高碘暴露儿童智商与单胺类神经递质的关系研究

Relationship between Intelligence Quotient and Monoamine Neurotransmitters in Children Exposed to Excessive Iodide

目的探讨高碘对儿童智力和单胺类神经递质的影响以及单胺类神经递质与智商高低的关系。方法根据水中碘化物质量浓度从天津市滨海新区和静海区中选取适碘地区(10μg/L≤水中碘化物质量浓度<150μg/L)、高碘一区(150μg/L≤水中碘化物质量浓度<300μg/L)和高碘二区(水中碘化物质量浓度≥300μg/L),按照整群随机抽样的方法从中抽取399名(7～12)岁儿童,采用《中国联合型瑞文测验》(中国农村版)测定儿童智商,采用ELISA测定血浆单胺类神经递质多巴胺(DA)、5-羟色胺(5-HT)、去甲肾上腺素(NE)和肾上腺素(E)的含量。结果高碘二区儿童的IQ值为109. 59±14. 24,低于适碘地区和高碘一区儿童,差异有统计学意义(均P<0. 05)。高碘二区儿童的DA质量浓度为(321. 69±104. 95) ng/m L,高于适碘地区和高碘一区,5-HT质量浓度为(142. 62±71. 64) ng/m L,比另外两个地区质量浓度低,差异均有统计学意义(均P<0. 05)。而NE和E的含量在3组地区无统计学差异(均P>0. 05)。阈值分析显示碘暴露与DA呈明显的非线性关系,当儿童尿碘水平在492. 75μg/L以下,血浆DA质量浓度随尿碘水平的升高而明显升高。DA与IQ也呈明显的非线性关系,当儿童DA质量浓度小于80. 0 ng/m L,体内DA每升高1 ng/m L,智商升高0. 1分;当DA质量浓度在(80. 0～359. 8) ng/m L范围内,DA每升高1 ng/m L,智商降低0. 1分。而尿碘对5-HT、NE和E的影响以及5-HT、NE和E与智力的关系均未见显著的线性关系或阈值效应。结论碘暴露过多儿童的DA代谢紊乱可能与其智商降低有关,且DA与智商存在阈值效应。

Objectives To explore the effect of iodide excess on children’s intelligence quotient(IQ)and monoamine neurotransmitters as well as investigate the relationship between monoamine neurotransmitters and IQ.Methods Normal iodide region(10μg/L≤water iodide<150μg/L),No.1 iodide-excess region(150μg/L≤water iodide<300μg/L),and No.2 iodide-excess region(iodide in water≥300μg/L)were selected from Binhai New Area and Jinghai District in Tianjin City according to the concentrations of iodine in drinking water.Via cluster random sampling,399 children aged from(7~12)years were chosen.Intelligence quotient of children was measured using the Combined Raven’s Test-The Rural in China(CRT-RC).The levels of monoamine neurotransmitters,including dopamine(DA),5-hydroxytryptamine(5-HT),norepinephrine(NE),and epinephrine(E),were measured using ELISA test.Results Children’s IQ in No.2 iodide-excess region was 109.59±14.24,which was significantly lower than that in normal iodide region and No.1 iodide-excess region,and the difference was statistically significant(all P<0.05).The level of DA of children in No.2 iodide-excess region(321.69±104.95)ng/m L was higher than that of DA in normal iodide region and No.1 iodide-excess region,while the level of 5-HT of children in No.2 iodide-excess region(142.62±71.64)ng/m L was lower than that of 5-HT in other two regions,and the differences were statistically significant(all P<0.05).While there was no significant difference in the levels of NE and E among the three regions(all P>0.05).Threshold analysis showed that there was a significant nonlinear relationship between iodide exposure and DA.The level of plasma DA increased significantly with the increase of urinary iodide in children with urinary iodide levels below 492.75μg/L.There is also a significant nonlinear relationship between DA and IQ.Every 1 ng/m L increment in the level of DA was associated with a raise of 0.1 in the IQ score when DA level was below 80 ng/m L in children.In contrast,every 1 ng/m L increment in the level of DA was associated with a decline of 0.1 in the IQ score when DA level was in the range of 80.0 to 359.8 ng/m L.There were no significant linear relationship or threshold effect for the effect of the urinary iodide on 5-HT,NE,and E and the relationship between IQ and 5-HT,NE and E.Conclusions The metabolic dysfunction of DA in children exposed to excessive iodide may be related to the decrease of intelligence quotient,and a threshold effect exists between DA and intelligence quotient.