Consumption of indigestible saccharides and administration of Bifidobacterium pseudolongum reduce mucosal serotonin in murine colonic mucosa.

SCFA increase serotonin (5-hydroxytryptamine, 5-HT) synthesis and content in the colon in vitro and ex vivo, but little is known in vivo. We tested whether dietary indigestible saccharides, utilised as a substrate to produce SCFA by gut microbiota, would increase colonic 5-HT content in mice. Male C57BL/6J mice were fed a purified diet and water supplemented with 4 % (w/v) 1-kestose (KES) for 2 weeks. Colonic 5-HT content and enterochromaffin (EC) cell numbers were lower in mice supplemented with KES than those without supplementation, while monoamine oxidase A activity and mRNA levels of tryptophan hydroxylase 1 (Tph1), chromogranin A (Chga), Slc6a4 and monoamine oxidase A (Maoa) genes in the colonic mucosa, serum 5-HT concentration and total 5-HT content in the colonic contents did not differ between groups. Caecal acetate concentration and Bifidobacterium pseudolongum population were higher in KES-supplemented mice. Similar trends were observed in mice supplemented with other indigestible saccharides, that is, fructo-oligosaccharides, inulin and raffinose. Intragastric administration of live B. pseudolongum (108 colony-forming units/d) for 2 weeks reduced colonic 5-HT content and EC cell numbers. These results suggest that changes in synthesis, reuptake, catabolism and overflow of 5-HT in the colonic mucosa are not involved in the reduction of colonic 5-HT content by dietary indigestible saccharides in mice. We propose that gut microbes including B. pseudolongum could contribute to the reduction of 5-HT content in the colonic mucosa via diminishing EC cells.

Skate-skin mucin, rich in sulfated sugars and threonine, promotes proliferation of Akkermansia muciniphila in feeding tests in rats and in vitro fermentation using human feces.

Dietary factors, affect Akkermansia muciniphila (AM) abundance in the colon, have attracted attention, driven by the inverse correlation between AM abundance and metabolic disorders. We prepared skate-skin mucin (SM), porcine stomach mucin (PM), and rat gastrointestinal mucin (RM). SM contained more sulfated sugars and threonine than PM or RM. Rats were fed a control diet or diets including SM, PM, or RM (15 g/kg), or SM (12 g/kg) from 5 different threonine contents for 14 d. Cecal total bacteria and AM were less and more numerous, respectively, in SM-fed rats than the others, but SM did not affect microbial species richness. Low-threonine SM did not induce AM proliferation. The in vitro fermentation with human feces showed that the rate of AM increase was greater with SM than PM. Collectively, heavy SM sulfation facilitates a priority supply of SM-derived amino sugars and threonine that promotes AM proliferation in rats and human feces.

Mucin-Derived O-Glycans Act as Endogenous Fiber and Sustain Mucosal Immune Homeostasis via Short-Chain Fatty Acid Production in Rat Cecum.

