Propolis has abundant polyphenolic constituents and is used widely as a health/functional food. Here, we investigated the effects of polyphenol-rich propolis extracts (PPE) on intestinal barrier function in human intestinal epithelial Caco-2 cells, as well as in rats. In Caco-2 cells, PPE increased transepithelial electrical resistance and decreased lucifer yellow flux. PPE-treated cells showed increased expression of the tight junction (TJ) loci occludin and zona occludens (ZO)-1. Confocal microscopy showed organized expressions in proteins related to TJ assembly, i.e., occludin and ZO-1, in response to PPE. Furthermore, PPE led to the activation of AMPK, ERK1/2, p38, and Akt. Using selective inhibitors, we found that the positive effects of PPE on barrier function were abolished in cells in which AMPK and ERK1/2 signaling were inhibited. Moreover, rats fed a diet supplemented with PPE (0.3% in the diet) exhibited increased colonic epithelium ZO-1 expression. Overall, these data suggest that PPE strengthens intestinal barrier function by activating AMPK and ERK signaling and provide novel insights into the potential application of propolis for human gut health.

In this study we investigated whetherL-cysteine (L-cys) could alleviate LPS-induced intestinal disruption and its underlying mechanism. Piglets fed with anL-cys-supplemented diet had higher average daily gain.L-cys alleviated LPS-induced structural and functional disruption of intestine in weanling piglets, as demonstrated by higher villus height, villus height (VH) to crypt depth (CD) ratio, and transepithelial electrical resistance (TER) and lower FITC-dextran 4 (FD4) kDa flux in jejunum and ileum. Supplementation withL-cys up-regulated occludin and claudin-1 expression, reduced caspase-3 activity and enhanced proliferating cell nuclear antigen expression of jejunum and ileum relative to LPS group. Additionally,L-cys suppressed the LPS-induced intestinal inflammation and oxidative stress, as demonstrated by down-regulated TNF-α, IL-6 and IL-8 mRNA levels, increased catalase, superoxide dismutase, glutathione peroxidase activity, glutathione (GSH) contents and the ratio of GSH and oxidized glutathione in jejunum and ileum. Finally, a diet supplemented withL-cys inhibited NF-κB(p65) nuclear translocation and elevated NF erythroid 2-related factor 2 (Nrf2) translocation compared with the LPS group. Collectively, our results indicated the protective function ofL-cys on intestinal mucosa barrier may closely associated with its anti-inflammation, antioxidant and regulating effect on the NF-κB and Nrf2 signaling pathways.

Weaning stress caused marked changes in intestinal structure and function. Transforming growth factor-β1 (TGF-β1) and canonical Smads signaling pathway are suspected to play an important regulatory role in post-weaning adaptation of the small intestine. In the present study, the intestinal morphology and permeability, developmental expressions of tight junction proteins and TGF-β1 in the intestine of piglets during the 2 weeks after weaning were assessed. The expressions of TGF-β receptor I/II (TβRI, TβRII), smad2/3, smad4 and smad7 were determined to investigate whether canonical smads signaling pathways were involved in early weaning adaption process. The results showed that a shorter villus and deeper crypt were observed on d 3 and d 7 postweaning and intestinal morphology recovered to preweaning values on d 14 postweaning. Early weaning increased (P<0.05) plasma level of diamine oxidase (DAO) and decreased DAO activities (P<0.05) in intestinal mucosa on d 3 and d 7 post-weaning. Compared with the pre-weaning stage (d 0), tight junction proteins level of occludin and claudin-1 were reduced (P<0.05) on d 3, 7 and 14 post-weaning, and ZO-1 protein was reduced (P<0.05) on d 3 and d 7 post-weaning. An increase (P<0.05) of TGF-β1 in intestinal mucosa was observed on d 3 and d 7 and then level down on d 14 post-weaning. Although there was an increase (P<0.05) of TβR II protein expression in the intestinal mucosa on d3 and d 7, no significant increase of mRNA of TβRI, TβRII, smad2/3, smad4 and smad7 was observed during postweaning. The results indicated that TGF-β1 was associated with the restoration of intestinal morphology and barrier function following weaning stress. The increased intestinal endogenous TGF-β1 didn't activate the canonical Smads signaling pathway.

