Characteristic Gut Bacteria in High Barley Consuming Japanese Individuals without Hypertension.

BACKGROUND: Barley, a grain rich in soluble dietary fiber ß-glucan, is expected to lower blood pressure. Conversely, individual differences in its effects on the host might be an issue, and gut bacterial composition may be a determinant. METHODS: Using data from a cross-sectional study, we examined whether the gut bacterial composition could explain the classification of a population with hypertension risks despite their high barley consumption. Participants with high barley intake and no occurrence of hypertension were defined as "responders" (n = 26), whereas participants with high barley intake and hypertension risks were defined as "non-responders" (n = 39). RESULTS: 16S rRNA gene sequencing revealed that feces from the responders presented higher levels of Faecalibacterium, Ruminococcaceae UCG-013, Lachnospira, and Subdoligranulum and lower levels of Lachnoclostridium and Prevotella 9 than that from non-responders. We further created a machine-learning responder classification model using random forest based on gut bacteria with an area under the curve value of 0.75 for estimating the effect of barley on the development of hypertension. CONCLUSIONS: Our findings establish a link between the gut bacteria characteristics and the predicted control of blood pressure provided by barley intake, thereby providing a framework for the future development of personalized dietary strategies.

Co-ingestion of traditional Japanese barley mixed rice (Mugi gohan) with yam paste in healthy Japanese adults decreases postprandial glucose and insulin secretion in a randomized crossover trial.

BACKGROUND AND OBJECTIVES: Barley mixed rice, "Mugi gohan," is traditionally eaten with yam paste in Japan. Both ingredients contain dietary fiber and reportedly reduce postprandial hyperglycemia. However, evidence supporting the benefits of combining barley mixed rice with yam paste is limited. In this study, we evaluated whether ingesting a combination of barley mixed rice and yam paste affected postprandial blood glucose concentration and insulin secretion. METHODS AND STUDY DESIGN: This study followed an open-label, randomized controlled crossover design, following the unified protocol of the Japanese Association for the Study of Glycemic Index. Fourteen healthy subjects each consumed four different test meals: white rice only, white rice with yam paste, barley mixed rice, and barley mixed rice with yam paste. We measured their postprandial blood glucose and insulin concentrations after every meal, and we calculated the area under curve for glucose and insulin. RESULTS: Participants had significantly reduced area under curve for glucose and insulin after eating barley mixed rice with yam paste compared to when they ate white rice only. Participants had similar area under curve for glucose and insulin after eating barley mixed rice only, or eating white rice with yam paste. Participants had lower blood glucose concentrations 15 min after eating barley mixed rice only, whilst eating white rice with yam paste did not maintain lower blood glucose after 15 min. CONCLUSIONS: Eating barley mixed rice with yam paste decreases postprandial blood glucose concentrations and reduces insulin secretion.

Metabologenomic Approach Reveals Intestinal Environmental Features Associated with Barley-Induced Glucose Tolerance Improvements in Japanese: A Randomized Controlled Trial.

(1) Background: Consumption of barley has been known to exert beneficial effects on glucose tolerance; however, it has also been reported that there are inter-individual differences in these responses. Recent evidence has suggested that these individual differences are mediated by the gut microbiota. (2) Methods: In the present study, we aimed to understand the relationship between the intestinal environment, including intestinal microbiome and their metabolome, and glucose tolerance. A randomized controlled trial with a 4-week consumption of barley or control food was conducted. We conducted an integrated analysis of the intestinal microbiome and metabolome and analyzed the relationship with improvement of glucose tolerance. (3) Results: We found that metabolites such as azelate were significantly increased after barley consumption. Furthermore, the subjects whose glucose tolerance was slightly impaired showed improvement in their glucose tolerance index following the barley consumption. Additionally, the analysis showed that the increase in the abundance of the Anaerostipes was correlated with the improvement in the glucose tolerance index. (4) Conclusions: Our findings indicate that the effects of barley consumption for glucose tolerance are partly defined by the intestinal environment of consumers, providing a quantitative measurement of the dietary effect based on the intestinal environment.

Effects of barley intake on glycemic control in Japanese patients with type 2 diabetes mellitus undergoing antidiabetic therapy: a prospective study.

