A comprehensive UHPLC-MS/MS method for metabolomics profiling of signaling lipids: Markers of oxidative stress, immunity and inflammation

Signaling lipids (SLs) play a crucial role in various signaling pathways, featuring diverse lipid backbone structures. Emerging evidence showing the biological significance and biomedical values of SLs has strongly spurred the advancement of analytical approaches aimed at profiling SLs. Nevertheless, the dramatic differences in endogenous abundances across lipid classes as well as multiple isomers within the same lipid class makes the development of a generic analytical method challenging. A better analytical method that combines comprehensive coverage and high sensitivity is needed to enable us to gain a deeper understanding of the biochemistry of these molecules in health and disease. In this study, we developed a fast and comprehensive targeted ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method for profiling SLs. The platform enables analyses of 260 metabolites covering oxylipins (isoprostanes, prostaglandins and other oxidized lipids), free fatty acids, lysophospholipids, sphingoid bases (C16, C18), platelet activating factors (C16, C18), endocannabinoids and bile acids. Various validation parameters including linearity, limit of detection, limit of quantification, extraction recovery, matrix effect, intra-day and inter-day precision were used to characterize this method. Metabolite quantitation was successfully achieved in both NIST Standard Reference Material for human plasma (NIST SRM 1950) and pooled human plasma, with 109 and 144 metabolites quantitated. The quantitation results in NIST SRM 1950 plasma demonstrated good correlations with certified or previously reported values in published literature. This study introduced quantitative data for 37 SLs for the first time. Metabolite concentrations measured in NIST SRM 1950 will serve as essential reference data for facilitating interlaboratory comparisons. The methodology established here will be the cornerstone for in-depth profiling of signaling lipids across diverse biological samples and contexts.

Synthesis of phospholipids in human placenta

INTRODUCTION

Placental phospholipid synthesis is critical for the expansion of the placental exchange surface area and for production of signaling molecules. Despite their importance, it is not yet established which enzymes involved in the de novo synthesis and remodeling of placental phospholipids are expressed and active in the human placenta.

METHODS

We identified phospholipid synthesis enzymes by immunoblotting in placental homogenates and immunofluorescence in placenta tissue sections. Primary human trophoblast (PHT) cells from term healthy placentas (n = 10) were cultured and exposed to 13C labeled fatty acids (16:0, 18:1 and 18:2 n-6, 22:6 n-3) for 2 and 24 h. Three phospholipid classes; phosphatidic acid, phosphatidylcholine, and lysophosphatidylcholine containing 13C fatty acids were quantified by Liquid Chromatography with tandem mass spectrometry (LC/MS-MS).

RESULTS

Acyl transferase and phospholipase enzymes were detected in human placenta homogenate and primarily expressed in the syncytiotrophoblast. Three representative 13C fatty acids (16:0, 18:1 and 18:2 n-6) were incorporated rapidly into phosphatidic acid in trophoblasts, but 13C labeled docosahexaenoic acid (DHA; 22:6 n-3) incorporation was not detected. 13C DHA was incorporated into phosphatidylcholine. Lysophosphatidylcholine containing all four 13C labeled fatty acids were found in high abundance.

CONCLUSIONS

Phospholipid synthesis and remodeling enzymes are present in the syncytiotrophoblast. 13C labeled fatty acids were rapidly incorporated into cellular phospholipids. 13C DHA was incorporated into phospholipids through the remodeling pathway rather than by de novo synthesis. These understudied pathways are highly active and critical for structure and function of the placenta.

Dietary lysophospholipids improves growth performance and hepatic lipid metabolism of largemouth bass (Micropterussalmoides)

This study was conducted to evaluate the influence of dietary lysophospholipids combined with 1% dietary fish oil reduction on the growth performance and hepatic lipid metabolism of largemouth bass (Micropterus salmoides). Five isonitrogenous feeds were prepared with lysophospholipids at 0% (fish oil group, FO), 0.05% (L-0.05), 0.1% (L-0.1), 0.15% (L-0.15) and 0.2% (L-0.2), respectively. The dietary lipid was 11% in the FO diet and 10% in the other diets. Largemouth bass were fed for 68 d (initial body weight = 6.04 ± 0.01 g) with 4 replicates per group and 30 fish per replicate. The results showed that the fish fed diet containing 0.1% lysophospholipids had higher digestive enzyme activity and obtained better growth performance compared to the fish fed FO diet (P < 0.05). The feed conversion rate in the L-0.1 group was significantly lower than that in the other groups. Serum total protein and triglyceride contents in L-0.1 group were significantly higher than those in other groups (P < 0.05) and the contents of total cholesterol and low-density lipoprotein cholesterol in L-0.1 group were significantly lower than those in FO group (P < 0.05). The activity and genes expression of hepatic glucolipid metabolizing enzymes in L-0.15 group were significantly increased compared to those in FO group (P < 0.05). Reducing 1% fish oil along with 0.1% lysophospholipids added to the feed could improve the digestion and absorption of nutrients, enhance the activity of liver glycolipid metabolizing enzymes, and thus effectively promote the growth of largemouth bass.

Monoacylglycerol lipase from marine Geobacillus sp. showing lysophospholipase activity and its application in efficient soybean oil degumming

Enzymatic degumming is an essential refining process to improve oil quality. In this study, a monoacylglycerol lipase GMGL was derived from marine Geobacillus sp., and was found that not only took monoacylglycerol (MAG) as substrate, but also had activity toward lysophosphatidylcholine (LPC), lysophosphatidylethanolamine (LPE) and glycerolphosphatidylcholine (GPC). Binding free energy showed LPC and LPE could bind with enzyme stably as MAG. It presented great potential in the field of enzymatic degumming. The phosphorus content in crude soybean oil decreased from 680.50 to 2.01 mg/kg and the yield of oil reached to 98.80 % after treating with phospholipase A1 (Lecitase Ultra) combined with lipase GMGL. An ultrahigh-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS) was developed to identify 21 differential phospholipids between crude soybean oil and enzymatic treatment. This work might shed some light on understanding the catalytic mechanism of monoacylglycerol lipase and provide an effective strategy for enzymatic degumming.

Lysophospholipids and their producing enzymes: Their pathological roles and potential as pathological biomarkers

Accumulating evidence suggests that lysophospholipids (LPL) serve as lipid mediators that exert their diverse pathophysiological functions via G protein-coupled receptors. These include lysophosphatidic acid (LPA), sphingosine 1-phosphate (S1P), lysophosphatidylserine (LysoPS) and lysophosphatidylinositol (LPI). Unlike S1P, which is produced intracellularly and secreted from various cell types, some LPLs, such as LPA, LysoPS and LPI, are produced in lesions, especially under pathological conditions, where they positively or negatively regulate disease progression through their autacoid-like actions. Although these LPLs are minor components of the cell membrane, recent developments in mass spectrometry techniques have made it possible to detect and quantify them in a variety of biological fluids, including plasma, serum, urine and cerebrospinal fluid. The synthetic enzymes of LPA and LysoPS are also present in these biological fluids, which also can be detected by antibody-based methods. Importantly, their levels have been found to dramatically increase during various pathological conditions. Thus, LPLs and their synthetic enzymes in these biological fluids are potential biomarkers. This review discusses the potential of these LPLs and LPL-related molecules as pathological biomarkers, including methods and problems in their measurement.

Effects of emulsifier, betaine, and L-carnitine on growth performance, immune response, gut morphology, and nutrient digestibility in broiler chickens exposed to cyclic heat stress

1. This experiment investigated the efficacy of varying doses of an emulsifier blend (EB; 0 and 1 g/kg of diet), betaine (BT; 0 and 1 g/kg of diet) and L-carnitine (CT; 0 and 0.5 g/kg of diet) in broilers subjected to circular heat stress (HS) conditions. A total of 1080 one-day-old male broiler chickens (Ross 308) were randomly assigned to one of nine treatment groups (six pens/treatment with 20 birds/pen) according to a completely randomised design. The thermoneutral control broiler chickens were housed at a comfortable temperature and fed a standard diet (no additives). The other eight groups were exposed to cyclic HS conditions (34°C) for 8 h (10:00-18:00).2. There were EB × BT × CT interactions for body weight (BW) at 24 d (P = 0.038) and average daily gain (ADG) during the 10-24 d period (P = 0.049), with the greatest values found with concurrent supplementation of three supplements.3. Inclusion of EB resulted in greater (P < 0.05) BW, ADG, European performance index, uniformity rate, primary antibody titres against sheep red blood cells (SRBC), duodenal villus height (VH) and villus surface area, digestible energy (DE) and the coefficient of apparent ileal digestibility (CAID) of dry matter, crude protein, and fat However, feed conversion ratio, mortality rate and heterophile to lymphocyte ratio were lower (P < 0.05).4. Dietary BT supplementation improved (P < 0.05) all performance indicators, primary antibody titres against SRBC and Newcastle disease virus, serum total antioxidant capacity, duodenal VH, Jejunal VH/crypt depth and the CAID of dry matter and crude protein. The effect of dietary supplementation with CT was limited to an increase (P < 0.05) in ADG (d 10-24) and a decrease (P < 0.05) in serum malondialdehyde concentration (42 d) and jejunal crypt depth (42 d).5. In conclusion, dietary supplementation of either EB or BT alone or in combination ameliorated some of the detrimental effects of HS on growth performance, immunity and intestinal health in broilers, while a minor positive effect on performance and antioxidant status was observed with CT supplementation.

