Food Allergy, the Microbiome and Epigenetics

Last week I wrote about how nitric oxide, a communication molecule naturally produced by our bodies, is also produced by the bacteria of our gut.  The molecule attaches to thousands of proteins in our bodies and can turn genes on and off, greatly affecting our health.  Alterations in the nitric oxide communication system are already known to be associated with diseases like Alzheimer’s, Parkinson’s, asthma, diabetes, heart disease and cancer…and this realization, that gut bacteria affect the nitric oxide system, may be a major breakthrough in understand the relationship between alterations of the microbiota and the development of disease.  As my regular readers are all aware, with every passing day, more is discovered about the relationship of our altered and depleted biomes to human illness.

With this in mind, I found an article from the journal, Nature Reviews: Gastroenterology & Hepatology, especially interesting.[i]  It describes recent research into the relationship of food allergy to the altered microbiome, and summarizes several really interesting studies.  One of them, out of the University of Chicago, I had already written about back in January, which compared the gut bacteria of babies with and without milk allergy. Scientists transferred the gut microbiota from healthy babies and allergic babies into different mice and then exposed the mice to milk.  Those who received the microbiota from allergic babies showed signs of allergy, while the mice who received bacteria from healthy babies were protected.

In particular, the species Anaerostipes caccae, which is a normal part of human gut flora, was isolated as suspect: healthy babies had it while allergic babies did not.  When mice were given this particular species, it did protect against milk allergy.

The article I read yesterday – which has me really excited! –  goes on to explain, that these scientists also discovered, “…32 genes that were deferentially expressed…between mice receiving faeces from donors with cow’s milk allergy and mice receiving faeces from healthy individuals.”  Of these, 3 were related to members of the Lachnospiraceae family of bacteria, which, “…the authors and other investigators have previously found to be associated with food-allergy-related outcomes.”  Anaerostipes caccae is the species “…most closely matching these three,” and as I mentioned above, when given this single species, the allergic response was attenuated.  The article goes on to say, “The results from this and other studies raise the intriguing translational [meaning epigenetic] question of whether the gut microbiota can be manipulated for food allergy prevention and therapy.”

Earlier in the article, by the way, the author describes findings from a different study that showed that mice engineered to be prone to food allergy have a genetic mutation in an immune receptor, and that these mice “…exhibit differential gut abundances of Lachnospiraceae…” (as well as two other species of bacteria).  In this study, the researchers transferred microbiota  from food-allergy-prone mice to germ-free mice, and in doing so, transmitted the tendency to develop food allergy.

The article concludes with a quick summary of some of the clinical trials that have been done on humans to treat food allergy, stating that while probiotics, prebiotics, synbiotics (combined pro- and prebiotics), all hold promise, as yet we have insufficient data to make any recommendations.  Still, I really am excited about this kind of work.  Finding out that gut bacteria have this epigenetic influence (which is defined as “the study of changes in organisms caused by modification of gene expression rather than alteration of the genetic code itself” – that is, turning genes on and off, changing the way the host organism functions) is just astounding to me.

Years ago, I watched a fascinating episode of the show, NOVA (The Ghost in Your Genes ), that introduced me to the concept of epigenetics. I cannot recommend it more highly.  A short version is also available for free here.

We know, as I’ve written  about before, depletion of the microbiota is passed down through generations.  And, as these researchers point out, epigenetic changes too are passed generationally.  Thus, we really do have a responsibility to our progeny to care for our epigenome!

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[i] Bunyavanich, S. Food allergy: could the gut microbiota hold the key?  Nature Reviews: Gastroenterology & Hepatology. 2019: Mar 1. doi: 10.1038/s41575-019-0123-0.