Short-chain fatty acids: ready for prime time?

Association between specific mucosa-associated microbiota in Crohn's disease at the time of resection and subsequent disease recurrence: a pilot study

BACKGROUND AND AIM

Crohn's disease pathogenesis involves alterations in the gut microbiota. We characterized the mucosa-associated microbiota at the time of surgical resection and 6 months later to identify bacterial profiles associated with recurrence and remission.

METHODS

Tissue samples were collected from surgical resection specimens in 12 Crohn's disease patients, and at 6 months postoperative colonoscopy from the neoterminal ileum and anastomosis. Endoscopic recurrence was assessed using the Rutgeerts score. Microbiota was characterized using microarray and 454 pyrosequencing. Longitudinal comparisons were made within patients, and cross-sectional comparisons made with colonoscopic biopsies from the terminal ileum and cecum of 10 healthy subjects.

RESULTS

Microbiota of healthy subjects had high diversity and was dominated by the Firmicutes, Bacteroidetes, and Proteobacteria phyla. Biodiversity was lower in Crohn's disease patients at the time of surgery, increased after surgery, but still differed from healthy subjects. Crohn's disease patients with recurrent disease retained a microbiota favoring proteolytic-fueled fermentation and lactic acid-producing bacteria, including Enterococcus and Veillonella spp., while those maintaining remission demonstrated predominant saccharolytic Bacteroides, Prevotella, and Parabacteroides spp., and saccharolytic, butyrate-producing Firmicutes.

CONCLUSION

In Crohn's disease, the mucosa-associated microbiota diversity is reduced at the time of surgery, but also differs between patients with different clinical outcomes at 6 months. These findings may provide prognostic information at the time of surgery, allowing identification of patients at increased risk of recurrence, and provide basis for a more targeted approach for therapeutic interventions after surgery.

The short-chain fatty acid receptor GPR43 is transcriptionally regulated by XBP1 in human monocytes

G-protein coupled receptor 43 (GPR43) recognizes short chain fatty acids and is implicated in obesity, colitis, asthma and arthritis. Here, we present the first full characterization of the GPR43 promoter and 5′-UTR. 5′-RACE of the GPR43 transcript identified the transcription start site (TSS) and a 124 bp 5′-UTR followed by a 1335 bp intron upstream of the ATG start codon. The sequence spanning -4560 to +68 bp relative to the GPR43 TSS was found to contain strong promoter activity, increasing luciferase reporter expression by >100-fold in U937 monocytes. Stepwise deletions further narrowed the putative GPR43 promoter (−451 to +68). Site-directed mutagenesis identified XBP1 as a core cis element, the mutation of which abrogated transcriptional activity. Mutations of predicted CREB, CHOP, NFAT and STAT5 binding sites, partially reduced promoter activity. ChIP assays confirmed the binding of XBP1 to the endogenous GPR43 promoter. Consistently, GPR43 expression is reduced in monocytes upon siRNA-knockdown of XBP1, while A549 cells overexpressing XBP1 displayed elevated GPR43 levels. Based on its ability to activate XBP1, we predicted and confirmed that TNFα induces GPR43 expression in human monocytes. Altogether, our findings form the basis for strategic modulation of GPR43 expression, with a view to regulate GPR43-associated diseases.

The role of gastrointestinal vagal afferent fibres in obesity

Gastrointestinal (GI) vagal afferents are a key mediatory of food intake. Through a balance of responses to chemical and mechanical stimuli food intake can be tightly controlled via the ascending satiety signals initiated in the GI tract. However, vagal responses to both mechanical and chemical stimuli are modified in diet-induced obesity (DIO). Much of the research to date whilst in relatively isolated/controlled circumstances indicates a shift between a balance of orexigenic and anorexigenic vagal signals to blunted anorexigenic and potentiated orexigenic capacity. Although the mechanism responsible for the DIO shift in GI vagal afferent signalling is unknown, one possible contributing factor is the gut microbiota. Nevertheless, whatever the mechanism, the observed changes in gastrointestinal vagal afferent signalling may underlie the pathophysiological changes in food consumption that are pivotal for the development and maintenance of obesity.

Direct In Vivo Human Intestinal Permeability (Peff ) Determined with Different Clinical Perfusion and Intubation Methods

Regional in vivo human intestinal effective permeability (Peff ) is calculated by measuring the disappearance rate of substances during intestinal perfusion. Peff is the most relevant parameter in the prediction of rate and extent of drug absorption from all parts of the intestine. Today, human intestinal perfusions are not performed on a routine basis in drug development. Therefore, it would be beneficial to increase the accuracy of the in vitro and in silico tools used to evaluate the intestinal Peff of novel drugs. This review compiles historical Peff data from 273 individual measurements of 80 substances from 61 studies performed in all parts of the human intestinal tract. These substances include: drugs, monosaccharaides, amino acids, dipeptides, vitamins, steroids, bile acids, ions, fatty acids, and water. The review also discusses the determination and prediction of Peff using in vitro and in silico methods such as quantitative structure-activity relationship, Caco-2, Ussing chamber, animal intestinal perfusion, and physiologically based pharmacokinetic (PBPK) modeling. Finally, we briefly outline how to acquire accurate human intestinal Peff data by deconvolution of plasma concentration-time profiles following regional intestinal bolus dosing.

An isotope-labeled chemical derivatization method for the quantitation of short-chain fatty acids in human feces by liquid chromatography-tandem mass spectrometry

Short-chain fatty acids (SCFAs) are produced by anaerobic gut microbiota in the large bowel. Qualitative and quantitative measurements of SCFAs in the intestinal tract and the fecal samples are important to understand the complex interplay between diet, gut microbiota and host metabolism homeostasis. To develop a new LC-MS/MS method for sensitive and reliable analysis of SCFAs in human fecal samples, 3-nitrophenylhydrazine (3NPH) was employed for pre-analytical derivatization to convert ten C2-C6 SCFAs to their 3-nitrophenylhydrazones under a single set of optimized reaction conditions and without the need of reaction quenching. The derivatives showed excellent in-solution chemical stability. They were separated on a reversed-phase C18 column and quantitated by negative-ion electrospray ionization - multiple-reaction monitoring (MRM)/MS. To achieve accurate quantitation, the stable isotope-labeled versions of the derivatives were synthesized in a single reaction vessel from (13)C6-3NPH, and were used as internal standard to compensate for the matrix effects in ESI. Method validation showed on-column limits of detection and quantitation over the range from low to high femtomoles for the ten SCFAs, and the intra-day and inter-day precision for determination of nine of the ten SCFAs in human fecal samples was ≤8.8% (n=6). The quantitation accuracy ranged from 93.1% to 108.4% (CVs≤4.6%, n=6). This method was used to determine the SCFA concentrations and compositions in six human fecal samples. One of the six samples, which was collected from a clinically diagnosed type 2 diabetes patient showed a significantly high molar ratio of branch-chain SCFAs to straight-chain SCFAs than the others. In summary, this work provides a new LC-MS/MS method for precise and accurate quantitation of SCFAs in human feces.

