Esophageal Remodeling Correlates With Eating Behaviors in Pediatric Eosinophilic Esophagitis.

INTRODUCTION: There are limited data characterizing eating habits among pediatric patients with eosinophilic esophagitis (EoE). We compared eating behaviors in pediatric patients with EoE with healthy controls and assessed the degree of correlation with symptomatology, endoscopic and histologic findings, and esophageal distensibility. METHODS: We conducted a prospective, observational study where subjects consumed 4 food textures (puree, soft solid, chewable, and hard solid) and were scored for eating behaviors including number of chews per bite, sips of fluid per food, and consumption time. Symptomatic, endoscopic, histologic, and esophageal distensibility data were collected for case subjects. RESULTS: Twenty-seven case subjects and 25 healthy controls were enrolled in our study (mean age 11.0 years, 63.5% male). Compared with healthy controls, pediatric patients with EoE demonstrated more chews per bite with soft solid (13.6 vs 9.1, P = 0.031), chewable (14.7 vs 10.7, P = 0.047), and hard solid foods (19.0 vs 12.8, P = 0.037). Patients with EoE also demonstrated increased consumption time with soft solid (94.7 vs 58.3 seconds, P = 0.002), chewable (90.0 vs 65.1 seconds, P = 0.005), and hard solid foods (114.1 vs 76.4 seconds, P = 0.034) when compared with healthy controls. Subgroup analysis based on disease status showed no statistically significant differences in eating behaviors between active and inactive EoE. Total endoscopic reference score positively correlated with consumption time ( r = 0.53, P = 0.008) and number of chews ( r = 0.45, P = 0.027) for chewable foods and with number of chews ( r = 0.44, P = 0.043) for hard solid foods. Increased consumption time correlated with increased eosinophil count ( r = 0.42, P = 0.050) and decreased esophageal distensibility ( r = -0.82, P < 0.0001). DISCUSSION: Altered eating behaviors including increased chewing and increased consumption time can be seen in pediatric patients with EoE, can persist despite histologic remission, and may be driven by changes in esophageal distensibility.

Trajectory of body mass index and obesity in children with Crohn's disease compared to healthy children.

BACKGROUND: There is increasing recognition that children with Crohn's Disease (CD) can develop obesity. METHODS: Using the RISK Study, an inception cohort of pediatric CD participants, and Bone Mineral Density in Childhood Study (BMDCS), a longitudinal cohort of healthy children, multivariable linear mixed effects, generalized linear mixed effects, and logistic regression models were used to evaluate factors associated with change in body mass index z-score (BMIZ), obesity, and excessive weight gain, respectively. RESULTS: 1029 CD participants (625 exposed to antitumor necrosis factor (anti-TNF) therapy) and 1880 healthy children were included. Change in BMIZ was higher in CD exposed to anti-TNF as compared to CD unexposed to anti-TNF and the healthy reference group. Sex, age, baseline BMIZ, C-reactive protein, anti-TNF, and steroids were associated with changes in BMIZ in CD. CD exposed (odds ratio [OR] 4.81, confidence interval [CI] 4.00-5.78) and unexposed (OR 3.14, CI 2.62-3.76) had a greater likelihood of becoming obese versus the healthy reference group. While the prevalence of obesity was higher at baseline in the healthy reference group (21.3%) versus CD participants (8.5% exposed vs. 11.1% unexposed), rates of obesity were similar by the end of follow-up (21.4% healthy vs. 20.3% exposed vs. 22.5% unexposed). Anti-TNF therapy was an independent risk factor for the development of obesity and excessive weight gain in CD participants. CONCLUSIONS: Patients with CD have dynamic changes in BMIZ over time, and while for most, this is restorative, for some, this can lead to obesity and excessive weight gain. It is important to understand the factors that may lead to these changes, including anti-TNF therapy. Counseling of patients and early lifestyle intervention may be necessary.

A prospective, controlled multisite trial of yoga in pediatric inflammatory bowel disease.

