Regulation of Leptin Production by Gonadotropes

描述（由申请人提供）：瘦素由脂肪细胞产生，并通过向大脑发送脂肪储存水平的信号来调节食欲。瘦素对生殖也很重要。没有瘦素受体的动物无法度过青春期，而瘦素水平低的动物繁殖效率低。最近的研究发现瘦素的生产地点在脑垂体。然而，很少有人知道的机制，调节瘦素的表达在垂体的变化，也没有协议的细胞类型，表达瘦素。这些可行性研究，因此，建议测试的整体假设，促性腺激素瘦素有助于在周期中垂体瘦素的表达上升，也许提供一个瘦素的来源，改变喂养支持怀孕。 目的研究促性腺激素细胞在体内受促性腺激素释放激素（GnRH）和雌二醇刺激时是否改变瘦素mRNA的表达。我们将使用新的双重原位杂交方案，以了解是否有类似的促性腺激素β亚基（LH β和FSH β）的瘦素的促性腺激素表达的变化。子目标1a将集中于排卵期，其特征在于雌激素和GnRH刺激以及促性腺激素β亚基mRNA的峰值水平。Sub Aim lb将使用已交配的发情前期雌性大鼠。这些研究将在怀孕的第一周测试促性腺激素的瘦素表达，以了解表达是否随着生殖系统的激活而变化。将在分散的细胞和垂体切片中检测瘦素和促性腺激素mRNA。 如果瘦素在促性腺激素细胞中产生，它可能受到促性腺激素释放激素（GnRH）或雌激素的调节。目的2研究促性腺激素释放激素（GnRH）和/或雌激素对促性腺激素细胞瘦素表达和分泌的影响。这些研究将在新鲜分散的垂体细胞或富集的促性腺激素细胞的混合群体上进行，以了解在响应GnRH时观察到的瘦素分泌是否反映了促性腺激素的分泌。这些试点研究的信息是至关重要的，然后才能制定和解决假说的意义瘦素生产在垂体。这些信息可以导致关于其对生育力，性发育或生殖系统调节的影响的假设。因此，这些可行性研究将提供信息，使我们能够设计未来的实验，以获得全额资助。

DESCRIPTION (provided by applicant): Leptin is produced by adipocytes, and regulates appetite by signaling levels of fat stores to the brain. Leptin is also important to reproduction. Animals without leptin receptors fail to go through puberty and those with low levels of leptin reproduce with low efficiency. Recent studies have found leptin production sites in the pituitary gland. However, little is known about mechanisms that regulate changes in leptin expression in the pituitary and there is no agreement about the cell types that express leptin. These feasibility studies are, therefore, proposed to test the overall hypothesis that gonadotrope leptin contributes to the rise in expression of pituitary leptin during the cycle, perhaps to provide a source of leptin that alters feeding in support of a pregnancy. Aim I studies will determine if gonadotropes change their expression of leptin mRNA as they are stimulated, in vivo, by GnRH and estradiol. We will use novel dual in situ hybridization protocols to learn if there are changes in gonadotropes expression of leptin that parallel those for the gonadotropin beta subunits (LHbeta and FSHbeta). Sub Aim la will focus on the periovulatory period, which is characterized by estrogen and GnRH stimulation and peak levels of gonadotropin beta subunit mRNAs. Sub Aim lb will use proestrous female rats that have mated. These studies will test leptin expression by gonadotropes during the first week of pregnancy to learn if expression changes as the reproductive system is activated. The leptin and gonadotropin mRNAs will be detected in both dispersed cells and pituitary sections. If leptin is produced in gonadotropes, it may be regulated by gonadotropin releasing hormone (GnRH) or estrogens. Aim 2 studies will learn how GnRH and/or estrogen affect expression and secretion of leptin by gonadotropes, in vitro. These studies will be conducted on freshly dispersed mixed populations of pituitary cells or enriched gonadotropes to learn if the leptin secretion seen in response to GnRH reflects that from the gonadotropes. Information from these pilot studies is vital before one can formulate and address hypotheses about the significance of leptin production in the pituitary. This information can lead to hypotheses about its impact on fertility, sexual development, or the regulation of the reproductive system. These feasibility studies will thus provide information that will allow us to design future experiments for full funding.