Optimal iodine supplementation during antithyroid drug therapy for Graves' disease is associated with lower recurrence rates than iodine restriction.

OBJECTIVE: A relationship between iodine intake and the effectiveness of antithyroid drug (ATD) therapy for Graves' disease (GD) has been suggested, and strict restriction of iodine intake has been tried in the treatment of GD in some studies. However, it is unclear whether dietary iodine supplementation improves the prognosis of ATD therapy for GD. This study aimed to clarify whether optimal iodine supplementation during antithyroid drug therapy for GD is associated with lower recurrence rates than iodine restriction. METHODS: This was a prospective randomized trial of newly diagnosed patients with GD. Patients with newly diagnosed GD were recruited. After ATD therapy and strict dietary iodine restriction for 1 month, patients (n = 459) were randomly assigned to iodine-supplemented and iodine-restricted groups. After exclusion, 405 patients finally completed the study. The iodine-supplemented group included 203 patients (61 males and 142 females) with an average age of 32.2 ± 10.5 years (17-65 years), and the iodine-restricted group included 202 patients (61 males and 141 females) with an average age of 31.9 ± 11.8 years (16-64 years). Patients in the iodine-supplemented group were given about 10 grams of iodized salt every day, while the iodine-restricted group received noniodized salt with low-iodine or noniodine diet. The dietary iodine intervention lasted for 24 months. Urinary iodine concentration (UIC), thyrotropin receptor antibody (TRAb), free T3 (FT3), free T4 (FT4) and thyrotropin (TSH) of 2 groups were measured every 3 months. The recurrence rates within 12 months after withdrawal of ATD were evaluated. RESULTS: UIC in the iodine-supplemented group was within the recommended range for optimal iodine intake (135-162 µg/L) and was significantly higher than that in iodine-restricted group (30-58 µg/L). Within 12 months of withdrawal of ATD, the total recurrence rate in the iodine-supplemented group was 35.5%, significantly lower than in the iodine-restricted group, which was 45.5%. CONCLUSION: Optimal dietary iodine supplementation during antithyroid drug therapy for GD is associated with lower recurrence rates than iodine restriction, and therefore, diet control with strict iodine restriction might be an adverse factor in the management of GD.

Iodinated TG in Thyroid Follicles Regulate TSH/TSHR Signaling for NIS Expression.

Our previous research has suggested that high degree of iodinated thyroglobulin (TG) may inhibit the expression and function of sodium iodide symporter (NIS), but the underlying mechanism remains unclear. In present study, we discuss a newly constructed follicle model in vitro, which was used to simulate the follicular structure of the thyroid and explore the regulatory roles of iodinated TG in the follicular lumen on NIS expression. The results showed that both NIS expression and PKA activity were increased in lowly iodinated TG group, while decreased NIS expression with increased PKC activity was found in highly iodinated TG group. Also, NIS expression was increased in PKA agonist-treated group, while decreased NIS was found in PKC agonist-treated group. Moreover, when the PLC-PKC pathway was blocked by PKC-specific inhibitor, highly iodinated TG significantly promoted the expression of NIS. However, when the cAMP-PKA pathway was blocked by a PKA-specific blocker, highly iodinated TG slightly suppressed NIS expression. TG with a low degree of iodination had the reverse effect on NIS. When the PLC-PKC pathway was blocked, TG with a low degree of iodination slightly promoted NIS expression. However, when the cAMP-PKA pathway was blocked, TG with a low degree of iodination greatly inhibited NIS expression. All these suggested that iodinated TG inhibited the expression of NIS by PLC-PKC pathway and promoted NIS expression via the cAMP-PKA pathway. When highly iodinated TG was present, the PLC-PKC pathway became dominant. In the presence of lowly iodinated TG, the cAMP-PKA became the major pathway.

Iodinated TG in Thyroid Follicular Lumen Regulates TTF-1 and PAX8 Expression via TSH/TSHR Signaling Pathway.

