Lipopolysaccharide endotoxemia reduces cell proliferation and decreases enterocyte apopotosis during intestinal adaptation in a rat model of short-bowel syndrome

Effects of Dietary Supplementation of Recombinant Plectasin on Growth Performance, Intestinal Health and Innate Immunity Response in Broilers

The present study was conducted to evaluate the effects of dietary supplementation of recombinant plectasin (Ple) on the growth performance, intestinal health, and serum immune parameters in broilers. A total of 288 1-day-old male broilers (Arbor Acres) were randomly allotted to four dietary treatments including the basal diet (NC) and basal diet supplemented with 10 mg enramycin/kg (PC), 100 mg Ple/kg (LPle), and 200 mg Ple/kg (HPle) diets. The results indicated Ple increased (P < 0.01) average daily gain and decreased (P ≤ 0.02) feed to gain ratio of broilers. In addition, the supplementation of Ple in the diets increased (P ≤ 0.01) duodenal lipase (day 21) and trypsin (day 42) activities compared with the NC group. Similar as the supplementation of enramycin, Ple also increased villus height and decreased crypt depth in jejunum (day 21), and thus the villus height to crypt depth ratio (P < 0.01) was increased compared to the NC group on day 42. The serum immunoglobulin M (days 21 and 42), immunoglobulin G (day 42), complement 3 (day 21), and complement 4 (days 21 and 42) were significantly increased (P ≤ 0.02) due to the supplementation of Ple and enramycin, while the concentration of malondialdehyde in jejunum was decreased (P < 0.01) in PC, LPle, and HPle groups on day 21 compared with those in the NC group. Furthermore, Ple reduced (P < 0.01) Escherichia coli and total aerobic bacteria population in ileum and cecum of birds on days 21 and 42. These results indicate that the recombinant plectasin has beneficial effects on growth performance, intestinal health, and innate immunity in broilers.

Microbial Metabolites and Intestinal Stem Cells Tune Intestinal Homeostasis

Microorganisms that colonize the gastrointestinal tract, collectively known as the gut microbiota, are known to produce small molecules and metabolites that significantly contribute to host intestinal development, functions, and homeostasis. Emerging insights from microbiome research reveal that gut microbiota-derived signals and molecules influence another key player maintaining intestinal homeostasis-the intestinal stem cell niche, which regulates epithelial self-renewal. In this review, the literature on gut microbiota-host crosstalk is surveyed, highlighting the effects of gut microbial metabolites on intestinal stem cells. The production of various classes of metabolites, their actions on intestinal stem cells are discussed and, finally, how the production and function of metabolites are modulated by aging and dietary intake is commented upon.

Increased intestinal permeability in patients with short bowel syndrome is not affected by parenteral nutrition

The aim of our study was to assess the presence and degree of intestinal leakage in subjects suffering from short bowel syndrome (SBS) and its modification by parenteral nutrition. To this end we assessed circulating levels of selected makers of intestinal permeability including zonulin, fatty acid binding protein 2 (FABP-2), citrulline and glucagon-like peptide 2 (GLP-2). We also measured lipopolysaccharide binding protein (LBP) as a marker of circulating levels of lipopolysaccharide acting through the CD14 molecule. Eleven SBS and 10 age- and BMI-matched control subjects were included into the study. The effect of parenteral nutrition was assessed after 14 days, 6 and 12 months from its initiation, respectively. At baseline, SBS patients had increased gut permeability as measured by zonulin (47.24+/-2.14 vs. 39.48+/-1.20 ng/ml, p=0.006) and LBP (30.32+/-13.25 vs. 9.77+/-0.71 microg/ml, p<0.001) compared to healthy controls. Furthermore, SBS subjects had reduced FABP-2, unchanged citrulline and increased sCD14 and GLP-2 relative to control group. Throughout the whole study period the administered parenteral nutrition had no significant effect on any of the studied parameters. Taken together, our data show that patients with short bowel syndrome have increased intestinal permeability that is not affected by parenteral nutrition.

Lipopolysaccharide from Crypt-Specific Core Microbiota Modulates the Colonic Epithelial Proliferation-to-Differentiation Balance

We identified a crypt-specific core microbiota (CSCM) dominated by strictly aerobic, nonfermentative bacteria in murine cecal and proximal colonic (PC) crypts and hypothesized that, among its possible functions, it may affect epithelial regeneration. In the present work, we isolated representative CSCM strains using selective media based upon our initial 16S rRNA-based molecular identification (i.e., Acinetobacter, Delftia, and Stenotrophomonas). Their tropism for the crypt was confirmed, and their influence on epithelial regeneration was demonstrated in vivo by monocolonization of germfree mice. We also showed that lipopolysaccharide (LPS), through its endotoxin activity, was the dominant bacterial agonist controlling proliferation. The relevant molecular mechanisms were analyzed using colonic crypt-derived organoids exposed to bacterial sonicates or highly purified LPS as agonists. We identified a Toll-like receptor 4 (TLR4)-dependent program affecting crypts at different stages of epithelial differentiation. LPS played a dual role: it repressed cell proliferation through RIPK3-mediated necroptosis of stem cells and cells of the transit-amplifying compartment and concurrently enhanced cell differentiation, particularly the goblet cell lineage.

