Understanding metabolic mechanisms underlying retinopathy of prematurity

项目摘要/摘要 早产儿出生时肺部发育不全，因此有必要为他们提供 补充氧气以防止死亡。然而，提供的补充氧气是 对发育中的视网膜有害，并导致早产儿视网膜病变。在宫内，视网膜血 通过感知缺氧，血管萌发并从高氧浓度迁移到低氧浓度。 与人类ROP相似，在小鼠模型中，高氧导致血管生长停滞在第一阶段 OIR，随后导致视网膜局部缺氧，并导致新生血管形成 OIR的第二阶段。低氧稳定低氧诱导因子(HIF)，使其分泌 血管生成生长因子，如血管内皮生长因子。这些生长因子的梯度驱动尖端细胞迁移 和柄细胞的增殖。越来越多的证据表明，增长因素 然而，生物合成的代谢物也是正常发育所必需的 血管。实验室和其他研究小组的最新发现表明，谷氨酰胺是一种 视网膜内皮细胞增殖所需的重要代谢物。除了谷氨酰胺， 内皮细胞也有增强的糖酵解、磷酸戊糖途径和脂肪酸 扩散过程中的利用通量。谷氨酰胺只由Müler细胞在体内产生 视网膜。在正常条件下，Müler细胞通过吸收铵废物来产生谷氨酰胺。我们 最近证实，高氧减少了进入三元酸的糖酵解通量 视网膜Müler细胞的循环(Tca)，从而导致谷氨酰胺的利用增加 由Müler细胞和饥饿的视网膜内皮细胞组成其生长前体。预防血液流失 OIR第1阶段的血管生长受阻可能对第2阶段的OIR提供保护。我们会 使用OIR抗性和OIR易感小鼠品系评估生物合成代谢途径 OIR的第一阶段。已公布的数据和我们的初步数据表明脂肪酸含量更高 OIR抗性小鼠品系的代谢通量。我们假设较高的甘油三酯 水平可通过产生乙酰基-1，2，4，6-二磷酸，从而完全减轻或减少血管增殖缺陷。 当糖酵解碳进入三氯乙酸减少时，辅酶A或琥珀酸辅酶A通过脂肪酸氧化。 这可以额外降低Müler细胞对谷氨酰胺的利用，从而节省谷氨酰胺用于 视网膜中的其他细胞类型。此外，在易感小鼠的饮食中添加 替代脂肪酸作为无氮抗逆底物可能保护敏感菌株 反对OIR。了解OIR抵抗患者和AN患者之间的这些基本代谢差异 OIR敏感株将阐明OIR中潜在保护的代谢途径 耐药小鼠品系，并可能导致可翻译的治疗。

PROJECT SUMMARY/ABSTRACT Premature infants are born with underdeveloped lungs, making it necessary to provide them oxygen supplementation to prevent mortality. However, the supplemental oxygen provided is deleterious to the developing retina and leads to retinopathy of prematurity. In utero, retinal blood vessels sprout and migrate from high oxygen to low oxygen concentrations by sensing hypoxia. Like in human ROP, hyperoxia leads to blood vessel growth arrest in phase 1 in the mouse model of OIR, which subsequently leads to local hypoxia in the retina and causes neovascularization in phase 2 of OIR. Hypoxia stabilizes hypoxia inducible factor (HIF) which leads to the secretion of angiogenic growth factors like VEGF. Gradient of these growth factors drive tip cell migration and stalk cell proliferation. There is a growing body of evidence suggesting that growth factors are guiding cues; however, biosynthetic metabolites are also necessary for normal development of blood vessels. Recent findings from lab and other groups demonstrate that glutamine is an important metabolite needed for retinal endothelial cell proliferation. In addition to glutamine, endothelial cells also have enhanced glycolytic, pentose phosphate pathway and fatty acid utilization fluxes during proliferation. Glutamine is solely produced by the Müller cells in the retina. Müller cells in normal conditions produce glutamine by assimilating ammonium waste. We have recently demonstrated that hyperoxia decreases glycolytic flux entry into tricarboxylic acid cycle (TCA) in the retinal Müller cells, consequently leading to increased utilization of glutamine by Müller cells and starving retinal endothelial cells of their growth precursor. Preventing blood vessel growth arrest in the phase 1 of OIR may provide protection against phase 2 of OIR. We will use OIR resistant and OIR susceptible mice strains to evaluate biosynthetic metabolic pathways in the phase 1 of OIR. Published data and our preliminary data points towards higher fatty acid metabolism flux in the OIR resistant mouse strains. We hypothesize that the higher triglyceride levels may mitigate or diminish blood vessel proliferation defect completely, by producing acetyl- CoA or succinyl-CoA via fatty acid oxidation when glycolytic carbon entry into TCA is decreased. This can additionally lower glutamine utilization by the Müller cells thereby sparing glutamine for other cell types in the retina. Additionally, supplementing diets of the susceptible mouse with alternative fatty acids as non-nitrogenous anaplerotic substrates may protect susceptible strain against OIR. Understanding these basic metabolic differences between an OIR resistant and an OIR susceptible strain will shed light on the metabolic pathways underlying protection in the OIR resistant mouse strain and may lead to translatable treatment.