Objective

Glucose production into the blood requires the expression of glucose-6 phosphatase (G6Pase), a key enzyme that allows glucose-6 phosphate (G6P) hydrolysis into free glucose and inorganic phosphate. We previously reported that the hepatic suppression of G6Pase leads to G6P accumulation and to metabolic reprogramming in hepatocytes from liver G6Pase deficient mice (L.G6pc^-/-). Interestingly, the activity of the transcription factor carbohydrate response element-binding protein (ChREBP), central for de novo lipid synthesis, is markedly activated in L.G6pc^-/- mice that in consequence rapidly develop NAFLD-like pathology. In the current work, we wished to address whether a selective deletion of ChREBP could prevent hepatic lipid accumulation and NAFLD initiation in L.G6pc^-/- mice.

Methods

We generated liver-specific ChREBP (L.Chrebp^-/-) and/or G6Pase (L.G6pc^-/-) deficient mice using a Cre-lox strategy in B6.SA^CreERT2 mice. Mice were fed a standard chow diet or a high fat diet for 10 days. Markers of hepatic metabolism and cellular stress were analysed in liver of control, L. G6pc^-/-, L. Chrebp^-/-, and double knockout (i.e L.G6pc^-/-.Chrebp^-/-) mice.

Results

We observed that the deletion of ChREBP in liver of L.G6pc^-/-.Chrebp^-/- mice drastically decreased lipid accumulation. Importantly, it also exacerbated glycogen accumulation leading to hepatic water retention and aggravated hepatomegaly. At the mechanistic level, in the absence of ChREBP, elevated G6P concentrations caused by lack of G6Pase are rerouted towards glycogen synthesis. This caused animal distress and hepatocyte damage, characterized by ballooning and moderate fibrosis, paralleled with acute endoplasmic reticulum stress.

Conclusions

Altogether, our study reveals the crucial role of the ChREBP-G6Pase duo in the regulation of G6P-regulated pathways in the liver.

中文翻译：

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肝葡萄糖-6 磷酸酶/ChREBP 对的缺失与小鼠的存活不相容

客观的

葡萄糖进入血液需要葡萄糖 6 磷酸酶 (G6Pase) 的表达，这是一种关键酶，可使葡萄糖 6 磷酸 (G6P) 水解为游离葡萄糖和无机磷酸盐。我们之前报道过 G6Pase 的肝脏抑制导致 G6P 积累和肝脏 G6Pase 缺陷小鼠 (L.G6pc ^-/- )肝细胞中的代谢重编程。有趣的是，转录因子碳水化合物反应元件结合蛋白 (ChREBP) 的活性是脂质从头合成的核心，在 L.G6pc ^{-/- 中}显着激活结果迅速发展为 NAFLD 样病理的小鼠。在目前的工作中，我们希望解决选择性删除 ChREBP 是否可以防止 L.G6pc ^-/-小鼠肝脏脂质积累和 NAFLD 启动的问题。

方法

我们在 B6.SA ^CreERT2小鼠中使用 Cre-lox 策略生成了肝脏特异性 ChREBP (L.Chrebp ^-/- ) 和/或 G6Pase (L.G6pc ^-/- ) 缺陷小鼠。小鼠被喂食标准食物或高脂肪饮食 10 天。在对照、L. G6pc ^-/-、L. Chrebp ^-/-和双敲除（即 L.G6pc ^-/- .Chrebp ^-/-）小鼠的肝脏中分析肝脏代谢和细胞应激的标志物。

结果

我们观察到 L.G6pc ^-/- .Chrebp ^-/-小鼠肝脏中 ChREBP 的缺失显着降低了脂质积累。重要的是，它还加剧了糖原积累，导致肝水潴留和肝肿大加重。在机制水平上，在没有 ChREBP 的情况下，由缺乏 G6Pase 引起的 G6P 浓度升高被重新导向糖原合成。这导致动物窘迫和肝细胞损伤，其特征是膨胀和中度纤维化，同时伴有急性内质网应激。

结论

总之，我们的研究揭示了 ChREBP-G6Pase 二重奏在调节肝脏 G6P 调节通路中的关键作用。