The LPS from crypt-specific core microbiota controls intestinal epithelium proliferation through necroptosis of stem cells and enhances cell differentiation, mainly the goblet cell lineage.

Dose-response effects of an antimicrobial peptide, a cecropin hybrid, on growth performance, nutrient utilisation, bacterial counts in the digesta and intestinal morphology in broilers

The aim of the present study was to evaluate the feasibility of an antimicrobial peptide, cecropin A(1-11)-D(12-37)-Asn (CADN), as an alternative to antibiotic growth promoter (AGP) in poultry diets. A total of 1500 14-d-old indigenous male chickens (222 (sd 13) g) were randomly allocated to five groups with five replicate cages of sixty birds each, and fed ad libitum five grower diets and subsequently five finisher diets for 14 d each. The diets were made up by supplementing their basal diets with a CADN liquid sample (CADNL) at 0, 2, 4, 6 and 8 ml/kg, respectively. During the feeding period, a metabolic experiment was carried out to determine the apparent digestibility of diethyl ether extract, nitrogen retention and apparent metabolisable energy of the diet sample fed to each cage of chicks. At the end of the feeding experiment, one chick from each cage was killed for bacteriological, light microscopic and scanning electron microscopic examination of the intestinal villi. CADN had a negative linear, positive quadratic and negative linear effect on feed intake (F), weight gain (G) and feed:gain ratio (F:G), respectively, for the growers; it had a quadratic effect on F, G or F:G for the finishers; it increased nutrient utilisation for both growers and finishers; it decreased aerobic bacterial counts in both jejunal and caecal digesta in a dose-dependent manner; it enhanced intestinal villus heights in a dose-dependent manner and made the duodenum villi of the CADNL8 group at 42 d appear as a netted leaf-like structure. CADN is therefore a possible alternative to AGP in broiler feeds.

Ursodeoxycholic acid promotes intestinal adaptation in a cat model of short bowel syndrome

The aim of this study was to assess the effect of ursodeoxycholic acid (UDCA) on the morphological and functional adaptive response of the jejunal remnant after massive intestinal resection in a cat model of short bowel syndrome (SBS). UDCA was administered to animals at a daily oral dose of 15 mg/kg for 6 weeks following a 85% jejunoileal resection. Resection alone caused extensive hyperplasia of jejunal mucosa, as evidenced by a significant increase in the weight of jejunal mucosa per unit length as well as by significant increases in DNA and protein concentration but no change in the protein/DNA ratio. Morphometric analysis using microscopy revealed no changes in jejunal mucosa thickness, jejunal crypt depth, villus height and villus surface area, although villus thickness was increased. The specific activities of jejunal sucrase and alkaline phosphatase were unaffected. UDCA treatment of resected animals, using doses that caused no toxicity, as evidenced by the absence of serum biochemistry abnormalities and histopathology, did not induce, compared to resection alone, any changes in mucosal cellularity and did not affect villus morphometry. On the other hand, UDCA administration increased crypt depth and, also, induced a profound increase in the specific activity of sucrase. UDCA improved diarrhoea, a core SBS symptom, reflected in a considerably reduced frequency of defaecation and improved form and texture of faeces. It is concluded that UDCA administration may enhance the natural adaptive response of the intestinal remnant following massive jejunoileal resection and may, thus, be beneficial in SBS treatment.

Detectable serum flagellin and lipopolysaccharide and upregulated anti-flagellin and lipopolysaccharide immunoglobulins in human short bowel syndrome

