Intestinal epithelial restitution after TcdB challenge and recovery from Clostridium difficile infection in mice with alanyl-glutamine treatment

Clostridioides difficile Infection in Aged Mice Decreases Memory Function, Which Can Be Protected with Alanyl-Glutamine Supplementation

BACKGROUND

Adults aged >65 face a higher risk of both Clostridioides difficile infection (CDI) and dementia. CDI in the elderly may exacerbate functional and cognitive impairments. Current CDI treatment options are limited. Alanyl-glutamine (AQ) is a dipeptide shown to decrease C. difficile toxin effects in vitro and in vivo.

OBJECTIVES

We tested the potential benefits of AQ on the clinical outcomes and cognitive impairment in the aged mouse model of CDI treated at various timings of AQ and vancomycin treatment.

METHODS

C57BL/6 retired breeder (9 mo) and aged (18 mo) mice were treated with AQ-supplemented water as a 2-wk pretreatment or continuously. The mice underwent a standard CDI protocol (VPI10463) and were treated, or not, with vancomycin. Disease severity was tracked for 14 d, then novel object recognition (NOR) tests for acute memory were performed. Hippocampal tissues were assayed for molecular markers.

RESULTS

NOR testing confirmed CDI-induced cognitive impairment (P = 0.0352). AQ pretreatment had mild neuroprotective effects during CDI. Mice treated with vancomycin and continuous AQ had better clinical scores and better memory performance than vancomycin controls (P = 0.0286). Continuous AQ treatment, when used alone or paired with vancomycin, offered protection against CDI-induced cognitive impairment. The mechanism of CDI-induced memory impairment remains unclear, but infected mice had elevated synaptobrevin-2 (P = 0.0396) and neural cell adhesion molecule (P = 0.008) compared with uninfected controls on day 14 post infection.

CONCLUSIONS

Our findings suggest that neuroinflammation and memory loss occur during CDI, which may be ameliorated by AQ supplementation. AQ supplementation may have both neurological and intestinal protective effects during CDI treatment.

Transcriptomic analysis of ileal adaptations and growth responses in growing hens supplemented with alanyl-glutamine dipeptide

The growing phase of laying hens is crucial for growth and development due to its direct impact on their productivity during laying phase. During initial growth phase, intestinal tract undergoes rapid development which requires plenty of nutrients to help laying hens grow and mature. This study investigated the effect of Alanyl-Glutamine (Aln-Gln) levels on growth performance, ileal morphology and transcriptomic analysis of growing Hy-line brown hens. A total of 480 day old Hy-line brown chicks having similar body weight (BW) were randomly divided to be fed diets having 0%, 0.1%, 0.2% and 0.3% Aln-Gln for 6-wks (8 replicates/group, 15 birds/replicate). One bird from every pen was slaughtered and morphological parameters of ileum were evaluated. Results taken on day 42 revealed an improved average daily gain (ADG), final body weight (FBW) and feed-to-gain ratio (F/G) in the birds that consumed 0.2% and 0.3% Aln-Gln supplemented diet (P < 0.05). Ileal morphological assays showed that villus height, villus width and villus to crypts ratio (V/C) were significantly increased at 42 days of age in birds fed diets with 0.2% Aln-Gln (P<0.05). The RNA sequencing (RNA-Seq) was executed to identify differentially expressed genes (DEGs) among groups that found 2265 DEGs (1256 up-regulated; 1009 down-regulated) in ileum tissue. According to the Kyoto Encyclopedia of Genes (KEGG) and Genomic Pathway Enrichment Analysis, majority of DEGs indicated change in metabolic pathways. Genes related to growth factors, intestinal morphology and protein metabolism were up-regulated in test groups as compared to control group. In conclusion, addition of Aln-Gln to the diet improved growth performance and ileum development in growing hens; transcriptomic analysis revealed up-regulation of genes related to growth and intestinal morphology.