Gut microbial metabolism drives transformation of MSH2-deficient colon epithelial cells

The etiology of colorectal cancer (CRC) has been linked to deficiencies in mismatch repair and adenomatous polyposis coli (APC) proteins, diet, inflammatory processes, and gut microbiota. However, the mechanism through which the microbiota synergizes with these etiologic factors to promote CRC is not clear. We report that altering the microbiota composition reduces CRC in APC(Min/+)MSH2(-/-) mice, and that a diet reduced in carbohydrates phenocopies this effect. Gut microbes did not induce CRC in these mice through an inflammatory response or the production of DNA mutagens but rather by providing carbohydrate-derived metabolites such as butyrate that fuel hyperproliferation of MSH2(-/-) colon epithelial cells. Further, we provide evidence that the mismatch repair pathway has a role in regulating β-catenin activity and modulating the differentiation of transit-amplifying cells in the colon. These data thereby provide an explanation for the interaction between microbiota, diet, and mismatch repair deficiency in CRC induction. PAPERCLIP:

Protective Effect of Agave salmiana Fructans in Azoxymethane-Induced Colon Cancer in Wistar Rats

Colon cancer is a world concerning disease; it shows a high mortality rate and may be related to eating habits. Studies using inulin-like fructans, which are produced as energy supplies by several plants, have demonstrated a chemo-protective effect of these fructans in colon cancer. However, agavins a structurally different type of fructans from the Agave genus with demonstrated prebiotic effects, have been poorly studied for their possible protective effects in cancer. The aim of the present study was to evaluate the effect of Agave fructan-rich diets in colon cancer progress using a rat model and “Agave mezcalero potosino” A. salmiana Otto ex Salm Dick, which is widely distributed in Mexico. Results showed a significant decrease (p<0.05) in early lesions of colon cancer (aberrant crypt foci) compared with the control group. These data suggest that fructans from A. salmiana may contribute to a reduction in the risk of colon cancer as well as inulin-like compounds.

Short bowel syndrome in infants: the critical role of luminal nutrients in a management program

Short bowel syndrome develops when the remnant mass of functioning enterocytes following massive resections cannot support growth or maintain fluid–electrolyte balance and requires parenteral nutrition. Resection itself stimulates the intestine’s inherent ability to adapt morphologically and functionally. The capacity to change is very much related to the high turnover rate of enterocytes and is mediated by several signals; these signals are mediated in large part by enteral nutrition. Early initiation of enteral feeding, close clinical monitoring, and ongoing assessment of intestinal adaptation are key to the prevention of irreversible intestinal failure. The length of the functional small bowel remnant is the most important variable affecting outcome. The major objective of intestinal rehabilitation programs is to achieve early oral nutritional autonomy while maintaining normal growth and nutrition status and minimizing total parenteral nutrition related comorbidities such as chronic progressive liver disease. Remarkable progress has been made in terms of survivability and quality of life, especially in the context of coordinated multidisciplinary programs, but much work remains to be done.

The role of short-chain fatty acids in health and disease

There is now an abundance of evidence to show that short-chain fatty acids (SCFAs) play an important role in the maintenance of health and the development of disease. SCFAs are a subset of fatty acids that are produced by the gut microbiota during the fermentation of partially and nondigestible polysaccharides. The highest levels of SCFAs are found in the proximal colon, where they are used locally by enterocytes or transported across the gut epithelium into the bloodstream. Two major SCFA signaling mechanisms have been identified, inhibition of histone deacetylases (HDACs) and activation of G-protein-coupled receptors (GPCRs). Since HDACs regulate gene expression, inhibition of HDACs has a vast array of downstream consequences. Our understanding of SCFA-mediated inhibition of HDACs is still in its infancy. GPCRs, particularly GPR43, GPR41, and GPR109A, have been identified as receptors for SCFAs. Studies have implicated a major role for these GPCRs in the regulation of metabolism, inflammation, and disease. SCFAs have been shown to alter chemotaxis and phagocytosis; induce reactive oxygen species (ROS); change cell proliferation and function; have anti-inflammatory, antitumorigenic, and antimicrobial effects; and alter gut integrity. These findings highlight the role of SCFAs as a major player in maintenance of gut and immune homeostasis. Given the vast effects of SCFAs, and that their levels are regulated by diet, they provide a new basis to explain the increased prevalence of inflammatory disease in Westernized countries, as highlighted in this chapter.

A review of the nutritional value of legumes and their effects on obesity and its related co-morbidities

Since the 1970s, the proportion of overweight and obese people in the United States has grown at an alarming rate. An awareness of the consequences of obesity on the health and well-being of individuals is evident in the plethora of strategic plans at the local and national levels, most of which have largely fallen short of their goals. If interventions continue to be unsuccessful, it is estimated that approximately three of four Americans will be overweight or obese by 2020. Prevention of excess weight gain can be accomplished with relatively small changes in lifestyle behaviours to control body weight. Small sustainable changes are perhaps better than efforts to achieve larger changes that cannot be sustained. Legumes can be a valuable food by which the needs of the undernourished or under-served populations could be met. They can be incorporated into meat products, such as sausages and burgers, to lower the energy density of these foods while providing important nutrients. Replacing energy-dense foods with legumes has been shown to have beneficial effects on the prevention and management of obesity and related disorders, such as cardiovascular disease, diabetes and the metabolic syndrome. This review explores the nutritional value and obesity-related health benefits of legume consumption while focusing on pulses.

Rapid and Sustained Long-Term Decrease of Fecal Short-Chain Fatty Acids in Critically Ill Patients With Systemic Inflammatory Response Syndrome

BACKGROUND

The gut is an important target organ for injury after severe insult. Short-chain fatty acids (SCFAs) are end-products of fermentation of dietary fibers by anaerobic microbiota. They are related to intestinal energy, motility, and transport and to protective effects against infection and inflammation. However, there are few clinical data on SCFAs in critically ill patients. We evaluated serial change in fecal SCFAs in patients with severe systemic inflammatory response syndrome (SIRS).

PATIENTS AND METHODS

This study included 140 intensive care unit (ICU) patients who fulfilled the criteria of SIRS and had a serum C-reactive protein level of >10 mg/dL. A fecal sample was used for quantitative measurement of fecal SCFA (butyrate, propionate, and acetate) concentrations by high-performance liquid chromatography. Fecal SCFAs were evaluated weekly for 6 weeks after admission. Data obtained from patients were compared with corresponding data from healthy volunteers.

RESULTS

SIRS resulted from infection in 78 patients, trauma in 30, burns in 12, and other causes in 20. Fecal concentrations of butyrate, propionate, and acetate in these patients decreased significantly compared with those in healthy volunteers and remained low throughout the 6 weeks of the patients' ICU stay. Fecal concentrations of SCFAs in the patients with gastrointestinal complications, including enteritis and dysmotility, were lower than those in the patients without gastrointestinal complications.

CONCLUSIONS

Concentrations of fecal SCFAs in patients with severe SIRS were significantly lower than those in healthy volunteers over a 6-week period. Maintenance of SCFAs may have therapeutic potential to prevent gastrointestinal complications in critically ill patients.

