Megasphaera elsdenii JCM1772T Normalizes Hyperlactate Production in the Large Intestine of Fructooligosaccharide-Fed Rats by Stimulating Butyrate Production

Reduced incidence of Prevotella and other fermenters in intestinal microflora of autistic children

High proportions of autistic children suffer from gastrointestinal (GI) disorders, implying a link between autism and abnormalities in gut microbial functions. Increasing evidence from recent high-throughput sequencing analyses indicates that disturbances in composition and diversity of gut microbiome are associated with various disease conditions. However, microbiome-level studies on autism are limited and mostly focused on pathogenic bacteria. Therefore, here we aimed to define systemic changes in gut microbiome associated with autism and autism-related GI problems. We recruited 20 neurotypical and 20 autistic children accompanied by a survey of both autistic severity and GI symptoms. By pyrosequencing the V2/V3 regions in bacterial 16S rDNA from fecal DNA samples, we compared gut microbiomes of GI symptom-free neurotypical children with those of autistic children mostly presenting GI symptoms. Unexpectedly, the presence of autistic symptoms, rather than the severity of GI symptoms, was associated with less diverse gut microbiomes. Further, rigorous statistical tests with multiple testing corrections showed significantly lower abundances of the genera Prevotella, Coprococcus, and unclassified Veillonellaceae in autistic samples. These are intriguingly versatile carbohydrate-degrading and/or fermenting bacteria, suggesting a potential influence of unusual diet patterns observed in autistic children. However, multivariate analyses showed that autism-related changes in both overall diversity and individual genus abundances were correlated with the presence of autistic symptoms but not with their diet patterns. Taken together, autism and accompanying GI symptoms were characterized by distinct and less diverse gut microbial compositions with lower levels of Prevotella, Coprococcus, and unclassified Veillonellaceae.

Propionic and butyric acids, formed in the caecum of rats fed highly fermentable dietary fibre, are reflected in portal and aortic serum

SCFA are important end products formed during colonic fermentation of dietary fibre (DF). It has been suggested that propionic and butyric acids affect metabolic parameters, low-grade systemic inflammation, insulin resistance and obesity. The aim of the present study was to investigate whether the various SCFA profiles observed after fermentation in the caecum of rats fed pectin, guar gum and fructo-oligosaccharides (FOS) were also represented in hepatic portal and aortic serum. The SCFA in serum were extracted using hollow fibre-supported liquid membrane extraction before GLC analysis. The concentrations of acetic, propionic and butyric acids in caecal content correlated well with those in portal serum (P< 0·001) for all the three diets. A weaker correlation was found for propionic and butyric acids between the caecal content and aortic serum (P< 0·05). Butyric acid concentration in caecal content was also reflected in the aortic serum (P= 0·019) of rats fed FOS. FOS gave rather low amounts of the SCFA, especially butyric acid, but caecal tissue weight was higher with FOS than with the other two diets. This may be explained by rapid fermentation and quick utilisation/absorption of the SCFA. The present study also showed that propionic acid was metabolised/utilised to a higher extent than butyric acid by colonocytes before reaching the liver. We conclude that the formation of propionic and butyric acids in the caecum is reflected by increased concentrations in the aortic blood. This approach may therefore simplify the evaluation and study of SCFA from DF in human subjects.

Effects of short-chain fructooligosaccharides on growth performance of preruminant veal calves

This study was conducted to evaluate the effects of 2 different daily doses of short-chain fructooligosaccharides (scFOS), a prebiotic ingredient, added to a calf milk replacer on growth performance, carcass characteristics, and fecal concentrations of short-chain fatty acids of preruminant veal calves. In total, 112 male Prim'Holstein calves, between 8 and 10d of age, were randomized in this study according to their body weight and were bred until the age of 168 d. They were fed a calf milk replacer containing 5% soluble wheat proteins as well as cereal-based pellets, the composition of which was adapted to cover the needs of the animals throughout the study. After 2 wk of adaptation, the calf milk replacer was supplemented or not supplemented with a daily dose of 3 or 6g of scFOS. Growth performance of calves, as measured by body weight, cold carcass weight, feed intake, average daily gain, and feed conversion ratio, was recorded and feces samples were taken to evaluate short-chain fatty acid concentrations. The inclusion of wheat proteins in milk replacer did not negatively affect the growth performance of calves in comparison with general standards. The addition of scFOS in the milk reduced the feed conversion ratio of veal calves in a dose-dependent manner and tended to increase the carcass weight. A general trend was observed for an increased production of total short-chain fatty acids in time, but scFOS decreased acetate proportion to the benefit of butyrate proportion. These data suggest that inclusion of scFOS in the calf milk replacer allowed the growth performance of preruminant calves to be enhanced, possibly via a modification of the activities of microbial fermentation.

