| Objective:Lupus nephritis is a common complication of Systemic lupus erythematosus(SLE).In recent years,Intestinal flora has been found to be involved in the pathogenesis of LN.Serum indoleol sulfate(IS)as a nephrotoxic substance produced by Faecalibacterium can cause kidney damage.The purpose of this study was to explore the imbalance of intestinal flora and its related metabolites in patients with LN by analyzing the structure and metabolites of intestinal flora between newly diagnosed LN patients and healthy people.By measuring the changes of serum IS concentration in patients with LN under different quantitative levels of 24-hour proteinuria,to further explore the relationship between serum IS level and the pathogenesis of LN,and to find a new strategy for the diagnosis and treatment of LN.Methods: 56 SLE patients were divided into 27 LN group and 29 N-LN group according to whether the urine protein content was more than 0.5g in 24 hours,and 58 healthy volunteers were selected as the HC group.The 16 S r RNA gene sequence V3-V4 high mutation region of three groups were amplified and sequenced by using the Illumina miseq platform.Alpha diversity analysis,beta diversity analysis and the difference analysis of bacteria group at the door and genus level were carried out.The representative intestinal flora of three groups was obtained by lefse cluster analysis.Based on KEGG,the function characteristics of intestinal flora were predicted by picrust software.The content difference of metabolites in three groups was detected by non targeted metabolomics.Indole,a non targeted metabolite of feces,was transformed into serum IS with renal toxicity after being injected into the blood.Enzyme linked immunoadsorption was used in this ELISA was used to determine the is concentration of three groups,compare the difference of is concentration in three groups,and analyze Pearson correlation between the concentration of is and 24 h urine protein of three groups respectively.In this experiment,the concentration of serum IS was quantitatively measured and analyzed by ELISA.The difference of serum IS concentration among the three groups was compared.The correlation between serum IS concentration and24-hour urinary protein in the three groups was analyzed by Pearson,and the ROC curve was used to determine the possible predictive value of serum IS for LN.Results:1.The species diversity of intestinal flora in LN group was significantly lower than that in healthy control group(P<0.05).At the gate level,the Firmicutes and the ratio of thick-walled bacteria to F/B in the LN group were significantly lower than those in the healthy control group(P<0.05).Compared with the healthy control group,the abundance of Faecalibacterium,Bacteroides,Ruminococcus,Streptococcus,Dialister increased significantly in LN group(P<0.05).However,the abundance of Bifidobacterium,Clostridium,Lachtobacillus and Lachonopira decreased significantly(P<0.05).Compared with N-LN group,the content of Faecalibacterium and Bacteroides(P<0.01)in LN group was significantly higher than that in N-LN group,while the contents of Blautia(P<0.01)and Streptococcus(P<0.05)were significantly lower than those in N-LN group.2.According to the set screening criteria(LDAscore > 4),the representative bacteria of each group were found.The results showed that the representative bacteria of the healthy control group were Bifidobacterium,Spirillum,Rumen cocci,Lactobacillus and Clostridium,the representative bacteria of LN group were Enterobacter and Streptococcus,and the representative bacteria of N-LN group were Bacteroides and Brucella.3.Based on KEGG,carbohydrate catabolism pathway was significantly down-regulated and amino acid catabolism pathway was significantly up-regulated in LN group.Metabolite analysis showed that in LN group,the contents of short-chain fatty acids such as Butyrate related to carbohydrate catabolism decreased significantly,while the contents of Indoxyl and TMAO related to amino acid metabolism increased significantly(P<0.05).4.The concentration of blood IS and the content of Enterobacter in LN group were significantly higher than those in healthy control group.In patients with LN,24-hour urinary protein was positively correlated with serum IS concentration(r=0.839,P<0.01),ROC curve analysis showed that the best cut-off value of serum IS for LN patients was 74 pg / ml.The area under the curve of LN predicted by serum IS was 0.755(95%CI:0.622～0.887),sensitivity was 0.778 and specificity was 0.625.Conclusion: There was imbalance of intestinal flora in patients with LN,and the ratio of thick-walled bacteria to Bacteroides decreased,in which the content of Enterobacter increased significantly,and the level of serum IS,its metabolite,increased,which could predict the occurrence of proteinuria in patients with LN.The imbalance of intestinal flora and abnormal metabolic pathways in patients with LN may be involved in the pathogenesis of LN. |
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