Generation and use of lipid emulsions to understand mechanisms of and optimally manage parenteral nutrition associated liver disease

描述（由申请方提供）：肠外营养（PN）对于支持肠衰竭婴儿和儿童的生长和发育至关重要。尽管PN在肠长度或功能不足时提供了必要的营养支持， 由于肠外营养的吸收，长期接受肠外营养的儿童发生肠外营养相关性肝病（PNALD）的风险很大，PNALD包括一系列肝酶升高和胆汁淤积，可进展为肝硬化、肝衰竭、需要移植和死亡。脂质是PN的重要成分，提供不能内源性产生的ω-3和ω-6多不饱和脂肪酸（PUFA）。这些脂肪酸对于预防必需脂肪酸缺乏症（EFAD）以及提供密集的热量来源以减少满足热量需求所需的碳水化合物热量非常重要，因为不含脂质的PN可促进PNALD。目前在美国获批用于PN的脂肪乳剂是大豆油或大豆/橄榄油脂肪乳剂（SOLE），其提供必需脂肪酸以避免EFAD，但会加重PNALD。最近的研究表明，富含ω-3脂肪酸的鱼油脂肪乳剂（FOLE）Omegaven可逆转小鼠模型和患者的PNALD。FOLE保护PNALD而SOLE加剧PNALD的机制仍有争议，因为SOLE和FOLE之间存在一些差异。SOLE含有丰富的ω-6脂肪酸，其被代谢为比抗炎介质更促炎，而FOLE主要含有ω-3脂肪酸，其被代谢为比促炎介质更抗炎。此外，SOLE含有植物甾醇，植物特有的胆固醇样物质，被认为是肝毒性，而FOLE没有;在本研究中，我们将制备高纯度的SOLE衍生（PSO）和FOLE衍生（PFO）脂肪乳剂，并平衡植物甾醇和α生育酚的含量，因此PUFA含量是两种乳液之间的唯一变量。使用这些PFO和PSO乳剂，我们的第一个目的是评估PUFA含量在PN诱导的脂肪变性小鼠模型中的作用。对于我们的第二个目标，我们将改变植物甾醇含量或α生育酚含量，以评估这些变量中的每一个在我们的小鼠模型中PN诱导的脂肪变性中的作用。我们还将测试这些变量对全球代谢参数的影响，使用质谱法确定脂肪酸代谢，炎症和氧化应激的关键介质;并量化先前确定为PNALD发病机制中重要的基因的表达。了解PNALD的机制和致病因素可能最终指导生产脂肪乳剂的方法，以最大限度地降低PNALD的风险，并最大限度地保护依赖PN营养的儿童的肝脏。

DESCRIPTION (provided by applicant): Parenteral Nutrition (PN) is critical for supporting growth and development in infants and children with intestinal failure. Although PN provides necessary nutritional support when there is insufficient bowel length or functionality for nutrient absorption, children on prolonged PN are at significant risk of developing parenteral nutrition-associated liver disease (PNALD), which includes a spectrum of elevated liver enzymes and cholestasis that can progress to cirrhosis, liver failure, need for transplantation, and death. Lipids are important components of PN, providing ω-3 and ω-6 polyunsaturated fatty acids (PUFA) that cannot be generated endogenously. These fatty acids are important for preventing essential fatty acid deficiency (EFAD), as well as providing a dense source of calories to decrease the carbohydrate calories required to meet caloric needs, as PN devoid of lipid can promote PNALD. Lipid emulsions currently approved in the United States for use in PN are soybean oil or soybean/olive oil lipid emulsions (SOLE), which provide essential fatty acids to avoid EFAD, but exacerbate PNALD. It has recently been shown that the fish oil-based lipid emulsion (FOLE), Omegaven, that is rich in ω-3 fatty acids, can reverse PNALD in a mouse model and in patients. The mechanisms by which FOLE protects from PNALD while SOLE exacerbates PNALD remain debated, as several differences exist between SOLE and FOLE. SOLE contains an abundance of ω-6 fatty acids that are metabolized to more pro-inflammatory than anti-inflammatory mediators while FOLE contains predominantly ω-3 fatty acids that are metabolized to more anti-inflammatory than pro-inflammatory mediators. Additionally, SOLE contains phytosterols, cholesterol-like substance unique to plants and believed to be hepatotoxic, while FOLE does not; and FOLE contains an abundance of the anti-oxidant tocopherol whereas SOLE contains markedly less. In this study we will generate highly-purified SOLE-derived (PSO) and FOLE-derived (PFO) lipid emulsions and equalize the phytosterol and α tocopherol content, so that PUFA content is the only variable between the two emulsions. Using these PFO and PSO emulsions, our first aim is to assess the role of PUFA content in a mouse model of PN-induced steatosis. For our second aim, we will vary the phytosterol content or the α tocopherol content to assess the roles of each of these variables in PN-induced steatosis in our mouse model. We will also test the effect of these variables on global metabolic parameters, using mass spectrometry to identify key mediators of fatty acid metabolism, inflammation, and oxidative stress; and quantify the expression of genes previously identified as important in the pathogenesis of PNALD. Understanding the mechanisms and causative factors in PNALD may ultimately guide methods to generate lipid emulsions tailored to minimize risk of PNALD and maximize hepato-protection in children dependent on PN for nutrition.