A 16SrRNA Sequence-based Analysis Of Differential Gut Flora In Patients With Alzheimer’s Disease And Mild Cognitive Impairment

Objectives: Current research on the gut flora of patients with Alzheimer’s disease(AD)and mild cognitive impairment(MCI)is inconsistent,and the composition of the gut flora can be influenced by different dietary habits.The aim of this study was to compare the differences in the abundance and composition of the gut microbiota between AD and MCI patients and to correlate the clinical characteristics in order to provide a useful clinical guide and reference.Methods: The study was a case-control study in which the case group was composed of Han Chinese people of Yunnan provincial household registration,aged≥ 60 years,from outpatients and inpatients of the First Affiliated Hospital of Kunming Medical University,with diagnoses meeting the diagnostic entry criteria for AD and MCI;the control group was composed of family members or healthy elderly people in the community who matched the patients’ age and dietary habits as normal healthy controls(HC).Stool specimens were collected after screening for compliance with the cognitive scale.The faecal specimens were sequenced and analysed for microbial 16 Sr RNA gene expression.Results: 1.A total of 30 patients with AD,39 patients with MCI and 33 patients in the HC group were included in this study,of which 14 patients with AD and 14 in the HC group were paired family members living for a long time.2.The diversity of intestinal flora was higher in AD patients than in HC group.3.There were significant differences between the three groups at the phylum,order,family and genus levels,and these differences were statistically significant(P<0.05).The HC group was lower than the AD and MCI groups at the level of Desulfobacterota,while at the phylum level the HC group was lower than the AD and MCI groups at the level of Desulfobacterota;at the order level the HC group was lower than the AD and MCI groups.The level of Desulfobacterota in the HC group was lower than that in the AD and MCI groups,and the level of Lachnospirales in the HC group was lower than that in the AD group.In Desulfovibrionia,the MCI group was significantly lower than the Burkholderiales group,while the AD group was significantly higher.At the family level,the HC group was lower than both the AD and MCI groups in the Lachnospiraceae and lower than the AD group in the Tannerellaceae;it was higher than the AD group in the Ruminococcaceae,while the MCI group was higher than the AD group and lower in the Burkholderiaceae than in the AD group.At the genus level,the HC group was lower than the AD and MCI groups in Lachnoclostridium,higher than the AD and MCI groups in Faecalibacterium,and lower than the AD group in Parabacteroides.The MCI group was lower than the AD group in Parabacteroides and higher than the AD group in Faecalibacterium.At the family level,Bacteroides＿stercoris was higher in the HC group than in the AD group.4.The level of gut microbial diversity correlated with MMSE and Mo CA.The abundance of Verrucomicrobiae,Desulfobacterota and Lachnospirales was negatively correlated with the MMSE and Mo CA scores;the abundance of Fusobacteriia and Pseudomonadales The abundance of Fusobacteriia and Pseudomonadales was positively correlated with MMSE and Mo CA.The abundance of Fusobacteriia and Pseudomonadales was negatively correlated with MMSE and Mo CA scores.5.Differences in intestinal flora between AD patients and long-term care controls: AD patients had higher abundance of Bacteroides than normal controls and lower abundance of Firmicutes,Faecalibacterium Prausnitzii,Ruminococcus and Coriobacteriaceae than long-term care controls6.Significant strains were screened and each model was cross-validated,using the ROC curve as an evaluation of the correctness and reliability of the model.In the top10 abundance rankings,AUC=99.84%(95% confidence interval 0.984-1.0,p<0.001)for the HC group compared to the AD group,AUC=96.09%(95% confidence interval0.913-0.1,p<0.001)for the MCI group compared to the AD group,and AUC=95.51%(95% confidence interval 0.891-0.1,p<0.001).The results suggest that the dominant flora can effectively distinguish patients with AD and MCI from the healthy population.Conclusions:1.The abundance and composition of the gut flora of AD and MCI patients differed significantly from that of the cognitively functioning population.2.The diversity of intestinal flora was higher in AD patients than in normal controls.Differences were found at the level of phylum,class,order,family,genus and species.3.Altered gut flora structure correlates with dementia severity and cognitive level scores in AD patients and long-term care normal controls.4.A discriminatory model based on the dominant genus can effectively distinguish between the AD,MCI and HC groups.