Nutritional impact of pre- and probiotics as protective gastrointestinal organisms

Silibinin modulates biotransforming microbial enzymes and prevents 1,2-dimethylhydrazine-induced preneoplastic changes in experimental colon cancer

Chemoprevention directed towards the control of colon carcinogenesis in its early stages should ultimately provide a higher quality of life for people than waiting to treat end-stage disease. Silibinin is a major bioactive compound that is present in the widely consumed dietary supplement Silymarin. The current investigation aimed to explore the effect of the phytochemical silibinin on the suppression of 1,2-dimethylhydrazine-induced colonic preneoplastic changes in a long-term preclinical model. Wistar male rats were divided into six groups: group 1 were control rats, group 2 were control rats that received silibinin alone (50 mg/kg body weight orally everyday), rats in group 3 were injected once weekly with 1,2-dimethylhydrazine (20 mg/kg body weight, subcutaneously 15 times), in addition, group 4 (initiation), group 5 (post initiation) and group 6 (entire period) received silibinin as in group 2. At the end of 32 weeks, the activities of the colonic and faecal biotransforming microbial enzymes were analysed. Modulatory effects were also evaluated using aberrant crypt foci (ACF), dysplastic ACF and tumour incidence as endpoint markers. Silibinin markedly reduced tumour incidence, as compared with the rats treated with unsupplemented 1,2-dimethylhydrazine. The most pronounced inhibition of ACF and dysplastic ACF development was observed in the rats fed with silibinin for the entire period and also during the post initiation period. Silibinin administration also significantly (P<0.05) modulated the biotransforming activity of microbial enzymes. The results of our study suggest that silibinin suppresses 1,2-dimethylhydrazine-induced colon carcinogenesis at various stages and exerts a potential chemopreventive action against colon cancer.

In vitro evaluation of Lactobacillus plantarum DSMZ 12028 as a probiotic: emphasis on innate immunity

In this study, we analyzed the probiotic potential of L. plantarum DSMZ 12028 in vitro using the pathogen E. coli K4 and a certified probiotic, L. paracasei F19, as controls. Adhesion to intestinal epithelial cells was evaluated using two cell lines, CaCo-2 and HT-29, through the plate dilution method. Moreover, the bacteria/epithelial dynamic interaction was continuously monitored using time-lapse microscopy. Expression of the innate immunity receptors, the TLRs, was evaluated by semi-quantitative PCR on an epithelial/bacteria co-culture. Real-time PCR was used to monitor expression of TLRs and cytokines in a monocytic cell line (THP-1) following bacterial exposure. The adherence of the strain to intestinal epithelial cells was comparable to that of the probiotic. Time-lapse experiments showed that E. coli K4 induced cell death while L. plantarum did not affect proliferation at a 10:1 bacteria/cell ratio. L. plantarum down-regulated TLR mRNAs with the exception of TLR2, while L. paracasei F19 and E. coli K4 caused a significant (p<0.05) up-regulation of TLR2 and 4, respectively. To simulate the activation of underlying immune cells in the lamina propria, we analyzed the immunomodulation of L. plantarum on a monocytic cell line, THP-1. Proinflammatory cytokines, such as TNFalpha, were increased by the presence of bacteria. The pathogen E. coli K4 also induced a strong up-regulation of proinflammatory cytokines, such as IL8, IL1beta and IL23. No differences were observed between experimental groups for IFNgamma, IL-10 and IL12p40. Overall, L. plantarum DSMZ 12028 demonstrated probiotic traits, inducing a proinflammatory response just above the "threshold level", which could prevent an inflammatory outcome, while inducing a higher state of alertness in the defense system of the host intestinal epithelial cells.

Protective efficacy of probiotic alone or in conjunction with a prebiotic in Salmonella-induced liver damage

In view of the increasing interest in the bioecological and nutritional control of diseases, use of probiotics alone or in combination with prebiotics (synbiotics) appears as a therapeutic option for various diseases. In this study, an attempt was made to explore the protective potential of Lactobacillus acidophilus as a probiotic, inulin as a prebiotic and both L. acidophilus and inulin as synbiotic against Salmonella-induced liver damage in a murine model. The probiotic, prebiotic and synbiotic supplementation resulted in decreased bacterial translocation in the liver of mice challenged with Salmonella typhimurium and decreased levels of serum aminotransferases, suggesting their protective role against Salmonella infection. Mice supplemented with these preparations before Salmonella challenge also revealed decreased levels of lipid peroxidation, increased levels of superoxide dismutase and glutathione, along with reduced levels of nitric oxide. Thus, bacteriological and biochemical alterations correlated well with the histological evidence. Protection afforded by supplementation with the probiotic alone was found to be more effective. None of the observations was suggestive of the synergistic effect in the synbiotic-supplemented animals. Thus, it is indicated that the probiotic and the prebiotic used in the present study may act by different mechanisms involved in affording protection against Salmonella-induced liver damage.

The bacterial fermentation product butyrate influences epithelial signaling via reactive oxygen species-mediated changes in cullin-1 neddylation

The human enteric flora plays a significant role in intestinal health and disease. Populations of enteric bacteria can inhibit the NF-kappaB pathway by blockade of IkappaB-alpha ubiquitination, a process catalyzed by the E3-SCF(beta-TrCP) ubiquitin ligase. The activity of this ubiquitin ligase is regulated via covalent modification of the Cullin-1 subunit by the ubiquitin-like protein NEDD8. We previously reported that interaction of viable commensal bacteria with mammalian intestinal epithelial cells resulted in a rapid and reversible generation of reactive oxygen species (ROS) that modulated neddylation of Cullin-1 and resulted in suppressive effects on the NF-kappaB pathway. Herein, we demonstrate that butyrate and other short chain fatty acids supplemented to model human intestinal epithelia in vitro and human tissue ex vivo results in loss of neddylated Cul-1 and show that physiological concentrations of butyrate modulate the ubiquitination and degradation of a target of the E3- SCF(beta-TrCP) ubiquitin ligase, the NF-kappaB inhibitor IkappaB-alpha. Mechanistically, we show that physiological concentrations of butyrate induces reactive oxygen species that transiently alters the intracellular redox balance and results in inactivation of the NEDD8-conjugating enzyme Ubc12 in a manner similar to effects mediated by viable bacteria. Because the normal flora produces significant amounts of butyrate and other short chain fatty acids, these data provide a functional link between a natural product of the intestinal normal flora and important epithelial inflammatory and proliferative signaling pathways.

