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Ecker J.,University of Regensburg | Ecker J.,ABF Analytisch Biologisches Forschungslabor GmbH | Scherer M.,University of Regensburg | Scherer M.,Nestlé | And 2 more authors.
Journal of Chromatography B: Analytical Technologies in the Biomedical and Life Sciences | Year: 2012

So far the most frequently used method for fatty acid (FA) analysis is GC coupled to flame ionization detector (FID). However, GC-FID does not allow profiling of FA synthesis and metabolism using stable isotopes. Here we present a rapid and sensitive GC-MS method for determination of fatty acid methyl esters (FAMEs). Fatty acid methylation was carried out by transesterification with acetyl-chloride and methanol. FAME separation applies a short and polar cyano-column resulting in an analysis time of 17.2. min. Separation was achieved for positional and geometrical (. cis/. trans) isomers with chain lengths between C8 and C28. Partial overlap of FAMEs (e.g. for C20:2 (. n-6) and C21:0) could be resolved using selected ion monitoring (SIM). The precisions for human plasma samples were better than 10% coefficient of variation (CV) except for very low abundant FAs and LODs were in the low femtomol range on column. The developed GC-MS method also allows quantification of conjugated FAs such as conjugated linoleic acid (CLA) isomers because lowering the derivatization temperature from 95. °C to room temperature prevented cis to trans double bond isomerization. Finally, profiling of fatty acid synthesis and metabolism was exemplified with stable isotope labeling of macrophages using fatty acid precursors or deuterated fatty acids. In summary, we present a fast and robust GC-MS method for fatty acid profiling of positional and geometrical isomers including CLAs as well as very long chain fatty acids (VLCFAs). The method is suitable for both clinical studies and basic research including application of stable isotope compounds. © 2012 Elsevier B.V.


Muller D.C.,ABF Analytisch Biologisches Forschungslabor GmbH | Muller D.C.,TU Munich | Degen C.,Friedrich - Schiller University of Jena | Scherer G.,ABF Analytisch Biologisches Forschungslabor GmbH | And 3 more authors.
Journal of Chromatography B: Analytical Technologies in the Biomedical and Life Sciences | Year: 2014

Mass spectrometry is an ideal tool for investigations of the metabolome in human plasma. To investigate the impact of smoking on the human metabolome, we performed an untargeted metabolic fingerprinting using GC-TOF-MS with EDTA-plasma samples from 25 smokers and 25 non-smokers. The observed elevated levels in the monounsaturated fatty acids (MUFAs) in smokers were verified by a targeted analysis using GC-FID, which revealed also significantly alterations in saturated and polyunsaturated fatty acids in smokers (p<. 0.05, Mann-Whitney U test). Since the main fraction of fatty acids in plasma is esterified to phospholipids, we analyzed phosphatidylcholine (PC) and phosphatidylethanolamine (PE) species composition in the plasma samples of the same subjects. The profiles of 39 PC and 40 PE species were analyzed with a newly developed and validated HILIC-ESI-MS/MS method. We were able to baseline separate the two lipid classes (PC from PE) by maintaining co-elution of individual lipid species of each class. The method shows a linear range from 0.5. μM to 2000. μM and an inter- and intraday coefficient of variation (CV). <. 20% across all analytes. Application of the validated method to the plasma samples of smokers and non-smokers, derived from a diet-controlled smoking study, revealed significantly elevated levels of PC and PE species containing MUFAs in smokers.In summary, we could demonstrate that there is a significantly altered total fatty acid profile, with increased MUFAs, in the plasma of smokers compared to non-smokers. Results obtained with the new HILIC-MS/MS method indicate that the altered fatty acid profile is also reflected in the PC and PE profile of smokers. © 2014 Elsevier B.V.


