PDF(Pubmed)
Abstract：
OBJECTIVE: Stable isotope studies have shown that hepatic de novo lipogenesis (DNL) plays an important role in the pathogenesis of intrahepatic lipid (IHL) deposition. Furthermore, previous research has demonstrated that fructose 1-phosphate (F1P) not only serves as a substrate for DNL, but also acts as a signalling metabolite that stimulates DNL from glucose. The aim of this study was to elucidate the mediators of F1P-stimulated DNL, with special focus on two key regulators of intrahepatic glucose metabolism, i.e., glucokinase regulatory protein (GKRP) and carbohydrate response element binding protein (ChREBP).
METHODS: Aldolase B deficient mice (Aldob-/-), characterized by hepatocellular F1P accumulation, enhanced DNL, and hepatic steatosis, were either crossed with GKRP deficient mice (Gckr-/-) or treated with short hairpin RNAs directed against hepatic ChREBP.
RESULTS: Aldob-/- mice showed higher rates of de novo palmitate synthesis from glucose when compared to wildtype mice (p < 0.001). Gckr knockout reduced de novo palmitate synthesis in Aldob-/- mice (p = 0.017), without affecting the hepatic mRNA expression of enzymes involved in DNL. In contrast, hepatic ChREBP knockdown normalized the hepatic mRNA expression levels of enzymes involved in DNL and reduced fractional DNL in Aldob-/- mice (p < 0.05). Of interest, despite downregulation of DNL in response to Gckr and ChREBP attenuation, no reduction in intrahepatic triglyceride levels was observed.
CONCLUSIONS: Both GKRP and ChREBP mediate F1P-stimulated DNL in aldolase B deficient mice. Further studies are needed to unravel the role of GKRP and hepatic ChREBP in regulating IHL accumulation in aldolase B deficiency.
METHODS: Aldolase B deficient mice (Aldob-/-), characterized by hepatocellular F1P accumulation, enhanced DNL, and hepatic steatosis, were either crossed with GKRP deficient mice (Gckr-/-) or treated with short hairpin RNAs directed against hepatic ChREBP.
RESULTS: Aldob-/- mice showed higher rates of de novo palmitate synthesis from glucose when compared to wildtype mice (p < 0.001). Gckr knockout reduced de novo palmitate synthesis in Aldob-/- mice (p = 0.017), without affecting the hepatic mRNA expression of enzymes involved in DNL. In contrast, hepatic ChREBP knockdown normalized the hepatic mRNA expression levels of enzymes involved in DNL and reduced fractional DNL in Aldob-/- mice (p < 0.05). Of interest, despite downregulation of DNL in response to Gckr and ChREBP attenuation, no reduction in intrahepatic triglyceride levels was observed.
CONCLUSIONS: Both GKRP and ChREBP mediate F1P-stimulated DNL in aldolase B deficient mice. Further studies are needed to unravel the role of GKRP and hepatic ChREBP in regulating IHL accumulation in aldolase B deficiency.
摘要：
目的：稳定同位素研究表明，肝脏从头脂肪生成（DNL）在肝内脂质（IHL）沉积的发病机理中起重要作用。此外，先前的研究表明，果糖1-磷酸（F1P）不仅是DNL的底物，但也作为一个信号代谢刺激DNL从葡萄糖。本研究的目的是阐明F1P刺激的DNL，特别关注肝内葡萄糖代谢的两个关键调节剂，即，葡萄糖激酶调节蛋白(GKRP)和碳水化合物反应元件结合蛋白(ChREBP)。
方法：醛缩酶B缺陷小鼠（Aldoba-/-），以肝细胞F1P积累为特征，增强型DNL,和肝脏脂肪变性，与GKRP缺陷小鼠(Gckr-/-)杂交或用针对肝ChREBP的短发夹RNA处理。
结果：与野生型小鼠相比，Aldobb-/-小鼠显示出更高的葡萄糖从头合成棕榈酸酯的速率（p<0.001）。Gckr敲除降低Aldobs-/-小鼠的从头棕榈酸酯合成（p=0.017），而不影响DNL相关酶的肝脏mRNA表达。相比之下,肝脏ChREBP敲低使参与DNL的酶的肝脏mRNA表达水平正常化，并降低Aldobb-/-小鼠的DNL分数（p<0.05）。感兴趣的，尽管DNL下调响应Gckr和ChREBP衰减，未观察到肝内甘油三酯水平降低.
结论:在醛缩酶B缺陷小鼠中,GKRP和ChREBP均介导F1P刺激的DNL。需要进一步的研究来阐明GKRP和肝ChREBP在调节醛缩酶B缺乏症中IHL积累中的作用。
方法：醛缩酶B缺陷小鼠（Aldoba-/-），以肝细胞F1P积累为特征，增强型DNL,和肝脏脂肪变性，与GKRP缺陷小鼠(Gckr-/-)杂交或用针对肝ChREBP的短发夹RNA处理。
结果：与野生型小鼠相比，Aldobb-/-小鼠显示出更高的葡萄糖从头合成棕榈酸酯的速率（p<0.001）。Gckr敲除降低Aldobs-/-小鼠的从头棕榈酸酯合成（p=0.017），而不影响DNL相关酶的肝脏mRNA表达。相比之下,肝脏ChREBP敲低使参与DNL的酶的肝脏mRNA表达水平正常化，并降低Aldobb-/-小鼠的DNL分数（p<0.05）。感兴趣的，尽管DNL下调响应Gckr和ChREBP衰减，未观察到肝内甘油三酯水平降低.
结论:在醛缩酶B缺陷小鼠中,GKRP和ChREBP均介导F1P刺激的DNL。需要进一步的研究来阐明GKRP和肝ChREBP在调节醛缩酶B缺乏症中IHL积累中的作用。