AIM: To investigate whether a structured yoga program improves health-related quality of life (HRQOL) and self-efficacy in pediatric patients receiving care for inflammatory bowel disease (IBD). METHODS: IBD patients who were 10-17 years old participated in a 12 week, in-person yoga intervention at two clinical sites. Outcomes were measured at time of consent (T0), start of yoga (T1), and completion of yoga (T2) and 3 months after yoga completion (T3) using the IMPACT-III, Pediatric Quality of Life Inventory (PedsQL), and General Self Efficacy (GSE) scales. RESULTS: Seventy-eight patients were enrolled. Fifty-six patients completed nine or more classes. 73.2% had Crohn's disease and 26.8% ulcerative colitis or IBD-unclassified. A significant increase in IMPACT-III was seen from T1 to T3 (mean change of 5.22, SD = 14.33, p = 0.010), in the PedsQL (mean change = 2.3, SD = 10.24, p = 0.050), and GSE (mean change = 1, SD = 3.60, p = 0.046). 85.2% of patients reported yoga helped them to control stress. Long-term data was available for 47 subjects with 31.9% (n = 15) continuing to practice yoga one to 3 years after study completion. CONCLUSION: This structured 12-week yoga program showed significant improvements in HRQOL and general self-efficacy, particularly 3 months after classes were concluded suggesting that yoga's benefits may persist. Yoga is a safe and effective adjunct to standard medical care to improve QOL and self-efficacy in youth with IBD.

Clinical characterization of Co-morbid autoimmune disease and eating disorders: a retrospective chart review.

Research suggests a link between autoimmune illnesses (AI) and eating disorders (ED). We retrospectively reviewed charts of adolescent patients presenting for eating disorder treatment. We compared the presentation and treatment course for those with an ED and comorbid AI [with (GI-AI, N = 59) or without (non-GI, N = 21) gastrointestinal inflammation] with matched ED-only cases. The sample was overwhelmingly female, with an average age of 15.40. Weight gain trajectories differed across groups, with similar rates of weight gain between controls and non GI-AI cases and with a lower rate of weight gain for individuals with comorbid GI-AI. Over half (56%) of patients reported an AI diagnosis prior to ED; 38% reported an AI diagnosis following ED, and 6% reported ED and AI simultaneous diagnosis. On presentation, ED-only controls had higher rates of comorbid anxiety than cases in either AI group, while those with non-GI AI were more likely to report depression. Mean total GI symptoms, % goal weight at presentation, vital sign instability, and markers of refeeding syndrome did not differ across groups. Health care professionals treating patients with either condition should have a low threshold for asking additional questions to identify the presence of the other condition.

Randomized Controlled-Feeding Study of Dietary Emulsifier Carboxymethylcellulose Reveals Detrimental Impacts on the Gut Microbiota and Metabolome.

BACKGROUND & AIMS: Epidemiologic and murine studies suggest that dietary emulsifiers promote development of diseases associated with microbiota dysbiosis. Although the detrimental impact of these compounds on the intestinal microbiota and intestinal health have been demonstrated in animal and in vitro models, impact of these food additives in healthy humans remains poorly characterized. METHODS: To examine this notion in humans, we performed a double-blind controlled-feeding study of the ubiquitous synthetic emulsifier carboxymethylcellulose (CMC) in which healthy adults consumed only emulsifier-free diets (n = 9) or an identical diet enriched with 15 g per day of CMC (n = 7) for 11 days. RESULTS: Relative to control subjects, CMC consumption modestly increased postprandial abdominal discomfort and perturbed gut microbiota composition in a way that reduced its diversity. Moreover, CMC-fed subjects exhibited changes in the fecal metabolome, particularly reductions in short-chain fatty acids and free amino acids. Furthermore, we identified 2 subjects consuming CMC who exhibited increased microbiota encroachment into the normally sterile inner mucus layer, a central feature of gut inflammation, as well as stark alterations in microbiota composition. CONCLUSIONS: These results support the notion that the broad use of CMC in processed foods may be contributing to increased prevalence of an array of chronic inflammatory diseases by altering the gut microbiome and metabolome (ClinicalTrials.gov, number NCT03440229).

