Experimental hyperthyroidism decreases gene expression and serum levels of adipokines in obesity.

AIMS: To analyze the influence of hyperthyroidism on the gene expression and serum concentration of leptin, resistin, and adiponectin in obese animals. MAIN METHODS: Male Wistar rats were randomly divided into two groups: control (C)-fed with commercial chow ad libitum-and obese (OB)-fed with a hypercaloric diet. After group characterization, the OB rats continued receiving a hypercaloric diet and were randomized into two groups: obese animals (OB) and obese with 25 µg triiodothyronine (T(3))/100 BW (OT). The T(3) dose was administered every day for the last 2 weeks of the study. After 30 weeks the animals were euthanized. Samples of blood and adipose tissue were collected for biochemical and hormonal analyses as well as gene expression of leptin, resistin, and adiponectin. RESULTS: T(3) treatment was effective, increasing fT(3) levels and decreasing fT(4) and TSH serum concentration. Administration of T(3) promotes weight loss, decreases all fat deposits, and diminishes serum levels of leptin, resistin, and adiponectin by reducing their gene expression. CONCLUSIONS: Our results suggest that T(3) modulate serum and gene expression levels of leptin, resistin, and adiponectin in experimental model of obesity, providing new insights regarding the relationship between T(3) and adipokines in obesity.

Effects of Triiodothyronine on Human Osteoblast-Like Cells: Novel Insights From a Global Transcriptome Analysis.

Background: Thyroid hormones play a significant role in bone development and maintenance, with triiodothyronine (T3) particularly being an important modulator of osteoblast differentiation, proliferation, and maintenance. However, details of the biological processes (BPs) and molecular pathways affected by T3 in osteoblasts remain unclear. Methods: To address this issue, primary cultures of human adipose-derived mesenchymal stem cells were subjected to our previously established osteoinduction protocol, and the resultant osteoblast-like cells were treated with 1 nm or 10 nm T3 for 72 h. RNA sequencing (RNA-Seq) was performed using the Illumina platform, and differentially expressed genes (DEGs) were identified from the raw data using Kallisto and DESeq2. Enrichment analysis of DEGs was performed against the Gene Ontology Consortium database for BP terms using the R package clusterProfiler and protein network analysis by STRING. Results: Approximately 16,300 genes were analyzed by RNA-Seq, with 343 DEGs regulated in the 1 nm T3 group and 467 upregulated in the 10 nm T3 group. Several independent BP terms related to bone metabolism were significantly enriched, with a number of genes shared among them (FGFR2, WNT5A, WNT3, ROR2, VEGFA, FBLN1, S1PR1, PRKCZ, TGFB3, and OSR1 for 1nM T3; and FZD1, SMAD6, NOG, NEO1, and ENG for 10 nm T3). An osteoblast-related search in the literature regarding this set of genes suggests that both T3 doses are unfavorable for osteoblast development, mainly hindering BMP and canonical and non-canonical WNT signaling. Conclusions: Therefore, this study provides new directions toward the elucidation of the mechanisms of T3 action on osteoblast metabolism, with potential future implications for the treatment of endocrine-related bone pathologies.

Triiodothyronine activated extranuclear pathways upregulate adiponectin and leptin in murine adipocytes.

Adiponectin and leptin, important for metabolic regulation, are synthesized and secreted by adipose tissue and are influenced by triiodothyronine (T3) that activates the MAPK/ERK and integrin αVß3 pathways, modulating gene expression. Adipocytes were treated with T3 (10 nM), for 1 h, in the absence or presence of PD98059 (PD) and tetraiodothyroacetic acid (Tetrac), which are pathways inhibitors. The cells were incubated with Adipo Red/Oil Red O reagents, and intracellular lipid accumulation [glycerol and triacylglycerol (TAG)], MTT, 8-hydroxideoxyguanosine (8-OH-dG), and mRNA and protein expression were assessed. T3 increased leptin mRNA and protein expression, and, in contrast, there was a decrease in the Tetrac + T3 group. Adiponectin mRNA expression was not altered by T3, though it had increased its protein expression, which was terminated by inhibitors PD + T3 and Tetrac + T3. However, T3 did not alter PPARγ protein expression, lipid accumulation, TAG, glycerol, and DNA damage, but PD + T3 and Tetrac + T3 reduced these parameters. T3 activated the MAPK/ERK pathway on adipocytes to modulate the adiponectin protein expression and integrin αvß3 to alter the leptin gene expression.

