Age-Related Variation of Syndecan-1 Levels in Saliva and Plasma of Healthy Individuals.

Background: Saliva contains various cells, proteins, and molecules, and it is emerging as a material for diagnosing various diseases. Syndecan-1 (SDC-1) is a member of cell surface heparan sulfate proteoglycans and is mainly expressed in epithelial cells and plasma cells. SDC-1 is known to be associated with various cancers and inflammatory response, but there are few studies related to the change of SDC-1 levels in the saliva and plasma of healthy individuals due to aging process.

Methods: The study was conducted on 61 females who were healthy without any metabolic diseases, systemic infection, and oral cavity lesions. The subjects were divided into two groups based on age. Those below 40 years were placed in Group I and those who were 40 years and above were placed in Group II. Saliva was collected according to the guideline and the salivary flow rate (SFR) was determined. SDC-1 levels in the plasma and saliva were measured using a commercially available sandwich ELISA method.

Results: Age was significantly different between Group I and II (28.0 ± 2.5 vs. 47.4 ± 5.5, p < 0.001). SFR also showed a significant difference between Group I and II [0.32 (0.13 - 0.39) vs. 0.25 (0.16 - 0.35) ng/mL, p = 0.003]. Salivary SDC-1 level in Group I was significantly higher than that in Group II (p < 0.001). In addition, plasma SDC-1 level in Group I was also higher than that in Group II (p < 0.001). SFR was not significantly correlated as age increased, but it showed a significant negative correlation with salivary SDC-1 (r = -0.607, p < 0.001) and plasma SDC-1 levels (r = -0.373, p = 0.003). Salivary SDC-1 level was significantly correlated with plasma SDC-1 level (r = 0.331, p = 0.012).

Conclusions: In the younger group, the SFR, salivary, and plasma SDC-1 levels were significantly higher than in the older group. Salivary and plasma SDC-1 showed significant negative correlation as age increased. Although this study was not conducted on a large scale, it might be thought to provide information on the age-related variation for salivary and plasma SDC-1 levels in the aging process.