregulation of the Kennedy and CDP-DG pathways responsible for biosynthesizing these lipids. Thus, this study further opens up opportunities to investigate the molecular hallmarks and potential therapeutic targets for TLE.

Emerging Role of Astrocyte-Derived Extracellular Vesicles as Active Participants in CNS Neuroimmune Responses

Astrocyte-derived extracellular vesicles (ADEVs) have garnered attention as a fundamental mechanism of intercellular communication in health and disease. In the context of neurological diseases, for which prodromal diagnosis would be advantageous, ADEVs are also being explored for their potential utility as biomarkers. In this review, we provide the current state of data supporting our understanding on the manifold roles of ADEVs in several common neurological disorders. We also discuss these findings from a unique emerging perspective that ADEVs represent a means by which the central nervous system may broadcast influence over other systems in the body to affect neuroinflammatory processes, with both dual potential to either propagate illness or restore health and homeostasis.

Therapeutic Plasma Exchange and Multiple Sclerosis Dysregulations: Focus on the Removal of Pathogenic Circulatory Factors and Altering Nerve Growth Factor and Sphingosine-1-Phosphate Plasma Levels

Multiple sclerosis (MS) is predominantly an immune-mediated disease of the central nervous system (CNS) of unknown etiology with a possible genetic predisposition and effect of certain environmental factors. It is generally accepted that the disease begins with an autoimmune inflammatory reaction targeting oligodendrocytes followed by a rapid depletion of their regenerative capacity with subsequent permanent neurodegenerative changes and disability. Recent research highlights the central role of B lymphocytes and the corresponding IgG and IgM autoantibodies in newly forming MS lesions. Thus, their removal along with the modulation of certain bioactive molecules to improve neuroprotection using therapeutic plasma exchange (TPE) becomes of utmost importance. Recently, it has been proposed to determine the levels and precise effects of both beneficial and harmful components in the serum of MS patients undergoing TPE to serve as markers for appropriate TPE protocols. In this review we discuss some relevant examples, focusing on the removal of pathogenic circulating factors and altering the plasma levels of nerve growth factor and sphingosine-1-phosphate by TPE. Altered plasma levels of the reviewed molecular compounds in response to TPE reflect a successful reduction of the pro-inflammatory burden at the expense of an increase in anti-inflammatory potential in the circulatory and CNS compartments.

Desipramine induces eryptosis in human erythrocytes, an effect blunted by nitric oxide donor sodium nitroprusside and N-acetyl-L-cysteine but enhanced by Calcium depletion

Background: Desipramine a representative of tricyclic antidepressants (TCAs) promotes recovery of depressed patients by inhibition of reuptake of neurotransmitters serotonin (SER) and norepinephrine (NE) in the presynaptic membrane by directly blocking their respective transporters SERT and NET.Aims: To study the effect of desipramine on programmed erythrocyte death (eryptosis) and explore the underlying mechanisms.Methods: Phosphatidylserine (PS) exposure on the cell surface as marker of cell death was estimated from annexin-V-binding, cell volume from forward scatter in flow cytometry. Hemolysis was determined photometrically, and intracellular glutathione [GSH]i from high performance liquid chromatography.Results: Desipramine dose-dependently significantly enhanced the percentage of annexin-V-binding cells and didn´t impact glutathione (GSH) synthesis. Desipramine-induced eryptosis was significantly reversed by pre-treatment of erythrocytes with either nitric oxide (NO) donor sodium nitroprusside (SNP) or N-acetyl-L-cysteine (NAC). The highest inhibitory effect was obtained by using both inhibitors together. Calcium (Ca2+) depletion aggravated desipramine-induced eryptosis. Changing the order of treatment, i.e. desipramine first followed by inhibitors, could not influence the inhibitory effect of SNP or NAC.Conclusion: Antidepressants-caused intoxication can be treated by SNP and NAC, respectively. B) Patients with chronic hypocalcemia should not be treated with tricyclic anti-depressants or their dose should be noticeably reduced.

Experimental Analysis of Tear Fluid and Its Processing for the Diagnosis of Multiple Sclerosis

A pilot analysis of the tear fluid of patients with multiple sclerosis (MS) collected by glass microcapillary was performed using various experimental methods: liquid chromatography-mass spectrometry, Raman spectroscopy, infrared spectroscopy, and atomic-force microscopy. Infrared spectroscopy found no significant difference between the tear fluid of MS patients and the control spectra; all three significant peaks were located at around the same positions. Raman analysis showed differences between the spectra of the tear fluid of MS patients and the spectra of healthy subjects, which indicated a decrease in tryptophan and phenylalanine content and changes in the relative contributions of the secondary structures of the polypeptide chains of tear proteins. Atomic-force microscopy exhibited a surface fern-shaped dendrite morphology of the tear fluid of patients with MS, with less roughness on both oriented silicon (100) and glass substrates compared to the tear fluid of control subjects. The results of liquid chromatography-mass spectrometry showed downregulation of glycosphingolipid metabolism, sphingolipid metabolism, and lipid metabolism. Proteomic analysis identified upregulated proteins in the tear fluid of patients with MS such as cystatine, phospholipid transfer protein, transcobalamin-1, immunoglobulin lambda variable 1-47, lactoperoxidase, and ferroptosis suppressor protein 1; and downregulated proteins such as haptoglobin, prosaposin, cytoskeletal keratin type I pre-mRNA-processing factor 17, neutrophil gelatinase-associated lipocalin, and phospholipase A2. This study showed that the tear proteome in patients with MS is modified and can reflect inflammation. Tear fluid is not a commonly used biological material in clinico-biochemical laboratories. Experimental proteomics has the potential to become a promising contemporary tool for personalized medicine, and it might be applied in clinical practice by providing a detailed analysis of the tear-fluid proteomic profile of patients with MS.