Lactate and acrylate metabolism by Megasphaera elsdenii under batch and steady-state conditions

The growth of Megasphaera elsdenii on lactate with acrylate and acrylate analogues was studied under batch and steady-state conditions. Under batch conditions, lactate was converted to acetate and propionate, and acrylate was converted into propionate. Acrylate analogues 2-methyl propenoate and 3-butenoate containing a terminal double bond were similarly converted into their respective saturated acids (isobutyrate and butyrate), while crotonate and lactate analogues 3-hydroxybutyrate and (R)-2-hydroxybutyrate were not metabolized. Under carbon-limited steady-state conditions, lactate was converted to acetate and butyrate with no propionate formed. As the acrylate concentration in the feed was increased, butyrate and hydrogen formation decreased and propionate was increasingly generated, while the calculated ATP yield was unchanged. M. elsdenii metabolism differs substantially under batch and steady-state conditions. The results support the conclusion that propionate is not formed during lactate-limited steady-state growth because of the absence of this substrate to drive the formation of lactyl coenzyme A (CoA) via propionyl-CoA transferase. Acrylate and acrylate analogues are reduced under both batch and steady-state growth conditions after first being converted to thioesters via propionyl-CoA transferase. Our findings demonstrate the central role that CoA transferase activity plays in the utilization of acids by M. elsdenii and allows us to propose a modified acrylate pathway for M. elsdenii.

The gut microbiome of kittens is affected by dietary protein:carbohydrate ratio and associated with blood metabolite and hormone concentrations

High-protein, low-carbohydrate (HPLC) diets are common in cats, but their effect on the gut microbiome has been ignored. The present study was conducted to test the effects of dietary protein:carbohydrate ratio on the gut microbiota of growing kittens. Male domestic shorthair kittens were raised by mothers fed moderate-protein, moderate-carbohydrate (MPMC; n 7) or HPLC (n 7) diets, and then weaned at 8 weeks onto the same diet. Fresh faeces were collected at 8, 12 and 16 weeks; DNA was extracted, followed by amplification of the V4–V6 region of the 16S rRNA gene using 454 pyrosequencing. A total of 384 588 sequences (average of 9374 per sample) were generated. Dual hierarchical clustering indicated distinct clustering based on the protein:carbohydrate ratio regardless of age. The protein:carbohydrate ratio affected faecal bacteria. Faecal Actinobacteria were greater (P< 0·05) and Fusobacteria were lower (P< 0·05) in MPMC-fed kittens. Faecal Clostridium, Faecalibacterium, Ruminococcus, Blautia and Eubacterium were greater (P< 0·05) in HPLC-fed kittens, while Dialister, Acidaminococcus, Bifidobacterium, Megasphaera and Mitsuokella were greater (P< 0·05) in MPMC-fed kittens. Principal component analysis of faecal bacteria and blood metabolites and hormones resulted in distinct clusters. Of particular interest was the clustering of blood TAG with faecal Clostridiaceae, Eubacteriaceae, Ruminococcaceae, Fusobacteriaceae and Lachnospiraceae; blood ghrelin with faecal Coriobacteriaceae, Bifidobacteriaceae and Veillonellaceae; and blood glucose, cholesterol and leptin with faecal Lactobacillaceae. The present results demonstrate that the protein:carbohydrate ratio affects the faecal microbiome, and highlight the associations between faecal microbes and circulating hormones and metabolites that may be important in terms of satiety and host metabolism.