BACKGROUND: Intestinal mucins escape digestion and enter the large bowel where they are degraded by the microbiota. To what extent and how mucins impact large-bowel physiology remain unclear. OBJECTIVE: This study examined the large-bowel fermentation characteristics of mucins and mucin-derived O-glycan sugars and whether they affect gut immunity. METHODS: Mucin secretion from the terminal ileum was determined from feces of ileorectostomized male Wistar rats (age 6 wk) fed an AIN76-based control diet (CD) for 15 d (experiment 1). Normal male Wistar rats (age 6 wk; 4 wk for experiment 4) were fed CD ± porcine stomach mucin (PM) at 6 or 12 g/kg diet, equivalent to 1.5 and 3 times the daily mucin secretion, for 14 d (experiment 2); CD ± N-acetylglucosamine (GlcNAc), fucose, or N-acetylneuraminic acid at 10 g/kg diet for 14 d (experiment 3); or CD ± PM (15 g/kg diet) or GlcNAc (10 g/kg diet) for 29 d (experiment 4). SCFAs, microbial composition, and cecal O-glycan content were assessed. IgA+ plasma cells and regulatory T cells and inflammatory cytokine expression in the cecum were evaluated (experiment 4). RESULTS: Daily mucin secretion corresponded to 43.2 µmol of O-glycans. Cecal O-glycan contents were comparable between CD- and PM-fed rats. PM-fed rats harbored more mucin-degrading bacteria. Cecal concentrations of acetate (+37%) and n-butyrate (+73%) were higher in 12-g/kg PM diet-fed rats versus CD (P < 0.05). Among O-glycan sugars, only GlcNAc produced higher n-butyrate concentrations (+68%) versus CD (P < 0.05), with increased numbers of butyrate-producing bacteria. GlcNAc increased the abundance of IgA+ plasma cells (+29%) and regulatory T cells (+33%) versus CD, whereas PM increased IgA+ plasma cells (+25%) (all P < 0.05). GlcNAc and PM decreased expression of Tnfa (-30%, -40%) and Ifng (-30%, -70%) versus CD (all P < 0.05). CONCLUSIONS: Mucin-derived O-glycans act as endogenous fiber and maintain mucosal immune homeostasis via large-bowel SCFA production in rats.

Oral intake of slowly digestible α-glucan, isomaltodextrin, stimulates glucagon-like peptide-1 secretion in the small intestine of rats.

To investigate whether oral intake of highly branched α-glucan isomaltodextrin (IMD) could stimulate ileal glucagon-like peptide-1 (GLP-1) secretion, we examined (1) the digestibility of IMD, (2) the digestion and absorption rates of IMD, in rat small intestine and (3) portal GLP-1 concentration in rats given IMD. In Expt 1, ileorectostomised rats were given a 3 % IMD diet for 10 d. Separately, a 16-h in vitro digestion of IMD, using porcine pancreatic α-amylase and brush-border membrane vesicles from rat small intestine, was conducted. In Expt 2, upon 24-h fasting, rats were given any of glucose, IMD and high-amylose maize starch (HAMS) (1 g/kg of body weight). In Expt 3, caecectomised rats were given 0·2 % neomycin sulphate and a 5 % IMD diet for 10 d. The in vivo and in vitro digestibility of IMD was 70-80 %. The fraction of IMD digested in vitro for the first 120 min was 67 % of that in maize starch. The AUC for 0-120 min of plasma glucose concentration was significantly lower in HAMS group and tended to be lower in IMD group than in the glucose group. Finally, we also observed that, when compared with control rats, glucose of IMD significantly stimulated and improved the concentration of portal active GLP-1 in antibiotic-administered, caecectomised rats. We concluded that IMD was slowly digested and the resulting glucose stimulated GLP-1 secretion in rat small intestine. Oral delivery of slowly released IMD glucose to the small intestine probably exerts important, yet unknown, physiological effects on the recipient.

Hydrogen produced in rat colon improves in vivo reduction-oxidation balance due to induced regeneration of α-tocopherol.

We investigated whether non-digestible saccharide fermentation-derived hydrogen molecules (H2) in rat colon could improve the in vivo reduction-oxidation (redox) balance via regeneration of α-tocopherol, by assessing their effect on hydroxyl radicals, the α-tocopherol concentration and the redox balance. In Expt 1, a Fenton reaction with phenylalanine (0 or 1·37 mmol/l of H2) was conducted. In Expt 2, rats received intraperitoneally maize oil containing phorone (400 mg/kg) 7 d after drinking ad libitum water containing 0 or 4 % fructo-oligosaccharides (FOS) (groups CP and FP, respectively). In Expt 3, rats unable to synthesise ascorbic acid drank ad libitum for 14 d water with 240 mg ascorbic acid/l (group AC), 20 mg of ascorbic acid/l (group DC) or 20 mg of ascorbic acid/l and 4 % FOS (group DCF). In the Fenton reaction, H2 reduced tyrosine produced from phenylalanine to 72 % when platinum was added and to 92 % when platinum was excluded. In Expt 2, liver glutathione was depleted by administration of phorone to rats. However, compared with CP, no change in the m-tyrosine concentration in the liver of FP was detected. In Expt 3, net H2 excretion was higher in DCF than in the other rats after 3 d of the experiment. Furthermore, the concentrations of H2 and α-tocopherol and the redox glutathione ratio in perirenal adipose tissue of rats were significantly higher in DCF than in DC. To summarise, in rat colon, fermentation-derived H2 further shifted the redox balance towards a more reducing status in perirenal adipose tissue through increased regeneration of α-tocopherol.

