Age-related Variations Of Three Aging Biomarkers In Saliva Of Healthy Adults

Background:Aging is defined as the degenerations which gradually reduce the level of fitness and the capacity to maintain homeostasis, simultaneously increasing the chance of death. The deteriorative alterations above mainly arise from the accumulation of oxidative damage to cells and tissues. The maintenance of homeostasis can be affected by the imbalance between ROS caused damages and antioxidant defenses, leading to age-related macromolecular structural damages, diseases, aging and death. Although the hypothesis above remained controversial, it was widely acknowledged that oxidative stress should be an important risk factor of aging and age-related diseases such as cancer, cardiovascular diseases, renal diseases, diabetes, Parkinson’s diseases and Alzheimer’s disease. Protein carbonyls as one of the most commonly used biomarkers of oxidative stress while sulfhydryl compounds and FRAP are widely utilized signs of antioxidant defenses. Oral health correlates with general health. But can oral health be related to diseases and aging? If useful data of saliva reflecting both oral and systemic health conditions could be unearthed, early detection of aging and diseases may be much easier and more convenient.Objective:To analyse age and gender factor on protein carbonyls, sulfhydryl compounds and FRAP concentration and study the relationship between saliva and plasma protein carbonyls, sulfhydryl compounds and FRAP concentration for further salivary clinical investigations.Materials and Methods:This cross-sectional study enrolled many Chinese healthy subjects who were divided into young group, middle-aged group and elderly group according to the standards of the United Nations World Health Organization. Saliva and plasma protein carbonyls, sulfhydryl compounds and FRAP concentration were detected.Results:Saliva protein carbonyls concentration was (2.391±0.639)nmol/mg and plasma protein carbonyls concentration was (0.838±0.274) nmol/mg. Sulfhydryl compounds content of saliva and plasma were respectively (122.914±27.246) and (427.189±124.140) μmol/L. Age factor had significantly positive effect on saliva and plasma protein carbonyls (r=0.6582 and r=0.5176, all P<0.01). Gender was discovered to be unrelated to saliva and plasma protein carbonyls levels (all P>0.05). Saliva protein carbonyls and plasma protein carbonyls were positively related (r=0.4405, P<0.01). Saliva and plasma protein carbonyls/FRAP ratios were proved to be more significantly correlated with age (r=0.7796 and r=0.6938, all P<0.01). Saliva protein carbonyls/FRAP ratio and plasma protein carbonyls/FRAP ratio were also better correlated (r=0.5573, P<0.01). Sulfhydryl compounds content of saliva and plasma were both significantly decreased with age (both P<0.01). Significant differences of sulfhydryl compounds content of saliva and plasma between young group, middle-aged group and elderly group were found (P<0.01). No gender-dependent difference was observed in saliva sulfhydryl compounds content (P=0.451) while the difference was significant in plasma sulfhydryl compounds content (P=0.006). There was a significantly positive correlation between sulfhydryl compounds content of saliva and plasma (r=0.5050, P<0.01).Conclusions:Saliva protein carbonyls and sulfhydryl compounds content can roughly reflect plasma protein carbonyls and sulfhydryl compounds content. Saliva protein carbonyls and sulfhydryl compounds test is a promising biological index of aging.