Whole Foods Introduction Associated With Symptomatic Anastomotic Ulceration in Children With Short Bowel Syndrome.

OBJECTIVES: Anastomotic ulceration (AU) is a rare but life-threatening complication of pediatric short bowel syndrome (SBS). AUs may be challenging to detect and refractory to treatment. This study aimed to identify features associated with symptomatic bleeding AUs in children with SBS and factors that may impact resolution of bleeding. The relationship between dietary changes and symptomatic anastomotic hemorrhage was also explored. METHODS: We conducted a retrospective chart review of 381 patients cared for in the Intestinal Rehabilitation Program at our center from 2013 to 2022. Patients with symptomatic AUs were identified based on at least 1 endoscopic procedure showing AUs and evidence of clinically significant gastrointestinal bleeding. We collected patient demographics, clinical characteristics, dietary history, radiologic imaging, and histopathology. We used descriptive statistics to identify patterns of presentation. RESULTS: AUs were identified in 22 patients who were followed for a median duration of 2.9 years after anastomotic ulcer identification. AUs uniformly evolved years after the initial anastomosis (median 3.2 years). Characteristics included bowel stricture (4/22), small bowel-colon anastomosis (19/22), partial colectomy (17/22), and an increase in whole foods fraction (12/18). Bleeding resolved with operative intervention in the majority with anastomotic stricture (3/4). Recurrent bleeding was common in those without stricture (13/18). In a subset of patients without stricture, whole food reduction was associated with improvement or resolution of bleeding (5/6). CONCLUSIONS: We observed a higher proportion of patients with AUs who responded to surgical intervention in the subset of children with definitive anastomotic strictures versus those without, suggesting that careful characterization of intestinal anatomy may be critical to predicting response to therapy. We also observed that bleeding from AU typically first manifested within 1 year of a shift from elemental or hydrolyzed enteral formula to a whole food-based diet (including commercial blenderized feeds), which may indicate that components of the enteral diet play a role in the pathogenesis of AU. Further studies are needed to validate these hypotheses.

Early Anti-Tumor-Necrosis-Factor Therapy for Crohn's Disease-Related Abdominal Abscesses and Phlegmon in Children.

BACKGROUND: Internally penetrating Crohn's Disease complications, including abscesses and phlegmon, represent a high-risk Crohn's Disease phenotype. Anti-tumor-necrosis-factor-α (Anti-TNF) therapies are effective in treating penetrating Crohn's Disease and early initiation has shown unique benefits. However, timing of anti-TNF initiation in the setting of internally penetrating Crohn's Disease complications is typically heterogenous due to concern over precipitating serious infections. Recent studies demonstrate such an association may not exist. AIMS: We aimed to describe the multidisciplinary management of pediatric patients with internally penetrating Crohn's Disease complications, focusing on the utilization and timing of anti-TNF therapy relative to complication resolution and adverse events. METHODS: We performed a single-center retrospective cohort study of pediatric patients with internally penetrating Crohn's Disease complications from 2007 to 2021. The safety and effectiveness of anti-TNF therapy initiation prior to complication resolution was assessed by comparing rates of infectious and Crohn's Disease-related adverse events between those who received anti-TNF therapy prior to complication resolution, versus those who did not. RESULTS: Twenty-one patients with internally penetrating Crohn's Disease complications were identified. 7/21 received anti-TNF therapy prior to complication resolution. Infectious adverse events within 90 days of complication occurred in 0/7 patients initiating anti-TNF therapy prior to complication resolution and 10/14 patients who did not (p = 0.004). Crohn's Disease-related surgeries and hospitalizations within 1 year of complication occurred in 12/20 patients, with similar frequency between groups. CONCLUSIONS: Initiating anti-TNF therapy prior to internally penetrating Crohn's Disease complication resolution may be a safe and effective strategy to improve clinical outcomes.

A Randomized Trial Comparing the Specific Carbohydrate Diet to a Mediterranean Diet in Adults With Crohn's Disease.

