Human saliva protein profile: Influence of food ingestion

- Salivary proteins (PRPs and statherin) do not vary significantly on different days.
- gPRPs and aPRPs vary throughout the day, mainly in the early afternoon.
- Circadian rhythms are relevant in the salivary proteins' amount throughout the day.
- Food ingestion influences the several salivary proteins differently.
- Feeding effect is more pronounced after a fasting period than after a short period.

Saliva is a mixture composed by the secretions of the major and minor salivary glands, together with the crevicular fluid, bacteria and cellular debris. Due to saliva being a complex and dynamic fluid, the protein profile may qualitatively vary under different conditions. So, in this work, the saliva protein composition on different days, throughout the day and in fasting and fed states was evaluated by high-performance liquid chromatography (HPLC) analysis. The results show that the saliva protein amount has the maximum peak at 2 p.m. and at this hour no differences on saliva protein composition were observed on different days. Nevertheless, gPRPs and aPRPs vary significantly throughout the day and after food ingestion in the early afternoon. However, feeding effect seems to be more pronounced in the morning after a fasting period. This fact suggests that besides the influence of food ingestion, saliva protein composition is also influenced by circadian rhythms. This work allows one to comprehend how the different families of salivary proteins (SP) may vary throughout the day and with the influence of food ingestion, which could be a helpful tool in several studies, such as, astringency perception and biological studies.