Measures of oxidized low-density lipoprotein and oxidative stress are not related and not elevated in otherwise healthy men with the metabolic syndrome

Objective - The metabolic syndrome predisposes to the development of cardiovascular diseases. Oxidative stress and elevated circulating oxidized low-density lipoprotein (LDL) concentrations are related to cardiovascular disease and proposed to be features of the metabolic syndrome. F-2-isoprostanes are lipid peroxidation products and considered the most reliable biomarkers of oxidative stress. Methods and Results - Plasma oxidized LDL (oxLDL) and urinary 8-iso-prostaglandin F-2 alpha (8-iso-PGF(2 alpha); the major F-2-isoprostane) were analyzed in a cross-sectional study of 289 healthy men (62 to 64 years of age). Individuals completed a 7-day dietary record, and fasting plasma insulin, lipid, and lipoprotein concentrations, LDL particle size, and inflammatory markers were determined. National Cholesterol Education Program/Adult Treatment Panel III (NCEP/ATPIII) criteria were used to define the metabolic syndrome and individuals were grouped according to the number of risk factors for the metabolic syndrome (0, [n = 88; 30%]; >= 1, [n = 179; 62%], metabolic syndrome [n = 22; 8%]). Group comparisons revealed no differences for oxLDL, 8-iso-PGF(2 alpha), or reported intake of macronutrients, whereas C-reactive protein and interleukin-6 were increased in the metabolic syndrome. LDL cholesterol strongly determined oxLDL in univariate and multivariate analysis, but no relationship to 8-iso-PGF(2 alpha) was found. In turn, 8-iso-PGF(2 alpha) was related to reported intake of fat, fatty acids, and dietary antioxidants. Conclusions - There were no increases in plasma oxLDL or measures of oxidative stress (urinary 8-iso-PGF(2 alpha)) in these otherwise healthy 63-year-old men with the metabolic syndrome. Furthermore, no relationship between oxLDL and 8-iso-PGF(2 alpha) was found, but our results suggest a role for dietary factors in oxidative stress.