Decline in intestinal mucosal IL-10 expression and decreased intestinal barrier function in a mouse model of total parenteral nutrition

Parenteral Nutrition, Inflammatory Bowel Disease, and Gut Barrier: An Intricate Plot

Malnutrition poses a critical challenge in inflammatory bowel disease, with the potential to detrimentally impact medical treatment, surgical outcomes, and general well-being. Parenteral nutrition is crucial in certain clinical scenarios, such as with patients suffering from short bowel syndrome, intestinal insufficiency, high-yielding gastrointestinal fistula, or complete small bowel obstruction, to effectively manage malnutrition. Nevertheless, research over the years has attempted to define the potential effects of parenteral nutrition on the intestinal barrier and the composition of the gut microbiota. In this narrative review, we have gathered and analyzed findings from both preclinical and clinical studies on this topic. Based on existing evidence, there is a clear correlation between short- and long-term parenteral nutrition and negative effects on the intestinal system. These include mucosal atrophic damage and immunological and neuroendocrine dysregulation, as well as alterations in gut barrier permeability and microbiota composition. However, the mechanistic role of these changes in inflammatory bowel disease remains unclear. Therefore, further research is necessary to effectively address the numerous gaps and unanswered questions pertaining to these issues.

Black soldier fly pulp in the diet of golden pompano: Effect on growth performance, liver antioxidant and intestinal health

Black soldier fly (Hermetia illucens) has been widely researched as a protein source for fish meal replacement in aquaculture, but few studies have focused on its potential as a feed additive for growth and immune enhancement. We conducted a 56-day culture experiment to determine the impact of feed addition of black soldier fly pulp (BSFP, with 86.2% small peptides in dry basis) on growth performance, plasma biochemistry, liver antioxidant levels, intestinal immunity, digestion and microbiota of juvenile golden pompano (Trachinotus ovatus, 5.63 ± 0.02 g). BSFP was added to the basal diet at 0%, 1%, 3%, 5%, 7% and 9% (named Control, BSFP-1, BSFP-3, BSFP-5, BSFP-7, BSFP-9), respectively. BSFP increased the weight gain rate, specific growth rate, protein efficiency ratio and reduced the feed conversion rate of juvenile T. ovatus, the optimal growth performance was reached at BSFP-1, after which a negative feedback phenomenon was observed. Low levels of BSFP upregulated the expression of hepatic antioxidant, intestinal tight junctions, anti-inflammatory related genes and enhanced antioxidant, immune and intestinal digestive enzyme activities, which simultaneously reduced hepatic malondialdehyde and plasma aspartate transaminase and alanine aminotransferase concentrations. However, at BSFP-7, catalase activity was significantly reduced, while NF-κB p65 and pro-inflammatory cytokines transcription was significantly enhanced (P < 0.05). The results suggest that high doses of BSFP addition may damage fish health by inhibiting small peptide uptake, decreasing the activity of antioxidant enzyme and activating the canonical NF-κB pathway. Conversely, low doses of BSFP enhanced intestinal tight junction protein transcription, digestive enzyme activity and immune performance, inhibited pathogenic microbiota, while enhancing liver antioxidant capacity, which was associated with activated Nrf2-Keap1 pathway and suppressed NF-κB pathway, showing its potential as a feed additive to aquafeeds.

Cytokines and intestinal epithelial permeability: A systematic review

BACKGROUND

The intestinal mucosa is composed of a well-organized epithelium, acting as a physical barrier to harmful luminal contents, while simultaneously ensuring absorption of physiological nutrients and solutes. Increased intestinal permeability has been described in various chronic diseases, leading to abnormal activation of subepithelial immune cells and overproduction of inflammatory mediators. This review aimed to summarize and evaluate the effects of cytokines on intestinal permeability.

METHODS

A systematic review of the literature was performed in the Medline, Cochrane and Embase databases, up to 01/04/2022, to identify published studies assessing the direct effect of cytokines on intestinal permeability. We collected data on the study design, the method of assessment of intestinal permeability, the type of intervention and the subsequent effect on gut permeability.

RESULTS

A total of 120 publications were included, describing a total of 89 in vitro and 44 in vivo studies. TNFα, IFNγ or IL-1β were the most frequently studied cytokines, inducing an increase in intestinal permeability through a myosin light-chain-mediated mechanism. In situations associated with intestinal barrier disruption, such as inflammatory bowel diseases, in vivo studies showed that anti-TNFα treatment decreased intestinal permeability while achieving clinical recovery. In contrast to TNFα, IL-10 decreased permeability in conditions associated with intestinal hyperpermeability. For some cytokines (e.g. IL-17, IL-23), results are conflicting, with both an increase and a decrease in gut permeability reported, depending on the study model, methodology, or the studied conditions (e.g. burn injury, colitis, ischemia, sepsis).

CONCLUSION

This systematic review provides evidence that intestinal permeability can be directly influenced by cytokines in numerous conditions. The immune environment probably plays an important role, given the variability of their effect, according to different conditions. A better understanding of these mechanisms could open new therapeutic perspectives for disorders associated with gut barrier dysfunction.

Dihydromyricetin Attenuates High-Intensity Exercise-Induced Intestinal Barrier Dysfunction Associated with the Modulation of the Phenotype of Intestinal Intraepithelial Lymphocytes

BACKGROUND

Exercise-induced gastrointestinal syndrome (GIS) has symptoms commonly induced by strenuous sports. The study aimed to determine the effect of dihydromyricetin (DHM) administration on high-intensity exercise (HIE)-induced intestinal barrier dysfunction and the underlying mechanism involved with intestinal intraepithelial lymphocytes (IELs).

METHODS

The HIE model was established with male C57BL/6 mice using a motorized treadmill for 2 weeks, and DHM was given once a day by oral gavage. After being sacrificed, the small intestines of the mice were removed immediately.

RESULTS

We found that DHM administration significantly suppressed HIE-induced intestinal inflammation, improved intestinal barrier integrity, and inhibited a HIE-induced increase in the number of IELs and the frequency of CD8αα⁺ IELs. Meanwhile, several markers associated with the activation, gut homing and immune functions of CD8αα⁺ IELs were regulated by DHM. Mechanistically, luciferase reporter assay and molecular docking assay showed DHM could activate the aryl hydrocarbon receptor (AhR).

CONCLUSIONS

These data indicate that DHM exerts a preventive effect against HIE-induced intestinal barrier dysfunction, which is associated with the modulation of the quantity and phenotype of IELs in the small intestine. The findings provide a foundation to identify novel preventive strategies based on DHM supplementation for HIE-induced GIS.

Selective Role of TNFα and IL10 in Regulation of Barrier Properties of the Colon in DMH-Induced Tumor and Healthy Rats

Recently it has been reported that the tumor adjacent colon tissues of 1,2-dymethylhydrazine induced (DMH)-rats revealed a high paracellular permeability. We hypothesized that the changes might be induced by cytokines. Colorectal cancer is accompanied by an increase in tumor necrosis factor alpha (TNFα) and interleukin 10 (IL10) that exert opposite regulatory effects on barrier properties of the colon, which is characterized by morphological and functional segmental heterogeneity. The aim of this study was to analyze the level of TNFα and IL10 in the colon segments of DMH-rats and to investigate their effects on barrier properties of the proximal and distal parts of the colon in healthy rats. Enzyme immunoassay analysis showed decreased TNFα in tumors in the distal part of the colon and increased IL10 in proximal tumors and in non-tumor tissues. Four-hour intraluminal exposure of the colon of healthy rats with cytokines showed reduced colon barrier function dependent on the cytokine: TNFα decreased it mainly in the distal part of the colon, whereas IL10 decreased it only in the proximal part. Western blot analysis revealed a more pronounced influence of IL10 on tight junction (TJ) proteins expression by down-regulation of the TJ proteins claudin-1, -2 and -4, and up-regulation of occludin only in the proximal part of the colon. These data may indicate a selective role of the cytokines in regulation of the barrier properties of the colon and a prominent role of IL10 in carcinogenesis in its proximal part.

