Intestinal Luminal Environment Research Articles

Sialic acid plays a pivotal role in licensing Citrobacter rodentium’s transition from the intestinal lumen to a mucosal adherent niche

Enteric bacterial pathogens pose significant threats to human health; however, the mechanisms by which they infect the mammalian gut in the face of daunting host defenses and an established microbiota remain poorly defined. For the attaching and effacing (A/E) bacterial family member and murine pathogen Citrobacter rodentium, its virulence strategy likely involves metabolic adaptation to the host's intestinal luminal environment, as a necessary precursor to reach and infect the mucosal surface. Suspecting this adaptation involved the intestinal mucus layer, we found that C. rodentium was able to catabolize sialic acid, a monosaccharide derived from mucins, and utilize it as its sole carbon source for growth. Moreover, C. rodentium also sensed and displayed chemotactic activity toward sialic acid. These activities were abolished when the nanT gene, encoding a sialic acid transporter, was deleted (ΔnanT). Correspondingly, the ΔnanT C. rodentium strain was significantly impaired in its ability to colonize the murine intestine. Intriguingly, sialic acid was also found to induce the secretion of two autotransporter proteins, Pic and EspC, which possess mucinolytic and host-adherent properties. As a result, sialic acid enhanced the ability of C. rodentium to degrade intestinal mucus (through Pic), as well as to adhere to intestinal epithelial cells (through EspC). We thus demonstrate that sialic acid, a monosaccharide constituent of the intestinal mucus layer, functions as an important nutrient and a key signal for an A/E bacterial pathogen to escape the colonic lumen and directly infect its host's intestinal mucosa.

Canna starch improves immune functions and the intestinal environment in mice.

The present study was conducted to elucidate the dietary effects of canna starch on the immune functions and intestinal luminal environment in mice. The amylose and resistant starch characteristics were determined for six types of starch, including edible canna. Canna starch was found to be higher in amylose and resistant starch compared with the other starches. BALB/c mice were fed 3.16% (low-canna group) and 6.32% (high-canna group) canna starch for 2 weeks, and then intestinal parameters were measured. Fecal IgA and mucin levels were markedly elevated by canna starch intake. IgA levels in serum and spleen lymphocytes were elevated by canna starch intake in the high-canna group, but not in the low-canna group. When the mice were fed canna starch, the cecum weight increased, and the pH in the cecum decreased. The high-canna group had significantly increased levels of Clostridium subcluster XIVa lactic acid, acetic acid, and n-butyric acid in the cecum compared with the control group. These results suggested that canna starch supplementation changed the intestinal microbiota and enhanced the intestinal immune and barrier functions and cecal organic acids in mice.

SATB2 Defect Promotes Colitis and Colitis-associated Colorectal Cancer by Impairing Cl-/HCO3- Exchange and Homeostasis of Gut Microbiota

SATB2 is a diagnostic biomarker and a favourable prognostic marker for colorectal cancer [CRC], but its role in colitis and colitis-associated colorectal cancer [CAC] is unknown. Colitis was induced in intestinal epithelial-specific Satb2 knockout [Satb2 IEC-KO] and control mice using dextran sulphate sodium [DSS]. RNA-seq analysis was performed on colonic tissues, and 16S rDNA-Seq on faecal bacterial DNA from Satb2 IEC-KO and control mice. Immunohistochemistry and flow cytometry were performed to reveal the proportions of different immune cells. Chromatin immunoprecipitation [ChIP] and luciferase reporter were applied to show the regulatory role of SATB2 on SLC26A3, of which the Cl-/HCO3- exchange activity was measured fluorometrically by the pHi-sensitive dye. Bacteroides were detected by fluorescence in situ hybridisation [FISH] on colonic tissue. Satb2 IEC-KO mice suffered from intestinal epithelial damage spontaneously, and developed more severe colitis and CAC. The expression of SLC26A3 correlated well with SATB2 revealed by RNA-seq and The Cancer Genome Atlas [TCGA] data, and was governed by SATB2 confirmed by ChIP and luciferase reporter experiments. Decreased intestinal flora diversity was seen in Satb2 IEC-KO mice. Bacteroides were more abundant and could colonise into the inner layer of colonic mucosa in Satb2 IEC-KO mice. Faecal microbiome transplantation from Satb2 IEC-KO mice aggravated colitis and M1 macrophages infiltration. SATB2 plays a vital role in maintaining intestinal homeostasis, and its deficiency promotes the development of colitis and CAC by influencing the intestinal luminal environment and gut flora.