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

Adipose tissue (AT), an endocrine organ that modulates several physiological functions by synthesizing and releasing adipokines such as adiponectin, is a metabolic target of triiodothyronine (T3). T3 and adiponectin play important roles in controlling normal metabolic functions such as stimulation of fatty acid oxidation and increase in thermogenesis. The phosphatidylinositol 3-kinase (PI3K) pathway is important for the differentiation of preadipocytes into adipocytes and can be activated by T3 for the transcription of specific genes, such as adiponectin. We examined the role of PI3K in adiponectin modulation by T3 action in murine adipocytes (3T3-L1). The 3T3-L1 adipocytes were treated with 1000 nM T3 for 1 h in the presence or absence of 50 µM LY294002 (LY), a PI3K inhibitor. Then, we assessed the expression of adiponectin and the phosphorylated serine/threonine kinase Akt (pAkt), a PI3K signaling protein, in the adipocytes. Adiponectin and pAKT levels were higher in the T3-adipocyte cells, whereas in the LY group adiponectin was elevated and pAKT was decreased compared to the control (C). PI3K pathway inhibition for 1 h and posterior treatment with T3, in LY + T3, reduced the adiponectin level and increased pAKT levels compared to those in LY. T3 stimulated adiponectin levels by PI3K pathway activation and T3 can compensate alteration in the PI3K pathway, because with inhibition of the pathway it is able to maintain the basal levels of adiponectin and pAKT.

The importance of estrogen for bone protection in experimental hyperthyroidism in human osteoblasts.

Triiodothyronine (T3) and estrogen (E2) play important roles in the bone remodeling process and signaling of receptor activator of the nuclear factor-kappa ß (RANKL) and osteoprotegerin (OPG) expressed by osteoblasts. However, little is known of the molecular action of these hormones in conditions of hyperthyroidism and associated E2 in human cells. AIMS: This study evaluated the effects of the physiological concentration of E2 (10 nM), alone or in association with physiological (1 nM) and supraphysiological (10 nM) concentrations of T3, on RANKL and OPG gene expression in human osteoblasts. MAIN METHODS: Alkaline phosphatase and osteocalcin assays were performed to verify the presence of mature osteoblasts. After mimicking the experimental hyperthyroidism in osteoblasts untreated or treated with E2, RANKL and OPG gene expression was analyzed by real-time PCR and protein expression by western Blot and ELISA. Alizarin Red staining analyzed the amount of bone matrix after hormonal treatments. KEY FINDINGS: E2 enhanced the gene expression of OPG when associated with 1 nM and 10 nM T3. E2 was able to restore the bone matrix after an initial decrease using 1 nM and 10 nM T3. The protective effect of E2 on the RANKL and OPG signaling pathway was demonstrated. E2 restored the bone matrix induced by experimental hyperthyroidism. SIGNIFICANCE: The data highlight the importance of E2 to maintain OPG expression and osteoblast activity against possible loss of bone mass, especially in conditions where T3 is in excess.

Disruptive Effect of Organotin on Thyroid Gland Function Might Contribute to Hypothyroidism.

A considerable increase in endocrine abnormalities has been reported over the last few decades worldwide. A growing exposure to endocrine-disrupting chemicals (EDCs) can be one of the causes of endocrine disorders in populations, and these disorders are not only restricted to the metabolic hormone system but can also cause abnormal functions. Thyroid hormone (TH) disruption is defined as an abnormal change in TH production, transport, function, or metabolism, which results in some degree of impairment in body homeostasis. Many EDCs, including organotin compounds (OTCs), are environmental contaminants that are commonly found in antifouling paints used on ships and in several other industrial procedures. OTCs are obesogenic and can disrupt TH metabolism; however, abnormalities in thyroid function resulting from OTC exposure are less well understood. OTCs, one of the most prevalent EDCs that are encountered on a daily basis, modulate the thyroid axis. In most toxicology studies, it has been reported that OTCs might contribute to hypothyroidism.

