Insights into the direction and extent of gut microbiota abnormalities in Alzheimer’s disease and mild cognitive impairment

In a recent study published in pro swanresearchers conducted a meta-analysis to clarify the association between gut microbiota and Alzheimer’s disease (AD).

Background

The gut microbiota primarily influences neuronal function via the nervous system and the production of neuromodulators through the gut-brain axis, a means of interaction between the brain and abdominal organs. Neurodegeneration includes immune activation, neuroinflammation, and blood-brain barrier impairment due to intestinal barrier defects.

AD, a neurodegenerative disease, is characterized by gradual cognitive decline and memory loss. Early stages of AD are characterized by mild cognitive impairment (MCI). There is no clear cure for AD. However, studies have demonstrated improvements in cognitive function using non-pharmacological treatments such as probiotics and fecal microbiota transplantation (FMT) in the early stages, suggesting that the gut microbiota may be involved in the pathophysiology of AD and MCI. A potential role is indicated. However, the extent and direction of gut microbial imbalance in patients with Alzheimer’s disease has not been well characterized.

About research

In the current meta-analysis, researchers reported on the contribution of gut bacteria to Alzheimer’s disease and associated mild cognitive impairment.

The research team searched Cochrane, EBSCO, Scopus, MEDLINE and other databases to find case-control and interventional studies on the gut microbiota in Alzheimer’s disease published in English between 1 January 2010 and 31 March 2022. We searched 16S and metagenomic studies.

In addition, the references of the included records were searched and data on location, sample size, mean age, proportion of women, eligibility criteria, sequencing platform, and bioinformatics tools used were independently analyzed by two investigators. extracted to

The primary study outcome was changes in alpha diversity and microbial taxa abundance, analyzed by inverse variance-weighted random-effects modeling. Secondary research findings highlighted linear discriminant analysis effect size (LEfSe) and qualitative beta-diversity ordering. Risk of bias was assessed using methods appropriate to the study type, and subgroups were analyzed when there was considerable heterogeneity in the included studies.

Only studies assessing the gut microbiota profile of patients with Alzheimer’s disease by metagenomic sequencing and documenting results such as alpha and beta diversity ordering, linear discriminant analysis effect sizes (LEfSe), and microbial taxon abundances was analyzed. AD was diagnosed using criteria from the National Alzheimer’s Association on Aging (NIA-AA) or the Diagnostic and Statistical Manual of Mental Disorders (DSM). Individuals who did not meet criteria for Alzheimer’s disease but reported cognitive decline and memory loss were grouped with those with MCI. Those who took antibiotics within 14 days of sample collection, or had a history of genetic or neurological disorders, depression or cancer were excluded from the analysis.

result

A total of 2,235 records were initially identified, 42 of which underwent full-text screening, and 17 studies of 679 and 632 AD patients and controls, respectively, were included in the final analysis. The average age of participants was 71 years and 62% were female. We included high-quality studies with a low risk of bias. Although an overall reduction in gut microbial richness was observed among Alzheimer’s disease patients, bacteroides Species proportions were consistently higher among US residents and lower among Chinese.

The results of this study showed that location, lifestyle and diet have a significant impact on the gut microbiota and the pathogenesis of Alzheimer’s disease. further away, fascolarctobacterium Species increased significantly only in early stages of mild cognitive impairment. A small but significant decrease in alpha diversity measured using the Simpson and Shannon indices occurred among Alzheimer’s disease patients. However, the study was significantly heterogeneous and subgroup analyzes yielded similar results for the Chinese.

Moreover, significant and moderate reductions occurred in the Chao index and species richness in AD patients. In the LEfSe analysis, actinomycetes, Proteobacteria, Bifidobacterium, Clostrididae, Enterobacteriaceae, Lactic acid bacteria, Ruminococcaceaeand Ackermanthia. on the contrary, relative abundance of bacteroides, Firmicutes, Bacteroidae, Lachnospiraceae, Prevotellaceae, Aristipesand Anerostipes decreased in patients with Alzheimer’s disease.

Conclusion

Overall, the findings suggest that AD progression is associated with more profound effects on species richness than on gut microbiota homogeneity, and that regional differences in lifestyle and diet affect gut composition. We have shown that it is possible to give bacteroides Abundant.

In addition, increased fascolarctobacterium and decreased bacteroides The number of MCI patients indicated that intestinal dysbiosis begins at the MCI stage. Studies of the gut microbiota therefore enable rapid diagnosis and early intervention in neurodegenerative diseases such as AD.

LEfSe synthesis showed increased abundance of propionate, lactate and acetate products such as: bifidobacteria, Lactic acid bacteriaand Ackermanthia, which was negatively correlated with clinical cognitive measures in previous studies. However, this result should be interpreted with caution due to possible confounding by polypharmacy.