MR定量磁敏感图评估大鼠肩胛区棕色脂肪代谢活性的价值

目的 初步探讨MR定量磁敏感图（quantitative susceptibility mapping，QSM）评估活体大鼠肩胛区棕色脂肪（brown adipose tissue，BAT）代谢活性的价值。方法雄性SD大鼠10只，随机分为对照组（n=5）和冷刺激组（n=5）。冷刺激组在4℃环境下暴露12 h，对照组进行室温饲养。冷刺激结束后即刻进行MRI扫描，观察大鼠肩胛区棕色脂肪影像学表现，并测量QSM相关定量表征；扫描结束立即处死动物并取材进行后续组织学分析。对照组与冷刺激组各参数采用独立样本t检验进行组间差异性比较。结果大鼠棕色脂肪冷刺激后QSM值（-0.05±0.08）及R2*值（109.25±5.77）较对照组（0.37±0.05）、（175.51±14.34）显著下降，UCP-1蛋白（解偶联蛋白1）半定量值（1 762.15±1 005.74）较对照组（478.46±446.14）增加。结论QSM可定量评估活体大鼠棕色脂肪的代谢活性，有望成为活体定量评估BAT代谢活性的潜在的一种新的生物学标记。

The value on the evaluation of metabolic activity of brown adipose tissue in interscapular region of rats using quantitative susceptibility mapping

Objective To investigate the value of quantitative susceptibility mapping (QSM) in assessing the metabolic activity of brown adipose tissue (BAT) in the interscapular region of rats in vivo. Methods Ten male SD rats were randomly divided into control group (n=5) and cold stimulated group (n=5). The cold stimulated group was exposed to 4℃ for 12 hours, and the control group was fed at room temperature. Immediately after cold stimulated, MRI scan was performed to observe the imaging manifestations of brown adipose tissue in the interscapular region of rats, and QSM related quantitative characterization was performed. Then, the animals were sacrificed for subsequent histological analysis. The differences of parameters between the control group and the cold stimulated group were compared by independent samples t-test. Results Compared with the control group, QSM (0.37±0.05 vs. -0.05±0.08), and R2* (175.51±14.34 vs.109.25±5.77) were both significantly reduced significantly after cold stimulated of brown adipose tissue, while UCP1 expression was significantly increased (478.46±446.14 vs.1 762.15±1 005.74). Conclusion QSM can quantitatively evaluate the metabolic activity of brown adipose tissue in vivo, which is expected to be a potential biomarker for quantitative assessment of metabolic activity in brown adipose tissue.