Alzheimer’s disease and colorectal cancer: an unexpected link

Mice in a model of Alzheimer’s disease that were injected with carcinogenic agents were less likely to develop colorectal cancer.

Scientists claim to have found the first experimental evidence of an inverse relationship between colorectal cancer and Alzheimer’s disease

Epidemiologic researchers have observed that people with Alzheimer’s disease are less likely to develop many common cancers than the general population, and that people with certain cancers also have a lower risk of developing Alzheimer’s disease. These observations caught the attention of scientists, but there was no evidence as to why these links occurred. Now the study authors say they have found experimental evidence that supports an inverse relationship between Alzheimer’s disease and colorectal cancer.

Although the phenomenon has received increasing attention, “the underlying molecular mechanisms remain unclear,” Shunjiang Xu, a pathophysiologist at Hebei Medical University who led the study, wrote in the report. “That is why we conducted this study.”

The scientists initially injected mice with azoxymethane and sodium dextran sulfate, which are used to induce colorectal cancer in mice. As a result, the researchers found that rodents with cognitive impairment similar to Alzheimer’s disease were less likely to develop colorectal cancer than healthy mice. The researchers called this experimental evidence of an inverse relationship between the two diseases.

The scientists also noticed that mice used as a model of Alzheimer’s disease, which were transplanted with feces from healthy mice, lost a distinct protective effect against colorectal cancer. This result suggested that an imbalance in the gut microbiome may be the cause of this phenomenon.

Further analysis showed that mice with a model of Alzheimer’s disease and people with mild cognitive impairment had higher levels of bacteria belonging to the genus Prevotella than control groups. Patients with colorectal cancer had lower levels of bacteria of the genus Prevotella than people without cognitive impairment.

Healthy mice fed lipopolysaccharides from the outer membrane of Prevotella bacteria showed signs of cognitive decline. When these mice were given carcinogenic drugs, their tumors developed less frequently and were smaller than those in control mice. The authors hypothesized that lipopolysaccharides derived from the Prevotella bacterium may be responsible for both the development of cognitive decline and the development of resistance to intestinal inflammation in mice. This resistance may also prevent the development of colorectal cancer, the researchers wrote. They emphasized that further studies are needed to confirm the findings.

“There is an inverse correlation. But they haven’t made any coordinated effort to really study this at the molecular level,” said Donald Weaver, a chemistry technologist and clinical neuroscientist at the University of Toronto who was not involved in the work.

Weaver added that the work could provide useful information for scientists who want to target the microbiome for therapeutic purposes in the future.

“The last thing we want to do is develop methods to fight cancer that will essentially encourage dementia,” Weaver said. “A better understanding of the molecular intricacies of this inverse correlation will be essential to efforts to develop effective therapeutics in the future.”

Romodanov Neurosurgery Institute National Academy of Medical Sciences of Ukraine Ukraine,KyivLeave a request

Rambam Medical Center Israel,HaifaLeave a request

Vitality Medical & Research Center Ukraine,KyivLeave a request

Published: 18.09.2024

Updated: 18.09.2024

Medical author, Medical editor:

Stepan Yuk

Medical expert:

PhD. Olexandr Voznyak