Simple chemical syntheses of TAG monohydroperoxides

Analysis of serum lysophosphatidylethanolamine levels in patients with non-alcoholic fatty liver disease by liquid chromatography-tandem mass spectrometry

Lysophosphatidylethanolamines (LysoPEs) are the partial hydrolysis products of phosphatidylethanolamine. Despite the unique in vitro bioactivities of LysoPEs, there are limited reports on the pathophysiological role of LysoPEs in the serum, due to the lack of sensitive analytical methods for determination of each molecular species in clinical samples. Herein, we developed a highly sensitive quantitative method to profile the serum LysoPE species by liquid chromatography-tandem mass spectrometry (LC-MS/MS) with selected reaction monitoring (SRM). The internal standard (IS), chemically synthesized in-house, and the lineup of seven major LysoPE species were used in this study. The limits of detection and quantification for each LysoPE species ranged within 0.5-3.3 pmol/mL and 1.0-5.0 pmol/mL, respectively. The combined concentrations of LysoPEs in the serum from healthy subjects (n = 8) and the patients with non-alcoholic fatty liver diseases (NAFLD) including simple steatosis (SS, n = 9) and non-alcoholic steatohepatitis (NASH, n = 27) were 18.030 ± 3.832, 4.867 ± 1.852, and 5.497 ± 2.495 nmol/mL, respectively. The combined and individual concentrations of LysoPEs, except for LysoPE 18:0, significantly decreased in the patients with NAFLD compared with those for the healthy subjects. However, no significant difference was observed between the SS and NASH groups. Our proposed LC-MS/MS method is valid and has advantages of small sample volume, high sensitivity, and simultaneous absolute quantitation for multiple molecular species. This method may enable diagnostic evaluation and elucidation of the as-yet uncovered pathophysiological role of LysoPEs.

Comprehensive lipidomic profiling in serum and multiple tissues from a mouse model of diabetes

INTRODUCTION

Diabetes mellitus is a serious metabolic disorder causing multiple organ damage in human. However, the lipidomic profiles in different organs and their associations are rarely studied in either diabetic patients or animals.

OBJECTIVES

To evaluate and compare the characteristics of lipid species in serum and multiple tissues in a diabetic mouse model.

METHODS

Semi-quantitative profiling analyses of intact and oxidized lipids were performed in serum and multiple tissues from a diabetic mouse model fed a high fat diet and treated with streptozotocin by using LC/HRMS and MS/MS. The total content of each lipid class, and the tissue-specific lipid species in all tissue samples were determined and compared by multivariate analyses.

RESULTS

The diabetic mouse model displayed characteristic differences in serum and multiple organs: the brain and heart showed the largest reduction in cardiolipin, while the kidney had more alterations in triacylglycerol. Interestingly, the lipidomic differences also existed between different regions of the same organ: cardiolipin species with highly polyunsaturated fatty acyls decreased only in atrium but not in ventricle, while renal cortex showed longer fatty acyl chains for both increased and decreased triacylglycerol species than renal medulla. Importantly, diabetes caused an accumulation of lipid hydroperoxides, suggesting that oxidative stress was induced in all organs except for the brain during the development of diabetes.

CONCLUSIONS

These findings provided novel insight into the organ-specific relationship between diabetes and lipid metabolism, which might be useful for evaluating not only diabetic tissue injury but also the effectiveness of diabetic treatments.

Identification of novel biomarkers of hepatocellular carcinoma by high-definition mass spectrometry: Ultrahigh-performance liquid chromatography quadrupole time-of-flight mass spectrometry and desorption electrospray ionization mass spectrometry imaging

RATIONALE

Hepatocellular carcinoma (HCC) is a highly malignant disease for which the development of prospective or prognostic biomarkers is urgently required. Although metabolomics is widely used for biomarker discovery, there are some bottlenecks regarding the comprehensiveness of detected features, reproducibility of methods, and identification of metabolites. In addition, information on localization of metabolites in tumor tissue is needed for functional analysis. Here, we developed a wide-polarity global metabolomics (G-Met) method, identified HCC biomarkers in human liver samples by high-definition mass spectrometry (HDMS), and demonstrated localization in cryosections using desorption electrospray ionization MS imaging (DESI-MSI) analysis.

