A mutation in the peroxisome proliferator-activated receptor γ-binding site in the gene for the cytosolic form of phosphoenolpyruvate carboxykinase reduces adipose tissue size and fat content in mice
A mutation in the peroxisome proliferator-activated receptor γ-binding site in the gene for the cytosolic form of phosphoenolpyruvate carboxykinase reduces adipose tissue size and fat content in mice
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DOI：
10.1073/pnas.022616299
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发表时间：
2002-01-22
影响因子：
11.1
通讯作者：
Reshef, L
中科院分区：
文献类型：
--
作者：
Olswang, Y;Cohen, H;Reshef, L
调节脂肪组织中甘油三酯的周转需要持续提供3-甘油磷酸，其可以通过葡萄糖代谢或甘油生成来提供，甘油生成是从己糖或甘油以外的来源来合成3-甘油磷酸。通过特异性消除磷酸烯醇丙酮酸羧激酶（PEPCK-C）（一种在途径中起关键作用的酶）的胞质形式的表达，在小鼠中评估脂肪组织中甘油生成的重要性。为了实现这一点，我们通过同源重组突变了小鼠PEPCK-C基因5′侧翼区的过氧化物酶体增殖物激活受体γ（PPARγ）（称为过氧化物酶体增殖物激活受体元件（PPARE））的结合位点。该突变消除了该基因在白色脂肪组织中的表达，并大大降低了其在棕色脂肪组织中的表达，而肝脏和肾脏中的PEPCK-C mRNA水平保持正常。这些小鼠的附睾白色脂肪组织甘油三酯沉积减少，25%的动物显示脂肪营养不良。棕色脂肪组织中的脂质积累水平也大大降低。PPARE−/−小鼠肝脏甘油三酯含量与附睾脂肪垫大小之间的强相关性表明，肝脏甘油三酯合成主要利用来自脂肪组织的游离脂肪酸。与其他模型不同，患有脂肪代谢障碍的PPARE−/−小鼠没有表现出糖尿病的脂肪代谢障碍相关特征，仅表现出中度高血糖。这些研究确定了PPARE位点对脂肪组织中PEPCK-C基因表达的重要性以及PEPCK-C在甘油生成调节中的作用，甘油生成是维持脂肪组织中甘油三酯沉积的关键途径。
Regulation of the turnover of triglycerides in adipose tissue requires the continuous provision of 3-glycerophosphate, which may be supplied by the metabolism of glucose or by glyceroneogenesis, thede novosynthesis of 3-glycerophosphate from sources other than hexoses or glycerol. The importance of glyceroneogenesis in adipose tissue was assessed in mice by specifically eliminating the expression of the cytosolic form of phosphoenolpyruvate carboxykinase (PEPCK-C), an enzyme that plays a pivotal role in the pathway. To accomplish this, we mutated the binding site for the peroxisome proliferator-activated receptor γ (PPARγ) called the peroxisome proliferator-activated receptor element (PPARE), in the 5′ flanking region of the PEPCK-C gene in the mouse by homologous recombination. The mutation abolished expression of the gene in white adipose tissue and considerably reduced its expression in brown adipose tissue, whereas the level of PEPCK-C mRNA in liver and kidney remained normal. Epididymal white adipose tissue from these mice had a reduced triglyceride deposition, with 25% of the animals displaying lipodystrophy. There was also a greatly reduced level of lipid accumulation in brown adipose tissue. A strong correlation between the hepatic content of triglycerides and the size of the epididymal fat pad in PPARE−/−mice suggests that hepatic triglyceride synthesis predominantly utilizes free fatty acids derived from the adipose tissue. Unlike other models, PPARE−/−mice with lipodystrophy did not exhibit the lipodystrophy-associated features of diabetes and displayed only moderate hyperglycemia. These studies establish the importance of the PPARE site for PEPCK-C gene expression in adipose tissue and the role of PEPCK-C in the regulation of glyceroneogenesis, a pathway critical for maintaining the deposition of triglycerides in adipose tissue.