Gut barrier dysfunction may occur in short bowel syndrome (SBS). We hypothesized that systemic exposure to flagellin and lipopolysaccharide (LPS) in SBS might regulate specific immune responses. We analyzed serial serum samples obtained from parenteral nutrition (PN)-dependent patients with SBS versus non-SBS control serum. Serum from 23 adult SBS patients was obtained at baseline and 4, 8, 12, 16, 20, and 24 wk in a trial of modified diet with or without growth hormone. Control serum was obtained from 48 healthy adults and 37 adults requiring PN during critical illness. Serum flagellin was detected by an ELISA recognizing an array of gram-negative flagellins, and LPS was detected by limulus assay. Serum flagellin- and LPS-specific immunoglobulin levels (IgM, IgA, and IgG) were determined by ELISA. Serum flagellin and LPS were undetectable in control subjects. In contrast, serum flagellin, LPS, or both were detected in 14 SBS patients (61%) during one or more time points [flagellin alone, 5/23 (22%); LPS alone, 6/23 (26%); or flagellin + LPS, 3/23 (13%)]. Flagellin-specific serum IgM, IgA, and IgG levels were markedly increased in SBS patients compared with both control populations and remained elevated during the 6-mo study period. LPS-specific IgA was significantly higher in SBS patients compared with healthy controls; LPS-specific IgM, IgA, and IgG levels each decreased over time in association with PN weaning. We conclude that adults with PN-dependent SBS are systemically exposed to flagellin and LPS, presumably from the gut lumen. This likely regulates innate and adaptive immune responses to these specific bacterial products.

A critical role for TLR4 in the pathogenesis of necrotizing enterocolitis by modulating intestinal injury and repair

Necrotizing enterocolitis (NEC) is the leading cause of death from gastrointestinal disease in preterm infants and is characterized by translocation of LPS across the inflamed intestine. We hypothesized that the LPS receptor (TLR4) plays a critical role in NEC development, and we sought to determine the mechanisms involved. We now demonstrate that NEC in mice and humans is associated with increased expression of TLR4 in the intestinal mucosa and that physiological stressors associated with NEC development, namely, exposure to LPS and hypoxia, sensitize the murine intestinal epithelium to LPS through up-regulation of TLR4. In support of a critical role for TLR4 in NEC development, TLR4-mutant C3H/HeJ mice were protected from the development of NEC compared with wild-type C3H/HeOUJ littermates. TLR4 activation in vitro led to increased enterocyte apoptosis and reduced enterocyte migration and proliferation, suggesting a role for TLR4 in intestinal repair. In support of this possibility, increased NEC severity in C3H/HeOUJ mice resulted from increased enterocyte apoptosis and reduced enterocyte restitution and proliferation after mucosal injury compared with mutant mice. TLR4 signaling also led to increased serine phosphorylation of intestinal focal adhesion kinase (FAK). Remarkably, TLR4 coimmunoprecipitated with FAK, and small interfering RNA-mediated FAK inhibition restored enterocyte migration after TLR4 activation, demonstrating that the FAK-TLR4 association regulates intestinal healing. These findings demonstrate a critical role for TLR4 in the development of NEC through effects on enterocyte injury and repair, identify a novel TLR4-FAK association in regulating enterocyte migration, and suggest TLR4/FAK as a therapeutic target in this disease.

Two-hit rat model of short bowel syndrome and sepsis: independent of total parenteral nutrition, short bowel syndrome is proinflammatory and injurious to the liver

INTRODUCTION

Infants with short bowel syndrome (SBS) are at a high risk for infectious complications and liver failure. We hypothesized that SBS, independent of total parenteral nutrition, is a proinflammatory state that is magnified by sepsis.

METHODS

Sprague-Dawley rats were divided into 2 groups: sham laparotomy (SH, n = 10) or 75% small bowel resection (n = 10). After 14 days, each group underwent a second sham laparotomy (SH/SH and SBS/SH) or cecal ligation and puncture, followed 16 hours later by cecal excision and peritoneal washout (SH/sepsis and SBS/sepsis). Animals were killed 56 hours later.

RESULTS

The SBS rats had higher serum levels of interleukin (IL) 6 vs SH (355 +/- 99 vs 104 +/- 71 pg/mL, P < .05). Liver injury scores were higher in SBS/sepsis compared with SBS/SH animals (3.7 +/- 0.7 vs 1.9 +/- 0.3, P < .05). Hepatic messenger RNA levels of IL-6 (12.8-fold change [FC]) and tumor necrosis factor alpha (5.65 FC) were elevated in SBS vs SH rats; and IL-6 (114 FC), tumor necrosis factor alpha (3.87 FC), and Toll-like receptor 4 (7.65 FC) were increased in SBS/sepsis compared with SH/sepsis animals.

CONCLUSION

Our results suggest that SBS, independent of total parenteral nutrition, is a proinflammatory state and that sepsis induces an exaggerated proinflammatory cytokine response that may play an important role in liver damage and may be mediated by Toll-like receptor 4.

Sepsis: Prognostic Role of Apoptosis Regulators in Gastrointestinal Cells

BACKGROUND

Intestinal epithelial cell apoptosis has been reported in sepsis as a mechanism of organ failure. The aim of this study was to clarify the role of apoptosis-regulating proteins (bcl-2, bax, cytochrome-c, and caspase-8) in septic rats by studying their expression in gastric and intestinal epithelial cells.

