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Two Studies Explore Gut Microbiome Links in Children with Autism

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Two New Studies Probe the Gut-Brain Connection in Autism

Two recent preliminary studies have explored the relationship between the gut microbiome and autism spectrum disorder (ASD) in children. One investigates a potential urine-based diagnostic marker, while the other evaluates a novel fecal transplant therapy. Both studies carry significant limitations.

Study 1: Urinary Metabolites as Potential Biomarkers for ASD

published in Molecular Psychiatry, this study explored whether specific microbially-derived metabolites (MDMs) in urine could reliably distinguish children with ASD from typically developing children.

Methodology

  • Participants: 52 children with ASD and 47 typically developing children, aged 2 to 11, recruited from four U.S. sites.
  • Confirmation: ASD diagnoses were confirmed using standard diagnostic scales.
  • Analysis: Researchers analyzed urine samples using liquid chromatography–mass spectrometry.
  • Novel Tool: A new multivariate analysis system, the Microbially-Derived Metabolite System™ (MDM System™), was developed to flag children with ASD who may have intestinal dysbiosis.

Key Findings

Using a threshold of one elevated metabolite, the semiquantitative analysis demonstrated 90% sensitivity and 100% specificity for distinguishing ASD.

  • Six phenylalanine-derived and eight tryptophan-derived metabolites were significantly elevated in the ASD group, with increases ranging from 29% to 1,882% higher than in typically developing children.
  • Arabinitol, a yeast metabolite, was 51% higher in the ASD group.
  • N-formyl methionine was 70% lower in the ASD group.
  • The targeted quantitative analysis showed 78% sensitivity and 100% specificity.
  • Multivariate models achieved area under the receiver operating characteristic curve values up to 0.86.

Proposed Subtype & Limitations

The findings led researchers to propose a hypothetical ASD subtype—"ASD associated with Microbially-Derived Metabolites" (ASD-MDM)—which they estimate may fit 80–90% of their ASD cohort.

However, the authors caution that this study is based on a small pilot cohort and that independent validation in larger groups is required before the test can be considered clinically established. Several authors hold patents, have filed patent applications, or have commercial interests related to ASD diagnostics and the MDM System™.

Study 2: Fecal Microbiota Transplant Using Hydrogen Nanobubble Water

published in Frontiers in Pediatrics, this study investigated a novel fecal microbiota transplant (FMT) method using hydrogen nanobubble water as a potential treatment for ASD in children.

Background & Study Design

  • ASD affects 1 in 36 eight-year-olds in the U.S. (2020 data), up from 1 in 68 a decade prior.
  • This prospective single-arm study involved 30 participants with ASD (approximately 3:1 male-to-female ratio).
  • The fecal microbiota solution, termed SHIN-1, was prepared under GMP guidelines and administered rectally via catheter or enema in doses of 3–13 g, mixed with saline.
  • Notably, the protocol did not require antibiotics or intestinal cleansing.

Assessment Tools

  • SRS-2: Measured core ASD symptoms (social communication/interaction and restricted/repetitive behavior).
  • Short Sensory Profile (SSP): Evaluated sensory processing.
  • GSRS & Bristol Stool Form Scale: Assessed gastrointestinal (GI) symptoms.
  • PHQ-4: Screened for depression and anxiety.

Key Findings

ASD severity scores declined by approximately 29% over 30 weeks, with roughly two-thirds of participants moving from severe or moderate to milder categories.

  • Microbiome Analysis: At 24 weeks post-treatment, microbial profiles shifted toward bacteria common in neurotypical children, including increases in Bacteroides, Prevotella, Akkermansia, and Clostridium Cluster XVIII—though a consistent microbial signature was not defined across all participants.
  • Social Communication Scores: Decreased by 28% across all four subscales.
  • Restricted/Repetitive Behavior Severity: Declined by 33%.
  • Sensory Processing Disorder Severity: Fell by 30% among 26 subjects, with comparable reductions across all subtypes.
  • Anxiety & Depression: Decreased by 50% in 87% of participants.
  • Safety: No adverse events were observed.
  • Notable Subgroup: Subjects without co-occurring GI disorders experienced a 45% SRS-2 reduction into the normal range, compared to 24% in those with GI involvement.

Conclusions & Limitations

The trial suggests this gut microbiota-targeted intervention may be associated with broad improvements across core and peripheral ASD symptom domains.

The findings should be interpreted cautiously due to several limitations:

  • Absence of a randomized control group.
  • Small sample size (30 participants).
  • Single-donor design.
  • Geographically limited cohort.
  • The study received partial internal funding and included an author affiliated with the developing company.

The researchers recommend further investigation through larger, double-blind, placebo-controlled trials.