Salivary proteome profile of women during fertile phase of menstrual cycle as characterized by mass spectrometry

Background: Human saliva contains several biomolecules, especially proteins, some of which have been found to serve as biomarkers of different physiological statuses and/or pathological conditions. Saliva is a much superior biological material for investigation over the other body fluids. Ovulation is such a critical physiological process that its non-invasive detection based on salivary protein biomarkers has several advantages in the human. Therefore, it was hypothesized that saliva would potentially contain non-invasive predictor(s)/detector(s) of ovulation. Methods: Samples were collected from women volunteers. The procedure adopted was approved by the Institutional Ethical Committee (DM/2014/101/38), Bharathidasan University. The saliva samples were collected between 8.00 to 9.00 AM from 30 healthy female volunteers (age, mean = 24, range = 19 - 30), with a prior written consent. The protein expression pattern during different phases of menstrual cycle was analyzed using gel-based HR-LC-MS/MS and MALDI TOF/TOF. Results: As many as 530 proteins showed up in the saliva during ovulation phase whereas there were only 251 proteins during post-ovulation phase. The functional annotation of salivary proteins revealed that the proteins got assigned to the class of “extracellular proteins” which are concerned with regulatory functions. The 16 unique/differentially expressed protein spots appeared during ovulation phase, among which Cystatin-S, Prolactin-inducible protein, Cystatin-A, Cystatin-SN, BPI fold-containing family A member 2, Alpha-tubulin N-acetyltransferase 1, Carbonic anhydrase-6, Protein LEG1 homolog, Hemoglobin subunit beta, Pancreatic alpha-amylase were identified. Conclusions: These ten proteins that were highly expressed during ovulation phase would serve as indicator(s) of ovulation, but extensive validation is required before arriving at a conclusion.