Vasorelaxant activity of twenty-one physiologically relevant (poly)phenolic metabolites on isolated mouse arteries.

Polyphenols are beneficial for health, but are metabolised after consumption. We compared the vasorelaxant capacity of twenty-one physiologically relevant polyphenol metabolites in isolated mouse arteries. Hesperetin, urolithins and ferulic acid-4-O-sulfate - not their glucuronidated forms or ferulic acid - caused vasorelaxation. Therefore, we advise the use of relevant conjugates in future mechanistic research.

Prebiotics to manage the microbial control of energy homeostasis.

The prevalence of obesity is continuously growing and has reached epidemic proportions. It is clear that current methods to combat obesity are not effective enough to reduce the problem. Therefore, further investigation is needed to develop new strategies. Recent research pointed out a potential role of the microbial community associated to the human host in controlling and influencing the energy homeostasis. According to the concept of Gastrointestinal Resource Management, this microbiota and its metabolic potential can be steered with the aim of improving host health. This review therefore focuses on the modulation of the intestinal microbiota through prebiotics with the aim to control several aspects of metabolic homeostasis. In a first part, the importance of host-microbe cross-talk at the intestinal epithelium is discussed. Yet, energy metabolism, which includes both lipid and glucose metabolism, is also regulated by several key organs including the adipose tissue, brain, liver, muscles, pancreas and gut. Therefore, in a second part, we will discuss the microbial factors that are involved in the communication between these different tissues, and their potential management. Finally, we will give some future prospects of the use of prebiotics in an individualised treatment of metabolic disorders.

Chemopreventive effects from prebiotic inulin towards microbial 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine bioactivation.

AIMS: Using a Simulator of the Human Intestinal Microbial Ecosystem (SHIME), we investigated the chemopreventive potential of prebiotic chicory inulin towards the in vitro bioactivation of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) by human intestinal microbiota. METHODS AND RESULTS: HPLC data revealed that inulin significantly decreased the formation of the genotoxic PhIP-M1 metabolite, with the highest inhibitory activity in the colon ascendens (87% decrease). Interestingly, this chemopreventive effect correlated with alterations of bacterial community composition and metabolism in the different colon compartments. Conventional culture-based techniques and PCR-DGGE analysis on the SHIME colon suspension revealed significant bifidogenic effects during inulin treatment, whereas the overall microbial community kept relatively unchanged. Additionally, the production of short-chain fatty acids increased with 12%, 3% and 7%, while ammonia concentrations decreased with 3%, 4% and 3% in the ascending, transverse and descending colon compartments, respectively. CONCLUSIONS: These results indicate that the prebiotic effects from inulin may also purport protective effects towards microbial PhIP bioactivation. SIGNIFICANCE AND IMPACT OF THE STUDY: As the colonic microbiota may contribute significantly to the carcinogenic potential of PhIP, the search for dietary constituents that decrease the formation of this harmful metabolite, may help in preventing its risk towards human health.

Arabinoxylan-oligosaccharides (AXOS) affect the protein/carbohydrate fermentation balance and microbial population dynamics of the Simulator of Human Intestinal Microbial Ecosystem.

Arabinoxylan-oligosaccharides (AXOS) are a recently newly discovered class of candidate prebiotics as - depending on their structure - they are fermented in different regions of gastrointestinal tract. This can have an impact on the protein/carbohydrate fermentation balance in the large intestine and, thus, affect the generation of potentially toxic metabolites in the colon originating from proteolytic activity. In this study, we screened different AXOS preparations for their impact on the in vitro intestinal fermentation activity and microbial community structure. Short-term fermentation experiments with AXOS with an average degree of polymerization (avDP) of 29 allowed part of the oligosaccharides to reach the distal colon, and decreased the concentration of proteolytic markers, whereas AXOS with lower avDP were primarily fermented in the proximal colon. Additionally, prolonged supplementation of AXOS with avDP 29 to the Simulator of Human Intestinal Microbial Ecosystem (SHIME) reactor decreased levels of the toxic proteolytic markers phenol and p-cresol in the two distal colon compartments and increased concentrations of beneficial short-chain fatty acids (SCFA) in all colon vessels (25-48%). Denaturant gradient gel electrophoresis (DGGE) analysis indicated that AXOS supplementation only slightly modified the total microbial community, implying that the observed effects on fermentation markers are mainly caused by changes in fermentation activity. Finally, specific quantitative PCR (qPCR) analysis showed that AXOS supplementation significantly increased the amount of health-promoting lactobacilli as well as of Bacteroides-Prevotella and Clostridium coccoides-Eubacterium rectale groups. These data allow concluding that AXOS are promising candidates to modulate the microbial metabolism in the distal colon.