Is there sufficient 'sink' in current bioaccessibility determinations of organic pollutants in soils?

Bioaccessibility tests can be used to improve contaminated land risk assessments. For organic pollutants a ‘sink’ is required within these tests to better mimic their desorption under the physiological conditions prevailing in the intestinal tract, where a steep diffusion gradient for the removal of organic pollutants from the soil matrix would exist. This is currently ignored in most PBET systems. By combining the CEPBET bioaccessibility test with an infinite sink, the removal of PAH from spiked solutions was monitored. Less than 10% of spiked PAH remained in the stomach media after 1 h, 10% by 4 h in the small intestine compartment and c.15% after 16 h in the colon. The addition of the infinite sink increased bioaccessibility estimates for field soils by a factor of 1.2–2.8, confirming its importance for robust PBET tests. TOC or BC were not the only factors controlling desorption of the PAH from the soils.

Ruminal dry matter and nitrogen degradation in relation to condensed tannin and protein molecular structures in sainfoin (Onobrychis viciifolia) and lucerne (Medicago sativa).

Sainfoin is a temperate legume that contains condensed tannins (CT), i.e. polyphenols that are able to bind proteins and thus reduce protein degradation in the rumen. A reduction in protein degradation in the rumen can lead to a subsequent increase in amino acid flow to the small intestine. The effects of CT in the rumen and the intestine differ according to the amount and structure of CT and the nature of the protein molecular structure. The objective of the present study was to investigate the degradability in the rumen of three CT-containing sainfoin varieties and CT-free lucerne in relation to CT content and structure (mean degree of polymerization, proportion of prodelphinidins and cis-flavanol units) and protein structure (amide I and II bands, ratio of amide I-to-amide II, α-helix, β-sheet, ratio of α-helix-to-β-sheet). Protein molecular structures were identified using Fourier transform/infrared-attenuated total reflectance (FT/IR-ATR) spectroscopy. The in situ degradability of three sainfoin varieties (Ambra, Esparcette and Villahoz) was studied in 2008, during the first growth cycle at two harvest dates (P1 and P2, i.e. 5 May and 2 June, respectively) and at one date (P3) during the second growth cycle (2 June) and these were compared with a tannin-free legume, lucerne (Aubigny). Loss of dry matter (DMDeg) and nitrogen (NDeg) in polyester bags suspended in the rumen was measured using rumen-fistulated cows. The NDeg of lucerne compared with sainfoin was 0·80 v. 0·77 at P1, 0·78 v. 0·65 at P2 and 0·79 v. 0·70 at P3, respectively. NDeg was related to the rapidly disappearing fraction (‘a’) fraction (r=0·76), the rate of degradation (‘c’) (r=0·92), to the content (r=−0·81) and structure of CT. However, the relationship between NDeg and the slowly disappearing fraction (‘b’) was weak. There was a significant effect of date and species×date, for NDeg and ‘a’ fraction. The secondary protein structure varied with harvest date (species×date) and was correlated with the fraction ‘b’. Both tannin and protein structures influenced the NDeg degradation. CT content and structure were correlated to the ‘a’ fraction and to the ‘c’. Features of the protein molecular secondary structure were correlated to the ‘b’ fraction.

Protection of dried probiotic bacteria from bile using bile adsorbent resins

Enteric coated oral tablets or capsules can deliver dried live cells directly into the intestine. Previously, we found that a live attenuated bacterial vaccine acquired sensitivity to intestinal bile when dried, raising the possibility that although gastric acid can be bypassed, significant loss of viability might occur on release from an enteric coated oral formulations. Here we demonstrate that some food-grade lyophilised preparations of Lactobacillus casei and Lactobacillus salivarius also show temporary bile sensitivity that can be rapidly reversed by rehydration. To protect dried bacterial cells from temporary bile sensitivity, we propose using bile acid adsorbing resins, such as cholestyramine, which are bile acid binding agents, historically used to lower cholesterol levels. Vcaps™ HPMC capsules alone provided up to 830-fold protection from bile. The inclusion of 50% w/w cholestyramine in Vcaps™ HPMC capsules resulted in release of up to 1700-fold more live Lactobacillus casei into simulated intestinal fluid containing 1% bile, when compared to dried cells added directly to bile. We conclude that delivery of dried live probiotic organisms to the intestine may be improved by providing protection from bile by addition of bile adsorbing resins and the use of HPMC capsules.

