Gut Bugs Revisited

The type of bugs that colonize your intestines (AKA the intestinal flora) may be a major determinant of your risk for obesity.

Apart from the studies that I have blogged about before, readers may have seen the paper on twins published in NATURE earlier this year by Jeffrey Gordon and colleagues from Washington University School of Medicine, St Louis, MI showing that the faecal microbial communities of adult female monozygotic and dizygotic twin pairs concordant for leanness or obesity, and their mothers showing that obesity is associated with phylum-level changes in the microbiota, reduced bacterial diversity and altered representation of bacterial genes and metabolic pathways.

In a paper, just out in Science Translational Medicine, Gordon and his colleagues provide new evidence that diets can modulate bacterial flora and that these changes can be associated with weight gain – at least in mice.

But these were special mice, grown to be germ-free and then colonized with human gut bugs.

Metagenomic analysis of the temporal, spatial, and intergenerational patterns of bacterial colonization showed that these “humanized” mice were stably and heritably colonized and reproduced much of the bacterial diversity of the human donor’s microbiota.

When these animal were switched from a low-fat, plant polysaccharide–rich diet to a high-fat, high-sugar “Western” diet, the structure of the microbiota changed within a single day, thereby also changing the representation of metabolic pathways in the microbiome.

A series of reciprocal “trans-colonization” experiments showed that although colonization history influences the initial structure of the microbial community, these effects can be rapidly altered by diet.

In summary, this latest study shows that humanized mice fed a “Western” diet have increased adiposity and that this trait is transmissible via microbiota transplantation.

The authors suggest that it may not be long before analyses of stool samples may soon provide a clinical test to determine people’s risk of developing excess weight.

Edmonton, Alberta