The protective effect of supplemental calcium on colonic permeability depends on a calcium phosphate-induced increase in luminal buffering capacity

An increased intestinal permeability is associated with several diseases. Previously, we have shown that dietary Ca decreases colonic permeability in rats. This might be explained by a calcium-phosphate-induced increase in luminal buffering capacity, which protects against an acidic pH due to microbial fermentation. Therefore, we investigated whether dietary phosphate is a co-player in the effect of Ca on permeability. Rats were fed a humanised low-Ca diet, or a similar diet supplemented with Ca and containing either high, medium or low phosphate concentrations. Chromium-EDTA was added as an inert dietary intestinal permeability marker. After dietary adaptation, short-chain fructo-oligosaccharides (scFOS) were added to all diets to stimulate fermentation, acidify the colonic contents and induce an increase in permeability. Dietary Ca prevented the scFOS-induced increase in intestinal permeability in rats fed medium- and high-phosphate diets but not in those fed the low-phosphate diet. This was associated with higher faecal water cytotoxicity and higher caecal lactate levels in the latter group. Moreover, food intake and body weight during scFOS supplementation were adversely affected by the low-phosphate diet. Importantly, luminal buffering capacity was higher in rats fed the medium- and high-phosphate diets compared with those fed the low-phosphate diet. The protective effect of dietary Ca on intestinal permeability is impaired if dietary phosphate is low. This is associated with a calcium phosphate-induced increase in luminal buffering capacity. Dragging phosphate into the colon and thereby increasing the colonic phosphate concentration is at least part of the mechanism behind the protective effect of Ca on intestinal permeability.

In vitro fermentation of linear and alpha-1,2-branched dextrans by the human fecal microbiota

The role of structure and molecular weight in fermentation selectivity in linear α-1,6 dextrans and dextrans with α-1,2 branching was investigated. Fermentation by gut bacteria was determined in anaerobic, pH-controlled fecal batch cultures after 36 h. Inulin (1%, wt/vol), which is a known prebiotic, was used as a control. Samples were obtained at 0, 10, 24, and 36 h of fermentation for bacterial enumeration by fluorescent in situ hybridization and short-chain fatty acid analyses. The gas production of the substrate fermentation was investigated in non-pH-controlled, fecal batch culture tubes after 36 h. Linear and branched 1-kDa dextrans produced significant increases in Bifidobacterium populations. The degree of α-1,2 branching did not influence the Bifidobacterium populations; however, α-1,2 branching increased the dietary fiber content, implying a decrease in digestibility. Other measured bacteria were unaffected by the test substrates except for the Bacteroides-Prevotella group, the growth levels of which were increased on inulin and 6- and 70-kDa dextrans, and the Faecalibacterium prausnitzii group, the growth levels of which were decreased on inulin and 1-kDa dextrans. A considerable increase in short-chain fatty acid concentration was measured following the fermentation of all dextrans and inulin. Gas production rates were similar among all dextrans tested but were significantly slower than that for inulin. The linear 1-kDa dextran produced lower total gas and shorter time to attain maximal gas production compared to those of the 70-kDa dextran (branched) and inulin. These findings indicate that dextrans induce a selective effect on the gut flora, short-chain fatty acids, and gas production depending on their length.

Development of a 16S rRNA gene primer and PCR-restriction fragment length polymorphism method for rapid detection of members of the genus Megasphaera and species-level identification

The genus Megasphaera is relevant to the environment, human health and food, and renewable energy for the future. In this study, a primer set was designed for PCR-restriction fragment length polymorphism (RFLP) analyses to detect and identify the members of Megasphaera. Direct detection and identification were achieved for environmental samples and isolates.

