Quercetin Ameliorates Comorbid Insomnia in Diarrhea-Predominant Irritable Bowel Syndrome via the PI3K/AKT/NF-κB Signaling Pathway

Background: Chronic insomnia disorder (CID) frequently coexists with diarrhea-predominant irritable bowel syndrome (IBS-D), a comorbidity characterized by gut–brain axis dysfunction and persistent inflammatory activation. However, the molecular mechanisms underlying this overlap remain incompletely understood, and effective multitarget interventions are lacking. Objectives: This study aimed to identify quercetin as a potential bioactive compound for IBS-D-associated insomnia and to investigate whether its protective effects are associated with modulation of the PI3K/AKT/NF-κB signaling pathway. Methods: CID- and IBS-D-related targets were collected from public databases. Candidate compounds were screened using bioinformatics and network pharmacology analyses, followed by molecular docking. Experimental validation was conducted in 36 male C57BL/6J mice assigned to control, CID+IBS-D model, quercetin-treated, and quercetin-plus-Recilisib-treated groups. Sleep-related behavior, EEG/EMG-derived sleep architecture, intestinal function, inflammatory markers, and pathway-related proteins were assessed. Results: Quercetin was identified as a core candidate compound. Network pharmacology revealed 43 shared targets among CID, IBS-D, and quercetin, with significant enrichment in PI3K/AKT-related signaling. In vivo, quercetin improved sleep-associated phenotypes and intestinal dysfunction; reduced visceral hypersensitivity; restored ZO-1 and Occludin expression; suppressed hypothalamic and colonic inflammatory responses; and was accompanied by reduced phosphorylation of PI3K, AKT, IκB, and NF-κB p65 in the hypothalamus. Quercetin also increased hypothalamic 5-HT1A and GABAA Rα5 expression. These effects were partially reversed by Recilisib, supporting the involvement of PI3K/AKT-associated signaling in quercetin-mediated protection. Conclusions: Quercetin alleviated key sleep-related and IBS-D-like phenotypes in a composite murine model of gut–sleep comorbidity. The protective effects were associated with reduced inflammatory activation and modulation of PI3K/AKT/NF-κB-related signaling. These findings support quercetin as a promising candidate for gut–brain axis-related comorbid disorders, while further studies are needed to define pathway specificity, tissue exposure, and translational applicability.