The Salivary Metabolome in Periodontitis and Health

Objectives: Saliva is a complex biological fluid whose composition can reflect the health and disease status of the oral cavity at the molecular level. Periodontitis is destructive disease of the supporting tissues of the teeth, initiated by a pathogenic biofilm and if left untreated leads to tooth loss. Understanding the molecular processes of the disease is vital to the development of better diagnostic and treatment strategies. Our objective was to determine alterations within the saliva metabolome associated with periodontitis.
Methods: Stimulated saliva was collected from 20 individuals: periodontally healthy volunteers (n=10) and volunteers with periodontitis (n=10) and immediately frozen (-80^oC). Saliva samples were defrosted and extracted applying protein precipitation with methanol and subsequent centrifugation. The supernatant was analysed by applying Ultra Performance Liquid Chromatography-Mass Spectrometry (Ultimate3000 UPLC, FT Ultra MS; Thermo Scientific). Relative concentration differences were determined by univariate (Mann Whitney U test) and multivariate (PCA, PLS-DA) analyses and metabolites were annotated by comparison of m/z to reference libraries.
Results: After removal of outliers, nine healthy versus nine periodontitis volunteers were analysed. 370 unique metabolites were shown to be statistically significantly different between groups (FDR<0.005) and robust PLS-DA models were constructed (R² >0.95 and Q² > 0.80). Changes were observed in sugars, organic acids and fatty acids.
Conclusions: The data shows that multiple metabolite classes are associated with periodontitis including sugars, organic acids and fatty acids, acyl glycerides and glycerophospholipids. Novel biological pathways appear active during periodontitis and may have diagnostic utility.