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The enzyme iodothyronine deiodinase type 3 (DIO3) contributes to cancer proliferation by inactivating the tumor-suppressive actions of thyroid hormone (T3). We recently established DIO3 involvement in the progression of high-grade serous ovarian cancer (HGSOC). Here we provide a link between high DIO3 expression and lower survival in patients, similar to common disease markers such as Ki67, PAX8, CA-125, and CCNE1. These observations suggest that DIO3 is a logical target for inhibition. Using a DIO3 mimic, we developed original DIO3 inhibitors that contain a core of dibromomaleic anhydride (DBRMD) as scaffold. Two compounds, PBENZ-DBRMD and ITYR-DBRMD, demonstrated attenuated cell counts, induction in apoptosis, and a reduction in cell proliferation in DIO3-positive HGSOC cells (OVCAR3 and KURAMOCHI), but not in DIO3-negative normal ovary cells (CHOK1) and OVCAR3 depleted for DIO3 or its substrate, T3. Potent tumor inhibition with a high safety profile was further established in HGSOC xenograft model, with no effect in DIO3-depleted tumors. The antitumor effects are mediated by downregulation in an array of pro-cancerous proteins, the majority of which known to be repressed by T3. To conclude, using small molecules that specifically target the DIO3 enzyme we present a new treatment paradigm for ovarian cancer and potentially other DIO3-dependent malignancies.

OBJECTIVE A unique clinical course was observed in a patient with resistance to thyroid hormone β (RTHβ) caused by a variant of the THRB gene leading to the replacement of glycine with arginine in codon 347 (p.G347R). He presented with the syndrome of inappropriate secretion of thyrotropin (TSH) (free T4 [fT4]: 32.43 pmol/L, TSH: 4.67 mIU/L), but slowly developed progressive hypothyroidism (fT4: 8.37 pmol/L, TSH: 100.90 mIU/L) that resolved after suspending bezafibrate (BZ) treatment (fT4: 32.18 pmol/L, TSH: 7.14 mIU/L). This study clinically and experimentally evaluated this interesting phenomenon. METHODS A retrospective cohort analysis of non-RTHβ patients was performed at Kyoto University Hospital. Data before BZ treatment were compared to the first data after treatment. Using reporter assays of iodothyronine deiodinases (DIO1, DIO2, DIO3) in HEK293T cells, we performed functional analyses of mutant thyroid hormone receptor β with p.G347R (G347R TRβ). Mice with G347R TRβ were generated by hydrodynamic gene delivery. RESULTS In non-RTHβ patients (n = 7), BZ treatment did not change serum free T3 and TSH but significantly increased fT4 (p = .008). BZ administration increased DIO3 reporter activity in the context of G347R TRβ, whereas did not change DIO1 and DIO2 reporter activity. In the livers of mice with G347R TRβ, BZ administration increased reverse T3 content, which corresponded to an increase in Dio3 messenger RNA. CONCLUSIONS While hypothyroidism associated with BZ treatment did not occur in non-RTHβ patients, it was observed in a patient with RTHβ due to the p.G347R variant. Liver DIO3 upregulation might involve this hypothyroidism.

Background: Iodothyronine deiodinase-1 (D1) selenoenzyme regulates the systemic supply of active thyroid hormone (TH). Transient decrease in D1 enzymatic activity is clinically relevant and adaptive in nonthyroidal illness such as fasting or acute illness. However, DIO1 gene defects have not been reported in humans. Methods: Genetic analysis was performed using whole-exome sequencing in members of two unrelated families presenting with abnormal serum thyroid function tests. Plasmid constructs containing the two pathogenic DIO1 variants were used for in vitro studies assessing the kinetics of their enzymatic activity. Thyroid function tests were measured in Dio1 heterozygous-null mice. Results: We report the novel identification and characterization of two missense DIO1 pathogenic variants (resulting in p.Asn94Lys and p.Met201Ile) in two unrelated families presenting with abnormal TH metabolism with elevated serum reverse triiodothyronine (rT3) levels and rT3/T3 ratios. These characteristic in vivo parameters are also present in Dio1 heterozygous-null mice. Kinetic studies of the resulting mutant D1 proteins demonstrate two- to threefold higher Km indicating lower substrate affinity and slower enzyme velocity. Conclusions: We report the identification and characterization of two missense DIO1 pathogenic variants identified in families with abnormal TH metabolism. This is the first demonstration of inherited D1 deficiency in humans.

Free triiodothyronine/free thyroxine (FT3/FT4) ratio is considered as an index of the activities of iodothyronine deiodinase types 1 and 2 (DIO1 and DIO2, respectively) and is reportedly associated with insulin resistance in euthyroid adults. Euthyroid women with polycystic ovary syndrome accompanied with insulin resistance have lesser deiodinase activities. Correspondingly, the serum insulin level in a fasted condition positively correlates with the FT3/FT4 ratio, and insulin depletion decreases the DIO2 activity in mice. Selected genetic variants in DIO1 are also associated with insulin resistance measures. Therefore, if insulin positively regulates DIO1 and DIO2, the FT3/FT4 ratio should decrease under impaired insulin action, and the casual insulin level and FT3/FT4 ratio should be negatively correlated. To evaluate this hypothesis, we conducted a single-center retrospective study between 2018 and 2021. All participants visited the selected hospitals monthly for type 2 diabetes mellitus treatment and casual plasma glucose and HbA1c level measurements. Furthermore, their casual serum insulin levels were measured annually. Meanwhile, we excluded patients treated with insulin injection. Ultimately, we evaluated 71 patients, which all exhibited euthyroid conditions. The FT3/FT4 ratio was independently associated with thyroid-stimulating hormone, casual plasma glucose, and casual insulin levels. In terms of the regression coefficients of the univariate linear regression analysis, the FT3/FT4 ratio negatively correlated with the casual serum insulin levels. Therefore, the risk of FT3/FT4 ratio underestimation should be considered when diagnosing Graves' disease, which is often accompanied with insulin resistance.

Skeletal muscle (SM) has been shown as a target of thyroid hormones (THs). However, the status of TH signaling in aged SM remains unclear. This study aimed to explore the mechanism of TH signaling in SM of aging mice. Thirty C57BL/6J male mice were divided into 6-, 15- and 22-month (6, 15 and 22M) groups according to different age. Physical parameters were evaluated by analytical balance, grip strength test and histological analysis. Thyroid function was detected by enzyme-linked immunosorbent assay. TH signaling was compared among the three groups by real-time PCR and western blotting analysis. p16, p21, and p53 mRNA levels in SM increased in age-dependent manner. The muscle weight and strength decreased in 22M group compared to 6 and 15M groups. Concentrations of thyroid hormones, including free triiodothyronine (FT3), free thyroxine (FT4) and thyroid-stimulating hormone (TSH) in 22 M mice were not shown significant difference compared to 6M or 15M mice, although FT3 showed slightly decrease and TSH appeared a mild increase accompanying with age. mRNA levels of TH transporters, including MCT8 and MCT10, as well as iodothyronine deiodinase type 2 (DIO2) and type 3 (DIO3), were higher in 22M, while TH receptor α (TRα) mRNA and protein expression was lower in 22M, compared to the other groups. Type-I myosin heavy chain (MyHC I), MyHC IIx, and MyHC IIa were upregulated and Type-IIb MyHC (MyHC IIb) was downregulated in SM with advancing age. TH signaling in SM changes with aging.

