Cardioprotection by extra-small HDL particles

摘要(项目1) 我们的长期目标是确定高密度脂蛋白对心脏保护的结构和功能特征 人类的功能，这可能对预测心血管疾病(CVD)风险具有重要意义 以及开发针对高密度脂蛋白的治疗方法。项目1的主要目标是确定具体的影响 高密度脂蛋白亚型对人类心血管风险的影响以及决定高密度脂蛋白大小的因素 在活体内。核心假设是，不同大小的高密度脂蛋白具有非常不同的促进能力 胆固醇通过ABCA1途径从巨噬细胞外流。 我们最近发现，较小的高密度脂蛋白通过ABCA1途径更多地促进胆固醇外流 比更大形式的高密度脂蛋白强。此外，在一项对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低密度脂蛋白是心脏病风险增加的最强预测因素 死亡、血运重建和心肌梗死。利用化学交联、蛋白质分解和MS/MS分析，我们 发现载脂蛋白A-I(APOA1)形成两种异构体(LL5/5和LL5/4)，我们称之为 旋转异构体，在人类高密度脂蛋白中。LL5/4旋转异构体在小鼠体内选择性升高的超小分子水平表达 高密度脂蛋白具有增强的胆固醇流出能力。 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对2型糖尿病患者(T2D)的影响。使用我们开发的最先进的方法来测量 总高密度脂蛋白的浓度(高密度脂蛋白-P)和四个高密度脂蛋白亚种的大小和浓度(超小， 小型、中型和大型高密度脂蛋白)，我们将确定特定大小的高密度脂蛋白预测心血管疾病风险是否比 500例前瞻性T2D患者的总高密度脂蛋白胆固醇和独立于传统血脂危险因素的研究 心血管事件风险的前瞻性研究。我们将补充这些研究，确定低水平的 在T1D患者的验证队列中，超低密度脂蛋白可预测心血管事件风险。我们还将确定是否 胆固醇流出能力、高密度脂蛋白氧化和高密度脂蛋白的抗炎特性可预测心血管疾病的风险。目标2将 确定两种主要的APOA1旋转体对高密度脂蛋白、胆固醇的大小和浓度的影响 人源化小鼠模型中高密度脂蛋白的流出能力和动脉粥样硬化。因为我们之前已经展示了 低水平的超小高密度脂蛋白强烈预测T1D患者的心血管事件，我们将研究这两个非糖尿病患者 和糖尿病小鼠，使用经过验证的T1D小鼠模型。我们将补充我们的老鼠机制研究 通过分析旋转异构体分布与T1D和T2D患者心血管疾病风险的关系。 高密度脂蛋白的结构特征与其大小、功能和心血管疾病风险相关的证明将提供 对高密度脂蛋白心脏保护功能的机械论和翻译学见解。

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.