哺乳期大鼠乳腺组织磷脂酰肌醇-3激酶-蛋白激酶B信号通路对摄碘功能的影响

Effects of phosphatidylinositol-3 kinase-protein kinase B signaling pathway on iodine-intake ability of lactating rats

目的观察不同碘营养水平下大鼠乳腺组织磷脂酰肌醇-3激酶（P13K）、蛋白激酶B（AKT）、钠碘转运体（NIS）mRNA和蛋白的表达，以及血清胰岛素样生长因子I（IGF-1）的变化，探讨该通路在哺乳期乳腺摄碘过程中所起到的作用。方法Wistar大鼠130只（雌鼠100只，雄鼠30只），按体质量采用随机数字表法将雌鼠分为5组：①对照组（NI组），普通饲料＋含碘50μg／L去离子水；②低碘1组（L11组），低碘饲料＋去离子水；⑧低碘2组（L12组），低碘饲料＋含碘5μg／L去离子水；④高碘1组（H11组），普通饲料＋含碘3000μg／L去离子水；⑤高碘2组（H12组），普通饲料＋含碘10000μg／L去离子水。每组20只，饲养3个月后，将雌鼠与雄鼠合笼，交配后，取出雄鼠，每只雌鼠单独喂养，在产后10d时，采集尿样，测定哺乳期大鼠尿碘，处死后取哺乳期大鼠的血液、乳腺组织。酶联免疫吸附法测定哺乳期大鼠血清IGF-1水平；实时荧光定量PCR法检测乳腺P13K、AKT、NISmRNA表达；蛋白印迹法检测乳腺P13K、总AKT、磷酸化AKT（p—AKT）和NIS蛋白表达。结果L11、L12组哺乳期大鼠尿碘中位数（3．16、6．36μg／L）明显低于NI组（162．59μg／L），H11、H12组（2356．27、11507．29μg／L）明显高于NI组，差异均有统计学意义（P均〈0．01）。与NI组[（8．84±2．12）μg／L]比较，L11、L12组哺乳期大鼠血清IGF-1含量[（13．30±2．37）、（10．90±1．92）μg／L]明显升高（P均〈0．01）。实时荧光定量PCR法检测结果显示．哺乳期大鼠乳腺组织NIS、AKT、P13KmRNA表达组间比较差异有统计学意义（F=14．916、36．477、14．994，P均〈0．01）。其中NISmRNA表达在L11、L12组（0．75±0．40、0．89±0．51）明显高于NI组（0．53±0.31），H12组（0．30±0．24）明显低于NI组（P〈0．05或〈0．01）；AKTmRNA表达在U1、U2组（0．90±0．19、0．64±0．22）均明显高于NI组（0．43±0．22），H12组（0．29±0．15）明显低于NI组（P〈0．05或〈0．01）；P13KmRNA表达在U1组（0．85±0．42）明显高于NI组（0．50±0．24），H12组（0．28±0．10）明显低于NI组（P均〈0．01）。蛋白印迹法检测结果显示，哺乳期大鼠乳腺NIS蛋白表达组间比较差异有统计学意义（F=4．510，P〈0．01），其中L11组（1．67±0．97）明显高于NI组（0．87±0．43，P〈0．05）；p-AKT蛋白表达组间比较差异有统计学意义（F：3．528，P〈0．05），其中H12组（1．10±0．30）明显高于NI组（0．75±0．23，P〈0．05）；总AKT、P13K蛋白表达组间比较差异无统计学意义（F=0．558、1．319，P均〉0．05）。结论P13K—AKT信号通路对乳腺NIS表达的抑制作用弱于碘摄入量本身的作用．而功能性p-AKT表达量随着碘浓度的逐渐增加呈上升趋势，表现出抑制哺乳期乳腺NIS表达的作用。

