New research has found that there is a genetic connection between Alzheimer's disease and gastrointestinal disorders like diverticulosis, gastroesophageal reflux disease, and irritable bowel syndrome (but not inflammatory bowel disease). While previous research has found evidence that dementia and especially Alzheimer's is linked to certain gastrointestinal tract (GIT) disorders, medications used to treat peptic ulcer disease (PUD), and the microbiome, this study has identified genes and pathways that are involved. The findings have been reported in Communications Biology.
This research also provides more support for the hypothesis that a bidirectional connection known as the gut-brain axis links gut function with the cognitive and emotional facets of the brain, said senior study author Professor Simon Laws, the Center for Precision Health director.
Right now, there are no treatments that can cure or reverse Alzheimer's, which is the most common form of dementia. As the world's population ages, more people are expected to be affected by the disorder, which already impacts about 55 million people.
This study was a genome-wide association study (GWAS), which looks for small changes in the genome that are linked to certain health conditions. In this work, data from about 400,000 people was included.
It showed that there is overlap in the genes that increase the risk of Alzheimer's and GIT disorders (such as ATG16L1, BRINP3, HLA-DRA, PDE4B, and SEMA3F). The study authors also suggested that certain pathways are influencing both sets of disorders, including some related to autoimmunity, lipid metabolism, and statin mechanisms.
The investigators found that abnormal cholesterol levels may be involved in both Alzheimer's disease (AD) and gut disorders.
"Looking at the genetic and biological characteristics common to AD and these gut disorders suggests a strong role for lipid metabolism, the immune system, and cholesterol-lowering medications," said first study author Dr. Emmanuel Adewuyi.
The researchers noted that abnormally high cholesterol levels in the brain have been associated with neurodegeneration that causes cognitive impairment.
"Whilst further study is needed into the shared mechanisms between the conditions, there is evidence high cholesterol can transfer into the central nervous system, resulting in abnormal cholesterol metabolism in the brain," Adewuyi explained.
Abnormal levels of lipids in the blood might also be exacerbated by a common gut microbe known as H. pylori. These findings show that disrupted lipid levels may play a role in Alzheimer's and gut disorders, added Adewuyi.
This work may open up treatment options for Alzheimer's as well. It may be possible to use statins, which lower cholesterol levels, as a therapy for gut disorders or Alzheimer's, for example.
"Evidence indicates statins have properties which help reduce inflammation, modulate immunity and protect the gut," noted Adewuyi. Diet could also be a way to treat gut disorders or Alzheimer's. More research will be necessary, however, the researchers cautioned.
Sources: Edith Cowan University, Communications Biology