ELEVATED LEVELS OF AUTHENTIC PLASMA HYDROPEROXIDES IN NIDDM

Using a precise technique for measuring authentic plasma lipid hydrope roxides (ROOHs), we show that individuals with non-insulin-dependent d iabetes mellitus (NIDDM) have higher levels of ROOH than do control su bjects. ROOHs were measured by the ferrous oxidation with xylenol oran ge assay coupled with the selective ROOH reductant triphenylphosphine. Formation of the ferric xylenol orange complex was determined at 560 nm and calibrated against H2O2. For 22 individuals with NIDDM, a conce ntration of 9.04 +/- 4.3 mu mol/l (mean +/- SD) ROOH was recorded. Thi s concentration was higher (P < 0.0005 by separate-variance t test) th an that of plasma ROOHs from control subjects (3.76 +/- 2.48 mu mol/l) . There was no difference between concentrations of plasma malondialde hyde measured as thiobarbituric acid-reactive material (TBARM) in NIDD M or control subjects (1.00 +/- 0.70 vs. 1.21 +/- 0.62 mu mol/l, respe ctively; P > 0.1). A trend to lower vitamin E levels in the NIDDM grou p (9.03 +/- 3.31 vs. 10.31 +/- 5.02 mu g/ml in control subjects) faile d to achieve significance at the 95% confidence level. Plasma ROOHs in the diabetic group did not correlate with total plasma cholesterol, t riglyceride, fasting glucose, WA,, vitamin E, or TBARM levels. These d ata indicate that measurement of authentic ROOHs shows NIDDM to be ass ociated with oxidative stress, which may be unrelated to abnormalities in lipid metabolism and glycemic control.