Time course of oxidative stress status in the postprandial and postabsorptive states in type 1 diabetes mellitus: Relationship to glucose and lipid changes

Objective: The aim of this study was to compare oxidative stress status (OSS) with blood glucose and lipid changes during the fasting, postprandial and postabsorptive phases in type 1 diabetes mellitus. Methods: Twenty-three patients on intensive insulin treatment received a standard fat-rich breakfast and lunch. OSS was monitored at fasting (F), just after the post-breakfast glycemia peak (BP) (identified by continuous subcutaneous glucose monitoring), 3.5-h post-breakfast (B3.5), just after the post-lunch peak (LP), just after the post-lunch dale (LD) and 5 hours after lunch (L5). Results: Whereas whole blood glutathione and plasma protein thiols increased in the postprandial period (from 6.52 +/- 1.20 (F) to 7.08 +/- 1.45 mu mol/g Hb (BP), p=0.005), ascorbate decreased gradually from 44 +/- 17 (F) to 39 +/- 19 mu mol/L (LD), p=0.015. Retinol and alpha-tocopherol also decreased from 27.1 +/- 7.0 (F) to 25.3 +/- 5.2 mu mol/L (BP), p=0.005. Uric acid decreased later, from 213 +/- 77 (BP) to 204 +/- 68 mu mol/L (133.5), p=0.01, but then increased in LP (231 +/- 70 mu mol/L) and LD to values higher than F (215 +/- 64, mu mol/L, p=0.01). Malondialdehyde increased gradually from 1.02 +/- 0.36 (F) to a maximum of 1.14 +/- 0.40 mu mol/L (LP). In the postabsorptive phase (1-5) all parameters except for thiols reverted to fasting concentrations. Conclusions: In type 1 diabetes lipid peroxidation increases during the postprandial phase in parallel to glucose and triglyceride changes. Blood antioxidants, however, followed diverse patterns of change.