Metagenomics study reveals altered composition of Avispirillum, Phocaeicola, Bacteroides, and Faecalibacterium in the gut of patients suffering with Alzheimer's disease

Abstract

Alzheimer's disease (AD) is a chronic neurodegenerative disorder that is characterized by memory loss and changes in behaviours, associated with the presence of amyloid-beta and tau proteins in the brain, which interferes with the normal functioning of the brain. Recent studies have tried to establish the structural relationship between the gut microbiota and the brain referred to as the Microbiota–Gut–Brain Axis. The present study aims to investigate a 16S rRNA gene sequencing sample, to analyze the differences in gut microbiota between 116 AD patients and 60 healthy controls retrieved from NCBI ((PRJNA770746, PRJNA533610, and PRJNA811324). Each sample was retrieved, demuxed and denoised to remove low-quality and chimeric sequences. The feature table was then constructed to determine the alpha diversity. The Kruskal-Wallis test done for prediction of alpha diversity calculated in patients with AD had a p-value of 0.0592. The bacterial features calculated through the Adonis test had a f-test value of 2.724 indicating huge microbial dysbiosis in the patient sample. Further ANCOM statistical test identified increased composition of Phocaeicola (clr 3.585), Bacteroides (clr 3.411) and Faecalibacterium (clr 3.3165) while Avispirillum (clr −1.0804) were found in reduced composition in patients with AD. The increasing microbes in Alzheimer's disease patients could be attributed to alterations in diet, immune system changes, and metabolic disturbances that create a gut environment conducive to the growth of these specific bacterial communities. Therefore, it can be an essential research area for neurodegenerative diseases, advancing our knowledge of potential biomarkers and therapeutic targets for minimizing the burden of AD.