We recently showed that adherence to the Mediterranean diet increased the proportion of plasma omega-3 polyunsaturated fatty acids (n-3 PUFAs), which was associated with an improved intestinal barrier integrity. In the present exploratory analysis, we assessed fecal fatty acids in the same cohort, aiming to investigate possible associations with intestinal barrier integrity. Women from the LIBRE randomized controlled trial, characterized by an impaired intestinal barrier integrity, followed either a Mediterranean diet (intervention group, IG, n=33) or a standard diet (control group, CG, n=35). At baseline (BL), month 3 (V1), and month 12 (V2), plasma lipopolysaccharide binding protein (LBP), fecal zonulin, and fecal fatty acids were measured. In the IG, fecal proportions of palmitoleic acid (16:1, n-7) and arachidonic acid (20:4, n-6) decreased, while the proportion of linoleic acid (18:2, n-6) and alpha linoleic acid (18:3, n-3) increased (BL-V1 and BL-V2, all P<0.08). In the CG, fecal proportions of palmitic acid and arachidic acid increased while the proportion of linoleic acid decreased (BL-V1, all P<0.05). The decrease in the proportion of palmitoleic acid correlated with the decrease in plasma LBP (∆V1-BL r=0.72, P<0.001; ∆V2-BL r=0.39, P<0.05) and correlated inversely with adherence to the Mediterranean diet (Mediterranean diet score; ∆V1-BL r=-0.42, P=0.03; ∆V2-BL r=-0.53, P=0.005) in the IG. Our data show that adherence to the Mediterranean diet induces distinct changes in the fecal fatty acid composition. Furthermore, our data indicate that the fecal proportion of palmitoleic acid, but not fecal n-3 PUFAs, are associated with intestinal barrier integrity in the IG.

This review aims to investigate the relationship between the health impact of whole grains mediated via the interaction with intestinal microbiota and intestinal barrier function with special interest on tryptophan metabolism, focusing on the role of the intestinal microbiota and their impact on barrier function. Consuming various types of whole grains can lead to the growth of different microbiota species, which in turn leads to the production of diverse metabolites, including those derived from tryptophan metabolism, although the impact of whole grains on intestinal microbiota composition results remains inconclusive and vary among different studies. Whole grains can exert an influence on tryptophan metabolism through interactions with the intestinal microbiota, and the presence of fibre in whole grains plays a notable role in establishing this connection. The impact of whole grains on intestinal barrier function is closely related to their effects on the composition and activity of intestinal microbiota, and SCFA and tryptophan metabolites serve as potential links connecting whole grains, intestinal microbiota and the intestinal barrier function. Tryptophan metabolites affect various aspects of the intestinal barrier, such as immune balance, mucus and microbial barrier, tight junction complexes and the differentiation and proliferation of epithelial cells. Despite the encouraging discoveries in this area of research, the evidence regarding the effects of whole grain consumption on intestine-related activity remains limited. Hence, we can conclude that we are just starting to understand the actual complexity of the intestinal factors mediating in part the health impacts of whole grain cereals.

Hesperidin and naringin are citrus flavonoids with known anti-oxidative and anti-inflammatory properties. Evidence from previous studies indicates that both these compounds and the metabolites that are formed during intestinal metabolism are able to exert beneficial effects on intestinal barrier function and inflammation. However, so far, studies investigating the relative contributions of the various compounds are lacking. Therefore, we assessed the effect of citrus flavonoids and their intestinal metabolites on immune-mediated barrier disruption in an in vitro co-culture model. Caco-2 cell monolayers were placed in co-culture with phorbol 12-myristate 13-acetate-stimulated THP-1-Blue™ NF-κB cells for 30 h. At baseline, the citrus flavonoids and their metabolites were added to the apical compartment (50 or 100 µM per compound). After 24 h, THP-1 cells were incubated with lipopolysaccharide (LPS) in the basolateral compartment for 6 h. Incubation with citrus flavonoids and their metabolites did not induce changes in transepithelial electrical resistance, fluorescein isothiocyanate–dextran 4 kDa permeation or gene expression of barrier-related genes for any of the compounds tested. After LPS stimulation, NF-κB activity was significantly inhibited by all compounds (100 µM) except for one metabolite (all P ≤ 0·03). LPS-induced production of the cytokines IL-8, TNF-α and IL-6 was inhibited by most compounds (all P < 0·05). However, levels of IL-1β were increased, which may contribute to the lack of an improved barrier effect. Overall, these results suggest that citrus flavonoids may decrease intestinal inflammation via reduction of NF-κB activity and that the parent compounds and their metabolites formed during intestinal metabolism are able to exert comparable effects.

