Mechanism Of Arsenic Exposure During Pregnancy Induced DNA Methylation And Caused Insulin Resistance In Male Offspring

Objective:In this paper,Apo E-knockout(Apo E^-/-)mice were used as subjects to investigate the effects of arsenic exposure during pregnancy on insulin resistance in male offspring and possible mechanisms of DNA methylation.Methods:The pregnant Apo E-knockout(Apo E^-/-)dams were randomly assigned to two groups,control and arsenic-treated group.Control group was given normal drinking water,while arsenic exposure group was maintained on tap water within 85ppm NaAsO₂ during 8-15 days of pregnancy.Arsenic-containing drinking water was refreshed every 3 days to minimize oxidation.After parturition,the pups were weaned at birth 21 days of age and maintained on a standard chow diet and drink.At 8、16and 24 weeks of age,glucose tolerance and insulin tolerance tests were performed;At 8 and 24 weeks of age,blood samples were taken and the concentrations of insulin,leptin,and adiponectin in the blood were measured by ELISA.In addition,the pancreatic tissue was dissected and fixed,sectioned,and immunohistochemically stained.The liver tissue was also taken for genomic DNA,RNA and protein extraction;Methylation kit detects whole-genome methylation level in mice liver;The expression levels of Glucokinase（Gck）and Glucose-6-phosphate（G6P）and Sterol regulatory element-binding protein 1c（SREBP-1c）genes were determined by real-time PCR;And the expression level of Glucokinase（GCK）protein was determined by Western Blot technique.Results:There was no significant on the body of dams and male offspring induced by arsenic exposure during pregnancy（P>0.05）.However,arsenic caused a significant increase in leptin and insulin levels in the serum of offspring male ApoE^-/- mice and adiponectin levels were significantly decrease（P<0.01）.At the 8、16and 24 weeks of age,the glucose tolerance and insulin tolerance of the offspring male ApoE^-/-mice were impaired.At 24 weeks of age,the number of isletβcells in the islets of male ApoE^-/-mice in the arsenic exposure group was significantly decreased（P<0.01）,and the whole genome methylation level was significantly increased（P<0.05）,and the expression levels of Gck gene and GCK protein were significantly down-regulated（P<0.05）;however,at 8 weeks of age,arsenic exposure during pregnancy did not change the number of pancreatic isletβcells,Gck gene and protein expression in offspring male ApoE^-/-mice（P>0.05）.Conclusion:Arsenic exposure during pregnancy induced impaired glucose tolerance and insulin tolerance、decrease the number of islet beta cells and insulin resistance in male offspring,which may be related to elevated levels of whole-genome methylation and down-regulation of Gck gene expression caused by arsenic exposure.