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疾病（NAFLD）是脂肪变性引发的一系列疾病，可以发展为非酒精性脂肪性肝炎（NASH）和肝硬化。尽管这是美国肝病的主要原因，但没有针对性的治疗干预措施，强调了识别分子过程的关键需求基本的病理学。跨膜蛋白55b（TMEM55B）是位于该PI（4,5）P2磷酸酶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 TMEM55B ASO治疗在西方饮食6周后在C57BL/6J小鼠中引起肝脂肪变性，而 TMEM55B敲除小鼠在补充高脂，胆固醇和果糖的12周后发展出NASH （gan）饮食。我们已经确定了TMEM55B敲低的几种影响，可以促进NAFLD：1）脂质体内脂质的积累，表明脂肪酸受损（FA）动员，2）受损线粒体FA氧化以及线粒体体积减小，线粒体碎片和增加氧化应激； 3）体内抑制肝甘油三酸酯分泌。溶酶体起关键在分类和加工脂质中的作用，在适当的溶酶体运动对于动员FA的能力至关重要的情况下，从脂质液滴中保持线粒体稳态。 TMEM55B在调节溶酶体中起关键作用定位，因此我们的中心假设是TMEM55B的丧失促进NAFLD发作和进展通过溶酶体对肝FA动员和贩运，线粒体FA氧化和甘油三酸酯的影响分泌。在AIM 1中，我们将确定TMEM55B是否影响FA动员和线粒体功能通过影响溶酶体定位的能力。我们还将检查TMEM55B对线粒体形态和功能障碍。肝甘油三酸酯（TG）是VLDL中的主要分泌通过从脂质液滴中动员的FA的脂质新生APOB的多步骤生成。目标 2a我们将测试TMEM55B敲低是否可以防止新生VLDL的脂化并测试依赖性这些对溶酶体的影响。男性众所周知，NAFLD的风险比绝经前女性更高，但是，这种性别差异的基础知之甚少。我们发现TMEM55B敲除造成雄性但不是雌性小鼠的脂肪变性，而肝TMEM55B的丧失抑制了TG分泌男性与雌性小鼠的程度更高。 TG分泌缺陷的性别依赖性差异是归因于性激素的差异。在AIM 2B中，我们将评估TMEM55B与性别之间的相互作用男性和雌性小鼠TG分泌的激素以及雌激素受体敲除小鼠的激素。最后，在目标3中我们将评估TMEM55B对药理和遗传抑制的影响 NAFLD的进展。了解损失TMEM55B影响多个关键的机制通过溶酶体，FA代谢的轴可以产生对有助于NAFLD的因素的新见解。