METHODS

Adult Wistar rats were subjected to the cecal ligation and puncture (CLP) model of sepsis and randomly divided into two study groups. Sixty-two animals were sacrificed 6, 12, 24, 36, 48, and 60 h post-procedure, and 50 animals served as the survival study group. Sham-operated animals (n = 40) were used as controls. Gastric and intestinal tissue was excised, and immunohistochemical detection of bcl-2, bax, cytochrome-c, and caspase-8 protein expression was performed.

RESULTS

In gastric mucosa, sepsis induced upregulation of bax and downregulation of caspase-8 expression (p = 0.053 and p = 0.05, respectively). Both bax and caspase-8 were upregulated as early as 6 h post CLP and progressively decreased (p = 0.001, p = 0.004 respectively). In contrast, the expression of the anti-apoptotic bcl-2 was upregulated progressively during the sepsis syndrome (p = 0.03). In intestine, sepsis induced a fourfold upregulation of the cytoprotective bcl-2 (p = 0.0001), accompanied by a remarkable increase in bax (p = 0.002) and caspase-8 (p = 0.0001) expression and a decrease in cytochrome-c expression (p = 0.02). The time distribution of the apoptosis regulators followed the same pattern as in gastric tissue, showing an upregulation of the proapoptotic bax and cytochrome c (p = 0.04) during the early phases and a progressively increased expression of bcl-2 during the late phases (p = 0.0001). Bax expression in gastric epithelium of subjects with septic syndrome was detrimental to survival (p = 0.0001), whereas the expression of the cytoprotective bcl-2 in intestinal epithelium appeared to favor a good prognosis (p = 0.0001).

CONCLUSIONS

Sepsis results in alterations of apoptosis regulators in gastrointestinal cells. Alterations of bax and bcl-2 expression in gastric and intestinal epithelial cells may predict the outcome in septic rats.

Review article: intestinal failure

Intestinal failure is a specific disease entity resulting from intestinal resection or disease-associated malabsorption and characterized by the inability to maintain protein-energy, fluid, electrolyte or micronutrient balance. We performed a MEDLINE search (1966-2006) to identify relevant articles, using keywords intestinal failure, parenteral or enteral nutrition, intestinal fistula and short bowel syndrome. Causes of intestinal failure are varied, with self-limiting or 'Type 1' intestinal failure occurring relatively commonly following abdominal surgery, necessitating short-term fluid or nutritional support. The rarer, 'Type 2' intestinal failure, is associated with septic, metabolic and complex nutritional complications, usually following surgical resection in patients with Crohn's or mesenteric vascular disease. A multidisciplinary approach to the management of patients with Type 2 intestinal failure is crucial: resolution of sepsis is required before adequate nutritional repletion can be achieved, and it is important to optimize nutritional status, not only through enteral or parenteral supplementation, but also by addressing complications of short bowel syndrome, before considering definitive surgical reconstruction. A structured approach to the management of Type 2 intestinal failure should reduce the likelihood of these complex patients developing 'Type 3' intestinal failure, which is characterized by the need for long-term parenteral nutrition.

Enterocyte apoptosis after enterectomy in mice is activated independent of the extrinsic death receptor pathway

Intestinal adaptation following small bowel resection (SBR) is associated with greater rates of enterocyte apoptosis by unknown mechanism(s). Because postresection adaptation is associated with increased translocation of luminal bacteria, we sought to characterize the role for the extrinsic, death receptor pathway for the activation of enterocyte apoptosis after massive SBR. We first performed SBR or sham operations in mice, and the temporal expression of caspases 8, 9, and 3, death receptors tumor necrosis factor receptor-1 (TNFR1) and Fas and corresponding ligands (TNF and Fas ligand) was determined in the remnant intestine at various postoperative time points. Ileal TNFR1 and Fas expression were then measured after SBR in the setting of increased (waved-2 mice) or decreased (exogenous EGF administration) apoptosis. Finally, intestinal adaptation and apoptosis were recorded in the remnant ileum after SBR in TNFR1-null and Fas-null mice. The expression of death receptor family proteins and caspases demonstrated only modest changes after SBR and did not correlate with the histological appearance of apoptosis. In the setting of accelerated apoptosis, TNFR1 and Fas expression were paradoxically decreased. Apoptotic and adaptive responses were preserved in both TNFR1-null and Fas-null mice. These results suggest that the mechanism for increased enterocyte apoptosis following massive SBR does not appear to involve the extrinsic, death receptor-mediated pathway.