FreeRadical Biology& Medicine, Vol. 15, pp. 597-602, 1993 0891-5849/93 $6.00 + .00 Printed in the USA. All rights reserved. Copyright © 1993 Pergamon Press Ltd. Original Contribution ANTIOXIDANTS IN THE SERUM OF CHILDREN WITH INSULIN-DEPENDENT DIABETES MELLITUS KOHTARO ASAYAMA, NORIHIKO UCHIDA, TAKAYA NAKANE, HIDEMASA HAYASHIBE, KAZUSHIGE DOBASHI, SHIN AMEMIYA, KIYOHIKO KATO, and SHINPEI NAKAZAWA Department of Pediatrics, Yamanashi Medical College, Tamahocho, Yamanashi, Japan (Received 13 February 1993; Revised and Accepted 20 April 1993) Abstract--To determine whether alteration in serum antioxidant status is related to the increased oxidative stress as a cause of diabetic angiopathy, we measured both the antioxidant activity (AOA) and total peroxyl radical-trapping antioxidant parameter (TRAP), and their component individual antioxidants in serum of children with insulin-dependent diabetes mellitus (IDDM). The AOA was measured as the ability to inhibit lipid autoxidation in brain homogenates. TRAP was assayed as the ability to delay lipid peroxidation induced by an azo initiator. Antioxidants measured were ceruloplasmin, transferrin, and albumin as components of AOA; and ascorbic acid, uric acid, protein sulfhydryl, and alpha-tocopherol as components of TRAP. Serum AOA appeared to be decreased in the diabetics in relation to poor glycemic control, corresponding to the decrease in transferrin and albumin. Serum haptoglobin level was also decreased in the diabetics. Similarly, the directly measured TRAP value was decreased in the diabetic serum mainly due to the decreased contribution of unidentified chain-breaking antioxidants, despite the increase in ascorbic acid and alpha-tocopherol. The decrease in both types of antioxidant activity in the diabetic serum, as new findings, suggests that a defective serum antioxidant status contributes to the increased oxidative stress in IDDM. Keywords--Free radicals, Antioxidants, Serum proteins, Insulin-dependent diabetes mellitus, Ascorbic acid, Alpha-tocopherol, Transitional metals, Lipid peroxidation, Free radicals INTRODUCTION Oxidative stress is postulated to be increased in pa- tients with diabetes mellitus.~ Accumulating evidence suggests that oxidative cell injury caused by free radi- cals contributes to the development of both macroan- giopathy2 and microangiopathy3 occurring as compli- cations of diabetes mellitus. Reactive oxygen species generated in the cells can be scavenged by antioxidant enzymes. Diabetes is well known to induce changes in the tissue content and activity of antioxidant en- zymes.4,5 On the other hand, extracellular fluids lack protection by the antioxidant enzymes but contain various antioxidants that delay or inhibit the oxida- tive process by their presence at a much lower concen- tration than that of an oxidizable substrate. 6 Thus, serum antioxidants can play a role in protecting vascu- lar endothelium against oxidative injury, and, there- Address correspondence to: Kohtaro Asayama, Department of Pediatrics, Yamanashi Medical College, I I l0 Shimokato, Tama- hocho, Nakakomagun, Yamanashi 409-38, Japan. fore, they may provide a significant defense against diabetic angiopathy. Antioxidants are classified, at least, into two catego- ties, depending on the action sites in an oxidative se- quence: preventive antioxidant and chain-breaking antioxidant. 6 The former prevents the initiation of radical chain reaction by scavenging reactive oxygen species, or, more importantly in serum, by binding transitional metals in forms that will not generate reactive species. Chain-breaking antioxidant in- terrupts the oxidative process by reacting with chain- propagating radicals, thereby forming a stable prod- uct. In clinical settings, the preventive antioxidant ac- tivity (AOA) in serum can be measured as the ability to inhibit lipid autoxidation in brain homogenates,7 and the AOA, measured by this method, is known to be largely determined by the metal-binding capacity of ceruloplasmin, transferrin, and albumin. 7 For chain-breaking antioxidants, an assay detect- ing peroxyl radical scavenging activity in serum has been developed by Ingold and co-workers,a by utiliz- ing an azo initiator that produces water-soluble per- 597