Salivary microRNA Signatures Associated with Autism Spectrum Disorder inBrazilian Adults

Abstract

Autism Spectrum Disorder (ASD) is a complex human neurodevelopmental condition with increasing prevalence, yet early diagnosis remains challenging, particularly in low- and middle-income countries such as Brazil, where molecular studies are scarce. This study investigated the salivary expression of four microRNAs (miR-23a-3p, miR-140-3p, miR-151a-3p, and miR-486-3p) in 45 Brazilian adults (24 with ASD and 21 neurotypical controls), using RT-qPCR and bioinformatic analyses of functional enrichment and gene target prediction. The results demonstrated significant overexpression of miR-23a-3p (FC=28.8-fold; p=0.0012), miR-140-3p (p=0.0352), and miR-486-3p (p=0.0352) in the ASD group, as well as co-expression among these miRNAs. miR-23a-3p showed the best diagnostic accuracy (AUC=0.827; specificity=100%), while miR-486-3p exhibited differential expression associated with the year of diagnosis (p=0.012). A very strong correlation was observed between miR-23a-3p and miR-151a-3p expression (ρ=0.973), along with co-regulation of gene targets across salivary gland, prefrontal cortex, and hypothalamic tissues. Enrichment analyses revealed association of gene targets with processes central to neurodevelopment, including forebrain and telencephalon development, cognition, social behavior, synaptic plasticity, and synaptic vesicle cycling. These findings provide novel evidence of salivary microRNA dysregulation in Brazilian adults with ASD, a demographic notably underrepresented in molecular autism research. Collectively, the evidence indicates that specific microRNAs involved in synaptic regulation are dysregulated in ASD and highlights the potential of saliva as a non-invasive and accessible biofluid for molecular screening in neurodevelopmental disorders.