Daniel Teupser

Ludwig-Maximilians-University of Munich, München, Bavaria, Germany

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Publications (160)692.03 Total impact

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    ABSTRACT: Profiling amino acids and acylcarnitines in whole blood spots is a powerful tool in the laboratory diagnosis of several inborn errors of metabolism. Emerging data suggests that altered blood levels of amino acids and acylcarnitines are also associated with common metabolic diseases in adults. Thus, the identification of common genetic determinants for blood metabolites might shed light on pathways contributing to human physiology and common diseases. We applied a targeted mass-spectrometry-based method to analyze whole blood concentrations of 96 amino acids, acylcarnitines and pathway associated metabolite ratios in a Central European cohort of 2,107 adults and performed genome-wide association (GWA) to identify genetic modifiers of metabolite concentrations. We discovered and replicated six novel loci associated with blood levels of total acylcarnitine, arginine (both on chromosome 6; rs12210538, rs17657775), propionylcarnitine (chromosome 10; rs12779637), 2-hydroxyisovalerylcarnitine (chromosome 21; rs1571700), stearoylcarnitine (chromosome 1; rs3811444), and aspartic acid traits (chromosome 8; rs750472). Based on an integrative analysis of expression quantitative trait loci in blood mononuclear cells and correlations between gene expressions and metabolite levels, we provide evidence for putative causative genes: SLC22A16 for total acylcarnitines, ARG1 for arginine, HLCS for 2-hydroxyisovalerylcarnitine, JAM3 for stearoylcarnitine via a trans-effect at chromosome 1, and PPP1R16A for aspartic acid traits. Further, we report replication and provide additional functional evidence for ten loci that have previously been published for metabolites measured in plasma, serum or urine. In conclusion, our integrative analysis of SNP, gene-expression and metabolite data points to novel genetic factors that may be involved in the regulation of human metabolism. At several loci, we provide evidence for metabolite regulation via gene-expression and observed overlaps with GWAS loci for common diseases. These results form a strong rationale for subsequent functional and disease-related studies.
    PLoS Genetics 09/2015; 11(9):e1005510. DOI:10.1371/journal.pgen.1005510 · 7.53 Impact Factor
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    ABSTRACT: Background: Despite the widespread use of noninvasive testing prior to invasive coronary diagnostic the diagnostic yield of elective coronary angiography has been reported low in subjects with suspected obstructive CAD. Objective: To determine the predictive value of noncoronary atherosclerosis (NCA) in subjects with suspected stable coronary artery disease (CAD) intended to invasive coronary angiography. Methods: Ultrasound-based assessment of carotid artery plaque (CAP), carotid intima-media thickness (CIMT) and ankle-brachial index (ABI) was performed in 2216 subjects with suspected CAD prior to coronary angiography. Logistic regression and c-statistics were used to analyze the diagnostic value of NCA for the presence of obstructive CAD and the intention to revascularization. Results: Percentage of positive results of elective coronary angiography was low but comparable to other studies (41 % obstructive CAD). We identified 1323 subjects (60 %) with NCA, most of them were characterized by CAP (93 %). CAP independently predicted obstructive CAD in addition to traditional risk factors and clinical factors while CIMT and ABI failed to improve the prediction. The presence of NCA and typical angina were the strongest predictors for obstructive CAD (OR 4.0 and 2.4, respectively). A large subgroup of patients (n = 703, 32 %) with atypical clinical presentation and lack of NCA revealed a low indication for revascularization <15 % indicating a large proportion of subjects with non-obstructive CAD in this subgroup. Conclusion: The evaluation of noncoronary atherosclerosis has the potential to impact clinical decision making and to direct subsequent diagnostic procedures in subjects with suspected coronary artery disease. Clinical trial registration: NCT00497887.