Linoleic acid (LA) is predominantly essential for poultry. Poultry lacking LA show retarded growth and reduced disease resistance. Intestinal barrier function plays an important role in pigeon squab growth, whereas research on the effects of LA on intestinal health in altrices is scant. Considering that squabs are fed by their parents, the study aimed to explore the effects of maternal dietary LA on intestinal morphology, tight junction proteins, immune cytokines and microbial flora in squabs. A completely randomised design with a control group, 1 % LA supplementation group, 2 % LA supplementation group and 4 % LA supplementation group was used. Six squabs from each treatment were randomly sampled at 21 d post-hatching. The results indicated that LA supplementation improved intestinal morphology, as reflected by increased villus height, villus area and the ratio of villi to crypts. Also, 1 % LA supplementation elevated the density of goblet cells in the intestine and strengthened tight junctions by up-regulating claudin-3 and occludin gene expression but down-regulating claudin-2 gene expression. Moreover, 1 % LA supplementation reduced the secretion of proinflammatory cytokines and partly increased anti-inflammatory cytokines. The intestinal microbial diversity in the 1 % LA supplementation group was higher than that in the other groups. As beneficial bacteria, Butyrivibrio was the biomarker of 1 % LA supplementation. However, excessive (4 %) LA supplementation led to adverse impacts on intestinal immunity and microbiota. In conclusion, maternal dietary LA might alter intestinal barrier function in pigeon squabs in a dose-dependent manner. Supplementation with 1 % LA was suggested in parental pigeons.

The present study investigated the effect of Bacillus subtilis DSM 29784 (Ba) and enzymes (xylanase and β-glucanases; Enz), alone or in combination (BE) as antibiotic replacements, on the growth performance, digestive enzyme activity, immune response and the intestinal barrier of broiler chickens. In total, 1200 1-d-old broilers were randomly assigned to five dietary treatments, each with six replicate pens of forty birds for 63 d as follows: (a) basal diet (control), supplemented with (b) 1 × 109 colony-forming units (cfu)/kg Ba, (c) 300 mg/kg Enz, (d) 1 × 109 cfu/kg Ba and 300 mg/kg Enz and (e) 250 mg/kg enramycin (ER). Ba, Enz and BE, similar to ER, decreased the feed conversion rate, maintained intestinal integrity with a higher villus height:crypt depth ratio and increased the numbers of goblet cells. The BE group exhibited higher expression of claudin-1 and mucin 2 than the other four groups. BE supplementation significantly increased the α-diversity and β-diversity of the intestinal microbiota and markedly enhanced lipase activity in the duodenal mucosa. Serum endotoxin was significantly decreased in the BE group. Compared with those in the control group, increased superoxide dismutase and glutathione peroxidase activities were observed in the jejunal mucosa of the Ba and BE groups, respectively. In conclusion, the results suggested that dietary treatment with Ba, Enz or BE has beneficial effects on growth performance and anti-oxidative capacity, and BE had better effects than Ba or Enz alone on digestive enzyme activity and the intestinal microbiota. Ba or Enz could be used as an alternative to antibiotics for broiler chickens.

