Division of Endocrinology, Department of Internal Medicine, Wayne State University School of Medicine, Detroit, MI 48201-1928, USA.
Biochem Biophys Res Commun. 2012 Aug 10;424(4):753-7. doi: 10.1016/j.bbrc.2012.07.027. Epub 2012 Jul 16.
The serine/threonine kinase Akt plays an important role in insulin-mediated glucose uptake. Adiponectin (Adp) is known to sensitize this process. The purpose of the current study is to investigate if Adp activates Akt independently from insulin; and if Adp synergizes with insulin on Akt phosphorylation in the rat skeletal muscle L6 cells. Differentiated L6 cells were serum-starved and exposed to various concentrations (0-100nM) of recombinant globular Adp (gAdp) and/or insulin for different time periods at 37°C. Phosphorylation of Akt was monitored by Western blot using an antiserum against pSer(473) or pThr(308) Akt. The results demonstrate that gAdp activates Akt in dose- and time-dependent manners. When L6 cells were treated with sub-maximal concentrations of both insulin (10nM) and gAdp (10nM) for 10 min neither synergistic nor additive activation of Akt was observed. Similar non-synergistic or non-additive effect of gAdp on insulin-induced Akt activation was also observed in mouse C2C12 myocytes and rat vascular smooth muscle PAC cells. Moreover, pretreatment of the L6 cells with wortmannin (100nM) for 20 min significantly reduced gAdp (100nM) induced and insulin (100nM) induced Akt activation by ∼80 and ∼70%, respectively. These data suggest that adiponectin stimulates Akt activation via the wortmannin sensitive pathway in L6 cells; and that its effects on Akt phosphorylation are not additive to those of insulin.
丝氨酸/苏氨酸蛋白激酶 Akt 在胰岛素介导的葡萄糖摄取中发挥着重要作用。脂联素（Adp）已知能使这一过程敏感化。本研究的目的是研究 Adp 是否能独立于胰岛素激活 Akt；以及 Adp 是否能在大鼠骨骼肌 L6 细胞中与胰岛素协同作用于 Akt 磷酸化。分化的 L6 细胞在血清饥饿状态下，在 37°C 下暴露于不同浓度（0-100nM）的重组球状 Adp（gAdp）和/或胰岛素不同时间。使用针对 pSer（473）或 pThr（308）Akt 的抗血清通过 Western blot 监测 Akt 的磷酸化。结果表明，gAdp 以剂量和时间依赖的方式激活 Akt。当 L6 细胞用胰岛素（10nM）和 gAdp（10nM）的亚最大浓度处理 10 分钟时，既没有观察到 Akt 的协同激活，也没有观察到相加激活。在小鼠 C2C12 肌细胞和大鼠血管平滑肌 PAC 细胞中也观察到 gAdp 对胰岛素诱导的 Akt 激活的类似非协同或非相加作用。此外，L6 细胞用渥曼青霉素（100nM）预处理 20 分钟，可显著降低 gAdp（100nM）诱导和胰岛素（100nM）诱导的 Akt 激活，分别降低约 80%和 70%。这些数据表明，脂联素通过 L6 细胞中渥曼青霉素敏感途径刺激 Akt 激活；并且其对 Akt 磷酸化的影响与胰岛素的作用不具有加性。
