Abstract
Purpose: To determine the effect of quercetin on bone metabolism and serum osteocalcin in osteoporotic rats.
 Methods: Sixty specific pathogen-free rats were randomly divided into control group, model group; high, medium and low dose quercetin groups, and diethylstilbestrol group, with 10 rats in each group. The high, middle and low dose quercetin groups were given quercetin suspension at doses of 200, 100, 50 mg/kg/day, respectively; the ethylene estradiol group was given ethylene estradiol (1.0 mg/kg/week), while control rats received ethylene estradiol at doses of 200, 100, 50 mg/kg/day. Rats in the model group were given saline. Samples were taken after 6 weeks of administration. The levels of serum bone-derived alkaline phosphatase (BALP), estradiol (E2) and serum osteocalcin (BGP) in femur tissue were measured using ELISA kits. Bone mineral density (BMD) was determined using BMD tester.
 Results: Relative to normal rats, BALP and BGP levels in the model rats were markedly increased, while E2 was significantly lower (p < 0.5). Quercetin treatment led to significant increases in BALP and E2 levels in the middle and high dose groups, relative to the model group, while BGP levels in all quercetin treatment groups decreased significantly, when compared to model rats (p < 0.05). There were higher BMD values in quercetin and diethylstilbestrol groups than in model (p < 0.05).
 Conclusion: Quercetin enhances bone formation and BMD, but decreases osteocalcin levels and maintains bone biomechanics in ovariectomized rats. Thus, it may find therapeutic application in maintaining bone health.
 Keywords: Quercetin, Osteoporosis, Bone metabolism, Osteocalcin
Highlights
Osteoporosis (OP), a metabolic disease of the bone, is characterized by absolute reduction in bone mass and degradation of bone tissue, resulting in increased bone fragility and even fracture
There were no significant differences in these parameters between the quercetin treatment groups and the model group
Rat weight was markedly lower in highdose quercetin rats group than in model rats (p < 0.05)
Summary
Osteoporosis (OP), a metabolic disease of the bone, is characterized by absolute reduction in bone mass and degradation of bone tissue, resulting in increased bone fragility and even fracture. Studies have shown that estrogens reduce the differentiation of osteoblasts and osteoclasts, as well as the frequency of bone turnover. They inhibit bone metabolism, and regulate osteoporosis. The mechanism involved in anti-osteoporotic effect of quercetin was investigated in a rat model of osteoporosis. Thereafter, the rats were assigned to control, model and 3 quercetin groups [high-, middle- and low-dose given quercetin at doses of 200, 100 and 50 mg/kg/day, respectively), and diethylstilbestrol group (1.0 mg/kg/week), with 10 rats in each group. The diethylstilbestrol group was given diethylstilbestrol at doses of 1.0 mg/kg/week, while control rats and model rat groups received equivalent volumes of saline in place of quercetin or diethylstilbestrol. Differences were taken as statistically significant at p < 0.05
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