Fungi: Friend or Foe? A Mycobiome Evaluation in Children With Autism and Gastrointestinal Symptoms

ABSTRACT

Gastrointestinal (GI) symptoms often affect children with autism spectrum disorders (ASD) and GI symptoms have been associated with an abnormal fecal microbiome. There is limited evidence of Candida species being more prevalent in children with ASD. We enrolled 20 children with ASD and GI symptoms (ASD + GI), 10 children with ASD but no GI symptoms (ASD - GI), and 20 from typically developing (TD) children in this pilot study. Fecal mycobiome taxa were analyzed by Internal Transcribed Spacer sequencing. GI symptoms (GI Severity Index [GSI]), behavioral symptoms (Social Responsiveness Scale -2 [SRS-2]), inflammation and fungal immunity (fecal calprotectin and serum dectin-1 [ELISA]) were evaluated. We observed no changes in the abundance of total fungal species (alpha diversity) between groups. Samples with identifiable Candida spp. were present in 4 of 19 (21%) ASD + GI, in 5 of 9 (56%) ASD - GI, and in 4 of 16 (25%) TD children (overall P = 0.18). The presence of Candida spp. did not correlate with behavioral or GI symptoms (P = 0.38, P = 0.5, respectively). Fecal calprotectin was normal in all but one child. Finally, there was no significance in serum dectin-1 levels, suggesting no increased fungal immunity in children with ASD. Our data suggest that fungi are present at normal levels in the stool of children with ASD and are not associated with gut inflammation.

Gastric Bezoar: Retrieve it, Leave it, or Disbelieve it?

OBJECTIVES

To determine the demographics, potential risk factors, endoscopic interventions and outcomes relating to gastric bezoars in pediatric patients; and comparing results with previously published literature.

METHODS

Retrospective series by chart review of patients identified by International Classification of Diseases-9 codes 938 and 935, using the following Medical Subject Headings: 1, term bezoar; 2, Keywords gastric bezoar∗ or gastric foreign body∗.

RESULTS

Thirty pediatric patients between ages of 2 to 18 years were found with gastric bezoars, with a female predominance. Majority had a phytobezoar. Six patients were diagnosed with dysautonomia, implying possible role of autonomic dysfunction contributing to abnormal gastric retention. Frequent symptoms included abdominal pain, nausea and vomiting, a decrease in appetite, and unintentional weight loss. A higher prevalence of underlying gastrointestinal disorders was found in those with bezoars. Nuclear medicine gastric emptying scan performed in 13 children was significantly abnormal in only 4 of these children. Most patients were treated with endoscopic removal of the bezoar. Endoscopic removal was accomplished by Roth net, generally requiring multiple passes. At follow-up, most of the children had improvement of symptoms, with bezoar recurrence in 1 patient.

CONCLUSIONS

This is to our knowledge the largest series of gastric bezoars in pediatrics. On the basis of our review, phytobezoars may be under-reported in pediatrics. Bezoars should be considered in children presenting with chronic abdominal pain, nausea, and vomiting; even in developmentally normal children and those with normal gastric emptying. We suggest that dysautonomia and underlying gastrointestinal disorders may be potential risk factors.

Recognizing a MIS-Chievous Cause of Acute Viral Gastroenteritis

Historically, children evaluated for vomiting and diarrhea secondary to viral enteritis have symptoms lasting 2-4 days and respond to supportive care, including oral rehydration and anti-emetics if required. Recently, within a 14-day timespan, we encountered three children with severe diarrhea who rapidly became dehydrated and went into hypotensive shock. Although SARS-CoV-2 molecular tests were negative by nasopharyngeal swab, all were later found to have MIS-C. This small case series underscores features reported in previous larger studies and emphasizes the rapid clinical evolution of this condition. We highlight the importance of early recognition of cardinal laboratory findings characteristic of MIS-C (i.e., lymphopenia, markedly elevated acute phase reactants, and hypoalbuminemia). We also show serologic evidence that the pathophysiological mechanism of SARS-CoV-2 related diarrhea may differ from other causes of dehydrating vomiting and diarrhea, with no serologic evidence of villus cell injury.

Antibiotic-modulated microbiome suppresses lethal inflammation and prolongs lifespan in Treg-deficient mice

BACKGROUND

Regulatory T cell (Treg) deficiency leads to IPEX syndrome, a lethal autoimmune disease, in Human and mice. Dysbiosis of the gut microbiota in Treg-deficient scurfy (SF) mice has been described, but to date, the role of the gut microbiota remains to be determined.

