Novel Roles for Phospholipids in Regulating Placental Function and in the Delivery of DHA to the Fetal Brain.

项目总结 胎盘中充足的脂质转移对于胎儿的正常发育和大脑发育至关重要，然而 涉及胎盘脂质处理和转运的机制在很大程度上是未知的。许多重要的 妊娠并发症，如宫内生长受限(IUGR)和产妇糖尿病 与胎儿脂肪沉积障碍有关，这可能会导致不利的短期和长期 结果。尽管胎盘脂肪处理和转运之间的机械联系，胎儿脂肪沉积和 胎儿大脑发育尚待确定，新的证据表明，这些怀孕 并发症与胎盘脂质代谢改变有关。合体滋养层细胞 人类胎盘上皮的运输，介导了脂质从母体到胎儿的转移 发行量。现在有令人信服的证据表明，复杂的脂质形式是由 合体滋养层细胞，并有可能释放给胎儿。特别是，原代人滋养层细胞 迅速吸收脂肪酸，并将其结合到磷脂中。从头合成与重塑 磷脂产生一系列生物活性中间体，包括磷脂酸 调节癌细胞中的mTOR信号。磷脂重塑产生溶血磷脂酰胆碱 含有二十二碳六烯酸(LPC-DHA)的物种，这是DHA的主要形式 由含2A的MajorFacilitator超家族结构域介导的跨血脑屏障运输 (MFSD2a)，LPC-DHA转运体。我们在胎盘组织和脐带组织中发现了高水平的LPC-DHA 静脉LPC-DHA水平高于母体循环浓度，表明DHA被传递到 胎儿为LPC-DHA。此外，我们还发现MFSD2a在人类体内表达 合体滋养层细胞基底膜，与该转运蛋白介导的可能性一致 将LPC-DHA转移到胎儿体内。这些观察结果为我们的中心假设提供了前提 滋养层细胞磷脂的合成和重塑非常活跃，产生磷脂酸( 调节TOR信号)和LPC-DHA，由MFSD2a介导转运到胎儿。我们的假设是 有令人信服的初步数据支持，包括磷脂酸调节胎盘的证据 通过mTOR信号和LPC-DHA介导的氨基酸转运在胎盘中产生和释放 传给胎儿。我们将使用人类胎盘组织，母体和脐带血样本从正常 和复杂妊娠，在培养的原代人滋养层细胞中进行siRNA基因打靶的方法 在13C稳定同位素标记的脂肪酸和滋养层特异性基因的生理混合物中孵育 以小鼠为靶点来解决这一假设。这些 机械论 胎盘 研究非常有意义，因为我们将使用nove 确定磷脂合成中间体是重要的调节因子的方法 胎盘转运DHA的功能和关键介质，对正常的大脑发育是必要的。 L

PROJECT SUMMARY An adequate placental transfer of lipids is critical for normal fetal growth and brain development, yet the mechanisms involved in placental lipid handling and transport are largely unknown. Many important pregnancy complications such as intrauterine growth restriction (IUGR) and maternal diabetes are associated with disturbances in fetal fat deposition that may contribute to adverse short-and long-term outcomes. Although mechanistic links between placental lipid handling and transport, fetal fat deposition and fetal brain development remain to be established, emerging evidence suggests that these pregnancy complications are associated with altered placental lipid metabolism. The syncytiotrophoblast, the transporting epithelium of the human placenta, mediates the transfer of lipids from the maternal to the fetal circulation. There is now compelling evidence that complex lipid forms are produced in large amounts by the syncytiotrophoblast and are potentially released to the fetus. In particular, primary human trophoblast cells rapidly take up fatty acids and incorporate them to phospholipids. De novo synthesis and remodeling of phospholipids generates a range of biologically active intermediates, including Phosphatidic Acid which regulates mTOR signaling in cancer cells. Phospholipid remodeling generates Lysophosphatidylcholine species containing docosahexaenoic acid (LPC-DHA) which is the predominant form in which DHA is transported across the blood brain barrier, mediated by MajorFacilitator Superfamily Domain Containing 2A (MFSD2a),an LPC-DHA transporter. We found high levels of LPC-DHA in placental tissue and that umbilical vein LPC-DHA levels are higher than maternal circulating concentrations, suggesting that DHA is delivered to the fetus as LPC-DHA. In addition, we discovered that MFSD2a is expressed in the human syncytiotrophoblast basal plasma membrane, consistent with the possibility that this transporter mediates transfer of LPC-DHA to the fetus. These observations provide the premise for our central hypothesis that trophoblast phospholipid synthesis and remodeling are highly active, produces phosphatidic acid (which modulates TOR signaling) and LPC-DHA for transport to the fetus, mediated by MFSD2a. Our hypothesis is supported by compelling preliminary data including evidence that phosphatidic acid regulates placental amino acid transport mediated through mTOR signaling and LPC-DHA is produced in placenta and released to the fetus. We will use human placental tissue, maternal and umbilical blood samples collected from normal and complicated pregnancies, siRNA gene targeting approaches in cultured primary human trophoblast cells incubated in a physiological mixture of 13C-stable isotope labelled fatty acids and trophoblast specific gene targeting in mice to address this hypothesis. These mechanistic placental studies are highly significant because we will use nove approaches to establish that phospholipid synthesis intermediates are important regulators of function and critical mediators of placental transfer of DHA, essential for normal brain development. l