Some individuals seem to be more susceptible to develop obesity or are more resistant to weight loss during dietary restriction.
Emerging evidence suggest that few bacterial genera (i.e., Bifidobacterium, Lactobacillus, Faecalibacterium and Akkermansia) are inversely associated with obesity, metabolic inflammation and related metabolic disorders in both human and rodent studies. However so far, a common integrative factor is still being sought. Researchers from the MetaHIT and MicroObes consortium published in Nature two joint-papers showing that richness of gut microbial genes and eventually microbial composition correlates with metabolic markers (e.g., body weight, fat mass, glucose and lipid metabolism, inflammation) and susceptibility to lose weight upon dietary restriction. Interestingly, using different sequencing technology they detected a bimodal distribution of microbial genes. They stratified the population as “low gene count” (LGC) and “high gene count” (HGC) according to the number of genes harbored in their gut microbiota and thereby different microbial communities. They also found that the microbial gene richness may be in part modified by dietary intervention.
In these studies, they found that individuals with a LGC (23% of the population) were characterized by more marked weight-gain over time, adiposity, insulin resistance and inflammation when compared with HGC individuals. Interestingly, they also found that the abundance of specific taxa were significantly associated with bacterial richness and thereby the phenotype. For instance, 36 genera were significantly associated with HGC, and among these genera at least 4 of them have been previously associated with an improved gut barrier function, reduced body weight or improved glucose and lipid metabolism (Faecalibacterium prausnitzii, Akkermansia muciniphila, Bifidobacterium spp., and Lactobacillus spp.) (Sokol et al PNAS 2008, Everard et al PNAS 2013, Delzenne et al Nat Reviews Endocrinology 2011). Conversely, specific genera known to be associated with inflammatory phenotype or altered gut barrier function were associated with LGC. Finally, they also identified signature of unknown species that were associated with HGC or LGC.
Thus, these Nature papers identified a unique concept “easy to handle” (the HGC vs LGC) that may help to stratify patients and highlight again that metabolic differences and susceptibilities to develop diseases that are observed between some patients may find their origin into this “small world within”.
- MetaHIT consotium. Richness of human gut microbiome correlates with metabolic markers. Nature. 2013
- MicroObes consortium. Dietary intervention impact on gut microbial gene richness. Nature. 2013