RESULTS

To examine how antibiotic-modified microbiota can inhibit Treg deficiency-induced lethal inflammation in SF mice, Treg-deficient SF mice were treated with three different antibiotics. Different antibiotics resulted in distinct microbiota and metabolome changes and led to varied efficacy in prolonging lifespan and reducing inflammation in the liver and lung. Moreover, antibiotics altered plasma levels of several cytokines, especially IL-6. By analyzing gut microbiota and metabolome, we determined the microbial and metabolomic signatures which were associated with the antibiotics. Remarkably, antibiotic treatments restored the levels of several primary and secondary bile acids, which significantly reduced IL-6 expression in RAW macrophages in vitro. IL-6 blockade prolonged lifespan and inhibited inflammation in the liver and lung. By using IL-6 knockout mice, we further identified that IL-6 deletion provided a significant portion of the protection against inflammation induced by Treg dysfunction.

CONCLUSION

Our results show that three antibiotics differentially prolong survival and inhibit lethal inflammation in association with a microbiota-IL-6 axis. This pathway presents a potential avenue for treating Treg deficiency-mediated autoimmune disorders.

Probiotics in Disease Prevention and Treatment

Few treatments for human diseases have received as much investigation in the past 20 years as probiotics. In 2017, English-language meta-analyses totaling 52 studies determined the effect of probiotics on conditions ranging from necrotizing enterocolitis and colic in infants to constipation, irritable bowel syndrome, and hepatic encephalopathy in adults. The strongest evidence in favor of probiotics lies in the prevention or treatment of 5 disorders: necrotizing enterocolitis, acute infectious diarrhea, acute respiratory tract infections, antibiotic-associated diarrhea, and infant colic. Probiotic mechanisms of action include the inhibition of bacterial adhesion; enhanced mucosal barrier function; modulation of the innate and adaptive immune systems (including induction of tolerogenic dendritic cells and regulatory T cells); secretion of bioactive metabolites; and regulation of the enteric and central nervous systems. Future research is needed to identify the optimal probiotic and dose for specific diseases, to address whether the addition of prebiotics (to form synbiotics) would enhance activity, and to determine if defined microbial communities would provide benefit exceeding that of single-species probiotics.

Lactobacillus reuteri Reduces the Severity of Experimental Autoimmune Encephalomyelitis in Mice by Modulating Gut Microbiota

The gut microbiome plays an important role in immune function and has been implicated in multiple sclerosis (MS). However, how and if the modulation of microbiota can prevent or treat MS remain largely unknown. In this study, we showed that probiotic Lactobacillus reuteri DSM 17938 (L. reuteri) ameliorated the development of murine experimental autoimmune encephalomyelitis (EAE), a widely used animal model of MS, a model which is primarily mediated by T_H17 and T_H1 cells. We discovered that L. reuteri treatment reduced T_H1/T_H17 cells and their associated cytokines IFN-γ/IL-17 in EAE mice. We also showed that the loss of diversity of gut microbiota induced by EAE was largely restored by L. reuteri treatment. Taxonomy-based analysis of gut microbiota showed that three “beneficial” genera Bifidobacterium, Prevotella, and Lactobacillus were negatively correlated with EAE clinical severity, whereas the genera Anaeroplasma, Rikenellaceae, and Clostridium were positively correlated with disease severity. Notably, L. reuteri treatment coordinately altered the relative abundance of these EAE-associated taxa. In conclusion, probiotic L. reuteri changed gut microbiota to modulate immune responses in EAE, making it a novel candidate in future studies to modify the severity of MS.

Infant Colic Represents Gut Inflammation and Dysbiosis

OBJECTIVE

To dissect potential confounding effects of breast milk and formula feeding on crying + fussing, fecal calprotectin, and gut microbiota in babies with colic. We hypothesized that infant colic is associated with gut inflammation linked to intestinal dysbiosis.

STUDY DESIGN

A nested case-control design of 3 of our studies was used to analyze clinical and laboratory data at presentation, comparing babies with colic with controls. All investigators other than the biostatistician were blinded during data analysis. Subjects were recruited based on their age and crying + fussy time. We screened 65 infants, 37 with colic, as defined by Barr diary (crying + fussing time >3 hours daily), who were compared with 28 noncolicky infants.

RESULTS

Fecal calprotectin was elevated in babies with colic. For each mode of infant feeding (breast milk, formula, or breast + formula), infants' fecal calprotectin was higher in babies with colic. Infants with colic had similar levels of fecal alpha diversity (richness) when compared with controls, and alpha diversity was lower in breast-fed babies. Beta diversity at the phylum level revealed significant differences in microbial population. A phylum difference resulted from reduced Actinobacteria (95% of which are Bifidobacilli) in babies with colic. Species significantly associated with colic were Acinetobacter and Lactobacillus iners.

CONCLUSIONS

Colic is linked with gut inflammation (as determined by fecal calprotectin) and dysbiosis, independent of mode of feeding, with fewer Bifidobacilli.

TRIAL REGISTRATION

Clinicaltrials.gov: NCT01279265 and NCT01849991.

