Intermittent hypoxia, adiponectin, and insulin resistance in cardiovascular risk

描述(申请人提供)：周期性间歇性低氧(IH)正在成为阻塞性睡眠呼吸暂停(OSA)患者胰岛素抵抗和心血管疾病发展的重要因素。OSA在充血性心力衰竭(CHF)中非常常见，多达三分之一的患者会发生OSA。胰岛素抵抗也与心脏功能障碍的发生有关。持续气道正压(CPAP)治疗阻塞性睡眠呼吸暂停综合征(OSA)可缓解睡眠时IH，提高胰岛素敏感性，改善心功能，提示IH是影响心肌功能的重要因素。IH导致胰岛素抵抗及相关的心血管疾病和心肌功能障碍的机制尚不清楚。脂肪组织合成和分泌多种生物活性多肽，统称为脂肪细胞因子。脂联素(adiponectin，Ad)是一种仅在白色脂肪组织中合成的脂联素，近年来因其强大的生理作用和抗糖尿病、抗动脉粥样硬化、抗炎等多种作用而备受关注。已有研究表明，在胰岛素抵抗的个体中，循环中的总Ad水平较低。目前尚不清楚周期性IH(类似于人类阻塞性睡眠呼吸暂停综合征期间遇到的IH)是否会减少脂肪细胞中Ad的表达和分泌。因此，在特定的目标1中，我们将研究IH是否改变了脂肪细胞的Ad分泌，从而导致这些细胞的胰岛素抵抗增加。AD可预防心肌梗死后收缩功能障碍的发展。AD缺乏可导致压力超负荷状态下的进行性心脏重塑，并可防止培养的心肌细胞肥大。目前尚不清楚IH诱导的胰岛素抵抗是否会导致心肌功能障碍。因此，在特定的目标2中，我们将在动物模型中确定脂联素在间歇性低氧所致的体内胰岛素抵抗和相关的心肌功能障碍的调节中发挥重要作用。由于胰岛素抵抗是左心室收缩和舒张期功能的危险因素，而且我们的初步数据显示，阻塞性睡眠呼吸暂停综合征患者的IH治疗增加了生物活性高分子形式的腺苷，这项建议的具体目标3将涉及翻译研究，以检验CPAP治疗对患有阻塞性睡眠呼吸暂停综合征和心力衰竭的患者的胰岛素抵抗和腺苷水平的影响，并利用心脏磁共振成像将这些影响与心脏结构和功能的变化联系起来。为了执行这一建议，我们组建了一个由临床医生、基础科学家和广告生物学领域的领先权威组成的团队。在俄亥俄州立大学医学院多萝西·M·戴维斯心肺研究所的支持性环境中，临床科学家和基础科学家的这些合作努力使我们能够执行从细胞和动物模型到人类受试者的这些实验。 公共卫生相关性：与阻塞性睡眠呼吸暂停相关的间歇性低氧是一个非常常见的问题，是心血管疾病的重要危险因素。了解脂联素如何预防间歇性低氧诱导的胰岛素抵抗和相关的心肌功能障碍的机制，可能为睡眠呼吸暂停和心血管疾病患者提供新的治疗策略。

DESCRIPTION (provided by applicant): Cyclic intermittent hypoxia (IH) is emerging as an important factor in the development of insulin resistance and cardiovascular diseases in patients with obstructive sleep apnea (OSA). OSA is very common in congestive heart failure (CHF) occurring in up to a third of patients. Insulin resistance has also been linked to the development of cardiac dysfunction. Treatment of OSA with continuous positive airway pressure (CPAP) alleviates the IH during sleep, increases insulin sensitivity, as well as improves cardiac function, suggesting that IH is a crucial factor affecting myocardial function. The mechanisms by which IH is responsible for insulin resistance and associated cardiovascular diseases and myocardial dysfunctions are unclear. Adipose tissue synthesizes and secretes a wide variety of bioactive peptides which are collectively called "adipocytokines". Adiponectin (Ad), an adipoctyokine that is exclusively synthesized in white adipose tissue, has received considerable attention in recent years because of its potent physiological effects and pleiotropic actions which include its antidiabetic, antiatherogenic, and anti-inflammatory effects. Total circulating Ad levels have been shown to be lower in insulin-resistant individuals. Whether cyclic IH (similar to that encountered during the IH associated with OSA in humans) decreases Ad expression and secretion in adipocytes is not known. Therefore, in Specific Aim 1, we will examine whether IH alters Ad secretion in adipocytes resulting in increased insulin resistance in these cells. Ad protects against the development of systolic dysfunction following myocardial infarction. Ad deficiency leads to progressive cardiac remodeling in pressure overloaded condition and it also prevents cellular hypertrophy in cultured myocytes. It is not known whether the insulin resistance induced by IH contributes to myocardial dysfunction. Therefore, in Specific Aim 2, we will establish that adiponectin plays an important role in the modulation of insulin resistance and associated myocardial dysfunction induced by intermittent hypoxia in vivo, in animal models. Since insulin resistance is a risk factor for left ventricular systolic and diastolic function, and also our preliminary data show that treatment of IH in OSA increases the biologically active high-molecular-weight form of Ad, Specific Aim 3 of this proposal will involve translational research to examine the effects of CPAP treatment in human patients with OSA and heart failure, on insulin resistance and Ad levels, and associate these with changes in cardiac structure and function using cardiac magnetic resonance imaging. To carry out this proposal, we have assembled a team consisting of clinicians, basic scientist, and a leading authority on Ad biology. These collaborative efforts among clinician scientists and basic scientists, in a supportive environment at the Dorothy M. Davis Heart & Lung Institute of the Ohio State University College of Medicine, allow us to perform these experiments from cells and animal models to human subjects. PUBLIC HEALTH RELEVANCE: Intermittent hypoxia associated with obstructive sleep apnea is a very common problem that is an important risk factor for cardiovascular disease. Knowledge of the mechanisms of how adiponectin protects against intermittent hypoxia-induced insulin resistance and associated myocardial dysfunction, may provide novel treatment strategies for patients with sleep apnea and cardiovascular disease.