ABSTRACT
Objective To observe the effect of long-term intake of low iodine diet on thyroid morphological structure and sodium iodine transporter (NIS) in parental and second filial generation rats, and to explore the changes of NIS protein expression in iodine deficiency disease (IDD), so as to further verify and explore the mechanism of IDD. Methods Referring to "Nutritional Composition of Experimental Animals With Feed" (GB 14924.3-2010), the crops widely planted and with high edible rate in the traditional cretinism epidemic area of Xinjiang were used as the main feed components to prepare different levels of iodine (low iodine groups 1 and 2 feed the iodine contents were about 50 and 20 μg/kg). The IDD rat model was established by the three-generation two-nest method, that is, 132 SPF Wistar rats were selected after weaning, half males and half females, randomly divided into 3 groups according to body mass by random number table method: control group (N, 52 rats, 22 females, 30 males, the iodine content was about 300 μg/kg), low iodine groups 1 and 2 (LⅠ, LⅡ, 40 rats, 22 females, 18 males in each group). Twelve rats in each group were sacrificed at the end of 3, 6, 9 months, respectively, half males and half females. The relative weight of thyroid was calculated and the gross structure and microscopic pathology were observed. The expression of NIS protein was determined by Western blotting. At the end of 3 months after feeding, four female rats in each group were selected to mate with male rats in group N in 1 : 1, and the newborn mice were fed the same way for three months and then subcultured again. The rat generation continued to be fed according to the mother group, and 10-12 rats were sacrificed at the end of 3, 6, 9 months, respectively, and the specimens and observation indexes results were collected same as the parental rats. Results The relative weight of the thyroid in parental LⅠand LⅡ groups were higher than those in the N group at 6 and 9 months [female:(19.67 ± 5.60), (23.81 ± 4.08) vs (10.14 ± 1.20);(22.24 ± 2.06), (33.51 ± 3.24) vs (9.80 ± 1.96);male:(13.0 ± 3.70), (13.84 ± 4.08) vs (5.90 ± 1.20);(14.20 ± 2.67), (19.98 ± 2.84) vs (6.06 ± 0.76), P < 0.05], the females were higher than the males at 3, 6, 9 months (P<0.05). The relative weight of the thyroid in second filial generation LⅠand LⅡgroups were higher than that in the N group at 3, 6 and 9 months (P < 0.05). Except the 6 month LⅠ group, the relative weight of thyroid in the other groups was higher than that in the male (P<0.05). In prolonged iodine-deficiency process, LⅠ and LⅡ groups, the color of the thyroid gland for parental and second filial generation rats appeared darkening, hyperemia and swelling. At the same time, microscopic pathology showed that the thyroid gland of different generations showed increased follicles and smaller follicular cavities. Epithelial cell hyperplasia and interstitial fibrosis and interstitial inflammatory cell infiltration at the end of 9 months were observed. At 3, 6, and 9 months after low iodine, the expression of NIS protein in the LⅠ and LⅡ parental and second filial generation rats was higher than that in the N group (P<0.05). Conclusions Long-term low iodine in different levels of feed can cause compensatory thyroid enlargement and hyperplasia in both parental and offspring rats, the expression of NIS protein has continued to rise.
ABSTRACT
Objective: To study the effect of iodine deficiency on body weight, food consumption, and food utilization rate of second filial generation Wistar rats. Methods: According to the food pattern of a high-iodine deficient population, two types of low-iodine food have been produced using the main crops grown in this area (iodine levels of 50 and 20 µg/kg, respectively). Wistar rats were randomly divided into three groups, normal iodine group (NI group), low-iodine group one (LI group) and low-iodine group two (LII group), using the random number table method and fed diets containing 300, 50, and 20 µg/kg of iodine, respectively. Parental generation rats were fed until they reached reproductive age; first filial generation rats were allocated to the same diet as their mothers. After 3 months of feeding, first filial generation rats gave birth to second filial generation rats; second filial generation rats were allocated to the same diet as their mothers. After feeding for 90, 180, and 270 days, rats were sacrificed. One-way analysis of variance was used to analyze body weight, food intake, and food utilization rate data collected during the time of feeding and blood iodine hormone level, which was determined after sacrifice. Results: The LI and LII groups generally demonstrated decreased activity, slow reaction, and growth retardation compared with the NI group. After 270 days, the urine iodine levels of the LI and LII groups were 1.7 and 0.2 µg/L, respectively, which were significantly lower than the NI group (255.2 µg/L) (P<0.001). Additionally, the weight of female rats in the LI and LII groups were (288.1±10.5) and (275.7±2.7) g, respectively, which was significantly lower than that of the NI group ((311.0±2.3) g) (P<0.001). The weight of male rats were (446.0±4.6) and (451.8±19.1) g, respectively, which were significantly lower than that of the NI group ((517.2±7.8) g) (P<0.001). In the LI and LII groups, food intake of female and male rats after 270 days were (465.0±27.7), (658.4±28.6) and (423.0±13.2), (548.0±18.8) g, respectively, which were significantly lower than that of the NI group ((499.5±21.8), (760.8±33.0) g) (P<0.001). Moreover, the food utilization rate of female rats in the LI and LII groups was (8.7±0.4)% and (6.0±0.58)%, which was lower than that of the NI group ((11.7±3.5)%) (P<0.001); similarly, male rats showed rates of (8.9±1.5)% and (6.9±1.31)%, respectively, which were lower than that of the NI group ((13.7±3.0)%) (P<0.001). After 270 days, the level of T3 in the LI and LII groups were (0.45±0.10) and (0.34±0.15) ng/ml, respectively, which was significantly lower than that of the NI group ((0.91±0.49) ng/ml) (P<0.01). Moreover, the level of T4 were (69.02±27.87) , (53.18±13.53) ng/ml in LI and LII groups, respectively, which was lower than that of the NI group ((76.69±29.42) ng/ml) (P<0.05). Conclusion: This study indicated that iodine deficiency induced by a long-term low-iodine diet can cause changes in weight, food intake, and food utilization rate among second filial iodine deficiency rats. More importantly, the iodine content in low-iodine food impacts these parameters.
