Nutrition Research Division, Food Directorate, Health Products and Food Branch, Health Canada, Ottawa, Ontario K1A 0K9, Canada.
Exp Biol Med (Maywood). 2013 Jun;238(6):623-30. doi: 10.1177/1535370213489488.
Soy consumption is associated with thyroid disorders such as hypothyroidism, goiter, and autoimmune thyroid disease (ATD) as well as increased iodine requirement in certain cases. However, the anti-thyroid component(s) in soy are yet to be identified and the molecular mechanism(s) involved remain unclear. This study examined the effects of soy isoflavones (ISF) on iodide uptake and expression of thyroglobulin (Tg) and sodium/iodide symporter (NIS) in thyrocytes. Fischer rat thyroid cells (FRTL) were treated with Novasoy (a soy alcohol extract containing 30% ISF) or major ISF aglycones or glycosides for 24 h. Iodide uptake was measured by a colorimetric assay. The protein level of Tg and NIS was measured by Western blotting. Cytotoxicity of tested compounds was determined by the MTT cell proliferation assay. Iodide uptake in FRTL cells was dose-dependently suppressed by Novasoy added into the cell culture (10, 25, or 50 µg/mL, P < 0.05). However, neither the major ISF aglycones nor glycosides alone or in combination had similar effects. Novasoy (up to 200 µg/mL) had no cytotoxic effect. Novasoy (1, 10, and 50 µg/mL) and genistein (1 and 10 µM) markedly increased the protein content of a 40 kDa Tg fragment (P40, a known autoimmunogen) and non-glycosylated NIS in the FRTL cells (P < 0.05). Overall, this study demonstrated that the alcohol soluble component(s) other than the major ISF in soy remarkably inhibited iodide uptake in the FRTL cells. Soy ISF, particularly genistein, induced the production of P40, which might be responsible for the higher incidence of ATD reported in soy infant formula-fed children.
大豆的摄入与甲状腺疾病有关，如甲状腺功能减退症、甲状腺肿和自身免疫性甲状腺疾病（ATD），以及某些情况下碘需求增加。然而，大豆中的抗甲状腺成分尚未被确定，涉及的分子机制仍不清楚。本研究探讨了大豆异黄酮（ISF）对甲状腺细胞碘摄取以及甲状腺球蛋白（Tg）和钠/碘转运体（NIS）表达的影响。用 Novasoy（一种含有 30%ISF 的大豆醇提取物）或主要 ISF 苷元或糖苷处理 Fischer 大鼠甲状腺细胞（FRTL）24 小时。通过比色法测定碘摄取。用 Western blot 法测定 Tg 和 NIS 的蛋白水平。用 MTT 细胞增殖试验测定测试化合物的细胞毒性。添加到细胞培养物中的 Novasoy（10、25 或 50μg/mL）呈剂量依赖性地抑制 FRTL 细胞的碘摄取（P<0.05）。然而，主要的 ISF 苷元单独或联合使用均没有类似的作用。Novasoy（高达 200μg/mL）没有细胞毒性作用。Novasoy（1、10 和 50μg/mL）和染料木黄酮（1 和 10μM）显著增加了 FRTL 细胞中 40 kDa Tg 片段（P40，一种已知的自身免疫原）和未糖基化 NIS 的蛋白含量（P<0.05）。总的来说，这项研究表明，大豆中除主要 ISF 以外的醇溶性成分显著抑制了 FRTL 细胞的碘摄取。大豆 ISF，特别是染料木黄酮，诱导 P40 的产生，这可能是大豆婴儿配方喂养的儿童中报道的 ATD 发生率较高的原因。
