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Antioxidant Effects of Zinc Supplementation in Tunisians with Type 2 Diabetes Mellitus

LBSO, Oxidative Stress Laboratory, Joseph Fourier University, Grenoble (A.M.R.), FRANCE
Laboratoires Labcatal, Montrouge Cedex (J.M.M.), FRANCE
Laboratoire de Biophysique, Faculté de Médecine, Monastir (A.K.),
Service d’Exploration fonctionnelle, Endocrinologie et Métabolisme, Hopital Habib Bourguiba, Sfax (N.Z.),
Service de Médecine interne, Hopital de Monastir (S.M.),
TUNISIA, Nutrient Requirements and Functions Laboratory, Beltsville Human Nutrition Research Center, USDA, ARS, Beltsville, MD (R.A.)

Address reprint requests to: Richard A. Anderson, Ph.D., Nutrient Requirements and Functions Laboratory, Bldg 307, Rm 224, Beltsville Human Nutrition Research Center, USDA, ARS, Beltsville, MD 20705. anderson{at}307.bhnrc.usda.gov

Objective: To determine the effects of zinc (Zn) supplementation on oxidative stress in persons with type 2 diabetes mellitus (type 2 DM).

Design: Tunisian adult subjects with HbA1c >7.5% were supplemented for six months with 30 mg/day of Zn as Zn gluconate or placebo. The effects of supplementation on plasma zinc (Zn), copper (Cu), urinary Zn, plasma thiobarbituric acid reactive substances (TBARS), Cu-Zn superoxide dismutase (SOD) and glutathione peroxidase activities (GPX) in red blood cells, blood lipids and lipoproteins, HbA1c and fasting glucose were measured at the beginning of the study and after three and six months.

Results: At the beginning of the study, more than 30% of the subjects exhibited plasma Zn values less than the normal minimum of 10.7 µmol/L, whereas levels of plasma Cu and antioxidant RBC Cu-Zn SOD and GPx enzyme activities were in the normal ranges. Oxidative stress, monitored by plasma TBARS, was increased in individuals with diabetes compared with healthy Tunisian subjects (3.32 ± 0.05 µmol/L vs. 2.08 ± 0.04 µmol/L) and an inverse correlation was found between Zn plasma levels and plasma TBARS. After three and six months of Zn supplementation, all of the subjects exhibited plasma Zn values greater than 10.7 µmol/L. There was a decrease of plasma TBARS in Zn supplemented group after six months (15%) with no significant changes in the placebo group. Supplementation did not alter significantly HbA1c nor glucose homeostasis. No adverse effects of Zn supplementation were observed on Cu status or HDL cholesterol.

Conclusions: These data suggest the potential beneficial antioxidant effects of Zn supplementation in persons with type 2 DM. These results are particularly important in light of the deleterious consequences of oxidative stress in persons with diabetes.

Key words: zinc, oxidative stress, TBARS, lipid peroxidation, diabetes, trace elements