Hormonal-inflammatory interference in the control of de novo glucose production by the liver [Elektronische Ressource] / presented by Evgeny Chichelnitskiy

Evgeny Epifanovsky*†

Sujets

• Biologie

Informations

• Publié par: ruprecht-karls-universitat_heidelberg
• Publié le: 01 janvier 2009
• Nombre de lectures: 38
• Langue: Deutsch
• Poids de l'ouvrage: 1 Mo

Extrait

Dissertation
submitted to the
Combined Faculties for Natural Sciences and for Mathematics
of the Ruperto-Carola University of Heidelberg, Germany
for the degree of
Doctor of Natural Sciences




HORMONAL-INFLAMMATORY INTERFERENCE
IN THE CONTROL OF DE NOVO GLUCOSE PRODUCTION
BY THE LIVER







Presented by

Evgeny Chichelnitskiy

Diploma: Microbiology and Molecular biology,
Kasan State University, Russia
Date and Place of Birth: 17.07.1983, Kasan, Russia


Heidelberg, 2009 HORMONAL-INFLAMMATORY INTERFERENCE
IN THE CONTROL OF DE NOVO GLUCOSE PRODUCTION
BY THE LIVER




















Referees:
PD Dr. Mathias Mayer
Dr. Stephan Herzig


“THE SEARCH FOR TRUTH IS MORE PRECIOUS THAN ITS
POSSESSION.”

Albert Einstein Nobel Prize f or Physics in 1921, 1879‐1955 
 




















Dedicated to my Parents Zusammenfassung


Eine Voraussetzung für die Gesundheit und das Überleben von Säugetieren ist die
Aufrechterhaltung des Blutglukosespiegels. Die Inhibition der stresskompensierenden de novo
Glukoseproduktion in der Leber, Glukoneogenese, während akuter Entzündungprozesse ist
eines der Hauptmerkmale eines veränderten Stoffwechsels und Haupttodesursache bei
Sepsispatienten. Störung der hormonellen Signaltransduktion und die daraus resultierende
Unterdrückung des Schlüsselenzyms der Glukoneogenese, der Phosphoenolpyruvate
Carboxykinase (PEPCK), durch pro-inflammatorische Mediatoren trägt wesentlich zur
schweren Hypoglykämie während einer Sepsis bei. Die molekularen Mechanismen der
veränderten PEPCK Genregulation unter diesen Bedingungen sind jedoch noch unklar. Diese
Arbeit stellt ein System für die Herstellung eines leberspezifischen adenoviralen
Reportersystems vor, das die Identifizierung von dysfunktionalen cis-regulatorischen DNA
Promoterelementen unter pathologischen Bedingungen in Mäusen erlaubt. Durch die Nutzung
dieser in vivo Promoterkartierung konnte die Glukokortikoid responsive Einheit (*GRU) und
das cAMP-responsabel Element (CRE) des PEPCK Gens-Genpromoters als wichtige
regulatorische Elementen für die pro-inflammatorische Signalübertragung identifiziert
werden. Die Deregulation der synergistischen Funktion dieser zwei Promoterelemente trägt
dabei zur Inhibition der PEPCK Genexpression unter septische Bedingungen bei. Zudem
konnte gezeigt werden, dass die Expression des Kernrezeptor Ko-Faktors PGC-1 α, dem
molekularem Vermittler des GRU/CRE-Zusammenspiels auf dem PEPCK-Promoter,
spezifisch in der septischen Leber herunterreguliert ist. Die Verminderung der endogenen
PGC-1 α Expression verhinderte den durch Entzündungsmediatoren ausgelösten
inhibitorischen Effekt auf die PEPCK Genexpression in primären Hepatozyten, während die
Überexpression von PGC-1 α die Expression von PEPCK unter den gleichen Bedingungen
wiederherstellen konnte. Diese Ergebnisse identifizieren einen neuartigen in vivo -
Mechanismus, der für die Suppression der glukoneogenetischen Genexpression in septischen
Mäusen verantwortlich ist. Die Erhaltung der PGC-1 α Aktivität könnte damit eine attraktive
therapeutische Maßnahme zur Aktivierung der Glukoneogenese und zu Verhinderung von
Hypoglykämie in septischen Patienten darstellen.

