On the relationship between metabolic capacities and in vivo viscoelastic properties of the liver

The liver is the central metabolic organ. It constantly adapts its metabolic capacity to current physiological requirements. However, the relationship between tissue structure and hepatic function is incompletely understood; this results in a lack of diagnostic markers in medical imaging that can provide information about the liver's metabolic capacity. Therefore, using normal rabbit livers, we combined magnetic resonance elastography (MRE) with proteomics-based kinetic modeling of central liver metabolism to investigate the potential role of MRE for predicting the liver's metabolic function in vivo. Nineteen New Zealand white rabbits were investigated by multifrequency MRE and positron emission tomography (PET). This yielded maps of shear wave speed (SWS), penetration rate (PR) and standardized uptake value (SUV). Proteomic analysis was performed after the scans. Hepatic metabolic functions were assessed on the basis of the HEPATOKIN1 model in combination with a model of hepatic lipid-droplet metabolism using liquid chromatography-mass spectrometry. Our results showed marked differences between individual livers in both metabolic functions and stiffness properties, though not in SUV. When livers were divided into 'stiff' and 'soft' subgroups (cutoff SWS = 1.6 m/s), stiff livers showed a lower capacity for triacylglycerol storage, while at the same time showing an increased capacity for gluconeogenesis and cholesterol synthesis. Furthermore, SWS was correlated with gluconeogenesis and PR with urea production and glutamine exchange. In conclusion, our study indicates a close relationship between the viscoelastic properties of the liver and metabolic function. This could be used in future studies to predict non-invasively the functional reserve capacity of the liver in patients

Transkriptionelle Regulation des Erythropoietin-Rezeptor-Gens im zentralen Nervensystem

Derzeit wird die Anwendung von Erythropoietin (Epo) zur Neuroprotektion in präklinischen und klinischen Studien intensiv untersucht. Für die Neuroprotektion ist die Regulation des Erythropoietin-Rezeptors (EpoR) in neuronalen Zellen von hoher Relevanz. In dieser Arbeit wurden die transkriptionellen Mechanismen der EpoR-Regulation in humanen Neuroblastom-Zellen SH-SY5Y mit neuronalem Phänotyp untersucht. Da der hämatopoietische Transkriptionsfaktor GATA-1 die EpoR-Transkription in erythroiden Vorläuferzellen in Kooperation mit Sp1 stimuliert, wurde die Rolle der in neuronalen Vorläuferzellen exprimierten GATA-Transkriptionsfaktoren bei der EpoR-Expression untersucht. Es wurde eine in vitro Bindung von GATA-2, -3 und -4 an zwei Motive in der EpoR 5’-flankierenden Region (-274/-271; -47/-44) nachgewiesen. In Reportergen-Assays zeigten diese Genabschnitte eine bis zu 4,8-fache Aktivitätssteigerung bei Überexpression von GATA-2, -3 oder -4. Die endogene EpoR mRNA-Expression wurde dadurch aber nicht erhöht. Hypoxie (2% O2, 3 d) erhöhte die EpoR-Expression signifikant (1,8-fach, p < 0,01), wobei überexprimierte GATA-Transkriptionsfaktoren diesen Effekt nicht weiter steigerten. Die Gabe von Epo (5 U/ml, 3 d) hatte weder unter Normoxie noch unter Hypoxie einen Einfluss auf die EpoR-Expression. Die Promotoraktivität der Reporterkonstrukte wurde durch Mutation der GATA-Bindungsstellen nicht verändert, jedoch bei mutierter Sp1-Bindungsstelle inhibiert. Ein Fragment der 5’-flankierenden Region (-449/-285), das ein Cluster von Bindungsstellen für unterschiedliche Transkriptionsfaktoren enthält, zeigte die stärkste Promotoraktivität und rekrutierte offenbar die RNA-Polymerase II. In unserem Modell spielen die GATA-Faktoren keine direkte Rolle für die EpoR-Genregulation in neuronalen Vorläuferzellen. Die EpoR mRNA-Expression wird eher durch einen Komplex aus verschiedenen Transkriptionsfaktoren reguliert, der an eine 5’ des minimalen Promotors liegende DNA-Region zu binden scheint.Since the use of erythropoietin (Epo) as neuroprotective agent is currently intensively studied in preclinical and clinical trials, regulatory mechanisms of the erythropoietin receptor (EpoR) in neuronal cells are of particular interest. In this study, the transcriptional mechanisms of EpoR regulation were analyzed in human neuroblastoma-derived SH-SY5Y cells, which exhibit a neuronal phenotype. Considering that the hematopoietic transcription factor GATA-1 stimulates EpoR transcription in cooperation with Sp1 in erythroid progenitors, the role of other GATA family members expressed in neuronal precursor cells were studied. In vitro, GATA-2, -3 and -4 were found to bind to two consensus motifs within the EpoR 5’-flanking region (-274/-271 and -47/-44). In reporter gene assays, these regions showed an up to 4.8-fold induction if GATA-2, -3 or -4 were overexpressed. However, forced expression of GATA-2, -3 and -4 did not enhance endogenous EpoR mRNA expression. Under hypoxia (2% O2, 3 d), EpoR expression was significantly upregulated in SH-SY5Y cells (1.8-fold, p < 0.01), but not further increased by the additional overexpression of the GATA factors. Incubation of the SH-SY5Y cells with recombinant Epo (5 U/ml, 3 d) had no effect on the EpoR expression under normoxia or hypoxia. The promoter activities of the reporter constructs were not changed by mutations in the GATA sites, but abolished by mutations of Sp1 binding sites. A fragment (-449/-285) of the 5’-flanking region that contains a cluster of binding sites for various transcription factors showed strongest promoter activity and was obviously directing the recruitment of RNA polymerase II. We conclude that GATA factors do not play a major role in regulating EpoR expression in our model for neuronal precursor cells. EpoR mRNA expression is rather regulated by a complex of various transcription factors, which may bind to a region upstream of the minimal promoter

