Key points
- Researchers analysed medical images to link changes in the structure of the brain to cognitive function and the progression of Alzheimer’s disease.
- They focused on the area of the brain that produces acetylcholine, a messenger chemical involved in cognitive function that is decreased in Alzheimer’s disease.
- Their findings provide a novel method to detect early changes in Alzheimer’s before cognitive symptoms appear and inform treatment.
Alzheimer’s disease affects up to one in 10 Australians over the age of 65. The disease is devastating for patients and their loved ones, and there is currently no cure.
Thankfully, new drugs to treat Alzheimer’s are close to being approved in Australia. These will bolster a growing arsenal of treatments that slow disease progression and improve quality of life.
The latest drugs target amyloid plaques, clumps of protein that build up in the brain in Alzheimer’s.
Ying Xia is a researcher with our Australian e-Health Research Centre (AEHRC). She said while this news is promising, we haven’t yet won the fight against Alzheimer’s.
"Alzheimer’s research has come a long way, but we still don’t have a complete picture of the disease," Ying said.
“We need that big picture if we want to offer treatment that’s personalised and effective.”
Ying and her team are investigating a different but related aspect of Alzheimer’s. They are exploring the disruption of signal transmission in the brain, which leads to cognitive symptoms.
Existing drugs that improve cognition, which can be used alone or in combination with new drugs targeting amyloid plaque build-up, may prove to be a winning formula and offer benefits to a wider range of patients.
Acetylcholine in Alzheimer’s
The brain relies on messenger molecules called neurotransmitters to communicate within itself and the rest of the body.
The neurotransmitter acetylcholine is involved in memory and attention, two aspects of cognition severely affected in Alzheimer’s. The cholinergic system, is the brain's messaging system. It is vital to memory and cognition functions and relies on acetylcholine.
"Low levels of acetylcholine in the brain have been linked with Alzheimer’s. Drugs that target the cholinergic system by increasing levels of acetylcholine have been used for some time," Ying said.
But cholinergic drugs are only effective in 30-35 per cent of cases. Ying and her team are determined to improve that figure.
"We need to understand the cholinergic system better so that we can identify who will benefit from this type of treatment and when the drug will have the most effect," she said.
Cognition and the cholinergic system
Ying's team recently published a study on the links between Alzheimer's disease, brain function, and the state of the cholinergic system.
They used artificial intelligence methods to analyse magnetic resonance imaging (MRI) brain scans of participants in the Australian Imaging, Biomarkers and Lifestyle (AIBL) study of ageing.
"We’re interested in differences in the basal forebrain, the area of the brain responsible for producing acetylcholine," Ying said.
They compared information from the scans to data on people’s cognitive state, ranging from unimpaired to mildly impaired, and the level of amyloid plaques in the brain.
"We found that the build-up of amyloid plaques is associated with shrinkage of the basal forebrain," Ying said.
Interestingly, changes to the acetylcholine-producing region of the brain seem to occur well before cognitive symptoms of Alzheimer’s appear.
"Diagnosing Alzheimer’s early is critical to treating the disease and slowing progression. Our findings offer a method to potentially detect the disease earlier," she said.
Targeted treatment of Alzheimer’s disease
Their findings are important pieces of the puzzle of using cholinergic drugs effectively and increasing the percentage of patients that benefit.
"We can use advanced imaging techniques to identify decline of the cholinergic system in patients that don’t yet have cognitive symptoms. It may be the case that if we can give the drugs early enough, we can slow the progression of cognitive decline," Ying said.
Unfortunately, not all patients will benefit from cholinergic drugs, and this may be because they are administered too late in the disease progression.
"If somebody is experiencing cognitive symptoms but there are no signs of cholinergic degeneration, it tells us that their cognitive symptoms are likely due to a different kind of dysfunction,” Ying said.
"And if someone is diagnosed too late, their cholinergic system may be too damaged to respond effectively to the treatment.
"This knowledge is important, so we can avoid giving the drugs when there’s likely to be no benefit and prevent people from experiencing unnecessary side effects."
The goal is to use these existing drugs more effectively alongside new treatments to improve quality of life for Australians with Alzheimer’s disease.