Vitamin D ₃ Spatially Regulates Gut Homeostasis in Obese Mice: Segmental Epithelial Integrity and Microbial Ecology

Obesity is closely linked to vitamin D₃ (VD₃) deficiency and intestinal homeostasis disruption, underscoring a VD₃-gut homeostasis-obesity triad. This study investigates how VD₃ spatially regulates gut epithelial homeostasis and microbiota in high-fat diet (HFD)-induced obese mice, highlighting its significance for obesity nutritional management. Mice fed with a standard HFD served as models of diet-induced obesity and were administrated VD₃. Epithelial oxidative stress/inflammation, barrier function, and microbiota were assessed across intestinal segments to evaluate VD₃’s spatially specific role in intestinal homeostasis regulation under obese physiology. It was found that VD₃ supplementation could suppress HFD-induced weight gain. Comparative analysis of duodenal, jejunal, ileal, and colonic epithelia revealed that VD₃ preferentially alleviated oxidative stress, inflammation, and barrier dysfunction in the ileum and colon: colonic pro-inflammatory cytokines decreased by 29.26–47.90%, markedly higher than in the ileum (8.68–34.18%); VD₃ upregulated ileal tight junction proteins mRNA and protein expression levels (73.26-197.62% and 66.63-199.89%) and mucin (8.68%), while balancing colonic pro-inflammatory macrophage (M1)/anti-inflammatory macrophage (M2) polarization. Gut microbiota analysis demonstrated VD₃ enriched <em>Lactobacillus</em> in the ileum and <em>Lachnospiraceae</em> in the colon, while suppressing <em>Faecalibaculum</em> and <em>Romboutsia</em>. VD₃ exhibits segment-specific gut homeostasis regulation in obesity through antioxidant, anti-inflammatory, barrier repair, and microbiota remodeling mechanisms, validating the necessity of micronutrient supplementation for obesity management.