The thyroid gland plays a crucial role in the regulation of metabolism, oxygen consumption, and the release of energy in the form of heat to maintain the body. Even at rest, these processes are sensitive to changes in thyroid function. This means that along with the adrenergic system, thyroid function determines the organism's ability to adapt to cold. Cold adaptation causes deiodination of thyroxine (T4) and thus promotes an increase in blood triiodothyronine (T3) levels in humans and animals. Triiodothyronine is an inductor of iodothyronine deiodinase expression in brown fat, liver, and kidney. Iodothyronine deiodinase plays an important role in adaptation of the organism to cold by contributing to high adrenergic reactivity of brown fat. T3 also leads to an increase in expression of uncoupling proteins and uncoupling oxidative phosphorylation and an increase in heat production. The aim of this article is to review the available literature regarding the role of thyroid hormones in adaptation to cold and to present the current knowledge of the understanding of the molecular mechanism underlying their action during cold adaptation.

Thyroid hormones (THs) are key players in the endocrine system and play pivotal roles in carbohydrate and fat metabolism, protein synthesis, overall growth, and brain development. The thyroid gland predominantly produces thyroxine or 3,5,3â�²,5â�²-tetraiodothyronine (T4) as a prohormone; three isoforms of a mammalian selenoenzymeâ��iodothyronine deiodinase (DIO1, DIO2 and DIO3)â��catalyze the regioselective deiodination of T4 to produce biologically active and inactive metabolites. Whereas DIO1 catalyzes both 5- and 5â�²-deiodination of T4, DIO2 and DIO3 selectively mediate 5- and 5â�²-deiodination, respectively. In this review we discuss the regioselective deiodination of THs in the presence of organochalcogen compounds. Naphthalene-based compounds containing sulfur and/or selenium at the peri positions mediate regioselective 5-deiodination of THs, detailed mechanistic studies having revealed that the heterolytic cleavage of the Câ��I bond is facilitated by the formation of cooperative Se/Sâ� â� â� I halogen bonds and Se/Sâ� â� â� Se chalcogen bonds. We also discuss the biomimetic deiodination of several TH metabolites, including sulfated THs, iodothyronamines, and iodotyrosines. A brief discussion on the dehalogenation of halogenated nucleosides and nucleobases in the presence of organochalcogen compounds is also included. © 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Polychlorinated biphenyl (PCB) flame retardants are persistent pollutants and inhibit neurodevelopment, particularly in the early stages of life. Halogen bonding (XB) to the iodothyronine deiodinases (Dios) that modulate thyroid hormones (THs) is a potential mechanism for endocrine disruption. Cl⋯Se XB interactions of PCBs with SeMe(−), a small model of the Dio active site selenocysteine, are compared with previous results on polybrominated diphenylethers (PBDEs) and THs using density functional theory. PCBs generally display weaker XB interactions compared to PBDEs and THs, consistent with the dependence of XB strength on the size of the halogen (I > Br > Cl). PCBs also do not meet a proposed energy threshold necessary for substrates to undergo dehalogenation, suggesting they may behave as competitive inhibitors to Dio in addition to other mechanisms of endocrine disruption. XB interactions in PCBs are position-dependent, with ortho interactions slightly more favorable than meta and para interactions, suggesting that PCBs may have a greater effect on certain classes of Dio. Flexibility of PCBs around the biphenyl C-C bond is limited by ortho substitutions relative to the biphenyl linkage, which may contribute to the ability to inhibit Dio and other TH-related proteins.

Left-right asymmetries in the nervous system (lateralisation) influence a broad range of behaviours, from social responses to navigation and language. The role and pathways of endogenous and environmental mechanisms in the ontogeny of lateralisation remains to be established. The domestic chick is a model of both endogenous and experience-induced lateralisation driven by light exposure. Following the endogenous rightward rotation of the embryo, the asymmetrical position in the egg results in a greater exposure of the right eye to environmental light. To identify the genetic pathways activated by asymmetric light stimulation, and their time course, we exposed embryos to different light regimes: darkness, 6 hours of light and 24 hours of light. We used RNA-seq to compare gene expression in the right and left retinas and telencephalon. As expected, no differential expression between left and right was present in darkness. We detected differential gene expression in right vs left retina after 6 hours of light exposure. This difference disappeared before 24 hours of light exposure, suggesting that light-induced activation is a self-terminating phenomenon. This transient effect of light exposure was associated with a downregulation of the sensitive-period mediator gene DIO2 (iodothyronine deiodinase 2) in the right retina. No differences between genes expressed in the right vs. left telencephalon were detected. Gene networks associated with lateralisation were connected to vascularisation, cell motility, and the extracellular matrix. Interestingly, we know that the extracellular matrix– including the differentially expressed PDGFRB (platelet-derived growth factor receptor β) gene – is involved in both sensitive periods and in the endogenous chiral mechanism of primary cilia, that drives lateralisation. Our data show a similarity between endogenous and experience-driven lateralisation, identifying functional gene networks that affect lateralisation in a specific time window.

Background: Iodothyronine deiodinase-1 (D1) selenoenzyme regulates the systemic supply of active thyroid hormone (TH). Transient decrease in D1 enzymatic activity is clinically relevant and adaptive in nonthyroidal illness such as fasting or acute illness. However, DIO1 gene defects have not been reported in humans. Methods: Genetic analysis was performed using whole-exome sequencing in members of two unrelated families presenting with abnormal serum thyroid function tests. Plasmid constructs containing the two pathogenic DIO1 variants were used for in vitro studies assessing the kinetics of their enzymatic activity. Thyroid function tests were measured in Dio1 heterozygous-null mice. Results: We report the novel identification and characterization of two missense DIO1 pathogenic variants (resulting in p.Asn94Lys and p.Met201Ile) in two unrelated families presenting with abnormal TH metabolism with elevated serum reverse triiodothyronine (rT3) levels and rT3/T3 ratios. These characteristic in vivo parameters are also present in Dio1 heterozygous-null mice. Kinetic studies of the resulting mutant D1 proteins demonstrate two- to threefold higher Km indicating lower substrate affinity and slower enzyme velocity. Conclusions: We report the identification and characterization of two missense DIO1 pathogenic variants identified in families with abnormal TH metabolism. This is the first demonstration of inherited D1 deficiency in humans.

Background: Poorly differentiated thyroid carcinoma is rare and patients are typically euthyroid. We report a novel rare case of poorly differentiated thyroid carcinoma with triiodothyronine (T3) t...

Nitrate is known to disrupt the thyroid hormone, which is essential for the metamorphosis of amphibians. However, few studies are focused on the effects of nitrate on the maternal thyroid hormone in early amphibian embryos. We aimed to determine the impact of nitrate on maternal thyroid hormone signaling pathway in Bufo gargarizans embryos. B. gargarizans embryos were exposed to different concentrations of nitrate-nitrogen (NO3-N) for 7 days. High concentration of NO3-N (50, 100, and 200 mg/L) could induce embryonic malformation and influence the development of embryos. In addition, maternal T4 and components of the thyroid hormone (TH) signaling pathway were detected by ELISA and RNA-seq, respectively. The expression levels of mRNA related to thyroid hormone and oxidative stress were affected in the early developing embryos in all NO3-N treatment groups. However, the T4 levels and the spatial expression patterns of type II iodothyronine deiodinase (D2), type III iodothyronine deiodinase (D3), thyroid hormone receptor α (TRα), and thyroid hormone receptor β (TRβ) mRNA were not changed by nitrate. In conclusion, the results of our study highlight the crucial role of the maternal thyroid hormone signaling pathway in normal embryonic development, and the adverse effects of nitrate on the expression levels of mRNA related to thyroid hormone signaling pathway and oxidative stress in B. gargarizans embryos.