Degen C.,Friedrich - Schiller University of Jena | Ecker J.,University of Regensburg | Ecker J.,ABF Analytisch Biologisches Forschungslabor GmbH | Piegholdt S.,Friedrich - Schiller University of Jena | And 3 more authors.
Biochimica et Biophysica Acta - Molecular and Cell Biology of Lipids | Year: 2011

Conjugated fatty acids (CFAs) exhibit growth inhibitory effects on colon cancer in vitro and in vivo. To investigate whether the anticancerogenic potency depends on number or configuration of the conjugated double bonds, the effect of conjugated linoleic acid (CLA; C18:2) isomers and conjugated linolenic acid (CLnA; C18:3) isomers on viability and growth of HT-29 cells were compared. Low concentrations of CLnAs (< 10 μM) yielded a higher degree of inhibitory effects compared to CLAs (40 μM). All trans-CFAs were more effective compared to cis/trans-CFAs as follows: t9,t11,t13-CLnA ≥ c9,t11,t13-CLnA > t11,t13-CLA ≥ t9,t11-CLA > c9,t11-CLA. The mRNA expression analysis of important genes associated with fatty acid metabolism showed an absence of Δ5-/Δ6-desaturases and elongases in HT-29 cells, which was confirmed by fatty acid analysis. Using time- and dose-dependent stimulation experiments several metabolites were determined. Low concentrations of all trans-CFAs (5-20 μM) led to dose-dependent increase of conjugated t/t-C16:2 formed by β-oxidation of C18 CFAs, ranging from 1-5% of total FAME. Importantly, it was found that CLnA is converted to CLA and that CLA is inter-converted (t11,t13-CLA is metabolized to c9,t11-CLA) by HT-29 cells. In summary, our study shows that growth inhibition of human cancer cells is associated with a specific cellular transcriptomic and metabolic profile of fatty acid metabolism, which might contribute to the diversified ability of CFAs as anti-cancer compounds. © 2011 Elsevier B.V. All rights reserved.


Mueller D.C.,ABF Analytisch Biologisches Forschungslabor GmbH | Mueller D.C.,TU Munich | Piller M.,ABF Analytisch Biologisches Forschungslabor GmbH | Niessner R.,TU Munich | And 2 more authors.
Journal of Proteome Research | Year: 2014

A GC-TOF-MS method was developed and validated for a metabolic fingerprinting in saliva of smokers and nonsmokers. We validated the method by spiking 37 different metabolites and 6 internal standards to saliva between 0.1 μM and 2 mM. Intraday coefficients of variation (CVs) (accuracies) were on average, 11.9% (85.8%), 8.2% (88.9%), and 10.0% (106.7%) for the spiked levels 25, 50, and 200 μM, respectively (N = 5). Interday CVs (accuracies) were 12.4% (97%), 18.8% (95.5%), and 17.2% (105.9%) for the respective levels of 25, 50, and 200 μM (N = 5). The method was applied to saliva of smokers and nonsmokers, obtained from a 24 h diet-controlled clinical study, in order to identify biomarkers of endogenous origin, which could be linked to smoking related diseases. Automated peak picking, integration, and statistical analysis were conducted by the software tools MZmine, Metaboanalyst, and PSPP. We could identify 13 significantly altered metabolites in smokers (p < 0.05) by matching them against MS libraries and authentic standard compounds. Most of the identified metabolites, including tyramine, adenosine, and glucose-6-phosphate, could be linked to smoking-related perturbations and may be associated with established detrimental effects of smoking. © 2013 American Chemical Society.


Michalke B.,Helmholtz Center Munich | Rossbach B.,Johannes Gutenberg University Mainz | Goen T.,Friedrich - Alexander - University, Erlangen - Nuremberg | Schaferhenrich A.,Friedrich - Alexander - University, Erlangen - Nuremberg | Scherer G.,ABF Analytisch Biologisches Forschungslabor GmbH
International Archives of Occupational and Environmental Health | Year: 2014

Purpose: Human biomonitoring (HBM) implies the assessment of internal exposure to hazardous substances by measuring the substances, their metabolites or reaction products, as well as effect parameters in human body fluids. Along with blood, plasma and urine, saliva is of increasing interest as an alternative matrix for HBM. Methods: This paper reviews studies that measure salivary background levels of hazardous substances, elevated levels after environmental or occupational exposure, as well as references which deal with physiological and toxicokinetic behaviour of saliva and salivary parameters, respectively. Results: The studies revealed that the determination of biomarkers in saliva is a promising approach for HBM, even if only few substances showed a satisfying correlation with exposure data or established biomonitoring matrices such as blood, plasma and urine. Saliva has been proven to be particularly suitable for substances of low molecular weight such as organic solvents, selected pesticides, cotinine, and for some specific trace elements. Besides several advantages, serious problems and limitations were identified. Above all, the complex interactions between substance properties, sampling procedure, sample preparation, measurement techniques or individual factors, and the salivary analyte level are discussed. Conclusions: A major conclusion of the review is that more scientific studies are needed in order to systematically collect data on parameters, influencing salivary analyte levels. Crucially required is a harmonisation of the sampling as well as the sample preparation techniques and procedures, which is indispensable to achieve an overall comparability and interpretability of salivary biomarker levels. © 2014 Springer-Verlag Berlin Heidelberg.


