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377 Publications visible to you, out of a total of 377
Single cell polarity in liquid phase facilitates tumour metastasis.

Abstract (Expand)

Dynamic polarisation of tumour cells is essential for metastasis. While the role of polarisation during dedifferentiation and migration is well established, polarisation of metastasising tumour cells … during phases of detachment has not been investigated. Here we identify and characterise a type of polarisation maintained by single cells in liquid phase termed single-cell (sc) polarity and investigate its role during metastasis. We demonstrate that sc polarity is an inherent feature of cells from different tumour entities that is observed in circulating tumour cells in patients. Functionally, we propose that the sc pole is directly involved in early attachment, thereby affecting adhesion, transmigration and metastasis. In vivo, the metastatic capacity of cell lines correlates with the extent of sc polarisation. By manipulating sc polarity regulators and by generic depolarisation, we show that sc polarity prior to migration affects transmigration and metastasis in vitro and in vivo.

Authors: A. Lorentzen, P. F. Becker, J. Kosla, M. Saini, K. Weidele, P. Ronchi, C. Klein, M. J. Wolf, F. Geist, B. Seubert, M. Ringelhan, D. Mihic-Probst, K. Esser, M. Roblek, F. Kuehne, G. Bianco, T. O'Connor, Q. Muller, K. Schuck, S. Lange, D. Hartmann, S. Spaich, O. Gross, J. Utikal, S. Haferkamp, M. R. Sprick, A. Damle-Vartak, A. Hapfelmeier, N. Huser, U. Protzer, A. Trumpp, D. Saur, N. Vartak, C. A. Klein, B. Polzer, L. Borsig, M. Heikenwalder

Date Published: 2nd Mar 2018

Publication Type: Not specified

The importance of membrane microdomains for bile salt-dependent biliary lipid secretion.

Abstract (Expand)

Alternative models explaining the biliary lipid secretion at the canalicular membrane of hepatocytes exist: successive lipid extraction by preformed bile salt micelles, or budding of membrane fragments … with formation of mixed micelles. To test the feasibility of the latter mechanism, we developed a mathematical model that describes the formation of lipid microdomains in the canalicular membrane. Bile salt monomers intercalate into the external hemileaflet of the canalicular membrane, to form a rim to liquid disordered domain patches that then pinch off to form nanometer-scale mixed micelles. Model simulations perfectly recapitulate the measured dependence of bile salt-dependent biliary lipid extraction rates upon modulation of the membrane cholesterol (lack or overexpression of the cholesterol transporter Abcg5-Abcg8) and phosphatidylcholine (lack of Mdr2, also known as Abcb4) content. The model reveals a strong dependence of the biliary secretion rate on the protein density of the membrane. Taken together, the proposed model is consistent with crucial experimental findings in the field and provides a consistent explanation of the central molecular processes involved in bile formation.

Authors: J. Eckstein, H. G. Holzhutter, N. Berndt

Date Published: 1st Mar 2018

Publication Type: Not specified

Could inherited predisposition drive non-obese fatty liver disease? Results from German tertiary referral centers.

Abstract (Expand)

Non-alcoholic fatty liver disease (NAFLD) is frequent among obese individuals with metabolic syndrome. Variants PNPLA3 p.I148M, TM6SF2 p.E167K and MBOAT7 rs641738 are associated with higher liver fat … contents. Here we analyzed 63 biopsied non-obese, non-diabetic patients with NAFLD (39 men, age: 20-72 years) recruited within the German NAFLD CSG program. The frequencies of the PNPLA3, TM6SF2 and MBOAT7 polymorphisms were compared with the remaining patients in the NAFLD CSG cohort and with a control population (n = 174). Serum CK18-M30 was measured by ELISA. In non-obese NAFLD patients, the frequency of the PNPLA3 p.I148M allele (74.6%), but not of the TM6SF2 or MBOAT7 polymorphisms, was significantly (P < 0.05) higher as compared to the other patients in the NAFLD CSG cohort (54.9%) or controls (40.2%). The presence of the minor PNPLA3 p.I148M risk allele increased the risk of developing NAFLD (OR = 3.29, P < 0.001) and was associated with higher steatosis, fibrosis, and serum CK18-M30 levels (all P < 0.05). According to the population attributable fraction (PAF), 49.8% of NAFLD cases could be eliminated if the PNPLA3 mutation was absent. The MBOAT7 polymorphism was more frequent (P = 0.019) in patients with severe hepatic steatosis. In conclusion, PNPLA3, and to a lesser extent, MBOAT7 variants are associated with NAFLD risk and modulate liver injury in non-obese patients without diabetes.

