转录因子SREBP1c在高脂诱导L6细胞胰岛素抵抗中的作用及机制  

Effects of transcription factor sterol regulatory element binding protein-1c in palmitate acid-induced L6 cells insulin resistance and its mechanism

作　　者：吴文君[1] 毕艳[2] 汤孙寅炎 尹雯雯[2] 陈莹莹[2] 朱大龙[2] 

机构地区：[1]南京医科大学附属无锡市人民医院内分泌科,江苏无锡214001 [2]南京医科大学鼓楼临床医学院内分泌科,210008

出　　处：《中华医学杂志》2015年第8期611-615,共5页National Medical Journal of China

基　　金：国家自然科学基金（81270906）;南京医科大学科技发展基金（2013NJMU155）

摘　　要：目的 探讨固醇调节元件结合蛋白-1c （SREBP-1c）对骨骼肌细胞胰岛素受体底物-1（IRS-1）的调控机制,以明确SREBP-1 c在高脂诱导骨骼肌胰岛素抵抗中的作用.方法 L6细胞经2％胎牛血清（FBS）诱导分化成肌管细胞,经500 μmol/L棕榈酸（PA）处理建立胰岛素抵抗模型.采用Western印迹检测L6肌管细胞经PA处理后0.5、1、3、6、12、24、48 h的SREBP-1c、p-IRS-1（Tyr608/612）、IRS-1、p-AKT（Ser473）、AKT的蛋白表达.检测L6肌管细胞过表达SREBP-1 c或用肝X受体（LXR）激动剂TO901317（5 μmol/L）处理后SREBP-1 c、脂肪酸合成酶（FAS）及胰岛素信号通路相关分子的蛋白表达.采用双荧光素酶报告基因实验分析SREBP-1 c转录因子对IRS-1启动子区域的调控作用.结果 L6肌管细胞经PA处理后,SREBP-1c蛋白表达在1h后即显著增高,胰岛素信号通路蛋白p-IRS-1（Tyr608/612）、IRS-1及p-AKT（Ser473）表达在6h后显著下降,AKT蛋白表达无变化.L6肌管细胞经LXR激动剂TO901317处理后SREBP-1c、FAS基因及蛋白表达增高,IRS-1基因表达下降,p-IRS-1（Tyr608/612）、IRS-1及p-AKT（Ser473）/AKT蛋白表达下降.L6肌管细胞过表达SREBP-1c后相关蛋白出现与LXR激动剂干预相似的变化.双荧光素酶报告基因实验结果显示SREBP-1c显著抑制IRS-1的启动子活性,SREBP-1c DNA结合域的酪氨酸突变成丙氨酸后则对IRS-1启动子无作用.结论 SREBP-1c通过抑制IRS-1基因转录表达而影响胰岛素信号通路,在高脂诱导骨骼肌胰岛素抵抗中起关键作用.Objective Sterol regulatory element binding protein-1c （SREBP-1c） is a master regulator of fatty acid synthase and controls lipogenesis.And insulin receptor substrate-1 （IRS-1） is a key insulin signaling mediator in skeletal muscle.The present study was conducted to explore the mechanism of SREBP-1c in the regulation of IRS-1 in skeletal muscle cells and elucidate the role of SREBP-1c in high fatinduced skeletal muscle insulin resistance.Methods L6 cells differentiated into myotubes in differentiation medium with 2% FBS.An in vitro insulin resistant model in L6 myotubes was established by 500 μmol/L of palmitate acid （PA）.SREBP-1c,p-IRS-1 （Tyr608/612）,IRS-1,p-AKT（Ser473） and AKT were detected by Western blot after incubating L6 myobutes with 500 μmol/L of PA for 0.5,1,3,6,12,18 or 24 h.SREBP-1c,FAS and molecules related to insulin signaling pathway were detected by Western blot when L6 myotubes over-expressed SREBP-1c or after a treatment of liver X receptor （LXR） agonist （TO901317,5 pmol/L）.The regulatory effects of transcription factor SREBP-lc on promoter region of IRS-1 were assessed by dualluciferase reporter assay.Results SREBP-1 c protein expression increased significantly after 1-hour exposure to PA.The protein levels of p-IRS-1 （Tyr608/612）,IRS-1 and p-AKT（Ser473） decreased significantly after a 6-hour incubation of PA.However AKT protein levels were unaffected.The protein expressions of SREBP-1 c and FAS were up-regulated by LXR agonist treatment versus controls.By contrast,LXR agonist treatment led to decreased expressions of IRS-1,p-IRS-1 （Tyr608/612） and p-AKT（Ser473）/AKT proteins versus controls.The expressions of related proteins were similar to the observations made with LXR agonist intervention.The results of dual-luciferase reporter assay indicated that IRS-1 promoter activity was repressed significantly by SREBP-lc over-expression or TO901317 treatment whereas the dominant negative form of SREBP-1 c （a mutant of Tyr320Ala lacking the ability of bi

关 键 词：固醇调节元件结合蛋白-1C 棕榈酸 骨骼肌 胰岛素抵抗 胰岛素受体底物-1 

分 类 号：R335[医药卫生—人体生理学]