The human placenta is an important organ that forms a barrier where maternal and fetal exchange takes place. The placenta transport iodine to the fetal circulation by transfer of maternal iodine and deiodination of thyroid hormones (THs). The aim of the study was to examine the distribution of iodine and thyroid hormone transporters in the maternal and fetal sides of human-term placenta. A cross-sectional study was performed at the First Affiliated Hospital of China Medical University. Placental samples (maternal and fetal surfaces) were collected from 113 healthy-term pregnant women. The iodine content; the concentration of thyroxine (T4), triiodothyronine (T3), and reverse T3 (rT3); and the enzyme activity of placental type 2 iodothyronine deiodinase (D2) and D3 were examined. The mRNA and protein localization/expression of iodine and thyroid hormone transporters in the placenta were also studied. We also analyzed the association between expression level of Na+/I- symporter (NIS), thyroid hormone transporter protein, D3 activity in maternal and fetal surfaces of placenta with iodine content, and thyroid hormone levels. Iodine levels in placental samples from the maternal side were significantly higher than those in samples from the fetal side. T3 and T4 expression in fetal placenta was significantly lower than in maternal placenta. D3 activity in the fetal side of the placentas was significantly higher than that in the maternal side. The mRNA and protein expression of monocarboxylate transporters 8 (MCT8), L-amino acid transporters 1 (LAT1), organic anion transporting polypeptides 4A1 (OATP4A1), and TH binding protein transthyretin (TTR) were significantly increased in maternal side, while the NIS expression was higher in fetal side of human-term placenta. In conclusion, the enzymatic deiodination of thyroid hormones forms a barrier which reduces transplacental passage of the hormones and that the maternal part of the placenta is the primary factor in the mechanism regulating the hormonal transfer.

The present study investigated the alterations in nerve function and its potential mechanism of offspring result from the decabromodiphenyl ether (BDE209) orally gavage (0, 1.5, and 225 mg/kg.d body weight) in pregnant and lactating mice. Weight gain and litter size of maternal mice and body weight of offspring were examined. Learning and memory abilities of offspring were tested by the Morris water maze experiment. Thyroid hormones (THs) concentrations in peripheral blood of offspring were detected by the chemiluminescence enzyme immunoassay. Relative mRNA expression of type 1 iodothyronine deiodinase (

The aim of this study was to evaluate the prevalence of the Iodothyronine Deiodinase 2 gene Thr92Ala polymorphism in children from West of Romania with congenital hypothyroidism (CH) and association with TSH levels in response to levothyroxine monotherapy. Genotyping in 50 children with CH and 52 healthy controls was done using real time PCR. The results showed that there was no statistical difference between the frequencies of genotypes in patients vs. controls. Patients were treated with L-thyroxine and most had normal values for fT3 and fT4. However, high TSH values were found in 21 patients (42%) after treatment. Among patients with high TSH values, AA genotypes were significantly more prevalent (p = 0.044) than TT and AT genotypes. Our results suggest that for the D2 gene Ala92Thr polymorphism, the AA genotype may be detrimental for achieving euthyroidism in patients with CH and levothyroxine monotherapy, therefore polytherapy could be considered as a better approach in these patients.

Thyroid hormones (THs) are indispensable for each phyla in Chordata, while their functions in the non-chordate invertebrates are indistinct. Studies on the TH system in non-chordate invertebrates are important for understanding the evolution of TH system and may be applied in aquaculture or biofouling control at the same time. Iodothyronine deiodinases are keys to studying the TH system, as they are critical enzymes in maintaining TH homeostasis by catalyzing the initiation and termination of the effects of thyroid hormone in vertebrates. Here, we report the primary physiological effects of T4, the outer ring deiodinase activity, and a similar transcription regulation of two oyster deiodinases by TH receptor (CgTR) in an invertebrate, Pacific oyster Crassostrea gigas. L-thyroxine (T4) may have an important physiological function in the oyster, suggested by the growth retardation effect of excessive T4 in umbo larvae stage. The outer ring deiodinase activity transforming T4 to T3 (3, 3', 5-triiodothyronine) was then detected in the Pacific oyster in vivo, which may be conducted by two oyster deiodinases (CgDx and CgDy). Transcription regulation of CgTR onto these two deiodinase genes was also verified by electrophoretic mobility shift assay and dual luciferase reporter assay in mammalian cells. These results contribute to a better understanding of the evolution of the TH system.

The serum free triiodothyronine (FT3)/free thyroxine (FT4) ratio in patients with huge goitrous Hashimoto’s thyroiditis (HG-HT) is relatively high. We investigated the cause of high FT3/FT4 ratios. We measured the serum FT3, FT4, and thyrotropin (TSH) levels of seven patients with HG-HT who had undergone a total thyroidectomy. Eleven patients with papillary thyroid carcinoma served as controls. The activities and mRNA levels of type 1 and type 2 iodothyronine deiodinases (D1 and D2, respectively) were measured in the thyroid tissues of HG-HT and perinodular thyroid tissues of papillary thyroid carcinoma. The TSH levels in the HG-HT group were not significantly different from those of the controls. The FT4 levels in the HG-HT group were significantly lower than those of the controls, whereas the FT3 levels and FT3/FT4 ratios were significantly higher in the HG-HT group. The FT3/FT4 ratios in the HG-HT group who had undergone total thyroidectomy and received levothyroxine therapy decreased significantly to normal values. Both the D1 and D2 activities in the thyroid tissues of the HG-HT patients were significantly higher than those of the controls. However, the mRNA levels of both D1 and D2 in the HG-HT patients’ thyroid tissues were comparable to those of the controls. Interestingly, there were significant correlations between the HG-HT patients’ D1 and D2 activities, and their thyroid gland volume or their FT3/FT4 ratios. Our results indicate that increased thyroidal D1 and D2 activities may be responsible for the higher serum FT3/FT4 ratio in patients with HG-HT.

THIS work aims at detecting the disturbances in thyroid hormone metabolism in male rats exposed to liver injury by γ- radiation and/or carbon tetrachloride (CCl4), in addition to investigating the modulatory role of N-acetyl cysteine (NAC) and sodium selenite (Se) supplementation. Subcutaneous injection of CCl4 twice a week for 8 weeks and/or whole-body irradiation (6 Gy, single dose) one day after the last dose of CCl4 induced hepatotoxicity as manifested by elevation of serum alanine aminotransferase and gamma-glutamyl transferase and oxidative stress in liver tissue. Moreover, significant increases were recorded in pro-inflammatory markers: nuclear factor kappa B and interleukin- 1beta levels. This was also accompanied by a significant decrease in the activity of type 1 iodothyronine deiodinase in the hepatic tissue and triiodothyronine and thyroxin levels in serum, while thyroid-stimulating hormone showed a non-significant increase. Histological examination of liver sections showed marked alterations. However, oral supplementation of NAC and Se for 2 weeks after exposure to CCl4 and/or γ- radiation attenuated the changes induced by these toxins. In conclusion, supplementation of NAC & Se may be useful to attenuate thyroid hormone metabolic disturbances associated with liver injury induced by chemical and physical environmental toxins.