    Clinical Research in Cardiology 09/2015; DOI:10.1007/s00392-015-0900-x · 4.56 Impact Factor
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    ABSTRACT: Background: Although therapeutic drug monitoring (TDM) for antibiotics in critically ill patients is recommended by expert panels, no commercial tests are available for most antibiotics. Therefore, we previously developed a multi-analyte method for the quantification of piperacillin, tazobactam, cefepime, meropenem, ciprofloxacin and linezolid in serum. However, limited stability data were available, and the relevant studies did not address the coefficients of variation of the methods applied, which may be important for verifying the storage dependency of the observed effects. Here we aimed to evaluate the storage effects of antibiotics by applying a novel evaluation protocol. Methods: Serum-based test samples were aliquoted and stored at room temperature, 4 °C, -20 °C or -80 °C for up to 180 days. Using an innovative evaluation protocol (considering the coefficient of variation, p-value, and criterion of monotony of observed changes), we assessed whether relevant changes (defined as ≥15% in comparison with baseline) were storage dependent (defined as substantial changes). Results: Storage at -80 °C for up to 180 days did not lead to substantial changes for any analyte. In contrast, storage at -20 °C induced substantial decreases after ≥7 days for piperacillin, tazobactam, cefepime and meropenem; after 90 days at -20 °C, only ≤23% of the initial concentrations were found for these parameters. No substantial changes were observed for linezolid and ciprofloxacin at any storage condition. All of the observed substantial changes were monotonic decreases. Conclusions: We recommend a storage temperature of -80 °C for β-lactam antibiotics. The applied evaluation protocol yielded conclusive results and may be generally useful for stability studies.
    Clinical Chemistry and Laboratory Medicine 09/2015; DOI:10.1515/cclm-2015-0325 · 2.71 Impact Factor
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    ABSTRACT: We investigated whether obese pregnant women negative for gestational diabetes (GDM) still experience dysglycemia, as indicated by high hemoglobin A1c (Hb A1c) at delivery, and whether this impacts offspring and long-term maternal outcomes. Data of 462 mother-child pairs of our prospective Programming of Enhanced Adiposity Risk in Childhood - Early Screening (PEACHES) cohort study were analyzed. Of 885 obese and normal-weight pregnancies prospectively enrolled after GDM testing according to the International Association of Diabetes and Pregnancy Study Groups criteria, 462 GDM-negative mothers and their offspring were investigated. We assessed associations of maternal Hb A1c at delivery with large-for-gestational-age (LGA) birth weights, cord-blood C-peptide, and biomarkers of glucose metabolism and inflammation in obese mothers followed for 2.9 years (median) postpartum (n = 42). Cumulative distribution analysis in GDM-negative normal-weight women (n = 155) revealed that 12% had Hb A1c ≥5.7% at delivery (high Hb A1c). Among obese GDM-negative women (n = 307), 31.9% (95% CI 26.7%-37.4%) equaled or exceeded this cutoff. In obese GDM-negative women with Hb A1c ≥5.7% (n = 98) vs <5.7% (n = 209) at delivery, newborns were more likely to be born LGA [adjusted odds ratio 3.56 (95% CI 1.64-8.02)], and mean cordblood serum C-peptide was increased by 0.09 ng/mL (95% CI 0.01-0.17 ng/mL). In the mothers at follow-up, mean postpartum Hb A1c, fasting glucose, high-sensitivity C-reactive protein, and fibrinogen concentrations were higher by 0.3% (95% CI 0.1%-0.5%), 6.0 mg/dL (95% CI 2.4-9.5 mg/dL), 6.8 mg/L (95% CI 1.4-12.3 mg/L), and 74.9 mg/dL (95% CI 13.6-136.2 mg/L), respectively. Increased Hb A1c in obese GDM-negative women at delivery indicates gestational dysglycemia, potentially conferring offspring and long-term maternal health risks. These findings should raise awareness as to careful monitoring of obese pregnancies. Measurement of Hb A1c at delivery could help select women who may need closer postpartum health checks. © 2015 American Association for Clinical Chemistry.
