Dysfunction of Salivary Glands, Disturbances in Salivary Antioxidants and Increased Oxidative Damage in Saliva of Overweight and Obese Adolescents

Abstract

Obesity is inseparably connected with oxidative stress. This process may disturb the functioning of the oral cavity, although the effect of oxidative stress on salivary gland function and changes in the qualitative composition of saliva are still unknown. Our study is the first to evaluate salivary redox homeostasis in 40 overweight and obese adolescents and in the age- and gender-matched control group. We demonstrated strengthening of the antioxidant barrier (superoxide dismutase, catalase, peroxidase, uric acid, total antioxidant capacity (TAC)) with a simultaneous decrease in reduced glutathione concentration in saliva (non-stimulated/stimulated) in overweight and obese teenagers compared to the controls. The concentration of the products of oxidative damage to proteins (advanced glycation end products), lipids (malondialdehyde, 4-hydroxynonenal) and DNA (8-hydroxydeoxyguanosine) as well as total oxidative status were significantly higher in both non-stimulated and stimulated saliva as well as plasma of overweight and obese adolescents. Importantly, we observed more severe salivary and plasma redox alterations in obese adolescents compared to overweight individuals. In the study group, we also noted a drop in stimulated salivary secretion and a decrease in total protein content. Interestingly, dysfunction of parotid glands in overweight and obese teenagers intensified with the increase of BMI. We also showed that the measurement of salivary catalase and TAC could be used to assess the central antioxidant status of overweight and obese adolescents.

Keywords: antioxidants; obesity; oxidative stress; saliva; salivary biomarkers.

Figure 1

Scatter plots for BMI and non-stimulated and stimulated salivary flow rate in healthy children (A) as well as overweight and obese adolescents (B). BMI- body mass index; NWS- non-stimulated whole saliva; SWS- stimulated whole saliva.

Figure 2

Enzymatic antioxidants in overweight and obese adolescents as well as healthy controls. C- control, CAT- catalase, NWS- non-stimulated whole saliva, OB- obese, OWT- overweight, Px- salivary peroxidase, SOD- superoxide dismutase, SWS- stimulated whole saliva. Differences statistically significant at: * p < 0.05, ** p < 0.005, *** p < 0.0005.

Figure 3

Non-enzymatic antioxidants in overweight and obese adolescents as well as healthy controls. C- control, GSH- reduced glutathione, NWS- non-stimulated whole saliva, OB- obese, OWT- overweight, SWS- stimulated whole saliva, UA- uric acid. Differences statistically significant at: ** p < 0.005, *** p < 0.0005.

Figure 4

Redox status in overweight and obese adolescents as well as healthy controls. C- control, NWS- non-stimulated whole saliva, OB- obese, OSI- oxidative stress index, OWT- overweight, SWS- stimulated whole saliva, TAC- total antioxidant capacity, TOS- total oxidative status. Differences statistically significant at: * p < 0.05, ** p < 0.005, *** p < 0.0005.

Figure 5

Protein, lipid, and DNA oxidation products in overweight and obese adolescents as well as healthy controls. AGE- advanced glycation end products, C- control, MDA- malondialdehyde, NWS- non-stimulated whole saliva, OB- obese, OWT- overweight, SWS- stimulated whole saliva, 4-HNE- 4-hydroxynoneal protein adduct, 8-OHdG- 8-hydroxy-D-guanosine. Differences statistically significant at: ** p < 0.005, *** p < 0.0005.

Figure 6

Area under the curve (AUC) of selected redox biomarkers in overweight and obese children. AGE- advanced glycation end products, CAT- catalase, GSH- reduced glutathione, NWS- non-stimulated whole saliva, OSI- oxidative stress index, SOD- superoxide dismutase, SWS- stimulated whole saliva, TOS- total oxidative status, UA- uric acid, 4-HNE- 4-hydroxynoneal protein adduct,.

Figure 7

Saliva–blood correlations of the analyzed redox biomarkers in healthy controls (A) as well as overweight and obese adolescents (B). CAT- catalase, NWS- non-stimulated whole saliva, SWS- stimulated whole saliva, TAC- total antioxidant capacity, UA- uric acid.

Figure 8

Correlations between BMI and salivary antioxidants in healthy children (A) as well as overweight and obese adolescents (B). BMI- body mass index, CAT- catalase, GSH- reduced glutathione, NWS- non-stimulated whole saliva, Px- salivary peroxidase, SOD- superoxide dismutase, SWS- stimulated whole saliva, TAC- total antioxidant capacity, UA- uric acid.

Figure 9

Correlations between BMI and salivary oxidative damage in healthy children (A) as well as overweight and obese adolescents (B). BMI- body mass index, AGE- advanced glycation end products, MDA- malondialdehyde, NWS- non-stimulated whole saliva, OSI- oxidative stress index, SWS- stimulated whole saliva, TOS- total oxidative status, 4-HNE- 4-hydroxynoneal protein adduct, 8-OHdG- 8-hydroxy-D-guanosine.