Lipidomics reveals a remarkable diversity of lipids in human plasma

Glial Biologist's Guide to Mass Spectrometry-Based Lipidomics: A Tutorial From Sample Preparation to Data Analysis

Neurological diseases are associated with disruptions in the brain lipidome that are becoming central to disease pathogenesis. Traditionally perceived as static structural support in membranes, lipids are now known to be actively involved in cellular signaling, energy metabolism, and other cellular activities involving membrane curvature, fluidity, fusion or fission. Glia are critical in the development, health, and function of the brain, and glial regulation plays a major role in disease. The major pathways of glial dysregulation related to function are associated with downstream products of metabolism including lipids. Taking advantage of significant innovations and technical advancements in instrumentation, lipidomics has emerged as a popular omics discipline, serving as the prevailing approach to comprehensively define metabolic alterations associated with organismal development, damage or disease. A key technological platform for lipidomics studies is mass spectrometry (MS), as it affords large-scale profiling of complex biological samples. However, as MS-based techniques are often refined and advanced, the relative comfort level among biologists with this instrumentation has not followed suit. In this review, we aim to highlight the importance of the study of glial lipids and to provide a concise record of best practices and steps for MS-based lipidomics. Specifically, we outline procedures for glia lipidomics workflows ranging from sample collection and extraction to mass spectrometric analysis to data interpretation. To ensure these approaches are more accessible, this tutorial aims to familiarize glia biologists with sample handling and analysis techniques for MS-based lipidomics, and to guide non-experts toward generating high quality lipidomics data.

High-resolution targeted mass spectrometry for comprehensive quantification of sphingolipids: clinical applications and characterization of extracellular vesicles

Sphingolipids (SL), a class of membrane lipids, play important roles in numerous biological processes. Their significant structural diversity poses challenges for accurate quantification. To address this, liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) has emerged as a powerful tool for sphingolipidomics, capable of profiling these lipids comprehensively. In this study, we utilized LC-MS/MS with high-resolution mass spectrometry (MRMHR) to develop a targeted method for the identification and quantification of various SL species. This method, based on validated parameters such as precursor/fragment ions (m/z) and retention time, demonstrated high sensitivity and accuracy, successfully identifying SL species across 12 distinct classes. Its open-panel design also facilitates the analysis of new SL-species targets. Notably, using this approach, we identified 40 SL species in plasma samples from COVID-19 patients, and we determined the influence of matrix metalloproteinase-3 (MMP-3) expression on the positive downstream of SL metabolism. Beyond plasma analysis, this method has potential applications in other biomedical contexts, such as extracellular vesicles (EVs), describing the cargo of sphingosine-1-phosphate (S1P) on macrophage-derived EVs. The establishment of this targeted workflow enabling precise quantification of a wide range of SL species, holds promise for identifying novel biomarkers and therapeutic targets.

Iron limitation triggers roseoceramide biosynthesis and membrane remodeling in marine roseobacter

Chemical communication between marine bacteria and their algal hosts drives population dynamics and ultimately determines the fate of major biogeochemical cycles in the ocean. To gain deeper insights into this small molecule exchange, we screened niche-specific metabolites as potential modulators of the secondary metabolome of the roseobacter, Roseovarius tolerans. Metabolomic analysis led to the identification of a group of cryptic lipids that we have termed roseoceramides. The roseoceramides are elicited by iron-binding algal flavonoids, which are produced by macroalgae that Roseovarius species associate with. Investigations into the mechanism of elicitation show that iron limitation in R. tolerans initiates a stress response that results in lowered oxidative phosphorylation, increased import and catabolism of algal exudates, and reconfiguration of lipid ynthesis to prioritize production of roseoceramides over phospholipids, likely to fortify membrane integrity as well as promote a sessile and symbiotic lifestyle. Our findings add new small molecule words and their "meanings" to the algal-bacterial lexicon and have implications for the initiation of these interactions.

Rapid and Reagent-Free Analysis of Dried Blood Spot by Paper Spray Mass Spectrometry Reveals Sex: Implications in Forensic Investigations

Identifying sex from an unknown dried blood spot (DBS), especially when the corpse remains undiscovered, often provides valuable evidence in forensic casework. While DNA-based sex determination is a reliable method in forensic settings, it requires expensive reagents and is time-consuming. To develop a rapid reagent-free blood test for sex, we employed paper spray ionization mass spectrometry (PSI-MS) to capture sex-discriminatory lipid profiles from 200 DBS samples comprising 100 males and 100 females. We conducted a supervised machine learning (ML) analysis on all detected lipid signals to hunt biomarkers of sex within the data set. This analysis unveiled significant differences in specific sphingomyelin and phospholipid species levels between male and female DBS samples. Using the parsimonious set of 60 lipid signals, we constructed a classifier that achieved 100% overall accuracy in predicting sex from DBS on paper. Additionally, we assessed three-day-old air-exposed DBS on glass and granite surfaces, simulating the typical blood samples available for forensic investigations. Consequently, we achieved ∼92% overall sex prediction accuracy from the holdout test data set of DBS on glass and granite surfaces. As a highly sensitive detection tool, PSI-MS combined with ML has the potential to revolutionize forensic methods by rapidly analyzing blood molecules encoding personal information.

LC-MS/MS based analytical strategies for the detection of lipid peroxidation products in biological matrices

Oxidative stress (OS) arises mainly from exposure to reactive oxygen species (ROS) such as superoxide anion, hydroxyl radical, and hydrogen peroxide. These molecules can cause significant damage to proteins, DNA, and lipids, leading to various diseases. Cells fight ROS with detoxifying enzymes; however, an imbalance can cause damage leading to ischemic conditions, heart disease progression, and neurological disorders such as Alzheimer's disease. Accurate assessment of OS levels is then crucial and oxidized lipidic products are considered relevant OS biomarkers. In fact, lipids are particularly prone to ROS attack, leading to lipid peroxidation, cell membrane damage, and toxic by-products affecting DNA, proteins, and low-density lipoproteins. This review reports on recent advances in LC-MS/MS approaches for OS lipidic biomarkers, focusing on overcoming analytical challenges. 3 different classes of biomarkers have been reported, malondialdehyde, isoprostanes and oxidised sterols. For each class, the main analytical challenges with a particular focus on derivatisation procedure, sensitivity, matrix effect, ionisation have been described and discussed. The recent advancements of the LC-MS-MS procedures move towards simpler approaches, reducing errors and improving the reliability of the measurement thus enabling a comprehensive and robust OS assessment.

Comprehensive, Quantitative Analysis of SRM 1950: the NIST Human Plasma Reference Material

Many analytical methods have been developed for performing targeted metabolomics. By combining multiple analytical techniques, comprehensive coverage of the metabolome can be achieved. We combined multiple analytical techniques to comprehensively and quantitatively characterize the widely studied NIST human plasma reference material, SRM 1950. Our goal was to provide a large, well-validated list of confident metabolite concentration values (i.e., benchmarks) to assist the metabolomics community in its calibration and comparison efforts. We used four analytical platforms: high-resolution NMR spectroscopy, direct injection tandem MS (DI-MS/MS), liquid chromatography tandem MS (LC-MS/MS), and inductively coupled plasma MS (ICP-MS). Eight validated analytical assays were run, yielding accurate quantitative measurements for 728 unique metabolites or metabolite species. Through computer-aided literature mining, we identified another 330 unique metabolites previously quantified in SRM 1950. We compared NIST-certified values along with literature-derived concentrations/ranges to the metabolite concentrations measured by our four platforms and eight assays. From these assays/platforms, we generated a list of high-confidence concentration values of 1058 metabolites or metabolite species in SRM 1950 including data for 60 amino acids/related compounds, 48 bile acids, 72 amines/sugars/alcohols, 21 metals, 8 catecholamines, 11 vitamins, 92 organic acids, 40 fatty acids/steroids/nucleobases/indole derivatives, 5 polyfluorinated compounds, 7 carotenoids, 39 acylcarnitines, 76 oxylipins, 13 sterols, and 566 lipids/lipid species. This data set represents the most complete quantitative characterization of SRM 1950. An online database (SRM1950-DB) containing 1058 plasma metabolites/metabolite species in SRM 1950, their structures, HMDB IDs, mass, chemical class, concentrations, references, and reliability is freely available at https://srm1950-data.wishartlab.com.

Don't Be Surprised When These Surprise You: Some Infrequently Studied Sphingoid Bases, Metabolites, and Factors That Should Be Kept in Mind During Sphingolipidomic Studies

Sphingolipidomic mass spectrometry has provided valuable information-and surprises-about sphingolipid structures, metabolism, and functions in normal biological processes and disease. Nonetheless, many noteworthy compounds are not routinely determined, such as the following: most of the sphingoid bases that mammals biosynthesize de novo other than sphingosine (and sometimes sphinganine) or acquire from exogenous sources; infrequently considered metabolites of sphingoid bases, such as N-(methyl)n-derivatives; "ceramides" other than the most common N-acylsphingosines; and complex sphingolipids other than sphingomyelins and simple glycosphingolipids, including glucosyl- and galactosylceramides, which are usually reported as "monohexosylceramides". These and other subspecies are discussed, as well as some of the circumstances when they are likely to be seen (or present and missed) due to experimental conditions that can influence sphingolipid metabolism, uptake from the diet or from the microbiome, or as artifacts produced during extraction and analysis. If these compounds and factors are kept in mind during the design and interpretation of lipidomic studies, investigators are likely to be surprised by how often they appear and thereby advance knowledge about them.

