Gut microbiomes are highly personal. We all know that from experience, but Federico Rey tells us that everyone’s gut microbiome is highly individual, with implications for our diet choices and medical treatment. Each person’s gut microbiome contains hundreds of species of bacteria, archaea, and fungi, and the composition and function of these communities interact with our diets to affect our health.
Using germ-free mice colonized with microbial communities of interest, Rey and his colleagues found that micribiota-diet interactions impact developent of atherosclerosis, and that patients with atherosclerosis have lower levels of butyrate-producing bacteria. Butyrate plays an anti-inflammatory role in the body, and fecal levels of butyrate vary widely from person to person. R. intestinalis is responsible for a significant amount of butyrate production in the human gut. Further experimentatation showed that a high plant polysaccharide diet led to increase in R. intestinalis, and increased R. intestinalis colonization led to higher butyrate levels in mice. The combination of R. intestinalis and high plant polysaccharide levels reduced atherosclerosis in mice, though there was no change observed in lipids. Further work showed that colonization with R. intestinalis regulated energy metabolism in the colons of mice on a high-plant diet, and that colonization with R. intestinalis improvedthe function of the intestinal barrier in mice on a high plant diet.
These findings begged the question of whether butyrate plays a causal role in these results. Rey colonized a group of mice with a microbiome that was unable to produce butyrate, then added tributyrin, a similar substance, to some of the mice. While their gut microbiome was uneffected, their health effects were improved unlike the control, showing that tributyrin had had a similar affect to the presence of R. intestinalis. Future work will examine how these results play out in more complex microbial communities, and how interactions with diet could be harnessed to promote human health.