Microbiota unbalance in the gut represents the signature of obesity the so called « microbial component », where an increased Firmicutes to Bacteroidetes ratio has been shown as a key hallmark.

In the quest of cellular/molecular origin of metabolic inflammation we hypothesized that peripheral tissues could be targeted by inflammatory antigens belonging to intestinal bacteria. To test our premise, 16 s bacterial ribosomal DNA (rDNA) was extracted from subcutaneous white adipose tissue (sWAT) and the stroma vascular fraction (svf) of healthy and obese patients with body mass index (BMI) ranging from 26 to 40. 16 s rDNA V2 region was amplified and analyzed by pyrosequencing.

The overall diversity linked to the amout of different counts of bacterial groups of sequences (OTUs) was increased both in sWAT (up to a 2-fold) and svf (up to a 1,8-fold) from patients with ranking degrees of obesity compared to their healthy counterpart. Importantly, in sWAT, as observed in intestinal microbiota, Firmicutes represented the most abundant phylum in both healthy and obese patients (88,5 % vs 84,6 %, respectively). The Firmicutes were also highly abundant in the svf, but a differential count was observed regarding the phenotype: healthy 84 %, overweight 78 %, obese 54 %, and mordibly obese 72 % of the overall tissue microbiota.

Altogether, these results show, for the first time, that bacterial DNA is present in sWAT and svf and can associate with different obese phenotypes. This new paradigm could be responsible for tissue inflammation and dysmetabolism, providing specific new bacterial targets for the treatment of metabolic diseases.