    Clinical Chemistry 08/2015; 61(11). DOI:10.1373/clinchem.2015.242206 · 7.91 Impact Factor
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    ABSTRACT: Background The LIFE-Adult-Study is a population-based cohort study, which has recently completed the baseline examination of 10,000 randomly selected participants from Leipzig, a major city with 550,000 inhabitants in the east of Germany. It is the first study of this kind and size in an urban population in the eastern part of Germany. The study is conducted by the Leipzig Research Centre for Civilization Diseases (LIFE). Our objective is to investigate prevalences, early onset markers, genetic predispositions, and the role of lifestyle factors of major civilization diseases, with primary focus on metabolic and vascular diseases, heart function, cognitive impairment, brain function, depression, sleep disorders and vigilance dysregulation, retinal and optic nerve degeneration, and allergies. Methods/design The study covers a main age range from 40-79 years with particular deep phenotyping in elderly participants above the age of 60. The baseline examination was conducted from August 2011 to November 2014. All participants underwent an extensive core assessment programme (5-6 h) including structured interviews, questionnaires, physical examinations, and biospecimen collection. Participants over 60 underwent two additional assessment programmes (3-4 h each) on two separate visits including deeper cognitive testing, brain magnetic resonance imaging, diagnostic interviews for depression, and electroencephalography. Discussion The participation rate was 33 %. The assessment programme was accepted well and completely passed by almost all participants. Biomarker analyses have already been performed in all participants. Genotype, transcriptome and metabolome analyses have been conducted in subgroups. The first follow-up examination will commence in 2016.
    BMC Public Health 07/2015; 15(1). DOI:10.1186/s12889-015-1983-z · 2.26 Impact Factor
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    ABSTRACT: Genetics of gene expression (eQTLs or expression QTLs) has proved an indispensable tool for understanding biological pathways and pathomechanisms of trait associated SNPs. However, power of most genome-wide eQTL studies is still limited. We performed a large eQTL study in peripheral blood mononuclear cells of 2,112 individuals increasing the power to detect trans-effects genome-wide. Going beyond univariate SNP-transcript associations, we analyse relations of eQTLs to biological pathways, polygenetic effects of expression regulation, trans-clusters, and enrichment of co-localised functional elements. We found eQTLs for about 85% of analysed genes, 18% of genes were trans-regulated. Local eSNPs were enriched up to a distance of 5 Mb to the transcript challenging typically implemented ranges of cis-regulations. Pathway enrichment within regulated genes of GWAS-related eSNPs supported functional relevance of identified eQTLs. We demonstrate that nearest genes of GWAS-SNPs might frequently be misleading functional candidates. We identified novel trans-clusters of potential functional relevance for GWAS-SNPs of several phenotypes including obesity-related traits, HDL-cholesterol levels, and haematological phenotypes. We used chromatin immunoprecipitation data for demonstrating biological effects. Yet, we show for strongly heritable transcripts that still little trans-chromosomal heritability is explained by all identified trans-eSNPs, however, our data suggests that most cis-heritability of these transcripts seems explained. Dissection of co-localised functional elements indicated a prominent role of SNPs in loci of pseudogenes and non-coding RNAs for the regulation of coding genes. In summary, our study substantially increases the catalogue of human eQTLs and improves our understanding of the complex genetic regulation of gene-expression, pathways and disease-related processes. © The Author 2015. Published by Oxford University Press.
