Tissue-specific expression and cold-induced mRNA levels of uncoupling proteins in the Djungarian hamster

The uncoupling protein 1 (UCP1), a mitochondrial transmembrane protein, is responsible for adaptive thermogenesis in brown adipose tissue (BAT). Two U CP1 homologues, UCP2 and UCP3, were recently discovered, but it is controve rsial whether they also play a role in energy homeostasis. Djungarian hamst er UCPs were found to exhibit high similarity with homologues known in othe r species. UCP1 mRNA was restricted to BAT, UCP2 mRNA was expressed in mult iple tissues, and UCP3 mRNA was detected mainly in BAT and skeletal muscles . We examined the cold-induced regulation of hamster UCP mRNA levels and te sted their correlation with serum free fatty acid (FFA) concentrations. In BAT UCP1, UCP2, and UCP3 expression was upregulated in the cold, but the in crease and time course of increase differed. In skeletal muscle, UCP2 and U CP3 mRNA levels were not altered. Cold-induced changes of serum FFA levels correlated with the stimulation of UCP1 mRNA in BAT but not with UCP2 and U CP3.