Modulations of urinary lipid mediators in acute bladder cystitis

Bioactive lipids, such as lysophospholipids, ceramides, and eicosanoids and related mediators, have been demonstrated to be involved in inflammation. We aimed to investigate the possible orchestral modulations of these bioactive lipids in human inflammation. We simultaneously measured the urinary levels of lysophospholipids, ceramides, and eicosanoids and related mediators by a liquid chromatography-mass spectrometry method in patients with cystitis and control subjects. The urinary levels of lysophosphatidylcholine, lysophosphatidylethanolamine, sphingosine 1-phosphate, ceramides, prostaglandin (PG)E₂ and its metabolites represented by tetranor-PGEM, several oxylipins, DHA, and lysoPAF were higher in patients with cystitis. Urinary levels of some species of glycerolysophospholipids were highly positively correlated with those of other species of the same glycerolysophospholipids. Cluster analyses revealed that lysophosphatidylcholine was close to a PGE₂ metabolite, lysophosphatidylethanolamine was close to DHA, and sphingosine 1-phosphate and ceramides were close to lysoPAF. The orchestral dynamism of the lipid mediators was observed in the urine of cystitis, suggesting the necessity for simultaneous investigation of lipid mediators for translational research.

Apolipoprotein D modulates lipid mediators and osteopontin in an anti-inflammatory direction

BACKGROUND

HDL has been proposed to possess anti-inflammatory properties; however, the detail mechanisms have not been fully elucidated.

METHODS

We investigated the roles of Apolipoprotein D (ApoD) in the pathogenesis of inflammation in the mouse model of diet-induced obesity and that of lipopolysaccharide-induced sepsis and the in vitro experiments. Furthermore, we analyzed serum ApoD levels in human subjects.

RESULTS

The overexpression of human ApoD decreased the plasma IL-6 and TNF-a levels in both mice models. Lipidomics analyses demonstrated association of ApoD with increase of arachidonic acid, eicosapentaenoic acid, and docosahexaenoic acid, as well as of their metabolites, and of the anti-inflammatory molecule sphingosine 1-phosphate, and decrease of proinflammatory lysophosphatidic acids and lysophosphatidylinositol. ApoD-containing lipoproteins might directly bind eicosapentaenoic acid and docosahexaenoic acid. The modulations of the lysophosphatidic acid and sphingosine 1-phosphate levels resulted from the suppression of autotaxin expression and elevation of apolipoprotein M (ApoM), respectively. Moreover, ApoD negatively regulated osteopontin, a proinflammatory adipokine. The activation of PPARg by ApoD might suppress autotaxin and osteopontin. Serum ApoD levels were negatively correlated with the serum osteopontin and autotaxin levels and, positively with serum ApoM levels.

CONCLUSION

ApoD is an anti-inflammatory apolipoprotein, which modulates lipid mediators and osteopontin in an anti-inflammatory direction.

Molecular insights into sex-specific metabolic alterations in Alzheimer's mouse brain using multi-omics approach

BACKGROUND

Alzheimer's disease (AD) is a progressive neurodegenerative disorder that is characterized by altered cellular metabolism in the brain. Several of these alterations have been found to be exacerbated in females, known to be disproportionately affected by AD. We aimed to unravel metabolic alterations in AD at the metabolic pathway level and evaluate whether they are sex-specific through integrative metabolomic, lipidomic, and proteomic analysis of mouse brain tissue.

METHODS

We analyzed male and female triple-transgenic mouse whole brain tissue by untargeted mass spectrometry-based methods to obtain a molecular signature consisting of polar metabolite, complex lipid, and protein data. These data were analyzed using multi-omics factor analysis. Pathway-level alterations were identified through joint pathway enrichment analysis or by separately evaluating lipid ontology and known proteins related to lipid metabolism.

RESULTS

Our analysis revealed significant AD-associated and in part sex-specific alterations across the molecular signature. Sex-dependent alterations were identified in GABA synthesis, arginine biosynthesis, and in alanine, aspartate, and glutamate metabolism. AD-associated alterations involving lipids were also found in the fatty acid elongation pathway and lysophospholipid metabolism, with a significant sex-specific effect for the latter.

CONCLUSIONS

Through multi-omics analysis, we report AD-associated and sex-specific metabolic alterations in the AD brain involving lysophospholipid and amino acid metabolism. These findings contribute to the characterization of the AD phenotype at the molecular level while considering the effect of sex, an overlooked yet determinant metabolic variable.

Development and validation of a simple and rapid HILIC-MS/MS method for the quantification of low-abundant lysoglycerophospholipids in human plasma

Lysoglycerophospholipids (Lyso-GPLs) are an essential class of signaling lipids with potential roles in human diseases, such as cancer, central nervous system diseases, and atherosclerosis. Current methods for the quantification of Lyso-GPLs involve complex sample pretreatment, long analysis times, and insufficient validation, which hinder the research of Lyso-GPLs in human studies, especially for Lyso-GPLs with low abundance in human plasma such as lysophosphatidic acid (LPA), lysophosphatidylinositol (LPI), lysophosphatidylglycerol (LPG), lysophosphatidylserine (LysoPS), lyso-platelet-activating factor (LysoPAF), and cyclic phosphatidic acid (cPA). Herein, we report the development and validation of a simple and rapid liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the quantification of Lyso-GPLs with low abundance in plasma. Protein precipitation using MeOH for Lyso-GPL extraction, quick separation (within 18 min) based on hydrophilic interaction liquid chromatography (HILIC), and sensitive MS detection under dynamic multiple reaction monitoring (dMRM) mode enabled efficient quantification of 22 Lyso-GPLs including 2 cPA, 4 LPG, 11 LPA, 2 LysoPS, and 3 LysoPAF in 50 μL of human plasma. The present method showed good linearity (goodness of fit, 0.99823-0.99995), sensitivity (lower limit of quantification, 0.03-14.06 ng/mL), accuracy (73-117%), precision (coefficient of variation ≤ 28%), carryover (≤ 17%), recovery (80-110%), and stability (83-123%). We applied the method in an epidemiological study and report concentrations of 18 Lyso-GPLs in 567 human plasma samples comparable to those of previous studies. Significant negative associations of LysoPAF C18, LysoPAF C18:1, and LysoPAF C16 with homeostatic model assessment for insulin resistance (HOMA-IR) level were observed; this indicates possible roles of LysoPAF in glucose homeostasis. The application of the present method will improve understanding of the roles of circulating low-abundant Lyso-GPLs in health and diseases.

Integrating transcriptome and metabolome to identify key genes regulating important muscular flavour precursors in sheep

Flavour precursors are the basis of meat flavour, and their metabolism is regulated by a variety of enzymes. Thus, it is of great significance to identify the key genes related to meat flavour precursors. In this study, the difference in flavour precursors and transcriptome between Hu sheep and Dorper with different intramuscular fat (IMF) content were investigated using widely targeted metabolomics and RNA-sequencing technologies. Then, the key genes regulating the metabolism of vital precursors were explored by integrating transcriptome and metabolome. Consequently, 594 metabolites were detected in sheep longissimus dorsi, and 76 differentially abundant metabolites (DAMs) were identified between Hu sheep and Dorper. No DAMs were observed between distinct IMF content groups within each breed. A total of 10 lysophospholipids (LPs), including four lysophospholipid ethanolamines and six lysophospholipid cholines, were identified as the main differential precursors between Hu sheep and Dorper. Furthermore, the weighted gene coexpression network analysis uncovered three differentially coexpression modules that were significantly associated with the content of differential LPs in Dorper. From the three modules, GLB1, PLD3, LPCAT2, DGKE, ACOT7, and CH25H genes were identified as key genes regulating the metabolism of LPs. This work provides an insight into understanding the difference in flavour between different sheep breeds, as well as a basis for further exploring the regulatory mechanism of key genes on LPs.

