Austin Reginald L, Rune Anna, Bouzakri Karim, Zierath Juleen R, Krook Anna
Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden.
Diabetes. 2008 Aug;57(8):2066-73. doi: 10.2337/db07-0763. Epub 2008 Apr 28.
Proinflammatory cytokines contribute to systemic low-grade inflammation and insulin resistance. Tumor necrosis factor (TNF)-alpha impedes insulin signaling in insulin target tissues. We determined the role of inhibitor of nuclear factor-kappaB kinase (IKK)beta in TNF-alpha-induced impairments in insulin signaling and glucose metabolism in skeletal muscle.
Small interfering RNA (siRNA) was used to silence IKKbeta gene expression in primary human skeletal muscle myotubes from nondiabetic subjects. siRNA gene silencing reduced IKKbeta protein expression 73% (P < 0.05). Myotubes were incubated in the absence or presence of insulin and/or TNF-alpha, and effects of IKKbeta silencing on insulin signaling and glucose metabolism were determined.
Insulin increased glucose uptake 1.7-fold (P < 0.05) and glucose incorporation into glycogen 3.8-fold (P < 0.05) in myotubes from nondiabetic subjects. TNF-alpha exposure fully impaired insulin-mediated glucose uptake and metabolism. IKKbeta siRNA protected against TNF-alpha-induced impairments in glucose metabolism, since insulin-induced increases in glucose uptake (1.5-fold; P < 0.05) and glycogen synthesis (3.5-fold; P < 0.05) were restored. Conversely, TNF-alpha-induced increases in insulin receptor substrate-1 serine phosphorylation (Ser(312)), Jun NH(2)-terminal kinase phosphorylation, and extracellular signal-related kinase-1/2 mitogen-activated protein kinase (MAPK) phosphorylation were unaltered by siRNA-mediated IKKbeta reduction. siRNA-mediated IKKbeta reduction prevented TNF-alpha-induced insulin resistance on Akt Ser(473) and Thr(308) phosphorylation and phosphorylation of the 160-kDa Akt substrate AS160. IKKbeta silencing had no effect on cell differentiation. Finally, mRNA expression of GLUT1 or GLUT4 and protein expression of MAPK kinase kinase kinase isoform 4 (MAP4K4) was unaltered by IKKbeta siRNA.
IKKbeta silencing prevents TNF-alpha-induced impairments in insulin action on Akt phosphorylation and glucose uptake and metabolism in human skeletal muscle.
促炎细胞因子导致全身低度炎症和胰岛素抵抗。肿瘤坏死因子（TNF）-α阻碍胰岛素靶组织中的胰岛素信号传导。我们确定了核因子-κB激酶（IKK）β抑制剂在TNF-α诱导的骨骼肌胰岛素信号传导和葡萄糖代谢损伤中的作用。
使用小干扰RNA（siRNA）使非糖尿病受试者的原代人骨骼肌肌管中的IKKβ基因表达沉默。siRNA基因沉默使IKKβ蛋白表达降低73%（P<0.05）。将肌管在有无胰岛素和/或TNF-α的情况下孵育，并确定IKKβ沉默对胰岛素信号传导和葡萄糖代谢的影响。
胰岛素使非糖尿病受试者的肌管中葡萄糖摄取增加1.7倍（P<0.05），葡萄糖掺入糖原增加3.8倍（P<0.05）。TNF-α暴露完全损害了胰岛素介导的葡萄糖摄取和代谢。IKKβ siRNA可防止TNF-α诱导的葡萄糖代谢损伤，因为胰岛素诱导的葡萄糖摄取增加（1.5倍；P<0.05）和糖原合成增加（3.5倍；P<0.05）得以恢复。相反，siRNA介导的IKKβ减少未改变TNF-α诱导的胰岛素受体底物-1丝氨酸磷酸化（Ser(312)）、Jun NH(2)-末端激酶磷酸化以及细胞外信号相关激酶-1/2丝裂原活化蛋白激酶（MAPK）磷酸化。siRNA介导的IKKβ减少可防止TNF-α诱导的Akt Ser(473)和Thr(308)磷酸化以及160-kDa Akt底物AS160的磷酸化导致的胰岛素抵抗。IKKβ沉默对细胞分化无影响。最后，IKKβ siRNA未改变GLUT1或GLUT4的mRNA表达以及丝裂原活化蛋白激酶激酶激酶激酶同工型4（MAP4K4）的蛋白表达。
IKKβ沉默可防止TNF-α诱导的人骨骼肌中Akt磷酸化以及胰岛素作用、葡萄糖摄取和代谢方面的损伤。
