Developmental changes of TGF-β1 and Smads signaling pathway in intestinal adaption of weaned pigs

Dietary nutrition, intestinal microbiota dysbiosis and post-weaning diarrhea in piglets

Weaning is a critical transitional point in the life cycle of piglets. Early weaning can lead to post-weaning syndrome, destroy the intestinal barrier function and microbiota homeostasis, cause diarrhea and threaten the health of piglets. The nutritional components of milk and solid foods consumed by newborn animals can affect the diversity and structure of their intestinal microbiota, and regulate post-weaning diarrhea in piglets. Therefore, this paper reviews the effects and mechanisms of different nutrients, including protein, dietary fiber, dietary fatty acids and dietary electrolyte balance, on diarrhea and health of piglets by regulating intestinal function. Protein is an essential nutrient for the growth of piglets; however, excessive intake will cause many harmful effects, such as allergic reactions, intestinal barrier dysfunction and pathogenic growth, eventually aggravating piglet diarrhea. Dietary fiber is a nutrient that alleviates post-weaning diarrhea in piglets, which is related to its promotion of intestinal epithelial integrity, microbial homeostasis and the production of short-chain fatty acids. In addition, dietary fatty acids and dietary electrolyte balance can also facilitate the growth, function and health of piglets by regulating intestinal epithelial function, immune system and microbiota. Thus, a targeted control of dietary components to promote the establishment of a healthy bacterial community is a significant method for preventing nutritional diarrhea in weaned piglets.

Purine Metabolism and Hexosamine Biosynthetic Pathway Abnormalities in Diarrheal Weaned Piglets Identified Using Metabolomics

Post-weaning diarrhea significantly contributes to the high mortality in pig production, but the metabolic changes in weaned piglets with diarrhea remain unclear. This study aimed to identify the differential metabolites in the urine of diarrheal weaned piglets and those of healthy weaned piglets to reveal the metabolic changes associated with diarrhea in weaned piglets. Nine 25-day-old piglets with diarrhea scores above 16 and an average body weight of 5.41 ± 0.18 kg were selected for the diarrhea group. Corresponding to the body weight and sex of the diarrhea group, nine 25-month-old healthy piglets with similar sex and body weights of 5.49 ± 0.21 kg were selected as the control group. Results showed that the serum C-reactive protein and cortisol of piglets in the diarrhea group were higher than those in the control group (p < 0.05). The mRNA expression of TNF-α, IFN-γ in the jejunum and colon, and IL-1β in the jejunum were increased in diarrhea piglets (p < 0.05), accompanied by a reduction in the mRNA expression of ZO-1, ZO-2, and CLDN1 in the jejunum and colon (p < 0.05); mRNA expression of OCLN in the colon also occurred (p < 0.05). Metabolomic analysis of urine revealed increased levels of inosine, hypoxanthine, guanosine, deoxyinosin, glucosamine, glucosamine-1-p, N-Acetylmannosamine, chitobiose, and uric acid, identified as differential metabolites in diarrhea piglets compared to the controls. In summary, elevated weaning stress and inflammatory disease were associated with the abnormalities of purine metabolism and the hexosamine biosynthetic pathway of weaned piglets. This study additionally indicated the presence of energy metabolism-related diseases in diarrheal weaned piglets.

The Use of Fruit and Vegetable by-Products as Enhancers of Health Status of Piglets after Weaning: The Role of Bioactive Compounds from Apple and Carrot Industrial Wastes

At weaning, piglets are exposed to a large variety of stressors, from environmental/behavioral factors to nutritional stress. Weaning transition affects the gastrointestinal tract especially, resulting in specific disturbances at the level of intestinal morphology, barrier function and integrity, mucosal immunity and gut microbiota. All these alterations are associated with intestinal inflammation, oxidative stress and perturbation of intracellular signaling pathways. The nutritional management of the weaning period aims to achieve the reinforcement of intestinal integrity and functioning to positively modulate the intestinal immunity and that of the gut microbiota and to enhance the health status of piglets. That is why the current research is focused on the raw materials rich in phytochemicals which could positively modulate animal health. The composition analysis of fruit, vegetable and their by-products showed that identified phytochemicals could act as bioactive compounds, which can be used as modulators of weaning-induced disturbances in piglets. This review describes nutritional studies which investigated the effects of bioactive compounds derived from fruit (apple) and vegetables (carrot) or their by-products on the intestinal architecture and function, inflammatory processes and oxidative stress at the intestinal level. Data on the associated signaling pathways and on the microbiota modulation by bioactive compounds from these by-products are also presented.

Early feeding leads to molecular maturation of the gut mucosal immune system in suckling piglets

Introduction

Diet-microbiota-host interactions are increasingly studied to comprehend their implications in host metabolism and overall health. Keeping in mind the importance of early life programming in shaping intestinal mucosal development, the pre-weaning period can be utilised to understand these interactions in suckling piglets. The objective of this study was to investigate the consequences of early life feeding on the time-resolved mucosal transcriptional program as well as mucosal morphology.

Methods

A customised fibrous feed was provided to piglets (early-fed or EF group; 7 litters) from five days of age until weaning (29 days of age) in addition to sow's milk, whereas control piglets (CON; 6 litters) suckled mother's milk only. Rectal swabs, intestinal content, and mucosal tissues (jejunum, colon) were obtained pre- and post-weaning for microbiota analysis (16S amplicon sequencing) and host transcriptome analysis (RNA sequencing).

Results

Early feeding accelerated both microbiota colonisation as well as host transcriptome, towards a more "mature state", with a more pronounced response in colon compared to jejunum. Early feeding elicited the largest impact on the colon transcriptome just before weaning (compared to post-weaning time-points), exemplified by the modulation of genes involved in cholesterol and energy metabolism and immune response. The transcriptional impact of early feeding persisted during the first days post-weaning and was highlighted by a stronger mucosal response to the weaning stress, via pronounced activation of barrier repair reactions, which is a combination of immune activation, epithelial migration and "wound-repair" like processes, compared to the CON piglets.

