Until now, the role of specific gut microbes in shaping body composition was poorly understood. A new study carried out by researchers in the Washington University School of Medicine in St. Louis clarified how diet and gut microbes interact to affect weight gain.
In this study, Ridaura and colleagues transplanted intact uncultured fecal microbiota from adult female twin pairs with differing body mass index (BMI) into separate groups of recipient adult germ-free mice. According to the researchers, the use of twins discordant for obesity provided an opportunity to examine interrelations between obesity and its associated metabolic disorders, diet, and the gut microbiota. Moreover, the transplantation facilitated the identification of structural and functional differences between their guts communities; it allowed to test the impact of these differences on body composition and metabolic phenotypes; and, finally, helped determine the effects of diet-by-microbiota interactions by dietary manipulation of mice (low-fat food or saturated fat diet).
The researchers discovered that adiposity was transmissible from human to mouse and that it was associated with changes in serum levels of branched-chain amino acids (valine and leucine/isoleucine), as well as other amino acids (methionine, serine and glycine). Moreover, cohousing mice harbouring an obese twin’s microbiota (Ob) with mice containing the lean co-twin’s microbiota (Ln) prevented the development of increased body mass and obesity-associated metabolic phenotypes in Ob cage mates. This finding was related to an increased representation of specific members of Bacteroidetes from the Ln microbiota into Ob microbiota, and it was found diet-dependent.
Finally, the authors concluded that these findings revealed transmissible, rapid, and modifiable effects of diet-by-microbiota interactions.