We’re much more than just a product of our genes. We’ve known for some time that the environment also plays a huge role in shaping who we are, and then there is epigenetics – a kind of bridge between these two influences. And while the adage “you are what you eat” has also been sung for many years, a new study is helping to reveal the extent of this sentiment.

Published in the journal Nature Microbiology, researchers from the University of Cambridge have demonstrated that products of metabolism are able to influence the activity of our genes. While the study focused on yeast cells, rather than humans, the findings likely have implications for our own species, and show us how metabolism and gene expression are intertwined in perhaps a previously underappreciated manner.

“The classical view is that genes control how nutrients are broken down into important molecules,” lead researcher Dr. Markus Ralser said in a statement, “but we’ve shown that the opposite is true, too: how the nutrients break down affects how our genes behave.”

For the investigation, the researchers wanted to see how metabolism – chemical reactions that generate energy and create the molecules needed to keep a cell alive – might determine gene expression, basically whether a gene is “switched on” and used to make proteins. They chose to use yeast because they’re a model organism in the lab, sharing a number of genetic and biochemical similarities with us. As single-celled organisms, they’re also much easier to manipulate than animals.

By disturbing the biosynthetic pathways of several key metabolites – products of metabolism – the researchers were able to examine what effect this had on the way that genes were expressed. Remarkably, messing up the availability of these molecules, which included three different amino acids, affected 85 percent of the yeast’s genome.

"This looks to be a very general response," Ralser told IFLScience. "We didn't see specific genes or pathways that were affected, but we were surprised to see how big the changes were." 

Of course, the yeast genome is much smaller than ours and we are significantly more complex organisms, so it’s unlikely such a dramatic effect would be seen in humans. Still, since metabolism is dependent on the availability of nutrients that are fed into the energy-making reactions, and therefore these two are tightly linked, the findings could indicate that diet plays an important role in gene expression.

Interestingly, the work also has implications for scientists working with cells in the lab, in particular with regards to reproducibility of studies. If scientists have been using cells with differences in their metabolic-genetic background, then this could unknowingly affect the results. 

While the scientists don't currently know how metabolic changes are affecting gene expression, Ralser said it's likely not one particular mechanism at work, but rather to do with alterations to the chemical makeup of a cell which affects how it's functioning.