The vitamin D analog ED-71 is a potent regulator of intestinal phosphate absorption and NaPi-IIb

Endocrinology. 2012 Nov;153(11):5150-6. doi: 10.1210/en.2012-1587. Epub 2012 Sep 4.

Abstract

The vitamin D analog ED-71 [1α,25-dihydroxy-2β-(3-hydroxypropyloxy)vitamin D(3)] has been approved for treatment of osteoporosis in Japan, but its effects on mineral metabolism have not been fully explored. We investigated the actions of ED-71 on phosphate (Pi) absorption and induction of the intestinal sodium/phosphate cotransporters. Oral treatment of vitamin D-deficient rats with ED-71 (20 pmol every other day for 8 d) produced a maximal 8-fold increase in duodenal Pi absorption, measured by the in situ loop method, whereas 1,25-dihyroxyvitamin D(3) [1,25(OH)(2)D(3]), at doses up to 150 pmol, had no effect. This action of ED-71 was attributable to a dramatic 24-fold induction of sodium-dependent Pi transporter type IIb (NaPi-IIb) mRNA in the duodenum; Pit-1 and Pit-2 mRNA levels were not increased. In vitamin D-replete rats, ED-71 treatment (50 pmol) at 72 and 24 h before death increased NaPi-IIb mRNA in the duodenum and jejunum, but not the ileum, whereas 1,25(OH)(2)D(3) at 1000 pmol was ineffective in all segments. Single oral doses of ED-71 increased mouse intestinal NaPi-IIb mRNA and protein between 6 and 24 h. Surprisingly, rat lung NaPi-IIb was not increased by ED-71, despite its coexpression with the vitamin D receptor in alveolar type II cells. However, ED-71 did not induce intestinal NaPi-IIb in vitamin D receptor-ablated mice. The greater potency of ED-71 than 1,25(OH)(2)D(3) on NaPi-IIb appears to be due to much higher and more prolonged levels of ED-71 in the circulation. In summary, ED-71, due to its disparate pharmacokinetics, is a much more potent inducer of intestinal Pi absorption and NaPi-IIb than 1,25(OH)(2)D(3), suggesting a role for this analog in the treatment of Pi-wasting disorders.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Absorption / drug effects
  • Animals
  • Calcitriol / analogs & derivatives*
  • Calcitriol / pharmacology
  • Intestinal Mucosa / metabolism
  • Intestines / drug effects*
  • Male
  • Mice
  • Mice, Knockout
  • Phosphates / metabolism*
  • Rats
  • Rats, Sprague-Dawley
  • Receptors, Calcitriol / genetics
  • Receptors, Calcitriol / metabolism
  • Sodium-Phosphate Cotransporter Proteins, Type IIb / genetics
  • Sodium-Phosphate Cotransporter Proteins, Type IIb / metabolism*
  • Vitamin D / analogs & derivatives
  • Vitamin D Deficiency / metabolism*

Substances

  • Phosphates
  • Receptors, Calcitriol
  • Slc34a2 protein, rat
  • Sodium-Phosphate Cotransporter Proteins, Type IIb
  • Vitamin D
  • Calcitriol
  • eldecalcitol