Rhizoma curcumae Longae ameliorates high dietary carbohydrate-induced hepatic oxidative stress, inflammation in golden pompano Trachinotus ovatus

In general, starch, as a complex carbohydrate, is the most economical energy source in aquaculture for its relatively low cost. However, excessive dietary levels of carbohydrate result in pathological conditions. An 8-week feeding trial with CT (control diet, containing 21% carbohydrate), HC (a high-carbohydrate diet, containing 50% carbohydrate) and HCR (a HC diet supplemented with 0.015% Rhizoma curcumae Longae) was performed to investigate the protective effect of curcumin on high-carbohydrate-induced hepatic oxidative stress and intestine lesion in juvenile Trachinotus ovatus. In the current study, HC group significantly decreased WGR, SGR, plasma CAT activity, intestinal C4 levels, hepatic Nrf2, Keap1, Bach1, HO1, CAT, and GPX mRNA expression as well as ZO-1, Occludin, and Claudin-3, TGF-β mRNA transcription levels, while the opposite was true for plasma AST activity, hepatic MDA contents, intestinal Claudin-15, NF-κB, IL-1β, IL-6, and TNF-α mRNA expression. In contrast with the HC group, the HCR group significantly increased the activities of hepatic CAT, SOD, intestinal C3, C4, IgG and LZM levels, hepatic Nrf2, Bach1, CAT, and GPX mRNA expression as well as intestinal ZO-1, Occludin, Claudin-3, TGF-β and IL-10 mRNA expression levels, but the opposite trend was found in plasma triglyceride content, hepatic lipid deposition, hepatic Keap1 mRNA level as well as intestinal NF-κB, IL-6. In conclusion, high-carbohydrate diet can cause detrimental effect on physiological health status in Trachinotus ovatus, while adding Rhizoma curcumae Longae can improve hepatic and intestinal health status via attenuating the oxidative stress, inflammation, and reducing lipid deposition.

Regulatory role of short-chain fatty acids in inflammatory bowel disease

Inflammatory bowel disease (IBD) comprises a group of chronic inflammatory disorders of the gastrointestinal tract. Accumulating evidence shows that the development of IBD is always accompanied by the dysbiosis of the gut microbiota (GM), causing a decrease in prebiotic levels and an increase in harmful metabolite levels. This leads to persistent immune response and inflammation in the intestine, greatly impairing the physiological function of the gastrointestinal tract. Short-chain fatty acids (SCFAs) are produced by probiotic gut bacteria from a fiber-rich diet that cannot be digested directly. SCFAs with significant anti-inflammatory functions regulate immune function and prevent an excessive immune response, thereby delaying the clinical progression of IBD. In this review, we summarize the generation of SCFAs and their potential therapeutic effects on IBD. Furthermore, we suggest that SCFAs may modulate innate immune recognition and cytokine production to intervene in the progression of IBD. Additional randomized controlled trials and prospective cohort studies should also investigate the clinical impact of SCFA. Video Abstract.

The Pathology and Physiology of Ileostomy

An ileostomy is a surgery that is commonly performed to protect low pelvic anastomoses or prevent high-risk anastomotic leakages. However, various postoperative complications remain of major concern. After an ileostomy, the distal intestinal segment is left open for an extended period and is in a non-functional state. Consequently, the intestinal mucosa, smooth muscle, and microbiota undergo significant changes that are closely related to postoperative recovery and complications. A systematic description of these changes is necessary to understand the relationship among them and take more effective measures for postoperative intervention.

Role of the Gut Microbiota in Parenteral Nutrition-Associated Liver Disease: From Current Knowledge to Future Opportunities

Parenteral nutrition-associated liver disease (PNALD) refers to a spectrum of conditions that can develop cholestasis, steatosis, fibrosis, and cirrhosis in the setting of parenteral nutrition (PN) use. Patient risk factors include short bowel syndrome, bacterial overgrowth and translocation, disturbance of hepatobiliary circulation, and lack of enteral feeding. A growing body of evidence suggests an intricate linkage between the gut microbiota and the pathogenesis of PNALD. In this review, we highlight current knowledge on the taxonomic and functional changes in the gut microbiota that might serve as noninvasive biomarkers. We also discuss the function of microbial metabolites and associated signaling pathways in the pathogenesis of PNALD. By providing the perspectives of microbiota-host interactions in PNALD for basic and translational research and summarizing current limitations of microbiota-based approaches, this review paves the path for developing novel and precise microbiota-based therapies in PNALD.

Rupatadine protects the intestinal mucosa from injury by 5-flurouracil via modulation of inflammation, apoptosis and intestinal permeability

Fluorouracil (5-FU) is a widely used chemotherapeutic agent in various malignant tumors. However, intestinal toxicity is considered the irritant unavoidable adverse effect during the course therapy. The aim of the current study was to screen the effect of a new selective histamine receptor 1 blocker and platelet-activating factor (PAF) blocker on 5-FU induced intestinal toxicity. Five groups (6 rats each) of adult male rats (Wistar) were arranged as follows: (1) control group that was treated with carboxymethylcellulose, (2) a group that received rupatadine (higher dose) only, (3) a group that received 5-FU and (4) and (5) groups that received 5-FU plus lower or higher dose rupatadine, respectively. At end of the experiment, we determined intestinal malondialdehyde (MDA), glutathione reduced (GSH), nitric oxide (NO), tumor necrosis factor (TNF-α), interleukin 1β, 6, 10 (IL-1β, IL-6, IL-10), PAF, histamine, myeloperoxidase, cysteine-aspartic acid protease-3 (caspase-3), and nuclear factor kappa B (NF-κB) as well as the histological analysis. 5-FU injection caused marked elevation of MDA, NO, TNF-α, IL-1β, IL-6, PAF, histamine, myeloperoxidase, caspase-3, and NF-κB expressions. The intoxicated animals showed deficient GSH and IL-10 along with significant loss of villi, disorganized crypts, and inflammatory cell infiltration. Rupatadine pretreatment reduced the previously mentioned parameters, preserved a nearly normal intestinal mucosa picture with replenished GSH and elevated IL-10. In conclusion, rupatadine is a dual histamine receptor 1, and a PAF blocker could reduce 5-FU-induced oxidative damage, inflammation, apoptosis, and ulceration of the intestinal epithelium. Rupatadine may be a valuable modality to decrease 5-FU induced intestinal mucositis.

Graft-versus-host disease: a disorder of tissue regeneration and repair

Regenerative failure at barrier surfaces and maladaptive repair leading to fibrosis are hallmarks of graft-versus-host disease (GVHD). Although immunosuppressive treatment can control inflammation, impaired tissue homeostasis leads to prolonged organ damage and impaired quality of life. In this Spotlight article, we review recent research that addresses the critical failures in tissue regeneration and repair that underpin treatment-resistant GVHD. We highlight current interventions designed to overcome these defects and provide our assessment of the future therapeutic landscape.

The Production and Function of Endogenous Interleukin-10 in Intestinal Epithelial Cells and Gut Homeostasis

The healthy gut is achieved and maintained through a balanced relationship between the mucosal immune system, microbial communities resident in the lumen, and the intestinal epithelium. The intestinal epithelium plays an exceptionally important role in harmonizing the interaction between the host immunity and the luminal residents, as this selectively permeable barrier separates but also allows interchange between the 2 environments. Interleukin (IL)-10 has been well established to play an important role in maintaining gut homeostasis by imparting diverse effects on a variety of cell types in this relationship. In the intestine, the source and the target of IL-10 include leukocytes and epithelial cells. Given that both the epithelium and IL-10 are essential players in supporting homeostasis, we discuss the relationship between these 2 factors, focusing on epithelial sources of IL-10 and the effects of IL-10 on the intestinal epithelium. Insight into this relationship reveals an important aspect of the innate immune function of intestinal epithelial cells.

Models to evaluate the barrier properties of mucus during drug diffusion

Mucus is widely disseminated in the nasal cavity, oral cavity, respiratory tract, eyes, gastrointestinal tract, and reproductive tract to prevent the invasion of pathogenic bacteria and toxins. The mucus layer through its continuous secretion can prevent the passage of macromolecular substances such as pathogenic bacteria and toxins, thereby reducing the occurrence of inflammation. Without a doubt, mucus also hinders oral absorption. The physiological and biochemical properties of intestinal mucus and the different types of mucus barrier models need to be predominated. To find ways to increase the bioavailability of drugs in the future, this article summarizes mucus composition, barrier properties, mucus models, and mucoadhesive/mucopenetrating particles to highlight the information they can afford. Collectively, the review seeks to provide a state-of-the-art roadmap for researchers who must contend with this critical barrier to drug delivery.