BACKGROUND & AIMS: This study compared the effectiveness of the Specific Carbohydrate Diet (SCD) to the Mediterranean diet (MD) as treatment for Crohn's disease (CD) with mild to moderate symptoms. METHODS: Adult patients with CD and with mild-to-moderate symptoms were randomly assigned 1:1 to consume the MD or SCD for 12 weeks. For the first 6 weeks, participants received prepared meals and snacks according to their assigned diet. After 6 weeks, participants were instructed to follow the diet independently. The primary outcome was symptomatic remission at week 6. Key secondary outcomes at week 6 included fecal calprotectin (FC) response (FC <250 µg/g and reduction by >50% among those with baseline FC >250 µg/g) and C-reactive protein (CRP) response (high-sensitivity CRP <5 mg/L and >50% reduction from baseline among those with high-sensitivity CRP >5 mg/L). RESULTS: The study randomized 194 patients, and 191 were included in the efficacy analyses. The percentage of participants who achieved symptomatic remission at week 6 was not superior with the SCD (SCD, 46.5%; MD, 43.5%; P = .77). FC response was achieved in 8 of 23 participants (34.8%) with the SCD and in 4 of 13 participants (30.8%) with the MD (P = .83). CRP response was achieved in 2 of 37 participants (5.4%) with the SCD and in 1 of 28 participants (3.6%) with the MD (P = .68). CONCLUSIONS: The SCD was not superior to the MD to achieve symptomatic remission, FC response, and CRP response. CRP response was uncommon. Given these results, the greater ease of following the MD and other health benefits associated with the MD, the MD may be preferred to the SCD for most patients with CD with mild to moderate symptoms. ClinicalTrials.gov Identifier: NCT03058679.

Tofacitinib Salvage Therapy for Children Hospitalized for Corticosteroid- and Biologic-Refractory Ulcerative Colitis.

OBJECTIVES: Colectomy rates following acute severe ulcerative colitis have plateaued around 20% despite intravenous corticosteroid and intensified anti-tumor necrosis factor (TNF) biologic dosing. Recent studies have shown tofacitinib to provide additional benefit in further decreasing colectomy rates among hospitalized adult patients with corticosteroid- and anti-TNF-nonresponsive ulcerative colitis. Pediatric data describing the effectiveness of tofacitinib for this indication does not yet exist. We aimed to describe the treatment courses and colectomy-free survival among pediatric patients treated with tofacitinib while hospitalized for refractory ulcerative colitis. METHODS: We performed a retrospective single-center cohort study of consecutive hospitalized pediatric patients initiating tofacitinib for refractory ulcerative colitis from 2018 to 2021. The primary outcome was 90-day colectomy-free survival. Secondary outcomes included colectomy-free clinical remission, corticosteroid independence, colectomy-free tofacitinib drug-persistence, tofacitinib-related adverse events, and postoperative complications. Baseline characteristics and details of the timing and positioning of therapies utilized during hospitalization were described. Outcomes were described using counts, percentages, and Kaplan-Meier curves. RESULTS: Eleven patients met inclusion criteria. All patients demonstrated nonresponse to both intravenous corticosteroids and anti-TNF therapy prior to tofacitinib initiation. Median hospitalization length was 22 days and mean maximum pediatric ulcerative colitis activity index during hospitalization was 68. Eight of 11 patients remained colectomy-free at 90 days following hospital admission and 6 remained colectomy-free over median 182-day follow-up, including 4 of whom remained on tofacitinib. CONCLUSIONS: Tofacitinib may represent a new treatment option for hospitalized pediatric patients with corticosteroid- and anti-TNF-nonresponsive ulcerative colitis. Future research is essential in determining the optimal positioning of these therapies.

Venous Thromboembolism in Pediatric Inflammatory Bowel Disease: A Case-Control Study.