Air pollution and fuel emissions are the common sources of human exposure to polycyclic aromatic hydrocarbons (PAHs) and heavy metals. Several studies have suggested potential associations between PAHs/heavy metals and thyroid hormones, however, reports have been inconsistent. In this study, we employed a subpopulation of the adults (n = 1254) who participated in the Korean National Environmental Health Survey 2015–2017, and investigated the association of PAHs and major heavy metals with thyroid hormones, and explored the underlying mechanisms of thyroid disruption. Four PAH metabolites and three heavy metals of lead (Pb), mercury (Hg), and cadmium (Cd) were measured either in urine or in total blood. In addition, thyroid hormones (T3 and T4), TSH, thyroxine-binding globulin (TBG), and thyroid autoantibodies were measured, and peripheral deiodinase activity (GD) and thyroid's secretory capacity (GT) were calculated. Urinary Hg was negatively associated with total T3 in both males and females, while it was positively associated with total T4 among females only. Urinary Hg was related to decreased GD and increased GT in both sexes. In contrast, urinary Cd was positively associated with total T3 and GD in both male and female populations. Urinary Cd also showed a positive association with thyroid autoantibodies, but only in males. A multi-factor model considering co-exposure to multiple chemicals also resulted in similar associations. Among the measured PAH metabolites, only urinary 1-hydroxypyrene showed a negative association with total T3 in males. However, this association was marginal, and disappeared in a multi-chemical model. The present observations are suggestive that exposures to Hg and Cd might disrupt thyroid hormones, possibly through an alteration of deiodinase activity. Association of PAH exposure with thyroid hormone appears to be insignificant.

Seasonal timing is important for many critical life history events of vertebrates, and photoperiod is often used as a reliable seasonal cue. In mammals and birds, it has been established that a photoperiod-driven seasonal clock resides in the brain and pituitary, and is driven by increased levels of pituitary thyroid stimulating hormone (TSH) and brain type 2 iodothyronine deiodinase (DIO2), which leads to local increases in triiodothyronine (T3). In order to determine if a similar mechanism occurs in fish, we conducted photoperiod manipulations in anadromous (migratory) Atlantic salmon (Salmo salar) that use photoperiod to time the preparatory development of salinity tolerance which accompanies downstream migration in spring. Changing daylength from short days (light:dark (LD) 10:14) to long days (LD 16:8) for 20 days increased gill Na+/K+-ATPase (NKA) activity, gill NKAα1b abundance and plasma growth hormone (GH) levels that normally accompany increased salinity tolerance of salmon in spring. Long-day exposure resulted in five-fold increases in pituitary tshβb mRNA levels after 10 days and were sustained for at least 20 days. tshβb mRNA levels in the saccus vasculosus were low and not influenced by photoperiod. Increased daylength resulted in significant increases in dio2b mRNA levels in the hypothalamus and midbrain/optic tectum regions of the brain. The results are consistent with the presence of a photoperiod-driven seasonal clock in fish which involves pituitary TSH, brain DIO2 and the subsequent production of T3, supporting the hypothesis that this is a common feature of photoperiodic regulation of seasonality in vertebrates.

Selenium, one of the essential trace minerals, is present in vivo in form of selenoproteins. Iodothyronine deiodinase, a selenoprotein, is involved in the activation and inactivation of thyroid hormone. Therefore, patients with selenium deficiency may present changes in thyroid hormone levels due to inhibition of T4 to T3 conversion; however, this assumption is still under debate. In the present study, we retrospectively investigated the thyroid function in 22 patients with selenium deficiency. Thyroid stimulating hormone (TSH) and free T4 (FT4) levels were increased in 3 (14%) and 5 (23%) patients, respectively, and free T3 (FT3) levels were decreased in 6 (27%) patients. The FT4/FT3 ratio was significantly higher in patients with selenium deficiency than that in the control group. There appeared to be a positive correlation between the decreased rate of selenium levels and FT4/FT3 ratio, thereby indicating that patients with severe selenium deficiency also exhibited abnormal thyroid hormone levels. Furthermore, when selenium was supplemented in seven patients with abnormal thyroid hormone levels, the TSH, FT4, and FT4/FT3 ratio were significantly decreased and FT3 levels were increased. Collectively, patients with selenium deficiency could present the characteristics of not only low FT3 but also high FT4 and FT4/FT3 ratio.

The effects on the activity of thyroxine (T4) due to the chalcogen replacement in a series of peri-substituted naphthalenes mimicking the catalytic function of deiodinase enzymes are computationally examined using density functional theory. In particular, T4 inner-ring deiodination pathways assisted by naphthyl-based models bearing two tellurols and a tellurol-thiol pair in peri-position are explored and compared with the analogous energy profiles for the naphthalene mimic having two selenols. The presence of a halogen bond (XB) in the intermediate formed in the first step and involved in the rate-determining step of the reaction is assumed to facilitate the process increasing the rate of the reaction. The rate-determining step calculated energy barrier heights allow rationalizing the experimentally observed superior catalytic activity of tellurium containing mimics. Charge displacement analysis is used to ascertain the presence and the role of the electron density charge transfer occurring in the rate-determining step of the reaction, suggesting the incipient formation or presence of a XB interaction. © 2019 Wiley Periodicals, Inc.

Polychlorinated biphenyls (PCBs) and halogen flame retardants (HFRs) are major pollutants in e-waste recycling area. High internal exposure levels of PCBs and HFRs are harmful to human thyroid hormone (TH) equilibrium. To examine their disrupting effects on TH, we conducted a study on children (n = 114) of an e-waste recycling and a control area in South China. Concentrations of PCBs, HFRs, and TH levels were determined in serum samples. TH related proteins and their corresponding gene were also monitored as markers of such disruption. Levels of these chemicals in the exposed group were much greater than those in the control group. Results of the linear regression and generalized additive model indicated the presence of close relationships between the internal exposure levels and the responses of TH related proteins, gene expression. More extensive exposure concentrations of these chemicals led to higher expression of iodothyronine deiodinase I and decreased the concentrations of thyroid-stimulating hormone, expression of TH receptor α, indicating the exertion of discrepant and even contrary influences on equilibrium of TH, and a compensation of these mechanisms may kept the homeostasis of TH. These results for children warrant further investigation on the health risks of PCBs and HFRs exposure in e-waste area.

Infantile hepatic hemangioma (IHH)-related consumptive hypothyroidism is rare and occurs as a result of excess thyroid hormone inactivating enzyme, type-3 iodothyronine deiodinase. We present an infant with IHH-related hypothyroidism, in whom treatment with propranolol led to regression of tumor and subsequent euthyroid status.

This study evaluated the effects of food availability on the transcript levels of genes related to reproduction and growth in the sapphire devil (Chrysiptera cyanea), a tropical damselfish. Nonbreeding fish were reared at high-food (HF) and low-food (LF) levels for 4 weeks under long-days. Vitellogenic oocytes could be observed in the ovaries of the HF group. The quantitative polymerase chain reaction analysis revealed that lhβ and cyp19b in the brains, vtg and igf1 in the livers and cyp19a in the ovaries of HF fish were significantly higher than that of LF fish, suggesting that estradiol-17β (E2) synthesis in the ovary and brain is activated when suitable permissive factors are available to fish. Food limitation lowered hepatic igf1 and dio2, suggesting that the TH-IGF1 signaling system functions in the liver, and that food availability altered hepatic deiodination activities related to intercellular levels of thyroid hormones. Hepatic dio2 significantly decreased when fish were immersed for 3 days in E2-containing seawater; this suggests that E2 impedes the conversion of T4 to T3 in the liver. Our study shows that igf1 was upregulated in accordance with HF-induced vitellogenesis but downregulated by E2 treatment, suggesting that igf1 is bidirectional and altered by maturational status. Once vitellogenesis begins under a suitable range of proximal factors, fish need to maintain their nutritional status because food availability is a permissive factor for their reproduction.