Background: Barley reportedly reduces postprandial hyperglycemia in healthy individuals. However, its effects in patients with type 2 diabetes mellitus (T2DM) undergoing antidiabetic therapy remains unclear. This study aimed to clarify the effects of barley intake on postprandial hyperglycemia in T2DM patients who use metformin or acarbose. Methods: T2DM patients who were undergoing dietary therapy without medications (naive), with metformin, or with acarbose (n = 10/group) were recruited. They were instructed to eat white rice twice per day for 5 days, followed by barley-mixed rice twice per day for 6 or 7 days. Subsequently, blood glucose fluctuations in the interstitial fluid glucose were measured using a continuous glucose monitoring device. Meal tolerance tests were performed using test diets containing white rice and barley-mixed rice before and after the trial, respectively. Results: Postprandial hyperglycemia was lower in patients taking barley-mixed rice than in those taking white rice in each group. However, the AUC of blood glucose concentration in the acarbose-treated patients showed only a trend. Mean amplitude of glycemic excursions (MAGEs) decreased in patients who consumed barley-mixed rice. Additionally, although MAGEs in the naive decreased, it did not in the metformin- (P = 0.098) and acarbose-treated (P = 0.29) patients. Conclusion: Barley-mixed rice lowers postprandial glucose concentrations in treatment-naive and metformin-treated T2DM patients, and shows a trend in acarbose-treated patients. Therefore, using barley-containing diets as dietary therapy may be useful in improving glycemic control in diabetes patients. Trial registration: UMIN000028623. Supplementary Information: The online version contains supplementary material available at 10.1007/s13340-021-00552-z.

Classification of the Occurrence of Dyslipidemia Based on Gut Bacteria Related to Barley Intake.

Barley is a grain rich in ß-glucan, a soluble dietary fiber, and its consumption can help maintain good health and reduce the risk of metabolic disorders, such as dyslipidemia. However, the effect of barley intake on the risk of dyslipidemia has been found to vary among individuals. Differences in gut bacteria among individuals may be a determining factor since dietary fiber is metabolized by gut bacteria and then converted into short-chain fatty acids with physiological functions that reduce the risk of dyslipidemia. This study examined whether gut bacteria explained individual differences in the effects of barley intake on dyslipidemia using data from a cross-sectional study. In this study, participants with high barley intake and no dyslipidemia were labeled as "responders" to the reduced risk of dyslipidemia based on their barley intake and their gut bacteria. The results of the 16S rRNA gene sequencing showed that the fecal samples of responders (n = 22) were richer in Bifidobacterium, Faecalibacterium, Ruminococcus 1, Subdoligranulum, Ruminococcaceae UCG-013, and Lachnospira than those of non-responders (n = 43), who had high barley intake but symptoms of dyslipidemia. These results indicate the presence of certain gut bacteria that define barley responders. Therefore, we attempted to generate a gut bacteria-based responder classification model through machine learning using random forest. The area under the curve value of the classification model in estimating the effect of barley on the occurrence of dyslipidemia in the host was 0.792 and the Matthews correlation coefficient was 0.56. Our findings connect gut bacteria to individual differences in the effects of barley on lipid metabolism, which could assist in developing personalized dietary strategies.

Relationships between barley consumption and gut microbiome characteristics in a healthy Japanese population: a cross-sectional study.

BACKGROUND: Barley contains abundant soluble beta-glucan fibers, which have established health benefits. In addition, the health benefits conferred by the gut bacteria have attracted considerable interest. However, few studies have focused on the barley consumption and gut bacteria of the Japanese population. In this study, we aimed to identify the relationship between the barley consumption and gut bacteria composition of the Japanese population. METHODS: In total, 236 participants were recruited in Japan, and 94 participants with no complications of diabetes, hypertension, or dyslipidemia were selected for the study. We analyzed fecal samples from the participants, their medical check-up results, and responses to questionnaires about dietary habits. The participants were grouped according to their median barley consumption. Then, we assessed the relative abundance of 50 genera. Characteristic bacteria were evaluated for their relationship with barley consumption by multiple regression analysis, adjusted for disease and dietary habits, in all participants. We also analyzed the networks and clustering of the 20 selected genera. RESULTS: According to the comparison between barley groups, Bifidobacterium, Butyricicoccus, Collinsella, Ruminococcus 2, and Dialister were characteristic candidate bacterias of the group that consumed large amounts of barley (P < 0.05). The relationship between barley consumption and Bifidobacterium remained after adjusting for disease and dietary habits, and that of Butyricicoccus remained after adjusting for disease. Furthermore, network and cluster analyses revealed that barley consumption was directly correlated with Bifidobacterium and Butyricicoccus. CONCLUSIONS: Barley consumption generates changes in the intestinal bacteria of the Japanese population. We found that Bifidobacterium and Butyricicoccus abundance was positively associated with barley consumption.

Ingestion of High ß-Glucan Barley Flour Enhances the Intestinal Immune System of Diet-Induced Obese Mice by Prebiotic Effects.

