Finding suggests dietary, environmental exposures may explain 'late onset' diseases
TUESDAY, June 24 (HealthDay News) -- A new finding about the chemical, or epigenetic, marks on an individual's DNA sequence may explain why people become more susceptible to disease as they age and why the health of one's genes is similar among families.
Researchers at Johns Hopkins University, reporting in the June 25 issue of the Journal of the American Medical Association, found that certain types of epigenetic marks change during a person's lifetime and the amount of change is similar among related people.
"We're beginning to see that epigenetics stands at the center of modern medicine, because epigenetic changes, unlike DNA sequence which is the same in every cell, can occur as a result of dietary and other environmental exposure," Dr. Andrew P. Feinberg, director of the Epigenetics Center at the Johns Hopkins School of Medicine, said in a prepared statement. "Epigenetics might very well play a role in diseases like diabetes, autism and cancer."
Researchers found in one study that methylation -- a specific type of epigenetic mark that can contribute to disease if levels are off -- changed over an 11-year period in a third of the 600 people whose DNA was studied. In some, the levels increased; in others, it decreased.
"What we saw was a detectable change over time, which showed us proof of the principle that an individual's epigenetics does change with age," M. Daniele Fallin, an associate professor of epidemiology at the Johns Hopkins Bloomberg School of Public Health, said in a prepared statement. "What we still didn't know was why or how, but we thought 'maybe this, too, is something that's heritable' and could explain why certain families are more susceptible to certain diseases."
In a second study, the team studied 126 people from two- and three-generation families over a 16-year period and found that the methylation changes tended to be similar among family members: if one's levels dropped over time, for example, a similar decrease occurred in other family members.
"We still haven't concretely figured out what this means for health and disease, but as an epidemiologist, I think this is very interesting, since epigenetic changes could be an important link between environment, aging and genetic risk for disease," Fallin said.
The U.S. National Library of Medicine has more about DNA.
-- Kevin McKeever
SOURCE: Johns Hopkins University, news release, June 24, 2008
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