CXCL12 promotes development of hypothalamic peptide neurons responsive to fat

描述(申请人提供)：全球肥胖是一个流行病问题，在过去的几十年里一直在稳步增加，导致女性在怀孕期间暴饮暴食和肥胖的比例更高。许多研究表明，怀孕期间的高脂肪饮食(HFD)和肥胖产生的后代同样容易患上 暴饮暴食和体重增加，进一步加剧了肥胖问题。最近的证据表明，这可能是由于子代下丘脑中的脑啡肽(ENK)、甘丙素(GAL)和黑色素浓缩激素(MCH)等促食欲肽的神经发生和表达增加，该脑区的这些肽是HFD摄取的刺激因素。虽然这种变化的机制尚未建立，但目前的证据表明，炎症介质可能参与了这一变化。趋化因子是一组小蛋白，已被发现在神经元的调节、发育、迁移和生长中发挥作用。有研究表明，随着高脂饮食的摄入和饮食肥胖，趋化因子会增加，但关于趋化因子与大脑中促食欲素的关系知之甚少。为了确定趋化因子和HFD摄入量之间的关系，这项拨款将在成年大鼠和产前暴露于HFD的子代中调查一种特定的趋化因子CXCL12与下丘脑肽、HFD摄入量和与过量摄取相关的行为的关系。目的1通过免疫组织化学、mRNA定量、Western blotting、siRNA敲除和行为模式等方法，确定CXCR4和CXCR7受体是否与ENK、GAL和MCH神经元共表达，以及CXCL12是否通过这些受体刺激多肽表达和HFD摄取。初步结果表明，HFD可刺激下丘脑CXCL12、CXCR4和CXCR7的表达，用CXCL12处理培养的神经元可增加ENK、GAL和MCH的表达。目的2通过免疫荧光组织化学和行为学测试，直接测试CXCL12在调节神经发生和多肽神经元迁移到下丘脑中的可能作用，以及在增加子代摄入HFD的倾向方面的作用。初步结果显示，摄入HFD的母鼠循环中CXCL12增加，胚胎下丘脑中CXCL12和CXCR4水平增加，培养的神经元对CXCL12的反应增加。到目前为止的数据表明，CXCL12参与了胎儿脂肪暴露的影响，也揭示了与食欲肽的重要关系。这些研究将提供新的证据，支持CXCL12在介导饮食脂肪诱导的行为编程中的功能。

DESCRIPTION (provided by applicant): Global obesity is an epidemic problem that has been steadily increasing over the past several decades, leading to a higher percentage of women overeating and being obese during pregnancy. Many studies have shown that high fat diet (HFD) and obesity during pregnancy produces offspring that are similarly prone to overeating and gaining weight, further exacerbating the obesity problem. Recent evidence suggests that this may be attributed to increased neurogenesis and expression of the orexigenic peptides, enkephalin (ENK), galanin (GAL) and melanin-concentrating hormone (MCH) in the hypothalamus of offspring, with these peptides in this brain region being stimulators of HFD intake. Although the mechanism for this change has not been established, current evidence suggests that inflammatory mediators may be involved. Chemokines are a group of small proteins that have been found to play a role in neuronal modulation, development, migration, and growth. There are studies showing chemokines to be increased with ingestion of a HFD and in dietary obesity, but there is little known about he relationship of chemokines to the orexigenic peptides in the brain. To establish the relationship between chemokines and HFD intake, this grant will investigate, both in adult rats and in offspring prenatally exposed to HFD, the relationship of a specific chemokine, CXCL12, to hypothalamic peptides, HFD consumption and behaviors associated with excess intake. Aim 1 will determine in adult animals whether the receptors, CXCR4 and CXCR7, are co-expressed with ENK, GAL and MCH neurons and if CXCL12 functions through these receptors to stimulate peptide expression and HFD intake, by using immunohistochemistry, mRNA quantification, western blotting, siRNA knockdown and behavioral paradigms. Preliminary results show that HFD stimulates the expression of CXCL12, CXCR4, and CXCR7 in the hypothalamus and that treatment of cultured neurons with CXCL12 increases the expression of ENK, GAL and MCH. Aim 2 will provide a direct test of the possible role of CXCL12 in mediating the neurogenesis and migration of peptide neurons into the hypothalamus and in increasing the propensity for increased HFD intake in the offspring, by using immunofluorescence histochemistry and behavioral tests. Preliminary results show an increase in circulating CXCL12 in dams ingesting the HFD, increased levels of CXCL12 and CXCR4 in the hypothalamus of embryos, and increased migration of cultured neurons in response to CXCL12. The data thus far implicate CXCL12 in mediating the effects of prenatal fat exposure and also reveal an important relationship to the orexigenic peptides. These studies will yield new evidence to support the function of CXCL12 in mediating the behavioral programming induced by dietary fat.