Characteristics Of Human Oral Microbiome And Its Non-invasive Diagnostic Value In Chronic Kidney Disease

Research backgroundChronic kidney disease(CKD)has become one of the main diseases threatening public health due to its high incidence,high mortality and high medical expenditure.Due to the insidious onset of CKD,there is no obvious clinical symptoms,which with low awareness rate and poor prognosis.With the progress of CKD,irreversible damage occurs to the kidney structure and renal function progressively declines,which would eventually develop into end-stage renal disease(ESRD).The CKD patients can only be treated with renal replacement therapy(such as hemodialysis,peritoneal dialysis and kidney transplantation),which imposes a heavy economic burden on patients,society and the country.Early screening,early intervention measures can delay the progression of the disease and reduce the burden on patients.Therefore,to find new diagnostic markers and explore new therapeutic targets is the focus of current work.The human micro-ecosystem is closely related to the health and disease state of the body.The normal bacterial community is not only in a symbiotic state with human body,but also plays an important role in maintaining human health,which participates in many physiological processes such as energy metabolism,nutrient intake,immune regulation,etc.The oral cavity is the starting point to enter the digestive tract and respiratory tract,and oral flora imbalance has become one of the main causes of many flora-related systemic infections.Oral microecological disorders are related to the occurrence and development of many diseases,such as craniofacial osteomyelitis,dental caries,rheumatoid arthritis,diabetes,and pancreatic cancer,etc.The relationship between oral flora and CKD has also received more and more attention.Studies have found that Neisseria and Streptococcus are negatively correlated with the renal function.Periodontal pathogens including Porphyromonas gingivalis,Treponema pallidum and Actinomyces haemophilus are correlated with serum IgG levels and the renal function,but are negatively correlated with eGFR.However,most studies currently focus on the relationship between CKD patients and periodontal disease.There are no reports on the composition of the oral flora of CKD patients and the application value of oral microbial markers in the non-invasive diagnosis of CKD.In order to clarify the changes of the human oral microbiome in CKD patients,and to explore the application value of oral microbial markers in the diagnosis of CKD,the following research was carried out.Research objectiveTo analyze the characteristics of the human tongue coating microbiome in chronic kidney disease(CKD),and investigate the application value of tongue coating microbial markers as a non-invasive diagnostic tool for CKD.MethodsIn this study,a total of 253 tongue coating samples from CKD patients and healthy controls from Zhengzhou and Hangzhou areas of China were collected.Screened by inclusion and exclusion criteria,a total of 250 tongue coating samples were finally completed with DNA extraction and 16S rRNA sequencing.After strict data quality control,a total of 235 tongue coating samples’ sequencing data were included in the final biological information and statistical analysis,which including 44 CKD samples from Zhengzhou area,59 CKD samples from Hangzhou area,and 132 healthy control samples from Zhengzhou area.The study is divided into the following two phases:the discovery phase(including 44 CKD patients and 88 healthy controls)and the validation phase(including 59 CKD patients and 44 healthy controls).In the discovery stage,the oral microbial system development of CKD patients and healthy volunteers from Zhengzhou(Central China)was described and compared,and its key biomarkers were identified,and a CKD diagnostic classifier model was constructed.The validation phase was to verified the classifier’s diagnostic efficacy by samples from CKD patients and healthy volunteers from Hangzhou,China(East China).Results1.Compared with the healthy controls group,the tongue coating microbial diversity of the CKD group was significantly increased,P<0.05.2.In the CKD group,twenty-eight bacterial genera including Streptococcus,Actinomyces,and Citrobacter are dominant,while 7 bacterial genera,including Prevotella,Haemophilus and Sphingomonas,were the dominant flora in the healthy controls group.3.To analyze the gene function spectrum of the tongue coating microbiome in the CKD group and the healthy controls group,the result suggested 49 microbial functions,including Ascorbate and aldarate metabolism,Pyruvate metabolism and Arginine and proline metabolism were dominant in the CKD.However,55 microbial functions,including lipopolysaccharide biosynthesis,peptidoglycan biosynthesis,purine metabolism and pyrimidine metabolism,were dominant in the healthy controls.4.The 5-fold cross-validation of the random forest model was used to determine the 7 optimal microbial markers.Based on the CKD classifier,the area under the curve(AUC)reached 0.9917 in the discovery phase and 0.8026 AUC was reached in the validation phase,realizing cross-region verification.Conclusions1.The diversity of the oral microbiome of CKD patients has increased,and the oral flora of CKD patients has changed significantly.2.Compared with healthy controls,the community composition,function and other aspects of the oral microbiome of CKD patients have distinguished changes.The abnormality of the gene function profile of the oral microbiome of CKD patients may participate in the progress of CKD by affecting the metabolism of the body.3.Oral microbial markers have strong diagnostic potential as a non-invasive diagnostic tool for CKD.