Antioxidant and Gene Regulation Laboratory, Pennington Biomedical Research Center, Antioxidant and Gene Regulation, Baton Rouge, Louisiana 70808, USA.
Endocrinology. 2011 May;152(5):1829-38. doi: 10.1210/en.2010-0828. Epub 2011 Mar 15.
We have reported that the nuclear factor-κB (NF-κB) induces chronic inflammation in the adipose tissue of p65 transgenic (Tg) mice, in which the NF-κB subunit p65 (RelA) is overexpressed from the adipocyte protein 2 (aP2) gene promoter. Tg mice suffer a mild lipodystrophy and exhibit deficiency in adipocyte differentiation. To understand molecular mechanism of the defect in adipocytes, we investigated glyceroneogenesis by examining the activity of cytosolic phosphoenolpyruvate carboxykinase (PEPCK) in adipocytes. In aP2-p65 Tg mice, Pepck expression is inhibited at both the mRNA and protein levels in adipose tissue. The mRNA reduction is a consequence of transcriptional inhibition but not alteration in mRNA stability. The Pepck gene promoter is inhibited by NF-κB, which enhances the corepressor activity through activation of histone deacetylase 3 (HDAC3) in the nucleus. HDAC3 suppresses Pepck transcription by inhibiting the transcriptional activators, peroxisome proliferator-activated receptor-γ, and cAMP response element binding protein. The NF-κB activity is abolished by Hdac3 knockdown or inhibition of HDAC3 catalytic activity. In a chromatin immunoprecipitation assay, HDAC3 interacts with peroxisome proliferator-activated receptor-γ and cAMP response element binding protein in the Pepck promoter when NF-κB is activated by TNF-α. These results suggest that HDAC3 mediates NF-κB activity to repress Pepck transcription. This mechanism is responsible for inhibition of glyceroneogenesis in adipocytes, which contributes to lipodystrophy in the aP2-p65 Tg mice.
我们曾报道过核因子-κB（NF-κB）会在 p65 转基因（Tg）小鼠的脂肪组织中引发慢性炎症，该基因中 NF-κB 亚基 p65（RelA）由脂肪细胞蛋白 2（aP2）基因启动子过表达。Tg 小鼠患有轻度脂肪营养不良，并表现出脂肪细胞分化缺陷。为了了解脂肪细胞缺陷的分子机制，我们通过检查胞质磷酸烯醇丙酮酸羧激酶（PEPCK）的活性来研究甘油生成。在 aP2-p65 Tg 小鼠中，脂肪组织中 Pepck 的表达在 mRNA 和蛋白质水平上均受到抑制。mRNA 的减少是转录抑制的结果，而不是 mRNA 稳定性的改变。NF-κB 抑制 Pepck 基因启动子，通过激活核内组蛋白去乙酰化酶 3（HDAC3）增强核心抑制子的活性。HDAC3 通过抑制转录激活剂过氧化物酶体增殖物激活受体-γ（PPAR-γ）和 cAMP 反应元件结合蛋白（CREB）来抑制 Pepck 转录。NF-κB 活性被 Hdac3 敲低或 HDAC3 催化活性抑制所消除。在染色质免疫沉淀测定中，当 TNF-α激活 NF-κB 时，HDAC3 与 Pepck 启动子中的过氧化物酶体增殖物激活受体-γ和 cAMP 反应元件结合蛋白相互作用。这些结果表明，HDAC3 介导 NF-κB 活性以抑制 Pepck 转录。该机制负责抑制脂肪细胞中的甘油生成，这是 aP2-p65 Tg 小鼠脂肪营养不良的原因。
