Researchers in China observed a lower incidence of colorectal cancer in mice with Alzheimer’s symptoms compared to model mice. However, when these mice were transplanted with feces from a healthy mouse, the incidence of cancer in the colon and rectum returned to normal.
The results indicate that Alzheimer’s symptoms are closely linked to the composition of the intestine. New evidence shows that some gut microbes can shape the immune system in ways that affect the brain.
Several previous studies in rodents have linked the gut microbiome to symptoms of Alzheimer’s disease.
In recent pioneering experiments, fecal transplants were found to transfer memory impairment problems from one rodent to another.
The new study further investigates the close connection between Alzheimer’s disease, the gut microbiome, and cancer.
Some recent studies have found that the risk of cancer in human Alzheimer’s patients was reduced by half. At the same time, the risk of developing Alzheimer’s disease in cancer patients was reduced by 35%. But no one really knows why this is, and colorectal cancer shows the strongest links to Alzheimer’s disease.
In a series of experiments at the First Hospital of Hebei Medical University in China, researchers found that mice with Alzheimer’s-like symptoms showed resistance to colon cancer when the disease was artificially induced.
Intestinal inflammation among these mice appeared to be suppressed. When a fecal transplant was transferred from a healthy, younger mouse to a mouse with Alzheimer’s-like symptoms, this repression was lifted.
To find out what microbes are present in the gut, the researchers sampled the microbes of their animal models and found several candidates, including a Gram-negative bacteria called Prevotella.
When mice were treated with Prevotella bacteria, the intestines produced fewer pro-inflammatory immune cells, even when the mouse was exposed to dangerous pathogens.
The researchers explain that the reduced inflammatory response may have occurred, in part, because the intestine was “More leaky“It is normal, which allows some microbial byproducts to enter the circulation more easily.
When mice were treated with compounds derived from Prevotella, the animals showed cognitive impairment and resistance to tumor development in the rectum and colon.
The researchers explain that several studies have shown that lipopolysaccharide (LPS) derived from the genus Prevotella is involved in inflammatory responses of the mucosal barrier.
For example, Prevotella bivia produces high concentrations of lipopolysaccharides. These may create a toxic environment that damages dopamine cells, which play a role in cognitive function and motor function.
A recent human clinical trial found evidence that fecal transplants, for example, can alleviate the motor symptoms of Parkinson’s disease, a disease closely linked to the degeneration of dopamine-releasing neurons.
“Since inflammation is a major component of the tumorigenesis process, the anticancer properties in mouse models of Alzheimer’s disease are likely due to tolerance to intestinal inflammation caused by several specific bacterial genera in the gut microbiome,” the study authors wrote.
The team concluded: “This is biological/experimental evidence that supports an inverse relationship between Alzheimer’s disease and colorectal cancer.”
Source: ScienceAlert
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2024-09-27 18:51:15