Plasticity of gastro-intestinal vagal afferent endings

Vagal afferents are a vital link between the peripheral tissue and central nervous system (CNS). There is an abundance of vagal afferents present within the proximal gastrointestinal tract which are responsible for monitoring and controlling gastrointestinal function. Whilst essential for maintaining homeostasis there is a vast amount of literature emerging which describes remarkable plasticity of vagal afferents in response to endogenous as well as exogenous stimuli. This plasticity for the most part is vital in maintaining healthy processes; however, there are increased reports of vagal plasticity being disrupted in pathological states, such as obesity. Many of the disruptions, observed in obesity, have the potential to reduce vagal afferent satiety signalling which could ultimately perpetuate the obese state. Understanding how plasticity occurs within vagal afferents will open a whole new understanding of gut function as well as identify new treatment options for obesity.

Protective role of sodium butyrate, a HDAC inhibitor on beta-cell proliferation, function and glucose homeostasis through modulation of p38/ERK MAPK and apoptotic pathways: study in juvenile diabetic rat

Type 1 diabetes (T1D) also known as juvenile diabetes is a chronic autoimmune disorder that precipitates in genetically susceptible individuals by environmental factors particularly during early age. Both genetic and epigenetic factors are implicated in the beta-cell development, proliferation, differentiation and function. Recent evidences suggested that there is a link between diabetes and histone deacetylases (HDACs), because HDAC inhibitors promote beta-cell development, proliferation and function as well as improve glucose homeostasis. Sodium butyrate (NaB) is a short chain fatty acid having HDAC inhibition activity. The present study was aimed to investigate the protective role of NaB treatment on the beta-cell proliferation, function and glucose homeostasis as well as apoptosis in juvenile diabetic rat. Diabetes was induced by single injection of STZ (60 mg/kg, i.p.) in chilled citrate buffer, while NaB (500 mg/kg/day) was administrated by i.p. route for 21 days as pre- and post-treatment schedule. Plasma glucose and insulin levels, HbA1c, glucose tolerance, apoptosis, and expression of proliferating cell nuclear antigen (PCNA), p38, p53, caspase-3, extracellular signal-regulated kinase-1/2 (ERK-1/2), forkhead box protein O1 (FOXO1) and insulin receptor substrate-1 (IRS-1) as well as histone acetylation were evaluated. NaB treatment decreased plasma glucose, HbA1c, beta-cell apoptosis and improved plasma insulin level and glucose homeostasis through HDAC inhibition and histone acetylation in diabetic animal as compared to control. NaB treatment improved the beta-cell proliferation, function and glucose homeostasis as well as reduced beta-cell apoptosis in juvenile diabetic rat by the modulation of p38/ERK MAPK and apoptotic pathway.

Structural and functional changes in the gut microbiota associated to Clostridium difficile infection

Antibiotic therapy is a causative agent of severe disturbances in microbial communities. In healthy individuals, the gut microbiota prevents infection by harmful microorganisms through direct inhibition (releasing antimicrobial compounds), competition, or stimulation of the host's immune defenses. However, widespread antibiotic use has resulted in short- and long-term shifts in the gut microbiota structure, leading to a loss in colonization resistance in some cases. Consequently, some patients develop Clostridium difficile infection (CDI) after taking an antibiotic (AB) and, at present, this opportunistic pathogen is one of the main causes of antibiotic-associated diarrhea in hospitalized patients. Here, we analyze the composition and functional differences in the gut microbiota of C. difficile infected (CDI) vs. non-infected patients, both patient groups having been treated with AB therapy. To do so we used 16S rRNA gene and metagenomic 454-based pyrosequencing approaches. Samples were taken before, during and after AB treatment and were checked for the presence of the pathogen. We performed different analyses and comparisons between infected (CD+) vs. non-infected (CD-) samples, allowing proposing putative candidate taxa and functions that might protect against C. difficile colonization. Most of these potentially protective taxa belonged to the Firmicutes phylum, mainly to the order Clostridiales, while some candidate protective functions were related to aromatic amino acid biosynthesis and stress response mechanisms. We also found that CDI patients showed, in general, lower diversity and richness than non-infected, as well as an overrepresentation of members of the families Bacteroidaceae, Enterococcaceae, Lactobacillaceae and Clostridium clusters XI and XIVa. Regarding metabolic functions, we detected higher abundance of genes involved in the transport and binding of carbohydrates, ions, and others compounds as a response to an antibiotic environment.

Fecal biomarkers of intestinal health and disease in children

The identification of various fecal biomarkers has provided insight into the intestinal milieu. Most of these markers are associated with the innate immune system of the gut, apart from the more novel M2-pyruvate kinase. The innate immunity of the gut plays a role in maintaining a fine balance between tolerance to commensal bacteria and immune response to potential pathogens. It is a complex system, which comprises of multiple elements, including antimicrobial peptides (e.g., defensins, cathelicidins, lactoferrin, and osteoprotegerin), inflammatory proteins (e.g., calprotectin and S100A12), and microbial products (e.g., short-chain fatty acids). Dysfunction of any component can lead to the development of intestinal disease, and different diseases have been associated with different fecal levels of these biomarkers. Each fecal biomarker provides information on specific biological and disease processes. Therefore, stool quantification of these biomarkers provides a non-invasive method to define potential pathways behind the pathogenesis of diseases and can assist in the assessment and diagnosis of various gastrointestinal conditions. The abovementioned fecal biomarkers and their role in intestinal health and disease will be reviewed in this paper with a pediatric focus.

Butyric acid in irritable bowel syndrome

Butyric acid (butanoic acid) belongs to a group of short-chain fatty acids and is thought to play several beneficial roles in the gastrointestinal tract. Butyric anion is easily absorbed by enteric cells and used as a main source of energy. Moreover, butyric acid is an important regulator of colonocyte proliferation and apoptosis, gastrointestinal tract motility and bacterial microflora composition in addition to its involvement in many other processes including immunoregulation and anti-inflammatory activity. The pathogenesis of irritable bowel syndrome (IBS), the most commonly diagnosed functional gastrointestinal condition, is complex, and its precise mechanisms are still unclear. This article describes the potential benefits of butyric acid in IBS.

Comparison of two different in vivo models and an in vitro model for caloric determination of four novel fiber ingredients

The objective of this study was to compare two in vivo methods using pigs and roosters and an in vitro method for determining the caloric value of four fiber sources [i.e., two resistant starches (RS 60 and RS 75), soluble corn fiber (SCF 70), and pullulan]. Metabolizable energy (ME) in pigs and true metabolizable energy (TMEn) in roosters were determined by using 72 barrows and 24 roosters, respectively. A two-step in vitro procedure was used to quantify monosaccharides released. Results of the two in vivo experiments corresponded well with RS 75 having the least caloric value (7.55 MJ/kg in pigs; 6.19 MJ/kg in roosters) and pullulan having the greatest caloric value (12.21 MJ/kg in pigs; 13.94 MJ/kg in roosters). The caloric values for all the fiber ingredients were less (P < 0.05) than in MD both in pigs and in roosters. Despite some limitations, results of the in vitro procedure corresponded well with the in vivo experiments where the concentration of glucose hydrolyzed from RS 60, RS 75, and SCF 70, but not pullulan, was less (P < 0.05) than the concentration of glucose hydrolyzed from MD. However, the greatest accuracy was obtained in the in vivo experiments.

