bims-metlip Biomed News
on Methods and protocols in metabolomics and lipidomics
Issue of 2019‒12‒29
twenty-two papers selected by
Sofia Costa
Cold Spring Harbor Laboratory


  1. J Chromatogr B Analyt Technol Biomed Life Sci. 2019 Dec 16. pii: S1570-0232(19)31293-0. [Epub ahead of print]1137 121941
    Rister AL, Dodds ED.
      Methods for the analysis of steroids have long been of interest due to the multiple uses for such methods in medical applications, sports monitoring, and environmental science. The analysis of steroids involves inherent analytical hurdles due to their low biological concentrations, poor ionization efficiencies, and frequent occurrence of isomerism. One analytical technique that has been recently applied to steroid analysis is ion mobility spectrometry (IMS). While previous work has focused on the use of metal adduction and multimer formation to enhance separation through IMS analysis coupled to mass spectrometry (MS), this work furthers this approach by coupling IMS-MS with liquid chromatography (LC). Three different LC methods with varying tradeoffs between chromatographic resolution and run time were developed, with one of these achieving a resolution above 1.5 for all steroid isomers. These results also indicate that the coupling of LC to IMS-MS can increase the overall resolution of steroid isomers relative to what can be achieved by either LC or IMS alone. Furthermore, the use of LC and IMS in concert can allow for a more rapid analysis of steroid isomers than can be achieved by LC-MS alone. Finally, the IMS dimension provided for measurements of ion-neutral collision cross sections (CCSs), which were found to be in good agreement with previously reported measurements. Thus, this approach provides three complementary quantitative parameters (retention time, CCS, and mass-to-charge ratio) that can contribute the identification of analytes. Overall, the work presented here demonstrates the potential of coupling LC, IMS, and MS for the analysis of isomeric steroid hormones.
    Keywords:  Ion mobility spectrometry; Liquid chromatography; Mass spectrometry; Steroids
    DOI:  https://doi.org/10.1016/j.jchromb.2019.121941
  2. Sci Rep. 2019 Dec 27. 9(1): 20198
    Martín-Blázquez A, Díaz C, González-Flores E, Franco-Rivas D, Jiménez-Luna C, Melguizo C, Prados J, Genilloud O, Vicente F, Caba O, Pérez Del Palacio J.
      Colorectal cancer is one of the main causes of cancer death worldwide, and novel biomarkers are urgently needed for its early diagnosis and treatment. The utilization of metabolomics to identify and quantify metabolites in body fluids may allow the detection of changes in their concentrations that could serve as diagnostic markers for colorectal cancer and may also represent new therapeutic targets. Metabolomics generates a pathophysiological 'fingerprint' that is unique to each individual. The purpose of our study was to identify a differential metabolomic signature for metastatic colorectal cancer. Serum samples from 60 healthy controls and 65 patients with metastatic colorectal cancer were studied by liquid chromatography coupled to high-resolution mass spectrometry in an untargeted metabolomic approach. Multivariate analysis revealed a separation between patients with metastatic colorectal cancer and healthy controls, who significantly differed in serum concentrations of one endocannabinoid, two glycerophospholipids, and two sphingolipids. These findings demonstrate that metabolomics using liquid-chromatography coupled to high-resolution mass spectrometry offers a potent diagnostic tool for metastatic colorectal cancer.
    DOI:  https://doi.org/10.1038/s41598-019-55952-8
  3. Anal Bioanal Chem. 2019 Dec 24.
    Lépine M, Sleno L, Lesage J, Gagné S.
      4,4'-Methylenediphenyldiisocyanate (MDI), toluenediisocyanate (2,4-TDI and 2,6-TDI), and 1,6'-hexamethylenediisocyanate (HDI) are all commonly used in the production of polyurethane-containing materials in different application areas. Workers exposed occupationally to these compounds may develop sensitization with the potential to lead to asthma. Isocyanates are metabolized in vivo by conjugation to macromolecules and/or by acetylation prior to being eliminated in urine. The hydrolysis of urine samples releases free amine compounds from these metabolites as biomarkers of exposure, specific to each parent isocyanate: 4,4'-methylenedianiline (MDA), toluenediamine (2,4-TDA and 2,6-TDA), and hexamethylenediamine (HDA). To address the need for a validated method that could be used for the simultaneous determination of biomarkers of aliphatic and aromatic isocyanates to monitor occupational exposure based on recommended thresholds, we have developed an UPLC-MS/MS method for the quantitation of MDA, TDA isomers, and HDA following acid hydrolysis, solid-phase extraction, and derivatization of urine samples. Free amine compounds were derivatized with acetic anhydride to augment chromatographic retention and signal intensity. The method was developed considering the biological guidance value (BGV) of MDA at 10 μg L-1, and biological exposure indices (BEI) of TDA isomers and HDA at 5 μg g-1 and 15 μg g-1 creatinine, respectively. Limits of detection allowed monitoring down to 6% of BGV/BEI, with precision within 8%. The accuracy and reliability of the method were assessed using inter-laboratory reference samples and deemed acceptable based on three rounds of measurements. This novel method has therefore been proven as useful for occupational safety and health assessments. Graphical Abstract.
