Interacting Impact of Adrenal and Ovarian Aging on the CNS

描述（由申请人提供）：更年期的一个特征是卵巢类固醇（如雌二醇和黄体酮）的分泌和释放明显减少。然而，这些变化对人体生理，特别是中枢神经系统（CNS）的影响尚不清楚。我们已经证明，雌性恒河猴和女性一样会经历更年期，血浆FSH和抑制素B水平的变化代表了这一事件的第一个内分泌表现。我们还发现血浆中肾上腺类固醇，脱氢表雄酮（DHEA）的水平在这个时候显著下降。脱氢表雄酮是血液循环中最丰富的类固醇之一；它以昼夜节律的方式释放到循环中，在许多组织中很容易转化为雌二醇。亲本R01基金（AG-029612）的总体目的是研究肾上腺和卵巢老化对灵长类动物中枢神经系统的相互影响。利用雌性恒河猴作为实用动物模型，我们提出验证衰老相关的DHEA释放衰减加剧了围绝经期雌二醇的下降，从而对认知、学习和注意力等核心生理过程产生负面影响，并导致昼夜睡眠-觉醒周期的扰动。Specific Aim 1将使用一系列行为测试来评估年轻人、经常骑车和不经常骑车的老年人之间的差异；这些年老的动物将作为未经治疗的对照进行测试，并在长期治疗后使用“年轻的”生理水平的脱氢表雄酮进行测试。认知和行为评估将包括：1)空间工作记忆延迟反应测试，该测试对年龄和前额皮质功能障碍特别敏感；2)延迟非匹配样本，一个主要探测基于海马体记忆的任务；3)雌激素敏感的视觉注意视觉空间线索测试；4)杏仁核损伤敏感行为反应性测试。此外，将使用Actiwatch记录仪持续监测睡眠-觉醒周期，并在DHEA替代前后进行MRI以监测大脑关键区域的形态和生化变化。特异性目标2将使用一系列生化和组织化学方法来阐明在肾上腺-卵巢老化过程中中枢神经系统内发生的可塑性。基因微阵列和RT-PCR将被用来鉴定在年轻和年老动物、规律和不规则的老年循环者、dhea治疗和未治疗的老年动物的中枢神经系统中差异表达的基因。重点将放在编码DHEA转化为雌二醇的酶的基因、类固醇受体以及与关键神经递质系统和生物钟相关的基因上。免疫组织化学，原位杂交组织化学，RIA和生化酶学将证实结果。补充目的：在2008年底，我们的试点R21拨款（AG-026472）将释放20只切除卵巢的恒河猴，这些恒河猴已经使用特定目标1中描述的相同程序进行了认知测试。更重要的是，其中一些动物已经（并且仍然）持续接受激素替代疗法（HRT），包括雌二醇和黄体酮的组合。因此，我们有一个独特的机会，将这些额外的动物整合到母体dhea替代研究中，而额外的费用很少。将切除卵巢、雌二醇治疗和雌二醇/黄体酮治疗的老动物结合起来，是对原始实验设计的重大加强，因为这将使我们能够比较和对比脱氢表雄酮替代疗法与更传统的激素替代疗法的疗效。公共卫生相关性：更年期的一个特征是卵巢类固醇（如雌二醇和黄体酮）的分泌和释放明显减少。然而，血浆中肾上腺类固醇，脱氢表雄酮（DHEA）的水平也在这个时候显著下降。脱氢表雄酮是血液循环中最丰富的类固醇之一；它以昼夜节律的方式释放到循环中，在许多组织中很容易转化为雌二醇。本研究的总体目的是研究肾上腺和卵巢老化对灵长类动物中枢神经系统的相互影响。利用雌性恒河猴作为实用动物模型，我们提出验证衰老相关的DHEA释放衰减加剧了围绝经期雌二醇的下降，从而对认知、学习和注意力等核心生理过程产生负面影响，并导致昼夜睡眠-觉醒周期的扰动。

DESCRIPTION (provided by applicant): A characteristic feature of the menopause is a marked attenuation in the production and release of ovarian steroids, such as estradiol and progesterone. However, the impact of these changes on human physiology, especially within the central nervous system (CNS), is far from being clear. We have already shown that female rhesus macaques, like women, undergo menopause, and that a change in plasma FSH and inhibin B levels represents the first endocrine manifestation of this event. We have also shown that plasma levels of the adrenal steroid, dehydroepiandrosterone (DHEA), fall markedly around this time. DHEA is one of the most abundant steroids in the circulation; it is released into the circulation in a circadian manner and is readily converted to estradiol in many tissues. The overall aim of the parent R01 grant (AG-029612) is to examine the interacting impact of adrenal and ovarian aging on the CNS of primates. Using the female rhesus macaque as a pragmatic animal model, we propose to test the hypothesis that the aging-related attenuation of DHEA release exacerbates the perimenopausal decline in estradiol, and thereby negatively impacts central physiological processes such as cognition, learning, and attention, and leads to perturbation of the circadian sleep-wake cycle. Specific Aim 1 will use a battery of behavioral tests to assess differences between young adults, and old regularly-cycling and irregularly-cycling adults; the old animals will be tested both as untreated controls and also after extended treatment with "young" physiological levels of DHEA. Cognitive and behavioral assessments will include: 