Metabolism of anthocyanins by human gut microflora and their influence on gut bacterial growth

Consumption of anthocyanins has been related with beneficial health effects. However, bioavailability studies have shown low concentration of anthocyanins in plasma and urine. In this study, we have investigated the bacterial-dependent metabolism of malvidin-3-glucoside, gallic acid and a mixture of anthocyanins using a pH-controlled, stirred, batch-culture fermentation system reflective of the distal human large intestine conditions. Most anthocyanins have disappeared after 5 h incubation while gallic acid remained constant through the first 5 h and was almost completely degraded following 24 h of fermentation. Incubation of malvidin-3-glucoside with fecal bacteria mainly resulted in the formation of syringic acid, while the mixture of anthocyanins resulted in formation of gallic, syringic and p-coumaric acids. All the anthocyanins tested enhanced significantly the growth of Bif idobacterium spp. and Lactobacillus−Enterococcus spp. These results suggest that anthocyanins and their metabolites may exert a positive modulation of the intestinal bacterial population.

Influence of 10 wk of soy consumption on plasma concentrations and excretion of isoflavonoids and on gut microflora metabolism in healthy adults

Although interindividual variation in isoflavone metabolism was high, intraindividual variation was low. Only concentrations of O-DMA in plasma and urine appeared to be influenced by sex. Chronic soy consumption does not appear to induce many significant changes to the gut metabolism of isoflavones other than higher beta-glucosidase activity.

Role of glutamate metabolism in bacterial responses towards acid and other stresses

Glutamate plays a central role in a wide range of metabolic processes in bacterial cells. This review focuses on the involvement of glutamate in bacterial stress responses. In particular it reviews the role of glutamate metabolism in response against acid stress and other stresses. The glutamate decarboxylase (GAD) system has been implicated in acid tolerance in several bacterial genera. This system facilitates intracellular pH homeostasis by consuming protons in a decarboxylation reaction that produces γ-aminobutyrate (GABA) from glutamate. An antiporter system is usually present to couple the uptake of glutamate to the efflux of GABA. Recent insights into the functioning of this system will be discussed. Finally the intracellular fate of GABA will also be discussed. Many bacteria are capable of metabolising GABA to succinate via the GABA shunt pathway. The role and regulation of this pathway will be addressed in the review. © 2012 The Authors Journal of Applied Microbiology © 2012 The Society for Applied Microbiology.

Insight into the prebiotic concept: lessons from an exploratory, double blind intervention study with inulin-type fructans in obese women

Objective To highlight the contribution of the gut microbiota to the modulation of host metabolism by dietary inulin-type fructans (ITF prebiotics) in obese women. Methods A double blind, placebo controlled, intervention study was performed with 30 obese women treated with ITF prebiotics (inulin/oligofructose 50/50 mix; n=15) or placebo (maltodextrin; n=15) for 3 months (16 g/day). Blood, faeces and urine sampling, oral glucose tolerance test, homeostasis model assessment and impedancemetry were performed before and after treatment. The gut microbial composition in faeces was analysed by phylogenetic microarray and qPCR analysis of 16S rDNA. Plasma and urine metabolic profiles were analysed by 1H-NMR spectroscopy. Results Treatment with ITF prebiotics, but not the placebo, led to an increase in Bifidobacterium and Faecalibacterium prausnitzii; both bacteria negatively correlated with serum lipopolysaccharide levels. ITF prebiotics also decreased Bacteroides intestinalis, Bacteroides vulgatus and Propionibacterium, an effect associated with a slight decrease in fat mass and with plasma lactate and phosphatidylcholine levels. No clear treatment clustering could be detected for gut microbial analysis or plasma and urine metabolomic profile analyses. However, ITF prebiotics led to subtle changes in the gut microbiota that may importantly impact on several key metabolites implicated in obesity and/or diabetes. Conclusions ITF prebiotics selectively changed the gut microbiota composition in obese women, leading to modest changes in host metabolism, as suggested by the correlation between some bacterial species and metabolic endotoxaemia or metabolomic signatures.