Gastrointestinal microbiota

Bacteria are associated with all areas of the human body from the skin to the genitourinary, respiratory and gastrointestinal (GI) tracts. The GI tract is the most heavily populated, with the majority of the total bacterial population of humans residing therein. The GI tract has evolved to become a functional organ comprising anatomically distinct areas. The digestive process starts in the oral cavity, then moves through the stomach, small and large intestine and finally the rectum. This chapter summarizes the functions of the human gastrointestinal tract. A main function of the GI microbiota is modulation of the immune system. The chapter focues on the factors influencing composition of the microbiota.

Gut permeability in autism spectrum disorders

Objective To test whether gut permeability is increased in autism spectrum disorders (ASD) by evaluating gut permeability in a population-derived cohort of children with ASD compared with age- and intelligence quotient-matched controls without ASD but with special educational needs (SEN). Patients and Methods One hundred thirty-three children aged 10–14 years, 103 with ASD and 30 with SEN, were given an oral test dose of mannitol and lactulose and urine collected for 6 hr. Gut permeability was assessed by measuring the urine lactulose/mannitol (L/M) recovery ratio by electrospray mass spectrometry-mass spectrometry. The ASD group was subcategorized for comparison into those without (n = 83) and with (n = 20) regression. Results There was no significant difference in L/M recovery ratio (mean (95% confidence interval)) between the groups with ASD: 0.015 (0.013–0.018), and SEN: 0.014 (0.009–0.019), nor in lactulose, mannitol, or creatinine recovery. No significant differences were observed in any parameter for the regressed versus non-regressed ASD groups. Results were consistent with previously published normal ranges. Eleven children (9/103 = 8.7% ASD and 2/30 = 6.7% SEN) had L/M recovery ratio > 0.03 (the accepted normal range cut-off), of whom two (one ASD and one SEN) had more definitely pathological L/M recovery ratios > 0.04. Conclusion There is no statistically significant group difference in small intestine permeability in a population cohort-derived group of children with ASD compared with a control group with SEN. Of the two children (one ASD and one SEN) with an L/M recovery ratio of > 0.04, one had undiagnosed asymptomatic celiac disease (ASD) and the other (SEN) past extensive surgery for gastroschisis.

In vitro colonic metabolism of coffee and chlorogenic acid results in selective changes in human faecal microbiota growth

Coffee is a relatively rich source of chlorogenic acids (CGA), which, like other polyphenols are postulated to exert preventative effects against cardiovascular disease and type-2 diabetes. As a considerable proportion of ingested CGA reaches the large intestine, CGA may be capable of exerting beneficial effects in the large gut. Here we utilise a stirred, anaerobic, pH controlled, batch culture fermentation model of the distal region of the colon in order to investigate the impact of coffee and CGA on the growth of the human faecal microbiota. Incubation of the coffee with the human faecal microbiota led to the rapid metabolism of CGA (4h) and the production of dihydrocaffeic acid and dihydroferulic acid, whilst caffeine remained un-metabolised. The coffee with the highest levels of CGA (p<0.05, relative to the other coffees) induced a significant increase in Bifidobacterium spp. relative to the control at 10 hours post exposure (p<0.05). Similarly, an equivalent quantity of CGA (80.8mg; matched with that in high CGA coffee) induced a significant increase in Bifidobacterium spp. (p<0.05). CGA alone also induced a significant increase in the Clostridium coccoides-Eubacterium rectale group (p<0.05). This selective metabolism and subsequent amplification of specific bacterial populations could be beneficial to host health.