Sterz K.,ABF Analytisch Biologisches Forschungslabor GmbH | Scherer G.,ABF Analytisch Biologisches Forschungslabor GmbH | Ecker J.,ABF Analytisch Biologisches Forschungslabor GmbH
Journal of Lipid Research | Year: 2012

Eicosanoids are key mediators and regulators of inflammation and oxidative stress often used as biomarkers for diseases and pathological conditions such as cardiovascular and pulmonary diseases and cancer. Analytically, comprehensive and robust quantification of different eicosanoid species in a multi-method approach is problematic because most of these compounds are relatively unstable and may differ in their chemical properties. Here we describe a novel ultra-performance liquid chromatography-selected reaction monitoring mass spectroscopy (UPLC-SRM/MS) method for simultaneous quantification of key urinary eicosanoids, including the prostaglandins (PG) tetranor PGE-M, 8-iso-, and 2,3-dinor-8-iso-PGF 2α; the thromboxanes (TXs) 11-dehydro-and 2,3-dinor-TXB 2; leukotriene E 4; and 12- hydroxyeicosatetraenoic acid. In contrast to previous methods, which used time-consuming and complex solid phase extraction, we prepared samples with a simple liquid/liquid extraction procedure. Because collision-induced dissociation produced characteristic product ions for all analytes, no derivatization step for SRM/MS analysis was necessary. Analytes were separated with a short UPLC reversed-phase column (1.7 μm particles), allowing shorter run times than conventional HPLC columns. The method was validated and applied to human urine samples showing excellent precision, accuracy, detection limits, and robustness. In summary, the developed method allows robust and sensitive profiling of urinary eicosanoid species, making it a useful and valuable tool for biomarker profiling in clinical/toxicological studies. Copyright © 2012 by the American Society for Biochemistry and Molecular Biology, Inc.


Sterz K.,ABF Analytisch Biologisches Forschungslabor GmbH | Kohler D.,ABF Analytisch Biologisches Forschungslabor GmbH | Schettgen T.,RWTH Aachen | Scherer G.,ABF Analytisch Biologisches Forschungslabor GmbH
Journal of Chromatography B: Analytical Technologies in the Biomedical and Life Sciences | Year: 2010

In benzene metabolism, pre-S-phenylmercapturic acid (pre-SPMA) is the precursor to S-phenylmercapturic acid (SPMA). Urinary pre-SPMA/SPMA ratios are variable. For the determination of urinary SPMA as a biomarker of exposure to benzene it is essential to completely convert pre-SPMA to SPMA. We developed a procedure for the enrichment and determination of urinary pre-SPMA by LC-MS/MS which allowed us to trace the conversion of pre-SPMA to SPMA. Complete conversion was found upon treatment of urine with HCl (37%) at pH 1.1. Previously reported treatment of urine with concentrated H2SO4 was found to yield SPMA levels higher than after HCl treatment. The origin of that extra SPMA amount is unknown. In conclusion, our findings suggest that pre-treatment of urine with HCl to adjust the pH to 0.5-1 is essential for complete conversion of pre-SPMA to SPMA and should be applied prior to analysis of SPMA in urine. © 2009 Elsevier B.V.


