Publications by authors named "Sabine Kern"

10 Publications

  • Page 1 of 1

Impact of Endothelial Lipase on Cholesterol Efflux Capacity of Serum and High-density Lipoprotein.

Sci Rep 2017 10 2;7(1):12485. Epub 2017 Oct 2.

Institute of Molecular Biology and Biochemistry, Center of Molecular Medicine, Medical University Graz, Neue Stiftingtalstraße 6/6, 8010, Graz, Austria.

Endothelial lipase (EL) is a potent modulator of the structural and functional properties of HDL. Impact of EL on cholesterol efflux capacity (CEC) of serum and isolated HDL is not well understood and apparently contradictory data were published. Here, we systematically examined the impact of EL on composition and CEC of serum and isolated HDL, in vitro and in vivo, using EL-overexpressing cells and EL-overexpressing mice. CEC was examined in a validated assay using H-cholesterol labelled J774 macrophages. In vitro EL-modification of serum resulted in complex alterations, including enrichment of serum with lipid-free/-poor apoA-I, decreased size of human (but not mouse) HDL and altered HDL lipid composition. EL-modification of serum increased CEC, in line with increased lipid-free/-poor apoA-I formation. In contrast, CEC of isolated HDL was decreased likely through altered lipid composition. In contrast to in vitro results, EL-overexpression in mice markedly decreased HDL-cholesterol and apolipoprotein A-I serum levels associated with a decreased CEC of serum. HDL lipid composition was altered, but HDL particle size and CEC were not affected. Our study highlights the multiple and complex effects of EL on HDL composition and function and may help to clarify the seemingly contradictory data found in published articles.
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http://dx.doi.org/10.1038/s41598-017-12882-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5624901PMC
October 2017

Adiponectin Predicts High-Density Lipoprotein Cholesterol Efflux Capacity in Adults Irrespective of Body Mass Index and Fat Distribution.

J Clin Endocrinol Metab 2017 11;102(11):4117-4123

Clinical Institute of Medical and Chemical Laboratory Diagnostics, Medical University of Graz, 8036 Graz, Austria.

Context: Obesity is associated with hypoadiponectemia, dyslipidemia, and increased risk of cardiovascular disease (CVD). Mechanisms linking these conditions remain to be fully understood. Cholesterol efflux capacity (CEC) is a crucial functional property of high-density lipoprotein (HDL) that strongly predicts CVD incidence.

Objective: We investigated whether age, fat distribution, and other obesity-related factors affect CEC in juvenile and adult overweight/obese participants of the STYJOBS/EDECTA cohort (NCT00482924).

Design: We performed an observational study.

Main Outcome Measures: CEC and its association with body measures and related metabolic parameters was assessed in 683 participants (281 juveniles, of whom 227 were overweight/obese; 402 adults, of whom 197 were overweight/obese).

Results: Pearson correlation analysis showed that, after Bonferroni correction, CEC was significantly inversely correlated with body mass index (BMI), carotid diameter, waist circumference, waist-to-hip, waist-to-height ratio, oxidized low-density lipoprotein, and uric acid and with the liver markers alanine-aminotransferase and choline esterase. CEC was positively correlated with HDL cholesterol, total cholesterol, apolipoprotein A1, and adiponectin in adults, whereas in juveniles only apolipoprotein A1 showed a significant positive correlation with CEC. Age-stratified linear regression analyses with CEC as the outcome variable identified adiponectin as the most significant predictor of CEC in adults. The results did not change when either BMI or waist-to-hip ratio as a factor of fat distribution was included in the models.

Conclusions: Hypoadiponectemia is a robust predictor of reduced cholesterol efflux capacity in adults irrespective of BMI and fat distribution. Further investigations are needed to assess whether adiponectin is a causal determinant of CEC.
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http://dx.doi.org/10.1210/jc.2017-00933DOI Listing
November 2017

HDL structure and function is profoundly affected when stored frozen in the absence of cryoprotectants.

J Lipid Res 2017 11 11;58(11):2220-2228. Epub 2017 Sep 11.

Institute of Experimental and Clinical Pharmacology, Medical University of Graz, Graz, Austria

Analysis of structural and functional parameters of HDL has gained significant momentum in recent years because they are stronger predictors of cardiovascular risk than HDL-cholesterol levels. Surprisingly, in most HDL studies, very low attention is paid to HDL storage, which might critically affect functional properties. In the present study, we systematically examined the impact of storage and freezing on the structural/functional properties of freshly isolated HDL. Initial damage to HDL starts between week 1 and week 4 of storage. We observed that prolonged freezing at -20°C or -70°C led to a shedding of apoA-I from HDL and to the formation of large protein-poor particles, indicating that HDL is irreversibly disrupted. These structural alterations profoundly affected key metrics of HDL function, including HDL-cholesterol efflux capacity and HDL paraoxonase activity. Flash-freezing of isolated HDL prior to storage at -70°C did not preserve HDL structure. However, addition of the cryoprotectants, sucrose or glycerol, completely preserved structure and function of HDL when stored for at least 2 years. Our data clearly indicate that HDL is a complex particle requiring special attention when stored. Addition of cryoprotectants to isolated HDL samples before storage will make biochemical and clinical HDL research studies more reproducible and comparable.
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http://dx.doi.org/10.1194/jlr.D075366DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5665661PMC
November 2017

Economic Evaluation of Pharmacologic Pre- and Postconditioning With Sevoflurane Compared With Total Intravenous Anesthesia in Liver Surgery: A Cost Analysis.