    Human Molecular Genetics 05/2015; 24(16). DOI:10.1093/hmg/ddv194 · 6.39 Impact Factor
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    ABSTRACT: A reduction in number and function of endothelial progenitor cells (EPCs) occurs in both physiologic aging and chronic heart failure (CHF). We assessed whether disease and aging have additive effects on EPCs or whether beneficial effects of exercise training are diminished in old age. We randomized 60 patients with stable CHF and 60 referent controls to a training or a control group. To detect possible aging effects we included subjects below 55 (young) and above 65 years (older). Subjects in the training group exercised four times daily at 60% to 70% of VO2max for four weeks under supervision. At baseline and after the intervention the number and function of EPCs were assessed. As compared with young referent controls, older referent controls showed at baseline a reduced EPC number (young: 190 ± 37 CD34/KDR positive cells/ml blood; older: 131 ± 26 CD34/KDR positive cells/ml blood; p < 0.05) and function (young: 230 ± 41 migrated cells/1000 plated cells; older: 185 ± 28 cells/1000 plated cells; p < 0.05). In young and older CHF patients EPC-number (young: 85 ± 21 CD34/KDR positive cells/ml blood; older: 78 ± 20 CD34/KDR positive cells/ml blood) and EPC-function (young: 113 ± 26 cells/1000 plated cells; older: 120 ± 27 cells/1000 plated cells) were impaired. As a result of exercise training, EPC function improved by 24% in older referent controls (p < 0.05), while it remained unchanged in young training referent controls and controls respectively. In young and older patients with CHF four weeks of exercise training resulted in a significant improvement in EPC numbers and EPC function (young: number +66% function +43%; p < 0.05; older: number +69% function +36%; p < 0.05). These results were accompanied by a significant increase in flow mediated dilatation in the training groups of young/older CHF patients and in older referent controls. Four weeks of exercise training are effective in improving EPC number and EPC function in CHF patients. These training effects were not impaired among older patients, emphasizing the potentials of rehabilitation interventions in a patient group where CHF has a high prevalence. © The European Society of Cardiology 2015 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.
    05/2015; DOI:10.1177/2047487315588391
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    ABSTRACT: Mevalonate kinase deficiency, a rare autosomal recessive autoinflammatory disease, is caused by mutations in the MVK gene encoding mevalonate kinase (MK). MK catalyzes the phosphorylation of mevalonic acid to mevalonate-5-phosphate (MVAP) in the pathway of isoprenoid and sterol synthesis. The disease phenotype correlates with residual activity ranging from <0.5 % for mevalonic aciduria to 1-7 % for the milder hyperimmunoglobulinemia D and periodic fever syndrome (HIDS). Hence, assessment of loss-of-function requires high accuracy measurements. We describe a method using isotope dilution UPLC-MS/MS for precise and sensitive determination of MK activity. Wild-type MK and the variant V261A, which is associated with HIDS, were recombinantly expressed in E. coli. Enzyme activity was determined by formation of MVAP over time quantified by isotope dilution UPLC-MS/MS. The method was validated according to the FDA Guidance for Bioanalytical Method Validation. Sensitivity for detection of MAVP by UPLC-MS/MS was improved by derivatization with butanol-HCl (LLOQ, 5.0 fmol) and the method was linear from 0.5 to 250 μmol/l (R(2)>0.99) with a precision of ≥89 % and an accuracy of ±2.7 %. The imprecision of the activity assay, including the enzymatic reaction and the UPLC-MS/MS quantification, was 8.3 %. The variant V261A showed a significantly decreased activity of 53.1 %. Accurate determination of MK activity was enabled by sensitive and reproducible detection of MVAP using UPLC-MS/MS. The novel method may improve molecular characterization of MVK mutations, provide robust genotype-phenotype correlations, and accelerate compound screening for drug candidates restoring variant MK activity. Copyright © 2015. Published by Elsevier Inc.
    Clinical biochemistry 05/2015; 48(12). DOI:10.1016/j.clinbiochem.2015.05.007 · 2.28 Impact Factor
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    Oliver Weingärtner · Daniel Teupser · Shailendra B Patel ·
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    ABSTRACT: The human diet is naturally varied and contains not only essential nutrients, but also contains molecules that the body actively excludes or minimizes exposure. Among these molecules are xenosterols, of which plant sterols comprise the greatest exposure risk. These sterols comprise approximately 50% of the total sterols we eat, yet we retain <0.5% of these in our bodies. The bulk of this exclusion takes place in the intestine and the heterodimeric transporters ABCG5 and ABCG8 are key to keeping these xenosterols out of our bodies. In normal humans, pharmacological supplementation with plant sterols (and stanols) has been used to lower cholesterol as these impair intestinal absorption/re-absorption of this molecule; lowering plasma cholesterol has cardiovascular risk benefits. This review challenges whether this intervention is beneficial and may even be harmful. We summarize the evidence involving humans who have genetic disruption of ABCG5/ABCG8 function, from clinical trial data examining plant sterols and cardiovascular risk, from genetic data affecting normal humans and ABCG5/ABCG8 variations to data obtained using animal models. Accumulation of xenosterols in any significant amount is clearly associated with increased toxicity, and data suggest that at even low levels there may be effects. Importantly, there is also a paucity of data showing cardiovascular end-point benefits with plant sterol/stanol supplementation. The summary of evidence highlights not only caution in recommending such strategies to lower plasma cholesterol, but also in investigating how these xenosterols can affect processes ranging from cardiovascular, endocrine, and neurological function.