Recent advances and remaining gaps in our knowledge of associations between gut microbiota and human health

The complex gut microbial flora harbored by individuals (microbiota) has long been proposed to contribute to intestinal health as well as disease. Pre- and probiotic products aimed at improving health by modifying microbiota composition have already become widely available and acceptance of these products appears to be on the rise. However, although required for the development of effective microbiota based interventions, our basic understanding of microbiota variation on a population level and its dynamics within individuals is still rudimentary. Powerful new parallel sequence technologies combined with other efficient molecular microbiota analysis methods now allow for comprehensive analysis of microbiota composition in large human populations. Recent findings in the field strongly suggest that microbiota contributes to the development of obesity, atopic diseases, inflammatory bowel diseases and intestinal cancers. Through the ongoing National Institutes of Health Roadmap ‘Human Microbiome Project’ and similar projects in other parts of the world, a large coordinated effort is currently underway to study how microbiota can impact human health. Translating findings from these studies into effective interventions that can improve health, possibly personalized based on an individuals existing microbiota, will be the task for the next decade(s).

Structurally different wheat-derived arabinoxylooligosaccharides have different prebiotic and fermentation properties in rats

To evaluate the prebiotic potential and intestinal fermentation products of wheat bran-derived arabinoxylooligosaccharides (AXOS) in relation to their structure, 5 preparations with structurally different AXOS were included ( approximately 4% wt:wt) in rat diets that mimicked the average Western human diet composition. Xylooligosaccharides (XOS), fructooligosaccharides (FOS), and inulin were used as references. The observed effects mainly depended on the average degree of polymerization (avDP) of the AXOS preparations. The AXOS and XOS preparations with a low avDP (<or=3) resulted in increased colonic acetate and butyrate production and boosted bifidobacteria concentrations in the cecum, but did not significantly lower the concentrations of branched SCFA, which are considered to be markers of protein fermentation by intestinal microbiota. In contrast, an AXOS preparation with a higher avDP (61) effectively suppressed branched SCFA concentrations and thus tipped the balance away from protein fermentation. However, it neither increased colonic butyrate concentrations nor stimulated cecal bifidobacteria development. Two AXOS preparations with a similar avDP (12 and 15) but different average degrees of arabinose substitution (avDAS) (0.69 and 0.27) affected the measured intestinal characteristics similarly, suggesting that the influence of the avDAS was apparently limited and possibly overshadowed by that of the avDP. Among those tested, an AXOS preparation with an avDP of 5 and an avDAS of 0.27 exhibited the best combination of desirable effects on gut health characteristics. Compared with this optimal AXOS preparation, FOS and inulin resulted in similar bifidogenic effects with increased production of colonic acetate (inulin) but not of butyrate. These new insights into the structure-activity relation of AXOS open up new perspectives for the production and application of AXOS preparations with optimized prebiotic and fermentation properties.

Modulation of Lactobacillus casei in ileal and fecal samples from healthy volunteers after consumption of a fermented milk containing Lactobacillus casei DN-114 001Rif

Lactobacillus casei DN-114 001 is a probiotic strain able to interact with the immune system and to interfere with gastrointestinal pathogens. The derived strain DN-114 001Rif was studied during its transit through the upper and distal intestine of human volunteers. Seven volunteers participated in the study, which involved intestinal intubation to sample ileal contents and collection of fecal samples, with a wash-out period of 8 days between the 2 steps. The retrieval of the probiotic was analyzed in the ileum every 2 h for 8 h following the ingestion of one dose of the test product and in the feces prior to, during, and after daily consumption of the test product for 8 days. Persistence of the probiotic amplifiable DNA was assessed using temporal temperature gradient gel electrophoresis and real-time PCR. Fluorescent in situ hybridization allowed analysis of the composition of the dominant digestive microbiota. The ingestion of L. casei DN-114 001Rif led to a significant and transient increase of its amplifiable DNA in ileal and fecal samples. This is related to a high stability in the composition of dominant groups of the gut microbiota. Data from ileal samples are scarce and our study confirms the potentiality for interaction between probiotics and the human immune system.

Mechanisms of action of probiotics

At birth, the newborn leaves the germ-free intrauterine environment and enters a highly contaminated extrauterine world, which requires potent host defenses to prevent disease. Intestinal defenses develop during gestation and have the capacity to respond but first must be exposed to colonizing bacteria. I review the importance of bacterial colonization for the appearance of normal mucosal immune function and the clinical consequences of inadequate colonization with regard to development of disease. For example, we now know that an imbalance in T-helper (Th) cells (e.g., Th2 levels greater than Th1 levels) can predispose to autoimmune disease and gut inflammation or disease, such as necrotizing enterocolitis. As we determine the role of bacterial colonization in the gut (bacterial-epithelial "cross talk"), we should have more-appropriate ways to modulate the gut immune responses-for example, by use of probiotics to prevent the expression of these gastrointestinal diseases.

Toll-like receptor 5 engagement modulates tumor development and growth in a mouse xenograft model of human colon cancer

BACKGROUND & AIMS

Toll-like receptor (TLR)-dependent signaling was proposed as immunotherapeutic targets against invading pathogens and tumorigenesis. Here, we investigated whether TLR5-dependent signaling modulates colonic tumor development in mouse xenograft model of human colon cancer.

METHODS

The expression of myeloid differentiation factor 88 (MyD88) or TLR5 was stably knocked down in human colon cancer cells (DLD-1). Nude mice were subcutaneously implanted with MyD88-knocked down (KD), TLR5-KD, or control cells (n = 16) to examine the pathophysiology of tumor xenografts. Protein microarray assessed the differential expression of cytokines in these tumors. Leukocyte infiltration and tumor angiogenesis were assessed by immunohistochemistry with antibodies against neutrophil (Gr-1, 7/4) or macrophage-specific antigens (CD68, F4-80) and the vascular endothelial cell marker CD31, respectively. Tumor xenografts from DLD-1 cells were treated with flagellin (5.0 microg/kg, 1 injection/every 2 days for 3 weeks), and tumor regression and histopathology were examined.

