2023-04-21 19:10:56
Chronological age refers to the time that has passed since our birth. Another thing is the biological age, which is the one that measures how old our cells, tissues, organs and systems are. The latter, both in humans and in mice, undergoes a rapid increase in response to various forms of stress, but the good news is that it is reversible when we recover, according to a study published in the journal ‘Cell Metabolism’. These changes occur over relatively short periods of time, from days to months, in accordance with multiple independent epigenetic aging clocks.
“This finding of a fluid, fluctuating and malleable age challenges the traditional conception of a unidirectional upward trajectory of biological age throughout the life course. Previous reports have hinted at the possibility of short-term fluctuations in biological age, but the question of whether such changes are reversible has, until now, remained unexplored,” said study co-lead author James White, from the School of Medicine. from Duke University.
It is believed that the biological age of organisms increases constantly throughout the life course, but it is now clear that biological age is not permanently linked to chronological age. Individuals may be biologically older or younger than what is listed on their identity card. In addition, growing evidence in animal and human models indicates that biological age can be influenced by diseases, drug treatments, lifestyle changes, and environmental exposures, among other factors.
“Despite widespread recognition that biological age is at least somewhat malleable, the extent to which it undergoes reversible changes throughout life and the events that trigger such changes are unknown,” says study co-lead author Vadim Gladyshev, of Harvard Medical School.
The researchers harnessed the power of DNA methylation clocks to measure changes in biological age in humans and mice in response to various stressful stimuli. In a series of experiments, the team surgically joined pairs of mice that were 3 and 20 months old of age in a procedure known as heterochronic parabiosis (a technique that unites the blood circulations of animals of different ages).
The results revealed that biological age can increase for relatively short periods of time in response to stress, but this increase is transient and tends to return to baseline after the recovery from stressful episode. The biological age of the young mice was increased by heterochronous parabiosis and restored after surgical separation from the older mice.
“An increase in biological age following exposure to aged blood is consistent with previous reports of detrimental age-related changes in heterochronous blood exchange procedures,” said first author Jesse Poganik, from Brigham and Women’s Hospital, Harvard Medical School. . “However, the reversibility of such changes, as we observed, has yet to be reported. From this initial insight, we hypothesized that other natural situations could also trigger reversible changes in biological age.”
As predicted, transient changes in biological age also occurred during major surgery, pregnancy and Covid-19 severe in humans or mice. For example, trauma patients experienced a sharp and rapid increase in biological age after emergency surgery. However, this increase was reversed and the biological age was restored to baseline in the days after the operation. Similarly, pregnant women experienced postpartum recovery of biological age at different speeds and magnitudes, and an immunosuppressive drug called tocilizumab enhanced the recovery of biological age in convalescent Covid-19 patients.
“The findings imply that severe stress increases mortality, at least in part, with increasing biological age. This hypothesis suggests that mortality may decrease by reducing biological age and that the ability to recover from stress may be an important determinant of successful aging and longevity. Finally, biological age can be a useful parameter to assess physiological stress and its relief,” says Gladyshev.
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