Different Profiles of the Triad of Lysophosphatidylcholine, Lysophosphatidic Acid, and Autotaxin in Patients with Neuropathic Pain Diseases: a Preliminary Observational Study

The mechanisms underlying neuropathic pain remain unclear. Lysophosphatidic acid (LPA) is a bioactive phospholipid derived mainly from lysophosphatidylcholine (LPC) by extracellular autotaxin (ATX), and has attracted attention as a candidate biomarker of neuropathic pain. We aimed to investigate the levels of LPA, LPC, and ATX in patients with lumbar spinal canal stenosis (LSCS) or other neuropathic pain diseases, and to distinguish the underlying mechanism of LSCS from other neuropathic pain conditions. Furthermore, the levels of phosphorylated neurofilament heavy chain (pNF-H), an objective surrogate marker of axonal damage, were also measured. Cerebrospinal fluid (CSF) samples were obtained from 56 patients with LSCS (n = 31) and various etiologies other than LSCS (n = 25). Patients with LSCS complained of pain intensity comparable to that of patients without LSCS. The LPA levels were significantly higher in patients with LSCS than in non-LSCS patients, while the ATX levels were significantly lower. However, the differences in LPC and pNF-H levels between the two patient groups were not significant. The LPA/LPC ratio was significantly higher in the LSCS group. Notably, the difference in LPA between the two groups diminished in the analysis of covariance (ANCOVA) with ATX as a covariate. Thus, it helped to reveal that LPA synthesis in patients with LSCS depends more efficiently on ATX than in non-LSCS neuropathic pain patients with other etiologies. Our findings further suggest that the triad of LPA, LPC, and ATX in LSCS may contribute to the development and maintenance of neuropathic pain in a manner different from non-LSCS neuropathic conditions.

RETRACTED ARTICLE: Effects of emulsifier, betaine, and L-carnitine on growth performance, immune response, gut morphology, and nutrient digestibility in broiler chickens exposed to cyclic heat stress

1. This experiment investigated the efficiency of varying doses of an emulsifier blend (EB; 0 and 1 g/kg of diet), betaine (BT; 0 and 1 g/kg of diet) and L-carnitine (CT; 0 and 0.5 g/kg of diet) in broilers subjected to circular heat stress (HS) conditions.2. A total of 1080 one-day-old male broiler chickens (Ross 308) were randomly assigned to nine treatment groups (six pens/treatment with 20 birds/pen) in a completely randomised design. The thermoneutral control broiler chickens were housed at a comfortable temperature and fed a standard diet (no additives). The other 8 groups were exposed to cyclic HS conditions (34°C) for 8 h (10:00-18:00).3. There were EB × BT × CT interactions for body weight (BW) at 24 d (P=0.038) and average daily gain (ADG) during the 10-24 d period (P=0.049), with the greatest values with concurrent supplementation of all three ingredients.4. Inclusion of EB resulted in greater (P<0.05) BW, ADG, European performance index, uniformity rate, primary antibody titres against sheep red blood cells (SRBC), duodenal villus height (VH) and villus surface area, nitrogen-corrected apparent metabolisable energy (AMEn) and apparent ileal digestibility (AID) of dry matter, crude protein and fat, but lower (P<0.05) feed conversion ratio, mortality rate and heterophile to lymphocyte ratio.5. Dietary BT supplementation improved (P<0.05) overall performance indicators, primary antibody titres against SRBC and Newcastle disease virus, serum total antioxidant capacity, duodenal VH, Jejunal VH/crypt depth, AID of dry matter and crude protein. The effect of dietary supplementation with CT was limited to an increase (P<0.05) in ADG (d 10-24) and a decrease (P<0.05) in serum malondialdehyde concentration (42 d) and jejunal crypt depth (42 d).6. In conclusion, dietary supplementation of either EB or BT alone or in combination can ameliorate some of the detrimental effects of HS on growth performance, immunity and intestinal health in broilers, while a minor positive effect on performance and antioxidant status was observed with CT supplementation.

LC/MS analysis of storage-induced plasmalogen loss in ready-to-eat fish

Plasmalogens are functional and oxidation-sensitive phospholipids abundant in fish. Chilling and freezing are common storage methods for maintaining the quality of fish, but their effect on plasmalogen preservation has not been studied. Therefore, plasmalogen loss in ready-to-eat tuna meat during storage under different conditions was investigated. LC/MS was used to analyze the time- and temperature-dependent changes of plasmalogens, which was the most evident for the species with an ethanolamine headgroup and polyunsaturated fatty acyl chains. Moreover, a series of oxidized plasmalogen molecules were identified, and their storage-induced accumulation was observed. Plasmalogen loss was strongly correlated with total lipid oxidation and phospholipid degradation. Repeated freeze-thaw cycles were found to accelerate the loss of plasmalogens, whereas the different thawing methods did not. The present study provides a deeper understanding of changes in lipid nutrients from fish meat during storage and demonstrates the importance of using advanced strategies to maintain food quality.

Campylobacter jejuni permeabilizes the host cell membrane by short chain lysophosphatidylethanolamines

Lysophospholipids (LPLs) are crucial for regulating epithelial integrity and homeostasis in eukaryotes, however the effects of LPLs produced by bacteria on host cells is largely unknown. The membrane of the human bacterial pathogen Campylobacter jejuni is rich in LPLs. Although C. jejuni possesses several virulence factors, it lacks traditional virulence factors like type III secretion systems, present in most enteropathogens. Here, we provide evidence that membrane lipids lysophosphatidylethanolamines (lysoPEs) of C. jejuni are able to lyse erythrocytes and are toxic for HeLa and Caco-2 cells. Lactate dehydrogenase (LDH) release assays and confocal microscopy revealed that lysoPE permeabilizes the cells. LysoPE toxicity was partially rescued by oxidative stress inhibitors, indicating that intracellular reactive oxygen species may contribute to the cell damage. Our results show that especially the short-chain lysoPEs (C:14) which is abundantly present in the C. jejuni membrane may be considered as a novel virulence factor.

A rapid increase in lysophospholipids after geranylgeranoic acid treatment in human hepatoma-derived HuH-7 cells revealed by metabolomics analysis

Geranylgeranoic acid (GGA) was developed as a preventative agent against second primary hepatoma, and was reported to induce cell death in human hepatoma cells via Toll-like receptor 4 (TLR4)-mediated pyroptosis. We recently reported that GGA is enzymatically biosynthesized from mevalonic acid in human hepatoma-derived HuH-7 cells and that endogenous GGA is found in most rat organs including the liver. An unbiased metabolomics analysis of ice-cold 50% acetonitrile extracts from control and GGA-treated cells was performed in this study to characterize the intracellular metabolic changes in GGA-induced pyroptosis and to analyze their relationship with the mechanism of GGA-induced cell death. The total positive ion chromatograms of the cellular extracts in ultra-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry were apparently unchanged after GGA treatment, but an orthogonal partial least squares-discriminant analysis score plot clearly discriminated the intracellular metabolite profiles of GGA-treated cells from that of control cells. S-plot analysis revealed 15 potential biomarkers up-regulated by 24-h GGA treatment according to their variable importance in the projection value of more than 1, and the subsequent metabolomics analysis identified nine of these metabolites as a group of lysophospholipids containing lysophosphatidylcholine with C16:0, C20:4, or C20:3 fatty acids. The possible roles of these lysophospholipids in GGA-induced pyroptosis are discussed.

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Metabolomics analysis was performed on geranylgeranoic acid (GGA)-treated cells.

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Total positive ion chromatograms were apparently similar after GGA treatment.

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The OPLS-DA score plot distinguished the GGA-treated cells from control cells.

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The S-plot analysis revealed GGA-induced upregulation of lysophospholipids.

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The possible roles of lysophospholipids in GGA-induced pyroptosis are discussed.

Serum lysophospholipidome of dietary origin as a suitable susceptibility/risk biomarker of human hypercholesterolemia: A cross-sectional study

BACKGROUND & AIMS

Whether bioactive lysophospholipids (lyso-PLs) and trimethylamine-N-oxide (TMAO) serve as non-invasive biomarkers in early human hypercholesterolemia (HC) is unknown. This study aimed to assess whether serum lyso-PLs and plasma TMAO may be suitable susceptibility/risk biomarkers of HC in humans. Secondarily, we aimed to evaluate the relationships between targeted metabolites, diet composition and circulating liver transaminases, and verify these results in hamsters.

METHODS

A targeted metabolomics and lipidomics approach determined plasma TMAO and serum lysophosphatidylcholines (lyso-PCs) and lysophosphatidylethanolamines (lyso-PEs) in low (L-LDL-c) and moderate to high (MH-LDL-c) LDL-cholesterol subjects. Additionally, the relationships between targeted metabolites, liver transaminases and diet, particularly fatty acid intake, were tested. In parallel, plasma and liver lyso-PL profiles were studied in 16 hamsters fed a moderate high-fat (HFD) or low-fat (LFD) diet for 30 days.

