Integrated multi-omics and functional analyses reveal a GDCA-TGR5-mediated immunometabolic signature in anorexia nervosa.

BACKGROUND: Anorexia nervosa (AN) is frequently accompanied by metabolic disturbances and immune dysregulation, yet its peripheral molecular mechanisms and therapeutic targets remain poorly understood. This study integrates multi-omics analyses with experimental validation to investigate causal relationships between circulating metabolites and immune features in AN. METHODS: Two-sample Mendelian randomization (MR) analyses based on two independent cohorts were conducted to screen metabolism- and immune-related factors associated with AN. Differential expression analysis combined with machine learning was used to identify core pathogenic genes and immune infiltration patterns, which were cross-validated with MR results. The immunoregulatory role of the core gene G protein-coupled bile acid receptor 1 (GPBAR1, also known as TGR5) was further validated in vitro using mouse bone marrow-derived macrophages (BMDMs) treated with the bile acid metabolite glycodeoxycholic acid (GDCA). RESULTS: MR analysis revealed significant causal associations between eight circulating metabolites, multiple immune cell traits, and AN. Integrated transcriptomic and machine learning analyses identified TGR5 as a key gene associated with AN. Functional enrichment and immune infiltration analyses indicated that AN is characterized by an immunosuppressive microenvironment, closely correlated with TGR5 expression and activation of the primary bile acid biosynthesis pathway. Molecular docking predicted a stable interaction between GDCA and TGR5. In vitro experiments showed that GDCA increased the proportion of CD206+macrophages and upregulated Arg1 and CD206 expression in a TGR5-dependent manner. Mechanistically, GDCA activated the TGR5/cAMP/PKA pathway, promoted STAT3 and STAT6 phosphorylation, and induced M2 macrophage polarization, shifting cytokine secretion toward an anti-inflammatory phenotype. CONCLUSIONS: These findings suggest that metabolic alterations in AN directly influence immune regulation. Activation of the GDCA/TGR5/cAMP/PKA/STAT3/6 axis promotes M2 macrophage polarization and anti-inflammatory responses, revealing a novel metabolic-immune pathway with therapeutic potential in AN.