Not so long ago, American and British scientists published a work in which it was argued that severe stress and serious injuries not only shorten a person's life, but can also affect the health of descendants. Previously, Dutch researchers reported that children conceived after their mothers experienced hunger have metabolic problems. RIA Novosti is examining whether a traumatic experience experienced by a person is really capable of having such a strong impact on offspring.
Over genes
Earlier this year, staff at the University of Cambridge and California studied lists of POWs from the American Civil War. Tracing the fate of soldiers in peacetime, the researchers found that the sons of those who were tortured and abused in captivity died young ten percent more often than their peers, whose parents were never captured.
This was explained by the inheritance of epigenetic factors. It is assumed that the traumatic experience leaves a chemical mark in a person's genes that is passed on to offspring. The DNA structure does not change, that is, no mutations occur, but gene expression is affected - their activity either increases or, conversely, decreases.
“Inheritance of traits acquired during life is possible. However, it is wrong to talk about the transfer of traumatic experiences. It is more correct to say that certain features of the environment that an organism encounters during life can affect the functioning of cells, and this is already passed on to the next generations. This phenomenon is called epigenetic inheritance,”explains Yulia Medvedeva, head of the group of regulatory transcriptomics and epigenomics at the Federal Research Center“Fundamental Foundations of Biotechnology,”RAS, to RIA Novosti.
Inheritance mechanism
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“There are several mechanisms for the transmission of epigenetic factors. In general, they are associated with one widespread modification of DNA, the so-called methylation - the attachment of carbon and hydrogen atoms to certain parts of DNA, which determines the activity of genes in cells, and sometimes even “turns them off”. And here changes are possible for many reasons: due to lifestyle, diseases and much more. But the inheritance of a certain methylation status and its relationship with a certain experience accumulated during a person's life is being studied relatively recently,”says Mikhail Skoblov, head of the functional genomics laboratory at the Medical Genetic Research Center.
According to him, scientists are still cautious about the inheritance of epigenetic factors from generation to generation: it is difficult to indicate what exactly can be transmitted in this way.
For the sins of the fathers
Here's an example of epigenetic inheritance. Male rats whose mothers were supplemented with the pesticide vinclozolin during pregnancy experienced problems with the quality and quantity of sperm. This effect was traced for four generations of laboratory animals, and in the fifth it already disappeared.
Such studies in humans are much more difficult - if only because humans live much longer.
However, Swedish scientists were incredibly lucky. Residents of the small town of Overkalix, in the north of the country, since the 16th century, have written down in detail everything they knew about themselves, their relatives and neighbors: origin, social status, cause of death. Information about the weather, harvests and the most important events in the city were also documented. The result was a huge amount of data about everything that a relatively isolated human population has lived for almost five hundred years.
After analyzing all this information, scientists made several important conclusions. First, it turned out that overeating in childhood (if this time fell on the harvest years) can lead to the development of diabetes and premature death from cardiovascular disease. Secondly, children and grandchildren will be predisposed to these diseases.
Researchers studying the so-called Hungry Winter - from September 1944 to May 1945, when about 18,000 Dutch citizens died from malnutrition - have found another pattern. Children born during this period had metabolic problems, obesity, diabetes and cardiovascular disease. Their DNA has not changed compared to siblings born earlier or later, but the gene that influences height and weight was adorned with special chemical structures that blocked its activity.
“Strictly speaking, it is impossible to clearly identify epigenetic inheritance from parents, since a direct effect on germ cells cannot be ruled out in humans. Egg precursors are formed even during the intrauterine development of the embryo. Therefore, any impact on the mother can directly affect the unborn child. With fathers, it's a little easier: sperm and predecessors do not live long. But a situation is possible when some substance simply accumulates in the father's body and directly affects the germ cells. Therefore, one can really judge about epigenetic inheritance only if the effect is visible on the second generation, that is, on grandchildren. In the most interesting works, it is possible to show the effect on more distant generations. I don’t know such research with a human,but there is work on epigenetic inheritance in worms up to the 14th generation,”says Yulia Medvedeva.
Note to biohackers
According to the researcher, epigenetic mechanisms do not have any positive or negative effects. But they are absolutely essential for the functioning of a multicellular organism.
As Mikhail Skoblov clarified, there are few works on epigenetics, so it is difficult to talk about examples of the positive influence of epigenetic factors, but in some animals it has been shown that, in addition to stress, these factors affect the life expectancy of offspring and its metabolism.
Agouti mice that change color due to epigenetic factors.
“Is it possible to somehow change the epigenetic profile under the influence of the environment so that it would benefit the body? Yes. There is a classic example with agouti mice. Their bright yellow color, excess weight and inherent diseases are provided by the expression of one gene. It has been established that if a mouse is fed food with methyl group donors, the promoter of this gene is methylated and suppressed, which leads to an inherited return to the usual mouse phenotype (gray color and normal weight). For a person, they tried to find similar effects from diet, exercise and other things, but so far not very convincingly,”concludes Yulia Medvedeva.
Alfiya Enikeeva