Role Of SCD1 In Regulating Palmitic Acid Tolerance Of Goose Hepatocytes

Increased saturated fatty acid content can cause mammalian hepatocytes endoplasmic reticulum(ER)stress,inflammation,apoptosis,and is one of the important factors leading non-alcohol fatty liver exacerbating to non-alcohol fatty hepatitis.Stearyl coenzyme A desaturase 1(SCD1)is the key enzyme responsible for the desaturation of saturated fatty acids,and both its expression abundance and genomic copy number are observed to be significantly higher in geese than in mammals.It is thus speculated that during the formation of goose fatty liver,SCD1 may have a role in protecting the liver from pathological injury.However,there is a paucity of information on the role of SCD1 in the saturated fatty acid tolerance of goose hepatocytes.In this study,different concentrations of palmitic acids were used to treat goose primary hepatocytes,with the human hepatic cell line(LO2 cells)as the reference.To evaluate the palmitic acid tolerance of cultured hepatocytes,MTT was examined to reflect the effect of palmitic acid on cell viability,and quantitative PCR(qPCR)was used to detect the mRNA expression levels of several genes related to ER stress,inflammation,and apoptosis,and the exact role of SCD1 in palmitic acid tolerance of goose hepatocytes was explored using RNA interfere.The main results were listed as follows:(1)The maximal tolerant concentration to palmitic acid of goose hepatocytes was 0.6 mM,while that of human hepatocytes(LO2 cells)was lower than 0.2 mM.(2)When treated with 0.6mM palmitic acid,the mRNA expression of the ER stress-related genes(XBP,BIP,ATF6),inflammatory response-related genes(IL-6,IL-1β,IFN-γ)and apoptosis-related genes(Bax,Bcl-2,Caspase-3,Caspase-9)were not significantly different from the control group in goose hepatocytes,but in the LO2 cells their expression levels significantly increased compared to the control group(P<0.05).(3)Under the treatment of 0.6 mM palmitic acid,the results of oil red O staining showed that it was not significantly different between the treatment and control groups in both cells;the mRNA expression of fatty acid desaturation-related genes(SCD1,FADS1,FADS2)was significantly higher than that in the control group(P<0.05)in goose hepatocytes,while no significant differences were seen in the LO2 cells.In addition,the mRNA expression of the fatty acid elongate enzyme-related gene(ELOVL6)in both cells significantly increased(P<0.05),whereas that of triglyceride synthesis-related gene(DGAT2)remained statically unchanged in these two cells.(4)Under the treatment of 0.6 mM palmitic acid,interference of SCD1 significantly reduced the tolerance of goose hepatocytes to palmitic acid(P<0.05),and significantly increased the mRNA expressions of inflammatory factors(IL-6,IL-1β),the protein expression of cytochrome C and the apoptosis rate.However,the ER stress-related genes(XBP,BIP,ATF6)and inflammatory factor(IFN-γ)and apoptosis related genes(Bax,Bcl-2,Caspase 3,Caspase 9)were not significantly changed under the treatment.(5)Under the treatment of 0.6 mM palmitic acid,interference of SCD1 in goose hepatocytes significantly increased the mRNA expression of several central pathway genes(AKT1,AKT2,FOXO1,SIRT1),while that of PI3 K,mTOR and AMPK were not no significantly altered.Besides,no significant change was observed in the mRNA expression of triglyceride synthesis-related key genes(FADS1、FADS2、ELOVL6、DGAT2).In summary,SCD1 may be involved in enhancing the tolerant capacity of goose hepatocytes to palmitic acid by regulating the mRNA expression of inflammation and apoptosis-related genes through both the AKT/FoxO1 and SIRT1/FoxO1 pathways.