Overconsumption of fructose aggravates acute GVHD by inducing gut dysbiosis and promoting macrophage-mediated inflammatory response.

Increased fructose intake is a triggering factor in a series of inflammatory diseases. However, the pathogenic role of fructose overconsumption in acute graft-versus-host disease (aGVHD) has not yet been clarified. In this study, we found that a high-fructose diet (HFR) aggravated the severity and mortality of aGVHD in mice and enhanced gut dysbiosis and bacterial translocation with impairment of the intestinal epithelial barrier. Fecal microbiota transplantation experiments further demonstrated that the microbiota derived from HFR-fed aGVHD mice was sufficient to reproduce intestinal barrier disruption and bacterial translocation in aGVHD recipients. HFR exacerbated the severity of aGVHD after depletion of the gut microbiota by antibiotics. Given the results that in vitro cultivated T-cells do not respond to fructose stimulation, we further investigated whether fructose overexposure affects macrophage activation. In fructose-treated bone marrow-derived macrophages (BMDMs), HIF-1α was stabilized by mitochondrial reactive oxygen species production, resulting in increased glycolysis and subsequently augmented expression of the inflammatory cytokines IL-6, IL-12, TNF-α, and IL-1β. Interestingly, we found that macrophages derived from HFR-fed aGVHD mice were able to enhance T-cell proliferation and Th1/Th17 differentiation. In parallel, correlation analysis integrating 16S rRNA and metabolomics sequencing data revealed that the abundances of Akkermansiaceae and Erysipelotrichaceae were positively correlated with the levels of indole-5,6-quinone and 6,7-dimethyl-8-(D-ribityl)lumazine. After depletion of macrophages and the gut microbiota in host mice, GVHD severity was significantly reversed even after HFR treatment. Taken together, our data reveal that high fructose intake exacerbated aGVHD by inducing a gut microbiota imbalance and promoting inflammatory macrophage activation. This provides a potential therapeutic strategy to alleviate aGVHD via precise adjustment of the fructose dietary.