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|Title:||Modern approach to study the osteoprotective effects of Herba Epimedii||Authors:||Mok, Sao-keng||Keywords:||Hong Kong Polytechnic University -- Dissertations
Osteoporosis -- Treatment.
|Issue Date:||2007||Publisher:||The Hong Kong Polytechnic University||Abstract:||Herba Epimedii is one of the most frequently herbs prescribed for treatment of osteoporosis in China over centuries. In this study we aimed to develop both in vivo and in vitro screening platforms to evaluate the osteoprotective effects of total extract (HEP), total flavonoids (TF), non-flavonoids (NF) and five flavonoid compounds from Herba Epimedii for identification of active ingredients using modern approach, and hence to provide scientific evidence at tissue, cellular and molecular levels for evaluating the use of Herba Epimedii. To verify the efficacy of HEP, TF and NF on BMD maintenance, ovariectomized C57BL/6J mice were orally administered with HEP (1.4 mg/g/day), TF (0.2 mg/g/day), NF (1.05 mg/g/day), 17β-estradiol (4 μg/g/day) or vehicle for four weeks. All treatments except vehicle prevented OVX-induced reductions in total and trabecular BMD of distal femur. Absence of uterotrophic effects of HEP, TF and NF suggested these treatments might be safer alternatives for potential prevention of osteoporosis. To determine the optimal dose of TF, ovariectomized mice were treated with four doses of TF (50, 100, 200 and 400 μg/g/day), 17β-estradiol (4 μg/g/day) or vehicle for six weeks. TF exerted osteoprotective effects by increasing bone mass and bone strength while decreasing bone turnover and calcium loss through urinary excretion. TF treatment at 100μg/g/day was the optimal dose for osteoprotection.
To study in vitro effects, rat osteoblast-like UMR-106 cells were treated with HEP (0.0625-1 μg/ml), TF (0.0625-2 μg/ml), NF (0.0625-2 μg/ml) or five flavonoids compounds (i.e. baohuoside I, sagittatoside B, korepimedoside C, epimedin B and sagittatoside A) (10⁻¹²-10⁻⁶ M) for 48hr. Their effects on cell proliferation, differentiation and modulation of osteoclastogenesis were evaluated by MTS assay, ALP activity assay and OPG/RANKL mRNA expression respectively. HEP, TF and NF exerted osteoprotective effects by increasing cell proliferation, differentiation and suppressing osteoclastogenesis. All five flavonoid compounds stimulated osteoblastic proliferation and differentiation. TF and sagittatoside A were more potent than the remaining fractions or compounds. In vivo and in vitro effects as well as the molecular actions of icariin, a marker flavonoid compound in Herba Epimedii, were studied. Icariin (0.3 mg/g/day) significantly increased BMD and bone strength and decreased urinary calcium loss in ovariectomized mice. UMR-106 cells treated with icariin (10⁻¹²10⁻⁶ M) increased cell proliferation and differentiation and suppressed osteoclastogenesis. Since the effects of icariin and HEP were similar to that of 17β-estradiol, their molecular actions might be mediated through activation of ER. The mechanistic study showed that the effects of icariin on the osteoblastic functions involved the participation of ER and its actions were mediated through ligand-independent phosphorylation of ER instead of direct ERE binding. Owing to the complex ingredients in HEP, the molecular action of HEP was less clearly defined that cell proliferation and upregulation of OPG mRNA expression but not differentiation, was ER-dependent and its action was not mediated by ERE binding. In conclusion, Herba Epimedii and its derived fractions or compounds demonstrated osteoprotective effects in vivo and in vitro, which might be regarded as a potential candidate for management of osteoporosis.
|Description:||xxiv, 212 leaves : ill. ; 30 cm.
PolyU Library Call No.: [THS] LG51 .H577M ABCT 2007 Mok
|URI:||http://hdl.handle.net/10397/3336||Rights:||All rights reserved.|
|Appears in Collections:||Thesis|
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