1) delayed response test of spatial working memory, which is particularly sensitive to aging and prefrontal cortex dysfunction; 2) delayed non-matching-to-sample, a task probing primarily hippocampus-based memory; 3) a visuospatial cueing test of visual attention that is estrogen-sensitive; and 4) a test of behavioral reactivity sensitive to amygdala damage. In addition, sleep-wake cycles will be continuously monitored using Actiwatch recorders, and MRI will be performed before and after DHEA replacement to monitor morphological and biochemical changes in the key brain regions. Specific Aim 2 will use a series of biochemical and histochemical methodologies to elucidate the plasticity that occurs within the CNS during adrenal-ovarian aging. Gene microarrays and RT-PCR will be used to identify genes that are differentially expressed in the CNS between young and old animals, regular and irregular old cyclers, and DHEA-treated and untreated old animals. The focus will be on genes encoding enzymes involved in the conversion of DHEA to estradiol, steroid receptors, and genes associated with key neurotransmitters systems and circadian clocks. Immunohistochemistry, in situ hybridization histochemistry, RIA and biochemical enzymology will be used to corroborate the results. Aim of Supplement: At the end of 2008, our pilot R21 grant (AG-026472) will be releasing 20 ovariectomized rhesus macaques, which have already been cognitively tested using the same procedures described in Specific Aim 1. More importantly, some of these animals have been (and still are) continuously exposed to hormone replacement therapy (HRT), involving combinations of estradiol and progesterone. We thus have a unique opportunity to integrate these additional animals into the parent DHEA-replacement study, with very little additional expense. This integration of old ovariectomized, estradiol-treated and estradiol/progesterone-treated animals represents a major strengthening of the original experimental design, because it will enable us to compare and contrast the efficacy of DHEA replacement therapy to that of more conventional HRT. PUBLIC HEALTH RELEVANCE: A characteristic feature of the menopause is a marked attenuation in the production and release of ovarian steroids, such as estradiol and progesterone. However, plasma levels of the adrenal steroid, dehydroepiandrosterone (DHEA), also fall markedly around this time. DHEA is one of the most abundant steroids in the circulation; it is released into the circulation in a circadian manner and is readily converted to estradiol in many tissues. The overall aim this research is to examine the interacting impact of adrenal and ovarian aging on the central nervous system of primates. Using the female rhesus macaque as a pragmatic animal model, we propose to test the hypothesis that the aging-related attenuation of DHEA release exacerbates the perimenopausal decline in estradiol, and thereby negatively impacts central physiological processes such as cognition, learning, and attention, and leads to perturbation of the circadian sleep-wake cycle.