Gut Health and Your Genes – FUT2 Genetic Variants

I am constantly amazed at the interaction between our bodies and the microbes within us.  Yes, a bit geeky, but this stuff is really cool!

Check your 23andMe results to see if you carry the FUT2 gene variant that indicates that you might want to try a bifidobacteria probiotic.

Whether or not you secrete your blood type plays a big role in the type of bacteria that dwell in our gut microbiome and whether you are likely to get sick from the norovirus.  A genetic variant in the FUT2 gene controls whether or not you secrete your blood type.

What does this have to do with our microbiome?  Bifidobacteria, a major genus of bacteria that are found in the colon, are thought to be one of the good guys when it comes to your gut microbiome.  They are lactic acid and acetic acid producing bacteria, and they help the immune system keep everything in check.  These bacteria are involved in breaking down carbohydrates (specifically, oligosaccharides) from the diet and also eat oligosaccharides produced by our body in the intestinal mucosa.[ref][ref]

Oligosaccharides are a carbohydrate that consists of three to nine monosaccharides (simple sugars). There are three types of oligosaccharides that are in the news these days as helpful prebiotics: fructooligosaccharides (FOS), galactooligosaccharides (GOS), and inulin. You can get oligosaccharides as pre-biotic supplements and they are also found in foods like leeks, Jerusalem artichokes, onions, chicory root, and oats.

ABO Blood Group Diagram. Wikimedia Commons - Public Domain.
ABO Blood Group Diagram. Wikimedia Commons – Public Domain.

The FUT2 gene encodes the enzyme fucosyltransferase, which plays a role in forming oligosaccharides. Most people are familiar with the ABO blood type system and probably learned in high school biology about the A antigens and B antigens. But what you may not know is that the antigens (A and B) are sugar molecules on the outside of the blood cell. The FUT2 gene comes into play when looking at the secretion of the blood type in bodily fluids such as saliva and intestinal mucosa.

The oligosaccharides secreted in the intestinal mucosa feed your intestinal flora, but not everyone secretes their blood type. In fact, about 20% of Caucasians are thought to be non-secretors. A FUT2 non-secretor has a homozygous mutation in the SNP rs601338 that changes G to A. Those with AG or GG (heterozygous and wild-type) are FUT2 secretors.

Check your 23andMe results for rs601338:

  •  GG: FUT2 secretor
  •  AG:  FUT2 secretor
  •  AA:  FUT2 non-secretor, lower amounts of bifidobacteria, resistant to norovirus

So what is the big deal about being a non-secretor?  Well, it comes back to our bodies interactions with the microbiome.  In a 2011 study, individuals with the AA allele on rs601338 (non-secretors) were shown to have significantly lower amounts of bifidobacteria in their gut microbiome. This makes sense when you think about bifidobacteria being fed, in part, by our intestinal mucosa.   Interestingly, the same study showed that non-secretors actually had a higher diversity of bacteria.  Another study in 2014 confirms those findings.

An infants microbiome is, in part, colonized from the mother, and bifidobacteria usually make up a large portion of an infant’s microbiome. Breastmilk contains oligosaccharides that feed the baby’s microbiome.

The effects on non-secretor status can also influence breastfed babies of non-secretor mothers. A 2015 study found that “Infants fed by non-secretor mothers are delayed in the establishment of a bifidobacteria-laden microbiota. This delay may be due to difficulties in the infant acquiring a species of bifidobacteria able to consume the specific milk oligosaccharides delivered by the mother.”[ref]

Non-secretor status plays a role in infectious diseases as well.  Both the norovirus (famous for spreading rapidly on cruise ships and through nursing homes) and the rotavirus are much less likely to infect a non-secretor.[ref][ref]  Children who are non-secretors are less likely to have diarrheal diseases.[ref]  H. pylori colonization is also less in non-secretors.[ref]

Secretor status also plays a role in non-infectious diseases as well, possibly through interactions with the gut microbiome. Non-secretors have a higher risk of Type 1 diabetes[ref], alcohol-induced pancreatitis[ref], Crohn’s disease[ref], and adverse outcomes in premature infants[ref].

This is one genetic mutation that is dependent on ancestry and applies mainly to Caucasians. The rs601338 mutation for non-secretors is not found in Japanese populations, but another SNP codes for non-secretors for Japanese, rs1047781 – TT genotype.


Lifehacks

Probiotics containing bifidobacteria:
Several places on the internet mention that bifidobacteria-containing probiotics are good for non-secretors. RenewLife’s Ultimate Flora has a high count of several types of bifidobacteria.   VSL #3 is another probiotic that has good reviews and contains bifidobacteria.

Microbiome sequencing:
If you want to know how many and what type of bifidobacteria are in your gut, you could do a microbiome sample from uBiome or American Gut.  Do read their privacy policies thoroughly before buying.

More to read:

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