The Effect Of TIGAR On Mitochondrial Biogenesis And Function In Skeletal Muscles During Normal And Exercise Conditions

Aim:TP53-induced glycolysis and apoptosis regulator(TIGAR),a glycolytic inhibitor,plays vital roles in regulating cellular metabolism and oxidative stress.TIGAR is highly expressed in skeletal muscles.Therefore,we attempted to explore the role of TIGAR in the functions of skeletal muscles and possible mechanisms.Methods:Different types of skeletal muscles under physiological and pathological conditions were isolated to detect the level of TIGAR.Exhaustive swimming test with a load corresponding to 5%of body weight was utilized in mice to assess the effects of TIGAR on exercise-induced fatigue and muscle damage.The contents of NADPH,lactate,glycogen,ATP and metabolic approaches were detected in WT and TIGAR KO mice.HE staining,RT-qPCR,Western blot,imunohistochemistry and immunofluorescence were used to measure different myofibers.The morphology and content of mitochondria were measured using electron microscope,RT-qPCR and Western blot.The activities and downstream proteins of SIRT1/PGC1? were also measure using Western blot and Co-IP assays.The mitochondrial translocation of TIGAR were further confirmed by immunofluorescence and immune electron microscopy.Mitochondrial targeting TIGAR was constructed.PPAR-Luc was transfected to measure the activity of upstream SIRT1/PGC1?.GST pull down and Co-IP assays were performed to detect the interaction between TIGAR and ATP5A1.JC-1 and MitoSOX dye were used to assess mitochondrial functions under hypoxia.Results:TIGAR levels in skeletal muscles had no significant differences under physiological and pathological conditions.The running time and metabolic indicators were significantly greater in WT mice compared with TIGAR KO mice.Poor exercise capacity was accompanied by decreased type IIA fibers in TIGAR KO mice.Decreased mitochondrial number and mitochondrial OXPHOS were observed in TIGAR KO mice than in WT mice,which were involved in SIRT1 mediated deacetylation of PGC1?,and resveratrol treatment in TIGRA KO mice can increase mitochondrial content and exercise time.Much more TIGAR was also detected in mitochondria during exhaustive exercise.In addition,TIGAR,rather than mitochondria-targeted TIGAR achieved by in vitro plasmid transfection,promoted SIRTl-PGCla pathway.GST-TIGAR pull down assay followed by LC/MS found that TIGAR interacted with ATP5A1,and its binding to ATP5A1 increased during exhaustive exercise.Overexpression of mito-TIGAR enhanced ATP generation,maintained mitochondrial membrane potential and reduced mitochondrial oxidative stress under hypoxia condition.Conclusion:Our results uncovered a novel role for TIGAR in mitochondrial regulation in fast-twitch oxidative skeletal muscle through SIRT1-PGC1? and translocation into mitochondria,which contribute to the increase in exercise endurance of mice.