Effect Of Hypoxia Preconditioning On Acute Hypoxic Exercise-induced Phosphorylation Of AMPKα In Mice Skeletal Muscle

Objective:AMP-activated protein kinase（AMPK）is a metabolic energy sensor and its activation plays an important role in the regulation of energy homeostasis.Increasing evidence indicates that AMPK activation depend on the phosphorylation sites in AMPKα.Thr¹⁷² is involved in AMPK activation,whereas Ser^485/491 are not.Under suitable stress stimulations,the phosphorylation of AMPKαat the Thr¹⁷² site can increase AMPK activation.However,serious hypoxic exercise or taking antioxidants before exercise can reduce the activation of AMPK by phosphorylating AMPKα1Ser⁴⁸⁵/α2Ser⁴⁹¹ sites.The aim of this study was to investigate the effects of hypoxia preconditioning on exhaustive exercise under hypoxic condition induced AMPKαThr¹⁷²and Ser^485/491phosphorylation in mice skeletal muscle.Methods:The 40 eight-week-old male C57BL/6J wild type mice were randomly divided into four groups（10 mice/group）:non-hypoxia preconditioning control group（NC）,hypoxia preconditioning control group（HC）,non-hypoxia preconditioning acute hypoxic exercise group（NE）,and hypoxia preconditioning acute hypoxic exercise group（HE）.Hypoxia preconditioning groups were exposure in hypoxia for 48h,with the oxygen concentration was 11.2%.Meanwhile,non-hypoxia preconditioning was in the normoxic condition for 48h.After hypoxia preconditioning,acute hypoxic exercise groups finished an exhaustive exercise.Tibialis anterior muscles of mice were collected immediately after the exhaustive exercise.The protein expression of the total AMPKα,Thr¹⁷²-AMPKαphosphorylation,Ser⁴⁸⁵-AMPKα1/Ser⁴⁹¹-AMPKα2 phosphorylation,total ACC and Ser⁷⁹-ACC phosphorylation were measured by Western Blot.Thr¹⁷²-AMPKαphosphorylation to total AMPKαratio,Ser⁴⁸⁵-AMPKα1/Ser⁴⁹¹-AMPKα2phosphorylation to total AMPKαratio and Ser⁷⁹-ACC phosphorylation to total ACC ratio was calculated.Results:Compared with NE group,The Thr¹⁷²-AMPKαphosphorylation to total AMPKαratio was increased significantly,whereas the relative expression of Ser⁴⁸⁵-AMPKα1/Ser⁴⁹¹-AMPKα2 phosphorylation to total AMPKαratio seemed to decreased in skeletal muscle of HE groups.Compared with NE group,The Ser⁷⁹-ACC phosphorylation to total ACC ratio was increased very significantly.Conclusion:Hypoxic preconditioning for 48 hours in hypoxia with an oxygen concentration of 11.2%can improve the ratio and exercise capacity of p-Thr¹⁷²-AMPKα/AMPKαand p-Ser⁷⁹-ACC/ACC in a hypoxic exercise.