Obesity, age, and oxidative stress in middle-aged and older women.

Recent evidence suggests that urinary F(2)-isoprostanes (F(2)-IsoPs) are more accurate markers of oxidative stress than other available biomarkers. Most previous studies used unmetabolized F(2)-IsoPs as a biomarker. Few previous studies measured 15-F(2t)-IsoP-M, a metabolite of one of the most common F(2)-IsoPs, 15-F(2t)-IsoP. Unlike 15-F(2t)-IsoP, 15-F(2t)-IsoP-M is not subject to autoxidation and renal production. To our knowledge, no study has compared the associations of age and body mass index (BMI) with F(2)-IsoPs to those with 15-F(2t)-IsoP-M. Urinary levels of F(2)-IsoPs and 15-F(2t)-IsoP-M were measured using gas chromatography-mass spectrometry for 845 healthy women aged 40-70 years. Both F(2)-IsoPs and 15-F(2t)-IsoP-M were elevated among smokers. The level of 15-F(2t)-IsoP-M increased with age, particularly after menopause, and with BMI. In contrast, F(2)-IsoPs decreased with age, regardless of menopausal status, and was not related to BMI. The association of 15-F(2t)-IsoP-M with age or menopausal status did not differ by BMI category, and the association with BMI was also independent of age or menopausal status. 15-F(2t)-IsoP-M appears to be a valuable biomarker of oxidative stress in age- and obesity-related diseases.