Читать книгу The Power Of Youth. How To Tune Our Mind And Body For A Long And Healthy Life - Андрей Фоменко - Страница 19

The main ways to control gene activity are histone modification and methylation. Histones are special proteins to which the DNA in the cell nucleus is wound around, like a coil, to form a tight pack, the nucleosome. The tighter this pack, the less DNA is available to the enzymes that conduct transcription – synthesis of RNA from the DNA matrix. And since there is less RNA, less protein is produced. This means that the gene in this area will have little or no activity. However, signals from the external environment can contribute to a looser arrangement of these "coils," so that enzymes gain access to this DNA section. This means that RNA, and then proteins, can be synthesized – the gene is active.

The second mode of gene regulation is methylation, i.e., the addition of a methyl group – CH3 – to DNA. As a result, cytosine is transformed into 5-methylcytosine. Once the signal is received, the methyl group attaches to the DNA, which prevents enzymes from binding to it and changes the density of the nucleosome, as with histone modification, making genes inactive. In contrast, the process opposite to methylation, i.e., demethylation, activates previously "silenced" genes, which promotes the formation of new proteins.

Understanding the mechanisms that "turn on" and "turn off" genes can give science and medicine the ability to regulate the aging process, as well as to control and treat various diseases, including those of genetic origin. For example, "uncontrollable" genes are often "guilty" in the development of cancer – their "silencing" will stop further growth of the tumor. Therefore, the most prestigious scientific prizes are awarded for research in this field: for example, in 2006, American scientists Andrew Fire and Craig Mello were awarded the Nobel Prize for the discovery of another epigenetic mechanism – RNA interference.

FUN FACT

ONLY 5-10 % OF DISEASE DEVELOPMENT DEPENDS ON GENETICS

Canadian scientists at the University of Alberta conducted the largest meta-analysis, summarizing data from 569 genetic studies over two decades, and concluded that the association between most human diseases and genetics is very low – only 5-10 %. This means that human life and health are not predetermined by genes, but depend more on lifestyle and environment.

In their work, the researchers studied the relationship between gene mutations known as single-nucleotide polymorphism (SNPs) and various diseases and conditions. Many SNPs are considered risk factors for the development of hundreds of diseases, but the results of a meta-analysis have shown that this relationship is highly questionable.

Experts have found that most diseases, including many cancers, diabetes mellitus type II, and Alzheimer's disease, are only 5-10 % or less dependent on genetic factors. However, there are exceptions: for example, Crohn's disease, gluten-sensitive enteropathy, and age-related macular degeneration, for which the genetic risk is 40–50 %.

Despite these rare exceptions, it has become apparent that in most cases the development of disease is related to metabolic disorders, environmental and lifestyle factors, or exposure to dangerous bacteria, viruses, and toxic substances. It can be concluded that we should not blame deviations in health on heredity, and it is better to monitor the ecological security in which people live and work: food, water, air quality, etc., as well as lead a healthy lifestyle.

We can monitor epigenetics in action through the observation of the lives of identical twins who have identical DNA at birth. These observations show how strong the differences in gene expression of twins can be if they live in different conditions and lead different lifestyles. In theory, the disease in twins should develop equally, but it is far from being true: depending on various factors, only one of them may have symptoms.

This finding supports a study conducted in 2005[28]. Scientists studied several dozen pairs of identical twins 3–74 years old. It turned out that people did have similar gene expression in childhood because they were in about the same conditions: they lived in the same house, went to the same school, and ate similar food. However, the older the twins got, the more differences there were between them. And when the siblings separated as adults, and started to lead different lifestyles, to have some different hobbies, to work in different fields, the number of these differences increased several times.

It is the same with ordinary people: as soon as you change your lifestyle in one way or another, your genes will manifest themselves differently. And this changed methylation profile we pass on to our children! Why don't we then take advantage of this ability to make genes work for better health, slower aging, and longer life? Knowing how the epigenetic mechanism works can enable you to control your genetic code and thereby silence the "bad" genes inherited and activate the "good" ones. So how do we start the chain of beneficial epigenetic changes?