Our previous study showed that highly iodinated thyroglobulin (TG) inhibited thyroid transcription factor-1 (TTF-1) and paired box gene 8 (PAX8) expression, but the potential mechanism remains unclear. In this study, we constructed a thyroid follicle model in vitro to mimic its natural physiological structure and explored how iodinated TG in the follicular lumen tuned TTF-1 and PAX8 expression. Our data showed that lowly iodinated TG enhanced PKA activity while upregulation of both TTF-1 and PAX8 expression; and that highly iodinated TG triggered PKC activity while suppression of TTF-1 and PAX8 expression. Further, PKA agonist alone could increase TTF-1 and PAX8 expression while PKC agonist decreased TTF-1 and PAX8 level. If blocking PLC-PKC pathway using PKC-specific inhibitor, highly iodinated TG significantly promoted the expressions of TTF-1 and PAX8, and similarly PKA-specific blocker moderately inhibited TTF-1 and PAX8 expression. And opposite tendencies of TTF1 and PAX8 aberrant expression were observed in the condition of low iodinated TG when blocking PLC-PKC and cAMP-PKA signaling pathways. Our results indicated that iodinated TG manipulated TTF-1 and PAX8 expression through PLC-PKC and cAMP-PKA pathways, and highly iodinated TG played inhibitory role via PLC-PKC pathway from the TTF1 and PAX8 perspective while low level of iodinated TG was an activator through cAMP-PKA pathway. Our findings proved that iodinated TG in thyroid follicular lumen regulated TTF-1 and PAX8 expression through thyroid stimulating hormone/thyroid stimulating hormone receptor (TSH/TSHR) mediated cAMP-PKA and PLC-PKC signaling pathways. J. Cell. Biochem. 118: 3444-3451, 2017. © 2017 Wiley Periodicals, Inc.

Low Iodine in the Follicular Lumen Caused by Cytoplasm Mis-localization of Sodium Iodide Symporter may Induce Nodular Goiter.

Iodine is a key ingredient in the synthesis of thyroid hormones and also a major factor in the regulation of thyroid function. A local reduction of iodine content in follicular lumen leads to overexpression of local thyroid-stimulating hormone receptor (TSHr), which in turn excessively stimulates the regional thyroid tissue, and result in the formation of nodular goiter. In this study, we investigated the relationship between iodine content and sodium iodide symporter (NIS) expression by using the clinical specimens from patients with nodular goiter and explored the pathogenesis triggered by iodine deficiency in nodular goiter. In total, 28 patients were clinically histopathologically confirmed to have nodular goiter and the corresponding adjacent normal thyroid specimens were harvested simultaneously. Western blot and immunohistochemistry were performed to assay NIS expression and localization in thyrocytes of both nodular goiter and adjacent normal thyroid tissues. NIS expression mediated by iodine in follicular lumen was confirmed by follicular model in vitro. Meanwhile, radioscan with iodine-131were conducted on both nodular goiter and adjacent normal thyroid. Our data showed that NIS expression in nodular goiter was significantly higher than that in adjacent normal tissues, which was associated with low iodine in the follicular lumen. Abnormal localization of NIS and lower amount of radioactive iodine-131 were also found in nodular goiter. Our data implied that low iodine in the follicular lumen caused by cytoplasm mis-localization of NIS may induce nodular goiter.

Glycolysis-associated enzymes existing in the follicular lumen of the thyroid may interfere with energy metabolism.

Synthesis and storage of the thyroid hormone precursor, thyroglobulin (TG), occurs within the follicular lumen of the thyroid and the TG is then absorbed into cells for further processing before release into the blood. However, the mechanism of energy metabolism in the follicular lumen of the thyroid remains unknown. In the present study, the three dimensional structure of thyroid follicles was constructed using a primary culture of swine cells and the follicular protein was identified via matrix-assisted laser desorption/ionization-time of flight mass spectrometry. Three glycolysis-associated enzymes, enolase, pyruvate kinase and phosphoglyceraldehyde dehydrogenase were identified in addition to TG. These results support the hypothesis that anaerobic glycolysis of glucose exists in the follicle and supports energy consumption for hormone synthesis.

