Equol is a metabolite of isoflavone daidzein and has an affinity to estrogen receptors. Although equol is produced by intestinal bacteria, the association between the status of equol production and the gut microbiota has not been fully investigated. The aim of this study was to compare the intestinal bacteria responsible for equol production in gut microbiota between equol producer and non-producer subjects regarding the intake of daidzein. A total of 1044 adult subjects who participated in a health survey in Hirosaki city were examined. The concentration of equol in urine was measured by high-performance liquid chromatography. The relative abundances of 8 bacterial species responsible for equol production in the gut microbiota was assessed using 16S rRNA amplification. There were 458 subjects identified as equol producers. The proportion of equol production status and the intake of daidzein increased with age. Daily intake of daidzein was larger in equol-producer. The intestinal bacteria, which convert daidzein to equol were present in both equol producers and non-producers. However, the relative abundance and the prevalence of Asaccharobacter celatus and Slackia isoflavoniconvertens were significantly higher in equol producers than those in equol non-producers. The intestinal bacteria that convert daidzein to equol are present in not only the equol producers but also in the non-producers. The daidzein intake is associated with the equol production status through an increase of A. celatus and S. isoflavoniconvertens in the gut microbiota.
BackgroundSuppression of gastric acid by proton pump inhibitors is associated with the increase of Lactobacillus in human gut microbiota. Gastric acid secretion is also suppressed by Helicobacter pylori infection and following atrophic gastritis. However, few studies have examined the association between H. pylori infection and Lactobacillus species in gut microbiota particularly in Japan.MethodsA total of 1,123 adult subjects who participated in a health survey in Hirosaki City were studied. Infection of H. pylori was defined by both serum antibody and stool antigen test. The presence and the severity of atrophic gastritis were defined by the serum level of serum pepsinogens. Using 16S ribosomal RNA amplification from fecal samples, the relative abundance of Lactobacillus was calculated, and the composition ratio of each Lactobacillus species was surveyed.ResultsThe relative abundance of the Lactobacillus in H. pylori-infected subjects with severe atrophic gastritis was higher comparing with those in subjects with mild atrophic gastritis and without atrophic gastritis (0.591 vs 0.068% and 0.033%, respectively; p < 0.001) and also that of non-infected subjects (0.033%; p < 0.001). In H. pylori non-infected subjects, both gender and age were not associated with the relative abundance of Lactobacillus in fecal samples. The proportion of Lactobacillus salivarius was high in H. pylori-infected subjects while that of Lactobacillus acidophilus was high in non-infected subjects.ConclusionLactobacillus in human gut microbiota could be influenced by H. pylori infection and severity of atrophic gastritis in Japanese subjects.
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