The objective of this study was to investigate the effects of dietary pyrroloquinoline quinone disodium (PQQ·Na2) supplementation on the reproductive performance and intestinal barrier functions of gestating and lactating female Sprague–Dawley (SD) rats and their offspring. Dietary supplementation with PQQ·Na2 increased the number of implanted embryos per litter during gestation and lactation at GD 20 and increased the number of viable fetuses per litter, and the weight of uterine horns with fetuses increased at 1 d of newborn. The mRNA expression levels of catalase (CAT), glutathione peroxidase (GPx2), superoxide dismutase (SOD1), solute carrier family 2 member 1 (Slc2a1) and solute carrier family 2 member 3 (Slc2a3) in the placenta were increased with dietary PQQ·Na2 supplementation. Dietary supplementation with PQQ·Na2 in gestating and lactating rats increased the CAT, SOD and GPx activities of the jejunal mucosa of weaned rats on PD 21. Dietary supplementation with PQQ·Na2 in female rats affected the expression of tight junction proteins (claudin, zonula occludens-1 (ZO-1) and occludin) in the jejunal mucosa of their offspring by increasing the expression of ZO-1 mRNA in the expression of ZO-1 and claudin mRNA in the jejunal mucosa of weaned rats on PD 21. In conclusion, dietary supplementation with PQQ·Na2 in gestating and lactating female rats had positive effects on their reproductive performance and on the intestinal barrier of weaned rats.

The animal gut effectively prevents the entry of hazardous substances and microbes while permitting the transfer of nutrients, such as water, electrolytes, vitamins, proteins, lipids, carbohydrates, minerals and microbial metabolites, which are intimately associated with intestinal homoeostasis. The gut maintains biological functions through its nutrient-sensing receptors, including the Ca-sensing receptor (CaSR), which activates a variety of signalling pathways, depending on cellular context. CaSR coordinates food digestion and nutrient absorption, promotes cell proliferation and differentiation, regulates energy metabolism and immune response, stimulates hormone secretion, mitigates secretory diarrhoea and enhances intestinal barrier function. Thus, CaSR is crucial to the maintenance of gut homoeostasis and protection of intestinal health. In this review, we focused on the emerging roles of CaSR in the modulation of intestinal homoeostasis including related underlying mechanisms. By elucidating the relationship between CaSR and animal gut homoeostasis, effective and inexpensive methods for treating intestinal health imbalance through nutritional manipulation can be developed. This article is expected to provide experimental data of the effects of CaSR on animal or human health.

Recent studies indicate that intestinal oxidative stress and microbiota imbalance is involved in weaning-induced intestinal dysfunction in piglets. We have investigated the effect of feeding a carvacrol–thymol blend supplemented diet on intestinal redox status, selected microbial populations and the intestinal barrier in weaning piglets. The piglets (weaned at 21 days of age) were randomly allocated to two groups with six pens per treatment and 10 piglets per pen. At weaning day (21 days of age), six piglets were sacrificed before weaning to serve as the preweaning group. The weaned group was fed with a basal diet, while the weaned-CB group was fed with the basal diet supplemented with 100 mg/kg carvacrol–thymol (1 : 1) blend for 14 days. On day 7 post-weaning, six piglets from each group were sacrificed to determine intestinal redox status, selected microbial populations, messenger RNA (mRNA) transcript levels of proinflammatory cytokines and biomarkers of intestinal barrier function. Weaning resulted in intestinal oxidative stress, indicated by the increased concentration of reactive oxygen species and thiobarbituric acid-reactive substances present in the intestine. Weaning also reduced the population of Lactobacillus genus and increased the populations of Enterococcus genus and Escherichia coli in the jejunum, and increased mRNA levels of tumor necrosis factor α (TNF-α), interleukin 1β and interleukin 6 (IL-6). In addition, decreased mRNA levels of zonula occludens and occludin in the jejunal mucosa and increased plasma diamine oxidase concentrations indicated that weaning induced dysfunction of the intestinal barrier. On day 7 post-weaning, supplementation with the carvacrol–thymol blend restored weaning-induced intestinal oxidative stress. Compared with the weaned group, the weaned-CB group had an increased population of Lactobacillus genus but reduced populations of Enterococcus genus and E. coli in the jejunum and decreased mRNA levels of TNF-α. The results indicated that weaning induced intestinal oxidative stress and dysfunction of the intestinal barrier. Dietary supplementation with 100 mg/kg carvacrol–thymol (1 : 1) decreased the intestinal oxidative stress and influenced selected microbial populations without changing the biomarkers of intestinal barrier in weaning piglets.

