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Superoxide dismutase antioxidant enzyme activity and copper and zinc levels in patients with type 2 diabetes mellitus

Abstract:

Living beings have developed diverse molecular mechanisms, including enzymatic antioxidants and their mineral cofactors, which allow for the stabilization of these reactive species in order to offer protection against their damaging effects. An elevated production of free radicals has been associated with diabetes. The objective of this study was to determinate the activity of the enzyme superoxide dismutase (SOD) and its relations with the levels of copper (Cu) and zinc (Zn) in patients with type 2 diabetes mellitus (DM2). Fasting blood samples were taken in 34 diabetics and 30 non diabetic subjects (controls), with the purpose of measuring the erythrocyte activity of Cu/Zn-SOD, as well as to quantify serum and erythrocyte Cu and Zn with spectrophotometric methods. The SOD activity in patients with DM2 was significantly lower (1839±101 U/g Hb) than in controls (2573±161 U/g Hb) (p<0.05). Copper levels in diabetic serum (59.50±6.02 mg/dL) and erythrocyte (1.76±0.14 μ g/g Hb) were significantly higher than in controls (55.45±5.80 mg/dL and 1.27±0.13 μ g/g Hb) (p<0.05). Serum Zn in diabetics (119.59±6.73 mg/dL) was significantly lower than in controls (134.74±9.43 mg/dL), but the diabetics had higher Zn in erythrocyte (39.13±1.05 μ g/g Hb) than the controls (31.62±1.75 μ g/g Hb) (p<0.05). A significant positive correlation between Cu/Zn-SOD activity and serum Zn (r=0.712, p<0.05) was only found in controls. These results suggest that the patients with DM2 present an alteration in the endogenous system of antioxidant defences mediated by the SOD and its cofactors. © 2007 Sociedad Venezolana de Farmacológia y Farmacológia Clínica y Terapéutica.