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

描述(由申请人提供)：肠外营养(PN)对于支持婴幼儿和肠衰竭儿童的生长发育至关重要。尽管当肠道长度或营养功能不足时，PN可提供必要的营养支持 长期接受肠外营养的儿童有发生肠外营养相关性肝病(PNALD)的极大风险，包括一系列肝酶升高和胆汁淤积，可发展为肝硬化、肝功能衰竭、需要移植和死亡。脂质是Pn的重要组成部分，提供内源不能产生的ω-3和ω-6多不饱和脂肪酸。这些脂肪酸对预防必需脂肪酸缺乏症(EFAD)很重要，也提供了密集的卡路里来源，以减少满足卡路里需求所需的碳水化合物卡路里，因为不含脂肪的PN可以促进PNALD。目前在美国被批准用于PN的脂肪乳剂是大豆油或大豆/橄榄油脂肪乳剂(SOLE)，它们提供必要的脂肪酸来避免EFAD，但会加剧PNALD。最近有研究表明，富含ω-3脂肪酸的鱼油脂肪乳剂(FOE)Omeaven可以逆转小鼠模型和患者的PNALD。Fole预防PNALD而Sole加重PNALD的机制仍然存在争议，因为Sole和Fole之间存在一些差异。SOLE含有丰富的ω-6脂肪酸，它们被代谢成比抗炎介质更亲炎症的物质，而FOE主要含有ω-3脂肪酸，被代谢成比促炎症介质更抗炎的物质。此外，比目鱼含有植物特有的胆固醇样物质植物甾醇，被认为具有肝脏毒性，而FOE没有；FOE含有丰富的抗氧化剂生育酚，而比目鱼含有明显较少的维生素E。在这项研究中，我们将产生高纯度的比目鱼油(PSO)和鱼油油(PFO)脂肪乳剂，并使植物甾醇和α生育酚的含量相等，因此多不饱和脂肪酸含量是两种乳剂之间的唯一变量。使用这些PFO和PSO乳剂，我们的第一个目标是评估PUFA含量在PN诱导的脂肪变性小鼠模型中的作用。为了我们的第二个目的，我们将改变植物类固醇或α生育酚的含量，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，使用质谱仪识别脂肪酸代谢、炎症和氧化应激的关键介质；并量化以前被认为在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产生脂肪乳剂的方法，以将PNALD的风险降至最低，并最大限度地保护依赖于PN的儿童的肝脏保护。

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.