Effects of a high-γ-polyglutamic acid-containing natto diet on liver lipids and cecal microbiota of adult female mice.

Natto is a traditional Japanese fermented soy product high in γ-polyglutamic acid (γ-PGA), whose beneficial effects have been reported. We prepared high-γ-PGA natto and compared the dietary influence on liver lipids and cecal microbiota in mice fed a diet containing it or a standard diet. The mice were served a 30% high-γ-PGA natto diet (PGA group) or standard diet (Con group) for 28 days. Liver lipids, fecal lipids, and fecal bile acids were quantified. Cecal microbiota were analyzed by PCR amplification of the V3 and V4 regions of 16S rRNA genes and sequenced using a MiSeq System. Additionally, the cecal short-chain fatty acid profile was assessed. The results revealed that the liver lipid and triglyceride contents were significantly lower (p<0.01) and amounts of bile acids and lipids in the feces were significantly higher in the PGA group than in the Con group. The cecal butyric acid concentration was observed to be significantly higher in the PGA group than in the Con group. Principal component analysis of the cecal microbiota revealed that the PGA and Con groups were distinct. The ratio of Firmicutes/Bacteroidetes was found to be significantly low in the PGA mice. The results revealed a significantly higher relative abundance of Lachnospiraceae (p<0.05) and significantly lower relative abundance of Coriobacteriaceae (p<0.01) in the PGA group. Analysis of the correlation between bacterial abundance and liver lipids, cecal short-chain fatty acids, fecal lipids, and fecal bile acids suggested that intestinal microbiota can be categorized into different types based on lipid metabolism. Hepatic lipid accumulation typically facilitates the onset of nonalcoholic fatty liver disease (NAFLD). Our findings suggest that high-γ-PGA natto is a beneficial dietary component for the prevention of NAFLD.

Plasma quercetin metabolites are affected by intestinal microbiota of human microbiota-associated mice fed with a quercetin-containing diet.

Protective effect of quercetin on high-fat diet-induced non-alcoholic fatty liver disease in mice has been reported. Recent research has revealed that several intestinal bacteria metabolize quercetin. We hypothesize that the difference in composition of intestinal microbiota affects quercetin absorption from the intestine. Germ-free BALB/cA female mice (18 weeks old) were randomly divided into four groups and orally administered with fecal suspension from four human individuals (HF1, HF2, HF3, HF4) to produce the human microbiota-associated mice. All mice were fed the 0.05% quercetin-containing pelleted diet for four weeks. Significant differences were observed in plasma total cholesterol and cecal microbiota among the four groups. Plasma quercetin concentration was significantly higher in the HF3 group than in the HF1 group. The plasma isorhamnetin/quercetin ratio showed significant negative correlation with visceral fat levels (r = -0.544, p = 0.013). Positive correlation was observed between the Log10 Enterobacteriaceae count and the plasma quercetin metabolites. Principal component analysis showed that all groups were distributed in different regions by using the correlation diagram with the second and third principal component. This study indicates that intestinal microbiota of human microbiota-associated mice inoculated with different fecal suspensions react to dietary quercetin in different ways.

Effects of an equol-producing bacterium isolated from human faeces on isoflavone and lignan metabolism in mice.

BACKGROUND: Equol is a metabolite of daidzein that is produced by intestinal microbiota. The oestrogenic activity of equol is stronger than daidzein. Equol-producing bacteria are believed to play an important role in the gut. The rod-shaped and Gram-positive anaerobic equol-producing intestinal bacterium Slackia TM-30 was isolated from healthy human faeces and its effects on urinary phyto-oestrogen, plasma and faecal lipids were assessed in adult mice. RESULTS: The urinary amounts of equol in urine were significantly higher in mice receiving the equol-producing bacterium TM-30 (BAC) group than in the control (CO) group (P < 0.05). However, no significant differences were observed between the urinary amounts of daidzein, dihydrodaidzein, enterodiol, and enterolactone between the BAC and CO groups. No significant differences in the plasma lipids were observed between the two groups. The lipid content (% dry weight) in the faeces sampled on the final day of the experiment tended to be higher in the BAC group than in the CO group (P = 0.07). CONCLUSION: Administration of equol-producing bacterium TM-30 affected the urinary amounts of phyto-oestrogens and the faecal lipid contents of mice. The equol-producing bacterium TM-30 likely influences the metabolism of phyto-oestrogen via changes in the gastrointestinal environment. © 2015 Society of Chemical Industry.

