VDR and Obesity: Moreover the above mechanisms would not explain why the differential release is only observed for 1,25(OH)2D3 and not for 25(OH)D3. Vitamin D 1,25(OH)2D3 is a ligand for vitamin D receptor (VDR), and it has been shown that vitamin D receptor (VDR) expression is increased in SAT of individuals with obesity (Jonas et al., 2019).