The Effect Of Hepatic Iron Deficiency Induced By High Fat Diet On Insulin Resistance And Mechanism

Objective: Obesity which is a pivotal contributor to insulin resistance is also one of the important risk factors for iron deficiency in the meantime.This study aimed to explore the effect of hepatic iron deficiency induced by high fat diet on insulin resistance and possible involved mechanisms.Methods: C57BL/6J mice were randomly divided into two groups which were fed low fat fodder and high fat fodder respectively for 10 weeks and each group contained 10 mice.The weight of mice were recorded weekly.And glucose tolerance test(GTT)and insulin tolerance test(ITT)were conducted in the last week before mice were executed.After 10 weeks,Mice were executed and the livers were removed for detection of related indicators: The hepatic protein expression levels of p-AKT,t-AKT,p-GSK3?,t-GSK3?,L-ferritin,Grp78,p-EIF2?,t-EIF2?,p-IRE1?,t-IRE1?,XBP1,ATF6? were detected by western blotting.Hepatic total iron and labile iron pool(LIP)were detected by flame atomic absorption spectrometry;HepG2 cells were incubated with 200 ?M palmitate acid(PA),for the establishment of insulin resistance model,and the iron chelating agent(deferoxamine mesylate salt,DFO)400 ?M or iron supplement(ammonium iron citrate,FAC)10 ?M at the same time.Calcein fluorescence spectrophotometry was used to detect LIP in cells.And the expression levels of the abovementioned proteins were detected by western blotting.Cells were incubated with endoplasmic reticulum stress(ERS)reliever(sodium phenylbutyrate,4-PBA)1 mM or IRE1 signaling pathway blockers(STF)100 ?M based on the PA and were detected about the protein expression change of p-AKT and t-AKT.Results:(1)Compared with the low-fat diet(LFD)group,the weight of highfat diet(HFD)group mice significantly increased over feeding time.The Glucose tolerance,insulin tolerance and the protein phosphorylation level of AKT,GSK3? distinctly declined.Accordingly,compared with the control group,the incubation of PA could also significantly reduced cellular protein phosphorylation level of AKT.(2)Compared with the LFD group,the HFD group mice had lower level of hepatic total iron,LIP,L-ferritin.At the same time,the incubation of PA could significantly reduced LIP in cells.(3)The protein phosphorylation level of AKT was further reduced when hepG2 cells were incubated with iron chelating agent DFO based on the PA.The iron supplement FAC could distinctly alleviate the inhibiting effect of PA on protein phosphorylation level of AKT.(4)Compared with the LFD group,the expression levels of hepatic ERS related protein p-IRE1?,p-EIF2?,XBP1,ATF6?,Grp78 significantly increased.Compared with control group,above-mentioned ERS related protein expression of PA-incubation hepG2 cells also markedly increased.The incubation of DFO could aggravate the expression of ERS-related protein induced by PA and incubation of FAC could alleviate this phenomenon.(5)The addition of both ERS reliever 4-PBA and IRE1 blockers STF based on the incubation of PA in hepG2 cells markedly increased protein phosphorylation level of AKT compared with PA-incubation group.Conclusion: The HFD-induced obese mice gave rise to serious hepatic iron deficiency and insulin resistance.Iron deficiency,to some extent,induced ERS through the IRE1 signal pathway and accordingly aggravated insulin resistance.Our results suggested that obesity-induced iron deficiency should attract more attention.