Mapping the Geographical Distribution of the Mucosa-Associated Gut Microbiome in GI-Symptomatic Children with Autism Spectrum Disorder.

Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by cognitive, behavioral, and communication impairments. In the last few years, it has been proposed that alterations in the gut microbiota may contribute to an aberrant communication between the gut and brain in children with ASD. Consistent with this notion, several studies have demonstrated that children with ASD have an altered fecal microbiota compared to typically developing (TD) children. However, it is unclear where along the length of the gastrointestinal (GI) tract these alterations in microbial communities occur. Additionally, the variation between specific mucosa-associated communities remains unknown. To address this gap in knowledge of the microbiome associated with ASD, biopsies from the antrum, duodenum, ileum, ascending colon, and rectum of children with ASD and age- and sex-matched TD children were examined by 16s rRNA sequencing. We observed an overall elevated abundance of Bacillota and Bacteroidota and decreased abundance of Pseudomonadota in all GI tract regions of both male and female ASD children compared to TD children. Further analysis at the genera level revealed unique differences in the microbiome in the different regions of the GI tract in ASD children compared to TD children. We also observed sex-specific differences in the gut microbiota composition in children with ASD. These data indicate that the microbiota of ASD children is altered at multiple regions of the GI tract and that different anatomic locations have unique alterations in mucosa-associated bacterial genera.

Gastrointestinal disease in children with autism spectrum disorders: Etiology or consequence?

Chronic gastrointestinal (GI) symptoms and disorders are common in children with autism spectrum disorder and have been shown to be significantly correlated with the degree of behavioral and cognitive impairment. In this unique population, GI symptoms often arise very early in development, during infancy or toddlerhood, and may be misdiagnosed - or not diagnosed at all - due in part to the challenges associated with recognition of symptoms in a minimally or non-communicative child. Evidence demonstrating that the gut-brain-axis can communicate gut dysbiosis and systemic immune dysregulation in a bidirectional manner raises the question as to whether an untreated gastrointestinal disorder can directly impact neurodevelopment or, conversely, whether having a neurodevelopmental disorder predisposes a child to chronic GI issues. From the data presented in this mini review, we conclude that the preponderance of available evidence would suggest the former scenario is more strongly supported.

A molecular biomarker for prediction of clinical outcome in children with ASD, constipation, and intestinal inflammation.

In children with autism spectrum disorder (ASD) who present to the gastroenterologist with chronic constipation on a background of colonic inflammation, we have identified two distinct clinical subtypes: (1) patients who experience a sustained state of GI symptomatic remission while on maintenance anti-inflammatory therapy (fast responders) and, (2) those with recurrent right-sided fecal loading requiring regular colon cleanouts during treatment for enterocolitis (slow responders). We hypothesized that a detailed molecular analysis of tissue from the affected region of the colon would provide mechanistic insights regarding the fast versus slow response to anti-inflammatory therapy. To test this, ascending colon biopsy tissues from 35 children with ASD (20 slow responders and 15 fast responders) were analyzed by RNAseq. Hierarchical cluster analysis was performed to assign samples to clusters and gene expression analysis was performed to identify differentially expressed transcripts (DETs) between samples within the clusters. Significant differences were found between the two clusters with fast responder-predominant cluster showing an upregulation of transcripts involved in the activation of immune and inflammatory response and the slow responder-predominant cluster showing significant over-representation of pathways impacting colonic motility (e.g. genes involved in tryptophan and serotonin degradation and mitochondrial dysfunction). Regression analysis identified a single long non-coding RNA that could predict cluster assignment with a high specificity (0.88), sensitivity (0.89) and accuracy (0.89). Comparison of gene expression profiles in the ascending colon from a subset of patients with ASD, chronic right-sided fecal loading constipation and a slow versus fast response to therapy has identified molecular mechanisms that likely contribute to this differential response following the primary therapeutic intervention (i.e. treatment for colonic inflammation with brief induction immunosuppression followed by maintenance non-steroidal anti-inflammatory therapy). Importantly, we have identified a transcript that, if validated, may provide a biomarker that can predict from the outset which patients will be slow responders who would benefit from an alternate therapeutic strategy in treating their constipation.

A Putative Blood-Based Biomarker for Autism Spectrum Disorder-Associated Ileocolitis.