Exploring the Toxin-Mediated Mechanisms in Clostridioides difficile Infection

Clostridioides difficile infection (CDI) is the leading cause of nosocomial antibiotic-associated diarrhea, and colitis, with increasing incidence and healthcare costs. Its pathogenesis is primarily driven by toxins produced by the bacterium C. difficile, Toxin A (TcdA) and Toxin B (TcdB). Certain strains produce an additional toxin, the C. difficile transferase (CDT), which further enhances the virulence and pathogenicity of C. difficile. These toxins disrupt colonic epithelial barrier integrity, and induce inflammation and cellular damage, leading to CDI symptoms. Significant progress has been made in the past decade in elucidating the molecular mechanisms of TcdA, TcdB, and CDT, which provide insights into the management of CDI and the future development of novel treatment strategies based on anti-toxin therapies. While antibiotics are common treatments, high recurrence rates necessitate alternative therapies. Bezlotoxumab, targeting TcdB, is the only available anti-toxin, yet limitations persist, prompting ongoing research. This review highlights the current knowledge of the structure and mechanism of action of C. difficile toxins and their role in disease. By comprehensively describing the toxin-mediated mechanisms, this review provides insights for the future development of novel treatment strategies and the management of CDI.

Reviewing the Clostridioides difficile Mouse Model: Insights into Infection Mechanisms

Clostridioides difficile is an anaerobic, spore-forming bacterium associated with intestinal infection, manifesting a broad spectrum of gastrointestinal symptoms, ranging from mild diarrhea to severe colitis. A primary risk factor for the development of C. difficile infection (CDI) is antibiotic exposure. Elderly and immunocompromised individuals are particularly vulnerable to CDI. A pivotal aspect for comprehending the complexities of this infection relies on the utilization of experimental models that mimic human CDI transmission, pathogenesis, and progression. These models offer invaluable insights into host-pathogen interactions and disease dynamics, and serve as essential tools for testing potential therapeutic approaches. In this review, we examine the animal model for CDI and delineate the stages of infection, with a specific focus on mice. Our objective is to offer an updated description of experimental models employed in the study of CDI, emphasizing both their strengths and limitations.

Alanyl-glutamine supplementation for Clostridioides difficile infection treatment (ACT): a double-blind randomised controlled trial study protocol

INTRODUCTION

Clostridioides difficile is the leading cause of healthcare-associated infections in the USA, with an estimated 1 billion dollars in excess cost to the healthcare system annually. C. difficile infection (CDI) has high recurrence rate, up to 25% after first episode and up to 60% for succeeding episodes. Preliminary in vitro and in vivo studies indicate that alanyl-glutamine (AQ) may be beneficial in treating CDI by its effect on restoring intestinal integrity in the epithelial barrier, ameliorating inflammation and decreasing relapse.

METHODS AND ANALYSIS

This study is a randomised, placebo-controlled, double-blind, phase II clinical trial. The trial is designed to determine optimal dose and safety of oral AQ at 4, 24 and 44 g doses administered daily for 10 days concurrent with standard treatment of non-severe or severe uncomplicated CDI in persons age 18 and older. The primary outcome of interest is CDI recurrence during 60 days post-treatment follow-up, with the secondary outcome of mortality during 60 days post-treatment follow-up. Exploratory analysis will be done to determine the impact of AQ supplementation on intestinal and systemic inflammation, as well as intestinal microbial and metabolic profiles.

ETHICS AND DISSEMINATION

The study has received University of Virginia Institutional Review Board approval (HSR200046, Protocol v9, April 2023). Findings will be disseminated via conference presentations, lectures and peer-reviewed publications.

TRIAL REGISTRATION NUMBER

NCT04305769.

Host and Clostridioides difficile-Response Modulated by Micronutrients and Glutamine: An Overview

Changes in intestinal microbiota are integral to development of Clostridioides difficile (C. difficile)—associated nosocomial diarrhea. Certain diets, especially Western diets, increase susceptibility to C. difficile infection (CDI). Here, we discuss recent findings regarding how nutrients modulate response of the host and C. difficile during infection. Calcium has a role in the sporulation and germination process. Selenium is effective in reducing the total amount of C. difficile toxin A (TcdA) and toxin B (TcdB) and in decreasing its cytotoxicity. In addition, selenium phosphate synthetase deficiency reduces C. difficile growth and spore production. On the other hand, iron has a dual role in C. difficile growth. For instance, high intracellular levels can generate reactive hydroxyl radicals, whereas low levels can reduce its growth. In humans, zinc deficiency appears to be related to the recurrence of CDI, in contrast, in the CDI model in mice a diet rich in zinc increased the toxin's activity. Low vitamin D levels contribute to C. difficile colonization, toxin production, and inflammation. Furthermore, glutamine appears to protect intestinal epithelial cells from the deleterious effects of TcdA and TcdB. In conclusion, nutrients play an important role in modulating host and pathogen response. However, further studies are needed to better understand the mechanisms and address some controversies.

