Effects of whole grain, fish and bilberries on serum metabolic profile and lipid transfer protein activities: a randomized trial (Sysdimet)

Abstract

Objective: We studied the combined effects of wholegrain, fish and bilberries on serum metabolic profile and lipid transfer protein activities in subjects with the metabolic syndrome.

Methods: Altogether 131 subjects (40-70 y, BMI 26-39 kg/m(2)) with impaired glucose metabolism and features of the metabolic syndrome were randomized into three groups with 12-week periods according to a parallel study design. They consumed either: a) wholegrain and low postprandial insulin response grain products, fatty fish 3 times a week, and bilberries 3 portions per day (HealthyDiet), b) wholegrain and low postprandial insulin response grain products (WGED), or c) refined wheat breads as cereal products (Control). Altogether 106 subjects completed the study. Serum metabolic profile was studied using an NMR-based platform providing information on lipoprotein subclasses and lipids as well as low-molecular-weight metabolites.

Results: There were no significant differences in clinical characteristics between the groups at baseline or at the end of the intervention. Mixed model analyses revealed significant changes in lipid metabolites in the HealthyDiet group during the intervention compared to the Control group. All changes reflected increased polyunsaturation in plasma fatty acids, especially in n-3 PUFAs, while n-6 and n-7 fatty acids decreased. According to tertiles of changes in fish intake, a greater increase of fish intake was associated with increased concentration of large HDL particles, larger average diameter of HDL particles, and increased concentrations of large HDL lipid components, even though total levels of HDL cholesterol remained stable.

Conclusions: The results suggest that consumption of diet rich in whole grain, bilberries and especially fatty fish causes changes in HDL particles shifting their subclass distribution toward larger particles. These changes may be related to known protective functions of HDL such as reverse cholesterol transport and could partly explain the known protective effects of fish consumption against atherosclerosis.

Trial registration: The study was registered at ClinicalTrials.gov NCT00573781.

Figure 1. Flow chart of the study.

Adapted from De Mello et al .

Figure 2. Fold changes in lipid variables at the end of the 12-week intervention period.

Bars represent mean ± SD. FDR p-values are based on mixed model comparisons, where the interaction of time and group compared to Controls (time*group) or only the effect of time within a group is tested. HealthyDiet n =  37, Whole grain enriched diet (WGED) n =  34 and Control n = 32.

Figure 3. HDL particles and fatty fish intake.

Changes in concentration of large HDL particles, mean particle diameter of HDL and serum concentrations of large HDL lipid components (mean ± SEM) according to tertiles of changes in fish intake. Changes in fish intake are calculated from 4-d food records which were kept once at baseline and three times during the intervention period.