Supplementary Material for: Aberrant Gut Microbiome Contributes to Barrier Dysfunction, Inflammation and Local Immune Responses in IgA Nephropathy

Introduction Numerous research have shown that serum Gal-deficient (Gd)-IgA1 levels are increased in IgA nephropathy (IgAN) patients and these levels are a dangerous risk factor for IgAN.It has been reported that a relationship between the gut microbiota and IgAN.Whether the gut microbiota participates in the pathogenesis of IgAN was still controversial. Methods We evaluated changes in the gut flora and the levels of Gd-IgA1 in IgAN patients and healthy controls (HCs). We investigated the Gd-IgA1 levels in both blood and urine specimens. C57BL/6 mice were given a broad-spectrum antibiotic cocktail to deplete the endogenous gut flora. We established a model of IgAN in pseudosterile mice and investigated the expression of the markers of intestinal permeability, inflammation, and local immune responses. Results Studies have shown that the levels of certain gut flora differ between IgAN patients and HCs. Moreover, elevated Gd-IgA1 levels were found in both the serum and urine. Interestingly, Coprococcus, Dorea, Bifidobacterium, Blautia and Lactococcus, selected from 10 candidate biomarkers to predict risk in IgAN patients according to random forest analysis, were inversely associated with urinary Gd-IgA1 levels. Notably, the urine level of Gd-IgA1 could best distinguish IgAN patients from HCs. Additionally, the degree of kidney damage in pseudosterile mice with IgAN was more severe than that in mice with IgAN. Furthermore, the markers of intestinal permeability were significantly elevated in pseudosterile IgAN mice. Moreover, the inflammation responses (TLR4, MyD88, and NF-κB in intestinal and renal tissues; TNF-α and IL-6 in serum) and Local Immune Responses (BAFF and APRIL in intestinal tissue) were upregulated in pseudosterile IgAN mice. Conclusions The urine Gd-IgA1 level may be as a biomarker for the early screening of potential IgAN, and Gut microbiota dysbiosis was demonstrated in IgAN, which might be involved the dysfunction of the mucosal barrier, inflammation and local Immune responses