RESULTS

Lack of MyD88 or TLR5 expression dramatically enhanced tumor growth and inhibited tumor necrosis in mouse xenografts of human colon cancer. In contrast, TLR5 activation by peritumoral flagellin treatment substantially increased tumor necrosis, leading to significant tumor regression. Tumors from MyD88-KD or TLR5-KD cells revealed the reduced production of neutrophil attracting chemokines (epithelial cell-derived neutrophil-activating peptide-78, macrophage-inflammatory protein alpha, and interleukin-8). Consequently, neutrophil infiltration was dramatically diminished in MyD88- or TLR5-KD xenografts, whereas tumor-associated macrophage infiltration or angiogenesis was not changed.

CONCLUSIONS

TLR5 engagement by flagellin mediates innate immunity and elicits potent antitumor activity, indicating that TLR5-dependent signaling could be a potential immunotherapeutic target to modulate colonic tumors.

Safety evaluation of oligofructose: 13 week rat study and in vitro mutagenicity

Oligofructose (OF), comprised of fructose oligomers with a terminal glucose unit, is a family of oligosaccharides derived from the hydrolysis of inulin. Consumption of OF in animals and humans increases colonic bifidobacteria levels. The present study evaluates the safety of OF in both a 13 week rat feeding study and using in vitro mutagenicity tests. Fecal bifidobacteria levels were also determined by in situ hybridization to assess a biological function of OF. Rats received either a control diet or diets containing one of four doses of OF. Total, HDL, and LDL-cholesterol levels were significantly lower at several time points during the study in groups receiving OF compared to controls with the largest effects occurring in the high dose male animals. Weight gain in the male high dose group was significantly lower at early time points compared to controls but not significantly different at the end of study. As expected, cecal weights increased in a dose-related manner and fecal bifidobacteria levels also demonstrated a dose-related increase. There were no consistent differences in gross pathology or histopathology related to dietary OF. OF did not induce a positive response in the Ames test or chromosomal aberration test with CHO cells. These results demonstrate no adverse effects of OF.

Probiotics for the prevention of necrotizing enterocolitis

Necrotizing enterocolitis (NEC) remains a significant cause of morbidity and mortality for low birth weight premature infants. Prematurity, ischemia, formula feeding, and bacterial colonization are risk factors for the self-perpetuating cycle of damaged intestinal epithelia, inflammation, bacterial entry, sepsis, and shock that characterizes NEC. Probiotics are food supplements containing live bacteria that benefit the recipient by improving the microflora balance within the intestine. Several studies suggest that the administration of probiotics may have a prophylactic effect for NEC and may reduce morbidity and mortality rates for low birth weight infants.

Effect of the administration of a fermented milk containing Lactobacillus casei DN-114001 on intestinal microbiota and gut associated immune cells of nursing mice and after weaning until immune maturity

Background

Microbial colonization of the intestine after birth is an important step for the development of the gut immune system. The acquisition of passive immunity through breast-feeding may influence the pattern of bacterial colonization in the newborn. The aim of this work was to evaluate the effect of the administration of a probiotic fermented milk (PFM) containing yogurt starter cultures and the probiotic bacteria strain Lactobacillus casei DN-114001 to mothers during nursing or their offspring, on the intestinal bacterial population and on parameters of the gut immune system.

Results

Fifteen mice of each group were sacrificed at ages 12, 21, 28 and 45 days. Large intestines were taken for determination of intestinal microbiota, and small intestines for the study of secretory-IgA (S-IgA) in fluid and the study of IgA+ cells, macrophages, dendritic cells and goblet cells on tissue samples. The consumption of the PFM either by the mother during nursing or by the offspring after weaning modified the development of bifidobacteria population in the large intestine of the mice. These modifications were accompanied with a decrease of enterobacteria population. The administration of this PFM to the mothers improved their own immune system and this also affected their offspring. Offspring from mice that received PFM increased S-IgA in intestinal fluids, which mainly originated from their mother's immune system. A decrease in the number of macrophages, dendritic cells and IgA+ cells during the suckling period in offspring fed with PFM was observed; this could be related with the improvement of the immunity of the mothers, which passively protect their babies. At day 45, the mice reach maturity of their own immune system and the effects of the PFM was the stimulation of their mucosal immunity.

Conclusion

The present work shows the beneficial effect of the administration of a PFM not only to the mothers during the suckling period but also to their offspring after weaning and until adulthood. This effect positively improved the intestinal microbiota that are related with a modulation of the gut immune response, which was demonstrated with the stimulation of the IgA + cells, macrophages and dendritic cells.

Probiotics in clinical practice: an overview

The observation that intestinal bacterial microflora might be able to influence immune system surveillance through changed nutritional habits has raised awareness of the role of probiotics. These are live microorganisms that are able to reach the gastrointestinal tract and alter its microfloral composition, producing beneficial health effects when consumed in adequate amounts. Recent clinical trials have evaluated the clinical effectiveness of probiotics in the treatment and prevention of a wide range of acute and chronic gastrointestinal diseases, and also non-gastrointestinal diseases, such as atopy, respiratory infections, vaginitis and hypercholesterolaemia. Probiotic supplements are generally regarded as safe because the microorganisms they contain are identical to those found in human gastrointestinal and vaginal microflora. Guidelines on the use of probiotics in the clinical setting require periodical updates for the latest data to be included in clinical applications. The purpose of this clinical report is to review current evidence on the use of probiotics in a variety of gastrointestinal and non-gastrointestinal conditions.

