Impact of wheat aleurone on biomarkers of cardiovascular disease, gut microbiota and metabolites in adults with high body mass index: a double-blind, placebo-controlled, randomized clinical trial

Abstract

Purpose: Aleurone is a cereal bran fraction containing a variety of beneficial nutrients including polyphenols, fibers, minerals and vitamins. Animal and human studies support the beneficial role of aleurone consumption in reducing cardiovascular disease (CVD) risk. Gut microbiota fiber fermentation, polyphenol metabolism and betaine/choline metabolism may in part contribute to the physiological effects of aleurone. As primary objective, this study evaluated whether wheat aleurone supplemented foods could modify plasma homocysteine. Secondary objectives included changes in CVD biomarkers, fecal microbiota composition and plasma/urine metabolite profiles.

Methods: A parallel double-blind, placebo-controlled and randomized trial was carried out in two groups of obese/overweight subjects, matched for age, BMI and gender, consuming foods supplemented with either aleurone (27 g/day) (AL, n = 34) or cellulose (placebo treatment, PL, n = 33) for 4 weeks.

Results: No significant changes in plasma homocysteine or other clinical markers were observed with either treatment. Dietary fiber intake increased after AL and PL, animal protein intake increased after PL treatment. We observed a significant increase in fecal Bifidobacterium spp with AL and Lactobacillus spp with both AL and PL, but overall fecal microbiota community structure changed little according to 16S rRNA metataxonomics. Metabolomics implicated microbial metabolism of aleurone polyphenols and revealed distinctive biomarkers of AL treatment, including alkylresorcinol, cinnamic, benzoic and ferulic acids, folic acid, fatty acids, benzoxazinoid and roasted aroma related metabolites. Correlation analysis highlighted bacterial genera potentially linked to urinary compounds derived from aleurone metabolism and clinical parameters.

Conclusions: Aleurone has potential to modulate the gut microbial metabolic output and increase fecal bifidobacterial abundance. However, in this study, aleurone did not impact on plasma homocysteine or other CVD biomarkers.

Trial registration: The study was registered at ClinicalTrials.gov (NCT02067026) on the 17th February 2014.

Keywords: Aleurone; Biomarkers of intake; Gut microbiota; Homocysteine.

Fig. 1

Schematic representation of study design. §Informed consent; Inclusion questionnaire. *Anthropometric and clinical parameters. **Anthropometric and clinical measurements; Biological sample collection; Diet diaries; Intestinal function diaries. # Weekly distribution of study foods

Fig. 2

Intestinal microbiota analysis. a Enumeration of fecal bacterial groups by quantitative PCR. *p < 0.05 (paired student ‘s t test). B Alpha diversity plots after V3–V4 16S rRNA sequencing analysis (*p = 0.0138, Mann–Whitney U test with FDR). Center lines of boxplots show the medians; box limits indicate the 25th and 75th percentiles; whiskers extend 15 times the interquartile range from the 25th and 75th percentiles. c Histograms of percentage relative abundance of fecal microbiota genera after taxonomic analysis of V3–V4 16S rRNA sequences. AL aleurone, PL placebo; d summary of significant changes in fecal microbiota (Mean ± SD). P p value after non parametric Mann–Whitney U test, FDR-P false discovery rate corrected p value. V1 before dietary supplementation with study foods and V2 after dietary supplementation with study foods

Fig. 2

Intestinal microbiota analysis. a Enumeration of fecal bacterial groups by quantitative PCR. *p < 0.05 (paired student ‘s t test). B Alpha diversity plots after V3–V4 16S rRNA sequencing analysis (*p = 0.0138, Mann–Whitney U test with FDR). Center lines of boxplots show the medians; box limits indicate the 25th and 75th percentiles; whiskers extend 15 times the interquartile range from the 25th and 75th percentiles. c Histograms of percentage relative abundance of fecal microbiota genera after taxonomic analysis of V3–V4 16S rRNA sequences. AL aleurone, PL placebo; d summary of significant changes in fecal microbiota (Mean ± SD). P p value after non parametric Mann–Whitney U test, FDR-P false discovery rate corrected p value. V1 before dietary supplementation with study foods and V2 after dietary supplementation with study foods

