Understanding the Role of HDL Subspecies in Adolescents with Type 2 Diabetes

描述(由申请人提供)：青少年2型糖尿病(T2D)的增加具有重大的医疗后果，因为它与过早发作心血管疾病(CVD)密切相关。T2D青年的常见发现包括脂蛋白异常，随着时间的推移迅速恶化，并可能导致这种心血管疾病风险的增加。由于高密度脂蛋白胆固醇(高密度脂蛋白胆固醇)浓度长期以来一直与心血管疾病的保护有关，最近旨在降低心血管疾病风险的治疗方法主要集中在提高高密度脂蛋白胆固醇。不幸的是，使用这些制剂的药物试验一直无法降低心血管疾病的风险，尽管高密度脂蛋白-C增加了约70%。这很可能是因为“高密度脂蛋白”实际上反映了不同颗粒的聚集，这些颗粒在大小和蛋白质组成上差异很大--而且可能具有功能，不分青红皂白地升高高密度脂蛋白并不能解释这种颗粒的异质性。我们实验室的工作与此一致。事实上，我们的初步工作表明，在患有T2D的青少年中，特定人群中大量富含载脂蛋白E(ApoE)的高密度脂蛋白颗粒枯竭，而这些高密度脂蛋白颗粒的缺乏与临床前心血管疾病(通过脉搏波速度测量的动脉僵硬)的增加有关。这项建议的科学目标是确定T2D是什么导致了这些高密度脂蛋白亚类的变化，并确定了这些高密度脂蛋白亚类变化对心血管疾病发展的功能影响。我们的假设是，T2D中特定的高密度脂蛋白亚型的组成和功能的改变与临床前心血管疾病风险的增加有关。其基本原理是，在高密度脂蛋白亚型改变和心血管疾病风险之间建立联系将为药物操作开辟新的途径，以减轻高危青年的心血管疾病负担。K23的目标1将侧重于分离肥胖、胰岛素抵抗和高血糖的影响，通过利用辛辛那提儿童医院提供的大量经过精心挑选的患者队列，确定导致青少年高密度脂蛋白亚类改变的风险因素。横断面研究将集中于胰岛素抵抗、体重增加和高血糖对高密度脂蛋白亚型的单独和联合影响，而纵向时间进程研究将集中在手术减肥后它们的逆转。在目标2中，我们将探讨T2D介导的大量富含apoE的高密度脂蛋白亚基缺失可能导致血管功能障碍的机制(S)。我们将利用凝胶过滤层析分离高密度脂蛋白亚类，并比较来自健康青少年和二维青少年的富含apoE的大颗粒高密度脂蛋白抑制动脉粥样硬化发展中的关键步骤的能力：低密度脂蛋白(LDL)颗粒的氧化以及阻止低密度脂蛋白与蛋白多糖结合的能力。在目标3中，我们将探索改变的高密度脂蛋白亚种对高密度脂蛋白两个最著名的心脏保护功能的影响：胆固醇外流和刺激一氧化氮产生的能力。这些高密度脂蛋白亚型功能将与临床前心血管疾病的非侵入性测量相关联，以确定T2D青少年高密度脂蛋白功能改变的心血管疾病后果。与K23课程配套的培训目标将把申请者培养成一名独立的、转译脂质研究人员，专注于脂蛋白对心血管疾病的作用机制。培训计划集中在六个关键领域：1)直接的脂类代谢实验室经验；2)教学课程；3)临床上的患者互动；4)撰写手稿和补助金；5)领导力培训；以及6)与该领域的导师和领导者互动。K23职业发展奖的结果将：i)确定高密度脂蛋白组成、功能和血管壁病理联系之间的相互关系，远远超出高密度脂蛋白-C与心血管疾病结局的简单相关性；ii)确定T2D如何影响脂蛋白代谢，可能为治疗操作提供新的途径；iii)为申请者提供全面的脂代谢培训经验，以便提交竞争性的R01申请，重点关注改善高危青年心脏保护的疗法。

DESCRIPTION (provided by applicant): The rise in adolescent type 2 diabetes (T2D) has significant health care consequences as it is strongly associated with a premature onset of cardiovascular disease (CVD). Common findings in T2D youth include lipoprotein abnormalities that worsen rapidly over time and likely contribute to this increased CVD risk. Because high density lipoprotein cholesterol (HDL-C) concentrations have long been associated with CVD protection, recent therapies aimed at lowering CVD risk have focused on raising HDL-C. Unfortunately, drugs trials using these agents have been unable to reduce CVD risk despite increasing HDL-C by some 70%. This is likely because "HDL-C" actually reflects a conglomeration of distinct particles that vary widely in size and protein composition - and presumably function and raising HDL-C indiscriminately does not account for this particle heterogeneity. Work from our laboratory is consistent with this. In fact, our preliminary work has shown that in adolescents with T2D, there is a depletion of a specific population of large apolipoprotein E (apoE) enriched HDL particles and that lack of these HDL particles is associated with an increase in preclinical CVD (arterial stiffness as measured by pulse wave velocity). The scientific goal of this proposal is to determine what it is about T2D that is responsible for these HDL subspecies changes and establish the functional implications of these HDL subspecies changes on CVD development. Our hypothesis is that alteration in the composition and function of specific HDL subspecies in T2D is associated with increased risk of pre-clinical CVD. The rationale is that an established connection between altered HDL subspecies and the risk for CVD will open new avenues for pharmacological manipulation to reduce the CVD burden in high risk youth. Aim 1 of this K23 will focus on isolating the effects of obesity, insulin resistance and hyperglycemia to determine the risk factors that contribute to altered HDL subspecies in adolescents by leveraging a wealth of highly selected patient cohorts uniquely available at Cincinnati Children's Hospital. Cross sectional studies will focus on the impact of insulin resistance, weight gain and hyperglycemia, on HDL subspecies individually and in combination, while longitudinal time course studies will focus on their reversal after surgical weight loss. In Aim 2, we will explore the mechanism(s) by which T2D-mediated depletion of large apoE rich HDL subspecies may result in vascular dysfunction. We will utilize gel filtration chromatography to isolate HDL subspecies and compare the ability of large apoE rich HDL particles from healthy and T2D adolescents to inhibit key steps in the development of atherosclerosis: oxidation of low density lipoprotein (LDL) particles and the ability to prevent LDL binding to proteoglycans. In Aim 3, we will explore the consequences of altered HDL subspecies on two of HDL best known cardioprotective functions: cholesterol efflux and the ability to stimulate nitric oxide production. These HDL subspecies functions will then be related to noninvasive measures of preclinical CVD to establish the CVD consequences of altered HDL function in T2D adolescents. The training goals that accompany this K23 will develop the applicant into an independent, translational lipid researcher focused on the mechanisms by which lipoproteins contribute to CVD. The training plan focuses on six keys areas: 1) a direct laboratory experience in lipid metabolism; 2) didactic coursework; 3) patient interactions in the clinic; 4) writing manuscripts and grants; 5) leadership training; and 6) interacting with mentors and leaders in the field. The outcomes of this K23 career development award will: i) identify the inter-relationships between HDL composition, function and vessel wall pathology connections that go well beyond simple correlations of HDL- C with CVD outcomes, ii) determine how T2D affects lipoprotein metabolism, potentially offering new avenues for therapeutic manipulation, and iii) provide the applicant with a comprehensive training experience in lipid metabolism positioned to submit a competitive R01 application focused on therapies to improve cardio- protection in high risk youth.