Commensal microbe-derived butyrate induces the differentiation of colonic regulatory T cells.

Gut commensal microbes shape the mucosal immune system by regulating the differentiation and expansion of several types of T cell. Clostridia, a dominant class of commensal microbe, can induce colonic regulatory T (Treg) cells, which have a central role in the suppression of inflammatory and allergic responses. However, the molecular mechanisms by which commensal microbes induce colonic Treg cells have been unclear. Here we show that a large bowel microbial fermentation product, butyrate, induces the differentiation of colonic Treg cells in mice. A comparative NMR-based metabolome analysis suggests that the luminal concentrations of short-chain fatty acids positively correlates with the number of Treg cells in the colon. Among short-chain fatty acids, butyrate induced the differentiation of Treg cells in vitro and in vivo, and ameliorated the development of colitis induced by adoptive transfer of CD4(+) CD45RB(hi) T cells in Rag1(-/-) mice. Treatment of naive T cells under the Treg-cell-polarizing conditions with butyrate enhanced histone H3 acetylation in the promoter and conserved non-coding sequence regions of the Foxp3 locus, suggesting a possible mechanism for how microbial-derived butyrate regulates the differentiation of Treg cells. Our findings provide new insight into the mechanisms by which host-microbe interactions establish immunological homeostasis in the gut.

Digestion-Resistant Dextrin Derivatives Are Moderately Digested in the Small Intestine and Contribute More to Energy Production Than Predicted from Large-Bowel Fermentation in Rats.

Background: Digestion-resistant dextrin derivatives (DRDDs), including resistant maltodextrin (RM), polydextrose, and resistant glucan (RG), have been developed as low-energy foods. However, data on the resistance of DRDDs to small-intestinal digestion are scarce.Objective: We sought to determine the site and extent of DRDD breakdown in the rat intestine and to predict its energy contributions.Methods: In vitro small-intestinal resistance of DRDDs was evaluated by the AOAC method for dietary fiber measurement and by artificial digestion with the use of pancreatic α-amylase and brush-boarder membrane vesicles. In vivo small-intestinal resistance of DRDDs was determined from the feces of male ileorectostomized Sprague-Dawley rats fed a control diet or a diet containing one of the DRDDs at 50 g/kg for 9 d (period 1) and then for 10 d (period 2), during which they received 1 g neomycin/L in their drinking water. Separately, male Sprague-Dawley rats were fed the same diets for 4 wk, and the whole-gut recoveries of DRDDs were determined from feces at days 8-10.Results: Small-intestinal resistances determined in vitro by artificial digestion (RM: 70%; polydextrose: 67%; RG: 69%) were lower than those measured by the AOAC method (RM: 92%; polydextrose: 80%; RG: 82%). In the ileorectostomized rats, fecal dry-matter excretions were consistently greater in the DRDDs than in the control. The small-intestinal resistances of the DRDDs were 68%, 58%, and 62% in period 1 and 66%, 61%, and 67% during period 2 for RM, polydextrose, and RG, respectively. The resistances did not differ among the DRDDs at either time. In the normal rats, food intakes and body weight gains did not differ among the groups. The whole-gut recovery of RM (13%) was lower than that of polydextrose (33%) and RG (29%), which did not differ.Conclusions: DRDDs were more digestible in the rat small intestine than the AOAC method. The energy contribution from small-intestine digestibility, not just large-bowel fermentability, must be considered in determining the energy contribution of DRDDs. Whether humans respond similarly needs to be tested.

