TMEM55B as a molecular determinant of NAFLD

TMEM55B 作为 NAFLD 的分子决定因素

基本信息

批准号：
10913882
负责人：
Marisa Wong Medina
金额：
$ 59.1万
依托单位：
UNIVERSITY OF CALIFORNIA, SAN FRANCISCO
依托单位国家：
美国
项目类别：
财政年份：
2023
资助国家：
美国
起止时间：
2023-09-01 至 2025-08-31
项目状态：
未结题

来源：
https://reporter.nih.gov/project-details/10913882
关键词：
Adult Animal Model Animals Antisense Oligonucleotide Therapy Biochemical Cholesterol Cirrhosis Defect Dependence Development Diet Disease Disease Progression Dynein ATPase Estrogen Receptors Estrogens Fatty Acids Fatty Liver Fatty acid glycerol esters Female Fibrosis Fructose Functional disorder Genetic Genetic Complementation Test Gonadal Steroid Hormones Hepatic Hepatocyte Histologic Homeostasis Impairment In Vitro Inflammation Integral Membrane Protein Intracellular Accumulation of Lipids Knockout Mice Link Lipid Mobilization Lipids Lipolysis Liver Liver diseases LoxP-flanked allele Lysosomes Maintenance Mediating Mitochondria Modeling Molecular Morphology Motor Mus Nuclear Onset of illness Oxidative Stress Pathology Peripheral Phosphoric Monoester Hydrolases Play Ploidies Positioning Attribute Premenopause Process Production Research Role Sex Chromosomes Sex Differences Sorting Testing Therapeutic Intervention Triglycerides Very low density lipoprotein Woman base cell motility disorder risk fatty acid metabolism fatty acid oxidation in vivo insight knock-down male men mouse model non-alcoholic fatty liver disease nonalcoholic steatohepatitis novel oxidation pharmacologic precision medicine prevent screening targeted treatment trafficking very low density lipoprotein triglyceride western diet

项目摘要

SUMMARY Non-alcoholic fatty liver disease (NAFLD) is a spectrum of disorders initiated by steatosis that can progress to nonalcoholic steatohepatitis (NASH) and cirrhosis. Although it is the leading cause of liver disease in the US, there are no targeted therapeutic interventions, highlighting the critical need for identifying molecular processes underlying its pathology. Transmembrane protein 55B (TMEM55B) is a PI(4,5)P2 phosphatase located on the lysosome that has been shown to impact lysosome levels and localization. In preliminary studies, we found that TMEM55B ASO treatment caused hepatic steatosis in C57BL/6J mice after 6 weeks on western diet, while TMEM55B knockout mice developed NASH after 12 weeks on a high-fat, cholesterol and fructose supplemented (GAN) diet. We have identified several effects of TMEM55B knockdown that can promote NAFLD: 1) accumulation of lipids within lysosomes, indicative of impaired fatty acid (FA) mobilization, 2) impaired mitochondrial FA oxidation together with reduced mitochondrial volume, mitochondrial fragmentation, and increased oxidative stress; and 3) in vivo inhibition of hepatic triglyceride secretion. The lysosome plays a critical role in sorting and processing lipids, where proper lysosome motility is essential for their ability to mobilize FA from lipid droplets and maintain mitochondrial homeostasis. TMEM55B plays a key role in regulating lysosomal positioning, thus our central hypothesis is that loss of TMEM55B promotes NAFLD onset and progression through lysosomal effects on hepatic FA mobilization and trafficking, mitochondrial FA oxidation, and triglyceride secretion. In Aim 1, we will determine whether TMEM55B impacts FA mobilization and mitochondrial function through its ability to impact lysosomal localization. We will also examine the impact of TMEM55B on mitochondrial morphology and dysfunction. Hepatic triglyceride (TG) is primary secreted within VLDL, which is generated through a multi-step process of lipidating nascent APOB with FA mobilized from lipid droplets. In Aim 2A we will test whether TMEM55B knockdown prevents lipidation of nascent VLDL and test the dependency of these effects on the lysosome. Men are well-known to have higher NAFLD risk than pre-menopausal women, however the basis for this sex difference is poorly understood. We found that TMEM55B knockdown caused steatosis in male, but not female, mice, and that loss of hepatic TMEM55B inhibited TG secretion to a much greater degree in male versus female mice. The sex-dependent differences in TG secretory defects were attributed to differences in sex hormones. In Aim 2B we will evaluate the interaction between TMEM55B and sex hormones on TG secretion in male and female mice, and in estrogen receptor knockout mice. Finally, in Aim 3 we will evaluate the effect pharmacologic and genetic inhibition of TMEM55B on the development and progression of NAFLD. Understanding the mechanism(s) by which loss of TMEM55B impacts multiple critical axes of FA metabolism through the lysosome can yield novel insight into factors contributing to NAFLD.