RESULTS

Predictive models identified lyso-PC15:0 and lyso-PE18:2 as the most discriminant lyso-PLs among groups. In MH-LDL-c (n = 48), LDL-cholesterol and saturated FAs were positively associated with lyso-PC15:0, whereas in L-LDL-c (n = 70), LDL-cholesterol and polyunsaturated fatty acids (PUFAs) were negatively and positively related to lyso-PE18:2, respectively. Interestingly, in MH-LDL-c, the lower lyso-PE 18:2 concentrations were indicative of higher LDL-cholesterol levels. Intrahepatic accumulation of lyso-PLs-containing essential n-6 PUFAs, including lyso-PE18:2, were higher in HFD-fed hamsters than LFD-fed hamsters.

CONCLUSIONS

Overall, results revealed a possible hepatic adaptive mechanism to counteract diet-induced steatosis in animal and hypercholesterolemia progression in humans. In particular, low serum lyso-PE18:2 suggests a suitable susceptibility/risk biomarker of HC in humans.

Qualitative Characterization of the Rat Liver Mitochondrial Lipidome Using All Ion Fragmentation on an Exactive Benchtop Orbitrap MS

Untargeted lipidomics profiling by liquid chromatography -mass spectrometry (LC-MS) allows researchers to observe the occurrences of lipids in a biological sample without showing intentional bias to any specific class of lipids and allows retrospective reanalysis of data collected. Typically, and in the specific method described, a general extraction method followed by LC separation is used to achieve nonspecific class coverage of the lipidome prior to high resolution accurate mass (HRAM) MS detection . Here we describe a workflow including the isolation of mitochondria from liver tissue, followed by mitochondrial lipid extraction and the LC-MS conditions used for data acquisition. We also highlight how, in this method, all ion fragmentation can be used to identify species of lower abundances, often missed by data dependent fragmentation techniques. Here we describe the isolation of mitochondria from liver tissue, followed by mitochondrial lipid extraction and the LC-MS conditions used for data acquisition.

Lysophospholipids in Lung Inflammatory Diseases

The lysophospholipids (LPLs) belong to a group of bioactive lipids that play pivotal roles in several physiological and pathological processes. LPLs are derivatives of phospholipids and consist of a single hydrophobic fatty acid chain, a hydrophilic head, and a phosphate group with or without a large molecule attached. Among the LPLs, lysophosphatidic acid (LPA) and sphingosine-1-phosphate (S1P) are the simplest, and have been shown to be involved in lung inflammatory symptoms and diseases such as acute lung injury, asthma, and chronic obstructive pulmonary diseases. G protein-coupled receptors (GPCRs) mediate LPA and S1P signaling. In this chapter, we will discuss on the role of LPA, S1P, their metabolizing enzymes, inhibitors or agonists of their receptors, and their GPCR-mediated signaling in lung inflammatory symptoms and diseases, focusing specially on acute respiratory distress syndrome, asthma, and chronic obstructive pulmonary disease.

The toc132toc120 heterozygote mutant of Arabidopsis thaliana accumulates decreased levels of the major chloroplast lipids

We used ESI-MS/MS to profile glycerolipids in a mutant of Arabidopsis thaliana that is null and heterozygous for the TOC132 and TOC120 genes, and is referred to as the toc132toc120± mutant. The goal was to assess the impact of a defective atToc132/120 receptor on the accumulation of chloroplast lipids. The mutant accumulated decreased amounts of monogalactosyldiacylglycerol (MGDG), digalactosyldiacylglycerol (DGDG) and phosphatidylglycerol (PG). In the cold-acclimated mutant, PG accumulated at the control levels. However, 34:4-PG (18:3/16:1Δ^3trans) was significantly decreased, which indicates that the mutant was impaired in synthesis of the chloroplast-derived PG. Major molecular species of MGDG and DGDG were significantly decreased, which was indicative of the decreased levels of triunsaturated fatty acids in galactolipids. The cold-acclimated mutant accumulated increased levels of phosphatidylcholine (PC), phosphatidylethanolamine (PE) and phosphatidylserine (PS), which indicate that defect in the atToc132/120 receptor did not impair the ER pathway of lipid synthesis. Both cold-acclimated wildtype and mutant plants accumulated increased levels of phosphatidic acid (PA). The increased levels of major molecular species of PA suggest that some pool of PA was derived from degradation of both the chloroplast and extra-chloroplast lipids. The cold-acclimated mutant had decreased double bond index (DBI) and increased acyl chain length (ACL), which was indicative of decreased membrane fluidity. However, a decrease in the ratio of MGDG to DGDG indicate that the mutant was capable of remodeling membrane lipids in response to low temperatures. We conclude that the defective Toc132/120 receptor resulted in decreased synthesis of chloroplast lipids and decreased membrane fluidity.

Metabolic profiling reveals interleukin-17A monoclonal antibody treatment ameliorate lipids metabolism with the potentiality to reduce cardiovascular risk in psoriasis patients

Background

Psoriasis is a common chronic inflammatory skin disease associated with overproduction of interleukin-17A (IL-17A). IL-17A monoclonal antibodies (mAbs) have shown clinical efficacy in psoriasis patients. Although a series of different overlapping mechanisms have been found to establish a link between psoriasis and cardiovascular diseases, the underlying mechanisms of the two types of diseases and the potential efficacy of IL-17A mAbs in amelioration of cardiovascular comorbidities remain unclear.

Methods

Serum samples from two study cohorts including 117 individuals were analyzed using a high-throughput UHPLC-MS platform. Non-targeted metabolic profiling analysis was first conducted with samples from 28 healthy individuals and from 28 psoriasis patients before and after 12-weeks of ixekizumab treatment in study cohort 1. Study cohort 2 was additionally recruited to validate the correlations of the identified metabolites with cardiovascular diseases.

Results

A total of 43 differential metabolites, including lysophospholipids, free fatty acids, acylcarnitines and dicarboxylic acids, were accurately identified in study cohort 1, and the analysis showed that lipid metabolism was impaired in psoriasis patients. Compared with healthy individuals, psoriasis patients had higher levels of lysophosphatidylcholines, lysophosphatidylinositols, lysophosphatidic acids and free fatty acids, but lower levels of acylcarnitines and dicarboxylic acids. The identified dicarboxylic acid levels were inversely correlated with psoriasis area and severity index (PASI) scores (P < 0.05). The results for study cohort 2 were largely consistent with the results for study cohort 1. Moreover, the levels of all identified lysophosphatidylcholines were higher in psoriasis patients with coronary heart diseases than in psoriasis without coronary heart disease. Notably, most of these lipidic changes were ameliorated by ixekizumab treatment.

Conclusion

The results of this non-targeted metabolomic analysis indicate that treatment with IL-17A mAbs can not only ameliorate psoriasis lesions but also restore dysregulated lipid metabolism to normal levels in psoriasis patients. Considering that dysregulated lipid metabolism has been regarded as the critical factor in cardiovascular diseases, the recovery of lipid metabolites in psoriasis patients indicates that IL-17A mAbs might have the potential protective effects against cardiovascular comorbidities.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12944-021-01441-9.

Evaluation of serum ATX and LPA as potential diagnostic biomarkers in patients with pancreatic cancer

BACKGROUND

Pancreatic cancer (PC) is a devastating disease that has a poor prognosis and a total 5-year survival rate of around 5%. The poor prognosis of PC is due in part to a lack of suitable biomarkers that can allow early diagnosis. The lysophospholipase autotaxin (ATX) and its product lysophosphatidic acid (LPA) play an essential role in disease progression in PC patients and are associated with increased morbidity in several types of cancer. In this study, we evaluated both the potential role of serum LPA and ATX as diagnostic markers in PC and their prognostic value for PC either alone or in combination with CA19-9.

METHODS

ATX, LPA and CA19-9 levels were evaluated using ELISA of serum obtained from PC patients (n = 114) healthy volunteers (HVs: n = 120) and patients with benign pancreatic diseases (BPDs: n = 94).

RESULTS

Serum levels of ATX, LPA and CA19-9 in PC patients were substantially higher than that for BPD patients or HVs (p < 0.001). The sensitivity of LPA in early phase PC was 91.74% and the specificity of ATX was 80%. The levels of ATX, LPA and CA19-9 were all substantially higher for early stage PC patients compared to levels in serum from BPD patients and HVs. The diagnostic efficacy of CA19-9 for PC was significantly enhanced by the addition of ATX and LPA (p = 0.0012).

CONCLUSION

Measurement of LPA and ATX levels together with CA19-9 levels can be used for early detection of PC and diagnosis of PC in general.

