Dysregulated Oxalate Metabolism in Cardiometabolic Diseases

项目概要/摘要 影响全球三分之一的人口，没有可用的药物治疗，非酒精性脂肪肝疾病 （NAFLD）已成为慢性肝病的主要原因。令人惊讶的是， NAFLD患者和更严重的非酒精性脂肪性肝炎（NASH）是动脉粥样硬化性心血管疾病， 疾病（CVD）。这突出表明迫切需要确定同时治疗的靶向途径， 由于对连接这两种疾病的病理生理学和代谢途径的了解有限， 疾病最近，我们和其他人发现草酸代谢在NAFLD和CVD中普遍失调。 虽然草酸盐在肾脏中的作用是众所周知的，但尚未在肝细胞中进行系统研究， 负责其形成的原代细胞。此外，在NASH和相关的动脉粥样硬化中， 草酸盐的作用，其潜在机制和靶向草酸盐过度产生的治疗潜力， 未知使用无偏转录组学，我们发现了限制草酸盐产生的基因的抑制， 来自患有NASH的人类和小鼠的肝脏。丙氨酸-乙醛酸转氨酶（AGXT），一种肝脏特异性酶 解毒乙醛酸，草酸盐前体，减少和草酸盐显着增加的相关性， NASH严重程度。值得注意的是，患有动脉粥样硬化的患者和小鼠的草酸盐也增加了。在 我们的小鼠肝脏草酸盐过度生成（Agxt-/-）模型，NASH和动脉粥样硬化均增加 具有抑制肝脂肪酸β-氧化（FAO）和诱导的促炎途径。粥样硬化 外源性草酸也能提高细胞凋亡率。在肝细胞中，草酸诱导线粒体功能障碍和脂质过氧化反应。 累积，同时下调过氧化物酶体增殖物激活受体α（PPARα）靶点， 上调C-C基序趋化因子配体5（CCL 5）。重要的是，通过肝脏特异性 AGXT过表达，作为概念验证，减弱NASH和动脉粥样硬化，强调了 草酸盐减少用于同时治疗。这个项目将解决的中心假设，肝草酸盐 过度生产通过线粒体功能障碍、受损的PPARα/FAO和 CCL 5诱导，而草酸盐形成的抑制减少了已建立的NASH和动脉粥样硬化。要求1 将使用新的小鼠来确定草酸盐驱动NASH和相关动脉粥样硬化的机制 肝脏草酸盐过度产生，PPARα和CCL 5缺乏，结合饮食和药物 草酸盐、线粒体功能和过氧化物酶体增殖物激活受体α的操纵，以及体外模型。目标2将定义草酸盐 使用遗传和饮食方法减少NASH和相关动脉粥样硬化的潜在治疗 以限制肝草酸盐形成并增强体内和体外乙醛酸解毒。目标3将描述 利用表观遗传学研究NASH和动脉粥样硬化中肝脏草酸盐过量产生及其遗传调控， GWAS和人肝脏样本。这项工作将描绘一个新确定的代谢途径连接NASH 和动脉粥样硬化，并将草酸盐减少的转化作为这些疾病的并发治疗。

PROJECT SUMMARY/ABSTRACT Affecting one third of the global population, with no pharmacotherapy available, nonalcoholic fatty liver disease (NAFLD) has become the leading cause of chronic liver disease. Surprisingly, the major cause of death in patients with NAFLD and the more severe nonalcoholic steatohepatitis (NASH) is atherosclerotic cardiovascular disease (CVD). This highlights a critical need to identify targetable pathways for concurrent treatment, which has been hampered by limited understanding of the pathophysiology and metabolic pathways linking these two diseases. Recently, we and others uncovered oxalate metabolism commonly dysregulated in NAFLD and CVD. While oxalate effects in the kidneys are well known, they have not been systematically studied in hepatocytes, the primary cells responsible for its formation. Moreover, in NASH and associated atherosclerosis, a causative role of oxalate, its underlying mechanisms and the therapeutic potential of targeting oxalate overproduction are unknown. Using unbiased transcriptomics, we uncovered suppression of genes that limit oxalate production in livers from humans and mice with NASH. Alanine-glyoxylate aminotransferase (AGXT), a liver-specific enzyme that detoxifies glyoxylate, the oxalate precursor, was reduced and oxalate was markedly increased in correlation with NASH severity. Remarkably, oxalate was also increased both in patients and mice with atherosclerosis. In our mouse model of hepatic oxalate overproduction (Agxt-/-), both NASH and atherosclerosis were increased with suppressed hepatic fatty acid β-oxidation (FAO) and induced proinflammatory pathways. Atherosclerosis was enhanced also by exogenous oxalate. In hepatocytes, oxalate induced mitochondrial dysfunction and lipid accumulation while downregulating peroxisome proliferator-activated receptor α (PPARα) targets and upregulating C-C motif chemokine ligand 5 (CCL5). Importantly, limiting oxalate production via liver-specific AGXT overexpression, as proof-of-concept, attenuated NASH and atherosclerosis, underscoring the potential of oxalate reduction for concurrent treatment. This project will address the central hypothesis that hepatic oxalate overproduction drives NASH and atherosclerosis via mitochondrial dysfunction, impaired PPARα/FAO, and CCL5 induction, while suppression of oxalate formation reduces established NASH and atherosclerosis. Aim 1 will determine the mechanisms by which oxalate drives NASH and associated atherosclerosis using novel mice with hepatic oxalate overproduction, PPARα and CCL5 deficiency, combined with dietary and pharmacological manipulation of oxalate, mitochondrial function and PPARα, and in vitro models. Aim 2 will define oxalate reduction as a potential therapy for NASH and associated atherosclerosis using genetic and dietary approaches to limit hepatic oxalate formation and enhance glyoxylate detoxification in vivo and in vitro. Aim 3 will characterize hepatic oxalate overproduction and its genetic regulation in human NASH and atherosclerosis using epigenetics, GWAS and human liver samples. This work will delineate a newly identified metabolic pathway linking NASH and atherosclerosis and advance translation of oxalate reduction as a concurrent treatment for these diseases.