Effects of novel probiotic strains of Bacillus pumilus and Bacillus subtilis on production, gut health, and immunity of broiler chickens raised under suboptimal conditions

Probiotics are being developed as alternatives to antibiotic growth promoters. The aim of the study was to investigate the effects of 2 novel strains of Bacillus pumilus and Bacillus subtilis on production, intestinal microbiota, gut health, and immunity of broilers raised under suboptimal conditions. Day-old chicks (Cobb 500, n = 2,073) were randomly assigned into 6 groups: Con group (group fed with basal diet), Ab group (group treated with virginiamycin), groups treated with 2 levels of B. pumilus (low dose: 3 × 10⁸ cfu/kg of feed [BPL] and high dose: 1 × 10⁹ cfu/kg [BPH]), and groups treated with 2 levels of B. subtilis (low dose: 3 × 10⁸ cfu/kg [BSL] and high dose: 1 × 10⁹ cfu/kg [BSH]). Production parameters were recorded weekly. Cecal tonsils and content as well as ileum samples were collected on day 14 and day 42. Cecal tonsils were used to sort T-regulatory cells (CD4+CD8–CD25+ and CD4+CD8+CD25+) to study expression of IL-10 and interferon gamma, whereas cecal content was used for bacterial culture. Ileum samples were used to measure gene expression of tight junction proteins, mucin, and cytokines. BW and feed intake increased in the Ab, BPL, BSL, and BSH groups compared with the Con group between day 35 and day 42. The CD4+CD8-CD25+ cells expressed high levels of IL-10 in the BSH group on day 14 and in the BPL, BSL, and BSH groups on day 42 and high levels of interferon gamma in the BPL, BSL, and BSH groups on day 14 and in the BSL and BSH groups on day 42. The expression of IL-10 and interferon gamma in CD4+CD8+CD25+ cells was higher only in the BSH group on day 14 and day 42. Cecal bacterial populations of genera, Lactobacillus (day 14 and day 42) and Clostridium (day 14), were higher in the BSH group. Expression of tight junction protein increased significantly in the ileum on day 14 in the BPL (occludin, zona occludens 1 [ZO-1]), BSL (occludin, ZO-1), and BSH (occludin, ZO-1, junctional adhesion molecule 2 [JAM-2]) groups compared with that in the Con group and declined in all groups except in the BSH group (occludin, ZO-1, JAM-2) on day 42. Expression of MUC2 and IL-17F increased in all groups on day 14 and remained high on day 42 in the BSL and BSH groups. Taken together, both Bacillus probiotics altered the intestinal and immune activities, particularly on day 14, suggesting beneficial influence of probiotics.

Asymptomatic Clostridium perfringens Inhabitation in Intestine Can Cause Inflammation, Apoptosis, and Disorders in Brain

Clostridium perfringens (CP) is a foodborne pathogen. The bacterium can also inhabit human gut without symptoms of foodborne illness. However, the clinical symptoms of long-term inhabitation have not been known yet. Therefore, the objective of this study was to elucidate the relationship between intestinal CP and other internal organs. Phosphate-buffered saline (PBS) and CP were orally injected into 5-week-old (YOUNG) and 12-month-old C57BL6/J (ADULT) mice. Gene expression levels related to inflammation (tumor necrosis factor-α [TNF-α], interleukin [IL]-1β, and IL-6) and oxidative stress (superoxide dismutase [SOD]1, SOD2, SOD3, glutathione reductase [GSR], glutathione peroxidase [GPx]3, and catalase [CAT]) responses were evaluated in the brain, small intestine, and liver. In addition, apoptosis-related (BCL2-associated X [BAX]1 and high-mobility group box-1 [HMGB1]) and brain disorder-related genes (CCAAT-enhancer-binding protein [C/EBP]-β, C/EBPδ, C/EBP homologous protein [CHOP], and amyloid precursor protein [APP]) as brain damage markers were examined. The protein expressions in the brain were also measured. Gene expression levels of inflammation and oxidative stress responses were higher (p < 0.05) in brains of CP-YOUNG and CP-ADULT mice, compared with PBS-YOUNG and PBS-ADULT, and the gene expression levels were higher (p < 0.05) in brains of CP-ADULT mice than CP-YOUNG mice. Apoptosis-related (BAX1 and HMGB1) and brain disorder-related genes (C/EBPβ, C/EBPδ, CHOP, and APP) were higher (p < 0.05) in brains of CP-challenged mice, compared with PBS-challenged mice. Even oxidative stress response (GPx and SOD2), cell damage-related (HMGB1), and β-amyloid proteins were higher (p < 0.05) in brains of CP- than in PBS-challenged mice. C/EBP protein was higher (p < 0.05) in CP-YOUNG, compared with PBS-YOUNG mice. However, these clinical symptoms were not observed in small intestine and liver. These results indicate that although asymptomatic intestinal CP do not cause foodborne illness, their inhabitation may cause brain inflammation, oxidative stress, apoptosis, and cell damage, which may induce disorders, especially for the aged group.

Early Enteral Nutrition Preserves Intestinal Barrier Function through Reducing the Formation of Neutrophil Extracellular Traps (NETs) in Critically Ill Surgical Patients

BACKGROUND

The gut was suggested as the driver of critical illness and organ injury. Recently, excessive formation of neutrophil extracellular traps (NETs) was associated with mucosal inflammation. Direct investigation of intestinal mucosa is essential to illuminate the potential mechanism of gut barrier in critically ill patients. We hypothesized that early enteral nutrition (EN) could decrease intestinal NETs and maintain the gut barrier.

METHODS

Intestinal biopsies were obtained using biopsy forceps from critically ill surgical patients complicated with enterocutaneous fistula. Expressions of tight junction (TJ) proteins, mucosal inflammation, and apoptosis were evaluated. Moreover, NET-associated proteins were evaluated in intestinal specimens of patients by Western blot and immunofluorescence analysis.

RESULTS

The intestinal barrier was significantly impaired in critically ill patients receiving early total parenteral nutrition (TPN), evidenced by intestinal villi atrophy, inflammatory infiltration, increased enterocyte apoptosis, and abnormal TJ expressions. Early EN significantly alleviated these intestinal injuries. In addition, we observed increased formation of the NET structure and elevated expressions of NET-associated proteins in intestines of critically ill surgical patients. Early EN was associated with the diminished presence of NETs and reduced expression of NET-associated proteins. Mechanically, analysis of the TLR4 pathway showed a significant increase in TLR4, NFκB, and MAPK signaling in patients receiving TPN when compared to those receiving early EN.

CONCLUSION

The intestinal barrier is disrupted in the human gut during critical illness. Our data suggests that an increased NET structure was showed in the gut of critically ill surgical patients, and early EN treatment was associated with the reduction of NET formation and the preservation of mucosal immunity.

Lin 28A/Occludin axis: An aberrantly activated pathway in intestinal epithelial cells leading to impaired barrier function under total parenteral nutrition

Disassembly of tight junctions is a major cause of intestinal barrier dysfunction under total parenteral nutrition (TPN), but the precise mechanisms have not been fully understood. Normally, RNA binding protein Lin 28A is highly restricted to embryonic stem cells and dramatically decreases as differentiation progresses; however, in our preliminary study it was found aberrantly increased in the intestinal epithelial cells of TPN rats, and thus its mechanism of action needs to be addressed. Herein, we report a pivotal role of Lin 28A in the regulation of tight junctions, which induces a sustained translational repression of Occludin, leading to disruption of intestinal barrier function under TPN. Using a rat model of TPN, we found time-dependent upregulation of Lin 28A, negatively correlated with Occludin. Using mouse intestinal organoids and human gut-derived Caco-2 cells as in vitro models, we found that expression of Occludin could be significantly suppressed by ectopic overexpression of Lin 28A. The underlying mechanisms may be partially attributed to translational repression, as the abundance of Occludin transcripts in polysomes was dramatically reduced by Lin 28A (polysomal profiling). Furthermore, Lin 28A was found to directly bind to Occludin mRNA 3' untranslated coding region (UTR), thereby repressing the translation of Occludin transcripts through decapping enzyme 1A (DCP1a). Taken together, our findings revealed that Lin 28A/Occludin axis may be a novel mechanism accounting for the development of barrier dysfunction under TPN.

Review of parenteral nutrition-associated liver disease

Parenteral nutrition has been widely used in patients whose gastrointestinal tract is anatomically or physiologically unavailable for sufficient food intake. It has been considered lifesaving but is not without adverse effects. It has been proven to cause liver injury through different mechanisms. We present a review of parenteral nutrition-associated liver disease.

