Oxidative stress in patients with type 1 diabetes mellitus: is it affected by a single bout of prolonged exercise?

Abstract

Presently, no clear-cut guidelines are available to suggest the more appropriate physical activity for patients with type 1 diabetes mellitus due to paucity of experimental data obtained under patients' usual life conditions. Accordingly, we explored the oxidative stress levels associated with a prolonged moderate intensity, but fatiguing, exercise performed under usual therapy in patients with type 1 diabetes mellitus and matched healthy controls. Eight patients (4 men, 4 women; 49±11 years; Body Mass Index 25.0±3.2 kg·m(-2); HbA1c 57±10 mmol·mol(-1)) and 14 controls (8 men, 6 women; 47±11 years; Body Mass Index 24.3±3.3 kg·m(-2)) performed a 3-h walk at 30% of their heart rate reserve. Venous blood samples were obtained before and at the end of the exercise for clinical chemistry analysis and antioxidant capacity. Capillary blood samples were taken at the start and thereafter every 30 min to determine lipid peroxidation. Patients showed higher oxidative stress values as compared to controls (95.9±9.7 vs. 74.1±12.2 mg·L(-1) H2O2; p<0.001). In both groups, oxidative stress remained constant throughout the exercise (p = NS), while oxidative defence increased significantly at the end of exercise (p<0.02) from 1.16±0.13 to 1.19±0.10 mmol·L(-1) Trolox in patients and from 1.09±0.21 to 1.22±0.14 mmol·L(-1) Trolox in controls, without any significant difference between the two groups. Oxidative stress was positively correlated to HbA1c (p<0.005) and negatively related with uric acid (p<0.005). In conclusion, we were the first to evaluate the oxidative stress in patients with type 1 diabetes exercising under their usual life conditions (i.e. usual therapy and diet). Specifically, we found that the oxidative stress was not exacerbated due to a single bout of prolonged moderate intensity aerobic exercise, a condition simulating several outdoor leisure time physical activities. Oxidative defence increased in both patients and controls, suggesting beneficial effects of prolonged aerobic fatiguing exercise.

Conflict of interest statement

Competing Interests: Part of this study was funded by unconditional financial support from Bayer Italia S.p.A. (Italy). There are no patents, products in development or marketed products to declare. This does not alter the authors' adherence to all the PLOS ONE policies on sharing data and materials, as detailed online in the guide for authors.

Figures

Figure 1. Glycemia and insulin concentration before and at the end of the 3-h exercises.

Panel A. Glycemia (mmol·L−1) was significantly higher in patients both before and at the end of the exercise (p<0.01) and decreased significantly in patients with type 1 DM at the end of the trial (p<0.05). Panel B. Insulin concentration (pmol·L−1) was significantly higher in patients both before and at the end of the exercise (p<0.001) and decreased significantly in both groups at the end of the trial (p<0.005). In both panels: shaded boxes = patients, open boxes = healthy control subjects.

Figure 2. Oxidative stress values throughout the 3-h exercises.

Oxidative stress was significantly higher in patients (p

Figure 3. Relationship between oxidative stress and HbA1c or uric acid.

Panel A. Relationship between baseline HbA1c values (mmol·mol−1) and oxidative stress (mg·L−1 H2O2). The relationship is statistically significant (n = 20, R = 0.649, p<0.005). Panel B. Relationship between baseline uric acid values (mg·dL−1) and oxidative stress (mg·L−1 H2O2). The relationship is statistically significant (n = 22, R = 0.621, p<0.005). In both panels: full dots = patients with type 1 DM, open dots = healthy control subjects, dotted lines = 95% confidence limits.