Kidney renal clear cell carcinoma (KIRC) is the most common and fatal subtype of renal cancer. Antagonistic associations between selenium and cancer have been reported in previous studies. Selenium compounds, as anti-cancer agents, have been reported and approved for clinical trials. The main active form of selenium in selenoproteins is selenocysteine (Sec). The process of Sec biosynthesis and incorporation into selenoproteins plays a significant role in biological processes, including anti-carcinogenesis. However, a comprehensive selenoprotein mRNA analysis in KIRC remains absent. In the present study, we examined all 25 selenoproteins and identified key selenoproteins, glutathione peroxidase 3 (GPX3) and type 1 iodothyronine deiodinase (DIO1), with the associated prognostic biomarker leucine-rich repeat containing 19 (LRRC19) in clear cell renal cell carcinoma cases from The Cancer Genome Atlas (TCGA) database. We performed validations for the key gene expression levels by two individual clear cell renal cell carcinoma cohorts, GSE781 and GSE6344, datasets from the Gene Expression Omnibus (GEO) database. Multivariate survival analysis demonstrated that low expression of LRRC19 was an independent risk factor for OS. Gene set enrichment analysis (GSEA) identified tyrosine metabolism, metabolic pathways, peroxisome, and fatty acid degradation as differentially enriched with the high LRRC19 expression in KIRC cases, which are involved in selenium therapy of clear cell renal cell carcinoma. In conclusion, low expression of LRRC19 was identified as an independent risk factor, which will advance our understanding concerning the selenium adjuvant therapy of clear cell renal cell carcinoma.

Selenium (Se) is an integral component of iodothyronine deiodinase, glutathione peroxidase and thioredoxin reductase enzymes and thus is important for normal thyroid function. This study investigated the influence of Se inadequacy on thyroid response of iodine-replete young children. Serum thyroxine (T4), triiodothyronine (T3), thyroglobulin (Tg), thyroid stimulating hormone (TSH), and Se were analyzed in 54–60 mo old children (n = 628) from the Amhara region of Ethiopia before salt iodization was commenced; analyses were repeated (n = 555) 15 mo after iodized salt became available. Iodized salt coverage increased from 12.2% to 91.6% of households. Median urinary iodine concentration (UIC) among children increased from 9 μg/l to 167 μg/l (p

Filial imprinting leads to the formation of social attachment if training is performed during a brief sensitive period after hatching. We found that thyroid hormone (3,5,3′-triiodothyronine, T3) acts as a critical determining factor of the sensitive period in domestic chicks. Imprinting upregulates gene expression of the converting enzyme (Dio2, type 2 iodothyronine deiodinase) in the telencephalon, leading to increased brain T3 content. If systemically applied, T3 facilitates imprinting in aged chicks even after the sensitive period is over. Imprinting is also associated with the rapid development of visual perception. Exposure to motion pictures induces a predisposed preference to Johansson’s biological motion (BM), and those individuals with higher BM preference are more easily imprinted. Here, we examined whether Dio2 expression is also linked with BM predisposition. Chicks were trained by a rotating red block, and tested for imprinting (experiment 1) and BM preference (experiment 2). To examine the time courses of behavioural and physiological processes, Dio2 expression in telencephalon was compared among three groups: naive control chicks, and chicks trained for a short (0.5 h) or long period (2 h). In experiment 1, higher Dio2 expression appeared in the 2-h group than in the 0.5-h/control groups, but it was not correlated with the individual imprinting score. In experiment 2, a significant positive correlation appeared between Dio2 expression and BM preference in 2-h-trained chicks. Memory priming by T3 is therefore functionally linked to BM preference induction, leading to successful imprinting to natural objects even when they are initially exposed to artificial objects.

The glass eel stage of the American Eel Anguilla rostrata marks the onset of the catadromous migration into estuarine or freshwater habitats, and the endocrine mechanisms underlying this habitat selection are still not well understood. Using a candidate genes approach, the aim of this study was to test for different patterns of gene expression related to (1) salinity preferences and/or (2) capture site to predict physiological differences between migratory behaviors. We performed analyses revealing the expression of genes coding for key hormonal factors or their receptors on glass eel‐stage American Eels collected at the mouths of three rivers on the east coast of Canada (Grande‐Riviere‐Blanche, St. Lawrence estuary; Riviere‐Saint‐Jean, Gaspe Peninsula; and the Mersey River, Nova Scotia); eels from the three systems displayed different salinity preferences (brackish water/salt water/freshwater) under laboratory conditions. Transcripts from genes coding for prolactin (PRL), thyroid‐stimulating hormone β subunit, type‐2 iodothyronine deiodinase (DIO‐2), thyroid hormone receptors αa and αb (THRαa and THRαb), growth hormone (GH), insulin‐like growth factor 1 (IGF‐1), and their respective receptors (GH‐R1 and IGF‐1R) were all detected in glass eels. No differences in the expression patterns were detected pertaining to salinity preference, but strong differences were found among rivers. Riviere‐Saint‐Jean glass eels, which were the longest and the least pigmented among the three rivers, were characterized by the highest expression of PRL, DIO‐2, and THRαb. Those from Grande‐Riviere‐Blanche showed an increase in IGF‐1R. Glass eels captured from these two rivers also exhibited the highest expression of GH and GH‐R1. Overall, these results confirm gene × environment interactions at the gene expression level when glass eels settle into their continental habitat. As such, our results also support the concept of the presence of different ecotypes in the Atlantic Canadian coast and in the estuary and Gulf of St. Lawrence.

Background Infantile hepatic haemangiomas (IHHs) produce an excess of the thyroid hormone inactivating enzyme type-3 iodothyronine deiodinase (D3), leading to rapid degradation of thyroid hormones and consumptive hypothyroidism. The L-thyroxine replacement dose in patients with consumptive hypothyroidism is inappropriately higher than that in congenital hypothyroidism. Case presentation A 4-month-old boy presented with abdominal distention. Thyroid function tests (TFTs) revealed an elevated thyroid-stimulating hormone (TSH) level of 177 mU/L, normal free thyroxine (fT4) of 1.23 ng/dL, low free tri-iodothyronine (fT3) of 1.55 pg/mL and increased reverse T3 (rT3) of 1240 ng/dL. Abdominal ultrasound and magnetic resonance imaging (MRI) revealed multiple IHHs. Based on his TFTs, ultrasonography and MRI evidence, he was diagnosed with consumptive hypothyroidism, and L-thyroxine replacement at 15 μg/kg/day was started. The L-thyroxine dose was increased gradually to 35 μ/kg/day until a stabilising euthyroid status was achieved. By the age of 8 months, the TSH concentration was decreased to normal levels; the L-thyroxine dose was gradually reduced and finally discontinued at the age of 12 months. Repeat abdominal ultrasound and MRI revealed a reduction in the number and size of the haemangiomas. The TFTs were at normal reference levels. The patient remains in active follow-up. Conclusions Neonatal screening for congenital hypothyroidism is usually negative in cases of IHH, as seen in our case. A high index of suspicion is necessary to diagnose hypothyroidism in cases of IHH. The present case required very high doses of levothyroxine to achieve a euthyroid status. In cases of hypothyroidism in the first year of life with consumptive hypothyroidism caused by hepatic haemangioma, aggressive L-thyroxine replacement is required with no upper limit. The dose should be increased gradually until a stabilising euthyroid status is achieved.

