Scientists have found that with age in chimpanzees increases the level of stress hormone cortisol and altered diurnal changes of allocation of this substance is similar to the process that is observed in humans. Apparently, the effects associated directly with the aging process, not a way of life, as it did not change depending on the quality of food and the social status of primates. Older males have softened the spike of cortisol, which occurred in the presence of the ready to mate females. And females with age increased connection between the level of glucocorticoid with the phase of the estrous cycle. Article published in the journal Proceedings of the National Academy of Sciences.
Glucocorticoids — hormones, the number of which in the blood increases under stress. These substances mobilize our body during the threat, but chronic stress and prolonged secretion of glucocorticoids has a negative impact on health. In addition, these hormones are closely associated with the processes of aging, including loss of neurons, muscular atrophy, cardiovascular disease and decreased immunity.
Aging humans and animals is associated with disruption of the hypothalamic-pituitary system, which entails long body’s response to stress excessive secretion of glucocorticoids by the adrenal cortex. In addition, the aging body produces more of the stress indicators, and it additionally stimulates the hypothalamic-pituitary-adrenal axis. As we age, disturbed circadian rhythm of glucocorticoids allocation: the normal concentration of these hormones reaches its maximum before lift and progressively decreases throughout the day.
But information about changes in the secretion of glucocorticoids with age is controversial: some studies provethat a basic level of these hormones increases during aging, and their allocation in response to stress is not modified, in others — Vice versa. Casts doubt that with age changes the functioning of the hypothalamic-pituitary system. Perhaps the reason for uncertainty is that these processes are not associated directly with aging, and are the result of lifestyle and hereditary factors. Studies described above do not account for these factors fully.
A group of scientists under the leadership of Melissa Thompson (Melissa Thompson) from the University of new Mexico analyzed data from 20 years of observations of chimpanzee groups Kanyawara (Kanyawara) in Kibale National Park in Uganda. This allowed us to see how changes with age the secretion of glucocorticoids in the natural conditions similar to those in which man evolved, related to us animals. The authors controlled the impact of such adverse factors as the quality of power, hierarchical status, and sexual behavior.
The project participants watched the behavior, diet and movement of about 50 chimpanzees, following those all day. The total time of observation amounted to more than 75 thousand hours in six and a half thousand days. In that time has gathered about 15 thousand images of urine for analysis of cortisol (the main glucocorticoid of primates).
As expected by authors, based on previous research, cortisol levels in urine of chimpanzees decreased during the day more smoothly from old primates. This effect persisted after taken into account all the adverse factors.