Differential responses to vitamin D2 and Vitamin D3 Are Associated with variations in free 25-Hydroxyvitamin D

Abstract

25-HydroxyVitamin D (25D) circulates bound primarily to serum Vitamin D binding protein (DBP), with DBP showing higher binding affinity for 25D3 than 25D2. We therefore hypothesized that vitaminD2(D2) promotes higher serum levels of unbound 25D (free 25D), with different functional responses, relative to Vitamin D3 (D3). Week 3 C56BL/6 mice were placed on diets containing either D2 or D3 alone (both 1000 IU/kg). At week 8 and week 16, D2 mice had only 25D2 in circulation (26.6 ± 1.9 and 33.3 ± 4.4 ng/mL), and D3 mice had only 25D3 (28.3 ± 2.0 and 31.7 ±2.1 ng/mL). At week 8 (44.5 ± 6.4 vs 62.4 ± 11.6 pg/mL, P < .001) and week 16 (17.4±0.43 vs 8.4±0.44,