Preliminary study on the biological characteristics of intestinal flora in IgA nephropathy based on high-throughput sequencing / 中华肾脏病杂志

ABSTRACT

Objective:To study the structure and diversity of intestinal flora in IgA nephropathy (IgAN) patients, and to explore the correlation of intestinal microorganisms with clinical indicators and renal pathology.Methods:Fifteen IgAN patients in the First Affiliated Hospital of Baotou Medical College from May 2020 to September 2020 were retrospectively enrolled as IgAN group, and 8 healthy families and 7 health checkups were enrolled as healthy control group. Illumina high-throughput sequencing technology was performed for DNA sequencing in the 16S rDNA-V4 region of all bacteria in the feces sample. QIIME 2 was used to process and analyze original sequence, compared with Greengenes (V138) database. The DADA2 software was called to denoise the data, which was equivalent to a 100% similarity cluster (OTU was a 97% similarity cluster). PCoA was used to analyze the structure and diversity of intestinal flora. Spearman correlation or Pearson correlation analysis was used to analyze the correlation of differential flora with renal pathology and clinical indicators.Results:(1) The intestinal microbial β diversity in IgAN patients was significantly different from that in healthy controls ( P=0.010). (2) Compared with the healthy control group, the numbers of intestinal flora species in IgAN group were significantly increased in 1 phylum, 3 families and 22 genus. At the levels from phylum to family, the species numbers of Firmicutes and Ruminococcaceae in IgAN patients reduced than those in healthy controls and the species numbers of Chloroflexi, Gaiellaceae, Staphylococcaceae and Family-XⅢ in IgAN patients increased than those in healthy controls (all P<0.05). At the genus level, compared with the healthy controls, the species number of Subdoligranulum in IgAN patients was significantly reduced ( P=0.020), and the species number of Ruminococcus- gnavus- group was significantly increased ( P=0.004). (3) At the phylum level of the species number, Firmicutes in IgAN patients was positively correlated to albumin (ALB) ( r=0.637, P=0.037) and IgG ( r=0.452, P=0.046), Gemmatimonadetes was negatively correlated to serum creatinine ( r=-0.453, P=0.045), Verrucomicrobia was negatively correlated to IgM ( r=-0.450, P=0.046), and Patescibacteria was positively correlated to IgA ( r=0.469, P=0.037). At the genus level of the species number, Ruminococcus- gnavus- group ( r=-0.614, P=0.004) and Megamonas ( r=-0.451, P=0.042) were negatively correlated to ALB; Subdoligranulum was positively correlated to ALB ( r=0.563, P=0.009); Dialister was negatively correlated to C3 ( r=-0.427, P=0.041) and was positively correlated to IgA ( r=0.434, P=0.035); Veillonella was positively correlated to estimated glomerular filtration rate ( r=0.452, P=0.043). The species numbers of Eisenbergiella ( r=-0.850, P=0.007), Holdemania ( r=-0.845, P=0.008), Flavonifractor ( r=-0.845, P=0.008), and Ruminiclostridium- 9 ( r=-0.845, P=0.008) were negatively correlated to glomerulosclerosis or adhesion (S) of Oxford classification; the species number of Fusicatenibacter was negatively correlated to mesangial hypercellularity ( r=-0.845, P=0.008); the number of Coprococcus- 2 was positively correlated to S ( r=0.738, P=0.037) and tubular atrophy or interstitial fibrosis ( r=0.756, P=0.030). (4) Random forest model was built with Ruminococcus- gnavus- group and Subdoligranulum, after fitting the area under the receiver operating characteristic curve was 0.927. Conclusions:The intestinal flora of IgAN patients is different from that in healthy subjects. Changes of intestinal flora in IgAN patients are related to clinical indicators and renal pathology. In particular, Ruminococcus- gnavus- group and Subdoligranulum may play an important role in IgAN.