Vitamin D regulates olfactory function via dual transcriptional and mTOR-dependent translational control of synaptic proteins

Vitamin D (VitD) deficiency, affecting over 1 billion people worldwide, is associated with neurological dysfunction, but its cell-type-specific neural mechanisms remain unclear. Using a dietary mouse model, we show that VitD bidirectionally regulates olfactory acuity: deficiency impairs odor discrimination, while supplementation enhances sensitivity. Single-nucleus and spatial transcriptomics pinpoint selective vitamin D receptor (VDR) expression in olfactory bulb (OB) tufted cells, where it drives synaptic protein expression. Genetic VDR knockdown replicates deficiency-associated olfactory deficits, establishing VDR as essential for synaptic and translational regulation. Notably, we identify mTOR-mediated protein synthesis as a critical convergence point--pharmacological mTOR inhibition (rapamycin) rescues synaptic protein deficits and behavioral impairments in VitD-deficient mice. These findings delineate a noncanonical VDR-mTOR-translational axis--complementing conventional transcriptional regulation--through which VitD serves as a nutrient-sensitive neuromodulator that integrates dietary status with synaptic functions and sensory processing. Our study expands the physiological role of VitD beyond traditional endocrine signaling and reveals mechanistic insights that may inform novel therapeutic strategies for neurological and psychiatric conditions associated with VitD deficiency.