It has been shown that circular RNAs, a class of non-coding RNA molecules, play an important role in the regulation of glucose and lipid homeostasis. In the present study, we sought to investigate the function of circular RNA HIPK3 (circHIPK3) in diabetes-associated metabolic disorders, including hyperglycemia and insulin resistance. Results show that oleate stimulated circHIPK3 increase, and that circHIPK3 enhanced the stimulatory effect of oleate on adipose deposition, triglyceride (TG) content, and cellular glucose content in HepG2 cells. MiR-192-5p was the potential target of circHIPK3, since circHIPK3 significantly decreased miR-192-5p mRNA level, whereas anti-circHIPK3 significantly increased miR-192-5p mRNA level. Further study shows that transcription factor forkhead box O1 (FOXO1) was a downstream regulator of miR-192-5p, since miR-192-5p significantly decreased FOXO1 expression, whereas circHIPK3 significantly increased FOXO1 expression. Notably, the inhibitory effect of miR-192-5p was significantly reversed by circHIPK3. In vivo study shows that anti-miR-192-5p significantly increased blood glucose content, which was significantly inhibited by FOXO1 shRNA. MiR-192-5p significantly decreased adipose deposition and TG content in HepG2 cells, which was significantly reversed by the co-treatment with circHIPK3. Forskolin/dexamethasone (FSK/DEX) significantly increased cellular glucose, mRNA level of phosphoenolpyruvate carboxykinase (PEPCK) and glucose 6-phosphatase (G6Pase), and this stimulatory effect of FSK/DEX was significantly inhibited by miR-192-5p. In the presence of circHIPK3, however, the inhibitory effect of miR-192-5p was totally lost. In summary, the present study demonstrated that circHIPK3 contributes to hyperglycemia and insulin resistance by sponging miR-192-5p and up-regulating FOXO1.

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.

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.

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.

Abstract. 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.