Suppression of Long Chain Acyl-CoA Synthetase 3 Decreases Hepatic de Novo Fatty Acid Synthesis through Decreased Transcriptional Activity
Suppression of Long Chain Acyl-CoA Synthetase 3 Decreases Hepatic de Novo Fatty Acid Synthesis through Decreased Transcriptional Activity
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DOI：
10.1074/jbc.m109.036665
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发表时间：
2009-10-30
影响因子：
4.8
通讯作者：
Mashek, Douglas G.
中科院分区：
文献类型：
--
作者：
Bu, So Young;Mashek, Mara T.;Mashek, Douglas G.
长链酰基辅酶a合成酶（ACSL）和脂肪酸转运蛋白（FATP）在脂肪酸代谢的初始阶段激活脂肪酸转化为酰基辅酶a。ACSL和FATP的许多异构体具有不同的组织分布模式、细胞内位置和底物偏好，这表明每种异构体在将脂肪酸引导到不同的代谢途径中具有不同的功能。由于脂肪酸、酰基辅酶a和下游脂质代谢物调节各种控制肝脏能量代谢的转录因子，我们假设ACSL或FATP亚型对肝脏基因表达的调节存在差异。利用小干扰RNA (siRNA)，我们敲除了大鼠原代肝细胞培养中每个肝脏特异性ACSL和FATP亚型，随后分析了许多转录因子的报告基因活性，并对其靶基因进行了定量mRNA分析。与转染对照siRNA的对照细胞相比，敲低酰基辅酶a合成酶3 （ACSL3）显著降低了几种脂肪生成转录因子的报告基因活性及其靶基因的表达，如过氧化物酶体增殖体激活受体- γ、糖反应元件结合蛋白、固醇调节元件结合蛋白-1c和肝脏X受体- α。代谢标记研究进一步支持了这些发现，表明ACSL3 sirna处理的细胞中[1-C-14]乙酸掺入脂质提取物减少，而在ob/ob小鼠和喂食高糖饮食的小鼠中，ACSL3表达上调。ACSL3敲低降低了总酰基辅酶a合成酶活性，但没有显著改变其他ACSL亚型的表达。总之，这些结果确定了ACSL3在介导肝脏脂肪生成转录控制中的新作用。
Long chain acyl-CoA synthetases (ACSL) and fatty acid transport proteins (FATP) activate fatty acids to acyl-CoAs in the initial step of fatty acid metabolism. Numerous isoforms of ACSL and FATP exist with different tissue distribution patterns, intracellular locations, and substrate preferences, suggesting that each isoform has distinct functions in channeling fatty acids into different metabolic pathways. Because fatty acids, acyl-CoAs, and downstream lipid metabolites regulate various transcription factors that control hepatic energy metabolism, we hypothesized that ACSL or FATP isoforms differentially regulate hepatic gene expression. Using small interference RNA (siRNA), we knocked down each liver-specific ACSL and FATP isoform in rat primary hepatocyte cultures and subsequently analyzed reporter gene activity of numerous transcription factors and performed quantitative mRNA analysis of their target genes. Compared with control cells, which were transfected with control siRNA, knockdown of acyl-CoA synthetase 3 (ACSL3) significantly decreased reporter gene activity of several lipogenic transcription factors such as peroxisome proliferator activation receptor-gamma, carbohydrate-responsive element-binding protein, sterol regulatory element-binding protein-1c, and liver X receptor-alpha and the expression of their target genes. These findings were further supported by metabolic labeling studies that showed [1-C-14] acetate incorporation into lipid extracts was decreased in cells treated with ACSL3 siRNAs and that ACSL3 expression is up-regulated in ob/ob mice and mice fed a high sucrose diet. ACSL3 knockdown decreased total acyl-CoA synthetase activity without substantially altering the expression of other ACSL isoforms. In summary, these results identify a novel role for ACSL3 in mediating transcriptional control of hepatic lipogenesis.