The Mechanism Of1,3-dichloro-2-propanol Induced Lipid Accumulation In Vivo And Vitro

1,3-DCP is one of the best-known component of a group of contaminants calledchloropropanols which are foodborne contaminants that can be formed when chlorideions react with glycerol and other lipids in different foodstuffs during food processing,cooking and storage, so the1,3-DCP pollution is difficult to avoid.1,3-DCP has gainedgreat attention for its toxic potential as carcinogen via genotoxic mechanism, and acts asan endocrine disruptor in humans and animals. Besides,1,3-DCP has hepatotoxicity,nephrotoxicity, neurotoxicity, teratogenicity and mutagenicity. To our knowledge, thereare no research concerned about the lipid metabolism exposure to1,3-DCP.Hyperlipidemia is characterized by abnormally elevated levels of one or more lipidsand/or lipoproteins in the blood and pathological lipid qualities. It is considered as one ofthe most important risk factor of cardiovascular disease, cancer, diabetes, diabeticneuropathy, primary aldosteronism and chronic kidney disease. Hyperlipidemia resultsfrom complex interactions between genetic, dietary and environmental factors. Amongthem, dysregulation of lipid metabolism along with diet is one of the major causes ofhyperlipidemia. Excessive absorption of lipids from diet or aberrant lipid metabolism inthe body will lead to hyperlipidemia. In addition to high fat diet, food additives andcontaminants in food have been shown to induce hyperlipidemia. Therefore, it isimportant to study these food pollutant effects on lipid metabolism and its mechanism.Thus, the present study was to investigate the effects of1,3-DCP on lipidmetabolism in mice under NOAEL and further to study the mechanism of1,3-DCPinduced hyperlipidemia. The results will provide evidence for understanding the toxicmechanism of1,3-DCP at low dose, thereby, will lay foundations for searching moresensitive biomarkers, which could be early detected of the toxicity exposure to1,3-DCP.The thesis includes two parts:1.1,3-DCP induced hyperlipidemia in C57BL/6J mice viaAMPK signaling pathway.2.1,3-DCP induced lipid accumulation in HepG2cellsthrough AMPK and PKA pathways.In chapter1: We first found1,3-DCP could induce hyperlipidemia in C57BL/6J mice below1mg/Kg bw/day. We investigated serum lipid profile, liver total cholesterol(TC) and triglyceride (TG), histopathology of liver and adipose tissue. The resultsshowed1,3-DCP dose dependently increased serum TG, TC and low-density lipoproteincholesterol (LDL-C), decreased serum high-density lipoprotein cholesterol (HDL-C),increased relative liver weight, liver TG and TC, relative adipose tissue weight andenlarged the size of adipose cells. Because AMPK signal pathway is important in theprocess of lipid metabolism, we further investigated the effects of1,3-DCP on AMPKsignaling pathway in murine models. The results showed that1,3-DCP decreasedp-AMPK/tAMPK ratio, p-ACC/tACC ratio, PPARα expression, but increased FAT,SREBP1, HMGCR and FAS expression. These observations indicated that1,3-DCPinduced hyperlipidemia in C57BL/6J mice at least partially through regulating AMPKsignaling pathway.In chapter2: We found that1,3-DCP could induced lipid accumulation in HepG2cells. The data showed1,3-DCP significantly increased intracellular content of TG andTC at0.5-2μg/mL. Thereby, we further studied possible underlying mechanism that1,3-DCP works. The results showed that1,3-DCP greatly decreased cAMP, AMP/ATPand ADP/ATP ratio, phosphorylated PKA, CREB, HSL, AMPK and ACC, LKB, SIRT1,PGC1, PPAR, CPT1, HNF4. However, SREBP1c, FAS, SCD1, GPAT, HMGCR, CD36expression and SREBP-2, LDLR and HMGCR genes expression were greatly increased.In addition, we investigated the effect of1,3-DCP on intracellular calcium and regulatedproteins. The results showed that there was no influence.Thus, we concluded that1,3-DCP induced lipid accumulation at least partiallythrough AMPK and PKA signaling pathways in vivo and vitro.And the results willprovide evidence for understanding the toxicity and mechanism of1,3-DCP, thus, will layfoundations for searching more sensitive biomarkers and setting up new safety limit of1,3-DCP.