    Keywords:  Acetylation; Biological monitoring; Isocyanate; Quantitative analysis; UHPLC-MS/MS; Urinary biomarkers
    DOI:  https://doi.org/10.1007/s00216-019-02295-y
  4. Anal Chem. 2019 Dec 23.
    van Harskamp D, Garrelfs SF, Oosterveld MJS, Groothoff JW, van Goudoever JB, Schierbeek H.
      Primary hyperoxalurias (PH) are inborn errors of glyoxylate metabolism characterized by an increase in endogenous oxalate production. Oxalate overproduction may cause calcium-oxalate crystal formation leading to kidney stones, nephrocalcinosis, and ultimately kidney failure. Twenty-four hour urine oxalate excretion is an inaccurate measure for endogenous oxalate production in PH patients and not applicable in those with kidney failure. Treatment efficacy cannot be assessed with this measure during clinical trials. We describe the development and validation of a gas chromatography-tandem mass spectrometry method to analyze the samples obtained following a stable isotope infusion protocol of 13C2-oxalate and 1-13C-glycolate in both healthy individuals and PH patients. Isotopic enrichments of plasma oxalate, glycolate, and glyoxylate were measured on a gas chromatography-triple quadrupole mass spectrometry system using ethylhydroxylamine and N-tert-butyldimethylsilyl-N-methyltrifluoroacetamide (MTBSTFA) for analyte derivatization. Method precision was good for oxalate and glycolate (coefficients of variation [CV] were <6.3% and <4.2% for inter- and intra-day precision, respectively) and acceptable for glyoxylate (CV <18.3% and <6.7% for inter- and intra-day precision, respectively). The enrichment curves were linear over the specified range. Sensitivity was sufficient to accurately analyze enrichments. This new method allowed calculation of kinetic features of these metabolites, thus enabling a detailed analysis of the various pathways involved in glyoxylate metabolism. The method will further enhance the investigation of the metabolic PH derangements, provides a tool to accurately assess the therapeutic efficacy of new promising therapeutic interventions for PH, and could serve as a clinical tool to improve personalized therapeutic strategies.
    DOI:  https://doi.org/10.1021/acs.analchem.9b03670
  5. Anal Bioanal Chem. 2019 Dec 26.
    Bowman AP, Bogie JFJ, Hendriks JJA, Haidar M, Belov M, Heeren RMA, Ellis SR.
      Matrix-assisted laser desorption/ionisation-mass spectrometry imaging (MALDI-MSI) is a powerful technique for visualising the spatial locations of lipids in biological tissues. However, a major challenge in interpreting the biological significance of local lipid compositions and distributions detected using MALDI-MSI is the difficulty in associating spectra with cellular lipid metabolism within the tissue. By-and-large this is due to the typically limited spatial resolution of MALDI-MSI (30-100 μm) meaning individual spectra represent the average spectrum acquired from multiple adjacent cells, each potentially possessing a unique lipid composition and biological function. The use of oversampling is one promising approach to decrease the sampling area and improve the spatial resolution in MALDI-MSI, but it can suffer from a dramatically decreased sensitivity. In this work we overcome these challenges through the coupling of oversampling MALDI-MSI with laser post-ionisation (MALDI-2). We demonstrate the ability to acquire rich lipid spectra from pixels as small as 6 μm, equivalent to or smaller than the size of typical mammalian cells. Coupled with an approach for automated lipid identification, it is shown that MALDI-2 combined with oversampling at 6 μm pixel size can detect up to three times more lipids and many more lipid classes than even conventional MALDI at 20 μm resolution in the positive-ion mode. Applying this to mouse kidney and human brain tissue containing active multiple sclerosis lesions, where 74 and 147 unique lipids are identified, respectively, the localisation of lipid signals to individual tubuli within the kidney and lipid droplets with lesion-specific macrophages is demonstrated. Graphical abstract.
    Keywords:  Brain; Kidney; Lipids; MALDI; Mass spectrometry imaging; Multiple sclerosis
    DOI:  https://doi.org/10.1007/s00216-019-02290-3
  6. J Chromatogr A. 2019 Dec 12. pii: S0021-9673(19)31235-X. [Epub ahead of print] 460787
    Zhang YY, Zhang Q, Zhang YM, Wang WW, Zhang L, Yu YJ, Bai CC, Guo JZ, Fu HY, She Y.