Fructo-oligosaccharide-Induced Transient Increases in Cecal Immunoglobulin A Concentrations in Rats Are Associated with Mucosal Inflammation in Response to Increased Gut Permeability.

Background: The mechanism underlying transient increases in immunoglobulin (Ig) A concentrations in the cecal contents of rats fed fructo-oligosaccharide (FOS) is unclear.Objective: This study was designed to test whether increased IgA concentrations represent one aspect of the inflammatory response to increased permeability induced by FOS in the cecum.Methods: Seven-week-old male Wistar rats were fed a fiber-free semipurified diet (FFP) with or without supplemental FOS (60 g/kg diet) for 9 or 58 d [experiment (expt.) 1], 7 d (expt. 2), or 7 or 56 d (expt. 3). In addition to measuring IgA concentrations in cecal content, we assessed gut permeability, inflammatory responses (expt. 1), the number of IgA plasma cells in the cecal lamina propria, polymeric Ig receptor (pIgR) expression in the cecal mucosa (expt. 2), and the condition of the cecal mucus layer (expt. 3).Results: The cecal IgA concentration in the FOS-fed rats was 15-fold higher than that of the rats fed FFP for 9 d (P < 0.05). Gut permeability estimated by urinary chromium-EDTA excretion, bacterial translocation to mesenteric lymph nodes, myeloperoxidase activity, and expression of inflammatory cytokine genes in the cecal mucosa was greater in the FOS-fed rats than in the rats fed FFP for 9 d. These effects were not observed in the rats fed FOS for 58 d (expt. 1). Accompanying the higher cecal IgA concentration, pIgR protein and the number of IgA plasma cells in the cecal mucosa were higher in the FOS-fed rats than in the rats fed FFP for 7 d (expt. 2). Destruction of the mucus layer on the epithelial surface, as evidenced by Alcian blue staining in the cecal sections, was evident in the rats fed FOS for 7 d, but the mucus layer appeared normal in the rats fed FOS for 56 d (expt. 3).Conclusions: These findings suggest that transient increases in cecal IgA concentrations induced by FOS in rats are associated with mucosal inflammation in response to increased gut permeability; these are presumably evoked by disruption of the cecal mucus barrier. The observed responses could contribute to the maturation of the gut immune system.

Evaluation of allergenic potential for rice seed protein components utilizing a rice proteome database and an allergen database in combination with IgE-binding of recombinant proteins.

Among 131 rice endosperm proteins previously identified by MS-based proteomics, most of the proteins showed low or almost no sequence similarity to known allergens in databases, whereas nine proteins did it significantly. The sequence of two proteins showed high overall identity with Hsp70-like hazel tree pollen allergen (Cor a 10) and barley α-amylase (Hor v 16), respectively, whereas the others showed low identity (28-58%) with lemon germin-like protein (Cit l 1), corn zein (Zea m 50 K), wheat chitinase-like xylanase inhibitor (Tri a XI), and kinase-like pollen allergen of Russian thistle (Sal k 1). Immuno-dot blot analysis showed that recombinant proteins for these rice seed homologs were positive in the IgE-binding, but not necessarily similarity dependent, from some allergic patients. These results suggest that utilization of proteome and sequence databases in combination with IgE-binding analysis was effective to screen and evaluate allergenic potential of rice seed protein components.

High wholegrain barley ß-glucan lowers food intake but does not alter small intestinal macronutrient digestibility in ileorectostomised rats.

