叉头状转录因子O1对游离脂肪酸诱导的人肝癌细胞株HepG-2胰岛素抵抗和脂质堆积作用的研究

Effect of forkhead transcription factor O1 on free fatty acid induced insulin resistance and steatosis by sterol-regulatory element binding protein-lc pathway

目的研究叉头状转录因子O1（FoxO1）对游离脂肪酸介导的人肝癌细胞株（HepG-2）胰岛素抵抗和脂质堆积的作用以及对固醇调节元件结合蛋白-1c（SREBP-1c）mRNA和蛋白表达的影响。方法将HepG-2细胞培养后用普通培养基培养为对照组，用含5．0×10μmol／L软脂酸的培养基诱导为软脂酸组，诱导后转染空白质粒为空白质粒组，诱导后转染FoxO1siRNA质粒载体为FoxO1siRNA载体组。运用实时定量聚合酶链反应（RT—PCR）方法检测FoxO1mRNA表达，噻唑蓝（M33＂）比色法检测细胞增殖，葡萄糖氧化酶法检测培养基中葡萄糖消耗量，油红O染色观察细胞脂质堆积；RT—PCR和Westernblot技术分别检测SREBP-1c mRNA表达量以及蛋白的表达量。各组间均值比较采用单因素方差分析，样本间比较采用t检验。结果软脂酸组较对照组细胞葡萄糖消耗量减少（1．174-0．56vsVS4．31±0．21，t=10．587，P〈0．01）、细胞中的脂质堆积增多、FoxO1mRNA升高（0．784-0．10vs0．51±0．12，t=3．629，P〈0．05）、SREBP-1cmRNA升高（0．71±0．17vs0．25±0．08，t=6．290，P〈0．05）、SREBP-1c蛋白升高（0．694-0．10vs0．41±0．07，t=4．797，P〈0．01）。转染FoxO1siRNA质粒载体后葡萄糖消耗量较软脂酸组增加（2．26±0．41vs1．17±0．56，t=3．144，P〈0．05），FoxO1mRNA、SREBP-1cmRNA、SREBP-1c蛋白的表达较软脂酸组均减少且接近于对照组（分别为0．38±0．06vs0．784-0．10，t=7．164，P〈0．01；0．45±0．13vs0．71±0．17，t=2．479，P〈0．05；0．41±0．06vs0．694-0．10，t=4．797，P〈0．01），细胞中的脂质堆积也较软脂酸组减少。结论抑制FoxO1的表达，可改善游离脂肪酸诱导的细胞胰岛素抵抗、减少肝脏细胞内脂肪变性，其机制可能是通过下调SREBP-1c的表达。

Objective To study the effects and potential mechanisms of Forkhead transcription factor O1 （FoxO1） on free fatty acid （FFA） induced insulin resistance （IR） and steatosis. Methods HepG-2 cells were induced to a status of insulin resistance by being exposed to 5.0 × 10 -4 mmo[/L palmitic acid （PA） for 24 hours. HepG-2 cells were devided into 4 groups, the HepG-2 cell group cultured with normal medium, the palmitic acid group, the blank plasmid group, and the siFoxO1 group. PA was added to normal medium to a final concentration of 5.0 × 10-4 mol/L. The expression levels of FoxO1 in different groups were detected by RT-PCR. The glucose consumption was detected by using glucose oxidase method. MIT method was used to detect the proliferation of HepG-2 cells. Steatosis of HepG-2 cells was observed by Oil Red O staining. The mRNA and protein expression of SREBP-1c were determined by RT-PCR and Western blot. Results Compared with control, the glucose consumption of cells cultured with FFA was significantly reduced（ 1.17 ± 0. 56 vs 4. 31 ± 0. 21 ,t = 10. 587,P 〈 0. 01 ）. Cellular lipid accumulation, the expressions of FoxO1 mRNA（0.78 ±0.10 vs 0.51 ±0.12,t =3.629,P 〈0.05）,SREBP-le mRNA （0. 71 ±0. 17 vs 0. 25 ±0. 08 ,t =6. 290,P 〈0. 05） ,and the protein of SREBP-1c （0. 69 ±0. 10 vs 0. 41 ± 0. 07, t= 4. 797,P 〈 0. 01 ） was increased . After transfected by siFoxO1 plasmids using Lipofectamine 2000, the mRNA expression of FoxO1 （0. 38 ± 0.06 vs 0. 78 ± 0. 10, t = 7. 164, P 〈 0. 01 ） , SREB9-1 c （ 0.45 ± 0. 13 vs 0. 71 ± 0.17, t = 2.479,P 〈 0.05 ） and the SREBP-1 e protein expression （0.41 ± 0.06 vs 0.69 ± 0. 10, t = 4. 797, P 〈 0.01 ） were significantly decreased after tranfected by siFoxO1 plasminds, whereas the glucose consumption obviously the glucose consumption obviously increased（2. 26 ± 0. 41 vs 1.17 ± 0. 56,t =3. 144,P 〈0. 05）. The cellular lipod accumulation was decrease after transfected by siFoxO1. There was no remarkable difference between the pahnitie acid group, and the blank plasmid group. Conclusions Inhibiting the expression of FoxO1 could improve FFA-indueed IR and steatosis by down-regulating SREBP1c expression.