Abstract
Avian uncoupling protein (avUCP), sharing 71-73% amino acid homology with both UCP2 and UCP3, is one of the mitochondrial anion carrier proteins. Its precise physiological roles in the cell remain elusive. A confusing aspect of these UCP variants (namely, UCP2, UCP3 and avUCP), is that their expression is enhanced in response to fasting ; that is, in response to basal metabolic state in which such energy expenditure would be expected to be depressed. In this study, we examined progressive alterations in the expression of genes encoding for mitochondrial uncoupling proteins, not only UCP but also avian adenine nucleotide translocator (avANT), in the skeletal muscle tissue of fasted chickens. The expression of avUCP gene was markedly enhanced after 12h of fasting and then diminished slightly but remained elevated after 96h of fasting compared to time 0 levels. In contrast, avANT was up-regulated only after 24h of fasting but continued to be further increased after 96h. Taken together, these results demonstrate that transcription of each of the mitochondrial anion carriers, avUCP and avANT, is independently up-regulated during fasting periods, implying different control mechanisms and consequences of each in metabolic adaptations involved in prolonged fasting.
