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- Barregård, Lars, 1948, et al.
(author)
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Human and Methodological Sources of Variability in the Measurement of Urinary 8-Oxo-7,8-dihydro-2 '-deoxyguanosine
- 2013
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In: Antioxidants and Redox Signaling. - : Mary Ann Liebert Inc. - 1523-0864 .- 1557-7716. ; 18:18, s. 2377-2391
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Journal article (peer-reviewed)abstract
- Aims: Urinary 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) is a widely used biomarker of oxidative stress. However, variability between chromatographic and ELISA methods hampers interpretation of data, and this variability may increase should urine composition differ between individuals, leading to assay interference. Furthermore, optimal urine sampling conditions are not well defined. We performed inter-laboratory comparisons of 8-oxodG measurement between mass spectrometric-, electrochemical- and ELISA-based methods, using common within-technique calibrants to analyze 8-oxodG-spiked phosphate-buffered saline and urine samples. We also investigated human subject- and sample collection-related variables, as potential sources of variability. Results: Chromatographic assays showed high agreement across urines from different subjects, whereas ELISAs showed far more inter-laboratory variation and generally overestimated levels, compared to the chromatographic assays. Excretion rates in timed 'spot' samples showed strong correlations with 24 h excretion (the 'gold' standard) of urinary 8-oxodG (r(p) 0.67-0.90), although the associations were weaker for 8-oxodG adjusted for creatinine or specific gravity (SG). The within-individual excretion of 8-oxodG varied only moderately between days (CV 17% for 24 h excretion and 20% for first void, creatinine-corrected samples). Innovation: This is the first comprehensive study of both human and methodological factors influencing 8-oxodG measurement, providing key information for future studies with this important biomarker. Conclusion: ELISA variability is greater than chromatographic assay variability, and cannot determine absolute levels of 8-oxodG. Use of standardized calibrants greatly improves intra-technique agreement and, for the chromatographic assays, importantly allows integration of results for pooled analyses. If 24 h samples are not feasible, creatinine- or SG-adjusted first morning samples are recommended.
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- Kyro, C., et al.
(author)
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ALKYLRESORCINOLS (BIOMARKERS OF WHOLE-GRAIN INTAKE) AND RISK OF COLORECTAL CANCER IN THE EUROPEAN PROSPECTIVE INVESTIGATION INTO CANCER AND NUTRITION
- 2013
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In: Annals of Nutrition and Metabolism. - : S. Karger. - 0250-6807 .- 1421-9697. ; 63:Supplement 1, s. 1207-1208
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Journal article (other academic/artistic)abstract
- Background and objectives: Few studies have investigatedthe association between whole-grain intake and colorectal cancer.Whole-grain products are one of the dietary items proneto measurement errors, making the use of objective measures,such as biomarkers, highly relevant. The objective of the studywas to investigate the association between biomarkers ofwhole-grain intake, alkylresorcinols, and colorectal cancer ina nested case-control study within the European ProspectiveInvestigation into Cancer and Nutrition (EPIC). Methods: We included 1372 first incident colorectal cancercases and 1372 individually matched controls and calculatedthe incidence rate ratios (IRR) for overall and sub-sites of colorectalcancer using conditional logistic regression adjusted forpotential confounders.Results: Plasma total alkylresorcinol concentrations werenot associated with risk of overall colorectal cancer, proximalcolon cancer or rectal cancer. However, high plasma total alkylresorcinolconcentrations were statistically significantly associatedwith lower incidence of cancer located in the distal (leftor descending) part of the colon. Adjusted IRR of distal coloncancer for highest versus lowest quartile of plasma alkylresorcinolwas 0.48 (95% confidence interval = 0.28 to 0.83). Furthermore,we observed an inverse association with colon cancerfor the Scandinavian part of the participants. Alkylresorcinolsmay be more appropriate as biomarkers in Middle Europe andScandinavia i.e. in areas where whole grains are regularly consumed.Conclusions: Whole-grain intake, assessed by alkylresorcinols,was associated with a lower incidence of distal coloncancer. Alkylresorcinols seem useful as objective biomarkersof whole-grain intake in populations where whole-grains are astaple part of the diet. Acknowledgements: This work was supportedby World Cancer Research Fund International (WCRF)and WCRF Netherlands (WCRF NL) (2011/436), and NordForsk(Centre of Excellence programme HELGA (070015)).
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