Relationships among fecal daidzein metabolites, dietary habit and BMI in healthy volunteers: a preliminary study.

To investigate the relationships among fecal isoflavone metabolism, dietary habit and Body Mass Index (BMI), 15 healthy men and 15 healthy women were recruited and provided stool samples for analysis of ex vivo anaerobic incubation of fecal suspension with daidzein. A negative correlation was observed between BMI and the dihydrodaidzein (DHD) production in men, and between BMI and the equol production in women. There was a positive correlation between intake of soluble dietary fiber and the DHD production in men. The results suggest that dietary habits and BMI are related to the metabolic activity of isoflavonoids by fecal intestinal microbiota.

Xylitol affects the intestinal microbiota and metabolism of daidzein in adult male mice.

This study examined the effects of xylitol on mouse intestinal microbiota and urinary isoflavonoids. Xylitol is classified as a sugar alcohol and used as a food additive. The intestinal microbiota seems to play an important role in isoflavone metabolism. Xylitol feeding appears to affect the gut microbiota. We hypothesized that dietary xylitol changes intestinal microbiota and, therefore, the metabolism of isoflavonoids in mice. Male mice were randomly divided into two groups: those fed a 0.05% daidzein with 5% xylitol diet (XD group) and those fed a 0.05% daidzein-containing control diet (CD group) for 28 days. Plasma total cholesterol concentrations were significantly lower in the XD group than in the CD group (p < 0.05). Urinary amounts of equol were significantly higher in the XD group than in the CD group (p < 0.05). The fecal lipid contents (% dry weight) were significantly greater in the XD group than in the CD group (p < 0.01). The cecal microbiota differed between the two dietary groups. The occupation ratios of Bacteroides were significantly greater in the CD than in the XD group (p < 0.05). This study suggests that xylitol has the potential to affect the metabolism of daidzein by altering the metabolic activity of the intestinal microbiota and/or gut environment. Given that equol affects bone health, dietary xylitol plus isoflavonoids may exert a favorable effect on bone health.

Effects of rice bran oil on the intestinal microbiota and metabolism of isoflavones in adult mice.

This study examined the effects of rice bran oil (RBO) on mouse intestinal microbiota and urinary isoflavonoids. Dietary RBO affects intestinal cholesterol absorption. Intestinal microbiota seem to play an important role in isoflavone metabolism. We hypothesized that dietary RBO changes the metabolism of isoflavonoids and intestinal microbiota in mice. Male mice were randomly divided into two groups: those fed a 0.05% daidzein with 10% RBO diet (RO group) and those fed a 0.05% daidzein with 10% lard control diet (LO group) for 30 days. Urinary amounts of daidzein and dihydrodaidzein were significantly lower in the RO group than in the LO group. The ratio of equol/daidzein was significantly higher in the RO group (p < 0.01) than in the LO group. The amount of fecal bile acids was significantly greater in the RO group than in the LO group. The composition of cecal microbiota differed between the RO and LO groups. The occupation ratios of Lactobacillales were significantly higher in the RO group (p < 0.05). Significant positive correlation (r = 0.591) was observed between the occupation ratios of Lactobacillales and fecal bile acid content of two dietary groups. This study suggests that dietary rice bran oil has the potential to affect the metabolism of daidzein by altering the metabolic activity of intestinal microbiota.

Effect of Dietary l-arabinose on the Intestinal Microbiota and Metabolism of Dietary Daidzein in Adult Mice.

This study examined the effects of L-arabinose on mouse intestinal microbiota and urinary isoflavonoids. Male mice were randomly divided into two groups: those fed a 0.05% daidzein-2.5% L-arabinose diet (AR group) and those fed a 0.05% daidzein control diet (CO group) for 28 days. The amounts of daidzein detected in urine were significantly lower in the AR group than in the CO group. The ratio of equol/daidzein was significantly higher in the AR group (p<0.01) than in the CO group. The composition of caecal flora differed between the AR and CO groups. The occupation ratios of Prevotella and Lactobacillales were significantly lower in the AR group. This study suggests that dietary L-arabinose has the potential to affect the metabolism of equol from daidzein by altering the metabolic activity of intestinal microbiota.

Lactobacillus rhamnosus JCM 2771: impact on metabolism of isoflavonoids in the fecal flora from a male equol producer.

