Michigami Toshimi
Department of Bone and Mineral Research, Osaka Women's and Children's Hospital, Osaka Prefectural Hospital Organization, Japan.
Clin Calcium. 2017;27(11):1517-1523.
Vitamin D is taken up from food as D and D. Vitamin D is also synthesized from 7-dehydrocholesterol in the skin by the exposure of ultraviolet B. The D and D, which are called native vitamin D, are hydroxylated at C25 in the liver by CYP2R1 and then at C1 in the kidney by CYP27B1, to be converted to an active vitamin D metabolite, 1,25-dihydroxyvitamin D[1,25(OH)D]. CYP24A1 converts 25-hydroxyvitamin D(25OHD)and 1,25(OH)D to 24,25-dihydroxyvitamin D[24,25(OH)D]and 1,24,25-trihydroxyvitamin D[1,24,25(OH)D], respectively, to decrease the level of 1,25(OH)D. CYP27B1 and CYP24A1 are mainly expressed in the kidney but also detected in other tissues, and it is suggested that 1,25(OH)D produced in the extra-renal tissues may exert its effects locally.
维生素D以D和D的形式从食物中摄取。维生素D也可由皮肤中的7-脱氢胆固醇经紫外线B照射合成。被称为天然维生素D的D和D在肝脏中由CYP2R1在C25位羟化，然后在肾脏中由CYP27B1在C1位羟化，转化为活性维生素D代谢物1,25-二羟基维生素D[1,25(OH)D]。CYP24A1分别将25-羟基维生素D(25OHD)和1,25(OH)D转化为24,25-二羟基维生素D[24,25(OH)D]和1,24,25-三羟基维生素D[1,24,25(OH)D]，以降低1,25(OH)D的水平。CYP27B1和CYP24A1主要在肾脏中表达，但在其他组织中也可检测到，提示肾外组织产生的1,25(OH)D可能在局部发挥作用。
