胚胎期高雌激素暴露对IGFBP-I调控子代出生体重的影响及分子机制研究

The influence of steroid hormone disorder during embryonic period on offspring development is the focus of the present research, and assisted reproductive technology (ART) provides an ideal model to study the problem. Our previous study found that there was a significant correlation between the increased risk of LBW and the high estrogen exposure during embryonic period, and that the expression of insulin-like growth factor binding protein 1 (IGFBP-1) abnormally elevated in the umbilical cord blood of ART-conceived offspring, especially in the ones with LBW. Accordingly we hypothesize: the high 17β-E2 exposure during embryonic period after ART may up-regulate IGFBP-1 expression, which leads to the increased risk of LBW in the ART-conceived offspring. This study is designed to prove this hypothesis in vivo through the case control study (fresh/freeze-thaw embryo transfer) and animal models of the high estrogen exposure during embryonic period. It remains unknown that in which way 17β-E2 up-regulates the transcription of IGFBP-1. In our former study we found the putative motif of estrogen response element (ERE) in the promoter of IGFBP-1. This study attempts to identify the functional ERE, investigate the role of estrogen receptor (ER) and ERE in the regulation of IGFBP-1, explore the downstream molecules of IGFBP-1 affecting growth, and hence prove the hypothesis in vitro. The results help uncover the mechanism of LBW in the ART-conceived offspring, and provide theoretic basis for the impact of steroid hormone environment during embryonic period on development.

胚胎期内分泌环境对子代生长发育的影响是目前研究关注的热点，辅助生殖技术（ART）为研究该问题提供了理想模型。本课题组前期研究发现ART子代低出生体重与胚胎期高雌激素暴露相关，胰岛素样生长因子结合蛋白1（IGFBP-1）表达在ART子代、尤其是低出生体重子代中异常升高。据此我们假设：胚胎期过高的17β-E2通过上调IGFBP-1导致子代低出生体重风险增加。本研究拟通过病例对照研究（新鲜/冻融胚胎移植）及胚胎期高雌激素暴露动物模型两个层面从在体水平验证该假说。17β-E2上调IGFBP-1机制不明，我们前期研究发现IGFBP-1启动子区存在雌激素反应元件（ERE）高度同源序列，本研究拟鉴定该ERE，明确其在17β-E2调控IGFBP-1中作用，并探索IGFBP-1影响生长发育的下游分子，从离体水平验证该假说。揭示ART子代低出生体重发生机制，为胚胎期内分泌紊乱干扰生长发育研究提供新的切入点。

研究背景：本课题组前期研究发现ART子代低出生体重可能与胚胎期高雌激素暴露相关，胰岛素样生长因子结合蛋白1（IGFBP-1）表达在ART子代、尤其是低出生体重子代中异常升高。本项目旨在明确胚胎期17β-E2水平对子代出生体重的影响，探讨17β-E2对IGFBP-1表达的调控作用，并建立胚胎期高雌激素暴露动物模型，模拟高雌激素对子代出生体重的影响及IGFBP-1在期间所起作用，验证17β-E2、IGFBP-1、出生体重三者关系。.研究内容：1. 本项目采用病例对照研究设计，对新鲜胚胎移植周期（高雌激素暴露）与冻融胚胎移植周期（非高雌激素暴露）中17β-E2、IGFBP-1及子代出生体重、甲状腺功能、脂质代谢行横向、纵向分析，从而明确高雌激素环境对子代出生体重及代谢的影响。2.培养滋养细胞，探讨17β-E2对IGFBP-1的调节作用。3. 建立动物模型模拟高雌激素调控IGFBP-1表达导致子代低出生体重及内分泌代谢异常发生的过程。.研究结果：新鲜ET的子代出生体重显著低于冻融ET和自然妊娠子代，同时小于胎龄儿和出生低体重儿发生率显著增加，母亲E2水平与出生体重呈负相关。新鲜ET受孕的孕妇其子代甲状腺功能受损，T4、游离T4及TSH水平显著增高，冻融ET可纠正其甲状腺功能异常，且子代的T4/游离T4水平与母亲早孕期E2水平正相关。孕早期高浓度的雌激素暴露，可能改变甲状腺功能相关基因的甲基化状态，进而使得出生子代出现甲状腺功能的异常。雌激素可上调肝脏细胞中IGFBP-1的mRNA及蛋白表达，使用雌激素受体阻断剂可阻断雌激素诱导的IGFBP-1上调。成功建立了宫内高雌激素暴露的小鼠模型，可稳定获得存活子代，早孕期高E2暴露可上调IGFBP-1表达，在宫内高雌激素暴露的小鼠胎盘及肝脏细胞中Igfbp-1的mRNA及蛋白表达显著上调，导致子代低出生体重风险增高。.结论：宫内高雌环境可导致子代出生体重减轻，进而干扰甲状腺激素分泌及脂质代谢。胚胎期过高的17β-E2水平可上调IGFBP-1表达，从而导致子代低出生体重风险增加。需密切监测母亲雌激素水平从而降低子代发育异常风险。