Effect And Mechanism Of Oleoylethanolamide On Nonalcoholic Fatty Liver Disease

Objective: To exploring the effect and probable mechanism of OEA (a endogenous ligand of peroxisome proliferator-activated receptor-alpha ) on nonalcohol fatty liver disease.Methods: We established HepG2 steatosis by 24 hours treatment of 0.25 mM oleic acid. Activeity of cells was measured by MTT, and lipid contends in cells were detected by oil red staining, triglyceride(TG)content of cell lysis supernatant and ALT/AST levels of cell culture medium were detected by commercial clinical diagnosis of kit.Cells were treated with OEA and Fenofibrate as positive control for 4/8 hours. The levels of gene expression were detected by quantitative real-time PCR using GAPDH as the internal standard. The change of lipid drop and triglyceride content in HepG2 cells were observed by red Oil O staining and commercial clinical diagnosis of kit, respectively.Results:(1) HepG2 cells were found with lipid accumulation by treatment of 0.25 mM OA 24h. Compared to the control group, there was no significant difference on ALT level in cell culture medium of OA group (P=0.18),but AST level changes significantly (([11.74±0.263)U/L vs (13.29±0.4638)U/L,P<0.05),and intracellular TG content increased [(1.258±0.1038)mg/dl vs (5.513±0.2612)mg/dl,P<0.001].(2) OA-induced fatty liver vitro model were treated with OEA and fenofibrate for 4/8 hours, Real-time PCR analysis showed that: mRNA expression of lipoprotein lipase (LPL) and stearoyl-coA desalurase-1(SCD-1) were changed significantly when treated with OEA and fenofibrate for 4h, Compared to the vehicle group, only 50μM OEA group could increase the mRNA expression level of LPL(0.00083±0.00044 vs 0.00409±0.00018,P <0.001),both 50μM OEA group and 50μM fenofibrate group reduce the mRNA expression level of SCD-1(43.94±1.312,51.69±0.725 vs 62.62±2.085,P <0.01); mRNA expression of acetyl CoA Carboxylase (ACC)and sterol regulatory element binding protein-1c (SREBP-1c) were decreased significantly when treated with OEA and fenofibrate for 8h, Compared to the vehicle group,only 50μM OEA group could dimish the mRNA expression level of SREBP-1C(2.268±0.1487 vs 0.704±0.0747,P<0.001),both 50μM OEA group and 50μM fenofibrate group reduce the mRNA expression level of ACC(1.765±0.5009,3.034±0.2839 vs 4.662±0.08452,P <0.01). (3) Compared to the vehicle group, lipid accumulation in groups treating with 10μM\ 50μMOEA and 50μM fenofibrate for 24h were markedly reduced by oil red lipid staining.and intracellular TG content of these three groups reduced significantly too[(4.239±0.1273)mg/d,(3.343±0.2395)mg/dl,(3.467±0.244)mg/dl vs(5.181±0.2512)mg/dl,P <0.05]Conclusion: OEA, a efficient ligand of PPAR-α, could reduce lipid accumulation and TG content in fatty liver vitro model through increasing the mRNA expression level of lipid lipolysis gene LPL and reducing the mRNA expression level of genes ACC and SREBP-1c involved fat synthesis. Together, these results suggest that OEA possess anti-steatosis function. In addition, the effect of OEA on reducing the expression of SCD-1 implies the possible role of OEA in preventing hepatocellular carcinoma development.