Lewis Sigler Institute for Integrative Genomics, Princeton University, Princeton, New Jersey 08544, United States.
Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States.
Anal Chem. 2023 Oct 10;95(40):14879-14888. doi: 10.1021/acs.analchem.3c01875. Epub 2023 Sep 27.
Detection of small molecule metabolites (SMM), particularly those involved in energy metabolism using MALDI-mass spectrometry imaging (MSI), is challenging due to factors including ion suppression from other analytes present (e.g., proteins and lipids). One potential solution to enhance SMM detection is to remove analytes that cause ion suppression from tissue sections before matrix deposition through solvent washes. Here, we systematically investigated solvent treatment conditions to improve SMM signal and preserve metabolite localization. Washing with acidic methanol significantly enhances the detection of phosphate-containing metabolites involved in energy metabolism. The improved detection is due to removing lipids and highly polar metabolites that cause ion suppression and denaturing proteins that release bound phosphate-containing metabolites. Stable isotope infusions of [C]nicotinamide coupled to MALDI-MSI ("Iso-imaging") in the kidney reveal patterns that indicate blood vessels, medulla, outer stripe, and cortex. We also observed different ATP:ADP raw signals across mouse kidney regions, consistent with regional differences in glucose metabolism favoring either gluconeogenesis or glycolysis. In mouse muscle, Iso-imaging using [C]glucose shows high glycolytic flux from infused circulating glucose in type 1 and 2a fibers (soleus) and relatively lower glycolytic flux in type 2b fiber type (gastrocnemius). Thus, improved detection of phosphate-containing metabolites due to acidic methanol treatment combined with isotope tracing provides an improved way to probe energy metabolism with spatial resolution .
由于存在其他分析物（如蛋白质和脂质）的离子抑制等因素，使用 MALDI 质谱成像（MSI）检测小分子代谢物（SMM），尤其是那些涉及能量代谢的代谢物，具有挑战性。一种潜在的解决方案是通过溶剂洗涤，在基质沉积之前从组织切片中去除引起离子抑制的分析物。在这里，我们系统地研究了溶剂处理条件，以提高 SMM 信号并保留代谢物定位。用酸性甲醇洗涤可显著增强对参与能量代谢的含磷酸盐代谢物的检测。这种改进的检测是由于去除了引起离子抑制和使结合的含磷酸盐代谢物变性的脂质和高极性代谢物。与 MALDI-MSI 结合的 [C]烟酰胺的稳定同位素注入（“同位素成像”）在肾脏中揭示了表明血管、髓质、外条纹和皮质的模式。我们还观察到小鼠肾脏区域中不同的 ATP:ADP 原始信号，这与有利于糖异生或糖酵解的葡萄糖代谢的区域差异一致。在小鼠肌肉中，使用 [C]葡萄糖进行的 Iso-imaging 显示在 1 型和 2a 纤维（比目鱼肌）中从输注的循环葡萄糖中具有较高的糖酵解通量，而在 2b 纤维类型（腓肠肌）中相对较低的糖酵解通量。因此，由于酸性甲醇处理结合同位素示踪而提高的含磷酸盐代谢物的检测提供了一种以空间分辨率探测能量代谢的改进方法。