Infantile Colic: New Insights into an Old Problem

Infant colic is a characteristic group of behaviors seen in young infants. The most prominent feature is prolonged crying. Additional characteristics, including clenching of the fists and flexion of the hips, have led to the suggestion that these behaviors are related to abdominal discomfort. In this article, we show emerging evidence to support the concept that infant colic could represent gut inflammation and microbial dysbiosis that impacts brain function and even brain development.

Probiotics in Autoimmune and Inflammatory Disorders

Probiotics have been used to ameliorate gastrointestinal symptoms since ancient times. Over the past 40 years, probiotics have been shown to impact the immune system, both in vivo and in vitro. This interaction is linked to gut microbes, their polysaccharide antigens, and key metabolites produced by these bacteria. At least four metabolic pathways have been implicated in mechanistic studies of probiotics, based on mechanistic studies in animal models. Microbial⁻immune system crosstalk has been linked to: short-chain fatty acid production and signaling, tryptophan metabolism and the activation of aryl hydrocarbon receptors, nucleoside signaling in the gut, and activation of the intestinal histamine-2 receptor. Several randomized controlled trials have now shown that microbial modification by probiotics may improve gastrointestinal symptoms and multiorgan inflammation in rheumatoid arthritis, ulcerative colitis, and multiple sclerosis. Future work will need to carefully assess safety issues, selection of optimal strains and combinations, and attempts to prolong the duration of colonization of beneficial microbes.

Plasma Urea Cycle Metabolites May Be Useful Biomarkers in Children With Eosinophilic Esophagitis

Background: Eosinophilic esophagitis (EoE) is a disorder of the esophagus that has become increasingly recognized in children. Because these children undergo multiple endoscopies, discovering a non-invasive biomarker of disease activity is highly desirable. The aim of this study was to use targeted plasma metabolomics to identify potential biomarker candidates for EoE in a discovery phase. Methods: A prospective, single-center clinical trial was performed on 24 children ages 2-18 years with and without EoE undergoing upper endoscopy for any indication. Blood samples were collected for metabolomics profiling using the subclasses: amino acids, tricarboxylic acid cycle, acetylation, and methylation. Using mass spectrometry and systematic bioinformatics analysis, 48 metabolites were measured and compared between children with active EoE (+EoE) and controls (-EoE). To investigate the effect of proton pump inhibitor (PPI) use on metabolites, patients were also stratified based on PPI use (+PPI, -PPI). Results: Seven children had active EoE at the time of endoscopy. Eleven children were on PPI (4 with EoE). Of the 48 metabolites measured, 8 plasma metabolites showed statistically significant differences (p < 0.05) comparing +EoE -PPI to -EoE -PPI, a few of which were upregulated metabolites involved in the urea cycle. There were 14 significant differences comparing +EoE +PPI to +EoE -PPI. This demonstrated that in EoE patients, PPI use upregulated metabolites involved in the urea cycle, while it downregulated metabolites involved in methylation. Comparison among all four groups, +EoE +PPI, +EoE -PPI, -EoE +PPI, and -EoE -PPI, revealed 27 significantly different metabolites. +EoE +PPI had downregulated methionine and N-acetyl methionine, while both +EoE groups and -EoE +PPI had upregulated homocysteine, N-acetylputrescine, N-acetylornithine, arginine, and ornithine. Conclusion: The present study revealed key plasma metabolite differences in children with EoE compared to unaffected controls. Notable candidate biomarkers include dimethylarginine, putrescine, and N-acetylputrescine. PPI use was shown to influence these urea cycle metabolites, regardless of EoE presence. Therefore, future studies should distinguish patients based on PPI use or determine metabolites while not on treatment. These findings will be confirmed in a larger validation phase, as this may represent a significant discovery in the search for a non-invasive biomarker for EoE. Clinical Trial Registration: This clinical trial was registered with ClinicalTrials.gov, identifier: NCT 03107819.

Adenosine A2A Receptor Deletion Blocks the Beneficial Effects of Lactobacillus reuteri in Regulatory T-Deficient Scurfy Mice

The lack of a functional Foxp3 transcription factor and regulatory T (Treg) cells causes lethal, CD4⁺ T cell-driven autoimmune diseases in scurfy (SF) mice and humans. Recent studies have shown that adenosine A_2A receptor activation limits inflammation and tissue damage, thereby playing an anti-inflammatory role. However, the role of the adenosine A_2A receptor in the development of disease in SF mice remains unclear. Using a genetic approach, we found that adenosine A_2A receptor deletion in SF mice (SF⋅A2A-/-) does not affect early life events, the development of a lymphoproliferative disorder, or hyper-production of pro-inflammatory cytokines seen in the Treg-deficiency state. As shown previously, Lactobacillus reuteri DSM 17938 treatment prolonged survival and reduced multiorgan inflammation in SF mice. In marked contrast, A_2A receptor deletion completely blocked these beneficial effects of L. reuteri in SF mice. Altogether, these results suggest that although absence of the adenosine A_2A receptor does not affect the development of disease in SF mice, it plays a critical role in the immunomodulation by L. reuteri in Treg-deficiency disease. The adenosine A_2A receptor and its activation may have a role in treating other Treg dysfunction-mediated autoimmune diseases.