Nutritional Support in Malnourished Children With Compromised Gastrointestinal Function: Utility of Peptide-Based Enteral Therapy

This review focuses on nutritional support in malnourished children with compromised gastrointestinal function addressing the interplay between malnutrition and gastrointestinal dysfunction, and the specific role of peptide-based enteral therapy in pediatric malnutrition. Malnutrition is associated with impaired gut functions such as increased intestinal permeability, malabsorption, and diarrhea, while pre-existing functional gastrointestinal disorders may also lead to malnutrition. Presence of compromised gastrointestinal function in malnourished children is critical given that alterations such as malabsorption and increased intestinal permeability directly interfere with efficacy of nutritional support and recovery from malnutrition. Appropriate nutritional intervention is the key step in the management of malnutrition, while alterations in gastrointestinal functions in malnourished children are likely even in those with mild degree malnutrition. Therefore, nutritional therapy in children with compromised gastrointestinal function is considered to involve gut-protective interventions that address the overlapping and interacting effects of diarrhea, enteropathy and malnutrition to improve child survival and developmental potential in the long-term. Peptide-based enteral formulas seem to have clinical applications in malnourished children with compromised gastrointestinal function, given their association with improved gastrointestinal tolerance and absorption, better nitrogen retention/ balance, reduced diarrhea and bacterial translocation, enhanced fat absorption, and maintained/restored gut integrity as compared with free amino acid or whole-protein formulas.

Clostridium difficile toxins or infection induce upregulation of adenosine receptors and IL-6 with early pro-inflammatory and late anti-inflammatory pattern

Clostridium difficile causes intestinal inflammation, which increases adenosine. We compared the expression of adenosine receptors (AR) subtypes A1, A2A, A2B, and A3 in HCT-8, IEC-6 cells, and isolated intestinal epithelial cells, challenged or not with Clostridium difficile toxin A and B (TcdA and TcdB) or infection (CDI). In HCT-8, TcdB induced an early A2BR expression at 6 h and a late A2AR expression at 6 and 24 h. In addition, both TcdA and TcdB increased IL-6 expression at all time-points (peak at 6 h) and PSB603, an A2BR antagonist, decreased IL-6 expression and production. In isolated cecum epithelial cells, TcdA induced an early expression of A2BR at 2s and 6 h, followed by a late expression of A2AR at 6 and 24 h and of A1R at 24 h. In CDI, A2AR and A2BR expressions were increased at day 3, but not at day 7. ARs play a role in regulating inflammation during CDI by inducing an early pro-inflammatory and a late anti-inflammatory response. The timing of interventions with AR antagonist or agonists may be of relevance in treatment of CDI.

Alanyl-glutamine protects the intestinal barrier function in trained rats against the impact of acute exhaustive exercise

Strenuous exercise triggers deleterious effects on the intestinal epithelium, but their mechanisms are still uncertain. Here, we investigated whether a prolonged training and an additional exhaustive training protocol alter intestinal permeability and the putative effect of alanyl-glutamine (AG) pretreatment in this condition. Rats were allocated into 5 different groups: 1) sedentary; 2 and 3) trained (50 min per day, 5 days per week for 12 weeks) with or without 6 weeks oral (1.5 g/kg) AG supplementation; 4 and 5) trained and subjected to an additional exhaustive test protocol with or without oral AG supplementation. Venous blood samples were collected to determine gasometrical indices at the end of the 12-week protocol or after exhaustive test. Lactate and glucose levels were determined before, during, and after the exhaustive test. Ileum tissue collected after all experimental procedures was used for gene expression analysis of Zonula occludens 1 (ZO-1), occludin, claudin-2, and oligopeptide transporter 1 (PepT-1). Intestinal permeability was assessed by urinary lactulose/mannitol test collected after the 12-week protocol or the exhaustive test. The exhaustive test decreased pH and base excess and increased pCO₂. Training sessions delayed exhaustion time and reduced the changes in blood glucose and lactate levels. Trained rats exhibited upregulation of PEPT-1, ZO-1, and occludin mRNA, which were partially protected by AG. Exhaustive exercise induced intestinal paracellular leakage associated with the upregulation of claudin-2, a phenomenon protected by AG treatment. Thus, AG partially prevented intestinal training adaptations but also blocked paracellular leakage during exhaustive exercise involving claudin-2 and occludin gene expression.