Anesth Analg 2017 03;124(3):925-933

From the *Winterthur Institute of Health Economics, Zurich University of Applied Sciences, Winterthur, Switzerland; †Institute of Anesthesiology, University of Zurich, Zurich, Switzerland; and ‡Institute of Anesthesiology and Pain Medicine, Kantonsspital Winterthur, Winterthur, Switzerland.

Background: Pharmacologic pre- and postconditioning with sevoflurane compared with total IV anesthesia in patients undergoing liver surgery reduced complication rates as shown in 2 recent randomized controlled trials. However, the potential health economic consequences of these different anesthesia regimens have not yet been assessed.

Methods: An expostcost analysis of these 2 trials in 129 patients treated between 2006 and 2010 was performed. We analyzed direct medical costs for in-hospital stay and compared pharmacologic pre- and postconditioning with sevoflurane (intervention) with total IV anesthesia (control) from the perspective of a Swiss university hospital. Year 2015 costs, converted to US dollars, were derived from hospital cost accounting data and compared with a multivariable regression analysis adjusting for relevant covariables. Costs with negative prefix indicate savings and costs with positive prefix represent higher spending in our analysis.

Results: Treatment-related costs per patient showed a nonsignificant change by -12,697 US dollars (95% confidence interval [CI], 10,956 to -36,352; P = .29) with preconditioning and by -6139 US dollars (95% CI, 6723 to -19,000; P = .35) with postconditioning compared with the control group. Results were robust in our sensitivity analysis. For both procedures (control and intervention) together, major complications led to a significant increase in costs by 86,018 US dollars (95% CI, 13,839-158,198; P = .02) per patient compared with patients with no major complications.

Conclusions: In this cost analysis, reduced in-hospital costs by pharmacologic conditioning with sevoflurane in patients undergoing liver surgery are suggested. This possible difference in costs compared with total IV anesthesia is the result of reduced complication rates with pharmacologic conditioning, because major complications have significant cost implications.
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http://dx.doi.org/10.1213/ANE.0000000000001814DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5305288PMC
March 2017

Refined purification strategy for reliable proteomic profiling of HDL: Impact on proteomic complexity.

Sci Rep 2016 12 5;6:38533. Epub 2016 Dec 5.

Institute of Experimental and Clinical Pharmacology, Medical University of Graz, Austria.

Proteomics have extended the list of high-density lipoprotein (HDL) associated proteins to about 90. One of the major issues of global protein characterization is establishing specificity of association as opposed to contamination, a fact which has never been addressed for isolated HDL. We have developed a refined purification strategy to isolate HDL by density, followed by purification by size to generate "highly purified" fractions of HDL, which allow the reliable quantification of the HDL proteome for biomarker discovery. Mass spectrometry analysis revealed that the proteome of HDL is composed of 10-16 different proteins, which is in striking contrast to previous reports. Importantly, proteomic analysis revealed that many proteins which have recently been described to be associated with HDL, including α-1-antitrypsin, α-2-HS-glycoprotein, serotransferrin, apolipoprotein A-IV and others, are not associated with HDL and are exclusively found in a different molecular weight fraction containing human serum albumin, lipid-poor apolipoprotein A-I and other proteins. Interestingly, proteins found in this lower molecular weight fraction commonly share lipid-binding properties and enrichment of serum with free fatty acids/lysophophatidylcholine led to a significant increase in co-isolation of lipid-binding proteins such as albumin and α-1-antitrypsin. We propose that this refined method might become a standard in proteomic assessment of HDL making data from clinical cohorts more comparable and reproducible.
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http://dx.doi.org/10.1038/srep38533DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5137140PMC
December 2016

Detection of circulating tumor cells in patients with esophagogastric or pancreatic adenocarcinoma using the CellSearch system: An observational feasibility study.

Oncol Lett 2016 Aug 30;12(2):1513-1518. Epub 2016 Jun 30.

Institute of Anesthesiology, University Hospital Zurich, 8091 Zurich, Switzerland.

