Behçet's syndrome patients exhibit specific microbiome signature.

Abstract BACKGROUND AND AIMS: Behçet syndrome is a systemic inflammatory condition characterized by muco-cutaneous and ocular manifestations, with central nervous system, vascular and/or gastro-intestinal involvement. The association of microbiota with Behçet syndrome has not been shown yet. Our work was aimed to compare the gut microbiota structure and the profiles of short-chain fatty acids production in Behcet syndrome patients and healthy control relatives. METHODS: Here, we compared the fecal microbiota of 22 patients with Behçet syndrome and that of 16 healthy co-habiting controls, sharing the same diet and lifestyle by pyrosequencing of the V3-V4 hypervariable regions of the 16 rDNA gene and biochemical analyses. RESULTS: Our analyses showed significant differences in gut microbiota between Behçet patients and healthy cohabitants. In particular we found that Behçet's patients were significantly depleted in the genera Roseburia and Subdoligranulum. Roseburia showed a relative abundance value of 10.45±6.01% in healthy relatives and 4.97±5.09% in Behçet's patients, and Subdoligranulum, which reached a relative abundance of 3.28±2.20% in healthy controls, was only at 1.93±1.75% of abundance in Behçet's patients. Here we report, for the first time, that a peculiar dysbiosis of the gut microbiota is present in patients with Behçet syndrome and this corresponds to specific changes in microbiome profile. A significant decrease of butyrate production (P=0.0033) in Behçet's patients was demonstrated. Butyrate is able to promote differentiation of T-regulatory cells, and consequently the results obtained prompt us to speculate that a defect of butyrate production might lead to both reduced T-reg responses and activation of immuno-pathological T-effector responses. CONCLUSIONS: Altogether, our results indicate that both a peculiar dysbiosis of the gut microbiota and a significant decrease of butyrate production are present in patients with Behçet syndrome.