Андрей Фоменко – The Power Of Youth. How To Tune Our Mind And Body For A Long And Healthy Life (страница 2)

WHAT BODY CHANGES ARE CAUSED DUE TO AGING?

As a person grows older, their appearance, health, and the function of most organs change. The set of these metamorphoses, which manifest both externally and internally, is called aging. Here are some signs characteristic of aging.

● Hearing impairment: children can hear high-frequency sounds (above 20 Hz) – this ability is usually lost by the end of adolescence. After age 75, more than half of older adults hearing gets worse so much that it prevents normal communication.

● Vision problems: after the age of 35, the tone of the ciliary muscle, responsible for accommodation[3] (change in the curvature of the lens) decreases. As a result, farsightedness (presbyopia) develops and progresses after the age of 40 – a deterioration in the ability to see near objects. In addition, over the years, the risk of cataracts (clouding of the lens) increases.

● Change in skin tone: due to lower production of hyaluronic acid, collagen, and elastin fibers over the years, the skin loses elasticity, which leads to wrinkles.

● Over the years, the function of cells producing melanin, the substance that determines hair color, suffers, and graying comes with this process. In addition, as we age, our hair begins to fall out more actively, and the risk of alopecia (hair loss) increases.

● As we age, we lose muscle mass and strength, and muscle's ability to regenerate deteriorates.

● After the age of 25, fertility (ability to conceive) in women starts to decline. At the age of 44 to 55 years, (there can be deviations in either direction) menopause occurs, and loss of the ability to childbirth. Men's sexual function also deteriorates over the years, increases the risk of erectile dysfunction, and decreases the fecundating ability.

● Cognitive function often deteriorates over the years: learning and memory deficit, the risk of dementia, including Alzheimer's and Parkinson's disease, increases.

● There is a higher risk for several diseases: osteoporosis (brittleness of the bones), osteoarthrosis, atherosclerosis, hypertension, obesity, diabetes, coronary heart disease, cerebrovascular disease, cancer, immune deficiency, etc.

In addition to symptoms of aging, changes at the cellular and molecular levels develop with age, and it has an impact on our bodies. Scientists from the Department of Biochemistry and Molecular Biology at the University of Oviedo (Spain) state that aging is based on the following biological processes[4].

● Accumulation of mutations in cells (genomic instability), which increases the risk of developing diseases and malignant tumors.

● Shortening of telomeres, end sections of chromosomes, that protect genetic material from damage. It also causes errors in the genome, protein production, and dysfunction of cell and organ function.

● Accumulation of so-called senescent cells, incapable of division or apoptosis (planned cell death leading to tissue renewal). Such cells do not die, but partially or completely lose their functions, leading to organ malfunction.

● Decreased sensitivity of cells to "positive" growth factors, and hormones, activating energy exchange in cells, which stimulate regeneration. At the same time, the sensitivity of cells to the action of damaging factors, such as radiation, toxic substances, antibiotics, etc., increases with age.

● Depletion of stem cells, which are "samples" for functional cells of various organs.

● Deterioration of intercellular communication, signaling between cells, which ensures a coordinated work of the body.

There is such a concept as biomarkers of aging – a set of physiological and biochemical indicators, that allow us to judge the biological age of a person. A table listing the basic biomarkers of aging is given at the end of the chapter.

THEORIES OF AGING

Although since antiquity, humans have tried to understand what biological aging is and how to prevent it, scientists have not yet come to a common understanding of the nature of aging. Today there are many theories explaining the reasons for the physical and mental decline that occurs with age. All these theories can be divided into two large categories: damage theories and evolutionary theories – theories of programmed aging[5].

AGING AS A PROCESS PROGRAMMED BY NATURE

Evolutionary theories of aging imply that aging is the result of the organism following a biological "schedule" regulating the main stages of human life: birth, growth and development, growth impairment, stagnation, biodegradation, and death. In the view of advocates of this approach, aging gives an advantage in the survival of a particular population and is evolutionary "beneficial" for species. In the first place, it is about resource allocation: individuals who have lost their reproduction capability shall age and die in order not to compete for resources with the younger generation.

There are some examples of the evolutionary theories of aging.

● Theory of programmed longevity. Throughout life, certain genes are "turned on" and others are "turned off" by nature, i.e., regulation of aging processes is embedded at the DNA level.