We recently reported the identification of a peptide from yoghurts with promising potential for intestinal health: the sequence (94-123) of bovine β-casein. This peptide, composed of 30 amino acid residues, maintains intestinal homoeostasis through production of the secreted mucin MUC2 and of the transmembrane-associated mucin MUC4. Our study aimed to search for the minimal sequence responsible for the biological activity of β-CN(94-123) by using several strategies based on (i) known bioactive peptides encrypted in β-CN(94-123), (ii) in silico prediction of peptides reactivity and (iii) digestion of β-CN(94-123) by enzymes of intestinal brush border membranes. The revealed sequences were tested in vitro on human intestinal mucus-producing HT29-MTX cells. We demonstrated that β-CN(108-113) (an ACE-inhibitory peptide) and β-CN(114-119) (an opioid peptide named neocasomorphin-6) up-regulated MUC4 expression whereas levels of the secreted mucins MUC2 and MUC5AC remained unchanged. The digestion of β-CN(94-123) by intestinal enzymes showed that the peptides β-CN(94-108) and β-CN(117-123) were present throughout 1·5 to 3 h of digestion, respectively. These two peptides raised MUC5AC expression while β-CN(117-123) also induced a decrease in the level of MUC2 mRNA and protein. In addition, this inhibitory effect was reproduced in airway epithelial cells. In conclusion, β-CN(94-123) is a multifunctional molecule but only the sequence of 30 amino acids has a stimulating effect on the production of MUC2, a crucial factor of intestinal protection.

Salmonellosis is one of the most frequent zoonotic diseases in humans and is associated with major public health and economic losses globally. Eggs and poultry meat represent one of the main sources of infection. Chickens are considered as a main carrier for salmonella and infected birds rarely show any clinical signs. The control of salmonella in commercial poultry production is essential because of the economic and public health consequences. Accordingly, the current European approach is based on a farm-to-fork strategy, in which each sector implements measures to minimise or reduce salmonella contamination. Control measures are most effective at the source, i.e. at farm level. Measures to decrease the prevalence of Salmonella enterica in poultry farms are expected to result in a lower incidence of human salmonellosis. The pre-harvest phase involves the use of all available tools, such as vaccination, implementation of biosecurity measures and additional efforts to achieve salmonella-free feed production. Amongst those tools, nutritional approaches can greatly contribute to reduce salmonella shedding and to minimise salmonella during processing, thereby producing safer food. Due to the high number of introductory sources for salmonella to infect a flock, various intervention strategies have to be implemented to minimise risks. Recently, it has been shown that salmonella impacts the gut integrity in chickens, therefore it is important to develop new strategies or combine different strategies to improve gut barrier function and gut health. This review describes certain selected strategies that may be used in farm control programmes in poultry.

Previous studies have shown that bovine lactoferrin (bLF) exerts antibacterial, immune-modulating and anti-inflammatory effects. The present study aimed to investigate the effect of enteral bLF supplementation on intestinal adaptation and barrier function in a rat model of short bowel syndrome (SBS). Male Sprague–Dawley rats aged 4 weeks were randomised into three groups (n 10 per group): Sham group (rats submitted to bowel transection and reanastomosis); SBS group (rats submitted to 80 % small-bowel resection); SBS-bLF group (rats submitted to 80 % small-bowel resection plus treatment with bLF (0·5 g/kg per d) by oral administration from day 2 to day 20). Despite similar food intake, both the SBS and SBS-bLF groups exhibited significantly lower body weight gain, but increased villus height and crypt depth and a higher intestinal epithelial cell proliferation index (P< 0·05) when compared with the Sham group. Compared with that in the SBS group, in the SBS-bLF group, bacterial translocation to regional organs was low and intestinal permeability was significantly reduced. The SBS-bLF group also had increased secretory IgA (sIgA) concentrations in ileal contents (29·9 (23·8–33·0) ng/ml), when compared with the other two groups having similar sIgA concentrations (17·5 (12·6–29·1) and 19·3 (11·5–27·0) ng/ml, respectively). The relative expression levels of two tight junction (TJ) proteins, occludin and claudin-4, in the SBS-bLF group were significantly higher than those in the SBS group (P< 0·05), but did not exhibit any significant differences when compared with those in the Sham group. In conclusion, enteral bLF supplementation up-regulates small-bowel sIgA concentrations and TJ protein expression and reduces intestinal permeability and could thus support intestinal barrier integrity and protect against bacterial infections in SBS.