OBJECTIVES: Inflammatory bowel disease (IBD) is associated with increased risk of venous thromboembolism (VTE). Despite this recognized risk, there are limited data and no anticoagulation guidelines for hospitalized pediatric IBD patients. The objectives of this study were to characterize pediatric IBD patients with VTE and determine risk factors. METHODS: This was a nested case-control study comparing hospitalized children with IBD diagnosed with VTE to those without VTE over a decade at a large referral center. Standard descriptive statistics were used to describe the VTE group. Multivariable conditional logistic regression was used to assess risk factors. RESULTS: Twenty-three cases were identified. Central venous catheter (CVC) presence (odds ratio [OR] 77.9; 95% confidence interval [CI]: 6.9--880.6; P < 0.001) and steroid use (OR 12.7; 95% CI: 1.3--126.4; P = 0.012) were independent risk factors. Median age at VTE was 17 years (interquartile range [IQR] 13.5--18.2), and in 48%, VTE was the indication for admission. Median duration of anticoagulation was 3.8 months (IQR 2.3--7.6), and there were no major bleeding events for patients on anticoagulation. There were no patients with known sequelae from VTE, though 22% had severe VTE that required interventions. CONCLUSIONS: Pediatric patients with IBD are at risk for VTE, although the absolute risk remains relatively low. The safety and efficacy of pharmacologic thromboprophylaxis needs to be further evaluated in this population with attention to risk factors, such as steroid use and presence of CVC.

A Diet Low in Red and Processed Meat Does Not Reduce Rate of Crohn's Disease Flares.

BACKGROUND & AIMS: Diet may be an important factor in the progression of Crohn's disease (CD). We performed a randomized controlled trial to determine whether reduced consumption of red and processed meats decreases the risk of symptomatic relapse of CD, analyzing results from the Food and Crohn's Disease Exacerbation Study (FACES) trial. METHODS: Adults with CD were recruited into the FACES trial from IBD Partners, an Internet-based cohort of patients with inflammatory bowel disease, from November 2013 through June 2015. Individuals who were in remission (CD activity index [sCDAI] scores of ≤150), had completed a biannual survey, and reported consumption of red meat at least once weekly were randomly assigned to groups that consumed a minimum of 2 servings/week of red or processed meat (high meat, n = 118) or not more than 1 serving per month (low meat, n = 96) for 49 weeks. The primary outcome was relapse of CD, defined as increase in sCDAI score by ≥70 points and to >150 or a need for CD surgery or new CD medication. A secondary outcome, moderate or severe relapse, was based on an increase in sCDAI to >219. RESULTS: During the trial, the high-meat groups reported consumption of 2 or more servings of red or processed meat during 98.5% of observed weeks compared with 18.8% of weeks for the low-meat group. Any and moderate to severe relapse occurred in 62% of participants in the high-meat group and 42% of participants in the low-meat group. There were no significant differences in time to any (P = .61) or moderate/severe (P = .50) relapse. CONCLUSIONS: In an analysis of data from the FACES trial, we found that among patients with CD in remission, level of red and processed meat consumption was not associated with time to symptomatic relapse. ClinicalTrials.gov, Number: NCT0192673.

Anemia in Children With Inflammatory Bowel Disease: A Position Paper by the IBD Committee of the North American Society of Pediatric Gastroenterology, Hepatology and Nutrition.

Anemia is one of the most common extraintestinal manifestations of inflammatory bowel disease (IBD). It can be asymptomatic or associated with nonspecific symptoms, such as irritability, headaches, fatigue, dizziness, and anorexia. In IBD patients, the etiology of anemia is often multifactorial. Various causes include iron deficiency, anemia of inflammation and chronic disease, vitamin deficiencies, hemolysis, or myelosuppressive effect of drugs. Anemia and iron deficiency in these patients may be underestimated because of their insidious onset, lack of standardized screening practices, and possibly underappreciation that treatment of anemia is also required when treating IBD. Practitioners may hesitate to use oral preparations because of their intolerance whereas intravenous preparations are underutilized because of fear of adverse events, availability, and cost. Several publications in recent years have documented the safety and comparative efficacy of various intravenous preparations. This article reviews management of anemia in children with IBD, including diagnosis, etiopathogenesis, evaluation of a patient, protocol to screen and monitor patients for early detection and response to therapy, treatment including parenteral iron therapy, and newer approaches in management of anemia of chronic disease. This report has been compiled by a group of pediatric gastroenterologists serving on the North American Society for Pediatric Gastroenterology, Hepatology and Nutrition (NASPGHAN) IBD committee, in collaboration with a pediatric hematologist, pharmacist, and a registered dietician who specializes in pediatric IBD (IBD Anemia Working Group), after an extensive review of the current literature. The purpose of this review is to raise awareness of under-diagnosis of anemia in children with IBD and make recommendations for screening, testing, and treatment in this population.

