TOTAL RADICAL-TRAPPING ANTIOXIDANT PARAMETER IN NIDDM PATIENTS

OBJECTIVE - The existence of an oxidative stress in diabetes is still debated. This is largely due to the lack of good tools to assay the le vel of oxidative stress. The use of total radical-trapping antioxidant parameter (TRAP) has recently been proposed to explore the antioxidan t property of a plasma sample. TRAP may be either directly measured by a fluorescence-based method (TRAPm) or calculated (TRAPc) by a mathem atical formula, taking into account the serum levels of four natural a ntioxidants: protein-bound SH (thiol) groups, uric acid, vitamin E, an d vitamin C. The difference between TRAPm and TRAPc is due to antioxid ants, which are still unidentified and to the possible synergism among the antioxidants. RESEARCH DESIGN AND METHODS - In this study, we eva luated malondialdehyde (MDA), TRWPm, TRAPc, protein-bound SH groups, u ric acid, vitamin E, and vitamin C in 40 NIDDM patients and 40 matched normal control subjects. RESULTS - TRAPm and TRAPc a ere significantl y lower in diabetic patients. A good correlation between TRAPm and TRA Pc was found in both NIDDM patients (r = 0.68, P < 0.0001) and control subjects (r = 0.74, P < 0.0001). Protein-bound SH groups and uric aci d were significantly lower in diabetic subjects, while MDA and vitamin E level were significantly higher. After correction for serum triglyc erides (MDA) and cholesterol (vitamin E), MDA lost significance, while vitamin E did not. Vitamin C was not different in the two groups. CON CLUSIONS - These data show decreased TRAP levels in NIDDM patients, su ggesting the existence of lower antioxidant defenses in diabetes. The decrease appears to be due to various antioxidants, some of them not y et clearly defined. TRAP may represent a more reliable estimation of s erum antioxidant capacity than the measurement of each known antioxida nts. The correlation found between TRAPm and TRAPc values suggests tha t TRAPc, easier to measure than TRAPm, might be adequately reliable fo r routine assessment of oxidative stress in diabetic patients.