Intestinal Mucin Secretion Research Articles

Effects of soluble glucomannan and insoluble cellulose treatment on mucin secretion and mucin glycosylation-related gene expression in the colons of mice.

Fiber added to the diet can promote intestinal mucin secretion, relieve intestinal inflammation, and enhance the intestinal barrier function. Glycosylation is the key to mucin function. However, there are few studies on the correlation between dietary fiber and mucin glycosylation, especially two kinds of dietary fiber with different solubility. The aim of this study was to investigate the effects of soluble glucomannan (GM) and insoluble cellulose (CL) treatment on mucin secretion and mucin glycosylation-related gene expression in the colons of mice. The GM group significantly increased the goblet cell number, crypt depth, and the expression of mucin 2 (Muc2) and mucin 3a (Muc3a) genes in the colon. At the same time, the analysis of the colon transcriptome showed that the GM group changed the expression of genes related to the mucin glycosylation process, and the GM group up-regulated the expression of Gcnt3, Gcnt4, St3gal1, Galnt13, and B3gnt6 genes involved in the O-glycosylation process. Similarly, Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis showed that differentially glycosylated genes in the GM group were mainly related to the biosynthesis of mucin type O-glycans, while the genes in the CL group were related to the biosynthesis of various types of N-glycans. The correlation analysis between colonic microbes and differentially glycosylated genes also showed that the abundance of Alistipes in the GM group was significantly associated with the expression of Gcnt3, a key glycosylation gene. Glucomannan treatment was more favorable for colonic Muc2 and Muc3a secretion and mucin O-glycosylation gene expression. © 2023 Society of Chemical Industry.

Effects of rumen cannulation combined with different pre-weaning feeding intensities on the intestinal, splenic and thymic immune system in heifer calves several month after surgery.

Fistulation is a helpful procedure in animal nutritional research and also common practise in human medicine. However, there are indications that alterations in the upper gastrointestinal tract contribute to intestinal immune modulations. The present study aimed to investigate effects of a rumen cannulation in week 3 of life on the intestinal and tissue specific immune system of 34-week old heifers. Nutrition influences the development of the neonatal intestinal immune system to a high extent. Therefore, rumen cannulation was investigated in combination with different pre-weaning milk feeding intensities (20% (20MR) vs. 10% milk replacer feeding (10MR). Heifers of 20MR without rumen cannula (NRC) showed higher cluster of differentiation (CD)8+ T cell subsets in mesenteric lymph nodes (MSL) compared to heifers with rumen cannula (RC) and 10MRNRC heifers. CD4+ T cell subsets in jejunal intraepithelial lymphocytes (IELs) were higher in 10MRNRC heifers compared to 10MRRC heifers. CD4+ T cell subsets in ileal IELs were lower and CD21+ B cell subsets were higher in NRC heifers compared to RC heifers. CD8+ T cell subsets in spleen tended to be lower in 20MRNRC heifers compared to all other groups. Splenic CD21+ B cell subsets were higher in 20MRNRC heifers compared to RC heifers. Splenic toll like receptor (TLR) 6 expression was increased and IL4 expression tended to be increased in RC heifers than NRC heifers. Splenic TLR2, 3 and 10 gene expression was higher in 20MR compared to 10MR heifers. Jejunal prostaglandin endoperoxide synthase 2 expression was higher in RC heifers than NRC heifers, and MUC2 expression tended to increase in 20MR heifers compared to 10MR heifers. In conclusion, rumen cannulation modulated T and B cell subsets in the down streaming gastrointestinal tract and spleen. Pre-weaning feeding intensity seemed to affect intestinal mucin secretion and T and B cell subsets in MSL, spleen and thymus until several month later. Interestingly, in MSL, spleen and thymus the 10MR feeding regime evoked similar modulations of T and B cell subsets like rumen cannulation.

