Antioxidant supplementation hinders the role of exercise training as a natural activator of SIRT1

Exercise training (ET) contrasts oxidative stress by activating the deacetylase SIRT1, a stress-sensor working to increase, when necessary, the endogenous antioxidant system. Other SIRT1 activators include polyphenols and vitamins whose antioxidant properties are well-known. Antioxidant supplements are used to improve athletes’ wellness and performance. However, they could blunt or even block ET-related benefits.

Two groups of middle-distance runners taking or not antioxidant supplements were compared with each other and with sedentary subjects to evaluate ET effects on mRNA and activity of SIRT1 and oxidative stress markers, and to investigate whether an exogenous source of antioxidants could interfere with such effects.

Twenty-five middle distance runners (MDR) and 14 sedentary controls (CTR) were enrolled. MDR assuming antioxidant supplements (240 mg vitamin C and 15 mg vitamin E, together with 861 mg sodium, 555 mg chlorine, 381 mg potassium, 66 mg magnesium) were indicated as MDR-S (n.12), MDR-noS indicated those not taking supplements (n.13). SIRT1 mRNA and activity were measured in PBMCs by a fluorimetric assay and RT-PCR, respectively. Total oxidative status (TOS), total antioxidant capacity (TEAC), and oxidative stress index (TOS/TEAC) were determined in plasma.

MDR showed higher levels of SIRT1 mRNA and activity than controls without reaching a statistical significance. SIRT1 activity was higher (p=0.019) in MDR-noS (1909±626) compared with MDR-S (1276±474). Similarly, SIRT1 mRNA was higher (p=0.03) in MDR-noS (0,006±0,002) compared with MDR-S (0,003±0,0005).

Regarding TOS, MDR-S showed the highest, while MDR-noS had the lowest value. MDR showed higher TEAC levels than CTR (2866±581 vs 2082±560, p=0.001) as well as MDR-S (2919±551) and MDR-noS (2784±643) (MDR-S vs CTR, p=0.008 and MDR-noS vs CTR, p=0.02). No difference was found between MDR-S and MDR-noS. The CTR had the OSI highest value than the other groups (MDR vs CTR, p=0.003; MDR-noS vs CTR, p=0.03; MDR-S vs CTR, p=0.01).

Systemic antioxidant activity was higher in middle-distance runners taking or not antioxidant supplements compared with that measured in sedentary controls. An antioxidant supplementation seems to hinder the role of ET as a natural activator of SIRT1.