Avenanthramides are a set of polyphenolic compounds present in whole grain oats that have demonstrated antioxidant, anti-inflammatory, and anti-proliferative effects. Metabolites of avenanthramides are produced by microbiota, which reduce a double bond producing dihydro-avenanthramide. However, this does not occur in all people, suggesting specific bacteria are responsible for the metabolism, and they are not universally present in all people. In order to determine which bacteria were responsible for the conversion, Wang and colleagues conducted a series of experiments and they report their results in the June 2021 issue of The Journal of Nutrition.
Experiments were conducted using human gut microbiota, mouse and human supernatants from liver and intestine, germ-free mice, gnotobiotic techniques, as well as a human feeding study. Microbial identification techniques included 16S rRNA sequencing and anaerobic cultures.
Mouse and human liver or intestinal supernatants were not able to generate the dihydro forms of avenanthramides. However, the metabolites were detected in the colon and distal regions of mouse intestines of pathogen free mice, but not the gnotobiotic mice. Microbial sequencing analyses identified Faecalibacterium prausnitzii as the bacterium responsible for the production of dihydro avenanthramides in those humans capable of producing the metabolites. When gnotobiotic mice were colonized with Faecalibacterium prausnitzii, their ability to generate dihydro avenanthramides was restored. The authors concluded that Faecalibacterium prausnitzii must be present for avenanthramides to be metabolized in humans and mice, and that the abundance of this bacterium can be used to categorize them as metabolizers or non-metabolizers.
In a commentary on this article, Campbell describes the systematic approach used by Wang and colleagues to conduct their work, and ultimately identify the bacterium responsible for metabolizing avenanthramides. Campbell also notes this approach should be used by others to conduct work to identify the mechanisms whereby microbiota influence health outcomes.
Wang P, Zhang S, Yerke A, Ohland CL, Gharaibeh RZ, Fouladi F, Fodor AA, Jobin C, Sang S. Avenanthramide metabotype from whole-grain oat intake is influenced by Faecalibacterium prausnitzii in healthy adults. The Journal of Nutrition, Volume 151, Issue 6, June 2021, Pages 1426–1435, https://doi.org/10.1093/jn/nxab006.
Commentary provided by:
Campbell SC. Faecalibacterium prausnitzii abundance in mouse and human gut can predict metabolism of oat avenanthramides. The Journal of Nutrition, Volume 151, Issue 6, June 2021, Pages 1369–1370, https://doi.org/10.1093/jn/nxab086.
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