A type of bacteria typically found in the human gut may hold the key to retarding the development of Alzheimer's disease symptoms.
Scientists at the University of Chicago are exploring the potential of using long-term antibiotic treatment to alter the microbiome in the gut.
Research involving male mice has shown that such a therapy may help reduce inflammation and even slow amyloid plaque growth in the brain. Both of these are common signs of Alzheimer development in people.
However, it is important to note that another experiment involving female mice did not yield similar results.
Impact Of Gut Microbiome On Alzheimer Symptoms
The gastrointestinal tract is home to a collection of bacteria that are generally considered harmless. These microorganisms are known to influence the body's immune system, which is why they can affect the onset of different diseases, even those in the brain and other distant tissues.
Sangram S. Sisodia, director of University of Chicago's Center for Molecular Neurobiology, said there is recent evidence to suggest that gut bacteria may play a key role in the development of certain neurological conditions such as Alzheimer's disease, autism spectrum disorders, multiple sclerosis, and Parkinson's disease.
Alzheimer's, in particular, often begins with a buildup of amyloid plaques in the brain. It also triggers the production of immune cells called microglia, which the body uses to help expel the plaques from the organ. However, the activation of these cells may also worsen the impact of the degenerative disease by causing neuroinflammation.
People suffering from Alzheimer's disease have experienced changes in the microbiome of their gut. Meanwhile, in their experiment, Sisodia and his team observed how these intestinal bacteria can affect the onset of disease symptoms in mice.
By targeting these microorganisms using long-term antibiotic treatment, the researchers believe it may help retard the development of amyloid plaques and limit the activation of microglia cells. This was seen in rodents that had mutant proteins typically linked to Alzheimer's disease.
However, the team clarified that earlier studies showing the impact of gut microbiome on amyloid plaque buildup were only limited to a single strain of mice.
Long-Term Antibiotic Treatment In Mice
Sisodia and his colleagues focused their experiment on a different mouse model carrying Alzheimer's symptoms known as APPS1-21.
To observe the impact of antibiotics on the mice, the researchers subjected the animals to long-term treatment using a cocktail of drugs. While the medication helped reduce amyloid plaque buildup in male mice, no similar effects were observed among females.
The antibiotic treatment may have also altered microglia activation in male rodents. Instead of having cells that promote the degeneration of the brain, the animals had microglia that helped keep their brain healthy throughout the study.
The researchers later confirmed these observations by transplanting fecal matter from untreated mice into rodents that have undergone antibiotic treatment. This restored the mice's gut microbiome, resulting in an increase in the formation of amyloid plaque and the activation of microglia cells.
Sisodia and his team found out that long-term antibiotic treatment affected intestinal bacteria differently for male and female rodents. The procedure caused the immune system of female mice to increase its production of proinflammatory factors, which in turn may have impacted microglia activation.
"Our study shows that antibiotic-mediated perturbations of the gut microbiome have selective, sex-specific influences on amyloid plaque formation and microglial activity in the brain," Sisodia explained.
"We now want to investigate whether these outcomes can be attributed to changes in any particular type of bacteria."
The findings of the University of Chicago study are featured in the Journal of Experimental Medicine.