Gut Microbiota between Environment and Genetic Background in Familial Mediterranean Fever (FMF).

The gastrointestinal tract hosts the natural reservoir of microbiota since birth. The microbiota includes various bacteria that establish a progressively mutual relationship with the host. Of note, the composition of gut microbiota is rather individual-specific and, normally, depends on both the host genotype and environmental factors. The study of the bacterial profile in the gut demonstrates that dominant and minor phyla are present in the gastrointestinal tract with bacterial density gradually increasing in oro-aboral direction. The cross-talk between bacteria and host within the gut strongly contributes to the host metabolism, to structural and protective functions. Dysbiosis can develop following aging, diseases, inflammatory status, and antibiotic therapy. Growing evidences show a possible link between the microbiota and Familial Mediterranean Fever (FMF), through a shift of the relative abundance in microbial species. To which extent such perturbations of the microbiota are relevant in driving the phenotypic manifestations of FMF with respect to genetic background, remains to be further investigated.

Specific changes in faecal microbiota are associated with familial Mediterranean fever.

OBJECTIVES: Familial Mediterranean fever (FMF) can be complicated by AA amyloidosis (AAA), though it remains unclear why only some patients develop amyloidosis. We examined the gut microbiota composition and inflammatory markers in patients with FMF complicated or not by AAA. METHODS: We analysed the gut microbiota of 34 patients with FMF without AAA, 7 patients with FMF with AAA, 19 patients with AAA of another origin, and 26 controls using 16S ribosomal RNA gene sequencing with the Illumina MiSeq platform. Associations between bacterial taxa and clinical phenotypes were evaluated using multivariate association with linear models statistical method. Blood levels of interleukin (IL)-1ß, IL-6, tumour necrosis factor-α and adipokines were assessed by ELISA; indoleamine 2,3-dioxygenase (IDO) activity was determined by high-performance liquid chromatography. RESULTS: Compared with healthy subjects, specific changes in faecal microbiota were observed in FMF and AAA groups. Several operational taxonomic units (OTUs) were associated with FMF. Moreover, two OTUs were over-represented in FMF-related AAA compared with FMF without AAA. Additionally, higher adiponectin levels and IDO activity were observed in FMF-related AAA compared with FMF without AAA (p<0.05). CONCLUSION: The presence of specific changes in faecal microbiota in FMF and in FMF-related AAA suggests that intestinal microorganisms may play a role in the pathogenesis of these diseases. These findings may offer an opportunity to use techniques for gut microbiota manipulation.

TLR2 and TLR4 polymorphisms in familial Mediterranean fever.

It has been suggested that MEVF mutations offer advantage against infections, including tuberculosis. Bearing in mind the central role of TLR-2 and TLR-4 in the recognition of pathogens, we conducted this study to examine whether the TLR2-R753Q, TLR4-D299G, TLR4-T399I common polymorphisms are associated with susceptibility to familial Mediterranean fever (FMF) or affect the course of the disease. A cohort of 169 FMF patients and 245 healthy bone marrow donors were enrolled in the study. FMF patients appeared with a significantly lower frequency of the TLR4-D299G mutated allele (3.2% vs 6.9%, p = 0.032). No association was observed with the other analyzed polymorphisms. Moreover, we found no association between polymorphisms and the frequency of attacks or the development of amyloidosis. Our results may reinforce the hypothesis that FMF patients display a better defense against pathogens, providing an additional mechanism and suggesting a positive selection advantage in the area of the Mediterranean basin.

Effect of Helicobacter pylori infection and eradication therapy on interleukin-6 levels in patients with Familial Mediterranean Fever.

It is being questioned if Helicobacter pylori infection, which causes a chronic inflammatory response, can increase the frequency and severity of attacks in patients with Familial Mediterranean Fever (FMF) and if the impact of inflammatory response can be diminished by eradication of the infection. To evaluate if there is difference in interleukin (IL)-6 levels of H. pylori-positive and -negative patients both before and during FMF attacks; if there is a change in IL-6 levels following successful eradication treatment; and if MEFV gene mutations have an effect on IL-6 levels. IL-6 levels were evaluated in 47 FMF patients before and during FMF attacks. Genetic testing to determine M694V, M694I, E148Q, V726V, M680I mutations was also performed in all patients. IL-6 levels were also determined after successful eradication of the infection in H. pylori-positive patients. IL-6 levels were compared in H. pylori-positive and -negative patients, and before and after eradication treatment in patients who cleared the infection. Number of patients in tested mutation groups was not enough to compare IL-6 levels in these groups. Thirty-four patients (73.9%) were H. pylori-positive. Before FMF attack there was no statistically significant difference in IL-6 levels of H. pylori-positive and -negative groups. IL-6 levels were significantly higher in both groups during the attacks than before the attacks (p < 0.05). There was a statistically significant decline in IL-6 levels both before and during FMF attacks, following eradication therapy in patients who cleared the infection (p < 0.05). In patients with homozygous M694V mutation, IL-6 levels before and during the FMF attacks were not significantly different in H. pylori-positive and -negative groups, despite a much lower level found in H. pylori-negative group (p > 0.05). Comparisons were not performed in other mutation groups because of small number of patients in each group. C-reactive protein (CRP) and fibrinogen levels were not significantly different between the groups (p > 0.05). We believe that the observation of IL-6 levels are lower both before and during FMF attacks both in H. pylori-negative patients and in patients who cleared the infection after eradication therapy is very important in the determination of the role of eradication of H. pylori on decreasing the frequency and severity of FMF attacks. As for today, the correlation between H. pylori infection and FMF seems unlikely; however, studies evaluating the interaction of cytokines in both diseases and their relations and roles will be needed to reach better conclusions.

Familial Mediterranean fever. No role of Mycobacterium tuberculosis in ten patients.

BACKGROUND: Tuberculosis (TB) and Familial mediterranean fever (FMF) are two common diseases in our region, Turkey. Both share some properties in common: Both cause AA type amyloidosis and have association with some immunological abnormalities. Upon incidentally observing Mycobacterium tuberculosis in bone marrow biopsies of three patients with FMF in a previous study, we intended to elucidate this association prospectively. MATERIAL AND METHODS: In this study, we examined prospectively 10 FMF patients, 5 male and 5 female, with a median duration of 31 years disease activity. All were under colchicine therapy. They had no sign of renal involvement. The bone marrow biopsies of these patients were examined for the presence of M. tuberculosis by Polymerase chain reaction (PCR), BACTEC culture and pathological stains. Pathological examination was performed for the existence of granuloma and amyloid deposition by hematoxylin-eosin, Crystal Violet and Congo red stains. RESULTS: The examination of all bone marrow specimens by the mentioned methods suggest that Mycobacterium tuberculosis has no role in the ethiopathogenesis of FMF. Although the patients had a positive family history of 60% for tuberculosis and in 80% of them with positive tuberculin skin test. CONCLUSIONS: We concluded that although there seemed to be a kind of association between both diseases, this relationship is not via the direct existence of bacteria itself. Considering high family history and skin test positivity, one should look for the presence of autoimmune mechanisms under this suspicious relationship between tuberculosis and FMF. Also, this is the first study examined the state of amyloidosis in the bone marrow at an earlier stage of FMF without overt renal findings.