The disciplines which study molecules with similar qualities are called “omic sciences”: the suffix -omics derives from the mix of words “oma” (name of mass or groups) and “ics” (fields of knowledge or practice).
Within these disciplines we can find genomics, science which studies everything about genes; transcriptomics, the study of mRNA molecules in a cell in a particular moment; proteomics, the study of proteins (which can also be described as phenotypical manifestation of genome content) and lastly metabolomics, the science which studies metabolites (small molecules produced as a consequence of enzymatic reactions and which interact with each other to give metabolism). Going from the first one to the last one, the complexity raises and the quantity of information decreases: nowadays genomics has the biggest quantity of information and it is even possible to divide it into different fields (structural genomics, functional genomics, comparative genomics, ecological genomics..); lastly, while Human Genome Project can be considered as finished and its data are easily accessible, researchers are still working on Human Metabolome Project and there is an esponential raise of information.
The integration of data of these disciplines is called “systems biology” and its aim is the analysis of a whole organism and the following generation of hypothesis (by contrast, classic approach needs an hypothesis to start analysis)
To give some numbers, in the human organisms there are about 20.000 genes and their study gives the idea of what could potentially happen at phenotypical level; starting from genes, throughout different mechanisms about 1.000.000 different transcripts can be obtained and they give the idea of what is currently happening in a particular cell. Lastly, some other mechanisms permit to obtain about 10.000.000 different proteins, the phenotypical manifestation of the genome content needed by a cell in a particular moment.
Proteins play different roles in a cell and within these ones, enzymes play an important role catalyzing cell reactions and so allowing the metabolites’ formation. Talking about the latters, nowadays the number of catalogued ones is about 100.000 but it is going to raise (just think about the number of metabolomic studies published in the last years: it is about 5000/year).
Why do we have to study metabolites?
The study of metabolites permits to draw a detailed profile about an individual’s metabolism: this latter can change even during a day, for example in the morning the stress due to work leads to the production of some metabolites which are different from the ones produced during relax. Some metabolites need more time to change significantly in body fluids, and so they can be an index of a long lasting condition which can lead to disease in the future. Nowadays their measurement is performed in urine and blood samples: the first gives information about a two-months-period before the urine sample is taken; in the second case information last two weeks.
Metabolomics is the most reliable way to analyze the final effect of epigenetic factors involved in diseases: we have to consider that health depends also on environmental influences like exercise and diet, and these also influence a person’s metabolism. Therefore an individual phenotype is more similar to the metabolome compared to the transcriptome and proteome, and even if the number of involved molecules is smaller, their diversity makes their study more complex and at the same time more informative about someone’s health.
In general, an increase of the quantity of a metabolite quantity is due to a block in the respective pathway which can be due to the lack of cofactors. These latter can then be given through a specific diet and supplements, and this leads to the recovery of that enzymatic reaction and so the pathway can be restored. The analysis of more metabolites at the same time permits to have a general idea of someone’s metabolism and to intervene in the aforementioned way where there’s the need to.
German JB, Hammock BD, Watkins SM (2005) Metabolomics
Fathoming Metabolism Harvard Mag. 2011
Clish C. 2015 Metabolomics: an emerging but powerful tool for precision medicine. Molecular Case Studies