Systemic and Oral Markers of Probable Alzheimer’s Disease

Purpose: The diagnosis of probable Alzheimer’s Disease (AD) is obtained by psychiatric testing and brain imaging, and can only be confirmed post mortem. We tested the hypothesis that the concentrations of certain factors potentially involved in the pathogenesis of AD, including the b-amyloid (Ab) protein, pro-inflammatory cytokines and markers of apoptosis, are elevated in the plasma and the saliva of subjects with probable AD compared to controls. Method: Subjects with probable AD and age-matched control subjects were recruited at the UCLA Alzheimer’s clinic. AD status was established by the standard battery of psychiatric assessments (e.g., minimental). Plasma and saliva levels of Ab, soluble Fas Ligand (sFasL) and Annexin, and of pro-inflammatory cytokines (IL-1b, TNF-a, IL-6) were tested by commercial ELISA. Results: Results show that plasma levels of TNF-a were significantly elevated in subjects with probable AD, compared to control subjects. Trends suggest that plasma concentrations of Ab protein and of IL-1b, as well as salivary levels of Ab protein, IL-1b, TNF-a and IL-6, as well as sFasL and Annexin were elevated, albeit not statistically significantly, in subjects with probable AD subjects. We present power analyses that provide realistic estimates of the sample sizes required to obtain statistical significance. Plasma and salivary levels of these markers showed no correlation. Conclusion: Taken together, these preliminary findings suggest that the markers tested here in plasma and total saliva could serve as confirmatory indicators for the early diagnosis of probable AD.