The study evaluated whether feeding diosmectite–ZnO composite (DS-ZnO) at 500 mg Zn/kg to early weaned pigs would alleviate the weaning-related intestinal disorders as a substitute for high concentration of ZnO (2250 mg Zn/kg). The pigs weaned at an age of 21 ± 1 d were allotted to four treatments groups as follows: (1) control; (2) DS-ZnO, 500 mg Zn/kg diet; (3) ZnO, 2250 mg Zn/kg diet; and (4) mixture of 2·0 g DS/kg and 500 mg Zn/kg from ZnO (equal amount of DS and ZnO in the DS-ZnO treatment group). The results showed that, compared with the control on days 7 and 14 post-weaning, addition of DS-ZnO at 500 mg Zn/kg improved (P< 0·05) daily gain and feed intake, decreased (P< 0·05) post-weaning scour scores, increased (P< 0·05) jejunal villus height and the ratio of villus height and crypt depth, decreased (P< 0·05) jejunal paracellular permeability of fluorescein isothiocyanate dextran 4 kDa and up-regulated (P< 0·05) tight junction protein expression of occludin, claudin-1 and zonula occludens-1 in jejunal mucosa. The mRNA levels of TNF-α, IL-6 and interferon-γ (IFN-γ) on day 7 post-weaning were also decreased (P< 0·05). The piglets fed DS-ZnO at 500 mg Zn/kg did not differ in the above parameters from those fed ZnO at 2250 mg Zn/kg, while they had better performance than those fed the mixture of DS and ZnO. Supplementation with DS-ZnO at 500 mg Zn/kg was effective in alleviating diarrhoea, barrier dysfunction and inflammatory cytokine expression and up-regulating tight junction protein expression.

Dietary methyl donors and their genetic determinants are associated with Crohn's disease risk. We investigated whether a methyl-deficient diet (MDD) may affect development and functions of the small intestine in rat pups from dams subjected to the MDD during gestation and lactation. At 1 month before pregnancy, adult females were fed with either a standard food or a diet without vitamin B12, folate and choline. A global wall hypotrophy was observed in the distal small bowel (MDD animals 0·30 mm v. controls 0·58 mm; P< 0·001) with increased crypt apoptosis (3·37 v. 0·4 %; P< 0·001), loss of enterocyte differentiation in the villus and a reduction in intestinal alkaline phosphatase production. Cleaved caspase-3 immunostaining (MDD animals 3·37 % v. controls 0·4 %, P< 0·001) and the Apostain labelling index showed increased crypt apoptosis (3·5 v. 1·4 %; P= 0·018). Decreased proliferation was observed in crypts of the proximal small bowel with a reduced number of minichromosome maintenance 6 (MDD animals 52·83 % v. controls 83·17 %; P= 0·048) and proliferating cell nuclear antigen-positive cells (46·25 v. 59 %; P= 0·05). This lack of enterocyte differentiation in the distal small bowel was associated with an impaired expression of β-catenin and a decreased β-catenin–E-cadherin interaction. The MDD affected the intestinal barrier in the proximal small bowel by decreasing Paneth cell number after immunostaining for lysosyme (MDD animals 8·66 % v. controls 21·66 %) and by reducing goblet cell number and mucus production after immunostaining for mucin-2 (crypts 8·66 v. 15·33 %; villus 7 v. 17 %). The MDD has dual effects on the small intestine by producing dramatic effects on enterocyte differentiation and barrier function in rats.

