title: Effects of energy restriction on thyroid hormone metabolism in chickens.
abstract: Energy restriction induces changes in thyroid hormone economy in the form of a complex adaptation mechanism, in order to conserve energy storage and protein reserves. In the present work, thyroid hormone serum concentrations, hepatic deiodinase enzyme activities and hepatic deiodinase mRNA expression were examined after feed restriction and fasting. We demonstrate that during energy restriction, T 3 concentration is lowered due to a decreased T 4 activation and increased T 3 inactivation. We show that hepatic type-I deiodinase (D1) is not affected by energy restriction, however, hepatic D2 is decreased on both transcriptional and enzyme activity levels. Furthermore, hepatic D3 is increased after feed restriction in the liver. We also show that the hypothalamic feedback is not involved in the changes in serum T 3 and T 4 concentrations. Our data indicate that D2 enzyme contributes to the special hormone-exporting role of the chicken liver and this enzyme can be modulated by feed restriction.
authors: Szent István University, Department of Physiology and Biochemistry, Faculty of Veterinary Science István u. 2 H-1078 Budapest, Hungary.
authors: Andrea
authors: A
authors: Gyorffy
authors: Ahmed
authors: A
authors: Sayed-Ahmed
authors: Attila
authors: A
authors: Zsarnovszky
authors: Vilmos László
authors: VL
authors: Frenyó
authors: Eddy
authors: E
authors: Decuypere
authors: Tibor
authors: T
authors: Bartha
mesh_terms: D000818:Animals; D002645:Chickens / Q000378:metabolism*; D002149:Energy Intake / Q000502:physiology*; D008297:Male; D013974:Thyroxine / Q000097:blood / Q000378:metabolism*; D014284:Triiodothyronine / Q000097:blood / Q000378:metabolism*
chemical_list: D014284:Triiodothyronine; D013974:Thyroxine