Modulation of thyroid hormone receptors, TRα and TRβ, by using different doses of triiodothyronine (T3) at different times

Abstract

Objective: To examine the effect of different doses of triiodothyronine (T3) on mRNA levels of thyroid hormone receptors, TRα and TRβ, at different times. Materials and methods: 3T3-L1 adipocytes were incubated with T3 (physiological dose: F; supraphysiological doses: SI or SII), or without T3 (control, C) for 0.5, 1, 6, or 24h. TRα and TRβ mRNA was detected using real-time polymerase chain reaction. Results: F increased TRβ mRNA levels at 0.5h. After 1h, TRα levels increased with F and SI and TRβ levels decreased with SII compared with C, F, and SI. After 6h, both genes were suppressed at all concentrations. In 24h, TRα and TRβ levels were similar to those of C group. Conclusions: T3 action with F began at 1h for TRα and at 0.5h for TRβ. These results suggest the importance of knowing the times and doses that activate T3 receptors in adipocytes. Arq Bras Endocrinol Metab. 2013;57(5):368-74 Keywords TRα; TRβ; triiodothyronine; adipocytes RESUMO Objetivo: Examinar o efeito de diferentes doses de triiodotironina (T3) sobre a expressão gêni-ca dos receptores TRα e TRβ em diferentes tempos. Materiais e métodos: Adipócitos, 3T3-L1, foram incubados com T3 nas doses fisiológica (F, 10nM) e suprafisiológicas (SI, 100nM ou SII, 1000nM) ou veículo (controle, C) durante 0,5, 1, 6 ou 24h. mRNA dos TRs foram detectados utilizando PCR em tempo real. Resultados: Níveis de TRβ aumentaram em F em 0,5h. Após 1h, níveis de TRα aumentaram em F e SI comparado ao C, enquanto TRβ diminuiu no SII comparado com C, F, e SI. Após 6h, ambos os genes foram suprimidos em todas concentrações. Em 24h, níveis de TRα e TRβ retornaram aos do C. Conclusões: Ação do T3 em F iniciou-se em 1h para TRα e 0,5h para TRβ. Esses resultados são importantes para determinar tempo inicial e dose de T3 em que os receptores de HT são ativados em adipócitos. Arq Bras Endocrinol Metab. 2013;57(5):368-74

Short-term effects of triiodothyronine on thyroid hormone receptor alpha by PI3K pathway in adipocytes, 3T3-L1

“…3T3-L1 pre-adipocytes represent a well-established model for adipogenesis (22). TRα expression is higher than TRβ in 3T3-L1 adipocytes (18), which is in accordance with the findings of Jiang and cols. (2004) (23).…”

“…(2004) (23). Studies from our group showed that a T3 physiological and supraphysiological dose, at different times, increase TRα in adipocytes, 3T3-L1 (18).…”

“…After differentiation, cells were incubated for 24 hours in DMEM supplemented with 10% charcoal stripped FBS (to deplete T3) and 1 µg/ml insulin. After incubation, cells were treated with physiological T3 (10 nM; P group) or supraphysiological T3 (100 nM; SI) (17)(18)(19) for one hour. A non-treated group, that received 0.1% NaOH (diluent T3), served as the control (C).…”

Adiponectin and Serine/Threonine Kinase Akt Modulation by Triiodothyronine and/or LY294002 in 3T3‐L1 Adipocytes

“…For this reason, selective and nonselective inhibitors are useful tools for determining the activation of signaling cascades for modulating target genes using diverse substances, such as T3. T3 activates the PI3K pathway leading to the transcription of specific genes such as leptin, as reported previously (de Oliveira et al, ).…”

“…The 3T3‐L1 cell line was used as described previously by de Oliveira et al ( and Oliveira et al (, , ). After confluence, the differentiation process was initiated by culturing the cells for 3 days in DMEM containing 10% FBS, 0.5 mM IBMX, 1 mM dexamethasone, and 1 mg/mL insulin.…”