Integrated omics reveal the effects of vitamin D deficiency on gut microbiota and plasma metabolism in experimental autoimmune uveitis.

Vitamin D deficiency (VD-deficiency) has been implicated in various autoimmune diseases, including uveitis, yet its mechanistic role remains unclear. Emerging evidence suggests that gut microbial dysbiosis and metabolic disturbances may serve as critical intermediates linking VD-deficiency and autoimmune disease pathogenesis. Here, using an experimental autoimmune uveitis (EAU) model induced in B10RIII mice, we demonstrate that VD-deficiency exacerbates EAU severity, accompanied by enhanced Th1 and Th17 responses, suppressed regulatory T cells, and disruption of both intestinal and blood–retinal barrier integrity. Integrated microbiota and metabolomic profiling revealed a coordinated pattern of gut dysbiosis, characterized by enrichment of opportunistic pathogens and depletion of beneficial commensals, together with host metabolic reprogramming in VD-deficient EAU mice. KEGG analysis highlighted disruption of vitamin-related pathways, particularly the vitamin digestion and absorption pathway. Mechanistically, VD-deficiency associated disturbances were linked to LRAT downregulation in retinal pigment epithelial (RPE) cells, accompanied by a pro-inflammatory intraocular microenvironment characterized by increased IL-6 and CXCL family chemokines expression. Gain- and loss-of-function studies in complementary in vivo and in vitro RPE-based models further demonstrated that LRAT functions as a negative regulator of retinal inflammatory responses, with LRAT knockdown enhancing, whereas LRAT overexpression suppressing, the production of IL-6, CXCL1, CXCL2, and CXCL8. Collectively, our findings suggest that VD-deficiency exacerbates autoimmune uveitis by disrupting effector–regulatory T cell balance and compromising blood–retinal barrier and intestinal integrity, accompanied by considerable alterations in gut microbiota and systemic metabolism, while identifying LRAT as a potential regulator linking VD-deficiency to retinal inflammatory amplification.