Effect of liquid whey feeding on fecal microbiota of mature and growing pigs

The effect of liquid whey feeding on fecal bacteria and their metabolites was assessed in five pregnant sows and 66 growing pigs. Sows were fed a control diet for 4 weeks (control period) followed by the same diet but with whey feeding (5 L/day/pig) for 4 weeks (whey period). One group of growing pigs was given 267 L of whey per pig (whey group), while the other group was not (control group). In both cases, liquid whey was given separately from control diet. Sows in the whey period had feces showing lower pH, lower ammonia concentration, and larger population sizes of total bacteria, lactobacilli and bifidobacteria. The bacterial gene library analysis indicated that Mitsuokella and Megasphaera were more frequently detected, while Clostridium disporicum were detected less frequently in the whey period. Feces from whey-fed growing pigs showed lower pH than that from control pigs in the early stage of growing. Also, larger populations of total bacteria, lactobacilli and bifidobacteria were recorded in the whey group. From the bacterial gene library analysis, the detection frequency of Lactobacillus reuteri tended to be higher in the whey group. These results indicate that whey feeding influences the hindgut microbiota of pigs, possibly leading to a fermentation shift that is favorable for animal health.

A dietary sodium gluconate supplement improves growth performance and prebiotic activity in the small intestine of nursery pigs grown under tropical conditions

This study was conducted to evaluate the effect of sodium gluconate (SG) supplementation in diets on growth performance, small intestinal morphology and short chain fatty acid concentration in the caecum of nursery pigs. One-hundred and forty-four piglets (bodyweight ~10.5 kg) were raised in conventional open housing and divided into four treatments with six replications. The pigs received diet supplemented without (control), or with SG at a level of 1000, 2500 or 5000 ppm for 6 weeks. The results indicated that increasing SG supplementation from 0 to 5000 ppm linearly improved final bodyweight, average daily gain, feed : gain ratio, caecal propionic acid and total short-chain fatty acid concentration (linear P < 0.05). Adding SG in diet tended to reduce Escherichia coli counts in the caecum (P = 0.09) and adding SG at 2500–5000 ppm significantly increased the villous height in the duodenum (linear, P < 0.01), whereas there were no increase in caecal acetic acid and lactic acid bacterial counts in the caecum and rectum, and E. coli counts in the rectum when compared with the control group. SG supplementation did not affect the pH values in gastrointestinal tract of nursery pigs. This study implied that SG supplementation improved growth rate and may be useful as a prebiotic to accomplish the maximum growth performances in nursery pigs.

Oral administration of Lactobacillus plantarum Lq80 and Megasphaera elsdenii iNP-001 induces efficient recovery from mucosal atrophy in the small and the large intestines of weaning piglets

Weaning causes atrophy of intestinal mucosa and a drop of IgA protection in piglets which increases vulnerability to pathogenic infections. Probiotic lactobacilli may support recovery from such weaning stresses. Butyrate-produce bacteria may support the growth of colonic mucosa. Megasphaera elsdenii, a lactate-utilizing butyrate producer, may help butyrate production particularly when combined with lactobacilli. Weaned piglets (Experiment 1: 20 days old, Experiment 2: 28 days old) were orally dosed once a day with either (L) 10(10) (cell/dose) L. plantarum Lq80, or (LM) 10(10) (cell/dose) Lq80 with 10(9) (cell/dose) M. elsdenii iNP-001. Lq80 was contained in capsules resistant to gastric digestion. M. elsdenii was contained in capsules resistant to gastric and intestinal digestion. An untreated control (C) was also prepared. After 2 weeks of administration, L. plantarum enhanced the recovery from the villous atrophy in both experiments. The rectal and colonic IgA tended to be higher in L and LM than in C in Experiment 1. Colonic butyrate was higher in LM than in the others in Experiment 1. The thickness of the colonic mucosa was greater in LM than in the others in Experiment 1. In early weaned piglets, the effects of L. plantarum and M. elsdenii were clear.

