Kristina Campbell is a science writer specializing in gut bacteria and health. Her Intestinal Gardener blog covers recent research and issues related to digestive health. Kristina lives in Vancouver, Canada, with her husband and yogurt-loving daughter.
When was the last time you thought about your genes?
A gene, of course, is a segment of DNA, which is like a blueprint for how to make a certain part of you. In your DNA are the “recipes” for proteins, and the proteins code for certain traits, like brown eyes or blonde hair. Your genome is your complete set of genetic material.
That’s the version we learn in biology class. It’s more complicated, however, because what you see in the DNA isn’t always what you get.
Your genome has a boss, as it turns out, called the epigenome. These are the things – called methyl groups and histones – that take the raw material of your genome and tell it what to do. In essence, it affects whether some genes are expressed (like an on-off switch), and if they are expressed, by how much (like a dimmer switch).
To take a theoretical example: say a person’s DNA gives him a high chance of developing type 2 diabetes. That’s the luck of the genetic draw. But say that eating cabbage conferred an epigenetic tag that prevented that gene from being expressed. If the person eats a lot of cabbage throughout his life, he will not develop diabetes.
Science has found that all kinds of things seem to control these epigenetic tags: diet, smoking, and stress levels, to name a few.
Perhaps most relevant to FMT, new research shows that gut bacteria itself can regulate gene expression. One 2013 study from Norway found that gut bacteria could initiate a cascade of effects in the intestine; this affected genes that regulate fat and carbohydrate metabolism. Lipid malabsorption was the likely result.
This is just one example, but it’s a hot area of research that will undoubtedly uncover a lot more in the years to come. So far, we know this much: it’s possible for gut bacteria to affect gene expression.
In terms of FMT, this means that the new gut bacteria you get are not just going to take up residence in your gut. They might actually change how your genes play out. They won’t change your DNA, of course, but they may help you make the best or worst of the DNA you already have.
How do you ensure you get a donor who helps you make the most of your own DNA? Here are my suggestions, based on the science to date:
1. Choose a donor with lifestyle habits that contribute to an epigenome-friendly set of gut bacteria:
- Healthy diet (Whole food or Mediterranean diet with minimal processed foods)
- No cigarettes
- Regular exercise
- Low levels of stress
- No antibiotics for several months or years
2. Consider choosing a donor with DNA close to yours.
This probably means a relative (unless you’re keen on genetically testing potential donors and comparing their genes to your own). Your parent or child are the ones with DNA most similar to yours. A sibling is the next choice, followed by more distant relatives like nieces, nephews, aunts, and uncles.
This assumes that you come from a family with good health. Where dysfunctional microbiota has been passed down through sickly families it’s best to avoid a family donor.
Donor genetics could also help answer a question about blood type. A 2012 study found that blood type (the ABO blood group) affected the types of bacteria people harboured in their guts, which led some to think that they needed to find an FMT donor with the same blood type in order to get the best results. But it may be that genes are the more relevant variable. The authors give away a key clue in their article: “…the ABO blood group is one of the genetically determined host factors modulating the composition of the human intestinal microbiota…” Basically, if people with similar blood types have similar gut bacteria, it’s probably because they have similar genes. (Granted, it’s easier and cheaper to test blood type rather than DNA. So in one sense it’s a sort of “shorthand” for gross genetic similarity.)
GIven all this, though, don’t stress yourself out trying to find a donor that meets all these criteria. If you increased your stress levels, you’d be already exerting a negative epigenetic influence on yourself, even before you do the FMT. And even if the donor meets these two criteria, they should be rigourously tested like any other donor. As far as your immediate health is concerned, it’s better to get an uninfected donor with dissimilar DNA than an infected one with similar DNA.
Visit Christina’s blog The Intestinal Gardener
Categories: fecal microbiota transplant