Reliability of fasting plasma alkylresorcinol metabolites concentrations measured 4 months apart

Abstract

Alkylresorcinols (AR) have been suggested as specific dietary biomarkers of whole-grain wheat and rye intake. AR are metabolised to 3,5-dihydroxybenzoic acid (DHBA) and 3-(3,5-dihydroxyphenyl)-1-propanoic acid (DHPPA), which have longer apparent half-lives and were recently proposed to better reflect long-term whole-grain consumption than the intact AR. The objective of this study was to analyse the reliability-expressed by the intraclass correlation coefficient (ICC)-of AR metabolite concentrations among 100 participants from the European Prospective Investigation into Cancer and Nutrition (EPIC)-Potsdam study who provided two fasting plasma samples 4 months apart. DHBA and DHPPA concentrations were not significantly different between the first and second measurement over the 4-month period (P40.05). The ICC was 0.32 (95% confidence interval (CI) ¼ 0.13-0.49) for DHBA and 0.37 (95%CI ¼ 0.19-0.53) for DHPPA. These results suggest that AR metabolites cannot be considered to be better biomarkers of whole-grain wheat and rye intake than the intact AR in fasting plasma (ICC ¼ 0.42). (2012) 66, 968-970; doi:10.1038/ejcn.2012 published online 20 June 2012 Keywords: alkylresorcinols; DHBA; DHPPA; biomarker; reliability; whole-grain INTRODUCTION Assessment of whole-grain consumption in epidemiological studies is usually based on self-reports. Besides measurement errors, the lack of standardised definitions of whole-grain foods challenge the accuracy of assessment. Alkylresorcinols (AR) are phenolic lipids present almost exclusively in the bran of rye and wheat, and have been suggested as promising candidate biomarkers of whole-grain consumption. 1,2 To gain reliable risk estimates with a single blood measurement, as is usually obtained in epidemiological studies, the withinperson variance over time should be small compared with between-person variance. 3 The intraclass correlation coefficient (ICC), defined as the ratio of between-person variance and the sum of between-and within-person variance, is an established indicator of reliability taking both components into account. 3 We previously observed moderate reliability in plasma of total and individual AR concentrations over time (ICC ¼ 0.42), 4 which could be due to the short half-life of AR (B5 h). 5 AR are metabolised in humans via oxidation. 1 The metabolites, 3,5-dihydroxybenzoic acid (DHBA) and 3-(3,5-dihydroxyphenyl)-1-propanoic acid (DHPPA) have longer half-lives (B11-16 h) and may better reflect long-term whole-grain consumption. 6 The aim of this study was to assess the reliability (as expressed by the ICC) of concentrations of AR metabolites, DHBA and DHPPA, in human fasting plasma over a 4-month period in a population-based sample, which we previously used to assess the reliability of AR. 4 European Journal of Clinical Nutrition SUBJECTS AND METHODSThis study was based on the European Prospective Investigation into Cancer and Nutrition (EPIC)-Potsdam study, 7,8 as described previously. 4 From EPIC-Potsdam, 407 persons were invited to participate in a val...

Plasma Alkylresorcinol Metabolite, a Biomarker of Whole-Grain Wheat and Rye Intake, and Risk of Type 2 Diabetes and Impaired Glucose Regulation in a Chinese Population

“…The nonsignificant association might result from a lack of the increased benefits of whole-grain intake when increasing intake from intermediate or high levels (5,25). In our population, plasma DHPPA concentration was significantly lower compared with that in European populations (21.9 nmol/L in elderly Swedish men [19] and 50.6 nmol/L in German men and women [29]). This could be attributed to dietary patterns in Asian countries where rice and wheat are the staple foods.…”

“…Our study has several strengths. Plasma concentration of alkylresorcinol metabolites is a novel and independent biomarker of whole-grain intake with modest long-term reproducibility (29), and it has been used in several studies to estimate the effect of whole-grain wheat and rye on human health (19,36). Moreover, participants in this study were confined to the newly diagnosed to avoid possible changes in diet and lifestyle, which may distort the association between whole-grain intake and T2D risk.…”

“…Second, the lack of information on dietary factors (especially refined-grain intake) and socioeconomic factors precluded us from assessing their confounding effects on the results. Third, plasma levels of alkylresorcinol metabolites can be influenced by between-subject differences in metabolism (29,37), which may distort the association under investigation. This problem is further accentuated when intake of whole grains is irregular.…”

Plasma Alkylresorcinol Metabolites as Biomarkers for Whole-Grain Intake and Their Association with Prostate Cancer: A Swedish Nested Case–Control Study

“…Although the mean concentrations of the metabolites did not differ significantly over the 4-month period, these results indicate a fairly poor reliability. The results from the study by Montonen and colleagues may however, not be transferable to the current study with a different population and a different methodology for the analyses of metabolite concentrations (36). However, additional studies are needed on the validity of alkylresorcinol metabolites as a biomarker for whole grains.…”

Biomarkers of Whole-Grain and Cereal-Fiber Intake in Human Studies: A Systematic Review of the Available Evidence and Perspectives

“…Studies on AR, its homologs, and metabolites generally showed a moderate short-term reproducibility, but a relatively poor reproducibility in the assessment of the medium-to long-term exposure to WG in the blood and urine [35,55,83,84]. To our knowledge, no study assessed the reproducibility of avenacosides and benzoxazinoid compounds.…”