      Automatic data analysis for gas chromatography-mass spectrometry (GC-MS) is a challenging task in untargeted metabolomics. In this work, we provide a novel comprehensive data analysis strategy for GC-MS-based untargeted metabolomics (autoGCMSDataAnal) by developing a new automatic strategy for performing TIC peak detection and resolution and proposing a novel time-shift correction and component registration algorithm. autoGCMSDataAnal uses original acquired GC-MS datafiles as input to automatically perform TIC peak detection, component resolution, time-shift correction and component registration, statistical analysis, and compound identification. We utilize standards and complex plant samples to comprehensively investigate the performance of autoGCMSDataAnal. The results suggest that the developed strategy is comparable with several state-of-the-art methods that are widely used in GC-MS-based untargeted metabolomics. Based on the proposed strategy, we develop a user-friendly MATLAB GUI for users who are unfamiliar with programming languages to facilitate their routine analysis, which can be freely downloaded at: http://software.tobaccodb.org/software/autogcmsdataanal.
    Keywords:  Automatic data analysis; Chemometrics; GC-MS; MCR-ALS; Untargeted metabolomics
    DOI:  https://doi.org/10.1016/j.chroma.2019.460787
  7. Anal Bioanal Chem. 2019 Dec 21.
    Reinicke M, Dorow J, Bischof K, Leyh J, Bechmann I, Ceglarek U.
      Polyunsaturated fatty acids (PUFAs) and eicosanoids are important mediators of inflammation. The functional role of eicosanoids in metabolic-syndrome-related diseases has been extensively studied. However, their role in neuroinflammation and the development of neurodegenerative diseases is still unclear. The aim of this study was the development of a sample pretreatment protocol for the simultaneous analysis of PUFAs and eicosanoids in mouse liver and brain. Liver and brain samples of male wild-type C57BL/6J mice (11-122 mg) were used to investigate conditions for tissue rinsing, homogenization, extraction, and storage. A targeted liquid chromatography-negative electrospray ionization tandem mass spectrometry method was applied to quantify 7 PUFAs and 94 eicosanoids. The final pretreatment protocol consisted of a 5-min homogenization step by sonication in 650 μL n-hexane/2-propanol (60:40 v/v) containing 2,6-di-tert-butyl-4-methylphenol at 50 μg/mL. Homogenates representing 1 mg tissue were extracted in a single step with n-hexane/2-propanol (60:40 v/v) containing 0.1% formic acid. Autoxidation was prevented by addition of 2,6-di-tert-butyl-4-methylphenol at 50 μg/mL and keeping the samples at 4 °C during sample preparation. Extracts were dried under nitrogen and reconstituted in liquid chromatography eluent before analysis. Recovery was determined to range from 45% to 149% for both liver and brain tissue. Within-run and between-run variability ranged between 7% and 18% for PUFAs and between 1% and 24% for eicosanoids. In liver, 7 PUFAs and 15 eicosanoids were quantified; in brain, 6 PUFAs and 21 eicosanoids had significant differences within the brain substructures. In conclusion, a robust and reproducible sample preparation protocol for the multiplexed analysis of PUFAs and eicosanoids by liquid chromatography-tandem mass spectrometry in liver and discrete brain substructures was developed.
    Keywords:  Brain lipids; Eicosanoids; Extraction; Mass spectrometry; Polyunsaturated fatty acids; Tissue sample preparation
    DOI:  https://doi.org/10.1007/s00216-019-02170-w
  8. Zhongguo Zhong Yao Za Zhi. 2019 Nov;44(22): 4918-4923
    Bi XN, Qi J, Huang YF, Wei GJ, Zhang T, Wang HY, Wang SQ, Li ZH, Zheng W, Wang Q, Zhang YJ.
      Ultra performance liquid chromatography-tandem mass spectrometry( UPLC-MS/MS) was used to establish the simultaneous determination method of eight neurotransmitters in brain,liver,kidney,adrenal gland,serum and urine,including serotonin,5-hydroxyindole acetic acid,epinephrine,norepinephrine,dopamine,glutamic acid,γ-aminobutyric acid,and acetylcholine,and then investigate the distribution characteristics of neurotransmitters in rat tissues,blood and urine. Waters ACQUITY UPLC BEH C_(18) column( 2. 1 mm×100 mm,1. 7 μm) was used,with 0. 3% formic acid solution-acetonitrile as the mobile phase for gradient elution.Multiple reaction monitoring( MRM) scanning method under positive mode by atmospheric pressure electrospray ion source( ESI) was also performed to establish the detection method of neurotransmitters for methodological research. The plasma,urine and tissues of normal rats were pre-treated including homogenization,centrifuging,and protein removal,then the 2 μL supernatant was injected for analysis. The results showed that eight kinds of neurotransmitters could be accurately determined within 7 min,with linear correlation coefficients all greater than 0. 99. This method showed high accuracy and good precision,with specificity,stability,extraction recovery and matrix effects all complying with the biological sample analysis requirements. The most abundant transmitters in the brain,liver,kidney,kidney gland,blood and urine were γ-aminobutyric acid,glutamic acid,glutamic acid,adrenaline,glutamic acid and dopamine.The method is sensitive,rapid,precise,accurate and specific,and can be used for simultaneous quantitative analysis of eight neurotransmitters in biological samples. The investigation of the distribution ratio of transmitters in rats is of important significance to disease prevention and treatment.