Diet and supplements and their impact on colorectal cancer

BACKGROUND

Colorectal cancer is the third commonest cancer and the third leading cause of cancer death among men and women. It has been proposed that dietary factors are responsible for 70-90% of colorectal cancer and diet optimization may prevent most cases.

AIM

To evaluate the role of dietary components and supplements in colorectal cancer.

METHODS

Bibliographical searches were performed in Pubmed for the terms "diet and colorectal cancer", "diet and colon cancer", "diet and rectal cancer", "nutrition and colorectal cancer", "probiotics and colorectal cancer", "prebiotics and colorectal cancer", "alcohol and cancer" and "colorectal cancer epidemiology".

RESULTS

Consumption of processed or red meat, especially when cooked at high temperatures may be associated with increased risk of colorectal cancer. The evidence for dietary fibre is unclear but foods that contain high amounts of fibre are usually rich in polyphenols which have been shown to alter molecular processes that can encourage colorectal carcinogenesis. Meta-analyses provide evidence on the benefits of circulating, diet-derived and supplemented, vitamin D and Calcium. We also found that diets rich in Folate may prevent colorectal carcinoma. The evidence on dietary micronutrients such as Zinc and Selenium in association with colorectal cancer is not conclusive. It has been suggested that there may be a direct association between alcohol intake and colorectal cancer. In vitro and in vivo studies have highlighted a possible protective role of prebiotics and probiotics.

CONCLUSIONS

The lack of randomized trials and the presence of confounding factors including smoking, physical activity, obesity and diabetes may often yield inconclusive results. Carefully designed randomized trials are recommended.

Is butyrate the link between diet, intestinal microbiota and obesity-related metabolic diseases?

It is increasingly recognized that there is a connection between diet, intestinal microbiota, intestinal barrier function and the low-grade inflammation that characterizes the progression from obesity to metabolic disturbances, making dietary strategies to modulate the intestinal environment relevant. In this context, the ability of some Gram-positive anaerobic bacteria to produce the short-chain fatty acid butyrate is interesting. A lower abundance of butyrate-producing bacteria has been associated with metabolic risk in humans, and recent studies suggest that butyrate might have an anti-inflammatory potential that can alleviate obesity-related metabolic complications, possibly due to its ability to enhance the intestinal barrier function. Here, we review and discuss the potential of butyrate as an anti-inflammatory mediator in metabolic diseases, and the potential for dietary interventions increasing the intestinal availability of butyrate.

Gut-derived short-chain fatty acids are vividly assimilated into host carbohydrates and lipids

Acetate, propionate, and butyrate are the main short-chain fatty acids (SCFAs) that arise from the fermentation of fibers by the colonic microbiota. While many studies focus on the regulatory role of SCFAs, their quantitative role as a catabolic or anabolic substrate for the host has received relatively little attention. To investigate this aspect, we infused conscious mice with physiological quantities of stable isotopes [1-(13)C]acetate, [2-(13)C]propionate, or [2,4-(13)C2]butyrate directly in the cecum, which is the natural production site in mice, and analyzed their interconversion by the microbiota as well as their metabolism by the host. Cecal interconversion, pointing to microbial cross-feeding, was high between acetate and butyrate, low between butyrate and propionate, and almost absent between acetate and propionate. As much as 62% of infused propionate was used in whole body glucose production, in line with its role as gluconeogenic substrate. Conversely, glucose synthesis from propionate accounted for 69% of total glucose production. The synthesis of palmitate and cholesterol in the liver was high from cecal acetate (2.8 and 0.7%, respectively) and butyrate (2.7 and 0.9%, respectively) as substrates, but low or absent from propionate (0.6 and 0.0%, respectively). Label incorporation due to chain elongation of stearate was approximately eightfold higher than de novo synthesis of stearate. Microarray data suggested that SCFAs exert a mild regulatory effect on the expression of genes involved in hepatic metabolic pathways during the 6-h infusion period. Altogether, gut-derived acetate, propionate, and butyrate play important roles as substrates for glucose, cholesterol, and lipid metabolism.

Epithelia of the ovine and bovine forestomach express basolateral maxi-anion channels permeable to the anions of short-chain fatty acids

It has long been established that the absorption of short-chain fatty acids (SCFA) across epithelia stimulates sodium proton exchange. The apically released protons are not available as countercations for the basolateral efflux of SCFA anions and a suitable transport model is lacking. Patch clamp and microelectrode techniques were used to characterize an anion conductance expressed by cultured cells of the sheep and bovine rumen and the sheep omasum and to localize the conductance in the intact tissue. Cells were filled with a Na-gluconate solution and superfused with sodium salts of acetate, propionate, butyrate, or lactate. Reversal potential rose and whole cell current at +100 mV decreased with the size of the anion. Anion-induced currents could be blocked by diisothiocyanato-stilbene-2,2'-disulfonic acid (DIDS), NPPB (200 μmol l(-1)), or pCMB (1 mmol l(-1)). In patches of bovine ruminal cells, single channels were observed with a conductance for chloride (327 ± 11 pS), acetate (115 ± 8 pS), propionate (102 ± 10 pS), butyrate (81 ± 2 pS), and gluconate (44 ± 3 pS). Channels expressed by sheep rumen and omasum were similar. Microelectrode experiments suggest basolateral localization. In conclusion, forestomach epithelia express basolateral maxi-anion channels with a permeability sequence of chloride > acetate > propionate > butyrate. SCFA absorption may resemble functionally coupled transport of NaCl, with the Na(+)/K(+)-ATPase driving the basolateral efflux of the anion through a channel. Since protons are apically extruded, the model accurately predicts that influx of buffers with saliva is essential for the pH homeostasis of the ruminant forestomach.

Novel Polyfermentor intestinal model (PolyFermS) for controlled ecological studies: validation and effect of pH

In vitro gut fermentation modeling offers a useful platform for ecological studies of the intestinal microbiota. In this study we describe a novel Polyfermentor Intestinal Model (PolyFermS) designed to compare the effects of different treatments on the same complex gut microbiota. The model operated in conditions of the proximal colon is composed of a first reactor containing fecal microbiota immobilized in gel beads, and used to continuously inoculate a set of parallel second-stage reactors. The PolyFermS model was validated with three independent intestinal fermentations conducted for 38 days with immobilized human fecal microbiota obtained from three child donors. The microbial diversity of reactor effluents was compared to donor feces using the HITChip, a high-density phylogenetic microarray targeting small subunit rRNA sequences of over 1100 phylotypes of the human gastrointestinal tract. Furthermore, the metabolic response to a decrease of pH from 5.7 to 5.5, applied to balance the high fermentative activity in inoculum reactors, was studied. We observed a reproducible development of stable intestinal communities representing major taxonomic bacterial groups at ratios similar to these in feces of healthy donors, a high similarity of microbiota composition produced in second-stage reactors within a model, and a high time stability of microbiota composition and metabolic activity over 38 day culture. For all tested models, the pH-drop of 0.2 units in inoculum reactors enhanced butyrate production at the expense of acetate, but was accompanied by a donor-specific reorganization of the reactor community, suggesting a concerted metabolic adaptation and trigger of community-specific lactate or acetate cross-feeding pathways in response to varying pH. Our data showed that the PolyFermS model allows the stable cultivation of complex intestinal microbiota akin to the fecal donor and can be developed for the direct comparison of different experimental conditions in parallel reactors continuously inoculated with the exact same microbiota.

