WASHINGTON, DC—Metabolomics analyses of saliva samples may discriminate between normal aging, mild cognitive impairment (MCI), and Alzheimer’s disease populations, according to research presented at the 2015 Alzheimer’s Association International Conference. In addition, the analyses may predict biomarker-cognition associations, said Shraddha Sapkota, MSc, a PhD student in the Neuroscience and Mental Health Institute at the University of Alberta in Canada.
To discover possible biomarker profiles that discriminate between the three clinical groups, Ms. Sapkota and her research colleagues collected salivary specimens, clinical classifications, and cognitive data from people in the normal aging, MCI, and Alzheimer’s disease groups in the Victoria Longitudinal Study.
The discovery sample (64% female) included 35 normal-aging subjects (mean age, 70), 25 MCI subjects (mean age, 70.4), and 22 Alzheimer’s disease subjects (mean age, 77.1). Validation samples—10 each for the normal aging and MCI groups and seven for the Alzheimer’s group—also were taken.
The investigators used the 13C/12C isotope dansylation labeling technique and liquid chromatography-mass spectrometry to identify metabolite biomarkers. They identified the top pool of discriminant metabolites using orthogonal partial least squares discriminant analyses and Variable Importance in Projection indices, Fold Change, and goodness of fit. Regression analyses determined biomarker-cognition associations for the top discriminative metabolites. The top six to 12 metabolites clearly discriminated the three groups.
Such noninvasive tests could advance early detection of Alzheimer’s disease risk in MCI and normal aging groups and help researchers understand mechanisms that lead to Alzheimer’s disease. Future longitudinal metabolomics analyses with larger sample sizes may permit prediction of status transitions.
“Saliva is easily obtained, safe, and affordable, and has promising potential for predicting and tracking cognitive decline, but we’re in the very early stages of this work and much more research is needed,” said Ms. Sapkota. “Equally important is the possibility of using saliva to find targets for treatment to address the metabolic component of Alzheimer’s, which is still not well understood.”
—Jake Remaly