The Effect of Lactoferrin and Pepsin-Treated Lactoferrin on IEC-6 Cell Damage Induced by Clostridium Difficile Toxin B

Clostridium difficile infections (CDI) have recently increased worldwide. Some CDI progress to fulminant and recurrent CDI and are associated with high mortality and morbidity. CD produces toxins A and B, which cause intestinal mucosal damage, although toxin B exhibits greater cytotoxicity. Pepsin-treated lactoferrin (PLF) is the decomposed product of lactoferrin (LF), a multifunctional glycoprotein with anti-inflammatory properties. Here, we investigate the effects of LF and PLF in toxin B-stimulated rat intestinal epithelial (IEC-6) cells. Different toxin B concentrations were added to IEC-6 cells with or without LF or PLF. Mitochondrial function and cell cytotoxicity were assessed by measuring WST-1 and LDH levels, respectively. WST-1 levels were higher in IEC-6 cells treated with toxin B and LF or PLF than in the toxin B-only control (P < 0.05). Compared with the toxin B-only control, LDH levels significantly decreased after toxin B and LF or PLF addition (P < 0.05). Wound restitution measurement using microscopy demonstrated significantly greater levels of wound restitution in cells treated with toxin B and LF or PLF than in those treated with toxin B alone after 12 h (P < 0.001). Furthermore, changes in IEC-6 cell tight junctions (TJs) were evaluated by immunofluorescence microscopy and zonula occludens-1 (ZO-1) protein expression. When LF or PLF were added to IEC-6 cells, TJ structures were maintained, and ZO-1 and occludin expression was upregulated. Taken together, these results demonstrate that LF and PLF prevent the cytotoxicity of toxin B and might have the potential to control CDI.

Dietary alanyl-glutamine improves growth performance of weaned piglets through maintaining intestinal morphology and digestion-absorption function

Alanyl-glutamine (Ala-Gln), a highly soluble and stable glutamine dipeptide, is known to improve gut integrity and function. The aim of this study was to evaluate whether dietary Ala-Gln supplementation could improve growth performance, intestinal development and digestive-absorption function in weaned piglets. A total of 100 purebred Yorkshire piglets weaned at 21 days of age were assigned randomly to four dietary treatment groups and fed a basal diet (control group) or a basal diet containing 0.15%, 0.30% and 0.45% Ala-Gln, respectively. Compared with the control group, piglets fed the Ala-Gln diets had higher average daily gain and lower feed : gain and diarrhea rate (P < 0.05). Moreover, dietary Ala-Gln supplementation increased villous height and villous height : crypt depth ratio in duodenum and jejunum (P < 0.05), as well as the activities of maltase and lysozyme in jejunum mucosa (P < 0.05). In addition, a decrease in serum diamine oxidase activity and crypt depth in duodenum and jejunum was observed in piglets fed the Ala-Gln diets (P < 0.05). Serum cytosolic phospholipase A2 (cPLA2) concentration and gene expression of cPLA2, Na+-dependent glucose transporter 1, glucose transporter 2 and peptide transporter 1 in jejunum were increased by feeding Ala-Gln diets relative to control diet (P < 0.05). These results indicated that feeding Ala-Gln diet has beneficial effects on the growth performance of weaned piglets, which associated with maintaining intestinal morphology and digestive-absorption function.

Alanyl-glutamine Protects Against Damage Induced by Enteroaggregative Escherichia coli Strains in Intestinal Cells

BACKGROUND

Enteroaggregative Escherichia coli (EAEC) is an important pathogen causing enteric infections worldwide. This pathotype is linked to malnutrition in children from developing countries. Alanyl-glutamine (Ala-Gln) is an immune modulator nutrient that acts during intestinal damage and/or inflammation. This study investigated the effect of EAEC infection and Ala-Gln on cell viability, cell death, and inflammation of intestinal epithelium cells (IEC-6).

METHODS

Cells were infected with an EAEC prototype 042 strain, an EAEC wild-type strain isolated from a Brazilian malnourished child, and a commensal E coli HS. Gene transcription and protein levels of caspases-3, -8, and -9 and cytokine-induced neutrophil chemoattractant 1 (CINC-1/CXCL1) were evaluated using RT-qPCR, western blot analysis, and ELISA.