Lipidomic Analysis of Postmortem Prefrontal Cortex Phospholipids Reveals Changes in Choline Plasmalogen Containing Docosahexaenoic Acid and Stearic Acid Between Cases With and Without Alzheimer's Disease

Alzheimer's disease (AD) is a progressive and incurable brain disorder that has been associated with structural changes in brain phospholipids (PLs), including diacyl species and ether-linked PLs known as plasmalogens. Most studies have characterized total changes in brain PL pools (e.g., choline plasmalogens), particularly in prefrontal cortex, but detailed and quantitative information on the molecular PL species impacted by the disease is limited. In this study, we used a comprehensive mass-spectrometry method to quantify diacyl and plasmalogen species, alkyl synthetic precursors of plasmalogens, and lysophospholipid degradation products of diacyl and plasmalogen PLs, in postmortem samples of prefrontal cortex from 21 AD patients and 20 age-matched controls. Total PLs were also quantified with gas-chromatography analysis of bound fatty acids following thin layer chromatography isolation. There was a significant 27% reduction in the concentration (nmol/g wet weight) of choline plasmalogen containing stearic acid (alkenyl group) and docosahexaenoic acid in AD compared to controls. Stearic acid concentration in total PLs was reduced by 26%. Our findings suggest specific changes in PLs containing stearic acid and docosahexaenoic acid in AD prefrontal cortex, highlighting structural and turnover PL pathways that could be targeted.

Roles for lysophosphatidic acid signaling in vascular development and disease

The bioactive lipid lysophosphatidic acid (LPA) is emerging as an important mediator of inflammation in cardiovascular diseases. Produced in large part by the secreted lysophospholipase D autotaxin (ATX), LPA acts on a series of G protein-coupled receptors and may have action on atypical receptors such as RAGE to exert potent effects on vascular cells, including the promotion of foam cell formation and phenotypic modulation of smooth muscle cells. The signaling effects of LPA can be terminated by integral membrane lipid phosphate phosphatases (LPP) that hydrolyze the lipid to receptor inactive products. Human genetic variants in PLPP3, that predict lower levels of LPP3, associate with risk for premature coronary artery disease, and reductions of LPP3 expression in mice promote the development of experimental atherosclerosis and enhance inflammation in the atherosclerotic lesions. Recent evidence also supports a role for ATX, and potentially LPP3, in calcific aortic stenosis. In summary, LPA may be a relevant inflammatory mediator in atherosclerotic cardiovascular disease and heightened LPA signaling may explain the cardiovascular disease risk effect of PLPP3 variants.

Advancements in understanding the role of lysophospholipids and their receptors in lung disorders including bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD) is a devastating chronic neonatal lung disease leading to serious adverse consequences. Nearly 15 million babies are born preterm accounting for >1 in 10 births globally. The aetiology of BPD is multifactorial and the survivors suffer lifelong respiratory morbidity. Lysophospholipids (LPL), which include sphingosine-1-phosphate (S1P), and lysophosphatidic acid (LPA) are both naturally occurring bioactive lipids involved in a variety of physiological and pathological processes such as cell survival, death, proliferation, migration, immune responses and vascular development. Altered LPL levels have been observed in a number of lung diseases including BPD, which underscores the importance of these signalling lipids under normal and pathophysiological situations. Due to the paucity of information related to LPLs in BPD, most of the ideas related to BPD and LPL are speculative. This article is intended to promote discussion and generate hypotheses, in addition to the limited review of information related to BPD already established in the literature.

Lysophosphatidylcholines inhibit human eosinophil activation and suppress eosinophil migration in vivo

Eosinophils are important multifaceted effector cells involved in allergic inflammation. Following allergen challenge, eosinophils and other immune cells release secreted phospholipases, generating lysophosphatidylcholines (LPCs). LPCs are potent lipid mediators, and serum levels of LPCs associate with asthma severity, suggesting a regulatory activity of LPCs in asthma development. As of yet, the direct effects of LPCs on eosinophils remain unclear. In the present study, we tested the effects of the major LPC species (16:0, 18:0 and 18:1) on eosinophils isolated from healthy human donors. Addition of saturated LPCs in the presence of albumin rapidly disrupted cholesterol-rich nanodomains on eosinophil cell membranes and suppressed multiple eosinophil effector responses, such as CD11b upregulation, degranulation, chemotaxis, and downstream signaling. Furthermore, we demonstrate in a mouse model of allergic cell recruitment, that LPC treatment markedly reduces immune cell infiltration into the lungs. Our observations suggest a strong modulatory activity of LPCs in the regulation of eosinophilic inflammation in vitro and in vivo.

Dietary lysophospholipids supplementation inhibited the activity of lipolytic bacteria in forage with high oil diet: an in vitro study

Objective

The objective of this study was to evaluate the effects of lysophospholipids (LPL) supplementation on rumen fermentation, degradability, and microbial diversity in forage with high oil diet in an in vitro system.

Methods

Four experimental treatments were used: i) annual ryegrass (CON), ii) 93% annual ryegrass +7% corn oil on a dry matter (DM) basis (OiL), iii) OiL with a low level (0.08% of dietary DM) of LPL (LLPL), and iv) OiL with a high level (0.16% of dietary DM) of LPL (HLPL). An in vitro fermentation experiment was performed using strained rumen fluid for 48 h incubations. In vitro DM degradability (IVDMD), in vitro neutral detergent fiber degradability, pH, ammonia nitrogen (NH₃-N), volatile fatty acid (VFA), and microbial diversity were estimated.

Results

There was no significant change in IVDMD, pH, NH₃-N, and total VFA production among treatments. The LPL supplementation significantly increased the proportion of butyrate and valerate (Linear effect [Lin], p = 0.004 and <0.001, respectively). The LPL supplementation tended to increase the total bacteria in a linear manner (p = 0.089). There were significant decreases in the relative proportions of cellulolytic (Fibrobacter succinogenes and Ruminococcus albus) and lipolytic (Anaerovibrio lipolytica and Butyrivibrio proteoclasticus) bacteria with increasing levels of LPL supplementation (Lin, p = 0.028, 0.006, 0.003, and 0.003, respectively).

Conclusion

The LPL supplementation had antimicrobial effects on several cellulolytic and lipolytic bacteria, with no significant difference in nutrient degradability (DM and neutral detergent fiber) and general bacterial counts, suggesting that LPL supplementation might increase the enzymatic activity of rumen bacteria. Therefore, LPL supplementation may be more effective as an antimicrobial agent rather than as an emulsifier in the rumen.

Lipids - two sides of the same coin in lung fibrosis

Idiopathic pulmonary fibrosis (IPF) is characterized by progressive extracellular matrix deposition in the lung parenchyma leading to the destruction of lung structure, respiratory failure and premature death. Recent studies revealed that the pathogenesis of IPF is associated with alterations in the synthesis and the activity of lipids, lipid regulating proteins and cell membrane lipid transporters and receptors in different lung cells. Furthermore, deregulated lipid metabolism was found to contribute to the profibrotic phenotypes of lung fibroblasts and alveolar epithelial cells. Consequently, several pharmacological agents, targeting lipids, lipid mediators, and lipoprotein receptors, was successfully tested in the animal models of lung fibrosis and entered early phase clinical trials. In this review, we highlight new therapeutic options to counteract disturbed lipid hemostasis in the maladaptive lung remodeling.

Associations between plasma lysophospholipids concentrations, chronic kidney disease and the type of renal replacement therapy

BACKGROUND

Lysophosphatidic acid (LPA) and lysophosphatidylcholine (LPC) are bioactive lysophospholipids involved in the pathogenesis of renal diseases, especially the renal fibrosis. Plasma LPC concentrations in chronic kidney disease (CKD) patients are lower or similar to those observed in control groups, but less is known about the LPA concentrations. The main aim of the study was the analysis of associations of chronic kidney disease and renal replacement therapy with the plasma LPA concentrations. We have also analyzed the relationship between the plasma concentrations of LPA and LPC.

MATERIAL AND METHODS

Study group consisted of 110 patients with CKD in stages G3-G5 according to the KDIGO guidelines and was divided into four subgroups: treated conservatively (CT, 30 patients), on hemodialysis (HD, 30 patients), on peritoneal dialysis (PD, 30 patients) and renal transplant recipients (RT, 20 patients). In HD the blood was collected immediately before (HD D1) and after the dialysis (HD D2). In RT the blood was collected immediately before (RT D1) and 3-14 days after the transplantation (RT D2). The control group (Con) consisted of 50 healthy volunteers. Plasma concentrations of LPA and LPC were measured using enzyme-linked immunosorbent assays.

RESULTS

In CT, PD and RT D2 plasma concentrations of LPA were significantly higher, compared to Con. In HD, LPA levels did not differ compared to Con and they were significantly lower compared to PD (HD D1 and HD D2), RT D2 (HD D1 and HD D2) and CT (HD D1). However, in most of patients concentrations of LPA were within the range of reference values established in healthy volunteers. Concentrations of LPC were significantly lower in almost all patients subgroups, compared to Con, except in PD. There were no significant correlations between plasma concentrations of LPA and LPC in any of patients subgroups.

CONCLUSIONS

Presence of CKD is associated with increased plasma LPA levels and the hemodialysis therapy reduces this influence. However, only in a small percentage of patients with CKD, LPA concentrations are out of the reference range, which makes LPA not useful as a diagnostic marker for CKD. Further studies are needed to confirm and explain observed relationships.

