Study Of Gut Microbiome And Gut Barrier Function In Patients With Alzheimer’s Disease

ObjectiveBy studying the characteristics of gut microbiome and intestinal barrier function in patients with Alzheimer’s disease,we will further explore the influence of gut-brain axis on Alzheimer’s disease,and provide reference for the prevention and treatment of AD.Methods118 subjects were recruited based on inclusion and exclusion criteria,including 45 with Alzheimer’s disease(AD),38 with mild cognitive impairment(MCI),and 35 with normal controls(NC).Face-to-face interviews and questionnaires were conducted to collect relevant information from all subjects,including clinical data,blood routine and biochemical examination results.The level of high-sensitivity C-reactive protein(hs-CRP)in serum was adopted to determine systemic inflammation.Based on the subjects’ description of feces,the defecation was classified by Bristol stool classification.The nutrition was evaluated by Mini Nutritional Assessment Short Form(MNA-SF).The cognitive function was assessed by Mini-Mental State Examination(MMSE),Montreal Cognitive Assessment Scale(Mo CA),and Activity of Daily Living Scale(ADL).16 S r RNA sequencing technology was used to detect intestinal microbiota,and QIIME 2.0 software and R language were used to realize the data analysis.The DAO/DA/ET kit was used to measure the contents of diamine oxidase(DAO),D-lactic acid(DA),and bacterial endotoxin(ET)in blood to evaluate gut barrier function.ResultsGoods Coverage showed that the sequencing captured most members of the gut microbiome from each individual,indicating that the sequencing depth was sufficient to represent the biological information of the microbial community.There was no significant difference in α-diversity of intestinal microbiome among three groups(chao1: P = 0.259;Shannon index: P = 0.138;Inverse Simpson index: P = 0.123),but Shannon index and Inverse Simpson index in AD and MCI groups were lower than those in NC group(median,Shannon index,AD vs.MCI vs.NC: 3.72 vs.4.02 vs.4.20;Inverse Simpson index,AD vs.MCI vs.NC: 0.83 vs.0.87 vs.0.88).Principal component analysis(PCA)showed that there were differences in gut microbial composition among three groups(P = 0.034),suggesting that each group had a unique intestinal microbial composition.Compared with normal controls,AD patients had higher β-diversity(P = 0.019).At the phylum level,Firmicutes,Bacteroidetes,Proteobacteria,Verrucomicrobia,and Actinobacteria were the main phylum of bacteria.There were significant differences in the abundance of Bacteroidetes and Actinobacteria among three groups(Bacteroidetes: P < 0.01;Actinobacteria: P = 0.028).At the genus level,Akkermansia,Bifidobacterium,Bacteroides,Escherichia-Shigella,Subdoligranulum,Faecalibacterium,Streptococcus,and Erysipelotrichaceae UCG-003 were the dominant genera.The abundance of Dorea in AD and MCI groups was significantly lower than that in NC group(P < 0.01),and the abundance of Streptococcus in MCI group was lower than that in NC group(P =0.015).AD patients had higher abundance of Catenibacterium(P = 0.039),Family XIII AD3011group(P = 0.011),and Vagococcus(P = 0.032)than MCI patients.Among NC group,MCI group and AD group,the contents of diamine oxidase,D-lactic acid and bacterial endotoxin in blood showed an increasing trend(mean,DAO,NC vs.MCI vs.AD: 10.47 vs.10.81 vs.11.66,P = 0.034;DA,NC vs.MCI vs.AD: 11.14 vs.12.43 vs.13.30,P < 0.01;ET,NC vs.MCI vs.AD:17.01 vs.18.21 vs.20.99,P < 0.01).But there was no statistical difference in hs-CRP levels among three groups(P = 0.146).Through correlation analysis,it was discovered that the abundance of Bacteroides and Faecalibacterium was negatively correlated with the content of endotoxin(Bacteroides: R =-0.23,P =0.014;Faecalibacterium: R =-0.19,P = 0.039),and positively correlated with the scores of MMSE and Mo CA(Bacteroides: MMSE,R = 0.24,P < 0.01;Mo CA,R = 0.19,P = 0.044;Faecalibacterium: MMSE,R = 0.23,P = 0.011;Mo CA,R =0.22,P = 0.015);the contents of diamine oxidase,D-lactic acid,and bacterial endotoxin were negatively correlated with the scores of MMSE and Mo CA(DAO:MMSE,R =-0.23,P = 0.011;Mo CA,R =-0.25,P < 0.01;DA: MMSE,R =-0.30,P < 0.01;Mo CA,R =-0.33,P < 0.01;ET: MMSE,R =-0.48,P < 0.01;Mo CA,R=-0.50,P < 0.01).ConclusionsAD patients had increased β-diversity of intestinal microbes,but the abundance of Dorea was significantly lower than that in NC group,and the contents of diamine oxidase,D-lactic acid,and bacterial endotoxin in blood increased,suggesting patients with Alzheimer’s disease had gut microbiome disturbances and intestinal barrier dysfunction.Maintaining the balance of intestinal microbiota and regulating gut barrier function may be a new direction to treat AD.