Hypothalamic leptin and insulin signals aligning metabolic state and fertility

描述(申请人提供)：美国儿童和青少年肥胖症的急剧增加对下一代的健康造成了严重的后果。除了众所周知的健康风险外，儿童肥胖还损害生殖健康和发育。的确，女孩早发肥胖，尤其是在青春期，有利于成年后月经不规律、慢性无排卵、不孕不育和多囊卵巢综合征的发展。虽然这种关系的主要原因尚不确定，但对胰岛素和瘦素的中枢抵抗似乎抑制了生殖轴。胰岛素和瘦素是肥胖的循环标志。然而，新陈代谢系统和生殖系统之间的关键沟通部位仍然不清楚。这项建议旨在推进我们阐明代谢性不孕症的分子和遗传决定因素的长期目标。我们假设瘦素和胰岛素直接作用于下丘脑POMC和NPY/AgRP神经元，为GnRH神经元提供输入。这一假说是建立在瘦素和胰岛素引起的POMC和NPY/AgRP神经元活性改变依赖于磷脂酰肌醇3-激酶(PI3K)细胞内信号通路的基础上的。此外，先前的研究表明，大脑特异的瘦素受体和胰岛素受体敲除对生殖轴有显著影响，但通过非PI3K途径阻止瘦素受体信号传递并不会损害生育能力。因此，我们的研究将确定正常(1)能量平衡和(2)生殖功能以及POMC神经元和/或NPY/AgRP神经元是否需要通过PI3K传递胰岛素和瘦素信号。为了实现这些目标，我们将使用cre/lox系统从基因上定位关键神经元。具体地说，我们将研究缺乏胰岛素和瘦素受体或功能性PI3K的小鼠的代谢和生殖表型，仅在POMC神经元和仅在NPY/AgRP神经元中。然后，我们将使用电生理学和一种在体外可视化Akt信号的新方法来确定PI3K缺失对神经元功能的影响。总的来说，这些数据可能为肥胖相关不孕症的治疗和预防方面的治疗进展提供新的靶点。 项目简介：希尔博士在生殖和新陈代谢的不同领域拥有丰富的背景，是唯一有资格从事这些研究的人。在她的博士后研究期间收集的新的遗传学方法将成为研究下丘脑代谢和生殖途径相互作用的未被充分研究的领域的有力工具。通过为她向研究独立性的过渡提供工具，这项提议为一个专注于生殖健康的研究项目奠定了基础，并发现了治疗营养和肥胖相关不孕症的新方法。

DESCRIPTION (provided by applicant): The dramatic increases in childhood and adolescent obesity in the U.S. have serious consequences for the health of the next generation. Along with its well-known health risks, childhood obesity impairs reproductive health and development. Indeed, early onset of obesity in girls, particularly during adolescence, favors the development of menses irregularities, chronic anovulation, infertility, and PCOS in adulthood. While the primary cause of this relationship is uncertain, central resistance to insulin and leptin, circulating markers of adiposity, appears to inhibit the reproductive axis. The key sites of communication between the metabolic and reproductive systems, however, remain unclear. This proposal is designed to advance our long-term goal of elucidating the molecular and genetic determinants of metabolic infertility. We hypothesize that leptin and insulin act directly on hypothalamic POMC and NPY/AgRP neurons that provide input to GnRH neurons. This hypothesis rests on findings that altered activity of POMC and NPY/AgRP neurons in response to leptin and insulin appear to depend on the phosphatidylinositol 3-kinase (PI3K) intracellular signaling pathway. In addition, previous studies have shown that brain-specific leptin receptor and insulin receptor knockouts have dramatic effects on the reproductive axis, but preventing leptin receptor signaling through non-PI3K pathways does not impair fertility. Thus, our studies will determine if insulin and leptin signaling through PI3K is required for normal (1) energy homeostasis and (2) reproductive functioning and in POMC neurons and/or in NPY/AgRP neurons. To accomplish these goals, we will genetically target the critical neurons using the cre/lox system. Specifically, we will examine the metabolic and reproductive phenotype of mice lacking insulin and leptin receptors or functional PI3K only in POMC neurons and only in NPY/AgRP neurons. We will then use electrophysiology and a novel method of visualizing Akt signaling in vitro to determine the impact of PI3K deletion on neuronal function. Collectively, these data may provide a new target for therapeutic advances in the treatment and prevention of obesity-related infertility. Project Narrative: With a background in the diverse fields of reproduction and metabolism, Dr. Hill is uniquely qualified to undertake these studies. The novel genetic approaches assembled during her post-doctoral fellowship will be powerful tools for investigating the understudied area of interacting hypothalamic metabolic and reproductive pathways. By providing a vehicle for her transition to research independence, this proposal lays the groundwork for a research program focused on reproductive health and the discovery of new approaches for treating nutritional and obesity-related infertility.