Juliet Ansell

Lactic Acid Bacteria Convert Glucosinolates to Nitriles Efficiently Yet Differently from Enterobacteriaceae

Glucosinolates from the genus Brassica can be converted into bioactive compounds known to induce phase II enzymes, which may decrease the risk of cancers. Conversion via hydrolysis is usually by the brassica enzyme myrosinase, which can be inactivated by cooking or storage. We examined the potential of three beneficial bacteria, Lactobacillus plantarum KW30, Lactococcus lactis subsp. lactis KF147, and Escherichia coli Nissle 1917, and known myrosinase-producer Enterobacter cloacae to catalyze the conversion of glucosinolates in broccoli extract. Enterobacteriaceae consumed on average 65% glucoiberin and 78% glucoraphanin, transforming them into glucoiberverin and glucoerucin, respectively, and small amounts of iberverin nitrile and erucin nitrile. The lactic acid bacteria did not accumulate reduced glucosinolates, consuming all at 30-33% and transforming these into iberverin nitrile, erucin nitrile, sulforaphane nitrile, and further unidentified metabolites. Adding beneficial bacteria to a glucosinolate-rich diet may increase glucosinolate transformation, thereby increasing host exposure to bioactives.

Digested and Fermented Green Kiwifruit Increases Human β-Defensin 1 and 2 Production In vitro

The intestinal mucosa is constantly exposed to a variety of microbial species including commensals and pathogens, the latter leaving the host susceptible to infection. Antimicrobial peptides (AMP) are an important part of the first line of defense at mucosal surfaces. Human β-defensins (HBD) are AMP expressed by colonic epithelial cells, which act as broad spectrum antimicrobials. This study explored the direct and indirect effects of green kiwifruit (KF) on human β-defensin 1 and 2 (HBD-1 and 2) production by epithelial cells. In vitro digestion of KF pulp consisted of a simulated gastric and duodenal digestion, followed by colonic microbial fermentation using nine human faecal donors. Fermenta from individual donors was sterile filtered and independently added to epithelial cells prior to analysis of HBD protein production. KF products obtained from the gastric and duodenal digestion had no effect on the production of HBD-1 or 2 by epithelial cells, demonstrating that KF does not contain substances that directly modulate defensin production. However, when the digested KF products were further subjected to in vitro colonic fermentation, the fermentation products significantly up-regulated HBD-1 and 2 production by the same epithelial cells. We propose that this effect was predominantly mediated by the presence of short-chain fatty acids (SCFA) in the fermenta. Exposure of cells to purified SCFA confirmed this and HBD-1 and 2 production was up-regulated with acetate, propionate and butyrate. In conclusion, in vitro colonic fermentation of green kiwifruit digest appears to prime defense mechanisms in gut cells by enhancing the production of antimicrobial defensins.

No difference in fecal levels of bacteria or short chain fatty acids in humans, when consuming fruit juice beverages containing fruit fiber, fruit polyphenols, and their combination ☆

This study examined the effect of a Boysenberry beverage (750 mg polyphenols), an apple fiber beverage (7.5 g dietary fiber), and a Boysenberry plus apple fiber beverage (750 mg polyphenols plus 7.5 g dietary fiber) on gut health. Twenty-five individuals completed the study. The study was a placebo-controlled crossover study, where every individual consumed 1 of the 4 treatments in turn. Each treatment phase was 4-week long and was followed by a 2-week washout period. The trial beverages were 350 g taken in 2 doses every day (ie, 175 mL taken twice daily). The hypothesis for the study was that the combination of polyphenols and fiber would have a greater benefit on gut health than the placebo product or the fiber or polyphenols on their own. There were no differences in fecal levels of total bacteria, Bacteroides-Prevotella-Porphyromonas group, Bifidobacteriumspecies, Clostridium perfringens, or Lactobacillus species among any of the treatment groups. Fecal short chain fatty acid concentrations did not vary among treatment groups, although prostaglandin E2 concentrations were higher after consumption of the Boysenberry juice beverage. No significant differences were found in quantitative measures of gut health between the Boysenberry juice beverage, the apple fiber beverage, the Boysenberry juice plus apple fiber beverage, and the placebo beverage.

Modification of the Colonic Microbiota

It is becoming clear that the ecology and functionality of the human gut microbiota are extremely diverse and complex. The microbiota have coevolved with us metabolically to live symbiotically and to share the workload of extracting nutrients and energy from the diet. It is also clear that a diet rich in fruit, vegetables, and whole grain cereals is good for general health and gut health and that this is due partly to the phytochemicals and partly to the nondigestible carbohydrates (or dietary fiber) that are present in plants. Kiwifruit contain polyphenolics and nondigestible carbohydrates in the form of pectic, hemicellulosic, and cellulosic polysaccharides, all of which can be degraded by various members of the gut microbiota and result in beneficial effects. This chapter summarizes how kiwifruit act to modify the colonic microbiota and the resultant beneficial effects on human health.

