Victory over aging is a long-standing human dream. However, scientists, despite numerous studies, still do not fully understand why with age, the functions of the body are gradually disrupted, and organs fail. "Lenta.ru" talks about a new job that explains the impossibility of eternal youth in modern reality.
One of the most important discoveries in the biology of human aging was made over 50 years ago. In 1961, anatomy professor at the University of California, Leonard Hayflick, discovered that human cells die after about 50 divisions, and as they approach this point, they show signs of aging. This phenomenon has been associated with the shortening of telomeres - the ends of chromosomes that protect a vital part of DNA from damage. When telomeres disappear completely, the cell starts a self-destruction mechanism.
Although telomere shortening is still believed by some anti-aging activists to be the main cause of slow decline and subsequent death, scientists have proposed other theories. For example, the gradual accumulation of mutations in DNA, evolutionary programming, or the influence of free radicals. Despite the fact that almost half a century has passed since the discovery of the Hayflick limit, there is still no full understanding of what exactly makes living organisms age.
Gerontologist Brett Augsburger of Auburn University in the United States has developed a new approach to elucidate the causes of aging. In his paper, a preprint of which was published in the bioRxiv.org repository, he suggested that the key to solving the problem could be nonequilibrium thermodynamics, which describes systems that are not in thermodynamic equilibrium. According to the scientist, life expectancy depends on the rate of destruction of biological molecules and the inevitable loss of information. It becomes clear why victory over aging is impossible in the near future: fundamental physical laws make the wear and tear of the body inevitable.
The new approach explains some of the paradoxes that arise in other aging models, and also reveals the fundamental flaws in the theory of the disposable catfish, which was proposed in 1977 by the English biologist Thomas Kirkwood.
The disposable soma theory assumes that the body must have a certain amount of energy to maintain metabolism, reproduction, recovery and other functions. Since the amount of food is always limited, you have to compromise. Since the mechanisms responsible for regeneration do not receive sufficient energy, the body begins to age. Some experts believe that the limiting resource is time, not energy. According to this point of view, for each organism there is an optimal duration of pregnancy, when the offspring will be most viable. However, it limits the amount of time that can be devoted to growth and development. Thus, the rate of development and gestation period are influenced by natural selection. Accelerating pregnancy limits the timeset aside for the repair of cellular damage. This, in turn, leads to the accumulation of defects and a decrease in life expectancy compared to organisms with a long gestation period.
Chromosomes with telomeres
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Image: US Department of Energy Human Genome Program
The second law of thermodynamics suggests that any form of energy tends to go into a less ordered state - in other words, to dissipate in space. Any non-equilibrium system, including living organisms, will transform energy in this way until a point of equilibrium is reached - in this case, the state of death. Many creatures are able to withstand the transition to a state of equilibrium long enough to develop and reproduce. For different species, this time takes from several hours to decades.
Hayflick limit, limiting division of somatic cells
In a living organism, far from the state of thermodynamic equilibrium, free energy is concentrated in the chemical bonds of large biomolecules. This makes it possible to proceed with various processes, from unfolding proteins and DNA untangling to hydrolysis, oxidation and methylation. Auxburger modeled a system that demonstrated that biomolecules must inevitably degrade, resulting in energy dissipation. Moreover, any processes occurring in the body contribute to the approach to a state of equilibrium, including the generation of electrical impulses.
The author of the work came to the conclusion that the mechanisms of the restoration of molecules do not guarantee that the information contained in the DNA will be preserved in individual cells, therefore it must inevitably decrease. As a result, the vitality of the organism is also reduced. Given that cells are influenced by a kind of natural selection, then due to mutations in DNA, a situation may arise when individual cells (dividing as a result of mitosis) gain advantages over other cells, which is not necessarily beneficial for the person as a whole. Removing them can delay the negative effects, but over time, more and more cells will become defective. Therefore, if the body lives long enough, it not only inevitably grows old, but sooner or later it is struck by cancer.
Naked mole rats, like many animals, have cancer.
Photo: Roman Klementschitz / Wikipedia
Certain animal species, such as the naked mole rat (Heterocephalus glaber), are believed to be free of cancer. However, this opinion is erroneous, since it takes time for a malignant tumor to appear. An article was recently published in which scientists described the first case of cancer in H.glaber.
The search for longevity genes is useless in the sense that editing them using genetic engineering methods will not significantly prolong the life of such complex organisms as humans. Moreover, such manipulations can be harmful, so the author advises to move away from an approach that focuses on establishing links between genes and certain signs of aging. At best, genes represent an incomplete set of factors in longevity.
What could be the way to beat aging? Very complex and beyond the capabilities of modern biotechnology. Since age processes are a consequence of fundamental laws, it is still unrealistic to eliminate the causes underlying aging. An effective approach in this case can be the creation of DNA libraries, which store information about intact genes. On their basis, young stem cells can be synthesized for transplantation into an old organism. According to Auxburger, such methods are more effective than existing ones.
Alexander Enikeev
