rAAV-GDNF to study mesolimbic control of body mass

描述（由申请人提供）：我们之前已经发现，在黑质纹状体束中，通过腺相关病毒（rAAV）过度表达胶质细胞系衍生的神经营养因子（GDNF）导致完整的老年肥胖大鼠和中年大鼠的体重显著下降，而年轻大鼠的体重没有增加。纹状体末端区GDNF过表达对体重增加无显著影响。到目前为止，我们已经追踪了神经过度表达的GDNF对下丘脑室旁核的影响。然而，当GDNF在下丘脑中直接过度表达，达到与神经性rAAV-GDNF相同的水平时，动物的体重减轻了。这些数据可能表明，神经性GDNF的过度表达仅对下丘脑以外的细胞核有影响。本研究旨在确定从腹侧被盖区（VTA）到伏隔核（nAcc）的中边缘多巴胺（DA）投射在多大程度上促进了gdnf过表达诱导的体重减轻。我们有初步的数据表明，在VTA中注射重组腺相关病毒载体(rAAV)-GDNF也会导致大鼠体重减轻。因此，到目前为止，还没有观察到GDNF对DA水平或转换的影响与GDNF过表达有关，但这并不能完全排除DA是GDNF过表达诱导体重减轻的重要介质。Aim 1旨在确定中边缘DA投射的末端场、nAcc或VTA本身是否是raav介导的GDNF过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边缘DA投射的共同表达是否对体重产生累加效应。目的2旨在确定中边缘DA在gdnf过表达诱导的体重减轻中起直接作用的程度。我们将注意确定我们的动物是否过度活跃，氧气利用率增加，或表现出焦虑样行为，以确定GDNF过度表达的潜在行为影响，这可能是观察到的体重减轻的原因。我们还将测量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，以试图充分表征HPA对GDNF过表达的反应。

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.