Nur77 Increases Glucose Transport By Activating P38MAPK In Mouse Skeletal Muscle Cells Under Lipotoxicity

Objective: Diabetes has become one of the chronic diseases that pose a serious threat to human health.Insulin resistance is a major feature of type 2 diabetes,and insulin resistance in skeletal muscle has been the focus of many studies and reviews.The orphan nuclear receptor Nur77 is a member of the nuclear receptor superfamily and a key regulatory protein in the process of glucose metabolism,which plays an important regulatory role in the process of glucose metabolism.While p38 MAPK is an important member of the MAPK family,it is activated under various extracellular stimuli,involved in inflammatory processes,cell growth and differentiation,cell cycle and cell death,and many studies have found that activated p38 MAPK can increase GLUT4-mediated glucose transport.Therefore,in this study,C2C12 myotubes under lipotoxicity were used as experimental subjects to investigate whether there is interaction between Nur77 and p38 MAPK and thus affect GLU4-mediated glucose transport.Methods: PA was used to treatment C2C12 myotubes resulted in an insulin resistance model,then detected cellular glucose uptake levels,24 h glucose consumption levels,and total protein levels of Nur77,GLUT4 and membrane translocation levels of GLUT4.After overexpressed and knocked down the Nur77,detected the glucose uptake level,24 h glucose consumption level and total protein and membrane translocation levels of GLUT4.After PA was used to treatment C2C12 myotubes resulted in insulin resistance model,Nur77 was overexpressed and p38 MAPK specific inhibitor SB203580 was administered to detect glucose uptake levels,24 h glucose consumption levels,and total protein of GLUT4,p38 MAPK,p-p38 MAPK and membrane translocation levels of GLUT4.Results: 1.Successfully constructed overexpressing Nur77 lentivirus and knocking down Nur77 lentivirus.2.After PA was used to treatment C2C12 myotubes caused insulin resistance,cell glucose uptake and 24 h glucose consumption were also significantly decreased under the basic state(P<0.05),and glucose uptake was not significantly increased after insulin stimulation(P>0.05).In addition,total proteinlevels of Nur77 and GLUT4 decreased,and membrane protein levels of GLUT4 were significantly reduced.3.After Nur77 knockdown,the cellular glucose uptake and 24 h glucose consumption were significantly decreased(P<0.05),and the total protein level and membrane protein level of GLUT4 were significantly decreased.4.After overexpression of Nur77,the cellular glucose uptake and 24 h glucose consumption were significantly increased in the basal state and insulin-stimulated state(P<0.05),and the total protein level and membrane protein level of GLUT4 were also significantly increased.5.In the lipid-toxic state,overexpression of Nur77 revealed a significant increase in cellular glucose uptake and 24 h glucose consumption under basal state and insulin stimulation(P<0.05),and total protein levels and membrane protein levels of GLUT4 were significantly increased.6.After overexpression of Nur77 under lipotoxicity,the phosphorylation level of p38 MAPK was significantly increased.After administration of p38 MAPK specific inhibitor SB203580,the phosphorylation level of p38 MAPK was significantly decreased,and the total protein level of GLUT4 and membrane turnover were observed.The level of water dropped significantly.At the same time,it was found that the cellular glucose uptake and 24 h glucose consumption were also significantly decreased under the basal state(P<0.05),while the cellular glucose uptake was not significantly increased under insulin stimulation(P>0.05).Conclusion: In the lipid-toxic state,after overexpressing of Nur77 in C2C12 myotubes can increase glucose transport in basal state and insulin-stimulated state,increasing insulin sensitivity.In addition to the direct effect of Nur77 on GLUT4,Nur77 also increases the activity of GLUT4 by increasing the phosphorylation level of p38 MAPK,thereby increasing glucose transport.