Using barley cultivars differing widely in ß-glucan content, we aimed to determine their effects on small intestinal macronutrient digestion in 24 ileorectostomised rats. The rats were fed 1 of 4 experimental diets, each containing a different barley variety, for 11 d. The diets had a content of 0, 2.1, 2.6 and 4.3 g of ß-glucan/100 g. Feed intake and faecal excretion of fat, protein, starch, and non-starch polysaccharides were determined in the final 5 d of the study and apparent macronutrient digestibility calculated. Higher dietary levels of ß-glucan (2.6% and 4.3%) lowered feed intake (by 15 and 19%, respectively) but final body weight was only lowered by the 4.3% ß-glucan diet relative to rats fed the 0% ß-glucan diet (all ps < 0.05). Protein, lipid and starch digestibility was unrelated to the dietary ß-glucan content. Higher dietary levels of barley ß-glucan lower feed intake of ileorectostomised rats, which is independent of intestinal fermentation and unrelated to macronutrient digestibility.

Elemental diet induces the proliferation of sialomucin goblet cells in the rat duodenum and jejunum.

We histologically examined the effects of elemental diet (ED) on the goblet cell profile in the rat small intestine. The sulfomucin goblet cells were predominant throughout the small intestine in the control group, while sialomucin goblet cells were manifest in the duodenum and jejunum in the ED group. Next, we investigated the possible relevance of luminal osmolality to the goblet cell profile. Gastric osmolality in the ED group was within the physiological range. Meanwhile, ingestion of high glucose diet elevated gastric osmolality and increased the number of sialomucin goblet cells in the duodenum and jejunum. Further, it turned out that the lower sulfur contents in ED was not related to the unique goblet cell profile by ED ingestion. It is inductively suggested that the influx of high concentrations of low molecular nutrients into the small intestine could be associated with the goblet cell alteration, but the alteration was not necessarily due to the changes in the gastric osmolality by ED ingestion.

A short-term ingestion of fructo-oligosaccharides increases immunoglobulin A and mucin concentrations in the rat cecum, but the effects are attenuated with the prolonged ingestion.

We examined the effects of fructo-oligosaccharides (FOS) on IgA and mucin secretion in the rat cecum after different ingestion periods. Rats were fed a control diet or a diet containing FOS for 1, 2, 4, and 8 wk. FOS ingestion greatly increased IgA and mucin concentrations at 1 and 2 wk, but the effects were disappeared or attenuated at 4 and 8 wk. After 1 wk, FOS induced higher lactobacilli and lactate concentrations and lower cecal pH in the cecum, but the alterations were moderated with the prolonged ingestion accompanying with increasing short-chain fatty acid concentrations. At 1 and 2 wk, FOS increased IgA plasma cells and polymeric immunoglobulin receptor expression in the cecal mucosa and strongly depressed fecal mucinase activities related to the lower cecal pH. These findings may explain the FOS-induced early elevation of IgA and mucin. Clearly, FOS effects on IgA and mucin secretion considerably differ depending on the ingestion period.

Dietary Supplementation of Vitamin B12 to Rats Fed High-Amylose Cornstarch Normalizes Propionate Fermentation in the Colon.

Since propionate exerts several physiological effects, maintenance of its normal colonic fermentation is essential. To investigate whether vitamin B12 (VB12) is essential for normal propionate fermentation by colonic bacteria, via the succinate pathway, we examined if high-amylose cornstarch (HACS) feeding activated such a pathway, if high HACS feeding impaired propionate fermentation, and if oral VB12 supplementation normalized propionate fermentation. Male rats were given control, 20% HACS or 3% fucose diets (Expt. 1); a VB12-free control diet or one supplemented with 5-30% HACS (Expt. 2); and the 20% HACS diet supplemented with 0.025-25 mg/kg of VB12 (Expt. 3), for 14 d. HACS feeding significantly increased cecal succinate concentration, activating the succinate pathway (Expt. 1). Cecal cobalamin concentration in 20% and 30% HACS groups was about 75% of that in the control group (Expt. 2). Cecal succinate and propionate concentrations significantly increased and decreased in 30% HACS groups, respectively, compared with the control group. Although HACS group supplemented with 0.025 mg/kg of VB12 had a low concentration of cecal propionate, adding high amounts of VB12 to HACS diets provided sufficient amounts of VB12 to rat ceca and increased cecal propionate concentration (Expt. 3). Compared with the non-HACS group, the relative abundance of Akkermansia muciniphila, but not Bacteroides/Phocaeicola, was lower in the HACS counterpart and showed improvement with increased VB12 doses. To summarize, feeding high HACS decreased and increased cecal VB12 and succinate concentrations, respectively. Furthermore, colonic delivery of sufficient amounts of VB12 to rats likely reduced accumulation of succinate and normalized propionate fermentation.

