A study published in the Nov 6 issue of Cell outlined results suggesting that an obscure family of bacteria colonizing the human gut may be inherited and may also have a direct influence on body weight. The paper is the first to identify such an association and to link a particular microbial colonist with lower BMI.
Previous studies on the human microbiome have used next-generation sequencing approaches to identify and characterize the many species involved in colonizing the gut and have begun to tease apart the exceedingly complex inter-relationships between gut microbial flora, host factors and environmental influences. Several of these studies have identified intriguing connections between microbiome composition and disease risk (see earlier blogs on this topic), raising the possibility that manipulation of the human gut bacterial population could be one way to improve health.
The authors of the Cell paper performed extensive sequence analysis of the gut flora of over 900 identical and non-identical twins, seeking to pinpoint any connections between the composition of these microbial populations and host genetics. They identified several bacterial groups that were more commonly associated with identical twins than fraternal twins, and found that, among these, the family Christensenellaceae was a highly heritable group.
Further analysis revealed an association between the presence of Christensenellaceae and a low BMI in the twins study. This association was confirmed by transferring microbial flora with and without Christensenellaceae sp into the guts of germ-free mice. Mice that received transplants rich in Christensenellaceae gained significantly less weight than those receiving transplants with undetectable of low amounts of Christensenellaceae.
So what does this mean? Our genes play a role in controlling the types of bacteria present in the gut, and some of these bacteria can be directly associated with a lean BMI. Thus this paper provides further evidence that obesity is influenced by both genetic and environmental factors, but also shows that some of these environmental factors (gut organisms) are themselves influenced by host genetics. The plot thickens.
Here’s the Paper
Goodrich JK, Waters JL, Poole AC, Sutter JL, Koren O, Blekhman R, Beaumont M, Van Treuren W, Knight R, Bell JT, Spector TD, Clark AG, & Ley RE (2014). Human genetics shape the gut microbiome. Cell, 159 (4), 789-99 PMID: 25417156