Triiodothyronine (T3) induces HIF1A and TGFA expression in MCF7 cells by activating PI3K.

High expression levels of hypoxia inducing factor 1 alpha are related to mammary carcinogenesis. In previous studies, we demonstrated that expression of transforming growth factor alpha increases upon treatment with triiodothyronine, but this expression does not occur in cellular models that do not express the estrogen receptor, or when cells are co-treated with the anti-estrogen, tamoxifen. The aim of this study was to determine the effect of the hormone triiodothyronine on the expression of the genes HIF1A and TGFA in the breast cancer cell line MCF7. The cell line was subjected to treatment with triiodothyronine at the supraphysiological dose of 10(-8)M for 10min, 30min, 1h, and 4h in the presence or absence of actinomycin D, the gene expression inhibitor, cycloheximide, the protein synthesis inhibitor, and LY294002, the phosphoinositide 3 kinase inhibitor. HIF1A and TGFA mRNA expression was analyzed by reverse transcription polymerase chain reaction. For data analysis, we used analysis of variance complemented by Tukey test and an adopted minimum of 5% significance. We found that HIF1A and TGFA expression increased in the presence of triiodothyronine at all times studied. HIF1A expression decreased in triiodothyronine-treated cells when gene transcription was also inhibited; however, TGFA expression decreased after 10 and 30min of treatment even when transcription was not inhibited. We found that activation of PI3K was necessary for triiodothyronine to modulate HIF1A and TGFA expression.

Triiodothyronine modulates the expression of leptin and adiponectin in 3T3-L1 adipocytes.

OBJECTIVE: To study the effect of different doses of triiodothyronine on gene expression of the adipokines leptin and adiponectin, at different times, and to evaluate the difference in expression between the two adipokines in each group. METHODS: 3T3-L1 adipocytes were incubated with triiodothyronine at physiological dose (10nM) and supraphysiological doses (100nM or 1,000nM), or without triiodothyronine (control, C) for 0.5, 6, or 24 hours. Leptin and adiponectin mRNA was detected using real-time polymerase chain reaction (RT-PCR). One-way analyses of variance, Tukey's test or Student's t test, were used to analyze data, and significance level was set at 5%. RESULTS: Leptin levels decreased in the 1,000nM-dose group after 0.5 hour. Adiponectin levels dropped in the 10nM-dose group, but increased at the 100nM dose. After 6 hours, both genes were suppressed in all hormone concentrations. After 24 hours, leptin levels increased at 10, 100 and 1,000nM groups as compared to the control group; and adiponectin levels increased only in the 100nM group as compared to the control group. CONCLUSION: These results demonstrated fast actions of triiodothyronine on the leptin and adiponectin expression, starting at 0.5 hour, at a dose of 1,000nM for leptin and 100nM for adiponectin. Triiodothyronine stimulated or inhibited the expression of adipokines in adipocytes at different times and doses which may be useful to assist in the treatment of obesity, assuming that leptin is increased and adiponectin is decreased, in obesity cases.

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

OBJECTIVE: The present study aimed to examine the effects of thyroid hormone (TH), more precisely triiodothyronine (T3), on the modulation of TH receptor alpha (TRα) mRNA expression and the involvement of the phosphatidyl inositol 3 kinase (PI3K) signaling pathway in adipocytes, 3T3-L1, cell culture. MATERIALS AND METHODS: It was examined the involvement of PI3K pathway in mediating T3 effects by treating 3T3-L1 adipocytes with physiological (P=10nM) or supraphysiological (SI =100 nM) T3 doses during one hour (short time), in the absence or the presence of PI3K inhibitor (LY294002). The absence of any treatment was considered the control group (C). RT-qPCR was used for mRNA expression analyzes. For data analyzes ANOVA complemented with Tukey's test was used at 5% significance level. RESULTS: T3 increased TRα mRNA expression in P (1.91±0.13, p<0.001), SI (2.14±0.44, p<0.001) compared to C group (1±0.08). This increase was completely abrogated by LY294002 in P (0.53±0.03, p<0.001) and SI (0.31±0.03, p<0.001). To examine whether TRα is directly induced by T3, we used the translation inhibitor cycloheximide (CHX). The presence of CHX completely abrogated levels TRα mRNA in P (1.15±0.05, p>0.001) and SI (0.99±0.15, p>0.001), induced by T3. CONCLUSION: These results demonstrate that the activation of the PI3K signaling pathway has a role in T3-mediated indirect TRα gene expression in 3T3-L1 adipocytes.