● Neuroendocrine theory. It suggests that aging is an impaired hormonal balance. This theory appeared in the XIX century, and in the early XX century experiments on transplanting various endocrine glands (ovaries and testicles, adrenal glands, basal glands) from young animals to elderly ones became popular. Today, some scientists associate aging with changes in insulin and insulin-like growth factor (IGF) signaling[6].

● Immunologic theory of aging. It views aging as a consequence of an evolutionarily programmed process of "immunological decline" that occurs with age. The efficiency of immunity peaks during adolescence. The ability to resist infections, destroy harmful microbes, identify mutated cells, and respond to vaccines, decreases over the which makes the body vulnerable to the negative joint action of external and internal factors, leading to disease and death. One of the key aspects underlying immunologic aging is the immunosenescence[7] – age-related changes in the thymus gland responsible for training immune cells[8].

AGING AS A RESULT OF DAMAGE (ERRORS) ACCUMULATION

While supporters of "programmed aging" theories view age-adverse changes as the result of an inevitable evolutionary program, followers of "damage theory" do not consider aging a "genetic doom." They believe that the body accumulates many "breakdowns" with age due to the influence of external factors, stress, etc. A gradual accumulation of such damages leads to the development of age-related diseases and, eventually, to death.

There are examples of damage accumulation theories.

● DNA damage theory. During cell division and copying of DNA molecules, there is always a risk of genetic errors (mutations) that accumulate with age and result in age-related diseases, primarily malignant tumors. In addition, adverse mutations, accumulating with age, can occur under the influence of factors external to the cell: ultraviolet radiation, virus entry, inserting their genome into hereditary material, etc.[9].

● Genetic instability theory. It is not about mutations associated with damage, but rather about various changes in the genome occurring in the chromosome division. For example, such things as aneuploidy, the presence of an abnormal number of chromosomes in a cell, are identified in the fetal brain at all stages of intrauterine development. After birth, the number of such neurons decreases significantly, but some of them remain and can cause brain cancer[10].

● Free radical theory. Supporters of this theory affirm that free radicals (particles, containing oxygen with one missing electron) are the cause of cellular malfunction. They are needed for many biochemical processes and are constantly formed in the body during breathing. By leaving the place where they needed, they sort of "take" an electron from the body, and this is called an oxidative reaction. Free radicals are a serious threat to cell activity because they damage proteins and lipids[11].

Among the numerous theories of aging today, the following concepts are also emphasized.

● Apoptosis theory. Body tissues are constantly updated: "worn-out" cells whose function is deteriorating, as well as cells damaged by infection, having genetic mutations, regularly commit "suicide." Programmed cellular self-destruction is called apoptosis. In Greek, ἀπόπτωσις means "leaf fall": old cells die, like autumn leaves, to make way for the younger generation. There is an apoptosis gene in the DNA of each cell that triggers cellular self-destruction in response to molecular signals. The problem is that over the years, the sensitivity of cells to signals, activating their "suicide," decreases, leading to an accumulation of damaged, low-functioning cells. The aging process is based on the decreased ability of tissues to remove aged cells[12].

● Elevational (ontogenetic) theory of aging. In the mid-twentieth century, the Soviet gerontologist V. M. Dilman related aging and ontogeny[13] (individual development) of the homeostatic systems of the organism. The scientist named an elevation in the hypothalamus sensitivity threshold – the "conductor" of an endocrine system – to homeostatic signals as the key mechanism of aging. In a series of experiments, it was proved that this mechanism is based on the adverse changes in the reproductive, hypothalamic-pituitary-adrenal axis, which provides the necessary number of glucocorticoids in the blood (the so-called stress hormones) and increases their secretion under stress, which eventually leads to hyperadaptosis, i.e., a condition of excessive body adaptation to stress. The same mechanism in the metabolic homeostasis system causes the accumulation of body fat, a decrease in tissue sensitivity to insulin, and the development of atherosclerosis. Dilman found that age-related transformations occurred because of homeostatic ontogenesis, creating conditions for the formation of malignancies. Thus, the scientist concluded that aging is not programmed, but is a byproduct of the genetic developmental program. This led to the belief that aging can be slowed down if homeostasis is stabilized at the level achieved by the end of the organism's development.