Lactobacillus reuteri for Infants with Colic: A Double-Blind, Placebo-Controlled, Randomized Clinical Trial

OBJECTIVE

To assess the safety of probiotic Lactobacillus reuteri strain Deutsche Sammlung von Mikroorganismen (DSM) 17938 with daily administration to healthy infants with colic and to determine the effect of L reuteri strain DSM 17938 on crying, fussing, inflammatory, immune, and microbiome variables.

STUDY DESIGN

We performed a controlled, double-blinded, phase 1 safety and tolerability trial in healthy breast-fed infants with colic, aged 3 weeks to 3 months, randomly assigned to L reuteri strain DSM 17938 (5 × 10⁸ colony-forming units daily) or placebo for 42 days and followed for 134 days.

RESULTS

Of 117 screened infants, 20 were randomized to L reuteri strain DSM 17938 or placebo (sunflower oil) (in a 2:1 ratio) with 80% retention. Eleven of the 20 (55%) presented with low absolute neutrophil counts (<1500/mm³), which resolved in all subjects by day 176. L reuteri strain DSM 17938 produced no severe adverse events and did not significantly change crying time, plasma bicarbonate, or inflammatory biomarkers. Fecal calprotectin decreased rapidly in both groups. In the infants with dominant fecal gram negatives (Klebsiella, Proteus, and Veillonella), resolution of colic was associated with marked decreases in these organisms.

CONCLUSIONS

Daily administration of L reuteri strain DSM 17938 appears to be safe in newborn infants with colic, including those with neutropenia, which frequently coexists. A placebo response of 66% suggests that many infants with colic will have resolution within 3 weeks.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT01849991.

Resetting microbiota by Lactobacillus reuteri inhibits T reg deficiency-induced autoimmunity via adenosine A2A receptors

He et al. show that T reg deficiency markedly induces autoimmunity and shifts gut microbiota. Remodeling microbiota by Lactobacillus reuteri was found to inhibit autoimmunity via the metabolite inosine, which interacts with the adenosine A_2A receptor. This finding establishes a link between the gut microbiota, A_2A receptors, and autoimmunity induced by T reg cell deficiency.

Regulatory T (T reg) cell deficiency causes lethal, CD4⁺ T cell–driven autoimmune diseases. Stem cell transplantation is used to treat these diseases, but this procedure is limited by the availability of a suitable donor. The intestinal microbiota drives host immune homeostasis by regulating the differentiation and expansion of T reg, Th1, and Th2 cells. It is currently unclear if T reg cell deficiency–mediated autoimmune disorders can be treated by targeting the enteric microbiota. Here, we demonstrate that Foxp3⁺ T reg cell deficiency results in gut microbial dysbiosis and autoimmunity over the lifespan of scurfy (SF) mouse. Remodeling microbiota with Lactobacillus reuteri prolonged survival and reduced multiorgan inflammation in SF mice. L. reuteri changed the metabolomic profile disrupted by T reg cell deficiency, and a major effect was to restore levels of the purine metabolite inosine. Feeding inosine itself prolonged life and inhibited multiorgan inflammation by reducing Th1/Th2 cells and their associated cytokines. Mechanistically, the inhibition of inosine on the differentiation of Th1 and Th2 cells in vitro depended on adenosine A_2A receptors, which were also required for the efficacy of inosine and of L. reuteri in vivo. These results reveal that the microbiota–inosine–A_2A receptor axis might represent a potential avenue for combatting autoimmune diseases mediated by T reg cell dysfunction.

Can probiotics benefit children with autism spectrum disorders?

Children with autism are commonly affected by gastrointestinal problems such as abdominal pain, constipation and diarrhea. In recent years, there has been a growing interest in the use of probiotics in this population, as it hypothetically may help to improve bowel habits and the behavioral and social functioning of these individuals. The gut microbiome plays an important role in the pathophysiology of organic as well as functional gastrointestinal disorders. Microbial modification with the use of antibiotics, probiotics, and fecal transplantation have been effective in the treatment of conditions such as recurrent Clostridium difficile infection, pouchitis, and irritable bowel syndrome. The present review presents a number of reported clinical, immunological and microbiome-related changes seen in children with autism compared to normally developed children. It also discusses gut inflammation, permeability concerns, and absorption abnormalities that may contribute to these problems. Most importantly, it discusses evidence, from human and animal studies, of a potential role of probiotics in the treatment of gastrointestinal symptoms in children with autism.

Is There a Role for the Enteral Administration of Serum-Derived Immunoglobulins in Human Gastrointestinal Disease and Pediatric Critical Care Nutrition?