Kiwifruit-derived supplements increase stool frequency in healthy adults: a randomized, double-blind, placebo-controlled study

The worldwide growth in the incidence of gastrointestinal disorders has created an immediate need to identify safe and effective interventions. In this randomized, double-blind, placebo-controlled study, we examined the effects of Actazin and Gold, kiwifruit-derived nutritional ingredients, on stool frequency, stool form, and gastrointestinal comfort in healthy and functionally constipated (Rome III criteria for C3 functional constipation) individuals. Using a crossover design, all participants consumed all 4 dietary interventions (Placebo, Actazin low dose [Actazin-L] [600 mg/day], Actazin high dose [Actazin-H] [2400 mg/day], and Gold [2400 mg/day]). Each intervention was taken for 28 days followed by a 14-day washout period between interventions. Participants recorded their daily bowel movements and well-being parameters in daily questionnaires. In the healthy cohort (n = 19), the Actazin-H (P = .014) and Gold (P = .009) interventions significantly increased the mean daily bowel movements compared with the washout. No significant differences were observed in stool form as determined by use of the Bristol stool scale. In a subgroup analysis of responders in the healthy cohort, Actazin-L (P = .005), Actazin-H (P < .001), and Gold (P = .001) consumption significantly increased the number of daily bowel movements by greater than 1 bowel movement per week. In the functionally constipated cohort (n = 9), there were no significant differences between interventions for bowel movements and the Bristol stool scale values or in the subsequent subgroup analysis of responders. This study demonstrated that Actazin and Gold produced clinically meaningful increases in bowel movements in healthy individuals.

Polyunsaturated fatty acids modify expression of TGF‐β in a co‐culture model ultilising human colorectal cells and human peripheral blood mononuclear cells exposed to Lactobacillus gasseri, Escherichia coli and Staphylococcus aureus

Commensal bacteria and polyunsaturated fatty acids (PUFAs) have both been shown independently to modulate immune responses. This study tested the hypothesis that the different colonic immunomodulatory responses to commensal (Lactobacillus gasseri) and pathogenic bacteria (Escherichia coli and Staphylococcus aureus) may be modified by PUFAs. Experiments used a Transwell system combining the colorectal cell line HT29, or its mucous secreting sub‐clone HT29‐MTX, with peripheral blood mononuclear cells to analyse immunomodulatory signalling in response to bacteria, with and without prior treatment with arachidonic acid, eicosapentaenoic acid or docosahexaenoic acid. L. gasseri increased transforming growth factor β1 (TGF‐β1) mRNA and protein secretion in colonic cell lines when compared with controls, an effect that was enhanced by pre‐treatment with eicosapentaenoic acid. In contrast, the Gram‐negative pathogen E. coli LF82 had no significant effect on TGF‐β1 protein. L. gasseri also increased IL‐8 mRNA but not protein while E. coli increased both; although differences between PUFA treatments were detected, none were significantly different to controls. Colonic epithelial cells show different immunomodulatory signalling patterns in response to the commensal L. gasseri compared to E. coli and S. aureus and pre‐treatment of these cells with PUFAs can modify responses. Practical applications: We have demonstrated an interaction between dietary PUFAs and epithelial cell response to both commensal and pathogenic bacteria found in the gastrointestinal tract by utilising in vitro co‐culture models. The data suggest that n‐3 PUFAs may provide some protection against the potentially damaging effects of pathogens. Furthermore, the beneficial effects of combining n‐3 PUFAs and the commensal bacteria, and potential probiotic, L. gasseri are illustrated by the increased expression of immunoregulatory TGF‐β1.

A Pilot Randomized Cross-Over Trial to Examine the Effect of Kiwifruit on Satiety and Measures of Gastric Comfort in Healthy Adult Males

‘Hayward’ kiwifruit anecdotally are associated with improved gastrointestinal comfort following the consumption of high protein meals, possibly because of the presence of a protease enzyme, actinidin. The study aimed to use SmartPill™ technology to investigate the acute effect of kiwifruit with actinidin (Actinidia chinensis var. deliciosa ‘Hayward’) and kiwifruit without actinidin (A. chinensis var. chinensis ‘Hort16A’) on digestion of a large protein meal. Ten healthy male subjects were recruited. The participants attended the clinic three times, having fasted overnight. They consumed a test meal consisting of 400 g lean steak and two ‘Hort16A’ or two ‘Hayward kiwifruit’. Subjects completed visual analogue scales (VAS) by rating feelings of hunger, satisfaction, fullness, and comfort and swallowed a SmartPill™ before completing further VAS scales. After 5 h, participants consumed an ad libitum lunch to assess satiety. SmartPill™ transponders were worn for five days. There were no significant differences in gastric emptying time, small bowel, or colonic transit time between the two kiwifruit arms of the study measured by SmartPill™. Similarly, no significant differences were observed in VAS satiety measures or energy consumption at the ad libitum meal. However, the measurement of overall gastric comfort tended to be lower, and bloating was significantly reduced following the consumption of the steak meal with ‘Hayward’ kiwifruit (p < 0.028). Conclusions: The SmartPill™ is marketed as a diagnostic tool for patients presenting with gastrointestinal disorders and is usually used with a standard ‘SmartBar’. This small pilot study suggests that it is less likely to measure gastric emptying effectively following a high protein meal, as it may be delayed because of the meal’s physical consistency. However, green kiwifruit, containing actinidin, may reduce bloating and other measures of gastric discomfort in healthy males. Possible future studies could use repeated measures with more readily digested protein and larger numbers of participants.

