| Osteoporosis (osteoporosis, OP) is a kind of bone systemic diseases, which is characterized by reduced bone mass and degradation of bone micro-structure, resulting in an increase of brittle bones prone to fracture. Its increasing incidence over the years has caused widespread concern around the world. Postmenopausal women are in low ovarian function, lack of estrogen, with bone transformation accentuation and bone loss due to more bone resorption than bone formation, which caused OP. Because lack of estrogen is the primary cause in postmenopausal osteoporosis (postmenopausal osteoporosis, PMO), the estrogen replacement therapy (hormonereplacement therapy, ERT) is the first-line therapy for PMO. In some clinical investigations hormone replacement therapy (HRT) can prevent the loss of bone mass and increase the bone density. However, estrogen may have side-effect on people in long-term treatment, for example, it may promote endometrial hyperplasia and enhance the incidence of coronary heart disease, stroke, pulmonary embolism and breast cancer. Because phytoestrogen has estrogen-like effect but no side effect of estrogen, so people use phytoestrogen(e.g. soybean isoflavone ) to prevent and treat osteoporosis.Isoflavone is a phytoestrogen, and its structure is similar to estrogen. By simulating the role of estrogen. It can regulate bone metabolism, and bind with hormonal receptor competively to regulate its activity. So flavanoid is very useful to prevent the hormonal dependent cancers and to delay or lessen women's complaint during the critique age. When the estrogen level in vivo is low, the estrogen function acts, while the anti-estrogen function acts when the estrogen level in vivo is high. It has the equilibrium of two-ways regulation, but its mechanism has not been known. Part of experiments in vivo show that its activity is regulated by contents of endogenous estrogen. Long-term clinical test verify that intake of a lot of bean products may prohibit estrogen circulation and affect female menstrual cycle before menopause.Soybean oflavone is a kind of phytoestrogen, whose structure is similar to estrogen. By simulating the role of estrogen it can regulate bone metabolism, promote osteoblast cell proliferation and bone formation, and reduce the loss of bone mass after ovary removal, resulting in prevention and treatment of OP.The mechanism of isoflavone to prevents osteoporotic is not clear, but it is definite that estrogen receptor is the key factor. Isoflavone enters cell nucleus to bind estrogen receptor and to change its configuration. Isoflavone shows both estrogen function for bone and cholesterol metabolism and anti-estrogen function for hystera and lacteal gland and are relate to high affinity of estrogen receptor. Estrogen receptor has two kinds of hypotype, ERαand ERβ. ERαlocates in urethra and lacteal gland, and ERβlocates in ossature, heart and blood vessel, immune system and central nervous system. Isoflavone combines ERαor ERβin different tissue or physiological conditions to show estrogen function or anti-estrogen function. Its tissue-selective function is explained by three kinds of mechanisms of interaction. It was reported that isoflavone binds with ERβin skeleton. Its affinity is 20 times than ERα's. Isoflavone can promote proliferation of osteoblast MC3T3-E1 which is associated with actuation of ERβ.Zinc is a trace element essential to animals, in addition to participation in growth and development, reproductive and immune and other physiological reactions, it also plays an important role in bone metabolism and function-related gene expression. It was realized that zinc can stabilize labrocyte and inhibit endogenous calparine to release. Zinc can also synergia cell factor and estrogen to regulate metabolism of bone cells. It was found that zinc and bone density are intimate correlation. In short, osteoporosis is complicated course of pathological changes. As a microelement zinc not only is composition of bone but also participates in bone metabolism. Zinc can promote osteoblasts transformation form G0/G1- stage to S-stage and accelerate cells to enter DNA synthesis period. In this way, it can also promote DNA synthesis and proliferation of cells.ObjectiveIn our experiments, we adopt osteoblast MC3T3-E1 cells to observe the effect of different concentrations of zinc and genistein on proliferation, alkaline phosphatase (ALP) activity and bone morphogenetic protein -2 (BMP-2) expression and to investigate whether the combination of zinc and genistein has additive effects on the prevention and treatment of osteoporosis.MethodsThe effect of different concentrations of genistein and zinc on proliferation of MC3T3-E1 cells was measured by MTT assay. The expression of BMP-2 was measured by Western blotting assay. Colorimetric method was employed to detect the activity of ALP. According to objective, the experiment is divided six groups as follows:(1) Normal control group: conventional culture with normal culture solution(2) Dissolvant control group: add DMSO to culture solution, its volume ratio is 0.1 %.(3) Positive control group(E2): add E2 to culture solution, its final concentration is 1×10-9 mol/L(4) Zn group: add Zn to culture solution, its final concentration are 1×10-6 mol/L,1×10-5 mol/L,1×10(-4 mol/L respectively(5) GS group: add GS to culture solution, its final concentration are 1×10-7mol/L,1×10-6 mol/L,1×10-5 mol/L,1×10-4 mol/L respectively(6) GS+ Zn group: add Zn(1×10-5 mol/L) to GS group respectivelyResults1. The MC3T3-E1 cell proliferation was significantly increased in the presence of zinc and genistein. Both genistein and zinc promoted MC3T3-E1 cells growth in a time and dose-dependent manner and the rate of cell proliferation was 160.8±20.9 % when the cells treated with 1×10-5 mol/L genistein and 1×10-5 mol/L zinc for 96 h.2. The activity of ALP and the expression of BMP-2 in cells treated with genistein and zinc were increased in a time and dose-dependent manner.3. After treatment with genistein and zinc, the activity levels of ALP and BMP-2 expression were increased more obviously than in the groups treated with either genistein or zinc alone. ConclusionThe combination of zinc and genistein demonstrated effects of estrogen, and this can promote the proliferation of osteoblast cells and increase bone mass through the enhancement of bone morphogenetic protein synthesis.
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