Decreased in vivo oxidative stress and decreased platelet activation following metformin treatment in newly diagnosed type 2 diabetic subjects

Background: In type 2 diabetes, metformin reduces cardiovascular risk beyond the effect of glycaemic control. Since oxidative stress and the consequent enhanced platelet activation contribute to accelerated atherosclerosis in diabetes, we hypothesized that metformin could reduce oxidative stress in this condition. Methods: We randomized 26 newly diagnosed type 2 diabetic subjects to assume either metformin (M, n = 13) or gliclazide (G, n = 13) for 12 weeks. Drugs were titrated as needed to achieve good glycaemic control. Before and after treatment, we determined blood glucose, insulin, HbA_1c, vitamin A and E levels and 8-iso-PGF_2α and 11-dehydro-thromboxane B₂ urinary excretion, an in vivo oxidative stress and a thromboxane-dependent platelet activation marker, respectively. Results: Notwithstanding a comparable improvement in metabolic control, 8-iso-PGF_2α (M from 708 ± 32 to 589 ± 45 pg/mg cr, p < 0.001; G from 646 ± 80 to 665 ± 79, pg/mg cr, p = ns) and 11-dehydro-thromboxane B₂ (M from 2190 ± 196 to 1753 ± 150 pg/mg cr, p < 0.05; G from 2048 ± 202 to 1923 ± 223, pg/mg cr, p = ns) urinary excretion decreased after metformin bur not after gliclazide treatment. After metformin, vitamin A and E levels significantly increased while they remained unchanged after gliclazide. Conclusions: These data suggest that metformin could improve oxidative stress, preserve antioxidant function and restrain platelet activation in type 2 diabetes.