Functional characterization of eicosanoid signaling in Drosophila development

20-carbon fatty acid-derived eicosanoids are versatile signaling oxylipins in mammals. In particular, a group of eicosanoids termed prostanoids are involved in multiple physiological processes, such as reproduction and immune responses. Although some eicosanoids such as prostaglandin E2 (PGE2) have been detected in some insect species, molecular mechanisms of eicosanoid synthesis and signal transduction in insects have been poorly investigated. Our phylogenetic analysis indicated that, in clear contrast to the presence of numerous receptors for oxylipins and other lipid mediators in humans, the Drosophila genome only possesses a single ortholog of such receptors, which is homologous to human prostanoid receptors. This G protein-coupled receptor, named Prostaglandin Receptor or PGR, is activated by PGE2 and its isomer PGD2 in Drosophila S2 cells. PGR mutant flies die as pharate adults with insufficient tracheal development, which can be rescued by supplying high oxygen. Consistent with this, through a comprehensive mutagenesis approach, we identified a Drosophila PGE synthase whose mutants show similar pharate adult lethality with hypoxia responses. Drosophila thus has a highly simplified eicosanoid signaling pathway as compared to humans, and it may provide an ideal model system for investigating evolutionarily conserved aspects of eicosanoid signaling.

Chiral supercritical fluid chromatography of monoacylglycerol and diacylglycerol enantiomers in biological samples: Adjusting selectivity via column coupling

The distinction of lipid isomers is gaining more attention in lipidomics due to their different biochemical properties in the organism. Herein, we aimed to develop a method for the analysis of monoacylglycerol (MG) and diacylglycerol (DG) enantiomers in biological samples using chiral supercritical fluid chromatography and mass spectrometry (SFC-MS). Amylose-based chiral columns showed a certain degree of separation of MG and DG isomers, but low selectivity for the acylglycerol classes in total lipid extracts, which could not be improved by modifier composition or other chromatographic conditions. The coelution of MG and DG enantiomers with highly concentrated triacylglycerols (TGs) negatively affected their MS determination based on the peak area ratio, therefore the interclass selectivity of chiral SFC was adjusted by coupling with an achiral column. The connection of the amylose tris-(3,5-dimethylphenylcarbamate) chiral column with octadecyl achiral column using a methanol as a modifier provided an excellent interclass separation of acylglycerols with the resolution of 5.53 and 15.17 for oleic acid-based MG/DG and DG/TG classes, respectively. The developed method enabled the determination of MG and DG enantiomers in complex total lipid extracts of biological samples in a 15 min gradient without time-consuming sample prefractionation. Chiral SFC-MS analysis of egg yolk, human plasma, and porcine brain samples showed different ratios of enantiomers, suggesting their unique roles within each sample type.

Serum metabolome profiling in patients with mild cognitive impairment reveals sex differences in lipid metabolism

Alzheimer's disease (AD) affects more women than men. Although women live longer than men, it is not longevity alone, but other factors, including metabolic changes, that contribute to the higher risk of AD in women. Metabolic pathways have been implicated in AD progression, but studies to date examined targeted pathways, leaving many metabolites unmeasured. Sex is often a neglected biological variable, and most metabolomic studies were not designed to investigate sex differences in metabolomic profiles. Here, we performed untargeted metabolomic profiling of sera from male and female patients with mild cognitive impairment (MCI), a common precursor to AD, and matched controls. We discovered significant metabolic changes in individuals with MCI, and found several pathways that were strongly associated with sex. Peptide energy metabolism demonstrated sexual dimorphism. Lipid pathways exhibited the strongest differences between female and male MCI patients, including specific phosphatidylcholine lipids, lysophospholipids, long-chain fatty acids, and monoacylglycerols. 1-palmitoleoyl glycerol and 1-arachidonoyl glycerol were higher in female MCI subjects than in male MCI subjects with no differences between control males and females. Conversely, specific dicarboxylic fatty acids were lower in female MCI subjects than male MCI subjects. In cultured astrocytes, 1-arachidonoyl glycerol promoted phosphorylation of the transcriptional regulator sphingosine kinase 2, which was inhibited by the transient receptor potential vanilloid 1 receptor antagonists, as well as chromatin remodelling. Overall, we identified novel sex-specific metabolites in MCI patients that could serve as biomarkers of MCI in both sexes, help further define AD etiology, and reveal new potential prevention strategies for AD.

Water fluxes and nutrient absorption along the midgut of three hemipterans, Mahanarva fimbriolata, Dysdercus peruvianus, and Rhodnius prolixus

Hemiptera Order comprises insect species adapted to different diets regarding water and nutrient content and availability, thus suggesting different combinations of proteins to ensure their absorption. To find out whether hemipterans use the same or distinct set of proteins and whether these differences are related to the phylogeny or the diet, RNAseq analyses were conducted in gut sections of three hemipterans, M. fimbriolata, D. peruvianus, and R. prolixus, with remarkable distinct diet. Since only a few of the selected proteins were functionally characterized, the coded putative proteins were manually curated by bioinformatics to infer their physiological function. The results suggest a relationship between gene expression patterns and water and nutrient dietary content and availability. In contrast, putative gene expansions and deletions are related to phylogeny, corresponding to evolutionary adaptations of ancestral forms to feed on xylem, cotton seeds, and blood, resulting in more resemblances between D. peruvianus and R. prolixus than M. fimbriolata. M. fimbriolata absorbs water through aquaporins Drip and Prip in the filtration chamber by passive diffusion, with a higher contribution of water-selective Drip. D. peruvianus water absorption involves Drip and Prip, but Prip contribution appears to be higher, and they probably cooperate with water-ion cotransporters in the posterior midgut. R. prolixus absorbs water in the anterior midgut involving a sodium transporter and a putative water-urea Prip. Sugars, amino acids, and lipids might be absorbed along the midgut in the three species, with a higher contribution of the posterior midgut for amino acid and lipid absorption in M. fimbriolata and D. peruvianus and the middle midgut in R. prolixus.

Serum lipid profiling reveals characteristic lipid signatures associated with stroke in patients with leukoaraiosis

Many lipid biomarkers of stroke have been identified, but the lipid metabolism in elderly patients with leukoaraiosis remains poorly understood. This study aims to explore lipid metabolic processes in stroke among leukoaraiosis patients, which could provide valuable insights for guiding future antithrombotic therapy. In a cohort of 215 individuals undergoing MRI, 13 stroke patients were matched with controls, and 48 stroke patients with leukoaraiosis were matched with 40 leukoaraiosis patients. Serum lipidomics was profiled using UPLC-TOF, and OPLS-DA was applied for metabolite identification. Partial Least Squares Path Model (PLS-PM) assessed pathway weights of novel metabolites in stroke risk, while linear regression explored correlations with clinical outcomes. Lipid profiling identified 168 distinct compounds. From these, 25 lipid molecules were associated with glycerolipid, glycerophospholipid, and sphingolipid metabolism. PLS-PM identified 12 key metabolites, including DG 36:4 (OR = 6.40) as a significant risk factor. Metabolites such as PE 38:5 and FA 16:1;O showed significant correlations with stroke in leukoaraiosis, particularly when the Fazekas score was ≥ 4. Twelve metabolites were identified as key factors in stroke incidence among leukoaraiosis patients. Lipid disturbances in glycerolipids and glycerophospholipids provide valuable insights for further studies on the progression from leukoaraiosis to stroke.

Approaching Two Decades: Biomolecular Coronas and Bio-Nano Interactions

It has been nearly two decades since the term "protein corona" was coined. This term has since evolved to "biomolecular corona" or "biocorona" to capture the diverse biomolecules that spontaneously form on the surface of nanoparticles upon exposure to biological fluids and drive nanoparticle interactions with biological systems. In this Perspective, we highlight the significant progress in this field, including studies on nonprotein corona components, lipid nanoparticles, and the role of the corona in endogenous organ targeting. We also discuss research opportunities in this field, particularly the need for improved characterization and standardization of analysis and how recent advances in artificial intelligence and ex vivo models can improve our understanding of the biomolecular corona in guiding nanomedicine design.

Investigation of the Cholesterol Biosynthesis by Heart-Cut Liquid Chromatography and Mass Spectrometric Detection

The biosynthesis and homeostasis of cholesterol are essential for cellular function. Cholesterol is a major lipid with multiple roles in membrane stability, signaling, or as a precursor for other molecules. Because of the structural similarity of the sterols involved in the biosynthesis, their accurate identification and quantification is still challenging. Moreover, the huge difference in the concentration of cholesterol and its precursors can cause interferences during the detection. To overcome these problems, a heart-cut liquid chromatographic method was developed by evaluating 38 different columns to achieve optimal separation. The method efficiently separates all sterol biosynthesis intermediates, with detection limits in the low nmol/L-range and an upper limit of quantification of 9 mmol/L for cholesterol by using triple quadrupole mass spectrometric detection. Investigation of lung carcinoma cells treated with statins demonstrated the capability to detect a biological response, showing inhibition of sterol synthesis. This technique offers a robust tool for studying cholesterol biosynthesis and its role in disease.