Discussion

Our study demonstrates the potential of early life nutrition in neonatal piglets as a means to support their intestinal development during the suckling period, and to improve adaptation during the weaning transition.

Lactating sows fed whey protein supplement has eventually increased the blood profile of piglets

BACKGROUND

The intension of this study was to examine the effect of dietary whey protein supplementation on the reproduction performance, growth performance and blood profile of sow and their offspring. From Day 114 of lactation to 21 days of weaning, a total of 21 sows (n = 7/ treatment) (Landrace × Yorkshire) were blocked according to average parity (2.4) and allocated to 1 of 3 dietary treatments: (i) CON-corn-soybean meal based basal diet, (ii) WPC-CON + 0.047% WPC whey protein concentrate (WPC) and (iii) WPH-CON + 0.02% whey protein hydrolysate (WPH).

RESULTS

The reproduction performance of sows was not affected by WPC or WPH supplementation. However, piglets that were born to WPC and WPH group sows showed higher body weight at birth (p = 0.057) and at weaning (p = 0.018). After farrowing, WPC and WPH group sows showed decreased (p = 0.043) RBC count and total iron-binding count (TIBC) (p = 0.046), whereas at the end of the experiment, the blood profile including red blood cells, iron, haemoglobulin and TIBC was significantly increased (p =0.042, 0.049, 0.051 and 0.052 respectively) in WPC group piglets compared to the CON and WPH groups.

CONCLUSION

Based on the positive impact on the blood profile of piglets, we conclude that whey protein supplement could serve as a potential energy source to suit lactating sows that could eventually benefit the performance of their offspring.

Embelin alleviates weaned piglets intestinal inflammation and barrier dysfunction via PCAF/NF-κB signaling pathway in intestinal epithelial cells

BACKGROUND

Intestinal barrier plays key roles in maintaining intestinal homeostasis. Inflammation damage can severely destroy the intestinal integrity of mammals. This study was conducted to investigate the protective effects of embelin and its molecular mechanisms on intestinal inflammation in a porcine model. One hundred sixty 21-day-old castrated weaned pigs (Duroc × Landrace × Yorkshire, average initial body weight was 7.05 ± 0.28 kg, equal numbers of castrated males and females) were allotted to four groups and fed with a basal diet or a basal diet containing 200, 400, or 600 mg embelin/kg for 28 d. The growth performance, intestinal inflammatory cytokines, morphology of jejunum and ileum, tight junctions in the intestinal mucosa of piglets were tested. IPEC-1 cells with overexpression of P300/CBP associating factor (PCAF) were treated with embelin, the activity of PCAF and acetylation of nuclear factor-κB (NF-κB) were analyzed to determine the effect of embelin on PCAF/NF-κB pathway in vitro.

RESULTS

The results showed that embelin decreased (P < 0.05) serum D-lactate and diamine oxidase (DAO) levels, and enhanced the expression of ZO-1, occludin and claudin-1 protein in jejunum and ileum. Moreover, the expression levels of critical inflammation molecules (interleukin-1β, interleukin-6, tumor necrosis factor-α, and NF-κB) were down-regulated (P < 0.05) by embelin in jejunal and ileal mucosa. Meanwhile, the activity of PCAF were down-regulated (P < 0.05) by embelin. Importantly, transfection of PCAF siRNAs to IPEC-1 cell decreased NF-κB activities; embelin treatment downregulated (P < 0.05) the acetylation and activities of NF-κB by 31.7%-74.6% in IPEC-1 cells with overexpression of PCAF.

CONCLUSIONS

These results suggested that embelin ameliorates intestinal inflammation in weaned pigs, which might be mediated by suppressing the PCAF/NF-κB signaling pathway.

Weaning stress and intestinal health of piglets: A review

Weaning is considered to be one of the most critical periods in pig production, which is related to the economic benefits of pig farms. However, in actual production, many piglets are often subjected to weaning stress due to the sudden separation from the sow, the changes in diet and living environment, and other social challenges. Weaning stress often causes changes in the morphology and function of the small intestine of piglets, disrupts digestion and absorption capacity, destroys intestinal barrier function, and ultimately leads to reduced feed intake, increased diarrhea rate, and growth retardation. Therefore, correctly understanding the effects of weaning stress on intestinal health have important guiding significance for nutritional regulation of intestinal injury caused by weaning stress. In this review, we mainly reviewed the effects of weaning stress on the intestinal health of piglets, from the aspects of intestinal development, and intestinal barrier function, thereby providing a theoretical basis for nutritional strategies to alleviate weaning stress in mammals in future studies.

Early Weaning Stress Induces Intestinal Microbiota Disturbance, Mucosal Barrier Dysfunction and Inflammation Response Activation in Pigeon Squabs

Early weaning stress has been reported to impair intestinal health in mammals. Like mammals, weaning of the pigeon squab, an altricial bird, is associated with social, environmental and dietary stress. However, understanding of weaning stress on intestinal functions is very limited in altricial birds, especially in squabs. This study was aimed to evaluate the effects of early weaning stress on intestinal microbiota diversity, architecture, permeability, the first line defense mechanisms, mucosal barrier functions, and immune cell responses. A total of 192 newly hatched squabs were randomly allocated into two groups, one weaned on day 7 and the other remained with the parent pigeons. Mucosal tissue and digesta in ileum, as well as blood samples, were collected from squabs (n = 8) on days 1, 4, 7, 10, and 14 postweaning. Our results showed that weaning stress induced immediate and long-term deleterious effects on both growth performance and intestinal barrier functions of squabs. Early weaning significantly increased ileal bacterial diversity and alters the relative abundance of several bacteria taxa. Weaning stress can also cause morphological and functional changes in ileum, including an atrophy in villi, an increase in permeability, and a variation in the mRNA expression of genes encoding mucins, immunoglobulins, tight junction proteins, toll-like receptors, and cytokines, as well as the concentration of secretory IgA. We concluded that the impaired intestinal barrier functions accompanied with early weaning stress seems to be the main reason for the poor growth rate after weaning in squabs. In addition, the disturbance of intestinal microbiota of early weaning stress in squabs coincided with dysfunction of intestinal mucosal barrier and activation of inflammation cell responses that were possibly mediated via the activation of toll-like receptors.

