Astrocyte insulin resistance-induced neuroendocrine defects in pubertal delay and hypogonadotropic hypogonadism

已知星形胶质细胞为控制促性腺激素释放激素(GnRH)的神经元提供支持 生殖轴，例如通过释放生育所需的前列腺素E2(PGE2)。星形胶质细胞可能 作为新陈代谢感应器，它在大脑中也起着关键作用。作为对胰岛素的反应，星形胶质细胞增加了血糖 通过血脑屏障摄取和释放代谢物和神经胶质递质来支持神经元 功能。我们最近证明了星形胶质细胞在连接生育和能量方面的独特生物学作用。 可用性。我们发现，星形胶质细胞中胰岛素信号的缺失会延迟青春期，导致 性腺激素减退症，并极大地降低生育能力。这一发现特别令人兴奋，因为 大量研究表明，神经元胰岛素感应对于生殖来说是不必要的。我们还发现了 星形胶质细胞胰岛素感应的丧失降低了PGE2合成酶水平，使我们假设星形胶质细胞 胰岛素感应通过促进星形胶质细胞PGE2的释放来促进GnRH的释放。新的初步数据表明 通过FOXO途径的胰岛素信号改变了PGE2生物合成途径中的酶的转录， 如COX-2。我们将通过追求三个具体目标来检验我们的假设。目标1)定义相关的 星形胶质细胞胰岛素信号的时间和空间参数。使用tet-on基因靶向系统，我们将 测试星形胶质细胞是否必须在成年期或青春期前感觉到胰岛素才能正常 生殖功能。星形胶质细胞特异性病毒cre的应用也将决定 星形胶质细胞在弓状核和吻侧视前区的胰岛素感觉。目标2)确定以下方面的影响 生殖回路附近星形胶质细胞PGE2神经递质产生的胰岛素信号。 AAV靶向干扰COX-2将补充对区域PGE2产量的测量 由星形胶质细胞产生，以确定其对生育的重要性。最后，我们将确定Kiss1是否 神经元感知PGE2，导致GnRH释放改变。目的3)确定胰岛素的分子作用。 星形胶质细胞前列腺素E_2合成中的FOXO途径一个星形细胞系将被用来系统地研究 胰岛素/FOXO/COX信号的主要方面，包括磷酸化、定位、启动子占位、 和定量转录活性测量。最后，我们将消融胰岛素信号通路。 以确定它们对生育和PGE2产生的影响。总的来说，这些研究将确定 星形胶质细胞中的胰岛素信号如何维持生殖回路功能。这项工作将阐明什么可能是 哺乳动物大脑中的主要机制，胰岛素允许正常生育和青春期 成熟。我们的结果将推进我们寻找生育力受损的治疗目标的长期目标 从能量缺乏中恢复的患者，肥胖和糖尿病人群，以及其他特发性 性腺激素减退症。

Astrocytes are known to provide support to gonadotropin releasing hormone (GnRH) neurons that control the reproductive axis, for example by releasing prostaglandin E2 (PGE2) required for fertility. Astrocytes may also play a critical role in the brain as metabolic sensors. In response to insulin, astrocytes increase glucose uptake across the blood brain barrier and release metabolites and gliotransmitters to support neuronal function. We have recently demonstrated a unique biological role for astrocytes in coupling fertility to energy availability. We found that the absence of insulin signaling in astrocytes delays puberty, causes hypogonadotropic hypogonadism, and dramatically reduces fertility. This finding is particularly exciting since numerous studies have shown neuronal insulin sensing is unnecessary for reproduction. We have also found that loss of astrocyte insulin sensing reduces PGE2 synthase levels, leading us to hypothesize that astrocyte insulin sensing facilitates GnRH release by promoting astrocyte PGE2 release. New preliminary data suggest that insulin signaling via FOXO pathways alter the transcription of enzymes in the PGE2 biosynthesis pathway, such as COX-2. We will test our hypothesis by pursuing three specific aims. Aim 1) Define the relevant temporal & spatial parameters of astrocyte insulin signaling. Using the tet-on genetic targeting system, we will test whether astrocytes must sense insulin during adulthood or prior to puberty in order to permit normal reproductive function. Astrocyte-specific viral cre administration will also determine the importance of astrocyte insulin sensing in the arcuate nucleus and the rostral preoptic area. Aim 2) Determine the impact of insulin signaling on astrocyte PGE2 gliotransmitter production proximal to reproductive circuits. Measurement of regional PGE2 production will be complemented by AAV targeted disruption of Cox-2 production by astrocytes to determine its importance for fertility. Finally, we will determine whether Kiss1 neurons sense PGE2, leading to altered GnRH release. Aim 3) Determine the molecular role of the insulin/ FOXO pathway in astrocyte PGE2 synthesis. An astrocyte cell line will be used to systematically investigate the major aspects of insulin/FOXO/COX signaling, including phosphorylation, localization, promoter occupancy, and quantitative transcriptional activity measurements. Finally, we will ablate insulin signaling pathways in astrocytes to determine their effect on fertility and PGE2 production. Collectively, these studies will identify how insulin signaling in astrocytes sustains reproductive circuit function. This work will elucidate what may be the dominant mechanism in the mammalian brain whereby insulin permits normal fertility and pubertal maturation. Our results will advance our long-term goal of finding treatment targets for impaired fertility in patients recovering from energy deficits, obese and diabetic populations, and others with idiopathic hypogonadotropic hypogonadism.