Study On Mechanism Of Lipid Metabolism Disorder In Mice Induced By Real-ambient Particulate Matter Exposure

Objective: In this study,PPAR? receptor agonists or inhibitors were used to intervene mice to establish a mouse model of PPAR? receptor activation or inhibition.Through “real-ambient PM exposure system”,To explore the effect of PM exposure on lipid metabolism in mice and the potential role of PPAR ? in lipid metabolism disorder caused by PM exposure.Methods: In Shijiazhuang City,Hebei Province,mice were intervened by intragastric administration of PPAR? receptor agonists or inhibitors applied on “real-ambient PM exposure system” to establish a mouse model of PPAR? receptor activation or inhibition.From November 2018 to January 2019,mice were exposed to PM for 42 days,and the mice were exposed to PM for 16 hours a day.A total of 186 male wild type c57 mice(48 in the first batch and 138 in the second batch)were randomly divided into two groups: control group(Con)and PM exposure group(Exp).The second group was randomly divided into 6 groups: PM exposure group(Exp),control group(Con),PPAR? receptor agonist PM exposure group(Exp-A),PPAR? receptor agonist control group(Con-A),PPAR? receptor inhibitor PM exposure group(Exp-I),PPAR? receptor inhibitor control group(Con-I).After 42 days of PM exposure,the deposition of heavy metals in the liver of mice was analyzed by ICP-MS.The changes of lipid components in mouse liver were analyzed by lipoomics.The pathological sections of mouse liver,white adipose tissue and brown adipose tissue were observed.The content of TG in serum was detected by triglyceride(TG)kit.The content of HDL-C in serum of mice was detected by biochemical analyzer.In the further mechanism study,the m RNA expression levels of genes(a-COX-1,CD36,FATP-1,LXR-?,SREBP-1c,CYP4A10,CYP4A12 a,CYP4A12b,CYP4A14,CYP7A1 a,CYP8B1,CYP27a1)in liver tissue of mice in each group were detected by RT-PCR.The expression level of CYP4A14 protein was detected by Western Blot.The expression of HSLprotein in white adipose tissue and UCP-1 protein in brown adipose tissue was detected by immunohistochemical.Results:(1)During the exposure period,the average concentrations of PM2.5 in outdoor and cage were 139.11 ?g/m3 and 82.49 ?g/m3,the lowest concentrations were 18.67 ?g/m3 and 10.33 ?g/m3,the highest concentrations were 383.67 ?g/m3 and 219.33 ?g/m3,and the days of severe pollution(150 ~ 250 ?g/m3)were 12 days.(2)The results of ICP-MS showed that after PM exposure,the levels of chromium and arsenic in the liver of mice.(3)Liposome PLS-DA showed that PM exposure resulted in differences in fatty acid composition and metabolism of 35 fatty acids in the liver of mice,with the metabolic difference of glycerol phospholipids as the main target.(4)Liver histopathological examination showed that PM exposure caused disorder of hepatic cord arrangement,hepatocyte swelling,cytoplasmic loosening and slight steatosis;liver injury was alleviated by PPAR? receptor agonis intervention,after intervention with PPAR ? receptor inhibitor,the destruction of hepatic lobule structure was more obvious.(5)Histopathological examination of white adipose tissue showed that PM exposure increased the volume of white adipocytes.After intervention with PPAR? receptor agonist,the volume of white adipocytes decreased compared with Exp group.(6)The pathological and immunohistochemical results of brown adipose tissue showed that PM exposure caused lipid droplet fusion and brown lipid albinism in brown adipocytes,and the degree of brown lipid albinism decreased in PPAR? receptor agonist group and aggravated in PPAR? receptor inhibitor group.(7).Serological results showed that serum TG increased and HDL-C decreased after PM exposure.TG decreased and HDL-C increased in PPAR? receptor agonist PM exposure group.(8)q PCR results showed that PM exposure caused significant changes in the m RNA expression of CYP4A14 and CYP4A12 b.Western blot results showed that PM exposure led to the coordination of CYP4A14 protein expression and up-regulation of CYP4A14 protein expression in PPAR? activation group.(9)The results of immunohistochemistry showed that PM exposure decreased the expression of HSL protein in white adipose tissue and UCP-1 protein in brown adipose tissue.The expression of UCP-1 protein was up-regulated in PPAR? agonist PM exposure group,while the expression of UCP-1 protein decreased in PPAR? inhibitor PM exposure groupConclusion;(1)Metabonomic results showed that PM exposure led to lipid metabolism disorder in the liver,with the metabolic difference of glycerol phospholipids as the main target.(2)The serological results showed that PM exposure resulted in the increase of serum TG and the decrease of HDL-C,and PPAR? receptor agonists played a protective role.(3)PM exposure leads to mild steatosis of hepatocytes.PM further participates in fatty acid metabolism of liver by regulating the expression of CYP4A14 in liver through PPAR ?.(4)PM exposure led to the enlargement of white adipocytes and the albinism of brown fat.PPAR? receptor agonists protected the metabolic disorder of brown adipose tissue induced by PM exposure,but the role of PPAR? in white adipose tissue was not obvious.