Probiotics: role in pathophysiology and prevention in necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is an inflammatory bowel disease largely affecting low birth weight, premature infants. Once acquired, NEC is accompanied by significant mortality and morbid sequelae. Our understanding of the pathophysiology of NEC continues to evolve, and the development of NEC is likely multifactorial with resultant bowel injury mediated through a final, common inflammatory pathway. The predisposition for NEC appears to involve the interplay between intestinal integrity and function, enteral feeding and bacterial colonization, and regulation of the gastrointestinal and systemic inflammatory response. Commensal organisms or probiotics have been shown to be crucial in the development and modulation of each of these factors within the intestinal epithelium. As a result, probiotic supplementation has been proposed as a promising new intervention for the prevention of NEC. To understand the potential utility of probiotics in NEC, we will discuss: the components of gut defense; the role of the intestinal ecosystem in modulating immunity and inflammation; bacterial colonization patterns in the preterm infant compared with patterns seen in the healthy, full-term infant; the evidence for probiotic use in other populations and diseases; and finally, the evidence of probiotic use specific to the preterm infant and NEC.

Splenda alters gut microflora and increases intestinal p-glycoprotein and cytochrome p-450 in male rats

Splenda is comprised of the high-potency artificial sweetener sucralose (1.1%) and the fillers maltodextrin and glucose. Splenda was administered by oral gavage at 100, 300, 500, or 1000 mg/kg to male Sprague-Dawley rats for 12-wk, during which fecal samples were collected weekly for bacterial analysis and measurement of fecal pH. After 12-wk, half of the animals from each treatment group were sacrificed to determine the intestinal expression of the membrane efflux transporter P-glycoprotein (P-gp) and the cytochrome P-450 (CYP) metabolism system by Western blot. The remaining animals were allowed to recover for an additional 12-wk, and further assessments of fecal microflora, fecal pH, and expression of P-gp and CYP were determined. At the end of the 12-wk treatment period, the numbers of total anaerobes, bifidobacteria, lactobacilli, Bacteroides, clostridia, and total aerobic bacteria were significantly decreased; however, there was no significant treatment effect on enterobacteria. Splenda also increased fecal pH and enhanced the expression of P-gp by 2.43-fold, CYP3A4 by 2.51-fold, and CYP2D1 by 3.49-fold. Following the 12-wk recovery period, only the total anaerobes and bifidobacteria remained significantly depressed, whereas pH values, P-gp, and CYP3A4 and CYP2D1 remained elevated. These changes occurred at Splenda dosages that contained sucralose at 1.1-11 mg/kg (the US FDA Acceptable Daily Intake for sucralose is 5 mg/kg). Evidence indicates that a 12-wk administration of Splenda exerted numerous adverse effects, including (1) reduction in beneficial fecal microflora, (2) increased fecal pH, and (3) enhanced expression levels of P-gp, CYP3A4, and CYP2D1, which are known to limit the bioavailability of orally administered drugs.

Influence of dietary components on development of the microbiota in single-stomached species

After birth, development of a normal microbial community occurs gradually, and is affected by factors such as the composition of the maternal gut microbiota, the environment, and the host genome. Diet also has a direct influence, both on composition and activity of this community. This influence begins with the milk, when specific components exert their growth-promoting effect on a beneficial microbiota, thereby suppressing potential pathogens. For example, breast-fed infants compared with formula-fed babies usually have a microbial community dominated by bifidobacteria. When solid food is introduced (weaning), dramatic changes in microbial composition occur, so pathogens can gain access to the disturbed gastrointestinal (GI) ecosystem. However, use of specific dietary components can alter the composition and activity of the microbiota positively. Of all dietary components, fermentable carbohydrates seem to be most promising in terms of promoting proliferation of beneficial bacterial species. Carbohydrate fermentation results in the production of SCFA which are known for their trophic and health-promoting effects. Fermentation of proteins, on the other hand, is often associated with growth of potential pathogens, and results in production of detrimental substances including NH3and amines. In terms of the GI microbiota, lipids are often associated with the antimicrobial activity of medium-chain fatty acids and their derivatives. The present review aims to provide deeper insights into the composition and development of the neonatal GI microbiota, how this microbiota can be influenced by certain dietary components, and how this might ultimately lead to improvements in host health.

Probiotics in children

The gastrointestinal flora plays a complex and important role in the development of healthy immunologic and digestive function in children. Probiotics are safe in healthy children and effective in reducing the risk of antibiotic-associated diarrhea and the duration of acute infectious diarrhea. Probiotics may also be effective in preventing community-acquired diarrheal infections, in reducing the risk of necrotizing enterocolitis in premature infants, and in the prevention and treatment of atopic dermatitis. The exact strain or combination of strains most effective for common clinical indications has yet to be determined, but the exact strain used seems less important than whether an adequate dose is used (typically 5 to 10 billion CFUs per day or higher). Clinicians should familiarize themselves with the products available because there is a wide range in their quality.

Dietary supplementation of short-chain fructooligosaccharides influences gastrointestinal microbiota composition and immunity characteristics of Pacific white shrimp, Litopenaeus vannamei, cultured in a recirculating system

Supplementation of prebiotic compounds, including short-chain fructooligosaccharides (scFOS) has been shown to confer benefits on nutrient utilization, growth, and disease resistance of various animal species through improved gastrointestinal (GI) microbiota. However, potential uses of prebiotics for shrimp have not been defined. A 6-wk feeding trial was conducted in a recirculating system to determine the effects of scFOS supplementation on growth performance, immune functions, and GI microbiota composition of Pacific white shrimp (Litopenaeus vannamei). scFOS was supplemented in a nutritionally complete diet (35% crude protein) at 0.025, 0.0500, 0.075, 0.100, 0.200, 0.400, and 0.800% by weight. After 6 wk of feeding, shrimp fed 0, 0.1, and 0.8% scFOS were sampled for assays of immune function and GI microbiota. Dietary supplementation of scFOS did not improve weight gain, feed conversion ratio, or survival of shrimp. Denaturing gradient gel electrophoresis analysis suggested the intestinal tract microbial community from shrimp fed the basal diet was different from that of shrimp fed the scFOS diets [similarity coefficient (SC) = 74.9%)], although the intestinal tract microbial community from shrimp fed the scFOS-supplemented diets was very similar (SC = 92.3%). All the bacterial species contributing to the GI microbial differences were identified, although most of them are uncultured species. Both total hemocyte count and hemocyte respiratory burst increased (P < 0.05) by incremental dietary supplementation of scFOS (0-0.8%). This study is the first to our knowledge to show that dietary scFOS can selectively support growth of certain bacterial species in the GI tract of shrimp and enhance immunity, which may facilitate development of alternative strategies, including novel probiotics and synbiotics, for shrimp growth and health management.

