The protective effect of iodide intake adjustment and 1,25(OH)D supplementation in rat offspring following excess iodide intake

Abstract

Background: In this study, we aimed to investigate the effect of iodide intake adjustment, 1,25(OH) 2 D 3 supplementation, or both, on the thyroid gland of rat offspring. Methods: The offspring of female rats administered 100 times the normal dose of iodide (100 HI; 750 μg/d) during pregnancy and lactation were divided into four different treatment groups. They were either having their iodide intake adjusted from 100 HI to normal iodide intake (7.5 μg/day) or supplemented with 25-hydroxy vitamin D 3 [1,25(OH) 2 D 3 ; 5 μg·kg −1 ·day −1 ], or both, for 4 weeks. Thyroid sodium pertechnetate (Na 99m TcO 4 ) uptake percentages were measured using single-photon emission computed tomography, while serum levels of free triiodothyronine (FT3), free thyroxine (FT4), thyroglobulin antibody (TgAb), thyroid peroxidase antibody (TPOAb), and vitamin D3 (VD3) were monitored using enzyme-linked immunosorbent assay. The messenger ribonucleic acid expression of interleukin (IL)-17A, interferon gamma (IFN-γ), and IL-10 in the thyroid gland was measured using quantitative real-time polymerase chain reaction, while the protein expression of thyroid-hormone-receptor α1 (TRα1) and thyroid-hormone-receptor β1 (TRβ1) in the thyroid gland was detected using Western blotting. Haematoxylin and eosin (H & E) and immunofluorescence staining were also used to assess thyroid follicular structure and lymphocytic infiltration in the thyroid glands. Results: The immunofluorescence staining showed CD4 + co-localized with TRβ1 or the vitamin D receptor in thyroid gland cells of rats that were continuously treated with 100 HI. Following iodide adjustment, 1,25(OH) 2 D 3 supplementation, or both, an increase in serum levels of FT3, free thyroxine, and VD3, protein expression of TRα1 and TRβ1 in the thyroid gland cells, and Na 99m TcO 4 thyroid uptake percentages was observed. The mRNA expression levels of IL-17A and IFN-γ, decreased, while the mRNA expression levels of IL-10 increased in the thyroid cells of each treatment group, except the group with continuous 100 HI intake. Conclusion: Iodide adjustment, 1,25(OH) 2 D 3 supplementation, or both may increase the serum levels of FT3, FT4, and VD3, as well as the protein expression levels of TRα1 and TRβ1, in thyroid cells. In addition, iodide adjustment, 1,25(OH) 2 D 3 supplementation, or both, may potentially reverse the imbalance in pro-inflammatory and anti-inflammatory cytokines (IL-17A, IFN-γ, and IL-10) caused by 100 HI, which may be beneficial in improving Na 99m TcO 4 thyroid uptake percentages.