THE ROLE OF PLACENTAL LACTOGEN IN FETAL DEVELOPMENT

描述(申请人提供)：催乳素(PRL)和胎盘催乳素(PL)刺激啮齿动物和人类的脂肪沉积、体重增加和瘦素的产生，表明催乳素在母胎脂肪代谢和肥胖中发挥作用。乳素促进脂肪储存和体重增加的机制尚不清楚。我们假设：(A)乳激素通过诱导脂肪细胞从基质前体分化为脂肪细胞来促进脂肪沉积；(B)乳激素的成脂作用是通过诱导包括PPARkhi-2在内的转录因子来介导的；(C)PPARkhi-2的诱导是通过激活Stat5来介导的；以及(D)乳激素的成脂作用受胰岛素、IGF-1、糖皮质激素和性激素的调节。为了验证这些假设，我们将检测外源性PRL和PL对3T3-L1前脂肪细胞、原代小鼠前脂肪细胞和胚胎成纤维细胞脂肪生成的影响，以及PL在一种新的3T3-L1细胞系中结构性表达的影响。为了确定前脂肪细胞分化是否需要产乳信号，我们将比较PRL受体(PRLR)缺陷小鼠前脂肪细胞的成脂率和野生型小鼠细胞的成脂率。为了研究催乳素对PPARkhi表达的影响，我们将检测PRL和PL对3T3-L1细胞、原代前脂肪细胞、小鼠胚胎成纤维细胞PPARkhi1和PPARkhi2mRNA和蛋白水平的影响，并将PRLR缺陷小鼠组织中的PPARkhi表达与野生型小鼠组织中的PPARkhi表达进行比较，我们将检测乳激素对3T3-L1细胞中表达的人和小鼠PPARkhi-2启动子转录激活的影响，并将PRL处理细胞中PPARkhi1I和2mRNAs的表达时间与Add1和c/EBPSβ、β和α进行比较。为了验证PPARkhi-2的诱导是通过激活Stat5介导的假设，我们将确定乳素是否诱导STAT 5与人和mPPAR c-2启动子中的共同结合部位结合。我们将检测突变的PPARkhi-2Stat5共有序列对PPAR Gamma2转录的乳素依赖激活的影响，以及显性-负STAT5结构对3T3-L1细胞中PPARkhi mRNA和蛋白水平的诱导的影响。最后，为了验证催乳素的成脂作用受性类固醇调节的假设，我们将研究孕酮和雌二醇对催乳素在3T3-L 1细胞中的成脂作用的影响，以及补充孕酮对催乳素受体缺陷小鼠脂肪沉积和瘦素产生的影响。我们的研究结果应该对脑下垂体和胎盘激素在脂肪发育和功能中的作用提供新的坚持。

DESCRIPTION (provided by applicant): Prolactin (PRL) and placental lactogen (PL) stimulate fat deposition, weight gain, and leptin production in rodents and humans, suggesting that lactogens play roles in maternofetal lipid metabolism and obesity. The mechanisms by which lactogens promote fat storage and weight gain are unknown. We hypothesize: (a) that lactogens promote fat deposition through induction of adipogenesis, the process of differentiation of adipocytes from stromal precursors; (b) that adipogenic effects of lactogens are mediated through induction of transcription factors including PPARkhi-2; (c) that PPARkhi-2 induction is mediated through activation of Stat5; and (d) that adipogenic effects of lactogens are modulated by insulin, IGF-1, glucocorticoids, and sex steroids. To test these hypotheses we will examine effects of exogenous PRL and PL on adipogenesis in 3T3-L1 preadipocytes, primary mouse preadipocytes and embryonic fibroblasts and the effects of constitutive expression of PL in a novel 3T3-L1 cell line. To determine if lactogenic signaling is required for preadipocyte differentiation, we will compare rates of adipogenesis in preadipocytes of PRL receptor (PRLR)-deficient mice with rates of adipogenesis in cells of wild-type littermates. To characterize effects of lactogens on PPARkhi expression we will examine effects of PRL and PL on PPARkhi1 and 2 mRNA and protein levels in 3T3-L1 cells, primary preadipoyctes, mouse embryonic fibroblasts and will compare PPARkhi expression in tissues of PRLR deficient mice with that in wild-type littermates, We will examine effects of lactogens on transcriptional activation of the human and mouse PPARkhi-2 promoters expressed in 3T3-L1 cells and will compare the time course of expression of PPARkhi1I and 2 mRNAs in PRL-treated cells with that of ADD1 and c/EBPs beta, delta, and alpha. To test the hypothesis that induction of PPARkhi-2 is mediated through activation of Stat5, we will determine if lactogens induce binding of STAT 5 to consensus binding sites in the human and mPPAR c-2 promoters. We will examine the effect of mutating PPARkhi-2 Stat5 consensus sequences on lactogen-dependent activation of PPAR gamma2 transcription, and the effect of a dominant-negative STAT5 construct on the induction of PPARkhi mRNA and protein levels in 3T3-L1 cells. Finally, to test the hypothesis that the adipogenic effects of the lactogens are modulated by sex steroids, we will examine the effects of progesterone and estradiol on the adipogenic effects of PRL in 3T3-L 1 cells and the effects of progesterone supplementation on fat deposition and leptin production in PRLR-deficient mice. The results of our studies should provide new insist into the roles of pituitary and placental hormones in adipose development and function.