Gastrointestinal symptoms are common in children with autism spectrum disorder (ASD). A significant proportion of children with ASD and gastrointestinal symptoms have histologic evidence of ileocolitis (inflammation of the terminal ileum and/or colon). We previously reported the molecular characterization of gastrointestinal biopsy tissue from ASD children with ileocolitis (ASDIC+) compared to anatomically similar inflamed tissue from typically developing children with inflammatory bowel disease (IBD; i.e. Crohn's disease or ulcerative colitis) and typically developing children with gastrointestinal symptoms but no evidence of gastrointestinal mucosal inflammation (TDIC-). ASDIC+ children had a gene expression profile that, while primarily overlapping with known IBD, had distinctive differences. The present study confirms these findings and replicates this molecular characterization in a second cohort of cases (ASDIC+) and controls (TDIC-). In these two separate case/control mucosal-based cohorts, we have demonstrated overlap of 59 differentially expressed transcripts (DETs) unique to inflamed ileocolonic tissue from symptomatic ASDIC+ children. We now report that 9 of these 59 transcripts are also differentially expressed in the peripheral blood of the second cohort of ASDIC+ children. This set of transcripts represents a putative blood-based biomarker for ASD-associated ileocolonic inflammation.

Identification of unique gene expression profile in children with regressive autism spectrum disorder (ASD) and ileocolitis.

Gastrointestinal symptoms are common in children with autism spectrum disorder (ASD) and are often associated with mucosal inflammatory infiltrates of the small and large intestine. Although distinct histologic and immunohistochemical properties of this inflammatory infiltrate have been previously described in this ASD(GI) group, molecular characterization of these lesions has not been reported. In this study we utilize transcriptome profiling of gastrointestinal mucosal biopsy tissue from ASD(GI) children and three non-ASD control groups (Crohn's disease, ulcerative colitis, and histologically normal) in an effort to determine if there is a gene expression profile unique to the ASD(GI) group. Comparison of differentially expressed transcripts between the groups demonstrated that non-pathologic (normal) tissue segregated almost completely from inflamed tissue in all cases. Gene expression profiles in intestinal biopsy tissue from patients with Crohn's disease, ulcerative colitis, and ASD(GI), while having significant overlap with each other, also showed distinctive features for each group. Taken together, these results demonstrate that ASD(GI) children have a gastrointestinal mucosal molecular profile that overlaps significantly with known inflammatory bowel disease (IBD), yet has distinctive features that further supports the presence of an ASD-associated IBD variant, or, alternatively, a prodromal phase of typical inflammatory bowel disease. Although we report qPCR confirmation of representative differentially expressed transcripts determined initially by microarray, these findings may be considered preliminary to the extent that they require further confirmation in a validation cohort.

Low serum myeloperoxidase in autistic children with gastrointestinal disease.

AIM: To assess serum myeloperoxidase (MPO) levels in autistic children with severe gastrointestinal (GI) disease and to test the hypothesis that there is an association between serum MPO concentration and inflammatory GI disease, including antineutrophil cytoplasmic antibodies (ANCA), previously seen in a subgroup of autistic children. SUBJECTS AND METHODS: Serum from 40 autistic children with chronic digestive disease (most with ileo-colonic lymphoid nodular hyperplasia (LNH) and inflammation of the colorectum, small bowel and/or stomach), and 48 controls (12 age-matched autistic children with no GI disease, 20 age-matched children without autism or GI disease, and 16 nonautistic individuals with no family history of autism) were tested using enzyme-linked immunosorbent assays designed to quantitate serum MPO levels. MPO serum concentration of autistic children with GI disease was compared to GI disease severity (including LNH and erythema) and presence of ANCA. RESULTS: We found that a significant number of autistic children with chronic digestive disease had low serum levels of MPO. However, there was no significant relationship between these levels and severity of GI disease, including the presence of ANCA. DISCUSSION: These results suggest a relationship between low MPO levels and GI disease seen in a subpopulation of autism spectrum disorders individuals. MPO concentration may therefore be a useful biomarker for GI disease in this group of autistic children.

Laryngeal dysfunction: a common cause of respiratory distress, often misdiagnosed as asthma and responsive to antireflux therapy.

Asthma is diagnosed frequently in patients with respiratory distress. However, laryngeal dysfunction, a common cause of dyspnea, may masquerade as asthma. This study investigated 158 consecutive patients referred to an allergy practice with a diagnosis of asthma. Pulmonary function testing with flow volume loops were used to separate the patients into four groups. These groups consisted of patients with asthma alone in 32%, asthma and laryngeal dysfunction in 16%, laryngeal dysfunction in 26%, and another group not meeting these criteria in 25%. Thirty patients, 10 each from the first three groups, were treated with antireflux medication and reevaluated. Symptom evaluation observed inspiratory difficulties in 73% of the laryngeal dysfunction group compared with 2% of the asthma group (p < 0.0001). Expiratory problems were present in 7% of the laryngeal dysfunction group and 71% of the asthma group (p < 0.0001). The laryngeal dysfunction group only had a 29% beneficial response to Albuterol inhalation compared with a 92% response in the asthma group (p < 0.0001). The laryngeal dysfunction group responded significantly less to both inhaled and oral steroids (p = 0.002). Among the 30 patients treated with antireflux medications, the peak flows improved by 38.7% in the laryngeal dysfunction group compared with 14.8% in the asthma group (p = 0.01).