Age-related Changes Of AOPP In Saliva Of Healthy Adults

Objective:The blood levels of advanced oxidative protein products (AOPP), as a novel important protein product of oxidative stress, elevate in aging and age-related diseases. However, saliva AOPP levels in healthy humans have been unexplored. Saliva sampling, compared with blood, is non-invasive, convenient and pain-free. Therefore, it is significant to evaluate the feasibility of saliva AOPP levels testing.Methods:Spectrophotometric determination was performed to investigate AOPP concentrations in saliva and plasma of143healthy adults. We divided119(66F/53M) healthy adults into three groups, namely45young (20-44years old),43middle-aged (45-59years old), and31elderly (60-79years old), which is to assay age-and gender-related changes in saliva and plasma AOPP levels. Another collection of saliva from the remaining24subjects was stored at-20℃and-80℃. AOPP levels were assayed both immediately and after7,14,21and28days of storage, which is to evaluate the stability of saliva AOPP stored both at-20℃and-80℃.Results:We found the mean saliva and plasma AOPP levels of119subjects were7.51±3.20and28.31±5.53μmol/L (μM). An age-dependent increase was observed in both saliva and plasma AOPP levels. Compared with both saliva and plasma AOPP levels in the young and middle-aged ones, this increase was particularly significant in the elderly subjects. A significant positive correlation among age, saliva and plasma AOPP levels was observed. No gender-dependent difference was observed in either saliva or plasma AOPP levels during the aging process. Furthermore, AOPP levels in the24saliva samples showed no significant change at every successive determination during four weeks at-80℃, whereas those levels significantly increased after7days of storage at-20℃.Conclusion:These results indicate the feasibility to screen aging biochemical indicators using saliva AOPP as an alternative to blood AOPP. Saliva AOPP samples are suitable to be stored at-80℃.