The prebiotic effect of high ß-glucan barley (HGB) flour on the innate immune system of high-fat model mice was investigated. C57BL/6J male mice were fed a high-fat diet supplemented with HGB flour for 90 days. Secretory immunoglobulin A (sIgA) in the cecum and serum were analyzed by enzyme-linked immunosorbent assays (ELISA). Real-time PCR was used to determine mRNA expression levels of pro- and anti-inflammatory cytokines such as interleukin (IL)-10 and IL-6 in the ileum as well as the composition of the microbiota in the cecum. Concentrations of short-chain fatty acids (SCFAs) and organic acids were analyzed by GC/MS. Concentrations of sIgA in the cecum and serum were increased in the HGB group compared to the control. Gene expression levels of IL-10 and polymeric immunoglobulin receptor (pIgR) significantly increased in the HGB group. HGB intake increased the bacterial count of microbiota, such as Bifidobacterium and Lactobacillus. Concentrations of propionate and lactate in the cecum were increased in the HGB group, and a positive correlation was found between these organic acids and the IL-10 expression level. Our findings showed that HGB flour enhanced immune function such as IgA secretion and IL-10 expression, even when the immune system was deteriorated by a high-fat diet. Moreover, we found that HGB flour modulated the gut microbiota, which increased the concentration of SCFAs, thereby stimulating the immune system.

Effects of ß-glucan Rich Barley Flour on Glucose and Lipid Metabolism in the Ileum, Liver, and Adipose Tissues of High-Fat Diet Induced-Obesity Model Male Mice Analyzed by DNA Microarray.

We evaluated whether intake of ß-glucan-rich barley flour affects expression levels of genes related to glucose and lipid metabolism in the ileum, liver, and adipose tissues of mice fed a high-fat diet. C57BL/6J male mice were fed a high-fat diet supplemented with high ß-glucan barley, for 92 days. We measured the expression levels of genes involved in glucose and lipid metabolism in the ileum, liver, and adipose tissues using DNA microarray and q-PCR. The concentration of short-chain fatty acids (SCFAs) in the cecum was analyzed by GC/MS. The metabolic syndrome indices were improved by barley flour intake. Microarray analysis showed that the expression of genes related to steroid synthesis was consistently decreased in the liver and adipose tissues. The expression of genes involved in glucose metabolism did not change in these organs. In liver, a negative correlation was showed between some SCFAs and the expression levels of mRNA related to lipid synthesis and degradation. Barley flour affects lipid metabolism at the gene expression levels in both liver and adipose tissues. We suggest that SCFAs are associated with changes in the expression levels of genes related to lipid metabolism in the liver and adipose tissues, which affect lipid accumulation.

Consumption of a meal containing refined barley flour bread is associated with a lower postprandial blood glucose concentration after a second meal compared with one containing refined wheat flour bread in healthy Japanese: A randomized control trial.

OBJECTIVE: Foods reducing postprandial hyperglycemia could suppress the postprandial blood glucose response after the next meal (a "second-meal" effect). However, the second-meal effect of refined barley flour bread has not been evaluated. The aim of this study is to determine whether consumption of refined barley flour bread reduces postprandial glucose concentrations after this and the subsequent meal. METHODS: We enrolled 23 healthy young Japanese adults and conducted a randomized, double-blind, placebo-controlled, crossover study. The participants consumed refined barley flour bread containing 2.5 g ß-glucan or refined wheat flour bread in a first meal, then consumed three rice balls as a second meal. Their postprandial blood glucose concentrations were measured 0, 15, 30, 45, 60, 90, and 120 min after both meals. Participants with fasting glucose concentrations above the diagnostic threshold for diabetes were excluded. RESULTS: The blood glucose concentration 30 min after the first meal was significantly lower (P < 0.05) if refined barley flour bread (7.1 ± 1.0 mmol/L) rather than refined wheat flour bread (7.7 ± 1.2 mmol/L) was consumed. Significantly lower glucose concentrations after the second meal measured at 60 (P < 0.05, barley flour bread: 8.7 ± 1.8 mmol/L, wheat flour bread: 9.3 ± 1.7 mmol/L) and 90 min (P < 0.01, barley flour bread: 7.8 ± 1.4 mmol/L, wheat flour bread: 8.8 ± 2.1 mmol/L) were lower in participants who had previously consumed the refined barley flour bread. CONCLUSIONS: Consumption of bread made with refined barley flour lowers postprandial blood glucose concentration after this and a subsequent meal compared with the consumption of refined wheat flour bread in healthy young Japanese adults.