Moreno María, Ortega Francisco, Xifra Gemma, Ricart Wifredo, Fernández-Real José Manuel, Moreno-Navarrete José María
Department of Diabetes, Endocrinology and Nutrition, Institut d'Investigació Biomèdica de Girona, CIBEROBN (CB06/03/010), and Instituto de Salud Carlos III, Girona, Spain.
Department of Diabetes, Endocrinology and Nutrition, Institut d'Investigació Biomèdica de Girona, CIBEROBN (CB06/03/010), and Instituto de Salud Carlos III, Girona, Spain
FASEB J. 2015 Apr;29(4):1529-39. doi: 10.1096/fj.14-258996. Epub 2014 Dec 30.
To gain insight into the regulation of intracellular iron homeostasis in adipose tissue, we investigated the role of iron regulatory protein 1/cytosolic aconitase 1 (ACO1). ACO1 gene expression and activity increased in parallel to expression of adipogenic genes during differentiation of both murine 3T3-L1 cells and human preadipocytes. Lentiviral knockdown (KD) of Aco1 in 3T3-L1 preadipocytes led to diminished cytosolic aconitase activity and isocitrate dehydrogenase 1 (NADP(+)), soluble (Idh1) mRNA levels, decreased intracellular NADPH:NADP ratio, and impaired adipogenesis during adipocyte differentiation. In addition, Aco1 KD in fully differentiated 3T3-L1 adipocytes decreased lipogenic, Idh1, Adipoq, and Glut4 gene expression. A bidirectional cross-talk was found between intracellular iron levels and ACO1 gene expression and protein activity. Although iron in excess, known to increase reactive oxygen species production, and iron depletion both resulted in decreased ACO1 mRNA levels and activity, Aco1 KD led to reduced gene expression of transferrin receptor (Tfrc) and transferrin, disrupting intracellular iron uptake. In agreement with these findings, in 2 human independent cohorts (n = 85 and n = 38), ACO1 gene expression was positively associated with adipogenic markers in subcutaneous and visceral adipose tissue. ACO1 gene expression was also positively associated with the gene expression of TFRC while negatively linked to ferroportin (solute carrier family 40 (iron-regulated transporter), member 1) mRNA levels. Altogether, these results suggest that ACO1 activity is required for the normal adipogenic capacity of adipose tissue by connecting iron, energy metabolism, and adipogenesis.
为深入了解脂肪组织中细胞内铁稳态的调节机制，我们研究了铁调节蛋白1/胞质乌头酸酶1（ACO1）的作用。在小鼠3T3-L1细胞和人前脂肪细胞分化过程中，ACO1基因表达和活性与脂肪生成基因的表达平行增加。在3T3-L1前脂肪细胞中，通过慢病毒介导敲低（KD）Aco1导致胞质乌头酸酶活性降低、异柠檬酸脱氢酶1（NADP(+)）可溶性（Idh1）mRNA水平下降、细胞内NADPH:NADP比值降低以及脂肪细胞分化过程中的脂肪生成受损。此外，在完全分化的3T3-L1脂肪细胞中敲低Aco1会降低脂肪生成、Idh1、Adipoq和Glut4基因的表达。细胞内铁水平与ACO1基因表达和蛋白活性之间存在双向交互作用。尽管已知过量铁会增加活性氧的产生，而铁缺乏都会导致ACO1 mRNA水平和活性降低，但敲低Aco1会导致转铁蛋白受体（Tfrc）和转铁蛋白的基因表达降低，从而破坏细胞内铁摄取。与这些发现一致，在2个独立的人类队列（n = 85和n = 38）中，ACO1基因表达与皮下和内脏脂肪组织中的脂肪生成标志物呈正相关。ACO1基因表达也与TFRC的基因表达呈正相关，而与铁转运蛋白（溶质载体家族40（铁调节转运蛋白），成员1）mRNA水平呈负相关。总之，这些结果表明，通过连接铁、能量代谢和脂肪生成，ACO1活性是脂肪组织正常脂肪生成能力所必需的。
