Assessing the actual utility of capillary electrophoresis-mass spectrometry for metabolic profiling of human plasma

Wei Zhang, LACDR, Leiden University, Leiden, Netherlands (w.zhang@lacdr.leidenuniv.nl)

Introduction:

Capillary electrophoresis-mass spectrometry (CE-MS) is a useful analytical technique for the profiling of highly polar and charged metabolites in biological samples. Although CE-MS has been often used for metabolic profiling of a wide range of samples in various application fields, the actual utility of this approach for biomarker discovery studies has not been properly demonstrated so far. As a significant fraction of the signals recorded in MS-based metabolic profiling studies are spurious, it is important to assess whether compounds that show up as potential biomarkers in comparative metabolic profiling studies are authentic. We have addressed this aspect in this study.

Methods:

In this study pooled human plasma samples were used, of which one set was spiked with cationic isotope-labeled metabolites at different concentration levels and denoted as “class I”, whereas another set was also spiked with cationic isotope-labeled metabolites at different concentration levels and denoted as “class II”. Blank pooled human plasma samples were used as a quality control (QC) sample to assess the performance of CE-MS over time. Cationic metabolites were analyzed at low-pH separation conditions using a fused-silica capillary. CE was coupled to MS via a conventional sheath-liquid interface. Recorded data  were processed with different multivariate data analysis tools.  

Results & Discussion:

A conventional CE-MS approach was used for the profiling of cationic metabolites in pretreated human plasma samples at low-pH separation conditions. The reliability of the analytical method was tested in terms of linearity, precision, accuracy and repeatability, and the method was proved to be suitable for metabolic profiling of human plasma. The examination of the metabolic features detected in the QC set by CE-MS showed that most of them had relative standard deviation (RSD) values for peak areas below 30% for an analysis carried out over two consecutive days. The obtained data was further evaluated using two different multivariate data analysis strategies. In both strategies, multivariate data analysis of the recorded metabolic profiles provided a clear distinction between class I and class II plasma samples. The metabolites primarily responsible for this classification were the isotope-labeled compounds spiked (“spiked biomarkers”) to the human plasma samples at different concentration levels. Therefore, these findings clearly indicate that our CE-MS approach can pick up the right chemical information in metabolic profiling studies used for biomarker discovery. Overall, the strategy proposed over here can be used to validate a given analytical method for comparative metabolomics studies.

---

Abstract Reference & Short Personal Biography of Presenting Author

Personal Biography

I obtained my MSc degree in pharmacokinetics from China Pharmaceutical Univerity in Nanjing in 2015. The main task in my master study was to develop LC-MS/MS methods for exogenous substances in various biological matrices, such as plasma, urine, and bile. My work also included in vitro drug-drug interaction study using the incubation schema of human/rat liver microsomes with classic substrates and compounds of interest.  

After obtaining my master degree, I came to the Netherlands and started working in the field of metabolomics within the Leiden Academic Centre for Drug Research. Over the last three years, I dedicated my efforts in the analysis of small polar charged metabolites in biological samples using capillary electrophoresis coupled to mass spectrometry (CE-MS). The application of CE-MS in metabolomics study can provide valuable complementary information, especially when dealing with very small sample amounts. With the advancement of CE-MS interfaces, higher sensitivity could be further achieved despite very small injection volumes in practice. This technique can also serve as a great tool for the detection of polar metabolites secreted from the body after the administration of exogenous compounds and help understand how the compound is metabolized inside a living organism.