An enzyme found in the fluid around the brain and spine is giving researchers a snapshot of what happens inside the minds of Alzheimer’s patients and how that relates to cognitive decline.
Iowa State University researchers say higher levels of the enzyme, autotaxin, significantly predict memory impairment and Type 2 diabetes. Autotaxin often studied in cancer research, is an even stronger indicator of Type 2 diabetes. A single point increase reflects a 300 percent greater likelihood of having the disease or pre-diabetes. The results are published in the Journal of Alzheimer’s Disease. Willette and Kelsey McLimans, a graduate research assistant, say the discovery is important because of autotaxin’s proximity to the brain.
“We’ve been looking for metabolic biomarkers which are closer to the brain. We’re also looking for markers that reliably scale up with the disease and have consistently higher levels across the Alzheimer’s spectrum,” said Auriel Willette, an assistant professor of food science and human nutrition at Iowa State. “This is as directly inside of the brain as we can get without taking a tissue biopsy.”
Willette’s previous research found a strong association between insulin resistance and memory decline and detrimental brain outcomes, increasing the risk for Alzheimer’s disease. Insulin resistance is a good indicator, but Willette says it has limitations because what happens in the body does not consistently translate to what happens in the brain. That is why the correlation with this new enzyme found in the cerebrospinal fluid is so important.
“It has a higher predictive rate for having Alzheimer’s disease,” McLimans said. “We also found correlations with worse memory function, brain volume loss and the brain using less blood sugar, which has also been shown with insulin resistance, but autotaxin has a higher predictive value.”
The fact that autotaxin is a strong predictor of Type 2 diabetes and memory decline emphasizes the importance of good physical health. Researchers say people with higher levels of autotaxin are more likely to be obese, which often causes an increase in insulin resistance. Willette says autotaxin levels can determine the amount of energy the brain is using in areas affected by Alzheimer’s disease. People with higher autotaxin levels had fewer and smaller brain cells in the frontal and temporal lobes, areas of the brain associated with memory and executive function. As a result, they had lower scores for memory and tests related to reasoning and multitasking.
Researchers analyzed data from 287 adults collected through the Alzheimer’s Disease Neuroimaging Initiative, a public-private partnership working to determine whether MRI and PET scans as well as biological markers can measure the progression of cognitive impairment and Alzheimer’s disease. The data came from adults ranging in age from 56 to 89 years old. Study participants completed various tests to measure cognitive function. This included repeating a list of words over various time increments.
Citation: McLimans, Kelsey E. and Auriel A. Willette. “Autotaxin is Related to Metabolic Dysfunction and Predicts Alzheimer’s Disease Outcomes”. Journal of Alzheimer’s Disease Volume 56, Number 1.
Research funding: Iowa State Presidential Initiative for Interdisciplinary Research and National Institutes of Health.
Adapted from press release by Iowa State University.