Phytoestrogens, insulin resistance and endothelial function

描述（由申请人提供）：为了减少与年龄相关的血管舒缩症状和降低心血管疾病的风险，许多妇女选择非处方植物雌激素，而不是医生开的雌激素。染料木黄酮是研究最深入和最常见的大豆来源的植物雌激素。染料木素在结构上与172雌二醇相似，对人血管中的ER2受体具有高亲和力，但对生殖器官中的ER1受体具有低亲和力。研究支持大豆来源的植物雌激素对血管反应性和内皮功能的有益作用。然而，在染料木素治疗期间，内皮依赖性扩张的预期改善在胰岛素抵抗个体中减弱。本项目旨在研究染料木素对健康女性和胰岛素抵抗女性微血管反应性的影响。我们的一般假设是染料木素通过一氧化氮机制改善健康女性的内皮功能，但这种机制对胰岛素抵抗的女性无效。我们将以皮肤血管系统为模型研究内皮功能，采用微透析将雌二醇和染料木素直接注入皮肤，同时用激光多普勒血流仪测量微血管血流。我们的第一个目的是使用剂量-反应曲线来确定172-雌二醇和染料木素对有和没有胰岛素抵抗的女性外周微血管的影响。我们假设两种激素的输注都会增加两组女性的血流量，但胰岛素抵抗的女性血管舒张会减弱。我们的第二个目的是验证一氧化氮在健康女性中介导雌二醇和染料木黄酮诱导的血管舒张的假设，但在胰岛素抵抗女性中，一氧化氮不是血管舒张的一个因素。女性服用染料木黄酮和其他植物雌激素，假设有一定程度的心血管保护作用，但数据并没有明确证明这些益处。我们的研究将直接评估染料木素影响血管舒张的程度，并检查其作用机制。此外，我们的研究结果将为研究染料木素和其他植物雌激素对其他与外周循环受损相关的疾病（如雷诺病和高血压）的影响提供基础。提出的研究不仅将提供雌二醇、染料木素、胰岛素抵抗和内皮功能之间相互作用的机制信息，而且将为今后对老年女性和男性胰岛素抵抗的研究奠定基础。

DESCRIPTION (provided by applicant): With the goal of reducing the age-associated vasomotor symptoms and decreasing the risk of cardiovascular disease, many women choose over the counter phytoestrogens in favor of estrogens prescribed by their physicians. Genistein is the best studied and most common of the soy-derived phytoestrogens. Genistein is structurally similar to 172-estradiol and has high affinity for the ER2 receptor present in the human vasculature, but low affinity for the ER1 receptor present in reproductive organs. Studies support beneficial effects of soy-derived phytoestrogens on vascular reactivity and endothelial function. However, during genistein treatment the expected improvement in endothelial dependent dilation is attenuated in individuals with insulin resistance. This project is designed to study the impact of genistein on microvascular reactivity both in healthy women and in women with insulin resistance. Our general hypothesis is that genistein improves endothelial function through a nitric oxide mechanism in healthy women, but that this mechanism is ineffective in women with insulin resistance. We will use the cutaneous vasculature as a model to study endothelial function, and will infuse estradiol and genistein directly into the skin using microdialysis while measuring microvascular blood flow with laser Doppler flowmetry. Our first Aim will use dose-response curves to determine the 172-estradiol and genistein effects on the peripheral microvasculature in women with and without insulin resistance. We hypothesize that both hormone infusions will increase blood flow in both groups of women, but the vasodilation will be attenuated in women with insulin resistance. Our second Aim tests the hypothesis that nitric oxide mediates the estradiol and genistein-induced vasodilation in healthy women, but is not a factor in the more moderate vasodilation seen in women with insulin resistance. Women take genistein and other phytoestrogens assuming a level of cardiovascular protection, but data have not definitively demonstrated these benefits. Our studies will directly assess the extent to which genistein impacts vasodilation and examine the mechanism for its effects. Moreover, our findings will provide a basis to study the impact of genistein and other phytoestrogens on other conditions associated with compromised peripheral circulation such as Reynaud's disease and hypertension. The proposed studies will not only provide mechanistic information on the interaction between estradiol, genistein, insulin resistance and endothelial function, but will serve as a basis for future studies in older women and men with insulin resistance. PUBLIC HEALTH RELEVANCE: With the goal of reducing vasomotor symptoms and protection against the age-associated increase in cardiovascular disease risk, women are increasingly choosing over the counter phytoestrogens (such as genistein) in favor of estrogens prescribed by their physicians. Genistein may improve vascular function but not carry with it the increased breast cancer risks that have been associated with estrogen exposure. Insulin resistance increases cardiovascular disease risk, and may also interfere with the actions of genistein on cardiovascular function. Therefore, these studies have broad public health implications because it is important that women not have a false sense of cardiovascular protection while taking genistein.