Colonization and impact of disease and other factors on intestinal microbiota

The aim of this study was to review the process of microbial colonization and the environmental and host factors that influence colonization and microbial succession. The impact of some diseases on intestinal microbiota composition is also described. Microbial colonization of the gut by maternal vaginal and fecal bacteria begins during and after birth. During the first 2 years of life, specific microbes become established in a process designated microbial succession. Microbial succession in the gastrointestinal tract is influenced by numerous external and internal host-related factors, and by the second year of life, the intestinal microbiota composition is considered identical to that of adults. Nevertheless, intestinal microbiota in both infants and adults remain incompletely characterized and their diversity poorly defined. The main explanation is that many intestinal bacteria that live in an anaerobic environment are difficult or impossible to culture outside the intestine. However, recent advances in molecular biology techniques have initiated the description of new bacteria species. The composition of gut microbiota can be modulated by host, environmental, and bacterial factors, and strong evidence has emerged of substantial modifications during illness or exposure to threatening experiences. It has been postulated that improvements in hygienic measures have led to an increase in allergic diseases ("hygiene hypothesis"). Alterations in gut microbiota and their functions have been widely associated with many chronic and degenerative diseases, including inflammatory bowel disease, colon cancer, and rheumatoid arthritis.

Selected prebiotics support the growth of probiotic mono-cultures in vitro

The aim of the present study was to identify suitable prebiotics for synergistic combinations with representative probiotics from the lactobacilli and bifidobacterium genera. Eleven different types of commercially available carbohydrates and compounds were screened in basal media for their effects on the growth of the probiotic cultures Lactobacillus acidophilus LAFTI L10 (L10), Bifidobacterium animalis lactis LAFTI B94 (B94) and Lactobacillus casei LAFTI L26 (L26). Growth of these probiotics was investigated by measuring optical density (OD) levels over a period of 48 h. The results of this study showed that all three probiotic strains were able to utilize a range of carbohydrates. Maximal growth of L10 was observed in basal medium supplemented with soybean oligosaccharide (SOS), followed by fructooligosaccharide (FOS) and inulin, while maximal growth of B94 was observed in basal medium supplemented with SOS, followed by raffinose, FOS, beta-glucan hydrolysate, inulin and Fibregum TAN. L26 was shown to exhibit maximal growth in basal medium supplemented with FOS followed by inulin, SOS, beta-glucan hydrolysate and beta-glucan concentrate. The results of this study indicate that several carbohydrates/compounds can enhance the growth of these representative probiotic strains in vitro.

Composition and metabolism of the intestinal microbiota in consumers and non-consumers of yogurt

The objective of the present study was to evaluate the impact of a regular consumption of yogurt on the composition and metabolism of the human intestinal microbiota. Adult subjects were selected on the basis of daily food records and divided into two groups: yogurt consumers (at least 200 g yogurt consumed per d, n 30); non-consumers (no yogurt, n 21). Their faecal microbiota was analysed using molecular methods (in situ hybridisation and PCR amplification combined with separation by denaturing gel electrophoresis) and its metabolic characteristics were assessed by measuring glycosidase, P-glucuronidase and reductase activities and profiling SCFA, neutral sterols and bile acids. The yogurt starter Lactobacillus delbrueckii ssp. bulgaricus (identity confirmed by 16S rRNA sequencing) was detected in 73% of faecal samples from fermented milk consumers v. 28% from non-consumers (P=0.003). In yogurt consumers, the level of Enterobacteriaceae was significantly lower (P=0.006) and 13-galactosidase activity was significantly increased (P=0.048). In addition, within this group, 3-galactosidase activity and the Bifidobacterium population were both positively correlated with the amount of fermented milk ingested (r 0.66, P<0.0001 and r 0.43, P=0.018, respectively). Apart from these effects, which can be considered beneficial to the host, no other major differences could be detected regarding the composition and metabolic activity of intestinal microbiota.

Non-digestible Oligosaccharides with Prebiotic Properties

The search for functional foods or functional food ingredients, i.e. foods or food ingredients that can enhance health, is beyond any doubt one of the leading trends in today's food industry. In this context, probiotics, i.e. living microbial food supplements, and prebiotics, i.e. non-digestible food ingredients, receive much attention. Both popular concepts target the gastrointestinal microbiota. While in the Western world, intake of probiotics has been recommended for long, prebiotics in general, and non-digestible oligosaccharides in particular, have only recently received attention. This review deals with production and characterization of non-digestible oligosaccharides and focuses on their role in promoting health and treating diseases. Attention is paid to the effects of non-digestible oligosaccharides on constipation, mineral absorption, lipid metabolism, cancer prevention, hepatic encephalopathy, glycemia/insulinemia, and immunomodulation.

Oral feeding of Bifidobacterium bifidum (BGN4) prevents CD4(+) CD45RB(high) T cell-mediated inflammatory bowel disease by inhibition of disordered T cell activation

Probiotics have been considered as preventive agents for the control of inflammatory bowel disease (IBD). In this study, we assessed the immunomodulatory effect of Bifidobacterium bifidum BGN4 on the control of IBD using the CD4(+) CD45RB(high) T cell transfer disease model. The mice were fed for 4 weeks with either a conventional diet containing only skim milk or a diet containing skim milk with 0.3% (w/w) BGN4. The BGN4-fed mice showed normal weight growth, fewer clinical symptoms such as thickened wall and inflammatory cell infiltration, and lower levels of CD4(+) T lymphocyte infiltration and inflammatory cytokine productions than the skim milk-fed mice with IBD in the large intestine. Suppression of these cytokine productions, particularly IFN-gamma and MCP-1, through BGN4 treatment was also observed in the in vitro co-culture between intestinal epithelial cells and T cells. These findings suggested that a BGN4 supplemented diet could be helpful for the control of aberrant immune responses in the intestinal tissue.