Authors: M. Krawczyk, H. Bantel, M. Rau, J. M. Schattenberg, F. Grunhage, A. Pathil, M. Demir, J. Kluwe, T. Boettler, S. N. Weber, A. Geier, F. Lammert

Date Published: 28th Feb 2018

Publication Type: Not specified

Full-Field-of-View Time-Harmonic Elastography of the Native Kidney.

Abstract (Expand)

The purpose of this study was to analyze full-field-of-view maps of renal shear wave speed (SWS) measured by time-harmonic elastography (THE) in healthy volunteers in terms of reproducibility, regional … variation and physiologic effects. The kidneys of 37 healthy volunteers were investigated by multifrequency THE. The complete renal parenchyma, as well as cortex and medulla, was analyzed. A subgroup was investigated to test reproducibility (n = 3). Significant differences between SWS in cortex, medulla and full parenchyma were observed (2.10 +/- 0.17, 1.35 +/- 0.11 and 1.71 +/- 0.16 m/s, all p values < 0.001) with mean intra-volunteer standard deviations of repeated measurements of 0.04 m/s (1.6%), 0.06 m/s (4.0%) and 0.08 m/s (4.5%), respectively. No effects of kidney anatomy, age, body mass index, blood pressure and heart rate on SWS were observed. THE allows generation of full-field-of-view SWS maps of native kidneys with high reproducibility.

Authors: S. R. Marticorena Garcia, M. Grossmann, S. T. Lang, M. Nguyen Trong, M. Schultz, J. Guo, B. Hamm, J. Braun, I. Sack, H. Tzschatzsch

Date Published: 27th Feb 2018

Publication Type: Not specified

Resolving the Combinatorial Complexity of Smad Protein Complex Formation and Its Link to Gene Expression.

Abstract (Expand)

Upon stimulation of cells with transforming growth factor beta (TGF-beta), Smad proteins form trimeric complexes and activate a broad spectrum of target genes. It remains unresolved which of the possible … Smad complexes are formed in cellular contexts and how these contribute to gene expression. By combining quantitative mass spectrometry with a computational selection strategy, we predict and provide experimental evidence for the three most relevant Smad complexes in the mouse hepatoma cell line Hepa1-6. Utilizing dynamic pathway modeling, we specify the contribution of each Smad complex to the expression of representative Smad target genes, and show that these contributions are conserved in human hepatoma cell lines and primary hepatocytes. We predict, based on gene expression data of patient samples, increased amounts of Smad2/3/4 proteins and Smad2 phosphorylation as hallmarks of hepatocellular carcinoma and experimentally verify this prediction. Our findings demonstrate that modeling approaches can disentangle the complexity of transcription factor complex formation and its impact on gene expression.

Authors: P. Lucarelli, M. Schilling, C. Kreutz, A. Vlasov, M. E. Boehm, N. Iwamoto, B. Steiert, S. Lattermann, M. Wasch, M. Stepath, M. S. Matter, M. Heikenwalder, K. Hoffmann, D. Deharde, G. Damm, D. Seehofer, M. Muciek, N. Gretz, W. D. Lehmann, J. Timmer, U. Klingmuller

Date Published: 19th Feb 2018

Publication Type: Not specified

A multiscale modelling approach to assess the impact of metabolic zonation and microperfusion on the hepatic carbohydrate metabolism.

