Abstract
As the first step to discover protein disease biomarkers from saliva, global analyses of the saliva proteome have been carried out since the early 2000s, and more than 3,000 proteins have been identified in human saliva. Recently, ethnic differences in the human plasma proteome have been reported, but such corresponding studies on human saliva in this aspect have not been previously reported. Thus, here, in order to determine ethnic differences in the human saliva proteome, a Korean whole saliva (WS) proteome catalogue indexing 480 proteins was built and characterized through nLC-Q-IMS-TOF analyses of WS samples collected from eleven healthy South Korean male adult volunteers for the first time. Identification of 226 distinct Korean WS proteins, not observed in the integrated human saliva protein dataset, and significant gene ontology distribution differences in the Korean WS proteome compared to the integrated human saliva proteome strongly support ethnic differences in the human saliva proteome. Additionally, the potential value of ethnicity-specific human saliva proteins as biomarkers for diseases highly prevalent in that ethnic group was confirmed by finding 35 distinct Korean WS proteins likely to be associated with the top 10 deadliest diseases in South Korea. Finally, the present Korean WS protein list can serve as the first level reference for future proteomic studies including disease biomarker studies on Korean saliva.
Highlights
Saliva is secreted from salivary glands, including three major glands and minor glands
In order to enhance the credibility of protein identification results, the following criteria were set: 1) any identification derived from only one unique peptide was rejected, 2) FDR was kept at no more than 1%, 3) only protein identification with at least 95% probability from ProteinLynx Global Server (PLGS) results were accepted, and 4) all results which passed the above criteria were verified manually
Over-representation of protein metabolic and catalytic activity categories in the Korean whole saliva (WS) proteome compared with the integrated human saliva proteome may be consistent with its larger portion of proteins with molecular weight of less than 60 kDa (82.3%, Fig 1A), partially resulting from the cleavage of higher-molecular-weight proteins, than that of Yan et al.’s report (68%) [1]. In line with these findings, our results suggest another clue to discover ethnic differences in the human saliva proteome and the possibility of using such difference for early diagnosis and/or prognosis of diseases
Summary
Saliva is secreted from salivary glands, including three major glands (parotid, submandibular, sublingual glands) and minor glands. It maintains oral cavity homeostasis, lubricates oral tissues, promotes chewing, swallowing, digestion, and speaking, and protects the oral cavity against microorganisms [1,2,3,4]. It is composed of water, proteins, peptides, lipids, other small molecules, and minerals. Healthy adults are known to produce 500–1500 mL of saliva daily at a rate of about 0.5 mL/min [1, 4].
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