Metabolomics is a discipline that takes all metabolites in living organisms as the research object, analyzes these metabolites quantitatively, and looks for their relative relationship with physiological and pathological changes. Mass spectrometry (MS) and nuclear magnetic resonance (NMR) are commonly used detection methods in metabolomics to detect the total amount of metabolites in the body after completing complex metabolism at a specific moment in the body, however, these two methods cannot accurately reveal the specific metabolic pathways in which metabolites are located.
Mass spectrometry (MS) is a technique that can be used to quantitatively analyze metabolites in living organisms by ionizing a sample and measuring its mass. However, due to the wide variety of metabolites in organisms and the huge differences in content, mass spectrometry methods can often only analyze some metabolites and cannot fully reflect the metabolism in organisms. In addition, mass spectrometry has problems such as low sensitivity and poor specificity, which limits its application in metabolomics.
Nuclear magnetic resonance imaging (NMR) is a technique that uses the nuclear spin magnetic moment to image and analyze matter, which can be used to detect metabolites in living organisms. Compared to mass spectrometry, NMR has higher sensitivity and resolution, allowing for more accurate quantification of metabolites. However, NMR also has the problem of not being able to reveal the specific metabolic pathways where metabolites are located, which makes its application in metabolomics also have certain limitations.
In general, although mass spectrometry and nuclear magnetic resonance (NMR) have certain application value in metabolomics, they both have the problem that they cannot be accurate to the specific metabolic pathways where metabolites are located, so we need to find new methods to compensate for this shortcoming, so as to more comprehensively and accurately study the metabolic processes in organisms and their relationship with physiological and pathological changes.
Currently, metabolic pathways can be inferred by introducing radioactive or stable isotope marker tracers into metabolomic analysis. However, radioactive isotopes have certain harm to the human body, and stable isotopes are non-radioactive, stable in physical properties, and harmless to the human body, so they are more popular with scientific researchers.
Stable isotope tracer metabolomics based on stable isotopes and metabolomics gives full play to the advantages of both and can more accurately study the specific metabolic pathways of a specific metabolite in the metabolic network.
Figure 1Metabolomics (stable isotope labeling) flowchart.
The metabolic process of labeled glucose in the body was detected by LC-MS, and the metabolic pathways of stable isotope-labeled glucose in related metabolic pathways were determined, and its metabolic mechanism was determined (red dot indicates 13C).
Combined with case studies.
Application of stable isotope markers in Alzheimer's disease (AD) biomarker research.
Professor Feng Yuqi's team from Wuhan University determined four types of metabolites (carboxyl, carbonyl, amine and thiol metabolites) in mouse fecal samples by using a stable isotope-labeled liquid chromatography mass spectrometry method (CIL-LC-MS), and a total of 2302 metabolites were detected by derivatization (chemical reaction) with substances containing stable isotope labels (such as DMED-D4, HIQB-D7, DMAP-D4, BQB-D7). of the 1388 potential metabolites that can be speculated, 308 metabolites were identified by chemically labeled standard libraries and mass spectrometry analysis.
Figure 2Derivatization of stable isotopes with metabolites of different functional groups.
Through the identification of metabolites in mouse feces, 211 metabolites were found to be significantly different between Alzheimer's disease (AD) model mice and wild-type (WT) mice, which also suggests that these fecal metabolites are closely related to AD pathology and provide new potential biomarkers for the diagnosis of AD.
Figure 3AD Potential Biomarker Research Methods.
l: metabolite ms after conventional derivatization;H: Label the derivatized metabolite MS with a stable isotope
Application of stable isotope markers in cancer metabolomics research.
Stable isotope resolved metabolomics (SIRM) is a process that uses advanced NMR and MS analysis methods to analyze the precursors of stable isotope enrichment to the single atom of the product. Denicola GM et al. used U-13C-Glucose to study the serine glycine metabolic pathway in NSCLC by metabolic tracking of non-small cell lung cancer (NSCLC) cell lines, which played an important role in the diagnosis and ** of NSCLC.