Functional characterisation of UCP1 in the common carp: uncoupling activity in liver mitochondria and cold-induced expression in the brain.

TitleFunctional characterisation of UCP1 in the common carp: uncoupling activity in liver mitochondria and cold-induced expression in the brain.
Publication TypeJournal Article
Year of Publication2007
AuthorsJastroch, M, Buckingham, JA, Helwig, M, Klingenspor, M, Brand, MD
JournalJ Comp Physiol B
Volume177
Issue7
Pagination743-52
Date Published2007 Oct
ISSN0174-1578
KeywordsAnimals, Brain, Carps, Cold Temperature, Ion Channels, Mitochondria, Liver, Mitochondrial Proteins, RNA, Messenger, Uncoupling Agents, Uncoupling Protein 1
Abstract

Mammalian uncoupling protein 1 (UCP1) mediates nonshivering thermogenesis in brown adipose tissue. We previously reported on the presence of a UCP1 orthologue in ectothermic fish and observed downregulation of UCP1 gene expression in the liver of the common carp. Neither the function of UCP1, nor the mode of UCP1 activation is known in carp liver mitochondria. Here, we compared the proton conductance at 25 degrees C of liver mitochondria isolated from carp either maintained at 20 degrees C (warm-acclimated, WA) or exposed to 8 degrees C (cold-acclimated, CA) water temperature for 7-10 days. Liver mitochondria from WA carp had higher state four rates of oxygen consumption and greater proton conductance at high membrane potential. Liver mitochondria from WA, but not from CA, carp showed a strong increase in proton conductance when palmitate (or 4-hydroxy-trans-2-nonenal, HNE) was added, and this inducible proton conductance was prevented by addition of GDP. This fatty acid sensitive proton leak is likely due to the expression of UCP1 in the liver of WA carp. The observed biochemical properties of proton leak strongly suggest that carp UCP1 is a functional uncoupling protein with broadly the same activatory and inhibitory characteristics as mammalian UCP1. Significant UCP1 expression was also detected in our previous study in whole brain of the carp. We here observed a twofold increase of UCP1 mRNA in carp brain following cold exposure, suggesting a role of UCP1 in the thermal adaptation of brain metabolism. In situ hybridization located the UCP1 gene expression to the optic tectum responsible for visual system control, the descending trigeminal tract and the solitary tract. Taken together, this study characterises uncoupling protein activity in an ectotherm for the first time.

DOI10.1007/s00360-007-0171-6
Alternate JournalJ. Comp. Physiol. B, Biochem. Syst. Environ. Physiol.
Citation Key10.1007/s00360-007-0171-6
PubMed ID17576568
Grant ListMC_U105663137 / / Medical Research Council / United Kingdom