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.

Non-effect of an antibiotic treatment on dietary fiber-induced goblet cell proliferation in the ileum of rats.

We examined the effect or not of an antibiotic treatment on dietary fiber-induced goblet cell proliferation in the rat ileum. The number of goblet cells in the ileum increased when rats consumed dietary fiber. However, this effect was maintained with a concurrent treatment of antibiotics, suggesting that the fiber effect on goblet cell response would remain irrespective of a bacterial component such as endotoxin.

Measurement of barley ß-glucan concentration in the plasma by sandwich ELISA using rat dectin-1.

We used recombinant rat dectin-1 proteins to newly establish sandwich ELISA for determining barley ß-glucan (BßG). The ELISA method had a working range of 15-4,000 µg/L. Plasma BßG was detectable up to 24 h after an intravenous administration of BßG (1 mg/kg of body weight) to rats. This method may be an effective tool for investigating the immune modulatory effects of BßG.

Discharge of solubilized and Dectin-1-reactive ß-glucan from macrophage cells phagocytizing insoluble ß-glucan particles: involvement of reactive oxygen species (ROS)-driven degradation.

Phagocytes engulf pathogenic microbes, kill them and degrade their cellular macromolecules by hydrolytic enzymes in phagolysosomes. However, such enzymes are unable to degrade some microbial polysaccharides, and fate of such indigestible polysaccharides in phagocytes remains uncertain. Using the extracellular domain of Dectin-1 as ß-glucan-specific probes, we succeeded in detection of soluble and Dectin-1-reactive ß-glucan discharged from mouse RAW 264.7 and human THP-1 macrophage cell lines as well as mouse peritoneal macrophages, which had phagocytized insoluble ß-glucan particles. The RAW 264.7 cell culture-supernatant containing the discharged ß-glucan stimulated naïve RAW 264.7 cells, resulting in the induction of cytokine expression. Such discharge of Dectin-1-reactive ß-glucan from macrophage cells was inhibited by either NADPH oxidase inhibitors (apocynin and diphenylene iodonium) or radical scavengers (N-acetyl cysteine and MCI-186). Moreover, reactive oxygen species (ROS) produced by a Cu(2+)/ascorbic acid system solubilized insoluble ß-glucan particles in vitro, and a part of the solubilized ß-glucan was Dectin-1 reactive and biologically active in macrophage activation. The soluble and biologically active ß-glucan was degraded further during prolonged exposure to ROS. These results suggest that degraded but Dectin-1-reactive ß-glucan is discharged from macrophage cells phagocytizing insoluble ß-glucan particles and stimulates not only themselves again but also the other naïve phagocytes, leading to the effective elimination of infecting microbes and the ultimate breakdown and inactivation of metabolically resistant ß-glucan.

Small intestinal goblet cell proliferation induced by ingestion of soluble and insoluble dietary fiber is characterized by an increase in sialylated mucins in rats.