Debaryomyces hansenii CBS 8339 promotes larval development in Seriola rivoliana

The present study aimed to know the effect of the administration of Debaryomyces hansenii yeast on growth, development and skeletal deformities, through the quantification of molecular and morphophysiological indicators in longfin yellowtail larvae. Larvae from the yeast group were fed with the rotifers and Artemia metanaupli half enriched with D. hansenii (50% of live prey) and half enriched with Origreen® (50% of live prey) and were compared to control (100% Origreen®) from 5 to 30 days post-hatching (DPH). Each treatment had two methodological replicates. Studies on bone mineralization, skeletal deformities, intestinal histological analysis, digestive enzyme activity, differential gene expression (RT-qPCR) and transcriptome analysis (RNA-Seq) were performed in whole larvae. Results showed that larvae fed D. hansenii encapsulated within enriched live preys had higher survival and growth, higher intestinal mucin secretion, as well as higher activity of alkaline phosphatase, pepsin and α-amylase. The degree of bone mineralization in the cranial and caudal fin complex was higher in larvae fed D. hansenii and a lower incidence of deformities at the vertebral column was also observed. In general, the gene expression throughout the development fluctuated between the control group and the yeast treatment; however, at 30 DPH, a higher expression of the bone morphogenetic protein type 2 (bmp2), collagen type 1α1 (col1α1) and proliferating cell nuclear antigen (pcna) genes was detected in larvae fed with yeast. The transcriptomic analyses using RNA-Seq revealed that the main genes related to bone mineralization degree and digestive tract maturation, were overrepresented in the D. hansenii treatment, 1,25-dihydroxyvitamin D (3) 24-hydroxylase (cyp24), cytochrome P450 family 27 subfamily A (cyp27a), protein 5 related to the low-density lipoprotein receptor (lrp5), myocyte-specific enhancing factor 2C (mef2), enterokinase (entk), pepsin and alkaline phosphatase. Based on the results, S. rivoliana larvae supplemented with the yeast D. hansenii presented higher growth and survival, a higher degree of maturation of the digestive tract, a higher degree of bone mineralization and a reduction in skeletal deformities, for which the continuous use of yeast is recommended as a food supplement to larvae from 5 days post-hatching onwards.

Evaluating the effect of yeast cell wall supplementation on ideal threonine to lysine ratios in broilers as measured by performance, intestinal mucin secretion, morphology, and goblet cell number

SUMMARY The objective of this study was to investigate whether or not a prebiotic yeast cell wall (YCW), previously shown to improve performance in challenge studies, affects threonine requirements of broilers. Gain, F/G, intestinal morphology, mucin secretion, and goblet cell (GC) number per villi were measured. A total of 240 1-d-old Ross 308 broiler chickens were distributed in 2 Petersime battery brooder units (48 pens; 5 birds per pen). Birds were fed for a 21-d trial with different threonine to lysine ratios (0.65, 0.70, and 0.75) with and without YCW at 250 ppm. A basal diet with 22% protein and 2,980 Kcal/kg ME was used for the dietary treatments. The calculated lysine concentration was 1.35%, while threonine was 0.88%, 0.95%, and 1.02%, respectively. Birds and feed were weighed by pen, and the weights recorded at days 0, 7, 14, and 21 of the experiment for general performance data. At day 21, samples from excreta and small intestine (jejunum and ileum) were collected. YCW did not show any significant effect with respect to the variables evaluated in this non-challenge study. There was no significant effect for threonine to lysine ratios for all performance variables that had been measured throughout the study. With respect to intestinal morphology, there were significant increases in main effects for the threonine to lysine ratio 0.75 compared with 0.65 in mucin secretion, GC, and jejunum VW, while the jejunum VH significantly increased compared with threonine to lysine ratio 0.70.

Ingestion of paddy rice increases intestinal mucin secretion and goblet cell number and prevents dextran sodium sulfate-induced intestinal barrier defect in chickens.

