Genistein aglycone effect on bone loss is not enhanced by supplemental calcium and vitamin D3: A dose ranging experimental study

Genistein aglycone (GEN) has a favorable effect on bone loss. We investigated the effects of GEN alone or in combination with supplemental calcium and vitamin D3 in an animal model of bone loss to evaluate if there was additional benefit. Ovariectomized (OVX) and SHAM-OVX rats were used. OVX were divided into 12 groups and randomized to receive: GEN at 27, 54, 200, 500 or 1000mg (human equivalent dose (HED)/day/ip injection alone or with calcium carbonate (Ca) (360mg/kg/day/gavages) and vitamin D3 (D3) (50IU/kg/day/gavages) or Ca/D3 without GEN or untreated for 6 weeks. SHAM-OVX were randomized into 7 groups and treated with: Ca and D3 alone or in combination with GEN (same doses as OVX), or left untreated. Bone mineral density (BMD), bone-alkaline phosphatase (b-ALP), collagen C-telopeptides (CTX), osteoprotegerin (OPG) and soluble receptor activator of NFκB ligand (sRANKL) were assessed. Femurs were excised and tested for breaking strength and histology. Uterine weight was analyzed to assess GEN's estrogenic effects on the SHAM-OVX. The most effective dose of GEN, independent of Ca/D3 supplementation, was 54mg/day. Higher doses yielded no further improvement in bone biomarkers, histology or strength. Only 1000mg/day HED of genistein produced statistically significant changes in uterine weight of the SHAM-OVX. This study suggests that 54mg/day of GEN is the threshold dose for efficacy. In addition, supplemental calcium and vitamin D3, beyond normal dietary intake do not enhance the effects of genistein on improving measures of bone loss. This observation has implications regarding the use of calcium and vitamin D3 supplementation.