Glutamine, glutamate, and aspartate differently modulate energy homeostasis of small intestine under normal or low energy status in piglets

Weaning stress may cause reduced energy intake for maintenance of mucosal structure. Gln, Glu, and Asp are major energy sources for the small intestine. This study investigated whether Gln, Glu, and Asp improve the intestinal morphology via regulating the energy metabolism in weaning piglets. A total of 198 weaned piglets were assigned to 3 treatments: Control (Basal diet + 1.59% L-Ala); T1 (Basal diet + 1% L-Gln + 0.5% L-Glu + 0.1% L-Asp); T2 (Low energy diet + 1% L-Gln + 0.5% L-Glu + 0.1% L-Asp). Jejunum and ileum were obtained on d 5 or 21 post-weaning. T1 enhanced growth performance. T1 and T2 treatments improved small intestinal morphology by increasing villus height, goblet cell number and decreasing crypt depth. Days post-weaning affected the efficacy of T2, but not T1, on energy metabolism. At normal energy supplementation, Gln, Glu, and Asp restored small intestinal energy homeostasis via replenishing the Krebs' cycle and down-regulating the AMPK (adenosine monophosphate activated protein kinase) pathway. As these are not sufficient to maintain the intestinal energy-balance of piglets fed with a low energy diet on d 5 post-weaning, the AMPK, glycolysis, beta-oxidation, and mitochondrial biogenesis are activated to meet the high energy demand of enterocytes. These data indicated that Gln, Glu, and Asp could restore the energy homeostasis of intestinal mucosa of weaning piglets under normal energy fed. Low energy feeding may increase the susceptibility of piglets to stress, which may decrease the efficacy of Gln, Glu, and Asp on the restoration of energy balance. These findings provide new information on nutritional intervention for insufficient energy intake in weaning piglets.

Glutamate attenuates lipopolysaccharide induced intestinal barrier injury by regulating corticotropin-releasing factor pathway in weaned pigs

Objective

The purpose of this study was to evaluate the protection of glutamate (GLU) against the impairment in intestinal barrier function induced by lipopolysaccharide (LPS) stress in weaned pigs.

Methods

Twenty-four weaned pigs were divided into four treatments containing: i) non-challenged control, ii) LPS-challenged control, iii) LPS+1.0% GLU, and iv) LPS+2.0% GLU. On day 28, pigs were treated with LPS or saline. Blood samples were collected at 0, 2, and 4 h post-injection. After blood samples collection at 4 h, all pigs were slaughtered, and spleen, mesenteric lymph nodes, liver and intestinal samples were obtained.

Results

Dietary GLU supplementation inhibited the LPS-induced oxidative stress in pigs, as demonstrated by reduced malondialdehyde level and increased glutathione level in jejunum. Diets supplemented with GLU enhanced villus height, villus height/crypt depth and claudin-1 expression, attenuated intestinal histology and ultrastructure impairment induced by LPS. Moreover, GLU supplementation reversed intestinal intraepithelial lymphocyte number decrease and mast cell number increase induced by LPS stress. GLU reduced serum cortisol concentration at 4 h after LPS stress and downregulated the mRNA expression of intestinal corticotropin-releasing factor signal (corticotrophin-releasing factor [CRF], CRF receptor 1 [CRFR1], glucocorticoid receptor, tryptase, nerve growth factor, tyrosine kinase receptor A), and prevented mast cell activation. GLU upregulated the mRNA expression of intestinal transforming growth factor β.

Conclusion

These findings indicate that GLU attenuates LPS-induced intestinal mucosal barrier injury, which is associated with modulating CRF signaling pathway.

Zearalenone Exposure Triggered Cecal Physical Barrier Injury through the TGF-β1/Smads Signaling Pathway in Weaned Piglets

This study aims to investigate the effects of exposure to different dosages of zearalenone (ZEA) on cecal physical barrier functions and its mechanisms based on the TGF-β1/Smads signaling pathway in weaned piglets. Thirty-two weaned piglets were allotted to four groups and fed a basal diet supplemented with ZEA at 0, 0.15, 1.5, and 3.0 mg/kg, respectively. The results showed that 1.5 and 3.0 mg/kg ZEA damaged cecum morphology and microvilli, and changed distribution and shape of M cells. Moreover, 1.5 and 3.0 mg/kg ZEA decreased numbers of goblet cells, the expressions of TFF3 and tight junction proteins, and inhibited the TGF-β1/Smads signaling pathway. Interestingly, the 0.15 mg/kg ZEA had no significant effect on cecal physical barrier functions but decreased the expressions of Smad3, p-Smad3 and Smad7. Our study suggests that high-dose ZEA exposure impairs cecal physical barrier functions through inhibiting the TGF-β1/Smads signaling pathway, but low-dose ZEA had no significant effect on cecum morphology and integrity through inhibiting the expression of smad7. These findings provide a scientific basis for helping people explore how to reduce the toxicity of ZEA in feeds.

