Cited by 142Gut microbiota and healthAutism Spectrum Disorder ResearchTryptophan and brain disorders

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Fecal Microbiome Transplantation from Children with Autism Spectrum Disorder Modulates Tryptophan and Serotonergic Synapse Metabolism and Induces Altered Behaviors in Germ-Free Mice

Open access
Xiao, Lu, Yan, Junyan, Yang, Ting, Zhu, Jiang, Li, Tingyu, Wei, Hong, Chen, Jie·2021·mSystems

Abstract

The relationship between the gut microbiota and ASD is not yet fully understood. Numerous studies have focused on the differences in intestinal microbial and metabolism profiles between TD and ASD children.

Overview

AI snapshot

Written from the paper’s full text.

TL;DR

Fecal microbiota from children with ASD transferred into germ-free mice induced ASD-like behaviors, distinct cecal microbial communities, and altered tryptophan/serotonin metabolism relative to mice receiving microbiota from typically developing children. The same tryptophan and serotonergic synapse pathways were altered in fecal samples from children with ASD, and key serotonin synthesis/transport proteins changed in mouse colon and prefrontal cortex.

Key findings

  • ASD-FMT mice showed ASD-like behaviors versus TD-FMT mice: shorter sniffing of mouse urine (P < 0.001), less time in the open-field center zone (P < 0.01), more self-grooming (P < 0.01), greater novel-object chamber preference (P < 0.001), and lesser strange-mouse chamber preference (P < 0.001) (n = 16).
  • Cecal microbiota differed between groups: no significant α-diversity differences, but ANOSIM showed between-group separation (R² = 0.78; P = 0.001). Verrucomicrobia was lower (P < 0.05) and unidentified_Bacteria higher (P < 0.01) in ASD-FMT; genera increased in ASD-FMT included Parabacteroides (P < 0.05), Alistipes (P < 0.01), Anaerotruncus (P < 0.01), and Helicobacter (P < 0.01), while Parasutterella (P < 0.05), Akkermansia (P < 0.05), Lachnoclostridium (P < 0.01), and unidentified_Erysipelotrichaceae (P < 0.01) were decreased (n = 8).
  • Untargeted metabolomics found 963 differential cecal metabolites (698 down, 265 up in ASD-FMT), 239 serum metabolites (122 down, 117 up), and 65 prefrontal cortex metabolites (36 down, 29 up). Tryptophan metabolism and serotonergic synapse pathways were enriched in cecal contents, serum, prefrontal cortex, and in feces from 120 children with ASD versus 60 TD children; picky eating differed (ASD 80/120 [66.7%] vs TD 26/60 [43.3%], P < 0.001).
  • Protein expression in ASD-FMT versus TD-FMT mice: colon TPH1 was upregulated (P < 0.05), colon SERT (P < 0.01) and 5-HT1AR (P < 0.05) were downregulated; prefrontal cortex TPH2 and SERT were upregulated (P < 0.05 for both), while prefrontal cortex 5-HT1AR did not differ (P > 0.05) (n = 3).

Methods

  • Thirty-two male germ-free BALB/c mice were randomized to receive 200 μl fecal suspension from 5 TD children or 5 children with ASD (boys aged 2–6 years); behavioral testing occurred after 3 weeks, and cecal contents, serum, prefrontal cortex, colon, and other tissues were collected.
  • Cecal microbiota was analyzed by 16S rRNA gene V4 sequencing with α/β diversity, PCoA, Wilcoxon tests, and LEfSe (LDA > 4); untargeted LC-MS/MS metabolomics was performed on mouse cecal contents, serum, and prefrontal cortex, plus fecal samples from 120 children with ASD and 60 TD children, with KEGG pathway enrichment and Spearman correlation.
  • Western blotting measured TPH1, SERT, and 5-HT1AR in mouse colon and TPH2, SERT, and 5-HT1AR in prefrontal cortex; differential metabolites were defined by VIP ≥ 1, P < 0.05, and fold change ≥ 1.25 or ≤ 0.8, with significance generally set at P < 0.05.

Limitations

  • The paper states that it is difficult to distinguish whether mouse cecal metabolites were host-derived or microbiota-derived; the causal relationship between gut microbes, metabolites, and key metabolic proteins remains unclear; and multiple factors affecting the microbiome and metabolomics could not be fully controlled.
  • Evident from the text: omics analyses used small mouse sample sizes (n = 8 per group; Western blot n = 3), and the mouse donors were only boys aged 2–6 years, limiting generalizability.
  • Evident from the text: the human validation cohort was separate from the 5+5 mouse donors and provided only fecal metabolomics, so human causal or protein-level findings were not directly tested.

