Intestinal Microbiota And Resting State Functional Magnetic Resonance Imaging Studies In Patients With Alzheimer's Disease And Amnestic Mild Cognitive Impairment

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Intestinal microbiota study in patients with Alzheimer,s disease and amnestic mild cognitive impairmentObjective:Alzheimer's disease(AD),clinically characterized by the progressive cognitive impairment,is one of the main causes of disability in elder people worldwide.Recently,animal studies indicated that the 'gut-brain axis' might contribute to the amyloid deposition of AD.However,reports on the changes of intestinal flora structure and function in patients with mild cognitive impairment,the predecessor of AD renain scare.In this study,we aimed at identifying differences in microbiome between patients with AD(Pre-onset stage of amnestic mild cognitive impairment,aMCI;and AD)and the normal cognition normal controls,NC).Additionally,the potential association between intestinal microbiota(IM)and clinical characteristics of AD was evaluated.Methods:A total of 97 subjects(33 AD,32 aMCI,and 32 NC)were recruited in the study.Fresh fecal specimens were collected in the morning and total DNA of fecal intestinal flora was extracted.The composition of gut bacterial communities was determined by 16S ribosomal RNA Miseq sequencing.In addition,Phylogenetic Investigation of Communities by Reconstruction of Unobserved States(PICRUSt)was used to predict function shift of IM.The Mini-Mental State Examination(MMSE),Montreal Cognitive Assessment(MoCA),Clinical Dementia Rating(CDR)scores were used to evaluate the severity of cognitive impairment in patients.Spearman or Pearson correlation analysis was used to analyze the correlation between relative abundance of gut bacteria and parameters of cognitive scale.Results:The fecal microbial diversity was decreased in AD patients compared with aMCI patients and NC.And the microbial composition was distinct among aMCI,AD and healthy control groups.Among bacterial taxa,the proportion of phylum Firmicutes was significantly reduced(p=0.008),whereas Proteobacteria(p=0.024)was highly enriched in the AD compared with HC.In addition,similar alterations were observed at the order,class and family levels of these two phyla.And Gammaproteobacteria,Enterobaeteriale and Enterobaeteriaeeae showed a progressive enriched prevalence from NC to aMCI and AD patients.Further,a significant correlation was observed between the clinical severity scores of AD and the abundance of altered microbiomes.The relative abundance of Enterobacteriaceae was positively correlated with CDR score(r=0.259,p=0.045),and correlated with MMSE score and MoCA score(r=-0.24,p=0.039;r=-0.32,p=0.04)negatively.The relative abundance of Bacteroidetes and Ruminococcaceae were positively correlated with MMSE scores(r=0.32,p=0.03;r=0.28,p=0.04)respectively.The relative abundance of Veillonellaceae was negatively correlated with MoCA score(r=-0.21,p=0.042).Moreover,the KEGG results showed the increased modules related to glycan biosynthesis and metabolism in AD and aMCI patients and decreased pathways related to immune system in AD patients.Importantly,the discriminating model based on predominant and differential microbiota could effectively distinguish aMCI,AD and NC.Notably,the model based on the abundance of family Enterobacteriaceae could distinguish AD from both aMCI(AUC=0.688)and NC(AUC=0.698).Conclusions:The intestinal microbiota diversity of AD patients was decreased.Distinct microbial communities,especially Enterobacteriaceae,were associated with the patients with AD when compared with aMCI and healthy subjects.A significant correlation was observed between the clinical severity scores of AD and the abundance of altered microbiomes.The functional shift of the microbiomes might contribute to the metabolic and immune disturbance in the pathogenesis of AD.Part ? Brain-gut mechanism of amnestic mild cognitive impairment:a case-control study based on resting state fMRIObjective:To explore the correlation between intestinal microbiota,local brain spontaneous activity and neuropsychological characteristics in patients with amnestic mild cognitive impairment(aMCI).Methods:This study was a case-control study.32 aMCI,and 32 NC were recruited in the study.Fresh fecal specimens were collected in the morning and total DNA of fecal intestinal flora was extracted.Resting state magnetic resonance imaging(resting state fMRI)was used to evaluate the spontaneous brain activity in resting state of aMCI patients.16s rRNA was used to detect intestinal microecological composition.MMSE and MoCA scales were used to evaluate cognitive function.Then Spearman or Pearson correlation analysis was used to analyze the relationship between spontaneous brain activity and cognitive function and intestinal flora structure in aMCI patients.Results:The relative abundance of Bacteroides from phylum to family,and genera level in aMCI group was higher than that in healthy control group(P<0.05).At the family level,the abundance of Lachnospiraceae decreased in aMCI group,while the relative abundance of Veronococcidae increased.There was a decrease tendency for in aMCI group(2.97%vs 5.78%,P=0.052).At generic level,the abundance of Ruminococcus and Blautia in aMCI group was lower than that in healthy control group(p<0.05).Rs-fMRI showed that the fALFF values of aMCI in the prefrontal lobe and left cerebellum were lower than those in the control group,and increased in the occipital lobe,especially in the right lingual gyrus and the calcarine gyrus.The correlation analysis showed that the relative abundance of Bacteroides from phylum to genus level was positively correlated with the fALFF value of the right middle temporal gyrus and negatively correlated with the fALFF value of the cerebellar vermis(p<0.05).The relative abundance of Clostridium and Blautia was positively correlated with the fALFF value of the left cerebellum in the slow 4 band,and the relative abundance of Clostridium was positively correlated with the fALFF value of the right lingual gyrus(p<0.05).Correlation analysis showed that there were different correlation patterms between the activity of different brain regions and the different microflora in aMCI and normal control groups.In aMCI group,the relative abundance of Bacteroides from phylum to genus level was positively correlated with fALFF value in the right inferior middle temporal gyrus(1=0.52,p=0.02)and negatively correlated with fALFF value in vermis(r=-0.49,p=0.03).The relative abundance of Clostridiaceae and Blautia was positively correlated with the fALFF value of the left cerebellum in slow 4 band(r=0.49,p=0.04;r=0.47,p=0.04).The relative abundance of Clostridiaceae was positively correlated with the fALFF value of the right lingual gyrus in the 0.01-0.08Hz band(r=0.51,p=0.02).At slow 5 band,the relative abundance of Firmicutes was negatively correlated with the fALFF value in the right inferior frontal gyrus(p=-0.45,p=0.047).In addition,the level of Bacteroides from phylum to genus was positively correlated with attention and computation(r=0.51,p=0.02;r=0.36,p=0.037),and negatively correlated with the three-step command score(r=0.458,p=0.007).Relative abundance of Lachnospiraceae and Blautia was positively correlated with repetition(r=0.375,p=0.038),three-step command score(r=0.352,p=0.041)respectively.Clostridium was positively correlated with orientation(r=0.41,p=0.016),Relative abundance of Veillonellaceae was negatively correlated with orientation and delayed recall scores(r=-0.34,p=0.049,r=-0.36,p=0.035).Relative abundance of Rumencoccus was positively correlated with naming scores(r=0.39,p=0.022).Conclusions:The intestinal flora composition and resting spontaneous brain activity of aMCI patients are different from those of age and sex matched normal controls.There may be a specific gut microbiota-spontaneous brain activity-cognitive function association model in aMCI patients.The value of this association model in disease diagnosis and prediction needs to be confirmed by further large sample and longitudinal follow-up studies.