Novel Strategies to Prevent Total Parenteral Nutrition-Induced Gut and Liver Inflammation, and Adverse Metabolic Outcomes

Total parenteral nutrition (TPN) is a life-saving therapy administered to millions of patients. However, it is associated with significant adverse effects, namely liver injury, risk of infections, and metabolic derangements. In this review, the underlying causes of TPN-associated adverse effects, specifically gut atrophy, dysbiosis of the intestinal microbiome, leakage of the epithelial barrier with bacterial invasion, and inflammation are first described. The role of the bile acid receptors farnesoid X receptor and Takeda G protein-coupled receptor, of pleiotropic hormones, and growth factors is highlighted, and the mechanisms of insulin resistance, namely the lack of insulinotropic and insulinomimetic signaling of gut-originating incretins as well as the potentially toxicity of phytosterols and pro-inflammatory fatty acids mainly released from soybean oil-based lipid emulsions, are discussed. Finally, novel approaches in the design of next generation lipid delivery systems are proposed. Propositions include modifying the physicochemical properties of lipid emulsions, the use of lipid emulsions generated from sustainable oils with favorable ratios of anti-inflammatory n-3 to pro-inflammatory n-6 fatty acids, beneficial adjuncts to TPN, and concomitant pharmacotherapies to mitigate TPN-associated adverse effects.

Sodium butyrate ameliorates insulin resistance and renal failure in CKD rats by modulating intestinal permeability and mucin expression

Background

The associated increase in the lipopolysaccharide (LPS) levels and uremic toxins in chronic kidney disease (CKD) has shifted the way we focus on intestinal microbiota. This study shows that a disruption of the intestinal barrier in CKD promotes leakage of LPS from the gut, subsequently decreasing insulin sensitivity. Butyrate treatment improved the intestinal barrier function by increasing colonic mucin and tight junction (TJ) proteins. This modulation further ameliorated metabolic functions such as insulin intolerance and improved renal function.

Methods

Renal failure was induced by 5/6th nephrectomy (Nx) in rats. A group of Nx and control rats received sodium butyrate in drinking water. The Nx groups were compared with sham-operated controls.

Results

The Nx rats had significant increases in serum creatinine, urea and proteinuria. These animals had impaired glucose and insulin tolerance and increased gluconeogenesis, which corresponded with decreased glucagon-like peptide-1 (GLP-1) secretion. The Nx animals suffered significant loss of intestinal TJ proteins, colonic mucin and mucin 2 protein. This was associated with a significant increase in circulating LPS, suggesting a leaky gut phenomenon. 5′adenosine monophosphate-activated protein kinase (AMPK) phosphorylation, known to modulate epithelial TJs and glucose metabolism, was significantly reduced in the intestine of the Nx group. Anti-inflammatory cytokine, interleukin 10, anti-bacterial peptide and cathelicidin-related antimicrobial peptide were also lowered in the Nx cohort. Butyrate treatment increased AMPK phosphorylation, improved renal function and controlled hyperglycemia.

Conclusions

Butyrate improves AMPK phosphorylation, increases GLP-1 secretion and promotes colonic mucin and TJ proteins, which strengthen the gut wall. This decreases LPS leakage and inflammation. Taken together, butyrate improves metabolic parameters such as insulin resistance and markers of renal failure in CKD animals.

The Importance of the Microbiome in Critically Ill Patients: Role of Nutrition

Critically ill patients have an alteration in the microbiome in which it becomes a disease-promoting pathobiome. It is characterized by lower bacterial diversity, loss of commensal phyla, like Firmicutes and Bacteroidetes, and a domination of pathogens belonging to the Proteobacteria phylum. Although these alterations are multicausal, many of the treatments administered to these patients, like antibiotics, play a significant role. Critically ill patients also have a hyperpermeable gut barrier and dysregulation of the inflammatory response that favor the development of the pathobiome, translocation of pathogens, and facilitate the emergence of sepsis. In order to restore the homeostasis of the microbiome, several nutritional strategies have been evaluated with the aim to improve the management of critically ill patients. Importantly, enteral nutrition has proven to be more efficient in promoting the homeostasis of the gut microbiome compared to parenteral nutrition. Several nutritional therapies, including prebiotics, probiotics, synbiotics, and fecal microbiota transplantation, are currently being used, showing variable results, possibly due to the unevenness of clinical trial conditions and the fact that the beneficial effects of probiotics are specific to particular species or even strains. Thus, it is of great importance to better understand the mechanisms by which nutrition and supplement therapies can heal the microbiome in critically ill patients in order to finally implement them in clinical practice with optimal safety and efficacy.

Biomaterial-tight junction interaction and potential impacts

The active pharmaceutical ingredients (APIs) have to cross the natural barriers and get into the blood to impart the pharmacological effects. The tight junctions (TJs) between the epithelial cells serve as the major selectively permeable barriers and control the paracellular transport of the majority of hydrophilic drugs, in particular, peptides and proteins. TJs perfectly balance the targeted transport and the exclusion of other unexpected pathogens under the normal conditions. Many biomaterials have shown the capability to open the TJs and improve the oral bioavailability and targeting efficacy of the APIs. Nevertheless, there is limited understanding of the biomaterial-TJ interactions. The opening of the TJs further poses the risk of autoimmune diseases and infections. This review article summarizes the most updated literature and presents insights into the TJ structure, the biomaterial-TJ interaction mechanism, the benefits and drawbacks of TJ disruption, and methods for evaluating such interactions.

Mechanisms by Which the Gut Microbiota Influences Cytokine Production and Modulates Host Inflammatory Responses

The gastrointestinal tract encounters a wide variety of microorganisms, including beneficial symbionts, pathobionts, and pathogens. Recent evidence has shown that the gut microbiota, directly or indirectly through its components, such as metabolites, actively participates in the host inflammatory response by cytokine-microbiota or microbiota-cytokine modulation interactions, both in the gut and systemically. Therefore, further elucidation of host cytokine molecular pathways and microbiota components will provide a novel and promising therapeutic approach to control or prevent inflammatory disease and to maintain host homeostasis. The purpose of this review is to summarize well-established scientific findings and provide an updated overview regarding the direct and indirect mechanisms by which the gut microbiota can influence the inflammatory response by modulating the host's cytokine pathways that are mostly involved, but not exclusively so, with gut homeostasis. In addition, we will highlight recent results from our group, which suggest that the microbiota promotes cytokine release from inflammatory cells though activation of microbial metabolite sensor receptors that are more highly expressed on inflammatory and intestinal epithelial cells.

The Effect of Butyrate-Supplemented Parenteral Nutrition on Intestinal Defence Mechanisms and the Parenteral Nutrition-Induced Shift in the Gut Microbiota in the Rat Model

Butyrate produced by the intestinal microbiota is essential for proper functioning of the intestinal immune system. Total dependence on parenteral nutrition (PN) is associated with numerous adverse effects, including severe microbial dysbiosis and loss of important butyrate producers. We hypothesised that a lack of butyrate produced by the gut microbiota may be compensated by its supplementation in PN mixtures. We tested whether i.v. butyrate administration would (a) positively modulate intestinal defence mechanisms and (b) counteract PN-induced dysbiosis. Male Wistar rats were randomised to chow, PN, and PN supplemented with 9 mM butyrate (PN+But) for 12 days. Antimicrobial peptides, mucins, tight junction proteins, and cytokine expression were assessed by RT-qPCR. T-cell subpopulations in mesenteric lymph nodes (MLN) were analysed by flow cytometry. Microbiota composition was assessed in caecum content. Butyrate supplementation resulted in increased expression of tight junction proteins (ZO-1, claudin-7, E-cadherin), antimicrobial peptides (Defa 8, Rd5, RegIIIγ), and lysozyme in the ileal mucosa. Butyrate partially alleviated PN-induced intestinal barrier impairment and normalised IL-4, IL-10, and IgA mRNA expression. PN administration was associated with an increase in Tregs in MLN, which was normalised by butyrate. Butyrate increased the total number of CD4+ and decreased a relative amount of CD8+ memory T cells in MLN. Lack of enteral nutrition and PN administration led to a shift in caecal microbiota composition. Butyrate did not reverse the altered expression of most taxa but did influence the abundance of some potentially beneficial/pathogenic genera, which might contribute to its overall beneficial effect.