Staphylococcus aureus MnhF mediates cholate efflux and facilitates survival under human colonic conditions

Resistance to the innate defences of the intestine is crucial for the survival and carriage of Staphylococcus aureus, a common coloniser of the human gut. Bile salts produced by the liver and secreted into the intestines are one such group of molecules with potent anti-microbial activity. The mechanisms by which S. aureus is able to resist such defences in order to colonize and survive in the human gut are unknown. Here we show that mnhF confers resistance to bile salts, which can be abrogated by efflux pump inhibitors. MnhF mediates efflux of radiolabelled cholic acid in both S. aureus and when heterologously expressed in Escherichia coli, rendering them resistant. Deletion of mnhF attenuated survival of S. aureus in an anaerobic three stage continuous culture model of the human colon (gut model), which represent different anatomical areas of the large intestine.

Probiotics, prebiotics, and the host microbiome: the science of translation

Recent advances in our understanding of the community structure and function of the human microbiome have implications for the potential role of probiotics and prebiotics in promoting human health. A group of experts recently met to review the latest advances in microbiota/microbiome research and discuss the implications for development of probiotics and prebiotics, primarily as they relate to effects mediated via the intestine. The goals of the meeting were to share recent advances in research on the microbiota, microbiome, probiotics, and prebiotics, and to discuss these findings in the contexts of regulatory barriers, evolving healthcare environments, and potential effects on a variety of health topics, including the development of obesity and diabetes; the long-term consequences of exposure to antibiotics early in life to the gastrointestinal (GI) microbiota; lactose intolerance; and the relationship between the GI microbiota and the central nervous system, with implications for depression, cognition, satiety, and mental health for people living in developed and developing countries. This report provides an overview of these discussions.

Apples and cardiovascular health: is the gut microbiota a core consideration?

There is now considerable scientific evidence that a diet rich in fruits and vegetables can improve human health and protect against chronic diseases. However, it is not clear whether different fruits and vegetables have distinct beneficial effects. Apples are among the most frequently consumed fruits and a rich source of polyphenols and fiber. A major proportion of the bioactive components in apples, including the high molecular weight polyphenols, escape absorption in the upper gastrointestinal tract and reach the large intestine relatively intact. There, they can be converted by the colonic microbiota to bioavailable and biologically active compounds with systemic effects, in addition to modulating microbial composition. Epidemiological studies have identified associations between frequent apple consumption and reduced risk of chronic diseases such as cardiovascular disease. Human and animal intervention studies demonstrate beneficial effects on lipid metabolism, vascular function and inflammation but only a few studies have attempted to link these mechanistically with the gut microbiota. This review will focus on the reciprocal interaction between apple components and the gut microbiota, the potential link to cardiovascular health and the possible mechanisms of action.

The impact of date palm fruits and their component polyphenols, on gut microbial ecology, bacterial metabolites and colon cancer cell proliferation

The fruit of the date palm (Phoenix dactylifera L.) is a rich source of dietary fibre and polyphenols. We have investigated gut bacterial changes induced by the whole date fruit extract (digested date extract; DDE) and its polyphenol-rich extract (date polyphenol extract; DPE) using faecal, pH-controlled, mixed batch cultures mimicking the distal part of the human large intestine, and utilising an array of microbial group-specific 16S rRNA oligonucleotide probes. Fluorescence microscopic enumeration indicated that there was a significant increase in the growth of bifidobacteria in response to both treatments, whilst whole dates also increased bacteroides at 24 h and the total bacterial counts at later fermentation time points when compared with DPE alone. Bacterial metabolism of whole date fruit led to the production of SCFA, with acetate significantly increasing following bacterial incubation with DDE. In addition, the production of flavonoid aglycones (myricetin, luteolin, quercetin and apigenin) and the anthocyanidin petunidin in less than 1 h was also observed. Lastly, the potential of DDE, DPE and metabolites to inhibit Caco-2 cell growth was investigated, indicating that both were capable of potentially acting as antiproliferative agents in vitro, following a 48 h exposure. This potential to inhibit growth was reduced following fermentation. Together these data suggest that consumption of date fruits may enhance colon health by increasing beneficial bacterial growth and inhibiting the proliferation of colon cancer cells. This is an early suggestion that date intake by humans may aid in the maintenance of bowel health and even the reduction of colorectal cancer development.