Abstract (Expand)

The capacity of the liver to convert the metabolic input received from the incoming portal and arterial blood into the metabolic output of the outgoing venous blood has three major determinants: The … intra-hepatic blood flow, the transport of metabolites between blood vessels (sinusoids) and hepatocytes and the metabolic capacity of hepatocytes. These determinants are not constant across the organ: Even in the normal organ, but much more pronounced in the fibrotic and cirrhotic liver, regional variability of the capillary blood pressure, tissue architecture and the expression level of metabolic enzymes (zonation) have been reported. Understanding how this variability may affect the regional metabolic capacity of the liver is important for the interpretation of functional liver tests and planning of pharmacological and surgical interventions. Here we present a mathematical model of the sinusoidal tissue unit (STU) that is composed of a single sinusoid surrounded by the space of Disse and a monolayer of hepatocytes. The total metabolic output of the liver (arterio-venous glucose difference) is obtained by integration across the metabolic output of a representative number of STUs. Application of the model to the hepatic glucose metabolism provided the following insights: (i) At portal glucose concentrations between 6-8 mM, an intra-sinusoidal glucose cycle may occur which is constituted by glucose producing periportal hepatocytes and glucose consuming pericentral hepatocytes, (ii) Regional variability of hepatic blood flow is higher than the corresponding regional variability of the metabolic output, (iii) a spatially resolved metabolic functiogram of the liver is constructed. Variations of tissue parameters are equally important as variations of enzyme activities for the control of the arterio-venous glucose difference.

Authors: N. Berndt, M. S. Horger, S. Bulik, H. G. Holzhutter

Date Published: 16th Feb 2018

Publication Type: Not specified

Effects of Gene Variants Controlling Vitamin D Metabolism and Serum Levels on Hepatic Steatosis

Abstract (Expand)

Background/Aims: Common genetic variations in vitamin D metabolism are associated with liver stiffness. Whether these genes are implicated in hepatic steatosis remains unclear. Here we aimed to analyse … the association of common vitamin D pathway gene variants with liver steatosis. Methods: Liver steatosis was assessed non-invasively in 241 patients with chronic liver conditions by controlled attenuation parameter (CAP). The following polymorphisms were genotyped using TaqMan assays: group-specific component ( GC ) rs7041, 7-dehydrocholesterol reductase ( DHCR7 ) rs12785878, cytochrome P450 2R1 ( CYP2R1 ) rs10741657, vitamin D receptor ( VDR ) rs7974353. Chemiluminescence immunoassay determined serum 25-hydroxyvitamin D (25(OH) D) concentrations. Results: Vitamin D deficiency (defined by 25(OH)D concentrations <20 ng/mL) occurred in 66% of patients. Median CAP was 296 (100–400) dB/m. Patients with advanced steatosis (CAP ≥ 280 dB/m) had significantly ( p = 0.033) lower 25(OH)D levels as compared to patients with CAP <280 dB/m. Moreover, the rare allele [T] in GC rs7041 was significantly ( p = 0.018) associated with higher 25(OH)D levels in patients with CAP <280 dB/m. However, GC , DHCR7, CYP2R1 , and VDR polymorphisms were not related to liver steatosis and obesity traits. Conclusions: Higher CAP values are associated with low serum 25(OH)D concentrations but not with common vitamin D pathway gene variants.

Authors: Malgorzata Jamka, Anita Arslanow, Annika Bohner, Marcin Krawczyk, Susanne N. Weber, Frank Grünhage, Frank Lammert, Caroline S Stokes

Date Published: 7th Feb 2018

Publication Type: Not specified

Ethanol sensitizes hepatocytes for TGF-β-triggered apoptosis

Abstract

Not specified

Authors: Haristi Gaitantzi, Christoph Meyer, Pia Rakoczy, Maria Thomas, Kristin Wahl, Franziska Wandrer, Heike Bantel, Hamed Alborzinia, Stefan Wölfl, Sabrina Ehnert, Andreas Nüssler, Ina Bergheim, Loredana Ciuclan, Matthias Ebert, Katja Breitkopf-Heinlein, Steven Dooley