    Keywords:  UPLC-MS/MS; biological samples; content determination; distribution characteristics; neurotransmitters
    DOI:  https://doi.org/10.19540/j.cnki.cjcmm.20190428.502
  9. Biomed Chromatogr. 2019 Dec 28. e4790
    Dittakavi S, Mahadevan L, Chandrashekar DV, Bhamidipati RK, Suresh J, Dhakshinamoorthy S, Li Z, Baerenz F, Tennagels N, Mullangi R.
      Ceramides are known to be involved in various biological processes and their physiological levels are elevated in various disease conditions like diabetes, Alzheimer's, atherosclerosis etc. To facilitate the rapid screening of Cer d18:1/16:0, d18:1/24:0, d18:1/24:1, d18:1/18:0, d18:1/14:0, d18:1/20:0 and d18:1/22:0 inhibition in HepG-2 cells, a RapidFire coupled to tandem mass spectrometry (RF-MS/MS) assay method has been developed. The RapidFire platform provides an automated solid-phased extraction system that gave a throughput of 12.6 sec per sample to an LC-MS/MS using electrospray ionization under positive-ion mode. Chromatographic separation of Cer d18:1/16:0, d18:1/24:0, d18:1/24:1, d18:1/18:0, d18:1/14:0, d18:1/20:0 and d18:1/22:0 was achieved using a ternary gradient on C8 type E cartridge. The MS/MS ion transitions monitored were 538.2→264.2, 650.7→264.2, 648.6→264.2, 566.4→264.2, 510.4→264.2, 594.4→264.2, 622.5→264.2 and 552.3→250.2 for Cer d18:1/16:0, d18:1/24:0, d18:1/24:1, d18:1/18:0, d18:1/14:0, d18:1/20:0 and d18:1/22:0 and the IS (Cer d17:1/18:0), respectively. The RF-MS/MS methodology showed excellent performance with an average Z' (Z prime) value of 0.5-0.7. This is the first report of RF-MS/MS assay for ceramides screening, which is amenable for high throughput screening.
    Keywords:  Ceramides; LC-MS/MS method; RapidFire; quantification
    DOI:  https://doi.org/10.1002/bmc.4790
  10. Endocrine. 2019 Dec 24.
    Yu H, Zhao Y, Zhang Y, Zhong L.
      PURPOSE: Acromegaly is a rare disease caused by chronic hypersecretion of growth hormone, which leads to multiple comorbidities and reduced life expectancy. The objective of this study was to characterize the serum metabolic profiles of acromegaly patients and identify metabolic biomarkers using metabolomics.METHODS: Twenty-nine active acromegaly patients and age- and sex-matched normal controls were recruited. Serum samples were collected, and serum metabolites were analyzed using gas chromatography-mass spectrometry coupled with a series of multivariate statistical analyses.
    RESULTS: The orthogonal projections to latent structures-discriminate analysis (OPLS-DA) model identified and validated significant metabolic differences between individuals with acromegaly and normal controls (R2Y = 0.908 and Q2Y = 0.601). Compared with normal controls, acromegaly patients had elevated levels of 5-aminovaleric acid, glyceric acid, L-dithiothreitol, dihydrocoumarin, N-acetyl-L-glutamic acid, gluconic acid, and monoolein (P < 0.05) and reduced serum levels of D-erythronolactone, taurine, carbamoyl-aspartic acid, and mucic acid (P < 0.01). Furthermore, glyceric acid and taurine possessed higher area under the receiver operating characteristic curve values (AUC values, 0.914 and 0.931, respectively), suggesting an excellent clinical ability to distinguish acromegaly patients from normal controls. Pathway analysis revealed that the pentose phosphate pathway and the taurine and hypotaurine metabolic pathway are significant pathways (P = 0.002 and 0.004, respectively).
    CONCLUSIONS: Metabolic activity is significantly altered in the serum of individuals with active acromegaly. Glyceric acid and taurine may be considered potential biomarkers for distinguishing acromegaly patients from normal controls.
