A new genetic link confirmed

A genetic link between Alzheimer’s disease and intestinal disorders has been discovered. Credit: Edith Cowan University

The groundbreaking research that established the link between Alzheimer’s Disease and gut health may allow for earlier diagnosis and new treatment options.

People who have digestive problems may be at higher risk of getting Alzheimer’s disease (AD). The link between the two has been verified by a groundbreaking study from Edith Cowan University (ECU), which could also lead to early identification and new treatment options.

The most common form of dementia, AD robs people of their memory and ability to think. More than 82 million people are expected to be affected by it by 2030, costing US$2 trillion, and there is no known cure. It has been hypothesized in previous observational studies that there is a link between Alzheimer’s disease and gastrointestinal disorders, but until recently the mechanisms behind these links have remained unclear.

ECU’s Center for Precision Health recently added to our understanding of these relationships by confirming a genetic link between Alzheimer’s disease and several gut disorders. The research analyzed large genetic datasets on AD and other gut disorder studies, each including around 400,000 participants.

The study’s lead researcher, Dr Emmanuel Adewuyi, said it was the first comprehensive examination of the genetic link between AD and several gut disorders. Researchers have found that people with AD and gut disorders share genes, which is important for a number of reasons.

“The study provides new insight into the genetics behind the observed co-occurrence of Alzheimer’s disease and gut disorders,” Dr Adewuyi said.

“This improves our understanding of the causes of these conditions and identifies new targets to study to potentially detect the disease earlier and develop new treatments for both types of conditions.”

Center for Precision Health director and study supervisor Professor Simon Laws said that although the study did not conclude that gut disorders cause AD or vice versa, the results are extremely valuable.

“These findings provide further evidence supporting the concept of the ‘gut-brain’ axis, a bi-directional link between the cognitive and emotional centers of the brain and the functioning of the gut,” Professor Laws said.

Is cholesterol a key?

When researchers conducted further analysis of shared genetics, they discovered other important links between Alzheimer’s disease and gut disorders, such as the role cholesterol may play.

Dr Adewuyi said abnormal cholesterol levels are a risk for both Alzheimer’s and gut disorders.

“Examination of genetic and biological features common to AD and these intestinal disorders suggests an important role for lipid metabolism, the immune system and cholesterol-lowering drugs,” he said.

“Although further studies are needed on the mechanisms shared between the conditions, there is evidence that high cholesterol can be transferred to the central nervous system, leading to abnormal cholesterol metabolism in the brain.

“There is also evidence to suggest that abnormal blood lipids may be caused or worsened by gut bacteria (H.pylori), all of which support the potential role of abnormal lipids in AD and gut disorders.

“For example, high cholesterol in the brain has been linked to brain degeneration and consequent cognitive impairment.”

Hope for the future

The link to cholesterol could prove vital in the treatment of AD in the future.

Although there is currently no known cure, the study results suggest that cholesterol-lowering drugs (statins) may be therapeutically beneficial in the treatment of AD and bowel disorders.

“Evidence indicates that statins have properties that help reduce inflammation, modulate immunity and protect the gut,” Dr. Adewuyi said.

However, he said more studies were needed and patients should be assessed individually to determine if they would benefit from statin use. Research has also indicated that diet may play a role in the treatment and prevention of Alzheimer’s disease and intestinal disorders.

Reference: “Large-scale genome-wide cross-trait analysis reveals shared genetic architecture between Alzheimer’s disease and disorders of the gastrointestinal tract” by Emmanuel O. Adewuyi, Eleanor K. O’Brien, Dale R. Nyholt, Tenielle Porter, and Simon M. Lois, July 18, 2022, Communications Biology.
DOI: 10.1038/s42003-022-03607-2

The study was funded by the National Board of Health and Medical Research.

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