Potential of phenolic compounds and their gut microbiota-derived metabolites to reduce microbial TMA formation: Application of an in vitro fermentation high throughput screening model

Trimethylamine N-oxide (TMAO) is a pro-atherosclerotic product of dietary choline metabolism generated by a microbiome-host axis. The first step in this pathway is enzymatic metabolism of choline to trimethylamine (TMA) by the gut microbiota. This reaction could be targeted to reduce atherosclerosis risk. We aimed to evaluate potential inhibitory effects of select dietary phenolics and their relevant gut microbial metabolites on TMA production via a human ex vivo-in vitro fermentation model. Various phenolics inhibited choline use and TMA production. The most bioactive compounds tested (caffeic acid, catechin and epicatechin) reduced TMA-d9 formation (compared to control) by 57.5 ± 1.3% to 72.5 ± 0.4% at 8 h and preserved remaining choline-d9 concentrations by 194.1 ± 6.4% to 256.1 ± 6.3% compared to control conditions at 8 h. These inhibitory effects were achieved without altering cell respiration or cell growth. However, inhibitory effects decreased at late fermentation times, which suggest that these compounds delay choline metabolism rather than completely inhibiting TMA formation. Overall, caffeic acid, catechin and epicatechin were the most effective non-cytotoxic inhibitors of choline use and TMA production. Thus, these compounds are proposed as lead bioactives to test in vivo.

Metabolism of Selected 2-Arylbenzofurans in a Colon In Vitro Model System

2-arylbenzofurans represent a small group of bioactive compounds found in the plant family Moraceae. As it has not been investigated whether these substances are stable during passage through the gastrointestinal tract, their biological effects may be altered by the metabolism of intestinal microbiota or cells. The aim of the present study was to investigate and compare mulberrofuran Y (1), moracin C (2), and mulberrofuran G (3) in an in vitro model of human intestinal bacterial fermentation and in an epithelial model using the Caco-2 cell line. The analysis of compounds by LC-MS-Q-TOF showed sufficient stability in the fermentation model, with no bacterial metabolites detected. However, great differences in the quantity of permeation were observed in the permeability assay. Moreover, mulberrofuran Y (1) and moracin C (2) were observed to be transformed into polar metabolites by conjugation. Among the test compounds, mulberrofuran Y (1) was mostly stable and accumulated in endothelial cells (85.3%) compared with mulberrofuran G (3) and moracin C (2) (14% and 8.2%, respectively). Thus, only a small amount of mulberrofuran Y (1) was conjugated. Moracin C (2) and mulberrofuran G (3) were metabolized almost completely, with only traces of the unchanged molecule being found on the apical and cellular sides of the system. Only conjugates of mulberrofuran Y (1) and moracin C (2) were able to reach the basolateral side. Our results provide the basic description of bioavailability of these three compounds, which is a necessary characteristic for final evaluation of bio-efficacy.

Potential of phenolic compounds and their gut microbiota-derived metabolites to reduce microbial TMA formation: Application of an in vitro fermentation high throughput screening model

Trimethylamine N-oxide (TMAO) is a pro-atherosclerotic product of dietary choline metabolism generated by a microbiome-host axis. The first step in this pathway is enzymatic metabolism of choline to trimethylamine (TMA) by the gut microbiota. This reaction could be targeted to reduce atherosclerosis risk. We aimed to evaluate potential inhibitory effects of select dietary phenolics and their relevant gut microbial metabolites on TMA production via a human ex vivo-in vitro fermentation model. Various phenolics inhibited choline use and TMA production, especially larger compounds or their larger metabolites, without altering cell respiration or cell growth. However, inhibitory effects decreased at late fermentation times, which suggest that these compounds delay choline metabolism rather than completely inhibiting TMA formation. Overall, caffeic acid, catechin and epicatechin were the most effective non-cytotoxic inhibitors of choline use and TMA production. Thus, these compounds are proposed as lead bioactives to test in vivo.

Psyllium reduces inulin-induced colonic gas production in IBS: MRI and in vitro fermentation studies

ObjectiveHealth-promoting dietary fibre including inulin often triggers gastrointestinal symptoms in patients with IBS, limiting their intake. Our aim was to test if coadministering psyllium with inulin would reduce gas production.DesignA randomised, four-period, four-treatment, placebo-controlled, crossover trial in 19 patients with IBS. Subjects ingested a 500 mL test drink containing either inulin 20 g, psyllium 20 g, inulin 20 g+ psyllium 20 g or dextrose 20 g (placebo). Breath hydrogen was measured every 30 min with MRI scans hourly for 6 hours. Faecal samples from a subset of the patients with IBS were tested using an in vitro fermentation model. Primary endpoint was colonic gas assessed by MRI.ResultsColonic gas rose steadily from 0 to 6 hours, with inulin causing the greatest rise, median (IQR) AUC(0–360 min) 3145 (848–6502) mL·min. This was significantly reduced with inulin and psyllium coadministration to 618 (62–2345) mL·min (p=0.02), not significantly different from placebo. Colonic volumes AUC(0–360 min) were significantly larger than placebo for both inulin (p=0.002) and inulin and psyllium coadministration (p=0.005). Breath hydrogen rose significantly from 120 min after inulin but not psyllium; coadministration of psyllium with inulin delayed and reduced the maximum increase, AUC(0–360 min) from 7230 (3255–17910) ppm·hour to 1035 (360–4320) ppm·hour, p=0.007.Fermentation in vitro produced more gas with inulin than psyllium. Combining psyllium with inulin did not reduce gas production.ConclusionsPsyllium reduced inulin-related gas production in patients with IBS but does not directly inhibit fermentation. Whether coadministration with psyllium increases the tolerability of prebiotics in IBS warrants further study.Trial registration numberNCT03265002.

Amino acid-derived quorum sensing molecule alanine on the GIT tolerance of the lactobacillus strains in the co-cultured fermentation model

As the importance of gut microbiota in health is increasingly recognized, the interest in interventions that can modulate the microbiota and its interactions with its host has soared. The survival status of the probiotics in the gastrointestinal environment and the microbial interactions between the LAB have also received considerable attention. In the present research, the gastrointestinal environment tolerance, adhesion ability, and biofilm formation of the lactobacillus strains in the co-culture system were explored, through the real-time fluorescence-based quantitative PCR, UPLC-MS/MS metabolic profiling analysis and Live/Dead® BacLightTM cell staining methods. The results show that the co-culture system can promote the release of signal molecules and can effectively protect the liability of the Lactobacillus acidophilus in the gastrointestinal environment. Meanwhile, amino acid-derived quorum sensing molecule L-alanine (1 %) can effectively enhance the communication of the cells in the complex fermentation model, which leads to the increase of the liability of the L. acidophilus in the gastrointestinal environment.