概括非酒精性脂肪肝 (NAFLD) 是由脂肪变性引发的一系列疾病，可进展为非酒精性脂肪性肝炎（NASH）和肝硬化。尽管它是美国肝病的主要原因，没有针对性的治疗干预措施，凸显了识别分子过程的迫切需要其病理基础。跨膜蛋白 55B (TMEM55B) 是一种 PI(4,5)P2 磷酸酶，位于溶酶体已被证明会影响溶酶体水平和定位。在初步研究中，我们发现西式饮食 6 周后，TMEM55B ASO 治疗导致 C57BL/6J 小鼠肝脏脂肪变性，而 TMEM55B 基因敲除小鼠在补充高脂肪、胆固醇和果糖 12 周后出现 NASH （GAN）饮食。我们已经确定了 TMEM55B 敲低可促进 NAFLD 的几种效应：1) 溶酶体内脂质积累，表明脂肪酸 (FA) 动员受损，2) 受损线粒体 FA 氧化以及线粒体体积减少、线粒体碎片化和氧化应激增加； 3)体内抑制肝脏甘油三酯的分泌。溶酶体起着关键作用在脂质分类和加工中的作用，其中适当的溶酶体运动对于它们动员 FA 的能力至关重要消除脂滴并维持线粒体稳态。 TMEM55B 在调节溶酶体中发挥关键作用因此我们的中心假设是 TMEM55B 的缺失会促进 NAFLD 的发病和进展通过溶酶体对肝脏 FA 动员和运输、线粒体 FA 氧化和甘油三酯的影响分泌。在目标 1 中，我们将确定 TMEM55B 是否影响 FA 动员和线粒体功能通过其影响溶酶体定位的能力。我们还将研究 TMEM55B 对线粒体形态和功能障碍。肝甘油三酯 (TG) 主要由 VLDL 分泌，VLDL 是通过用从脂滴中动员的 FA 对新生 APOB 进行脂化的多步骤过程产生。瞄准 2A 我们将测试 TMEM55B 敲低是否可以防止新生 VLDL 的脂化，并测试这些对溶酶体的影响。众所周知，男性患 NAFLD 的风险高于绝经前女性，然而，人们对这种性别差异的基础知之甚少。我们发现TMEM55B敲低导致雄性小鼠（而非雌性小鼠）出现脂肪变性，并且肝脏 TMEM55B 的缺失会在很大程度上抑制 TG 分泌雄性小鼠比雌性小鼠的程度更大。 TG 分泌缺陷的性别依赖性差异为归因于性激素的差异。在目标 2B 中，我们将评估 TMEM55B 与性别之间的相互作用激素对雄性和雌性小鼠以及雌激素受体敲除小鼠中 TG 分泌的影响。最后，在目标 3 中我们将评估 TMEM55B 对发育和发育的药理和遗传抑制作用 NAFLD 的进展。了解 TMEM55B 丢失影响多个关键因素的机制通过溶酶体的 FA 代谢轴可以对导致 NAFLD 的因素产生新的见解。