Background/Purpose: The gut microbiome and its metabolites are dysregulated in RA and other immune-mediated inflammatory diseases. However, the significance of this observation and its implications in pathogenesis and therapeutics is less understood. We have previously shown that gut microbiome composition can be a predictive marker of MTX responsiveness, likely due to microbes’ abilities to metabolize MTX.  Short chain fatty acids (SCFAs), microbial fermentation byproducts of certain gut microbes, are known to improve gut epithelial barrier integrity and to induce regulatory immune responses. Unsurprisingly, SCFA are found at reduced levels in both murine models of RA and in patients. Further, SCFA butyrate has been shown to ameliorate inflammatory arthritis in murine models. We therefore hypothesized that butyrate supplementation may promote favorable gut microbial community variations that can potentially, in turn, improve MTX response in new-onset, drug-naïve RA patients initiating treatment.

Methods: We designed a proof-of-principle study to determine the effects of butyrate supplementation in new-onset RA (NORA) patients that fulfilled 2010 ACR/EULAR RA criteria. We evaluated the effects of MTX plus butyrate in NORA (n=17; 1 gm butyrate, 3 times daily) compared to MTX alone (n=19) over 4 months. MTX responders were defined by change in DAS-28 ESR of > 1.8 at 4 months. Fecal samples were collected at baseline and follow up for 16s rRNA sequencing and metabolite quantification by 1H NMR spectroscopy. Unpaired-t, paired-t, Wilcox and Fisher’s exact test were performed as appropriate.

Results: MTX responders in the MTX only group had higher concentration of fecal butyrate than non-responders at baseline (p=0.045). Fecal butyrate concentration decreased over time in treatment responders in MTX group (p=0.05) whereas butyrate concentration remained similar in MTX/butyrate group. Prior to treatment, both MTX and MTX/butyrate groups demonstrated similar levels of gut bacterial alpha diversity (Shannon index), yet only the MTX/butyrate group demonstrated a significant increase in alpha diversity by 4 months (p=0.022). LefSe analysis demonstrated increased abundances of Bacteroides, Clostridium, and Phascolarctobacterium in responders in the MTX/butyrate group by 4 months. Ten (52.6%) patients in MTX and 11 (64.7%) in MTX/butyrate group were considered MTX responders by 4 months (p=0.516).

Conclusion: Butyrate supplementation increased gut microbial diversity in NORA patients, an effect not observed in those treated with MTX alone. Additionally, butyrate led to increased abundance of Bacteroides, which has been implicated in efficacy of MTX treatment (Zhou et al. Front Microbiol. 2022). Intriguingly, butyrate supplementation appeared to have a stabilizing effect on fecal butyrate concentration in responders at 4 months. MTX response was numerically (but not statistically significantly) greater in MTX/butyrate group. Taken together, these findings suggest that butyrate is capable of modifying the gut microbiota, which may have potential implications in maximization of MTX effectiveness for new-onset RA. Further studies on larger cohorts are necessary to validate these findings.

ACR Meeting Abstracts - https://acrabstracts.org/abstract/effects-of-butyrate-supplementation-in-modulation-of-gut-microbiome-and-its-metabolites-in-new-onset-rheumatoid-arthritis/