*Glucocorticoid response unit (GRU)
1
Abstract

Abstract

In mammals the maintenance of an appropriate glucose level in the blood is a prerequisite of
good health and survival. The blockade of stress compensatory de novo glucose production by
the liver, gluconeogenesis, during acute inflammation is one of the major characteristics of the
aberrant metabolic state and a reason of death in septic patients. Interference with hormone
signaling and the subsequent suppression of key rate limiting gluconeogenic enzyme
phosphoenolpyruvate carboxykinase (PEPCK) through pro-inflammatory mediators
importantly contribute to severe hypoglycemia in sepsis. However, the molecular mechanisms
of aberrant PEPCK gene regulation under these conditions in vivo remain largely unknown.
In the present study we report the generation of a liver-specific adenoviral reporter system for
the identification of dysfunctional gene cis-regulatory promoter elements under pathological
conditions in mice. By employing in vivo promoter reporter technology, the glucocorticoid
response unit (GRU) and the cAMP-response element (CRE) of the PEPCK gene were
identified as critical promoter target sites of pro-inflammatory signaling. The disruption of the
synergistic function of these two promoter elements was found to mediate PEPCK gene
inhibition under septic conditions. Furthermore, the expression of nuclear receptor co-factor
PGC-1 α, the molecular mediator of GRU/CRE synergism on the PEPCK promoter, was found
to be specifically repressed in septic liver. The depletion of endogenous PGC-1 α with RNAi
blunts the inflammatory suppressive effect on the PEPCK gene in cytokine-exposed primary
hepatocytes while PGC-1 α over-expression restores PEPCK expression under the same
conditions.
These results provide an in vivo mechanism involved in the suppression of the key
gluconeogenic gene PEPCK in septic mouse. The maintenance of PGC-1 α activity might
represent an attractive therapeutic defense for the rescue of gluconeogenic program repression
and hypoglycemia in septic patients.



2
Acknowledgements

Acknowledgements

First and foremost I would like to express my sincerest gratitude to Dr Stephan Herzig, my
project supervisor, whose outstanding scientific knowledge and intuition together with
incredible optimism contributed a lot in the success of my project even at the very difficult
stages. It was a great honor to fulfill my PhD thesis work in his lab that significantly enhanced
my scientific expertise and awareness.
I am grateful to other members of thesis advisory committee, namely Dr Mathias Mayer who
has also agreed to review the thesis and be a chairman on my PhD defence and Dr Doris
Mayer for their helpful suggestions and interesting discussions. I also thank Dr Karin Müller-
Decker and Dr Anne Regnier-Vigouroux for agreeing to participate in my PhD examination.
I deeply thank Dr Alex Vegiopoulos with whom I have worked a lot together over the time of
my PhD and learnt much from his great scientific experience and expertise and for his
precious suggestions and discussions. I also thank Dr Mauricio Berriel Diaz for the productive
collaborative work and his helpful personality who also shared with me some of his important
scientific experience. I am very thankful to Anka Ostertag, Anna Margareta Gail, Prachiti
Narvekar, Ulrike Lemke and others lab members for important discussions and being nice and
helpful bench-workers. To this I want additionally thank Anna Margareta Gail for bringing
some color in sometimes black and white everyday scientific life that was very helpful for
recovering a motivation and a productive scientific atmosphere. Special thanks to Dr Anja
Krones-Herzig for her expertise and very valuable advice for some tricky scientific
experiments.
I want also to thank Anja Ziegler for highly professional mouse injections and Daniela
Strzoda who both helped a lot with mouse experiments.
I thank Dr Adam Rose and Alex V. for precious suggestions and grammatical corrections that
crucially contributed to the improving of this thesis manuscript.
Finally I accord my sincere thanks to my first academic supervisor Prof. Dr Olga Ilinskaya,
who taught me to do first steps in scientific work during my study in Kasan State University.



3
Index

Index

ZUSAMMENFASSUNG ......................................................................................................... 1
ABSTRACT .............................................................................................................................. 2
ACKNOWLEDGEMENTS ..................................................................................................... 3
INDEX ....................................................................................................................................... 4

1. INTRODUCTION ................................................................................ 10
1.1 Metabolism and Metabolic diseases in XXI century ...................... 10
1.2 Inflammation as a hallmark of a variety of metabolic diseases ...... 11
1.2.1 Sepsis as a model of inflammatory-metabolic interference .... 13
1.3 Liver in metabolism and immunity ................................................. 13
1.4 Regulation of stress response. The control of PEPCK gene
expression under physiological and septic conditions ............................ 16
1.5 Adenoviral gene delivery as robust tool