Preliminary Study Of The Effect Of Iron Accumulation On The Bone Metabolism Of Ovariectomized Rats

Iron is an important element of body, participating in the process of DNA synthesis,the transfer of oxygen and the redox reaction of cellular respiratory chain. Howerver, theabnormity of iron homeostasis could result to disfunction of the body. As ironaccumulation could catalyze oxygen radical and stimulate the peroxidatic reaction of cellmembrane thus lead to the injury of cell and tissue. In skeletal system, recently manystudies showed that when aging in women, ferritin increases while estrogen decreases. Andmoreover, a positive relation was found between the increase of ferritin and the bone lossas well as the risk of fracture. Iron accumulation is one risk factor of postmenopausalosteoporosis(PMOP). So not only the decrease of estrogen but also the iron accumulationlead to PMOP and lowering iron accumulation was suggested as a strategy for PMOP.Therefore, it is very important to create the animal model which imitating the estrogendecrease and iron accumulation, though rare reported. In addition, the universally usedexperimental animal rats do not exist menstruation as primates (a way for iron ejection). Sowhether iron accumulation happen when estrogen decreases is not comformed. This studywas firstly aimed to study the effect of ovariectomy on iron metabolism in rats. In addition,We explore the effect of iron accumulationon bone metabolism under postmenopausalconditions.PartⅠEffect of ovariectomy on iron metabolism in ratsObjective: To explore the effect of ovariectomy on iron metabolism in ratsMethods: Twelve3-month-old female SD rats were divided into2groups: OVX group andSham group.The OVX group underwent bilateral ovariectomized,while the Sham grouprats were only excised some fat surround the ovaries.12weeks later,serum,liver andduodenum were harvested.Serum iron and E2were detected.The iron content in liver and tibia were measured by ICP tester.The expressions of hepcidin and ferropotin mRNAin liver, and ferropotin,DMT-1and DCYTB mRNA in duodenum were dectected withone-step reverse transcription–polymerase chain reaction (RT-PCR).Results: The levels of serum E2and iron，as well as the iron content in tibia of OVX groupwere（19.45±2.28）ng/L,(36.36±9.34) μmol/L,(41.00±5.59) μg/g, respectively，which werestrikingly lower than those of Sham group [(34.98±4.48)ng/L,(54.73±11.08)μmol/L,(66.92±21.94)μg/g,P<0.05],while the iron content in the liver of OVX group weresiglificantly higher than Sham group [(750.20±94.08) μg/g VS (369.60±61.87)μg/g(P<0.05)].Compared with the Sham group,the expressions of Hepcidin mRNA inliver,and FPN mRNA both in the liver ane duodenum were down-regulated,while theexpression of DCYTB mRNA was up-regulated;Expression of DMT-1mRNA in theduodenum did not change significantly.Conclusions: the decline of estrogen after ovariectomy may affect the iron channel proteinthus modulate the asorption and distribution of iron. PartⅡIron accumulationenhanced osteoporosis in ovariectomized ratsObjective: We use ovarietected rats to imitate postmenopausal osteoporosis,and the ironaccumulationconditions were established by the intraperitoneal injection of ferricammonium citrate (FAC) as iron donor. We then explore the effect of iron accumulationonbone metabolism under postmenopausal conditions.Methods:32three-month-old female SD rats were randomly divided into5groups(n=8each): SHAM group，OVX group and two iron accumulationgroups,FAC1and FAC2group,which were intervened by FAC.One week after the operation，all groups wereestablished by the intraperitoneal injection of normal saline and FAC， twice perweek.Three months later，serum ferritin，estrogen，β-CTX，BGP were measured inperipheral blood.The iron content of the tibia was measured by ICP tester. The iron particle in the liver was observed by Perls’ Prussian-blue method.The trabecular architecturechanges of the right femur were observed by histomorphology.A high resolution micro-CTwas used to scan the left femur， and mircro-architecture parameters were analysed.Results: The serum E2were lowered in OVX group and FAC groups than in Sham group（P<0.05）.There were no significant difference between the Sham group and the OVXgroup in serum ferritin and Perls’ staining of the liver, while the tibia iron content in OVXgroup is lower than the Sham group（P<0.05）.The FAC groups showed significant higherserum iron and tibia iron content，and obvious blue iron particles. Both β-CTX and BGPincreased significantly in OVX group than the Sham group（P<0.05）. Compared with theOVX group, β-CTX rather than BGP increased significantly in FAC1group and FAC2group. The morphology of trabecular in FAC1and FAC2is further deteriorated than theOVX group. Compared with the OVX group,the microtomograph reconstruction analysisshowed the BV/TV，Tb.N，Tb.th and BMD in FAC groups decreased significantly（P<0.05），while the Tb.Sp、SMI、DAare significantly higher（P<0.05）.Conclusion: Iron accumulationcould promote post-menopausal osteoporosis，which mightbe through the pathological mechanism of enhancing bone resorption. This studyprovide the experimental data for the effect of iron accumulationon postmenopausalosteoporosis,which will enrich the concept of the pathological mechanism of this disease.