Combined Maternal and Offspring Vitamin D3 Supplementation Ameliorates Autism-Like Behaviors via VDR Pathway Activation, Neuroinflammatory Suppression, and Metabolic Homeostasis Restoration

Background: Autism Spectrum Disorder (ASD) is a widespread neurodevelopmental disorder with no approved medications targeting its core symptoms. Based on the "dual-hit" hypothesis combining Maternal Immune Activation (MIA) and Maternal Separation (MS), this study investigated whether combined maternal and offspring vitamin D3 supplementation could ameliorate autism-like behaviors by modulating the VDR pathway, neuroinflammation, and metabolic homeostasis. Materials and Methods: A "dual-hit" ASD mouse model was established in C57BL/6 offspring by combining maternal immune activation (MIA) with maternal separation (MS). Pregnant mice were randomly allocated into three groups (n = 5 per group): Control, Model (MIA+MS), and Intervention (MIA+MS + high vitamin D diet). Offspring in the intervention group continued to receive vitamin D supplementation post-weaning (from 3 weeks of age) until 8 weeks. Offspring behavioral tests were conducted on postnatal days 42-56, with the litter serving as the unit of analysis. Serum, brain tissue, colon contents, and liver samples were subsequently collected and analyzed using ELISA, Western blot, LC-MS, and immunohistochemistry. Results: Compared with controls, MIA+MS offspring exhibited significant social deficits, anxiety, and repetitive behaviors. Combined vitamin D supplementation markedly improved social preference (P