The Role Of Intestinal Microbiota In Early Renal Injury Induced By High Salt Diet

BackgroundsIntestinal abnormalities,including enteric dysbiosis and increased gut permeability,are associated with many extraintestinal diseases.For example,alcohol and high fat diet consumption can induce enteric dysbiosis and disrupt gut barrier integrity,which allows pathogen associated molecular patterns to penetrate the blood and translocate into the liver to result in hepatic steatosis.Chronic high-salt diet-associated renal injury may be a key risk factor for the development of hypertension.It is deserved to be further studied whether high-salt diet can also directly disrupt intestinal homeostasis which causes bacterial products translocate into the kidney and induces renal injury.ObjectivesTo investigate the mechanism of the intestine microbiota in high salt diet-induced renal injury and supplement the gut-kidney axis theory.MethodsExperiment 1:16 C57BL/6J mice were randomly divided into two groups:control group and high salt group.Mice in Control group were given normal water while HS group were fed with 2%(w/w)sodium chloride(NaCl)in drinking water continuously for 8 weeks.All mice had free access to food and water and were maintained in a temperature-controlled colony room on a 12:12-h light/dark cycle.At the 0th and 8th week,feces from each mouse in each group were collected.At the end of the experiment,the visceral tissues were preserved and tested.Intestinal flora,intestinal pathophysiology,intestinal permeability and bacterial translocation were detectedExperiment 2:24 C57BL/6J mice were randomly divided into three groups:Control group,HS group and HS+ABX group.Mice in Control group were given normal water,HS group were fed with 2%(w/w)sodium chloride(NaCl)in drinking water and HS +ABX group were fed with non-absorbable antibiotic(polymyxin B,150 mg/L and neomycin,200 mg/L)and 2%sodium chloride(NaCl)in drinking water continuously for 8 weeks.All mice had free access to food and water and were maintained in a temperature-controlled colony room on a 12:12-h light/dark cycle.At the 0th and 8th week,feces and urine from each mouse in each group were collected.At the end of the experiment,the visceral tissues were preserved and tested.Intestinal immunological gene expression,fecal albumin content,FD-4 permeability experiment,relative plasma endotoxin level,early renal injury and renal apoptotic were detected.Experiment 3:18 C57BL/6J mice were randomly divided into two groups:control receptor group and high salt receptor group.The mice in both groups were given sterile water and SPF sterile feed and received antibiotics(vancomycin,25mg/ml;neomycin sulfate,50 mg/ml;metronidazole,50 mg/ml and ampicillin,50 mg/ml)intragastrically once each day for 1 week to deplete gut microbiota.The feces of the donor mice(control and chronic HS-fed mice)were collected and resuspended in PBS at 0.125 g/ml.The solution was administered to mice in the corresponding receptor groups orally via gastric gavage tube three times a week and continuously for 5 weeks.All mice had free access to food and water,and the feces and urine were collected every week for further examination.Mice were killed at 5 weeks after transplantation,and tissues were harvested for further analysis.Intestinal permeability and early renal injury and disfunction were detected.ResultsResults 1:Our data has showed that the bacterial abundance and composition were significantly altered after chronic HS feeding,which indicated the occurrence of enteric dysbiosis.In addition,ileum immunological gene expression was impaired in mice with HS intake.The mRNA expression level of inflammatory cytokines was up-regulated in ileum in HS mice.Intestinal permeability was monitored by fecal albumin content,which showed that HS feeding promoted gut leakiness and increased fecal albumin content.Simultaneously,tight-junction mRNA and protein levels were statistically down-regulated in intestinal.These data clearly demonstrated that the intestinal gut barrier.We found that enteric bacteria was enriched in the kidney exposed to the high salt compared with the kidney of the control animals.Chronic HS intake specifically promoted bacterial translocation into the kidney.Results 2:Gut bacteria depletion by non-absorbable antibiotic administration restored HS loading induced gut leakiness,renal injury and systolic blood pressure elevation.Results 3:After 5 weeks of fecal microbiota transplantation,the fecal microbiota from mice fed chronic HS could independently cause microbiota composition alteration,gut leakiness and renal injuryConclusionsEnteric dysbiosis caused by Chronic high salt feeding is associated with gut inflammatory response disruption which results in the loss of intestinal barrier function and promote bacterial translocation into the kidney.Intestinal microbiota plays an important regulatory role in chronic kidney injury induced by high salt diet.