New findings link the activity of the gut and liver to Alzheimer’s risk

24 July 2018

Four new studies being presented at the Alzheimer’s Association International Conference (AAIC) 2018 in Chicago today (Tuesday 24 July) have highlighted a link between the action of the gut and liver, and brain changes associated with Alzheimer’s disease.

  • Fat production in the liver and the link to Alzheimer’s risk
  • Bile acid levels associated with key Alzheimer’s brain changes
  • Liver and gut activity and Alzheimer’s risk genes
  • Circulating fats and their link to the brain

Dr David Reynolds, Chief Scientific Officer at Alzheimer’s Research UK, said:
“The brain doesn’t operate in isolation from the rest of the body and there is growing evidence to suggest that gut bacteria and the way that our bodies process fats could have knock-on effects on our brain health.

“These new studies further support a link between certain digestive processes and Alzheimer’s, with findings pointing to an association with brain changes, genetics and symptoms of the disease.

“A better understanding of how the digestive system could affect the development of Alzheimer’s may help pave the way to new approaches for tackling the disease. People may be able to positively influence gut bacteria through a healthy diet and there is already some evidence to suggest that a Mediterranean-style diet that is high in healthy fats may help to support healthy brain ageing.

“As well as eating a healthy balanced diet, keeping physically and mentally active, not smoking,only drinking within government guidelines and keeping blood pressure and cholesterol in check, is currently the best advice to help reduce the risk of dementia.”

Fat production in the liver and the link to Alzheimer’s risk

Researchers from the Alzheimer’s Disease Metabolics Consortium identified an association between a reduced production of certain fats in the liver and an increased risk of Alzheimer’s disease. By measuring key fats in blood samples collected from over 1,700 people with and without Alzheimer’s disease, they found that reduced levels of fats known as plasmalogens were associated with impaired cognitive function and Alzheimer’s disease. These fats play an important role in helping to keep brain cells healthy and the researchers suggest that a reduced production of these fats in the liver resulted in lower levels in the brain.

Bile acid levels associated with key Alzheimer’s brain changes

Researchers investigated a link between Alzheimer’s risk and bile acids- a component of bile that aids the digestion of fats and oils. Bile acids can be produced in the liver or by bacteria in the gut. The team looked at indicators of 20 different types of bile acid to see if there was an association with Alzheimer’s brain changes.

The team found that relative levels of these different bile acids were linked to brain energy use, brain shrinkage, and levels of the hallmark Alzheimer’s proteins amyloid and tau in spinal fluid. The researchers suggest the processes controlling bile acid in the body may play a role in Alzheimer’s disease.

Liver and gut activity and Alzheimer’s risk genes

The third study investigated the link between genes associated with Alzheimer’s risk and markers of gut and liver function found in the blood. The researchers analysed blood samples from over 6,000 participants, testing for 26 genetic variants associated with Alzheimer’s risk and relating them to chemical compounds that are produced by the activity of the gut or liver and present in blood.

The researchers found that genetic variations in Alzheimer’s risk genes APOE and SORL1 were linked with lower levels of certain forms of cholesterol that may be important for the health and repair of brain cell membranes. Rarer Alzheimer’s risk genes, including TREM2, were linked to levels of two circulating bile acids. The researchers suggest that these liver and gut-derived markers may be involved in the development of Alzheimer’s disease.

Circulating fats and their link to the brain

US-based researchers are investigating how fats that are produced in the liver and the gut can influence brain function. Measuring the levels of over 400 different types of fats in blood samples from over 800 participants of the Alzheimer’s Disease Neuroimaging Initiative, they found that there were features of these circulating fats that were more common in people with Alzheimer’s disease. The researchers suggest that the profile of fats that circulate in the blood may one day be useful in supporting a diagnosis of Alzheimer’s and could point towards new targets for future drugs.