Efficacy of probiotics and nutrients in functional gastrointestinal disorders: a preliminary clinical trial

The purpose of this study was to evaluate the efficacy and safety of commonly used probiotics and nutrients available for functional gastrointestinal disorders (FGID). Five different combinations of probiotics and nutrients, or placebo, were taken daily over 12 weeks. In this randomized controlled clinical trial, men and women 21 to 72 years of age with FGID symptoms of indigestion, bloating, and abdominal discomfort were assigned to one of six groups, 12 patients per group. Gastrointestinal Quality of Life Index (GIQLI) and visual analogue scale (VAS) for GI symptoms, SF-36, lactulose and mannitol test (LMT), and urine indican levels were evaluated. GIQLI, VAS scores, and LMT did not change significantly (P > 0.05). There were clinically notable improvements in two of the combination formulations. While the nonsignificant improvements in GI symptoms could suggest that combination probiotics and nutrients may be beneficial in conditions such as FGID, no conclusive evidence was found in this pilot trial. Further investigations to explore the findings are discussed.

Prebiotics in human milk: a review

The microbic colonization of human intestine begins at birth, when from a sterile state the newborn is exposed to an external environment rich in various bacterial species. The kind of delivery has an important influence on the composition of the intestinal flora in the first days of life. Thereafter, the microflora is mainly influenced by the kind of feeding: breast-fed infants show a predominance of bifidobacteria and lactobacilli, whereas bottle-fed infants develop a mixed flora with a lower number of bifidobacteria. The "bifidogenic effect" of human milk is not related to a single growth-promoting substance, but rather to a complex of interacting factors. In particular the prebiotic effect has been ascribed to the low concentration of proteins and phosphates, the presence of lactoferrin, lactose, nucleotides and oligosaccharides. The real prebiotic role of each of these substances is not yet clearly defined, with the exception of oligosaccharides which undoubtedly promote a bifidobacteria-dominant microflora.

Metabolic syndrome and obesity in an insect

Dragonflies infected with noninvasive gregarine gut parasites (Apicomplexa: Eugregarinorida) [corrected] have reduced flight-muscle performance, an inability to metabolize lipid in their muscles, twofold-elevated hemolymph carbohydrate concentrations, and they accumulate fat in their thorax in a manner analogous to mammalian obesity. Gregarine infection is associated with inappropriate responses of hemolymph carbohydrate concentration to insulin and with chronic activation in the flight muscles of p38 MAP kinase, a signaling molecule involved in immune and stress responses. Short-term exposure to gregarine excretory/secretory products caused elevated blood carbohydrate and p38 MAPK activation in healthy individuals. These characteristics comprise a set of symptoms and processes that are known in mammals as metabolic syndrome but which have not previously been described in other animal taxa. In addition to expanding the known taxonomic breadth of metabolic disease, these results indicate that insects may be useful experimental models for studying its underlying biology and mechanisms.

Konjac acts as a natural laxative by increasing stool bulk and improving colonic ecology in healthy adults

OBJECTIVE

Konjac glucomannan (KGM) has been shown to relieve constipation, which could be associated with increased stool bulk and improved colonic ecology.

METHODS

This placebo-controlled study consisted of a 21-d placebo period, a 7-d adaptation period when volunteers consumed KGM progressively, and a 21-d KGM-supplemented period (1.5 g/meal, 4.5 g/d). Eight healthy adults consumed 7-d cycle menus of typical low-fiber Chinese food throughout the study. The gastrointestinal response was monitored daily. Stools were fully collected on days 15 to 21 of placebo and KGM periods to determine the fecal mass, components, microflora, and short-chain fatty acid contents.

RESULTS

The KGM supplement significantly increased the mean defecation frequency (number/day), wet stool weight, and dry stool weight (g/d) by approximately 27.0% (P < 0.05), 30.2% (P < 0.05), and 21.7% (P < 0.05), respectively. The dry fecal mass increased mainly in the plant and soluble material, whereas bacterial mass tended to increase from 12.9 +/- 1.6 to 13.6 +/- 2.7 g/d (P > 0.05). However, KGM significantly promoted the fecal concentrations (log counts/g wet feces) of lactobacilli (P < 0.05) and total bacteria (P < 0.05), and promoted the daily output (log counts per day) of bifidobacteria (P < 0.05), lactobacilli (P < 0.05), and total bacteria (P < 0.05) as evaluated by the fluorescence in situ hybridization method. KGM supplement also promoted colonic fermentation as shown in the decreased fecal pH (P < 0.05) and increased fecal short-chain fatty acid concentrations (P < 0.05).

CONCLUSION

Supplementation of KGM into a low-fiber diet promoted the defecation frequency in healthy adults, possibly by increasing the stool bulk, thus promoting the growth of lactic acid bacteria and colonic fermentation.

Inflammatory bowel disease and Streptococcus bovis

Evidence suggests a trend for a higher fecal carriage rate of Streptococcus bovis in adult patients with inflammatory bowel disease (IBD). This study defines the fecal carriage rate of S. bovis among children with IBD compared to controls. Subjects with IBD were prospectively enrolled from the patient population of a pediatric gastroenterology practice. Stool samples from IBD patients as well as controls were analyzed within 24 hr for the presence of S. bovis. The study enrolled 47 patients with IBD and 34 controls. Among the 47 IBD patients, 3 had a positive stool culture for S. bovis (6%) and 1 had an equivocal result between S. bovis and S. salivarius. Including this equivocal result, 8.5% of IBD patients were S. bovis carriers. Among the 34 controls, 3 (9%) were found to be fecal carriers of S. bovis. Assuming that the equivocal stool was indeed S. bovis, these groups are not statistically different as determined by Fisher's exact test (P=0.6). We conclude that the fecal carriage rate of S. bovis is not increased among pediatric patients with IBD compared with controls.

