Department of Health Sciences, Brock University, St. Catharines, ON L2S 3A1, Canada.
Centre for Bone and Muscle Health, Brock University, St. Catharines, ON L2S 3A1, Canada.
Int J Mol Sci. 2020 Jul 11;21(14):4900. doi: 10.3390/ijms21144900.
Insulin resistance, a main characteristic of type 2 diabetes mellitus (T2DM), is linked to obesity and excessive levels of plasma free fatty acids (FFA). Studies indicated that significantly elevated levels of FFAs lead to skeletal muscle insulin resistance, by dysregulating the steps in the insulin signaling cascade. The polyphenol resveratrol (RSV) was shown to have antidiabetic properties but the exact mechanism(s) involved are not clearly understood. In the present study, we examined the effect of RSV on FFA-induced insulin resistance in skeletal muscle cells in vitro and investigated the mechanisms involved. Parental and GLUT4myc-overexpressing L6 rat skeletal myotubes were used. [H]2-deoxyglucose (2DG) uptake was measured, and total and phosphorylated levels of specific proteins were examined by immunoblotting. Exposure of L6 cells to FFA palmitate decreased the insulin-stimulated glucose uptake, indicating insulin resistance. Palmitate increased ser (131% ± 1.84% of control, < 0.001) and ser (148% ± 10.1% of control, < 0.01) phosphorylation of IRS-1, and increased the phosphorylation levels of mTOR (174% ± 15.4% of control, < 0.01) and p70 S6K (162% ± 20.2% of control, < 0.05). Treatment with RSV completely abolished these palmitate-induced responses. In addition, RSV increased the activation of AMPK and restored the insulin-mediated increase in (a) plasma membrane GLUT4 glucose transporter levels and (b) glucose uptake. These data suggest that RSV has the potential to counteract the FFA-induced muscle insulin resistance.
胰岛素抵抗是 2 型糖尿病(T2DM)的主要特征,与肥胖和血浆游离脂肪酸(FFA)水平过高有关。研究表明,FFA 水平显著升高会导致骨骼肌胰岛素抵抗,从而使胰岛素信号级联中的步骤失调。多酚白藜芦醇(RSV)具有抗糖尿病作用,但具体机制尚不清楚。在本研究中,我们研究了 RSV 对体外骨骼肌细胞中 FFA 诱导的胰岛素抵抗的影响,并探讨了相关机制。使用亲本和 GLUT4myc 过表达的 L6 大鼠骨骼肌成肌细胞。通过 [H]2-脱氧葡萄糖(2DG)摄取来测量,通过免疫印迹检查特定蛋白质的总水平和磷酸化水平。将 L6 细胞暴露于脂肪酸棕榈酸酯中会降低胰岛素刺激的葡萄糖摄取,表明存在胰岛素抵抗。棕榈酸酯增加了 IRS-1 的丝氨酸(131%±1.84%对照,<0.001)和丝氨酸(148%±10.1%对照,<0.01)磷酸化,并增加了 mTOR(174%±15.4%对照,<0.01)和 p70 S6K(162%±20.2%对照,<0.05)的磷酸化水平。RSV 处理完全消除了这些棕榈酸酯诱导的反应。此外,RSV 增加了 AMPK 的激活,并恢复了胰岛素介导的(a)质膜 GLUT4 葡萄糖转运体水平和(b)葡萄糖摄取的增加。这些数据表明 RSV 有可能对抗 FFA 诱导的肌肉胰岛素抵抗。