TMEM55B as a molecular determinant of NAFLD

TMEM55B 作为 NAFLD 的分子决定因素

• 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
• 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

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.

总结 非酒精性脂肪性肝病（NAFLD）是一系列由脂肪变性引起的疾病，可进展为 非酒精性脂肪性肝炎（NASH）和肝硬化。虽然它是美国肝病的主要原因， 没有针对性的治疗干预措施，突出了识别分子过程的迫切需要 这是其病理学的基础。跨膜蛋白55 B（TMEM 55 B）是位于膜上的PI（4，5）P2磷酸酶。 已经显示影响溶酶体水平和定位。在初步研究中，我们发现， TMEM 55 B阿索治疗在西方饮食6周后引起C57 BL/6 J小鼠的肝脂肪变性，而TMEM 55 B ASO治疗在C57 BL/6 J小鼠中引起肝脂肪变性。 TMEM 55 B基因敲除小鼠在高脂肪、胆固醇和果糖补充的12周后发生NASH。 (GAN)饮食.我们已经确定了TMEM 55 B基因敲除的几种可能促进NAFLD的影响：1） 溶酶体内脂质蓄积，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，以及 增加的氧化应激;和3）体内抑制肝甘油三酯分泌。溶酶体在细胞内起着关键的 在分选和处理脂质中的作用，其中适当的溶酶体运动对其动员FA的能力至关重要 并维持线粒体的体内平衡。TMEM 55 B在调节溶酶体中起关键作用 定位，因此我们的中心假设是TMEM 55 B的缺失促进NAFLD的发生和进展 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， 分泌物。在目标1中，我们将确定TMEM 55 B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TMEM 55 B对 线粒体形态和功能障碍。肝脏甘油三酯（TG）主要在VLDL内分泌， 通过用从脂滴动员的FA使新生APOB脂化的多步骤过程产生。在Aim中 图2A我们将测试TMEM 55 B敲低是否阻止新生VLDL的脂化，并测试TMEM 55 B的依赖性。 这些对溶酶体的影响众所周知，男性比绝经前女性有更高的NAFLD风险， 然而，人们对这种性别差异的基础知之甚少。我们发现TMEM 55 B基因敲除导致 雄性而非雌性小鼠脂肪变性和肝脏TMEM 55 B的缺失抑制TG分泌到更高的水平 在雄性小鼠和雌性小鼠中的比例更大。TG分泌缺陷的性别依赖性差异为： 这是由于性激素的差异。在目标2B中，我们将评估TMEM 55 B和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TG分泌的影响。最后，在Aim 3中 我们将评估TMEM 55 B的药理学和遗传抑制对发育的影响， NAFLD的进展。了解TMEM 55 B缺失影响多个关键 通过溶酶体的FA代谢轴可以产生对NAFLD促成因素的新见解。