Rye (Secale cereale) is a grass grown extensively as a cereal grain. It is a member of the wheat tribe (Triticeae) and is closely related to barley (genus Hordeum) and wheat (Triticum). Rye grain is used for flour, bread, beer, crisp bread, some whiskeys, some vodkas, and animal fodder. It can also be eaten whole, either as boiled rye berries or by being rolled, similar to rolled oats.
The cereal species seems to have an impact both on the quality and quantity of the gut microbiota.
Gut Microbial Composition
A rye bran-enriched diet can have a pronounced effect on gut microbial composition. Studies show a strong association with an increased abundance of several beneficial gut microbes, and a decreased abundance of bacteria associated with adverse health effects.
Bran-enriched diets showed an increased abundance of several microbial taxa, including the following:
- Akkermansia (Akkermansia muciniphila)
- Akkermansia muciniphila has been shown to be related to decreased fasting glucose and plasma triglycerides in a human intervention study involving a calorie-restricted diet.
- An increase in Akkermansia population and metabolic improvements were observed in mice fed with a high-fat diet containing whole-grain barley.
- This genus is also increased in abundance among multiple sclerosis patients, suggesting that it may have a role in (or increase as a consequence of) the pathogenesis of autoimmune diseases.
- Bacteroides were increased in their relative abundance after the consumption of bran-enriched diets.
- Bacteroides are a predominant bacterial group with health-promoting properties, such as the down-regulation of inflammatory biomarkers.
- The increased abundance of Bacteroides has also been associated with type I diabetes and celiac disease, and some Bacteroides species (e.g. B. ovatus) have been positively correlated with gastrointestinal dysbiosis and Crohn’s disease.
- An uncharacterized genus within the Coriobacteriaceae family, Enterorhabdus
- Members of the family Coriobacteriaceae carry out conversions of bile salts, steroids and polyphenols, and are involved in the metabolism of amino acids, nitrogen cycling, and the production of ammonia.
- These bacteria could partly be responsible for the production of amino acid-derived betaines.
- Coriobacteriaceae are associated with resistance to obesity and liver pathologies during the consumption of a high-fat diet.
- Enterorhabdus, a genus within the Coriobacteriaceae and associated with bran-enriched diets, was shown to be specific to microbiota in lean animals.
- Some genera within Coriobacteriaceae may be involved in the development of various pathologies, including infections outside of the GI tract and tumorous growths, indicating that the family should be considered as pathobionts (potentially pathogenic commensal bacteria).
- Ruminococcus species, such as R. bromii, are key microorganisms in the degradation of resistant starch, which likely explains their increased relative abundance in the bran-enriched diet.
All of these have previously been associated with improved metabolic status. Bifidobacteria and Lactobacilli are particularly well-recognized as major contributors to improved gut and overall health.
- Rye bran-enriched diets elevate the levels of betainized compounds in the colonic content and caecal tissues.
- Rye bran was shown to act as a source of glycine betaine, which is later metabolized into other betainized compounds, a process likely contributed by the same gut microbes that are favorably affected by the bran-enriched diet.
Disease / Symptom Treatment
A rye bran-enriched diet reduces the relative abundance of several bacterial taxa that are associated with adverse effects in the gut and overall health.
A bran-enriched diets showed a decreased abundance of several microbial taxa, including the following:
- Alistipes was positively associated with frailty in the elderly.
- It has been shown that Rikenella was exclusively present in the gut of type 2 diabetic mice compared to healthy mice.
- Mucispirillum is strongly correlating with genes over-expressed in colitis-associated cancer.
Study Type: Animal Study: In Vivo; Human Study: In Vitro (using a model of the human gut)
Title: Contribution of gut microbiota to metabolism of dietary glycine betaine in mice and in vitro colonic fermentation
Author(s): Ville M. Koistinen, Olli Kärkkäinen, Klaudyna Borewicz, Iman Zarei, Jenna Jokkala, Valérie Micard, Natalia Rosa-Sibakov, Seppo Auriola, Anna-Marja Aura, Hauke Smidt & Kati Hanhineva
Institution(s): Institute of Public Health and Clinical Nutrition, University of Eastern Finland, P.O. Box 1627, FI-70211, Kuopio, Finland; Laboratory of Microbiology, Wageningen University & Research, Stippeneng 4, 6708 WE, Wageningen, the Netherlands; JRU Agropolymers Engineering and Emerging Technologies (IATE 1208), SupAgro-INRA-University of Montpellier-CIRAD, Montpellier CEDEX 1, France; School of Pharmacy, University of Eastern Finland, P.O. Box 1627, FI-70211, Kuopio, Finland; VTT Technical Research Centre of Finland, P.O. Box 1000, Tietotie 2, FI-02044 VTT, Espoo, Finland
Publication: Springer Nature: BioMed Central: Microbiome Journal
Date: July 10 2019
Abstract: 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/6 J 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/6 J 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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