Transcriptional programmes underlying cellular identity and microbial responsiveness in the intestinal epithelium.

The intestinal epithelium serves the unique and critical function of harvesting dietary nutrients, while simultaneously acting as a cellular barrier separating tissues from the luminal environment and gut microbial ecosystem. Two salient features of the intestinal epithelium enable it to perform these complex functions. First, cells within the intestinal epithelium achieve a wide range of specialized identities, including different cell types and distinct anterior-posterior patterning along the intestine. Second, intestinal epithelial cells are sensitive and responsive to the dynamic milieu of dietary nutrients, xenobiotics and microorganisms encountered in the intestinal luminal environment. These diverse identities and responsiveness of intestinal epithelial cells are achieved in part through the differential transcription of genes encoded in their shared genome. Here, we review insights from mice and other vertebrate models into the transcriptional regulatory mechanisms underlying intestinal epithelial identity and microbial responsiveness, including DNA methylation, chromatin accessibility, histone modifications and transcription factors. These studies are revealing that most transcription factors involved in intestinal epithelial identity also respond to changes in the microbiota, raising both opportunities and challenges to discern the underlying integrative transcriptional regulatory networks.

Lactose-Induced Chronic Diarrhea Results From Abnormal Luminal Microbial Fermentation and Disorder of Ion Transport in the Colon.

Diarrhea is one of the major abdominal symptoms in lactose-intolerant subjects. The changes in the large intestinal luminal environment and disorder of the epithelial ion transport in lactose-induced diarrhea remain unclear. The present study aimed to investigate the effect of an incremental high-lactose diet (IHLD, 30%/40%/50%) on luminal microbiota, microbiota-derived metabolite concentrations and colonic ion transport. Gut microbiota were analyzed by 16S rRNA amplicon sequencing and the concentration of SCFAs by gas chromatography, galactose, lactose and lactic acid through assay kit; Ussing chamber was performed to detect basal and stimulated ion transport; The expression and location of SCFA transporters, the Na-H exchanger 3(NHE3), cystic fibrosis transporter regulater (CFTR) and NKCC1 in the colon mucosa were analyzed by western and immunostaining. The concentrations of lactose, galactose and lactic acid of the cecal content were markedly increased (P < 0.01) and SCFA concentration was significantly decreased (P < 0.01). This was associated with depletion of the Lachnospiraceae NK4A136 group and Ruminococcaceae UCG-005 and increased relative abundance of Lactobacillus, escherichia-shigella and megamonas in the cecal microbiota. The expression of monocarboxylate transporter 1 was decreased in the colonic mucosa of the IHLD group. Low NHE3 expression and phosphorylation levels, and decreases in delta basal short circuit current after apical Na+ removal in the colonic mucosa of the IHLD group contributed to Na+ accumulation in the lumen and decrease stimulated Cl– secretion with low CFTR and NKCC1 expression would compensate for water and electrolyte loss during the diarrhea process. These results indicated that the persistence of the diarrhea state was maintained by abnormal colonic microbiota fermentation leading to high concentrations of lactose, galactose and lactic acid and low SCFAs in the lumen, and decreased Na+ absorption with the low NHE3 expression and phosphorylation levels.

Systematic Review of Fecal and Mucosa-Associated Microbiota Compositional Shifts in Colorectal Cancer