Paddy rice is a potential feed grain for chickens, whose strong gizzards can crush the hull. Here, we investigated whether paddy rice rich in hull-derived water-insoluble dietary fiber stimulates intestinal mucin secretion and production, as well as the possible involvement of paddy rice in intestinal barrier function. Layer male chicks at 7 d of age were divided into four groups according to the diet: corn, polished rice, brown rice, or paddy rice (650g/kg diet), which they ate for 14 consecutive days. At 21 d of age, the birds were refed their experimental diets, and small intestinal mucin fractions were collected to determine intestinal mucin content. Small intestinal mucin secretion was induced most strongly in the paddy rice group (Experiment 1). The rank order of diet-induced mucin secretion was paddy rice > corn = brown rice > polished rice. Ileal MUC2 gene expression and ileal number of goblet cells were highest in the paddy rice group (Experiment 1). A study of bromodeoxy-U uptake into ileal epithelial cells indicated the increase in goblet cells in the paddy rice group was related to accelerate epithelial cell migration (Experiment 2). A single supplementation of isolated rice hulls without kernels increased MUC2 gene expression and goblet cell numbers (Experiment 3), suggesting the importance of the hull's bulk-forming capacity on mucin production. Finally, chicks fed corn or paddy rice were orally administered dextran sodium sulfate (DSS) to disrupt intestinal barrier function. In the DSS-treated birds, the intestinal permeability of fluorescein isothiocyanate dextran in the everted gut sacs was much lower in the paddy rice group than in the corn group (Experiment 4), showing that paddy rice protects against mucosal disruption. In conclusion, ingestion of paddy rice increases intestinal mucin secretion and production through enhanced MUC2 gene expression and epithelial turnover and prevents DSS-induced intestinal barrier defects in chickens.

Pectin and Its Hydrolysates Stimulate Intestinal Mucin Secretion

ObjectivesSoluble dietary fibers (SDF) increase small intestinal mucin secretion by increasing the number of goblet cells in proportion to the viscosity of the SDF ingested. Our recent study showed in rats that low methoxyl pectin (LPC) enhanced mucin secretion irrespective of goblet cell number in the small intestine. Mucin secretory effects of LPC were also confirmed in vitro using HT‐29MTX cells, suggesting that pectin directly stimulates mucin secretion from the individual goblet cells. The present study aimed to characterize the mucin secretory effect of pectin among SDF and to clarify active components of pectin related to mucin secretion.Materials & MethodsHT‐29MTX cells were cultured with 6.25–100 mg /L of the respective SDF including pectin for 24 h. The culture media were gathered and subjected to MUC5AC determination. RNA was extracted from the cells and subjected to gene expression analysis for MUC5AC. Pectin hydrolysates were obtained from citrus pectin using pectinase (polygalacturonase) and fractionated by diethylaminoethanol cellulose column. Mucin secretory effects of the hydrolysates were also examined.Results & FindingsOnly pectin stimulated mucin secretion from HT‐29MTX cells. Mucin secretory effects of pectin were observed irrespective of molecular size, their origins and degree of methoxylation. Pectin hydrolysates also stimulated mucin secretion accompanied by the increase in MUC5AC expression, but oligo‐galacturonic acids did not. The minimal effective concentrations of pectin hydrolysates were 100‐fold lower than those of pectin. Sugar composition analysis showed that pectin hydrolysates contained higher concentrations of rhamnose and neutral sugars compared with the pectin. From these results, it is plausible to assume that hairy region (rhamnogalacturonan carrying side chains) rather than smooth region (homogalacturonan) in the pectin molecule is responsible for mucin secretory effects.ConclusionAmong the various SDF tested, only pectin and pectin hydrolysates have exerted significant increases in mucin release from the cells. Clearly, they act as mucin secretagogue.

Dietary threonine response of Pekin ducks from hatch to 14 d of age based on performance, serology, and intestinal mucin secretion

Two experiments were conducted to determine the dietary threonine (Thr) requirement of Pekin ducks from hatch to 14 d of age. In experiment 1, practical corn-soybean meal diets were formulated to contain 0.78, 0.84, 0.90, 0.96, and 1.02% Thr (0.74, 0.83, 0.88, 0.92, and 1.00% Thr on an analyzed basis). In experiment 2, corn-soybean meal diets supplemented with 11 crystalline amino acids were formulated to contain 0.60, 0.70, 0.80, 0.90, 1.00, and 1.10% Thr (0.60, 0.75, 0.89, 0.95, 1.01, and 1.09% Thr on an analyzed basis). In both experiments, diets were fed to 8 replicate cages with 6 male ducks per cage. Body weight and feed intake from each cage were recorded weekly. At 14 d of age, breast meat, ileal digesta, and serum were collected to determine breast meat yield, mucin secretion, and serology parameters. In both studies, the estimated Thr requirement (expressed as % dietary Thr basis) for 14 d BW and BW gain (BWG) by quadratic broken-line (QBL) regression were similar, which were 0.87 and 0.86%, respectively. Additional measures in both experiments resulted in Thr requirements via QBL regression in rank order of crude mucin secretion < breast meat yield < serum immune activity. Summing up the estimates from both studies, the Thr requirement ranged from a low of 0.81% to maximize feed intake (FI) to a high of 1.00% to maximize serum Rb L100 by QBL regression. Correspondingly, the Thr requirement varied between a low of 0.90% to maximize crude mucin secretion on a dry matter intake (DMI) basis and a high of 0.98% to maximize feed-to-gain when using quadratic regression.