Postnatal growth retardation is associated with deteriorated intestinal mucosal barrier function using a porcine model

Individuals with postnatal growth retardation (PGR) are prone to developing chronic diseases. Abnormal development in small intestine is casually implicated in impaired growth. However, the exact mechanism is still implausible. In this present study, PGR piglets (aged 42 days) were employed as a good model to analyze developmental changes in intestinal mucosal barrier function. Our data demonstrated that PGR piglets exhibited impaired jejunal and ileal epithelial villous morphology and permeability, accompanied by decreased cell proliferation ability and increased apoptosis rate. In addition, the expression of tight junction proteins (ZO-1, claudin 1, and occludin) and E-cadherin was markedly inhibited by PGR. The expression of P-glycoprotein was significantly reduced in PGR piglets, as well as decreased activity of lysozyme. Moreover, the mRNA abundance and content of inflammatory cytokines were significantly increased in the intestinal mucosa and plasma of PGR piglets, respectively. PGR also contributed to lower level of sIgA, and higher level of CD68-positive rate, β-defensins, and protein expression involved p38 MAPK/NF-κB pathway. Furthermore, PGR altered the intestinal microbial community such as decreased genus Alloprevotella and Oscillospira abundances, and led to lower microbial-derived butyrate production, which may be potential targets for treatment. Collectively, our findings indicated that the intestinal mucosal barrier function of PGR piglets could develop the nutritional intervention strategies in prevention and treatment of the intestinal mucosal barrier dysfunction in piglets and humans.

Dietary supplementation of l-arginine and N-carbamylglutamate enhances duodenal barrier and mitochondrial functions and suppresses duodenal inflammation and mitophagy in suckling lambs suffering from intrauterine-growth-restriction

The current work aimed at investigating the effects of the dietary supplementation of N-carbamylglutamate (NCG) or l-arginine (Arg) on the duodenal mitophagy, mitochondrial function, inflammation, and barrier function in suckling lambs suffering from intrauterine-growth-retardation (IUGR). Forty-eight neonate Hu lambs were used in this study: 12 lambs with normal birth weight (NBW: 4.25 ± 0.14 kg) and 36 lambs with IUGR (3.01 ± 0.13 kg). Seven day old lambs were assigned to 4 treatment groups (12 lambs in each group) as follows: control group (CON), IUGR group, IUGR + Arg, and IUGR + NCG. Lambs were fed the experimental diets for 21 days from 7 days to 28 days of age. Compared with IUGR lambs, the Arg or NCG-treated IUGR lambs had a markedly higher duodenal transepithelial electrical resistance (TER) and lower fluorescein isothiocyanate dextran (FD4) (P < 0.05), respectively. The duodenal mitochondrial membrane potential change (ΔΨ_m), relative mitochondrial DNA (mtDNA) content, adenosine triphosphate (ATP) level, together with the activities of the respiratory complexes I, III, and IV were markedly higher in Arg or NCG-treated IUGR lambs than those in non-supplemented IUGR lambs (P < 0.05). The expressions of the integrity-related proteins (occludin and zonula occludens-1 (ZO-1)), antioxidant- and apoptosis-related proteins (B-cell lymphoma/leukaemia 2 (Bcl2), superoxide dismutase 2 (SOD2), catalase (CAT), and glutathione peroxidase 1 (GPx1)), and the nitric oxide-dependent pathway-related proteins (epithelial NO synthase (eNOS) and inducible NO synthase (iNOS)) were higher in NCG or Arg-supplemented IUGR lambs than those in nontreated IUGR lambs (P < 0.05). The duodenal expressions of the mitophagy-related proteins (microtubule-associated protein light chain 3 (LC3) I, LC3 II, Belin1, PTEN induced putative kinase 1 (PINK1), and Parkin) and the immune function-related proteins (myeloid differentiation factor 88 (MyD88), IL-6, nuclear factor kappa B (p65), toll-like receptor (TLR4) and TNF-α) were reduced (P < 0.05) in NCG or Arg-supplemented IUGR lambs compared with non-supplemented IUGR lambs. These results demonstrated that the dietary supplementation of Arg or NCG enhanced the duodenal barrier function and mitochondrial function, mitigated duodenal inflammation, and suppressed mitophagy in suckling lambs suffering from IUGR.

Burn-Induced Impairment of Ileal Muscle Contractility Is Associated with Increased Extracellular Matrix Components

INTRODUCTION

Severe burns lead to marked impairment of gastrointestinal motility, such as delayed gastric emptying and small and large intestinal ileus. However, the cellular mechanism of these pathologic changes remains largely unknown.

METHODS

Male Sprague Dawley rats approximately 3 months old and weighing 300-350 g were randomized to either a 60% total body surface area full-thickness scald burn or sham procedure and were sacrificed 24 h after the procedure. Gastric emptying, gastric antrum contractility ileal smooth muscle contractility, and colonic contractility were measured. Muscularis externa was isolated from the ileal segment to prepare smooth muscle protein extracts for Western blot analysis.

RESULTS

Compared with sham controls, the baseline rhythmic contractile activities of the antral, ileal, and colonic smooth muscle strips were impaired in the burned rats. Simultaneously, our data showed that ileal muscularis ECM proteins fibronectin and laminin were significantly up-regulated in burned rats compared with sham rats. TGF-β signaling is an important stimulating factor for ECM protein expression. Our results revealed that TGF-β signaling was activated in the ileal muscle of burned rats evidenced by the activation of Smad2/3 expression and phosphorylation. In addition, the total and phosphorylated AKT, which is an important downstream factor of ECM signaling in smooth muscle cells, was also up-regulated in burned rats' ileal muscle. Notably, these changes were not seen in the colonic or gastric tissues.

CONCLUSION

Deposition of fibrosis-related proteins after severe burn is contributors to decreased small intestinal motility.

