Naringin improves bone properties in ovariectomized mice and exerts oestrogen-like activities in rat osteoblast-like (UMR-106) cells.
OBJECTIVE
Naringin, a flavanone glycoside in citrus fruits, has been recently reported to stimulate bone formation in vitro and in vivo. The present study was designed to determine if naringin could exert oestrogen-like protective actions in bone.


METHODS
Young C57/BL6J mice were ovariectomized (OVX) and treated orally with naringin (0.2 or 0.4 mg*g(-1)*day(-1)), 17beta-oestradiol (2 microg*g(-1)*day(-1)) or its vehicle for 6 weeks. Bone mineral densities (BMD) and polar stresss-train index (SSI) were measured by peripheral quantitative computed tomography. Rat osteoblast-like UMR-106 cells were co-incubated with the oestrogen receptor (ER) antagonist ICI 182780 to determine if the effects of naringin on osteoblastic functions were ER dependent. Functional transactivation of ERalpha and ERbeta as well as ERalpha phosphorylation by naringin were also studied.


RESULTS
Naringin at 0.4 mg*g(-1)*day(-1) increased BMD at trabecular-rich bone in OVX mice. Naringin (at both doses) significantly increased SSI at distal femur and lumbar spine and increased biomechanical strength (ultimate load and energy for breaking) at tibia diaphysis in OVX mice. The stimulatory effects of naringin on osteoblastic functions could be abolished by co-incubation with ICI 182780 in UMR-106 cells. Naringin failed to stimulate ERalpha- or ERbeta-mediated oestrogen response element-dependent luciferase activity but could significantly induce ERalpha phosphorylation at serine 118, in UMR-106 cells.


CONCLUSIONS
Naringin was effective in protecting against OVX-induced bone loss in mice and its actions might be mediated through ligand-independent activation of ER in osteoblastic cells.
Pang
Wai-Yin
WY
Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hung Hom, Kowloon, China.
Wang
Xin-Lun
XL
Mok
Sau-Keng
SK
Lai
Wan-Ping
WP
Chow
Hung-Kay
HK
Leung
Ping-Chung
PC
Yao
Xin-Sheng
XS
Wong
Man-Sau
MS
D000818:Animals; D001483:Base Sequence; D001835:Body Weight / Q000187:drug effects; D015519:Bone Density; D002460:Cell Line; D017931:DNA Primers; D004965:Estrogen Antagonists / Q000494:pharmacology; D004967:Estrogens / Q000494:pharmacology*; D005260:Female; D044950:Flavanones / Q000494:pharmacology*; D051379:Mice; D008810:Mice, Inbred C57BL; D009929:Organ Size / Q000187:drug effects; D010006:Osteoblasts / Q000187:drug effects*; D010052:Ovariectomy; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014057:Tomography, X-Ray Computed; D014599:Uterus / Q000187:drug effects
D017931:DNA Primers; D004965:Estrogen Antagonists; D004967:Estrogens; D044950:Flavanones; C005274:naringin
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