二甲双胍对高尿酸诱导HepG2细胞脂质沉积的作用及其机制研究

Effects of metformin on lipid deposition in HepG2 cells induced by high uric acid

目的:探讨二甲双胍对高尿酸诱导HepG2脂质沉积的作用及其可能机制。方法:将HepG2细胞按照不同处理因素分为5组:对照组(不干预)、高尿酸组(12 mg/dl尿酸)、高尿酸+二甲双胍组(12 mg/dl尿酸+10μmol/L二甲双胍)、高尿酸+二甲双胍+单磷酸腺苷酸活化的蛋白激酶(AMPK)抑制剂组(10μmol/L AMPK特异性抑制剂Compound C预处理30 min后,再加12 mg/dl尿酸+10μmol/L二甲双胍)和高尿酸+二甲双胍+烟酰胺腺嘌呤二核苷酸磷酸氧化酶4(NOX4)抑制剂组(100μmol/L NOX4特异性抑制剂Apocynin预处理30 min后,再加12 mg/dl尿酸+10μmol/L二甲双胍),每组设置3个平行组。培养48 h后,油红“O”检测细胞脂滴分布,试剂盒检测细胞甘油三酯(TG)含量、线粒体内活性氧簇(ROS)和丙二醛(MDA)含量、黄嘌呤氧化酶(XO)和谷胱甘肽过氧化物酶(GSH-Px)活性,实时聚合酶链反应检测细胞脂质合成相关基因的mRNA及线粒体NOX4 mRNA水平,Western blot检测细胞AMPK、p-AMPK及线粒体NOX4蛋白水平,免疫荧光检测线粒体内NOX4分布。组间比较采用单因素方差分析和t检验。结果:与高尿酸组相比,高尿酸+二甲双胍组HepG2细胞内脂滴数量减少,TG含量明显减少(t=8.181,P<0.05),线粒体ROS、MDA水平及XO活性降低,GSH-Px活性增加(t=5.472~8.242,均P<0.05),脂质合成相关基因mRNA表达降低(t=7.835~11.013,均P<0.05),AMPK蛋白的磷酸化水平显著增加(t=7.000,P<0.05),线粒体NOX4的mRNA及蛋白表达明显下调(t=6.190、14.199,P<0.05),差异均具有统计学意义。与高尿酸+二甲双胍组相比,高尿酸+二甲双胍+AMPK抑制剂组的上述作用减弱,高尿酸+二甲双胍+NOX4抑制剂组的上述作用增强,差异具有统计学意义(均P<0.05)。结论:二甲双胍可以减少高尿酸诱导的HepG2细胞脂质沉积,其机制与激活AMPK/NOX4信号通路、改善线粒体氧化应激有关。

Objective To study the effects of metformin on lipid deposition induced by high uric acid in HepG2 cells and its underlying mechanisms.Methods HepG2 cells were divided into five groups according to different treatment factors:control group(no intervention),high uric acid group(12 mg/dl uric acid),high uric acid+metformin group(12 mg/dl uric acid+10μmol/L metformin),high uric acid+metformin+adenosine monophosphate activated protein kinase(AMPK)inhibitor group(after pretreatment with 10μmol/L AMPK inhibitor Compound C for 30 min,12 mg/dl uric acid and 10μmol/L metformin were added),high uric acid+metformin+nicotinamide adenine dinucleotide phosphate oxidase 4(NOX4)inhibitor group(after pretreatment with 100μmol/L AMPK inhibitor Apocynin for 30 min,12 mg/dl uric acid and 10μmol/L metformin were added).Each group was set three parallels and incubated for 48 h.Oil Red O stain was used to detect intracellular lipid droplet distribution.The biochemical kits were used to measure intracellular triglyceride levels(TG),mitochondrial reactive oxygen species(ROS),mitochondrial malondialdehyde(MDA),the activity of mitochondrial xanthine oxidase(XO)and glutathione peroxidase(GSH-Px).The real-time polymerase chain reaction was used to measure mRNA levels of lipid synthesis related genes and mitochondrial nicotinamide adenine dinucleotide phosphate oxidase 4(NOX4).Western blotting was used to detect the protein levels of AMPK,phosphorylated AMPK(p-AMPK)and mitochondrial NOX4.immunofluorescence staining was used to detect NOX4 concentrations in mitochondria.One-way analysis of variance and t test were used for comparison among groups.Results Compared with high uric acid group,metformin significantly decreased the number of intracellular lipid droplets and TG contents(t=8.181,P<0.05),reduced the mitochondrial ROS and MDA levels,inhibited the activity of mitochondrial XO,increased the activity of mitochondrial GSH-Px(t=5.327-8.242,all P<0.05),down-regulated the mRNA expression of lipid synthesis related genes(t=7.835-11.013,all P<0.05),significantly increased the phosphorylation of AMPK protein(t=7.000,P<0.05),reduced the mRNA and protein expressions of NOX4 in mitochondria(t=6.190-14.199,all P<0.05),and the differences were statistically significant.Compared with high uric acid+metformin group,AMPK inhibition attenuated the effects of metformin,NOX4 inhibition further enhanced those effects,and the differences were statistically significant(all P<0.05).Conclusion Metformin could reduce high uric acid-induced intracellular lipid deposition in HepG2 cells via a mechanism related to activation of AMPK/NOX4 signaling pathway and improvement of mitochondrial oxidative stress.