Beta-ecdysone has bone protective but no estrogenic effects in ovariectomized rats

Abstract

Estrogens exert beneficial effects in the bone. Their chronic use however bares several risks. Therefore intensive search for non-estrogenic, bone protective compounds is going on. We observed that an extract of Tinospora cordifolia has antiosteoporotic effects and identified 20-OH-Ecdysone (beta-Ecdysone=Ecd) as a possible candidate for this action. Ovariectomized (ovx) rats were treated orally over 3 months with no Ecd (control) or 18, 57 or 121 mg Ecd/day/animal. Estradiol-17beta benzoate (E2) 159 microg/day/animal) fed animals served as positive controls. Bone mineral density (BMD) of tibia was measured by quantitative computer tomography, serum Osteocalcin and CrossLaps were measured in a ligand binding assay. Utilizing an estrogen receptor (ER) containing cytosolic extract of porcine uteri the capability of Ecd to bind to ER was tested. Ecd did not bind to ER. BMD was reduced by more than 50% in the control. In the Ecd animals BMD was dose dependently higher. Serum CrossLaps was lower in the Ecd and E2 group while serum Osteocalcin levels were decreased in the E2 but increased in the Ecd fed animals. Ecd has an antiosteoporotic effect which does not involve activation of ER.