Link Between Gut Inflammation and Alzheimer’s Disease Reconfirmed

Researchers are piecing together the complex relationship between gut health and Alzheimer’s disease, revealing yet another connection between our digestive system and brain function. Animal studies have shown that gut microbes can transmit Alzheimer’s to young mice, reinforcing this link.

Furthermore, a 2023 study supports the idea that inflammation may be the mechanism behind this connection. “We found that individuals with the disease experience more gut inflammation,” said University of Wisconsin psychologist Barbara Bendlin. She noted that higher gut inflammation correlates with increased amyloid plaque accumulation in the brains of Alzheimer’s patients.

Led by University of Wisconsin pathologist Margo Heston, an international team tested for fecal calprotectin, an inflammation marker, in stool samples from 125 participants in two Alzheimer’s prevention studies.

Participants completed cognitive tests and provided family histories, along with tests for a high-risk Alzheimer’s gene. The study revealed that while older patients generally had higher calprotectin levels, those with amyloid plaques showed even more pronounced inflammation, highlighting its potential role in Alzheimer’s pathology.

Link Between Inflammation and Alzheimer’s

Researchers found that higher inflammation levels correlated with increased Alzheimer’s biomarkers, while memory test scores declined alongside rising calprotectin levels. Notably, even participants without an Alzheimer’s diagnosis exhibited poorer memory performance with elevated calprotectin.

However, Heston cautioned, “We can’t infer causality from this study; for that, we need to conduct animal studies.” Previous laboratory analyses have indicated that gut bacteria can trigger inflammatory signals in the brain, and other studies have confirmed greater gut inflammation in Alzheimer’s patients compared to controls.

Heston and her team propose that changes in the microbiome lead to gut alterations, resulting in mild but chronic systemic inflammation. This ongoing inflammation may gradually weaken the body’s barriers. “Increased gut permeability could raise blood levels of inflammatory molecules and toxins from the gut, leading to systemic inflammation that may impair the blood-brain barrier and promote neuroinflammation, potentially resulting in neural injury and neurodegeneration,” explained University of Wisconsin bacteriologist Federico Rey.

Currently, the researchers are testing mice to determine if diet-induced inflammation can trigger the rodent equivalent of Alzheimer’s. Despite decades of research yielding no effective treatment for the millions affected this disease, scientists are gradually advancing their understanding of the biological processes involved.

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