Effects of Genetic ANGPTL3 Deficiency on Hepatic Lipid Regulation and Lipoprotein Production

抽象的。心血管疾病是世界范围内主要的死亡原因。药理学的一个主要目标 治疗方法是降低血脂，特别是低密度脂蛋白胆固醇(LDL)，这是高血压的主要危险因素 冠状动脉疾病。家族性高胆固醇血症(FH)患者患 低密度脂蛋白从循环中清除功能障碍和血浆水平升高导致的早发性冠心病 这种致动脉粥样硬化的脂蛋白。有限的治疗加剧了FH的诊断不足和治疗不足 选择。然而，有一种策略已经成功地降低了FH患者的低密度脂蛋白：抑制肝脏 分泌蛋白血管生成素样蛋白3(Angptl3)。一种单抗(Evinacumab)抑制 由于低密度脂蛋白的大幅降低，循环Angptl3最近获得了FDA的批准，用于治疗FH。 即使在低密度脂蛋白受体(LDLR)完全缺乏的患者中也是如此。相比之下，现有的降脂剂 很大程度上依赖LDLR功能从血液中清除这种致动脉粥样硬化的脂蛋白。根据《公约》 NHLBI研究重点，对研究人员来说，重要的是定义可以预测的分子特征 在不同的心血管疾病人群中，对治疗有意义的反应或反应不足。尽管 有希望的临床试验数据显示，血管紧张素转换酶3抑制降低低密度脂蛋白的非低密度脂蛋白受体依赖机制 没有被充分描述的。这是一个需要解决的重要问题，不仅要描述药物抑制 Angptl3不仅可以通过一种新的LDLR非依赖途径来推荐降低血脂的靶点 脂蛋白新陈代谢。这一建议的主要假设是，Angptl3缺乏在一定程度上降低了低密度脂蛋白 通过调节肝脂蛋白组装和脂代谢，同时改变 分泌极低密度脂蛋白颗粒。这一假设将通过实现本提案中概述的目标来解决。这个 拟议的实验采用了肝细胞培养系统的组合，包括永生化癌症。 从诱导多能细胞产生肝细胞样细胞的先进细胞培养模型 干细胞(IPSCs)。这些ipscs来自一组独特的具有完整基因的人类受试者。 血管紧张素转换酶3缺乏。Aim 1将使用这些模型来测试脂蛋白分泌转运和/或 脂代谢参与了血管紧张素转换酶3缺乏症患者的低密度脂蛋白降低。目标2将测试脂蛋白颗粒 分泌动力学、清除性、大小和/或脂质成分也可能有助于降低低密度脂蛋白。这些 实验将作为严格的团契培训计划的一部分在一个资源充足和高度 协作环境。与NHLBI战略计划相一致，拟议的研究将有助于未来 临床医生-研究人员和他们服务的患者通过提高对Angptl3功能的理解- 抑制药物；描述Angptl3在肝脂蛋白代谢中的作用；以及潜在的建议 通过阐明LDLR非依赖清除机制为降脂药物提供新的治疗靶点 循环中的低密度脂蛋白。

ABSTRACT. Cardiovascular disease is the leading cause of death worldwide. A major goal of pharmacologic therapy is to lower plasma lipids, especially low-density lipoprotein cholesterol (LDL), the cardinal risk factor for coronary artery disease (CAD). Patients with familial hypercholesterolemia (FH) have increased risk of developing early-onset CAD due to dysfunctional clearance of LDL from circulation and increased plasma levels of this atherogenic lipoprotein. Underdiagnosis and undertreatment of FH are exacerbated by limited therapeutic options. However, one strategy has been successful at lowering LDL in FH patients: Inhibition of the hepatically secreted protein Angiopoietin-like protein 3 (ANGPTL3). A monoclonal antibody (evinacumab) inhibiting circulating ANGPTL3 recently obtained FDA approval for treatment of FH due to substantial reductions in LDL, even in patients with complete deficiency of the LDL receptor (LDLR). In contrast, existing lipid-lowering agents largely rely on LDLR function to remove this atherogenic lipoprotein from the blood. In accordance with the NHLBI Research Priorities, it is important for researchers to define molecular characteristics that can predict meaningful or inadequate responses to therapy in different populations with cardiovascular disease. Despite promising clinical trial data, the LDLR-independent mechanisms by which ANGPTL3 inhibition lowers LDL have not been fully characterized. This is an important question to address not only to describe how drugs inhibiting ANGPTL3 work but also to recommend targets for reducing plasma lipids via a novel LDLR-independent pathway of lipoprotein metabolism. The main hypothesis of this proposal is that ANGPTL3 deficiency lowers LDL in part by modulating hepatic lipoprotein assembly and lipid metabolism while simultaneously altering characteristics of secreted VLDL particles. This hypothesis will be addressed by achieving the goals outlined in this proposal. The proposed experiments employ a combination of hepatocyte cell culture systems, including immortalized cancer cells and an advanced cell culture model that produces hepatocyte-like cells (HLCs) from induced pluripotent stem cells (iPSCs). These iPSCs are derived from a unique population of human subjects with complete genetic ANGPTL3 deficiency. Aim 1 will use these models to test whether changes in lipoprotein secretory transit and/or lipid metabolism contribute to LDL lowering in ANGPTL3 deficiency. Aim 2 will test whether lipoprotein particle secretion kinetics, clearance, size, and/or lipid composition could also be contributing to LDL lowering. These experiments will be carried out as part of a rigorous fellowship training plan in a well-resourced and highly collaborative environment. Consistent with the NHLBI Strategic Plan, the proposed studies will help future clinician-investigators and the patients they serve by improving understanding of the functions of ANGPTL3- inhibiting drugs; describing a role for ANGPTL3 in hepatic lipoprotein metabolism; and potentially recommending new therapeutic targets for lipid-lowering agents by elucidating an LDLR-independent mechanism for clearance of circulating LDL.