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Integrity signals

Registry

Crossref · 10.1128/msystems.01343-20

Cites

64 of 64 references verified0 citation errors · 0 not checkable

Statistics

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Figures

FIG 1 Behavioral tests on mice colonized with fecal samples from typically developing control (TD) donors and donors with autism spectrum disorder (ASD). (A) Olfactory habituation/dishabituation test: cumulative time spent sniffing cotton swabs. (B) Open-field test: comparison of times spent in the center zone between the two groups. (C) Open-field test: comparison of the self-grooming times between the two groups. (D) Three-chamber sociability test: time spent in different boxes in the two groups. Values are expressed as means ± SEM (n = 16). *, P < 0.05; **, P < 0.01; ***, P < 0.001; ns, not significant (based on post hoc tests). TD-FMT, mice transplanted with the fecal microflora of TD donors; ASD-FMT, mice transplanted with the fecal microflora of donors with ASD.
FIG 1 Behavioral tests on mice colonized with fecal samples from typically developing control (TD) donors and donors with autism spectrum disorder (ASD). (A) Olfactory habituation/dishabituation test: cumulative time spent sniffing cotton swabs. (B) Open-field test: comparison of times spent in the center zone between the two groups. (C) Open-field test: comparison of the self-grooming times between the two groups. (D) Three-chamber sociability test: time spent in different boxes in the two groups. Values are expressed as means ± SEM (n = 16). *, P < 0.05; **, P < 0.01; ***, P < 0.001; ns, not significant (based on post hoc tests). TD-FMT, mice transplanted with the fecal microflora of TD donors; ASD-FMT, mice transplanted with the fecal microflora of donors with ASD.CC BY · PubMed Central
FIG 2 Comparison of microbial characteristics of cecal contents between the TD-FMT mice (mice transplanted with the fecal microflora of typically developing donors) and ASD-FMT mice (mice transplanted with the fecal microflora of donors with autism spectrum disorder). (A and B) Rarefaction curves (A) and alpha diversity indices (B) of cecal samples from TD-FMT and ASD-FMT mice. (C) Principal-coordinate analysis (PCoA) plots based on the unweighted UniFrac distance metrics of the cecal microbiota compositions between the two groups at the operational taxonomic unit (OTU) level. Anosim, analysis of similarity. (D and E) Percentages of community abundance in the TD-FMT and ASD-FMT mice at the phylum (D) and genus (E) levels. (F and G) Comparison of the dominant microflora at the phylum (F) and genus (G) levels between the TD-FMT and ASD-FMT mice according to the Wilcoxon rank sum test. (H) Histogram of the linear discriminant analysis (LDA) value distribution for the most abundant phylotypes of the cecal microbiota in the TD-FMT and ASD-FMT mice. *, P < 0.05; **, P < 0.01; ns, not significant (based on post hoc tests) (n = 8).
FIG 2 Comparison of microbial characteristics of cecal contents between the TD-FMT mice (mice transplanted with the fecal microflora of typically developing donors) and ASD-FMT mice (mice transplanted with the fecal microflora of donors with autism spectrum disorder). (A and B) Rarefaction curves (A) and alpha diversity indices (B) of cecal samples from TD-FMT and ASD-FMT mice. (C) Principal-coordinate analysis (PCoA) plots based on the unweighted UniFrac distance metrics of the cecal microbiota compositions between the two groups at the operational taxonomic unit (OTU) level. Anosim, analysis of similarity. (D and E) Percentages of community abundance in the TD-FMT and ASD-FMT mice at the phylum (D) and genus (E) levels. (F and G) Comparison of the dominant microflora at the phylum (F) and genus (G) levels between the TD-FMT and ASD-FMT mice according to the Wilcoxon rank sum test. (H) Histogram of the linear discriminant analysis (LDA) value distribution for the most abundant phylotypes of the cecal microbiota in the TD-FMT and ASD-FMT mice. *, P < 0.05; **, P < 0.01; ns, not significant (based on post hoc tests) (n = 8).CC BY · PubMed Central
FIG 3 Differentially abundant metabolites identified by untargeted metabolomics in different tissues of TD-FMT mice (mice transplanted with the fecal microflora of typically developing control donors) and ASD-FMT mice (mice transplanted with the fecal microflora of donors with autism spectrum disorder). (A, C, and E) Principal-component analysis (PCA) of the cecal contents (A), serum samples (C), and prefrontal cortex (PFC) samples (E) between the TD-FMT and ASD-FMT groups. (B, D, and F) Volcano plots of the altered metabolites in the cecal contents (B), serum samples (D), and PFC samples (F) between the two groups (n = 8). The abscissa represents the log2(fold change) of metabolite expression, and the ordinate represents the level of the −log10(P value). VIP, variable importance in the projection; pos, positive-ion mode; neg, negative-ion mode; UP, the upregulated metabolites in ASD-FMT group compared with TD-FMT group; DW, the downregulated metabolites in ASD-FMT group compared with TD-FMT group; NoDiff, the metabolites with no difference between TD-FMT and ASD-FMT groups.
FIG 3 Differentially abundant metabolites identified by untargeted metabolomics in different tissues of TD-FMT mice (mice transplanted with the fecal microflora of typically developing control donors) and ASD-FMT mice (mice transplanted with the fecal microflora of donors with autism spectrum disorder). (A, C, and E) Principal-component analysis (PCA) of the cecal contents (A), serum samples (C), and prefrontal cortex (PFC) samples (E) between the TD-FMT and ASD-FMT groups. (B, D, and F) Volcano plots of the altered metabolites in the cecal contents (B), serum samples (D), and PFC samples (F) between the two groups (n = 8). The abscissa represents the log2(fold change) of metabolite expression, and the ordinate represents the level of the −log10(P value). VIP, variable importance in the projection; pos, positive-ion mode; neg, negative-ion mode; UP, the upregulated metabolites in ASD-FMT group compared with TD-FMT group; DW, the downregulated metabolites in ASD-FMT group compared with TD-FMT group; NoDiff, the metabolites with no difference between TD-FMT and ASD-FMT groups.CC BY · PubMed Central
