Telomeres: what they are, their characteristics and how they are related with age

Time flies for everyone and it is an undeniable reality. Conceiving life without death is impossibleAs all organic matter degrades, loses its shape and is transformed. Without going any further, the most appropriate definition one can think of to define life from a biological point of view is: the intermediate state between birth and death.

Time passes inalienably, yes, but you’ll be surprised to learn that it doesn’t do the same for everyone. Chronological (chronometric) age indicates the movement of the hands of the clock, but this physical magnitude has nothing to do with what is happening inside our body. The phases of a biological process do not have the same quality or the same nature as those of a simply successive physical process.

In the physiological study of living things, the phases of a process are determined by the dynamics of the “intrinsic process”, and not by the impositions of a physical element, such as a clock. So a 40-year-old alcoholic might have the liver of an 80-year-old man, for example, while an athlete in his eighties might have the lower back muscles typical of a sedentary 60-year-old. Time flies, yes, but biological age may be different than what the calendar says.

Many parameters that alter the biological age of living tissue are completely related to the individual’s lifestyle, but there are other complex and fascinating concepts that explain, in part, why the process of cellular aging is unique and interchangeable. . We tell you the secret of life and death with a term that is as exciting as it is useful: all about telomeres.

    How are the chromosomes organized and where are the telomeres?

    We start from the beginning, like life itself. Humans have DNA enclosed in a nucleus in each of our cells. Through a series of processes that do not compete with us here, the information in DNA is transported from the nucleus to the ribosomes in the cell cytoplasm, so that they can synthesize proteins. Protein synthesis is the basis of the metabolism of living things, so we could say that DNA contains all the information necessary for life to be such.

    In humans, DNA condenses into chromatin, forming chromosomes. Each non-sex cell in our body (in general) has 23 pairs of chromosomes (46 in total), of which 23 are from the female gamete (n) and 23 from the male (n), which together form a zygote (2e). The parts of a chromosome are as follows:

    • Film and matrix: each chromosome is delimited by a membrane which contains a gelatinous substance.
    • Chromomonemes: filamentous structure that makes up each of the sister chromatids (being one chromatid each half of the chromosome in the shape of an “X”)
    • Chromomers: succession of granules which accompany the chromomoneme in its length.
    • Centromere: meeting place of the two sister chromatids. So that we understand each other, it is the center of the “X”.
    • Telomeres: the terminal parts of the chromosome, their “tips”.

    We have left a specific section in the inkwell so as not to get lost in the technical details, but we have already encountered for the first time the term that belongs to us here. It’s time to explore it in depth.

    What are telomeres?

    Based on what we’ve seen so far, the telomere is defined almost by itself: is the tip of the chromosome. Telomeres are highly repetitive, non-coding regions of DNA (lacking information necessary for protein synthesis), whose function is to provide chromosome stability in eukaryotic cells throughout their life. From the existence of these structures, we can partly explain two phenomena that take the breath away of any human being: aging and cancer. Let’s see how.

    1. When DNA is duplicated, telomeres do not fully replicate

    Somatic cells divide by mitosis, and for this to be possible, the DNA from the original cell that will give rise to the offspring line must be duplicated. With each process of replication, and due to certain characteristics of the enzymes which allow it, the telomeres are shortened..

    The length of telomeres in humans decreases at a rate of 24.8 to 27.7 base pairs per year. Over time and cell division, the telomeres on the chromosomes of the descending cells become so short that the cell can no longer divide and therefore with the death of the last cell entities, tissue death occurs. To draw a parallel with “being around the house” is like drawing water every time we pass it from one glass to another. At first it may not be noticed, but after repeating the process X times, the transfer cannot be done anymore, because there is no water left to move.

    For this reason, telomeres are said to be an excellent marker of biological age: Based on its length, scientists can estimate what is left in front of a group of cells and therefore the whole organism. Telomeric shortening is part of the normal aging process, but certain agents associated with a specific lifestyle can promote chromosomal DNA damage and therefore faster telomere shortening.

      2. The importance of telomerase

      We have explained the mechanism of old age, but the thing becomes even more interesting if we know that, unbelievably as it may seem, the body itself has the solution to immortality on a theoretical level, at least in the early years. stages of life.

      Telomerase is an enzyme responsible for maintaining the length of telomeres by adding repeated genetic sequences.. This biological process has a “trick”: the activity is present in germ cells and some hematopoietic cells, but mature somatic cells inhibit their functionality after birth. Thus, it is the organism itself which codes its programmed degradation.

      3. Telomeres and cancer

      Current studies suggest that humans could reverse the process of cellular senescence if we artificially increase telomerase activity in the somatic cells that make up the tissues of our body. Unfortunately, this could have a double effect: in experimental settings, if telomerase activity is stimulated and certain tumor suppressing genes are inactivated, it happens. 1 cell immortalization which considerably favors the appearance of a tumor.

      We go further in this line of thought, because 75 to 80% of cancers originating from somatic cells exhibit telomerase activity. This does not necessarily mean that telomerase causes cancer, but all indications are that high levels of this enzyme are a clear indication of a possible tumor malignancy. If a cell is immortal, it can replicate itself indefinitely: we explain almost word for word the formation of cancer.

      Based on this premise, several anti-telomerase treatments are being developed in the experimental field. In cell culture, the results are at least promising: in some carcinogenic cell lines, by inhibiting the activity of telomerase, spontaneous death of the strain occurs after about 25 divisions, Since the telomeres are shortening and in no case can be spared.

      summary

      After exposing data like this, it is impossible not to have hope. Cancer is one of the most important and tragic health problems today, because after every death and every character there is a story of struggle, sadness and hope. A neoplastic tumor is not just a group of cells that grow uncontrollably: it is fear, a battle of science against physiology, acceptance or denial, and in the worst case, loss. early in life.

      The mechanisms of cell senescence help us understand the aging tissue and the process that leads us to death, but the ultimate goal is not to find immortality. The real challenge today is to save all those lives hanging on a thread from a group of rebel cells. who have mutated to turn against their guest.

      Bibliographical references:

      • Arvelo, F. and Morales, A. (2004). Telomere, telomerase and cancer. Venezuelan Scientific Report, 55, 288-303.
      • Couto, AB (2008). Telomerase: source of youth for the cell. Medisur: Electronic Journal of Medical Sciences in Cienfuegos, 6 (2), 68-71.
      • The influence on lifestyle and longevity of telomeres, genotype. Collected March 4 from https://genotipia.com/estilo-vida-telomeros-longevidad/
      • Membrive Moyano, J. (2017). The enzyme telomerase as a therapeutic target.
      • Moyzis, RK (1991). The human telomere. Research and Science, (181), 24-32.
      • Salamanca-Gómez, F. (1997). Telomerase. Immortalize without malignancy. Gac Med Mex, 8, 385.
      • Telomere, NIH. Retrieved March 4, from https://www.genome.gov/es/genetics-glossary/Telomero
      • Vargas, E. and Espinoza, R. (2013). Biological time and age. Arbor, 189 (760), 022.

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