Objective To observe the variation of phosphatidylinositol-3 kinase （PI3K）, protein kinase B （AKT）, sodium iodide symporter （NIS） mRNA and protein expression in rat mammary tissues and serum insulin growth factor I （IGF-1） under different iodine nutrition levels, and to study the role of PI3K-AKT signaling pathway in the process of mammary gland intaking iodine during lactation period. Methods Totally 130 Wistar rats （100 female rats, 30 male rats） were randomly divided into five groups with 20 female rats in each group： （1）control group （NI）： was feed with normal diet and iodine content 50 μg/L in deionized water; （2）low iodine group 1 （LI1 group）： was feed with low iodine diet and deionized water;, （3）low iodine group 2 （LI2）： was feed with low iodine diet and iodine content 5 μg/L in deionized water; （4）high iodine group 1 （HI1 group）： was feed with normal diet and iodine content 3 000 μg/L in deionized water; （5）high iodine group 2 （HI2）： was feed with normal diet and iodine content 10 000 μg/L in deionized water. After feeding for 3 months, females were mated with male rats, then male rats were taken out and every female rat was feed individually. Urinary iodine level of rats in lactation period 10 days after giving birth was tested. Blood and mammary tissue samples of rats in lactation period were taken after killing them. Enzyme linked immunosorbent assay （ELISA） was used to detect serum IGF-1 level, real-time fluorescence quantification PCR to detect the mRNA expression of mammary gland PI3K, AKT and NIS, Western blotting to detect mammary gland PI3K, total AKT, phosphorylation AKT （p-AKT） and NIS protein expression. Results The medians urinary iodine of lactation period rats in LI1 and LI2 （3.16, 6.36 μg/L） were significantly lower than that in NI group （162.59 μg/L）, and were significantly higher in HI1 and HI2 （2 356.27, 11 507.29 μg/L） than that in NI group. The differences were statistically significant （all P 〈 0.01）. Compared with control group [（8.84± 2.12） μg/L], the content of serum IGF-1 increased significantly in lactation period rats in LI1 and LI2 groups [（13.30 ±2.37） and （10.90 ± 1.92） μg/L, all P 〈 0.01]. The real-time fluorescence quantification PCR detection results indicated that the differences were statistically significant by comparing NIS, AKT, PI3K mRNA expression of the mammary tissues of lactation period rats in the five groups （F = 14.916, 36.477, 14.994, all P 〈 0.01）. Among them, NIS mRNA expression quantities in LI1 and LI2 groups （0.75 ± 0.40, 0.89 ± 0.51） were significantly higher than that in NI group （0.53 ±0.31）, and significantly lower in HI2 group （0.30 ± 0.24） than that in NI group （P 〈 0.05 or 〈 0.01）. AKT mRNA expression quantities in LI1 and LI2 groups （0.90 ± 0.19, 0.64 ± 0.22） were significantly higher than that in NI group （0.43 ± 0.22）, and significantly lower in HI2 group （0.29 ＋ 0.15） than that in NI group （P 〈 0.05 or 〈 0.01）. PI3K mRNA expression quantity in LI1 group （0.85± 0.42） was significantly higher than that in NI group （0.50 ±0.24）, and significantly lower in HI2 group （0.28 ± 0.10） than that in NI group （all P 〈 0.01）. Western blot detection results indicated that the differences were statistically significant by comparing mammary gland NIS protein expression of lactation period rats in the five groups （F = 4.510, P 〈 0.01）. Among them, LI1 group （1.67 ± 0.97） was significantly higher than NI group （0.87±0.43, P 〈 0.05）. The differences were statistically significant by comparing the p-AKT protein expression among groups （F = 3.528, P 〈 0.05）. Among them, HI2 group （1.10 ± 0.30） was significantly higher than NI group （0.75 ± 0.23, P 〈 0.05）. The differences were not statistically significant by comparing total AKT and PI3K protein expression among groups （F = 0.558, 1.319, all P 〉 0.05）. Conclusion The inhibitory effect of PI3K-AKT signaling pathways on NIS in the mammary gland was weaker than the effect of iodine intake. But the expression of functional p-AKT was gradually increased with the increment of iodine intake, which had been presented inhibit effect on NIS expression in lactating mammary gland.