Fig. 2

Intestinal microbiota analysis. a Enumeration of fecal bacterial groups by quantitative PCR. *p < 0.05 (paired student ‘s t test). B Alpha diversity plots after V3–V4 16S rRNA sequencing analysis (*p = 0.0138, Mann–Whitney U test with FDR). Center lines of boxplots show the medians; box limits indicate the 25th and 75th percentiles; whiskers extend 15 times the interquartile range from the 25th and 75th percentiles. c Histograms of percentage relative abundance of fecal microbiota genera after taxonomic analysis of V3–V4 16S rRNA sequences. AL aleurone, PL placebo; d summary of significant changes in fecal microbiota (Mean ± SD). P p value after non parametric Mann–Whitney U test, FDR-P false discovery rate corrected p value. V1 before dietary supplementation with study foods and V2 after dietary supplementation with study foods

Fig. 3

a Boxplots showing urinary metabolites that were found significantly higher in urine of AL V2 compared to AL V1 and also compared to PL V2. b Correlation heatmap relating urinary metabolites to fecal microbial populations. Dark red indicates strong positive correlation and dark red strong negative correlation (Spearman’s). c Boxplots showing metabolites that were significantly different between after aleurone supplementation both in urine and plasma (P < 0.01). Center lines of boxplots show the medians; box limits indicate the 25th and 75th percentiles; whiskers extend 15 times the interquartile range from the 25th to 75th percentiles. d Alkylresorcinol- and Benzoxazinoid-related metabolites. Fragmentation patterns and adjusted p values are reported in Supplementary Information Table 1

Fig. 3

a Boxplots showing urinary metabolites that were found significantly higher in urine of AL V2 compared to AL V1 and also compared to PL V2. b Correlation heatmap relating urinary metabolites to fecal microbial populations. Dark red indicates strong positive correlation and dark red strong negative correlation (Spearman’s). c Boxplots showing metabolites that were significantly different between after aleurone supplementation both in urine and plasma (P < 0.01). Center lines of boxplots show the medians; box limits indicate the 25th and 75th percentiles; whiskers extend 15 times the interquartile range from the 25th to 75th percentiles. d Alkylresorcinol- and Benzoxazinoid-related metabolites. Fragmentation patterns and adjusted p values are reported in Supplementary Information Table 1

Fig. 3

a Boxplots showing urinary metabolites that were found significantly higher in urine of AL V2 compared to AL V1 and also compared to PL V2. b Correlation heatmap relating urinary metabolites to fecal microbial populations. Dark red indicates strong positive correlation and dark red strong negative correlation (Spearman’s). c Boxplots showing metabolites that were significantly different between after aleurone supplementation both in urine and plasma (P < 0.01). Center lines of boxplots show the medians; box limits indicate the 25th and 75th percentiles; whiskers extend 15 times the interquartile range from the 25th to 75th percentiles. d Alkylresorcinol- and Benzoxazinoid-related metabolites. Fragmentation patterns and adjusted p values are reported in Supplementary Information Table 1

Fig. 3

a Boxplots showing urinary metabolites that were found significantly higher in urine of AL V2 compared to AL V1 and also compared to PL V2. b Correlation heatmap relating urinary metabolites to fecal microbial populations. Dark red indicates strong positive correlation and dark red strong negative correlation (Spearman’s). c Boxplots showing metabolites that were significantly different between after aleurone supplementation both in urine and plasma (P < 0.01). Center lines of boxplots show the medians; box limits indicate the 25th and 75th percentiles; whiskers extend 15 times the interquartile range from the 25th to 75th percentiles. d Alkylresorcinol- and Benzoxazinoid-related metabolites. Fragmentation patterns and adjusted p values are reported in Supplementary Information Table 1

Fig. 4

Correlation heatmap relating clinical and anthropometric parameters to fecal microbial populations in the aleurone supplemented group. Dark red indicates strong positive correlation and dark blue strong negative correlation (Spearman’s). *Statistically significant (FDR p < 0.05)