Plasma alkylresorcinols C17:0/C21:0 ratio, a biomarker of relative whole-grain rye intake, is associated to insulin sensitivity: a randomized study.

BACKGROUND/OBJECTIVES: Few studies have used biomarkers of whole-grain intake to study its relation to glucose metabolism. We aimed to investigate the association between plasma alkylresorcinols (AR), a biomarker of whole-grain rye and wheat intake, and glucose metabolism in individuals with metabolic syndrome (MetS). SUBJECTS/METHODS: Participants were 30-65 years of age, with body mass index 27-40 kg/m(2) and had MetS without diabetes. Individuals were recruited through six centers in the Nordic countries and randomized to a healthy Nordic diet (ND, n=96), rich in whole-grain rye and wheat, or a control diet (n=70), for 18-24 weeks. In addition, associations between total plasma AR concentration and C17:0/C21:0 homolog ratio as an indication of the relative whole-grain rye intake, and glucose metabolism measures from oral glucose tolerance tests were investigated in pooled (ND+control) regression analyses at 18/24 weeks. RESULTS: ND did not improve glucose metabolism compared with control diet, but the AR C17:0/C21:0 ratio was inversely associated with fasting insulin concentrations (P=0.002) and positively associated with the insulin sensitivity indices Matsuda ISI (P=0.026) and disposition index (P=0.022) in pooled analyses at 18/24 weeks, even after adjustment for confounders. The AR C17:0/C21:0 ratio was not significantly associated with insulin secretion indices. Total plasma AR concentration was not related to fasting plasma glucose or fasting insulin at 18/24 weeks. CONCLUSIONS: The AR C17:0/C21:0 ratio, an indicator of relative whole-grain rye intake, is associated with increased insulin sensitivity in a population with MetS.