[The clinical study on the correlation of lysophosphatidic acid and vascular endotheli growth factor and endothelin in serum of pneumoconiosis]

Objective: To explore the role of lysophosphatidic acid, vascular endothelial growth facor and endothelin in the pathogenesis of pulmonary fibrosis in coal workers'pneumoconiosis patients, the relationship of lysophosphatidic acid, VEGF and ET in serum was studied. Methods: Sixty two pneumoconiosis patients were selected as cases group, which included 23 cases of stage Ⅰ, 25 cases of stageⅡand 14 cases of stageⅢ. Twenty workers were selected as dust exposure group who exposed to coal dust for more than 2 years and had not been diagnosed as pneumoconiosis. Ten healthy people who had no occupational dust exposure were simultaneously selected as the control group. The serum levels of LPA, VEGF and ET were measured by ELISA. Results: The serum levels of VEGF and ET in coal dust exposed group and pneumoconiosis group were much higher than in the control group. The differences were statistically significant among the three groups (P<0.01) . The serum levels of LPA increased in the dust exposed group, stage Ⅰand stage Ⅱgroup. The serum levels of LPA correlated positively with the levels of VEGF and ET (P<0.05) . Conclusions: The serum levels of LPA, VEGF and ET had evident correlation with the pulmonary fibrosis caused by coal dust, which indicate that LPA, VEGF and ET may play a pivotal role in the process of pulmonary fibrosis. The study will throw light on both pathogenesis and early intervention for pneumoconiosis.

Lysophosphatidylinositols in inflammation and macrophage activation: Altered levels and anti-inflammatory effects

Lysophosphatidylinositols (LPI) are bioactive lipids that are implicated in several pathophysiological processes such as cell proliferation, migration and tumorigenesis and were shown to play a role in obesity and metabolic disorders. Often, these effects of LPI were due to activation of the G protein-coupled receptor GPR55. However, the role of LPI and GPR55 in inflammation and macrophage activation remains unclear. Therefore, we thought to study the effect of macrophage activation and inflammation on LPI levels and metabolism. To do so, we used J774 and BV2 cells in culture activated with lipopolysaccharides (LPS, 100 ng/mL) as well as primary mouse alveolar and peritoneal macrophages. We also quantified LPI levels in the cerebellum, lung, liver, spleen and colon of mice with a systemic inflammation induced by LPS (300 μg/kg) and in the colon of mice with acute colitis induced by dextran sulfate sodium (DSS) or trinitrobenzene sulfonic acid (TNBS) and chronic DSS-induced colitis. Our data show that LPS-induced macrophage activation leads to altered LPI levels in both the cells and culture medium. We also show that cytosolic phospholipase A2α (cPLA2α) and α/β‑hydrolase domain 6 (ABHD6) are among the enzymes implicated in LPI metabolism in J774 macrophages. Indeed, ABHD6 and cPLA2α inhibition increased 20:4-LPI levels in LPS-activated macrophages. Furthermore, incubation of LPS-activated cells with LPI decreased J774 activation in a GPR55-dependent manner. In vivo, LPI levels were altered by inflammation in the liver, spleen and colon. These alterations are tissue dependent and could highlight a potential role for LPI in inflammatory processes.

Changes in lysophospholipids and liver status after weight loss: the RESMENA study

Background

Obesity and comorbidities such as non-alcoholic fatty liver disease (NAFLD) are major public health burdens. Alterations in lipid metabolism are involved in hepatic diseases. The objective of this study was to assess the influence of weight loss on lysophospholipid (LP) metabolism and liver status in obese subjects as well as to provide new evidence regarding the interaction of LP metabolism as a key factor in the onset and management of obesity-related diseases such as liver damage.

Methods

Thirty-three subjects from the RESMENA (Reduction of Metabolic Syndrome in Navarra, NCT01087086) study were selected based on their Fatty Liver Index (FLI). Plasma lipid species (lysophosphatidilcholine: LPC, lysophosphatidilethanolamines: LPE and lysophosphatidylinositols: LPI specifically) were determined by LC-MS, while waist circumference (WC) and other non-invasive liver markers such as, FLI and BAAT scores as well as dietary records, anthropometrical measurements, body composition by DXA and other metabolic determinants were analyzed before and after a six-month hypocaloric nutritional intervention.

Results

Computed Z-scores of total LP (LPC, LPE, and LPI) were significantly decreased after 6-months of following a hypocaloric diet. Specifically, LPC14:0, LPC15:0, LPC16:1, LPC18:4, LPC20:4, showed clear relationships with weight loss. Changes in FLI score, WC and BAAT score revealed associations with general changes in LPC score. Interestingly the BAAT score was statistically associated with the LPC score after adjustment for weight loss.

Conclusion

The lipidomic LPC profile analysis revealed a generalized decrease in circulating lysophospholipids after weight loss. The involvement of particular LP in liver metabolism and obesity merit further attention, as some of these specific non-invasive liver markers were reduced independently of weight loss.

Trial registration

NCT01087086. Registered 15 March 2010, retrospectively registry.

Group 1B phospholipase A2 in metabolic and inflammatory disease modulation

The group 1B phospholipase A₂ (PLA2G1B) is a secreted phospholipase that catalyzes the hydrolytic removal of the sn-2 fatty acyl moiety from phospholipids. This enzyme is synthesized most abundantly in the pancreas and is also expressed in the lung. The first part of this review article focuses on the role of pancreatic-derived PLA2G1B in mediating lipid absorption and discusses how the PLA2G1B-derived metabolic product contributes to cardiometabolic diseases, including obesity, hyperinsulinemia, hyperlipidemia, and atherosclerosis. The anti-helminth properties of PLA2G1B will also be discussed. The second part of this review will focus on PLA2G1B expressed in the lung, and in vitro data suggest that how this enzyme may modulate lung inflammation via both hydrolytic activity-dependent and -dependent mechanisms. Finally, recent studies revealing a relationship between PLA2G1B and cancer will also be discussed. This article is part of a Special Issue entitled Novel functions of phospholipase A2 Guest Editors: Makoto Murakami and Gerard Lambeau.

Specific binding of human C-reactive protein towards supported monolayers of binary and engineered phospholipids

Circulating C-reactive protein (CRP) recognizes altered plasma membranes and activates complements systems in the acute phase of inflammation and infection in human. We have shown previously the calcium-independent adsorption of CRP toward 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and lysophosphatidylcholine (LPC) on supported phospholipid monolayers. Here, we extended our study to other phospholipids and additives to elucidate the pattern recognition of CRP using a surface plasmon resonance biosensor. Surface density and lateral fluidity depended on the type of phospholipids in the monolayers as characterized by SPR and fluorescence recovery after photobleaching measurements. CRP recognized 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-l-serine (POPS) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-(1'-rac-glycerol) (POPG) in the supported POPC monolayers without calcium at pH 7.4 and 5.5. As opposed to LPC, CRP did not recognize 3-sn-lysophosphatidylethanolamine in the POPC monolayers in calcium-free conditions. While, the addition of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine (POPE) or sphingomyelin to supported POPC monolayers blocked CRP adsorption. Calcium-dependent CRP binding was observed only at pH 5.5 on supported monolayers of engineered phospholipids with inverted headgroups relative to POPC. The complement 1q (C1q) protein recognized the active form of CRP on the supported phospholipid monolayers. The discovery of CRP recognition with these phospholipids aids our understanding of the activation dynamics of CRP with phospholipid-based biomaterials when used during the acute phase.

Chronic vitamin E deficiency impairs cognitive function in adult zebrafish via dysregulation of brain lipids and energy metabolism

Zebrafish (Danio rerio) are a recognized model for studying the pathogenesis of cognitive deficits and the mechanisms underlying behavioral impairments, including the consequences of increased oxidative stress within the brain. The lipophilic antioxidant vitamin E (α-tocopherol; VitE) has an established role in neurological health and cognitive function, but the biological rationale for this action remains unknown. In the present study, we investigated behavioral perturbations due to chronic VitE deficiency in adult zebrafish fed from 45 days to 18-months of age diets that were either VitE-deficient (E-) or VitE-sufficient (E+). We hypothesized that E- zebrafish would display cognitive impairments associated with elevated lipid peroxidation and metabolic disruptions in the brain. Quantified VitE levels at 18-months in E- brains (5.7 ± 0.1 nmol/g tissue) were ~20-times lower than in E+ (122.8 ± 1.1; n = 10/group). Using assays of both associative (avoidance conditioning) and non-associative (habituation) learning, we found E- vs E+ fish were learning impaired. These functional deficits occurred concomitantly with the following observations in adult E- brains: decreased concentrations of and increased peroxidation of polyunsaturated fatty acids (especially docosahexaenoic acid, DHA), altered brain phospholipid and lysophospholipid composition, as well as perturbed energy (glucose/ketone), phosphatidylcholine and choline/methyl-donor metabolism. Collectively, these data suggest that chronic VitE deficiency leads to neurological dysfunction through multiple mechanisms that become dysregulated secondary to VitE deficiency. Apparently, the E- animals alter their metabolism to compensate for the VitE deficiency, but these compensatory mechanisms are insufficient to maintain cognitive function.