Laminarin-rich extract improves growth performance, small intestinal morphology, gene expression of nutrient transporters and the large intestinal microbial composition of piglets during the critical post-weaning period

The identification of natural bioactive compounds which can prevent the post-weaning growth check and enhance gastrointestinal health in the absence of in-feed medications is an urgent priority for the swine industry. The objective of this experiment was to determine the effects of increasing dietary inclusion levels of laminarin in the first 14 d post-weaning on pig growth performance and weaning associated intestinal dysfunction. At weaning, ninety-six pigs (8·4 (sd 1·09) kg) (meatline boars × (large white × landrace sows)) were blocked by live weight, litter and sex and randomly assigned to: (1) basal diet; (2) basal + 100 parts per million (ppm) laminarin; (3) basal + 200 ppm laminarin and (4) basal + 300 ppm laminarin (three pigs/pen). The appropriate quantity of a laminarin-rich extract (65 % laminarin) was added to the basal diet to achieve the above dietary inclusion levels of laminarin. After 14 d of supplementation, eight pigs from the basal group and the best-performing laminarin group were euthanised for sample collection. The 300 ppm laminarin group was selected as this group had higher ADFI compared with all other groups and higher ADG than the basal group (P < 0·05). Laminarin supplementation increased villus height in the duodenum and jejunum (P < 0·05). Laminarin supplementation increased the expression of SLC2A8/GLUT8 in the duodenum, SLC2A2/GLUT2, SLC2A7/GLUT7, SLC15A1/PEPT1 and FABP2 in the jejunum and SLC16A1/MCT1 in the colon. Laminarin supplementation reduced Enterobacteriaceae numbers in the caecum (P < 0·05) and increased lactobacilli numbers (P < 0·05), total volatile fatty acid concentrations and the molar proportions of butyrate (P < 0·01) in the colon. In conclusion, 300 ppm laminarin from a laminarin-rich extract has potential, as a dietary supplement, to improve performance and prevent post-weaning intestinal dysfunction.

Growth Performance, Diarrhoea Incidence, and Nutrient Digestibility in Weaned Piglets Fed an Antibiotic-Free Diet with Dehydrated Porcine Plasma or Potato Protein Concentrate

Two experiments were conducted to test if dehydrated porcine plasma (DPP) and potato protein concentrate (PPC) could be used as an alternative to antibiotics in starter diets for piglets. Experiment one was conducted to test if DPP and PPC in an antibiotic-free diet affected pig performance, and faecal consistency. Eighty-four piglets weaned at 22 days and weighing 6.9 kg were used. Piglets were fed for two weeks with one of four diets: a positive control diet with antibiotics (C+); and three other diets without antibiotics added with DPP, PPC, or DPP and PPC (DPP+PPC) to measure the average daily feed intake (ADFI), average daily gain (ADG), feed efficiency (FE), and incidence and severity of diarrhoea (ID and ISD respectively). In experiment two, twenty-four piglets weaned at 17 days and weighing 5.7 kg, were implanted at 21 days of age with a T-cannula at the terminal ileum to measure the apparent ileal digestibility (AID) and the apparent total tract digestibility (ATTD) of nutrients. Piglets were fed one of four diets: a positive control diet with antibiotics (C+); a negative control diet without antibiotics (C–), and two diets without antibiotics added with DPP, or PPC. The results of experiment one showed that the DPP diet was the most consumed diet during the first week, and the ADG and FE were similar among treatments. During the second week and the total experimental period the ADFI, ADG, and FE were similar among diets. The ID was lower in the C+ diet than other diets. The ISD was lower in the C+ diet than DPP and DPP+PPC diets; piglets fed PPC diet were similar to piglets fed C+ and DPP and DPP+PPC diets. The results of digestibility showed that crude protein AID was higher in piglets fed C+ and PPC diets than C– and DPP diets. Dry matter ATTD and energy ATTD were higher for piglets fed PPC than other diets. Further, crude protein ATTD of DPP and PPC diets tended to have a similar digestibility to that of C+ diet. The results suggest that PPC is a potential controller of post-weaning diarrhoea.

Resveratrol improves intestinal barrier function, alleviates mitochondrial dysfunction and induces mitophagy in diquat challenged piglets1

This study evaluated whether resveratrol can alleviate intestinal injury and enhance the mitochondrial function and the mitophagy level in diquat induced oxidative stress of piglets.

Weaning disrupts intestinal antioxidant status, impairs intestinal barrier and mitochondrial function, and triggers mitophagy in piglets

In the present study, we investigated the influence of weaning on antioxidant status, intestinal integrity, mitochondrial function, and the mitophagy level in piglets (weaned at 21 d) during the 1 wk after weaning. The redox status was measured by antioxidant enzymes activities, related genes expression, and malondialdehyde (MDA) content in jejunum. The intestinal barrier function was assessed by the Ussing chamber and expression of tight junction proteins in the jejunum. The function of intestine mitochondria was measured by mitochondrial DNA (mtDNA) content and activities of mitochondria oxidative phosphorylation complexes. The levels of light chain 3-1 (LC3-I), light chain 3-II (LC3-II), PTEN-induced putative kinase 1 (PINK1), and Parkin were determined to investigate whether mitophagy is involved in the weaning process. The results showed that, as compared with the preweaning phase (d 0), weaning suppressed (P < 0.05) the activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) on d 3 and d 7 postweaning, decreased (P < 0.05) the expression of copper and zinc superoxide dismutase (Cu/Zn-SOD), manganese-containing superoxide dismutase (Mn-SOD) on d 3 postweaning, declined (P < 0.05) the level of glutathione peroxidase 1 (GPX-1) and glutathione peroxidase 4 (GPX-4) on d 3 and d 7 postweaning, and increased (P < 0.05) MDA content in jejunum on d 3 and d 7 postweaning. The jejunal transepithelial electrical resistance and levels of occludin, claudin-1, and zonula occludens-1 on d 3 and d 7 postweaning were reduced (P < 0.05), and paracellular flux of fluorescein isothiocyanatedextran (4 kDa) on d 3 and d 7 postweaning was increased (P < 0.05). Weaning induced mitochondrial dysfunction, as demonstrated by decreased (P < 0.05) content of mtDNA on d 3 and d 7 postweaning and declined (P < 0.05) activities of mitochondria complexes (I, II, III, IV) in jejunum on d 1, d 3, and d 7 postweaning. Weaning led to an increased (P < 0.05) expression level of mitophagy-related proteins, PINK1 and Parkin, in the intestinal mitochondria, as well as an enhancement (P < 0.05) of the ratio of LC3-II to LC3-I content in the jejunal mucosa on d 1, d 3, and d 7 postweaning. These results suggest that weaning disrupted intestinal oxidative balance, and this imbalance may impair intestinal barrier and mitochondrial function and trigger mitophagy in piglets.

