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.