Upregulation of TSHR, TTF-1, and PAX8 in Nodular Goiter Is Associated with Iodine Deficiency in the Follicular Lumen.

Objective. It has been testified that iodine regulates thyroid function by controlling thyroid-restricted genes expression and is closely related to diffuse goiter and thyroid dysfunction. However, the effects of follicular lumen iodine, the main form of iodine reserve in the body, on thyroid-restricted genes in nodular goiter are poorly understood. In this study, correlations between follicular lumen iodine and the expressions of thyroid stimulating hormone receptor (TSHR), its transcription factors TTF-1, and PAX8 in nodular goiter were investigated. Patients. In this study, 30 resection specimens clinically histopathologically confirmed to have nodular goiter and 30 normal thyroid specimens from adjacent tissues of nodular goiter are used. Measurement. Western blot immunohistochemistry was performed to assay TSHR, TTF-1, and PAX8 in thyrocytes of nodular goiter as well as in extranodular normal thyroid tissues. Meanwhile, follicular lumen iodine of both nodular goiter and extranodular normal thyroid tissues was detected as well. Results. The TSHR, TTF-1, and PAX8 in nodular goiter were significantly higher than those in the controls. The iodine content in nodular goiter was significantly lower than those in control tissues. Conclusion. Upregulation of TSHR, TTF-1, and PAX8 is associated with low follicular lumen iodine content in nodular goiter.

Presence of free triiodothyronine and free thyroxine in thyroid follicles may be correlated with the quick secretion of thyroid hormones under certain physiological conditions.

Thyroid cells are polarized and the follicle structure, consisting of follicle epithelial cells, is a prerequisite for thyroid hormone synthesis. However, a reliable in vitro model simulating thyroid function is not currently available. To the best of our knowledge, the present study reports for the first time a simulated follicle by inoculation of human thyroid cells on the filter in a Transwell plate to maintain the polarity of thyroid cells. The iodine uptake was analyzed by arsenic and cerium catalysis spectrophotometry, as well as the secretion of free triiodothyronine (FT3) and free thyroxine (FT4) by direct chemiluminescence. The data showed that thyroid cells growing in the Transwell chamber synthesized and secreted FT3 and FT4, while the monolayer cells directly seeded in the 6-well-plate did not produce these two thyroid hormones. Regarding the iodine uptake, cells in the Transwell chamber demonstrated a markedly higher capability than the monolayer cells. The data proved that the polarity of thyroid cells could be restored using the Transwell plate, which was critical for iodine uptake and thyroid hormone synthesis. The presence of FT3 and FT4 in follicles may be correlated with the quick secretion of thyroid hormones under certain physiological conditions.

[Association between polymorphisms in pigment epithelium-derived factor gene promoter region and non-alcoholic fatty liver disease in type 2 diabetes mellitus].

OBJECTIVE: To investigate the association of serum pigment epithelium-derived factor (PEDF) level and polymorphisms in PEDF gene promoter region -358G→A with non-alcoholic fatty liver disease (NAFLD) in patients with type 2 diabetes mellitus (T2DM) of Han Nationality in Fujian Province. METHODS: A total of 282 T2DM patients with NAFLD (DM1 group) and 170 age- and gender-matched T2DM patients without NAFLD (DM2 group) were examined for PEDF gene SNP-358G→A polymorphisms using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Serum pigment epithelium-derived factor(PEDF) level, fasting plasma glucose (FPG), fasting insulin (FINS) and glycosylated hemoglobin (HbA1c) were also measured. RESULTS: The patients in DM1 group showed a significantly higher mean level of serum PEDF than those in DM2 group (P<0.05). Logistic regression analysis revealed that PEDF level was an independent risk factor for NAFLD in T2DM. The frequencies of PEDF gene -358G→A genotypes (GG, GA, and AA) and alleles (G/A) differed significanly between DM1 and DM2 groups (P<0.05). In terms of PEDF gene SNP -358G→A alleles, the GA genotype carriers had a 2.032 times higher risk of developing NAFLD compared with the GG genotype carriers, and the risk increased to 2.068 times in the carriers of the A allele (GA and AA genotypes; P<0.05). CONCLUSION: Serum PEDF level is an independent risk factor of NAFLD in T2DM. Elevated serum PEDF level is a protective factor against insulin resistance. In T2DM patients, PEDF gene promoter region -358G→A polymorphism is associated with NAFLD, and the A allele contributes to an increased risk of NAFLD.