Phenotypic upregulation of hexocylceramides and ether-linked phosphocholines as markers of human extreme longevity

Centenarians and their relatives possess a notable survival advantage, with higher longevity and reduced susceptibility to major age-related diseases. To date, characteristic omics profiles of centenarians have been described, demonstrating that these individuals with exceptional longevity regulate their metabolism to adapt and incorporate more resilient biomolecules into their cells. Among these adaptations, the lipidomic profile stands out. However, it has not yet been determined whether this lipidomic profile is specific to centenarians or is the consequence of extreme longevity genetics and is also present in centenarians' offspring. This distinction is crucial for defining potential therapeutic targets that could help delay the aging process and associated pathologies. We applied mass-spectrometry-based techniques to quantify 569 lipid species in plasma samples from 39 centenarians, 63 centenarians' offspring, and 69 noncentenarians' offspring without familial connections. Based on this profile, we calculated different indexes to characterize the functional and structural properties of plasma lipidome. Our findings demonstrate that extreme longevity genetics (centenarians and centenarians' offspring) determines a specific lipidomic signature characterized by (i) an enrichment of hexosylceramides, (ii) a decrease of specific species of ceramides and sulfatides, (iii) a global increase of ether-PC and ether-LPC, and (iv) changes in the fluidity and diversity of specific lipid classes. We point out the conversion of ceramides to hexosylceramides and the maintenance of the levels of the ether-linked PC as a phenotypic trait to guarantee extreme longevity. We propose that this molecular signature is the result of an intrinsic adaptive program that preserves protective mechanisms and cellular identity.

Alahmari A, A. Alqabbani A, Aldayel AM. Exploring the landscape of Lipid Nanoparticles (LNPs): A comprehensive review of LNPs types and biological sources of lipids

Lipid nanoparticles (LNPs) have emerged as promising carriers for delivering therapeutic agents, including mRNA-based immunotherapies, in various biomedical applications. The use of LNPs allows for efficient delivery of drugs, resulting in enhanced targeted delivery to specific tissues or cells. These LNPs can be categorized into several types, including liposomes, solid lipid nanoparticles, nanostructured lipid carriers, and lipid-polymer hybrid nanoparticles. The preparation of LNPs involves the manipulation of their structural, dimensional, compositional, and physical characteristics via the use of different methods in the industry. Lipids used to construct LNPs can also be derived from various biological sources, such as natural lipids extracted from plants, animals, or microorganisms. This review dives into the different types of LNPs and their preparation methods. More importantly, it discusses all possible biological sources that are known to supply lipids for the creation of LNPs. Natural lipid reservoirs have surfaced as promising sources for generating LNPs. The use of LNPs in drug delivery is expected to increase significantly in the coming years. Herein, we suggest some environmentally friendly and biocompatible sources that can produce lipids for future LNPs production.

Monitoring concentration and lipid signature of plasma extracellular vesicles from HR+ metastatic breast cancer patients under CDK4/6 inhibitors treatment

Extracellular vesicles (EVs) are cell-derived small membrane structures that transport various molecules. They have emerged as potential circulating biomarkers for monitoring responses to cancer therapies. This study aimed to comprehensively characterize plasma-carried EVs in hormone receptor-positive (HR+) metastatic breast cancer (MBC) patients treated with first-line CDK4/6 inhibitors (iCDK4/6) combined with endocrine therapy. MBC patients were classified into three groups based on their response to therapy: resistant, intermediate or sensitive. In a prospective cohort, we monitored the concentration of circulating EVs, analyzed their lipid signature and correlated these factors with treatment response. To facilitate the translation of EV research to clinical practice, we established a three-step procedure: (1) EVs were isolated from plasma using semi-automatized size exclusion chromatography (SEC); (2) EV concentration, termed vesiclemia, was determined by drop counting via interferometric light microscopy (ILM); and (3) EV lipid composition was analyzed by mass spectrometry. ILM-based vesiclemia values were highly fluctuating upon iCDK4/6 treatment, while early increase associated with accelerated progression. Of note, vesiclemia remained a steady parameter over a 1-year period in age-matched healthy women. Additionally, analysis of the EV cargo unveiled a distinct sphingolipid profile, characterized by increased levels of ceramides and sphingomyelins in resistant patients within the first 2 months of treatment. Based on 16 sphingolipid species, sensitive and resistant patients were correctly classified with an overall accuracy of 82%. This specific sphingolipid pattern was exclusively discernible within EVs, and not in plasma, highlighting the significance of EVs in the early prediction of individual responses to iCDK4/6 and disease progression. Overall, this study provides insights of the longitudinal characterization of plasma-borne EVs in both a healthy group and HR+ MBC patients under iCDK4/6 therapies. Combined vesiclemia and EV sphingolipid profile emphasize the promising potential of EVs as non-invasive biomarkers for monitoring early treatment response.

A lipidomic dataset for epidemiological studies of acute myocardial infarction

Understanding the cause of coronary heart diseases relies on the analysis of data from a range of techniques on an epidemiological scale. Lipidomics, the identification and quantification of lipid species in a system, is an omic approach increasingly used in epidemiology. The altered concentration of lipids in plasma is one of the recognised risk factors for these diseases. An important first step in the analysis is to profile lipids in healthy volunteers at an epidemiological level to understand how the geneome influences risk factors; for this reason we made use of the control samples within a bigger case-control sample collection in Pakistan from patients with first acute myocardial infarctions. After extraction, the samples were infused into a Thermo Exactive Orbitrap, without any up-front chromatographic separation. The use of direct infusion allowed fast experiment, facilitating the analysis of large sets of samples. The raw data were processed and analysed using scripts within R, to extract all the meaningful information. The data set originated from this study is a valuable resource to both increase our knowledge in lipid metabolism associated with myocardial infarction, and test new methods and strategy in analysing big lipidomic data sets.

St. John's Wort Extract Ze 117 and Escitalopram Alter Plasma and Hippocampal Lipidome in a Rat Model of Chronic-Stress-Induced Depression

Chronic stress is a key factor in the development of depression. It leads to hyperactivation of the hypothalamic-pituitary-adrenal (HPA) axis, which in turn increases the formation of glucocorticoids (GCs). Chronically elevated GC levels disrupt neuroplasticity and affect brain lipid metabolism, which may, ultimately, contribute to the development of depression. This study aimed to investigate the effects of the antidepressants St. John's Wort extract and escitalopram on lipid metabolism in vivo. Therefore, repeated corticosterone injections were used to induce depression-like behavior in rats. Male Sprague-Dawley rats were stressed with corticosterone injections (40 mg/kg, s.c.) over 22 consecutive days and were concomitantly treated with varying doses of the St. John's wort extract Ze 117 (30, 90 or 180 mg/kg, p.o.) or escitalopram (10 mg/kg, p.o.) and behavioral changes were evaluated using a modified forced swim test. The results indicate that repeated corticosterone injections significantly decreased the latency to first immobility. Furthermore, co-treatment of corticosterone with Ze 117 increased latency to first immobility significantly compared to rats treated with corticosterone alone. To further investigate the biochemical effects of corticosterone-induced stress, as well as the possible counter-regulation by antidepressants, the lipidomes of the plasma and hippocampus samples were analyzed by shotgun mass spectrometry. Corticosterone-induced stress significantly altered key lipid metabolites in the plasma but not in the hippocampal samples. In the hippocampus, however, specific glycerophospholipids such as lysophosphatidylethanolamines (LPEs) increased with escitalopram treatment and with Ze 117, both showing significant correlations with behavioral parameters. In summary, our study shows significant behavioral- and lipidome-altering processes with Ze 117 and escitalopram in rat plasma and hippocampal samples, thereby providing new targets and biomarker ideas for clinical diagnosis and antidepressant intervention.

Pentadecanoic acid (C15:0, PA) induces mild maternal glucose intolerance and promotes the growth of the offspring partly through up-regulating liver PPARα and MAPK signaling pathways

Gestational diabetes mellitus (GDM) is one of the most common metabolic disturbances during pregnancy, which poses a serious threat to both maternal and offspring health. Pentadecanoic acid (C15:0, PA) is one of the most common odd-chain saturated fatty acids (OCS-FAs). However, its safety and nutritional value are yet to be verified. Herein, we provide a systematic assessment of the effects of PA on maternal and progeny health and insulin sensitivity for the first time. Our results showed that consumption of 1% PA during pregnancy could increase the contents of PA and heptadecanoic acid (C17:0) in maternal plasma, fetal tissue and offspring plasma, but it had no effect on embryonic development. During pregnancy, PA treatment caused mild insulin resistance, while it had little effect on the maternal body composition. During lactation, PA treatment caused mild insulin resistance and oxidative stress. Maternal body fat deposition was also reduced, but the growth rate of the offspring was faster. It is worth noting that PA treatment decreased plasma and liver TG content and increased the antioxidant capacity of the offspring. The effect of PA on the transcription and expression genes in the liver of pregnant mice was investigated using RNA-seq. PPARα and MAPK signaling pathways, both closely related to lipolysis, inflammation, oxidative stress, and insulin resistance were significantly increased. The expression of c-JUN, ERK, JNK and P65 proteins was also significantly up-regulated. In conclusion, our results suggest that 1% PA can induce a mild decrease in the maternal glucose tolerance and lipolysis mainly by activated MAPK and PPARα signaling. Moreover, low concentrations of PA may be an effective nutrient to alleviate the oxidative stress and reduce blood lipid levels of offspring.

