| BackgroundObesity is an important component of metabolic syndrome,in which the characteristic lipid change is hypertriglyceridemia and decreased HDL-C level.Low HDL-C is more prominent when obesity is accompanied by deposition of adipose tissue(such as fatty liver), suggesting that there were some direct or indirect effects of adipose tissue on metabolism of HDL in liver.However,the mechanism by which obesity causes low HDL-C is not yet fully clear.ObjectiveTo investigate the effect of adipocyte coculturing on expression of ABCA1 and ABCG1 in hepatic cell and its potential mechanism..MethodTranswell system was used to do coculture of HepG2 cell and 3T3-L1 cell-derived mature adipocyte,with undifferentiated 3T3-L1 cell and blank being the negative controls.After 48 hours of coculture, HepG2 cells were collected for RNA and protein extraction.Western blot and RT-PCR were used to assess the protein and mRNA expression of ABCA1,ABCG1,LXRα,and SREBP1c mRNA.Results1.Compared with normal control group and 3T3 group,ABCA1 protein levels of adipocyte group HepG2 cells decreased by 83%(P＜0.05) and by 80%(P＜0.05),and ABCA1 mRNA level was decreased by 30%(P＜0.05) and 26%(P＜0.05) respectively.2.Compared with normal control group and 3T3 group,the ABCG1 protein levels of adipocyte group HepG2 cells was decreased by 34%(P＜0.05) and by 30%(P＜0.05),and ABCG1 mRNA level was decreased by 41%(P＜0.05) and 36%(P＜0.05).3.Compared with normal control group and 3T3 group,LXRαmRNA levels of the adipocyte group HepG2 cells was decreased by 54% (P＜0.05) and 51%(P＜0.05) respectively. 4.Compared with normal control group and 3T3 group,the SREBP1c mRNA levels of adipocyte group HepG2 cells was increased by 73%(P＜0.05) and 62.5%(P＜0.05) respectively.Conclusion1.Adipocyte-induced downregulation of ABCA1 and ABCG1 in HepG2 cell is an important mechanism by which obesity caused low HDL-C.2.LXRαmay be the upper pathway for adipocyte-induced downregulation of hepatic ABCA1 and ABCG1. |
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