Butyric acid in functional constipation

Butyric acid, a short-chain fatty acid, is a major energy source for colonocytes. It occurs in small quantities in some foods, and in the human body, it is produced in the large intestine by intestinalkacteria. This production can be reduced in some cases, for which butyric acid supplementation may be useful. So far, the use of butyric acid in the treatment of gastrointestinal disorders has been limited because of its specific characteristics such as its rancid smell and rapid absorption in the upper gastrointestinal tract. In the Polish market, sodium butyrate has been recently made available, produced by the modern technology of microencapsulation, which allows the active substance to reach the small and large intestines, where butyrate easily dissociates into butyric acid. This article presents the potential beneficial mechanisms of action of butyric acid in defecation disorders, which are primarily associated with reductions in pain during defecation and inflammation in the gut, among others.

Transporters and receptors for short-chain fatty acids as the molecular link between colonic bacteria and the host

The mutually beneficial relationship between colonic bacteria and the host has been recognized but the molecular aspects of the relationship remain poorly understood. Dietary fiber is critical to this relationship. The short-chain fatty acids acetate, propionate and butyrate, generated by bacterial fermentation of dietary fiber, serve as messengers between colonic bacteria and the host. The beneficial effects of these bacterial metabolites in colon include, but are not limited to, suppression of inflammation and prevention of cancer. Recent studies have identified the plasma membrane transporter SLC5A8 and the cell-surface receptors GPR109A and GPR43 as essential for the biologic effects of short-chain fatty acids in colon. These three proteins coded by the host genome provide the molecular link between colonic bacteria and the host.

Development of a complex amino acid supplement, Fatigue Reviva™, for oral ingestion: initial evaluations of product concept and impact on symptoms of sub-health in a group of males

Background

A new dietary supplement, Fatigue Reviva™, has been recently developed to address issues related to amino acid depletion following illness or in conditions of sub-health where altered amino acid homeostasis has been associated with fatigue. Complex formulations of amino acids present significant challenges due to solubility and taste constraints. This initial study sets out to provide an initial appraisal of product palatability and to gather pilot evidence for efficacy.

Methods

Males reporting symptoms of sub-health were recruited on the basis of being free from any significant medical or psychological condition. Each participant took an amino acid based dietary supplement (Fatigue Reviva™) daily for 30 days. Comparisons were then made between pre- and post-supplement general health symptoms and urinary amino acid profiles.

Results

Seventeen men took part in the study. Following amino acid supplementation the total Chalder fatigue score improved significantly (mean ± SEM, 12.5 ± 0.9 versus 10.0 ± 1.0, P<0.03). When asked whether they thought that the supplement had improved their health, 65% of participants responded positively. A subgroup of participants reported gastrointestinal symptoms which were attributed to the supplement and which were believed to result from the component fructooligosaccharide. Analysis of urinary amino acids revealed significant alterations in the relative abundances of a number of amino acids after supplementation including an increase in valine, isoleucine and glutamic acid and reduced levels of glutamine and ornithine. Discriminant function analysis of the urinary amino acid data revealed significant differences between the pre- and post-supplement urine excretion profiles.

Conclusions

The results indicated that Fatigue Reviva™ was palatable and that 65% of the study group reported that they felt the product had improved their health. The product could provide an effective tool for the management of unexplained fatigue and symptoms of sub-health. Further product development may yield additional options for those patients susceptible to fructooligosaccharide.

Age, dietary fiber, breath methane, and fecal short chain fatty acids are interrelated in Archaea-positive humans

Recent attention has focused on the significance of colonic Archaea in human health and energy metabolism. The main objectives of this study were to determine the associations among the number of fecal Archaea, body mass index (BMI), fecal short chain fatty acid (SCFA) concentrations, and dietary intakes of healthy humans. We collected demographic information, 3-d diet records, and breath and fecal samples from 95 healthy participants who were divided into 2 groups: detectable Archaea (>10(6) copies/g; Arch+ve) and undetectable Archaea. Dietary intakes, BMI, and fecal SCFAs were similar in both groups. The mean number of Archaea 16S rRNA gene copies detected in Arch+ve participants' feces was 8.9 ± 0.2 log/g wet weight. In Arch+ve participants, there were positive correlations between breath methane and age (r = 0.52; P = 0.001), total dietary fiber (TDF) intake (r = 0.57; P = 0.0003), and log number of fecal Archaea 16S rRNA gene copies (r = 0.35; P = 0.03). In the Arch+ve group, negative correlations were observed between TDF/1000 kcal and fecal total SCFA (r = -0.46; P ≤ 0.01) and between breath methane and fecal total SCFA (r = -0.42; P = 0.01). Principal component analysis identified a distinct Archaea factor with positive loadings of age, breath methane, TDF, TDF/1000 kcal, and number of log Archaea 16S rRNA gene copies. The results suggest that colonic Archaea is not associated with obesity in healthy humans. The presence of Archaea in humans may influence colonic fermentation by altering SCFA metabolism and fecal SCFA profile.

Fecal microbial metabolism of polyphenols and its effects on human gut microbiota

We investigated the biotransformation of four common dietary polyphenols, rutin, quercetin, chlorogenic acid and caffeic acid, in an in vitro mixed culture model of human intestinal microbiota, to determine effects on human gut bacteria. All four compounds were biotransformed rapidly, disappearing from the medium within 0.5 h and later replaced by known phenolic acid breakdown products, at concentrations up to hundreds of micromolar, much higher than in no-polyphenol control experiments. Quantitative PCR was used to measure effects of the polyphenols on the balance between the major groups of intestinal bacteria that are known to influence gut health, i.e., Bifidobacterium spp., Bacteroidetes, and Firmicutes. Fermentation of polyphenols stimulated proliferation of bifidobacteria and decreased the ratio of Firmicutes to Bacteroidetes, relative to controls. Polyphenols also stimulated short chain fatty acid production by the bacteria. Pure bifidobacterial cultures were treated separately with either fermented media isolated from the incubations, the pure test polyphenols, or the biotransformation products detected in the fermentations. Growth stimulation was observed only with fermented polyphenol media and the pure biotransformation products. It appears that dietary polyphenols may have the ability to modify the gut microbial balance, but this effect is indirect, i.e., it is mediated by biotransformation products, rather than the original plant compounds.

