Effects Of Diethylhexyl Phthalate And Bisphenol A On Lipid Metabolism And The Relationship With Oxidative Stress Of Liver In Rats

ObjectivesLipid metabolism abnormality is often manifested as the changes of blood cholesterol,triglyceride,apolipoprotein content,and related with atherosclerosis,hyperlipidemia,diabetes.Lipid metabolism is regulated by insulin,glucagon,diet nutrition and enzyme activity in vivo.Diethylhexyl phthalate(DEHP)and bisphenol A(BPA)are both raw materials in industry.Surveys show that they had endocrine disrupting effects,which were related to adverse multiple health effects in tissues,organs or systems,including increased incidence of endocrine system,immune system,neurological system and reproductive system.Due to the wide application of industrial products related with DEHP and BPA in life,they and their metabolites have be detected in pregnant women and children.Their health effects should be emphasized.As an important metabolic organ of the human body,the liver is the main place of oxidative stress induced by various chemicals in the process of metabolism.Therefore,it is greater significance to study the damage of chemical substances in liver and its corresponding mechanism.In view of this,our study establish animal model by mixed exposure DEHP and BPA in the weaning rat,detecting lipid metabolism and oxidative stress index at different time,analysising the difference of toxicity between mixed exposure and single exposure.Lipid metabolism effects mixed exposure to DEHP and BPA in rats and the relationship to oxidative stress were discussed,in order to better protect the health of the population.Methods4 weeks of age,96 rats with no specific pathogen grade(SPF)healthy SD rats were randomly divided into four groups according to weight,with 24 rats in each group.They were control group,DEHP 750 mg/kg group,BPA 100 mg/kg group and DEHP 750 mg/kg+BPA 100 mg/kg group,respectively,and the corresponding concentration was formulated with corn oil.The control group was given the solvent corn oil,and was continuously administered with 5 ml/kg volume for 6 weeks,7 days per week,1 time/day.The experimental animals in each group were divided into three groups according to the initial weight,and 8 animals were treated in each group for first,third,and sixth week respectively.The levels of lipids and lipid metabolism enzymes in serum were separated,and the total lipase,oxidative stress index,histopathology,PPARy,SOD3 and GPx mRNA expression were detected in liver.During the whole experiment,the growth and development of the rats were observed.Biochemical kit were measured with the contents of total cholesterol(TC),triglyceride(TG),low density lipoprotein(LDL-C)and high density lipoprotein(HDL-C)in serum.the total lipase of lipoprotein lipase(LPL)and liver esterase(HL)in liver was tested.Biochemical index of oxidative stress in liver testing:malondialdehyde(MDA),hydrogen peroxide(H2O2),glutathione(GSH),superoxide dismutase(SOD),glutathione peroxidase(GSH-Px),catalase(CAT).Serum hormone sensitive lipase(HSL)and lecithin cholesterol transferase(LCAT)were measured by ELISA kit.Genes expression peroxisome proliferators-activated receptor-gamma(PPAR?)and SOD3,GPx related with oxidative stress tested by RT-PCR.Results1.General situation:The body weight of the DEHP group and the mixed group was significantly lower than that of the control group from first weeks.The liver organ coefficients of the DEHP group and the mixed group were significantly higher than those of the control group at all stages(p<0.05).2.Pathology:necrosis of hepatocyte found in DEHP group,vacuolar degeneration of hepatocyte cytoplasm in group BPA,and severe inflammatory cell infiltration in the mixed dose group in sixth week.3.Serological index:The content of TC increased in BPA group and mixed group in first week,increased in three exposure groups in sixth week,the content of TG decreased in DEHP group and mixed group in first and third weeks,decreased in group DEHP in sixth week,the contents of LDL-C decreased in BPA group and mixed group in first week,increased in mixed group in the sixth week,the content of HDL-C decreased in mixed group in first week,decreased in DEHP group and mixed group in third week,decreased in three exposure groups in the sixth week(p<0.05).The content of HSL decreased in three exposure groups in first and sixth weeks,while the content of LCAT was decreased in group BPA and mixed group in third week,and decreased in three exposure groups in sixth weeks(p<0.05).4.The expression of hepatic total lipase and gene expression:The activity of LPL increased in the DEHP group and BPA group in third weeks,decreased in three exposure groups in the sixth week.The activity of HL decreased in the mixed group in first weeks,and lower than other two exposure group,decreased in DEHP group and mixed group in third and sixth weeks,and mixed group was lower than BPA group(p<0.05).The gene expression level showed that PPARy mRNA decreased in mixed group in third week,decreased in DEHP group and mixed group in sixth week,and the mixed group was lower than the other two exposure group in third weeks(p<0.05).5.Oxidative stress and gene expression level:The levels of MDA were increased in BPA group and mixed group in sixth week,the levels of H2O2 were increased in three exposure groups in sixth week,the levels of GSH increased in mixed group in first week,increased in DEHP group and mixed group in third and sixth weeks,the activity of SOD decreased in DEHP group and mixed group in third week,decreased in three exposure groups in sixth week,the activity of GSH-Px increased in mixed group in first week,decreased in three exposure groups in third and sixth weeks,the activity of CAT increased in DEHP group and mixed group in sixth week,the difference was statistically significant(p<0.05).SOD3 mRNA decreased in DEHP group and mixed group in third and sixth weeks,and the level in mixed group is lower than that in the BPA group,GPx mRNA decreased in three exposure groups in the sixth week,the difference was statistically significant(p<0.05).6.The relationship between lipid metabolism and oxidative stress:the content of TC was respectively positively correlated with MDA,H2O2 and GSH in three stages,was negatively correlated with SOD and GSH-Px in sixth week,the content of TG was negatively correlated with GSH in the three stage,but was positively correlated with GSH-Px in first week,negatively correlated with GSH-Px in third week,the content of LDL was negatively correlated with GSH-Px and GSH in first week,positively correlated with GSH in third week,negatively correlated with CAT in sixth week,the content of HDL was negatively correlated with MDA and GSH-Px in first week,positively correlated with SOD and negatively correlated with GSH in third week,positively correlated with GSH-Px and SOD,and negatively correlated with GSH in sixth weeks.Conclusions1.DEHP,BPA and mixed exposure interfered with the normal development of rats,hepatocytes necrosis,cytoplasmic vacuolation and severe inflammatory cell infiltration were found in the liver of rats.2.DEHP and BPA induced abnormal blood lipid levels in rats,the gene expression of PPARy was inhibited,the enzymes activity of lipid metabolism in serum and liver was decreased,liver peroxide was increased,antioxidant enzyme activity was decreased,antioxidant gene SOD3 and GPx were inhibited.3.There was interaction between DEHP and BPA in mixed exposure group,compared with the single exposure group,the level of blood lipid and oxidative stress increased or weakened.4.The effects of DEHP and BPA on lipid metabolism in rats are related to the oxidative stress disorder by inhibiting SOD3 and GPx gene expression.