Effects of Boswellia Serrata Roxb. and Curcuma longa L. in an In Vitro Intestinal Inflammation Model Using Immune Cells and Caco-2

Inflammatory bowel diseases, which consist of chronic inflammatory conditions of the colon and the small intestine, are considered a global disease of our modern society. Recently, the interest toward the use of herbal therapies for the management of inflammatory bowel diseases has increased because of their effectiveness and favourable safety profile, compared to conventional drugs. Boswellia serrata Roxb. and Curcuma longa L. are amongst the most promising herbal drugs, however, their clinical use in inflammatory bowel diseases is limited and little is known on their mechanism of action. The aim of this work was to investigate the effects of two phytochemically characterized extracts of B. serrata and C. longa in an in vitro model of intestinal inflammation. Their impact on cytokine release and reactive oxygen species production, as well as the maintenance of the intestinal barrier function and on intestinal mucosa immune cells infiltration, has been evaluated. The extracts showed a good protective effect on the intestinal epithelium at 1 µg/mL, with TEER values increasing by approximately 1.5 fold, compared to LPS-stimulated cells. C. longa showed an anti-inflammatory mechanism of action, reducing IL-8, TNF-α and IL-6 production by approximately 30%, 25% and 40%, respectively, compared to the inflammatory stimuli. B. serrata action was linked to its antioxidant effect, with ROS production being reduced by 25%, compared to H₂O₂-stimulated Caco-2 cells. C. longa and B. serrata resulted to be promising agents for the management of inflammatory bowel diseases by modulating in vitro parameters which have been identified in the clinical conditions.

Enhanced gut barrier integrity sensitizes colon cancer to immune therapy

Oral IL-10 suppressed tumor growth in the APCmin/+ mouse/Bacteroides fragilis colon cancer model while a similar formulation of IL-12 exacerbated disease. In contrast, combined treatment with IL-10 and IL-12 resulted in near-complete tumor eradication and a significant extension of survival. The cytokines mediated distinct immunological effects in the gut, i.e. IL-10 diminished Th17 cell prevalence whereas IL-12 induced IFNγ and enhanced CD8 + T-cell activity. Loss-of-function studies demonstrated that IL-12-driven CD8 + T-cell expansion was only partially responsible for the synergy, and that both the detrimental and the beneficial activities of IL-12 required IFNγ. Examination of colon physiology in mice receiving single vs dual treatment revealed that exacerbation of disease by IL-12 monotherapy was associated with compromised gut barrier integrity whereas combined treatment reversed this effect, uncovering additional activity by the cytokines on the stroma. Further analysis showed that the stromal effects of IL-12 included a 6-fold increase in IL-10RA expression in the colon epithelium, linking the epithelial activity of the cytokines. Finally, dual but not monotherapy induced a 3-fold increase in tight junction protein levels in the colon, identifying the mechanism by which IL-10 blocked the detrimental effect of the IL-12-IFNγ axis on barrier function without interfering with its beneficial immunological activity. These findings establish that the synergy between IL-12 and IL-10 was mediated by pleiotropic effects on the immune and the non-immune compartments and that the latter activity was critical to therapeutic outcome.

Identification of key genes and pathways using bioinformatics analysis in septic shock children

Background and hypothesis

Sepsis is still one of the reasons for serious infectious diseases in pediatric intensive care unit patients despite the use of anti-infective therapy and organ support therapy. As it is well-known, the effect of single gene or pathway does not play a role in sepsis. We want to explore the interaction of two more genes or pathways in sepsis patients for future works. We hypothesize that the discovery from the available gene expression data of pediatric sepsis patients could know the process or improve the situation.

Methods and results

The gene expression profile dataset GSE26440 of 98 septic shock samples and 32 normal samples using whole blood-derived RNA samples were generated. A total of 1,108 upregulated and 142 downregulated differentially expressed genes (DEGs) were identified in septic shock children using R software packages. The Gene Ontology (GO) enrichment and the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway were analyzed using DAVID software; Gene Set Enrichment Analysis method was also used for enrichment analysis of the DEGs. The protein-protein interaction (PPI) network and the top 10 hub genes construction of the DEGs were constructed via plug-in Molecular Complex Detection and cytoHubba of Cytoscape software. From the PPI network, the top 10 hub genes, which are all upregulated DEGs in the septic shock children, were identified as GAPDH, TNF, EGF, MAPK3, IL-10, TLR4, MAPK14, IL-1β, PIK3CB, and TLR2. Some of them were involved in one or more significant inflammatory pathways, such as the enrichment of tumor necrosis factor (TNF) pathway in the activation of mitogen-activated protein kinase activity, toll-like receptor signaling pathway, nuclear factor-κB signaling pathway, PI3K-Akt signaling pathway, and TNF signaling pathway. These findings support future studies on pediatric septic shock.

Effects of imipenem combined with low-dose cyclophosphamide on the intestinal barrier in septic rats

Anti-infection therapy combined with immunotherapy is one of the important research approaches for treating sepsis. However, the combination of anti-infection and immunotherapy therapeutic agents may have an adverse effect on intestinal barrier function. In the present study, it was hypothesized that imipenem combined with low-dose cyclophosphamide (CTX) could improve the sepsis survival rate compared with imipenem treatment alone. In addition, the alterations in the intestinal barrier were investigated and the possible mechanisms of altering intestinal barrier function in septic rats treated with imipenem combined with low-dose CTX or imipenem alone were explored. To investigate the effect of imipenem combined with low-dose CTX on the intestinal barrier, the markers of histopathology, intestinal permeability, intestinal epithelial apoptosis, cytokines interleukin (IL)-6, IL-10 and tumor necrosis factor (TNF)-α, and tight junction proteins zonula occludens (ZO)-1, occludin and claudin-2, were quantitatively and qualitatively evaluated. The results indicated that imipenem combined with low-dose CTX significantly improved the survival rate of rats compared with imipenem alone (P<0.05). However, no significantly difference between the treatment with imipenem combined with low-dose CTX and imipenem treatment alone was indicated with regard to histopathology, intestinal permeability, intestinal epithelial apoptosis and the expression of claudin-2, ZO-1 and TNF-α. However, imipenem combined with low-dose CTX significantly reduced IL-6 and IL-10 expression and significantly increased occludin expression compared with imipenem alone (P<0.05). It was concluded that imipenem combined with low-dose CTX could improve the survival rate of rats with sepsis compared with rats treated with imipenem alone. The present findings suggest that imipenem combined with low-dose CTX may cause damage to the intestinal barrier function and the mechanism may be associated with a reduction in IL-10 expression.

Distinct roles of intracellular heat shock protein 70 in maintaining gastrointestinal homeostasis

The inducible heat shock protein 70 (Hsp70) is both cytoprotective and immunomodulatory, potentially accounting for its critical role in maintaining gastrointestinal homeostasis. When levels are reduced in conditions like inflammatory bowel diseases (IBD), loss of function contributes to the severity and chronicity of these diseases, although through which cell types and mechanisms remains unclear. Here, the role of Hsp70-mediated intestinal epithelial protection and immune regulation in experimental colitis was examined by using a villin promoter-driven Hsp70 transgene in the 2,4,6-trinitrobenzene sulfonic acid (TNBS) and dextran sodium sulfate (DSS) models and in IL-10/Hsp70 double knockout (IL10-/-/Hsp70-/-) mice. In addition, Hsp70-mediated IL-10 production and immune protection were investigated using a CD45RBhigh transfer model and measuring colonic and immune cell cytokine expression during colitis. We found that the epithelial-specific expression of Hsp70 transgene attenuated DSS-induced colitis in Hsp70-/- mice by protecting tight junctions (TJ) and their interaction with the TJ-associated protein ZO-1. In the TNBS colitis and CD45RBhigh model, Hsp70 carried out its intracellular anti-inflammatory function by maintaining IL-10 production. Impaired ERK phosphorylation, but not p38 or JNK phosphorylation pathways, was associated with decreased IL-10 production in Hsp70-deficient cells. Together, these actions can be leveraged in the context of cellular specificity to develop complementary strategies that can lead to reduction in mucosal injury and immune activation in colonic colitis development. NEW & NOTEWORTHY Using four different experimental colitis models, we filled an important gap in knowledge by defining essential roles of intracellular heat shock protein 70 in different cell types in maintaining intestinal integrity and immune regulation. These findings are relevant to human inflammatory bowel diseases and represent potential avenues for developing therapeutic strategies, not only to counter the destructive processes of inflammation but also to promote tissue healing and prevent complications frequently associated with chronic intestinal inflammation.

