Eddy Sean F, Storey Kenneth B
Institute of Biochemistry, Carleton University, 1125 Colonel By Drive, Ottawa, ON K1S 5B6, Canada.
Biochem Cell Biol. 2003 Aug;81(4):269-74. doi: 10.1139/o03-056.
The effects of hibernation on the expression of Akt (protein kinase B), the peroxisome proliferator-activated receptor gamma isoform (PPARgamma), and the PPARgamma coactivator PGC-1 were assessed in seven tissues of the little brown bat, Myotis lucifugus. Western blotting revealed that the levels of active phosphorylated Akt were strongly reduced in brain, kidney, liver, and white adipose during torpor as compared with aroused animals and that total Akt protein was also reduced in white adipose during torpor. By contrast, both total and phospho-Akt were elevated in brown adipose tissue, the thermogenic organ. PPARgamma and PGC-1 levels showed parallel changes in all organs. Both were strongly suppressed in brain, but levels increased significantly in all other organs during hibernation (except for PGC-1 in heart). Reduced Akt activity is consistent with a probable reduced insulin response during torpor that facilitates the mobilization of lipid reserves for fuel supply and is further supported by increased gene expression of enzymes and proteins involved in lipid catabolism under the stimulation of enhanced PPARgamma and PGC-1 levels.
研究评估了冬眠对小棕蝠（Myotis lucifugus）七种组织中Akt（蛋白激酶B）、过氧化物酶体增殖物激活受体γ亚型（PPARγ）以及PPARγ共激活因子PGC-1表达的影响。蛋白质印迹法显示，与苏醒状态的动物相比，蛰伏期间脑、肾、肝和白色脂肪组织中活性磷酸化Akt的水平大幅降低，并且蛰伏期间白色脂肪组织中总Akt蛋白也减少。相比之下，产热器官棕色脂肪组织中的总Akt和磷酸化Akt均升高。PPARγ和PGC-1水平在所有器官中呈现平行变化。二者在脑中均受到强烈抑制，但在冬眠期间所有其他器官中水平均显著升高（心脏中的PGC-1除外）。Akt活性降低与蛰伏期间可能降低的胰岛素反应一致，这有助于动员脂质储备以供能，并且在增强的PPARγ和PGC-1水平刺激下，参与脂质分解代谢的酶和蛋白质的基因表达增加进一步支持了这一点。
