Platelet antioxidant enzymes in insulin-dependent diabetes mellitus

Background: The measurement of the peroxidase scavenging system represented by the activities of superoxide dismutase (SOD), catalase and glutathione peroxidase (GSH-Px) in blood cells of diabetic patients has, in the past, g iven equivocal results, Likewise, the role of these intracellular enzymatic scavengers against the oxidative stress of diabetes-associated microangiop athic complications is unknown. Methods: Choosing platelets as cell model ( as commonly done in previous studies), the aim of this study was to relate the platelet content of SOD, catalase and GSH-Px to the presence of diabete s, as well as to the presence of nephropathy and retinopathy in 35 insulin- dependent diabetic patients, as compared to 10 age-matched control subjects , Results: The enzymatic activities were not changed in diabetic patients i n comparison with healthy controls. After stratifying patients according to presence of nephropathy (24-h urinary albumin excretion rate persistently greater than or equal to 70 mug min(-1)) or retinopathy, the group of album inuric patients was characterized by a significant decrease in SOD activity as compared to those in the normoalbuminuric range (4.36 +/- 1.06 vs. 6.81 +/- 2.26 mU 10(-9) platelets; p = 0.01). Catalase and GSH-Px did not chang e. No modification in platelet enzyme activities has been found in diabetic subjects with retinopathy. Conclusions: These results suggest that diabeti c nephropathy, at least in its early stage, may be related to an altered re dox state of platelets, as tested by the reduction in SOD activity, thus, i ndicating that the renal damage in these patients may be associated to a se lective increase in platelet susceptibility to variation in the redox state . (C) 2001 Elsevier Science B.V. All rights reserved.