FIG 4 Metabolite enrichment analysis highlighted altered KEGG (Kyoto Encyclopedia of Genes and Genomes) pathways. (A to C) Differential KEGG pathways in the cecal contents (A), serum samples (B), and prefrontal cortex (PFC) samples (C) in the TD-FMT mice (mice transplanted with the fecal microflora of typically developing control donors) and ASD-FMT mice (mice transplanted with the fecal microflora of donors with autism spectrum disorder) (n = 8). (D) Differential KEGG pathways in the feces of TD children (n = 60) and children with ASD (n = 120). PPAR, peroxisome proliferator-activated receptor.
FIG 4 Metabolite enrichment analysis highlighted altered KEGG (Kyoto Encyclopedia of Genes and Genomes) pathways. (A to C) Differential KEGG pathways in the cecal contents (A), serum samples (B), and prefrontal cortex (PFC) samples (C) in the TD-FMT mice (mice transplanted with the fecal microflora of typically developing control donors) and ASD-FMT mice (mice transplanted with the fecal microflora of donors with autism spectrum disorder) (n = 8). (D) Differential KEGG pathways in the feces of TD children (n = 60) and children with ASD (n = 120). PPAR, peroxisome proliferator-activated receptor.CC BY · PubMed Central
FIG 5 Changed metabolites in the tryptophan and serotonin metabolic pathways between TD (typically developing control) (n = 60) and ASD (autism spectrum disorder) children (n = 120). Differential metabolites were screened according to a fold change of >1.25 or <0.8 and a P value of <0.05 (by a t test). *, P < 0.05; **, P < 0.01.
FIG 5 Changed metabolites in the tryptophan and serotonin metabolic pathways between TD (typically developing control) (n = 60) and ASD (autism spectrum disorder) children (n = 120). Differential metabolites were screened according to a fold change of >1.25 or <0.8 and a P value of <0.05 (by a t test). *, P < 0.05; **, P < 0.01.CC BY · PubMed Central
FIG 6 Differential metabolites in the tryptophan and serotonin metabolic pathways at different tissue sites between the TD-FMT (mice transplanted with the fecal microflora of typically developing control donors) and ASD-FMT (mice transplanted with the fecal microflora of donors with autism spectrum disorder) groups (n = 8). Shown are changed metabolites in the tryptophan and serotonin metabolic pathways in the cecum (A), serum (B), and prefrontal cortex (PFC) (C) between the TD-FMT and ASD-FMT groups. Differential metabolites were screened according to a fold change of >1.25 or <0.8 and a P value of <0.05 (by a t test). *, P < 0.05; **, P < 0.01; ***, P < 0.001.
FIG 6 Differential metabolites in the tryptophan and serotonin metabolic pathways at different tissue sites between the TD-FMT (mice transplanted with the fecal microflora of typically developing control donors) and ASD-FMT (mice transplanted with the fecal microflora of donors with autism spectrum disorder) groups (n = 8). Shown are changed metabolites in the tryptophan and serotonin metabolic pathways in the cecum (A), serum (B), and prefrontal cortex (PFC) (C) between the TD-FMT and ASD-FMT groups. Differential metabolites were screened according to a fold change of >1.25 or <0.8 and a P value of <0.05 (by a t test). *, P < 0.05; **, P < 0.01; ***, P < 0.001.CC BY · PubMed Central
FIG 7 Correlations of significantly different metabolites in the tryptophan and serotonin metabolic pathways with genera in the TD-FMT (mice transplanted with the fecal microflora of typically developing control donors) and ASD-FMT (mice transplanted with the fecal microflora of donors with autism spectrum disorder) groups. The correlation effect is indicated by a color gradient from blue (negative correlation) to red (positive correlation) (n = 8). *, P < 0.05; **, P < 0.01; ***, P < 0.001.
FIG 7 Correlations of significantly different metabolites in the tryptophan and serotonin metabolic pathways with genera in the TD-FMT (mice transplanted with the fecal microflora of typically developing control donors) and ASD-FMT (mice transplanted with the fecal microflora of donors with autism spectrum disorder) groups. The correlation effect is indicated by a color gradient from blue (negative correlation) to red (positive correlation) (n = 8). *, P < 0.05; **, P < 0.01; ***, P < 0.001.CC BY · PubMed Central
FIG 8 (A) Protein expression levels of TPH1 (tryptophan hydroxylase), SERT (serotonin transporter), and 5-HT1AR (serotonin 1A receptor) in the colons of the TD-FMT (mice transplanted with the fecal microflora of typically developing control donors) and ASD-FMT (mice transplanted with the fecal microflora of donors with autism spectrum disorder) groups. (E) Protein expression levels of TPH2, SERT, and 5-HT1AR in the prefrontal cortex (PFC). (B to D) Western blot (WB) signal quantification for TPH1 (B), SERT (C), and 5-HT1AR (D) in the colon. (F to H) WB signal quantification for TPH2 (F), SERT (G), and 5-HT1AR (H) in the PFC. Values are expressed as means ± SEM (n = 3). *, P < 0.05; **, P < 0.01; ns, not significant (based on post hoc tests).
FIG 8 (A) Protein expression levels of TPH1 (tryptophan hydroxylase), SERT (serotonin transporter), and 5-HT1AR (serotonin 1A receptor) in the colons of the TD-FMT (mice transplanted with the fecal microflora of typically developing control donors) and ASD-FMT (mice transplanted with the fecal microflora of donors with autism spectrum disorder) groups. (E) Protein expression levels of TPH2, SERT, and 5-HT1AR in the prefrontal cortex (PFC). (B to D) Western blot (WB) signal quantification for TPH1 (B), SERT (C), and 5-HT1AR (D) in the colon. (F to H) WB signal quantification for TPH2 (F), SERT (G), and 5-HT1AR (H) in the PFC. Values are expressed as means ± SEM (n = 3). *, P < 0.05; **, P < 0.01; ns, not significant (based on post hoc tests).CC BY · PubMed Central

