In a previous post I considered internal specificity (genome, proteome, metabolome), now I am going to look at the external factors that need to be considered in precision health, starting with the Microbiome, a sort of a bridge between the internal and external specificity.
Our body is composed of cells and this seems to us what our body is all about. Actually, for any single cell we have there is at least another living cells (a microbe) that forms who we are. There are an estimated 30 trillion bacteria on and in our body. This bacterial population keeps changing, however, at a macro level, looking at the types and distribution of bacteria we realise that they are specific to us. A different species, say a cat or an oak, have a different set and distribution of bacteria, characteristic of that species. This characteristic set is the microbiome of that species.
It has been observed that the microbiome may change during the course of a disease (and during recovery) and it has also been pointed out that complex pathologies (where there is not a single factor leading to the disease, like psoriasis, skin ulcers, obesity, depression) are tied one way or another to some variation in the microbiome. Also, and possibly even more important in the context of precision health (personalised medicine), it has been noted that certain drugs effectiveness depends on the microbiome since they are involved in how drugs are metabolised and absorbed.
The human microbiome project aims at identifying the various species of bacteria living in symbioses with us and set up methods to identify the specific microbiome of a specific person to help in diagnoses and cure.
The circadian rhythm is a sort of clock regulating the activities of living beings, and is typical of each species, including bacteria and plants. They are regulated by a number of genes that activate one another.
It has been discovered that each person has her own specific circadian rhythm and that its variation are connected to environmental causes and have an impact on the insurgence of some pathologies like diabetes, obesity, cardiovascular diseases and psychiatric disorders.
Recently researchers have developed a blood test to check the actual clock inside your body that may not correspond to the one of your watch. As we move from one time zone to another we experience this problem and it is normal since your watch immediately synchronize to the new time zone whilst your body will take almost one day per every hour difference. Sometimes, however, the internal clock and the external one may not be aligned even if you haven’t travelled to a different part of the world.
Coordinating the cure with your internal clock may be important, that’s why this test to check your body “time zone”.
Well before the discovery of the DNA role in traits inheritance scientists noted that external conditions experienced by the mother during the pregnancy could have an impact on the fetus and thereafter on the development of the new born, increasing the risk of certain pathologies. When the role of DNA became clear scientists discovered that these external conditions could affect not the DNA as such but its expression, that is when and how the various genes would be activated. In technical terms they found that for a given genotype (a DNA sequence) external factors during pregnancy and also (to a more limited extent) during the lifetime could affect the expression of genes thus changing the phenotype. The study on the impact of external factors, including lifestyle, on the expression of genes is the “epigenetics”.
It has been found that diet and pollution have an effect on the gene expression and can be a factor in asthma, coronary and neurological pathologies.
There are at least three mechanism affecting the gene expression: DNA methylation, histone modification and non-coding RNA gene silencing. These epigenetics variation may be a factor in certain diseases, including cancer, and in the effectiveness of a cure.
This is why epigenetics is important in Precision Health.
The exposome represents all the exposure to external factors, environment, diet, work activities… of a person. These exposure have an impact on that person health and influence the effectiveness of cure.
The Human Exposome project has the goal of analysing the various factors potentially influencing human health:
“The exposome, conceptually and practically, provides a holistic view of human health and disease. It includes exposures from our diets, our lifestyles, and our behaviors. It also includes how our bodies respond to these challenges. When coupled with advances in genetics and medicine, the exposome will help lead to improved strategies aimed at preventing and treating diseases, such as autism, diabetes, heart disease, and Alzheimer’s disease. We believe that pursuit of a Human Exposome Project, similar to the Human Genome Project or the BRAIN Initiative, will help reveal the importance of the environment in our lives.”
We are now seeing a growing possibility of monitoring the exposure of a person through his lifetime recording them in that person “digital twin” (an extension of the health record). We are just starting but it is already clear that having a digital twin of a person would give a boost to precision health care. Of course that means to be able to analyse and correlate data, i.e. to move into “digital medicine”. This is something I will address in following posts.
Precision medicine is clearly opening up a much better way of understanding a person’s health, the risks and the optimal cure. Assessing the risk at a personal level increases the effectiveness of proactive actions to avoid pathologies, hence increasing that person wellbeing.
Precision medicine is leading to a disruption in the health care sector since it shifts the focus from the statistical approach on which the big pharma is based to a focussed approach that can well be provided, in a more effective way, by smaller and geographically focussed companies, thus breaking today’s established value chains.