    Journal of AOAC International 05/2015; 98(3). DOI:10.5740/jaoacint.SGEWeingartner · 1.12 Impact Factor
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    ABSTRACT: Deficiency in the serine protease inhibitor, alpha-1 antitrypsin (AAT), is known to cause emphysema and liver disease. Other manifestations, including airway disease or skin disorders, have also been described. A 44-year-old woman presented to our emergency department with dyspnea and respiratory insufficiency. She had never smoked, and had been diagnosed with COPD 9 years earlier. Three months previously, she had suffered a pulmonary embolism. Chest computed tomography scan revealed severe cystic bronchiectasis with destruction of the lung parenchyma. The sweat test was normal and there was no evidence of the cystic fibrosis transmembrane conductance regulator (CFTR) mutation. Capillary zone electrophoresis showed a decrease of alpha-1 globin band and AAT levels were below the quantification limit (<25 mg/dL). No S or Z mutation was identified, but sequencing analysis found a homozygous cytosine and adenine (CA) insertion in exon 2 of the SERPINA-1 gene, probably leading to a dysfunctional protein (PI Null/Null). This mutation has not been previously identified. The atypical presentation of the patient, with severe cystic bronchiectasis, highlights AAT deficiency as a differential diagnosis in bronchiectasis. Further, awareness should be raised regarding a possible increased risk of thromboembolism associated with AAT deficiency.
    International Journal of COPD 05/2015; 10:891. DOI:10.2147/COPD.S80173 · 3.14 Impact Factor
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    ABSTRACT: Chronic systemic inflammation in obesity originates from local immune responses in visceral adipose tissue. However, assessment of a broad range of inflammation-mediating cytokines and their relationship to physical activity and adipometrics has scarcely been reported to date. To characterize the profile of a broad range of pro- and anti-inflammatory cytokines and the impact of physical activity and energy expenditure in individuals with general obesity, central obesity, and non-obese subjects. A cross-sectional study comprising 117 obese patients (body mass index (BMI) ≥ 30) and 83 non-obese community-based volunteers. Serum levels of interleukin (IL)-2, IL-4, IL-5, IL-10, IL-12, IL-13, granulocyte-macrophage colony-stimulating factor (GM-CSF), interferon (IFN)-γ and tumor necrosis factor (TNF)-α were measured. Physical activity and energy expenditure (MET) were assessed with actigraphy. Adipometrics comprised BMI, weight, abdominal-, waist- and hip-circumference, waist to hip ratio (WHR), and waist-to-height-ratio (WHtR). General obesity was associated with significantly elevated levels of IL-5, IL-10, IL-12, IL-13, IFN-γ and TNF-α, central obesity with significantly elevated IL-5, IL-10, IL-12, IL-13 and IFN-γ-levels. In participants with general obesity, levels of IL-4, IL-10 and IL-13 were significantly elevated in participants with low physical activity, even when controlled for BMI which was negatively associated with physical acitivity. Cytokines significantly correlated with adipometrics, particularly in obese participants. Results confirm up-regulation of certain pro- and anti-inflammatory cytokines in obesity. In obese subjects, physical activity may lower levels and thus reduce pro-inflammatory effects of cytokines that may link obesity, insulin resistance and diabetes.