Diverting Ileostomy for the Treatment of Severe, Refractory, Pediatric Inflammatory Bowel Disease.

OBJECTIVES: Diverting ileostomy is used as a temporizing therapy in patients with perianal Crohn disease; however, little data exist regarding its use for colonic disease. The primary aim of the present study was to determine the role of diversion in severe refractory colonic inflammatory bowel disease (IBD) in a pediatric population. METHODS: Retrospective study of patients who underwent diverting ileostomy at The Children's Hospital of Philadelphia from 2000 to 2014 for the management of severe, refractory colonic IBD. Clinical variables were compared in the 1 year before ileostomy and 1 year after diversion. Surgical and disease outcomes including changes in diagnosis were reviewed through 2015. RESULTS: Twenty-four patients underwent diverting ileostomy for refractory colonic disease. Initial diagnoses were Crohn disease in 10 (42%), ulcerative colitis in 1 (4%), and IBD-unclassified in 13 patients (54%). Comparing data before and after surgery, there were statistically significant improvements in height and weight velocities, height velocity z score, blood transfusion requirement, hemoglobin, and hospitalization rates. Chronic steroid use decreased from 71% to 22%. At the conclusion of the study, 10 patients had undergone subsequent colectomy, 7 had successful bowel reanastomosis, and 7 remain diverted. Seven patients (29%) had a change in diagnosis. There were 13 surgical complications in 7 subjects, including prolapse reduction, stoma revision, and resection of ischemic bowel. CONCLUSIONS: In pediatric patients with refractory colonic IBD, diverting ileostomy can be a successful intervention to induce clinical stability. Importantly, diversion is a steroid-sparing therapy and allows additional time to clarify the diagnosis.

Comparative metabolomics in vegans and omnivores reveal constraints on diet-dependent gut microbiota metabolite production.

OBJECTIVE: The consumption of an agrarian diet is associated with a reduced risk for many diseases associated with a 'Westernised' lifestyle. Studies suggest that diet affects the gut microbiota, which subsequently influences the metabolome, thereby connecting diet, microbiota and health. However, the degree to which diet influences the composition of the gut microbiota is controversial. Murine models and studies comparing the gut microbiota in humans residing in agrarian versus Western societies suggest that the influence is large. To separate global environmental influences from dietary influences, we characterised the gut microbiota and the host metabolome of individuals consuming an agrarian diet in Western society. DESIGN AND RESULTS: Using 16S rRNA-tagged sequencing as well as plasma and urinary metabolomic platforms, we compared measures of dietary intake, gut microbiota composition and the plasma metabolome between healthy human vegans and omnivores, sampled in an urban USA environment. Plasma metabolome of vegans differed markedly from omnivores but the gut microbiota was surprisingly similar. Unlike prior studies of individuals living in agrarian societies, higher consumption of fermentable substrate in vegans was not associated with higher levels of faecal short chain fatty acids, a finding confirmed in a 10-day controlled feeding experiment. Similarly, the proportion of vegans capable of producing equol, a soy-based gut microbiota metabolite, was less than that was reported in Asian societies despite the high consumption of soy-based products. CONCLUSIONS: Evidently, residence in globally distinct societies helps determine the composition of the gut microbiota that, in turn, influences the production of diet-dependent gut microbial metabolites.

