Cardioprotection by extra-small HDL particles

摘要（项目1） 我们的长期目标是确定负责HDL的心脏保护作用的结构和功能特征。 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的治疗方法。项目1的主要目标是确定具体的 研究HDL亚种对人类心血管风险的影响，并确定决定HDL大小的因素。 in vivo.中心假设是不同大小的HDL具有非常不同的促进 胆固醇通过ABCA 1途径从巨噬细胞流出。 我们最近发现，较小的HDL通过ABCA 1途径促进胆固醇流出的作用更大 强于更大形式的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。通过化学交联、蛋白水解和MS/MS分析， 证明载脂蛋白A-I（APOA 1）形成两种异构体（LL 5/5和LL 5/4），我们称之为 旋转异构体，在人类HDL中。LL 5/4旋转异构体在小鼠中的表达选择性地升高了超小RNA的水平。 高密度脂蛋白与增强胆固醇流出能力。 根据这些观察，我们提出了两个具体目标。目的1将扩大我们对患者的观察 2型糖尿病（T2 D）患者的血糖水平。使用我们开发的最先进的方法来测量 总HDL（HDL-P）的浓度和四种HDL亚种（超小， 小，中，大HDL），我们将确定是否特定尺寸的HDL预测CVD风险更强， Look AHEAD研究中500例T2 D患者的总HDL-P和独立于传统脂质风险因素， 心血管事件风险的前瞻性研究。我们将通过确定是否存在低水平的 在T1 D患者的验证队列中，超小HDL可预测发生CVD的风险。我们还将确定， 胆固醇流出能力、HDL氧化和HDL的抗炎特性预测CVD风险。目标2将 确定两种主要的载脂蛋白A1旋转异构体对HDL、胆固醇 HDL的流出能力和人源化小鼠模型中的动脉粥样硬化。因为我们之前已经证明， 在T1 D患者中，低水平的超小HDL强烈预测CVD事件，我们将研究非糖尿病 和糖尿病小鼠，使用经验证的T1 D小鼠模型。我们将补充我们的小鼠机制研究， 通过分析T1 D和T2 D患者中旋转异构体分布与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 机制和翻译的见解HDL的心脏保护功能。

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.