Introduction: Gut microbiota is a major component of the intestinal luminal environment and plays important roles in colorectal cancer. Object: systematically review all the existing literature on the association of mucosa-associated and fecal microbiota with incidence, location, and stage of colorectal adenoma and carcinoma. Methods: The scientific search was done up to July 2018. The search was limited to the English language with predefined and proper keywords. Among 616 articles some of them were eliminated due to some reasons. The inclusion and exclusion criteria were defined. In the next step two reviewers (M.M and Z.K) independently scanned the titles of all retrieved articles, removed duplicates, and identified potentially relevant abstracts for further assessment. The Newcastle-Ottawa Scale (NOS) for assessing the Quality was used for quality control. Result: Finally, 54 articles were entered into the study. Fusobacteria 39 (72%), Firmicutes 22(40%), Bacteroidetes 20 (37%), Proteobacteria 15(27%), Actinobacteria 10(18%) was the most prevalent phylum which was found in colorectal cancer patients. Among these taxa some of them were increased in colorectal cancer patients compared to the control; on the other hand, some taxon was declined in colorectal cancer patients. Besides this, in some taxon there were controversies among articles. Conclusion: Early detection of CRC is essential because patients whose cancer are detected at an early stage have more chance of survival. Until now there are several studies have demonstrated the potential rule of gut microbiota to be used for detection of CRC, but there is not any predefining protocol for screening. Although we found lots of articles which were published in this area, for defining a precise microbiota profile we need large multicenter case-control studies, where can show the effect of most important confounding factors like nutrition, ethnicity, physical activity, smoking consumption, and genetic background.

A REVIEW ON APPLICATIONS OF PROBIOTICS IN HUMAN HEALTH AND DISEASE

The emergence of resistance and tolerance to the existing drugs has created a decreased efficacy of these drugs in use. Along with the advancement in other fields of medicine, the problem of resistance has been tried to be overcome by increasing the drug delivery to the target site by the use of polymers or through nanotechnology, synthesis of new drugs, either by the use of proteomics or synthesis from lactic acid bacteria, or marine microorganisms. Recent research has revealed a potential therapeutic role for the manipulation of the microbiota in the maintenance of human health and treatment of various mucosal disorders. Probiotic microorganisms can shape the immune system both at the local and systemic level which will allow future probiotics as treatments for many diseases. The benefits include either a shortened duration of infections or decreased susceptibility to pathogens.&#x0D; Probiotic bacteria have multiple and various influences onthe host. Different organisms can influence the intestinal luminal environment, epithelial and mucosal barrier function, and the mucosal immune system. The numerous cell types affected by probiotics involve epithelial cells, dendritic cells, monocytes/macrophages, B cells, T cells. Probiotics do not always colonize the intestinal tract to exert their effects. Some probiotics like Bifidobacterium longum become part of the human intestinal microflora, whereas others like Lactobacillus casei indirectly exert their effects in a transient manner as they pass through by remodeling or influencing the existing microbial community. &#x0D; Probiotics seem to have promising role in shortening duration of infections or decreasing susceptibility to the pathogens. Incorporation of probiotics in nutrition as a means of derivation of health benefits. The best documented effects include bowel disorders such as lactose intolerance, antibiotic-associated diarrhea and infectious diarrhea, emerging evidence accumulates concerning their potential role in various other conditions. In the same time as relevant consumer awareness grows, such products are becoming increasingly popular and tend to represent one of the largest functional food markets.&#x0D; Key words: probiotics, Antibiotic associated diarrhea, microorganisms, Antibiotic resistance, Lactic acid bacteria.

Green tea polyphenol (epigallocatechin-3-gallate) improves gut dysbiosis and serum bile acids dysregulation in high-fat diet-fed mice.

Gut microbiota have profound effects on bile acid metabolism by promoting deconjugation, dehydrogenation, and dehydroxylation of primary bile acids in the distal small intestine and colon. High-fat diet-induced dysbiosis of gut microbiota and bile acid dysregulation may be involved in the pathology of steatosis in patients with non-alcoholic fatty liver disease. Epigallocatechin-3-gallate (EGCG), the most abundant polyphenolic catechin in green tea, has been widely investigated for its inhibitory or preventive effects against fatty liver. The aim of the present study was to investigate the effects of EGCG on the abundance of gut microbiota and the composition of serum bile acids in high-fat diet-fed mice and determine the specific bacterial genera that can improve the serum bile acid dysregulation associated with EGCG anti-hepatic steatosis action. Male C57BL/6N mice were fed with the control diet, high-fat diet, or high-fat diet + EGCG at a concentration of 0.32% for 8 weeks. EGCG significantly inhibited the increases in weight, the area of fatty lesions, and the triglyceride content in the liver induced by the high-fat diet. Principal coordinate analysis revealed significant differences in microbial structure among the groups. At the genus level, EGCG induced changes in the microbiota composition in high-fat diet-fed mice, showing a significantly higher abundance of Adlercreutzia, Akkermansia, Allobaculum and a significantly lower abundance of Desulfovibrionaceae. EGCG significantly reversed the decreased population of serum primary cholic acid and β-muricholic acid as well as the increased population of taurine-conjugated cholic acid, β-muricholic acid and deoxycholic acid in high-fat diet-fed mice. Finally, the correlation analysis between bile acid profiles and gut microbiota demonstrated the contribution of Akkermansia and Desulfovibrionaceae in the improvement of bile acid dysregulation in high-fat diet-fed mice by treatment with EGCG. In conclusion, the present study suggests that EGCG could alter bile acid metabolism, especially taurine deconjugation, and suppress fatty liver disease by improving the intestinal luminal environment.