Genome Informatics 2009:Genome Informatics Series Vol. 22

This volume contains 17 peer-reviewed papers based on the presentations at the 9th Annual International Workshop on Bioinformatics and Systems Biology (IBSB 2009) held at the Life Science Engineering Building of Boston University from July 27 to 29, 2009. This workshop started in 2001 as a platform for doctoral students and young researchers to present and discuss their research results and approaches in bioinformatics and systems biology. It is part of a collaborative educational program involving leading institutions and leaders committed to the following institutions and programs: Boston University Graduate Program in Bioinformatics Charité – Universitätsmedizin Berlin Freie Universität Berlin Global COE Program — Center of Education and Research for Advanced Genome-Based Medicine, University of Tokyo The International Research Training Group (IRTG) Genomics and Systems Biology of Molecular Networks International Research and Training Program on Bioinformatics and Systems Biology, Kyoto University Bioinformatics Center Max-Delbrück Center for Molecular Medicine in Berlin Max Planck Institute for Molecular Genetics in Berlin Max Planck Institute of Molecular Plant Physiology in Potsda

Sevoflurane Effects on Neuronal Energy Metabolism Correlate with Activity States While Mitochondrial Function Remains Intact

During general anesthesia, alterations in neuronal metabolism may induce neurotoxicity and/or neuroprotection depending on the dose and type of the applied anesthetic. In this study, we investigate the effects of clinically relevant concentrations of sevoflurane (2% and 4%, i.e., 1 and 2 MAC) on different activity states in hippocampal slices of young Wistar rats. We combine electrophysiological recordings, partial tissue oxygen (ptiO2) measurements, and flavin adenine dinucleotide (FAD) imaging with computational modeling. Sevoflurane minimally decreased the cerebral metabolic rate of oxygen (CMRO2) while decreasing synaptic transmission in naive slices. During pharmacologically induced gamma oscillations, sevoflurane impaired network activity, thereby decreasing CMRO2. During stimulus-induced neuronal activation, sevoflurane decreased CMRO2 and excitability while basal metabolism remained constant. In this line, stimulus-induced FAD transients decreased without changes in basal mitochondrial redox state. Integration of experimental data and computer modeling revealed no evidence for a direct effect of sevoflurane on key enzymes of the citric acid cycle or oxidative phosphorylation. Clinically relevant concentrations of sevoflurane generated a decent decrease in energy metabolism, which was proportional to the present neuronal activity. Mitochondrial function remained intact under sevoflurane, suggesting a better metabolic profile than isoflurane or propofol

sj-pdf-2-jcb-10.1177_0271678X231170746 - Supplemental material for Metabolic implications of axonal demyelination and its consequences for synchronized network activity: An <i>in silico</i> and <i>in vitro</i> study

Supplemental material, sj-pdf-2-jcb-10.1177_0271678X231170746 for Metabolic implications of axonal demyelination and its consequences for synchronized network activity: An in silico and in vitro study by Zoltan Gerevich, Richard Kovács, Agustin Liotta, Luisa A Hasam-Henderson, Ludwig Weh, Iwona Wallach and Nikolaus Berndt in Journal of Cerebral Blood Flow & Metabolism</p

sj-pdf-1-jcb-10.1177_0271678X231170746 - Supplemental material for Metabolic implications of axonal demyelination and its consequences for synchronized network activity: An <i>in silico</i> and <i>in vitro</i> study

Supplemental material, sj-pdf-1-jcb-10.1177_0271678X231170746 for Metabolic implications of axonal demyelination and its consequences for synchronized network activity: An in silico and in vitro study by Zoltan Gerevich, Richard Kovács, Agustin Liotta, Luisa A Hasam-Henderson, Ludwig Weh, Iwona Wallach and Nikolaus Berndt in Journal of Cerebral Blood Flow & Metabolism</p