Abstract
Objectives
Osteoporosis is a major health problem in the elderly characterized by bone loss and micro-architectural deterioration of bone tissue and associated with an increased risk of fracture. Prolonged bed rest, or physical inactivity during space flight causes rapid and marked bone loss. The effects of catechin, the main ingredient of Japanese green tea, on the bone are currently under study. It has been shown that green tea catechin modulates bone resorption in osteoclasts. However, there is no evidence supporting its inhibitory effect on bone loss during physical inactivity. In the present study, we investigated whether green tea catechin prevented bone loss through skeletal hindlimb-unloading in mice.
Methods
Female 8-week-old ddY mice were divided into five groups (n = 6–8 each) and subjected to: (1) normal housing fed a control diet, (2) sham unloading fed a control diet, (3) hind limb-unloading fed a control diet, (4) hind limb-unloading fed a 0.05% epigallocatechin gallate (EGCG)-containing diet, and (5) hind limb-unloading fed a 0.25% EGCG-containing diet for three weeks. Purified EGCG (97%) was used for green tea catechin.
Results
Bone mineral density of the tibia significantly decreased in hind limb-unloading mice. Treatment with 0.25% EGCG prevented bone loss and maintained trabecular bone mineral density more significantly than in cortical bones. The 0.25% EGCG diet inhibited decrease in the gene expression of alkaline phosphatase, a marker of bone formation, in the bone marrow in hind limb-unloading mice.
Conclusions
These results suggest that EGCG has ability to prevent bone loss induced by hindlimb-unloading in mice. These osteoprotective effects of EGCG may result from the inhibition of unloading-induced decrease in bone formation.
Funding Sources
This work was supported by the Honjo International Scholarship Foundation of Japan.
β-Carotene prevents bone loss in hind limb unloading mice