    PLoS ONE 03/2015; 10(3):e0121971. DOI:10.1371/journal.pone.0121971 · 3.23 Impact Factor

  • Journal of the American College of Cardiology 03/2015; 65(10):A1898. DOI:10.1016/S0735-1097(15)61898-8 · 16.50 Impact Factor
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    ABSTRACT: Various types of automated hematology analyzers are used in clinical laboratories. Here, we performed a side-by-side comparison of five current top of the range routine hematology analyzers in the setting of a university hospital central laboratory. Complete blood counts (CBC), differentials, reticulocyte and nucleated red blood cell (NRBC) counts of 349 patient samples, randomly taken out of routine diagnostics, were analyzed with Cell-Dyn Sapphire (Abbott), DxH 800 (Beckman Coulter), Advia 2120i (Siemens), XE-5000 and XN-2000 (Sysmex). Inter-instrument comparison of CBCs including reticulocyte and NRBC counts and investigation of flagging quality in relation to microscopy were performed with the complete set of samples. Inter-instrument comparison of five-part differential was performed using samples without atypical cells in blood smear (n=292). Automated five-part differentials and NRBCs were additionally compared with microscopy. The five analyzers showed a good concordance for basic blood count parameters. Correlations between instruments were less well for reticulocyte counts, NRBCs, and differentials. The poorest concordance for NRBCs with microscopy was observed for Advia 2120i (Kendall’s τ To the best of our knowledge, this is the most comprehensive side-by-side comparison of five current top of the range routine hematology analyzers. Variable analyzer quality and parameter specific limitations must be considered in defining laboratory algorithms in clinical practice.
    Clinical Chemistry and Laboratory Medicine 01/2015; 53(7). DOI:10.1515/cclm-2014-0945 · 2.71 Impact Factor
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    ABSTRACT: -Epigenetic mechanisms might be involved in the regulation of inter-individual lipid level variability and thus may contribute to the cardiovascular risk profile. The aim of this study was to investigate the association between genome-wide DNA methylation and blood lipid levels HDL-C, LDL-C, triglycerides (TG) and total cholesterol (TC). Observed DNA methylation changes were further analyzed to also examine their relationship with previous hospitalized myocardial infarction. -Genome-wide DNA methylation patterns were determined in whole blood samples of 1776 subjects of the KORA F4 cohort using the Infinium HumanMethylation450 BeadChip (Illumina). Ten novel lipid-related CpG sites (CpGs) annotated to various genes including ABCG1, MIR33B/SREBF1 and TNIP1 were identified. CpG cg06500161, located in ABCG1, was associated in opposite directions with both HDL-C (β coefficient=-0.049, p=8.26E-17) and TG levels (β=0.070, p=1.21E-27). Eight associations were confirmed by replication in KORA F3 (N=499) and InCHIANTI (N=472). Associations between TG levels and SREBF1 and ABCG1 were also found in adipose tissue of the MuTHER cohort (N=634). Expression analysis revealed an association between ABCG1 methylation and lipid levels that might be partly mediated by ABCG1 expression. DNA methylation of ABCG1 might also play a role in previous hospitalized myocardial infarction (odds ratio 1.15, 95%CI=1.06-1.25). -Epigenetic modifications of the newly identified loci might regulate disturbed blood lipid levels and thus contribute to the development of complex lipid-related diseases.
