The Essential Role Of REGγ In Regulating Lipid Metabolism

The proteasome activator REGγ has been reported to promote ubiquitin-and ATP-independent proteolysis in eukaryotes and plays an important role in cell cycle regulation and a variety of human diseases development. Lipid metabolism abnormality may lead to many diseases such as liver steatosis, obesity and other metabolic syndrome. But the relationship between REGy and lipid metabolism has rarely been reported. In this thesis, we use high-fat diet feeding REG7knockout mice to imitate the non-alcoholic fatty liver development in human and study the relationship between REGy and liver steatosis. The results indicate that REGy knockout can protect mice from high-fat diet induced fatty liver. Furthermore, REGy deficiency inhibits the organic acid-induced accumulation of lipids in mouse primary hepatocytes. Gene expression results show that the key enzymes and transcription factor involved in liver lipid accumulation have no significantly difference in wild-type and REGy knockout mice. TEM analysis of liver showes that REGy knockout led to marked increase of the number of autophagic vacuoles(AVs).In addition, we observes AVs enwrapped lipid droplets or mixed lipid droplets and AVs. We use radioisotope labeled substrate to detect lipid metabolism in primary hepatocytes and results indicate that the fatty acid β-oxidation level has significantly increased in knockout cell while the lipid synthesis and fatty acid uptake level have no difference.These findings prompted us to suppose that REGy regulate liver lipid metabolism through autophagy.Next we verify the hypothesis in the liver tissue and cells, the WB experimental results indicate REGγ knockout can increase autophagy activity. Immunofluorescence experiments showed REGγ deletion increase the punctate form of LC3in the cytoplasm. Regulation of REGγ on lipid metabolism can reverse when cell be treated with the autophagy inhibitor3-MA. Meanwhile the protect effect of REGγ on high-fat diet induced liver steatosis diminished when mice injected with autophagy inhibitor chloroquine. Furthermore we also conducted a preliminary study of the regulation of REGy on adipogenesis and insulin sensibility in high-fat diet fed and old mice.These findings reveal the regulation between REGγ and lipid metabolism, providing the theoretical basis for fatty liver, obesity and other metabolic syndrome and hoping to provide new drug targets for the treatment of human fatty liver and other metabolic diseases.