Twenty years ago, there was profound, international interest in developing oral human, bovine, or chicken egg-derived immunoglobulin (Ig) for the prevention and nutritional treatment of childhood malnutrition and gastrointestinal disease, including acute diarrhea and necrotizing enterocolitis. Although such Ig products were shown to be effective, with both nutritional and antidiarrheal benefits, interest waned because of their cost and because of the perceived risk of bovine serum encephalitis (BSE). BSE is no longer considered a barrier to use of oral Ig, because the WHO has declared the United States to be BSE-free since the early 2000s. Low-cost bovine-derived products with high Ig content have been developed and are regulated as medical foods. These new products, called serum bovine Igs (SBIs), facilitate the management of chronic or severe gastrointestinal disturbances in both children and adults and are regulated by the US Food and Drug Administration. Well-established applications for use of SBIs include human immunodeficiency virus (HIV)-associated enteropathy and diarrhea-predominant irritable bowel syndrome. However, SBIs and other similar products could potentially become important components of the treatment regimen for other conditions, such as inflammatory bowel disease, by aiding in disease control without immunosuppressive side effects. In addition, SBIs may be helpful in conditions associated with the depletion of circulating and luminal Igs and could potentially play an important role in critical care nutrition. The rationale for their use is to facilitate intraluminal microbial antibody coating, an essential process in immune recognition in the gut which is disturbed in these conditions, thereby leading to intestinal inflammation. Thus, oral Ig may emerge as an important "add-on" therapy for a variety of gastrointestinal and nutritional problems during the next decade.

Hypoallergenic formula with Lactobacillus rhamnosus GG for babies with colic: A pilot study of recruitment, retention, and fecal biomarkers

AIM: To investigate recruitment, retention, and estimates for effects of formula supplementation with Lactobacillus rhamnosus GG (LGG) on inflammatory biomarkers and fecal microbial community in infants with colic.

METHODS: A prospective, double-blind, placebo-controlled trial was conducted in otherwise healthy infants with colic. We screened 74 infants and randomized and analyzed results in 20 infants [9 receiving LGG (LGG+) and 11 not receiving LGG (LGG-)]. LGG was incorporated in the formula (Nutramigen^®) (minimum of 3 × 10⁷ CFU/d) in the LGG+ group. Fecal microbiota and inflammatory biomarkers, including fecal calprotectin (FC), plasma cytokines, circulating regulatory T cells (Tregs), and crying + fussing time were analyzed to determine optimal time points and effect sizes for a larger trial.

RESULTS: Recruitment in this population was slow, with about 66% of eligible infants willing to enroll; subject retention was better (75%). These rates were influenced by parents’ reluctance to volunteer their infant for a clinical trial and by their tendency to change formulas. The maximal difference of crying + fussing time was observed at day 14, comparing the 2 groups, with a mean difference of -91 (95%CI: -76, 259) min (P = NS). FC showed no significant difference, but the optimal time to determine a potential effect was at day 90 [with a mean difference of 121 (95%CI: -48, 291) μg/g stool], observing a lower level of FC in the LGG+ group. The fecal microbial communities were chaotic, as determined by Shannon’s diversity index and not apparently influenced by the probiotic. No significant change was observed in plasma inflammatory cytokines or Tregs, comparing LGG+ to LGG- groups.

CONCLUSION: Designing future colic trials involving a probiotic-supplemented formula for infants in the United States will require consideration for difficult enrollment. Infants with colic have major variations in feal microbiota and calprotectin, both of which improve with time, with optimal time points for measurement at days 14 and 90 after treatment.

Review on hepatic explant pathology of pediatric intestinal transplant recipients: Is it time for an oil change?

A recent study attempts to add to the body of evidence that is emerging regarding the fish oil parenteral lipid product Omegaven™. The authors have shown from explant livers of children on chronic parenteral nutrition with Omegaven™ that biochemical improvement in cholestasis does not always reflect improvement in liver histology. These findings support 2 small case series that were previously published. Despite improvement and resolution of hyperbilirubinemia in all six infants, five of six infants had persistent or progressive hepatic fibrosis, while only one infant had regression of fibrosis. The study raises questions of whether there is a window of opportunity for efficacy of this preparation; also, an important question is if this omega-3 fatty acid-rich preparation is superior to newer “blended lipids” containing olive, coconut, soy, and fish oil.