Circulating tumor cells (CTCs) in the blood of cancer patients have been demonstrated to be of prognostic value regarding metastasis and survival. The CellSearch system has been certified for the detection of CTCs and as a prognostic tool in patients with metastatic breast, colon and prostate cancer. Few studies have evaluated the detection of CTCs originating from esophagogastric or pancreatic cancer with the CellSearch system. In the present small pilot study, a total of 16 patients with either esophagogastric (n=8) or pancreatic (n=8) adenocarcinomas at various disease stages were randomly screened and included. A total of 7.5 ml of blood was drawn from each patient and analyzed for CTCs using the CellSearch device. CTCs could be detected in 1 out of 8 patients (12.5%) with esophagogastric and in 7 out of 8 patients (87.5%) with pancreatic cancer. The preliminary data obtained from this observational feasibility study suggested that the CellSearch system may become a valuable tool for the detection of CTCs in patients with pancreatic adenocarcinoma, whereas the usefulness in patients with early-stage esophagogastric adenocarcinoma may be limited. This study clearly points towards a requirement for larger studies focusing on patients with pancreatic adenocarcinoma at various disease stages and assessing CTCs, whereas patients with esophagogastric adenocarcinomas should be part of further pilot studies.
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http://dx.doi.org/10.3892/ol.2016.4809DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4950490PMC
August 2016

High-Density Lipoprotein Function in Exudative Age-Related Macular Degeneration.

PLoS One 2016 12;11(5):e0154397. Epub 2016 May 12.

Institute of Experimental and Clinical Pharmacology, Medical University of Graz, Graz, Austria.

Purpose: High-density lipoproteins (HDL) have long been implicated in the pathogenesis of age-related macular degeneration (AMD). However, conflicting results have been reported with regard to the associations of AMD with HDL-cholesterol levels. The present study is the first to assess HDL composition and metrics of HDL function in patients with exudative AMD and control patients.

Methods: Blood samples were collected from 29 patients with exudative AMD and 26 age-matched control patients. Major HDL associated apolipoproteins were determined in apoB-depleted serum by immunoturbidimetry or ELISA, HDL-associated lipids were quantified enzymatically. To get an integrated measure of HDL quantity and quality, we assessed several metrics of HDL function, including cholesterol efflux capacity, anti-oxidative and anti-inflammatory activities using apoB-depleted serum from study participants.

Results: In our study, we observed that the HDL associated acute phase protein serum amyloid A (SAA) was significantly increased in AMD patients (p<0.01), whereas all other assessed apolipoproteins including ApoA-I, apoA-II, apoC-II, apoC-III and apoE as well as major HDL associated lipids were not altered. HDL efflux capacity, anti-oxidative capacity and arylesterase activity were not different in AMD patients when compared with the control group. The ability of apoB-depleted serum to inhibit monocyte NF-κB expression was significantly improved in AMD patients (mean difference (MD) -5.6, p<0.01). Moreover, lipoprotein-associated phospholipase A2 activity, a marker of vascular inflammation, was decreased in AMD subjects (MD -24.1, p<0.01).

Conclusions: The investigated metrics of HDL composition and HDL function were not associated with exudative AMD in this study, despite an increased content of HDL associated SAA in AMD patients. Unexpectedly, anti-inflammatory activity of apoB-depleted serum was even increased in our study. Our data suggest that the investigated parameters of serum HDL function showed no significant association with exudative AMD. However, we cannot exclude that alterations in locally produced HDL may be part of the AMD pathogenesis.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0154397PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4865135PMC
July 2017

Biomarker discovery in heterogeneous tissue samples -taking the in-silico deconfounding approach.

BMC Bioinformatics 2010 Jan 14;11:27. Epub 2010 Jan 14.

Department of Genetics and Biometry, Research Institute for Biology of Farm Animals, Wilhelm-Stahl Allee 2, D 18196 Dummerstorf, Germany.

Background: For heterogeneous tissues, such as blood, measurements of gene expression are confounded by relative proportions of cell types involved. Conclusions have to rely on estimation of gene expression signals for homogeneous cell populations, e.g. by applying micro-dissection, fluorescence activated cell sorting, or in-silico deconfounding. We studied feasibility and validity of a non-negative matrix decomposition algorithm using experimental gene expression data for blood and sorted cells from the same donor samples. Our objective was to optimize the algorithm regarding detection of differentially expressed genes and to enable its use for classification in the difficult scenario of reversely regulated genes. This would be of importance for the identification of candidate biomarkers in heterogeneous tissues.

Results: Experimental data and simulation studies involving noise parameters estimated from these data revealed that for valid detection of differential gene expression, quantile normalization and use of non-log data are optimal. We demonstrate the feasibility of predicting proportions of constituting cell types from gene expression data of single samples, as a prerequisite for a deconfounding-based classification approach.Classification cross-validation errors with and without using deconfounding results are reported as well as sample-size dependencies. Implementation of the algorithm, simulation and analysis scripts are available.

Conclusions: The deconfounding algorithm without decorrelation using quantile normalization on non-log data is proposed for biomarkers that are difficult to detect, and for cases where confounding by varying proportions of cell types is the suspected reason. In this case, a deconfounding ranking approach can be used as a powerful alternative to, or complement of, other statistical learning approaches to define candidate biomarkers for molecular diagnosis and prediction in biomedicine, in realistically noisy conditions and with moderate sample sizes.
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http://dx.doi.org/10.1186/1471-2105-11-27DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3098067PMC
January 2010