The concept of metabolomics comes from the metabolome, which refers to all low-molecular-weight metabolites produced by a particular organism or cell during a specific physiological period. Metabolomics is a new discipline that qualitatively and quantitatively analyzes all low-molecular-weight metabolites produced by a particular organism or cell during a specific physiological period. It is a branch of systems biology based on group indicator analysis, high-throughput detection and data processing, and information modeling and system integration goals.
Metabolomicsis a newly developed discipline after genomics and proteomics and an important part of systems biology. It has subsequently rapidly developed and penetrated into many fields closely related to human health care, such as disease diagnosis, pharmaceutical research and development, nutrition and food science, toxicology, environmental science, botany, etc. Genomics and proteomics explore the activities of life at the gene and protein levels, respectively. However, many life activities actually occur at the metabolite level, such as cell signal release, energy transfer, and intercellular communication, which are all regulated by metabolism.
Generally, there are various types of samples for metabolomics, including serum, plasma, urine, feces, cells, bacteria, tissues, and culture fluid, as well as flowers, stems, leaves, etc. of plants. Suitable samples can be selected according to the research purposes. Sample collection and handling for metabolite analysis should follow the principle of "maintaining the freshest state," and samples should be stored in liquid nitrogen, dry ice, or a refrigerator at-80℃, immediately after collection to prevent further metabolic activity after the samples have been separated from the body, ensuring that the samples are kept at-80℃ or below before the experiment.
Due to the high dynamic variability of metabolites downstream of biological activities compared to genes and proteins, many biological replicates are needed to increase data reliability and persuasiveness.
For whole-substance identification projects: Biological replicates can generally be omitted or set, and there are no particular regulations, which can be set according to actual experimental needs.
Untargeted metabolomics projects: biological replicates must be set. Generally, each group of cell or microbial samples requires at least six biological replicates, animal or plant samples requires at least 10 biological replicates per group, and clinical samples require at least 30 biological replicates per group. The number of sample replicates is strongly recommended to be more than six. If the sample size is too small, the subsequent multivariate statistical analysis model is prone to overfitting, and the statistical results will be unreliable, which may be subject to questioning.
Targeted metabolomics projects are generally used for verification, so the more biological replicates the better. Generally, at least three biological replicates are required for each group of targeted metabolites, and the result is unreliable if the number of biological replicates is less than three.