Genetics, disease activity impact microbiota in patients with spondyloarthritis
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In patients with spondyloarthritis, genetics and disease activity levels likely impact the composition of gut microbiota, according to data published in Arthritis & Rheumatology.
“This multifaceted disease is thought to result from complex interactions between genetic background and environmental factors,” Magali Berland, PhD, of the University of Paris-Saclay, in France, and co-authors wrote. “Given that deregulated gut microbial composition, ie dysbiosis, is a hallmark of [inflammatory bowel disease (IBD)], the foregoing observations lend support to the hypothesis that microbial dysbiosis could also contribute to SpA pathogenesis.”
To continue the investigation into the role of microbiota and genetics in patients with SpA, Berland and colleagues collected stool samples from 197 volunteers. Patients with SpA, all enrolled through a tertiary care center, were required to fulfill the Assessment of Spondyolarthritis International Society classification guidelines and to have abstained from antibiotic use for at least 1 month prior to sample collection. Patients additionally could not have undergone colonoscopy preparatory procedures for at least 6 months. The researchers also enrolled 40 volunteers who were siblings of the included patients with SpA.
The authors used shotgun sequencing on DNA isolated from the stool samples. Metagenomic Species Pangenome (MSP) was used to identify and measure the presence of certain microbes. Finally, the potential of the microbiome was assessed through an in-house pipeline. The authors used species abundance tables to perform enterotyping and enterotypes corresponding to Bacteroides, Firmicutes and Prevotella, the authors wrote. In all, the analysis included samples from 102 patients with SpA and 63 healthy controls.
According to the researchers, dysbiosis was confirmed in the patients with SpA more than the healthy controls. In addition, enterotypes of the bacteroides variety were more common in patients with severe SpA, compared with the healthy controls. The researchers also found that diversity restriction was present more often in patients exhibiting more severe disease activity. Certain bacteria prevalence was additionally associated with Bath Ankylosing Spondylitis Disease Activity Index. Ruminococcus gnavus was one of the most prevalent differentiating species present.
In patients with SpA not undergoing therapy, there was no significant difference in MSP richness between patients with SpA and the healthy controls, according to the researchers.
“First, the extent of dysbiosis appeared to correlate strikingly with disease activity,” Berland and colleagues wrote. “Second, the HLA-B27 genotype, that strongly predisposes to SpA, was associated with significant dysbiosis in healthy siblings of patients, so that inclusion of this group of [health controls (HC)] in the primary whole analysis resulted in somewhat blunted differences between SpA and HC.
“The analysis of possible confounder — especially medication — is always an interesting point as it may impact the gut microbiota composition,” they added. “In our analysis, we did not observe a strong effect of the medication on the dysbiosis, but that does not mean that the medication taken by the patients have no effect at all.”
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