Combination of mass spectrometry-based targeted lipidomics and supervised machine learning algorithms in detecting adulterated admixtures of white rice

The mixing of extraneous ingredients with original products is a common adulteration practice in food and herbal medicines. In particular, authenticity of white rice and its corresponding blended products has become a key issue in food industry. Accordingly, our current study aimed to develop and evaluate a novel discrimination method by combining targeted lipidomics with powerful supervised learning methods, and eventually introduce a platform to verify the authenticity of white rice. A total of 30 cultivars were collected, and 330 representative samples of white rice from Korea and China as well as seven mixing ratios were examined. Random forests (RF), support vector machines (SVM) with a radial basis function kernel, C5.0, model averaged neural network, and k-nearest neighbor classifiers were used for the classification. We achieved desired results, and the classifiers effectively differentiated white rice from Korea to blended samples with high prediction accuracy for the contamination ratio as low as five percent. In addition, RF and SVM classifiers were generally superior to and more robust than the other techniques. Our approach demonstrated that the relative differences in lysoGPLs can be successfully utilized to detect the adulterated mixing of white rice originating from different countries. In conclusion, the present study introduces a novel and high-throughput platform that can be applied to authenticate adulterated admixtures from original white rice samples.

Lysophosphatidic acid plasma concentrations in healthy subjects: circadian rhythm and associations with demographic, anthropometric and biochemical parameters

Background

Lysophosphatidic acid (LPA) is a bioactive lipid with a wide biological activity. Previous studies have shown its potential usefulness as a diagnostic marker for ovarian cancer. The aim of the study was to investigate which factors may influence plasma LPA concentrations in healthy subjects and to propose reference values.

Methods

The study group consisted of 100 healthy subjects. From all of them the blood samples were taken at 7 a.m. (fasting state). From 40 volunteers additional blood samples were taken at 2 p.m., at 8 p.m. and at 2 a.m. next morning. Concentrations of LPA were measured in plasma samples using enzyme-linked immunosorbent assay.

Results

Analysis of samples from 100 healthy volunteers showed significant influence of sex and age on plasma LPA. The reference range for the plasma LPA concentration corrected for age and sex, determined at 2.5–97.5 percentile interval is 0.14–1.64 μM. LPA correlates positively with BMI, serum total cholesterol, triacylglycerols, uric acid and negatively with estimated glomerular filtration rate and serum albumin. Concentration of LPA at 2 a.m. was lower than at 2 p.m. There were not any significant differences between plasma LPA at 7 a.m. and any other time of the day.

Conclusions

Plasma LPA is associated with demographic, anthropometric and biochemical parameters. It seems that LPA concentrations have no specific circadian rhythm and the time of donation and fasting state have marginal effect on plasma LPA. These findings may be helpful in future incorporation of LPA as a diagnostic marker.

Lysophosphatidylcholine activates caspase-1 in microglia via a novel pathway involving two inflammasomes

Inflammasomes regulate microglial caspase-1 activation and subsequent neuroinflammatory processes in brain pathology. In the present study, we have identified inflammasomes causing caspase-1 activation following stimulation of microglia with lysophosphatidylcholine (LPC), a proinflammatory lipid generated under pathological conditions in the brain. LPC-induced caspase-1 activation in microglia was found to depend on LPS prestimulation, inflammasome NLRP3 and adaptor molecule ASC. Furthermore, knockdown of inflammasome NLRC4 inhibited LPC-stimulated caspase-1 activity in microglia, suggesting the requirement of two inflammasomes for optimal caspase-1 activity.

Measurement of Lysophosphatidic Acid and Sphingosine-1-Phosphate by Liquid Chromatography-Coupled Electrospray Ionization Tandem Mass Spectrometry

Lysophosphatidic acids and sphingosine-1-phosphate are bioactive lipids that regulate diverse cellular and physiological processes through actions that are largely mediated by cell surface receptors. The roles played by these lipids in multiple disease processes make the enzymes and receptors involved in their synthesis, inactivation, and signaling attractive targets for pharmacological therapies. In this chapter we describe methods for sensitive accurate quantitation of LPA and S1P levels in biological fluids using liquid chromatography-coupled electrospray ionization tandem mass spectrometry.

Lysophosphatidylcholines activate PPARδ and protect human skeletal muscle cells from lipotoxicity

Metabolomics studies of human plasma demonstrate a correlation of lower plasma lysophosphatidylcholines (LPC) concentrations with insulin resistance, obesity, and inflammation. This relationship is not unraveled on a molecular level. Here we investigated the effects of the abundant LPC(16:0) and LPC(18:1) on human skeletal muscle cells differentiated to myotubes. Transcriptome analysis of human myotubes treated with 10μM LPC for 24h revealed enrichment of up-regulated peroxisome proliferator-activated receptor (PPAR) target transcripts, including ANGPTL4, PDK4, PLIN2, and CPT1A. The increase in both PDK4 and ANGPTL4 RNA expression was abolished in the presence of either PPARδ antagonist GSK0660 or GSK3787. The induction of PDK4 by LPCs was blocked with siRNA against PPARD. The activation of PPARδ transcriptional activity by LPC was shown as PPARδ-dependent luciferase reporter gene expression and enhanced DNA binding of the PPARδ/RXR dimer. On a functional level, further results show that the LPC-mediated activation of PPARδ can reduce fatty acid-induced inflammation and ER stress in human skeletal muscle cells. The protective effect of LPC was prevented in the presence of the PPARδ antagonist GSK0660. Taking together, LPCs can activate PPARδ, which is consistent with the association of high plasma LPC levels and PPARδ-dependent anti-diabetic and anti-inflammatory effects.

iPLA2β deficiency attenuates obesity and hepatic steatosis in ob/ob mice through hepatic fatty-acyl phospholipid remodeling

PLA2G6 or GVIA calcium-independent PLA2 (iPLA2β) is identified as one of the NAFLD modifier genes in humans, and thought to be a target for NAFLD therapy. iPLA2β is known to play a house-keeping role in phospholipid metabolism and remodeling. However, its role in NAFLD pathogenesis has not been supported by results obtained from high-fat feeding of iPLA2β-null (PKO) mice. Unlike livers of human NAFLD and genetically obese rodents, fatty liver induced by high-fat diet is not associated with depletion of hepatic phospholipids. We therefore tested whether iPLA2β could regulate obesity and hepatic steatosis in leptin-deficient mice by cross-breeding PKO with ob/ob mice to generate ob/ob-PKO mice. Here we observed an improvement in ob/ob-PKO mice with significant reduction in serum enzymes, lipids, glucose, insulin as well as improved glucose tolerance, and reduction in islet hyperplasia. The improvement in hepatic steatosis measured by liver triglycerides, fatty acids and cholesterol esters was associated with decreased expression of PPARγ and de novo lipogenesis genes, and the reversal of β-oxidation gene expression. Notably, ob/ob livers contained depleted levels of lysophospholipids and phospholipids, and iPLA2β deficiency in ob/ob-PKO livers lowers the former, but replenished the latter particularly phosphatidylethanolamine (PE) and phosphatidylcholine (PC) that contained arachidonic (AA) and docosahexaenoic (DHA) acids. Compared with WT livers, PKO livers also contained increased PE and PC containing AA and DHA. Thus, iPLA2β deficiency protected against obesity and ob/ob fatty liver which was associated with hepatic fatty-acyl phospholipid remodeling. Our results support the deleterious role of iPLA2β in severe obesity associated NAFLD.

Placental MFSD2a transporter is related to decreased DHA in cord blood of women with treated gestational diabetes

BACKGROUND & AIMS

Maternal-fetal transfer of docosahexaenoic acid (DHA) is impaired by gestational diabetes mellitus (GDM), but the underlying mechanisms are still unknown. MFSD2a was recently recognized as a lyso-phospholipid (lyso-PL) transporter that facilitates DHA accretion in brain. The role of this transporter in placenta is uncertain. We evaluated effects of GDM and its treatment (diet or insulin) on phospholipid species, fatty acid profile in women, cord blood and placental fatty acid carriers.

METHODS

Prospective observational study of pregnant women recruited in the third trimester (25 controls, 23 GDM-diet, 20 GDM-insulin). Fetal ultrasound was performed at gestational week 38. At delivery, maternal and neonatal anthropometry was performed, and fatty acids in total lipids and phospholipid species were analyzed in placenta, maternal and venous cord blood. Western-blot analyses were performed for placental fatty acid carriers.