Interlaboratory comparison of standardised metabolomics and lipidomics analyses in human and rodent blood using the MxP® Quant 500 kit

Metabolomics and lipidomics are pivotal in understanding phenotypic variations beyond genomics. However, quantification and comparability of mass spectrometry (MS)-derived data are challenging. Standardised assays can enhance data comparability, enabling applications in multi-center epidemiological and clinical studies. Here we evaluated the performance and reproducibility of the MxP® Quant 500 kit across 14 laboratories. The kit allows quantification of 634 different metabolites from 26 compound classes using triple quadrupole MS. Each laboratory analysed twelve samples, including human plasma and serum, lipaemic plasma, NIST SRM 1950, and mouse and rat plasma, in triplicates. 505 out of the 634 metabolites were measurable above the limit of detection in all laboratories, while eight metabolites were undetectable in our study. Out of the 505 metabolites, 412 were observed in both human and rodent samples. Overall, the kit exhibited high reproducibility with a median coefficient of variation (CV) of 14.3 %. CVs in NIST SRM 1950 reference plasma were below 25 % and 10 % for 494 and 138 metabolites, respectively. To facilitate further inspection of reproducibility for any compound, we provide detailed results from the in-depth evaluation of reproducibility across concentration ranges using Deming regression. Interlaboratory reproducibility was similar across sample types, with some species-, matrix-, and phenotype-specific differences due to variations in concentration ranges. Comparisons with previous studies on the performance of MS-based kits (including the AbsoluteIDQ p180 and the Lipidyzer) revealed good concordance of reproducibility results and measured absolute concentrations in NIST SRM 1950 for most metabolites, making the MxP® Quant 500 kit a relevant tool to apply metabolomics and lipidomics in multi-center studies.

Serum metabolome profiling in patients with mild cognitive impairment reveals sex differences in lipid metabolism

Alzheimer's disease (AD) affects more women than men. Although women live longer than men, it is not longevity alone, but other factors, including metabolic changes, that contribute to the higher risk of AD in women. Metabolic pathways have been implicated in AD progression, but studies to date examined targeted pathways, leaving many metabolites unmeasured. Sex is often a neglected biological variable, and most metabolomic studies were not designed to investigate sex differences in metabolomic profiles. Here, we performed untargeted metabolomic profiling of sera from male and female patients with mild cognitive impairment (MCI), a common precursor to AD, and matched controls. We discovered significant metabolic changes in individuals with MCI, and found several pathways that were strongly associated with sex. Peptide energy metabolism demonstrated sexual dimorphism. Lipid pathways exhibited the strongest differences between female and male MCI patients, including specific phosphatidylcholine lipids, lysophospholipids, long-chain fatty acids, and monoacylglycerols. 1-palmitoleoyl glycerol and 1-arachidonoyl glycerol were higher in female MCI subjects than in male MCI subjects with no differences between control males and females. Conversely, specific dicarboxylic fatty acids were lower in female MCI subjects than male MCI subjects. In cultured astrocytes, 1-arachidonoyl glycerol promoted phosphorylation of the transcriptional regulator sphingosine kinase 2, which was inhibited by the transient receptor potential vanilloid 1 receptor antagonists, as well as chromatin remodelling. Overall, we identified novel sex-specific metabolites in MCI patients that could serve as biomarkers of MCI in both sexes, help further define AD etiology, and reveal new potential prevention strategies for AD.

Lipid Dynamics in Pancreatic β-Cells: Linking Physiology to Diabetes Onset

Significance: Glucose-induced lipid metabolism is essential for preserving functional β-cells, and its disruption is linked to type 2 diabetes (T2D) development. Lipids are an integral part of the cells playing an indispensable role as structural components, energy storage molecules, and signals. Recent Advances: Glucose presence significantly impacts lipid metabolism in β-cells, where fatty acids are primarily synthesized de novo and/or are transported from the bloodstream. This process is regulated by the glycerolipid/free fatty acid cycle, which includes lipogenic and lipolytic reactions producing metabolic coupling factors crucial for insulin secretion. Disrupted lipid metabolism involving oxidative stress and inflammation is a hallmark of T2D. Critical Issues: Lipid metabolism in β-cells is complex involving multiple simultaneous processes. Exact compartmentalization and quantification of lipid metabolism and its intermediates, especially in response to glucose or chronic hyperglycemia, are essential. Current research often uses non-physiological conditions, which may not accurately reflect in vivo situations. Future Directions: Identifying and quantifying individual steps and their signaling, including redox, within the complex fatty acid and lipid metabolic pathways as well as the metabolites formed during acute versus chronic glucose stimulation, will uncover the detailed mechanisms of glucose-stimulated insulin secretion. This knowledge is crucial for understanding T2D pathogenesis and identifying pharmacological targets to prevent this disease. Antioxid. Redox Signal. 41, 865-889.

Phospholipid-derived lysophospholipids in (patho)physiology

Phospholipids (PL) are major components of cellular membranes and changes in PL metabolism have been associated with the pathogenesis of numerous diseases. Lysophosphatidylcholine (LPC) in particular, is a comparably abundant component of oxidatively damaged tissues. LPC originates from the cleavage of phosphatidylcholine (PC) by phospholipase A2 or the reaction of lipids with reactive oxygen species (ROS) such as HOCl. Another explanation of increased LPC concentration is the decreased re-acylation of LPC into PC. While there are also several other lysophospholipids, LPC is the most abundant lysophospholipid in mammals and will therefore be the focus of this review. LPC is involved in many physiological processes. It induces the migration of lymphocytes, fostering the production of pro-inflammatory compounds by inducing oxidative stress. LPC also "signals" via G protein-coupled and Toll-like receptors and has been implicated in the development of different diseases. However, LPCs are not purely "bad": this is reflected by the fact that the concentration and fatty acyl composition of LPC varies under different conditions, in plasma of healthy and diseased individuals, in tissues and different tumors. Targeting LPC and lipid metabolism and restoring homeostasis might be a potential therapeutic method for inflammation-related diseases.

Highly reliable LC-MS lipidomics database for efficient human plasma profiling based on NIST SRM 1950

Liquid chromatography coupled to high-resolution mass spectrometry (LC-HRMS)-based methods have become the gold standard methodology for the comprehensive profiling of the human plasma lipidome. However, both the complexity of lipid chemistry and LC-HRMS-associated data pose challenges to the characterization of this biological matrix. In accordance with the current consensus of quality requirements for LC-HRMS lipidomics data, we aimed to characterize the NIST® Standard Reference Material for Human Plasma (SRM 1950) using an LC-ESI(+/-)-MS method compatible with high-throughput lipidome profiling. We generated a highly curated lipid database with increased coverage, quality, and consistency, including additional quality assurance procedures involving adduct formation, within-method m/z evaluation, retention behavior of species within lipid chain isomers, and expert-driven resolution of isomeric and isobaric interferences. As a proof-of-concept, we showed the utility of our in-house LC-MS lipidomic database -consisting of 592 lipid entries- for the fast, comprehensive, and reliable lipidomic profiling of the human plasma from healthy human volunteers. We are confident that the implementation of this robust resource and methodology will have a significant impact by reducing data redundancy and the current delays and bottlenecks in untargeted plasma lipidomic studies.

Selective Enrichment via TiO2 Magnetic Nanoparticles Enables Deep Profiling of Circulating Neutral Glycosphingolipids

Circulating neutral glycosphingolipids (neutral GSLs (nGSLs)) are a unique subset of nGSLs that detach from organs or cell membranes and enter the bloodstream. Altered molecular distribution of circulating nGSL is increasingly associated with diseases. However, profiling of circulating nGSLs presents a lasting challenge due to their low abundances and structural complexity. Although TiO2 magnetic nanoparticles (TiO2 MNPs) were effective for the enrichment of nGSLs in brain tissue, the protocol showed limited selectivity for circulating nGSLs because their abundances were 100-times lower in human plasma than in brain tissue. In this work, we optimized the key parameters of selective enrichment by TiO2 MNPs and achieved 1:10,000 selectivity for nGSLs over interfering phospholipids, while maintaining ∼70% recovery for different subclasses of nGSLs. By integrating TiO2 MNP-based selective enrichment with reversed-phase liquid chromatography mass spectrometry and charge-tagging Paternò-Büchi derivatization, we achieved deep profiling of over 300 structures of nGSLs and sulfatides across 5 orders of magnitude in relative abundances, a significant leap regarding lipid coverage. We also depicted the structural atlas of nGSLs with defined headgroup, long-chain base, N-acyl chain, the location of desaturation, and 2-hydroxylation. Such information provides a valuable resource for lipidomic studies concerning the roles of circulating nGSLs in health and diseases.

The Biological Effect of Enriching the Plasma Content in Platelet-Rich Plasma: An In Vitro Study

BACKGROUND

Platelet-rich plasma (PRP) formulations have become valuable therapeutic tools in regenerative medicine. In addition, these blood derivates have been successfully included in cell therapy as fetal bovine serum substitutes, due to the real need to avoid the risk of host immunologic reactions and the animal disease transmission associated with reagents from animal origin. However, the protocols for obtaining them should be optimized to improve their biological potential.

METHODS

PRP-derived preparations with different concentrations of the platelet and plasma components were obtained from the blood of five donors by freeze-drying. Measurements of the pH, protein, and growth factor concentration were performed. Moreover, their biological effects on cell proliferation and migration and their angiogenic potential were assessed.

RESULTS

An increased plasma component concentration resulted in an augmented quantity of the total protein content, a significative variation in the hepatocyte growth factor concentration, and an experimental but clinically irrelevant alteration of the pH value. No significant changes were induced in their potential to enhance proliferative and migratory responses in epithelial cells, with the latter being reduced for dermal fibroblasts. The endothelial cell capacity for tube formation was significatively reduced.

