胰高糖素样肽-1通过修饰叉头状转录因子O1磷酸化位点影响脂肪肝细胞中的脂质代谢

Effect of glucagon-like peptide-1 on lipid metabolism in hepatocytes by modification of forkhead box protein O1 phosphorylation sites

目的探讨胰高糖素样肽-1(GLP-1)是否能够通过修饰叉头状转录因子O1(FoxO1)磷酸化位点调控肝细胞中的脂质代谢。方法利用人肝癌细胞系HepG2细胞构建脂肪肝细胞模型[溶于异丙醇的无白蛋白棕榈酸组(PA组)]。GLP-1处理脂肪肝细胞模型后(GLP-1处理组)测定细胞内甘油三酯(TG)的变化;利用Western blot检测细胞内FoxO1三个磷酸化Thr24、Ser256和Ser319的变化;构建和转染FoxO1-Ser256突变质粒,利用RT-PCR检测GLP-1对调脂基因ACC和Fasn mRNA表达的影响。多组间比较采用方差分析,2组间比较采用t检验。结果与PA组比较,GLP-1处理组ACC和Fasn mRNA显著降低(分别为1.33±0.30比4.21±0.66、1.41±0.48比3.05±0.67,t=5.31、4.16,均P<0.05)。与PA组比较,GLP-1处理显著升高ser256和ser319位点磷酸化水平(t=7.34、8.79,均P<0.05)。转染FoxO1野生型质粒入HepG2细胞脂肪变性模型中后,GLP-1可显著降低ACC和Fasn的mRNA表达(t=5.28、4.33,均P<0.05)。而转染突变质粒FoxO1-MT入HepG2细胞脂肪变性模型中后,GLP-1不能抑制ACC和Fasn的mRNA表达(F=1.16、2.51,均P>0.05)。结论GLP-1可能通过修饰FoxO1的磷酸化位点影响其下游调脂基因ACC和Fasn的表达,进而减少脂肪肝细胞模型中TG的合成。

ObjectiveTo investigate whether glucagon-like peptide-1 (GLP-1) can regulate lipid metabolism in hepatocytes by modifying forkhead box protein O1 (FoxO1) phosphorylation sites.MethodsThe hepatic carcinoma cell line HepG2 cells were used to construct the hepatic steatosis model. Measuring the change of intracellular triglyceride (TG) of the GLP-1 treated cells fatty liver model, Western blot was used to detect changes in phosphorylation of Thr24, Ser256, and Ser319 in FoxO1;construction and transfection of the FoxO1-Ser256 mutant plasmid, RT-PCR was used to detect the changes of ACC and Fasn genes regulated by FoxO1.ResultsCompared with model group, ACC and Fasn mRNA level were lower than in GLP-1 treated model group, the difference was statistically significant (1.33±0.30 vs 4.21±0.66, 1.41±0.48 vs 3.05±0.67, t=5.31,4.16, all P<0.05). Compared with model group, the phosphorylation levels of ser256 and ser319 significantly elevated in GLP-1 group (t=7.34, 8.79, all P<0.05). After transfected with FoxO1-WT, the expression of ACC and Fasn mRNA were reduced in GLP-1 group (t=5.28, 4.33, all P<0.05). After transfected with FoxO1-MT, the expression of ACC and Fasn mRNA were not reduced in GLP-1 group (t=1.16, 2.51, all P>0.05).ConclusionsGLP-1 may affect the expression of Foxol downstream gene ACC andFasn by modifying the phosphorylation sites of FoxO1, and reduce lipid formation in the fatty liver cell model.