Fu Dan, Yu Yong, Folick Andrew, Currie Erin, Farese Robert V, Tsai Tsung-Huang, Xie Xiaoliang Sunney, Wang Meng C
Department of Chemistry and Chemical Biology, Harvard University , Cambridge, Massachusetts 02138, United States.
J Am Chem Soc. 2014 Jun 18;136(24):8820-8. doi: 10.1021/ja504199s. Epub 2014 Jun 9.
Metabolic fingerprinting provides valuable information on the physiopathological states of cells and tissues. Traditional imaging mass spectrometry and magnetic resonance imaging are unable to probe the spatial-temporal dynamics of metabolites at the subcellular level due to either lack of spatial resolution or inability to perform live cell imaging. Here we report a complementary metabolic imaging technique that is based on hyperspectral stimulated Raman scattering (hsSRS). We demonstrated the use of hsSRS imaging in quantifying two major neutral lipids: cholesteryl ester and triacylglycerol in cells and tissues. Our imaging results revealed previously unknown changes of lipid composition associated with obesity and steatohepatitis. We further used stable-isotope labeling to trace the metabolic dynamics of fatty acids in live cells and live Caenorhabditis elegans with hsSRS imaging. We found that unsaturated fatty acid has preferential uptake into lipid storage while saturated fatty acid exhibits toxicity in hepatic cells. Simultaneous metabolic fingerprinting of deuterium-labeled saturated and unsaturated fatty acids in living C. elegans revealed that there is a lack of interaction between the two, unlike previously hypothesized. Our findings provide new approaches for metabolic tracing of neutral lipids and their precursors in living cells and organisms, and could potentially serve as a general approach for metabolic fingerprinting of other metabolites.
代谢指纹图谱提供了有关细胞和组织生理病理状态的有价值信息。传统的成像质谱和磁共振成像由于缺乏空间分辨率或无法进行活细胞成像，无法在亚细胞水平探测代谢物的时空动态。在此，我们报告一种基于高光谱受激拉曼散射（hsSRS）的互补代谢成像技术。我们展示了hsSRS成像在定量细胞和组织中两种主要中性脂质：胆固醇酯和三酰甘油方面的应用。我们的成像结果揭示了与肥胖和脂肪性肝炎相关的脂质组成中先前未知的变化。我们进一步使用稳定同位素标记，通过hsSRS成像追踪活细胞和活秀丽隐杆线虫中脂肪酸的代谢动态。我们发现不饱和脂肪酸优先摄取到脂质储存中，而饱和脂肪酸在肝细胞中表现出毒性。对活秀丽隐杆线虫中氘标记的饱和脂肪酸和不饱和脂肪酸进行同时代谢指纹图谱分析发现，与先前假设不同，两者之间缺乏相互作用。我们的研究结果为活细胞和生物体中中性脂质及其前体的代谢追踪提供了新方法，并有可能作为其他代谢物代谢指纹图谱分析的通用方法。
