The Study Of The Correlation Between The Gut Bacteria-derived Short Chain Fatty Acids And The Chronic Kidney Disease

Background and aimThe gut microbiota plays a important role in human's health and disease by contributing to its metabolism,nutrition,physiology,and immune function.The patients with chronic kidney disease(CKD)has a quantitative and qualitative alteration in gut microbiota which may contribute to the progression of CKD,especially the depletion of butyrate producing bacteria and bacteria that possess short chain fatty acids forming enzymes.The gut bacteria can contribute to the health maintenance and disease generation and development of the host by producing beneficial metabolites such as short chain fatty acids(SCFAs)and harmful metabolites such as Trimethylamine-N-oxide(TMAO).TMAO,which is one of the risk factors of Cardiovascular disease,can damage the renal function and exacerbate the CKD progression.SCFAs are produced by gut anaerobic bacteria fermenting organic macromolecular substances such as dietary fiber.The main SCFAs including acetate,propionate,butyrate.SCFAs can affect various physiological processes and disease progression of humans by directly activating G-coupled-receptors,inhibiting histone deacetylases,and serving as energy substrates.Many studies had found different disease can affect the production of SCFAs,such as inflammatory bowel disease,constipation,autism,congenital megacolon.In this study,we aimed to explore the alteration of the fecal SCFAs concentration in CKD patients and chronic renal failure animal models,and analyze the role of SCFAs in the progression of CKD.Methods1.To establish a method for quantitative detection of fecal SCFAs using GC-MS.2.Subjects enrollment and specimen collection:128 CKD patients and 61 healthy controls were enrolled from NanFang Hospital.Fresh feces were collected and frozen in the-80? refrigerator.fasting venous peripheral blood was collected in the morning to detect relevant biochemical indicators by Nanfang hospital laboratory.3.Rats were killed and the tissue,blood and colon contents were collected 8 weeks post 5/6 nephrectomy or sham operation.4.The levels of SCFAs in feces were measured by GC-MS.TMA and TMAO in the samples were measured by LC-MS.5.Statistical analysis:Data were analysed using SPSS 19.0 software,One-Way ANOVA followed by LSD methods was applied for comparison of continuous variables.If equal variances not assumed,Satterthwaite estimation t test and Dunnett T3 was used.Two independent samples t test were used to compare two independent samples which were normal distribution,the data which is non-normal distribution was analyzed with nonparametric test.According to whether the bivariate is normal distribution,the Pearson coefficient or Spearman coefficient is used to test the bivariate correlation.The level for statistical significance was set at p<0.05.Results1.A fast,simple and stable quantitative detection method of SCFAs in feces were established.2.56 CKD stage 1-4 patients,72 CKD stage 5 patients,61 healthy controls were enrolled in the study.38 CKD stage 5 patients received hemodialysis therapy,12 CKD stage 5 patients complicated with diabetes mellitus,8 CKD stage 3-4 patients complicated with diabetes mellitus.The age,sex,and BMI are matched between CKD patients and healthy controls.3.Compared with the control group,the concentration of acetate and butyrate in feces of CKD stage 5 patients were significantly lower,the isobutyrate and isovalerate were marked higher,and the level of butyrate was significantly decreased and isovalerate concentration were increased in the patients with CKD stage 1-4.The butyrate concentration were declined in CKD stage 5 patients compared to CKD stage 1-4 patients.4.Compared to the CKD stage 5 patients without diabetes mellitus,propionate level of CKD stage 5 patients with diabetes mellitus were lower.Compared to the CKD stage 3-4 patients without diabetes mellitus,the concentrations of acetate,propionate,butyrate in feces were significantly reduced in CKD stage 3-4 patients with diabetes mellitus.There was no significant difference of SCFAs level between patients receiving hemodialysis or without hemodialysis.5.There was a significant negative correlation between fecal butyrate levels and serum cystatin,creatinine,urea and phosphorus levels,and butyrate was positively correlated with eGFR.6.The concentration of butyrate in colonic contents of 5/6 nephrectomy rats was significantly decreased and the levels of TMA and TMAO were significantly increased compared to the sham operation rats.The concentration of butyrate was significantly adverse associated with TMA,TMAO and BUN levels respectively.ConclusionThe SCFAs concentrations in CKD patients and 5/6 nephrectomy rats were changed,and the fecal concentration of butyrate were decreased gradiently with the progression of CKD.In CKD patients,fecal butyrate concentration was negatively correlated with serum cystatin C which is sensitive for kidney function and positively associated with eGFR level.Butyrate level was decreased and TMAO level were increased in 5/6 nephrectomy rats,and the butyrate level were adverse correlated with the TMAO level.These study results suggest that SCFAs especially the butyrate may play a important role in CKD progression,and the alteration of SCFAs may reflect the dysbiosis of gut microbiota.As a result,the SCFAs are expected to be a biomaker of CKD or served as a new adjuvant therapy tragedy for CKD.