| Objective: In our previous study,we reported that Taurine（Tau）could inhibit autophagy induced by arsenic via Peroxisome proliferator-activated receptor-γ（PPARγ）pathway,but the mechanism and target of Tau to relieve insulin resistance are not clear.Therefore,our study intends to explore the feasibility and possible mechanisms of Tau for nutritional intervention on arsenic-induced insulin resistance.Methods: In vivo,C57BL/6J male mice were exposed to As2O3 at a concentration of 14 mg/L.The Tau intervention group was pretreated with Tau（250 mg/kg）before treatment with 4 mg/L As2O3.At the end of experiment,oral glucose tolerance test（OGTT）was performed to detected blood glucose;liver weight of mice was measured;liver paraffin sections were made and the expression of carbohydrates in liver tissue were detected by glycogen staining（PAS staining）;The expression of p-Akt protein was detected by immunofluorescence analysis;The expression of gluconeogenesis and glycolytic related genes in liver tissues was detected by Real Time-Polymerase Chain Reaction（RT-PCR）;The expression of glycogen synthase kinase 3（GSK3β）,phosphorylated GSK3β（p-GSK3β）,GLUT2,and the related pathway proteins of Akt,p-Akt and PPARγ were detected by western blot.In vitro,we used human HepG2 cells for the study.The cytotoxicity of Na As O2 was detected by MTT assay.The expression of PPARγ,mammalian rapamycin target protein complex 2（mTORC2）,Akt,p-Akt,LC3-Ⅱ and P62/SQSTM1 in HepG2 cells treated with 14 μM Na As O2 for 24 h were detected by Western blot.HepG2 cells were pretreated with PPARγ activator Rosiglitazone（RGS）,mTORC2 activator palmitic acid（PA）,autophagosome formation inhibitor 3-methyladenine（3-MA）and Tau before treatment with 4 μM Na As O2 for 24 h.Western blot was used to detect the expression of PPARγ,mTORC2,Akt,p-Akt,LC3-Ⅱ,P62,GSK3β,p-GSK3β and GLUT2 in HepG2 cells.The insulin sensitivity analysis in HepG2 cells was detected by glucose oxidase-peroxidase method.Results: Liver weight of mice was significantly reduced after exposure to As2O3 at a concentration of 14 mg/L,after Tau administration the liver weight was increased after Tau administration.The results of OGTT showed that at 0,15,30 and 120 min,the blood glucose of mice exposed to 4 mg/L As2O3 was significantly higher than that of the control group,and the difference was statistically significant.The blood glucose level decreased with Tau administration.The OGTT-AUC showed that exposure to 4 mg/L As2O3 could impair glucose tolerance and Tau administration relieved glucose tolerance induced by As2O3.PAS staining showed that the content of glycogen in mice liver was significantly decreased with the increase of As2O3 concentration,while the content of glycogen was significantly increased after administration with Tau.The results of RT-PCR showed that the expression of gluconeogenesis genes increased and the expression of glycolysis genes decreased with As2O3 treatment,the protective effects of Tau intervention group was obvious.Western blot showed that the expression of PPARγ,p-Akt and GLUT2 in liver were significantly decreased and the expression of p-GSK3β was significantly increased with the increase of As2O3 concentration.The results of immunofluorescence analysis showed that the expression of p-Akt in liver decreased with the increase of As2O3 concentration,the protective effect of Tau intervention was also obvious.In vitro,HepG2 cells were treated with different concentrations of Na As O2 for 24 h,and cell viability decreased with the increase of Na As O2 concentration.After treated with 14 μM Na As O2 for 24 h,the expression of PPARγ,mTORC2,p-Akt and LC3-Ⅱ were decreased,P62 was increased.RGS and Tau pretreatment could significantly increase PPARγ expression compared with the Na As O2-treated group.RGS,PA and Tau pretreatment could increase the expression of mTORC2 and p-Akt protein compared with the Na As O2-treated group.After pretreatment with RGS,PA,3-MA and Tau,the expressions of LC3-Ⅱ and p-GSK3β were significantly decreased and the expressions of P62 and GLUT2 were increased compared with the Na As O2-treated group.Glucose oxidase-peroxidase assay showed that the glucose content in the Na As O2-treated group increased compared with the control group.After pretreated RGS,PA,3-MA and Tau,the content of glucose decreased compared with the Na As O2 treated group,suggesting glucose intake was increased.Conclusion: Tau administration could ameliorate low level arsenic-induced insulin resistance by the activation of PPARγ-mTORC2 signaling and inhibition of the hepatic autophagy pathway. |
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