Triiodothyronine and breast cancer.

The thyroid hormones (THs), triiodothyronine (T3) and thyroxine (T4), are essential for survival; they are involved in the processes of development, growth, and metabolism. In addition to hyperthyroidism or hypothyroidism, THs are involved in other diseases. The role of THs in the development and differentiation of mammary epithelium is well established; however, their specific role in the pathogenesis of breast cancer (BC) is controversial. Steroid hormones affect many human cancers and the abnormal responsiveness of the mammary epithelial cells to estradiol (E2) in particular is known to be an important cause for the development and progression of BC. The proliferative effect of T3 has been demonstrated in various types of cancer. In BC cell lines, T3 may foster the conditions for tumor proliferation and increase the effect of cell proliferation by E2; thus, T3 may play a role in the development and progression of BC. Studies show that T3 has effects similar to E2 in BC cell lines. Despite controversy regarding the relationship between thyroid disturbances and the incidence of BC, studies show that thyroid status may influence the development of tumor, proliferation and metastasis.

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

OBJECTIVE: To examine the effect of different doses of triiodothyronine (T3) on mRNA levels of thyroid hormone receptors, TRα and TRß, 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 TRß mRNA was detected using real-time polymerase chain reaction. RESULTS: F increased TRß mRNA levels at 0.5h. After 1h, TRα levels increased with F and SI and TRß levels decreased with SII compared with C, F, and SI. After 6h, both genes were suppressed at all concentrations. In 24h, TRα and TRß levels were similar to those of C group. CONCLUSIONS: T3 action with F began at 1h for TRα and at 0.5h for TRß. These results suggest the importance of knowing the times and doses that activate T3 receptors in adipocytes.

Triiodothyronine increases mRNA and protein leptin levels in short time in 3T3-L1 adipocytes by PI3K pathway activation.

The present study aimed to examine the effects of thyroid hormone (TH), more precisely triiodothyronine (T3), on the modulation of leptin mRNA expression and the involvement of the phosphatidyl inositol 3 kinase (PI3K) signaling pathway in adipocytes, 3T3-L1, cell culture. We examined the involvement of this pathway in mediating TH effects by treating 3T3-L1 adipocytes with physiological (P=10nM) or supraphysiological (SI=100 nM) T3 dose during one hour (short time), in the absence or the presence of PI3K inhibitor (LY294002). The absence of any treatment was considered the control group (C). RT-qPCR was used for mRNA expression analyzes. For data analyzes ANOVA complemented with Tukey's test was used at 5% significance. T3 increased leptin mRNA expression in P (2.26 ± 0.36, p< 0.001), SI (1.99 ±0.22, p< 0.01) compared to C group (1± 0.18). This increase was completely abrogated by LY294002 in P (1.31±0.05, p< 0.001) and SI (1.33±0.31, p< 0.05). Western blotting confirmed these results at protein level, indicating the PI3K pathway dependency. To examine whether leptin is directly induced by T3, we used the translation inhibitor cycloheximide (CHX). In P, the presence of CHX maintained the levels mRNA leptin, but was completely abrogated in SI (1.14±0.09, p> 0.001). These results demonstrate that the activation of the PI3K signaling pathway has a role in TH-mediated direct and indirect leptin gene expression in 3T3-L1 adipocytes.

A comparative genotoxicity study of a supraphysiological dose of triiodothyronine (T3) in obese rats subjected to either calorie-restricted diet or hyperthyroidism.

