Metabolism is the assembly of biochemical reactions in living organisms, the material basis for life maintenance of living organisms, and an important basis for the study of life activities. Metabolomics studies the endogenous metabolic activities of life under the influence of the internal and external environments, including the detection and analysis of metabolite types and quantities and their change patterns, thus studying the nature of the occurrence and development of collective life activities. Compared with other histologies, metabolomics has several advantages.
- Changes in the type and quantity of metabolites are easy to detect.
- The technical means are simpler compared to genomics and proteomics.
- Compared with genomics and of proteomics, the number of metabolites is small and easy to detect, verify and analyze.
- Changes in metabolite levels can reveal the physiopathological state of the organism in real time.
Classification of metabolomics
Metabolomics can be divided into untargeted and targeted metabolomics depending on the purpose of the study.
Untargeted metabolomics is a comprehensive and systematic analysis of endogenous metabolites in organisms, and is an unbiased metabolomic analysis that can identify new biomarkers. Targeted metabolomics focuses on the study of a specific class of metabolites.
As both metabolomics approaches have their own advantages and disadvantages. Untargeted metabolomics is unbiased and provides a comprehensive and systematic response to the metabolomic profile of living organisms, but is less reproducible and has a limited linear range. Targeted metabolomics, on the other hand, has improved reproducibility and sensitivity, simple metabolite confirmation, and a wide linear range, but requires a prior knowledge background and is a biased metabolomic analysis method. Therefore, in practice, both are often used in combination and work together.
Fig 1. Flowchart for metabolomic studies (Tugizimana et al., 2013).
What are the types of samples that can be tested in metabolomics?
Metabolomics focuses on small molecule metabolites (molecular weight <1000) that serve as substrates and products of various metabolic pathways. The samples analyzed in metabolomics are mainly plasma or serum, urine, saliva, cells, and animal and plant tissues. In addition, plant, fungal and microbial extracts, cerebrospinal fluid, lymphatic fluid, insect hemolymph, amniotic fluid, follicular fluid, knee synovial fluid, tears, semen, placenta, fecal and intestinal contents extracts can also be tested.
How many substances can be detected by metabolomics?
Different mass spectrometry platforms have different sensitivities and biases, and the different platforms are complementary to each other. In general, GC-MS can accurately characterize about 200 substances for serum samples, about 200 substances for urine samples, and several hundred for other samples (e.g. liver, stool, intestinal contents). If comprehensive two-dimensional gas chromatography–mass spectrometry (GC×GC–MS) is used, the number of detectable substances can be more than 1,000. LC-MS can detect far more substances than GC-MS, and depending on the detector (TQ, QTOF, etc.), it may be possible to detect tens to 2-3 hundred substances.
Applications of metabolomics
Metabolomics can be used to discover and quantify differentiated metabolites, to delve into and analyze subsequent metabolic molecular markers, and to play an important role in food identification, disease research, animal model validation, biomarker discovery, disease diagnosis, drug development, drug screening, drug evaluation, clinical research, plant metabolism research, and microbial metabolism research.
- Tugizimana, F., Piater, L., & Dubery, I. (2013). Plant metabolomics: A new frontier in phytochemical analysis. South African Journal of Science, 109(5-6), 01-11.
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