APOE genotype influences triglyceride and C-reactive protein responses to altered dietary fat intake in UK adults

Background: The response of plasma lipids to dietary fat manipulation is highly heterogeneous, with some indications that APOE genotype may be important. Objective: The objective was to use a prospective recruitment approach to determine the effect of dietary fat quantity and composition on both lipid and nonlipid cardiovascular disease biomarkers according to APOE genotype. Design: Participants had a mean (±SD) age of 51 ± 9 y and a BMI (in kg/m2) of 26.0 ± 3.8 (n = 44 E3/E3, n = 44 E3/E4) and followed a sequential dietary intervention (the SATgenϵ study) in which they were assigned to a low-fat diet, a high-fat high-SFA (HSF) diet, and the HSF diet with 3.45 g DHA/d (HSF-DHA), each for 8 wk. Fasting blood samples were collected at the end of each intervention arm. Results: An overall diet effect was evident for all cholesterol fractions (P < 0.01), with no significant genotype × diet interactions observed. A genotype × diet interaction (P = 0.033) was evident for plasma triglycerides, with 17% and 30% decreases in APOE3/E3 and APOE3/E4 individuals after the HSF-DHA diet relative to the low-fat diet. A significant genotype × diet interaction (P = 0.009) was also observed for C-reactive protein (CRP), with only significant increases in concentrations after the HSF and HSF-DHA diets relative to the low-fat diet in the APOE3/E4 group (P < 0.015). Conclusions: Relative to the wild-type APOE3/E3 group, our results indicate a greater sensitivity of fasting triglycerides and CRP to dietary fat manipulation in those with an APOE3/E4 genotype (25% population), with no effect of this allelic profile on cholesterol concentrations. The SATgenϵ study was registered at clinicaltrials.gov as NCT01384032.

Fermentable carbohydrate alters hypothalamic neuronal activity and protects against the obesogenic environment

Obesity has become a major global health problem. Recently, attention has focused on the benefits of fermentable carbohydrates on modulating metabolism. Here, we take a system approach to investigate the physiological effects of supplementation with oligofructose-enriched inulin (In). We hypothesize that supplementation with this fermentable carbohydrate will not only lead to changes in body weight and composition, but also to modulation in neuronal activation in the hypothalamus. Male C57BL/6 mice were maintained on a normal chow diet (control) or a high fat (HF) diet supplemented with either oligofructose-enriched In or corn starch (Cs) for 9 weeks. Compared to HF+Cs diet, In supplementation led to significant reduction in average daily weight gain (mean ± s.e.m.: 0.19 ± 0.01 g vs. 0.26 ± 0.02 g, P < 0.01), total body adiposity (24.9 ± 1.2% vs. 30.7 ± 1.4%, P < 0.01), and lowered liver fat content (11.7 ± 1.7% vs. 23.8 ± 3.4%, P < 0.01). Significant changes were also observed in fecal bacterial distribution, with increases in both Bifidobacteria and Lactobacillius and a significant increase in short chain fatty acids (SCFA). Using manganese-enhanced MRI (MEMRI), we observed a significant increase in neuronal activation within the arcuate nucleus (ARC) of animals that received In supplementation compared to those fed HF+Cs diet. In conclusion, we have demonstrated for the first time, in the same animal, a wide range of beneficial metabolic effects following supplementation of a HF diet with oligofructose-enriched In, as well as significant changes in hypothalamic neuronal activity.

Microbiological, chemical and rheological properties of low fat set yoghurt produced with exopolysaccharide (EPS) producing Bifidobacterium strains.