Lactobacillus reuteri DSM 17938 differentially modulates effector memory T cells and Foxp3+ regulatory T cells in a mouse model of necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is an inflammatory disease with evidence of increased production of proinflammatory cytokines in the intestinal mucosa. Lactobacillus reuteri DSM 17938 (LR17938) has been shown to have anti-inflammatory activities in an experimental model of NEC. Activated effector lymphocyte recruitment to sites of inflammation requires the sequential engagement of adhesion molecules such as CD44. The phenotype of CD44(+)CD45RB(lo) separates T effector/memory (Tem) cells from naive (CD44(-)CD45RB(hi)) cells. It is unknown whether these Tem cells participate in the inflammation associated with NEC and can be altered by LR17938. NEC was induced in 8- to 10-day-old C57BL/6J mice by gavage feeding with formula and exposure to hypoxia and cold stress for 4 days. Survival curves and histological scores were analyzed. Lymphocytes isolated from mesenteric lymph nodes and ileum were labeled for CD4, CD44, CD45RB, intracellular Foxp3, and Helios and subsequently analyzed by flow cytometry. LR17938 decreased mortality and the incidence and severity of NEC. The percentage of Tem cells in the ileum and mesenteric lymph nodes was increased in NEC but decreased by LR17938. Conversely, the percentage of CD4(+)Foxp3(+) regulatory T (Treg) cells in the intestine decreased during NEC and was restored to normal by LR17938. The majority of the Treg cells preserved by LR17938 were Helios+ subsets, possibly of thymic origin. In conclusion, LR17938 may represent a useful treatment to prevent NEC. The mechanism of protection by LR17938 involves modulation of the balance between Tem and Treg cells. These T cell subsets might be potential biomarkers and therapeutic targets during intestinal inflammation.

Lactobacillus reuteri DSM 17938 changes the frequency of Foxp3+ regulatory T cells in the intestine and mesenteric lymph node in experimental necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is an inflammatory disease of the intestine in premature infants. Lactobacillus reuteri DSM 17938 improves survival and reduces the incidence and severity of NEC in a rodent model. Foxp3⁺ regulatory T cells (Tregs) maintain intestinal homeostasis by controlling inflammation and inducing tolerance. To determine whether there are insufficient numbers of Tregs to control inflammation in NEC and to determine if LR17938 increases the frequency of Tregs, we studied selected groups of newborn Sprague-Dawley rats according to feeding plan: dam±LR17938, formula±LR17938, and NEC±LR17938. NEC was induced by gavage feeding with special formula and exposure to hypoxic conditions. Lymphocytes isolated from ileum, mesenteric lymph nodes (MLN), spleen and thymus were labeled for T cell surface markers (CD3, CD4, CD8) and intracellular Foxp3; and labeled cells were analyzed by flow cytometry. The percentage of CD3⁺ T cells and Foxp3⁺ Tregs in the ileum significantly decreased in pups with NEC, compared to normal controls. Feeding LR17938 to neonatal rats with NEC increased the % of Foxp3⁺ T cells in the ileum while decreasing the percentage of cells in the MLN. Administration of LR17938 to dam-fed rats significantly increased Foxp3⁺Tregs in the ileum as early as day of life (DOL)1 but did not produce an increase in Tregs in formula-fed rats on DOL1. These results suggest that factors in breast milk may enhance the early immunomodulatory effects of LR17938. An anti-inflammatory effect of LR17938 in NEC was associated with the modulation of immune responses and induction and what appears to be migration of Foxp3⁺ Tregs to the diseased gut. Probiotic-facilitated development of Tregs might play an important role in the prevention of NEC.

Lactobacillus reuteri strains reduce incidence and severity of experimental necrotizing enterocolitis via modulation of TLR4 and NF-κB signaling in the intestine

Necrotizing enterocolitis (NEC) is the leading gastrointestinal cause of mortality and morbidity in the premature infant. Premature infants have a delay in intestinal colonization by commensal bacteria and colonization with potentially pathogenic organisms. Lactobacillus reuteri is a probiotic that inhibits enteric infections, modulates the immune system, and may be beneficial to prevent NEC. In previous studies, L. reuteri strains DSM 17938 and ATCC PTA 4659 differentially modulated inflammation in vitro; however, the strains had equivalent anti-inflammatory responses in LPS feeding-induced ileitis in neonatal rats in vivo. The impact of these two strains in the prevention of NEC has not been previously investigated. NEC was induced in newborn rats by orogastric formula feeding and exposure to hypoxia. L. reuteri was added to the formula to prevent NEC. NEC score, Toll-like receptor (TLR)-signaling genes, phospho-IκB activity, and cytokine levels in the intestine were examined. Both strains significantly increased survival rate and decreased the incidence and severity of NEC, with optimal effects from DSM 17938. In response to probiotic, mRNA expression of IL-6, TNF-α, TLR4, and NF-κB was significantly downregulated, while mRNA levels of anti-inflammatory cytokine IL-10 were significantly upregulated. In parallel, L. reuteri treatment led to decrease intestinal protein levels of TLR4 and cytokine levels of TNF-α and IL-1β in newborn rats with NEC. Both strains significantly inhibited not only intestinal LPS-induced phospho-IκB activity in an ex vivo study but also decreased the levels of phospho-IκB in the intestines of NEC rat model. Cow milk formula feeding produced a similar but milder proinflammatory profile in the intestine that was also ameliorated by 17938. Our studies demonstrate that each of the two L. reuteri strains has potential therapeutic value in our NEC model and in enteritis associated with cow milk feeding. These results support the concept that L. reuteri may represent a valuable treatment to prevent NEC.

