Divergence between LDL oxidative susceptibility and urinary F(2)-isoprostanes as measures of oxidative stress in type 2 diabetes.
BACKGROUND
Oxidative stress is pivotal in atherogenesis. Although the most widely used indirect assay to quantify oxidative stress is LDL oxidative susceptibility, direct assays such as urinary F(2)-isoprostanes have shown great promise.


METHODS
We evaluated the utility of both a direct measure of oxidative stress (urinary F(2)-isoprostanes) and an indirect measure of copper-catalyzed, LDL oxidation in a model of increased oxidative stress (diabetes). We also evaluated an enzyme immunoassay (EIA) method for urinary F(2)-isoprostanes with a gas chromatography-mass spectrometry method.


RESULTS
Excellent intraassay and interassay CVs of <4% were obtained with our EIA method. A good correlation was obtained between the two methods (r = 0.80; n = 68) of F(2)-isoprostane measurement. An excellent correlation for F(2)-isoprostane concentrations was obtained between a timed collection vs 24-h urine (r = 0.96; n = 46). Baseline F(2)-isoprostane concentrations by EIA were significantly higher in both type 2 diabetics with and without macrovascular complications compared with controls (P <0.001). Supplementation with alpha-tocopherol led to a significant reduction in F(2)-isoprostane concentrations in all diabetic patients compared with baseline values (2.51 +/- 1.76 compared with 1.69 +/- 1.32 ng/mg creatinine; P <0.001). There were no significant differences in LDL oxidation in both diabetic groups compared with controls. alpha-Tocopherol supplementation led to significant increases in the lag phase of oxidation as measured by 3 indices in all groups.


CONCLUSIONS
The measurement of urinary F(2)-isoprostanes provides a direct measure of in vivo lipid peroxidation and oxidative stress and appears to be superior to an indirect measure, e.g., LDL oxidative susceptibility, in type 2 diabetes.
Devaraj
S
S
Division of Clinical Biochemistry and Human Metabolism and the Center for Human Nutrition, Department of Pathology and Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX 75390-9073, USA.
Hirany
S V
SV
Burk
R F
RF
Jialal
I
I
D003924:Diabetes Mellitus, Type 2 / Q000378:metabolism* / Q000652:urine; D015237:Dinoprost / Q000031:analogs & derivatives / Q000652:urine*; D028441:F2-Isoprostanes; D005260:Female; D008401:Gas Chromatography-Mass Spectrometry; D006801:Humans; D007124:Immunoenzyme Techniques; D008077:Lipoproteins, LDL / Q000378:metabolism*; D008297:Male; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D015203:Reproducibility of Results
D028441:F2-Isoprostanes; D008077:Lipoproteins, LDL; D015237:Dinoprost