Slowly digestible starch influences mRNA abundance of glucose and short-chain fatty acid transporters in the porcine distal intestinal tract

The relationship between starch chemistry and intestinal nutrient transporters is not well characterized. We hypothesized that inclusion of slowly instead of rapidly digestible starch in pig diets will decrease glucose and increase short-chain fatty acid (SCFA) transporter expression in the distal gut. Weaned barrows (n = 32) were fed 4 diets containing 70% starch [ranging from 0 to 63% amylose and from 1.06 (rapidly) to 0.22%/min (slowly) rate of in vitro digestion] at 3 × maintenance energy requirement in a complete randomized block design. Ileal and colon mucosa was collected on day 21 to quantify mRNA abundance of Na(+)-dependent glucose transporter 1 (SGLT1), monocarboxylic acid transporter 1 (MCT1), and Na(+)-coupled monocarboxylate transporter (SMCT). Messenger RNA was extracted and cDNA manufactured prior to relative quantitative reverse transcription PCR. Data were analyzed using the 2(-Δ ΔC)(T) method, with β-actin and glyceraldehyde-3-phosphate dehydrogenase as reference genes, and regression analysis was performed. As in vitro rate of digestion decreased, SGLT1 linearly increased (P < 0.05) in the ileum. Contrary to SGLT1, MCT1 tended to linearly decrease (P = 0.08) in the ileum and increased quadratically (P < 0.001) in the colon with decreasing rate of digestion. Starch digestion rate did not affect SMCT in the ileum; however, colonic SMCT quadratically decreased (P < 0.01) with decreasing rate of digestion. In conclusion, in contrast to our hypothesis, slowly digestible starch increased ileal glucose and decreased ileal SCFA transporter mRNA abundance, possibly due to an increased glucose in the luminal ileum. Effects of starch on colonic SCFA transporter mRNA abundance were inconsistent.

Effects of sodium butyrate and its synthetic amide derivative on liver inflammation and glucose tolerance in an animal model of steatosis induced by high fat diet

Background & Aims

Nonalcoholic fatty liver disease (NAFLD) is the most common form of chronic liver disease. Insulin resistance (IR) appears to be critical in its pathogenesis. We evaluated the effects of sodium butyrate (butyrate) and its synthetic derivative N-(1-carbamoyl-2-phenyl-ethyl) butyramide (FBA) in a rat model of insulin resistance and steatosis induced by high-fat diet (HFD).

Methods

After weaning, young male Sprague-Dawley rats were divided into 4 groups receiving different diets for 6 weeks: 1. control group (standard diet); 2. HFD; 3. HFD plus butyrate (20 mg/kg/die) and 4. HFD plus FBA (42.5 mg/Kg/die, the equimolecular dose of butyrate). Liver tissues of the rats were analyzed by Western blot and real-time PCR. Insulin resistance, liver inflammation and Toll-like pattern modifications were determined.

Results

Evaluation of these two preparations of butyrate showed a reduction of liver steatosis and inflammation in HFD fed animals. The compounds showed a similar potency in the normalisation of several variables, such as transaminases, homeostasis model assessment for insulin resistance index, and glucose tolerance. Both treatments significantly reduced hepatic TNF-α expression and restored GLUTs and PPARs, either in liver or adipose tissue. Finally, FBA showed a higher potency in reducing pro-inflammatory parameters in the liver, via suppression of Toll-like receptors and NF-κB activation.

Conclusions

Our results demonstrated a protective effect of butyrate in limiting molecular events underlying the onset of IR and NAFLD, suggesting a potential clinical relevance for this substance. In particular, its derivative, FBA, could represent an alternative therapeutic option to sodium butyrate, sharing a comparable efficacy, but a better palatability and compliance.

The role of short-chain fatty acids in the interplay between diet, gut microbiota, and host energy metabolism

Short-chain fatty acids (SCFAs), the end products of fermentation of dietary fibers by the anaerobic intestinal microbiota, have been shown to exert multiple beneficial effects on mammalian energy metabolism. The mechanisms underlying these effects are the subject of intensive research and encompass the complex interplay between diet, gut microbiota, and host energy metabolism. This review summarizes the role of SCFAs in host energy metabolism, starting from the production by the gut microbiota to the uptake by the host and ending with the effects on host metabolism. There are interesting leads on the underlying molecular mechanisms, but there are also many apparently contradictory results. A coherent understanding of the multilevel network in which SCFAs exert their effects is hampered by the lack of quantitative data on actual fluxes of SCFAs and metabolic processes regulated by SCFAs. In this review we address questions that, when answered, will bring us a great step forward in elucidating the role of SCFAs in mammalian energy metabolism.

Potential of probiotics, prebiotics and synbiotics for management of colorectal cancer

Colorectal Cancer (CRC) is the second leading cause of cancer-related mortality and is the fourth most common malignant neoplasm in USA. Escaping apoptosis and cell mutation are the prime hallmarks of cancer. It is apparent that balancing the network between DNA damage and DNA repair is critical in preventing carcinogenesis. One-third of cancers might be prevented by nutritious healthy diet, maintaining healthy weight and physical activity. In this review, an attempt is made to abridge the role of carcinogen in colorectal cancer establishment and prognosis, where special attention has been paid to food-borne mutagens and functional role of beneficial human gut microbiome in evading cancer. Further the significance of tailor-made prebiotics, probiotics and synbiotics in cancer management by bio-antimutagenic and desmutagenic activity has been elaborated. Probiotic bacteria are live microorganisms that, when administered in adequate amounts, confer a healthy benefit on the host. Prebiotics are a selectively fermentable non-digestible oligosaccharide or ingredient that brings specific changes, both in the composition and/or activity of the gastrointestinal microflora, conferring health benefits. Synbiotics are a combination of probiotic bacteria and the growth promoting prebiotic ingredients that purport "synergism."

Preventive effect of resistant starch on activated carbon-induced constipation in mice

The aim of this study was to investigate the effects of resistant starch (RS) on activated carbon-induced constipation in ICR mice. ICR mice were fed on diet containing 15% RS of type RS2, RS3 or RS4 for 9 days. Gastrointestinal transit, defecation time and intestinal tissue histopathological sections, as well as motilin (MTL), gastrin (Gas), endothelin (ET), somatostatin (SS), acetylcholinesterase (AChE), substance P (SP) and vasoactive intestinal peptide (VIP) levels in serum were used to evaluate the preventive effects of RS on constipation. Bisacodyl, a laxative drug, was used as a positive control. The time to the first black stool defecation for normal, control, bisacodyl-treated (100 mg/kg, oral administration) and RS2-, RS3- and RS4-treated mice was 78, 208, 109, 181, 144 and 173 min, respectively. Following the consumption of RS2, RS3 and RS4 or the oral administration of bisacodyl (100 mg/kg), the gastrointestinal transit was reduced to 37.7, 52.1, 39.3 and 87.3%, respectively, of the transit in normal mice, respectively. Histopathological sections of intestinal tissue also underscored the protective effect of RS3. The serum levels of MTL, Gas, ET, AChE, SP and VIP were significantly increased and the serum levels of SS were reduced in the mice treated with RS compared with those in the untreated control mice (P<0.05). These results demonstrate that RS has preventive effects on mouse constipation and RS3 demonstrated the best functional activity.

