Studies reveal gut bacteria role in Alzheimer’s development

Gut health plays a significant role in the development of Alzheimer’s disease, multiple new studies have found.

Alzheimer’s is the leading cause of dementia, a condition which will likely affect one in three people in their lifetime.

The gut contains intestinal bacteria called intestinal microbiome, the make-up of which varies from person to person.

The composition of microbiome can have far reaching effects throughout the body, with emerging evidence linking it to brain health and the risk of Alzheimer’s.

Dr Edina Silajdžić, a postdoctoral fellow working in the research lab of Prof Sandrine Thuret from the Institute of Psychiatry, Psychology & Neuroscience (IoPPN) at King’s College London, said:

“Most people are surprised that their gut bacteria could have any bearing on the health of their brain, but the evidence is mounting, and we are building an understanding of how this comes about.

“Our gut bacteria can influence the level of inflammation in our bodies, and we know that inflammation is a key contributor to Alzheimer’s disease.”

The researchers analysed blood samples of 68 people with Alzheimer’s and a similar number of people without the disease.

The research revealed a “distinct gut bacteria makeup” among the participants with Alzheimer’s.

Silajdžić said:

“When we treated brain stem cells with blood from people with Alzheimer’s they were less able to grow new nerve cells than those treated with blood from people without memory problems.

“This leads us to believe that the inflammation associated with gut bacteria can affect the brain via the blood.”

In the second study, stool samples were taken from people with Alzheimer’s and without the disease and then implanted into rats.

The rats with gut bacteria from people with Alzheimer’s performed worse in memory tests, had higher levels of inflammation in the brain and didn’t grow as many nerve cells in areas of the brain linked to memory.

Prof Yvonne Nolan, who is leading this collaborative Centres of Excellence in Neurodegeneration (CoEN) project with partners in King’s College London and IRCCS, Italy said:

“Our findings suggest that symptoms of Alzheimer’s may, in part, be caused by abnormalities in the gastrointestinal tract.

“While it is currently proving difficult to directly tackle Alzheimer’s processes in the brain, the gut potentially represents an alternative target that may be easier to influence with drugs or diet changes.”

Dr Susan Kohlhaas, Director of Research at Alzheimer’s Research UK said:

“Taking these results together reveals differences in the makeup of gut bacteria between people with and without dementia and suggest that the microbiome may be driving changes linked to Alzheimer’s disease.

“Future research will need to build on these findings so that we can understand how gut health fits in to the wider picture of genetic and lifestyle factors that impact a person’s dementia risk.”