Bifidobacterium breve alleviates dry eye disease by regulating gut microbiota and vitamin A metabolism.

The gut microbiota can metabolize vitamin A and may thereby alleviate symptoms of dry eye disease. Bifidobacterium breve CCFM1489 was investigated, a commensal strain capable of converting vitamin A (VA) into retinoic acid (RA), in a benzalkonium chloride-induced DED mouse model. The results demonstrated that CCFM1489 alleviated dry eye symptoms, as evidenced by reduced fluorescein sodium staining of the cornea, improved corneal and conjunctival histopathology. These effects were accompanied by reducing oxidative stress and inflammation whilst elevating systemic RA levels. Integration of gut metagenomic and faecal/serum metabolomic analyses provided preliminary insights into the underlying mechanisms. CCFM1489 reshaped the gut microbial composition and structure, increasing the abundance of specific taxa, including Parabacteroides goldsteinii and Lactiplantibacillus plantarum, that were associated with metabolic improvements. Functional shifts indicated enhanced microbial VA metabolism and modulation of host-microbiota pathways. Collectively, CCFM1489 regulates gut microbiota involved in VA metabolism and represents a promising microbiota-targeted strategy for ameliorating dry eye disease.