CONCLUSIONS

An increased blood plasma content did not improve the biological potential of the formulations. However, they have emerged as a promising approach for regenerative therapies where neovascularization must be avoided.

Investigation of Lysophospholipids-DHA transport across an in vitro human model of blood brain barrier

Several studies emphasized on the preventive and therapeutic potential of Docosahexaenoic Acid (DHA, 22:6n-3) supplementation in chronic and age-related disorders including neurodegenerative diseases. Researchers principally studied the cerebral accretion of Lysophosphatidylcholine (LysoPC-DHA), the furthermost vital Lysophospholipid-DHA (LysoPL-DHA) in blood plasma. Nevertheless, the cerebral bioavailability of other LysoPL-DHA forms including Lysophosphatidylethanolamine (LysoPE-DHA), and Lysophosphatidylserine (LysoPS-DHA) were not extensively examined even though their vital biological functions in the brain. Hence, the aim of the present study was to evaluate the toxicity and transport of DHA in comparison to several LysoPL-DHA including LysoPC-DHA, LysoPE-DHA and LysoPS-DHA across a human model of blood-brain barrier (BBB). The human brain-like endothelial cells (hBLECs) monolayer tightness was evaluated by the parallel assessment of the permeability of fluorescent marker Lucifer yellow (LY) and revealed the absence of toxicity of non-esterified DHA and all LysoPL-DHA towards hBLECs. LysoPC-DHA, LysoPE-DHA and LysoPS-DHA displayed a higher recovery in the abluminal medium in comparison to non-esterified DHA at 30, 60 and 120 min post-incubation. Among all, LysoPS-DHA revealed the highest apparent coefficient permeability (Papp) 85.87 ± 4.24 x 10-6 cm s-1 and was significantly different than DHA, LysoPC-DHA and LysoPE-DHA. More interestingly, when studying the time course of Papp of DHA, LysoPC-DHA and LysoPE-DHA, at different post-incubation time, this permeability decreases with time especially for LysoPC-DHA and LysoPE-DHA, not for DHA. Furthermore, LysoPS-DHA exhibited the highest intracellular accumulation (10.39 ± 0.49 %) in hBLECs in comparison to all other tested lipids. Finally, differences in 3D structures and molecular electrostatic potential maps calculation of LysoPL-DHA could explain the dissimilar cerebral uptake of LysoPL-DHA. Altogether, our findings raise the novel hypothesis that LysoPS-DHA may represent a preferred physiological carrier of DHA to the brain.

Mapping the lipidomic secretome of the early equine embryo

The lipidomic secretions of embryos provide a unique opportunity to examine the cellular processes of the early conceptus. In this study we profiled lipids released by the early equine conceptus, using high-resolution mass spectrometry to detect individual lipid species. This study examined the lipidomic profile in embryo-conditioned media from in vivo-produced, 8-9 day-old equine embryos (n = 3) cultured in vitro for 36 h, analyzed over 3 timepoints. A total of 1,077 lipid IDs were recorded across all samples, containing predominantly glycerolipids. Seventy-nine of these were significantly altered in embryo conditioned-media versus media only control (p < 0.05, fold-change >2 or < 0.5). Fifty-five lipids were found to be released into the embryo-conditioned media, of which 54.5% were triacylglycerols and 23.6% were ceramides. The sterol lipid, cholesterol, was also identified and secreted in significant amounts as embryos developed. Further, 24 lipids were found to be depleted from the media during culture, of which 70.8% were diacylglycerols, 16.7% were triacylglycerols and 12.5% were ceramides. As lipid-free media contained consistently detectable lipid peaks, a further profile analysis of the various components of non-embryo-conditioned media consistently showed the presence of 137 lipids. Lipid peaks in non-embryo-conditioned media increased in response to incubation under mineral oil, and contained ceramides, diacylglycerols and triacylglycerols. These results emphasize the importance of a defined embryo culture medium and a need to identify the lipid requirements of the embryo precisely. This study sheds light on early embryo lipid metabolism and the transfer of lipids during in vitro culture.

Concordant inter-laboratory derived concentrations of ceramides in human plasma reference materials via authentic standards

In this community effort, we compare measurements between 34 laboratories from 19 countries, utilizing mixtures of labelled authentic synthetic standards, to quantify by mass spectrometry four clinically used ceramide species in the NIST (National Institute of Standards and Technology) human blood plasma Standard Reference Material (SRM) 1950, as well as a set of candidate plasma reference materials (RM 8231). Participants either utilized a provided validated method and/or their method of choice. Mean concentration values, and intra- and inter-laboratory coefficients of variation (CV) were calculated using single-point and multi-point calibrations, respectively. These results are the most precise (intra-laboratory CVs ≤ 4.2%) and concordant (inter-laboratory CVs < 14%) community-derived absolute concentration values reported to date for four clinically used ceramides in the commonly analyzed SRM 1950. We demonstrate that calibration using authentic labelled standards dramatically reduces data variability. Furthermore, we show how the use of shared RM can correct systematic quantitative biases and help in harmonizing lipidomics. Collectively, the results from the present study provide a significant knowledge base for translation of lipidomic technologies to future clinical applications that might require the determination of reference intervals (RIs) in various human populations or might need to estimate reference change values (RCV), when analytical variability is a key factor for recall during multiple testing of individuals.

Novel eicosanoid signature in plasma provides diagnostic for metabolic dysfunction-associated steatotic liver disease

There is a clinical need for a simple test implementable at the primary point of care to identify individuals with metabolic dysfunction-associated steatotic liver disease (MASLD) in the population. Blood plasma samples from adult patients with varying phenotypes of MASLD were used to identify a minimal set of lipid analytes reflective of underlying histologically confirmed MASLD. Samples were obtained from the NIDDK Nonalcoholic Steatohepatitis Clinical Research Network (NASH CRN) NAFLD Database prospective cohort study (MASLD group; N = 301). Samples of control subjects were obtained from cohort studies at the University of California San Diego (control group; N = 48). Plasma samples were utilized for targeted quantitation of circulating eicosanoids, related bioactive metabolites, and polyunsaturated fatty acids by ultra-high performance liquid chromatography-mass spectrometry (UPLC-MS) lipidomics analysis. Bioinformatic approaches were used to discover a panel of bioactive lipids that can be used as a diagnostic tool to identify MASLD. The final panel of fifteen lipid metabolites consists of 12 eicosanoid metabolites and 3 free fatty acids that were identified to be predictive for MASLD by multivariate area under the receiver operating characteristics curve (AUROC) analysis. The panel was highly predictive for MASLD with an AUROC of 0.999 (95% CI = 0.986-1.0) with only one control misclassified. A validation study confirmed the resulting MASLD LIPIDOMICS SCORE, which may require a larger-scale prospective study to optimize. This predictive model should guide the development of a non-invasive "point-of-care" test to identify MASLD patients requiring further evaluation for the presence of metabolic dysfunction-associated steatohepatitis.

Identification of blood lipid markers of docetaxel treatment in prostate cancer patients

Docetaxel is commonly used for treatment of castration-resistant prostate cancer. Unfortunately, many prostate cancer patients develop resistance to docetaxel. Clinical markers less invasive than biopsies, such as blood samples, would be ideal for monitoring and predicting patient treatment outcomes to docetaxel. Lipid alterations are often associated with the progression of many cancers, including prostate cancer. This study investigated the use of lipids from whole blood as clinical markers for docetaxel resistance in a small cohort of patients with prostate cancer. Qualitative lipidomics was performed by liquid chromatography-tandem mass spectrometry to assess the lipid composition of prostate cancer cells exposed to docetaxel as well as whole blood from prostate cancer patients before, during and after docetaxel treatment. Three patients had castration resistant prostate cancer, three had castration sensitive prostate cancer, and four had de novo prostate cancer during the extent of the study. Mean decrease accuracy and classical univariate receiving operating characteristic curve analyses were performed to identify potential biomarkers. In total, 245 and 221 altered lipids were identified from a second stage of mass spectrometry analysis of prostate cancer cells and clinical blood samples, respectively. Both models indicated that docetaxel treatment altered ether-linked phosphatidylcholines, lysophosphatidylcholine, diacylglycerols, ceramides, hexosylceramides, and sphingomyelins. The results also indicated several lipid changes were associated with sphingolipid signaling and metabolism, and glycerophospholipid metabolism. Collectively, these data suggest the potential usage of identified lipid species as indicators of docetaxel resistance in prostate cancer.

Plasma Ceramides and Other Sphingolipids in Relation to Incident Prediabetes in a Longitudinal Biracial Cohort

CONTEXT

Sphingolipids are linked to the pathogenesis of type 2 diabetes.

OBJECTIVE

To test the hypothesis that plasma sphingolipid profiles predict incident prediabetes.

DESIGN

A case-control study nested in the Pathobiology of Prediabetes in a Biracial Cohort study, a 5-year follow-up study.

SETTING

Academic health center.

PARTICIPANTS

Normoglycemic adults enrolled in the Pathobiology of Prediabetes in a Biracial Cohort study. Assessments included oral glucose tolerance test, insulin sensitivity, and insulin secretion. Participants with incident prediabetes were matched in age, sex, and ethnicity with nonprogressors.

INTERVENTIONS

We assayed 58 sphingolipid species (ceramides, monohexosyl ceramides, sphingomyelins, and sphingosine) using liquid chromatography/tandem mass spectrometry in baseline plasma levels from participants and determined association with prediabetes risk.

