Changes in Placental Thyriod Hormone Transport Associated with Maternal Obesity

描述（由申请人提供）：根据成人健康和疾病的发育起源假说，子宫内的不良暴露会使个体在成年后易患代谢综合征。怀孕期间的肥胖会给母体和胎儿带来独特的风险，包括胎儿过度生长、产科并发症以及胎儿在青春期和成年期患肥胖和 2 型糖尿病的风险增加。然而，胎儿过度生长背后的分子机制仍不清楚。我们在非人类灵长类动物模型中发现，在子宫内暴露于母体高脂肪饮食（MHFD）的胎儿表现出非酒精性脂肪肝病的病理学，血清游离脂肪酸和甘油三酯增加，并表现出胎儿肝脏组蛋白密码的变化。此外，我们发现在妊娠晚期，暴露于 MHFD 的胎儿游离 T4 (FT4) 显着下降，而母体 FT4 保持不变。胎儿甲状腺激素 (TH) 的这种变化伴随着脱碘酶基因表达的变化，脱碘酶基因调节胎儿肝脏、下丘脑和甲状腺中 FT3 和 FT4、TH 受体和 TH 结合蛋白之间的平衡。我们假设母亲肥胖导致胎儿 TH 稳态的改变可能是胎儿过度生长的分子介质。甲状腺激素参与产热、脂肪分解和体重的调节。母亲和胎儿的 TH 水平对于确定婴儿出生体重都很重要。 TH 对胎儿发育至关重要；在妊娠 16-20 周期间胎儿甲状腺变得活跃之前，所有必需的 TH 都必须由母亲提供。然而，一旦胎儿甲状腺活跃，穿过胎盘的母体 TH 就会减少。因此，胎盘能够调节在整个妊娠过程中进入胎儿血液的母体 TH 的量。我们建议研究与母亲肥胖相关的胎盘调节 TH 转运和 TH 代谢的变化，以确定导致胎儿过度生长的分子机制。在本提案中，我们的目标是通过母亲 TH 水平和母亲 BMI 来测量和分层脐带血 TH 水平。我们假设病态肥胖母亲的胎儿将患有亚临床甲状腺功能减退症，表现为高 TSH 水平和低 FT4。我们将使用免疫组织化学和 qPCR 检查瘦女性和肥胖女性胎盘中 TH 受体、转运蛋白、结合蛋白和脱碘酶基因的丰度和定位。我们将使用来自瘦和肥胖女性胎盘的培养原代滋养层细胞，使用微阵列和 ChIP-Seq 测试细胞转录和表观遗传对 TH 的反应。此外，我们建议使用永生化滋养层以及胎盘灌注模型来研究在不同量的TH存在下氨基酸、脂肪酸和葡萄糖转运的变化。综合起来，这些研究不仅将提供关于 TH 在胎儿过度生长中的作用的信息，而且可能提供一种治疗机制，通过该机制来靶向和预防过度生长，即使是在母亲持续肥胖的情况下。

DESCRIPTION (provided by applicant): According to the developmental origins of adult health and disease hypothesis, adverse in utero exposures predispose an individual to metabolic syndrome in adulthood. Obesity during pregnancy bears unique maternal and fetal risks, including fetal overgrowth, obstetrical complications, and an increased risk for the fetus to develop obesity and type 2 diabetes in adolescence and adulthood. However, the molecular mechanisms behind fetal overgrowth remain unclear. We have found in our non-human primate model that fetuses exposed in utero to maternal high fat diet (MHFD) show the pathology of non-alcoholic fatty liver disease, have increased serum free fatty acids and triglycerides, and exhibit changes in the fetal hepatic histone code. Furthermore, we have found at the beginning of the third trimester, fetuses exposed to a MHFD show a significant decrease in free T4 (FT4) while maternal FT4 remains unchanged. This change in fetal thyroid hormone (TH) is accompanied by changes in the expression of the deiodinase genes which regulate the balance between FT3 and FT4, TH receptors, and TH binding proteins in fetal liver, hypothalamus and thyroid gland. We hypothesize that alterations in fetal TH homeostasis due to maternal obesity are likely molecular mediators of fetal overgrowth. Thyroid hormones are involved in the regulation of thermogenesis, lipolysis, and body weight. Both maternal and fetal TH levels are important for determining infant birth weight. THs are essential for fetal development; before the fetal thyroid gland becomes active between 16-20 weeks of gestation, all necessary THs must be provided by the mother. However once the fetal thyroid gland is active, less maternal TH crosses the placenta. Therefore the placenta is able to regulate the amount of maternal THs which enter the fetal bloodstream throughout the course of gestation. We propose to study changes in the placental regulation of TH transport and TH metabolism associated with maternal obesity to determine a molecular mechanism contributing to fetal overgrowth. In this proposal we aim to measure and stratify cord blood TH levels by maternal TH levels and maternal BMI. We hypothesize that fetuses of morbidly obese mothers will have subclinical hypothyroidism showing high TSH levels and low FT4. We will examine the abundance and localization of TH receptors, transporters, binding proteins and deiodinase genes in placentas from lean and obese women using immunohistochemistry and qPCR. Using cultured primary trophoblast cells derived from placentas from lean and obese women we will test the cellular transcriptional and epigenetic response to TH using microarray and ChIP-Seq. Furthermore, we propose to use immortalized trophoblasts as well as the placental perfusion model to study the changes in amino acid, fatty acid and glucose transport in the presence of differing quantities of TH. Combined, these studies will not only provide information on the role of TH in fetal overgrowth but may offer a therapeutic mechanism by which to target and prevent overgrowth even with persistent maternal obesity.