Escherichia coli lipopolysaccharide affects intestinal mucin secretion in weaned pigs

&nbsp; Background: to the best of our knowledge, the effects of lipopolysaccharide (LPS) from Escherichia coli on goblet cells and intestinal mucin secretion of weaned pigs has not been reported, and it is unknown whether these effects could trigger enteritis. Objective: to determine the effect of E. coli LPS on intestinal mucin secretion in weaning piglets. Methods: fifty-two piglets weaned at 21 days of age were fed a basal diet supplemented with four LPS levels (0.0, 0.3, 0.5, and 1.0 μg/mg) during 10 days. Piglets were slaughtered on days 1, 5, 7, and 10 post-weaning and samples of small and large intestine were taken for histochemical staining to determine goblet cell population and type of mucins produced (acidic, sulphated, non-sulphated, or neutral). Results: acidic mucin was reduced on day 5 post-weaning independently of the dietary LPS level supplied to piglets. Recovery of acidic mucins was observed during days 7 and 10 post-weaning. Neutral mucins increased on day 5 and decreased on days 7 and 10 post-weaning. High LPS levels decreased goblet cells population and secretion of all types of mucins. This effect was remarkably high for diet two (D2: 0.5 mg LPS/mg food). Conclusions: early weaning (21 d) and LPS addition to the diet affect mucin secretion and intestinal epithelium integrity by modifying goblet cell populations and their balance between acidic and neutral mucin secretion. These findings explain some abnormalities related with post-weaning diarrhea syndrome and help to explain its pathophysiology.

Escherichia coli lipopolysaccharide affects intestinal mucin secretion in weaned pigs

Background: to the best of our knowledge, the effects of lipopolysaccharide (LPS) from Escherichia coli on goblet cells and intestinal mucin secretion of weaned pigs has not been reported, and it is unknown whether these effects could trigger enteritis. Objective: to determine the effect of E. coli LPS on intestinal mucin secretion in weaning piglets. Methods: fifty-two piglets weaned at 21 days of age were fed a basal diet supplemented with four LPS levels (0.0, 0.3, 0.5, and 1.0 μg/mg) during 10 days. Piglets were slaughtered on days 1, 5, 7, and 10 post-weaning and samples of small and large intestine were taken for histochemical staining to determine goblet cell population and type of mucins produced (acidic, sulphated, non-sulphated, or neutral). Results: acidic mucin was reduced on day 5 post-weaning independently of the dietary LPS level supplied to piglets. Recovery of acidic mucins was observed during days 7 and 10 post-weaning. Neutral mucins increased on day 5 and decreased on days 7 and 10 post-weaning. High LPS levels decreased goblet cells population and secretion of all types of mucins. This effect was remarkably high for diet two (D2: 0.5 mg LPS/mg food). Conclusions: early weaning (21 d) and LPS addition to the diet affect mucin secretion and intestinal epithelium integrity by modifying goblet cell populations and their balance between acidic and neutral mucin secretion. These findings explain some abnormalities related with post-weaning diarrhea syndrome and help to explain its pathophysiology.

