Alkylresorcinols in adipose tissue biopsies as biomarkers of whole-grain intake: an exploratory study of responsiveness to advised intake over 12 weeks

BACKGROUND/OBJECTIVES: Alkylresorcinols (ARs) have been suggested as biomarkers of whole-grain wheat and rye intake. Plasma AR concentrations have a short half-life; hence, long-term biomarkers are needed. This study evaluated the responsiveness of ARs in adipose tissue biopsies as biomarkers after a whole-grain intake intervention. SUBJECTS/METHODS: Samples and data of 27 participants from a 12-week randomized parallel-group dietary intervention were available. The participants were replacing their habitual diet with a whole-grain-enriched diet (WGDG) or a refined grain diet (RDG) during the intervention. Blood samples and adipose tissue biopsies were collected at baseline and after 12 weeks, and AR concentrations in the plasma and adipose tissues from the participants were compared against estimated whole-grain intake. RESULTS: AR concentrations in the adipose tissue and plasma did not change after 12 weeks in the WGDG group, as no significant increase in whole-grain intake was observed, but was significantly lower than baseline in the RDG group (P < 0.05), owing to decreased whole-grain intake in this group. Plasma and adipose tissue AR concentrations were significantly higher in the WGDG group than in the RDG group (P < 0.05), and were highly correlated with average whole-grain intake estimated by food records (Spearman's r = 0.60-0.72 (P < 0.05, n = 16) for total and individual AR homolog concentrations in the plasma; r = 0.60-0.84, (P < 0.05, n = 16) for total and individual AR homolog concentrations in the adipose tissue). CONCLUSIONS: In this small pilot study, AR concentrations in adipose tissue responded to reduced intake of whole grain over 12 weeks. Although not significantly different from plasma AR, adipose tissue AR concentrations were highly correlated with whole-grain intake after a 12-week intervention. These results show that adipose tissue AR concentrations have promise as biomarkers of whole-grain wheat and rye intake. Larger studies are needed to evaluate whether they are better long-term biomarkers than AR in the plasma.