Many beneficial effects of probiotics have been reported; however, few have focussed on the effects of Lactobacillus, a probiotic, on the bioconversion of isoflavonoids. We hypothesized that Lactobacillus rhamnosus will modify the metabolism of isoflavone. In an in vitro incubation, L. rhamnosus JCM 2771 produced daidzein from daidzin along with genistein. However, daidzin and genistein were not detected in the incubation solution of daidzein with L. rhamnosus. In the fecal suspension from a male equol producer with daidzein, equol was detected in the presence of a low or high concentration of L. rhamnosus. In the fecal incubation with daidzin, the equol concentration increased with an increasing concentration of L. rhamnosus JCM 2771. L. rhamnosus affected the equol production in the in vitro incubation of daidzein with fecal flora from a male equol producer. We demonstrated for the first time that L. rhamnosus JCM 2771 could produce genistein from daidzin and affect the equol production of fecal flora from a male equol producer in vitro.

Dihydrodaidzein-producing Clostridium-like intestinal bacterium, strain TM-40, affects in vitro metabolism of daidzein by fecal microbiota of human male equol producer and non-producers.

Much attention has been focused on the biological effects of equol, a metabolite of daidzein produced by intestinal microbiota. However, little is known about the role of isoflavone metabolizing bacteria in the intestinal microbiota. Recently, we isolated a dihydrodaidzein (DHD)-producing Clostridium-like bacterium, strain TM-40, from human feces. We investigated the effects of strain TM-40 on in vitro daidzein metabolism by human fecal microbiota from a male equol producer and two male equol non-producers. In the fecal suspension from the male equol non-producer and DHD producer, DHD was detected in the in vitro fecal incubation of daidzein after addition of TM-40. The DHD concentration increased as the concentration of strain TM-40 increased. In the fecal suspension from the equol producer, the fecal equol production was increased by the addition of strain TM-40. The occupation ratios of Bifidobacterium and Lactobacillales were higher in the equol non-producers than in the equol producer. Adding isoflavone-metabolizing bacteria to the fecal microbiota should facilitate the estimation of the metabolism of isoflavonoids by fecal microbiota. Studies on the interactions among equol-producing microbiota and DHD-producing bacteria might lead to clarification of some of the mechanisms regulating the production of equol by fecal microbiota.

Dietary cholesterol lowers plasma and cecal equol concentrations in mice.

This study examined the effects of cholesterol on mouse intestinal microflora and on isoflavonoids in the cecum and plasma. Dietary cholesterol affects bile acid metabolism and bile acids can influence the intestinal microorganisms. Intestinal microflora appear to play an important role in isoflavone metabolism. We hypothesized that dietary cholesterol changes the metabolism of isoflavonoids and intestinal microorganisms in mice. Male mice were randomly divided into two groups, which were fed a cholesterol-daidzein (CDA) or daidzein (DA) diet (control diet) for 60d. Plasma equol and cecal equol concentrations were significantly higher in the DA group (control group) than in the CDA group. However, plasma cholesterol concentrations were significantly higher in the CDA group compared to the DA group. The composition of cecal microorganisms differed between the two dietary groups. The occupation ratios of Clostridium cluster XI, Clostridium subcluster XIVa, and Lactobacillales were significantly higher in the CDA group. The occupation ratio of Bifidobacterium was significantly lower in the CDA group. This study suggests that dietary cholesterol has the potential to affect the metabolism of equol from daidzein by altering the metabolic activity of the intestinal microorganisms and gut physiological function.

Lactobacillus collinoides JCM1123(T): effects on mouse plasma cholesterol and isoflavonoids in the caecum.

The effects of Lactobacillus collinoides JCM1123(T) on plasma cholesterol levels, isoflavonoids in the caecum and faecal flora were assessed in adult mice. L. collinoides JCM1123(T) altered the equol production status in in vitro incubation of daidzein with faecal flora of mice. In in vivo investigation, mice were fed an AIN-93M purified diet for 13 days, and then randomly divided into two groups of seven animals each. All mice were fed an AIN-93M diet for 6 days; then the diet was replaced with a 0.05% daidzein diet, the mice received a 0.05% daidzein diet for 4 days. Two groups of mice were administered either L. collinoides JCM1123(T) (the experimental group) or a physiological saline solution (the control group) daily for 10 days and dissection was performed on the following day. The total plasma cholesterol concentration was significantly higher in the control group than in the experimental group. The amount of daidzein present in the caecum was significantly higher in the control group than in the experimental group. Significantly higher numbers of lactobacilli were observed in the experimental group than in the control group. Our data suggest that the administration of L. collinoides is likely to influence the metabolism of isoflavonoids and endogenous cholesterol via changes in the gastrointestinal environment.