Supplemental glycine and threonine effects on performance, intestinal mucosa development, and nutrient utilization of growing broiler chickens

A study was conducted to evaluate Gly requirements in low-CP diets with different levels of digestible (dig) Thr, and their effects on performance, intestinal mucosal development, and nutrient utilization of broiler chickens from 21 to 35 d age. A total of 240 twenty-one-day-old Cobb-Vantress male broiler chickens were distributed in a completely randomized 4 × 2 factorial arrangement for a total of 8 treatments with 5 replicates of 6 birds each. The treatments consisted of 4 levels of Gly+Ser (1.47, 1.57, 1.67, or 1.77%) and 2 levels of dig Thr (0.70 or 0.77%, corresponding to 100 or 110% of Thr requirements, respectively). Common diets were fed to broilers until 20 d of age. At d 35, an interaction (P ≤ 0.01) was observed between the Gly+Ser and dig Thr levels for G:F. Glycine supplementation resulted in a linear increase (P < 0.05) in BW gain, G:F, intestinal mucin secretion, apparent digestibility of fat, and AME values of the experimental diets. Threonine levels greater than the levels required (0.77%) improved (P < 0.05) G:F and increased (P < 0.05) intestinal mucin secretion. However, intestinal morphometry and the number of goblet cells in the duodenum, jejunum, and ileum were not affected by the treatments. The dietary Gly+Ser level necessary to optimize G:F in low-CP diets containing 0.77% Thr for broiler chickens during growth was estimated to be 1.54%; however, this requirement may be greater than 1.77% in diets with 0.70% Thr. Supplemental Gly may be essential to support maximum performance for broiler chickens from 21 to 35 d of age when they are fed diets based exclusively on vegetable ingredients and with low protein levels. Glycine can directly or indirectly influence the proper function of the intestinal mucosa and improve dietary energy utilization.

Low-Methoxyl Pectin Stimulates Small Intestinal Mucin Secretion Irrespective of Goblet Cell Proliferation and Is Characterized by Jejunum Muc2 Upregulation in Rats

Generally, soluble fibers increase small intestinal mucin secretion by increasing the number of goblet cells in a viscosity-dependent manner. The present study aimed to examine the mechanism by which low-methoxyl pectin (LPC) affects mucin secretion in the small intestine. First, diets containing 50 g/kg of low-viscosity fiber (LPC, gum arabic, guar gum, low-molecular konjac mannan, arabinogalactan, sodium alginate) or high-molecular konjac mannan (KMH) were fed to Wistar rats for 10 d. Luminal mucin was greater in the LPC and KMH groups than in the fiber-free control group, but only the KMH group had more goblet cells in the ileum compared with the other groups. Next, Sprague-Dawley rats were fed LPC, KMH, or high-methoxyl pectin (HPC) diets (50 g/kg) for 10 d. The KMH and LPC groups, but not the HPC group, had greater luminal mucin than the control group, whereas jejunum Muc2 expression was higher only in the LPC group. Sprague-Dawley rats fed the LPC diet for 1 or 3 d had greater luminal mucin and jejunum Muc2 expression than those fed the control diet. In vitro studies using HT-29MTX cells showed that, of the various fibers studied, only LPC and HPC affected mucin secretion. Finally, Wistar rats were fed the LPC diet with or without neomycin in drinking water for 10 d; neomycin treatment did not compromise the effect of LPC on mucin secretion. We conclude that LPC does not affect the number of goblet cells but can interact directly with the epithelium and stimulate small intestinal mucin secretion.

Effect of β-lactoglobulin hydrolysate and β-lactorphin on intestinal mucin secretion and gene expression in human goblet cells

A hydrolysate obtained from a whey protein concentrate rich in β-lactoglobulin has been shown to stimulate mucin secretion and mucin 5AC gene expression in human intestinal goblet cells HT29-MTX. Mass spectrometry-based peptidomic analysis allowed the identification of the peptides contained in the hydrolysate. None of them had the required structure to bind opioid receptors, except for the sequence YLLF, corresponding to β-lactorphin. The exposure of the cells to synthetic β-lactorphin evoked a mucin secretory effect although no change in the mucin gene expression was observed. The amidated homolog of this peptide, which has been reported as a more potent opioid, induced mucin gene expression after incubation for 4h. This supports the hypothesis that induction of the mucin secretory response can be mediated by μ-opioid receptors in HT29-MTX cells, although other mechanisms responsible for the hydrolysate activity cannot be excluded. Protein hydrolysates with the ability to induce mucin secretion could be promising for improving gastrointestinal protection.

