The gut microbiota produces a variety of bioactive molecules that facilitate host–microbiota interaction. Indole and its metabolites are focused as possible biomarkers for various diseases. However, data on indole metabolism and individual metabolites remain limited. Hence, we investigated the metabolism and distribution of indole, indolin-2-one, isatin, and 3-hydroxyindolin-2-one. First, we orally administered a high dose of indole into C57BL/6J mice and measured the concentrations of indole metabolites in the brain, liver, plasma, large and small intestines, and cecum at multiple time points using HPLC/MS. Absorption in 30 min and full metabolization in 6 h were established. Furthermore, indole, indolin-2-one, and 3-hydroxiindolin-2-one, but not isatin, were found in the brain. Second, we confirmed these findings by using stable isotope-carrying indole. Third, we identified 3-hydroxyindolin-2-one as an indole metabolite in vivo by utilizing a 3-hydroxyindolin-2-one-converting enzyme, IifA. Further, we confirmed the ability of orally administered 3-hydroxyindolin-2-one to cross the blood–brain barrier in a dose-dependent manner. Finally, we detected upregulation of the CYP1A2 and CYP2A5 genes, confirming the importance of these cytochrome isoforms in indole metabolism in vivo. Overall, our results provide a basic characterization of indole metabolism in the host and highlight 3-hydroxyindolin-2-one as a potentially brain-affecting indole metabolite.

Background and Objectives: Autism spectrum disorder (ASD) is a prevalent neurodevelopmental disorder with an increasing global incidence. Gut microbiota dysbiosis is believed to be playing a role in ASD pathogenesis. Fecal microbiota transplantation (FMT) is emerging as a potential therapeutic strategy to alleviate ASD-related and gastrointestinal symptoms, but data in pediatric ASD populations remain limited. Materials and Methods: We conducted a prospective, single-center, open-label controlled study to evaluate the efficacy of colonoscopic FMT in children with ASD. Participants were allocated to two groups: an intervention group that underwent a single FMT procedure and a control group. Gastrointestinal Symptoms Rating Scale (GSRS), Autism Diagnostic Observation Schedule (ADOS), Childhood Autism Rating Scale (CARS), Child Behavior Checklist (CBCL), and Parent Global Impression (PGI-R) scales were assessed for both groups at baseline and at set time points. Results: 30 participants were enrolled, with 15 in each group. At 8 weeks, no significant between-group differences were observed for the prespecified primary endpoint, change in ADOS scores. The intervention group showed significantly greater improvements in CARS (p < 0.001), PGI-R (p < 0.001), CBCL Internalizing Problems (p = 0.001), and GSRS (p = 0.037) compared with controls; CARS and PGI-R improvements persisted at 6 months. Within the intervention group, sustained improvements were noted in CARS, GSRS, and PGI-R up to 18 months. No serious adverse events were observed; three mild, self-limited adverse events were recorded following FMT. Conclusions: Colonoscopic FMT was associated with significant short-term improvements in gastrointestinal and caregiver-reported ASD symptoms (CARS), but not in ADOS scores. Some effects persisted long-term. However, due to a lack of blinding and possible selection bias, these findings should be interpreted as exploratory. Larger randomized controlled trials are needed to confirm efficacy and optimize protocols.

Background: Autism spectrum disorder (ASD) is a multifactorial neurodevelopmental condition in which pharmacological and microbiota-targeted interventions are emerging as promising therapeutic avenues. Animal models are the main tool to investigate etiology, molecular mechanisms and screening for pharmacological therapies. Methodological differences, outcome measure variability, incomplete reporting, biological confounders, and overgeneralization of the results made evaluating innovative pharmacological agents challenging. These limitations in the field highlight a need for systematic and standardized research to reliably assess and translate pharmacological interventions from ASD animal models to human clinical relevance. Subjects: This systematic review synthesized efficacy evidence for pharmacological and microbiota-based therapies across established ASD animal models. Results: We identified 52 recent (2010–2025) studies that reported key ASD behavioral outcomes after pharmacological or microbiota-focused treatments. Interventions were grouped into therapeutic classes - including oxytocinergic agents, E/I balance therapeutic targets, metabolic drugs, cannabinoids, purine-based interventions and emerging targets - alongside microbiota-directed strategies such as probiotics, prebiotics, and fecal microbiota transplantation. By integrating effect directions and robustness across models, we identified most potential drug candidates, evaluated the efficacy of novel strategies, and recognized critical translational gaps. The reviewed studies demonstrate that ASD-like behavioral deficits in preclinical models can be modulated through interventions targeting diverse biological systems, including neurotransmission, neuroinflammation, metabolism, and the gut-brain axis. Conclusions: These findings support the multifactorial nature of ASD pathophysiology which arises from a network of interacting systemic processes rather than a single molecular defect. It could explain the limited success of traditionally narrowly targeted interventions and suggest a paradigm shift into a more systemic approach.