In this work, the microbiological and physicochemical differences of three types of low fat set yoghurts were studied, as well as the changes taking place during storage at 4 °C for 28 days. The first yoghurt was produced with yoghurt starters and exopolysaccharide (EPS) producing Bifidobacterium longum subsp. infantis CCUG 52486 (CCUGY), the second with yoghurt starters and Bifidobacterium infantis NCIMB 702205 (NCIMBY) and the third with just yoghurt starters (control yoghurt). No significant differences were observed in terms of cell concentrations; for all three yoghurts, similar final cell concentrations were obtained for the yoghurt starter cultures (~7.5 log cfu g−1) and the Bifidobacterium strains (~7.8 log cfu g−1). Both Bifidobacterium survived well during storage, as in both cases the cell viability decreased by less than 0.5 log cfu g−1after 28 days of storage. A decrease in pH followed by an increase in lactic acid was observed during storage for all three yoghurts, which was mostly attributed to the activity of the yoghurt starter cultures. The two yoghurts with the EPS producing Bifidobacterium strains exhibited lower syneresis than the control yoghurt. The lowest was shown by CCUGY, which also exhibited the highest storage modulus and firmness, and a well defined porous web-like structure in cryo-SEM. Examination of the micro-structure of the yoghurts using cryo-scanning electron microscopy (cryo-SEM) indicated that the above observations were due to the interaction between the EPS and the milk proteins. Overall, the results indicated that the EPS producing Bifidobacterium longum subsp. infantis CCUG 52486 is the most promising strain, and can be used with yoghurt starter cultures to manufacture low fat set yoghurt with probiotic activities and at the same time enhanced physicochemical and rheological properties.

Gene-nutrient interactions on the phosphoenolpyruvate carboxykinase influence insulin sensitivity in metabolic syndrome subjects

Genetic background may interact with habitual dietary fat composition, and affect development of the metabolic syndrome (MetS). The phosphoenolpyruvate carboxykinase gene (PCK1) plays a significant role regulating glucose metabolism, and fatty acids are key metabolic regulators, which interact with transcription factors and influence glucose metabolism. We explored genetic variability at the PCK1 gene locus in relation to degree of insulin resistance and plasma fatty acid levels in MetS subjects. Moreover, we analyzed the PCK1 gene expression in the adipose tissue of a subgroup of MetS subjects according to the PCK1 genetic variants.

Impact of probiotics, prebiotics and synbiotics on lipid metabolism in humans

Public health strategies for reducing the risk of coronary heart disease have focused on lowering plasma lipids, particularly cholesterol levels, with recent studies also highlighting triacylglycerol (TAG) as an important modifiable risk factor. One approach is to supplement the diet with probiotics, prebiotics or synbiotics. Probiotics are live microorganisms which when administered in adequate amounts confer a health benefit on the host. Putative health benefits include improved resistance to gastrointestinal infections, reduction in lipid levels and stimulation of the immune system. Prebiotics are selectively fermented dietary components that are aimed at improving host health through selective fermentation by the gut microbiota, such as bifidobacteria and lactobacilli. Animal studies have shown prebiotics to markedly reduce circulating TAG and to a lesser extent cholesterol concentrations, with favourable but inconsistent findings with respect to changes in lipid levels in human studies. Here we provide an overview of the effects, and possible mechanisms, of probiotics, prebiotics and synbiotics (combination of a probiotic and prebiotic) on circulating lipeamia in humans.

Sustainable urban metabolism as a link between bio-physical sciences and urban planning: the BRIDGE project

Urban metabolism considers a city as a system with flows of energy and material between it and the environment. Recent advances in bio-physical sciences provide methods and models to estimate local scale energy, water, carbon and pollutant fluxes. However, good communication is required to provide this new knowledge and its implications to endusers (such as urban planners, architects and engineers). The FP7 project BRIDGE (sustainaBle uRban plannIng Decision support accountinG for urban mEtabolism) aimed to address this gap by illustrating the advantages of considering these issues in urban planning. The BRIDGE Decision Support System (DSS) aids the evaluation of the sustainability of urban planning interventions. The Multi Criteria Analysis approach adopted provides a method to cope with the complexity of urban metabolism. In consultation with targeted end-users, objectives were defined in relation to the interactions between the environmental elements (fluxes of energy, water, carbon and pollutants) and socioeconomic components (investment costs, housing, employment, etc.) of urban sustainability. The tool was tested in five case study cities: Helsinki, Athens, London, Florence and Gliwice; and sub-models were evaluated using flux data selected. This overview of the BRIDGE project covers the methods and tools used to measure and model the physical flows, the selected set of sustainability indicators, the methodological framework for evaluating urban planning alternatives and the resulting DSS prototype.