The freeze-tolerant wood frog, Rana sylvatica, is one of few vertebrate organisms that can tolerate freezing, with up to 70% of its total body water being converted into extracellular ice. Physiologically, wood frogs show no signs of muscle movement, breathing, heartbeat, or brain activity for several weeks or months at a time but emerge unharmed upon thawing. Given that wood frogs rely mainly on carbohydrate metabolism during freezing, the involvement of the carbohydrate-responsive element-binding protein (ChREBP) in response to freezing is of interest. In liver tissue, protein and transcript levels of ChREBP increased by 1.4±0.09-fold and 1.9±0.26-fold, respectively, and nuclear distribution and DNA-binding activity rose by 2.0±0.08-fold and 1.5±0.08-fold, respectively. This enhanced transcriptional activity of ChREBP was corroborated by increased transcript expression of select downstream genes of fatty acid synthase, pyruvate kinase, and stearoyl-CoA desaturase in liver tissue. While liver tissue displayed ChREBP activation, in muscle tissue, ChREBP protein levels, DNA-binding activity, and downstream gene targets were generally found to decrease or to remain unchanged during freezing. Overall, our results demonstrate that ChREBP regulates metabolism in a tissue-dependent manner during freezing, when its activity is required for liver tissue but not for skeletal muscle tissue in wood frogs.

中文翻译：

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碳水化合物装载：木蛙中葡萄糖反应性ChREBP转录网络的冻结诱导激活。

耐冷冻的木蛙蛙蛙（Rana sylvatica）是为数不多的能耐受冷冻的脊椎动物之一，其体内最高70％的水被转化为细胞外冰。从生理上讲，青蛙在数周或数月内一次都没有表现出肌肉运动，呼吸，心跳或大脑活动的迹象，但融化后却无害。鉴于木蛙在冷冻过程中主要依赖碳水化合物的代谢，因此引起人们关注的是碳水化合物反应性元素结合蛋白（ChREBP）参与了冷冻反应。在肝组织中，ChREBP的蛋白质和转录水平分别增加了1.4±0.09倍和1.9±0.26倍，核分布和DNA结合活性分别增加了2.0±0.08倍和1.5±0.08倍。肝脏组织中脂肪酸合成酶，丙酮酸激酶和硬脂酰-CoA去饱和酶的选定下游基因的转录表达增加证实了ChREBP增强的转录活性。尽管肝脏组织显示ChREBP活化，但在肌肉组织中，通常发现ChREBP蛋白水平，DNA结合活性和下游基因靶点在冷冻过程中降低或保持不变。总的来说，我们的研究结果表明，ChREBP在冷冻过程中以组织依赖的方式调节新陈代谢，这是木蛙的肝脏组织而不是骨骼肌组织需要其活性时。通常发现在冷冻过程中，DNA结合活性和下游基因靶点减少或保持不变。总的来说，我们的研究结果表明，ChREBP在冷冻过程中以组织依赖的方式调节新陈代谢，这是木蛙的肝脏组织而不是骨骼肌组织需要其活性时。通常发现在冷冻过程中，DNA结合活性和下游基因靶点减少或保持不变。总的来说，我们的研究结果表明，ChREBP在冷冻过程中以组织依赖的方式调节新陈代谢，这是木蛙的肝脏组织而不是骨骼肌组织需要其活性时。