RESULTS

Fetal abdominal circumference z-score at 38 weeks tended to higher values in GDM (P = 0.071), pointing toward higher fetal fat accretion in these babies. DHA percentage in cord serum total lipids (P = 0.029) and lyso-PL (P = 0.169) were reduced in GDM. Placental MFSD2a was reduced in both GDM groups and was positively correlated to DHA values in cord serum total lipids (r = 0.388, P = 0.003). Among established placental lipid carriers, only FATP4 was correlated to DHA concentration in placental lyso-PL. In all compartments, DHA percentage was inversely correlated to fetal abdominal circumference.

CONCLUSIONS

In offspring of women with GDM treated either with diet or insulin, higher fetal fat accretion and lower placental MFSD2a contribute to reduce DHA availability. Lyso-PL appear to contribute to materno-fetal DHA transport.

Hydrophilic interaction liquid chromatography-mass spectrometry of (lyso)phosphatidic acids, (lyso)phosphatidylserines and other lipid classes

The goal of this work is a systematic optimization of hydrophilic interaction liquid chromatography (HILIC) separation of acidic lipid classes (namely phosphatidic acids-PA, lysophosphatidic acids-LPA, phosphatidylserines-PS and lysophosphatidylserines-LPS) and other lipid classes under mass spectrometry (MS) compatible conditions. The main parameters included in this optimization are the type of stationary phases used in HILIC, pH of the mobile phase, the type and concentration of mobile phase additives. Nine HILIC columns with different chemistries (unmodified silica, modified silica using diol, 2-picolylamine, diethylamine and 1-aminoanthracene and hydride silica) are compared with the emphasis on peak shapes of acidic lipid classes. The optimization of pH is correlated with the theoretical calculation of acidobasic equilibria of studied lipid classes. The final method using the hydride column, pH 4 adjusted by formic acid and the gradient of acetonitrile and 40 mmol/L of aqueous ammonium formate provides good peak shapes for all analyzed lipid classes including acidic lipids. This method is applied for the identification of lipids in real samples of porcine brain and kidney extracts.

Phospholipase A2 as a Molecular Determinant of Store-Operated Calcium Entry

Activation of phospholipases A2 (PLA2) leads to the generation of biologically active lipid products that can affect numerous cellular events. Ca(2+)-independent PLA2 (iPLA2), also called group VI phospholipase A2, is one of the main types forming the superfamily of PLA2. Beside of its role in phospholipid remodeling, iPLA2 has been involved in intracellular Ca(2+) homeostasis regulation. Several studies proposed iPLA2 as an essential molecular player of store operated Ca(2+) entry (SOCE) in a large number of excitable and non-excitable cells. iPLA2 activation releases lysophosphatidyl products, which were suggested as agonists of store operated calcium channels (SOCC) and other TRP channels. Herein, we will review the important role of iPLA2 on the intracellular Ca(2+) handling focusing on its role in SOCE regulation and its implication in physiological and/or pathological processes.

Lysophospholipids and their G protein-coupled receptors in atherosclerosis

Lysophospholipids (LPLs) are bioactive lipid-derived signaling molecules generated by the enzymatic and chemical processes of regiospecific phospholipases on substrates such as membrane phospholipids (PLs) and sphingolipids (SLs). They play a major role as extracellular mediators by activating G-protein coupled receptors (GPCRs) and stimulating diverse cellular responses from their signaling pathways. LPLs are involved in various pathologies of the vasculature system including coronary heart disease and hypertension. Many studies suggest the importance of LPLs in their association with the development of atherosclerosis, a chronic and severe vascular disease. This paper focuses on the pathophysiological effects of different lysophospholipids on atherosclerosis, which may promote the pathogenesis of myocardial infarction and strokes. Their atherogenic biological activities take place in vascular endothelial cells, vascular smooth muscle cells, fibroblasts, monocytes and macrophages, dendritic cells, T-lymphocytes, platelets, etc.

Lysophosphatidic acid signaling in ovarian cancer

Lysophosphatidic acid (LPA) is a bioactive phospholipid that is involved in signal transduction between cells. Plasma and ascites levels of LPA are increased in ovarian cancer patients even in the early stages and thus LPA is considered as a potential diagnostic marker for this disease. This review presents the current knowledge regarding LPA signaling in epithelial ovarian cancer. LPA stimulates proliferation, migration and invasion of ovarian cancer cells through regulation of vascular endothelial growth factor, matrix metalloproteinases, urokinase plasminogen activator, interleukin-6, interleukin-8, CXC motif chemokine ligand 12/CXC receptor 4, COX2, cyclin D1, Hippo-Yap and growth-regulated oncogene α concentrations. In this article, all of these targets and signal pathways involved in LPA influence are described.

Apolipoprotein A-I: A Molecule of Diverse Function

Apolipoprotein A-I (apo A-I) an indispensable component and a major structural protein of high-density lipoprotein (HDL), plays a vital role in reverse cholesterol transport and cellular cholesterol homeostasis since its identification. Its multifunctional role in immunity, inflammation, apoptosis, viral, bacterial infection etc. has crossed its boundary of its potential of protecting cardiovascular system and lowering cardiovascular disease risk, attributing HDL to be known as a protective fat removal particle. Its structural homology with prostacyclin stabilization factor has contributed to its anti-clotting and anti-aggregatory effect on platelet which has potentiated its cardio-protective role as well as its therapeutic efficacy against Alzheimer's disease. The binding affinity and neutralising action against endotoxin lipopolysaccharide, reduces the toxic manifestations of septic shock. As a negative acute phase protein, it blocks T-cell signalling of macrophages. However the recently identified anti-tumor activity of apo A-I has been highlighted in various models of melanoma, lung cancer, ovarian cancer, lymphoblastic leukaemia, gastric as well as pancreatic cancers. These cancer fighting effects are directed towards regression of tumor size and distant metastasis by its immuno modulatory activity as well as its clearing effect on serum lysophospholipids. This lowering effect on lysophospholipid concentration is utilized by apo A-I mimetic peptides to be used in retarding tumor cell proliferation and as a potential cancer therapeutic agent. Not only that, it inhibits the tumor associated neo-angiogenesis as well as brings down the matrix degrading enzymes associated with tumor metastasis. However this efficient therapeutic potential of apo A-I as an anti tumor agent awaits further future experimental studies in humans.

Changes of murine sperm phospholipid composition during epididymal maturation determined by MALDI-TOF mass spectrometry

After leaving the testis, spermatozoa undergo several important steps of biochemical maturation during the passage through the epididymis, increasing their motility and fertilizing ability. These changes comprise (among others) the modification of the phospholipid composition of the sperm membrane. This process is thought to be important for the achievement of motility and fertilizing capacity. The lipids of the sperm membrane are characterized by a significant content of unsaturated fatty acyl residues, resulting in a high sensitivity against oxidative stress. This is evidenced by the appearance of lysolipids, for example, lysophosphatidylcholine, which acts like a detergent and is normally present in only very small amounts in biological membranes. The epididymis represents a tubular system comprising three main parts (caput, corpus, and cauda), through which the spermatozoa are consecutively transported undergoing distinct maturation stages. Using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, we established three striking differences in the lipid composition of murine spermatozoa from the different epididymal regions: in comparison to the caput sperm, sperm from the cauda are characterized by (1) a higher degree of unsaturation (PC 18:0/22:5 and 18:0/22:6 vs. 18:0/20:4 and 18:0/18:1), (2) an enhanced plasmalogen content, and (3) an enhanced content of lysolipids. These changes are likely to be of physiological relevance and potentially useful as diagnostic markers of sperm maturation and acquisition of motility.

Seasonal changes in minor membrane phospholipid classes, sterols and tocopherols in overwintering insect, Pyrrhocoris apterus

Ectotherm animals including insects are known to undergo seasonal restructuring of the cell membranes in order to keep their functionality and/or protect their structural integrity at low body temperatures. Studies on insects so far focused either on fatty acids or on composition of molecular species in major phospholipid classes. Here we extend the scope of analysis and bring results on seasonal changes in minor phospholipid classes, lysophospholipids (LPLs), free fatty acids, phytosterols and tocopherols in heteropteran insect, Pyrrhocoris apterus. We found that muscle tissue contains unusually high amounts of LPLs. Muscle and fat body tissues also contain high amounts of β-sitosterol and campesterol, two phytosterols derived from plant food, while only small amounts of cholesterol are present. In addition, two isomers (γ and δ) of tocopherol (vitamin E) are present in quantities comparable to, or even higher than phytosterols in both tissues. Distinct seasonal patterns of sterol and tocopherol concentrations were observed showing a minimum in reproductively active bugs in summer and a maximum in diapausing, cold-acclimated bugs in winter. Possible adaptive meanings of such changes are discussed including: preventing the unregulated transition of membrane lipids from functional liquid crystalline phase to non-functional gel phase; decreasing the rates of ion/solute leakage; silencing the activities of membrane bound enzymes and receptors; and counteracting the higher risk of oxidative damage to PUFA in winter membranes.