Genetics or Aging Environment: What Determines How We Age?

Aging and the environment play a far greater role in the expression of your gene profiles as you grow older than your genetic variations at birth.

This is according to a recent study carried out by researchers from the University of California, Berkeley; which analyzed the effects of genetics, aging, and the environment on some 20,000 human genes. The researchers found that aging and the environment have a far greater influence on the level at which these genes are expressed—determining everything from your hormone levels, metabolism, and the mobilization of enzymes to repair the body.

“There’s been a huge amount of work done in human genetics to understand how genes are turned on and off by human genetic variation. Our project came about by asking, ‘How is that influenced by an individual’s age?’ And the first result we found was that your genetics actually matter less the older you get,” noted Peter Sudmant, the UC Berkeley assistant professor of integrative biology, and a member of the campus’s Center for Computational Biology.

Sudmant and his colleagues created a statistical model to analyze the roles of aging and genetics in 27 different human tissues derived from 1000 individuals. They found that the impact of aging varied widely among the tissues, especially for individuals aged 55 years and above.

As Sudmant explains, “Across all the tissues in your body, genetics matters about the same amount. It doesn’t seem like it plays more of a role in one tissue or another tissue. But aging is vastly different between different tissues. In your blood, colon, arteries, esophagus, fat tissue, age plays a much stronger role than your genetics in driving your gene expression patterns.”

The findings agree with Medawar’s hypothesis, which states that genes turned on in our younger years are more limited by evolution to focus on making sure we survive until we reproduce. On the other hand, genes activated once we reach reproductive age face lesser evolutionary pressure. So, there’s a lot more variation in how these genes are expressed.

But Sudmant and his colleagues observed that the hypothesis does not hold true for 5 distinct tissues they studied. These 5 tissues; blood, colon, arteries, esophagus, and fat tissue, undergo the most replication throughout our life. So, it’s no surprise that they produce the most cancers. Because every time these tissues replicate (especially in old age) they risk triggering a genetic mutation that can lead to disease.

“Your blood, for instance, always has to proliferate for you to live, and so these super-conserved, very important genes have to be turned on late in life. This is problematic because it means that those genes are going to be susceptible to getting somatic mutations and getting turned on forever in a bad, cancerous way. So, it kind of gives us a little bit of a perspective on what the limitations of living are like. It puts bounds on our ability to keep living.”

The study, therefore, highlights the effect of aging and the environment; which not only constitutes our age, but also factors in the food we consume, the air we breathe, the level of physical exercise we exert, and the water we drink. And according to the study, the environment can contribute up to a third of your gene expression as you age.