Role of non-genomic regulation of mitochondrial trifunctional protein in NAFLD

非酒精性脂肪性肝病(NAFLD)的特征是肝脏中脂肪沉积增加，可能 炎症、肝细胞癌和肝功能衰竭的进展。非酒精性脂肪肝与2型密切相关 糖尿病和肥胖症。它仍然是一个主要的公共卫生问题，在其方面进展甚微 治疗。令人不安的是，与军人和退伍军人相比，非酒精性脂肪肝似乎更常见 与普通美国人的关系。因此，努力了解有助于 NAFLD将为我们的退伍军人群体开发治疗方案提供宝贵的见解。 线粒体功能障碍在NAFLD的发展中起着至关重要的作用，然而，关于线粒体功能障碍是如何发生的，人们却知之甚少 治疗线粒体功能障碍，挽救相关的NAFLD。线粒体三功能蛋白(MTP) 是线粒体脂肪酸氧化的主要酶复合体，由4个α和4个β亚基组成 携带三种酶活性可以分解线粒体中的脂肪酸。一个关键悬而未决的问题是 MTP的调节是否对NAFLD有调节作用。在一种有MTP缺陷的小鼠模型中，小鼠 缺失杂合子(MTP+/-)会发展成线粒体功能障碍，并易患NAFLD。 在这个小鼠模型中，确定参与调节MTP的机制对于理解 线粒体在非酒精性脂肪肝发生和挽救中的作用。此应用程序中的假设是 增加MTP复合体的组装增加了它的稳定性，这导致了 线粒体脂肪酸氧化与非酒精性脂肪肝的挽救此应用程序中的建议是，两个 NAD+依赖的SIRT3和三碘甲腺原氨酸(T3)激素通过非基因组途径提高MTP的稳定性 机制通过增强MTP复合体的组装。初步数据有力地支持了 假设。首先，从中国获得的肝脏样本中，线粒体FAO、MTP和SIRT3的水平降低 患有非酒精性脂肪肝的受试者。第二，SIRT3在MTP+/-小鼠中的过表达减少了乙酰化 与对照组相比，MTP增加了线粒体FAO，减少了脂肪变性和炎症标志物 肝脏。第三，培养细胞的体外研究表明，MTP的稳定性和它的水平被提高了 T3治疗。为了验证这一假设，我们将使用从一位资深患者那里获得的人类肝脏样本。 种群和MTP小鼠模型进行以下体外、体内和体外研究 具体目标：1)明确肝脏MTP-α水平、SIRT3水平、线粒体粮农组织之间的关系 从退伍军人人群中获得的人类肝脏样本中的疾病严重程度。2)确定潜在的 SIRT3过表达增加小鼠MTP水平的机制。3)测试T3是否拯救了NAFLD 在MTP小鼠模型中，以及它是否通过增加MTP的稳定性来改善肝脏线粒体FAO 通过与线粒体的相互作用，缩短了甲状腺受体。这是第一次对监管进行研究。 SIRT3和T3对MTP的影响，以及这对线粒体粮农组织和NAFLD的影响。这项建议解决了关键问题 领域中影响我们退伍军人重大健康问题的未解答问题和知识差距 人口。确定SIRT3和T3调节MTP的机制将具有重要意义 并将为未来发现治疗NAFLD的新疗法带来希望。NAFLD是一种日益常见的疾病 治疗选择有限的退伍军人。

Nonalcoholic fatty liver disease (NAFLD) is characterized by increased deposition of fat in the liver that may progress to inflammation, hepatocellular carcinoma, and liver failure. NAFLD is closely linked to type 2 diabetes mellitus and obesity. It remains a major public health problem with little progress made on its treatment. Disturbingly, NAFLD appears to be more common in the military and Veteran population compared with the general US population. Thus, efforts to understand the underlying mechanisms that contribute to NAFLD will provide valuable insight into developing therapeutic options for our Veteran population. Mitochondrial dysfunction plays a crucial role in the development of NAFLD, however, little is known about how to treat mitochondrial dysfunction and rescue the associated NAFLD. Mitochondrial trifunctional protein (MTP) is the major enzymatic complex in mitochondrial fatty acid oxidation (FAO) that consists of 4 α and 4β subunits carrying three enzymatic activities breaks down fatty acids in the mitochondria. A key unanswered question is whether regulation of MTP modulates NAFLD. In a reported mouse model with an MTP defect, mice heterozygous for the defect (MTP+/-) develop mitochondrial dysfunction and are susceptible to NAFLD. Determining the mechanisms involved in regulating MTP in this mouse model is critical to the understanding of the role of mitochondria in development and rescue of NAFLD. The hypothesis in this application is that increasing the assembly of the MTP complex increases its stability, which leads to improvement in mitochondrial fatty acid oxidation (FAO) and rescue of NAFLD. The proposal in this application is that both the NAD+-dependent SIRT3 and the triiodothyronine (T3) hormone improve MTP stability by nongenomic mechanisms through enhancement of the MTP complex assembly. The preliminary data strongly support the hypothesis. First, mitochondrial FAO, MTP and SIRT3 levels were reduced in liver samples obtained from human subjects with NAFLD. Second, overexpression of SIRT3 in the MTP+/- mice reduced the acetylation of MTP compared to controls, increased mitochondrial FAO, and reduced steatosis and inflammatory markers in the liver. Third, in vitro studies in cultured cells demonstrate that MTP stability and its levels were increased by T3 treatment. To examine this hypothesis, we will use human liver samples obtained from a Veteran patient population and the MTP mouse model to conduct ex vivo, in vivo, and in vitro studies towards the following specific aims: 1) To define the relationship between hepatic MTP-α levels, SIRT3 levels, mitochondrial FAO and disease severity in human liver samples obtained from Veteran population. 2) To determine the underlying mechanisms of increased MTP levels by SIRT3 overexpression in mice. 3) To test whether T3 rescues NAFLD in the MTP mouse model and whether it improves hepatic mitochondrial FAO by increasing MTP stability through interaction with mitochondrial shortened thyroid receptors. This is the first study to examine regulation of MTP by SIRT3 and T3, and how that impacts mitochondrial FAO and NAFLD. This proposal addresses key unanswered questions and knowledge gaps in the field that impact a significant health problem in our Veteran population. Identifying the mechanisms by which SIRT3 and T3 regulate MTP will have important implications and will hold promise for future discovery of novel treatments for NAFLD, an increasingly common disease in Veterans with limited therapeutic options.