Aging epigenetics is an emerging field that promises exciting revelations in the near future. Functional and biological significance of the epigenetic alterations that accumulate during aging are important in tumourigenesis. Examples of this phenomenon include the loss of DNA methylation in aging and cancer, and by the hypermethylation of genes with a dual role in tumour suppression.
Epigenetics is the study of heritable changes in gene function that occur without a change in the DNA sequence over a person's lifetime. The degree of change is often similar among related family members.
In Journal of the American Medical Association
it was recently suggested that overall genome health is heritable and that epigenetic changes occurring over one's lifetime may explain why disease susceptibility increases with age. Epigenetic changes, unlike DNA sequence which is the same in every cell, can occur as a result of dietary and other environmental exposure. As a result, epigenetics may play a role in diseases like diabetes, autism and cancer.
Scientists at Johns Hopkins in Baltimore hypothesised that if epigenetics contribute to such diseases through interaction with environment or aging, then a person's epigenetic marks would change over time. They therefore established an international collaboration study to determine if that was true. They focused on methylation-one particular type of epigenetic mark, where chemical methyl groups are attached to DNA.
Inappropriate methylation levels can contribute to disease-too much might turn necessary genes off, too little might turn genes on at the wrong time or in the wrong cell. Methylation levels can vary subtly from one person to the next, so the best way to get a handle on significant changes is to study the same individuals over time.
DNA samples were collected from people involved in the AGES Reykjavik Study (formerly the Reykjavik Heart Study). Within the study, about 600 people provided DNA samples in 1991, and again between 2002 and 2005. Of these, the research team measured the total amount of DNA methylation in each of 111 samples and compared total methylation from DNA collected in 2002 to 2005 to that person's DNA collected in 1991.
What was interesting is they found that in almost a third of individuals, methylation changed over that 11 year span, but not all in the same direction. Some individuals gained total methylation in their DNA, while others lost it. In other words, there was proof of principle that an individual's epigenetics does change with age.
The team then measured total methylation changes in a different set of DNA samples collected from Utah residents of northern and western European descent. These DNA samples were collected over a 16 year period from 126 individuals from two- and three-generation families.
What was fascinating was the Utah family members also showed varied methylation changes over time, but family members tended to have the same kind of change; if one individual lost methylation over time, they saw similar loss in other family members too.
It is not yet known why or how the changes occur, but this may also be something that's heritable and could explain why certain families are more susceptible to certain diseases. Further research may tell us the clues.