Contribution of gut microbiota to metabolism of dietary glycine betaine in mice and in vitro colonic fermentation
Koistinen, Ville M. | Kärkkäinen, Olli | Borewicz, Klaudyna | Zarei, Iman | Jokkala, Jenna | Micard, Valerie | Rosa-Sibakov, Natalia | Auriola, Seppo | Aura, Anna-Marja | Smidt, Hauke | Hanhineva, Kati | Institute of Public Health and Clinical Nutrition ; University of Eastern Finland | Laboratory of Microbiology ; Wageningen University and Research [Wageningen] (WUR) | Ingénierie des Agro-polymères et Technologies Émergentes (UMR IATE) ; Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut National de la Recherche Agronomique (INRA)-Université Montpellier 2 - Sciences et Techniques (UM2)-Centre international d'études supérieures en sciences agronomiques (Montpellier SupAgro)-Université de Montpellier (UM)-Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro) | VTT Technical Research Centre of Finland (VTT) | School of Pharmacy ; Shujitsu University | Faculty of Health Sciences (University of Eastern Finland) ; the Academy of Finland
Background: Accumulating evidence is supporting the protective effect of whole grains against several chronic diseases. Simultaneously, our knowledge is increasing on the impact of gut microbiota on our health and on how diet can modify the composition of our bacterial cohabitants. Herein, we studied C57BL/6J mice fed with diets enriched with rye bran and wheat aleurone, conventional and germ-free C57BL/6NTac mice on a basal diet, and the colonic fermentation of rye bran in an in vitro model of the human gastrointestinal system. We performed 16S rRNA gene sequencing and metabolomics on the study samples to determine the effect of bran-enriched diets on the gut microbial composition and the potential contribution of microbiota to the metabolism of a novel group of betainized compounds.Results: The bran-enriched study diets elevated the levels of betainized compounds in the colon contents of C57BL/6J mice. The composition of microbiota changed, and the bran-enriched diets induced an increase in the relative abundance of several bacterial taxa, including Akkermansia, Bifidobacterium, Coriobacteriaceae, Lactobacillus, Parasutterella, and Ruminococcus, many of which are associated with improved health status or the metabolism of plant-based molecules. The levels of betainized compounds in the gut tissues of germ-free mice were significantly lower compared to conventional mice. In the in vitro model of the human gut, the production of betainized compounds was observed throughout the incubation, while the levels of glycine betaine decreased. In cereal samples, only low levels or trace amounts of other betaines than glycine betaine were observed.Conclusions: Our findings provide evidence that the bacterial taxa increased in relative abundance by the bran-based diet are also involved in the metabolism of glycine betaine into other betainized compounds, adding another potential compound group acting as a mediator of the synergistic metabolic effect of diet and colonic microbiota.
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