Chronic metabolic stress leads to cellular dysfunction, characterized by excessive reactive oxygen species, endoplasmic reticulum (ER) stress and inflammation, which has been implicated in the pathogenesis of obesity, type 2 diabetes and cardiovascular disease. The ER is gaining recognition as a key organelle in integrating cellular stress responses. ER homeostasis is tightly regulated by a complex antioxidant system, which includes the seven ER-resident selenoproteins — 15 kDa selenoprotein, type 2 iodothyronine deiodinase and selenoproteins S, N, K, M and T. Here, the findings from biochemical, cell-based and mouse studies investigating the function of ER-resident selenoproteins are reviewed. Human experimental and genetic studies are drawn upon to highlight the relevance of these selenoproteins to the pathogenesis of metabolic disease. ER-resident selenoproteins have discrete roles in the regulation of oxidative, ER and inflammatory stress responses, as well as intracellular calcium homeostasis. To date, only two of these ER-resident selenoproteins, selenoproteins S and N have been implicated in human disease. Nonetheless, the potential of all seven ER-resident selenoproteins to ameliorate metabolic dysfunction warrants further investigation.

Contains fulltext : 196376.pdf (Publisher’s version ) (Closed access) BACKGROUND: Subclinical hypothyroidism is associated with dyslipidemia and atherosclerosis. Whether these effects are in part mediated via direct effects of thyrotropin (TSH) on peripheral thyroid hormone (TH) metabolism and/or concentrations of serum lipids is not clear. OBJECTIVE: This study examined whether TSH has direct effects on peripheral TH metabolism and serum lipids. METHODS: Eighty-two patients with differentiated thyroid cancer were retrospectively analyzed. All patients had undergone total thyroidectomy and (131)I remnant ablation. During follow-up, two successive injections of recombinant human TSH (rhTSH) were administered to patients on a stable dose of levothyroxine. In all patients, TSH, thyroxine (T4), free T4 (fT4), triiodothyronine (T3), reverse T3 (rT3), total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, apolipoprotein B, lipoprotein(a), and triglyceride levels were measured immediately before the first and approximately 72 hours after the second injection of rhTSH. RESULTS: After rhTSH stimulation, T3 values decreased (from 1.91 to 1.81 nmol/L; p < 0.001). T4, fT4, and rT3 did not change. After rhTSH, median apolipoprotein B increased from 0.90 to 0.92 g/L (p = 0.03), lipoprotein(a) from 0.21 to 0.24 g/L (p < 0.001), and triglycerides from 1.98 to 2.50 mmol/L (p < 0.001). Serum high-density lipoprotein cholesterol decreased from 0.98 to 0.81 mmol/L (p < 0.001). Multiple regression analysis showed that the changes in lipids were most closely associated with the decrease in T3 levels. CONCLUSIONS: TSH has direct effects on peripheral TH metabolism by decreasing T3 levels in levothyroxine-treated thyroidectomized patients. This decrease in T3 levels is accompanied by unfavorable changes in serum lipids.

This case report describes a male neonate with Graves’ disease. The mother’s pregnancy was complicated by poorly controlled Graves’ disease. The neonate was diagnosed with thyroxine (T3)-predominant Graves’ disease with low free triiodothyronine (T4) and high free T3 during antithyroid drug therapy. The patient also presented with persistent pulmonary hypertension of the newborn due to hyperthyroidism and airway stenosis caused by goiter. It was difficult to control thyroid function and maintain free T4 levels with inorganic iodine, thiamazole, and levothyroxine sodium hydrate. We successfully controlled thyroid function using the previous treatments in combination with propylthiouracil. Propylthiouracil suppresses type 1 iodothyronine deiodinase, and its pharmacological action suppresses the conversion of T4 to T3. Therefore, we used propylthiouracil at an earlier stage of intervention in this case. We ceased administration of antithyroid drugs on day 85 of life. Subsequently, as the TRH loading test revealed central hypothyroidism, oral administration of levothyroxine sodium hydrate was continued. Its administration was discontinued at the age of 1 yr. Thyroid-stimulating hormone recovered to normal values, and his development had progressed without complications by the age of 2 yr.

Selenium (Se) is an essential trace element that is involved in numerous biological processes in the form of a selenoprotein such as iodothyronine deiodinase (DIO). Se deficiency may prevent the conversion of T4 to T3 through reducing DIO expression and thereby affecting thyroid hormone status. However, this has not been well documented in humans. In this study, to clarify the association between Se and thyroid hormone status, we investigated the thyroid hormone levels in patients with severe Se deficiency (< 2 µg/dl). Severe Se deficiency was associated with increases in free T4 levels, but not with decreases and increases in free T3 and thyroid stimulating hormone (TSH) levels, respectively. Increases in free T4 levels during Se deficiency were reduced with Se supplementation; however, neither free T3 nor TSH levels were affected. Taken together, these findings indicate that free T4 may be a useful biomarker for Se status when serum Se levels are severely low.

Thyroid hormone (TH) is critical for the maintenance of cellular homeostasis during stress responses, but its role in lung fibrosis is unknown. Here we found that the activity and expression of iodothyronine deiodinase 2 (DIO2), an enzyme that activates TH, were higher in lungs from patients with idiopathic pulmonary fibrosis than in control individuals and were correlated with disease severity. We also found that Dio2-knockout mice exhibited enhanced bleomycin-induced lung fibrosis. Aerosolized TH delivery increased survival and resolved fibrosis in two models of pulmonary fibrosis in mice (intratracheal bleomycin and inducible TGF-β1). Sobetirome, a TH mimetic, also blunted bleomycin-induced lung fibrosis. After bleomycin-induced injury, TH promoted mitochondrial biogenesis, improved mitochondrial bioenergetics and attenuated mitochondria-regulated apoptosis in alveolar epithelial cells both in vivo and in vitro. TH did not blunt fibrosis in Ppargc1a- or Pink1-knockout mice, suggesting dependence on these pathways. We conclude that the antifibrotic properties of TH are associated with protection of alveolar epithelial cells and restoration of mitochondrial function and that TH may thus represent a potential therapy for pulmonary fibrosis.

The aim of this study was to examine the adverse effects of lead (Pb) exposure on Bufo gargarizans embryos. The 96 h-LC50 of Pb2+ for B. gargarizans embryos was determined to be 26.6 mg L-1 after an acute test. In the chronic test, B. gargarizans embryos at Gosner stage 3 were exposed to 10~2000 μg Pb2+ L-1 during embryogenesis. Total length, weight, developmental stage, and malformation were monitored. In addition, the transcript levels of type II and type III iodothyronine deiodinase (Dio2 and Dio3) and thyroid hormone receptors (TRα and TRβ) were determined to assess the thyroid-disrupting effects of Pb2+. Slightly increased growth and development of B. gargarizans embryos were observed at low concentrations of Pb2+ (10, 50, and 100 μg L-1), while retarded growth and development were found at high concentrations of Pb2+ (1000 and 2000 μg L-1). In addition, Pb2+ exposure induced morphological abnormalities, which were characterized by edema at tail, wavy fin, abdominal edema, stunted growth, hyperplasia, and axial flexures in B. gargarizans embryos. Furthermore, our results showed that exposure to 2000 μg Pb2+ L-1 decreased the transcript levels of Dio2, TRα, and TRβ, but it increased Dio3 mRNA level. In contrast, exposure to 50 μg Pb2+ L-1 increased TRα mRNA level and decreased Dio3 mRNA level. These results suggested that Pb2+ might have thyroid-disrupting effects, leading to the disruption of growth and development in B. gargarizans embryos.

Circadian clocks regulate various aspects of photoreceptor physiology, but their contribution to photoreceptor development and function is unclear. Cone photoreceptors are critical for color vision. Here, we define the molecular function of circadian activity within cone photoreceptors and reveal a role for the clock genes Bmal1 and Per2 in regulating cone spectral identity. ChIP analysis revealed that BMAL1 binds to the promoter region of the thyroid hormone-activating enzyme type 2 iodothyronine deiodinase (Dio2) and thus regulates the expression of Dio2. Thyroid hormone treatment resulted in a partial rescue of the phenotype caused by the loss of Bmal1, thus revealing a functional relationship between Bmal1 and Dio2 in establishing cone photoreceptor identity. Furthermore, Bmal1 and Dio2 are required to maintain cone photoreceptor functional integrity. Overall, our results suggest a mechanism by which circadian proteins can locally regulate the availability of thyroid hormone and influence tissue development and function.

