ABSTRACT
Objective:To explore the role of SIRT3 down-regulation in skeletal muscle injury through the changes of sirtuin 3 (SIRT3) expression in mouse skeletal muscle under iron excess in vitro or in vivo.Methods:Murine preosteoblast myoblast C2C12 cells were incubated in a medium supplemented with ferric ammonium citrate (FAC). The proliferation, apoptotic were assessed, the cell morphology was observed, and the expression of SIRT3 mRNA, protein and activity were detected. ICR mice were randomly divided into control group, FAC group and FAC+ deferrioxamine (deferoxamine, DFO) group. Normal saline was injected in the control group. FAC followed by injection of normal saline in the FAC group; and FAC followed by DFO in the FAC+ DFO group. The non-heme iron level, content of SIRT3 protein and in situ apoptosis were detected, morphology of skeletal muscle was observed.Results:Proliferation of C2C12 cells was inhibited, and the apoptotic rate were increased by FAC ( P<0.05). The mRNA, protein and activity of SIRT3 decreased by FAC ( P<0.05). The cells gradually shrank, and the length and number of myotubes were decreased by FAC. Both control and FAC+ DFO groups showed lower levels of non-heme iron in skeletal muscle compared with FAC group ( P<0.05). The levels of SIRT3 protein were decreased in FAC group compared with control group, while increased in FAC+ DFO group with FAC group ( P<0.05). The apoptotic indexes in control and FAC+ DFO groups were lower than that in FAC group. Compared with the control group, the disordered cell arrangement, fat deposition and inflammatory cell infiltration were presented in FCA group, and the change was alleviated in FAC+ DFO group. Conclusion:Iron excess can lead to the decrease of skeletal muscle mass in mice, and the mechanism may be related to the down-regulation of SIRT3 level.
ABSTRACT
Objective To explore the changes of type H vessel during the low bone mineral density caused by iron accumulation and discuss its clinical meaning.Methods Ten 8-week old male C57BL/6J mice were used for experiments,and randomly divided into two groups:control group and iron group,and 5 mice in each group.In the iron group,0.1 g/kg of iron dextran was injected intraperitoneally once a week for 8 weeks.The control group was injected with the same amount of saline.The femoral and tibial specimens were examined by microscopic CT scan and bone tissue type H vessel immunohistochemical staining.Liver tissue from the two groups were collected for the content of iron by atomic absorption spectroscopy.All experimental data were analyzed with t-test.Results The content of hepatic iron in mice was significantly higher than that in the control group,which indicating that the model was successfully established.The tibia specimens were collected for immunostaining.The vascular area of type H at metaphyseal regions is 11.24％± 1.76％ in iron group and 30.69％±2.78％ in control group,respectively.There is significant difference between the two groups (P＜0.005).The femur specimens were collected for Micro-CT scan,the value of bone mineral density (BMD),bone volume/tissue volume (BV/TV),trabecular thickness (Tb.Th),trabecular number (Tb.N) and trabecular separation (Tb.Sp) was (0.19±0.013) g/cm3,11.92％±1.199％,(35.66±2.684) μm,(2.36±0.429)/mm and (284.41±23.197) μm in iron group and (0.37±0.023) g/cm3,35.76％± 1.336％,(62.05±2.238) μm,(5.68± 1.039)/mm and (163.23± 13.203) μm in control group,respectively.The differences between the two groups were statistically significant (P＜0.05).Conclusion Iron accumulation can lead to low BMD and suppress type H vessel formation in bone,which might provide a new experimental value for mechanism research on osteoporosis caused by iron accumulation.