    Keywords:  Acromegaly; Gas chromatography–mass spectrometry; Glyceric acid; Metabolic biomarkers; Metabolomics; Taurine
    DOI:  https://doi.org/10.1007/s12020-019-02143-0
  11. Metabolites. 2019 Dec 21. pii: E8. [Epub ahead of print]10(1):
    Reisdorph NA, Walmsley S, Reisdorph R.
      Metabolomics has the potential to greatly impact biomedical research in areas such as biomarker discovery and understanding molecular mechanisms of disease. However, compound identification (ID) remains a major challenge in liquid chromatography mass spectrometry-based metabolomics. This is partly due to a lack of specificity in metabolomics databases. Though impressive in depth and breadth, the sheer magnitude of currently available databases is in part what makes them ineffective for many metabolomics studies. While still in pilot phases, our experience suggests that custom-built databases, developed using empirical data from specific sample types, can significantly improve confidence in IDs. While the concept of sample type specific databases (STSDBs) and spectral libraries is not entirely new, inclusion of unique descriptors such as detection frequency and quality scores, can be used to increase confidence in results. These features can be used alone to judge the quality of a database entry, or together to provide filtering capabilities. STSDBs rely on and build upon several available tools for compound ID and are therefore compatible with current compound ID strategies. Overall, STSDBs can potentially result in a new paradigm for translational metabolomics, whereby investigators confidently know the identity of compounds following a simple, single STSDB search.
    Keywords:  compound identification; database; metabolite identification; metabolomics; spectral library
    DOI:  https://doi.org/10.3390/metabo10010008
  12. Wei Sheng Yan Jiu. 2019 Nov;48(6): 981-987
    Chen X, Zhou J, Jin M.
      OBJECTIVE: To establish a rapid and accurate method for determination of 25-hydroxyl vitamin D2, 25-hydroxyl vitamin D3 and 3-epi-25-hydroxyl vitamin D3 in serum by isotope dilution ultra-fast liquid chromatography-tandem mass spectrometry(UFLC-MS/MS).METHODS: The serum sample was extracted by nhexane after methanol/acetonitrile precipitation protein, and then the extract was concentrated by nitrogen and volumed with the primary mobile phase. The chromatographic separation was carried out on a Phenomenex Kinetex F5 column(2. 1 mm × 150 mm, 1. 7 μm) by using 0. 1%(V/V) formic acid and 0. 1%(V/V) formic acid/methanol solution as the mobile phase with the gradient elution. Detection was performed in positive multi-reaction monitoring(MRM) mode with the isotope internal labeling method for quantification.
    RESULTS: The baseline separation was obtained within 6 min for the epimer 25-hydroxyl vitamin D3 and 3-epi-25-hydroxyl vitamin D3, and the accurate qualification was obtained for the simultaneous determination of 25-hydroxyl vitamin D2, 25-hydroxyl vitamin D3 and 3-epi-25-hydroxyl vitamin D3. The three analytes showed good linear relationship within the range of 0. 5-50. 0 μg/L with a correlation coefficient r >0. 9995. The limits of detection(LODs) and the limits of quantitation(LOQs) of the method were 0. 15 μg/L and 0. 5 μg/L, respectively. The recoveries of the method were84. 3%-109. 0%(n = 11) at the three spiked levels of 1. 0, 10. 0 and 30. 0 μg/L, and the relative standard deviations(RSDs) were between 0. 8%-6. 8%. At the same time, the certified standard reference materials(SRM) of the America National Institute of Standards and Technology(NIST) Level 1, Level 2, Level 3 and Level 4(SRM 972 a)were used as the quality control samples for verification, the relative deviations of the measurement result were less than 5% compared with the reference values.
    CONCLUSION: The developed method has the characteristics of simplicity, rapidity, sensitivity and accuracy, and is suitable for the simultaneous rapid determination of 25-hydroxyl vitamin D2, 25-hydroxyl vitamin D3 and 3-epi-25-hydroxyl vitamin D3 in serum.
    Keywords:  25-hydroxyl vitamin D_2; 25-hydroxyl vitamin D_3; 3-epi-25-hydroxyl vitamin D_3; UFLC-MS/MS; epimer; isotopic internal standard method; serum
  13. Heliyon. 2019 Dec;5(12): e02978
    Nandini E, Arunraj B, Rajesh N, Rajesh V.
