The human genome reading has opened new perspectives on the knowledge of the human beings, particularly on Modern Medicine which instead of be merely curative to being predictive and preventive.
The group of genes that a person owns is called genotype and its expression is called phenotype.Although all humans share the same genes, there are small variations on the DNA sequence that constitute every gen, which allows the existence of people’s inter-individual variation. We are all the same, but different, and these subtle differences make us unique and unrepeatable.
Regarding the functional point of view, there are two different classes of genes: minor genes and major genes. The Major genes are responsible of rare diseases. Changes on the DNA sequence are called mutations and are deterministic, because every time they are present they show their action. The minor genes are responsible for common diseases; the change on the DNA sequence is called polymorphism
and its effect depends on its interaction with the environment, so they are not deterministic. This interaction between genes and the environment is called multifactorial inheritance.
Minor genes confer susceptibility to the different diseases, and this susceptibility is quantitative, because genes add or multiply their effects, existing a threshold from which the disease appears. There’s a clear distinction between normal and abnormal phenotypes due to the absence of expression of the abnormal characteristic, until a certain threshold is reached. It’s said that chronic diseases like obesity, diabetes or cardiovascular diseases have a multi-factorial etiology, which is determined by a predisposition genotype and environmental factors that modulates its expression.
Therefore, predictive genetics allows us to know the risk population and be able to apply precautionary measures that prevent the development of the disease or its complications.
From the knowledge of the relation between genes and the environment comes along a new area of knowledge: nutritional genomics, that entail the joint study of nutrition and genome. From this relation, emerge two disciplines known as NUTRIGENETICS AND NUTRIGENOMICS.
Nutrigenetics studies the genetic variations on each individual, and its response to diet’s different bioactive components, according to the individual’s genotype: a different clinical response to nutrients and specific metabolites.
Nutrigenomics studies the molecular basis of the interaction between the dietary components and the genes, according to its expression regulation, and the metabolism, depending on individual genetic’s constitution: dietary components effects on the gene expression.
Nutrigenetics goes from the gene to the nutrient whereas nutrigenomics goes from the nutrient to the gene. For this reason, interindividual genetic variability is a crucial determinant of each person’s different nutritional requirements, as well as the response to the different environmental factors related.
Regarding obesity, Nutrigenetics performs gene’s identification whose polymorphisms can provide greater susceptibility to obesity development and its comorbidities: type 2 diabetes and cardiovascular diseases. On the other hand, nutrigenomics focuses on the description of characteristic changes in gene expression patterns in the adipose tissue and other obesity related tissues.
Moreover, we can consider there’s not only one type of obesity, but several genotypes with similar phenotypes; and it’s very important to know the total genetic load, take it into account in relation to the environmental factors and know which genes interact on each person to be able to offer a personalized treatment.
A more exhaustive nutrigenetic study allows getting to know obesity conditioning polymorphisms and the cardiometabolic risk by analysing 21 thrifty genes, validates by the scientific community, backed by verified bibliographic references and involved in the patient’s nutritional response, in Spanish population.
It’s a non invasive test because a saliva sample is used. In this way the patient can take itself his/her own sample, and it’s only taken once in one’s lifetime, since genes don’t change. They can be activated or desactivated due to environmental factors (epigenetic factors), which means genes are present from the moment of conception even though its effects can appear later in adulthood, like diabetes.
It should be noted that this study is not a diagnostic test, but a genetic risk estimation which will allow to develop a more accurate prognostic, in connection with the established therapeutic measures, personalizing the treatment.
On the other hand, the study on cardiometabolic risk is predictive of metabolic and cardiovascular complications, even when they’re not present. This way, it’s possible to detect the risk population and take preventive measures that could low the intensity or prevent the development of these comorbidities.
It’s very important the genetic analysis will be done through a specialist’s physician and not directly the patient at the laboratory. The treatment must be personalized and the recommendations must be explained by the specialist who knows the patient better, and thus be able to evaluate, and give the proper steps to follow up, to improve the quality of his/her life, depending on the genetic result of every patient.
Dr. Dolores Saavedra
Medical Director GENYCA