Specific roles of threonine in intestinal mucosal integrity and barrier function

Threonine is the second or third limiting amino acid in swine or poultry diets. This nutrient plays a critical role in the maintenance of intestinal mucosal integrity and barrier function, which can be indicated by intestinal morphology, mucus production (number of goblet cells), transepithelial permeability, brush border enzyme activity, and growth performance. Dietary threonine restriction may decrease the production of digestive enzymes and increase mucosal paracellular permeability. A large proportion of dietary threonine is utilized for intestinal-mucosal protein synthesis, especially for mucin synthesis, and there is no oxidation of threonine by enterocytes. Because mucin proteins cannot be digested and reused, intestinal mucin secretion is a net loss of threonine from the body. Luminal threonine availability can influence synthesis of intestinal mucins and other proteins. Under pathological conditions, such as ileitis and sepsis, threonine requirement may be increased to maintain intestinal morphology and physiology. Collectively, knowledge about the role of threonine in mucin synthesis is critical for improving gut health under physiological and pathological conditions in animals and humans.

Intestinal mucin dynamics: Response of broiler chicks and White Pekin ducklings to dietary threonine

Mucin dynamics may be particularly sensitive to a Thr deficiency due to the high concentration and structural importance of Thr in the mucin protein backbone. Intestinal mucin secretion, expression of mucin gene (MUC2), and histological characteristics were investigated in male broilers and White Pekin ducklings offered diets containing 3.3, 5.8, or 8.2 g of Thr/kg in 4 studies. Seventy-two birds of each species were fed a standard broiler starter diet from 1 to 14 d of age followed by assignment to 3 dietary treatments in a randomized complete block design for a 7-d feeding trial in experiment 1 (broilers) and experiment 2 (ducklings). The dietary treatments consisted of an isonitrogenous corn-soybean meal-based diet with the addition of crystalline amino acids and graded levels of Thr. Dietary treatments contained 3.3, 5.8, or 8.2 g of Thr/kg. Dietary formulation and experimental design for experiments 3 (broilers) and 4 (ducklings) were similar to experiments 1 and 2 except that birds were fed 3.3 or 8.2 g of Thr/kg for durations of 7 or 14 d. For chicks, increased dietary Thr resulted in higher levels of intestinal crude mucin excretion in experiment 1 (P = 0.04) but not in experiment 3, whereas intestinal sialic acid excretion increased in experiment 3 (P = 0.02) but not in experiment 1. Furthermore, there was no effect of Thr on intestinal goblet cell density or MUC2 mRNA abundance for broilers. For ducklings, there was an increase in intestinal crude mucin excretion in both experiments (P < 0.05) as dietary Thr increased, although there was no effect of Thr on intestinal sialic acid excretion. There was a tendency for an increase in intestinal goblet cell density (cells/μm of villus length; P = 0.09) as dietary Thr increased in experiment 2. For experiment 4, intestinal MUC2 mRNA abundance increased (P = 0.03) as dietary Thr increased for the 14-d feeding trial but not for the 7-d feeding trial. The data establish a link between dietary Thr and intestinal crude mucin dynamics in chicks for experiment 1 and ducklings for both experiments.

Soluble Fiber Viscosity Affects Both Goblet Cell Number and Small Intestine Mucin Secretion in Rats

We examined the role of soluble fiber viscosity in small intestinal mucin secretion. Viscosities were defined as the area under the viscosity curve (VAUC). Rats were fed a control diet or diets containing konjac mannan (KM) [low, medium, or high molecular weight (LKM, MKM, HKM), respectively] at 50 g/kg diet for 10 d. Luminal mucin content and goblet cell number increased in proportion to the molecular weight of KM. Such effects with the HKM diet were nullified by the concurrent ingestion of 2 g cellulase/kg diet. Diet containing LKM, MKM, HKM, guar gums (high or low molecular weight; HGG, LGG), psyllium (PS), or pectin (PC) at 50 g/kg was fed to rats. Fibers with higher VAUC (MKM, HKM, HGG, and PS) increased goblet cell numbers, but not those with lower VAUC (LKM, LGG, and PC). Luminal mucins were greater in rats fed HKM, PC, and PS diets. Goblet cell numbers and VAUC were correlated (r = 0.98; P < 0.01). In rats fed the HKM diet, ileal Muc2 gene expression was not affected, but that of Muc3 was lower than in those fed the control diet, indicating that the increase in luminal mucins after ingestion of HKM diet occurred independently of enhanced Muc gene expression. An incorporation study of 5′-bromo-deoxyuridine (BrdU) showed the position of the uppermost-BrdU labeled cell along the villi was higher in rats fed the HKM diet than in those fed the control diet. The results suggest that soluble fibers, except PC, upregulate baseline secretion of luminal mucins by increasing goblet cell numbers in proportion to fiber VAUC.

