Intra-Person Variation of Urinary Biomarkers of Oxidative Stress and Inflammation Xiaoyan Wu 1,3 , Hui Cai 1 , Yong-Bing Xiang 4 , Qiuyin Cai 1 , Gong Yang 1 , Dake Liu 4 , Stephanie Sanchez 2 , Wei Zheng 1 , Ginger Milne 2 , and Xiao-Ou Shu 1 Abstract Background: Oxidative stress and inflammation have been linked to many chronic diseases including cancer and cardiovascular diseases. Urinary levels of F 2 -isoprostanes (F 2 -IsoPs), 2,3-dinor-5,6-dihydro-15-F 2t -IsoP (15-F 2t -IsoP-M), a major metabolite of F 2 -IsoPs, prostaglandin E 2 metabolite (PGE-M), and leukotriene E 4 (LTE 4 ) have been proposed as biomarkers for oxidative stress and inflammation. However, little information is available regarding the intra-person variation of these biomarkers, hindering their application in epidemiologic studies. Methods: We evaluated the intra-person variation of these four urinary biomarkers among 48 randomly chosen participants of a validation study of a population-based cohort, the Shanghai Men's Health Study. Four spot urine samples, collected during each season over a 1-year period, were measured for these biomarkers. Results: The intraclass correlation coefficients for F 2 -IsoPs, 15-F 2t -IsoP-M, PGE-M, and LTE 4 were 0.69, 0.76, 0.67, and 0.64, respectively. The Spearman correlation coefficients, derived by using bootstrap analysis of sin- gle spot measurements and the average of the other three seasonal measurements, were 0.47, 0.60, 0.61, and 0.57 for F 2 -IsoPs, 15-F 2t -IsoP-M, PGE-M, and LTE 4 . Except for high correlations between F 2 -IsoPs and 15-F 2t - IsoP-M (r = 0.65), the other biomarkers were moderately correlated (r = 0.21-0.44). Conclusions: Our study results suggest that these four urinary biomarkers have relatively low intra-person variation over a 1-year period. Impact: Spot measurements of F 2 -IsoPs, 15-F 2t -IsoP-M, PGE-M, and LTE 4 could be useful as biomarkers of oxidative stress and inflammation status for epidemiologic studies. Cancer Epidemiol Biomarkers Prev; 19(4); 947–52. ©2010 AACR. Introduction Oxidative stress, the adverse effect of oxidants on physiologic function, has been implicated in the patho- genesis of a variety of human conditions and diseases, such as cancers, cardiovascular disease, neurodegenera- tive disease, and aging (1, 2). F 2 -isoprostanes (F 2 -IsoPs) are a unique series of prostaglandin-like compounds formed in vivo via a nonenzymatic mechanism involving the free radical–initiated peroxidation of arachidonic acid (3). F 2 -IsoPs are further metabolized to form 2,3-dinor- 5,6-dihydro-15-F 2t -IsoP (15-F 2t -IsoP-M), a major end product of F 2 -IsoPs excreted in urine (4). Urine is consid- ered to be an ideal biological material for the measure- ment of F 2 -IsoPs because, unlike plasma, it does not contain high lipid content, which minimizes concern about the artifactual generation of isoprostanes by lipid autoxidation during sampling (5). Urinary F 2 -IsoPs mea- sured by mass spectrometric methods is considered as a reliable and accurate biomarker of oxidative stress in vivo (6, 7). Measurement of its end metabolite 15-F 2t -IsoP-M in urine may offer an additional advantage over its parent compounds, potentially providing a better integrated in- dex of oxidative stress status in vivo (5). We have recently reported in a nested case-control study that elevated le- vels of urinary 15-F 2t -IsoP-M are associated with in- creased risk of breast cancer among obese women (8). Cumulative evidence from both in vitro and animal studies suggests that cyclooxygenase-2 may be involved in the development and progression of cancer (9) and other diseases (10, 11). It is believed that the proinflam- matory effects of the cyclooxygenase-2 pathway are largely mediated through prostaglandin E 2 (PGE 2 ). PGE 2 is quickly converted to 11α-hydroxy-9,15-dioxo- 2,3,4,5-tetranor-prostane-1,20-dioic acid (PGE-M), a major PGE 2 metabolite, and excreted in urine (12). It is generally accepted that the most accurate approach for the assess- ment of the endogenous production of prostaglandins in Authors' Affiliations: 1 Division of Epidemiology, Department of Medicine, Vanderbilt University Medical Center and Vanderbilt-Ingram Cancer Center, Nashville, Tennessee; 2 Division of Clinical Pharmacology, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee; 3 Department of Biostatistics, Public Health College, Harbin Medical University, Harbin, P.R. China; and 4 Department of Epidemiology, Shanghai Cancer Institute, Shanghai, P.R. China Corresponding Author: Xiao-Ou Shu, Division of Epidemiology, Vander- bilt University Medical Center, 2525 West End Avenue, Suite 600, IMPH, Nashville, TN 37203-1738. Phone: 615-936-0713; Fax: 615-936-8291. E-mail: Xiao-ou.shu@vanderbilt.edu doi: 10.1158/1055-9965.EPI-10-0046 ©2010 American Association for Cancer Research. www.aacrjournals.org CEBP Focus: Biomarkers and Biospecimens 947 Downloaded from http://aacrjournals.org/cebp/article-pdf/19/4/947/2271837/947.pdf by guest on 13 April 2023