Maternal N-acetylcysteine Supplement During Pregnancy Protects Against Cadmium-induced Hepatic Glucose Metabolism Disorders In Male Offspring Mice

Objective:Maternal cadmium（Cd）exposure during pregnancy can cause fetal growth restriction（FGR）.However,the long-term effects and the mechanism of environmental Cd exposure in offspring remain unclear.The purpose of this study was to investigate the effect and mechanism of environmental Cd exposure during pregnancy on hepatic glucose metabolism in male mouse offspring at different stages,and the preventive effect of N-acetylcysteine（NAC）on glucose metabolism in male mouse offspring.Methods:In this study,the effect and mechanism of environmental Cd exposure during pregnancy on hepatic glucose metabolism were investigated in mouse offspring at different stages.Fifty-two gestational mice were randomly divided into four groups:control（CTRL）group,low-dose Cd（LCd）group,high-dose Cd（HCd）group and NAC+HCd group（13 pregnant mice per group）.Pregnant mice in CTRL group drank reverse osmosis water（RO water）.Pregnant mice in LCd group drank RO water containing CdCl₂（50 mg/L）from gestational day（GD）8-GD17.Pregnant mice in HCd group drank RO water containing CdCl₂（150 mg/L）from GD8-GD17.In each group,4-5 pregnant mice were delivered by cesarean section on GD18.And then fetal livers of mice were collected and weighted quickly.The remaining pregnant mice were allowed to give birth naturally.The offspring mice were euthanized on postnatal day（PND）35and PND98.Serum and livers of pubertal and adult offspring mice were collected.Fasting blood glucose test,glucose tolerance test and insulin tolerance test were performed on PND35,p ND70 and p ND84,respectively.Fetal liver samples were collected for RT-PCR,Western blotting,Hepatic glutathione（GSH）and superoxide dismutase（SOD）assay to evaluate the status of fetal liver oxidative stress.Sera were collected for ELISA to measure serum insulin and serum glucagon levels.Liver samples from pubertal mice and adult mice were collected for Western blotting to detect the protein expression of gluconeogenesis and insulin signaling pathways.Results:Maternal Cd exposure during pregnancy causes hyperglycemia in pubertal male offspring.Further mechanistic investigations showed that maternal cadmium exposure during pregnancy did not inhibit the hepatic insulin signaling pathway in pubertal male offspring.And the expression of key proteins in hepatic gluconeogenesis,including p-CREB,PGC-1α,PEPCK and G6PC,in pubertal offspring were markedly upregulated in HCd group as compared with the CTRL group.Furthermore,maternal Cd exposure during pregnancy impairs glucose tolerance and insulin tolerance as well as increases the level of serum glucagon and the levels of key proteins in hepatic gluconeogenesis,including p-CREB,PGC-1αand G6PC,in adult male offspring.Moreover,maternal cadmium exposure during pregnancy significantly reduces the serum insulin level and HOMA-βvalue of adult male offspring,and there are no significant difference in HOMA-IR value among all groups.Consistent with the results in pubertal male offspring of hepatic insulin signaling pathway,maternal cadmium exposure during pregnancy did not inhibit the hepatic insulin signaling pathway even compensated for the activation of hepatic p-IRS-1 and p-Akt protein expression in insulin-treated adult offspring.These data suggest that maternal cadmium exposure during pregnancy does not cause insulin resistance in male offspring but enhances hepatic gluconeogenesis.In addition,we demonstrated that Cd exposure during pregnancy markedly elevated the activity of superoxide dismutase（SOD）and the level of oxidative stress related proteins,including NOX2,NOX4,HO-1 and SOD2 in the fetal liver.Glutathione（GSH）content and GSH/GSSG value were significantly decreased in Cd-treated fetal livers.These data suggest that Environmental Cd exposure during pregnancy causes oxidative stress in fetal livers.Further investigation showed that NAC supplementation alleviated hepatic oxidative stress in fetuses,and thereby reversed hyperglycemia and glucose intolerance in mouse offspring.Conclusion:Maternal Cd exposure during gestation disturbs hepatic glucose metabolism via enhancing hepatic gluconeogenesis in male offspring mice.And maternal NAC supplementation improves Cd-induced glucose metabolic disorders in offspring maybe through alleviating oxidative stress in fetal livers.