British Journal of Nutrition

Full Papers

Molecular Nutrition

Erythrina variegata extract exerts osteoprotective effects by suppression of the process of bone resorption

Yan Zhanga1, Qi Lia2, Xiaoli Lia3, Hoi-Ying Wana4 and Man-Sau Wonga2a4 c1

a1 Centre of System Biomedical Sciences, University of Shanghai for Science and Technology, Shanghai 200093, People's Republic of China

a2 State Key Laboratory of Chinese Medicine and Molecular Pharmacology, Shenzhen 518057, People's Republic of China

a3 Tang Center for Herbal Medicine Research, University of Chicago, Chicago, IL 60637, USA

a4 Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, People's Republic of China

Abstract

Our previous study showed that Erythrina variegata L. (EV) inhibited bone loss and improved bone properties in ovariectomised rats. The purpose of the present study is to investigate the potential mechanism involved in mediating the osteoprotective actions of EV. Female Sprague–Dawley rats were fed a phyto-oestrogen-free diet and subjected to either ovariectomy or a sham operation. Ovariectomised rats were treated with genistein (40 mg/kg) as well as low (200 mg/kg), medium (500 mg/kg) or high (1000 mg/kg) doses of EV extract. Bone properties and mRNA expressions were evaluated by micro-computed tomography and quantitative RT-PCR, respectively. Osteoclast differentiation in RAW 264·7 cells was studied by tartrate-resistant acid phosphatase (TRAP) staining. High doses of EV could decrease urinary Ca and P excretion, maintain serum Ca and P level, and exert beneficial effects on the micro-structure and morphology of trabecular bone and cortical bone in ovariectomised rats. EV suppressed the up-regulation of cathepsin K mRNA and the down-regulation of osteoprotegrin mRNA in the tibia of ovariectomised rats. TRAP-positive cell numbers were significantly decreased in receptor activator of nuclear factor-κB ligand (RANKL)-induced RAW 264·7 cells when co-cultured with EV extracts. The present study indicated that the protective effects of EV on bone properties in ovariectomised rats are likely to be mediated by its inhibitory actions on the process of bone resorption via the suppression of osteoclast differentiation and maturation.

(Received October 28 2009)

(Revised April 07 2010)

(Accepted April 08 2010)

(Online publication May 21 2010)

Correspondence:

c1 Corresponding author: Dr Man-Sau Wong, fax +852 23649932, email bcmswong@polyu.edu.hk

Footnotes

Abbreviations: ALP, alkaline phosphatase; BS/BV, bone surface/bone volume; Cbfa1, core-binding factor α1; Conn.D, connectivity density; CtsK, cathepsin K; EV, Erythrina variegata L.; OPG, osteoprotegerin; OVX, ovariectomised only (vehicle-treated); RANKL, receptor activator of nuclear factor-κB ligand; SMI, structure model index; TRAP, tartrate-resistant acid phosphatase