Serotonin Variants & Gut Microbiota in Mental Health

Background: The gut-brain-microbiota axis (GBA) represents a complex, bidirectional communication system. Microbial tryptophan metabolism is a key mechanism within this axis - approximately 95% of the body's serotonin is synthesized peripherally in the gut. Host genetic variants can influence both serotonin biology and gut microbiome composition. Objective: To explore correlations between multi-system genetic variants (TPH2, SLC6A4, MTHFR, FUT2, MUC1, IL-6, and others) and gut microbiome compositional and functional profiles (particularly tryptophan metabolism pathways) in adults with self-reported mental health conditions. Design: Decentralized observational pilot study. Participants complete digital questionnaires and provide at-home biospecimen collections (saliva and stool) using prepaid medical-grade kits. Genomic Methodology: Saliva samples undergo DNA extraction and array-based genotyping (Illumina GSA-24 v3.0) at Gene By Gene (CLIA No. 45D1102202, CAP-accredited). Data processed via OmicsEdge bioinformatics platform. Metagenomic Methodology: Stool samples analyzed by Tiny Health using whole-genome shotgun metagenomics. Human reads are depleted against GRCh38. Taxonomic profiling via GTDB/GenBank database (111,000+ genomes). Functional annotation via KEGG Orthology and CAZy. Statistical Analysis: Descriptive statistics; alpha diversity (Shannon index); beta diversity (Bray-Curtis dissimilarity); PERMANOVA; exploratory non-parametric comparisons between genotype-defined groups. Effect sizes calculated for future study design. IRB: Approved by Sterling Institutional Review Board (Atlanta, GA), IRB ID 16153.