Laboratory of Biodefense and Regulation, Osaka University of Pharmaceutical Sciences, Takatsuki, Osaka, Japan.
Am J Physiol Endocrinol Metab. 2012 Jun 15;302(12):E1461-71. doi: 10.1152/ajpendo.00623.2011. Epub 2012 Mar 20.
Here, we show that Elovl3 (elongation of very long-chain fatty acids 3) was involved in the regulation of the progression of adipogenesis through activation of peroxisome proliferator-activated receptor (PPAR)γ in mouse adipocytic 3T3-L1 cells. The expression of the Elovl3 gene increased during adipogenesis, the expression pattern of which was similar to that of the PPARγ gene. Troglitazone, a PPARγ agonist, enhanced Elovl3 expression in adipocytes, as it did that of other PPARγ target genes. Promoter-reporter analysis demonstrated that three PPAR-responsive elements in the Elovl3 gene promoter had the potential to activate its expression in 3T3-L1 cells. Moreover, a chromatin immunoprecipitation assay revealed that PPARγ bound these PPAR-responsive elements of the Elovl3 promoter. When the Elovl3 mRNA level was suppressed by its siRNAs, the level of intracellular triglycerides was significantly decreased, and the expression levels of adipogenic, lipolytic, and lipogenic genes were also repressed. In a mammalian two-hybrid assay, C18:1 and C20:1 very long-chain fatty acids (VLCFAs), which are the products of Elovl3 and activated PPARγ function. In addition, these same VLCFAs could prevent the Elovl3 siRNA-mediated suppression of adipogenesis by enhancing the expression of adipogenic, lipolytic, and lipogenic genes in adipocytes. Moreover, this VLCFAs-mediated activation was repressed by a PPARγ antagonist. These results indicate that the expression of the Elovl3 gene was activated by PPARγ during adipogenesis. Elovl3-produced C18:1 and C20:1 VLCFAs acted as agonists of PPARγ in 3T3-L1 cells. Thus, the Elovl3-PPARγ cascade is a novel regulatory circuit for the regulation of adipogenesis through improvement of PPARγ function in adipocytes.
在这里，我们表明 Elovl3（长链脂肪酸延长酶 3）通过激活过氧化物酶体增殖物激活受体（PPAR）γ参与调节脂肪生成。在脂肪生成过程中，Elovl3 基因的表达增加，其表达模式与 PPARγ 基因相似。PPARγ 激动剂曲格列酮增强了脂肪细胞中 Elovl3 的表达，正如它对其他 PPARγ 靶基因的表达增强一样。启动子-报告基因分析表明，Elovl3 基因启动子中的三个 PPAR 反应元件具有在 3T3-L1 细胞中激活其表达的潜力。此外，染色质免疫沉淀分析显示，PPARγ 结合了 Elovl3 启动子中的这些 PPAR 反应元件。当用其 siRNA 抑制 Elovl3 mRNA 水平时，细胞内甘油三酯水平显著降低，脂肪生成、脂肪分解和脂肪生成基因的表达水平也受到抑制。在哺乳动物双杂交测定中，C18:1 和 C20:1 长链脂肪酸（VLCFAs）是 Elovl3 的产物和激活的 PPARγ 功能的产物。此外，这些相同的 VLCFAs 可以通过增强脂肪细胞中脂肪生成、脂肪分解和脂肪生成基因的表达来防止 Elovl3 siRNA 介导的脂肪生成抑制。此外，这种 VLCFAs 介导的激活被 PPARγ 拮抗剂抑制。这些结果表明，在脂肪生成过程中，Elovl3 基因的表达被 PPARγ 激活。Elovl3 产生的 C18:1 和 C20:1 VLCFAs 在 3T3-L1 细胞中作为 PPARγ 的激动剂发挥作用。因此，Elovl3-PPARγ 级联反应是通过改善脂肪细胞中 PPARγ 功能来调节脂肪生成的新的调节回路。
