25 February 2016

Anti-aging only for the fair sex

Researchers from the University of Southern California and Hangzhou Electrotechnical University (China), working under the guidance of Professor John Tower, analyzed the results of earlier studies on the effect of dietary and pharmaceutical interventions on the longevity of fruit flies and mice, and concluded that such interventions can have the opposite effect on representatives of different the floors. According to Professor Tower, these findings are in good agreement with the available scientific data on human aging.

The authors found that exposure to drosophila flies with the steroid hormone mifepristone/RU486, used to terminate pregnancy in humans, reduces the production of eggs in females, while increasing their life expectancy. Similar effects were found in various manipulations of the diet of fruit flies and mice, but in some cases they had the opposite effect on males.

An increase in life expectancy also increased the age-related mortality rate for the population. This is a confirmation of the strong Streler-Mildvan correlation described by the Gompertz equation, a mortality model named after the British mathematician who first proposed it in 1825.

Briefly, it can be described as follows: suppose we can create a mortality graph for everyone born in a certain year, from the moment of birth to the death of the last person. We will see two key points: first we will note that from time to time a small number of people die, usually from diseases. This is a non-age mortality.

Subsequently, as the group ages, we will see an exponential increase in mortality, continuing until the death of the last representative of the group. It is believed that this growth is a reflection of real aging – an unexplained deterioration of the body that occurs over time.

According to Tower, experts make various assumptions, but no one has been able to find out the reason for this growth. And the results obtained indicate that dietary and genetic interventions sometimes have the opposite effect on it, depending on the sex of the individual.

The Streler-Mildvana correlation indicates that this equation is influenced by the ratio of strong and weak individuals in the population, as well as the fact that a change in this ratio will lead to corresponding changes in mortality rates.

Tower explains that if weak individuals with low viability are removed from the population, then the predominance of individuals with high viability slows down the growth of the age-related mortality rate. According to Tower, the figures obtained by analyzing this pattern are the most convincing data he has ever seen, which confirms the fundamental nature of the described relationship.

He also notes that the results obtained support the aging model proposed in 1957 by George Williams of Michigan State University, known as the antagonistic pleiotropy model. (Pleiotropy is the effect of one gene on several physical characteristics.)

Williams suggests that natural selection may lead to the preservation in the population of a gene that causes a defect incompatible with life at a late age, but provides a significant advantage earlier, which contributes to successful reproduction. In general, such a gene may be favorable for the survival of a population even if it ultimately shortens the life expectancy of its members.

Apparently, the effect of mifepristone cancels this compromise between life expectancy and reproductive ability, although this effect depends on the sex of the individual.

Over the past half century, the model of antagonistic pleiotropy has been criticized more than once, including the idea that if it really is the driving force of aging, then somewhere in the history of evolution some organism somehow managed to overcome it.

The results obtained by Tower indicate that sexual antagonistic pleiotropy, in which a certain gene is favorable for one sex and harmful for the other, ensures the preservation of genes in the genome that limit the life expectancy of both sexes.

Article by Shen J et al. Multiple Metazoan Life-span Interventions Exhibit a Sex-specific Strehler-Mildvan Inverse Relationship Between Initial Mortality Rate and Age-dependent Mortality Rate Acceleration published in The Journals Of Gerontology. Series A, Biological sciences and medical sciences.

Evgeniya Ryabtseva
Portal "Eternal youth" http://vechnayamolodost.ru Based on materials from the University of Southern California, Los Angeles: Some aging treatments shown to have opposite effects on males and females.


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