| Objective To study the effects of different iodine intake on thyroid function and the protein expression and the methylation of 5'-Cp G island in the promoter region of sodium iodine transporter(NIS)gene in rats,and to explore whether iodine affects the expression level of NIS through regulating the methylation of NIS gene.Methods Forty female SD rats were randomly divided into five groups with 8 rats in each group.The rats in NI group(control)were fed with normal content of iodine,and the rats in LI group,5HI group,10 HI Group and 20 HI group were fed with water with different amounts of potassium iodide.After 3 months,the animals were sacrificed,and urine samples of the rats were collected in a metabolic cage for 24 h.Then the rats were anesthetized by intraperitoneal injection of chloral hydrate.Blood was collected from the inferior vena cava to collect serum.The thyroid glands were stripped and stored in liquid nitrogen.Inductively coupled plasma mass spectrometry(icp-ms)was used to measure urine iodine,and the positive correlation between urine iodine and the dose of iodine suggested that the experiment was successful.All serum samples were tested for free triiodothyronine(FT3),free thyroxine(FT4),and thyroid stimulating hormone(TSH),using chemiluminescent detection technology;The expressions of NIS protein in the rats,thyroid tissues were determined by immunohistochemical staining;The status of 5?-Cp G island promoter methylation of NIS gene in the rats' thyroid tissues was detected by Bisulfite Sequencing PCR(BSP).Results1 It was found that the median urine iodine of the five groups of rats was positively correlated with iodine intake,indicating that the model was successful,however,compared with the normal iodine group,the median urine iodine in the 5-fold,10-fold and 20-fold high iodine group did not reach the corresponding multiple difference.2 Compared with the iodine-adapted group,the serum FT3 concentration of the low-iodine group and the high-iodine group decreased,and the difference was significant(P < 0.05).Compared with the iodine-adapted group,the serum FT4 in the low-iodine group and the high-iodine group was not statistically significant(P >0.05).There was no significant difference in TSH levels between groups(P > 0.05).3 The expression level of NIS in thyroid tissues of the LI group was higher than that of the NI group,with statistically significant difference(P < 0.05),while that of the5 HI group was lower than that of the NI group,with no statistically significant difference(P > 0.05),while that of the 10 HI group and the 20 HI group was lower than that of the NI group(P < 0.01);4 There was no significant difference in Cp G1 methylation ratio and Cp G2 methylation ratio between the groups(P > 0.05).Further study on the sequence of-420 to-110 nucleotides in the NIS promoter region(Cp G3)showed that compared with the normal iodine group,the methylation ratio of Cp G3 in the low-iodine group and the high-iodine group decreased,but the difference was not statistically significant(P > 0.05).Conclusion(1)Either excessive iodine or iodine deficiency can cause iodine nutritional disorders,different iodine intake can affect thyroid hormone levels in rats.(2)The results of this experiment show that there is no significant difference in the methylation status of the 5?-Cp G island promoter region of sodium Iodide symporter gene in rats,but the expression level of NIS in different iodine nutrition groups is different,which suggests that iodine may regulate the protein expression of NIS through other mechanisms.In addition to DNA methylation,epigenetics also has histone modification,non-coding RNA and other pathways,so other pathways need to be further explored. |
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