A Microfluidic‐Based Model for Spatially Constrained Culture of Intestinal Microbiota

AbstractPerturbation of the microbiome is implicated in the pathogenesis of many human ailments, including inflammatory bowel diseases such as Crohn's disease (CD). Recapitulating the microbiome associated with health and disease necessitates controlling the composition of multiple bacterial species. This is difficult to achieve in vitro due to the overgrowth of bacterial species over time. Here, a microfluidic‐based model incorporating bacteria‐embedded hydrogel microfibers for the coculture of human enteric bacteria is introduced. Employing bacterial species and strains associated with CD, it is shown that the hydrogel‐based bacteria‐embedded microfiber model is physically and mechanically robust, and tunable. Metabolite analysis of the medium in both mono‐ and coculture revealed the interfiber exchange of soluble mediators and their impact on the growth of different bacterial species. This novel approach should enhance the ability to decipher contact‐independent cross‐talk within the polymicrobial intestinal luminal environment, and its impact on the intestinal epithelium.

Dietary supplementation with chitooligosaccharides alters gut microbiota and modifies intestinal luminal metabolites in weaned Huanjiang mini-piglets

In this study, we tested the effects of dietary supplementation with chitooligosaccharides (COS) on the gut microbiota and its metabolites using the Huanjiang mini-piglet model. Ten weaned mini-piglets were randomly assigned to 2 groups, receiving no COS or dietary supplementation with 0.5g/kg of COS in a basal diet. After a 14-day trial period, the luminal contents of ileum and colon were collected to analyze short-chain fatty acids (SCFAs) and ammonia, as well as gut microbiota populations. Our results show that dietary supplementation with COS modifies the composition of ileal and colonic microbiota, and increased the amounts of some presumably beneficial intestinal bacteria and concentrations of SCFAs in the intestinal luminal content, while suppressed the growth of potential bacterial pathogens and the amount of several protein-derived catabolites, when compared with the control group. These findings suggest that the COS presents prebiotic activities and modifies the intestinal luminal environment in a presumably beneficial way in weaning Huanjiang mini-piglets.

Burdock Fermented byAspergillus awamoriElevates CecalBifidobacterium, and Reduces Fecal Deoxycholic Acid and Adipose Tissue Weight in Rats Fed a High-Fat Diet

This study investigated the effects of dietary supplementation with burdock powder and Aspergillus awamori-fermented burdock powder at 5% on the intestinal luminal environment and body fat in rats fed a high-fat (HF) diet. Food intake and growth were unaffected by dietary manipulation. Consumption of the burdock and fermented burdock diets significantly elevated fecal IgA and mucins (indices of intestinal immune and barrier functions) and reduced fecal lithocholic acid (a risk factor for colon cancer) (p<0.05). The fermented burdock diet markedly elevated cecal Bifidobacterium and organic acids, including lactate, acetate, propionate, and butyrate, and reduced fecal deoxycholic acid (a risk factor for colon cancer) and perirenal adipose tissue weight (p<0.05), but the burdock diet did not. These results suggest that consumption of fermented burdock improves the intestinal luminal environment and suppresses obesity in rats fed a HF diet.

