Regulation Of RANK/RANKL/OPG Signal Pathway By Bone Collagen Peptide And Calcium Chelated Collagen Peptide In Inhibiting The Occurrence Of Osteoporosis

RANK,as the only known receptor for RANKL,is highly expressed in the surfuce of osteoclast(OC)precursor cells and mature cells.Combination of RANK and RANKL which is synthesized by bone marrow mese nchymal cells can improve the proliferation and maturation of osteoclasts,strengthen the osteoclast bone resorption activity and inhibit the osteoclast apoptosis.OPG,synthesized by osteoblast,is a decoy receptor of RANKL.OPG can break the combination of RANK and RANKL through competitively binding to RANKL with RANK,accordingly inhibiting osteoclast formation and bone resorption.RANK/RANKL/OPG signaling pathway plays a vital role in osteoclast differentiation.Our study will probe the signal mechanism of RANK/RANKL/OPG in the process that sheep bone collagen peptide(SBCP),sheep bone collagen peptide chelated calcium(SBCP-Ca),sheep bone collagen peptide-Xylose Maillard reaction product(SBCP-X),Amino acid chelated calcium(AA-Ca)and estrogen inhibit osteoporosis(OP)and compare them.We established OP model by removal of bilateral ovaries in rats,and set up sham surgery group(Sham),model group(Model),17p-estradiol group(E2)and the low,medium and high dose treatment groups of SBCP,SBCP-Ca,SBCP-X and AA-Ca.The oral doses of SBCP in each dose group were 6.8,20.5,34 g/(kg·d).SBCP-Cadose groups were 10,30,50 g/(kg-d).SBCP-X dose groups were 10,20,30 g/(kg·d).AA-Ca SBCP-X dose groups were 1,3,5 gl(kg d).The subcutaneous dose of E2 was 8 g/(kg·d).The Sham and Model groups were given an equal volume of distilled water for 8 w.After eight weeks,the level of PINP and β-CTx expressed the bone formation and resorption in the blood of Model groups rats were significantly higher than Sham group.Scanning electron microscopy observation of distal femoral metaphysis also indicated that model building was successfully prepared.Compared to Model group,the level of PINP and P-CTx in all of SBCP,SBCP-Ca,SBCP-X,AA-Ca and E2 groups showed a decreasing trend.The number of trabecular bone in all treatment groups increased,and the microstructure of bone had been improved to different degrees.The results of RT-PCR indicated that the relative expression of RANK and RANKL in femoral tissue of model groups were siginificant higher than the sham group(P<0.01).The ovariectomy showed no siginificant difference to the expression of OPG(P>0.05).The relative expression of RANK and RANKL in different dose of SBCP,SBCP-Ca,AA-Ca and E2 groups were siginificant lower than the model group(P<0.01).Compared with the sham group,the expression of RANK in AA-Ca-M,AA-Ca-H and of RANKL in SBCP-Ca,AA-Ca had no difference(P>0.05).The relative expression of RANK in SBCP-X groups were significant lower than the model group(P<0.01).The relative expression of RANKL in SBCP-X group elevated with the increasing of the dose.In the group of the high dose,the expression of RANK was siginificant higher than the group of medium and little dose groups and model group.As to the relative expression of OPG,SBCP,SBCP-Ca,SBCP-X and AA-Ca groups with different dose were siginificant higher than the Model and Sham groups(P<0.01).While the expression of OPG in E2 group showed no difference compared with Model and Sham groups(P>0.05).According to the measurment,the ratio of RANKL and OPG in SBCP,SBCP-Ca,SBCP-X,AA-Ca and E2 groups were significant lower than the Model group(P<0.01)and had no significantly difference compared with the sham group(P>0.05).The value of RANKL/OPG in AA-Ca groups were even lower than the Sham group.In the dynamic equilibrium between bone formation and resorption,the activity of bone resorption elevated with the increasing of the RANKL/OPG.The results of comparision between the least RANKL/OPG in different drug treatment groups demonstrated that:AA-Ca-H<SBCP-Ca-M<E2<SBCP-M<SBCP-X-L.In conclusion,the ovariectomy would increase the expression level of RANK and RANKL in femoral tissue even though it has no effect on the OPG While,the E2 also has on effect on the OPG,it would decrease the expression level of RANK and RANKL.SBCP-X could inhibit the expression of RANK and promote the OPG,but it has no influences even could promote the expression of RANKL.By inhibiting the expression of RANK,RANKL and promoting the OPG,the SBCP,SBCP-Ca,AA-Ca play a role on inhibiting the formation of osteoclast and the activity of bone resorption to prevent the occour of OP effectively.