LPS challenge increased intestinal permeability, disrupted mitochondrial function and triggered mitophagy of piglets

Here we investigated the influence of LPS-induced gut injury on antioxidant homeostasis, mitochondrial (mt) function and the level of mitophagy in piglets. The results showed that LPS-induced intestinal injury decreased the transepithelial electrical resistance, increased the paracellular permeability of F1TC dextran 4 kDa, and decreased the expression of claudin-1, occludin and zonula occludens-1 in the jejunum compared with the control group. LPS decreased the activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px), and increased the content of malondialdehyde in the jejunum. Meanwhile, the expression of SOD-related genes ( Cu/Zn-SOD, Mn-SOD) and GSH-Px-related genes ( GPX-1, GPX-4) declined in LPS-challenged pigs compared with the control. LPS also increased TNF-α, IL-6, IL-8 and IL-1β mRNA expression. LPS induced mt dysfunction, as demonstrated by increased reactive oxygen species production and decreased membrane potential of intestinal mitochondria, intestinal content of mt DNA and activities of the intestinal mt respiratory chain. Furthermore, LPS induced an increase in expression of mitophagy related proteins, PTEN-induced putative kinase (PINK1) and Parkin in the intestinal mitochondria, as well as an enhancement of the ratio of light chain 3-II (LC3-II) to LC3-I content in the jejunal mucosa. These results suggested that LPS-induced intestinal injury accompanied by disrupted antioxidant homeostasis, caused mt dysfunction and triggered mitophagy.

Qihuang decoction promotes the recovery of intestinal immune barrier dysfunction after gastrectomy in rats

OBJECTIVE

This study aims to observe the effect of Qihuang decoction on small intestinal mucosal barrier after gastrectomy in rats.

MATERIALS AND METHODS

A total of 80 Wistar rats were randomly divided into normal group, sham operation group, enteral nutrition group (EN) and Qihuang decoction group (EN+QH), there were 20 rats in each group. Both the EN group and the EN+QH group underwent gastrectomy. Instillation of enteral nutrition in the small intestine was performed after operation in the EN group. Instillation of enteral nutrition and Qihuang decoction in the small intestine was performed after operation in the EN+QH group. Only the abdominal incision and closing was performed in the sham operation group without drug and nutritional intervention. The expression levels of tight junction proteins in intestinal epithelial cells were determined by western blotting method. The sIgA content in different anatomic sites of intestinal mucosa was determined by double antibody-PEG radioimmunoassay technique. The number of IgA+B cells in different anatomic sites of intestinal mucosa was determined by immunohistochemical method.

RESULTS

The sIgA content in the sham operated group was significantly lower than that of normal group (P<0.05). The sIgA content and the number of IgA+B cells in Peyer's patches and lamina propria lym-phocytes in the EN+QH group were significantly higher than that of EN group (P<0.01, P<0.05). The expression levels of RhoA, Rac1 and Cdc42 increased in the EN group, and the phosphorylation levels of occludin, claudin-1, claudin-5, ZO-1 and ZO-2 also increased in the EN group, while the expression levels of non-phosphorylated occluding, claudin-1, claudin-5, ZO-1 and ZO-2 proteins decreased in the EN group (P<0.01, P<0.05). After treatment of Qihuang decoction for 7 days, compared with EN group, the expression levels of RhoA, Rac1 and Cdc42, and the phosphorylation levels of occludin, claudin-1, claudin-5, ZO-1 and ZO-2 significantly decreased in the EN+QH group, while the expression levels of non-phosphorylated occluding, claudin-1, claudin-5, ZO-1 and ZO-2 proteins significantly increased in the EN+QH group (P<0.01, P<0.05).

CONCLUSIONS

Qihuang decoction can promote the proliferation and differentiation of IgA+B lymphocytes and increase the sIgA content in intestinal mucosal immune barrier after gastrectomy in rats, it also can promote the expression of tight junction proteins to improve the permeability of intestinal mucosa and promote the recovery of intestinal immune barrier dysfunction in rats after gastrectomy by inhibiting the tight junction associated proteins' phosphorylation induced by Rho/ROCK signaling pathway.

TGF-β1 protects intestinal integrity and influences Smads and MAPK signal pathways in IPEC-J2 after TNF-α challenge

The aim of this study was to investigate the protective effects of TGF-β1 on intestinal epithelial barrier, as well as canonical Smad and MAPK signal pathways involved in these protection processes by a IPEC-J2 model stimulated with TNF-α. IPEC-J2 monolayers were treated without or with TNF-α in the absence or presence of TGF-β1. The results showed that TGF-β1 pretreatment ameliorated TNF-α-induced intestinal epithelial barrier disturbances as indicated by decrease of transepithelial electrical resistance (TER) and increase of paracellular permeability. TGF-β1 also dramatically alleviated TNF-α-induced alteration of TJ proteins ZO-1 and occludin. Moreover, TGF-β1 pretreatment increased TβRII protein expression in IPEC-J2 monolayers challenged with TNF-α. In addition, a significant increase of Smad4 and Smad7 mRNA was also observed in the TGF-β1 pretreatment after TNF-α challenge compared with the control group. Furthermore, TGF-β1 pretreatment enhanced smad2 protein activation. These results indicated that the canonical Smad signaling pathway was activated by TGF-β1 pretreatment. Finally, TGF-β1 pretreatment decreased the ratios of the phosphorylated to total JNK and p38 (p-JNK/JNK and p-p38/p38) and increased the ratio of ERK (p-ERK/ERK). Anti-TGF-β1 Abs reduced these TGF-β1 effects. These results indicated that TGF-β1 protects intestinal integrity and influences Smad and MAPK signal pathways in IPEC-J2 after TNF-α challenge.