RESULTS

Infections with both EAEC strains decreased cell viability and induced apoptosis and necrosis after 24 hours. Ala-Gln supplementation increased cell proliferation and reduced cell death in infected cells. Likewise, EAEC strain 042 significantly increased the transcript levels of caspases-3, -8, and -9 when compared to the control group, and Ala-Gln treatment reversed this effect. Furthermore, EAEC induced CXCL1 protein levels, which were also reduced by Ala-Gln supplementation.

CONCLUSION

These findings suggest that EAEC infection promotes apoptosis, necrosis, and intestinal inflammation with involvement of caspases. Supplementation of Ala-Gln inhibits cell death, increases cell proliferation, attenuates mediators associated with cell death, and inflammatory pathways in infected cells.

Disentangling Microbial Mediators of Malnutrition: Modeling Environmental Enteric Dysfunction

Environmental enteric dysfunction (EED) (also referred to as environmental enteropathy) is a subclinical chronic intestinal disorder that is an emerging contributor to early childhood malnutrition. EED is common in resource-limited settings, and is postulated to consist of small intestinal injury, dysfunctional nutrient absorption, and chronic inflammation that results in impaired early child growth attainment. Although there is emerging interest in the hypothetical potential for chemical toxins in the environmental exposome to contribute to EED, the propensity of published data, and hence the focus of this review, implicates a critical role of environmental microbes. Early childhood malnutrition and EED are most prevalent in resource-limited settings where food is limited, and inadequate access to clean water and sanitation results in frequent gastrointestinal pathogen exposures. Even as overt diarrhea rates in these settings decline, silent enteric infections and faltering growth persist. Furthermore, beyond restricted physical growth, EED and/or enteric pathogens also associate with impaired oral vaccine responses, impaired cognitive development, and may even accelerate metabolic syndrome and its cardiovascular consequences. As these potentially costly long-term consequences of early childhood enteric infections increasingly are appreciated, novel therapeutic strategies that reverse damage resulting from nutritional deficiencies and microbial insults in the developing small intestine are needed. Given the inherent limitations in investigating how specific intestinal pathogens directly injure the small intestine in children, animal models provide an affordable and controlled opportunity to elucidate causal sequelae of specific enteric infections, to differentiate consequences of defined nutrient deprivation alone from co-incident enteropathogen insults, and to correlate the resulting gut pathologies with their functional impact during vulnerable early life windows.

Novel therapies and preventative strategies for primary and recurrent Clostridium difficile infections

Clostridium difficile is the leading infectious cause of antibiotic-associated diarrhea and colitis. C. difficile infection (CDI) places a heavy burden on the healthcare system, with nearly half a million infections yearly and an approximate 20% recurrence risk after successful initial therapy. The high incidence has driven new research on improved prevention such as the emerging use of probiotics, intestinal microbiome manipulation during antibiotic therapies, vaccinations, and newer antibiotics that reduce the disruption of the intestinal microbiome. While the treatment of acute C. difficile is effective in most patients, it can be further optimized by adjuvant therapies that improve the initial treatment success and decrease the risk of subsequent recurrence. Finally, the high risk of recurrence has led to multiple emerging therapies that target toxin activity, recovery of the intestinal microbial community, and elimination of latent C. difficile in the intestine. In summary, CDIs illustrate the complex interaction among host physiology, microbial community, and pathogen that requires specific therapies to address each of the factors leading to primary infection and recurrence.

A Review of Experimental and Off-Label Therapies for Clostridium difficile Infection

In spite of increased awareness and the efforts taken to optimize Clostridium difficile infection (CDI) management, with the limited number of currently available antibiotics for C. difficile the halt of this increasing epidemic remains out of reach. There are, however, close to 80 alternative treatment methods with controversial anti-clostridial efficacy or in experimental phase today. Indeed, some of these therapies are expected to become acknowledged members of the recommended anti-CDI arsenal within the next few years. None of these alternative treatment methods can respond in itself to all the major challenges of CDI management, which are primary prophylaxis in the susceptible population, clinical cure of severe cases, prevention of recurrences, and forestallment of asymptomatic C. difficile carriage and in-hospital spread. Yet, the greater the variety of treatment choices on hand, the better combination strategies can be developed to reach these goals in the future. The aim of this article is to provide a comprehensive summary of these experimental and currently off-label therapeutic options.

Therapeutic effect of Qingyi decoction in severe acute pancreatitis-induced intestinal barrier injury

AIM: To investigate the effect of Qingyi decoction on the expression of secreted phospholipase A₂ (sPLA₂) in intestinal barrier injury.