Verification

Claims the paper makes

43 Own result · 20 Not checked yet · 16 Own method · 9 Own interpretation · 1 No basis given

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  • It may state two separate claims as one. 19
  • Probably not a substantial claim. 23
37 of 37
  • The paper relies on this without support.

    The causal relationship between gut microbes and metabolites and ASD symptoms is not yet established.

    “The relationship between the gut microbiota and ASD is not yet fully understood.”
    “However, it is still not clear if these microbes and metabolites cause the development of ASD symptoms.”
  • The paper relies on this without support.

    The 5 ASD donors are representative of children with ASD.

    “In this study, 5 TD children and 5 ASD children were recruited, and their fecal samples were collected as donor samples.”
  • The paper relies on this without support.

    The 5 TD donors are representative of typically developing children.

    “In this study, 5 TD children and 5 ASD children were recruited, and their fecal samples were collected as donor samples.”
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Metadata

Authors
Xiao, L., Yan, J., Yang, T., Zhu, J., Li, T., Wei, H., & Chen, J.
Affiliations
  • Children's Hospital of Chongqing Medical University (CN)
  • Army Medical University (CN)
Corresponding author
  • Wei, Hong
  • Chen, Jie
Venue
mSystems
Published
2021-04-27
Volume
6
Issue
2
ISSN
2379-5077 (ISSN-L)
OpenAlex
W3144114196
Cited by
141
References
64
Citations by year
2026: 30 · 2025: 32 · 2024: 27 · 2023: 25 · 2022: 19 · 2021: 8
FWCI
6.27
Type
journal article
Language
en
Open access
Locations
  • mSystems (publishedVersion, cc-by)
  • Europe PMC (PubMed Central) (publishedVersion, other-oa)
  • PubMed Central (publishedVersion, cc-by)
  • PubMed (publishedVersion)
  • DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion)
  • DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion, cc-by-sa)
Funders
National Natural Science Foundation of China (81470799, 31971089, 81770526)
Topics
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Gut microbiota and health
  • Life Sciences › Neuroscience › Cognitive Neuroscience › Autism Spectrum Disorder Research
  • Life Sciences › Neuroscience › Biological Psychiatry › Tryptophan and brain disorders
Keywords
autism spectrum disorder, gut microbiota, germ-free mice, tryptophan metabolism, serotonin metabolism, microbial metabolites

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