Aims:  Lactobacilli should resist stress environments in industry process and gastrointestinal tract before exerting their beneficial effects. To explore the possible stabilizers in probiotic products, prebiotic oligosaccharides were investigated. Methods and Results:  We investigated the effect of four selected oligosaccharides on the survival of probiotic Lactobacillus plantarum and L. acidophilus to simulated stress conditions. It was found that the tolerance of lactobacilli to simulated artificial gastrointestinal juice, heat treatment and phenol solution was obviously enhanced in fructo‐oligosaccharides (FOS) and xylo‐oligosaccharides (XOS) group. In addition, chito‐oligosaccharides (COS), manno‐oligosaccharides (MOS) and glucose also had positive effect compared with control group (without sugar). Conclusions:  Prebiotic oligosaccharides, especially XOS and FOS added in medium have protection function to lactobacilli in stress environments. The protection function of oligosaccharides may correlate with the bacteria growth, which was stimulated by these oligosaccharides. Significance and Impact of the Study:  Prebiotic oligosaccharides may be used as stabilizers in probiotic products.

No abstract

Protein fermentation has an adverse effect on colonic health; high-quality proteins and reducing the protein level (protein restriction) can effectively decrease the amount of proteins flowing into the colon for microbial protein fermentation.

L-theanine, a natural nonprotein amino acid with a high biological activity, is reported to exert anti-stress properties. An experiment with a 3 × 2 factorial arrangement was conducted to investigate the effects of dietary L-theanine on growth performance and immune function in lipopolysaccharide (LPS)-challenged broilers. A total of 432 one-day-old male yellow-feathered broilers were randomly assigned to 3 dietary treatments (control, antibiotic and L-theanine diets) with 2 subgroups of each (6 replicate cages; 12 birds/cage). Birds from each subgroup of the 3 dietary treatments were intra-abdominally injected with the same amount of LPS or saline at 24, 25, 26 d of age. Both dietary L-theanine and antibiotic improved (P < 0.05) the growth performance of birds before LPS injection (d 1 to 21). The effect of dietary L-theanine was better (P < 0.05) than that of antibiotic. Lipopolysaccharide decreased feed intake (FI) and body weight gain (BWG) from d 22 to 28 (P < 0.05), BWG and feed to gain ratio (F:G) from d 29 to 56 (P < 0.05), increased mortality in different growth periods (P < 0.05), elevated the levels of serum cortisol, α1-acid glycoprotein (α1-AGP), interleukin-6 (IL-6) on d 24 and 25 (P < 0.05), reduced immune organ indexes and contents of jejunal mucosal secretory immunoglobulin A (sIgA) on d 28 (P < 0.05). The decreased FI and BWG, as well as increased F:G and mortality in LPS-challenged birds, were alleviated by dietary L-theanine or antibiotic from d 29 to 56 and from d 1 to 56. Dietary L-theanine mitigated the elevated serum α1-AGP level on d 25, serum IL-6 concentration on d 24 and 26, and the decreased jejunal mucosal sIgA content on d 28 of the LPS-challenged birds. The results indicated that L-theanine had potential to alleviate LPS-induced immune stress in broilers.

Psychosocial stress is a major factor driving gastrointestinal (GI) pathophysiology and disease susceptibility in humans and animals. The mechanisms governing susceptibility to stress-induced GI disease remain poorly understood. In the present study, we investigated the influence of chronic social stress (CSS) in pigs, induced by 7 d of chronic mixing/crowding stress, on intestinal barrier and nutrient transport function, corticotropin releasing factor (CRF) signaling and immunological responses. Results from this study showed that CSS resulted in a significant impairment of ileal and colonic barrier function indicated by reduced transepithelial electrical resistance (TER) in the ileum and increased FD4 flux in the ileum (by 0.8 fold) and colon (by 0.7 fold). Ileal sodium glucose linked transporter 1 (SGLT-1) function, measured as glucose-induced changes in short-circuit current (Isc), was diminished (by 52%) in CSS pigs, associated with reduced body weight gain and feed efficiency. Although reductions in SGLT-1 function were observed in CSS pigs, mRNA expression for SGLT-1, villus heights were increased in CSS pigs. Corticotropin releasing factor (CRF) mRNA was upregulated (by 0.9 fold) in the ileum of CSS pigs but not in the colon. Urocortin 2 (Ucn2) mRNA was upregulated (by 1.5 fold) in the colon of CSS pigs, but not in the ileum. In CSS pigs, a downregulation of pro-inflammatory cytokines mRNA (IL1B, TNFA, IL8, and IL6) was observed in both ileum and colon, compared with controls. In contrast CSS induced a marked upregulation of mRNA for IL10 and mast cell chymase gene (CMA1) in the ileum and colon. Together, these data demonstrate that chronic stress in pigs results in significant alterations in intestinal barrier and nutrient transport function and neuro-immune mediator and receptor expression.