A diet high in resistant starch modulates microbiota composition, SCFA concentrations, and gene expression in pig intestine

Resistant starch (RS) is highly fermentable by microbiota in the colon, resulting in the production of SCFAs. RS is thought to mediate a large proportion of its health benefits, including increased satiety, through the actions of SCFAs. The aim of this study was to investigate the effects of a diet high in RS on luminal microbiota composition, luminal SCFA concentrations, and the expression of host genes involved in SCFA uptake, SCFA signaling, and satiety regulation in mucosal tissue obtained from small intestine, cecum, and colon. Twenty adult female pigs were either assigned to a digestible starch (DS) diet or a diet high in RS (34%) for a period of 2 wk. After the intervention, luminal content and mucosal scrapings were obtained for detailed molecular analysis. RS was completely degraded in the cecum. In both the cecum and colon, differences in microbiota composition were observed between DS- and RS-fed pigs. In the colon these included the stimulation of the healthy gut-associated butyrate-producing Faecalibacterium prausnitzii, whereas potentially pathogenic members of the Gammaproteobacteria, including Escherichia coli and Pseudomonas spp., were reduced in relative abundance. Cecal and colonic SCFA concentrations were significantly greater in RS-fed pigs, and cecal gene expression of monocarboxylate transporter 1 (SLC16A1) and glucagon (GCG) was induced by RS. In conclusion, our data show that RS modulates microbiota composition, SCFA concentrations, and host gene expression in pig intestine. Combined, our data provide an enhanced understanding of the interaction between diet, microbiota, and host.

Regulation of bacterial pathogenesis by intestinal short-chain Fatty acids

The human gut microbiota is inextricably linked to health and disease. One important function of the commensal organisms living in the intestine is to provide colonization resistance against invading enteric pathogens. Because of the complex nature of the interaction between the microbiota and its host, multiple mechanisms likely contribute to resistance. In this review, we dissect the biological role of short-chain fatty acids (SCFA), which are fermentation end products of the intestinal microbiota, in host-pathogen interactions. SCFA exert an extensive influence on host physiology through nutritional, regulatory, and immunomodulatory functions and can also affect bacterial fitness as a form of acid stress. Moreover, SCFA act as a signal for virulence gene regulation in common enteric pathogens. Taken together, these studies highlight the importance of the chemical environment where the biology of the host, the microbiota, and the pathogen intersects, which provides a basis for designing effective infection prevention and control.

Butyrate increases IL-23 production by stimulated dendritic cells

The gut microbiota is essential for the maintenance of intestinal immune homeostasis and is responsible for breaking down dietary fiber into short-chain fatty acids (SCFAs). Butyrate, the most abundant bioactive SCFA in the gut, is a histone deacetylase inhibitor (HDACi), a class of drug that has potent immunomodulatory properties. This characteristic of butyrate, along with our previous discovery that conventional dendritic cells (DCs) are required for the development of experimental colitis, led us to speculate that butyrate may modulate DC function to regulate gut mucosal homeostasis. We found that butyrate, in addition to suppressing LPS-induced bone marrow-derived DC maturation and inhibiting DC IL-12 production, significantly induced IL-23 expression. The upregulation of mRNA subunit IL-23p19 at the pretranslational level was consistent with the role of HDACi on the epigenetic modification of gene expression. Furthermore, the mechanism of IL-23p19 upregulation was independent of Stat3 and ZBP89. Coculture of splenocytes with LPS-stimulated DCs pretreated with or without butyrate was performed and showed a significant induction of IL-17 and IL-10. We demonstrated further the effect of butyrate in vivo using dextran sulfate sodium (DSS)-induced colitis and found that the addition of butyrate in the drinking water of mice worsened DSS-colitis. This is in contrast to the daily intraperitoneal butyrate injection of DSS-treated mice, which mildly improved disease severity. Our study highlights a novel effect of butyrate in upregulating IL-23 production of activated DCs and demonstrates a difference in the host response to the oral vs. systemic route of butyrate administration.

Short-chain fatty acid fermentation products of the gut microbiome: implications in autism spectrum disorders

Recent evidence suggests potential, but unproven, links between dietary, metabolic, infective, and gastrointestinal factors and the behavioral exacerbations and remissions of autism spectrum disorders (ASDs). Propionic acid (PPA) and its related short-chain fatty acids (SCFAs) are fermentation products of ASD-associated bacteria (Clostridia, Bacteriodetes, Desulfovibrio). SCFAs represent a group of compounds derived from the host microbiome that are plausibly linked to ASDs and can induce widespread effects on gut, brain, and behavior. Intraventricular administration of PPA and SCFAs in rats induces abnormal motor movements, repetitive interests, electrographic changes, cognitive deficits, perseveration, and impaired social interactions. The brain tissue of PPA-treated rats shows a number of ASD-linked neurochemical changes, including innate neuroinflammation, increased oxidative stress, glutathione depletion, and altered phospholipid/acylcarnitine profiles. These directly or indirectly contribute to acquired mitochondrial dysfunction via impairment in carnitine-dependent pathways, consistent with findings in patients with ASDs. Of note, common antibiotics may impair carnitine-dependent processes by altering gut flora favoring PPA-producing bacteria and by directly inhibiting carnitine transport across the gut. Human populations that are partial metabolizers of PPA are more common than previously thought. PPA has further bioactive effects on neurotransmitter systems, intracellular acidification/calcium release, fatty acid metabolism, gap junction gating, immune function, and alteration of gene expression that warrant further exploration. These findings are consistent with the symptoms and proposed underlying mechanisms of ASDs and support the use of PPA infusions in rats as a valid animal model of the condition. Collectively, this offers further support that gut-derived factors, such as dietary or enteric bacterially produced SCFAs, may be plausible environmental agents that can trigger ASDs or ASD-related behaviors and deserve further exploration in basic science, agriculture, and clinical medicine.

Gut microbial translocation in critically ill children and effects of supplementation with pre- and pro biotics

Bacterial translocation as a direct cause of sepsis is an attractive hypothesis that presupposes that in specific situations bacteria cross the intestinal barrier, enter the systemic circulation, and cause a systemic inflammatory response syndrome. Critically ill children are at increased risk for bacterial translocation, particularly in the early postnatal age. Predisposing factors include intestinal obstruction, obstructive jaundice, intra-abdominal hypertension, intestinal ischemia/reperfusion injury and secondary ileus, and immaturity of the intestinal barrier per se. Despite good evidence from experimental studies to support the theory of bacterial translocation as a cause of sepsis, there is little evidence in human studies to confirm that translocation is directly correlated to bloodstream infections in critically ill children. This paper provides an overview of the gut microflora and its significance, a focus on the mechanisms employed by bacteria to gain access to the systemic circulation, and how critical illness creates a hostile environment in the gut and alters the microflora favoring the growth of pathogens that promote bacterial translocation. It also covers treatment with pre- and pro biotics during critical illness to restore the balance of microbial communities in a beneficial way with positive effects on intestinal permeability and bacterial translocation.