Surgical Anatomy Does Not Affect the Progression of Intestinal Failure-Associated Liver Disease in Neonatal Piglets

BACKGROUND

Intestinal failure-associated liver disease (IFALD) causes significant morbidity in neonates with short bowel syndrome (SBS) dependent on parenteral nutrition (PN). Resected ileum, with loss of the ileocecal valve (ICV), is the most common anatomy in SBS, yet its impact on IFALD has not been adequately studied.

METHODS

Neonatal piglets were randomized to 75% intestinal resection with jejunocolic anastomosis (JC, n = 12), 75% resection with jejunoileal anastomosis and intact ICV (JI, n = 13), PN-fed sham (sham, n = 14), or sow-fed control (SF, n = 8). Surgical and sham piglets received 100% PN for 14 days before bile flow was measured and blood chemistry, liver pathology, jejunal permeability, and bacterial translocation were assessed.

RESULTS

Bile flow was lower for PN-fed compared with SF (P = .002) but not different between the PN-fed groups. Total bilirubin (P = .03) and liver pathology (P < .001) were greater in PN-fed than SF groups but not different between PN-fed groups. Serum bile acids were increased in sham (P = .01) but not different between SBS groups. PN-fed piglets with sepsis had lower bile flow (P = .001) and increased bilirubin (P = .04). Neither jejunal permeability nor bacterial translocation were different between JC, JI, or sham groups.

CONCLUSION

Contrary to our hypothesis, the remnant anatomy does not appear to worsen the progression of IFALD. However, the role of sepsis in IFALD should be further explored, in addition to other mechanisms, including PN factors, host immune responses, and intestinal bacterial dysbiosis.

Targeting the gut barrier for the treatment of alcoholic liver disease

Alcohol consumption remains one of the predominant causes of liver disease and liver-related death worldwide. Intriguingly, dysregulation of the gut barrier is a key factor promoting the pathogenesis of alcoholic liver disease (ALD). A functional gut barrier, which consists of a mucus layer, an intact epithelial monolayer and mucosal immune cells, supports nutrient absorption and prevents bacterial penetration. Compromised gut barrier function is associated with the progression of ALD. Indeed, alcohol consumption disrupts the gut barrier, increases gut permeability, and induces bacterial translocation both in ALD patients and in experimental models with ALD. Moreover, alcohol consumption also causes enteric dysbiosis with both numerical and proportional perturbations. Here, we review and discuss mechanisms of alcohol-induced gut barrier dysfunction to better understand the contribution of the gut-liver axis to the pathogenesis of ALD. Unfortunately, there is no effectual Food and Drug Administration-approved treatment for any stage of ALD. Therefore, we conclude with a discussion of potential strategies aimed at restoring the gut barrier in ALD. The principle behind antibiotics, prebiotics, probiotics and fecal microbiota transplants is to restore microbial symbiosis and subsequently gut barrier function. Nutrient-based treatments, such as dietary supplementation with zinc, niacin or fatty acids, have been shown to regulate tight junction expression, reduce intestinal inflammation, and prevent endotoxemia as well as liver injury caused by alcohol in experimental settings. Interestingly, saturated fatty acids may also directly control the gut microbiome. In summary, clinical and experimental studies highlight the significance and efficacy of the gut barrier in treating ALD.

A study of the damage of the intestinal mucosa barrier structure and function of Ctenopharyngodon idella with Aeromonas hydrophila

The aim of this study is to explore the effect of Aeromonas hydrophila on the intestinal mucosal barrier structure and intestinal permeability in grass carp (Ctenopharyngodon idella). Histopathological examinations showed that A. hydrophila induced severe intestinal lesions, including inflammatory cell infiltration and intestinal villus fusion and swelling. Messenger RNA (mRNA) expression of the inflammatory cytokines TNF-α, IL-1β, IL-8, IL-10 and MyD88 was significantly increased after infection with A. hydrophila. The permeability of intestinal mucosa was determined using Evans blue (EB) and D-lactic acid. The results indicated that the levels of EB and serum D-lactic acid were significantly increased after infection with A. hydrophila (p < 0.05). Our results also indicated that the intestinal mucosal barrier injury induced by A. hydrophila infection was closely associated with the expression of the tight junction (TJ) protein zonula occludens-1 (ZO-1), occludin, claudin b and claudin c as well as the activity of Na⁺, K⁺-ATPase and Ca²⁺, Mg²⁺-ATPase. Lower mRNA levels of occludin and lower Na⁺, K⁺-ATPase and Ca²⁺, Mg²⁺-ATPase activity in the intestines were observed after challenge. ZO-1 and claudin c were significantly increased 24 h after infection with A. hydrophila. The most interesting finding was that claudin b also significantly increased 24 h after challenge and then decreased to lower levels at 72, 120 and 168 h post-infection compared to the PBS-treated control group. The results demonstrated that grass carp infection with A. hydrophila induced intestinal inflammation and impaired the structure and function of the intestinal mucosal barrier.

Parenteral Nutrition-Associated Liver Disease: The Role of the Gut Microbiota

Parenteral nutrition (PN) provides life-saving nutritional support in situations where caloric supply via the enteral route cannot cover the necessary needs of the organism. However, it does have serious adverse effects, including parenteral nutrition-associated liver disease (PNALD). The development of liver injury associated with PN is multifactorial, including non-specific intestine inflammation, compromised intestinal permeability, and barrier function associated with increased bacterial translocation, primary and secondary cholangitis, cholelithiasis, short bowel syndrome, disturbance of hepatobiliary circulation, lack of enteral nutrition, shortage of some nutrients (proteins, essential fatty acids, choline, glycine, taurine, carnitine, etc.), and toxicity of components within the nutrition mixture itself (glucose, phytosterols, manganese, aluminium, etc.). Recently, an increasing number of studies have provided evidence that some of these factors are directly or indirectly associated with microbial dysbiosis in the intestine. In this review, we focus on PN-induced changes in the taxonomic and functional composition of the microbiome. We also discuss immune cell and microbial crosstalk during parenteral nutrition, and the implications for the onset and progression of PNALD. Finally, we provide an overview of recent advances in the therapeutic utilisation of pro- and prebiotics for the mitigation of PN-associated liver complications.

Animal models for studying epithelial barriers in neonatal necrotizing enterocolitis, inflammatory bowel disease and colorectal cancer

The intestinal epithelial cells line the luminal surface of the entire gastrointestinal tract which is crucial for the absorption of nutrients and prevention of pathogens entering from the external environment. The epithelial barrier plays an important role in organ development, disease pathogenesis, and aging. The major component of an epithelial barrier is the single columnar epithelium and tight junctions. Tight junctions are located at the most apical region of the junctional complex and contain many integral membrane proteins, such as occludin, the claudin family, and junctional adhesion molecules (JAMs). The disruption of intestinal epithelial barriers may lead to several pathophysiological conditions causing malabsorption of nutrition and chronic inflammation. In this review, we provide an update on the alterations of epithelial barriers associated with gut diseases using experimental animal models; we appraise the role of tight junctions in neonatal necrotizing enterocolitis (NEC), inflammatory bowel disease (IBD), and colorectal cancer; we also compare some common features as well as differences and similarities in the pathophysiology of intestinal inflammation in neonatal (NEC) and adult (IBD) gut.

Suppression of Immunotherapy on Group 2 Innate Lymphoid Cells in Allergic Rhinitis

Background:

Group 2 innate lymphoid cells (ILC2s) are regarded as a novel population of lineage-negative cells that induce innate Type 2 responses by producing the critical Th2-type cytokines interleukin (IL)-5 and IL-13. ILC2s as key players in the development of allergic rhinitis (AR) have been proved, however, the effect of subcutaneous immunotherapy (SCIT) with dermatophagoides pteronyssinus extract (Der p-SCIT) on ILC2s in AR patients is not clear. This study aimed to investigate the response of ILC2s of peripheral blood in house dust mites (HDM)-sensitized Chinese patients with AR who received SCIT with Der P extract.

Methods:

Seven healthy controls without symptoms of AR who had negative reactions to any of the allergens from skin-prick testing, nine patients diagnosed with persistent AR according to the Allergic Rhinitis and its Impact on Asthma (ARIA) guidelines, and 24 AR patients who received Der p-SCIT for 1.0–3.5 years were recruited for the study. ILC2s in the peripheral blood were evaluated using flow cytometry. The severity of their symptoms of all participants was rated based on the Total 5 symptom score.

