Probiotics for Alzheimer’s Disease: A Systematic Review

Abstract

Alzheimer’s disease (AD) is the most common form of neurodegenerative disorders affecting mostly the elderly. It is characterized by the presence of Aβ and neurofibrillary tangles (NFT), resulting in cognitive and memory impairment. Research shows that alteration in gut microbial diversity and defects in gut brain axis are linked to AD. Probiotics are known to be one of the best preventative measures against cognitive decline in AD. Numerous in vivo trials and recent clinical trials have proven the effectiveness of selected bacterial strains in slowing down the progression of AD. It is proven that probiotics modulate the inflammatory process, counteract with oxidative stress, and modify gut microbiota. Thus, this review summarizes the current evidence, diversity of bacterial strains, defects of gut brain axis in AD, harmful bacterial for AD, and the mechanism of action of probiotics in preventing AD. A literature search on selected databases such as PubMed, Semantic Scholar, Nature, and Springer link have identified potentially relevant articles to this topic. However, upon consideration of inclusion criteria and the limitation of publication year, only 22 articles have been selected to be further reviewed. The search query includes few sets of keywords as follows. (1) Probiotics OR gut microbiome OR microbes AND (2) Alzheimer OR cognitive OR aging OR dementia AND (3) clinical trial OR in vivo OR animal study. The results evidenced in this study help to clearly illustrate the relationship between probiotic supplementation and AD. Thus, this systematic review will help identify novel therapeutic strategies in the future as probiotics are free from triggering any adverse effects in human body.

Understanding How Physical Exercise Improves Alzheimer’s Disease: Cholinergic and Monoaminergic Systems

“…Donepezil hydrochloride combined with swimming exercise (7 sessions/week for 4 weeks with no weight bearing) improved learning and memory in Aβ 1–40 -induced rats, and the mechanism was related to increased ChAT activity and decreased AChE activity in the cortex and hippocampus ( Jiangbo and Liyun, 2018 ). Probiotics can modulate the inflammatory process, counteract oxidative stress, and modify gut microbiota and are considered to be among the best preventive measures against cognitive decline in AD ( Naomi et al, 2021 ). A study found that mono or combined progressive treadmill running (5 sessions/week for 8 weeks) and probiotic (e.g., Bifidobacterium bifidum and Lactobacillus plantarum) treatment significantly increased levels of ACh in the brains of Aβ 1–42 -induced rats and reversed spatial learning impairment ( Shamsipour et al, 2021 ).…”

High-Throughput Screening of Microbial Isolates with Impact on <em>Caenorhabditis elegans</em> Health

“…Looking at the plates from Step 3.5., assess the worms' developmental stage. Once >90% of worms have reached L4 34 , collect the worms in up to 10 mL of sterile M9 solution in 15 mL conical tubes.…”

“…simpler genome, body plan, nervous system, gut, and microbiome, yet complex and similar enough to humans, make it a powerful preclinical model, where mechanistic insight can be gained while testing for bioactive efficacy or toxicity. As interest is growing in developing microbial interventions for diseases 8 , 9 , 34 , 35 , taking advantage of such preclinical models to rapidly investigate probiotics is an attractive option with the largely untapped and near-unlimited therapeutic potential of microbes 34 . The protocol described here is suitable to study the impact of environmental bacteria on C. elegans health but can be readily adapted for other purposes.…”

Probiotic Bifidobacterium breve MCC1274 Mitigates Alzheimer’s Disease-Related Pathologies in Wild-Type Mice

“…Moreover, some probiotics, such as Lactobacillus and Bifidobacterium, have been used as anti-aging agents [17]. Growing evidence suggests that supplementation with probiotics has the potential to prevent neurodegenerative diseases, including AD and Parkinson's disease [18,19]. It is well known that probiotics influence brain function by one of these three pathways: endocrine pathway, immune modulation, or neural regulation [19].…”

“…Growing evidence suggests that supplementation with probiotics has the potential to prevent neurodegenerative diseases, including AD and Parkinson's disease [18,19]. It is well known that probiotics influence brain function by one of these three pathways: endocrine pathway, immune modulation, or neural regulation [19]. Moreover, the administration of bifidobacteria improves brain function; Bifidobacterium bifidum BGN4, Bifidobacterium breve, and Bifidobacterium Lactis Probio-M8 have beneficial effects on cognition improvement, reduction of amyloidosis, and enhancement of synaptic function [20][21][22].…”