Immunometabolic Modulation by Low‐Dose Sodium Butyrate: PI3K /Akt/ mTOR Signalling Orchestrates Macrophage Polarization to Protect Against Clostridioides difficile Colitis

Clostridioides difficile infection (CDI) remains a major cause of antibiotic-associated colitis and is characterized by excessive intestinal inflammation, epithelial barrier disruption and impaired mucosal repair. Although sodium butyrate (NaB), a microbiota-derived short-chain fatty acid, has demonstrated anti-inflammatory and barrier-protective properties, the immunological mechanisms underlying its protective effects during CDI remain incompletely understood. In this study, we investigated the role of NaB in regulating macrophage polarization and epithelial repair using murine CDI models, primary bone marrow-derived macrophages, THP-1-derived macrophages, Caco-2 epithelial cells and macrophage-epithelial co-culture systems. NaB treatment significantly alleviated CDI-associated weight loss, colonic shortening, histopathological injury and inflammatory cytokine production while restoring epithelial barrier integrity and tight junction protein expression. Mechanistically, NaB promoted macrophage polarization towards an anti-inflammatory M2 phenotype, characterized by increased CD206 and IL-10 expression and reduced CD86 and IL-1β expression. These immunomodulatory effects were accompanied by suppression of PI3K/Akt/mTOR signalling in both colonic tissues and macrophages. Pharmacological inhibition and activation studies further supported the involvement of this pathway in NaB-mediated macrophage reprogramming. Importantly, conditioned medium from NaB-treated macrophages enhanced epithelial viability, migration and barrier-associated protein expression, whereas IL-10 neutralization partially abolished these protective effects, highlighting a critical role for macrophage-epithelial crosstalk. Collectively, our findings demonstrate that low-dose NaB protects against CDI-induced intestinal injury through coordinated regulation of macrophage polarization and epithelial barrier repair, at least in part via modulation of PI3K/Akt/mTOR signalling. These results identify NaB as a promising host-directed therapeutic strategy for CDI and provide new insights into microbiota-derived metabolite-immune interactions during intestinal inflammation.