MAIN OUTCOME MEASURE

The primary outcome was progression from normoglycemia to prediabetes, defined as impaired fasting glucose or impaired glucose tolerance.

RESULTS

The mean age of participants (N = 140; 50% Black, 50% female) was 48.1 ± 8.69 years, body mass index 30.1 ± 5.78 kg/m2, fasting plasma glucose 92.7 ± 5.84 mg/dL, and 2-hour plasma glucose 121 ± 23.3 mg/dL. Of the 58 sphingolipid species assayed, higher ratios of sphingomyelin C26:0/C26:1 (OR, 2.73 [95% CI, 1.172-4.408], P = .015) and ceramide C18:0/C18:1 (OR, 1.236 [95% CI, 1.042-1.466], P = .015) in baseline plasma specimens were significantly associated with progression to prediabetes during the 5-year follow-up period, after adjustments for age, race, sex, body mass index, fasting plasma glucose, 2-hour plasma glucose, insulin sensitivity, and insulin secretion.

CONCLUSION

We conclude that the saturated-to-monounsaturated ratios of long-chain ceramide C18:0/C18:1 and very-long-chain sphingomyelin C26:0/C26:1 are potential biomarkers of prediabetes risk among individuals with parental history of type 2 diabetes.

Metabolic ripple effects - deciphering how lipid metabolism in cancer interfaces with the tumor microenvironment

Cancer cells require a constant supply of lipids. Lipids are a diverse class of hydrophobic molecules that are essential for cellular homeostasis, growth and survival, and energy production. How tumors acquire lipids is under intensive investigation, as these mechanisms could provide attractive therapeutic targets for cancer. Cellular lipid metabolism is tightly regulated and responsive to environmental stimuli. Thus, lipid metabolism in cancer is heavily influenced by the tumor microenvironment. In this Review, we outline the mechanisms by which the tumor microenvironment determines the metabolic pathways used by tumors to acquire lipids. We also discuss emerging literature that reveals that lipid availability in the tumor microenvironment influences many metabolic pathways in cancers, including those not traditionally associated with lipid biology. Thus, metabolic changes instigated by the tumor microenvironment have 'ripple' effects throughout the densely interconnected metabolic network of cancer cells. Given the interconnectedness of tumor metabolism, we also discuss new tools and approaches to identify the lipid metabolic requirements of cancer cells in the tumor microenvironment and characterize how these requirements influence other aspects of tumor metabolism.

A Direct Link Implicating Loss of SLC26A6 to Gut Microbial Dysbiosis, Compromised Barrier Integrity, and Inflammation

BACKGROUND & AIMS

Putative anion transporter-1 (PAT1, SLC26A6) plays a key role in intestinal oxalate and bicarbonate secretion. PAT1 knockout (PKO) mice exhibit hyperoxaluria and nephrolithiasis. Notably, diseases such as inflammatory bowel disease are also associated with higher risk of hyperoxaluria and nephrolithiasis. However, the potential role of PAT1 deficiency in gut-barrier integrity and susceptibility to colitis is currently elusive.

METHODS

Age-matched PKO and wild-type littermates were administered 3.5% dextran sulfate sodium in drinking water for 6 days. Ileum and colon of control and treated mice were harvested. Messenger RNA and protein expression of tight junction proteins were determined by reverse transcription polymerase chain reaction and western blotting. Severity of inflammation was assessed by measuring diarrheal phenotype, cytokine expression, and hematoxylin and eosin staining. Gut microbiome and associated metabolome were analyzed by 16S ribosomal RNA sequencing and mass spectrometry, respectively.

RESULTS

PKO mice exhibited significantly higher loss of body weight, gut permeability, colonic inflammation, and diarrhea in response to dextran sulfate sodium treatment. In addition, PKO mice showed microbial dysbiosis and significantly reduced levels of butyrate and butyrate-producing microbes compared with controls. Co-housing wild-type and PKO mice for 4 weeks resulted in PKO-like signatures on the expression of tight junction proteins in the colons of wild-type mice.

CONCLUSIONS

Our data demonstrate that loss of PAT1 disrupts gut microbiome and related metabolites, decreases gut-barrier integrity, and increases host susceptibility to intestinal inflammation. These findings, thus, highlight a novel role of the oxalate transporter PAT1 in promoting gut-barrier integrity, and its deficiency appears to contribute to the pathogenesis of inflammatory bowel diseases.

Polygenic scores for complex traits are associated with changes in concentration of circulating lipid species

Understanding perturbations in circulating lipid levels that often occur years or decades before clinical symptoms may enhance our understanding of disease mechanisms and provide novel intervention opportunities. Here, we assessed if polygenic scores (PGSs) for complex traits could detect lipid dysfunctions related to the traits and provide new biological insights. We constructed genome-wide PGSs (approximately 1 million genetic variants) for 50 complex traits in 7,169 Finnish individuals with routine clinical lipid profiles and lipidomics measurements (179 lipid species). We identified 678 associations (P < 9.0 × 10-5) involving 26 traits and 142 lipids. Most of these associations were also validated with the actual phenotype measurements where available (89.5% of 181 associations where the trait was available), suggesting that these associations represent early signs of physiological changes of the traits. We detected many known relationships (e.g., PGS for body mass index (BMI) and lysophospholipids, PGS for type 2 diabetes and triacyglycerols) and those that suggested potential target for prevention strategies (e.g., PGS for venous thromboembolism and arachidonic acid). We also found association of PGS for favorable adiposity with increased sphingomyelins levels, suggesting a probable role of sphingomyelins in increased risk for certain disease, e.g., venous thromboembolism as reported previously, in favorable adiposity despite its favorable metabolic effect. Altogether, our study provides a comprehensive characterization of lipidomic alterations in genetic predisposition for a wide range of complex traits. The study also demonstrates potential of PGSs for complex traits to capture early, presymptomatic lipid alterations, highlighting its utility in understanding disease mechanisms and early disease detection.

Daily koumiss has positive regulatory effects on blood lipids and immune system: A metabolomics study

Koumiss, a traditional Mongolian beverage, is believed to possess high nutritional value and potential medical benefits. However, there is a lack of comprehensive research on its potential impact on the human body. Metabolomics, as a sensitive approach in systems biology, offers a new avenue for studying the overall effects of koumiss. In this work, metabolomics was utilized to identify potential biomarkers and pathways associated with koumiss using UPLC-MS detection, pattern recognition analysis, pathway enrichment, network pharmacology. The findings indicated that koumiss exerts a beneficial regulatory influence on lipid metabolism, neurotransmitters, hormones, phospholipids and arachidonic acid metabolism, besides up regulating the content of nutrients. It could reduce the risks of dyslipidemia and inflammatory responses. This study confirmed the benign regulatory effect of koumiss on normal organism from the perspective of endogenous metabolites, and provided objective support for the promotion and application of this ethnic food.

A plasma lipid signature in acute human traumatic brain injury: Link with neuronal injury and inflammation markers

Traumatic brain injury (TBI) leads to major membrane lipid breakdown. We investigated plasma lipids over 3 days post-TBI, to identify a signature of acute human TBI and assess its correlation with neuronal injury and inflammation. Plasma from patients with TBI (Abbreviated Injury Scale (AIS)3 - serious injury, n = 5; AIS4 - severe injury, n = 8), and controls (n = 13) was analysed for lipidomic profile, neurofilament light (NFL) and cytokines, and the omega-3 index was measured in red blood cells. A lipid signature separated TBI from controls, at 24 and 72 h. Major species driving the separation were: lysophosphatidylcholine (LPC), phosphatidylcholine (PC) and hexosylceramide (HexCer). Docosahexaenoic acid (DHA, 22:6) and LPC (0:0/22:6) decreased post-injury. NFL levels were increased at 24 and 72 h post-injury in AIS4 TBI vs. controls. Interleukin (IL-)6, IL-2 and IL-13 were elevated at 24 h in AIS4 patients vs. controls. NFL and IL-6 were negatively correlated with several lipids. The omega-3 index at admission was low in all patients (controls: 4.3 ± 1.1% and TBI: 4.0 ± 1.1%) and did not change significantly over 3 days post-injury. We have identified specific lipid changes, correlated with markers of injury and inflammation in acute TBI. These observations could inform future lipid-based therapeutic approaches.

High-throughput relative quantification of fatty acids by 12-plex isobaric labeling and microchip capillary electrophoresis - Mass spectrometry

BACKGROUND

Fatty acids (FAs) are essential cellular components and play important roles in various biological processes. Importantly, FAs produced by microorganisms from renewable sugars are considered sustainable substrates for biodiesels and oleochemicals. Their complex structures and diverse functional roles in biochemical processes necessitate the development of efficient and accurate methods for their quantitative analysis.

RESULTS

Here, we developed a novel method for relative quantification of FAs by combining 12-plex isobaric N,N-dimethyl leucine-derivatized ethylenediamine (DiLeuEN) labeling and microchip capillary electrophoresis-mass spectrometry (CE-MS). This method enables simultaneous quantification of 12 samples in a single MS analysis. DiLeuEN labeling introduced tertiary amine center structure into FAs, which makes them compatible with the positive mode separation of commercial microchip CE systems and further improves the sensitivity. The CE separation parameters were optimized, and the quantification accuracy was assessed using FA standards. Microchip CE-MS detection exhibited high sensitivity with a femtomole level detection limit and a total analysis time within 8 min. Finally, the applicability of our method to complex biological samples was demonstrated by analyzing FAs produced by four industrially relevant yeast strains (Saccharomyces cerevisiae, Yarrowia lipolytica YB-432, Yarrowia lipolytica Po1f and Rhodotorula glutinis). The analysis time for each sample is less than 1 min.

