Macconi Daniela, Perico Luca, Longaretti Lorena, Morigi Marina, Cassis Paola, Buelli Simona, Perico Norberto, Remuzzi Giuseppe, Benigni Ariela
IRCCS-Istituto di Ricerche Farmacologiche "Mario Negri", Centro Anna Maria Astori, Science and Technology Park Kilometro Rosso, Via Stezzano 87, 24126 Bergamo, Italy.
IRCCS-Istituto di Ricerche Farmacologiche "Mario Negri, Clinical Research Center for Rare Diseases "Aldo e Cele Daccò", Via Camozzi 3, 24020 Ranica, Bergamo, Italy.
PLoS One. 2015 May 19;10(5):e0127172. doi: 10.1371/journal.pone.0127172. eCollection 2015.
Angiotensin II promotes insulin resistance. The mechanism underlying this abnormality, however, is still poorly defined. In a different setting, skeletal muscle metabolism and insulin signaling are regulated by Sirtuin3.
Here, we investigate whether angiotensin II-induced insulin resistance in skeletal muscle is associated with Sirtuin3 dysregulation and whether pharmacological manipulation of Sirtuin3 confers protection.
Parental and GLUT4-myc L6 rat skeletal muscle cells exposed to angiotensin II are used as in vitro models of insulin resistance. GLUT4 translocation, glucose uptake, intracellular molecular signals such as mitochondrial reactive oxygen species, Sirtuin3 protein expression and activity, along with its downstream targets and upstream regulators, are analyzed both in the absence and presence of acetyl-L-carnitine. The role of Sirtuin3 in GLUT4 translocation and intracellular molecular signaling is also studied in Sirtuin3-silenced as well as over-expressing cells.
Angiotensin II promotes insulin resistance in skeletal muscle cells via mitochondrial oxidative stress, resulting in a two-fold increase in superoxide generation. In this context, reactive oxygen species open the mitochondrial permeability transition pore and significantly lower Sirtuin3 levels and activity impairing the cell antioxidant defense. Angiotensin II-induced Sirtuin3 dysfunction leads to the impairment of AMP-activated protein kinase/nicotinamide phosphoribosyltransferase signaling. Acetyl-L-carnitine, by lowering angiotensin II-induced mitochondrial superoxide formation, prevents Sirtuin3 dysfunction. This phenomenon implies the restoration of manganese superoxide dismutase antioxidant activity and AMP-activated protein kinase activation. Acetyl-L-carnitine protection is abrogated by specific Sirtuin3 siRNA.
Our data demonstrate that angiotensin II-induced insulin resistance fosters mitochondrial superoxide generation, in turn leading to Sirtuin3 dysfunction. The present results also highlight Sirtuin3 as a therapeutic target for the insulin-sensitizing effects of acetyl-L-carnitine.
血管紧张素II可促进胰岛素抵抗。然而，这种异常现象背后的机制仍不清楚。在另一种情况下，骨骼肌代谢和胰岛素信号传导受Sirtuin3调节。
在此，我们研究血管紧张素II诱导的骨骼肌胰岛素抵抗是否与Sirtuin3失调有关，以及对Sirtuin3进行药物干预是否具有保护作用。
将暴露于血管紧张素II的亲代和GLUT4-myc L6大鼠骨骼肌细胞用作胰岛素抵抗的体外模型。在不存在和存在乙酰-L-肉碱的情况下，分析葡萄糖转运蛋白4（GLUT4）易位、葡萄糖摄取、细胞内分子信号，如线粒体活性氧、Sirtuin3蛋白表达和活性，以及其下游靶点和上游调节因子。还在Sirtuin3沉默和过表达的细胞中研究了Sirtuin3在GLUT4易位和细胞内分子信号传导中的作用。
血管紧张素II通过线粒体氧化应激促进骨骼肌细胞中的胰岛素抵抗，导致超氧化物生成增加两倍。在这种情况下，活性氧打开线粒体通透性转换孔，并显著降低Sirtuin3水平和活性，损害细胞抗氧化防御。血管紧张素II诱导的Sirtuin3功能障碍导致AMP活化蛋白激酶/烟酰胺磷酸核糖基转移酶信号传导受损。乙酰-L-肉碱通过降低血管紧张素II诱导的线粒体超氧化物形成，防止Sirtuin3功能障碍。这种现象意味着锰超氧化物歧化酶抗氧化活性和AMP活化蛋白激酶激活的恢复。特异性Sirtuin3小干扰RNA可消除乙酰-L-肉碱的保护作用。
我们的数据表明，血管紧张素II诱导的胰岛素抵抗促进线粒体超氧化物生成，进而导致Sirtuin3功能障碍。目前的结果还突出了Sirtuin3作为乙酰-L-肉碱胰岛素增敏作用的治疗靶点。
