Age-related genome changes may explain late-onset diseases
US scientists have found that 'epigenetic' markers on DNA - akin to chemical 'Post-It notes' on the double helix, that do not affect the actual DNA sequence - change over a person's lifetime and may therefore help to explain why a person's susceptibility to certain diseases such as cancer increases with age.
Chemical changes to a person's DNA can contribute to disease as they may cause genes to be turned off and on unnecessarily.
A team at Johns Hopkins School of Medicine analysed DNA samples from around 111 people who provided repeat samples in 1991, 2002 and 2005.
The researchers measured the amount of DNA methylation - a type of epigenetic mark where chemical methyl groups are attached to DNA - in each sample.
They then recorded the extent to which each individual's amount of DNA methylation changed over time.
In nearly a third of people, there were changes in the amount of DNA methylation over time, with some people gaining methylation while others lost chemical groups.
Dr Andrew Feinberg, professor of molecular biology and genetics and director of the Epigenetics Centre at Johns Hopkins, commented: "We're beginning to see that epigenetics stands at the centre 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.
"Epigenetics might very well play a role in diseases like diabetes, autism and cancer."
Dr M Daniele Fallin, an associate professor of epidemiology at the Johns Hopkins Bloomberg School of Public Health, revealed: "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.
"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."
The researchers therefore measured methylation changes in a separate set of DNA samples taken from 126 individuals in two- and three-generation families.
Their findings, which are published in the Journal of the American Medical Association, show that the degree of epigenetic change tends to be similar among members of the same family, suggesting that overall genome health can be partly inherited.
Family members tended to have the same kind of epigenetic change - for example if one individual lost methylation over time, other family members tended to experience the same changes.
Dr Fallin added: "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, ageing and genetic risk for disease."