      Gut microbiota has been implicated in many disorders including Autism Spectrum Disorder (ASD). ASD is a neurodevelopmental brain disorder affecting individuals leading to restricted and repetitive pattern of behaviour and disruption of communication and social interactions. Altered microbiome and the presence or absence of key species capable of affecting specific responses in levels of their fermentation products are reflected in the urinary metabolite profile of patients. The aim of our study is to develop an improvised method for the detection and quantification of urinary p-cresol levels which could serve as an indicator for GI microbial dysbiosis. The p-cresol analysis was achieved using HPLC by a reverse phase C18 column with mobile phase composition of Acetonitrile/water/formic acid (10:90:0.05, v/v/v) in an isocratic mode of elution with a flow rate of 1.0 mL/min. The mass analysis of p-cresol was performed using LC-MS [Triple Quadrupole Liquid Chromatography Mass Spectrometer] in negative ESI mode with electron multiplier detector. p-cresol was eluted at a retention time of approximately 3.4 min. The standard calibration curves had a superior regression coefficient of greater than 0.99 (R2 > 0.99) and were linear over a range from 0.0005 mg/mL to 0.015 mg/mL. The method was validated by analysis of six replicates with 0.08% relative standard deviation and method detection and quantification limits were 20 ng/mL and 50 ng/mL respectively. Further validation of method on real urine samples from two groups of children (Control population:< 10 years of age; 5M: 3F and ASD individuals: <10 years of age; All males) showed that detection was effective over a wide range of metabolite at levels as high as 149.73 μg/mL to as low as 0.897 μg/mL. This study reports a rapid, validated and sensitive method for the detection of p-cresol in urine samples.
    Keywords:  Analytical chemistry; Biochemistry; HPLC; LC-MS; Metabolite; Urinary p-cresol
    DOI:  https://doi.org/10.1016/j.heliyon.2019.e02978
  14. Anal Chim Acta. 2020 Jan 25. pii: S0003-2670(19)31239-5. [Epub ahead of print]1095 38-47
    Kellogg JJ, Kvalheim OM, Cech NB.
      Metabolomics-based approaches are becoming increasingly popular to interrogate the chemical basis for phenotypic differences in biological systems. Successful metabolomics studies employ multivariate data analysis to compare large and highly complex datasets. A primary tool for unsupervised statistical analyses, principal component analysis (PCA), relies on the selection of a subsection of a maximum of three components from a larger model to visually represent similarity. The use of only three principal components limits the comprehensiveness of the model and can mask discrimination between samples. We have developed a new statistical metric, the composite score (CS), as a univariate statistic that incorporates multiple principal components to calculate a correlation matrix that enables quantitative comparisons of sample similarity between samples within one dataset based upon measured metabolome profiles. Composite score values were tabulated using profiles of complex extracts of dietary supplements from the plant Hydrastis canadensis (goldenseal) as a case study. Several outliers were unambiguously identified, and a PCA composite score network was developed to provide a graphical representation of the composite score matrix. Comparison with visualization using PCA score plots or dendrograms from hierarchical clustering analysis (HCA) demonstrates the utility of the composite score to as a tool for metabolomics studies that seek to quantify similarity among samples. An R-script for the calculation of composite score has been made available.
    Keywords:  Mass spectrometry; Metabolomics; Multivariate statistical analysis; Natural products; PCA; R; Untargeted
    DOI:  https://doi.org/10.1016/j.aca.2019.10.029
  15. J Mass Spectrom. 2019 Dec 27. e4493
    Korban A, Charapitsa S, Čabala R, Sobolenko L, Sytova S.
      The potential use of ethanol as an internal standard (IS) for GC-MS analysis was studied. The paper describes the analysis of spirit drinks and other alcoholic products which consist of a mixture of water, ethanol and volatile compounds. In the suggested method, ethanol was employed as an IS for the common procedure of volatile compounds quantification. A number of standard solutions of 9 compounds with different concentrations was prepared in a water-ethanol matrix and measured with GC-MS in the SIM mode. Two possible approaches were suggested to avoid detector saturation during ethanol detection. The first one consisted in using less abundant m/z 47 as quantifiers. These ions mainly correspond to unfragmented heavy ethanol molecules containing one 13 C isotope. The second method consisted in reduction of the voltage of MS electron multiplier. The experiment also included the preparation and subsequent dilution of the standard solution and ethanol with water, which determined the linearity of the modified MS response relative to the ethanol content. Analysis of the obtained results revealed that volatile compounds can be successfully accurately determined with GC-MS by employing ethanol as an IS. Application of the suggested method is not limited to the reported volatile compounds and alcoholic products.
    Keywords:  GC-MS; alcoholic products; ethanol; internal standard; quantification; volatile compounds
    DOI:  https://doi.org/10.1002/jms.4493
  16. Mass Spectrom Rev. 2019 Dec 25.
    Milewska A, Ner-Kluza J, Dabrowska A, Bodzon-Kulakowska A, Pyrc K, Suder P.
