Previous studies on mice have already shown that inflammation may be transmitted to younger individuals through gut microbiota. This has established a connection between the digestive system and brain health.
Now, researchers have confirmed this theory in humans, demonstrating that intestinal inflammation could help trigger that link. “We found that individuals with Alzheimer’s disease exhibit more pronounced intestinal inflammation. When we analyzed their neuroimaging data, those with greater intestinal inflammation showed an accumulation of amyloid plaques in the brain,” said Professor Barbara Bendlin of the University of Wisconsin.
The team conducted an analysis of fecal calprotectin (a marker of inflammation) collected from 125 individuals participating in cohort studies aimed at preventing Alzheimer’s disease.
Participants underwent several cognitive tests, interviews about family history, and genetic testing for a gene associated with increased Alzheimer’s risk. Some participants also had clinical scans to check for amyloid protein accumulations, a common sign of neurodegenerative pathology.
While calprotectin levels were generally higher in older patients, this marker was most pronounced in those with the characteristic amyloid plaques associated with Alzheimer’s disease.
Science Alert reported that levels of other Alzheimer’s biomarkers also increased as inflammation progressed.
Even participants without an Alzheimer’s diagnosis showed poorer memory performance when calprotectin levels were higher.
Preliminary laboratory analyses indicated that chemicals released by gut bacteria may stimulate inflammatory signals in the brain.
The authors of the new study suggested that changes in the microbiome trigger processes in the gut that lead to systemic inflammation. That inflammation is moderate but chronic, causing gradual, subtle damage that can compromise the body’s barrier function.
“Increased intestinal permeability can lead to elevated levels of inflammatory molecules and toxins in the bloodstream, which originate from the gut lumen; this will cause systemic inflammation, which in turn can disrupt the blood-brain barrier and contribute to neuroinflammation, potentially leading to nerve tissue damage and neurodegeneration,” stated co-author Federico Rey.
Researchers are now conducting experiments on rodents to determine whether dietary changes that promote inflammation can trigger the development of Alzheimer’s.
This research matters especially because effective treatments for the millions of people worldwide who suffer from Alzheimer’s disease are still lacking.
The study’s findings were published in the journal Scientific Reports.
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