    Circulation Cardiovascular Genetics 01/2015; 8(2). DOI:10.1161/CIRCGENETICS.114.000804 · 4.60 Impact Factor
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    Lesca M Holdt · Daniel Teupser ·

    Arteriosclerosis Thrombosis and Vascular Biology 01/2015; 35(1):7-8. DOI:10.1161/ATVBAHA.114.304485 · 6.00 Impact Factor
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    ABSTRACT: Whole blood expression profiling is frequently performed using PAXgene (Qiagen) or Tempus (Life Technologies) tubes. Here, we compare 6 novel generation RNA isolation protocols with respect to RNA quantity, quality and recovery of mRNA and miRNA. 3 PAXgene and 3 Tempus Tubes were collected from participants of the LIFE study with (n = 12) and without (n = 35) acute myocardial infarction (AMI). RNA was extracted with 4 manual protocols from Qiagen (PAXgene Blood miRNA Kit), Life Technologies (MagMAX for Stabilized Blood Tubes RNA Isolation Kit), and Norgen Biotek (Norgen Preserved Blood RNA Purification Kit I and Kit II), and 2 (semi-)automated protocols on the QIAsymphony (Qiagen) and MagMAX Express-96 Magnetic Particle Processor (Life Technologies). RNA quantity and quality was determined. For biological validation, RNA from 12 representative probands, extracted with all 6 kits (n = 72), was reverse transcribed and mRNAs (matrix metalloproteinase 9, arginase 1) and miRNAs (miR133a, miR1), shown to be altered by AMI, were analyzed. RNA yields were highest using the Norgen Kit I with Tempus Tubes and lowest using the Norgen Kit II with PAXgene. The disease status was the second major determinant of RNA yields (LIFE-AMI 11.2 vs. LIFE 6.7 µg, p<0.001) followed by the choice of blood collection tube. (Semi-)automation reduced overall RNA extraction time but did not generally reduce hands-on-time. RNA yields and quality were comparable between manual and automated extraction protocols. mRNA expression was not affected by collection tubes and RNA extraction kits but by RT/qPCR reagents with exception of the Norgen Kit II, which led to mRNA depletion. For miRNAs, expression differences related to collection tubes (miR30b), RNA isolation (Norgen Kit II), and RT/qRT reagents (miR133a) were observed. We demonstrate that novel generation RNA isolation kits significantly differed with respect to RNA recovery and affected miRNA but not mRNA expression profiles.
    PLoS ONE 12/2014; 9(12):e113298. DOI:10.1371/journal.pone.0113298 · 3.23 Impact Factor
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    ABSTRACT: Background: Recent studies have demonstrated highly variable blood concentrations of piperacillin, tazobactam, cefepime, meropenem, ciprofloxacin and linezolid in critically ill patients with a high incidence of sub-therapeutic levels. Consequently, therapeutic drug monitoring (TDM) of these antibiotics has to be considered, requiring robust and reliable routine analytical methods. The aim of the present work was to develop and validate a multi-analyte ultra high performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) method for the simultaneous quantification of the above mentioned antibiotics. Methods: Sample preparation included a manual protein precipitation step followed by two-dimensional ultra high performance liquid chromatography (2D-UHPLC). Corresponding stable isotope-labeled substances were used as internal standards for all of the analytes, with the exception of tazobactam. The injected sample volume was 7 μL. The run time was 5.0 min. Results: Inaccuracy was ≤8% and imprecision coefficient of variation (CV) was <9% for all analytes. Only minor matrix effects and negligible carry-over was observed. The method was found to be robust during the validation period. Conclusions: We were able to develop a reliable 2D-UHPLC-MS/MS method addressing analytes with highly heterogeneous physico-chemical properties. The novel assay may be an efficient tool for an optimized process workflow in clinical laboratories for important antibiotics in regards to TDM.
    Clinical Chemistry and Laboratory Medicine 10/2014; 53(5). DOI:10.1515/cclm-2014-0746 · 2.71 Impact Factor
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    ABSTRACT: Background: Hevylite™ chain (HLC) assays with specificity for epitopes at the junction between heavy and light chains of intact immunoglobulins (Ig) allow quantification of Ig K/) ratios of the three major Ig classes. Calculated Ig K/ ratios outside the reference range indicate a monoclonal background. The primary aim of the present study was to analytically validate HLC assays and to investigate their diagnostic potential in relation to immunofixation electrophoresis (IFE) as the standard method for identification of monoclonal proteins (MPs). A second aim was to investigate the diagnostic potential of IILC assays in disease monitoring.
