Effects And Mechanism Of Phosphorylated Peptides From Antarctic Krill On Increasing Bone Mineral Density In Osteoporosis Rats

Osteoporosis is a bone metabolism disease, characteristics of increased bone fragility and incidence of fracture, due to low bone mass, damaged bone tissue microstructure. Postmenopausal osteoporosis is the most common type of osteoporosis. Characteristic of its is the high conversion type, resulting bone resorption and bone formation both in the active state. The world has more than 200 million osteoporosis patients which accounted for about 33% of postmenopausal women. Hence, looking for safe and effective anti-osteoporosis active substances is important. The Antarctic krill contains rich high quality protein. The protein phosphorylation is an effective means to improve protein function. Phosphorylated protein can promote the absorption of calcium. The peptide of Antarctic krill has many kinds of fuction, but phosphorylated peptides from Antarctic krill (PP-AKP) on improving osteoporosis has not reported. In this study, effects of PP-AKP on improving osteoporosis of ovariectomized rats was studied, and its mechanism was systematically undertaken. The main results were as follows:The molecular weight of PP-AKP was ranged from 2000 to 200Da. The organic phosphorus content in PP-AKP was 1.52%; the protein content was 90.71%; the fluorine content was 2.49ppm in accordance with national food safety standards. The osteoporosis rats were orally administered daily with PP-AKP for 90days. The bone metabolic indexes were determined and results suggested that PP-AKP significantly reduced the level of BALP, OCN, PICP, TRACP, Cath-K, CTX-1, Ca, P, DPD and RANKL; increased the level of OPG. The inflammatory cytokines induced osteoclast differentiation and mediated bone resorption. The results suggested that PP-AKP significantly reduced the level of TNF-α, IL-6, IL-1β,NO, and COX-2. These indicated that PP-AKP could inhibit high bone turnover state and bone absorption of model rat.Bone mineral density is the gold standard in diagnosis of osteoporosis. Bone biomechanics is the key index of predicting fracture occurred. The results showed that PP-AKP significantly improved the bone mineral density and increased the maximum load and structural strength. The histomorphology result showed that PP-AKP significantly increased the number and area of trabecular bone, reduced the bone trabecular spacing. These indicated that PP-AKP could enhance bone strength of model rats.Osteoblast played a key role in osteoporosis. It mediated bone formation and regulated bone resorption of osteoclast. The classical Wnt/β-catenin signaling pathway was a major pathway. The results showed that PP-AKP inhibited the level of LRP-5b,β-catenin, RUNX2, OSX genes expression, inhibited osteoblast function marker indexes COL I, OCN, ALP genes expression. These indicated that PP-AKP could inhibit high bone turnover state through down-regulating the Wnt/β-catenin signaling pathway.OPG/RANKL/RANK signaling pathway played an improtant role in osteoblast regulating osteoclast fuction. The activation of NF-κB and MAPKs pathways was the signal transmission symbol of OPG/RANKL/RANK pathway. The results showed that PP-AKP inhibited the level of RANKL, TRAF6, NF-κB, p38, ERK, JNK, c-fos, NFATC1 genes expression, enhanced OPG genes expression, inhibit osteoclast function marker indexes Cath-K, MMP-9, TRACP genes expression. These indicated that PP-AKP could inhibit bone resorption through inhibiting the activation of OPG/RANKL/NF-κB and OPG/RANKL/MAPKs signaling pathways.For the first time, this paper proved the effects of PP-AKP in increasing bone mineral density and charified the mechanism. Researches in this thesis would provide scientific foundation for the high value of utilization of Antarctic krill and the development of anti-osteoporosis fuction food.