Myocardial infarction (MI) in rats is accompanied by apoptosis in the limbic system and a behavioural syndrome similar to models of depression. We have already shown that probiotics can reduce post-MI apoptosis and designed the present study to determine if probiotics can also prevent post-MI depressive behaviour. We also tested the hypothesis that probiotics achieve their central effects through changes in the intestinal barrier. MI was induced in anaesthetised rats via 40-min transient occlusion of the left anterior coronary artery. Sham rats underwent the same surgical procedure without actual coronary occlusion. For 7 d before MI and between the seventh post-MI day and euthanasia, half the MI and sham rats were given one billion live bacterial cells of Lactobacillus helveticus R0052 and Bifidobacterium longum R0175 per d dissolved in water, while the remaining animals received only the vehicle (maltodextrin). Depressive behaviour was evaluated 2 weeks post-MI in social interaction, forced swimming and passive avoidance step-down tests. Intestinal permeability was evaluated by oral administration with fluorescein isothiocyanate–dextran, 4 h before euthanasia. MI rats displayed less social interaction and impaired performance in the forced swimming and passive avoidance step-down tests compared to the sham controls (P < 0·05). Probiotics reversed the behavioural effects of MI (P < 0·05), but did not alter the behaviour of sham rats. Intestinal permeability was increased in MI rats and reversed by probiotics. In conclusion, L. helveticus R0052 and B. longum R0175 combination interferes with the development of post-MI depressive behaviour and restores intestinal barrier integrity in MI rats.

Under commercial conditions, weaning of piglets is associated with social, environmental and dietary stress. Consequently, small-intestinal barrier and absorptive functions deteriorate within a short time after weaning. Most studies that have assessed small-intestinal permeability in pigs after weaning used either Ussing chambers or orally administered marker probes. Paracellular barrier function and active absorption decrease when pigs are weaned at 3 weeks of age or earlier. However, when weaned at 4 weeks of age or later, the barrier function is less affected, and active absorption is not affected or is increased. Weaning stress is a critical factor in relation to the compromised paracellular barrier function after weaning. Adequate feed intake levels after weaning prevent the loss of the intestinal barrier function. Transcellular transport of macromolecules and passive transcellular absorption decrease after weaning. This may reflect a natural intestinal maturation process that is enhanced by the weaning process and prevents the pig from an antigen overload. It seems that passive and active absorption after weaning adapt accurately to the new environment when pigs are weaned after 3 weeks of age. However, when weaned at 3 weeks of age or earlier, the decrease in active absorption indicates that pigs are unable to sufficiently adapt to the new environment. To improve weaning strategies, future studies should distinguish whether the effect of feed intake on barrier function can be directed to a lack of a specific nutrient, i.e. energy or protein.

The mechanism of impaired gut barrier function in patients with short bowel syndrome (SBS) is poorly understood and includes decreased intestinal motility leading to bacterial overgrowth, a reduction in gut-associated lymphoid tissue following the loss of intestinal length, inhibition of mucosal immunity of the small intestine by intravenous total parental nutrition, and changes in intestinal permeability to macromolecules. Novel therapeutic strategies (i.e. nutritive and surgical) have been introduced in order to prevent the establishment or improve the outcome of this prevalent disease. Pre- and probiotics as a nutritive supplement are already known to be very active in the intestinal tract (mainly in the colon) by maintaining a healthy gut microflora and influencing metabolic, trophic and protective mechanisms, such as the production of SCFA which influence epithelial cell metabolism, turnover and apoptosis. Probiotics have been recommended for patients suffering from SBS in order to decrease bacterial overgrowth and prevent bacterial translocation, two major mechanisms in the pathogenesis of SBS. The present review discusses the research available in the international literature, clinical and experimental, regarding probiotic supplementation for this complicated group of patients based on the clinical spectrum and pathophysiological aspects of the syndrome. The clinical data that were collected for the purposes of the present review suggest that it is difficult to correctly characterise probiotics as a preventive or therapeutic measure. It is very challenging after all to examine the relationship of the bacterial flora, the intestinal barrier and the probiotics as, according to the latest knowledge, demonstrate an interesting interaction.