Aging and nonequilibrium thermodynamics
An old dream: what could be the way to defeat aging?
Victory over aging is a long–standing human dream. However, scientists, despite numerous studies, still do not have a complete understanding of why the functions of the body are gradually disrupted with age, and organs fail, informs news.eizvestia.com .
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Gerontologist Brett Augsburger from Auburn University in the USA has developed a new approach to elucidate the causes of aging. In his article, the preprint of which is published in the repository bioRxiv.org (Nonequilibrium Thermodynamics and Fitness Costs Associated with Information Preservation May Explain Longevity Differences between Species – VM), he suggested that the key to solving the problem may be nonequilibrium thermodynamics, which describes systems that are not in a state of 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 the 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 within the framework of other models of aging, and also reveals fundamental flaws in the theory of disposable catfish, which was proposed in 1977 by the English biologist Thomas Kirkwood.
The theory of disposable catfish proceeds from the fact 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, we have to compromise. Since the mechanisms responsible for regeneration do not receive enough energy, the body begins to age. Some experts believe that the limiting resource is time, not energy at all. According to this point of view, there is an optimal duration of pregnancy for each organism, when the offspring will be the most viable. However, it limits the time that can be devoted to growth and development. Thus, the rate of development and the period of pregnancy are influenced by natural selection. The acceleration of pregnancy limits the time allotted 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.
The second law of thermodynamics assumes that any forms of energy tend to move 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 they reach the point of equilibrium - in this case, the state of death. Many creatures are able to resist the transition to a state of equilibrium long enough to develop and reproduce. For different species, this time takes from several hours to decades.
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 for various processes to take place, from the unfolding of proteins and the unraveling of DNA to hydrolysis, oxidation and methylation. Auxburger modeled a system that demonstrated that biomolecules must inevitably degrade, as a result of which energy is dissipated. Moreover, any processes occurring in the body contribute to approaching a state of equilibrium, including the generation of electrical impulses.
The author of the work came to the conclusion that the mechanisms of molecular recovery do not guarantee that the information contained in DNA will be preserved in individual cells, so it must inevitably decrease. As a result, the vitality of the body is also reduced. If we consider that cells are affected 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 useful for humans as a whole. Their removal may delay the negative consequences, but over time more and more cells will become defective. Therefore, if the body lives long enough, it not only inevitably ages, but sooner or later it is affected by cancer.
It is believed that some animal species – for example, naked diggers (Heterocephalus glaber) – do not suffer from cancer. However, this opinion is erroneous, since it takes time for a malignant tumor to appear. Recently, an article was published in which scientists described the first case of cancer in H.glaber.
The search for longevity genes is useless in the sense that their editing 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 the approach that focuses on establishing links between genes and certain signs of aging. At best, genes are far from a complete set of longevity factors.
What could be the way to defeat aging? Very complex and beyond the capabilities of modern biotechnologies. Since age-related processes are a consequence of fundamental laws, it is still unrealistic to eliminate the causes underlying aging. An effective approach in this case may be to create DNA libraries that store information about intact genes. On their basis, it is possible to synthesize young stem cells for transplantation into an old organism. According to Auxburger, such methods are more effective than currently existing ones.
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01.09.2016