Date Published: 1st Feb 2018

Publication Type: Not specified

Hepatic Smad7 overexpression causes severe iron overload in mice

Abstract

Not specified

Authors: Dilay Lai, Feng Teng, Seddik Hammad, Julia Werle, Thorsten Maas, Andreas Teufel, Martina U. Muckenthaler, Steven Dooley, Maja Vujić Spasić

Date Published: 1st Feb 2018

Publication Type: Not specified

Electrosurgical liver resection has a superior regeneration outcome as compared to en-bloc ligation in a novel model of partial hepatectomy in mice

Abstract (Expand)

Background: The extent of resection and the frequency of liver surgery have increased over the past decades, enabled by improved haemostasis provided by electrosurgical liver dissection. Because extensive … liver surgery is still associated with lethal complications, further optimisation of the technique and a better molecular understanding of hepatic wound healing and regeneration are needed. Systematic studies and a mouse model reflecting the clinical reality of liver surgery are lacking. Methods: We performed liver resection in mice with a monopolar electrocautery device in comparison to the classical en-bloc ligation method. Regeneration was assessed using liver weight and BrDU immunohistochemistry after sacrifice and non-invasively using micro computed tomography (µCT). Results: Mortality in the electrosurgical model was similar to the ligation method given an identical extent of resection. Regeneration of liver proceeded significantly faster in the electrosurgical group: Liver weight was 25.6% higher at sacrifice after 168h (p=0.0003). Concordantly, both µCT analysis (22.6% higher liver volume at 168h, p=0.008) and BrDU staining (71.4% higher proliferation at 72h, p=0.0005) indicated superior regeneration of liver after electrosurgical partial hepatectomy. Conclusions: The mode of liver resection has a profound impact on regeneration and should be studied molecularly using the presented novel model of electrosurgical liver resection.

Authors: W. von Schonfels, Clemens Schafmayer, Jochen Hampe

Date Published: 27th Jan 2018

Publication Type: Not specified

Harmonizing semantic annotations for computational models in biology.

Abstract (Expand)

Life science researchers use computational models to articulate and test hypotheses about the behavior of biological systems. Semantic annotation is a critical component for enhancing the interoperability … and reusability of such models as well as for the integration of the data needed for model parameterization and validation. Encoded as machine-readable links to knowledge resource terms, semantic annotations describe the computational or biological meaning of what models and data represent. These annotations help researchers find and repurpose models, accelerate model composition and enable knowledge integration across model repositories and experimental data stores. However, realizing the potential benefits of semantic annotation requires the development of model annotation standards that adhere to a community-based annotation protocol. Without such standards, tool developers must account for a variety of annotation formats and approaches, a situation that can become prohibitively cumbersome and which can defeat the purpose of linking model elements to controlled knowledge resource terms. Currently, no consensus protocol for semantic annotation exists among the larger biological modeling community. Here, we report on the landscape of current annotation practices among the COmputational Modeling in BIology NEtwork community and provide a set of recommendations for building a consensus approach to semantic annotation.

Authors: M. L. Neal, M. Konig, D. Nickerson, G. Misirli, R. Kalbasi, A. Drager, K. Atalag, V. Chelliah, M. T. Cooling, D. L. Cook, S. Crook, M. de Alba, S. H. Friedman, A. Garny, J. H. Gennari, P. Gleeson, M. Golebiewski, M. Hucka, N. Juty, C. Myers, B. G. Olivier, H. M. Sauro, M. Scharm, J. L. Snoep, V. Toure, A. Wipat, O. Wolkenhauer, D. Waltemath

Date Published: 22nd Jan 2018

Publication Type: Not specified

Ethanol sensitizes hepatocytes for TGF-beta-triggered apoptosis.

