Effects of energy restriction on thyroid hormone metabolism in chickens

Győrffy, Andrea and Sayed-Ahmed, Ahmed and Zsarnovszky, Attila and Frenyó, Vilmos and Decuypere, Eddy and Bartha, Tibor (2009) Effects of energy restriction on thyroid hormone metabolism in chickens. Acta Veterinaria Hungarica, 57 (2). pp. 319-330. ISSN 0236-6290

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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, T3 concentration is lowered due to a decreased T4 activation and increased T3 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 T3 and T4 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.

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