Estrogen Regulation of Fetal Microvessel Development During Primate Pregnancy: Impact on Insulin Sensitivity in Offspring

我们最近发现，雌性激素(E_2)抑制的狒狒所生的后代表现出胰岛素抵抗、糖耐量异常和第一时相胰岛素分泌不足，这些都会进展为2型糖尿病(T2 DM)。然而，支持这一E2调控事件的机制(S)尚不清楚。微血管(MV)单位(即小动脉和相关毛细血管[CAP])在胰岛素作用中起着至关重要的作用，它使胰岛素和葡萄糖能够输送到靶组织，特别是骨骼肌(SM)。然而，在胎儿发育过程中，胰岛素靶组织内形成了广泛的MV网络，但几乎没有 了解胎儿这一极其重要的发育过程的调节。血管生成是 血管内皮生长因子-A(VEGF)是SM血管生成的主要调节因子。因此，这项“健康和疾病的发育起源”研究的最新概念是，子宫内的E2促进了胎儿SM MV的发育，从而形成了广泛的MV网络，对于将胰岛素和葡萄糖输送到SM，从而在后代SM内发挥胰岛素作用和葡萄糖动态平衡至关重要。在目标1中，我们将检验这一假设，即E2促进了狒狒胎儿SM MV的形态和功能发育，这是导致后代胰岛素敏感性的关键步骤。SM VEGF的表达、帽密度和MV成熟和形态将在怀孕中期(第100天)和晚期(第165-175天；足月=184天)的胎儿以及2、3和4岁的后代中进行量化，这些后代在未经治疗或其中的E2产生/水平已被母亲给予芳香酶抑制剂letrozole抑制并由letrozole加E2恢复的情况下出生。SM血管功能将通过臂动脉血流介导的扩张和通过对比增强超声/微泡技术量化的帽状血流来评估，在给缺乏/补充E2的狒狒分娩的后代进行血管挑战之前/期间。目的2将确定目标1中建立的E2促进胎儿SM血管生成的机制。我们将检验以下假设：E2迅速刺激SM血管内皮生长因子的表达，帽内皮细胞(EC)紧密连接(TJ)/黏附连接(AJ)破坏，以及帽EC 在给来曲唑治疗的狒狒胎儿静脉注射E2后0-24小时，在妊娠165天的早期，血管生成的早期步骤是增殖。这项拟议的研究具有临床意义，因为早产、芳香酶突变、类固醇硫酸酯酶缺乏、雌激素受体零突变以及母婴暴露于内分泌干扰物，减少了胎儿对正常E2升高或作用的暴露，与人类后代胰岛素抵抗/T2 DM的发生率增加有关。确定E2对胎儿MV发育和灵长类后代启动胰岛素敏感性的重要性，为人类的治疗应用提供了基础。

We recently showed that offspring delivered to estrogen (E2)-suppressed baboons exhibited insulin resistance, glucose intolerance, and a deficit in first phase insulin secretion, steps that progress to type 2 diabetes mellitus (T2DM). However, the mechanism(s) underpinning this E2 regulated event are unknown. The microvessel (MV) unit (i.e. arterioles and associated capillaries [cap]) has a fundamentally important role in insulin action by enabling insulin and glucose delivery to target tissue, notably skeletal muscle (SM). An extensive MV network forms within insulin target tissues during fetal development, however, little is known about the regulation of this critically important developmental process in the fetus. Angiogenesis is foundational for expansion of the cap network during fetal development and vascular endothelial growth factor-A (VEGF) is a predominant regulator of angiogenesis in SM. Therefore, the over-arching highly novel concept of this “developmental origin of health and disease” study is that E2 in utero promotes SM MV development in the fetus and consequently formation of an extensive MV network critical for the delivery of insulin and glucose to and thus insulin action and glucose homeostasis within SM in the offspring. In Aim 1, we will test the hypothesis that E2 promotes SM MV morphological and functional development in the baboon fetus as an essential step leading to insulin sensitivity in the offspring. SM VEGF expression, cap density and MV maturation and morphology will be quantified in the fetus at mid (day 100) and late (days 165-175; term = 184 days) gestation and in offspring at 2, 3 and 4 years of age delivered to baboons untreated or in which E2 production/levels have been suppressed by maternal administration of the aromatase inhibitor letrozole and restored by letrozole plus E2. SM vascular function will be assessed by brachial artery flow-mediated dilation and by cap flow, as quantified by contrast-enhanced ultrasound/microbubble technology, before/during vasochallenge of offspring delivered to E2-deprived/-replenished baboons. Aim 2 will determine the mechanisms by which E2 acts to promote SM angiogenesis in the fetus as established in Aim 1. We will test the hypothesis that E2 rapidly stimulates SM VEGF expression, cap endothelial cell (EC) tight junction (TJ)/adherens junction (AJ) breakdown, and cap EC proliferation as early steps in angiogenesis on day 165 of gestation 0-24 h after an iv bolus injection of E2 to fetuses of letrozole-treated baboons. The proposed study is clinically significant since preterm birth, aromatase mutation, steroid sulfatase deficiency, estrogen receptor null mutation, and maternal/fetal exposure to endocrine disruptors, which curtail exposure of the fetus to the normal elevation in or action of E2, are associated with increased incidence of insulin resistance/T2DM in human offspring. Establishing the importance of E2 to fetal MV development and onset of insulin sensitivity in primate offspring provides a basis for therapeutic application to the human.