METHODS

Metabolic profiling of tumor (n = 38) and nontumor (n = 72) regions in human livers of HCC was performed by an ultrahigh-performance liquid chromatography quadrupole time-of-flight MS (UHPLC/QTOFMS) instrument equipped with a mixed-mode column. The HCC biomarker candidates were extracted by multivariate analyses and identified by matching values of the collision cross section and their fragment ions on the mass spectra obtained by HDMS. Cryosections of HCC livers, which included both tumor and nontumor regions, were analyzed by DESI-MSI.

RESULTS

From the multivariate analysis, m/z 904.83 and m/z 874.79 were significantly high and low, respectively, in tumor samples and were identified as triglyceride (TG) 16:0/18:1(9Z)/20:1(11Z) and TG 16:0/18:1(9Z)/18:2(9Z,12Z) using the synthetic compounds. The TGs were clearly localized in the tumor or nontumor areas of the cryosection.

CONCLUSIONS

Novel biomarkers for HCC were identified by a comprehensive and reproducible G-Met method with HDMS using a mixed-mode column. The combination analysis of UHPLC/QTOFMS and DESI-MSI revealed that the different molecular species of TGs were associated with tumor distribution and were useful for characterizing the progression of tumor cells and discovering prospective biomarkers.

Chemical Composition of an Aphid Antifeedant Extract from an Endophytic Fungus, Trichoderma sp. EFI671

Botanical and fungal biopesticides, including endophytes, are in high demand given the current restrictive legislations on the use of chemical pesticides. As part of an ongoing search for new biopesticides, a series of fungal endophytes have been isolated from selected medicinal plants including Lauraceae species. In the current study, an extract from the endophytic fungus Trichoderma sp. EFI 671, isolated from the stem parts of the medicinal plant Laurus sp., was screened for bioactivity against plant pathogens (Fusarium graminearum, Rhizoctonia solani, Sclerotinia sclerotiorum and Botrytis cinerea), insect pests (Spodoptera littoralis, Myzus persicae, Rhopalosiphum padi) and plant parasites (Meloidogyne javanica), with positive results against M. persicae. The chemical study of the neutral fraction of the active hexane extract resulted in the isolation of a triglyceride mixture (m1), eburicol (2), β-sitostenone (3), ergosterol (4) and ergosterol peroxide (5). The free fatty acids present in the acid fraction of the extract and in m1 (oleic, linoleic, palmitic and stearic) showed strong dose-dependent antifeedant effects against M. persicae. Liquid (potato dextrose broth, PDB and Sabouraud Broth, SDB) and solid (corn, sorghum, pearl millet and rice) growth media were tested in order to optimize the yield and bioactivity of the fungal extracts. Pearl millet and corn gave the highest extract yields. All the extracts from these solid media had strong effects against M. persicae, with sorghum being the most active. Corn media increased the methyl linoleate content of the extract, pearl millet media increased the oleic acid and sorghum media increased the oleic and linoleic acids compared to rice. The antifeedant effects of these extracts correlated with their content in methyl linoleate and linoleic acid. The phytotoxic effects of these extracts against ryegrass, Lolium perenne, and lettuce, Lactuca sativa, varied with culture media, with sorghum being non- toxic.

Choline and Ethanolamine Plasmalogens Prevent Lead-Induced Cytotoxicity and Lipid Oxidation in HepG2 Cells

Plasmalogens derived from dietary phospholipids are considered to be potential protectors against oxidation-related disorders, while lead (Pb) is an environmental contaminant worldwide and is known to induce oxidative stress. However, the protective and antilipid oxidative effects of individual plasmalogen species against Pb damage have received little attention. In this study, six plasmalogen species (with either choline or ethanolamine as the headgroup and p16:0/18:1, p16:0/18:2, or p16:0/20:5 as the side chains) were evaluated in human hepatoma cells. Plasmalogen species showed a remarkable recovery in cell viability as well as elimination of reactive oxygen species and suppressed the accumulation of phosphatidylcholine hydroperoxides (from 63.6 ± 1.8% to 80.3 ± 2.9%) and phosphatidylethanolamine hydroperoxides (from 25.7 ± 9.3% to 76.1 ± 3.7%). Moreover, plasmalogens significantly upregulated the gene expression levels of a series of antioxidant enzymes that are regulated via the Nrf-2-dependent pathway. This study suggested that choline and ethanolamine plasmalogens could prevent Pb-induced cytotoxicity and lipid oxidation in HepG2 cells.