This study was designed to determine the genotoxicity of a supraphysiological dose of triiodothyronine (T3) in both obese and calorie-restricted obese animals. Fifty male Wistar rats were randomly assigned to one of the two following groups: control (C; n = 10) and obese (OB; n = 40). The C group received standard food, whereas the OB group was fed a hypercaloric diet for 20 weeks. After this period, half of the OB animals (n = 20) were subjected to a 25%-calorie restriction of standard diet for 8 weeks forming thus a new group (OR), whereas the remaining OB animals were kept on the initial hypercaloric diet. During the following two weeks, 10 OR animals continued on the calorie restriction diet, whereas the remaining 10 rats of this group formed a new group (ORS) given a supraphysiological dose of T3 (25 µg/100 g body weight) along with the calorie restriction diet. Similarly, the remaining OB animals were divided into two groups, one that continued on the hypercaloric diet (OB, n = 10), and one that received the supraphysiological dose of T3 (25 µg/100 g body weight) along with the hypercaloric diet (OS, n = 10) for two weeks. The OB group showed weight gain, increased adiposity, insulin resistance, increased leptin levels and genotoxicity; T3 administration in OS animals led to an increase in genotoxicity and oxidative stress when compared with the OB group. The OR group showed weight loss and normalized levels of adiposity, insulin resistance, serum leptin and genotoxicity, thus having features similar to those of the C group. On the other hand, the ORS group, compared to OR animals, showed higher genotoxicity. Our results indicate that regardless of diet, a supraphysiological dose of T3 causes genotoxicity and potentiates oxidative stress.

Triiodothyronine modulates the expression of leptin and adiponectin in 3T3-L1 adipocytes / Triiodotironina modula a expressão de leptina e adiponectina em adipócitos 3T3-L1

Objective To study the effect of different doses of triiodothyronine on gene expression of the adipokines leptin and adiponectin, at different times, and to evaluate the difference in expression between the two adipokines in each group. Methods 3T3-L1 adipocytes were incubated with triiodothyronine at physiological dose (10nM) and supraphysiological doses (100nM or 1,000nM), or without triiodothyronine (control, C) for 0.5, 6, or 24 hours. Leptin and adiponectin mRNA was detected using real-time polymerase chain reaction (RT-PCR). One-way analyses of variance, Tukey’s test or Student’s t test, were used to analyze data, and significance level was set at 5%. Results Leptin levels decreased in the 1,000nM-dose group after 0.5 hour. Adiponectin levels dropped in the 10nM-dose group, but increased at the 100nM dose. After 6 hours, both genes were suppressed in all hormone concentrations. After 24 hours, leptin levels increased at 10, 100 and 1,000nM groups as compared to the control group; and adiponectin levels increased only in the 100nM group as compared to the control group. Conclusion These results demonstrated fast actions of triiodothyronine on the leptin and adiponectin expression, starting at 0.5 hour, at a dose of 1,000nM for leptin and 100nM for adiponectin. Triiodothyronine stimulated or inhibited the expression of adipokines in adipocytes at different times and doses which may be useful to assist in the treatment of obesity, assuming that leptin is increased and adiponectin is decreased, in obesity cases. .

Objetivo Examinar o efeito de diferentes doses de triiodotironina sobre a expressão gênica das adipocinas leptina e adiponectina, em diferentes períodos de tempo, além de avaliar a diferença de expressão entre as duas adipocinas em cada grupo. Métodos Adipócitos 3T3-L1 foram incubados com triiodotironina nas doses fisiológica (10nM) e suprafisiológicas (100nM ou 1.000nM), ou na ausência de triiodotironina (controle, C) durante 0,5, 6 ou 24 horas. O mRNA das adipocinas foi analisado em tempo real, utilizando a reação em cadeia de polimerase. Para as análises dos dados, foi utilizada a análise de variância, complementada com o teste de Tukey, ou o teste t de Student com 5% de significância. Resultados Os níveis de leptina diminuíram no grupo com dose de 1.000nM em 0,5 hora. A adiponectina também diminuiu no grupo com dose de 10nM, porém se elevou com a dose de 100nM. Após 6 horas, ambos os genes foram suprimidos em todas concentrações de hormônio. Em 24 horas, os níveis de leptina foram elevados em 10, 100 e 1.000nM, em relação ao grupo controle. No que concerne à adiponectina, observou-se aumento apenas no grupo cuja dose foi de 100nM, em comparação ao controle. Conclusão Foram demonstradas ações rápidas da triiodotironina sobre a expressão da leptina e da adiponectina, iniciando em 0,5 hora na dose de 1.000nM, para a primeira, e na dose de 100nM, para a segunda. A triiodotironina estimulou ou inibiu a expressão de adipocinas em adipócitos em diferentes tempos e doses, o que pode auxiliar no tratamento da obesidade, levando em consideração que, nesta, a leptina está aumentada e adiponectina, diminuída. .