Human-derived probiotic Lactobacillus reuteri strains differentially reduce intestinal inflammation

Lactobacillus reuteri (L. reuteri) is a probiotic that inhibits the severity of enteric infections and modulates the immune system. Human-derived L. reuteri strains DSM17938, ATCC PTA4659, ATCC PTA 5289, and ATCC PTA 6475 have demonstrated strain-specific immunomodulation in cultured monocytoid cells, but information about how these strains affect inflammation in intestinal epithelium is limited. We determined the effects of the four different L. reuteri strains on lipopolysaccharide (LPS)-induced inflammation in small intestinal epithelial cells and in the ileum of newborn rats. IPEC-J2 cells (derived from the jejunal epithelium of a neonatal piglet) and IEC-6 cells (derived from the rat crypt) were treated with L. reuteri. Newborn rat pups were gavaged cow milk formula supplemented with L. reuteri strains in the presence or absence of LPS. Protein and mRNA levels of cytokines and histological changes were measured. We demonstrate that even though one L. reuteri strain (DSM 17938) did not inhibit LPS-induced IL-8 production in cultured intestinal cells, all strains significantly reduced intestinal mucosal levels of KC/GRO (∼IL-8) and IFN-γ when newborn rat pups were fed formula containing LPS ± L. reuteri. Intestinal histological damage produced by LPS plus cow milk formula was also significantly reduced by all four strains. Cow milk formula feeding (without LPS) produced mild gut inflammation, evidenced by elevated mucosal IFN-γ and IL-13 levels, a process that could be suppressed by strain 17938. Other cytokines and chemokines were variably affected by the different strains, and there was no toxic effect of L. reuteri on intestinal cells or mucosa. In conclusion, L. reuteri strains differentially modulate LPS-induced inflammation. Probiotic interactions with both epithelial and nonepithelial cells in vivo must be instrumental in modulating intrinsic anti-inflammatory effects in the intestine. We suggest that the terms anti- and proinflammatory be used only to describe the effects of a probiotic in the living host.

Altered fecal microflora and increased fecal calprotectin in infants with colic

OBJECTIVE

We explored whether gut inflammation, colonic fermentation, and/or an altered colonic flora could provide a pathophysiological mechanism for colic.

STUDY DESIGN

The study population consisted of 36 term infants ranging in age from 14 to 81 days. We measured fecal calprotectin (a marker of neutrophil infiltration) by ELISA; stool microorganisms by denaturing gradient gel electrophoresis, cloning, and sequencing; and breath hydrogen levels using gas chromatography.

RESULTS

During 24 hours, infants with colic (n = 19) cried and fussed for a mean of 314 +/- 36 (SEM) minutes, compared with control infants (n = 17, 103 +/- 17 minutes). Fecal calprotectin levels were 2-fold higher in infants with colic than in control infants (413 +/- 71 vs 197 +/- 46 microg/g, P = .042). Stools of infants with colic had fewer identifiable bands on denaturing gradient gel electrophoresis. Klebsiella species were detected in more colic patients than in control patients (8 vs 1, P = .02), whereas Enterobacter/Pantoea species were detected only in the control patients. These differences could not be attributed to differences in formula versus breast milk feeding, consumption of elemental formula, or exposure to antibiotics.

CONCLUSIONS

Infants with colic, a condition previously believed to be nonorganic in nature, have evidence of intestinal neutrophilic infiltration and a less diverse fecal microflora.

Glutamine, arginine, and leucine signaling in the intestine. Amino Acids. 2009;37:111-122. [PMID: 19130170 DOI: 10.1007/s00726-008-0225-4]

Glutamine and leucine are abundant constituents of plant and animal proteins, whereas the content of arginine in foods and physiological fluids varies greatly. Besides their role in protein synthesis, these three amino acids individually activate signaling pathway to promote protein synthesis and possibly inhibit autophagy-mediated protein degradation in intestinal epithelial cells. In addition, glutamine and arginine stimulate the mitogen-activated protein kinase and mammalian target of rapamycin (mTOR)/p70 (s6) kinase pathways, respectively, to enhance mucosal cell migration and restitution. Moreover, through the nitric oxide-dependent cGMP signaling cascade, arginine regulates multiple physiological events in the intestine that are beneficial for cell homeostasis and survival. Available evidence from both in vitro and in vivo animal studies shows that glutamine and arginine promote cell proliferation and exert differential cytoprotective effects in response to nutrient deprivation, oxidative injury, stress, and immunological challenge. Additionally, when nitric oxide is available, leucine increases the migration of intestinal cells. Therefore, through cellular signaling mechanisms, arginine, glutamine, and leucine play crucial roles in intestinal growth, integrity, and function.

