基于定量磁敏感成像检测棕色脂肪的实验研究

Obesity is a major public health problem worldwide, posing a heavy burden on society and families. Activating brown adipose tissue (BAT) to enhance its function of producing heat has been one of the most promising therapy targets for the prevention and treatment of obesity and its associated disorders. The heat producing function of BAT depends on its volume and activation status. Intense research of methods measuring BAT in vivo is crucial for well understanding of the effect and mechanism of BAT. MRI is a suitable imaging technology to evaluate BAT for its free of radiation, relatively low-cost and advantages of quantifying fat and multi-parameter imaging. However, there still lacks an accurate and effective MR quantitative parameters to assess BAT. Quantitative susceptibility mapping (QSM) is a new MR quantitative tool, which can be used to reflect the characteristics of biology tissue. Therefore, this work aims to identify BAT and quantify its volume and activation status using QSM. We attempt to establish an obesity model induced by high fat diet in rats and activate its BAT with cold exposure. In addition, we use QSM to establish an model to detect BAT and its activation status using histology as a reference. In this way, we can provide an effective and non-invasive method to monitor BAT, which is helpful for deeply understanding the role of BAT in the development of obesity.

肥胖是一项重大的公共卫生问题，给社会及家庭造成沉重的负担。激活棕色脂肪（BAT）进而增加BAT的产热功能是目前防治肥胖及相关代谢性疾病最具潜力的新靶点之一。BAT的产热功能与BAT的体积和激活状态密切相关，深入研究活体检测BAT的方法对深刻理解BAT的作用及作用机制具有重要的意义。MR具有无辐射、价格适中且可实现脂肪定量及多参数成像的优势，是最具潜力的BAT活体检测方法，但目前尚缺乏准确有效的反映BAT特性的MR检测指标。定量磁敏感成像（QSM）是新兴的可敏感地反映出生物组织特性的MR定量技术。因此，本项目将开展基于QSM识别BAT、检测BAT体积及激活状态的研究，拟通过建立高脂饮食诱导大鼠肥胖模型，用冷刺激方法激活BAT，通过组织学验证，建立基于QSM的BAT识别及激活状态检测模型，有望为无创监测BAT提供准确有效的新方法及检测指标，有助于充分理解BAT在肥胖发生发展过程中的作用。

激活棕色脂肪（BAT）进而增加BAT的产热功能是目前防治肥胖及相关代谢性疾病最具潜力的新靶点之一。BAT的产热功能与BAT的体积和激活状态密切相关，深入研究活体检测BAT的方法对深刻理解BAT的作用及作用机制具有重要的意义。本项目通过对正常大鼠和高脂饮食诱导肥胖大鼠BAT进行MR定量成像研究，首先，为BAT的识别和激活状态构建了一种新的影像学检测方法和MR量化指标，可通过mGRE序列一次成像同时获得QSM、FF及R2*值，这些定量参数可以区分BAT和WAT及检测BAT的活性状态；其中QSM及FF值在检测BAT的活性方面具有良好的可靠性和一致性；其次，用FF值定量评估了在高脂饮食诱导增重及间歇冷刺激与限时饮食干预减重过程中BAT的变化，并首先阐述了BAT、皮下白色脂肪组织（SAAT）及局部白色脂肪-髌下脂肪垫（IFP）之间关联的可能性，可为临床以BAT为靶点指导肥胖及肥胖相关性疾病治疗提供更多有价值的信息。