Results:

Among 40 participants, 9 AR patients were assigned to the untreated group, 24 AR patients receiving Der p-SCIT were assigned to the immunotherapy group, and 7 healthy controls without symptoms of AR were assigned to healthy control group. The mean Total 5 symptom score of immunotherapy group was significantly lower than that of untreated group (4.3 ± 1.4 vs. 10.1 ± 2.5, P < 0.001). Similarly, the levels of ILC2s in the peripheral blood of immunotherapy group were significantly reduced compared with that in untreated group (P < 0.001), but were not significantly different from healthy controls (P = 0.775). Further subgroup analysis based on the duration of SCIT therapy (1.0–2.0 years [SCIT_1-2], 2.0–3.0 years [SCIT_2-3], and 3.0–3.5 years [SCIT_3-3.5]) showed that the percentage of ILC2s was not significantly different between SCIT_1-2, SCIT_2-3, and SCIT_3-3.5 groups (SCIT_1-2 vs. SCIT_2-3: P = 0.268; SCIT_1-2 vs. SCIT_3-3.5: P = 0.635; and SCIT_2-3 vs. SCIT_3-3.5: P = 0.787).

Conclusions:

The present study highlighted the suppression of Der p-SCIT on ILC2s in HDM-AR patients. ILC2s identified in peripheral blood can be used as an effective biomarker for Der p-SCIT.

P38 MAPK Pharmacological Inhibitor SB203580 Alleviates Total Parenteral Nutrition-Induced Loss of Intestinal Barrier Function but Promotes Hepatocyte Lipoapoptosis

BACKGROUND & AIMS

Our previous studies have provided evidence that p38 mitogen-activated protein kinase (MAPK) is involved in total parenteral nutrition (TPN)-associated complications, but its exact effects and mechanisms have not been fully understood. This study aimed to evaluate the roles of p38 MAPK inhibitor SB203580 in the TPN-induced loss of intestinal barrier function and liver disease.

METHODS

A rodent model of TPN was used to analyze the roles of SB203580 in TPN-associated complications.Intestinal barrier function was evaluated by transepithelial electrical resistance (TER) and paracellular permeability in Caco-2 cells. The palmitic acid (PA) was used to induce hepatic lipoapoptosis in vitro. The lipoapoptosis was detected using Caspase-3/7 and lipid staining.

RESULTS

In the present study, we showed that SB203580 treatment significantly suppressed TPN-mediated intestinal permeability in rats. SB203580 treatment significantly inhibited IL-1β-induced an increase in tight junction permeability of Caco-2 cells via repressing the p38/ATF-2 signaling. Unexpectedly, SB203580 treatment enhanced hepatic lipoapoptosis in the model of TPN. Palmitic acid (PA)-induced hepatic lipoapoptosis in human liver cells was significantly augmented by the SB203580 treatment.

CONCLUSIONS

We demonstrate that the p38 MAPK inhibitor SB203508 ameliorates intestinal barrier function but promotes hepatic lipoapoptosis in model of TPN.

Bacterial nutrient foraging in a mouse model of enteral nutrient deprivation: insight into the gut origin of sepsis

Total parenteral nutrition (TPN) leads to a shift in small intestinal microbiota with a characteristic dominance of Proteobacteria This study examined how metabolomic changes within the small bowel support an altered microbial community in enterally deprived mice. C57BL/6 mice were given TPN or enteral chow. Metabolomic analysis of jejunal contents was performed by liquid chromatography/mass spectrometry (LC/MS). In some experiments, leucine in TPN was partly substituted with [¹³C]leucine. Additionally, jejunal contents from TPN-dependent and enterally fed mice were gavaged into germ-free mice to reveal whether the TPN phenotype was transferrable. Small bowel contents of TPN mice maintained an amino acid composition similar to that of the TPN solution. Mass spectrometry analysis of small bowel contents of TPN-dependent mice showed increased concentration of ¹³C compared with fed mice receiving saline enriched with [¹³C]leucine. [¹³C]leucine added to the serosal side of Ussing chambers showed rapid permeation across TPN-dependent jejunum, suggesting increased transmucosal passage. Single-cell analysis by fluorescence in situ hybridization (FISH)-NanoSIMS demonstrated uptake of [¹³C]leucine by TPN-associated bacteria, with preferential uptake by Enterobacteriaceae Gavage of small bowel effluent from TPN mice into germ-free, fed mice resulted in a trend toward the proinflammatory TPN phenotype with loss of epithelial barrier function. TPN dependence leads to increased permeation of TPN-derived nutrients into the small intestinal lumen, where they are predominately utilized by Enterobacteriaceae The altered metabolomic composition of the intestinal lumen during TPN promotes dysbiosis.

Lipid Emulsion Formulation of Parenteral Nutrition Affects Intestinal Microbiota and Host Responses in Neonatal Piglets

BACKGROUND

Total parenteral nutrition (TPN) is a cause of intestinal microbial dysbiosis and impaired gut barrier function. This may contribute to life-threatening parenteral nutrition-associated liver disease and sepsis in infants. We compared the effects of a lipid emulsion containing long-chain ω-3 polyunsaturated fatty acids (PUFAs; SMOFlipid) and a predominantly ω-6 PUFA emulsion (Intralipid) on microbial composition and host response at the mucosal surface.

MATERIALS AND METHODS

Neonatal piglets were provided isocaloric, isonitrogenous TPN for 14 days versus sow-fed (SF) controls. Equivalent lipid doses (10 g/kg/d) were given of either SMOFlipid (ML; n = 10) or Intralipid (SO; n = 9). Ileal segments and mucosal scrapings were used to characterize microbial composition by 16S rRNA gene sequencing and quantitative gene expression of tight junction proteins, mucins, antimicrobial peptides, and inflammatory cytokines.

RESULTS

The microbial composition of TPN piglets differed from SF, while ML and SO differed from each other (analysis of molecular variance; P < .05); ML piglets were more similar to SF, as indicated by UniFrac distance ( P < .05). SO piglets showed a specific and dramatic increase in Parabacteroides ( P < .05), while ML showed an increase in Enterobacteriaceae ( P < .05). Gene expression of mucin, claudin 1, β-defensin 2, and interleukin 8 were higher in TPN; overall increases were significantly less in ML versus SO ( P < .05).

CONCLUSION

The formulation of parenteral lipid is associated with differences in the gut microbiota and host response of TPN-fed neonatal piglets. Inclusion of ω-3 long-chain PUFAs appears to improve host-microbial interactions at the mucosal surface, although mechanisms are yet to be defined.

Cysteinyl-glycine reduces mucosal proinflammatory cytokine response to fMLP in a parenterally-fed piglet model

BACKGROUND

PepT1 transports dietary and bacterial peptides in the gut. We hypothesized that cysteinyl-glycine would ameliorate the inflammatory effect of a bacterial peptide, formyl-methionyl-leucyl-phenylalanine (fMLP), in both sow-fed and parenterally-fed piglets.

METHODS

An intestinal perfusion experiment was performed in piglets (N = 12) that were sow-reared or provided with parenteral nutrition (PN) for 4 d. In each piglet, five segments of isolated intestine were perfused with five treatments including cysteine and glycine, cysteinyl-glycine, fMLP, free cysteine and glycine with fMLP, or cysteinyl-glycine with fMLP. Mucosal cytokine responses and intestinal morphology was assessed in each gut segment.

RESULTS

PN piglets had lower mucosal IL-10 by approximately 20% (P < 0.01). Cysteinyl-glycine lowered TNF-α response to fMLP in PN-fed animals and IFN-γ response to fMLP in both groups (P < 0.05). The free cysteine and glycine treatment reduced TNF-α in sow-fed animals (P < 0.05). fMLP affected villus height in parenterally (P < 0.05), but not sow-fed animals.

CONCLUSION

Parenteral feeding conferred a susceptibility to mucosal damage by fMLP. The dipeptide was more effective at attenuating the inflammatory response to a bacterial peptide than free amino acids. This may be due to competitive inhibition of fMLP transport or a greater efficiency of transport of dipeptides.