Microcystin-LR (MC-LR) in the aquatic environment may disturb thyroid hormone (TH) homeostasis. It is not clear how MC-LR affects downstream biological processes after TH disturbance. After exposure to 50, 100, 200 and 400 μg/L MC-LR for 24, 48, 72, or 96 h, alterations of the TH metabolism of adult zebrafish at thyroxine (T4), triiodothyronine (T3) levels, and iodothyronine deiodinase (Dio) activity, were observed. After exposure to MC-LR at 400 μg/L, T3 and T4 levels decreased significantly in females (p 0.05) and returned to normal levels at 96 h. In males, T4 levels were not significantly different between groups. The expression of corticotropin releasing hormone, thyroid-stimulating hormone beta subunit, transthyretin, sodium/iodide cotransporter, thrombopoietin, thyroid hormone receptor alpha and beta changed, but not in a dose-dependent manner. Acute MC-LR exposure induced a negative feedback regulation of the hypothalamic-pituitary-thyroid axis in adult zebrafish, and females were more sensitive than males. In conclusion, acute MC-LR exposure disrupted the TH metabolism by altering Dio activity and gene expression of the HPT axis; these changes may affect the complement system through regulation of c9 mRNA synthesis.

Plastics are ubiquitously present in our daily life and some components of plastics are endocrine-disrupting chemicals, such as bisphenol A and phthalates. Herein, we aimed to evaluate the effect of plastic endocrine disruptors on type 1 and type 2 deiodinase activities, enzymes responsible for the conversion of the pro-hormone T4 into the biologically active thyroid hormone T3, both in vitro and in vivo. Initially, we incubated rat liver type 1 deiodinase and brown adipose tissue type 2 deiodinase samples with 0.5 mM of the plasticizers, and the deiodinase activity was measured. Among them, only BPA was capable to inhibit both type 1 and type 2 deiodinases. Then, adult male Wistar rats were treated orally with bisphenol A (40 mg/kg b.w.) for 15 days and hepatic type 1 deiodinase and brown adipose tissue type 2 deiodinase activities and serum thyroid hormone concentrations were measured. In vivo bisphenol A treatment significantly reduced hepatic type 1 deiodinase activity but did not affect brown adipose tissue type 2 deiodinase activity. Serum T4 levels were higher in bisphenol A group, while T3 remained unchanged. T3/T4 ratio was decreased in rats treated with bisphenol A, reinforcing the idea that peripheral metabolism of thyroid hormone was affected by bisphenol A exposure. Therefore, our results suggest that bisphenol A can affect the metabolism of thyroid hormone thus disrupting thyroid signaling.

Thyroid hormone (TH) is involved in regulating the reproduction of vertebrates. Its physiological action in the target tissues is due to the conversion of TH by iodothyronine deiodinases. In this study, we aimed to clone and characterize type 2 (sdDio2) and type 3 (sdDio3) of the sapphire devil Chrysiptera cyanea, a tropical damselfish that undergoes active reproduction under long-day conditions, and to study the involvement of THs in the ovarian development of this species. When the cDNAs of sdDio2 and sdDio3 were partially cloned, they had deduced amino acid sequences of lengths 271 and 267, respectively, both of which were characterized by one selenocysteine residue. Real-time quantitative PCR (qPCR) revealed that both genes are highly expressed in the whole brain, and sdDio2 and sdDio3 are highly transcribed in the liver and ovary, respectively. In situ hybridization analyses showed positive signals of sdDio2 and sdDio3 transcripts in the hypothalamic area of the brain. Little change in mRNA abundance of sdDio2 and sdDio3 in the brain was observed during the vitellogenic phases. It is assumed that simultaneous activation and inactivation of THs occur in this area because oral administration of triiodothyronine (T3), but not of thyroxine (T4), upregulated mRNA abundance of both genes in the brain. The transcript levels of sdDio2 in the liver and sdDio3 in the ovary increased as vitellogenesis progressed, suggesting that, through the metabolism of THs, sdDio2 and sdDio3 play a role in vitellogenin synthesis in the liver and yolk accumulation/E2 synthesis in the ovary. Taken together, these results suggest that iodothyronine deiodinases act as a driver for vitellogenesis in tropical damselfish by conversion of THs in certain peripheral tissues.

Polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs) and new flame retardants (NFRs) are known thyroid hormone (TH) disruptors, but their disrupting mechanisms in humans are not completely understood. In this study, we aimed to explore the disrupting mechanisms of the aforementioned chemicals via examining TH-regulated proteins and gene expression in human serum. Adult participants from an e-waste dismantling (exposed group) and a control region (control group) in South China provided blood samples for the research. Some compounds of PCBs, PBDEs, and NFRs showed strong binding affinity to the thyroid-stimulating hormone (TSH), thyroglobulin, thyroxine-binding globulin (TBG), gene expression of TH receptor α (TRα) and β, and iodothyronine deiodinase I (ID1). The highly exposed individuals had lower levels of TBG, TSH, and expression of TRα, but higher expression of ID1 than those of the control group. The disruption of TH-regulated proteins and gene expression suggested the exertion of different and, at times, even contradictory effects on TH disruption. However, no statistically significant difference was found in the TH levels between the exposed and the control group, implying that the TH disruption induced by these chemicals depends on the combined influence of multiple mechanisms. Gene expression appears to be an effective approach for investigations of TH disruption and the potential health effects.

Decabromodiphenyl ether (BDE209) has been widely used as a flame retardant in the past four decades, leading to human health consequences, especially neurological impairments. Our previous in vivo studies have suggested that developmental neurotoxicity in offspring may be the result of BDE209-induced placental type III iodothyronine deiodinase (Dio3) disturbance and consequent thyroid hormone (TH) instability. Dio3 is paternally imprinted gene, and its balanced expression is crucial in directing normal development and growth. In this study, we used placenta-derived cells to investigate how BDE209 affected Dio3 expression through interfering imprinting mechanisms in the delta-like homolog 1 (Dlk1)-Dio3 imprinted region. Gene chip analysis and RT-qPCR identified miR409-3p, miR410-5p, miR494-3p, miR668-3p and miR889-5p as potential candidates involved in Dio3 deregulation. The sodium bisulfite-clonal sequencing revealed the BDE209 affect methylation status of two differentially methylated regions (DMRs), intergenic-DMR (IG-DMR) and maternally expressed gene 3-DMR (MEG3-DMR). Our data indicate that placental Dio3 may be a potential molecular target for future study of BDE209 developmental toxicity. In particular, miRNAs, IG-DMR and MEG3-DMR in the Dlk1-Dio3 imprinted locus may be informative in directing studies in TH disturbance and developmental toxicity induced by in utero exposure to environmental persistent organic pollutants (POPs), and those candidate miRNAs may prove to be convenient and noninvasive biomarkers for future large-scale population studies.