      Virology, as a branch of the life sciences, discovered mass spectrometry (MS) to be the pivotal tool around two decades ago. The technique unveiled the complex network of interactions between the living world of pro- and eukaryotes and viruses, which delivered "a piece of bad news wrapped in protein" as defined by Peter Medawar, Nobel Prize Laureate, in 1960. However, MS is constantly evolving, and novel approaches allow for a better understanding of interactions in this micro- and nanoworld. Currently, we can investigate the interplay between the virus and the cell by analyzing proteomes, interactomes, virus-cell interactions, and search for the compounds that build viral structures. In addition, by using MS, it is possible to look at the cell from the broader perspective and determine the role of viral infection on the scale of the organism, for example, monitoring the crosstalk between infected tissues and the immune system. In such a way, MS became one of the major tools for the modern virology, allowing us to see the infection in the context of the whole cell or the organism. © 2019 Wiley Periodicals, Inc. Mass Spec Rev.
    Keywords:  GEMMA-MS; capsids; charge-detection mass spectrometry; viral infections
    DOI:  https://doi.org/10.1002/mas.21617
  17. Molecules. 2019 Dec 21. pii: E48. [Epub ahead of print]25(1):
    Errico S, Chioccarelli T, Moggio M, Diano N, Cobellis G.
      Bisphenol A (BPA), an endocrine disruptor, may affect in situ steroidogenesis and alter steroids levels. The present work proposes a liquid chromatography tandem mass spectrometry method to simultaneously quantify BPA, 17β-Estradiol and testosterone in two target tissues: testis and visceral fat mass. Analytes were isolated and lipophilic impurities removed by two serial steps: liquid-liquid and solid phase extraction. All compounds were separated in a single gradient run by Kinetex F5 column and detected via multiple reaction monitoring using a triple quadrupole with a TurboIon electrospray source in both negative and positive modes. The method is selective and very sensitive. In the investigated concentration range, the linearity of the detector response is verified in both tissues. The use of specific SPE cartridges for affinity chromatography purification allows obtaining high percentages of process efficiency (68.0-83.3% for testicular tissue; 63.7-70.7% for visceral fat mass). Good repeatability and reproducibility was observed. The validated method can be efficiently applied for direct biological monitoring in testis and visceral fat mass from mice exposed to BPA. The quantification of compounds in a single assay could be achieved without a loss of sensitivity.
    Keywords:  17β-estradiol; Bisphenol A; LC-MS/MS; testis; testosterone; visceral fat
    DOI:  https://doi.org/10.3390/molecules25010048
  18. Metabolism. 2019 Dec 21. pii: S0026-0495(19)30266-5. [Epub ahead of print] 154051
    Khan A, Choi Y, Back JH, Lee S, Jee SH, Park YH.
      BACKGROUND: Identifying changes in serum metabolites before the occurrence of acute myocardial infarction (AMI) is an important approach for finding novel biomarkers of AMI.METHODS: In this prospective cohort study, serum samples obtained from patients at risk of AMI (n = 112) and non-risk controls (n = 89) were tested using high-resolution metabolomics (HRM). Partial least-squares discriminant analysis (PLS-DA), along with univariate analysis using a false discovery rate (FDR) of q = 0.05 were performed to discriminate metabolic profiles and to determine significantly different metabolites between healthy control and AMI risk groups.
    RESULTS: PLS-DA significantly separated the AMI risk sera from control sera. The metabolites associated with amino acid biosynthesis, 2-oxocarboxylic acid, tryptophan, and amino sugar and nucleotide sugar metabolism pathways were mainly elevated in patients at risk of AMI. Further validation and quantification by MS/MS showed that tryptophan, carnitine, L-homocysteine sulfinic acid (L-HCSA), and cysteic acid (CA) were upregulated, while L-cysteine and L-cysteine sulfinic acid (L-CSA) were downregulated, specifically among AMI risk sera. Additionally, these discriminant metabolic profiles were not related to hypertension, smoking or alcoholism.
    CONCLUSION: In conclusion, detecting upregulated L-HCSA and CA along with carnitine among patients at risk for AMI could serve as promising non-invasive biomarkers for early AMI detection.
    Keywords:  Biomarker; Homocysteine; Mass spectrometry; Metabolomics; Myocardial infarction
    DOI:  https://doi.org/10.1016/j.metabol.2019.154051
  19. J Chromatogr A. 2019 Dec 16. pii: S0021-9673(19)31232-4. [Epub ahead of print] 460784
    Navarro-Huerta JA, Vargas-García AG, Torres-Lapasió JR, García-Alvarez-Coque MC.