Distinct immune tones are established by Lactococcus lactis BFE920 and Lactobacillus plantarum FGL0001 in the gut of olive flounder (Paralichthys olivaceus)

The immune tone is defined as an immunological state during which the readiness for immune response is potentiated. The establishment of immune tone in the gut of olive flounder (Paralichthys olivaceus) was investigated by feeding Lactococcus lactis BFE920 (LL) or Lactobacillus plantarum FGL0001 (LP). LL-fed flounder showed significantly increased levels of regulatory genes (FOXP3, IL-10, and TGF-β1), CD18, and CD83 in the gut. In contrast, LP feeding drastically increased proinflammatory genes (T-bet, IL-1β, and IFN-γ) and CD18. This indicates that LL and LP establish different types of local immune tones in the gut through differential activation of innate immune cells: LL activates both macrophages and dendritic cells while LP activates macrophages only. Both of the immune tones required at least a total of 6 probiotic feeds during 72 h for a stable establishment. Once established, the type of immune tone remained steady even up to 30 days (a total of 60 feeds) probiotics feeding. The LL-induced regulatory immune tone enhanced the level of occludin, a tight junction molecule, significantly more than that observed with the proinflammatory immune tone established by LP feeding. Consequently, LL-fed fish showed considerably lower gut permeability than that of the LP-fed group. Furthermore, when orally challenged by Edwardsiella tarda, LL-fed flounder survived at a significantly higher rate than LP-fed fish. The data clearly demonstrate that individual probiotics establish distinct types of immune tone in the fish gut, which in turn influences the immunological status as well as the physiology of the gut. Selection of proper probiotics may be essential for optimal effects in aquaculture farming.

Diet-dependent, microbiota-independent regulation of IL-10-producing lamina propria macrophages in the small intestine

Intestinal resident macrophages (Mϕs) regulate gastrointestinal homeostasis via production of an anti-inflammatory cytokine interleukin (IL)-10. Although a constant replenishment by circulating monocytes is required to maintain the pool of resident Mϕs in the colonic mucosa, the homeostatic regulation of Mϕ in the small intestine (SI) remains unclear. Here, we demonstrate that direct stimulation by dietary amino acids regulates the homeostasis of intestinal Mϕs in the SI. Mice that received total parenteral nutrition (TPN), which deprives the animals of enteral nutrients, displayed a significant decrease of IL-10-producing Mϕs in the SI, whereas the IL-10-producing CD4⁺ T cells remained intact. Likewise, enteral nutrient deprivation selectively affected the monocyte-derived F4/80⁺ Mϕ population, but not non-monocytic precursor-derived CD103⁺ dendritic cells. Notably, in contrast to colonic Mϕs, the replenishment of SI Mϕs and their IL-10 production were not regulated by the gut microbiota. Rather, SI Mϕs were directly regulated by dietary amino acids. Collectively, our study highlights the diet-dependent, microbiota-independent regulation of IL-10-producing resident Mϕs in the SI.

Tight Junction Ultrastructure Alterations in a Mouse Model of Enteral Nutrient Deprivation

BACKGROUND

Total parenteral nutrition (TPN), a necessary treatment for patients who cannot receive enteral nutrition, is associated with infectious complications due in part to a loss of intestinal epithelial barrier function (EBF). Using a mouse model of TPN, with enteral nutrient deprivation, we previously demonstrated an increase in mucosal interferon-γ and tumor necrosis factor-α; these cytokine changes are a major mediator driving a reduction in epithelial tight junction (TJ) protein expression. However, the exact ultrastructural changes to the intestinal epithelial barrier have not been previously described.

AIM

We hypothesized that TPN dependence results in ultrastructural changes in the intestinal epithelial TJ meshwork.

METHODS

C57BL/6 mice underwent internal jugular venous cannulation and were given enteral nutrition or TPN with enteral nutrient deprivation for 7 days. Freeze-fracture electron microscopy was performed on ileal tissue to characterize changes in TJ ultrastructure. EBF was measured using transepithelial resistance and tracer permeability, while TJ expression was measured via Western immunoblotting and immunofluorescence staining.

RESULTS

While strand density, linearity, and appearance were unchanged, TPN dependence led to a mean reduction in one horizontal strand out of the TJ compact meshwork to a more basal region, resulting in a reduction in meshwork depth. These findings were correlated with the loss of TJ localization of claudin-4 and tricellulin, reduced expression of claudin-5 and claudin-8, and reduced ex vivo EBF.

CONCLUSION

Tight junction ultrastructural changes may contribute to reduced EBF in the setting of TPN dependence.

Homeostasis alteration within small intestinal mucosa after acute enteral refeeding in total parenteral nutrition mouse model

Feeding strategies to care for patients who transition from enteral nutrient deprivation while on total parenteral nutrition (TPN) to enteral feedings generally proceed to full enteral nutrition once the gastrointestinal tract recovers; however, an increasing body of literature suggests that a subgroup of patients may actually develop an increased incidence of adverse events, including death. To examine this further, we studied the effects of acute refeeding in a mouse model of TPN. Interestingly, refeeding led to some beneficial effects, including prevention in the decline in intestinal epithelial cell (IEC) proliferation. However, refeeding led to a significant increase in mucosal expression of proinflammatory cytokines, including tumor necrosis factor-α (TNF-α), as well as an upregulation in Toll-like receptor 4 (TLR-4). Refeeding also failed to prevent TPN-associated increases in IEC apoptosis, loss of epithelial barrier function, and failure of the leucine-rich repeat-containing G protein-coupled receptor 5-positive stem cell expression. Transitioning from TPN to enteral feedings led to a partial restoration of the small bowel microbial population. In conclusion, while acute refeeding led to some restoration of normal gastrointestinal physiology, enteral refeeding led to a significant increase in mucosal inflammatory markers and may suggest alternative strategies to enteral refeeding should be considered.

The tight junction protein transcript abundance changes and oxidative damage by tryptophan deficiency or excess are related to the modulation of the signalling molecules, NF-κB p65, TOR, caspase-(3,8,9) and Nrf2 mRNA levels, in the gill of young grass carp (Ctenopharyngodon idellus)

This study is for the first time to explore the possible effects of dietary tryptophan (Trp) on structural integrity and the related signalling factor gene expression in the gill of young grass carp (Ctenopharyngodon idella). Fish were fed with six different experimental diets containing graded levels of Trp at 0.7 (control), 1.7, 3.1, 4.0, 5.2 and 6.1 g kg(-1) diet for 8 weeks. The results firstly demonstrated that Trp deficiency or excess caused increases in reactive oxygen species (ROS) contents, and severe oxidative damage (lipid peroxidation and protein oxidation) in the gill of fish, and those negative effects could be reversed by optimal Trp levels. Secondly, compared with the optimal Trp levels, Trp deficiency could cause decreases in the mRNA levels of the barrier functional proteins (occludin, zonula occludens-1, claudin-c, and -3) and increases in the mRNA levels of the pore-formation proteins (claudin-12 and -15) mRNA levels in the gill of fish, and those were reversed by the optimal levels of Trp. The negative effects of Trp deficiency on those tight junction protein gene expression might be partly related to the increases in the mRNA levels of pro-inflammatory cytokines and related signalling factors (tumor necrosis factor α, interleukin 8, interleukin 1β and transcription factor-κB) and decreases in the mRNA levels of anti-inflammatory cytokines and related signalling factors [interleukin 10, transforming growth factor-β1, nuclear inhibitor factor κBα (iκBα), target of rapamyc and ribosome protein S6 kinase 1 (S6K1)] in the gill of fish. In addition, optimal dietary Trp protected the gill of fish against its deficiency-caused increases in the mRNA levels of the apoptosis signalling (caspase-3, caspase-8, caspase-9) and decreases in anti-superoxide radicals capacity, anti-hydroxyl radical capacity, glutathione contents and the activities of Cu/Zn superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR) and glutathione-S-transferase (GST) in the gill of fish. Additionally, compared with the Trp deficiency, optimal Trp up-regulated the mRNA levels of SOD, CAT, GPx, GR and GST, which might be partly ascribed to the up-regulation of the NF-E2-related factor 2 (Nrf2) mRNA levels and the down-regulation of Kelch-like-ECH-associated protein 1 (Keap1) mRNA levels in the gill of fish. Interestingly, excessive Trp caused similar results with its deficiency. Collectively, Trp deficiency or excess could cause antioxidant system disruption and change tight junction protein transcription abundances, which were partly related to the signalling factors, NF-κB p65, TOR, caspase-(3,8,9) and Nrf2, in fish gill, those could be blocked by the optimal Trp levels.