Effect of Masticatory Stimulation on Salivary Metabolomic Profile

Objectives: This study characterized the changes in quality and quantity of saliva by analyzing metabolomic profiles, to understand the effects of masticatory stimulation.
Methods: This study was approved by the Ethics Committee of Kanagawa Dental University (no. 243). Both stimulated and unstimulated saliva samples were collected from 55 subjects and salivary hydrophilic metabolites were comprehensively quantified using capillary electrophoresis-mass spectrometry.
Results: Totally, 137 metabolites were identified and quantified. The concentrations of 44 metabolites in stimulated saliva were significantly higher than those in unstimulated saliva. Pathway analysis identified the upregulation of the urea cycle and synthesis and degradation pathways of glycine, serine, cysteine and threonine in stimulated saliva. A principal component analysis revealed that the effect of masticatory stimulation on salivary metabolomic profiles was less dependent on sample population sex, age, and smoking. The concentrations of only 1 metabolite in unstimulated saliva, and of 3 metabolites stimulated saliva while the rest showed no correlation with salivary secretion volume, indicating that the salivary metabolomic profile and salivary secretion volume were independent feature.
Conclusions: Masticatory stimulation affected salivary secretion volume as well as metabolite concentration patterns. A low correlation between the secretion volume and metabolite patterns, suggesting that the salivary metabolomic profile may be a new indicator to characterize masticatory stimulation.