RETRACTED: Visualization of lipid metabolism in the zebrafish intestine reveals a relationship between NPC1L1-mediated cholesterol uptake and dietary fatty acid

The small intestine is the primary site of dietary lipid absorption in mammals. The balance of nutrients, microorganisms, bile, and mucus that determine intestinal luminal environment cannot be recapitulated ex vivo, thus complicating studies of lipid absorption. We show that fluorescently labeled lipids can be used to visualize and study lipid absorption in live zebrafish larvae. We demonstrate that the addition of a BODIPY-fatty acid to a diet high in atherogenic lipids enables imaging of enterocyte lipid droplet dynamics in real time. We find that a lipid-rich meal promotes BODIPY-cholesterol absorption into an endosomal compartment distinguishable from lipid droplets. We also show that dietary fatty acids promote intestinal cholesterol absorption by rapid re-localization of NPC1L1 to the intestinal brush border. These data illustrate the power of the zebrafish system to address longstanding questions in vertebrate digestive physiology.

Current and emerging concepts on the role of peripheral signals in the control of food intake and development of obesity

The gastrointestinal peptides are classically known as short-term signals, primarily inducing satiation and/or satiety. However, accumulating evidence has broadened this view, and their role in long-term energy homeostasis and the development of obesity has been increasingly recognised. In the present review, the recent research involving the role of satiation signals, especially ghrelin, cholecystokinin, glucagon-like peptide 1 and peptide YY, in the development and treatment of obesity will be discussed. Their activity, interactions and release profile vary constantly with changes in dietary and energy influences, intestinal luminal environment, body weight and metabolic status. Manipulation of gut peptides and nutrient sensors in the oral and postoral compartments through diet and/or changes in gut microflora or using multi-hormone 'cocktail' therapy are among promising approaches aimed at reducing excess food consumption and body-weight gain.

Consumption of a Resistant Protein, Sericin, Elevates Fecal Immunoglobulin A, Mucins, and Cecal Organic Acids in Rats Fed a High-Fat Diet

AbstractWe previously reported that consumption of a resistant protein, sericin, reduces colon tumorigenesis, constipation, and serum TG in rodents. The present study was conducted to elucidate the effects of dietary sericin on the intestinal luminal environment in rats fed a high-fat (HF) diet. Rats were fed 300 or 50 g/kg of beef tallow with or without 40 g/kg sericin, a protein purified from cocoons of Bombix mori, for 3 wk. Intestinal luminal variables, including IgA (index of intestinal immune function), mucins (index of barrier function), organic acids, microflora, and secondary bile acids, were measured. Dietary sericin markedly elevated fecal IgA in the HF diet group (3-fold, P < 0.05) but not in the low-fat (LF) diet group. Fecal mucin levels were elevated by sericin intake in the HF diet group (P < 0.05). Cecal organic acids, including acetate, propionate, n-butyrate, and succinate, were significantly lower in the HF diet group compared with the LF diet group. Dietary sericin significantly elevated cecal acetate and n-butyrate in the HF diet group but not in the LF diet group. Compared with the LF diet, the HF diet significantly increased serum TG in the untreated group but not in those fed sericin. The HF diet increased lower density lipoprotein (VLDL + IDL + LDL) cholesterol and it was reduced by sericin intake (P < 0.05). There was an inverse correlation between serum TG and cecal acetate (Spearman rank correlation coefficient = -0.63; P < 0.001). The profile of microflora in cecal digesta and fecal secondary bile acids (a risk factor for colon cancer) did not differ between the HF diet and HF diet with sericin groups. These results suggest a novel and favorable effect of sericin on colon health by modulating intestinal immune and barrier functions and fermentation in rats fed a HF diet.

Changes in the Paneth cell population of human small intestine assessed by image analysis of the secretory granule area.

Estimates of the Paneth cell population in human jejunum and ileum were made using measurement of the granule area in micron2 by image analysis in a defined number of crypts. This figure was preferable to granule area per mm as there was a significant difference in crypts per mm between biopsies and surgical samples. In the jejunum no significant difference was found between normal children and adults with and without peptic ulcer. In adults with subtotal or partial villous atrophy the decrease in area was not statistically significant and there was no decrease in area in children with partial villous atrophy and coeliac disease. There was a marked increase in granule area in the jejunum of patients who had had a previous partial gastrectomy which was statistically significant. In the ileum patients with carcinoma of the caecum had higher values than patients with non-inflammatory non-malignant conditions but this was not statistically significant and two patients with Crohn's disease had an increased granule area. Paneth cell populations are affected by alterations in the intestinal luminal environment due to previous surgery or neoplastic or inflammatory disease.