The role of subcellular vitamin E deficiency and the α-tocopherol transfer protein in non-alcoholic fatty liver disease

非酒精性脂肪性肝病（NAFLD）是一种以肝脏脂质过度积累为特征的疾病，正在成为西方世界最常见的肝脏疾病。目前，没有EMA批准的NAFLD治疗方法，脂溶性维生素E，特别是α生育酚（αT），已被研究为潜在的治疗方法。肝脂肪作为脂滴的积累增加被认为导致氧化应激增加，特别是脂质过氧化。αT是一种脂溶性抗氧化剂，目前有证据表明，它被隔离在脂滴中，消耗αT的其他细胞器，可能局部增加氧化应激。细胞内维生素E转运蛋白α-生育酚转运蛋白（αTTP）的表达在NAFLD中降低，而其在将αT转运至脂滴中的作用目前尚不清楚。本项目的总体目标是确定脂滴对αT亚细胞分布的影响以及αTTP的作用。为此，将在不存在和存在脂滴的情况下，在有和无αTTP表达的细胞中研究αT的亚细胞分布。将在从纯合和杂合αTTP敲除小鼠及其野生型对照中分离的原代小鼠肝细胞中验证结果。将在上述喂食致肥胖饲料的小鼠模型中评价αTTP对脂滴中αT蓄积以及对脂肪变性的影响。最后，将分析来自NAFLD患者和对照组的人肝脏样本中的维生素E和甘油三酯，以研究甘油三酯含量与αT之间的潜在/可能相关性，为脂质储存增加增加αT螯合，可能导致亚细胞维生素E缺乏的观点提供进一步支持。 该提案将确定脂滴对维生素E亚细胞分布的影响以及α-生育酚转移蛋白（αTTP）在非酒精性脂肪性肝病（NAFLD）背景下的作用。此外，本研究的结果将表明αTTP是否是治疗NAFLD的一个有希望的新靶点。

Non-alcoholic fatty liver disease (NAFLD), a disease characterized by excessive accumulation of hepatic lipids, is becoming the most common liver disorder in the Western world. Currently, there are no EMA approved treatments for NAFLD and the lipid soluble vitamin E, specifically alpha tocopherol (αT), has been investigated as a potential treatment. Increased accumulation of hepatic fat as lipid droplets is believed to lead to increased oxidative stress, especially lipid peroxidation. αT is a fat-soluble antioxidant and there is currently evidence to suggest that it is sequestered in lipid droplets depleting other organelles of αT, possibly increasing oxidative stress locally. The expression of the intracellular vitamin E trafficking protein, alpha tocopherol transfer protein (αTTP) is decreased in NAFLD whereas its role in trafficking αT to lipid droplets is currently unknown. The overall goal of this project is to identify the impact of lipid droplets on subcellular distribution of αT and the role of αTTP. To this end, subcellular distribution of αT will be investigated in cells with and without the expression of αTTP in the absence and presence of lipid droplets. Findings will be validated in primary mouse hepatocytes, isolated from homo- and heterozygous αTTP knockout mice and their wildtype controls. The impact of αTTP on αT accumulation in lipid droplets as well as on steatosis will be evaluated in the aforementioned mouse model fed an obesogenic diet. Lastly, vitamin E and triglycerides in human liver samples from NAFLD patients and controls will be analyzed to investigate a potential/possible correlation between triglyceride content and αT, providing further support to the notion that increased lipid storage increases αT sequestration, possibly leading to subcellular vitamin E deficency. This proposal will identify the effect of lipid droplets on the subcellular distribution of vitamin E as well as the role of the α-tocopherol transfer protein (αTTP) in the context of non-alcoholic fatty liver disease (NAFLD). Furthermore, the results of this project will show if αTTP is a promising novel therapeutic target for the treatment of NAFLD.