Toll-Like Receptor 4 Participates In Non-Alcoholic Fatty Liver Ischemia-Reperfusion Injury By Regulating The Expression Of Mfn 2 And PGC-1α

[Background and Aims] Now Non-alcoholic fatty liver disease(NAFLD)has become the second largest liver disease after viral hepatitis in the world,which can lead to end-stage liver disease.It is a common phenomenon in combination with other liver diseases and has become a new important risk factor in liver surgery.ischemiareperfusion(IR)affects liver function recovery after liver transplantation and resection,while NAFLD’s tolerance to ischemia-reperfusion injury(IRI)is far worse than that of normal liver,which leads to a significant increase in the incidence of serious complications after surgery.In NAFLD-based ascending IRI,the injury changes are still unknown,and the related molecular mechanism and targeted therapy have not been fully understood.Bacterial lipopolysaccharide(LPS)in NAFLD and IRI can reduce the expression of Mfn2 by inhibiting the activity of PGC-1α in liver cells.Toll-like receptor 4(TLR4),which is an LPS receptor,can up-regulate TNF-α and IL-6.However,it is unclear whether TLR4 affects the expression of PGC-1α and Mfn2,and whether the of TLR4 knockout(KO)has an effect on Mfn2 expression and mitochondrial fusion in the liver tissues of mice models in the combination of both exist.This experiment will explore the changes of liver and mitochondrial injury and the effects of TLR4 KO on Mfn2 expression and mitochondrial structure and function in a composite model of NAFLD and IRI,and whether TNF-α and IL-6 levels can be predictors of mitochondrial injury and liver tolerance injury.[Methods] By establishing WT(C57BL/10J)and TLR4KO(C57BL/10 Sc NJ)NAFLD mice models,we studied changes in the expression of inflammatory factors(IL-6,TNF-α),PGC-1α and Mfn2,mitochondrial fusion,and functional expression(ATP,ROS),liver injury index(ALT,AST,HE,Oil Red O,NAS)after ischemia(1h)-reperfusion(6h)in NAFL.[Results] In a mice model in which NAFLD or IRI exists alone,its liver structure is disordered,the levels of inflammatory factors(IL-6,TNF-α)increased(P <0.05),and the expression of PGC-1α and Mfn2 is down-regulated(P <0.05);in addition,mitochondrial structure was destroyed and fusion disorder appeared,ATP consumption increased(P <0.05),and ROS production increased(P <0.05).However,in a mice model in which both NAFLD and IRI coexist,liver and mitochondrial injury were further significantly worsened(P <0.05).After TLR4 KO,IL-6 and TNF-α expressions were significantly down-regulated(P <0.05),while PGC-1α and Mfn2 expressions were significantly up-regulated(P <0.05),mitochondrial fusion increased,ATP consumption decreased(P <0.05),ROS reduced significantly(P <0.05).[Conclusions] In a mice model of NAFLD-based ascending IRI,the degree of structural and functional injury to the liver and mitochondria is much greater than that caused by a single factor or a simple superposition of both.TLR4 KO increased the expression of Mfn2,and promoted mitochondrial fusion.Compared with the reduction degree of single factor injury by TLR4 KO,the degree of reduction of joint injury by TLR4 KO was more significant.In addition,TNF-α and IL-6 expression levels have certain predictive effects on the degree of mitochondrial injury and liver tolerance.