Riboflavin ameliorates intestinal inflammation via immune modulation and alterations of gut microbiota homeostasis in DSS-colitis C57BL/6 mice

While there have been advancements in understanding the direct and indirect impact of riboflavin (B₂) on intestinal inflammation, the precise mechanisms are still unknown. This study focuses on evaluating the effects of riboflavin (B₂) supplementation on a colitis mouse model induced with 3% dextran sodium sulphate (DSS). We administered three different doses of oral B₂ (VB2L, VB2M, and VB2H) and assessed its impact on various physiological and biochemical parameters associated with colitis. Mice given any of the three doses exhibited relative improvement in the symptoms and intestinal damage. This was evidenced by the inhibition of the pro-inflammatory cytokines TNF-α, IL-1β, and CALP, along with an increase in the anti-inflammatory cytokine IL-10. B₂ supplementation also led to a restoration of oxidative homeostasis, as indicated by a decrease in myeloperoxidase (MPO) and malondialdehyde (MDA) levels and an increase in reduced glutathione (GSH) and catalase (CAT) activities. B₂ intervention showed positive effects on intestinal barrier function, confirmed by increased expression of tight junction proteins (occludin and ZO-1). B₂ was linked to an elevated relative abundance of Actinobacteriota, Desulfobacterota, and Verrucomicrobiota. Notably, Verrucomicrobiota showed a significant increase in the VB2H group, reaching 15.03% relative abundance. Akkermansia exhibited a negative correlation with colitis and might be linked to anti-inflammatory function. Additionally, a remarkable increase in n-butyric acid, i-butyric acid, and i-valeric acid was reported in the VB2H group. The ameliorating role of B₂ in gut inflammation can be attributed to immune system modulation as well as alterations in the gut microbiota composition, along with elevated levels of fecal SCFAs.