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

已知星形胶质细胞为促性腺激素释放激素（GnRH）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（PGE 2）。星形胶质细胞可能 在大脑中也起着代谢传感器的重要作用。作为对胰岛素的反应，星形胶质细胞增加葡萄糖 通过血脑屏障吸收并释放代谢物和胶质递质以支持神经元 功能我们最近已经证明了星形胶质细胞在将生育力与能量耦合中的独特生物学作用 空房的我们发现星形胶质细胞中胰岛素信号的缺失延迟了青春期， 低促性腺激素性腺功能减退症，并显着降低生育能力。这一发现特别令人兴奋，因为 许多研究已经表明神经元胰岛素感应对于生殖是不必要的。我们还发现 星形胶质细胞胰岛素敏感性的丧失降低了PGE 2合酶的水平，这使我们假设星形胶质细胞 胰岛素敏感通过促进星形胶质细胞释放PGE 2来促进GnRH释放。新的初步数据表明 通过FOXO途径的胰岛素信号传导改变了PGE 2生物合成途径中酶的转录， 例如考克斯-2。我们将通过追求三个具体目标来检验我们的假设。（1）定义相关 星形胶质细胞胰岛素信号转导的时间和空间参数。使用tet-on基因定位系统，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知胰岛素，以允许正常的 生殖功能星形胶质细胞特异性病毒cre的管理也将决定的重要性， 弓状核和吻侧视前区的星形胶质细胞胰岛素感受。（2）确定影响 胰岛素信号对生殖回路附近星形胶质细胞PGE 2神经胶质递质产生的影响。 区域PGE 2产生的测量将通过考克斯-2的AAV靶向破坏来补充 以确定其对生育的重要性。最后，我们将确定Kiss 1是否 神经元感知PGE 2，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PGE 2合成中的FOXO通路。星形胶质细胞系将用于系统地研究 胰岛素/FOXO/考克斯信号传导的主要方面，包括磷酸化、定位、启动子占据， 和定量转录活性测量。最后，我们将消融胰岛素信号通路， 星形胶质细胞，以确定其对生育力和PGE 2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，胰岛素使正常生育和青春期 成熟我们的研究结果将推进我们的长期目标，即寻找生育能力受损的治疗靶点， 从能量不足中恢复的患者、肥胖和糖尿病人群以及其他特发性 低促性腺激素性腺功能减退症

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.