Effect of Aging on the Oral Fluids Proteome among Males

Recently interest in finding disease bio-markers exploring human body fluids has increased tremendously. In order to establish a clinical diagnostic tool based on oral fluids, the physiologic differences in salivary proteins according to age should be investigated. Objectives: To identify differences in salivary protein expression according to age. Methods: Unstimulated oral fluids samples were collected from 8 healthy male volunteers, 4 young (ages between 22y and 26y) and 4 old (ages between 78y and 88y). Proteins were extracted and separated by 2-D SDS-PAGE using pH range of 3-10 followed by 9.5-16.5% gradient gel. Gels were stained by ammonical silver stain and digitalized. Protein spots were processed using PDQuest software (BioRad, USA). Selected protein spots were excised from gel and were analyzed by electrospray ionization - tandem mass spectrometry (ESI-MS/MS). Obtained data were searched against the NCBI non-redundant protein database using Mascot software (Matrix-Science, USA). Results: Fifty-one proteins in 37 protein spots were identified by ESI-MS/MS of which 5 proteins demonstrated significant lower expression in elders compared to young subjects. Two of these proteins - polymeric Ig receptor and prolactin induced protein were suggested previously to be decreased with age. Conclusion: Our work demonstrates physiological protein composition differences according to age within the oral fluids of healthy male subjects. We found the proteomic analysis of oral fluids to be sensitive to the detection of expression differences; this may be relevant in searching for crucial salivary biomarkers in diseases of the elderly.