Intracellular iodinated compounds affect sodium iodide symporter expression through TSH-mediated signaling pathways.

The mechanisms by which thyroid stimulating hormone (TSH) regulates the expression and activity of sodium iodide symporter (NIS) through cAMP-PKA have been partially elucidated by many studies. However, the effects of the TSH-mediated PLC-IP3 signaling pathway on the expression of NIS and how intracellular iodinated compounds interfere with these signaling pathways are poorly understood. In this study, we investigated the effects of the TSH-mediated cAMP-PKA and PLC-IP3 pathways on the expression of NIS in the presence of various intracellular iodinated compounds. The intracellular iodinated compounds were formed by treating cells with different concentrations of iodine with or without methimazole (MMI), an inhibitor of iodine organification, in a pig monolayer thyrocyte in vitro. A high concentration of iodine increased NIS expression at the mRNA and protein levels; however, this phenomenon was not observed in the presence of MMI. Both the cAMP-PKA and PLC-IP3 signaling pathways inhibited the expression of NIS at low iodine concentrations; however, in thyrocytes treated with high concentrations of iodine, the effect of cAMP-PKA on the expression of NIS changed from inhibition to promotion, while the PLC-IP3 pathway continued to inhibit NIS expression. These findings indicate that intracellular iodinated compounds affect NIS expression through the TSH-mediated cAMP-PKA and PLC-IP3 pathways.

Upregulation of thyroid transcription factor-1 and human leukocyte antigen class I in Hashimoto's disease providing a clinical evidence for possible triggering autoimmune reaction.

OBJECTIVE: An increase in the expression of autoantigens and their presenting molecules human leukocyte antigen (HLA) class I has been demonstrated to be responsible for autoimmune diseases. Thyroid transcription factor-1 (TTF-1 or NKX2-1) synchronously upregulates both HLA class I and thyroid-specific autoantigen, which may be involved in the pathological process of autoimmune thyroiditis. In this study, the expressions and potential role of TTF-1 and HLA class I in Hashimoto's disease (HT) were examined. PATIENTS: In this study, 22 resection specimens clinically and histopathologically confirmed to have Hashimoto's disease and 30 normal thyroid specimens from adjacent tissues of thyroid adenoma were used. MEASUREMENT: Western blot, real-time PCR, and immunohistochemistry were performed to assay TTF-1 and HLA class I in the thyrocytes of Hashimoto's disease as well as in the normal thyroid from adjacent tissues of thyroid adenoma. RESULTS: The TTF-1 and HLA class I in Hashimoto's disease were significantly higher than those in the controls. CONCLUSION: Upregulation of TTF-1 and HLA class I in Hashimoto's disease provide a clinical evidence for possible triggering of autoimmune reaction.

Inhibition of thyroid-restricted genes by follicular thyroglobulin involves iodinated degree.

Follicular thyroglobulin (TG) reflects the storage of both iodine and thyroid hormone. This is because it is a macromolecular precursor of thyroid hormone and organic iodinated compound in follicular lumen. Thus, it may have an important feedback role in thyroid function. In this study, monolayer cells were cultured and follicles were reconstituted with primary pig thyroid cells in vitro. Reconstituted follicles were treated with iodine and methimazole (MMI), a drug that blocks iodine organification and reduces the degree of TG iodination in follicular lumen. The high degree of iodinated TG in follicular lumen was observed to inhibit thyroid-restricted gene expression. To confirm this finding, monolayer thyroid cells were treated with a different degree of TG iodination at the same concentration. These iodinated TG were extracted from reconstituted follicles of different groups. In this manner, this study provides firsthand evidence suggesting that follicular TG inhibits the expressions of thyroid-restricted genes NIS, TPO, TG, and TSHr.