Design: Placebo for 3 months, followed by 30 mg/day zinc gluconate in identical capsules.
Setting: Diabetic out patients clinic at the University Hospital, Grenoble.
Subjects: Diabetic patients cared for type I diabetes mellitus. 22 patients began the study, 4 dropped out. 10 patients suffered of an early retinopathy, 8 patients had no retinopathy.
Interventions: In this order: T0 biological measurements, 3 months placebo treatment, T1 biological measurements, 3 months zinc gluconate treatment, T2 biological measurements. Plasma Zn, Cu, Se, thiobarbituric acid reactants and antioxidant enzymes were measured [plasma and red glutathione peroxidase (Se-GPx), red cell superoxide dismutase (Cu-Zn-SOD)].
Results: Lower plasma zinc level in the two groups. An increase in zinc level was observed and was more important in diabetic patients with no retinopathy (P = 0.05). The thiobarbituric acid reactants were above the reference values in all the patients, and were decreased at T2 (P < 0.05). Increase of GPx activity after zinc supplementation in patients with retinopathy.
Conclusions: Zinc deficiency in insulin-dependent diabetic patients is corrected by a zinc supplementation. Moreover this supplementation decreases lipid peroxidation. The effects of zinc are different in diabetic patients with or without retinopathy. The increase in Se-GPx activity observed in patients with retinopathy could be linked to the protective effect of zinc on the protein itself.