Short-term effects of triiodothyronine on thyroid hormone receptor alpha by PI3K pathway in adipocytes, 3T3-L1 / Efeitos rápidos da triiodotironina no receptor de hormônio tireoidiano alfa pela via PI3K em adipócitos, 3T3-L1

Objective The present study aimed to examine the effects of thyroid hormone (TH), more precisely triiodothyronine (T3), on the modulation of TH receptor alpha (TRα) mRNA expression and the involvement of the phosphatidyl inositol 3 kinase (PI3K) signaling pathway in adipocytes, 3T3-L1, cell culture. Materials and methods: It was examined the involvement of PI3K pathway in mediating T3 effects by treating 3T3-L1 adipocytes with physiological (P=10nM) or supraphysiological (SI =100 nM) T3 doses during one hour (short time), in the absence or the presence of PI3K inhibitor (LY294002). The absence of any treatment was considered the control group (C). RT-qPCR was used for mRNA expression analyzes. For data analyzes ANOVA complemented with Tukey’s test was used at 5% significance level. Results T3 increased TRα mRNA expression in P (1.91±0.13, p<0.001), SI (2.14±0.44, p<0.001) compared to C group (1±0.08). This increase was completely abrogated by LY294002 in P (0.53±0.03, p<0.001) and SI (0.31±0.03, p<0.001). To examine whether TRα is directly induced by T3, we used the translation inhibitor cycloheximide (CHX). The presence of CHX completely abrogated levels TRα mRNA in P (1.15±0.05, p>0.001) and SI (0.99±0.15, p>0.001), induced by T3. Conclusion These results demonstrate that the activation of the PI3K signaling pathway has a role in T3-mediated indirect TRα gene expression in 3T3-L1 adipocytes. .

Objetivo O objetivo do presente estudo foi analisar os efeitos do hormônio tireoidiano (HT), triiodotironina (T3), na modulação da expressão de mRNA do receptor alfa (TRα) de HT e o envolvimento da via de sinalização da via fosfatidilinositol 3-quinase (PI3K) em adipócitos, 3T3-L1. Materiais e métodos: Foi examinado o envolvimento da via PI3K nos efeitos do T3 nos tratamentos de adipócitos, 3T3-L1, nas doses fisiológica (P=10nM) ou suprafisiológica (SI =100 nM) durante uma hora (tempo curto), na ausência ou na presença do inibidor da PI3K (LY294002). A ausência de qualquer tratamento foi considerada o grupo controle (C). RT-qPCR foi utilizado para analisar a expressão do mRNA. Para as análises dos dados, utilizou-se ANOVA complementada com o teste de Tukey a 5% de significância. Resultados O T3 aumentou a expressão de mRNA de TRα em P (1,91±0,13, p<0,001) e SI (2,14±0,44, p<0,001) em comparação com o grupo C (1±0,08). Esse aumento foi completamente abolido por LY294002 em P (0,53±0,03, p<0,001) e SI (0,31±0,03, p<0,001). Para examinar se a expressão de TRα foi diretamente induzida pelo T3, utilizou-se o inibidor de tradução, ciclohexamida (CHX). A presença de CHX reduziu os níveis de mRNA de TRα em P (1,15±0,05, p>0,001) e SI (0,99±0,15, p>0,001), induzidos pelo T3. Conclusão Esses resultados demonstram que a ativação da via de sinalização de PI3K tem um papel importante na expressão do gene TRα mediada indiretamente pelo T3, em adipócitos 3T3-L1. .

Modulation of thyroid hormone receptors, TRα and TRβ, by using different doses of triiodothyronine (T3) at different times / Modulação dos receptores de hormônio tireoidiano, TRα e TRβ, utilizando diferentes doses de triiodotironina (T3) em diferentes tempos

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.

OBJETIVO: Examinar o efeito de diferentes doses de triiodotironina (T3) sobre a expressão gênica 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.