    Clinical laboratory 10/2014; 60(9):1491-500. DOI:10.7754/Clin.Lab.2013.131010 · 1.13 Impact Factor
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    ABSTRACT: Unlabelled: Reduction of β-catenin (CTNNB1) destroying complex components, for example, adenomatous polyposis coli (APC), induces β-catenin signaling and subsequently triggers activation of genes involved in proliferation and tumorigenesis. Though diminished expression of APC has organ-specific and threshold-dependent influence on the development of liver tumors in mice, the molecular basis is poorly understood. Therefore, a detailed investigation was conducted to determine the underlying mechanism in the development of liver tumors under reduced APC levels. Mouse liver at different developmental stages was analyzed in terms of β-catenin target genes including Cyp2e1, Glul, and Ihh using real-time RT-PCR, reporter gene assays, and immunohistologic methods with consideration of liver zonation. Data from human livers with mutations in APC derived from patients with familial adenomatous polyposis (FAP) were also included. Hepatocyte senescence was investigated by determining p16(INK4a) expression level, presence of senescence-associated β-galactosidase activity, and assessing ploidy. A β-catenin activation of hepatocytes does not always result in β-catenin positive but unexpectedly also in mixed and β-catenin-negative tumors. In summary, a senescence-inducing program was found in hepatocytes with increased β-catenin levels and a positive selection of hepatocytes lacking p16(INK4a), by epigenetic silencing, drives the development of liver tumors in mice with reduced APC expression (Apc(580S) mice). The lack of p16(INK4a) was also detected in liver tumors of mice with triggers other than APC reduction. Implications: Epigenetic silencing of p16(Ink4a) in selected liver cells bypassing senescence is a general principle for development of liver tumors with β-catenin involvement in mice independent of the initial stimulus.
    Molecular Cancer Research 09/2014; 13(2). DOI:10.1158/1541-7786.MCR-14-0278-T · 4.38 Impact Factor
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    ABSTRACT: Endolysosomal organelles play a key role in trafficking, breakdown and receptor-mediated recycling of different macromolecules such as low-density lipoprotein (LDL)-cholesterol, epithelial growth factor (EGF) or transferrin. Here we examine the role of two-pore channel (TPC) 2, an endolysosomal cation channel, in these processes. Embryonic mouse fibroblasts and hepatocytes lacking TPC2 display a profound impairment of LDL-cholesterol and EGF/EGF-receptor trafficking. Mechanistically, both defects can be attributed to a dysfunction of the endolysosomal degradation pathway most likely on the level of late endosome to lysosome fusion. Importantly, endolysosomal acidification or lysosomal enzyme function are normal in TPC2-deficient cells. TPC2-deficient mice are highly susceptible to hepatic cholesterol overload and liver damage consistent with non-alcoholic fatty liver hepatitis. These findings indicate reduced metabolic reserve of hepatic cholesterol handling. Our results suggest that TPC2 plays a crucial role in trafficking in the endolysosomal degradation pathway and, thus, is potentially involved in the homoeostatic control of many macromolecules and cell metabolites.
    Nature Communications 08/2014; 5:4699. DOI:10.1038/ncomms5699 · 11.47 Impact Factor

Publication Stats

2k Citations
692.03 Total Impact Points


  • 2001-2015
    • Ludwig-Maximilians-University of Munich
      • • Institute of Laboratory Medicine
      • • Institute of Clinical Chemistry
      München, Bavaria, Germany
    • University of Leipzig
      • • Department of Cardiac Surgery
      • • Institute of Biochemistry
      • • Institut für Laboratoriumsmedizin, Klinische Chemie und Molekulare Diagnostik
      • • Institute of Pathology
      Leipzig, Saxony, Germany
  • 2002-2013
    • The Rockefeller University
      • Laboratory of Biochemical Genetics and Metabolism
      New York, New York, United States
  • 2010
    • Universität zu Lübeck
      Lübeck Hansestadt, Schleswig-Holstein, Germany
  • 2003
    • Institute of Medical Molecular Diagnostics GmbH
      Berlín, Berlin, Germany
  • 1997-1999
    • Technische Universität München
      München, Bavaria, Germany