Diet in the pathogenesis and treatment of inflammatory bowel diseases.

Some of the most common symptoms of the inflammatory bowel diseases (IBD, which include ulcerative colitis and Crohn's disease) are abdominal pain, diarrhea, and weight loss. It is therefore not surprising that clinicians and patients have wondered whether dietary patterns influence the onset or course of IBD. The question of what to eat is among the most commonly asked by patients, and among the most difficult to answer for clinicians. There are substantial variations in dietary behaviors of patients and recommendations for them, although clinicians do not routinely endorse specific diets for patients with IBD. Dietary clinical trials have been limited by their inability to include a placebo control, contamination of study groups, and inclusion of patients receiving medical therapies. Additional challenges include accuracy of information on dietary intake, complex interactions between foods consumed, and differences in food metabolism among individuals. We review the roles of diet in the etiology and management of IBD based on plausible mechanisms and clinical evidence. Researchers have learned much about the effects of diet on the mucosal immune system, epithelial function, and the intestinal microbiome; these findings could have significant practical implications. Controlled studies of patients receiving enteral nutrition and observations made from patients on exclusion diets have shown that components of whole foods can have deleterious effects for patients with IBD. Additionally, studies in animal models suggested that certain nutrients can reduce intestinal inflammation. In the future, engineered diets that restrict deleterious components but supplement beneficial nutrients could be used to modify the luminal intestinal environment of patients with IBD; these might be used alone or in combination with immunosuppressive agents, or as salvage therapy for patients who do not respond or lose responsiveness to medical therapies. Stricter diets might be required to induce remission, and more sustainable exclusion diets could be used to maintain long-term remission.

Diet and the intestinal microbiome: associations, functions, and implications for health and disease.

The mutual relationship between the intestinal microbiota and its mammalian host is influenced by diet. Consumption of various nutrients affects the structure of the microbial community and provides substrates for microbial metabolism. The microbiota can produce small molecules that are absorbed by the host and affect many important physiological processes. Age-dependent and societal differences in the intestinal microbiota could result from differences in diet. Examples include differences in the intestinal microbiota of breastfed vs formula-fed infants or differences in microbial richness in people who consume an agrarian plant-based vs a Western diet, which is high in meat and fat. We review how diet affects the structure and metabolome of the human intestinal microbiome and may contribute to health or the pathogenesis of disorders such as coronary vascular disease and inflammatory bowel disease.

Correlation between intraluminal oxygen gradient and radial partitioning of intestinal microbiota.

BACKGROUND & AIMS: The gut microbiota is a complex and densely populated community in a dynamic environment determined by host physiology. We investigated how intestinal oxygen levels affect the composition of the fecal and mucosally adherent microbiota. METHODS: We used the phosphorescence quenching method and a specially designed intraluminal oxygen probe to dynamically quantify gut luminal oxygen levels in mice. 16S ribosomal RNA gene sequencing was used to characterize the microbiota in intestines of mice exposed to hyperbaric oxygen, human rectal biopsy and mucosal swab samples, and paired human stool samples. RESULTS: Average Po2 values in the lumen of the cecum were extremely low (<1 mm Hg). In altering oxygenation of mouse intestines, we observed that oxygen diffused from intestinal tissue and established a radial gradient that extended from the tissue interface into the lumen. Increasing tissue oxygenation with hyperbaric oxygen altered the composition of the gut microbiota in mice. In human beings, 16S ribosomal RNA gene analyses showed an increased proportion of oxygen-tolerant organisms of the Proteobacteria and Actinobacteria phyla associated with rectal mucosa, compared with feces. A consortium of asaccharolytic bacteria of the Firmicute and Bacteroidetes phyla, which primarily metabolize peptones and amino acids, was associated primarily with mucus. This could be owing to the presence of proteinaceous substrates provided by mucus and the shedding of the intestinal epithelium. CONCLUSIONS: In an analysis of intestinal microbiota of mice and human beings, we observed a radial gradient of microbes linked to the distribution of oxygen and nutrients provided by host tissue.