rAAV-GDNF to study mesolimbic control of body mass

描述(申请人提供)：我们先前发现，通过腺相关病毒(RAAV)在黑质纹状体束过表达胶质细胞系衍生神经营养因子(GDNF)，可以导致正常老年肥胖大鼠、中年大鼠体重显著减轻，以及年轻大鼠体重缺乏增加。此外，GDNF在纹状体终末区域的过度表达对体重增加没有显著影响。到目前为止，我们已经追踪到黑质过表达的GDNF对下丘脑室旁核的影响。然而，当GDNF在下丘脑直接过度表达时，其水平与黑质rAAV-GDNF的水平相同，动物的体重减轻较少。这些数据可能表明，黑质GDNF的过度表达仅在下丘脑以外的核产生了影响。本研究旨在确定腹侧被盖区(VTA)至伏核(NACC)的中脑边缘多巴胺(DA)投射在多大程度上参与了GDNF过度表达诱导的体重减轻。我们有初步数据表明，在VTA内注射重组腺相关病毒载体(RAAV)-GDNF也能导致大鼠体重减轻。到目前为止，还没有观察到GDNF对DA水平或转归的影响与GDNF的过度表达有关，但这并不能最终排除DA是GDNF过度表达导致体重减轻的重要中介。目的1旨在确定中脑边缘DA投射的终端场、NACC或VTA本身是否是rAAV介导的GDNF过度表达诱导体重减轻的作用部位。其次，我们将确定黑质纹状体束和中脑边缘DA投射的共同表达是否会对体重产生相加效应。目的2旨在确定中脑边缘DA在GDNF过度表达诱导的体重减轻中起直接作用的程度。我们将谨慎地确定我们的动物是否过度活跃，是否增加了氧气利用率，或是否表现出类似焦虑的行为，以确定GDNF过度表达可能导致观察到的体重下降的潜在行为影响。我们还将检测血清和脑脊液中下丘脑-垂体-肾上腺(HPA)轴激素和下游信号分子的水平，试图全面描述HPA对GDNF过度表达的反应。 与公共卫生相关：该项目旨在跟进Mandel实验室的一项新发现，该发现表明，如果胶质细胞系衍生神经营养因子(GDNF)在黑质纹状体束的多巴胺细胞中过度表达，不同年龄和代谢功能的大鼠都会体重减轻(中年肥胖大鼠)或体重无法增加(年轻大鼠)。建议进行一系列实验，以了解哪些解剖结构有助于这一重要的新效应，并确定是否需要多巴胺来观察GDNF诱导的体重减轻。

DESCRIPTION (provided by applicant): We have previously discovered that over-expression of glial cell line-derived neurotrophic factor (GDNF) via adeno-associated virus (rAAV) in the nigrostriatal tract in leads to highly significant weight loss in intact aged obese rats, middle aged rats, and lack of weight gain in young rats. Moreover, GDNF over-expression in striatal terminal fields has no significant effect on weight gain. To date, we have traced the effect of nigral over-expressed GDNF to the paraventricular nucleus of the hypothalamus. However, when GDNF is over-expressed directly in hypothalamus at levels equal to those achieved with nigral rAAV-GDNF, the animals lose less weight. These data may suggest that nigral GDNF over-expression is having effects in nuclei outside just the hypothalamus. The present proposal is designed to determine the extent to which the mesolimbic dopamine (DA) projection from the ventral tegmental area (VTA) to the nucleus accumbens (nAcc) contributes to GDNF-over-expression induced weight loss. We have preliminary data indicating that injections of recombinant adeno-associated viral vector (rAAV)-GDNF in VTA also leads to weight loss in rats. Thus, far, no effect of GDNF on DA levels or turnover has been related to GDNF over-expression has been observed but this does not conclusively rule out DA as an important mediator of GDNF over-expression induced weight loss. Aim 1 is designed to determine if the terminal field of the mesolimbic DA projection, the nAcc or the VTA itself is the site of action of rAAV-mediated GDNF over-expression induced weight loss. Secondarily, we will determine if co-expression in the nigrostriatal tract and the mesolimbic DA projection produces an additive effect on body weight. Aim 2 is designed to determine the extent to which mesolimbic DA plays a direct role in GDNF-over-expression induced weight loss. We will take care to determine if our animals are hyperactive, have increased oxygen utilization, or display anxiety-like behaviors to determine potential behavioral effects of GDNF over-expression that may account for the observed weight loss. We will also measure serum and CSF levels of hypothalamic-pituitary-adrenal (HPA) axis hormones and downstream signaling molecules to try to fully characterize the HPA response to GDNF over-expression. PUBLIC HEALTH RELEVANCE: This project is aimed at following up on the novel discovery from the Mandel laboratory showing that if glial cell line-derived neurotrophic factor (GDNF) is over-expressed in the dopamine cells of the nigrostriatal tract, rats of varying ages and metabolic function all lose weight (middle aged- aged obese rats) or fail to gain weight (younger rats). A series of experiments are proposed to look at which anatomical structures contribute to this important novel effect and to determine if dopamine is required to observe GDNF-induced weight loss.