Biological variation of plasma F2-isoprostane-III and arachidonic acid in healthy individuals.

Abstract

F2-Isoprostanes (iPF2α) are formed by free radical peroxidation of esterified arachidonic acid (AA) in situ on phospholipids and are subsequently released in free form by the action of phospholipases (1). One of the iPF2α isomers, iPF2α-III, is recognized as a sensitive and reliable index of lipid peroxidation in vivo. iPF2α-III is increased in conditions associated with increased oxidative stress and decreased after dietary supplementation with antioxidants (2). Despite its increasing usage in clinical and nutritional studies, there has been no report on the biological variation in plasma iPF2α-III. The aims of this study were ( a ) to investigate the biological variation of plasma total iPF2α-III in healthy individuals over a period of 4 months, and ( b ) to determine whether the use of the plasma iPF2α-III/AA ratio can facilitate interpretation and improve clinical utility. We recruited 20 healthy nonsmoking Chinese individuals (10 women and 10 men; age range, 31–51 years) for this study. Medical histories were obtained from a questionnaire survey. Comprehensive profiles including commonly used blood and urine tests were performed to exclude common diseases. Other exclusion criteria included pregnancy, hormonal therapy, and body mass index ≥25. These individuals maintained their usual lifestyle throughout the study and were not taking any other medications (including antioxidant supplements). The study protocol, approved by the Clinical Research Ethics Committee of The Chinese University of Hong Kong, was explained thoroughly to the participants before their informed consent was obtained. Once a month for 4 months, the same phlebotomist collected venous blood from each participant after an overnight fast. Blood (4 mL) was collected into lithium-heparin tubes containing 15 μmol/L indomethacin as a cyclooxygenase inhibitor. Blood samples were centrifuged at 2400 g for 10 min at 4 °C. Aliquots (1 mL) of …