Anemonin improves intestinal barrier restoration and influences TGF-β1 and EGFR signaling pathways in LPS-challenged piglets

The present study was aimed at investigating whether dietary anemonin could alleviate LPS-induced intestinal injury and improve intestinal barrier restoration in a piglet model. Eighteen 35-d-old pigs were randomly assigned to three treatment groups (control, LPS and LPS+anemonin). The control and LPS groups were fed a basal diet, and the LPS + anemonin group received the basal diet + 100 mg anemonin/kg diet. After 21 d of feeding, the LPS- and anemonin-treated piglets received i.p. administration of LPS; the control group received saline. At 4 h post-injection, jejunum samples were collected. The results showed that supplemental anemonin increased villus height and transepithelial electrical resistance, and decreased crypt depth and paracellular flux of dextran (4 kDa) compared with the LPS group. Moreover, anemonin increased tight junction claudin-1, occludin and ZO-1 expression in the jejunal mucosa, compared with LPS group. Anemonin also decreased TNF-α, IL-6, IL-8 and IL-1β mRNA expression. Supplementation with anemonin also increased TGF-β1 mRNA and protein expression, Smad4 and Smad7 mRNA expressions, and epidermal growth factor and epidermal growth factor receptor (EGFR) mRNA expression in the jejunal mucosa. These findings suggest that dietary anemonin attenuates LPS-induced intestinal injury by improving mucosa restoration, alleviating intestinal inflammation and influencing TGF-β1 canonical Smads and EGFR signaling pathways.

Diosmectite-zinc oxide composite improves intestinal barrier restoration and modulates TGF-β1, ERK1/2, and Akt in piglets after acetic acid challenge

The present study evaluated the beneficial effect of diosmectite-zinc oxide composite (DS-ZnO) on improving intestinal barrier restoration in piglets after acetic acid challenge and explored the underlying mechanisms. Twenty-four 35-d-old piglets (Duroc × Landrace × Yorkshire), with an average weight of 8.1 kg, were allocated to 4 treatment groups. On d 1 of the trial, colitis was induced via intrarectal injection of acetic acid (10 mL of 10% acetic acid [ACA] solution for ACA, DS-ZnO, and mixture of diosmectite [DS] and ZnO [DS+ZnO] groups) and the control group was infused with saline. Twenty-four hours after challenged, piglets were fed with the following diets: 1) control group (basal diet), 2) ACA group (basal diet), 3) DS-ZnO group (basal diet supplemented with DS-ZnO), and 4) DS+ZnO group (mixture of 1.5 g diosmectite [DS]/kg and 500 mg Zn/kg from ZnO [equal amount of DS and ZnO in the DS-ZnO treatment group]). On d 8 of the trial, piglets were sacrificed. The results showed that DS-ZnO supplementation improved (P < 0.05) ADG, ADFI, and transepithelial electrical resistance and decreased (P < 0.05) fecal scores, crypt depth, and fluorescein isothiocyanate-dextran 4 kDa (FD4) influx as compared with ACA group. Moreover, DS-ZnO increased (P < 0.05) occludin, claudin-1, and zonula occluden-1 expressions; reduced (P < 0.05) caspase-9 and caspase-3 activity and Bax expression; and improved (P < 0.05) Bcl2, XIAP, and PCNA expression. Diosmectite-zinc oxide composite supplementation also increased (P < 0.05) TGF-β1 expression and ERK1/2 and Akt activation. These results suggest that DS-ZnO attenuates the acetic acid-induced colitis by improving mucosa barrier restoration, inhibiting apoptosis, and improving intestinal epithelial cells proliferation and modulation of TGF-β1 and ERK1/2 and Akt signaling pathway.

Oral administration of putrescine and proline during the suckling period improves epithelial restitution after early weaning in piglets

Polyamines are necessary for normal integrity and the restitution after injury of the gastrointestinal epithelium. The objective of this study was to investigate the effects of oral administration of putrescine and proline during the suckling period on epithelial restitution after early weaning in piglets. Eighteen neonatal piglets (Duroc × Landrace × Large Yorkshire) from 3 litters (6 piglets per litter) were assigned to 3 groups, representing oral administration with an equal volume of saline (control), putrescine (5 mg/kg BW), and proline (25 mg/kg BW) twice daily from d 1 to weaning at 14 d of age. Plasma and intestinal samples were obtained 3 d after weaning. The results showed that oral administration of putrescine or proline increased the final BW and ADG of piglets compared with the control (P < 0.05). Proline treatment decreased plasma D-lactate concentration but increased the villus height in the jejunum and ileum, as well as the percentage of proliferating cell nuclear antigen (PCNA) positive cells and alkaline phosphatase (AKP) activity in the jejunal mucosa (P < 0.05). The protein expressions for zonula occludens (ZO-1), occludin, and claudin-3 (P < 0.05) but not mRNA were increased in the jejunum of putrescine- and proline-treated piglets compared with those of control piglets. The voltage-gated K+ channel (Kv) 1.1 protein expression in the jejunum of piglets administrated with putrescine and the Kv1.5 mRNA and Kv1.1 protein levels in the ileum of piglets administrated with proline were greater than those in control piglets (P < 0.05). These findings indicate that polyamine or its precursor could improve mucosal proliferation, intestinal morphology, as well as tight junction and potassium channel protein expressions in early-weaned piglets, with implications for epithelial restitution and barrier function after stress injury.