Gastrointestinal Microflora and Mucins May Play a Critical Role in the Development of 5-Fluorouracil-Induced Gastrointestinal Mucositis

5-Fluorouracil (5-FU) is a commonly used chemotherapy agent in clinical oncology practice. Two of its major side effects are mucositis and diarrhoea. The structure of mucins offers mucosal protection, and allows maintenance of intestinal flora by providing attachment sites and preventing bacterial overgrowth and/or penetration. The aim of this study was to investigate changes in mucin secretion and microflora following treatment with 5-FU. Female DA rats were given a single 150 mg/ kg i.p. dose of 5-FU. Rats were killed at various time points after treatment. Control rats received no treatment. Jejunum, colon and faecal samples were collected. Standard microbiological culture techniques were used to identify bacteria, and real-time PCR was used to quantify bacteria in faecal samples. Goblet cells and cavitated goblet cells (having undergone mucus exocytosis) were also counted. Statistical analysis was carried out using Kruskal-Wallis test, a non-parametric method of testing equality of group medians. Following treatment with 5-FU, we showed decreases in Clostridium spp., Lactobacillus spp. and Streptococcus spp., and an increase in Escherichia spp. in the jejunum. In the colon, 5-FU caused decreases in Enterococcus spp., Lactobacillus spp. and Streptococcus spp. Real-time PCR of faecal samples showed decreasing trends in Lactobacillus spp. and Bacteroides spp., and an increasing trend in E. coli. Significant increases (P < 0.05) were seen in Clostridium spp. and Staphylococcus spp. at 24 h. Goblet cell numbers decreased significantly in the jejunum from 24-72 h, with a significant increase in the percentage of cavitated goblet cells. In conclusion, 5-FU treatment causes significant changes in intestinal flora and mucin secretion in rats. These changes could result in systemic effects and, in particular, may contribute to the development of chemotherapy-induced mucositis.

PAR-2 activation increases human intestinal mucin secretion through EGFR transactivation

PAR-2 (protease-activated receptors-2) are G protein-coupled receptors whose action on mucin secretion by intestinal epithelial cells is still unknown. The aim of this study was to examine the effect of PAR-2 activation on mucin secretion in the human colonic goblet cell line HT29-Cl.16E and the intracellular pathways involved. We found that PAR-2 mRNA was constitutively expressed by HT29-Cl.16E cells as well as by isolated human normal colonocytes. The PAR-2-activating peptide SLIGKV-NH2 elicited rapid mucin secretion in HT29-Cl.16E, which was partially inhibited by calcium chelator BAPTA. Inhibitors of MAPK activation (PD98059) and EGFR tyrosine kinase activity (AG1478) abrogated PAR-2-induced ERK1/2 and EGFR tyrosine phosphorylation, respectively, and subsequent mucin secretion. Finally, PAR-2-induced EGFR transactivation was involved upstream of ERK1/2 activation. Our results show that the activation of PAR-2 expressed by human intestinal epithelial cells enhances mucin secretion, a component of the intestinal innate defence, via a pathway involving EGFR transactivation.