Abstract (Expand)

Alcohol abuse is a global health problem causing a substantial fraction of chronic liver diseases. Abundant TGF-beta-a potent pro-fibrogenic cytokine-leads to disease progression. Our aim was to elucidate … the crosstalk of TGF-beta and alcohol on hepatocytes. Primary murine hepatocytes were challenged with ethanol and TGF-beta and cell fate was determined. Fluidigm RNA analyses revealed transcriptional effects that regulate survival and apoptosis. Mechanistic insights were derived from enzyme/pathway inhibition experiments and modulation of oxidative stress levels. To substantiate findings, animal model specimens and human liver tissue cultures were investigated. RESULTS: On its own, ethanol had no effect on hepatocyte apoptosis, whereas TGF-beta increased cell death. Combined treatment led to massive hepatocyte apoptosis, which could also be recapitulated in human HCC liver tissue treated ex vivo. Alcohol boosted the TGF-beta pro-apoptotic gene signature. The underlying mechanism of pathway crosstalk involves SMAD and non-SMAD/AKT signaling. Blunting CYP2E1 and ADH activities did not prevent this effect, implying that it was not a consequence of alcohol metabolism. In line with this, the ethanol metabolite acetaldehyde did not mimic the effect and glutathione supplementation did not prevent the super-induction of cell death. In contrast, blocking GSK-3beta activity, a downstream mediator of AKT signaling, rescued the strong apoptotic response triggered by ethanol and TGF-beta. This study provides novel information on the crosstalk between ethanol and TGF-beta. We give evidence that ethanol directly leads to a boost of TGF-beta's pro-apoptotic function in hepatocytes, which may have implications for patients with chronic alcoholic liver disease.

Authors: H. Gaitantzi, C. Meyer, P. Rakoczy, M. Thomas, K. Wahl, F. Wandrer, H. Bantel, H. Alborzinia, S. Wolfl, S. Ehnert, A. Nussler, I. Bergheim, L. Ciuclan, M. Ebert, K. Breitkopf-Heinlein, S. Dooley

Date Published: 21st Jan 2018

Publication Type: Not specified

Liver-specific Repin1 deficiency impairs transient hepatic steatosis in liver regeneration.

Abstract (Expand)

Transient hepatic steatosis upon liver resection supposes functional relationships between lipid metabolism and liver regeneration. Repin1 has been suggested as candidate gene for obesity and dyslipidemia … by regulating key genes of lipid metabolism and lipid storage. Herein, we characterized the regenerative potential of mice with a hepatic deletion of Repin1 (LRep1-/-) after partial hepatectomy (PH) in order to determine the functional significance of Repin1 in liver regeneration. Lipid dynamics and the regenerative response were analyzed at various time points after PH. Hepatic Repin1 deficiency causes a significantly decreased transient hepatic lipid accumulation. Defects in lipid uptake, as analyzed by decreased expression of the fatty acid transporter Cd36 and Fatp5, may contribute to attenuated and shifted lipid accumulation, accompanied by altered extent and chronological sequence of liver cell proliferation in LRep1-/- mice. In vitro steatosis experiments with primary hepatocytes also revealed attenuated lipid accumulation and occurrence of smaller lipid droplets in Repin1-deficient cells, while no direct effect on proliferation in HepG2 cells was observed. Based on these results, we propose that hepatocellular Repin1 might be of functional significance for early accumulation of lipids in hepatocytes after PH, facilitating efficient progression of liver regeneration.

Authors: K. Abshagen, B. Degenhardt, M. Liebig, A. Wendt, B. Genz, U. Schaeper, M. Stumvoll, U. Hofmann, M. Frank, B. Vollmar, N. Kloting

Date Published: 18th Jan 2018

Publication Type: Not specified

Genetic determinants of steatosis and fibrosis progression in pediatric non-alcoholic fatty liver disease.