Deubiquitinase USP20/VDU2 (VHL-interacting Deubiquitinating Enzyme 2) has been proved to play vital roles in multiple cellular processes by controlling the life-span of substrate proteins including hypoxia-inducible factor HIF1α, β2-adrenergic receptor, and type 2 iodothyronine deiodinase etc. USP20 contains four distinct structural domains, which include the N-terminal zinc-finger ubiquitin binding domain (ZnF-UBP), the catalytic domain (USP domain), and two tandem DUSP domains (DUSP1 and DUSP2). Here in this study, we report the setting up of the production approach for USP20 DUSP2, and the NMR characterization of the produced target protein. With the assistance of GB1 tag and glycerol, both the solubility and stability of USP20 DUSP2 are significantly enhanced. And by using the optimized protein production procedure, monomeric and stable 15N, 13C-labeled USP20 DUSP2 sample for NMR data acquisition was obtained. The secondary structural elements of USP20 DUSP2 were then revealed by the analysis of recorded NMR spectra, and USP20 DUSP2 forms an AB3 fold in solution. The production protocol and NMR characterization results reported in this manuscript could be utilized in the extended structural and functional studies of USP20 DUSP2.

Type 1 iodothyronine deiodinase (DIO1) regulates peripheral metabolism of thyroid hormones that control cellular proliferation, differentiation and metabolism. The significance of DIO1 in cancer is unknown. In this study we hypothesized that diminished expression of DIO1, observed in renal cancer, contributes to the carcinogenic process in the kidney. Here, we demonstrate that ectopic expression of DIO1 in renal cancer cells changes the expression of genes controlling cell cycle, including cyclin E1 and E2F5, and results in inhibition of proliferation. The expression of genes encoding collagens (COL1A1, COL4A2, COL5A1), integrins (ITGA4, ITGA5, ITGB3) and transforming growth factor-β-induced (TGFBI) is significantly altered in renal cancer cells with induced expression of DIO1. Finally, we show that overexpression of DIO1 inhibits migration of renal cancer cells. In conclusion, we demonstrate for the first time that loss of DIO1 contributes to renal carcinogenesis and that its induced expression protects cells against cancerous proliferation and migration.

Polybrominated diphenyl ethers (PBDEs) have the potential to disturb the thyroid endocrine system in vertebrates, but little is known about the disruptive effects of PBDEs on marine bivalves. In this study, we first examined the effects of BDE-47 exposure on growth of juvenile manila clams Ruditapes philippinarum. The result showed that 1.0 and 10 μg L(-1) BDE-47 had adverse effects on 14-d shell-length growth of juvenile clams. Then, one-year-old adult clams were exposed to 0, 0.1 and 1 μg L(-1) BDE-47 for 15 d. BDE-47 (1 μg L(-1)) exposure caused significant decreases of total T4 (thyroxine) by 40% and T3 (3,5,3'-triiodothyronine) by 75% concentrations in haemolymph of the clams. Transcription of genes involved in thyroid hormone synthesis and metabolism were also studied by quantitative RT-PCR. Gene expression levels of sodium iodide symporter (rp-NIS), iodothyronine deiodinase (rp-Deio) and thyroid peroxidase (rp-TPO) were increased in a dose-dependent manner at day 5 and day 10, while monocarboxylate transporter 8 (rp-Mct8) was downregulated at day 5, day 10 and day 15. The effect and preliminary mechanism observed in the present study were consistent with the results from previous studies on rodent and fish, implying that exposure to BDE-47 may pose threat to thyroid hormone homeostasis in bivalves through thyroid synthesis and metabolism pathways. This study may provide a first step towards understanding of the thyroid function disruptive effects of PBDEs on marine bivalves and the underlying mechanism across taxonomic groups and phyla.

BACKGROUND The involvement of cytochrome P450 (CYP450) isozymes and the selenogenome in selenium-mediated protection against aflatoxin B1 (AFB1)-induced adverse effects in broilers remains unclear. OBJECTIVE This study was designed first to determine whether selenium could reduce AFB1-induced hepatotoxic effects and then to determine whether these effects were due to changes in the CYP450 isozymes and selenogenome expression in the liver of chicks. METHODS Male avian broilers (aged 120 d) were allocated to 4 groups with 5 replicates of 6 birds to be included in a 2-by-2 factorial trial in which the main factors included supplementation of AFB1 (

Disruption of the thyroid hormone (TH) system, an important mode of action, can lead to ecologically relevant adverse outcomes, especially during embryonic development. The present study characterizes the effects of disruption of TH synthesis on swim bladder inflation during zebrafish early-life stages using 2-mercaptobenzothiazole (MBT), a thyroid peroxidase (TPO) inhibitor. Zebrafish were exposed to different MBT concentrations until 120/168h post fertilization (hpf) and 32days post fertilization (dpf), in two sets of experiments, to investigate the effects of TPO inhibition on posterior and anterior swim bladder inflation respectively, as well as whole body thyroid hormone concentrations (triiodothyronine (T3) and its prohormone, thyroxine (T4)). At 120hpf, MBT did not directly impair posterior chamber inflation or size, while anterior chamber inflation and size was impaired at 32dpf. As previously shown in amphibians and mammals, we confirmed that MBT inhibits TPO in fish. Whole-body T4 decreased after MBT exposure at both time points, while T3 levels were unaltered. There was a significant relationship between T4 levels and the anterior chamber surface at 32dpf. The absence of effects on posterior chamber inflation can possibly be explained by maternal transfer of T4 into the eggs. These maternally derived THs are depleted at 32dpf and cannot offset TPO inhibition, resulting in impaired anterior chamber inflation. Therefore, we hypothesize that TPO inhibition only inhibits swim bladder inflation during late development, after depletion of maternally derived T4. In a previous study, we showed that iodothyronine deiodinase (ID) knockdown impaired posterior chamber inflation during early development. Our findings, in parallel with similar effects observed in fathead minnow (see part I, this issue) suggest that thyroid disruption impacts swim bladder inflation, and imply an important distinction among specific subtypes of TH disrupting chemicals. However, the existence of another - yet unknown - mode of action of MBT impacting swim bladder inflation cannot be excluded. These results can be helpful for delineating adverse outcome pathways (AOPs) linking TPO inhibition, ID inhibition and other TH related molecular initiating events, to impaired swim bladder inflation in fish during early life stages. Such AOPs can support the use of in vitro enzyme inhibition assays for predicting reduced survival due to impaired posterior and anterior chamber inflation.

Endocrine disrupting chemicals (EDCs) have been considered as one of the major contributors of growing burden of thyroid disorders across the globe, and most of these chemicals have the potential to disrupt thyroid hormones (THs) synthesis and other regulatory pathways of thyroid gland function. Butylparaben (BP), an established xenobiotic used as synthetic preservative, has not been thoroughly evaluated for its molecular mechanism of thyroid disrupting potential. We investigated the effects of BP on activity and gene expression of thyroid peroxidase (TPO) and type 1 iodothyronine deiodinase (D1) in female Wistar rats following subcutaneous exposure to BP at doses of 1, 5 and 10 mg/kg BW/day (expressed as BP1, BP5 and BP10 respectively) for 7 and 21 days. The results showed that BP1 and BP5 significantly increased serum T3/T4 ratio and TSH level, while BP10 reduced the level of T4 significantly without any apparent consequences on TSH and T3 levels. TPO activity in thyroid was significantly increased (p 0.05) at BP1 and BP5, but BP10 treatment showed no effect like 17β-estradiol (E2). After 7 days of exposure, BP reduced D1 activity in kidney in a dose-dependent manner, while decrease in D1 activity was significant only after dosing with BP1 for 21 days (p 0.05). Moreover, 7 and 21 days of BP exposure caused significant fold increase of Tpo mRNA levels in thyroid. In kidney, BP down-regulated the Dio1 gene (encodes D1) expression after 7 days, but significant fold increase was observed following 21 days of treatment. In conclusion, the present study revealed that BP exposure altered the transcriptional expression and activity of TPO and D1, where TSH reinforced possible association with TPO activity.