[Surgical treatment of gastric carcinoma]

The gastric cancer is the most common cancer in Korea. The only treatment modality showing improved survival for gastric cancer is curative surgical resection, which comprises the resection of stomach, proper lymphadenectomy, and reconstruction. However, specific surgical procedures should be decided according to the location of the cancer, advancement of the tumor, and patients condition. Surgical treatment for gastric cancer has been developed toward two directions that are minimal invasive surgery for early gastric cancer and multi-disciplinary approach for advanced gastric cancer. Laparoscopic surgery for early gastric cancer has been accepted for minimally invasive surgery. Moreover, the advancement of diagnostic tools to assess biological aggressiveness of the tumor enables physicians to perform endoscopic resection or minimized resection for early gastric cancer. Recently, surgeons try to extend the application of laparoscopic gastric resection and D2 lymphadenectomy to advanced gastric cancer. However, technical and oncological evidences based on clinical trials should be filed up before adopting it as a standard therapy. In case of advanced gastric cancer, in addition to radical surgery, various treatment modalities including chemotherapy, radiation, and molecular target therapy also have been applied in many clinical trials. However, it should be stressed that a prerequisite for precise evaluation of the efficacy of these combined treatment modalities would be the standardization of surgical procedure.

The effects of several organic acids on growth performance, nutrient digestibilities, and cecal microbial populations in young chicks

Four experiments were conducted to evaluate the effects of citric, gluconic, fumaric, and malic acids on growth and nutrient digestibility in New Hampshire x Columbian male chicks from hatch to 21 d. For growth performance, chicks fed 1 to 4% gluconic acid, 4% citric acid, or 4% malic acid in a corn-soybean meal diet generally showed reductions (P < 0.05) in growth to 21 d, whereas 3% citric acid, 2% malic acid, or 1.5 to 4.5% fumaric acid had no significant effect. In the first experiment, 2, 4, and 6% gluconic acid increased ME(n) values at 7, 14, and 21 d, but in experiment 2, 1 and 2% gluconic acid decreased ME(n) at 4 and 7 d, but had no effect at 14 and 21 d. The 4% level of citric acid increased ME(n) at 4 d. Digestibility of most amino acids (AA) was reduced by gluconic acid in some treatments, whereas citric acid (3%) increased AA digestibility at 4 d but not at 21 d. For cecal microbial populations at 21 d, bifidobacteria were reduced when 2% gluconic acid and 3% citric acid were fed to chicks in a corn-soybean meal diet, whereas 4% gluconic acid had no effect when fed in a dextrose-casein diet to chicks. In a dextrose-isolated soy protein diet, 4% gluconic acid reduced the cecal populations of Lactobacillus, Escherichia coli, and Clostridium perfringens. The results of this study indicated that feeding organic acids did not have any consistent effects on growth performance, ME(n), AA digestibility, or cecal microbial numbers.

Impact of pH on lactate formation and utilization by human fecal microbial communities

The human intestine harbors both lactate-producing and lactate-utilizing bacteria. Lactate is normally present at <3 mmol liter(-1) in stool samples from healthy adults, but concentrations up to 100 mmol liter(-1) have been reported in gut disorders such as ulcerative colitis. The effect of different initial pH values (5.2, 5.9, and 6.4) upon lactate metabolism was studied with fecal inocula from healthy volunteers, in incubations performed with the addition of dl-lactate, a mixture of polysaccharides (mainly starch), or both. Propionate and butyrate formation occurred at pH 6.4; both were curtailed at pH 5.2, while propionate but not butyrate formation was inhibited at pH 5.9. With the polysaccharide mix, lactate accumulation occurred only at pH 5.2, but lactate production, estimated using l-[U-(13)C]lactate, occurred at all three pH values. Lactate was completely utilized within 24 h at pH 5.9 and 6.4 but not at pH 5.2. At pH 5.9, more butyrate than propionate was formed from l-[U-(13)C]lactate in the presence of polysaccharides, but propionate, formed mostly by the acrylate pathway, was the predominant product with lactate alone. Fluorescent in situ hybridization demonstrated that populations of Bifidobacterium spp., major lactate producers, increased approximately 10-fold in incubations with polysaccharides. Populations of Eubacterium hallii, a lactate-utilizing butyrate-producing bacterium, increased 100-fold at pH 5.9 and 6.4. These experiments suggest that lactate is rapidly converted to acetate, butyrate, and propionate by the human intestinal microbiota at pH values as low as 5.9, but at pH 5.2 reduced utilization occurs while production is maintained, resulting in lactate accumulation.

