Regulation of Leptin Production by Gonadotropes

描述(申请人提供)：瘦素是由脂肪细胞产生的，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，那些瘦素水平低的动物繁殖效率低。最近的研究发现，瘦素的产生部位位于脑下垂体。然而，对于调节脑下垂体中瘦素表达变化的机制知之甚少，对于表达瘦素的细胞类型也没有达成一致意见。因此，这些可行性研究是为了检验促性腺激素瘦素在周期中有助于脑下垂体瘦素表达上升的总体假设，或许是为了提供一种瘦素的来源，改变喂养以支持怀孕。 目的研究促性腺激素释放激素(GnRH)和雌二醇在体内刺激促性腺激素释放激素(GnRH)时，是否会改变其瘦素mRNA的表达。我们将使用新的双重原位杂交方法来了解瘦素的促性腺激素表达是否发生了与促性腺激素β亚基(LHbeta和FSHbeta)平行的变化。亚目标LA将重点放在排卵期，这是以雌激素和GnRH刺激和促性腺激素β亚基mRNAs水平达到峰值为特征的。SubAim lb将使用已交配的发情雌性大鼠。这些研究将测试怀孕第一周促性腺激素的瘦素表达，以了解生殖系统激活时瘦素的表达是否会发生变化。瘦素和促性腺激素的mRNAs将在分散的细胞和垂体切片中检测到。 如果瘦素是在促性腺激素产生的，它可能受促性腺激素释放激素(GnRH)或雌激素的调节。目的研究促性腺激素释放激素(GnRH)和/或雌激素在体外对促性腺激素细胞表达和分泌瘦素的影响。这些研究将在新分散的垂体细胞或浓缩的促性腺激素的混合种群中进行，以了解对GnRH的反应中的瘦素分泌是否反映了促性腺激素的分泌。来自这些先导研究的信息是至关重要的，然后才能形成和解决关于瘦素在脑下垂体中产生的重要性的假说。这些信息可能导致关于它对生育、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金。

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.