Age leaves a variety of molecular traces in the body. For example, we know that over time, telomeres shorten in our cells - the ends of chromosomes that do not encode any information, but which are necessary for the stability of the chromosomes themselves. With each cell division, telomeres become shorter, and by their length you can understand how much the cell has already lived and how much is left for it - when the telomere sites become very short, the mechanism of cellular self-destruction is activated, Science and Life reported.
But short telomeres are not the only molecular sign of age. There are also epigenetic tags for DNA. Epigenetic labels are chemical groups that appear both on the DNA itself and on the histone proteins that pack it. Such chemical modifications performed by special enzymes occur in response to various factors, external and internal, and permanently change the activity of genes.
For example, an epigenetically modified histone protein can pack a piece of DNA in such a way that the genes recorded in this piece will not be accessible to molecular machines that read genetic information - that is, the genes will simply shut up. The same thing can happen if epigenetic tags get on the DNA itself - usually they talk about DNA methylation, that is, about the attachment of methyl groups.
With age, the pattern of epigenetic labels on DNA changes. And this is not just a pattern: it affects the work of genes, and the work of genes causes age-related changes in our body. Perhaps if you twist the epigenetic clock in the opposite direction, then our cells will become younger.
Researchers at the University of California, Los Angeles, write about how to reverse the molecular epigenetic clock. Initially, they solved the problem of how to restore an aged thymus, or thymus gland. T-lymphocytes born in the bone marrow mature in the thymus, where they acquire specialization and learn to recognize infection and cancer cells. But after puberty, the thymus begins to gradually degrade, decreasing in size and filling with adipose tissue. It is known that thymus can be restored using growth hormone. But by restoring the thymus, growth hormone increases the likelihood of diabetes. However, diabetes can be protected with the help of special drugs, metformin (one of the most famous drugs prescribed for type 2 diabetes) and the male steroid hormone dehydroepiandrosterone.
A mixture of growth hormone, metformin and dehydroepiandrosterone was tested on nine men aged 51 to 65 years. As shown by magnetic resonance imaging, seven of them in the thymus adipose tissue disappeared, replaced by normal thymic tissue; judging by the T-lymphocytes in the blood of the participants in the experiment, their thymus did indeed recover. And, finally, when their epigenetic clocks were checked in the experimental subjects, it turned out that these clocks receded some time ago - that is, the new pattern of methyl marks on DNA corresponded to an earlier age compared to what it was before the experiment. Moreover, in six people, a younger-looking epigenetic pattern persisted six months after they stopped taking anti-aging cocktails.
Perhaps this effect is manifested not only in the thymus gland, but also in other organs. But even if everything is limited to the thymus, it is not so little: a lot depends on our immunity, and an elderly person can generally feel younger if you rejuvenate his immune system.