Dietary fructooligosaccharides affect intestinal barrier function in healthy men

In contrast to most expectations, we showed previously that dietary fructooligosaccharides (FOS) stimulate intestinal colonization and translocation of invasive Salmonella enteritidis in rats. Even before infection, FOS increased the cytotoxicity of fecal water, mucin excretion, and intestinal permeability. In the present study, we tested whether FOS has these effects in humans. A double-blind, placebo-controlled, crossover study of 2 x 2 wk, with a washout period of 2 wk, was performed with 34 healthy men. Each day, subjects consumed lemonade containing either 20 g FOS or placebo and the intestinal permeability marker chromium EDTA (CrEDTA). On the last 2 d of each supplement period, subjects scored their gastrointestinal complaints on a visual analog scale and collected feces and urine for 24 h. Fecal lactic acid was measured using a colorimetric enzymatic kit. The cytotoxicity of fecal water was determined with an in vitro bioassay, fecal mucins were quantified fluorimetrically, and intestinal permeability was determined by measuring urinary CrEDTA excretion. In agreement with our animal studies, FOS fermentation increased fecal wet weight, bifidobacteria, lactobacilli, and lactic acid. Consumption of FOS increased flatulence and intestinal bloating. In addition, FOS consumption doubled fecal mucin excretion, indicating mucosal irritation. However, FOS did not affect the cytotoxicity of fecal water and intestinal permeability. The FOS-induced increase in mucin excretion in our human study suggests mucosal irritation in humans, but the overall effects are more moderate than those in rats.

Lactate is mainly fermented to butyrate by human intestinal microfloras but inter-individual variation is evident

AIM

To assess the role of lactate as a precursor for butyrate biosynthesis in human colonic microflora.

METHODS AND RESULTS

Three human faecal microfloras were incubated in vitro with media supplemented with 30 mmol l(-1) unenriched or 13C-enriched lactate. Lactate metabolism and short-chain fatty acid (SCFA) production were quantified. Lactate conversion to butyrate was investigated by gas chromatography-mass spectrometry and the pathways involved were identified by 13C nuclear magnetic resonance spectroscopy. All human faecal microfloras rapidly and completely fermented lactate, yielding approx. 19 mmol l(-1) total SCFAs. However, the SCFA composition varied markedly between microfloras. Butyrate was the main end-product for two microfloras but not for the third (60 and 61%vs 27% of the net concentration of SCFA produced respectively). The latter was typified by its ability to produce propionate as a major product (37%), and valerate (3%). 13C-Labelling showed that butyrate was produced through the acetyl-CoA pathway and that the three microfloras possessed significant differences in their metabolic pathways for lactate consumption.

CONCLUSIONS

In contrast to the ruminal microflora, the human intestinal microflora can utilize both d- and l-lactate as precursors for butyrate synthesis. Inter-individual variation is found.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study suggests that the butyrogenic capability of colonic prebiotics could be related to lactate availability. These findings will direct the development of selection strategies for the isolation of new butyrate-producing bacteria among the lactate-utilizing bacteria present in the human intestinal microfloras.

Prebiotic effects of chicory inulin in the simulator of the human intestinal microbial ecosystem

The prebiotic potential of native chicory inulin was assessed in the Simulator of the Human Intestinal Microbial Ecosystem (SHIME) by monitoring microbial community from the colon compartments, its metabolic activity and community structure. Inulin addition selected for a higher short chain fatty acid production with shifts towards propionic and butyric acid. Conventional culture-based techniques and PCR-denaturing gradient gel electrophoresis analysis showed no remarkable changes in the overall microbial community from the colon compartments of the SHIME, whereas selective effects were seen for lactic acid bacteria. Quantitative PCR with bifidobacteria-specific primers revealed a significant increase with more than 1 log CFU ml(-1) from the proximal to distal colon, in contrast to culture-based techniques, which only showed a minor bifidogenic effect in the ascending colon. Our results indicate that inulin purports prebiotic effects from the proximal to distal colon and that real-time PCR is a more precise technique to detect differences in bifidobacterial populations whereas conventional culturing techniques are much more variable.