Arginine stimulates cdx2-transformed intestinal epithelial cell migration via a mechanism requiring both nitric oxide and phosphorylation of p70 S6 kinase

In intestinal cells, arginine (Arg) is 1 of the 2 most potent amino acid activators of p70(s6k), a key regulator of 5'- terminal oligopyrimidine mRNA translation, a necessary condition for increased cell migration. To investigate the mechanism of response to Arg, we used the rat crypt cell line cdx2-transformed IEC-6 cells (cdx2-IEC) and measured cell migration, immunocytochemical analysis of p70(s6k) activation in response to Arg, and production of nitric oxide (NO). When treated with Arg, cdx2-IEC increased in phosphorylation on Thr-389 of p70(s6k) (pp70(s6k)) compared with control (P < 0.01). Phospho-Thr-421/Ser-424-p70(s6k) was located in the nucleus shortly after Arg treatment. Arg enhanced pp70(s6k), cell migration (55% wound coverage), and NO production. In comparison, the branched-chain amino acid leucine (Leu) activated pp70(s6k), was a weaker stimulator of migration (23% coverage), and did not increase NO. A total of 25 micromol/L DETA-NONOate (DETA/NO) did not significantly enhance phosphorylation of p70(s6k) but enhanced the rate of cell migration by approximately 25%. Wound coverage with Leu plus DETA/NO (25 micromol/L) was greater than coverage with DETA/NO alone (P < 0.01). These and our previous studies lead to a model in which Arg must stimulate both pp70(s6k) (in the nucleus) and NO release to enhance intestinal epithelial cell migration, which may be relevant to diseases that involve intestinal villous injury.

Intestinal ribosomal p70(S6K) signaling is increased in piglet rotavirus enteritis

Recent identification of the mammalian target of rapamycin (mTOR) pathway as an amino acid-sensing mechanism that regulates protein synthesis led us to investigate its role in rotavirus diarrhea. We hypothesized that malnutrition would reduce the jejunal protein synthetic rate and mTOR signaling via its target, ribosomal p70 S6 kinase (p70(S6K)). Newborn piglets were artificially fed from birth and infected with porcine rotavirus on day 5 of life. Study groups included infected (fully fed and 50% protein calorie malnourished) and noninfected fully fed controls. Initially, in "worst-case scenario studies," malnourished infected piglets were killed on days 1, 3, 5, and 11 postinoculation, and jejunal samples were compared with controls to determine the time course of injury and p70(S6K) activation. Using a 2 x 2 factorial design, we subsequently determined if infection and/or malnutrition affected mTOR activation on day 3. Western blot analysis and immunohistochemistry were used to measure total and phosphorylated p70(S6K); [(3)H]phenylalanine incorporation was used to measure protein synthesis; and lactase specific activity and villus-crypt dimensions were used to quantify injury. At the peak of diarrhea, the in vitro jejunal protein synthetic rate increased twofold (compared with the rate in the uninfected pig jejunum), concomitant with increased jejunal p70(S6K) phosphorylation (4-fold) and an increased p70(S6K) level (3-fold, P < 0.05). Malnutrition did not alter the magnitude of p70(S6K) activation. Immunolocalization revealed that infection produced a major induction of cytoplasmic p70(S6K) and nuclear phospho-p70(S6K), mainly in the crypt. A downregulation of semitendinosus muscle p70(S6K) phosphorylation was seen at days 1-3 postinoculation. In conclusion, intestinal activation of p70(S6K) was not inhibited by malnutrition but was strongly activated during an active state of mucosal regeneration.

Role of mTOR signaling in intestinal cell migration

An early signaling event activated by amino acids and growth factors in many cell types is the phosphorylation of the mammalian target of rapamycin (mTOR; FRAP), which is functionally linked to ribosomal protein s6 kinase (p70(s6k)), a kinase that plays a critical regulatory role in the translation of mRNAs and protein synthesis. We previously showed that intestinal cell migration, the initial event in epithelial restitution, is enhanced by l-arginine (ARG). In this study, we used amino acids as prototypic activators of mTOR and ARG, IGF-1, or serum as recognized stimulators of intestinal cell migration. We found that 1) protein synthesis is required for intestinal cell migration, 2) mTOR/p70(s6k) pathway inhibitors (rapamycin, wortmannin, and intracellular Ca(2+) chelation) inhibit cell migration, 3) ARG activates migration and mTOR/p70(s6k) (but not ERK-2) in migrating enterocytes, and 4) immunocytochemistry reveals abundant p70(s6k) staining in cytoplasm, whereas phospho-p70(s6k) is virtually all intranuclear in resting cells but redistributes to the periphery on activation by ARG. We conclude that mTOR/p70(s6k) signaling is essential to intestinal cell migration, is activated by ARG, involves both nuclear and cytoplasmic events, and may play a role in intestinal repair.