Significance of Pituitary Leptin to Gonadotropes

描述（由申请人提供）：前列腺素leptin以周期性方式变化，表明其可能促进或允许促性腺激素分泌。在食物剥夺和葡萄糖介导的平行恢复期间，垂体瘦素和LH平行减少。这种间接证据表明，垂体瘦素可能作为一个代谢网关，允许促性腺激素功能，如果营养状况是最佳的。这项拟议的试点研究旨在开发细胞和动物模型，测试的假设，垂体瘦素从促生长激素是至关重要的正常发育和促性腺激素释放激素（GnRH）的反应。这些研究将在目标1中用体外方法检验假设，其中将使用针对瘦素mRNA的siRNA敲除垂体瘦素。在目的2中，将通过体内研究来检验该假设，其中通过Cre-loxP技术在促生长素中缺失瘦素表达。为了消除生长激素中的瘦素基因，将携带转基因rGhp-Cre的突变小鼠与携带瘦素基因侧翼的loxP的小鼠杂交。在这两组目标中，将检测促性腺激素对GnRH的反应，以确定体外或体内（生长激素）垂体瘦素消融是否影响促性腺激素功能。促性腺激素发育和生育力也将在生长激素中切除瘦素的突变小鼠中进行测试。这项试点研究提供了一个集中的方法来回答垂体瘦素促性腺激素功能的意义的问题，避免了与全球瘦素基因敲除影响促性腺激素和混淆瘦素功能的解释看到的代谢问题。该初步研究将为未来研究的发展奠定基础，这些研究将测试垂体瘦素对促性腺激素对其他调节剂（类固醇，神经肽Y和激活素）的反应的影响。未来的Cre-loxP技术的体内研究，可以提出测试瘦素产生的其他垂体细胞类型（促肾上腺皮质激素和促性腺激素）的意义。这项研究的最终目的将是确定瘦素如何支持生殖能力，以及营养不良的信息如何与不孕症联系在一起。 公共卫生相关性：这项初步研究的重点是垂体瘦素的意义，促性腺激素，测试的假设，垂体瘦素是至关重要的促性腺激素的发展和/或功能。目的1建立一种体外模型，利用瘦素基因的siRNA阻断垂体瘦素表达，研究瘦素对促性腺激素功能的影响。目的二是建立一种利用Cre-loxP技术特异性阻断生长激素细胞内瘦素表达的转基因小鼠模型。转基因小鼠，其中瘦素是敲除的生长激素，将进行测试的时间开始青春期，生育能力，并通过促性腺激素对刺激的反应。这些研究侧重于将营养状况与生育力联系起来的基本调节机制。

DESCRIPTION (provided by applicant): Pituitary leptin changes in a cyclic manner that indicates it may facilitate or permit the secretion of gonadotropins. There are parallel reductions in pituitary leptin and LH during food deprivation and a parallel recovery mediated by glucose. This circumstantial evidence suggests that pituitary leptin may serve as a metabolic gateway to permit gonadotrope function, if the nutritional status is optimal. This proposed pilot study is designed to develop cellular and animal models that test the hypothesis that pituitary leptin from somatotropes is vital for the normal development and responses of gonadotropes to gonadotropin releasing hormone (GnRH). The studies will test the hypothesis with in vitro approaches in Aim 1 in which siRNA for leptin mRNA will be used to knock out pituitary leptin. In Aim 2, the hypothesis will be tested by in vivo studies, in which leptin expression is deleted in somatotropes by Cre-loxP technology. To ablate the leptin gene in somatotropes, mutant mice bearing the transgene rGHp-Cre will be crossed with mice that bear loxP flanking the leptin gene. In both sets of aims, gonadotrope responses to GnRH will be tested to determine if ablation of pituitary leptin in vitro or in vivo (in somatotropes) affects gonadotrope functions. Gonadotrope development and fertility will also be tested in the mutant mice that have leptin excised in somatotropes. This pilot study provides a focused approach to answer the question of the significance of pituitary leptin to gonadotrope functions, which avoids metabolic problems seen with global leptin knockouts that affect gonadotropes and confound interpretation of leptin functions. The pilot study will lay the foundation for the development of future studies that test the effect of pituitary leptin on gonadotrope responses to other regulators (steroids, neuropeptide Y and activin). Future in vivo studies with Cre-loxP technology can be proposed to test the significance of leptin produced by other pituitary cell types (corticotropes and gonadotropes). The ultimate aim of the study will be to determine how leptin supports reproductive competence and how information about malnutrition may be linked with infertility. PUBLIC HEALTH RELEVANCE: This proposed pilot study is focused on the significance of pituitary leptin to gonadotropes; testing the hypothesis that pituitary leptin is vital for gonadotrope development and/or functions. Aim 1 will develop an in vitro model; the studies will use siRNA for leptin mRNA to ablate pituitary leptin to determine its effects on gonadotrope function. Aim 2 will develop an in vivo transgenic mouse model in which leptin is ablated specifically in somatotropes by Cre-loxP technology. Transgenic mice, in which leptin is knocked out in somatotropes, will be tested for the time of onset of puberty, fertility, and responses by gonadotropes to stimuli. These studies focus on basic regulatory mechanisms that link nutritional status to fertility.