Identification of molecular species of oxidized triglyceride in plasma and its distribution in lipoproteins

The role of triglycerides carried in the triglyceride-rich lipoproteins (TRL) in the progression of atherosclerosis is uncertain. Identification of oxidized triglycerides and its possible association with atherosclerosis were largely ignored. Here we applied mass spectrometric approach to detect and identify triglyceride hydroperoxides (TGOOH) in human plasma and lipoproteins.

EDTA plasma was collected from healthy human volunteers (n=9) after 14–16 h of fasting. Very low-density lipoprotein (VLDL)

We identified 11 molecular species of TGOOH in either plasma or VLDL and IDL, of which TGOOH-18:1/18:2/16:0, TGOOH-18:1/18:1/16:0, TGOOH-16:0/18:2/16:0, TGOOH-18:1/18:1/18:1, and TGOOH-16:0/20:4/16:0 were most dominant. These TGOOH molecules are carried by TRL but not by LDL and HDL. Mean concentration of TGOOH in plasma, VLDL and IDL were, respectively, 56.1±25.6, 349.8±253.6 and 512.5±173.2 μmol/mol of triglycerides.

This is the first report to identify several molecular species of oxidized triglycerides in TRL. Presence of oxidized triglyceride may contribute to the atherogenicity of TRL. Further work is needed to elucidate the association of the oxidized triglyceride in atherosclerosis.

Analysis of triacylglycerol hydroperoxides in human lipoproteins by Orbitrap mass spectrometer

Herein, we represent a simple method for the detection and characterization of molecular species of triacylglycerol monohydroperoxides (TGOOH) in biological samples by use of reversed-phase liquid chromatography with a LTQ Orbitrap XL mass spectrometer (LC/LTQ Orbitrap) via an electrospray ionization source. Data were acquired using high-resolution, high-mass accuracy in Fourier-transform mode. Platform performance, related to the identification of TGOOH in human lipoproteins and plasma, was estimated using extracted ion chromatograms with mass tolerance windows of 5 ppm. Native low-density lipoproteins (nLDL) and native high-density lipoproteins (nHDL) from a healthy donor were oxidized by CuSO4 to generate oxidized LDL (oxLDL) and oxidized HDL (oxHDL). No TGOOH molecular species were detected in the nLDL and nHDL, whereas 11 species of TGOOH molecules were detected in the oxLDL and oxHDL. In positive-ion mode, TGOOH was found as [M + NH4](+). In negative-ion mode, TGOOH was observed as [M + CH3COO](-). TGOOH was more easily ionized in positive-ion mode than in negative-ion mode. The LC/LTQ Orbitrap method was applied to human plasma and three molecular species of TGOOH were detected. The limit of detection is 0.1 pmol (S/N = 10:1) for each synthesized TGOOH.

Improved HPLC assay for lipid peroxides in human plasma using the internal standard of hydroperoxide

We have developed a sensitive reversed-phase chemiluminescence HPLC approach for simultaneous quantitative and qualitative analyses of hydroperoxides of cholesteryl ester and TG in human plasma. Standard hydroperoxides of cholesteryl ester and TG and a novel internal standard (1-tetradecanyl 3-octadecenoyloxy-5beta-cholan-24-oate monohydroperoxide) (I.S.) were chemically synthesized and the standard curves confirmed to be linear throughout the calibration range (1-1000 pmol). Within-day and between-day CV were less than 7%, and the recoveries were within the range of 84-93%. With sample size minimized to 0.1 mL of plasma for each run, plasma cholesteryl ester hydroperoxide levels were 189 +/- 87 nM (mean +/- SD) in healthy young (22-25 yr old; n = 15, male/female = 6:9) and 210 +/- 69 nM in healthy elderly (39-60 yr old; n = 6, male/female = 3:3). TG hydroperoxide was not detected in healthy subjects. In patients with advanced liver failure (36-67 yr old; n = 4, male/female = 2:2), hydroperoxide levels of plasma cholesteryl ester and TG were 11,903 +/- 9,553 nM and 3,318 +/- 1,590 nM, respectively, indicating an involvement of lipid oxidation. Sensitive and specific monitoring of plasma lipid peroxides using the present chemiluminescence HPLC approach with the synthesized I.S. may help our understanding of chemical and pathophysiological aspects of lipid peroxidation.