Vitamin D hormone regulates serotonin synthesis. Part 1: relevance for autism
The FASEB Journal. June 2014. 28(6): 2398-2413
Rhonda P. Patrick and Bruce N. Ames
Serotonin and vitamin D have been proposed to play a role in autism; however, no causal mechanism has been established.
Here, we present evidence that vitamin D hormone (calcitriol) activates the transcription of the serotonin-synthesizing gene tryptophan hydroxylase 2 (TPH2) in the brain at a vitamin D response element (VDRE) and represses the transcription of TPH1 in tissues outside the blood-brain barrier at a distinct VDRE.
The proposed mechanism explains 4 major characteristics associated with autism:
- the low concentrations of serotonin in the brain and its elevated concentrations in tissues outside the blood-brain barrier;
- the low concentrations of the vitamin D hormone precursor 25-hydroxyvitamin D [25(OH)D3];
- the high male prevalence of autism;
- and the presence of maternal antibodies against fetal brain tissue.
Two peptide hormones, oxytocin and vasopressin, are also associated with autism and genes encoding the oxytocin-neurophysin I preproprotein, the oxytocin receptor, and the arginine vasopressin receptor contain VDREs for activation.
Supplementation with vitamin D and tryptophan is a practical and affordable solution to help prevent autism and possibly ameliorate some symptoms of the disorder.