Scherer G.,ABF Analytisch Biologisches Forschungslabor GmbH
Beitrage zur Tabakforschung International/ Contributions to Tobacco Research | Year: 2014

Individual uptake of tobacco smoke constituents by smoking is highly variable in cigarette smokers and cannot be predicted by smoking behaviour variables and machinederived smoke yields. It is well established that uptake of smoke constituents is best described by a series of biomarkers of exposure (BOEs) such as metabolites of nicotine, tobacco-specific nitrosamines (TSNAs), polycyclic aromatic hydrocarbons (PAHs), aromatic amines, benzene, 1,3-butadiene, acrolein, hydrogen cyanide, 2,5-dimethylfuran and other smoke constituents.The purpose of this review is to investigate the relationship between BOE levels and machine-derived smoking yields on the basis of published data. The influence of other smoking behaviour variables, in particular the number of cigarettes smoked per day (CPD) and smoking topography (puffing and inhalation patterns) is also considered, provided suitable data are available.Twenty eight (28) published studies, which report data on machine-derived smoke yields and biomarker concentrations in body fluids of smokers of these products were identified. In total, 33 different BOEs were applied in these studies. Important properties of the BOEs used in the further evaluation were described and discussed.In almost all studies selected, data for CPD were reported. In only a few studies, puffing and inhalation profiles have been determined so that no systematic evaluation of the association between smoking topography and BOE levels was possible. In the studies evaluated, no statistically significant association between daily cigarette consumption (CPD) and smoke yields was observed. This clearly indicates that low machine-derived yields were not compensated by increasing the daily cigarette consumption. As expected, positive and statistically significant relationships were found between CPD and BOE levels for most of the biomarkers investigated.Bi- and multivariate linear regressions were calculated for the relationships between BOE levels (dependent variable) and machine-derived yields as well as CPD (independent variables). Whenever possible, results from various studies were combined (this was only possible, when identical biomarkers and yield types were available). Aggregation of the results from all studies independent of BOE and yield type used is feasible on the basis of relative BOE and yield levels. The multivariate linear regression models obtained reveal that both CPD and machine-derived yields are significant predictors of the measured BOE levels. The models predict that, on average, a 50% reduction in CPD or yield are accompanied by a 33 or 15% reduction, respectively, in smoke uptake, as measured by various BOEs.Taken together, the evaluated data from the literature show that lower machine-derived yields lead to a reduced uptake of smoke constituents. The reduction is statistically significant, but substantially lower than the decrease in machinederived yields. © 2014,Institut Fur Takforschung GMBH. All right reserved.


Ecker J.,ABF Analytisch Biologisches Forschungslabor GmbH
Journal of Separation Science | Year: 2012

Eicosanoids are potent lipid mediators involved in numerous physiological and pathophysiological processes. Precursors are polyunsaturated fatty acids liberated from membrane phospholipids. Thus, profiling and quantification of these molecules has gained a lot of attention during last years. Eicosanoids and phospholipids are commonly profiled by LC-MS/MSbecause this technique allows accurate quantification within acceptable run-times. This article therefore focuses on liquid chromatography and the ESI-MS/MS analysis of proinflammatory lipid mediators, particularly arachidonic acid (C20:4) derived eicosanoids and their precursors phospholipids. Recent analytical developments for quantification of these compounds are highlighted and analytical challenges are discussed. Furthermore, applications such as the use of these molecules as biomarkers are presented. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Scherer G.,ABF Analytisch Biologisches Forschungslabor GmbH | Lee P.N.,P.N. Lee Statistics and Computing Ltd
Regulatory Toxicology and Pharmacology | Year: 2014

The extent of compensation when switching to lower yield cigarettes is important for assessing risk of reduced yield products. Both completeness of and reasons for compensation are judged differently in the scientific and health community. We quantified compensation in a meta-analysis of suitable cross-sectional and brand-switching studies. For each dataset, we derived a compensation index (CI), 1 indicating complete and 0 no compensation. Meta-analyses provided overall estimates. We also reviewed evidence on compensation for nicotine and other factors. The unweighted mean CI (95% confidence interval) was 0.628 (0.513 to 0.742) from 38 estimates from 26 cross-sectional studies, and 0.723 (0.651 to 0.796) from 23 estimates from 19 brand-switching studies. Inverse-variance weighted estimates were 0.781 (0.720 to 0.842) and 0.744 (0.682 to 0.806). Brand-switching data indicate smokers compensate more completely over a narrower yield range. Smokers predominantly compensate by changing puffing volume, and little by changing cigarette consumption. The findings support compensation for nicotine, but other factors may also be relevant. Further investigation is needed using larger studies and different approaches to elucidate their role. We conclude that smokers switching to lower-yield cigarettes only partially compensate. Pharmacological nicotine effects are important, but other factors, including cigarette draw resistance, sensory effects of nicotine and conditioned stimuli may also contribute. © 2014 Elsevier Inc.

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