Downregulation of skeletal muscle UCP-3 gene expression during refeeding is prevented by cold exposure.

Abstract	We wished to gain insights into the role of skeletal muscle uncoupling protein-3 (UCP-3) in the elevated efficiency of fat recovery during refeeding after starvation. Previous observations have revealed that muscle UCP-3 expression is downregulated in rats during refeeding at 22 degrees C. Therefore, we investigated whether this also occurs during refeeding at thermoneutrality (29 C) or in the cold (6 C), since at these environmental temperatures the refed animals also show diminished thermogenesis and a higher rate of fat deposition than controls. The UCP-3 mRNA level in the skeletal muscles studied (soleus, gastrocnemius and tibialis anterior) was significantly lower in the refed group than in controls at thermoneutrality, but there were no such differences between these two groups in the cold. This effect of cold, namely abolishing refeeding-induced downregulation of skeletal muscle UCP, is specific to UCP-3 since the gene expression of skeletal muscle UCP-2 remained significantly lower in the refed than in the controls both at thermoneutrality and in the cold. These findings during refeeding in the cold therefore dissociate UCP-3 gene regulation from the adaptive reduction in thermogenesis that accelerates fat deposition during weight recovery. They also reveal differential responses of UCP-3 and UCP-2, whose significance is discussed in the light of our previously proposed hypothesis, which centers upon a role for these UCP homologues in the regulation of lipids as a fuel substrate.
Authors	S Samec, J Seydoux, A G Dulloo
Journal	Pflugers Archiv : European journal of physiology (Pflugers Arch) Vol. 439 Issue 6 Pg. 723-9 (Apr 2000) ISSN: 0031-6768 [Print] Germany
PMID	10784346 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
Chemical References	Carrier Proteins Ion Channels Membrane Transport Proteins Mitochondrial Proteins Proteins RNA, Messenger Ucp2 protein, rat Ucp3 protein, rat Uncoupling Protein 2 Uncoupling Protein 3
Topics	Animal Feed Animals Carrier Proteins (genetics) Cold Temperature Down-Regulation Gene Expression Ion Channels Male Membrane Transport Proteins Mitochondrial Proteins Muscle, Skeletal (metabolism) Proteins (genetics) RNA, Messenger (metabolism) Rats Rats, Sprague-Dawley Starvation (genetics) Temperature Uncoupling Protein 2 Uncoupling Protein 3

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