By Julia Ferrante
LEWISBURG, Pa. - Biology professor Mark Haussmann and a team of researchers have discovered a direct correlation between prenatal stress and aging, in a study conducted at Bucknell University. See related Bucknell news story.
The study, published in Proceedings of the Royal Society B Wednesday, showed that chickens that received stress hormones during their fetal development were more apt to "overreact" to stressful situations later in life. The same chickens also took a longer time to recover from stress and displayed early signs of aging.
"We showed that when a mother experiences stress during pregnancy, her stress hormones cross the placenta and affect the fetus, which at that time is developing its own stress regulatory system," Haussmann said. "When those offspring grow up, they have a hyperactive stress response. This means that their own stress hormones are high for longer and it is harder to turn that stress response off, which causes health risks in the long term."
In trials conducted in spring 2010 at Bucknell, Haussmann and then-student researchers Nicole Marchetto and Andrew Longenecker, both Class of '10, mimicked real-life stressful conditions by injecting chicken eggs with glucocorticoids, or stress hormones. After the chickens hatched, they were placed in mildly stressful situations for short periods of time, and their responses were measured.
All vertebrates produce certain hormones when they experience stress, Haussmann explained. During those times, the body releases adrenaline, which increases blood flow and oxygen intake. It also releases glucocorticoids, which mobilize energy stores, giving us the fuel to respond.
"Every single day, we are faced with stress," Haussmann said. "Your alarm didn't go off, and you're late and have to rush to work. Or you're crossing the street and step in front of an oncoming car, forcing you to jump out of the way quickly. These hormones help us to cope. Once you escape the stress, the hormones return to normal levels."
When we face prolonged stress or worry, however, such as with a troubled relationship or difficult situation at work, the hormones stay at a high level for a longer time and have long-term effects such as immune suppression, heart disease and oxidative damage, the last of which causes aging, Haussmann said.
The chickens in the study that were exposed to glucocorticoids in the egg stage not only maintained higher levels of stress hormones, but they also had higher levels of oxidative damage and displayed shorter telomere length in their DNA, indicating premature or advanced age. Telomeres are the protective caps on DNA.
"The cells in the chickens with the hyperactive response actually were aging much more quickly than you'd expect, in some cases five or 10 years faster," Haussmann said. "We found that birds that experience high levels of glucocorticoids also had shorter telomeres. Birds that were 3 weeks old had cells that looked like they were about 5 years old."
Haussmann's collaborators included Steven A. Juliano and Rachel M. Bowden of the Department of Biological Sciences at Illinois State University in Normal, Ill. Haussmann's 11-year-old nephew, Ben, also helped out in the lab.
"I expect one day he will be a member of the next generation of scientists asking the age-old question, 'Why do we age?'" Haussmann said.
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