Probiotics are known to have beneficial effects on gut microbiota and the gut-brain axis, through which they are said to influence behaviour and the central nervous system.
This suggests that probiotics may also be effective against neurodegenerative disorders such as Alzheimer's disease (AD).
As such, researchers from Morinaga Milk Industry Co, the Kanagawa Institute of Industrial Science and Technology, and the University of Tokyo conducted a study to explore how B. breve A1 might affect behaviour and physiological processes in mice with Alzeheimer's disease.
Bacterium versus Alzheimer's
They divided 10-week-old male mice into a control group, a B. breve A1 group, and an acetate group. The control group was given donepezil hydrochloride daily, while the other two groups received daily oral doses of B. breve A1 and sodium acetate, respectively.
The mice were then injected with amyloid-β (Aβ) to induce cognitive dysfunction (Aβ is the main component of senile plaques associated with Alzheimer's disease). They were then subject to a Y maze test six days later.
The researchers subsequently found that "administration of B. breve A1 to AD mice reversed the impairment of alternation behaviour in a Y maze test and the reduced latency time in a passive avoidance test, indicating that it prevented cognitive dysfunction".
They also observed through gene profiling analysis that oral intake of B. breve A1 restricted Aβ-induced inflammation and immune-reactive genes in the hippocampus.
In fact, almost all the differentially expressed genes found in the Aβ-injected mice were later normally expressed in the hippocampus of the mice that had been administered B. breve A1.
This led the researchers to state that B. breve A1 intake "suppressed the toxicity induced by Aβ and normalised the gene expression profile".
Furthermore, the expression of brain-derived neurotrophic factor (BDNF), a protein that plays a vital part in learning and memory processes, was shown to be up-regulated to normal levels in the B. breve A1 group.
Based on the results, the researchers hypothesised that B. breve A1 administration prevented cognitive decline by modulating immune response and neuronal inflammation in the mice.
They concluded: "Oral administration of B. breve A1 to AD model mice not only improved cognitive dysfunction but also suppressed the expression of inflammation and immune-reactive genes induced by Aβ.
"These results suggest (the) therapeutic potential of B. breve A1 for preventing cognitive impairment in AD."
Source: Scientific Reports
"Therapeutic potential of Bifdobacterium breve strain A1 for preventing cognitive impairment in Alzheimer's disease"
Authors: Yodai Kobayashi, et al.