Viana Amelia Y I, Sakoda Hideyuki, Anai Motonobu, Fujishiro Midori, Ono Hiraku, Kushiyama Akifumi, Fukushima Yasushi, Sato Yuzo, Oshida Yoshiharu, Uchijima Yasunobu, Kurihara Hiroki, Asano Tomoichiro
Department of Sports Medicine, Graduate School of Medicine, Nagoya University, 65 Tsurumai-cho, Showa-ku, Nagoya 466-8550, Japan.
Diabetes Res Clin Pract. 2006 Aug;73(2):135-42. doi: 10.1016/j.diabres.2005.12.011. Epub 2006 Feb 28.
To elucidate the role of AMPK in hepatic glucose metabolism, dominant negative (DN), constitutively active (CA) forms of the AMPKalpha1 subunit and control vector LacZ were overexpressed by means of adenovirus-mediated gene transfer. Five days after virus injection, hepatic AMPK activity was five-fold higher in CA mice than in DN mice. DN mice were apparently glucose intolerant with a higher fasting plasma glucose level (DN 82.3+/-0.7mg/dl, CA 42.5+/-4.8mg/dl and LacZ 54.3+/-2.4mg/dl). PEPCK, a gluconeogenic key enzyme, mRNA was increased 131.54% and 48.92% in DN mice compared to that of CA and LacZ, respectively. Thus, hepatic AMPK activation plays a role in the suppression of gluconeogenesis and this might be the cause of decreased fasting plasma glucose level in CA mice. We also investigated the effects of dexamethasone on hepatic AMPK expression and activity in rat liver, mice liver, as well as primary cultured hepatocytes. Subcutaneously injecting mice with dexamethasone (1mg/day) for 5 days significantly upregulated hepatic AMPKalpha1 and alpha2 expressions. Similarly, the treatment of primary cultured rat hepatocytes with dexamethasone (1microM) increased expression of the AMPKalpha1 subunit, AICAR-induced AMPK phosphorylation and kinase activity. Although increased AMPK expression cannot be attributed to dexamethasone-induced glucose intolerance, taken together our results raise the possibility that AMPK control liver glucose output and its expression in liver might be modulated by various hormones and growth factors.
为阐明AMPK在肝脏葡萄糖代谢中的作用，通过腺病毒介导的基因转移，过表达了AMPKα1亚基的显性负性（DN）、组成型激活（CA）形式以及对照载体LacZ。病毒注射5天后，CA小鼠肝脏中的AMPK活性比DN小鼠高5倍。DN小鼠明显存在葡萄糖不耐受，空腹血糖水平较高（DN为82.3±0.7mg/dl，CA为42.5±4.8mg/dl，LacZ为54.3±2.4mg/dl）。与CA和LacZ相比，糖异生关键酶磷酸烯醇式丙酮酸羧激酶（PEPCK）的mRNA在DN小鼠中分别增加了131.54%和48.92%。因此，肝脏AMPK的激活在抑制糖异生中发挥作用，这可能是CA小鼠空腹血糖水平降低的原因。我们还研究了地塞米松对大鼠肝脏、小鼠肝脏以及原代培养肝细胞中肝脏AMPK表达和活性的影响。给小鼠皮下注射地塞米松（1mg/天）5天可显著上调肝脏AMPKα1和α2的表达。同样，用地塞米松（1μM）处理原代培养的大鼠肝细胞可增加AMPKα1亚基的表达、AICAR诱导的AMPK磷酸化和激酶活性。尽管AMPK表达增加不能归因于地塞米松诱导的葡萄糖不耐受，但综合我们的结果提出了一种可能性，即AMPK控制肝脏葡萄糖输出，其在肝脏中的表达可能受到多种激素和生长因子的调节。
