title: Neue Einblicke in die Evolution des braunen Fettgewebes der Säugetiere
title: New perspectives on the significance of brown adipose tissue in mammals
Creators: name: Ölkrug, Rebecca
Publisher: name: Philipps-Universität Marburg
Year: 2013
Subjects: Afrotheria
UCP1, Afrotheria
Biowissenschaften, Biologie
Braunes Fettgewebe
Eutheria
UCP1
Brown adipose tissue

description: Ziel dieser Doktorarbeit war es die
      Bedeutung des braunen Fettgewebes, über seine anerkannte
      Funktion hinaus, in Säugetieren zu charakterisieren.
      Besonders die Rolle von aktivem UCP1 während des
      Aufwachvorgangs auf dem Torpor und in der Prävention von
      reaktiven Sauerstoffradikalen während der zitterfreien
      Wärmebildung standen im Fokus dieser Arbeit. Um den
      evolutionären Ursprung von UCP1 und braunem Fett besser zu
      verstehen, wurden Studien an zwei Vertretern der
      phylogenetisch ursprünglichen Überordnung Afrotheria
      durchgeführt. Anhand dieser Ergebnisse sollte ein neues Licht
      auf die Evolution des braunen Fettgewebes geworfen werden.
      War wirklich die Migration in kältere, holarktische Regionen
      der Hauptgrund seiner Entstehung? Die vorliegende Arbeit ist
      in vier Kapitel gegliedert, deren Inhalt im Folgenden
      zusammengefasst wird.
description: Although textbook knowledge
      inevitable associates brown adipose tissue with cold and body
      temperature regulation (regulatory thermogenesis), we are far
      from understanding how, why and when Eutherian mammals gained
      full UCP1-mediated thermogenic support. Brown adipose tissue
      is also present in humans, and it is currently considered a
      major therapeutic target in the treatment of obesity. To
      fully appreciate and to potentially modulate the function of
      this unique tissue, comparative studies from nature’s toolbox
      will prove invaluable new insights. In my PhD-thesis I
      therefore sought to expand our knowledge on brown adipose
      tissue thermogenesis and its significance in various
      mammalian orders, spanning from the in vitro to the in vivo
      level. In doing so, I aimed to uncover novel aspects
      regarding the evolution of its thermogenic function. In my
      studies, I used artificially generated UCP1-ablated mice to
      evaluate further benefits of UCP1 expression on brown adipose
      tissue function (ROS prevention) and the torpor behavior of
      Eutherian mammals from Holartic regions. Furthermore I tried
      to clarify the function of UCP1-mediated nonshivering
      thermogenesis in more “ancient” mammals from Afrotropical
      regions, is brown adipose tissue of Afrotherians seasonally
      regulated? Therefore I worked with two members of the
      Afrotherian clade, Western rock elephant shrews (Elephantulus
      rupestris) and protoendothermic Lesser hedgehog tenrecs
      (Echinops telfairi). The later additionally provided me the
      perfect model organism for another approach; the function of
      brown adipose tissue in protoendothermic mammals and the
      revealing of selection constraints that supported the
      evolution of brown adipose tissue and mammalian endothermy.
      Specifically, the following questions were addressed: 1.What
      are the effects of UCP1 activity on the torpor behavior of
      Eutherian mammals, can they arouse from hypometabolic and
      hypothermic states (torpor) without UCP1-mediated
      nonshivering thermogenesis? If so, what are the benefits of
      UCP1 activity for arousal? 2.Does UCP1 play a role in the
      prevention of reactive oxygen species during nonshivering
      thermogenesis? Was the prevention of ROS the ancient function
      of UCP1? 3.Do species from the Afrotropics adjust their
      thermoregulatory capacities during winter? Is nonshivering
      thermogenesis in Western rock elephant shrews adaptive and a
      common feature of the Afrotherian clade? 4.Do
      protoendothermic Lesser hedgehog tenrecs possess functional
      brown adipose tissue and adaptive thermogenesis? If so, is
      the specific function of UCP1 comparable between
      protoendothermic and endothermic mammals? 5.Was brown adipose
      tissue involved in the evolution of endothermy?