FBT-PET Study of Aging Skeletal Muscle

描述(申请人提供)：本项目响应RFA-DA-001。其目的是将正电子发射断层扫描(PET)氟苯三氮唑(FBT)放射性配基在脑研究中的应用扩展到骨骼肌衰老的研究。越来越多的证据支持神经退行性变在骨骼肌慢性、年龄相关的结构和功能衰退中所起的作用。它将检验这样一个假设，即非侵入性成像程序FBT-PET可以用于评估啮齿类动物整个衰老过程中的骨骼肌神经支配。结果将为分析其在人类石棺减少症中的作用提供依据。 以下特定目标将在年轻成年(7个月)和老年(24个月)小鼠中进行分析，这些小鼠喂食自由饮食和卡路里限制，这是一种已知可以延缓运动神经元随年龄增长而丧失的动作。 具体目的1.应用FBT-PET对后肢肌神经支配进行定量。将测量下后肢肌肉的时间/活动曲线以及三个实验组之间的FBT摄取差异。随着年龄的增长，肌肉体积的丧失将通过MRI进行分析。FBT-PET和MRI信号将被共同注册。信号特异性将通过测量：(A)FBT血管清除，(B)[~3H]FBT结合，(C)[~H]FBT放射自显影，(D)冷FBT/维沙米考阻断18F-FBT摄取，和(E)Vacht基因敲除小鼠摄取FBT来分析。 具体目的2.分别使用功能评估组件和单肌力测量方法研究FBT-PET与小鼠骨骼肌功能的关系。这些研究将确定与年龄相关的肌肉功能下降与肌肉失神经的程度和程度之间的关系。 具体目的3.用体外测定方法定量测定小鼠肌肉Vacht密度，并与FBT-PET建立联系。Vacht的免疫组织化学(IH)将使我们能够测量纵向肌肉的多个部分中转运蛋白的密度。IH信号的特异性将通过标记的a-银环蛇毒素双重染色来确定，该毒素染色后的AChR。 公共卫生相关性：肌肉失神经对骨质疏松症的影响仍然难以捉摸，尤其是在人类中。FBT(氟苯三氮唑)-正电子发射断层扫描(PET)作为一种新的、准确的、无创的啮齿动物骨骼肌神经支配测量方法的验证将提供有价值的数据，这些数据可以迅速转化为动物和人类的有效研究工具。在临床上，它可以用来评估旨在预防和/或改善肌肉失神经对老年人骨骼肌减少和随后的身体残疾的影响的干预措施。该项目的结果旨在为准备和提交必要的申请提供信息，以获得监管部门的批准，以检查骨骼肌去神经及其对人类骨骼肌减少的影响。在第二阶段，将放射性示踪剂FBT分发给其他机构将允许多中心评估其在量化与人类骨骼肌减少相关的肌肉失神经方面的效用。

DESCRIPTION (provided by applicant): This project responds to RFA-DA-001. Its objective is to extend the utility of positron emission tomography (PET) flurobenzyltrozamicol (FBT) radioligand in the study of brain to the study of aging skeletal muscle. Growing evidence supports a role for neural degeneration in the chronic, age-related structural and functional decline of skeletal muscle. It will test the hypothesis that the noninvasive imaging procedure FBT-PET can be used to assess skeletal muscle innervation throughout the aging process in rodents. Results will inform an analysis of its role in human sarcopenia. The following specific aims will be analyzed in young adult (7-month) and aged (24-month) mice fed ad libitum and calorie-restricted, a maneuver known to retard motor neuron loss with aging. Specific Aim 1. To quantify hindlimb muscle innervation using FBT-PET. Time/activity curves in lower hindlimb muscles and differences in FBT uptake between three experimental groups will be measured. Loss of muscle volume with aging will be analyzed by MRI. FBT-PET and MRI signals will be co-registered. Signal specificity will be analyzed by measuring: (a) FBT vascular clearance, (b) [3H]FBT binding, (c) [3H]FBTautoradiography, (d) blocking of 18F-FBT uptake with cold FBT/vesamicol, and (e) FBT uptake by VAChT knock-down mice. Specific Aim 2. To examine the relationship between FBT-PET and mouse skeletal muscle function in vivo and in vitro using a well-characterized functional assessment battery and single muscle force measurement, respectively. These studies will determine a relationship between age-related decrease in muscle function and the magnitude and extension of muscle denervation. Specific Aim 3. To quantify mouse muscle VAChT density using in vitro determinations and to establish a relationship with FBT-PET. Immunohistochemistry (IH) for VAChT will allow us to measure the transporter's density in multiple sections of longitudinal muscle. IH signal specificity will be determined by double staining with labeled a-bungarotoxin, which stains the post-terminal AChR. PUBLIC HEALTH RELEVANCE: The contribution of muscle denervation to sarcopenia remains elusive, particularly in humans. Validation of FBT (flurobenzyltrozamicol)-Positron Emission Tomography (PET) as a novel, accurate, noninvasive measure of skeletal muscle innervation in rodents will provide valuable data that can be rapidly translated into an effective research tool in animals and humans. Clinically, it can be used to evaluate interventions aimed at preventing and/or ameliorating the contribution of muscle denervation to sarcopenia and subsequent physical disability in the elderly. Results of this project are intended to inform the preparation and submission of applications necessary to gain regulatory approval to examine skeletal muscle denervation and its influence on sarcopenia in humans. In a second phase, distribution of the radiotracer FBT to other institutions will allow a multi-center evaluation of its utility in quantifying muscle denervation associated with human sarcopenia.