A Microbiota-Driven C-C Motif Chemokine Ligand 25–C-C Motif Chemokine Receptor 9 Axis Reprograms Intestinal Type 2 Innate Lymphoid Cells in the Distal Small Intestine to Promote Metabolic Dysfunction in Obesity

BACKGROUND & AIMS: Metabolically unhealthy obesity is characterized by chronic inflammation and metabolic dysfunction; however, how intestinal immune organization shapes systemic metabolic outcomes remains unclear. We investigated whether region-specific intestinal immune remodeling contributes to obesity-associated metabolic dysfunction. METHODS: Human serum chemokine profiling was performed in patients with severe obesity before and after bariatric surgery. Diet-induced obesity models in male mice, microbiota manipulation, single-cell RNA sequencing, genetic and pharmacologic C-C motif chemokine receptor 9 perturbation, parabiosis, and adoptive transfer experiments were used to define the mechanisms regulating intestinal innate lymphoid cells. RESULTS: The levels of circulating C-C motif chemokine ligand 25 correlated with visceral adiposity in patients with severe obesity and declined following bariatric surgery. Segment-specific analyses demonstrated preferential upregulation of C-C motif chemokine ligand 25 and C-C motif chemokine receptor 9 in the distal small intestine under metabolic stress. In obese mice, microbiota-dependent induction of epithelial C-C motif chemokine ligand 25 promoted C-C motif chemokine receptor 9-dependent accumulation of type 2 innate lymphoid cells in the ileum, accompanied by reduced adipose-resident type 2 innate lymphoid cells. Small-intestinal type 2 innate lymphoid cells underwent selective inflammatory reprogramming toward a type 1 innate lymphoid cells-like phenotype, whereas adipose tissue type 2 innate lymphoid cells remained comparatively stable. Genetic or pharmacologic disruption of C-C motif chemokine receptor 9 signaling reversed obesity-associated skewing of type 2 innate lymphoid cell distribution, suppressed intestinal inflammatory remodeling, preserved epithelial barrier integrity, and improved glucose homeostasis without affecting body weight, even in the absence of adaptive immunity. Parabiosis and adoptive transfer experiments further demonstrated that disruption of the C-C motif chemokine ligand 25-C-C motif chemokine receptor 9 axis redirected circulating type 2 innate lymphoid cells from the small intestine toward peripheral tissues. CONCLUSIONS: These findings identify the distal small intestine as a microbiota-responsive immune trafficking checkpoint linking regional immune remodeling to systemic metabolic dysfunction and establish intestinal immune positioning pathways as potential therapeutic targets in metabolically unhealthy obesity.