title: 3,5-di-iodothyronine stimulates tilapia growth through an alternate isoform of thyroid hormone receptor β1.
abstract: Recent studies in our laboratory have shown that in some teleosts, 3,5-di-iodothyronine (T2 or 3,5-T2) is as bioactive as 3,5,3'-tri-iodothyronine (T3) and that its effects are in part mediated by a TRβ1 (THRB) isoform that contains a 9-amino acid insert in its ligand-binding domain (long TRβ1 (L-TRβ1)), whereas T3 binds preferentially to a short TRβ1 (S-TRβ1) isoform that lacks this insert. To further understand the functional relevance of T2 bioactivity and its mechanism of action, we used in vivo and ex vivo (organotypic liver cultures) approaches and analyzed whether T3 and T2 differentially regulate the S-TRβ1 and L-TRβ1s during a physiological demand such as growth. In vivo, T3 and T2 treatment induced body weight gain in tilapia. The expression of L-TRβ1 and S-TRβ1 was specifically regulated by T2 and T3 respectively both in vivo and ex vivo. The TR antagonist 1-850 effectively blocked thyroid hormone-dependent gene expression; however, T3 or T2 reversed 1-850 effects only on S-TRβ1 or L-TRβ1 expression, respectively. Together, our results support the notion that both T3 and T2 participate in the growth process; however, their effects are mediated by different, specific TRβ1 isoforms.
authors.affiliation: Instituto de Neurobiología, Universidad Nacional Autónoma de México (UNAM), Boulevard Juriquilla 3001, Queretaro 76230, Mexico.
authors.forename: Pamela
authors.initials: P
authors.lastname: Navarrete-Ramírez
authors.forename: Maricela
authors.initials: M
authors.lastname: Luna
authors.forename: Carlos
authors.initials: C
authors.lastname: Valverde-R
authors.forename: Aurea
authors.initials: A
authors.lastname: Orozco
mesh_terms: D000818:Animals; D001835:Body Weight / Q000187:drug effects; D004104:Diiodothyronines / Q000008:administration & dosage / Q000494:pharmacology*; D005786:Gene Expression Regulation / Q000187:drug effects; D007334:Insulin-Like Growth Factor I / Q000235:genetics / Q000378:metabolism; D007453:Iodide Peroxidase / Q000235:genetics / Q000378:metabolism; D008099:Liver / Q000187:drug effects / Q000378:metabolism; D020033:Protein Isoforms; D037042:Thyroid Hormone Receptors beta / Q000819:agonists / Q000037:antagonists & inhibitors / Q000378:metabolism*; D017210:Tilapia / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism*; D014284:Triiodothyronine / Q000378:metabolism; D000097564:Iodothyronine Deiodinase Type II
chemical_list: D004104:Diiodothyronines; D007334:Insulin-Like Growth Factor I; D007453:Iodide Peroxidase; D020033:Protein Isoforms; D037042:Thyroid Hormone Receptors beta; D014284:Triiodothyronine; D000097564:Iodothyronine Deiodinase Type II; C030103:3,5-diiodothyronine
keywords: 1–850; 3,5-T2; growth; thyroid hormone receptor