VDR and Hyperglycemia: Hyperglycemia negatively affects bone formation by inhibition of calcium absorption and reabsorption in the duodenum and kidneys through regulation of transcellular calcium transporting proteins via decreasing the expressions of vitamin D receptor (VDR), transient receptor potential V6 (TRPV6), and calcium-binding protein-28k (CaBP-28k) (Zhang et al., 2011, 2014).