Cxcl9 as a Marker of Adipose Tissue Changes Caused by Bariatric Surgery and Psoriasis.

Background: Bariatric surgery has been shown to improve psoriasis, but the underlying molecular mechanisms remain unclear. This study aimed to investigate shared molecular mechanisms between bariatric surgery-induced adipose changes and psoriasis using bioinformatics approaches. Methods: Transcriptomic data from adipose tissue before and after bariatric surgery and from psoriatic lesions were obtained from the GEO database. Common differentially expressed genes (co-DEGs) were identified and subjected to GO/KEGG enrichment analysis, protein-protein interaction network construction, and machine learning-based hub gene selection. Diagnostic performance and immune infiltration characteristics were evaluated. Results: Co-DEGs were significantly enriched in the IL-17 signaling pathway, defense response to bacterium, response to lipopolysaccharide, cytolysis, and collagen-containing extracellular matrix. CXCL9 was identified as a key hub gene via multiple machine learning algorithms, showing good diagnostic performance in external validation (AUC > 0.85). Immune infiltration analysis revealed that CXCL9 expression was positively correlated with M1 macrophage and CD8⁺ T cell abundance, and negatively correlated with M2 macrophages. Conclusion: CXCL9, through its involvement in the IL-17 signaling pathway and lipopolysaccharide response, may serve as a critical bridge linking adipose tissue inflammation and psoriatic skin immunity, providing a novel molecular target for the improvement of psoriasis following bariatric surgery.