Multi-Omics Analysis Identifies Gut-Associated Metabolic Signatures Associated with Metformin-Mediated Protection Against LPS-Induced Lung Injury

Background/Objectives: Lipopolysaccharide (LPS)-induced lung injury involves pulmonary inflammation, metabolic disturbance, and intestinal dysregulation. This study investigated whether metformin attenuates LPS-induced lung and colonic injury and characterized associated gut microbiota–metabolite changes. Methods: Male C57BL/6J mice were assigned to control (CON), LPS, metformin 200 mg/kg (MET 200 mg/kg), and metformin 400 mg/kg (MET 400 mg/kg) groups. Metformin was administered by gavage for 7 days before intranasal LPS challenge. Lung and colon injury were assessed by histology, immunostaining, ELISA, and RT-qPCR. Untargeted serum metabolomics, colonic-content metabolomics, and colonic-content shotgun metagenomics were performed in the CON, LPS, and MET 400 mg/kg groups. Differential-feature, pathway-enrichment, and exploratory Spearman correlation analyses were conducted. Results: Metformin reduced LPS-induced lung injury, inflammatory cytokine production, F4/80- and MPO-positive immune-cell infiltration, and colonic inflammatory and barrier-related abnormalities. Serum metabolomics identified 468 differential features in LPS versus CON and 286 in MET versus LPS, with 218 overlapping features. Colonic-content metabolomics identified 1000 and 554 differential features, respectively, with 328 overlapping features. Eight metabolites showed metformin-associated directional shifts toward control levels in both serum and colonic contents. Metagenomics showed metformin-associated remodeling of gut microbial composition and predicted gene-content functional potential. Exploratory integrated analyses linked metformin-responsive genera and shared metabolites with pulmonary inflammatory indicators. Conclusions: Metformin was associated with attenuated LPS-induced lung and colonic injury and coordinated gut-associated microbiota–metabolite remodeling. Because the study did not include a metformin-only group or causal perturbation experiments, these findings identify candidate associations rather than demonstrating a causal gut microbiota–metabolite–lung mechanism.