Insulin Signaling in the Anterior Pituitary

描述（由申请人提供）：来自人类，动物模型和体外细胞模型系统的研究证据表明，生殖适应性的严格代谢控制。特别是，胰岛素受体信号已被证明在秀丽隐杆线虫和小鼠的生殖系统中发挥重要作用。人类的临床研究和敲除小鼠模型的观察表明，胰岛素作用与生殖的神经内分泌控制之间存在直接联系。对叙利亚仓鼠、大鼠、母羊等动物模型系统的研究和一些临床观察表明，胰岛素可以抑制垂体生殖激素的合成。垂体初级培养研究表明，胰岛素是激素合成的积极调节因子。因此，胰岛素作为生殖功能的积极或消极调节的作用仍然存在争议。我们将利用垂体促性腺激素的体外细胞模型和小鼠垂体原代培养来研究胰岛素信号在调节促性腺激素输出中的作用，并解决这一作用的机制基础。我们将确定促性腺激素的合成和释放是由胰岛素调节的点。我们还将确定GnRH和胰岛素信号的趋同机制。我们的总体目标是了解胰岛素如何作为促性腺激素合成的调节剂，并最终调节生殖功能。目的1：胰岛素调节促性腺激素的产生。循环胰岛素水平与促性腺激素的产生呈负相关。使用促性腺激素细胞系LbetaT2，我们将通过评估对激素分泌、蛋白质合成和促性腺激素转录的影响来确定胰岛素的作用点。目的2：促性腺激素细胞模型中GnRH和胰岛素的交叉受体信号传导。初步观察表明，胰岛素可减弱对GnRH刺激的反应。我们假设这是应该的。对GnRH受体靶向的信号成分进行修饰。我们将确定GnRH和胰岛素的细胞内信号汇合点。我们将研究PIS激酶、MAP激酶和G蛋白信号级联以及受体信号的负反馈调节因子，以确定哪些级联和中间蛋白介导促性腺激素中胰岛素对GnRH信号的影响。

DESCRIPTION (provided by applicant): Evidence from studies in humans, animal models, and in vitro cell model systems suggest the tight metabolic control of reproductive fitness. In particular, insulin receptor signaling has been shown to play an important role in fertility in systems ranging from C. elegans to mice. Clinical studies in humans and observations in knockout mouse models suggest a direct link between insulin action and the neuroendocrine control of reproduction. Studies in animal model systems ranging from Syrian hamsters, rats, ewes and some clinical observations indicate that insulin can suppress pituitary reproductive hormone synthesis. Studies in primary pituitary culture indicate that insulin is a positivie regulator of hormone synthesis. Thus the role of insulin as a positive or negative regulator of reproductive function is still controversial. We will utilize an in vitro cell model of the pituitary gonadotropes and mouse primary pituitary culture to investigate the role of insulin signaling in the modulation of gonadotropin output and to address the mechanistic basis for this action. We will identify the point in gonadotropin synthesis and release that is regulated by insulin. We will also identify the mechanism of convergent GnRH and insulin signaling. It is our overall goal to understand how insulin serves as a modulator of gonadotropin synthesis, and ultimately of reproductive function. Aim 1: Insulin regulation of gonadotropin production. Circulating insulin level inversely correlates with gonadotropin production. Using the gonadotrope cell line, LbetaT2, we will determine the point of insulin action by assessing the effects on hormone secretion, protein synthesis, and transcription of gonadotropins. Aim 2: Cross receptor signaling of GnRH and insulin in a gonadotrope cell model. Preliminary observations indicate that insulin attenuates the response to GnRH stimulation. We hypothesize that this is due .to modification of signaling components targeted by the GnRH receptor. We will determine the points of convergent intracellular signaling by GnRH and insulin. We will investigate PIS kinase, MAP kinase, and G protein signalling cascades and negative feedback regulators of receptor signaling to determine which cascades and intermediate proteins mediate insulin effects on GnRH signaling in gonadotropes.