VDR and liver dysplastic nodule: Celikbilek and colleagues [36] examined the relation between serum vitamin D, vitamin D-binding protein (VDBP), and vitamin D receptor (VDR) with PDN; they found patients with DN had significant lower levels of vitamin D than that in patient without DN, while there were similar values of VDBP and VDR in two groups of diabetic patients with and without DN.