Consumption of antimicrobial manuka honey does not significantly perturb the microbiota in the hind gut of mice

The aim of this study was to test the hypothesis that consuming manuka honey, which contains antimicrobial methylglyoxal, may affect the gut microbiota. We undertook a mouse feeding study to investigate whether dietary manuka honey supplementation altered microbial numbers and their production of organic acid products from carbohydrate fermentation, which are markers of gut microbiota function. The caecum of C57BL/6 mice fed a diet supplemented with antimicrobial UMF® 20+ manuka honey at 2.2 g/kg animal did not show any significantly changed concentrations of microbial short chain fatty acids as measured by gas chromatography, except for increased formate and lowered succinate organic acid concentrations, compared to mice fed a control diet. There was no change in succinate-producing Bacteroidetes numbers, or honey-utilising Bifidobacteria, nor any other microbes measured by real time quantitative PCR. These results suggest that, despite the antimicrobial activity of the original honey, consumption of manuka honey only mildly affects substrate metabolism by the gut microbiota.

Equicarbohydrate partial exchange of kiwifruit for wheaten cereal reduces postprandial glycaemia without decreasing satiety

Kiwifruit is a carbohydrate food of low glycaemic potency which could potentially be exchanged for starch-based foods in management of postprandial glycaemia. The effect of equicarbohydrate partial exchange of kiwifruit varieties ‘Hayward’ green (GR) and ‘Zesy002’ (SunGold; SG) for a starchy wheat-based breakfast cereal (WB) on the characteristics of the postprandial glycaemic response and satiety was therefore determined. A total of twenty non-diabetic subjects (mean age 36 years; mean BMI 24·5 kg/m2) consumed four meals, each containing 40 g available carbohydrate, in random order, after an overnight fast. The meals were: (1) glucose; (2) 70·29 g breakfast cereal; (3) 200 g of GR plus breakfast cereal (30·93 g); and (4) 200 g of SG plus breakfast cereal (27·06 g). Throughout the 180 min postprandial period, capillary blood glucose concentrations were monitored, and satiety rated by a visual analogue scale. Partial kiwifruit substitution of WB significantly reduced postprandial glycaemic response amplitude (glucose, 3·91; WB, 3·66; WB + GR, 2·36; WB + SG, 2·31 mmol/l; least significant difference (LSD) 0·64; P < 0·001) and incremental area under the blood glucose response curve (0–120 min) (glucose, 228; WB, 180; WB + GR, 133; WB + SG, 134 mmol/l × min; LSD 22·7; P < 0·001). The area between baseline and response remained positive in kiwifruit-substituted meals but became negative after 120 min with glucose and WB, indicating that kiwifruit improved homeostatic control. Kiwifruit substitution of cereal did not significantly reduce satiety. We conclude that either ‘Hayward’ or ‘Zesy002’ kiwifruit may be used in equicarbohydrate partial substitution of starchy staple foods to reduce glycaemic response and improve glucose homeostasis without decreasing satiety.

Biotransformation of glucosinolates from a bacterial perspective

Epidemiological studies have shown an association between the consumption of cruciferous vegetables and a reduced risk of certain types of cancers, in particular, pancreatic, bladder and colorectal. This is thought to be the result of the conversion of glucosinolates (GSLs) present in the vegetables into bioactive isothiocyanates (ITCs) that in turn stimulate a host response involving detoxification pathways. Conversion of GSLs is catalysed by the enzyme myrosinase, co-produced by the plant but stored in separate tissue compartments and brought together when the tissue is damaged. Myrosinase activity can be lost during storage of vegetables and is often inactivated by cooking. In the absence of active plant myrosinase the hosts gut bacteria are capable of carrying out a myrosinase-like activity on GSLs in the lower gut. Several micro-organisms are known to be capable of metabolizing GSLs leading to the production of ITCs and nitriles, and this review examines the bacterial biotransformation of GSLs and a role for the microbiota in their biotransformation.