METHODS: Fifty healthy Sprague-Dawley rats were randomly divided into control, severe acute pancreatitis (SAP), Qingyi decoction-treated (QYT), dexamethasone-treated (DEX), and verapamil-treated (VER) groups. The SAP model was induced by retrograde infusion of 1.5% sodium deoxycholate into the biliopancreatic duct of the rats. All rats were sacrificed 24 h post-SAP induction. Arterial blood, intestine, and pancreas from each rat were harvested for investigations. The levels of serum amylase (AMY) and diamine oxidase (DAO) were determined using biochemical methods, and serum tumor necrosis factor (TNF)-α level was measured by an enzyme linked immunosorbent assay. Pathologic changes in the harvested tissues were investigated by microscopic examination of hematoxylin and eosin-stained tissue sections. The expressions of sPLA₂ at mRNA and protein levels were detected by reverse transcriptase PCR and Western blot, respectively. A terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling assay was used to investigate apoptosis of epithelial cells in the intestinal tissues.

RESULTS: Compared to the control group, the expression of sPLA₂ at both the mRNA and protein levels increased significantly in the SAP group (0.36 ± 0.13 vs 0.90 ± 0.38, and 0.16 ± 0.05 vs 0.64 ± 0.05, respectively; Ps < 0.01). The levels of AMY, TNF-α and DAO in serum were also significantly increased (917 ± 62 U/L vs 6870 ± 810 U/L, 59.7 ± 14.3 ng/L vs 180.5 ± 20.1 ng/L, and 10.37 ± 2.44 U/L vs 37.89 ± 5.86 U/L, respectively; Ps < 0.01). The apoptosis index of intestinal epithelial cells also differed significantly between the SAP and control rats (0.05 ± 0.02 vs 0.26 ± 0.06; P < 0.01). The serum levels of DAO and TNF-α, and the intestinal apoptosis index significantly correlated with sPLA₂ expression in the intestine (r = 0.895, 0.893 and 0.926, respectively; Ps < 0.05). The levels of sPLA₂, AMY, TNF-α, and DAO in the QYT, VER, and DEX groups were all decreased compared with the SAP group, but not the control group. Qingyi decoction intervention, however, gave the most therapeutic effect against intestinal barrier damage, although the onset of its therapeutic effect was slower.

CONCLUSION: Qingyi decoction ameliorates acute pancreatitis-induced intestinal barrier injury by inhibiting the overexpression of intestinal sPLA_2. This mechanism may be similar to that of verapamil.

Glutamine Improves Innate Immunity and Prevents Bacterial Enteroinvasion During Parenteral Nutrition

BACKGROUND

Patients receiving parenteral nutrition (PN) are at increased risk of infectious complications compared with enteral feeding, which is in part explained by impaired mucosal immune function during PN. Adding glutamine (GLN) to PN has improved outcome in some clinical patient groups. Although GLN improves acquired mucosal immunity, its effect on innate mucosal immunity (defensins, mucus, lysozymes) has not been investigated.

METHODS

Forty-eight hours following venous cannulation, male Institute of Cancer Research mice were randomized to chow (n = 10), PN (n = 12), or PN + GLN (n = 13) for 5 days. Small intestine tissue and luminal fluid were collected for mucin 2 (MUC2), lysozyme, cryptdin 4 analysis, and luminal interleukin (IL)-4, IL-10, and IL-13 level measurement. Tissue was also harvested for ex vivo intestinal segment culture to assess tissue susceptibility to enteroinvasive Escherichia coli.

RESULTS

In both luminal and tissue samples, PN reduced MUC2 and lysozyme (P < .0001, respectively) compared with chow, whereas GLN addition increased MUC2 and lysozyme (luminal, P < .05; tissue, P < .0001, respectively) compared with PN alone. PN significantly suppressed cryptdin 4 expression, while GLN supplementation significantly enhanced expression. IL-4, IL-10, and IL-13 decreased significantly with PN compared with chow, whereas GLN significantly increased these cytokines compared with PN. Functionally, bacterial invasion increased with PN compared with chow (P < .05), while GLN significantly decreased enteroinvasion to chow levels (P < .05).

CONCLUSIONS

GLN-supplemented PN improves innate immunity and resistance to bacterial mucosal invasion lost with PN alone. This work confirms a clinical rationale for providing glutamine for the protection of the intestinal mucosa.