title: Uncoupling protein and ATP/ADP carrier increase mitochondrial proton conductance after cold adaptation of king penguins.
abstract: Juvenile king penguins develop adaptive thermogenesis after repeated immersion in cold water. However, the mechanisms of such metabolic adaptation in birds are unknown, as they lack brown adipose tissue and uncoupling protein-1 (UCP1), which mediate adaptive non-shivering thermogenesis in mammals. We used three different groups of juvenile king penguins to investigate the mitochondrial basis of avian adaptive thermogenesis in vitro. Skeletal muscle mitochondria isolated from penguins that had never been immersed in cold water showed no superoxide-stimulated proton conductance, indicating no functional avian UCP. Skeletal muscle mitochondria from penguins that had been either experimentally immersed or naturally adapted to cold water did possess functional avian UCP, demonstrated by a superoxide-stimulated, GDP-inhibitable proton conductance across their inner membrane. This was associated with a markedly greater abundance of avian UCP mRNA. In the presence (but not the absence) of fatty acids, these mitochondria also showed a greater adenine nucleotide translocase-catalysed proton conductance than those from never-immersed penguins. This was due to an increase in the amount of adenine nucleotide translocase. Therefore, adaptive thermogenesis in juvenile king penguins is linked to two separate mechanisms of uncoupling of oxidative phosphorylation in skeletal muscle mitochondria: increased proton transport activity of avian UCP (dependent on superoxide and inhibited by GDP) and increased proton transport activity of the adenine nucleotide translocase (dependent on fatty acids and inhibited by carboxyatractylate).
authors.affiliation: Medical Research Council Dunn Human Nutrition Unit, Hills Road, Cambridge CB2 2XY, UK.
authors.forename: Darren A
authors.initials: DA
authors.lastname: Talbot
authors.forename: Claude
authors.initials: C
authors.lastname: Duchamp
authors.forename: Benjamin
authors.initials: B
authors.lastname: Rey
authors.forename: Nicolas
authors.initials: N
authors.lastname: Hanuise
authors.forename: Jean Louis
authors.initials: JL
authors.lastname: Rouanet
authors.forename: Brigitte
authors.initials: B
authors.lastname: Sibille
authors.forename: Martin D
authors.initials: MD
authors.lastname: Brand
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology*; D000818:Animals; D001833:Body Temperature Regulation / Q000502:physiology; D002352:Carrier Proteins / Q000378:metabolism*; D003080:Cold Temperature; D005227:Fatty Acids / Q000378:metabolism; D005260:Female; D007473:Ion Channels; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism*; D008928:Mitochondria / Q000378:metabolism*; D000226:Mitochondrial ADP, ATP Translocases / Q000378:metabolism*; D024101:Mitochondrial Proteins; D018482:Muscle, Skeletal / Q000378:metabolism; D011522:Protons; D046429:Spheniscidae / Q000378:metabolism*; D013481:Superoxides / Q000378:metabolism; D000071256:Uncoupling Protein 1
chemical_list: D002352:Carrier Proteins; D005227:Fatty Acids; D007473:Ion Channels; D008565:Membrane Proteins; D024101:Mitochondrial Proteins; D011522:Protons; C000604371:UCP1 protein, human; D000071256:Uncoupling Protein 1; D013481:Superoxides; D000226:Mitochondrial ADP, ATP Translocases