28 November 2022

The fragrance of a woman

The smell of adult mice extended the life of the mice by eight percent

However, only the smell of female mice and only female mice

Sergey Zadvoryev, N+1

Physiologists and gerontologists have studied how the odorous environment of animals affects their life expectancy. They kept laboratory mice surrounded by the scent tags of adult mice of their own or the opposite sex. A study involving 352 animals showed that females growing up in a cage with the scent tags of adult females live on average eight percent longer. The study, published as a preprint on the bioRxiv website and has not yet passed the scientific review procedure (Garratt et al., Lifespan Extension in Female Mice By Early, Transient Exposure to Adult Female Olfactory Cues), shows how intraspecific communication between animals can affect their life expectancy.

Smell plays an important role in communication between animals. In many species, odors regulate the work of the endocrine system — the development of olfactory structures of the forebrain is closely related to the development of the hypothalamus, and violations of their work and development are associated with aging processes and with life expectancy.

In mice, the department of the endocrine system that controls reproduction, growth and puberty reacts sensitively to odor tags. At the same time, puberty can be considered as the reverse side of the beginning of the aging process. But if the effect of pre-puberty scent marks on reproduction in animals is fairly well studied, then the effect on life expectancy is less clear.

Researchers from University of Michigan, Saarland University and The University of Otago, led by Richard Miller, decided to fill this gap and study how the perception of odor tags before puberty affects life expectancy in mice. They took 178 males and 176 females aged two days (at this age, the mice are completely dependent on the mother). At the age of 3-60 days, the scientists gave the animals to smell the odors of male or female mice. Up to 18-19 days of life, scientists applied urine samples of males or females to the muzzle of mice. Adolescent mice, which no longer need to be fed milk and which can be kept separately from their mother, were moved by scientists to cages with litter impregnated with the scent marks of males or females.

On average, females from the control group lived 576 days, and males — 741 days. Females who smelled the scent of adult female mice lived on average eight percent longer than females from the control group (p=0.01). Such animals had a higher body temperature (p=0.007) at the age of 22 months — higher energy consumption in warm-blooded animals is considered a marker of young biological age.


The lifespan of mice depending on sex and odor tags in childhood (Michael Garratt et al.)

Animals that grew up surrounded by the smells of other mice were lighter (p=0.03), but their muscle strength was the same as in the control groups. In males, the scent marks in the cage did not affect the lifespan (p=0.8).

Most often, hormonal changes under the influence of odors are associated with the work of the vomeronasal organ — the part of the nasal mucosa responsible for the perception of pheromones. To understand whether his work is involved in changes in the development, maturation and lifespan of mice, Dr. Miller and colleagues repeated the experiment with mice knocked out by the Gnao1 gene, the product of which is necessary for chemoreception by cells of the vomeronasal organ. But it turned out that females knocked out by Gnao1 develop in the same way as in the first experiment: they lived longer if they were kept in a cage with adult female scent tags in childhood (p=0.039).

Since brothers and sisters from the same litters participated in the experiments, genetic variation within the mouse line should not have affected the results. Thus, the authors conclude, it is precisely in the epigenetic modulation of life expectancy. According to their assumption, the high density of the animal population (it was her scientists simulated with scent tags) suppresses the production of somatotropic hormone by the pituitary gland of mice. In turn, a decrease in hormone levels suppresses growth and increases life expectancy. Future experiments will allow us to understand whether this discovery can be used to prolong people's lives.

Chemical signals are not the only epigenetic modulator of aging in animals. Such examples include elevated ambient temperature (but apparently not body temperature) and hibernation. By influencing such factors, you can try to rejuvenate animals. For example, scientists did this with old mice by injecting them with cerebrospinal fluid from young animals.

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