Impact of Nutrients on the Functioning of Intestinal Goblet Cells: Health and Therapeutic Perspectives

Secreted by goblet cells, intestinal mucins play a crucial role in cytoprotective functions against mechanical insults, colonisation by pathogenic bacteria and their toxins, luminal proteases and potential carcinogens. The present paper provides a review of the effect of nutrients on intestinal mucin secretion. In the small intestine, the secretion of mucus is modulated by hydrolysates of milk proteins and by β-casomorphins (a family of peptides derived from β-casein). Other factors present in milk, like EGF, also stimulate mucus discharge. In the new-born baby, such an effect of proteins of milk or bioactive peptides on the secretion of mucus could play a role in the control of the mechanism of defence and similar protective effects could be expected in the adults. In the colon, some dietary fibres increase the discharge of mucus. The metabolic product of dietary fibres, the short chain fatty acids (SCFA), also induce mucus secretion in the colon. Additionally, butyrate modulates mucin expression, suggesting that SCFA are influential in increasing the synthesis and secretion of colonic mucin. In conclusion, bioactive peptides, fibres and SCFA appear to be liable nutrients to induce mucus secretion. New researches are required to determine whether they can be used to achieve preventive or therapeutic effects in human. Keywords: Mucin, mucus, gut, milk bioactive factors, dietary fibre, short chain fatty acid

Small Intestinal Mucins Are Secreted in Proportion to the Settling Volume in Water of Dietary Indigestible Components in Rats

The aim of this study was to clarify the effect of dietary indigestible components on small intestinal mucin secretion. We prepared polystyrene foam (PSF) with different expansion ratios (PSF-30, -60 and -90) in which powders had different settling volumes in water (SV). Rats were fed a purified diet containing 0, 10, 30, or 90 g of PSF-60/kg for 10 d. After 8 h of food deprivation, rats were refed 3 g of their respective diets within 90 min. Small intestinal mucin fractions were prepared, and periodic acid/Schiff-reactive substances and O-linked oligosaccharide chains were determined as mucin markers. Feeding of PSF-60 increased the small intestinal mucin secretion dose dependently (control vs. 30 or 60 g of PSF-60/kg, P < 0.05). When rats were fed either purified diet or diets containing PSF-30, 60, or 90 at 10 g/kg for 7 d, small intestinal mucins were greatly affected by the SV of the respective PSF tested. Rats fed the diet containing PSF-90 with the highest SV had the highest amount of mucins (vs. control, P < 0.05). In some natural dietary fibers, the small intestinal mucins and SV were correlated (r = 0.967, P = 0.002). Finally, rats were fed a purified diet or that diet containing 50 g of PSF-60/kg for 7 d. Then, each dietary group was further divided into 2 groups. After 8 h of food deprivation, rats were refed 3 g of purified or PSF diet. Greater mucins in the small intestine were manifest only in rats previously fed the PSF diet whether they were refed purified or PSF diet (control vs. PSF, P < 0.05). These results suggest that the small intestinal mucins are secreted in proportion to the SV of dietary indigestible components, and chronic ingestion of indigestible components is required for the appearance of enhanced mucin secretion.

A high-density putative monomeric mucin is the major [ 35S]labelled macromolecular product of human colorectal mucins in organ culture

We have studied the biosynthesis of mucins in organ cultures of human colon using isopycnic density-gradient centrifugation following pulse labelling with [ 35S]sulphate and [ 3H]-D-glucosamine. A high-density [ 35S]sulphate labelled component, of larger size than MUC2 monomers, appeared in the tissue and also in the medium. It was not degraded by reduction, trypsin digestion, digestion with chondroitin ABC lyase or heparan sulphate III lyase, but was cleaved into smaller fragments following alkaline borohydride treatment and appears to be a monomeric, mucin-like molecule containing a protease-resistant domain with a larger hydrodynamic volume than MUC2 monomers. Although this macromolecule incorporated much more radiolabel than MUC2, it was not detected using chemical analysis and thus appears to be a component with a high metabolic turnover present in a very small amount. Most of the [ 3H]-D-glucosamine label was associated with low-density material that was well separated from MUC2, which was poorly labelled. Most of MUC2 was associated with the tissue as an ‘insoluble’ complex. The amount of MUC2 remained constant and its associated radiolabel increased only slightly with time. Analysis of the MUC2 subunits from the reduced ‘insoluble’ complex showed the typical reduction-insensitive oligomers and confirmed that the radiolabel was associated with this mucin. The large size of the [ 35S]-labelled putative monomeric mucin makes it difficult to separate it from reduced insoluble complex MUC2. As a result, many studies of intestinal mucin synthesis and secretion in the past have most likely been performed on ‘mixtures’ of this mucin and MUC2 and are thus not possible to interpret as the metabolic behaviour of oligomeric mucins.