Antibiotics may weaken Alzheimer's progression: study

Long-term treatment with antibiotics may weaken Alzheimer's disease progression through changes in the gut microbiome, scientists including one of Indian-origin have found.
Treatment with broad spectrum antibiotics in long term decreased levels of amyloid plaques, a hallmark of Alzheimer's disease, and activated inflammatory microglial cells in the brains of mice, researchers said.
The study by University of Chicago in the US also showed significant changes in the gut microbiome after antibiotic treatment, suggesting the composition and diversity of bacteria in the gut play an important role in regulating immune system activity that impacts progression of Alzheimer's disease.
"We're exploring very new territory in how the gut influences brain health," said Sangram Sisodia, professor at the University of Chicago.

"This is an area that people who work with neurodegenerative diseases are going to be increasingly interested in, because it could have an influence down the road on treatments," said Sisodia.
Two of the key features of Alzheimer's disease are the development of amyloidosis, accumulation of amyloid-beta (A-beta) peptides in the brain, and inflammation of the microglia, brain cells that perform immune system functions in the central nervous system.

Buildup of A-beta into plaques plays a central role in the onset of Alzheimer's, while the severity of neuro-inflammation is believed to influence the rate of cognitive decline from the disease.

For the study, researchers administered high doses of broad-spectrum antibiotics to mice over five to six months.
At the end of this period, genetic analysis of gut bacteria from the antibiotic-treated mice showed that while the total mass of microbes present was roughly the same as in controls, the diversity of the community changed dramatically.
The antibiotic-treated mice also showed more than a two-fold decrease in A-beta plaques compared to controls, and a significant elevation in the inflammatory state of microglia in the brain.
Levels of important signalling chemicals circulating in the blood were also elevated in the treated mice.

While the mechanisms linking these changes is unclear, the study points to the potential in further research on the gut microbiome's influence on the brain and nervous system.
"We don't propose that a long-term course of antibiotics is going to be a treatment - that's just absurd for a whole number of reasons," said Myles Minter, a postdoctoral scholar at University of Chicago.
"But what this study does is allow us to explore further, now that we're clearly changing the gut microbial population and have new bugs that are more prevalent in mice with altered amyloid deposition after antibiotics," said Minter.

The study was published in the journal Scientific Reports.