Gut microbial communities modulating brain development and function

Mammalian brain development is initiated in utero and internal and external environmental signals can affect this process all the way until adulthood. Recent observations suggest that one such external cue is the indigenous microbiota which has been shown to affect developmental programming of the brain. This may have consequences for brain maturation and function that impact on cognitive functions later in life. This review discusses these recent findings from a developmental perspective.

Safety and efficacy of Profermin® to induce remission in ulcerative colitis

AIM: To test the efficacy and safety of Profermin^® in inducing remission in patients with active ulcerative colitis (UC).

METHODS: The study included 39 patients with mild to moderate UC defined as a Simple Clinical Colitis Activity Index (SCCAI) > 4 and < 12 (median: 7.5), who were treated open-label with Profermin^® twice daily for 24 wk. Daily SCCAI was reported observer blinded via the Internet.

RESULTS: In an intention to treat (ITT) analysis, the mean reduction in SCCAI score was 56.5%. Of the 39 patients, 24 (62%) reached the primary endpoint, which was proportion of patients with ≥ 50% reduction in SCCAI. Our secondary endpoint, the proportion of patients in remission defined as SCCAI ≤ 2.5, was in ITT analysis reached in 18 of the 39 patients (46%). In a repeated-measure regression analysis, the estimated mean reduction in score was 5.0 points (95% CI: 4.1-5.9, P < 0.001) and the estimated mean time taken to obtain half the reduction in score was 28 d (95% CI: 26-30). There were no serious adverse events (AEs) or withdrawals due to AEs. Profermin^® was generally well tolerated.

CONCLUSION: Profermin^® is safe and may be effective in inducing remission of active UC.

The role of bacterial vaginosis and trichomonas in HIV transmission across the female genital tract

Bacterial vaginosis (BV) and Trichomonas vaginalis (TV) infections are both very common and are associated with increased risk of sexual transmission of HIV. There are several mechanisms by which BV and TV could affect susceptibility including inducing pro-inflammatory cytokines and disrupting mucosal barrier function. This review highlights recent advances in our understanding of how these genital conditions lead to an increased risk of HIV infection in women.

Characterization of the gastrointestinal microbiota in health and inflammatory bowel disease

The enteric bacterial flora play a key role in maintaining health. Inflammatory bowel disease is associated with quantitative and qualitative alterations in the microbiota. Early characterization of the microbiota involved culture-dependent techniques. The advent of metagenomic techniques, however, allows for structural and functional characterization using culture-independent methods. Changes in diversity, together with quantitative alterations in specific bacterial species, have been identified. The functional significance of these changes, and their pathogenic role, remain to be elucidated.

The early settlers: intestinal microbiology in early life

The human intestinal microbiota forms an integral part of normal human physiology, and disturbances of the normal gut microbiology have been implicated in many health and disease issues. Because newborns are essentially sterile, their microbiota must establish and develop from the very first days of life. The first colonizers play an important role in the development of the ecosystem and may impact the long-term composition and activity of the microbiota. These first settlers obviously develop and proliferate dependent on host characteristics and diet, but other factors can also significantly contribute to this vital biological process. Considering the importance of the microbiota for the human immune, metabolic, and neurological systems, it is important to understand the dynamics and driving determinants of this development. This review gives a global overview of our current understanding of the different factors impacting the intestinal microbiology in early life.

Effect of prebiotic carbohydrates on the growth and tolerance of Lactobacillus

Resistance to gastrointestinal conditions is a requirement for bacteria to be considered probiotics. In this work, we tested the resistance of six different Lactobacillus strains and the effect of carbon source to four different gastrointestinal conditions: presence of α-amylase, pancreatin, bile extract and low pH. Novel galactooligosaccharides synthesized from lactulose (GOS-Lu) as well as commercial galactooligosaccharides synthesized from lactose (GOS-La) and lactulose were used as carbon sources and compared with glucose. In general, all strains grew in all carbon sources, although after 24 h of fermentation the population of all Lactobacillus strains was higher for both types of GOS than for glucose and lactulose. No differences were found among GOS-Lu and GOS-La. α-amylase and pancreatin resistance was retained at all times for all strains. However, a dependence on carbon source and Lactobacillus strain was observed for bile extract and low pH resistance. High hydrophobicity was found for all strains with GOS-Lu when compared with other carbon sources. However, concentrations of lactic and acetic acids were higher in glucose and lactulose than GOS-Lu and GOS-La. These results show that the resistance to gastrointestinal conditions and hydrophobicity is directly related with the carbon source and Lactobacillus strains. In this sense, the use of prebiotics as GOS and lactulose could be an excellent alternative to monosaccharides to support growth of probiotic Lactobacillus strains and improve their survival through the gastrointestinal tract.

Short-chain fatty acids induce pro-inflammatory cytokine production alone and in combination with toll-like receptor ligands

PROBLEM

Short-chain fatty acids (SCFAs), produced at relatively high levels by anaerobic bacteria in bacterial vaginosis (BV), are believed to be anti-inflammatory. BV, a common alteration in the genital microbiota associated with increased susceptibility to HIV infection, is characterized by increased levels of both pro-inflammatory cytokines and SCFAs. We investigated how SCFAs alone or together with Toll-like receptor (TLR) ligands affected pro-inflammatory cytokine secretion.

METHOD OF STUDY

Cytokines were measured by ELISA. Flow was used for phenotyping and reactive oxygen species (ROS) measurement.

RESULTS

Short-chain fatty acids, at 20 mM, induced interleukin (IL)-8, IL-6, and IL-1β release, while lower levels (0.02-2 mM) did not induce cytokine secretion. Levels >20 mM were toxic to cells. Interestingly, lower levels of SCFAs significantly enhanced TLR2 ligand- and TLR7 ligand-induced production of IL-8 and TNFα in a time- and dose-dependent manner, but had little effect on lipopolysaccharide-induced cytokine release. SCFAs mediated their effects on pro-inflammatory cytokine production at least in part by inducing the generation of ROS.

CONCLUSION

Our data suggest that SCFAs, especially when combined with specific TLR ligands, contribute to a pro-inflammatory milieu in the lower genital tract and help further our understanding of how BV affects susceptibility to microbial infections.

Nutrition and gut immunity

The human intestine contains huge amounts of nonpathologic bacteria surviving in an environment that is beneficial to both the host and the bacterial populations. When short pauses in oral intake occur with minimal alterations in the mucosa-microbial interface, critical illness, with its attendant acidosis, prolonged gastrointestinal tract starvation, exogenous antibiotics, and breakdown in mucosal defenses, renders the host vulnerable to bacterial challenge and also threatens the survival of the bacteria. This review examines the altered innate and adaptive immunologic host defenses that occur as a result of altered oral or enteral intake and/or injury.