Probiotic bacteria Bifidobacterium animalis MB5 and Lactobacillus rhamnosus GG protect intestinal Caco-2 cells from the inflammation-associated response induced by enterotoxigenic Escherichia coli K88

Probiotic bacteria may provide protection against intestinal damage induced by pathogens, but the underlying mechanisms are still largely unknown. We investigated whether Bifidobacterium animalis MB5 and Lactobacillus rhamnosus GG (LGG) protected intestinal Caco-2 cells from the inflammation-associated response induced by enterotoxigenic Escherichia coli (ETEC) K88, by inhibiting pathogen attachment to the cells, which is the first step of ETEC pathogenicity, and regulating neutrophil recruitment, a crucial component of inflammation. A partial reduction of ETEC adhesion was exerted by probiotics and their culture supernatant fractions either undigested or digested with proteases. ETEC viability was unaffected by the presence of B. animalis, LGG or their supernatant fractions in the culture medium, indicating an absence of probiotic bactericidal activity. Probiotics and their supernatant fractions, either undigested or digested with proteases, strongly inhibited the neutrophil transmigration caused by ETEC. Both B. animalis and LGG counteracted the pathogen-induced up regulation of IL-8, growth-related oncogene-alpha and epithelial neutrophil-activating peptide-78 gene expression, which are chemokines essential for neutrophil migration. Moreover, the probiotics prevented the ETEC-induced increased expression of IL-1beta and TNF-alpha and decrease of transforming growth factor-alpha, which are regulators of chemokine expression. These results indicate that B. animalis MB5 and LGG protect intestinal cells from the inflammation-associated response caused by ETEC K88 by partly reducing pathogen adhesion and by counteracting neutrophil migration, probably through the regulation of chemokine and cytokine expression.

Probiotics as flourishing benefactors for the human body

This article provides a comprehensive review of the beneficial effects of various strains of probiotics in preventing and treating certain diseases. Currently, changed lifestyles as well as the increased use of antibiotics are significant factors challenging the preservation of a healthy intestinal microflora. The concept of probiotics is to restore and uphold a microflora advantageous for the human body. Probiotics are found in a number of fermented dairy products, infant formula, and dietary supplements. In the presence of prebiotics, which are nondigestible food ingredients favorable for probiotic growth, their survival in the intestine is ameliorated.

Adhesion of Lactobacillus plantarum 423 and Lactobacillus salivarius 241 to the intestinal tract of piglets, as recorded with fluorescent in situ hybridization (FISH), and production of plantaricin 423 by cells colonized to the ileum

AIMS

To determine which intestinal section of pre and postweaned piglets are colonized by Lactobacillus plantarum 423 and Lactobacillus salivarius 241, and follow production of plantaricin 423 in a gastro-intestinal model.

METHODS AND RESULTS

Lactobacillus plantarum 423 and Lact. salivarius 241, single or in combination, were administered to 1-, 14- and 28-day-old (postweaned) piglets. According to results obtained by fluorescent in situ hybridization (FISH), Lact. plantarum 423 adhered strongly to the ileum and posterior colon and Lact. salivarius 241 to the duodenum in preweaned piglets. High numbers of strain 241 were recorded in the duodenum and posterior colon of postweaned piglets, whereas strain 423 remained localized to the ileum. Lowering in Enterococcus faecalis cell numbers were recorded when preweaned piglets were challenged with strain 241. Plantaricin 423 was produced for 96 h in the ileum section of a gastro-intestinal model.

CONCLUSIONS

Lactobacillus plantarum 423 and Lact. salivarius 241 adhere to different sections of the intestinal tract, depending on the piglet's age. Ent. faecalis were inhibited in vivo, probably by plantaricin 423.

SIGNIFICANCE AND IMPACT OF THE STUDY

Fluorescent in situ hybridization proved valuable in the detection of probiotic bacteria adhered to the intestine. This is the first report of bacteriocin production in a model simulating the porcine gastro-intestinal tract.

Comparison of antagonistic ability against enteropathogens by G+ and G− anaerobic dominant components of human fecal microbiota

To confirm if anaerobic G+-components are those responsible for the function of colonization resistance, obligate anaerobic G+- and G- -bacteria from normal dominant microbiota of human feces were isolated from three successive collections and then used in in vitro assays for antagonism against two enteropathogenic bacteria. The production of inhibitory diffusible compounds was determined on supplemented BHI agar and MRS agar media for G- - and G+-bacteria, respectively. Salmonella enterica subsp. enterica serovar Typhimurium and Shigella sonnei were used as indicators. G+-bacteria presented a higher overall antagonistic frequency against both pathogenic bacteria (57 and 64 % for S. enterica serovar Typhimurium and S. sonnei, respectively) when compared to G+-microorganisms but with a quite elevated variation between volunteers (0-100 %) and collection samples (40-72 and 40-80 % for S. enterica sv. Typhimurium and S. sonnei, respectively). On the other hand, only three among 143 G- -isolates tested showed antagonistic activity. The results showed that, at least in vitro, obligate anaerobic G+-components of the dominant human fecal microbiota present a higher potential for antagonism against the enteropathogenic models tested than do G- -bacteria.

Probiotics and chronic disease

In today's climate, changed lifestyles and the increased use of antibiotics are significant factors that affect the preservation of a healthy intestinal microflora. The concept of probiotics is to restore and maintain a microflora advantageous to the human body. Probiotics are found in a number of fermented dairy products, infant formula, and dietary supplements. Basic research on probiotics has suggested several modes of action beneficial for the human body and clinical research has proven its preventive and curative features in different intestinal and extraintestinal diseases. Chronic diseases cause considerable disablement in patients and represent a substantial economic burden on healthcare resources. Research has demonstrated a crucial role of nutrition in the prevention of chronic disease. Thus, positive, strain-specific effects of probiotics have been shown in diarrheal diseases, inflammatory bowel diseases, irritable bowel syndrome, and Helicobacter pylori-induced gastritis, and in atopic diseases and in the prevention of cancer. As the majority of probiotics naturally inhabit the human intestinal microflora, their use has been regarded as very safe. However, in view of the range of potential benefits on health that might be achieved by the use of some probiotic bacteria, major and thorough evaluation is still necessary. In conclusion, probiotics act as an adjuvant in the prevention and treatment of a wide variety of chronic diseases.

Unhydrolyzed and hydrolyzed konjac glucomannans modulated cecal and fecal microflora in Balb/c mice

OBJECTIVE

The prebiotic role of intact konjac glucomannan (KGM) is contradictory. Short-chain glucomannan may cause a greater or faster effect on colonic microflora compared with KGM. Therefore, time-course and dose-dependent studies were conducted to examine and compare effects of unhydrolyzed KGM with those of acid-hydrolyzed glucomannan (KH) on cecal and fecal microflora. Short-chain fatty acid concentrations in cecal content were also determined.