The study aimed to examine the effects of insoluble and soluble fibers on mucin sialylation and sulfation in the small intestine. First, diets containing soluble [konjac mannan (KM), psyllium, or guar gum; 50 g/kg) or insoluble (polystyrene foam, wheat bran, or cornhusk; 80 g/kg) fiber were fed to rats for 13 d. The fiber-fed groups had more goblet cells in the ileum than the fiber-free control group. High-iron diamine/alcian blue staining showed more sialylated mucin-producing cells in the fiber-fed groups than in the control, whereas sulfated mucin-producing cells were fewer (insoluble fibers) or unchanged (soluble fibers). Second, feeding KM (50 g/kg) and beet fiber (BF) (80 g/kg) diets for 7 d yielded a higher ileum Siat4C expression than the control, but Gal3ST2 and Gal3ST4 expression was comparable. Luminal mucin content correlated with sialic acid (r = 0.96; P < 0.001) or sulfate (r = 0.62; P < 0.01), but the slope of the sialic acid-derived equation was greater than that of the sulfate-derived equation, indicating a preferred increase in sialylated mucins. Third, rats were fed the control diet for 10 d while receiving antibiotic treatment. Analysis of the luminal mucin showed that sialylated mucins were more vulnerable to bacterial degradation than sulfated mucins. Finally, a study of bromo-deoxyuridine incorporation in rats fed a BF diet indicated that goblet cell proliferation accompanied by increased sialylated mucin appeared to be related to accelerated ileal epithelial cell migration. We conclude that intestinal goblet cell responses to insoluble and soluble fibers are characterized by increases in sialylated mucin production.

Oral Intake of Slowly Digestible α-Glucan Such as Resistant Maltodextrin Leads to Increased Secretion of Glucagon-Like Peptide-2 in Rats and Helps Thicken Their Ileal Mucosae.

To investigate whether the oral intake of slowly digestible α-glucan (SDG) could have a trophic (i.e., thickening) effect on their ileal mucosae, for 10 d, rats were given control (non-SDG), 10% isomaltodextrin (IMD) or 10% resistant maltodextrin (RMD) diets. In addition, experimental rat groups were further divided into two groups each and their diets either had or had not 1% sodium carboxymethylcellulose (CMC) added as a thickening agent. In the jejuna and the ilea, compared with control rats, the villus length and the mucosal thickness, but not the crypt depth, were significantly greater in the RMD-fed rats, with the trophic effect being weaker in the IMD-fed rats than in the RMD-fed rats. The colonic crypt depth was significantly greater in SDG groups than in the control group. The concentration of plasma glucagon-like peptide (GLP)-2 in the portal veins of the RMD group but not the IMD group was significantly higher than in the control group, with no effect of CMC supplementation on its concentration. The concentrations of cecal short-chain fatty acids did not significantly increase with SDG supplementation except for propionate concentration of the IMD-supplemented rats, compared with those in the control rats. We concluded that SDGs, especially RMD, thickened the mucosae of the rat distal small intestines. In particular, this effect of RMD but not IMD could have resulted from increased glucose available as a secretagogue of the trophic hormone GLP-2, in the ileum.

Local free fatty acids trigger the expression of lipopolysaccharide-binding protein in murine white adipose tissue.

Although lipopolysaccharide (LPS)-binding protein (LBP) is an acute-phase protein mainly produced by hepatocytes, it has also been proposed to be a pro-inflammatory adipokine. Obesity and the consumption of a high-fat diet (HFD) are reportedly associated with elevated levels of LPS in plasma and free fatty acids (FFAs) in white adipose tissue (WAT). We examined whether circulating LPS or local FFAs are responsible for the HFD-induced increase of LBP in WAT. Male C57BL/6J mice were fed either a normal-fat diet (NFD) or an HFD. The mRNA levels in the liver and mesenteric WAT (mWAT), total FFA content in mWAT, and LBP and LPS concentrations in plasma were determined. The Lbp mRNA level in mWAT was higher in mice fed the HFD than in those fed the NFD for 3, 7, or 28 days or 14 weeks, whereas the hepatic Lbp mRNA level did not differ between the groups. The Lbp mRNA level in mWAT was also increased by the HFD in germ-free mice, which do not have gut microbiota, the source of LPS. The plasma LPS level did not show a significant correlation with the mWAT Lbp mRNA level. The total FFA content in mWAT was higher in mice fed the HFD than in those fed the NFD and positively correlated with the Lbp mRNA level. Supplementation with palmitic acid increased the Lbp mRNA level in 3T3-L1 adipocytes. We propose that local FFAs, but not circulating LPS, are the trigger for increased Lbp expression in mWAT of mice fed the HFD.