Cardioprotection by extra-small HDL particles

摘要（项目 1） 我们的长期目标是确定 HDL 心脏保护作用的结构和功能特征 人类功能，这可能对预测心血管疾病 (CVD) 风险具有重要意义 并开发针对 HDL 的疗法。项目 1 的主要目标是确定具体的影响 HDL 亚种对人类心血管风险的影响，并确定控制 HDL 大小的因素 体内。中心假设是不同大小的 HDL 具有非常不同的促进能力 胆固醇通过 ABCA1 途径从巨噬细胞流出。 我们最近表明，较小的 HDL 更能通过 ABCA1 途径促进胆固醇流出 强于较大形式的 HDL。此外，在一项针对 550 多名心脏健康的 1 型糖尿病患者的研究中 (T1D)，我们发现低水平的超小 HDL 是心脏病风险增加的最强预测因子。 死亡、血运重建和心肌梗死。使用化学交联、蛋白水解和 MS/MS 分析，我们 证明载脂蛋白 A-I (APOA1) 形成两种异构体（LL5/5 和 LL5/4），我们将其称为 人类 HDL 中的旋转异构体。小鼠中 LL5/4 旋转异构体的表达选择性提高了超小分子的水平 HDL具有增强胆固醇流出能力。 基于这些观察，我们提出了两个具体目标。目标 1 将扩大我们对患者的观察 T1D 患者与 2 型糖尿病 (T2D) 患者。使用我们开发的最先进的方法来测量 总 HDL (HDL-P) 浓度以及四个 HDL 亚种（超小、 小、中、大 HDL），我们将确定特定大小的 HDL 是否比特定大小的 HDL 更能预测 CVD 风险 Look AHEAD 中的 500 名 T2D 患者的总 HDL-P 和独立于传统脂质危险因素的研究 CVD 事件风险的前瞻性研究。我们将通过确定是否低水平来补充这些研究 超小 HDL 可预测 T1D 患者验证队列中的 CVD 风险。我们还将确定是否 胆固醇流出能力、HDL 氧化和 HDL 的抗炎特性可预测 CVD 风险。目标2将 确定两种主要 APOA1 旋转异构体对 HDL、胆固醇的大小和浓度的影响 HDL 的流出能力和人源化小鼠模型中的动脉粥样硬化。因为我们之前已经表明 低水平的超小 HDL 强烈预测 1 型糖尿病患者的 CVD 事件，我们将研究非糖尿病患者 和糖尿病小鼠，使用经过验证的 T1D 小鼠模型。我们将补充我们的小鼠机制研究 通过分析 T1D 和 T2D 患者的旋转异构体分布与 CVD 风险之间的关联。 HDL 的结构特征与其大小、功能和 CVD 风险相关的证明将提供 对 HDL 心脏保护功能的机制和转化见解。

SUMMARY (Project 1) Our long-term goal is to identify the structural and functional features responsible for HDL’s cardioprotective functions in humans, which may have important implications for predicting cardiovascular disease (CVD) risk and developing therapeutics targeted to HDL. The main goal of Project 1 is to determine the impact of specific subspecies of HDL on cardiovascular risk in humans and to determine the factors that govern the sizes of HDL in vivo. The central hypothesis is that different sizes of HDL have very different abilities to promote cholesterol efflux from macrophages by the ABCA1 pathway. We recently showed that smaller HDLs promote cholesterol efflux by the ABCA1 pathway much more strongly than larger forms of HDL. Moreover, in a study of over 550 heart-healthy patients with type 1 diabetes (T1D), we found that a low level of extra-small HDL was the strongest predictor of an increased risk of cardiac death, revascularization, and MI. Using chemical crosslinking, proteolysis, and MS/MS analysis, we demonstrated that apolipoprotein A-I (APOA1) forms two isomers (LL5/5 and LL5/4), which we termed rotamers, in human HDL. Expression of the LL5/4 rotamer in mice selectively elevated levels of extra-small HDL with enhanced cholesterol efflux capacity. Based on these observations, we propose two specific aims. Aim 1 will extend our observations in patients with T1D to patients with type 2 diabetes (T2D). Using state-of-the art methods we developed to measure the concentration of total HDL (HDL-P) and the sizes and concentrations of four HDL subspecies (extra-small, small-, medium- and large-HDL), we will determine if specific sizes of HDL predict CVD risk more strongly than total HDL-P and independently of traditional lipid-risk factors in 500 patients with T2D in Look AHEAD, a prospective study of incident CVD risk. We will complement these studies by determining whether low levels of extra-small HDL predict incident CVD risk in a validation cohort of T1D patients. We will also determine if cholesterol efflux capacity, HDL oxidation, and HDL’s anti-inflammatory properties predict CVD risk. Aim 2 will determine the impact of the two major APOA1 rotamers on the sizes and concentrations of HDL, cholesterol efflux capacity of HDL, and atherosclerosis in humanized mouse models. Because we previously showed that low levels of extra-small HDL strongly predict incident CVD in patients with T1D, we will study both nondiabetic and diabetic mice, using a validated mouse model of T1D. We will complement our mouse mechanistic studies by analyzing the association between rotamer distribution and CVD risk in patients with T1D and T2D. The demonstration that HDL’s structural features associate with its size, function, and CVD risk will provide mechanistic and translational insights into HDL’s cardioprotective functions.