METHODS

Seven-week-old male Balb/c mice were fed 5% (w/w) cellulose and KGM or KH diets for 2 or 4 wk in a time-course study. Cecal total anaerobes, bifidobacteria, Clostridium perfringens and Escherichia coli counts, and short-chain fatty acid concentrations were determined. In a subsequent dose-dependent study, Balb/c mice were fed AIN-93 fiber-free diets supplemented with 2.5%, 5%, or 7.5% of KGM or KH for 4 wk. Anaerobes, bifidobacteria, C. perfringens, and E. coli were enumerated in the cecal content and feces.

RESULTS

KGM and KH significantly increased cecal anaerobes and bifidobacteria counts at weeks 2 and 4, respectively, compared with cellulose. In contrast, KGM and KH significantly decreased cecal C. perfringens counts only at week 4. Acetate and propionate concentrations in cecal contents were increased by KGM and KH diets at weeks 2 and 4, respectively. In the dose-dependent study, KH increased cecal bifidobacteria counts only at the 2.5% level but increased fecal bifidobacteria count and suppressed C. perfringens counts at each dose level as compared with KGM.

CONCLUSION

Hydrolyzed glucomannan exerts a greater prebiotic effect than does KGM in Balb/c mice.

Phytase activity as a novel metabolic feature inBifidobacterium

Phytase activity has been detected for the first time in Bifidobacterium spp. These bacteria were able to dephosphorylate phytic acid (myo-inositol hexaphosphate, IP(6)) and generate several myo-inositol phosphate intermediates (IP(3)-IP(5)). B. globosum and B. pseudocatenulatum were optimally active at neutral-alkaline pH and B. adolescentis, B. angulatum and B. longum at acid pH. B. pseudocatenulatum showed the highest levels of phytase activity. This species produced maximum activity in the exponential phase of growth and when fructo-oligosaccharides were used as carbon source in the culture medium. The potential role of phytase activity from Bifidobacterium spp. in the reduction of the antinutritional properties of IP(6) is discussed.

Aetiology of inflammatory bowel disease (IBD): role of intestinal microbiota and gut-associated lymphoid tissue immune response

The aetiology of inflammatory bowel disease (IBD) probably involves a combination of genetic predisposition and environmental factors that may be channelled through an abnormality in gut-barrier function, with a loss of antigen tolerance. Some genetic markers that predispose to inflammatory disease have been identified (alleles DR2, DRB1*0103, DRB1*12 and mutations in the NOD2/CARD15 gene on chromosome 16). Alterations in the pattern of cytokine production by T cell subclasses leading to loss of tolerance to oral antigens have been documented. Moreover, a number of environmental factors (cigarette smoking, use of non-steroid anti-inflammatory drugs, psychological stress and the presence of the caecal appendix) have been postulated as a trigger of IBD. It has also been suggested that the gut microbiota plays a major role in the development and persistence of IBD, and numerous modifications of intestinal microbiota composition have been identified. As a result, manipulation of the microbiota with antibiotics is a current therapeutic strategy; more recently, however, a number of studies have reported promising results when using probiotic organisms to manipulate gut microbiota composition in order to restore tolerance to microbial antigens of the host's own microbiota.

Intestinal immunity of rats with colon cancer is modulated by oligofructose-enriched inulin combined with Lactobacillus rhamnosus and Bifidobacterium lactis

Probiotics (PRO) are known to modulate immunity in animals and human subjects and to inhibit colon carcinogenesis in experimental models, but the effects of synbiotics (SYN) are not well understood. Therefore, the effects of PRO (Lactobacillus rhamnosus GG and Bifidobacterium lactis Bb12), PRE (inulin-based enriched with oligofructose, 100 g/kg) and SYN (combination of PRO and PRE) on the immune system of rats were investigated in the azoxymethane (AOM)-induced colon cancer model. After 33 weeks, rats with and without AOM treatment were killed and immune cells were isolated from spleen, mesenterial lymph nodes (MLN) and Peyer's patches (PP). AOM treatment significantly reduced natural killer (NK) cell-like cytotoxicity in control rats and in PRO- and PRE-supplemented rats. SYN supplementation prevented the AOM-induced suppression of NK cell-like cytotoxicity in PP compared with control rats (P<0.01). SYN and PRE supplementation stimulated IL-10 production in PP in these rats (P<0.01) and in MLN of rats not treated with AOM (P<0.05). Interferon-gamma production in PP was decreased by PRO supplementation (PRO and SYN groups combined; P<0.05). Proliferative responsiveness of lymphocytes (PP) from AOM-treated rats was suppressed in SYN-supplemented rats (P<0.01). Overall, SYN supplementation in carcinogen-treated rats primarily modulated immune functions in the PP, coinciding with a reduced number of colon tumours. PRE and PRO provided in combination as SYN may contribute to the suppression of colon carcinogenesis by modulating the gut-associated lymphoid tissue.

Probiotics and prebiotics: role in clinical disease states

Parents of pediatric patients are seeking alternatives to conventional therapy in the prevention and treatment of gastrointestinal disease states because of therapeutic failures caused by the increased incidence of antibiotic resistance. One such alternative is the use of probiotics and prebiotics to stimulate health-promoting indigenous flora to affect pathogen colonization and expression of disease. Probiotics are live flora given in oral quantities that allow for colonization of the colon. Probiotics are given as functional foods or dietary supplements, and function to activate the mucosal immune system and prevent pathogen colonization and translocation by strengthening the mucosal barrier, interfering with pathogen colonization, and in some instances, producing secretory antibacterial substances. Prebiotics are nondigestible carbohydrates, principally oligosoccharides, that are fermented by colonic commensals, stimulating their proliferation and producing short-chain fatty acids. Both protective nutrients have been shown to reduce the incidence and severity of infantile diarrhea, particularly rotaviral gastroenteritis, prevent antibiotic-induced diarrhea, and prevent and treat intestinal food allergy. With additional multicenter clinical trial confirmations, these substances may become routine in the care of infants and young children.