Developmental changes in intercellular junctions and Kv channels in the intestine of piglets during the suckling and post-weaning periods

Background

The intestinal epithelium is an important barrier that depends on a complex mixture of proteins and these proteins comprise different intercellular junctions. The purpose of this study was to investigate the postnatal and developmental changes in morphology, intercellular junctions and voltage-gated potassium (Kv) channels in the intestine of piglets during the suckling and post-weaning periods.

Results

Samples of the small intestine were obtained from 1-, 7-, 14-, and 21-d-old suckling piglets and piglets on d 1, 3, 5, and 7 after weaning at 14 d of age. The results showed that the percentage of proliferating cell nuclear antigen (PCNA)-positive cells and alkaline phosphatase (AKP) activity, as well as the abundances of E-cadherin, occludin, and Kv1.5 mRNA and claudin-1, claudin-3, and occludin protein in the jejunum were increased from d 1 to d 21 during the suckling period (P < 0.05). Weaning induced decreases in the percentage of PCNA-positive cells, AKP activity and the abundances of E-cadherin, occludin and zonula occludens (ZO)-1 mRNA or protein in the jejunum on d 1, 3 and 5 post-weaning (P < 0.05). There were lower abundances of E-cadherin, occludin and ZO-1 mRNA as well as claudin-1, claudin-3 and ZO-1 protein in the jejunum of weanling piglets than in 21-d-old suckling piglets (P < 0.05). The abundances of E-cadherin, occludin, ZO-1 and integrin mRNA were positively related to the percentage of PCNA-positive cells.

Conclusion

Weaning at 14 d of age induced damage to the intestinal morphology and barrier. While there was an adaptive restoration on d 7 post-weaning, the measured values did not return to the pre-weaning levels, which reflected the impairment of intercellular junctions and Kv channels.

Whey protein concentrate enhances intestinal integrity and influences transforming growth factor-β1 and mitogen-activated protein kinase signalling pathways in piglets after lipopolysaccharide challenge

Whey protein concentrate (WPC) has been reported to have protective effects on the intestinal barrier. However, the molecular mechanisms involved are not fully elucidated. Transforming growth factor-β1 (TGF-β1) is an important component in the WPC, but whether TGF-β1 plays a role in these processes is not clear. The aim of this study was to investigate the protective effects of WPC on the intestinal epithelial barrier as well as whether TGF-β1 is involved in these protection processes in a piglet model after lipopolysaccharide (LPS) challenge. In total, eighteen weanling pigs were randomly allocated to one of the following three treatment groups: (1) non-challenged control and control diet; (2) LPS-challenged control and control diet; (3) LPS+5 %WPC diet. After 19 d of feeding with control or 5 %WPC diets, pigs were injected with LPS or saline. At 4 h after injection, pigs were killed to harvest jejunal samples. The results showed that WPC improved (P<0·05) intestinal morphology, as indicated by greater villus height and villus height:crypt depth ratio, and intestinal barrier function, which was reflected by increased transepithelial electrical resistance and decreased mucosal-to-serosal paracellular flux of dextran (4 kDa), compared with the LPS group. Moreover, WPC prevented the LPS-induced decrease (P<0·05) in claudin-1, occludin and zonula occludens-1 expressions in the jejunal mucosae. WPC also attenuated intestinal inflammation, indicated by decreased (P<0·05) mRNA expressions of TNF-α, IL-6, IL-8 and IL-1β. Supplementation with WPC also increased (P<0·05) TGF-β1 protein, phosphorylated-Smad2 expression and Smad4 and Smad7 mRNA expressions and decreased (P<0·05) the ratios of the phosphorylated to total c-jun N-terminal kinase (JNK) and p38 (phospho-JNK:JNK and p-p38:p38), whereas it increased (P<0·05) the ratio of extracellular signal-regulated kinase (ERK) (phospho-ERK:ERK). Collectively, these results suggest that dietary inclusion of WPC attenuates the LPS-induced intestinal injury by improving mucosal barrier function, alleviating intestinal inflammation and influencing TGF-β1 canonical Smad and mitogen-activated protein kinase signalling pathways.

All-Trans Retinoic Acid Induces TGF-β2 in Intestinal Epithelial Cells via RhoA- and p38α MAPK-Mediated Activation of the Transcription Factor ATF2

Objective

We have shown previously that preterm infants are at risk of necrotizing enterocolitis (NEC), an inflammatory bowel necrosis typically seen in infants born prior to 32 weeks’ gestation, because of the developmental deficiency of transforming growth factor (TGF)-β₂ in the intestine. The present study was designed to investigate all-trans retinoic acid (atRA) as an inducer of TGF-β₂ in intestinal epithelial cells (IECs) and to elucidate the involved signaling mechanisms.

Methods

AtRA effects on intestinal epithelium were investigated using IEC6 cells. TGF-β₂ expression was measured using reverse transcriptase-quantitative polymerase chain reaction (RT-qPCR) and Western blots. Signaling pathways were investigated using Western blots, transiently-transfected/transduced cells, kinase arrays, chromatin immunoprecipitation, and selective small molecule inhibitors.

Results

AtRA-treatment of IEC6 cells selectively increased TGF-β₂ mRNA and protein expression in a time- and dose-dependent fashion, and increased the activity of the TGF-β₂ promoter. AtRA effects were mediated via RhoA GTPase, Rho-associated, coiled-coil-containing protein kinase 1 (ROCK1), p38α MAPK, and activating transcription factor (ATF)-2. AtRA increased phospho-ATF2 binding to the TGF-β₂ promoter and increased histone H2B acetylation in the TGF-β₂ nucleosome, which is typically associated with transcriptional activation.

Conclusions

AtRA induces TGF-β₂ expression in IECs via RhoA- and p38α MAPK-mediated activation of the transcription factor ATF2. Further studies are needed to investigate the role of atRA as a protective/therapeutic agent in gut mucosal inflammation.