Lactate-utilizing bacteria, isolated from human feces, that produce butyrate as a major fermentation product

The microbial community of the human colon contains many bacteria that produce lactic acid, but lactate is normally detected only at low concentrations (<5 mM) in feces from healthy individuals. It is not clear, however, which bacteria are mainly responsible for lactate utilization in the human colon. Here, bacteria able to utilize lactate and produce butyrate were identified among isolates obtained from 10(-8) dilutions of fecal samples from five different subjects. Out of nine such strains identified, four were found to be related to Eubacterium hallii and two to Anaerostipes caccae, while the remaining three represent a new species within clostridial cluster XIVa based on their 16S rRNA sequences. Significant ability to utilize lactate was not detected in the butyrate-producing species Roseburia intestinalis, Eubacterium rectale, or Faecalibacterium prausnitzii. Whereas E. hallii and A. caccae strains used both D- and L-lactate, the remaining strains used only the d form. Addition of glucose to batch cultures prevented lactate utilization until the glucose became exhausted. However, when two E. hallii strains and one A. caccae strain were grown in separate cocultures with a starch-utilizing Bifidobacterium adolescentis isolate, with starch as the carbohydrate energy source, the L-lactate produced by B. adolescentis became undetectable and butyrate was formed. Such cross-feeding may help to explain the reported butyrogenic effect of certain dietary substrates, including resistant starch. The abundance of E. hallii in particular in the colonic ecosystem suggests that these bacteria play important roles in preventing lactate accumulation.

Probiotics and the management of inflammatory bowel disease

The demonstration that immune and epithelial cells can discriminate between different microbial species has extended our understanding of the actions of probiotics beyond simple barrier and antimicrobial concepts. Several probiotic mechanisms of action, relative to inflammatory bowel disease, have been elucidated: (1) competitive exclusion, whereby probiotics compete with microbial pathogens for a limited number of receptors present on the surface epithelium; (2) immunomodulation and/or stimulation of an immune response of gut-associated lymphoid and epithelial cells; (3) antimicrobial activity and suppression of pathogen growth; (4) enhancement of barrier function; and (5) induction of T cell apoptosis in the mucosal immune compartment. The unraveling of these mechanisms of action has led to new support for the use of probiotics in the management of clinical inflammatory bowel disease. Though level 1 evidence now supports the therapeutic use of probiotics in the treatment of postoperative pouchitis, only levels 2 and 3 evidence is currently available in support of the use of probiotics in the treatment of ulcerative colitis and Crohn's disease. Nevertheless, one significant and consistent finding has emerged during the course of research in the past year: not all probiotic bacteria have similar therapeutic effects. Rigorously designed, controlled clinical trials are vital to investigate the unresolved issues related to efficacy, dose, duration of use, single or multi-strain formulation, and the concomitant use of probiotics, synbiotics, or antibiotics.

Dietary sodium gluconate protects rats from large bowel cancer by stimulating butyrate production

Butyrate has an antitumorigenic effect on colorectal cancer cell lines. Dietary sodium gluconate (GNA) promotes butyrate production in the large intestine. Accordingly, we examined the effect of dietary GNA on tumorigenesis in the large intestine in rats. Male Fisher-344 rats (n = 32) were divided into 4 groups: 2 diets (with or without 50 g GNA/kg basal diet) x 2 treatments (with or without carcinogen administration). Colonic tumors were induced by 3 intraperitoneal injections of azoxymethane (15 mg/kg body wt, 1 time/wk) and dietary deoxycholic acid (2 g/kg basal diet). The experiment was conducted for 33 wk except for a few rats. Ingestion of GNA increased cecal butyrate concentration at the end of experiment (P < 0.01). No tumor development occurred in the untreated groups. Ingestion of GNA decreased the incidence of tumors in rats administered the carcinogen (37.5 vs. 100%, P < 0.05). Ingestion of GNA also decreased the mean number of tumors per rat (0.5 +/- 0.8 vs. 2.8 +/- 1.5, P < 0.01). beta-Catenin accumulation and TdT-mediated dUTP nick end labeling (TUNEL) positive cells in tumors were histochemically examined. The results of this study suggested that the antitumorigenic effect of GNA may involve the stimulation of apoptosis through enhanced butyrate production in the large intestine.