      Micellar liquid chromatography (MLC) is a reversed-phase mode with mobile phases containing an organic solvent and a micellised surfactant. Most procedures developed in MLC are implemented in the isocratic mode, since the general elution problem in chromatography is less troublesome. However, gradient elution may be still useful in MLC to analyse mixtures of compounds within a wide range of polarities, in shorter times. MLC using gradients is attractive to determine by direct injection moderate to low polar compounds in physiological samples. In these analyses, the use of initial micellar conditions (isocratic or gradient) with a fixed amount of surfactant above the critical micellar concentration, keeping the organic solvent content low, will provide better protection of the column against the precipitation of the proteins in the physiological fluid. Once the proteins are swept away, the elution strength can be increased using a positive gradient of organic solvent to reduce the analysis time. This may give rise to the transition from the micellar to the submicellar mode, since micelles are destroyed at sufficiently high concentration of organic solvent. In this work, several retention models covering extended solvent domains in MLC are developed and tested, and applied to investigate the performance in isocratic, linear and multi-linear gradient separations. The study was applied to the screening of β-adrenoceptor antagonists in urine samples, using mobile phases prepared with sodium dodecyl sulphate and 1-propanol. Predicted chromatograms were highly accurate in all situations, although suffered of baseline problems and minor shifts for peaks eluting close to a steep gradient segment. Two columns (C18 and C8) were investigated, with the C8 column being preferable owing to the smaller amount of adsorbed surfactant.
    Keywords:  C8 and C18 columns; High submicellar liquid chromatography; Interpretive optimisation; Micellar liquid chromatography; Retention models; β-Adrenoceptor antagonists
    DOI:  https://doi.org/10.1016/j.chroma.2019.460784
  20. J Sep Sci. 2019 Dec 27.
    Qiao L, Yu C, Sun R.
      Surface-bonded zwitterionic stationary phases have showed highlighted performances in separation of polar and hydrophilic compounds under hydrophilic interaction chromatography mode. So, it would be helpful to evaluate the characteristics of zwitterionic stationary phases with different arranged charged groups. The present work involved the preparation and comparison of three zwitterionic stationary phases. An imidazolium ionic liquid was designed and synthesized, and the cationic and anionic moieties respectively possessed positively charged imidazolium ring and negatively charged sulfonic groups. Then, the prepared ionic liquid, phosphorylcholine and an imidazolium-based zwitterionic selector were bonded on the surface of silica to obtain three zwitterionic stationary phases. The selectivity properties were characterized and compared through the relative retention of selected solute pairs, and different kinds of hydrophilic solutes mixtures were used to evaluate the chromatographic performances. Moreover, the zwitterionic stationary phases were further characterized by the modified linear solvation energy relationship model to probe the multiple interactions. All the results indicated that the types and arrangement of charged groups in zwitterionic stationary phases mainly affect the retention and separation of ionic or ionizable compounds, and for interaction characteristics the contribution from n and π electrons and electrostatic interactions displayed certain differences. This article is protected by copyright. All rights reserved.
    Keywords:  hydrophilic interaction liquid chromatography; imidazolium ionic liquid; linear solvation energy relationship; zwitterionic stationary phase
    DOI:  https://doi.org/10.1002/jssc.201901087
  21. Analyst. 2019 Dec 23.
    Okotrub KA, Zykova VA, Adichtchev SV, Surovtsev NV.
      The orientation of lipid molecules is an essential characteristic of supported phospholipid layers, synthetic lipid structures, and biological specimens. Here, we perform Raman spectroscopy to analyze the orientation order in lipid structures. For this purpose, we studied dry oriented planar DMPC samples and multilamellar DPPC vesicles in water using Raman mapping. Principal component analysis (PCA) was applied to extract the information about the orientational order of lipid molecules. Using PCA, we revealed the features observed in the phospholipid spectra that are sensitive to hydrocarbon chain orientation relative to the polarization of laser radiation. These spectral features include Raman peaks corresponding to stretching C-C, twisting CH2, rocking and stretching CH3 modes. We suggest to use them as markers of hydrocarbon chain orientation along with light polarization. The proposed Raman analysis can be used to study samples with different levels of hydration.
    DOI:  https://doi.org/10.1039/c9an01499c
  22. J Thromb Haemost. 2019 Dec 23.
    Chatterjee M.
      The platelet-lipid chapter in the story of atherothrombosis is an old one, recapitulated and revised in many contexts. For decades several stimulating facets have been added to it, both unraveling and increasing the perplexity of platelet-lipid interplay and its pathophysiological consequences. The recent paradigm shift in our perspective has evolved with lipidomic analysis of the intraplatelet compartment and platelet releasate. These investigations have disclosed that platelets are in constant interaction with circulatory lipids, often reflected in their lipid repertoire. Besides, they offer a shielded intracellular space for oxidative lipid metabolism generating "toxic" metabolites that escape degradation by plasma lipases and anti-oxidant defense, circulate undetected by conventional plasma lipid profile, and deposited at atherosclerotic lesions or thrombus. Lipidomics divulges this silent invader in platelet vehicles, thereby provides potential biomarkers of pathologic manifestations and therapeutic targets to be exploited, which is surmised in this review.
    Keywords:  Cardiovascular disease; Lipidomics; Platelets; Thromboinflammation
    DOI:  https://doi.org/10.1111/jth.14721