Anthelmintic activity of trans-cinnamaldehyde and A- and B-type proanthocyanidins derived from cinnamon (Cinnamomum verum)

Cinnamon (Cinnamomum verum) has been shown to have anti-inflammatory and antimicrobial properties, but effects on parasitic worms of the intestine have not been investigated. Here, extracts of cinnamon bark were shown to have potent in vitro anthelmintic properties against the swine nematode Ascaris suum. Analysis of the extract revealed high concentrations of proanthocyanidins (PAC) and trans-cinnamaldehyde (CA). The PAC were subjected to thiolysis and HPLC-MS analysis which demonstrated that they were exclusively procyanidins, had a mean degree of polymerization of 5.2 and 21% of their inter-flavan-3-ol links were A-type linkages. Purification of the PAC revealed that whilst they had activity against A. suum, most of the potency of the extract derived from CA. Trichuris suis and Oesophagostomum dentatum larvae were similarly susceptible to CA. To test whether CA could reduce A. suum infection in pigs in vivo, CA was administered daily in the diet or as a targeted, encapsulated dose. However, infection was not significantly reduced. It is proposed that the rapid absorption or metabolism of CA in vivo may prevent it from being present in sufficient concentrations in situ to exert efficacy. Therefore, further work should focus on whether formulation of CA can enhance its activity against internal parasites.

Acute benefits of the microbial-derived isoflavone metabolite equol on arterial stiffness in men prospectively recruited according to equol producer phenotype: a double-blind randomized controlled trial

There is much speculation with regard to the potential cardioprotective benefits of equol, a microbial-derived metabolite of the isoflavone daidzein, which is produced in the large intestine after soy intake in 30% of Western populations. Although cross-sectional and retrospective data support favorable associations between the equol producer (EP) phenotype and cardiometabolic health, few studies have prospectively recruited EPs to confirm this association. The aim was to determine whether the acute vascular benefits of isoflavones differ according to EP phenotype and subsequently investigate the effect of providing commercially produced S-(–)equol to non-EPs. We prospectively recruited male EPs and non-EPs (n = 14/ group) at moderate cardiovascular risk into a double-blind, placebocontrolled crossover study to examine the acute effects of soy isoflavones (80-mg aglycone equivalents) on arterial stiffness [carotid-femoral pulse-wave velocity (cfPWV)], blood pressure, endothelial function (measured by using the EndoPAT 2000; Itamar Medical), and nitric oxide at baseline (0 h) and 6 and 24 h after intake. In a separate assessment, non-EPs consumed 40 mg S-(–)equol with identical vascular measurements performed 2 h after intake. After soy intake, cfPWV significantly improved in EPs at 24 h (cfPWV change from 0 h: isoflavone, 20.2 6 0.2 m/s; placebo, 0.6 6 0.2 m/s; P , 0.01), which was significantly associated with plasma equol concentrations (R = 20.36, P = 0.01). No vascular effects were observed in EPs at 6 h or in non-EPs at any time point. Similarly, no benefit of commercially produced S-(–)equol was observed in non-EPs despite mean plasma equol concentrations reaching 3.2 mmol/L. Acute soy intake improved cfPWV in EPs, equating to an 11–12% reduced risk of cardiovascular disease if sustained. However, a single dose of commercially produced equol had no cardiovascular benefits in non-EPs. These data suggest that the EP phenotype is critical in unlocking the vascular benefits of equol in men, and long-term trials should focus on confirming the implications of EP phenotype on cardiovascular health. This trial was registered at clinicaltrials.gov as NCT01530893. Am J Clin Nutr doi: 10.3945/ajcn.115.125690.