SIGNIFICANCE

This work addresses the current challenges in the field by introducing a method that combines microchip-based capillary electrophoresis separation with multiplex isobaric labeling. Our method not only offers remarkable sensitivity and rapid analysis speed but also the capability to quantify fatty acids across multiple samples simultaneously, which holds significant potential for extensive application in FA quantitative studies in diverse research areas, promising an enhanced understanding of FA functions and mechanisms.

Valproic acid targets IDH1 mutants through alteration of lipid metabolism

Histone deacetylases (HDACs) have a wide range of targets and can rewire both the chromatin and lipidome of cancer cells. In this study, we show that valproic acid (VPA), a brain penetrant anti-seizure medication and histone deacetylase inhibitor, inhibits the growth of IDH1 mutant tumors in vivo and in vitro, with at least some selectivity over IDH1 wild-type tumors. Surprisingly, genes upregulated by VPA showed no enhanced chromatin accessibility at the promoter, but there was a correlation between VPA-downregulated genes and diminished promoter chromatin accessibility. VPA inhibited the transcription of lipogenic genes and these lipogenic genes showed significant decreases in promoter chromatin accessibility only in the IDH1 MT glioma cell lines tested. VPA inhibited the mTOR pathway and a key lipogenic gene, fatty acid synthase (FASN). Both VPA and a selective FASN inhibitor TVB-2640 rewired the lipidome and promoted apoptosis in an IDH1 MT but not in an IDH1 WT glioma cell line. We further find that HDACs are involved in the regulation of lipogenic genes and HDAC6 is particularly important for the regulation of FASN in IDH1 MT glioma. Finally, we show that FASN knockdown alone and VPA in combination with FASN knockdown significantly improved the survival of mice in an IDH1 MT primary orthotopic xenograft model in vivo. We conclude that targeting fatty acid metabolism through HDAC inhibition and/or FASN inhibition may be a novel therapeutic opportunity in IDH1 mutant gliomas.

Ammonium bicarbonate buffers combined with hybrid surface technology columns improve the peak shape of strongly tailing lipids

BACKGROUND

Lipids such as phosphatidic acids (PAs) and cardiolipins (CLs) present strongly tailing peaks in reversed phase liquid chromatography, which entails low detectability. They are usually analyzed by hydrophilic interaction liquid chromatography (HILIC), which hampers high-throughput lipidomics. Thus, there is a great need for improved analytical methods in order to obtain a broader coverage of the lipidome in a single chromatographic method. We investigated the effect of ammonium bicarbonate (ABC) on peak asymmetry and detectability, in comparison with ammonium formate (AFO) on both a conventional BEH C18 column and an HST-CSH C18 column.

RESULTS

The combination of 2.5 mM ABC buffer pH 8 with an HST-CSH C18 column produced significantly improved results, reducing the asymmetry factor at 10 % peak height of PA 16:0/18:1 from 8.4 to 1.6. Furthermore, on average, there was up to a 54-fold enhancement in the peak height of its [M - H]- ion compared to AFO and the BEH C18 column. We confirmed this beneficial effect on other strongly tailing lipids, with accessible phosphate moieties e.g., cardiolipins, phosphatidylinositol phosphate, phosphatidylinositol bisphosphate, phosphorylated ceramide and phosphorylated sphingosine. Furthermore, we found an increased detectability of phospho- and sphingolipids up to 28 times in negative mode when using an HST-CSH C18 column. The method was successfully applied to mouse liver samples, where previously undetected endogenous phospholipids could be analyzed with improved chromatographic separation.

SIGNIFICANCE

In conclusion, the use of 2.5 mM ABC substantially improved the peak shape of PAs and enhanced the detectability of the lipidome in negative mode on an RPLC-ESI-Q-TOF-MS system on both BEH C18 and HST-CSH C18 columns. This method provides a wider coverage of the lipidome with one single injection for future lipidomic applications in negative mode.

Bilayer lipids modulate ligand binding to atypical chemokine receptor 3

Chemokine receptors belong to the large class of G protein-coupled receptors (GPCRs) and are involved in a number of (patho)physiological processes. Previous studies highlighted the importance of membrane lipids for modulating GPCR structure and function. However, the underlying mechanisms of how lipids regulate GPCRs are often poorly understood. Here, we report that anionic lipid bilayers increase the binding affinity of the chemokine CXCL12 for the atypical chemokine receptor 3 (ACKR3) by modulating the CXCL12 binding kinetics. Notably, the anionic bilayer favors CXCL12 over the more positively charged chemokine CXCL11, which we explained by bilayer interactions orienting CXCL12 but not CXCL11 for productive ACKR3 binding. Furthermore, our data suggest a stabilization of active ACKR3 conformations in anionic bilayers. Taken together, the described regulation of chemokine selectivity of ACKR3 by the lipid bilayer proposes an extended version of the classical model of chemokine binding including the lipid environment of the receptor.

Associations of Plasma Lipidomic Profiles with Uric Acid and Hyperuricemia Risk in Middle-Aged and Elderly Chinese

Little is known about the links of disturbed lipid metabolism with hyperuricemia (HUA). We aimed to investigate the associations of lipidomic profiles with uric acid (UA)/HUA and their modifying factors in middle-aged and elderly Chinese. A total of 350 lipids were quantified in 2247 community-based Chinese aged 50-70 years by high-coverage targeted lipidomics. HUA was defined by plasma UA > 420 μmol/L in men or > 360 μmol/L in women. The prevalence of HUA in this population was 10.4%. After multivariable adjustment including BMI and lifestyle, 123 lipids were significantly associated with UA, predominantly glycerolipids (GLs) and glycerophospholipids (GPs). Specifically, diacylglycerol [DAG (16:0/22:5), DAG (16:0/22:6), DAG (18:1/20:5), DAG (18:1/22:6)], phosphatidylcholine [PC (16:0/20:5)), and triacylglycerol (TAG (53:0)] were the most significant lipid signatures positively associated with HUA risk, while lysophosphatidylcholine (LPC (20:2)) was inversely associated with HUA risk (p < 0.05). Network analysis also showed a positive association between TAGs/PCs/DAGs contained module and HUA risk (p < 0.01). Notably, HUA-related lipids were associated with de novo lipogenesis fatty acids, especially 16:1n-7 (Spearman correlation coefficients = 0.32-0.41, p < 0.001). Reduced rank regression showed that increased aquatic products intake was correlated to elevated HUA risk and HUA-associated lipids; while high dairy consumption was correlated with low level of HUA-associated lipids (|factor loadings| ≥ 0.2). Moreover, mediation analyses suggested that the lipid-HUA associations were partially mediated by retinol-binding protein 4 (RBP4, mediation proportion 5-14%), an adipokine linked with dyslipidemia and insulin resistance. In conclusion, disturbed specific metabolisms of GLs and GPs were associated with high prevalent HUA, partially mediated by RBP4 and/or influenced by certain dietary factors.

Supplementary Information

The online version contains supplementary material available at 10.1007/s43657-024-00157-x.

Biomarker Predictors of Clinical Efficacy of the Anti-IgE Biologic Omalizumab in Severe Asthma in Adults: Results of the SoMOSA Study

Background: The anti-IgE monoclonal antibody omalizumab is widely used for severe asthma. This study aimed to identify biomarkers that predict clinical improvement during 1 year of omalizumab treatment. Methods: One-year open-label Study of Mechanisms of action of Omalizumab in Severe Asthma (SoMOSA) involving 216 patients with severe (Global Initiative for Asthma step 4/5) uncontrolled atopic asthma (at least two severe exacerbations in the previous year) taking high-dose inhaled corticosteroids and long-acting β-agonists with or without maintenance oral corticosteroids. It had two phases: 0-16 weeks, to assess early clinical improvement by Global Evaluation of Therapeutic Effectiveness (GETE); and 16-52 weeks, to assess late responses based on ⩾50% reduction in exacerbations or mOCS dose. All participants provided samples (exhaled breath, blood, sputum, urine) before and after 16 weeks of omalizumab treatment. Measurements and Main Results: A total of 191 patients completed phase 1; 63% had early improvement. Of 173 who completed phase 2, 69% had reduced exacerbations by ⩾50% and 57% (37 of 65) taking mOCSs had reduced their dose by ⩾50%. The primary outcomes 2,3-dinor-11-β-PGF2α, GETE score, and standard clinical biomarkers (blood and sputum eosinophils, exhaled nitric oxide, serum IgE) did not predict either clinical response. Five volatile organic compounds and five plasma lipid biomarkers strongly predicted the ⩾50% reduction in exacerbations (receiver operating characteristic areas under the curve of 0.780 and 0.922, respectively) and early responses (areas under the curve of 0.835 and 0.949, respectively). In an independent cohort, gas chromatography/mass spectrometry biomarkers differentiated between severe and mild asthma. Conclusions: This is the first discovery of omics biomarkers that predict improvement in asthma with biologic agent treatment. Prospective validation and development for clinical use is justified.