Abstract (Expand)

BACKGROUND & AIMS: Non-alcoholic fatty liver disease (NAFLD) is the most common chronic liver disease in children and adolescents today. In comparison to adult disease, pediatric NAFLD may show a … periportal localization, which is associated with advanced fibrosis. This study aimed to assess the role of genetic risk variants for histologic disease pattern and severity in childhood NAFLD. METHODS: We studied 14 single nucleotide polymorphisms (SNP) in a cohort of 70 adolescents with biopsy-proven NAFLD. Genotype was compared to an adult control cohort (n=200) and analyzed in relation to histologic disease severity and liver tissue proteomics. RESULTS: Three of the 14 SNPs were significantly associated with pediatric NAFLD after FDR adjustment, rs738409 (PNPLA3, P=2.80x10(-06) ), rs1044498 (ENPP1, P=0.0091) and rs780094 (GCKR, P=0.0281). The severity of steatosis was critically associated with rs738409 (OR=3.25; 95% CI: 1.72-6.52, FDR adjusted P=0.0070). The strongest variants associated with severity of fibrosis were rs1260326, rs780094 (both GCKR) and rs659366 (UCP2). PNPLA3 was associated with a portal pattern of steatosis, inflammation and fibrosis. Proteome profiling revealed decreasing levels of GCKR protein with increasing carriage of the rs1260326/rs780094 minor alleles and down-regulation of the retinol pathway in rs738409 G/G carriers. Computational metabolic modelling highlighted functional relevance of PNPLA3, GCKR and UCP2 for NAFLD development. CONCLUSIONS: This study provides evidence for the role of PNPLA3 as a determinant of portal NAFLD localization and severity of portal fibrosis in children and adolescents, the risk variant being associated with an impaired hepatic retinol metabolism. This article is protected by copyright. All rights reserved.

Authors: C. A. Hudert, S. Selinski, B. Rudolph, H. Blaker, C. Loddenkemper, R. Thielhorn, N. Berndt, K. Golka, C. Cadenas, J. Reinders, S. Henning, P. Bufler, P. L. M. Jansen, H. G. Holzhutter, D. Meierhofer, J. G. Hengstler, S. Wiegand

Date Published: 18th Jan 2018

Publication Type: Not specified

The formation of estrogen-like tamoxifen metabolites and their influence on enzyme activity and gene expression of ADME genes.

Abstract (Expand)

Tamoxifen, a standard therapy for breast cancer, is metabolized to compounds with anti-estrogenic as well as estrogen-like action at the estrogen receptor. Little is known about the formation of … estrogen-like metabolites and their biological impact. Thus, we characterized the estrogen-like metabolites tamoxifen bisphenol and metabolite E for their metabolic pathway and their influence on cytochrome P450 activity and ADME gene expression. The formation of tamoxifen bisphenol and metabolite E was studied in human liver microsomes and Supersomes. Cellular metabolism and impact on CYP enzymes was analyzed in upcyte(R) hepatocytes. The influence of 5 microM of tamoxifen, anti-estrogenic and estrogen-like metabolites on CYP activity was measured by HPLC MS/MS and on ADME gene expression using RT-PCR analyses. Metabolite E was formed from tamoxifen by CYP2C19, 3A and 1A2 and from desmethyltamoxifen by CYP2D6, 1A2 and 3A. Tamoxifen bisphenol was mainly formed from (E)- and (Z)-metabolite E by CYP2B6 and CYP2C19, respectively. Regarding phase II metabolism, UGT2B7, 1A8 and 1A3 showed highest activity in glucuronidation of tamoxifen bisphenol and metabolite E. Anti-estrogenic metabolites (Z)-4-hydroxytamoxifen, (Z)-endoxifen and (Z)-norendoxifen inhibited the activity of CYP2C enzymes while tamoxifen bisphenol consistently induced CYPs similar to rifampicin and phenobarbital. On the transcript level, highest induction up to 5.6-fold was observed for CYP3A4 by tamoxifen, (Z)-4-hydroxytamoxifen, tamoxifen bisphenol and (E)-metabolite E. Estrogen-like tamoxifen metabolites are formed in CYP-dependent reactions and are further metabolized by glucuronidation. The induction of CYP activity by tamoxifen bisphenol and the inhibition of CYP2C enzymes by anti-estrogenic metabolites may lead to drug-drug-interactions.

Authors: J. Johanning, P. Kroner, M. Thomas, U. M. Zanger, A. Norenberg, M. Eichelbaum, M. Schwab, H. Brauch, W. Schroth, T. E. Murdter

Date Published: 28th Dec 2017

Publication Type: Not specified

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