An E115A Missense Variant in CERS2 Is Associated With Increased Sleeping Energy Expenditure and Hepatic Insulin Resistance in American Indians

Genetic determinants of interindividual differences in energy expenditure (EE) are largely unknown. Sphingolipids, such as ceramides, have been implicated in the regulation of human EE via mitochondrial uncoupling. In this study, we investigated whether genetic variants within enzymes involved in sphingolipid synthesis and degradation affect EE and insulin-related traits in a cohort of American Indians informative for 24-h EE and glucose disposal rates during a hyperinsulinemic-euglycemic clamp. Association analysis of 10,084 genetic variants within 28 genes involved in sphingolipid pathways identified a missense variant (rs267738, A>C, E115A) in exon 4 of CERS2 that was associated with higher sleeping EE (116 kcal/day) and increased rates of endogenous glucose production during basal (5%) and insulin-stimulated (43%) conditions, both indicators of hepatic insulin resistance. The rs267738 variant did not affect ceramide synthesis in HepG2 cells but resulted in a 30% decrease in basal mitochondrial respiration. In conclusion, we provide evidence that the CERS2 rs267738 missense variant may influence hepatic glucose production and postabsorptive sleeping metabolic rate.

ARTICLE HIGHLIGHTS

Synovial 5-Lipoxygenase-Derived Oxylipins Define a Lympho-Myeloid-Enriched Synovium

OBJECTIVE

Oxylipins are bioactive lipids derived from polyunsaturated fatty acids (PUFAs) that modulate inflammation and may remain overexpressed in refractory synovitis. In plasma, they could also be biomarkers of synovial pathology. The aim of this study is to determine if synovial oxylipins in inflamed joints correlate with plasma oxylipins and with synovial histologic patterns.

METHODS

Patients with established rheumatoid or psoriatic arthritis with active disease despite treatment were recruited, and paired synovial tissue (ST) and plasma were collected. Oxylipins were determined by liquid chromatography with tandem mass spectrometry and were classified into groups according to their PUFA precursor and enzyme. The expression of CD20, CD68, CD3, and CD138 was obtained to describe synovial histology. Cell-specific expression of oxylipin-related genes was identified by examining available synovial single-cell RNA sequencing data.

RESULTS

We included a total of 32 ST and 26 paired-plasma samples. A total of 71 oxylipins were identified in ST, but only 24 were identified in plasma. Only levels of 9,10-dihydroxyoctadecenoic acid and tetranor-Prostaglandin FM had a significant positive correlation between plasma and ST. Several oxylipins and oxylipin-related genes were differentially expressed among synovial phenotypes. Specifically, several 5-lipoxygenase (LOX)-derived oxylipins were statistically elevated in the lympho-myeloid phenotype and associated with B cell expression in rheumatoid arthritis samples.

CONCLUSION

The lack of correlation between ST and plasma oxylipins suggests that ST lipid profiling better characterizes active pathways in treated joints. Synovial 5-LOX-derived oxylipins were highly expressed in lympho-myeloid-enriched synovium. Combination therapy with 5-LOX inhibitors to improve refractory inflammation may be needed in patients with this histologic group.

The fate of intracellular S1P regulates lipid droplet turnover and lipotoxicity in pancreatic beta-cells

Lipotoxicity has been considered the main cause of pancreatic beta-cell failure during type 2 diabetes development. Lipid droplets (LD) are believed to regulate the beta-cell sensitivity to free fatty acids (FFA), but the underlying molecular mechanisms are largely unclear. Accumulating evidence points, however, to an important role of intracellular sphingosine-1-phosphate (S1P) metabolism in lipotoxicity-mediated disturbances of beta-cell function. In the present study, we compared the effects of an increased irreversible S1P degradation (S1P-lyase, SPL overexpression) with those associated with an enhanced S1P recycling (overexpression of S1P phosphatase 1, SGPP1) on LD formation and lipotoxicity in rat INS1E beta-cells. Interestingly, although both approaches led to a reduced S1P concentration, they had opposite effects on the susceptibility to FFA. Overexpression of SGPP1 prevented FFA-mediated caspase-3 activation by a mechanism involving an enhanced lipid storage capacity and prevention of oxidative stress. In contrast, SPL overexpression limited LD biogenesis, content, and size, while accelerating lipophagy. This was associated with FFA-induced hydrogen peroxide formation, mitochondrial fragmentation, and dysfunction, as well as ER stress. These changes coincided with the upregulation of proapoptotic ceramides but were independent of lipid peroxidation rate. Also in human EndoC-βH1 beta-cells, suppression of SPL with simultaneous overexpression of SGPP1 led to a similar and even more pronounced LD phenotype as that in INS1E-SGPP1 cells. Thus, intracellular S1P turnover significantly regulates LD content and size and influences beta-cell sensitivity to FFA.

Soluble epoxide hydrolase inhibition reverses cognitive dysfunction in a mouse model of metabolic syndrome by modulating inflammation

Midlife metabolic syndrome (MetS) is associated with cognitive impairment in late life. The mechanism of delayed MetS-related cognitive dysfunction (MetSCD) is not clear, but it has been linked to systemic inflammation and chronic cerebral microangiopathy. Currently there is no treatment for late life MetSCD other than early risk factor modification. We investigated the effect of soluble epoxide hydrolase (sEH) inhibitor 4-[[trans-4-[[(tricyclo[3.3.1.13,7]dec-1-ylamino)carbonyl]amino]cyclohexyl]oxy]-benzoic acid (t-AUCB) on cognitive performance, cerebral blood flow (CBF), and central and peripheral inflammation in the high-fat diet (HFD) model of MetS in mice. At 6 weeks of age, male mice were randomly assigned to receive either HFD or standard chow (STD) for 6 months. Mice received either t-AUCB or vehicle for 4 weeks. Cognitive performance was evaluated, followed by CBF measurement using magnetic resonance imaging (MRI). At the end of the study, blood was collected for measurement of eicosanoids and inflammatory cytokines. The brains were then analyzed by immunohistochemistry for glial activation markers. The HFD caused a significant impairment in novel object recognition. Treatment with t-AUCB increased plasma levels of 14,15-EET, prevented this cognitive impairment and modified hippocampal glial activation and plasma cytokine levels, without affecting CBF in mice on HFD. In conclusion, sEH inhibition for four weeks prevents cognitive deficits in mice on chronic HFD by modulating inflammatory processes without affecting CBF.

The Non-Targeted Lipidomic-Based Classifier Reveals Two Candidate Biomarkers for Ischemic Stroke in Hypertensive Individuals

Introduction

Traditional clinical risk factors are insufficient to estimate the residual risk of large-vessel ischemic stroke. Non-targeted lipidomic techniques provide an opportunity to evaluate these risks.

Methods

Plasma samples were collected from 113 hypertensive individuals, including 55 individuals at high risk of ischemic stroke and 58 matched individuals, in a prospective nested case-control cohort. To identify dysregulated lipid metabolites, we conducted multivariate and univariate analyses. A classifier based on a cross-validated procedure was employed to select the optimal combination of lipid species and their ratios.

Results

We identified 23 dysregulated lipid species in patients with and without ischemic stroke, including 16 (69.6%) up-regulated and 7 (30.4%) down-regulated lipid species. Through internal cross-validation, the optimal combination of two lipid features (phosphatidylcholine 34:2 and triglyceride 18:1/18:1/22:1 / phosphatidylcholine 34:2, referred to as ischemic stroke-related 2 lipid features - IS2LP) was selected, leading to a more precise prediction probability for ischemic stroke within 3.9 years. In the comparison of different risk factors, the traditional risk score, the IS2LP risk score, and the combination of the traditional risk score with IS2LP yield AUC values of 0.613(95% CI:0.509-0.717), 0.833(95% CI:0.755-0.911), and 0.843(95% CI:0.777-0.916), respectively. The combination of the traditional risk score and IS2LP exhibited significantly improved discriminative performance, with an integrated discrimination improvement (IDI) of 0.31 (p<0.001) and a continuous net reclassification improvement (NRI) of 1.06 (p < 0.001) compared to the traditional risk score.

Conclusion

We identified new lipidomic biomarkers associated with the futural event of large-vessel ischemic stroke. These lipid species could serve as potential blood biomarkers for assessing the residual risk of ischemic stroke in hypertensive individuals.

Dysfunctional VLDL metabolism in MASLD

Lipidomics has unveiled the intricate human lipidome, emphasizing the extensive diversity within lipid classes in mammalian tissues critical for cellular functions. This diversity poses a challenge in maintaining a delicate balance between adaptability to recurring physiological changes and overall stability. Metabolic Dysfunction-Associated Steatotic Liver Disease (MASLD), linked to factors such as obesity and diabetes, stems from a compromise in the structural and functional stability of the liver within the complexities of lipid metabolism. This compromise inaccurately senses an increase in energy status, such as during fasting-feeding cycles or an upsurge in lipogenesis. Serum lipidomic studies have delineated three distinct metabolic phenotypes, or "metabotypes" in MASLD. MASLD-A is characterized by lower very low-density lipoprotein (VLDL) secretion and triglyceride (TG) levels, associated with a reduced risk of cardiovascular disease (CVD). In contrast, MASLD-C exhibits increased VLDL secretion and TG levels, correlating with elevated CVD risk. An intermediate subtype, with a blend of features, is designated as the MASLD-B metabotype. In this perspective, we examine into recent findings that show the multifaceted regulation of VLDL secretion by S-adenosylmethionine, the primary cellular methyl donor. Furthermore, we explore the differential CVD and hepatic cancer risk across MASLD metabotypes and discuss the context and potential paths forward to gear the findings from genetic studies towards a better understanding of the observed heterogeneity in MASLD.